EP4299266A1 - Method for manufacturing a cap for closing a bottle including sheets of cork glued to both mirrors and to the roll - Google Patents

Abstract

Process for manufacturing a stopper for sealing a bottle so that it can be inserted by force into the neck of the bottle, comprising the following steps:
- cutting (the) sheets of cork to stick on the mirrors and on the roll of the cork,
- bonding (2a, 2b, 2c) of one of said cork sheets on the roll of the semi-finished cork of reduced diameter via a deposition of a binder suitable for food contact, followed by steaming, And
- bonding (3a, 3b, 3c) of each of the other cork sheets on each mirror of the semi-finished cork of reduced diameter via a deposition of a binder suitable for food contact, followed by steaming,
the semi-finished stopper of reduced diameter being a crushed cork stopper glued under pressure with a polyurethane binder, having a uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll.

Description

Technical area

The technical field of the invention is cork stoppers, and more particularly, such stoppers reconstituted from cork elements.

Previous techniques

Cork is a natural, waterproof and lightweight material, which comes from the bark of certain species of oaks, such as cork oaks, which are typically found in countries around the Mediterranean, in Europe and in North Africa.

Cork is particularly used in the manufacture of stoppers, which are used to seal containers such as bottles containing liquids intended for food, in particular still or sparkling wine, spirits or other drinks. Corks are produced either by casing cork boards or by reconstitution using crushed cork sifted with polymers.

Cork is an elastic, resilient, compressible material, impermeable to liquids and with a high coefficient of friction. Its structure offers gas permeability allowing the exchange of oxygen useful for the maturation of the product in the bottle. The structure of the cork stoppers resulting from tubing, the aesthetics of which are very appreciated, is however very variable leading to the variability of this passage of oxygen.

Conversely, reconstituted corks, called agglomerates or microagglomerates, produced from cork crushed into granules, are much more homogeneous in structure.

Such agglomerated or microagglomerated corks are manufactured in several successive stages during which we first obtain a raw cork following the step of crosslinking the binder between the pieces of cork. These raw plugs are then machined to give them the required diameter and length. We then obtain so-called semi-finished corks.

These corks then undergo various more or less optional stages in order to make them conform to a marketed cork ready for bottling. The corks are then called finished corks.

Reconstituted corks, called agglomerated or microagglomerated, have the major disadvantage in aesthetic terms of moving away from the classic visual appearance of so-called “natural” corks tubed directly into the cork board. In return, they offer much better permeability characteristics, beneficial for the aging of the wine, as well as the possibility of treating the cork so as to reduce the presence of TCA (acronym for “2,4,6 trichloroanisole”) at trace level. . Remember that TCA is the cause of a change in the taste of the wine through the appearance of a so-called cork taste.

Nevertheless, this move away from the classic visual appearance of natural corks is at the origin of a priori on the part of both consumers and winegrowers, even if progress has been made regarding the appearance of these corks. We can cite, for example, laser screen printing which reproduces the appearance of pores and lenticels visible in natural corks. However, this progress is still insufficient so that consumers and winegrowers are still able to distinguish agglomerated or microagglomerated corks from so-called “natural” corks.

Various documents have been published to try to resolve both the preconceptions of certain users or consumers and the use of cork parts whose size or appearance does not allow a natural cork stopper to be extracted.

Each document provides a technical solution to the use of a part of the cork by seeking to visually come as close as possible to a traditional natural cork.

Among these solutions, we note cork stoppers called 1+1 whose opposite end faces (commonly called “mirrors”) are made of cork slices and the central body of agglomerated cork granules.

The mirrors of the reconstituted cap are thus masked by the cork washers both from an aesthetic and mechanical point of view.

In such a 1+1 cap, the side face of the cap (commonly called "roll"), in contact with the bottle, is not modified. The user and consumer can then identify the nature of the stopper, which is the cause of prejudice and, for some, rejection.

Until now, it was commonly accepted that it was not possible to modify the roll of a reconstituted cork, due to the forces involved both during bottling and during extraction of the cork. Specifically, it was considered that these forces would cause the glued cork sheet to separate. However, such lateral bonding is necessary to make the corks, natural or reconstituted, visually very similar, in order to overcome the prejudices linked to technical corks.

A technical problem to be solved is how to make a cork for corking a bottle in which the mirrors and the roller are covered with a layer of natural cork, and which resists bottling and uncorking.

