| 摘要 |
Isoprene is polymerized in the presence of a complex aluminium hydride of the formula M Al H4 and titanium tetraiodide where M is lithium, sodium, potassium, rubidium or caesium; the products have a trans-1, 4 structure of 75-95% the majority of the remainder being 3, 4-addition with some cis-1, 4. The mol ratio of hydride to titanium tetraiodide may be 0,5-6,0 : 1 and the catalyst composition is used in amounts of 0,1-10% based on monomer. Reaction temperatures of 0-150 DEG C. are used with reaction times of 1 second to 24 hours. A diluent may be used e.g. benzene, toluene, xylene, ethylbenzene, propane, n-butane, n-pentane, isopentane, n-hexane, isohexane, iso-octane, n-decane or cyclohexane. The complex hydride may be added in solution in an ether such as diethyl ether, dioxane or tetrahydrofuran and the catalyst and diluent may be aged at 30-100 DEG C. for 10 minutes to 24 hours. Batch or continuous processes can be used, additional monomer, catalyst or diluent being added at intermediate points in the latter case if desired and when using a tubular reactor a temperature gradient may be used. Although water, oxygen and carbon dioxide are preferably excluded, up to 1,000 parts per million of water can be tolerated. The catalyst is destroyed by addition of an alcohol.ALSO:A catalyst for polymerizing isoprene comprises titanium tetraiodide and a complex aluminium hydride of the formula MAlH4 where M is lithium, sodium, potassium, rubidium or cesium. The mol ratio of complex hydride to titanium tetraiodide may be 0.5-6:1. The catalyst may be aged in the presence of a hydrocarbon diluent at 30-100 DEG C. for 10 minutes to 24 hours.
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