EP1714908A2 - Package suitable for microwave - Google Patents

Abstract

A packaging suitable for heating in a microwave oven, in an oven or in a water bath, consisting of a multilayer film material which has at least one region which becomes permeable when an internal pressure generated by the microwave heating is exceeded, the film comprising an outer layer 1 and an inner layer 2 , wherein the inner layer has a recess 3 extending through the entire thickness of the inner layer, and the inner layer is connected to the outer layer by means of an adhesive, such as laminating adhesive or heat seal adhesive, characterized in that the outer layer at least in the region defined by the recess of the inner layer and / or in the region surrounding the recess, an energy-absorbing coating or printing, which is heated by the sealing layer and the sealing adhesion is reduced or dissolved.

Description

The invention relates to food packaging, ready meals, non food products such as cold hot packs, packaged towelettes and the like which are suitable for microwave, oven or water bath use.

Foods or ready meals that are heated in a package, especially in a microwave oven or oven or water bath, are known.
Packaging is understood to be rigid, semi-rigid or flexible packaging.
Such packages tend to burst or rupture due to the expansion of content and expansion of air and gases associated with heating.
To a limited extent, this risk can be reduced by using packaging that is significantly larger than the volume of the product.
Furthermore, the water present in the product is converted into steam when heated. This steam can not or hardly escape through the usual sealed packaging, so it is not possible crispy heating of ready meals.

From the EP 661 219 B1 a package is known which has a multilayer structure. The outer layer and the inner layer are heat-fusible merge together. Further, there is provided a connecting part by which the outer layer is connected to an inner layer by a connecting means and a region where the outer layer is not connected to the inner layer so that a communicating passage having an exit opening to the outer space is formed.
On the inside means are provided which connect the interior with the communicating passage. The exit opening is with a Adhesive layer provided that breaks when a certain pressure in the interior of the package breaks.
This ensures a certain overpressure in the package when heated in the microwave, and also ensures controlled release of the overpressure above a certain value.

From the WO 03/051745 A a package of an unopened heatable, in particular microwave heatable material is known, which has at least one sealing region which becomes locally permeable when a certain internal pressure is exceeded, said sealing region has at least one Solldurchlassabschnitt forming a throttle for the package contents, and in the form of a channel-like Passage is formed, and comprises a packaging interior facing the tip, which is preferably sealed.

Disadvantage of this valve construction is that the valve opens easily not only in the case of overpressure induced by heating, but also under mechanical pressure. Furthermore, the passage is not exactly dimensioned. In addition, there is the possibility that migrated during production, autoclaving, sterilization, storage or heating filling material from the package into the valve, the contents presses the valve then prematurely and can escape into the surrounding space of the microwave oven. But there is also the possibility that the valve is clogged by the infiltrated contents and the steam can not escape to the extent necessary.

From the WO 04/13015 A For example, a package is known which has an absorber for the moisture escaping on heating, which makes a crisper preparation possible. Without a valve, through which excess steam can escape, the absorber is used up too quickly.

The object of the invention was to provide a suitable for heating in the microwave, in the oven or in a water bath packaging in the one hand, the construction of a defined overpressure and a controlled escape of steam is possible, on the other hand, depending on a crispy browning preparation or a Steam cooking of the contents is guaranteed.

The invention therefore relates to a packaging suitable for heating in a microwave oven, in an oven or in a water bath, consisting of a multilayer film material which has at least one region which becomes permeable when an internal pressure generated by the microwave heating is exceeded, the film forming an outer layer 1 and an inner layer 2, wherein the inner layer has a recess 3 extending through the entire thickness of the inner layer, and the inner layer is connected to the outer layer by means of an adhesive, such as laminating adhesive or heat-seal adhesive, characterized in that the outer layer has an energy-absorbing coating or printing at least in the region defined by the recess of the inner layer and / or in the region surrounding the recess, whereby the sealing layer heats up and the sealing adhesion is reduced or released.

As a result, the valve can only be opened when the package is heated in the microwave.

The outer layer 1 preferably consists of a film of plastic, for example polyester, such as oriented PET amorphous PET, polyolefins such as polypropylene, cast-PP, blown, stretched, biaxially oriented PP films, or polyethylene, polystyrene, polycarbonate, cellophane, polyamide, Polyvinyl chloride or copolymers thereof. However, coextruded or laminated plastic composite films or composites with paper can be used. It is also possible coated films, biodegradable films, aluminum foils and the like. The thickness of the outer layer is preferably 8-200 μm.

