Abstract: Smooth surfaced panels e.g. of oriented strand board are prepared by producing a thin uniform mat of high density made from bonded wood particles, fibers or strands. The mat is produced by passing it between a pair of rollers one of which is heated to produce a smooth cured surface on the corresponding side of the mat, and the other of which is unheated, the corresponding side of the mat containing uncured adhesive. The mat is subsequently bonded to a panel, e.g. an oriented strand board core under conditions of heat and pressure to produce a composite panel having a smooth surface.

Abstract: A low cost method of binding lignocellulosic materials utilizing ammonium based spent sulfite liquor alone as the binder. Hot pressing a mat comprising lignocellulosic material and ammonium spent sulfite liquor at a temperature above 170.degree. C. decomposes the spent sulfite liquor. The decomposition products subsequently condense and polymerize in the presence of lignocellulosic materials to produce a composite product. An exterior grade board can be produced under certain operating conditions. Utilizing the lower molecular weight fraction of the liquor provides a more efficient binder.