RECENT DEVELOPMENTS IN SURFACTANT SYNTHESIS
The widely used nonionic surfactants include nonyl phenol-ethylene oxide (1:9.5) condensate, octyl phenol-ethylene oxide (1:9.5) condensate, fatty alcohol (cetyl/oleyl/stearyl alcohol)-etylene oxide (1:20) condensate, castor oil-ethylene oxide (1:40) condensate, fatty acid (stearic acid)-ethylene oxide (1:6) condensate, fatty amine-ethylene oxide condensate, fatty acid amide-ethylene oxide condensate (with different number of ethylene oxide) etc. Of these, nonionic surfactants based on nonyl phenol and octyl alcohol are not biodegradable and are toxic to aquatic organisms and hence are non-ecofriendly chemicals.
Certain nonionic surfactants are converted into anionics by sulphating the end primary hydroxy group. Thus, M. Shi have prepared several polyoxyethylene alkyl ether sodium sulphates and characterized them. The kraft point and critical micelle concentration of these compounds were also determined. The surfactant properties of triethylene glycol alkyl ether sodium sulphates (I) were found to be better than those of ethylene glycol (II) or diethylene glycol alkyl ether sodium sulphates (III).
Picture. 1
where R is fatty radical (perhaps lauryl, myristyl, cetyl, stearyl, oleyl).
Another series of anionic surfactants are synthesised in efficient, high yields. These are fatty acid monoglyceride sulphates, made from fatty acids (or fatty acid methyl esters), glycerine, chlorosulphonic acid in chloroform, using stoichiometric amounts of the reagents. Sodium coco monoglyceride sulphate was prepared in 79% yield with 93% purity from coco fatty acids. Similarly sodium palm kernel mono-glyceride sulphate in 57% yield and sodium palm monoglyceride sulphate in 71% yield were obtained from palm kernel fatty acid methyl esters and palm fatty acids respectively. This new synthetic method produced better quality products with higher active ingredients and improved yields without having to use high purity fatty acid monoglycerides and it reduced the undersirable aqueous sodium sulphate byproduct by 60% over a current commercial process. The composition and purity of the products were confirmed by cationic titration, infra red spectroscopy and C-NMR spectroscopy. The following reactions take place:
Sulphation of glycerine
Picture. 2
(Glycerine trisulphuric acid)
Condensation of the above product with fatty acid or fatty acid ester
Picture. 3
L. Milic have synthesised sodium stearoyl ethanol amide sulphate by first heating stearic acid ethanolamine at 140ºC to get the amide, followed by sulphating with chlorosulphonic acid in isopropanol or butanol at 30ºC and finally by neutralising with aqueous 18 M sodium hydroxide. The following reactions take place:
Picture. 4
The yield of the sodium salt is to the extent of 70.34-78.24%. This salt is stable under alkaline conditions but is hydrolysed in acid medium to give hydroxyethyl stearoyl amide
(C17H35-CO NH-CH2-CH2-OH)
A. Riva have carried out experiments to test a new auxiliary, which has been suggested as a substitute for an electrolyte (levelling agent) in wool dyeing with acid dyes. The experiments compared the traditional process using an electrolyte (sodium sulphate) with a process using an auxiliary along with an enzyme. The tests were carried out on wool fabric with C.I. Acid Blue 80, a nonionic auxiliary based on organic fats and enzyme, Proteasi Streptomices Fradiae. The new auxiliary gave results similar to the conventional method with regard to level of exhaustion and kinetics of absorption and had environmental advantages. The combined auxiliary and the enzyme gave slightly better absorption, but the levels of exhaustion were not sufficient to ensure low temperature dyeing. Dioctyl sodium sulpho-succinate, commercially known as "OT Paste" or "OT Liquid" is generally made by esterification of maleic anhydride and 2-ethyl hexanol (octanol of commerce), followed by sulphonation with sodium bisulphite. Some details of these reactions are available for the synthesis of an allied surfactant, dihexyl sodium sulpho-succinate.
The first reaction is carried out by esterifying maleic anhydride with hexanol in the presence of p-toluene sulphonic acid (PTSA) and then sulphonating with sodium bisulphite in the presence of azobisisobutyro nitrile (AIBN).
Picture. 5
The effects of the reactant ratio, addition of a azeotrope former (benzene or toluene), addition of catalyst (PTSA), temperature and reaction time on the synthesis were studied. The optimum conditions are: the mole ratio of hexanol to maleic anhydride is 2.2:1 to 2.25:1; reaction temperature, about 130ºC; the ratio of benzene to maleic anhydride, 2.5:1; the ratio of sodium bisulphite to the dihexyl ester 1.05:1; and sulphonating temperature, 110-115ºC (Perhaps the same conditions may be used for the synthesis of the corresponding di-octyl product, OT paste).
Nonionic surfactants
Ethoxylation of C9-11 alcohol waste fractions have been used by I. Premyanova for the production of inexpensive nonionic surfactants. These waste fractions are obtained during the production of 2-ethyl hexanol. The effect of temperature and degree of ethoxylation (n) on the surface tension and foaming capacity of 0.1-1.0% aqueous solutions of the ethoxylated products was deterimed. They found that the foaming capacity increased sharply, and the surface tension decreased with increasing n (2-6). These products are used as foaming agents in flotation and for the manufacture of detergents and emulsifiers.
Lauryl polyoxyethylene ethers with narrow molecular weight distribution have been synthesised, by ethoxylation of lauryl alcohol in the presence of calcium acetate. The molecular weight distribution of these surfactants was narrower and the content of unreacted lauryl alcohol was lower compared with that using sodium hydroxide catalyst, instead of calcium acetate. When the number of ethylene oxide moles was high the content of polyethylene glycol byproduct was about the same for both catalysts. The induction period of ethoxylation catalysed by calcium acetate decreased with increasing temperature. The suitable reaction temperature was found to be 140ºC. The reaction rate increased with increasing catalyst concentration at 1-5.3 mole-% and with increasing ethylene oxide pressure. The structure of the final product is given below:
C12H25-O-(CH2-CH2-O)-nH
Methyl ester ethoxylates, incorporating C6-18 fatty acids and ethoxylation degree of 1-20 are of interest as biodegradable surfactants. The compounds are prepared by C. Littau in a single step, waste-free process of direct ethoxylation of fatty acid methyl esters in the presence of Al/Mg catalyst via coordination/insertion mechanism. The detergency and Schlag foaming of the surfactants alone or in combination with anionic surfactants were evaluated in laundering of soiled cotton and cotton/polyester blend fabrics at 25ºC and 40ºC. The detergents show comparable or better detergency than that of commercial formulations, lower tendency to foam, faster foam breaking and significantly lower tendency to form gels. J. Szymanowsky have studied the surface activity of narrow range ethoxylated methyl dodecanoate with an average degree of ethoxylation from 3-14. The reaction of ethylene oxide with methyl dodecanoate was carried out in the presence of calcium-based w-catalyst (185ºC at 0.4 M Pa and catalyst content of 0.25%). The surface tension of solutions of the surfactant was determined by the ring method with tensiometer using tripple-distilled water at 22ºC. Various themodynamic parameters of these solutions were also determined. The effect of the average degree of ethoxylation on these parameters was determined. Micellisation was observed at a concentration of 4.5 Ã- 10-5M. Ethoxylated methyl dodecanoates exhibit surface activity similar to the classical alcohol ethoxylates.
The products made are:
Picture. 6
X-Lei Zhang have studied the synthesis of stearic acid monoethanolamide by a two-step method. The total mole ratio of stearic acid to ethanolamine was kept at 1:1.1. In the first the mole ratio was controlled at 1:0.7 and the reaction was carried out at 170°C for 4 hours. In the second step, the reaction was carried out in the presence of potassium hydroxide as the catalyst (0.076 mole/mole of stearic acid) and the remaining amount of ethanolamine was added and kept at 100°C for 4 hour more. The yield of stearic acid monoethanolamide reached 86.9%. The melting point of the final product was found to be 88-90ºC.
