Mold for synthetic resin molding

Abstract

It has been conventionally considered difficult to adhere a mold metal and a polyimide, etc. whose coefficients of thermal expansion differ from each other by one figure and to retain the adhesion in injection molding, etc. involving severe heating-cooling cycles over several tens of thousands of times. The greatest merit of injection molding resides in that a molded article of complicated shape can be obtained through one shot. It has been demanded to obtain a mirror-smooth injection molded article with good molding surface reproduction without extending the mold-cooling time while retaining this merit. The present invention provides a mold satisfying both of the durability and the demand. The present invention relates to a mold for synthetic resin molding comprising a mold body made of a metal having a heat conductivity of not less than 0.05 cal/cm.multidot.sec.multidot..degree.C. at room temperature having provided on the cavity wall thereof a polyimide layer, characterized in that said polyimide layer has a thickness of from 0.02 to 2 mm, has a heat conductivity of not more than 0.002 cal/cm.multidot.sec.multidot..degree.C., has a glass transition temperature of not less than 200.degree. C., has been formed by coating a solution of a precursor of a linear high-molecular weight polyimide on the cavity wall followed by heating, has an elongation at break of not less than 10%, and has an adhesive strength of not less than 500 g/10 mm to the cavity wall.

Dependencies are inferred from the claim text.