Translated by P. CurtisThe study of the metathesis degradation of unsaturated polymers goes back 30 years [1]. The metathesis of a polymer product and a low-molecular-weight alkene has been used as a means of investigating the microstructure of the most varied rubbers. In Russia, an extensive cycle of studies of the polymerisation and copolymerisation of dienes and also the metathesis of cycloolefins under the influence of organometallic catalysts has been carried out under the supervision of academician B.A. Dolgoplosk and E.I. Tinyakova at the A.V. Topchiev Institute of Petrochemical Synthesis. In studies by Russian scientists [2][3][4] it has been shown that cis-polybutadiene in solutions rapidly undergoes degradation under the influence of metathesis catalysts at room temperature. The chain nature of this process was demonstrated by conducting the reaction in a weak (1%) solution of cispolybutadiene in the presence of minimum amounts of catalyst [4]. Under these conditions, active carbene centres arise only on individual polymer molecules, and, owing to the low polymer concentration in the solution, intramolecular reactions of chain transfer develop.One of the areas of application of the degradation of unsaturated polymers is the cleaning of polymerisation reaction vessels to remove gel formations building up inside reaction vessel equipment, on stirrers, and in piping in the production of rubbers. Without using catalytic breakdown, the cleaning of polymerisation reaction vessels to remove rubber gel is a very laborious process.Metathesis catalysts based on molybdenum and tungsten could have been widely used for depolymerisation and the cleaning of reaction vessel equipment to remove gel formations, but considerable shortcomings of catalysts of this kind are their high consumption norms, which can reach 5-20 parts catalysts per 100 parts polymer, the need to use olefins and an appropriate solvent, and also their sensitivity to air oxygen, moisture, and other catalyst poisons. On account of the range of shortcomings, they have not enjoyed technological application in this area [5,6]. The ruthenium-based metathesis catalysts discovered in 1992 by R.H. Grubbs [7] are free of these shortcomings. They have proved to be a very powerful tool for controlling the structure of substances carrying in their structure unsaturated C=C bonds, including polymers, which is borne out by data on the degradation of butadiene and butadiene-acrylonitrile rubbers, and also by the possibility of using them for the breakdown of gel formations of rubbers [8, 9].In solution technology for the production of synthetic rubbers (SKD-ND, SKI-3, SKI-5), organoaluminium compounds (OACs) are used as components of the catalytic system. Whereas for tungsten and molybdenum complexes these are components of the metathesis catalyst, their influence on ruthenium catalysts has not been investigated. Taking into account the fairly high content of OACs in the charge (up to 3 mmol/L) and, probably, in rubber gel, and also the low working
