Patent ID: 6113981
Filing Date: 2000-09-05
Classification: C08G,D21H

Abstract:
A continuous process for forming a polyester film on a surface of a web of paperboard with a polyester polymer in an aqueous dispersion so as to lower the moisture vapor transfer rate of the paperboard and form a moisture barrier to the paperboard with a coating apparatus with a series of rollers for moving and conditioning the web comprising the following steps in sequence:(a) flame-treating the surface of the paperboard to be coated to remove substantially all of any surface debris and fibers on said surface and to reduce the moisture content to an acceptable limit;(b) heating the paperboard for a sufficient time and temperature to reduce the moisture content to the desired level;(c) applying an aqueous dispersion with a water-dispersible polyester resin to said surface of the paperboard utilizing an application roller, and then distributing the aqueous dispersion across the paperboard with a jet of air from an air-knife so as to remove any excess dispersion across the paperboard with the jet of air from the air-knife so as to form a uniform layer of the aqueous dispersion across the paperboard and to remove any excess dispersion deposited by the roller;(d) heating said paperboard to a temperature and for a time sufficient to at least partially cure said polyester;(e) cooling the paperboard to at least a 160.degree. F. to reduce the tackiness of said at least partially cured polyester;the temperatures, times and application of the polyester polymer and its distribution being controlled so as to deposit a film of the polyester on the paperboard that is at least partially cured so as to permit the subsequent repulping of the paperboard, and recycling of the paperboard into recycled paper products that can be readily glued and printed.