Du Pont of Canada Limited

James F Pilgrim

Ronald A Hunter

An improved process for coating sheet substrates with thermoplastic polymer is disclosed. In the process the sheet substrate forms one die lip of the extrusion coating die. The sheet substrate is passed from face-to-face contact with the metal block of the extrusion coating die into a spaced apart relationship with one die lip of the extrusion coating die, the sheet substrate forming the second die lip. Molten thermoplastic polymer is extruded into the space between the one die lip and the sheet substrate, thereby coating the sheet substrate with polymer. The preferred polymer is a poly-.alpha.-olefin, especially polyethylene or a copolymer of ethylene and butene-1. The preferred sheet substrate has orifices in the surfaces thereof. The process may be used to coat sheet substrates with a thermoplastic polymer, e.g. in the manufacture of form boards for the construction industry.

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Elginburg, Canada

James F Pilgrim