Patent ID: 6124426
Filing Date: 2000-09-26
Classification: C08F

Abstract:
A method for removing volatile materials from a polymer composition containing 2% by weight or less of the volatile materials, comprising the steps of:forming a molten flow of said polymer composition;combining the molten polymer composition with a blowing aid by discharging the blowing aid from an addition nozzle apparatus into the molten polymer composition in a direction opposing the direction of flow of the molten polymer composition;introducing the polymer composition and the blowing aid into a static mixing apparatus to mix the polymer composition and blowing aid therein, the mixing being conducted at a temperature higher than the vaporization temperature of the blowing aid at a normal pressure but lower than the decomposition temperature of the polymer and at a pressure higher than the vapor pressure of the blowing aid so that blowing does not take place and a resultant mixture is formed;introducing the resultant mixture into an extruding apparatus and extruding it therein to form an extruded mixture;discharging the extruded mixture out of a downwardly facing opening member of the extruding apparatus into a devolatilizing tank where the mixture is blown at such a temperature and pressure that a blowing coefficient B given by the following expression (1) is at least 1.4 to form a blown product of the polymer composition from which the volatile materials have been removed and the blowing aid released,B=A'/A (1)wherein A is the cross-sectional area of the opening member of the extruding apparatus and A' is the average cross-sectional area of the polymer composition in a direction perpendicular to the vertical direction of the blown polymer composition at a point where the polymer composition is dropped from said opening member vertically 50 cm to 1 m.