EP1103488B1 - Film for reclosable package and package incorporating it - Google Patents

Abstract

Wrapping sheet (14,16) comprises an external primary layer (30), an internal layer (32) and a layer of permanent adhesive in between (34). A zone of the sheet (22) is heat-sealable. The main zone (36) of the sheet is gas-permeable apart from the zone around the seal, used to initiate the opening of the package. Independent claims are also included for the packages obtained with the wrapping sheet.

Description

The present invention relates to a laminated packaging sheet of the type having a primary layer associated with a weldable layer between which is interposed, in at least one marked zone, a layer of a permanent adhesive, said sheet having in a marked area where the permanent adhesive is present, a heat-sealing region allowing the sealing by thermal welding of the packaging and allowing a reclosing packaging after an initial opening.

Nowadays, many food products, including fresh products are marketed by being packed in sachets or in trays made essentially based on polymers.

In order to allow satisfactory preservation of these foods, is advantageous that the polymer sheets, simple or complex incoming in the composition of the package, undergo a treatment which makes it possible make them permeable to gases. In particular, these treatments allow control of the atmosphere inside the packaging, particularly in regulating the permeation of the gases generated by the packaged product inverse gases from the outside atmosphere through the sheet thus treated. The sheet then forms a permeable membrane. Permeability conferred the leaf usually relates to oxygen, carbon dioxide and the water vapour.

Several mechanical treatments of the leaves are known allowing to create such a permeability to gases. For example, these sheets can be perforated or micro-perforated.

Moreover, it is currently desired that the packaging made by heat sealing, be it sachets or trays, can be closed to allow only a fraction of the packaged product in the package is consumed, the remaining fraction that can be stored for later consumption.

In particular, in order to allow such a reclosing, it is known to use a shutter sheet with two layers of polymer between which is interposed a layer of a permanent adhesive. The leaf is welded on a support according to one of the layers to ensure sealing of the packaging. When opening the package, the welded layer is torn, thus revealing the permanent adhesive which allows a subsequent re-closing of the packaging.

However, it can be seen that the treatments making it possible to permeable sheet can not be applied to a sheet a resealable opening of the bag. Indeed, in this case, when opening, and especially the rupture of the welded layer, the polymer sheet tends to tear, making it impossible to reclose later of the packaging.

DE-76 17 442 U discloses a sachet formed of a packaging sheet folded on itself. The packing sheet has perforations only in its middle part and the opposite lateral margins of the sheet to be welded are devoid of perforations.

FR-A-2.741.605 discloses a laminated packaging sheet comprising a primary layer associated with a weldable layer between which is interposed a layer of a permanent adhesive. This packing sheet, which corresponds to the preamble of claim 1, is adapted to ensure the reclosing of a package after an initial opening.

The invention aims to provide a packaging sheet and packaging the package allowing both packages to be opened and closed several times and allowing the flow of gas between the interior and the outside of the package.

For this purpose, the subject of the invention is a packaging sheet, according to claim 1.

Particular embodiments, are defined in the dependent claims.

The invention further relates to a package according to claim 4.

Finally, the invention relates to a packaging bag according to claim 5.

• les figures 1 et 2 sont des vues en élévation respectivement de face et de côté d'un sachet d'emballage selon l'invention ;
• la figure 3 est une vue de détail en section de la région d'obturation soudée du sachet de la figure 1 ;
• la figure 4 est une vue en section analogue à celle de la figure 3, prise après une ouverture initiale du sachet ;
• la figure 5 est une vue en section analogue à celle des figures 3 et 4 après refermeture du sachet ;
• la figure 6 est une vue en perspective d'une barquette d'emballage dont le passage d'accès est obturé par une feuille stratifiée selon l'invention ;
• les figures 7 et 8 sont des vues partielles en section de la barquette de la figure 6 prise suivant la ligne VII-VII respectivement avant et après ouverture ; et
• la figure 9 est une vue en perspective d'une variante de réalisation d'une barquette selon l'invention.

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

• Figures 1 and 2 are elevational views respectively front and side of a packaging bag according to the invention;
• Figure 3 is a detailed sectional view of the welded closing region of the bag of Figure 1;
• Figure 4 is a sectional view similar to that of Figure 3, taken after an initial opening of the bag;
• Figure 5 is a sectional view similar to that of Figures 3 and 4 after reclosing the bag;
• Figure 6 is a perspective view of a packaging tray whose access passage is closed by a laminate sheet according to the invention;
• Figures 7 and 8 are partial sectional views of the tray of Figure 6 taken along the line VII-VII respectively before and after opening; and
• Figure 9 is a perspective view of an alternative embodiment of a tray according to the invention.

