WO2012127418A1

WO2012127418A1 - Information medium or paper comprising a self-repairing material

Info

Publication number: WO2012127418A1
Application number: PCT/IB2012/051333
Authority: WO
Inventors: Pierre Sarrazin
Original assignee: Arjowiggins Security
Priority date: 2011-03-21
Filing date: 2012-03-20
Publication date: 2012-09-27
Also published as: ES2574828T3; EP2689068B2; EP2689068A1; EP2689068B1; FR2973049B1; FR2973049A1; ES2574828T5

Abstract

The invention relates to an information medium, especially a security or valuable document, or paper for producing such an information medium, comprising a substrate and at least one self-repairing material.

Description

Information carrier or paper with a self-healing material

The present invention relates to information carriers, in particular intended to be handled frequently, and more particularly but not exclusively supports comprising a substrate, in particular fibrous, and for example intended for the manufacture of security or valuable documents such as banknotes bank and the processes for making such papers and documents.

Bank notes are exposed during their lifetime to many manipulations and therefore to physical and chemical degradations and to the risk of soiling. In order to give them better resistance to these degradations and a high durability, the fibrous substrate is protected by one or more layers of a protective coating that also has a barrier effect against soiling. By "soiling" is meant in particular aqueous or oleaginous liquids, or even sub-millimeter particles, and mixtures thereof.

Physical degradations, especially due to wrinkling, folding or pulling, of a substrate such as paper used for the manufacture of banknotes, cause a structural change of the substrate. An information carrier subject to these degradations undergoes a weakening of the surface of the information medium, for example a coating covering the substrate. In particular, a fibrous substrate subjected to these degradations repeatedly undergoes a process of destructuring which is characterized in particular by untying the fibers of the substrate. There is then a significant increase in the thickness of the paper but also its porosity, which facilitates the penetration and grip of dirt.

Treatments based on film-forming polymers, for example polyvinyl alcohol (PVA) and / or polyurethane (PU), as described in publications EP 1 319 104 or EP 0 514 455, make it possible, among other things, to reduce the effects these degradations on the porosity of the fibrous substrate and thus increase the durability of the paper.

The choice of the protective coating is complex because it must provide both a barrier function and not unduly affect the printability of the paper during the manufacture of the notes.

Many protective coatings have already been disclosed in the prior art. Patent EP 514 455 B1 thus discloses improving the circulation resistance of bank notes by impregnating the fibrous substrate, before printing, with a composition which contains one or more binders chosen for their mechanical characteristics.

According to this patent, at least one of the faces of the fibrous substrate is treated with a composition comprising one or more fillers chosen from mineral fillers and / or plastic coating pigments, and at least one elastomeric binder in an amount greater than 25. parts per 100 parts by weight of dry weight. The elastomeric binder can be chosen from the group formed by aqueous dispersions of polyurethane, acrylate copolymer, optionally carboxylated styrene-butadiene copolymer, polymers of which one of the monomers is acrylonitrile or isoprene or neoprene, or their mixtures. Preferably, a polyurethane is used. The filler is preferably mineral, selected from silicas or kaolin.

WO 96/28610 discloses applying a liquid polyurethane composition to a fibrous substrate to form a protective coating.

US 2006/0127649 indicates that the application of a liquid composition makes it possible to obtain a better resistance to soiling but does not improve the mechanical stability of the substrate.

The application US 2004/0023008 A1 discloses a security paper for the manufacture of banknotes. The paper comprises a fibrous substrate which is coated on at least one of its faces with a transparent or translucent protective layer comprising colloidal silica and at least one transparent or translucent elastomeric binder.

The publication WO 2008/054580 A1 discloses a method for imparting to a fibrous substrate a resistance to moisture and soiling, comprising impregnating the substrate on two opposite sides with an aqueous composition comprising one or more thermoplastic resins.

No. 1,499,235 discloses improving the resistance to circulation of a bank note by impregnating the fibrous substrate with a latex comprising a copolymer based on carboxylated styrene and butadiene. EP 815 321 B1 discloses a paper for the production of banknotes, in which an aqueous dispersion of polyurethane is deposited on the fibrous substrate, this polyurethane dispersion being free of charges and transparent.

Even if the papers thus treated have a better durability, this one would benefit from being further improved. Indeed, during repeated mechanical stresses, the fibrous structure and the protective coating are still damaged permanently and sufficiently to generate a porosity that allows the soil to be inserted into the substrate.

There is thus a need to further improve the durability of media information or value vis-à-vis mechanical aggression, including wrinkling.

The invention meets this need with an information carrier, comprising at least one self-repairing material.

By "self-repairing material", it is necessary to understand a material, in particular a polymer, capable of itself or under the effect of an energy stimulus, for example mechanical, luminous and / or thermal, to restructure locally, in particular by structural reorganization of the material or by a chemical reaction, so as to reduce the effects of damage due to mechanical aggression.

Thanks to the invention, the durability of the information carrier is improved. The invention makes it possible in particular to improve the resistance to mechanical stresses by a restructuring of the self-repairing material as soon as the degradations due to said stresses appear.

The restructuring of the self-repairing material notably takes place on the surface of the information carrier or at least partially within the substrate in an area close to the surface of the substrate of said information carrier.

