Patent ID: 6521159
Filing Date: 2003-02-18
Classification: B29B,B29C,B29D,B29K,B32B,B65D,Y10T

Abstract:
A method of injection molding a plastic preform comprising a neck portion, a body portion defining a cylindric wall portion adjacent to said neck portion, and a bottom portion adjacent to said body portion opposite said neck portion, wherein at least said cylindrical wall and a portion of said bottom portion comprise an outer layer, an inner layer and an intermediate layer between said outer layer and said inner layer, said method comprising the steps of:a) initiating a flow of a first material into a preform mold cavity at a first injection pressure to form at least one of said inner layer and said outer layer; b) initiating a flow of a second material into the preform mold cavity at a second injection pressure to form said intermediate layer, c) reducing said first injection pressure to a packing pressure; and d) maintaining said second injection pressure while the first injection pressure is reduced to the packing pressure.