FR2797622A1 - LAMINATE PACKAGING SHEET FOR CLOSING AND PACKAGING COMPRISING SAME - Google Patents

Abstract

The packaging film for food containers has a support layer (24) and a weldable layer (26) connected by a layer (28) of permanent adhesive. In corresponding areas (22A) of the layers, the weldable layer has a line of weakness defining an area for connective welding of the layers. The line of weakness aids tearing of the package along them.

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

permanent adhesive.

  The invention further relates to a package comprising an external wall delimiting a housing provided with an access passage to said housing

  comprising such a packaging sheet.

  Packages with a packaging sheet allowing easy opening and reclosing are currently used, for example, for packaging food products. The structure of such leaves is

  described in particular in patent application FR-A-95-14117.

  In this document, the laminated sheet used to allow the opening

  ture and reclosing of the package has two layers of polymer between which a layer of permanent adhesive is interposed. One of the layers, called "weldable or weldable layer" is intended to be oriented towards the inside of the packaging. It is suitable for being welded to the peripheral edge of a tray. The other layer, called the "support layer", is intended to form the external face of the packaging, this layer being able to be printed. During the opening of the tray described in the aforementioned document, the welding layer tears on either side of the welded region. After opening the tray, there remains on the periphery thereof

  residual welded, consisting of the welded part of the welding layer.

  The opening of the tray being obtained by rupture of the layer

  weldable, it should be chosen so that it has characteristics

  rupture characteristics compatible with the conditions of use of the packaging

  age. In particular, the sealing layer should be able to be torn manually, without it being necessary to exert an excessive pulling force on the packaging sheet. So the welding layers used

are rather of reduced thickness.

  However, the weldable layer should also have

  good welding characteristics, to ensure a reliable connection

  ble from the packaging sheet on the tray. In addition, the welding layer must be compatible with the permanent adhesive interposed between the two layers of the sheet. To meet this condition, choose

a rather thick layer.

  Thus, it is understood that the choice of the welding layer is relatively delicate, due to the many constraints which it must satisfy. This choice is in particular dictated by the possibility that the layer is torn manually. However, this characteristic is difficult to reconcile

  with the other properties necessary for the layer.

  The object of the invention is to propose a packaging sheet allowing the opening and reopening of a packaging, the sealing layer of which can

be chosen from a wide range.

  To this end, the invention relates to a laminated packaging sheet, of the aforementioned type, characterized in that, in a marked area of the sheet where the permanent adhesive is present, the weldable layer comprises, on the one hand and

  on the other side of a region intended to be welded, at least one line of weakness-

  sement of the weldable layer favoring its rupture along said lines.

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

  - at least one weakening line has a predefined line -

  chopped off; - The pre-cut line has a continuous groove opening onto the welding face of the weldable layer; - the pre-cut line has a continuous groove opening

  on the face of the weldable layer in contact with the layer of adhesive

  manent; - the weldable layer comprises, on each side of the region intended

  to be welded, at least two lines of weakness extending substantially-

parallel.

  The invention further relates to a package comprising an external wall 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

  on said outer wall at the periphery of the passage along its subsoil

  devil in a region demarcated essentially between the lines of weakness-

sement.

  The invention will be better understood on reading the description which will

  follow, given only 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 tray whose access passage is closed by a laminated sheet according to the invention; Figure 2 is a top view of the tray of Figure 1, the closure sheet extending on either side of the tray;

  Figure 3 is a view similar to that of Figure 1, after opening

  packaging size; Figure 4 is a top view of an alternative embodiment of the packaging of Figures 1 to 3; Figure 5 is a cross-sectional view of the welded region of an alternative embodiment of a sheet according to the invention applied to the edge of a packaging tray;

  FIG. 6 is a perspective view in section of a bag of em-

  baling consisting of a packaging sheet according to the invention, before opening; and

  Figure 7 is a view similar to that of Figure 6, after opening

size of the sachet.

  The package 10, shown in Figure 1, consists of a bar-

  rectangular quette 12 and a flexible cover 14 for closing a passage

  access 16 inside the tray.

  The tray 12 consists for example of a support layer

  outer material suitable, for example polyvinyl chloride

  covered on its inner surface with a weldable layer, for example,

polyethylene.

  The tray defines a receptacle 18 bordered over its entire periphery with a rim 20 delimiting a planar surface for welding the cover 14, according to

straight welding 22.

  The cover 14 is laminated, that is to say made of several layers

  superimposed. For reasons of clarity, the thickness of the layers is exa-

  slightly increased in the figures.

  The cover 14 essentially consists of a support layer 24 and a weldable layer 26 with a layer of permanent adhesive 28

  layered flat across them over the entire surface.

  The support layer 24 advantageously includes impressions on its external face. It can also include a transparent layer

  bearing such laminated prints on the outer surface of the

  che support by means of a layer of glue applied on its printed face. The support layer 24 is, for example, a polyethylene layer

36 µm thick.

