WO2022003647A1

WO2022003647A1 - Anti-blocking adhesive valve, sheet including this adhesive valve, packaging made from this sheet and process for producing them

Info

Publication number: WO2022003647A1
Application number: PCT/IB2021/055969
Authority: WO
Inventors: Valerio Binda
Original assignee: Masterpack S.P.A.
Priority date: 2020-07-03
Filing date: 2021-07-02
Publication date: 2022-01-06
Also published as: IT202000016132A1

Abstract

The invention relates to a food container, a semi-finished product from which this container is made, an adhesive valve incorporated in said semi-finished product, and the method for manufacturing them, wherein the adhesive valve (100) comprises: an adhesive label (101 ) which has an upper surface (101a) and a lower surface (101 b), where at least one first incision (102) connects the two upper and lower surfaces so as to form a passage for a fluid. a covering membrane (103) applied to the upper surface (101a) of the adhesive label (101 ). The adhesive valve (100) has, between the adhesive label (101 ) and the covering membrane (103); a first zone (A), in which the adhesive label (101 ) and the covering membrane (103) are not joined together by means of adhesive and which, viewing the adhesive valve (100) in plan view, overlaps the first incision (102); a second zone (B), in which the adhesive label (101 ) and the covering membrane (103) are not joined together by means of adhesive, and which is adjacent to the first zone (A) or integral therewith so as to define with the latter a discharge channel for a fluid, which extends from the at least one first incision (102) towards a perimeter edge of the covering membrane (103); a third zone (C), in which a second adhesive (105) fixes the covering membrane (103) to the adhesive label (101 ).

Description

ANTI-BLOCKING ADHESIVE VALVE, SHEET INCLUDING THIS ADHESIVE VALVE, PACKAGING MADE FROM THIS SHEET AND PROCESS FOR

PRODUCING THEM

TECHNICAL SECTOR

The present description relates to an anti-blocking adhesive valve, a sheet which comprises said valve and a food container made with this sheet, as well as a method for manufacturing them

This flexible adhesive valve may be applied onto incisions or openings formed on hermetically sealed containers, for example for coffee, and similar packaging for shelf products, where it is required to be able to discharge gas from the inside - while always maintaining a sealed closure with respect to the entry of gas - in order to avoid the visual effect of an inflated package.

In particular, the adhesive valve in question allows the discharging of gas from inside a container incorporating it also in the case where it is pressed against another container or against another object, for example when a stack of containers is formed such that the valves of the containers are acted on by other containers in the stack.

The adhesive valve in question in particular is able to provide an "anti blocking" effect owing to the weak molecular interaction between the surfaces which define a discharge duct therein; moreover the adhesive valve in question may be preferably of the multi-laminated type made of polymeric material with control of the blocking effect, i.e. the tendency of the polymeric film to adhere onto another polymeric layer.

The present teaching also relates to a sheet and a container for food products comprising said adhesive valve as well as a method for manufacturing the adhesive valve and/or the sheet which comprises it.

PRIOR ART

Nowadays adhesive valves are known and very popular, as described for example in EP2275252, WO2015/111015A1 and WO/2019/0771536 in the name of the present Applicant. A conventional valve, described in US20060076058, is also known, said valve comprising an adhesive label having a plurality of holes and a flexible membrane which covers the holes so as to keep them closed in a rest condition and which adheres to the flexible label.

This adhesive valve is configured to be associated with a sheet suitable for forming a container for food products.

In particular, the flexible membrane has a venting hole which, when the adhesive valve is fixed to the sheet, is arranged above a plurality of holes formed in the sheet, so as to discharge gas from the inside of the container.

The hole in the membrane is out-of-alignment with the holes in the flexible label so that, if gas pushes out from inside the sheet through the holes in the latter and the hole in the membrane, it tends to raise the flexible label, working its way in between it and the flexible membrane, thus opening up a discharge channel which passes towards and through the holes in the flexible label.

One problem associated with this conventional adhesive valve is that, if an object is placed on top of the container provided with this valve, pressing against it, the valve is kept closed and venting of the gas is thus prevented or hindered.

This drawback may for example result in the unattractive swelling effect of food containers in the event of them being stacked with the valves compressed.

SUMMARY

The problem underlying the present teaching is therefore that of making it possible to perform the discharging of gases from food containers provided with valves, even when they are stacked or arranged on top of each other with the valves covered and in some cases compressed.

In connection with this task, an object of the present teaching is to provide an adhesive valve which allows faster venting of gases than conventional adhesive valves should the valve be compressed or an object be placed on top of it.

Another task of the present teaching is to propose an adhesive valve which is resistant, while remaining sensitive to pressures even of a limited nature, for example of the order of 4 mbar or less.

Another task of the present teaching is to provide an adhesive valve which is simple and low-cost to implement, while allowing the creation of adhesive valves which allow gases to be discharged at low pressures and more rapidly compared to conventional valves.

Yet another task of the present teaching is to propose a semi-finished product for forming a food container which incorporates said adhesive valve, such a food container and a method for manufacturing the adhesive valve or the semi-finished product, which fulfil the aforementioned tasks.

This task, as well as these and other objects which will become clearer below, are achieved by an adhesive valve, a semi-finished product, a container and a method according to the respective attached independent claims.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and characteristic features of the adhesive valve, the semi-finished product, the container and the method according to the present description will become clear to persons skilled in the art from the following detailed and non-limiting description of embodiments thereof with reference to the attached drawings in which:

Figure 1 shows in schematic form a portion of a semi-finished product according to the present teaching in which some parts have been partially removed so that other parts may be seen more easily, in a perspective view, where the dimensions of the parts shown have been exaggerated so that they be more easily understood;

Figures 2a to 2d show in schematic form variants of an adhesive label of an adhesive valve according to the present teaching, in a top plan view; Figures 3a to 3f show in schematic form first variants of a third zone C provided with a second adhesive according to the present teaching, in a top plan view;

