Process for making a wood-thermoplastic composite

In 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, the improvement comprising:

• (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.

A method for making a dimensionally stable wood-thermoplastic composite material composed of a wood component and a thermoplastic component comprising the steps of:

• (a) forming a wood-thermoplastic mass, the mass being at a temperature above melting temperature of the thermoplastic component;
• (b) passing the mass through a converging die having an exit end to form a shaped extrudate profile having a cross sectional shape;
• (c) feeding the profile through a low friction thermally insulating land section, the land section having the substantially the same cross sectional shape as the converging die exit end;
• and
• (d) quenching the profile in a non-oxidizing environment to form a composite material.

A method for making a dimensionally stable wood-thermoplastic composite material composed of a wood component and a thermoplastic component comprising the steps of:

• (a) forming a wood-thermoplastic mass, the mass being at a temperature above melting temperature of the thermoplastic component;
• (b) passing the mass through converting die having an exit end to form a shaped extrudate profile having a cross sectional shape;
• (c) feeding the profile through a low friction thermally insulating land section, the land section having substantially the same cross sectional shape as the converging die exit end;
• and
• (d) quenching the profile in a non-oxidizing environment to form a composite material having a substantially dimensionally stable outer shell.

A method for making a dimensionally stable wood-thermoplastic composite material composed of a wood component and a thermoplastic component comprising the steps of:

• (a) forming a wood-thermoplastic mass, the mass being at a temperature above melting temperature of the thermoplastic component;
• (b) passing the mass through a converging die having an exit end to form a shaped extrudate profile having a cross sectional shape;
• (c) feeding the profile through a low friction thermally insulating land section, the land section having the substantially the same cross sectional shape as the converging die exit end;
• and
• (d) quenching the profile in a non-oxidizing environment to form a composite material having a substantially dimensionally stable outer shell.