Characteristics and Application of Emulsifiers
Introduction
Emulsifier is an organic compound that encompasses in the same molecule two dissimilar structural groups e.g. water soluble and a water insoluble moiety. The composition solubility properties location and relative sizes of these dissimilar groups in relation to the overall molecular configuration determine the surface activity of a compound. The water soluble moiety is generally referred to as hydrophilic lipophobic and oleophobic and the water insoluble moiety is called hydrophobic lipophilic and oleophilic. A surfactant in general possesses the following characteristic properties.
It must be soluble in at least one phase of a liquid system. Its molecules are composed of groups with opposing solubility tendencies. At the interphase of a liquid system it must form oriented monolayers and its equilibrium concentration at a phase interface is greater than its concentration in the bulk of the solution. It forms micelles if the concentration of the solute exceeds a limiting value in the bulk of the solution. Solutions of surfactants exhibit detergency foaming wetting emulsifying solubilizing and dispersing properties either individually or collectively.
Classification of Emulsifiers
Emulsifiers are classified on the basis of their hydrophilic or solubilizing groups into four categories anionics non ionics cationics and amphoterics. The anionic solubilizing groups are carboxylates sulfonates sulfates and phosphates. Non ionics are solubilized by hydroxyl groups and polyoxyethylene chains. Primary Secondary and tertiary amines and quaternary ammonium groups are the cationic solubilizers. Amphoteric surfactants are solubilized by some combination of anionic and cationic moieties non ionic solubilizing groups may also be part of amphoteric molecules. In addition to the primary solubilizing groups other structural units c ntribute to the hydrophilic tendencies of molecules e.g. ester linkages and amide linkages. The hydrophobic i.e. lipophilic moieties are almost invariably hydrocarbon or halogen substituted hydrocarbon groups. Olefin linkages are less hydrophobic than carbon to carbon single bonds. Products based on silicon containing hydrophobes are just beginning to be offered in commercial quantities.
Solubility & Surface Activity of Emulsifiers
Emulsifier solute usually displays maximum surface activity and functional effectiveness when it is near the threshold of insolubility. Moreover the solubility of surfactants is markedly affected by temperature and electrolyte concentrations. Thus for each set of conditions there is usually an optimum solubility balance for each type of surfactant. Relatively small changes in the composition of a surfactant are often sufficient to change its solubility and hence its surface activity. There are many ways to effect such changes for example the average molecular weight of the raw material mixture i.e. hydrophobe can be increased slightly or the degree of sulfation sulfonation or ethoxylation can be increased or decreased. Empirical solubility tests rank with charge weights and chemical analysis as control techniques for surfactant manufacturing processes. They make it possible to produce to tight specifications by compensating for variations in successive lots of raw materials or to adjust a process to obtain a range of optimum performance conditions for essentially the same product but are pointed to different uses.
Wetting and Detergent Structures in Emulsifier
Correlations of functional properties with molecular structures have been sought by numerous investigators. One result has been the identification of strong wetting and strong detergent structures. The hydrophilic group of strong wetting agents is located at the middle of the hydrophobic chain or at the central branching point if the molecule contains two or more chains. Conversely the hydrophilic group in strong detergents is located at the end of the hydro Characteristics and Application of Emulsifiers phobic chain.
Although the wetting and detersive properties of unformulated anionic and non ionic compounds follow this structural pattern usefulness of the generalization is limited to the selection of surfactants for a few specialized applications e.g. textile wetting agents. This limitation is due to the pronounced superiority of formulated or built products over pure compounds for detergency emulsification etc. In formulations detergency and wetting strength of individual components lose much of their significance. Textile wetting efficiency is not simply related to surface tension lowering but dilute aqueous solutions of strong wetting agents characteristically have low surface tensions.
Effect of Surfactant on the Properties of Solutions
A surfactant changes the properties of a solvent in which it is dissolved to a much greater extent than would be expected from its concentration. This marked effect is due to (1) adsorption at the solution interfaces (2) orientation of the adsorbed surfactant ions of molecules (3) miscelle formation in the bulk of the solution and (4) orientation of the surfactant ions or molecules in the micelles. These effects are caused by the amphipathic structure of a surfactant molecule and the magnitude of the effects depends to a large extent on the solubility balance of the molecule. An efficient surfactant is usually relatively insoluble as individual ions in the bulk of a solution.
Wetting Characteristics of Emulsifiers
Wetting of a solid by a surfactant solution may represent either the displacement of air or some other gas from the solid surface by the solution of a liquid e.g. an oil from the solid surface. Wettability represents the tendency of a solid to be wetted and wetting power the tendency of a liquid to wet a solid. The wetting of one liquid by another immiscible liquid is visually apparent by the spreading of a film to create a large liquid liquid interface and lack of wetting is evidenced by the tendency of one liquid to form droplets in the form of a lens on the surface of the other.
The attraction between a solid or liquid to be wetted and the wetting solution determines the degree or completeness of wetting that can be attained. In practical applications the speed of wetting may be as important as the completeness of wetting at equillibrium.
Many investigators have pointed out that rate of migration of surfactant molecules from the bulk of the solution to maintain the concentration of the interface is one limiting factor on the speed of wetting. Dynamic methods for measurement of the lowering of surface free energy have been used to estimate the significance of this factor. The effectiveness of mechanical agitation thermal agitation or capillerity in bringing the solid or liquid to be wetted quickly into intimate contact with the wetting solution often influences the speed of wetting more than the migration rate of the surfactant.
Micellar Solubilization of Emulsifiers
The spontaneous dissolutions of a normally insoluble substance by a relatively dilute solution of a surfactant are called Solubilization. The substance dissolved is referred to as the solubilizate and the surfactant as the solubilizer. There are no simple quantitative relationships between solubilizing power of a surfactant and the micellar or surface properties of its solutions. Solubilization is primarily a phenomenon of importance in dilute solutions. In more concentrated solutions it is sometimes difficult to distinguish between Solubilization and cosolvency which is a term applied to a mixture of solvents that takes into solution a higher concentration of solute than would be expected from the sum of their individual Characteristics and Application of Emulsifiers solubilizing powers. Solubilization does not introduce another phase and solutions containing solubilized material are thermodynamically stable. It is a reproducible phenomenon but the rates of attainment of equilibrium differ greatly when approached from different directions.
Surfactant molecules or ions at concentrations above a minimum value characteristic of each solvent solute system associate into aggregates called micelles. The term critical micelle concentration (CMC) is used to denote the concentration at which micelles start to form in a system comprising solvents surfactants possibly other solutes and a defined physical environment. The CMC of surfactants in aqueous solutions depends on the structure of the compounds and the environment but for many anionics at low electrolyte concentrations and room temperature it is close to 10 2 mols/litre for non ionics under comparable condition it is less about 10 4 moles/litre. In many surfactants where the hydrophilic group is unchanged but the size of the hydrophobic group is increased CMC values decrease with increasing size of the hydrophobe for both ionic and nonionic types. If the hydrophobic group is held constant CMC values decrease with decreasing ethylene oxide content of non ionic. Increasing the electrolyte concentration decreases CMC values for both anionics and non ionics. The CMC of anionic micelles increases as the temperature increases whereas the CMC of non ionics decreases with the increase in temperature as would be expected from the cloud point phenomenon.
Solubilizations is a micellar phenomenon that occurs only at concentrations above the CMC. It is of considerable importance in non aqueous applications of surfactants particularly where water is the solubilizate. Typical applications are in dry cleaning solutions and engine lubricants. Essential oils vitamins cosmetic emollients and textile mill processing oils are typical solubilizates in aqueous systems. Mixtures of surfactants are generally better solubilizers than the same surfactants used individually. Ionic non ionic com binations are especially effective.
Formulated Emulsifiers
Formulated surfactant products may be roughly divided into two major groups. One group is designed to perform surfactant functions e.g. cleaning wetting foaming emulsifying and dispersing. The other group is designed to convey a non surfactant functional ingredient to the point of use e.g. a herbicide or insecticide toxicant a textile mill processing oil. In addition to primary surfactants the components of formulated surfactant products may be classified as (1) Non surfactant functional additives (2) Inert fillers and (3) Functional surfactant additives.
Non surfactant Functional Additives
The art of surfactant formulation is directed to finding a combination of components that will be compatible and perform satisfactorily at the least cost to the user. Frequently a surfactant is the most expensive component of a formulation and the mixture is designed so that less expensive inorganic additives contribute as much as possible to the functional performance of the product. Hydrotropic agents are used to solubilize the ingredients in concentrated liquid surfactant formulations. The most common hydrotropes are the sodium or potassium salts of benzene cumene toluene or xylene sulfonates. These highly soluble solutes when present at relatively high concentrations i.e. 5 15 wt percent increase the solubility of sulfonate and sulfate surfactants in concentrated aqueous compositions. Solvents are also incorporated in surfactant products to obtain homogeneous concentrates and also as functional additives. For example ethanol is used as a solvent to clarify liquid shampoos. Pine oil and/or deodorized kerosene are often functional components of industrial and consumer detergent products.
Inert Fillers
Many surfactants are viscous liquids or low melting solids that Characteristics and Application of Emulsifiers are difficult to handle as 100 per cent active materials. Sodium sulfate clays or other inexpensive fillers are added as diluents and carriers to the concentrated surfactants to obtain free flowing dry powders. Sometimes a portion of the sulfonating or sulfating reagent from the manufacturing process is neutralized and left in finished products as a filler.
Functional Surfactant Additives
Foam boosters viscosity builders and co emulsifiers are the most important functional additives to surfactant formulations. The fatty acid alkanolamides and the alkylamine oxides are the outstanding examples of products in this category. They are effective surfactants on the basis of their own properties but one of their principal uses is to enhance the foaming and detergency of less expensive materials e.g. LAS. In these applications the performance of the mixture exceeds a projection based on the sum of the contributions of the components tested individually. The alkanolamides also increase the viscosity and emolliency of aqueous solutions. The lipophilic emulsifiers are another group of functional surfactant additives. Many of these materials are so hydrophobic that they have almost no utility when used alone but in mixtures with hydrophilic emulsifiers they are exceedingly useful as co solvents solubilizers dispersants and emulsifiers.
Industrial Uses of Emulsifier
Agriculture
Emulsifiers are used in phosphate fertilizers to shorten manufacturing cycle and prevent caking during storage. In spray applications of herbicides insecticides and fungicides they are used in wetting dispersing and suspending of powdered pesticides and emulsification of pesticide solutions to promote wetting spreading and penetration of the toxicant.
Building and Construction
In paving they prevent stripping by improving the bond of asphalt to gravel and sand. Their use promote air entrainment in concrete for control of density plasticity and insulating properties etc.
Elastomers and Plastics
In emulsion polymerization they effect the emulsification of monomers by solubilization of monomers and catalyst which react in surfactant micelles. They also help in stabilization of latexes. In foamed polymers they effect the introduction of air and control of cell size. In latex adhesive they promote wetting and thus improve bond strength. In plastic articles they are used as antistatic agents and in plastic coating and laminating they are used as wetting agents.
Food and Beverages
In food processing plants they are used for cleaning and sanitizing walls floors and process equipment. They give improved removal of pesticide residues and aid in wax coating of fruits and vegetables. In bakery products and ice cream they solubilize flavor oils control consistency and retard staling. In beverages they solubilize flavor oils. In crystallization of sugar they improve washing and reduce processing time. In frying with cooking fats and oils they prevent spattering due to superheating and sudden volatilization of water.
Industrial Cleaning
In miscellaneous cleaning janitorial supplies and clothes they are used for cleaning and sanitizing walls floors windows vehicles engines etc. and as detergents for laundry and dry cleaning. In descaling they are used as wetting agents and corrosion inhibitors in acid cleaning of boiler tubes and heat exchanges. In wax strippers they are used to improve wetting and penetrations of the old finish.
Leather
In leather industry they are used as detergent and emulsifier in degreasing skins to promote wetting and penetration in tanning as emulsifiers in fat liquoring of hides to promote wetting penetration and leveling in dyeing.
Metals
In concentration of ores they are used for wetting and foaming i.e. collecting and frothing in ore flotation. In cutting and forming of metals they are used for wetting emulsification lubrication and corrosion inhibition in rolling oils drawing lubricants buffing and grinding compounds. In casting they are used as mold release additives. In rust and scale removal they are used for wetting foaming and corrosion inhibition in pickling and electrolytic cleaning. In electroplating they are used for wetting and foaming in electrolytic plating baths.
Paper
In pulp treatment they are used for derinsification pitch dispersion and washing. In paper machine they are used fordefoaming felt washing colour leveling and dispersing. In calendaring they are used for wetting and leveling in coating and colouring operations. In towels and pads they are used for wetting to improve absorption of moisture. Industrial Uses of Emulsifier
Paints and Protective Coatings
In pigment preparation they are used for flushing i.e. promote preferential wetting by the paint vehicle dispersing and wetting of the pigment during grinding. In latex paints they are used to emulsify the oil or polymer disperse the pigment stabilizes the latex retard sedimentation and pigment separation modifies wetting and rheological properties. In waxes and polishes they are used for emulsifying waxes stabilize emulsions and wet substrates in finishes for floor and automobiles. Petroleum Production and Products they are used in drilling fluids to emulsify oils disperse solids and modify rheological properties of drilling and completion fluids for oil and gas wells. In mist drilling they are used to convert intrusion water to foam in air drilling. In work over of producing wells they are used to emulsify and disperse sludge and sediment in clean out of wells modify wetting of formation at producing zone. In producing wells they are used to demulsify crude petroleum and inhibit corrosion of well tubing storage tanks and pipe lines. They are used for secondary recovery in flooding operations to release crude oil from the formation surface i.e. preferential wetting. Their application in refined petroleum products include as detergent sludge dispersant and corrosion inhibitor in fuel oils crank case oils and turbine oils.
Textiles
In the preparation of fibres and filaments they are used as detergent and emulsifier in raw wool scouring dispersant in viscose rayon spin baths lubricant and antistat in spinning of hydrophobic filaments. In gray goods preparation they are used for wetting and detergency in slashing and sizing formulations wetting and detergency in kier boiling and bleaching of cotton and carbonizing of wool detergency in scouring piece goods emulsification of processing oils. In dyeing and printing they are used for wetting penetration solubilization emulsification dye leveling detergency and dispersion. In finishing of textiles they are used for wetting and emulsification in finishing formulations softening lubricating and antistatic additives to finishes.
Biodegradable Emulsifiers and Water Pollution
The Heavy duty household laundry detergents have been in use in largest amounts all over the world as the major products of the surfactant industry for the last forty five years. The key ingredient that made this growth possible was ABS an inexpensive alkylbenzene sulfonate in which the alkyl group was a highly branched propylene tetramer. Its continued discharge in rivers and lakes results in formation of excessive foams in rivers and lakes causing pollution of water. This fact became apparent for the first time in United States in 1950. Researches carried out later soon revealed that some types of synthetic detergents were more resistant than soap to degradation in sewage treatment plants and attempts were made in 1963 in U.S. to replace ABS the largest volume synthetic surfactant by LAS (Linear Alkylbenzene Sulphonate) a more biodegradable surfactant in a move to facilitate the degradation of detergent products in sewage plants.
