Kaneka Corporation

Tsuyoshi Yoshida

Tsukasa Makino

Toshihiko Kimura

Tomoaki Nakagawa

Yoichi Uchida

A process for preparing a vinyl chloride paste resin comprising the steps of homogenizing a vinyl chloride monomer in an aqueous medium together with an oil-soluble polymerization initiator to form a first aqueous dispersion, and subjecting the first dispersion to a micro-suspension polymerization wherein a second aqueous dispersion containing a vinyl chloride monomer and a surface active agent is added to the reaction system in such a manner that the addition is started after starting the polymerization but by the time the polymerization conversion of the initially charged monomer reaches 30%, and is terminated by the time the polymerization conversion of the initially charged monomer reaches 95%. The process has an improved productivity since the heat removing area of a jacket of a reactor is prevented from lowering during the polymerization to increase the amount of heat removed and since the polymer yield per unit volume of the reactor is increased.

Process for preparing vinyl chloride paste resin

As a method of vacuum recovery of residual monomers from PVC paste resin latex by heating the latex, the present invention is capable of breaking foam derived from foamable PVC paste resin latex after polymerization by utilizing the methods: using a residual monomer vacuum recovery apparatus having a foam separator and transferring the foam which overflows from the vacuum recovery vessel to the foam separator so that the foam makes direct contact with steam causing a breakdown of the foam. This is done without reducing operability, without lowering stable operation, without degrading product quality, and without reducing the solid concentration of the latex.

Method of breaking foam generated from PVC paste resin latex

A method for continuously stripping an unreacted monomer from a vinyl chloride paste resin latex, comprising the steps of continuously supplying the latex to a vacuum recovery vessel, wherein the latex is boiling with generation of foam, under the condition that the temperature of the latex to be supplied is higher than that of the latex in the recovery vessel, withdrawing a monomer gas generated in the recovery vessel through an exhaust line provided with a foam separator, contacting the foam entrained into the exhaust line with steam introduced to the exhaust line and/or the foam separator, thereby destroying the foam, and returning the resulting latex in the separator to the recovery vessel. The unreacted monomer can be efficiently recovered from the latex by a continuous operation, and defoaming can be achieved without deteriorating the quality and without lowering the productivity.

Method of stripping for latex of vinyl chloride paste resin, stripping apparatus, and vinyl chloride paste resin latex having low concentration of residual monomer

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Himeji, Japan

Tsuyoshi Yoshida