Method of manufacturing a stopper for closing a bottle, comprising sheets of cork glued to the two mirrors and to the roll and stopper

Abstract

A method for manufacturing a stopper for sealing a bottle so that it can be forced into the neck of the bottle, comprising the following steps: - cutting (a) sheets of cork to be glued onto the mirrors and the roll of the stopper, - gluing (2a,2b,2c) one of said sheets of cork onto the roll of the semi-finished stopper of reduced diameter by means of a deposit of a binder suitable for food contact, followed by steaming, and - gluing (3a,3b,3c) each of the other sheets of cork onto each mirror of the semi-finished stopper of reduced diameter by means of a deposit 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 of a thickness equal to twice the thickness of a sheet of cork glued onto the roll.

Description

technical field

[0001] The invention relates to a method for manufacturing a stopper according to the preamble of claim 1 and a stopper, according to the preamble of claim 15. Such a method and such a stopper are known from document ES288387 Al. Previous techniques

[0002] Cork is a natural, waterproof and lightweight material that comes from the bark of certain species of oak trees, such as cork oaks, which are typically found in countries around the Mediterranean, in Europe and North Africa.

[0003] Cork is notably used in the manufacture of stoppers, which serve to seal containers such as bottles containing liquids intended for consumption, particularly still or sparkling wine, spirits, or other beverages. Stoppers are produced either by tubing cork planks or by reconstitution using crushed and sieved cork mixed with polymers.

[0004] Cork is an elastic, resilient, compressible material that is impermeable to liquids and has a high coefficient of friction. Its structure allows for gas permeability, enabling oxygen exchange that is beneficial for the maturation of the bottled product. However, the structure of cork stoppers produced from tubing, while highly valued for their aesthetic appeal, varies considerably, resulting in variability in this oxygen transmission.

[0005] Conversely, reconstituted corks, known as agglomerated or micro-agglomerated corks, produced from crushed cork into granules, are much more homogeneous in structure.

[0006] Such agglomerated or micro-agglomerated corks are manufactured in several successive stages, during which a raw cork is first obtained after the binder has been cross-linked between the pieces of cork. These raw corks are then machined to give them the required diameter and length. The result is what are called semi-finished corks.

[0007] These corks then undergo various stages, some more optional than others, to make them conform to a commercially available cork ready for bottling. At this stage, the corks are called finished corks.

[0008] Reconstituted corks, also known as agglomerated or micro-agglomerated corks, have the major aesthetic drawback of deviating from the classic look of so-called "natural" corks, which are inserted directly into the cork block. However, they offer significantly better permeability characteristics, beneficial for wine aging, as well as the possibility of treating the cork to reduce the presence of TCA (2,4,6-trichloroanisole) to trace levels. It is worth noting that TCA is responsible for a change in the taste of wine, resulting in a characteristic known as cork taint.

[0009] Nevertheless, this departure from the classic appearance of natural corks has led to preconceived notions among both consumers and winemakers, even though progress has been made in their appearance. For example, laser screen printing reproduces the appearance of the pores and lenticels visible in natural corks. However, these advances are still insufficient, meaning that consumers and winemakers can still distinguish between agglomerated or micro-agglomerated corks and so-called "natural" corks.

[0010] Various documents have been published to try to resolve both the preconceptions of some users or consumers and the use of parts of cork whose size or appearance does not allow the extraction of a natural cork stopper.

[0011] Each document provides a technical solution for the use of a part of the cork, seeking to visually approximate a traditional natural cork as closely as possible.

[0012] Among these solutions, we note the cork stoppers called 1+1, whose opposite end faces (commonly called "mirrors") are made of cork discs and the central body of agglomerated cork granules.

[0013] The mirrors of the reconstituted cork are thus masked by the cork washers from both an aesthetic and mechanical point of view.

[0014] In such a 1+1 closure, the lateral face of the closure (commonly called the "roll"), which is in contact with the bottle, remains unchanged. The user and the consumer can then identify the nature of the closure, which is the source of prejudice and, for some, rejection.