Research soon established that degradation of surfactants by the bacteria in sewage disposal plants is slower and less complete if the hydrophobic chain is branched rather than linear. In the early 1950 s no economically feasible technology was known for replacing ABS by a biodegradable substitute. The logical approach to the problem was replacement of the propylene tetramer by an equally inexpensive linear 12 carbon alkylation feedstock from a petrochemical source. However technological breakthroughs in the early 1960 s opened up several possible routes to biodegradable alkylbenzene sulfonates.
(1) Separation of n paraffins from kerosene feedstocks in molecular sieves (or alternatively by complexing with urea). Alkylation with the n paraffins involves only conventional processing i.e. monochlorination followed by a Friedel Crafts reaction or dehydro Industrial Uses of Emulsifier halogenation and alkylation.
(2) Synthesis of linear 1 olefin or alcoholic detergent hydrophobes from ethylene is carried out by the Ziegler process using an aluminium catalyst. The trialkyl aluminium intermediate in this process can be oxidized to yield linear secondary alcohol suitable for detergent bases or catalytically decomposed to yield 1 olefins that can be used as alkylate feedstocks or hydrated to alcoholic hydrophobes.
(3) The 1 olefins obtained by cracking of petroleum waxes can also be used either as alkylation feedstocks or hydrated to alcoholic detergent bases.
Biodegradation
Microorganisms have an inherent ability to convert organic matter including surfactants into new cell material food and energy. The predominant mechanisms by which surfactant hydrophobes are attacked have been described as b oxidation methyl oxidation and aromatic oxidation. In b oxidation the most important process a linear hydrocarbon chain is oxidized at two carbons at a time a branch in the chain interrupts the degradation. Methyl oxidation which is less well understood attacks terminal methyl groups. Aromatic oxidation proceeds through cat echol (1 2 benzenediol) as an intermediate which is cleaved to form an aliphatic dicarboxylic acid. The poly oxyethylene chains of non ionics are probably degraded stepwise through a carboxylation and hydrolysis mechanism that splits glycol units from the chain. From a practical viewpoint secondary and tertiary carbons in aliphatic chains and some phenolic nuclei slow the biodegradation process to rates that are unacceptable in present day sewage treatment systems. Very large polyoxyethylene chains are also degraded slowly. In terms of products carboxylic acids and salts linear alcohol sulphates sulfated fatty acids sulfated fatty amides sulfated esters glycol esters glycerol esters and fatty alkanolamides are most readily biodegradable. The ethoxylated and sulfated linear alcohols linear alkylbenzene sulphonates and ethoxylated linear alcohols (upto about 70 wt per cent of polyoxyethylene) are readily biodegradable. The residual polyoxyethylene chains from high polyethene content non ionics are not surface active and are not a problem in sewage systems at this time. Ethoxylated linear alkylphenols are more slowly biodegradable than aliphatic based non ionics. There is still some question about the acceptability of these products for all uses. Unacceptable products on the basis of biodegradability are the branched chain substituted alkylphenol derivatives branched chain substituted alkylbenzene sulfonates and the derivatives of branched chain aliphatic alcohols i.e. sulfates or sulfated ethyoxylates.
Development of methods to measure biodegradability of surfactants paralleled the development of biodegradable materials. Three methods out of the many screened have received widespread acceptance. Two of these the river die away method and shake flask methods. Biodegradation Test Methods are suitable for quick screening and/or routine use. The third a semi continuous activated sludge method is more time consuming but is accurate and reproducible enough to serve as a reference method The determination of biological oxygen demand also provides useful data on biodegradation processes.
Anionic Surfactants
Introduction
The hydrophilic moiety in anionic surfactants is a polar group that is negatively charged in aqueous solutions or dispersions. In commercial products it is either a carboxylate sulphonate sulfate or phosphate group. In dilute alkaline solutions in soft water the solubilizing power of the sodium salts of the four anionic radicals is approximately equal and strong enough to balance the hydrophobic tendency of a 12 carbon saturated hydrocarbon group the sulfate is actually a somewhat stronger solubilizer than the sulphonate. In neutral or acidic media or in the presence of heavy metal ions the solubilizing power of the carboxylate is markedly less than that of the other groups.
The ionic environment associated with anionic surfactants influences the properties of their solutions. Sodium and potassium salts are generally more soluble in water and less soluble in hydrocarbons. Conversely the calcium barium and magnesium salts are more compatible with hydrocarbon solvents and less so with water. Ammonium and amine salts e.g. triethanolamine improve the compatibility of anionics with water and hydrocarbons and are widely used in emulsification and detergent applications. Higher total ionic strengths are usually associated with lower solubilities of anionic surfactants. To offset this effect the molecular weight of the hydrophobe is lower in products designed for use at high electrolyte concentrations. Micellar solubilization by anionics is markedly affected by total ionic strength and also by the identity of the associated cations. The anionic surfactants can be divided into four groups according to their anionic groups (1) Carboxylates (2) Sulfonates (3) Sulfates and Sulfated Products (4) Phosphate Esters.
Carboxylates
Soaps and a small volume of aminocarboxylates are the only Anionic Surfactants commercial products in the carboxylate class of surfactants. Two types of aminocarboxylate surfactants N acy lsarcosinates and acylated protein hydrolysates are produced in small quantities as specialties.
Both series of products are fatty acyl derivatives of aminocraboxylates. As compared to the corresponding soaps the hydrophilic tendency of the amide linkages in these molecules is strong enough to significantly lessen inactivation of the carboxylate ions by the calcium and magnesium ions that are present in hard water.
Soap
For many years soap was the only surfactant produced commercially. Inspite of the development of many new surfactant types it may be noted that soap possesses some desirable properties which are not found in many other surfactants. The sodium and potassium cocofatty acid soaps are unexcelled as lathering and cleansing agents in bar detergents for personal use in soft to medium hard water. The C14 to C18 fatty acid sodium soaps are effective laundry and industrial detergents in soft to medium hard hot water. Soaps especially amine salts are excellent emulsifiers dispersants and solubilizing agents with a wide range of industrial uses. Soaps have an emollient action in contact with the skin and leave a soft feel on textile fabrics.
N Acylsarcosinates
Sodium N lauroylsarcosinate and the sodium N acylsarcosinate derived from coconut fatty acids are soap like detergents with good lathering properties. They are principally used in dentifrices where it is claimed they also inactivate the enzymes that convert glucose to lactic acid in the mouth. N Oleoy1 sarcosinate is used as a textile auxiliary and detergent. The N acylsarcosinates are prepared by the condensation of a fatty acid chloride with sarcosine (i.e. N methylglycine obtained from the reaction of methylamine formal dehyde and sodium cyanide) in alkaline aqueous solution.
Acylated Protein Hydrolysates
Fatty acyl aminocarboxylates are prepared from protein hydrolysates by acylation with fatty acid chlorides or by direct condensation with fatty acids. The commercial products are mixtures that vary in composition from acyl derivatives of polypeptides from incompletely hydrolyzed protein to mixtures of acylated amino acids derived from completely hydrolyzed protein. Collagen from leather scraps and low grade hide glues is used as a source of protein. Derivatives of the incompletely hydrolyzed peptides have a great tolerance for hard water but their effective ness as surfactants is lower.
Sulfonates
The most effective structure for an anionic surfactant is a sulfonate of the general formula RSO3Na where R is a biodegradable hydrocarbon group in the surfactant molecular weight range. The R group can be alkyl or alkylarylene and the product can be a random mixture of isomers as long as it does not contain chain branching that interferes with biodegradability. The surface activity of the SO3 group is not oversensitive to variations in the pH or to heavy metal ions and the C S linkage is not susceptible to hydrolysis or oxidation under normal conditions of use.
Sulfonation processes on surfactant raw materials can usually be adjusted to increase or decrease slightly the degree of substitution of the solubilizing group on the hydrophobe. The average molecular weight of the hydrophobic bases can also be increased or decreased slightly. Minor adjustments in these two variables produce significant differences in performance. Sulfonates are usually obtained in the production process as free acids that can be neutralized to form alkali metal salts alkaline earth metal salts or amine salts thus neutralization is another parameter for modification of properties. Manipulation of these variables leads to products with a multiplicity of combinations of properties from the same raw materials and production equipment.
The surfactants of commercial importance in this group are alkylbenzene sulfonates petroleum sulfonates di alkyl sulfosuccinates naphthalene sulfonates N acyl N alkyltaurates 2 sulfo ethyl esters of fatty acids and olefin sulfonates.
Alkylbenzene Sulfonates
Linear dodecylbenzene sulfonates rank next to soaps in total usage. The sodium salt of linear dodecylbenzene sulfonate is commonly referred to as LAS . Linear dodecylbenzene sulfonic acid is called LAS acid and salts other than sodium are named in an analogous manner e.g. LAS salt. Commercial dodecylbenzene sulfonic acid is a light coloured viscous liquid that is used almost entirely as an intermediate for the manufacture of alkalimetal alkaline earth metal and amine salts.
In comparisons of the performance of alkylbenzene sulfonates to that of aliphatic sulfonates the effect of the benzene ring is often considered as approximately equivalent to three carbon atoms in an aliphatic chain.
Alkylbenzene sulfonic acids are strong organic acids and form essentially neutral alkalimetal salts that have a good solubility in aqueous solutions at use concentrations over the entire pH range.
These acids are not sensitive to precipitation by the natural hardness of the surface waters but the alkaline earth metal salts are less water soluble than the alkali metal and amine salts. The calcium salts are sufficiently soluble in hydrocarbons for use in these media. The alkylbenzene sulfonates are one of the most chemically stable types of surfactants. The sulfonic group is not susceptible to acidic or ammonium alkaline hydrolysis under normal conditions of storage or use. The compounds are stable to strong oxidising agents is aqueous solutions at use concentrations and are stable in carefully formulated products containing oxidizing agents.
The surface activity of unformulated unbuilt dodecyl benzene sulfonates is sufficiently strong for the salts to be useful for their detersive wetting emulsifying dispersing and foaming properties but they are not outstanding surfactants. The widespread usage of LAS stems from other factors which include their low cost reproducible quality adequate supply light colour low odour and excellent response to formulation and builders. For example LAS solutions are only average foamers but mixtures of LAS with alkanolamine or alkylamine oxide foam boasters have excellent foaming properties. Similarly LAS performs well in built heavy duty cleaning products where the wetting foaming emulsifying and dispersing properties of the surfactant component are as important as the detergency power. Amine salts of LAS & ABS acids are used in blends with other emulsifiers particularly the non ionic types in emulsifiable concentrates of pesticides.
Petroleum Sulfonates
The petroleum sulfonates are the only large volume class of surfactants that are used predominantly in non aqueous systems. They are available as co products of the refining of certain petroleum fractions. They are usually grouped into two broad classes water soluble types called green soaps and oil soluble types called mahogany soaps (which may also be soluble in water).
The green soaps are of little use. The mahogany soaps are valuable for their properties of solubilization detergency dispersion emulsification and corrosion inhibition. Their principal use is in lubricating oils for sludge dispersion detergency micellar solubilization of water and corrosion inhibition. They are also widely used in other products for corrosion inhibition and emulsification. Alkylaromatic hydrocarbon sulfonates are the surfactant components in both product types. The green soaps contain a higher proportion of disulfonates than the mahogany sulfonates which are principally monosul fonates.
Dialkyl Sulfosuccinates
Sodium di (2 ethyl hexyl) sulfosuccinate is the largest volume product of this group. It is now a widely used specialty surfactant.These sulfosuccinates as sodium salts are available as white waxy odourless solids or as concentrated colourless solutions. The di C8 esters have the optimum solubility balance for use in tap water or aqueous solution with low inorganic salt content lower alkyl esters are more effective in saline solutions. Sodium dialkyl sulfosuccinates are highly surface active but the susceptibility of the ester linkage to acidic or alkaline hydrolysis limits their usefulness. The products have strong wetting rewetting penetration and solubilization properties. The symmetrical diesters are produced by esterification of maleic anhydride using conventional technology followed by addition of sodium bisulfite across the olefin linkage.
Naphthalene Sulfonates
Four series of specialty surfactants make up the widely used but relatively low volume group naphthalene sulfonate products viz. salts of alkylnaph thalene sulfonates salts of sulfonated formaldehyde naphthalene condensates salts of naphthalene sulfonates and salts of tetrahydronaphalene sulfonates.
In the concentrated dry form most of the salts are almost odourless light grey solids. They are readily and highly soluble in water. In fact except for the nonyl derivatives the naphthalene sulfonates are generally too soluble to be strongly surface active in soft water. The naphthalene sulfonates are stable to hydrolysis in acidic or alkaline media and are not sensitive to oxidation by strong oxidizing agents under use conditions.
The naphthalene sulfonates are used in many different applications as wetting and dispersing agents. Several members of the series are effective as stabilizing and suspending agents in disperse systems. Some of the products are useful for their solubilizing properties. Hard water does not adversely affect the surface activity of typical members of the series.
N acyl N alkyl taurates
The taurates are technically interesting as the only class of anionic surfactants with the combination of many advantages. They are stable against hydrolysis by acidic or alkaline media at use concentrations. They show no loss of performance in hard water. They have soap like biodegradability and residual feel on washed fabrics and they have a molecular structure capable of yielding either strong wetting or strong detergent configurations. For example the products RCON (R`) CH2CH2SO3Na are strong detergents when R = C11 C17 and R` = CH3 or C2H5 but are strong wetters when R = R` = C6 9. Relatively high raw material costs have held usage of the presently available N acyl N alkyl taurates in the specialty category and have precluded the introduction of additional products with markedly different properties.
The commercial product N Oleoyl N methyltaurate is marketed as a light yellow solid at about 70 per cent assay or at lower concentrations in water as a light coloured slurry solution or gel. It is principally used in detergent applications with out builders. Foaming of the N methyl derivatives is only moderate and is not readily improved by the usual foam builders the N cyclohexyl derivatives are low foaming detergents with good wetting power.
The production of sodium N oleoyl N methyltaurate involves three chemical steps and yields average 95 percent or higher in each step.
2 Sulfoethyl Esters of Fatty Acids
These products known commercially as b sulfoesters resemble closely in properties the fatty acids from which they are derived but they have the advantage that hard water does not impair their performance. Only the sensitivity of the ester linkage to hydrolysis has prevented their widespread usage in consumer detergents. Hydrolysis is not a problem with detergents for personal use and the sodium salt of the 2 sulfoethyl ester of lauric acid or similar coconut acid mixture has found acceptance as the foaming and cleansing ingredient in synthetic detergent bars. The oleic acid analog is less foaming but is a good detergent with specialty uses in neutral or mildly alkaline systems.
The esters can be produced commercially from isethionate (obtained by the reaction of ethylene oxide with a concentrated solution of sodium bisulfite) and the fatty acid or acyl chloride. The reaction between the acyl chloride which is a viscous liquid and the powdered anhydrous sodium isethionate is carried out in the absence of water or solvent under vacuum in a heavy duty mixer. After the total charge is added to the reactor and brought to temperature HCL is rapidly evolved leaving the finally divided light coloured product as the sodium salt.
Olefin Sulphonates
The increasing availability of relatively low cost linear 1 olefins in the C14 to C18 range has spurred research and commercial development of their sulfonate derivatives.
The 3 and 4 hydroxysulfonates which may amount to as much as half of the yield of sulfonated products are not very water soluble but they are solubilized in the presence of the more soluble olefin sulfonate. The sulfonation mixture which is referred to as a olefin sulfonate or AOS has detergency and foaming properties similar to C11 14 LAS. It is superior in performance to similar products made from internal straight chain olefins. Biodegradability of the AOS is slightly better than LAS toxicity and skin irritation are slightly less.
