METHOD FOR THE EPOXIDATION OF UNSATURATED POLYMERS

Abstract: A process for epoxidizing unsaturated polymers comprising reacting an unsaturated polymer with hydrogen peroxide in the presence of (a) tungstic acid or a metal salt thereof or molybdic acid or a molybdenum oxide, (b) phosphoric acid or a metal salt, and (c) at least one phase transfer catalyst.

Description: METHOD FOR THE EPOXIDATION OF UNSATURATED POLYMERS. This invention relates to processes for epoxidation of unsaturated polymers. Epoxidation of unsaturated polymers is well studied and has been reviewed (Rubber Chemistry and Technology, 1982, 55, 809). Epoxidation is widely used as a way to functionalize polymers by introducing oxirane groups which can be further converted. Peracids, particularly peracetic acid, have been used as the epoxidation agents. Peroxyformic acid has been used for the epoxidation of styrene-butadiene block copolymers (J. App. Pol. Sci. 1979, 23, 3301 & 3311). Similarly, cis-polyisoprene, butyl rubber, EPDM, and polybutadiene have been epoxidized (Polymer, 1983, 24, 107 ; J. Appl. Polym. Sci. Polm. Sy p. 1977, 60, 47 ; Makromol. Chem. , 1983, 184, 1153 ; Makromol. Chem., 1986, 187, 2761). Recently, a variety of unsaturated polymers have been epoxidized with hydrogen peroxide in the presence of a quaternary ammonium tetrakis (diperoxotungsto) phosphate catalyst (J. Poly. Sci. Part C : Poly. Lett. 1990, 28, 285 ; J. Poly. Sci. : Part A ; Poly. Chem. 1991, 29, 547). This process suffers from certain disadvantages, e.g., the catalyst is not readily available. This invention relates to process for epoxidizing unsaturated polymers comprising reacting an unsaturated polymer or oligomer with hydrogen peroxide in the presence of (a) tungstic acid or its metal salts or molybdic acid or a molybdenum oxide, (b) phosphoric acid or its metal salts, and (c) at least one phase transfer catalyst. The term "polymers" as used herein includes polymers from the oligomeric range of about 500 to 5000 molecular weight to the high molecular weight polymers of above 5000. Unsaturated polymers suitable for epoxidation are polybutadienes, polyisoprene, styrene-butadiene block copolymers, EPDM, butyl rubber, unsaturated polyesters, unsaturated polymers bearing cycloaliphatic unsaturation and CONRRMAΠON COFY preferably bearing tetrahydrophthalic and/or dicyclopentadienic unsaturation, alkyds, vegetable oils such as, for example, soybean oil, linseed oil, verona oils and the like. The method of the invention allows use of a low level of catalyst composition free of organic acid and/or peracid, resulting in simple product workup and process, and using readily available catalysts. The process comprises use of hydrogen peroxide in the presence of : (a) tungstic acid or a metal salt thereof or molybdic acid or a molybdenum oxide ; (b) phosphoric acid or a metal salt thereof ; and (c) at least one phase transfer catalyst. The epoxidation of unsaturated polymers can be performed at any temperature which is sufficient to react. Particularly suitable temperatures are between 0°C and 100° C, preferably from 25 °C to 70°C, and more particularly from 50 to 70 °C. The reaction takes place faster at higher temperature and requires shorter time to complete. The reaction is typically exothermic and slow addition of hydrogen peroxide is preferred to control the exother . At higher temperatures, hydrogen peroxide undergoes decomposition. The reaction can be performed at subat ospheric to superatmospheric pressures ; however, the reaction is preferably carried out at atmospheric pressure. The epoxidation can be performed with or without solvent. The use of solvent is preferred because it reduces the viscosity. If solvent is desired, a water-immiscible organic solvent such as chlorinated hydrocarbons, and ethers, glycol ethers, hydrocarbons, alkyl esters, and combinations thereof, are especially useful. Particularly suitable organic solvents are toluene, chlorobenzene, chloroform, methylene chloride, heptane, and the like. Hydrogen peroxide solution is used as oxidant in a concentration in water of about 5 to 70% by weight. The amount of hydrogen peroxide can vary depending on the desired degree of epoxidation, typically about 0.1 to 1.5 equivalent, and preferably between 1 and 1.5 equivalent, per equivalent of unsaturated double bond of the unsaturated polymer or oligomer. The phase transfer catalyst can be used in amounts of about 0.001 to 1, preferably 0.05 to 0.1, equivalent per equivalent of carbon-carbon double bond of the unsatured polymer or oligomer. Suitable phase transfer catalysts includes quaternary ammonium salts, quaternary phosphonium salts, polyethers and polyether derivatives such as polycondensates of polyethers or functional polyethers, and the like. Examples of phase transfer catalysts include, for example, trioctylmethylammonium chloride, trioctylmethylammonium bromide, trioctylmethylammonium iodide, trioctylmethylammonium hydrogen sulfate, trioctylmethylammonium nitrate, tetrahexylammonium chloride, tetrahexylammonium bromide, tetrahexylammonium iodide, tetrahexylammonium hydrogen sulfate, tetrahexylammonium nitrate, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium nitrate, tetrabutylammonium hydrogen sulfate, dioctadecyldimethylammonium chloride, dioctadecyldimethyl ammonium bromide, dioctadecyldimethylammonium nitrate, dioctadecyldimethylammonium hydrogen sulfate, dihexadecyldimethylammonium chloride, dihexadecyl- dimethylammonium