FR3088940A1 - METHOD OF MARKING A LEATHER ELEMENT WITH A FLUORESCENT MOLECULE - Google Patents

Abstract

Method for marking a leather element, comprising at least the following steps: a) supplying a leather element, comprising collagen chains, having amine functions, b) bringing the leather element into contact with an aromatic aldehyde, and with carbon dioxide under a pressure and a temperature such that carbon dioxide is in the supercritical state or close to the supercritical state, so as to react the aromatic aldehyde with the amine functions of the leather, whereby the leather element is covalently marked by the aromatic aldehyde via imine functions. Figure for the abstract: Figure 2a.

Description

Description

Title of the invention: METHOD OF MARKING A LEATHER ELEMENT BY A FLUORESCENT MOLECULE [0001] TECHNICAL FIELD AND PRIOR ART [0002] The present invention relates to a method of marking a leather element, for the fight against counterfeiting, with a fluorescent molecule.

Many manufactured products are the object of counterfeits by fraudulent reproduction of their appearance and / or their characteristics in order to deceive consumers. The scale of this phenomenon is increasing. It is difficult to distinguish these reproductions from the original products, due to the quality of reproduction of their packaging and / or the fact that they are distributed through the same distribution networks as the original products.

The textile sector is one of the most affected by counterfeiting. In question: the brand relocation strategy, distributors, the inventiveness of counterfeiters, and the development of Internet sales.

The fight against counterfeiting is an economic battle (job destruction, loss of earnings for businesses) but also health because the reproductions are generally made in deplorable hygienic conditions, which makes them dangerous for health. workers and consumers.

[0006] Certain brands, in order to limit the economic and social impact of fraud, are led to set up actions aimed at protecting their intellectual property and their products.

To facilitate the systematic detection of copies, the products can be marked with an authenticating element. Among the authentication solutions adopted by the market is optical marking.

As described in document WO2014 / 133384, it is possible to mark a textile with a tracer, such as for example a luminescent agent, in the presence of supercritical CO ₂ . This marking can be authenticated by a person who knows the specificity of the marking. Authentication is, for example, carried out by placing the luminescent agent in the presence of an activator and a metal ion which catalyzes the luminescence reaction. Small amounts of tracers are enough to mark a textile. Nylon, cotton, or silk fibers can be marked.

[0009] However, with such a method, it is easy to mark textile fibers, but it is much more difficult to mark leather durably.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method of marking a leather element, easy to implement, the marking having to be fluorescent and resistant over time.

This object is achieved by a method of marking a leather element, comprising at least the following steps:

a) supply of a leather element, comprising collagen chains having amine functions,

b) contacting the leather element [0012] with an aromatic aldehyde, [0013] and [0014] with carbon dioxide under a pressure and a temperature such that carbon dioxide is in the supercritical state or close to the supercritical state, so as to react the aromatic aldehyde with the amine functions of the collagen chains, whereby the leather element is covalently marked by the aromatic aldehyde via imine functions.

By aromatic aldehyde is meant a compound of the benzaldehyde type, substituted or not, that is to say a benzene ring comprising at least one formyl group.

By carbon dioxide in the supercritical state (or supercritical carbon dioxide) is meant carbon dioxide which is beyond its critical point, that is to say heated above its temperature critical (31 ° C) and compressed above its critical pressure (74bar). When carbon dioxide is kept beyond its critical point, it has properties intermediate between those of a gas (for example, low surface tension) and those of a liquid (for example, high solvent power). Carbon dioxide in the supercritical state can, like a gas, readily diffuse into materials, such as leather. Due to its strong solvating power, it can entrain aldehyde and thus mark the leather element homogeneously on the surface and / or in volume.

By close to the supercritical state, it is meant that the carbon dioxide is at a pressure higher than 80% of its critical pressure and at a temperature higher than 80% of its critical temperature (in ° C or in K) .

