US3254097A - Solvent extraction of epoxidized oils - Google Patents

Description

United States Patent 3,254,097 SOLVENT EXTRACTION OF EPOXIDIZED OILS David S. Darrow, Munster, Ind., assignor to Swift & Company, Chicago, 11]., a corporation of Illinois No Drawing. Filed Oct. 5, 1962, Ser. No. 228,762 7 Claims. (Cl. 260--348) This invention relates to fatty epoxides and, more particularly, to improvements in the production of oxirane-substituted higher fatty acid derivatives and to the product thereby produced.

Fatty epoxides in general have developed as an increasingly important industrial chemical over the last several years and it is anticipated that the growth of this industry will expand to an even greater extent in the near future. Esters of oxirane-substituted higher fatty acids find extensive use as plasticizer-stabilizers for vinyl halide resins such as polyvinyl chloride, polyvinylidene chloride and copolymers thereof. These esters are excellent stabilizers for vinyl halide polymers and copolymers against heat and light degradation. In addition, because of the good compatibility of these esters with vinyl resins, plasticizing efliciency is also very favorable.

Oxirane content (percent oxirane oxygen) of a given epoxy derivative such. as the ester is an important criterion in the evaluation of a fatty epoxide and for many uses high-oxirane or completely epoxidized fatty acid.

derivatives are specified in order to obtain superior results. High-oxirane epoxidized glycerides. such as epoxidized naturally-occurring glyceride oils are of considerable value inasmuch as the high-oxirane content insures greater compatibility of the epoxidized material with vinyl resins when employed as a plasticizer. Similarly, where the epoxidized ester is used as a polymerizable material, the higher the oxirane content the greater will be the reactivity of the epoxidized fat.

Epoxidation of naturally-occurring fatty acid esters such as animal, vegetable, and fish oils having ethylenic unsaturation using percarboxylic acids is a procedure well known in the art. The lower percarboxylic acids such as peracetic acid or performic acid are preferred for use in the epoxidation reaction, although others such as perpropionic acid have been suggested. The peracid can be preformed or formed in situ and the reaction can be uncatalyzed or catalyzed with acidic materials such as sulfuric acid, phosphoric acid, mixtures of these acids, cation exchange resins in the acid form, and alkyl sulfonic acids.

The product obtained from such epoxidation reactions, while primarily consisting of the epoxidized fatty acid ester, usually contains some ethylenic unsaturation, hydroxyl substituents and some esters which, because of the compositionof the starting material, contain saturated fatty acids and, thus, are not epoxidized. Esters containing oleic, linoleic, and linolenic acids esterified with glycerine will contain, after epoxidation, esterified epoxy stearic acid, esterified diepoxy stearic acid, and esterified triepoxy stearic acid. Nevertheless, since naturallyoccurring fatty materials are mixed glycerides, the epoxidation of an oil such as soybean oil will result in a mixture of individual glycerides some of which have a substantially higher percentage of oxirane substitution than others. Those triglyceride compounds containing substantial saturated fatty acids will exhibit a much lower oxirane content than an epoxidized dioleyl linolein, for example. It is highly desirable, where the product is to be employed for a specific purpose, to concentrate the high-oxirane-substituted materials and separate the less highly epoxidized esters and other impurities from the high-oxirane esters.

It is, accordingly, an object of this invention to provide a method for separating oxirane-substituted fatty acid derivatives having a high-oxirane content from the low-oxirane-substituted fatty derivatives from a mixture containing the high-oxirane and low-oxirane materials.

Another object of the invention is to provide a method for treating mixtures of epoxidized higher fatty acid esters by solvent extraction to provide improved epoxidized fatty acid ester compositions.

Still another object of the invention is the provision of a method for improving the plasticizing effectiveness of epoxidized oils with vinyl resins.

Additional objects, if not specifically set forth herein, will be readily apparent to those skilled in the art from the detailed description of the invention which follows.

Generally, the invention is concerned with the fractionation of mixtures of epoxidized higher fatty acid esters with an inert liquid solvent to separate compounds having a substantial amount of oxirane substitution from compounds having a lesser degree of oxirane substitution. The solvent employed can be one which selectively dissolves more of the high-oxirane compounds, leaving the compound having relatively less oxirane substitution immiscible, or the solvent can be one which preferentially dissolves more of the less highly substituted oxirane compounds. Lower oxirane-substituted oils are miscible with lower aliphatic nonpolar hydrocarbon solvents, whereas highly epoxidized oils are not. The highly epoxidized oils, on the other hand, are miscible with acetonitrile and methanol, whereas the less highly epoxidized oils are not miscible with these water-soluble solvents.

