EP3697701A1

EP3697701A1 - Adhesive valve, sheet and container for food, support as well as process for manufacturing this adhesive valve

Info

Publication number: EP3697701A1
Application number: EP18796498.6A
Authority: EP
Inventors: Valerio Binda
Original assignee: Masterpack SpA
Current assignee: Masterpack SpA
Priority date: 2017-10-20
Filing date: 2018-10-18
Publication date: 2020-08-26
Also published as: IT201800004610A1

Abstract

Adhesive valve comprising at least one flexible label (1) having an upper surface and a lower surface (1a), wherein at least the lower surface (1a) is provided with adhesive and at least one incision (1b, 1d) connects the two surfaces, wherein at least one flexible membrane (2) having an upper surface and a lower surface (2a) adheres to at least one portion provided with adhesive of the lower surface (la) of the flexible label (1), wherein the lower surface (2a) of the flexible membrane (2) is substantially non-adhesive, wherein a portion (2b) of the flexible membrane (2) is arranged under the incision (1b, 1d) of the flexible label (1), wherein the flexible label (1) extends beyond the flexible membrane (2) and the bottom surface (1a) of the flexible label (1) comprises at least one non-stick portion (4) that is adjacent to or at least partially overlapping the flexible membrane (2) and is arranged at distance (d) from the incision (1b, 1d) in the flexible label (1). The present disclosure also relates to a sheet and a food container comprising said adhesive valve, a support as well as a process for manufacturing this adhesive valve.

Description

Adhesive valve, sheet and container for food, support as well as process for manufacturing this adhesive valve

TECHNICAL FIELD

The present description relates to an adhesive valve, in particular an adhesive and flexible valve which can be applied onto incisions or openings made on hermetic containers, for example for food to be heated, in order to release gases which develop therein. The present disclosure also relates to a sheet and a food container comprising said adhesive valve, a support as well as a process for manufacturing this adhesive valve.

BACKGROUND OF THE DESCRIPTION European patent 2275252 describes an adhesive valve which comprises a flexible label having at least one lower surface provided with adhesive, wherein a flexible membrane is applied to the lower surface of the flexible label, is completely covered by the flexible label and has a substantially non-adhesive lower surface. To act as a gas relief valve, one or more incisions are made in the flexible label straddling the geometric projection of the perimeter of the flexible membrane. In this known adhesive valve the gas flow rate of the vent is greatly influenced by the type of adhesive used to fix the valve to the container, so if the adhesive is too strong it is difficult for the label to rise at the incisions, whereas if it is too weak there is the risk that the valve does not correctly perform its closing function.

To solve this technical problem WO 2015/111015 A1 describes a similar adhesive valve, in which the flexible membrane is always completely covered by the flexible label but is provided with incisions which intersect incisions made in the flexible label.

The adhesive valves known from these publications, however, have a not entirely optimal functioning, namely a gas release greater or less than expected according to the size and shape of the flexible label and the flexible membrane, when they are pulled or bent, in particular due to the swelling or bending of the sheet on which they are applied. US 2006/0076058 Al describes an adhesive valve in which the flexible label and the flexible membrane have the same extension, so that the flexible label cannot adhere to the sheet of the container, with consequent production problems, since the sheet or strip support of the adhesive valves cannot be punched for obtaining the respective flexible membranes. Moreover, in this known adhesive valve there is no adherent portion of the flexible label between the openings in the container sheet and the openings in the flexible label, i.e. there is a very large non-stick portion which is not spaced from the openings in the flexible label, so that the valve has a relatively low gas tightness and therefore requires a certain amount of liquid, in particular oil, disposed between the flexible label and the flexible membrane to maintain gas tightness. This liquid makes the adhesive valve more expensive and more complex to manufacture, preventing also relatively wide openings in the flexible label, otherwise the fluid would escape from the adhesive valve, so as to limit the possible uses of the adhesive valve. SUMMARY OF THE DESCRIPTION

The object of the present description is therefore to provide an adhesive valve free from such drawbacks. Said object is achieved with an adhesive valve, a sheet, a container, a support and a process, the main characteristics of which are specified in the claims.

