Weyerhaeuser Company Limited

Timnit Ghermay

Jack G Winterowd

David W Park

Roland E Kreibich

Roger M Shantz

J Harry Wirz

Charles C Childress

A method of producing a surfaced composite panel of cellulosic particulates, such as wood flakes, involves the application of polymer forming foamable material to at least one of the first and second major surfaces of the panel, contacting said at least one of the first and second surfaces with a pressure applying surface to apply pressure thereto, foaming the polymer forming foamable material while pressure is applied and curing the applied foam material to produce a polymeric coating on the panel with the desired surface, which is typically extremely smooth. One or both surfaces may be surface treated in this manner. A skin formed on the surface of the panel is believed to add to the strength and stiffness of the coating on the panel. A wide variety of foaming systems may be used to accomplish this surface treating. By avoiding sanding the surface treated panel, the skin remains intact. The resulting panel, in addition to being extremely smooth as desired, resists water penetration when subjected to water or high humidity conditions. The resulting panel is receptive to adhesives for purposes of securing overlaying materials such as vinyl, reduces formaldehyde emissions when a panel formed of the resin which emits formaldehydes is surface treated.

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Seattle, WA, United States of America

Timnit Ghermay