Detergents from Petroleum1 L A W R E N C E FLETT, National Aniline Division, Allied Chemical and Dye Corp., Buffalo, Ν. Υ.
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BOUT 1930
a new era in the science of
washing agents started with the in troduction of the synthetic deter gent. F o r several thousand years, in fact for practically the entire existence of civ ilization, soap has had a monopoly of the cleaning business. Soap was a very worthy monopolist. We should have been much l e s s happy without it. W e have a general word, "detergent", which em braces soap and other cleaning agents, but it found practically no use up to about 1930 because there w a s no real detergent other t h a n soap. Today we must take out this word detergent, dust it off, and put it to use because the new cleaning agents are not soaps. We d o not now have a good name for these n e w washing agents. They are generally called "synthetic detergents". That is not a good name because soap is a synthetic detergent. The new agents have been called "soapless soaps", and that name is not correct because they are not soaps. Another name is "detergents" and that name is safe enough, but it includes soaps. Still more recently these new products have been referred to as "surface active agents". Although this term is broad enough t o in clude s o a p and the wetting agents, it has come t o have a more specific meaning. It is being applied t o those agents which have a n unusual surface active action. T h e activity of the new detergents comes from their ability t o coat over surfaces with layers s o thin t h a t they do not visibly change the coated material. T h e material so coated no longer presents i t s own sur face to a surrounding solution, with the re sult t h a t i t s properties in solution are changed. Soap has become such a common factor in our lives t h a t we do not realize the lim ited conditions under which it can be used. Soap must b e used in warm t o hot water. The washing solution must be al kaline. Lime salts and heavy metal salts must n o t be present in sufficient amounts t o precipitate all the soap. Such salts should preferably be absent. The water used must n o t be t o o salty. I n the indus trial world these conditions are not easily arranged. There are m a n y operations preferably carried out in neutral or acid solutions, i n the presence of heavy metals, or in cold water. There was real need for a powerful cleaning and dispersing agent which would be effective under any condi tions. T h e new detergents, which came with this n e w era, are detergents which would work under any and all conditions. They 1 Jacob F. Schoellkopf medal address, presented before the Western Nov York Section of the
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wash in acid as well as in alkaline solution; t h e y clean cold ; a n d they clean hot. They wash better in hard water than in distilled water. They wash in sea water. These de tergents can be used even with the heavy metal salts in electroplating baths. T h e man who dyes and finishes cloth m u s t use cleaning agents, and he has been forced to confine h i s cleaning t o operations which are compatible with soap. Soap precipitates in sticky curds w i t h the lime salts and magnesium salts. The precipi tated curds have a w a y of gathering on textile goods; and of course, a fabric spotted with lime soaps will not dye evenly. This trouble is so serious that the dyer has been willing t o pay a premium t o obtain a detergent which did not precipi t a t e in sticky curds with lime salts. T h e n e w synthetic detergents were developed b y companies serving the textile industry t o solve the problems of the dyer and finisher. T h e use of these detergents soon spread until today practically every in dustry uses these new surface active agents a n d their use is being extended to the household. Attempts to develop new agents which would not cause thadirficulties soap caused, began b y coincidence soon after the pe troleum business started. I t began with t h e development of t h e "wetting agent". Before textile goods can b e dyed or fin ished, they must be wet. I f they are not w e t , they cannot absorb d y e s or anything else from a solution. The first really important wetting agent t o substitute s o a p came into general use about 1875, and was the sulfonated castor oil, sometimes known as Turkey red oil. About 30,000,000 pounds a year are still used. Sulfonated castor oil precipitates t o some extent i n hard water, b u t the pre cipitate remains dispersed and relatively innocuous. Turkey red oil used with soap made the lime soap precipitates less dam aging. T h e present use of Turkey red oil i s largely that of an oil t o lubricate and soften textile materials. Although sul fonated castor oil had many of t h e proper ties of soap and although i t lacked some of t h e undesirable properties of soap, its use as a soap substitute was limited because it was not a cleaning agent. Products like sulfonated castor oil which cause textile materials to w e t o u t but which had no washing power were called "wetting agents". In the period from 1912 to 1920, during the last war, t h e propylated and butylated naphthalene sulfonates appeared commercially a s soap substitutes in Ger many. These agents gave clear solutions in hard water, they were stable in acid solution, and they lacked m a n y of the
CHEMICAL
faults of soap. Since they did not wash, these agents were classified as wetting agents. T h e commercial introduction of wetting agents which were also detergents started in t h e United States about 1930 when the National Aniline Division of the Allied Chemical and D y e Corp. introduced a wetting agent called Gardinol, which was at that time manufactured in Europe. Gardinol was a mixture of sulfates made from alcohols derived from coconut oil. It w a s a white solid, stable in warm or hot hard water, reasonably stable in neutral solutions, and not too quickly broken down in cold acid solution. The remark able thing about this new wetting agent was that it could wash and clean. Soap had a challenger. T h e high price a t which Gardinol was introduced did not prevent its ready acceptance by the dyers. Gar dinol was the first product of commercial importance in this new era of synthetic detergents. After the stock market crash of 1929 upset our economic system, this is how things stood: 1. There was the unsolved riddle of how to make a low-cost but good washing agent from petroleum. 2 . There were miraculous new wash ing agents like Gardinol for which there w a s a demonstrated demand at a high >rice, and there was an insistant demand rom industry for the new detergents at a price more comparable to that of soap.
