EP2064036B1 - Method for producing an agglomerated cork product and product obtained thus - Google Patents

Abstract

The invention relates to a method for producing an agglomerated cork product from natural cork aggregate, characterized in that it comprises the following steps: a) preparation of a starch-based binder; b) coating and/or impregnation of the cork aggregate with the binder; c) agglomeration of the impregnated aggregate; d) mechanical finishing of the product obtained in order to give it the desired dimensions and shape, and in that the amount of water introduced in the coating and/or impregnation and/or agglomeration steps is less than or equal to 25% of the weight of the cork.

Description

The invention relates to a process for producing a cork product and more specifically to agglomerated natural cork. The invention relates more particularly to the use of such a method for producing a plug.

Sintered cork stoppers such as champagne corks are called "technical" stoppers. Their manufacture is made from casing residues resulting from the manufacture of natural cork stoppers.

The residues are transformed into cork aggregates which are then agglomerated to form the technical stopper. The agglomeration of aggregates is achieved by impregnating the aggregates with an adhesive. The product thus obtained then undergoes a mechanical finishing step for shaping the cap to the desired dimensions.

The document FR-A-2,799,183 discloses a process according to the preamble of claim 1 and an article according to the preamble of claim 13.

The adhesives used to impregnate cork aggregates are generally based on isocyanate, for example polyurethane glues, and are used in aqueous form.

The use of such glues has a number of disadvantages.
First, these glues are toxic to the personnel involved in the production of corks. Indeed, the glue is toxic by inhalation and ingestion and is highly irritating to the skin and mucous membranes.
The use of this glue therefore requires special precautions to use in order to protect the staff which complicates the production line and increases the cost price.

In addition, some components of the glue can migrate into the liquid with which the cap is in contact, for example with wine or alcohol, which can denature the taste of the liquid, but also carry health risks.

Aqueous adhesives may furthermore have storage stability problems such as, for example, microbial contamination, which requires the addition of biocide to the adhesive.
The aqueous adhesives also generate effluents, which will therefore be treated later.

There are also other methods of using liquid glues obtained from a cold soluble starch preparation containing a mixture of melamine and formaldehyde.
This technique which is described in particular in the US 2,562,558 has the major disadvantage of leading to a significant release of free formaldehyde which is particularly volatile and toxic.

In addition, the solubilization of the starch requires the addition of a significant amount of water, which causes problems of vapor overpressure and the risk of explosion during the subsequent agglomeration step which includes a phase compression and a heating phase with a very significant rise in the temperature of the cork.

Finally, these aqueous glues have a long drying time and agglomerated cork products obtained do not dry easily and quickly to heart.

The aim of the invention is to overcome these drawbacks by proposing a method of producing an agglomerated product made of natural cork, such as a stopper, according to claim 1, in which a binder of natural origin, possibly derived from the binder, is used. organic farming, which does not present a health risk and is used in powder form by using only a very small amount of water.

1. a) préparation d'un liant à base d'amidon en poudre soluble à froid,
2. b) enrobage et/ou imprégnation des granulats de liège au moyen du liant à base d'amidon ;
3. c) agglomération des granulats imprégnés ;
4. d) finition mécanique du produit obtenu afin de lui donner les dimensions et forme souhaitées et,

en ce que la quantité d'eau introduite dans les étapes d'imprégnation et /ou d'agglomération est inférieure ou égale à 25% du poids du liège.To this end, the invention relates to a method for producing a product made of agglomerated cork from natural cork aggregates, characterized in that it comprises the following steps:

1. a) preparation of a binder based on cold-soluble powdered starch,
2. b) coating and / or impregnating the cork aggregates with the starch-based binder;
3. c) agglomeration of the impregnated aggregates;
4. d) mechanical finishing of the product obtained to give it the desired dimensions and shape and,

in that the quantity of water introduced into the impregnation and / or agglomeration stages is less than or equal to 25% of the weight of the cork.

