Paper coating formulation

Abstract

The present invention relates to a laminate comprising coated or uncoated paperboard coated with a film that comprises a polymeric binder, TiO 2 , and tetrapotassium pyrophosphate. Paper or paperboard coated with a film containing tetrapotassium pyrophosphate shows excellent optical properties.

1 . A laminate comprising coated or uncoated paperboard; and a 5- to 35-μm thick layer of a film adhered to the coated or uncoated paper or paperboard; wherein the film comprises a) from 3 to 25 weight percent of a polymeric binder; b) from 5 to 35 weight percent TiO 2 ; and
 c) from 0.05 to 2 weight percent tetrapotassium pyrophosphate; wherein the polymeric binder comprises vinyl acetate, vinyl-acrylic, styrene-acrylic, or styrene-butadiene polymer, and blends thereof; and wherein the weight percentages are all based on the weight of the film. 
 
     
     
         2 . The laminate of  claim 1  wherein the polymeric binder contains less than 0.05 weight percent of phosphate and phosphonate groups, based on the weight of the binder. 
     
     
         3 . The laminate of  claim 2  wherein the concentration of tetrapotassium pyrophosphate is from 0.1 to 0.8 weight percent, based on the weight of total solids in the film. 
     
     
         4 . The laminate of Claim  1  wherein the film further includes a clay or calcium carbonate or both. 
     
     
         5 . The laminate of  claim 1  wherein the binder is a vinyl acetate polymer. 
     
     
         6 . The laminate of  claim 1  wherein the binder is a styrene-acrylic polymer. 
     
     
         7 . The laminate of  claim 1  wherein the binder is a styrene-butadiene. 
     
     
         8 . The laminate of  claim 1  wherein the film comprises one or more additives selected from the group consisting of rheology modifiers; hollow sphere pigments; natural binders; optical brightening agents; lubricants; antifoamers; crosslinkers; and polyacrylic acid. 
     
     
         9 . A method comprising the step of applying a 5- to 35-μm thick layer of a composition to paper or paperboard, wherein the composition comprises an aqueous dispersion of a) from 3 to 25 weight percent polymeric binder particles; b) from 5 to 35 weight percent TiO 2 ; and
 c) from 0.05 to 2 weight percent of tetrapotassium pyrophosphate; wherein the polymeric binder particles comprise vinyl acetate, vinyl-acrylic, styrene-acrylic, or styrene-butadiene polymer particles and blends thereof; and wherein the weight percentages are all based on the weight of total solids of the composition.