The successive stresses experienced by the support according to the prior art result in successive and permanent degradations of the substrate, in particular the fibrous substrate, and of the protective coating, which will progressively lead to obtaining a non-zero porosity then to an increase in porosity, and therefore allow the penetration of soiling in the substrate of the information carrier and the attachment of dirt on the information carrier. On the other hand, the self-repairing material of a support according to the invention is restructured as soon as successive degradations appear which are therefore not permanent. The restructuring of the self-repairing material therefore prevents the cumulative effect of successive degradations on the porosity and tends to maintain a low or even zero porosity, despite the successive constraints experienced by the information carrier. In particular, said restructuring may tend to maintain hydrophobic and oleophobic properties of the information carrier.

Advantageously, the repair enables the document to maintain zero porosity (0 mL / min according to ISO 5636-3) during its lifetime, and thus to avoid the insertion of dirt into the pores created by the successive mechanical stresses. as well as their grip on the successive degradations of the information medium, for example due to wrinkles.

In addition, the self-repairing material can provide a protection of the surface of the document and the preservation of a flat surface appearance and clean, because the surface aggressions, including scratches, tend to disappear under the effect of the restructuring of the self-repairing material.

The invention applies in particular to information carriers comprising a thermoplastic base material substrate, for example a sheet of Polyart ^® sold by the company Arjobex. The substrate may include a core layer and at least one skin layer overlying the core layer, the core layer being further away from the surface than the skin layer. The core layer may contain voids as in the case of Polyart ^® . The heart layer can be sandwiched between two layers of skin. The substrate may be as claimed in EP 0 470 760 B1 and EP 0 703 071 B1. The core layer may be polyethylene-based, stretched to generate voids. The skin layers can be coextruded with the heart layer.

The invention applies more preferentially but not exclusively to supports comprising a substrate, preferably fibrous, such as banknotes and papers intended for their manufacture.

The fibrous substrate preferably comprises cellulosic fibers.

In particular, in the case where the self-repairing material is located between the fibers of a fibrous substrate, the self-repairing material makes it possible to repair the degradations successively suffered by the substrate as soon as they appear. Thus the self-repairing material spontaneously restructures so as to compensate for internal degradation of the fibrous substrate.

In an exemplary implementation of the invention, the self-repairing material covers at least one face of the substrate and preferably its two faces. Thus, the substrate is advantageously sandwiched between two layers of self-repairing material.

In particular, the coating of self-repairing material covering the substrate forms a layer at least partly superficial, in particular completely superficial, and self-repairs as soon as the successive degradations appear. Said successive degradations may in particular be ruptures, scratches, impacts or deterioration of the coating, and they are in particular due to creasing, bending or punctual impacts, or to abrasion phenomena.

Thus, the information carrier according to the invention preferably comprises at least one coating of the self-repairing material in the form of a film covering the substrate. The substrate extends in an exemplary implementation between two films of the self-repairing material. When the self-repairing material forms a film, the thickness of the latter is preferably between 1 μιη and 15 μιη, better 5 and 8 μιη.

According to one variant, the self-repairing material, in particular the coating of self-repairing material, penetrates, at least partially, into the substrate of the information medium, in particular in an area close to the surface.

Several types of self-repairing materials exist which can be used in the context of the invention.

The self-repairing material may require an energy stimulus, especially mechanical, thermal and / or light, especially UV, to self-repair. It can also, depending on the choice made of the self-repairing material, self-repair without energy supply, at room temperature. For example, self-repair takes less than 30 minutes at room temperature (between 20 and 25 ° C).

By ambient temperature is meant in particular the average current temperature of the place of circulation and / or manufacture and / or storage of said substrate comprising the self-repairing material. This temperature is for example between 20 and 25 ° C. The subject of the invention is also a method of processing a used information carrier, in which an information carrier comprising a self-repairing material requiring an energy supply to self-repair is subjected to a stimulus. energetic so that it self-repairs.

Stimulus exposure occurs, for example, in a sorting facility designed to eliminate documents that no longer have certain required traffic characteristics. The documents pass for example between heated rollers, are conditioned under appropriate temperature and / or humidity conditions, and / or are exposed to intense light, for example UV.

If necessary, pressure is exerted on the self-repairing material to facilitate contact between remote areas and promote restorative action.

The invention further relates to a method of manufacturing an information carrier, wherein a substrate, preferably fibrous, is coated with a self-repairing material.

The method comprises for example the formation of a coating, in particular a homogeneous film or a surface layer, on both sides of the substrate from a solution based on a solvent or an aqueous dispersion of a polymer self-repairing, for example by an impregnation treatment, surfacing, sizing, coating, printing, depositing and / or coating, or complexation on both sides of the substrate with a film of a self-repairing polymer previously formed. The process can take place in line, at the output of a papermaking machine, or, alternatively, the fibrous substrate can be manufactured and stored, and subsequently unrolled and coated with self-healing material.

A combination of the above-mentioned methods can be used to apply successive coatings. In particular impregnation, for example by means of a size press, followed by a coating, can be implemented.

All of the above-mentioned coating forming methods can allow the formation of a homogeneous film or a surface layer which self-repairs as soon as the successive degradations appear, as previously described.

