WO1993017934A1

WO1993017934A1 - Food packaging container

Info

Publication number: WO1993017934A1
Application number: PCT/FR1993/000226
Authority: WO
Inventors: Augustin Gras
Original assignee: E.P.I. - Lauragri S.A.
Priority date: 1992-03-10
Filing date: 1993-03-08
Publication date: 1993-09-16
Also published as: ES2082658T3; EP0629168B1; FR2688474A1; DE69300869D1; DE69300869T2; EP0629168A1; FR2688474B1; ATE130574T1

Abstract

A food packaging container, particularly a tray (1) made by forming a composite material including an upper layer (6) and a lower layer (7) of liquid-proof synthetic material, having therebetween a middle layer (8) wholly or partially made of an absorbent or adsorbent inorganic material, wherein said middle layer communicates with the upper layer (6) via perforations (9) provided therein.

Description

Food packaging container

The present invention is in the field of packaging containers for food products, for example of the trays type, more particularly intended for foodstuffs liable to exudation during storage, for example in refrigerated display cases in shops.

The invention also relates to a method of manufacturing a composite material suitable for producing this type of packaging container.

In the prior art, trays are known which, as a general rule, consist of a bottom part, secured to transverse and longitudinal sides so as to produce, for example by forming a composite material, a container comprising an upper layer and a lower layer of synthetic material, impermeable to liquids, and between which an absorbent lining is interposed - in communication with the upper layer by perforations made in the latter.

Documents DE-U-8 801 585, PR-A-2 586 653, GB-A-1 168 925 and

US-A-3 932 575 illustrate the prior techniques of implementation in the manufacture of trays such as bonding, the laying of the film constituting the upper layer, the perforation of the latter and thermoforming.

A tray of this type is described in document EP-0 182 139 in which an absorbent lining and upper and lower layers as defined are produced, by cuts of the same ^* length of corresponding strips, the perforations of the upper layer being produced. both at the bottom and on the transverse zones of said upper layer, in line with the lining which covers them as an extension of the bottom.

In fact, the filling is, in this embodiment, continuously unrolled continuously on the lower layer, in the form of a strip, before the upper layer is put in place, the cutting and then the forming of the tray being carried out successively.

It is easy to understand that such a process does not allow the recycling of waste from cutting. Indeed, these consist, in this case, of materials waterproof synthetics loaded with a material having on the contrary an absorbent power and which comes from the transverse sides coated with the lining, in extension of the bottom.

It is obvious that the incompatibility of the materials present makes it impossible to recycle them simultaneously.

Furthermore, the presence of the absorbent pad on the transverse sides impairs a perfect and homogeneous connection of the periphery of the tray, and what is more, creates unsightly differences in thickness, certain zones comprising two layers, others three .

In addition, due to capillary phenomena, the exudate, for example the blood of a piece of meat, can rise through the transverse sides and cause unpleasant stains when the container is gripped by a consumer. This phenomenon is further favored by the fact that perforations are provided longitudinally on either side of the bottom and extend over said transverse edges.

Furthermore, the absorbent pads which should ensure the preservation of the meat, are not entirely satisfactory and allow the juices of the meat to flow and come into contact with the latter. The fact that the packaging containers cannot be stored, in stores, at a temperature below about 5 ° C., brings a certain limitation to the storage period of the packaged foodstuffs.

The applicant, in order to extend the shelf life of foodstuffs, in particular fresh meat or fish, has carried out studies which have made it possible to follow the path of bacteria bringing deterioration in the form of rot. It has been observed that this rotting begins at the level of the absorbent lining. Within these linings, especially cellulose absorbent pads, there is _r following the reactions that inevitably occur with the components of meat juice, heat generation which promotes the growth of bacteria fermentation. Because the area of the juice spread by absorption on the blotting paper is considerably greater than that of the meat, the growth of said bacteria is considerably greater than in meat. Part of the bacteria nest in the enclosure of the tray. In addition, during the fermentation time, bacteria are at the origin of an evolution of gas presenting an unpleasant odor.

