US2435456A - Fatty acids from cottonseed foots - Google Patents

Description

Patented Feb. 3 1948 i 7. .J.

FATTY ACIDS FROM COTTONSEED FOOTS Herbert K. McClain, Wyoming, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio o No Drawing. Application December Serial No. 513,172

8 Claims.

This invention relates to a process for prowhich is commonly referred to as cottonseed It is an emulsified mixture of hydrated foots. sodium soaps of the fatty acids of cottonseed oil and neutral triglyceride oil, together with coloring matter, mucilaginous materials, and other impurities removed from the crude cottonseed oil during the refining process. The soaps and the neutral oil have commercial value, and this is enhanced by freeing them, or their fatty acids, from the impurities with which they are associated in the foots.

The undesired impurities in cottonseed foots have been separated more or less completely, and useful products prepared from the soaps and glyceride oil of the foots in various ways. One of the oldest procedures is to boil the foots with caustic soda until the neutral oil is saponified, wash the soap several times with water or dilute caustic solutions, and finally pitch the soap as in making any fitted or neat kettle soap. ,Although this procedure has the advantage of simplicity, it is today of limited utility because the resulting soap is dark or yellowish in color, strong in odor, and poor in keeping quality when exposed to the air.

The procedure most commonly employed in ,recent years, which employs the so-called Twit- -chell process, consists in acidulating the foots to convert the soaps tofree fatty acids, followed by boiling the oily mass with dilute sulfuric acid solution and an emulsifying agent (a saponifier) .to hydrolyze the glyceride oil and convert it into free fatty acids and glycerin. The mixture .of fatty acids thus obtained is black in color, and is usually purified by distillation. The distilled cottonseed foots fatty acids are relatively light in color and are suitable for use in the manufacture of laundry soaps and intermediate grade general household soaps.

Another procedure that had its origin many years ago is a combination of parts of each of the two preceding methods. It consists in boiling the foots with caustic soda in a soap kettle, to saponify the neutral oil, washing several times with water or dilute caustic solutions to remove some of the coloring matter and impurities, graining out with salt after each of these kettle operations, then acidulating the finally settled soap with mineral acid to liberate the free fatty acids from the soaps, and finally purifying the free fatty acids by distillation. This produces a somewhatbetter quality of fatty acids than the Twitchell method, but usually at the sacrifice of the glycerin, which is readily recoverable from the Twitchell saponification acid water but which is not so economically recoverable from the caustic saponification lye.

The present invention is an improvement on the procedure described in the preceding paragraph, although it is applicable not only to the original or, raw foots from the oil refining process, but also to acidulated foots such as those normally subjected to Twitchell saponification. By means of this invention the quality of the resulting distilled fatty acids is strikingly improved. Furthermore, the kettle boiling process is simplified because the washing of the caustic saponified foots with water or dilute caustic is rendered unnecessary.

An object of the invention is to produce from cottonseed foots a quality of fatty acids superior to that resulting from prior methods, and suitable for use in lighter colored soaps.

Another object is to lessen the cost and shorten .the time required for the making of soaps from cottonseed foots.

Another object is to produce cottonseed foots fatty acids which are relatively stable in color, and which produce light colored soaps which retain a good color with relatively little reversion even under severe aging conditions, and which are relatively very free from disagreeable fatty acid odors.

Another object is to provide a process for accomplishing the foregoing ends which is applicable to both raw cottonseed foots and acidulated cottonseed foots.

Another object is to fix-or transform the coloring materials in cottonseed foots in such a manner that they do not distill over with the foots fatty acids.

, Other objects are to accomplish these ends by means of an oxidizing agent which is efiective under alkalineconditions, and by means of an oxidizing agent having a cation which forms watersoluble soaps.

In the practice'of a preferred modification of the present invention, a quantity of the foots resulting from the caustic refining of crude cottonseed oil is pumped into a soap kettle in which there is a boiling solution containing a low concentration of sodium hydroxide and a somewhat higher concentration of ordinary salt. After saponification of the oil in the foots is well started, a small quantity of an oxidizing agent, of the per cent being a suitable amouatin-niany cases;

After the addition of the oxidizingagent, which has been found to cause the boili'iig mass 1:

- fresh color of 3.4 redwere produced by the process come darker in color, the boilifig cftlfe'kttleiis.

continued for several hours until the saponifica tion of the ioots is substantially 'completw ea'ddi tional caustic soda ((usually as a fairly strong solution) being added from time to time Lf'required. The soap if not already in a grainy condition is then grainedi'out by addingsalt, the

steam heat is shut oil; and v the kettle is allowed 'tdsettl'e'foi' severa 'neurs. aqueous layer, 1; eth'eh'with' a small amount ofjfln'ely divided in oiubi'e impurities; 'sett'lesbut'below an upper layer o'f'soa'p. I

