Retention and drainage aid for alkaline fine papermaking process
First Claim
1. A process in which fine paper is made by forming an aqueous cellulosic suspension having a pH in the range between about 6.8 to about 9.0, said cellulosic suspension comprising fibers, a precipitated calcium carbonate filler and a cationic starch strengthening agent, passing the suspension through one or more shear stages, draining the suspension to form a sheet and drying the sheet, wherein a cationic coagulant having a molecular weight in the range between about 2,000 to about 500,000 is added to said suspension in an amount between about 0.001% to about 0.5%, based on the dry weight of said suspension, prior to any of said shear stages, an anionic flocculant having a molecular weight of at least 5000,000 is added to said suspension in an amount between about 0.001% to about 0.8%, based on the dry weight of said suspension, after said coagulant but before any of said shear stages, and an inorganic material selected from the group consisting of:
- bentonite and colloidal silica, is added to said suspension after at least one of said shear stages.
2 Assignments
0 Petitions
Accused Products
Abstract
A process in which fine paper is made by forming an aqueous cellulosic suspension comprising fibers, a precipitated calcium carbonate filler and a cationic starch strengthening agent, passing the suspension through one or more shear stages, draining the suspension to form a sheet and drying the sheet. The retention and drainage properties of the suspension are substantially improved via the addition of a cationic coagulant having a molecular weight in the range between about 2,000 to about 500,000 to the suspension prior to any of the shear stages, an anionic flocculant having a molecular weight of at least 500,000 to the suspension after the low molecular weight coagulant but before any of the shear stages, and an inorganic material selected from the group consisting of: bentonite, colloidal silica and other inorganic microparticle materials, to the suspension after at least one of the shear stages.
-
Citations
10 Claims
-
1. A process in which fine paper is made by forming an aqueous cellulosic suspension having a pH in the range between about 6.8 to about 9.0, said cellulosic suspension comprising fibers, a precipitated calcium carbonate filler and a cationic starch strengthening agent, passing the suspension through one or more shear stages, draining the suspension to form a sheet and drying the sheet, wherein a cationic coagulant having a molecular weight in the range between about 2,000 to about 500,000 is added to said suspension in an amount between about 0.001% to about 0.5%, based on the dry weight of said suspension, prior to any of said shear stages, an anionic flocculant having a molecular weight of at least 5000,000 is added to said suspension in an amount between about 0.001% to about 0.8%, based on the dry weight of said suspension, after said coagulant but before any of said shear stages, and an inorganic material selected from the group consisting of:
- bentonite and colloidal silica, is added to said suspension after at least one of said shear stages.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
Specification