Figures 4a to 4I, 5m and 5n show in schematic form second variants of a third zone C provided with a second adhesive according to the present teaching, in a top plan view, superimposed on an example of a variant of an adhesive label of an adhesive valve according to the present teaching; Figures 5a to 51 show in schematic form variants of a non-stick portion E, superimposed on examples of variants of an adhesive label of an adhesive valve according to the present teaching;

Figure 6 shows in schematic form a cross-section through an adhesive valve according to the present teaching, where the proportions are not to actual size in order to facilitate comprehension;

Figure 7a shows in schematic form a cross-section through an adhesive label of an adhesive valve according to the present teaching, where the proportions are not to actual size in order to facilitate comprehension; Figure 7b-7h: shows a plan view of possible embodiments of an adhesive valve according to the present invention;

Figure 8a shows in schematic form a protective membrane of an adhesive valve according to the present teaching in a bottom plan view, provided with a protective layer;

Figures 8b to 8g show further embodiments of an adhesive valve according to the present invention, provided with separation zones;

Figures 9 and 10 show in schematic form parts of a plant for the production of an adhesive valve, a semi-finished product and/or a storage means according to the present teaching;

Figures 11 a-11 d show further embodiments of an adhesive valve according to the present invention, provided with discharge passages, in which some components are not shown so that others are more clearly visible.

DETAILED DESCRIPTION

With particular reference to the said figures, an adhesive valve 100 according to the present teaching comprises:

- an adhesive label 101 which has an upper surface 101a and a lower surface 101 b, where a first incision 102 connects the two surfaces, i.e. upper surface 101a and lower surface 101b, so as to form a passage for a gas; at least one portion of the lower surface 101 b may be provided with a first adhesive 101 c;

- a covering membrane 103 applied to the upper surface 101 a of the adhesive label 101 ;

The adhesive valve 100 has, between the adhesive label 101 and the covering membrane 103:

- a first zone A, in which the adhesive label 1010 and the covering membrane 103 are not joined together by means of adhesive and which, viewing the adhesive valve 100 in plan view, overlaps the first incision 102 at least partially;

- a second zone B, in which the adhesive label 101 and the covering membrane 103 are not joined together by means of adhesive, and which is adjacent to the first zone or integral therewith so as to define a discharge channel for a gas, and which extends from the at least one first incision 102 towards a perimeter edge of the covering membrane 103;

- a third zone C, in which a second adhesive 105 fixes the covering membrane 103 to the adhesive label 101 .

The first incision 102 may consist of a single hole passing through the adhesive label 110, for example as can be seen in Figure 1 and 2a, or of a plurality of micro holes passing through the adhesive label 101 which may be formed continuously, for example as shown in Figures 2b and 2d, or in register, for example as shown in Figure 2c.

The at least one first incision 102 may optionally comprise one or consist of a linear incision or a plurality of linear incisions which may be curved and combined with one or more though-holes, such as the linear incisions indicated by the reference numbers 102a in Figure 2d.

The adhesive label 101 and the covering membrane 103 extend mainly in a first and second direction having a thickness in a third direction, perpendicular to the first two directions.

They are stacked in the third direction so as to be superimposed and define between them a discharge channel which extends in a direction substantially perpendicular to this third direction. For the sake of constructional simplicity they may have a perimeter which is substantially superimposed, in plan view, namely along said third direction.

Or else the covering membrane 101 may extend beyond the perimeter of the adhesive label 101 so as to be fixed, by means of the second adhesive 105, to a sheet 200 to which the adhesive label 101 may be fixed, as can be seen by way of a non-limiting example in Figures 5a, 5b, 5c, 11a and 11 b where the perimeter of the covering membrane 103 surrounds the perimeter of the adhesive label 101 .

Clearly, for example in order to ensure better deformability of the adhesive valve 100, the opposite arrangement may be provided, namely the adhesive label 101 may extend beyond the perimeter of the covering membrane 103.

In general, it can be understood therefore how an adhesive valve 100 according to the present teaching allows the discharging of a gas, as for example shown in Figure 1 , by means of arrows, from a container incorporating the adhesive valve 100, even when the valve is compressed, namely in particular in the case where containers are stacked or when the container rests on a face thereof which comprises the adhesive valve 100.

In other words, even though a foreign object presses against the covering membrane 103, since the discharge channel defined by the first and second zones A and B extends parallel thereto, the gas may escape laterally from the adhesive valve 100, as can be seen in Figure 1 , where the path followed by the gas is indicated by arrows.

Indeed the channel formed by the second zone B and optionally also by the zone A extends in fact parallel to the wall of the container which incorporates the adhesive valve 100, making it easier for the gas to pass through it compared to the conventional solutions which envisage a flow path for the gas which is overall perpendicular to the wall of the containers since the openings in conventional vales define a passage which allows the gas to pass only in this direction.

With particular reference to Figures 3a to 3f, the form and the arrangement of the first, second and third zones A, B and C may be chosen depending on the particular implementational requirements of the present teaching.

For example, the discharge channel formed by the first and second zones A and B may be broader, as shown in Figure 3a or 3b, or narrower, as shown in Figures 3c, 3d, 3e, 4d or 4e, than the width of first incision 102 when the latter forms a hole which is for example central to the adhesive label 101 .

Thus, for example, it may have a greater venting speed or smaller venting speed, respectively.

Said discharge channel may have a spoke-like form, as for example shown in Figures 3f, 4a, 4b, 4f, which may therefore have a plurality of parts which diverge for example form the first zone A.

In this way, any blockage of one of the parts, for example, due to soiling or damage to the adhesive valve 100, may be compensated for by the presence of the other parts.

The size and number of these parts may be chosen so as to modulate the discharge pressure of the gas and the discharge speed thereof, in a manner known per se.

Moreover, the discharge channel may extend along a path which has a curved or winding form, as shown for example in Figure 4c or 4g, so as to allow sophisticated adjustment of both the opening pressure and the venting speed by means of modulation of the length and width of the discharge channel along this path.

The adhesive valve 100 may also comprise at least one auxiliary passage which crosses the covering membrane 103 and, if present, any protective membrane 107 described below.

