US2792347A - Fatty acid mixtures and soaps derived therefrom - Google Patents

Description

United States Patent LouA. Stegemeyer, Cincinnati, Ohio, assignor to Emery Industries, Inc., Cincinnati, Ohio, a corporation of Chic Application October 30, 1953, Serial No. 389,487

4 Claims. (Cl. 252-108) No Drawing.

.This invention relates to compositions of fatty acids which may be employed to enhance certain desirable physical properties of soaps.

.By the term soaps is generally meant the sodium and potassium salts of aliphatic monocarboxylic acids having 12 to 18 carbon atoms in the chain. Soaps are produced in various physical forms such as in concentrated solutions in water, the so-called liquid soaps, in the form of bars or in flakes or granules. Soaps are also produced for various specific purposes, for example, toilet soaps, general household soaps, textile soaps, etc.

-The variation in physical properties and in other properties for specific uses are achieved by selection of the appropriate oil or fat orblends of oils or fats used to manufacture the soap and by selection of the alkali used for saponification. Modifications in properties may also beza'chieved by selectioniand variation in the alkaline builders which are often incorporated in soaps but such modifications are not the subject matter of this invention.

For soap-making purposes, the various oils and fats differ from one another primarily in the kind and proportions. of the various higher fatty acids which they contain. Thus, the fats which are liquid at normal temperatures, generally termed fattyoils, contain higher percentages of .the unsaturated normally liquidacids, such as oleic, linoleic, and linolenic acids. The lower melting animal ,fats,.such as hog fats or greases, contain moderate amounts of .the normally solid saturated fatty acids, such as'stearic and palmitic acids, and the higher melting animal fats, such as beef fat or tallow, contain still greater percentages of the solid acids. V

.rCertain of the tropical vegetable oils such as palm kernel oil'and coconut oil are characterized by a high content of saturated acids of shorter chain length than stean'c and palmitic, namely lauric and myristic acids.

gAs a'very rough generalization, the unsaturated liquid acids. produce soaps which are physically soft and readily soluble in water. The solid acids of C16 and Cmcarbon chain length produce hard soaps which are readily soluble only in hot water. The saturated acids oflower chain length produce hard soaps which, however, are quite soluble in water at normal temperatures. The terms hard and soft, as used, refer to the physical characteristics of the soaps with a normal moisture content of 20 30% as even the soaps of the unsaturated acids can be produced in a solid form when dried to a sufiiciently low moisture content. All percentages and proportions disclosed herein are by weight.

. The alkali most'commonly used to neutralize the acids is sodium hydroxide, but potassium hydroxide, which is more costly, may be used where the maximum of water solubility is desired. Potassium hydroxide is also used extensively in the manufacture of concentrated liquid soaps wherein clarity at low temperature is desired.

theselection and blending of fats and oils to obtain appropriate fatty acid compositions, or by the addition ofspecific previously separated fatty acids, and by the choice of alkalia wide variety of physical characteristics 2 and solubilities can .be obtained. One of the more diflicult combinations of properties to achieve satisfactorily is that of a high degree of solubility and appropriate physical firmness. One of the most useful fats to enhance these properties is coconut oil or coconut fatty acids. Coconut oil may be used either alone or blended with other'fats for a variety of purposes. Liquid soaps of 35 to 36% soap content, in .which the high water solubility of the soap is utilized, usually contain a high per centage of coconut oil. Coconut oil is also used in toilet soaps as it increases the firmness of the cake while at the same time increasing the ease of solubility andthe amount of lather produced. Coconut oil may also be used in granulated soaps to prevent the granules from gumming and sticking together when introduced into water.

.Although coconut oil is a very versatile raw material for the soap maker and, therefore, is widely used, there are certain'disadvantages attendant to its use. Its price is subject to wide variations which are often independent of the prices of other fats. Being produced far from the point of use, the supply of coconut oil is often erratic. The soaps of coconut oil are also considered to be irritating to the skin, affecting some individuals more than others. This undesirable property tends to limit its use. Attempts have been made to reduce the irritating prop erty by removing the lower molecular weight C6 to C10 acids, which are present to the extent of about 15%, usually by fractional distillation of the acids. There appears, however, to be considerable difference of opinion as to whether this treatment is eifective or whether the irritation is due to some other cause.

It is the purpose of this invention to provide fatty acid compositions which may be employed in soap compositions'to achieve thebenefits derived from coconut fatty It has been generally assumed that the high content of C12 lauric acid, in coconut and similar fats, has been responsible for properties of the soaps and that the other acids present were largely inert if not actually detrimental. We have found, however, that a very much smaller amount of lower chain length acids ranging from Ca to C10 in chain length will confer upon soapsthe properties ordinarily obtainable only with considerable larger" amounts of coconut or similar 'oils containing a high percentage of lauric acid.

We have found, for example, that a composition consist-ing of 15% of C9 pelargonic acid and commer' cial oleic acid will produce a liquid potash soap of 36%" concentration and a viscosity of 82 centipoises. It is necessary to use approximately 50% of coconut acids and 50% oleic acid to obtain an equivalent soapsolution,

Pelargonic acid is readily produced by the oxidation of oleic acid obtainable from a wide variety'of 'fatsarid is, therefore, not dependent upon the price of anysingle' The Cs, Ca, and C10 acids which are obtainable from the fractionation of coconut acids are also suitable raw fat.

for improving soap properties but are dependent upon the price and availability of coconut and similar oils.

