US 11,685,800 B2
Multi-stage polymer with low MW shell and high Tg core for early block resistance
Gianna Pastena, Flanders, NJ (US); and Hrire Gharapetian, Ridgewood, NJ (US)
Assigned to Columbia Insurance Company, Omaha, NV (US)
Filed by Columbia Insurance Company, Omaha, NE (US)
Filed on Jul. 6, 2020, as Appl. No. 16/921,059.
Prior Publication US 2022/0002459 A1, Jan. 6, 2022
Int. Cl. C08F 2/22 (2006.01); C08F 220/40 (2006.01); C08K 5/20 (2006.01); C08L 33/08 (2006.01); C08L 33/12 (2006.01)
CPC C08F 220/40 (2013.01) [C08K 5/20 (2013.01); C08L 33/08 (2013.01); C08L 33/12 (2013.01); C08L 2207/53 (2013.01)] 18 Claims
 
1. A copolymer multi-stage latex particle comprising a first stage and a second stage,
wherein the first stage comprises one or more film forming monomers copolymerized with at least one crosslinking monomer and having a calculated glass transition temperature (Tgc) from about 25° C. to about 100° C., wherein the at least one crosslinking monomer ranges from about 1 wt. % to about 8 wt. % of the total monomers in the latex particle,
wherein the second stage comprises one or more film forming monomers copolymerizes with at least one chain transfer agent (CTA), wherein the CTA ranges from about 0.2 wt. % to about 2 wt. % of the total monomers in the latex particle, wherein the weight average molecular weight of the second stage ranges from about 8,000 Daltons to about 30,000 Daltons, wherein the CTA is distributed throughout the second stage, and wherein the weight percentage of the second stage ranges from about 40 wt. % to about 65 wt. %,
wherein the Tgc of the first stage is higher than a Tgc of the second stage from about 45° C. to about 90° C.
wherein the first stage is an inner stage and the second stage is an outer stage.