| 摘要 |
1,192,333. Closed cell olefine polymers. JAPAN GAS CHEMICAL CO. Inc. 23 April, 1968 [24 April, 1967; 2 Nov., 1967; 27 Dec., 1967; 28 Dec., 1967], No. 19187/68. Headings C3C and C3P. A closed-celled, foamed shaped product of an olefin polymer is made by (1) contacting in a melt extruder a molten crystalline, linear polymer containing at least 80 mol. per cent of monomer units, at least one of which is an olefin of 2 to 6 carbon atoms with 2 to 50 parts by weight, per 100 parts by weight of the polymer, of a pressurized foaming agent which is a normally gaseous or liquid hydrocarbon, ether, ketone, ester or chlorinated hydrocarbon with a boiling point of -45‹ to +70‹ C., (2) cooling the blend of the polymer and the foaming agent in the extruder to a temperature which is at least 2‹ C. lower than the melting point of the polymer and which is not lower than the temperature at which - dP/dT becomes 20 (kg./cm.<SP>2</SP>, ‹C.), T being the temperature in ‹C. of the blend at the extruding die of the extruder, and P being the extruding pressure (kg./cm.<SP>2</SP>) of the blend at the said die; and (3) extruding the blend at a temperature as defined above into a zone at a lower pressure than the extruder. The polymer may be a polyethylene which may be blended with a butyl or butadiene rubber, polypropylene or an ethylene/vinyl acetate copolymer. The foaming agent may be pentane propane or dimethyl or methyl ethyl ether or a mixture, e.g. of n- and isobutane and butene-1 and a nucleating agent may be used, e.g. monosodium citrate, citric acid, sodium bicarbonate, sodium hydrogen tartrate, monoglyceride stearate and/or monoglyceride oleate; talc and diatomaceous earth; or azodicarbonamide. |