More particularly, the method of this invention comprises the selective extraction of mixtures of epoxidized glycerides containing highly epoxidized glycerides and less highly epoxidized glycerides to separate the higher oxirane compounds from those of lower oxirane content. The selective separation of these materials is achieved by mixing a solvent in which either the high-oxirane or lowoxirane component is preferentially soluble to form a twophase liquid or liquid-solid system and separating the two phases thus formed. In this manner, a solvent solution of the high-oxirane material is'isola-ted from the solventimmiscible, low-oxirane material or a solvent solution of epoxidation techniques can now be prepared having a high oxirane and a low iodine value. Thus, soybean oil having an unsaturation represented by an iodine value of before epoxidation can be substantially completely epoxidized so that the percentage of oxirane oxygen in the epoxidized product is around 6.5-7%, whereas'the iodine value is generally less than 5 and around 1-3. Linseed oil having an iodine value before epoxidation of or above can be substantially completely epoxidized to an oxirane oxygen content of about 8.3-9.7 or above and a residual iodine value of 3-5 or less. It is possible in the case of synthetic or highly purified triglycerides to epoxidize to an oxirane oxygen content of around 12%.

Even when substantially completely epoxidized, however, these oxirane-containing triglycerides are mixtures of individual triglycerides some of which have a high percentage of oxirane substitution, while others have a low percentage of oxirane substitution. It is possible :by the method of this invention to separate uch mixtures into a fraction enriched in high-oxirane compounds.

In the fractionation of the mixed glyceride ester-s, the mixture is contacted with sufficient solvent to provide a two-phase system. The system is subjected to agitation, and after the phases are allowed to separate, the solvent solution is separated from the immiscible tfraction. In that embodiment of the invention wherein the less highly substituted oxirane fatty acid esters are soluble in the solvent, while high-oxirane esters are immiscible, lowboiling aliphatic hydrocarbon solvents are employed. The amount of solvent employed is that amount which when added to the epoxidized oil causes the formation of two phases. Because of variations in the solubility of difierent oils in difierent solvents the ratio of solvent to oil will vary. In all cases, however, enough solvent should be employed to produce two phases. Usually, a solvent to epoxidized triglyceride ratio of at least 0.5:1 is sufiieient to obtain good separation, although some deviation from this general rule is apparent. At room temperature, hexane, for example, used in a SOlVCllt-iO-Oll ratio of 0.5 :1 will not provide a two-phase system; whereas, isopentane used in the same amount and with the same epoxidized ester will provide the desired two-phase system. If the amount of hexane is increased to a solvent-toepoxidized-oil ratio of 1:1, two phases will appear.

Generally, the higher the solvent-to-oil ratio the better the separation and the greater the certainty of formation of two phases. Solvent-to-oil ratios as high as 20:1 can be used, but increasing the ratio of solvent beyond this amount serves only to render the process less economical without increasing the separation efiiciency commensu- -found very satisfactory for eifective fractionation. Separation in some cases into two phases may be facilitated by chilling of the two-phase system below room temperature. Temperatures in the range of about 3270 F. can sometimes be employed to improve the separation. Temperaturs above room temperature can be employed so long as the temperature is maintained below the boiling point of the solvent.

Solvent-s in which the highly epoxidized fraction of the mixed esters preferentially soluble include methanol, acetonitrile, acrylonitrile, acetone, lower nitro paraflins rately. Solvent ratios of 05:1 through 4:1 have been and an oxirane content of 8.7%.

such as nitromethane, nitroethane and nitroproipa-ne, and

dimethyl sulfoxide. Enough of any of these solvents or mixtures thereof when added to the mixture of epoxidized esters induces two phases; that is, a solvent phase containing a large proportion of the highly epoxidized material and an oil phase rich in the less highly epoxidized material. In general, any solvent in which the highly epoxidized fraction is soluble can be employed. This solvent should also be immiscible with nonpolar solvents such as lower aliphatic hydrocarbons.

