Production of paper and paper board
AssigneeAllied Colloids Limited
InventorsJohn Langley, David Holroyd
Life of this patent
Estimating the term…
Abstract
Paper or paper board is made by passing an aqueous cellulosic suspension through a centriscreen or other shear device and then draining the purified suspension, and an improved combination of retention, drainage, drying and formation is achieved by adding to the suspension an excess of high molecular weight linear synthetic cationic polymer before shearing the suspension and adding bentonite after shearing.
Claims16
A process in which paper or paper board is made by forming an aqueous cellulosic suspension, passing the suspension through one or more shear stages, said shear stages being selected from cleaning, mixing and pumping stages, draining the suspension to form a sheet and drying the sheet and in which the suspension that is drained includes organic polymeric material that is flocculant or retention aid and inorganic material, and in which the inorganic material comprises bentonite which is added in an amount of at least 0.03% to the suspension after one of the said shear stages, and the organic polymeric retention aid or flocculant comprises a substantially linear synthetic cationic polymer having molecular weight above 500,000 and having a charge density of at least about 0.2 equivalents of nitrogen per kg polymer which is added to the suspension before that shear stage in an amount that is effective to give improved retention upon the addition of bentonite.
A process in which paper or paper board is made by forming an aqueous cellulosic suspension, passing the suspension through one or more shear stages, said shear stages being selected from cleaning, mixing and pumping stages, draining the suspension to form a sheet and drying the sheet and in which the suspension that is drained includes organic polymeric material that is flocculant or retention aid and inorganic material, and in which the inorganic material comprises bentonite which is added in an amount of at least 0.03% to the suspension after one of the said shear stages, and the organic polymeric retention aid or flocculant comprises a substantially linear synthetic cationic polymer having molecular weight above 500,000 and having a charge density of at least about 0.2 equivalents of nitrogen per kg polymer which is added to the suspension before that shear stage in an amount such that flocs are formed by the said addition of the polymer and the said flocs are broken by the shearing to form microflocs that resist further degradation by the shearing and that carry sufficient cationic charge to interact with the bentonite to give better retention that is obtainable when adding the polymer alone after the last point of high shear.
A process in which paper or paper board is made by forming an aqueous cellulosic suspension containing low molecular weight cationic polymeric material, adding high molecular weight cationic polymeric material, passing the suspension through one or more shear stages, said shear stages being selected from cleaning, mixing and pumping stages, adding bentonite in an amount of at least 0.03% to the suspension after one of the said shear stages, draining the suspension to form a sheet and drying the sheet, and in which the low molecular weight cationic polymer has intrinsic viscosity below 2 dl/g, the high molecular weight cationic polymer is a substantially linear synthetic cationic polymer having intrinsic viscosity above 4 dl/g and is added in an effective amount of above about 0.01%, and the bentonite is added in an amount of at least 0.03%.
Dependencies are inferred from the claim text.