초록 ▼

A method for making closures resembling natural cork for sealing liquid product containers is described. A strand of expandable plastic material is injected into each mold cavity and is permitted to collect in that cavity in randomly oriented groups of coils which expand to fill the cavity and coale

A method for making closures resembling natural cork for sealing liquid product containers is described. A strand of expandable plastic material is injected into each mold cavity and is permitted to collect in that cavity in randomly oriented groups of coils which expand to fill the cavity and coalesce to create randomly oriented grain lines on the surface of the closure resembling the appearance of natural cork. Also described are methods of molding the closures which preclude the formation of leakage channels on the closure surface and preferred blends of plastic resins and pigment particles used to achieve the cork-like appearance.

대표청구항 ▼

A method for making a closure made of a thermoplastic resinous material and having a natural cork-like appearance which comprises, providing a mold cavity with an entrance orifice, said mold cavity having the shape of said closure with predetermined internal dimensions, the wall of said mold cavity

A method for making a closure made of a thermoplastic resinous material and having a natural cork-like appearance which comprises, providing a mold cavity with an entrance orifice, said mold cavity having the shape of said closure with predetermined internal dimensions, the wall of said mold cavity opposite the entrance orifice being sufficiently spaced from said entrance orifice to permit the formation of a strand of thermoplastic resinous material therein, rapidly injection, at high pressure an expandable thermoplastic resinous material in an amount less than that required to fill the mold cavity and in the form of a strand, into said mold cavity, said strand collecting in said cavity as randomly-oriented coils, the pressure produced in said mold cavity by said injection temporarily pressurizing said cavity, thereby retarding the expansion of the thermoplastic resinous material sufficiently to allow completion of the injection of said thermoplastic resinous material, while maintaining the integrity of the strand configuration, simultaneously with said temporary pressurization, gradually removing a portion of the air displaced by said injected thermoplastic resinous material through controlled minimum venting of said mold cavity, thereby expanding the coiled resinous material in a controlled manner through a continuation of said minimum venting to fill said mold cavity, the walls of said mold cavity being maintained at a temperature sufficiently cool to cause the resinous material to solidify into a rigid, outer skin when it contacts said walls, whereby the coalesence of said coils during expansion creates randomly-oriented grain lines in the surface of said closure which resembles the appearance of natural cork. The product formed by the process of claims 1, 2 or 21.