Solvents in which the less highly epoxidized substance is preferentially soluble include the liquid lower aliphatic hydrocarbons, both saturated and unsaturated, such as prolpane, the butanes, pentanes, hexanes, heptanes, and octanes. Aliphatic hydrocarbons higher in the series than octanes are more difficult to remove from the separated epoxy ester because of their generally higher boiling point and, although they can be employed in the process, they are not recommended, if lower boiling solvents are readily available. Hydrocarbon mixture-s containing aliphatic hydrocarbons of 5-7 carbons such as ligroin and petroleum ether are very suitable for use in the method of the invention. These materials have boiling points in the range of around IOU-140 F. and are liquids at atmospheric pres-sure.

The method of the invention is applicable in the treatment of a wide variety of epoxidized zfatty materials, particularly esters of epoxidized higher fatty acids having 10-22 carbons. Included within the scope of the materials to which the invention may be applied are triglycerides such as epoxidized animal, vegetable, and marine fats. Examples of these fats are epoxidized tallow, epoxidized soybean oil, epoxidized linseed oil, epoxidized tall oil, epoxidized safilower oil, epoxidized perilla oil, epoxidized sperm oil, epoxidized menhaden oil, and epoxidized permitted to separate into two phases.

oils when stored at room temperature for an extended period of time such as a week or more show some sedimentation of solids or partial solidification. If the oils are first treated by the process described and claimed herein, this sedimentation and partial solidification is obviated. Furthermore, some untreated epoxidized oils when used at a high level (around 50% by weight) in plasticizing vinyl halide resins appear to cause or induce the development of an exudate on vinyl films prepared from resins rplasticized with such oils. Epoxidized oils treated in the manner described herein do not cause or promote this development of exudate. As a result, in cases where the epoxidized oil is to be employed in combination with polyvinyl chloride or polyvinylidene chloride or copolymers thereof, the method of the invention can be used to substantially increase the efiectiveness of the plasticizer-stabilizer.

The following examples show the treatment of oils havingvarious oxirane contents with various solvents. The examples are intended to be illustrative rather than limitative.

Example] 300 grams of petroleum ether was added to 300 grams of epoxidized linseed oil having an iodine value of 8 The mixture was agitated and then permitted to settle. The. two phases which developed were separated in a separatory funnel and the two fractions were analyzed. The fraction soluble in petroleum ether contained 6.41% oxirane oxygen and had an iodine value of 7.4. The fraction-insoluble in the petroleum ether contained 8.84% oxirane oxygen and had an iodinevalue of 9.4.

Example 11 A mixture of 300 grams of epoxidized linseed oil having an iodine value of 9.3 and an oxirane content of 8.5% was admixed with 240 grams petroleum ether and 60 grams of hexane. After agitating the mixture to obtain substantially complete contact of the oil with the solvent mixture, the mix was permitted to stand, at which point the two phases separated. The portion soluble in the hydrocarbon mixture contained 6.5% oxirane oxygen and had an iodine value of 7.4. That portion insoluble in the hydrocarbon solvent had 8.6% oxirane oxygen and an iodine value of 9.4. The hydrocarbon soluble portion represented 15% of the starting material.

Example III 1,000 grams of petroleum ether was added to 1,000 grams of epoxidized linseed oil having an oxirane oxygen content of 9.08% and an iodine value of 2.33. The mixture thus formed was stirred for 3-5 minutes, at which timet-he stirring was terminated and the mixture was v The fraction soluble in the petroleum ether contained 5.82% oxirane oxygen and had an iodine value of 1.49. The fraction which was insoluble in the petroleum ether had an oxirane oxygen value of 9.59% and an iodine value of 2.43. Further treatment of the portion insoluble in the petroleum ether (approximately 900 grams) was again extracted with 11 grams additional petroleum ether. The insoluble portion derived from this extraction contained 9.66% oxirane oxygen and had an iodine value of 2.4, while the portion soluble in petroleum ether had an oxirane oxygen content of 6.34% and an iodine value of 1.66.

Example IV A highly epoxidized linseed oil having an oxirane oxygen content of 9.73% and an iodine value of 3.98 was mixed with an equal portion of petroleum ether. The 2,000- gram mixture was agitated and then permitted to settle. The petroleum ether soluble fraction contained 6.30% oxirane oxygen and had an iodine value of 2.91.' The fraction insoluble in petroleum ether contained 10.0% oxirane oxygen and had an iodine value of 4.1.

