Production of cellulsar polyvinyl plastics

Claim 1

A PROCESS FOR THE PRODUCTION OF HARD CELLULAR PRODUCTS FROM A POLYVINYL TYPE PLASTIC SELECTED FROM THE GROUP CONSISTING OF POLYVINYL CHLORIDE, CO-POLYMERS OF VINYL CHLORIDE WITH VINYL ACETATE, CO-POLYMERS OF VINYL CHLORIDE WITH VINYLIDINE CHLORIDE AND MIXTURES OF AT LEAST ONE OF SAID CO-POLYMERS WITH BUTADIENE ACRYLONITRILE COPOLYMER, WHICH PROCESS COMPRISES IN COMBINATION THE FOLLOWING STEPS: (A) HEATING IN A CONFINED SPACE A PASTE CONSISTING OF THE POWDERED VINYL POLYMER, A POLYMERIZABLE SOLVENT SELECTED FORM THE GROUP CONSISTING OF STYRENE, ALKYL SUBSTITUTED STYRENES IN WHICH THE SUBSTITUENT IS IN THE NUCLEUS, METHYL METHACRYLATE AND BUTYL METHARCYLATE, AND A BLOWING AGENT WHICH AT THE TEMPERATURE OF GEL FORMATION WILL FORM AN INERT GAS, AND CONTINUING THE HEATING UNTIL THE PASTE IS CONVERTED INTO A GEL: (B) COOLING UNTIL THE GEL SETS TO A HARD MASS; (C) RE-HEATING THE MASS WITHOUT APPLIED PRESSURE UNTIL IT IS SOFTENED AND EXPANDED UNDER THE INFLUENCE OF THE GAS WITH WHICH IT IS IMPREGNATED, AND CONTINUING THE HEATING UNTIL THE MASS IS HARDENED BY POLYMERISATION OF THE POLYMERIZABLE SOLVENT.