The package 10 shown in FIGS. 1 and 2 is a bag intended to packaging fresh products such as vegetables or fruits. The bag is formed of two rectangular main soft sheets 14, 16 disposed opposite and a bottom 18 consisting of a third flexible sheet.

The two main flexible sheets 14, 16 are connected to each other by thermo-welding along two longitudinal edges 20A and 20B. The edge lower leaves 14, 16 is bonded by a weld to the edge of the sheet 18 forming background.

Next to their upper edge, the two sheets 14, 16 are linked to each other. the other an upper weld 22 arranged transversely of a longitudinal edge to the other. This weld forms a means of opening and closing of the packaging. It is arranged at a distance from the upper edge sheets 14 and 16, thus forming, beyond the weld 22, two ranges free grip 14A, 16A.

The three sheets 14, 16, 18 define between them an enclosure 24 in which the packaged products are contained.

As shown in FIG. 3, the leaves 14 and 16 constituting the main faces of the bag 10 have a laminated structure. These two leaves have for example the same structure.

Each has a primary layer 30 facing outward and a sealing layer 32 turned towards the inside of the bag. Between the layer 30 and the solder layer 32 is disposed a layer 34 of a permanent adhesive.

The longitudinal weld 22, made between the two faces opposite soldering layers 32, is a flesh-flesh type welding. The two welding layers 32 are welded together by heat sealing.

According to the invention, each of the sheets 14 and 16 constituting the faces of the present packaging, outside the formed opening region by the upper weld 22, a treatment ensuring permeability to gases.

Thus, apart from the weld 22, each sheet 14, 16 presents, in a predetermined region 36 extending over most of its surface a treatment making the sheet permeable to gases. This treated area 36 is represented by a grid of dots in the figures.

The upper boundary 37 of region 36 is separated from the weld 22 by a strip 38 left without treatment.

The weld 22 and the border 37 extend substantially in parallel to each other and are separated by a distance of between 4 mm and 2 cm and preferably greater than 7 mm.

The treated regions 36 extend over the entire width of the leaves 14 and 16 from one longitudinal edge 20A to the other 20B. They extend from the border 37 to the welding area with the bottom 18.

Alternatively, these regions are limited to windows located in the part of leaves 14 and 16. In this case, to carry out the treatment on the windows in question, it is necessary to print spots on the sheet for tracking.

The treatment rendering permeable to gases consists, for example, in the perforations distributed over the surface of the regions 36.

The perforations are made for example by means of an installation mechanical system comprising two cylinders rotating about parallel axes, these cylinders being in contact along a line of tangency. One of the cylinders is equipped on its surface with a perforation matrix made in general made of metal. The other cylinder forming a bearing surface is generally realized in a plastic material. The matrix of perforations penetrates the surface the cylinder next to the line of tangency. The film intended for forming the sheets 14 and 16 of the bags circulates between the two cylinders and thus found perforated with a set of holes by removal of material.

As a variant of this perforation technique known as rotary perforation, it is also possible to use one or other of the two processes known under the designation of flame perforation and hot tip perforation.

The level of gas permeability is adjusted by varying the density perforation organs, their size and applied pressure between the two cylinders.

In order to make perforations only in the regions 36 and to keep hole-free band 38, the perforation matrix has a profile adapted and includes in particular beaches without perforating organs. The beaches provided with perforating members form strips following the entire periphery of the cylinder carrying the matrix, or extend according to marked regions extending along generatrices of the cylinder.

In a variant, the perforations are replaced by micro-perforations, formed without removal of material and forming incisions in the material of the sheets 14 and 16. These micro-perforations are obtained by passing each sheet between adjacent rolls, one of which has blades or micro-knives that may incise the next sheet all its thickness.

According to a third variant, the gas permeability is obtained by performing micro-perforations using a discontinuous laser beam. As the film circulates continuously, a laser beam modifies the structure locally of the material, thus creating micro-holes of defined diameter and in particular between 100 and 200 μm. The level of permeability is adjusted by modifying the diameter of the micro-holes and their density.

According to a fourth variant, a treatment rendering porous the sheet is applied, conferring on it a porosity.

This porosity is obtained thanks to two adjacent cylinders between which circulates the sheet, one of the cylinders being covered with a rough deposit, creating a weakening of the leaf. The level of permeability can to be adjusted essentially by varying the pressure between the rolls of job.

According to a fifth variant, the gas permeability is obtained by permeable treatment as described in European patents No. 351,115 B1 and No. 351,116B1.

To proceed with the opening of the sachet, the operator enters in each hand an extension of the leaves 14 and 16 constituting the gripping ranges 14A, 16A located beyond the weld 22. It then spreads the pieces opposite of the bag to cause the opening of the bag. When traction of the two gripping surfaces in opposite directions, constraints are applied to the weld 22.

