EP1138610A1 - Laminated packaging sheet and reclosable package containing this laminated sheet - Google Patents

Abstract

Resealable packaging sheet with a weldable sheet comprising a welding film and a gas barrier film which is e.g. a copolyester. Laminated packaging sheet (14) which is resealable and comprises a support film (24) next to a welded film (26) between which is interposed in at least one of the zones, a layer (28) of a permanent adhesive attached to the film support (24) and the welded film (26), characterized in that the welded film (26) has a welding layer (36) and at least one gas barrier layer (37), where at least one of the barrier layers is a composition selected from vinyl alcohol/ethylene copolymer, polyvinylidene chloride, polyvinyl alcohol, silica, aluminum oxide, polyester and copolyester. An INDEPENDENT claim is included for packaging (10) especially a sachet type, with an external wall (16) defining an opening (15) characterised in that the opening is closed by laminated sheet (14) such that it welds to the external wall (16) at the periphery of the opening (15) by means of the weldable film (26) in a part of the sheet which is filled with a permanent adhesive (28).

Description

The present invention relates to a laminated packaging sheet of the type comprising a support film associated with a welding film between which is interposed, at least in identified areas, a layer of permanent adhesive, linked to the support film and the welding film.

It further relates to a package comprising such a sheet, this packaging may be a sachet or a container closed by such a leaf.

Packages with a packaging sheet allowing easy opening and reclosing are currently used for example for packaging food products. The structure of such a sheet is described in particular in French patent application FR-95 14117.

In this document, the laminated sheet used to allow the opening and the reclosure of the packaging comprises two films of polymer between which a layer of permanent adhesive is interposed.

One of the films, called "welding film" is intended to be oriented towards inside the package. It is suitable to be welded to the peripheral rim a tray. The other film, called "support film", is intended to form the outer side of the package. The welding film consists of a single layer of the same polymer or of a mixture of polymers.

It can be seen that, when such packaging is used for packaging of food, the taste and smell of it can be altered. In particular, the smell and taste of the products can be unpleasant for the user, the user perceiving that the food stored in the package have a smell or taste of "plastic" or "petroleum".

The invention aims to provide a solution to taste degradation and olfactory of food stored in packaging highlighting works at least one packaging sheet allowing reclosure.

To this end, the subject of the invention is a laminated packaging sheet of the aforementioned type, characterized in that it comprises barrier-forming means to gases and molecular migrations, integrated in the welding film.

• le film soudant comporte une couche soudante et au moins une couche formant barrière aux gaz et aux migrations moléculaires ;
• la ou chaque couche formant barrière aux gaz et aux migrations moléculaires comporte un copolymère d'éthylène et d'alcool vinylique ;
• la ou chaque couche formant barrière aux gaz et aux migrations moléculaires comporte au moins un composé choisi dans le groupe consistant en le polychlorure de vinylidène, le polyester terephtalate, l'alcool polyvinylique, l'oxyde de silice et l'oxyde d'aluminium ;
• la ou chaque couche formant barrière aux gaz et aux migrations moléculaires a une épaisseur comprise entre 2 et 15 microns et de préférence sensiblement égale à 3 microns ;
• le film soudant a une épaisseur totale comprise entre 20 et 60 microns et de préférence sensiblement égale à 35 microns ;
• la ou chaque couche formant barrière aux gaz et aux migrations moléculaires est disposée par rapport à la couche soudante du côté de la couche d'adhésif permanent ;
• ledit film soudant comporte en outre une couche de liaison disposée du côté de la couche d'adhésif permanent, la couche formant barrière aux gaz et aux migrations moléculaires étant disposée entre la couche soudante et la couche de liaison ;
• la couche soudante et la couche de liaison sont réalisées dans le même matériau ;
• elle est obtenue par coextrusion ; et
• le film soudant est obtenu par co-extrusion.

