round surface active properties have had a fairiy critical hydrophobic niolccular weight and a fairly definite hydrophobic-hydrophilic balance. The present solid nonionics possess too high a molecular n-eight and do not have the proper hydrophobic-hydrophilic balance. The development of a highly surface active solid nonionic may very n d l require a different approach from using a hydrophobic base of high molecular weight. As for future marli-et developments, the alkylbenzenesulfonates are versatile products also and because of their lower cost they have in many inst,ances been used instead of the ethylene oxide products. However, the alkylbenzenesulfonates are mass production chemicals. As t,he ethylene oxide-derived nonionics attain larger volume production, their prices should fali in relation to the sulfonates. If t'hese scientific goals for the nonionics can be reached, their use in the next decade will increase t o a marked extent. RCKNOWLEDGIIEYT
The a,uthors n-ish t o thank J. 11. Cloney, G. 11. Gantz, and C. E. Stevens of the Antara Chemicals Division, General *hiline & Film Corp., for their helpful suggcslions i n t,he prepamtion of this paper. LITER-iTURE CITED
(1) Barker, G. E. (to the Atlas Powder Co.), U. S.Patent 2,559,583 (July 10, 1951). ( 2 ) Barker. G . E., and Ranauto, H. J., Snal:, Sunit. Chemicals, 27, 1-0. G , 43 (1951).
ui
(3) Black, E. J. (to General Aniline & Film Corp.), U. S. Patent 2,555,285 (May 29, 1951). (4) Cross, J. N., Proc. Chem. Speciulties M f r s . Assoc., pp. 135-Y9 143 (June 1950). ( 5 ) Fineman, 11.N., Soup, Sunit. Cheniicals, 29, No. 2, 46 (1953). (8) Zbid., No. 3 , p. 50. (7) Harris, J. C., and Kosmin, AI, (to Monsanto Chemical C o . ) , U. S.Patent 2,594,431 (dpril 29, 1952). (8) Jelinek, C. F., and Nayhew, R. L., Testile Research J., 24, 765 (1954). (9) Kosinin, M., and Harris, J. C. (to Nonsanto Chemical Co.). U. 8. Patent 2,594,453 (hpril 29, 1952). (10) Lehmicke, D . J., Am. Dyestu$ Rcptr., 38, 863 (1949). (11) Ilayhew, R . L., and Hyatt, R. C., ,I. Am. Oil Chemists' Suc., 23, 357 (1952). (12) Sanders, H. L. (to General Bniline 8: Film Corp.), E.S.Patcnt 2,623,856 (December 30, 1952). (13) Sanders, H.L., and Knagg., A. E., Soap, Sanit. Chemicals, 29, S o . 8. 45 (1953). (14) Sanders, H . L., and Lambert, J. M., Teztile Research .I., 21, 680 (1951). (15) Sanders, 1%.L., and Yeager, J. A , , IND.EXG.CHEX, 43, 8GO (1951). (16) U. S.Tariff Commission, Wazhington 25. D . C., Rept. Synthetic Organic Chemicals, 1952. (17) T-aughn, T. H . , Jackson, D. R., and Lundsted, L. G., J . Am. 8 1 7 2 . Oil C h ~ i i s t s S' O C . , 29, 240 (1952). (16) Vaughn, T. €I., Suter. El. R.,Lundsted, L. G., and Kramer, AI. F.,Ibid., 28, 294 (1931). RECEIVE for; ~review ?.larch 2.5 1 0 , i l .
1954.
e TFHOtL4hS H. j-.4UGHNi, H. R. SUTER, 4s'~ 31. G. IBRAtIEK f 7 y a n d o t t e C h e m i c a l s C a r p . , Wyandotte, Mich.
