Patent ID: 8163134

Claim:
A method of increasing the filler content of a sheet of paper or paperboard, comprising: (a) combining a heterogeneous polymer blend, comprising: (i) one or more anionic polymers formed from monomers selected from the group consisting of: (1) acrylic acid, (2) methacrylic acid, (3) styrenesulfonic acid, (4) vinylsulfonic acid, (5) acrylamidomethylpropane sulfonic acid, and (6) mixtures thereof; and (ii) one or more cationic polymers formed from monomers selected from the group consisting of: (1) diallyldimethylammonium chloride, (2) acryloylethyltrimethyl ammonium chloride (3) methacryloylethyl trimethyl ammonium chloride, (4) acryloylethyltrimethylammonium sulfate (5) methacryloylethyl trimethyl ammonium sulfate, (6) acrylamidopropyltrimethyl ammonium chloride, (7) methacrylamidopropyl trimethyl ammonium chloride, (8) non-quaternized forms of (2)-(7), (9) vinylformamide (subsequently hydrolyzed to vinylamine), and (10) mixtures thereof; and (iii) one or more non-ionic polymers formed from monomers selected from the group consisting of: (1) acrylamide, (2) methacrylamide, (3) N-alkylacrylamide, (4) vinylformamide, and (5) mixtures thereof; with a precipitated calcium carbonate filler to form a mixture; (b) combining the mixture with a pulp slurry; and (c) processing the resulting pulp slurry mixture to form a sheet of paper or paperboard.