Presentation of the invention

• découpe de feuilles de liège à coller sur les miroirs et sur le roule d'un bouchon semi-fini de diamètre réduit,
• collage d'une desdites feuilles de liège sur le roule d'un bouchon semi-fini de diamètre réduit par l'intermédiaire d'un dépôt d'un liant apte au contact alimentaire, suivi d'un étuvage, et
• collage de chacune des autres feuilles de liège sur chaque miroir du bouchon semi-fini de diamètre réduit par l'intermédiaire d'un dépôt d'un liant apte au contact alimentaire, suivi d'un étuvage, le bouchon semi-fini de diamètre réduit étant un bouchon en liège trituré collé sous pression avec un liant polyuréthane, présentant un diamètre uniformément réduit d'une épaisseur égale à deux fois l'épaisseur d'une feuille de liège collée sur le roule.

The subject of the invention is a method of manufacturing a cap for sealing a bottle comprising two mirrors and a wheel so that it can be inserted by force into the neck of the bottle, comprising the following steps:

• cutting cork sheets to stick on the mirrors and on the roll of a semi-finished cork of reduced diameter,
• bonding one of said cork sheets to the roll of a semi-finished cork of reduced diameter via the deposition of a binder suitable for food contact, followed by steaming, and
• bonding of each of the other cork sheets on each mirror of the semi-finished cork of reduced diameter by means of a deposit of a binder suitable for food contact, followed by steaming, the semi-finished cork of reduced diameter being a crushed cork stopper glued under pressure with a polyurethane binder, having a uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll.

The cork sheets glued to the cork roll can be cut from cork in a direction perpendicular to the lenticels.

The cork sheets glued to the mirrors of the cork can be cut from cork in a direction parallel or perpendicular to the lenticels.

Cork sheets can be treated so as to have a tricholoranisole level of less than 0.3ng/l, preferably by treatment with supercritical carbon dioxide.

The semi-finished cork of reduced diameter can be sanded and/or trimmed after gluing a sheet of cork to adapt the dimensions of the glued cork sheet to the dimensions of a semi-finished cork which has not undergone any reduction in diameter. diameter.

The binder may be a one-component polyurethane, a two-component polyurethane or a hot melt polyurethane.

Water can be applied before, during, or after the binder application to accelerate the crosslinking of the binder.

Steaming can be carried out at a temperature between 80°C and 150°C for a period of between 10min and 1h30 for a polyurethane binder.

Steaming can be carried out in an autoclave or a tunnel.

The semi-finished stopper of reduced diameter with a glued cork sheet can be placed in a mold allowing pressure to be applied in a direction normal to the surface of the cork sheet, the mold being preheated to the steaming temperature.

To prepare a semi-finished cap of reduced diameter, a semi-finished cap can be machined so as to uniformly reduce its diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll.

To prepare a semi-finished cork of reduced diameter, a raw cork of reduced diameter can be formed in a mold of uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll corresponding to the diameter of a semi-finished cap of reduced diameter, then the raw cap of reduced diameter can be machined so as to obtain a semi-finished cap of reduced diameter.

A sheet of cork glued to the roll can have a thickness of between 0.3mm and 1mm.

A sheet of cork glued to a mirror can have a thickness of between 0.3mm and 2mm.

• un bouchon semi-fini de diamètre réduit comprenant deux miroirs et un roule,
• une feuille de liège collée sur chacun des miroirs et du roule du bouchon semi-fini de diamètre réduit,

le bouchon semi-fini de diamètre réduit étant un bouchon en liège trituré collé sous pression avec un liant polyuréthane, présentant un diamètre uniformément réduit d'une épaisseur égale à deux fois l'épaisseur d'une feuille de liège collée sur le roule.The invention also relates to a cap for corking a bottle comprising two mirrors and a roll so that it can be inserted by force into the neck of the bottle, comprising:

• a semi-finished cap of reduced diameter comprising two mirrors and a wheel,
• a sheet of cork glued to each of the mirrors and the roll of the semi-finished cork of reduced diameter,

the semi-finished stopper of reduced diameter being a crushed cork stopper glued under pressure with a polyurethane binder, having a uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll.

