| 摘要 |
The process for the production of closed-cell, extra soft polyvinylchloride foam plastics having improved volume stability at elevated temperatures. The process includes heating a plastisol or plastigel comprised of a plasticizer and foaming agent containing polyvinyl chloride or vinyl chloride copolymerizate in a pressure mold at a pressure of up to 300 atm. to a temperature of 150 DEG to 180 DEG C. for 1 to 2 hours. The plastigel or plastisol is cooled, at an unchanged closing force of the press of said pressure mold, to a temperature of 20 DEG to 70 DEG C. The plastigel or plastisol is removed from the pressure mold, a crude foam plastic forming. The crude foam plastic is heated under a gas pressure of 2 to 10 atm. to a temperature of 140 DEG to 170 DEG C. The crude foam plastic is cooled at said pressure of 2 to 10 atm. to a temperature of 100 DEG to 130 DEG C. The pressure is lowered to atmospheric pressure, the foam plastic simultaneous expanding. The resultant foam plastic will not shrink or expand more than 5 percent after storage for one week at 60 DEG C. |
