US2389260A - Producing unsaturated compounds - Google Patents

Description

Patented Nov. 20, i945 UNlTED STATES PATENT OFFICE PRODUCING UNSATURATED COMPOUNDS Hans George Kirschenbauer, Allendale, N.-J., as-

signor to Colgate-Palmolive-Peet Company, Jersey City, N. J a corporation of Delaware No Drawing. Application July 22, 1942, Serial N0. 451,976

11 Claims.

that its drying properties are associated with the presence of constituents having a conjugated double bond structure. Other natural oils, the polyunsaturated constituents of which have unconlugated doublebonds, do not exhibit such fast-drying effect and in their natural state cannot be successfully substituted for tung oil,

It has been proposed to process these oils to improve their drying properties, and a recent patent describes a method for refluxing them in alcoholic solution with a basic reagent to convert constituents having 'unconjugated double bonds to conjugated systems, The patented process employs an amount of alcohol several times the weight of the oil treated, and the refluxing operation is carried on over a period of several hours. So far as is known, the art has not been able to develop a method on a practical and industrial scale for successfully causing migration of the double bonds to a conjugated position in a relatively short time and without the use of solvents.

It is an object of the present invention to provide an improved process for causing the double bonds of polyunsaturated organic materials to become conjugated in a relatively short time.

It is also an object of the invention to provide a novel process for convertingfatty oils, fatty acids and other fatty matter having unconlugated double bonds into materials having conjugated double bonds without the use of added solvents.

Other objects and advantages of this invention will be apparent from the following description.

According to the present invention, materials containing organic aliphatic compounds having at least two double bonds in unconjugated position are treated, with or without additional fatty material, with suitable alkaline agents and subjected in an inert atmosphere, and preferably in the presence of excess alkali or other suitable catalyst, to a temperature above the melting point of the resulting anhydrous soaps. The treatment takes place in 9. closed vessel in the substantial alkaline or neutral catalysts.

absence of liquid water and of air or other oxidizing atmosphere, and an inert gas, such as steam, hydrocarbon vapor or nitrogen,'is preferably passed through the molten reaction mixture.

Although the treatment may be carried out at superatmosph'eric pressure, at atmospheric pressure or under reduced pressure, it is preferred that a partial vacuum be applied. Glycerine, if any, and unsaponifiable material are vaporized by this treatment, and their removal from the reaction vessel is facilitated by the inert gas, where such gas is employed. The vaporized material may be recovered, if desired.

The resulting mixture of anhydrous soap is drawn off in the fluid state, while taking suitable precautions to exclude harmful contact of air with the hot soap. One way of accomplishing such withdrawal is to discharge the fluid soap into and beneath the surface of a body of water or aqueous solution. The soap is dissolved in water to give an aqueous solution thereof, and this solution is acidulated, preferably by the addition of dilute mineral acid. The fatty acid can then be separated out by decantation, withdrawal of the lower aqueous solution, centrifuging or the like, and may be subjected to fractional distillation, fractional crystallization and/or other separation and purification procedures, if desired; The fatty acids may then be esterified with glycerine to produce an oil with fast-drying properties, or other esters may be formed by esterification with the corresponding alcohols.

Esterification of the free fatty acids with glycerine may be accomplished by heating the mixture, preferably under vacuum, to about 200 C. or higher, with or without the presence of a suitable catalyst, such as beta-naphthalene sulphonic acid, beta-camphor sulphonic acid, or other acid,

Care should be exercised in this operation, as excessive temperatures or large amounts of catalysts may cause polymerization of the unsaturated acids. Glycerides may also be formed by first esterifying with a lower monobasic alcohol, such as methyl alcohol, and then distilling the resulting ester with glycerine, with or without a catalyst, continually adding fresh glycerine and removing the alcohol as liberated. Another procedure for producing glycerides is directly to react the anhydrous soap formed with 1,2,3-trichlor propane and to remove sodium chloride therefrom.

Saturated and monounsaturated constituents of the oils may be separated out in the form of their free fatty acids or esters, either before or after treatment in accordance with the present process, by fractional distillation, fractional crystallization and/or solvent extraction, or other methods. However, the occurrence of some of the more saturated materials as modifiers is sometimes of value in the product.

