| 摘要 |
PURPOSE:To provide the titled composition of good balance between rigidity and impact resistance with high elongation at break, having both specific melt flow index (MFI) and molecular weight distribution. CONSTITUTION:The objective composition can be obtained by (co)polymerization using a stereoregular catalyst [e.g. (C2H5)2 AlCl-TiCl3], of either propylene singly or propylene with a small amount of ethylene followed by, pref. in the same system, reaction between ethylene and propylene so that the weight ratio of the ethylene to the propylene falls between 20/80 and 95/5. The resulting composition has the following characteristics: (1) MFI >=20; (2) kerosene-soluble (at 30 deg.C) fraction (A) accounts for 5-20wt%; (3) ethylene content of the fraction (A) 20- 70wt%; (4) kerosene-insoluble (at 30 deg.C) and boiling n-heptane-insoluble fraction (B) accounts for 50-90wt%; (5) MW/MN values for both the fractions (A) and (B) >=5.0, respectively. This ratio is calculated by the following procedures: said fractions (A) and (B) are each subjected to gel permeation chromatography (GPC) to determine molecular weight distribution curve, the high-molecular weight region of which is approximated with Gaussian distribution.
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