Polypropylene composition combining low sealing initiation temperature and high melting temperature

Patent metadata

Field	Value
Publication number	US-10487203-B2
Application number	US-201716464933-A
Country	US
Kind code	B2
Filing date	Dec 19, 2017
Priority date	Dec 29, 2016
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

The invention relates to a polypropylene composition which combines low sealing initiation temperature (SIT) and high melting point (Tm), thus having a broad sealing window.

First claim

What is claimed is:

1. A polypropylene composition being a binary blend comprising two propylene polymer fractions PPF1 and PPF2 in specific amounts:
a) less than or equal to 50 wt % of propylene polymer fraction PPF1 being a propylene copolymer comprising propylene monomers and 1.50 to 7.00 mol % of one comonomer selected from C 4 -C 10 alpha-olefin
and
b) more than or equal to 50 wt % of propylene polymer fraction PPF 2 being a propylene terpolymer comprising propylene monomers, 3.00 to 12.00 mol % of ethylene comonomer and 1.50 to 17.00 mol % of one comonomer selected from C 4 -C 10 alpha-olefin, characterized in that the polypropylene composition:
i) has a melting temperature (Tm) in the range of 135 to 160° C. as determined by DSC according to ISO 11357
ii) satisfies the equation:
Delta=Tm−SIT

wherein Delta is in the range of 39 to 50° C., and
wherein Tm is the melting temperature, in ° C., of the polypropylene composition, SIT is the sealing initiation temperature, in ° C., of the polypropylene composition, as calculated from pellets via DSC analysis,

the amount of PPF1 and PPF2 being relative to the total sum of the propylene polymer fractions PPF1 and PPF2.

2. The polypropylene composition according to claim 1 , characterized in that the polypropylene composition has an MFR 2 in the range of 3.0 to 10.0 g/10 min, as measured at 230° C. under a load of 2.16 kg according to ISO 1133.

3. The polypropylene composition according to claim 1 , characterized in that the polypropylene composition has amount of xylene soluble (XS) in the range of 15 to 40 wt %, as determined at 25° C. according ISO 16152; 5 th edition; 2005-07-01.

4. The polypropylene composition according to claim 1 , wherein the composition is obtainable in the presence of a Ziegler-Natta catalyst.

5. The polypropylene composition according to claim 1 , wherein the Ziegler-Natta catalyst is free of phthalic compound.

6. The polypropylene composition according to claim 1 characterized in that the propylene polymer fraction PPF1 is a propylene copolymer comprising 1-butene (C 4 ) and the propylene polymer fraction PPF2 is a propylene terpolymer comprising ethylene comonomer and 1-butene (C 4 ).

7. A process for producing the polypropylene composition according to claim 1 by a sequential polymerisation process comprising at least two reactors connected in series, said process comprising the steps:
a) polymerising in a first reactor being a slurry reactor propylene and one comonomer selected from C 4 -C 10 alpha-olefin obtaining a propylene polymer fraction (PPF1)
b) transferring the propylene polymer fraction (PPF1) and unreacted comonomers of the reactor (R-1) into a second reactor (R-2) being a first gas-phase reactor-1 (GPR-1),
c) in the gas-phase reactor-1 (GPR-1) propylene, ethylene and one comonomer selected from C 4 -C 10 alpha-olefin are polymerised in the presence of the propylene polymer fraction (PPF1), obtaining a propylene polymer fraction (PPF2), and
d) recovering the polypropylene composition.

8. An article comprising the polypropylene composition according to claim 1 .

9. A film comprising the polypropylene composition according to claim 1 .

10. The film according to claim 9 wherein said film is a blown film or a cast film.

11. The film according to claim 9 wherein said film is a multilayer film.

12. A method comprising producing an article, a film or a multilayer film with the polypropylene composition according to claim 1 .

13. The film according to claim 10 wherein said film is a multilayer film.

Assignees

• Borealis Ag

Inventors

• Boragno Luca
• Leskinen Pauli
• Resconi Luigi
• Hoff Matthias
• Berger Friedrich

Classifications

• C08L23/142 Primary

  at least partially crystalline copolymers of propene with other olefins · CPC title

• C08F2/001

  Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer (C08F295/00, C08F297/00 take precedence) · CPC title

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08F210/16 Primary

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title