Thanks to its particular non-stick portion, the adhesive valve allows to adjust the passage of gas through the incision or incisions in the sheet on which the adhesive valve is applied. In particular, the non-stick portion allows the flexible label to be lifted from the flexible membrane of the valve in the presence of gases under pressure, to create a passage of gas between the incisions of the sheet and of the flexible label, even when this sheet is pulled or bent.

Since the non-stick portion is at a distance from the incision in the flexible label, the adhesive valve closes after use due to the adhesive portion present between the nonstick portion and the incision in the flexible label.

This gas passage can be optimized with weakening zones in the flexible label obtained by means of particular further incisions which do not cross the label. Thanks to the particular arrangements, dimensions and shapes of the flexible label, of the flexible membrane, of the non-stick portion and/or of the incision in the flexible label, the effects of the possible deformation of the adhesive valve on its functionality are further limited.

The flexible membrane may include incisions to more accurately adjust the rate and the direction of the gas flow.

The flexible label may comprise a further particular incision which can act as an anti-tamper seal and which may be formed together with the other incisions of the flexible label. This further incision may form an appendix which tears off the seal and determines that the package has been opened.

Thanks to this further incision, the slot formed on the flexible label during the lifting of the latter allows the user to insert a finger inside it and hook the label so that it can be lifted without having to hold it between the fingers. For this purpose, a further non-stick portion can be arranged around the further incision.

The valve and the sheet according to the present description can furthermore be manufactured with a relatively simple, economical and fast procedure, preferably with a series production, especially if continuous and uniform layers are used to make the flexible label, the flexible membrane and/or the adhesive layer between them. BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the adhesive valve, the sheet, the container, the support and the process according to the present description will be clear to those skilled in the art from the following detailed and non-limiting description of their embodiments with reference to the attached drawings wherein:

Figure 1 shows a top view of a first embodiment of the adhesive valve arranged on a support;

Figure 2 shows a bottom view of the adhesive valve of Figure 1 without the support;

- Figure 3 shows a top view of a sheet prepared for the application of the adhesive valve of figure 1 ; Figure 4 shows a top view of the sheet of Figure 3 with the adhesive valve of Figure 1;

Figure 5 shows the section V-V of Figure 4;

Figure 6 shows the sheet of Figure 5 during use;

Figure 7 shows a scheme of the manufacturing process of the adhesive valve; Figure 8 shows a bottom view of a second embodiment of the adhesive valve; Figure 9 shows a top view of the adhesive valve of Figure 8 arranged on a sheet; Figure 10 shows a bottom view of a third embodiment of the adhesive valve; Figure 11 shows a top view of the adhesive valve of Figure 10 arranged on a sheet;

Figure 12 shows a bottom view of a fourth embodiment of the adhesive valve; Figure 13 shows a top view of the adhesive valve of Figure 12 arranged on a sheet;

Figure 14 shows a bottom view of a fifth embodiment of the adhesive valve; Figure 15 shows a bottom view of a sixth embodiment of the adhesive valve; Figure 16 shows a bottom view of a seventh embodiment of the adhesive valve; Figure 17 shows a bottom view of an eighth embodiment of the adhesive valve; Figure 18 shows a bottom view of a ninth embodiment of the adhesive valve; Figure 19 shows a top view of a tenth embodiment of the adhesive valve;

Figure 20 shows a bottom view of an eleventh embodiment of the adhesive valve; Figure 21 shows a top view of the adhesive valve of Figure 20 arranged on a sheet;

Figures 22 to 31 show bottom views of further embodiments of the adhesive valve.

EXPLANATORY EMBODIMENTS

With reference to Figures 1 and 2, it is seen that the adhesive valve according to a first embodiment of the present description comprises in known manner at least one flexible label 1 having two surfaces and at least one lower surface la provided with adhesive. At least one flexible membrane 2 having two surfaces may be applied below the lower surface la of the flexible label 1, so that the flexible membrane 2 adheres to a portion provided with adhesive of the lower surface la of the flexible label 1. The flexible membrane 2 has in turn two surfaces, in which the lower surface 2a is substantially non-adhesive, i.e. it is not provided with adhesive or is substantially less adherent than the lower surface la of the flexible label 1 provided with adhesive. Preferably, also the upper surface of the flexible membrane 2, in contact with the lower surface la of the flexible label 1, is substantially non-adhesive. The flexible membrane 2 is preferably obtained by punching a support 3 of the same material, in sheet or strip, which has a larger extension than the flexible label 1 and on which one or more flexible labels 1 of the same type are applied, arranged on at least one row. Also the label or the flexible labels 1 can be obtained by punching a larger sheet or strip having a surface provided with adhesive, in which the exceeding part, i.e. the part not including the label or the labels 1, is removed after the application of the same on the support 3.

