FR2972958A1 - Method for manufacturing two-component container for packing food, involves covering portion of inner surface of plastic film by adhesive material, where film is placed against outer envelope and fastened by adhesive material - Google Patents

Abstract

The method involves providing an outer envelope (5) and a plastic film (6), where a portion of an inner surface (6c) of the plastic film is covered by an adhesive material (2) consisting of an adhesive i.e. Thermodex(RTM: industrial adhesive) that is activatable by heat at a temperature. The plastic film is placed against the outer envelope and fastened by the adhesive material to provide a container (7). The plastic film is heated to another temperature higher than the former temperature to cause activation of the adhesive material for constituting joining zones.

Description

The present invention relates to the general field of packaging; it relates more particularly to a new process for the manufacture of a two-component tray, of the type comprising an outer casing (for example of cardboard) lined internally with a plastic film, in particular for food use. Some two-component trays consist of an outer casing with an inner lining consisting of a plastic film to seal. Such trays, described for example in document FR-2 826 937, have the advantage of being waterproof and recyclable. For this recycling, it is important to be able to easily separate the outer shell and the inner liner of plastic. Document FR-2 826 937 recommends for this purpose to secure the two constituent materials of the tray by a few suitably distributed bonding areas. This type of tray is currently manufactured using a quick-setting glue which is applied to the inner surface of the outer shell. The inner plastic film must then be reported immediately on this bonded surface of the outer envelope.

But, in spite of all its interest, this manufacturing process is not totally satisfactory, and the use of such a quick-setting adhesive causes many constraints in the manufacturing process. This adhesive requires in particular to juxtapose the sizing station and that of setting up the plastic film, so as to quickly position the plastic film in the outer envelope glued. However, this gluing station is often at the origin of a glue-laden atmosphere, which is then likely to contaminate the position of placement of the plastic film. The glue used also has the disadvantage of being particularly messy for the machines, requiring frequent cleaning and maintenance operations and thus reducing the assembly rates.

The present invention aims to remedy these drawbacks by proposing a new process for manufacturing two-component trays, allowing the sizing step to be totally dissociated and the plastic film placing operation in the outer casing.

The method according to the invention thus relates to a succession of operations for the manufacture of a tray formed of a bottom element bordered by a belt of side walls, which tray consists of an outer envelope internally covered by a plastic film. reported waterproof, the adjoining inner surfaces of said outer envelope and said inner plastic film being secured together by an adhesive material distributed in one or more assembly areas; and which method is of the type comprising an operation of supplying the outer envelope and the plastic film, followed by an operation of placing said sealed plastic film against said inner surface of said outer envelope, secured together by said adhesive material to constitute said tray. In this context, the method according to the invention is characterized in that, on the one hand, the supply operation consists of providing an outer envelope and / or a plastic film at least a part of the inner surface of which is covered. by said adhesive material consisting of a heat-activatable adhesive at a first temperature Ti, and secondly, the setting operation comprises a heating phase of said plastic film to a second temperature T2, greater than said first temperature Ti, able to cause the activation of said adhesive material to form said assembly areas. By such a manufacturing method, it is possible to pre-deposit the glue on the materials to be assembled (and in particular on one of them) at a station or a place separate from the assembly station , thus eliminating any risk of contamination of this glue on the assembly station.

It is thus possible to ensure regular assembly rates, without the usual maintenance problems related to the cleaning of the glue deposited on the tools. This method is also advantageous for using the heating of the plastic film as a means of activating the adhesive material for assembling the two components of the container. Other advantageous features of the invention, which can be taken in combination or independently of one another, are specified below: the operation of placing the internal plastic film consists of a thermoforming operation of this plastic film directly in the outer envelope; preferably, the heat-activatable adhesive is deposited on the outer envelope, and the supplying operation consists in providing this external adhesive-coated envelope comprising a bottom element and a sidewall belt, in which the adhesive activatable by the heat is located at least on said side walls, in the form of a band whose height is less than that of said side walls and preferably located on the side of the free edge of said side walls; the operation of supplying the external adhesive-coated envelopes successively comprises: an operation for manufacturing said adhesive-coated envelopes, an operation of stacking these adhesive-coated envelopes, a transport and / or storage operation of these envelopes, suitably stacked, and - an unstacking operation of said adhesive-coated outer envelopes, before the operation of placing said plastic films; the supply operation is preceded by a manufacturing operation comprising a step of depositing the heat-activatable adhesive, by means of a printing technique, on the outer envelope and / or on the plastic film.

