Flexible coated substrate with barrier and heat-sealing properties

Abstract

Flexible coated support with barrier and heat-sealing properties. The invention relates to a flexible coated support (4), intended for the manufacture of a finished product, in particular packaging, the flexible coated support having a flat shape when freely laid flat, this flexible coated support comprising a flexible support containing, by weight, at least 90%, or at least 95%, of a first natural material, this flexible support being coated with a coated layer containing, by weight, at least 50%, or at least 80%, or at least 90%, or at least 95%, of a second natural material formed by at least one heat-sealing polymer, this or these heat-sealing polymers (10) having in particular at least one of the following properties: oxygen barrier, oil / grease barrier, water barrier. Figure for the abstract: Figure 1

Description

Title of the invention: Coated flexible support with barrier and heat-sealing properties

[0001] The present invention relates to a method for manufacturing a flexible support, in particular paper, having one face (front or back) or two faces (front and back) with a coated layer composed of one or more film-forming barrier and heat-sealing polymers.

[0002] The invention also relates to a coated flexible support. The invention also relates to a packaging comprising the coated flexible support according to the invention.

[0003] The use of film-forming polymers is widespread in the field of surface coatings, in particular in the field of coating, lamination or complexing on a support, in particular paper or cardboard.

[0004] Indeed, these film-forming polymers make it possible to waterproof a surface in order to make it a barrier to elements such as grease.

[0005] For example, patent application FR 3107529 A describes these film-forming polymers comprising a thermoplastic material based on casein and / or caseinate, intended to coat a layer of paper or cardboard.

[0006] These polymers, for example initially in the form of a solution or a liquid, may or may not require additional treatment allowing stabilization of the functionalities.

[0007] When the surface to be waterproofed is on one of the faces of a flexible support, in particular on a low-weight paper, for example less than 200 g / m2, where the rigidity of the flexible support is not sufficient to counter the shrinkage induced by these film-forming polymers, the edges of the flexible support tend, after a certain time, to curl up on themselves.

[0008] This tendency for the edges of a flexible support coated with the film-forming polymer(s), initially flat, to rise, then to curl, on each side is defined as being a “curl effect” or a “curl” (English terminology).

[0009] The “curl” is all the more important as the retraction induced by the film-forming polymers is important.

[0010] Generally speaking, the coated flexible support obtained using a conventional process is characterized by a very significant "curl", namely that the edges are rolled up several times. Too marked a "curl" prevents the final coated flexible support from being used in industrial conditions.

[0011] Furthermore, this type of conventional coated flexible support often requires a multitude of separate layers in order to obtain sufficient barrier properties.

[0012] The invention aims in particular to develop a new coated flexible support.

[0013] The invention thus relates to a coated flexible material, intended for the manufacture of a finished product, in particular packaging, the coated flexible support having a flat shape when it is freely laid flat, this coated flexible support comprising a flexible support containing, by weight, at least 90%, or at least 95%, of a first natural material, this flexible support being coated with a coated layer containing, by weight, at least 50%, or at least 80%, or at least 90%, or at least 95%, of a second natural material formed by at least one heat-sealing polymer, this or these heat-sealing polymers having in particular at least one of the following properties: oxygen barrier, oil / grease barrier, water barrier.

[0014] Thanks to the invention, it is possible to obtain a naturally coated flexible support, having grease and / or water and / or steam and / or gas barrier properties and / or being heat-sealing. This is particularly advantageous in terms of compliance with environmental protection.

[0015] According to the invention, the finished coated flexible support may contain, by weight, at least 80% or at least 90%, or even at least 95%, of natural materials, when taking into account both the first natural material of the flexible support and the second natural material formed by the heat-sealing polymer.

[0016] According to one aspect of the invention, the heat-sealing polymer(s) forming the coated layer comprise at least one natural wax such as a carnauba wax, a soy wax, a beeswax, a pine wax or even a rice wax.

[0017] According to another aspect of the invention, the heat-sealing polymer(s) forming the coated layer are based on polysaccharides such as alginate or starch, or chitosan or a cellulose derivative.

[0018] According to one aspect of the invention, the heat-sealing polymer is biodegradable such as a polyhydroxyalkanoate acid (PHA), a polyhydroxybutyrate acid (PHB), a polylactic acid (PLA) or a lignin.

[0019] According to another aspect of the invention, the heat-sealing polymer(s) forming the coated layer comprise:

[0020] - at least one caseinate and / or at least one casein.

[0021] According to one aspect of the invention, the heat-sealing polymer(s), in particular the wax, are present in the coated layer with a percentage by weight of between 1% and 30%, in particular between 5% and 20%, in particular between 10% and 15%, in particular between 5% and 15%.

[0022] According to one aspect of the invention, the weight of the coated flexible support is between 20 and 300 g / m2, preferably between 40 and 100 g / m2.

[0023] The invention also relates to packaging comprising two zones belonging to the same coated flexible support as described above, or belonging respectively to two coated flexible supports as described above, these areas being applied against each other by their respective coated faces.

