Patent ID: 8519060

Claim:
An amphiphilic graft polymer prepared by free-radical polymerization of (B) from 30 to 80% by weight of a vinyl ester component comprising (B1) from 70 to 100% by weight of vinyl acetate and/or vinyl propionate and (B2) from 0 to 30% by weight of another ethylenically unsaturated monomer, in the presence of (A) from 20 to 70% by weight of a water-soluble polyalkylene oxide of mean molar mass M n of from 1500 to 20 000, (C) from 0.25 to 5% by weight, based on component (B), of a free radical-forming initiator and (D) from 0 to 40% by weight, based on the sum of components (A), (B) and (C), of an organic solvent at a mean polymerization temperature at which the initiator (C) has a decomposition half-life of from 40 to 500 min, wherein said graft polymer is polymerized in such a way that the fraction of unconverted graft monomer (B) in the reaction mixture is not more than 5% by weight and the proportion of undecomposed initiator (C) in the reaction mixture is not more than 15% by weight based on the total amount of initiator metered in during the monomer addition.