EP1103488A1 - 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 comprising a primary layer associated with a weldable layer between which is interposed, in at least one marked area, 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 heat sealing of the packaging and allowing reclosing packaging after initial opening.

Today, many food products, including fresh products are marketed by being packed in sachets or in trays made essentially from polymers.

In order to allow a satisfactory conservation of these foods, it is advantageous that the polymer sheets, simple or complex entering in the composition of the packaging, undergo a treatment allowing make them permeable to gases. In particular, these treatments allow control of the atmosphere inside the packaging, in particular by regulating the permeation of gases generated by the packaged product and in direction reverse gases from the outside atmosphere through the sheet thus treated. The sheet then forms a permeable membrane. The permeability conferred per sheet generally relates to oxygen, carbon dioxide and water vapour.

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

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

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

However, it can be seen that the treatments making it possible to render a gas permeable sheet cannot be applied to a sheet allowing a resealable opening of the bag. Indeed, in this case, when opening, and in particular from the rupture of the welded layer, the polymer sheet tends to tear, making subsequent reclosure impossible of the packaging.

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

To this end, the subject of the invention is a packaging sheet, of the type of cited above, characterized in that said sheet has at least one region identified, a treatment ensuring gas permeability, the or each treated spotted region extending outside at least part of said heat seal region, the or each part of the heat seal region devoid of treatment forming an initiation region of the opening of the packaging.

• la ou chaque région repérée traitée présente l'un des traitements choisis dans le groupe consistant en : des perforations, des micro perforations, un traitement mécanique rendant poreux, et des lumières localisées réalisées au laser ;
• la distance minimale entre la frontière de la ou chaque région repérée traitée et la ou chaque partie de la région de thermosoudage dépourvue de traitement est supérieure à 7 mm ;
• la ou chaque région repérée traitée s'étend sur la région de thermosoudage en dehors de la ou chaque partie formant une région d'initiation de l'ouverture de l'emballage ; et
• la ou chaque région repérée traitée s'étend uniquement en dehors de la région de thermosoudage.

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

• the or each region marked treated presents one of the treatments chosen from the group consisting of: perforations, micro-perforations, mechanical treatment making it porous, and localized lights produced by laser;
• the minimum distance between the border of the or each region marked treated and the or each part of the heat-sealed region without treatment is greater than 7 mm;
• the or each region marked treated extends over the heat-sealing region outside the or each part forming a region for initiating the opening of the package; and
• the or each region marked treated extends only outside the heat-sealing region.

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 according to any one of the preceding claims, which sheet is welded thermally on said outer wall at the periphery of the passage along its weldable layer in said heat-sealing region, the or each part welded from the heat-sealable region without treatment forming a initiation region of the opening of the package.

Finally, the invention relates to a packaging bag comprising at at least one wall delimited by a sheet as defined above, characterized in that said sheet is thermally welded against another wall the sachet according to its weldable layer in said heat-sealing region, the or each welded part of the heat-sealing region devoid of treatment forming an initiation region of the opening of the package

• 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 made with reference to the drawings in which:

• Figures 1 and 2 are elevational views respectively from the front and side of a packaging bag according to the invention;
• Figure 3 is a detail view in section of the welded closure 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 closing the bag;
• Figure 6 is a perspective view of a packaging tray whose access passage is closed by a laminated sheet according to the invention;
• Figures 7 and 8 are partial sectional views of the tray of Figure 6 taken along 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 packaging 10 represented in FIGS. 1 and 2 is a sachet intended the packaging of fresh products such as vegetables or fruit. The bag consists of two main rectangular flexible sheets 14, 16 arranged opposite and a bottom 18 consisting of a third flexible sheet.

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

According to their upper edge, the two sheets 14, 16 are linked one to the other an upper weld 22 arranged transversely of a longitudinal edge to the other. This weld forms a means of opening and reclosing of the packaging. This is provided at a distance from the upper edge sheets 14 and 16, thus forming, beyond the weld 22, two areas grip free 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 sheets 14 and 16 constituting the main faces of the bag 10 have a laminated structure. These two sheets have for example the same structure.

Each has a primary layer 30 facing outwards and a sealing layer 32 facing the inside of the bag. Between the layer primer 30 and the welding layer 32 is arranged a layer 34 of a permanent adhesive.

The longitudinal weld 22, produced between the two opposite faces welding layers 32, is a weld of the flesh against flesh type. The two welding layers 32 are welded against each other by heat sealing.

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

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

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

The weld 22 and the border 37 extend substantially 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 sheets 14 and 16 from one longitudinal edge 20A to the other 20B. They extend from the border 37 to the welding region with the bottom 18.