[0024] Thus the sealing is preferably carried out from one coated face to another coated face, this sealing also being called flesh-to-flesh sealing. The sealing may, as a variant, be of the flesh-to-skin type.

[0025] According to one aspect of the invention, the heat-sealing polymer is chosen to obtain a sealing force between the areas sealed together which is greater than or equal to 2.5 N / 15 mm and preferably greater than or equal to 3.5 N / 15 mm.

[0026] The invention also relates to a method of manufacturing packaging comprising the following steps: - provide two areas of coated flexible support as described above, - seal these two areas together by pressing these two areas against each other the other by providing heat, in particular by means of heating jaws, so as to obtain the packaging.

[0027] Sealing can be carried out with flow-pack machines (or in English "flow-pack machines") in order to produce different types of packaging, this is called heat sealing. Under the effect of heat, the heat-sealing polymer will seal the two areas of coated flexible support together to obtain a package. It is also possible to use other technologies such as ultrasonic sealing which will allow the heat-sealing polymer to be fined until a hermetic seal is obtained. Sealing can be both vertical and horizontal.

[0028] The manufacturing method may include the step of coating the flexible support on a front side and / or a back side, with one or more water-based sauces containing one or more film-forming barrier and heat-sealing polymers.

[0029] The manufacturing process may then include a step of drying the coated flexible support.

[0030] A distinction is made between "flexible support" and "coated flexible support". The flexible support is raw, not yet coated. The coated flexible support corresponds to the flexible support having received the coated layer.

[0031] This is also applicable for any type of flexible support, namely “paper” and “coated paper”.

[0032] Thanks to the method according to the invention, the tendency ("curl") of the edges of the coated flexible support to curl up on themselves after the manufacture of said coated flexible support is prevented.

[0033] Thus, the method according to the invention allows the industrial manufacture of said coated flexible support in an automated manufacturing line whereas such a coated flexible support with barrier and heat-sealing properties could not be obtained until now due to both the winding effect of the coated flexible support, the deposition made as well as the results obtained. The invention makes it possible to obtain a complementarity between barrier and heat-sealing functions, the level of barrier functions and the natural composition of at least 90% of the coated flexible support.

[0034] This is enabled by the different steps of the method according to the invention, as explained below.

[0035] The drying step(s) of the invention make it possible to dry the coated flexible support as much as possible so that said coated flexible support contains the residual moisture which is suitable for obtaining a flat support, without surface cracks or other defects which would then limit its use in printing or degrade its barrier or heat-sealing functionalities.

[0036] Drying can take place immediately after the deposition of the barrier and heat-sealing layer so that this layer does not yet have time to dry naturally, in order to maximize the stresses to which the elements contained in the layer are subjected.

[0037] Thus, when these effects have been compensated, the coated flexible support, placed on a flat surface, has satisfactory flatness.

[0038] The heat-sealing barrier film-forming polymer deposited on the coated flexible support is sufficient in itself to heat-seal the coated flexible support. In other words, said heat-sealing film-forming polymer does not require an additional adhesive layer or an additional polymer layer in order to heat-seal the coated flexible support.

[0039] Thus, a number of layers required for the coated flexible support is reduced in order to simplify the structure of said coated flexible support, while optimizing the optimal mechanical and chemical properties.

[0040] This is more particularly advantageous in that the method according to the invention is more environmentally friendly and more economical than the conventional method involving several layers, because fewer steps, less material, less energy and less time are necessary to obtain a coated flexible support with optimal properties.

[0041] According to one aspect of the invention, the weight of the flexible support is between 20 and 300 g / m2, is between 20 and 100 g / m2, preferably is between 40 and 100 g / m2.

[0042] According to one aspect of the invention, the surface density of the deposit of the heat-sealing film-forming polymer, measured by the difference in weight between the dry coated flexible support and the dry flexible support, is between 6 and 18 g / m2.

[0043] In these surface density ranges, the barrier properties can be optimally obtained. The flexible support and the coated flexible support were dried before weighing to remove any traces of residual water.

[0044] According to one aspect of the invention, it is possible to apply the heat-sealing film-forming polymer at least twice to the front and / or back of the flexible support so as to obtain a layer of the heat-sealing film-forming polymer.

[0045] For example, in the case of a deposition layer of the heat-sealing film-forming polymer of 10 g / m2, this deposition can be carried out by two successive coating stations of the same polymer of 5 g / m2. Thus, the layer of the heat-sealing film-forming polymer has a uniform surface and good sealing.

[0046] According to one aspect of the invention, the drying temperature during is greater than or equal to 100°C.

[0047] According to one aspect of the invention, wherein the deposition method is chosen between coating or printing.

[0048] According to one aspect of the invention, the flexible support is chosen from paper, cardboard or any other flexible material composed of natural polymer, existing in its natural state. This or these polymers are thus without specific chemical transformation modifying their nature. Preferably, the paper has at least one smooth face obtained by at least one of the following methods: rubbing, calendering or coating. Advantageously, the flexible support contains the first natural material formed by natural fibers. This flexible support is for example a paper made of natural fibers.