The overall reaction occurred:
Picture. 7
Two reactions are important for the manufacture of cationic softeners. In these stearic acid is condensed with either diethylene triamine or hydroxy ethyl amino ethylene diamine, followed by cyclizing to give the corresponding imidazoline derivatives:
Picture. 8
G. Hu and L. Zhou have investigated the mechanism of hydrolysis of II and of the corresponding imidazoline made from lauric acid and hydroxy-ethylamino ethylene diamine. The hydroylsis is catalysed by bases and inhibited by acids. The hydrolysis kinetic equations followed pseudo-first order. The effect of pH on the variation of rate constants and salf effect were observed. A hydroylsis mechanism was suggested in which the C-2 atom of the imidazoline ring (i.e. attached to the long alkyl chain) was first attacked by hydroxide and amides were then formed by reaction with water, with the intermediate compound. These results are useful for imidazoline-based surfactants.
Amphoteric surfactants
An amphoteric surfactant, (carboxy methyl) dodecyl dimethyl ammonium chloride, has been synthesised by Y. Fang and P. Qing. Initially dodecyl dimethyl amine (I) was prepared from dodecylamine and formaldehyde in the presence of formic acid. This amine is then reacted with sodium monochloro-acetate (II) to give dodecyl (carboxymethyl) dimethyl ammonium chloride (III). The structure and purity of the amphoteric auxiliary were determined. The effect of I/II ratio, r (mol/mol), reaction time, t, and reaction temperature, T, on the yield for the preparation of III were studied. The optimum conditions for 83.4% yield are as follows:
r=1.1; t=5 hour; T=75ºC
Recemic and optically active amphoteric surfactants, sodium salts of N-substituted amino acids (I) and amino alkane sulphonates (II) were prepared by S. Osanai to determine physico-chemical relations of cheril isomers with chemical structures among chiral isomers. The amphoterics had a phenyl ethyl group as the hydrophobic chiral centre.
The recimates showed no difference with optically active isomers with respect to the capacity to lower the surface tension and critical micelle concentration (CMC). The influence of the chain length of the hydrophobic group on CMC was essentially the same as that of the other types of surfactants, governed by Traube's rule, while the influence of the chain length between the two hydrophobic groups could not be determined exactly.
The pH of the solution affected the solubility of the amphoterics and an aqueous solution of the amino acid derivative surfactants became turbid at pH [ 4. The hydrophobic long alkyl group significantly influenced antimicrobial activity more than the chiral isomerism. N-Dodecylated homologues were more antimicrobial than N-decylated homologues.[/P]
- C12H25-NH-CH2-COO Na
- CH2-CH2-NH-(CH2)-nSO3 Na
Anionic surfactants
J. Cao has described the technology of sulphation of dodecyl alcohol, involving treating the alcohol with sulphur trioxide, followed by neutralisation with sodium hydroxide. Suitable production conditions are: sulphur trioxide concentration, 4.5-5.5%; reaction temperature about 40ºC, neutralisation temperature, 40-45ºC, and the pH of the final product, 7.5-9.5.
D. Brian have compared the surfactants derived from alcohols derived from petrochemical and oleochemical sources. Thus, samples of lauryl range alcohols, derived from palm kernel oil, coconut oil and ethylene (Zeigler) were converted into alcohol sulphates and alcohol ether sulphates (after treating with two moles of ethylene oxide). Physical properties and performance characteristics of each surfactant were evaluated both individually and in light duty liquid (LDL) dispersion-washing formulations.
The slight differences observed in the physical and performance properties of the surfactants and their formulations were assignable to the slight differences in the individual alcohol, alcohol sulphtae and alcohol ether sulphate samples employed in the study. The magnitude of type of variation found in the samples resulted from the normal production variation and not from any proportions inherent to the nature of the source of the alcohol. It is concluded that alcohol sulphates, ether sulphates and LDLs formulated from these exhibit identical physical properties and performance characteristics, regardless of whether the original alcohol was manufactured from petrochemical or oleochemical sources.
Synthesis of sulpho-succinate-type anionic surfactants have been dealt with by M. Matsuda. They have prepared sufactants having two long lipophile chains, such as sulphosuccinate-type surfactants and measured their surface tension (by Wilhelmy surface tension meter). The relevant alcohol and maleic acid (instead of maleic anhydride, which is normally used in such synthesis) using sulphuric acid catalyst. The sulphosuccinate was prepared by sulphonation of the ester formed in the first step, by using sodium bisulphite. The products (with different alcohols) by the above method were analysed by thin layer chromatography and C-NMR spectroscopy. The chemical shifts, d of the carbon atoms of the carboxyl group in the maleate and sulphosuccinate were measured at d = 165 ppm and + d = 169 and 171 ppm respectively. The critical micelle concentration (CMC) value was determined from the relationships of surface tension versus concentration graphically. The CMC value of sodium dioctyl sulphosuccinate was 4 Ã- 10-2 N/m.
Organic carboxylic acids can exist in their dimeric forms. Thus acetic, stearic and oleic acids are shown below in the dimeric forms:
Picture. 9
In all the above cases, two hydrogen bonds are formed between the ketonic oxygen and hydroxy hydrogen of the two acid groups.
J.P. Canselier and M. Paubert have published two papers on the surfactant properties of sulphonates prepared from monomeric and dimeric fatty acids. In one they have reported the sulphonation of free monomeric and dimeric fatty acids and some of their esters with sulphur trioxide or chlorosulphonic acid.
Adsorption and aggregation properties of the anionic surfactants formed through neutralisation with alkali or organic bases are studied, viz., surface tension lowering, foaming power and critical micelle concentration (CMC). Due to the presence of several hydrocarbon chains, solubility and CMC are much higher than expected, considering the total number of carbon atoms. Surface tension lowering of unsaturated dimer products is quite favourable, whereas their foaming power is about half as great as that of the corresponding sulphonated monomers.
On the whole, sulphonated unsaturated dimer acids and their esters show interesting surfactant performances. In another sulphonation of stearic and oleic acids, oleic acid dimer and their methyl, 2-ethyl hexyl or n-decyl esters in a batch reactor with liquid sulphur trioxide or chloro sulphonic acid is described. The sulphonation products were neutralised with various alkalies or organic bases, leading to the production of anionic surfactants. The surface tension, foaming power and CMC of the surfactants were measured.
The solubility and CMC values of the surfactants are found to be much higher than those expected for the longchain sulphonates. The surface tension of the unsaturated dimer sulphonate decreased with respect to their saturated analogs and for oleic acid n-decyl ester sulphonate the decrease is quite noticeable. The foaming power of the sulphonated unsaturated dimers is about half that of the corresponding sulphonated monomers. According to the physico-chemical properties of the sulphonated quasi-saturated dimers and to the evaluation of these properties with such surfactant structures, sulphonated unsaturated dimer acids and their esters perform better than similar saturated sulphonates.
Fatty acid acyl ester sulphonates have been synthesised by L. Daradics and J. Palinkas. For this purpose, coco and sunflower fatty acid chlorides were reacted with an aqueous solution of sodium sulphite and formaldehyde to give sodium fatty acid alkoxy methane sulphonates and soap byproducts:
Picture. 10
Hydrogen chloride produced is neutralised by sodium hydroxide released from sodium sulphite, which then releases further amount of sodium hydroxide. This is the route by which soap (R-COO Na) is formed as a by product.
The ester sulphonate/soap ratio is directly proportional to (Na2So3 + CH2O)/fatty acid chloride mole ratio and is in inverse proportion with temperature. The fatty acid acetyloxy methane sulphonates were determined in the presence of soaps by 2-stage titration using Hyamin 1622 (quaternary ammonium salt).
Nonionic surfactants
In the field of nonionic surfactants, synthesis and micellar properties of some homogeneously ethoxylated nonyl phenols have been reported by A. Voicu in which a convenient method is proposed for the same. The method consists of reacting p-nonyl phenol with the corresponding polyethylene glycol in the presence of dicyclo-hexylcarbodi-imide.
The yields of p-nonyl phenol trioxy-ethylene glycol monoether and p-nonyel phenol-octaoxyethylene glycol mono ether (NP-E8) were 17.2 and 13.5% respectively. The micelle concentration of NP-E8, obtained by the spectral change method was 1.9 Ã- 10-4 M, which is less than the corresponding value of a polydisperse ethoxy-lated surfactant (2.1 Ã- 10-4M).
New low-foaming surfactants were synthesised by Williamson's etherification of the hydroxy group of polyethoxylated fatty alcohols with benzyl chloride by E. Bednarek.
Earlier, the course of the reaction has usually been controlled by the detergent and the hydroxy number. Instead of using this method, the authors have used the 1H- and 13C NMR method. NMR spectroscopy was used to study the course of the reaction, as well as the number and structure of the reaction products. Water solubility, cloud point, foaming power and foam stability were determined for the products obtained. These properties depend on the alcohol use and on the degree of ethoxylation of the hydroxyl group. The final products have the following structure.
