METHOD OF MANUFACTURING A MULTILAYERED COMPOSITE FILM, A MULTILAYERED COMPOSITE FILM AND ITS USE

Abstract

The present patent application relates to a method of manufacturing a multilayered composite film comprising a step of co-extruding at least three layers (a), (b) and (c), of which the layer (a) forms an outward surface of the composite film; the layer (c) forms a surface of the composite film facing or coming in contact with a good to be packaged; and the layer (b) is disposed between the layer (a) and the layer (c). Further, the method includes a step of biaxial orientation of the composite film thus co-extruded. Therein, the layer (a) contains or consists of a thermoplastic resin. The layer (b) contains or consists of a polyvinylidene chloride (PVdC) resin. The layer (c) contains or consists of a resin, preferably sealable, in particular heat-sealable resin. Therein, any crosslinking of the composite film by means of radioactive radiation, in particular by means of beta, gamma, X-ray and/or electron irradiation, is omitted during the manufacturing of the composite film and/or thereafter.

Claims

1. Method for manufacturing a multilayered composite film, wherein the method includes at least the following steps: a step of co-extruding at least three layers (a), (b) and (c) of which the layer (a) forms an outward surface of the composite film; the layer (c) forms a surface of the composite film facing or coming in contact with a good to be packaged; and the layer (b) is disposed between the layer (a) and the layer (c); and a step of biaxial orientation of the composite film thus co-extruded; wherein the layer (a) contains or consists of a thermoplastic resin; wherein the layer (b) contains or consists of a polyvinylidene chloride (PVdC) resin; wherein the layer (c) contains or consists of a resin, preferably a sealable resin, in particular a heat-sealable resin; wherein the thermoplastic resin of the layer (a) is a material having a melting temperature or melting point of 170° C. or higher, preferably 175° C. or higher, preferably 180° C. or higher, preferably a polyethylene terephthalate (PET), or a polylactic acid or a polylactide (PLA), or a polyamide (PA), respectively having a melting temperature or melting point of 170° C. or higher, preferably 175° C. or higher, preferably 180° C. or higher, or any mixture thereof; and wherein any crosslinking of the composite film by means of radioactive radiation, in particular by means of beta, gamma, X-ray and/or electron irradiation, is omitted during the manufacturing of the composite film and/or thereafter.

2. Method according to claim 1, wherein the thermoplastic resin of the layer (a) contains or consists of a polyester, preferably a polyethylene terephthalate (PET), or a polylactic acid or a polylactide (PLA), a polyamide (PA), a polyolefin (PO), an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), an ionomer (IO), or any mixture thereof; and/or the thermoplastic resin of the layer (a) has a sealing temperature equal to or higher than the sealing temperature of the resin of the layer (c); and/or the thermoplastic resin of the layer (a) has a density of 0.94 g/cm.sup.3 or more.

3. Method according to claim 1, wherein the resin of the layer (c) contains or consists of a polyolefin (PO), preferably a polyethylene (PE) and/or a polypropylene (PP), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof

4. Method according to claim 1, wherein the layer (a) has a thickness in the range of 0.5 to 20 μm, preferably 1 to 10 μm; and/or the thickness of the layer (a) is at most 30%, preferably at most 10%, in particular at most 5%, of the thickness of the entire composite film.

5. Method according to claim 1, wherein none of the layers of the composite film which are disposed between the layer (a) and the layer (c) contains a polyamide (PA).

6. Method according to claim 1, wherein none of the layers of the composite film which are disposed between the layer (a) and the layer (c) contains an ethylene-vinyl alcohol copolymer (EVOH).

7. Method according to claim 1, wherein the composite film has a shrinkage of at least 20%, preferably at least 25%, in particular at least 50%, in each of the longitudinal and transverse directions, measured in water at 90° C., preferably within 1 second after immersion, but at least within 10 seconds after immersion; an/or the composite film has a total area shrinkage of at least 40%, preferably at least 50%, more preferably at least 100%, measured in water at 90° C., preferably within 1 second after immersion, but at least within 10 seconds after immersion.

