Patent ID: 6773656
Filing Date: 2004-08-10
Classification: B29C,B29K,B29L,Y10S,Y10T

Abstract:
A method for producing blow moldings, which comprises preparing a crystalline resin melt parison in the space of a blow mold, clamping the mold, and introducing a pressure fluid into the parison to blow and tightly press the parison against the inner wall of the mold, thereby solidifying the parison along the wall; the method being characterized in that the temperature of the inner wall of the mold is so controlled that it falls between a temperature lower by 20Â° C. than the crystallization temperature of the crystalline resin and a temperature below the temperature lower by 5Â° C. than the melting point of the crystalline resin, while the parison is prepared in the mold, and that, after the mold has been clamped to pinch the parison therein, a pressure fluid is introduced into the thus-pinched parison, then the mold with the parison therein is so heated that the temperature of its inner wall falls between a temperature lower by 10Â° C. than the melting point of the crystalline resin and a temperature below the melting point of the crystalline resin, the parison is kept in the mold at the controlled temperature falling between a temperature lower by 10Â° C. than the melting point of the crystalline resin and a temperature below the melting point of the crystalline resin for a satisfactory period of time enough for the thus blow-molded article of the parison to have a surface hardness of not lower than the level of HB in terms of the pencil hardness measured in a pencil scratch test, and finally the mold is cooled and the blow-molded article is released from the mold.