In particular, the impregnation, surfacing or sizing processes applied to a fibrous substrate may allow the application of the self-repairing material at least in part within the fibrous substrate so as to compensate for the internal damage sustained by the support, as previously described.

In particular, the amount of self-repairing material on or in the substrate is between 1 and 20 g / m ² , preferably between 1 and 5 g / m ² .

The method may comprise steps of applying to the substrate at least one barrier layer and / or a printability layer, before or after the deposition of the self-repairing material.

According to a variant of the invention, the self-repairing material is printable and / or has barrier properties, and in particular said self-repairing material is hydrophobic and / or oleophobic.

According to an exemplary implementation of the invention, the substrate is exposed to a composition for producing a barrier layer, it is coated with a layer of self-repairing material, then optionally deposited a printability layer on the layer of self-healing material.

Before the application of the barrier layer or the self-repairing material, the substrate may be pretreated, for example by impregnation or pre-gluing so as to reduce the porosity, for example by a composition based on PVA or any other binder.

All the layers, especially those of impregnation, pre-gluing, forming barrier and / or printability, of the information medium or the paper intended for the manufacture thereof can be applied according to the methods and by the tools conventionally used in the field of paper, including impregnating, surfacing, sizing, removal and / or coating.

The barrier layer is preferably applied by impregnation or surfacing. The printability layer is preferably applied by surfacing, coating or coating. When the layer of self-repairing material is applied in the fluid state, it is preferably applied by surfacing, coating, printing or coating.

Self-repairing material

So-called self-healing materials (Self-healing, Self-Restoring, Self-Restoring or Self-Mendable) are already known in other applications. These are mainly polymeric-based film coatings used for protection against external aggressions in the fields of automotive (body painting), electronics (protection of electrical sheath) or building (cement reinforcement).

The publication "self-healing and self-mendable polymers" Jay A. Syrett, Remzi C. Becer and David M. Haddleton, Polym. Chem. 2010, 1, 978-987, discloses examples of self-repairing materials that may be suitable for the invention.

Self-repairing materials of irreversible type

By irreversible is meant a self-repair that can not effectively take place repeatedly on a targeted area of the substrate having undergone successive attacks. This phenomenon is preferably due to the depletion, during successive aggressions, of compounds involved in the self-repair process.

The irreversible self-repairing materials involve a covalent chemical reaction and rely for example on the release, during a mechanical aggression such as a crack, of a compound which will cause a repair by reacting with another compound present locally. to restore the material.

Examples of self-repairing material comprise, in a form dispersed in a matrix, microcapsules, carbon nanotubes, hollow fibers or microcavities containing a monomer-type active product for example. Distributed in the matrix of the composite, these microcapsules open under the action of an impact creating for example a crack and release the active product. The crack or defect is then usually filled by the polymerization or crosslinking product formed from the active product, following the contacting thereof with a catalyst also dispersed in the matrix.

For example, microcapsules containing a cyclopentadiene monomer (CDP) may be dispersed in an epoxy matrix which otherwise contains the Grubbs catalyst as an initiator. This catalyst is likely to cause the metathesis of CDP, when that is released into the matrix in response to damage to the self-repairing material. The metathesis product fills the damage and thus makes it possible to reconstitute the material.

Operating according to this same scheme, a self-repairing system was recently developed using a compound derived from the coupling of a natural polysaccharide such as, for example, chitosan with an oxide ring such as oxetane, said compound being linked to a chain polyurethane. During the damage, it is caused an opening of the oxetane cycle thus creating two functional groups. In response to UV exposure of daylight, the polysaccharide chain splits to form functional patterns that interact with the functions generated by ring opening, thus bridging the damage. This system is more particularly described in application US 20100266784.

Other examples of irreversible self-repairing materials are described in publications US20100264553; EP2172518; US20100075134; EP2098912; US20090191402; WO200955772; US20080299391; US20080173382; US20090036568; US7569625; EP1973972; US7108914; EP1360217; US20100308276; CN101671474; CN101659719; CN101629024; CN101619156; EP2242774; CN101508823; EP2257422; CN101274248; CN101319055; CN100587005C; CN1927187; CN1927443; EP1907202; US20080234463.

Reversible self-repairing materials

Preferably, the self-repairing material is of the reversible type, because with a self-repairing material of the irreversible type, the ability of the material to self-repair may decrease with time, since self-repair can result from chemical reactions that result in stable covalent bonds. In this case, over time, the formation capacity of these links decreases. It may, alternatively, there is a gradual depletion of active product within the matrix. For example, in the case of the use of microcapsules, their number decreases as and when external aggression.

Although self-repairing materials of the reversible type are preferred in the context of the present invention to those of the irreversible type, irreversible self-repairing materials nevertheless remain usable in the invention.

By "reversible self-repair" is meant a self-repair which can efficiently take place repeatedly on a targeted area of the substrate having undergone successive aggressions, in particular spaced apart over time, the self-healing capacity being preferably substantially constant. for different successive attacks.

The so-called reversible systems are generally based on the establishment of either covalent bonds, for example by Diels-Aider and retro Diels-Aider reactions, or non-covalent interactions (weak bonds) such as hydrogen bonds, ionic bonds, coordination bonds (metal-ligand type) or type interaction "Π-Π stacking". The covalent bonds or non-covalent interactions can be triggered under the action of an energy source such as heat, irradiation, traction, compression or electrochemistry.

