Patent ID: 7838112

Claim:
A core-shell particle which consists essentially of (1) a crosslinked elastomeric core consisting of repeat units that are derived from isoprene monomer and divinyl benzene, wherein the divinyl benzene is present in the crosslinked elastomeric core at a level which is within the range of 15 weight percent to 30 weight percent based upon the weight of the crosslinked elastomeric core, and wherein the crosslinked elastomeric core is a polymeric composition having a glass transition temperature which is within the range of −20° C. to 20° C., and (2) a polymeric shell which is derived from styrene monomer, wherein the shell is comprised of at least 75 weight percent repeat units that are derived from the styrene monomer wherein the polymeric shell has a glass transition temperature which is within the range of 50 ° C. to 160° C., wherein the glass transition temperature of the elastomeric core differs from the glass transition temperature of the polymeric shell by at least 30° C., and wherein the weight ratio of the core to the shell is within the range of 20:1 to 7:1.