Application and Formulae of Detergents
Foam
It is expedient, however, that a few words be said on foam. At one time the amount of foam formed by a detergent was considered to be a measure of its effectiveness. It is true that foam is formed when surface tension is low, but lowering of surface tension is not always a criterion of detergency because this is in actual fact related to the lowering of interfacial tension.
In certain detergent operations high foam is a definite requirements, in certain cases it is immaterial whether the detergent foams or not, and in other cases foam can be considered a nuisance if not a prohibition to the use of the detergent for a particular operation.
It is obvious that a hair shampoo, shaving cream (other than the brushless type) and bubble bath preparations need to produce copious foam. Dishwashing compounds which are primarily meant for washing by hand in a sink full of water also need to foam copiously but the reason is not so obvious. As the plates are dipped in the solution and washed the oil is freed from the surface of the plate and floats to the top of the solution and in time this fatty layer can become appreciably thick. When the plate is withdrawn from the liquid it will pass through this layer last and part of the oil might become redeposited on the surface. If, however, a thick foam is developed in the liquid by the physical actions of washing, the oil will be trapped in the tremendous surface area of the foam and the amount of oil available for redeposition on the plate in its passage out of the solution is greatly reduced. When the foam becomes saturated with oil it collapses and this is an indication that the solution is no longer suitable for washing. For detergents intended for hand-washing of clothes foam is desirable as a sales-appeal factor.
Commercial and automatic household laundry machines are almost without exception 'foam sensitive.' If the detergent foams unduly the foam overflows on to the floor and also can interfere with the free flow of clothes through the water. In automatic machines the foam can interfere with water level pumps and the proper working of the control in the machine. A small amount of foam is necessary as this trends to trap dirt particles.
Similarly, dishwashing machines cannot tolerate foam, firstly because again the foam might overflow and also interfere with the pumping of the liquid and secondly, once foam forms, bubbles remain on the dishes and leave spots on drying.
Hard and fast rules cannot be laid down as certain household washing machines (usually those with a propeller) can tolerate foam, and in dish washing machines using a propeller a small amount of foam is not harmful but in the case of those working with jets the smallest trace of foam leave spots on glassware.
From our experience we can lay sown the following guidelines for foam :
- Anionic detergents in general produce voluminous foam; somewhat less is produced in hard water but foam is always increased with an increase in temperature.
- Non-ionic detergents foam considerably less than anionics, but this depends on the type of non-ionic. There are 'low-foam' non-ionic which can be used alone for most operations, while other non-ionic still need 'foam control'. Non-ionics usually foam somewhat less in hot water than in cold.
- When soap is added to an anionic detergent, foam is depressed.
- Non-ionic detergents do not depress foam of anionics; they can even enhance it.
- Alkaline builders in general enhance the foaming power of all type of detergents.
We shall later in this chapter include formulations for both powders and liquids with foam control but cognizance should be taken of Proctor and Gamble patent whereby a foam control agent is added to a ready-made powder.
The patent describes a combination of white mineral oil, paraffin wax of microcrystalline wax and/or glycerol monostearate and microfine precipitated hydrophobic silica in the proportions :
| Mineral Oil |
80 parts |
| Paraffin wax or microcrystalline wax and/or glycerol monostearate |
2-12 parts |
| Microfine hydrophobic silica |
0.31-1 parts |
The solid waxes are dissolved in the oil with warming and the silica dispersed in it.
To give a non-foaming detergent, 100 parts of finished powder are sprayed with one part of this solution/dispersion.
Household Cleaning
The days of one bar of soap, which served as a hair shampoo, toilet bar, laundry soap, for general washing and (mixed with sand from the garden) for pot-scouring, have long since passed. Nowadays, materials are manufactured for special purposes, such as heavy-duty laundering (the washing of cotton goods which by their very nature are usually heavily soiled), fine wash (the laundering of delicate fabrics such as silks, nylons, woollens), general purpose, dishwashing, floor-washing, window-cleaning, tile-cleaning, etc.
Heavy-Duty Laundering
Detergents should be formulated with the type of clientele in mind. Werdelmann has made a study of the differences between European and American washing habits.
The obvious differences are that Europeans use a front-loading, rotating drum washer whereas the Americans use a top-loading agitator machines. The Europeans also wash at a higher temperature than the Americans. These two factors require European powders to be low-foaming, while American machines can tolerate a moderate-foaming washing powder or liquid.
Without going into details we also quote the figures for the range of hardness of water :
Hardness parts/106
| | 0-90 | 90-270 | 270 and higher |
| USA |
60% |
35% |
5% |
| Europe |
9% |
49% |
42% |
Although these figures can be meaningless for the continents as a whole, they do provide some indication.
Again washing habits both personal and for clothes differ greatly in the two continents. Table 1 shows the comparison of formulae of heavy-duty detergents quoted.
Table 1: Comparison of Formulae of Heavy-duty Detergents
| | USA | Europe |
| Surfactant |
10-20 |
20-15 |
| STP |
35-60 |
35-45 |
| Sodium silicate |
4-10 |
3-5 |
| Sodium perborate |
- |
20-35 |
| Optical brighteners |
0.1-1.0 |
0.7-0.8 |
| Dosage |
1-2 g/litre |
7-8 g/litre |
| Clothes : liquid ratio |
1:15-1:25 kg/litre |
1:5 kg/litre |
Since this report was published, however, perborate together with an activator are gradually appearing on the US market. Enzymes which had their ups and downs in the USA are also increasing in popularity.
Non-ionics perform better than other detergents on fabrics made from synthetic fibres and also under cold water conditions. They also find use as 'rubbing agents' for badly soiled collars.
Cotton goods, which are still the bulk of the household wash require a moderately high alkalinity. In contact with a solution of a pH of 10 or more, the cellulose fibre swells slightly, allowing the water to penetrate into the fibre and thus loosen adhering dirt.
Household heave-duty washing powders are generally of two types for hand washing and for fully automatic washing machines. The hand-washing type of powder requires a copious lather for psychological reasons. Fully automatic washing machines, which have a drum which revolves around a horizontal axis, cannot use a power with a copious foam. Because of the action of the drum, the foam can spill out of the machine, and also the foam interferes with the action of the automatic floats which adjust the level of the water. However, a small amount of foam is necessary, as some of the dirt is trapped by this foam. For these reason the powder has to have 'controlled foam'. Semi-automatic machines, i.e., those that have propellers or impellers to do the agitation, or with drums rotating about a vertical axis, can in general, utilize either of the two types of powders.
A formulation for a hand-washing or semi-automatic machine, manufactured by simultaneous absorption and neutralization, has already been discussed in Chapter 6. Formulae 2 and 3. The addition of sodium perborate is, of course, optical and depends on washing practices in the particular area. We recommend the addition of at least 10 per cent sodium perborate to all laundry powders. In countries where this is not normal practice the addition of sodium perborate might make the powder expensive, but the extra whiteness achieved will compensate for the increased cost.
If the powder is being manufactured by the spray-drying process, the formulation can, if desired, be the same as that given in Formula 2 or 3, but an infinitely better powder can be made by using Formula 9 :
Formula 9
Spray-dried Heavy-duty Household Hand-washing Powder
| Sodium alkyl benzene sulphonate (or equivalent) |
25 |
| Sodium tripolyphosphate |
25 |
| CMC (66% basis) |
2.5 |
| Sodium silicate (1:2;4 ratio) |
15 |
| Optical brightening agent |
0.2 |
| Sodium sulphate |
32.3 |
and to this powder after spray-drying add sodium perborate at the rate of
| Spray-dried powder |
90 |
| Sodium perborate |
10 |
Foam Control
The above formula cannot be used in form-sensitive washing machines. To overcome the foaming problem several methods of foam control are used. One is to use a low-foaming non-ionic detergent as the active matter. An alkyl phenol condensed with not more than eight molecules of ethylene oxide will not foam unduly, but the physical characteristics (free-flowing, stickiness) both of spray-dried powders and those made by others methods will suffer when using low ethylene oxide content non-ionics and therefore the amount of active matter it is possible to incorporate in the powder is limited.
A typical powder to be made by either spray-drying or spray mixing is given in Formula 10.
Formula 10
Heavy-duty Fully Automatic Washing Machine Powder
| Non-ionic detergent (low-foaming) |
10 |
| Sodium tripolyphosphate |
30 |
| CMC (66% basis) |
1.5 |
| Sodium silicate (1 : 2.4 ratio) |
15 |
| Optical brightening agent |
0.2 |
| Sodium sulphate (can be partially replaced by soda ash) |
43.3 |
Another trend is to use a moderately high-foaming non-ionic such as iso tridecyl alcohol with 15 molecules of ethylene oxide, tallow alcohol or alkyl phenol both with 10-12 molecules of ethylene oxide. All of these detergents foam quite highly, and to depress the foam a nonyl phenol with 1½ molecules of ethylene oxide is used. The addition of this foam-depressor is critical and if proportions different from the optimum are used the foam is likely to be enhanced. The amount suggested is normally 15 percent of the total active matter, but this figure should be checked against the particular type of active matter with the exact proportions of builders being used.
Sodium perborate can be added in the same manner as in Formula 9, if the powder is spray-dried. If the powder is manufactured by a spray-mixing process with arrangements for continuous discharge of the powder, the sodium perborate can be fed continuously on to the conveyor belt which receives the discharged powder. If not, the perborate can be incorporated batch-wise in a powder mixer. On we describe methods for the incorporation of perborate both continuously and batchwise.
To incorporate appreciable quantities of non-ionics into spray-dried powders, recourse must be made to the 'Pluronics, some of which are available as flakes, prills, or flakeable solids. Alternatively all the methods described on should be considered.
A simpler and cheaper 'controlled foam' powder can be made by the use of a mixture of soap and alkyl benzene sulphonic acid. This will give both lower foam and higher detergency that when either is used alone in comparable proportions. It has been found that the foam is at a minimum when the soap proportion of the total active matter is between 30 and 60 per cent. Outside these limits, foam begins to form. If hard water is prevalent in the area, the detergent/soap ratio should be richer in the synthetic portion. If there is predominantly soft water in the area, more soap can be used if required. A word of caution needs to be given in the use of soap or soap mixtures in automatic washing machines. Some automatic machines have their heating elements protruding directly into the water, while others have the elements protected by a sleeve, which disperses the initial heat over a greater surface area. If the element is itself immersed in the water, it has been found that in areas of moderate to very hard water, a layer of insoluble limesoap can form on the element, decreasing the efficiency of the heat transfer. This can to a certain extent be eliminated by the inclusion of NTA or EDTA in the formula, but this leads to a further complication in that both NTA and EDTA in the presence of oxidizing agents (perborate) are corrosive to copper and zinc. Inhibitors have been developed to minimize this corrosion to an acceptable level.
A powder of this type can be made by the absorption and neutralization process according to Formula 11.
Formula 11
Low-foaming Machine Powder for Soft-water Areas
Mix together with warming to 45°C
(a) LAS (100 per cent) 11.6
Distilled tallow fatty acid 6.4
In the powder mixer, mix together:
Sodium tripolyphosphate 15
(b) Soda ash light 55
CMC (66% basis) 2
When uniform, add (a) with mixing. When the LAS/tallow fatty acid mixture has been dispersed, add immediately in order
| Sodium hypochlorite |
2 |
| Sodium silicate 40% |
8 |
This is mixed for a few minutes until the reaction is seen to have been completed, and then discharged for ageing. Next day the powder is ground and recharged to the mixer in the following proportions :
| Milled powder from Formula 6 |
90 |
| Sodium perborate |
10 |
| Optical brightening agent |
0.15 |
and mixed until uniform and then send to packing.
If one of the mixers is used the ageing and grinding can of course be dispensed with.
To manufacture the same formula using ready-made soap powder the formulation is :
Formula 12
Low-foaming Machine Powder for Soft-water Areas using
per cent fatty acids 7.9
| Ready-made Soap Powder Mix together : Sodium tripolyphosphate |
15 |
| Soda ash, light |
53.7 |
| CMC (66% basis) |
2 |
| Add in order : LAS (100%) |
11.4 |
| Sodium hypochlorite |
2 |
| Sodium silicate |
8 |
| when the reaction is completed add : High titre soap powder |
82 |
| Thereafter proceed as in Formula |
11 |
The same powder can of course be made by spray-drying, but a vastly superior one can be made in a spray-drier according to Formula 13. Modern tendencies are to manufacture 'ternary' powders, that is, powders having the active matter made up of three constituents, soap an anionic and a low-foaming non-ionic detergent, a formula for which is given in Formula 14.
Formulae 13-14.
Spray- dried Household Low-foaming Laundry Powders
| |
13 |
14 |
| Sodium dodecyl benzene sulphonate (100% basis) |
15 |
7 |
| Tallow soap, soda based (100% basis) |
10 |
5 |
| Low-foaming non-ionic detergent |
- |
7 |
| Sodium tripolyphosphate |
15 |
15 |
| Tetrasodium pyrophosphate (optical, can be completely replaced by Sodium tripolyphosphate) |
10 |
10 |
| Sodium silicate (anhydrous basis, ration 1:2.5) |
7 |
7 |
| CMC (66% basis) |
2.5 |
2.5 |
| Optical brightening agent |
0.2 |
0.2 |
| Soda ash |
0-20 |
0-20 |
| Sodium sulphate |
to make |
100 |
Sodium perborate is added at the rate of 10 per cent (or more if desired) after drying.