[0049] According to one aspect of the invention, the paper is chosen from offset paper, recycled paper, tracing paper, greaseproof paper, and Kraft paper.

[0050] For example, Kraft paper, the characteristics of which are known per se, has optimal mechanical resistance in view of the paper weight.

[0051] According to one aspect of the invention, the paper has a white appearance or a brown appearance.

[0052] The barrier and heat-sealing polymer is coated homogeneously and has a uniform thickness on the front side of the flexible support. Thus, the coating of the barrier and heat-sealing polymer thus obtained is very regular and without marks, scratches or faults through which a fluid (gas, liquid) could enter the coated flexible support and generate softening or leaks of said coated flexible support.

[0053] Among the different coating techniques, the air knife coater or the curtain coater equipped with a coating nozzle, makes it possible to precisely control the coating deposit with high quality and to ensure a uniform and regular coating on the flexible support.

[0054] According to one aspect of the invention, the heat-sealing film-forming polymer has one or a combination of the following properties: oxygen barrier, oil / grease barrier, water barrier, water vapor barrier, and / or antifungal barrier.

[0055] According to one aspect of the invention, the heat-sealing film-forming polymer has one of or the combination of the following properties: oxygen barrier, oil / grease barrier.

[0056] According to one aspect of the invention, the heat-sealing film-forming polymer is food compatible.

[0057] According to one aspect of the invention, the heat-sealing film-forming polymer comprises a thermoplastic polymer.

[0058] According to one aspect of the invention, the heat-sealing film-forming polymer has at least one of the following properties: biosourced, biodegradable, compostable. In any event, the coated flexible support is advantageously at least 90% natural.

[0059] According to one aspect of the invention, the coated flexible support has at least one of the following properties: biosourced, biodegradable, compostable and / or re-pulpable.

[0060] According to one aspect of the invention, the coated flexible support has the following properties: biosourced, biodegradable, compostable and repulpable.

[0061] According to one aspect of the invention, the heat-sealing film-forming polymer comprising at least one caseinate and / or one casein having oil / grease barrier and oxygen barrier properties.

[0062] The quantity of water in the coating solution (also called coating sauce) depends on the desired viscosity and may depend on the nature of the flexible support.

[0063] According to one aspect of the invention, the viscosity of the coating sauce is less than 250 mPa.s, or less than 200 or 120 mPa.s.

[0064] According to one aspect of the invention, the heat-sealing film-forming polymer further comprises:

[0065] - water; and

[0066] - at least one plasticizer other than water.

[0067] According to one aspect of the invention, the heat-sealing film-forming polymer comprises: - at least one water-soluble polymer, namely a water-soluble polymer, preferably soluble in water at room temperature when the mass concentration of the water-soluble polymer is greater than or equal to 2.5%.

[0068] Thus, the heat-sealing film-forming polymer has improved mechanical and chemical properties.

[0069] According to one aspect of the invention, the heat-sealing film-forming polymer is associated with: - at least one water-soluble polymer, namely a water-soluble polymer, preferably soluble at room temperature.

[0070] Thus, the heat-sealing film-forming polymer has improved mechanical and chemical properties.

[0071] Preferably, the water-soluble polymers comprise hydrophilic units. For example, the water-soluble polymers may comprise heteroatoms such as O or N in their main chain. The water-soluble polymers may also comprise hydrophilic groups such as -OH, -NH2, -NH-, -CO2-, or -SO3-

[0072] According to one aspect of the invention, the water-soluble polymer is chosen from non-ionic water-soluble polymers, amphoteric water-soluble polymers, cationic water-soluble polymers, anionic water-soluble polymers, and mixtures thereof.

[0073] According to one aspect of the invention, the water-soluble polymer is chosen from polyvinyl alcohols, polyoxyalkylenes, polyvinylpyrrolidones, poly(meth)acrylic acids, cationic polymers, and mixtures thereof.

[0074] Among the water-soluble polymers, polyacrylamides may also be mentioned.

[0075] According to one aspect of the invention, the elements of the coating sauce are chosen from polyols, glycerol acetates, glycerol propionates and mixtures thereof. Examples of polyols that may be mentioned are glycerol, hexane triol, mannitol, sorbitol, glycols, including ethylene glycol and their derivatives. Preferably, the elements of the coating sauce are chosen from glycerol, sorbitol, and mixtures thereof. According to one embodiment, the plasticizer is glycerol.

[0076] Thus, the elements of the coating sauce make it possible to increase the mechanical properties of the heat-sealing film-forming polymer against humidity.

[0077] According to one aspect of the invention, the surfactant is chosen from lecithin, diacetylenic phosphonates, polysorbates. Preferably, the surfactant is lecithin.

[0078] According to one aspect of the invention, the hydrophobic agent may be chosen from:

[0079] - polycarboxylic acid esters;

[0080] - C3-C33 carboxylic acids, preferably C4-C28 fatty acids, and, even more preferentially unsaturated fatty acids in C6-C28; and

[0081] - their mixtures.

[0082] The polycarboxylic acid esters may be derived from at least one polycarboxylic acid and at least one alcohol, preferably a Cl-Cl8 alcohol.

