| 摘要 |
1328525 Foamed olefine and chlorinated olefine polymers SANWA KAKO CO Ltd 30 Sept 1970 [4 Oct 1969] 46563/70 Heading C3C A foamed olefin polymer or chlorinated product thereof having a chlorine content of up to 65% by wt. is made by providing a foaming composition containing the olefin polymer, or chlorinated product thereof, a heat-decomposable solid foaming agent having a decomposition point above the melting point of the polymer or chlorinated product, and a cross-linking agent; heating the foaming composition in a closed mold under superatmospheric pressure until there is obtained a primary foamed product containing undecomposed foaming agent in an amount of from 40 to 85% by weight of the original quantity of foaming agent and crosslinked to a degree sufficient to prevent rupture of the formed cells upon release of said superatmospheric pressure at an elevated temperature; heating the primary foamed product at atmospheric pressure to decompose from 90 to 95% by weight of the undecomposed foaming agent in the primary foamed product; allowing the secondary foamed product thereby obtained to stand at atmospheric pressure and ambient temperature for a time sufficient to decompose the remaining undecomposed foaming agent. In the examples polyethylene or an ethylene/ vinyl acetate copolymer was foamed, as above, using azodicarbonamide as a blowing agent together with urea as a foaming assistant and alpha-dicumyl peroxide as the cross-linking agent. |
