Patent ID: 7431872
Filing Date: 2008-10-07
Classification: B27N,B29C,B29K,C08J

Abstract:
1. A process for simultaneously forming a stable cellular wood plastic composite, the composite having an outer layer and an inner layer wherein the inner layer density is lower than the outer layer density and wherein the composite is formed in an extruder, the extruder having a feeding zone 1 , a first metering zone 2 , a venting zone 3 , and a second metering zone 4 ; the process comprising: a. mixing finely ground wood flour with a thermoplastic material at a temperature between about 325 and 350° F. (163 and 177° C.) in the feeding zone b. metering the plasticated mixture in the first metering zone c. introducing a physical blowing agent into the plasticated mixture in the venting zone d. metering the plasticated mixture of venting zone e. reducing the pressure prior to removing the plasticated mixture from the extruder.