Multilayer cap liner, container cap or neck comprising same, and methods for making same

Abstract

The invention concerns a cap liner (9) comprising: a middle layer made of a plastic material with gas barrier effect; first and second outer layers comprising each a polyolefin resin and arranged on either side of the middle layer; an intermediate polyethylene layer, placed between the middle layer and each of the outer layers, the intermediate layers being designed to protect the middle layer against moisture and to prevent degradation of said middle layer gas barrier properties. The cap liner can be placed in a cap near its transverse wall or towards the free end of its skirt or on a container neck. It can be planar or thermoformed. The invention also concerns methods for producing a neck-joint cap assembly.

Description

[0001] The invention concerns a composite seal able to be placed in a stopper or on a receptacle neck, a stopper comprising such a seal, a neck comprising such a seal as well as an assembly comprising a stopper, a receptacle and such a seal, the receptacle being empty or at least partially filled with a certain content.

[0002] The invention also concerns a method of corking a receptacle with a stopper provided with such a seal, and a method of producing and corking a neck provided with such a thermoformed seal.

[0003] The invention applies more particularly to the case of receptacles intended to contain gaseous drinks, the seal according to the invention providing liquidtightness and impermeability to gases between the inside and outside of the receptacle closed by the said stopper.

[0004] Such seals are already known, which generally comprise a middle layer produced from a material having properties of a barrier to gases, as well as additional external layers disposed on each side of the middle layer, intended in particular to confer a certain flexibility on the seal.

[0005] The gas barrier properties of the middle layer of the seal placed in a stopper make it possible to effect closure of receptacles so that there is neither entry of oxygen inside the receptacle nor exit of carbonic gas from the receptacle, in the case of carbonated drinks for example.

[0006] In this way impairment of the products contained in these receptacles is avoided, in particular their gustatory qualities when it is a question of drinks.

[0007] However, the material from which the middle layer is formed is very porous and absorbs water easily. This material does however lose its gas barrier properties when it absorbs water.

[0008] Consequently, the seals of the prior art, sensitive to moisture, may undergo degradation of their gas barrier properties and no longer fulfil their role when they are placed in a stopper on a receptacle neck.

[0009] The patent FR 2 704 805, from the applicant, describes a seal as described previously, which can also comprise, optionally, two intermediate layers, each placed between the middle layer and an external layer.

[0010] The intermediate layers are produced from polypropylene or elastomeric polypropylene. They have a high rigidity modulus, between 1300 and 2200 MPa, and a relatively small thickness, between 10 and 50 &mgr;m.

[0011] Because of the material employed for producing the intermediate layers and the small thickness of these layers, this seal structure does not provide an effective barrier against moisture, for protecting the middle layer. Consequently preservation of the gas barrier properties of the seal is not guaranteed.

[0012] In addition, this seal is relatively rigid, and therefore does not give full satisfaction with regard to mechanical sealing.

[0013] Moreover, the patent U.S. Pat. No. 6,139,931 describes several embodiments of a seal comprising a middle layer having gas barrier properties.

[0014] According to a first embodiment, the seal also comprises:

[0015] external layers made from polyolefin resin of high quality, suitable for contact with food. These strong external layers are in particular intended to prevent the entry of moisture into the seal, which could affect the gas barrier properties of the middle layer;

[0016] intermediate layers, each placed between the middle layer and an external layer, produced from a polyolefin resin. These intermediate layers are preferably produced from recycled material, or material of poor quality, in order to reduce the production cost of the seal.

[0017] The fact that the layers protecting the middle layer are situated on each side of this seal rather than inside it presents a certain number of drawbacks.

[0018] Firstly, the external layers of the seal are subjected to attacks which may damage them and thus affect their integrity. In particular contact of the seal with the end wall of the stopper in which the seal is intended to be placed can be cited, as well as contact with the edge of the neck of the receptacle intended to cooperate with the said stopper. The seal may also suffer damage, even unintentional, on the part of the user. Protection of the middle layer against moisture is then no longer ensured.

[0019] Secondly, it has been found that the protection against moisture of the middle layer is not optimal when the protective layers are disposed at a distance from the said middle layer, on each side of the seal.

[0020] According to a second embodiment, the seal comprises, in addition to the middle layer, solely the intermediate layers, but not the external layers. In this case, the intermediate layers are produced from a high-quality polyolefin resin, suitable for contact with food.

[0021] According to a third embodiment, the seal comprises, in addition to the middle layer, solely the external layers, but not the intermediate layers.

[0022] These last two seal structures also do not give full satisfaction since the layers intended to protect the seal, placed on the outside, are liable to be damaged, and therefore no longer fulfil their function.

[0023] The aim of the invention is to resolve these problems. Another aim of the invention is to provide a simple method of fitting a stopper comprising such a seal on a receptacle neck or a stopper on a receptacle neck provided with such a seal.

