David A Townsend

US Patent:

6784253, Aug 31, 2004

Filed:

Jul 23, 2002

Appl. No.:

10/200877

Inventors:

Shripathy Vilasagar - Parkersburg WV
Vern Lowry - Ottawa IL
Dane M. Ferraris - Parkersburg WV
Ke Feng - Vienna WV
Robert E. Colborn - Niskayuna NY
Matthew Hal Littlejohn - Green Island NY
David Francis Townsend - Loganville GA

Assignee:

General Electric Company - Pittsfield MA

International Classification:

C08L 5104

US Classification:

525316, 525 86, 525314, 525263

Abstract:

An emulsion polymerization process for the preparation of polybutadiene grafted with styrene and acrylonitrile monomers in a reaction system is provided. The resultant product has a low end content of unreacted residual monomers, low yellowness index, and improved impact strength. The diene rubber is prepared via a process wherein a chain transfer agent is added on a continuous basis to give a rubber substrate having a low crosslink density. In one embodiment of the invention, the process includes charging the reaction system with a pre-selected diene emulsion with a low crosslink density, adding a first portion of at least one of a styrene monomer and acrylonitrile monomer to the diene emulsion, adding to the reaction system, over a predetermined time, an initiator and a second portion of acrylonitrile and styrene monomer, and polymerizing the catalyzed reaction mixture of diene substrate, styrene and acrylonitrile to form ABS graft polymers. In another embodiment, a third monomer is added after the conversion rate of the monomers is greater than 98%.