According to a preferred embodiment, the outer envelope is made of a material based on fibers, preferably vegetable fibers (for example cardboard); the operation of supplying this external adhesive-coated envelope is advantageously preceded by a manufacturing operation in the course of which are implemented: a step of depositing the heat-activatable adhesive on at least one of the faces of a flat blank, then - a step of setting volume of said adhesive-coated blank, to obtain said adhesive-coated envelope. This blank preferably comprises a central panel extended by lateral flaps, intended respectively to form the bottom element and the side wall belt of the envelope; the step of depositing the heat-activatable adhesive comprises applying said adhesive at least on the side of the side flaps of said blank intended to come into contact with the plastic film. Moreover, the side flaps of the blank advantageously comprise tabs. assembly for maintaining the volume of the side wall belt, and the volume-building step is preceded by a step of applying a quick-setting adhesive to said assembly lugs or to said lateral flaps for constitute useful assembly areas during the aforementioned step 20 of setting volume of the envelope. The invention will be further detailed, without being limited in any way, by the following description in relation to the appended FIGS. 1 to 5, which schematically represent the main operations implemented during the process according to the invention, for manufacture of a two-component container from an outer casing made of cardboard, against which an internal plastic film is attached. The process according to the invention advantageously starts with an operation for manufacturing the external adhesive-coated envelope, as described below in relation to FIGS. 1 to 3. This manufacturing operation begins with the supply of a carton blank 1 flat, shown in elevation in Figure 1.

In practice, this cardboard blank 1 is advantageously delivered by a feed station (for example of the vertical or horizontal feed magazine type), which is conventional in the field concerned. The cardboard blank 1 is suitably cut and scored to form, once set in volume, the outer casing of the tray described in more detail below in connection with FIGS. 4 and 5. This carton blank 1 comprises, in the occurrence, a rectangular central panel 1a whose sides are extended by two pairs of side flaps 1b, namely two longitudinal side flaps 1 b 'and two lateral transverse flaps 1 b ", these parts 1a and 1b are intended to form respectively the bottom element and the side wall belt of the outer casing of the tray Fig. 1, two of the side flaps 1b facing each other (in this case the longitudinal side flaps 1 b ') are themselves laterally extended by two one-piece assembly tabs 1c, as specified below, these tabs 1c are used to maintain the volume of the outer cardboard envelope.The manufacture of the tray continues with the operation of sizing one of the faces of the blank 1, as shown schematically in Figure 2.

In practice, in a sizing station, a first adhesive material 2, consisting of a heat-activatable adhesive, is deposited on the blank of cardboard 1 advantageously still flat. This heat-activatable adhesive 2 is advantageously chosen from "thermo-activatable", "heat-sealable", "thermoadhesive" or "hot-reactive" adhesives. By "heat-activatable" is meant an activation of the adhesive characteristics of the adhesive at a temperature which is above the average ambient temperature. The activation temperature T1 of this heat-activatable adhesive 2 is, for example, of the order of 100.degree.

There may be mentioned for example the glue called "THERMODEX" offered for sale by the company VALSTAR. This first adhesive 2 is preferably deposited by a printing technique.

