Papermaking process
First Claim
1. A papermaking process in which a paper product is made by forming an aqueous cellulosic slurry, adding a mineral filler to said slurry, adding a cationic charge-biasing species to said slurry after said addition of said mineral filler, whereby said cationic charge-biasing species at least partially neutralizes anionic surface charges on solid surfaces in said slurry and provides cationic patches for an anionic flocculant on solid surfaces in said slurry, draining said slurry to form a sheet, and drying said sheet to form said paper product, wherein said slurry is subjected to at least one shear stage, characterized by:
- adding an anionic flocculant to said slurry after said addition of cationic charge-biasing species in an amount sufficient to effectuate floc formulation, said anionic flocculant being substantially linear and having at least 2 mole percent anionic mer units and a weight average molecular weight of at least 500,000;
subjecting said slurry to a shear stage after said addition of said anionic flocculant; and
subsequentlyadding a microparticle to said slurry prior to said draining of said slurry in an amount effective to provide improved retention performance;
wherein said microparticle is an inorganic, cationic source of aluminum having at least 5 weight percent aluminum and having a particle size distribution within the range of from about 1 to about 1,000 nm.
11 Assignments
0 Petitions
Accused Products
Abstract
In a papermaking process a paper product is formed from a mineral filler containing cellulosic slurry. Retention performance is provided by the sequential addition of a cationic charge-biasing species, an anionic flocculant, and then a certain microparticle. A shear stage is interposed between the flocculant addition and the microparticle addition. The microparticle is a inorganic, cationic source of aluminum.
132 Citations
23 Claims
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1. A papermaking process in which a paper product is made by forming an aqueous cellulosic slurry, adding a mineral filler to said slurry, adding a cationic charge-biasing species to said slurry after said addition of said mineral filler, whereby said cationic charge-biasing species at least partially neutralizes anionic surface charges on solid surfaces in said slurry and provides cationic patches for an anionic flocculant on solid surfaces in said slurry, draining said slurry to form a sheet, and drying said sheet to form said paper product, wherein said slurry is subjected to at least one shear stage, characterized by:
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adding an anionic flocculant to said slurry after said addition of cationic charge-biasing species in an amount sufficient to effectuate floc formulation, said anionic flocculant being substantially linear and having at least 2 mole percent anionic mer units and a weight average molecular weight of at least 500,000; subjecting said slurry to a shear stage after said addition of said anionic flocculant; and
subsequentlyadding a microparticle to said slurry prior to said draining of said slurry in an amount effective to provide improved retention performance; wherein said microparticle is an inorganic, cationic source of aluminum having at least 5 weight percent aluminum and having a particle size distribution within the range of from about 1 to about 1,000 nm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A papermaking process in which a paper product is made by forming an aqueous cellulosic slurry, adding a mineral filler to said slurry, adding a cationic charge-biasing species to said slurry after said addition of said mineral filler, whereby said cationic charge-biasing species at least partially neutralizes anionic surface charges on solid surfaces in said slurry and provides cationic patches for an anionic flocculant on solid surfaces in said slurry, draining said slurry to form a sheet, and drying said sheet to form said paper product, wherein said slurry is subjected to at least one shear stage, characterized by:
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adding an anionic flocculant to said slurry after said addition of cationic charge-biasing species in an amount sufficient to effectuate floc formulation, said anionic flocculant being substantially linear and having at least 2 mole percent anionic mer units and a weight average molecular weight of at least 500,000; subjecting said slurry to a shear stage after said addition of said anionic flocculant; and
subsequentlyadding a microparticle to said slurry prior to said draining of said slurry; wherein said microparticle is a polyaluminum chloride having at least 5 weight percent aluminum having a particle size distribution within the range of from about 1 to about 1,000 nm, and wherein said polyaluminum chloride is added in an amount of from about 0.05 to about 0.20 parts by weight per hundred parts by weight of dry slurry solids. - View Dependent Claims (22, 23)
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23. The process of claim 22 wherein m is a number having a numerical value of from about n to about 2n.
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Specification