Patent Description:
A study by the consultant company "Frontier Economics" [<NUM>] estimates that worldwide counterfeiting losses during <NUM> will reach the alarming amount of <NUM>-<NUM> billion euros ("USD $<NUM>-$<NUM> trillion" in the original). But what is less mentioned is the dissatisfaction by the consumer, who usually does not have the means to verify the authenticity of the products and documentation purchased. Counterfeit products are not only generally of poorer quality, they also involve funding from criminal organizations. Faced with such a serious problem, different inventions of anti-counterfeiting technologies have recently emerged, which often require additional equipment.

<CIT> [<NUM>] features papers with watermarks that are sensitive to ultraviolet and infrared radiation. In <CIT> [<NUM>], watermarks are sensitive to the voltage supplied by a current source. <CIT> [<NUM>] introduces a method for producing unique dendritic structures, which shows efficient adhesion to a paper substrate and which can be identified under a microscope or X-ray scanner.

<CIT> [<NUM>] provides a method for verifying the authenticity of bar codes based on a fluorescent material.

In scientific literature, luminescent pigments and inks and small particles (such as quantum dots) are the most common solutions proposed for paper authentication [<NUM>-<NUM>]. In these cases, excitation with ultraviolet radiation is necessary to reveal the markers, normally invisible to the naked eye. Furthermore, the use of complexes with metals, including heavy metals, affects the sustainability of these proposals.

<CIT> discloses methods of preparing a crosslinked polymer having increased chemical durability resulting from the inclusion of antioxidants, or free-radical scavengers, to neutralize the radicals causing polymer membrane degradation.

There is thus a need for a material for application in the detection of counterfeiting and authentication of products which overcomes the difficulties of the prior art, namely the identification and authentication of products in a simple, immediate and sustainable way, without the need to resort to any specific equipment and in a sustainable way. Additionally, this material should have a good affinity with cellulose or textile substrates and be easily incorporated into different products which allows its use as, and not limited to, liquid products, paints and coatings.

The present invention according to the appended claims relates to a chromogenic copolymer comprising at least two monomeric units, of general formula I:
<CHM>
wherein at least one of the R1-R5 groups is an NH<NUM> group or contains an aromatic ring with an NH<NUM> group, and where at least one of the R6-R10 groups is an aromatic ring activating group.

In a preferred form of the invention the copolymer is described in which at least one of the R1-R5 groups is an NH<NUM> group and in that at least one of the R6-R10 groups is a OH group.

In a preferred form of the invention the copolymer is described in which at least one of the R1-R5 groups contains at least one aromatic ring substituted with an NH<NUM> group and in that at least one of the R6-R10 groups is an OH group.

In a preferred form of the invention the copolymer is described in which at least one of the R1-R5 groups is an NH<NUM> group and in that at least one of the R6-R10 groups contains at least one aromatic ring substituted with an OH group in at least one position.

In a preferred form of the invention the copolymer is described in which at least one of the R1-R5 groups is an NH<NUM> group and in that at least one of the R6-R10 groups contains at least one aromatic ring substituted, in at least one position, by a tertiary amino group.

In a preferred form of the invention, the copolymer is described in which at least one of the R1-R5 groups contains at least one aromatic ring substituted, in at least one position, by an NH<NUM> group, and in that at least one of the R6-R10 groups is substituted on the aromatic ring, in at least one position, by a tertiary amino group.

In a preferred form of the invention, the copolymer is described in which at least one of the monomeric units is a vinyl monomer, acrylate, methacrylate, acrylamide, methacrylamide, alcohol, monosaccharides, vinyl oxide, carboxylic diacid, acid dichloride, diester, diamine or silicon monomers.

In a preferred form of the invention the copolymer is soluble in solvents such as water, N, N-dimethylformamide, N-methyl-<NUM>-pyrrolidone, acetonitrile, ethanol, methanol, dimethylsulfoxide and N,N-dimethylacetamide.

The present invention further relates to a method of obtaining the copolymer which includes the following steps:.

The present invention further relates to a liquid product which includes the copolymer object of the present invention. In a preferred form of the invention this liquid product is sprayable.

