| abstract |
This invention relates to an improved process for producing a clear solution of vinylpyrrolidone (VP) and vinyl acetate (VA) monomers which comprises, in an anhydrous system, (a) reacting a C2 to C3 alcoholic solution containing said VA monomer and between about 60 and about 80 wt. % portion of total VP monomer in the presence of between about 0.05 and about 0.3 wt. % of a free radical initiator selected from the group consisting of tertamylperoxy pivalate and 2,2-azobis(2-methylbutyronitrile) or a mixture thereof for a period of from about 5 to about 10 hours, at a temperature between about 60 DEG and about 110 DEG C.; (b) gradually adding the remaining VP monomer in C2 to C3 alcohol solution at reaction temperature after the addition of the VA monomer is complete; (c) raising the temperature of the resulting reaction mixture to between about 110 DEG and about 150 DEG C.; (d) continuing the polymerization reaction at said higher temperature in the presence of from about 0.11 to about 0.6 wt. %, based on total monomers, of 2,5-dimethyl-2,5-bis(tert-butylperoxy) hexane and (e) cooling the resulting reaction mixture and recovering a homogeneous VP/VA copolymer C2 to C3 alcohol solution containing less than 100 ppm of residual vinylpyrrolidone monomer or vinyl acetate residual monomer. |