US3503896A - Compositions containing soaps of monounsaturated fatty acids derived by selective hydrogenation of polyunsaturated fatty acid soaps - Google Patents

Description

United States Patent COMPOSITIONS CONTAINING SOAPS OF MONO- UNSATURATED FATTY ACIDS DERIVED BY SE- LECTIVE HYDROGENATION OF POLYUNSATU- RATED FATTY ACID SOAPS Adolph E. Fishman, Baton Rouge, La., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Aug. 30, 1966, Ser. No. 575,963

" Int. Cl. C07c 57/02, /06; C11d 13/00 US. Cl. 252-367 15 Claims ABSTRACT OF THE DISCLOSURE Soaps of monounsaturated fatty acids are prepared by reacting fatty alcohols of the C to C range with caustic alkali at elevated temperatures to form a mixture of soaps of varied degrees of unsaturation and liberate hydrogen, the reaction being carried out in the presence of soaps of polyunsaturated acids so that at least part of the liberated hydrogen selectivelysaturates the latter soaps to produce the desired soaps of monounsaturated acids.

This invention relates to the preparation of synthetic carboxylic acid materials at low cost having superior characteristics as regards properties which are critical in connection with large-scale uses of such acids.

There exists a vast utility for higher synthetic carboxylic acids provided they can be produced in large quantity and at costs and with properties at least comparable to those involved in acids derived from natural sources such as coconut oil. To the present day, such coconut oil-derived carboxylic acids have remained the commercial standard of industry not only because this has been the only significant commercial source of acids of such skeletal configuration and molecular weight characteristics, but because use patterns have developed which make these characteristics particularly desirable in the manufacture of preparations for cleaning purposes such as soaps, detergents and related compounds. For a long time these coconut-derived natural acids have also provided a standard forcomparison or, more properly, a goal for synthetic acids. Recently, however, it has become possible to produce synthetic acids having from about 4 to about 30 or more carbon atoms per molecule, particularly those in the range normally provided by coconut oil, which are vastly superior to the naturally-derived acids according to the normalstandards used for determining the quality of acids, namely, straight carbon chain skeletal configuration, capability for limitation to exclusively even numbers of carbon atoms per molecule, extremely low iodine value as a measure of unsaturation, virtually no coloration, and freedom from non-natural odor characteristics. The present synthetic acids are of such high quality that there is no longer need forconcern over rancidity development or over keeping qualities during transportation and moderate storage periods even without antioxidants which is a fact that is quite surprising to those accustomed to dealing with naturally-derived acids where the preferred practice generally is to avoid any storage or transportation of acids whatever, utilizing them directly as produced. In those instances where it has been necessary to transport or store naturally-derived acids, the desirability of a distillation immediately prior to use in critical applications is generally recognized A further advantage of the new synthetic acids is that they are produced from raw materials which are of petroleum origin readily available as basic materials of low cost in reasonable proximity to, the areas of greatest prior use of the normal. natural acids. The processing involved in the production of such synthetic acids is complicated but Patented Mar. 31, 1970 not prohibitively expensive on a large scale resulting in a stable cost situation free of the uncertainties involved in agriculture and in the vagaries of politics at distant points of the globe.

As a result of the foregoing, it is now possible to replace a significant portion of the commercially used naturally-derived carboxylic acids with synthetically produced acids which are direct and even superior substitutes for the previously used coconut oil derived natural acids. This is a very significant advance in technology, however, it is only part of the acid problem in a large segment of the process industry, namely, the soap industry. In the production of soaps such as high quality toilet bar or hand soap, there are certain essential considerations that must be met. Cost is, of course, a paramount consideration, however, other considerations such as foam producing properties under the conditions in which such soaps are normally used, the optimum solubility compromise between the limits of excessive solubility which on the one hand causes rapid and inefiectual use of soap bars and poor solubility on the other which limits the rate of entry of the soap into solution at the usual temperatures employed and hence also limits eifectiveness. Considerations such as these coupled with cost normally require the use of acid materials from mixed sources. Not only were the coconut range natural acids employed in the prior art formulation of soap, but also prior practice has dictated the joint use of another naturally-derived series of acids, namely, the tallow acids. The tallow acids are normally used at this point because of low cost and ready availability, however, such tallow acids leave much to be desired as regards ability to produce directly a high quality bar of soap for personal washing purposes and almost universal practice with regard to such has been to use such materials in admixture with coconut-derived acids in a ratio of approximately percent tallow acids to 20 percent whole cut coconut acids on a weight basis. The 80:20 ratio was determined to a large extent on a basis of the fact that this is about the highest proportion of tallow acids of low cost that could be used without adversely alfecting normally desired characteristics of soap. Under normal conditions using the aforementioned high quality synthetic coconut range acids in substitution for the naturally-derived coconut range acids, a higher percentage of tallow constituents is permissible for equivalent results to those using natural whole cut coconut acids.