Sulfates & Sulfated Products
The hydrophilic group in the surfactants falling in this group is SO3 attached through an oxygen atom to a carbon atom in the hydrophobic moiety. The additional oxygen makes the sulfate a stronger solubilizing group than the sulfonate but the C O S linkage of the sulfates is more easily hydrolyzed than the C S linkage of the sulfonates. This susceptibility to hydrolysis especially in acidic media limits the utility of the sulfates. Solubilization of hydrophobes through the combination of ethoxylation and sulfation is frequently used to obtain the optimum solubility balance and also to utilize less expensive raw materials that cannot be solubilized sufficiently by sulfation alone e.g. derived from tallow alcohols. The shift of the detergent industry to more biodegradable products has started a trend away from ethoxylated and sulfated alkyl phenols and towards ethoxylated and sulfated aliphatic alcohols. The principal sub groups of this class of surfactants are discussed below.
Alkyl Sulfates (Sulfated Alcohols)
The hydrophobes of this class of surfactants are obtained by reduction of fatty acids or esters of C12 to C20 hydrocarbon groups.
Secondary olefins sulfates are prepared by the addition of sulfuric acid to an olefin. These products have been marketed under the Teepol trademark of shell Oil Company. Sulfates obtained from the normal primary alcohols are similar in performance properties and in feel or emollient characteristics to the soaps of corresponding molecular weight. The branched chain alkyl sulfates are strong wetters. As the carbon chain length increases the temperature needed to attain maximum detergent and wetting effects also increases. The stability of alkyl sulfates to hard water is excellent. In fact magnesium lauryl sulfate forms voluminous foams with a low water content that is useful in rug shampoos where the soil is removed by vacuum pick up of the foam that is generated by vigorous brushing with a minimum volume of detergent solution. Sensitivity to hydrolysis in hot alkaline or acidic media is one of the principal disadvantages of the alkyl sulfates. Alkyl sulfates are high foaming detergents and strong wetters as well as effective emulsifiers and dispersants. Some of the products are used as leathering and cleansing agents in shampoos and dentifrices. Others are detergent and wetting agents for textile processing. Another use of the alkyl sulfates is as emulsifiers and dispersents in emulsion polymerization.
Lauryl sulfates can be prepared as the ammonium sodium potassium magnesium diethanolamine and triethanolamine salts which is indicative of the marked influence of the cations on the performance properties of this series of anionic surfactants.
Sulfated Natural Fats and Oils
The sulfated surfactants from natural fats and oils are obtained by the reaction of sulfuric acid which either CH = CH or OH groups in natural fats and oils. The sulfate half esters so obtained are neutralized with caustic soda in a later step.
Olive oil was the first oil to be sulfated to obtain a commercial surfactant other than soap. Later on almost every potentially available animal vegetable and fish oil was tried and it was found that ricinoleic acid which contains one hydroxyl group and one double bond is a desirable constituent of an oil for sulfation. Oleic acid is also satisfactory. Esters of these acids can usually be sulfated with a minimum of hydrolysis. Polyunsaturated fatty acid moieties are undesirable components of glycerides for sulfation since the resulting surfactants are usually dark in colour and sensitive to oxidation.
NON IONIC Surfactants
Introduction
A non ionic surfactant as the name implies bears essentially no charge when dissolved or dispersed in aqueous media. The hydrophilic tendency in a non ionic is due primarily to oxygen in the molecule which hydrates by hydrogen bonding to water molecules. The strongest hydrophilic moieties in non ionics are ether linkages and hydroxyl groups but ester and amide linkages which are also hydrophilic are present in many non ionics. The contribution of each oxygen to solubilization is weak and non ionic molecules must contain a multiplicity of them in order to be water soluble. Nearly all of the unmodified polyol surfactants are lipophilic and they are frequently used as coemulsifiers in combinations with more hydrophilic surfactants. One advantage of the non ionics is that they are compatible with ionic and amphoteric surfactants. Polyoxyethylene solubilization is the key to the substantial and continuing growth of the non ionics. Since the polyoxyethylene group can be introduced into almost any organic compound that has reactive hydrogen a wide range of organic substances can be solubilized by ethoxylation. Sub division of the non ionics into classes in accordance with the composition of the solubilizing groups is not as straight forward as with the ionic surfactants.
Polyoxyethylene Surfactants
The polyoxyethylene solubilized non ionics are mainly used as textile auxiliaries. The solubility of these products depends on recurring ether linkages in a polyoxyethylene chain. A solubilized molecule contains many such chains and its hydrophilic tendency increases with the polyoxyethylene content of the molecule and 60 70 per cent by weight is required on most surfactant hydrophobes for complete miscibility with water at room temperature. A rule of thumb is that the hydrophilic strength of one ethylene oxide unit is approximately equal to the hydrophobic strength of one methylene unit. The water solubility of polyoxyethylene compounds decreases as the temperature increases which is attributed to a decrease in the degree of hydration or to an increase in the size of the micelles. The temperature at which a second phase appears is called the cloud point a practical solubility test that is not sensitive to concentration differences in the range between 0.5 to 10 per cent by weight. A minor proportion of anionic mixed with a non ionic will often raise the cloud point to several degrees. Surface activity and performance efficiency of polyoxyethylene non ionics is not adversely affected by hard water. High electrolyte concentrations in which sodium ions are the predominant component decrease the solubility of polyoxyethylene compounds by a salting out effect whereas hydrochloric acid and calcium ions increase their solubility. Non ionic surfactants solubilize iodine in aqueous solutions and lessen its toxicity to humans but do not weaken its biocidal activity to the lower forms of life. The polyoxyethylene surfactants are moderate foamers and do not respond to the conventional foam boosters. They exhibit a foam maximum as a function of polyoxyethylene content. Low foaming non ionics are prepared by terminating the polyoxyethylene chain with a less soluble group e.g. polypropylene oxide. A significant advantage of solubilization by means of polyoxyethylene is the capacity of attaining almost any hydrophilic/hydrophobic balance. A shortcoming is that the polyoxyethylene non ionics tends to be liquids or low melting waxes that are difficult to incorporate into dry free flowing powders. Flaked solid products containing a high ratio of polyoxyethylene are manufactured but their surface activity is low because they are too hydrophilic.
The conversion of an aliphatic alcohol alkyl phenol or fatty acid into a polyoxyethylene derivative can be divided into two steps addition of ethylene oxide to the hydrophobe to form a monoadduct and subsequent additions of ethylene oxide in a polymerization reaction. Ethoxylations of these hydrophobes are catalyzed by bases. Ethoxylation is normally carried out as a batch re action although continuous reactors have been designed and operated. The hydrophobe and a solution of catalyst are charged into a reactor. Air and solvent for the catalyst are removed by agitating and heating under a vacuum or purging with nitrogen or both. When the hydropbobe is at the reaction temperature addition of ethylene oxide is started. The polymerization is exothermic (20 kcal/mole of ethylene oxide reacted) and the rate of ethylene oxide addition should not exceed the cooling capacity of the reactor since careful maintenance of the reaction temperature is essential for reproducible manufacture of products to specifications. The end point of ethylene oxide addition is often determined by testing the solubility of a sample for its cloud point in water a salt solution or a water solvent mixture. After the reaction is complete the catalyst is neutralized and the product is discharged to storage or packaged. Polyoxyethylene solubilized non ionics are poly disperse mixtures of compounds that differ principally in the distribution of the polymer chain lengths. Their properties usually approximate those of the pure isomer represented by their average composition.
Ethoxylated Alkyl Phenols
Undiluted polyoxyethylated C8 to C12 alkyl phenols have a slight aromatic odour and vary from pale yellow to almost colourless. Products with low polyoxyethylene content are liquids and their viscosity increases with the content of combined ethylene oxide. High ratios of polyoxyethylene to hydrophobe are waxes. The specific gravity at room temperature increases with polyoxyethylene content from less than 1 to 1.2 Physical properties of the polyoxyethylated higher alkyl phenols e.g. dinonylphenol and hexadecylphenol are similar to those of the C8 to C12 derivatives with the same wt. percentage of combined ethylene oxide.
The solubility in water of the ethoxylated alkyl phenols increases with the polyoxyethylene content. About 60 per cent by weight of polyoxyethylene is required for complete miscibility in cold water and at above 75 per cent of polyoxyethylene the products do not cloud out at the boiling point. Water hardness does not adversely affect the surface activity of the products. The solubility of polyoxyethylene alkyl phenols in highly aliphatic mineral oils decreases faster with increasing polyoxyethylene content than the corresponding increase in solubility in water. Solubility in aromatic solvents and unsaturated triglycerides persists at higher mole ratios of combined ethylene oxide to hydrophobe. The excellent stability of the polyoxyethylene alkyl phenols against decomposition is demonstrated by their uses in formulations for acid cleaning of metals in hot alkaline detergent systems and in oil well drilling fluids for use at high bottom hole temperatures.
The maximum surface activity of the unformulated polyoxyethylene alkyl phenols in water hardness of 0 300 ppm is associated with polyoxyethylene proportions in the range of 50 75. per cent by wt. The optimum composition varies somewhat within this range depending upon the property. Typical commercial products of polyoxyethylene alkyl phenols include nonyl octyl and doceyl phenoxy polyethylene oxy ethanols. Uses of polyxyethylene alkyl phenols as a function of polyoxyethylene content can be summarized as follows
Alkyl phenols containing 20 40 per cent polyoxyethylene are used as defbamers in surfactant solutions detergent and/or dispersing agents in petroleum oils coemulsifiers intermediates for sulfation.
Alkyl phenols containing 40 60 percent polyoxyethylene are used for oil soluble detergents dispersants and emulsifiers emulsifiers in emulsifiable concentrates of insecticides and herbicides intermediates for sulfation.
Alkyl phenols containing 60 70 per cent polyoxyethylene are used for textile detergents and processing auxiliaries pitch control in manufacture of paper pulp rewetting agents in paper towels processing assistants in leather manufacture detergents in industrial and consumer cleaning products wetting agents in acid and alkaline cleaners emulsifiers in emulsifiable concentrates of insecticides and herbicides.
Alkyl phenols containing 70 80 per cent poly oxyethylene are used for detergents and wetters at high temperature and/or electrolyte concentrations emulsifiers for fats oils and waxes stabilizers for synthetic latexes wetting and penetrating agents in caustic solutions.
Alkyl phenols containing 80 95 per cent poly oxyethylene are used as stabilizers synthetic latexes emulsifiers for vinyl acetate and acrylate emulsion polymerization dyeing and leveling assistants lime soap dispersants.
Commercial ethoxylations of Alkyl phenols are always alkali catalyzed but the reaction conditions catalyst and catalyst concentration are chosen to obtain optimum properties for the intended use. All of the Alkyl phenol combines with one molecule of ethylene oxide to form the monoadduct before the build up of linear polyoxyethylene chains start but by relatively minor variations in reaction conditions it is possible to obtain either a broad or narrow distribution of isomers at the same percentage content of polyoxyethylene. These differences are reflected in the properties of the products particularly the solubilities. Another variant at constant gross composition is the percentage of polyglycol in the product i.e. ethylene oxide polymer not combined with the Alkyl phenol.
Ethoxylated Aliphatic Alcohols
The ethoxylated aliphatic alcohols are costlier than the ethoxylated Alkyl phenols but due to recent change over to biodegradable products in the ensuing reformulation of industrial and consumer products a shift in non ionic types appears to be taking place with polyoxyethylene alcohols instead of polyoxyethylene linear Alkyl phenols replacing the branched chain Alkyl phenol derivatives in a significant fraction of the newer formulations. In the products of commerce which include oleyl cetyl stearyl lauryl tridecyl myristyl and tallow polyethylene oxy ethanols the hydrophobes are generally mixtures of straight chain alcohols in the range from C12 to C18 and contain combined ethylene oxide in more ratios varying from 1 to 50 to hydrophobe. The undiluted products vary in physical form from liquids to many solids viscosity in each homologous series increases as the polyoxyethylene content increases. The products have a slight odour characteristic of the hydrophobe that decreases as the polyethelene content increases. The liquids vary from pale yellow to almost colourless and the solids from yellow to white waxes the products become lighter coloured as the polyoxyethylene content increases. Within each homologous series the specific gravity at room temperature increases with the polyoxyethylene content from slightly less than 1 until it levels off a little under 1.2. Solubility of the alkylpoly (ethyleneoxy) ethanols in water increases with the ethylene oxide content about 65 70 vol percent of polyethylene is required for complete miscibility at room temperature. The solubility of the polyoxyethylene derivatives of straight chain alcohols in aliphatic solvents is slightly greater than for the Alkyl phenols of comparable polyoxyethylene content. The water hardness does not impair the surface activity of the alkylpoly (ethyleneoxy) ethanols.
The functional properties and uses of the polyoxyethylene alcohols parallel very closely those of the polyoxyethylene Alkyl phenols. The usage of alkylpoly (ethyleneoxy) ethanols is divided more evenly among the available hydrophobes than with Alkyl phenols. This makes available a wider range of solubilities in water insoluble liquids and contributes to the widespread use of the products as special purpose emulsifiers. The Alkyl polyethyleneoxy ethanols have certain uses such as textile fibre lubrication that are due to properties of the hydrophobe and for which the comparable polyoxyethylene Alkyl phenols are not applicable.
Ethoxylation processes and equipment for manufacture of the alkylpoly (ethyleneoxy) ethanols are similar to those described for the Alkyl phenols. However the rate of reaction of primary alcohols with ethylene oxide is much faster than it is with Alkyl phenols it is much closer to the rate at which the polyoxyethylene chains grows. Thus the build up of polyoxyethylene polymer chain starts before all of the hydrophobe has reacted with one unit of ethylene oxide. The reactivity of alcohols with ethylene oxide varies in the order primary > secondary > tertiary. It is difficult to prepare polyoxyethylene derivatives of tertiary alcohols by direct reaction of the alcohol with ethylene oxide.
Carboxylic Esters
The carboxylic esters may be polyolsolubilized or poly oxyethylene solubilized or both for surfactant use. They are based on several different types of hydrophobes and accordingly they are classified as glycerol esters polyethylene glycol esters anhydrosorbitol esters ethoxylated nhydrosorbitol esters ethylene a and diethylene glycol esters propanediol esters ethoxylated natural fats and oils carboxylic acid esters silicone compounds etc.
Glycerol Esters
These are partial fatty acid esters either mono or diglycerides of fatty acids. The products of commerce are almost invariably mixtures of mono and diglycerides that also differ in respect to the positions of the hydroxyl group that are esterified. Typical products in the series include the mono and diglycerides of stearic lauric oleic and ricinoleic acids and coconut tallow lard cottonseed and safflower oils.
Mono and di glycerol esters of the saturated fatty acids are light coloured solids with melting points between 25 and 85°C. The 1 monoglycerides have higher melting points than the corresponding 2 monoglycerides. The glycerides of the unsaturated fatty acids are liquids at room temperature. The partial glycerol fatty esters have the characteristic odour of the fats from which they are derived. The polyol group of a monoglyceride is not strong enough as a hydrophilic moiety to carry even an easily solubilized acid like oleic into aqueous solution. Despite their lack of water solubility the partial glycerol esters have commercially important and technically interesting surfactant uses.