A wide variety o f inorganic and organic builders i s used to give detergents specific attributes required for specialized uses and to improve their performance properties. Builders are an important outlet for chemical production. The function of builders in altering the chemical and physical properties of synthetic detergents and the specific effect of such alterations in the laundering of cotton, as measured by laboratory test methods, is discussed in this paper' A classification of builders, with designation of principal uses, is presented. NORGA4KICbuilders have been associated n-ith the use of eurface active agents since their earliest inception. In some instances thie came about coincidentally-for example, via neutralization of excess sulfuric acid used in sulfonation. I n fact, the use of a syndet without' builders is uncommon, except in certain nonionic detergents used in the textile indust'ry and in synthetic emulsifiers. Generally, 1007Gactive organic syndet's are unsuitable in one way or another for most' uses. The difficulties may lie eit,her in physical form, performance properties, or economy. I n t,he case of many of the early synthetic detergents, sodiuni sulfate served to overcome these shortcomings. Today a variety of inorganic and organic builders is used t o provide the specific attributes required for specialized uses and, generally, performance properties of the detergents are greatly improved. Builders are materials that are added t o improve the utility of a detergent. T h e syndete considered in this paper are members of t'he broad classifications of anionic and nonionic detergents. Although certain cationic detergents such as higher fatty amines 1
Present address, Colgate-Palmolive Co., Jersey City 2, X. J.
1934
are known t o possess detergent propel ties, this class is technologically relatively unimportant in the cleaning industr) a t present. I n addition, builders have assumed substantial economic importance and they represent a major outkt for a variety of chemical pioducts. The consumption of builders in household synthetic detergent products may be estimated roughly by referener t o the rcpoits of the Association of American Soap and Glycerin Producers, Inc., in which I952 sales of built jyndets are ieported to be 1,530,000,000 pounds. By assuming an average active agent content of 25%, the consumption of builders is estimated a t 1,147,500,000 pounds. Estimates published by SnelI (11) in January of 1953 indicate the sales of syndets in 1853 increaeed over 1952 by about 24YG. This brings consumption of builder^ t o close t o 1,500,000 pounds in 1953. I n addition, large quantities of inorganic builders are used in products for industrial use, and proprietary builders are sold in large voIume for commercia1 laundering in conjunction Kith either soap or synthetic detergents. Together with the builders used in soap products for household uee, sales of which are approximately equal t o those of syndets, it is probable that the total production of builders for
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 9
-Synthetic soap and synthetic detergents is well in excess of 2 billion pounds annually. This represents a sizable volume for the chemical industry both in tons and dollars. Although a wide variety of syndets has been marketed and used for industrial purposes for a long period of years, the rapid growth over the past 5 years was made possible by developments in the field of builders, both organic and inorganic, that have brought about the successful use of synthetic detergents in the laundering of cotton. FUNCTION OF BUILDERS
I n general, builders for syndets have three functions-to improve the performance for general or specific uses, to improve the physical properties with respect to handling and storage characteristics, and to achieve favorable end use economy. The mechanism of action in improving performance properties is not me11 established in all of its aspects, and the improvement is probably not attributable to any single physical or chemical effect. There is no doubt concerning the reality of the gross effects, either as shown by empirical laboratory testing or by actual use. Alkaline builders are frequently assumed to exert their effect by virtue of their alkalinity, but this is only part of their function. I n the case of soap, since there is a tendency for hydrolysis to form acid soaps that adsorb on fabrics and function generally as soil rather than detergent, the pH effect contributed by alkaline builders is undoubtedly one of the prime factors in their function. A similar building effect has been repeatedly observed and reported in the case of synthetic detergents, however, when the prevention of hydrolysis is not a factor. This is particularly true when heavy, oily soils are involved, as in certain classifications of work in commercial laundering. I n fact, builders