WO2002047904A2

WO2002047904A2 - Multiple layer films with defined gas permeability and their use as packaging material, especially as cheese maturing packaging

Info

Publication number: WO2002047904A2
Application number: PCT/EP2001/014589
Authority: WO
Inventors: Peter Beckmann
Original assignee: Wipak Walsrode Gmbh & Co. Kg
Priority date: 2000-12-14
Filing date: 2001-12-12
Publication date: 2002-06-20
Also published as: CA2431692A1; PL362180A1; NO20032660L; AU2002229652A1; RU2003120515A; WO2002047904A3; DE10062417A1; EP1358070A2; NO20032660D0

Abstract

The invention relates to multiple layer films, comprising at least one outer seal layer, a < 10 νm thick barrier layer consisting of a partially crystalline polyamide mixture of a xylylenediamine adipate and an aliphatic polyamide containing solid, nanoscale fillers as nucleation agents, which for the number-weighted average of all of the dispersed fillers have an extension of ≤ 10 nm for at least one dimension and an extension of at least 100 nm for another dimension 100 nm; and a plastic support layer, with the exception of a corresponding polyamide layer.

Description

Multi-layer films with a defined gas permeability and their use as packaging material, in particular as cheese maturing packaging

The present invention relates to multilayer films with which the aim is not to minimize the permeability to water vapor, gases and aromas, but which have a defined gas permeability and thus enable the contents packed therein to be in a permanent, quality-maintaining balance with the external environment to deliver.

Numerous products of everyday life and in particular foodstuffs are produced industrially and packaged in various types of film which are suitable for maintaining the desired properties of the respective filling material over as long a period as possible. The best-before date (best before) is the day / month / year until which a packaged product can be safely used or consumed.

As the state of the art regarding plastic films, Joachim Nentwig: Kunststoff-Folien, Carl-Hanser Verlag 1994, Munich, regarding polyamide films on Dr. Ing. Klaus Stoeckhert: polyamides, polyamide foils and polyamide composite foils, new packaging 8/1984, regarding polypropylene foils on H. Wagner and P. Beckmann: oriented polypropylene foils, new packaging 2/1979 and regarding plastic composite foils on Dipl.- Ing Hermann Hinsken: Plastic composite films, New packaging referenced 2/1990.

Heat-sealable packaging films are used for the production of food packaging, which are used for the preservation, distribution and hygienic self-service packaging of foodstuffs, with different foodstuffs making different demands on the gas permeability of the packaging films to be used.

For a chip packaging, for example, a water vapor-tight packaging film is necessary to maintain the crispness. Pre-baked baguettes or bread rolls packed in a protective gas atmosphere a gas-tight packaging, so that the protective gas is retained as a fungistatic and so that no CO ₂ loss leads to a product-deforming pseudo-vacuum.

Composite films containing gas barrier layers with an oxygen permeability of <2.0 cm ³ / m ² x day x bar have proven successful for this.

Special requirements are also placed on the industrial packaging of natural cheese in pieces, slices or in a grated or grated form, if the cheese's maturing process, which varies in duration and intensity, continues beyond the time of packaging, in particular depending on the variety. H. the cheese in the packaging is still ripening and hermetically sealed packaging would bomb due to the development of carbon dioxide.

For such packaging, composite films consisting of an optionally printed biaxially oriented polyamide layer (PAB) are suitable as a carrier film with a thickness of 12 or 15 μm and 35 to 60 μm thick, olefinic sealing layers that have an oxygen permeability between 30 and 50 cm ³ / m ² × Day x bar. For particularly gassing cheeses or for products with a proven short shelf life, biaxially oriented polyester films (PET) are used instead of PAB carrier films, with an increased risk of kink breakage, which gives an oxygen permeability of approx. 90 cm ³ / m ² x day x bar ,

Since biaxially oriented polyamide films are relatively expensive and, particularly when used as a carrier film, have disadvantages due to the existing hygroscopy, there is a need for replacement packaging material in particular in the cheese packaging industry which does not have these disadvantages.

