Paper coating compositions comprising a polymer dispersion from room temperature liquid and gaseous monomers

Abstract

Paper coating compositions comprise inorganic pigments and an aqueous polymeric dispersion comprising dispersed polymeric particles. The polymers are obtainable by polymerization of a first monomer that is liquid at room temperature, has a boiling point of at least 50° C. and a glass transition temperature of at least 20° C. as homopolymer, and a second monomer that is gaseous at room temperature, has a boiling point of below 0° C. and a glass transition temperature of below −30° C. as homopolymer. The dispersed polymeric particles have an average size of below 150 nm and a glass transition temperature in the range from −10 to +30° C.

1 . A paper coating composition, comprising
 (i) at least one inorganic pigment; and   (ii) an aqueous polymeric dispersion comprising dispersed polymeric particles, wherein:   the polymer of the polymeric particles is obtainable by polymerization of
 (a) at least one first monomer that is liquid at room temperature (20° C.), has a boiling point of at least 50° C. and a glass transition temperature of at least 20° C. as homopolymer, and 
 (b) at least one second monomer that is gaseous at room temperature (20° C.), has a boiling point of below 0° C. and a glass transition temperature of below −30° C. as homopolymer; and, 
   the dispersed polymeric particles have an average size of below 150 nm and a glass transition temperature in the range from −10 to +30° C.   
     
     
         2 . The paper coating composition according to  claim 1 , wherein the polymeric particles have an average size of 80 nm to below 150 nm. 
     
     
         3 . The paper coating composition according to  claim 1 , wherein:
 the at least one first monomer (a) is at least one of a vinylaromatic compound and a vinyl ester; and   the at least one second monomer (b) is a mono- or poly-ethylenically unsaturated C2 to C4 hydrocarbon.   
     
     
         4 . The paper coating composition according to  claim 1 , wherein:
 the at least one first monomer (a) is at least one of styrene and vinyl acetate; and   the at least one second monomer (b) is at least one of 1,3-butadiene and ethylene.   
     
     
         5 . The paper coating composition according to  claim 1 , wherein the polymer is selected from the group consisting of a polymer formed from ethylene and vinyl acetate to an extent of at least 60% by weight, a polymer formed from styrene and vinyl acetate to an extent of at least 60% by weight, and mixtures thereof. 
     
     
         6 . The paper coating composition according to  claim 1 , wherein the polymer is formed either from
 (a) 4.8 to 95 parts by weight of styrene or methylstyrene,   (b) 4.8 to 95 parts by weight of butadiene,   (c) 0.1 to 10 parts by weight of at least one ethylenically unsaturated acid, and   (d) 0 to 15 parts by weight of at least one other monoethylenically unsaturated monomer,   or from   (a) 4.8 to 95 parts by weight of vinyl acetate,   (b) 4.8 to 95 parts by weight of ethylene, and   (c) 0 to 10 parts by weight of at least one other monoethylenically unsaturated monomer,   such that the parts by weight of monomer each sum to 100.   
     
     
         7 . The paper coating composition according to  claim 1 , wherein the polymer is formed either from
 (a) 9.8 to 75 parts by weight of styrene or methylstyrene,   (b) 24.8 to 90 parts by weight of butadiene,   (c) 0.1 to 10 parts by weight of at least one ethylenically unsaturated acid, and   (d) 0 to 15 parts by weight of at least one other monoethylenically unsaturated monomer,   or from   (a) 39.8 to 85 parts by weight of vinyl acetate,   (b) 14.8 to 60 parts by weight of ethylene, and   (c) 0 to 10 parts by weight of at least one other monoethylenically unsaturated monomer,   such that the parts by weight of monomer each sum to 100.   
     
     
         8 . The paper coating composition according to  claim 1 , wherein an amount of the polymer in the aqueous polymeric dispersion is 1 to 50 parts by weight, based on the total amount of the at least one pigment which is present in an amount of 80 to 95 parts by weight, based on a total solids content. 
     
     
         9 . The paper coating composition according to  claim 1 , wherein the at least one pigment is selected from the group consisting of calcium sulfate, calcium aluminate sulfate, barium sulfate, magnesium carbonate, calcium carbonate, a silica, an alumina, aluminum hydrate, a silicate, titanium dioxide, zinc oxide, kaolin, argillaceous earth, talc and silicon dioxide. 
     
     
         10 . The paper coating composition according to  claim 1 , further comprising at least one assistant selected from the group consisting of a thickener, a further polymeric binder, a cobinder, an optical brightener, a filler, a flow control agent, a dispersant, a surfactant, a slip agent, a neutralizing agent, a defoamer, a deaerator, a preservative and a dye. 
     
     
         11 . A paper or board coated with the paper coating composition of  claim 1 . 
     
     
         12 . A process for coating paper or board, the process comprising:
 applying the paper coating composition of  claim 1  to at least one surface of a paper or a board.