Patent ID: 8889033

Claim:
An aqueous solution of an acrylic acid polymer, obtained by polymerization of acrylic acid in feed mode with peroxodisulfate as initiator in the presence of hypophosphite in water as solvent, wherein: (i) water and optionally one or more ethylenically unsaturated comonomers are initially charged; and (ii) acrylic acid in acidic, unneutralized form, optionally one or more ethylenically unsaturated comonomers, aqueous peroxodisulfate solution and aqueous hypophosphite solution are added continuously; and (iii) a base is added on completion of the acrylic acid feed to the aqueous solution, and wherein: the comonomer content does not exceed 30% by weight, based on total monomer content; said acrylic acid polymer has a weight average molecular weight ranging from 1000 to 2500 g/mol; and at most 8% of phosphorous contained in said acrylic acid polymer is present in the form of phosphinate and/or phosphonate groups bound at a polymer chain end.