"The soap layer is then transferred to awoode'n or to a lead-lined tub oontai'riii'iga bbiling's'ulfuric acid'soIiition. This: s'ohitibii may b'foi any conyenientconcentration; e. g." 50% sulfuric acid. Theamount of the solution used is preferably such that when the acid hasbroken up substantially all the soaps'an'dhas' liberated their fatty acidsfa' sli'ght excess cffs'uli'uric acid will remain; this pcmttiiasfseen'r achedthe boiling'is disontinued, thetub'is allowed to stand until tijii'e aqueous acid layer has "dropped from the fatty acids; this aque'ousse'at is withdrawn; hot water containing azsmail i'ai'iiquntof sulfuric acid is added and boiled witflthe Ta-lityfacid's' to compiete the acidulation jofthe 'soap'saiidto wash out sodiumsulfate; the tubijs'ajgain settled, and this second seat is withdrawn; Thi's'fw'ashing and settling procedure is repeated at masterin inoi'e, thisti'inewith water alone anuiiic*acia. The trace of mineral acid which inaythen jbe'pr'esent in the fatty acids is neutralized," for exampleby addinga small amount of bariumcarbon'ate; The fatty acids are th'efitransferred to a vacuum still, and distilled 'accordingto'weil: known pramtltep" As compared with the former practice ofcaustic saponification of the'foots followed by acidulation and distillation, withoutthe use of an oxidizing "agent; this new process has the odd characteristic of darkening the boiling soap in the kettle and or producing exceedingly darkcolo'red'fatty acids upon acidulating the soap, and yet of ending with distilled fatty acids ioi." much lighter color and keepingqualitiesefatty acids from which a $051) I ofhigher quality may be made; The function of the oxidizing agent appears to be to convert inrpurities in the foots to forms which settle out of thesoap in the 'kettl'e and/or which are non volatile in the fatty acid still; 7: The maniier in which the oxidizing agent functionsis,fhowever,

not well understood, and the' 'i!l'vl'a'ntiiivnis not-to be limited to any theory as to its mechanism.

In a number of typical comparisons it has kettle, acidulation, anddistiliatieiigwithoutthe use of an oxidizin agentpwnereeswher i the same foots were similarly processed, with the inclusion of the oxidizing step of the present invention during the kettle boiling procedure, using 0.1 per cent of potassium persulfate, the. resulting acidulated and distilled fatty acids had aged colors ranging from about 9 to. 12 ,re,d., By aged color lE refer to a color measured it I ample of the fatty acids had been neuter-mi F. to 140 F. in contact with air,

In another typical case, fatty acids having a of the present invention, as compared with a eoiortraareeby'prior practice in which 3 caustic washes in the'kettle took the place of the oxidiziii'g step of theinirhtion. The aged colors in this case-were 4.7 and 12.3 respectively.

caps made from fatty acids of the foregoing exampleswhich were processed according to this irivefi'tidn" were much lighter than those made by the comparable older process, and they held their color very' much bette when subjected to hi h temperatures and oxidizing conditions. i ts another exampleo'f the invention; aquam of; acidulated cottonseed roots are pumped intoasoap kettleeontaining about one h'ali their bulkoi dilute (e; g., '7 per cent) salt solution. This kettle charge is then brought up to the boilifi'g-'point, and 34 caustic soda solution'is' slowly added while gentle oning is "continued; Soon after the'addi'tion' of caustic solution has comn'ie'nce'dj 0.1 'per cent of owdered potassiump'rsulfate (calculated ontheWeight of the *acidu lated-roots charged into the kettle) is dusted ov'er the surface-of the boiling charge. Aifterseveral neat-"sci boiling and when saponi ficationds complete, sufficient salt to grain the soap-is added, the boiling is" discontinued, the kettle is settled and the soap layer is" transferred to acidulati'on and distillation treatments. These follow the same general procedure as outlined in the'pi'e cedi'ng example; 7 1 When acidulated cottonseed roots are thus treated by the present-invention',; it is us'ually feundsatisfactoiy to emplo about the Same percentag'eof persulfate as when 'treatin'g'raw foots. Theacidulated'foots are about twoor-three tliiies as coneentrate in 17017241 fatty acidcontnfi as the raw f'oots, and it therefore follows that the lalriiount of persulfate normally usedin processing acidulated facts is much less-per pound of roots fatty acids thanthe amount used in treating raw foots'. oxidizing agent perpound of fatty acids 'than raw roots; presumably because the acidulation and the settling after acidulation remove L a certain amount of 'oxidizable tarry material. Nofix'ed rule can be given for determining the optimum amount of oxidizing agent to use in treatin'g'any given amount offootawhetherrawfor acidul'ated, because the cclor and general quality of' foots is highly"variable. A favorable a-mount'of oxidizing agent can be approximated by subjecting several previously indicated, the'useof 0.1.per centoi'an V alkaline persulfate has beenfoundto be an effective amount in a great many cases; and the :use

