Improvements in catalysts for the preparation of trans 1,4-polyisoprene (synthetic balata) and methods for their preparation and use

摘要

Trans-1 : 4-polyisoprene is prepared from isoprene in presence of a solvent, using a catalyst composed of a finely-divided inert support, of surface area 3-50 M2/gm., coated with a layer of AlR3-VCl3 reaction product (R=alkyl) to an average thickness corresponding to 5-100 mg./M2 of VCl3. The catalyst is prepared by reducing VCl4 in a liquid hydrocarbon suspension of the support, removing the solvent and thereafter contacting the supported VCl3 with AlR3. The reduction is preferably effected by heating at 50 DEG -200 DEG C. while agitating the suspension until the VCl4 decomposes; alternatively, the suspension may be exposed to ultra-violet or visible radiation, or the support may be tumbled in a closed container at 100-160 DEG C. while passing through it an inert gas carrying VCl4 vapour. Kaolin and TiO2 are the preferred supports; others listed are SiO2, Al2O3, MgO, ZrO2, talc, calcium silicate, BaSO4, SrSO4 and CaSO4. In specified trialkyls, R=ethyl, isobutyl or dodecyl. Specification 834,554 is referred to.ALSO:Trans-1:4-polyisoprene is prepared from isoprene in presence of a solvent, using a catalyst composed of a finely-divided inert support, of surface area 3-50 M2/gm., coated with a layer of AlR3-VCl3 reaction product (R=alkyl) to an average thickness corresponding to 5-100 mg/M2 of VCl3. The catalyst is prepared by reducing VCl4 in a liquid hydrocarbon suspension of the support, removing the solvent and thereafter contacting the supported VCl3 with AIR3. The reduction is preferably effected by heating at 50-200 DEG C. while agitating the suspension until the VCl4 decomposes; alternatively, the suspension may be exposed to ultraviolet or visible radiation, or the support may be tumbled in a closed container at 100-160 DEG C. while passing through it an inert gas carrying VCl4 vapour. Kaolin and TiO2 are the preferred supports; others listed are SiO2, Al2O3, MgO, ZrO2, talc, calcium silicate, BaSO4, SrSO4, and CaSO4. In specified trialkyls, R=ethyl, isobutyl or dodecyl. Specification 834,554 is referred to.