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Abstract

The present invention relates to copolymers consisting of (a) 1-99% by weight of structural units of the formula (1) ##STR1## where R.sup.1 is hydrogen or methyl, R.sup.4 is C.sub.1 -C.sub.22 -alkylene, R.sup.5 is C.sub.1 -C.sub.22 -alkyl or hydrogen, and X is ammonium, lithium, sodium, potassium, an amine or a mixture of these substances, and (b) 99-1% by weight of structural units of the formula (2) ##STR2## where R.sup.1 is hydrogen or methyl, R.sup.2 and R.sup.3, independently of one another, are hydrogen, or C.sub.2 -C.sub.22 -alkyl, wherein component b) is not hydrolysed and the copolymers have been prepared by a solution precipitation polymerization in a nonaqueous solvent or a water-miscible, organic solvent having a low water content which is a precipitant for the copolymer. The invention furthermore relates to a process for cementing subterranean wells using a cement slurry comprising the following components: a) water of various salinity cement a novel copolymer in a concentration of 0.01-5% bwoc, preferably from 0.05 to 0.9% bwoc.

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First Claim