According to the sanitary regulations in force in most countries, it is forbidden to treat with chemicals the filling volume of a packaging container of the tray type. It will therefore be necessary to treat only said container only at the level of said absorbent lining, that is to say the intermediate layer.

An object of the present invention is to provide a packaging container, which is easy to produce, making it possible to remedy the drawbacks resulting from the multiple problems set out above. Another object of the present invention is to provide a composite material more particularly suitable for the manufacture of packaging containers according to the invention.

The invention also relates to a method of manufacturing this composite material so as to adapt it more particularly to the production of packaging containers of the invention.

The present invention therefore relates to a container. ^• packaging of food products of the tray type, more particularly intended to receive materials capable of generating exudates during storage, in particular foods based on meat and / or fish and other consumer products, this container being constituted by a bottom portion, from which transverse and longitudinal sides extend so as to form a container obtained by forming a composite material and comprising an upper layer and a lower layer, of a liquid-tight synthetic material, and between which is interposed at least one absorbent and / or adsorbent intermediate layer in communication with the upper layer by perforations made in the latter, characterized in that each absorbent and / or adsorbent intermediate layer or lining is made up in whole or in part by a inorganic material, possibly associated with at least one mat riau organic having the same properties or properties compatible 1'utilisation.

According to another essential feature of the present invention, the surface of the intermediate layer or absorbent pad or adsorbent is less than the ^'developed surface of the container formed by the upper and lower layers of plastic material, positioning said intermediate layer with respect to these last being substantially centered on the abscissa and on the ordinate, so as to leave a peripheral band free of absorbent or adsorbent material around the lining and capable of allowing the two upper and lower layers to be joined around their entire periphery according to a homogeneous thickness, thus avoiding leave a peripheral empty space between the periphery of the intermediate layer and the junction zone between the upper and lower layers.

The invention is further remarkable by the following points:

- The inorganic material constituting the intermediate layer is in powder form.

- The inorganic material and / or the organic material is in expanded form.

- The particles of organic and / or inorganic material are associated with a support or with a binding agent forming a support with said elements or particles.

- The inorganic material is chosen from the group consisting of pulverulent perlil preferably obtained by cooking a perlite, dehydrated silica gel, inorganic salts, activated carbon, ores, minerals and the like. - The lower layer is obtained from an expanded, extrudable and thermoformable plastic.

- The expanded plastic material forming the lower layer is chosen from polystyrenes and expanded polyethylenes.

- The upper layer is a film made of a plastic material chosen from polystyrenes, polyethylenes, polyvinyl chloride and polycarbonates. _%

- The film constituting the upper layer has a nature such that it allows the printing of a decorative and / or advertising motif. The film constituting the upper layer is provided with micro-perforations made in line with the intermediate layer or absorbent or adsorbent lining, thereby obtaining a better distribution of the absorption or adsorption of the exudates and these excluding any other place on the tray. For the production of three-layer composite materials according to the present invention, the process for manufacturing a multi-layer material, described in the certificate, will preferably be used. French Utility No. 2,491,826 in the name of the Applicant, in which it teaches the joining by calendering of a layer of polyethylene in the form of an extruded thin film, with a layer of expanded polystyrene also obtained by extrusion, the calendering allowing the joining of the layers.

The invention also relates to a process for the manufacture of a packaging container of the tray type according to the invention, this process being characterized by the following successive steps:

- A strip or sheet of plastic foam intended to constitute the lower layer of the composite material is prepared, by extrusion ^• from an expanded plastic material;

- A positive thermal gradient is applied to the inner layer so as to make it adhesive;

- There is on the lower layer made adhesive, an absorbent or adsorbent intermediate layer obtained from a soft width fed discontinuously and calibrated according to a predetermined surface and disposed on said lower layer according to predetermined marks relative to a center;

- An extruded plastic film is applied constituting the upper layer of the composite material so as to completely cover the lower layer;

- The three layers of the composite material thus obtained are calendered, so as to secure the plastic film constituting the upper layer with the lower layer of expanded plastic foam over all of the areas not occupied by the absorbent or adsorbent intermediate layer, surrounding this one *;

- The plastic film is perforated in line with the absorbent or adsorbent intermediate layer, according to the same positioning marks thereof; - The complex thus formed is wound on a reel which is stored for a period of 36 to 60 hours, preferably 48 hours;

- A blank obtained in this way is formed by thermoforming in order to produce a number of containers each having the appropriate shape, which will be separated by cutting from one another in order to obtain the packaging containers or trays of the invention .