Said at least one auxiliary passage may comprise incisions 1031 and/or holes 1032 which, in a plan view of the adhesive valve 100, do not overlap the first zone A, but are arranged to overlap the second zone B so as to define one or more outlets of the discharge channel, transverse to the thickness of the adhesive valve 100.

Preferably, incisions 1031 and/or holes 1032 will be provided in specular positions with respect to the first zone A so as to induce a gas flow which crosses the discharge channel as for example shown in broken lines in Figures 11 a and 11 b and in dot-dash lines in Figures 11 c and 11 d.

The incisions 1031 may extend as far as the edge of the covering membrane 103, in a plan view of the adhesive valve 100.

Thus, for example, following heating in a microwave oven of food closed inside a container with an adhesive valve according to the present invention, optimum discharging of the vapour and resealing of the adhesive valve 100 is possible.

In fact the incisions 1031 allow the covering membrane 103 to lift partially, allowing optimum discharging of the vapours also for one hour or more. Once the cooking has been completed and therefore discharging of the vapour completed, the covering membrane 103 rests again on the adhesive label 101 , therefore ensuring hermetic closure again of the adhesive valve 100.

Recent tests have shown that the covering membrane 103 readapts in an optimum manner to the surface of the adhesive membrane 101 with the hermetic closure of the adhesive valve 100 being restored also in the event of swelling or bending of the container part on which the adhesive valve 100 is fixed or owing to deformation due to the high temperature and to the long dwell time at this temperature due, for example, to the cooking time.

With particular reference to Figures 1 1a and 11 b, the perimeter of the covering membrane 103 may be configured to extend beyond the perimeter of the adhesive label 101 so as to be fixed, by means of the second adhesive 105, to the sheet 200 of the food containers.

For example, according to a plan view of the adhesive valve 100, the perimeter of the covering membrane 103 may surround the perimeter of the adhesive label 101 , defining an annular portion of the covering membrane 103 which is free from the adhesive label 101 , i.e. which does not overlap it, and therefore is designed to be fixed to the sheet 200.

In such a case, the at least one auxiliary passage, for example in the form of incisions 1031 and/or holes 1032, will define the only cross-section for exit of the gas through the adhesive valve 100. In order to facilitate the discharge of gas, the adhesive valve 100 may comprise a separator element 104 located between the adhesive label 101 and the covering membrane 103 in the first zone A and/or in the second zone B and designed to space the adhesive label 101 from the covering membrane 103 so as to allow the separation of the label and membrane, even when they compressed against each other, in order to allow a fluid to pass between them.

The separator element 104 may comprise a paint and/or an insert which may be made of polymeric material.

The separator element 104 may have a thickness of between 1 and 300 microns so as to separate correspondingly the adhesive label 101 from the covering membrane 103.

The separator element 104 may comprise:

- at least one long section which extends at least mainly in an extension direction along which the second zone B extends, as for example shown in Figures 1 and 2a and/or

- at least one curved section which extends in the first zone A and/or in the second zone B, for example as shown in Figures 2b and 2c.

Moreover, with particular reference to Figures 5i and 5I, the separator element 104 may consist of a plurality of layers, for example two layers.

Figures 5j and 5k show examples of two possible layers 1041 and 1042 which, superimposed, form a separator element, as shown by way of example in Figure 5i or 5I.

These layers 1041 and 1042 may consist of an opaque paint.

A first one 1041 of these layers 1042 and 1042 may extend, in plan view, so as to cover only partially the second one 1042 of the layers 1041 and 1042 so as to form in cooperation therewith a plurality of preferential passages for the gas.

The adhesive label 101 and/or the covering membrane 103 are configured to adhere to each other by means of an electrostatic action in at least the second zone B, so that the channel defined by the second zone B is sealingly closed when it is not crossed by a fluid coming from the first incision 102 of the adhesive label 101 .

Depending on the particular implementational requirements of the present teaching, the adhesive label 101 and/or the covering membrane 103 may have at least one non-stick portion E configured so as to prevent or counteract the sticking together of the adhesive label 101 and the covering membrane 103 by means of the electrostatic action or by the action of the Van der Waals forces in the first zone A and/or in the second zone B.

For example, the non-stick portion E may comprise a lacquer which may be silica-based and which covers a part of the upper surface 101 a of the adhesive label 101 in the first zone A and/or in the second zone B and/or of a part of the side of the covering membrane 103 facing the upper surface 101a.

In particular, for embodiments of the present invention intended to ensure a low venting pressure of a gas contained in a package provided with the adhesive valve 100, the non-stick portion E may extend over the whole of the first zone A and the second zone B or at least over the whole of the latter, as for example shown in the versions of Figure 5i and 5I.

The non-stick portion E may be made of a resin spread with a gramme amount which may be between 0.5 g/m² and 5 g/m², able to provide an active and not simply passive non-stick effect.

The non-stick portion E may have a thickness of between about 0.1 microns and 20 microns where it is realized by means of a lacquer for example.

With particular reference to Figures 5a to 5I, the form and area and number of the non-stick portions E may be chosen so as to modulate the gas discharge pressure and ensure at the same time optimum sealing of the adhesive valve 100 with respect to the undesirable infiltration of gas from the outside through the discharge channel.

In general, the presence of a non-stick portion E which has a greater area and/or is closer to the perimeter of the adhesive valve 100, viewed in plan view, as for example shown in Figures 5a and 5b, may result in a smaller discharge pressure compared to configurations which have a smaller area of the non-stick portion E or of the non-stick portions E or a greater distance from the perimeter of the adhesive valve 100.

The adhesive label 101 and/or the covering membrane 103 may comprise a polymeric material with an additive suitable for obtaining the effect commonly known referred to as "anti-blocking effect",

This effect may be obtained by increasing the superficial roughness of a surface which comes into contact with another surface, so to prevent them sticking together.