We will choose temperature and pressure conditions such that the aromatic aldehyde is either in the liquid state (carbon dioxide close to the supercritical state, with a temperature above the melting point of the aromatic aldehyde) either dissolved in carbon dioxide (carbon dioxide in the supercritical state).

Preferably, the carbon dioxide is in the supercritical state.

The aromatic aldehyde, entrained by carbon dioxide, which acts as a carrier fluid, reacts with the NH ₂ amine functions of the collagen chains (especially with amino acids, such as lysine and arginine) present on the surface and / or in the volume of the leather element, to form imine bonds. The imine bonds obtained are strong, covalent bonds, irreversible under normal conditions of use of leather. The marking is directly integrated into the product. It is resistant to tearing and rubbing. It does not leave, with a simple wash or in the rain, for example. It has a good resistance over time and it is possible to authenticate it throughout the product life cycle.

The conjugated system of the aldehyde aromatic cycle is extended by the bond C = N, which allows good delocalization of the electrons and a strong fluorescence. The marking is easily detectable.

The marked leather element has a beautiful texture: the fluorescent marking does not alter the leather.

Advantageously, the aromatic aldehyde comprises a condensed aromatic ring, optionally substituted.

Advantageously, the aromatic aldehyde comprises an OH group in the alpha position (also called the ortho position). The OH pendant group in alpha dissipates energy by rotation without breaking down the molecule. The organic compound, in addition to being fluorescent, absorbs ultra-violet radiation (absorption at 365nm in particular). The leather obtained is thus protected from aging with UV radiation.

According to this particular embodiment, the aromatic aldehyde, advantageously, has the general formula (I):

[Chem 1]

O

H g

With R chosen from a hydrogen atom, L, CI, Br, 1, OH, a vinyl group, a linear or branched alkyl group, and a CO ₂ group R 'with R' an alkyl group.

By alkyl is meant a hydrocarbon chain having from 1 to 12 carbon atoms and, preferably, from 1 or 4 carbon atoms. The linear alkyl group is, for example, chosen from methyl, ethyl, propyl, and isopropyl groups. The branched alkyl group is for example tert-butyl (t-Bu).

Advantageously, the aldehyde is methyl 3-formyl-4 hydroxybenzoate. This compound has a melting point around 80-84 ° C, which allows it to be easily used in the liquid state (conditions close to the supercritical state) or dissolved (supercritical conditions). The temperatures involved remain moderate (typically less than or equal to 120 ° C).

According to a first advantageous variant, step b) is carried out in a closed reaction chamber.

According to another advantageous variant, step b) is carried out by simultaneously spraying the aromatic aldehyde and the fluid in the supercritical state or close to the supercritical state on the leather element, for example, with a spray nozzle. This allows marking in the form of a pattern in a targeted area.

Advantageously, glutaraldehyde is added during step b). Glutaraldehyde is a tanning agent. The process makes it possible, in addition to marking the leather, to tan it homogeneously on the surface and / or in the volume. With such a tanning, the leather obtained has a good visual quality. Tanning and marking are carried out simultaneously, which limits the stages of the leather preparation process and energy consumption. In addition, it avoids using chrome tannins and having leather containing metal.

The invention also relates to a leather element marked with an aromatic aldehyde covalently via imine functions, obtained by the method described above. The labeling is fluorescent. The entire surface of the leather element can be marked, or a single part, for example in the form of a pattern.

According to an advantageous embodiment, the marking is visible to the naked eye.