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Here then was a conjunction of t w o stars to both of which you could hitch your wagon. The problem was no longer howto produce a low-cost soap from petroleum b u t how to make one of the valuable new synthetic detergents from petroleum at a cost comparable t o that of soap. T h e successful production of the new detergents from petroleum b y the National Aniline Division was a project of considerable magnitude. No one should get the idea t h a t it was done in any reasonable period of time by any one man. It was a project requiring the team work of an organiza tion. From this work emerged the first com mercially important detergent from pe troleum which had a powerful washing action—a product which was stable in hard water and in neutral or acid solutions and was a powerful dispersing agent under a n y conditions of use. I t was t h e first of t h e synthetic detergents which was com pletely stable t o acid and alkaline solu tions. In general, all detergents are made up of two parts. There is a long hydrocarbon chain sometimes called the hydrophobic group- In the detergents made from pe-
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troleum the long hydrocarbon chain or hy drophobic group is the part of t h e mole cule derived from petroleum. Then there is the group which makes the product water-soluble, known as the hydrophilic group. Practically all of the commer cially important new detergents are sulfuric acid derivatives. They are practically all sodium salts. Sodium sulfate is well known. It is soluble in water and causes water to froth slightly. All are acquainted with the two petroleum distillates known as white oil and kerosene. If y o u had a chemical product which was half oil and half sodium sulfate, y o u would have a detergent. That is the type of detergent which we make from petroleum. The first step in the process which we have devised for manufacturing detergents from petroleum is t o make the petroleum distillate chemically reactive. This can be done in one way b y reacting it with chlorine. The aliphatic chloride so pro duced is still difficult t o convert to a sul furic acid derivative, but it is easily con verted to an alkyl aryl compound. The resulting aliphatic aromatic compound m a y be sulfonated to give the sulfonic acid which is generally converted to the sodium salt. Other metal salts may b e made. Practically all of the metal salts, as well as the ammonium salt of this type of com pound, are sufficiently soluble t o give an adequate cleansing or surface active ac tion. The basic process is very simple. I t s operation is complicated by many pur ification operations directed to giving a cleaning agent which will be effective and relatively colorless and odorless. The importance of cleaning agents from petroleum has increased since Pearl Har bor. Cleansing agents which can be made entirely from domestic ingredients today assume national importance because the importation of vegetable and animal oils has substantially stopped. Foremost in the list of oils which we no longer re ceive is coconut oil, most of which came from the Philippines. Coconut oil was used in practically all household soaps. Six hundred million pounds of it were im ported in 1941, of which almost 500,000,000 pounds found their way t o the soap ket tle. The loss of coconut oil will not make itself felt at once because there are large stocks, but when these are consumed what shall we use as a substitute? W e cannot use tallow since 90 per cent of that goes to soap now. There is no vegetable or animal oil which is now available in amounts far in excess of the wartime needs. Sales of practically all vegetable and animal oils are under limited restrictions. T h e soap industry is one of three which are large consumers of oils. The other two are having their own difficulties so they have no oil to contribute to soap. T h e paint industry for one has been handicapped for some time by the loss of china wood oil from China, and from other consumers it is drawing castor oil which is dehydrated t o give a drying oil. In the food industry V O L U M E
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the edible oils and fats are in greater demand t h a n ever because of declining im ports. Whatever our shortages in animal and vegetable oils may be, we do have an abundant supply of petroleum. The United States production of petroleum is not measured by a billion pounds, but by a billion barrels every year. Our ability t o make detergents from petroleum makes potentially possible the release of 2,000,000,000 pounds of fats and oils to become foodstuffs. This would increase by more than 30 per cent the amount of oils and fats available for food. The field of synthetic detergents a n d wetting agents is likewise affected by the loss of coconut oil. Some of the more important synthetic detergents are made from coconut oil, and it is to be hoped that t h e dwindling supply of coconut oil will be conserved t o make those surface active agents which are more valuable than soap. If the situation arises where synthetic detergents from petroleum must be used, several basic principles which govern their use should be known. T o point out certain peculiarities of the synthetic detergents, it is necessary t o select one for illustration, in t h i s case Nacconol N R . Nacconol NR i s truly representa tive of the new detergents from pe troleum. I t is a product which is stable under any conditions of use which we have yet encountered. Nacconol N R is a little
