PROCESS FOR PRODUCING POLYACRYL-ACID-ESTER/VINYL-CHLORIDE GRAFTED POLYMER WITH LARGE SPECIFIC IMPACT ENERGY

摘要

A process is described for the preparation of thermoplastic compositions based on vinyl chloride homopolymers or copolymers and polyacrylates and having a glass transition temperature of below -20 DEG C. First, the acrylate is polymerised in aqueous emulsion in the presence of crosslinking compounds which are copolymerisable with the acrylates and have at least two non-conjugated double bonds. In the second step of the process, the vinyl chloride or vinyl chloride with up to 20% by weight of copolymerisable monomers is heated to a temperature of /= 30 DEG C in aqueous suspension with an initiator, a suspending agent system and optionally additives. Only then is the polyacrylate added and polymerised at temperatures of  30 DEG C to the desired conversion. The polymers prepared in this way have an improved particle size distribution and good reproducibility of the bulk density, and in particular caking on the walls of the reactor during the polymerisation is drastically reduced.