PROCESS FOR REDUCING THE RESIDUAL CONTENT OF VINYL CHLORIDE MONOMER IN VINYL CHLORIDE POLYMERS

摘要

Residual monomers are removed from homopolymers, copolymers or graft polymers containing at least 50% by weight of polymerised vinyl chloride. After removal of the majority of the unreacted monomers and, if present, the water, the polymer in the pulverulent state is subjected to heat treatment at from 75 to 120 DEG C for from 10 to 360 minutes at atmospheric pressure or under reduced pressure. The heat treatment is carried out in the presence of from 0.01 to 5% by weight, based on the polymer, of at least one aliphatic, saturated or unsaturated, branched or unbranched compound containing two free hydroxyl groups and from 2 to 24 carbon atoms and no heteroatoms connecting the carbon atoms, or containing two free hydroxyl groups, from 4 to 24 carbon atoms, at least one ether oxygen atom and, apart from the ether oxygen, no further heteroatoms connecting the carbon atoms. The use properties of the polymers are not impaired by the above treatment, in particular significant discolouration is not observed.