US2091988A - Process for producing lauric-aceticglyceride - Google Patents

Description

Patented Se t. 7, 1937 rnocsss FOR PRODUCING LAURIO-ACETIO- GLYCERIDE Leo Phillip Hubbuch, Wihnington, Del., and Rayi-mond E. Thomas,;.Newburgh, N. Y., assignors to E. I. du Pont de'Nemours & Company, '11- mington, Del., a corporation of Delaware No Drawing. Application April 2'4, 1934,

Serial No. 122,128

1 Claim. .(01. zoo-'10s) This invention relates to improvements in the manufacture of mixed-esters of polyhydric alcohols, and more particularly to a new method for preparing mixed glycerides especially suitable as softeners for nitro-cellulose compositions hich'are to he used in the manufacture of artificial leather.

To those skilled in the art it is known that a suitable softener for artificial leathers has two 0 functions, (1) to ,soften the coating without making it sticky or oily, and (2) tokeep the coating I standing. It is notorious} soft and pliable over a long period of time. We

have discovered that to accomplish the first resuit, the softener must have the proper degree of solvent action'for the film-forming ingredient of the coating composition, and to obtain the second result, the softener must be substantially non-volatile and not susceptible to oxidation under the usual conditions for use of artificial leathers. use, meets the first requirement but is not outy deficient in regard to the second requirement because it oxidizes g readily and causes embrittlement of the coating.

Long chain saturated or non-oxidizable glycerides such as coconut oil are sufiiciently nonvolatile incharacter for use as softeners but have low solvent power and consequently render the surface of the coating oily or greasy. Short chain saturated glycerides such as trlacetin are not only too volatile, but are also writer sensitive .and have too great a solvent power,-thus renderingthe coating sticky. Mixtures of these exhibit Y the.bad features off-"both. However, when they are chemically combined by'a method which assures that neither type is present as such in substantial amounts, an extremely useful softening agent is produced, so that a pure mixed glyceride .of the proper type should be the ideal softener for'artificial leather coating compositions.

Various methods of making mixed glycerides have been disclosed in the prior art. 'Ihus, Schwartz U. 8. Patent No. 1,558,299 discloses the direct esterification of the polyhydric alcohol with a mixture of organic acids, with or without sulfuric acid as a catalyst, the sulfuric acid being later removed either by washing or neutralization with sodium acetate; the heating of coconut oil and glacialacetic acid, followed by esterification of the liberated coconut oil acids by Castor oil, the chief softener now in oil and triacetin with or without sulfuric acid as a catalyst; and ester interchange by heating a coconut oil, glacial acetic acid, glycerol, and sulfuric acid together. .None of the above methods involve an-ester interchange of the coconut oil acid-radicals of coconut oil to a productwherein some of the glycerol hydroxyls are rendered free, the remainer being esterified by coconut oil acid radicals. All of the processes given above result in a product whichis non-uniform, containing either free triacetin or free coconut oil in greater or less amounts, and objectionable therefore for usein artificial leathersv This invention has as anobject the provision of pure mixed polyhydric alcohol, especially glycerol, esters of long and short chain essentially saturated fatty acids, and processes for making them. "A further object is the provision of cellulose derivative compositions containing these uncontaminated mixed glycerides. Other obiects willappear hereinafter.

These objects are accomplished by the following invention wherein the glycerol ester of tain other auxiliary steps. The initial glycerol ester should have an iodin number of not more than 35, i e. the long chain acid must be essentially saturated. This is necessary because materials with higher iodine num bers will yield oxidizable softeners. The long 40v chain fatty acid should have 10 to '18 carbon atoms and the short chain fatty acid 1 to 4 carbon atoms. The long chain fatty acid should have at least ten carbon atoms because the lower acids impart objectionable odors; it should have '45 not more than 18 carbon atoms in order to obtain liquid products. The short chain fatty acid should have less than five carbon atoms. in order to produce products which will not exude from The process of the present invention is illustrated by the following examples which illustrate more specific details of the invention, but are not to be regarded as limitative thereof.

