Polypropylene composition
Polypropylene composition comprising a heterophasic polypropylene (HECO) and a bimodal metallocene linear low-density polyethylene (mLLDPE), as well as articles obtained from said polypropylene composition. The present invention is further related to the use of a bimodal metallocene linear low-density polyethylene (mLLDPE) as modifier for heterophasic polypropylenes (HECOs) to improve impact strength and optics.
1. A polypropylene composition, comprising
(A) a heterophasic polypropylene (HECO), said heterophasic polypropylene comprising a matrix (M) being a propylene homopolymer and an elastomeric propylene-ethylene copolymer dispersed in said matrix (M), and
(B) a bimodal metallocene linear low-density polyethylene (mLLDPE), said bimodal metallocene linear low-density polyethylene (mLLDPE)
(a) being a terpolymer of ethylene and two different comonomers selected from alpha olefins having from 4 to 10 carbon atoms and
(b) being produced with a metallocene catalyst and
(c) having a density of 915 to 930 kg/m 3 (according to ISO 1183), and
(C) optionally a polypropylene homopolymer with a melt flow rate MFR2 (ISO 1133; 230° C.; 2.16 kg) in the range of 0.5 to 100.0 g/10 min and/or
(D) optionally an alpha nucleating agent.
2. The polypropylene composition according to claim 1 comprising
component (A) in an amount of from 95.0 to 55.0 wt %,
component (B) in an amount of from 5.0 to 45.0 wt %,
component (C) in an amount of from 0.0 to 6.0 wt % and
component (D) in an amount from 0.0 to 1.0 wt %, based on the total weight of the composition.
3. The polypropylene composition according to claim 1 , which has:
a haze according to ASTM D 1300-00 determined on 1 mm plaques below 35.0% and
a Charpy notched Impact strength (NIS, ISO 179 1eA determined at 23° C.) of at least 15.0 kJ/m 2 .
4. The polypropylene composition according to claim 1 , which has an optomechanical ability (OMA) according to formula
O
M
A
=
Flex
Modulus
[
MPa
]
*
NIS
[
kJ
m
2
]
Haze
(
1
mm
)
[
%
]
of at least 500 or more;
wherein NIS refers to the Charpy notched impact strength measured according to ISO 179 1eA at +23° C.
5. The polypropylene composition according to claim 1 , wherein the heterophasic polypropylene (HECO) has a xylene cold soluble (XCS) fraction in the range of from 5.0 to 25.0 wt %, as determined at 25° C., wherein said xylene cold soluble (XCS) fraction has an ethylene content in the range of from 8.0 to 70.0 wt % and an intrinsic viscosity (iV) from 1.0 to 5.0 dl/g and a crystalline fraction in the range of from 75.0 to 95.0 wt %, wherein said crystalline fraction has an ethylene content in the range of from 0.0 to 5.0 wt % and an intrinsic viscosity (iV) from 1.0 to 5.0 dl/g, as determined according to CRYSTEX QC method, ISO 6427-B.
6. The polypropylene composition according to claim 1 , wherein the heterophasic polypropylene (HECO) is prepared by a sequential polymerization process in the presence of a metallocene-based catalyst.
7. The polypropylene composition according to claim 1 , wherein the bimodal metallocene linear low-density polyethylene (mLLDPE) comprises at least
(i) an ethylene polymer component (A) having an MFR2 of 1.0 to 10.0 g/10 min (according to ISO 1133 at 190° C. under 2.16 kg load) and
(ii) an ethylene polymer component (B) having an MFR2 of 0.2 to 0.9 g/10 min (according to ISO 1133 at 190° C. under 2.16 kg load).
8. The polypropylene composition according to claim 1 , wherein the bimodal metallocene linear low-density polyethylene (mLLDPE) (B) comprises an ethylene polymer component (A′) and an ethylene polymer component (B′), wherein the ethylene polymer component (A′) has a lower amount (mol %) of comonomer than the ethylene polymer component (B′).
9. The polypropylene composition according to claim 8 , wherein the amount of comonomer in the ethylene polymer component (A′) is from 0.05 to 0.9 mol %, and the amount of comonomer in the ethylene polymer component (B′) is from 1.0 to 5.0 mol %.
10. The polypropylene composition according to claim 1 , wherein the bimodal metallocene linear low-density polyethylene (mLLDPE) has a total amount of comonomers present in the bimodal metallocene linear low-density polyethylene in the range of 1.0 to 6.0 mol %.
11. An article comprising the polypropylene composition according to claim 1 .
12. The article according to claim 11 , wherein the article is an unoriented mono-layer film, comprising at least 90 wt % of the polypropylene composition.
13. The article according to claim 11 , wherein the article is a moulded article.