These reversible systems can therefore be distinguished according to whether or not they lead to the formation of covalent or non-covalent bonds.

A - Reversible system with covalent bonds

The self-repairing material can implement a Diels-Aider reaction.

The Diels-Aider reaction is the process in which a conjugated diene and a molecule with a double or triple bond, called a dienophile, react, in response to a stimulus, to form a six-membered ring with unsaturation, called Diels- Help. Advantageously, such a process can be reversible. For example, in response to a rise in temperature, the adduct can dissociate, thereby giving back the diene and the dienophile.

It should be noted that a Diels-Alder reaction is not limited to fully carbon-based systems. A reaction for which one or more atoms of the diene and / or of the dienophile are not carbon atoms (typically nitrogen with a N = N double bond, or oxygen with a C = O double bond, but also the double bonds C = N, S = 0, N = 0, C = S, C = P and C = Se) is also referred to as Diels-Alder and more precisely the reaction of hetero-Diels-Aid.

As specified above, this type of interaction, conditioning the repair of the damage via the formation of polymers, generally requires exposure of the self-repairing material to a source of energy, usually thermal.

This "self-repair" mode has been widely used for the preparation of self-repairing polymers via the introduction, at the ends of the polymer chain or on the monomeric units constituting it, with adequate chemical functions. ie reactive according to a Diels-Alder reaction. For example, these functions can be represented on the one hand, a furan unit, representative of a conjugated diene, and on the other hand, a maleimide unit, representative of a dienophile, and both present on distinct polymer chains. forming the self-healing material. An inter-molecular Diel-Alder reaction is likely to occur between these two types of function. Other chemical reactions can be exploited according to this same scheme. Thus, other self-repairable materials are possible via the use of the dicyclopentadiene to access Diels-Alder reversible reticulated networks. This compound has the advantage of being able to include both the conjugated diene and the dienophile.

Applications US20080207793, US20090062453 and US20100266784 disclose materials of this type.

B - Non-covalent reversible system

Systems forming covalent bonds require an energy supply, for example thermal for the Diels-Alder reactions, to break and reform covalent bonds.

In contrast to these, systems that take advantage of non-covalent bonds such as ionic bonds, metal coordination and hydrogen bonds provide access to assemblies with much lower energy.

In view of this advantage, self-repairing materials of the reversible type but based on the generation of non-covalent bonds have been developed.

By way of illustration, compounds which are suitable for the formation of such materials may in particular be cited as elastomers interacting via supramolecular bonds, crosslinking elastomers via hydrogen bond formation, and more particularly mobile chain polymers and ionic thermoplastic polymers, also known as ionic polymers. mothers.

In addition, some of these compounds, in particular based on acrylic or urethane, have intrinsic antifouling properties, for example because of their hydrophobic or oleophobic nature.

Bl - Ionomers

Ionomers are thermoplastic elastomers with ionic charges in their structure. More specifically, it is most often hydrocarbon chains carrying acid functions which are totally or partially neutralized by quaternary ammonium salts or metal. The charges thus created form ionic clusters which crosslink the hydrocarbon chains together by electrostatic interactions. During mechanical aggression, this crosslinking is damaged but can reform rapidly at room temperature due to the electrostatic attraction of the charged groups. US20100174041 describes an example of self-repairing material of this type.

Surlyn ^® , especially references 8940 and 8140, from DuPont is a commercial example.

B2 - Mobile Chain Polymer

In this case, the mechanism of self-repair is based on a molecular diffusion of the mobile polymer chains attached to the main structure of this polymer. After diffusion of the mobile chains Γ self-repair is completed by chemical or physical interactions of the polymer with the mobile chains. A polymer with mobile chains may in particular be a polymer with a low glass transition temperature Tg, especially less than or equal to 20 ° C. The glass transition temperature Tg is measured according to the ISO 11357-2 standard. The movement of the chains ("flowability") of a low Tg polymer can facilitate the restructuring of the polymer after deterioration due to mechanical aggression. When the material is damaged, the chains have a great freedom of movement and tend to find their initial place. The time required for repair decreases with temperature. It should be noted that the movement of these chains can also be facilitated by the presence of repellent groups between them, for example fluorinated or silicone, on the main structure of the polymer.

Polymers of this type belonging to the family of polyurethanes and acrylics may be suitable.

Publications JP2008239722; WO200769765; EPI 190424; US20020108774; KR20090109459 and WO9610595 disclose such materials.

B3 - Supramolecular connections

This type of compound is generally represented by elastomers forming a supramolecular network and associated by hydrogen bonds, weak and reversible. Once formed by molding or pressing, these supramolecular elastomers have low self-adhesive surfaces. On the other hand, the simple fact of putting in contact the surfaces of a fracture allows the material to repair itself and to recover its original mechanical properties.

The repair is obtained via the establishment of supramolecular bonds, for example of the hydrogen bonding type or of the "stacking" type, via or without the migration of free monomers towards the interface of the two parts of the tear. For example, polymers whose chemical structure favors supramolecular bonds, for example polymers having amine functions to create hydrogen bonds, may be used. A commercial example of this type of material is the Reverlink ™ polymer from Arkema.