The invention also relates to a method of authenticating a marked leather element as defined above, in which the leather element is subjected to the step of detection by fluorescence. This type of secure optical marking is easy to authenticate by the actors in charge of control (customs, resellers, etc.) who know these characteristics. The means used to verify its presence (control with the naked eye and / or using a simple portable fluorometer, an ultra-violet lamp) are easy to implement.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood on the basis of the description which follows and of the accompanying drawings in which:

[Fig.l] is a photographic image representing unmarked leather elements (Al and Bl) and marked leather elements (A2 and B2) according to a particular embodiment of the method of the invention, under light natural, [fig.2a] and [fig.2b] are fluorescence spectra, respectively, of a marked leather element and an unmarked leather element, observed under UV irradiation at 365nm , according to a particular embodiment of the method of the invention, [fig.3] is a photographic photograph representing unmarked leather elements (Cl and Dl) and marked leather elements (C2 and D2) with a europium complex, under natural light.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS [0041] Leather element [0042] The element supplied in step a) is a leather part.

The leather is derived from animal skin, for example, from a bovine such as a cow, buffalo or bison, from an sheep, from a goat such as a goat, from a pig, from 'a reptile, like a crocodile or a lizard, or an ostrich.

It can be raw leather (untreated raw hide), tanned or boiled leather. It can be full grain leather, sawn grain leather or even split leather.

The part can be of any shape. It is, for example, a square or rectangular piece of leather or an object, such as a jacket, a shoe, a belt, a glove, a handbag, a wallet or a saddle.

Leather is a material containing collagen chains. It is a protein, having a helical structure, and comprising a chain of amino acids, including arginine and lysine. These amino acids have primary amines, which are very nucleophilic, accessible, and which can react with an aldehyde to form covalent bonds (imine bonds).

The marking can be carried out on part of the surface of the leather element or on its entire surface.

Aromatic aldehyde During the process, the part can be marked by one or more aromatic aldehydes. It is thus possible to carry out a marking in the form of a code with different fluorophores which may have different fluorescence intensities.

The aromatic aldehyde is fluorescent. It can be visible to the naked eye (and also have an aesthetic function) or invisible to the naked eye (stealth marking).

The aromatic aldehyde is advantageously benzaldehyde or one of its derivatives. The aldehyde may include one or more aromatic rings. They can be aromatic heterocycles, comprising for example a nitrogen atom, and / or condensed aromatic rings. For example, the aromatic aldehyde is naphthaldehyde or one of its derivatives.

Advantageously, the aromatic aldehyde comprises an OH group in the alpha position to give the leather protection against aging by UV radiation. For example, the aromatic aldehyde is 2-hydroxy-naphthaldehyde, 2-hydroxybenzaldehyde or one of their derivatives.

We will choose, for example, the aromatic aldehyde from the following compounds:

- 3-tert-butyl-2-hydroxybenzaldehyde (2725-53-3), 3-chloro-2-hydroxybenzaldehyde (1927-94-2), - 4-bromo-2-hydroxybenzaldehyde (22532-62-3 ), 3-bromo-2-hydroxybenzaldehyde (1829-34-1), 3,5-ditert-butyl-2-hydroxybenzaldehyde (3794207-7),

2- chloro-6-hydroxybenzaldehyde (18362-30-6), 4,6-dimethoxysalicylaldehyde (708-769), 4- (diethylammo) salicylaldehyde (17754-90-4), 5-fluorosalicylaldehyde (347-54 -6), and 5-chloro-2-hydroxy-3-iodobenzaldehyde (215124-03-1).

The aromatic aldehyde can also be chosen from methyl

3- formyl-4-hydroxybenzoate (24589-99-9), ethyl 3-formyl-4-hydroxybenzoate (8230499-2), 8-hydroxy-2-qumolmecarboxaldehyde (14510-066), and 2-hydroxy -l-naphthhaldehyde (708-06-5).

Preferably, it is methyl 3-formyl-4 hydroxybenzoate.

By way of illustration, the aromatic aldehyde of general formula (I) reacts with the amino acids of leather according to the following reaction:

[Chem 2]

With RiNH ₂ an amino acid of the collagen chain, and preferably lysine or arginine.

