HEAT-SEALABLE TWO-PART SEAL WITH REMOVABLE COVER

Description

[0001] The invention relates to the technical field of sealing means for glass containers, particularly those with stopper or cap closures, especially in the area of ​​dry food products such as freeze-dried coffee or spreads, without limitation. More specifically, it concerns a two-piece seal comprising a peelable lid. The sealing of containers with stopper or cap closures, prior to their first opening, can be achieved by means of a two-piece seal or, in some cases, a simple lid that can be glued or sealed onto the rim.

[0002] The invention, as defined in claim 1, relates to a double-piece joint only.

[0003] A double-piece seal consists of a lid placed around the entire circumference of the upper rim of the container's neck or drinking vessel, thus isolating the container from the outside, and a generally thicker support inserted, but not fixed, into the base of the cap. Before the container is first opened, the support and the lid can be temporarily joined using adhesive.

[0004] The primary role of the seal is to ensure the container is tamper-evident before first opening. Furthermore, it provides a basic seal against external elements. In addition, it must possess certain properties compatible with the contents it is intended to seal, and for example, be food-grade if the contents themselves are food products.

[0005] The support, for its part, is designed to absorb tolerances between the base of the capsule and / or stopper and the upper part of the container neck, and furthermore, to ensure secondary sealing once the cap has been partially or completely removed. It is therefore capable of providing a certain degree of compression with a memory effect to allow for the absorption of these tolerances.

[0006] In practice, the seal is inserted into the bottom of the cap or lid. Once the container is filled, the cap or lid with the seal is screwed or clipped onto the container. The sealing surface of the seal then comes into contact with the drinking rim.

[0007] When the container is opened for the first time, the support inserted at the bottom of the cap separates from the seal that remains fixed to the rim. Only then is the seal removed by the consumer; at that point, when the container is closed, the seal is maintained solely by the support portion of the gasket pressing against the rim.

[0008] The sealing of the lid on the rim is carried out by gluing or induction heat sealing using a heat-sealing film or varnish.

[0009] The invention is limited to a double-piece heat-sealable seal, which means that the sealing of the lid on the rim is achieved by induction heat sealing as mentioned above and not by gluing.

[0010] Heat sealing is made possible by the combined action of a conductive material, inserted within the thickness of the seal, which heats up under the effect of electrical induction, causing the sealing film or varnish on the rim to soften. The conductive material can be inserted either into the base or the lid. Most often, it is inserted within the lid. In practice, it has a thickness of at least 12 micrometers to ensure heat conduction.

[0011] Documents EP 2 045 194 A1 and WO 2010 / 115811 describe, for example, double-piece gaskets in which the lid incorporates an aluminum foil as a conductive material. A primary drawback of the prior art lies in the fact that the lid cannot be peeled off in a single step because the aluminum tears during the peeling process.

[0012] Indeed, consumers typically tear off the foil seal either by grasping its edge or by piercing it roughly in the center. In either case, the seal cannot be removed in one go.

[0013] A second drawback, which is a consequence of the first, lies in the fact that the removal of the aluminum generates the presence of metallic residues on the surface of the drinking glass, which are likely to fall inside the container and thus contaminate the contents.

[0014] The first problem that the invention aims to solve is therefore that of developing a lid that can be peeled off without leaving metallic traces on the drinking glass, ideally a lid that can be peeled off in one go.

[0015] This problem to be solved is accompanied by an additional constraint resulting from the uses or habits of consumers, since, as mentioned above, some of them are in the habit of opening the seal by piercing it with their fingers and then gradually tearing off the pieces of aluminum.

[0016] US patent 4,917,949 A describes a two-piece heat-sealable gasket consisting of a backing and a lid, typically made of aluminum. The backing and lid are bonded together with a temporary adhesive. A 12.7 µm thick polyester layer is bonded to the aluminum foil, and then a heat-sealable adhesive layer is bonded to the polyester layer. The patent states that the reinforcing layer is used to strengthen the aluminum layer. The combined thickness of the polyester layer and the aluminum layer makes it impossible to pierce the lid with a finger.

