| 摘要 |
A process is for preparing polyvinyl alcohol-stabilized addition polymers based on (meth)acrylate monomers in the form of their aqueous dispersions and water-redispersible dispersion powders by means of free-radically initiated emulsion polymerization or suspension polymerization of one or more monomers selected from the group consisting of the esters of acrylic acid and methacrylic acid and, if desired, further monomers copolymerizable therewith in the presence of one or more protective colloids from the group of the polyvinyl alcohols and, if appropriate, with drying of the resultant aqueous dispersion, which includesa) conducting polymerization in the presence of from 0.001% to 0.02% by weight of initiator and, if desired, from. 0.001% to 0.03% by weight of reducing agent, based in each case on the overall weight of the monomers, andb) including from 10% to 50% by weight of the monomers, based on the overall weight of the monomers, in the initial charge and metering in the rest, and,c) metering in the initiator and, if present, the reducing agent in toto, from 25% to 60% by weight of the total amount of initiator and, if present of reducing agent being metered in continuously until from 50% to 80% of the total polymerization time has elapsed, andd) in the remaining polymerization time, adding the remaining amount of initiator and, if present, reducing agent at an accelerated metering rate which is at least twice as high as in step c).
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