The flexible label 1 and the flexible membrane 2 can be obtained from a film of a plastic material suitable for coming into contact with food belonging in particular to the group consisting of polypropylene (for example, between 35 and 60 microns thick), polyester (for example, between 25 and 45 microns thick) or plastic materials with equivalent characteristics. In particular, the film of the layer of the flexible membrane 2 may comprise paper, polyethylene terephthalate and/or enriched polypropylene or a PE- Evoh laminate. The film of the flexible label 1 can be formed by a laminate with several layers, in particular comprising the same plastic materials, polyethylene, paper, aluminum and/or a polyamide film (for example between 10 and 20 microns thick), or a PE-Evoh-PE laminate. Further, the film of the flexible label 1 may be formed from recyclable materials such as polylactic acid and/or may be a multilayer laminate, comprising an inner layer, which comprises the lower surface la, made for example in a material among those indicated above, as well as an outer layer, which comprises the upper surface, preferably made of a barrier material which increases the impermeability of the label 1.

Preferably, the material forming the flexible label 1 is less rigid than the material forming the flexible membrane 2. For example, the flexible label may comprise a combination of polypropylene, having a thickness of about 30 microns, and PE-Evoh, having a thickness of about 40 microns, while the flexible membrane 2 may comprise a layer of polyethylene terephthalate, having a thickness of about 12 microns. In another embodiment, the flexible label 1 comprises a PE-Evoh-PE layer which has a thickness of 35-45 microns and/or a polypropylene layer which has a thickness of 45-55 microns, while the flexible label 2 comprises a layer of polyethylene terephthalate having a thickness of 25-35 microns.

One or both surfaces of the flexible membrane 2 are treated with a material, preferably compatible with a food use, which is suitable to make it non-adherent or limitedly adherent, in particular silicone or vaseline oil, which is then dried, so that the flexible membrane 2 is solid.

The adhesive layer applied to the lower surface la of the flexible label 1 may be a pressure-activated adhesive or PSA (Pressure Sensitive Adhesive), in particular an aqueous-based acrylic or UV or acrylic cross-linking adhesive with an organic solvent, or a silicone based adhesive for high temperatures (up to 250 ⁰ C).

Further features of the materials and of the manufacturing process of the flexible label 1 and of the flexible membrane 2 are described in the European patent 2275252 and in the publication WO 2015/111015 Al.

The flexible label 1 is shaped with at least one incision lb so as to connect the two surfaces of the flexible label 1. In particular, the incision lb can be rectilinear or curvilinear or, as in the present embodiment, can be closed, so as to define at least one opening, for example a substantially circular hole having a diameter not greater than 10 mm, in the flexible label 1, so that at least one portion 2b of the upper surface of the flexible membrane 2 is not covered by the flexible label 1. In an alternative embodiment, the incision lb forms a recess on the edge of the flexible label 1, such that a portion of the perimeter of the flexible label 1 passes over the flexible membrane 2 and this portion then divides the flexible membrane 2 in a portion 2b not covered by the flexible label 1 and in at least one remaining portion covered by the flexible label 1. In this alternative embodiment, the area of the portion of the flexible membrane 2 covered by the flexible label 1 is in any case larger than the area of the portion of the flexible membrane 2 not covered by the flexible label 1. The flexible label 1 may have a substantially polygonal and/or curvilinear shape, for example substantially square, circular or triangular with corners rounded and provided with anti-tampering notches lc.

The flexible label 1 preferably extends over an area x mm wide and y mm long, with x and y between 15 and 50, in particular between 30 and 40, more particularly between 33 and 36. The flexible label 1 extends beyond the flexible membrane 2. The extension of the flexible membrane 2 is in particular included between 10% and 80% of the extension of the flexible label 1. As shown in the figures, no liquids are arranged between the flexible label 1 and the flexible membrane 2.