8. Method according to claim 1, wherein the composite film further comprises the following layered structure, counting from the outside to the inside, comprising at least seven layers, wherein: a first layer from the outside contains or consists of a polyethylene terephthalate (PET), a polyamide (PA), a polylactic acid (PLA), or any mixture thereof, as a layer component; a second layer from the outside contains or consists of a adhesion promotor (HV) as a layer component; a third layer from the outside contains or consists of a polyolefin (PO), preferably a polypropylene (PP) or a polyethylene (PE), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof, as a layer component; a fourth layer from the outside contains or consists of an adhesion promoter (HV) as a layer component; a fifth layer from the outside contains or consists of a polyvinylidene chloride (PVdC) as a layer component; a sixth layer from the outside contains or consists of a adhesion promoter (HV) as a layer component; and a seventh layer from the outside contains or consists of a polyolefin (PO), preferably a polyethylene (PE) or a polypropylene (PP), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof, as a layer component.

9. Method according to claim 1, wherein the composite film has a haze of at most 15%, preferably at most 12%, preferably at most 10%, preferably at most 7%, in particular at most 5%; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the machine direction, of at least 200 MPa, preferably at least 250 MPa, preferably at least 300 MPa, preferably at least 350 MPa, preferably at least 400 MPa, in particular at least 450 MPa; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the transverse direction, of at least 200 MPa, preferably at least 250 MPa, preferably at least 300 MPa, preferably at least 350 MPa, preferably at least 400 MPa, in particular at least 450 MPa; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the machine direction, of at most 700 MPa, preferably at most 650 MPa, preferably at most 600 MPa, preferably at most 550 MPa, in particular at most 500 MPa, and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the transverse direction, of at most 700 MPa, preferably at most 650 MPa, preferably at most 600 MPa, preferably at most 550 MPa, in particular at most 500 MPa.

10. A multilayered composite film manufactured by the method of claim 1.

11. Multilayered composite film, preferably manufactured by means of the jet-blow method or jet blow molding method or nozzle blow molding method and biaxially oriented, in particular manufactured by the method according to claim 1; wherein the composite film includes at least three layers (a), (b) and (c), of which the layer (a) forms an outward surface of the composite film; the layer (c) forms a surface of the composite film facing or coming in contact with a good to be packaged; and the layer (b) is disposed between the layer (a) and the layer (c); wherein the layer (a) contains or consists of a thermoplastic resin; wherein the layer (b) contains or consists of a polyvinylidene chloride (PVdC) resin, wherein the layer (c) contains or consists of a resin, preferably a sealable, especially heat-sealable resin; wherein the thermoplastic resin of the layer (a) is a material having a melting temperature or melting point of 170° C. or higher, preferably 175° C. or higher, preferably 180° C. or higher, preferably a polyethylene terephthalate (PET), or a polylactic acid or a polylactide (PLA), or a polyamide (PA), respectively having a melting temperature or melting point of 170° C. or higher, preferably 175° C. or higher, preferably 180° C. or higher, or any mixture thereof; and wherein any crosslinking of the composite film by means of radioactive radiation, in particular by means of beta, gamma, X-ray and/or electron irradiation, is omitted during the manufacturing of the composite film and thereafter.

12. Composite film according to claim 11, wherein the thermoplastic resin of the layer (a) contains or consists of a polyester, preferably a polyethylene terephthalate (PET) or a polylactic acid or a polylactide (PLA), a polyamide (PA), a polyolefin (PO), an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), an ionomer (IO), or any mixture thereof; and/or the thermoplastic resin of the layer (a) has a sealing temperature equal to or higher than the sealing temperature of the resin of the layer (c); and/or the thermoplastic resin of the layer (a) has a density of 0.94 g/cm.sup.3 or more.

