Repulpable, water repellant paperboard
AssigneeInternational Paper Company
InventorsArnold L. Berzins, Tung C. Ma, Charles J. Davis
Life of this patent
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Abstract
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.
Claims13
A water-repellant paperboard comprising a fibrous web having a coating consisting essentially of:
- a wax component selected from the group consisting of paraffin wax and polyethylene wax emulsions and mixtures thereof;
- and
- a polymer matrix of polymer chains comprising a polystyrene-butadiene polymer copolymerized with a monomer having pendant carboxylic acid groups;
- wherein said pendant carboxylic acid groups of said polymer chains are cross-linked by a zinc ion ionically bonded between carboxylic acid groups of adjacent polymer chains.
A coating formulation for application to a surface of a paperboard to provide a water-repellant coating which consists essentially of:
- a carboxylated polymer comprising a polystyrene-butadiene polymer copolymerized with a monomer having carboxylic acid pendant groups;
- a wax component selected from the group consisting of paraffin wax and polyethylene wax emulsions and mixtures thereof;
- and
- a cross-linking agent which provides zinc ions;
- wherein said cross-linking agent reacts with said polymer to provide ionic cross-linking between the carboxylic acid groups of the carboxylated polymer to create an ionically cross-linked polymer matrix in the resulting coating.
A corrugated board which comprises:
- fluting having a first side and a second side;
- a first linerboard having an inner surface adjacent to, facing and adhered to said first side of said fluting and an outer surface opposite said inner surface;
- a second linerboard having an inner surface adjacent to, facing and adhered to said second side of said fluting and an outer surface opposite said inner surface;
- and
- at least one of said outer surfaces of said first or second linerboard having a coating thereon which consists essentially of a wax component selected from the group consisting of paraffin wax and polyethylene wax emulsions and mixtures thereof;
- in a polymer matrix of polymer chains comprising a polystyrene-butadiene polymer copolymerized with a monomer having pendant carboxylic acid groups;
- wherein said pendant carboxylic acid groups of said polymer chains are cross-linked by a zinc ion ionically bonded between carboxylic acid groups of adjacent polymer chains;
- wherein the corrugated board exhibits improved repulpability and resistance to blocking.
A method of making a water-repellant fibrous web which comprises:
- providing a fibrous web having a surface to be made water-repellant;
- applying to the surface of the web an aqueous coating which consists essentially of a carboxylated polymer comprising a polystyrene-butadiene polymer copolymerized with a monomer having carboxylic acid pendant groups, a wax component selected from the group consisting of paraffin wax and polyethylene wax emulsions and mixtures thereof and a cross-linking agent which provides zinc ions;
- and
- reacting the cross-linking agent with the carboxylic acid groups of the polymer to cause the formation of ionic cross-linkages between the carboxylic acid groups of adjacent polymer chains and provide a substantially solid water-repellant coating on the surface of the web.
Dependencies are inferred from the claim text.