This heat-activatable adhesive 2 is distributed over the cardboard blank 1 so as to allow a subsequent separation of the two materials constituting the tray with a relatively small force, and especially with a minimal amount of material torn from the outer carton during this separation (in order to allow optimal recycling of materials). For this purpose, the heat-activatable adhesive 2 is applied to the carton blank 1 according to a plurality of bonding zones. To simplify the remainder of the description, the bonding zones, and the constitutive thermo-activatable adhesive, will be designated by the same numerical mark 2. The bonding zones 2 in question here are in the form of discontinuous lines or strips ( Figure 2); these bonding areas 2 may also be in any other suitable form, for example continuous lines or bands, glue points, etc. The bonding areas 2 are formed on the side of the side flaps 20 1b which is intended to come into contact with the attached plastic film. The width of these bonding strips 2 is smaller than that of the side flaps 1 b and these strips 2 extend over a portion of the length of said side flaps 1 b; the adhesive strips 2 are additionally applied on the side of the free edge 1b "'of the side flaps 1b, while preserving a space 25 between them and this free edge 1b"'. In a complementary manner, these first areas of adhesive 2 (for the cardboard / plastic assembly) can be applied at the level of the central panel 1 to the carton blank 1. According to an alternative embodiment, it could still be envisaged to apply a single bonding area, corresponding for example to the entire surface of the blank 1 intended to come into contact with the plastic film reported. In the gluing station, a second adhesive material 3 is again applied here on two lateral flaps 1b (namely the two lateral transverse flaps 1b ") so as to form second bonding areas against which will come to be pressed. assembly tabs 1 ç above (folded internally) To simplify the following description, the second bonding areas, and the second constituent adhesive material, are designated by the same numerical mark 3. These second bonding areas 3 go here The second adhesive material 3 consists of a quick-setting adhesive, for example an acrylic or hot-melt type of glue, which is used to assemble the cardboard / cardboard assembly. is for example applied by means of a spraying technique or by a buffering process (that is to say a glue removal by direct contact of a glue buffer on the Alternatively or additionally, these second areas of glue 3 can be applied directly to the assembly lugs 1c, this on their side coming to press against the adjacent side flaps 1b ". The next step corresponds to the volume of this adhesive cardboard blank 1 (as shown schematically in a side view and in section in Figure 3).

In practice, this step of setting volume of the carton blank 1 is advantageously carried out by means of a dedicated conformer. This step consists in particular to raise the side flaps 1b relative to the central panel 1 a; in parallel, the assembly lugs 1c are folded internally and pressed against the inner face of the lateral transverse flaps 1b ", so as to be held together by the second bonding areas 3 provided for this purpose.

The outer casing 5 obtained, shown from the side and in section in FIG. 4, thus comprises a base element 5a (corresponding to the central panel 1a of the blank 1) extended by a wall belt 5b 'and 5b "(obtained by the proper positioning of the side flaps 1 b 'and 1 b "of the same blank 1). The first bonding areas 2 (for cardboard / plastic assembly) together form a circumferential band of heat-activatable adhesive which is located near the free edge 5b '' of the side wall belt 5b. Due to their particular positioning on the blank 1, these first bonding zones 2 form a discontinuous annular line or band on the volume envelope 5. These bonding zones 2 may also be in any other suitable form, for example lines or continuous webs, dots of glue, etc. A single bonding area may still be provided, covering the entire inner surface 5c of the envelope 5. The outer envelopes 5 thus obtained may be used immediately for the positioning of Alternatively, these adhesive cardboard envelopes 5 can be conveniently stacked into each other at their manufacturing site. t then be transported and / or stored, for example on a second site, and then depilated for the implementation of the final operation of securing with the reported sealed plastic film. According to yet another alternative embodiment, the adhesive cardboard blanks 1, still flat, can be suitably superposed / stacked on each other, for example on a first site. These cardboard blanks 1, which are adhesive and stacked, can then be transported and / or stored, for example at a second site, then be stripped and placed in volume in the form of external envelopes 5 for the implementation of the invention. final operation of joining the waterproof plastic film.

