Patent GB-811852-A (GB)
Title: Method of epoxidation of esters
Filed: 1955-08-26
Abstract: <PICT:0811852/IV (b)/1> Water-insoluble olefinically unsaturated ester material is epoxidized by reacting with an aqueous mixture of acetic acid and/or anhydride, hydrogen peroxide and an ionizable auxiliary acidic agent other than an agent which under the reaction conditions is such as to cause decomposition of more than 35 per cent of the epoxy groups formed, the reaction being effected at a temperature between 10 DEG  C. and the boiling point of the reaction mixture, the acetic compound being employed in a total amount in the range from 0.05 to 0.7 mol. calculated as acetic acid, for each double bond in each mol. of ester, the hydrogen peroxide being employed in a total amount sufficient to provide at least one mol. of H2O2 for each double bond and in an aqueous concentration which is such as to be represented by a point within the area bounded by the lines joining the points A, B, C and D on the accompanying drawing, and lying on a vertical line drawn through that point on the axis which represents the amount of acetic compound employed and the auxiliary acidic agent being employed in such an amount that the pH of the reaction mixture is between + 1.0 and -1.0 when the reaction starts.  It is preferred to use a water-immiscible solvent for the ester starting material such as benzene, toluene, xylene, heptane, octane, ethylene dichloride and carbon tetrachloride.  Commercial grades of hydrogen peroxide containing 35 to 90 per cent by weight of peroxide may be used in an amount of up to two mols. per mol. of unsaturation.  Typical acidic agents used are inorganic acids such as phosphoric, sulphuric, hydrochloric, nitric and boric acids; acid-forming salts such as sodium acid sulphate, potassium acid sulphate, potassium persulphate and zinc chloride; organic sulphonic acids such as toluene sulphonic and methane sulphonic acids; and acidic esters such as ethyl di-acid phosphate, isopropyl di-acid phosphate and monomethyl sulphate.  The starting materials are esters of water-insoluble, olefinically unsaturated, aliphatic acids such as oleic, linoleic, linolenic, undecylenic, myristolenic, palmitolenic, petroselic and erucic acids, with mono- or polyhydric alcohols typified by ethyl, isopropyl, n, sec. or t-butyl, t-amyl, n-octyl, 2-ethylhexyl, octadecyl, lauryl, cyclohexyl, benzyl, oleyl, linoleyl and linolenyl alcohols, the so-called "oil alcohols" obtainable by sodium and alcohol reduction of esters of mixed fatty acids of vegetable oils, ethylene glycol, 1,2-propylene glycol, 2 - ethylhexandiol - 1,3, butandiol - 1,2, butandiol - 1,3, butandiol 1,4, dodecandiol-1,12, di and triethylene glycols, glycerol and pentaerythritol.  Esters of a mixture of alcohols such as mixtures of ethyl oleate and butyl oleate, or of benzyl linoleate and cyclohexyl linoleate, or of octyl oleate and dodecyl linoleate, or of octyl linolenate and dodecyl linolenate may also be used.  Vegetable oils such as soybean, corn, cottonseed, safflower, sunflower, sesame, poppyseed, walnut, peanut, linseed and perilla oils are also successfully epoxidized by the process. It is preferred to add the hydrogen peroxide, acetic compound and auxiliary acidic agent to the ester simultaneously and at such a rate that the temperature can be held within the desired range. Alternatively the reactants can be added portionwise in the proper ratios so that the pH of the aqueous phase is + 1.0 to - 1.0.  A satisfactory method comprises adding the reactants to the ester in about nine equal portions at intervals of about 30 minutes.  After all the reactants have been added the mixture is stirred at elevated temperature until epoxidation is complete, a period of 3 hours usually being adequate at 50 DEG  to 80 DEG  C.  In examples: (1) and (2) soybean oil is epoxidized using hydrogen peroxide, acetic anhydride, and phosphonic acid in toluene; (3) the process of (1) is followed using acetic acid; (4) 2-ethylhexyl epoxystearate is obtained from 2-ethylhexyl oleate using the procedure of (1) with octane as solvent; (5) safflower oil dissolved in benzene is epoxidized by the process; (6) the process of (1) is followed using toluene sulphonic acid, HBF4 or KHSO4 in place of phosphoric acid; (7) epoxystearyl butyrate is obtained from oleyl butyrate; (8) 2-ethyl butyl epoxystearate is obtained from 2-ethylbutyl oleate.  The preparation of the epoxidized ester of oleic acid and soybean oil alcohols is also mentioned.  The products are useful as plasticizers and stabilizers for polyvinyl chloride, vinyl copolymers and chlorinated rubber.  Specification 739,609 is referred to.