FR2783512A1 - Reclosable welded multilayer packaging, includes planar closure structure with permanent adhesive and divisible strip which can be applied to wide range of sizes and shapes of pack in mass production - Google Patents

Abstract

A layer of adhesive (11) is applied, forming an additional thickness on a pack wall (3). It covers an edge of the closure (10). During initial pack closure, the adhesive joins with a strip (12) on the opposing pack wall (4). This strip is divisible, and tears on opening the pack. Part of it (12a) remains welded as an additional thickness on the pack wall (4), leaving the adhesive uncovered in the corresponding zone (11a) (see illustration). An Independent claim is included for the method of making the pack. Preferred features: The permanent layer of adhesive is joined with the first pack wall, by the intervening strip (13) which is welded to the pack wall (3). The divisible material is welded to the other wall of the pack, its height (h) being less than that (H) of the strip (13), over its entire length. The divisible tape (12) is 15-100 mu m thick. The permanently-adhesive layer (11) is a hot melt, or an acrylic polymer, and has a thickness of 3-100 mu m before welding. An intermediate layer has sufficient thermal stability to take molten adhesive, as a coating support between adhesive and tape. The weld bead at the transverse closure edge has a V-shape, pointing externally, to assist opening. Further claims concern the band closing a pack of the type described, a further pack employing the band, and a flexible bag based on the preceding claims.

Description

PACKAGING THAT CAN BE CLOSED AFTER OPENING, IN

  PARTICULAR PLASTIC BAG AND PROCESS FOR PRODUCING THE SAME

MANUFACTURE OF SUCH A PACKAGING.

  The invention relates to a package which can be closed after opening, and which comprises, in an initial closed state, a weld along at least one closing edge with, between welded areas, a layer of permanent adhesive, the assembly being provided so that when the package is opened, by cutting or tearing the closing edge, the adhesive layer is exposed so that the package can be closed by pressing the

  packaging walls against each other.

  The invention relates in particular to a packaging produced in the form of a plastic bag and intended to package liquid and / or solid products, in particular food products. The ability of a package to be closed allows the user to protect the contents after removal or use. In particular, in the case of a bag containing a consumable product, it is possible after taking a dose to keep the product away from

  air until a next dose is taken.

  Document WO 93/08982 shows this type of packaging in the form of a plastic bag. The bag is produced with a multilayer plastic sheet comprising, at determined locations, a layer of adhesive embedded between the plastic sheet and an adhesive protective film, which film is placed against the entire surface of the sheet, including in areas where there is no adhesive. The manufacture of a bag from such a sheet of plastic material requires a certain precision of execution so that the layers of adhesive embedded in the sheet are correctly positioned. In the case where it is desired to manufacture bags of dimensions or shapes different from that for which the sheet was intended, difficulties arise and it is necessary, practically, to provide an arrangement of the sheet according to the type of bag to be manufactured . This results in a lack of flexibility which does not allow to easily change the manufacturing. In addition, the layer of adhesive embedded in the sheet creates a local allowance which, when the sheet is rolled up in particular for storage, causes folds and / or deformations of this sheet, and can

generate floating edges.

  In addition to document WO 93/08982, document FR 2 741 605 from the applicant company is known, relating to a closure structure for a container allowing successive openings and closings. Document US 4,673,601 also relates to a container of this type. According to these other documents, the composite film, comprising a layer of adhesive embedded between at least two sheets, covers a much larger surface than

that corresponding to the weld.

  The invention aims, above all, to provide a packaging which, while being able to be closed after opening, is of a simple and easy to manufacture.

  modify in case of change of dimensions or shapes.

  It is also desirable, in order to produce the packaging, to be able to use sheets of plastic material of constant thickness, not requiring special manufacture, and to use only a minimum surface of a composite film comprising the layer adhesive. It is also desirable that the packaging can be produced according to a continuous process, avoiding modifying the transformation processes upstream of the

packaging manufacturing.