bromide, dihexadecyldimethylammonium nitrate, dihexadecyldimethylammonium hydrogen sulfate, trioctylmethylphosphonium chloride, trioctylmethylphosphonium bromide, trioctylmethylphosphonium nitrate, trioctylmethylphosphonium hydrogen sulfate, tetrahexylphosphonium chloride, tetrahexylphosphonium bromide, tetrahexylphosphonium nitrate, tetrahexylphosphonium hydrogen sulfate, tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium nitrate, tetrabutylphosphonium hydrogen sulfate, tetrabutylphosphonium iodide, dioctadecyldimethylphosphonium chloride, dioctadecyldimethyl phosphonium bromide, dioctadecyldimethylphosphonium nitrate, dioctadecyldimethylphosphonium hydrogen sulfate, dihexadecyldimethylphosphonium chloride, dihexadecyldimethylphosphonium bromide, dihexadecyldi ethylphosphonium nitrate, dihexadecyldimethylphosphonium hydrogen sulfate, tetraalkylammonium hydroxide, tetraalkylammonium tribromide, tetraalkylammonium trifluoromethanesulfonate, and any combination thereof. Phosphoric acid or its various salts can be used in amounts of about 0.001 to 1.0 equivalent per equivalent of carbon-carbon double bond in the unsaturated polymer or oligomer. Sodium or potassium monobasic, dibasic, or tribasic phosphoric acid salts can also be used. The final pH can be adjusted by other acids or bases to a value between 0 and 5. Either tungstic acid which is not water soluble or its metal salts which are soluble or molybdic acid or molybdenum oxide can be used as the metal catalyst. The typical catalyst is used in amounts of about 0.005 to 5%, based on weight of unsaturated polymer or oligomer. The preferred metal catalyst is tungstic acid ; molybdic acid may also be used advantageously. The epoxidized unsaturated polymers produced by the process of the invention are conventional and can be used in applications such as coatings, epoxy/amine cure, cationic cure, and chemical intermediates for functionalizations. The following non-limiting examples are presented to illustrate a few embodiments of the invention. All parts and percentages are by weight unless otherwise indicated. EXAMPLE 1 Epoxidation of polybutadiene The polybutadiene used in this example was of a polybutadiene homopolymer produced by Advanced Resins, Inc., molecular weight is 5500 g/mol, and 16-20% 1, 2-unsaturation, 44% of trans- 1, 4-unsatura ion and 36% of cis-1,4- unsaturation, referred to hereafter as Ricon 131. 0.17 g tungstic acid, 0.10 g phosphoric acid (85%), 67.0 ml hydrogen peroxide, 0.35 g trioctyl methyl ammonium chloride, 100 g of polybutadiene Ribon 131 and 100 ml toluene were charged to a reactor which was equipped with mechanical stirrer, thermocouple, and condenser. The mixture was stirred and heated to 55 °C. The reaction was shut down after 3 hours at 55 °C. To the reaction mixture, 200 ml toluene and 100 ml of 20% sodium chloride were added and kept at 50-55 °C, which resulted in a two phase system. The aqueous phase was clear and the organic phase was cloudy. The organic phase was washed twice with 20% NaCl and solvent was removed at 90°-95°C at 3.33 x 10 3 - 4.66 x 10 3 Pa (25-35 mm Hg) . A light yellow liquid was obtained with epoxy value of 182.7 mgKOH/g and viscosity of 6 Pa.s (6000 cP) at 25°C. EXAMPLE 2 Epoxidation of Polybutadiene The polybutadiene used in this example was hydroxy terminated with molecular weight of 1100 g/mol , and 20% 1,2-unsaturation, 20% cis-1, 4-unsaturation, 60% trans- 1,4-unsaturation, produced by Elf Atochem, referred to hereafter as Polybd-R-20LM. 212.6 g polybutadiene, 2.10 g methyl trioctyl ammonium chloride, 600 ml toluene, 1.0 g tungstic acid, 0.25 ml phosphoric acid (85%) , and 400 ml hydrogen peroxide (30%) were placed into a reactor which was equipped with a thermocouple, a mechanical stirrer and a condenser. The reaction mixture was stirred and heated to 60 °C. Stirring was continued for 8.0 hours at 60 °C. The reaction mixture was then allowed to separate into two phases. The organic phase was isolated and washed twice with 200 ml of water. The solvent was removed under a reduced pressure of 3.33 x 10 3 Pa (25 mm Hg) at 60 °C. Viscous light yellow epoxidized polybutadiene was obtained with viscosity of 85.4 Pa.s (85,400 cP) at 25°C and epoxy value of 183.3 mgKOH/g. EXAMPLE 3 Epoxidation of Polybutadiene The polybutadiene used in this example was hydroxy terminated with molecular weight of 2800 g/mol, and 20% 1,2-unsaturation, 20% cis-l,4-unsaturation, 60% trans- 1, -unsaturation, referred to as Polybd-45HT, produced by Elf Atochem. Polybutadiene (110.2 g) , toluene (200 ml), methyl trioctyl ammonium chloride (1.0 g) , tungstic acid (0.34 g) , phosphoric acid (85%, 0.38 g) , hydrogen peroxide (30%, 50 ml) , were charged to a reactor which was equipped with a thermocouple, a mechanical stirrer, and a condenser. The mixture was stirred and heated to 60 °C. The reaction was stopped after 4.0 hours at 60°C. The organic phase was isolated and washed with 100 ml water. A clear, yellow viscous material was obtained after solvent removal under reduced pressure at 75 °C. Final product physical properties : color 5 Gardners ; 4.187 Pa.s (4187 cP) viscosity at 65°C ; epoxy value of 172.8 mgKOH/g. While the invention has been described in sufficient detail for those skilled in the art to make and use it, various modifications, alternatives, and improvements should become readily apparent without departing from the spirit and scope of the invention as set forth in the following claims.