Example V 100 grams of epoxidized soybean oil having an oxirane oxygen content of 7.02% and an iodine value of 3.0 was mixed with 200 grams of isopentane. The mixture was agitated for about 35 minutes, stirring was then terminated, and the mixture was permitted to separate into two phases. The isopentane phase was removed and the isopentane insoluble portion was again extracted with an additional 100 gram portion of isopentane. The isopentane extracts were combined and the solvent was removed by evaporation. 34 grams of highly epoxidized glycerides having an oxirane content of 7.72% was obtained.

Example VI A mixture was formed of 85 grams of epoxidized soybean oil having an oxirane oxygen content of 7.02% and an iodine value of 3, and 100 grams of acetonitrile. The solvent solution of the epoxidized oil was then extracted with 100 grams of petroleum ether. The petroleum ether soluble fraction was isolated and after removal of the petroleum ether the product which represented about 19% of the original epoxidized soybean oil had an oxirane oxygen content of 5.81%. The acetonitrile solution of the epoxidized oil was then extracted with an additional 100 gram portion of petroleum ether, and after removal of the petroleum ether, the residue which represented about 11% of the original epoxidized soybean oil analyzed 5.68% oxirane oxygen.

After removal of the acetonitrile from the acetonitrile solution, the residue which represented 60% of the original charge analyzed 7.50% oxirane oxygen. The portions soluble in petroleum ether were combined and these materials were semisolid to solid at room temperature. The acetonitrile soluble portion remained as a clear liquid even after holding for one week at 40 F.

Example VI] 100 grams of epoxidized soybean oil having an oxirane oxygen content of 7.02% and an iodine value of 3 was dissolved in 100 grams of nitromethane. The epoxidized oil was completely miscible with the nitromethane. This solvent solution was then admixed with 100 grams of petroleum ether. The mixture was agitated and the petroleum ether fraction was separated from the nitromethane fraction. The residue obtained after removal of the petroleum ether weighed 11 grams and analyzed 5.02% oxirane oxygen. An additional extraction of the nitromethane with 100 grams of petroleum ether resulted in the removal of an additional 12.5 grams of a fraction containing 5.16% oxirane oxygen.

After removal of the nitromethane from the nitromethane fraction, '76 grams of an oil having 7.53% oxirane oxygen was obtained. While the petroleum ether soluble fractions were semisolid at room temperature, the

nitromethane soluble oil was an optically clear liquid even after four days at 40 F.

It will he noted that the separations in accordance with the method of this invention have no bearing on nor relation to the amount of unsaturation present in the epoxidized materials. All of the starting materials are essentially saturated inasmuch as each has a lower iodine value than the well-known single-pressed stearic acid.

It is apparent that by use of the instant invention it is possible to produce epoxidized higher fatty acid derivatives having a greater chemical reactivity due to the higher epoxy oxygen content. Also, it is possible to produce epoxidized higher fatty acid esters having a greater compatibility with vinyl resins and superior heat and ultraviolet stability. Again, the products of the invention do not exhibit partial solidification or sedimentation during handling and storing.

While the invention has been described as applying particularly to the treatment of mixtures of glyceride esters of epoxidized higher fatty acids, it can also be employed to separate mixtures of other alcohol esters of epoxidized higher fatty acids. Thus the lower aliphatic monohydric alcohol esters of fatty acid mixtures such as those obtained from epoxidized glyceride oils can also be treated to separate the high or low oxirane fractions. The methyl, ethyl, propyl, octyl esters of epoxidized soybean, linseed, tall, or perilla oil fatty acids, for example, can be fractionated by the method of the invention, particularly that embodiment involving the use of nitro parafiins along with cooling.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, accordingly, only those limitations should *be imposed as are indicated in the appended claims.

I claim: 1. Process for treating oxirane substituted higher fatt materials containing highly epoxidized triglycerides and less highly epoxidized triglycerides comprising: contacting said materials with a liquid lower aliphatic hydrocar- I bon solvent in which said less highly epoxidized materials are soluble, said solvent being selected from the group consisting of propane, butane, pentane, hexane, heptane, and octane and mixtures thereof, and separating the solvent solution of said less highly epoxidized triglycerides from the insoluble more highly epoxidized triglycerides.

