| 主权项 |
1. A process comprising steps of:
(a) contacting a mixture of i) an aqueous dispersion of TiO2 particles and a sulfur-acid containing polymer; ii) an anionic surfactant; and iii) an aqueous solution of sodium styrene sulfonate with a redox initiator system; then (b) adding to the mixture of step (a) an aqueous dispersion of a first monomer mixture comprising monomers selected from the group consisting of acrylic monomers, ethylene monomers, styrene monomers, vinyl ester monomers, and combinations thereof; wherein said first monomer mixture comprises at least 60 wt % acrylic monomers, based on total weight of monomers in the first monomer mixture; (c) polymerizing the first monomer mixture to form an aqueous dispersion of a first polymer that at least partially encapsulates the TiO2 particles; (d) adding to the aqueous dispersion of step (c) an aqueous dispersion of a second monomer mixture comprising monomers selected from the group consisting of acrylic monomers, ethylene monomers, styrene monomers, vinyl ester monomers, and combinations thereof; wherein said second monomer mixture comprises at least 50 wt % vinyl ester monomers, based on total weight of monomers in the second monomer mixture; and (e) polymerizing the second monomer mixture. |