[0015] Until now, it was generally accepted that it was impossible to alter the roll of a reconstituted cork due to the forces involved in both bottling and extraction. More specifically, it was believed that these forces would cause the glued cork layer to separate. However, such lateral gluing is necessary to make natural and reconstituted corks visually very similar, thus overcoming prejudices associated with technical corks.

[0016] A technical problem to solve is how to manufacture a stopper to seal a bottle in which the mirrors and the roll are covered with a layer of natural cork, and which resists bottling and uncorking. Description of the invention

[0017] The invention relates to a method for manufacturing a stopper for sealing a bottle comprising two mirrors and a roller so as to be able to be forced into the neck of the bottle, comprising the following steps: cutting of cork sheets to be glued onto the mirrors and the roll of a semi-finished stopper of reduced diameter, gluing one of said cork sheets onto the roll of a semi-finished stopper of reduced diameter by means of a deposit of a binder suitable for food contact, followed by steaming, and gluing each of the other cork sheets onto each mirror of the semi-finished stopper of reduced diameter by means of a deposit 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 of a thickness equal to twice the thickness of a cork sheet glued onto the roll.

[0018] The cork sheets glued onto the cork roll can be cut from cork in a direction perpendicular to the lenticels.

[0019] The cork sheets glued onto the mirrors of the stopper can be cut from cork in a direction parallel or perpendicular to the lenticels.

[0020] Cork sheets can be treated to have a trichloroanisole level of less than 0.3ng / l, preferably by treatment with supercritical carbon dioxide.

[0021] The semi-finished cork with a reduced diameter can be sanded and / or trimmed after a cork sheet has been glued on to adapt the dimensions of the glued cork sheet to the dimensions of a semi-finished cork that has not undergone a diameter reduction.

[0022] The binder can be a one-component polyurethane, a two-component polyurethane, or a hot-melt polyurethane.

[0023] Water can be applied before, during, or after the application of binder to accelerate the crosslinking of the binder.

[0024] Oven curing can be carried out at a temperature between 80°C and 150°C for a duration of between 10 minutes and 1 hour 30 minutes for a polyurethane binder.

[0025] Steaming can be carried out in an autoclave or a tunnel.

[0026] 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.

[0027] To prepare a semi-finished cork of reduced diameter, a semi-finished cork is formed according to the invention so as to uniformly reduce its diameter by a thickness equal to twice the thickness of a sheet of cork glued onto the roll.

[0028] 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 onto the roll corresponding to the diameter of a semi-finished cork of reduced diameter, then the raw cork of reduced diameter can be machined so as to obtain a semi-finished cork of reduced diameter.

[0029] A sheet of cork glued onto the roll can have a thickness of between 0.3mm and 1mm.

[0030] A sheet of cork glued onto a mirror can have a thickness of between 0.3mm and 2mm.

[0031] The invention also relates to a stopper for sealing a bottle comprising two mirrors and a roller so as to be able to be forced into the neck of the bottle, comprising: a semi-finished stopper of reduced diameter comprising two mirrors and a roller, a sheet of cork glued onto each of the mirrors and the roller of the semi-finished stopper 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 of a thickness equal to twice the thickness of a sheet of cork glued onto the roll. Brief description of the drawings

[0032] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which: there figure 1 illustrates the main steps of a manufacturing process according to the invention, the figures 2 to 4 illustrate the cutting direction of cork sheets in a cork parallelepiped, the figure 5illustrates the results of soaking tests of stoppers according to the invention and of reference stoppers, the figure 6 illustrates the results of elastic return tests of stoppers according to the invention and of reference stoppers, the figure 7 illustrates the results of pull-out force tests of stoppers according to the invention and of reference stoppers, and the figure 8 illustrates the main elements of a stopper according to the invention. Detailed description

[0033] The manufacturing process for a stopper according to the invention is illustrated by the figure 1 .

[0034] During a first sub-step 1a of the first step 1, cork strips of a thickness between 0.3mm and 2mm are cut from a cork parallelepiped having a shape suitable for gluing onto the mirrors and rolling of a semi-finished stopper described below.