  According to the invention, a package of the kind defined above is characterized in that the adhesive layer is added in excess thickness on a first wall of the package, only along the closing edge and, only in the state initial closure of the packaging, the adhesive layer is attached, on the side opposite to the first wall, to a strip of breakable material welded to the other wall of the packaging, this strip of breakable material being provided to tear at the opening of the packaging and to remain, at least in part, welded in excess thickness to the wall of the bag, the layer of adhesive

  being discovered in the corresponding area.

  Preferably, the layer of permanent adhesive is attached to the first wall of the packaging by means of a strip of material welded to the first wall of the packaging. The strip of breakable material is welded to the other wall of the package at a width less than that of the tape, which is welded according to

all its width.

  The strip of breakable material provided on one side of the adhesive layer, and the strip of material possibly provided on the other side of the adhesive layer, are made of a weldable layer or material or film, preferably in medium or high density polyethylene, or as propylene homopolymer or as a copolymer of propylene and ethylene, whatever the mode of catalysis, ziegler, metallocene. The strip of breakable material has, in particular, a

  thickness between 15 and 100 micrometers.

  Preferably, each side wall of the package is produced from a multilayer sheet comprising at least one external layer which can be printed, in particular polyester such as polyethylene terephthalate (commonly known as PET) or simple oriented or bioriented polypropylene. , coextruded or varnished, or in oriented or bi-oriented polyamide extruded in a flat die (called "polyamide cast") and an inner weldable layer, in particular in polyethylene or

polypropylene.

  The layer of permanent adhesive can be, for example, a "hot melt" or an acrylic polymer. The adhesive layer preferably has a thickness of between 3 and 100 micrometers, before welding. The adhesive can be

  composed of EVA (common name of the ethylene copolymer-

  vinyl acetate), or a copolymer of styrene and butadiene, a styrene - butadiene - styrene copolymer (commonly known as SBS), a styrene - ethylene - butylene - styrene copolymer (commonly known as SEBS), or a copolymer of styrene and l can be a styrene-isoprene-styrene copolymer (commonly called

  SIS), tackifying resins, oil and / or waxes.

  This list is not exhaustive and it is also possible to use pressure-sensitive adhesives, commonly

called PSA, in solvent.

  An intermediate layer of polyester, in particular with a thickness of 5 to 100 micrometers, may be provided between the layer of adhesive and a layer of polyethylene. Advantageously the weld bead from the edge of

  closure present, preferably substantially half

  length, a V shape turning its tip outward to facilitate opening by a primer

tear in this place.

  The invention also relates to a composite strip for closing a package as defined above, characterized in that it comprises a layer of permanent adhesive between a layer of breakable welding material and another layer of welding material forming a tape and having a higher tear resistance than that of the layer of breakable material. The width of the composite strip can be understood

  between 5 mm and 15 cm, terminals included.

  The strip may comprise, between the layer of adhesive and the layer of welding material, an intermediate layer which is thermally stable enough to receive the molten adhesive, and serve as a coating support. Advantageously, the layer of welding material is made of polyethylene or polypropylene, while the intermediate layer is made of

polyester or polyamide oriented.

  A notch may be provided at each end of the repositionable "peelable" composite strip to allow direct welding of the internal faces facing the walls of the packaging. Preferably, the notch has a width less than that of the composite strip and borders remain on either side of this notch,

  allowing continuity of the composite strip.

  The invention also relates to a plastic bag, forming a packaging as defined above, for liquid and / or solid products, in particular food products, comprising a bottom, two side walls, two closed longitudinal edges and a transverse, opposite edge. at the bottom, with a weld in the initial closed state, characterized in that the layer of permanent adhesive is provided along this transverse edge. The bottom of the bag may have a substantially W-shaped cross section, suitable for opening when

the bag is full.

  Preferably, the two longitudinal edges of the bag extend substantially perpendicular to the direction

  from the bottom and are closed by welds.

  Welding creates embrittlement of the layers

  adhesive and breakable material from the composite strip.