Alternatively, these regions are limited to windows located in the part of sheets 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 location.

The treatment making it permeable to gases consists for example of the making perforations distributed over the surface of the regions 36.

The perforations are made for example thanks to an installation mechanical comprising two cylinders rotating around 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 generally produced made of metal. The other cylinder forming a bearing surface is generally produced in a plastic material. The perforation matrix penetrates the surface of the cylinder opposite along the line of tangency. The film intended for form the sheets 14 and 16 of the bags circulates between the two cylinders and finds thus perforated with a set of holes by removal of material.

As a variant of this perforation technique called rotary perforation, one or the other of the two methods known under the designation of flame perforation and hot point perforation.

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

In order to make perforations only in regions 36 and keep strip 38 free of holes, the perforation matrix has a profile adapted and in particular includes areas without perforation members. The areas provided with perforating members form bands along the entire circumference of the cylinder carrying the matrix, or extend along marked regions extending along generatrices of the cylinder.

As a variant, the perforations are replaced by micro-perforations, formed without removing material and forming incisions in the material of sheets 14 and 16. These micro-perforations are obtained by passing each sheet between adjacent cylinders, one of which has blades or micro-knives capable of cutting the next sheet all its thickness.

According to a third variant, gas permeability is obtained by making micro-perforations using a discontinuous laser beam. The film circulating continuously, a laser beam locally modifies the structure 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 making the porous porous sheet is applied, giving it porosity.

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

According to a fifth variant, gas permeability is obtained by a treatment making permeable as described in European patents n ° 351.115 B1 and n ° 351.116B1.

To open the bag, the operator enters in each hand an extension of the sheets 14 and 16 constituting the gripping areas 14A, 16A located beyond the weld 22. It then spreads the sides opposite of the sachet in order to cause the opening of the sachet. When traction of the two gripping pads in opposite directions, constraints are applied to the weld 22.

Under the action of these constraints, the welding layer 32 tears on either side of the weld 22.

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

The adhesive of layer 34 remains attached to layer 30 at the bottom of the groove 48 and / or remains carried by the welded strip 46 to form thereon a sticky coating 50, as illustrated in FIG. 4.

It can be seen, as illustrated in FIG. 5, that the approximation of the two sheets and the replacement of the welded strip 46 in the groove 48 allows the packaging to be closed again, by the action of the permanent adhesive of the coating 50 against the bottom 52 left clean of the groove.

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

Indeed, the absence of treatment conferring gas permeability in the region of the weld 22 avoids creating tear primer leaves in this highly stressed region during opening, which eliminates any risk of deterioration of the sheets when the sealing layer ruptures 32.

The package 100, shown in Figure 6, consists of a tray circular 112 and a flexible cover 114 for closing a passage access 116 inside the tray.

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

The tray defines a receptacle 118 bordered around its entire periphery a rim 120 delimiting a planar welding surface of the cover 114, following a circular weld 122.

The cover 114 is laminated, that is to say made of several layers superimposed. For reasons of clarity, the thickness of the layers is excessively augmented in the figures.

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

The support layer 124 advantageously includes prints on its outer face. It can also include a transparent layer bearing such laminated prints on the outer surface of the diaper support by means of a layer of glue applied on its face printed.

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

The layer of permanent adhesive 128 is produced 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 ideal for this application. It is possible in particular to use Plastoflex 87.18 marketed by the company Paramelt in Netherlands.

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

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 made in a material allowing welding with the layer facing the tray 112.

As shown in Figure 6, the peripheral weld bead 122 extends over the entire periphery of the tray. It provides watertight sealing from the tray. For reasons of clarity, the peripheral weld 122 has been marked with a frame in this figure.

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

The peripheral weld 122 is obtained by heat sealing. When of welding, the weldable layer of the tray and the weldable layer 126 of the packaging sheet melt together, making it possible to obtain, after cooling, a very reliable weld.

As illustrated in Figure 8, when opening the packaging by traction on the edge of the cover 114 located in the vicinity of the welded region 122, the weldable layer 126 breaks.

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

As known per se, the presence of the permanent adhesive on the surface next to the support layer 124 and possibly on the bead welded 140 allows the later closing of the packaging by repositioning of the cover 114.

In this embodiment also, the limitation of the processing making gas permeable the initiation region of the opening of the package prevents this treatment from promoting the complete tearing of the seal during the application of the stresses necessary for the rupture of its weldable layer.

