Heterophasic propylene copolymer with low shrinkage
View Patent ↗A heterophasic propylene copolymer (HECO) comprising a polypropylene matrix having a melt flow rate MFR 2 (230° C.) in the range of 40 to 120 g/10 min and a comonomer content in the range of 30 to 75 mol-% for the preparation of molded articles with low CLTE.
1. An automotive article comprising at least 60 wt. % of a heterophasic propylene copolymer (HECO) having comonomers being ethylene and/or a C 4 to C 8 α-olefin, and comprising:
(a) a (semi)crystalline polypropylene (PP) having a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 40 to 120 g/10 min; and
(b) an elastomeric propylene copolymer (ESC) dispersed in said (semi)crystalline polypropylene (PP);
wherein said heterophasic propylene copolymer (HECO) has:
(i) a xylene cold soluble (XCS) fraction in the range of 22 to 64 wt. %;
(ii) a comonomer content in the range of 30.0 to 75.0 mol %;
(iii) a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 15 to 70 g/10 min; and
(iv) a xylene cold insoluble (XCI) fraction;
wherein further the intrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction of said heterophasic propylene copolymer (HECO) is in the range of 1.30 to 2.20 dl/g; and
wherein the intrinsic viscosity (IV) of the xylene cold insoluble (XCI) fraction of the heterophasic propylene copolymer (HECO) is in the range of 1.05 to 1.45 dl/g.
2. The automotive article according to claim 1 , wherein the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) has a comonomer content in the range of 40.0 to 75.0 mol %.
3. The automotive article according to claim 1 , wherein the comonomers of the heterophasic propylene copolymer (HECO) are ethylene and/or the comonomers of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) are ethylene.
4. The automotive article according to claim 1 , wherein:
(a) the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) has an intrinsic viscosity (IV) in the range of 1.30 to 2.00 dl/g, and/or
(b) the heterophasic propylene copolymer (HECO) complies with the in-equation (2):
0.90
≤
IV
(
XCS
)
IV
(
XCI
)
≤
2.00
(
2
)
wherein;
IV (XCS) is the intrinsic viscosity (IV) [dl/g] of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO), and
IV (XCI) is the intrinsic viscosity (IV) [dl/g] of the xylene cold insoluble (XCI) fraction of the heterophasic propylene copolymer (HECO).
5. The automotive article according to claim 1 wherein the heterophasic propylene copolymer (HECO) complies with the in equation (1):
C
2
(
XCS
)
C
2
(
T
)
≤
2.5
(
1
)
wherein;
C2 (XCS) is the comonomer content of the xylene cold soluble (XCS) fraction; and
C2 (T) is the comonomer content of heterophasic propylene copolymer (HECO).
6. The automotive article according to claim 1 , wherein the heterophasic propylene copolymer (HECO) complies with the in-equation (3):
MFR
(
M
)
MFR
(
T
)
≤
5.0
(
3
)
wherein;
MFR (M) is the melt flow rate MFR 2 (230° C.) measured according to ISO 1133 (g/10 min) of the (semi)crystalline polypropylene (PP); and
MFR (T) is the melt flow rate MFR 2 (230° C.) measured according to ISO 1133 (g/10 min) of the heterophasic propylene copolymer (HECO).
7. The automotive article according to claim 1 , wherein the (semi)crystalline polypropylene (PP) is a (semi)crystalline propylene homopolymer (H-PP) having a xylene cold soluble (XCS) fraction of less than 4.5 wt. %.
8. The automotive article according to claim 1 , wherein the elastomeric propylene copolymer (ESC) is an ethylene propylene rubber (EPR).
9. The automotive article according to claim 1 , wherein the heterophasic propylene copolymer (HECO) has:
(a) impact strength at +23° C. of at least 10 kJ/m 2 ; and/or
(b) a coefficient of linear thermal expansion (CLTE) performed in a temperature range from −30 to +80° C. of not more than 92 μm/mK.
10. The automotive article according to claim 1 , wherein the heterophasic propylene copolymer (HECO) has:
(a) a shrinkage in flow (60×60×2 mm) of below 0.50%, and/or
(b) a shrinkage across flow (60×60×2 mm) of below 0.70%.
11. The automotive article according to claim 1 , wherein the automotive article is an exterior automotive article.