| 摘要 |
A method for preparing a stable vinyl chloride based resin emulsion which comprises a copolymer colloidally dispersed in an aqueous medium, the copolymer having a Tg from 0 DEG to 50 DEG C., about 65 to 90 wt % vinyl chloride, about 5 to 35 wt % ethylene, 0 to 10 wt % olefinically unsaturated copolymerizable monomer and prepared by emulsion polymerization of vinyl chloride, ethylene and, optionally, an olefinically unsaturated comonomer in the presence of about 3 to 15 wt % polyvinyl alcohol as the dispersing agent, the polymerization method comprising (a) forming an aqueous emulsion reaction mixture containing substantially all the polyvinyl alcohol and a portion, preferably at least 5%, of the total vinyl chloride monomer, (b) pressurizing the reaction mixture with an ethylene pressure sufficient to provide the copolymer with a 5 to 35 wt % ethylene content, (c) initiating the reaction mixture by the addition of a free radical generating source and continuing polymerization until the rate of polymerization begins to decrease to provide a prepolymer emulsion, and (d) adding the remaining vinyl chloride at a substantially uniform rate and continuing polymerization until the polymerization reaction is not longer self-sustaining, ethylene being neither withdrawn nor added during the polymerization in one embodiment.
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