containing very alkaline substances such as caustic soda, sodium orthosilicate, and soda ash are most successful in these operations. On the other hand, the high pH characteristics of these builders are not tolerable in products for household laundering; the major products of this class have builders with pH values within the range of water to neutral soap-that is, 7.0 to 10.5. Certain specialty detergents for washing industrial equipment such as dairy equipment, railway coaches, etc., have rather strongly acid ingredients. For strongly alkaline builders i t can be postulated that their success may be due partly t o the formation of soap in Ritu by saponification of fatty acids in the soils. Acid builders dissolve milkstone and metallic oxide soils. Thus, the buffering action of builders may be a n important factor in that pH conditions most favorable for removal of soil from a particular substrate are maintained, but, on a generalized basis, the action of builders cannot be attributed solely to the effect of pH. Effect on Surface Tension. Organic detergents generally exhibit the phenomenon of surface activity to a greater or lesser degree. While all surface active materials are by no means detergents, there is no question that the wetting action associated with surface activity plays an important part in cleaning processes. Builders are generally not regarded as surface active-they do not reduce surface tension at the solution-air interface. On the contrary, in aqueous solutions of most builders, surface tensions are higher than that of water, indicating negative adsorption. This arises from the more intense fields of attractive force surrounding their ions than the water molecules, resulting in a tendency to draw the ions into the body of the solution. The opposite effect occurs with organic detergents. I n spite of this, in the proportions ordinarily used, builders actually bring about somewhat lower surface tension of solutions than are observed with surface active agents alone. The effect of builders in reducing interfacial tension between detergent solutions and oils ( 1 ) is of considerably greater importance in cleaning. This action facilitates removal of oily soils by emulsification. There is evidence that builders Kith polyvalent anions are superior in this regard, and this probably con-
September 1954
Detergents-
stitutes a partial explanation of the effectivenessof the phosphate and silicate builders. It has been pointed out by Reich and Snell (9) that another factor is operating in this case-the preferential wetting of the substrate by the aqueous detergent system. Thus, while low interfacial tension would certainly be expected to permit an increase in the surface area of oily soil and thue allow removal of the bulk of this material, removal of the last layers from the substrate involves displacement or preferential wetting. Reich and Snell devised a test based on sinking tillla of fabrics through oil-water interfaces that meaauIas this effect. Polyphosphates and carboxymethylcellulose were found to be strikingly effective in this regard when cotton fabrics were employed as substrates. Effect on Micelles. A11 detergents have properties in aqueous solutions that have led to their designation a3 colloidal electrolytes ( 4 ) . When the physical properties of their solutions are plotted against concentration, nearly normal functions obtain at very low concentrations, but these relationships are soon interrupted by striking abnormalities. This is attributed to the formation of micelles of anions in the case of anionic detergents. Thus, the active detergent seeks to escape from homogeneous molecular or ionic distribution throughout the body of the solution, by adsorption and orientation at the surfaces of air or restraining solids and by association into micelles. The latter phenomenon has a bearing on performance inthat it isundoubtedly associated with the capability of the aqueous system to solubilize oily materials not normally soluble in water. There is ample experimental evidence to indicate that this property goes beyond emulsification and that the insoluble substances are taken within the body of the micelles. Especially in dishwashing. this is important because i t represents, in part, the capacity of the detergent to carry away large amounts of greasy matter without allowing redeposition on the ware during rinsing. Various techniques have been developed both for determination of the critical concentrations for micelle formation and for measurement of the solubilizing capacity. Builders have been found to exert profound influence in such systems, reducing niarkedly the critical concentration for micelle formation and lending charges to the micelles by adsorption of ions. It is easy to visualize the function of the builder in bringing this property into play a t the low concentrations employed in the laundering of