Solution rubbers containing hydroxyl groups

Details Solution rubbers containing hydroxyl groups Solution rubbers containing hydroxyl groups

1999-07-08

2001-06-26

Cain, Edward J. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S332600, C525S332900, C525S350000, C524S575000, C524S418000, C524S427000, C524S750000

Reexamination Certificate

active

06252008

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to rubber blends containing solution-polymerized rubbers with a hydroxyl group, especially primary, content of 0.1 to 5 wt.%, and their mixtures with fillers, optionally other rubbers and rubber aids, and to vulcanized products manufactured therefrom. The rubber blends according to the present invention are suitable for the production of highly reinforced, abrasion-resistant moldings, especially for the manufacture of tires which have a particularly high wet grip.
BACKGROUND OF THE INVENTION
Compared with corresponding emulsion rubbers, anionically polymerized solution rubbers containing double bonds, such as solution polybutadiene and solution styrene/butadiene rubbers, have advantages in the manufacture of tire treads with a low rolling resistance. The advantages lie inter alia in the ability to control the vinyl content and the associated glass transition temperature and the molecular branching. This gives rise in practical use to particular advantages in the relationship between the wet grip and the rolling resistance of the tire. Thus, U.S. Pat. No. 5,227,425 describes the manufacture of tire treads from a solution SBR and silica. Numerous methods of end group modification have been developed to improve the properties further, e.g., with dimethylaminopropylacrylamide as described in EP-A 334,042 or with silyl ethers as described in EP-A 447,066. Because of the high molecular weight of the rubbers, however, the proportion by weight of the end group is small and cannot, therefore, greatly influence the interaction between filler and rubber molecule. One object of the present invention is to prepare solution SBRs with a markedly higher content of effective groups for interaction with the filler.
Solution polybutadiene rubbers containing hydroxyl groups are also described in DE-OS 2,653,144.However, because their strength is too low, these rubbers are not suitable as the main component in tire treads.
EP-A 464,478 describes a process for the hydroxylation of rubbers, but this involves the introduction of secondary hydroxyl groups, which are far less effective than the primary hydroxyl groups of the present invention.
Emulsion and solution rubbers containing hydroxyl groups are also described in EP 806,452 A1, the hydroxyl contents described in this case for solution rubbers being in an appreciably lower range (0.009 to 0.061%) as a consequence of the process. The present invention shows that these contents have no significant effect on the wet grip.
SUMMARY OF THE INVENTION
It has now been found that rubber blends and vulcanized rubber products with surprisingly improved dynamic damping properties in the temperature range relevant to wet grip and in the temperature range relevant to rolling resistance, as well as improved abrasion behavior, can be prepared from solution vinylaromatic/diolefin rubbers containing hydroxyl groups with a bonded hydroxyl group, especially, a primary hydroxyl group, content of 0.1 to 5 wt.% and a 1,2-vinyl content of 5 to 60 wt.%. Other surprising advantages were obtained when the rubber blend was prepared not in a kneader, as is customary, but by mixing a solution of rubber containing hydroxyl groups and oxide or silicate filler in an organic solvent, and then removing the solvent with steam, because in that case, the filler is completely precipitated with the rubber and does not remain in the effluent, as would be the case when using unmodified rubber.


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