Therefore, at least one portion of the lower surface la of the flexible label 1 is not in contact with the flexible membrane 2 and surrounds the flexible membrane 2. The distance between the edges of the flexible label 1 and of the flexible membrane 2 is prevalently between 5 and 15 mm.

The flexible membrane 2 preferably has a substantially polygonal and/or curvilinear shape, so that the flexible membrane 2 can have a tapered shape towards the incision lb of the flexible label 1. In the present embodiment, this tapered shape of the flexible membrane 2 is substantially semicircular, whereas in other embodiments the flexible membrane 2 may have another tapered shape, for example substantially trapezoidal, pentagonal or triangular, also with one or more curved sides.

The lower surface la of the flexible label 1 comprises at least one non-stick portion 4 which can be obtained by avoiding the application of the adhesive in this portion or more preferably by applying and drying a substance suitable for preventing or limiting adhesion, in particular a paint or non-stick lacquer, for example of the type known in the art as "glue killer". Therefore, this substance, once applied on the adhesive of the flexible label 1, deactivates its adhering action. The non-stick portion 4 can also be obtained by applying a shaped film on the adhesive of the flexible label 1. The non- stick portion 4 preferably has a tapered shape towards the incision lb of the flexible label 1, for example a partially rectangular shape, i.e. with three substantially perpendicular sides and rounded corners and with a fourth substantially convex side facing the incision lb, while in other embodiments it may have another tapered shape, for example substantially trapezoidal, pentagonal or triangular also with one or more curved sides. The non-stick portion 4 at least partially covers a portion 2c, preferably tapered towards the incision lb, of the flexible membrane 2. In particular, the distance d between the incision lb of the flexible label 1 and the non-stick portion 4 is preferably between 2 and 10 mm.

With reference to Figure 3, it is seen that a sheet 5 suitable for closing or forming a food container, for example a sheet of plastic material which can be used to make a bag or to be heat-sealed to the edges of a rigid tray, comprises at least one incision 5a which connects the two surfaces of the sheet 5 and which can be covered by the adhesive valve. The incision 5a in the sheet 5 can be rectilinear, curvilinear or closed, so that the portion of the sheet 5 surrounded by the incision 5a can be removed and form an aperture, for example substantially circular. In an alternative embodiment, the incision 5a in the sheet 5 can be arched, so as to form a tongue-shaped portion which can be bent towards the adhesive valve or to the opposite side. At least one adhesive layer 6, in particular PSA adhesive, for example of rectangular shape, is preferably arranged on a portion of the sheet 5 beside the incision 5a.

Further embodiments may comprise a plurality of incisions 5a, for example a group of closed incisions suitable to form small apertures, i.e. small holes, in a portion of the sheet 5.

With reference to Figures 4 and 5, it is seen that the lower surface la of the flexible label 1 can be joined to the upper surface of the sheet 5 thanks to the adhesive applied to the lower surface la, so that the flexible membrane 2 is arranged between the flexible label 1 and the sheet 5. In particular, the non-stick portion 4 of the adhesive valve at least partially covers the incision 5a of the sheet 5, so that the incision 5a can connect the non-sticking portion 4 with the surface of the opposite sheet 5 to the adhesive valve. The flexible membrane 2 of the adhesive valve at least partially covers the adhesive layer 6. The adhesive layer 6 is also arranged on the sheet 5 between the incision lb of the flexible label 1 and the incision 5a of the sheet 5.

Referring to Figure 6, it can be seen that if in a container comprising the sheet 5 a pressure substantially greater than the pressure outside the container is generated, for example caused by cooking food in the container, the gases 7 under pressure in the container move the non-stick portion 4 of the flexible label 1 from the flexible membrane 2, thus creating a passage between the flexible label 1 and the flexible membrane 2, preferably held on the sheet 5 by the adhesive layer 6, so that these gases 7 pass towards the outside of the container through the incision 5a of the sheet 5, the space between the flexible membrane 2 and the flexible label 1 and the incision lb of the flexible label 1. When the pressure in the container returns to be substantially equal to the external pressure, the flexible label 1 may again adhere to the flexible membrane 2, thus closing the passage of gases 7 between the sheet 5 and the flexible label 1, in particular thanks to the elasticity of the materials and to electrostatic forces and/or Van der Waals forces which are created between the flexible membrane 2 or the sheet 5 and the flexible label 1.

