The New Detergents R.A. DUNCAN Procter & Gamble Company, Ivorydale, Ohio
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N ORDER to appreciate the technical and possible com-
mercial importance of the new detergents, we should first consider briefly the detergent field as a whole. Sumerous materials are used as detergents, including alkalies, alkaline salts, soaps, and solvents. Among these, soap has had the widest range of usefulness and might be called our standard detergent. Just how long soap has been used as a detergent is not known, but the discovery of a wellequipped soap factory in the ruins of Pompeii, destroyed in 79 A. D., indicates the probability of its use 2000 years ago. During this period soap has been improved in many ways, but one of its most serious shortcomings could not be overcome. Stated broadly, this difficulty is due to the limited number of the soluble salts of the higher fatty acids, but most of the trouble is caused by calcium and magnesium. Salts of both these metals are present in practically all natural waters, and they are precipitated as insoluble calcium and magnesium soaps. The quantity of soap consumed in this way is considerable and means a serious economic loss. For water of 15 to 20 grains hardness, which is typical of a considerable portion of our midwestern and other districts, half of the total soap used is required to soften the water. But a n even more serious objection, a t least in many cases, is that the insoluble curds are slimy in character and tend to stick to the sides of the vessel and to the materials being washed. This in turn results in a poor appearance of the finished goods and has been partly responsible for the trend .I 2
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oil served the purpose fairly well; hence this and similar materials have been in use for many years. The so-called sulfonated oils are numerous and varied, and include both straight-chain and aromatic compounds, but it will be simpler if we omit the latter from our consideration. I n these products the sulfuric radical generally attaches itself to the fatty acid or hydrocarbon chain by breaking a double bond, so it is linked up as a side chain. It was found that these sulfonated oils are not only good sudsing and wetting agents in acid solutions, but that in addition they are not affected by hard waters. This means that their calcium and magnesium salts are moderately soluble, but unfortunately all of these products are relatively poor detergents. During the World War when Germany was hemmed in on all sides and painfully short of fats, the problem of finding a detergent made r i t h o u t fats became important. Khile no really good detergent was produced a t that time, the ideas stimulated by the war-time needs continued to develop and bore fruit only within the last fern years. Comparing the structure of the sulfonated oils with that of soap, it was reasoned that the detergency of the latter is due to the basic group being attached to the end carbon of the chain, while in the sulfonated oils it is attached through the sulfonic group to an inside carbon. It was also reasoned that the way to obtain the detergency of soap and a t the same time retain the acid resistance and the insensitivity t o hard water of the sulfonated oils is to sulfonate, or to sulfate the end carbon of a fatty acid or hydrocarbon chain of proper length. Since these radicals cannot easily be directed to the end carbon of such a group, various other means were tried to attain this end. Work along this line has led to the development of a t least two types of compounds which the author has chosen to call the “new detergents.’, These are (1) the sulfated alcohols and (2) the Igepons. SULFATED .kLCOHoLs
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IO 15 H A a D N i S S O F WATER, GRAINS
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The sulfated alcohols used are the sulfuric esters of the straight-chain fatty alcohols ranging from eight to eighteen carbons and possibly higher. I n order to simplify the nomenclature, these salts of the high molecular weight alcohols may be referred to as hymolal salts. The sodium hymolal salts, for example, are white solids and rather more crystalline than soap. They have certain characteristics in common, but, as mould be expected, they show marked differences among themselves according to the length of the carbon chain. Some of the more striking characteristics are as follows: At suitable temperatures they are not affected by the hardness in water. They are good sudsing and wetting agents in acid solutions. While they are slowly decomposed by acids, the rate is sufficiently slow that this change - causes little or no trouble for ordinary uses. Aqueous solutions are stable in alkalies and retain their soaplike properties. Increasing the molecular v-eight of the alkyl group results in (1) improved detergency and (2) lower solubility of the hymolal salts. The salts are neutral in reaction, both in the solid form and in solution. At a concentration of 0.1 per cent the pH of sodium lauryl sulfate is about 7.5. The salts of some of the other metals have interesting characteristics. Unlike the corresponding soaps, the hymolal salts of most of the metals are soluble to a t least a moderate
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PURE SOAP FLAKES AND PURE SODIUMALKYL SULFATEREQUIRED FOR WASHING IN WATEROF VARYINGHARDXESS towards dry cleaning of fine fabrics, even in spite of the fact that much of the soil on such goods is more readily removed by soap and water than by dry solvents. Such difficulties can be overcome by the use of softened water, but for the average citizen this is not economically possible; hence the curse of hard water has been one to be endured. Still another serious limitation of soap is its lack of stability towards acids. This causes no trouble to the average user of soap, but in the textile industry it is an important matter. A good wetting agent facilitates dyeing, but many dyes must be used in acid solution, and the acid eliminates soap from this field. For such work it was found that sulfonated castor 24
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INDUSTRIAL AND ENGINEERING
