Method for the production of nitrile rubber

Abstract

Nitrile rubber can be synthesized by copolymerizing acrylonitrile and 1,3-butadiene in an aqueous emulsion. After these monomers have been polymerized, it is, of course, necessary to recover the polymer from the aqueous emulsion. The present invention discloses an improved method for the recovery of nitrile rubber from a nitrile rubber containing emulsion, said method comprising the steps of (1) adding an antioxidant to the nitrile rubber containing emulsion to produce a stabilized nitrile rubber emulsion, (2) adding a salt and an acid to said stabilized nitrile rubber emulsion to produce a coagulated nitrile rubber slurry, wherein said coagulated nitrile rubber slurry is comprised of serum and nitrile rubber crumb, (3) separating the nitrile rubber crumb from the serum in the coagulated nitrile rubber slurry, (4) mixing the nitrile rubber crumb into wash water to produce a nitrile rubber reslurry, (5) adjusting the pH of the nitrile rubber reslurry so as to be within the range of about 5 to about 8, and (6) separating the nitrile rubber crumb from the wash water of the nitrile rubber reslurry. Nitrile rubber which is recovered from emulsions utilizing this technique typically exhibits improved stability and cure characteristics.

Dependencies are inferred from the claim text.