' The temperature of the treatment has been described supra as above the melting point of the resulting anhydrous soaps. Normally, while this temperature is high enough to effect a desirable change in the properties of the soap, migration of the double bonds to conjugated positions occurs at a somewhat higher temperature. In the usual case, such temperature will generally be of the orderof about 285 C. to about'3l0 0., though temperatures up to about 350 C. or higher may sometimes be used, and in most cases temperatures of about 290 C. to about 300 C. will be found suitable. The temperature limits are necessarily set by the character of the resulting soap, as the migration occurs-at somewhat lower temperatures with some soaps. With respect to the upper limit, the temperature above which substantial polymerization or decomposition of the resulting soap occurs is not to be exceeded. It is advantageous at all times to prevent local overheating and decomposition at surfaces of contact between the reaction vessel and the product. During the treatment, the mass is thoroughly agitated, and the inert gas which is passed through the material may be employed as the sole or the supplementary means for such agitation, as well as for facilitating the carrying off of volatilized material. Stirrers and/or other means for mechanically agitating the molten mass may also be used to advantage.

The treatment of this invention is also applicable to materials which are already in saponified form, and such saponified substances may be treated alone or with unsaponified fatty oils, esters and acids. Where part of the material subjected to the treatment is already saponified, it is advantageous during the initial stages of heating to prevent local overheating and decomposition at the surface of contact between the reaction vessel and the product by first heating the saponified material and maintaining it at a temperature of about 290 C. to about 300 C. where it is fluid, and then adding the unsaponified material at a rate not substantially greater than the rate at which it may be heated to the temperature necessary for fluidity. The process may be operated with continuous, intermittent, or batch additions of crude materials and withdrawals of treated products.

An excess of caustic alkali is preferably employed, and, although various alkaline materials may be used for the saponiiication, free alkali in excess of the amount of alkaline material required for saponification is added. Such excess of free alkali is preferably equivalent to up to about 25% (usually more than about 0.5%) of the alkaline agent needed for saponifying the fatty material. The alkaline materials which may be used include caustic alkalies like sodium or potassium hydroxide, lime, carbonated alkalies like sodium or potassium carbonate, magnesium carbonate, etc., or mixtures thereof. If alkaline materials other than caustic soda and soda ash are employed, it may be necessary or desirable to change thetemperatures used, because of the differences in the melting points of soaps formed with materials other than sodium. In any event, the temperature should be sufiiciently high to insure fluidity, being above the melting point of the resulting anhydrous soap and below the temperatu're of substantial decomposition or polymerization.

The following examples are merely illustrative of the present invention, and it will be understood that the invention is not limited thereto.

Example I phere above the reaction mass. The molten reaction mass is then pumped from the vessel into about 300 parts of water, the reaction mass being admitted under the surface of the water to avoid oxidation. A suflicient amount of dilute sulphuric acid for completely liberating the mixture of fatty acids is added, and the aqueous mass is vigorously agitated. Upon settling, two layers are formed, and the lower aqueous layer is withdrawn. The residue is washed with water to remove any retained sulphuric acid from the fatty acids. The maleic anhydride value of the product is determined, and a value of 24 is obtained, as compared with a maleic anhydride value of 2.5 for the original untreated linseed oil fatty acids. The acids produced thus give evidence of containing a large proportion of constituents having conjugated dou-v ble bonds not present in the untreated acids, and glycerides formed therefrom exhibit fast-drying efiects.

Example II About 200 parts of cottonseed oil and about 33 parts of pulverized'caustic soda are intermittently fed into a reaction vessel provided with a mechanical stirrer, and the mixture is heated to about 260 0. A stream of nitrogen is passed through the mass, and the temperature of the reaction mass is rapidly raised to about 290 C. to about 300 C. and held'at this temperature for about one hour. During this time, the reaction mass is vigorously agitated with the aid of .the nitrogen stream, and glycerine and unsaponiflable and odoriferous matter are removed as vapors from the reaction chamber. The molten reaction mass is then pumped into a pressure mixing vessel, where it is dissolved in water. The soap formed is acidulated, using dilute sulphuric acid therefor,

V and, after .settling, the lower aqueous layer is Example III About 200 parts of cottonseed oil and about 33 parts of pulverized caustic soda are fed into a reaction vessel and subjected to the treatment of Example II, except that steam is passed through the mixture instead of nitrogen. The maleic an-.

hydride value of the fatty acids obtained in this manner is 11.8.

