CZ314198A3 - Packaging material with oxygen barrier - Google Patents

Abstract

A packaging material with an O2 barrier, in particular for flexible packagings, comprises a plastic film (1) coated with an organic coating (4) comprising at least one of the materials ethylene vinyl alcohol (EVOH) and polyvinyl alcohol (PVOH) applied to the plastic film (1) in fluid form. The organic coating (4) is coated with an inorganic coating (5) comprising a metal oxide or a non-metal oxide.

Description

Technical field

The invention relates to oxygen barrier packaging material, in particular for flexible packaging.

BACKGROUND OF THE INVENTION

In the packaging of certain products, such as foods which are sensitive to oxygen and / or water vapor, it is known to use packaging materials in the form of plastic laminates having an oxygen and / or water vapor barrier. It is also known to use such laminates with barrier properties for packaging foodstuffs in a gas atmosphere to prevent leakage of gas from the package.

Said barrier properties can be obtained by means of metallized layers which form part of the plastic laminate. Furthermore, it is known from US-A-4,457,977 and EP-A-2-0,340,910 that improved barrier properties can be obtained by coating the plastic film with an organic, subsequently metallized coating.

In order to ensure transparency or translucency of barrier materials, it has been proposed to coat plastic films with translucent metal oxides or non-metal oxides by vacuum deposition (cf. GB-B-22 108 826, GB-B-2 246 794, GB-B-22 46,795 and EP-B-00 70,875). Thus obtained oxygen barrier greater than 1 cm ³ / m ^2/24 hr.

Finally, ΕΡ-Β-00 70 875 and EP-A-0 437 946 disclose a combination of a metal coating and a metal oxide coating for obtaining improved barrier properties while maintaining the translucent or transparent nature of the packaging material. Further, it is clear from the publications that the plastic film may be primed prior to metal / metal oxide deposition.

SUMMARY OF THE INVENTION

The present invention provides an oxygen barrier coating material, in particular for flexible packaging, and which consists of a plastic film coated with an organic coating applied to a plastic film in liquid form, the organic coating being coated with an inorganic coating containing a metal oxide or non-metallic oxide and in that the organic coating comprises at least one of ethylene vinyl alcohol (EVOU) and polyvinyl alcohol (PVOH). Surprisingly, by applying a metal oxide or non-metal oxide coating to the EVOH or PVOH coating, improved barrier properties have been obtained compared to direct coating of the metal oxide or non-metal oxide onto a plastic film or a primer without barrier properties applied to the plastic film. An oxygen permeability of 0.1 cm / m / 24 h was thus achieved. In addition, it was found that these good oxygen barrier properties are maintained even after bending (Gelbo-bends) despite the high brittleness of the non-metallic oxide coating. Good barrier properties are believed to be due to the smoother surface provided by the EVOH or PVOH coating, providing a smoother and more uniform coating of the metal oxide or non-metallic oxide and a synergistic effect between the EVOH or PVOH coating and the metal oxide or non-metallic oxide coating. It is believed that the good oxygen barrier properties achieved after bending are due to the elasticity of the EVOH or PVOH layer and the surprisingly good adhesion of the EVOH or PVOH coating to the metal oxide or non-metal oxide coating as well as the above synergistic effect of the two coatings.

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According to the invention, a base layer can be inserted between the plastic film and the organic coating (EVOH or PVOH coating) to increase the adhesion of the organic coating to the plastic film.

Further according to the invention the organic coating per se may have 0 * 3 an oxygen permeability of less than 10 cm / m / 24 hours, preferably less than 5 cm ³ / m ^2/24 hr.

In addition, according to the invention, the organic coating may be prepared from a dispersion or solution comprising at least one of EVOH and PVOH and preferably have a thickness of preferably 0.5 to 3 μπι, more preferably between 0.7 to 1.8 μπι. In practice, excellent results have been obtained at thicknesses of 1.2 μη, corresponding to an oxygen permeability of 3 cm / m / 24 h of this coating. The coating may be obtained by means known from coating processes such as roll coating, for example smooth roll coating, gravure roll coating, spray coating and dip coating. In practice, excellent results were achieved by applying a smooth roller.

In addition, according to the invention, the organic coating may comprise EVOH deposited by extrusion coating or co-extrusion coating and have a thickness of between 2 and 10 μπ, preferably between 3 and 5 μτη.

Furthermore, according to the invention, the plastic film may be oriented in the longitudinal direction and preferably be bi-directionally oriented.

Furthermore, according to the invention, the plastic film, which is preferably transparent, may comprise at least one material selected from polyolefins, polyamides, polyesters and polycarbonates. In this context, it should be noted that the transparent film may advantageously be reverse printed and provided with an intermediate base layer prior to application of the organic coating and the inorganic coating to the printed side.

In addition, according to the invention, the organic coating may comprise an oxide selected from the group consisting of aluminum oxides, magnesium oxides and silicon oxides. In this connection, it should be noted that in addition to said oxides, the inorganic coating may also contain corresponding metals or non-metals, preferably in such an amount that the inorganic coating remains transparent or at least translucent.

Moreover, according to the invention, the inorganic coating may have a thickness of between 0.005-0.1 µmη (50-1000 angstroms), preferably between 0.01-0.03 µm (100-300 angstroms).

