RU2671745C2 - Paper comprising fibrillated synthetic fibres - Google Patents

Abstract

FIELD: textile and paper.

SUBSTANCE: invention relates to documents made of fibrous material, in particular, security documents. Paper comprises fibrillated synthetic fibres, non-fibrillated synthetic fibres and a security element.

EFFECT: improved mechanical properties of the security paper, such as tear resistance and breaking strength.

19 cl, 5 tbl

Description

The present invention relates to documents of fibrous material, in particular to security documents.

The invention in particular, but not exclusively, relates to paper suitable for the manufacture of security documents, and to a manufacturing method thereof.

The term “security document” means a security document or a valuable document, such as a means of payment, for example, a banknote, check, bank card or food voucher, an identity document, for example, an identity card, visa, passport, in particular the passport page with personal information, an “insert” or driver’s license, a lottery ticket, a travel ticket or a document, or an entrance ticket to cultural or sports events.

It is known that in order to prevent attempts to falsify or counterfeit a security document, security elements are added to the document substrate, for example, in the form of fibers, confetti, film, knitted structure or security threads. The backing of the document itself may consist of material that is difficult to fake, in which case it is called a “protected backing”.

Since the life span of security documents is usually critical, security substrates with "very high strength" have been developed.

In the field of protected sheet substrates, cellulose substrates, substrates called “composite substrates”, plastic substrates and substrates called “hybrid substrates” are known.

Cellulosic substrates are fibrous substrates, which are usually obtained by a paper manufacturing method, also called a wet method, from cellulosic fibers such as deciduous wood, coniferous fibers, annual fibers, especially cotton fibers or mixtures thereof.

The terms “paper making method” or “wet method” mean a general paper production process, in particular including the following successive steps:

- drainage of a suspension of fibers, which can be pre-refined and in some cases contain fillers and additives commonly used in the manufacture of paper and / or specific security elements,

- getting pressed wet sheet, and then

- drying.

Substrates called “composite substrates” are cellulosic substrates whose fibrous composition includes, in addition to cellulose fibers, synthetic fibers. Such fibers are typically introduced in an amount of less than 20% of the 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 cellulosic fibers plays an important role in weaving and fixing synthetic fibers, which makes it possible to identify the characteristic potential of synthetic fibers. In fact, in developments relating to the mechanical strength of sheet material, the strength of the polymer of synthetic fibers is important, but the ability of the fibers to interact with each other is also a determining factor. The presence of refined cellulose fibers greatly contributes to the crosslinking of cellulose fibers with a polymer of synthetic fibers.

Compound substrates are more resistant to circulation than cellulose substrates. The expression "resistance to circulation" means a combination of the following properties: fracture strength, tear resistance and resistance to pollution.

Substrates called "hybrid" contain at least one cellulosic or composite substrate in combination with at least one layer of plastic. As for the cellulosic or composite substrates forming them, they generally have equivalent tear resistance and increased fracture strength.

Hybrid substrates used in the field of protected substrates are described in particular in patent applications WO 2006/066431, WO 2004/028825, EP 1854641, WO 03/054297 and WO 94/29105.

Plastic substrates are usually obtained by extrusion of a polymer. These substrates typically have "very high strength."

Such plastic substrates are described, in particular, in applications EP 2225102, WO 99/67093, WO 97/01438 and WO 83/00659. These substrates have good fracture strength and good resistance to contamination, but their initiated tear resistance is relatively low.

Converting such plastic substrates into protected ones is also difficult, since these substrates are incompatible with the basic safety measures used for paper (cellulose, composite or hybrid) substrates, such as watermarking and embedding, at least partially, into the thickness of the substrate, protective threads such as described, for example, in applications EP 0059056, GB 2388377 and GB 2381539.

