Heat-expandable polyvinylidene chloride microsphere and its preparation method

A preparation method of a heat-expandable polyvinylidene chloride microsphere composition, comprising the following steps:

• (1) by weight, dissolving 250 to 550 parts of an polymerization inhibitor, 20 to 100 parts of an aqueous solution of a dispersant with a concentration of 10 to 35% by mass, and 3 to 15 parts of a co-dispersing monomer in 5000 to 8000 parts of deionized water, adjusting pH of the mixed solution to 3 to 5, cooling to 0 to 10° C. to obtain an aqueous phase for later use, wherein the co-dispersing monomer is prepared as follows:
• by weight, adding 1 to 5 parts of the tetrahydrofuran solution of chloroplatinic acid, 50 to 70 parts of vinylpyrrolidone, 0.5 to 2.5 parts of zinc methacrylate, and 10 to 30 parts of dimethylallylsilane to a reactor to carry out a hydrosilylation reaction at a temperature of 70 to 100° C. for 1 to 5 h to obtain the co-dispersing monomer;
• (2) dissolving 5 to 15 parts of a crosslinking agent and 20 to 45 parts of an initiator in 1000 to 2000 parts of the mixed monomer, and cooling to 0 to 10° C. to obtain an oil phase for later use, wherein by weight, the mixed monomer comprises:
• 800 to 1200 parts of vinylidene chloride, 320 to 800 parts of acrylonitrile, and 160 to 320 parts of methyl methacrylate;
• (3) mixing and homogenizing the aqueous phase and the oil phase for 2 to 10 min at a stirring speed of 2000 to 8000 rpm to obtain a homogenized mixed solution;
• (4) adding 300 to 550 parts of a foaming agent to the homogenized mixed solution obtained in step (3), and homogenizing for 2 to 10 min at 0.10 to 0.5 MPa, 2000 to 8000 rpm to obtain a homogenized mixed solution containing the foaming agent;
• and
• (5) allowing the homogenized mixed solution containing the foaming agent obtained in step (4) to react for 10 to 30 h at 50 to 90° C., 300 to 600 rpm;
• at the end of the reaction, cooling to room temperature, and filtering the resulting suspension to obtain filtrate;
• centrifuging and dehydrating the filtrate;
• and finally drying to obtain the heat-expandable polyvinylidene chloride microsphere product.