[0035] In one particular embodiment, the cork strips glued to the mirrors of the semi-finished stopper of reduced diameter are cut from cork along a direction parallel to the lenticels. Lenticels are defined as the veins opening onto the pores of the cork bark. The cork strip glued to the roll of the semi-finished stopper of reduced diameter is cut from cork along a direction perpendicular to the lenticels.

[0036] There figure 2 illustrates a natural cork parallelepiped 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.

[0037] There figure 3This illustrates the surface of a first type 4a of cork strips cut along plane A, parallel to the lenticels. It is noted that lenticels or fragments of lenticels are visible on the surface of a strip cut in this way. Such a strip is glued according to the invention onto the mirrors of a cork stopper.

[0038] There figure 4 Figure 4b illustrates the surface of a second type of cork strip cut along plane B, perpendicular to the lenticels. Pores 6 resulting from the cutting of the lenticels 5 are visible on the surface of the cork strip. Such a strip is glued according to the invention to the roll of a cork. In a particular embodiment, such a strip is also glued to the mirrors of the cork. This embodiment has the advantage of reducing costs due to the cutting of the cork strips glued to the roll and the mirrors in the same direction, both in terms of the industrial process and the cork supply.

[0039] It should be noted that the commercially available cork parallelepipeds correspond to the parallelepipeds referenced 4 on the figure 2 These corks are generally 25mm wide. This width limits the cutting possibilities for a cork sheet to be glued onto the cork stopper's rim. Indeed, a cork is generally between 38mm and 54mm long with a diameter of 24mm. This 24mm diameter implies a perimeter of approximately 75mm. The cork sheet glued to the rim is therefore 75mm long with a width between 38 and 54mm, exceeding the width of a cork rectangular prism. Such sheets must therefore be cut perpendicular to the width of the prism and perpendicular to the lenticels.

[0040] The cork strips thus cut present a visual similar to the visual observed in a cork tubed in a cork parallelepiped, so as to reinforce the visually very close appearance of the corks obtained compared to corks tubed in cork.

[0041] In a second substep 1b of the first step 1, a semi-finished cork is prepared whose diameter, after the application of a cork sheet, is equal to or substantially equal to the diameter of a semi-finished cork not produced by this manufacturing process. A finished cork is defined as a cork made of crushed cork bonded under pressure with a polyurethane binder and machined to be ready for bottling. Patent application FR2672002 in the name of the applicant illustrates such a cork. Only finishing steps separate a semi-finished cork from a finished cork. This reduction in diameter is important to ensure that the finished cork has a diameter sufficient to guarantee that the extraction force will be less than the 50 daN limit.

[0042] In one embodiment according to the invention, a semi-finished stopper is machined so as to reduce its diameter uniformly by a thickness equal to twice the thickness of a sheet of cork glued onto the roll.

[0043] In a second embodiment, a raw cork is formed in a mold with a reduced internal diameter and a thickness equal to twice the thickness of a cork sheet glued to the roll, relative to the diameter of the mold, to form a raw cork of reduced diameter. The resulting raw cork of reduced diameter is then machined in a manner similar to the machining of a raw cork, in accordance with industry practice. This yields a semi-finished cork of reduced diameter similar to that obtained by the first embodiment.

[0044] In a second step 2, a sheet of cork is glued onto the roll of the semi-finished cork of reduced diameter obtained in the previous step.

[0045] In a first sub-step 2a, a food contact suitable binder is deposited on the semi-finished stopper of reduced diameter and / or the cork sheet.

[0046] The binder can be, in particular, a one-component polyurethane binder, a two-component polyurethane binder, or a hot-melt polyurethane binder.

[0047] In one 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 saturated atmosphere.

[0048] In a second substep (2b), the assembly formed by the reduced-diameter semi-finished cork and the cork sheet is steamed by applying normal pressure to the glued sheet using a mold, possibly preheated to the steaming temperature. Finally, in a third substep (2c), the glued cork sheet is sanded and trimmed to adapt its dimensions to the dimensions of the cork. This step is optional and depends on the result obtained in substep 2b.