  The layer of permanent adhesive 28 is produced by coating with an adhesive mass initially in solution, in particular in dispersion.

  aqueous. It can also be applied hot, in particular by extrusion

  if we. A permanent adhesive, commonly referred to as "hot melt" is ideal for this application. It is possible in particular to use Plastoflex 87.18 sold by the company Paramelt in the Netherlands. The thickness of the adhesive layer 28 is advantageously included

  between 10 and 30 pm and is in particular equal to approximately 20 pm.

  The weldable layer 26 is for example a layer of polyethylene or polypropylene whose thickness is between 20 and 60 μm, and is in particular advantageously equal to 40 μm. This layer is made of a material allowing welding with the layer facing the

tray 12.

  As shown in FIG. 2, the peripheral weld bead 22 extends on the four sides of the rim 20 of the rectangular tray. It ensures the watertight sealing of the tray. For reasons of clarity, the

  peripheral weld 22 has been grayed out in FIG. 2.

  The weldable layer 26 has two lines 30A, 30B of weakening.

  lying parallel to each other. A welded rectilinear region 22A of the peripheral weld which extends along the length of a rim

  of the tray is bordered by these two lines 30A, 30B.

  The weakening lines 30A, 30B each consist of a precut line formed by a continuous groove or notch opening onto the face of the weldable layer which is oriented towards the tray, thus

  as shown in Figure 2.

  The depth of the groove is between 25 and 100% of the thickness of the weldable layer 26. It is preferably substantially

  equal to 50% of the thickness of the weldable layer.

  The welded region 22A advantageously extends over the entire width

  denoted i of the band delimited by the weakening lines 30A and 30B.

  However, the width i is such that the lines of weakness are outside

laughter of the welded region 22A.

  As shown in FIG. 2, the weakening lines 30A and B are advantageously made in the weldable layer while the

  packaging sheets are still assembled to form a continuous strip

  bare of adjacent packaging sheets. The weakening lines 30A,

  30B are arranged in the machine direction, that is to say the direction of circulation

  tion of the strip formed from the adjacent sheets. These lines therefore extend

  parallel to the longitudinal edge of the strip.

  The weakening lines 30A, 30B consisting of contiguous grooves

  nudes are made before the sheet forming the cover is placed on the tray. They are for example produced by continuous cutting with the aid of a laser beam during the movement of the strip. Alternatively, the lines

  of weakening are carried out by cutting with a knife. In this last-

  last solution, when the belt is circulating, of the rotating members

  pants are brought into contact with the free surface of the weldable layer 26, in order to cut the latter to a determined depth corresponding to the

  desired depth for grooves 30A, 30B.

  The peripheral weld 22 is obtained by heat sealing. During the

  welding, the weldable inner layer of the tray and the weldable layer

  ble 26 of the packaging sheet melt together, making it possible to obtain,

  after cooling, a very reliable weld.

  As illustrated in FIG. 3, when the packaging is opened by pulling on the edge of the cover 14 located in the vicinity of the welded region 22A, the weldable layer 26 easily breaks along the lines of contact.

bleaching 30A, 30B.

  Only a residual strip from the weldable layer 26 remains present on the rim 20. It forms a welded bead, denoted 40. The latter

  is delimited laterally on both sides by the sides of the bus lines

notching 30A and 30B.

  As known per se, the presence of the permanent adhesive 28 on a welded bead and / or the facing surface of the support layer 24 allows the

  subsequent closing of the packaging by replacing the cover 14.

  It is understood that the presence of the weakening lines 30A, 30B

  promotes the opening of the tray by pulling on the cover 14. In particular

  bond, whatever the initial thickness and tear strength of the weldable layer 26, it is possible to determine the depth of the grooves forming the weakening lines so that these allow manual tearing of the weldable layer 26 by simple pull on

Cover 14.

  Thus, the characteristics of the weldable layer 26 can be determined.

  completed according to the constraints linked to welding, to compatibility with the permanent adhesive or to any other constraint linked to the protection of

  packaged products, without it being necessary to take account of the characteristics

  tearing ticks necessary to open the packaging. Indeed, the tearability of the weldable layer 26 is determined by the

  nature of the weakening lines.

  In Figure 4 is shown an alternative embodiment of a bar-

quette according to the invention.

  In this embodiment, the weakening lines 30A and 30B are spaced apart by an interval I greater than the width, denoted i, of the welds 42 made along the other three sides of the tray. The fourth weld, noted 44, of the cover on the tray is made along the entire extent delimited between the lines of weakness 30A and 30B. So the

  weld 44 has a greater width, and in particular advantageously com-

  taken between double and quadruple the thickness of the other welds 42.

  It is understood that the widening of the weld 44 makes it possible to increase the surface of the permanent adhesive discovered after opening the cover.

  Thus, the reliability of reclosing the packaging is improved.

