PURPOSE: To retain the secondary foamability of a sheet, by packing a thermoplastic resin foamed sheet that has been allowed to stand under the atmospheric pressure in a film having the permeability of the foaming agent therein up to 0.2g/m2.24hr.atm. per 0.01mm at 20°C.
CONSTITUTION: After a thermoplastic resin such as polystyrene, polyethylenes, etc. is melted and kneaded together with a foaming agent such as trichlorofluoromethane, etc. under heating and pressure, the mixture is extruded at normal temperatures under normal pressures into a thermoplastic resin foamed sheet. Then enough air is allowed to penetrate into the cells in the sheet and after the sheet is allowed to stand in the atmosphere to be aged, the sheet is packed in a film having the permeability of the foaming agent therein up to 0.2g/m2.24hr.atm. per 0.01mm at 20°C. According to this method, a large quantity of a foamed sheet can be produced previously to improve the production efficiency.
| JPS5386769 | POLYESTER HOLLOW BODY |
HASEGAWA TAKESHI
OGURA CHIYUUKIYUU
KUROSAWA EIJI
NIHON ZANPATSUKU KK
Next Patent: SCREW OF FRP