One of the objects of the present invention is to provide a new process whereby new soap compositions can be made wherein the entire acid content of soaps can be provided by acids synthetically derived from low cost materials. A portion of the raw materials is available in significant quantities from waste materials and although the source of such is in a sense natural or agricultural, it does not depend upon year by year weather or growing conditions and hence represents a predictable supply and demand picture.

An important factor in the suitability of tallow fatty acids for the production of soaps in even the 80:20 ratio is the solubilizing effect provided by the oelic acid content of the acids which compensates in large measure for the poor solubility characteristics of the saturated C and C acids that are present. Thus in providing a substitute for a completely natural prior art tallow coconut formulation, one seeks to duplicate not merely distribution as to molecular weight or numbers of carbon atoms per molecule, but also the distribution as to the percentage of the unsaturate content particularly that of the C acids. It is worth noting at this point that tallow acids contain some plurally unsaurated acids such as linoleic acid and linolenic acid, however, these acids are not desired in soap formulation and in fact they contribute rancidity due to their tendency toward oxidative degradation under comparatively mild conditions. Unfortunately, all sources of naturally-derived acids in the tallow range contain significant quantities of such plurally unsaturated molevclues. In addition to this, the basic process whereby the high quality synthetic coconut range acids are produced inherently produces only saturated acids so that it alone is not readily adaptable to providing a direct contribution to oleic acid content in synthetic mixtures of acids for exclusive use in soap manufacture.

The preferred process whereby the high quality synthetic coconut range acids is derived is by the reaction of certain high quality normal alcohols with caustic at elevated temperature. As to the compositions per se they are preferably produced through the involvement of this process because of cost and quality consideration but they are not limited to this process since they can be produced per se in other ways as for example by blending various components and mixtures derived from natural sources. In the preferred alcohol-caustic reaction, the alcohols are converted to the corresponding soaps or salts of the caustic employed in extremely high yield and without the formation of significant quantities of difficulty removable by-product materials. The only significant by-products are unreacted or excess alcohols which are readily removed from the soaps by steam stripping. For the most part, isomeric alcohols react slowly or not at all under the conditions preferred for the caustic fusion reaction.

According to the teachings of the present invention, a low cost acid material having significant quantity of molecules in the 18 carbon atom per molecule range and possessing unacceptable plural unsaturation is combined with the high quality alcohols fed to the caustic fusion reaction with the surprising result that without any need for vigorous catalytic activity beyond that inherently present, the plurally unsaturated molecules are selec tively partially saturated so as to yield mono-unsaturated molecules providing an excellent and even superior substitute for the tallow fatty acid content previousl used in soap manufacture. The result of this is that superior synthetic tallow range acids are produced for soap manufacture through simple processing and in substantial quantity at low cost and furthermore that the synthetic acids, like the synthetic coconut range acids, are also superior to the naturally-derived acids formerly used for this purpose particularly with regard to the important properties of color, odor, stability and freedom from sterols, proteins and naturally-occurring impurities so important to soap manufacturers. The tall oil fatty acids can be saponified prior to admission to the caustic fusion reaction or can be saponified concurrently with the reaction since transient or intermediate formation of esters do not cause problems under the fusion reaction conditions.

It is considered particularly significant that the process of the present invention achieves hydrogenation of a selective nature to the level desired using hydrogen which is inherently generated in the processing due to the reaction of the alcohols and that the desired result is obtained without the necessity for the addition of any catalyst or supplemental hydrogen that must be recovered for economy purposes or removed from the product to provide required purity of product.

One of the preferred natural materials used in accordance with the present invention is a mixture of tall oil fatty acids (or their alkali soaps or salts). Another typical material is fish oil which is also rich in materials of the foregoing type and which contains plurally unsaturated molecules as well as the others that are desired.

