Method of making cellulosic filled thermoplastic composites of an anhydride containing copolymer

A method of making a foamed cellulosic fiber-thermoplastic composite article comprising:

• A) providing a copolymer composition that includes:
• i) at least about 20 wt. % of a copolymer formed by polymerizing a mixture comprising:
• a) about 51% to about 99.9% by weight of one or more primary monomers,
• b) about 0.1% to about 49% by weight of one or more anhydride containing monomers, and
• c) optionally about 1% to about 25% by weight of one or more other polymerizable monomers;
• and
• ii) optionally about 0.1% to about 30% by weight of one or more elastomeric polymers based on the weight of the copolymer;
• B) combining about 30% to about 99.9% by weight of the copolymer composition with about 0.01% to about 70% by weight of one or more cellulosic fibers based on the weight of the combination;
• C) applying an amount of heat, mixing energy and pressure sufficient to provide:
• i) mixing of the copolymer composition and the cellulosic fibers;
• ii) reaction of anhydride groups in the copolymer with hydroxyl groups in the cellulosic fibers;
• and
• iii) production of a blowing agent as a byproduct of the reaction in ii) to provide a foamable mixture of the copolymer composition and the cellulosic fibers;
• and
• D) forming the foamed article by placing the foamable mixture in a molding or extruding operation;
• wherein the foamed article has a structured foam central portion and micro foamed outer portion that surrounds the structured foam portion and has a higher density than the central portion;
• and
• wherein the micro foamed outer portion comprises from about 5 to about 22 percent of the overall thickness of the article.