The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 09, 2002
Filed:
Dec. 22, 1999
Michael Leslie Senyek, Tallmadge, OH (US);
Joseph John Kulig, Tallmadge, OH (US);
Dane Kenton Parker, Massillon, OH (US);
The Goodyear Tire & Rubber Company, Akron, OH (US);
Abstract
Mercaptans are normally used as chain transfer agents in emulsion polymerizations. The mercaptans used in commercial applications are typically complex mixtures of hundreds of similar compounds having boiling points within a narrow range. The chain transfer activity of different mercaptans with such mixtures can vary substantially. To further complicate the situation, the distribution of various mercaptans can also vary substantially between lots of material obtained from commercial sources. Thus, consistent molecular weight control is typically difficult to attain in free radical emulsion polymerizations. This invention is based upon the unexpected discovery that dibenzyltrithiocarbonate will act as a pure compound to effectively and consistently control molecular weight in free radical emulsion polymerizations. The polydispersity of polymers made using dibenzyltrithiocarbonate as a molecular weight regulator is similar to that obtained using conventional mercaptan systems. This invention more specifically discloses a process for controlling the molecular weight of a polymer synthesized by free radical emulsion polymerization that comprises polymerizing at least one monomer by free radical polymerization in an aqueous emulsion in the presence of dibenzyltrithiocarbonate. For instance, dibenzyltrithiocarbonate can be used as a molecular weight regulator in the synthesis of styrene-butadiene rubber by emulsion polymerization. Accordingly, this invention further discloses a process for synthesizing styrene-butadiene rubber (SBR) that comprises copolymerizing styrene monomer and 1,3-butadiene monomer by free radical polymerization in an aqueous emulsion in the presence of dibenzyltrithiocarbonate. The use of dibenzyltrithiocarbonate is inherently less odorous than the use of mercaptans.