Method for rotational molding
OwnerWilliam E. Mastersinventor
Life of this patent
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Abstract
A method for rotational molding a thermoplastic article using a mold made of a fiber reinforced thermoset resin which has a heat distortion point above the melting point of the thermoplastic material. Metal or other materials may be used to provide different coefficients of heat transfer at preselected portions of the mold. The entire mold may include a thermal coefficient modifier to increase the heat transfer rate of the mold uniformly over the entire mold in addition to the preselected portions.
Claims13
In a rotational molding process for molding an article from a thermoplastic material which includes rotating a mold containing said thermoplastic material bi-axially to distribute the material in the mold, heating the mold to fuse the thermoplastic material together against an inner surface of the mold, and cooling the mold and removing the article wherein the improvement comprises:
- (a) utilizing a thermoset mold constructed from a thermoset plastic material;
- (b) loading a thermoplastic material in said thermoset mold to form said article being molded;
- (c) heating said thermoset mold and thermoplastic material to a temperature in a range of 300 to 500 degrees F., and a temperature below a heat distortion point of said thermoset mold and above a melt point of said thermoplastic material to cure said thermoplastic material without distorting the thermoset mold;
- and
- (d) including heat conductive modifiers in said thermoset mold to compensate for a low rate of heat transfer in said thermoset material.
In a rotational molding process for molding an article from a thermoplastic material which includes rotating a mold containing said thermoplastic material bi-axially to distribute the material in the mold, heating the mold to fuse the thermoplastic material together against an inner surface of the mold, and cooling the mold and removing the article wherein the improvement comprises:
- (a) utilizing a thermoset mold constructed from a thermoset plastic material;
- (b) loading a thermoplastic material in said thermoset mold to form said article being molded;
- (c) heating said thermoset mold and thermoplastic material to a temperature in a range of 300 to 500 degrees F., and a temperature below a heat distortion point of said thermoset mold and above a melt point of said thermoplastic material to cure said thermoplastic material without distorting the thermoset mold;
- (d) including a first heat transfer modifying material in said thermoset mold to increase the overall heat transfer rate of said thermoset mold;
- and
- (e) including a second heat transfer modifying material at preselected portions of said thermoset mold to increase the heat transfer heat rate of said preselected portions to provide a preselected thickness profile for the article being molded.
Dependencies are inferred from the claim text.