oflarger amounts "of oxidizing agent havernot been found to be proportionately more Feifec'tive. in'pia'ce of potassiumpersmrate, a persunate oi any'otner'catioa which form watersoiubie soaps y be -use g., s dmm -sersuuate or ti-rims nium i persu fate Similarly; ot er oxidizing ageats ermeates may be employed; prodays at 130' Acidulat'ed foots' appear "to require =-1es's' may be varied within the range of conditions known to any skilled soap maker. Washing the caustic saponified charge with water Or caustic soda followed by graining out with salt may be practiced if desired, and the soap may be pitched and settled to produce neat kettle soap, although these additional steps have not been found to be particularly advantageous. The oxidizing agent may be added after the caustic saponification is complete instead of during the early stages of the saponification, although I prefer to provide the additional boiling time which is gained by adding the oxidizing agent early in the process. The steps of acidulating the soap and washing the resulting fatty acids may also be varied Within the knowledge of the art, employing any convenient mineral acid, the only precaution being to provide fatty acids for distillation which are substantially free from inorganic materials.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. The process which comprises treating cottonseed oil refining foots with caustic soda to saponify the glyceride oil in the foots, adding from about 0.05 per cent to about 0.5 .per cent (calculated on the weight of the original foots subjected to treatment with caustic) of potassium persulfate during said saponifying step while in a boiling condition, graining out the soaps, separating the grained soap from the aqueous phase, acidulating the soap with mineral acid to liberate the fatty acids of the soap, washing the fatty acids to remove inorganic impurities and distilling the fatty acids under reduced pressure.

2. The process which comprises treating acidulated cottonseed oil refining foots with caustic soda to saponify the glyceride oil in the foots, adding from about 0.05 per cent to about 0.5 per cent (calculated on the weight of the original foots subjected to treatment with caustic) of potassium persulfate during said saponifying step while in a boiling condition, graining out the soaps, separating the grained soap from the aqueous phase, acidulating the soap with sulfuric acid to liberate the fatty acids of the soap, washing the fatty acids to remove inorganic impurities, and distilling the fatty acids under reduced pressure.

3. The process which comprises saponifying with caustic soda cottonseed oil refining foots selected from the group consisting of raw foots and acidulated foots, treating the resulting soaps with a peroxide of a cation which forms watersoluble soaps, acidulating these treated soaps thereby forming dark colored oxidation products in the resulting fatty acids, and distilling these fatty acids.

4. The process which comprises sapon'ifying withcaustic soda cottonseed oil refining foots selected from the group consisting of raw foots and acidulated foots, treating the resulting soaps with from about 0.05 per cent to 0.5 percent (calculated on the weight of the foots before saponification) of a persulfate of a cation which forms water-soluble soaps, acidulating these treated soaps with mineral acid, and distilling the resulting fatty acids.

5. The process which comprises saponifying with caustic soda cottonseed oil refining foots selected from the group consisting of raw foots and acidulated foots, treating the resulting soaps with a minor proportion of a persulfate of a cation which forms water-soluble soaps, acidulating these soaps with mineral acid, and distilling the resulting fatty acids.

6. The process of claim 5 in which the persulfate is potassium persulfate.

7. The process which comprises saponifying with caustic soda cottonseed oil refining foots selected from the group consisting of raw foots and acidulated foots, treating the resulting soap with a hypochlorite of a cation which forms water-soluble soaps, acidulating these treated soaps thereby forming dark colored oxidation products in the resulting fatty acids, and distilling these fatty acids.

8. The process which comprises saponifying with caustic soda cottonseed oil refining foots selected from the group consisting of raw foots and acidulated foots, treating the resulting soaps with an oxidizing agent selected from the group consisting of persulfates, peroxides and hypochlorites of cations which form water-soluble soaps, acidulating these treated soaps thereby forming dark colored oxidation products in the resulting fatty acids, and distilling these fatty acids.

HERBERT K. McCLAIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 290,079 Longmore Dec. 11, 1883 2,224,985 Potts Dec. 17, 1940 FOREIGN PATENTS Number Country Date 198,706 Great Britain June 4, 1923