EP0046956B1 - Tray-like packaging container with fluid-absorbing bottom and method for producing it - Google Patents

Description

The invention relates to dimensionally stable, bowl-shaped packaging containers for liquid-secreting fillings, the bottom of which is capable of absorbing and retaining liquid. The invention further relates to methods of manufacturing the products.

In self-service shops in particular, it is customary to offer foods, such as fresh meat, fresh fish and fresh fruit, in bowl-shaped packaging containers, which are usually additionally wrapped in film.

The packaging trays usually used either consist of ground wood or of closed-cell foam made of plastic, for example polystyrene. Packaging trays made of ground wood have the disadvantage as packaging means for oozing filling goods that they lose their shape stability and their stability due to the soaking of their walls due to the absorption of the liquid separated from the filling material. Closed-pore packaging trays made of plastic foam do not have the disadvantages of trays made of ground wood, but the liquid separated from wetting filling material accumulates in them on the bottom of the container, and there is a risk that the filling material will lie in the liquid separated from it and thereby suffer damage. Plastic packaging trays are also known, from the bottom surface of which protrude into the container cavity a multiplicity of projections of the same height, which in their entirety form the support surface for the filling material. In these known trays there is only selective contact between the support surface and the filling material, this does not come into contact with the liquid separated from it, and air has access to the underside of the filling material. However, the liquid collected in the container and separated from the filling material has a sales-inhibiting effect, and there is also the risk that the liquid will run out of the shell during transport.

There are also packaging trays on the market in which a liquid-absorbent fibrous insert lies loosely on the bottom of the tray. Such a bowl is described in US-A-3,209,978. These shells have the disadvantage that the loose insert can slip and that the filling material directly adjoins the fibrous material, so that there is a risk that small fiber parts stick to the filling material; in the case of a liquid-moistened insert, the filling material is in direct contact therewith, there is a risk that the filling material will be changed in an undesirable manner.

In GB-PS 11 68 925 a packaging tray made of plastic is described, the bottom of which has openings and is capable of absorbing liquid. The part of the bottom of the packaging tray which forms the support surface for the filling material consists of perforated plastic film, on the inside of which a liquid-absorbing layer is connected, on the other surface of which an uninterrupted plastic film is adjacent. The two plastic films mentioned completely shoot in the liquid-absorbing layer. The packaging tray side wall is constructed in two layers; the film layers forming the side wall can be connected to one another.

In the known shell there is a risk that the liquid absorbed by the liquid-absorbing layer of the base will either cause delamination of the shell side walls or - if these are not connected to one another - that the liquid will be undesirable. Penetrates into the cavity between the two film layers forming the side wall.

It is further described in the prior art by AT-B-327 783 that a packaging tray can be produced from outer and inner layers from plastic which can be shaped by heating and from intermediate layers from liquid-absorbing material by deep drawing. The layers mentioned are first brought together in a heating zone in the form of a web, then brought into the shape of the shell by deep drawing and finally separated from the web. During the deep-drawing process, the intermediate layer consisting of absorbent material is to tear in the region of the side walls of the shell, and the plastic layers which are thereby freely opposite one another are to be pressed together. This process can only be used to produce packaging trays with multilayer side walls for which the disadvantages described above apply. In addition, the process is complicated and therefore expensive.

The invention has for its object to propose simply designed bowl-shaped packaging containers, the side walls of which are formed in one layer, which are able to take up wetting contents without losing the dimensional stability and stability of the shell.

The object on which the invention is based is achieved by a product of the design specified in claim 1. Particularly advantageous embodiments of the product according to the invention are specified in the subclaims which refer back to claim 1.

The tray-shaped packaging container according to the invention consists of a single-layer tray made of plastic, the bottom of which has perforations and a sheet which is capable of being attached to the side of the tray bottom facing away from the tray cavity by spot or area sealing, spot or area welding or spot or area gluing, which is capable of doing so several times its own weight in water, to absorb and retain aqueous fluid or blood.

