Multi-layer cast film

1. Process for producing a multi-layer polymer film comprising:

providing a core layer (CL) selected from the group consisting of polyvinyl alcohols, polyacrylates, polyamides, poly(ethylene terephthalate), polyolefins (PO) and mixtures thereof, a sealing layer (SL), and optionally an outer (OL), a further sealing layer (SL) or a metal layer (ML) wherein:

(a) the core layer (CL);

(a1) is coated on the one side with a propylene copolymer composition (P) obtaining a sealing layer (SL); and

(a2) optionally;

(a2-i) is on the other side coated with a polyolefin (PO) obtaining an outer layer (OL); or

(a2-ii) is on the other side coated with a propylene copolymer composition (P) obtaining a second sealing layer (SL); or

(a2-iii) is on the other side metallized obtaining a metal layer (ML), wherein;

(b) said propylene copolymer composition (P);

(b1) has a comonomer content in the range of 3.0 to 8.0 wt. %, the comonomer is C 6 α-olefin,

(b2) comprises a polypropylene (A) and a polypropylene (B) in the weight ratio [(A)/(B)] of 35/65 to 50/50, wherein

said polypropylene (A) is a propylene homopolymer (H-A) or a propylene copolymer (C-A) having a comonomer content of below 4.0 wt. %, the comonomers are C 5 to C 12 α-olefins, and

said propylene copolymer (B) has a comonomer content of 4.0 to 20.0 wt. %, the comonomer is C 6 α-olefin, and

(b3) fulfills the

ratio MFR (A)/MFR (P)<1.0

wherein MFR(A) is the melt flow rate MFR 2 (230° C.) [g/10 min] measured according to ISO 1133 of the polypropylene (A), MFR(P) is the melt flow rate MFR 2 (230° C.) [g/10 min] measured according to ISO 1133 of the propylene copolymer composition (P), and

(b4) has a xylene soluble content (XCS) determined at 25° C. according to ISO 16152 of below 16.0 wt. %;

(b5) a melting temperature Tm determined by differential scanning calorimetry (DSC) of at least 135° C., and

(b6) a heat sealing temperature (SIT) of equal or below 115° C., and

(b7) is free of any elastomeric polymer component, and

wherein the multilayer polymer film is cast and not subjected to a stretching step.

2. Process according to claim 1 , wherein polymer layers of the multilayer polymer film are coextruded on a cast film line.

3. Process according to claim 1 , wherein the propylene copolymer composition (P) and/or the polyolefin (PO) has/have

(a) a core layer (CL) being selected from the group consisting of polyvinyl alcohols, polyacrylates, polyamides, poly(ethylene terephthalate), polyolefins (PO) and mixtures thereof, and

(b) a sealing layer (SL), said sealing layer (SL) comprises a propylene copolymer composition (P), said propylene copolymer composition (P).

4. Process according to claim 2 , wherein molten polymers are extruded through slot extrusion dies onto a chill roll to cool the polymers to a solid cast film of at least two layers.

5. Process according to claim 2 , wherein melts for the core layer (CL) and the propylene copolymer composition (P) for the sealing layer (SL) are coextruded through flat-film multilayer die, and taken off the resultant multi-layer polymer film over one or more rolls for solidification.

6. Process according to claim 2 , wherein melts for the core layer (CL), the propylene copolymer composition (P) for the sealing layer (SL) and the polymer for the outer layer (OL) are coextruded through flat-film multilayer die, and taken off the resultant multi-layer polymer film over one or more rolls for solidification.

7. Process according to claim 2 , wherein melts for the core layer (CL), the propylene copolymer composition (P) for the sealing layer (SL) and the polymer for a further sealing layer (SL) are coextruded through flat-film multilayer die, and taken off the resultant multi-layer polymer film over one or more rolls for solidification.

8. Process according to claim 5 , wherein the take-off roll or the rolls, by means of which the extruded film is cooled and solidified, are kept at a temperature from 10 to 50° C.

9. Process according to claim 5 , wherein the take-off roll or the rolls, by means of which the extruded film is cooled and solidified, are kept at a temperature from 15 to 40° C.

10. Process according to claim 5 , wherein the take-off roll or the rolls, by means of which the extruded film is cooled and solidified, are kept at a temperature from 10 to 50° C.

11. Process according to claim 1 , wherein the multi-layer film is corona-treated or flame-treated.

12. Process according to claim 11 , wherein the corona treatment or flame treatment is carried out by passing the film between two conductor elements serving as electrodes with high voltage.

13. Process according to claim 12 , wherein the high voltage is an alternating voltage.