In place of tallow soap, the soap of behenic acid (a C22 saturated acid) is being used. Sodium behenate in the formulation acts mainly as a foam control agent (a very efficient one) and at a maximum concentration of 2 percent. The synthetic active agents can then be increased to give a more effective wash, even at low temperatures.
Behenic acid has a high melting point (80°C), therefore special precautions need to be applied for its introduction and saponification.
For dry neutralized powders it is best dissolved in the LAS and the liquid non-ionic (if being used) or a solvent with the aid of heat (for solvent detergent powders) and the mixture is sprayed hot on to the powders.
For spray-drying it can be dissolved in the LAS, and the mixture kept at a higher than normal temperature in the supply tank. The neutralized paste or slurry, which should also be kept at a higher temperature than normal, will probably have a higher viscosity than normal. Contrary to generally accepted principles, lowering the water content of the slurry slightly will, in this case, also decrease the viscosity.
As mentioned non-ionics can cause trouble on being spray-dried, pluming and also auto-oxidation.
Pluming can be minimized by the use of the narrow range ethoxylates. Auto-oxidation, which at best can discolour the fines and at worst will discolour the powder, can be inhibited according to a lever patent4 by the inclusion of about 1 per cent of charge transfer agent, two examples of which are stannic chloride or tetrachlorobenzoquinone. The most efficient methods of incorporation are of course the methods already described. These methods also tend themselves to the incorporation of enzymes, perborate etc.
Even in areas where there are no restrictions (total or partial) on the use of phosphates, consideration should be given to the use of zeolites, either the zeolite itself or the zeolite/silicate blend. This will have the added advantage, particularly in dry mixed or agglomerated powders, of surface adsorption. The zeolite can absorb on its surface larger amounts of liquid surfactants than the normal builders are able to, thus drier, more free-flowing powders with higher active matter can be produced.
Where there are bans or restrictions on the use of phosphate, the STP suggested in the formulations can be replaced by mixtures of zeolites on the one hand and NTA or one of the polycarboxylic acids.
Enzymatic laundry powders for automatic washing machines are now being produced in large quantities. It is difficult to give directions as to the amount of enzyme concentrate to add to powder as the concentration of the 'net' enzyme varies from manufacturer to manufacturer, but they give explicit instructions as to usage. Enzymes for washing machine powders are commonly used together with perborate. The enzyme operates while the temperature of the water is low and it is rapidly inactivated when the temperature reaches 60°C, perborate taking over. Although the manufacturers state that the enzymes are stable to perborate, this stability is only relative and if both enzymes and perborate are included in a powder, it is advisable to increase the enzyme concentration over that normally recommended. Formula 14 with little or no soda ash can serve as a useful base for enzymatic powders.
In all of the above and subsequent formulae which are to be spray-dried, consideration should be given to the addition of 3-5 per cent of sodium toluene sulphonate. This does not serve the purpose that it does in a liquid detergent. In this instance the function of the toluene sulphonate is twofold : it lowers the viscosity of the slurry, allowing a higher solids content, and also promotes the free-flowing characteristics of finished powder, particularly when linear alkyl benzene sulphonate is used. Also when powders are made by processes other than spray-drying, the inclusion of toluene sulphonate is essential if linear alkyl benzene sulphonate is being used.
Heavy-duty liquid detergents are now making headway for household laundering. The problem here is that the solution for efficient laundering needs a certain amount of alkali, sequestering agent and soil-suspending agent. To incorporate sufficient of these with a detergent into a solution which will stay bright and clear is not easy. As a result, new materials are coming on the market specially for this purpose and new techniques are being employed. Many patents for heavy-duty liquids are daily appearing in the literature and as a result the trend is to move away from conventional materials The active ingredient can be chosen from one or more of the alkyl benzene sulphonates, olefin sulphonates, paraffin sulphonates or ethylene oxide condensates. For reasons given below the anionic should preferably not be neutralized with a sodium ion, rather potassium or an ethanolamine. This condition cannot always be observed, particularly if paraffin or olefin sulphonates are bought as the already hydrolysed/neutralized solution.
The linear alkyl benzene sulphonates show better solubility in water than do the branched. For the production of liquids the choice should be in the lower register of molecular weight (C10-12 rather than C11-13). EniChem of Italy is fractionating its detergent alkylate into high and low 2-phenyl fractions. Again the high 2-phenyl fraction is more suitable for the production of liquids for reasons of solubility. True the detergency is somewhat lower than for the low 2-phenyl isomers, but the production of liquid detergents does require some compromises and the detergency can be enhanced in different ways.
On this score it should be pointed out that, contrary to expectation, the potassium salt of LAS is not more soluble than the sodium salt; it is less soluble. However, the potassium salts are used on occasion because the inorganic constituents are often potassium salts and to introduce a sodium salt would result in precipitation of the sodium salt of the inorganic compound by double decomposition. This also works the other way in that the potassium ion of the salt could precipitate the LAS. More often than not, however, the LAS is neutralized with an ethanolamine to obviate this problem.
The problem in heavy-duty liquid detergents (HDLD) formulations is incorporating the builders into the solution in such a way that the liquid has enough of all the necessary ingredients for efficient washing without detracting from the appearance of the product.
The builders in question are sequestering agents, which are usually phosphates; alkalis, which are invariably silicates; anti-soil redeposition agents (CMC) and optical brighteners.
Spray-dried heavy-duty powders invariably contain sodium tripolyphosphate as the sequestering agent, sometimes with the addition of other sequestering agents. Polyphosphates hydrolyse rapidly in neutral or acid solutions, first to a mixture of ortho-and pyrophosphates, and the pyrophosphates in turn hydrolyse further, albeit at a slower rate, to the simple phosphates. If the pH of the solution is 9 or higher, the hydrolysis of polyphosphates is slow5 so much so that a solution containing polyphosphates at this pH can be stored for a year at 25°C with no appreciable hydrolysis having taken place.
The solubility of sodium tripolyphosphate in pure water is 15 per cent at room temperature, but this figure will be considerably lower in the presence of other dissolved materials, particularly anionic, due to the common ion effect. The solubility of tetrapotassium pyrophosphate in water is over 60 per cent whereas the corresponding sodium salt is only soluble to the extent of 5 per cent. It is for this reason that tetrapotassium pyrophosphate is often used as a constituent of liquid detergents, however sodium salts need to be excluded almost completely because, due to the common ion effect, tetrasodium pyrophosphate can be precipitated from a solution containing both sodium and potassium ions. Again the use of pyrophosphate is a compromise as it does not have the sequestering and peptizing properties found in the polyphosphates.
Potassium tripolyphosphate, with a solubility in water of 55 per cent, has appeared on the market and this does not suffer from the same defect in that its sodium salt might precipitate due to the increased solubility of its sodium analogue.
Alternatively, phosphates are completely dispensed with the organic sequestering agents, such as sodium (or potassium) ethylene diamine tetra-acetate, or nitrilo triacetate6 are employed.
The alkali required is obtained from the colloidal silicates. Potassium silicate has been found to be superior to sodium silicate in this respect and silicates act as corrosion inhibitors against the action of phosphates on stainless steels.
However, to get sufficient of all three of the above ingredients into solution is virtually impossible, as the presence of one affects the solubility of the others. For this reason it is necessary to use a hydrotope, i.e., a solvent aid, a product which is itself soluble in the medium and aids in the solution of other products. There are a variety of these, but the most commonly used are potassium (or sodium) xylene, toluene, cumene or ethyl benzene sulphonates. These have to be used in relatively large quantities, of the order of 5-10 per cent of the finished product. They can either be sulphonated (or bought) as such, or else co-sulphated in the correct proportion with the original sulphonate, if the basic detergent is one of the sulphonate types.
Urea, apart from its other uses in the detergent industry, is an efficient hydrotrope as efficient as the lower alkyl sulphonates. However, it suffers from one disadvantage. If one considers its method of manufacture, the combination of carbon dioxide with ammonia :
CO2 + 2NH3 ® NH4 CONH2
Ammonium carbamate
NH4CO2NH2® NH2CONH2 + H2O
Urea
it is conceivable that industrial urea can contain small proportions of unreacted ammonium carbamate. In water solution this can hydrolyse :
NH4CO2NH2 + H2O ® (NH4)2 CO3
to ammonium carbonated. If the solution is alkaline, which it almost invariably is, a smell of ammonia will become apparent, which might be objectionable to some people. Thus if urea is to be considered as the hydrotope, the purchase specification should stipulate no ammonium carbamate to be present.
Berol of Sweden has developed potassium salts of lower molecular weight phosphate esters specifically as hydrotropes for the production of liquid detergents based on alkyl phenol ethoxylates in admixture with potassium tripolyphosphate. These phosphate esters have a further advantage in that they have detergent or wetting properties in their own right, thus aiding in the washing process, a property which none of the other hydrotropes can claim.
CMC now has to be brought into this solution. It is best incorporated by making a 10 per cent 'solution' separately, when it swells and forms a gel. This swelling and gelling, however, is influenced by ions already in solution and, if present, the CMC in a very short time precipitates out and sinks to the bottom. This problem can be overcome in three ways. One method is to adjust the density of the solution so that it is the same as the density of the precipitated CMC (±1.37) and the precipitate will therefore not settle. This is achieved by the addition of sodium sulphate or chloride. In another method carboxymethyl cellulose and methyl cellulose are used. Both cellulose compounds tend to precipitate from the solution. By itself, the methyl cellulose would normally rise to the top and the CMC by itself would normally sink to the bottom. By using this pair in equimolar proportions, however, they precipitate, but neither rise nor fall. Finally, Hercules Powder Co has brought on the market a new type of low molecular weight CMC which has excellent stability to HDLD solutions with high percentage of electrolytes.
With the incorporation of CMC as outlined above, one tends to get an opaque type of suspension. It is felt that once the solution tends to be thick and opaque, it should be made to look like a lotion, and the incorporation of sodium nitrate10 is said to give a better appearance and easier density control. Alternatively one of the opacifying agents mentioned can be used.
If it is decided to dispense with phosphates, one of the organic chelating acids neutralized preferably in this case by monoethanolamine, can be used. Alkalinity can also be obtained by excess monoethanolamine.
In the manufacture of these liquids, very often a sludge of insoluble material settles out. This has been identified as traces of iron contamination in the ingredients or even the water. The addition of 1 per cent triethanolamine, over and above any base needed for neutralization will eliminate this sediment.
Finally, it is desirable to incorporate an optical brightener in the solution. This is the least of the producer's problem, as optical brighteners are now available which are stable in water solutions. The amount is so small that this has no effect on the solubility of the other materials, nor have they any bearing on the solubility of the dye.
Thus, to summarize, the following formulae could be used as heavy duty liquid detergents.
Formulae 15, 16, 17, 18
Heavy-duty Liquid Detergents
18
| |
15 |
16 |
17 |
| Alkyl aryl sulphonic acid (ABS) |
10 |
20 |
9 |
12 |
| Diethanolamine |
3.6 |
7.2 |
3.3 |
4 |
| Non-ionic (100%) |
2 |
- |
3 |
- |
| PVP (100°) |
0.7 |
- |
- |
0.7 |
| K4P2O7 (100%) |
12 |
12 |
10 |
- |
| Potassium silicate (100%) |
4 |
3 |
4 |
- |
| Monoethanolamine |
- |
- |
- |
3 |
| EDTA |
- |
- |
- |
5 |
| CMC (100%) |
- |
1 |
1 |
- |
| Potassium xylene sulphonate or other hydrotope |
5 |
5 |
4 |
4 |
| Optical brightening agent |
0.1 |
0.1 |
0.1 |
0.1 |
| Water to |
100 |
100 |
100 |
100 |
All the above formulae are of the medium- to high-foaming type and thus unsuitable for fully automatic washing machines.
A formulation for a heavy-duty liquid detergent with a 'controlled foam, using the normal type of CMC is given in Formula 19 :
Formula 19
Heavy-duty Liquid Detergent with 'Controlled Foam'
| Disperse with gentle mixing CMC (66% basis) |
2 |
| in water |
18 |
| Into a stainless-steel vessel equipped with a slow-speed stirrer charge : distilled coconut oil fatty acid |
8 |
| Water |
25 |
| Caustic potash (40% solution) |
5 |
| Stir and warm gently until the solution attains a clear and homogeneous appearance, then add with stirring in order : Non-ionic detergent |
4 |
| Monoethanolamine |
1.7 |
| LAS |
4 |
| NTA or EDTA (acid form) |
1 |
| Hydrotrope |
8 |
| Tetrapotassium pyrophosphate or Potassium tripolyphosphate |
10 |
| Potassium silicate (40% solution, 1 : 2.5 mol ratio) |
10 |
| Optical brightening agent |
0.2 |
The CMC gel prepared above is now added, mixing continued, and water added to make this solution up to 100.
This will produce a lotion type of liquid. It is not necessary to 'saponify' by boiling, because if all the above directions are adhered to, the coconut fatty acid will be completely neutralized and no free unsaponified oil will be present.
PVP is being used with success in place of the CMC. The PVP is added as a 5 per cent pre-prepared solution, and the water adjusted accordingly. This will produce a clear solution, possibly with a slight haze due to insoluble matter sometimes found in poly-or pyrophosphates.
As mentioned trace quantities of iron contamination in the raw materials can cause a sludge of ferric hydroxide to separate. This separation is not always immediately visible and an insurance against this is the addition of 1 per cent triethanolamine to chelate the ferric ions. The iron will still be present in the solution, but inactivated.
