Blownfilm grade showing superior stiffness, transparency and processing behaviour

1. Extrusion blown film comprising a polypropylene composition, said polypropylene composition comprising a random propylene copolymer (R-PP), a high melt strength polypropylene (HMS-PP), a polypropylene (B) and optionally a clarifier (C), wherein

(a) the random propylene copolymer (R-PP) comprises units derived from propylene and at least another C 2 to C 20 α-olefin,

(b) the high melt strength polypropylene (HMS-PP) has a branching index g′ of less than 1.0,

(c) the polypropylene (B) has a MFR 2 (230° C.) measured according to ISO 1133 of at least 400 g/10 min,

(d) the clarifier (C) comprises at least one α-nucleating agent (N), and wherein further

(i) the branching index g′ of the random propylene copolymer (R-PP) and the branching index g′ of the polypropylene (B) are higher than the branching index g′ of the high melt strength polypropylene (HMS-PP),

(ii) the random propylene copolymer (R-PP) has lower melt flow rate MFR 2 (230° C.) measured according to ISO 1133 than the polypropylene (B),

(iii) the extrusion melt blown film

(α) fulfill(s) the equation (I)

Tm−Tc≦ 30  (I)

wherein

Tm is the melting temperature [° C.] making up more than 50% of the total melting enthalpy Hm of the extrusion melt blown film measured by DSC according to ISO 11357-3;

Tc is the crystallization temperature [° C.] of the extrusion blown film measured by DSC according to ISO 11357-3; and

(β) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of 1.0 to 5.5 g/10 min,

wherein the polypropylene (B) has been visbroken.

2. Extrusion blown film according to claim 1 , wherein the film and/or the polypropylene composition has (have)

(a) a strain hardening factor (SHF) of 1.2 to 3.0 measured at a strain rate of 3.0 s −1 and a Hencky strain of 3.0,

and/or

(b) a gel content determined as the xylene hot insoluble (XHI) fraction of equal or below 1.0 wt.-%

and/or

(c) a xylene cold soluble fraction (XCS) of not more than 15.0 wt-%.

3. Extrusion blown film according to claim 1 , wherein the amount of units derived from C 2 to C 20 α-olefins other than propylene is not more than 7.0 wt.-% in the extrusion blown film and/or in the polypropylene composition.

4. Extrusion blown film according to claim 1 , wherein the amount of units derived from C 2 to C 20 α-olefins other than propylene is in the range of 1.0 to 7.0 wt.-% in the random propylene copolymer (R-PP).

5. Extrusion blown film according to claim 1 , wherein the random propylene copolymer (R-PP) has

(a) a xylene cold soluble fraction (XCS) determined according to ISO 6427 of not more than 15.0 wt-%,

and/or

(b) a MFR 2 (230° C.) measured according ISO 1133 of not more than 4.5 g/10 min.

6. Extrusion blown film according to claim 1 , wherein the high melt strength polypropylene (HMS-PP) has strain hardening factor (SHF) of 3.5 to 30.0 measured at a strain rate of 3.0 s −1 and a Hencky strain of 3.0.

7. Extrusion blown film according to claim 1 , wherein the high melt strength polypropylene (HMS-PP) comprises units derived from

(i) propylene and

(ii) bifunctionally unsaturated monomer(s) and/or multifunctionally unsaturated low molecular weight polymer(s).

8. Extrusion blown film according to claim 1 , wherein the high melt strength polypropylene (HMS-PP) has

(a) an xylene hot insoluble (XHI) fraction of not more than 1.0 wt.-% and/or

(b) a MFR 2 (230° C.) measured according ISO 1133 of 1.0 to 10.0 g/10 min.

9. Extrusion blown film according to claim 1 , wherein the polypropylene (B) is a propylene homopolymer (H-PP).

10. Extrusion blown film according to claim 1 , wherein the visbroking ratio (final MFR 2 (230° C.)/initial MFR 2 (230° C.)) of the polypropylene (B) is 3.0 to 40.0.

11. Extrusion blown film according to claim 1 , wherein the α-nucleating agent(s) (N) are selected from the group consisting of

(i) salts of monocarboxylic acids and polycarboxylic acids, and

(ii) dibenzylidenesorbitol and C 1 -C 8 -alkyl-substituted dibenzylidenesorbitol derivatives, and

(iii) salts of diesters of phosphoric acid, and

(iv) vinylcycloalkane polymer and vinylalkane polymer.

12. Extrusion blown film according to claim 1 , wherein the polypropylene composition comprises

(a) 50.0 to 92.0 wt.-% of the random propylene copolymer (R-PP),

(b) 5.0 to 26.0 wt.-% of the high melt strength polypropylene (HMS-PP),

(c) 1.0 to 15.0 wt.-% of the polypropylene (B), and

(d) 0.01 to 5.0 wt.-% of the clarifier (C),

based on the total polypropylene composition.

13. Extrusion blown film according to claim 1 , wherein said extrusion blown film comprises at least 80 wt.-% of said polypropylene composition.

14. A packaging material comprising the extrusion blown film according to claim 1 .

15. Extrusion blown film according to claim 1 , wherein said extrusion blown film consists of said polypropylene composition.