" maintained for about forty minutes.

bubbledthrough the molten mass throughout this aseaao treated esters and the treated product are then .1

Example IV About 200 grams of menhaden oil are heated to about 275 C., while a stream of steam is passed therethrough. About 45 grams of caustic potash are then added to the oil, a vacuum of about 26 virich'es of mercury is applied, and thetemperature is rapidly raised to about 288 C. and there Steam is period, serving to agitate themixture, to provide an inert atmosphere and to facilitate removal of glycerine and unsaponifiable matter. The soap formed is pumped into water containing sumcient hydrochloric acid to acidulate'th'e soap, and it is there vigorously agitated. The liquid mass settles into two layers, and the upper layer is de canted, washed and dried. The free fatty acids thus recovered are mixed with glycerine anda small amount of beta-naphthalene sulphonic acid as an esterification catalyst, and the mixture is heated under partial vacuum at about 200 C. for about two hours to esterify. The glyceride formed is found to have a maleic anhydride value of 16 and-to exhibit the properties of materials having conjugated double bonds, including. fastdrying effects.

Emample V Cottonseed oil is alcoholized with methyl alcohol, and the resulting esters are distilled to remore a largeproportion of the palmitic acid esters. A fraction having an iodine value of 121.5 and a saponification value of 19.17% potassium hydroxide is recovered and contains most of the methyl oleate and methyl linoleate. A sample of this material is reserved without further treatment for subsequent comparison. About 200 parts of the methyl esters are mixed with about 30 parts of ground caustic soda and fed into a heated reaction vessel equipped with a mechanical agitator. Steam is passed through the reaction mass continuously, and the temperature is maintained at about 250 C. throughout the feeding and is then rapidly raised to about 290 C. to about 300 C. and kept at this temperature range for about one hour, during which time the steam is continuously bubbled therethrough to aid in the agitation of the reaction mixture and to provide an inert atmosphere th'ereover. The reaction mass is thereafter run into water, and dilute sulphuric acid is added to the aqueous mass to acidulate the soap. The material settles into two layers; the upper layer is siphoned off, washed and dried and is then treated with about three to four times its volume of methyl alcohol. A small amount of concentrated sulphuric acid is added as an esterifying agent, and the mass is refluxed for about an hour. It is then permitted to stand in a warm place for about twenty-four hours, whereafter it is cooled, diluted'with water and extracted with ethyl ether. The ether extract is distilled to remove the ether and to recover the methyl esters, and the esters are distilled at a pressure of about 2 mm. of mercury from a Claisen flask to separate them from polymerized matter. About 85.5% distill below 200 C. and are recovered.

The methyl esters distilling below 200 C. at 2 mm. of mercury pressure are then compared with the untreated methyl esters of the sample reserved for comparison, with reference to constituents of conjugated double bond structure. anhydride value of the esters of the treated product is found to be 19.4, while the untreated esters have a maleic anhydride value of 0.9. Th unexamined with -a photoelectric spectrophotometer to determine their spectral extinction coefficients. spectrophotometry has become recognized as'a valuable means of identifying conjugated constitutents in the composition of fatty oils, esters, acids and the like, the conjugated due to the conjugation of the methyl linoleate' structures being characterized by intense absorption bands, the location of which depends upon the nature of the specific chromoph'ore present in the molecule. A numerical comparison of the extinction coefflcient of an. unknown, such as the treated product in the present example, with the extinction coefficient exhibited by a reference compound, such as the untreated esters herein described, at the same characteristic wave length is a measure of the increase in condugation effected. At about 2350 Angstrom units, the spectral extinction coefficient of the untreated esters is 6.3, while, at the same wave length, the extinction coeflicient'of the product methyl esters is 378. The increase .in the extinction coeflicient is double bonds.