Brief description of the drawings

• la figure 1 illustre les principales étapes d'un procédé de fabrication selon l'invention,
• les figures 2 à 4 illustrent la direction de découpe des feuilles de liège dans un parallélépipède de liège,
• la figure 5 illustre les résultats de tests d'imbibition de bouchons selon l'invention et de bouchons de référence,
• la figure 6 illustre les résultats de tests de retour élastique de bouchons selon l'invention et de bouchons de référence,
• la figure 7 illustre les résultats de tests de force d'extraction de bouchons selon l'invention et de bouchons de référence, et
• la figure 8 illustre les principaux éléments d'un bouchon selon l'invention.

Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

• there figure 1 illustrates the main stages of a manufacturing process according to the invention,
• THE figures 2 to 4 illustrate the cutting direction of the cork sheets in a cork parallelepiped,
• there Figure 5 illustrates the results of imbibition tests of caps according to the invention and of reference caps,
• there Figure 6 illustrates the results of elastic return tests of caps according to the invention and of reference caps,
• there Figure 7 illustrates the results of extraction force tests of caps according to the invention and of reference caps, and
• there figure 8 illustrates the main elements of a cap according to the invention.

detailed description

The method of manufacturing a stopper according to the invention is illustrated by the figure 1 .

During a first sub-step la of the first step 1, cork blades with a thickness of between 0.3mm and 2mm are cut from a parallelepiped of cork having a shape adapted to their bonding on the mirrors and the rolls from a semi-finished cap described below.

In a particular embodiment, the cork blades glued to the mirrors of the semi-finished stopper of reduced diameter are cut from cork in a direction parallel to the lenticels. Lenticels are defined as the veins opening into the pores of the cork bark. The cork blade glued to the roll of the semi-finished cork of reduced diameter is cut from cork in a direction perpendicular to the lenticels.

There figure 2 illustrates a parallelepiped of natural cork referenced 4 comprising lenticels 5 opening onto pores 6. We define the cutting plane A parallel to the lenticels and the cutting plane B perpendicular to the lenticels.

There Figure 3 illustrates the surface of a first type 4a of cork blades cut along plane A, parallel to the lenticels. We note that we find lenticels or fragments of lenticels visible on the surface of a blade thus cut. Such a blade is preferably glued to the mirrors of a cap.

There Figure 4 illustrates the surface of a second type 4b of cork blade cut along plane B, perpendicular to the lenticels. Pores 6 resulting from the cutting of lenticels 5 are visible on the surface of the cork blade. Such a blade is preferably glued to the roll of a cork. In a particular embodiment, such a blade is also glued to the mirrors of the cap. Such an embodiment has the advantage of reducing costs by cutting the cork blades glued to the roll and the mirrors in the same direction, both in terms of the industrial process and the supply of cork.

It should be noted that the commercially available cork parallelepipeds, corresponding to the parallelepipeds referenced 4 on the figure 2 generally have a width of 25mm. Such a width limits the possibilities of cutting a sheet of cork to stick on the roll of a cork. In fact, a cap generally has a length of between 38mm and 54mm for a diameter of 24mm. Such a diameter of 24mm implies a perimeter of approximately 75mm. The cork sheet glued to the roll thus has a length of 75mm for a width of between 38 and 54mm, exceeding the width of a cork parallelepiped. Such sheets must therefore be cut perpendicular to the width of the parallelepiped and perpendicular to the lenticels.

The cork strips thus cut present a visual similar to the visual observed in a cork cased in a parallelepiped of cork, so as to reinforce the visually very similar appearance of the corks obtained compared to corks cased in cork.

During a second sub-step 1b of the first step 1, a semi-finished cork is prepared whose diameter after gluing a sheet of cork is equal or substantially equal to the diameter of a semi-finished cork resulting not of this manufacturing process. By finished cork, we mean a crushed cork stopper glued under pressure with a polyurethane binder machined so as to be ready for the traffic jam. The request for patent FR2672002 in the name of the plaintiff illustrates such a stopper. Only finishing steps separate a semi-finished cork from a finished cork. Such a reduction in diameter is important in order to ensure that the cap produced, after finishing, has a diameter ensuring that the extraction force will be less than the limit of 50daN.

In a first embodiment, a semi-finished cork is machined so as to reduce its diameter uniformly by a thickness equal to twice the thickness of a sheet of cork glued to the roll.