As illustrated in FIG. 4, the plastic film 6, intended to constitute the sealed inner lining of the tray, is advantageously thermoformed directly into the adhesive-coated outer envelope 5, the latter being in a thermoforming mold of suitable shape (not shown). ). This conformation is allowed by a prior phase of heating the plastic film 6 to a temperature T2 adapted to make it malleable. For example, this temperature T2 is between 100 ° C and 150 ° C, depending on the material constituting the film to be thermoformed. According to the invention, this heating temperature T2 is greater than the temperature Ti corresponding to the thermal threshold for the activation of the heat-activatable adhesive 2. The preheated plastic film 6 is shaped directly in the outer envelope 5, for example by means of a thermoforming die 7; alternatively or additionally, this thermoforming operation can be performed by a suction technique applied by means of an air gap at the lower face of the plastic film 6, by a technique of air pressure at the level of from the upper face of the plastic film 6 or by a combination of these techniques. During this setting volume, the inner face 6c of the plastic film 6 is pressed against the adhesive-coated inner surface 5c of the outer casing 5. At the time of this plating, the temperature of the plastic film 6 (preferably a temperature close to its temperature T2) is greater than the activation temperature T1 of the heat-activatable adhesive 2. Part of the thermal energy of this plastic film 6 is then transferred to the inner surface 5c juxtaposed with the outer envelope 5, which causes the activation of the adhesive material 2 to form the cardboard / plastic assembly areas.

The thermal energy transferred to the plastic film 6 for its thermoforming is thus used for the activation of the heat-activatable adhesive 2. This adhesive 2 is activated without complementary heat source, nor additional consumption of energy. All assembly areas 2, here forming a discontinuous circumferential annular band, thus participate in the cardboard / plastic assembly (as shown schematically in FIG. 5). The trays 7 obtained (FIG. 5), each formed by the combination of the outer envelope 5 with the plastic film 6, thus comprise a bottom element 5a and 6a (corresponding to the central panel 1a of the blank 1 and to the part adjacent plastic film 6) extended by a belt walls 5b and 6b (corresponding to the side flaps 1b of the same blank 1 and the adjoining portion of the same plastic film 6).

These trays 7 can then be stored by stacking. They are ready to be filled with a foodstuff before being hermetically sealed by the removal of a lid. The sealed packaging volume is then defined by the plastic film 6 and the operculum reported; depending on the conditioned foodstuff, this volume of packaging is either filled with a protective atmosphere (nitrogen, oxygen, etc.), filled with surrounding air, or evacuated with total or partial air. According to an alternative embodiment, the carton blank used for the manufacture of the tray may be free of assembly tabs 1c. In this case, the side flaps 1 b of this blank 1 are held in volume by the simple fact of their attachment to the plastic film 6, by the heat-activatable adhesive 2. Still according to an alternative embodiment, the adhesive cardboard envelope 5 is manufactured according to the following phases: - a phase of setting volume of the cardboard blank, to obtain said cardboard envelope, then only thereafter, - a phase of depositing the heat-activatable adhesive on at least one of the side walls of this cardboard envelope volume, to obtain the adhesive cardboard envelope. According to another embodiment, the thermo-activatable adhesive 2 is deposited on the flat cardboard blank, before it is cut, at the portion intended to form the central panel 1a and / or the lateral flaps 1b. After cutting, there is obtained a blank of cardboard as described above 1 o in relation to Figure 2. According to yet another alternative embodiment, the heat-activatable adhesive 2 is deposited on the inner face 6c of the plastic film 6, before it is put into place in the cardboard envelope 5 (that is to say, if necessary before its thermoforming).

In this case also, it is advantageously the heating of the plastic film 6 during its thermoforming operation that activates the heat-activatable adhesive 2. In general, the material constituting the outer envelope is made based on fibers, advantageously based on plant fibers and in particular wood fibers, preferably chosen from corrugated cardboard or compact cardboard, paper, molded fibers; a cardboard of recyclable type is advantageously used. This outer casing 5 can be made of any other suitable semi-rigid or rigid material. The person skilled in the art is able to industrialize this process of manufacturing trays (mechanization, automation, etc.), by suitable assembly of the various apparatus and devices at his disposal.

