Method for the epoxidation of unsaturated polymers

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

BACKGROUND OF THE INVENTION 
1. Field of the Invention This invention relates to processes for 
epoxidation of unsaturated polymers. 
2. Description of the Prior Art 
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. Peracides, 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. Plym. Sci. Polm. Symp., 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: Polly. 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. 
SUMMARY OF THE INVENTION 
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, (b) 
phosphoric acid or its metal salts, and (c) at least one phase transfer 
catalyst.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
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, 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 its metal salts, (b) phosphoric acid or its metal salts, 
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.degree. C. and 100.degree. C., preferably from 25.degree. C. to 
70.degree. C. The reaction takes place faster at higher temperature and 
requires shorter time to complete. The reaction is typically exothermic 
and so addition of hydrogen peroxide is preferred to control the exotherm. 
At higher temperatures hydrogen peroxide undergoes decomposition. The 
reaction can be performed at subatmospheric to superatmospheric pressures; 
however, the reaction is preferably carried out at atmospheric pressure. 
The expoxidation 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, 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 per equivalent of unsaturated double bond. 
The phase transfer catalyst can be used in amounts of about 0.001 to 1, 
preferably 0.05 to 0.1, equivalents per equivalent of carbon--carbon 
double bond. Suitable phase transfer catalysts includes quaternary 
ammonium salts, quaternary phosphonium salts, 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, 
dioctadecyldimethylammonium bromide, dioctadecyldimethylammonium nitrate, 
dioctadecyldimethylammonium hydrogen sulfate, dihexadecyldimethylammonium 
chloride, dihexadecyldimethylammonium 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, 
dioctadecyldimethylphosphonium bromide, dioctadecyldimethylphosphonium 
nitrate, dioctadecyldimethylphosphonium hydrogen sulfate, 
dihexadecyldimethylphosphonium chloride, dihexadecyldimethylphosphonium 
bromide, dihexadecyldimethylphosphonium nitrate, 
dihexadecyldimethylphosphonium hydrogen sulfate, tetraalkylammonium 
hydoxide, tetraalkylammonium tribromide, tetraalkylammonium 
trifluoromethanesulfonate, and any combination thereof. 
Phosphoric acid or its various salts can be used in amounts of about 0.001 
to 0.5 equivalents per equivalent of carbon--carbon double bond. Sodium or 
potassium salts of monobasic, dibasic, or tribasic phosphoric acid can 
also be used. The final pH can be adjusted by other acids or bases to 
about 0-5. 
Either tungstic acid which is not water soluble or its metal salts which 
are soluble can be used as the metal catalyst. The typical catalyst is 
used in amounts of about 0.005 to 1%, based on weight of unsaturated 
compound. The preferred metal catalyst is tungstic acid. 
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. 
EXAMPLES 
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-unsaturation 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, 1,2-polybutadiene and 
100 ml toluene were changed to a reactor which was equipped with 
mechanical stirrer, thermocouple, and condenser. The mixture was stirred 
and heated to 55.degree. C. The reaction was shut down after 31/2 hours at 
55.degree. C. 
To the reaction mixture, 200 ml toluene and 100 ml of 20% sodium chloride 
were added and kept at 50.degree.-55.degree. 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.degree.-95.degree. C. at 25-35 mm Hg. A light yellow liquid 
was obtained with epoxy value of 182.7 MgKOH/g and viscosity of 6000 cps 
at 25.degree. 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-1,4unsaturation, produced by Elf Atochem, 
referred to hereafter as Polybd-R-20LM. 
212.6 g polybutadiene, 2.10 g 600 methyl ammonium chloride 600 ml toluene, 
1.0 g tungstic acid, 0.25 mil 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.degree. C. Stirring was continued for 8.0 
hours at 60.degree. C. The reaction mixture was then allowed to separate 
into two phases. The organic phase was isolated and washed twice with 200 
ml water. The solvent was removed under a reduced pressure of 25 mm Hg at 
60.degree. C. Viscous light yellow epoxidized polybutadien was obtained 
with viscosity of 85,400 cps at 25.degree. 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-1,4-unsaturation, 60% trans-1,4unsaturation, referred to as 
Polybd-45HT, produced by Elf Atochem. 
Polybutadiene (110.2 g), toluene (200 ml), (methyl 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.degree. C. The reaction was stopped after 4.0 
hours at 60.degree. 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.degree. C. 
Final product physical properties: color G5; 4187 cps viscosity at 
65.degree.; 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.