Browse Prior Art Database

INSULATIVE SHELL STRUCTURE FOAM PROCESS

IP.com Disclosure Number: IPCOM000024999D
Original Publication Date: 1983-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 69K

Publishing Venue

Xerox Disclosure Journal

Abstract

Structural foam can be produced by many subprocesses on different types of equipment. However, it is basically made by injecting a thermoplastic resin in its melted condition with some form of a blowing agent blended into it. This material is injected into a closed mold. The blowing agent produces a foam core in a structure which is sandwiched by a solid skin. The skins have always exhibited a splay-swirl pattern caused by small amounts of blowing agent migrating to the part surface. This pattern must be hidden via the finishing/painting operation to achieve an aesthetically acceptable part. To overcome this problem, a 7 to 20 thousandths of an inch thick plastic sheet material, i.e., cellulose acetate, polycarbonate, etc., thermoformed to the shape of the injection mold cavity is placed in the cavity. The thermoformed plastic sheet is secured adhesively to the cavity.

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IEROX DISCLOSURE JOURNAL

INSULATIVE SHELL STRUCTURE

FOAM PROCESS
P. A. Rodriguez
R. W. Reynolds

Proposed Classification
U.S. Cl. 35513 Int. C1. G03g 15/00

Structural foam can be produced by many subprocesses on different types of equipment. However, it is basically made by injecting a thermoplastic resin in its melted condition with some form of a blowing agent blended into it. This material is injected into a closed mold. The blowing agent produces a foam core in a structure which is sandwiched by a solid skin. The skins have always exhibited a splay-swirl pattern caused by small amounts of blowing agent migrating to the part surface. This pattern must be hidden via the finishing/painting operation to achieve an aesthetically acceptable part. To overcome this problem, a 7 to 20 thousandths of an inch thick plastic sheet material, i.e., cellulose acetate, polycarbonate, etc., thermoformed to the shape of the injection mold cavity is placed in the cavity. The thermoformed plastic sheet is secured adhesively to the cavity. This results in a smooth, glossy surface devoid of surface splay that has not been produced by any previous structural foam molding process. The plastic sheet insulates a thin outer layer of the structural foam melt from the cold mold surface allowing it to flow more easily by reducing turbulance and keeping the foam bubbled in solution longer versus migrating to the surface and producing the undesirable swirl. Thus, the plastic sheet acts as a h...