Reducing vinyl chloride content of PVC powders - by mixing and heating in high speed mixer with continuous or portionwise addn. of water

摘要

PVC powder compsns. with low vinyl chloride monomer content are made by subjecting the PVC, opt. together with known additives such as stabilisers, plasticisers, fillers, pigments and modifiers, to intensive mechanical mixing while simultaneously heating it to a final temp. of >=70 degrees C and with the addn. of water, either portionwise or continuously, before the mixt. reaches the final temp. Pref. 1-10 wt% water is added and the final temp. is 140 degrees C. The water may be added e.g. in 2-4 virtually equal portions, the first portion being added at about 70-80 degrees C and the remaining portions at 10-30 degrees intervals in the range 80-120 degrees C, or continuously, starting at about 70 degrees C and finishining at about 120 degrees C. The heating may be completely or substantially caused by the intensive mixing. The process gives good removal of vinyl chloride monomer from the powder compsns. and gives prods. which can be processed without releasing toxic vinyl chloride vapours into the atmos.