| 摘要 |
PURPOSE:Highly expanded foams having uniform fine cellular structure, excellent heat resistance, and a low thermal expansion (excellent dimensional stability), being inexpensive as well, made by foam-molding a composition consisting mainly of a vinyl chloride resin, an acrylic resin, and wood flour. CONSTITUTION:100pts.wt. vinyl chloride resin [the reduced viscosity (0.1g/100ml chloroform solution at 20 deg.C) of about 3dl/g or higher], about 3-30pts.wt. acrylic resin and/or styrene resin (preferably obtained by emulsion polymerization), and about 10-100pts.wt. wood flour (the average particle diameter of about 500mum or smaller; the moisture content of about 5,000ppm or less) are mixed. The composition is fed in an extruder, and an organic solvent type foaming agent (a volatile organic compound with a boiling point of about 90 deg.C or lower, e.g. propane, petroleum ether, or trifluoromethane) is introduced under pressure into the heated resin composition, which is extruded to be foam-molded. |