In particular, this increase in roughness may be obtained by adding to a polymeric material a granular additive which, being dispersed in the matrix of the said polymeric material and projecting from the surface thereof, generates an effect which favours separation of the said surface from a further surface to which it would tend to adhere, as in the case of the tendency of the adhesive label 101 and/or the covering membrane 103 to stick together.

This polymeric material may also comprise or consist of branched monomers for altering and controlling the blocking effect and the weak molecular interaction so as to ensure a smaller presence of residual monomers which could migrate to the surface and which appear to be responsible for the actual blocking effect.

In PE LLD for example, the use of EVA may be limited.

Moreover, an excessive use of slip agents in the composition of the polymeric material, migrating to the surface, may adversely affect the superficial crown treatment, limiting its affinity for coating and therefore it is preferably to be avoided or limited.

It can therefore be understood how a balance in the formulation of the composition of said polymeric material, as discussed in the present document, is therefore fundamental for the purposes of a product which is stable over time in view of the specific implementation

The anti-blocking effect obtained by the adoption of at least one surface layer, the adhesive label 101 and/or the covering membrane 103 made of this material with anti-blocking additive allows a reduction in the force required to separate them and therefore reduces the pressure of a gas which, coming from a first incision 102, might pass between them.

In other words, it is possible to obtain the venting of a gas also at a very low pressure, namely at a relative pressure of about 4 mbar.

For this purpose, the adhesive label 101 and the covering membrane 103 may consist of a polymeric material with anti-blocking additive or comprise a surface layer made thereof.

The choice of the polymeric material and the additive depends on the particular implementation requirements of the present teaching.

Generally, spealing, the polymeric material may consist of LDPE, LLDPE, PP, PET or PA, in which case the concentration of the additive may be chosen as being roughly between 0.10% and 0.20% by weight and the additive may consist of synthetic silica with a surface area roughly of between 50 and 1000 m²/g and with a particle size roughly of between 2 microns and 10 microns.

Although having a less pronounced anti-blocking effect, it is also possible to use natural silica as an additive which may have a surface area roughly of between 2 and 70 m²/g and with a particle size of roughly between 40 microns and 100 microns, where LDPE or LLDPE with a concentration of additive for example of between 0.25% and 0.45% by weight may be chosen as polymeric material.

It is also possible to choose as additive: calcium, kaolin, clay and talc with a concentration roughly of between about 0.35% and 0.65% by weight of a polymeric material which may be chosen from LDPE and LLDPE.

Zeolites with a concentration of roughly between 0.20% and 0.40% by weight may be chosen as additives for example for a polymeric material chosen from LLDPE, PVC, PET and PA.

Moreover, organic anti-blocking agents such as zinc stearate, silicone oils or rubbers, polytetrafluoroethylene PFTE, glycerol monostearate GMS, erucamide, stearamide, stearyl-erucamide, ethyl-bis-stearamide EBS, may also be used.

Generally speaking, in accordance with the present teaching, silicas are the preferred additives. The choice to use natural silicas or synthetic silicas depends on the particular implementational requirements of the present teaching.

Generally speaking, natural silicas have advantageously a low cost, a masterbatch with a high concentration, absorb fewer other additives compared to synthetic silicas, but pose risks for health during production of the masterbatches, contain impurities and have a less pronounced anti-blocking effect compared to synthetic silicas.

Synthetic silicas instead are preferable because of their high surface area, the possibility of inserting reactive groups, the substantial absence of impurities, the absence of risks for health during production of the masterbatches; however, they currently have a higher cost, a maximum concentration in the masterbatch equal to 20% and a greater absorption of other additives compared to natural silicas.

The first incision 102 may form a plurality of holes 102a and/or a plurality of incisions 102b which pass through the adhesive label 101 and which may be obtained for example by means of register or continuous die-cutting of a strip of material from which a plurality of adhesive labels 101 may be obtained.

The lower surface 101 b of the adhesive label 101 may have a non-stick operating portion 106.

At least some of said holes 102a and/or incisions 102a extend from the operating portion 106 through the adhesive label 101.

The operating portion 106 may be devoid of the first adhesive 101a, as for example in the embodiment of Figure 6, or may have a film 106a which covers the first adhesive 101 c, as shown for example in Figures 7a-7h.

The film 106a may be provided with slits or through-cuts 106a through which the gas may pass and which may be staggered or aligned, across the thickness of the adhesive valve 100, so as to define a more or less winding path for the outflowing gas in order to obtain the desired discharge pressure.

This film may be formed by a film of polymeric material and/or may be obtained by means of die-cutting from a liner which, during the process for production of the adhesive valve 100, could initially be completely coated with the first adhesive 101a and which, following die-cutting of the film, is removed from the first adhesive 101 c, except along the operating portion 106 such as to leave the film which covers it.

Alternatively, the film may be formed by a lacquer which is deposited on the first adhesive 101 c along the corresponding part of the operating portion 106.

For example, the said lacquer may be material which is known in the sector as a "glue killer".

The first incision 102 and in particular the holes 102a and the incisions 102b, according to a plan view of the adhesive valve 100, may be arranged straddling an edge of the operating portion 106, for example as can be seen in Figures 7c, 7f, 7g or 7h, or be superimposed on it, for example as can be seen in Figures 7d or 7e, depending on the particular implementational requirements of the invention and in particular depending on the gas discharge pressure which is to be obtained. The choice of the embodiments proposed in the attached figures may be easily obtained by means of simple tests carried out on samples.

The upper surface 101a of the adhesive label 101 may comprise at least one first portion, which faces a second portion of the covering membrane 103 so as to form the first zone A and/or the second zone B.

Depending on the particular implementational requirements of the present invention, for example in order to optimize the production process, as required:

- the first portion and/or the second portion are, as required, either without adhesive or coated with an adhesive which is covered by a non-stick layer which comprises a lacquer and/or a film of polymeric material;

- either one of the first portion and the second portion is coated with a further adhesive, the other one being coated with a non-stick material, for example with a silicone coating suitable for opposing an adhesive action of the further adhesive thereon.