  In addition, whatever the embodiment, when opening the

  tray, the absence of a weakening line along the household welds

  gées on the parallel edges adjacent to the edge carrying the welded region 22A or 42 delimited by such weakening lines has no influence on the ease of opening. Indeed, if the traction applied to the cover is exerted from the welded region 22A or 42, after rupture of the layer 26 along the lines 30A and 30B, the subsequent traction is carried out in parallel with

  the direction of the weld. It therefore breaks the welds already

  centes by propagation of a tear zone along the length of these welds. The tearing is carried out without excessive difficulty whatever the nature of the weldable layer since at a given instant all the stresses are applied at the same point of the layer and are not

  distributed along the entire length of the weld.

  In Figure 5 is shown an alternative embodiment of a packaging sheet according to the invention welded to the rim of a tray, denoted 52. In this embodiment, the weldable layer 26 comprises on either side of the weld 22 two weakening lines 56A, 56B and

58A, 58B.

  These lines extend parallel to each other and parallel-

welding 54.

  In this embodiment, the lines of weakness are

  killed by continuous grooves leading to the layer of adhesive

manent 28.

  The present, on either side of the weld 22, of two lines of af-

  weakening guarantees that, even in the presence of slight shifts in the weld 22 due to the imprecision of the process used, at least one of the weakening lines is located outside the weld, thus allowing

  easy opening of the cover, as previously explained.

  The packaging shown in Figures 6 and 7 forms a packaging bag.

  age. This consists of a packaging sheet according to the invention folded back on itself welded laterally on either side and the two ends of which are joined to each other by welding, with overlap. . More specifically, a weld 100 is made between the free surface of the support sheet 24 and the free surface facing the weldable layer 26. The

  sealing of the sachet is of the leather against flesh type.

  According to the invention, and as before, the welding is carried out between weakening lines 30A, 30B formed initially in the

  sheet on either side of the region to be welded.

  Advantageously, the weakening lines are arranged according to

  the machine direction, that is to say the direction of unwinding of the strip on the ma-

  china manufacturing bags. This sense of sequence also corresponds

  in the direction of travel of the strip during the manufacture of the sachets.

  Thus the weakening can be easily carried out continuously.

  It can be seen, as illustrated in FIG. 7, that, when pulling on

  the free end of the sheet, the weldable layer 26 breaks along the lines

  weakening genes 30A, 30B on either side of the welded region.

  Also, the weldable layer 26 can be chosen with characteristics

  suitable for the type of packaging desired, regardless of its

  breaking characteristics. Indeed, the presence of weakening lines-

  It allows, whatever the characteristics of the layer, to ensure

  that it can be torn manually along the lines of weakness.

  sement. In the embodiments described in the present application,

  the permanent adhesive extends over the entire surface of the weldable layer.

  However, the permanent adhesive may not be placed between the support layer

  24 and the weldable layer 26 that in identified areas, the sealing

  tion of the packaging then being carried out in at least one of these marked zones having the permanent adhesive between lines of weakness

previously arranged.

  In all embodiments, the sheet can be manufactured by

  laminating and laminating. It can also be manufactured by co-

extension of the overlapping layers.

Claims (8)

  1.- Laminated packaging sheet, of the type comprising a primary layer   mayor (24) associated with a weldable layer (26) between which is   applied, in at least one marked area, a layer (28) of a permanent adhesive   nent, characterized in that, in a marked area (22A) of the sheet where the permanent adhesive is present, the weldable layer (26) comprises, on either side of a region (22A) intended to be welded , at least one line   weakening (30A, 30B) of the weldable layer (26) promoting its rup- along the said lines.   2. A packaging sheet according to claim 1, characterized in that at least one weakening line (30A, 30B) has a precut line. 3.- packaging sheet according to claim 2, characterized in that the pre-cut line has a continuous groove opening on   the welding face of the weldable layer (26).   4. A packaging sheet according to claim 2, characterized in that the precut line comprises a continuous groove opening onto the face of the weldable layer (26) in contact with the layer (28) of adhesive. permanent (28).   5.- packaging sheet according to any one of claims   above, characterized in that the weldable layer (26) comprises,   each side of the region (22A) intended to be welded, at least two lines   weakening genes (56A, 56B; 58A, 58B) extending substantially pa-   rallying. 6.- Package comprising an external wall delimiting a housing (20) provided with an access passage (16) to said housing, characterized in that   said passage (16) is closed by a laminated sheet (14) according to one which   conch of the preceding claims, which sheet (14) is welded to   said external wall at the periphery of the passage (16) along its sub-layer   dable (26) in a region (22A) delimited essentially between the lines weakening (30A, 30B).   7.- Packaging according to claim 6, characterized in that the lar-   gor of the weld (22) formed between the weakening lines (30A,   B) is greater than the current width of the weld formed at the peri fountain of said passage (16).   8.- Bag comprising a laminated packaging sheet according to one   any of claims 1 to 5, which sheet is folded over it   same and welded laterally on both sides, the two ends being welded with overlap along the weldable layer (26) in a region   (100) essentially delimited between the weakening lines (30A, 30B).