According to particular embodiments, the packaging sheet includes one or more of the following characteristics:

• the welding film comprises a welding layer and at least one layer forming a barrier to gases and to molecular migrations;
• the or each layer forming a barrier to gases and to molecular migrations comprises a copolymer of ethylene and of vinyl alcohol;
• the or each layer forming a barrier to gases and to molecular migrations comprises at least one compound chosen from the group consisting of polyvinylidene chloride, polyester terephthalate, polyvinyl alcohol, silica oxide and aluminum oxide;
• the or each layer forming a barrier to gases and to molecular migrations has a thickness of between 2 and 15 microns and preferably substantially equal to 3 microns;
• the welding film has a total thickness of between 20 and 60 microns and preferably substantially equal to 35 microns;
• the or each layer forming a barrier to gases and to molecular migrations is arranged with respect to the weldable layer on the side of the layer of permanent adhesive;
• said welding film further comprises a bonding layer disposed on the side of the permanent adhesive layer, the layer forming a barrier to gases and to molecular migrations being disposed between the welding layer and the bonding layer;
• the welding layer and the bonding layer are made of the same material;
• it is obtained by coextrusion; and
• the welding film is obtained by co-extrusion.

The invention further relates to a packaging comprising a wall external delimiting a housing provided with an access passage to said housing, characterized in that said passage is closed by a laminated sheet as defined above, which sheet is welded to said outer wall at the periphery of said passage, following its film which can be welded in a area of the sheet which is provided with permanent adhesive.

• la figure 1 est une vue partielle en perspective et en coupe d'une barquette d'emballage dont le passage d'accès est obturé par une feuille stratifiée selon l'invention, et
• la figure 2 est une vue analogue à celle de la figure 1, après ouverture de l'emballage.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings, in which:

• FIG. 1 is a partial perspective view in section of a packaging container, the access passage of which is closed off by a laminated sheet according to the invention, and
• Figure 2 is a view similar to that of Figure 1, after opening the package.

The packaging 10 shown in Figure 1 consists of a tray rigid rectangular 12 and a flexible cover 14 for closing a access passage 15 inside the tray. The cover 14 is reclosable.

The total thickness of the cover is generally less than 150 µm to get the flexibility you want.

The tray 12 consists of a support layer 16 made of material suitable, for example polyvinyl chloride or amorphous polyester (APET, CPET), covered on its inner surface with a weldable film 18, for example polyethylene.

The tray defines a receptacle 20 bordered around its entire periphery rim 22 delimiting a flat welding surface of the flexible cover 14 following a straight weld 23.

The cover 14 consists essentially of a support film 24 and a multilayer film welding 26 with a layer of permanent adhesive 28 interposed flat between them over the entire surface. Alternatively, the adhesive permanent 28 can be placed only in marked areas of the cover, these zones being intended to form the welding regions of the cover.

A transparent film 30 carrying impressions 32 is secured to the support film 24 by means of a layer of adhesive 34 applied to its printed side.

As a variant, the prints 32 are produced on the film 30 and / or 24 front and / or back.

The multilayer welding film 26 has a welding layer 36 adapted to form the inner surface of the package. It is intended for be welded by heat sealing on the weldable film 18 of the tray 12. According to the invention, the welding film 26 further comprises at least one layer 37 forming a barrier to gases and molecular migrations. This layer 37 is able to block the movement of small molecules or oligomers.

In the example given, the welding film 26 has a single layer forming a barrier.

As a variant, the prints 32 are produced on the film 30 and / or 24 front and / or back.

Advantageously, the welding film 26 comprises a bonding layer 38 disposed in contact with the layer of permanent adhesive 28. Thus, the layer forming a barrier to migration and gases is interposed between the layer welding 36 and the bonding layer 38.

The sealing film 26 can be obtained by bubble type coextrusion or of the cast type ("cast" in English) or by extrusion of each of the layers, coating and layers thereof.

The longitudinal weld 23 is obtained by heat sealing. During the welding, the welding film 18 and the welding layer 36 melt together, allowing to obtain after cooling a very reliable weld. In particular, the tensile strength of the weld 23 is greater than the strength tearing of the sealing film 26, the tensile strength of interfaces between the permanent adhesive layer and films in contact 24 and 26, as well as the tensile strength of the core of the adhesive layer 28.

For example, the different layers and films of the cover 14 have the following features.

The support film 24 is a polyester film 36 microns thick.

The layer of permanent adhesive 28 is produced by coating using a liquid or solid adhesive mass.

The layer of permanent adhesive can still be applied hot, especially by extrusion.