The lower surface 101b of the adhesive label 101 may have at least one non-stick separation zone D which may be realized as described above in relation to the operating portion 106.

In particular, there may be at least two separation zones D which, according to a plan view of the adhesive valve 100, may be provided on the opposite sides of the adhesive label 101 so as to allow a partial separation thereof from the wall forming a food container to which the adhesive valve 100 during use is applied.

Examples of embodiment of an adhesive valve 100 provided with separation zones D are shown by way of a non-limiting example in Figures 8b to 8g.

For example, Figure 8c shows a simplified diagram of the configuration of the adhesive valve 100, for example that shown in Figure 8b, during the outflow of gas from an inflated package, the outer wall of which is represented by the bottom convex line.

In this diagram, the separation zones D allow the adhesive valve 100 to bend, in the concave configuration shown in Figure 8c, so as to allow the gas to exit easily through the plurality of holes 102a or, generally, from the first incision 102.

Mutatis mutandis, this description is also applicable to the solutions shown in Figures 8b-8g.

In particular, the separation zones D may be provided, according to a plan view of the adhesive valve 100, at least partially in the third zone C and/or on the sides of the second zone B, so as to limit the possible tension on the said adhesive valve 100 and/or on the container following swelling of the latter as a result of the presence of a gas inside it.

Optionally, the separation zones D may be shaped so as to be symmetrical along two axes, i.e. a longitudinal axis and a transverse axis (perpendicular to each other) of the adhesive valve 100, as shown for example in the embodiments of Figures 8f and 8g, in which there are four separation zones symmetrical longitudinally and transversely with respect to the adhesive valve 100.

In order to prevent possible damage to the covering membrane 103 and/or to the adhesive label 101 , the adhesive valve 100 may comprise a protective membrane 107 fixed onto the covering membrane 103 and/or onto the adhesive label 101 so as to cover it and protect it from interaction with objects extraneous to the adhesive valve 100.

The adhesive valve 100 may also comprise a third adhesive 108 which fixes the protective membrane 107 to the covering membrane 103.

At least one area F without adhesive may be present between the protective membrane 107 and the covering membrane 103, said area being positioned and/or shaped to limit the stress of separation of the covering membrane 103 from the adhesive label 101 , which would be generated by a retaining action by the protective membrane 107 on the covering membrane 103 following bending of the adhesive valve 100, for example as shown in Figure 8a.

The present teaching also relates to a semi-finished product 1000 from which a food container can be obtained.

The semi-finished product 1000 comprises:

- a sheet 200 for forming a food container which has two surfaces and has at least one second incision 201 which connects the two surfaces;

- an adhesive valve 100 which covers the second incision 201 so that at least one first incision 102 of the adhesive label 101 is superimposed on at least one second incision 201 of the sheet 200 so as to define a possible gas venting path from a container, which may be formed with the sheet 200.

The present teaching also relates to a food container which comprises a semi-finished product 1000 and which has an internal compartment for housing food, inside which the second incision 201 of the sheet 200 emerges so as to be crossed by a fluid and in particular by a gas contained inside the internal compartment and having a pressure greater than the pressure on the outside of the food container.

Generally speaking, the flexible label 101 and/or the covering membrane 103 may be obtained from a film of plastic material suitable for coming into contact with food products, for example belonging to the group composed of polypropylene (for example with a thickness of between 35 and 300 microns and preferably 90 microns), polyester (for example with a thickness of between 25 and 45 microns) or plastic materials with equivalent characteristics, such as PET or PE.

The adhesive label 101 may be formed by a laminate with several layers, in particular comprising plastic material, polyethylene, cellulose material, aluminium and/or a polyamide film, for example with a thickness of between for example 10 and 20 microns, or a PE-EVOH-PE laminate. Moreover, the adhesive label 101 may be formed by recyclable materials such polylactic acid and/or may be a multilayer laminate, comprising an inner layer, which defines the lower surface 101b, made for example of a material from among those indicated above, and an outer layer, which defines the upper surface 101a, preferably made of a barrier material which increases the impermeability of the adhesive valve 100.

For example, the adhesive label 101 may comprise a layer of polyethylene terephthalate, PET, with a thickness of about 30 microns having a layer of polypropylene, PP, with a thickness of about 90 microns, but which may also be as much as 300 microns depending on the particular implementational requirements of the present teaching, with a further layer of PE-EVOH, or PET or PP or PA, with a thickness of about 40 microns,

The adhesive label 101 may comprise a combination of polypropylene, which may have a thickness of about 30 microns, and PE-EVOH, which may have a thickness of about 40 microns.

The lower surface of the covering membrane 103 may be coated, in the first zone A, with a material which is suitable for alimentary use and able to make the membrane non-adherent or only slightly adherent, in particular silicone or another coating of the type per se conventional, but in any case a dry coating.

The first adhesive 101c may be an adhesive of the PSA (Pressure Sensitive Adhesive) type, in particular may be an acrylic adhesive which is water-based or of the UV crosslinking type or an acrylic adhesive with organic solvent, or may be a silicone-based adhesive suitable for high temperatures (up to 250°C) depending on the particular implementational requirements of the invention.

In a preferred, albeit non-exclusive embodiment of the present teaching, the adhesive label 101 and/or the covering membrane 103 may be made of a material such as to have an elastic modulus greater than low-density linear polyethylene, LLDPE, used for comparable applications, and allow an electrostatic attraction towards the substrate on which it rests which is not strong, namely which does not create an intense intermolecular attraction.

For example, the adhesive label 101 and/or the covering membrane 103 may be made preferably of a polyethylene, PE, which is practically devoid of all additives, except for nanometric silica, which has an attraction force which is sufficient for closing the gas discharge channel, in order to prevent infiltration from the outside, but at the same time is weak enough to favour the venting of gas under pressure from the inside of the container which comprises the adhesive valve 100.

Further characteristics of the materials and the method for manufacturing the adhesive label 101 may be those described in European Patent EP2275252 and in the publication WO2015/111015 A1 .