  Given this embrittlement effect, it is important to choose: the breakable material and in particular its melting point; - the material of the ribbon and in particular its melting point; - the viscosity of the adhesive and the thickness of the adhesive layer so that the temperature applied to the weld (s) does not result in pure evacuation and

single layer of adhesive.

  The invention also relates to a method of manufacturing packaging as defined above according to which a composite strip is welded along an edge

  closure between two sheets of packaging.

  The invention also relates to a method of manufacturing a packaging, in particular a bag, as defined above, comprising two side walls

  formed by plastic sheets.

  According to the invention, a layer of permanent adhesive is fixed on the internal face of one of the sheets of plastic material, parallel to the bottom and at a distance from this bottom, and on the side of this adhesive opposite the sheet, a layer of breakable material, in particular polyethylene, and after filling, the strip is welded

  breakable material against the other wall of the bag.

  According to a first possibility, a composite strip is prefabricated and consists of the layer of permanent adhesive between the strip of breakable material and a strip of welding material, and the fixing of the layer of adhesive to the first sheet is carried out by welding. of

this ribbon against the sheet.

  Alternatively, the layer of permanent adhesive is continuously deposited, either against the first sheet of plastic and the strip of breakable material is laminated against this layer, or against the strip of breakable material which is then glued against the

  first sheet of plastic.

  The invention consists, apart from the arrangements set out above, of a certain number of other

  provisions which will be more explicitly discussed below

  after about the embodiments described with reference to the accompanying drawings, but which are not

in no way limiting.

  Figure 1 of these drawings is a schematic elevational view of a filled, closed bag according to the invention. Figure 2 is a section along line II-II of

Figure 1.

  Figure 3 is an enlarged view of the

  detail of the welded transverse edge of Figure 2.

  Figure 4 is a schematic partial section on a larger scale of the transverse edge after opening the

bag.

  Figure 5 is an elevational view of a variant

  of the weld bead of the transverse edge.

  Figure 6 shows, similarly to Figure 4,

an alternative embodiment.

  Figure 7 shows, similarly to Figure 6,

  a tear variant at the opening.

  Figure 8 shows, partly in cross section and partly in perspective, a composite strip according to

the invention, on a large scale.

  Figure 9 is a schematic perspective illustration of the method of manufacturing a bag according to

the invention.

  Figure 10 schematically represents the

filling a bag.

  Figure 11 shows a full closed bag.

  Figures 12 and 13 partially represent, in

  perspective, variants of the process of Figure 9.

  Figure 14 is a schematic elevational view

  of an alternative embodiment of the bag.

  Figure 15 is a schematic elevational view

  of another alternative embodiment of the bag.

  Figure 16, finally, is a schematic elevation view of an alternative embodiment of the bag with spout. Referring to Figures 1 to 3 of the drawings, one can see a package consisting of a bag 1, or a sachet, of plastic material containing a liquid L, by

  example a food liquid such as a sauce.

  The bag 1 has a bottom 2 which has a cross section substantially in W, as visible in FIG. 2, suitable for opening when the bag is filled, so as to constitute a seat allowing the bag to

stand up.

  The bag 1 has two side walls 3, 4, which, in the example considered, have a rectangular shape. The side walls 3 and 4 are welded to each other along their longitudinal edges 5, 6, substantially perpendicular to the mean direction of the bottom 2. The

walls 3 and 4 are flexible.

  The welded edges 5, 6 extend over the entire height of the two side walls, including the area of the bottom, for the assembly of these walls together. 7.8 curvilinear or broken line welds join each side wall with a facing bottom zone. The starting points of the welds 7,8 are located on the welded longitudinal edges 5,6 near the central edge of the W which constitutes a kind of articulation allowing a variation of the angle formed by the internal branches of the W. The bag 1, in the closed state, comprises a weld along a closing edge 10, transverse, opposite and

  parallel to the bottom 2, as illustrated in Figures 2 and 3.

  The side walls 3, 4 extend beyond the edge 10 over a distance e, according to non-welded extensions t3,

t4 can be discarded.