The inner layer 2 is preferably made of a recoverable medium, for example of plastic films of polyolefins such as polyethylene, polypropylene, EVOH, EVA, and / or its copolymers or terpolymers, polystyrene, polycarbonate, cellophane, polyamide, polyvinyl chloride. The inner layer can also be formed by extrusion coating or painting the outer film with one of the plastics mentioned.
The thickness of the inner layer is preferably 0.5-100 μm.

The recess may extend from edge to edge of the package or only over a particular area. In this case, several such recesses may be distributed over the area.
The recesses may be formed, for example, in the form of a slot, circle, rectangle, trapezium, triangle, etc.
In the area of the valve, a protective seal is provided for protection against unintentional and / or premature opening. Due to the adhesion of the protective seal, the opening pressure of the valve is set when heated. Depending on the requirement, depending on the adhesive force of the protective seal, the required opening pressure can be varied within a wide range. The adhesive force is determined primarily by the shape of the protective seal and the adhesive.

If necessary, a weak spot can be installed in the protective seal to ensure reliable opening of the valve. This can be done for example by a defined limited interruption of the sealing layer or by introducing defined Vorsiegelbereichen or points.
The protective seal surrounding the valve can have different shapes. It may be in the form of the valve, or else regardless of the shape of the valve, for example in the form of a tip, a trapezoid, in the form of line structures, in the form of a grid, in the form of a double point and the like.

Intermediate layers may optionally be located between the outer and inner layers. Such interlayers may include, for example, barrier layers such as alumina layers or silicon oxide layers, organic barrier layers such as polyamide layers, absorber layers, for example, gas absorber layers such as O ₂ , CO ₂ absorber layers, water vapor absorber layers, ethylene absorber layers, printed layers, layers providing increased flexibility or strength or stiffness, and the like be.
The entire layer composite of the packaging according to the invention can optionally comprise a plurality of intermediate layers and combinations of these intermediate layers, wherein the layers either each have good adhesion to one another or can be interconnected by adhesive aids, such as adhesives.

The energy-absorbing coating present in the region of the recess of the inner layer can be present over the full area or partially. It can for example be applied to the outer layer. However, it may also be present in the protective seal, or applied to any pre-seal points or areas.
The energy absorbing coating may be, for example, a metallic coating.
Examples of suitable metallic coatings are Al, Cu, Fe, Ag, Au, Cr, Ni, Zn or their compounds, for example their oxides or alloys. Further, graphite, for example, can be used as an energy absorbing coating.
Further, the energy absorbing coating may be a printing with an energy absorbing pigment or particle containing ink. In particular, particles and pigments come into question that by the incident microwave radiation come into resonance and are put into thermal oscillation.
These are understood in particular to mean pigments or particles which contain molecular water, such as water glass or zeolites.

The coating can be applied by known printing or painting methods, by sputtering, vapor deposition and the like.

In order to detect the opening of the valve, a feature can be applied around the region of the recess of the inner layer, both on the inner layer and on the outer layer, that a distinct change in the appearance upon opening of the valve.
In this case, for example, two different colored features can be applied, which form a mixed color in the closed state of the valve. After opening the valve, the two layers are separated, the pure colors appear.
Furthermore, provision can be made to provide partial information for proving the opening of the valve on the separating layers, which information is then supplemented after opening to understandable information, for example lettering, for example "open" or "open" and the like. This can be done using auxiliary layers with different adhesive strength.
In a further embodiment, an acoustic opening detection, for example a whistling sound, can be generated via the geometry of the valve. When the valve is opened, a tone lip begins to vibrate, which then generates the whistling sound.

Furthermore, on the side of the inner layer facing the interior of the packaging, one or more absorber layers can be provided for the steam arising during the heating. Examples of such absorber layers are hydrophilic polymers, such as EVA, zeolite-filled polymers, silica gel, nonwovens, or fabrics which are hydrophilic Embedded polymers, zeolite-coated nonwovens or tissue in question.

In one embodiment, the absorber layer may be applied to the inner layer by printing processes.

