FIELD: chemistry.
SUBSTANCE: present invention pertains to compositions of stereoselective Ziegler-Natta catalysts, meant for use in polymerising propylene. The catalyst composition for polymerising propylene or a mixture of propylene and one or more copolymerisable comonomers, contains one or more Ziegler-Natta meshes, containing one or compounds of transition metals and one or more internal electron donors in form of monoesters of aromatic carboxylic acids; one or more aluminium-containing cocatalysts; and a mixture of two or more different selectivity receptors (SCA). The above mentioned mixture of selectivity regulators contains from 98.5 to 99.9 molar percentage of one or more esters of one or more aromatic monocarboxylic acids or their substituted derivatives and from 1.5 to 0.1 molar percentage of one or more alkoxysilane compounds. The polymerisation method involves bringing into contact propylene or a mixture of propylene and one or more copolymerisable comonomers in polymerisation conditions at temperature lying between 45 and 100°C with the above given composition of catalyst.
EFFECT: obtaining compositions, which are auto-extinguishing with regards to catalyst activity, depending on temperature, leading to reduced formation of polymer agglomerates, improved regulation of the polymerisation process and increased nonsusceptibility to break down of reactor operation or electrical power cuts.
18 cl, 1 ex, 1 tbl