There are also substrates called “non-woven substrates”. A nonwoven substrate is defined in ISO 9092 and EN 29092 as a fabricated sheet consisting of a fabric or felt of directionally or randomly oriented fibers bonded by friction and / or adhesion and / or adhesion, not including paper and woven, knitted, pubescent or knitting and piercing products, including binder threads or fibers, or felted by wet milling, with or without additional firmware.

The Association of the Nonwoven Fabrics Industry, or INDA, defines them as “a sheet or web of natural and / or artificial fibers or yarns, with the exception of paper that has not been woven and that may be bonded to each other any of several ways. "

" [Нетканые материалы] (

Coste, 25 июня 2004) и "Материаловедение & Инжениринг 554 - Материаловедение и технология нетканых материалов II" (Larry С. Wadsworth, весна 2004), доступных в интернете по следующим адресам, соответственно:These substrates and the production thereof are described in more detail in the documents "Les

"[Nonwovens] (

Coste, June 25, 2004) and "Materials Science & Engineering 554 - Materials Science and Nonwovens Technology II" (Larry S. Wadsworth, Spring 2004), available on the Internet at the following addresses, respectively:

- http://cerig.efpg.inpg.fr/tutoriel/non-tisse/sommaire.htm, and

- http://web.utk.edu/~mse/Textiles/index.html.

In patent applications WO 2002/38368 and FR 2447995 it is described that nonwoven materials can be used as protected substrates. These substrates mainly consist of long, non-cellulosic fibers, for example, having a length of 3 to 25 mm and a high specific volume and high porosity, which determine their low resistance to pollution.

Non-woven materials are produced in accordance with various technologies, in particular a dry laying method, for example by combing, or an aerodynamic method (also called an air laying method), a melting laying method, especially by extrusion (also called a spinning method) or extrusion blow molding molding (also called melt blowing), a wet styling method similar to the paper manufacturing process, or other methods, especially by dissolving in a solvent ( also called "flash-spinning").

Non-woven materials obtained by wet laying typically contain cellulose fibers, for example, in an amount of at least 10%, in particular in order to give the resulting substrates better adhesion.

Moreover, when the content of cellulose fibers in the nonwovens obtained by wet laying is small, or even zero, the hydrogen bonds formed between these fibers make it impossible to provide sufficient adhesion to the substrates and, therefore, it is necessary to use at least one binding step. Such bonding can be carried out by impregnation, spraying or coating of latex, by thermal bonding, by stamping with a needle, or by hydro-weaving.

An example of a non-woven substrate containing a small amount or not containing cellulose fibers is described in patent application EP 2438599.

The mechanical properties of the paper can be further improved by introducing reinforcing fibers into the paper. These reinforcing fibers are typically introduced in an amount of more than 3% of the dry weight relative to the total weight of the paper fibers, and they are usually based on synthetic polymers such as polyamide 6.6 (PA 6.6) or polyethylene terephthalate (PET), to achieve the mechanical strength that these polymers bring, as well as for economic reasons, production reasons and considerations related to good interaction with cellulose fibers of paper.

The term "synthetic fibers" is understood to mean fibers obtained using one or more synthetic polymers, which are polymers obtained in the course of chemical synthesis, in particular by means of a polymerization reaction of a monomer, if necessary in combination with a vulcanization reaction.

The table below contains orders of magnitude of tear resistance and fracture strength of the substrates discussed above.

The tearing resistance is determined according to ISO 1974 "Paper - Determination of tearing resistance - Elmendorf method", and the fracture strength is determined according to ISO 5626 "Paper - Determination of fracture strength".

There is a need for the development of new substrates that have improved mechanical strength characteristics, especially increased tear resistance and fracture strength, in particular, greater tear resistance than security paper substrates according to the prior art, and fracture strength, at least equivalent to that in plastic substrates.

There is also a need for a backing that is compatible with the basic security measures used for paper, especially watermarking and the incorporation of at least partially protective threads into the backing.