The invention also relates to an agglomerated natural cork article according to claim 13.

The method according to the invention can be used to produce technical plugs, but also other agglomerated cork products, such as floor coverings, decorative products, products for textile and clothing, household products or industrial, products intended for building and / or civil engineering (acoustic and thermal insulation, anti-vibration elements, ...), etc.

Starch is a natural binder that can be ingested without dietary risk. Thus, the migration of starch into a liquid does not make it unfit for consumption.
The process according to the invention is therefore particularly well suited to the manufacture of cork stoppers, for the packaging of beverages and, in particular, wines, spirits and champagnes.

In addition, the starch-based binder is not toxic to the personnel involved in the production of the cork product. This staff can therefore handle it safely.

The cork granulates can be obtained in the traditional way, that is to say by trituration of the casings of the plugs of natural plugs to obtain the desired particle size.

According to a particular embodiment, the binder is mixed with a powder crosslinking agent, suitable for food contact. This agent has an insolubilizing function.

According to an advantageous characteristic, this mixture comprises from 70% to 100% by weight of starch and comprises, in addition, substantially from 0% to 30% by weight of crosslinking agent.

Preferably, the mixture comprises substantially from 80% to 95% by weight of starch and substantially from 5% to 20% by weight of the crosslinking agent.

The starch is in the form of a cold soluble powder and optionally chemically modified.

The starch binder is produced as a cold-soluble powder. Thus, it avoids the problems related to aqueous adhesives of the prior art: simplicity of storage without risk of microbial migration, short drying time, removal of the subsequent risk of steam explosion, etc ...

The cold solubilization is obtained, preferably, by pre-gelatinization by means of an extruder or a drying drum according to techniques known elsewhere.
The pregelatinized starch is starch which has been mechanically treated in the presence of water, using a thermal process or not, to break all the part of the starch grains and which has then been dried out. It normally contains no added substance, but can be modified to make it compressible and improve its fluidity characteristics.

After wetting, the powder binder forms a gel capable of adhering because of its high viscosity.

The Applicant has found that the quality of the stoppers was improved when the starch used to make the binder is starch extracted from vegetables such as peas.

In fact, the pea starch has a naturally high content of amylose, which improves the flexibility and water resistance of the starch.

In addition, the pea starch has a higher viscosity than other starches and a better stability in gel form.

However, other types of starches can be used, for example starches from corn, wheat, waxy maize, potato, tapioca, rice, etc.

In order to facilitate the dispersion of the powdered starch, the method may provide a step of moistening the cork granules before impregnation with the binder.

According to yet another alternative embodiment, the proportion of starch relative to cork is between 10% and 25% by weight.

The agglomeration step of the process for manufacturing agglomerated cork according to the invention comprises a compression phase and a temperature increase phase.

Agglomeration of cork granulates can be carried out by direct molding or by extrusion. For example, extrusion is provided at a temperature of between 120 ° C and 130 ° C for 3 to 10 minutes. In the case of direct molding, the agglomeration is between 110 ° C and 120 ° C for about 1 hour.

During the compression phase the pressure reached is of the order of 2 MPa (20 bar).

The method implies that the amount of added water is less than 25% of the weight of the cork to prevent the risk of steam explosion, especially during the agglomeration phase and to allow rapid drying in the heart of the cork chipboard.

When the method described above is used to make a stopper, that is to say when the mechanical finishing step is a step of forming a technical cork stopper, it is possible to provide additional steps for fixing the cork. 'a cork disc at one or both ends of the cork, this fixing being carried out by gluing using the starch-based binder coating the face of the disc to be bonded.

Indeed, for some plugs, in order to limit the contact between wine or, more generally, alcoholic beverages and cork aggregates, it is expected to have solid cork discs at the ends of the cap. The starch-based binder is solubilized before being applied to the cork disc.

Preferably, the crosslinking agent is in the form of powder previously mixed with the starch.