degree and combine the characteristics of the metal used with the good wetting arid detergent properties of the alkyl sulfate group. I n predicting the solubility of the metallic salts, they should be thought of as sulfates, and they show considerable parallel to the solubility of the corresponding metallic sulfates, For instance, the magnesium and copper alkyl sulfates are much more soluble than the corresponding sodium salts which, in turn, are more soluble than the potassium salts. ils would be expected, the lead and calcium salts are among the least soluble. The detergency is apparently unaffected by the metallic radical. Within the last few months a number of sulfated alcohol products have become available on the market, mostly in the form of the sodium salts. I n addition to several specialties, the salts of three different sulfated alcohols are now made, but in each case the alcohol is a mixture covering a given range. The first product marketed was made from the saturated alcohols in the range CV,to C18. More recently the saturated alcohol sulfates, mainly of the range Cm to CM, and the unsaturated alcohol sulfates of the range C16 to C18 have been offered. The higher molecular weight alcohols were originally obtained from sperm oil, but the saturated alcohols are now made by high-temperature high-pressure hydrogenation of animal or vegetable oils of suitable molecular weight. This is a process and technology which has been developed entirely as a result of the need of these alcohols for sulfation. The relation between these products can best be shown by the forinulas of their principal components:
CHEMISTRY
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Oleyl alcohol is obtained from sperm oil, and the sodium salt bears about the same relation to the products described above as sodium oleate does to coconut and tallow soaps. It is not easy t o sulfate this alcohol without some sulfonation of the double bond; hence the commercial product is a mixture of the sulfate ester and sulfonate.
IGEPONS The second group of the new detergents is represented on the market by two products sold under the brand names of “Igepon A” and “Igepon T.” Igepon A is made by causing isethionic acid or its salt to combine Kith oleic acid or its derivatives. This product is a good detergent, is neutral in its reaction, is resistant to hard water, and can be used in
Sodium lauryl sulfate: CH3(CH2)10CH20S03Na Sodium octadecvl sulfate: C H ~ ( C H ~ ) I ~ C H ~ O S O ~ N ~ Sodium oleyl sulfate: CH~(CHZ),CH :CH(CH2),CH20S03Na 23
Of the three types of products offered, that made from the has excited most saturated alcohols o f the range Clo to interest in this country and seems to hare the widest range of usefulness. The alcohol is made by hydrogenating either coconut or palm kernel oils, which is then generally fractionally distilled. The sodium salt is marketed in the textile trade under the name of “Gardinol WA” and of “Orws” in the nontextile bulk trade. For the retail trade it is being offered as a spray-dried granulated product under the name “Dreft,” and there is the probability that it will soon be offered as a liquid shampoo and as a bar for toilet use. I n physical characteristics the sodium salt is similar to soap, and it shows similar phase relations. Solubility in water is more affected by temperature than in the case of soaps of a corresponding molecular weight, but it is still sufficiently soluble to suds well in ice water. This remarkable showing is due in part to a high rate of solution and in part to the smaller amount required to give a suds in ordinary water than in the case of soap. It will not withstand calcium hardness a t temperatures much below 100” F., but it precipitates slowly and redissolves readily when warmed. It is not easily affected by salt and performs as well in sea water as in ordinary tap water. Since the calcium and magnesium salts are good sudsents and good detergents, the amount of sodium lauryl sulfate required for washing is practically independent of the hardness of the water, while the amount of soap required to do the same work increases rapidly with the hardness. The salts of the other t v o sulfated alcohols have not found as broad a field of usefulness as the sodium lauryl sulfate, but are used extensively in the textile field. They can be briefly described as follows: The octadecyl alcohol can be made from sperm oil or by high-pressure hydrogenation of tallow or other suitable animal or vegetable oils. It is marketed as the sodium salt and is suitable for use a t temperatures of 130” F. or higher. At lower temperatures the limited solubility of its calcium salt begins to be noticeable,
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also help solve many troublesome problems in industry. An enthusiastic letter was recently received from the superintendent of a zinc smelter who feels they are the answer to a difficult problem a t this plant. Workmen handling zinc sulfate solutions tend to develop sores unless both their persons and their clothes are kept-clean. This is difficult &th soap or other detergents, but simple in the case of a detergent which forms a soluble zinc salt. Many other such special uses will undoubtedly be found as the properties of these materials become better known. The work which resulted in the development of these new detergents has not been limited to any one individual or group, but a few have been outstanding in their contributions. Among these is H. Bertsch, of H. T. Bohme, A.-G., who was the first to point out that the carboxyl group must either be eliminated or “blocked” by other groups in order to achieve hard water insensitivity. Schrauth and his associates of Deutsche Hsdrierwerke A,-G. worked out the methods for making alcohois by catalytic hydrogenation and have
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produced these alcohols on a factory scale. The Igepons were worked out and are produced by I. G. Farbenindustrie Akt.-Ges., the great German chemical combine. BIBLIOGRAPHY (1) Anonymous, W o o l Record Textile W o r l d , 40, 1369-70, 1423-5 (1931). (2) Bray, W. W., Am. Dyestuff Beptr., 22, 247-52 (1933). (3) Briscoe, M., J. SOC.Dyers Colourists, 48, 127-31 (1932); 49, 71-3 (1933). (4) Kertess, A. F., Ibid., 48, 7-9 (1932); 49, 69-70 (1933). (5) Killeffer, D. H., ISD. ENG.CHEM.,25, 138 (1933). (6) Lederer, H., Soap, 8, KO.4,71-3,77 (1932). (7) Lottermoser, A., and Stoll, F., Kolloid-Z., 63, 49-61 (1933). (8) Xusslein, J., J. Soc. Dyers Colourists, 47, 309-12 (1931); Meltiand Textilber.. 13. 27-9 (1932). (9) Schrauth, W., &ifksieder-Ztg.; 58, 61-3 (1931); 2. anoew. Chem., 46, 410, 459-61 (1933). (10) Stadlinger, H., Kunslsedde, 14, 398-404 (1932) ; Melliand Textile Monthlu, 4, 417-20, 499-502 (1933). RECEIVED September 12, 1933.