The adhesive label 101 may have a substantially polygonal and/or curvilinear form, for example substantially square form, or for example a circular or triangular form, with the corners which are rounded and may be provided with anti-tamper slits, not shown. The adhesive label 101 , viewed in plan view, may extend over an area x mm wide and y mm long, with x and y ranging between 20 and 40, in particular between 25 and 26 and preferably where x = y = 25.

The covering membrane 103 preferably has a shape identical to that of the adhesive label, viewed in plan view, or may extend beyond the perimeter of the adhesive label at least in one direction and, depending on the particular implementational requirements, for example in at least two diverging opposite directions, such that it is arranged substantially straddling the adhesive label 101 so as to assist retention thereof on the sheet 200. The protective membrane 107 may have a shape which is identical to that of the covering membrane 103, viewed in plan view, extending beyond the perimeter of the latter in at least one direction.

In a rest condition of the adhesive valve 100, the first incision 102 is closed owing to the mutual adhesion effect between the adhesive label 101 and the covering membrane 103, for example owing to the electrostatic action or the Van der Waals interaction, as described further above.

The covering membrane 103 may be made of any material, preferably polymeric material, coated with a lacquer which increases the affinity with the upper surface of the adhesive label 101 so as to allow gas to pass between them.

Said lacquer may consist of a chemical coating having a distribution, on the covering membrane 103 and/or on the adhesive label 101 which is between 1 g/m² and 10 g/m²

The size, as well as the form and number of the non-stick-portions E is chosen depending on the particular implementational requirements of the present teaching.

In particular, the non-stick portion E may have cusp-shaped parts which are directed towards the outer perimeter of the adhesive valve 100 so as to form guides for a pressurized gas which infiltrates between the covering membrane 103 and the adhesive label 101.

This cusp-shaped form, moreover, on the one hand facilitates the passage of gas from the first zone A, across the second zone B towards the perimeter of the adhesive valve 100, viewed in plan view, and on the other hand opposes the access of air in the opposite direction, namely from the outside of the adhesive valve 100 across the channel defined by the second zone B towards the first zone A.

As mentioned above, the adhesive label 101 may also have anti-tamper slits which, for example, may be arranged in mutually opposite positions and be shaped so as to extend along a curved path and in particular circular or elliptical path so as to define, with their ends, a preferential initial-breakage portion of the adhesive label 101 , should it be removed from a sheet onto which it has been applied.

The sheet 200 may be designed to close or form a container for food products, for example may be made of plastic material and used to form a bag or be hot-welded to the edges of a rigid tray, and may have at least one second incision 201 which connects the two surfaces of the sheet and is covered by the adhesive valve 100 in order to seal the inside of the container, while allowing gas to be discharged therefrom.

The second incision 201 in the sheet may be straight, curved or closed, so that the portion of the sheet surrounded by the second incision 201 may be removed and form an opening, which is for example substantially circular. The second incision 201 in the sheet may also be curved, so as to form a tongue shaped portion which may be bent towards the adhesive valve or the opposite side. At least one adhesive layer, in particular the PSA adhesive layer, for example with a rectangular shape, may be arranged on a portion of the sheet around the second incision 201 so as to promote the adhesion, to the sheet, of the adhesive label 101 and/or of at least one portion of the covering membrane 103 and/or of at least one portion of the protective membrane 107 which extends beyond the perimeter of the adhesive label 101 and/or of the covering membrane 103, respectively.

The protective membrane 107 may be made of a plastic material, for example PE, PEHD, PP, MDO, polyesters.

In connection with the capacity for production of the adhesive valve 100, the present teaching also relates to a storage means 2000 for the applicator of adhesive valves 100, which comprises:

- a support membrane 2001 having an operating face;

- a plurality of adhesive valves 100 applied to the operating face and fixed thereto in a removable manner.

The support membrane 2001 may consist, for example, of a strip which extends mainly in a longitudinal extension direction along which a plurality of adhesive valves 100 are aligned so as to form at least one row. The adhesive valves 100 may be fixed to the operating face by means of the first adhesive 101c and, during a process for production of a food container, be detached from the support 2001 so as to be applied onto a sheet 200 in order to form and cover the at least one second incision 201 of the latter.

The present teaching also relates to a method of manufacturing an adhesive valve 100 which comprises the following steps:

- step A of applying a first adhesive 101a to a lower surface 101b of a first layer;

- step B of cutting the first layer so as to form said at least one first incision

102;

- step C of fixing a second layer to an upper surface of the first layer by means of a second adhesive 105 so as to form the first zone A, the second zone B and the third zone C of the adhesive valves 100;

- step D of cutting the first layer and/or the second layer so as to obtain respectively the adhesive label 101 and/or the covering membrane 103.

Moreover, the method may comprise a step E of applying the separator element 104 between said first layer and said second layer, in each first zone A and/or second zone B.

This method may also comprise a step F of applying the first layer to a support membrane 2001 which can be cut to form the aforementioned storage means 2000, for example in the form of a strip.

Moreover, the method may comprise a step G of fixing a third layer to an upper face of the second layer, in order to form protective membranes 107.

Moreover, a step H may be provided for cutting the third layer, for example for register die-cutting thereof, in order to obtain the protective membrane 107 of the adhesive valve 100 so that it covers the covering membrane 103.

In one embodiment of the present method the protective membrane 107, covering membrane 103 and the adhesive label may be obtained at the same time by means of cutting, for example by means of register die-cutting, of the respective first, second and third layers.

The first layer, the second layer and the optional third layer may be in the form of strips which are continuously machined along a processing direction.

In this case, as mentioned, step D is performed preferably by means of continuous die-cutting or register die-cutting along said processing direction.

The method of manufacturing the adhesive valve 100 may therefore involve a strip 11 preferably wound onto a reel 12 being pulled, for example in the direction of the arrows shown, by one or more first auxiliary rollers 13. The strip 11 may comprise a first layer 14 of suitable material for forming the adhesive labels 101 , which may be joined by means of at least one layer of a second adhesive 105 to a support 3 of material suitable for forming the covering membranes 103.

