US2162542A - Treatment of fatty acids - Google Patents

Description

Patented June 33, f

' r or marry a thor, East Rutherford, George Boonton, N. 3.. gnors to Wecoline s, Ina, Boonton, N. J., a coratlon of New Jersey No Drawing.

7 Ciaim s.

This invention relates to the higher fatty acids, and more particularly to the treatment thereof whereby discoloration of such compounds on standing is substantially prevented.

- Higher fatty acids of both drying and nondrying types are in considerable demand for various uses. In some such uses, as for example, in the manufacture of allnrd resins, which are combinations of phthalic anhydride, glycerine hi and higher fatty acids, the demand is becoming increasingly one for the lightest possible color in the fatty acids. One of the reasonsfor such a demand is that it is desired to make the resins of the lightest possible color and this necessitates 15 Various attempts to produce light colored higher fatty acids have been made, and it is now standard practice to distill such acids under conditions whereby the resulting product is light colored. However, the distilled fatty acids do not retain their color andthey gradually darken on ageing. The cause of the darkening has not been definitely established, although it is suspected by some that oxidation plays some part in the discoloration and, also, that some polymerization or even decomposition may take place. It is the view of some that impurities either naturally contained in the fatty acids or introduced by contamination may be a cause of or an influ- 30 ence in discoloration. However, none of these views have been fully corroborated at the present time, and the cause of the discoloration may be said to be unknown.

The invention described herein is intended to overcome the difiiculties previously experienced in the discoloration of the fatty acids, it being among the objects thereof to provide a light colored fatty acid composition which is substantially stable in the presence of light and air, and 40 which does not materially discolor after standing for long periods of time or under the influence of heat.

The present invention is based upon a discovery made as the result of a considerable amount 45 of experimentation with substances of widely varied chemical and physical character, that if one adds to fatty acids a small amount of oxalic acid in suitable proportions and under certain conditions, discoloration of distilled fatty acids 50 is practically prevented. This preservation is not temporary, but continues over a long period of time and even under severe conditions.

I Fatty acids thus stabilized against color ce by oxalic acid have been heated accord- 5 ing time standard test, to 285 C. for five hours in correspondingly light colored raw materials Application, October 3, was. sci-a1 No. 43,300

used to give the results desired according to the present invention, is very small. It has been found that when one part of oxalic acid to 100 parts of fatty acids is used, the results are not at all beneficial. The fatty acids so treated darken on ageing, on heat and on exposure to air and light, to even .a greater degree than an untreated fatty acid. However, if one uses 1 part.

of oxalic acid to more than 1000 parts of fatty acid, that is, less than 0.1% of oxalic acid, preservation of the color is obtained. Reducing the amount of oxalic acid used increases the extent of the preservation obtained up to a maximum, after which the effect decreases to that when 1 part of oxalic acid is used with 20,000 parts of fatty acids, the beneficial effect is still noticeable, but in further decreasing the proportion of oxalic acid, the effect becomes negligible. Specifically, we have found that the best results are obtained when there is used 1 part of oxalic acid to 5,000 10,000 parts of fatty acids; that 'is, when the amount of oxalic acid in the final composition is from 0.02% to 0.01%.

We have also found that when, in conjunction with the oxalic acid, a small amount of water is introduced in the fatty acids, the beneficial effects are improved. We, therefore, prefer-usually to use oxalic acid in the crystalline state having two molecules of water of crystallization therein. In some cases, more than the two molecules of water may be introduced into the composition, but if too much water is used it tends to render the fatty acids somewhat cloudy, and this is ordinarily to be avoided.

It is also desirable that distilled fatty acids to be treated should not be allowed to come in contact with air between the distillation operation and the treatment. On a large scale, the treatment may very conveniently be performed by passing the liquid fatty acids substantially con;

tinuously as they are being condensed, through, a.

body of oxalic acid crystals and without allowing contact of the same with air, whereby solution of a very small amount of oxalic acid in the fatty acids takes place. fihe speed with which and eventually becoming brittle.

the fatty acids pass through the oxalic acid or the depth ofthe body crystals, or both, may be varied in order to give the desired amount of oxalic acid in the fatty acids. However, it is usually more convenient to by-pass a portion of the fatty acidsthrough the oxalic acid crystals in order that a saturated solution of oxalic acid in-the fatty acids may be obtained. Then, the treated fatty acids may be combined in the desired proportions with untreated fatty acids to give close control over the final proportions of the ingredients of the composition.

