Polypropylene composition combining low sealing initiation temperature and high melting temperature

Patent metadata

Field	Value
Publication number	US-11292858-B2
Application number	US-201716469034-A
Country	US
Kind code	B2
Filing date	Dec 19, 2017
Priority date	Dec 29, 2016
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

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

The invention claimed is:

1. Polypropylene composition that is a binary blend comprising two propylene polymer fractions PPF1 and PPF2 in specific amounts:
a) 30 to 50 wt % of propylene polymer fraction PPF1 that is a propylene copolymer comprising propylene monomer and 1.50 to 7.00 mol % of one comonomer selected from C 4 -C 10 alpha-olefin, and
b) 70 to 50 wt % of propylene polymer fraction PPF2 that is a propylene terpolymer comprising propylene monomer, 0.30 to 3.00 mol % of ethylene comonomer and 3.50 to 12.00 mol % of one comonomer selected from C 4 -C 10 alpha-olefin, wherein the polypropylene composition:
i. has a melting temperature (Tm) in a 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 a range of 30 to 43° C., and wherein
Tm is melting temperature, in ° C., of the polypropylene composition,
SIT is sealing initiation temperature, in ° C., of the polypropylene composition, as calculated from pellets via DSC analysis,
wherein amounts of PPF1 and PPF2 being are relative to a total sum of the propylene polymer fractions PPF1 and PPF2, and
wherein the polypropylene composition has an amount of xylene soluble (XS) in a range of 3 to 15 wt %, as determined at 25° C. according ISO 16152; 5 th edition; 2005-07-01.

2. Polypropylene composition according to claim 1 , wherein the polypropylene composition has an MFR 2 in a 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. Polypropylene composition according to claim 1 , wherein 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 ).

4. 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 that is a slurry reactor propylene and one comonomer selected from C 4 -C 10 alpha-olefin and obtaining a propylene polymer fraction PPF1,
b) transferring the propylene polymer fraction PPF1 and unreacted comonomers of a reactor (R-1) into a second reactor (R-2) that is a gas-phase reactor-1 (GPR-1),
c) polymerising in the gas-phase reactor-1 (GPR-1) propylene, ethylene and one comonomer selected from C 4 -C 10 alpha-olefin in the presence of the propylene polymer fraction PPF1, and obtaining a propylene polymer fraction PPF2, that is a propylene terpolymer, said propylene polymer fraction PPF2 and the propylene polymer fraction PPF1 forming the polypropylene composition,
d) recovering the polypropylene composition.

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

6. The film according to claim 5 wherein said film is a blown film or a cast film.

7. The film according to claim 5 , wherein said film is a multilayer film.

Assignees

• Borealis Ag

Inventors

• Boragno Luca
• Resconi Luigi
• Hoff Mattias
• Das Shital
• Alastalo Kauno
• Vahteri Markku
• Berger Friedrich
• Tranchida Davide

Classifications

• 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

• C08F2/38

  Polymerisation using regulators, e.g. chain terminating agents {, e.g. telomerisation} · CPC title

• C08F4/651

  Pretreating with non-metals or metal-free compounds · 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

• C08F210/06 Primary

  Propene · CPC title