EP2689068B2 - Information support or paper comprising a self-healing material - Google Patents

Description

The present invention relates to information carriers, in particular intended to be handled frequently, and more particularly the supports comprising a substrate, in particular fibrous, and for example intended for the manufacture of security or valuable documents such as banknotes, as well as 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 the publications EP 1 319 104 or EP 0 514 455 Among other things, they make it possible to reduce the effects of these degradations on the porosity of the fibrous substrate and thus to 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.

The patent EP 514 455 B1 discloses thereby improving the circulation resistance of bank notes by impregnating the fibrous substrate, before printing, 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.

Requirement US 2004/0023008 A1 discloses a security paper for the manufacture of bank notes. 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 a moisture and soil resistance to a fibrous substrate, comprising impregnating the substrate on two opposite sides with an aqueous composition comprising one or more thermoplastic resins.

US 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.

The patent EP 815 321 B1 discloses a paper for the production of banknotes, wherein 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 responds to this need by means of an information medium, security document or value, or a paper intended for the manufacture of such an information carrier, according to claim 1.

By "self-repairing material", it is necessary to understand a material, in particular a polymeric material, 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 substrate based on a thermoplastic material, for example a Polyart® sheet sold by the company Arjobex. The substrate may comprise a core layer and at least one layer of skin covering the core layer, the core layer being further from the surface than the skin layer. The core layer may comprise, as in the case of Polyart®, voids. The core layer can be sandwiched between two layers of skin. The substrate may be as claimed in the patents 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 core 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 successive degradations 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 μm and 15 μm, better 5 and 8 μm.

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 invention further relates to a method of processing a used information carrier according to claim 10.

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 according to claim 11.

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 self-repairing material to be applied at least partly 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 polymer-based film-forming coatings used for protection against external aggressions in the fields of automotive (body painting), electronics (protection of electrical sheath) or the 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.

Reversible self-repairing materials

The self-repairing material is of the reversible type, because with a self-repairing material of the irreversible type, the The ability of the material to self-repair may decrease over time, since self-healing may 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.

By "reversible self-repair" is meant a self-repair which can effectively take place repeatedly on a targeted area of the substrate having undergone successive attacks, in particular spaced apart over time, the self-healing capacity preferably being 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-Alder and retro Diels-Alder reactions, or of non-covalent (weak linkage) interactions such as hydrogen bonds, ionic bonds, coordination bonds (metal-ligand type) or interaction of "Π-Π stacking" type. 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.

Reversible system with non-covalent bonds

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, elastomers crosslinking via hydrogen bond formation, and most particularly mobile chain polymers and ionic thermoplastic polymers known as ionomers. .

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.

1 - 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.

Requirement US20100174041 describes an example of self-repairing material of this type.

Surlyn®, in particular references 8940 and 8140, from DuPont is a commercial example.

2 - Polymer with mobile chains

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 the 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.

The publications JP2008239722 ; WO200769765 ; EP1190424 ; US20020108774 ; KR20090109459 and WO9610595 disclose such materials.

3 - 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 Reverlin ™ polymer from Arkema.

Requirement CN 101671474 also describes an example of such material.

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, have the disadvantage of requiring a mechanical action, for example contacting the two faces of the tear or affixing an pressure to allow repair.

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.

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 performed 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 processing 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 pre-treatment is preferably carried out before the self-healing material is applied 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 μm, before and / or after depositing 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 for the manufacture of the support, some are detectable to the eye, daylight or artificial light, without use of a device particular. 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. It is for example chemical or biochemical reagents tampering and / or authentication and / or identification 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 producing this layer, at least hydrophobic and oleophobic and also film-forming, 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 μm, better still from 1 to 15 μm, more preferably from 2 to 7 μm.

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)

Compound Provider Family / Function Quantity per 100 g Cromelastic SE871 Cromogenia Units Polyurethane / Binder 38 g Cab-O-Sperse PG002 Pooch Pyrogenous Colloidal Silica / Printability Charge 59 g 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, better still between 3% and 6%, before impregnation of the paper substrate, and the insolubilizer is preferably dissolved at a level of 0.05. at 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 self-healing 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 microns.

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 fluid form, in particular of aqueous dispersion or solvent, preference is given to dipping, sizing, impregnating, surfacing, coating, printing means. or coating to apply it.