[0083] Among the polycarboxylic acids preferentially retained within the scope of the invention, mention may be made of citric acid, hydroxycitric acid, tartaric acid, malic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid.

[0084] Among the preferred alcohols in accordance with the invention, mention may be made of alcohols in C2-C6, such as ethanol, n-propanol, iso-propanol, n-butanol and tert-butanol.

[0085] According to one aspect of the invention, the hydrophobic agent is chosen from triethyl citrate, tributyl O-acetyl citrate, tributyl citrate and mixtures thereof.

[0086] According to one aspect of the invention, the hydrophobic agent is a C3-C33 carboxylic acid, preferably a C4-C28 fatty acid, and even more preferably an unsaturated C6-C28 fatty acid.

[0087] Among the C4-C28 fatty acids retained within the scope of the invention, mention may be made of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and mixtures thereof.

[0088] Among the particularly interesting C6-C28 unsaturated fatty acids, mention may be made of palmitoleic acid, oleic acid, linoleic acid, and mixtures thereof.

[0089] According to one aspect of the invention, the coated flexible support can be printable and / or printed.

[0090] According to one aspect of the invention, the oil and / or grease barrier property of the heat-sealing film-forming polymer has a Cobb 1800 index of less than 10 g / m2, preferably less than 6 g / m2, more particularly less than 3 g / m2. The Cobb 1800 index is ideally between 1 and 2.5 g / m2.

[0091] The Kit level for obtaining the oil and / or grease barrier property of the heat-sealing film-forming polymer is greater than or equal to 7, preferably greater than or equal to 10.

[0092] According to one aspect of the invention, the oxygen barrier property of the heat-sealing film-forming polymer has a permeability level of less than or equal to 1000 cm3 / (m2.24h), preferably less than or equal to 100 cm3 / (m2.24h), more particularly less than or equal to 100 cm3 / (m2.24h).

[0093] According to one aspect of the invention, the water barrier property of the heat-sealing film-forming polymer has a Cobb 1800 index of less than or equal to 15 g / m2, preferably less than or equal to 5 g / m2, more particularly between 1 and 2.5 g / m2.

[0094] According to one aspect of the invention, the water vapor barrier property of the heat-sealing film-forming polymer has a water vapor transmission coefficient (WVTR) of less than or equal to 10 g / (m2.24h) and ideally less than or equal to 5 g / (m2.24h) under standard conditions (23°C / 50%RH). Under tropical conditions (38°C / 90%RH), the WVTR is less than or equal to 100 g / (m2.24h) and ideally less than or equal to 50 g / (m2.24h).

[0095] The manufacturing process may comprise the following steps: a. apply a first coating sauce, in particular water-based, containing one or more barrier and heat-sealing polymers, in particular on the front side; b. apply a second coating sauce, in particular water-based, in particular containing one or more barrier and heat-sealing polymers, in particular on the reverse side; c. dry said coated flexible support.

[0096] The sauces, after drying, form the coated layers of the coated flexible support.

[0097] Thus, the first and second coating sauces, after drying, allow the “curls” to compensate each other so that the coated flexible support has good flatness and good surface homogeneity.

[0098] According to one aspect of the invention, at least one of the first and second coating sauces contains at least one caseinate and / or one casein.

[0099] The first and second water-based coating sauces may have some or all of the characteristics described above in connection with the barrier and heat-sealing film-forming polymer(s).

[0100] According to one aspect of the invention, the first and second coating sauces both comprise at least one caseinate and / or one casein.

[0101] According to another embodiment of the invention, the deposition method is chosen from extrusion-coating and lamination, complexing.

[0102] The deposition of the heat-sealing film-forming polymer in the form of a film with low humidity, namely less than 8%, can be carried out on the front side of the flexible support in order to form a coated flexible support. The heat emitted by the machine used to make the deposition makes it possible to remove this residual humidity.

[0103] The invention also relates to a coated flexible support obtained by the method according to the invention.

[0104] The invention also relates to packaging comprising the coated flexible support obtained by the method according to the invention.

[0105] According to one aspect of the invention, the packaging comprises a stack of several flexible supports obtained by the method according to the invention.

[0106] According to one aspect of the invention, the packaging is obtained from a coated flexible support by heat-sealing certain areas of coated flexible support together.

[0107] According to one aspect of the invention, the flexible support has an appearance chosen from: white appearance, brown appearance, matt appearance, silk effect appearance, or shiny appearance.

[0108] According to one aspect of the invention, the packaging is manufactured by lamination, coating, laminating, co-extrusion or extrusion-coating processes.

[0109] The invention also relates to a packaged product comprising:

[0110] - a content, for example a foodstuff, solid or liquid; and

[0111] - the packaging according to the invention enveloping the contents.

[0112] According to one aspect of the invention, the content is chosen from pharmaceutical products maceuticals, food, chemicals and cosmetics.

[0113] According to one aspect of the invention, the foodstuff of the contents of the packaged product is, for example, chosen from meat, fish, vegetables, fruits, pastries, Viennese pastries, food additives, ingredients, dry foods, dry preparations, food powders, tea and herbal tea bags, dried tea leaves, animal feed.