Fatty acids thus treated'retain their natural color under a wide variety of adverse conditions and the product itself is usable for all the purposes for which the untreated fatty acids are adaptable. The amount of oxalic acid present is so small as to be substantially negligible for all uses, and, furthermore, if the fatty acids are to be heated, as in chemical processes, the oxalic acid will decompose to H2O, C0, and CO2, which will pass out of the reaction vessel leaving behind fatty acids practically free from oxalic acid.

The present invention is particularly desirable for use in connection with unsaturated fatty acids, more specially such acids as are ordinarily considered to be of the drying type, such as linseed, soya bean and Chinawood oil fatty acids. However, equally good results areobtained in treating other fatty acids, such as oleic, stearic,

cotton seed oil, fish oil, perilla oil, castor oil fatty acids, or the fatty acids of mixed vegetable oils.

We are aware that it had previously been proposed to treat certain organic compositions ,withoxalic or other acids. For example, alkali earth metal compounds of certain organic acids present in turpentine or the like, such as calcium aliietate, have been stated to act during distillation of turpentine as accelerators of oxidation and also to form complex compounds with other constituents of the turpentine, all of which rendered the subsequently distilled turpentine dark colored. It was, therefore, proposed to add oxalic acid to the turpentine for the purpose of reacting with the alkali earth metal and to precipitate an insoluble oxalate thereof, which was removed by flltration. This procedure is entirely different from the present invention, both in that the oxalic acid remains dissolved in the fatty acids and does not function as a precipitant, and we utilize the same to prevent discoloration in a distilled product, whereas the prior process utilizes a treatment prior to distillation.

It has also been proposed to use various organic compounds including oxalic acid or oxalates, in the treatment of compositions used in making coated fabrics. The composition is generally one of nitrocellulose containing a softener such as castor oil, and a solvent with which the fabric is impregnated, and the fabric is then dried. One of the difliculties encountered was in preventing the coated fabric on ageing from becoming sticky To .prevent this, it was proposed to add oxalic acid or salts in subtantial amounts to the composition in order to maintain the coated fabric in its initial pliable state. Our invention has not relation to such a process and does not introduce oxalic acid for the purpose of maintaining pliability of the composition, but to prevent discoloration of fatty acids.

It is also well known that fats on standing develop rancidity due either to oxidation or the action of enzymes formed by fungi, resulting in the development of objectionable odor and taste in Although we have described our invention set-.

ting forth several variations in the treatment to obtain the desired results, it is understood that variations, such as will become apparent to those skilled in the art, may be made in the details within the scope of the invention. It may be possible to use other .compounds in place of oxalic acids, as, for example, it has been found that a concentrated water solution of calcium hypochlorite also gives definitely favorable results. In the treatment of varying types of fatty acids. it is found that somewhat different amounts of oxalic acid are required to give optimum results, and therefore the present inventioncontemplatesvariations in the amounts to be used, although in all cases the optimum amounts fall within the limits set forth above. ,In the claims appended hereto, the term higher fatty acids is intended to include not only mixtures of fatty acids, but

also individual and substantially pure fatty acids, as well as distilled or crude fatty acids. These and other changes may be made in our invention, the scope of which is defined in the claims appended hereto.

What we claim is:

l. A method -of treating higher fatty acids which comprises adding thereto a small amount of oxalic acid, whereby discoloration of said fatty acids is substantially prevented, the ratio of oxalic to fatty acids being 1 to LOGO-20,000. 2. A method of treating higher fatty acids which comprises adding thereto a small amount of oxalic acid, whereby discoloration of said fatty acids is substantiallyprevented, the ratio of oxalic to fatty acids being 1 to 5,000-10,000.

3. A. method of treating higher fatty acids which comprises adding thereto a small amount of oxalic acid containing water, said amount being sufficient to stabilize said fatty acid against color change, the amount of water being insufficient to cause turbidity in the product, whereby discoloration of said fatty acids is substantially prevented, the ratio of oxalic to fatty acids being 1 to 1,000-20,000.

4. A method of treating higher fatty acids.

which comprises adding thereto a small amount of oxalic acid containing water, the amountof water being insufficent to cause turbidity in the product, whereby discoloration of said fatty acids is substantially prevented, the ratio of oxalic to fatty acids being 1 to 5,000-10,000.

5. A composition consisting of higher fatty acids containing a small amount of oxalic acid.

from 0.1% to 0.005%.

6. A composition consisting of higher fattyacids containing a small amount of oxalic acid from 0.02% to 0.01%.

'7. A composition consisting of distilled linseed oil fatty acids containing an amount of oxalic acid from 0.02% to 0.01%.

FRANK G. AMTHOR. GEORGE ZINZALIAN.