It was therefore an object of the present invention to provide packaging material, in particular packaging films with a defined gas permeability, which are suitable for gassing packaging goods, such as still ripening foods, in particular natural cheese, and which have no biaxially oriented polyamide films as carrier films, the entire packaging film having one should have defined, content-dependent oxygen permeability, the preferably in the range of <100 cm ³ / m ² x day x bar, particularly preferably in the range from 30 to 50 cm ³ / m ² x day x bar.

According to the invention, this object is achieved by providing a multilayer film which at least

a) a sealing layer as the surface layer b) a layer with a layer thickness of <10 μm and based on a partially crystalline polyamide mixture of m-xylylenediamine adipate and an aliphatic polyamide containing dispersed, solid, anisotropic, nanoscale, nucleating fillers, which in a number-weight average of all dispersed fillers an extent of no more than one of their dimensions

10 nm and in at least one further dimension have an extent of at least 100 nm and c) comprises a carrier layer made of plastic, with the exception of a biaxially oriented carrier layer made of polyamide.

The total thickness of the multilayer film according to the invention is preferably 30 to 90 μm, particularly preferably 40 to 70 μm, layer b) of the polyamide mixture containing the nanoscale particles preferably being 2 to 7 μm, particularly preferably 3 to 5 μm.

The multilayer films according to the invention have a defined oxygen permeability <100 cm ³ / m ² x day x bar, preferably in the range from 20 to 60, particularly preferably from 30 to 50 cm ³ / m ² x day x bar. Completely unexpectedly, this could be achieved with the multilayer film structure according to the invention containing layer b) as a barrier layer with a layer thickness of less than 10 μm, whereas a corresponding oxygen permeability can only be achieved when using biaxially oriented polyamide carrier foils with a larger layer thickness, as are usually used for cheese packaging can.

As layer c), the carrier layer, the usual plastics used for the production of carrier films, preferably polyesters, such as polyethylene terephthalate, or polyolefins, such as polypropylene, can be used. The carrier film is preferably biaxially oriented. The carrier layer is preferably transparent. The layer thickness is preferably 10 to 25 μm, particularly preferably 12 to 20 μm. The carrier film can have on its surface facing away from the further film composite a sealing layer, preferably a heat sealing layer, which can correspond to the sealing layer a).

The sealing layer a) is preferably a heat seal layer, which forms a surface layer of the multilayer film according to the invention. Layer a) preferably consists of polyolefins, particularly preferably of polyethylene, polypropylene, an ethylene-propylene copolymer, of a mixture of polyolefins, of an olefinic terpolymer, of mixtures of the polymers mentioned, very particularly preferably of linear low-density polyethylene (LLDPE), optionally mixed with Polybutene, or from polyvinyl acetate.

Layer b) of the multilayer film according to the invention, which has a layer thickness of <10 μm, preferably a layer thickness of 2 to 7 μm, has at least one adjacent layer on each of its surfaces, i. H. it has no uncovered surface. Layer b) is based on a partially crystalline polyamide mixture of m-xylylenediamine adipate and an aliphatic polyamide, and has dispersed, nanoscale, solid, anisotropic particles which act as nucleating fillers. Solid, anisotropic particles are preferably dispersed as nucleating fillers, which have a number-weight average of all dispersed particles in at least one dimension, preferably freely selectable for each dispersed particle, of an extent of not more than 10 nm. These particles particularly preferably have an extent in at least one further dimension in the range from at least 100 nm to at most 1,000 nm. Platelet-shaped particles are particularly preferably used, the thickness of which is <10 nm, such as. B. Layered Silicates. These can be selected from the group comprising phyllosilicates, such as magnesium silicate or aluminum silicate, montmorillonite, saponite, beidellite, nontronite, hectorite, stevensite, vermiculite, halloysite or their synthetic analogs.

The at least partially crystalline polyamide mixture preferably consists of 60 to 98% by weight, preferably 65 to 85% by weight, based on the total mixture of Polyamides, made from a partially aromatic polyamide composed of m-xylylenediamine and adipic acid and 2 to 40% by weight, preferably 15 to 35% by weight, based on the total mixture of the polyamides, of an aliphatic polyamide, such as PA 6, PA 11, PA 12, PA 66, PA 610, PA 6/66, particularly preferably polyamide 6. Layer b) contains in each case <10% by weight, preferably 1 to 5% by weight, based on the aliphatic polyamide component, of nanoscale, nucleating, solid particles are particularly preferably added during the production of the respective aliphatic polyamide.