[0049] In a third step (3), a cork sheet is glued to each mirror of the stopper. This is achieved by following steps similar to substeps 2a to 2c. In the first substep (3a), a food-grade binder is applied to the semi-finished stopper with a reduced diameter and / or the cork sheets, possibly followed by moistening the cork sheet and / or the stopper. The cork sheets are then applied to the semi-finished stopper with a reduced diameter.

[0050] In a second substep 3b, the assembly formed by the reduced-diameter semi-finished cork and the cork sheets is steamed by applying normal pressure to the glued sheets using a mold, possibly preheated to the steaming temperature. Finally, as in the third substep 2c, sanding and trimming are carried out to adapt the dimensions of the glued cork sheets to the dimensions of the cork, if necessary.

[0051] It will be understood that steps 2 and 3 are interchangeable. It will also be understood that the sub-steps of steaming can be carried out under other conditions that maintain uniform heat, notably by means of a heating tunnel.

[0052] Various tests were carried out to determine the temperature and time conditions required to glue the cork sheets while maintaining the mechanical properties of the stopper.

[0053] During testing, the maximum temperature was determined to be 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, was determined to be satisfactory.

[0054] In certain embodiments of agglomerated or micro-agglomerated corks, thermo-expandable microspheres are added to the polyurethane binder. The maximum temperature is then equal to 110°C, a temperature beyond which the corks are damaged by the expansion of the microspheres.

[0055] Several tests were carried out to determine the optimal drying time in order to obtain good crosslinking of the binder.

[0056] For polyurethane binders, a curing time of 1 hour is sufficient to achieve good polymerization. However, curing times exceeding 1 hour and 30 minutes do not improve crosslinking and therefore represent a drawback of the manufacturing process, leading to a reduction in productivity.

[0057] A curing process at a temperature between 100°C and 110°C for a duration of 1 to 1.5 hours was determined to result in satisfactory bonding of the cork sheet to the semi-finished stopper with a polyurethane binder. Other temperatures and durations may be necessary for other binders.

[0058] This curing process is achieved by placing corks glued to a sheet of cork in a mold that applies force to the sheet being glued. For gluing a sheet of cork to a mirror, a cylindrical mold with a hinge, piston, or screw is used to apply pressure along the axis of the cork. For gluing a sheet of cork to a roller, a cylindrical mold with hinges and latches or bolts is used to apply pressure to the cork radially.

[0059] It is possible to reduce the curing time by preheating the molds, allowing a normal force to be applied to the cork sheets. The applicant then observed that the curing time is reduced to 10 minutes at a curing temperature of 150°C, to 40 minutes at a curing temperature of 100°C, and to 1 hour at a curing temperature of 80°C.

[0060] The crosslinking of the binder has been described in relation to oven curing. However, other heating methods can be used, notably a heating tunnel equipped with a conveyor belt that allows the molds to pass through while being heated. The speed of movement is then correlated with the length of the tunnel to obtain the heating times described above.

[0061] The applicant took care to conduct a preliminary testing campaign on approximately thirty corks manufactured according to the manufacturing process of the invention in order to verify that the corks obtained with the present manufacturing process offer characteristics similar to the corks on which they are based. In other words, it was verified that the glued cork sheets do not degrade the performance of the cork, particularly for bottling or uncorking the bottle. The testing campaign thus aimed to measure the soaking, elastic return, and extraction force. figures 5 to 7 illustrate the results of these tests and their comparison to reference caps.

[0062] The results for the plugs according to the invention are represented by disc-shaped symbols, while the results for the reference plugs are represented by triangle-shaped symbols. Similarly, the trend associated with the plugs according to the invention is represented by dashed lines, while the trend associated with the reference plugs is represented by dashed lines.

[0063] The soaking of a cork characterizes its absorption of water under specific temperature and pressure conditions. A cork's soaking is generally measured as a function of pressure to determine its behavior after bottling. During bottling, the air inside the bottle, between the liquid and the bottle, is compressed to pressures that can reach several tens of bars. Such pressures can lead to corks losing their seal.