  The edge 10 comprises, between the welded areas, a layer of permanent adhesive 11. According to the embodiment of FIGS. 3 and 4, the layer of adhesive 11 is sandwiched between a strip 12 of breakable material capable of being welded against the internal face of the wall 4 and a strip 13 of material capable of being welded against the face

internal wall 3.

  To facilitate explanation and understanding, the thicknesses of the layer 11, of the strip 12 and of the tape 13 have been exaggerated in the drawings. Each wall 3, 4 can be constituted by a flexible multilayer sheet comprising at least one external layer 3a, 4a which can be printed, in particular in polyester or in polyethylene terephthalate (PET) and an internal layer 3b, 4b which is weldable, in particular in polyethylene or polypropylene. The strip 12 and the ribbon 13 are advantageously made of preferably medium density polyethylene (density between 0.925 and 0.940) or

  high density (density between 0.940 and 0.960).

  The breakable strip 12 has a thickness of between micrometers and 100 micrometers, and is easy to tear. The tape 13 has resistance to

  tear greater than that of the strip 12.

  The layer 11 of permanent adhesive consists of "Hot melt" on the basis of a thermoplastic elastomer or equivalent material, and has a thickness of between 3 and micrometers. Examples of the composition of "Hot melt"

have been provided previously.

  The adhesive can also be a resin made of an acrylic polymer having a permanent tacky effect which is in a solid form at room temperature. The adhesion of the adhesive layer 11 on its support, for example the tape 13, is greater than the breakability (resistance to tearing) and peelability of the

layer 12 breakable / sealable.

  The tape 13, the adhesive layer 11 and the strip 12 can be preassembled to form a composite strip B which, for the manufacture of the bag, is fixed by welding the tape 13 against the face 3b, parallel to the bottom 2, before

filling the bag 2.

  The welding parameters (pressure, temperature and time) are adjusted according to the nature of the welding layer 12 and the other layers. The welding is carried out using a heating strip capable of exerting a clamping of the sheets in the zone of the strip B. The sheets will undergo a momentary deformation during the welding, leading to permanent deformations which remain after removal of the bar. Due to the nature of the outer layer, it does not undergo fusion and is very little permanently deformed. On the other hand, the welding layer 12 undergoes deformation due to its melting and the pressure exerted by the solder bar. It is the same for the adhesive layer 11. A weakening of the welding layer 12 and of the adhesive layer 11 is thus obtained in the region of the strip B. The strip 12 which covers the adhesive layer 11 fulfills a double function. on the one hand, it makes it possible, during filling of the bag 1, to avoid contact between the filling product and the adhesive layer 11 and, on the other hand, it allows assembly by welding against the face 4b for closing the bag. The tape 13 is welded along its entire width H (Figure 4) to the face 3b. This width H is also that of the layer 11 and of the whole of the composite strip B. The breakable strip 12 is welded along a width h less than the width H, leaving on either side of the welded zone, a guard zone not welded g which, on the one hand, makes it possible to avoid directly welding the two faces 3b, 4b of the bag to them and, on the other hand, promotes the rupture of the strip 12 during

from the opening of the bag.

  The opening is obtained, for example, by inserting a blade between the extensions t3, t4 so as to separate them and tear the weld from the edge 10, or by pulling on the extensions t3, t4 to separate them. The assembly is provided so that, at least in places, the adhesive layer 11 remains attached, on one side, to the first wall 3 of the bag, by means of the tape 13 in the example of FIG. 4 , and be discovered at least on part lla. The strip 12 of breakable material tears and remains, for part 12a, welded in excess thickness to the wall 4b. The exposed part 11a of the adhesive layer 11 corresponds to the part 12a. The part 11a is delimited by projecting selvedges corresponding to the guard zones g of the strip 12 which have been torn and

  which remained adjacent to layer 11.

  By reapplying part 11a of the coat

  11 against part 12a, the bag can be closed.

  The adhesive layer 11 is added in excess thickness on the first wall 3 only along the closing edge 10. In the closed state of the bag, the adhesive layer 11l is attached to the strip of breakable material 12

welded to the other wall 4.