Under the action of these constraints, the welding layer 32 tears on both sides of the weld 22.

Thus, as illustrated in FIG. 4, the two sheets 14, 16 of the bag are then separated, one still having on the inner side a welded strip 46 resulting from the welding layer 32 and the other sheet having a groove 48 corresponding to the imprint of the band 46.

The adhesive of the layer 34 remains attached to the layer 30 at the bottom of the bleed 48 and / or remains carried by the welded strip 46 to form thereon a tacky coating 50, as shown in FIG.

It is conceivable, as illustrated in Figure 5, that the approximation of two sheets and the repositioning of the welded strip 46 in the bleeding 48 allows the reclosing of the packaging, by action of the permanent adhesive the coating 50 against the bottom 52 left clean of the kerf.

When opening, the opening region of the packaging, formed by the welding 22, opens without risk of complete tearing of one of the sheets 14, 16, since the weld 22 is disposed away from the rendered region 36 permeable to gases.

Indeed, the lack of treatment conferring gas permeability in the region of the weld 22 avoids creating tear primers leaves in this highly stressed area when opening, which spreads any risk of degradation of the leaves during the breaking of the welding layer 32.

The package 100, shown in FIG. 6, consists of a container circular 112 and a flexible cover 114 shutter a passage 116 access inside the tray.

The tray 112 consists of an outer support layer in suitable material, for example polyvinyl chloride, coated on its inner surface of a weldable layer, for example, polyethylene.

The tray defines a receptacle 118 bordered on all its periphery a flange 120 delimiting a flat surface for welding the lid 114, following a circular weld 122.

The operculum 114 is laminated, that is to say made of several layers superimposed. For reasons of clarity, the thickness of the layers is exaggerated increased in the figures.

As shown in FIG. 7, the operculum 114 consists essentially of a support layer 124 and a weldable layer 126 with a layer of permanent adhesive 128 interposed in flat between them over the entire area.

The support layer 124 advantageously comprises impressions on its outer face. It can also include a transparent layer carrying such laminated impressions on the outer surface of the diaper support through a layer of glue applied on its face printed.

The support layer 124 is, for example, a polyethylene layer terephthalate 36 μm thick.

The permanent adhesive layer 128 is made by coating using an adhesive mass initially in solution, especially in dispersion aqueous. It can also be applied hot, in particular by extrusion.

A permanent adhesive, commonly referred to as "hot melt "is particularly suitable for this application. to use Plastoflex 87.18 sold by the company Paramelt to Netherlands.

The thickness of the adhesive layer 128 is advantageously included between 10 and 30 microns and is in particular equal to about 20 microns.

The weldable layer 126 is for example a polyethylene layer or polypropylene whose thickness is between 20 and 60 μm, and is in particular advantageously equal to 40 μm. This layer is realized in a material allowing welding with the layer facing the tray 112.

As shown in FIG. 6, the peripheral weld seam 122 extends around the entire edge of the tray. It ensures the sealing shutter of the tray. For the sake of clarity, the peripheral weld 122 was marked with a frame on this figure.

The operculum 114 has in its region closing the passage 116 a region 130 disc-shaped made permeable to gases. This region 130 extends away from the weld 122. Advantageously, the distance between the 122 and the region 120 made permeable to gas is greater than 5 mm and for example equal to 7 mm.

The peripheral weld 122 is obtained by heat sealing. then welding, the weldable layer of the tray and the weldable layer 126 of the packing sheet melt together, allowing to obtain, after cooling, a very reliable welding.

As illustrated in FIG. 8, when the packaging is opened by traction on the edge of the lid 114 located in the vicinity of the welded region 122, the sealable layer 126 breaks.

Only a residual band 140 issuing from the weldable layer 126 remains present on the edge 120. It forms a welded bead. Conversely, a groove 142 is formed in the weldable layer 126 of the lid. The bottom of this bleeding is formed by the permanent adhesive layer 128.

As known per se, the presence of the permanent adhesive on the surface facing the support layer 124 and possibly on the cord welded 140 allows the subsequent closure of the packaging by refitting of the operculum 114.

In this embodiment also, the limitation of the treatment making the opening region of the package opening gas permeable prevents this treatment from promoting complete tearing of the lid when the application of the constraints necessary to break its weldable layer.

For the manufacture of such a package, the sealing sheet is issued a band in which is formed a succession of shutter sheets successive. These leaves are delimited between them by a visual cue 150 disposed in a corner of each sheet. This marker allows positioning correct of each leaf on a tray.

When processing the tape, the treatment makes the leaves locally permeable to gases is realized in regions positioned by report to successive benchmarks 150.