[0024] To this end, and according to a first aspect, the invention concerns a composite seal able to be placed on a neck of a receptacle or in a stopper comprising an annular skirt provided with an internal thread intended to cooperate with the external thread of a neck of a receptacle for mounting the stopper by screwing on the said neck, the said seal comprising firstly a middle layer produced from a plastics material with a gas barrier effect and secondly first and second external layers each comprising a polyolefin resin and disposed on each side of the said middle layer.

[0025] According to the invention, the seal also comprises, between the middle layer and each of the external layers, an intermediate polyethylene layer, with a thickness of between 80 and 150 &mgr;m, the said intermediate layers being intended to protect the middle layer from moisture and thus to prevent degradation of the gas barrier properties of the said middle layer.

[0026] The thickness of the intermediate layers is thus sufficiently great for the said layers to provide an excellent barrier to water. The use of polyethylene reinforces the protection against moisture.

[0027] In addition, the layers protecting the middle layer being inside the seal, they are no longer subjected to external attacks and therefore keep their integrity and their function.

[0028] According to one possible embodiment, the intermediate layers are produced from low or medium density polyethylene, and can have a thickness of around 115 &mgr;m.

[0029] According to other characteristics, the polyethylene making up the intermediate layers can have a rigidity modulus of between 250 and 500 MPa.

[0030] Because of this, the seal has a certain flexibility and therefore makes it possible to obtain a high-performance mechanical seal.

[0031] The middle layer can consist of a sheet of EVOH and its thickness can be between 35 and 65 &mgr;m.

[0032] The first external layer can be produced from EVA comprising between 7% and 15% VA, and its thickness can be between 90 and 160 &mgr;m.

[0033] This EVA content confers good flexibility on the first external layer. It is thus not necessary for this layer to have great thickness for the seal to be compressible. Consequently this seal makes it possible to obtain very good impermeability, whilst having reduced thickness, and therefore a cost lower than the seals of the prior art.

[0034] The second external layer can comprise polyethylene or EVA, as well as a compound with oxygen absorbing effect, comprising sodium ascorbate and/or sodium sulphite.

[0035] The thickness of the second external layer can be between 130 and 230 &mgr;m. This thickness is less than that generally chosen in the prior art, for reasons related to the manufacturing process and the presence of two layers of different materials on this side of the middle layer. Naturally, this structure is not prejudicial to the performance of the seal.

[0036] According to a second aspect, the invention concerns a stopper comprising firstly a transverse end wall and secondly an annular skirt projecting substantially perpendicular to the said transverse wall and comprising an internal thread intended to cooperate with the external thread on a neck of a receptacle for mounting the stopper by screwing on the said neck, the stopper also comprising a substantially discoid seal as described previously, the said seal being placed inside the stopper, substantially perpendicular to the axis of the said stopper, and being intended to provide impermeability to liquids and impermeability to gases between the inside and outside of the receptacle closed by the said stopper.

[0037] The seal is placed inside the stopper so that the first external layer is situated opposite the transverse end wall.

[0038] According to a first embodiment, the seal is substantially flat and is situated close to the transverse wall.

[0039] According to a second embodiment, the seal is thermoformed, so that it has a shape complementary firstly to that of the neck of the receptacle with which the stopper is intended to be associated and secondly to that of the internal face of the transverse end wall of the stopper, the said seal being situated, before the stopper is placed on the receptacle neck, towards the free end part of the skirt opposite to the transverse wall and, after the stopper is placed on the receptacle neck, close to the transverse wall.

[0040] The stopper can also comprise a tamper-evident band comprising means of holding the seal before the stopper is placed on the receptacle neck.

[0041] According to one possible embodiment, the stopper comprises a substantially annular lip projecting from the transverse wall in the same direction as the skirt, the said lip being intended to cooperate with the internal face of the receptacle neck, the seal being thermoformed so as to have a recess forming a housing able to receive the said lip.

[0042] The stopper can also have a lug projecting substantially radially from the annular skirt towards the axis of the stopper, the said lug being situated towards the end part of the skirt connected to the transverse wall of the stopper, the lip being slightly divergent externally in a truncated cone from its base in the direction of its free end, so that, after the stopper is placed on the receptacle neck, the seal is placed between the transverse wall of the stopper and the lug, the divergence of the lip ensuring the holding of the seal at the bottom of the stopper.

[0043] According to a third aspect, the invention concerns a receptacle neck or a receptacle having a neck, the said neck being provided with an external thread intended to cooperate with the internal thread on a stopper, and comprising a substantially discoid seal as previously described, the said seal covering the opening of the neck and being thermoformed, so that it has a shape complementary firstly to that of the receptacle neck and secondly to that of the internal face of the transverse end wall of the stopper intended to be associated with the neck.

