| abstract |
This invention relates to the water-soluable cross-linkable copolymer with a molecule weight <= 500,000 wherein comprising: (a) the monomer unit of 20 to 95 % by weight contains the sulfonic acid group or sulfonic salt group; (b) the monomer unit of 4 to 80 % by weight contains N-hydroxyl methyl group or N-alkoxyl methyl group; and (c) the hydrophobic monomer unit of 0.1 to 20 % by weight is selected from a group that includes: water-insoluble, unsaturated vinyl compound and the hydrophobic terminal of the triggering base or regulating agent molecules ; wherein the % by weight is based on the overall weight of the copolymer, and (if appropriate) it is possible that as high as 50 % by weight of the monomer unit containing the sulfonic acid/ sulfonic salt [based on the weight content of the monomer unit (a)] is replaced by the monomer unit (d) containing the carboxyl group or the monomer unit (e) containing the acyl amine group. |