According to another variant embodiment, the crosslinking agent is in liquid form and is mixed with a proportion or all of water and this crosslinking / water mixture is added during the wetting of the cork granules before or after their coating. and / or their impregnation with the binder.
The crosslinking agent employed is officially authorized for food contact.

According to a particular variant embodiment, the crosslinking agent used is Urecoll SMV, the composition of which complies with the recommendations of the European health authorities concerning food packaging papers which also stipulate that "cold water extract" must not contain more than 1.0 mg of formaldehyde per 100 cm ² of paper.

The applicant has carried out several tests in two series to demonstrate that the cold-soluble pea starch is particularly suitable for use as a binder, in particular for cork.

The purpose of these tests was to aggregate cork aggregates with pea starch in order to produce cork stoppers that meet the food standards and have the necessary mechanical strength properties. To do this, cork blocks were formed by mixing cork aggregates, pre-gelatinized (cold-soluble) starch, water and a crosslinking agent, followed by agglomeration with the aid of a heating press.

The cork blocks should have a density between 250 and 300 g / dm ³ and withstand the water immersion test at 100 ° C for 1 hour.

• mélange d'eau et de l'agent réticulant avec les granulats de liège ;
• mélange à la cuillère jusqu'à humidification de tout le liège;
• ajout de l'amidon progressivement en poursuivant le mélange ;
• remplissage d'un moule avec une partie du mélange obtenu ;
• pressage à froid à 2 MPa (20 bars) ;
• nouveaux remplissages du moule et pressages jusqu'à épuisement du mélange ;
• pressage du mélange à 2 MPa (20 bars) pendant 30 minutes à 110°C ;
• (éventuellement) pressage du bloc formé à 2 MPa (20 bars) pendant 10 minutes à température ambiante ;
• démoulage du bloc de liège ;
• découpe du bloc en rectangles d'environ 2,5 cm x 2,5 cm x 5 cm.

The cork blocks were made in the following way:

• mixture of water and the crosslinking agent with the cork granulates;
• spoon mixture until moistening all the cork;
• adding the starch gradually while continuing the mixing;
• filling a mold with a part of the mixture obtained;
• cold pressing at 2 MPa (20 bar);
• new filling of the mold and pressing until the mixture is exhausted;
• pressing the mixture at 2 MPa (20 bar) for 30 minutes at 110 ° C;
• (optionally) pressing the block formed at 2 MPa (20 bar) for 10 minutes at room temperature;
• demolding the cork block;
• cutting the block into rectangles of about 2.5 cm x 2.5 cm x 5 cm.

The crosslinking agent used in all the tests is a liquid crosslinking agent (70% DM) and the quantity indicated in the tables is therefore each time the percentage of the liquid quantity (by weight) relative to the amount of starch (by weight ).

Several cork blocks of different compositions have been made. These compositions are grouped in the following table:

From the point of view of density, the following results were obtained: Sample Density (g / dm ³ ) Ni-0 239 NiG-1 230 NiG-3 241 ERL-1 229 NIU-3 228 NiU-3 (bis) 238 NIU-4 255 NIU-5 241 EMU-5 259 MU-5 252

As can be seen, the densities obtained are close to the desired range. It is likely that this density can be further increased with more suitable equipment.

A test immersion test was performed. This test consists of recording the time after which the cork block is totally dislocated when it is immersed in water at 100 ° C. The caps must be perfectly formed after one hour of immersion for the result to be considered positive.

The test was conducted on the tests mentioned above one day after their manufacture and eight days after their manufacture.

The results of this test are mentioned in the tables below: Sample Time ⁽¹⁾ to D + 1 (min) Time ⁽¹⁾ to D + 8 (min) Ni-0 2 2.5 NiG-1 2.5 3 NiG-3 5 6 ERL-1 2 2.5 NIU-3 10.5 13 NiU-3 (bis) 16 20 ⁽¹⁾ Time after which the block of cork is totally dislocated

As can be seen this first series of results is not satisfactory, the blocks falling apart before an hour of immersion. These results were obtained for blocks having a crosslinking agent content of less than or equal to 10% of starch.

