Reduction of monomer content of solid PVC - by heat treatment with exposure to dilute chlorine

摘要

Treatment f PVC powder contg. 57% Cl, or vinyl chloride copolymers by heating at 50-100 degrees C for >=10 mins. while in motion. During or after heating, the powder is treated with highly diluted chlorine (PCl2 is not >100 torr) in amount of >=10 ppm polymer, in absence of chlorination catalysts. Remaining chlorine is subsequently removed from the polymer. Pref. PCl2 is 0.01-10 (0.03-3) torr, mixed with an inert gas (air). Treatment is effected at 10-100 degrees (30-90 degrees) esp. 40-70 degrees C. More intensive heat-treatment to remove residual monomer is possible, without discolouration of the PVC. Chlorine content is not increased above 57%, and processing and application properties are not affected. The process can be carried out continuously, using simple, compact and cheap plant, esp. in the polymerisation reactor.