13. Composite film according to claim 11, wherein the resin of the layer (c) contains or consists of a polyolefin (PO), preferably a polyethylene (PE) and/or a polypropylene (PP), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof.

14. Composite film according claim 11, wherein the layer (a) has a thickness in the range of 0.5 to 20 μm, preferably 1 to 10 μm; and/or the thickness of the layer (a) is at most 30%, preferably at most 10%, in particular at most 5%, of the thickness of the entire composite film.

15. Composite film according to claim 11, where none of the layers of the composite film which are disposed between the layer (a) and the layer (c) contains a polyamide (PA).

16. Composite film according to claim 11, wherein none of the layers of the composite film which are disposed between the layer (a) and the layer (c) contains an ethylene-vinyl alcohol copolymer (EVOH).

17. Composite film according to claim 11, wherein the composite film has a shrinkage of at least 20%, preferably at least 25%, in particular at least 50%, in each of the longitudinal and transverse directions, measured in water at 90° C., preferably within 1 second after immersion, but at least within 10 seconds after immersion; an/or the composite film has a total area shrinkage of at least 40%, preferably at least 50%, more preferably at least 100%, measured in water at 90° C., preferably within 1 second after immersion, but at least within 10 seconds after immersion.

18. Composite film according to claim 11, wherein the composite film further comprises the following layered structure, counting from the outside to the inside, comprising at least seven layers, wherein: a first layer from the outside contains or consists of a polyethylene terephthalate (PET), a polyamide (PA), a polylactic acid (PLA), or any mixture thereof, as a layer component; a second layer from the outside contains or consists of a adhesion promotor (HV) as a layer component; a third layer from the outside contains or consists of a polyolefin (PO), preferably a polypropylene (PP) or a polyethylene (PE), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof, as a layer component; a fourth layer from the outside contains or consists of an adhesion promoter (HV) as a layer component; a fifth layer from the outside contains or consists of a polyvinylidene chloride (PVdC) as a layer component; a sixth layer from the outside contains or consists of a adhesion promotor (HV) as a layer component; and a seventh layer from the outside contains or consists of a polyolefin (PO), preferably a polyethylene (PE) or a polypropylene (PP), an ethylene-vinyl acetate copolymer (EVA), an ionomer (IO), an ethylene-methyl methacrylate copolymer (EMMA), an ethylene-methacrylic acid copolymer (EMA), or any mixture thereof, as a layer component.

19. Composite film according to claim 11, wherein the composite film has a haze of at most 10%, preferably at most 5%; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the machine direction, of at least 200 MPa, preferably at least 250 MPa, preferably at least 300 MPa, preferably at least 350 MPa, preferably at least 400 MPa, in particular at least 450 MPa; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the transverse direction, of at least 200 MPa, preferably at least 250 MPa, preferably at least 300 MPa, preferably at least 350 MPa, preferably at least 400 MPa, in particular at least 450 MPa; and/or the composite film has a stiffness, expressed as modulus of elasticity, measured in the machine direction, of at most 700 MPa, preferably at most 650 MPa, preferably at most 600 MPa, preferably at most 550 MPa, in particular at most 500 MPa, and/or the composite film has a stiffness, expressed as modulus of elasticity measured in the transverse direction, of at most 700 MPa, preferably at most 650 MPa, preferably at most 600 MPa, preferably at most 550 MPa, in particular at most 500 MPa.

20. Use of a composite film according to claim 10, or of a casing made therefrom for packaging an item, preferably a food or luxury food product, in particular a food product containing meat, fish or cheese.