The application CN 101671474 also describes an example of material of this type.

The self-repairing material may comprise a polymer whose chemical structure favors the assembly in sheets by the aromatic rings via the doubles double bonds.

As opposed to ionomers and mobile chain polymers, these compounds, although easy to use, nevertheless have the disadvantage of requiring a mechanical action, for example contacting the two faces of the tear or affixing a film. pressure to allow repair.

Fibrous substrate

An information carrier according to the invention or a paper intended for the manufacture of such a support preferably comprises a fibrous substrate. Such a substrate is flexible and would be, in the absence of self-repairing material, capable of destructuring, with generation of porosity, under the action of a wrinkling. The substrate is then called crumpled.

The fibrous substrate according to the invention may be of natural or synthetic origin.

The substrate may comprise cellulosic fibers, more preferably cotton, especially when it is intended for the production of banknotes. Other plant fibers of annual plants may enter the composition of the fibrous substrate.

The fibrous substrate comprises, in addition to the paper fibers, any additives suitable for its manufacture. In particular, a fibrous substrate of mainly cellulosic nature may be reinforced by the addition of synthetic fibers. The substrate may thus comprise a mixture of cellulosic and synthetic fibers, with preferably less than 30% by mass of synthetic fibers, for example 75% by weight of cellulose and 25% by mass of synthetic fibers.

The substrate may comprise adjuvants, for example retention agents, biocides, fillers and pigments, which are en masse or deposited by impregnation, and binders.

The substrate may undergo any surface treatment, especially a surface treatment, sizing, coating, coating, printing, deposition, extrusion, lamination (lamination) or impregnation.

The treatment can be carried out by any suitable tool, impregnator, size press, squeegee coater, air knife coater, curtain coater, extruder, laminating press, gravure printing, screen printing ...

The substrate may be exposed to various treatment solutions, and in particular to the application of an organic solution or an aqueous dispersion of the self-repairing material. An aqueous dispersion of the self-repairing material is preferred for better compatibility with paper processes.

Preferably, the fibrous substrate is pre-treated, especially by impregnation, surfacing or sizing, with a composition comprising a binder for reducing its porosity, preferably based on polyvinyl alcohol (PVA) as detailed below. This pretreatment is preferably performed prior to applying the self-healing material to the substrate.

The fibrous substrate may have one or more jets of paper assembled in the wet state.

The fibrous substrate may have, as finished and dry paper, a basis weight of between 30 and 180, preferably between 80 and 120 g / m ² and a thickness of between 30 and 180, preferably between 80 and 120 μιη, before and / or after deposition of the self-repairing material.

The document, and in particular the fibrous substrate, may comprise one or more watermarks and possibly one or more other security elements.

Security elements

Among the security elements that can be incorporated in the information carrier, and in particular in the paper intended for the manufacture of the support, certain are detectable by eye, daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level.

Other types of security elements are detectable only with a relatively simple device, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, boards, strips, wires 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 security elements require for their detection a more sophisticated detection device. 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 information carrier. 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.

Reagents may also be incorporated in the information carrier, in particular in the paper intended for the manufacture of the support. These are, for example, chemical or biochemical tampering and / or authentication and / or identification reagents that may in particular react respectively with at least one forgery agent and / or authentication and / or identification.

The security element (s) present in the information carrier, in particular paper intended for its manufacture, may have first, second or third level security features.

Additional layers

The information carrier may comprise additional layers covering the substrate, in particular fibrous.

Barrier layer If the "barrier" properties of the self-repairing material are insufficient, it is possible to apply a barrier layer (for example based on PVA, PU, etc.) between the substrate and the self-repairing material. The barrier layer is preferably, by the chemical structure of the polymer used for the production of this layer, at least hydrophobic and oleophobic and also flexible, and can facilitate the deposition of the self-repairing material.

The barrier layer may comprise any polymer adapted to impart barrier properties to the coating to protect the fibrous substrate from soiling.

The barrier layer is present, preferably, per face at 1 to 24 g / m ² dry weight, more preferably 1 to 15 g / m ² , more preferably 2 to 5 g / m ² .

Preferably, the material used for the barrier layer and the amount of barrier layer make it possible to attain hydrophobic and / or oleophobic properties such as the contact angle of a drop, respectively of water, of hexadecane, diiodomethane, ethylene glycol and glycerol, measured with a Digidrop goniometer, in particular marketed by GBX is greater than 90 °, preferably greater than 100 °.

The thickness per face of the barrier layer is, for example, from 1 to 24 μιη, more preferably from 1 to 15 μιη, and even more preferably from 2 to 7 μιη.

The barrier layer is preferably deposited on each side in the liquid state by coating or impregnation, preferably in line on the paper machine, preferably with the aid of an impregnator.

The barrier layer is initially, preferably, an aqueous phase preparation, in particular an emulsion or a dispersion.

The barrier layer is preferably based on PU. Alternatively, an acrylic or styrenic polymer can be used.

