THERMOPLASTIC RESIN FOAM AND ITS MANUFACTURE

PROBLEM TO BE SOLVED: To efficiently manufacture thermoplastic resin foam having beautiful surface appearance, excellent mechanical strength and uniform fine foams. SOLUTION: A continuous plasticizing apparatus uses a resin compsn. consisting of 50-99 pts.wt. of a styrenic resin and 1-50 pts.wt. of a polypropylene resin and has a foaming agent supply line. In this case, a gas dissolving process adding 0.1-30 pts.wt. of inert gas in a super-critical state being a foaming agent to a molten thermoplastic resin to form a perfect compatible state of the thermoplastic resin and the inert gas and a cooling process lowering the temp. of the molten resin are performed and a measuring injection process is performed in an injection apparatus having an injection plunger. Further, a foaming control process generating a large number of air bubble nuclei by the sudden lowering of pressure in a mold to control an air bubble diameter is performed and the inert gas is held to a super-critical state until at least the measuring injection process.