Partly crystalline propylene polymer composition, used e.g. for production of biaxially oriented film, comprises three molecular weight fractions as determined by temperature rising elution fractionation in xylene

摘要

Propylene copolymer with a composition determined by temperature rising elution fractionation in xylene, comprising 65-85 wt% high-molecular weight component (A) eluting at above Tx, 10-35 wt% component (B) eluting at Tx and 0-25 wt% lower-molecular weight component (C) eluting at above Tx, where Tx = (polymer melting point) / 2 + 7.5[deg]C. Partly crystalline propylene polymer composition (I) obtained by polymerisation of propylene, ethylene or 4-18C alk-1-enes, in which at least 50 mol% of the monomer units are derived from propylene and at least 20 wt% of (I) is obtained by polymerisation with metallocene catalysts. Composition (I) has a melting point (Tm) in the range 65-170 [deg]C (DSC peak temperature obtained by heating a premelted sample at 20 [deg]C/min) and comprises 65-85 wt% main component (A), 10-35 wt% further component (B) and 0-25 wt% further component (C), these amounts being determined by temperature rising elution fractionation (TREF) by dissolving (I) in boiling xylene, cooling to 25 [deg]C at 10 [deg]C/hour, dissolving the component which is soluble in xylene at Tm/2 + 7.5 [deg]C (temperature Tx), separating from any solid, eluting the fractions which are soluble in the range between successive elution temperatures of 70, 75, 80, 85, 90, 94, 98, 102, 107, 112, 117, 122 and 125 [deg]C, retaining for further evaluation those fractions which make up at least 1 wt% of (I) and determining the mol. wt. distribution of these fractions by GPC in 1,2,4-trichlorobenzene at 145 [deg]C. Component (A) comprises all fractions with a number-average mol. wt. (Mn) of at least 120,000 which are eluted at above Tx, component (B) comprises fractions eluted at Tx and component (C) comprises fraction with an Mn of less than 120,000 which are eluted at above Tx. Independent claims are also included for: (a) production of (I) by polymerisation in a single reactor with a catalyst system containing at least two metallocene compounds; (b) film, fibres or molded products containing (I); and (c) biaxially oriented film made from (I), with stretch ratios of at least 1:3 in the machine direction and at least 1:5 in the transverse direction.