The first layer 14, the support 3 and/or the second adhesive layer 105, contained between them, are preferably continuous and uniform and for example formed as strips.

A first of the auxiliary rollers 13 may separate the first layer 14 from the support 3, these being able to be pulled separately by other auxiliary rollers 13, for example as shown in Figure 9.

The first layer 14 of the strip 11 may be provided with a series of non-stick portions E which may be arranged at a unform distance from each other in succession on the adhesive surface of the first layer 14 which, with reference to the example shown in Figure 9 is directed upwards, so as to form the first zones A and the second zones B.

The series of non-stick portions E may be arranged by an applicator 16 which, for example, applies and dries an anti-adhesive substance onto the non stick portions 4, for example a lacquer which may be silica-based.

In an alternative not shown in the attached figures, the first layer 14 and the support 3 may be pulled from respective reels and the layer of second adhesive 105 may be deposited on either of them in continuous or register mode, leaving areas free from the second adhesive 105 so as to form the first zones A and the second zones B.

In this variant, in a manner similar to that described above, the first layer 14 of the strip 11 or the support 3 may be provided with a series of non-stick portions E which may be placed at a uniform distance from each other in succession by an applicator 16 which, for example, applies and dries an anti adhesive substance on the non-stick portions E, for example a lacquer which may be a silica-based lacquer.

The first layer 14 may be provided with a series of incisions 1 b formed at the same uniform distance between the non-stick portions 4, by a perforator device 20, for example laser perforator, if necessary with the aid of a sensor 21 designed to detect the position of a non-stick portion E on the first layer 14, so that the non-stick portion 4 is crossed by the incision 1 b, viewing it in plan view.

The incisions 1 b in the first layer 14 may also be formed before forming the non-stick portions E.

The support 3 of the strip 11 may be joined to the first layer 14 by one or more second auxiliary rollers 23, with optional non-stick portions E arranged between the first layer 14 and the support 3.

The first layer 14 of the strip 11 may then be die-cut by a first mechanical die-cutter, in particular a roller die-cutter 24, so as to form in the first layer 14 a series of adhesive labels 1 where the cut made by the die-cutter may surround the non-stick portions 4, being separated from these or also intersecting them.

In particular, the material of the first layer 14 which is surplus with respect to the series of adhesive labels 1 (not shown in the figures) may be removed. The support 3 of the strip 11 may be die-cut by a second mechanical die-cutter, in particular a roller die-cutter 25, so as to form in the support 3 a series of covering membranes 103 which are each covered by an adhesive label 1 with the non-stick portion E, where necessary, arranged between them.

In this way it is possible to obtain the storage means 2000, where the strip 11 , which may be cut longitudinally, acts as a support for a series of adhesive vales 100, forming the support membrane 2001.

Thus the strip 11 , with the adhesive valves 100 may be wound onto a reel

26.

With reference to Figure 10 it can be seen that, during a first operating step of the method for manufacturing a sheet 200 in order to form containers, a support membrane 6, preferably wound onto a reel 31 , is pulled, for example by one or more auxiliary rollers 32, following which a die-cutter 33 forms the second incisions 201 in the support membrane 6.

Optionally, an applicator 34 applies adhesive layers onto the base membrane 6 close to the second incisions 201 , following which a labelling machine 34 applies adhesive valves 100, for example removing them from the support membrane 2001 , above the second incisions 201 of the base membrane 6, with the lower surface of the adhesive label 101 in contact with the sheet 200 in the manner described above. The sheet 200 with one or more adhesive valves 100 for forming the semi-finished product 1000, which may be pulled by further auxiliary rollers 32, is wound onto a reel which may form the storage means 2000, as for example shown in Figure 10.

During a subsequent step, not shown in the Figures, the sheet may be removed from the reel 36 and cut to obtain a plurality of sections which comprise at least one adhesive valve 100 and may be used to form containers for alimentary use, for example a lid of a container in which the sheet portion is joined to the edge of other sheet portions to form the container, in particular by means of adhesive or heat-welding.

It can be understood therefore how an adhesive valve, a semi-finished product comprising said valve, a container comprising said valve and a method for the manufacture thereof are able to fulfil the task and achieve the predefined objects.

In particular, a container which incorporates an adhesive valve according to the present invention is able to avoid the swelling or "puffing" effect which has a particularly negative effect on the appearance of the product.

The invention thus devised may be subject to numerous modifications and variations, all of which fall within the scope of protection of the attached claims.

Moreover, all the details may be replaced by other technically equivalent elements.

Where the operational characteristics and the techniques mentioned in the following claims are followed by reference numbers or symbols, these reference numbers or symbols have been assigned with the sole purpose of facilitating understanding of the said claims and consequently they do not limit in any way the interpretation of each element which is identified, purely by way of example, by said reference numbers or symbols. In particular, the present teaching is to be understood as comprising further embodiments which may comprise the technical characteristics of one of the following claims, with the addition of one or more technical characteristics described in the text above or shown in the drawings, considered singly or in in any mutual combination.

Claims

1 . Adhesive valve (100) which comprises:

- an adhesive label (101 ) which has an upper surface (101a) and a lower surface (101 b), wherein at least one first incision (102) connects the two upper and lower surfaces to form a passage for a fluid;

- a covering membrane (103) applied to the upper surface (101a) of the adhesive label (101 ); said adhesive valve (100) has, between the adhesive label (101 ) and the covering membrane (103):

- a first zone (A), in which the adhesive label (101 ) and the covering membrane (103) are not joined together by adhesive and which, viewing the adhesive valve (100) in plan view, overlaps the first incision (102);

- a second zone (B), in which the adhesive label (101) and the covering membrane (103) are not joined together by adhesive and which is adjacent to the first zone (A) or integral with the latter so as to define a discharge channel, for a fluid, which extends from the at least one first incision (102) towards a perimeter edge of the covering membrane (103);

- a third zone (C), in which a second adhesive (105) fixes the covering membrane (103) to the adhesive label (101 ).