The C6 acid, caproic, can be manufactured synthetically or separated from natural fats and is suitable for improving soap.

A mixture of from 10 to 15% of Ca toCio acids with to 85% of oleic acid or olive, oil acids provides bar soaps which do not show a surface sliminess in use, which is characteristic of low titre bar soaps composed primarily of unsaturated acids. From 40 to 50% of coconut oil must be used to accomplish this same result. Likewise, 15 to 20% of low molecularweight acids may be blended with tallow acids to. prepare a granular laundry 'soap whose particle's will'not fuse together or ball. when poured into water. a

Whereasit has been widely assumed that the lower chain length acids present in coconut oil were'responsible for its:irritant properties, we have found that soaps prepared from a mixture of representative low molecular weight "acids of the type previously described and the usual C1s'-.C1a acidsare actually less irritating than soaps having similar physical properties prepared with coconut 'oil. The soaps. prepared with the representative C or lower acids will contain a somewhat greater amount of the soaps of the C6 and Cm acids than the same soaps prepared with coconut oil but will contain little or no soaps of the C12 and C14 acids. Whether the irritation caused by coconut oil is due to the presence of the soaps of C12 and C14 acids or to a greater total percentage of soaps of acids lower than C16 or to some other irritant present in the natural oil has not been determined but the fact remains that, surprisingly enough, blended soaps containing sufiicient representative Cw'or lower acids to achieve desirable physical propertiesare less irritating than the high proportion of coconut oil which would be ordinarily required to produce equivalent results.

I The comparative irritant effect was determined by the Rabbits Eye Test (Draize, J. Pharmacol and Exp. Therap., vol. 82, No. 4,'December 1944) in which a few drops-of soap solutions of 10% concentration were placed in the eyes of test rabbits and the degree of redness, swelling, or other damage estimated by observation according to a preset scale of values. By this test, the soaps containing representative low molecular weight acids consistently showed less irritation than soaps containing coconut oil acids.

The soaps were also used and graded under code numbers by various individuals and the soaps containing representative low molecular weight acids were judged to be less irritating.

Ourinvention is more fully illustrated but is not' limited by the following examples:

Example 1.--A 36% liquid potash soap is prepared by mixing 85 parts of commercial oleic acid, parts commercial pelargonic acid, 26.7 parts solid potassium hydroxide, and 193.3 parts water. The resulting soap solution is clear and sparkling having a viscosity of 82 centipoises at 70 F.

A 20% liquid potash soap is prepared by mixing 100 parts of commercial oleic acid, 23.7 parts of solid potassium hydroxide, and 444.3 parts water. The viscosity ofthe resulting soap solution is 280 centipoises at 70 F.

Example 2.-A 36% liquid potash soap is prepared by mixing .85 parts of commercial oleic acid, 15 parts commercial pelargonic acid, 26.7 parts solid potassium hydroxide, and 193.3 parts water. The resulting soap solution is clear and sparkling having a viscosity of 82 centipoises at 70 F. The soap solution does not gel or sep arate when cooled to 35 F. and held at this temperature for 24 hours. 7

An equivalent liquid soap solution requires the use of 50 parts of coconut fattyacid and 50 parts of commercial oleic acid, 27.7 parts potassium hydroxide, and 195.3 parts water. The viscosity of this soap solution is 89.5 centipoises. Storage properties are similar to the previously described soap of oleic and pelargonic acids.

Example 3.A 36% liquid potash soap is prepared having a viscosity of 48 centipoises at 70 F, Thesoap solution does not gel or separate when cooled to 35 F. and held at this temperature for 24 hours.

Example 4.A 25% soap solution is prepared by mixing 90 parts commercial distilled tall oil acids, 20 parts solid potassium hydroxide and 295 parts water. The soap solution is slightly hazy exhibits a viscosity of 125 centipoises'at 70 F.

A 33% soap solution is prepared by' mixing 81 parts commercial distilled tall oil, 9 parts commercial pelargonic acid, 22 parts potassium hydroxide, and 202-parts water. The resulting soap solution is clear and sparkling having a viscosity of 65 centipoises at 70 'F. The soap solution does not gel or se'parate when cooled to 35 F. and held at this temperature for 24 hours.

Example 5.-Bar soaps suitable for hand and body washing are prepared by mixing (A) 98 parts commercial oleic acid, 2 parts adipic acid, 15.2 parts solid sodium hydroxide, and 35.3 parts water, (B) 78 parts commer-' cial oleic acid, 20 parts commercial pelargonic acid, '2 parts adipic acid, 17.6 gms. sodium hydroxide, and 35.4 parts water, (C) 48 parts commercial oleic acid, 50 parts coconut fatty acids, 2 parts adipic acid, 17.6 parts sodium hydroxide, and 35.4 parts water.

