FR3011011A1 - PAPER COMPRISING FIBRILLED SYNTHETIC FIBERS. - Google Patents

Abstract

The present invention relates to a paper, comprising: fibrillated synthetic fibers; and non-fibrillated synthetic fibers.

Description

The present invention relates to fibrous documents, including secure documents. The invention relates more particularly but not exclusively to a paper suitable for producing secure documents and to its manufacturing process. By "secure document" is meant a security document or value document, such as a means of payment, for example a bank note, a check, a bank card or a restaurant ticket, an identity document, such as an identity card, a visa, a passport, including the personal data page of a passport, an "inlay" or a driving license, a lottery ticket, a ticket or a ticket for entrance to cultural or sports events. In order to guard against attempts to falsify or counterfeit a secure document, it is known to add security elements to a substrate of the document, for example in the form of fibers, boards, films, knitted structures. or security son. The document substrate may itself be made of a material that is difficult to counterfeit, and is then referred to as a "safety substrate". Since the lifespan of secure documents is generally critical, "very high durability" security substrates have been developed. In the field of sheet security substrates, cellulosic substrates, so-called "composite" substrates, plastic substrates and so-called "hybrid" substrates are known. Cellulosic substrates are fibrous substrates generally obtained by the papermaking process, also called wet process, from cellulosic fibers such as hardwood fibers, conifers, annuals, especially cotton, or mixtures thereof. The term "papermaking" or "wet process" denotes a common papermaking process, comprising in particular the following successive stages: draining of a suspension of fibers which may be refined beforehand and possibly comprising fillers and additives conventionally used in paper industry and / or specific safety elements, - pressing of the wet sheet obtained, and then - drying .. The so-called "composite" substrates are cellulosic substrates whose fiber composition comprises, in addition to the cellulosic fibers, synthetic fibers. Such fibers are generally introduced at levels of less than 20% by dry weight relative to the total weight of the substrate, and their use makes it possible to increase the mechanical strength of the substrate. The presence of the cellulosic fibers plays an important role in the entanglement and the fixing of synthetic fibers, which reveals the intrinsic potential of synthetic fibers. Indeed, in the development of the mechanical performance of a sheet material, the performance of the polymer of the synthetic fibers are important but the ability of interaction of the fibers between them is also critical. The presence of refined cellulosic fibers greatly favors the bridging between the cellulose and the polymer of the synthetic fibers.

Composite substrates have better resistance to circulation than cellulosic substrates. The term "resistance to. the circulation 'the combination of the following properties: folding resistance, tear resistance and dirt resistance. The so-called "hybrid" substrates comprise at least one cellulosic or composite substrate associated with at least one plastic layer. With respect to the cellulosic or composite substrate that composes them, they generally exhibit equivalent tear resistance and improved bending resistance. Hybrid substrates used in the field of security substrates are described in particular in applications WO 2006/066431, WO 2004/028825, EP 1 854 641, WO 03/054297 and WO 94/29105. Plastic substrates are conventionally obtained by extrusion of a polymer. These substrates are normally of "very high durability". Such plastic substrates are especially described in applications EP 2 225 102, WO 99/67093, WO 97/01438 and WO 83/00659. These substrates exhibit good bending and soiling resistance, as their initial tear strength is relatively low. Their security is also more difficult, insofar as these substrates are not compatible with the main safeguards implemented for paper substrates (cellulosic, composite or hybrid) such as watermarking and insertion, at least partially in bulk. safety wires, for example as described in applications EP 0 059 056, GB 2 388 377 and GB 2 381 539. There are also substrates called "non-woven". A nonwoven substrate is defined in ISO 9092 and EN 29092 as being a manufactured sheet, consisting of a directionally or randomly oriented fiber web or web, bonded by friction and / or cohesion, and / or adhesion , excluding paper and products obtained by weaving, knitting, tufting or seaming, incorporating binding yarn or filament or felts by wet embossing, whether or not needle punched. The association of the nonwoven industry (or INDA) defines them as "a sheet or veil of natural fibers and / or manufactured fibers or filaments, excluding paper, which have not been woven and that can be linked together in different ways. " These substrates and their manufacture are described in more detail in the files "Non-woven fabrics" (Gérard Coste, 25 June 2004) and "Material science & 10 engineering 554 - Nonwovens science and technology II" (Laxry C. Wadsworth, spring 2004) accessible on the Internet at the following addresses: - http://cerig.efpg.inpg.fr/tutoriel/non-tisse/soinmaire.htm, and http://web.utk.edu/-mse/Textiles/index .html. The nonwovens are described as being suitable for use as safety substrates in WO 2002/38368 and FR 2 447 995. These substrates generally consist of long non-cellulosic fibers, for example of lengths between 3 and 25 μm. mm, and have a high mass volume and porosity, which gives them a low resistance to soiling. The nonwovens are manufactured according to various processes, especially in the dry process, for example by carding or aerodynamic process (also called "Airlaid"), in the melted process, in particular by extrusion (also called "Spunbond") or extrusion blow molding (also called "Meltblown"), wet (also called "Wetlaid") according to a process similar to the paper process, or in other ways, especially by dissolving in a solvent (also called "flash spirming"). Nonwovens made in the wet process generally comprise cellulosic fibers, for example at least 10%, especially in order to ensure better cohesion to the substrate obtained. On the other hand, when the proportion of cellulosic fibers in nonwovens made in the wet process is low or even zero, the hydrogen bonds formed between these fibers do not make it possible to ensure sufficient cohesion to the substrate and it is therefore necessary to at least one bonding step. Such a bond can be achieved by impregnation, spraying or coating of latex, by thermo-fixing, by needling or water jet binding (also called "Spunlace").