Example of a barrier layer based on PU (called PU formula for the continuation)

Quantity

Supplier Compound Family / Function

per 100g

Cromelastic SE871 Cromogenia Units Polyurethane / Binder 38 g

Cab-O-Sperse PG002 Cabot Colloidal silica fumed / 59 g

Printability load

Polyaziridine Polyaziridine / Reticulant 3 g Pretreatment

Preferably, as mentioned above, the fibrous substrate is pre-treated, for example by impregnation, surfacing or pre-sizing before coating, re-impregnation, surfacing, coating, extrusion, printing, deposition or complexing with the composition intended to form the substrate. barrier layer and / or the self-repairing material.

The pretreatment is preferably carried out with a PVA-based binder and an insolubilizer, for example of the polycarbodiimide type. The polyvinyl alcohol is preferably dissolved in water at a level of from 1% to 10% by weight, more preferably from 3% to 6%, before impregnation of the paper substrate, and the insolubilizer is preferably dissolved at a level of from 0.05 to 1% by weight before impregnation of the paper substrate. Other binders may be envisaged in addition to or in substitution for PVA, such as dispersions based on styrenic or acrylic polymers.

Preferably the pre-treatment is carried out so as to deposit a quantity of PVA of between 2 and 3.5 g / m ² .

External printability layer

If the printability of the layer of self-healing material is not sufficient, an external printability layer may be applied to the layer of the self-repairing material.

The information carrier may thus comprise an external printability layer, which advantageously comprises a filler, preferably a mineral filler, which makes it possible to improve the printability.

The external printable layer is preferably transparent or translucent.

The mineral filler advantageously comprises silica and / or kaolin and / or talc and / or calcium carbonate. Preferably, the mineral filler is non-opacifying thanks to its natural transparency and / or its dimensions of the order of one micron, especially less than 10 μιη.

In a particular embodiment of the invention, the external printability layer comprises a filler of polymeric particles, preferably an organic one, for example a powder of polyethylene, of polyamide, of polypropylene, of an acrylic or styrenic polymer. The external printability layer may be deposited in contact with the self-repairing material or not.

The deposition of the external printable layer preferably takes place on both sides of the substrate, covering the self-repairing material.

It is possible to use for depositing the external printability layer or layers any suitable coating system, especially two-sided coating (C-2-S). Preferably, an air knife coating system is used. The deposit may also be made, inter alia, by curtain coating, by pencil coating, by coating with rollers, in particular pre-coated, engraved or transfer, or by dipping, impregnation, surfacing, coating, by coating, gravure printing or spraying.

The outer layer is initially, preferably, a preparation in aqueous phase, in particular an emulsion or a dispersion, for example.

For example, polyurethane is applied, preferably in the form of an aqueous dispersion of polyurethane or pro-polyurethane particles.

The composition intended to form the outer layer may comprise a crosslinking agent chosen from isocyanates, carbodiimides or aziridines. The crosslinking agent may be in a mass content, by dry weight, of between 1 and 15%, better still 1 to 3%, relative to the total weight of the composition before coating.

Example of external printability layer: same PU formula as above.

Means of application

When the self-repairing material is applied in a fluid form, in particular an aqueous dispersion or a solvent, preference is given to dipping, sizing, impregnating, surfacing, coating, printing or coating means. apply.

To apply the barrier layer is preferably used, as mentioned above, an in-line impregnator, including in particular pre-dosing rollers, engraved rollers, transfer roll before dosing output.

To apply the external printability layer, it is preferable to use a double-sided coater with an air knife, for example of the TWIN ™ ABC type. In addition, simultaneous coating units for example of the TWIN ABC type, or roller type, for example TWIN Sizer Etching type or TWIN ™ Sizer HSM, can be envisaged to lay both sides in a single pass.

The application of each layer, or possibly all of the layers, may be followed by drying, for example by hot air or infrared, possibly seconded by driving rollers. The surface temperature reached will be at least 30 ° C and at most 180 ° C, and this in relation to the residence time of the coated paper in the heating unit.

The self-repairing material can also be applied in the form of film already formed by complexing on the substrate.

Proposed examples

Examples 1 to 3 below were prepared from a fibrous substrate composed of cellulosic and synthetic fibers, namely of polyamide for Example 1 and the comparative example and of polyester for Example 2, with proportions respective amounts of 75% and 25% by mass. The fibrous substrate contains conventional adjuvants. For all the examples, the fibrous substrate is glued at the exit of the paper forming tank by dipping in a bath of PVA and insolubilizer dissolved respectively at 3 and 0.25% by mass in water so as to deposit 2 g / m ² of PVA in dry weight.

The characteristics of the additional layers deposited on the paperboard substrate and the properties obtained are detailed below.

In the drawing, the real proportions have not been respected for the sake of clarity.

Example 1 according to the invention

A 30% aqueous dispersion of a polyurethane-type mobile chain self-repairing polymer obtained by a process such as for example described in the publication "Interdiffusion of dangling chains in" is applied to the paperboard substrate pre-treated with PVA above. weak gel and its application to self-repairing materials "by Masayuki Yamaguchi, Susumu Ono and Kenzo Okamoto (Materials Science and Engineering B, vol.162, year 2009, pages 189-194).