The Gantrez resins were mentioned as chelating agents. GAF, the manufacturer, has published a detailed description of an addition use, that as a stabilizer for liquid detergent solutions containing non-ionics.
These resins are high-molecular-weight polymers with anhydride rings, which on hydrolysis with water form dibasic acids. Thus for a typical molecular weight of 40,000, the hydrolysed resin can have 250 dibasic acid groups per molecule. These need to be neutralized and in fact the maximum chelating action is attained at a pH of 10 minimum. These acid groups can also be esterified and in our particular field the esterification agent they suggest is a non-ionic detergent, which normally has a terminal -OH group available for reaction with a carboxylic acid. If the major portion of the carboxylic groups is esterified, an insoluble mass is obtained, but if a partial ester is formed (1 per cent non-ionic based on the weight of the resin), this serves as a stabilizing agent for non-ionic liquids.
The non-ionic of choice is an alkyl phenol with 15 ethylene oxide units and the procedure is important. A stock solution of the resin is made, the type suggested is Gantrez AN-149 (medium viscosity). Dissolve in water.
and raise the temperature to 90°C. Add slowly with stirring
keeping the temperature at 90°C, and continue stirring till a clear solution is obtained. (Caution, a large amount of foam might be formed in this esterification.)
A formulation we have found to give excellent results as a heavy duty liquid is
| Water |
4.0 |
| Gantrez stock solution |
10.0 |
| NaOH (45% solution) |
2.0 |
| CMC |
0.5 |
| Nonyl phenol-9 ethoxylate |
3.5 |
| NaOH (45% solution) |
29.0 |
| Potassium silicate (1: 3 mol ratio, 36%) |
51.0 |
| Optical brightner, dye, perfume |
qs |
The solution is made at 60°C, every ingredient to be dissolved completely before the next one is added.
The first addition of caustic soda is to neutralize the Gantrez resin. The second is to convert the silicate to metasilicate. We have found that a mixture of potassium/sodium metasilicate gives better freeze-thaw characteristics than pure sodium metasilicate as recommended by GAF. This can also be reversed, to use potassium hydroxide and sodium silicate to achieve the same purpose.
Finally, mention must be made of the fact that in the United States, one of the giant soapers, after ignoring the liquid household heavy-duty market almost completely, introduced its new liquid heavy-detergent, and from all accounts, at the time of going to press, this liquid is making remarkable inroads into the existing liquid market and also taking a large portion of the powder business. From the press release, this liquid is more concentrated than normal liquid in the market, being termed ½ cup (rather than 1 cup for existing brands) and contains 12 active ingredients; four surfactants, anionic, non-ionic and cationic (thus it seems to have a softener built in), two builders stated to be citrate and laurate (the laurate is obviously a soap, they use it as a chelating agent), three 'stain fighters' (two enzymes and one chemical never before used in heavy duty liquids), two brightening agent and a 'revolutionary molecule that makes all the 12 ingredients work together', apparently a hydrotrope. The problem of inactivation of enzymes (the calcium ions are chelated) has obviously been overcome by a method known only to this company.
An interesting and new development in the liquid heavy-duty household laundering field is a liquid containing a mixture of active chlorine and anionic detergent. It had been generally considered that chlorine (derived from sodium hypochlorite) could not be stable in the presence of considerable amounts of organic matter. However, sodium toluene of xylene sulphonates seem to stabilize sodium hypochlorite and mixtures of sodium hypochlorite with sodium ether sulphates can now be produced with the chlorine reasonably stable for over three months.
Formula 20
Heavy-duty Liquid Detergent and Bleach
| Sodium lauryl ether sulphate (60% concentration) |
20 |
| Sodium toluene sulphonate |
5 |
| Sodium hypochlorite solution (10% available chlorine) |
75 |
Even better results have been obtained in using Dowfax 2A1, one of the range of alkylated diphenyloxide disulphonates of the generic formula
produced by Dow. In the 2A1 version 'X' is the sodium ion. This novel surface active material is stable in moderately strong alkali and acid solutions, in the presence of large amounts of inorganic materials and in solutions of oxidizing agents. The high stability of hypochlorite in admixture with di-sulpho-diphenyl type of detergent is due to the inertia against chlorination of the multisubstituted benzene ring, one of the rings being tri-substituted, the other di-substituted. To achieve maximum stability, it is suggested that the diluted Dowfax 2A1 be heated to 70°C together with 2 per cent of a 12 per cent active chlorine hypochlorite solution, then cooled to 30°C and 20 per cent of a 12 per cent active chlorine hypochlorite solution added. This will give a 2.5 per cent active chlorine solution stable for a reasonable period, when packed in a plastic bottle. For a 6 per cent active detergent solution the formulation could be :
| Soft water |
65.4 |
| Dowfax 2A1 |
13.0 |
| Sodium hypochlorite 12% active |
1.6 |
| heat to 70°C, then cool to 30°C and add Sodium hypochlorite, 12% active |
20.0 |
Free alkalinity should then be adjusted by the addition of caustic soda solution to 0.5-1.0 per cent. This free alkalinity, in addition to stabilizing the hypochlorite, reacts with the water hardness lowering the pH for maximum disinfecting and bleaching action of the active chlorine.
In the field of light-duty detergents, or (as it is sometimes called) find wash, are the materials for washing delicate fabrics such as wool, nylon, silk, etc. Also, in general, this type of detergent is suitable for household dishwashing by hand as well.
Synthetic detergents first took a hold in the household for this purpose, and liquids consisting only of detergents diluted with water very quickly achieved a large sale and large quantities are still being sold. Nowadays, liquid detergents are more sophisticated than the plain solutions that were originally sold. They can be based on anionic detergents only, usually dodecyl or tridecyl benzine sulphonate, or can utilize a mixture of the above anionics with a non-ionic, or a sulphated either. In addition to foam boosters, these liquids can have viscosity increasers and cloud-point depressants Furthermore, they need not necessarily be transparent liquids, but can be opaque lotions.
The concentration of active matter present in a liquid detergent of this type varies from country to country, but an average figure is 12 per cent for the simpler liquids, but this can go up to 40 per cent for the more sophisticated market.
The cloud point of a detergent is an important factor in its sales appeal, as it is axiomatic that no housewife will buy a liquid which tends to deposit a precipitate or to cloud over on storage. Requirements for the actual cloud point will vary from place to place and no hard-and fast rules can be given. The cloud point naturally obtained from a particular concentration of active matter depends on the type of material used and the method of neutralization.
In general, the sodium salt of the alkyl benzene sulphonic acids, at a concentration of 12 percent active matter, gives a cloud point too high for commercial use. The diethanolamine and triethanolamine salts of the alkyl benzene sulphonic acids give a very low cloud point, lower than is needed generally. Thus for economic reasons, neutralization is usually done partially with caustic soda and partially with an ethanolamine.
Among the alkyl benzene sulphonates, all other things being equal, the cloud point of the neutralized solutions rises in the following order :
linear dodecyl benzene sulphonate;
linear tridecyl benzene sulphonate;
branched dodecyl benzene sulphonate;
branched tridecyl benzene sulphonate.
The viscosity of the final solution, all other things being again equal, rises in the same order.
In addition to the above factors, the method of sulphonation is important, since on this method depends the amount of free sulphuric acid present. When neutralized, the acid produced inorganic sulphates, both of which raise the cloud point and the viscosity. SO3 sulphonated material will give the lowest free sulphuric acid present; and normal oleum sulphonation will produce the highest. (The figure is normally as high as 7-8 per cent).
The factors involved in producing an acceptable liquid detergent are therefore dependent on :
- the type of alkyl benzene sulphonate;
- the method of manufacture of this sulphonate;
- whether any other active material is used.
To taken an average case, if conventional dodecyl benzene, sulphonated with SO3, is to be used as the base material for the manufacture of a 12 per cent liquid, a cloud point of below 5°C can be obtained by neutralizing half of the active matter with caustic soda and the other half with diethanolamine of triethanolamine. The neutralization with diethanolamine will give a slightly higher viscosity than if neutralization had been done with triethanolamine. Diethanolamine is a solid, except in very hot climates, and therefore is more difficult to handle. On the other hand, when alkyl benzene sulphonate are wholly or partially neutralized with triethanolamine, which is a liquid, a buffer is formed at a pH of approximately 6. To pass this buffer, it is necessary to use a large excess of base. To preserve a low cloud point, it is not advisable to use too much caustic soda to overcome this butter, so a fair excess of triethanolamine must therefore be used. The manufacturer must consequently consider the disadvantages involved in handling diethanolamine against the extra cost of triethanolamine.
If in the examples of alkyl benzene sulphonates given above, one of the sulphonates which normally gives a low cloud point were to be used to maintain the same cloud point level, the proportion of caustic soda can be raised and that of the ethanolamine correspondingly reduced.
Furthermore, if an acid sulphonated material is used as the base material, the proportion of ethanolamine needs to be raised considerably (and the caustic soda to be lowered) to maintain the low cloud point.
If it is required to raise the viscosity of the solution, a simple but limited method is the addition of an inorganic salt, like sodium sulphate or sodium chloride. This is limited in that it raises the cloud point. A better and more efficient method of increasing the viscosity is the use of an alkylolamide, preferably a diethanolamide.
Because of the various factors involved in the formulation of a liquid, it is not possible to describe formulations for all possible permutations and combinations.
Formula 21 gives a basic formula to be used as a starting-point. The manufacturer is advised to modify this according to the conditions he requires and the materials available to him.
Formula 21
Light-duty Household Liquid Detergent
| LAS (SO3 sulphonate) |
10 |
| Triethanolamine |
2 |
| Caustic Soda (45% solution) |
1.7 |
| Sodium hypochlorite (10% solution) |
0.6 |
| Lauric acid diethanolamide |
1 |
| Sodium sulphate |
1 |
| Water |
83.7 |
An opaque lotion type of liquid can be made (taking into account the same factors as mentioned above) from Formula 22.
Formula 22
Lotion-type Light-duty Liquid Detergent
| LAS |
19.5 |
| Monoethanolamine |
4 |
| Lauric acid monoethanolamide |
1.5 |
| Sodium hypochlorite (10% solution) |
0.6 |
| Sodium sulphate |
0.9 |
| Water |
73.5 |
In this case the dodecyl benzene sulphonic acid, the sodium sulphate and the water are mixed in the neutralization vessel, the sodium hypochlorite added and mixing continued for at least 20 min. The lauric acid monoethanolamide, being solid, is best dissolved in the monoethanolamine with heating. The mixture of the two is then added to the vessel, after the bleaching has if necessary been completed. If an opaque solution is required an opacifier can be added. The product can now be dyed and perfumed.
To manufacture a liquid from an alkyl benzene sulphonate neutralized only with caustic soda ( in practice, a concentrated paste of the sodium sulphonate is used as the starting material), a low cloud point can be achieved by the addition of urea. With the sodium sulphonate however, urea lowers the viscosity considerably. Addition of a fatty acid dialkylolamide will restore the viscosity.
Modern tendencies are to use both stronger solutions and mixtures of active matter. One of the main uses for light-duty liquid detergents is hand dishwashing, and for this particular application foam is important other than from the point of view of sales appeal. Grease released from the dishes floats to the top of the washing solution and forms an oily film which can be redeposited on the plate when it is withdrawn from the sink after having been washed. Due to the enormous surface area in a foam, this grease is held in a thin, easily rinsable film on the bubbles, preventing redeposition. When the foam collapses due to saturation with oil, the solution is considered to be exhausted and methods of test for the efficiency of dishwashing liquids are based on this foam collapse.
Ether sulphates, both of the alcohol and alkyl phenol types are finding more and more use as constituents of dishwashing liquids. If the ammonium salt of the alkyl phenol type is used care must be taken not to raise the pH of the final liquid over 8 or otherwise a smell of ammonia will appear. If a high pH is desired without the ammonia smell, the ammonium ether sulphates can be heated with a stoichiometric amount of caustic soda until the ammonia is distilled off. Alternatively an 'ammoniated' cleaner, which has some sales appeal, can be made at the high pH.
The choice of the type of ether sulphate is rather wide, as the base material can be any one of the alcohols available on the market or any of the alkyl phenols and then again the amount of ethylene oxide can be varied from between 1.7-4 molecules per molecule. Gohlke and Bergerhausen have investigated viscosity and foam height with different alcohols and different degrees of ethoxylation. They have come to the conclusion that the best foamers are a C12-14 alcohol with 2 molecules of ethylene oxide. Another important fact in the make-up of the ether sulphate is the amount of polyethylene glycol present. The authors have found that relatively large (of the order of 3 per cent) amounts of polyethylene glycol can act as a solvent of 'thinner' on the final sulphate to reduce the viscosity of the solution.
As the wetting properties of either sulphates are low they are not recommended as dishwashing agents alone, rather in conjunction with non-ionic or other anionic detergents.
Alcohol, sulphates, neutralized with ethanolamines can, of course, be used alone, or with an alkylolamide as a foam booster. It is interesting to note that alkylolamide have no effect on the foaming properties of ether sulphates. Some typical basic formulations are given in formulae 23-27.