[0064] In this case, the imbibition measurement verifies that the impregnation of the cork prior to gluing the cork sheet does not lead to deterioration during the curing process. The imbibition of the corks was estimated by measuring their mass after they were fully immersed in water at 100°C for 15 minutes. This temperature allows for an accelerated visualization of the corks' behavior under extreme conditions. Imbibition is then determined as the ratio of the difference in mass before immersion to the mass after immersion, divided by the mass before immersion.

[0065] 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.

[0066] The soaking of the stoppers according to the invention is thus similar in magnitude and deviation to that of the reference stoppers. The soaking is therefore between 3 and 6% by mass, which is significantly lower than the conformity limit of 11%.

[0067] The springback was then measured. Springback is one of the mechanical properties of a cork and allows us to quantify the force generated by the cork's reaction to the neck of the bottle. Springback is measured automatically using the "Multitest 10i" machine from Mecmesin.

[0068] During these measurements, the cork is compressed until it reaches a diameter between 15 mm and 16 mm, which corresponds to the diameter of the jaws of a corking machine. Compression is achieved using a piston moving at a speed of 10 mm / min. The force required (in Newtons) to perform this compression is measured. The compression value is then normalized to the cylindrical surface area of ​​the cork. This value must be between 15 and 60 N / cm² and preferably between 25 and 60 N / cm², depending on the cork diameter.

[0069] The plates will then release the pressure and position themselves 21 millimeters apart, a distance known as the return distance. After 180 seconds, the pressure exerted by the cork on the plates is measured. This pressure corresponds to the elastic return force (also measured in Newtons). For the interpretation of the results, these forces will be calculated relative to the surface area of ​​each cork, and therefore expressed in Newtons per square centimeter.

[0070] There figure 6 illustrates the results obtained for the caps according to the invention and for the reference caps.

[0071] The elastic return of the stoppers according to the invention is substantially lower, at constant density compared to that of the reference stoppers, while remaining above the limit of 3.2 N / cm² of the standard.

[0072] It should be noted that during these tests, no tearing of glued cork sheets was observed.

[0073] The extraction forces used to quantify the force required to remove the cork from the bottle neck were then measured. They were measured as follows: First, corks to be tested were placed in bottle necks. After two hours of rest in the necks, the corks were extracted using a corkscrew connected to a force measurement system, such as the "Multitest 2.5 - d" machine from Mecmesin. The extraction force value should be between 100 and 600 N, preferably between 200 and 500 N, depending on the cork diameter.

[0074] There figure 7 illustrates the results obtained for the caps according to the invention and for the reference caps.

[0075] The extraction force of the stoppers according to the invention is thus similar in order of magnitude to that of the reference stoppers, while exhibiting a greater deviation but nevertheless close to that of the reference stoppers.

[0076] There figure 8 illustrates the main parts of the stopper according to the invention.

[0077] A stopper according to the invention comprises in its center a semi-finished stopper of reduced diameter having a reduced length, referenced 10. It comprises two mirrors 10a and a roller 10b.

[0078] A 20a cork sheet is glued onto each 10a mirror of the reduced diameter semi-finished stopper.

[0079] A 20b cork sheet is glued onto the 10b roll of the semi-finished cork with reduced diameter.

[0080] The semi-finished stopper with a reduced diameter is a cork stopper made of crushed cork bonded under pressure with a polyurethane binder. French patent application FR2672002, filed in the name of the applicant, illustrates such a stopper.

Claims

1. A method for manufacturing a cap for plugging a bottle comprising two lids and a roll so as to be able to be forcibly inserted into the neck of the bottle, characterised in that it comprises the following steps: - cutting two types of cork sheets (20a, 20b), - preparing a semi-finished cap with a reduced diameter from a cap made of crushed cork glued under pressure with a polyurethane binder, by reducing the diameter of said crushed cork cap uniformly by a thickness equal to twice a predetermined thickness, the semi-finished cap with a reduced diameter comprising a lateral face in contact with the bottle and two opposite end faces, - gluing a cork sheet of a first type to each end face (10a) of the semi-finished cap with a reduced diameter by depositing a binder suitable for food contact, each glued cork sheet of the first type forming a lid for the cap for plugging a bottle, followed by baking, - gluing a cork sheet of a second type on the lateral face (10b) of the semi-finished cap with a reduced diameter by depositing a binder suitable for food contact, each glued cork sheet of the second type forming the roll for the cap for plugging a bottle, followed by baking, the predetermined thickness being equal to the thickness of the cork sheet of a second type glued on the lateral face of the semi-finished cap.