In a second embodiment, a raw cork is formed in a mold having an internal diameter reduced to a thickness equal to twice the thickness of a sheet of cork glued to the roll in relation to the diameter of a mold for form a raw plug of reduced diameter. The raw plug of reduced diameter obtained is then machined in a manner similar to the machining of a raw plug, in accordance with industry practice. We then obtain a semi-finished plug of reduced diameter similar to that obtained by the first embodiment.

During a second step 2, a sheet of cork is glued to the roll of the semi-finished cork of reduced diameter obtained in the previous step.

During a first sub-step 2a, a binder suitable for food contact is deposited on the semi-finished cork of reduced diameter and/or the cork sheet.

The binder may in particular be a one-component polyurethane binder, a two-component polyurethane binder or a hot-melt polyurethane binder.

In a particular embodiment, the crosslinking of the binder is improved by wetting the sheet and/or the cap by spraying water or by condensation of water in a humid or humidity-saturated atmosphere.

During a second sub-step 2b, the assembly formed by the semi-finished stopper of reduced diameter and the cork sheet is steamed by applying pressure normal to the glued sheet. via a mold, possibly preheated to the steaming temperature. Finally, sanding and trimming are carried out during a third sub-step 2c to adapt the dimensions of the glued cork sheet to the dimensions of the cork. This step is optional and depends on the result obtained at the end of the second sub-step 2b.

During a third step 3, a sheet of cork is glued to each mirror of the cork. To achieve this, we carry out steps similar to substeps 2a to 2c. During a first sub-step 3a, a binder suitable for food contact is deposited on the semi-finished cork of reduced diameter and/or the cork sheets, possibly supplemented by humidification of the cork sheet and/or the cork . The cork sheets are then applied to the semi-finished cork of reduced diameter.

During a second sub-step 3b, the assembly formed by the semi-finished stopper of reduced diameter and the cork sheets is steamed by applying normal pressure to the glued sheets via a mold. , possibly preheated to the steaming temperature. Finally, just as for the third sub-step 2c, sanding and trimming are carried out, to adapt the dimensions of the glued cork sheets to the dimensions of the cork, when this proves necessary.

It will be understood that the two steps 2 and 3 are interchangeable. It will also be understood that the steaming sub-steps can be carried out under other conditions making it possible to maintain uniform heat, in particular via a heating tunnel.

Various tests were carried out to determine the temperature and duration conditions allowing the cork sheets to be bonded while maintaining the mechanical properties of the cork.

During the tests, the maximum temperature was determined to be equal to 150°C, the temperature at which cork burns. A temperature between 80°C and 150°C, preferably between 90°C and 115°C, or preferably between 100°C and 110°C has been determined to be satisfactory.

In certain embodiments of agglomerated or microagglomerated caps, thermoexpandable microspheres are added to the polyurethane binder. The maximum temperature is then equal to 110°C, a temperature beyond which the plugs are damaged by the expansion of the microspheres.

Several tests were carried out to determine the optimal baking duration in order to obtain good crosslinking of the binder.

For the polyurethane binder, a duration of 1 hour allows good polymerization to be obtained. On the other hand, durations greater than 1h30 do not provide any improvement in crosslinking, so that they rather represent a disadvantage of the production process by leading to a reduction in productivity associated with the manufacturing process.

Steaming at a temperature between 100°C and 110°C for a period of between 1 hour and 1 hour 30 minutes was thus determined to lead to satisfactory bonding of the cork sheet to the semi-finished cork with a polyurethane binder. Other temperatures and times may be required for other binders.

This steaming is carried out by placing the corks glued with a sheet of cork in a mold allowing a force to be exerted on the sheet to be glued. For bonding a sheet of cork to a mirror, a cylindrical mold with hinge, piston or screw is used so as to apply pressure in an axial direction of the cork. For gluing a sheet of cork to the roll, a cylindrical mold with hinge and latches or bolted is used so as to apply pressure on the cork radially.

It is possible to reduce the steaming time by preheating the molds to apply normal force to the cork sheets. The applicant then noted that the baking time is reduced to 10 minutes for a baking temperature of 150°C, to 40 minutes for a baking temperature of 100°C, and to 1 hour for a baking temperature of 80°C. °C.

