Process and apparatus for the preexpansion of vinyl polymeric materials

Claim 1

IN A METHOD OF MAKING FREE-FLOWING, PARTICULATE, LOW DENSITY PARTIALLY EXPANDED VINYL POLYMERS WHICH ARE CAPABLE OF FURTHER EXPANSION FROM FOAMABLE VINYL POLYMERS, HAVING INCORPORATED THEREIN 3-15% BY WEIGHT OF A NORMALLY LIQUID, VOLATILE ALIPHATIC HYDROCARBON HAVING A BOILING POINT BELOW THE SOFTENING POINT OF THE POLYMER, BY TREATMENT WITH STEAM, THE IMPROVEMENT COMPRISING CONTINUOUSLY FEEDING THE FOAMABLE POLYMER PARTICLES TO THE LOWER PORTION OF A STEAM-FILLED ZONE WHEREIN THE PARTICLES ARE SUBJECTED TO A TEMPERATURE AT WHICH PARTIAL VOLATILIZATION OF THE ALIPHATIC HYDROCARBON OCCURS, THEREBY FORMING A LOW DENSITY PARTIALLY EXPANDED POLYMER CAPABLE OF FURTHER EXPANSION, RAPIDLY AGITATING THE MASS OF PARTICLES IN SAID ZONE TO CAUSE SAID PARTIALLY EXPANDED PARTICLES TO TRAVEL CENTRIFUGALLY AND UPWARDLY THROUGH SAID ZONE BY RAPIDLY ROTATIVELY STIRRING THE MASS OF PARTICLES IN SAID ZONE WHILE PASSING STEAM THERETHROUGH THEREBY ELIMINAT-