ES2267693T3 - USE OF A STRATIFIED PACKING 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

Use of a packing sheet stratified

The present invention relates to the use of a stratified packing sheet.

Packaging comprising a sheet of packaging that allows easy opening and closing once opened, they are currently used for example to condition the products food The structure of such a sheet is described. especially in the French patent application FR-95 14117.

In this document, the stratified sheet used to allow the opening of the packaging and the closing of the once opened, it consists of two polymer films between which is interposed a layer of a permanent adhesive.

One of the movies, the so-called "movie sealant "is intended to be oriented inside the packaging. It adapts to be sealed on the peripheral flange of a plate. The other movie, called "support movie", is intended to form the outer face of the packaging. The movie sealant consists of a single layer of the same polymer or of A mixture of polymers.

It is checked that when a packaging is used of this type for the conditioning of food products, the Taste and smell of these foods can be altered. In In particular, the smell and taste of the products can be unpleasant for the user, perceiving that the food preserved in the packaging have the smell or taste altered.

The document FR-A-2,669,607 describes a package comprising a packaging sheet comprising a layer of permanent adhesive and a sealant film. Sealant film It comprises a layer of aluminum, thermo-moldable lacquer or material thin plastic to prevent the material contained in the packaging contact the permanent adhesive layer.

The object of the invention is to provide a solution to the taste and olfactory degradation of food preserved in packages that use at least one packing sheet which allows them to close again once opened.

For this purpose, the invention aims at use according to claim 1.

According to particular embodiments, the use consists of one or more of the characteristics of the dependent claims.

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

Figure 1 is a partial perspective and sectional view of a packing tray  in which the access is sealed by a stratified sheet according to the invention, and

Figure 2 is a view analogous to that of figure 1, after the opening of the packaging.

The packaging 10 depicted on figure 1 It consists of a rectangular rigid tray 12 and an operculum flexible 14 for sealing an access 15 to the interior of the tray. The operculum 14 can be closed again once open.

The total thickness of the operculum is usually less than 150 µm to obtain the desired flexibility.

Tray 12 consists of a layer support 16 of suitable material, for example poly (chloride of vinyl) or amorphous polyester (APET, CPET), coated on its surface inside of a sealable film 18, for example of polyethylene.

The tray defines a receptacle 20 bordered on its entire perimeter of a flange 22 that delimits a flat surface of sealing the flexible operculum 14 following a rectilinear seal 2. 3.

The operculum 14 consists essentially of a support film 24 and a multilayer sealant film 26 with a layer of permanent adhesive 28 interposed in a plane between They over the entire surface. In a variant, the adhesive permanent 28 may be arranged only in the designated areas of the operculum, these areas being destined to form the regions sealing of the operculum.

A transparent film 30 that bears the impressions 32 is attached on the support film 24 by intermediate a layer of glue 34 applied on its face printed.

In a variant, prints 32 are made on film 30 and / or 24 on the face and / or on the back.

The multilayer sealant film 26 consists of a sealing layer 36 adapted to form the inner surface of the packaging. It is intended to be sealed by heat sealing on the sealable film 18 of tray 12. According to the invention, the sealing film 26 also comprises at least one layer 37 that It forms a barrier for gases and molecular migrations. This layer 37 is appropriate to block the movement of the molecules of Small size or oligomer.

In the example given, the sealing film 26 It consists of a single layer that forms a barrier.

In a variant, prints 32 are made on film 30 and / or 24 on the face and / or on the back.

Advantageously, the sealing film 26 it consists of a bonding layer 38 arranged for contact with the permanent adhesive layer 28. Thus, the layer that forms a barrier for migrations and for gases it is interposed between the layer sealant 36 and tie layer 38.

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

The longitudinal seal 23 is obtained by heat seal. After sealing, the sealing film 18 and the layer sealant 36 melts together, allowing to obtain after Cooling a very reliable seal. In particular, resistance to the tensile of the seal 23 is superior to the breaking strength of the sealing film 26, to the tensile strength of the interfaces between the permanent adhesive layer and the films in contact 24 and 26, as well as the tensile strength of the heart of the adhesive layer 28.

