The actual process of extrusion coating involves extruding resin from a slot die at temperatures up to 320°C directly onto the moving web which may then passed through a nip consisting of a rubber covered pressure roller and a chrome plated cooling roll. The latter cools the molten film back into the solid state and also imparts the desired finish to the plastic surface. The web is normally run much faster than the speed at which the resin is extruded from the die, creating a coating thickness which is in proportion to the speed ratio and the slot gap.[2][3][4]
Laminating
Extrusion laminating is a similar process except that the extruded hot molten resin acts as the bonding medium to a second web of material.
Co-extrusion
Co-extrusion is, again, a similar process but with two, or more, extruders coupled to a single die head in which the individually extruded melts are brought together and finally extruded as a multi-layer film.
Uses
The market for extrusion coating includes a variety of end-use applications such as liquid packaging, photographic, flexible packaging, mill and industrial wrappings, transport packaging, sack linings, building, envelopes, medical/hygiene, and release base.
^US 6336988, Enlow, Howard H.; McCready, Russell J. & Roys, John E. et al., "Extrusion coating process for making protective and decorative films", published 2002-01-08, assigned to Avery Dennison Corp.
^US 2714571, Irion, Clarence E. & Prindle, Karl E., "Process for bonding a polyethylene film to a fibrous web", published 1955-08-02, assigned to Dobeckmun Co.