The multi-layer composite material will advantageously be produced in the form of. continuous strips so that a roll can be formed suitable for being unwound during the thermoforming operation of the blanks, before cutting.

According to an advantageous embodiment, the sheets or strips are arranged in multi-poses for a simultaneous unfolding of these various operations.

According to another embodiment of the invention, a layer of crystal polystyrene is applied to the composite material before the winding operation, which adheres to the upper layer.

The invention also relates to a device for carrying out the method specified above, this device comprising means for feeding a sheet of expanded polystyrene, means for feeding a sheet made of an adsorbent or absorbent material, means for longitudinal cutting of the sheet of absorbent or adsorbent material from a number of secondary sheets, means of cutting the secondary sheets of absorbent or adsorbent material into unitary intermediate layers, means of centering and positioning the unitary intermediate layers on the sheet of polystyrene, means for applying an upper layer to the assembly formed by the unitary intermediate layers and the lower layer, means for perforating the superimposed layer, winding means for storage and thermoforming means, this device being characterized in that it further comprises:

- Means allowing the discontinuous transfer of the primary intermediate layer to means of longitudinal cutting of the intermediate layer;

- Marking means allowing synchronization between the transverse cutting of the intermediate layer and the application of the unitary intermediate layers thus formed on the intermediate layer; and ^_ means making it possible to reactivate, by application of a positive thermal gradient, the adhesive power of the lower layer at the level of its junction with the unitary intermediate layers.

It is clear that, according to the invention, the intermediate layer being placed in the center, it cannot be affected by the cutting of the transverse or even longitudinal sides.

Other characteristics and advantages of the present invention will appear on reading the following nonlimiting description, made with reference to the accompanying drawings in which: FIG. 1 represents a tray seen in perspective, with partial cutaway so as to show in section the structure of the composite material which constitutes it; Figure 2 shows on a larger scale, in cross section, the bottom and one of the transverse sides of the tray; FIG. 3 represents a strip of thermoformed composite material, before cutting the blanks of the trays; Figure 4 is a schematic illustration, in side elevation, of the production line of the packaging containers of the present invention. As shown more particularly in FIGS. 1 and 2, the tray, designated as a whole by the reference numeral 1, consists of a bottom part 2 from which depart transverse 3 and longitudinal 4 sides so as to form a container for general parallelepiped shape, provided with an upper flange which surrounds said sides 3, 4 in order to give the assembly a certain rigidity.

This container or container which can serve as a packaging container for food products. and which is more particularly intended for the packaging of foodstuffs of animal origin susceptible to exudation, such as meat and fish, 'is obtained by thermoforming of a composite material consisting of an upper layer 6 and a lower layer 7, both being made of a liquid-tight synthetic material.

Between the upper 6 and lower 7 layers is interposed an absorbent or adsorbent intermediate layer 8 which communicates with the upper layer 6 by means of micro-perforations 9 made in the latter. According to the invention, the surface S of the intermediate layer or absorbent or adsorbent lining 8 is smaller than the developed surface SI of the container formed by the layers 6, 7 of plastic material. In fact, the intermediate layer 8 occupies a surface S substantially corresponding to the bottom 2 of the tray 1 and its positioning relative to the layers 6, 7 is centered on the abscissa ^' and on the ordinate along the axes XX' and YY 'intersecting at the point 0 (Figure 3). In this last figure, it can be seen particularly clearly that, in this way, there remains around the intermediate layer 8 a peripheral strip formed by all of the surfaces of the transverse and longitudinal sides 3, 4 and by the flange 5, not comprising of intermediate layer 8 and therefore able to allow a tight connection of the upper 6 and lower 7 layers over their entire periphery, according to a uniform thickness.