Layer b) preferably has a layer a) on each of its surfaces for procedural reasons, which is connected to layer b) via an adhesion promoter layer in order to increase the bond strength. The adhesion promoter layer is preferably coextruded and is preferably based on a polyethylene with grafted maleic anhydride. To connect this composite to the respective carrier film c), a solvent-free polyurethane adhesive is preferably used as the adhesion promoter, which is preferably applied with a layer thickness of less than 5 μm.

In addition, the carrier film can be colored, printed or unprinted, it being possible for the printing to be carried out using a gravure or flexographic printing machine. The pressure is preferably not arranged on the outer surface.

The multilayer film according to the invention can be produced by known techniques, such as adhesive lamination, sandwich coating or extrusion coating, the carrier film preferably being combined with the remaining film composite produced by a separate process step.

This can be produced with the help of multilayer blown film, flat film, coating or extrusion laminating systems, the Blasbzw. Flat film coextrusion is preferred.

Since the multilayer films according to the invention have a defined gas permeability, ie barrier function, in a certain range of gas permeability, can be printed excellently due to the minimized hygroscopy of the barrier layer and show the necessary repeat and register maintenance when printed and in particular when combined with a biaxially oriented carrier film made of polypropylene, a reduced water vapor permeability and thus less weight loss Having packaged good in it, the multilayer films according to the invention are particularly suitable as packaging material, very particularly preferably as packaging material for gassing foods, such as. B. cheese.

Another object of the present invention is therefore the use of the multilayer films according to the invention as packaging material, preferably for gassing foods, in particular as packaging material for natural cheese.

The present invention also relates to packaging made from a multilayer film according to the invention for gassing foods, preferably natural cheese, very particularly preferably cheese ripening packaging. With the aid of the multilayer films according to the invention, this packaging can be produced both on horizontal and on vertical, automatically running packaging machines.

Test Methods

The oxygen permeability is determined in accordance with draft DIN 53380, part 3 in the version from July 1989, using the carrier gas method. It is defined as the amount of oxygen Nml that diffuses through a square meter of film at a differential pressure of one bar in a given climate in 24 hours. It is measured with the Oxtran 100 from Mocon Instrument. Unless otherwise specified, the oxygen permeability is given in cm ³ / m ² * d * bar at 23 ° C and 75% relative humidity (d = day).

The amount of light in% is indicated as cloudiness, which the film after scattering with a central beam as scattered light, based on the total amount of light passing through Amount of light, leaves again. The measurement is carried out according to ASTM test standard D 1003-61, Procedure A.

The force in N, based on the test strip width of 15 mm, is determined as the seal strength, which is required for the splitting separation of a seal seam produced under defined conditions (pressure, temperature, time).

Sieαelbedinαunαen: pressure 5 N / cm2, time 0.5 sec, temperature 105 to 170 ° C, five

Kelvin graduated wisely.

Measuring devices: sealing device from Brugger

Test strip cutter with cutting width 15 mm tensile testing machine with

Measuring range 10 N and take-off speed 100 mm / min.

Examples

All substances mentioned are commercially available commercial products.

example 1

A mixture of 80% by weight, based on the total mixture of polyamides, a polyamide of m-xylylenediamine and adipic acid (PA MXD6) and 20% by weight, based on the total mixture of polyamides, polyamide 6, the 2% by weight, based on polyamide 6, of a platelet-shaped aluminum layer silicate as a 4 μm thick middle layer b) embedded between each of an adhesion promoter layer and a layer a) of linear low-density polyethylene. The melt temperature was 270 ° C, the expansion ratio of the coextruded blown film was 1: 1.6.