less than 4 0 per cent alkyl aryl sulfonate and about 60 per cent sodium sulfate. First and foremost in the use of Nac conol NR, the effect of t h e inorganic salt which it contains should b e appreciated. The alkyl aromatic sulfonates, unlike soap, are salts of strong acids. In very weak solutions they give true solutions in contradistinction to the colloid-like solu tions of soap. Sulfonates in very dilute solutions are surprisingly improved in their washing action by the addition of salts, possibly as a result of their conversion by such additions t o the colloidal state of solu tion. The effect of salt is shown in Figure 1 which shows squares taken from pieces of washed wool. The wool is first soiled in a special machine with a mixture of lamp black, fat, and oil. The washings are then made in a Launderometer which gives light scrubbing action. The amount of sulfonate used for washing is reduced, going from left t o right, and is replaced by an equal amount of sodium sulfate. The fourth square was washed with only 40 per cent as much sulfonate as the first square where 100 per cent detergent was used and yet it washed whiter. This mix ture represents Nacconol N R which is about 40 per cent alkyl aryl sulfonate and 60 per cent salt. In the sixth square was only a fifth as much sulfonate as in the first square and yet the washing ob tained was better than the washing ob tained with the pure product t o which no addition of salt had been made.
Economical use of any of the new deter gents from petroleum requires a careful consideration of the correct amount of salt. In the washing represented by this slide, the product could advantageously have had half of the organic matter re placed b y salt. However, this is an un usual condition since a relatively strong solution is needed to wash the heavy soil. Ordinarily wool washing is carried on with Figure 1 1 part per 1,000 or 0.1 per cent. The next consideration is the amount of NACCONOL NR DETERGENCV I detergent required. Commercially deter on gents are used at concentrations from SPECIALLY SOILED WOOL ΊΟΨΛιη - I 2 2 T 0.001 per cent t o 20 per cent. There is a damaging misconception that the more de tergent used the better cleaning. Figure 2 C0MC:7* 005 0.1 ÙJ2 0Λ 0.6 0s\ shows that this is not true. Here is a heav ily soiled wool. When the Nacconol is used at a strength of 0.05 per cent there is practically no washing; a t 0.2 per cent or Figure S 2 parts per 1,000 the washing is practically complete. By the time a 0.6 per cent con centration is reached, washing action is falling off; at 0.8 per cent the washing is no better than was obtained at 0.1 per cent, although 8 times as much Nacconol is used. N o detergent should be tested at high concentrations with the idea that the greatest effect will be obtained. Figure 3 is the first of a series of three slides comparing Nacconol with soap. The wool used in this test has a very heavy soil that is difficult to remove. The dark squares show substantially no washing. First, note that the soap at 0.3 per cent Figure 3
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concentration gives a white washing in '20 minutes, and that the longer time t h e washing is carried on using soap the whiter the wool is. With the Nacconol a white wool is obtained at 0.2 per cent concen tration or two thirds the concentration of the soap, and the organic content of N a c conol is only 40 per cent as compared t o soap because of the supplemental use of sodium sulfate. The actual organic m a terial required for a white washing in t h e case of the Nacconol is only 25 t o 30 p e r cent as much as in the case of soap which is practically pure organic material. Another characteristic of the Nacconols is their rapid action. You will note t h a t the Nacconol gives substantially complete washing in two t o five minutes while t h e soap requires 20 minutes. This quick action is very desirable in washing things like wool blankets or sweaters where pro longed washing changes a soft, fluffy m a a terial to a stiff feltlike fabric. T h e longer wool is washed the more it shrinks. Figure 4 shows the same test as does Figure 3 but was made in Buffalo c i t y water which is about 7 ° hard. N o t e t h a t the washing with Nacconol is substan tially unchanged, while soap has lost its ability to make this wool white within t h e limits of this test.
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Moth repelling action of Naccono! NR
Figure 4 Figure 8.