If the hydrophilic fabric is attached to the outside of the tray bottom by gluing, after the tray-shaped packaging container has been produced, either the outside of the tray bottom is coated with an adhesive which is capable of firmly bonding the hydrophilic sheet to the tray bottom, for example using a pressure sensitive adhesive or the like starts with the manufacture of the bowl-shaped packaging container from a hydrophilic fabric, one side of which is coated with the designated adhesive, and adheres the hydrophilic fabric, the outside of which advantageously also has an adhesive layer made of pressure-sensitive adhesive, to the outside of the tray bottom.

If one proceeds in the production of the bowl-shaped packaging containers in such a way that the surface structure is first attached to the surface of a film made of thermoformable plastic, which has been converted into a shell body by thermoforming according to a deep-drawing process, the hydrophilic surface structure is attached to the film Gluing analogous to that of the production of the shell-shaped body, in which the hydrophilic surface structures are fixed to the outside of the shell bottom by gluing as indicated after thermoforming the thermoplastic plastic film to form a shell body. In the context of the present invention, the terms “sealing” or “welding” are intended to have the same technical significance with regard to their effect with regard to the strength of the bond between the hydrophilic fabric and the shell bottom or between the hydrophilic fabric and the surface of the thermoformable film made of thermoplastic.

The sheet with high fluid retention capacity is referred to below as a hydrophilic sheet.

The shell of the product according to the invention consisting of the bottom and side wall is dimensionally stable and consists of water-resistant plastic; it is designed in one layer.

The side wall of the bowl is also called a jacket.

The term perforations is also used for the passage openings in the shell bottom; the shell bottom having through openings is referred to as being perforated.

The shell preferably consists of a closed-pore structured film made of foamed polystyrene. The thickness of the shell wall or the shell bottom is advantageously in the range from 100 to 500 μm.

The passage openings (perforations) in the bottom of the shell are preferably delimited in a circular manner and preferably each have a diameter of 2 to 10 mm.

The perforated shell bottom advantageously has a number of perforations such that the total area taken up by this forms at least 1% of the total floor surface. By definition, a single-layer shell is to be understood as being one that is homogeneous in terms of material and does not comprise welding, sealing or adhesive zones or gap-shaped cavities that extend parallel to the wall surface within the film forming the shell.

The breakthrough-free hydrophilic fabric attached to the outside of the shell bottom has such a shape and area that it covers all perforations in the shell bottom.

In the bowl-shaped packaging container according to the invention, the entire peripheral surface of the hydrophilic fabric attached to the bottom of the bowl is exposed.

• a) offenzellig bzw. offenporig strukturiert ausgebildeten Schichten aus chemischem Stoff mit hydrophilen Eigenschaften,
• b) fasrigen Schichten papierähnlich strukturierten Aufbaus aus Fasern bzw. faserähnlichen Teilchen, die jeweils aus chemischem Stoff mit hydrophilen Eigenschaften bestehen, insbesondere Vliespapier,
• c) Wirrfaservliesschichten, deren Fasern aus chemischem Stoff mit hydrophilen Eigenschaften bestehen,
• d) Schichten mit papierähnlich strukturiertem Aufbau aus Polymerfibriden mit hydrophilen Eigenschaften, beispielsweise hydrophilierte Fibride aus Polyethylen.

The hydrophilic fabric preferably consists of the following material or the following material layers:

• a) open-cell or open-pore structured layers of chemical material with hydrophilic properties,
• b) fibrous layers of paper-like structure composed of fibers or fiber-like particles, each consisting of chemical material with hydrophilic properties, in particular non-woven paper,
• c) random fiber fleece layers, the fibers of which consist of chemical material with hydrophilic properties,
• d) Layers with a paper-like structure made of polymer fibrids with hydrophilic properties, for example hydrophilized fibrids made of polyethylene.

Hydrophilized polymer fibrids or layers made of these are known and are not per se the subject of the present invention.

The term “hydrophilic fabric” definitely also includes fabrics made of two or more layers of the above-specified design.