The crosslinking of the binder has been described in relation to steaming. It is nevertheless possible to use other means of heating, in particular a heating tunnel, equipped with a conveyor belt and allowing the molds to pass through while heating them. The speed of movement is then correlated with the length of the tunnel so as to obtain the heating times described above.

The applicant took care to carry out a preliminary test campaign on around thirty caps manufactured according to the manufacturing process of the invention in order to verify that the caps obtained with the present manufacturing process offer characteristics similar to the caps on which they are based. In other words, it has been verified that the glued cork sheets do not degrade the performance of the cork, particularly for bottling or uncorking the bottle. The test campaign therefore aimed to measure imbibition, elastic return and extraction force. THE figures 5 to 7 illustrate the results of these tests and their comparison with reference caps.

The results of the plugs according to the invention are represented by disc-shaped symbols while the results of the reference plugs are represented by symbols in the shape of a triangle. Likewise, the trend associated with the caps according to the invention is represented in dotted lines, while the trend associated with the reference caps is represented in dashes.

The imbibition of a cork characterizes its absorption of water under particular conditions of temperature and pressure. We generally measure the imbibition of a cork according to the pressure, so as to know its behavior after bottling. Indeed, during bottling, the air present in the bottle between the liquid and the bottle is compressed, to pressures that can reach a few dozen bars. Such pressures can cause the plugs to lose their tightness.

In the present case, the imbibition measurement makes it possible to verify that the impregnation of the cork prior to gluing the cork sheet does not lead to deterioration during steaming. The imbibition of the caps was estimated following a mass measurement of the caps totally immersed in water at 100°C for 15 min. This temperature makes it possible to visualize the behavior of the plugs. accelerated manner in extreme conditions. We then determine the imbibition as the ratio of the difference in mass before immersion and after immersion by the mass before immersion.

There Figure 5 illustrates the results obtained for the caps according to the invention and for reference caps having a structure similar to that of the semi-finished caps in the manufacturing process according to the invention.

The imbibition of the caps according to the invention is thus similar in order of magnitude and in deviation to that of the reference caps. The imbibition is thus between 3 and 6% mass imbibition, i.e. significantly lower than the compliance limit of 11%.

The springback was then measured. Elastic return is one of the mechanical properties of a cork and makes it possible to quantify the force generated in reaction by the cork on the wall of the neck of the bottle. The elastic return is measured automatically with the “Multitest 10i” machine from the Mecmesin company.

During these measurements, the cork undergoes compression until it reaches a diameter of between 15mm and 16mm, which corresponds to the diameter of the jaws of a corker. Compression is obtained using a piston which moves at a speed of 10 mm/min. The force required (in Newtons) to perform this compression is measured. The compression value is reduced to the cylindrical surface of the cap. This must be between 15 and 60 N/cm ² and preferably between 25 and 60 N/cm ² depending on the diameters of the plugs.

The plates will then release the pressure and position themselves at a distance of 21 millimeters from each other, called the return distance. After 180 seconds, the pressure exerted by the cap on the plates is noted. This pressure corresponds to the elastic return force (also in Newton). For the interpretation of the results, these forces will be calculated in relation to the surface of each plug, and therefore expressed in Newton per square centimeter.

There Figure 6 illustrates the results obtained for the caps according to the invention and for the reference caps.

The elastic return of the caps according to the invention is significantly lower, at constant density compared to that of the reference caps, while remaining higher than the limit of 3.2 N/cm ² of the standard.

It should be noted that during these tests, no tearing of the glued cork sheet was observed.

The extraction forces making it possible to quantify the force necessary to extract the cork from the neck of the bottle were then measured. They are measured as follows. First, caps to be tested are introduced into bottle necks. After 2 hours of rest in the necks, the corks are extracted using a corkscrew connected to a system for measuring the force necessary to extract the cork from the neck of the bottle, such as the machine " Multitest 2.5 - d” from the company Mecmesin. The extraction force value must be between 100 and 600 N, preferably between 200 and 500 N depending on the diameters of the plugs.

There Figure 7 illustrates the results obtained for the caps according to the invention and for the reference caps.

The extraction force of the plugs according to the invention is thus similar in order of magnitude to that of the reference plugs, while presenting a greater deviation but nevertheless close to that of the reference plugs.

There figure 8 illustrates the main parts of the cap according to the invention.

A cap according to the invention comprises in its center a semi-finished cap of reduced diameter having a reduced length, referenced 10. It comprises two mirrors 10a and a wheel 10b.

