International Paper Company

Tung C Ma

Charles J Davis

Arnold L Berzins

Bruce T Watson

Robert L Gordon

Linda A Bernstein

Robert Sosnowksi

Paperboard having a water-repellant coating which includes a polymer matrix/wax/pigment mixture and is applied to the paperboard as an aqueous formulation. The polymer matrix includes polymer chains which are ionically cross-linked through pendant carboxylic acid groups to provide, together with the wax and pigment components, a substantially continuous, water-repellant film which more readily breaks down under the alkaline conditions of repulping. The coated board also exhibits low slip and resistance to blocking, and is particularly well-suited in corrugated box constructions used in shipping containers for perishable food items such as meats, poultry, fishery products, fruits and vegetables. The pigmented or unpigmented coating formulations are also used as an overcoat over preprinted paperboard surfaces to simultaneously provide scuff and water resistance.

Repulpable, water repellant paperboard

The specification discloses paperboard having a water-repellant coating which includes a polymer matrix/wax mixture and is applied to the paperboard as an aqueous formulation. The polymer matrix includes polymer chains which are ionically cross-linked through pendant carboxylic acid groups to provide, together with the wax, a substantially continuous, water-repellant film which more readily breaks down under the alkaline conditions of repulping. The coated board also exhibits improved release characteristics and resistance to blocking, and is particularly well-suited in corrugated box constructions used in shipping containers for perishable food items such as meats, poultry, fishery products, fruits and vegetables.

A flanged tray and preform for making it. The preform includes a cut and scored paperboard blank having a polygonal bottom forming base panel. Each edge of the base is foldably joined to a radially outwardly extending, regular trapezoidal sidewall forming panel. The radially outermost portion of each sidewall panel carries a horizontal flange forming flap. The preform also includes a thin plastic sheet adhered to one surface of the paperboard blank. The plastic sheet covers the blank and extends over radially extending gaps between the side edges of next adjacent sidewall panels. The preform is placed in a female die with the plastic film facing upwardly. A male die presses the preform downwardly to form it into a tray having a peripheral, horizontally extending flange. The step of permanently attaching the plastic film to the paperboard blank may be carried out concurrently with the step of deforming the blank in the die. The plastic film secures the sidewalls together and provides a liquid impervious coating on the tray interior surfaces. The tray may be provided with a paperboard lid having a tear off portion. The tray and lid exhibit utility for the packaging of foods. A layer of polymer barrier film is sealed over the formed tray to provide barriers to oxygen and water vapor. In a modification, integral gussets are provided between next adjacent side edges of the sidewalls.

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Fort Lee, NJ, United States of America

Tung C Ma