Formulae 23-27
Light-duty Liquid Detergents
<td colspan='3' align='center'>to make 100
| |
23 |
24 |
25 |
26 |
27 |
| LAS (SO3 sulphonated) |
10 |
15 |
20 |
12 |
- |
| Caustic soda (40% solution) |
3.2 |
3.2 |
3.2 |
3.2 |
- |
| Triethanolamine |
- |
2.2 |
4.4 |
9 |
- |
| Sodium alcohol ether sulphate (100% basis) |
- |
3 |
3 |
- |
- |
| Ethanolamine alcohol sulphate (100% basis) |
- |
- |
- |
- |
24 |
| Coconut diethanolamide* |
2 |
1 |
1 |
- |
2 |
| Sodium sulphate or chloride |
qs |
qs |
qs |
qs |
qs |
| Dye, perfume |
qs |
qs |
qs |
qs |
qs |
| Water |
It will be observed that the first and fourth formulation are relatively cheap, the others more sophisticated.
SO3 sulphonated LAS can be considered the work-horse of liquid detergent formulations. It is good practice, when mixtures of LAS with alcohol or ether sulphates are used to ensure that the LAS is neutralized completely before the sulphate is introduced into the reactor. This will eliminate hydrolysis of the acid-unstable sulphates. To facilitate formulation the following data show the alkali requirement of a typical LAS.
100 kg LAS requires for complete neutralization :
12.8 kg NaOH (100%)
18.8 kg KOH (100%)
45.5 kg Triethanolamine
33.6 kg Diethanolamine
19.7 kg Monoethanolamine
The inorganic salts are included only if it is desired to increase the viscosity. The diethanolamide acts as a viscosity booster but particularly where the ether sulphates are included coconut monoethanolamide will be more effective. To incorporate the monoethanolamide, the solution is merely warmed to 60°C with mixing, when all the monethanolamide will melt and dissolve and will not be thrown out of solution on cooling.
Household fine-wash detergents are, of course, not limited to liquids. They can be made as spray-dried powders, sometimes only with 20-30 per cent active matter and the balance sodium sulphate as the inert filler, but more often than not they include sodium tripolyphosphate, some silicate occasionally CMC, and an optical brightening agent, substantive to the fibres for which the powder is being used. The phosphate, of course, helps in the detergency, and the silicate acts in this case as a corrosion inhibitor. Here, the action of the CMC is not as pronounced as it is on cottons, but on woollen fabrics it does aid in preventing redeposition, and as these powders are meant for hand-washing, it does tend to give a protective colloidal action on the skin.
A powder of this type can be manufactured as detailed in Formula 28.
Formula 28
Household Fine-wash Spray-dried Powder
| | Minimum | Maximum |
| Sodium alkyl benzene sulphonate |
10 |
25 |
| Sodium tripolyphosphate |
15 |
25 |
| Sodium silicate (preferably 1 : 3 ratio) anhydrous |
3 |
5 |
| CMC (100%) |
0 |
1 |
| Lauric acid monethanolamide |
0 |
2.5 |
| Optical brightening agent |
0.2 |
0.2 |
| Sodium sulphate |
|
Balance |
By virtue of the nature of manufacture, fine-wash powders of this type can not be made by the absorption methods, as the surplus of soda ash will prove detrimental to the operation of the powder. However, a dry mixed type of powder can easily be made to Formula 28, using as a base a concentrated powder of about 60 per cent active matter.
In certain parts of the world, neutral pastes of sodium alkyl benzene sulphonate are sold also for fine-wash purposes. These pastes very in concentration between 20 per cent and 50 per cent active matter. The consistency of the paste varies with the ingredients and the method of manufacture of the alkyl benzene sulphonic acid. Stiffer pastes are obtained with tridecyl benzene sulphonic acid, sulphonated with oleum; and the softest paste is linear dodecyl benzene sulphonic acid, sulphonated with SO3 gas.
The alkyl benzene sulphonates have limited solubility in water. They, however, can absorb water to form a natural paste. If the amount of water present is above that which can naturally be absorbed, the mass will separate into two phases on standing : a concentrated phase of alkyl benzene sulphonate on top and a weak solution of alkyl benzene sulphonate and inorganic salts at the bottom. The concentration of the sodium alkyl benzene sulphonate in the upper phase varies with the material, but is of the order of 55 per cent active matter. This means that pastes of 55 per cent can be manufactured with no special additions. If lower concentrations are required, it is necessary to add certain ingredients to prevent this separation. Materials that can be used : are hydrotropes, which will make the final paste thinner in consistency, so that stiffening materials have again to be added; alkylolamides, which have the added advantages of foam boosting and skin protection (these pastes are to be used by hand); and CMC. Both the CMC and the alkylolamides tend to increase the viscosity of the mass in such a way that separation cannot take place.
If only CMC is used as the thickening agent, a general rule is to manufacture the paste to a 55 per cent concentration and then to add sufficient of a 10 per cent CMC solution in water to bring the concentration down to he required amount. Sodium sulphate is then added to increase the consistency.
A 40 per cent active paste, using both conventional dodecyl benzene and linear dodecyl benzene sulphonic acids, both sulphonated by SO3 gas, is given in Formula 29.
Formula 29
40 per cent Detergent Paste
| ABS (100%) |
40 |
| Caustic soda (45% solution) |
11.4 |
| Sodium sulphate |
2 |
| Sodium hypochlorite solution |
0.6 |
| Water |
29.3 |
| CMC |
1.7 |
| Water |
15 |
This paste may be reduced to 30 per cent by increasing CMC to 2.5 or 3.5 per cent and adding water.
General-Purpose Detergents
Powders of this type are the most popular for household use. They are not harshly alkaline, and contained relatively large quantities of both active matter and sodium tripolyphosphate. These achieve the action on cottons without the addition of further alkalies, and the alkalinity naturally present from the phosphate does not harm delicate fabrics.
By virtue of their formulation these powders are truly general-purposes and can be used for virtually every household job. They suffer from the disadvantage, however, of being unsuitable for fully automatic household washing machines, as, in general, they foam too much.
A generally accepted formula for this type of powder to be manufactured by a spray-drier is given in Formula 30.
Formula 30
Spray-dried General-purpose Powder
| Active matter as alkyl benzene sulphonic acid |
25 |
| neutralized with caustic soda Sodium toluene sulphonate* |
2.5 |
| Lauric monethanolamide |
3 |
| Sodium tripolyphosphate |
30 |
| Sodium silicate (1:2 ratio) anhydrous |
10 |
| CMC (100% basis) |
2 |
| Optical brightening agent |
0.2 |
| Sodium sulphate |
27.3 |
The addition of 10 per cent sodium perborate is, in our opinion, advisable, but again is dependent on washing practices in the particular country. As a guide, in the United Kingdom, powders of this sort have at least 8 per cent sodium perborate added, and in most of Europe even more.
If sodium perborate is to be added, we suggest that 2 per cent of the sodium sulphate be replaced by magnesium sulphate on any anhydrous basis. This magnesium sulphate is added to the slurry prior to spray drying.
A general-purpose powder can be made by the absorption and mixing process as well, but in this case, due to the limitations of the process, the active matter is limited. The formulation suggestion is give in Formula 31.
Formula 31
General-purpose Powder
| Dodecyl benzene sulphonic acid |
18 |
| Sodium tripolyphosphate |
25 |
| Sodium silicate (1:2 ratio) 40% solution |
5 |
| CMC (100% basis) |
5 |
| Sodium bicarbonate |
28 |
| Soda ash |
20 |
| Optical brightening agent |
0.15 |
| Water (or sodium hypochlorite solution) |
2 |
As in Formula 31, the same remarks apply regarding the addition of sodium perborate. If this is to be introduced, it is suggested; that the sodium bicarbonate be lowered to 25 per cent and 3 per cent magnesium sulphate crystals added. If sodium hypochlorite is used to bleach the powder and if sodium perborate is to be incorporated, the precautions as detailed must be observed.
A general-purpose powder can be manufactured by dry-mixing according to Formula 32.
Formula 32
General-purpose Powder
| 60% alkyl benzene sulphonate powder containing silicate |
45 |
| Sodium tripolyphosphate |
30 |
| CMC (100% basis) |
2 |
| Optical brightening agent |
0.2 |
| Sodium sulpahte |
22.8 |
Here, if sodium perborate is to be used, no special precautions need to be taken and it can, of course, be added initially with all the other ingredients.
In all the formulations given hitherto, we have included relatively large amounts of sodium tripolyphosphate, this despite the fact that in certain countries there is a complete of partial ban on the use of phosphates. To date no 'plug-in' replacement for this excellent builder has been developed. Where this is a partial ban, the above formulations to include STP up to the limit allowed and to add a zeolite to make up the differences is suggested. Where there is a total ban, the available alternatives must be considered; increasing the silicate, use of NTA, use of zeolite (the zeolite/silicate co-crystal mentioned might be eminently suitable), or one of the polymers specially mooted for this purpose. The final formulation will probably be a combination of any two or more of the above.
For fully automatic, front-loading household washing machines, foam control needs to be applied. This can be by the use of soap as for heavy duty powders, but infinitely better performance will be attained if the ternary mixture of the anionic/non-ionic/soap is used as described. With the new processes and mixing equipment for the inclusion of non-ionics into powders, there need be no practical limits to the formulation.
Choice of Non-Ionic
As can be appreciated from the description of the possible non-ionic surfactants, the choice is wide and often confusing. Much work has been done on the optimization of the molecule. Cox and Matson have compared various molecules for their cleaning efficiency in hard-surface cleaning. Kravetz has done the same for soil removal on cloth. It is true that the results cannot be compared directly because of the different substrates, but the results are revealing.
Their results can be summarized :
- From Cox and Matson's work on hard-surface cleaning it appears that linear alcohols with a low molecular weight and containing 50 per cent ethylene oxide (average chain length 8.6 carbons with 3.1 moles EO) in a relatively high concentration (5 per cent), are better in cleaning efficiency for grease, wax and particulate soil than the molecules containing C10 and higher chain lengths with the appropriate amount of the ethylene oxide to maintain the balance. [p align="justify"]This was explained by the fact that the low-molecular-weight hydrophobe acts as a solvent and this was confirmed by adding a glycol ether when no improvement of soil removal was noted.
- For low dilutions of the surfactant the optimum chain length was shifted to the C8-10 range. Under these conditions of dilution the hydrophobe can no longer act as a solvent and performance was dependent solely on the surface active effect.
- Comparison of the low carbon number ethoxylated alcohols with a built formulation containing nonyl phenol with 9½ EO units again showed a better performance for the low-molecule weight alcohol ethoxylates.
- Kravetz compared the performance of a linear primary alcohol ethoxylate, a linear secondary alcohol ethoxylate, both of approximately C13 average chain length, and a branched octyl phenol ethoxylate, each with varying amounts of ethylene oxide and for both cotton and cotton/ polyester blends.
- The results show that 7-9 EO units one each give optimum performance for Sebum, oil and clay removal on the blend but for sebum removal from pure cotton 12-15 EO was superior.
Further work by Rosen confirms the above in that he found that short-chain non-ionics are better in removing water repellent soils.
The above facts and figures do not take into accounts the added complications of the presence of anionic detergents and builders but they do indicate a trend.
From the above it appears that any of the commercially available non-ionic types with approximately 8 EO units will give good all round performance. For powders, for technological consideration, the choice of non-ionic has been in somewhat higher register hitherto.
With the development of system for incorporation of non-ionics into powders without spray-drying the problem associated with making powders using these (relatively) low-molecular-weight materials no longer apply.
The use of this type of non-ionic in liquids will tend to give a low cloud point but this can be overcome by the judicious use of co-solvents and hydrotropes.
The term cloud point can be somewhat confusing. Normally it is the temperature at which a cloud forms on cooling. This demonstrates the lowest temperature at which a liquid can be stored and still remain clear. When applied to non-ionic solutions it indicates the temperature at which the solution becomes cloudy on heating, at this temperature the solution separates into two phases, one of which will be richer in non-ionic than the other.
Concentrated Powders
A new approach to the manufacture of powders is what is called the ½ or ¼ cup concentrates, where a minimum of inert filler, if any at all, is used. A patent by Colgate describes the technology for the production of these powders.
In brief the process is to mix STP with water and sodium silicate in a crutcher to allow the STP to hydrate to its hexahydrate, then to added a further quantity of STP and water under conditions that this second addition does not hydrate and to spray-dry the mix. To the spray-dried beads non-ionic detergent is added in a special mixer.
The details are :
Mix together
| STP |
14.5 |
| Sodium silicate (1:2.4 ratio, 50% solution) |
15.2 |
| Deionized water |
21.0 |
Maintain the slurry at 60°C for hydration and then raise the temperature to approximately 90°C, add
| STP |
28.3 |
| Deionized water |
21.0 |
At this higher temperature no hydration takes place, this slurry is then spray-dried to a bead containing 10% moisture, with a bulk density of ± 0.55 g/ml.
The finished beads are then sprayed, either continuously or batch-wise with a non-ionic, of the alcohol ethoxylate type mixed with minor ingredients; optical brighteners, dye, perfume, etc. The post-mixer mentioned in the patent is one of the Patterson-Kelley types but it is conceivable that any of the mixers described can be used. The finished powder has a bulk density of 0.68 g/ml and contains.
| Base bead |
78.0 |
| Non-ionic |
19.7 |
| Minor ingredients |
2.3 |
The granules are attractive and dustless and a further claim by the patentors is that they are sufficiently pourable to be packed in a transparent specially designed bottle.
Further embodiments of the patent include adding fillers other than STP to the hydrated STP. No mentioned of the inclusion of CMC is made but it is envisaged that it could quite easily be added to the slurry prior to spray drying.
Cold Water Washing
A generation or so ago all washing was done at the boil or near it. With the advent of synthetic fibres wash temperatures came down drastically and now in an attempt at energy conservation householders are beginning to use cold water only, for washing of clothes.