Modern Developments in Applied Cellulose Chemistry GUSTAVTJSJ. ESSELEN, Gustavus J. Esselen, Inc., Boston, Mass.
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that time. Even nitrocellulose ODERN developments The cellulose chemical industries may be dilacquers were being used in a i n applied c e l l u l o s e vided into three general classes. The first comvery limited way, but the proper chemistry have been prises those in which the ultimate use of the cellucombination of economic, i n among the most spectacular of lose is as such or in a slightly modified form. d u s t r i a1 , and technical condirecent industrial advances. It This includes paper, three types of rayon, and tions, all of which were necesis a strange coincidence that sary for the establishment of the many of them depend for their the transparent wrapping material Cellophane. modern nitrocellulose lacquer inusefulness largely upon their apThe second class is that in which the ultimate use dustry in a large way, did not peal to the eye. Celluloid, for is in the form of cellulose nitrate. I n this group occur until about ten years ago. example, found wide use as a raw are to be found the pyroxylin plastics (such as Since then, progress along this material from which to manufacce 11uloid, Fiber loid, and Pyral in), photographic line has been rapid. Table I ture toilet articles because of the shows approximately the annual endless variety of combinations film, lacquers, artijicial leather, and cements of production of nitrocellulose lacof color and form into which it various forms. The third class comprises those quers in the United States in could be fabricated with relative products whichjnd their ultimate use in the form certain selected years beginning ease. The appeal of the modern of cellulose acetate. Among these may be cited with 1909, and Table I1 gives a u t o m o b i l e finish is also atthe cellulose acetate type of synthetic fibers, the the annual consumption of cellutained by means of a cellulose lose nitrate in lacquers during compound, and the attractivetransparent wrapping material Kodapak, the the last seven years. ness of modified cellulose in the safety type of photographicjlm, and new slowIt is sometimes thought that form of Cellophane has revoluburning plastic materials to replace celluloid and thelarge increase in the use of tionized the packaging of prodsimilar pyroxylin plastic products. I n all of cellulose lacquers has been due ucts for domestic consumption. primarily to the rapid growth these groups there is continuing progress and deThe fact that cellulose should of t h e a u t o m o b i l e industry. serve in a large way as a raw velopment. While it is true that large quanmaterial for chemicaI industry tities have been used in this ini s h a r d l y surprising in view of the fact that it isavailable in large quantity in nature dustry, there are other uses far too numerous to list, rangand in forms from which a reasonably pure cellulose can be ing from artificial flowers and artificial legs to window shades separated without undue difficulty. Empirically i t has long and xylophones. That the automobile industry alone is not been used for the manufacture of paper and, during the closing responsible for the remarkable increase in the uses of lacquers quarter of the last century, for making celluloid, but it is only is well illustrated by the fact that in 1927 when the prosince the beginning of the present century that most of the duction of automobiles decreased 23 per cent, the sales of spectacular cellulose products which now attract so much at- lacquers increased 38 per cent. The modern cellulose nitrate lacquer depends for its poputention, made their appearance. larity upon the fact that it dries rapidly to give a hard surCELLULOSE NITRATE face which is very resistant to moisture. Present-day lacThe &st of the cellulose compounds to achieve industrial quers contain, in addition to the cellulose nitrate base, natural importance was the nitrate. By the end of the nineteenth or synthetic gums or both, plasticizers, and sometimes oils. century it was well established as smokeless powder and as together with the necessary coloring materials, the whole the basis of the celluloid industry. The nitrocellulose base being blended with suitable volatile solvents. They are disfor photographic film was also on a firm industrial footing a t tinguished from the earlier nitrocellulose lacquers by the fact