[0114] According to one aspect of the invention, the content is chosen from newspapers, magazines and advertisements.

[0115] Definitions

[0116] By “coating” is meant, for example, a surface treatment consisting of applying a generally liquid coating to a support. The coating may have a composition such as a film-forming polymer.

[0117] By “complexing” is meant, for example, a mechanical action making it possible to inseparably assemble two or more materials with different mechanical and physicochemical properties.

[0118] By “lamination” is meant, for example, a mechanical action allowing a film to be applied to a support

[0119] By “extrusion-coating” is meant, for example, the technique consisting of coating a support by depositing a layer of molten polymer thereon by extrusion.

[0120] By “printing” is meant, for example, an application of a coating via a flexographic or gravure printing system.

[0121] By "humidity" is meant the water or water vapor content in a substance. It can be expressed as a mass percentage, namely a ratio of the mass of water to the total mass of the substance.

[0122] “Grammage” is a quantity characterizing a flexible support, not yet coated, such as paper, corresponding to its surface mass, that is to say its mass per unit of surface. The grammage includes a residual humidity which varies in particular between 4 and 8% of the total weight of the flexible support, in particular paper.

[0123] The weight of a flexible support such as paper is between 20 and 300 g / m2, preferably between 40 and 100 g / m2.

[0124] A “thin” paper has a weight between 10 and 60 g / m2, advantageously between 30 and 50 g / m2.

[0125] By "heat sealing" is meant, for example, a process during which the The edges of the support are welded using heat, with or without direct contact with the support.

[0126] By "heat sealant" is meant, for example, the quality that a material has to be welded by heat sealing without adding an additional adhesive layer, an additional polymer layer or an additive. In other words, the ther- moscellant is sufficient in itself to achieve heat sealing.

[0127] By "barrier" is meant, for example, the properties which protect the contents of a package formed by the support against external aggressions and substances, or which protect the exterior of the contents of the package. The most common barriers are those against oxygen, oil, grease, water, water vapor, and fungi and microorganisms.

[0128] By "oxygen barrier" is meant, for example, a barrier with a low oxygen permeability level, i.e. less than 100 cm3 / (m2.24h) and preferably less than 10 cm3 / (m2.24h). This property may be required, for example, for food products requiring protection from oxidation such as chocolate, cheese or dry foods.

[0129] By "oil or fat barrier" is meant, for example, a barrier whose Kit level is between 6 and 12. This property may be required, for example, for food products such as pastries or fast food.

[0130] By "water barrier" is meant, for example, a barrier whose Cobb index is advantageously less than or equal to 15 g / m2, preferably less than or equal to 5 g / m2 and for the Cobb duration of 1800 seconds. This property may be required, for example, for food products such as fruits and vegetables and disposable tableware.

[0131] By "water vapor barrier" is meant, for example, a barrier whose water vapor transmission coefficient (WVTR) is less than 10 g / (m2.24h) and ideally less than 5 g / (m2.24h) under standard conditions (23°C / 50%RH). The WVTR coefficient is less than 100 g / (m2.24h) and ideally less than 50 g / (m2.24h) under tropical conditions (38°C / 90%RH).

[0132] By "antifungal barrier" is meant, for example, a barrier resistant to the proliferation of fungi and microorganisms. This property may be required, for example, for food products such as soft fruits, such as strawberries or raspberries.

[0133] The "Cobb" test consists of measuring the quantity of water that the flexible support, in particular paper, can absorb over a defined time. For example, the Cobb index 1800 means that the Cobb test was carried out for 1,800 seconds, or 30 minutes.

[0134] This Cobb 1800 index is expressed in grams per square meter (g / m2). The lower the Cobb 1800 index value, the better the water barrier. Values ​​below 15 g / m2 correspond to very good water barriers for Cobbl800.

[0135] This Cobb test is carried out by pouring 100 ml of distilled or demineralized water onto a sample of treated paper with a surface area of ​​100 cm2 for 30 minutes (ISO 535 standard: 2014). The difference in weight before and after the test corresponds to the quantity of water absorbed and therefore to the Cobb index.

[0136] Measurements of vapor permeation or water vapor transmission coefficient (Water Vapor Transmission Rate (WVTR) in English terminology),

[0137] These measurements assess the amount of water vapor that passes through the support in 24 hours at predefined temperature and humidity conditions. Generally, these tests are either carried out in “standard” conditions at 23°C / 50% relative humidity (RH), or in “tropical” conditions at 38°C / 90% RH.

[0138] The test is carried out according to ISO 2528, a cup of anhydrous CaCl2 is sealed by the support to be tested. The assembly is placed in a regulated climatic chamber. The water vapor which passes through the support is trapped by the CaCl2. The difference in weight of the CaCl2 measured between the initial moment and that measured after 24 h corresponds to the value of the WVTR expressed in g / m2 / 24 h.

[0139] The lower the WVTR value, the better the water vapor barrier.