R-O-(CH2-CH2-O)n-CH2
where R is the fatty alkyl group.
S. Yapar and S. Peker have studied the synergistic behaviour of nonyl phenol-9 ethoxylate (NP-9 EO) and alkyl benzene dimethly ammonium chloride (ABDAC) binary mixtures. The interaction between ABDAC and NP-9 EO is expected to be very weak according to the criteria proposed by Rosen. The criteria for synergism were found to be in the order of magnitude of an anionic-cationic surfactant pair. The reasons for the strong interaction were explained with the help of the shift in the peaks of characteristic IR absorption bands. Disappearance of the peaks, corresponding to C-N stretches are appearance of the peaks of C-C stretching in the wavelength interval of 1250-1000 cm-1 region, was interpreted as the inclusion of the positively charged amino group of ABDAC the electrophilic ethoxylate group of NP?9 EO.
Cationic surfactants
A.M. crutzen has studied the interaction of ditallow dimethyl ammonium chloride (DTDMAC) with cellulose. A hydrophobic interaction model is proposed to explain the deposition of DTDMAC and other quarternary ammonium salt-based fabric softeners onto cotton fabrics. Due to its strong hydrophobicity, DTDMAC is expelled out of the aqueous rinse bath and deposits onto the available fabric surfaces.
Besides, its tendency not to leave the cotton surface and return to the solution (hydrophobic effect), DTDMAC binds to cellulose by weak London dispersion forces. The strong Coulombic interaction occurs only when a negative charge is present. Consequently, the strong affinity of DTDMAC for cellulose mainly results from the large specific area of the fibre; negative charges play a secondary role.
DTDMAC deposits onto charge-free surfaces; its deposition is mainly governed by the available surface area, not by the nature of the surface. Structural effects demonstrate the correlation between the hydrophobicity, deposition and softening power of quaternaries. The hydrophobic model accounts for the deposition of DTDMAC onto cotton and clarifies the facts that are not explained by the electrostatic model.
S.T. Giolando have studied the environmental fate and the effects of di (tallow fatty acid) ester of di-2-hydroxy-ethyl dimethyl ammonium chloride (DEEDMAC), which is a new rapidly biodegradable cationic fabric softener. They have introduced the environmental safety database for the softener. The physico-chemical properties of DEEDMAC are similar to those of DTDMAC, the major cationic surfactant used in the fabric softening formulations the worldwide over 30 years.
Importantly, however, DEEDMAC differs substantially from DTDMAC by the inclusion of two weak ester linkages between the ester and tallow chains. The ester linkages allow DEEDMAC to be rapidly and completely biodegraded in standard laboratory screening tests and a range of environmental compartments, including raw sewage, activated sludge, anaerobic digestor sludge, sludge amended soil and river waters. Removal of DEEDMAC during sewage treatment is more than 99%, as determined by computer model predictions and confirmed by laboratory simulation testing (OECD continuous activated confimatory test).
Using the estimated tonnages, per capita wastewater flows, incidences of sewage treatment for individual countries, measured removal rates, and validated computer models, maximum river water and soil concentrations of DEEDMAC have been established for representative usage scenarios. Based upon these maximum predicted environmental concentrations, acute and chronic toxi-city testing of fish, invertebrates and algae, predicted aquatic saftey factors range from 272 to more than 1,000. Predicted steady state terrestrial safety factors are more than 1,000 based on EC50 values to earthworms and plants, more than 50 mg/kg. The environmental saftey data base developed for DEEDMAC indicates that this cationic surfactant is rapidly and completely biodegraded, will be highly removed during sewage treatment, has an ecotoxicological profile similar to broadly used anionic and nonionic surfactants, and is environmentally safe at intended maximum usage volume.
Amphoteric surfactants
Palm and palm kernel fatty acids have been used for producing imidazoline amphoteric surfactants. They synthesised various imidazoline-type amphoteric surfactants from diethylene triamine and monochloracetic acid, based on palm oil and palm kernel
Picture. 11
oil fatty aids. The surface-active parameters of the surfactants, such as surface tension, CMC, antistatic electrical conductivity, dispersing power, wetting power, anti-rust and antimicrobial action, were determined. The advantages of palm-based amphoteric surfactants in terms of antistatic, dispersing and wetting power and rust prevention properties were described.
A new amphoteric surfactant has been synthesised by Z. Shi. For this purpose, lauric acid was condensed with N-b-hydroxyethyl ethylene diamine, cyclised to give imidazoline derivative, which was then reduced, formulated and finally quaternised with sodium monochloro acetate. The surface tension and foaming capability of this surfactant were determined. The following reactions take place during the synthesis of the surfactant:
Two studies on amido carboxy-betaine-type amphoteric surfactants have been reported. In one, M. Nakamura have examined some properties of aqueous solutions of amidocarboxy betaine-type amphoteric surfactants derived from dimeric and pentameric condensed castor oil fatty acid (ricinoleic acid) by comparing those of a surfactant derived from monomeric ricinoleic acid. Their surface tension, foam stability, calcium resistance, solubility in organic solvents, emulsifying property, permeability, dispersability and biodegradability were studied. In another study, T. Takeda have synthesised a bisamidohydroxy sulphobetaine-type amphoteric surfactant (ASHSB) from the reaction of dimethyl alkyl succinate, which is prepared from alkyl succinic anhydride with N-dimethyl-1, 3-propane diamine, followed by quaternisation with sodium-3-chloro-2-hydroxy propane sulphonate. The surface tension lowering ability of ASHSB was good and its dispersing ability of lime soap, excellent. The following reactions take place during the synthesis of the amphoteric surfactant:
Picture. 12
Miscellaneous surfactants
Hydroxyethyl cellulose-based polymeric surfactants have been prepared by I. Srokova. In this synthesis, hydroxy ethyl cellulose (degree of substitution, 1.3) was esterified with lauroyl chloride or stearoyl chloride in dimethyl formamide at 90-100ºC for 30 min -10 hours in the presence of pyridine as the catalyst to give derivatives which are soluble in water and have surface activity, depending on the degree of substitution and the degree of esterification.
Derivatives with esterification degree, not more than 0.01 showed good water solubility, high surface activity, good foaming ability and foam stability, excellent emulsifying ability, but not very high dispersing and laundering power. Surface activity of a novel fatty acid derivative has been reported by G. Zaho. They chormatographycally separated esterification products of carpylic acid and triethanolamine to get mono-, di-, and triesters:
Picture. 13
They found that the mono-, and diesters had surface activity similar to that of nonionic surfactants. The triethanolamine monoester showed strong interaction with sodium dodecyl sulphate in aqueous solution and the surface activity of the mixture (esters) was higher than that of the individual components, indicating synergistic effect in the mixture
B. Qiao have reported the synthesis of glyceryl mono laurate. This was prepared from glycerine and lauric acid by direct esterification. The influencing factors on the synthesis of the ester were studied.
The most favourable catalyst was found to be phosphoric acid and the optimum mole ratio of glycerine to lauric acid was 2.5:1. An yield of 99.27% of glyceryl mono laurate was obtained when the reaction was carried out at 180ºC for three hours. The content of glyceryl mono laurate in the product mix was more than 75.34%.
Phosphoric acid esters with high monoester content have been prepared by W. Schroeder and W. Rubach. This method of synthesis of 3.5:1 phosphoric mono/diester surfactant mixtures produces products with a higher monoester content (about 70%) than the conventional process (about 50%), regardless of the alcohol used i.e., from butanol up to C16-18 fatty alcohols with various degrees of ethoxylation.
The basic performance properties, such as foaming capacity, surface tension and interfacial tension are described. Skin tolerance studies indicate that these phosphoric esters with a high monoester content can be used more universally than the conventional phosphoric esters. The following products are formed:
Picture. 14
New types of cationic fabric softeners have been suggested by M. Brock. Thus, uarternisation of triethanolamine ditallow fatty acid ester by dimethyl sulphate in 30% propoxylated palm oil (PPO) instead of the usual 10% isopropanol, gives a product with comparable softening effect on textiles at a lower quaternisaton content.
