Patent ID: 6489391
Filing Date: 2002-12-03
Classification: C08J,C08L,C09J

Abstract:
A process for manufacturing a protective colloid-stabilized vinyl ester homopolymer or copolymer product dispersion of a specified polymer solids content in the range of 50 to 75 weight percent solids based on the weight of the dispersion, and a Brookfield viscosity measured at 20 rpm of from 20,000 mPas to 60,000 mPas, said process comprising the steps of:a) emulsion polymerizing one or more vinyl ester monomers and, in the case of vinyl ester copolymers, one or more vinyl ester monomers and one or more non-vinyl ester comonomers, in the presence of a protective colloid, to form a first protective colloid-stabilized vinyl ester homopolymer or copolymer dispersion, and spray drying said first protective colloid-stabilized vinyl ester homopolymer or copolymer dispersion to form a water-redispersible polymer powder; b) emulsion polymerizing the same vinyl ester monomers and non-vinyl ester comonomers employed in step a) in the presence of a protective colloid to form a second protective colloid-stabilized vinyl ester homopolymer or copolymer dispersion having a Brookfield viscosity measured at 20 rpm of from 10,000 mPas to 15,000 mPas and a solids content lower than said specified solids content and in the range of 30 to 65 weight percent based on the weight of said second protective colloid-stabilized vinyl ester homopolymer or copolymer dispersion; and c) adding to said second protective colloid-stabilized vinyl ester homopolymer or copolymer dispersion, sufficient of said water-redispersible polymer powder to increase the solids content of said second protective colloid-stabilized dispersion to the specified solids content of said vinyl ester homopolymer or copolymer product dispersion, and to increase the viscosity to the range of from 20,000 mPas to 60,000 mPas.