Polypropylene composition with improved sealing and thermal properties

Patent metadata

Field	Value
Publication number	US-9512253-B2
Application number	US-201314379935-A
Country	US
Kind code	B2
Filing date	Feb 26, 2013
Priority date	Feb 27, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

The present invention relates to a polypropylene composition comprising comonomer units derived from ethylene in an amount of from 0.5 wt % to 25 wt %, and from at least one C 5-12 alpha-olefin in an amount of from 1.0 mol % to 3.0 mol %, wherein the polypropylene composition has an amount of xylene solubles XS of at least 20 wt %, and the xylene solubles have an amount of ethylene-derived comonomer units of from 4 wt % to 50 wt %.

First claim

The invention claimed is:

1. A polypropylene composition comprising comonomer units derived from ethylene in an amount of from 0.5 wt % to 25 wt %, and from at least one C 5-12 alpha-olefin in an amount of from 1.0 mol % to 3.0 mol %, wherein the polypropylene composition has an amount of xylene solubles (XS) of at least 20 wt %, and the xylene solubles have an amount of ethylene-derived comonomer units of from 4 wt % to 50 wt %.

2. The polypropylene composition according to claim 1 , wherein the at least one C 5-12 alpha-olefin is selected from 1-hexene, 1-octene, or any mixture thereof.

3. The polypropylene composition according to claim 1 , wherein the following relation is satisfied:
[C2(XS)×XS/100]/C2(total)≧0.90

wherein
C2(XS) is the amount in wt % of the ethylene-derived comonomer units in the xylene solubles,
XS is the amount in wt % of xylene solubles of the polypropylene composition, and
C2(total) is the amount in wt % of the ethylene-derived comonomer units in the polypropylene composition.

4. The polypropylene composition according to claim 1 , wherein the xylene solubles contain an amount of comonomer units which are derived from the least one C 5 -C 12 alpha-olefin of from 0.01 mol % to 2.0 mol %.

5. The polypropylene composition according to claim 1 , wherein the total amount of comonomer units in the polypropylene composition is from 1.7 mol % to 33 mol %.

6. The polypropylene composition according to claim 1 , wherein the polypropylene composition is a blend, comprising the following propylene polymer fractions P1, P2 and P3, wherein
P1 is a propylene homopolymer or a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of less than 1.0 mol %,
P2 is a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of from 2.0 mol % to 7.0 mol %, and
P3 is a propylene copolymer comprising ethylene-derived comonomer units in an amount of from 4 wt % to 50 wt %.

7. A polymer film comprising the polypropylene composition according to claim 1 .

8. The polymer film according to claim 7 , having a sealing initiation temperature SIT of 110° C. or less and/or satisfying the following relation:
Tm−SIT≧35° C.

wherein
Tm is the melting temperature of the polymer film, and
SIT is the sealing initiation temperature of the polymer film.

9. A process for preparing the polypropylene composition according to claim 1 , comprising:
(i) preparing as a first propylene polymer fraction a propylene homopolymer or a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in a first polymerization reactor PR1,
(ii) transferring the first propylene polymer fraction obtained in the first polymerization reactor to a second polymerization reactor PR2 and preparing a second propylene polymer fraction by polymerizing propylene and at least one C 5-12 alpha-olefin in the presence of the first propylene polymer fraction, thereby obtaining a reactor blend of the first and second propylene polymer fractions,
(iii) transferring the reactor blend of step (ii) into a third polymerization reactor PR3 and preparing a third propylene polymer fraction by polymerizing propylene and ethylene in the presence of the reactor blend of step (ii), thereby obtaining a reactor blend of the first, second and third propylene polymer fractions.

10. The process according to claim 9 , wherein the split between the first propylene polymer fraction of PR1 and the second propylene polymer fraction of PR2 is 70/30 to 30/70; and/or wherein the split between the reactor blend of step (ii) and the third propylene polymer fraction of PR3 is 80/20 to 50/50.

11. The process according to claim 9 , wherein the first polymerization reactor PR1 is a slurry reactor, and the second and third polymerization reactors are both gas phase reactors.

12. The process according to claim 9 , wherein a single site catalyst is used in at least one of the polymerization reactors PR1 to PR3.

Assignees

• Borealis Ag

Inventors

• Reichelt Kristin
• Paavilainen Juha
• Parkinson Matthew

Classifications

• C08L2203/162

  sealable films · CPC title

• C08L23/142

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

• C08J2423/12

  Polypropene · CPC title

• C08L2205/03

  containing three or more polymers in a blend · CPC title

• C08L23/10 Primary

  Homopolymers or copolymers of propene · CPC title