fabrics and in rinsing of dishes. The relative importance of the roles of the associated and unassociated anions has never been clearly established. It must be admitted that the precise mechanism of operation is imperfectly understood. Redeposition. The gross cumulative effect of these builder functions is to facilitate removal of soil. Another factor which must be considered is the action of builders in preventing redeposition of soil. Actually, syndets were used largely for industrial purposes for many years before the technology of builders, and especially of sodium carboxymethylcellulose, advanced t o a point which permitted their use in the laundering of cotton where redeposition is of prime importance. Perhaps inorganic builders affect redeposition through modification of electrical forces between soil and substrate and, in some cases, by protective colloid action. Carboxymethylcellulose has the latter effect t o a high degree and, in addition, is apparently adsorbed on fabric with resultant formation of a surface condition that is less receptive to soil. Inorganic builders that have polyvalent anions-for example, the polyphosphates and silicates-are superior ( 5 ) . Materials such as sodium sulfate, sodium carbonate, and caustic soda, while they assist in soil removal, greatly reduce the whiteness retention of syndets as well as that of soap and, accordingly, are usually supplemented by antiredeposition agents. Testing. Although the effect of the individual factors involved in detergency on gross cleaning effectiveness is not thoroughly understood, these gross effects may be measured by empirical laboratory tests. Harris (I), among others, showed hy
I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y
1935
soil removal tests that detergency is improved by the addit'ion of electrolyte; sodium sulfate is very effective. The common 40% active sodium alkyl aryl sulfonates built' v-ith sodium sulfate have the optimum proportions within t'his binary system for soil removal, and have much superior physical properties in comparison with products having SOY0 or more active agent. JVhiteness retention properties, however, are impaired by t'he builder. Additional improvement in detergency properties can be obtained by further building. The effect of adding other builders on such a base, as measured hy empirical tests, may be used t o illustrate certain principles. For esarnple, t'he effect of a n alkaline salt and of carboxymethylcellulose on soil removal and ahiteness retention of a 40% active alkyl aryl sulfonate, as measured by laboratory tests (12), is illustrated in Figure 1 (3). The addition of soda ash improves the soil removal and depreciat'es the whiteness retention properties of the 40% active synthetic. Carbosymethylcellulose improves both soil removal and whiteness retention and serves t o overcome the depreciat'ive effect of t8healkaline builder on whiteness retention. Silicates and phosphates are very useful in improving soil removal of alkyl aryl sulfonate-sodium sulfate mixtures, as shown by the work of Harris and Brown (a)which is partially summarized in Table I. They are generally prcferreh t o carbonates, and hIerrill and Getty ( 6 ) attributed this in large part t o their abilit,y to prevent soil redeposition. Among others, Morrisroe and Kewhall ( 7 ) reported similar results. Although less widely studied, the same general detergency effects occur with other anionic detergents such as the sodium alkyl sulfatcs.
W
k400 z
Eo-1
3
-1
300
a > -1 200 w
t
0
S
3
00
0 ib
S
0
CARBON
SOIL REMOVAL
WHITENESS
RETENTION
Figure 1. Effect of Carboxymethylcellulose (CMC) and Soda Ash o n Properties of Alkyl -4ry1 Sulfonate Distilled water at 140' F. Concn.,
Alkyl aryl sulfonate Carhoxymethylcellulose Soda ash
70
0.1 0.025 0.15
V h e n tested in distilled wat'cr, nonionics generally shovi a decrease in carbon soil removal and whiteness retention when builders are added. Unbuilt nonionics have considerably lov-er carbon soil removal and whiteness retention values in hard than in distilled water, and these values are improved by builders. One study ( I S ) of soda ash, modified soda, sodium metasilicate, and sodium tripolyphosphat,e, indicated the latter t'o be the most effective Tvith an ethylene-propylene oxide condensate. The effect of tripolyphosphate alone and wit,h carboxymethylcellulose on the detergency propert,ies of several t,ypes of nonionics in hard mat,er is shown in Table 11. Both carbon soil removal and whiteness retention properties are generally improved by the addition of tripolyphosphatr and further improvement, in most cases of a highly significant degree, is obtained by addition of carboxymethylcellulose.
1936
TABLE I.
EFFECT O F BCII,II~;RS os SOILRELIOTILOF A 4 ~ ~ ~ ~ . ARYL SULFO x ATE
(Launder-Oiiieter; rotton soiled v i t h Oildag and Xesson oil; 300 hard water; 0.073Vo built detergent mixture)
b
pp111
+.