[0044] The seal is preferably placed on the neck so that the last external layer is situated opposite the inside of the neck.

[0045] According to a fourth aspect, the invention concerns an assembly comprising a stopper, a receptacle and such a seal.

[0046] When the stopper is screwed on the neck, the seal is compressed, towards its peripheral area, between the edge of the neck of the receptacle and the transverse end wall of the stopper, so as to provide liquidtightness and impermeability to gases between the inside and outside of the receptacle.

[0047] Finally, according to a fifth aspect, the invention relates to methods of corking a neck by means of a stopper provided with a seal and methods of corking a neck provided with a seal by means of a stopper.

[0048] The other characteristics of the invention result from the following description of embodiments, a description given with reference to the accompanying figures, in which:

[0049] FIG. 1 is a greatly enlarged transverse section of a sheet of composite material making up a seal according to the invention;

[0050] FIG. 2 is a view in partial radial section of a stopper comprising a seal produced from the sheet in FIG. 1, according to a first variant of a first embodiment;

[0051] FIG. 3 is a view in partial radial section of a stopper comprising a seal produced from the sheet in FIG. 1, according to a second variant of a first embodiment;

[0052] FIG. 4 is a view in radial section of the stopper in FIG. 2, mounted on a receptacle neck, in the totally screwed-in position, before first opening;

[0053] FIG. 5 is a view in partial radial section of a stopper comprising a thermoformed seal produced from the sheet in FIG. 1, according to a second embodiment;

[0054] FIG. 6 is a view in partial radial section of the stopper in FIG. 5, provided with a seal, when the stopper is mounted on the neck of a receptacle;

[0055] FIG. 7 is a view in partial radial section of a receptacle neck provided with a thermoformed seal, according to a third embodiment of the invention;

[0056] FIG. 8 is a view in partial radial section of an assembly consisting of stopper, neck and seal, obtained after the placing of the stopper of FIG. 5 on a receptacle neck, or after a stopper is placed on the neck in FIG. 7;

[0057] FIG. 9 is a view in partial radial section of the stopper of FIG. 8 after unscrewing.

[0058] Reference is made first of all to FIG. 1, which depicts in transverse section a sheet 1 of composite material comprising several juxtaposed layers.

[0059] The sheet 1 comprises first of all a middle layer 2, produced from a plastics material with a gas barrier effect. The middle layer 2 can for example consist of a sheet of EVOH (ethyl vinyl alcohol copolymer), with a thickness of between 35 and 65 &mgr;m, in particular 50 &mgr;m, the EVOH having a rigidity modulus of between 1500 and 2500 MPa, for example 2000 MPa.

[0060] The sheet 1 next comprises two intermediate layers 3, 4, disposed on each side of the middle layer 2 and connected to the said intermediate layer 2 by a layer of adhesive 5, 6.

[0061] Each of the two intermediate layers 3, 4 is produced from low or medium density polyethylene, with a rigidity modulus of between 250 and 500 MPa. The thickness of each of the two intermediate layers 3, 4 is between 80 and 150 &mgr;m, in particular around 115 &mgr;m.

[0062] The role of these intermediate layers 3, 4 is to provide protection of the middle layer 2 against moisture, so that the latter will keep its gas barrier properties. The polyethylene makes it possible to obtain much better performance than the EVA (ethylene and vinyl acetate copolymer) used in the prior art.

[0063] The sheet 1 finally comprises two external layers 7, 8, each connected to one of the intermediate layers 3, 4. The materials making up the external layers 7, 8 have a rigidity modulus of between 50 and 100 MPa.

[0064] A first external layer 7 is produced from EVA comprising between 7% and 15% VA (vinyl acetate), in particular 9.4% VA. The thickness of the first external layer 7 is between 90 and 160 &mgr;m. It may for example be around 125 &mgr;m.

[0065] A second external layer 8 comprises a polyolefin, polyethylene or EVA, as well as a compound with oxygen-absorbing effect, such as a mixture of sodium ascorbate and sodium sulphite.

[0066] The thickness of the second external layer 8 is between 130 and 230 &mgr;m, and in particular around 180 &mgr;m.

[0067] The manufacture of the sheet 1 is effected by coextrusion. The intermediate and middle layers are assembled by adhesive bonding.

[0068] A seal 9, in the general shape of a disc, is then cut from the sheet 1, for example using a punch with the required diameter, the said seal 9 being able to be placed in a stopper intended to cork a receptacle, or on a receptacle neck.

[0069] Three embodiments of the invention are now described, making it possible to obtain an assembly consisting of stopper, receptacle neck and seal having very good liquidtightness and very good impermeability to gases.

[0070] First of all, a stopper 10 comprising such a seal 9, according to a first embodiment of the invention, is described with reference to FIGS. 2, 3 and 4.