The PPO acts as a solvent and shows a synergistic effect and has good biodegradability and toxicological acceptability. The following product is formed:
Picture. 15
Surfactant synthesis
Alkyl polyglycosides from different feedstocks have been prepared by M. Dopico. These nonionics were prepared from fatty alcohols, especially palmitic (cetyl) alcohol and n-octanol. Palmitic acid was first treated with sulphuric acid/methyl alcohol to obtain its methyl ester, which was then reduced to the fatty alcohol. The palmitic alcohol was mixed with glucose, p-toluene sulphonic acid was added as the catalyst and the reaction was allowed to proceed for 3 hours under nitrogen at 100-102ºC. The reaction mixture was neutralised with sodium hydroxide solution and the product palmitic glucoside, was separated by centrifugation, then distilled under vacuum. The n-octanol analogue was prepared in the same manner. The products obtained are of high purity, as verified by measurement of viscosity, refractive index, density, melting point, acidity value (acid value) and IR spectra. The polyglucoside surfactants are suitable for use in the manufacture of detergents, cosmetics, gels, pharmaceutical products, having good skin compatibility and are biodegradable and nonionic.
The influence of block structure on conformation and properties of carboxy methyl cellulose (CMC) series of polymeric surfactants has been studied by Y. Cao. A novel family of these surfactants were synthesised by them through ultrasonic irradiation. The polymeric surfactants prouced are block copolymers having low surface and interfacial tension, comparable to those of low molecular weight surfactants. The high molecular weight of the polymeric surfactants has only limited influence on the surface and interfacial activity. The excellent property displayed by the polymeric surfactants result from the special blocky structure, obtained during ultrasonic irradiation. CMC blocks contribute to the high viscosity and the surface active macro monomer blocks contribute to high surface activity.
In the manufacture of linear alkyl benzene (LAB) for n-paraffinic detergents, one of the raw materials comes usually from UOP MOLEX plant. Three LAB complexes were built in China in the past ten years but there are only two MOLEX plants, so the supply of n-paraffin has been in shortage. In order to find new materials to replace the paraffin, light ends, byproduct of Shell OXo plant was used in producing LAB. The properties of LAB produced by using light ends is compared with LAB produced with light paraffin. The LAB was used as the raw material in the manufacture of linear alkyl benzene sulphonic acid and give a total conrast to the sulphuric acid. It is believed that the sulphonic acid content of the product produced using this material is lower, its colour deeper than the normal sulphonic acid and it can be used in the situation that the requirement to the colour and purity is low.
An environmentally benign nonionic surfactant system has been developed by I. Johansson, based on the specific cloud point (CP) profile that can be achieved by mixing alkyl ethoxylates with alkyl glucosides. Alkyl ethoxylates are good wetting agents, emulsifiers and cleansing agents, but are not usually soluble in concentrated electrolytes and/or alkali. The alkyl glucoside surfactants have the polyhydroxyl functionality, as the hydrophilic part, arising from natural sources, such as carbohydrates, and offer better solubility and strong surface activity. When combining these two categories of surfactants, good solubility in alkali is achieved and a special concentration dependent cloud point curve results.
This phenomenon can be used both to fine-tune the detergency and wetting efficiency and to stimulate separation of emulsified oil from waste water. The C4-glucoside used was simulsol SL4 (DP-1), the C8 Akzo Nobel Surface Chem; the C5-, C6-, and C7 glucosides were prepared from glucose, isoamyl alcohol, hexanol, and Exxal-7 alcohol respectively; the ethoxylate C10- (4EO) is a commercial product; hydrotropes, sodium cumene sulphonate and octyl amino dipropionate (Ampholak YJH-40) were used as references. M. Dopico, have prepared alkyl polyglucoside surfactants from fatty alcohols, especially cetyl alcohol and n-octanol. Palmitic acid was first esterified with methyl alcohol in the presence of sulphuric acid catalyst to give methyl palmitate, which was then reduced to palmityl (cetyl) alcohol. This alcohol was mixed with glucose and p-toluene sulphonic acid catalyst and the reaction was allowed to proceed for three hours under nitrogen at 100-102ºC. The reactive mixture was neutralised with a solution of sodium hydroxide and the product cetyl glucoside was separated by centrifugation and finally distilled under vacuum. The octanol-analogue was prepared in the same manner. The product obtained are of high purity, as verified by the measurements of viscosity, refractive index, density, melting point, acidity index (acid value), and IR spectra. The polyglucoside surfactants are suitable for use in the manufacture of detergents, cosmetics, gels, pharmaceutical products, etc., and have good skin compatibility, are biodegradability and are nontoxic.
R. Clerici, have described the development and formulation of a stable gel laundry detergent system, based on anionic and nonionic surfactants. The surfactants used are linear alklyl benzene sulphonates [LAS Sirene X 12L and Isorchem 113], Lialet 125/7 [ethoxylated linear C12-15 alcohols], and Loradac 7/14 [ethoxylated linear C12-14 alcohols, Condea Augusta] in mixtures with soaps, based on cocofatty acid esters, water, propylene glycol, sodium hydroxide and ethanol. They have evaluated surfactant systems in terms of phase properties and selected optimum proportions for further formulation.
T
he detergent compositions contain in addition to surfactants, sodium citrate, sodium phosphonate, optical brightening agents, enzymes, dyes, and perfumes. Concentrated laundry detergents are also described, which comprise LAS, Lialet 125/7, dipropylene glycol, ethoxylated fatty alcohols, diethanolamine, triethanolamine, potassium hydroxide, water, alcohol, etc. A dishwashing formulation, based on sodium-LAS, ethoxylated alcohols, alkyl betaines, amine oxides and monoalkanol amines, is discussed. Detergent tablets, based on two components, LAS and carbonates or borates and EDTA as bleaching system in two layers or in a homogeneous mixtures are also discussed.
A two-step method for the synthesis of stearic acid diethanolamide has been reported by Q. Ning. This amide (I) is an oil-soluble nonionic surfactant and has the function of thickening. It has better emulsifying property for wax. As a coating additive, it can promote waxy and oily effect for leather finish. The two-step synthesis of I gives the product as pure as the product of ester exchange method. The proper conditions are as follows: The reaction was carried out at 170-175ºC with an inventory ratio of 1:7 for 4-5 hours in the first step and at 95ºC with catalyst for 2.5-3 hours in the second step.
The interaction of benzene sulphonate anion and its derivatives by the micellar system of tetradecyl trimethyl ammonium bromide (TTAB) has been studied by UV-VIS spectrophotometric method by B-Hwan Lee. The solubilisation constants (Ks) of benzene sulphonate anions into the micellar phase of this surfactant have been measured with the change of temperature. The effects of additives (n-pentanol and sodium bromide) on the solubilisation of benzene sulphonates by this surfactant system were also measured. There was a great decrease in the values of Ks and CMC (critical miceller concentration) simultaneously with these additives so that the measured values of Ink had linear relationships with the values of CMC. For the thermodynamic study, various parameters were determined and analysed from the dependence of Ks values on temperature. In addition to benzene sulphonate anion, p-toluene sulphonate and p-ethyl benzene sulphonate anions were also studied.
Toxicological studies
Collaboration between D. Hinks and cowokers and J. Sokolowsk has resulted in the design, synthesis, characterisation and genotoxicity of 4, 4'-diamino biphenyl (benzidine) analogues with substituents in the 3,3'- and/or 2,2'-positions. They found that 2,2'-dimethyl benzidine was mutagenic in the standard mammalian mutagenic assay in strains TA-98 and TA-100 with S9 metabolic activation. Hence, incorporation of a high dihedral angle across the biphenyl linkage does not appear to significantly reduce the genotoxicity of benzidine-type compounds. However, tetra-substituted benzidines, incorporating ]C3 alkyl or alkoxy groups in positions o,o' to the amino groups were found to be non-mutagenic, irrespective of chloro, methyl and methoxy groups in positions o,o' to the biphenyl linkage.
They have succeeded in synthesising tetra-substituted benzidines, 2,2'-dimethyl-5, 5'-dipropoxy benzidines, and 2,2'-dimethoxy-5, 5'-dipropoxy benzidine in good yield with minimal purification. Hence, the non-genotoxicity, and ease of synthesis of these intermediates in the synthesis of dyes and pigments. E. Barni, have synthesised novel azobenzene derivatives, containing a glucopyranoside moiety, characterised them by proton NMR technique and studied their genotoxicity by the Ames test and compared with p-methoxy-N, N'-dimethyl azobenzene (the basic dye molecule has no methoxy group).
