Patent ID: 8002119

Claim:
A method of reverse-osmosis, comprising: adding at least one copolymer having a mean molecular weight Mw of at least 3000 g/mol to at most 60 000 g/mol and a random structure, the at least one copolymer comprising: (A) 20 to 99.98% by weight of at least one monoethylenically unsaturated monocarboxylic acid; (B) 0.01 to 70% by weight of at least one monoethylenically unsaturated dicarboxylic acid of selected from the group consisting of maleic acid, itaconic acid, hydrolyzable derivatives thereof and mixtures thereof; and also (C) 0.01 to 40% by weight of at least one further ethylenically unsaturated comonomer different from (A) and (B) and selected from the group vinyl phosphonic acid and hydrolyzable groups thereof, wherein a polymerization for producing the copolymer is performed in the presence of 0.01 to 100 mol % of at least one base, based on a total amount of all COOH groups of the monocarboxylic and dicarboxylic acids, the quantities in % by weight given in each case being based on a total amount of all monomers, to treated or untreated water, to give an aqueous solution comprising the at least one copolymer; then subjecting the aqueous solution to reverse-osmosis.