Method of press-molding thermoplastic resins

摘要

A thermoplastic resin is molded by a press-molding method wherein a thermoplastic resin in a molten state is compressed to flow between a pair of female and male molds so as to be formed into a predetermined shape. A compression rate of the mold is controlled so that the following expression (1) is satisfied: 0.5 APPROXLESS B/A APPROXLESS 2(1) wherein A (mm/s2) is an acceleration which is realized at a time when the compression rate is 75% of a maximum rate in a compression-acceleration region, which region is defined as a period of time from a moment when the compression of the molten thermoplastic resin is started to a moment when the compression rate reaches the maximum rate; and B (mm/s2) is a deceleration which is realized at a time when the compression rate is 75% of the maximum rate in a compression-deceleration region, which region is defined as a period of time from a moment when the compression rate reaches the maximum rate to a moment when the closing of the molds is complete. By this method, a molded article having excellent surface appearance free from unevenness of gloss and surface irregularity can be obtained.