[0140] The “Test Kit” makes it possible to determine the resistance of a paper to the penetration of fatty products such as fats or oil.

[0141] This test kit comprises, for example, at least 12 reagent mixtures containing varying amounts of castor oil, toluene and heptane. The test consists of determining the number of the highest mixture for which there is no penetration or soiling of the surface. The barrier level increases from 1 to 12.

[0142] A drop of the mixture is placed on a sheet, then it is wiped off after 15 seconds, and the appearance of the paper is observed (ISO 16532-2 standard).

[0143] For certain particular applications, more drastic tests can be carried out by increasing the surface area to be tested, and by carrying out tests at high temperature, namely above room temperature, or by increasing the proportion of the most aggressive reagent in the mixtures, namely heptane.

[0144] The oil Cobb test is based on the same principle as the aforementioned water Cobb test but this time using castor oil (SCAN-P 37 standard).

[0145] A palm oil impermeability test can also be carried out (ISO 16532-1 standard), if the results are good enough, the turpentine test can be carried out (ISO 16532-3 standard).

[0146] By "film-forming" is meant, for example, a material that can be applied in a thin layer, mainly in liquid form, on a support, and which then becomes a solid film, a film, or a sheet. This film-forming material can also be applied in another form, for example by extrusion-coating in the form of a softened or molten material. Generally speaking, by "film-forming" is meant, in particular, the tendency of a material to form a film.

[0147] By "polymer" is meant, for example, molecules with long chains of mass high molecular weight. A polymer can be a substance consisting of molecules characterized by the sequence of one or more types of monomer units. A "natural" polymer can include, for example, proteins.

[0148] By "thermoplastic" is meant, for example, a material which becomes malleable and pliable above a given temperature, the glass transition temperature Tg, but which below this Tg becomes hard again, these transformations being reversible.

[0149] By “plasticizer” is meant, for example, a substance making it possible to lower the glass transition temperature Tg of the material.

[0150] By "surfactant" is meant, for example, an amphiphilic molecule, that is to say a molecule possessing both hydrophilic and hydrophobic properties.

[0151] By "hydrophobic" is meant, for example, a compound having little affinity for water and tending not to dissolve in it. Typically, this is a predominantly apolar compound.

[0152] By "hydrophilic" is meant, for example, a compound having an affinity for water and having a tendency to dissolve therein. Typically, it is a compound having polar groups capable of forming hydrogen bonds.

[0153] By "water-soluble" is meant, for example, that which dissolves in water, preferably at room temperature. The water solubility of a polymer can be measured as follows: a polymer is added to water at a mass concentration of 2.5%. After stirring for 48 hours, the solution is filtered to check whether any particles remain. When there are no particles in the filter, the polymer is considered water-soluble.

[0154] By "bio-sourced" is meant, for example, a material containing all or part of elements of natural or renewable origin. The bio-sourced material is, for example, paper comprising cellulose that is extracted from trees or plants for different applications.

[0155] By "natural material" is meant a material which exists naturally in the environment and which has not undergone any chemical modification, in particular a material whose chemical structure remains unchanged, even if it has been subjected to a chemical process or treatment or to a physical process of mineralogical transformation, for example to eliminate impurities.

[0156] By "biodegradable" we mean a material that can be decomposed under the action of micro-organisms (bacteria, fungi, algae etc.). The result of this decomposition is the formation of water, CO2 and / or methane and possibly by-products (residues, new biomass) that are non-toxic to the environment. This is, for example, a biodegradable material according to the European standard EN NF 13432.

[0157] By "compostable" is meant, for example, a biodegradable product putting to term the product cycle according to standard EN 13432.

[0158] According to this standard EN13432, a material can be described as “compostable” if it has the following characteristics:

[0159] - be able to achieve 90% biodegradation in less than 6 months if it is subjected to an environment rich in carbon dioxide; these values ​​are tested with the standard method EN14046 (also called ISO 14855);

[0160] - when brought into contact with organic waste for 3 months, the mass of material must consist of at least 90% of residues less than 2 mm in diameter; these values ​​are tested with the standard method EN14045;

[0161] - the material must not have negative effects on the composting process;

[0162] - a low concentration of heavy metals;

[0163] - pH values ​​within established limits;

[0164] - a mineral salt content within the established limits;

[0165] - a concentration of volatile solid elements within the established limits;

[0166] - a concentration of nitrogen, phosphorus, magnesium and potassium within the limits established.

[0167] It is noted that a “bio-sourced” material can be compostable.

[0168] By "repulpable" is meant, for example, a fibrous material, in particular paper, for which it is possible to disperse the fibers in an aqueous medium in order to produce a paste called pulp. Thus, the repulpable material can be reintegrated into the paper processing chain. This "repulpable" characteristic does not concern certain polymers such as polyolefins, for example polyethylene, or polypropylene. These polymers are not soluble in water and interfere with the process of dispersing the fibers in an aqueous medium, thus preventing a flexible support coated with such polyolefins or polypropylene from being made "repulpable". This "repulpable" characteristic also does not concern waxes, for example polyethylene- or alkane-based waxes, or ester waxes, for example beeswax.In fact, these waxes are not water-soluble, thus making it possible to make a flexible support coated with such waxes "repulpable".