With reference to Figure 7, it is seen that in a first operating step of the manufacturing process of the adhesive valve a strip 11 preferably wound around a bobbin 12 is pulled in the direction of the arrows by one or more first auxiliary rollers 13. The strip 11 comprises a first layer 14 of the same material of the above mentioned flexible labels 1, which is joined by at least one adhesive layer to a second layer 15 of the same material of the flexible membranes 2 and the support 3 mentioned above. The first layer 14, the second layer 15 and/or the adhesive layer between them are preferably continuous and uniform. A first auxiliary roller 13 separates the first layer 14 from the second layer 15, which are pulled separately by other auxiliary rollers 13.

The first layer 14 of the strip 11 is provided with a series of non-stick portions 4 placed at regular distances one after the other on the adhesive surface of the first layer 14, facing upwards, by an applicator 16 which applies and dries an anti-adherent substance on the non-stick portions 4. The first layer 14 is then provided with a series of incisions lb placed at the same regular distances between the non-stick portions 4 by a perforator 20, for example a laser perforator, with the aid of a sensor 21 adapted to detect the position of a non-stick portion 4 on the first layer 14, so that the distance d between a non-stick portion 4 and the adjacent incision lb is maintained. The incisions lb in the first layer 14 can also be made before making the non-stick portions 4.

The second layer 15 of the strip 11 is joined to the first layer 14 by one or more second auxiliary rolls 23, with the non-stick portions 4 arranged between the first layer 14 and the second layer 15.

The first layer 14 of the strip 11 is then punched by a first mechanical punch- cutter, in particular a roller punch-cutter 24, to form in the first layer 14 a series of flexible labels 1 according to the present description around the non-stick portions 4, with possible removal of the excess material (not shown in the figure). The second layer 15 of the strip 11 is punched by a second mechanical punch-cutter, in particular a roller punch-cutter 25, to form in the second layer 15 a series of flexible membranes 2 according to the present description and the support 3 which surrounds them. The strip 11 comprising the support 3 with a series of adhesive valves described above, which are formed by a flexible label 1, a flexible membrane 2 and a non-stick portion 4 arranged between the flexible label 1 and the flexible membrane 2, is then rolled up on a bobbin 26.

Figures 8 to 31 show further embodiments of the adhesive valve which comprise a flexible membrane 2, so that they will be described by highlighting the differences with respect to the first embodiment described above.

Figures 8 and 9 show a second embodiment which differs from the first embodiment for the presence, in addition to the incision lb, of further incisions Id which connect the two surfaces of the flexible label 1. Preferably, these further incisions Id have a curvilinear shape and they are preferably arranged symmetrically with respect to the incision lb. The flexible membrane 2 has a substantially rectangular shape with rounded or smoothed corners and covers the incisions lb and Id formed in the flexible label 1. The non-stick portion 4 has a substantially rectangular shape with a convex side facing the incision lb.

Figures 10 and 11 show a third embodiment which differs from the second embodiment in that the flexible membrane 2 is covered by the incision lb in the flexible label 1, not by the further incisions Id, which are arranged substantially along an edge of the membrane flexible 2, which is in turn arranged between the non-stick portion 4 and the further incisions Id. Furthermore, in this embodiment there are weakening incisions 8a, 8b in the flexible label 1 which extend partially within the thickness of the flexible label 1 starting from the upper surface without reaching the lower surface la, or vice versa. The weakening incisions 8a, 8b may be rectilinear, curvilinear or mixed as in the present embodiment. Preferably, the weakening incisions 8a, 8b are obtained in the flexible label 1 in correspondence of the membrane 2 and/or of the non-stick portion 4. In particular, an incision 8a is arranged centrally with respect to two other incisions 8b. The incisions 8a, 8b favor the deformation and the raising of the flexible label 1 during the release of the gases 7. In the present embodiment the flexible label 1 is formed by two layers and the weakening incisions 8a, 8b completely cross the layer of the flexible label 1 comprising the lower surface la of the flexible label 1.