A sheet of cork 20a is glued to each mirror 10a of the semi-finished cork of reduced diameter.

A sheet of cork 20b is glued to the roll 10b of the semi-finished cork of reduced diameter.

The semi-finished stopper of reduced diameter is a crushed cork stopper glued under pressure with a polyurethane binder. The patent application FR2672002 in the name of the plaintiff illustrates such a stopper.

Claims (15)

Process for manufacturing a stopper for sealing a bottle comprising two mirrors and a roll so that it can be inserted by force into the neck of the bottle, comprising the following steps: - cutting cork sheets (20a20b) to stick on the mirrors (10a) and on the roll (10b) of a semi-finished cork of reduced diameter, - gluing one of said cork sheets onto the roll (10b) of a semi-finished cork of reduced diameter via the deposition of a binder suitable for food contact, followed by steaming, and - gluing each of the other cork sheets on each mirror (10a) of the semi-finished cork of reduced diameter via a deposit of binder suitable for food contact, followed by steaming, the semi-finished stopper of reduced diameter being a crushed cork stopper glued under pressure with a polyurethane binder, having a uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the roll. Manufacturing method according to claim 1, in which the cork sheets glued to the roll of the cork are cut from cork in a direction perpendicular to the lenticels. Manufacturing method according to any one of claims 1 or 2, in which the cork sheets glued to the mirrors of the stopper are cut from cork in a direction parallel or perpendicular to the lenticels. Manufacturing process according to any one of claims 1 to 3, in which the cork sheets are treated so as to have a tricholoranisole level of less than 0.3ng/1, preferably by treatment with supercritical carbon dioxide. Manufacturing method according to any one of claims 1 to 4, in which the cork is sanded and/or trimmed semi-finished with reduced diameter after gluing a sheet of cork to adapt the dimensions of the glued cork sheet to the dimensions of a semi-finished cork which has not undergone a reduction in diameter. Manufacturing method according to any one of claims 1 to 5, in which the binder is a one-component polyurethane, a two-component polyurethane or a hot melt polyurethane. Manufacturing method according to any one of claims 1 to 6, in which water is applied before, during, or after the application of binder in order to accelerate the crosslinking of the binder. Manufacturing process according to any one of claims 1 to 7, in which the steaming is carried out at a temperature between 80°C and 150°C for a period of between 10 min and 1h30 for a polyurethane binder. Manufacturing process according to any one of claims 1 to 8, in which the steaming is carried out in an autoclave or a tunnel. Manufacturing method according to any one of claims 1 to 9, in which the semi-finished stopper of reduced diameter with a glued sheet of cork is placed in a mold making it possible to apply pressure in a direction normal to the surface of the cork sheet, the mold being preheated to the steaming temperature. Manufacturing method according to any one of claims 1 to 10, in which, to prepare a reduced semi-finished plug, a semi-finished plug is machined so as to uniformly reduce its diameter by a thickness equal to twice l thickness of a sheet of cork glued to the roll. Manufacturing method according to any one of claims 1 to 10, in which, to prepare a semi-finished stopper of reduced diameter, a raw stopper of reduced diameter is formed in a mold of uniformly reduced diameter with a thickness equal to two times the thickness of a sheet of cork glued to the roll corresponding to the diameter of a semi-finished cork of reduced diameter, then the raw cap of reduced diameter so as to obtain a semi-finished cap of reduced diameter. Manufacturing method according to any one of claims 1 to 12, in which a sheet of cork glued to the roll has a thickness of between 0.3mm and 1mm. Manufacturing method according to any one of claims 1 to 13, in which a sheet of cork glued to a mirror has a thickness of between 0.3mm and 2mm. Stopper for stopping a bottle comprising two mirrors and one roll so that it can be inserted by force into the neck of the bottle, characterized in that it comprises: - a semi-finished cap of reduced diameter (10) comprising two mirrors (10a) and a wheel (10b), - a sheet of cork (20a, 20b) glued to each of the mirrors and the roll of the semi-finished cork of reduced diameter (10), the semi-finished stopper of reduced diameter (10) being a crushed cork stopper glued under pressure with a polyurethane binder, having a uniformly reduced diameter with a thickness equal to twice the thickness of a sheet of cork glued to the rolled.

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