Propylene Block Copolymer and Process for Production Thereof
AssigneeJapan Polypropylene Corporation
InventorsKiyoshi Yukawa, Takehiro Sagae
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Abstract
Disclosed is a propylene block copolymer having excellent flexibility and impact resistance and showing a good polymer powder form. Also disclosed is a process for producing the copolymer. More specifically, the copolymer is a novel propylene block copolymer which satisfies a specific requirement and is produced by a process comprising continuously performing a multi-step polymerization composed of a former step in which a propylene homopolymer component or a specific propylene copolymer component is produced in the presence of a metallocene catalyst carried on a support and a latter step in which propylene and a specific copolymer component are produced by gas phase polymerization.
Claims20
A propylene block copolymer obtainable by a multi-step polymerization in the presence of a metallocene catalyst supported on a carrier comprising:
- a former step for producing a propylene homopolymer component, or a propylene copolymer component (hereafter referred to as PP) composed of propylene and at least one kind of a comonomer selected from the group consisting of ethylene and/or a C4-20 α-olefin, wherein content of said comonomer being equal to or less than 10% by weight;
- and
- a latter step for producing a copolymer component (hereafter referred to as CP) composed of propylene and at least one kind of a comonomer selected from the group consisting of ethylene and/or a C4-20 α-olefin,
- characterized by satisfying the following requisites (1) to (4):
- Requisite (1):
- Content of CP in the propylene block copolymer is from 45 to 99% by weight.
- Requisite (2):
- Polymerization ratio of the comonomer in CP is from 30 to below 100% by mole.
- Requisite (3):
- Weight average molecular weight of CP is from 100,000 to 2,000,000.
- Requisite (4):
- Ratio of amount of a component with a molecular weight of equal to or less than 5000 (M<5000), by measurement with gel permeation chromatography (GPC), is equal to or less than 2.0% by weight of the total.
Dependencies are inferred from the claim text.