FIG. 9 shows again a variant embodiment of the package according to the invention.

This package 200 consists of a tray 202 closed by a opercule 204 made from a sheet according to the invention. The operculum 204 is formed of three layers of the same nature as in the embodiment Figures 6 to 8.

The tray 202 has a cylindrical housing 206 having in section the shape of a disk sector. This one is intended to receive, by example, a portion of cheese.

The opening of the housing 206 is surrounded by a rim 208 comprising two secant main edges 210, 212, extending parallel to the rectilinear edge of the disk sector forming the housing 206. A trailing edge 214 rectilinear extends perpendicular to the bisector of the angle delimited by the edges 210 and 212.

Finally, the connection between the edges 210, 212 and the rear edge 214 is ensured by parallel straight sections 216, 218 extending laterally. These edges define opening regions of the packaging noted 220, 222. These regions extend in the corners defined between the main edges 210, 212, and the trailing edge 214.

These opening regions are marked for the user by a marking adapted inviting the user to initiate the opening of the packaging in this region.

As in the previous embodiment, the operculum 204 is welded along a peripheral weld 224 around the rim 208.

The operculum 204 has, in its median part defined between the rectilinear sections 216, 218, a region 226 made permeable to gases by alignments 228 of perforations carried out continuously using a beam laser, for example. These lines of perforations 228 extend in parallel at the bisector of the angle defined by the main edges 210, 212. The region 226 extends away from weld sections 230, 232, extending parallel to the edges 216, 218 in the opening regions 220, 222. The distance between these welding sections 230, 232 and the extreme lines of perforations 228 is for example equal to 7 mm.

The lines of perforations 228 extend over the sections of the peripheral weld 224 extending parallel to the main edges 210, 212 and at the rear edge 214.

It is conceivable that with such a package, the opening being initiated in one of the zones 220, 222, one of the welded sections 230, 232 is first released by breaking of the welding layer. This break is made without risk tearing of the film, since no treatment makes it permeable to gas is present in this region.

When continuing the opening of the packaging, the sections of welding extending along the edges 210, 212 and 214 are released. Although the treated area extends along these weld seams, the risk that the leaf is torn apart is extremely reduced, since the spread of the tearing of the welding layer takes place according to the length of these sections welded, so that only a very small force is needed for cause tearing of the weldable film. So, this weak force is not sufficient to initiate a complete tearing of the leaf despite treatments making the sheet gas permeable.

In this embodiment, the cap 204 is advantageously made from a reel film, in which the lines of perforations 222 are made according to the length of the film. This treatment is performed in continuous by scrolling the film on a suitable equipment.

Claims (5)

1. Laminated packaging film (14, 16; 204), of the type comprising a primary layer (30) associated with a weldable layer (32) between which there is interposed, in at least one marked zone, a layer (34) of a permanent adhesive, said film having in a marked zone where the permanent adhesive is present, a heat-sealing region (22; 224) allowing the sealing by thermal welding of the packaging and allowing reclosing of the package after an initial opening,
   characterised in that said film has in at least one marked region (36; 228) a treatment ensuring permeability to gases, the region or each region (36; 228) which is marked and treated extending outwith at least one portion of said heat-sealing region, the portion or each portion (22; 224) of the heat-sealing region devoid of treatment forming an initiation region (22; 230, 232) for opening the package; and in that the region or each region (36; 228) which is marked and treated extends over the heat-sealing region (20A, 20B) outwith the portion or each portion (22) forming an initiation region for opening the package.
2. Packaging film according to claim 1, characterised in that the region or each region (36; 228) which is marked and treated has one of the treatments chosen from the group comprising: perforations, micro-perforations, mechanical treatment making it porous and localised apertures produced by laser.
3. Packaging film according to claim 1 or 2, characterised in that the minimum distance between the boundary (37) of the region or each region (36; 228) which is marked and treated and the portion or each portion (22; 224) of the heat-sealing region devoid of treatment is greater than 7 mm.
4. Package comprising an external wall delimiting a housing provided with an access passage to said housing, characterised in that said passage is sealed by a laminated film according to any of the preceding claims, said film is welded thermally on said external wall at the periphery of the passage along its weldable layer in said heat-seating region, the welded portion or each welded portion of the heat-sealing region devoid of treatment forming an initiation region (230, 232) for opening the package.
5. Packaging bag comprising at least one wall delimited by a film according to any of the claims 1 to 3, characterised in that said film (14, 16) is welded thermally against another wall (16, 14) of the bag along its weldable layer (32) in said heat-sealing region (22), the welded portion or each welded portion (22) of the heat-sealing region devoid of treatment forming an initiation region for opening the package.

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