SYNTHETIC RESIN FOAM AND ITS PRODUCTION

PURPOSE:To produce a good foam in a stable state by adding a fine mineral powder and/or a water-absorptive polymeric compound and a phenolic antioxidant to a synthetic resin, further adding water to the obtained mixture, melt- kneading the resulting mixture by heating, injecting a volatile blowing agent into this mixture, and extrusion-foaming the final mixture. CONSTITUTION:100pts.wt. synthetic resin is mixed with a fine mineral powder of a particle diameter of 1,000nm or below and/or 0.05-2pts.wt. water-absorptive polymeric compound, 0.01-5pts.wt. cell modifier and 0.02-1pt.wt. phenolic antioxidant; 0.05-1.5pts.wt. water is added to the obtained mixture after or during the mixing; the resulting mixture is melt-kneaded by heating; a volatile blowing agent is injected into this mixture; and the final mixture is extrusion-foamed into a lower-pressure zone. In this way, a synthetic resin foam in which cells of a cell diameter of 0.3mm or below and cells of a cell diameter of 0.4-1mm are chiefly dispersed can be obtained.