An example of a non-woven substrate comprising little or no cellulosic fibers is described in application EP 2 438 599. The mechanical properties of a paper may also be improved by introducing into the mass of it reinforcing fibers. . These reinforcing fibers are generally introduced at a rate of more than 3% by dry weight, relative to the total mass by dry weight of the paper fibers, and are most often based on synthetic polymers type polyamide 6.6 (PA 6.6) or polyethylene terephthalate (PET) for the mechanical strength that these polymers confer and for economic reasons, manufacturing and good interaction with the cellulosic fibers of the paper.

By "synthetic fibers" it is necessary to understand fibers made with one or more synthetic polymers, which are polymers obtained from a chemical synthesis, in particular by a polymerization reaction of monomers, coupled or not to a crosslinking reaction. . By way of information, the table below groups together the orders of magnitude of the tear strength and the folding resistance of the substrates discussed above. The tear strength is determined according to ISO 1974 "Paper - Determination of Tear Strength - Elmendorf Method" and bending strength according to ISO 5626 "Paper; determination of the folding resistance ". Cellulosic substrates Substrates Substrates Hybrid composite plastic substrates Resistance to 800 1100 800 250 tear (mN) Resistance to 2500 5000> 5000> 50000 bend There is a need to develop new substrates with improved strength properties, including resistance to improved tearing and bending resistance, in particular a higher tear resistance than prior art paper security substrates and a folding resistance at least equivalent to that of plastic substrates.

