Manufacture of paper and paperboard
AssigneeCiba Specialty Chemicals Water Treatments Ltd.
InventorGordon Cheng I Chen
Life of this patent
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Abstract
A process for making paper comprising forming a cellulosic suspension, flocculating the suspension, draining the suspension on a screen to form a sheet and then drying the sheet, wherein the cellulosic suspension is flocculated by addition of a water soluble polymer which is selected from a) a polysaccharide or b) a synthetic polymer of intrinsic viscosity at least 4 dl/g and then reflocculated by a subsequent addition of a reflocculating system, wherein the reflocculating system comprises i) a siliceous material and ii) a water soluble polymer. In one aspect the siliceous material is added prior to or simultaneous with the water soluble polymer. In an alternative for the water soluble polymer is anionic and added prior to the siliceous material.
Claims26
A process for making paper or paper board comprising forming a cellulosic suspension, flocculating the suspension, draining the suspension on a screen to form a sheet and then drying the sheet, wherein the cellulosic suspension is flocculated by addition of a water soluble polymer which is selected from
- a) a polysaccharide or
- b) a synthetic polymer of intrinsic viscosity at least 4 dl/g
- and then reflocculated by a subsequent addition of a reflocculating system,
- wherein the reflocculating system comprises i) a siliceous material and ii) a water soluble polymer, characterised in that either, the siliceous material and water soluble polymer are added the suspension simultaneously or by addition of the siliceous material and then addition of the water soluble polymer, and wherein the water soluble polymer added to the cellulosic suspension prior to the reflocculating system is a branched water soluble polymer which has an intrinsic viscosity above 4 dl/g and exhibits a rheological oscillation value of tan delta at 0.005 Hz of above 0.7.
A process for making paper or paper board comprising forming a cellulosic suspension, flocculating the suspension, draining the suspension on a screen to form a sheet and then drying the sheet, wherein the cellulosic suspension is flocculated by addition of a substantially water soluble polymer selected from,
- a) a polysaccharide or
- b) a synthetic polymer of intrinsic viscosity at least 4 dl/g
- and then reflocculated by a subsequent addition of a reflocculating system,
- wherein the reflocculating system comprises i) a siliceous material and ii) a substantially water soluble anionic polymer,
- characterised in that the water soluble anionic polymer is added to the cellulosic suspension before the addition of the siliceous material, and wherein the water soluble polymer added to the cellulosic suspension prior to the reflocculating system is a branched water soluble polymer which has an intrinsic viscosity above 4 dl/g and exhibits a rheological oscillation value of tan delta at 0.005 Hz of above 0.7.
Dependencies are inferred from the claim text.