Heterophasic propylene ethylene copolymer composition with desirable balance of mechanical properties

1 . A heterophasic propylene ethylene copolymer composition having an MFR 2 measured according to ISO 1333 at 230° C. and 2.16 kg in the range from 1.0 to 55.0 g/10 min and a melting temperature (T m ) measured by differential scanning calorimetry (DSC) in the range from 155 to 162° C., comprising:

a) a crystalline matrix (M) being a propylene homo-or copolymer;

b) an amorphous propylene-ethylene elastomer (E);

wherein the heterophasic propylene ethylene copolymer composition is characterized in terms of its soluble fraction (SF) and crystalline fraction (CF) as determined by CRYSTEX analysis obtained through temperature cycles of dissolution at 160° C., crystallization at 40° C. and re-dissolution in 1,2,4-trichlorobenzene at 160° C.:

i) from 60 to 88 wt. %, based on the total weight of the heterophasic propylene ethylene copolymer composition, of a crystalline fraction (CF) having an intrinsic viscosity iV(CF) measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.) in the range from 1.40 to 2.50 dl/g, a an isotactic pentad concentration [mmmm] as determined by 13 C-NMR spectroscopy of more than 97.0% and a content of 2,1-regiodefects in the range from 0.1 to 0.4 mol %,

ii) from 12 to 40 wt. %, based on the total weight of the heterophasic propylene ethylene copolymer composition, of a soluble fraction (SF) having an intrinsic viscosity iV(SF) measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.) in the range from 1.80 to 3.20 dl/g and an ethylene content C2(SF), as determined by quantitative 13 C-NMR spectroscopy, in the range from 25 to 80 wt. %,

wherein the ratio of the intrinsic viscosities of the two fractions, iV(SF)/iV(CF), is in the range from 1.25 to 2.0.

2 . The heterophasic propylene ethylene copolymer composition according to claim 1 , wherein:

i) the melt flow rate MFR 2 measured according to ISO 1133 at 230° C. and 2.16 kg is in the range from 10.0 to 55.0 g/10 min,

ii) the crystalline fraction (CF), as determined by CRYSTEX analysis obtained through temperature cycles of dissolution at 160° C., crystallization at 40° C. and re-dissolution in 1,2,4-trichlorobenzene at 160° C., is present in an amount in the range from 70 to 88 wt. %,

iii) the soluble fraction (SF), as determined by CRYSTEX analysis obtained through temperature cycles of dissolution at 160° C., crystallization at 40° C. and re-dissolution in 1,2,4-trichlorobenzene at 160° C., is present in an amount in the range from 12 to 30 wt. %,

iv) the intrinsic viscosity of the soluble fraction iV(SF) is in the range from 1.80 to 2.90 dl/g, and

v) the intrinsic viscosity of the crystalline fraction iV(CF) is in the range from 1.40 to 2.00 dl/g.

3 . The heterophasic propylene ethylene copolymer composition according to claim 1 , wherein the crystalline matrix (M) has a melt flow rate (MFR 2 ) measured according to ISO 1333 at 230° C. and 2.16 kg in the range from 1.0 to 100 g/10 min.

4 . The heterophasic propylene ethylene copolymer composition according to claim 1 , additionally comprising:

iii) at least one nucleating agent in an amount in the range from 0.1 to 2.0 wt. %.

5 . The heterophasic propylene ethylene copolymer composition according to claim 1 , having:

i) an ethylene content C(C2), as determined by quantitative 13 C-NMR spectroscopy, in the range from 4 to 20 wt. %, and/or

ii) an intrinsic viscosity (iV) measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.) in the range from 1.30 to 3.00 dl/g.

6 . The heterophasic propylene ethylene copolymer composition according to claim 1 , having a glass transition temperature associated with the amorphous propylene-ethylene elastomer (T g (E)), measured according to ISO 6721-7, in the range from −170 to −135° C.

7 . The heterophasic propylene ethylene copolymer composition according to claim 1 , wherein the numerical values of the flexural modulus measured according to ISO 178, given in MPa, and the content of xylene cold solubles C(XCS), determined at 23° C. according to ISO 16152, given in wt. %, follow inequation (I):

Flexural

⁢

modulus

≥

1650

-

3

⁢

5

×

C

⁢

(

X

⁢

CS

)

.

(

I

)

8 . The heterophasic propylene ethylene copolymer composition according to claim 1 , wherein the numerical values of the Charpy Notched Impact Strength (NIS) measured according to ISO 179-1 eA at 23° C., given in kJ/m 2 , and the content of xylene cold solubles C(XCS) determined at 23° C. according to ISO 16152, given in wt. %, follow inequation (II):

NIS

≥

1.

6

×

e

(

0.098

×

C

⁡

(

X

⁢

C

⁢

S

)

)

.

(

II

)

9 . The heterophasic propylene ethylene copolymer composition according to claim 1 , having:

i) a melting enthalpy (H m ) measured by differential scanning calorimetry (DSC) in the range from 50 to 110 J/g, and/or

ii) a crystallisation temperature (T c ) measured by differential scanning calorimetry (DSC) in the range from 115 to 125° C.

10 . The heterophasic propylene ethylene copolymer composition according to claim 1 , wherein the heterophasic propylene ethylene copolymer composition is free from radical initiators and decomposition products thereof.

11 . The heterophasic propylene ethylene copolymer composition according to claim 1 , having:

i) a flexural modulus measured according to ISO 178 in the range from 400 to 1400 MPa,

ii) a Charpy Notched Impact Strength (NIS) measured according to ISO 179-1 eA at 23° C. in the range from 8.0 to 100 kJ/m 2 , and/or

iii) a Charpy Notched Impact Strength (NIS) measured according to ISO 179-1 eA at −20° C. in the range from 2.0 to 100 KJ/m 2 .

12 . An article comprising more than 75 wt. % of the heterophasic propylene ethylene copolymer composition according to claim 1 .

13 . The article according to claim 12 , wherein the article is a part of household appliances, or of washing machine or dishwasher components, or automotive articles, or of car interiors and exteriors, or instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, and interior trims.