The industry is facing and meeting the challenge, and a challenge it is because the highly complicated washing processed requires, among other things, energy to break the bond of the dirt to the substrate. This energy can come from lowering of the interfacial tension, the mechanical energy imparted by the motor of the machine and from heat.
For cold washing the thermal energy needs to be replaced, and one method is by increasing the amount of active matter in solution and using more non-ionics which are better for soil removal from synthetics. Zweig and her co-workers have studied the parameters involved in cold washing with non-ionics and have come up with some surprising and novel findings. The conclusions can be summarized:
- Non-polar soils are difficult to remove from polyester/cotton fabrics at low temperatures, thus the inherent detergency needs to be enhanced.
- Optimum detergency for this system is found with non-ionic mixtures which have cloud points in the range of 15-25°C below the wash temperature. This is explained by the fact that a surfactant-rich pseudo-phase separates at temperatures above the cloud point. This can be considered to be globules of concentrated surfactant which are attracted to the soil (note also the remarks of Rosen).
- Low cloud points were obtained by blending lightly ethoxylated alcohol or unethoxylated alcohol with a normal detergent non-ionic.
In figures, a blend of 3 mol ethoxylated alcohol with an 8 mol non-ionic to give a cloud point close to 0°C enhanced the mineral oil detergency of the 8 mol alcohol ethoxylate by 50 per cent and a blend of a 9 mol non-ionic with decanol, again to give a cloud point close to zero enhanced the detergency of the alcohol-9 ethoxylate by 20 per cent.
These are the bare figures, but as the authors state there is a window through which efficient detergent systems for cold water washing can be seen. The technological problems of formulating these low cloud point non-ionics into liquid detergents need to be investigated.
As can be seen from the foregoing, possibilities of formulating are varied and later in this chapter we also discuss solvent powder detergents. The actual formulations to be used depend on many factors, mainly the materials easily available and the trends in the area where the powder be sold. The above statement also holds good for liquids.
To sum up we give in Tables 2 and 3 formulations which can be as starting points for the manufacture of both dry-mixed and spray-dried powders. These formulations do not necessarily parallel those already described in the text, but do give an indication of what is being made.
Table 2: Typical Formulations for Powders Produced by Dry Neutralization
-
| All purpose non-machine | All purpose machine | Light-duty hand | Heavy-duty non-machine | Heavy duty machine | Solvent powder |
| LAS |
14-15 |
5 |
15 |
12-15 |
5 |
5 |
| Distilled-fatty acids |
- |
4 |
- |
4 |
3 |
| Non-ionic |
2-3 |
6 |
2 |
- |
4 |
3 |
| STP |
30 |
30 |
20 |
15 |
20 |
20 |
| Metasilicate (5H2O) or spray-dried disilicate |
3 |
3 |
- |
5-6 |
5-6 |
5 |
| Soda ash |
15-20 |
15-20 |
20 max |
to 100 |
to 100 |
to 100 |
| Sodium bicarbonate |
- |
- |
30 |
- |
- |
- |
| Sodium sulphate |
to 100 |
to 100 |
to 100 |
- |
- |
- |
| CMC |
2 |
2 |
- |
1.5 |
1.5 |
1.5 |
| Optical brightener |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
| Perborate |
10 |
10 |
- |
10 |
10 |
- |
| Enzymes as 300,000 DU |
- |
0.5 |
- |
0.5 |
- |
- |
| Perfume |
qs |
qs |
qs |
qs |
qs |
qs |
| NaOH (30% solution) |
2-3 |
2-3 |
2-3 |
2-3 |
2-3 |
2-3 |
| Solvent deodorized kerosine |
- |
- |
- |
- |
- |
4 |
Table 3 : Typical Formulae for Powders Produced by Spray-drying
| Heavy-duty hand | All-purpose Cold Water hand | Heavy-duty Machine | Light-duty hand |
| LAS (Na salt) |
12 |
16 |
6 |
18 |
| Non-ionic |
3 |
4 |
4 |
2 |
| Soap or distilled fatty acids |
- |
- |
6 |
- |
| CMC |
2 |
3 |
2 |
2 |
| Sodium silicate 1:2.45 ratio (100% basis) |
3 |
3 |
4 |
- |
| Soda ash |
10 |
10 |
- |
- |
| STP |
30 |
35 |
30 |
15 |
| MgSO4 |
1.5 |
- |
1.5 |
- |
| Optical brightener |
0.15 |
0.15 |
0.15 |
0.15 |
| Na2SO4 |
22 |
28 |
30 |
60.1 |
| Perborate |
15 |
- |
15 |
- |
| Sodium toluene sulphonate |
1 |
1 |
1 |
1 |
| Perfume |
qs |
qs |
qs |
qs |
| Enzymes |
- |
- |
0.5-0.8 |
- |
| Residual moisture (approx). |
10 |
5 |
10 |
5 |
Notes
- Part of all of the LAS can be replaced by sulphonated methyl esters.
- Perfumes for this type of powder should be of low volatility and added after spray dried.
- All the above formulation lend themselves to production by the combined system described.
Hard-Surface Cleaners
A new development in both the household and the institutional cleaners field is the all-purpose liquid meant specifically for hard-surface cleaners-by hard surfaces are meant those surfaces that cannot be immersed in a bath or basin for cleaning, and the operation needs to be done in situ. These cleaners are usually liquid, alkaline and often contains solvents. Their purpose is to clean grease, mud, and atmospheric grime from walls, doors, glass, tiles, etc. Alkalinity can be derived from alkaline salts, or ammonia (occasionally caustic soda or potash) can be added. The solvent is added because it has been found that oil stains, although theoretically saponifiable by the alkali, cannot always be removed without it. This solvent needs to be soluble in water (unless an emulsion is to be made), reasonably odourles, non-toxic, with a fairly high flash-point and last but not least, a good fat solvent. The glycol ethers, in particular ethylene glycol monobutyl ether or dipropylene glycol methyl ether answer to all the above requirements admirably. Silicates are added both to buffer the alkalinity and to minimize corrosion on metallic surfaces. A typical formulation is :
Formula 33
Hard-surface Cleaner
| Sodium alkyl benzene sulphonate (100% basis) |
15 |
| EDTA sodium salt |
4 |
| Ammonia (100% basis) (optional) |
5 |
| Butyl cellosolve |
7 |
| Sodium silicate (1:2 ratio, 100% basis) |
3 |
| Water |
to 100 |
it goes without saying that if ammonia is to be added the solution cannot be used on copper surfaces.
A generalized formulation which is becoming popular in household use is :
| Syndet |
5-8 wt% |
| Hydrotrope |
6 |
| Alkali |
5 |
| Dipropylene glycol methyl ether |
4 |
| pine oil |
2 |
| Water |
Balance |
The syndet can be non-foaming (non-ionic) or medium foaming (LAS) or high foaming (mixture of LAS and ether sulphate). The alkali can be ammonia, trisodium phospahte, tetrasodium pyrophosphate or sodium silicate, or one of the organic amines such as monoethanolamine. If organic alkine salts are not used the hydrotrope can be dispensed with. It is necessary to use softened water for this formulation as otherwise the hardness salts with precipitate or form a haze due to the high pH.
A particular instance of hard-surface cleaning is the oven cleaner. The above formula will theoretically clean ovens, but as grease is normally heavily encrusted on the surfaces of ovens more alkalinity than that provided in this formula is needed. A typical formula could be :
Formula 34
Hard-surface Cleaner
[/
| Alkyl benzene sulphonate, sodium salt |
4 |
| Phosphoric acid (85%) |
4.5 |
| Caustic potash (100%) or monoethanolamine |
9 |
| Tetrapotassium pyrophosphate |
4.5 |
| Ethylene glycol monobutyl ether |
6 |
| Isopropyl alcohol |
2 |
| Sodium silicate 1:2 ratio (100%) |
2 |
| Water |
68 |
It will be noted that the amount of caustic potash suggested is in excess of that required to neutralize the phosphoric acid, the surplus is needed to provide alkalinity. In the above formula the glycol ether is not completely soluble but the isopropyl alcohol acts as a coupling agent. Contrary to general belief, isopropyl alcohol is in itself a good fat solvent.
For certain institutional purposes it might be necessary or desirable to produce an oven cleaner as a paste or viscous liquid so that it will not drain down vertical surfaces. Formulae 34 and 35 can be modified by addition of either a thickening agent or colloidal silica. If a viscous liquid is to be made it can be conveniently packed as an aerosol. Vanderbilt Corporation suggests the following formula for an aerosol oven cleaner :
Formula 35
Aerosol Oven Cleaner
| Veegum-T* |
1.5 |
| Ammonia solution |
6 |
| 1,1,1-Trichlorethane |
18 |
| Water |
24 |
| Ethanol |
7.5 |
| Tergitol NPX†|
18 |
| Propellant : |
|
| Dichlorodifluoromethane |
17.5 |
| Dichlorotetrafluoroethane |
7.5 |
* Vanderbilt Corporation.
†Union Carbide.
A low temperature oven cleaner has been described in a patent where mannitol or sorbitol is used for alcoholysis of the fat deposited, with sodium or potassium bicarbonate as the alcoholysis catalyst and salts of low molecular weight organic acids to esterify the alcoholysis product. The formulation could be :
| Sorbitol |
2-5 |
| Potassium |
0.1-4.0 |
| Eutectic mixture of Sodium acetate Lithium acetate |
1-5 |
| Potassium acetate Thickener |
qs |
| Precipitated chalk |
20-30 |
| Wetting agent |
qs |
The eutectic mixture is to lower the melting point of the salts to allow them to react easily. Other salts recommended could be sodium tartrate. Rochelle salt or sodium glycolate.
Machine Dishwashing
Until a few years ago household dishwashing was done by using one of the fine-wash or general purpose formulations mentioned above. Of recent years the household dishwashing machine has come into popular use and this has requirements of its own. The mechanical cleaning action is done by means of jets of water. These jets are produced by a high-pressure pump or by the whipping action of a fast revolving propeller. In either case it is essential to the operation of the machine that the detergent added be completely non-foaming (and not even with a 'controlled foam' as in household laundry).
Non-ionics, in general, foam considerably less than anionics, but even they do foam slightly, so the amount of detergent is therefore kept to a minimum and the cleaning effect is achieved by the use of alkalis and phosphates. Almost completely non-foaming non-ionics have now been developed by blocking the terminal-OH group. One of the common methods is to add a methyl group to the terminal-OH, if, for example, a non-ionic is to be made by the esterification of polyethylene glycol and a fatty acid, instead of the polyethylene glycol a methoxy-polyethylene glycol is used. Another method is to condense to the finished non-ionic detergent a further molecule of butylene oxide. The formulation also depends to a very great extent on the type of water being used. Household water-softeners are only now beginning to appear on the market; so the formula must take into account whether the water being used is soft, moderately hard or hard.
For soft-water areas, soda ash, besides being cheap, can provide a portion of the alkalinity, but in moderately hard and hard water the soda ash will leave a scum of calcium carbonate on crockery and cutlery.
For moderately hard water tetrasodium pyrophosphate can be used to give both detergency and alkalinity, but for hard water sodium tripolyphosphate in combination with strong alkalis must be employed.
Most dishwashing machines have a drying cycle as well as the rinsing cycles, or at least dishes are left hot and the last traces of moisture on them dry very quickly on contact with the air. It is, therefore necessary to provide for the last traces of water to drain from the dishes in a uniform film to avoid water spots particularly on glassware.
This effect can be achieved by incorporating solvents or an organic chlorine-releasing compound into the powder. Chlorine-releasing materials react with non-ionic detergents and it has been found by the authors that these powders work very successfully without any detergent at all. If, however, it is desired to incorporate a detergent, a very small amount of non-ionic detergent can be used. FMC has suggested a method whereby non-ionic detergents can be incorporated into these powders in the presence of chlorine releasing agents. It recommends the low-foam modified non-ionic detergents mentioned above. This detergent, at the rate of 1-2 per cent based on the final weight, is pre-mixed with the most alkaline ingredient present (anhydrous metasilicate), the tripolyphosphate added next and then the other ingredients and finally the chlorine releasing compound.
Highly alkaline materials such as metasilicate can affect the over-glaze on delicate china and cause 'crazing' of the glaze. This can be eliminated by the incorporation of boric acid (not more than 5 per cent), sodium aluminate (2 per cent) or zinc salts in the formula.
Since these powders usually contain large amounts of sodium metasilicate, they are not normally made by spray-drying, as there is a limit to the amount of sodium metasilicate (which is hygroscopic) which can be incorporated into a spray-dried powder. They are produced instead, by a mixing and absorption technique.
To make these powders dustless, granulation techniques are used. The powders and the non-ionic detergent are mixed as described above, without the chlorine-releasing material. On to this mixture a small amount of waterglass is sprayed in a mixer with a revolving to tumbling action, when the waterglass glues the particles together and the revolving action gives them a spherical shape. The chlorine-containing material is then added.
A formula suitable for use in soft-water areas is given in Formula 36.
Formula 36
Machine Dish-washing Powder for Soft-water Areas
| Tetrasodium pyrophosphate |
49 |
| Sodium metasilicate anhydrous |
25 |
| Soda ash |
22.5 |
| Sodium dichloro-iso-cyanurate (60% available chlorine) |
1.5-4.5 |
| Non-ionic detergent, eg, nonyl-phenol 9 mol ethox |
2 |
This formulation is also suitable for dishwashing machines used in catering establishments.