Among other materials containing-constituents having unconiugated systems. which may be treated by the present process are various natural oils, includingcorn oil, soya bean oil, whaleoil, sardine and other fish oils.sesame seed oil, cottonseed foots, saillower seed oil, Perilla oil, sunflower oil, and the like, as well as fatty acids,

. esters and salts thereof. Materialscontaining smaller proportions of unconjugated double bond constitutents, such as tallow, garbage grease and the like and their derivatives, can also be treated by this process to cause migration of the double bonds of said'constituents into conjugated positions, although it-is preferred to employ these materials in admixture with materials containing 40 larger proportions of constituents having uncon- The maleic jugated double bonds. Various synthetic materials, including fatty acids having unconjugated double bonds and prepared by dehydrohalogenation of polychlorinated saturated acids or dehydration of hydroxy-unsaturated acids, such as ricinoleic acid, or the like, may also be treated by this process. I

Various fatty'materials and fatty acids may be employed in admixture'with the fats and oils containing constituents having unconjugated double bonds, and it is also possible to add other organic materials at any point during the process. For example, various oils, fats, waxes, and resins may be added to the reaction vessel, and these include wool fat, spermaceti, various grades of wood and gum rosin, coconut oil, olive oil, palm oil, tung 0il,' oitic ica oil, montan wax, carnauba wax, Japanese wax and Chinese wax, as well as the various individual fatty or resin acids or derivatives thereof .or mixtures of any of these fats, oils, waxes, resins and acids.

Besides their availability as a source of fastdrying oils, the products of the process of the present invention containing constituents having conjugated double bonds, with or without the addition of other fatty materials, can be used for many other purposes. As will be apparent from the foregoing, they may be used in the synthesis of various organic compounds, such as tricarboxylic acids. The free fatty acids may also be mixed with other acids, such as phthalic acid, maleic acid, succinic acid, abietic acid, etc., and the mixture esterified with glycerine or other polyhydric alcohols to form alkyd resins for use as bonding materials. These materials are generally more reactive in the conjugated form, and, due to the migration of the double bond, diflerent carbon atoms are made availablefor additions.

The term "polyunsaturated" as applied to the raw materials and products of the present process is intended to include materials having two or more double bonds, whether conjugated or unconjugated.

Aithough the present invention has been de-- scribed with respect to particular embodiments and examples thereof, it will be understood by those skilled in the art that other variations and modifications of the invention can be made and that various equivalents can be substituted'therefor without departing from the principles disclosed herein. Such variations and modifications are believed to be within the scope of the present specification and within the purview of the appended claims.

Iclaim:

1. A process which comprises heating a polyunsaturated fatt material having unconlugated double bonds with an amount of alkaline agent from about 1.005 to 1.25 times that required for saponification in an inert atmospher at a temperature within the range of about 285 C. to

about 350 C. but below the temperature of substantial polymerization of, the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous condition, whereby a product containing polyunsaturated compounds having conjugated double bonds is formed, acidifying said product, recovering fatty acids from said acidified product and esterifying said fatty acids with alcohol.-

2. A process which comprises heating at a pressure not substantially in excess of atmospheric pressure a polyunsaturated fatty material having unconlugated double bonds with an excess of alkaline agent not substantially greater than'25% of that required for saponification in the absence of air at a temperature within therange of about 285 C. to about 350 C. but below the temperature of substantial polymerization of the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous condition and while thoroughly agitating and intimately contacting the mixture with a stream of an inert gas, whereby a'product containing polyunsaturated compounds having conjugated double bonds is formed, acidifying said product, recovering fatty acids from said acidified product, and esterifying said fatty acids with alcohol 3. A process which comprises heating at substantially atmospheric pressure a polyunsaturated fatty material having unconjugated double bonds with an alkaline agent in the'absence of air at a temperature of about 285 C. to about 310 C. but below the temperature of substantial polymerization of the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous condition and while passing a current of steam through said mixture, said alkaline agent comprising free alkali up to 25% excess of the amount of alkaline agent required to saponify said fatty material, whereby a product containing polyunsaturated compounds having conjugated double bonds is formed, acidifying the product, recovering fatty acids from said acidified product, and esterifying said fatty acids with polyhydric alcohol to produce a drying oil.

