Patent ID: 7250462
Filing Date: 2007-07-31
Classification: B01D,C02F,C08F,D21H

Abstract:
1. A method for dewatering organic sludge, the method comprising steps of: dissolving an amphoteric water-soluble polymer dispersion in water; adding and mixing the resulting solution to and with organic sludge; and dewatering the sludge by a dewatering apparatus so as to obtain a dewatered cake improved in water content thereof, said amphoteric water-soluble polymer dispersion being an amphoteric water-soluble polymer dispersion containing polymer fine particles having particle diameters of 100 μm or less and produced by dispersion polymerization of a monomer mixture consisting of monomers represented by the following general formulas (1), (2), and (3), and (meth)acrylamide in mole % ratios a, b, c, and d, respectively; satisfying 30≧a≧5, 30≧b≧10, 50≧c≧5, 65≧d≧0 and in the presence of a cross-linking monomer in a mole % ratio of 0.0001 to 0.01 on the basis of the total mole number of the monomer mixture, in an aqueous divalent anionic salt solution in the presence of a polymer dispersant soluble in the aqueous divalent anionic salt solution, wherein R 1 and R 2 independently denote alkyl or alkyloxy having 1 to 3 carbon atoms, or benzyl, R3 denotes hydrogen, or alkyl or alkyloxy having 1 to 3 carbon atoms, or benzyl, they may be similar or dissimilar, A denotes an oxygen atom or NH, B denotes alkylene or alkoxylene having 2 to 4 carbon atoms, and X 1 denotes an anion, (wherein R 4 and R 5 independently denote alkyl or alkyloxy having 1 to 3 carbon atoms, or benzyl, R 6 denotes hydrogen, alkyl or alkyloxy having 1 to 3 carbon atoms, or benzyl, they may be similar or dissimilar, A denotes an oxygen atom or NH, B denotes alkylene or alkoxylene having 2 to 4 carbon atoms, and X 2 denotes an anion, and wherein R 7 denotes hydrogen, methyl, or carboxymethyl, R 8 denotes hydrogen or carboxy, Q denotes SO 3 , C 6 H 4 SO 3 , CONHC(CH 3 ) 2 CH 2 SO 3 or COO, and Y 1 denotes hydrogen or a cation, and wherein said amphoteric water-soluble polymer has a weight average molecular weight of 100,000 to 20,000,000.