• - Cellulose- oder Stärkeäther, die aufgrund des Substitutionsgrades (DS oder MS) zu mehr als 25 Gew.-% wasserunlöslich sind, beispielsweise Carboxymethylcellulosen eines DS von < 0,3 (s. dazu Stichwörter Celluloseäther In Ullmanns Enzyklopädie der technischen Chemie, 4. Auflage, Band 9, 1975, Seite 192 ff und « Stärkeäther in R.L. Whistler, Methods In Carbohydrate Chemistry, Academic Press, New York u. Lohdon, Vol. IV, 1964, Seite 304 ff),
• - thermisch vernetzte Carboxymethylcellulose nach der US-PS 26 39 239 oder der DE-OS 2314689,
• - durch chemische Verbindungen vernetzte Celluloseäther nach den DE-OSen 19 12 740, 23 57 079 und 2519927,
• - durch chemische Verbindungen modifizierte Celluloseäther nach der DE-OS 23 58 150,
• - durch Strahlung vernetzte Kohlehydratderivate nach der DE-AS 22 64 027,
• - durch chemische Verbindungen vernetzte oder anderweitig modifizierte Stärkeäther nach der DE-OS 26 34 539,
• - unter speziellen Verfahrensbedingungen hergestellte Carboxymethylcellulose nach der DE-OS 21 51 973 oder der DE-PS 10 37 076,
• - phosphorylierte Cellulosefasern nach der DE-OS 24 47 282,
• - Cellulose- oder Stärkeäther in Salzform mit einem mindestens zweiwertigen Metallkation (wie AI⁺¹⁺, Ca^*+), z. B. nach der DE-OS 26 09144,
• - Cellulose- oder Stärkepfropfpolymerisate nach den DE-OSen 25 16 380, 25 28 555 und 26 47 420 oder US-PS 36 61 815 oder
• - durch die Trocknung oder eine spezielle Modifizierung behandelte Carboxymethylcellulose nach der DE-AS 19 32 753 oder der DE-OS 27 57 096,
• - sowie bevorzugt Cellulosehydrat.

By definition, “chemical substances with hydrophilic properties” are understood to mean those which consist of at least 25% by weight, advantageously more than 35% by weight, of water-insoluble carbohydrate derivatives or water-insoluble chemically modified carbohydrate derivatives which are selected from one Comprehensive group

• - Cellulose or starch ethers, which are more than 25% by weight water-insoluble due to the degree of substitution (DS or MS), for example carboxymethyl celluloses with a DS of <0.3 (see also keywords cellulose ether in Ullmann's Encyclopedia of Industrial Chemistry, 4. Edition, volume 9, 1975, page 192 ff and «Starch ether in RL Whistler, Methods In Carbohydrate Chemistry, Academic Press, New York and Lohdon, Vol. IV, 1964, page 304 ff),
• thermally crosslinked carboxymethyl cellulose according to US Pat. No. 2,639,239 or DE-OS 2314689,
• cellulose ethers crosslinked by chemical compounds according to DE-OSes 19 12 740, 23 57 079 and 2519927,
• cellulose ether modified by chemical compounds according to DE-OS 23 58 150,
• carbohydrate derivatives crosslinked by radiation according to DE-AS 22 64 027,
• starch ether crosslinked or otherwise modified by chemical compounds according to DE-OS 26 34 539,
• carboxymethyl cellulose produced under special process conditions according to DE-OS 21 51 973 or DE-PS 10 37 076,
• phosphorylated cellulose fibers according to DE-OS 24 47 282,
• - Cellulose or starch ether in salt form with an at least divalent metal cation (such as AI ⁺¹⁺ , Ca ^{* +} ), e.g. B. according to DE-OS 26 09144,
• - Cellulose or starch graft polymers according to DE-OSen 25 16 380, 25 28 555 and 26 47 420 or US-PS 36 61 815 or
• carboxymethyl cellulose treated by drying or a special modification according to DE-AS 19 32 753 or DE-OS 27 57 096,
• - and preferably cellulose hydrate.

The hydrophilic fabrics advantageously have a thickness in the range from 20 to 3,000 _IL m and preferably consist of sponge-like layers of cellulose hydrate or absorbent paper, for example nonwoven paper.

The mouth opening of the shell of the shell-shaped packaging container is delimited by the upper peripheral edge of the shell shell; A flange edge surrounding the shell mouth opening advantageously projects horizontally outward from the peripheral edge of the jacket.