[0017] Document FR 2 693 986 A1 describes a multilayer lid intended to seal the neck of a container, and which generally includes, incidentally, a metal disc and a synthetic disc intended to be welded to the neck of the container during an induction process to which the lid in contact with the container is subjected.

[0018] The solution to the problem posed must therefore take this state of affairs into account so as not to disrupt consumer habits, especially when it comes to mass-market products such as freeze-dried coffee or spreadable paste.

[0019] Consequently, the problem that the invention aims to solve is that of developing a double-piece seal, the lid of which can ideally be peeled off in one go, without leaving metallic traces on the drinking glass, while being able to be pierced by the consumer's fingers at the time of opening.

[0020] For this purpose, a double-piece heat-sealing gasket has been developed for sealing a container with a stopper or cap closure, comprising a support made solid by means of a temporary adhesive, a lid without a tab and comprising a sheet of conductive material.

[0021] According to the invention, the sheet of conductive material is provided on its underside with a reinforcing film with a thickness of less than 6 µm, on the underside of which is applied a heat-sealing film intended to be in contact with the drinking of said container.

[0022] According to the invention, a reinforcing film is applied under the conductive material sheet, thus preventing the deposition of metallic residues on the drinking vessel at the time of peeling, all combined with a specific thickness of said reinforcing film making it possible for the consumer to pierce the lid.

[0023] According to the invention, the reinforcing film has a thickness of less than 6 µm. Indeed, it must be thick enough not to tear during peeling but thin enough to remain perforable. In practice, the reinforcing film has a thickness between 4 and 6 µm, advantageously 4.5 µm.

[0024] According to another characteristic, the reinforcing film is made of a material chosen from the group including polyester (PET), biaxially oriented polypropylene, biaxially oriented polyamide and biaxially oriented PET.

[0025] In a preferred embodiment, the reinforcing film is a PET film and has a thickness between 4 and 5 µm.

[0026] According to an essential feature of the invention, the lid contains a sheet of conductive material. In practice, this is an aluminum sheet.

[0027] For the double-piece seal of the invention to be heat-sealable, the conductive material sheet, in this case the aluminum sheet, must have sufficient thickness. In practice, the sheet thickness is between 20 and 40 micrometers, advantageously between 10 and 30 micrometers.

[0028] In practice, the reinforcing film, and more generally the constituent layers of the substrate and / or the lid, can be bonded directly to each other or via a binder layer. In all cases, the bond is preferably permanent so that the constituent layers of the lid and / or the substrate are inseparable.

[0029] To ensure the lid adheres to the rim of the container, the underside of the reinforcing film is fitted with a heat-sealable film. This heat-sealable film is made of a polyolefin-type material, chosen from the group including EVA, polyethylene, polypropylene, or PET, and is either a holt-melt type, terpolymer, or ionomer. Generally, the material of the heat-sealable film is selected based on the type of container.

[0030] The heat-sealing film can be a single-layer film applied to the underside of the reinforcing film by extrusion. It can also be a two-layer film (a lower heat-sealing layer and an upper bonding layer) applied to the underside of the reinforcing film by co-extrusion.

[0031] The operculum has, in practice, a thickness of between 20 and 200 µm, preferably between 30 and 120 µm.

[0032] According to the invention, the double-piece seal cover advantageously contains only three layers, respectively from bottom to top: a heat-sealing layer, a reinforcing film, and a conductive material sheet. In some cases, the upper surface of the conductive material sheet is covered with a print applied by a pre-coating and then overcoating operation.

[0033] The support can be made of any type of compressible material with recovery memory, particularly expanded polyethylene or expanded polypropylene, possibly with a polypropylene or polyethylene film on at least one of its two sides to give it some rigidity. It can also be made of paper or cardboard.

[0034] In practice, the supports envisaged have a thickness of between 0.5 and 4 mm, advantageously between 0.8 and 2 mm.

