EFFECT OF THE CONDITIONS OF CATALYST SYNTHESIS AND POLYMERISATION ON THE MACROSTRUCTURE AND MOLECULAR WEIGHT CHARACTERISTICS OF 'COBALT' AND CIS-POLYBUTADIENE

摘要

In this work, the polymerisation of butadiene was carried out in n-hexane in the presence of a pre-synthesised cobalt-containing catalyst. The catalyst was synthesised in a toluene solution by mixing cobalt salt and diisobutylaluminium chloride in the presence of water and small quantities of isoprene at temperatures ranging from -14 to -30 degrees C. The interaction of the catalyst components was studied by electron spin resonance. Gel permeation chromatography indicated that the molecular weight of cobalt polybutadiene depended on the initial polymer concentration in tetrahydrofuran solvent. The water content in the polymerised mixture also affected the nature of the molecular weight distribution. The formation of high and low molecular weight fractions of polybutadiene was attributed to the occurrence of reactions of chain transfer to the polymer (branching). To reduce the molec. wt. ethylene was introduced during polymerisation. The statistical processing of data of the continuous process of butadiene polymerisation in the presence of ethylene showed that, apart from branching and the amount of low molecular weight fraction, the properties of polybutadiene depended on the molecular weight distribution. From an analysis of data on the continuous process, it followed that, with content in the polybutadiene of fraction with a molec. wt. of 50,000 - 100,000 in a quantity of 50-60%, the nominal strength amounted to 19.6-21.5 MPa. With a reduction in the amount of the given fraction to ~40%, the nominal strength decreased to 18.1 - 18.5 MPa. 6 Refs. (Article translated from Kauchuk i Rezina, No.1, 2005, p.5-8)