Importance

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Abstract

The method of the present invention includes mixing a low viscosity thermoset resin and microspheres together without melting the thermoset resin and extruding the mixture to form a continuous strand of paste-like uncured material. The continuous strand is gelled on a conveyor which preferably includes a radiant heater or other means for accelerating the gelling of the continuous strands into solid form. The strands are then cut or chopped into pellet form and may be coated with an adhesive or B-staged material in preparation for forming into structural reinforcements. The pellets are filled with microspheres in the amount of 20 to 35% of resin weight. The pellets may include unexpanded thermally expandable microspheres which permit expansion of the pellets when exposed to heat to provide a pellet having a bulk density as low as 9 pounds per cubic foot. The pellets may be formed of a thermoset resin such as a polyester resin or epoxy resin, vinylester resin, polyurethane resin, or phenolic resin and may include organic, inorganic or glass pre-expanded microspheres. Alternatively, the pellets may include unexpanded thermally expandable thermoplastic microspheres or a liquid blowing agent if expansion of the pellets is desired. A cure aid or curing agent may be included in the pellet mix to facilitate curing of the pellet in the final reinforcement and other additives may be incorporated in the pellet mix to improve extrudability or other properties of the pellets.

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First Claim