The manufacturing process of the present embodiment corresponds to the process used for the first embodiment but includes a further step in which the weakening incisions 8a, 8b are formed on the first layer 14, for example by means of the perforator 20 of Figure 7, when making the incisions lb and Id, which instead cross the first layer 14.

Figures 12 and 13 show a fourth embodiment of the present description, which, unlike the first embodiment, has a plurality of non-stick portions 4. In particular, two non-stick portions 4 are arranged symmetrically around the incision lb in the flexible label 1. The profile of each of the non-stick portions 4 is made so as to surround at least partially the incision lb, while maintaining a certain distance between a non-stick portion 4 and the incision lb. The non-stick portions 4 are completely covered by the flexible membrane 2. In this embodiment the flexible membrane 2 has at least one incision 9 which has a linear, curvilinear, mixed or closed shape and connects the two surfaces of the membrane 2. The incision 9 is obtained in the flexible membrane 2 at the non-stick portions 4 of the flexible label 1. The incision 9 is contained at least partially or completely inside the area subtended by the non-stick portions 4. The incision 9 in the flexible membrane 2 facilitates the deformation of the membrane 2 and/or creates a path for the release of the gases 7.

Figure 13 shows a sheet 5 suitable for closing or forming a food container, coupled with the flexible label 1 and the flexible membrane 2. In particular, in this embodiment, the sheet 5 has closed incisions 5a which form two holes circular. The adhesive layer 6, for example of rectangular shape, is preferably arranged between the incisions 5a and/or at a central region of the flexible label 1 which comprises the incision lb. Preferably, the flexible membrane 2, in particular its portion surrounded by the incision 9, covers at least partially, in particular completely, the incisions 5a of the sheet 5.

The manufacturing process of this embodiment is similar to that of the first embodiment and further comprises a step (not shown in Figure 7) in which the incisions 9 are formed on the second layer 15, for example by means of a further perforator, after the second layer 15 has been joined to the first layer 14, or by means of the same roller punch-cutter 25 when forming the flexible membranes 2 in the second layer 15.

Figure 14 illustrates a fifth embodiment of the adhesive valve according to the present description, wherein the flexible label 1 and the flexible membrane 2 have a triangular shape with rounded or smoothed corners. The non-stick portion 4 on the lower surface la of the flexible label 1 does not cover a portion of the flexible membrane 2 but is arranged to at least partially surround the profile of the flexible membrane 2. The non-stick portion 4 is V-shaped and is arranged adjacent to the flexible membrane 2, in particular around two edges of the flexible membrane 2.

Figure 15 shows a sixth embodiment of the adhesive valve, in which the flexible label 1 has a square shape with rounded or smoothed corners, as well as a plurality of incisions lb, preferably rectilinear and/or parallel to each other. The flexible membrane 2 has substantially the same shape of the flexible label 1. The non-stick portion 4 has a substantially rectangular shape and is arranged straddling an edge of the flexible membrane 2, preferably so that the major side of the rectangle is parallel to the incisions lb in the flexible label 1.

Figure 16 shows a seventh embodiment of the adhesive valve, wherein the flexible label 1 has a substantially circular shape. The flexible label 1 has a plurality of incisions lb, preferably curvilinear and arranged so as to form at least one arc, and a plurality of non-stick portions 4 joined together so as to form an arc with a radius of curvature greater than the radius of the arc formed by incisions lb. Preferably, such non-stick portions 4 have a tapered shape towards the incisions lb. For example, the non-stick portions 4 are triangles with a vertex facing the incisions lb. The flexible membrane 2 has a substantially circular shape and comprises an incision 9, substantially arc-shaped, at least partially covered by the arc formed by the non-stick portions 4.

Figure 17 shows an eighth embodiment of the adhesive valve, wherein the flexible label 1 has a substantially circular shape and has a substantially arcuate incision lb. The non-stick portion 4 also has a substantially arcuate shape, with a radius of curvature greater than the radius of the arc formed by the incision lb. The flexible membrane 2 has a substantially circular shape and comprises a substantially arcuate incision 9 at the arc formed by the non-stick portion 4.

As for the fourth embodiment, the manufacturing process of the seventh and eighth embodiments further comprises a step of making the incisions 9 on the second layer 15, for example by means of a perforator.