The shell casing advantageously has an inclination with respect to the horizontal that the shell cavity widens in the direction from the shell bottom to the cavity opening. Shell bottom and jacket are integral integral with each other.

In a variant of the invention, the product is constructed in such a way that an uninterruptible liquid-impermeable film is provided on the side of the hydrophilic fabric that faces away from the bottom of the shell, the shape and dimensions of the shape and dimensions of the designated area of the hydrophilic fabric correspond and completely covers. The water-impermeable, breakthrough-free film is connected to the hydrophilic fabric by flat or selective gluing, welding or sealing. The uninterrupted liquid-impermeable film advantageously has a thickness in the range from 5 to 30 J.Lm and advantageously consists of plastic, for example polyethylene, polypropylene, polystyrene or plasticizer-free polyvinyl chloride.

The product can also be designed in such a way that the shell bottom has a plurality of openings only within a zone which is delimited, for example, by a circular line at the bottom.

According to a further variant, the invention comprises a product in which the hydrophilic fabric on the perforated bottom of the shell also has a large number of through openings (perforations) which are adapted in shape and dimension to the through openings (perforations) of the bottom of the shell.

The perforations in the shell bottom and in the hydrophilic fabric advantageously correspond in terms of number, shape and area and are preferably arranged in pairs to cover one another.

This special design also ensures the desired liquid-absorbing and restraining effect of the hydrophilic fabric at the bottom of the shell: liquid passing through the passage openings in the bottom of the shell comes into contact with the peripheral surfaces of the openings in the hydrophilic fabric and is thereby sucked up and retained.

The bottom of the shell of the product according to the invention can also be designed such that it has a plurality of nub-like bulges, each of the same height, which protrude from the shell bottom into the shell cavity.

• 1. Man geht beispielsweise von einem aus geschlossenporig strukturierter Folie aus geschäumten Polystyrol bestehenden geeignet dimensionierten Zuschnitt aus, führt diesen durch Wärmebeaufschlagung in warmformbaren Zustand über und verformt ihn durch Tiefziehen in bekannter Weise und mittels bekannter Tiefziehvorrichtungen durch Einformen in ein Formwerkzeug, dessen formende Fläche gegengleich zur Form der gewünschten Schale ausgebildet ist, ein. Nach Abkühlung des Formkörpers aus dem Formwerkzeug werden in den Schalenboden mit Hilfe eines Mehrfach-Stanzwerkzeuges eine Vielzahl von Durchbrechungen (Perforationen) eingeformt. Danach wird auf der dem Schalenhohlraum abgewandten Oberfläche des perforierten Schalenbodens ein hydrophiles Flächengebilde, beispielsweise ein solches aus Vliespapier angeordnet und mit dieser befestigt, beispielsweise durch Verklebung, Versiegelung oder Verschweißung. Das hydrophile Flächengebilde ist in Form und Abmessung der Form und Abmessung des Schalenbodens angepaßt.
• 2. Die Herstellung des erfindungsgemäßen Erzeugnisses kann auch in der Weise erfolgen, daß man zunächst die Schale wie unter 1. angegeben formt, danach den Schalenboden wie angegeben an dem hydrophilen Flächengebilde befestigt und dann mittels eines Mehrfach-Stanzwerkzeuges den Schalenboden und hydrophiles Flächengebilde gleichzeitig perforiert.
• 3. Nach einer weiteren Variante kann das Erzeugnis auch in der Weise hergestellt werden, daß man zunächst von einem Folienzuschnitt ausgeht, wie er bei der ersten Verfahrensvariante verwendet wird, diesen dann in demjenigen Bereich, der nach seiner Warmformung mit Hilfe eines Tiefziehverfahrens zu einer Schale zur Bodenfläche derselben wird, mit einem hydrophilen Flächengebilde der Schalenbodenfläche in Form und Abmessung entsprechend derart abdeckt und an der Folie befestigt, daß die Schalenbodenfläche des Folienzuschnitts und das hydrophile Flächengebilde deckungsfähig zueinander angeordnet sind.