The aim of the present invention is to satisfy all or some of the above needs, and it is achieved through paper, including:

- fibrillated synthetic fibers; as well as

- non-fibrillated synthetic fibers.

The substrate in accordance with the invention is a paper, which means that it is obtained by making paper, in particular in accordance with the inclined Furdrinier process, the horizontal Furdrinier process and / or the cylindrical process. A cylindrical process is preferred, for example, in order to obtain a better watermark or to embed a security thread at least partially in the thickness of the substrate.

The methods commonly used for the manufacture of security paper, thus, in accordance with the present invention can be used to manufacture a security substrate. In addition, the substrate in accordance with the present invention has improved properties compared to cellulose paper, in particular excellent tear resistance.

Fibrillated synthetic fibers

Fibrillated fibers are fibers that have fibrils, i.e. branches diverging from the body of the fiber. Fibrillated fibers can be, in particular, fibers having at least one wall that is partially damaged, resulting in partial release of the fibrils.

Fibrils branch off from such fibers, the cross section of which is much smaller than that of the whole fiber, which increases the interaction of these fibers with other fibers, especially synthetic fibers, and also limits the ability of the fibers to slide relative to each other. Such fibers are described, for example, in documents FOR 1317778 and FR 2199015.

Fibrillated fibers thus play an important role in the cohesion of the paper in accordance with the present invention, in particular due to adhesion effects.

The paper in accordance with the invention may contain fibrillated synthetic polyamide fibers (PA), polyethylene fibers (PE), polypropylene fibers (PP), polyethylene terephthalate fibers (PET), polyvinyl alcohol (PVA) fibers, aromatic polyester fibers (e.g. Vectran®, sold by Kuraray), polyamide-imide fibers, polyolefin fibers, and preferably polyacrylic fibers, for example, such as those sold by Sterling at CFF 111-2. Preferably, the synthetic fibrillated fiber material has a tear resistance of 300 to 600 MPa.

According to the invention, the presence of fibrillated synthetic fibers compensates for the absence or smaller amount of cellulose fibers and also makes it possible to obtain the desired mechanical characteristics, such as tear resistance and breaking strength.

According to one preferred embodiment of the present invention, the paper comprises fibrillated polyethylene fibers, in particular high density fibrillated polyethylene fibers.

Indeed, in addition to the ease of use, these fibers provide the opportunity to get a good finish watermark. The proportion of fibrillated polyethylene fibers should preferably be more than 50% of the dry weight relative to the total dry weight of the fibers. The average length of the fibrillated polyethylene fibers is preferably from 0.5 to 2 mm.

The fibrillated synthetic fibers preferably have an average length of from 0.5 mm to 8 mm, more preferably from 2 mm to 8 mm, even more preferably from 4 to 6.5 mm.

The specific surface area of the synthetic fibrillated fibers according to the present invention is preferably from 35 to 75 m ² / g, more preferably from about 50 m ² / g. It is measured in accordance with ISO 9277, "Determination of surface area per unit mass (specific surface area) of solids by gas adsorption — by the BET method (Brunauer, Emmett and Teller Method)."

Preferably, the paper according to the invention contains more than 5% of the dry weight, more preferably more than 10% of the dry weight, and even more preferably more than 20% of the dry weight of fibrillated synthetic fibers with respect to the total weight of the paper. Alternatively, paper in accordance with the invention may contain more than 50% of the dry weight of fibrillated synthetic fibers with respect to the total weight of the paper.

The fibrillated synthetic fibers can be white or dyed, in particular, have a color that can be the same or different from the color of other synthetic fibers.

The degree of fibrillation of the fibers can range from 5 to 700 ml and, preferably, from 5 to 100 ml in accordance with CSF (canadian standart freeness - canadian standard of bulkiness).

The fibers may contain at least one marker, and this marker allows you to identify the fibers using certain means, in particular under the influence of UV (ultraviolet) and / or IR (infrared) radiation and / or under the influence of a chemical developer. Thus, this marker may be a marker that is luminescent, in particular fluorescent under the influence of UV or IR radiation.

