Multi-layer biaxially oriented polymer film
View Patent ↗A multi-layer biaxially oriented polymer film comprising a core layer (CL) and at least one sealing layer (SL), said sealing layer(s) (SL) comprise(s) a propylene copolymer composition (P) having a comonomer content in the range of 3.0 to 8.0 wt.-%, the comonomers are C 5 to C 12 α-olefins, said propylene copolymer composition (P) comprises a polypropylene (A) and a polypropylene (B) in the weight ratio [(A)/(B)] of 20/80 to 80/20, wherein said polypropylene (A) has a comonomer content of equal or 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 comonomers are C 5 to C 12 α-olefins.
1. A multi-layer biaxially oriented polymer film comprising:
(a) a core layer (CL) 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)
(c1) has a comonomer content in the range of 3.0 to 8.0 wt. %, the comonomer is C 6 alpha olefin,
(c2) comprises a polypropylene (A) and a propylene copolymer (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 comonomer is C 6 alpha olefin, and said propylene copolymer (B) has a comonomer content of 4.0 to 20.0 wt. %, the comonomer is C 6 alpha olefin,
(c3) 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);
(c4) has a melting temperature Tm determined by differential scanning calorimetry (DSC) of at least 135° C.; and
(c5) has a heat sealing initiation temperature (SIT) of equal or below 115° C.; and
(c6) has a xylene soluble content (XCS) determined at 25° C. according to ISO 16152 of below 20.0 wt. %; and
(c7) is free of any elastomeric component.
2. A multi-layer biaxially oriented polymer film according to claim 1 , wherein the sealing layer (SL) and/or the propylene copolymer composition (P) has/have a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 2.0 to 50.0 g/10 min.
3. A multi-layer biaxially oriented polymer film according to claim 1 , wherein the sealing layer (SL) and/or the propylene copolymer composition (P) has/have:
a molecular weight distribution (MWD) measured by gel permeation chromatography (GPC) of at least 2.5.
4. A multi-layer biaxially oriented polymer film according to claim 1 , wherein:
(a) the comonomer content in the polypropylene (A) is lower compared to the comonomer content in the propylene copolymer (B), and/or
(b) com (P)−com (A) is at least 1.0,
wherein com (A) is the comonomer content of the polypropylene (A) given in weight percent [wt. %], com (P) is the comonomer content of the propylene copolymer composition (P) given in weight percent [wt. %].
5. A multi-layer biaxially oriented polymer film according to claim 1 , wherein the sealing layer (SL) and/or the propylene copolymer composition (P) fulfill(s) the equation (I):
Tm −SIT≥22° C. (I)
wherein Tm is the melting temperature of the sealing layer (SL) and/or of the propylene copolymer composition (P) determined by differential scanning calorimetry (DSC) and given in centigrade [° C.], SIT is the heat sealing initiation temperature (SIT) given in centigrade [° C.] of the sealing layer (SL) and/or of the propylene copolymer composition (P).
6. A multi-layer biaxially oriented polymer film according to claim 1 , wherein the polypropylene (A) of the propylene copolymer composition (P):
(a) is a propylene copolymer (C-A) with a comonomer content in the range of 0.5 to below 4.0 wt. %, and/or
(b) has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of at least 1.5 g/10 min, and/or
(c) has a xylene soluble content (XCS) of below 2.5 wt. %.
7. A multi-layer biaxially oriented polymer film according to claim 1 , wherein said core layer (CL) comprises a propylene homopolymer.
8. A multi-layer biaxially oriented polymer film according to claim 1 , wherein said core layer (CL) is a polypropylene (PP) or a propylene homopolymer (H-PP) having:
(a) a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in the range of 1.0 to 15.0 g/10 min, and/or
(b) a melting temperature Tm determined by differential scanning calorimetry (DSC) of at least 155° C.
9. A multi-layer biaxially oriented polymer film according to claim 1 , wherein:
(a) core layer (CL) has a thickness in the range of 5 to 80 μm, and/or
(b) the sealing layer (SL) has a thickness in the range of 0.2 to 15 μm.
10. A multi-layer biaxially oriented polymer film according to claim 1 , wherein said multi-layer biaxially oriented polymer film comprises three layers, namely the core layer (CL), the sealing layer (SL) and at least one of:
(a) an outer layer (OL) being a polyolefin (PO), or
(b) a further sealing layer (SL), or
(c) a metal layer (ML),
wherein the multi-layer biaxially oriented polymer film has the stacking order:
(a1) sealing layer (SL)-core layer (CL) outer layer (OL), or
(b1) sealing layer (SL)-core layer (CL)-sealing layer (SL), or
(c1) sealing layer (SL)-core layer (CL)-a metal layer (ML).