| 摘要 |
High molecular weight butyl-type rubbers of high or low unsaturation are prepared by polymerizing a mixture of a C4 to C7 isoolefine with up to 25 weight per cent of a C4 to C10 multiolefine based on the isoolefine, in the presence of an alkyl aluminium halide catalyst having a molar ratio of alkyl groups to halogen atoms in the range 0.4:1 to 0.7:1, the halogen being chlorine or bromine dissolved in an alkyl halide or polyhalide or hydrocarbon solvent. Less than 0.1 weight per cent of water or hydrogen halide promoters, based on the total reaction mixture, is present in the reaction zone. In a preferred embodiment 10 to 25 weight per cent of multiolefine, preferably isoprene, based on the isoolefine, preferably isobutylene, is used, and the polymer obtained has a viscosity average molecular weight above 300,000. The polymerization temperature is in the range -120 DEG to -160 DEG F. and the preferred alkyl halide solvent is methyl chloride. The preferred hydrocarbon solvents are C4 to C8 paraffins. Cyclodiolefines such as cyclopentadiene and methylcyclopentadiene may be incorporated in amounts up to 6 weight per cent based on the isoolefine, with the amount of acyclic diolefine then being between 2 and 6 weight per cent based on the isoolefine. Copolymers having a high unsaturation, e.g. 5 to 12 mole per cent, terpolymers having a relatively high unsaturation, e.g. 1.4 to 4 mole per cent and butyl rubbers having a low unsaturation may be prepared by this invention. The preferred catalyst of ethyl aluminium dichloride may be prepared by contacting solid aluminium chloride with aluminium triethyl at temperatures from -70 DEG to -110 DEG F. to dissolve solid aluminium chloride and obtain a solution containing preferably 0.2 to 0.1 weight per cent of aluminium chloride. To this solution is added aluminium triethyl in the amount necessary to provide the desired ratio of alkyl groups to halogen atoms. The polymers may be cured using conventional curing agents. |