In this example, illustrated in FIG. 2, the substrate 11 pre-treated with the layer

12 of PVA is thus effectively protected by the layer 14 of self-repairing material. The BENDTSEN porosity test before and after wrinkling according to the wrinkle test described below gives 0 mL / min.

According to one variant, the fibrous substrate is replaced by a plastic sheet of

Polyart ^® .

Example 2 according to the invention

In this example, illustrated in Figure 3, a barrier layer 17 of the same formulation as that given in Example 1 of patent EP 514 455, is applied by surfacing on the layer 12 of pre-treatment based on PVA. The layer of Reverlink ™ self-healing material marketed by Arkema is deposited by gravure printing in an ethyl methyl ketone (MEK) solvent medium on the barrier layer 17 so as to obtain a layer of 5 g / m ² per polymer polymer face. -réparant.

The layer 14 of self-repairing material is covered by an external printability layer 16 according to the PU formula described above.

The wrinkle test gives a porosity after creasing of 0 mL / min. According to a variant the substrate is a plastic sheet Polyart ^®.

Comparative example

The pre-bonded PVA papermaking substrate above is coated with a PU-based layer in an amount of 5 g / m ² / face dry weight. The PU-based layer has the formulation of Example 2 of EP 1 319 104, with 39% by weight of polyurethane dry weight.

The structure 10 illustrated in section is shown schematically and partially in FIG. 1, in which the substrate 11 covered with the pre-gluing layer 12 is protected by the barrier layer 13 based on PU.

The wrinkle test gives 0 mL / min before wrinkling and 35 mL / min after.

Crease test

Bendtsen porosity is measured according to ISO 5636-3.

The wrinkle test is used to determine the wrinkle resistance of papers such as banknote papers and wrapping paper.

The device corresponds to that described by the NATIONAL OFFICE OF

STANDARDS (CARSON, FT SHAW, MB Wearing quality of experimental currency type papers, J. Research NBS 36, 256-257 (1946) RP 1701). The apparatus comprises:

a) a device for rolling the paper test specimen into a cylinder. This device consists of a split sleeve inside which is placed a movable fork with two teeth.

(b) a tube with one end provided with a movable lid. c) a sliding cylinder guide inside the tube.

d) a cylindrical guide for maintaining inside and in vertical position the piston whose lower base rests at the end of a lever. The cylindrical guide is designed such that the tube can slide between this guide and the piston.

e) a lever mounted on a pivot.

f) a weight at the end of the long arm of the lever, opposite to that of the short arm which supports the piston.

The creasing force is adjusted by the weight position on the lever arm, so that the pressure on the piston is 10 kg / cm ² ± 0.1 kg / cm ² .

The various cylindrical parts: guide, tube, piston must be able to slide freely and in particular slide under their weight.

Tube and piston being in place in the guide, the piston must fall or rise as one raises or lowers the weight at the end of the lever.

Sampling and packaging

Sampling and conditioning of the specimens are done in accordance with standards NFQ 03-009 and NFQ 03-010. For a particular purpose, the specimens can be measured as such. Since the specimen is constantly handled, it is necessary, in order to avoid moisture exchange with the operator, that the operator wears gloves of a moisture-barrier material during the preparation of the specimens and the run the test.

Preparation of test pieces

67 mm test pieces are cut using a template. The running direction is marked on each specimen.

Operating mode

With the fork and the two slots in the sleeve aligned, insert the test specimen in the direction of travel until halfway, then roll it by turning the fork. The tube, closed lid, is then slid in continuity with the sleeve and the rolled test piece is transferred there by a return movement of the fork.

The tube, held by the lid with one hand, is then placed in a vertical position on the piston. The wrinkling is performed by pressing on the lid until the end of the long arm of the lever is raised above its rest position. It is important that the pressure exerted is sufficient to lift the weight, but neither too strong nor too fast for the lever to come into abutment. One way to control the effort is to use both hands on each other to press the lid.

The lid is open and the test piece is crumpled in the shape of a small accordion, and out of the tube. It is put flat by carefully straightening the hand: acting too abruptly could produce notches on the side that would lead to tearing of the specimen.

The straightened specimen is presented again for rolling in front of the slot of the sleeve but rotated 90 ° with respect to the first introduction; the complete cycle is repeated.

This is done eight cycles, with rotation each time 90 °, and returning the specimen after the fourth time.

In particular, it is possible to wait a certain time between each cycle, for example thirty minutes, to allow the self-repairing material to restructure itself. This makes it possible to get closer to the real traffic conditions that the wrinkle resistance test seeks to reproduce. Indeed, during the circulation of the information media, the constraints are applied repeatedly but episodically.

Measure wrinkle resistance

The air permeability of each specimen is measured before and after creasing using a BENDTSEN porosimeter according to ISO 5636-3.

The measurement to be made under the same conditions before and after creasing, it is necessary in both cases to remove the stopper of the porosimeter head if the normal stroke is insufficient to slip the crumpled test piece.

After crumpling, the porosity is measured as follows: each specimen is straightened until it is reasonably flat. This can easily be done by holding between thumb and forefinger, the test piece by two opposite sides and then stretching it in three or four places. This operation is repeated by the other two sides; do this operation in all four times is usually sufficient to obtain a sufficiently flat specimen.