There is also a need to develop a substrate compatible with the main security implementations for papers, including watermarking and the insertion, at least partially by mass, security son. The invention aims to meet all or part of the aforementioned needs, and it achieves it through a paper, comprising: - fibrillated synthetic fibers; and - non-fibrillated synthetic fibers. The substrate according to the invention is a paper, which means that it is obtained by papermaking, in particular according to an inclined table method, flat table and / or round shape. It is preferably a round shape process, for example to obtain a better watermark definition or to incorporate, at least partially by mass, a security thread. The techniques conventionally used to secure the papers can thus be used to secure the substrate according to the invention. In addition, the substrate according to the invention has improved properties over cellulosic papers, especially superior tear strength. Fibrillated Synthetic Fibers Fibrillated fibers are fibers with fibrils, that is, extensions that deviate from the body of the fiber. The fibrillated fibers may in particular be fibers in which at least one wall has been partially broken off, causing the partial release of fibrils. Such fibers are branched by the fibrils, the section of which is much smaller than that of the fiber as a whole, which increases the interaction of these fibers with the other fibers, in particular synthetic fibers, and limits the ability of the fibers to slip the fibers. 25 to each other. Such fibers are described for example in documents FR1317778 and FR2199015. The fibrillated fibers therefore play an important role in the cohesion of a paper according to the invention, in particular by entanglement effects. The paper of the invention may comprise fibrillated synthetic fibers which are polyamide (PA), polyethylene (PE), polypropylene (PP), poly (ethylene terephthalate) (PET), alcohol polyvinyl (PVA), aromatic polyester (for example Vectran® marketed by Kuraray), polyamide imide, polyolefin and preferably polyacrylic fibers, for example such as those marketed by Sterling under the reference CFF 111- 2. Preferably, the material of the fibrillated synthetic fibers has a tensile strength of between 300 and 600 MPa. The presence of the fibrillated synthetic fibers in the invention overcomes the absence or lower amount of cellulosic fibers, and provides the desired mechanical performance in tear and bend resistance. Preferably, the synthetic fibers. fibrillates have an average length of between 2 mm and 8 mm, and preferably between 4 mm and 6.5 mm. The specific surface of the fibrillated synthetic fibers according to the invention is preferably between 35 and 75 m 2 / g, more preferably about 50 m 2 / g. It is measured according to ISO 9277 "Determination of the mass area (specific surface area) of solids by gas adsorption - BET method". Preferably, the paper according to the invention comprises more than 5% by dry weight, better still more than 10% by dry weight and more preferably more than 20% by dry weight, of synthetic fibers fibrillated with respect to the total weight of the paper. The fibrillated synthetic fibers may be white or colored, in particular of a color which may be the same or different from that of the other synthetic fibers. The level of fibrillation of the fibers may be between 5 and 700 ml and preferably between 5 and 100 ml according to the CSF standard. The fibers may contain at least one tracer, said tracer to identify the fibers by a specific means, in particular by exposure to UV radiation and / or IR and / or by exposure to. a chemical developer. This tracer can thus be a luminescent tracer, especially fluorescent under UV or IR. The fibrillated fibers may not all have the same formulation. Non-fibrillated synthetic fibers Preferably, the non-fibrillated synthetic fibers are selected from polyamide (PA), polyacrylic, polypropylene (PP), poly (ethylene terephthalate) (PET), polyvinyl alcohol fibers. (PVA), aromatic polyester (for example Vectran® marketed by Kuraray), polyamide imide, polyolefin and preferably polyethylene (PE). In particular, the non-fibrillated synthetic fibers may be polyamide 6.6 1.7dTex 4mm fibers marketed by Rhodia or polyethylene terephthalate fibers marketed by Kuraray under the reference EP023 5nurt. The paper according to the invention preferably comprises less than 95% by dry weight, better less than 90% by dry weight and more preferably less than 80% by dry weight of non-fibrillated synthetic fibers, based on the total weight of the paper. Preferably, the non-fibrillated synthetic fibers have a number average length of between 3 and 6 mm, and a titer of between 0.3 and 1.7 dtex. Preferably, the non-fibrillated synthetic fibers have a titration of less than 2 dtex, better still less than 1 dtex, and even more preferably less than 0.5 dtex. The non-fibrillated synthetic fibers are, for example, the fibers marketed under the mini Eslon reference by the company Woongjin, and are PET fibers of 0.3 dtex, or for example the fibers marketed under the reference EP023 by the company Kuraray, and are PET fibers of 0.33 dtex. The non-fibrillated synthetic fibers may have the same color as the fibrillated fibers or a different color. Other fibers The paper according to the invention may comprise less than 5% by dry weight of non-synthetic fibers, such as cellulosic fibers, based on the total weight of the paper, and preferably less than 2% by dry weight of fibers. non-cellulosic relative to the total weight of the paper, still better be free of non-synthetic fibers, such as cellulosic fibers. In particular, in a preferred embodiment, the fibers of the paper according to the invention consist exclusively of fibrillated synthetic fibers and non-fibrillated synthetic fibers. Treatments It is possible to strengthen the cohesion of a paper according to the invention by introducing a polymeric binder such as polyvinyl alcohol, which has a synergy with the synthetic fibers, surprisingly allowing the development folding resistance. The application of the polymeric binder may be by impregnation, surfacing or coating, preferably the polymeric binder being introduced at least partially by mass.

The composition may comprise an anionic polymeric dispersion, in particular flocculated. Preferably, the composition comprises at least 10% by dry weight of anionic polymeric dispersion, in particular flocculated, such an anionic polymer dispersion makes it possible to improve the folding resistance of the paper.