Claims (1)

1. A method for manufacturing a two-component container (7) comprising a bottom member (5a, 6a) bordered by a side wall belt (5b, 6b), which tray (7) consists of an outer casing (5) internally covered by a sealed plastic film (6), the adjoining inner surfaces (5c, 6c) of said outer casing (5) and said plastic film (6) being secured together by an adhesive material (2); ) distributed according to one or more assembly zones, which manufacturing method comprises the following successive operations: - an operation of supplying said outer envelope (5) and said plastic film (6), then - an operation of setting up said waterproof plastic film (6) against said outer shell (5), secured together by said adhesive material (2) to form said tray (7), characterized in that, on the one hand, said supplying operation consists of providing a wrapper external pe (5) and / or a plastic film (6) of which at least a part of the inner surface (5c, 6c) is covered by said adhesive material (2) consisting of an adhesive which is heat-activated at a first temperature Ti, and secondly, said setting operation comprises a heating phase of said plastic film (6) to a second temperature T2, greater than said first temperature Ti, capable of causing the activation of said adhesive material (2) to form said assembly areas. 2. A process according to claim 1, characterized in that the operation of placing the plastic film (6) consists of a thermoforming operation of said plastic film (6) directly into the outer casing (5). 3. A process according to any one of claims 1 or 2, characterized in that the supply operation consists in providing an adhesive-coated outer envelope (5) comprising a bottom element (5a) and a side wall fabric (5b) and in that the heat-activatable adhesive (2) is located at least on said side walls (5b), in the form of a strip whose height is less than that of said side walls (5P). 4. A process according to claim 3, characterized in that the heat-activatable adhesive strip (2) is located on the side of the free edge (5b "') of the side walls (5b). 5. A process according to any one of claims 1 to 4, characterized in that the operation of supplying the outer envelopes 1 o adhesive (5) comprises successively: - an operation of manufacturing said external envelopes adhesive (5), - a stacking operation of said adhesive-coated outer envelopes (5), - an operation of transporting and / or storing said appropriately stacked external envelopes (5), and - an unstacking operation of said adhesive-coated outer envelopes (5), before the operation of placing said plastic films (6). 6. A process according to any one of claims 1 to 5, characterized in that the operation of supplying said outer envelope (5) and said plastic film (6) is preceded by a manufacturing operation comprising a step of depositing the heat-activatable adhesive (2) by a printing technique on said outer envelope (5) and / or on said plastic film (6). 7. A process according to any one of claims 1 to 6, characterized in that the outer casing (5) is made of a fiber-based material. 8. A process according to claim 7, characterized in that the operation of supplying the external adhesive-coated envelope (5) is preceded by an operation of manufacturing said external adhesive-coated envelope (5) during which are implemented. the following steps: - a step of depositing the heat-activatable adhesive (2) on at least one of the faces of a blank (1) flat, then-a step of volume development of said adhesive-coated blank (1), to obtain said adhesive envelope (5). 9. A method according to claim 8, characterized in that the blank (1) comprises a central panel (1a) extended by side flaps (1b), intended to form respectively the bottom member (5a) and the belt of side walls (5b) of the envelope (5), and in that the step of depositing the heat-activatable adhesive (2) consists of applying said adhesive (2) at least on the face of the shutters side (1b) of said blank (1) intended to come into contact with the plastic film (6). 10.- Method according to claim 9, characterized in that the side flaps (1b) of the blank (1) comprise assembly tabs (1) for maintaining the volume of the side wall belt (5b), and in that the volume-setting step is preceded by a step of applying a quick setting adhesive (3) to said assembly lugs (1Q) or said lateral flaps (1 b) to form zones assembly useful during said step of setting volume of the outer casing (5).