Processes of making paper
AssigneeCiba Specialty Chemicals Water Treatments Ltd.
InventorsMichael Heard, Gordon Chen, John Oliver Stockwell
Life of this patent
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Abstract
Paper is made by a dual soluble polymer process in which a cellulosic suspension which usually contains alum or cationic coagulant is first flocculated with a high intrinsic viscosity cationic synthetic polymer or cationic starch and, after shearing, the suspension is reflocculated by the addition of a branched anionic water soluble polymer having an intrinsic viscosity above 3 dl/g and tan delta at 0.005 Hz of at least 0.5. The process gives an improved combination of formation, retention and drainage.
Claims12
A process of making paper comprising flocculating a cellulosic suspension with a water soluble, cationic, first, polymeric retention aid to form cellulosic flocs, mechanically degrading the flocs, reflocculating the suspension by adding a solution of a water soluble, anionic, second polymeric retention aid made by polymerising a water soluble anionic ethylenically unsaturated monomer charge under polymerisation conditions, forming a sheet by draining the reflocculated suspension and drying the sheet
- characterised in that the water soluble anionic polymeric retention aid
- (a) is a branched water soluble polymer made by including branching agent in the monomer charge, and
- (b) has intrinsic viscosity above 3 dl/g and
- (c) has a tan delta rheological oscillation value on a 1.5% solution at 0.005 Hz of at least 0.5, or has a deionised SLV viscosity number which is at least three times the salted SLV viscosity number of the polymer made under the same polymerisation conditions from the same monomer charge in the absence of branching agent.
Dependencies are inferred from the claim text.