Products according to the invention can be produced by processes which are specified below:

• 1. For example, one starts from a suitably dimensioned blank consisting of a closed-pore structured film made of foamed polystyrene, converts it into a thermoformable state by applying heat, and deforms it by deep drawing in a known manner and by means of known deep-drawing devices by molding into a mold, the shaping surface of which is opposite is formed to the shape of the desired shell. After the molded body has cooled off from the molding tool, a multiplicity of perforations (perforations) are formed in the base of the shell using a multiple punching tool. A hydrophilic fabric, for example one made of nonwoven paper, is then arranged on the surface of the perforated shell base facing away from the shell cavity and fastened to it, for example by gluing, sealing or welding. The shape and size of the hydrophilic fabric is adapted to the shape and size of the shell bottom.
• 2. The manufacture of the product according to the invention can also be carried out by first molding the shell as indicated under 1., then attaching the base of the shell to the hydrophilic fabric as indicated, and then using a multiple punching tool perforated the shell bottom and hydrophilic fabric at the same time.
• 3. According to a further variant, the product can also be manufactured in such a way that it is initially assumed that the film is cut to size, as is used in the first method variant, and then in the area which, after it has been thermoformed, is thermoformed to form a shell the bottom surface thereof is covered with a hydrophilic fabric of the shell bottom surface in shape and dimension accordingly and fastened to the film in such a way that the shell bottom surface of the film blank and the hydrophilic fabric are arranged to cover one another.

The two elements mentioned are then connected to one another in a planar or punctiform manner, for example by planar or punctual sealing or gluing.

Thereafter, the flat element is subjected to heat in such a way that the plastic film blank is thereby converted into a thermoformable state. With the help of a deep-drawing process, the two-piece flat structure is then molded into the mold cavity of a molding tool of the deep-drawing device in such a way that the free surface of the hydrophilic flat structure connected to the film blank is on the outside of the shell body formed by thermoforming the film or represents the standing surface of the process product.

Thereafter, openings are simultaneously formed in the shell bottom and the hydrophilic fabric attached to it using a punching device.

If a product is to be manufactured in which the base consists of water-impermeable breakthrough-free film, for example plastic film, the manufacture of the product in each case is based on hydrophilic flat structures which are firmly connected on one side to a breakthrough-free water-resistant film, for example by gluing. The hydrophilic fabric coated on one side is then attached to the tray bottom in such a way that the plastic film on the hydrophilic fabric faces away from the tray bottom.

When the process is carried out, these special hydrophilic fabrics are arranged in the manner of the shell bottom (according to the 1st manufacturing variant) or for film cutting (according to the 3rd method variant) in such a way that the side of the hydrophilic fabrics not covered by film is the shell bottom or the cutting surface are facing.

When the products according to the invention are used as intended, in which they contain, for example, fresh meat or fresh fish as the filling material, the bowl-shaped packaging container is completely encased in an advantageously clear plastic film in order to protect the filling material.

The drawing explains the invention by way of example.

FIG. 1 of the drawing shows in cross section and in a schematic representation two variants of the product according to the invention, the part of the shell lying to the left of line AB being the product variant with a non-perforated, hydrophilic fabric at the bottom of the shell and the part lying to the right of line AB, for reasons of drawing simplification the same shows the product variant in which the hydrophilic fabric has through openings at the bottom of the shell.

In FIG. 2, a product according to the invention is shown in cross section and in a schematic representation, the bottom inside of which is particularly structured.

FIG. 3 shows, in a semi-perspective representation and schematically, a product according to the invention, in which the openings in the shell bottom are connected to it by channels.

In Figure 1, 1 means the bowl-shaped packaging container in its entirety; 2 the shell of the shell; 3 the flange at the top of the jacket; 4 is the shell cavity; 5 the perforated shell bottom, which is integral with the sheath of the same material; 6 are perforations in the shell bottom; 7 is the tray bottom surface on which the filling material lies; 8 is the hydrophilic fabric in its entirety; 8a is a breakthrough in the hydrophilic fabric; 9 is the footprint of the bowl-shaped packaging container; 10 represents filling material lying on the tray bottom; 11 is a film wrap that surrounds the bowl-shaped packaging container 1 on all sides.