The uses of mono and diglycerides centre around applications involving emulsification dispersion suspension solubilization and lubrication. One important use is as additives to foods and pharmaceuticals. Products intended for ingestion are prepared from edible fats. Mono and di glycerides are widely used in bread cakes and other bakery products for their emulsifying dispersing and lubricating properties. They are also used in candies ice creams yeasts butter whipped tappings and icings. Flavour oils for carbonated beverages as well as bakery products are emulsified or solubilized by surfactant mixtures that include blends of mono and diglycerides. Glycerol mono stearate is used as an emulsifier and opacifier in cosmetic formulations. The partial glycerol esters are used as compounds of textile mill processing and in lubricants and softener formulations. The products also find application as emulsifiers lubricants and corrosion inhibitors in cutting drawing and finishing of metal products. In the manufacture of paints and polymers the mono and diglycerides are used as emulsifiers dispersants suspending agents and grinding oils.
Alcoholysis of fats with glycerol is the most important industrial method for the preparation of the partial fatty acid esters of glycerol. In this reaction the fatty acid groups are redistributed between the original combined glycerol and the added glycerol without weight loss by heating at 180 250°C in the presence of an alkaline catalyst.
Polyethylene Glycol Esters
The polyoxy ethylene esters of fatty acids and of aliphatic carboxylic acids related to abietic acid comprise the polyethylene glycol series of surfactants. Properties and uses of these two groups of products differ markedly. Commercial polyoxyethylene fatty acid esters are mixtures that contain varying proportions of mono esters di esters and polyglycol. The composition of the mixture can be forced toward the mono or di ester by the ratio of reactants and process of manufacture. The polyoxyethylene esters of fatty acids range in consistency from free flowing liquids to slurries to firm waxes.
Within a homologous series the products change from liquids to waxes as the polyethylene content increases. Only low mole ratios of polyoxyethylene to unsaturated fatty acids or lower molecular weight acids yield liquid products. The odour of the products is characteristic of the fatty acid hydrophobe and decreases as the polyoxyethylene content increases. Odour and odour stability are important characteristics of these products because of their use in textile finishing. Colour stability is also important for the same reason. The oleates for example have good softening and lubricating properties but are precluded from some uses because of yellowing on exposure to air and heat.
The ester linkage is slightly hydrophilic and only about 60 wt. per cent of polyoxyethylene is required to solubilize the saturated fatty acids in water at room temperature. The surface activity of the fatty acid polyglycol esters e.g. wetting and surface tension lowering is in the useful range but less than for ethoxylated Alkyl phenols or aliphatic alcohols. The products are low foamers in aqueous solutions which is advantageous for certain uses. Emulsification is a key property of this series of compounds and its importance is reflected in the wide range of lipophilic solubilities that are available in commercial products. Susceptibility to hydrolysis in hot acidic or alkaline solutions is their principal limitation. The fatty acid that is formed by acidic hydrolysis either separates as oil or forms an insoluble precipitate with the heavy metal ions in hard water.
The Polyoxyethylene fatty acids are used extensively in the textile industry as emulsifiers for processing oils antistatic agents softeners fibre lubricants and detergents for neutral scouring operations. The products are also used as emulsifiers in cosmetic preparations pesticide formulations etc.
Two methods are used commercially for manufacture of the polyoxyethylene acids. One is the alkali catalyst reaction of a fatty acid with ethylene oxide. The other is esterification of a fatty acid with a preformed polyethylene glycol in the presence of an acid catalyst. Some manufacturers claim that the properties are different for products of the same gross composition as prepared by the two methods. However the ethoxylation catalysts also catalyze trans esterification and the products of direct ethoxylation approach closely those obtained by esterification if the manufacturing process is directed to this end. Deodourization and decolorization treatments are commonly incorporated in manufacturing processes.
The polyoxyethylene derivatives of the rosin acids are generally similar to the corresponding polyoxyethylene fatty acids in surfactant properties and processes of manufacture except that they are stable towards hydrolysis. The chemical stability of the polyoxyethylene tallates together with their characteristic low foam generation at use concentrations makes themuseful as components of consumer deter include the mono and diglycerides of stearic lauric oleic and ricinoleic acids and coconut tallow lard cottonseed and safflower oils.
Mono and di glycerol esters of the saturated fatty acids are light coloured solids with melting points between 25 and 85°C. The 1 monoglycerides have higher melting points than the corresponding 2 monoglycerides. The glycerides of the unsaturated fatty acids are liquids at room temperature. The partial glycerol fatty esters have the characteristic odour of the fats from which they are derived. The polyol group of a monoglyceride is not strong enough as a hydrophilic moiety to carry even an easily solubilized acid like oleic into aqueous solution. Despite their lack of water solubility the partial glycerol esters have commercially important and technically interesting surfactant uses. The uses of mono and diglycerides centre around applications involving emulsification dispersion suspension solubilization and lubrication. One important use is as additives to foods and pharmaceuticals. Products intended for ingestion are prepared from edible fats. Mono and di glycerides are widely used in bread cakes and other bakery products for their emulsifying dispersing and lubricating properties. They are also used in candies ice creams yeasts butter whipped tapings and icings. Flavour oils for carbonated beverages as well as bakery products are emulsified or solubilized by surfactant mixtures that include blends of mono and diglycerides. Glycerol mono stearate is used as an emulsifier and opacifier in cosmetic formulations. The partial glycerol esters are used as compounds of textile mill processing and in lubricants and softener formulations. The products also find application as emulsifiers lubricants and corrosion inhibitors in cutting drawing and finishing of metal products. In the manufacture of paints and polymers the mono and diglycerides are used as emulsifiers dispersants suspending agents and grinding oils.
Alcoholysis of fats with glycerol is the most important industrial method for the preparation of the partial fatty acid esters of glycerol. In this reaction the fatty acid groups are redistributed between the original combined glycerol and the added glycerol without weight loss by heating at 180 250°C in the presence of an alkaline catalyst.
Anhydrosorbitol Esters
Fatty acid esters of anhydrosorbitol are the second largest class of polyol solubilized surfactants. The important commercial products in the group are mono di or triesters of sorbitan and fatty acids. Sorbitan is a mixture of anhydrosorbitols with the principal isomers being 1 4 sorbitan and isosorbide.
The sorbitan oleates and the monolaurate are pale yellow liquids. The palmitates and stearates are light tan solids. Sorbitan is not a strong hydrophilic group and its derivatives are not water soluble but they are soluble in a wide range of mineral and vegetable oils. The sorbitan esters are lipophilic emulsifiers solubilizers softeners and fibre lubricants. Many of the products have been approved for human ingestion and are widely used as emulsifiers and solubilizers in foods beverages and pharmaceuticals. Another important application is in synthetic fibre manufacture and textile processing as antistats fibre lubricants softeners and emulsifiers of textile mill processing oils. The sorbitan esters are also widely used as emulsifiers in cosmetic products.
The anhydrosorbitol esters are prepared commercially by direct esterification of sorbitol with a fatty acid in the presence of an acidic catalyst at temperatures in the range 225 250 °C. Internal ether formation as well as esterification takes place under these conditions. The commercial products of importance in this group include the mono and trilaurates oleates stearates and palmitates.
Ethoxylated Anhydrosorbitol Esters
Ethoxylation of the sorbitan fatty acid esters leads to a series of more hydrophilic surfactants. They are widely used as emulsifiers antistats softeners fibre lubricants and solubilizers. The ethoxylated sorbitan esters are often used as co emulsifiers with the unethoxylated sorbitan fatty acid esters or the glycerol partial fatty acid esters. Sorbitan fatty acid esters can be reacted with ethylene oxide in the presence of an alkaline catalyst at temperatures from 130 to 170°C to produce the ethoxylated derivatives.
Glycol Esters of Fatty Acids
The ethylene glycol diethylene glycol and 1 2 propanediol esters of fatty acids are widely used surfactants. The commercial products are mixtures of mono and diesters even though the stated composition usually refers only to the principal component. The mono and dilaurates and oleates of ethyleneglycol diethylene glycol and propylene glycol are liquids. Stearates of these glycols are solids. The glycol esters are strongly lipophilic emulsifiers opacifiers and plasticizers that are normally formulated in combination with hydrophilic emulsifiers. They are used as components of cosmetic preparations. The monoesters of glycols can be manufactured by the alkali catalyzed reaction of ethylene or propylene oxide with fatty acids. Mono and diesters are also prepared by esterification of a fatty acid with a glycol.
Ethoxylated Natural Fats Oils and Waxes
The products of commercial importance in this group of surfactants are chiefly ethoxylated castor oil and ethoxylated lanolin derivatives.
Castor oil is a triglyceride with a high content of esterified ricinoleic acid. Its ethoxylation in the presence of an alkaline catalyst to a polyoxyethylene content of 60 70 wt. per cent yields water soluble surfactants. The composition of the ethoxylated derivatives is more complex than might be expected. The ethoxylates are yellow to amber viscous liquids with specific gravities slightly greater than 1.0 at room temperature. Ethoxylated castor oils are hydrophilic emulsifiers dispersants and lubricants. They are used as processing assistants and finishing agents in the manufacture of paper leather and textile products. Other uses are in emulsion polymerizations paints polishes and cosmetic products. Skin irritation and phytotoxicity are usually low.
Lanolin alcohols are derived from the fat that is stripped from raw wool. They are a mixture of cholesterol isocholesterol and other higher alcohols. Lanolin alcohols purified by bleaching solvent extraction crystallization or molecular distillations are ethoxylated to yield non ionic emulsifiers. The mole ratios of ethylene oxide to alcohols that are offered commercially represent a full series of lipophilic and hydrophilic products. Their largest use is as emulsifiers in cosmetic preparations.
Sulfonated Oils
Historical Background
In the early days of textile industry soap in one form or the other was the only cleansing wetting emulsifying and dispersing agent available. Its inability to stand hard water and acid led to the development of a product possessing the valuable properties of soap without its defects. The first successful attempt towards this was of Fremy a Frenchman who studied the effect of concentrated sulfuric acid on olive oil but it was A. Runge who first prepared sulfated olive oil by first reacting the olive oil with concentrated sulfuric acid and then neutralized the reaction product with cold caustic potash solution. The product was an oily water dispersible substance. A British patent was granted to Mercer in 1847 for sulfonating olive oil which was to be used in dyeing madder Turkey Reds. Since then many different oils have been sulfated e.g. rapeseed oil cottonseed oil castor oil groundnut oil and corn oil etc and neutralized with alkalies. The term Turkey Red Oil has since been used for sulfonated castor oil.
The reaction between any oil and sulfuric acid takes place in several ways depending on the temperature the intimacy with which the materials are brought into contact and the time. The major reaction results in a sulfated rather than a sulfonated product. With ordinary oils sulfation occurs at the double bonds of the fatty acids resulting in triolein hydrogen sulfate. Sulfuric acid reacts with the hydroxyl group of the ricinoleyl (12 hydroxy 9 octadecenoic acid) radical of castor oil to form the sulfate.
These products when used in the last stage of wet processing of textiles impart the fabric a desirable softness or fullness and thus by the end of the 19th century the use of sulfated oils as an important textile auxiliary chemical and finishing agent became well established. The sulfated oils of the late nineteenth century were usually only partially sulfated and thus contained a proportion of unchanged fatty glycerides. Sulfated oils in which a large part of the glycerides had been hydrolysed to the fatty acids possessed all the faults of the fatty acids themselves particularly their sensitivity to hard water and to acidic conditions. These defects led to the production (in the 1920 35 period) of so called highly sulfonated oils.
Chemistry of Sulfation and Sulfonation
In sulfonated oils the strongly polar sulfo group appears in the centre or thereabouts of a C18 alkyl chain and the specific properties of the products although useful are not so highly developed as in compounds in which the polar group terminates a long alkyl or acyl carbon chain. Hence for many purposes the sulfonated oils are being replaced by one or other of the more recent preparations.
The oils have therefore not been sulfonated but sulfated and the term sulfonated oil does not convey an accurate picture of the process. Other side reactions proceed concurrently during either of the above two main actions. The sulfate group is fairly easily removed in an acid medium in presence of moisture and consequently the final product contains a certain proportion of hydroxy acids. Further estolides and possibly other anhydride like compounds are produced during the reaction by elimination of water between the alcoholic group of one molecule of sulfated fatty acid and the carboxyl (or possibly sulfate) groups of another. Finally in the case of sulfation of oils the sulfated derivatives have the typical constitution of fat splitting (hydrolytic) agents and considerable production of free fatty acid sulfated or otherwise from neutral oil usually takes place during their manufacture.
On the other hand production of true sulfonic derivatives in place of or accompanying the sulfated products may occur if the action is allowed to take place under strongly dehydrating conditions and especially if fuming sulfuric acid (oleum) sulfur trioxide or chlorosulfonic acid is used in place of sulfuric acid as the sulfonating agent. In these cases the reaction probably takes a course such as the acid sulfate group in the complex formed is comparatively easily hydrolyzed during subsequent washing of the product with water and true (hydroxy) sulfonic acids CH (SO3H) CH (OH) and their condensation products are present in the material finally obtained. These compounds will of course be completely stable in so far as the direct attachment of the sulfonic group SO3H to a carbon atom is concerned whereas the hydrogen sulfate groups of turkey red and the ordinary sulfonated oils and oleins are liable to hydrolyse in presence of water of dilute acid yielding free sulfuric acid and a neutral hydroxy fatty compound as between the true fatty (hydroxy) sulfonates and the unhydrolysed sulfate derivatives of the type of turkey red oil there is probably little to choose on the score of relative efficiency. Claims that the true sulfonates are more effective textile assistants may in reality be based upon their greater stability which is due to their incapacity to loose the polar sulfo acid group by hydrolytic action.
Applications of Sulfonated Oils
Sulfonated oils and fats fulfill many vital needs in the textile processing industry. Their earliest use as assistants in the dyeing of fabrics still remains one of their dominant functions in this field. They are characterized by their dispersing properties surface activity and colloidal nature. These characteristics suit them admirably to the dyeing process. Sulfated castor oil is used in dyeing cotton and rayon fabrics with direct dyeing colours to facilitate penetration and ensure level dyeing. It is also used as dispersing and penetrating agent in the application of vat and naphthol colours. Sulfated oil containing high organically combined sulfate contents (5 to 7 percent) is most suitable for these uses as they generally possess greater penetrating power and exhibit high tolerance to electrolyte. Excessive sulfation however reduces the softening properties of sulfated oils and destroys the natural antioxidant which helps to prevent rancidity. For this reason finishing oils should be prepared to contain a minimum amount of organically combined sulfate consistent with good solubility and stability.
Sulfated oils and fats are probably consumed in greater quantities in finishing operation. Here they are incorporated into the fabric in the final wet process for the purpose of enhancing its appearance and feel. Sulfated olive oil is now almost universally used as a softener on cotton and rayon fabrics where extreme silkiness and drape are desired. Sulfated olive and castor oils are used as lubricants for soaping and as tinting oil ingredients for natural silk and rayon. In both cases the sulfated oil is generally combined with gelatin and dispersed in water as is the case when they are used in warp sizing formulation. Sulfated oils are sometimes combined with highly purified mineral oils to impart added surface lubrication and sleekness to the fabric.