Specifically, they synthesised the penta-acetate-b-glucoside of the above azobenzidine dye, and the corresponding free b-glucoside. They selected five strains of Salmonella typhimurium, TA-1535, TA-1537, TA-1538, TA-98, and TA-100 (Ames test) to evaluate the mutagenic properties of the above two dyes with and without exogenous activation. Both dyes appeared inactive in all the strains in the absence of metabolic activation. With S9 activation, the free b-glucoside-containing dye appeared non-mutagenic in all the strains, while the penta-acetate-containing dye was active in TA-1538 and TA-98, and inactive in the remaining strains. They have concluded that the b-glucopyranosyl group in the azobenzene dye reduces mutagenicity. In a recent study on the comparison between brominated flame-retardants and dioxins or organochlorine compounds in blood levels of Japanese adults. J. Nagayama determined the contamination levels of tetrabromo bisphenol-A (TBBPA) and polybrominated diphenyl ethers (PBDEs) in the blood of Japanese adults were compared with those of polychlorinated dibenz-p-dioxins, dibenzofurans, biphenyls (PCB) and pesticides. Mean level of TBBPA was around 1000-pg/g lipids. 2,2', 4,4', 5,5'-Hexabromo biphenyl ether showed the highest concentrations with the median level of 2,250 pg/g lipid. Taking eleven unidentified amino peaks into consideration, mean concentrations of total PBDEs were 4,946-pg/g lipids. Mean levels of organochloro pesticides and PCBs were 4-70 times higher than that of PBDEs. In dioxins the mean total crude concentration was about 28,000 pg/g lipid, 97.4% of which was attributable to coplanar PCBs and 5,600 times greater than that of PBDEs. PBDE levels showed a positive correlation with those of the total TEQ.
The drycleaning industry is worldwide in change as environmental reasons cause a diversification in solvents. While until now perchloroethylene (PCE) is the main solvent all over the world, some new organic solvents are going to be introduced in the industry. But this does not mean to ban PCE, but rather to make it more sustainable by reducing emissions. In some countries, wet cleaning processes try to substitute organic solvents, especially PCE. The Hohenstein Institutes have performed an extensive research on new solvent PCE/water, in order to find reasonable solutions for both-the drycleaning industry and the environment.
In the future, PCE can only be used for drycleaning purposes, if loss into air and ground water is strictly reduced. Research works have shown that the emissions caused by insufficient drying processes in drycleaning machines, can be reduced by more than 70% when using a technologically innovative drying system. Another source of emissions is the residual PCE in the drycleaned textiles. Research results have shown that there are significantly different contents of PCE in textiles. Consistent reduction of transfer of PCE via textiles to remarkable reduction of the workroom concentration.
Effluent decolorisation
Some ecological and toxicological aspects of dyeing have been discussed by V. Rossbach. Dyes and dyeing require light to give the colourfulness necessary to satisfy the ever-changing fashions and purpose-oriented needs of the consumer. The public also expect a flowless dyeing to have good fastness to light, washing and rubbing. In the last few decades, the dye producer, dyeing mills and textile machinery manufacturers have all been striving to meet these demands as well as that for intense/strong colours and to turn them into commercial reality. However, they discovered that in the end, these obviously so successful developments have also their dark side. The increasingly uneasy consumer no longer accepts e.g., the temporary discoloration of natural rivers and streams through washwater from dyeworks. The basis for the good fastness properties of dyed textiles is the excellent stability of dyes against all possible types of influences. A consequence of this stability is that these dyes are not readily degradable in the washwater treatment plant. It is also shown that azo dyes are degradable by anaerobic/aerobic processes. In vitro studies have revealed that certain azo dyes can be reductively split into carcinogenic amines by human skin bacteria. Some other dyes have the potential to cause skin or respiratory allergies. The different ideas for solving these problems range from the revival of natural dyes, over the labelling of the textile contents to the dyeing of textiles in super critical media.
Colour in effluents poses a major problem in industries, such as dyestuff and textile industries, distilleries and tanneries. Apart from projecting an image of water being unclean, coloured water, containing azo dyes, is now thought to be mutagenic, carcinogenic and toxic. Keeping these factors in mind, S. Murali and A.E. Narayan conducted a laboratory scale study on decolorizing dyes. Since biological methods of decolorisation are inherently advantageous to physical and chemical methods, they were used in the study, in which Aspergillus niger was employed to decolorise different concentrations of Methyl Red solution, which gave encouraging results. In the second trial in which rot fungi polyporus hirsutus was used to decolorise Congo Red, a dye known to be resistant to degradation, where nearly total decolorisation was obtained. This in indicative of polyporus hirsutus's excellent aromatic compound-degrading capacity.
In another study, oxidative degradation of dyes and a surfactant in the Fenton and Photo-Fenton treatment of dyehouse effluents has been studied by F. Ferrero. Crystal Ponceau 6R (CI Acid Red 44) and Methylene Blue (CI Basic Blue 9) were the dyes and nonyl phenol-ethylene oxide (1:10) adduct was the nonionic surfactant selected for the study. Fenton's reagent (ferrous sulphate and hydrogen peroxide) was used in the presence and absence of UV irradiation (low pressure 500 W tubular mercury lamp). The degradation kinetics were followed by measuring the residual total organic carbon (TOC) value, as a function of time at different initial TOC concentrations and temperatures. The curves interpolating the kinetic data show that the residual TOC values attained a stable level after a given treatment time; a similar trend was observed in the treatment of some dyehouse effluent samples. The TOC removal rate was found to depend on reagent concentration, initial TOC value and UV irradiation. The latter strongly accelerated the degradation reactions and considerably reduced the residual TOC. Temperature, however, was not found to be very influential. The same behaviour was observed in dyehouse waste water treatment, indicating that this type of approach could provide the basis for evaluating the effectiveness of Fenton and Photo-Fenton treatments of dyehouse effluents.
In a yet another study, S. Papic, have developed a method for removing reactive dyes from waste water, using the coagulation-flocculation process for the purpose, using ferric chloride hexahydrate as the coagulant. The method was found to be very effective with a more than 95% colour removal. Typical representatives of monochloro-triazine reactive dyes with azo and anthraquinone chromphores were CI Reactive Red 45 and CI Reactive Green 8, were selected for the study. In this method, there is an optimum pH that is dependent on the amount of the coagulant added and the type of the dye.
For waste waters, containing the chosen model dyes above mentioned red and green dyes) the optimum pH values were 2.55 and 2.70 respectively, and 6 kg/cu.m. and 3 kg/cu.m. ferric chloride hexahydrate respectively. The optimisation of initial rapid mixing, which has an important role in the overall coagulation process efficiency, was carried out. The optimum combination of velocity gradient and the duration of rapid mix was suggested for the treatment of reactive dye waste water. The optimal rapid mix velocity gradient of 400/sec and the duration of 30 sec are recommended.
J. Oakes has studied the influence of surfactants on homogenous and heterogeneous sodium hypochlorite oxidation of azo dyes-1-phenylazo-2-naphthol-6 sulphonic acid; 2-phenylazo-1-naphthol-3, 6-disulphonic acid; and a commercial reactive dye with both monochlorotriazinyl and sulphatoethyl sulphone groups, popularly known as ME-dyes. A kinetic and spectroscopic investigation of the oxidation of the dyes, bound to cotton has been studied. It was found that the physical state of the bound dye, e.g., pKa value, tautomeric form and its oxidation profile with pH, are similar to those of the dyes in solution, suggesting that the mechanism in homogeneous and heterogeneous oxidation is similar. The oxidation rates of the second dye by hypochlorite were unaffected by the presence of anionic (sodium dodecyl sulphate) or nonionic (lauryl alcohol-ethylene oxide (1:5) adduct) surfactants, either in the micellar or sub-micellar regions, indicating that dye-surfactant interactions are absent. Specific dye interactions were observed with cationic surfactants (cetyl trimethyl ammonium tosylate and lauryl trimethyl ammonium chloride) in sub-micellar regions. In micellar regions, the dye becomes incorporated into the surface of the micelles and is rendered inert to reaction with hypochlorite.
In another study, I.R. Hadrin, investigated the decolorisation of textile waste water by selective fungi. A way to decolorise waste water, that eliminates the need for inorgnic oxidizing agents, such as ozone or precipitating agents, such as polymeric flocculants. This biological approach is unique to the industry, and builds on expertise gained from experience with white rot fungi (e.g., P. Chrysosporium) that have been isolated and characterised. Enzymes, such as laccases and manganese peroxidases can cleave aromatic rings. These have potential for destroying dyes through individual enzymes, capable of breaking down one type of dye molecular structure and from attacking another dye structure. Another drawback of the specific enzyme approach may be the reaction rate.
