Nalco Chemical Company

Thomas C Fallon

Robert W Novak

A process in which paper or paperboard is made by forming an aqueous cellulosic slurry, draining said slurry on a screen to form a sheet and drying said sheet, employs a cationic polymer as a substantially single component retention aid. The cationic polymer has a cationic charge density of at least about 3.2 equivalents of cationic nitrogen per kilogram of dry polymer. The cationic polymer also has an Intrinsic Viscosity of at least about 8 dl/g. The polymer is added to the slurry prior to sheet formation in an amount effective to provide at least about a 50 percent increase in retention without more than about a 10 percent decrease in formation.

Papermaking process with improved retention and maintained formation

The invention provides a method for improving the retention of mineral fillers and cellulose fibers on a cellulosic fiber sheet. The method comprising the steps of preparing a cellulose pulp slurry; adding before a shearing step an effective amount of a copolymer flocculant to the cellulose pulp slurry, the copolymer flocculant is a high molecular weight cationic copolymer of acrylamide and diallyl dimethyl ammonium chloride, the flocculant copolymer should contain from about 20 to about 60 mole percent diallyl dimethyl ammonium chloride mer units. After a shearing step adding an effective amount of a high molecular weight water-soluble anionic flocculant. A cellulosic fiber sheet is then formed from the cellulose pulp slurry which includes both the copolymer flocculant and anionic flocculant.

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West Chicago, IL, United States of America

Thomas C Fallon