[0169] By “caseinate” is meant, for example, a casein salt whose counter cation is chosen from the group comprising calcium, potassium, ammonium, sodium and magnesium.

[0170] "Casein" is a protein derived from milk which is mainly obtained by precipitation by adding an acid (acid casein) or rennet (rennet casein) to the milk, or by filtration (micellar casein). There are several types of casein in milk, namely alpha, beta, gamma and kappa caseins.

[0171] Caseinate and casein form a biodegradable heat-sealing film-forming polymer gradable, compostable, and food compatible. Casein and caseinate are also compatible with a bio-based, biodegradable, compostable, and / or repulpable coated flexible support.

[0172] Unless otherwise indicated, the percentages are expressed by mass relative to the total mass of the material. Brief description of the figures

[0173] Other characteristics, details and advantages of the invention will emerge more clearly on reading the detailed description given below, and several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0174] [Fig-1] is a schematic view of the automated manufacturing line of the support flexible coated according to the invention,

[0175] [Fig.2] is a schematic view of a coated paper, in cross-section, obtained by the process according to the invention,

[0176] [Fig.3] is a schematic view of a coated paper, in cross-section, obtained by a variant of the process according to the invention,

[0177] [Fig.4] is a schematic view, in cross-section, of an assembly of two heat-sealed coated papers.

[0178] Detailed description of the figures

[0179] [Fig.l] shows an automated manufacturing line 2 for implementing the method according to the invention for manufacturing coated paper samples 4 having a front face 6 coated 8 with a film-forming barrier and heat-sealing polymer 10 comprising a caseinate and a casein. Reference 10 also designates the coated layer obtained at the end of the process.

[0180] The heat-sealing polymer(s) of the coated layer 10 comprise at least one natural wax such as a carnauba wax, a soy wax, a beeswax, a pine wax or even a rice wax.

[0181] The paper 12 used for the coated paper 4 has a weight of 50 g / m2.

[0182] The method according to the invention comprises the following steps:

[0183] a) depositing a coating sauce in order to form the coated layer 10 on the front face 6 of each paper 12;

[0184] b) drying the coated paper 4 so that the humidity of the coated paper 4 is greater than 5%;

[0185] c) applying water to a back face 16 of the coated paper 4 so as to create a difference in humidity between the front face 6 and the back face 16 of each coated paper 4; and

[0186] d) drying the coated paper 4.

[0187] Step a) of the method according to the invention is implemented by means of a coating technique which is an air knife coater 18 which comprises rollers 22, an air knife 24 and a tank of heat-sealing film-forming polymer 26.

[0188] The coating sauce contained in a tank 26 is abundantly deposited on the front face 6 of the paper 12 by one of the rollers 22 which is directly in contact with said heat-sealing film-forming polymer 10.

[0189] The excess of the heat-sealing film-forming polymer 10 is removed by means of an air jet emitted by the air blade 24. This excess is recovered in the recovery tank 28 arranged to recycle said excess in the tank of the heat-sealing film-forming polymer 10.

[0190] This air knife coater 18 makes it possible to control the coating deposition with high quality and to ensure a uniform and regular coating on the paper 12.

[0191] The coating deposit having a surface density of 8 to 12 g / m2, produced with this air knife coater 18 makes it possible to confer the grease and oxygen barrier properties to the coated paper 4. The oxygen barrier properties are improved compared to the case where the paper 12 is not coated.

[0192] Thus, the coated paper 4 has a Cobb index 1800 of the order of 1 to 4 g / m2 and a Kit level of the order of 7 to 12.

[0193] Step b) of the method according to the invention is carried out by means of a dryer 30.

[0194] This step b) makes it possible to dry the coated paper 4 as much as possible so that said coated paper 4 contains as little residual moisture as possible.

[0195] Following this high intensity drying, the coated heat-sealing barrier sauce causes high stresses on the paper 12, on fibers of this paper 12, stresses which would have the effect of rolling up the coated paper 4 laid flat after manufacturing. It is desired to avoid this rolling up effect.

[0196] Thus, the drying step b) occurs immediately after the deposition of the coated heat-sealing barrier sauce so that this sauce does not yet have time to dry naturally, in order to maximize the stresses to which the coated layer 10 resulting from the sauce is subjected.

[0197] Step c) of the method according to the invention is carried out with water applied to the back face 16 of the coated paper 4 using a roller 22 rotating in contact with water contained in a water tank 32.

[0198] Step d) of the method according to the invention is carried out with a dryer 30.

[0199] During the drying step d), the humidity of the front face 6 being very low, the water evaporates very largely from the back face 16, causing stress on the fibers forming the paper 12, stress which will induce a winding effect on the back face 16. This winding effect on the back face 16 is opposite to the winding effect of the front face 6 so that compensation can be obtained for the curling effects on the front 6 and back 16 sides. This compensation may require a certain amount of time for the coated paper 4 to stabilize.

