CRYSTALLINE PROPYLENE COPOLYMER-BASED COMPOSITION CHARACTERIZED BY IMPROVED WELDABILITY AND OPTICAL PROPERTIES AS WELL AS REDUCED SOLUBILITY Russian patent published in 2007 - IPC C08L23/14 C08L23/16 C08J5/18 

FIELD: polymer materials.

SUBSTANCE: invention relates to crystalline propylene copolymer-based compositions suitable to manufacture heat-weldable films and sheets. Composition according to invention contains 15-60% propylene copolymer having at least one C₄-C₈-α-olefin in amount 10-14% and 40-85% propylene copolymer having at least one C₄-C₈-α-olefin containing 14-30% of indicated C₄-C₈-α-olefin and optionally 0.5-3% ethylene, total proportion of C₄-C₈-α-olefin in propylene polymer-based composition being more than 10%. Melt flow rate MFR L of composition varies between 1 and 15 g/10 min. Such composition can be obtained by destroying composition-precursor prepared via stepped polymerization and containing the same components as above in the same proportions but having melt flow rate MFR L within a range of 0.1 to 5 g/10 min. Owing to combining two propylene copolymers containing more than 10% of C₄-C₈-α-olefins, composition possesses an useful balance of heat weldability, low content of fraction soluble in organic solvents, and optical properties (in particular very low turbidity and high brightness, and thereby good surface properties such as low tackiness and printing ability.

EFFECT: improved performance characteristics of material.

6 cl, tbl, 6 ex