[0071] The stopper 10, of axis 11, is for example produced from plastics material.

[0072] The stopper 10 comprises first of all a transverse end wall 12, from which projects an annular skirt 13, substantially perpendicular to the said transverse end wall 12.

[0073] The annular skirt 13 has, on its internal face 14, a thread 15, for mounting the stopper 10 by screwing on the neck of a receptacle, the said neck comprising an external thread complementary to the thread 15 on the stopper 10, as will be described below.

[0074] The skirt 13 also has knurling 16 on its external face 17, this knurling 16 being intended to facilitate the screwing and unscrewing of the stopper 10 by a user, by offering a better grip for the hand and limiting the slipping of the fingers of the user on the external face 17 of the skirt 13.

[0075] The stopper 10 next comprises a tamper-evident band 18, connected to the free end part 19 of the annular skirt 13 by breakable bridges 20 or a line of least strength. The tamper-evident band 18 comprises an annular attachment projection 18a, projecting substantially radially towards the axis 11 of the stopper 10 and intended to cooperate with an external projection on a receptacle neck in order to prevent the tamper-evident band 18 being released from the said neck.

[0076] The stopper 10 also comprises a seal 9, substantially discoid, cut from the previously described sheet 1. The diameter of the seal 9 is substantially equal to the internal diameter of the skirt 13 of the stopper 10.

[0077] The seal 9 is placed at the bottom of the stopper 10, close to the transverse end wall 12. When it is placed at the bottom of the stopper 10, the seal 9 is substantially flat, or slightly curved, the concavity being for example directed towards the free end part 19 of the annular skirt 13, as illustrated in the figures.

[0078] According to a first variant embodiment, illustrated in FIG. 2, the seal 9 is held at the bottom of the stopper 10 by the thread 15 on the internal face 14 of the annular skirt 13.

[0079] According to a second variant embodiment, illustrated in FIG. 3, the seal 9 is held at the bottom of the stopper 10 by serrations 21 projecting radially from the annular skirt 13 towards the axis 11 of the stopper 10, the said serrations 21 being situated towards the end part 22 of the skirt 13 connected to the transverse wall 12 of the stopper 10 so that the seal 9 can be placed between the said serrations 21 and the transverse wall 12.

[0080] When it is placed at the bottom of the stopper 10, the seal 9 is therefore prevented from emerging from the said stopper 10, but is on the other hand free to be moved in rotation about the axis 11 of the said stopper 10.

[0081] In addition, the seal 9 is held at a distance from the transverse wall 12 of the stopper 10 by a projection 23, situated on the internal face 14 of the skirt 13, towards the end part 22 of the skirt 13 connected to the transverse wall 12.

[0082] The seal 9 is placed inside the stopper 10 so that the first external layer 7 is situated opposite the transverse end wall 12.

[0083] Reference is made to FIG. 4, which shows a neck 24 of a receptacle 25 on which a stopper 10 comprising a seal 9 is mounted by screwing.

[0084] The neck 24 is substantially cylindrical, of axis 26, has an annular rim 27 and defines an opening 28.

[0085] The neck 24 has, on its external face 29, a thread 30 complementary to the internal thread 15 on the stopper 10, as well as a seat 31. The neck 24 also comprises an annular projection 29a, projecting substantially radially from the external face 29, towards the outside of the said neck 24.

[0086] When the stopper 10 has been put in place on the neck 24, the annular projection 29a on the neck 24 forms a stop for the annular attachment projection 18a on the stopper 10, and prevents the axial movement of the tamper-evident band 18 towards the outside of the receptacle 25, so as to prevent the tamper-evident band 18 escaping from the neck 24—before or after first use.

[0087] When the stopper 10 is completely screwed onto the neck 24, as illustrated in FIG. 4, the seal 9 covers the opening 28 of the neck 24, the peripheral area 32 of the said seal 9 being in contact with the rim 27 of the neck 24.

[0088] The peripheral area 32 of the seal 9 is thus compressed between the rim 27 of the neck 24 of the receptacle 25 and the transverse wall 12 of the stopper 10, so that a good seal is provided between the inside and outside of the receptacle 25 closed by the stopper 10.

[0089] When the stopper 10 is completely screwed onto the neck 24, the seal 9 is curved, its concavity being directed towards the transverse wall 12 of the stopper 10.

[0090] The middle layer 2 of the seal 9 fulfils the role of a barrier to gases. Thus there can be neither entry of gas (in particular oxygen) inside the receptacle 25 nor the exit of gas (in particular carbon dioxide) from the receptacle 25. The quality of the content of the receptacle 25 is therefore preserved, even after several months storage.

