| 摘要 |
PROBLEM TO BE SOLVED: To suppress foaming in the in-plane direction in a foamable thermoplastic resin sheet by a method wherein a foamable sheet is obtd. by laminating a sheet-like article with a strength which can suppress foaming in the in-plane direction of the sheet and integrating them and the foamable sheet is foamed by heating the foamable sheet at a decomposition temp. or higher of a thermodegradable foaming agent. SOLUTION: A thermoplastic resin, a silane-modified thermoplastic resin, a silane crosslinking catalyst and a thermodegradable foaming agent are mixed and melt-kneaded. In addition, the mixture is extruded from a T-die into a sheet-like shape to obtain a foamable thermoplastic resin sheet 2 and after papers 3 and 4 contg. glass fibers are laminated above and below it, it is passed through between facing cooling rolls 5 and 6 whose temp. is set at 25 deg.C to integrally laminate them and to obtain a foamable sheet 7. Then, the foamable sheet 7 is immersed in a hot water at 99 deg.C, for 2hr to generate crosslinkings and then, it is placed between two sheets of upper and lower belts wherein polytetrafluoroethylene is the main ingredient and is heated at 230 deg.C to foam. After foaming, it is cooled and solidified and the foamable sheet 7 is released from the belts. |