Figure 18 shows a ninth embodiment of the adhesive valve, wherein the flexible label 1 has a substantially square shape with rounded or smoothed corners, as well as a plurality of incisions lb, preferably arcuate and/or arranged so as to form a cross or star. The flexible membrane 2 has a substantially circular shape, while one or more non-stick portions 4 have a substantially arcuate shape and/or are arranged straddling one edge of the flexible membrane 2, preferably so that most of the edge or edges of the flexible membrane 2 are adjacent to a non-stick portion 4.

Figure 19 shows a tenth embodiment of the adhesive valve, in which the flexible label 1 has a substantially pentagonal shape, with rounded or smoothed corners, preferably with a side substantially perpendicular to the two adjacent sides. At least one incision lb, preferably wavy, is formed in the flexible label 1. The flexible membrane 2 has a substantially circular shape, while one or more non-stick portions 4 have a substantially arcuate shape and/or are arranged straddling an edge of the flexible membrane 2, preferably so that most of the edge or edges of the flexible membrane 2 are adjacent to a non-stick portion 4. The non-stick portions 4 may have a tongue 4a extending towards the incision lb. The flexible label 1 may comprise at least one further incision le which connects the upper surface with the lower surface la of the flexible label 1 and is shaped to form an anti-tamper seal. The further incision forming the seal is shaped to define also an appendix 10 which projects towards the inside of the seal and is joined to a portion of the flexible label 1 external to the seal. An additional non-stick portion 4 is disposed around the incision le, preferably straddling the appendix 10. The further incision le occupies in the flexible label 1 at least one surface equal to a circle having a diameter of at least 13 mm, preferably greater than 15 mm and/or has a substantially circular or ellipse arc shape. At least two portions of the further incision le define the appendix 10 and are substantially parallel to each other and/or parallel to a diameter of the perimeter of the further incision le. At least one free end of at least one of the portions of the further incision le defining the appendix 10 is connected to a curved portion extending in the further incision le and externally with respect to the appendix 10. The end of the appendix 10 which is joined to the portion of the flexible label 1 faces the edge of the flexible label 1 closer to the further incision le. The further incision le can be made together with the incision lb in the manufacturing process described above.

Figure 20 shows an eleventh embodiment of the adhesive valve, wherein the flexible label 1 has a substantially square shape with rounded or smoothed corners, as well as one or more arcuate incisions lb. The flexible membrane 2 has a substantially circular shape, while one or more non-stick portions 4 have an arcuate shape and completely cover respective incisions 9, also arcuate, in the flexible membrane 2. Figure 21 shows the flexible label 1 applied on a sheet 5 provided with small pore-shaped incisions 5a, which are covered by the flexible membrane 2 and are arranged between the incisions lb of the flexible label 1 and/or between the incisions 9 of the flexible membrane 2.

Figures 22 to 25 show respectively a twelfth, thirteenth, fourteenth and fifteenth embodiment of the adhesive valve, similar to the eleventh embodiment, wherein the flexible membrane 2 has no incisions and the non-stick portions 4 are arranged straddling an edge of the flexible membrane 2. The non-stick portions 4 of the embodiment of Figure 24 have at least one tapered portion 4a facing a respective incision lb in the flexible label 1. The non-stick portions 4 of the embodiment of Figure 25 are adjacent and substantially outside an edge of the flexible membrane 2.

Figures 26 to 30 show further embodiments of the adhesive valve, similar to the thirteenth embodiment, wherein the flexible membrane 2 has two or more incisions 9 which are covered by a non-stick portion 4 and start from an edge of the flexible membrane 2, preferably in a substantially perpendicular and/or radial way from this edge. In the embodiments of Figures 28, 29 and 30 the flexible membrane 2 is elliptical and/or the incisions lb in the flexible label 1 can intersect at least one edge of the flexible membrane 2. In the embodiments of Figures 29 and 30 one or more incisions 9 in the flexible membrane 2 intersect at least one incision lb in the flexible label 1. In the embodiment of Figure 30 two incisions lb in the flexible label 1 intersect the edge of the flexible membrane 2 and two other incisions lb in the flexible label 1 do not intersect the edge of the flexible membrane 2.

In the embodiment of Figure 31, four incisions lb in the flexible label 1 are completely surrounded, however spaced from, by a non-stick portion 4 straddling the edge of the flexible membrane 2.