The blown film thus obtained, which was separated into two webs and wound up with electrical pretreatment on one side, was applied to a carrier film made of polyethylene terephthalate (PET) with a thickness of 12 μm or onto a film using a commercially available laminating system using a solvent-free polyurethane adhesive (Primacor 1410 from DOW) Backing film made of biaxially oriented polypropylene (BOPP) with a layer thickness of 15 μm or a carrier film made of polypropylene coextruded with a sealing layer made of polyethylene and biaxially stretched with a thickness of 20 μm.

The oxygen permeability, the haze and the seal strength of the multilayer films according to the invention thus obtained were determined by the methods given above. The corresponding values can be found in Table 1 below.

Structure of the blown film A

* MXD 6-6121, Mitsubishi

** Nanoparticles made of aluminum silicate

LLDPE = linear low density polyethylene

Table 1

PET = polyethylene terephthalate

BOPP = biaxially oriented polypropylene

Coex-Bopp = biaxially oriented coextrudate with a 5 μm thick polyethylene

Heat seal layer

Comparative Example 1

A commercially available packaging film made of biaxially oriented polyamide (PAB) and a sealing layer made of linear low-density polyethylene, as is usually used for cheese packaging, has the values for oxygen permeability, haze and seal strength given in Table 2, according to the methods given above were found.

Table 2

suitable for natural cheese packaging in any dosage form

Claims

claims:

1. Containing multilayer film

a) at least one sealing layer as the surface layer, b) a layer with a layer thickness <10 μm and based on a partially crystalline polyamide mixture of m-xylylenediamine adipate and an aliphatic polyamide containing dispersed, solid, anisotropic, nanoscale, nucleating fillers, which all dispersed on a number-weighted average Fillers have an extent of not more than 10 nm in one of their dimensions and an extent of at least 100 nm in at least one further dimension

and c) a carrier layer made of plastic, with the exception of a biaxially oriented carrier layer made of polyamide.

2. Multi-layer film according to claim 1, characterized in that the thickness of layer b) is in the range from 2 to 7 μm, preferably 3 to 5 μm.

3. Multi-layer film according to claim 1 or 2, characterized in that it has an oxygen permeability of <100 cm ³ / m ² x day x bar, preferably from 20 to 60 cm ³ / m ² x day x bar.

4. Multi-layer film according to one of claims 1 to 3, characterized in that the sealing layer a) from a polyvinyl acetate, a polyolefin, preferably from polyethylene, polypropylene, an ethylene-propylene copolymer, an olefinic terpolymer, a mixture of polyolefins, particularly preferably from a linear polyethylene low density (LLDPE).

5. multilayer film according to one of claims 1 to 4, characterized in that the layer b) from a polyamide mixture of 60 to 98 wt.%, preferably 65 to 85% by weight, based on the total mixture of the polyamides, of m-xylylenediamine adipate and 2 to 40% by weight, preferably 15 to 35% by weight, based on the total mixture of the polyamides, of an aliphatic polyamide, preferably polyamide 6 , and <10% by weight, preferably 1 to 5% by weight, based on the aliphatic polyamide component, of the nanoscale fillers.

6. Multi-layer film according to one of claims 1 to 5, characterized in that the nanoscale fillers are platelet-shaped.

7. Multi-layer film according to claim 6, characterized in that the fillers consist of natural or synthetic layered silicates.

8. Multi-layer film according to one of claims 1 to 7, characterized in that the aliphatic polyamide was produced in the presence of the dispersed, nanoscale fillers.

9. Multi-layer film according to one of claims 1 to 8, characterized in that layer c) consists of polyester, preferably polyethylene terephthalate or a polyolefin, preferably polypropylene.

10. Multi-layer film according to one of claims 1 to 9, characterized in that the carrier layer is biaxially oriented.

11. Multi-layer film according to one of claims 1 to 10, characterized in that the layer b) is in each case connected to a layer a) via an adhesion promoter layer on each of its surfaces.

12. Multi-layer film according to one of claims 1 to 11, characterized in that the total thickness of the film is in the range of 30 to 90 microns.

13. Use of a multilayer film according to one of claims 1 to 12 as or in packaging material, preferably as or in packaging films.

- - - ιι

4. cheese ripening packaging made of a multilayer film according to one of claims 1 to 12.