[0002] It is known to make containers for liquids, such as bottles for drinks, by extrusion/blowing or injection/blowing of plastics material. It is known to equip such bottles with a cap, likewise made of plastics material. It is essential that these containers be closed hermetically with a view to allowing prolonged storage of the products that they contain. In effect, it should be avoided that oxygen can penetrate inside a closed container in order to limit the risks of oxydation of its contents. In addition, in the case of containers containing a gaseous liquid, such as beer or a carbonated drink, it should be avoided that the gas contained in the liquid escape outside the container. The transfers between the interior and the exterior of a container should also be limited in order to prevent a degradation of the organoleptic properties or of the taste of a drink such as a fruit juice or mineral water. For the principal part of the container, such as a bottle made of plastics material, it is known to prevent the migrations of gas from or towards the interior volume of the container by affixing an internal or external coating, for example of silica oxide or polyamide, on this body.
[0003] In that case, the leakages of gas are concentrated at the level of the cap of the closure device. In effect, the cap cannot be gas-tight by itself. If it is equipped with a gas-tight pellet, the material used for this pellet is relatively rigid, with the result that it cannot follow the shape of the neck with which it must cooperate sufficiently precisely, this inducing a risk of leakage at the interface between the neck and this pellet. On the contrary, if a supple material is used for constituting a seal as in EP-A-0 970 893, this material does not make it possible to limit efficiently the leakages of gas by permeability through the cap. In effect, in this state of the art, the same plastics material, for example of the ethylene/l-butene copolymer type, may possibly be applied in successive layers but is not completely tight since its coefficient of oxygen transfer remains non-zero. Moreover, the seal obtained is not always satisfactory. These imperfect properties of barrier or of seal are a consequence of the necessary compromises to be employed in order to make the same material perform hardly compatible functions.
[0004] It has been envisaged to equip a cap with an aluminium foil on which would be affixed a polypropylene foam intended to come into abutment against the neck of a bottle. Such a cap does not give satisfaction insofar as an interstice is created between the aluminium foil, which is floating, and the bottom web of the cap, this interstice promoting the development of germs and/or bacteria likely to contaminate the contents of the container. In addition, the cost price of such a device is high. Finally, the aluminium foil proves to be a hindrance when such a cap is reprocessed, as it must be processed differently from the plastics material.
[0005] It is a more particular object of the invention to overcome these drawbacks by proposing an economical method for making a closure device which makes it possible to render a container tight, particularly by avoiding the migrations of gas from inside the container towards the outside or from outside towards the inside.
[0006] In this spirit, the invention relates to a method for making a closure device in which a cap moulded from plastics material is equipped with a seal adapted to be arranged in abutment against the neck of a container. This method is characterized in that it comprises steps consisting in:
[0007] positioning, in the vicinity of an inner surface of a bottom web of the cap a first layer of material impermeable to a predetermined gas or gases, and
[0008] depositing on this first layer, in place in this cap, a second layer made of an elastic material and different from the material constituting the first layer, this second layer being intended to form the seal, by isolating this first layer from the ambient atmosphere.
[0009] Thanks to the method of the invention, the development of germs in the vicinity of the impermeable layer is avoided by isolating the latter from the ambient atmosphere thanks to the second layer which forms the seal. This second layer is advantageously made by overmoulding on the first layer, this guaranteeing its adaptation to the exact geometry of the interior of the button (sic). According to the invention, the material of the first layer may be chosen principally for the gas-tight properties of this first layer, while the material of the second layer may be chosen specifically as a function of its elasticity in order to perform its role of seal efficiently.
[0010] According to a first advantageous form of embodiment of the invention, the method comprises a step consisting in overmoulding, by injection or compression, the first layer against the web. Thanks to this aspect of the invention, no interstice can be created between the first layer, which is impermeable, and the bottom web of the cap.
[0011] According to another advantageous form of embodiment of the invention, there is provided the positioning of a plate, pre-cutout in material impermeable to the gas, in the vicinity of the bottom web of the cap, this plate then being immobilized against this web by the deposit of the second layer.
[0012] According to another advantageous form of embodiment of the invention, the first layer is projected onto the inner surface of the bottom web of the cap.