Finally, according to the invention, viewed from the plastic film to the coatings, the packaging material may comprise an inner layer of a sealing medium made after coating and containing a polyolefin, preferably polyethylene or polypropylene or a copolymer thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below with reference to a drawing, the sole illustration of which is a cross-sectional view of an embodiment of a packaging material according to the invention.

Viewed from the outer surface to the surface of the inner packaging, the packaging material consists of an outer substantially transparent film 1, which may be a monolayer film or a laminate formed by several films and preferably comprise a bi-directional oriented polyolefin, polyamide or polyester. The outer film 1 is reverse printed on its inwardly facing surface. In order to ensure good adhesion to the organic coating 4 containing EVOH or PVOH, a primer coat 3 is applied to the printing 2. The organic coating 4 is applied to the primer coat either by extrusion coating or in the form of a solution or dispersion which is applied after roller coating dried. The inorganic coating 5 is applied to the PVOH layer 4 under vacuum and the coating 5 comprises a metal oxide, preferably in the form of aluminum oxide or magnesium oxide or non-metal oxide, preferably in the form of silicon oxide. The inner layer of the sealing medium 7 adheres to the inorganic coating 5 by means of a binder 6. The inner heat sealing layer 7 is usually a polyolefin, preferably polyethylene or a copolymer thereof.

In addition, the invention is illustrated by the following examples.

Example 1

A bi-directional oriented polyester (PETP) film 1 having a thickness of 12 µm is coated on its inwardly facing side with a polyurethane-based primer 3. The base coat 3 is coated with EVOH in the form of an EVOH granular alcoholic solution A in an amount of 1.2 g / m (dry weight) corresponding to a thickness of 1 µm (dried). The EVOH coating was dried. At EVOH coating was vacuum-deposited coating of A1 ₂ O ₃ having a thickness of 0.015 pm (150 angstroms). With a two-component polyurethane binder 6, a PE film is laminated to the Al ₂ O ₃ 5 coating.

The prepared laminate is transparent and has an oxygen permeability of <0.1 ^cm3 / ^m2 / 24 h.

The Gelbo-bend test shows that the oxygen barrier remains unchanged after twenty Gelbo-bends performed according to Test Method No. 2017, MIL-V-131G, FED-STD-101.

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Example 2

According to Example 1, a laminate is prepared in which the EVOH coating is omitted.

The laminate has an oxygen permeability before bend 4 cm ³ / m ^2/24 h

After twenty-Gelb bends the laminate has an oxygen permeability of 25 cm ³ / m ^2/24 hr.

These two examples show that a combination of EVOH and Al ₂ O ₃ coating compared to Al ₂ O ₃ coating without EVOH coating provides a significantly improved oxygen barrier both before and after bending. The high oxygen barrier, both before and after bending, is considered surprising, although the EVOH coating used as such has an oxygen permeability of about 3 cm / m / 24 h.

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Claims (10)

NÁ A Τ Ε Ν ΤΟ CLAIMS Oxygen barrier packaging material, in particular for flexible packaging, consisting of a plastic film (1) coated with an organic coating (4) applied to a plastic film in liquid form and the organic coating (4) being coated with an inorganic coating (5) comprising a metal oxide or non-metal oxide, characterized in that the organic coating (4) comprises at least one of ethylene vinyl alcohol (EVOH) and polyvinyl alcohol (PVOH). Packaging material according to claim 1, characterized in that a base layer (3) is provided between the plastic film (1) and the organic coating (4) (EVOH or PVOH coating). Packaging material according to claim 1 or 2, characterized in that the organic coating as such has an oxygen permeability less than 10 cm ³ / m ^2/24 hours, preferably less than 5 cm ³ / m ^2/24 hr. Packaging material according to one or more of the preceding claims, characterized in that the organic coating (4) is prepared from a dispersion or solution containing at least one of EVOH and PVOH and having a thickness of preferably 0.5 to 3 μιη, most preferably between 0.7 to 1.8 μιη. Packaging material according to one or more of claims 1 to 3, characterized in that the organic coating (4) comprises EVOH deposited by extrusion coating or co-extrusion coating in a thickness of between 2 to 10 μκ, preferably between 3 to 5 μπι. Packaging material according to one or more of the preceding claims, characterized in that the plastic film (1) is oriented at least in the longitudinal direction and is preferably bi-directionally oriented. Packaging material according to claim 6, characterized in that the plastic film (1) comprises at least one material selected from polyolefins, polyamides polyesters and polycarbonates. Packaging material according to one or more of the preceding claims, characterized in that the inorganic coating (5) comprises an oxide selected from the group consisting of aluminum oxides, magnesium oxides and silicon oxides. Packaging material according to claim 8, characterized in that the inorganic coating has a thickness of between 0.005 to 0.01 µm (50-1000 angstroms), preferably between 0.01 to 0.03 µm (100-300 angstroms). Packaging material according to one or more of the preceding claims, characterized in that, when viewed from the plastic film (1) towards the coatings, it comprises an inner layer of a sealing medium (7) made after coating and containing polyolefin, preferably polyethylene or polypropylene; their copolymer.