Patent ID: 7411024

Claim:
A process for forming interpolymer resin particles comprising: a) suspending in an aqueous medium from about 20% to 60% by weight of polyolefin resin particles having a VICAT softening temperature greater than 85° C. and a melt index of about 2.1 g/10 minutes (Condition I, 190° C., 2.16 kg); b) adding to the aqueous suspension a first vinyl aromatic monomer composition comprising vinyl aromatic monomer and a polymerization initiator for polymerizing the vinyl aromatic monomer within the polyolefin resin particles; c) adding to the aqueous suspension a second vinyl aromatic monomer composition comprising vinyl aromatic monomer, said second vinyl aromatic monomer composition being substantially free of polymerization initiator, said second vinyl aromatic monomer composition being added to said aqueous suspension after addition of said first vinyl aromatic monomer composition, said first vinyl aromatic monomer composition and said second vinyl aromatic monomer composition together providing from 40 to 80 percent by weight of vinyl aromatic monomer, based on total weight of polyolefin resin particles and vinyl aromatic monomer; and d) polymerizing said vinyl aromatic monomer within said polyolefin resin particles, thereby forming said interpolymer resin particles, polymerization of said vinyl aromatic monomer being performed in the substantial absence of cross-linking agent such that said interpolymer resin particles have a gel content ranging from about 0 to about 1.5% by weight, based on the weight of the interpolymer resin particles, wherein said interpolymer resin particles have a VICAT softening temperature ranging from about 90° C. to about 115° C. and a melt index value ranging from about 0.2 to about 35g/10 minutes (Condition G).