[0091] The intermediate layers 3, 4, placed on each side of and in the immediate vicinity of the middle layer 2, guarantee the preservation of the gas barrier properties of the middle layer 2 whilst protecting it from moisture. The middle layer 2 is thus protected firstly from moisture in the ambient air, outside the receptacle 25, and secondly from contact with the content—for example liquid—of the receptacle 25.

[0092] The second external layer 8, situated towards the inside of the receptacle 25, makes it possible to absorb the oxygen contained in the receptacle 25, between the level of the content of the said receptacle 25 and the rim 27 of the neck 24, preserving even better, because of this, the qualities of the content of the receptacle 25.

[0093] The seal 9 according to the invention therefore guarantees very good preservation of the content of the receptacle 25, for a long storage time.

[0094] Reference is now made to FIG. 5, which shows a stopper 10 provided with a seal 9, according to a second embodiment of the invention, before it is mounted on a receptacle neck.

[0095] The stopper 10 is similar overall to the stopper in FIG. 2, and is intended to be associated with a neck 24 of a receptacle 25 similar to the neck in FIG. 4.

[0096] The stopper 10 also comprises a substantially annular lip 33, projecting from the transverse wall 12 of the stopper 10 in the same direction as the skirt 13. The lip 33 is intended to cooperate with the internal face 34 of the neck 24 of the receptacle 25, for the purpose of sealing. The lip 33 is slightly divergent externally in a truncated cone from its base in the direction of its free end 35.

[0097] Moreover, the stopper 10 comprises a lug 36 projecting substantially radially to the annular skirt 13 towards the axis 11 of the stopper 10, the said lug 36 being situated towards the end part 22 of the skirt 13 connected to the transverse wall 12 of the stopper 10. The role of the lug 36 will be described later.

[0098] The stopper 10 also comprises a seal 9, substantially discoid, cut from the previously described sheet 1.

[0099] The seal 9 is placed inside the stopper 10 and is situated, before the first mounting of the stopper 10 on the neck 24 of the receptacle 25, towards the free end part 19 of the skirt 13 of the stopper 10, or towards the tamper-evident band 18, as illustrated in FIG. 5. To this end, the tamper-evident band 18 comprises a substantially annular protrusion 18b, situated close to the attachment projection 18a, towards the transverse wall 12 of the stopper 10. A space 37 is thus provided towards the tamper-evident band between the attachment projection 18a and the protrusion 18b, this space 37 being able to receive part of the seal 9 in order to ensure its holding in the stopper 10 before the first mounting of the stopper 10 on the neck 24 of the receptacle 25.

[0100] The seal 9 has a particular shape, obtained for example by thermoforming, this shape being complementary both to that of the neck 24 of the receptacle 25 with which the stopper 10 is intended to be associated, and to that of the internal face 38 of the transverse wall 12 of the stopper 10.

[0101] Thus, starting from the centre of the seal 9 and travelling over a radius of the said seal 9, there are encountered successively:

[0102] a substantially flat central part 39 parallel to the transverse wall 12 of the stopper 10;

[0103] a recess 40 situated substantially in line with the lip 33, formed moving away from the transverse wall 12 and possessing, in radial section, the general shape of a U whose bottom 41 is substantially parallel to the transverse wall 12, the said recess forming a housing 42 able to receive the said lip 33, as described below;

[0104] a peripheral area 32 substantially situated in the same plane as the central part 39;

[0105] an end 43 intended to be engaged in the space 37 provided in the tamper-evident band 18 of the stopper 10.

[0106] The diameter of the thermoformed seal 9 is substantially equal to the internal diameter of the skirt 13 or of the tamper-evident band 18 of the stopper 10.

[0107] In a similar fashion to the first embodiment, the seal 9 is placed inside the stopper 10 so that the first external layer 7 is situated opposite the transverse end wall 12.

[0108] Reference is now made to FIGS. 6, 8 and 9.

[0109] When the stopper 10 is first mounted on the neck 24 (FIG. 6), the rim 27 of the neck 24 comes into contact with the peripheral area 32 of the seal 9. The stopper 10 is given an axial movement directed towards the inside of the receptacle 25, and then a helical movement, so that the thread 15 on the stopper 10 and the thread 30 on the neck 24 come into mutual engagement. Consequently the seal 9 is moved axially by the rim 27 on the neck 24, towards the transverse wall 12 of the stopper 10, the end 43 of the seal being disengaged from the space 37 in which it was initially held.

[0110] When the stopper 10 is completely screwed onto the neck 24 (FIG. 8), the central part 39 of the seal 9 is substantially in contact with the transverse wall 12 of the stopper 10, the lip 33 is engaged in the housing 42, the peripheral area 32 of the seal 9 is compressed between the rim 27 of the neck 24 and the transverse wall 12 of the stopper 10, and the end 43 of the seal 9 is situated between the transverse wall 10 and the lug 36.