Because of the small amount of detergent involved, it is not necessary to use any special procedure for the incorporation of the active matter. The easiest method is to blend in with the other powders a concentrated detergent powder. Alternatively, any other already prepared detergents powder can be used as the source of the active matter and due allowance must then be made for the other ingredients in this powder.
Where the water is moderately hard the product should be made according to Formula 37.
Formula 37
Machine Dish-washing Powder for Moderately Hard-water Areas
| Tetrasodium pyrophosphates |
60 |
| Sodium metasilicate anhydrous |
38 |
| Trichloro-iso-cyanuric acid |
1-3.5 |
| Non-ionic detergent |
1 |
For very hard water areas the following formulation will be suitable :
Formula 38
Machine Dish-washing Powder for Hard-Water Areas
| Sodium tripolyphosphate |
50 |
| Sodium metasilicate pentahydrate |
25 |
| Trisodium phosphate anhydrous |
15 |
| Non-ionic detergent |
3 |
| Hexylene glycol |
2 |
| Isopropyl alcohol |
1.5 |
| Water |
3.5 |
The liquids are pre-mixed and then the powders are charged into the mixer and the liquid sprayed on to the powders while mixing.
For institutional machine dishwashing the tendency is to move away from powders to liquids as these can be done either continuously or in accordance with pre-set requirements based on electronic controls.
Liquid for dishwashing machines can be formulated with either a non-ionic component or active chlorine, but not both.
Alkalinity is obtained from caustic alkali (soda or potash) with the addition of the corresponding silicate, together with a condensed phosphate. The same problem of common ion effect occur as described for HDLD, thus a basic formula could be :
| Tetrapotassium pyrophosphate |
15 |
| Potassium silicate (1:2 mol ratio, 40% solution) |
8 |
| Potassium hydroxide (45%) |
10 |
| Soft water |
67 |
Potassium tripolyphosphate, if available, would obviously give vastly improved performance.
To this solution is added a per cent of a non-foaming non-ionic or 2 per cent active chlorine. The chlorine in this instance can be added by direct injection of chlorine gas to form potassium hypochlorite in the solution.
Abrasive-Type Cleaners
The most popular household abrasive cleaners are scouring powders. These are usually dry mixes of all of the ingredients. A typical formulation is given in Formula 39.
Formula 39
Household Scouring Powder
| Abrasive |
87 |
| Soda ash |
5 |
| 60% concentrated detergent powder |
8 |
If desired, this can also be manufactured from sulphonic acid by mixing together :
| Abrasive (powder calcite or marble) |
85 |
| Soda ash |
7 |
| then adding in the mixer : 100% alkyl benzene sulphonic acid (ABS) |
5 |
| and water |
3 |
If this scouring powder is to contain active chlorine, as is becoming the fashion now, it is advisable not to use soda ash, as concentrated organic-chlorine-releasing materials are not in general stable in the presence of soda ash, except for the potassium salt of trichloro-iso-cyanuric acid.
Alkalinity can be obtained by anhydrous sodium tripolyphosphate or tetrasodium pyrophosphate. To avoid introducing moisture into the powder, the active matter can best be put in by the use of an already made detergent powder, not necessarily a concentrated one. A chlorine containing powder is best packed in plastic containers.
A suggested formulation is Formula 40 which is a chlorine-containing household scouring powder.
Formula 40
Chlorine-containing Detergent Scouring Powder
| Detergent powder containing 20% active matter (without soda ash) |
15 |
| Tetrasodium pyrophosphate |
5 |
| Abrasive |
79 |
| Trichloro-iso cyanuric acid |
1 |
Where a spray-drier is being operated. Formula 40 is a useful outlet for the cyclone fines produced by the spray-drier. A scouring liquid can be made according to Formula 41.
Formula 41
Household Scouring Liquid
| Disperse Bentonite |
5 |
| in water |
25 |
| Add 12% active ready-made liquid detergent and dissolve in the liquid : |
35 |
| Sodium metasilicate pentahydrate or water-glass |
3 |
| and then disperse in this solution Abrasive |
32 |
Special suspending agents suitable for this type of product are now available. These prevent settling of the abrasives.
Miscellaneous Household Cleaners
Window cleaners of the gentle abrasive type, using whiting, were once popular. These have now been superseded by liquids like those of Formula 42.
Formula 42
Household Window-cleaning Liquid
| Active detergent matter |
0.25-0.5 |
| Isopropyl alcohol |
15-35 |
| Water |
to 100[[/TD]/tr] |
| Dye |
as required |
Similarly, for stone or tile floors, although materials such as that given in Formula 1 are used, liquid floor cleaners according to Formula 43 are now also being manufactured.
Formula 43
Floor Cleaner
I
| Active detergent matter |
2-5 |
| sopropyl alcohol |
8-15 |
| Pine oil |
1-2 |
| Water |
to 100 |
Commercial Laundering
In commercial laundering, powders are used which do not foam and which are in general more alkaline than household powders. Most commercial laundries use soft water, and we suggest to the detergent manufacturer that if he supplies washing powders to a laundry which does not use soft (or softened) water, he should make every effort to convince his customer that it is essential for him to use it.
Laundry powders can be made both by spray-drying and by absorption and neutralization. The two formulations below have been used with success in commercial laundries.
Formula 44
Spray-dried Industrial Laundry Powder
| Alkyl benzene sulphonic acid |
20} Neutralized with |
| Distilled tallow fatty acid |
15} NaOH to sodium salts |
| Tetrasodium pyrophosphate |
15 |
| Sodium metasilicate |
15 |
| CMC (100% basis) |
2 |
| Optical brightening agent |
0.15 |
| Soda ash |
33 |
Formula 45
Industrial Laundry Powder not Spray-dried
| Alkyl benzene sulphonic acid |
11 |
| Distilled tallow fatty acid |
7 |
| Tetrasodium pyrophosphate |
10 |
| Sodium metasilicate pentahydrate |
7 |
| CMC (100% basis) |
1.8 |
| Optical brightening agent |
0.1 |
| Soda ash |
61.1 |
| Water |
2 |
It is obvious that for a given load of washing more of Formula 45 will need to be used than of Formula 44.
Many laundries carry out a pre-wash at a lower temperature.* One of the above powders can be added to the pre-wash, but a more effective method is to use for the pre-wash a solvent detergent.
Solvent Detergents
It is not too difficult to combine non-ionics with solvents, but anionics are not easy to combine, especially those of the alkyl aryl sulphonate type, as most of these are insoluble, or only slightly soluble, in most non-polar solvents such as kerosene or deodorized kerosene which, of course, are generally the least expensive ones.
Detergents often serve only as emulsifying agents for the solvents, and not so much as detergents or cleaning agents. Emulsifiable insecticide concentrates, for example, are based on a solution of the emulsifying agent within the insecticide solvent mixture, forming a clear stable solution which, on dilution, gives a milky white emulsion with water. Here the emulsifying agent is a very often a non-ionic detergent acting as an emulsifier, rather than as a detergent proper. However, in this book, we are more concerned with solvent-detergent combination, in which the detergent acts both as an emulsifying agent for the solvent, and as a detergent in its own right.
In detergent-solvent combinations, the job of the solvent is to dissolve grease and similar oily dirt. The function of the detergent is to act as a penetrating and wetting agent and as an emulsifying agent for carrying off solvent after it has dissolved the oil or grease from the material to be cleaned, but it also keeps solid dirt particles in suspension. In many cleaning operations the detergent, by its surface activity alone, is simply not powerful enough to loosen dirt which is kept strongly attached to the surface by oily or resinous matter. This is very often encountered in metal-cleaning, or during the laundering of oil overalls. On the other hand, it is often impossible for a solvent alone to develop its full dissolving power where the oil matter is covered by solid crusts of insoluble matter. This is the case in the decarbonizing operations carried out on the working parts of internal combustion engines. It is the combination of surface activity plus solvent powder which makes solvent-detergents to useful in widely different fields of application.
The most easily produced type of solvent-detergent is a combination of non-ionic detergent with solvents. Very often a simple mixing of solvents with detergents is sufficient to obtain a clear, stable product, which generally forms milky emulsions in water. However, not all non-ionics are soluble in any proportion in any solvent. Very often they are only slightly soluble in non-polar solvents of the aliphatic type. Here it is necessary to use so-called 'co-solvents', together with the non-polar aliphatic solvent, to give the desired results.
The subject of solvency is of the greatest importance in working out effective products. By giving concrete examples, it will be made clear how important this type of solvent is in formulating high-grade products.
Generally speaking, the non-ionic detergents are more easily soluble in solvents than most anionic detergents. It is, nevertheless, quite incorrect to assume that they are soluble in all kinds of solvents. Thus, for example, a condensation product of nonyl phenol with 9-10 moles ethylene oxide is readily soluble in chlorinated solvents, xylene benzene, and in most polar solvents; it is, however, only slightly soluble in kerosene and white spirit and even less so in dearomatized (deodorized) kerosene. To increase the degreasing power of trichlorethylene, it is possible to add a certain percentage of non-ionic e.g. 3-5 per cent, to the solvent. Furthermore, a stable solution of trichlorethylene may be produced by dissolving 10-15 per cent of non-ionic in trichlorethylene. On dilution of the clear solution with water, a milky-white emulsion will be obtained. In order to prevent corrosion due to free hydrochloric acid, an addition of about 0.5 per cent monoethanolamine to the composition is advisable.
Chlorinated solvents should be used with cautions preferably they should be used in closed system, where the solvents is distilled, condensed and recycled, such as in dry cleaning and closed metal degreasing systems. The low heat of vaporization of these chlorinate solvents (210 J/g for perchlorethylene) and non-inflammability are distinct advantages.
As already pointed out, most non-ionic detergents are soluble in aromatic solvents and by dissolving 10 per cent in xylene and diluting the clear xylene solution with water, stable milky white emulsions may be obtained which are very useful for metal-degreasing compounds. Aromatic solvents may serve as co-solvents for dissolving non-ionic in aliphatic non-polar solvents such as dearomatized kerosene and white spirit. To obtain clear solution, a proportion of about 30-40 per cent of aromatic solvents is necessary, eg, 10 parts non-ionic; 30 parts aromatic solvent; 60 parts kerosene.
Formula 46
Detergent-solvent Combination
| Nonyl phenol 9 EO |
30 parts |
| Isopropanol |
20 parts |
| Xylene |
50 parts |
Formula 47
Detergent-solvent Combination
| Nonyl phenol 9 EO |
30 parts |
| Methylethyketone |
35parts |
| Deodorized kerosene |
50 parts |
Mix the materials in the order given. A clear solution is obtained which becomes blue-white opalescent when diluted with water (hard or soft). Nonyl phenol-9 ethox. behaves similarly to octyl phenol ethoxylates.
For the internal degreasing of motors, etc., such combinations with non-ionic detergents and solvents should prove very useful, possibly in combination with flushing oils. Even in the unlikely event of solvent-detergent remaining in the engine, practically no danger of subsequent corrosion should exist, because of the complete volatility of the products of combustion, which are hardly any more corrosive than the combustion products of motor fuels. It would even be possible to formulate an 'internal' decarbonizer on the basis of anionic detergents (AB sulphonic acid neutralized with alkanolamine of alkylamine), which does not leave any residues in the engine. Here again, an entire field for further research is open.
Another non-ionic detergent useful for formulating solvent-detergents is alkylolamide. Experiments with this compound (which is a condensation product of ethanolamine with fatty acids) have yielded very efficient solvent-detergents. However, the wetting power of alkylolamide is somewhat lower than that of water-soluble alkyl phenol of fatty alcohol ethoxylates.
A special solvent-detergent combination of interest is one which gives a clear solution of kerosene in water according to Formula 48.
Formula 48
Kerosene Water Solution
| Coconut fatty acid diethanolamide |
20 |
| Kerosene |
20 |
| Water |
20 |
On dilution with soft or hard water., all these products give very stable solvent emulsions of good detergent powder.
The alkyl benzene sulphonic acids can also be used as the basis of solvent-detergent combinations.
It is essential to start operations with the unneutralized sulphonic acid. SO3 sulphonated sulphonic acid, because they contain minimal amounts of inorganic acids, can quite easily be incorporated into these combinations, but oleum sulphonated dodecyl benzene, if treated as described below, can also be turned into an acceptable solvent-detergent.
Formula 49
Solvent detergent Combination
| Mix together : |
|
| SO3 produced alkyl benzene sulphonic acid (ABS) |
50 parts |
| Kerosene |
50 parts |
| Aromatic solvent |
25 parts |
| Then slowly add : |
|
| Caustic soda solution (38°Be) |
17-18 parts |
| After cooling to about 50°C add: |
|
| Isopropanol |
10 parts |
| Pine oil |
2 parts |
A clear liquid is obtained, which at low temperatures becomes gel-like.
A small amount of water from both the water of solution of the caustic soda and the water produced by neutralization, will be presented. If a completely anhydrous material is required, the lower amines, isopropyl or butyl, can be used for neutralization. Care should be exercised in their use as they are volatile, toxic and inflammable.
The product is completely soluble in soft water, somewhat turbid in hard water, and is completely soluble in organic solvents. It is almost completely soluble in non-polar paraffinic solvents, such as kerosene, petrol, etc. By diluting the solvent detergent with solvents, eg, 1:10 with white spirit or kerosene, a solvent-emulsion concentrate is formed which gives very stable emulsions on dilution with water. This is important for metal-degreasing operations.
