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:
Jun. 05, 2001
Filed:
Dec. 11, 1997
James E. Hall, Mogadore, OH (US);
Daniel F. Graves, Canal Fulton, OH (US);
Hideo Takeichi, Akron, OH (US);
Bridgestone Corporation, Tokyo, JP;
Abstract
The dispersibility of the initial polystyrene block in forming a S-B-S type of copolymer is improved by first preparing a small block of homopolydiene such as homopolybutadiene as a dispersing agent. Onto this small block of homopolybutadiene, the first block of polystyrene is formed and affixed and thereby made dispersible in a mixture of alkanes and 15 to 60% by weight of cycloalkanes, preferably hexane and cyclohexane. After the preparation of the dispersing agent and the first styrene block, the remaining monomer charges to the reactor are fed in aliphatic hydrocarbon diluents, preferably hexane or technical hexane, thereby greatly reducing the final percentage of cycloalkanes including cyclohexane in the reactor to less than 25% of total dispersing medium. The block copolymers produced according to the present process display a narrow molecular weight distribution and improved tensile strength over block copolymers produced in the absence of the additional cycloalkanes in the solvent system.