[0111] In addition, a recess area 40 of the seal 9 is compressed between the lip 33 and the internal face 34 of the neck 24.

[0112] Thus a good seal is provided between the inside and outside of the receptacle 25 closed by the stopper 10.

[0113] This embodiment makes it possible, because of the position of the seal 9 close to the tamper-evident band 18, to limit the introduction of oxygen into the receptacle 25 via the stopper 10 when the said stopper 10 is put in place on the neck 24, thus making any nitrogen inerting carried out before the mounting of the stopper 10 more effective.

[0114] When the thread 15 on the stopper 10 and the thread 30 on the neck 24 are at the start of mutual engagement, and before the stopper 10 is totally screwed onto the neck 24, it is possible to clean the external face 29 of the neck 24 with a water jet in order to remove any traces of product contained in the receptacle 25 on the said neck 24. This cleaning operation in no way impairs the properties of the content of the receptacle 25, since the seal 9 covers the opening 28 of the neck 24.

[0115] When a user unscrews the stopper 10, the seal 9 remains held at the bottom of the stopper 10, substantially against the transverse wall 12, firstly because of the lug 36 and secondly because of the divergence of the lip 33. Moreover, the tamper-evident band 18 is detached from the skirt 13 close to the breakable bridges 20 or the line of least strength. FIG. 9 depicts such a stopper 10, after fitting on a neck 24 and unscrewing.

[0116] Reference is now made to FIG. 7, which illustrates a third embodiment of the invention.

[0117] A neck 24 of a receptacle 25, similar to the neck in FIG. 4, is intended to receive a stopper 10, similar to the stopper in FIG. 5 but not having any seal.

[0118] The neck 24 is provided with a seal 9, substantially discoid, cut from the previously described sheet 1, the axis of the seal 9 and the axis 26 of the neck 24 being substantially merged. The seal 9 is placed on the neck 24 so as to entirely cover the opening 28 in the said neck 24, the diameter of the seal 9 therefore having to be sufficiently great. The seal 9 is placed on the neck 24 so that the second external layer 8 is situated opposite the inside of the neck 24.

[0119] The seal 9 is thermoformed, so that it has a shape complementary both to that of the neck 24 of the receptacle 25 whose opening 28 it covers and that of the internal face 38 of the transverse wall 12 of the stopper 10 intended to be associated with the said neck 24.

[0120] In the embodiment depicted, the seal 9 has a shape identical to that in FIG. 5, namely a substantially flat central part 39, a recess 40 situated so as to be recessed, towards the inside of the receptacle 25, with respect to the rim 27 of the neck 24—forming a housing 42 intended to receive the lip 33 of the stopper 10—one area of the said recess 40 being substantially tangent to the internal face 34 of the neck 24, a peripheral area 32 resting on the rim 27 of the neck 24, and an end 43 projecting beyond the outside of the neck 24.

[0121] The diameter of the thermoformed seal 9 is slightly greater than the outside diameter of the neck 24 and substantially equal to the inside diameter of the skirt 13 of the stopper 10 intended to cooperate with said neck 24.

[0122] According to a first variant, the seal 9, previously thermoformed, is placed on the neck 24 so that the shapes of the seal 9 and neck 24 cooperate.

[0123] According to a second variant, a substantially flat seal 9 is placed on the neck 24 so as to cover its opening 28, the said seal 9 then being fashioned by thermoforming in order to confer the required shape on it.

[0124] As previously described for the second embodiment of the invention, a cleaning of the neck 24 is then possible, the seal 9 providing the necessary sealing.

[0125] The stopper 10 can then be fitted by screwing onto the neck 24.

[0126] The assembly consisting of stopper 10, neck 24 and seal 9 thus formed is similar to that obtained with the second embodiment and is depicted in FIG. 8.

[0127] The peripheral area 32 of the seal 9 is then compressed between the rim 27 of the neck 24 of the receptacle 25 and the transverse wall of the stopper, and a recess area 40 of the seal 9 is compressed between the lip 33 and the internal face 34 of the neck 24, so that a good seal is provided between the inside and outside of the receptacle 25 closed by the stopper 10.

[0128] In addition, the end 43 of the seal 9 is situated between the transverse wall 12 and the lug 36. Thus, when the stopper 10 is unscrewed, the seal 9 is held at the bottom of the stopper 10, and the configuration illustrated in FIG. 9 is found.

[0129] As with the first and second embodiments, the seal:

[0130] prevents the entry and exit of gas into or out of the receptacle 25 (middle layer 2);

[0131] preserves the gas barrier properties of the middle layer (intermediate layers 3, 4);

[0132] absorbs the oxygen contained in the receptacle 25 (external layer 8) or entering the receptacle 25, because of the permeability of the said receptacle 25.

[0133] The quality of the content of the receptacle 25 is therefore preserved, even after several months of storage.