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Figure 6 846
Mothproofing action of Nacconol NR
Figure 5 shows the washing in 2 0 ° hard water where soap has lost all its washing action within the limits of the test. T h e Nacconol o n the other hand still shows a fine "washing action. S o a p must be used in alkaline solution. Alkaline solutions are damaging t o many products such as paint, linoleum, and wool. Many industrial operations, such as a c i d dyeing and pickling, are carried out advantageously in neutral or acid solution. Figure 6 shows the effect of the hydrogen-ion concentration on washing. As solutions become strongly alkaline, s o a p increases in efficiency. In neutral or acid solution it becomes worthless. A h y drogen-ion concentration of 10 is about t h a t of a weak modified soda solution. T h e Nacconol, on the other hand, is effec tive in neutral solutions and is excellent in strong acid. In strongly alkaline solutions it is not so effective although it still shows a considerable washing action.
CHEMICAL
Nacconols are insecticides. Whale oil soap was used as an insecticide, but unlike whale oil soap the Nacconols are retained by a substantive action of the wool. T h e y are held in small amounts by the wool much as a dye might be held. Figure 7 shows the moth repellent action of N a c conol N R . In this test the wool washed with Nacconol and moth eggs are placed in the same container as a piece of un washed wool. Vitamin Β is added so that the moth larvae will thrive. In all cases the larvae made a good meal of the un washed wool. In the case of the washed wool there is a slight attack at 0.1 per cent, a very slight attack at 0.2 per cent, and no attack at 0.3 or 0.4 per cent. Figure 8 shows mothproofing action as compared to the moth repellent action shown in the last slide. I t also shows the effect of water rinsing after washing. In these tests there is no untreated wool for the larvae to thrive on. T h e y must eat
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until the suds are gone. The stacks of plates in back are those washed with N a c conol; the stacks in front are washed with soap. Water which is 3 ° hard is known as soft water. The Nacconol in this water washed 22 plates, while soap washed only 16 plates. Water 7.5° hard is equivalent to Buffalo city water. In this water the number of plates washed with Nacconol increased to 25 while the number of plates washed with soap dropped t o 4. In water of 20° hardness, 5.6 grams of soap in 6
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The chemist uses small amounts of Nacconols t o speed chemical reactions and to obtain uncontaminated precipitates. Many special uses are made of the new washing agents because of their powerful antiseptic action. Bacteria do not grow in the ordinary Nacconol washing solutions. Such solutions are al^o powerful insecticides and fungicides. A Nacconol solution is particularly valuable to clean a cellar infected with mildew or insects. For such uses do n o t bother to rinse the
Figure 9 the Nacconol washed wool or die. Here 0.2 per cent of Nacconol is adequate protection since there is no untreated wool for the larvae t o grow on. The wool sustains one light rinse without loss of its mothproofing action, and some mothproofing action remains even after the third rinse. Wool washed with 0.1 per cent Nacconol N R sustained moth larvae when they had to eat it, although where other wool was available the moth larvae ate very little of the wool washed with 0.1 per cent Nacconol NR. Many alkaline cleaners are used particularly in the metal industry. In some cases it is necessary to have better cleaning than is obtained from the alkaline solutions alone. When Nacconol N R is added to improve the cleaning of alkaline solutions, small additions of 5 to 10 per cent based on the weight of the alkaline salts are extremely effective. Large additions generally offer no advantage over the small additions and, since Nacconol costs more than alkaline salts such as sodium phosphate, sodium silicate, caustic soda, and soda ash, it is uneconomical t o add more than 5 to 10 per cent. T h e effect of this small addition is shown in Figure 9. This is a series of metal strips treated with oil and cleaned. The strips are then photographed under ultraviolet light where the oil residues fluoresce and become readily apparent. T h e upper row shows oiled steel cleaned with a 5 per cent solution of sodium metasilicate. A t the left is a blank of unoiled steel; then the cleaned strips. The oily residue is very evident, although this is a good cleaning solution. The different strips represent 2, 4, 6, 8, and 10 minutes' washings without scrubbing. The second row is washed in the same way with a 5 per cent solution of a mixture of 95 parts of sodium metasilicate and 5 parts of Nacconol N R . All of the plates compare favorably with the clean reference strip a t the left.