As an example, the different layers and operculum 14 films have the following characteristics.

The support film 24 is a film of 36 micron thick polyester.

The permanent adhesive layer 28 is made by Enduction with the help of a liquid or solid adhesive mass.

The permanent adhesive layer can be applied also hot, mainly by extrusion.

A permanent adhesive normally designated with the name "hot melt" is perfectly suited to this application. It is especially possible to use PLASTOFLEX 8718 marketed by PARAMELT in the Netherlands.

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

The transparent film 30 is for example a polyester film with a thickness of 12 microns. This movie may have particular functional characteristics, especially tightness characteristics against certain gases For this purpose, it is treated following known techniques adapted, such as enduction.

The tail used to ensure the union between the film 30 and the support film 24 is of all kinds, adapted in function of the nature of the movies to join.

The following characteristics are related to the sealing film 26. Of course it can be used, with a layer 28 of permanent adhesive of any nature as well as with a support film 24 of an appropriate nature, being optional layers 30 and 32.

Preferably, the layer that forms a barrier 37 contains a copolymer resin of ethylene and vinyl alcohol (EVOH) while the two layers 36 and 38 among which is interposed, they are layers of polyethylene that can be attached to the EVOH layer by a compatibilization bonding layer.

Preferably, the sealing film 26 is obtained by co-extrusion of the EVOH layer together with the extrusion of the two polymer layers between which it is included

The ethylene vinyl alcohol copolymer is for example, the one sold under the reference EVAL LCH 101BD by KURA-RAY society, being ethylene content of 38%.

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

In a variant, the layer or layers that form a barrier for gases and for molecular migrations are formed for example of PVDC [polyvinylidene chloride], PETP [poly (ethylene terephthalate)], PVOH [polyvinyl alcohol], SIOX (silicon oxide) or Al 2 O 3 (aluminum oxide).

The total thickness of the sealing film 26, constituted by the three aforementioned layers, it is comprised between 20 and 60 microns and is preferably approximately equal to 35 microns

The thicknesses of the sealing layer 36 and the tie layer 38 are preferably approximately equal, each of them being between 10 and 20 microns, and with Preference approximately equal to 15 microns. These layers are preferably made with the same polymer and especially with polyethylene.

Preferably, the polyethylene used for forming layers 36 and 38 has an index of fluidity comprised between 1.5 and 4.5 g / 10 minutes. Advantageously, this index is between 3 and 4 g / 10 minutes and is preferably approximately equal to 3.5 g / 10 minutes. The flow rate is Calculates following the ASTM D1238 standard.

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

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

In the embodiment represented in the figures, the sealing film 26 consists of three layers. But nevertheless, in a variant, the bonding layer 38, has been deleted and the layer 28 of permanent adhesive is then applied directly on the layer that forms a barrier for gases and for migrations molecular 37.

The tie layer 38 can also suffer a appropriate treatment that confers barrier properties to gases and for molecular migrations. This treatment is for example a tank under vacuum of aluminum oxide, oxide of silicon or a metal with different levels of purity.

In addition, layer 38 may be made in a material that forms a barrier, of a different nature to the one that forms layer 37. Thus layer 38 can be made for example in polyester.

According to another embodiment, the film sealant 26 consists of at least two distinct layers that form a barrier for gases and molecular migrations, being these two layers separated from each other by an intermediate layer.

In another variant embodiment, the film sealant consists for example of five layers consisting of two layers that form barriers that can be of the same nature or different and with an equal or different thickness and that may be constituted for example of EVOH, of an interposed intermediate layer between the two layers that form barriers, of a sealant layer that forms the inner surface of the packaging and a bonding layer over which the permanent adhesive layer is applied.

The sealing film 26 consisting of at least two layers that form a barrier are advantageously obtained by coextrusion

As depicted on figure 2, when exerts traction on operculum 14 to open the operculum lifting packing, sealing film 26 is breaks from one and another part of the sealed area. In particular, it they break the sealing layer 26, the layer that forms a barrier 37 and the tie layer 38.