Not all fibrillated fibers may have the same composition.

Unfibrillated Synthetic Fibers

Preferably, the non-fibrillated synthetic fibers are selected from polyamide (PA) fibers, polyacrylic fibers, polypropylene (PP) fibers, polyethylene terephthalate fibers (PET), polyvinyl alcohol (PVA) fibers, aromatic polyester fibers (e.g., Vectran® sold by Kuraray), polyamide -imide fibers, fibers from a copolymer of ethylene / vinyl alcohol (ethylene / vinyl alcohol copolymer, EVOH), polyolefin fibers and, preferably, polyethylene fibers (PE).

Preferred non-fibrillated synthetic fibers are polyamide fibers.

In particular, non-fibrillated synthetic fibers may be 4 mm 1.7 dtex polyamide 6.6 fibers sold by Rhodia or polyethylene terephthalate fibers sold by Kuraray under the name EP023 (5 mm).

The paper in accordance with the present invention preferably contains less than 95% of the dry weight, more preferably less than 90% of the dry weight, and even more preferably less than 80% of the dry weight of unfibrillated synthetic fibers with respect to the total weight of the paper.

Preferably, the non-fibrillated synthetic fibers have a number average length of 3 to 6 mm and a nominal linear density of 0.3 to 1.7 dtex.

Preferably, the non-fibrillated synthetic fibers have a nominal linear density of less than 2 dtex, preferably less than 1 dtex, even more preferably less than 0.5 dtex. Non-fibrillated synthetic fibers may, for example, be fibers sold by Woongjin under the name Mini-Eslon and 0.3 dtex PET fibers, or, for example, fibers sold by Kuraray under the name EP023 and 0.33 dtex PET fibers.

Non-fibrillated synthetic fibers can have the same color as fibrillated synthetic fibers, or a different color.

Other fibers

The paper in accordance with the present invention may contain less than 5% of the dry weight of non-synthetic fibers, such as cellulose fibers, in relation to the total weight of the paper, and preferably less than 2% of the dry weight of non-synthetic fibers in relation to the total weight of the paper, even more preferably - completely free of non-synthetic fibers, such as cellulose fibers.

In particular, in one preferred embodiment, the paper fibers of the invention are comprised solely of fibrillated synthetic fibers and unfibrillated synthetic fibers.

Treatment

It is possible to enhance the cohesion of the paper in accordance with the invention by introducing a polymeric binder, such as polyvinyl alcohol, which has a synergy with synthetic fibers, which in an unexpected way allows to increase fracture strength. The use of a polymeric binder can be carried out by impregnation, surface coating or coating; preferably, the polymer binder is introduced at least partially in the thickness. In particular, the paper may contain a decorative substance, in particular, may be impregnated with a decorative substance that contains or preferably consists of polyvinyl alcohol.

The composition may include an anionic polymer dispersion system, in particular flocculated. In a preferred embodiment, at least 10% of the anionic polymer dispersion system, in particular flocculated, based on dry weight, is included. Such an anionic polymer dispersion system can improve fracture strength of paper.

The paper may contain latex, for example, in an amount of at least 3% of the dry weight, in particular a flocculated matrix, in relation to the total weight of the paper.

The latex used may, for example, be latex sold by Dow Chemicals under the name 94755.04, or another latex, as described in international patent application WO 2008/152299.

The paper composition of the present invention may also contain a primary cationic flocculating agent in an amount of from 1% to 5% of dry weight relative to the total weight of the paper, and, in some cases, a secondary cationic flocculating agent in an amount of from 0.1% up to 0.5% of the dry weight selected from cationic resin, polyacrylamides, polyethyleneimines, polyvinyl amines and mixtures thereof; preferably it should be a cationic resin, more preferably a polyamidamine-epichlorohydrin resin.