It is therefore very clear that, during the cutting of the trays, the waste 10 caused by said cutting will be recovered then recycled without difficulty, since they are only composed of plastics compatible with each other.

In order to facilitate and make profitable the implementation of a manufacturing process which will be described below, the three-layer composite material 6,7,8 is produced in the form of a continuous strip 11 so as to produce a roller capable of being unwound during the aforementioned cutting operation of the blanks before their shaping to form a tray.

Of course, for the sake of efficiency, the sheets or strips 11 do not comprise a single row of absorbent or adsorbent linings but are arranged in multi-poses.

The three-layer composite material used therefore comprises, as described above, an upper layer 6 and a lower layer 7 of waterproof synthetic material.

More precisely, the lower layer 7 is obtained from an foam of expanded plastic material, extrudable and thermoformable, for example a polystyrene, a polyethylene, a polypropylene and the like.

As regards the upper layer 6, the latter is in the form of a thin film obtained by extruding a polystyrene, a polypropylene, a polyvinyl chloride, a polyethylene, a polycarbonate. and the like.

Furthermore, the film 6 is of such a nature as to allow the printing of a decorative and / or advertising motif.

In addition, the film 6 is able to undergo micro-perforations 9 which are only made in line with the intermediate layer 8. This gives a better distribution of the absorption or of the adsorption of the exudates and this at 'exclusion from any other place on the tray.

According to a preferred embodiment of the present invention, as shown in Figures 3 and 4, from two unwinding reels (20,21), we take a primary width of adsorbent or absorbent material, for example cotton wool, which is made to run on an idler roller ( 22) fitted with a magnetic contactor (P), after which this width is transferred, using two actuating rollers, to a first storage magazine (24) where it is piled up in the form of a soft strand or of soft width. Inside the magazine (24) is mounted a photoelectric cell (25) which, when it no longer detects the presence of absorbent or adsorbent material, actuates the actuating rollers (23) which unwind the web, thereby causing the raising the idler roller (22), releasing the magnetic contactor (P), which has the effect of releasing the pneumatic brake from the reel reel. There then occurs a normal unwinding of the width until the cell (25) again detects the presence of soft strand. Once the width has been delivered, it passes over a series of idle rollers (26) to come into the storage position in a second magazine (28) provided with a cell (29). When the latter no longer detects the presence of soft strand in the magazine (28), it actuates the rollers (27) which drive the width to the longitudinal cutting station where discs (RI, R2, R3), adjustable and controlled by pneumatic cylinders, divide the width, for example, of 320 mm into four widths, for example, of 80 mm, and which are advantageously positioned at the correct center distance by the passage in guide elements (38) previously adjusted.

All the widths are transferred by means of a drive roller (30), slaved to an encoder at a transverse cutting station or a guillotine device (31), actuated by "pneumatic" cylinder, cuts material absorbent according to a predetermined length, corresponding substantially to the bottom of the thermoformed tray. Concomitantly, a sheet of expanded polystyrene passing over rollers (41, 42) is transferred to an anchoring station where an ink roller (I) comes press on the polystyrene sheets to print at regular intervals (corresponding to the thermoforming step) a spot of black color, for example, a square with a side of 25 mm. This spot, passing in front of the cell (F) activates the rollers (30) so as to unwind a length of intermediate layer corresponding substantially to the bottom of the tray to be thermoformed, further pushing the already cut length of unitary layer which is positioned on the expanded polystyrene sheet whose surface has been reactivated by hot air from ά ^ a blowing thermal device (), which makes it very adhesive. The intermediate layer and the width of expanded polystyrene are brought into contact by the action of a pressing device (32) actuated by pneumatic cylinder. In (30), the guillotine (31) is simultaneously actuated, once the intermediate layer length has been reached. Once this cycle has ended, another spot reaches the cell (H) actuating the roller (30) and the next cycle can take place. The secondary widths, covered with unitary interlayer layers, deposited at regular intervals, are then transferred to a station for depositing a covering film of impact polystyrene, a station consisting of an extruder (J ') associated with a flat die (J ) which cooperates with a calendering device with 3 thermoregulated rollers (K). This calendering device is optionally supplied with a christal polystyrene film fed by a reel reel (L) with a control roller (S) for the web tension. This last film can be previously printed with any motif on request. It is advisable that these films are dyed and those in order to hide from view the intermediate layers filled with exudates.