Claims

1. A composite seal able to be placed on a neck (24) of a receptacle (25) or in a stopper (10) comprising an annular skirt (13) provided with an internal thread (15) intended to cooperate with the external thread (30) of a neck (24) of a receptacle (25) for mounting the stopper (10) by screwing on the said neck (24), the said seal (9) comprising firstly a middle layer (2) produced from a plastics material with a gas barrier effect and secondly first and second external layers (7, 8) each comprising a polyolefin resin and disposed on each side of the said middle layer (2), the said seal also comprising, between the middle layer (2) and each of the external layers (7, 8), an intermediate polyethylene layer (3, 4), the said intermediate layers (3, 4) being intended to protect the middle layer (2) from moisture and thus to prevent degradation of the gas barrier properties of the said middle layer (2), characterized in that the middle layer (2) has a thickness of between 35 and 65 &mgr;m.

2. A seal according to claim 1, characterised in that the intermediate layers (3, 4) are produced from low or medium density polyethylene.

3. A seal according to claim 1, characterised in that the intermediate layers (3, 4) have a thickness of between 80 and 150 &mgr;m and in particular, around 115 &mgr;m.

4. A seal according to claim 1, characterised in that the intermediate layers (3, 4) are connected to the middle layer (2) by a layer of adhesive (5, 6).

5. A seal according to claim 1, characterised in that the polyethylene making up the intermediate layers (3, 4) has a rigidity modulus of between 250 and 500 MPa.

6. A seal according to claim 1, characterised in that the middle layer (2) consists of a sheet of EVOH (ethyl vinyl alcohol copolymer).

7. A seal according to claim 1, characterised in that the material making up the middle layer (2) has a rigidity modulus of between 1500 and 2500 MPa.

8. A seal according to claim 1, characterised in that the materials making up the external layers (7, 8) have a rigidity modulus of between 50 and 100 MPa.

9. A seal according to claim 1, characterised in that the first external layer (7) is produced from EVA (ethylene and vinyl acetate copolymer) comprising between 7% and 15% VA (vinyl acetate).

10. A seal according to claim 1, characterised in that the first external layer (7) has a thickness of between 90 and 160 &mgr;m.

11. A seal according to claim 1, characterised in that the second external layer (8) comprises polyethylene or EVA (ethylene and vinyl acetate copolymer).

12. A seal according to claim 1, characterised in that the second external layer (8) comprises a compound with an oxygen-absorbing effect.

13. A seal according to claim 12, characterised in that the compound with an oxygen-absorbing effect comprises sodium ascorbate and/or sodium sulphite.

14. A seal according to claim 1, characterised in that the second external layer (8) has a thickness of between 130 and 230 &mgr;m.

15. A stopper comprising firstly a transverse end wall (12) and secondly an annular skirt (13) projecting substantially perpendicular to the said transverse wall (12) and comprising an internal thread (15) intended to cooperate with the external thread (30) on a neck (24) of a receptacle (25) for mounting the stopper (10) by screwing on the said neck (24), characterised in that it also comprises a substantially discoid seal (9) according to any one of claims 1 to 14, the said seal (9) being placed inside the stopper (10), substantially perpendicular to the axis (11) of the said stopper (10), and being intended to provide impermeability to liquids and impermeability to gases between the inside and outside of the receptacle (25) closed by the said stopper (10).

16. A stopper according to claim 15, characterised in that the seal (9) is placed inside the stopper (10) so that the first external layer (7) is situated opposite the transverse end wall (12).

17. A stopper according to claim 15, characterised in that the seal (9) is substantially flat.

18. A stopper according to claim 15, characterised in that the seal (9) is situated close to the transverse wall (12).

19. A stopper according to claim 15, characterised in that it also comprises at least one serration (21) projecting radially from the annular skirt (13) towards the axis (11) of the stopper (10), the said serration (21) being situated close to the end part (22) of the skirt (13) connected to the transverse wall (12) of the stopper (10) so that the seal (9) can be placed between the said serration (21) and the transverse wall (12), the said serration (21) being intended to hold the seal (9) at the bottom of the stopper (10).

20. A stopper according to claim 15, characterised in that the seal (9) is thermoformed, so that it has a shape complementary firstly to that of the neck (24) of the receptacle (25) with which the stopper (10) is intended to be associated and secondly that of the internal face (38) of the transverse end wall (12) of the stopper (10), the said seal (9) being situated, before the stopper (10) is fitted on the neck (24) of the receptacle (25), close to the free end part (19) of the skirt (13) opposite to the transverse wall (12).

21. A stopper according to claim 19, characterised in that it also comprises a tamper-evident band (18) comprising means (18a, 18b, 37) of holding the seal (9) close to the said tamper-evident band (18) before the stopper (10) is fitted on the neck (24) of the receptacle (25).