A permanent adhesive commonly referred to as "hot melt ”is ideal for this application. It is possible in particular to use PLASTOFLEX 8718 sold by the company PARAMELT in Holland.

The thickness of the adhesive layer 28 is advantageously included between 10 and 30 microns and preferably between 15 and 20 microns.

The transparent film 30 is for example a polyester film of a thickness of 12 microns. This film may have functional characteristics particular, in particular sealing characteristics vis-à-vis certain gases. To this end, it is treated according to known techniques adapted, such as coating.

The adhesive used to ensure the connection between the film 30 and the support film 24 is of any type adapted according to the nature of the films to be bound.

The characteristics which follow relate to the welding film 26. This film can, of course, be implemented with a layer 28 of adhesive permanent of any kind as well as a support film 24 of any kind layers 30 and 32 being optional.

Preferably, the barrier layer 37 comprises a resin of copolymer of ethylene and vinyl alcohol (EVOH) while the two layers 36 and 38 between which it is interposed are layers of polyethylene can be linked to the EVOH layer by a tie layer of compatibilization.

Preferably, the welding film 26 is obtained by co-extrusion of the layer of EVOH during the extrusion of the two layers of polymer between which it is enclosed

The copolymer of ethylene and vinyl alcohol is for example that marketed under the reference EVAL LCH 101BD by the company KURARAY, the ethylene content being 38%.

Advantageously, the thickness of the barrier layer 37 is between 2 and 15 microns, that being preferably equal to substantially 3 microns.

As a variant, the layer or layers forming a barrier to gases and to molecular migrations are formed for example of PVDC (polyvinylidene chloride), PETP (polyethylene terephthalate), PVOH (polyvinyl alcohol), SIOX (silica oxide) or Al ₂ O ₃ (aluminum oxide).

The total thickness of the sealing film 26, consisting of the three layers above, is between 20 and 60 microns and is preferably substantially equal to 35 microns.

The thicknesses of the welding layer 36 and of the bonding layer 38 are preferably substantially equal, each of them being included between 10 and 20 microns, and preferably substantially equal to 15 microns. They are preferably produced in the same polymer and in particular in polyethylene.

Preferably, the polyethylene used to form the layers 36 and 38 has a flow index between 1.5 and 4.5 g / 10 minutes. Advantageously, this index is between 3 and 4 g / 10 minutes and is preferably substantially equal to 3.5 g / 10 minutes. The fluidity index is calculated according to ASTM D1238 standard.

Likewise, the density of the polyethylene used for layers 36 and 38 is preferably between 0.920 and 0.940. Advantageously, this density is between 0.930 and 0.936. It is preferably substantially equal, for example, to 0.933.

Alternatively, layers 36 and 38 are formed from LDPE (polyethylene low density), LLDPE (linear polyethylene), MDPE (polyethylene medium density) or an ionomer (for example "SURLYN" sold by Dupont de Nemours), a mixture of these products, or polypropylene (homo or copolymer).

In the embodiment shown in the figures, the film welding 26 has three layers. However, as a variant, the bonding layer 38 is removed and layer 28 of permanent adhesive is then applied directly on the layer forming a barrier to gases and molecular migrations 37.

The bonding layer 38 can also undergo an appropriate treatment. giving it barrier properties to gases and molecular migrations. This treatment is for example a vacuum deposition of aluminum oxide, of silica or metal oxide at different levels of purity.

In addition, the layer 38 can be made of a material forming barrier, of a different nature from that forming the layer 37. Thus the layer 38 can for example be made of polyester.

According to another embodiment, the welding film 26 comprises at at least two separate layers forming a barrier to gases and migration molecular, these two layers being separated from each other by a layer intermediate.

In such an alternative embodiment, the welding film comprises by example five layers consisting of two layers forming barriers which can be of the same or different nature and of equal or different thickness and consisting for example of EVOH, of an interposed intermediate layer between the two barrier layers, a welding layer forming the inner surface of the package and a bonding layer on which is applied the layer of permanent adhesive.

The welding film 26 comprising at least two barrier layers is advantageously obtained by coextrusion.

As shown in FIG. 2, during a traction exerted on the cover 14 for opening the packaging by lifting the cover, the welding film 26 breaks on either side of the welded zone. In particular, the welding layer 26, the barrier layer 37 and the layer of link 38 break.