The composite webs thus formed are transferred via a guide roller (33) to the perforation station comprising spiked rollers (M) by bringing the previously printed spots facing the electrical cells (.Tl, T2), of which one (Tl) triggers the descent of the spiked rollers and the other the ascent of the latter. According to one. variant, it is possible to use * a single cell which triggers the descent of the pin rollers, the ascent of which is engaged according to a preset time delay as a function of the length of a unitary intermediate layer. Once the plastic film (6) has been perforated in line with the absorbent lining (8), as described above, the composite product obtained is wound up on a storage reel for, for example, 48 hours, after which the composite product is transferred to a thermoforming station, not shown in the drawings, after which the trays thus formed are cut and the cutting waste is recycled 10. It should be noted that the micro-perforations 9 are advantageously of frustoconical shape using needles shape punches. corresponding opening onto the lower layer 8, this shape making it impossible to raise the exudates. '

The thermoforming of the film 6 prevents the ejudates from coming out of the absorbent or adsorbent intermediate layer and allows the tray to remain clean, whatever its position on a display.

Thus is solved simultaneously the problem of ^" peripheral tightness of the tray, that of the constant thickness of the periphery and also the problem of harmful bacterial developments due to the migration of exudates in the prior conditioning devices.

It is clear that the invention is in no way limited to the form and to the embodiment described above with reference to the appended drawings, but that it encompasses all the modifications and variants, derived from the same basic principle. Thus, the above enumerations relating to the plastics used as well as to the absorbent and adsorbent materials used are in no way limiting and that any material or material can be used provided that it has the physicochemical characteristics appropriate to the use.

Claims

1) packaging container for food products, of the tray type, more particularly intended for receiving materials liable to generate exudates during storage, in particular food and other consumer products, this container being constituted by a bottom part ( 2), from which the transverse and longitudinal sides start • to form a container obtained by forming a composite material comprising an upper layer and a lower layer, made of liquid-tight synthetic material, and between which at least is interposed an intermediate-absorbent and / or adsorbent layer in communication with the upper layer by perforations made in the latter, characterized in that each absorbent or adsorbent intermediate layer or lining (8) consists, in whole or in part, of at least- an absorbent or adsorbent inorganic material, optionally a associated with an organic material having the same properties or properties compatible with use.

2) packaging container according to claim 1, characterized in that the surface (S) of the absorbent or adsorbent intermediate layer (8) is smaller than the developed surface (SI) of the container formed by the layers (6,7) made of synthetic material, its positioning relative thereto being substantially centered (0) on the abscissa and on the ordinate, so as to leave a peripheral band (3,4,5) free of absorbent or adsorbent material around the lining, and able to allow the two upper (6) and lower (7) layers to be joined together over their entire periphery, according to a uniform thickness, thus avoiding leaving a peripheral void space between the periphery of the intermediate layer (8) and the zone of junction between the upper (6) and lower (7) layers.

3) Packaging container according to claims 1 or 2, characterized in that the inorganic material constituting the intermediate layer (8) is in powder form.

4) Packaging container according to any one of claims 1 to 3, characterized in that the organic material and / or the inorganic material is in expanded form. 5) packaging container according to any one of claims 1 to 4, characterized in that the material particles organic or inorganic are associated with a support or with a binding agent forming a support with said particles.

6) Container. packaging according to any one of claims 1 to 5, characterized in that the inorganic material is chosen from the group consisting of perlil, dehydrated silica gels,., inorganic salts, activated carbon, ores and minerals having the physico-chemical properties appropriate for the use.