Sulfated tallow is commonly used for moderate softening effects and to add body or apparent weight to the fabric. For additional body and firmness the sulfated tallows are sometimes combined with gums and starches. They may also be combined with polyoxyethylene condensate and salt or an alkylolamide condensate and alkali for the dual purpose of scouring and fulling of woollen fabrics. Sulfated tallow has proved to be an excellent emulsifying agent with all types of waxes and thus it has been possible to formulate many types of wax emulsions based on sulfated tallow. These wax emulsions are applied to cotton and rayon to produce an effect of fullness and body enhancing the lustre of calendared fabric s surface.
One of the greatest uses of sulfated tallow is in the warp sizing of cotton yarns where it is generally used in conjunction with gums or starches. Here it serves the dual function of plasticizing the size film and lubricating the yarn to reduce the frictional resistance in the loom. Mixtures of sulfated oils with white mineral oils impart excellent softness and lubrication and are quite commonly used on high quality cotton rayon fabrics. The presence of high grade mineral oils improves materially the heat and ageing stability of sulfated finishing oils.
Pine oil xylol and cresylic acid are mixed with sulfated oils to improve their penetrating and detergency power. They are then used as kier boiling assistants general scouring agents and agents for removal of grease and tar stains.
Manufacture of Sulfonated Oils
Fatty oils are sulfated with concentrated sulfuric acid and sulfonated with sulfur trioxide. Both processes are of semi batch type and the sulfur trioxide process gives a product containing a much higher combined SO3.
Sulfation
The sulfation is carried out in a lead lined vessel jacketed or fitted with cooling coils and agitator. The reactor is fed with appropriate amounts of the oil and about 25 to 50 per cent on the basis of the amount of oil charged cold and concentrated sulfuric acid is added to the oil with constant stirring. The circulation of cooling water is started simultaneously. The rate of addition of acid must be so adjusted that the temperature does not exceed 35°C. With olive or rapeseed a some what lower temperature is safer and the less saturated oil e.g. fish linseed soyabean etc are better treated at or below 10°C to avoid undesirable results. After the addition of all the acid cooling and agitation are continued for some more time in order to complete the reaction. The mixture is left overnight and again stirred next day. The reaction is considered complete when a sample of the product completely solubilizes in a given amount of water depending upon the degree of sulfation desired.
The free sulfuric acid is removed by adding a quantity of cold water equal in weight to the reaction mixture and allowing it to settle overnight. The aqueous acid layer is then drawn off and the oil is either washed several times with sodium chloride solution or treated with dilute caustic soda solution until the mixture is neutral to Congo red paper. Exacting control during washing and neutralizing step is essential. Conditions occur during this operation which tends to promote desulfation and hydrolysis resulting in an end product low in organic sulfur trioxide and high in free fatty acids. When it is desired to prevent splitting to the greatest possible extent washing is done with sodium sulfate solution instead of salt solution. Washing and neutralization temperature are kept low time of reaction short and pH adjustment accurate. After neutralization the oil is allowed to settle out from the excess of the solution of inorganic salts. The finished product usually contains about 35 per cent water. Optimum conditions for individual oil should be determined by experiments. Monel and nickel clad steel are excellent materials of construction for the reactor but since they are costly lead lined steel is most often used.
Sulfonation
The process development work for sulfonation with SO3 was Sulfonated Oils carried out by flask sulfonation. In a typical laboratory batch reaction castor oil is charged to a reaction flask and SO3 diluted to 4 per cent by volume with dry air is introduced below the surface while agitating vigorously. The reaction temperature is maintained between 45 50°C and the reaction time is between 20 25 minutes. After all of the SO3 has been added the reaction mass is drowned in 15 per cent sodium hydroxide. The resulting product contains about 25 percent water and has 8 per cent organically combined SO3 based on 100 per cent solids. It also displays excellent water solubility at all concentrations.
Results obtained in the laboratory sulfonation can generally be duplicated in the pilot plant and product quality is often improved because of better heat removal and SO3 distribution in the continuous reactor. The continuous reactor used for this work consists of a set of vertically mounted water jacketed stainless steel concentric cylinders divided into three sections the distribution section the reaction section and the separation section. The main function of the distribution section is to direct flow so as to deposit continuously an even film of oil to the inner and outer walls of the reaction section. This is accomplished by pumping the castor oil through small peripheral shots in the distributor.
The SO3/air mixture is introduced above the distributor and passes through the annular space between the concentric cylinders in such a way that contact is made with the castor oil just at the point where the film is developed. In the upper part of the reaction section the gas stream containing the initial concentration of SO3 contacts the unreacted castor oil. As the gas stream and the organic film continue to move together down the reactor waIls SO3 is absorbed by the liquid organic phase reacting with it so that at the end of the reaction section SO3 remaining in the gas phase approaches zero concentration. Virtually all the SO3 in the entering gas stream is absorbed by the organic film and converted to organic sulfate or sulfonate. The film is in intimate contact with the water jacketed reactor walls and movement in the liquid film generated by differential velocity of the gas stream provides an efficient heat removal and excellent temperature control. It also minimizes localized overheating. The reaction mass then passes into the separation section where acid product is withdrawn for subsequent processing and spent gas is separated and exhausted to atmosphere through a suitable mist filter.
A batch SO3/air system on the other hand would operate in a manner similar to that used in the continuous system except that the continuous reactor would be replaced by a stainless steel reaction vessel equipped with a turbine agitator and circulating pump and a heat exchanger.
In India sulfuric acid is generally used for sulfation of oils and thus most of the products marketed are sulfated oils rather than sulfonated oils although they are marketed under the latter name. They contain about 30 50 and 75 percent sulfated organic matter and free oil the rest is mainly water.
Sulfation of Individual Oils
This product was at one time manufactured according to a German process as practiced by M/s. Bohme Felt Chemie. The product was marketed as A Virol K M. In this process 200 kg. sulfuric acid is slowly added into 1600 kg. castor oil with continuous stirring in about four and a half hours. The temperature of the mixture is maintained between 25 30°C by circulating water in cooling coils and/or jacket. After stirring for 1½ hour further 130 kg. of sulfuric acid is added slowly and With continuous stirring in over 3 hours and the batch is allowed to stand for 13 hours without stirring. Finally a further quantity 50 kg. of sulfuric acid is added in about 1 hour and stirring is continued for another hour. The batch is then neutralized as quickly as possible by stirring with 40°Be caustic soda (860 kg.). The temperature rises 90 to 100°C. The product should now show an acid reaction to phenolphthalein. Live steam is now passed in for 1/2 hour. After standing overnight the aqueous salt layer is run off. The product is settled for 2 weeks the aqueous layer is run off and it is then standardized by addition of requisite quantity of water.
Alkylolamides
Introduction
Alkylolamides are condensates of alkylolamines and fatty acids and are generally referred to as foam boosters or additives. Their use in detergent formulation goes a long way towards solving the problems of stabilization improvement and creaming of lather which are so important to the success of compounded detergents. They can be used as detergents in their own right but probably their main outlet is as ingredients in shampoo and liquid and powder detergent production.
The condensates of commercial interest can be divided into three classes
Products from the reaction of one mole of a monoalkylolamine and one mole of fatty acid.
Products of reaction of one mole of a dialkylolamine with one mole of fatty acid.
Condensation products of more than one mole of a dialkylolamine with one mole of fatty acid.
The products of the class (1) with free fatty acid contents in the range of 5 10 per cent are oily light brown liquids which are soluble in water and are quite good detergents particularly for cleaning hard surfaces walls tiles floors etc. These products can be used in the formulation of liquid cleaners and the following formula has been suggested.
This type of formulation is advocated for packing in mild steel drums for sale to hospitals institutions bakeries etc.
The products of the class (2) with low free fatty acid contents are used as foam boosters particularly in the formulation of liquid cleaners. They also act as solubilizing agents for alkyaryl sulfonates and sodium lauryl sulfates depressing the cloud points of mixtures and helping to ensure that no separation of active matter occurs at low temperatures. These products are also used to a more limited extent as additives for powder detergents they are incorporated by spraying in the molten state on to spray dried or physically mixed powders.
The monoalkylolamine derivatives find their major outlet as builders for all purpose spray dried powder detergents where they are normally used at the level of 1 3 per cent. The range of useful additives is wide but can be limited to some extent by economic considerations. In the choice of additive for any particular formulation the following points must be considered
Does the additive have the desired foam boosting properties when added at the desired economic level ?
Are the raw materials available at a reasonable and stable price?
Can the additive be made consistently or does it suffer batch to batch variation which impairs its properties.
(d) Is it compatible with other ingredients in formula e.g. if used with a liquid product can it be sufficiently solubilized together with the other solution ?
(e) Can it be easily incorporated at the right concentration in the powder e.g. can it be sprayed evenly on to the powder will it be stable at spray drying temperatures or will it result in a sticky powder and tend to bleed out ?
(/) Is it stable under long term storage conditions or will it turn rancid or affect the perfume in anyway ?
(g) Has it any disadvantages in use e.g. does it leave streaks on glasses washed in the detergent solution?
The time taken between laboratory trials and launching a detergent powder on a commercial scale may be anything from six months to three years depending on time taken for consumer trials necessary plant alterations stability testing etc. When asked to recommend an additive for any particular proposed formula the additive manufacturer must weigh all these points carefully and if necessary carry out extensive tests. There is no one additive which will perform satisfactorily with all formulae and the additive makers have constantly to be searching for new and improved products particularly in view of such developments as the increasing use of primary alkyl sulfates in all purpose formulae.
Alkylolamides in Shampoo Formulations
The mono and dialkylolamides are widely used in liquid and liquid cream shampoo formulations. They exhibit additive powers so far as volume of foam goes and also help to ensure the creamy thick lather desired by the customer. They are of great assistance in thickening liquid shampoos and by their addition to alkylolamine neutralized lauryl sulfate practically any desired viscosity can be achieved.
They may be looked upon as amides derived by condensing an aliphatic acid of moderate or long chain length with an amino alcohol.
However it does not necessarily follow that amides actu ally used are produced by direct condensation. The RCO will be derived from any of the natural fatty acids in the range of capric caprylic to oleic and stearic and behenic.
Mono Alkylolamides
The substance in class I are waxy materials and on their own are substantially insoluble in water. The members of this class derived from the fatty acids of moderate chain length such as lauric and myristic can however be soluble in water when they form part of a composition with other synthetic detergents which are themselves water soluble. These particular alkylolamides have the power of improving the soil removal efficiency of other detergents particularly sulfated and sulfonated detergents such as sodium lauryl sulfate and sodium dodecyl benzene sulfonate. They also have the power of enhancing the foaming powers of detergents particularly those just named under the appropriate conditions.
Alkylolamide falling in class (1) but derived from higher fatty acids are practically insoluble in water and do not improve the lathering power or soil removal efficiency of detergents but they are valuable emulsifying agents and in some cases they serve to render translucent detergent compositions opaque or pearly in appearance. It is also stated in the literature that certain alkylolamides derived from higher unsaturated fatty acids are useful as conditioning agents for the hair when incorporated in shampoos. The alkylolamides derived from lauric and myristic acids which are probably the most used in this class are generally chosen to enhance the foaming or detergent power of other surface active agents in preparations which are to be marketed as powders. Generally speaking these alkylolamides even in the presence of substantial quantities of sulfated anionic detergents are not sufficiently soluble to enable clear or translucent liquid preparations to be formulated. However under some conditions in the presence of other materials which act as coupling agents clear liquid products can be produced. The coupling agents may be aliphatic alcohols or may even be alkylolamides derived from other fatty acids. As an example of the latter it may be noted that the mono ethanolamide derived from coconut oil fatty acids which will contain approximately 65 per cent of the lauric and myristic ethanolamides is much more soluble in liquid detergents concentrates than an alkylolamide derived from pure lauric or myristic acid.
Di Alkylolamides
The alkylolamides falling in class (2) are more soluble than those in the previous class. Until recently the alkylolamides in this class were most frequently made not as the pure amides represented by the formula given but in the form of a complex composed of genuine amide free amino alcohol and some soap. There is considerable evidence that the complex does not function as simple mixture and in this form many alkylolamides of class (2) are readily soluble in water although they may be salted out by electrolytes under certain conditions.
On account of their solubility in water di alkylolamides derived from lauric or myristic acid and diethanolamine in the form of the complex containing excess diethanolamine have found extensive application in the formulations of liquid detergent preparations. These alkylolamides have the power to augment the foaming power of other surface active agents under certain conditions and at the same time they have a thickening effect upon liquid detergent preparations generally. Unlike the products in class (1) which are purely effective as improvers for other detergents the alkylolamides in this class possess in the form of the complex very considerable detergent power in their own right and are frequently used without the admixture of other surface active agents in the formulation of the general cleaning and so called sanitizing detergent preparations.
The alkylolamides represented by formula (3) are interesting in that the balance may be altered by varying the number of molecules of ethylene oxide in the two radicals attached to the nitrogen atom. Compounds in this group show reason able wetting properties and the precise wetting power depends upon the balance of the molecule. Thus if RCO is derived from short chain fatty acids such as lauric or myristic the wetting power is at its highest when the side chains contain not more than five molecules of ethylene oxide (in other words when m+n in the formula does not exceed 5). Whether RCO is derived from a longer fatty acid such as stearic or oleic it is necessary for the hydrophilic properties of the molecule to be increased to achieve optimum wetting power. In this case the best results are obtained when the number of molecules of ethylene oxide is about 10 (that is where m+n = 10). The alkylolamides however in this class have never become as extensive in use as the alkylolamides in the other two groups. They are principally of interest for their value as emulsifiers. The products from coconut oil fatty acids and containing 10/50 molecules of ethylene oxide are good oil in water emulsifiers for carnauba wax.
Pure Di Alkylolamides
Until recently the alkylolamides in class (2) have generally been available and used in the form of a complex. This was in many ways convenient as the complexes were more soluble and possessed better wetting and detergent power than the pure amides and also because it is simpler and therefore cheaper to manufacture this type of product free from undesirable by products if an excess of alkylolamine is present. Where however these products are used in conjunction with sulfated detergents to enhance the foam of the latter the effective material is the true amide while excess diethanolamine contained in the complex does not contribute towards the effect. In cases such as these the di alkylolamides can normally be adequately solubilized by the sulfated detergent and therefore the excess diethanolamine serves no useful purpose.
For the majority of applications however the whole issue would seem to hinge on the price one is paying for 100 per cent active amide when one buys it in the nearly pure state as compared with the conventional complex. It cannot of course be overemphasized that where di alkylolamide is being used as a detergent in its own right alone or with only minor amounts of other detergents the complex will of course be preferred on account of its allround greater solubility and wetting and detergent power.
Phosphoxylated Alkylolamides
Recently interest has been taken in the production of phosphoric acid esters of the alkylolamides. These have been claimed to have an anti static effect when used in the washing of synthetic fibres such as nylon. Other phosphoric acid esters of alkylolamides have found application to produce a pearly effect in some types of cream shampoos.
Sulphated Alkylolamides
The product so far described where they have been soluble in water and possessed surface active properties have been essentially non ionic in their behaviour. It is possible by preparing the acid esters of sulfuric acid or phosphoric acid of these alkylolamides to produce detergents which are anionic in their behaviour. In general the mono alkylolamides falling in class (1) are preferred for sulfation or phosphorylation. The sulfated mono alkylol amides of coconut oil fatty acids have excellent lathering power comparable with that possessed by sodium or triethanolamine lauryl sulfate. They show a superior detergency to the latter materials and also greater ability when in dilute solution to retain dirt particles in suspension.