Other binders can be used, in particular a transparent or translucent elastomeric binder, such as polyurethane and colloidal silicon dioxide, or a binder of an acrylic polymer or a styrene-acrylic copolymer.

In order to enhance the strength of the paper, polyurethane flakes (aggregates) having a high elongation at break, for example, more than 600%, can be included in the paper by means of an anionic dispersion system, in particular in a proportion of 5% to 45% of the dry weight in relation to the total weight of the paper.

Other paper constituents

The paper in accordance with the present invention may contain any auxiliary substances and compounds that are commonly used in the manufacture of paper during papermaking, such as fillers, retention aids, sizing agents and / or substances that increase moisture resistance, in particular epichlorohydrin resins.

The paper in accordance with the present invention can, in particular, include fillers, in particular plastics, such as, for example, particles of polyvinyl chloride (PVC) sold by Kem One under the name Lacovyl Pb 1302. Such fillers make it possible, in particular, to seal the paper in accordance with the present invention.

Paper production

Paper in accordance with the present invention can be made in accordance with standard technologies for the production of pulp paper, with the exception of the stages specifically associated with the presence of cellulose fibers, if they are absent. In particular, the grinding step, which is particularly energy intensive, can be eliminated, which is an advantage.

The manufacturing process can be adapted to the presence of security features such as a watermark or security thread.

The paper preferably has a specific volume less than or equal to 2.5 cm ³ / g, preferably less than or equal to 2 cm ³ / g, and even more preferably less than or equal to 1.5 cm ³ / g.

The paper may have a thickness of 100 to 300 microns, preferably in the range of 100 to 150 microns. It is measured in accordance with ISO 534, Paper and board - Determination of thickness, density and specific volume.

The paper grammar can range from 70 g / m ² to 150 g / m ² , preferably from 90 g / m ² to 110 g / m ² . It is measured in accordance with ISO 536, Paper and Cardboard - Grammar Definition.

Watermark

Paper in accordance with the present invention may contain a watermark. This watermark can be formed on a round-mesh machine or a Fourdrinier machine.

The watermark can be of any known type, for example, light and / or dark, possibly multi-tone or having a multi-tone effect, for example, as described in patents EP 1122360, EP 2350384 and EP 2550395.

Security thread

The paper in accordance with the present invention may include a security thread embedded in the thickness of the paper or between two layers of paper in accordance with the present invention, bound in the wet phase. The security thread may be at least partially inserted into the paper.

The paper may comprise a fibrous tape, in particular a cellulosic fibrous tape, as described in WO 2008/043965, a plastic tape or also a knitted tape, in particular as described in WO 2006/016088.

The thread may be metallized and / or holographic and / or have the effect of interference and / or be equipped with optical structures, in particular lenses or mirrors.

Multilayer paper

The paper in accordance with the present invention may be single-layer or multi-layer.

In the case of a multilayer structure, the layers may or may not have the same fiber composition. In particular, paper may include, on the one hand, a layer of synthetic fibers in accordance with the present invention, and, on the other hand, a layer of cellulose fibers collected in the wet phase, a layer in accordance with the present invention, subsequently forming a reinforcing layer.

Layers may or may not be the same color.

The properties

Bendtsen's paper porosity can range from 0 ml / min to 10,000 ml / min, preferably from 1 ml / min to 7,000 ml / min. It is measured in accordance with ISO 5636-3, Paper and Cardboard - Determination of Air Permeability (Mid Range) - Part 3: Bendtsen Method.

Preferably, the Shopper double-kink strength is 5,000 or more, more preferably 10,000 or more, preferably 20,000 or more, even more preferably 25,000 or more, even more preferably more than 50,000. It is measured in accordance with ISO 5626 "Paper - Determination of fracture strength. "

Preferably, the paper tearing resistance (measured in accordance with ISO 1974) is more than 1000 mN, more preferably more than 2000 mN, even more preferably more than 3000 mN. It is measured in accordance with ISO 1974, Paper - Determination of Tear Resistance - Elmendorf Method.