Figure 10 quarts of water is not enough to wash any dishes. With the Nacconol the number of plates washed in 20° hard water is 40 per cent greater than the number which could be washed in soft water. The principal uses for the new detergents are those in which soap is at a disadvantage for one reason or another. For example, special Nacconols are used in foods where the taste of soap is objectionable. They can he used t o make an angel food cake which seems t o melt in the mouth. Weak solutions of Nacconol N R are used to wash insects and insect fragments from vegetables such as broccoli, spinach, and lettuce. From petroleum products we have produced special detergents which are completely odorless and tasteless. The Nacconols are used in dentifrices. Enameled woodwork, painted houses, and automobiles can be washed with a tablespoonful of Nacconol in a pail of water. T h e solution is neutral and does not dull the glossy finish of the coating material. I t may be easily rinsed, and t h e surface will dry clean without polishing. N a c conols are useful in nonaqueous mediums and they disperse pigments in enamels. They clean in a dry cleaner's solvent much as soap does in water. In lubricants they keep the inside of automobile engines clean. They enhance the fungicidal properties of oils and keep leather clean while it is being defatted.
Figure 10 shows the number of dinner plates which can be washed with 5.6 grams (about 0.2 ounce) of soap or Nacconol in 6 quarts of water. Each plate is soiled with 2 teaspoons of a mixture of grease, vegetable juice, and flour. The Nacconol is dissolved in the water and a suds is beaten up. Plates are then washed V O L U M E
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solution off after washing. In tanning leather Nacconol assists the tanning. I t is a mild tanning agent b y itself. It keeps the leather clean and uniform. Nacconols are used in laundry work and dishwashing where it is desired t o reduce bacteria counts. A pile of dinner plates washed with t h e Nacconol squeaks when you move it because there is no fatty soap residue left to lubricate the surface of the plates. Many people are allergic to soap, particularly in hard water areas. N a c conol N R is used t o wash diapers to avoid diaper rash which often is an allergic reaction t o lime soap. A special product called Dermanac is prescribed with which people w h o are unable to use soap can wash. Nacconol added to the bathtub before drawing the bath gives an amusing and cleansing layer of bubbles, and when the water runs o u t there will be no soap ring around t h e tub. Wool blankets washed in a t u b of almost cold water with a cup or less of Nacconol for three to five minutes and hung in the breeze to dry are enticingly soft, beautifully cleaned, and obnoxious to moths. Since they are not washed long they d o n o t shrink so much as they ordinarily would in washing. H o t water is a problem with the dairy farmer since t h e barn is always a long way from the house, b u t the detergents from petroleum are effective washing agents in cold water and, because the washing solutions are antiseptic, serve t o protect the 847
milking equipment. Because the Nacconol NR emulsifies odoriferous oils, it is valuable for washing dogs. Since the washing solutions are neutral they do not hurt the dogs' eyes, but because the solutions are insecticidal they devastate the fleas. In acid baths where steel is pickled t o remove the rust, soap would precipitate, forming fatty or oily acids. The Nacconols are stable in acid. They not onlyserve to clean the steel during pickling, but they protect the steel itself from attack by the acid. In electroplating baths the heavy metal salts precipitate the heavy metal soaps. The Nacconols on the other hand are adequately soluble and serve t o avoid pits, pinholes, and other plating difficulties. Very few persons realize the extent t o which Nacconol used industrially influences the things they wear, the things they eat, and the things they use. Every one has benefited unknowingly from its industrial application. New Zealand Government Plans Mica Development P L A N S for exploiting, under national restrictions, of what are believed to be extensive mica deposits are reported from New Zealand. Preliminary geological examination is said to warrant a more detailed survey, deposits being reported over an area of 89 square miles at elevations of 4,000 and 5,000 feet. It is planned to check indiscriminate licensing, to ensure the area being worked for national and allied benefit under existing mining laws and, if these are not adequate, by special emergency powers. © ^ © — —
FORMATION recently of a company in Hungary to produce plastics and synthetic resins, rubber, and leather has been reported from abroad. The company, Hungary Plastics and Chemical Works, Ltd., is said to be capitalized at 2,000,000 pengo. e^© U . 8. O. A .
PHOTO BY F O R S Y T H E
Lacquer Substitute for Tin Coatings Above. Paul D . Watson, chemist in the Bureau of Dairy Industry, U . S. Department of Agriculture, contrasts two milk can covers. The one at left is an ordinary tin-coated cover, the other a cover coated with the lacquer he has developed as a substitute for t i n o n cans for evaporated and condensed milk a n d for cheese. To test the practicability, the lacquer-coated m i l k cans, along with tin-coated cans for comparison, are used t o haul milk to the department laboratories in Washington, D . C., from the department's dairy farm about 13 miles away in Beltsville, M d . Below. In working out t h e lacquer formula, samples of dozens of different combinations of materials were baked o n glass dishes (in foreground) a n d small steel strips, and subjected to various tests. The lacquer that proved most promising consists essentially of lactic acid a n d vegetable oil. 848
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