Patent ID: 6936200

Claim:
A process for producing plastic/wood fiber composite foamed structures comprising the steps of: pre-drying wood fiber filler having a degradation temperature and an active volatization temperature and maintaining the pre-drying temperature below the degradation temperature to produce dried wood fiber filler; mixing the dried wood fiber filler with plastic to produce a plastic/wood fiber mixture and maintaining the mixing temperature below the active volatilizing temperature; feeding the plastic/wood fiber mixture into an extruder and maintaining the temperature of the plastic/wood fiber mixture below the active volatilizing temperature; introducing a blowing agent into the plastic/wood fiber mixture and mixing it therewith to produce a plastic/wood fiber/gas mixture and maintaining the temperature of the plastic/wood fiber/gas mixture below the active volatilizing temperature; subjecting the plastic/wood fiber/gas mixture to high shear forces in the presence of high pressures and maintaining a processing temperature below the active volatilizing temperature; and extruding the plastic/wood fiber/gas mixture to produce a plastic/wood fiber composite foamed structure and maintaining the temperature of the plastic/wood fiber/gas mixture below the active volatilizing temperature.