Thus, the cover 14 is separated from the tray 12, following at least part of the length of the rim 22. It forms a welded bead denoted 40.

Under the action of traction, the layer of permanent adhesive 28 breaks in its intermediate part or delaminates at its interface with the film 24 or film 26.

For example, part, denoted 42, of the layer of permanent adhesive remains on the welded bead 40, while the complementary part, noted 44, remains on the support film 24. The two complementary parts 42, 44 each have a thickness substantially equal to half the thickness total of layer 28.

Thus, when replacing the cover 14, the two parts of the adhesive layer 28 are brought back into contact ensuring the reclosing of packaging.

It can be seen that with a packaging sheet as described here and comprising a layer forming a barrier to gases and to molecular migrations interposed between the layer of permanent adhesive and a sealant layer suitable for sealing with the complementary part of the packaging, the foodstuffs contained in the packaging do not have their degraded taste and / or olfactory properties.

In the example described above, the cover is obtained by association of films extruded separately, these being linked to each other in particular by collage. As a variant, the cover is formed by coextrusion of the different films, the layers constituting the welding film then being coextruded simultaneously with the other films of the cover.

In a variant not shown, the laminated sheet has a layer permanent adhesive only in areas to be welded on the edge of the tray. In this case, the support film and the weldable film are linked to each other by a layer of glue of any suitable type.

The sheet according to the invention is described here applied to the obturation of a tray. However, it could be used to form a resealable bag. In the latter case, the permanent adhesive can also be placed only in the sealing areas of the bag.

Furthermore, it can be seen that the presence of a barrier layer integrated into the weldable film also provides a solution to the problem the ineffectiveness of a possible barrier layer when it is arranged, as is the case in the prior art, on the side of the film base relative to the layer of permanent adhesive.

Indeed, it is known, in order to avoid the circulation of gases, and in particular oxygen and / or carbon dioxide between the interior and exterior of packaging, have the same side of the permanent adhesive as the film base, a layer forming a barrier to gases and molecular migrations.

It can be seen that due to the welding of the weldable film, the cover is found mechanically held at its periphery along one of its faces. On the contrary, the other side of the film is left free, we see the risk delamination phenomenon at one or other of the interfaces of the permanent adhesive layer with the base film or the weldable film. This phenomenon is known as "tunnel effect" or "chimney effect". Air can then circulate through delaminated areas and thus gas exchanges can take place through the welding layer.

When the layer forming a barrier to gases and molecular migrations is arranged on the inner side of the package relative to the layer permanent adhesive, even if this layer is delaminated, the layer forming barrier to gases and molecular migrations remains maintained over the entire surface of the packaging opening since this layer forming a barrier to gases and molecular migrations is integrated in the welding film.

Thus, even if outside air is introduced into possible regions delaminated from the permanent adhesive layer, that a gas exchange does not may occur between the inside of the package and this region, due to the presence of the layer forming a barrier to gases and to molecular migrations.

Furthermore, excellent results are observed when the layer forming barrier to gases and molecular migration is formed of polyester or copolyester. These are advantageously formed from copolyester amorphous.

Advantageously, the amorphous copolyester used is of the PETG type or PCTG.

The amorphous copolyester of the PETG type is an amorphous polyester obtained from terephatalic acid and a pre-eminent mixture of ethylene glycol with, in a lesser amount by mole of 1,4-cyclohexanedimethanol.

PCTG type amorphous polyester is an amorphous polyester obtained from terephthalic acid and a pre-eminent mixture of 1,4-cyclohexanedimethanol with, in a lesser amount by mole of ethylene glycol.

With packaging sheets in which the barrier layer to gases and molecular migrations is formed from copolyester amorphous of the PETG or PCTG type, the welding layer and the layer forming barrier to gases and molecular migrations are advantageously a one and the same layer.

