MULTILAYER POLYOLEFIN FILM CAPABLE OF LINEAR TEAR PROPAGATION
Multilayer polyolefin film comprising a layer sequence of a sealable layer (a) based on a polyethylene component, a layer (b) based on a polymer mixture of 51-85 wt. % of at least one polyethylene and 15-49 wt. % of at least one propylene homopolymer or copolymer and a sealable layer (c) based on a polyethylene component, wherein the melting point of the layer (a) or the layer (c) is at least 5° C. lower than the melting point of the layer (b); the tear propagation capability of the polyolefin film in the machine direction is <5 N, and the tear propagation capability transverse to the machine direction is at least four times higher than in the machine direction, and the tensile strength is >15 N approximately equal manner in machine direction as well as transversally to the machine direction.
1 . A multilayer polyolefin film comprising a layer sequence of
a) a sealable layer (a) having a layer thickness of 5-30 μm based on a polyethylene component having a density in the range from 0.910 to 0.940 g/cm 3 and a melting point in the range from 110° C. to 130° C.,
b) a layer (b) having a layer thickness of 20-90 μm based on a polymer mixture of 51-85 wt % of at least one polyethylene having a density of 0.910 to 0.940 g/cm 3 and 15-49 wt %, based in each case on the total weight of the polymer mixture, of at least one propylene homopolymer or copolymer,
c) a sealable layer (c) having a layer thickness of 5-30 μm based on a polyethylene component having a density in the range from 0.910 to 0.940 g/cm 3 and a melting point in the range from 110° C. to 130° C., wherein the melting point of the layer (a) or of the layer (c), or of each of them, is at least 5° C. lower than the melting point of the layer (b),
wherein the tear propagation resistance of the polyolefin film in machine direction [MD] is ≤5 N and the tear propagation resistance crosswise to the machine direction [CD] is at least four times higher than in [MD], measured in each case according to DIN 53356, and the tensile strength is of approximately equal magnitude in machine direction [MD] as crosswise to the machine direction [CD] and is in each case ≥15 N, measured according to DIN ISO 527-3.
2 . A polyolefin film as claimed in claim 1 , wherein the polyethylene component of the layer (a) consists of at least one low-density polyethylene (LDPE), at least one linear low-density polyethylene (LLDPE) or a mixture of LDPE and LLDPE.
3 . A polyolefin film as claimed in claim 1 , wherein the polyethylene component of the layer (a) and of the layer (c) has an identical or different composition.
4 . A polyolefin film as claimed in claim 1 , wherein the polyethylene component of the layer (a) and of the layer (c) consists of a mixture of 55-80 wt % LDPE and 45-20 wt % LLDPE.
5 . A polyolefin film as claimed in claim 1 , wherein the layer (b) is based on a polymer mixture of 51-85 wt % of at least one polyethylene having a density in the range from 0.910 to 0.940 g/cm 3 and a melting point in the range from 110° C. to 130° C. and of 15-49 wt % of a propylene homopolymer or copolymer.
6 . A polyolefin film as claimed in claim 1 , wherein the polyethylene of the layer (b) is a low-density polyethylene (LDPE) or a linear low-density polyethylene or a mixture of LDPE and LLDPE.
7 . A polyolefin film as claimed in claim 1 , wherein the propylene copolymer of the layer (b) is a propylene/ethylene copolymer having up to at most 20 wt % of ethylene.
8 . A polyolefin film as claimed in claim 1 , wherein the polymer mixture of the layer (b) consists of an LDPE and of a propylene/ethylene block copolymer or of an LLDPE and of propylene/ethylene block copolymer.
9 . A polyolefin film as claimed in claim 1 , wherein the polymer mixture of the layer (b) consists of a mixture of LDPE and of a propylene homopolymer or of LLDPE and of a propylene homopolymer.
10 . A polyolefin film as claimed in claim 1 , wherein the polymer mixture of the layer (b) contains 20-49.0 wt % of propylene homopolymer or copolymer, in addition to the PE component.
11 . A polyolefin film as claimed in claim 1 , wherein the polyolefin film comprises auxiliaries in at least one of its layers.
12 . A polyolefin film as claimed in claim 1 , wherein the polyolefin film, produced as a blown film, is unoriented or is oriented monoaxially in MD.
13 . A polyolefin film as claimed in claim 1 , wherein the polyolefin film is printed, embossed, or both.
14 . A method for the packaging of food wherein said food is packaged in a polyolefin film of claim 1 .
15 . A packaging comprising a polyolefin film as claimed in claim 1 .
16 . A packaging as claimed in claim 15 in the form of a pouch, a sachet or stick pack.
17 . A polyolefin film as claimed in claim 1 , wherein a surface layer (a) or (c) has a release coating of cured polysiloxane.
18 . A release film or packaging film for the individual packaging of adhesive hygiene articles for single use, comprising the polyolefin film of claim 17 .