Abstract: A mold for injection molding of a thermoplastic resin. The mold comprises a cavity block, a core block, and a cavity formed between the cavity block and the core block and adapted to be filled with a molten resin. The cavity block includes an insulating layer on a cavity side thereof, the insulating layer being made of a material selected from the group consisting of ceramic materials, porcelain enamel, glass materials, heat resistant plastic materials and their composites. The core block includes a release insulating layer on a cavity side thereof, the release insulating layer being made of a material selected from the group consisting of fluorocarbon resins, fluorocarbon resin composite materials, silicone resin composite materials and metal platings with fluorocarbon resin dispersion, the release insulating layer further being adapted to effect both mold releasing and heat insulation.

Abstract: An insulated metal mold having a molding surface defining the cavity of a mold for molding thermoplastic resin. To regulate the cooling speed of the molten resin to be injected or placed into the cavity, the molding surface is provided by a thin metal layer and a layer of heat insulating material is formed on the inner side of the metal layer.