When this content is greater than 10% of starch, the following results are obtained: Sample Time ⁽¹⁾ D + 1 and D + 8 (min) Appearance ⁽²⁾ at D + 1 Appearance ⁽²⁾ at D + 8 NIU-4 > 60 Highly deformed cap (disemboweled in the middle) but not totally dislocated Cap soaked in water and deformed NIU-5 > 60 Cap soaked in water and slightly distorted Stopper soaked with water and undistorted EMU-5 > 60 Cap soaked in water and slightly distorted Stopper soaked with water and undistorted MU-5 > 60 Cap soaked in water and slightly distorted Stopper soaked with water and undistorted ⁽¹⁾ Time after which the block of cork is totally dislocated
⁽²⁾ Visual appearance after immersion 1 h at 100 ° C

As can be seen, the cork blocks meet the immersion test criteria and the results are significantly better after one week of storage of the blocks.

A second series of tests was carried out. The composition of starch, water and crosslinking agent is given in the following table: testing Cork aggregates (g) Water (% / cork) Crosslinking agent (% / starch) Crosslinking type Starch (% / cork) Extruded pregelatinized pea starch EMU-6 102.5 13.3 20 Urecoll ® SMV 20 EMU-7 16.7 25 EMU-8 25 15 EMU-9 20 10

The building market requires densities of some 500 g / dm ³ for some of its products.
The Bât EmU-5 test was carried out with cork of smaller grain size also called "cork dust" commonly used in some building products. The low density of cork allows better compression and, by the same token, obtaining a higher density of the finished product. The composition of the test is reported in the following table: testing Cork aggregates (g) Water (% / cork) Crosslinking agent (% / starch) Type (% / starch) Starch (% / cork) (g) Extruded Pregelatinized Pea Starch EmU-5 building 102.5 20 20 Urecoll SMV 15

The different tests are characterized by their density expressed in g / dm ³ , by their flexibility measured with TA-XT2i texture analyze and by their resistance to the boiling water immersion test.

Density results obtained for the different tests: Sample Density (g / dm ³ ) EMU-6 261 EMU-7 268 EMU-8 253 EMU-9 251 EmU-5 building 414

The densities of the EmU-6, EmU-7, EmU-8 and EmU-9 tests are within the desired range of values (250-300 g / dm ³ ).
The density of the EmU-5 Bât test is close to the expected 500 g / dm ³ while remaining lower. The use of a more adapted material makes it possible to reach them.

The determination of the texture of the cork articles is carried out using the texture analyzer TA-XT2i Texture Analyze.
The cork article to be analyzed is previously cut in the form of a rectangle with the following dimensions: 2.5 cm × 2.5 cm × 5 cm.
The measurement is made according to the height of the sample and corresponds to the maximum force applied to compress it by 3 mm.

• Type de sonde : P25 22mm DIA CYLINDER ALUMINIUM
• Tête d'analyse : 25 kg
• Durée du test : 15.60 s
• Mode d'analyse : mesure d'une force en compression
• Vitesse :
  • Pre-test : 2.0 mm/s
  • Test : 0.2 mm/s
  • Post-test : 5.0 mm/s
• Distance de compression : 3.0 mm

The analysis is performed as follows:

• Probe type: P25 22mm DIA CYLINDER ALUMINUM
• Analysis head: 25 kg
• Duration of the test: 15.60 s
• Analysis mode: measurement of a compressive force
• Speed:
  • Pre-test: 2.0 mm / s
  • Test: 0.2 mm / s
  • Post-test: 5.0 mm / s
• Compression distance: 3.0 mm

The force required to compress the 3 mm samples was measured over time, the results are reported in the following table: Max force (g) EMU-6 EMU-7 EMU-8 EMU-9 EmU-5 building T0 14582 14064 9532 8028 9341 T + 1 month 20134 21952 14154 13500 16508 T + 2 months 29600 33223 20110 15458 19801 T + 3 months 30313 35000 23600 17196 23114

The tests show that the starch content is decisive in the flexibility of agglomerated cork samples. Samples with a high starch content have a harder texture and this phenomenon persists over time. The hardness of the samples increases during aging.

