Patent ID: 8735516

Claim:
A process for preparing aqueous solutions of acrylic acid polymers by polymerization of acrylic acid in feed operation with a free-radical initiator in the presence of hypophosphite in water as solvent, which process comprises (i) initially charging water and optionally one or more ethylenically unsaturated comonomers, (ii) continuously adding acrylic acid in acidic, unneutralized form, optionally one or more ethylenically unsaturated comonomers, aqueous free-radical initiator solution and aqueous hypophosphite solution, (iii) adding a base to the aqueous solution on completion of the acrylic acid feed, wherein the comonomer content does not exceed 30% by weight, based on the total monomer content, wherein the aqueous hypophosphite solution is added during a total feed time made up of three consecutive feed time spans Δt I , Δ II and Δt III , wherein the average feed rate in the second feed time span Δt II is greater than the average feed rates in the first and third feed time spans Δt I and Δt III .