2. Adhesive valve (100) according to the preceding claim, which comprises a separator element (104) arranged between the adhesive label (101 ) and the covering membrane (103) in said first zone (A) and/or in said second zone (B) and adapted to space the adhesive label (101 ) from the covering membrane (103) so as to allow the separation of the label and membrane even when they are pressed against each other, in order to allow the passage of a fluid between them.

3. Adhesive valve (100) according to the preceding claim, wherein the separator element (104) comprises a paint and/or an insert having a thickness of between 100 and 300 microns so as to separate correspondingly the adhesive label (101 ) from the covering membrane (103).

4. Adhesive valve (100) according to one of the preceding claims, wherein the adhesive label (101 ) and/or the covering membrane (103) are configured to adhere by means of electrostatic action to each other at least in the second zone (B) of the covering membrane (103), so that the channel defined by said second zone (B) is sealed when it is not crossed by a fluid coming from the first incision (102) of the adhesive label (101 ).

5. Adhesive valve (100) according to one of the preceding claims, wherein the adhesive label (101 ) and/or the covering membrane (103) have at least one non-stick portion (E) configured in such a way as to prevent or oppose the sticking together of the adhesive label (101 ) and the covering membrane (104) by the electrostatic action or by the action of Van der Waals forces in the first zone A and/or in the second zone B.

6. Adhesive valve (100) according to one of the preceding claims, wherein said at least one first incision (102) forms a plurality of holes (102a) passing through the adhesive label (101 ); the lower surface (101 b) of the adhesive label (101 ) has a non-adhesive operating portion (106); at least some of said holes (102a) extend from said operating portion (106) through the adhesive label (101 ).

7. Adhesive valve (100) according to the preceding claim, wherein the lower surface (101 b) of the adhesive label (101 ) is coated with a first adhesive (101 c) wherein said operating portion (106) is devoid of said first adhesive (101 c) or has a film covering said first adhesive (101 c).

8. Adhesive valve (100) according to the preceding claim, wherein said film is formed by a lacquer or by a film of polymeric material.

9. Adhesive valve (100) according to one of the preceding claims, wherein the upper surface (101 a) of the adhesive label (101 ) comprises at least one first portion, which faces a second portion of the covering membrane (103) so as to form said first zone (A) and/or said second zone (B); said first portion and/or said second portion are optionally:

- without adhesive;

- coated with an adhesive which is covered with a non-stick layer which comprises a lacquer and/or a film of polymeric material. 10. Adhesive valve (100) according to one of claims 1 to 8, wherein the upper surface (101 a) of the adhesive label (101 ) comprises at least one first portion, which faces a second portion of the covering membrane (103) so as to form said first zone (A) and/or said second zone (B); wherein either one of said first portion and said second portion is coated with a third adhesive (108), the other one being coated with a non-stick material, for example with a silicone coating, adapted to oppose the adhesive action of said third adhesive (108) thereon.

11 . Adhesive valve (100) according to one of the preceding claims, which comprises a protective membrane (107) fixed on the covering membrane (103) and/or on the adhesive label (101 ) so as to cover them and protect them from interaction with objects extraneous to the adhesive valve (100).

12. Adhesive valve (100) according to the preceding claim, which comprises a third adhesive (108) which fixes the protective membrane (107) to the covering membrane (103), wherein between the protective membrane (107) and the covering membrane (103) there is at least one adhesive-free area (D) positioned and/or shaped so as to limit a stress of separation of the covering membrane (103) from the adhesive label (101 ), which is generated by a retaining action of the protective membrane (107) on the covering membrane (103) following bending of the adhesive valve (100).

13. Semi-finished product (1000) which comprises a sheet (200) for forming a food container which has two surfaces and has at least one second incision (201 ) connecting the two surfaces; said semi-finished product (1000) comprises an adhesive valve (100) according to one of the preceding claims which covers the second incision (201 ) in such a way that at least one first incision (102) is superimposed on at least one second incision (201 ).

14. Food container which comprises a semi-finished product (1000) according to claim 13, and which has an internal compartment for housing food inside which the second incision (201 ) of the sheet (200) emerges so as to be crossed by a fluid contained in the internal compartment and having a pressure greater than the pressure on the outside of said food container. 15. Storage means (2000) for an applicator of adhesive valves (100) which comprises:

- a support membrane (2001) having an operating face;

- a plurality of adhesive valves (100) according to one of claims 1 to 12 applied to said operating face and fixed in a removable way.

16. Storage means (2000) according to claim 15, wherein the support membrane (2001) consists of a strip which extends mainly in a longitudinal extension direction along which a plurality of said adhesive valves (100) are aligned so as to form at least one row.

17. Storage means (2000) according to one of claims 15 and 16, wherein said adhesive valves (100) are fixed to said operating face by means of said first adhesive (101c).

18. Method for manufacturing an adhesive valve (100) according to one of claims 1 to 12, which comprises the following steps: step A of applying a first adhesive (101c) to a lower surface (101 b) of a first layer; step B of cutting the first layer so as to form said at least one first incision

(102); step C of fixing a second layer to an upper surface (101a) of the first layer by means of a second adhesive (105) in such a way as to form the first zone (A), the second zone (B) and the third zone (C) of said adhesive valves (100); step D of cutting the first layer and/or the second layer so as to obtain respectively said adhesive label (101) and/or said covering membrane (103).

19. Method according to the preceding claim, which comprises a step E of applying said separator element (104) between said first layer and said second layer.

20. Method according to claim 18 or 19, which comprises a step F of applying said first layer to a support membrane (2001) which can be cut so as to form a storage means (2000) according to one of claims 15 to 17.

21. Method according to one of claims 18 or 20, which comprises a step G of attaching a third layer to an upper face of the second layer and a step H of cutting the third layer so as to obtain the protective membrane (107) of the adhesive valve (100) according to claim 10 or 11 .

22. Method according to one of the preceding claims, wherein the first layer, the second layer and the optional third layer are strips processed continuously along a processing direction; said step D is carried out by means of continuous or register die-cutting.