Cationic wet strength resin modified pigments in water-based latex coating applications
View Patent ↗Methods for improving one or more surface properties of a sheet of paper or paperboard, which method comprises (a) coating at least one side of the sheet of paper or paperboard with a dispersion having a cationic zeta potential formed by combining (1) a mixture containing one or more anionic pigments with (2) one or more polyamine-epihalohydrin cationic wet strength resins at a coating weight of from about 0.1 g/m 2 to about 20 g/m 2 ; (b) drying the coated sheet of paper or paperboard; (c) applying a functional barrier top coating that resists one or more of the following: liquid water, water vapor, gas permeability, oil and grease, slip, and static or an anionic latex based pigment coating that imparts improved opacity, brightness, or printability. The invention also includes the dispersions as well as paper or paperboard coated with the dispersion.
1. A method of coating a sheet of paper or paperboard, comprising:
(a) coating at least one side of the sheet of paper or paperboard with a dispersion wherein the dispersion has an overall cationic zeta potential comprising (1) an anionic kaolin clay and/or an anionic talc in an amount of at least about 20% dry weight of the dispersion, and (b) one or more polyaminopolyamide-epihalohydrin resins, wherein the weight ratio of polyaminopolyamide-epihalohydrin resin to anionic clay or talc is from about 0.03:1 to about 0.2:1 and wherein the sheet is coated at a coating weight of from about 0.1 g/m 2 to about 20 g/m 2 ; and
(b) drying the coated sheet of paper or paperboard.
2. The method claimed in claim 1 further comprising:
coating the dried sheet of paper or paperboard with a functional barrier top coating formulated to provide resistance to one or more of the following (1) liquid water, (2) water vapor, (3) oil, (4) grease, (5) gas permeability, (6) skid, or (7) static.
3. The method of claim 2 where the functional barrier top coating contains a water based polymer latex and optionally contains one or more of the following: (1) a natural or synthetic water soluble polymer, (2) a pigment, (3) a wax, (4) a cross-linker, and (5) a sizing agent.
4. The method of claim 3 wherein one or more of the natural or synthetic water soluble polymers is selected from the group consisting of: starch; ethylated starch; oxidized starch; enzyme converted starch; succinic anhydride modified starch; polyvinylalcohol; ethylene/vinylalcohol copolymers; or polylactic acid.
5. The method of claim 2 , wherein the functional barrier top coating is applied at a coating weight of not more than about 25 g/m 2 .
6. The method claimed in claim 1 further comprising coating the dried sheet of paper or paperboard with a water based pigment coating.
7. The method claimed in claim 6 wherein said water based pigment coating comprises an anionic polymeric latex binder and at least one pigment.
8. The method of claim 1 wherein a water soluble binder comprises up to about 80% dry weight of said dispersion, and said binder is selected from the group consisting of: neutral natural water soluble polymer binders; cationic natural water soluble polymer binders; neutral synthetic water soluble polymer binders; and cationic synthetic polymer binders.
9. The method of claim 8 wherein the water soluble polymer binder is one or more of the group consisting of: starch; ethylated starch; cationic starch; oxidized starch; enzyme converted starch; alginates; casein; cellulose derivatives; polyvinyl alcohol; ethylene/vinyl alcohol copolymers; polyvinyl amine; polyacrylamide; polyacrylamide copolymers; glyoxylated polyacrylamide; polydiallylamine; polydiallylamine copolymers; polydimethyldiallylamine; and polydimethyldiallylamine copolymers.
10. The method of claim 9 wherein the cellulose derivative is one or more of the group consisting of hydroxyethylcellulose; methylhydroxyethylcellulose; methyl cellulose; hydroxypropyl cellulose; and hydroxypropylguar.
11. The method of claim 1 wherein said dispersion is at least about 25% dry weight of the dispersion of either anionic kaolin clay or anionic talc.
12. The method of claim 1 wherein said dispersion is at least about 50% dry weight of the dispersion of either anionic kaolin clay or anionic talc.