| 摘要 |
A curable rubber bladder stock containing esters of ricinoleic acid or derivatives thereof has reduced viscosity as compared to stocks containing castor oil. The rubber stocks of the present invention generally retain a very high percentage of the initial cure tensile strength and have improved modulus as compared to castor oil, both upon initial cure and upon aging. Lower viscosity and higher modulus of the rubber stocks of the present invention readily permit the production of thinner bladders. The bladders can fit within an article such as a tire during vulcanization of the tire as in an automatic vulcanizing press. Thinner bladders effect a greater heat rate and result in shorter cure times for articles such as tires. The esters of ricinoleic acid and derivatives thereof have the formula <IMAGE> where R is H or <IMAGE> where R1 is an aliphatic, preferably an alkyl, having from 1 to 12 carbon atoms, desirably from 1 to 4 carbon atoms, and preferably 1 carbon atom, i.e., methyl, and R2 is an aliphatic, desirably an alkyl, having from 1 to 12 carbon atoms and preferably from 1 to 4 carbon atoms.
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