  The film constituting each wall 3, 4 has a thickness of between 30 and 700 micrometers. This film is generally multilayer and constituted by an assembly of it polyester and preferably of polyethylene constituting the internal face, or failing this of polypropylene, or by a polyester-aluminum-polyethylene (or polypropylene) assembly, or by an assembly (of the exterior to interior) of polyamide oriented polyethylene (or polypropylene). Figure 5 illustrates a possible geometry for the weld bead 14 between the strip 12 and the face 4b. The weld bead has, substantially at mid-length, a V-shaped shape turning its point outward to facilitate opening by a tear initiation at this point. The width of the weld bead 14 is less than that of the strip 12. The force required for opening is smaller and the propagation is more

  easier than in the case of a straight weld.

  Figure 6 illustrates an alternative embodiment in which the tape 13 is removed and the layer 11 of permanent adhesive is applied directly against the face 3b. The strip 12 of weldable breakable material is laminated to the layer 11. The welding of the strip 12 to the wall 4b takes place after filling the bag to close this bag. As illustrated in Figure 6, the opening is also obtained by breaking the strip 12. The bag can be closed in the same way as in the case of the

Figure 4.

  Figures 4 and 6 correspond to the case where

  the adhesion between the layers 11a and 12a is weak.

  However, as illustrated in Figure 7, it often happens that a little adhesive llb remains stuck to the

layer 12a.

  In practice, after opening, the adhesive may alternately be in certain places on one side, in other places on the other side, and in other places on both sides, the layer of adhesive having separated in the middle. But in any case an area of the layer

adhesive is discovered.

  Figure 8 illustrates in section a composite strip B for the production of an edge closed by welding which, after a first opening can be closed. We find my breakable layer 12, the adhesive layer 11. An intermediate layer E is provided, on the side of the adhesive opposite to the layer 12 of breakable material. The intermediate layer E is mainly used as a coating support for the adhesive 11 which is applied melted on the support; this support should therefore be sufficiently thermally stable. Polyethylene melts at a relatively low temperature; depending on the adhesive and the material of the weldable layer, it may be advantageous to use an intermediate support layer E which is thermally stable enough, for example made of polyester or oriented polyamide, or oriented polypropylene. The connection of the intermediate layer E and of the ribbon 13 is ensured by

  a layer S of lamination adhesive.

  The composite strip B is advantageously manufactured starting from a polyester film which is coated, on one side, with the layer of permanent adhesive 11 on which the layer 12 of breakable polyethylene is laminated. On the other side of the polyester film, the polyethylene tape 13 is put in place by lamination with a polyurethane adhesive,

with or without solvent.

  The composite strip B can have a width ranging from 5mm to 15cm and more, depending on the size of the targeted packaging. The strip B can be produced by cutting from a wider film, for example having a width of 10 cm to m. Figure 9 schematically illustrates a method of manufacturing bags according to the invention, known in its most

  large part, in particular according to US Pat. No. 3,380,646.

  Two coils B3, B4, of plastic film are rotatably mounted around a horizontal axis. The coil B3 is arranged above the coil B4. The sheets F3 and F4 are unwound from the respective reels B3, B4, in the same vertical plane and pass between horizontal rollers R3, R4 which return in a horizontal plane the sheets F3, F4 applied against each other. A strip C folded in V turning its concavity towards the outside, is introduced between two edges opposite the sheets F3, F4 at the level of the rollers R3, R4 so as to constitute the bottom 2 of the bags. This bottom 2 is first welded to a station P1, then the longitudinal edges, 6 are welded to a station P2. A composite strip B according to the invention is unwound continuously, from a reel D with an axis parallel to that of the reel B3. The strip B is welded against the internal face of the sheet F3, at a distance e from the edge of this sheet F3 opposite the bottom 2. The welding can be carried out by passing the strip B and the sheet F3 between rollers R5, R6 comprising heating means in the zone where the strip B passes. The longitudinal edges 5, 6 subsequently welded trap the strip B. In an empty bag i cut, as shown on the right of FIG. 9, the segment of composite strip B East

  adjoining the wall 3 which can be moved away from the wall 4.