[0013] Whatever the form of embodiment considered, there may be provided a prior step of moulding of the cap, the positioning of the first layer and the deposit of the second layer being effected continuously, immediately after the moulding of the cap. This continuous aspect of the method avoids the possible deposit of impurities on the bottom web of the cap, during an intermediate storage step.
[0014] The invention also relates to a closure device capable of being manufactured in accordance with the method described hereinabove and, more precisely, to a closure device which comprises a layer of material impermeable to a predetermined gas or gases interposed between a seal and the bottom web of its cap, this layer being isolated from the ambient atmosphere by this cap and this seal which is made of a material different from that of the layer of gas-impermeable material.
[0015] According to advantageous aspects of the invention, this method and this device comprise one or more of the following characteristics:
[0016] The layer of impermeable material comprises a layer of silica oxide, or of carbon in diamond or amorphous form, integrated in a multi-layer complex arranged against the bottom web and covered with a layer of elastic material forming the seal.
[0017] The seal is made on the basis of a ethyl vinyl acetate (EVA) copolymer, of elastomer, in particular a derivative of polyamide (PA), of polyamide and/or polyether copolymer. This seal may also receive, in its composition, a component which renders it adapted to absorb a gas such as oxygen, in particular the oxygen of the “top empty space” of a bottle and/or the oxygen coming from the product contained in a bottle.
[0018] The seal is in the overall form of a disc, with a radius substantially equal to the inner radius of the cap, with the result that it efficiently isolates the layer of impermeable material by simply being positioned in the cap. The layer of impermeable material may thus be totally isolated from the outside medium, this allowing this layer to be made with specific materials which could not necessarily be used alone as they are capable of degrading upon contact with the product or with the air.
[0019] Finally, the invention relates to a container for liquid, particularly a bottle made of plastics material, equipped with a closure device such as described hereinabove. Such a container makes it possible to store the product that it contains for a relatively long period of time and without risk of alteration.
[0020] The invention will be more readily understood and other advantages thereof will appear more clearly in the light of the following description of three closure devices in accordance with the invention and of their respective methods of manufacture, given solely by way of example and made with reference to the accompanying drawings, in which:
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
[0035] The cap
[0036] The cap
[0037] The cap
[0038] Taking into account the manufacturing tolerances of the neck
[0039] Before such a seal is placed in position, an impermeable complex
[0040] As is more clearly seen in
[0041] The complex
[0042] The afore-mentioned complex
[0043] a very fine deposit, on a support disc, of diamond carbon or of amorphous carbon, this deposit being effected by a plasma deposit or pulverization technique. These deposit techniques are also applied to the deposit of the layer
[0044] a particular material, of PVC, PVDC, EVOH, PA type or a mixture of these materials. PEN (polyethylene napthalate), PVA (polyvinyl alcohol), the acrylate copolymers of PAN (polyacrylonitrite), PPMA (polymethylmethacrylate), the copolymers of butadiene, styrene, BOPP (bi-oriented polypropylene) or one of the mixtures thereof may also be used.
[0045] A seal
[0046] The seal
[0047] As is seen in
[0048] The seal
[0049] The operation of overmoulding of the seal
[0050] As is more particularly visible in
[0051] In the second form of embodiment of the invention shown in FIGS.
[0052] On this inner surface there is deposited a quantity Q of plastics material impermeable to oxygen and to carbon dioxide. It may be question of polyvinylchloride (PVC), of polyvinylidene chloride (PVDC), of ethylene vinyl alcohol (EVOH), of polyamide or of a mixture based on one of these products. In a variant, polyethylene naphthalate (PEN), polyvinyl acohol (PVA), acrylate copolymer of polyacrylnitrile (PNA) type, polymethylmethacrylate (PPMA), copolymer of butadiene, styrene, bi-oriented polypropylene (BOPP), may be used for this layer.
[0053] A plunger
[0054] A seal
[0055] As previously, the impermeable layer
[0056] As previously, the radii R of the seal
[0057] The closure device of this second form of embodiment may be obtained thanks to an installation similar to that shown in
[0058] In the third form of embodiment of the invention shown in
[0059] As shown in
[0060] The layer
[0061] After the deposit of the layer
[0062] As previously, the layer forming the seal
[0063] The fact of moulding the cap
[0064] However, the cap might equally well be moulded by injection.
[0065] In order to limit the risks of migration of oxygen towards the outside, the layer