Anionic water soluble polymer made by reverse phase emulsion polymerization
AssigneeCiba Specialty Chemicals Water Treatment Limited
InventorsMichael Heard, Gordon Chen, John Oliver Stockwell
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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 IV cationic synthetic polymer or cationic starch and, after shearing, the suspension is reflocculated by the addition of a branched anionic water soluble polymer having IV 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.
Claims10
A branched and wholly water soluble anionic polymer which has been made by conventional reverse phase emulsion polymerization of a water soluble ethylenically unsaturated anionic monomer, branching agent and optionally a water soluble, nonionic, ethylenically unsaturated monomer to form an emulsion,
- and then substantially dehydrating the emulsion to form a stable dispersion of substantially anhydrous polymer droplets dispersed in oil,
- and wherein the polymer has
- (a) intrinsic viscosity above 3 dl/g;
- (b) tan delta rheological oscillation value at 0.005 Hz of above 0.7 or deionised SLV viscosity number which is at least three times the salted SLV viscosity number of the corresponding polymer made in the absence of branching agent;
- (c) a saline Brookfield viscosity of at least 2 mPa.s and
- (d) the branching agent is a polyethylically unsaturated monomer used in an amount of from 1 to 10 ppm molar.
Dependencies are inferred from the claim text.