  The bag 1 is then installed at a filling station with its opening facing upwards as illustrated in Figure 10. After filling the edge 10 is welded along the strip B by plates P3 which tighten the upper part of the bag 1 at this strip B. The two walls 3 and 4 are then joined according to

the edge 10 (Fig. 11).

  As a variant, as illustrated in FIG. 12, instead of welding a composite strip B consisting of the tape 13 of the adhesive layer 11 and of the breakable strip 12, it is possible to coat the sheet F3 continuously with a layer 11 and laminate the breakable strip 12 which is unrolled at

from a D 'coil.

  According to another possibility, illustrated in FIG. 13, the adhesive layer 11 is applied continuously to the breakable strip 12 which is then glued against the

sheet F3.

  FIG. 14 illustrates an alternative embodiment of the bag 1 making it possible to avoid embrittlement of the longitudinal edges 5, 6 at the level of the transverse edge where the composite strip B, or equivalent, is "peelable" and repositionable. A notch 16, in particular substantially in a semicircle, turning its concavity towards the outside, is provided at each end of the band B. The width of the notch 16 is less than the width of the band B

  so that a border 17,18 remains above and below

  below the notch 16. The strip B can thus be produced continuously with distributed openings, each opening being constituted by the union of two notches 16 turning their concavities towards one another. In the case of semi-circular indentations 16, the continuous strip B has circular holes, the

  centers are spaced the width of a bag 1.

  At the notches 16, the internal faces 3b, 4b of the walls 3 and 4 are directly welded one to the other.

  the other, which reinforces the closure at this location.

  Figure 15 shows an alternative embodiment of a bag or sachet 101 in flexible material in which a closing edge 110a, 11Ob allowing a repositionable opening-closing is perpendicular to the bottom line, and provided on each side. The transverse edge parallel to the bottom is closed, after filling, by a weld 19 which is not concerned with the opening of the bag. The lateral opening of the sachet is obtained by breaking or tearing a weld 114a or 114b located on the side of the weld 19, perpendicular thereto. The welds 114a, 114b extend the welds 5,6 of the two longitudinal edges of the bag with, however, a narrower width. A median zone 115a, 115b, in V, turning its point towards

  the outside is provided to facilitate opening.

  This structure is advantageously obtained with a composite strip B of width W1 relatively large corresponding to the length of the desired lateral opening. The strip B extends, in length, over the entire width of the bag, which allows continuous manufacture as illustrated in Figures 9, 12 and 13. The strip B is welded to one of the inner faces of the bag at least over its entire perimeter, or preferably over its entire surface. The strip B is only welded to the other inner face of the bag along the welding strips 114a, 114b. The opening of the bag is carried out by spreading the layers of the strip B at the level of the weld 114a or 114b and thereby releasing the layer of adhesive, which makes it possible to

close the bag.

  Figure 16 shows a variant of Figure 15, in which the bag or sachet 201 has a pouring spout K on one of its longitudinal edges, located at the level of the composite strip B. As in Figure 15, the strip B, parallel at the bottom, is welded to one of the inner faces of the bag at least over its entire perimeter, or preferably over its entire surface. The strip B is only welded to the other inner face of the bag along the convex contour 114c of the pouring spout. The faces of the bag extend beyond the spout K by non-welded zones J. The opening of the spout K is obtained by spreading the zones J and causing the strip B to break at the level

contour 114c.

  The bag according to the invention can be manufactured in a simple, continuous manner. Usual plastic sheets can be used to make the walls 3 and 4. The position of the strip B can be easily modified, depending on the dimensions of the bag, which gives great flexibility of adaptation. The filling is carried out in good conditions since the adhesive layer is masked by the breakable strip 12. The composite film constituting the strip B, or the equivalent zone, has a reduced surface, much less than that of the walls of the bag. The invention provides several improvements, in particular as regards the ease of opening. This results from the breakability of the layer 12 with respect to the adhesion of the adhesive to its support and to the breakable strip; the width of the last weld relative to the width of

  the band, as well as its inverted V shape.