Any variants or additions may be made by those skilled in the art to the embodiments described and illustrated herein while remaining within the scope of the following claims. In particular, further embodiments may include the technical features of one of the following claims with the addition of one or more technical features described in the text or illustrated in the drawings, taken singularly or in any mutual combination.

Claims

1. Adhesive valve comprising at least one flexible label (1) having an upper surface and a lower surface (la), wherein at least the lower surface (la) is provided with adhesive and at least one incision (lb, Id) connects the two surfaces, wherein at least one flexible membrane (2) having an upper surface and a lower surface (2a) adheres to at least one portion provided with adhesive of the lower surface (la) of the flexible label (1), wherein the lower surface (2a) of the flexible membrane (2) is substantially non- adhesive, wherein a portion (2b) of the flexible membrane (2) is arranged under the incision (lb, Id) of the flexible label (1), wherein the flexible label (1) extends beyond the flexible membrane (2), characterized in that the lower surface (la) of the flexible label (1) comprises at least one non-stick portion (4) that is adjacent to or at least partially overlapping the flexible membrane (2) and is arranged at distance (d) from the incision (lb, Id) in the flexible label (1).

2. Adhesive valve according to the preceding claim, characterized in that the flexible membrane (2) comprises at least one incision (9) which connects its two surfaces.

3. Adhesive valve according to the previous claim, characterized in that the incision (9) in the flexible membrane (2) is contained completely or at least partially inside the area subtended by the non-stick portion (4) of the flexible label (1).

4. Adhesive valve according to one of the preceding claims, characterized in that the upper surface of the flexible membrane (2) is substantially non-adhesive.

5. Adhesive valve according to one of the preceding claims, characterized in that the non-stick portion (4) is arranged straddling at least one edge of the flexible membrane (2).

6. Adhesive valve according to one of the preceding claims, characterized in that the flexible label (1) comprises at least one further incision (le) which connects the upper surface with the lower surface (la) and is shaped to form a seal.

7. Adhesive valve according to one of the preceding claims, characterized in that the flexible label (1) comprises at least one further incision (8a, 8b) which does not connect its two surfaces.

8. Sheet (5) which has two surfaces and comprises at least one incision (5a) connecting the two surfaces, characterized in that this incision (5a) is covered by an adhesive valve according to one of the preceding claims.

9. Sheet (5) according to the previous claim, characterized in that the incision (5a) in the sheet (5) is at least partly covered by the flexible membrane (2) of the adhesive valve.

10. Sheet (5) according to claim 8 or 9, characterized in that the flexible membrane (2) of the adhesive valve covers at least partially at least one layer of adhesive (6) arranged on a portion of the sheet (5) next to the incision (5a) in the sheet (5).

11. Food container, characterized in that it comprises at least one adhesive valve according to one of the claims from 1 to 7 or at least one sheet (5) according to one of the claims 8 to 10.

12. Support (3) in sheet or strip comprising one or more rows of adhesive valves according to any one of claims 1 to 7, wherein the support (3) is made of the same material of the flexible membrane (2) of the adhesive valves and is punched in order to obtain one or more rows of flexible membranes (2) which are covered by respective flexible labels (1) of the adhesive valves.

13. Process for manufacturing an adhesive valve according to one of the claims 1 to 7, characterized in that it comprises the following operating steps:

making at least one non-stick portion (4) on the adhesive surface of a first layer

(14);

making at least one incision (lb, Id, le) in the first layer (14);

punching the first layer (14) around the non-stick portion (4) and the incision (lb, Id, le) to form the adhesive label (1) of the adhesive valve.

joining the first layer (14) to a second layer (15), with the non-stick portion (4) arranged between the first layer (14) and the second layer (15);

punching the second layer (15) to form at least one flexible membrane (2) of the adhesive valve in the second layer (15).

14. Process according to the previous claim, characterized in that at the beginning of the process the first layer (14), the second layer (15) and/or the adhesive layer comprised between these two layers (14, 15) are continuous and uniform.

15. Process according to claim 13 or 14, characterized in that it comprises at least one of the following further operating steps:

making in the first layer (14) at least one incision (8a, 8b) which does not connect its two surfaces;

making at least one incision (9) in the second layer (15) which connects its two surfaces.