2. The manufacturing method according to claim 1, wherein the cork sheets of a second type glued on the lateral face of the semi-finished cap with a reduced diameter are cut in cork in a direction perpendicular to the lenticels.

3. The manufacturing method according to any one of claims 1 or 2, wherein the cork sheets of a first type glued on the end faces of the semi-finished cap with a reduced diameter are cut in cork in a direction parallel or perpendicular to the lenticels.

4. The manufacturing method according to any one of claims 1 to 3, wherein the cork sheets are treated so as to have a trichloroanisole level lower than 0.3 ng / l, preferably by a supercritical carbon dioxide treatment.

5. The manufacturing method according to any one of claims 1 to 4, wherein the semi-finished cap with a reduced diameter is ground and / or trimmed after gluing a cork sheet to adapt the dimensions of the glued cork sheet to the dimensions of a semi-finished cap having undergone no diameter reduction.

6. The manufacturing method according to any one of claims 1 to 5, wherein the binder is a mono-component polyurethane, a bi-component polyurethane or a hot-melt polyurethane.

7. The manufacturing method according to any one of claims 1 to 6, wherein water is applied before, during, or after the application of binder in order to accelerate crosslinking of the binder.

8. The manufacturing method according to any one of claims 1 to 7, wherein the baking is carried out at a temperature comprised between 80°C and 150°C for a duration comprised between 10 min and 1h30 for a polyurethane binder.

9. The manufacturing method according to any one of claims 1 to 8, wherein the baking is carried out in an autoclave or a tunnel oven.

10. The manufacturing method according to any one of claims 1 to 9, wherein the semi-finished cap with a reduced diameter with a glued cork sheet is disposed in a mould making it possible to apply pressure in a direction normal to the surface of the cork sheet, the mould being preheated to the baking temperature.

11. The manufacturing method according to any one of claims 1 to 10, wherein, to prepare a reduced semi-finished cap, a semi-finished cap is machined so as to uniformly reduce its diameter by a thickness equal to twice the predetermined thickness.

12. The manufacturing method according to any one of claims 1 to 10, wherein, to prepare a semi-finished cap with a reduced diameter, a blank cap with a reduced diameter is formed in a mould with a diameter uniformly reduced by a thickness equal to twice the predetermined thickness corresponding to the diameter of a semi-finished cap with a reduced diameter, then the blank cap with a reduced diameter is machined so as to obtain a semi-finished cap with a reduced diameter.

13. The manufacturing method according to any one of claims 1 to 12, wherein a cork sheet of a second type glued on the lateral face of the semi-finished cap with a reduced diameter has a thickness comprised between 0.3 mm and 1 mm.

14. The manufacturing method according to any one of claims 1 to 13, wherein a cork sheet of a first type glued on an end face of the semi-finished cap with a reduced diameter has a thickness comprised between 0.3 mm and 2 mm.

15. A cap for plugging a bottle comprising two lids and a roll so as to be able to be forcibly inserted into the neck of the bottle, which comprises: - a semi-finished cap with a reduced diameter (10) formed by a cap made of crushed cork glued under pressure with a polyurethane binder, having a diameter uniformly reduced by a thickness equal to twice a predetermined thickness, - the semi-finished cap with a reduced diameter (10) comprising two end faces (10a) and a lateral face (10b), characterised in that it also comprises: - a cork sheet of a first type (20b) glued on each end face of the semi-finished cap with a reduced diameter so as to form the lids of a cap for plugging a bottle - a sheet of cork of a second type (20a) glued on the lateral side of the semi-finished cap with a reduced diameter (10) so as to form the roll of the cap for plugging a bottle.

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