2. Process for improving the plasticizer-stabilizer properties of epoxidized triglycerides comprising: contacting said triglycerides with an amount of a nonpolar liquid lower aliphatic hydrocarbon solvent having a boiling point of about -140 F. and being selected from the group consisting of ligroin and petroleum ether sufiicient to form two phases, one comprising a solvent solution of less highly epoxidized triglycerides and the other phase being substantially immiscible with said solvent, and separating the two phases.

3. A method for improving the plasticizer-stabilizer properties of epoxidized soybean oil comprising: contacting said epoxidized soybean oil with an amount of nonpolar aliphatic hydrocarbon solvent selected from the group consisting of propane, butane, pentane, hexane, heptane, and octane and mixtures thereof sufficient to form two phases when admixed with said soybean oil, one phase comprising a solvent solution of less highly epoxidized triglycerides and the other phase being substantially immiscible with said solvent, and separating the two phases.

4. A method for improving the plasticizer-stabilizer properties of epoxidized naturally occurring triglycerides comprising: contacting naturally occurring triglycerides with an amount of low boiling liquid nonpolar aliphatic hydrocarbon solvent selected from the group consisting of propane, butane, pentane, hexane, heptane, and octane and mixtures thereof suflicient to form two phases with said epoxidized triglycerides, one phase comprising a solvent solution of less highly epoxidized triglycerides, the other phase being substantially immiscible with said solvent, separating the two phases, and removing solvent from said two phases.

5. A method for separating the high oxirane components from the low oxirane components in a mixture of epoxidized triglycerides comprising: contacting said mixture with an amount of a solvent selected from the group consisting of methanol, acetonitrile, acrylonitrile, acetone, lower nitroparaflins, dimethyl sulfoxide, and mixtures thereof, sufiicient to dissolve said epoxidized triglycerides, adding to the solvent solution of saidepoxidized triglycerides an amount of a nonpolar aliphatic hydrocarbon solvent selected from the group consisting of propane, butane, pentane, hexane, heptane, and octane and mixtures thereof sufiicient to form two solvent phases, one comprising a solvent solution of more highly epoxidized triglycerides, the other phase being substantially immiscible with said solvent solution, separating the two phases and removing the solvent from each fraction.

6. Highly epoxidized glycerides substantially free of hydroxyl substituents, sediment and other impurities, prepared in accordance with the method of claim 5.

' 7. A method for separating the high-oxirane components from the low-oxirane components in a mixture of epoxidized triglycerides comprising: contacting said mixture with an amount of a first solvent selected from the group consisting of methanol, acetonitrile, acrylonitrile, acetone, lower nitro parafiins, dimethyl sulfoxide, and mixtures thereof to form a solution of said triglycerides, adding an amount of a nonpolar aliphatic hydrocarbon solvent selected from the group consisting of propane, butane, pentane, hexane, heptane, and octane and mixtures thereof sufficient to form two substantially immiscible phases, one phase comprising a solution of References Cited by the Examiner UNITED STATES PATENTS 2,773,918 12/1956 Stephens 260-705 2,798,093 7/ 1957 Stein 260-348 2,822,368 2/1958 Rowland et al 260-348 2,852,558 9/1958 Feldman 260-705 2,895,966 7/1959 Ault et a1. 260-348 3,041,352 6/1962 Newey 260-348 FOREIGN PATENTS 770,481 3/1957 Great Britain. 808,955 2/ 1959 Great Britain.

2 IRVING MARCUS, Primary Examiner.

NICHOLAS S. RIZZO, WALTER A. MODANCE,

. Examiners.

Claims (1)

1. PROCESS FOR TREATING OXIRANE SUBSTITUTED HIGHER FATTY MATERIALS CONTAINING HIGHLY EPOXIDIZED TRIGLYCERIDES AND LESS HIGHLY EPOXIDEZED TRIGLYCERIDES COMPRISING: CONTACTING SAID MATERIALS WITH A LIQUID LOWER ALIPHATIC HYDROCARBON SOLVENT IN WHICH SAID LESS HIGHLY EPOXIDIZED MATERIALS ARE SOLUBLE, SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF PROPANE, BUTANE, PENTANE, HEXANE, HEPTANE, AND OCTANE AND MIXTURES THEREOF, AND SEPARATING THE SOLVENT SOLUTION OF SAID LESS HIGHLY EPOXIDIZED TRIGLYCERIDES FROM THE INSOLUBLE MORE HIGHLY EPOXIDIZED TRIGLYCERIDES.