Soft and transparent polypropylene composition

Patent metadata

Field	Value
Publication number	US-11084919-B2
Application number	US-201716310036-A
Country	US
Kind code	B2
Filing date	Jun 26, 2017
Priority date	Jun 28, 2016
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

The present invention is directed to a polypropylene composition (C) comprising a heterophasic propylene copolymer (RAHECO) and a propylene homopolymer (H-PP) as well as a process for the preparation of said polypropylene composition and a film obtained from said polypropylene composition (C).

First claim

The invention claimed is:

1. A polypropylene composition (C), comprising:
a) a matrix (M) comprising a random propylene copolymer (R-PP) and a propylene homopolymer (H-PP) and
b) an elastomeric propylene copolymer (E) dispersed in said matrix (M),
wherein said polypropylene composition (C) has:
i) a xylene soluble content (XCS) with
a) an intrinsic viscosity (IV) determined according to DIN ISO 1628/1 (in Decalin at 135° C.) of the xylene soluble content (XCS) of at least 1.8 dl/g, and
b) an ethylene content of the xylene soluble content (C2 (XCS)) of at least 30.0 mol %, and

iii) a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of at least 2.0 g/10 min; and
wherein the random propylene copolymer (R-PP) and the elastomeric propylene copolymer (E) form a heterophasic propylene copolymer (RAHECO), said heterophasic propylene copolymer (RAHECO) having a xylene soluble content (XCS) in the range of 37.0 to 50.0 wt. % and a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 0.1 to 10.0 g/10 min.

2. The polypropylene composition (C) according to claim 1 , having a melting temperature Tm above 153° C.

3. The polypropylene composition (C) according to claim 1 , wherein the polypropylene composition (C) has:
i) a xylene soluble content (XCS) in the range of 10.0 to 45.0 wt. %, and/or
ii) an ethylene content in the range of 5.0 to 25.0 mol %, and/or
iii) a hexane soluble content in the range of 2.0 to below 16.0 wt. %.

4. The polypropylene composition (C) according to- claim 1 , wherein the ratio between the hexane soluble content C6 and the xylene soluble content XCS (C6/XCS) is below 0.45.

5. The polypropylene composition (C) according to claim 1 , wherein the polypropylene composition (C) has:
i) a haze before sterilization measured according to ASTM D 1300-00 on a 100 μm thick film below 20.0% and/or
ii) a haze after sterilization measured according to ASTM D 1300-00 on a 100 μm thick film below 12.0%.

6. The polypropylene composition (C) according to claim 1 , wherein the difference between the haze after sterilization and the haze before sterilization measured according to ASTM D 1300-00 on a 100 μm thick film is below 4.0%.

7. The polypropylene composition (C) according to claim 1 , comprising:
i) 75 to 95 wt. % of the matrix (M) and
ii) 5 to 25 wt. % of the elastomeric propylene copolymer (E),
based on the overall weight of the polypropylene composition (C), and/or
i) 30 to 75 wt. % of the random propylene copolymer (R-PP),
ii) 15 to 70 wt. % of the propylene homopolymer (H-PP) and
iii) 5 to 25 wt. % of the elastomeric propylene copolymer (E),
based on the overall weight of the polypropylene composition (C).

8. The polypropylene composition (C) according to claim 1 , wherein the comonomers of the random propylene copolymer (R-PP) and/or the comonomers of the elastomeric propylene copolymer (E) are ethylene and/or C 4 to C 8 α-olefins.

9. The polypropylene composition (C) according to claim 1 , wherein said heterophasic propylene copolymer (RAHECO) having
a) a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 0.1 to 10.0 g/10 min, and/or
b) a comonomer content in the range of 5.0 to 35.0 mol % based on the amount of the heterophasic propylene copolymer (RAHECO).

10. The polypropylene composition (C) according to claim 1 , wherein the heterophasic propylene copolymer (RAHECO) comprises:
i) 60 to 90 wt. % of the random propylene copolymer (R-PP) and
ii) 10 to 40 wt. % of the elastomeric propylene copolymer (E),
based on the overall weight of the heterophasic propylene copolymer (RAHECO).

11. The polypropylene composition (C) according to claim 1 , wherein the propylene homopolymer (H-PP) has a melt flow rate MFR (230° C.) measured according to ISO 1133 in the range of 0.1 to 15.0 g/10 min.

12. Film, comprising the polypropylene composition (C) according to claim 1 .

13. A polymerization process for producing the polypropylene composition (C) according to claim 1 , comprising the steps of:
a) providing a propylene homopolymer (H-PP),
b) polymerizing in a first reactor (R1) propylene and ethylene and/or a C 4 to C 8 α-olefin, obtaining a first random propylene copolymer fraction (R-PP1),
c) transferring the first random propylene copolymer fraction (R-PP1) into a second reactor (R2),
d) polymerizing in said second reactor (R2) in the presence of the first random propylene copolymer fraction (R-PP1) propylene and ethylene and/or a C 4 to C 8 α-olefin, obtaining a second random copolymer fraction (R-PP2), said first random propylene copolymer fraction (R-PP1) and said second random copolymer fraction (R-PP2) forming the random propylene copolymer (R-PP),
e) transferring said random propylene copolymer (R-PP) into a third reactor (R3),
f) polymerizing in said third reactor (R3) in the presence of the random propylene copolymer (R-PP) propylene and/or a C 4 to C 8 α-olefin, obtaining a third polymer fraction, said polymer fraction is the elastomeric copolymer (E), said propylene copolymer (R-PP) and said elastomeric propylene copolymer (E) form the heterophasic propylene copolymer (RAHECO),
g) melt blending the heterophasic propylene copolymer (RAHECO) obtained in step f) with the propylene homopolymer (H-PP) of step a).

14. The process according to claim 13 , wherein the first random propylene copolymer fraction (R-PP1), the random propylene copolymer (R-PP) and the elastomeric copolymer (E) have been polymerized in the presence of:
a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic compound;
b) optionally a co-catalyst (Co), and
c) optionally an external donor (ED).

Assignees

• Borealis Ag

Inventors

• Wang Jingbo
• Berger Friedrich
• Doshev Petar
• Gruenberger Manfred
• Sandholzer Martina
• Gahleitner Markus

Classifications

• C08L2203/16

  used for films · CPC title

• C08F210/16

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

• C08L2205/03

  containing three or more polymers in a blend · CPC title

• C08L2207/02

  Heterophasic composition · CPC title

• C08L23/12 Primary

  Polypropene · CPC title