METHOD OF PREPARING LATEX WITH HOLLOW POLYMER PARTICLES Russian patent published in 1999 - IPC

FIELD: polymer production. SUBSTANCE: hollow polymer particles find use as filler and/or pigments in paintwork materials production, when manufacturing coating on high-quality paper, and as fillers decreasing density of plastics. In particular, preparation of latex with hollow polymer particles involves water-emulsion copolymerization of mixture of ethylenically unsaturated monomers containing methylmethacrylate and methacrylic acid at 60-85 C in presence of water-soluble free-radical initiator and anionic surfactant to form inoculating latex of polymer particles. Further, copolymerization of methylmethacrylate and methacrylic acid with cross-linking comonomer in presence of freshly formed inoculating latex proceeds to give latex of particles of cross-linked high-carboxylation copolymer (nucleus). In presence of these particles, mixture of comonomers containing vinylaromatic monomer, cross-linking comonomer, and optionally acrylonitrile or methylmethacrylate is subjected to copolymerization to form outside copolymer shell of nucleus particles with vitrification temperature above 80 C, after which carboxylic groups of latex polymer particles are neutralized by volatile base. Method is distinguished by that, when preparing inoculating latex, methylmethacrylate-to-methacrylic acid ratio ranges from 97.0:3.0 to 99.5:0.5, total concentration of comonomers represents 0.8-1.0% of the weight of water-emulsion medium, and free-radical initiator is used in amount 8.6 to 24.5% of the weight of comonomers; copolymerization in presence of latex of nucleus copolymer particles is carried out with monomer mixture containing methylmethacrylate, acrylic acid ester, methacrylic acid, and cross-linking comonomer to form, on nucleus particles, an intermediate shell with vitrification temperature 80 C; and neutralization of carboxylic groups by volatile base is then performed before formation of outside shell. The whole process is conducted in single polymerization zone. EFFECT: simplified technology and increased covering power of coatings including latex with hollow particles. 4 cl, 6 ex