Emulsion process for preparing elastomeric vinyl acetate-ethylene copolymer and high Mooney viscosity low gel content elastomer obtained therefrom

摘要

In a process for preparing an elastomeric vinyl acetate- ethylene copolymer having high Mooney viscosity and low gel content wherein vinyl acetate monomer is copolymerized with ethylene monomer in an aqueous emulsion reaction medium containing surface active agent, polymerization catalyst and protective colloid to provide a latex and vinyl acetate- ethylene elastomer is recovered from the latex, an improvement is disclosed which comprises:PPcopolymerizing from about 40% to about 70% by weight of vinyl acetate monomer with from about 60% to about 30% by weight of ethylene monomer in an aqueous emulsion reaction medium to provide a latex, the reaction medium for vinyl acetate-ethylene elastomer containing:PP(i) at least one surface active agent having a hydrophilic lipophilic balance value of at least 22 in an amount above about 2.0% by weight of the total monomer,PP (ii) a polymerization catalyst, andP P(iii) at least one protective colloid in an amount of less than about one part for each part by weight of total surface active agent, with the total weight of the surface active agent and vinyl acetate being present in the reaction medium at the commencement of copolymerization.