Claims (23)

Flexible laminated packaging sheet (14) and reclosable, of the type comprising a support film (24) associated with a sealing film (26) between which is interposed, at least in marked areas, a layer (28) of an adhesive permanent bonded to the support film (24) and to the welding film (26), characterized in that the welding film (26) comprises a welding layer (36) and at least one layer forming a barrier to gases and to molecular migrations (37), and in that the or each layer forming a barrier to gases and to molecular migrations (37) comprises at least one compound chosen from the group consisting of a copolymer of ethylene and of vinyl alcohol, polyvinylidene chloride, polyvinyl alcohol , silica, aluminum oxide, polyester and copolyester. Packaging sheet according to claim 1, characterized in that the material forming a barrier to molecular migrations (37) comprises at least one compound chosen from the group consisting of polyvinylidene chloride, aluminum oxide, polyester and copolyester. Packaging sheet according to claim 2, characterized in that the copolyester is an amorphous polyester. Packaging sheet according to claim 2, characterized in that the polyester is polyethylene terephthalate. Packaging sheet according to claim 3, characterized in that the amorphous copolyester is a polyester obtained from terephthalic acid and a mixture of ethylene glycol and 1,4-cyclohexanedimethanol, the mole amount of ethylene glycol being greater than the amount by mole of 1,4-cyclo-hexanedimethanol. Packaging sheet according to claim 3, characterized in that the amorphous polyester is a polyester obtained from terephthalic acid and a mixture of 1,4-cyclohexanedimethanol and ethylene glycol, the quantity in moles of 1, 4-cyclohexanedimethanol being greater than the amount by mole of ethylene glycol. Packaging sheet according to any one of the preceding claims, characterized in that the sealing layer and the layer forming a barrier to gases and to molecular migrations are different. Packaging sheet according to claim 5 or 6, characterized in that the sealing layer and the layer forming a barrier to gases and to molecular migrations are one and the same layer. Packaging sheet according to claim 2, characterized in that the sealing layer and the layer forming a barrier to gases and to molecular migrations are a single layer of polyester. Packaging sheet according to any one of the preceding claims, characterized in that the total thickness of the sheet is less than 150 µm. Packaging sheet according to any one of the preceding claims, characterized in that the or each layer (37) forming a barrier to gases and to molecular migrations comprising at least one compound chosen from the group consisting of a copolymer of ethylene and d vinyl alcohol, polyvinylidene chloride, polyethylene terephthalate and polyvinyl alcohol has a thickness of between 2 and 15 microns and preferably substantially equal to 3 microns. Packaging sheet according to any one of the preceding claims, characterized in that the sealing film (26) has a total thickness of between 20 and 60 microns and preferably substantially equal to 35 microns. Packaging sheet according to any one of the preceding claims, characterized in that the or each layer forming a barrier to gases and to molecular migrations (37) is arranged with respect to the welding layer (36) on the side of the layer of permanent adhesive (28). Packaging sheet according to claim 13, characterized in that said sealing film (26) further comprises a bonding layer (38) disposed on the side of the layer of permanent adhesive (28), the layer forming a gas barrier and to molecular migrations (37) being disposed between the weldable layer (36) and the bonding layer (38). Packaging sheet according to claim 14, characterized in that the bonding layer (38) and the sealing layer (36) are made of polyethylene. Packaging sheet according to claim 15, characterized in that the layer forming a barrier to gases and to molecular migrations comprises a copolymer of ethylene and polyvinyl alcohol. Packaging sheet according to claim 15 or 16, characterized in that the melt index of the polymer forming the bonding layer (38) and the welded layer (36) is between 1.5 and 4.5. Packaging sheet according to claim 17, characterized in that the melt index of the polymer forming the bonding layer (38) and the sealing layer (36) is between 3 and 4. Packaging sheet according to any one of claims 15 to 18, characterized in that the density of the polymer forming the bonding layer (38) and the sealing layer (36) is between 0.920 and 0.940. Packaging sheet according to claim 19, characterized in that the density of the polymer forming the bonding layer (38) and the welding layer (36) is between 0.930 and 0.936. Packaging sheet according to any one of the preceding claims, characterized in that it is obtained by coextrusion. Packaging sheet according to any one of the preceding claims, characterized in that the sealing film (26) is obtained by co-extrusion. Packaging (10), in particular sachet or tray, comprising an external wall (16) delimiting a housing (20) provided with an access passage (15) to said housing, characterized in that said passage (15) is closed by a laminate sheet (14) according to any one of the preceding claims, which sheet is welded to said outer wall (16) at the periphery of said passage (15), following its weldable film (26) in an area of the sheet which is provided permanent adhesive (28).

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