METHOD FOR THE PREPARATION AND USE OF A SINTERABLE, FINELY DISTRIBUTED MOULDING COMPOSITION BASED ON POLYVINYL CHLORIDE

摘要

Prodn. of a sinterable, fine-particle PVC moulding compsn. by homo-, CO- or graft suspension polymerisation of VC monomer in presence of an oil-soluble free-radical initiator, a suspension stabiliser, emulsifier and opt. other polymerisation aids. After ending the polymerisation and sepg. the bulk of the polymer a non-ionic or amphoteric wetting agent is added before drying. The process novelty claimed is the addn. at this stage of an aq. soln. of a non- surface active acid with an acid dissociation constant up to 3 pKs at 20 deg.C.. Pref. 0.01-5 wt.% on dry polymer of a phosphorus or sulphur contg. acid, esp. P contg. acid, with low volatility at 120 deg.C. is added after sepg. the greater part of the polymer from the aq. phase after polymerisation has ended. The polymer has a K-value =55-90, bulk density =400-700g/cdm, and a particle distribution of 99-30 wt.% less than 33 microns, 1-60 wt.% 33-63 microns, 0-9 wt.% 63-125 microns and 0.1 wt.% greater than 125 microns. Sintered shaped articles esp. separator plates for electric cells are claimed.