The sulfated alkylolamides however are not one of the big volume detergents and they have never equaled the alkyl sulfates in popularity. Probably one of the reasons for this is that it is extremely difficult to control the sulfation procedure to ensure that the finished product is free from undesirable by products which impair efficiency. The fact that on paper the preparation of sulfated alkylolamide detergents appeared relatively easy at one time tempted some firms to try and produce these materials without adequate research. The earlier products however were very variable and frequently contained substantial amounts of undesirable side products. Properly prepared however the sulfated alkylolamides are excellent products. Probably the best known of this type of detergent is the sulfated monoethanol amide or isopropanolamide derived from coconut oil fatty acids. Detergents have been prepared however from higher unsaturated fatty acids and though under some conditions they lack the lathering power of the products from coconut oil they do possess exceptionally good detergency and also incidentally exceptional power to disperse lime soaps.
Whereas the sulfated fatty alcohols are generally processed so as to ensure the maximum degree of sulfation and the minimum residual amount of unsulfated fatty alcohols it is not usual in the case of such materials as coconut oil fatty acids monoethanolamide to secure such a high degree of sulfation. Frequently 75 percent to 85 percent sulfation is the maximum desired. The reason for this is that unsulfated and unsulfated material is vary effective in use. Products containing as much as 50 percent unsulfated material (provided always that they are free from undesirable side reaction products) have excellent lathering and cleaning power.
Foam Stabilization
The original patents which referred to the use of alkylolamides in detergent compositions were mainly concerned with the improving effect that the alkylolamides exerted upon the soil removal efficiency of other detergents.However alkylolamides today are most frequently added to detergent compositions in order to improve the lathering power under the conditions of use. When we come to consider how to estimate quantitatively the effect of the alkylolamides the position is by no means simple. Many compositions in practical use are improved by the presence of an alkylolamide. However it is not always easy to measure this improvement quantitatively under laboratory conditions. For example it is often quite useless attempting to infer how a shampoo composition will behave in use of the hair by measuring the foam obtained by shaking solutions of the detergent preparation in measuring cylinders in the laboratory.
One satisfactory way consists in devising a laboratory test which simulates the actual conditions under which a detergent product is to be used. The effect that an alkylolamide exerts upon the foam of a preparation when the foam is created in narrow capillary in a relatively narrow foam cylinder is quite different from that exerted when the foam is produced on a wide surface area such as one has in a sink during dishwashing operation. The conditions which apply during a shampooing operation on the hair are different again. It is further most important that in tests designed to evaluate detergent preparations in the laboratory soil such as would be expected in actual practice should be present. It is also important that the tests should be carried out at the same active detergent concentration as would apply in practice.
The effect of concentrations on lathering power is readily illustrated by an example concerning the sulfated alkylolamides. Salts of sulfated lauric acid mono ethanolamide possess excellent lathering power at high concentrations such as might be employed in shampooing or for the washing of clothes under domestic conditions but if a solution of the detergent is excessively diluted once the detergent concentration falls below a certain critical level the foaming power disappears. Sulfated alkylolamides derived from C19 unsaturated acids however behave quite differently. These give however at a similar concentration level to that at which the sulfated lauric mono ethanolamide would have ceased to lather these produce extremely stable foam. The detergent concentration in a washing machine in a commercial laundry would be at a low level.
Another interesting method for testing a shampoo product under pratical conditions has recently been described in the literature. The effect of alkylolamides on sulfated and sulfonated anionic detergents is not normally to improve the lathering power of the detergent in plain water. Alkylolamides offset the deleterious action of oily or fatty soiling matter on the foam of these detergents. Many anionic detergents though they lather well in plain water tend to lose their lather to an astonishing extent in the presence of oil and fatty soiling matter and this effect is prevented by the use of suitable alkylolamides. The effect however is not quite true at all concentrations and the effectiveness of the alkylolamide only takes place above a certain threshold concentration of active detergent in solution. Fortunately this threshold concentration where lauric or myristic monoalkylolamides or dialkylolamides used in conjunction with such detergents as the alkylaryl sulfonates or alkyl sulfates is below the concentration at which most domestic washing operations are carried out.
An alkylolamide of much higher threshold concentration is capable of improving the lather of anionic detergents at high concentrations (e.g. 3 per cent and over) such as would be used when shampooing the hair. Where however the dilution becomes much greater the lathering power rapidly diminishes. Thus using this particular alkylolamide it is possible to prepare a composition which yields rich stable foam on the hair but immediately the rising operation commences the foam disappears. This effect would notappeal to consumers who like to judge the lathering power of a shampoo by the amount of lather to be seen in the washbowl after rinsing. However it would appeal to those who find stable detergent foams difficult to rinse away down the sink and to the sewage authorities who find stable detergent foams so difficult to handle.
The most commonly used alkylolamides for the purpose of stabilizing foam are the monoalkylolamides which fall in class (1) and the alkylolamides which fall in class (2) derived from either lauric or myristic acids. Products derived from mixed fatty acids containing substantial proportions of lauric or myristic acid such as coconut oil or palm kernal fatty acids are also used. In general however when one comes to measure effective foam stabilization as such it is generally found that the products derived from mixed fatty acids associated with them behave virtually as no more than inert diluents although in the case of the monoalkylolamides products from mixed fatty acids sometimes have the advantage of greater solubility in liquid detergent preparations. Therefore it is frequently a better economic proposition to buy what is initially a more expensive product devised from a fractionated lauric acid than to use a mixed product which has a lower market price.
These observations apply to the stabilization of foam and there are of course other aspects of the use of alkylolamides where the mixed products may be more worthwhile. Generally the lauric monoalkylolamides are preferred for use in powder compositions. Frequently they are here associated with polyphosphates and in the case of some alkylolamides particularly isopropanolamides the presence of polyphosphates seems to be necessary for the maximum stabilising effect to be produced. The monoalkylolamides are generally dispersed in detergent slurry at an elevated temperature before it is mixed with the phosphates or other builders and fed to the spray drier. Mono alkylolamides are now available in powder form which greatly facilitates the operation of dispersing them in a detergent slurry. Lauric diethanolamides either in the form of complex previously referred to or in the pure state are used in the formulation of liquid detergents since they do not impair the cloud point of these products. In actual fact diethanolamides in the form of the complex frequently effectively lower the point at which alkylaryl sulfonate and other compositions cloud. However there is no hard and fast rule concerning the use of the different types of alkylolamides. Dialkylolamides may be incor porated into powders in quite significant amounts and on the other hand mono alkylolamides may be included in liquid composition either in restricted amounts alone or solubilized by the addition of alcohol.
Vinylarene Polymers
This article covers polymers derived from monomers that have a vinyl group attached to an aromatic ring (1). It does not cover aromatic monomers having a heteroatom in the ring styrenes or except for 4 vinylbiphenyl Substituted styrenes.
Monomers
Vinylarene monomers are general1y prepared by dehydration of the corresponding carbinol which can usually be obtained by the acetylation of the corresponding hydrocarbon and reduction of the ketone. The carbinol can also be obtained by the reaction of the aryl Grignard reagent with acetaldehyde (eq.1)
In Table 1 are listed some vinylarene monomers and their physical properties.
Anionic Polymerization
Kinetics of the anionic homopolymerization of 1 vinylnaphthalene 2 vinylnaphthalene and 9 vinylanthracene in tetrahydrofuran at 25°C have been determined and propagation rate constants of 500 300 and 0.2 l mole 1 sec 1 found. The greater reactivity of 1 and 2 vinylnaphthalene as compared with that of styrene has been attributed to their lower localization energies.
The anionic polymerization of 9 vinylanthracene produces only low molecular weight polymer and initation by naphthalene or biphenyl radical anions or by butyllithium yields oligomers having a DP of 4 12. A study of the reaction has shown that although the concentration of the living ends remains unchanged during the reaction the degree of polymerization does not correspond to the concentration of initiator indicating an efficient chain transfer reaction. When additional monomer is supplied to the polymerized system more polymer forms without affecting its molecular weight thus indicating that no chain transfer to polymer takes place.
It has been shown that 9 vinylanthracene can polymerize both along the vinyl group and across the central ring of the anthracene system and structural analysis has shown that material polymerized in the presence of lithium potassium and sodium contains a lower percentage of anthracene rings than material polymerized with cesium.
The polymerization mechanism shown in equations 2 4 has been proposed. Accumulated physical and chemical evidence indicates that the predominant structure for the polymer is that resulting from a 1 6 across the ring addition. To account for the low molecular weight of the polymer the chain transfer reaction shown in equation 5 has been proposed.
A kinetic study of the anionic polymerization of acenaphthylene has shown that the reaction follows pseudo first order kinetics and that a chain transfer reaction to monomer similar to that observed for 9 vinylanthracene takes place. The highest molecular weight that could be obtained by anionic polymerization was 8000 although thermal polymerization in bulk produced polymers having very high molecular weight (ca 2 000 000). Although the chain transfer mechanism has not been established it probably involves electron transfer to monomer coupled with hydrogen abstraction from solvent. The copolymerization of 1 vinylnaphthalene with 2 vinylpyridine and with styrene has been investigated in both sequential and simultaneous polymerizations and good yields of copolymers were obtained when 1 vinylnaphthalene was initiated with a polystyrene anion. Interesting results are reported when styrene is initiated with a poly(l vinylnaphthalene) anion addition of two or three equivalents of styrene to living poly(l vinylnaphthalene) leads to the disappearance of the characteristic 558 mm absorption maximum of the poly(1 vinylnaphthalene) anion but the expected 340 mm maximum of the polystyrene anion does not appear. Instead a new absorption peak at 440 mm appears but on standing for 24 hr the original 558 mm peak of poly(l vinylnaphthalene) reappears. When a large excess of styrene twentyfold or more is added the characteristic spectrum of polystyrene appears permanently.
The observations were explained by assuming that the reaction involves three steps (eqs. 6 8).
The addition of the first styrene molecule produces a benzyl type anion that froms a bond with the preceding naphthalene group. The product resembles the adduct of living Polystyrene and thracene and the product very slowly adds a second molecule of styrene. The addition of the second molecule destroys the complexing with naphthalene and the resulting polymer propagates as ordinary polystyrene does.
The complex formed on addition of a small excess of styrene to living poly(l vinylnaphthalene) must be unstable because the spectrum of the poly(l vinylnaphthalene) reappears within 24 hr. It has been concluded that the formation of the complex is reversible and that the equilibrium concentration of styrene is given by the reaction shown in equation 9. The reaction mixture must however contain some living polystyrene anions since some segments have added two or more styrene units. Hence another equilibrium is established (eq. 10). These three equilibria are coupled in the overall process and the equilibrium of the overall process favors the right side (eq. 11). This scheme has been tested with a methylstyrene the propagation of which is thermodynamically unfavorable and a stable complex was formed when this monomer was added to living poly(l vinylnaphthalene).
ABA block copolymers of 4 vinylbiphenyl and isoprene have been prepared using living polymer techniques Because of difficulties in achieving a rigorous purification of 4 vinylbiphenyl a coupling technique was used whereby the A monomer was polymerized first the B monomer was then added and the AB anion was next coupled with a reactive dihalide. Using this technique the residual impurities in the A monomer only destroy some initiator by estimating the degree of purity it is easy to use a slight excess of initiator to compensate for the amount destroyed by the impurities Coupling of the AB anions was achieved by using phosgene which was allowed to diffuse very slowly into a vigorously agitated polymer solution.
The block copolymers were characterized by gel permeation chromatography and from knowledge of the ratio of the refractive index increments of the two homopolymers and the overall composition a quantitative analysis was carried out.
Polymer Reactions
The transfer of an electron from alkali metals to an aromatic hydrocarbon such as naphthalene or biphenyl is well known. The same reaction occurs when the vinylarene group is attached to a polymer chain. The products have been referred to as polyradical anions and are formed experimentally in all glass highvacuum systems by the reaction of the polymer in tetrahydrofuran with a sodium mirror at temperatures ranging from 80 to 30°C.
The reaction products have been characterized by viscometric spectrophotometric and electron spin resonance measurements. It was found that the viscosity of the solution decreases with time and that the final viscosity depends essentially on the alkali metal concentration. Spectrophotometric data have shown that with time the spectrum becomes almost identical to living polymer dianions and electron spin resonance studies have indicated the presence of unpaired electrons in concentrations proportional to the sodium content. The disappearance of the signal to practically zero the formation of anions and the decrease in viscosity with time are consistent with a cleavage mechanism in which an electron migrates from the aromatic ring to the a carbon of the aliphatic chain with formation of a negatively charged end (eq. 12). The same mechanism has been proposed for poly (N vinylcarbazole) poly (l vinylnaphthalene) poly (2 vinylnaphthalene) and poly (4 vinylbiphenyl). Poly (acenaphthylene) degrades so fast that it is not possible to follow changes in viscosity as a function of time. It has also been found that monomeric fragments are produced (eq. 13).
Polyradical anions have been used to initiate graft polymerization reactions. The reaction is not applicable to monomers that polymerize by an electrontransfer mechanism where only homopolymerization is achieved. However monomers such as cyclic ethers that cannot polymerize by an electron transfer process but do polymerize anionically do form graft copolymers. The mechanism of the polymerization is similar to that proposed for the carbonation of the naphthalene radical anion (eqs. 14 16).
Poly (2 vinylfluorene) has been metalated with metallic sodium or lithium or with the corresponding naphthalene radical anions (eq. 17) and graft copolymers with a variety of vinyl monomers such as styrene methyl methacrylate or vinylpyridine in addition to ethylene oxide have been prepared.
Metalation of 2 vinylnaphthalene units incorporated into a copolymer has also been used to provide sites for anionic grafting reactions. Thus a copolymer of butadiene containing small proportions of 2 vinylnaphthalene has been prepared by free radical copolymerization techniques the resulting copolymer metalated with butyllithium and styrene or 2 vinylnaphthalene graft copolymerized on the anionic sites. The resulting materials exhibited elastomeric properties similar to those of styrene butadiene ABA block copolymers provided the number of grafts per backbone was small.
Stereoregular Polymerization
Although the stereoregular polymerization of styrene and substituted styrenes has received considerable attention other vinylarene monomers have been studied much less extensively. Natta and co workers have surveyed the stereoregular polymerization of over 20 vinyl aromatic monomers among these were1 vinylnaphthalene 2 vinylnaphthalene 1 vinyl 4 chloronaphth alene 1 2 3 4 tetrahydro 6 viny1 naphthalene 4 vinylbiphenyl 9 vinylphenanthrene and 9 vinylanthracene. This study established that Ziegler Natta polymerizations are very sensitive to steric hindrance about the double bond and when the steric hindrance is excessive such as in 9 vinylanthracene no polymerization takes place. Although one study does report a polymerization of 9 vinylanthracene in yields from 20 to 90% depending on the Al/Ti ratio with an Al (C2H5)3 TiCl4 catalyst system the results indicate a cationic polymerization.
Stereoregular polymers of 1 vinylnaphthalene 2 vinylna phthalene and 4 vinylbiphenyl have been prepared using a (C2H5)3Al TiCl4 (C2H5)2AlCl TiCl3 or (C2H5)3 AI TiCl3 catalyst system . The latter catalyst gave polymers in 75 95% conversion that were at least 90% isotactic. The atactic fraction could be separated from the isotactic ones by extraction with methyl ethyl ketone. The isotactic polymers were also characterized by infrared and nuclear magnetic resonance spectroscopy (35).