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 of the TWIN ™ engraving type or TWIN ™ Sizer HSM, can be envisaged to coat 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 outlet of the paper-forming tank by dipping in a bath of PVA and insolubilizer respectively dissolved 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 material " Masayuki Yamaguchi, Susumu Ono and Kenzo Okamoto (Materials Science and Engineering B, vol.162, year 2009, pages 189-194 ).

In this example, shown in figure 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 polyart® plastic sheet.

Example 2 according to the invention

In this example, shown in figure 3 a barrier layer 17 of the same formulation as that given in Example 1 of the patent EP 514 455 , is applied by surfacing to the PVA-based pre-treatment layer 12. 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 one variant, the substrate is a polyart® plastic sheet.

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 the patent EP 1 319 104 with 39% by weight of polyurethane dry weight.

The structure 10 illustrated in section is schematically and partially shown in FIG. figure 1 , where 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 apparatus 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 ).

1. a) un dispositif pour rouler l'éprouvette de papier en un cylindre. Ce dispositif est constitué d'un manchon fendu à l'intérieur duquel est placée une fourche mobile à deux dents.
2. b) un tube dont l'une des extrémités est pourvue d'un couvercle mobile.
3. c) un guide cylindre glissant à l'intérieur du tube.
4. d) un guide cylindrique permettant de maintenir à l'intérieur et en position verticale le piston dont la base inférieure repose à l'extrémité d'un levier. Le guide cylindrique est conçu de telle manière que le tube peut coulisser entre ce guide et le piston.
5. e) un levier monté sur un pivot.
6. f) un poids à l'extrémité du bras long du levier, opposée à celle du bras court qui supporte le piston.

The apparatus comprises:

1. 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.
2. (b) a tube with one end provided with a movable lid.
3. c) a sliding cylinder guide inside the tube.
4. 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.
5. e) a lever mounted on a pivot.
6. 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 of the sleeve aligned, introduce the test tube in the direction of travel up to its half, then roll it by rotation of 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, and acting too abruptly could produce notches on the side which 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; to 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 brightness meter and is applied during two seconds enough pressure to mark the paper. Porosity is measured by ensuring that the BENDTSEN porosimeter head is centered on the surface squeezed to the brightnessometer.

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.

We have shown figure 4 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.

The self-repairing polymers of Examples 1 and 2 can be replaced by the Surlyn® polymers 8940, 8920 or 8140 from 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 (11)

1. Security document or document of value, or paper for the manufacture of such a security document or document of value, comprising a substrate and at least one self-healing material, said self-healing material being of the reversible type without formation of covalent bonds.
2. Security document or document of value, or paper for the manufacture of such a security document or document of value, according to the preceding claim, also comprising a layer forming a barrier (17), particularly a hydrophobic and oleophobic barrier, between the self-healing material and the substrate, particularly a fibrous substrate.
3. Document or paper according to any one of the preceding claims, the substrate being a fibrous substrate (11) preferably comprising cellulosic fibres.
4. Document according to any one of Claims 1 to 2, the substrate being of plastic material, particularly thermoplastic material, preferably containing voids.
5. Document or paper according to Claim 3, the self-healing material covering at least one face of the fibrous substrate or penetrating at least partially into the substrate, in particular close to its surface.
6. Document or paper according to any one of the preceding claims, comprising a coating of the self-healing material in the form of a film (14) covering the substrate (11).
7. Document or paper according to any one of Claims 1 and 3 to 6, the self-healing material comprising a polymer with mobile chains.
8. Document or paper according to any one of Claims 1, 3 to 6 and 7, the self-healing material comprising a polymer with a Tg less than or equal to 20°C, or at least one ionomer or polymer with supramolecular bonds.
9. Document or paper according to any one of the preceding claims, comprising a printable layer (16) deposited on to the self-healing material.
10. Process for treating a used security document or document of value wherein a document as defined in Claims 1 and 3 to 6 is exposed to an energetic stimulus so that the self-healing material can self-heal, the exposure to the stimulus preferably taking place within a sorting installation designed to reject documents not possessing certain characteristics required for circulation.
11. Process for the manufacture of a security document or document of value or paper according to any one of Claims 1 to 9 in which a substrate, particularly fibrous, is coated with self-healing material.

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