| 摘要 |
PURPOSE:To obtain a foamed and crosslinked PVC, by kneading and sheet- forming a composition containing PVC, a chemical foaming agent and a reactive plasticizer while suppressing the reaction of said plasticizer, and reacting and crosslinking the plasticizer in the foaming stage. CONSTITUTION:PVC is mixed homogeneously with a foaming agent (e.g. azodicarbonamide), a reactive plasticizer (e.g. ethylene/vinyl acetate/carbon monoxide terpolymer) and if necessary, a stabilizer, etc. The obtained composition is preliminarily kneaded e.g. with a Banbury mixer at 120-150 deg.C to obtain a kneaded mixture having a gel fraction of <=5%, preferably <=1%, and the mixture is formed to a sheet by melting at a temperature below the decomposition point of the foaming agent, preferably at 110-150 deg.C. The sheet is foamed by heating at 180-250 deg.C, preferably 190-230 deg.C under normal pressure to produce the objective crosslinked closed-cell foam having a gel fraction of 10-70% and an expansion ratio of 3-30.
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