The invention will be discussed further with particular attention to tall oil which is a readily available low cost by-product of the paper industry and which frequently is merely burned to recover its fuel value. Other sources of tall oil fatty acids can be used. Tall oil is a mixture of rosin and tall oil fatty acids. The rosin is readily removed and in fact it normally is the case in the paper industry that the rosin is removed and used as a sizing for paper and in other uses. The remaining tall oil fatty acids are approximately 50 percent oleic acid which is a C straight chain mono-unsaturated acid having the unsaturation in the central or 9 position. The other 50 percent of the tall oil fatty acids is made up of C plurally unsaturated acids, particularly linoleic acid, and these are present in the conjugated and in the non-conjugated form. In the conjugated form the acid has unsaturation in the 9 and in the 12 position and is known as linoleic. Although the results are not yet established with certainty, it appears that the conjugated acids are hydrogenated at the 12 position so as to yield only oleic acid unsaturated in the 9 position or that if a mixed saturation occurs producing a mixture of 9 and 12 mono-unsaturated acids that the resulting mixture has for all practical purposes substantially the same properties as pure oleic acid. Of course, this does not rule out the possibility that acids once formed with the 12 position unsaturated are subsequently isomerized to what may be the more stable position with the unsaturation at the 9 position. With the C conjugated acids being thus saturated selectively to mono-unsaturated acids, the non-conjugated acids are first isomerized under the influence of the alkaline presence in the caustic fusion reaction environment to produce additional quantities of conjugated'acids which are then selectively hydrogenated to yield a product which has the properties of oleic acid as far as soap solubilizing action is concerned.

From the preceding paragraph it is evident that the exact mechanism whereby the hydrogenation and isomerizations occur and in fact if some of them occur at all, is not yet established with certainty but that whatever does occur under the conditions employed for the caustic fusion reaction itself, the result is the production of mono-unsaturated carboxylic aids having 18 carbon atoms and which exihibit substantially the same properties as oleic acid as far as soap formulations are concerned.

Tallow acids as normally employed in an 20 Weight ratio with whole cut coconut acids in soap manufacture may be described in further detail as containing approximately equal parts of oleic acid and of combined saturated hexadecanoic acid (palmitic) and octadecanoic acid (Stearic) with traces of other unsaturated and poly-unsaturated acids. The palmitic/stearic ratio may be characterized as 1:1. Thus a typical synthetic tallow fatty acid mixture may contain 50 percent oleic acid, 25 percent stearic acid and 25 percent palmitic acid. Such a mixture of acids is an excellent and even superior substitute for tallow fatty acids used in soap formulations in the 80/20 tallow/ coconut acid proportions of the prior art. Significant superiority of the synthetic tallow constituency arises through freedom from poly-unsaturation. Although the coconut oil portion used in such soap formulations can be whole cut naturally-derived coconut acids, it is preferred and now possible commercially that it be synthetic acid and soap combinations in accordance with the teachings of copending application of Robert J. Fanning and Adolph E. Fishman, filed Aug. 3, 1966, S. N. 569,823, entitled Chemical Composition, in which instance the superior properties of such synthetic acid mixtures permits a tallow acid/ coconut acid ratio of as high as 15 for results equal to those of the 80/20 ratios based upon natural materials and it must be observed that many properties of such all synthetic 85/ 15 soaps are superior to those of the 80/20 soaps based upon solely natural materials.

EXAMPLE 1 A synthetic 80/20 tallow fatty acid/coconut acid soda soap composition was made using the following constituents: (Toilet bar soap of commerce)- Normal alcohols: Parts by weight C alcohol (lauryl) C alcohol (myristyl) '50 C alcohol (palmityl) 220 Normal alcohols: Parts by weight C alcohol (stearyl) 200 Tall oil fatty acids:

Oleic acid 200 Linoleic acid 200 Sodium hydroxide (100 percent active basis) 160 The mixture of alcohols and tall oil fatty acid was reacted with the caustic at 340 C. and 400 psi. until hydrogen liberation ceased. This took approximately 15-30 minutes. The molten soap was cooled in a nitrogen atmosphere to ambient temperature. The anhydrous soap so produced was white, of'yery bland odor .and exhibited good foaming and cleaning properties in hand washing tests conducted with 60 F. to 100 F. wash water.