Advantage is taken of the environmentally friendly action of enzymes and use the entire micro-organisms to decolorize waste water. The fungal degradation was carried out using CI Direct Red 16, Acid Blue 113, Acid Yellow 17, Disperse Blue 73, and Vat Golden Yellow RK (the structures of the last two dyes are interchanged by an error). It was found that the fungi can decolorise the dyes faster in nitrogen-limit medium than in nitrogen-sufficient medium.
The change of environmental loads of surfactants has been established by Y. Kobuke by using a simple model developed from the statistical treatments of surfactant products. The practical application of this model in the cities of Hyogo Prefecture elucidated that the yearly changes of estimated loads of anionic surfactants were in good agreement with those of riverine methylene blue active substance (MBAS) concentrations, indicators of synthetic anionic surfactants.
The analysis of nationwide loads of surfactants indicated that the load of anionics reduced significantly since 1993 due to the decrease of the production amount itself and the differentiation of sewerage, whereas that of nonionic surfactants remained unchanged at the level of 1992. The analysis for the environmental loads of surfactants in seven cities of Hyogo Prefecture also led to similar results.
SYNTHESIS OF SURFACTANTS AND THEIR TOXICITY-IV
Trends and technical developments in laundry products in Japan have been traced by M. Tsumadori. It is pointed out that since launching the first compact powder laundry detergent that has a dosage of 25 gm/30 litres, sales of these compact powders have taken over conventional powders and liquids. Since the middle of 1990s, a further progress in compaction is seen. At present, ultra compact detergents, having a dosage of 20 gm/30 litres and 15 gm/30 litres have caputred a dominant market share. The spreading of compact and/or ultracompact detergents has led to a change in the consumption of surfactants. Although LAS is still the main ingredient for compact powders fatty alcohol ethoxylates and a-sulpho-fatty acid esters have gained a stronger position in surfactant markets. Other recent developments and trends include detergents formulated with bleach, employing various types of bleach activators, tablet detergents, and sheet type detergents have also been introduced into the Japanese market. In the fabric softeners market, concentrated products are gradually becoming dominant. Most of these are sold in eco-type (economy-type) packages, which make a significant contribution to save resources. As well, a readily biodegradable softening agent has been employed as a main ingredient in Japan. Another exciting major innovation has been in bleaching. Since 1990, the use of liquid oxygen bleach has been increasing steadily. In 1996, the first liquid oxygen bleach, formulated with a long chain activator, satisfying both superb bleaching performance and activator stability was launched. It has gained a strong position in the market. Glycosides are one group of ogranic compounds, which can be split by hydrolysis into sugars and other organic compounds known as glycones. Specifically glycosides are acetals (addition compounds of an alcohol and an aldehyde) derived from various hydroxy compounds with various sugars. They are called individually as glucosides, mannosides, galactosides, etc. Glycosides were formerly called glucosides, but the latter term now refers to any glycoside having glucose as its sugar constitutent. The various reactions mentioned above are shown below:
Acetal formation
Picture. 16
When the acetal is formed from aldehyde and hydroxy groups present in the same molecule, the resulting compound is called a hemiacetal. Thus the linear structure of b-glucose leads to the formation of the ring form (hemi-acetal):
Picture. 17
Picture. 18
Diastereoisomers
In any group of four optical isomers occurring in compounds containing two asymmetric carbon atoms, such as 4-carbon sugars, there are two pairs of enantiomers (structures, which are mirror images of each other) indicated by the letters D and L.
The two D and the two L isomers are not mirror images and these are called diastereoisomers. Thus, in the structures given below:
(1) And (2) and enantiomers, and so are (3) and (4); (1) and (3), and (2) and (4) are diastereoisomers:
Picture. 19
An epimer is an isomer which differs from the compound with which it is being compared only in the relative positions of hydrogen and hydroxyl. The isomerism may be represented as -H-C-OH and -HO-C-H-. It is common in sugars. An anomer is a specific kind of diastereoisomer (or epimer) occurring in some sugars and other substances having asymmetric carbon atoms.
Sugar esters
The primary hydroxy group of a hexose (e.g., glucose) can be esterified with a fatty acid to give sugar ester. Glucose stearate, laurate etc. are such surfactants:
Picture. 20
Fructose C6H12O6
This is a sugar occurring naturally in a large number of fruits and in honey. This occurs in both pyranose (I) and furanose (II) forms:
Picture. 21
Saccharose or sucrose or table sugar C12H22O11
This is called b-D-fructo furanosyl-a-D-gluco pyranoside. On hydrolysis by dilute acids or by invertase (yeast enzyme), it forms a-glucose and fructose. This mixture is called invert sugar.
Picture. 22
D-Mannose
This occurs in guar gum, alongwith galactose. This is a carbohydrate (hexose). It has the following structure:
Picture. 23
D-Galactose
This is a constituent of many oligo- and polysaccharides occurring in pectins, gums (guar gum, locust bean gum, etc.) and mucilages. This has the following structure:
Picture. 24
b-Glucosamine
This is found in chitin, muco-proteins and in mucopolysac-charides. This has the following structure:
Picture. 25
Anionic surfactants
L. Cohen have synthesised sulphoxylated methyl esters (f MES) via sulphoxidation of fatty acid methyl esters with a mixture of sulphur dioxide and oxygen in the presence of UV light of appropriate wavelength. The resulting products may be used as co-surfactants with alkylbenzene sulphonate and alkyl ether sulphate, either in heavy duty or hand dish washing liquids. Standard hand dish washing formulations, based on f MES-C16 are presented and discussed with regard to solubility, viscosity, performance and skin compatibility. The experimental results obtained indicate that the above mentioned products can be regarded as potential components for liquid formulations. The f MES-16 can be prepared as follows. These are also called a-sulphofatty acid esters.
Picture. 25
In continuing the study on polymeric surface active agents, N.H. Jeong have synthesised anionic polymeric surfactant with a-sulpho alkanoic acid. Specifically, dodecyl polyoxyethylene-a-sulpho alkanoates have been synthesised through the esterification of dodecyl poly (ethylene glycol) and a-sulpho alkanoic acids with straight chain alkyl groups having 10-18 carbon atoms. a-Sulpho alkanoic acids were obtained by reaction with long chain alkanoic acids with sulphur trioxide-dioxane complex, and dodecyl PEGs by addition reaction with dode-cyl alcohol and ethylene oxide (5, 10, and 20 mole) respectively. All the synthesised products can be separated by means of TLC and column chromatography and their structures have been characterised by IR, 'HNMR and elemental analysis'.
Cationic surfactants
Cationic imidazoline surfactants have been synthesised by H. Sheng Zhong. For this purpose, palmitic acid and diethylene triamine (DETA) were reacted under reduced pressure to form 2-alkyl-l-amino ethyl imidazolene, a ring compound (I):
Picture. 26
Then dimethyl sulphate (DMS) was added dropwise and the quaternary compound, i.e., cationic imidazoline surfactant was obtained. Reaction temperature, pressure and operation time were studied. The yield under optimum conditions was 85% and the purity of the product was 93%. The final product has the following structure:
Picture. 27
A new cationic surfactant has been synthesised by K. Yne. This was made from benzoic acid, DETA, steraric acid and epichlorohydrin acid cyclisation to give an imidazoline derivative, reduction, ring opening, amidation and quaternisation.
The reduction-ring opening conditions include molar ratio of the imidazoline intermediate to sodium borohydride (NaBH4, a strong reducing agent) 1:2; reaction temperature, 20ºC for 1 hour at pH 7 in isopropanol (IPA), acting as a solvent. The probable sequence of reactions is as follows:
Picture. 28
Another product is reported and is made by the same reaction, except that benzoic acid is replaced by phenyl acetic acid.
In another case, P. Jiang, have synthesised new types of polymerisable dimethyl dodecyl methacryloyl ethyl ammonium bromide, which was prepared from dimethyl iminoethyl methacrylate and dodecyl bromide:
Picture. 29
The final quaternary compound can polymerise at the ethylenic function of the compound. The polymerisable compound had a critical micellar concentration of 6 Ã- 10-5 m/litre. The electrical conductivity study revealed that there were three regions in the micro emulsion, viz., W/O region, [ 20%, a bicontinuous region, 20-65%; and an O/W region, ] 65%.
