Patent ID: 8323545

Claim:
A co-extrusion process for making decorative moldings having a simulated wood appearance and a given profile, comprising: mixing a base material and colour particles to form a mixture, the base material comprising rigid polymer and the colour particles having a different colour from the base material and a higher melt temperature than the base material; heating and displacing the mixture using a feed screw such that the colour particles move helically along the trajectory of the feed screw while avoiding backflow and melting to thereby create corresponding helical vein segments within the base material; forcing the mixture through a tubular channel while controlling heat and shear conditions such that the helical vein segments remain substantially intact; feeding the mixture 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 in 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; and co-extruding the surface coating onto a first side of a core comprising cellular polymer material, thereby producing the decorative mouldings; wherein a fraction of the color particles are sized and selected such that the color particles partially melt to form partially melted helical vein segments each of the partially melted helical vein segments having a head end and a tail end, thereby leaving a residual nodule of the color particle at each head end.