Polymerdispersionen

A dispersion in organic liquid of crosslinkable addition polymers contains one polymer containing a reactive group which is capable of reacting with a complementary reactive group in another of the polymers to crosslink the polymers, each polymer being in a different part of the disperse phase. In one embodiment, the dispersion contains a mixture of two types of dispersed polymer particles, in which the reactive groups may be confined to the inner layers of the particles. In another embodiment, a monomer containing a first reactive group is polymerized in dispersion in an initial stage and a monomer containing a complementary reactive group is polymerized in a later stage to form particles containing reactive groups in different layers. The polymerization is carried out in the presence of a stabilizer which may be formed in situ by copolymerizing the monomer with a polymeric precursor to form a block or graft copolymer. Pigments may be incorporated in the dispersion prior to removal of the organic liquid, the resulting dry polymer particles being cross-linked by fusion or dispersed in a plasticizer, e.g. a phthalate ester to form a plastisol, in which crosslinking occurs on heating and gelling. In the first stage of Example 1, methyl methacrylate and methacrylic acid are copolymerized in petroleum ether using azodiisobutyronitrile as catalyst in the presence of poly (lauryl methacrylate-glycidyl methacrylate) as stabilizer precursor, in the second stage butyl methacrylate, methyl methacrylate and methacrylic acid are copolymerized in the dispersion from the first stage and in the third stage butyl methacrylate, methyl methacrylate and butoxymethyl acrylamide are copolymerized. Octyl meraptan is present as molecular weight regulator. In Example 2, a two-stage process is employed, the monomers being (1) methyl methacrylate and (2) methyl methacrylate and methacrylic acid and the resulting dispersion is mixed with a similar one in which butoxymethyl acrylamide replaces the methacrylic acid. The monomers employed in Example 3 are (1) vinyl acetate, (2) vinyl acetate and methyl hydrogen maleate and (3) vinyl acetate and butoxymethyl acrylamide. In Example 7 the monomers are (1) methyl methacrylate and 2-hydroxypropyl methacrylate, (2) butyl methacrylate, methyl methacrylate and the reaction product of 2-hydroxypropyl methacrylate and toluene diisocyanate and (3) butyl methacrylate, 2-hydroxypropyl methacrylate and methyl methacrylate, in Example 8 the butyl met