F. Wang have described the properties of alkyl imidazoline ester softener and of its quaternary ammonium salt. It appears that it is made by using a fatty acid, hydroxy ethyl amino ethylene diamine, a carboxylic acid (perhaps benzoic acid or phenyl acetic acid) and epichlorohydrin (or dimethyl sulphate). The final product may have the following structure:
Picture. 30
Two other possible structures are the same as above but the quaternising agents are interachanged (DMS and epichlorohydrin). This compound has softening antistatic and rewetting properties. The quaternary compound has good properties and is easy to formulate products of high concentrations and of low viscosity.
Nonionic surfactants
Direct ethoxylation of a long-chain aliphatic ester has been reported by W. Hreczuch. In this case, 2-ethyl hexyl laurate, as an exemplary longer chain aliphatic ester, was subjected to direct ethoxylation. The synthesis was described and the obtained products were analysed qualitatively by means of mass spectrometry and chromatography. Solubility of the obtained ethoxylates was studied by the determination of their cloud points in selected model solutions. It was shown that longer chain aliphatic esters are feasible as new materials for ethoxylation in the presence of an appropriate catalyst (perhaps calcium oxide). They undergo an effective and selective reaction with ethylene oxide without the formation of excessive amounts of byproducts. The obtained products exhibit typical properties of ethoxylate-type nonionic surfactants. Their solubility in water and butyl diglycol solution was relatively lower compared to their methyl ester equivalent. Perhaps the final product is formed in the following manner:
Picture.31
Synthesis of a series of ethoxylated fatty acid methyl esters with a discussion of reaction path ways has been described by W. Hreczuch and J. Szymanowski. These new perspective nonionic surfactants were obtained in a one-step process from fatty acid methyl esters. The path way of direct oxyethylation of fatty acid methyl esters was discussed and compared with the oxyethylation of typical hydrophobic reagents with a labile hydrogen. Various possible mechanisms and catalysts, including homogeneous and heterogeneous catalysts, were discussed and compared. The composition and homologous distribution of oxyethylates was discussed. It seemed that although direct oxyethylation of fatty acid methyl esters could be carried out in the presence of various catalyts, the role of acidic catalysts were very important. In heterogeneous catalysis, ethylene oxide reacted with a leaving methoxy group and the recombination gave a final product with a high selectivity. In the homogeneous catalysis, the oxyethylation of polyvalent metal alkoxide, followed by transesterification with the fatty acid methyl esters was postulated. Polyoxyethylene glycol monomethyl ether and polyoxyethylene glycol diesters of fatty acids were formed as byproducts.
Sugar-based surfactants
When sugars are etherified with alcohols or esterified with fatty acids, surfactants are produced, in which alkyl groups act as hydrophobic portions and the many hydroxy groups of the sugars as hydrophilic centres. A number of studies on the synthesis and properties of such surfactants are reported. Thus, K. Fukuda have reviewed the physical properties of sugar-based surfactants, such as alkyl glucosides, alkyl maltosides (acetals), sucrose mono-alkanoates (esters) and alkanoyl glucosides with their anomeric effects of the head group, sugar. Phase behaviours of surfactant-solid and surfactant-water two-component systems for a-anomer of alkyl glucosides differed considerably from that of b-anomer. Chain length effects of the hydrophobic group on phase behaviour of alkyl glucoside-water system were studied for b-anomers and a liquid-liquid phase separation region was confirmed to exist for decyl-b-glucoside (0.1-17 weight-%) [but not for octyl and nonyl-b-glucoside]. The growth of micells of decyl-b-glucoside would thus appear to be prompted by increase in surfactant concentration and micellar network structure was noted to form at ] 17 weight-% solution. The size and shape of micellar aggregates for octyl glucoside, dodecyl maltoside and octanoyl glucoside showed significant anomeric effects.
X. Gu has reported direct synthesis of alkyl glucoside from glucose and lauryl alcohol by glycosidation. This was carried out in the presence of self-made (in situ) composite catalyst by direct glycosidation. The effects of catalysts, temperature, ratio of glucose to lauryl alcohol and processing of raw materials on the reaction were studied. The optimum reaction parameters are: pressure, 4.05 KPa; temperature, 120ºC; mol ratio of lauryl alcohol to glucose, 5:1; and weight ratio of catalyst to glucose, 0.008:1.
A biosurfactant has been prepared enzymatically from fructose and palm fatty acid and its properties have been determined by R.A. Rahman. For this purpose, fructose and palm fatty acid distillate (PFAD) were reacted with each other in the presence of Lipozyme I M as a biocatalyst. Analysis of its physical and chemical properties showed that this surfactant had a melting point of 49-52.3ºC and an HLB value of 16, which is in the suitable range for use in cosmetics, detergents and foods. This surfactant, which is a fructose ester, also reduced the surface tension of water to 38.3 dynes/cm. The structure of the surfactant is shown below:
Picture.32
where R-COO comes from palm fatty acid residue.
Ho-I, have synthesised readily biodegradable noionic surfactants of glucamide, N-alkyl-N-acyl glucamine by a two-step reaction. The first step was the amination of glucose by an alkylamine in methanol. Then the alkyl glucamines were obtained by reduction using a nickel catalyst under high pressure, which resulted in 86-93% yield. The second step was the synthesis of glucamides from alkyl glucamines and fatty acid methyl esters in methanol under alkaline catalytic conditions under reflux. The yield of this step was 84-95%, except of benzyl glucamine, which was 50-70%. The molecular structure of alkyl glucamines and glucamides with different alkyl and acyl groups was studied by IR, MS and NMR spectromerty. The following reactions take place:
Picture.33
Picture.34
Surfactants from glucamines and a-epoxides have ben studied by S. Warwel et. al. Specifically, the synthesis of sugar-based surfactants by ring opening of a-epoxides with amino polyols based on glucose is described. By reacting a-epoxides with chain length C4-C18 or styrene oxide with N-methyl glucamine, N-dodecyl glucamine or glucamine under mild conditions in methanol or methanol/water mixture. N-2-hyroxyalkyl-N-methyl glucamine, N-2-hydroxyalkyl-glucamines, and N, N-bsis (2-hydroxy alkyl)-N-dodecyl glucamines, and N, N-bis (2-hydroxyalkyl) glucamines were obtained in high yields (70-100%) with purity of ]95%. Depending on the glucamines used, the products may have a linear structure of Y-type structure with two hydrophobic alkyl chains of equal or differing chain lengths. Studies of these surfactants and their hydrobromides, which were obtained by acidification, demonstrate different surface properties in aqueous solutions. Measurements of their critical micellar concentration (CMC) values were successful for several of the products. Some of the CMC values are in the range 2-500 mg/litre. Some of the synthesised sugar-based surfactants reduce the surface tension of water down to 25 mN/m (N-2-hydroxydodecyl-N-methyl glucamine) and N, N-bis (2-hydroxydodecyl-N-methyl glucamine at pH 2). Most of the ring opening products are rather poor foamers, whereas some of the corresponding hydrobromides show good foaming properties. The structures of some of the final products are shown below:
Picture.35
Picture.36
Toxicity of surfactants
Commerical surfactants like linear alkyl benzene sulphonates (LAS), alkyl sulphates (AS) and akyl ethoxy sulphates (AES), alkyl ethoxylates (AE), alkyl phenol ethoxylates (APE), cetyl trimethyl ammonium bromide (CTAB), etc. are synthetic chemicals, used in large amounts in detergents, soaps, shaving creams, fabric softeners, additives for food, paint, leather, and textile items, pesticides, defoliants, antiseptics, disinfectants, etc. Several types of toxicity tests conducted on them indicate that chronic toxicity of anionic and nonionic surfactants occur at concentrations of ]1 mg/litre (1 ppm). Their effects on several behavioural and physiological parameters range from 0.002-40 ppm. The most common test compounds have been LAS with single species, such as Daphnia Magna, fathead minnow and benthic midge. Of the sixty reports reviewed, those describing the toxicites of the mixtures, containing surfactants are numerous. The effects of most surfactants on the structural and functional aspects of animal communities in nature are unknown. C. Verge and A. Moreno have studied the effects of anionic surfactants on Daphnia Magna (a type of fish). In this study, the acute toxicity at 48 hours of various linear alkyl benzene sulphonates (LAS), alkyl sulphates and alkyl ethoxy sulphates to Daphnia Magna was determined. Also chronic toxicity tests were carried out with the same test species. The study was carried out to obtain a valid set of data of the above surfactants for environmental classification and labelling according to European legislation. The results (LC50]1 ppm) indicate that neither commercial LAS nor the alcohol derivatives, which are used in the household products should be classified as dangerous for the environment with respect to their effects on Daphnia Magna. The relationship between the interfacial properties of surfactants and their toxicity to aquatic organisms have been studied by R.J. Rosen et al. In their previous work they have shown that the toxicity of several anionic and nonionic surfactants to rotifer (Brachionus calyciflorus) is highly correlated with the interfacial activity. In the present study, the relationship between interfacial properties of surfactants and their effects on aquatic organisms is extended to include toxicity of cationic surfactant class (homologues of alkyl trimethyl ammonium chloride and alkyl hydroxy ethyl dimethyl ammonium chloride to green algae (selenastrum capricornutum) and the bioconcentration of linear alkyl benzene sulphonate (LAS) isomers and homologues by fish (pimephales promelas and Ictalurus punctants).