The invention allows to obtain synthetic paper, the mechanical properties of which, in particular, the fracture strength and tear resistance, are better than ordinary paper, and at the same time makes it possible to apply watermarks of satisfactory quality and resolution.

The use of non-wettable synthetic fibers, which are less sensitive to water than cellulose fibers, makes it possible to obtain a material with increased strength, which, in particular, is naturally more resistant to mold damage.

Security Features and Protected Document

The paper in accordance with the present invention preferably comprises a security element, in particular a watermark or security thread, for example, a window-fed thread, as mentioned above.

Another object of the present invention is a security document containing paper in accordance with the present invention.

In one preferred embodiment of the present invention, the security document is a banknote. A security document may also be another type of payment instrument, such as a check or food voucher, an identity document, such as an identity card, visa, passport, in particular a passport page with personal information, a security label, a secure heat shrink sleeve, an insert “prelam” or “inlay” for a passport or card, in particular a smart card, or a driver’s license, lottery ticket, travel ticket or document, entrance ticket to cultural or sports events, a playing card or card lecture card. The insert is a layer that supports a contactless, preferably radio frequency, communication device.

Paper in accordance with the present invention and / or a security document made using paper in accordance with the present invention may contain one or more additional security elements, as defined below.

Among the additional protective elements, some can be detected with the naked eye, in daylight or under artificial lighting, without using a specific device. These security features include, for example, colored fibers or confetti. These security features are called first level security features.

Other types of additional security elements can only be detected with a relatively simple device, such as a lamp that emits in the ultraviolet (UV) or infrared (IR) range. These security elements include, for example, fibers, confetti or particles. These protective elements may or may not be visible to the naked eye, for example, by luminescent when illuminated by a Wood lamp that emits 365 nm wavelengths. These security features are called second level security features.

Other types of additional security features require a more sophisticated detection device to detect them. These protection elements, for example, are capable of generating a specific signal when they are exposed, simultaneously or non-simultaneously, to the action of one or more external excitation sources. Automatic signal detection allows you to verify the authenticity of a document, where appropriate. These security elements include, for example, markers in the form of active substances, particles or fibers capable of generating a specific signal when these markers are subjected to optoelectronic, electrical, magnetic or electromagnetic excitation. These security features are called third level security features.

Additional security element (s) present in the paper in accordance with the present invention or in a security document in accordance with the present invention may have security features of the first, second or third level.

In the case where the composition of the synthetic fiber composition contains fibers of a hot-melt or thermoplastic material, in particular polyethylene, the additional security element (s) can be attached to the document by simple heating, thereby avoiding the use of thermally activated glue.

Comparative tests

Various comparative tests have been carried out in order to demonstrate the beneficial properties of the paper in accordance with the present invention.

The properties of the substrate, the fibrous composition of which is 100% fibrillated fibers, were compared with those of the substrate containing 50% fibrillated fibers and 50% polyethylene terephthalate fibers (PET), as well as those containing 50% fibrillated fibers and 50% polyamide fibers (PA 6.6).

The results in the table below demonstrate the fact that a substrate consisting of 100% fibrillated fibers has a lower tear resistance than a substrate in which fibrillated fibers are used in combination with non-fibrillated synthetic fibers, such as PET fibers or polyamide fibers 6, 6. In this way, satisfactory properties are achieved, in particular good tear resistance.

Weight proportions indicated

The fracture strength is increased by treatment with a binder, such as polyvinyl alcohol (PVA). The results shown in the table below demonstrate that it is possible to achieve a very satisfactory fracture strength of more than 27,000 double bends in the case of a composition containing fibrillated fibers and / or polyamide fibers 6,6, the surface of which is treated with polyvinyl alcohol.