An objectionable slime develops on the surface of the bar soap represented by formula (A) when this bar is used for hand washing. The objectionable sliminess does not appear when bars represented by formulas (B) and (C) are used for hand washing under the same conditions.

Bars represented by formulas (A), (B) and (C) are immersed in water for 16 hours at 70 F. At the end of this period, the bar soap represented by formula (A) has approximately doubled in size and has'almost disintegrated, becoming so'slimy and soft as to be entirely unsuitable as a bar soap. Under the same condition of immersion in water for 16 hours at 70 F., the bar soaps represented by formulas (B) and (C) have increased'in size only approximately 1020%. After immersion in water, bar soaps (B) and (C) have softened to some extent but still retain suitability as bar soaps.

Example 6.Soaps are prepared by mixing (A) 100 parts commercial distilled tallow fatty acids, 14.6 parts sodium hydroxide, 10 parts commercial sodium silicate, and 43.4 parts water, (B) 85 parts commercial distilled tallow fatty acids, 15 parts commercial pelargonic acid, 16.5 parts sodium hydroxide, 10 parts sodium silicate and 44.5 parts water, (C) parts commercial distilled talfrom parts commercial oleic acid and 15 parts caprylic v acid. The soap solution is prepared in the same manner as the soaps described in Example 2 with an appropriate adjustment in the quantity of'potassium hydroxide and water. The resulting soap solution is clear andxsparkling low fatty acids, 40 parts commercial coconut fatty acids, 16.5 parts sodium hydroxide, 10 parts sodium silicate,'and 44.5 parts water.

The soaps represented by formulas (A), (B) and (C) a are dried and converted to powder andgranulated'soaps.

The conversion maybe accomplished by spraying molten soap through a nozzle into a cylindrical vertical tower containing circulating hot air or passing the soap in a. flake form through a Procter-Schwartz drier with subsequent grinding. to a powder. Whichever methods may be used, soaps (A), (B) and (C) are converted to powders or granules containing an appreciable proportion, say 10%, that will pass through a mesh screen. The comminuted soaps are then tested by pouring 10 to 50 gms. of the soap into a'dishpan of water at 100 'F. to F. and allowed to stand for five (5) minutes with no agitation or gentle agitation. After this treatment the powdered soap represented by formula (A) has formed a gummy, sticky paste that is diflicult to disperse even with considerable agitation. Under the same conditions, the powdered soaps represented by formulas (B) and (C) are easily dispersed in hot water.

In general, the liquid soaps of this invention are constituted by making water solutions of the potassium salts of mixed fatty acids, 75 to 95% of the fatty acids being predominantly aliphatic, monocarboxylic, unsaturated acids of 18 carbon chain length and 25 'to 5% aliphatic,

monocarboxylic, saturated acids of 6 to 10 carbons chain length. The bar soaps of this invention may utilize substantially the same ratios of the same acids as the liquid soaps, but the bar soaps are preferably constituted by neutralizing the acids with sodium compounds to provide sodium salts rather than potassium salts.

In general, the fatty acids utilized are not absolutely pure fatty acids, that is, commercial oleic acid conventionally contains both stearic and palmitic acids in minor amounts and also polyunsaturated acids such as linoleic acid in minor amounts. In general, the liquid acids are cheaper than the solid acids, but the separation need not be complete. Any naturally occurring mixture of fatty acids may be used for manufacturing these soaps and the percentage of short chain length acids adjusted to provide a soap of characteristics desired for any specific purpose. Also, all of the recognized soap builders and additives may be incorporated in the soaps of this invention, the amount of short chain length acids being adjusted to provide the desired characteristics for the soap in question.

Having described my invention, I claim:

1. A bar soap comprising the sodium salts of 75 to 95% liquid unsaturated aliphatic monocarboxylic acids of 18 carbons chain length and the sodium salts of 25 to aliphatic monocarboxylic saturated acids of from 6 to 10 carbons chain length.

2. A liquid soap comprising water and the potassium salts of fatty acids, 75 to 95 of said fatty acids being liquid unsaturated aliphatic monocarboxylic acids of 18 carbons chain length and to 5% of said fatty acids being aliphatic monocarboxylic saturated fatty acids of from 6 to 10 carbons chain length.

3. An admixture of aliphatic monocarboxylic acids adapted for the manufacture of sodium and potassium soaps consisting essentially of to acids of 16 to 18 carbon atoms chain length and 25-5% acids of 6 to 10 carbon atoms chain length.

4. An admixture set forth in claim 3 wherein said acid of 16 to 18 carbon atoms chain length is commercial oleic acid and said acid of 6-10 carbon atoms chain length is commercial pelargonic acid.

Chemical Formulary, Bennett, Van Nostrand C0. New York, vol. 3 (1936), page 323.

Claims (1)

1. A BAR SOAP COMPRISING THE SODIUM SALTS OF 75 TO 95% LIQUID UNSATURATED ALIPHATIC MONOCARBOXYLIC ACIDS OF 18 CARBONS CHAIN LENGTH AND THE SODIUM SALTS OF 25 TO 5% ALIPHARIC MONOCARBOXYLIC SATURATED ACIDS OF FROM 6 TO 10 CARBONS CHAIN LENGTH.