Sodiuni dodecylbenzesieEiiiiuliatc 99% Represents actual whiteness after four 10-minute wasliea
TABLE 11. EFFECT O F I~UILDERS o s DETERGENCY PROPI~~IP:Y OF KONIOSICS (0.1 C/o Nonionic, 0 15% tripolypliospliate, 0.025% of 65% active carbo\ymethylcellulose (CRIC): 257 p.p.in. hard water; 40" C . )
Nonionic Detergent .41kyl aryl polpglycol e t h w F a t t y acid-ethylene oxide coilTall densate oil-etiivlene oxide mndensate Ethylene-pi opylene oxide condensate
Increase, %, Duc t o Addition of Tripol3;phosi,liate-+~ CblC Tripolyphosphate Carbon Carbon soil n'hiteness soil Whitei?css removal retention removal retention 129
120
216
430
118
118
187
203
107
110
143
171
166
122
2GG
172
Alt,hough empirical tests certainly leave something to bc dcsired, the general behavior of builders as ind-icated by t,licse methods has been borne out in practical performance in the caw of both anionic and nonionic detergents. The results of thc performance teste cit,ed, however, bear only on the use of the dctergents in the washing of cotton. Xashing woolens and most synthetic fabrics is less difficult; the requirements for b u i l d e i ~ are less critical by a viide margin. The same thing is true in t,hc washing of dishes, silvermw, tile, and other matcririls having impervious surfaces. For t h e uses many syndets are passable, so far as detergency is conccrncd, without builders. They are usually used, however, if only a,s extenders. Thus there are two classes of the built synthetic detergent products on the ret'aii market-those designed for light duty jobs and those which will do these jobs and Tash cotton as well. C: LA S SlFICATION
The principal builders currently used in syndets for household and industrial purposes may be classified as follows. Inorganic Builders. PHOSPHATES. Sodium tripolyphosphatt: and other condensed phosphates are without doubt the niosis widely used of t,he inorganic builders. These products arc writcr softeners, they are relat'ively nonirritating t80the skin! and they are suitable for admixture by all manufacturing procedures, including spray drying. 0rt)hophosphates are extensively used in indust,rial specialty detergents. The detergent industry consumes a substant,ial proportion of the United States phosphate production. SILICATE:^. The alkali silicates are excellcnt builders for syndets as ~ w l as l soap. They are extensively used in household laundry products, where t>heyserve t o inhibit corrosive effects on soft metals. Sodium ortho-, met'a-, and eesquisilicates are employed in industrial specialty detergents; in thc manufact,urc of spray dried household detergents, waterglass is added t o thr slurry prior to drying. CARBOSATES.The major built syndets for household use are prepared b y spray drying and carbonates are not includrti, except that formed by carbonation of alkaline ingredient$ during
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 9
-Synthetic the spray-drying operation. The p H of soda ash is too high for products that are to be used for dishwashing as well as laundering, and bicarbonate is subject to thermal decomposition during the spiny-drying operation. Soda ash is extensively used in industrial specialty detergents, and modified sodas and sodium bicarbonate are extensively usedin household products prepared by dry blending. Modified sodas and sodium sesquicarbonate are admirably suited to this use because they are nonirritating t o the skin and have satisfactory detergent building characteristics. HYDROXIDES. Sodium hydroxide is extensively used with syndets in metal cleaning and as a n ingredient in proprietary buildeis used in commercial laundering. B o 1 2 . 4 ~ ~ ~The . borates are not used extensively in this country. Their principal application is in household cleaner 8 wheie their mild alkalinity is desirable. XEUTRALINORGAUIC SALTS. Sodium sulfate and other neutral salts are extensively used in both household and industrial syndets. The presence of sodium sulfate in practically all anionic detergents arises from excess sulfuric acid used in sulfonating, and large proportions are used in light duty dishwashing and laundry products to provide satisfactory physical properties. It aids in micelle formation by its simple electrolytic effect. Sodium sulfate is the major builder used in rommercial grades of anionic detergents. CLAYS. Bentonites are important components of certainindustrial cleaners, including commercial laundry products, where the cia!