Weight proportions indicated

Depending on the intended application, it may be important to obtain a dense, not very porous substrate, which, in particular, makes it possible to obtain a high-quality watermark.

Comparative tests were conducted to compare the effect exerted on the density of the substrate, various ratios of unfibrillated synthetic fibers of polyamide 6.6 and fibrillated fibers. In the table below, it is shown that the most satisfactory ratio is about 50%.

Weight proportions indicated

Other formulations, including flocculated latex particles, were tested to improve tear resistance. The results shown in the table below demonstrate that the use of latex slightly improves the density properties of the substrate, improving fracture strength. A significant improvement in porosity is also observed, which is particularly important for the strength of the substrate, especially for its resistance to contamination.

Weight proportions indicated

The expression “comprising” should be understood as a synonym for “comprising at least one,” and the expression “between” should be considered to include limiting values unless otherwise indicated.

Claims (21)

1. Paper containing: fibrillated synthetic fibers, unfibrillated synthetic fibers and security element. 2. The paper according to claim 1, containing a watermark. 3. The paper of claim 1, wherein the non-fibrillated synthetic fibers are selected from polyamide fibers, polyethylene terephthalate fibers, polyvinyl alcohol fibers, fibers from an ethylene / vinyl alcohol copolymer and polyolefin fibers, preferably polyethylene fibers. 4. The paper according to claim 1, containing more than 5% by dry weight, preferably more than 10% by dry weight, even more preferably more than 20% by dry weight of fibrillated synthetic fibers with respect to the total weight of the paper. 5. The paper of claim 1, wherein the fibrillated synthetic fibers are fibrillated polyethylene fibers. 6. The paper of claim 1, wherein the fibrillated synthetic fibers have a number average length of from 0.5 to 8 mm, preferably from 2 to 8 mm, more preferably from 4 to 6.5 mm. 7. The paper according to claim 1, containing less than 95% of the dry weight, preferably less than 90% of the dry weight, even more preferably less than 80% of the dry weight of unfibrillated synthetic fibers with respect to the total weight of the paper. 8. The paper according to claim 1, containing a decorative substance, in particular impregnated with a decorative substance, where the decorative substance contains or preferably consists of polyvinyl alcohol. 9. The paper according to claim 1, containing latex, in particular flocculated latex. 10. The paper according to claim 9, containing latex in an amount of at least 3% of the dry weight, in particular flocculated latex, in relation to the total weight of the paper. 11. The paper according to claim 1, containing less than 5% of the dry weight of non-synthetic fibers, such as cellulose fibers, in relation to the total weight of the paper, preferably less than 2% of the dry weight in relation to the total weight of the paper, even more preferably not containing non-synthetic fibers such as cellulosic fibers. 12. The paper of claim 1, wherein the paper fibers consist solely of fibrillated synthetic fibers and unfibrillated synthetic fibers. 13. The paper according to claim 1, having a specific volume less than or equal to 2.5 cm ³ / g, more preferably less than or equal to 2 cm ³ / g. 14. The paper according to claim 1, having a grammage between 70 and 150 g / m ² , preferably between 90 and 110 g / m ² . 15. The paper according to claim 1, in which the fracture strength at double bending according to Shopper is 5000 or more, preferably 10000 or more, even more preferably 25000 or more. 16. The paper according to claim 1, having a tear resistance, measured in accordance with ISO 1974, comprising more than 1000 mN, more preferably more than 2000 mN, even more preferably more than 3000 mN. 17. The paper according to claim 1, containing a security thread, in particular, at least partially inserted into the paper. 18. A security document containing paper according to claim 1. 19. A security document according to claim 18, which is a means of payment, such as a banknote, check or food voucher, identification document, such as an identity card, visa, passport, security label, security shrink sleeve, passport or card insert , in particular smart cards, or a driver’s license, a lottery ticket, a travel ticket or a document, an entrance ticket to cultural or sports events, a playing card or a collection card.