Not all stereoregular polymers could be crystallized. In polymers in which steric factors lead to a crystalline phaseNot all stereoregular polymers could be crystallized. In polymers in which steric factors lead to a crystalline phase that would have a lower density than the amorphous phase no crystallization took place. Thus only 1 vinylnaphthalene produced a crystallizable polymer .An x ray diffraction study on this polymer has been carried out. The Bragg distances in the unit cell are a = b = 21.20 Å and c = 8.12 Å and the specific gravity is 1.12.
The stereoregular ionic polymerization of acenaphthylene has been investigated in some detail. Although four stereoisomers can be written eg cis and trans isotactic and cis and trans syndiotactic a study of molecular models has shown that only the trans isotactic and trans syndiotactic conformations can exist in polymers. The trans isotactic poly(acenaphthylene) forms a helix and the trans syndiotactic poly (acenaphthylene) forms a stair stepped rigid rod. These stereoisomers were obtained by n butyllithium or boron trifluoride polymerizations and characterized by infrared and nuclear magnetic resonance spectroscopy.
Acenaphthylene has also been polymerized with an Al(C2H5)3 Ti(OC3H7)4 catalyst system but no mention of stereoregularity was made.
Cationic Polymerization
The cationic polymerization of vinylarene monomers other than styrene is not well understood and little reliable quantitative information is available. Acenaphthylene readily forms polymers of high molecular weight although a dimer can be obtained when a solution of acenaphthylene in glacial acetic acid is treated with a small quantity of concentrated hydrochloric acid. The kinetics of the cationic polymerization catalyzed by boron trifluoride and iodine has also been studied. In the first case a second order reaction with respect to boron trifluoride was observed and in the second case a high order reaction with respect to iodine concentration and cocatalysis by hydrogen iodide was noted.
Unlike free radical polymerization the cationic polymerization of 9 polymerization rates. Early studies assumed a normal vinyl polymerization but it was later shown that the normal addition takes place to only a very minor extent and that polymerization across the ring similar to that already discussed in the anionic polymerization takes place. A wide variety of catalyst systems and solvents was also investigated.Very little information is available on the cationic polymerization of other vinylarene monomers. l Vinylnaphthalene apparently can be polymerized to a high molecular weight product but monomers substituted in the a or b position of the vinyl group yield mainly dimers. The polymerization of 4 vinylbiphenyl with Friedel Crafts catalysts has been reported and l vinylpyrene and 2 vinylfluorene have also been polymerized with BF3.
Stable carbonium ions such as tropylium hexachloro antimonate (C7H7 SbC16 ) and tetrafluoroborate (C7H7 BF4 ) have been used to initiate the polymerization of acenaphthylene and 1 and 2 vinylnaphthalene.
Free Radical Polymerization
The kinetics of the 2 2 azobisisobutyronitrile initiated bulk polymerization of 1 vinylnaphthalene have been reported. The polymerization rate is proportional to the 1/2 power of the initiator concentration and the first power of the monomer concentration. The molecular weight of the polymer was shown to be controlled by a chain transfer reaction with the monomer and a chain transfer constant of 0.03 about 300 times that for styrene was found. As a consequence only low molecular weight polymers (2000 6000) were obtained. The bulk polymerization of 2 vinylnaphthalene leads to a product having a molecular weight of about 66 000. Emulsion polymerization techniques yielded a poly(l vinylnaphthalene) having a molecular weight of 25 000 and a poly (2 vinylnaphthalene) having a molecular weight of 115 000.
The relative ease of bulk polymerization of 1 vinylnaphthalene 2 vinylnaphthalene 6 vinyl 1 2 3 4 tetrahydronaphthalene and vinyldecahydronaphthalene has been compared 1 and 2 vinylnaphthal enes were the easiest to polymerize 6vinyl 1 2 3 4 tetrahydronaphthalene had polymerization rates comparable with those of unsubstituted styrene and vinyldecahydronaphthalene did not polymerize during 30 days at 100°C.
The solid state postpolymerization of 60Co g irradiated 2 vinylnaphthalene has been studied. The monomer was irradiated at 78°C and then postpolymerized at temperatures ranging from 20 to 41°C. A limiting conversion of about 40% was obtained. The soild state polymerization under pressure has also been investigated.
The polymerization rates of 1 and 9 vinylanthracene and 9 vinylphenanthrene have also been compared. The highest reactivity was shown by 9 vinylphenanthrene and the lowest by 9 vinylanthracenc. The reactivities were explained on the basis of steric hindrance to conjugation between the ring system and the vinyl group and the nonaromatic character of the 9 10 double bond in phenanthrene. The free radical polymerization of 9 vinylanthracene proceeds so slowly that it holds little promise as an acceptable polymerization technique. No studies have been reported in which the structure of this polymer has been examined.
Acenaphthylene can be polymerized to a high molecular weight polymer using free radical initiators and a molecular weight of over 150 000 has been reported. The kinetics of the thermal polymerization of a highly purified sample have been studied dilatometrically and a high activation energy for both initiation and propagation was found.
The effect of high pressure on the free radical polymerization of acenaphthylene has also been investigated. It was found that the rate of polymerization is not increased as much by pressure as is that of other olefinic monomers such as styrene. The effect of pressure on molecular weight was also less than for polystyrene and the molecular weight of the polymer increased by a factor of 2.6 between 1 and 2880 atm.
The solid state polymerization of acenaphthylene initiated by x rays has been studied in air in nitrogen and under vacuum. The results indicate that the molecular weight is essentially independent of the total dose rate and the rate of polymerization is proportional to the first power of the dose rate. The polymer was amorphous as indicated by x ray diffraction.
The polymerization rates of a series of substituted vinylbiphenyls have been found to be first order in monomer and they were claimed to increase with increased conjugation and polarity of the substituents. Reactivity ratios for various vinylarene monomers are shown in Table 2.
As indicated by the 1/r1 values all vinylarene monomers shown with the exception of 9 vinylanthracene are more reactive in copolymerization than is monomer M1.
A series of copolymers of 4 vinylbiphenyl with styrene and vinylchlorobiphenyl and vinylfluorobiphenyl each with a methylstyrene or a p dimethylstyrene have been prepared by mass and emulsion copolymerization. The 4 vinylbiphenyl styrene copolymer was claimed to have improved resistance to heat distortion.
The effect of styrene on bulk polymerization rates and molecular weights of copolymers with various vinyl naphthalenes has received considerable attention. Thus the bulk polymerization rateof 1 vinylnaphthalene is decreased by the addition of styrene and the rate reaches a minimum with 60 mole % styrene in the feed. In general the addition of styrene to vinylnaphthalene increases the molecular weight of the copolymer. With 1 vinylnaphthalene addition of styrene had little effect until about 60% had been added and then the molecular weight increased almost linearly from 20 000 to 110 000. The increase in molecular weight of poly(2vinylnaphthalene) by addition of styrene was in general more gradual but was more rapid at low styrene concentration. The same effect was also noted in methyl methacrylate 2 vinylnaphthalene copolymerization. As in homopoly merization emulsion copolymerizations produce copolymers having higher molecular weights relative to those prepared by bulk polymerization.
Addition of styrene to 6 chloro 2 vinylnaphthalene leads to increasing rates with increasing styrene content in the feed whereas the opposite is true with 4 chloro 1 vinylnaphthalene. The addition of methyl methacrylate has little or no effect on 4 chloro l vinylnaphthalene but decreases the rate of copolymerization of 6 chloro 2vinylnaphthalene.
The copolymerization behavior of anthracene and phenanthrene derivatives with styrene has been investigated. The same order of decreasing activity (9 vinylphenanthrene> l vinylanthracene > 9 vinylanthracene) as in homopoly merization is also noted in copolymerization. Although the rate of copolymerization of 9 vinylanthracene with styrene is faster than that of 9 vinylanthracene alone 9 vinylanthracene feeds greater than 25% by weight inhibit the polymerization of styrene 2 And 3 vinylphenanthrenes have been copolymerized with methyl acrylate. Even though both monomers are more reactive than styrene toward methyl acrylate radicals the addition of methyl acrylate to either of the phenanthrenes reduced both the molecular weight of the polymer and the rate of copolymerization.
Various copolymers of 1 vinylpyrene have been prepared and their softening points determined.
The copolymerization of acenaphthylene with other vinyl monomers has been described. Of these the most extensively investigated was the copolymerization of styrene with acenaphthylene. Mass polymerizations using peroxide initiators or thermal polymerizations at 120 125°C for as long as 10 days yielded only low molecular weight copolymers. However emulsion polymerization at 30°C with redox catalyst systems gave excellent yields and high molecular weight products. Terpolymers of acenaphthylene styrene and butadiene have also been prepared. Acenaphthylene has been copolymerized with divinylbenzene and the crosslinked network sulfonated. Strongly acidic ion exchange series were thus produced.
Solid state g radiation induced copolymerization studies of acenaphthylene with acrylamide and maleic anhydride have been carried out. Only polyacrylamide homopolymers could be obtained in attempted copolymerizations of eutectic mixtures with acenaphthylene. Solid state copolymerizations of maleic anhydride with acenaphthylene produced 1 1 copolymers.The same alternating copolymer was also obtained in free radical solution copolymerization.
Graft copolymers of acenaphthylene onto polyethylene have been prepared by roll mixing polyethylene acenaphthylene and benzoyl peroxide in air at 100°C. Maximum grafting was obtained at 30 min and thereafter the amount grafted decreased because the grafted branches were selectively masticated. No grafting was obtained in the absence of benzoyl peroxide.
Polymer Properties
Characterization. In Table 3 are collected the parameters for the Mark Houwink equation for some vinylarene polymers correlating intrinsic viscosity with molecular weight.
Light scattering studies have shown that the coil size of poly (2 vinylnaphthalene) exceeds that of polystyrene by a factor of 1.4 indicating that substitution of benzene by a naphthalene ring increases the thermodynamic stiffness of the polymer. However another study has shown that even though considerable hindrance to rotational motion of chain segments should be expected in poly (acenaphthylene) its dilute solution behavior indicates that it has a hydrodynamic volume comparable with that of polystyrene. It has also been shown that poly (4 vinylbiphenyl) poly (l vinylnaphthalene) and poly(2 vinylnaphthalene) can be represented by a common plot of intrinsic viscosity times the molecular weight of the repeat unit versus weight average degree of polymerization and that they also exhibit a common gel permeation chromatography calibration plot. These results lead to the some what surprising conclusion that all these vinylarene polymers have similar hydrodynamic volumes. Poly (acenaphthylene) could not be included in these studies be cause it has been found to be unstable in solution and to degrade by a free radical mechanism that is at least partially an unzipping process.
Electrical Properties.
A number of charge transfer complexes have been prepared in which the electron donor is a vinylarene polymer. They are of interest because the complexes are known to show semi conductive properties in the solid state.
N Acyl N Alkyltaurates
Introduction
N acyl N alkyltaurates have a general formula RR`NCH2 CH2SO3Na where R may be oleoyl cocoacyl taIl oil or taIlow group and R may be a methyl or cyclohexyl group. However the most commonly used and produced product in this group of compounds is sodium N Oleoyl N methyltaurate. It is sold throughout the world under various trade names most common among them being IGEPON T.
Igepon T was first introduced by I.G. Farben industries in Germany and is still in the market in its original form. It is sufficiently stable for most textile processing work except the carbonizing of wool where a strong sulfuric acid bath is encountered. Igepon T has enjoyed a steady expansion of market upto the present time in U.S.A. and Germany and most other developed countries inspite of the advent of alkyl benzene sulfonates. In India however most of its requirements are met through imports.
In a more general formula of N acyl N alkyltaurates
R1 represents hydrocarbon radicals of the fatty acid series which for economic reasons may contain twelve to eighteen carbon atoms. R2 represents an alkyl or cycloaliphatic group which should range from one to eight carbon atoms. Total carbons in Rl and R2 preferably should not be less than twelve nor more than twenty one. Beyond these limits the quality of the product falls off sharply in one of several properties. R3 may be a metal or an organic base or hydrogen. A computation of the number of possible products under the above stated limits might reach 1000.
The effect of changes in structure is fairly well defined. Little detergency is obtained unless Rl and R2 combined contain at least twelve carbon atoms. Detergency is increased by increasing the length of either Rl or R2 or both. The limit is reached at approximately sixteen carbon atoms for Rl if the chain is straight and saturated. If unsaturated then maximum detergency occurs at approximately eighteen carbons and it is believed that with more unsaturation the maximum length of carbons is further increased Departures from straight chain in R1 by branching or by introduction of a solubilizing group will de crease detergency but increase the wetting power. A decrease in the length of Rl increases both solubility and wetting power. If Rl is kept within twelve to sixteen carbon atoms and if the size of the R2 group is increased from a methyl to a higher homolog such as the butyl or amyl group the resulting Igepon becomes more soluble inspite of the molecular weight increase. If Rl is twelve carbons the solubility of the Igepon passes through a maximum when R2 is a four carbon straight chain. Wetting increases with increase in the lengths of R2 until Rl and R2 combined contain approximately eighteen carbons. Further increase in R2 brings on a decrease in wetting. R2 may be hydrogen but when a taurine is used a substitution of at least one carbon group enhances the properties of the resulting product tremendously. The choice of a metal for R3 may affect foaming and the power to emulsify and disperse other substances. There is little difference in solubility between the sodium and potassium salts in the Igepon compounds investigated. The calcium salts are much less soluble. The representative types of Igepon T currently manufactured in developed countries such as U.S.A. and Germany are given in Table 1.
Although one primary factor in determining which Igepon type compounds will be commercially important is the cost of raw materials the economic limitations stilI permit a relatively wide area of investigation. The product derived from oleic acid and N methyl taurine provides the optimum combination of desirable proper ties. This compound is further recommended by the relatively low price of its raw materials.
Applications of Igepon T Products
Igepon T finds its greatest use today in the textile field where it was first introduced. It finds its way into almost every phase of textile wet processing. The list of uses include scouring wetting out degumming kier boiling dye leveling dye pasting chlorine and peroxide bleaching fulling lime soap dispersing and finishing. It also finds application in agriculture paper leather and metal cleaning and also to a small extent in household products including dentrifices shampoos cosmetics and pharmaceutical preparations. It is also used in the scouring of feathers in electrolytic plating baths in the washing of automobiles airplanes rail road coaches and locomotives rugs floors buildings and for cleaning streets and roads and in the dairy food and for industries.
Igepon T can be prepared in a variety of forms. One is a clear liquid suitable for incorporation into consumer products. It looks much like a conventional liquid soap and is available with 15 and 25 per cent active ingredients. Another form is a slurry or an opaque heavy liquid. This material contains 28 per cent active ingredients and is essentially the product as it comes from the condensation kettles it contains no added chemicals. It may be used by formulators who will process it further by adding it to other ingredients or drying it to a powder. It can be shipped in tank cars and is the least expensive of the various Igepons.
Future of Igepons
The future of Igepon T its analogs and homologs is bright. The economic existence of this type of product is assured by the fact that the biggest weight in its molecule is a fatty acid. The principal fatty acid used is oleic acid which is found abundantly in vegetable and animal oils. As synthetic detergents derived from non fatty soures encroach on the soap market the fats and particularly tallow from which oleic acid is largely derived will tend to become more a surplus product.