  The weldable and repositionable composite strip B dissociates the functions of breakability and adhesion from that of general weldability of the others

  parts of the packaging, in particular of the sachet.

  It is thus possible to produce packaging, in particular sachets, having excellent mechanical properties thanks to a very particular quality of the base film, which no longer needs to take into account the criterion of

  breakability integrated in the added composite band B.

  The invention applies to many types of bags, sachets or packaging other than that described above; the invention applies in particular to sachets produced on VFFS (vertical closing and filling), HFFS (horizontal closing and filling), "flowpack" or process according to which the film, for packaging, is wound

around the content.

  Inviolability can be obtained, if necessary, by making a normal weld above (ie on the side opposite the bottom) of the repositionable part. This additional welding is not essential as a tamper-evident seal when a layer of adhesive 11 is provided which, after opening and closing the packaging, undergoes very clear whitening or clouding. This change in appearance immediately signals the opening of the sachet, and constitutes a witness to inviolability. In particular, the breakable strip may be charged with a mineral material, so that an opaque line, white in the case where the charge is white, will appear at the

first opening.

  A packaging according to the invention can give rise to numerous applications, such as the packaging of dry products, wet products, crisps, candies, rice, pulses, cookies, breads, animal kibbles, detergents, glitter soap, hardware, toys, parts for electronics,

  this list is not exhaustive.

Claims (24)