-servestoadsorbsoil anddyes. Thedispersedclayhasemulsifj ing properties and is sometimes used because of its mild abrasive action. Organic Builders. COLLOIDAL ADDITIJES. Sodium carboxprncthylcellulose is the major colloidal additive and is used in thi. majority of household and industrial synthetic laundry detergents. It aids in removal of pigment qoils, but is used primarih because of its antiredeposition effect. It contributes a desirable emollient effect on the skin when built syndets are used for dishwashing. Other products having the same general functions but of considerably less commercial importance are water-soluble rellulose ethers, sodium starch glycollate, methylethyl- and hydroxyethylcellulose, and various proteins and protein derivatives. Other materials reported to have specialized uses in synthetic detergents include peptides, amino acids, and certain fatty amides, and nitriles. SEQUESTERING AGENTS, Sodium salts of polyamino carboxylic acids have been recommended for use with synthetic detergents in hard water, because of their sequestering action. Cconomic factors have limited this use; the largest established outlet is use in liquid soap products for the preservation of clarity. OPTICALBRIGHTENERS.Optical brighteners are extensively used in products intended for household laundering. They are substantive t o fabrics and absorb ultraviolet light, emitting in the blue region of the visible spectrum. This masks yellowish casts and results in a whiter and brighter appearance. Greatest
-
Detergents-
usage is in soaps and detergents for cottons and woolens. Special types have been developed for use on synthetic fabrics. Many products in current use are not susceptib:e to decomposition when used in the presence of bleaches. FOAMEXTENDERS. Alkylolamides of fatty acids are used rather ext'ensively in synthetic detergents, principally because of their effect in extending the capacity of the solution to solubilize grease without loss of foaming. SOLVENTS.Solvents such as pine oil, petroleum fractions, and chlorinated solvent's are frequently used in industrial cleaning compositions, particularly where t,he prodiirt, is required to remove heavy or solid greases. The solvents soften or liquefy the greases and thus facilitate their emulsification and removal. PERFLWES.Perfumes are occasionally used as masking agents in industrial cleaners. They are widely used in household detergents where they influence consumer acceptance and make the products more pleasant to use. This is a summary of current commercial practice in the building of synthetic detergents. KO attempt' is made to provide a comprehensive bibliography on the subject or to add another review to the literature. Comprehensive texts by Niven ( 8 ) and Schwartz and Perry (10) include bibliographies. Know-how in the compounding of detergents and builders has developed rapidly in the past decade, and has been a powerful factor in the growth of the synthetic detergent industry. The possibilities of compounding improved products, even utilizing only known materials, are by no means exhausted. The development of better products for the future hinges on further understanding of the mechanism of the action of builders and detergents, better performance testing methods, and, of course, the discovery and use of new basic materials. LITERATURE CITED
(1) Harris, J. C., Oil d% Soap, 23, 101-10 (1946). (2) Harris, J. C., and Brown, C. L., Ihid.,22, 3 (1945). (3) Kramer, Maurice G., .I. A m . Oil Chemists' SOC.,29, 529-34 (1952). (4) McBain, J. W., and associates, J . Chem.Soc., 101, 2042 (1912); 105, 417 (1914); 113, 825 (1918). (5) Merrill, Reynold C., J . Am. Oil Chemists'Soc., 25, 84 (1948). (6) Merrill, Reynold C., and Getty, Raymond, IND.EKG.C H E h f . , 42, 856 (1950). (7) hlorrisroe, J. J., and Newhall, R. G., Ihid.,41, 423 (1949). (8) Kiven, William W..Jr., "Fundamentals of Detergency," Reinhold, New York, 1950. (9) Reich, Irving, and Snell, Foster Dee, IND.ENG. CHEK, 41, 2797 (1949). (10) Schwartz, Anthony ill., and Perry, James W., "Surface-Active Agents," Interscience, Kexv York, 1949. (11) Snell, Foster Dee, Chem.Eng. .I'ews, 32, 36 (1953). (12) Vaughn, Thomas H., and Suter, H. R., J . A m .Oil Chemists'Soc., 27, 249-57 (1960). (13) Vaughn, Thomas H., Snter, H. R., and associates, Ihid.,28,294-9 (1951). RECEIVEDfor review March 25, 1 9 2
ACCEPTEDJUIY9, 19.54.
( L e f t ) Standard Soiled Strip Sewed to Tow-el for Detergency Tests Using Home Laundry Procedures
(Right) Measurement of Tnterfacial Tension Shows Surface Activity of Products
September 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
1937