Another advantage enjoyed by the taurine type Igepon (N acyl N alkyltaurates) is the fact that the Igepon T gel largest seller in the group today is not the best wetter in the series nor is it the best emulsifier or dispersant. It is not the best foamer the best textile softening agent or lime soap dispersant nor is it the most soluble member of the group. It has a good high average on all counts which led its developers to call it the universal soap. The taurine type Igepon can be modified to well over 100 varieties. Any one of the various surfactant properties may be obtained to a high degree by making changes in the structure of the 1gepon molecule. Consequently it is predicted that the 1gepon type surfactants will have an important future in the development of special purpose products where price is not the primary consideration.
Manufacture of Igepon T
Raw materials
The major materials required for the production of sodium N oleoyl N methy ltaurine are oleic acid phosphorous trichloride N methyltaurine and caustic soda. It is extremely important that a high quality of oleic acid be used in the process. If an excessive amount of esters or unsaponifiable material is present the resultant Igepon will have an excess of free fat which tends to make the gels cloudy.
The N methyItaurine may be used as a 25 to 30 percent filtered aqueous solution. The 30 and 50 per cent caustic soda solutions and the hydrochloric acid used to control the pH of the batch at various points in the processes can be the standard commercial products.
Oleic Acid Chloride
The first step in manufacturing Igepon T gel or Igepon T powder is the production of oleic acid chloride (oleoylchloride) from oleic acid and phosphorous trichloride. Acid chlorides other than oleic may be used to make special Igepon compounds.
The reaction takes place in a jacketted lead lined kettle equipped with both cooling water and low pressure steam connections. A horse shoe type agitator stirrs the charge. A 1.5 lead vent to the roof of the building removes volatile acid fumes and decomposition products of phosphorous trichloride from the kettle. It is essential that the kettle be dry before charging is begun to prevent hydrolysis of the phosphorous trichloride. If any condensation accumulates on the kettle due to extended inactivity it is driven off by introducing steam into the jacket while the kettle is empty.
To begin the operation oleic acid is blown by air from a feed tank to a steel weigh tank phosphorous trichloride is similarly blown into a lead lined weigh tank. A 400 kg. charge of acid is drawn from the weigh tank and dropped by gravity into the kettle. Phosphorous trichloride (103 kg.) at room temperature is introduced from the weigh tank over a period of one hour while cooling water is circulated through the jacket of the kettle. A sight glass in the lead line through which the phosphorous trichloride is charged permits the operator to judge the flow rate of this stream. After the kettle has been completely charged the temperature is raised. to 50°C to 52oC and is held there for 6 hours by introducing 15 kg. steam into the jacket. At the end of this period the temperature is raised to 60°C for an additional 15 minutes to ensure completion of reaction.
About 60 per cent of excess phosphorous trichloride is used in the process. This excess about 38 kg. is partially retained in solution in the fatty acid chloride and appears in the final product as phosphite salt.
The finished product is blown by air pressure into two lead lined cone shaped tanks and allowed to stand over night settle out the by product phosphorous acid. The bases of the cones are heated with extended 1.5`` lead steam coils to thin down the heavy acid sludge and aid in the separation. After drawing off the first waste acid the contents of the cone tanks are agitated and then a second separation of acid is drawn off. The point of separation is determined by observation through sight classes in the draw off lines. The spent acid is piped direct to the sewer through lead pipes traced with 1.5 outside diameter pipes carrying low pressure steam.
Oleic acid achloride will descompose on standing if exposed to atmospheric moisture consequently it is made up only as needed and is piped through steam traced lead lines direct from the cone tanks to the weigh tanks of the Igepon unit.
This product is made in a brick lined kettle equipped with a four fingered stainless steel agitator. A stainless steel submerged coil provides temperature control. The kettle has stainless steel feed lines for oleic acid chloride and hydrochloric acid and caustic solution a stainless steel thermometer well and a lead vent pipe. Air for forcing the charge out of the kettle is introduced into the vent pipe.
A stainless steel kettle equipped with an anchor type agitator is also available. Process temperatures in this kettle are controlled by a steel jacket connected to both steam and cooling water lines. Inlets and vents are arranged similarly to those in the larger kettle.
To begin the batch 25 to 30 percent aqueous solution of N methyl taurine is blown over from the storage tanks until an amount of solution equal to 89.25 kg. of N methyltaurine has entered the weigh tank. The correct gross weight of this charge based on the N methyltaurine analysis of the storage tank is supplied to the operator by the analytical laboratory. This charge is then dropped by gravity into the reaction kettle and the flow of cooling water is started in the jacket to bring the temperature of the charge down to 22° to 25°C. Water weighed in the same weigh tank is then added to bring the total weight of the charge at that point to 1296 kg. Addition of 30 per cent aqueous caustic solution is begun and when the equivalent of 14.25kg. of sodium hydroxide has been weighed in oleic acid chloride is introduced from a lead lined weigh tank.
The caustic and acid chloride enters the kettle through separate perforated stainless steel pipes below the level of the initial taurine charge. This practice minimizes the liberation of noxious fumes reduces the corrosive effect of the acid chloride above the liquid level and safeguards against side reaction between sodium hydroxide and oleic acid chloride.
Simultaneous addition of the two reactants is continued for 4 to 6 hours until a total of 43.5 kg. of sodium hydroxide and 214.2 kg. of about 92 per cent oleic acid and chloride have been charged. The rate of addition of these two solutions is adjusted to maintain a slight stoichiometeric excess of sodium hydroxide in the kettle at all time as determined by spot tests on triazine paper 2 (4 nitro O tolyldiazoamino 4 sulfobenzoic acid).
After all the reagents have been added the charge is agitated for an additional hour to ensure completion of reaction. Cooling water is circulated through the coils at maximum flow rate during the entire reaction period. During the winter months the temperature of the charge is about 22°C at the beginning of the reaction and rises to 27°C. However in the summer time the final temprature may go as high as 40°C.
After the reaction has been completed a sample is taken and the percentage of excess N methyItaurine is determined by coupling with diazotized mnitraniline. It is desirable to have a slight excess of N methyltaurine in theproduct to ensure that the reaction has gone to completion. After completion of the reaction hydrochloric acid is added to the kettle through a glass and rubber siphon from a carbon mounted on a platform scale. Acid is added until the charge gives a slightly red spot test with brilIiant yellow paper (pH 6 to 8). This neutralization usually requires about 15.3 kg. of acid. In making some of the special Igepon products additional hydrochloric acid may be needed at this point.
In making the standard T gel the neutralized batch is diluted to 1734 kg. with water and 0.725 kg. of a light floral liquid perfume. The charge is then heated to 55°C and held there for 1.5 hours. The charge is blown into white oak gum or ash wood barrels. Air used to blow out the batch passes through a trap to remove rust particles which would tend to darken the finished product. As a further precaution against contamination a 0.007 opening stainless steel filter on the product discharge line removes all solid particles from the liquid product before it enters the shipping containers. The barrels are allowed to cool on the shipping platform and when the Igepon reaches a temperature of about 40°C it sets up as a firm opalescent gel.
Igepon T gel may be shipped in polyethylene lined fibre board drums or wooden barrels. The batch yields about 1090 kgs. gel having a composition of 15.3 to 16.3 per cent Sodium N oleoyl N methyltaurine 0.8 to 1.0 per cent sodium oleate 0.14 per cent N methyltaurine 4.0 per cent sodium chloride and 78 per cent water. This represents approximately the theoretical yield.
Igepon T Powder
In manufacturing this product the initial charge of 30 per cent N methyltaurine solution contains 95 kg. of 100 per cent N methyltaurine and when diluted with water to 1224 kg. it gives a slightly more concentrated solution than that used in the gel process. As a 30 per cent solution 17.6 kg. of sodium hydroxide are added to this intial charge to keep the reaction mixture on the alkaline side. Then 226.5 kg. of technical oleic acid ehloride are added simultaneously with 30 kgs. of sodium hydroxide as a 30 per cent solution over a period of 4 to 6 hours as in gel production.
The batch is stirred for 1 hour after charging is completed and any excess of N methyltaurine is reactcd with additional acid chloride and caustic soda as in the production of gel. The completely reacted charge is then heated to 50°C by the steam coils and neutralized to the brilliant yellow and point with hydrochloride acid. Immediately after neutralization 530 kgs. of common salt are dumped into the batch from bags and water is added to bring the total weight of the batch to about 2652 kgs. At this concentration about 36 percent solids the saIt is completely dissolved. It is important that no suspended solid material remains in the charge because it would plug up the nozzles of the spray drier. If the pH of the batch after the addition of the salt does not fall between 7.1 and 7.3 sodium hydroxide or hydrochloric acid is added to adjust the pH within these limits.
The salt loaded mixture is blown from the reaction kettles into a 3/8 lead lined sted feed tank. The charge is heated to 50°C by lead steam coils in the feed tank and then is pumped to the three 10 gauon feed pots of the spray dryer. The dryer atomizers use air at 80 Ibs/in2 pressure heated to maintain 501bs. pressure at the injection nozzles to ensure adequate atomization in the tower. Air supplied to top of the dryer is preheated to about 225°C by an oil fired furnace and forced into the dryer by a centrifugal fan at a rate of about 250 cubic feet per minute. The major part of the dried powder is discharged from the bottom of the dryer tower and carried along by the added cold air into the primary cyclone separator from which it drops directly into a transfer drum. About 10 per cent of the product however is carried through the cyclone and is reintroduced into the dryer chamber. A second take off from the dryer chamber is located just above the bottom taper. This duct carries a more dilute stream of air borne powder into a larger secondary cyclone separator. The solids which fall out in this separator are refluidized by more cold air and returned to the top of the primary cyclone. The overhead from the secondary cyclone containing 7 to 10 percent of the product is introduced into a water scrubber. One water spray above the inlet and three below remove all but about 2 per cent of the product from the dryer exhaust. The scrubbed air is vented to the atmosphere. The liquor is drawn from the bottom of the tower into a storage tank. Make up water is added to this tank by an automatic level control. A high silicon iron pump drawing from the tank recycles water to the spray nozzles and supplies process water to the condensation kettle.
If a kettle batch is made each day the dryer feed pots can be kept full and provide an uninterrupted feed to the dryer. Under these circumstances the dryer can handle as much as 180 to 200 kg. Igepon per hour as it has a rated capacity of 335 kg. water per hour. The product comes from the dryer as low density granules which are lightly milled in a paddle mixer to break up the larger lumps and to mix in 500 grams of a light floral perfume per ton of Igepon. From the mill the powder is dropped directly into the open top steel drums in which it will be shipped. Yields of powdered product run about 836.4 kg. per batch and analyze about 30.5 to 32.5 per cent oleoylmethyltaurine 1.5 to 3.0 per cent sodium oleate and 0.14 to 0.8 per cent N methyItaurine the remainder of the powder comprises inorganic salts. Chief among these is sodium chloride and a trace of sodium sulfate. However phosphite salts (about 3 per cent) are also present these are formed from the excess phosphorous trichloride dissolved in the oleic acid chloride. The yield is about 91 per cent of theory.
Chemical Control
Chemical control on the Igepon T operation is relatively simple. By experience rule of thumb knowledge can be accumulated which tells the operators whether the reaction is going properly. At some points analytical samples are taken merely as a precaution and only analyzed if trouble develops later in the operation.
The phosphorous trichloride oleic acid and N methyItaurine are checked for rigid spacifications each time a shippment of materials arrive at the factory. The acid chloride charged to the reaction kettle is analyzed the oleic acid chloride phosphorous trichloride and free fatty acid. After the condensation is complete the batch is checked for pH and residual N methyltaurine. The pH is checked by a standard calomel cell pH meter and is then adjusted as explained in the operation procedure.
After the pH has been adjusted it is checked again and the final shipping sample is sent to the laboratory. This final sample is examined for clarity viscosity and alkalinity. A 10 percent water solution of this sample must be perfectly clean and must have a pH between 7.2 and 7.5 at this point.
The Igepon T powder undergoes an almost identical analysis routine. If the content of oleoylmethyltaurine falls outside of the permissible limits it is blended into the subsequent batches at the ribbon blender.
Utilities
In the Igepon process steam is used only for process heating. Since the temperatures required are all reasonably low steam at 100 psi is adequate for this operation. Compressed air is used in the plant for forcing liquids from one vessel to another the 45 psi air is sufficient. The air used for transfering phosphorous tricoloride is passed through a dryer and filter to present hydrolysis and contamination. The purifying unit consists of a liquid trap a steel chamber 12 in diameter and 6 long filled with quick lime to dry the steam and a similar tank 4 long containing a cloth bag filler to remove any particles of lime or other solids that might be carried over into the phosphorous trichloride tanks.
The spray drier may have a separate compressor which provides 90 Ib/in2 air for atomization.
Materials of Construction
The corrosion problem is not critical in the operations as described but some special materials must be used. Carbon steel is suitable for most vessels. However those which must contain phosphorous trichloride or oleic acid chloride are homogeneously lead bonded. This type of lining is applied by tinning the entire inner surface of the steel vessel and then soldering the lead lining plates to the whole steel surface. This technique eliminates the problem of buckling and blistering. It also means that in the event of failure of the lining only the steel directly behind the gap in the lining is attacked. In the so called loose lining technique in which the lead sheets are tacked to the shell only along with seams a failure at any point usually means that the corrosive contents of the vessel will shortly enter the entire space between the lining and the vessel wall. The spray drier feed tank may be lined in this fashion but only moderate temperature are encountered in this tank and the agitation is never violent.
In general the lead linings in the Igepon process equipment last 7 to 9 years before they must be replaced. The reaction kettles may be of stainles steel. If however it is brick lined construction it may require re lining after about each two years. All equipment which comes in contact with finished liquid Igepon is made of stainless steel. since the detergent will exchange cations with ordinary steel to form iron salt which has an undesirable dark colour.
Submerged steam lines in the brick lined kettle are stainless steel in the spray dryer feed tank these are lead. The other kettles are equipped with external jackets. Agitators are either lead cov N Acyl N Alkyltaurates ered stainless steel or in the case of the spray drier feed tank wooden.Neither stainless steel nor lead will stand up in the duct which carries the moist exhaust from the spray drier. Nickel or high nickel alloy serves well. The spray drier itself is made of carbon steel.
Tanks which must with stand static pressure such as those employing air pressure transfer are entered and inspected and subjected to hydraulic testing every 2 years. Unpressurized steel tanks which store corrosive liquids are on a similar inspection schedule. Storage tanks in non corrosive service are inspected every 5 years. Kettles are also inspected at 5 years intervals. Jacketed kettles are lifted out of their jackets and the surfaces are cleaned and inspected for pits. Pits usually occur in the welded seams. If the welds are badly pitted below the surface of the adjacent plates the bead is chipped off and the seam rewelded.
Since most of the materials involved in the process are transferred through the plant by air pressure pumps present only a limited corrosion problem. Where pumps are used they are of motor driven centrifugal type. Where pure oleic acid must be pumped a high alloy steel pump is used. All other pumps are of carbon steel.
Stainless steel valves are used on all lines which transfer finished liquid Igepon T. Pipe lines which carry liquid Igepon T also are of stainless steel. Those which transfer oleic acid chloride are lead lined and steam traced. The steam tracing is only used in the winter when the acid chloride has a tendency to thicken and move sluggishly.
