Polypropylene composition with excellent paint adhesion
The present invention is directed to a polypropylene composition, an article comprising the polypropylene composition as well as the use of the polypropylene composition to enhance paint adhesion of a molded article.
1. Polypropylene composition (C), the polypropylene composition (C) comprising:
(a) 15.0 to 60.0 wt. %, based on the total weight of the composition (C), of a heterophasic propylene copolymer (HECO),
(a1) said heterophasic propylene copolymer (HECO) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of above 1.0 to 20.0 g/10 min;
(a2) the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) has an intrinsic viscosity determined according to DIN ISO 1628/1 (in decalin at 135° C.) in the range of more than 2.1 to 9.0 dl/g; and
(a3) the comonomer content of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is in the range of 10.0 to 45.0 wt. %;
(b) 10.0 to 45.0 wt. %, based on the total weight of the composition (C), of a propylene copolymer (R-PP) having
(b1) a comonomer content in the range of 1.5 to 8.0 wt. %; and
(b2) a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 5.0 to 100.0 g/10 min; and
(c) 20.0 to 40.0 wt. %, based on the total weight of the composition (C), of a mineral filler (F) being selected from the group consisting of talcum, wollastonite, caolin and mica.
2. The polypropylene composition (C) according to claim 1 , wherein the polypropylene composition (C) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 3.0 to 45.0 g/10 min.
3. The polypropylene composition (C) according to claim 1 , wherein the heterophasic propylene copolymer (HECO) comprises a propylene homopolymer (H-PP) acting as a matrix and an elastomeric propylene copolymer (E) being dispersed in said matrix, wherein:
(a) said propylene homopolymer (H-PP) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of above 35 to 400 g/10 min; and/or
(b) the heterophasic propylene copolymer (HECO) fulfills the in-equation (III):
MFR
(
HPP
)
MFR
(
HECO
)
≥
3.0
(
III
)
wherein:
MFR(HPP) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the propylene homopolymer (H-PP), and
MFR(HECO) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the heterophasic propylene copolymer (HECO).
4. The polypropylene composition (C) according to claim 1 , wherein the heterophasic propylene copolymer (HECO) has
(a) a comonomer content in the range of 5.0 to 20 wt. %; and/or
(b) a xylene cold soluble content (XCS) determined according to ISO 16152 (25° C.) of below 45.0 wt. %.
5. The polypropylene composition (C) according to claim 1 , wherein the polypropylene composition (C) fulfils:
(a) the in-equation (I):
MFR
(
RPP
)
MFR
(
HECO
)
>
1.70
(
I
)
wherein:
MFR(RPP) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the propylene copolymer (R-PP), and
MFR(HECO) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the heterophasic propylene copolymer (HECO); and/or
(b) the in-equation (II)
MFR
(
HPP
)
MFR
(
RPP
)
>
1.80
(
II
)
wherein:
MFR(HPP) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the propylene homopolymer (H-PP) of the heterophasic propylene copolymer (HECO), and
MFR(RPP) is the melt flow rate MFR (230° C.) measured according to ISO 1133 of the propylene copolymer (R-PP).
6. The polypropylene composition (C) according to claim 1 , wherein the propylene copolymer (R-PP) has:
(a) a glass transition temperature in the range of −12 to +2° C.; and/or
(b) no glass transition temperature below −20° C.
7. The polypropylene composition (C) according to claim 1 , wherein the propylene copolymer (R-PP) has
(a) a melting temperature in the range of 135 to 165° C., and/or
(b) a tensile modulus of at least 800 MPa, and/or
(c) a Charpy notched impact strength at +23° C. of ≧4 kJ/m 2 .
8. The polypropylene composition (C) according to claim 1 , wherein the propylene copolymer (R-PP):
(a) has 2,1 regio-defects of at most 0.4% determined by 13 C-NMR spectroscopy; and/or
(b) is monophasic.
9. The polypropylene composition (C) according to claim 1 , wherein the propylene copolymer (R-PP) comprises a comonomer selected from ethylene, C 4 to C 12 α-olefin, and mixtures thereof.
10. The polypropylene composition (C) according to claim 1 , wherein the propylene copolymer (R-PP) comprises two fractions, a first propylene copolymer fraction (R-PP1) and a second propylene copolymer fraction (R-PP2), said first propylene copolymer fraction (R-PP1) differs from said second propylene copolymer fraction (R-PP2) in the comonomer content.
11. The polypropylene composition (C) according to claim 10 , wherein:
(a) the weight ratio between the first propylene copolymer fraction (R-PP1) and the second propylene copolymer fraction (R-PP2) of the propylene copolymer (R-PP) [(R-PP1):(R-PP2)] is 70:30 to 30:70; and/or
(b) the comonomers for the first propylene copolymer fraction (R-PP1) and the second propylene copolymer fraction (R-PP2) of the propylene copolymer (R-PP) are selected from ethylene, C 4 to C 12 α-olefin, and mixtures thereof.
12. The polypropylene composition (C) according to claim 10 , wherein:
(a) the first propylene copolymer fraction (R-PP1) of the propylene copolymer (R-PP) is the comonomer lean fraction and the second propylene copolymer fraction (R-PP2) of the propylene copolymer (R-PP) is the comonomer rich fraction, and/or
(b) the first propylene copolymer fraction (R-PP1) of the propylene copolymer (R-PP) has a lower comonomer content than the propylene copolymer (R-PP).
13. The polypropylene composition (C) according to claim 10 , wherein:
(a) the first propylene copolymer fraction (R-PP1) and the second propylene copolymer fraction (R-PP2) of the propylene copolymer (R-PP) fulfill together the in-equation (IV):
Co
(
R
-
PP
2
)
Co
(
R
-
PP
1
)
≥
1.0
;
(
IV
)
wherein:
Co (R-PP1) is the comonomer content [wt.-%] of the first propylene copolymer fraction (R-PP1),
Co (R-PP2) is the comonomer content [wt.-%] of the second propylene copolymer fraction (R-PP2), and/or,
(b) the first propylene copolymer fraction (R-PP1) and the propylene copolymer fraction (R-PP) fulfill together the in-equation (V):
Co
(
R
-
PP
)
Co
(
R
-
PP
1
)
≥
1.0
(
V
)
wherein:
Co (R-PP1) is the comonomer content [wt.-%] of the first propylene copolymer fraction (R-PP1),
Co (R-PP) is the comonomer content [wt.-%] of the propylene copolymer (R-PP).
14. The polypropylene composition (C) according to claim 1 , wherein the mineral filler (F) is talc.
15. Article comprising a polypropylene composition (C) according to claim 1 .
16. The article according to claim 15 , wherein the article is an automotive article selected from bumpers, body panels, rocker panels, side trims, step assists, spoilers and dash boards.