Manufacture of polyvinyl chloride foams

A process for producing a soft polyvinyl chloride foam which comprises feeding a foamable soft polyvinyl chloride plastisol to a high speed mixing zone, agitating said foamable soft polyvinyl chloride plastisol at high speed in said high speed mixing zone at a pressure not exceeding about 15 atmospheres gauge to thereby generate, by friction, at least about 60 percent of the heat necessary for foaming and gelatination of said plastisol and cause foaming and gelling of said plastisol within said mixing zone, and discharging an at least partially gelled and at least partially foamed polyvinyl chloride from said mixing zone.