| abstract |
Methods for making a heterogeneous polymer blend comprising one or more anionic polymers, one or more cationic polymers, and one or more non-ionic polymers, which method comprises (a) adding to a non-neutral solution a first amount of polymerization initiator and one or more anionic or cationic monomers, wherein each monomer has the same charge; (b) adding a second amount of the polymerization initiator and one or more non-ionic monomers; (c) adding a third amount of the polymerization initiator and one or more ionic monomers that are oppositely charged from the monomers of (a); adding stepwise, a fourth amount of the polymerization initiator to react any residual monomer, and (e) neutralizing the resulting polymer blend. Also claimed are heterogeneous polymer blends containing polymers formed from one or more anionic, cationic, and non-ionic monomers, either polymerized in situ or separately and then combined. Also claimed are methods for increasing the filler content of paper or paperboard, which methods comprises (a) combining the heterogeneous polymer blend with a precipitated calcium carbonate filler; (b) combining the resulting mixture with a pulp slurry; and (c) processing the resulting slurry mixture to form a sheet of paper or paperboard. Finally, also claimed are methods of increasing the filler content of paper or paperboard, which method comprises (1) combining either the heterogeneous blend or the precipitated calcium carbonate filler with a pulp slurry, (2) combining the remaining component with the pulp slurry; and (c) processing the resulting pulp slurry mixture to form a sheet of paper or paperboard. |