COMPOSITION BASED ON CRYSTALLINE POLYPROPYLENE AND METHOD OF PREPARATION THEREOF Russian patent published in 1997 - IPC

FIELD: production of polymers. SUBSTANCE: composition based on crystalline polypropylene including high- a low- molecular fractions is distinguished with that the former has intrinsic viscosity measured in tetrahydronaphthalene at 135 C from 4.2 to 8.0 dl/g and the latter from 0.5 to 0.74 dl/g, whereas flow index of the latter measured in accordance with ASTM D 1238 condition L is 190-500 g/10 min, general intrinsic viscosity measured in tetrahydronaphthalene at 135 C is 1.6-2.8 dl/g, chain-length distribution 21.8-26.0, content of fraction insoluble in xylene at 25 C 97.2-98.0 wt %, modulus of elasticity 2330-2580 MPa, shock strength at 23 C 16-40 J/m, and yield point 38.3-41.4 MPa. This fraction is prepared via successive polymerization in at least two steps in presence of certain Ziegler-Natta catalysts on magnesium halide carriers. Polymers are characterized with high strength of melt, high mechanical properties, and are virtually appropriate to produce ware using various conversion technologies such as extrusion into thin sheets subjected to thermal shaping as well as for pressure molding and blowing. EFFECT: improved performance characteristics. 3 cl