Co-extrusion process for making decorative moldings having simulated wood appearance and decorative molding made thereby

Abstract

A co-extrusion process for making decorative moldings having a simulated wood appearance and a given profile includes mixing a base material and color particles to form a mixture, the base material having a rigid polymer and the color particles having a different color from the base material and a higher melt temperature than the base material. The mixture is heated and displaced using a feed screw such that the color particles move helically along the trajectory of the feed screw while avoiding backflow and melting to create corresponding helical vein segments within the base material. The mixture is forced through a tubular channel while controlling heat and shear conditions such that the helical vein segments remain substantially intact. The mixture is fed into a die having at least a first tubular inlet communicating with the tubular channel, a first outlet having a planar shape corresponding to the given profile, and a first cavity between the inlet and the outlet, the cavity having a form to flatten and widen the mixture to produce a planar surface coating at the outlet wherein the helical vein segments are transposed into two-dimensional nested arches simulating wood appearance. The surface coating is extruded onto a first side of a core having cellular polymer material, producing the decorative mouldings.