5 Example 1 Constituents Parts coconut an 43. 2 Glycer 10.0 Acetic anhydride 32. 6

The coconut oil and glycerol are placed in a kettle or flask fitted with a reflux condenser and an arrangement for stirring and blowing with carbon dioxide. Thesetwo ingredients are not miscible. The mixture is blown with CO2 and stirred very rapidly during the heating operation which consists of bringing the charge up to 250 C. in two hours time and maintaining it at this temperature for approximately four hours or until a sample removed from the kettle and cooled shows no tendency to exude glycerol and contains no free glycerol, as shown by extraction with water. The charge is then cooled to 130 C. and the acetic anhydride added gradually-over a period of minutes. The mixture is then refluxed for 1 /4 hours. The condenser is changed to a distilling position and the charge is blown with CO2 and heated to 170 C. in about two .hours and maintained at this temperature for about 3 hours longer or until no odor of acetic acid can be detected in the'liquid in the kettle. The charge is then cooled and the blowing with CO2 discontinued. The product is a thin, brown. oil of an acid number of approximately 2.0. The yield is 96.8% of the theory. (The major portion of the acetic acid liberated by the acetic anhydride can 40 be reclaimed; in one experiment 78.5% of the acid was recovered as an 82.5% solution.) The product as judged by its acid number has very little uncombined acetic'and/or coconut oil acids.

Practically no water-soluble portion can be re- 45 moved by extraction thus showing the substantial absence of glycerol and triacetin. The oil when used in the proper proportions gives an artificial leather of excellent feel'and unusual durability. The film shows nozgreasiness; thus indieating that substantially no coconut oil is present. In,case asoftener with less solvent action on nitrocellulose than the above is desired, it can be made by varying the-proportions of coconut oil. glycerol and acetic anhydride. The following example will serve to illustrate this:

Example 2 Constituents Acetic The equipment and procedure are practically the same as for the preceding experiment. The oil and glyc'erolare heated at 250" C. for about 5 hours or until the mixture becomes homogeneous.

. The charge is cooled to 130 C. andthe acetic anhydride added. The solution is then refluxed 7 for 2' hours. The condenser is changed to a distilling position and the charge is blown with CO1.

and heated to 170 C. in about 2 hours and maintainedat this temperature for about 2 hours or until .no odor of acetic acid can be detected in the liquid in the kettle. The product is a light brown thin oil of acid number around 2.0. The yield is 96.2% of the theory. (In this experiment, 80.9% of the acetic acid formed was recovered as a 94.4% solution.) The product, similar to that from Example 1, contains practically no free acetic and/or coconut oil acids and only a trace soluble in water, thus indicating the presence of only a minute amount of free triacetin and glycerol. This softener when used in the proper proportions with nitrocellulose makes an artificial leather coating ideal from the standpolnts of-quality and durability.

The product is greatly improved and the time of preparationshortened by using a slightly alkaline catalyst in the first step of the reaction. he following example will illustrate this:

Example 3 Constituents Parts Coconut oil 42. 7 Glycerol l0. 0 Lithium 0. 3 Acetic anhydride I 33. 6

The apparatus is the same thatused in Ex-- ample 1. The coconut'oil, glycerol, and litharge are blown with CO2, stirred rapidly and heated up to 170 C. in About and kept at170 C. for 1 hour. Generally suitable conditions are 150- 225 C. for' 3 hours at the lower temperature varying to of an hour at the higher temperature. The charge is cooled to 130 C., the acetic anhydride added and the solution refluxed for 2 hours. The acetic acid formed is finally removed by vacuum distillation by heating the charge in vacuo for'one hour up to 130 C. followed by 3 hours at 130 C. The charge is then given a short steaming to distill oil. the remaining acid and to regenerate the litharge which is easily removed by filtration. The product is a light yellow, thin oil of acid number around. 2.0. The product has no odorof acetic acid. No portion of it is extracted with water. The product, un-

Example! Constituents The apparatus is the same as that used in the other examples. The coconut oil is alcohoiized with the glycerol .by blowing with CO2, stirring rapidlyand'heating for about 4 hours at 250" C.

The monoglyceride formed iatransferred to an open" kettle and cooled to C. The oxalic acid -The product prepared by this method is not nearly so satisfactory as those made by the above methods as shown by the fact that it tends to form a greasy film of lower durability when used 5 as an artificial leather softener.

The mixed lauric-acetic glyceride type of softener can be made by using malonic acid in place of oxalic acid as the following example will illustrate:

m Example 5 Constituents Parts Coconut no 144. 1 5 Glycerol I 10.0 Malonic 36 7 over a period of 2 hours and is held at this temperature' for 1 hours longer. The product so obtained after the charge has been cooled is a thin, brown oil of acid number of 6.3. It can be useri as a softener in artificial leather, in which capacity it gives a coating of the proper limpness without undesirable stickiness or greasiness. This artificial leather does not show the outstanding durability characteristic of those containing improved softeners as prepared under Examples 1 to 3 inclusive.