16. A polypropylene composition comprising a random propylene copolymer (R-PP), a high melt strength polypropylene (HMS-PP), a polypropylene (B) and optionally a clarifier (C), wherein

(a) the random propylene copolymer (R-PP) comprises units derived from propylene and at least another C 2 to C 20 α-olefin,

(b) the high melt strength polypropylene (HMS-PP) has a branching index g′ of less than 1.0,

(c) the polypropylene (B) has a MFR 2 (230° C.) measured according to ISO 1133 of at least 400 g/10 min,

(d) the clarifier (C) comprises at least one α-nucleating agent (N), and

wherein further

(i) the branching index g′ of the random propylene copolymer (R-PP) and the branching index g′ of the polypropylene (B) are higher than the branching index g′ of the high melt strength polypropylene (HMS-PP),

(ii) the random propylene copolymer (R-PP) has lower melt flow rate MFR 2 (230° C.) measured according to ISO 1133 than the polypropylene (B),

(iii) the polypropylene composition

(α) fulfill(s) the equation (I)

Tm−Tc≦ 30  (I)

wherein

Tm is the melting temperature [° C.] making up more than 50% of the total melting enthalpy Hm of the polypropylene composition measured by DSC according to ISO 11357-3;

Tc is the crystallization temperature [° C.] of the polypropylene composition measured by DSC according to ISO 11357-3; and

(β) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of 1.0 to 5.5 g/10 min,

(iv) the polypropylene (B) has been visbroken,

wherein the high melt strength polypropylene (HMS-PP) has

(a) an xylene hot insoluble (XHI) fraction of not more than 1.0 wt.-% and/or

(b) a MFR 2 (230° C.) measured according ISO 1133 of 1.0 to 10.0 g/10 min.

17. Process for the preparation of an extrusion blown film comprising steps of:

providing a polypropylene composition, said polypropylene composition comprising a random propylene copolymer (R-PP), a high melt strength polypropylene (HMS-PP), a polypropylene (B) and optionally a clarifier (C), wherein

(a) the random propylene copolymer (R-PP) comprises units derived from propylene and at least another C 2 to C 20 α-olefin,

(b) the high melt strength polypropylene (HMS-PP) has a branching index g′ of less than 1.0,

(c) the polypropylene (B) has a MFR 2 (230° C.) measured according to ISO 1133 of at least 400 g/10 min,

(d) the clarifier (C) comprises at least one α-nucleating agent (N), and wherein further

(i) the branching index g′ of the random propylene copolymer (R-PP) and the branching index g′ of the polypropylene (B) are higher than the branching index g′ of the high melt strength polypropylene (HMS-PP),

(ii) the random propylene copolymer (R-PP) has lower melt flow rate MFR 2 (230° C.) measured according to ISO 1133 than the polypropylene (B),

(iii) the polypropylene composition

(α) fulfill(s) the equation (I)

Tm−Tc≦ 30  (I)

wherein

Tm is the melting temperature [° C.] making up more than 50% of the total melting enthalpy Hm of the polypropylene composition measured by DSC according to ISO 11357-3;

Tc is the crystallization temperature [° C.] of the polypropylene composition measured by DSC according to ISO 11357-3; and

(β) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of 1.0 to 5.5 g/10 min,

(iv) the polypropylene (B) has been visbroken, and

providing cooling of said polypropylene composition; and

extruding said polypropylene composition for forming said extrusion blown film.

18. Process for the preparation of an extrusion blown film of claim 17 , wherein said cooling includes air forming air cooled extrusion blown film.

19. Extrusion blown film comprising a polypropylene composition, said polypropylene composition comprising a random propylene copolymer (R-PP), a high melt strength polypropylene (HMS-PP), a polypropylene (B) and optionally a clarifier (C), wherein

(a) the random propylene copolymer (R-PP) comprises units derived from propylene and at least another C 2 to C 20 α-olefin,

(b) the high melt strength polypropylene (HMS-PP) has a branching index g′ of less than 1.0,

(c) the polypropylene (B) has a MFR 2 (230° C.) measured according to ISO 1133 of at least 400 g/10 min,

(d) the clarifier (C) comprises at least one α-nucleating agent (N), and wherein further

(i) the branching index g′ of the random propylene copolymer (R-PP) and the branching index g′ of the polypropylene (B) are higher than the branching index g′ of the high melt strength polypropylene (HMS-PP),

(ii) the random propylene copolymer (R-PP) has lower melt flow rate MFR 2 (230° C.) measured according to ISO 1133 than the polypropylene (B),

(iii) the extrusion blown film

(α) fulfills the equation (I)

Tm−Tc≦ 30  (I)

wherein

Tm is the melting temperature [° C.] making up more than 50% of the total melting enthalpy Hm of the extrusion blown film measured by DSC according to ISO 11357-3;

Tc is the crystallization temperature [° C.] of the extrusion blown film measured by DSC according to ISO 11357-3;

(β) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of 1.0 to 5.5 g/10 min, and

wherein the polypropylene composition comprises

(a) 50.0 to 92.0 wt.-% of the random propylene copolymer (R-PP),

(b) 5.0 to 26.0 wt.-% of the high melt strength polypropylene (HMS-PP),

(c) 1.0 to 15.0 wt.-% of the polypropylene (B), and

(d) 0.01 to 5.0 wt.-% of the clarifier (C),

based on the total polypropylene composition.