It is interesting to note that the wetting power of the ABS detergents is practically unaffected if only aromatic and polar solvents are used, and only slightly affected when non-polar paraffin solvents are present. In all cases, sinking time as measured by the Draves test is not greater than 25 s at a concentration of 0.1 per cent active detergent matter in distilled water.
A completely anhydrous solvent-detergent can be manufactured from SO3 sulphonated LAS according to Formula 50.
Formula 50
Solvent-detergents based on 100 per cent ABS (So3 produced)
| Kerosene |
35 |
| ABS (100% basis) |
35 |
| Monoethanolamine |
15 |
| Trichlorethylene |
13 |
| Pine oil |
2 |
All the ingredients, except for the trichlorethylene, are merely mixed together until uniform. When the liquid has cooled to below 50°C, the trichlorethylene is added and the pH adjusted to 8 by using monoethanolamine. This pH was found to be advisable as the trichlorethylene might release traces of hydrochloric acid and the surplus monoethanolamine will absorb this. Trichlorethylene may be replaced by higher boiling perchlorethylene. Formula 50 is an excellent general-purpose combination and can be used for adding to the pre-wash in laundering, as an additive for dry-cleaning fluids, and for degreasing of engine parts, etc.
One of the most important uses of solvent-detergents is as a dry-cleaning aid. The purpose of the dry-cleaning detergent is a multiple one, to increase the effectiveness of the solvent in dissolving solvent-soluble spots and stains, to aid in the removal of water-soluble stains by dispersing or solubilizing a small percentage of water in solvent, and to increase the dispersion of these water-soluble stains in this water. To achieve this effect generally a combination of non-ionic and anionic detergents is used together with a coupling agent. For example.
Formula 51
Dry-cleaning Detergent
| Nonyl phenol 9 ethylene oxide |
40 |
| Propylene glycol |
17 |
| Butyl cellosolve |
3 |
| Monoethanolamine |
7 |
| Alkyl benzene sulphonic acid |
33 |
| (SO3 sulphonated to minimize inorganic salts) |
|
All the ingredients are mixed together and the pH (tested at a dilution of 1: 10 in water) is adjusted to between 7 and 8 with small additions of either monoethanolamine or sulphonic acid.
This is added to the dry-cleaning solvent at the rate of 1-1½ per cent with or without the addition of small quantities of water.
If a readily dispersible product is required, the above formula can be diluted 1:1 with a dry cleaning solvent (for example, perchlorethylene) and is then used at the rate of 2-3 per cent based on the volume of the solvent in the machine.
Although dodecyl benzene sulphonic acid gives excellent results in the above formulation, even better results are obtainable by replacing the ABS with heavy alkylate-sulphonic acid, which has a higher molecular weight and renders the sulphonate more oil soluble. Of course, with a higher molecular weight, the acid value will obviously we lower. The amount of alkali in the above formulations should, therefore, be correspondingly reduced. (This is best determined by the acid value of the heavy alkylate sulphonic acid.)
Carpet and Upholstery Cleaners
Fabric cleaners of this type differ in their operation from other detergent materials in that it is usually very difficult to rinse the material being cleaned. To overcome this, methods of cleaning have been developed where a solution of the detergent is applied to the carpet by 'shampooing' to form copious foam, or a foam is formed first and the carpet sponged with this foam,. In either instance the combination of the detergency of the cleaner and the mechanical energy applied lifts and holds the dirt in the foam.
The foam, having very thin walls and enormous surface area dries relatively quickly into brittle particles of dust and this dust is either vacuum cleaned or brushed away.
Initial formulations for these carpet shampoos were normal light-duty detergents with the addition of tetrasodium pyrophosphate, its function being both to increase detergency and to make the dried residue more brittle. A suitable detergent material which is also in itself fairly brittle when dehydrated is the sodium or magnesium salt, or one of the fatty alcohol sulphates. Some formulae also called for the incorporation of a solvent but with the newer fabrics and rubberized bases being used, the solvent should be chosen with care of left out.
These formulation were not, however, the complete answer to the problem. A portion of the active matter became absorbed into the fibre and when dried this left a deposit which tended to attract dirt. Carpets cleaned in this manner became soiled very quickly.
This problem has been overcome by using more crystalline detergents as the base. Such detergents are the half ester of sodium sulphosuccinates used alone or in admixture with fatty alcohol sulphates. Witco (France) is manufacturing the lithium salt of fatty alcohol sulphate for this specific purpose. The detergent then absorbed on the fibre is more brittle and when dried will shatter and can easily be brushed away. Another line of attack is to add colloidal silica to the formula to produce the same effect.
Textile Dressing
Detergents of the anionic type have to a large extent replaced soap in the scouring of wool and cotton. The main factor involved is that anionic detergents do not precipitate their lime and magnesia salts on to the fibres, and thus give a better 'handle' to the finished goods.
As textile processing is a complex process, the detergents manufacturer can only be called upon to supply a concentrated detergent; the various alkalis, phosphates or solvents are added by the textile processor himself. This concentrated detergent is usually manufactured by agreement between the textile scourer and the detergent manufacturer. Fatty alcohol sulphate pastes, neutralized immediately after sulphation, are as often used as are alkyl benzene sulphonate pastes. Depending on the requirements of the textile mill, the alkyl benzene sulphonate can be a concentrated paste neutralized only with caustic soda, or a semi-liquid paste neutralized with ethanolamine. A typical formula can be :
Formula 52
Textile Scouring Paste
| Alkyl benzene sulphonic acid (ABS 100%) |
375 |
| Diethanolamine |
130 |
| Water |
495 |
The ingredients are mixed together and the final pH adjusted according to the buyer's requirements.
On occasion, especially for degumming, detergents compounded with pine oil are preferred for textile scouring, particularly of wools.
We suggest the following formulation :
Formula 53
Textile Degumming Detergent Paste
| Pine oil |
250 |
| Alkyl benzene sulphonic acid (ABS 100%) |
280 |
| Diethanolamine |
97 |
| Water |
373 |
Mercerizing
Cotton cloth is a treated for anti-shrink properties by dipping in a concentrated (of the order of 12-18 per cent) caustic soda solution. To allow the solution to penetrate well and evenly into the fibres a detergent or rather a wetting agent is necessary. The bulk of detergents are either not soluble or not effective (or both) in strong caustic soda solutions. A commonly used wetting agent for this purpose is the sodium salt of sulphated 2-ethyl hexanol. By itself it is not completely effective but if blended with 10 per cent each of the unsulphated 2-ethyl hexanol and butanol, the material becomes soluble in caustic soda solutions, the solution remains stable and the wetting properties are greatly enhanced. Ethoxylated glycosides (moderate to high foaming) and the low-molecular-weight phosphate esters (low foaming) are also used for this purpose. Another possibility which has not yet been exploited commercially, is SO3 sulphonated olefins.
Food and Dairy Industries
As with any food industry, dairies require spotless cleanliness to prevent spoilage, and sterilization against bacterial contamination. The tolerance for residual bacteria is, however, lower for dairies than for other food industries, as in this case bacteria can cause the milk to turn sour. A further complication is the presence of high amounts of lime salts in the milk.
Many plants use strong alkalis only or cleaning, and sterilization is achieved by steam. These materials have their limitations, as can be seen from Table 4, detailing the properties of various alkalis for dairies.
It will be noticed that no one material supplies all the requirements. Chlorinated trisodium phosphate adds a sterilizing action. For this reason it is often desirable to combine several of these alkalies to produce a blended material which will provide all the requirements. The addition of a detergent greatly enhances the performance of these alkalis, but in certain processes foaming will interfere with the operation. Even low-foaming non-ionics foam slightly, and the use of detergent is thus sometimes excluded. Formulae 54-56 give some typical formulations for food-and dairy cleaning alkaline detergents.
Formulae 54-56
Food and Dairy Alkaline Detergent Cleaner
| | Non-foaming | Medium foam | High foam |
| |
54 |
55 |
56 |
| Trisodium phosphate |
15 |
- |
10 |
| Sodium Carbonate |
10 |
39 |
35 |
| Sodium metasilicate pentahydrate |
40 |
20 |
20 |
| Tetrasodium pyrophosphate |
- |
40 |
- |
| Sodium tripolyphosphate |
35 |
- |
30 |
| Non-ionic detergent |
- |
1 |
- |
| Concentrated anionic detergent powder |
- |
- |
5 |
To produce a powder that simultaneously sterilizes and cleans, the metasilicates must be of the anhydrous variety, and soda ash and non-ionic detergents should not be used. Subject to the above conditions, sufficient organic-chlorine bearing materials can be added to the above formulation to give, say 3 per cent active chlorine in the finished powder.
For bottle-washing in the food industry the pH required is very high. Sodium gluconate should be added for its sequestering action.
Formula 57
Bottle-washing Compound
| Caustic soda flakes |
55 |
| Sodium metasilicate |
20 |
| Soda ash |
17 |
| Sodium gluconate |
5 |
| 60% anionic detergent concentrate |
3 |
In addition to the above alkaline cleaning materials, in the dairy industry it is necessary as a routine to give the pipelines, etc., acid wash to dissolve milkstone deposited on the walls.
Very often concentrated hydrochloric acid is used. This is very corrosive and although the dairy plant is invariably stainless steel it is advisable to add an inhibitor. Nitric acid is also used on occasion. Although nitric acid is both a strong acid and an oxidizing agent, sight must not be lost of the fact that the original stainless steels were developed to withstand this acid, so no inhibitor is necessary. Both these acids are unpleasant to handle and environmentally unsound, therefore, to overcome these difficulties less corrosive materials have been developed.
Combinations of lactic acid with acid-resistant detergents have found application. So, also have, combinations of phosphoric, citric, and tartaric acid with acid-resistant detergents. The most recent development in this important field is the application of sulphamic acid. This has the structural formula :
It is the half amide of sulphuric acid.
| Molecular weight |
97.09 |
| Specific gravity |
2.03 |
Figure. 1 shows the pH of sulphamic acid in comparison with some other acids. The following advantages of sulphamic acid are enumerated.
- It crystalline, non-volatile nature, which makes it easy, safe and economical to handle, and eliminates the evolution of objectionable fumes when solutions are needed.
- Its strong acid character gives the 'bite' necessary for the removal of deposits.
- All salts of sulphamic acid (eg, calcium, magnesium, iron) are readily soluble in water. Hence, adequate dissolving and thorough rinsing of scale is assured. Further, it is expected that less sulphamic acid is needed than other commonly used acids.
- In spite of its strong acid character, dilute sulphamic acid solutions are not unduly corrosive to dairy equipment.
- It is simpler and less hazardous in handling.
The following five general steps are recommended for cleaning heat-transfer equipment and vats, using sulphamic acid :
- Thoroughly rinse or flush the equipment with warm water until the water is no longer milky.
- Prepare an adequate quantity of sulphamic acid solution of 0.2-2 per cent concentration (1.6-16 kg/m3), heat the solution to 65-70°C, and circulate for 10-30 min. Because of the many variables in equipment, composition of deposits and preferred cleaning practices, precise recommendations suitable for all cleaning applications cannot be given. The above ranges of concentration, temperature and time have developed from experience and should cover most situations.
- Rinse thoroughly with warm water.
- Flush the equipment with a cleaning and neutralizing solution consisting of 15-85 g of trisodium phosphate or other alkaline-type detergent compound for each gallon of water. The alkaline treatment should consist of approxmiately the same concentration, temperature and time as used with the sulphamic acid cleaning solution.
- Rinse the equipment again with warm water.
In the case of some stubborn or fat-containing depostis which tend to be water-repellent, it is sometimes advantageous to use a small amount of a wetting agent along with the sulphamic acid, so as to enhance the rate at which it penetrates and attacks the material to be moved Alkyl benzene sulphonic acid is suitable for this purpose.
Since uninhibited sulphamic acid is rather corrosive to ordinary steel and cast iron, it is wise to provide a separate pump for circulating solutions if existing pumps have ferrous metal parts in contact with the fluid.
The authors have conducted experiments with 100 per cent dodecyl benzene sulphonic acid to clean milkstone. The calcium salts of DDBS are dispersible in water and therefore the acid should be suitable. However, the 100 per cent acid dissolves with difficulty in water in low concentrations. It was found that the addition of 10 per cent xylene sulphonic acid to the 100 per cent DDBS rendered the mixture very easily soluble. A 5 per cent solution of this mixture dissolves the milkstone readily and the surplus is easily rinsed away.
Detergent Sanitizers
The halogens have long been known to be effecitve germicides, and chlorinated trisodium phosphate is used pretty effectively to clean and disinfect miling equipment.
There also has been a tendency in the past years to use bromine as such for disinfection but it has no real advantage over chlorine and is much less pleasant to handle.
Iodine is now gaining considerably in this field, particularly combinations of iodine with non-ionic surfactants.
These products called iodosphors with a 1-3 per cent iodine content are active against bacteria at a concentration of 0.012-0.025 g/litre and it has been found that maximum activity is obtained in an acid environment.
The iodophors are prepared by mixing nonylphenol adducts containing at least 8 mol ethylene oxide or ethoxylated propylene glycols with 20-25 per cent iodine and heating this mixture of 50-60°C. Care should be taken with ventilation as iodine sublimes, even at room temperatures. Under these conditions 75 per cent of the iodine combines chemcially with the nonylphenol ethoxylate.
Typical formulae 58, 59 are given below.