The latex used is for example the latex marketed by Dow Chemicals under the reference 94755.04 or a latex as described in the international application WO2008152299. The formulation of the paper according to the invention may also comprise a main cationic flocculating agent, in an amount of between 1 and 5% by dry weight relative to the total weight of the paper, and optionally a secondary cationic flocculation agent, of an amount of between 0.1 and 0.5% by dry weight, chosen from a cationic resin, polyacrylamides, polyethyleneimines, polyvinylamines and their mixtures, preferably a cationic resin, and better a polyamide-amineepichloridin resin. The paper according to the invention may comprise at least 3% by dry weight of latex, in particular flocculated, relative to the total weight of the paper. Other binders may be used, including a transparent or translucent elastomeric binder, such as polyurethane and colloidal silica. In order to enhance the strength of the paper, jaws (aggregates) of a polyurethane having a substantial elongation at break, for example greater than 600%, can be incorporated into the paper by anionic dispersion, especially in a proportion of between 5 and 45% by dry weight relative to the total weight of the paper. Other paper constituents The paper according to the invention may comprise any adjuvants and compounds conventionally used in papermaking, such as fillers, retention agents, gluing agents and / or bleaching agents. wet strength, especially epichlorohydrin resins. The paper according to the invention may in particular comprise filler-blocking fillers, in particular plastic filler, for example the polyvinyl chloride (PVC) particles marketed by the company Kem One under the reference Lacovyl Pb 1302. Such fillers make it possible in particular to densify the paper according to the invention. Papermaking The paper according to the invention can be manufactured according to the usual manufacturing techniques of cellulosic papers, except for the steps specifically related to the presence of cellulosic fibers if they are absent. In particular, the radiation step, which is particularly energy-consuming, can be advantageously suppressed. The manufacturing method can be adapted to the presence of security elements such as a watermark or security thread. The paper preferably has a hand less than or equal to 2.5 cm3 / g, better a hand less than or equal to 2 cm3 / g and more preferably less than or equal to 1.5 cm3 / g. The paper may have a thickness of between 100 and 300 μm, more preferably between 100 and 150 μm. It is measured according to ISO 534 "paper and board - determination of thickness, density and specific volume". The grammage of the paper may be between 70 g / m2 and 150 g / m2 and preferably between 90 g / m2 and 110 g / m2. It is measured in accordance with ISO 536 "Paper and board - Determination of grammage".

Watermark The paper according to the invention may comprise a watermark. This watermark can be formed on round shape or flat table. The watermark may be of any known type, for example light or dark, possibly multiton or multi-toned, for example as described in patent EP 1 122 360. Safety thread The paper according to the invention may comprise a thread of security introduced in mass or between two jets of paper according to the invention bonded in the wet phase. The security thread can be at least partially introduced into the paper. The paper may comprise a fibrous ribbon, in particular a cellulosic fibrous ribbon as described in the application WO2008043965, a plastic ribbon or a knitted ribbon, especially as described in application WO2006016088. The wire may be metallized and / or holographic and / or interferential and / or provided with optical structures, including lenses or mirrors. Multijet Paper The paper of the invention may be single-ended or multi-jet. In the case of a multijet structure, the jets may or may not have the same fibrous composition. In particular, the paper may comprise firstly a jet of synthetic fibers according to the invention, and secondly a jet of cellulosic fibers, assembled in wet phase, the jet according to the invention then constituting a reinforcing jet. The jets can be of the same color or not.

Properties The Bendsten porosity of the paper may be between 0 mL / min and 10000 mL / min, better between 1 mL / min and 7000 mL / min. It is measured according to ISO 5636-3 "Paper and cardboard; determination of air permeability (average value); Part 3: Bendtsen method »Preferably, the double-fold folding resistance Schopper of the paper according to the invention is greater than 5000, better still greater than 10000, more preferably greater than or equal to 25000, better still greater than 50000. It is measured according to ISO 5626 "Paper; determination of the folding resistance ". Preferably, the tear strength of the paper (measured according to ISO 17074) is greater than 1000 mN, more preferably greater than 2000 mN, more preferably greater than 3000 mN. It is measured according to ISO 1974 "Paper - Determination of tear resistance - Elmendorf method" The invention makes it possible to obtain a synthetic paper whose mechanical properties, in particular the resistance to bending and tearing, are greater than 20 those of a conventional paper, while allowing if it is desired to produce watermarks of satisfactory quality and resolution. The use of synthetic fibers, non-wettable and less sensitive to water than cellulosic fibers, provides a substrate with increased durability, including naturally more resistant to attack by mold. Security elements and secure document The paper according to the invention preferably comprises a security element, in particular a watermark or a security thread, for example a wire introduced into window (s), as mentioned above. The invention also relates to a secure document comprising a paper according to the invention. In a preferred embodiment of the invention, the secure document is a bank note. The secure document can also be another type of payment method such as a check or a restaurant ticket, an identity document such as an identity card, a visa, a passport, including the personal data page of a passport, an inlay or a driving license, a lottery ticket, a ticket, a ticket to cultural or sports events, a playing card or a collectible card.

