LATEX FOR LOW VOC PAINT HAVING IMPROVED BLOCK RESISTANCE, OPEN TIME AND WATER-SOFTENING RESISTANCE

摘要

The invention is directed to latex compositions comprising sequentially designed polymer having a first stage, a second stage and a third stage corresponding to a seed, a core and a shell. The latex polymer is suitable for aqueous low volatile organic compounds ("VOC") paint (less than 50 g/L) with good block resistance, improved open time and increased water softening resistance. To attain good block resistance, the seed and the core contain monomers that form polymers with relatively harder characteristics and higher glass transition temperature ("T_g") while the shell contains monomers that form polymers with softer characteristics and lower T_g. To gain improved open time, the latex polymer contains suitable level of hydrophilic monomers necessary to hold water. To achieve water softening resistance, hydrophobic monomers are grafted on hydrophilic portions of the shell or the core layers. The invention is also directed to the process of making the latex by a sequential emulsion polymerization.