The titre of fatty acids sprung from the soap was 39 C. and the iodine value was 30 centi'grams of I per gram of acid. Both specifications are typical of an 80/ 20 tallow fatty acid/ coconut oil fatty acid soap stock. In the caustic fusion process the Iodine value had been reduced from 52 to 30 cgms. l /gm. of acid. All data were consistent with the reduction of diunsaturates ofthe tall oil fatty acids to monounsaturates.

The soap had excellent keeping qualities. No antioxidant was added. Color over a 3 month storage period remained white and odor bland or mild.

EXAMPLE 2 s A low titre soap was produced from the following principal components:

i Parts by weight C normal alcohol ..J

Tall oil fatty acids:

Oleic 250 Linoleic 25,0

- 1000 Sodium hydroxide (100 percent active basis) 173 For production of even more highly soluble soaps the fats of Example .2 are caustic fused with potassium hydroxide.

Parts by weight C alcohol 500 Tall oil fatty acids: t I

Oleic 250 Linoleic 250 Potassium hydroxide 240 The resulting soaps :are used to prepare aqueous liquid hand soap of up to 30 to 40 percent Soap concentrations. Such soaps are useful when reduced to about 15 percent soap concentration for shampoos and liquid hand soaps.

EXAMPLE 4 Oleic acid low in polyunsaturates is obtained from tall oil by first reacting as in Example 2 where hydrogen from the reaction of dodecanol converts polyunsaturated molecules to monounsaturates. The soap (from Example 2) is acidified with aqueous sulfuric acid to liberate a mixture of lauric and oleic acids. Due to the large difference in boiling points between the lauric and oleic, a clean fractionation by distillation is readily made yielding economically a synthetic oleic acid of low polyunsaturate content plus a pure lauric acid stream.

EXAMPLE 5 Acids from various fish oils such as menhaden and herring are used in preparing mild-odored and light colored soaps. Herring oil acids are high in clupanodonic acid (C H O lodine value 384) and arachidonic acid (c H O lodine value 333.5). Menhaden oil is high in these same acids.

A typical soap is made from a blend of the following:

Normal alcohols: Parts by weight C alcohol C14 alcohol C16 C18 alcohol Menhaden oil 400 Sodium hydroxide (100 percent active basis) The mixture is caustic fused as in Example 1 and a soap of properties similar to that of Example 1 is prepared.

Typical rnenhaden oil fatty acid composition as used here- EXAMPLE 6 Examples 1-5 are repeated with the tall oil and other fatty acids being saponified with caustic prior to admixture with the normal alcohols and caustic for the caustic fusion reaction. Comparable results are obtained.

EXAMPLE 7 Examples l-4 and 6 are repeated using a tall oil fraction of the following typical composition in place of the specified total weight of tall oil fatty acids. Comparable results are obtained.

Fatty acid composition: Percent Linoleic, non-conjugated 38.5 Linoleic, conjugated 5.0 Oleic 51.2 Stearic acid 2.7 Other fatty acids 2.6

EXAMPLE 8 The foregoing examples are repeated using other primary alcohols in place of the normal alcohols specifically used in addition to the tall oil or other such acids (typically the Menhaden of Example 5). The other alcohols of this example include normal alcohols of difi'erent molecular weights and percentage distributions as well as mixtures thereof including branched primary alcohols and unsaturated primary alcohols. Such alcohols are derived in numerous well known processes such as the 0x0 process. In the case of mixtures of normal and branched alcohols the condition of the fusion reaction can be controlled to selectively convert the normal alcohols to acids. Where the feed alcohols in addition to the tall oil acids group components also contain polyunsaturation, a selective hydrogenation to the monounsaturated form occurs. Monounsaturation in the feed alcohols, acids and soaps has no untoward effect upon the course of the caustic fusion reaction, such molecules reacting similarly to equivalent saturated molecules. As to product however different characteristics are obtained such as increased solubility or lowered melting point for the corresponding monounsaturated derivatives. The general principle followed is to provide a stoichiometric excess of hydrogen liberated in the fusion reaction over that required to selectively saturate the polyunsaturates present to monounsaturates. Suppplemental or recycle hydrogen is added to the reaction mass where reaction mixtures are used to produce product wherein the derivatives of the polyunsaturated feed molecules are the most desired product and one wishes to limit the co-production of derivatives of molecules which were not polyunsaturated by using lesser quantities of such in the feed.