[0035] Regarding the temporary bonding between the substrate and the lid, this can be achieved using a temporary adhesive applied as a film, preferably extruded or co-extruded. Each of the two sides of the film has a different adhesive strength, with the stickier side applied to the underside of the substrate and the less sticky side to the upper side of the lid. In practice, such a film is polymer-based, generally synthetic, and carefully selected by a person skilled in the art to achieve the desired differential bonding properties. Examples of such polymers include acetate, acrylate, and polyethylene-based polymers or copolymers.

[0036] Temporary adhesive can also come in the form of a layer of wax.

[0037] The lid and the double-piece seal of the invention are more particularly suited for sealing a glass container with a stopper or capsule closure containing dry products, such as freeze-dried coffees or spreadable paste.

[0038] The invention and its resulting advantages will be more clearly illustrated by the following example, which represents a preferred embodiment.

[0039] A seal according to the invention is a two-piece heat-sealable seal. The seal consists of a support and a lid without a tab.

[0040] The support comprises a layer made of expanded polypropylene or polyethylene and has a thickness of between 1.4 and 1.7 mm.

[0041] The lid presents its upper surface opposite the support, towards its lower surface opposite the rim of the pot: an aluminium sheet with a thickness of 30 µm, a PET reinforcing film with a thickness of 4.5 µm, a PE type heat-sealing film.

[0042] The aluminum foil and the PET reinforcing film are bonded together by means of a binding layer.

[0043] According to the invention, the support and the lid are joined by means of a temporary extruded polyethylene adhesive film, each of the two faces of the film having a different stickiness, the stickier face being applied to the lower surface of the support, while the less sticky face is applied to the upper face of the lid.

[0044] In practice, these seals are positioned as is at the bottom of the cap, the cap then being screwed or clipped, as appropriate, onto the neck of the container. The seal is heat-sealed by induction.

[0045] When the container is opened for the first time, the support inserted at the bottom of the cap separates from the seal that remains fixed to the rim. Only then is the seal removed by the consumer; at that point, when the container is closed, the seal is maintained solely by the support portion of the gasket pressing against the rim.

[0046] As explained previously, the seal can be removed by the consumer either by grasping the periphery of the seal protruding from the drinking hole or by piercing the seal with a finger, roughly in its center.

[0047] Due to the presence of the reinforcing film combined with its thickness, the cap can be removed without leaving any metallic trace on the rim and potentially in a single step.

[0048] The invention and its resulting advantages are clearly illustrated in the preceding description. In particular, it offers the possibility of using a two-piece seal with a peelable lid that leaves no metallic residue on the rim of the container, thus preventing any risk of contamination of foodstuffs such as freeze-dried coffee or spreads that it may contain.

Claims

1. A heat-sealing two-piece seal for sealing a container having a stopper or a cap-type closure, comprising a support secured, by means of a temporary adhesive, to a lid with no tab, and comprising a sheet of conductive material, provided on its lower face with a reinforcing film having a thickness smaller than 6 µm, on the lower face of which a heat-sealing film is applied, intended to be in contact with the mouth of said container.

2. The seal according to claim 1, characterised in that the reinforcing film has a thickness of between 4 and 6 µm, advantageously equal to 4.5 µm.

3. The seal according to one of the preceding claims, characterised in that the reinforcing film is made of a material selected from the group comprising polyester (PET), bi-oriented polypropylene, bi-oriented polyamide and bi-oriented PET.

4. The seal according to one of the preceding claims, characterised in that the sheet of conductive material is an aluminium sheet.

5. The seal according to one of the preceding claims, characterised in that the sheet of conductive material has a thickness of between 20 and 40 µm.

6. The seal according to one of the preceding claims, characterised in that the heat-sealing film is made of a polyolefin-type material, selected from the group comprising EVA, polyethylene, polypropylene or PET, of the hot melt type or also of the terpolymer or ionomer type.

7. The seal according to one of the preceding claims, characterised in that the support is made of a compressible material with recovery memory, in particular made of expanded polyethylene or of expanded polypropylene.

8. The seal according to one of claims 1 to 6, characterised in that the support is made of paper.

9. A use of the seal according to one of claims 1 to 8 for sealing a glass container containing dry products.