  1. Packaging which can be closed after opening, comprising in an initial closed state a weld along at least one closing edge with, between welded zones, a layer of permanent adhesive, the assembly being provided so that at the opening of the package, by cutting or tearing the welded edge, the adhesive layer is exposed so that the package can be closed by pressing the walls of the package against each other, characterized by the fact that the adhesive layer (11) is added in excess thickness on a first wall (3) of the packaging, only along the closing edge (10) and, only in the initial state of closure of the packaging , the adhesive layer (11) is attached, on the side opposite to the first wall, to a strip of breakable material (12) welded to the other wall (4) of the packaging, this strip (12) of material breakable being provided to tear at the opening of the package and to remain, at least in part (12a), welded in excess thickness to the wall (4) of the packaging, the adhesive layer being exposed in the area corresponding (lia).   2. Packaging according to claim 1, characterized in that the layer (11) of permanent adhesive is attached to the first wall (3) of the packaging by means of a strip (13) of material welded to the first wall (3) of the packaging.   3. Packaging according to claim 2, characterized in that the strip (12) of breakable material is welded to the other wall (4) of the packaging with a width (h) less than that (H) of the tape ( 13) welded according to all its width.   4. Packaging according to one of the preceding claims,   characterized by the fact that the strip (12) of weldable and breakable material provided on one side of the adhesive layer (11), and the tape (13) possibly provided on the other side of the adhesive layer, are made of medium or high density polyethylene, or polypropylene, propylene homopolymer, or copolymer of propylene and ethylene or mixture, whatever the type of catalysis. 5. Packaging according to claim 4, characterized in that the strip (12) of breakable material has a thickness   between 15 and 100 micrometers.   6. Packaging according to one of the preceding claims,   characterized in that each side wall (3,4) of the packaging is produced from a multilayer sheet comprising at least one external layer which can be printed, in particular polyester or polyethylene terephthalate PET, and an internal layer weld in   especially in polyethylene or polypropylene.   7. Packaging according to one of the preceding claims,   characterized in that the layer (11) of permanent adhesive consists of "hot melt" or of an acrylic polymer, and has a thickness of between 3 and 100 micrometers before welding.   8. Packaging according to one of the preceding claims,   characterized in that an intermediate layer (E) thermally stable enough to receive the molten adhesive is provided as a coating support between the adhesive (11) and the tape (13)   9. Packaging according to one of the preceding claims,   characterized by the fact that the weld bead (14) of the transverse closing edge (10) has, substantially at mid-length, a V shape turning its point towards   outside to facilitate opening.   10. Composite strip for closing a packaging according to   one of the preceding claims, characterized by   having a layer (11) of permanent adhesive between a layer (12) of breakable welding material and another layer (13) of welding material having a tear strength greater than that of the layer of breakable material . 11. A strip according to claim 10, characterized in that its width is between 5 mm and 15 cm, terminals included.   12. Strip according to claim 10 or 11, characterized in that it comprises, between the layer (11) of adhesive and the layer (13) of welding material, an intermediate layer (E) sufficiently thermally stable to receive the melted adhesive.   13. Strip according to claim 12, characterized in that the layer (13) of welding material is made of polyethylene or poypropylene, while the layer   intermediate (E) is made of polyester or oriented polyamide.   14. Packaging according to one of claims 1 to 9 provided   of a composite strip according to one of claims 10 to   13, characterized in that a notch (16) is provided at each end of the composite strip (B) to allow direct welding of the internal faces (3b, 4b)   opposite the walls (3,4) of the packaging.   15. Packaging according to claim 14, characterized in that the notch (16) has a width less than that of the composite strip (B) and that the edges (17,18) remain on either side of this notch,   allowing continuity of the composite strip.   16. Plastic bag, according to one of   claims 1 to 9, 14 and 15 for packaging products   liquids and / or solids, in particular foodstuffs, comprising a bottom (2), two side walls (3,4), two closed longitudinal edges (5,6) and a transverse edge (10), opposite the bottom, with a weld at the closed state of the bag, characterized in that the layer of permanent adhesive   (11) is provided along this transverse edge.   17. Bag according to claim 16, characterized in that the two longitudinal edges (5,6) of the bag extend substantially perpendicular to the direction of the bottom   (2), and are closed by welds.   18. Bag (101) of flexible material according to claim 1, characterized in that it comprises at least one closing edge (110a, 11Ob) allowing an opening-closing repositionable perpendicular to the bottom line, and that the lateral opening of the bag is obtained by breaking or   tear in a weld (114a or 114b).   19. Bag according to claim 16, characterized in that a composite strip (B) of relatively large width (Wl) corresponding to the length of the desired lateral opening, extends over the entire width of the sachet, the strip (B) being welded to one of the inner faces of the bag at least over its entire perimeter, and being welded to the other inner face of the bag only along the weld strips (114a, 114b), the opening of the bag made by spreading the layers of the strip (B) at the weld (114a or 114b) and thereby releasing the layer   adhesive, which allows to close the bag.   20. Bag according to claim 19, characterized in that it comprises a pouring spout (K) on one of its edges   longitudinal, located at the level of the composite strip (B).   21. Bag according to claim 20, characterized in that the strip (B) is welded to one of the inner faces of the bag at least over its entire perimeter and is only welded to the other inner face of the bag according to the contour (114c) of the spout.   22. A method of manufacturing a packaging, in particular a bag, according to claim 1, comprising two side walls formed by plastic sheets, characterized in that 1 'is fixed on the internal face of the one (F3) of plastic sheets, parallel to the bottom (2) and at a distance from this bottom, a layer (11) of permanent adhesive and, on the side of this adhesive opposite the sheet (F3), a layer of breakable material (12), in particular polyethylene, and after filling the bag, the strip (12) of breakable material is welded against the other wall of the bag.   23. The method of claim 22, characterized in that a composite strip (B) is prefabricated and consists of the layer (11) of permanent adhesive between the strip (12) of breakable material and a tape (13) of welding material, and that the fixing of. the layer (11) of adhesive on the first sheet (F3) is produced by   welding the tape (13) against the sheet.   24. The method of claim 22, characterized in that a layer (11) of permanent adhesive is deposited either against the first sheet (F3) of plastic material, the strip (12) of breakable material then being laminated to this layer (11), either against the strip (12) of breakable material which is then glued against the first sheet (F3) of plastic.