Patent ID: 7294676

Claim:
A method for preparing a rubber modified styrenic resin composition with at least improved toughness properties, consisting of from about 92.0% to about 99.9% by weight of a rubber modified styrene maleic anhydride copolymer, from about 0.1% to about 8.0% by weight of polybutene based on the weight of the rubber modified styrenic resin composition, and optionally, customary additives including stabilizers, antioxidants, lubricants, fillers, pigments, and/or plasticizers; and wherein said rubber modified styrenic resin composition is produced in a polymerization process and said polybutene is part of the reactive mixture of said styrene, said maleic anhydride and said rubber in said polymerization process, the steps comprising: in said polymerization process, adding the polybutene to partially polymerized syrup comprised of rubber, styrene, and maleic anhydride after the syrup exits a reactor and enters a devolatilizer.