What is claimed is:

1. A process of producing, synthetically, soaps of monounsaturated acids, which comprises:

reacting aliphatic alcohols having from 12 to about 22 carbon atoms in the molecule with one or more alkali or alkaline earth metal hydroxides at a temperature in the range of from about 280 to about 350 C. and at a pressure of up to about 25 atmospheres whereby the alcohols are converted to soaps and hydrogen is liberated,

and conducting said reaction in the presence of soaps of polyunsaturated acids whereby at least part of the liberated hydrogen selectively and partially saturates the soaps of polyunsaturated acids to produce a mixture of soaps of monounsaturated acids with soaps or saturated acids.

2. The process of claim 1 wherein the fusion-saturation reactions are conducted at about 340 C. and at about 400 pounds per square inch gage.

3. The process of claim 1 wherein the soaps of polyunsaturated acids are produced in situ from said polyunsaturated acids and alkali or alkaline earth metal hydroxides added to the reaction system.

4. The process of claim 1 wherein the soaps of polyunsaturated acids are derived from tall oil fatty acids.

5. The process of claim 1 wherein the soaps of polyunsaturated acids are obtained by saponifying tall oil fatty acids and the saponification mixture is in admixture with the caustic fusion reaction mass during the period of time in which the caustic fusion reaction is in progress.

6. The process of claim 1 wherein the soaps of polyunsaturated acids are derived from menhaden oil.

7. The process of claim 1 wherein the soaps of polyunsaturated acids are predominantly soaps of linoleic and linolenic acids.

8. The process of claim 1 wherein the soaps of polyunsaturated acids are predominantly soaps of linoleic and linolenic acids and wherein oleic acid is also present, the proportions approximating the proportions of said linoleic, linolenic and oleic acids in conventional crude tall oil fatty acids.

9. The process of claim 1 wherein the amount of alcohols reacted is at least that required to liberate in the fusion reaction the stoichiometric amount of hydrogen required for selective hydrogenation to monounsaturated molecules of the polyunsaturated molecules present.

10. A method of producing a synthetic monounsaturated organic acid comprising:

reacting aliphatic alcohols having from 12 to about 22 carbon atoms in the molecule with one or more alkali or alkaline earth metal hydroxides at a temperature in the. range of from about 280 to about 350 C. and at a pressure ofup to about 25 atmospheres, whereby the alcohols are converted to soaps of saturated acids and hydrogen is liberated,

conducting said reaction in the presence of soaps of polyunsaturated acids, whereby at least part of the liberated hydrogen selectively saturates the soaps of polyunsaturated acids to produce a mixture of soaps of monounsaturated acids with the soaps of saturated acids,

acidifying said mixture to produce an acid mixturehaving essentially the same anion distribution as said mixture of soaps of saturated and monounsaturated acids,

and recovering the monounsaturated acids.

11. The process of claim 10 wherein the alcohols reacted are normal having from about 10 to 14 carbon atoms per molecule and the polyunsaturated soaps have from about 16 to 24 carbon atoms per molecule.

12. The process of claim 10 wherein the alcohol reactants approximate commercial lauryl range alcohol mixtures in chemical composition and the monounsaturated organic acid product approximates commercial oleic acid in chemical composition.

13. A mixture of arboxylic acid soaps derived by the process of claim 1 consisting essentially of about 13 percent of laurate soap, about 5 percent of myristate soap, about 22 percent of palmitate soap, about 20 percent of stearate soap andabout 40 percent of oleate soap, all percentages being by weight.

14..The.soap mixture of claim 13 wherein the oleic acid is synthetic, said mixture being characterized by substantially less polyunsaturation than that characterizing conevntional nonhydrogenated tallow acid derived soaps.

15. The soap mixture of claim 13 wherein the oleic acid is derived from selectively hydrogenated tall oil.

References Cited UNITED STATES PATENTS 2,159,700 5/1939 Hennig 2604l3 2,954,347 9/1960 St. John et al 252109 3,020,237 2/1962 Dunn 252109 .U.S. Cl. X.R.