High flow heterophasic polypropylene copolymers with improved mechanical and optical properties
The present invention is directed to a new heterophasic polypropylene composition showing a good balance between stiffness and impact at low haze, as well as to its use for injection molded articles. The present invention is also directed to provide such heterophasic polypropylene composition in a more simplified mode of production.
1. A heterophasic polypropylene composition comprising:
a) 80.0-96.0 wt.-% of a polypropylene random copolymer;
b) 3.0-18.0 wt.-% of a polypropylene homopolymer or polypropylene random copolymer;
c) 0.5-2.50 wt.-% of an elastomeric ethylene-propylene copolymer fraction characterised by an IV of 0.7-2.0 dl/g and an C2(XCS) of 12.0-35.0 wt.-%.; and
d) 0.002-0.60 wt.-% of a nucleating or clarifying agent;
wherein the heterophasic polypropylene composition has an MFR230/2.16 according to ISO1133 of 10.0 g/10 min or more.
2. The heterophasic polypropylene composition according to claim 1 , wherein the polypropylene homopolymer or polypropylene random copolymer b) and the elastomeric ethylene-propylene copolymer fraction c) are present in in a ratio of from 60:40 (b:c) to 90:10 (b:c).
3. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition comprises a polypropylene random copolymer as b) and the polypropylene random copolymer a) differs from the polypropylene random copolymer b) in view of comonomer content and/or MFR230/2.16.
4. The heterophasic polypropylene composition according to claim 1 , wherein
the polypropylene random copolymer (a) comprises ethylene as a comonomer and has an ethylene content of 0.2 to 3.5 wt.-%; and/or
the polypropylene homopolymer or polypropylene random copolymer (b) is a polypropylene random copolymer comprising ethylene as a comonomer and has an ethylene content of 0-1.0 wt.-%.
5. The heterophasic polypropylene composition according to claim 1 , wherein
the polypropylene random copolymer a) has an MFR230/2.16 according to ISO1133 of ≥8.0 g/10 min, and
the polypropylene homopolymer or polypropylene random copolymer b) has an MFR230/2.16 according to ISO1133 of at most 8.0 g/10 min.
6. The heterophasic polypropylene composition according to claim 1 , wherein the sum of the weight fractions of the polypropylene homopolymer or polypropylene random copolymer (b) and the elastomeric ethylene-propylene copolymer fraction (c) together form at most 20.0 wt.-% based on the weight of the heterophasic polypropylene composition.
7. The heterophasic polypropylene composition according to claim 1 , wherein the nucleating or clarifying agent (d) is a soluble nucleating or clarifying agent.
8. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition comprises at least two nucleating or clarifying agents.
9. The heterophasic polypropylene composition according to claim 1 , wherein the nucleating or clarifying agent comprises a polymeric nucleating agent.
10. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition has having a Tensile Modulus measured according to ISO527 of at least 1200 MPa, a notched impact strength measured according to ISO179/1eA+23° C. of at least 5.0 kJ/m 2 , and a Haze value measured according to ASTM 1003D on a 1 mm injection moulded plaque of at most 25.0%.
11. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition has an optomechanical ability (OMA) of at least 300, as determined according to formula:
OMA
=
Tensile
Modulus
[
MPa
]
*
NIS
[
kJ
m
2
]
Haze
(
1
mm
)
[
%
]
wherein
Tensile Modulus [MPa] is the tensile modulus in MPa;
NIS
[
kJ
m
2
]
is notched impact strength in kJ/m 2 ; and
Haze (1 mm) [%] is the Haze value according to ASTM 1003D on a 1 mm injection moulded plaque in %.
12. The heterophasic polypropylene composition according to claim 1 , the heterophasic polypropylene composition being polymerised in the presence of a Ziegler-Natta catalyst, wherein the Ziegler Natta catalyst comprises
a compound of a transition metal of IUPAC Group 4 to 6,
a Group 2 metal compound,
an internal donor, wherein said internal donor is a non-phthalic compound, and
a co-catalyst.
13. The heterophasic polypropylene composition according to claim 12 , wherein the internal donor is selected from the group consisting of (di)esters of non-phthalic carboxylic (di)acids, 1,3-diethers, derivatives thereof, and mixtures thereof.
14. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition is free of phthalic acid esters as well as their respective decomposition products.
15. A moulded article comprising the heterophasic polypropylene composition of claim 1 .
16. A method of use of the heterophasic polypropylene composition according to claim 1 , the method comprising using the heterophasic polypropylene in a packaging application.
17. The heterophasic polypropylene composition according to claim 12 , wherein the internal donor is a non-phthalic acid ester.
18. The heterophasic polypropylene composition according to claim 12 , wherein the Ziegler Natta catalyst further comprises an external donor.