Description

EMBODIMENTS

[0089]

TABLE-US-00010 TABLE 10 Layered structures of exemplary composite films according to the invention with seven layers, not radiation crosslinked: layer components and layer thicknesses (total thickness 50 μm each) Layer 1 Layer 7 Example (outside) Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 (inside) 1 PET HV PP HV PVDC HV PE 5 μm 2.5 μm   20 μm 2.5 μm 5 μm 2.5 μm 12.5 μm   2 PET HV IO HV PVDC HV EVA 2.5 μm   2.5 μm   20 μm 2.5 μm 5 μm 2.5 μm 15 μm 3 PA HV EVA HV PVDC HV EVA 5 μm 2.5 μm 17.5 μm 2.5 μm 5 μm 2.5 μm 15 μm

[0090] However, the invention is not limited to the embodiments mentioned, in particular not to the total thickness of the layer structure and the thickness ratios of the individual layers as indicated in Table 10. Thus, the invention also expressly includes the layer sequences of Examples 1 to 3 of Table 10, but with different layer thicknesses than those indicated in Table 10 and different overall thicknesses in each case.

FURTHER DISCLOSURE AND ALTERNATIVES

[0091] The method according to the invention and the composite film according to the invention can preferably be carried out or manufactured using the so-called double-bubble and in particular the triple-bubble method, for which the applicant provides suitable equipment, which are known to the skilled person. Therein, the multilayered composite film can be co-extruded from the respective resin melts, for example, by means of a nozzle blow head of the applicant, set up for manufacturing composite films with three or more layers, preferably with thermal separation of the individual layers, cooled with a water cooling system of the applicant, reheated, biaxially oriented by means of an enclosed compressed air bubble and finally thermoset or thermofixed in a further step in a defined temperature regime. The composite film according to the present invention can be a composite film comprising a barrier against gas diffusion, in particular oxygen diffusion, and/or against water vapor diffusion.

[0092] The composite film of the present invention can be advantageously obtained on a device or system of the same applicant for manufacturing tubular food films for food packaging, such as, for example, shrink films or shrink bags, by the jet-blow method or jet blow molding method or nozzle blow molding method, if the device disclosed in patent specification DE 199 16 428 B4 of the same applicant for rapidly cooling thin thermoplastic tubes after their extrusion is additionally used. For this purpose, a corresponding further development according to patent specification DE 100 48 178 B4 can also be taken into account.

[0093] Therein, the tubular film produced from the plastic melt in the nozzle blow head is subjected to intensive cooling, during which the amorphous structure of the thermoplastic from the plastic melt is retained. The tubular film extruded vertically from the plastic melt in the nozzle blow head initially moves without wall contact into the cooling device for cooling, as described in detail in the patent documents or publications DE 199 16 428 B4 and DE 100 48 178 B4. In order to avoid repetition, full reference is made to the contents of DE 199 16 428 B4 and DE 100 48 178 B4 with regard to details of the methods, structure and mode of operation of this cooling system, which is also referred to as a calibration system.

[0094] The tubular film then passes through supports in the cooling system, against which the film is supported as a result of a differential pressure between the interior of the tubular film and the coolant, wherein a liquid film is maintained between the film and the supports, so that sticking of the tubular film is excluded. The diameter of the supports influences the diameter of the tubular film, which is why this cooling system of the same applicant is also referred to as a calibration system.

[0095] According to the invention, polyvinylidene chloride (PVdC) is a thermoplastic formed from vinylidene dichloride (1,1-dichloroethene) analogous to PVC. PVdC decomposes near the melting point of about 200° C.

[0096] According to the invention, polyamide (PA) may be a substance selected from a group consisting of PA of ε-caprolactam or poly(ε-caprolactam) (PA6), PA of hexame-thylenediamine and adipic acid or polyhexamethyleneadipinamide (PA6.6), PA of ε-ca-prolactam and hexamethylenediamine/adipic acid (PA6.66), PA of hexamethylenediamine and dodecanedioic acid or polyhexamethylenedodecanamide (PA6.12), PA of 11-aminoundecanoic acid or polyundecanamide (PA11), PA of 12-laurinlactam or poly(ω-laurinlactam) (PA12), or a mixture of these PAs or a mixture of these PAs with amorphous PA or with other polymers. The generic notation PAx.y is synonymous with PAx/y or PAxy.