Claims: CLAIMS 1 - A process for epoxidizing unsaturated polymers comprising reacting an unsaturated polymer or oligomer with hydrogen peroxide in the presence of : (a) tungstic acid or a metal salt thereof or molybdic acid or a molybdenum oxide ; (b) phosphoric acid or a metal salt thereof ; and (c) at least one phase transfer catalyst. 2 - Process according to claim 1, characterized by the fact that said unsaturated polymer is selected from the group consisting of polybutadienes, polyisoprene, styrene-butadiene block copolymers, EPDM, butyl rubber, unsaturated polyesters, unsaturated polymers bearing cycloaliphatic unsaturation and preferably bearing tetrahydrophthalic and/or dicyclopentadienic unsaturation, vegetable oils and alkyds. 3 - Process according to claims 1 or 2, characterized by the fact that said hydrogen peroxide is introduced in an amount of about 0.1 to 1.5 equivalent, particularly of about 1.0 to 1.5 equivalent, per equivalent of unsaturated double bond in the unsaturated polymer or oligomer. 4 - Process according to any of claims 1 to 3 , characterized by the fact that the reaction is conducted at a temperature of about 0°C to 100°C. 5 - Process according to claim 4 , characterized by the fact that the reaction is conducted at a temperature of about 25°C to 70°C, particularly of about 25 to 70°C. 6 - Process according to any of claims l to 5 characterized by the fact that the phase transfer catalyst is present in an amount of about 0.001 to 1 equivalent, particularly of about 0.05 to 0.1 equivalent, per equivalent of carbon-carbon double bond in the unsaturated polymer or oligomer. 7 - Process according to any of claims 1 to 6 characterized by the fact that the phase transfer catalyst is selected from the group consisting of quaternary ammonium salts, quaternary phosphonium salts, polyethers and polyether derivatives. 8 - Process according to any of claims 1 to 7, characterized by the fact that the reaction is conducted in the presence of a water-immiscible organic solvent. 9 - Process according to claim 8, characterized by the fact that the reaction is conducted in the presence of a water-immiscible organic solvent selected from the group consisting of chlorinated hydrocarbons, ethers, glycol ethers, hydrocarbons, alkyl esters, and combinations thereof, particularly selected from the group consisting of toluene, chlorobenzene, chloroform, methylene chloride and heptane. 10 - Process according to any of claims 1 to 9, wherein the phosphoric acid or phosphoric acid salt comprises about 0.001 to 1.0 equivalent per equivalent of carbon-carbon double bond in the unsaturated polymer or oligomer. 11 - Process according to any of claims 1 to 10, wherein the phosphoric acid salt is a sodium or potassium monobasic, dibasic, or tribasic phosphoric acid salt. 12 - Process according to any of claims 1 to 11, wherein the pH of the reaction is adjusted by acids or bases to a value between 0 and 5. 13 - Process according to any of claims 1 to 12, characterized by the fact that the tungstic acid or a salt thereof or molybdic acid or molybdenum oxide is present in an amount of about 0.005 to 5%, based on weight of the unsaturated polymer or oligomer.

Inventors: CESKA GARY W, FAN MINGXIN, HORGAN JAMES, CESKA, GARY, W., FAN, MINGXIN, HORGAN, JAMES
Applicants: CESKA GARY W, CRAY VALLEY SA, FAN MINGXIN, HORGAN JAMES, SARTOMER CO INC, CESKA, GARY, W., CRAY VALLEY S.A., FAN, MINGXIN, HORGAN, JAMES, SARTOMER COMPANY, INC.
Application year: 1997
Main classification: C08C19
IPC codes: C08C19, C08F8