Soft polypropylene composition with improved properties

1. Soft heterophasic propylene copolymer composition, which comprises:

(A) 50.0 to 99.0 wt % of a heterophasic polypropylene copolymer, said heterophasic propylene copolymer comprises:

(a-1) a matrix (M) being a crystalline polypropylene homo- or copolymer and

(a-2) elastomeric propylene copolymer (E) dispersed in said matrix (M),

wherein the heterophasic polypropylene copolymer has;

(i) a melt flow rate (MFR 230° C./2.16 kg, ISO1133) of 0.5 to 20.0 g/10 min,

(ii) a xylene cold soluble (XCS) content determined according to ISO 16152 (25° C.) in the range of 15.0 to 30.0 wt %,

(iii) a total ethylene or C 4 -C 8 comonomer content in the range of 5.0 to 13.0 wt %,

(iv) wherein the heterophasic polypropylene copolymer is free of phthalic acid esters or their decomposition products originating from a Ziegler-Nata catalyst, and

(B) 1.0 to 50.0 wt % of a styrene-based elastomer (B) being a saturated block copolymer of styrene with ethylene and butylene or propylene, having a styrene content in the range of 5.0 to 22.0 wt % (measured with FTIR),

the soft heterophasic propylene copolymer composition having a flexural modulus measured according to ISO 178 on injection moulded specimens of below 450 MPa.

2. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the xylene cold soluble (XCS) content (ii) of the heterophasic polypropylene copolymer has:

(ii-1) a comonomer content in the range of 15.0 to 40.0 wt % and

(ii-2) an intrinsic viscosity (iV) determined according to DIN ISO 1628/1 (in decalin at 135° C.) in the range of 1.0 to 2.0 dl/g.

3. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the matrix (M) of the heterophasic polypropylene copolymer is a random propylene-copolymer (R-PP) wherein the random propylene copolymer (R-PP) has:

a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 0.5 to 20.0 g/10 min, and

a comonomer content in the range of 1.0 to 12.0 wt %.

4. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the comonomer of the random propylene copolymer (R-PP) and the comonomer of the elastomeric propylene copolymer (E) are ethylene.

5. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the styrene based elastomer (B) has a:

melt flow rate MFR 2 (230° C., ISO 1133) in the range of 1.0 to 20.0 g/10 min and

a density of below 0.905 g/m 3 or

a Shore A hardness measured according to ASTM D 2240 in the range of 25 to 70.

6. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the heterophasic propylene copolymer has a tensile modulus according to ISO 527-1,2 measured on a 50 μm cast film of below 320 MPa.

7. The soft heterophasic propylene copolymer composition according to claim 1 , wherein the heterophasic propylene copolymer has

i) a haze before steam sterilization according to ASTM D 1003-00 measured on a 1 mm thick injection molded specimen from 5.0 to below 50.0%, and/or

ii) a haze before steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film of below 5.0%, and/or

iii) a haze after steam sterilization determined according to ASTM D 1003-00 measured on a 50 μm cast film of below 10.0%.

8. Process for producing a soft heterophasic propylene copolymer composition according to claim 1 , which process comprises the steps of:

(i) preparing a matrix (M),

(ii) preparing the elastomeric propylene copolymer (E) and dispersing the elastomeric copolymer (E) in the matrix (M) to obtain a heterophasic propylene copolymer (A), whereby the heterophasic propylene copolymer is prepared in the presence of:

a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), said internal donor (ID) is a non-phthalic compound,

b) a co-catalyst (Co), and

c) optionally an external donor (ED),

and subsequently

(iii) mixing said heterophasic propylene copolymer (A) with a saturated block copolymer of styrene with ethylene and either butylene or propylene, having a styrene content in the range of 5.0 to 22.0 wt % (measured with FTIR) (B), and

iv) extruding said mixture.

9. The process according to claim 8 , wherein:

a) the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and/or mixtures thereof;

b) the molar-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

10. The process according to claim 8 , wherein the heterophasic propylene copolymer comprising a matrix (M) being a random propylene copolymer (R-PP) and an elastomeric propylene copolymer (E) dispersed in said matrix (M) is produced in a multistage process comprising at least two reactors connected in series.

11. The process according to claim 10 , wherein:

(a) in a first reactor propylene and ethylene and/or C 4 to C 8 α-olefin are polymerized obtaining a first propylene copolymer fraction (R-PP1),

(b) transferring said first propylene copolymer fraction (R-PP1) to a second reactor,

(c) polymerizing in said second reactor in the presence of the first propylene copolymer fraction (R-PP1) propylene and ethylene and/or C 4 to C 8 α-olefin obtaining a second propylene copolymer fraction (R-PP2), said first propylene copolymer fraction (R-PP1) and said second propylene copolymer fraction (R-PP2) form the matrix (R-PP),

(d) transferring said matrix (M) to a third reactor,

(e) polymerizing in said third reactor in the presence of the matrix (M) propylene and ethylene and/or C 4 to C 8 α-olefin obtaining an elastomeric propylene copolymer (E), said matrix (M) and said elastomeric propylene copolymer (E) form the heterophasic propylene copolymer.

12. A film, comprising the heterophasic propylene copolymer composition as defined in claim 1 , the film being either a cast or a blown film and can be unoriented or oriented.

13. The film according to claim 12 , being subjected to a steam sterilisation treatment.