METHOD FOR PRODUCING MULTI-LAYER FOAMED SHEET

摘要

PURPOSE: Provided is a method for producing a multi-layer foamed sheet consisting of a structure having plural layers by means of a circular die coextrusion method. The method controls the shear stress at a layer interface in a die and stabilizes a layer structure, whereby providing a multi-layer foamed sheet having a satisfactory layer structure from various raw resins under various processing conditions. CONSTITUTION: The method for producing a multi-layer foamed sheet having foam layers and non-foam layers by a multi-layer circular die coextrusion method is characterized in that the shear stress at the interface of each layer is 5000 Pa or higher and not higher than 50000 Pa. Also, the resin of the non-foam layer is a linear propylenic resin having a melt flow rate of 5 to 30 g/10 minutes. In a method for producing a multi-layer foamed sheet, the resin of said foam layer is a propylenic resin whose melt tension (MT) at 190 C. and melt flow rate (MFR) at 230 C. satisfy the following equation A: MT>=7.52xMFR(-0.576).