In general, the starch content of the blocks obtained in the examples is between 9% and 20% by weight.

An immersion test was performed on the samples previously cut into rectangles of dimensions 2.5 cm x 2.5 cm x 5 cm. The test consists in recording the time at which the sample is completely dislocated when it is immersed in water at 100 ° C. The sample must be perfectly formed after one hour for the result to be considered positive. The results of this test are mentioned in the table below: Sample Time ⁽¹⁾ D + 1 (min) Appearance ⁽²⁾ at D + 1 EMU-6 > 60 Sample not soaked with water and not deformed EMU-7 > 60 Sample not soaked with water and not deformed EMU-8 > 60 Sample soaked with water and deformed EMU-9 > 60 Sample soaked with water and deformed EmU-5 building block EmU-5 building block > 60 Sample soaked in water and slightly deformed ⁽¹⁾ Time after which the block of cork is totally dislocated
⁽²⁾ Visual appearance after immersion 1 h at 100 ° C

The 4 tests are resistant to immersion in boiling water.
The EmU-6 and EmU-7 tests, which have higher starch contents, give better results in that the samples absorb less water and do not deform.

In conclusion, it is found that corks meeting the standards required for applications of the technical cap type, can be manufactured by replacing the glue obtained from synthetic products with a natural binder based on starch without alteration or degradation of the mechanical properties .

Claims (14)

1. Method for producing an agglomerated cork product from aggregates of natural cork characterized in that it comprises the following steps of:

   a) preparing a cold water soluble starch-based powder binder,

   b) coating and/or impregnating cork aggregates with the binder,

   c) agglomerating the impregnated aggregates;

   d) performing a mechanical finish of the product obtained so as to provide it with the required dimensions and shape and,

   in that the amount of water introduced in the coating and/or impregnating and/or agglomerating steps is lower than or equal to 25% of the cork weight.
2. Method according to claim 1, characterized in that the binder is mixed with a cross-linking powder agent adapted to be in contact with food products.
3. Method according to claim 2, characterized in that the mixture contains from 70% to 100% by weight of starch and from 0% to 30% by weight of cross-linking agent.
4. Method according to claim 3, characterized in that the mixture substantially comprises from 80% to 95% by weight of starch and substantially from 5% to 20% by weight of cross-linking agent.
5. Method according to claim 1 characterized in that the cross-linking agent is in liquid form and is mixed with water before being added to the aggregates.
6. Method according to any one of claims 1 to 5, characterized in that the cork aggregates are humidified before their coating and/or their impregnation by the binder.
7. Method according to any one of the preceding claims characterized in that said binder is made from chemically modified starch.
8. Method according to any one of claims 1 to 7, characterized in that the starch used for producing the binder is a pea-based starch.
9. Method according to any one of claims 1 to 8, characterized in that the agglomeration of cork aggregates is performed by direct die casting or by extrusion.
10. Method according to any one of claims 1 to 9, characterized in that the starch to cork ratio ranges between 10% and 25% by weight.
11. Method according to any one of claims 1 to 10, characterized in that the mechanical finish step is a step of producing a technical cork cap.
12. Method according to claim 11, characterized in that it comprises the additional steps of adhering a cork disk to one or both ends of the cap, said adhering being carried-out by means of the starch-based binder coated on the side of the disk to be adhered.
13. Article made from natural aggregated cork produced through the method according to any one of claims 1 to 12, characterized in that it comprises from 9% to 20% by weight of starch.
14. Article made from natural aggregated cork according to claim 13 characterized in that its specific gravity ranges between 250 and 500 g/dm³.