In each case, the interfacial activity is expressed by the physico-chemical parameter, DGºad/Amin, where the numerator is the standard free energy of adsorption of the surfactant at the air/solution interface and Amin is the minimum cross-sectional area of the surfactant, or the analogous parameter Dºs Gºad/ls Amin, at the solid/liquid interface, where the solid is an immobilised artificial membrane that mimics a biological cell membrane. The general nature of the relationships between interfacial activity of the surfactants and their biological effects in aquatic systems indicate that sorption to biological membranes is a critical parameter for predicting and understanding environmental effects. While specific interactions probably occur once a surfactant has penetrated a membrane bilayer, nonspecific hydrophobic interactions appear to be driving the sorption process.
In clinical practice, cutaneous exposure to a variety of irritants such as surfactants and solvents is frequent. Although the induction of irritant dermatitis (skin disease) by single irritants has been extensively studied in recent years, the knowledge of the effects of simultaneous application of different irritants is limited. In view of this W. Wigger-Aberti, studied experimental irritant contact dermatitis due to cumulative epicutaneous exposure to sodium lauryl sulphate (SLS) and toluene. Specifically, single and concurrent applications were studied. Using non-invasive techniques for the measurements of transepidermal water loss (TEWL) and skin colour reflectance, the irritant effects of single and concurrent application of 0.5% SLS and undiluted toluene (TOL) in vivo were quantified. The irritants were applied twice daily for 30 min to the volar fore arms of twenty volunteers. Repeated application of SLS+TOL induced an irritant reaction, as indicated by an increase in TEWL and skin redness. In contrast to SLS alone, the application of TOL is alone induced only moderate TEWL, confirming the previous results. Concurrent application of SLS/TOL and TOL/SLS induced significantly stronger reactions than those caused by twice-daily application of each irritant on its own. The results indicate that a mixed application of an anionic detergent and an organic solvent has an additive effect on skin irritation. It is suggested that a pretreatment with SLS causes an increased susceptibility to TOL irritation and vice versa. Thus, the necessity for special precautions against skin absorption of TOL, when handling detergents such as SLS is emphasised.
A four-part series on the effects and risk assessment of linear alkyl benzene sulphonates (LAS) in agricultural soils has been reported. In the first part, L. Eisgaard, have dealt with short-term effects on soil microbiology. LAS may be present in sewage sludge that is applied to agricultural soil, in which the LAS can be inhibitory to biological activity. As a part of the broader risk assessment of LAS in the terrestrial environment, short-term effects of LAS on microbial parameters in a sandy agricultural soil that was incubated for up to 11 days. The assays included ten microbial parameters-(1) ethylene degradation; (2) potential ammonium oxidation; (3) potential dehydrogenase activity; (4) b-glucosidase activity; (5) iron reduction; (6-8) the populations of cellulolytic bacteria, fungi, and actinomycetes; (9) the basal soil respiration; and (10) the phospholipid fatty acid (PLFA) content. Except for b-glucosidase activity, basal respiration and total PLFA content, all the other soil parameters were sensitive to LAS with EC10 values in the range 8-22 mg/kg dry weight. This probably reflected a similar mode of LAS toxicity ascribed to cell membrane interactions and showed that sensitivity to LAS was common for various soil microorganisms. The extra-cellular b-glucosidase activity was rather insensitive to LAS (EC10, 47 mg/kg dry weight) whereas the basal soil respiration was not inhibited even at 793-mg/kg dry weight. This was interpreted as a combined response of inhibited and stimulated component of microbial community. However, PLFA content showed no decrease even at 488 mg/kg. In conclusion LAS inhibited specific microbial activities although this could not be deduced from the basal respiration or the total PLFA content. The lowest EC10 values for microbial soil parameters were slightly higher than the predicted no effect concentrations (NEC), recently derived for plants and soil fauna (5 mg/kg dry weight).
In the second part, L. Eisgaard studied the effects of LAS on soil microbiology as influenced by sewage sludge and incubation time. This surfactant may inhibit soil microorganisms. For five microbial parameters-(1) microbial biomass C and (2) the potentials of iron reduction; (3) ammonium oxidation; (4) dehydrogenase activity; and (5) aryl sulphatase activity the effects of aqueous LAS and LAS-spiked sewage sludge added to existing levels of 0, 3, 8, 22, 62, 174 and 488 mg/kg soil dry weight in a Danish agricultural soil that was incubated for 5 days to 8 weeks were compared. Aryl sulphatase activity (measured after four weeks of incubation) was rather unsensitive to LAS, with an EC10 value of 222 and ] 488 mg/kg in soil samples, treated with aqueous LAS and LAS-spiked sewage sludge respectively. For the other microbial parameters, the short-term effects (approximately 1-2 weeks) of LAS were characterised by an EC10 in the range 3-39 mg/kg. Application of LAS via sewage sludge generally reduced the short-term effects for the microbial parameters and to the EC10 for LAS in sludge-amended soil after approximately 1-2 weeks of incubation ranged from [8 to 102 mg/kg. Recovery potential was seen for most microbial parameters as a result of prolonged incubation under both conditions of LAS persistence (anaerobic conditions, the iron reduction test), and LAS and LAS depletion (aerobic incubations, all other assays). In conclusion, the short-term inhibitory effects of LAS on soil microbials were decreased in the presence of sewage sludge and by a prolonged (2-8 weeks) laboratory incubation period.[/P]
In the third part, M. Holmstrup and P. Krogh have dealt with sub-lethal effects on soil invertebrates. Toxic effects of LAS on soil organisms should be evaluated to ensure safe use of sewage sludge as a fertiliser. In this study, dose-response relation-ships for the toxicity of sodium-LAS to six species of soil invertebrates (survival, reproduction, and growth) were established using a sandy agricultural soil as test substrate. In general, toxic effects on reproduction and growth appeared when the conentration of Na-LAS in the soil exceeded 40-60 mg/kg. Reproduction was approximately 4-fold more sensitive in earthworms and enchytraeids that in springtails and mites. It is argued that this difference in sensitivity is related to the dependency of soil pore water, which is high in the annelids but comparatively low in anthropods.
In the fourth part, M. Holmstrup, have studied the influence of salt specification, soil type and sewage sludge (containing LAS) on its toxicity using the Collembolan Folsomia fimetaria and the earthworm Apporetodea caliginosa as test organisms. Studies of LAS toxicity to soil organisms are few and the factors that may influence the toxicity in the field have not been studied. In this study, the effect of the specification of LAS in the test solution added to the soil (solution of Na-LAS versus poorly soluble Ca-LAS or Mg-LAS), the influence of soil type and the modifying effects of sludge amendment on the toxicity of LAS were studied. These issues were investigated using reproduction of Collembola and growth of juvenile earthworms as test parameters. Specification of the LAS to test soil did not have any influence on the toxicity for any of the test specimens. Likewise in three different agricultural soils (sand, loam, and clay), equal toxicities were found. The LAS added to the test soil in a sludge water suspension was equally toxic as when it was added in an aqueous solution. However, anaerobic incubation for 7 and 14 days of the LAS-sludge suspension (with no decay of LAS) caused the toxicity to increase 3-fold in both Collembolan and earthworms. The relationships between soil constituents, bioavailability and toxicity were discussed.