4. A process which comprises heating at substantially atmospheric pressure a polyunsaturated fatty material having unconiugated double bonds 1.25 times. the amount required for saponifica- I with an alkaline agent in an amount from about 1.005 to 1.25 times that required for saponiflcation in the absence of air at a. temperature of about 290C. to about 300 C. while maintaining the heated mixture in molten and substantially anhydrous condition and while passing a current of steam through said mixture, whereby a product containing polyunsaturated compounds having coniugated double bonds is formed, acidifying said product, recovering fatty acids from said acidified product, and esterifying said fatty acids with polyhydric alcohol, said csteriflcation being carried out in admixture with other carboxylic acids.

5. A process which comprises heating at a pressure not substantially in excess of atmospheric pressure a fatty material selected from the group consisting of natural oils containing polyunsaturated constituents having unconjugated double bonds and acids, esters and soaps of said oils with an excess of alkaline agent up to 1.25 times that required to saponify the fatty material in the absence of air at a. temperature within the range of about 285 C. to about 350 C.- but below the tem: perature of substantial polymerization of the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous condition and while thoroughly agitating and intimately contacting the material with a current of steam, whereby polyunsaturated compounds having conjugated double bonds are formed, and converting said compounds to polyhydric alcohol esters of thefatty acid radicals thereof.

6. A process which comprises heating a fatty material selected from the group consisting of natural oils-containing polyunsaturated constituents having uncondugated double bonds and acids, esters and soaps of said oils with an alkaline agent comprising excess free alkali up to about tion under reduced pressure and in the absence of air at a temperature of about 285 C. to about 310 C. but below the temperature of substantial polymerization of the resulting anhydrou product while maintaining the heated mixture in molten and substantially anhydrous condition and while thoroughly agitating and intimately contacting the mixture with a stream of an inert gas, whereby a product containing polyunsaturated com pounds having conjugated double bonds is formed,

acidifying the product recovering fatty acids from said acidified product, and esterifying said fatty acids with glycerlne.

7. A process which comprise heating a fatty material selected from the group consisting of natural oils containing polyunsaturated constituents having unconjugated double bonds and acids, esters and soaps of said oils with excess alkaline agent up to 1.25 times the amount required for saponification in the absence of air at a temperature of about 290 C. to about 300 C. while maintaining the heated mixture in molten and substantially anhydrous condition and while passing a current of steam through said mixture, whereby a product containing polyunsaturated compounds having conjugated double bond is formed, acidifying the product, recovering fatty acids from rated constituents having unconjugated double bonds and acids, esters and soap of said oil with an alkaline agent in the absence of air at a temperature within the range of about 285 C. to about 350 C. but below the temperature of substantial polymerization of the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous con-' stantially atmospheric pressure a fatty material selected from the group consisting of natural oils containing polyunsaturated constituents having unconjugated double bonds and acids, esters-and soaps of said oils with an alkaline agent in the absence of air at a temperature of about 285 C. to about 310 C. but below the temperature of substantial polymerization of the resulting anhydrous product while maintaining the heated mixture in molten and substantially anhydrous condition and while passing a current of steam through said mixture, said alkaline agent comprising an excess of free alkali equivalent to up to about 25% of the amount of alkaline agent necessary not containing polyunsaturated compound; having conjugated double bond is formed, acidifying the reaction product, recovering fatty acids from said product, and reacting said fatty acids with polybasie carboxylic acids and polyhydric alcohol to form a resin.

10. A process which comprises heating at a pressure not substantially higher than atmospheric pressure a soap of fish oil fatty acids with up to 25% excess of sodium hydroxid in the absence of air at a temperature of about 285 0.120 about 300 C. while maintaining the heated mixture in molten and substantially anhydrous condition and while passing a current of steam therethrough, whereby a product containing polyunsaturated compounds having conjugated double bonds is formed, acidifying said product, recovering fatty acids from said acidified product, and reacting said fatty acids with alcohol.

11. A process which comprises heating at a pressure not substantially higher than atmospheric pressure a soap of linseed oil fatty acids with up to 25% exces of sodium hydroxide in the absence of air at a temperature of about 290 C. to about 300 C. while maintaining the heated mixture in molten and substantially anhydrous condition and while passing. a current of steam therethrough, whereby a product containing polyunsaturated compounds having conjugated double bonds is formed, acidifying said product, recovering fatty acids from said product, and

esterifying said fatty acids with polyhydric alcoto saponify said fatty material, whereby a prod hol to form a drying oil.

HANS GEORGE HENBAUER.