Patent ID: 8221663

Claim:
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.