In Figure 2, the numbers 1 to 8 have the same meaning as in Figure 1. The number 12 represents an uninterruptible, water-impermeable film; 13 are projections that protrude from the bottom of the shell into the shell cavity.

The product shown in FIG. 1 can also have projections on the shell bottom corresponding to 13 in FIG.

The product shown in FIG. 1 can also be designed in such a way that it has an uninterruptible, water-impermeable film corresponding to 12 from FIG. 2, which adjoins and is attached to the side of the hydrophilic fabric applied to the shell bottom.

In Figure 3, 14 means the shell jacket; 15 the shell bottom as a whole; 16 are openings in the shell bottom; 17 are channels with which the openings 16 are connected.

Claims (9)

1. Dish-shaped packaging container (1) having a perforated bottom section (5) and a liquid- absorbing bottom, wherein the container comprises a single-layer dish produced by thermoforming a single plastic film blank, with a hydrophilic planar structure (8) being attached to the outside of the perforated bottom (5) of the dish, in such a way that its peripheral area is exposed.

2. A dish-shaped packaging container as claimed in claim 1, wherein the dish is formed of a closed-cell film comprising foamed polystyrene.

3. A dish-shaped packaging container as claimed in claim 1 or claim 2, wherein the hydrophilic planar structure (8) has a spongelike texture and comprises cellulose hydrate.

4. A dish-shaped packaging container as claimed in claim 1 or claim 2, wherein the hydrophilic planar structure (8) comprises an absorbent paper.

5. A process for manufacturing a dish-shaped packaging container having a perforated bottom section by deep drawing, wherein a single blank comprising a hot-formable single-layer plastic film is converted into the hot-formable state by heat treating in a first process step, the blank is formed into a dish by deep drawing in a second process step, the dish is cooled in a third process step, and at least one perforation (6) is then formed in the bottom (5) of the dish in a fourth process step and, in a fifth process step, a blank of a hydrophilic planar structure (8) which corresponds in shape and dimension to the shape and dimension of the bottom (5) of the dish is thereafter attached to the bottom (5) of the dish on its side which faces away from the cavity of the dish, in such a way that it covers the perforations (6).

6. A process as claimed in claim 5, which is modified in such a way that, after the third process step, a blank of a hydrophilic planar structure (8) is attached to the bottom (5) of the dish, on its side which faces away from the cavity (4) of the dish and the bottom (5) of the dish and the hydrophilic planar structure (8) are then simultaneously perforated such that the perforation or perforations (6) in the bottom of the dish are congruent with the perforation or perforations (8a) in the hydrophilic planar structure.

7. A process for manufacturing a dish-shaped packaging container having a perforated bottom section by deep drawing, wherein a blank of a hot-formable plastic film is used to form the dish, the area of the film blank, which after thermoforming the blank into a dish with the aid of a deep drawing process, constitutes the bottom surface (5) of the dish is covered with a hydrophilic planar structure (8) which corresponds in shape and dimension to the bottom of the dish, in such a way that the bottom surface (5) of the dish and the hydrophilic planar structure (8) are arranged to be congruent and the hydrophilic planar structure (8) and the film are firmly bonded to each other and heat is then applied to the planar element, such that the plastic film blank is converted into the hot-formable state and is then formed into a dish-shaped body (1) by deep drawing in such a way that the hydrophilic planar structure (8) is present on the outer surface of the bottom of the dish-body produced by thermoforming the plastic film and thereafter perforations (6, 8a) are punched simultaneously into the bottom of the dish and the planar structure.

8. A process as claimed in any of claims 5 to 7, wherein a blank of a film having a closed-cell structure and comprising foamed polystyrene is used as a starting material for manufacturing the dish (1).

9. A process as claimed in any of claims 5 to 8, wherein the hydrophilic planar structure (8) comprises an absorbent paper or a sponge-like porous film of cellulose hydrate and is attached to the bottom (5) of the dish at its surface which faces away from the cavity (4) of the dish or to the surface of the film which is to be formed into a dish, by gluing with a contact adhesive.

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