The above examples are for the preparation of the softeners of the mixed lauric-acetic glyceride ,0 type for use in artificial leathenetc. The following coating compositions containing these products are illustrative of their usefulness.

Examplefi Parts by I weight Softener of Example 1 15.1

' Extracted pyro nitrocellulose J.. 15.1 Lithopone pigment 13.6 Ethyl acetate 22.4 Ethyl alc 33.8

This composition, when" spread on cloth and suitably dried, gives an excellent artificial leather which has a limp feel 'without'stickiness or.

5 g'reasinss and which can be embossed, printed, etc. readily in accordance with well-known methods. The durability of this artificial leather is outstanding.

The artificial leather produced from this coating.

composition is pliable, non-sticky, non-greasy, and after six months exposure is still. very pli-s' able. A similar composition with castor oil' as the softener becomes brittle in about three months. I

In the foregoing examples glycerol, coconut oil,

5 and acetic anhydride have represented the reactants and litharge the catalyst. Other fatty glycerides such as palm kernel oil, porpoise ofl, Japan wax (tripalmitin), Chinese vegetable tallow, cohune oil, myrtle wax, coconut stearin, babasu oil, etc. may be used. Difierent proportions of 5 oil, glycerol, and acid anhydride may be used, depending upon the ratio of low molecular weight to high molecular weight acid radicals desired in the final softener. Alcoholysis catalysts other than litharge such as lime, barium oxide, zinc 1o oxide, etc. may be employed in the alcoholysis step. In the alcoholysis step the glycerol may be replaced by other polyhydric alcohols such as diethylene glycol, sorbitol, pentaerythritol, monobutylin, monobenzylin, and the like. The relative amounts of fatty glyceri'de and polyhydric alcohol and the alcoholysis conditions should be so chosen that substantially all polyhydric alcohol is present as an only partially esterified compound. In the final esteriflcationstep the acetic anhydride may be replaced by other saturated aliphatic monobasic acids and acid derivatives such as propionic acid, butyryl chloride, proplonic anhydride, acetyl chloride, etc. The acid anhydride is preferred because of ease and rapidity of reaction (as compared to the acid) and because no hydrohalide, which discolors the product, is formed. In view of the necessity for final removal of by-products, it is necessary that the acid or acid derivative be a volatile one. Acetic acid may be used in the esterification step, provided no more than, an amount molecularly equivalent to the free hydroxyls of the alcoholyzed oil is used. Then in the final steaming or blowing step the by-products removed are essen- 86 tially water. The saturated monobasic fatty acid should contain not more than four carbon atoms, or the esterlfylng fatty acid derivative should be derived from such a fatty acid. 4 a

The chief uses for products of the present invention are as softeners in cellulose derivativecompositions e. g. nitrocellulose, ethyl, cellulose,

cellulose isobutyrate, anzyl cellulose, cellulose propionate, cellulose but-yrate, etc., for the-manufacture of artificial leather. They may also be employed, however, with natural resins, with synthetic resins, with-bitumens, with other plasticizer's, with solvents, pigments, fillers, etc. for use in molding. as adhesives ormbinders, and as impregnating, toughening and water-proofing agents for paper, wood, textiles, stone, etc.

The softeners of the mixed .glyceride or lauricacetic glyceride type are characterized in being adapted to be made in a' great variety of compositions with a uniformity therein not hitherto obtained, a greatly improved color, and at a cost of preparation much less than the methods hitherto used. I

The above description and examples are intended'to be illustrative only. Any modification of or variation therefrom which conforms to the spirit of the invention is intended to be included 4 within the scope of the claim.

We claim: A process for preparing lauric-acetic glyceride which comprises heating approximately 43 parts of coconut oil, approximately' lo parts of glycerol, and approximately 0.3 part flitharg'e at 150- 225 C, for A to 3 hours, esterifying the inter-, mediate-glyceride with acetic anhydride, remov-' ing the acetic acid formed by distillation. and steaming. and the litharge by: filtration.

LEO PHILLIP HUBBUCH. RAYMOND E. THOMAS.