| 摘要 |
1400494 Foamed olefine polymer or polyamide sheets SEKISUI KASEIHIN KOGYO KK 14 July 1972 [14 July 1971] 33193/72 Heading C3C [Also in Division B5] A foamed sheet of a non-rubbery olefine polymer or a linear polyamide has surfaces impervious to liquid which enclose an intermediate foamed layer composed of pores which become progresively more elongated in the direction perpendicular to the sheet as the distance from the surface increases and which at the middle of the sheet are ruptured into a plurality of transverse films. The sheet is made by extruding a mixture of foaming agent and the polymer through a slit or annular orifice into a cooled passage where the mixture is allowed to form and increase in thickness to at least 3 times its thickness as it leaves the orifice without increasing in width or internal diameter by more than 30%, removing the foamed sheet or tube from the passage so that it can undergo any further free expansion of which it is capable and slitting the tube to form a sheet. A foamed sheet having one smooth and one rough surface is formed by separating the surfaces of the above sheet by rupturing the sheet along the middle plane of the intermediate layer. The polymers foamed may be poly. ethylene, polypropylene or nylon-12. Figs. 1-4, 7 and 8 illustrate apparatus used to form the above foamed sheets wherein polymer and foaming agent is fed through extruder 1, having screw 2, via die 3 and orifice 5 to passageway 7 where the polymer is foamed in 8. In Figs. 23 and 8 passageway 8 is lined with tetrafluoroethylene resin at 81 or 76. Figs. 4 and 7 show a foamed tube being produced in passageway 8 defined by core 71, the annular orifice being formed by core 31 supported by bridging member 32 in die 3, the foamed tube being supported on core 12 secured to core 71 by shaft 13 and then cut at 14 to produce a sheet. |