22. A stopper according to claim 20, characterised in that it comprises a substantially annular lip (33) projecting from the transverse wall (12) in the same direction as the skirt (13), the said lip (33) being intended to cooperate with the internal face (34) of the neck (24) of the receptacle (25), the seal (9) being thermoformed so as to have a recess (40) forming a housing (42) able to receive the said lip (33).

23. A stopper according to claim 20, characterised in that, after the stopper (10) is fitted on the neck (24) of the receptacle (25), the seal (9) is situated close to the transverse wall (12).

24. A stopper according to claim 23, further characterised in that it comprises a lug (36) projecting substantially radially from the annular skirt (13) towards the axis (11) of the stopper (11), the said lug (36) being situated close to the end part (22) of the skirt (13) connected to the transverse wall (12) of the stopper (10) and in that the lip (33) is slightly divergent towards the outside in a truncated cone from its base in the direction of its free end (35), so that, after the stopper (10) is fitted on the neck (24) of the receptacle (25), the seal (9) is placed between the transverse wall (12) of the stopper (10) and the lug (36), the divergence of the lip (33) providing the holding of the seal (9) at the bottom of the stopper (10).

25. A receptacle neck or a receptacle having a neck, the said neck (24) being provided with an external thread (30) intended to cooperate with the internal thread (15) on a stopper (10) for mounting the stopper (10) by screwing onto the said neck (24), characterised in that it also comprises a substantially discoid seal (9), said seal (9) covering the opening (28) of the neck (24) and being thermoformed so that it has a shape complementary firstly to that of the neck (24) of the receptacle and secondly to that of the internal face (38) of the transverse end wall (12) of the stopper (10) intended to be associated with the neck (24), the said receptacle (25) being empty or at least partially filled with a certain content.

26. A receptacle neck or a receptacle having a neck according to claim 25, characterised in that the seal (9) is placed on the neck (24) so that the second external layer (8) is situated facing the inside of the neck (24).

27. An assembly comprising a stopper (10) according to claim 15, further comprising a neck (24) of a receptacle (25) or a receptacle (25) having a neck (24), the said receptacle (25) being empty or at least partially filled with a certain content.

28. An assembly according to claim 27, further characterised in that, when the stopper (10) is screwed onto the neck (24), an area of the seal (9) is compressed between the annular lip (33) and the internal face (34) of the neck (24) of the receptacle (25).

29. An assembly comprising a stopper and a receptacle neck (24), a receptacle neck or a receptacle having a neck, the said neck (24) being provided with an external thread (30) intended to cooperate with the internal thread (15) on a stopper (10) for mounting the stopper (10) by screwing onto the said neck (24), characterised in that it also comprises a substantially discoid seal (9), said seal (9) covering the opening (28) of the neck (24) and being thermoformed so that it has a shape complementary firstly to that of the neck (24) of the receptacle and secondly to that of the internal face (38) of the transverse end wall (12) of the stopper (10) intended to be associated with the neck (24), the said receptacle (25) being empty or at least partially filled with a certain content.

30. An assembly according to claim 27, further characterised in that, when the stopper (10) is screwed onto the neck (24), the seal (9) is compressed, close to its peripheral area (32), between the rim (27) of the neck (24) of the receptacle (25) and the transverse end wall (12) of the stopper (10), so as to ensure liquidtightness and impermeability to gases between the inside and outside of the receptacle (25).

31. A method of corking a neck (24) of a receptacle (25) or a receptacle (25) having a neck (24) with a stopper (10), according to claim 20, characterised in that, when an axial and/or helical screwing movement is imparted to the stopper (10), so that the thread (15) on the stopper (10) and the thread (30) on the neck (24) come into mutual engagement, the seal (9) is moved by the rim (27) of the neck (24) axially towards the transverse wall (12) of the stopper (10) until it comes substantially into contact with the said transverse wall (12).

32. A method of producing a receptacle neck, or a receptacle having a neck, provided with a seal, in accordance with claim 25, characterised in that a previously thermoformed seal (9) is placed on the said neck (24), the said seal (9) covering the opening (28) in the neck (24).

33. A method of producing a receptacle neck, or a receptacle having a neck, provided with a seal, in accordance with claim 25, characterised in that it comprises the following steps:

a substantially discoid and flat seal (9) is placed on the neck (24), the said seal (9) covering the opening (28) in the said neck (24);

the seal (9) is fashioned by thermoforming so as to give it a shape complementary firstly to that of the neck (24) and secondly to that of the internal face (38) of the transverse end wall (12) of the stopper (10) intended to be associated with the neck (24).

34. A method of corking a neck (24) of a receptacle (25) or a receptacle (25) having a neck (24) according to claim 25, further characterised by placing a stopper on the said neck (24) provided with the thermoformed seal (9).