7) Packaging container according to one of claims 1 and 2, characterized in that the lower layer (7) is obtained from an expanded plastic material, extrudable and thermoformable.

8) A packaging container according to claim 7, characterized in that the expanded plastic material forming the lower layer (7) is chosen from polystyrenes and expanded polyethylenes. 9) A packaging container according to claims 1 or 2, characterized in that the upper layer (6) is a plastic material chosen from polystyrenes, polyethylenes, polyvinyl chlorides and polycarbonates.

10) A container according to claim 9, characterized in that the film constituting the upper layer (6) has a nature such that it allows the printing of a decorative and / or advertising pattern.

11) Container according to one of claims 9 and 10, characterized in that the film (6) is perforated with micro-perforations (9) for example of frustoconical shape, made in line with the absorbent intermediate layer (8).

12) Process for the manufacture of a material with several layers (6,7,8) in particular intended for the realization of packaging containers of the tray type according to any one of Claims 1 to 11, characterized by the following successive steps:

- Preparing a strip or sheet of plastic foam (20) intended to constitute the lower layer. composite material, by extrusion from an expanded plastic;

- a positive thermal gradient (W) is applied to the lower layer so as to make it adhesive;

- There is (32) on the lower layer (7) made adhesive, an absorbent or adsorbent intermediate layer (8) obtained from a soft width fed discontinuously (7,10) to a positioning station (31,32) where it is calibrated according to a predetermined surface (S) and placed on said lower layer according to predetermined marks (A, B, C , D) with respect to ι _, a center (0); - an extruded plastic film (22) constituting the upper layer (6) of the composite material is laid, so as to completely cover the lower layer (7) -

- the three layers (6,7,8) of the composite material thus obtained are calendered in (K), so as to secure the plastic film constituting the upper layer (6) with the lower layer (7) of expanded plastic foam over all of the areas not occupied by the absorbent or adsorbent intermediate layer (8), surrounding the latter;

- The plastic film (6) is perforated in (M) in line with the absorbent or adsorbent intermediate layer (8), according to the same positioning marks (A, B, C, D) thereof;

- The complex thus formed is wound on coils (N) which are stored for a period of 36 to 60 hours, preferably 48 hours;

- Shaping a blank (1A) thus obtained by thermoforming, in order to produce a number of containers each having the appropriate shape, after which the containers are separated by cutting so as to obtain the packaging containers;

- the cutting waste (10) is recycled.

13) Method according to claim 12, characterized in that the sheets or strips (11) are arranged in multipose for a simultaneous course of these various operations.

14) Method according to which a layer of crystal polystyrene is applied to the composite material before the winding operation, which adheres to the upper layer (6). 15) Device for implementing the method according to any one of claims 12 to 14, this device comprising means for feeding a sheet of expanded polystyrene, means for feeding a sheet of absorbent or adsorbent material, means for longitudinal cutting of the primary sheet into a number of secondary sheets, means for transversely cutting the secondary sheets of absorbent or adsorbent material into unitary intermediate layers, means for centering and positioning the layers absorbent or adsorbent units on the expanded polystyrene sheet, means for applying an upper layer to the assembly formed by the unitary intermediate layers and the lower layer, means for perforating the upper layer, means for winding for storage and thermoforming means, this device being further characterized in that it comprises:

- Means (23,24,25,26) allowing the discontinuous transfer of the absorbent or adsorbent primary intermediate layer, to means of longitudinal cutting (Rl, R2, R3) of the primary intermediate layer;

- Means (27,28,29,30) allowing the discontinuous transfer of the secondary intermediate layers, absorbent and adsorbent, to a transverse cutting station (G) in absorbent unit layers;

- Marking means (42,1) allowing, in association with photo-optical means (H), synchronization between the transverse cutting of the intermediate layer and the application of the unitary intermediate layers, already formed, on the lower layer ;

- Means for reactivating, by the action of a positive thermal gradient, the adhesive power of the lower layer at the level of its junction with the unitary intermediate layers, absorbent or adsorbent.