Marking Step The leather element is brought into contact with the aromatic aldehyde, in the presence of carbon dioxide under a pressure and a temperature such that the carbon dioxide is in the supercritical or near state. from the supercritical state, so as to entrain and react the aldehyde with the amine functions of the leather.

Carbon dioxide plays the role of carrier fluid. Its only role is to transport the aldehyde. It is lipophilic, that is to say inert towards collagen-containing materials, such as leather. In addition, carbon dioxide is non-toxic, non-flammable, and inexpensive.

When the carbon dioxide is in the supercritical state (CO ₂ SC), the aldehyde is dissolved in the CO ₂ SC, which makes it possible to transport and react the aldehyde with the amines of the leather not only on the surface, but also in volume, that is to say inside, in the heart of the leather element. The part is uniformly impregnated with the aldehyde, in surface distribution and in thickness.

Carbon dioxide has a technically reasonable start to the supercritical range. Advantageously, the pressure and temperature ranges, to have

C0 ₂ in the supercritical state, are from 50 to 350 bars and from 20 to 100 ° C, preferably from 250 bars to 350 bars and from 70 to 100 ° C.

It is also possible to position oneself in a temperature and pressure range such that the carbon dioxide is close to the supercritical state, and that the aldehyde is in liquid form. Carbon dioxide carries the aldehyde to the surface of the leather item. The marking is surface.

The contact time between the aldehyde and the leather element, in the presence of CO ₂ SC or CO ₂ close to the supercritical state, ranges, for example, from 30 minutes to 10 hours, preferably from 30 minutes to 3 hours, for example of the order of 1 hour. The duration of the treatment will control the amount and / or the depth of penetration of the aldehyde into the leather.

According to a first embodiment, bringing the leather element and the fluid in the supercritical state into contact can take place in a sealed reaction chamber. It is a closed reactor, in particular an autoclave, for example made of stainless steel.

The reaction chamber can be connected to a so-called secondary chamber for storing and / or preparing the reagents. The reaction chamber may include means for introducing one or more compounds into the fluid. Advantageously, means for recycling and / or purifying the fluid can be provided.

The fluid can be introduced into the chamber at ambient pressure and at ambient temperature: the supercritical fluid is introduced in non-supercritical form, for example, in gaseous form or, preferably, in liquid form. The reaction chamber comprises means of regulation (in temperature and in pressure) to bring the fluid which is in the liquid or gaseous state, under normal conditions of temperature and pressure, in the supercritical state. The reactor is then closed, pressurized and brought to the desired temperature, so that the fluid is in supercritical form in the reaction chamber. The temperature and the pressure are maintained for the time necessary to obtain the marking of the leather.

The fluid can be introduced into the chamber in the supercritical state.

The fluid and the aldehyde can be introduced into the reactor, concomitantly or simultaneously.

According to another embodiment, the marking is carried out by spraying, at high speed, a jet, containing carbon dioxide in the supercritical state and the aldehyde, on the leather element. Spraying can be carried out using a spray nozzle. The spraying device can comprise one or more nozzles, fixed or mobile, arranged downstream of an enclosure configured to maintain the carbon dioxide in the supercritical state. The enclosure includes a fluid inlet (CO ₂ ) and a reagent inlet (aromatic aldehyde).

Carbon dioxide and aldehyde form an ink which is sprayed onto the leather element.

The leather element is placed on a fixed or mobile platform, facing the spray nozzle.

It is possible to produce patterns, for example to reproduce logos.

According to a particular embodiment, the leather element is put in the presence, simultaneously, of an aromatic aldehyde, glutaraldehyde and carbon dioxide in the supercritical state or close to the state supercritical. This embodiment allows both tanning and marking of the leather element. The glutaraldehyde molecule can thus diffuse on the surface or even to the heart of the leather element.

At the end of the process, a leather element is obtained, marked with one or more fluorescent aldehydes, visible or invisible to the naked eye, secure and easily authenticated by a person who knows the characteristics of the fluorescent marking.