Thus, operculum 14 separates from tray 12, following at least a part of the length of the flange 22. This form a sealed cord marked 40.

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

For example, a part, marked as 42, of the permanent adhesive layer subsists on sealed bead 40, while the complementary part, marked 44, remains on the support film 24. The two complementary parts 42, 44 each have a thickness approximately equal to half of the total thickness of layer 28.

Thus, when opercle 14 is replaced, the two parts of the adhesive layer 28 are put back into contact ensuring the closure of the packaging once opened.

Check that with such a packing sheet as described here and consisting of a layer that forms a barrier for gases and for molecular migrations interposed between the permanent adhesive layer and an appropriate sealant layer for ensure the sealing with the complementary part of the packaging, the food products contained in the packaging do not have degraded taste and / or olfactory properties.

In the example described here before, you get the operculum by association of extruded films separately, being these united with each other especially by gluing. In a variant, the operculum is formed by coextrusion of the different films, then the layers constituting the sealant film simultaneously with the other films of the opercle

In a variant not shown, the sheet Layered consists of a layer of permanent adhesive only in the regions intended to be sealed on the edge of the tray. In this case, the support film and the sealable film they are joined to each other by a layer of glue of all kinds adapted

The sheet according to the invention is described here. adapted for the shutter of a tray. However, it could be used to form an envelope that can be resealed once open. In the latter case, the permanent adhesive may be also arranged only in the sealing areas of the on.

On the other hand, it is verified that the presence of a layer that forms a barrier incorporated in the sealable film it also provides a solution to the problem of inefficiency of a eventual layer that forms a barrier when said layer is arranged, as is the case in the most advanced technique, on the side of the base film with respect to the adhesive layer permanent.

Indeed, it is known, in order to avoid the circulation of gases, and especially oxygen and / or dioxide carbon between the inside and outside of the packaging, dispose of same side of the permanent adhesive as the base film, of a layer that forms a barrier for gases and for migrations molecular.

It is verified that by the fact of sealing the sealable film, the operculum is mechanically maintained in its periphery according to one of its faces. On the contrary, the other side of the film is left free, and thus the risk of a phenomenon is checked of delamination on one or another of the contact surfaces of the permanent adhesive layer with the base film or with the sealable film. This phenomenon is known under the name of "tunnel effect" or "chimney effect". The air can circulate then through the delaminated areas and so changes can take place gaseous through the sealant layer.

When the layer that forms a barrier for gases and for molecular migrations is arranged on the side inside of the packaging with respect to the permanent adhesive layer, even in the case of delamination of this layer, the layer that forms a barrier for gases and for molecular migrations is keeps over the entire surface of the opening of the packaging since this layer that forms a barrier for gases and for molecular migrations is incorporated into the film sealant

Thus, even if outside air is introduced into the possible delaminated regions of the adhesive layer permanent, a gaseous change between interior cannot occur of the packaging and this region, due to the fact of the presence of the layer that forms a barrier for gases and for migrations molecular.

On the other hand, they prove excellent results when the layer that forms a barrier to gases and for molecular migrations it is formed of polyester or of copolyester. These are advantageously formed of copolyester amorphous.

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

The amorphous PETG copolyester is a amorphous polyester obtained from terephthalic acid and from a mixture with ethylene glycol preeminence with a lower amount in moles of 1,4-cyclohexanedimethanol.

The amorphous polyester of the PCTG type is a polyester amorphous obtained from terephthalic acid and a mixture with preeminence of 1,4-cyclohexanedimethanol with a less moles of ethylene glycol.

With the packing sheets in which the layer that forms a barrier for gases and molecular migrations It is formed of amorphous copolyester of the PETG or PCTG type, the layer sealant and the layer that forms a barrier for gases and for Molecular migrations are advantageously a single layer.