Formula 58 and Formula 59
20% avialable iodine in nonylphenol ethoxylate 8.75 8.75 Phosphoric acid (75%) 8.00 0.60 Nonylphenol+ 30 mol ethylene oxide 5.00 5.00 Water 78.25 85.65
Metal Cleaners
The cleaning of metal is done with either acid or alkaline materials. The acid treatment is meant for the removal of rust and other products of corrosion, and for the solution of 'scale'. This is a very wide term and includes both the layer of insoluble heavy metal salts precipitated on the walls and tubes of steam boilers, and also the layer of oxides (as opposed to rust) formed on steel surfaces under certain conditions of heating. The alkaline treatment is for the removal of grease, oil, paint and foreign matter, and is also necessary as a preliminary treatment prior is pickling (acid treatment) to remove the film of the oil which at best will hinder the pickling acid in its work and at worst will only allow this acid to work in patches, producing an uneven finish.
Scale removal by picking calls for cleaning compounds (which are added to help the acid to penetrate and give a uniform finish) that will resist the strong acids used in pickling processes. Generally, detergents without any special additions of builders are used in these cases. However, it is of great advantge to use detergents in conjunction with 'inhibitors' which prevent (or retard) the attack of the pickling acid on the metal itself. The detergent has no much inhibiting effect, but its wetting action is apt to prevent pitting to a certain extent-a very important reason for using detergents in the pickling bath. The most suitable detergents are the alkyl benzene sulphonates, but certain petroleum sulphonates or heavy alkylate sulphonates may also be used with advantage. In these instances it is not necessary to neutralize the sulphonic acids, merely to add the material to the bath. If, however, a ready-neutralized material is all that is available, this can be used. These detergents need to be highly acid-resistant and to stand up to severe conditions, such as a 5 per cent sulphuric acid solution at 70°C. The amount of detergent to be added to the bath is on the average between 0.1 and 0.2 per cent, calculated as active detergent matter.
As inhibitors, phenylthiourea and thiourea are very effective. They are solid substances which can be compounded with powderd detergents to increase the rapidly of the pickling effect (in this case a neutralized concentrated detergent powder is used), and to prevent excessive corrosin of the metal proper. The amout of corrosin inhibitor require is 0.01 to 0.05 per cent, based on the sulphuric acid content of the pickling bath. If the concentration of the active detergent in the bath is of the order of 0.1 per cent, it follows that the compounding of an effecitve pickling bath is not very difficult. An example would be: a concentrated detergent powder containing 40 per cent active dodecyl benzene sulphonate is mixed with 10 per cent of its weight of phenylthiourea of thiourea. This mixture is added to the pickling bath in the proportions of 0.25-0.5 per cent. An alkyl aryl sulphonate of the alkyl naphthalene type was effective in concentrations of 0.1 per cent, both as an inhibitor and a wetting agent.
The following inhibitors were also found to be effective in sulphuric acid pickling baths:
Butyl sulphide, o-tolythiourea, p-tolythiourea, butyl disulphide, amyl mercaptan, ethyl selenide, propyl sulphide, buty-methyl-sulphide, butyl mercaptan, p-tiocersol, iso-butyl mercaptan, trainylamine, m-thiocersol, thrihexylamine, ethyl sulphide, phenyl morpholine, ethyl mercaptan, formaldehyde, methyl sulphide, 2- thionaphtol, crotonaldehyde. (This is only a selection from a list of more than a hundred compounts listed).
In the past types of inhibitors especially suitable for acid cleaners, such as cleaners for automobile cooling systems, etc,have been devloped. The Sharples Chemical Corp brought its alkyl-substituted thioureas, diethyl-and dibutylthiourea, on to the market. These are suitable for use with 10 per cent hydrochloric acid solutions in concentration as low as 0.05 per cent. Other type of acid inhibitors, marketed by the Hercules Powder Co, are based on rosin amine derivatives, namely polyoxethylated dehydroabeitylamines. They are sold under the trade names Polyrades.These inhibitors were found to be effective in the range of 0.05-0.2 per cent in hydrochloric acid.
The effect of inhibitors in conjunction with surface-active agents is of great importance when removing water scale from steel pipes with hydrochloric acid. Again it was found that thioruea and phenylthiourea are very effective inhibitors whose effect is strongly enhanced by the use of detergents. A further line of research is the use of surfaces active agents in conjunction with corrosion inhibitors, such as sodium chromate, in brine solutions, calcium chloride refrigeration solutions and in autmobile radiators.
For autombile cooling systems, acid mixtures are often used to remove hard and adherent scale. The effect of these mixtures is often greatly increased by the addtion of detergents, which help in the penetration and removal of grease and oil which may have entered the cooling system and which prevent the acid cleaners from exerting their full effect on the scale. Mixtures of the solid acids, such as oxalic acid or sulphamic acid, and acid salts such as sodium bisulphate, may be improved by the additon of DDB sulphonate powders. The following formula is a suggestion for such a product :
Formula 60
Acid Cleaner for Water-cooling Systems
| Oxalic acid |
80 |
| Sodium bisulphate |
10 |
| Concentrated detergent 40 per cent active |
10 |
The concentrated detergent can be either dodecyl benzene sulphonate or an acid-resistant petroleum sulphonate.
Aluminium is often cleaned and brightened by acid solutions containing hydrofluoric acid. One of the few detergents found to be compatible with this highly corrosive acid is an amphoteric of the dicarboxyethylated derivative of cocoimidzoline. A formula suggested by the Miranol Chemical Company, which we have found to be effecive is :
| Miranol C2M-SF Conc. |
5 |
| Glycol ether |
6 |
| Phosphoric acid (85%) |
38 |
| Hydrofluroic acid (70%) |
8 |
| EDTA |
1 |
| Water |
42 |
Although this is called a cleaner, it acutally removes the oxides on the surface thus giving a brightning effect.This solution should be used after an alkaline wash to remove the surface film of dirt and oil. Aluminium is attached by alkali, but silicates effectively inhibit this attach.
Besides the acid-type metal cleaners described above, metals are cleaned in strongly alkaline solutions to remove grease, oil and foreign matter prior to plating, painting, enamelling or other protective treatment used nowadays.
The method of removing this foreign matter determines the composition of the alkaline cleaner. It is obvious that, if a spray method is to be used the cleaning solution cannot foam. The principal methods of alkaline metal treatment are soaking, spraying and electrolytic or combinations of two of these processes. In the soaking process, the cleaning effect is obtained by the high concentration of the detergent, and also a possible circulation of the solution by a pump. The spray process added mechanical energy form the jet to aid in the removal of the dirt. The electrolytic process produces the cleanest surfaces because of the scrubbing action of the gases evolved and the attraction of the electrically charged dirt particles by the electrodes.
In additions to the types of cleaning process used, the type of metal to be cleaned influences the choice of formulation of the detergent. No detergent can do the universal job of cleaning very surfaces, and various formulations for differnt types of metals and also the different cleaning process are given in Formulae 61-74.
In these formulae, mention is made of sodium resinate, which is saponified tall oil, obtained as a by-product in the paper industry. This soap is relatively cheap and in addition has good emulsificaiton properties for oil. As its detergency is poor, it is invariably used in conjuction with a detergent. We suggest that the same emulsification can be achieved by the use of a sulphonated heavy alkylate. The formulae also call for alkyl aryl sodium sulphonate. This is meant to be a concentrated powder containing 40 per cent sodium dodecyl benzene sulphonate. If another concentration is available the proportion should be varied accordingly.
Miscellaneous Cleaners
Lavatory Cleaner
The universal ingredient of lavatory cleaners is sodium bisulphate (NaHSO4, technically called nitre cake). The most popular lavatory cleaner is based on this compound. Caking of sodium bisulphate can easily be overcome by adding to the ground salt some 0.5-1 per cent pine oil or a mixture of pine oil and kerosene. This also largely prevents corrosion of the metal containers in which these products may be marketed. (Recently, high density polythene containers have been adopted in many European countries. These are completely unaffected by lavatory-cleaning compounds.)
The cleaning effect can be improved by adding to the sodium bisulphate not only the 0.5-1.0 per cent pine oil, but also approximately 1 per cent alkyl benzene sulphonic acid.
In the last few years liquid toilet bowl cleaners have appeard on the European market, particularly in Germany. These are packed in specially designed plastic bottles so that they can be dispensed on to the inner, invisible, rim of the toilet pan. these liquids are acid, either mineral or organic acids being the acidic component, contain relatively large amounts of surfactants, are dyed and perfumed and have medium visocosity. A typical representative formulation is given by Dragoco :
| Non-ionoc detergent |
11.0 |
| Hydrochloric acid (33%) |
10.0 |
| Phosphoric acid (85%) |
10.0 |
| Perfume |
0.2 |
| Water |
68.8 |
Due to the acidity of the solution, the non-ionics need to be chosen with care and are usually a blend of alkyl phenol ethoxylates of both short and long chains. The perfume needs to be matched to the formulation to render is stable under acid conditions.
A viscous lavatory cleaner with both sanitizing and deodorizing effects may be produced by using LAS (So3 sulphonated) and pine oil as its two components :
| LAS (acid form) |
100 |
| Pine oil |
50-70 |
| Water |
150 |
The LAS and the pine oil are mixed and the water added immediately to prevent reaction of he sulphonic acid with the pine oil.
The water and/or the pine oil are varied to produce the desired viscosity.
An oily liquid with lower viscosity but faster dispersibility in water is obtained by adding 10 to 20 parts isopropanol.
Hand Cleaners
The manufacture of hand cleaner is similar to that of other abrasive cleaners. Thus a hand soap in paste form may be produced according to Formula 75 :
Formula 75
Hand Cleanser
| 40% SodiumABS paste |
130 parts |
| Bentonite |
150 parts |
| Fine sand |
200 parts |
| Sodium carbonate |
10 parts |
Or it can be manufactured by using as the base a detergent paste according to Formula 76.
Formula 76
Detergent Hand Cleanser
| 40-50% Sodium alkyl benzene sulphonate paste |
100 parts |
| Bentonite |
30 parts |
| Abrasive powder |
200 parts |
| Sodium carbonate |
10 parts |
The solid materials are incorporated into the soft soap or paste. Some water may need to be added to regulate consistency. A hand cleanser in powder form may be produced with Formula 77.
Formula 77
Hand Cleanser in Powder Form
| Pure powder soap or concentrated detergent powder |
26 parts |
| Abrasive material |
70 parts |
| Borax |
4 parts |
Some of the abrasive material may be replaced by vegetable abrasives, sawdust, etc.
A special hand-cleansing compound containing approximately 75 per cent borax and 25 per cent of dry soap was found by the laboratories of Borax Consolidated Ltd to posses desirable fungicidal properties, and yet to be so mild in its action on the skin as to reduce any tendency to dermatitis. The borax is in finely granulated form, so that, when mixed with dry, powdered soap, gumming or caking is avoided. The product is described as a good cleanser, and will effectively, and with out the use of waste, remove dirt from hands. The borax is not merely a diluent for the soap. Its hardness of two makes it even softer than chalk; it is readily soluble, and its abrasive action is only temporary, as the sharp edges of the grains become blunted almost immediately. It has detergent and water softening properties of its own and it is a mild alkaline salt possessing the characteristic properties of imparting to a soap solution a pH value lower than that of soap alone.
Waterless Hand Cleansers
This type of hand cleanser is specially suitable for motorists, for removing oil, grease and grime after changing tyres or doing repairs while on the road. We confine ourselves to giving some formulae which we have worked out and found suitable for the purpose. We found Formula 78 especially useful to motorists for removing oil, paint, tar, etc, from the hands.
Formula 78
Waterless Hand Cleanser
| Stearic acid and/or 100% alkyl benzene |
25 |
| sulphonic acid |
|
| Lanolin and/or lecithin |
15 |
| are dissolved in : |
|
| Deodorized kerosene |
350 |
The mixture is kept at a temperature of about 70°C.
To this solution the following mixture, having the same temperature of 70°C, is added
| Triethanolamine |
25 |
| Water |
95 |
Stir constantly until the mixture is cold
3.5 parts of pine oil is recommended as a cheap perfume and disinfectant.
Formula 79
Waterless Hand Cleanser
| White mineral oil |
40.5 |
| Oleic acid |
10.5 |
| Non-ionic detergent |
6.0 |
| Propylene glycol |
5.0 |
| Triethanolamine |
2.6 |
| Morpholine |
1.0 |
| Water |
34.4 |
Formula 80
Waterless Hand Cleanser
| Deodorized kerosne |
42.8 |
| Lanoline |
0.9 |
| Oleic acid |
5.9 |
| Cetyl alcohol |
0.4 |
| Triethanolamine |
2.9 |
| Propylene glycol |
2.7 |
| Sodium lauryl alcohol sulphate |
1.4 |
| Water |
43.0 |
The present authors are not in favour of adding abrasives to this type of waterless hand cleanser, because they cannot be completely wiped off the hands after use and are likely to choke the pores and thereby irritate the skin. If, for very heavy-duty waterless cleansers, an abrasive cannot be dispensed with, only the softest kinds, such as whiting, bole, kaolin, etc, should be used, and in the instructions for use it should be recommended to wash the hands with soap and water as soon after the applicaiton of the cleaner as possible. Neither halogenated solvents nor aromatic solvents should be used.
- The ethanolamide might contain some free ethanolamine, in which case this can be used as a partial neutralizing agent for the LAS, reducing the amount of NaOH or triethanolamine.
- Optional. Its purpose is to lower the viscosity of the slurry and increase the hardness of the beads.