Advantageously, this process does not require the use of a co-solvent. There are no aqueous / organic discharges to treat. The process is completely green. At the end of the labeling process, the carbon dioxide can be reused for another labeling.

Illustrative and nonlimiting example of an embodiment:

Different leather samples are selected: C3 white leather (402 mg), C10 pink leather (256 mg), white leather thread (56 mg), orange leather thread (49 mg) and black leather thread (51.5 mg).

These samples are introduced into a tubular reactor. Methyl 3-formyl-4-hydroxybenzoate (81 mg) is also introduced into the reactor.

The reactor is connected to a pump supplied with liquid CO ₂ . The system is stabilized at 70 bar, then the reactor is heated in order to reach the conditions of supercritical CO ₂ . The system is stabilized for 1 hour at 280 bar and 100 ° C. Then the heating is stopped and the pressure is broken. The aldehyde was completely consumed.

The samples taken out of the reactor show a fluorescence undetectable with the naked eye (Figure 1), and observable under UV lamp (Figure 2).

By way of comparison, different samples of leather were brought into contact with a europium complex in the presence of carbon dioxide in the supercritical state.

The leather samples are: C3 white leather (645 mg), C5 brown leather (1254 mg), white leather thread (107 mg), orange leather thread (104 mg) and black leather thread (101 mg ).

These samples are introduced into a tubular reactor. The tris (dibenzoylmethane) mono (1,10-phenanthroline) complex of europium is added (100 mg). To ensure proper dissolution of the latter, acetone (ImL) was added as a co-solvent. The reactor is connected to a pump supplied with liquid CO ₂ . The system is stabilized at 70 bar, then the reactor is heated in order to reach the conditions of supercritical CO ₂ . The system is stabilized for 1 hour at a pressure between 250 and 300 bar and at 100 ° C. Then the heating is stopped and the pressure is broken.

The samples are deteriorated (Figure 3) and show no fluorescence. There is little or no affinity of the fluoropohore for the leather substrate.

Claims (1)

Claims [Claim 1] Method for marking a leather item, comprising at least the following steps: a) supply of a leather element, comprising collagen chains, having amine functions, b) contacting the leather element with an aromatic aldehyde, and with carbon dioxide under a pressure and a temperature such that carbon dioxide is in the supercritical state or close to the supercritical state, so as to react the aromatic aldehyde with the amine functions of the collagen chains, whereby the leather element is covalently marked by the aromatic aldehyde via imine functions. [Claim 2] Process according to claim 1, characterized in that the aldehyde comprises an optionally substituted condensed aromatic ring. [Claim 3] Method according to one of the preceding claims, characterized in that the aromatic aldehyde comprises an OH group in the alpha position. [Claim 4] Process according to Claim 3, characterized in that the aldehyde has the general formula (I): [Chem 3] 0 H 'Ύ R with R chosen from a hydrogen atom, F, Cl, Br, I, OH, a vinyl group, a linear or branched alkyl group, and a CO ₂ R 'group with R' an alkyl group. [Claim 5] Process according to claim 4, characterized in that the aldehyde is methyl 3-formyl-4 hydroxybenzoate. [Claim 6] Process according to any one of Claims 1 to 5, characterized in that step b) is carried out in a closed reaction chamber. [Claim 7] Process according to any one of Claims 1 to 5, characterized in that step b) is carried out by simultaneously spraying the aromatic aldehyde and the fluid in the supercritical state on the leather element. [Claim 8] Process according to any one of Claims 1 to 6, characterized in [Claim 9] what glutaraldehyde is added in step b). Leather element marked with an aromatic aldehyde covalently via imine functions. [Claim 10] Element according to the preceding claim, characterized in that the [Claim 11] marking is visible to the naked eye. Method of authenticating a marked leather element as defined in one of claims 9 and 10, in which the leather element is subjected to the step of fluorescence detection. 1/2