METHOD FOR PRODUCING VINYL CHLORIDE-BASED RESIN FOAM

PROBLEM TO BE SOLVED: To provide a method for producing a vinyl chloride-based resin foam with fine and uniform foams, which method does not cause uneven foaming even when a raw material resin contains a recycled resin, and is capable of producing over a long period of time using one extruder without causing molding defects such as plate-out. SOLUTION: The method for producing the vinyl chloride-based resin foam employs an apparatus composed of an extruder, a feeder supplying an inert gas foaming agent, a temperature control adapter and a mold for extrusion molding. The method comprises the steps of adding 0.1-3 pts.wt. inert gas to 100 pts.wt. vinyl chloride-based resin composition, sealing the gas in the extruder where a part of screw flights is made as a reverse-flight structure, melt kneading the resin composition at 160-200°C cylinder temperature and Q/Ns≥0.7 and, feeding the kneaded material to a temperature control adapter at 180-200°C resin temperature, and after cooling down to ≤180°C, feeding the material to a mold for extrusion molding, to form a foam of 1.1-5.0 times expansion ratio at 165-180°C and 30-100 μm mean cell diameter. COPYRIGHT: (C)2007,JPO&INPIT