High-mooney NDBR having mooney jump

#The invention relates to a method for achieving a step increase in the Mooney viscosity in production of high-molecular-weight polybutadiene having high content >95% by weight of cis-1,4 units and having low 1,2-vinyl content <1% by weight.

#Polybutadienes are used as important constituents of rubber mixtures in the tyre industry, and it is desirable here to achieve an improvement in final properties, for example a reduction in rolling resistance and in abrasion value. Another application sector is provided by golf-ball cores or shoe soles, where high rebound resilience is a primary concern.

#Polybutadienes having high content of cis-1,4 units have been produced on a large industrial scale for quite some time and are used for the production of tyres and of other rubber products, and also for impact-modification of polystyrene.

#FIG. 1 shows comparative results of Garvey extrudates of a rubber according to an inventive embodiment and rubbers of comparative examples.

#Another term used for addition of sulphur chlorides to the polymer is “modification” of the polymer.

#Surprisingly, it was found that the treatment of the sulphur chlorides prior to addition with a carboxylic acid, fatty acid and/or fatty acid ester permits achievement of a greater “step-increase reaction” or modification, without any resultant undesired gelling.

#Polymerization Process:

#8500 g of hexane (dried over molecular sieve), 1300 g of 1,3-butadiene, 21.4 mmol of a 20% solution of diisobutylaluminium hydride in hexane, 1.44 mmol of a 10% solution of ethylaluminium sesquichloride in hexane, and 1.44 mmol of a 40% solution of neodymium versatate in hexane were introduced into a dry, nitrogen-inertized 20 L steel autoclave. The system was heated to 73° C., with stirring, and the mixture was polymerized for 60 min, with stirring. A conversion sample was taken. Butadiene conversion after the polymerization process was 99.7%.

#The polymerization process was terminated by addition of 3.75 g of stearic acid (0.25 phr), and 1.3 g of Irganox 1520 (0.1 phr) were used for stabilization. The solution was kept at 65° C. for a further 15 min.