The paper according to the invention and / or the secure document made with the paper according to the invention may comprise one or more additional security elements as defined below. Among the additional security features, some are detectable in the eye, daylight or artificial rut, without the use of a particular device. These security elements comprise, for example, colored fibers or boards. These security elements are called first level. Other types of additional security features are detectable only with a relatively simple device, such as a UV (UV) or IR (1R) lamp. These security elements comprise, for example, fibers, boards or particles. These security elements may be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting in a wavelength of 365 nm. These security elements are said to be second level. Other types of additional security features require for them. 20 detection a more sophisticated detection apparatus. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level. The additional security element or elements present in the paper according to the invention or the secure document according to the invention may have first, second or third level security features. In the case where the formulation of the synthetic fibrous composition comprises fibers of a thermoplastic material, in particular of polyethylene, hot melt, the additional safety element or elements can be fixed to the document by simple heating, thus avoiding the use of a heat activatable adhesive. Comparative Tests Various comparative tests have been carried out in order to demonstrate the advantageous properties of a paper according to the invention. The properties of a substrate whose fibrous composition is 100% fibrillated fibers were first compared to those of a substrate comprising 50% fibrillated fibers and 50% polyethylene terephthalate (PET) fibers and those of a substrate 10 comprising 50% fibrillated fibers and 50% polyamide fibers (PA 6.6). The results, shown in the table below, reflect the fact that a substrate composed of 100% fibrillated fibers is less resistant to tearing than when the fibrillated fibers are used in combination with non-fibrillated synthetic fibers such as fibers. PET or polyamide 6.6. Satisfactory properties are then obtained, in particular good tear resistance. Example 1 Example 2 Example 3 Fibrilated Polyacrylic Fibers CFF 11-2 100% 50% Other Fibers, Non-Fibrillated 50% PET 50% Rhodia Kuraray EP023 PA 6-6 1.7 dtex 5mm 4 mm Weight g / m2 98.6 87, 2 92.6 Main cm3 / g 2.90 3.58 3.69 Tear strength mN 540 1620 1600 index (tearing) mNm2 g 5.5 18.6 17.3 The proportions are by mass. The folding resistance is improved by treatment with a binder such as polyvinyl alcohol (PVOH). The results grouped in the table below show that it is possible to obtain a very satisfactory folding resistance greater than 27,000 double folds in the case of a composition comprising fibrillated fibers and / or polyamide 6 fibers. 6, surface treated with polyvinyl alcohol.

PVOH-free With PVOH Fibrillated polyacrylic fibers CFF 11-2 50% Other fibers 50% Non-fibrillated fibers Rhodia PA6-6 1.7 dtex 4mm Weight g / m2 92.6 I 104.2 Main cm3 / g 3.69, 1 2 , 43 Folding Double Schopper I fold 13 1 27532 ii Tear strength mN 1600 3780 Index (tear) mNm2 / g 17.3: 36.3 The proportions are by mass. Depending on the intended application, it may be important to obtain a dense and low porous substrate, allowing in particular the realization of a quality watermark.

Comparative tests were conducted to compare the substrate density impact of different ratios of non-fibrillated synthetic fibers of polyamide 6.6 to fibrillated fibers. The table below shows that the most satisfactory ratio is around 50%.

