Abstract: The invention relates to a process and an apparatus for the microsuspension polymerization of vinyl chloride in vessels whose contents are agitated predominantly by natural convection where, in a reactor having a ratio of height H to diameter D of H/D 2, which is equipped externally or internally with a heat exchanger provided with water and connected to a pumped circulation system provided with water, the introduction of the cooling water takes place in the upper third of the heat exchanger and the cooling water is conducted downward and is conducted away in the lower third of the heat exchanger.

Abstract: 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.