AQUEOUS HETEROPOLYMERIC DISPERSION FOR PREPARING COVERS AND METHOD OF ITS PREPARING Russian patent published in 2002 - IPC

FIELD: polymers, chemical technology. SUBSTANCE: invention relates to dispersions used for preparing covers, in part, transparent, shock-resistant covers on glass articles, for example, light-technical articles, display screens, glass fibers and so on. Particles of an aqueous heteropolymeric dispersion used for covers making comprise copolymers including links of acrylic monomers and consist of a core, intermediate envelope and external envelope. The core copolymer is a copolymer of (meth)acrylic ester or a mixture of (meth)acrylic esters, ethylene-unsaturated monomer comprising two or three bonds C=C and, possibly, ethylene-unsaturated monomer comprising carboxyl-groups and it shows a vitrification point less 7 C. Copolymer of an intermediate envelope is a copolymer of methacrylic ester or a mixture of methacrylic esters, ethylene- unsaturated monomer comprising two or three bonds C=C and, possibly, ethylene-unsaturated monomer comprising carboxyl-groups and showing a vitrification point 50-85 C. Copolymer of an external envelope is a copolymer of methacrylic ester or a mixture of methacrylic esters and ethylene-unsaturated monomer comprising carboxyl-groups with a vitrification point 25-70 C. Mass ratio of core copolymers, intermediate and external envelopes is in the range = (60-75) : (7.5-20) : (10-22.5), respectively, and mean size of particles dispersion is 50-220 nm. An aqueous heteropolymeric dispersion for covers making is prepared by multistage emulsion copolymerization involving successive stages of emulsion copolymerization of core monomers and envelope monomers at temperature less 100 C in the presence of a water-soluble free-radical initiating agent and an anionic surface-active substance. The stage of core copolymer preparing is carried out for two steps. At the first step emulsion copolymerization is carried out in the presence of an initiating agent and an anionic surface-active substance in a one-time loading 10- 30% of the total amount of the core monomer mixture. In the second step the remained part of core monomers or emulsion of this part of core monomer stabilized with an anionic surface-active substance is dosed to the formed primer latex. The stage of preparing a copolymer of intermediate envelope is carried out by continuous dosing a monomeric mixture forming an intermediate envelope to a core copolymer dispersion. Before onset of this stage an aqueous solution of initiating agent is added to a core copolymer dispersion. The preparation of copolymer of an intermediate envelope can be made for two steps being compositions of a monomeric mixture are different in indicated steps. The stage of preparing the external envelope copolymer is carried out by emulsion copolymerization of monomers forming an external envelope in the presence of a dispersion obtained in a previous stage. The prepared heteropolymeric aqueous dispersions provide the transparency, hardness, nonsticking and shock-resistance of covers. EFFECT: simplified technology, improved and valuable properties of dispersion, improved method of making. 7 cl, 2 tbl, 1 dwg