Composite molding tools and parts and processes of forming...

Details Composite molding tools and parts and processes of forming... Composite molding tools and parts and processes of forming...

1999-08-13

2001-10-30

Mackey, James P. (Department: 1722)

Plastic and nonmetallic article shaping or treating: processes

Direct application of fluid pressure differential to...

Producing multilayer work or article

C249S080000, C249S114100, C249S134000, C264S219000, C264S225000, C264S571000

Reexamination Certificate

active

06309587

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a composite molding tool, and a process of forming a tool and, more particularly, to a high metallic composite molding tool and composite parts formed by compression.
2. Discussion of the Related Art
Generally, plastic molding tools are known in the art and can be used to produce, for example, automobile parts. It has also been recognized that the use of metal or metal radiating wires within the molding tool composition increases heat conduction from within the tool during a molding process. See, e.g., U.S. Pat. Nos. 4,105,184 and 4,980,112, hereby incorporated by reference. These patents do not, however, teach the use of pressure to compress the plastic and metal content, thereby maximizing the use of metal and minimizing the use of plastic to accomplish more uniform, efficient heat conduction throughout the molding tool. Moreover, U.S. Pat. No. 4,105,184 discloses the use of radiating wires, resulting in an uneven distribution of the wire and little thermal conductivity. Therefore, there also does not exist a process for forming a molding tool under high pressure that has an increased dense metallic content as compared to the resin content, resulting in a tool having an improved thermal and electrical conductivity.
There thus exists a need in the art to provide a composite molding tool and process of making a tool which has a high metal density and heat capacity. This is done in the present invention by forming the tool under increased pressure and temperature and by utilizing preselected forms and quantities of metal content.
SUMMARY OF THE INVENTION
The present invention provides a composite molding tool for molding thermoplastic and thermoset resins into, for example, automobile parts. The completed molding tool comprises a surface coat that includes metal powders and mineral fillers, and a composition comprising a resin mixture and metallic fillers, the composition including at least about 45% metallic fillers, based on the weight percent of the total composition.
The present invention also provides a composite part comprising a composition that includes a resin mixture and metallic fillers, where the composition includes at least about 45% metallic fillers, based on the weight percent of the total composition.
The present invention further provides a process of forming such composite molding tools comprising applying at least one layer of a surface coating mixture to a model, producing a surface coat. At least one layer of metal wool saturated in a resin coating mixture is then applied to the surface coat, producing a metal wool/resin mixture layer. Pressure, such as by a vacuum bag system, is also applied to the metal wool/resin mixture layer, compressing the layer and drawing out excess resin mixture and air pockets.
The present invention further provides a process of forming composite molding tools comprising providing a model having a surface for forming the composite molding tools, and applying a surface coating mixture layer to the model, producing a surface coat. A second coating of surface coating mixture is applied to the surface coat, and at least one layer of metal wool saturated in the resin coating mixture is applied to the second coating of surface coating mixture, producing a metal wool/resin mixture layer.
The process also includes applying pressure, such as with a vacuum bag system at room temperature, to the metal wool/resin mixture layer, compressing the metal wool/resin mixture layers and drawing out excess resin mixture and any voids or air pockets. In one embodiment, the composite molding tool is then placed in an autoclave, where further pressure is applied to compress the wool/resin mixture layer. Autoclaving is generally employed where the molding tool requires increased density, such as molding tools for injection molding, blow molding, and compression molding. The vacuum bag system is then removed, exposing a back surface of the molding tool, and a cooling system comprising copper tubing is fitted to the back surface. At least one layer of a conductive aluminum slurry mixture is then applied to the copper tubing system.
A chase or perimeter wall is constructed and attached to the back surface, where the chase is cross-braced with an eggcrate structure within the perimeter of the chase. The eggcrate structure is made of plywood, welded aluminum sheet, steel sheet, composite board, aluminum/epoxy cell panel or cast aluminum armature. Finally, the back surface and eggcrates are filled with a resin mixture, resulting in one half of the composite molding tool being formed. A second half of said composite molding tool is constructed, for example, by repeating each of these steps. Alternatively, the corresponding halves may be different shapes and sizes from one another depending on the part being molded and the process being employed.


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