In order to form on the test specimen a circular surface whose flatness is such that surface leakage is negligible with respect to the porosity measurement, each specimen is introduced between the jaws of the clamping device of a burst and applied for two seconds sufficient pressure to mark the paper. Porosity is measured by ensuring that the BENDTSEN porosimeter head is centered on the surface being squeezed.

Loyalty

The number of test pieces to be tested depends on the sample studied. The reproducibility of the test is such that a sample per sample sheet is sufficient.

Other tests

Other methods can be used to measure the high durability of an information medium and in particular the restructuring of the self-repairing material.

In particular, a reference information carrier according to the prior art and a support according to the invention may be subjected to folding, abrasion, traction or impact operations. As before, it is possible to wait for a certain time between the various operations to which the information media are subjected.

The measurement can be carried out by measuring the porosity as described above, or by imaging, in particular by microscopy, in particular scanning electron microscopy, possibly coupled with an image processing method, in order to measure the deterioration of the document and the restructuring effect provided to the information carrier according to the invention by the self-repairing material.

When the document comprises a coating of the self-repairing material, said measurement can be carried out by topography, for example by means of an Altisurf apparatus marketed by Altimed. In this case it will be possible to verify the repair or not of the degradation of the coating, respectively according to the invention or according to the prior art, for example by means of a roughness measurement or a surface profile.

FIG. 4 shows a bank note according to the invention. This note was made from a paper comprising a self-repairing material according to the invention. The bill has at least one impression 20, for example soft-cut. The bill also includes at least one security element 21, for example a security thread visible in windows.

The invention is not limited to the illustrated examples.

You can replace the self healing polymers of Examples 1 and 2 by the Surlyn ^® polymers 8940, 8920 or 8140 of the company Dupont De Nemours.

The invention applies to all types of information media, for example books, identity documents, identity cards, passports, residence permits, banknotes, paper or plastic, tickets, payment, access to sports or cultural events, playing cards, this list is not exhaustive.

The phrase "having one" is synonymous with "having at least one".

Claims

1. An information medium, in particular a security or valuable document, or paper intended for the production of such an information medium, constituting a banknote or being intended for the manufacture of banknotes and comprising a substrate and at least one self-repairing material.

2. Safety or valuable document, or paper intended for the manufacture of such a security document or of value, comprising a substrate and at least one self-repairing material, said self-repairing material being of the reversible type without formation of covalent bonds.

3. Safety or valuable document, or paper intended for the production of such a security document or of value, comprising a substrate and at least one self-repairing material, and further comprising a barrier layer (17). ) between the self-repairing material and the substrate, in particular fibrous material.

4. Safety or valuable document, or paper intended for the manufacture of such a security document or of value, comprising a substrate and at least one self-repairing material, said self-repairing material requiring an energy stimulus, in particular a thermal stimulus and / or bright, to self-repair.

5. Document or paper according to any one of the preceding claims, the substrate being a fibrous substrate (11).

6. Document according to any one of claims 1 to 4, the substrate being made of plastic, in particular a thermoplastic material, preferably having voids.

7. Document or paper according to claim 5, the self-repairing material covering at least one side of the fibrous or penetrating substrate, at least partially in the substrate, especially near its surface.

8. Document or paper according to claims 5 or 7, the fibrous substrate (11) comprising cellulosic fibers.

9. Document or paper according to any one of the preceding claims, comprising a coating of the self-repairing material, in the form of a film

(14) covering the substrate (11).

10. Document or paper according to any one of claims 1, 3 and 4 to 9, the self-repairing material being irreversible type.

11. Document or paper according to any one of claims 1, 3 and 4 to 9, the self-repairing material being of the reversible type with formation of covalent bonds.

12. Document or paper according to claim 11, the self-repairing material making use of a Diels-Aider or retro-Diels-Aider reaction.

13. Document or paper according to any one of claims 2 and 5 to 9, the self-repairing material comprising a polymer with moving chains.

14. Document or paper according to one of claims 2, 5 to 9 and 13, the self-repairing material comprising a polymer of Tg less than or equal to 20 ° C.

15. Document or paper according to one of claims 2, 5 to 9 and 13, the self-repairing material comprising at least one ionomer.

16. Document or paper according to one of claims 2, 5 to 9 and 13, the self-repairing material comprising a polymer with supramolecular bonds.

17. Document or paper according to any one of the preceding claims, being configured to exhibit zero porosity after creasing.

18. Document or paper according to any one of the preceding claims, comprising at least one security element of first, second or third level.

19. Document or paper according to any one of the preceding claims, comprising an impression.

20. Document or paper according to any one of claims 3 and 5 to 19, the barrier layer being hydrophobic and oleophobic.

21. Document or paper according to any one of the preceding claims, comprising a printability layer (16) deposited on the self-repairing material.

22. A method of processing a security document or used value in which a document as defined in claims 2 and 5 to 9 is exposed to an energy stimulus so that the self-repairing material can auto-repair itself. to fix.

23. Method according to the preceding claim, the exposure to the stimulus taking place in a sorting facility intended to eliminate documents no longer having certain required circulation characteristics.

24. A method of manufacturing a security or valuable document or paper according to any one of claims 1 to 21, wherein a substrate, particularly fibrous, is coated with a self-repairing material.