[0097] For the purpose of this application, polyolefin (PO) may be a substance selected from a group consisting of PP, PE, LDPE, LLDPE, polyolefin plastomer (POP), ethylene-vinyl acetate copolymers (EVA), ethylene-methyl methacrylate copolymers (EMMA), ethylene-methacrylic acid copolymers (EMA), ethylene-acrylic acid copolymers (EAA), copolymers of cycloolefins/cycloalkenes and 1-alkenes or cycloolefin copolymers (COC), ionomers (IO), or a mixture or blend thereof. Furthermore, PO can be a mixture of the above PO with ionomers.

[0098] In the context of the present invention, polyester can be used as a layer component for the layer (a). Polyesters are polymers with ester functions in their main chain and can in particular be aliphatic or aromatic polyesters. Polyesters can be obtained by polycondensation of corresponding dicarboxylic acids with diols. Any dicarboxylic acid suitable for forming a polyester can be used to synthesize the polyester, in particular terephthalic acid and isophthalic acid, as well as dimers of unsaturated aliphatic acids. As the further component for the synthesis of the polyester, diols can be used, such as: polyalkylene glycols, such as ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, diethylene glycol, polyethylene glycol and polytetramethylene oxide glycol; 1,4-cyclohexanedimethanol, and 2-alkyl-1, 3-propanediol.

[0099] PET, which stands for the polyester polyethylene terephthalate, is particularly preferred. PET can be obtained by polycondensation of terephthalic acid (1,4-benzenedicarboxylic acid) and ethylene glycol (1,2-dihydroxyethane).

[0100] Another preferred polyester is the polylactides or polylactic acids (PLA), which can be included as layer components in the layers for which a polyester is provided as a layer component. These polymers are biocompatible/biodegradable and have high melting temperatures or high melting points and a good tensile strength in addition to a low moisture absorption.

[0101] In the context of the present invention, EVOH stands for EVOH as well as for a blend of EVOH with other polymers, ionomers, EMA or EMMA. In particular, EVOH also includes a blend of EVOH and PA or of EVOH and ionomer.

[0102] The adhesion promotors (HV) stand for adhesive layers that ensure good adhesion of the individual layers to each other. HV can be based on a base material selected from a group, consisting of PE, PP, EVA, EMA, EMMA, EAA and an ionomer, or a mixture thereof. Particularly suitable adhesion promotors (HV) according to the invention are EVA, EMA or EMMA, each with a purity of >99%, preferably >99.9%.

[0103] According to a further preferred embodiment, layers comprising HV as a layer component may also comprise a mixture of PO and HV or a mixture of EVA, EMA, EMMA and/or EAA and HV or a mixture of ionomer and HV or a mixture of a plurality of HV.

[0104] For the purposes of the present invention, a processability (number of cycles) means the speed (units per unit time) at which the composite film produced according to the invention can be further processed into usable packaging units, such as shrink bags for food products. This can include, for example, the formation of a bag shape, the application of sealing seams and, in a broader sense, possibly also the filling with the good to be packaged and the sealing of the filled package.

[0105] For the purposes of the present invention, the designation of a material as a “layer component” means that a layer of the food film according to the invention comprises this material at least in part. In this context, the designation “layer component” within the meaning of the present invention may in particular include that the layer consists entirely or exclusively of this material.

[0106] The composite film according to the invention is preferably sheet-like or tubular. Preferably, the composite film is a food product film or food product casing. The composite film is further preferably suitable for use as a heat-shrinkable packaging material.

[0107] In the context of this application, “crosslinked by radiation” or “radiation crosslinked” means crosslinking by means of radioactive radiation, preferably “crosslinking by means of beta, gamma, X-ray and/or electron radiation”. According to the invention, the omission of radiation crosslinking includes integrated and downstream radiation crosslinking during the manufacturing of the composite film.