Patent ID: 6710113
Filing Date: 2004-03-23
Classification: C04B,C08F

Abstract:
A process for preparing two-phase polymers based on vinyl ester(s) and ethylene, in the form of their aqueous polymer dispersions or water-redispersible polymer powders, comprising polymerizing one or more vinyl esters of carboxylic acids having 1 to 12 carbon atoms and ethylene as monomers and optionally further monomers copolymerizable therewith by means of free-radical initiated emulsion or suspension polymerization, in the presence of one or more protective colloids and/or emulsiflers, and optionally drying the resultant aqueous polymer dispersion, wherein said polymerizing takes place in minimally two steps, said steps comprisingpolymerizing ethylene in a first polymerization phase at a low ethylene pressure less than or equal to 20 bar, and in a second polymerization phase, increasing the ethylene pressure to greater than 20 bar and less than 60 bar, wherein the resultant polymer has an ethylene distribution of less than 50% by weight resulting from the first polymerization phase and greater than 50% by weight resulting from the second polymerization phase, based in each case on the total amount of ethylene in said polymer.