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The invention relates to a method for making a dimensionally stable wood-thermoplastic composite material composed of a wood component and a thermoplastic component comprising the steps of forming a wood-thermoplastic mass at a temperature above the melting temperature of the thermoplastic component

The invention relates to a method for making a dimensionally stable wood-thermoplastic composite material composed of a wood component and a thermoplastic component comprising the steps of forming a wood-thermoplastic mass at a temperature above the melting temperature of the thermoplastic component. The mass is then passed through a converging die to form a shaped extrudate profile having a cross sectional shape wherein at least a part of the converging die is maintained at a substantially higher temperature than that of the mass. The profile is then fed through a low friction thermally insulating land section, the land section having the substantially the same cross sectional shape as the exit end of the converging die. The profile is then quenched in a non-oxidizing environment to form a substantially dimensionally stable outer shell around the profile, the shell having a temperature below the melting temperature of the thermoplastic component. The invention also relates to a die assembly for making a wood-thermoplastic composite material.

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[ What is claimed is:] [1.] A method for forming an extruded composite product containing cellulosic particles in a thermoplastic binder wherein an extrusion mass is forced through a die at an elevated extrusion temperature to form a hot shaped extrudate and cooled thereafter, said method including

[ What is claimed is:] [1.] A method for forming an extruded composite product containing cellulosic particles in a thermoplastic binder wherein an extrusion mass is forced through a die at an elevated extrusion temperature to form a hot shaped extrudate and cooled thereafter, said method including the steps of:(a) heating the extrusion mass in a die means to a first temperature sufficient to decrease the shear stresses generated between the mass and the die means to form a hot shaped extrudate profile;(b) passing the profile from the die through an intermediate temperature zone wherein the extrudate surface is thermally insulated from exterior cooling; and(c) quenching the profile directly in a non-oxidizing fluid to a second temperature thereby setting the composite surface to form the composite product.