| 摘要 |
PURPOSE:To avoid a foreign substance layer on a joint of each foamed sheet by a method wherein the viscosity of a foamable molten substance obtd. by incorporating a volatile foaming agent in a styrene resin is made in such a way that the viscosity of the molten substance coming to the inside of a laminated body is at most 1.1 times of that coming to the outside thereof and under this condition, both flows are joined together and are extruded from a nozzle and are foamed outside of the nozzle. CONSTITUTION:Foamed molten substances are prepared by pressing a volatile foaming agent such as an aliph. hydrocarbon in a styrene resin and extruding the mixture by means of extruders 1 and 2 and they are joined together by means of a joint flow adaptor 21 and are extruded from a nozzle 22. In this case, the melt viscosity of the intermediate layer of the foamable molten substance from the extruder 1 positioned on both sides of the intermediate layer from the extruder 2 is made in such a way that the viscosity of the outer side thereof is in the range of 1.1-0.5 of that of the inner side and are extruded from the nozzle. Therefore, when they are joined together in the nozzle 22, they are adhered into accurate layers and are foamed out of the nozzle 22 and as foaming is performed at the same density even at the joint of each layer, no layer of foreign substance with low foaming occurs at the joint. |