However, the absorber layer can also be fixed to the inner layer with a thin sealing layer or membrane. The fixation layer or the membrane may have a predetermined breaking point. When a defined pressure in the package is exceeded, the membrane is stretched and ruptures at the predetermined breaking point, whereby the absorber layer is exposed and the resulting water vapor can be absorbed.

Instead of the absorber layer, such an additional membrane may also contain flavoring substances, for example smoking substances, or the like, which are then released when the defined pressure is exceeded by opening the membrane.
In order to produce a characteristic aroma, encapsulated aroma substances can also be introduced in the valve region, which are released when the valve is opened.

Furthermore, a browning layer may be provided in the package. The tanning layer may consist of a paper composite with a metallized plastic film, such as a polyester film or a polypropylene film.

In a particular embodiment, the packaging may be designed in the form of a two- or multi-chamber packaging with different contents, it also being possible for a valve to be provided between the chambers. In this case, for example, be packed in a chamber, a meat dish, in the second chamber a side dish, for example, rice or potatoes or potato preparations and the like.

When a defined pressure in the chamber of the meat dish is exceeded, the valve located between the chambers opens, the resulting water vapor can escape into the chamber containing the supplement. Preferably, the chamber containing the meat dish has a tanning foil for crispy cooking of the dish while in the chamber containing the garnish there is steam cooking through the water vapor escaping from the secondary chamber.
Optionally, another valve may be provided to the outside space.

The connection of the individual layers can be effected by heat seal adhesive or a laminating adhesive or by extrusion laminating.

Furthermore, the packaging may have an opening aid, for example a perforation, a tear thread or notches.

The packaging may be in the form of a bag, a bag, a stand-up pouch, a tablet, sachet, pouch or in the form of a sealing foil for containers.

In Fig. 1 different shapes of the valve or the valve surrounding the protective seal are shown.
1 is the valve, 2 is the protective seal, 3 are the seal areas, 4 is the energy-absorbing coating.

Claims (16)

A packaging suitable for heating in a microwave oven, in an oven or in a water bath, consisting of a multilayer film material which has at least one region which becomes permeable when an internal pressure generated by the microwave heating is exceeded, the film comprising an outer layer 1 and an inner layer 2 , wherein the inner layer has a recess 3 extending through the entire thickness of the inner layer, and the inner layer is connected to the outer layer by means of an adhesive, such as laminating adhesive or heat seal adhesive, characterized in that the outer layer at least in the region defined by the recess of the inner layer and / or in the region surrounding the recess, an energy-absorbing coating or printing, which is heated by the sealing layer and the sealing adhesion is reduced or dissolved. Packaging according to claim 1, characterized in that the recesses extend from edge to edge of the package. Packaging according to claim 1, characterized in that the recesses are present only in defined areas of the package. Packaging according to one of claims 1 to 3, characterized in that the recesses in the form of a slot, circle, triangle, trapezium or rectangle. Packaging according to one of claims 1 to 4, characterized in that a protective seal is provided around the recesses. Packaging according to one of claims 1 to 5, characterized in that intermediate layers are provided between the outer and inner layer. Packaging according to claim 6, characterized in that the intermediate layers are barrier layers, absorber layers, browning layers, flexibility or strength or stiffness and / or printed layers. Packaging according to one of claims 1 to 7, characterized in that on the interior of the packaging facing side of the inner layer, an absorber layer is present, which is fixed by a membrane having a predetermined breaking point. Packaging according to one of claims 1 to 8, characterized in that are fixed by a membrane having a predetermined breaking point, flavorings. Packaging according to one of claims 1 to 9, characterized in that in the region of the valve encapsulated flavoring substances are introduced, which are released upon opening of the valve. Packaging according to one of claims 1 to 10, characterized in that in the region of the recess of the inner layer on the inner layer and the outer layer different features are applied, which show a significant change in the visual appearance after opening the valve. Packaging according to one of claims 1 to 11, characterized in that when opening the valve, an acoustic signal is generated. Packaging according to one of claims 1 to 12, characterized in that the energy absorbing coating is a metallic coating or a coating with a printing ink, the energy absorbing pigments or particles. Packaging according to one of claims 1 to 13, characterized in that the packaging is designed as Mehrkammemverpackung. Packaging according to claim 14, characterized in that a valve is provided between the chambers. Film material for the production of packaging according to one of claims 1 to 15.

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