Claims (22)

1. The use in a packing sheet stratified (14) and that can be closed again once opened, comprising a support film (24) associated with a film sealant (26) between which it is interposed, at least in the designated areas, a layer (28) of a permanent adhesive attached to the support film (24) and the sealant film (26), of at least one layer that forms a barrier to molecular migrations (37) incorporated in the sealing film (26) to prevent degradation of the taste and / or olfactory properties of the products food packaged with this wrapper, which results from a delamination phenomenon on one or another of the surfaces of contact of the permanent adhesive layer (28) with the film support (24) or with the sealant film (26), containing the layer or each of the layers that form a barrier for gases and for molecular migrations (37), at least one compound chosen from group consisting of a copolymer of ethylene and vinyl alcohol, poly (vinylidene chloride), poly (vinyl alcohol), silicon oxide, aluminum oxide, polyester and copolyester. 2. The use according to claim 1, characterized in that the material that forms a barrier for molecular migrations (37) contains at least one compound selected from the group consisting of polyvinylidene chloride, aluminum oxide, polyester and copolyester. 3. The use according to claim 2, characterized in that the polyester is an amorphous polyester. 4. The use according to claim 2, characterized in that the polyester is poly (ethylene terephthalate). 5. The use 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 mole amount of 1,4-cyclohexanedimethanol. 6. The use according to claim 3, characterized in that said amorphous polyester is a polyester obtained from terephthalic acid and a mixture of 1,4-cyclohexanedimethanol and ethylene glycol, the mole amount of 1,4-cyclohexanedimethanol being greater than Mole amount of ethylene glycol. 7. The use according to any one of the preceding claims, characterized in that the sealing layer and the layer that forms a barrier for gases and for molecular migrations are different. 8. The use according to claim 5 to 6, characterized in that the sealing layer and the layer that forms a barrier for gases and for molecular migrations are a single layer. 9. The use according to claim 2, characterized in that the sealing layer and the layer that forms a barrier for gases and for molecular migrations are a single layer of polyester. 10. The use according to any one of the preceding claims, characterized in that the total thickness of the sheet is less than 150 µm. The use according to any one of the preceding claims, characterized in that the layer or each of the layers (37) that form a barrier for gases and for molecular migrations containing at least one compound chosen from the group consisting of a copolymer of ethylene and vinyl alcohol, poly (vinylidene chloride), poly (ethylene terephthalate) and poly (vinyl alcohol) have a thickness between 2 and 15 microns and preferably approximately equal to 3 microns. The use according to any one of the preceding claims, characterized in that the sealing film (26) has a total thickness between 20 and 60 microns and preferably approximately equal to 35 microns. 13. The use according to any one of the preceding claims, characterized in that the layer or each of the layers forming a barrier for gases and for molecular migrations (37) are arranged with respect to the sealing layer (36) on the side of the permanent adhesive layer (28). 14. The use according to claim 13, characterized in that said sealing film (26) further comprises a bonding layer (38) disposed on the side of the permanent adhesive layer (28), the layer forming a barrier for the gases and for molecular migrations (37) between the sealing layer (36) and the bonding layer (38). 15. The use according to claim 14, characterized in that the bonding layer (38) and the sealing layer (36) are made of polyethylene. 16. The use according to claim 15, characterized in that the layer that forms a barrier for gases and for molecular migrations contains a copolymer of ethylene and polyvinyl alcohol. 17. The use according to claim 15 or 16, characterized in that the melt flow index of the polymer forming the bonding layer (38) and the sealing layer (36) is between 1.5 and 4.5. 18. The use according to claim 17, characterized in that the melt flow index of the polymer forming the bonding layer (38) and the sealing layer (36) is between 3 and 4. 19. The use according to any one of claims 15 to 18, characterized in that the density of the polymer forming the bonding layer (38) and the sealant layer (36) is between 0.920 and 0.940. 20. The use according to claim 19, characterized in that the density of the polymer forming the bonding layer (38) and the sealing layer (36) is between 0.930 and 0.936. 21. The use according to any one of the preceding claims, characterized in that it is obtained by coextrusion. 22. The use according to any one of the preceding claims, characterized in that the sealing film (26) is obtained by coextrusion.