For the manufacture of such packaging, the sealing sheet is issued a strip in which a succession of cover sheets is formed successive. These sheets are delimited between them by a visual reference 150 arranged in a corner of each sheet. This mark allows positioning correct of each sheet on a tray.

When processing the tape, the processing making the sheets locally permeable to gases is produced in regions positioned by relative to successive benchmarks 150.

In FIG. 9 is still shown an alternative embodiment of the packaging according to the invention.

This packaging 200 consists of a tray 202 closed by a cover 204 produced from a sheet according to the invention. Lid 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 is intended to receive, by example, a portion of cheese.

The opening of the housing 206 is surrounded by a flange 208 comprising two main intersecting edges 210, 212, extending parallel to the rectilinear edge of the disc sector forming the housing 206. A rear edge 214 straight extends perpendicular to the angle bisector bounded by edges 210 and 212.

Finally, the connection between the edges 210, 212 and the rear edge 214 is ensured by parallel rectilinear sections 216, 218 extending laterally. These edges delimit opening regions of the packaging noted 220, 222. These regions extend into the corners defined between the main edges 210, 212, and the rear 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 cover 204 is welded according to a peripheral weld 224 on the periphery of the rim 208.

The lid 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 made continuously using a beam laser, for example. These perforation lines 228 extend 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 edges 216, 218 in the opening regions 220, 222. The distance between these weld sections 230, 232 and the extreme lines of perforations 228 is for example equal to 7 mm.

The perforation lines 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 understood that with such packaging, the opening being initiated in one of the zones 220, 222, one of the welded sections 230, 232 is first released by rupture of the welding layer. This break occurs without risk film tear, since no treatment making permeable to gas is not present in this region.

As the packaging continues to open, the sections of weld extending along the edges 210, 212 and 214 are released. Although the treated area extends along these weld beads, the risk that the leaf to be torn is extremely reduced, since the spread of the tearing of the welding layer takes place along the length of these sections welded, so only very little force is needed to tear the sealable film. So this weak force is not sufficient to initiate a complete tear in the sheet despite the treatments making the sheet permeable to gases.

In this embodiment, the cover 204 is advantageously made from film reel, in which the perforation lines 222 are produced along the length of the film. This treatment is carried out in continuous by running the film on suitable equipment.

Claims (7)

Laminated packaging sheet (14, 16; 114; 204), of the type comprising a primary layer (30; 124) associated with a weldable layer (32; 126) between which is interposed, in at least one marked area, a layer (34; 128) of a permanent adhesive, said sheet having in a marked area where the permanent adhesive is present, a heat-sealing region (22; 122; 224) allowing the sealing by thermal welding of the package and allowing a re-closing of the packaging after an initial opening,
characterized in that said sheet has in at least one marked region (36; 130; 228), a treatment ensuring gas permeability, the or each treated marked region (36; 130; 228) extending outside of at least a part of said heat-sealing region, the or each part (22; 122; 224) of the heat-sealing region devoid of treatment forming a region (22; 122; 230, 232) for initiating the opening of the packaging. Packaging sheet according to claim 1, characterized in that the or each region marked treated (36; 130; 228) has one of the treatments chosen from the group consisting of: perforations, micro perforations, mechanical treatment making it porous, and lights localized performed by laser. Packaging sheet according to claim 1 or 2, characterized in what the minimum distance between the border (37) of the or each region identified processed (36; 130; 228) and the or each part (22; 122; 224) of the heat-sealing region without treatment is greater than 7 mm. Packaging sheet according to any one of the claims previous, characterized in that the or each region identified treated (36; 130; 228) extends over the heat sealing region (20A, 20B) outside of the or each part (22) forming an initiation region of the opening of the packaging. Packaging sheet according to any one of claims 1 to 3, characterized in that the or each region marked treated (130) extends only outside the heat seal region (122). Packaging comprising an external wall delimiting a housing (118) provided with an access passage (116) to said housing, characterized in that said passage (116) is closed by a laminated sheet (114) according to one any of the preceding claims, which sheet (114) is welded thermally on said outer wall at the periphery of the passage (116) along its weldable layer (126) in said heat sealing region (122), the or each welded part of the heat-sealable region lacking processing forming a region (230, 232) initiating the opening of packaging. Packaging bag comprising at least one wall delimited by a sheet according to any one of claims 1 to 5, characterized in that said sheet (14, 16) is thermally welded against another wall (16, 14) of the sachet according to its sealable layer (32) in said region of heat seal (22), the or each welded portion (22) of the heat seal region devoid of treatment forming an initiation region of the opening of the packaging.

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