PROCESS FOR THE PRODUCTION OF A FILLER FOR PVC MOULDING MATERIALS, THE USE OF THE FILLER PRODUCED BY THIS PROCESS AND PVC MOULDING MATERIALS CONTAINING THE FILLER PRODUCED BY THIS PROCESS

摘要

The invention concerns a process for the production of a filler, based on an hydrous calcium sulphate II, for PVC moulding materials in which finely divided calcium sulphate dihydrate is moistened with a dilute dessicating acid and the mixture subjected to heat treatment at elevated temperatures, viz: either (a) the mixture is heated at temperatures of 50-190 °C and the acid remaining in the product obtained is neutralized with an alkali metal carbonate or alkaline earth carbonate, distilling off the water which is still present or which forms, plus the carbon dioxide which forms: or (b) the mixture is heated in a counter-current of hot gas to temperatures of over 350 °C, then cooled, separated by sieving from all particles greater than 90 νm, preferably greater than 63 νm, in diameter and, optionally, ground.