With PVOH Fibrillated polyacrylic fibers CFF 11-2 50% 30% 10% Fibrous fibers Rhddia PA6-6 1.7 50% 70% 90% dtex 4mm Weight g / m2 107 104 100 Hand cm3 / g 1.99 2.28 2.74 Folding Schopper double 44515> 150000 38045 fold Tear strength mN 3880 6480 5760 Index (tear) mNm2 / g 36.4 62.4 57.5 The proportions are mass. In order to improve the tear resistance of the substrate, other formulations, including flocculated latex particles were tested. The results, shown in the table below, show that the use of latex slightly improves the dense character of the substrate while improving the folding resistance. There is also a significant improvement in porosity, which is particularly important for the durability of the substrate, especially for its resistance to soiling. With PVOH Fibrillated polyacrylic fibers CFF 11-2 50% 45% 40% Fibrous fibers Rhodia PA6-6 1.7 Cltex 50% 45% 40% 4mm Latex Dow 94755.04 0% 10% 20% Weight g / m2 104 , 2 106 102 Main cm3 / g 2.43 1.94 1.93 Folding Schopper double 27532> 54263> 100000 fold Tear strength mN 3780 4800 3600 Index (tear) mNm2 / g 36.3 45.1 35.5 The proportions are mass. The expression "having one" shall be understood as being synonymous with "having at least one", and "included" shall mean included terms, unless the contrary is specified.

Claims (23)

REVENDICATIONS1. Paper, comprising: fibrillated synthetic fibers; and non-fibrillated synthetic fibers. 2. Paper according to claim 1, comprising a security element. 3. Paper according to one of the preceding claims, comprising a watermark. 4. The paper according to any one of the preceding claims, wherein the non-fibrillated synthetic fibers are selected from polyamide fibers, poly (ethylene terephthalate) fibers and polyolefin fibers, preferably polyethylene fibers. A paper according to any one of the preceding claims, comprising more than 5% by dry weight, preferably more than 10% by dry weight, and more preferably more than 20% by dry weight, of fibrillated synthetic fibers by weight. 15 total paper. A paper as claimed in any one of the preceding claims, wherein the fibrillated synthetic fibers are fibrillated polyacrylic fibers. A paper according to any one of the preceding claims, wherein the fibrillated synthetic fibers have a number average length of between 2 mm and 8 mm, and preferably between 4 mm and 6.5 mm. A paper according to any one of the preceding claims, wherein the material of the fibrillated synthetic fibers has a tensile strength of between 300 and 600 MPa. A paper according to any one of the preceding claims, wherein the fibrillated synthetic fibers have a specific surface area of between 35 and 75 m 2 / g. A paper according to any one of the preceding claims, comprising less than 95% by dry weight, preferably less than 90% by dry weight, and more preferably less than 80% by dry weight, of non-fibrillated synthetic fibers relative to the total weight of the paper. 30 11. Paper according to any one of the preceding claims, comprising a surfacer, in particular being impregnated with a surfacing agent, the surfacing agent comprising or preferably consisting of polyvinyl alcohol. 12. Paper according to any one of the preceding claims, comprising a latex, in particular flocculated. 13. Paper according to the preceding claim, comprising at least 3% by dry weight of latex, in particular flocculated, relative to the total weight of the paper. A paper according to any one of the preceding claims, comprising less than 5% by dry weight of non-synthetic fibers, such as cellulosic fibers, based on the total weight of the paper, preferably less than 2% by dry weight per relative to the total weight of the paper, even better being free of non-synthetic fibers, such as cellulosic fibers. 15. Paper according to any one of the preceding claims, the fibers of the paper being exclusively constituted by fibrillated synthetic fibers and non-fibrillated synthetic fibers. 16. Paper according to any one of the preceding claims, having a hand less than or equal to 2.5 cm3 / g, more preferably less than or equal to 2 cm3 / g. 17. Paper according to any one of the preceding claims, having a basis weight of between 70 g / m 2 and 150 g / m 2 and preferably between 90 g / m 2 and 110 g / m 2. 18. Paper according to any one of the preceding claims, wherein the Bendsten porosity of the paper is between 0 mL / min and 10000 mL / min, and preferably between 1 mL / min and 7000 mL / min. 19. Paper according to any one of the preceding claims, having a double-ply folding resistance Schopper greater than or equal to 5000, preferably greater than or equal to 10000, more preferably greater than or equal to 25000. 20. Paper according to any one of the preceding claims, having a tear resistance measured according to ISO 1974 greater than or equal to 2000 mN, and preferably greater than or equal to 3000 mN. 25 21. Paper according to any one of the preceding claims, comprising a security thread, in particular at least partially introduced into the paper. 22. Secure document comprising a paper as defined in any one of claims 1 to 21. 23. Secure document according to the preceding claim, constituting a means of payment such as a bank note, a check or a restaurant ticket, an identity document such as an identity card, a visa, a passport, or a driving license, a lottery ticket, a ticket, a ticket to cultural or sports events, a playing card or a collectible card.