Polymer particles and process for producing the same

Abstract

An aqueous dispersion of polymer particles each consisting essentially of (a) a syndiotactic 1,2-polybutadiene having 70% or more of unsaturated hydrocarbon groups in the side chains and having a melting point of 70.degree. C. or higher, (b) a polymer mixture of said polybutadiene (a) and other polymer in the form that (a) and (b) co-exist in the same particle, or (c) a copolymer obtained by graft-polymerizing a conjugated diene and/or other polymerizable monomer on said polybutadiene (a), each of said particles having an average diameter of 10 .mu.m or less. Said aqueous dispersion can be produced by a process comprising steps of adding, to an aqueous dispersion of a first catalyst component solution, a conjugated diene monomer and a second catalyst component and polymerizing said conjugated diene monomer, characterized in that the first catalyst component solution contains (A) a cobalt compound, (B) at least one member selected from the group consisting of alkali metals, organometallic compounds of metals of Groups I to III of the Periodic Table and hydrides of metals of Groups I to III of the Periodic Table, and (C) 1 to 1,000 moles, per mole of the cobalt compound (A), of a conjugated diene compound and then the second catalyst component is at least one compound selected from the group consisting of carbon disulfide, phenylisothiocyanic acid and a xanthogen compound.