| 摘要 |
PURPOSE:To make it possible to easily perform temp. regulation at the time of extrusion foaming and to enable the enhancement of a foaming property, by melting and kneading a polyethylene mixture, which is prepared by mixing straight chain low density polyethylene and low density polyethylene in a specific ratio, along with a foaming agent. CONSTITUTION:A polyethylene mixture, which consists of 10-40wt% of straight chain low density polyethylene with density of 0.920-0.940g/cm<2> and a melt flow rate of 0.3-10g/10min having relation of Mw/Mn>=4 between the wt. average molecular wt. Mw and the number average molecular wt. Mn and 90-60wt% of low density polyethylene with density of 0.918-0.923g/cm<2> and a melt flow rate of 0.1-10g/10min, is used. This polyethylene mixture is melted and kneaded along with a foaming agent under pressure by an extruder and extruded into a low pressure atmosphere and foamed. As the foaming agent, an inorg. foaming agent such as carbon dioxide, a volatile foaming agent such as propane and a decoposable type foaming agent such as sodium bicarbonate are designated. By this method, a foam body can be easily prepared in a wide extrusion foaming appropriate temp. range at high foaming magnification. |