[0200] Thus, when these effects have compensated for each other, the paper 12, placed on a flat surface, has satisfactory flatness.

[0201] [Fig.2] shows schematically, in cross-section, a coated paper 4 obtained by the method according to the invention.

[0202] The coated paper 4 comprising the front 6 and back 16 faces, comprises on its front 6 face a coated layer 10 while the back 16 face of said coated paper 4 does not comprise a heat-sealing film-forming polymer 10.

[0203] [Fig.3] shows schematically, in cross-section, a coated paper 400 obtained by a variant of the method according to the invention.

[0204] The coated paper 400 thus obtained has a front face 6 on which a coated layer 50 is deposited and a back face 16 on which a second layer 60 is deposited, the first and second coated layers 50, 60 comprising natural polymers with the compositions presented above.

[0205] [Fig.4] shows schematically, in cross-section, an assembly 70 by heat-sealing two coated papers 4 obtained by the method according to the invention.

[0206] Two coated papers 4 having a front face 6 and a back face 16, each coated paper 4 having on its front face 6 a coated layer 10, are assembled without the need to insert an additional adhesive layer (not shown) between each layer of the heat-sealing film-forming polymer 10.

[0207] It is remarkable to note that the method according to the invention makes it possible to obtain a coated paper 4 intended for packaging, said coated paper 4 being biosourced, biodegradable, compostable and repulpable with mechanical and chemical properties equivalent to a paper coated with a non-biodegradable film-forming polymer (not shown), namely a plastic film-forming polymer commonly used commercially.

[0208] In particular, said coated paper 4 obtained with the process according to the invention has barrier properties to oil and grease (a Cobb index 1800 of the order of 1 to 4 g / m2 and a Kit level of the order of 7 to 12) and to oxygen (oxygen permeability level less than 10 cm3 / (m2.24h)) in combination with heat-sealing properties.

[0209] Furthermore, the method according to the invention allows the industrial manufacture of said coated paper 4 in an automated paper manufacturing line whereas such coated paper 4 could not be obtained via this manufacturing line until now because of the winding effect of the coated paper 4.

[0210] Furthermore, the method according to the invention makes it possible to reduce the number of layers required necessary for coated paper 4 while making it more environmentally friendly, economical and compatible with various applications such as packaging applications, including food packaging applications.

[0211] In a variant of the invention, the coated layer is based on a natural wax such as a carnauba wax, a soy wax, a beeswax, a pine wax or even a rice wax.

[0212] Preferably, the heat-sealing polymer(s), in particular the wax, are present in the coated layer with a percentage by weight of between 1% and 30%, in particular between 5% and 20%, in particular between 10% and 15%, in particular between 5% and 15%.

Claims

Claims

1. Coated flexible support (4), intended for manufacturing a finished product, in particular a packaging, the coated flexible support having a flat shape when it is freely laid flat, this coated flexible support comprising a flexible support containing, by weight, at least 90%, or at least 95%, of a first natural material, this flexible support being coated with a coated layer containing, by weight, at least 50%, or at least 80%, or at least 90%, or at least 95%, of a second natural material formed by at least one heat-sealing polymer, this or these heat-sealing polymers (10) having in particular at least one of the following properties: oxygen barrier, oil / grease barrier, water barrier.

2. Coated flexible support according to the preceding claim, in which the heat-sealing polymer(s) of the coated layer comprise at least one natural wax such as a carnauba wax, a soy wax, a beeswax, a pine wax or even a rice wax.

3. Coated flexible support according to claim 1, in which the heat-sealing polymer(s) forming the coated layer are based on polysaccharides such as alginate or starch, chitosan or a cellulose derivative.

4. Coated flexible support according to one of the preceding claims, in which the heat-sealing polymer(s), in particular wax, are present in the coated layer with a percentage by weight of between 1% and 30%, in particular between 5% and 20%, in particular between 10% and 15%, in particular between 5% and 15%.

5. Coated flexible support according to one of the preceding claims, in which the weight of the coated flexible support (4) is between 20 and 300 g / m2, preferably between 40 and 100 g / m2.

6. Packaging comprising two zones belonging to the same coated flexible support according to one of the preceding claims or belonging respectively to two coated flexible supports according to one of the preceding claims, these zones being applied against each other by their respective coated faces.

7. Packaging according to the preceding claim, in which the heat-sealing polymer is chosen to obtain a sealing force between areas sealed together which is greater than or equal to 2.5 N / 15mm and preferably greater than or equal to 3.5 N / 15mm.

8. Method of manufacturing a package, comprising the following steps: - providing two zones of coated flexible support according to one of claims 1 to 5, - sealing these two zones together by pressing these two zones against each other by applying heat, in particular by means of heating jaws, so as to obtain the package.

9. Method according to the preceding claim, comprising the step of coating the flexible support on a front side and / or a back side, with one or more water-based sauces and containing one or more film-forming barrier and heat-sealing polymers, the viscosity of the coating sauce is in particular less than 250 mPa.s, or less than 200 or 120 mPa.s.

10. Method according to one of claims 8 and 9, comprising a step of drying the coated flexible support.

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