초록 ▼

Method and apparatus for injection molding plastic articles having solid exterior surfaces and porous interior cores wherein a molten mixture of a chemically reactive foaming agent and a thermoplastic resin is injected into a mold so as to fill the mold cavity with unfoamed resin and form an outer s

Method and apparatus for injection molding plastic articles having solid exterior surfaces and porous interior cores wherein a molten mixture of a chemically reactive foaming agent and a thermoplastic resin is injected into a mold so as to fill the mold cavity with unfoamed resin and form an outer solid skin on the molded article. Immediately prior to injection, an activator additive is introduced into the mixture, the additive reacting chemically with the foaming agent after a time delay of no more than a few seconds to provide for cellular expansion within the core of the molded article. The result is a molded body with a solid unfoamed skin which accurately relicates the surface of the mold and a cellular inner core.

대표청구항 ▼

The method for producing injection molded plastic articles from a thermoplastic resin comprising: a. melting a thermoplastic resin containing a chemically reactive foaming agent; b. injecting said thermoplastic resin containing said foaming agent as a stream into a mold so as to fill the mold cavity

The method for producing injection molded plastic articles from a thermoplastic resin comprising: a. melting a thermoplastic resin containing a chemically reactive foaming agent; b. injecting said thermoplastic resin containing said foaming agent as a stream into a mold so as to fill the mold cavity with unfoamed molten resin containing the foaming agent; c. introducing an activator additive into said stream immediately prior to injection of said stream into said mold cavity, said material in the mold cavity solidifying on engagement with the mold cavity surface to form a solid skin at the mold surface, said additive chemically reacting with said foaming agent after a time delay in said mold resulting in the generation of gas bubbles in said resin within the confines of said skin whereby to form a molded article having a solid exterior surface which is a detailed replicate of the mold surface and a porous interior which expands in the mold to maintain the solid exterior surface in pressured contact with the mold surface.