| abstract |
For the preparation of 100 parts by weight of the water-soluble copolymer which, in a statistical distribution, 5 to 95% by weight from residues of the formula I and 5 to 95% by weight of residues of the formula II 0 to 80% by weight of residues of the formula III exists, wherein R 'and R 2 are the same or different and hydrogen. Methyl or ethyl and X⊕ is a cation, 5 to 95 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid (3) of the formula la dissolved in water or a water-miscible organic solvent, the sulfonic acid is neutralized by adding a base, then 5 to 95 parts by weight of a vinyl acylamide of the formula IIa and optionally 0 to 80 parts by weight of acrylamide are added and the copolymerization is initiated in a manner known per se and is carried out at 10 to 120 ° C. The copolymers prepared can be used as drilling fluid aids. |