| 摘要 |
A process for the manufacture of vinyl chloride polymers or copolymers by microsuspension polymerization of vinyl chloride or vinyl chloride and up to 30% by weight, based on the total monomer content, of alpha -olefinically unsaturated monomers copolymerizable with vinyl chloride comprising the steps of: (1) dispersing the monomer or the monomer mixture in water in the presence of from 0.1 to 3% by weight, based on the total weight of the monomer content, of microsuspension dispersion auxiliaries and from 0.001 to 3% by weight, based on the total weight of the monomer content, of microsuspension monomer - soluble radical - initiators; (2) homogenizing said dispersion so that monomer droplets mostly having a mean diameter of from 0.1 to 3 mu m are obtained; (3) polymerizing said homogenized dispersion in a vertically elongated reactor area at a preselected elevated temperature and elevated pressure, while (4) maintaining an inert gas cushion over said aqueous polymerization mixture in said reactor area; (5) during said polymerization withdrawing gas from said inert gas cushion and, inserting a substantially inert gas only slightly soluble in the reaction mixture and substantially free of vinyl chloride into said aqueous polymerization mixture at the lower part of said vertically elongated reactor area in the form of small bubbles so that the partial pressure of said substantially inert gas is from 0.5 to 10 bar and the volume of the gas inserted is, under the reaction conditions, from 1 to 100% of the volume of said vertically elongated reaction area per hour or taking the inert gas from an external supply, the pressure in the reactor held constant and the same amount of gas blown into the autoclave is released; and (6) recovering said vinyl chloride polymer or copolymer resulting in more uniform polymers and an improved space/time yield.
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