The present invention further relates to a fiber that includes the copolymer object of the present invention.

The present invention further relates to an ink that includes the copolymer object of the present invention.

The present invention further relates to a coating for paper or textile material which includes the copolymer object of the present invention.

The present invention further relates to a paper or textile material that includes the copolymer object of the present invention.

The present invention further relates to a paper or textile material which includes the fiber described above and/or, on at least one of its surfaces, the ink described above and/or the coating described above.

The present invention further relates to a paper material that includes the copolymer object of the present invention such as packaging, printing and writing paper and cardboard.

The present invention further relates to a textile material that includes the copolymer object of the present invention as clothing, blanket, fabric for decoration or furniture, fabric for filtration and tissue paper.

The present invention further relates to a method of preparing paper or textile materials that include the copolymer object of the present invention, described by the following steps:.

The present invention further relates to a method of detecting counterfeiting and for authenticating products that includes the following steps:.

In a preferred form of the invention the method further includes a step of spraying the paper or textile material with an alkaline solution after step a).

A sensor and chromogenic copolymer is defined here, as described in this invention and claim <NUM>, which allows a new verification and authentication technique, simple and sustainable, with security and anti-counterfeiting applications, based on an organic material with properties of colorimetric sensor, without the need to use any specific equipment. Simultaneously, this material is a copolymer based on commercially available monomers, which have a good affinity with surfaces of, for example, any paper or textile material, includes sensor or responsive units and is easily incorporated in different products that allow its use as, and not limited to, liquid products, paints and coatings.

The end user only needs to apply an extremely inexpensive aqueous solution of sodium nitrite (example: using a sprayer or a pen), and the chromogenic copolymer changes color under visible light; i.e. with the naked eye. The cause of this color change is an azo coupling reaction between the sensing units of the polymer. Depending on the combination of these units, different azo dyes, having different colors, are formed. In this way, a much greater chromatic variety is achieved than in the cellulosic sensor for nitrites as proposed in the literature, such as in <CIT> [<NUM>], where the Griess reaction produces a reddish color (with absorption at <NUM>), which is suitable for detecting nitrite in water but does not provide authentication applications. The possibility of obtaining different colors makes it possible, allowing a large number of color codes to the consumer.

Within the scope of the present invention chromogenic means capable of producing color, with light absorption in the visible region, by means of a chemical reaction.

Within the scope of the present invention aromatic ring activating group means a functional group which makes some of the positions of the aromatic ring more nucleophilic.

Within the scope of the present invention activated aromatic ring relates to an aromatic ring substituted with at least one electron donor group.

Within the scope of the present invention an amino group means a functional group containing a nitrogen atom with a free pair of electrons, with the chemical formula - NH<NUM>, -NH- or >N-, such that the nitrogen atom is bonded to at least one carbon atom, and none of the carbon atoms attached to the nitrogen atom has a double bond with an oxygen atom (>C=O).

Within the scope of the present invention a primary amino group means a functional group with the chemical formula -NH<NUM> where the nitrogen atom is attached to a single carbon atom.

Within the scope of the present invention primary aromatic amino group means a functional group with the chemical formula -NH<NUM>, -NH- or >N-, such that the nitrogen atom is bonded to, at least, one aromatic ring-membered carbon atom.

Within the scope of the present invention hydroxyl group means a functional group consisting of an oxygen atom covalently bonded to a hydrogen atom, with the chemical formula -OH.

Within the scope of the present invention diazonium salt means an electrolyte of chemical formula R-N<NUM>+X- , where R is an organic group and X- is an organic or inorganic counteranion.

Within the scope of the present invention tertiary amino group means (>N-), such that the nitrogen atom is bonded to three carbon atoms.

Within the scope of the present invention azo coupling means a reaction between a diazonium compound or monomer and a compound or monomer with, at least, one activated aromatic ring, to produce an -N=N- bond.

Within the scope of the present invention sprayable means that it can be reduced to very fine droplets or particles.

Within the scope of the present invention silicon monomers means any units with, at least, one silicon atom (>Si<), such as silane, vinylsilane or trimethylvinylsilane.

Within the scope of the present invention, a fiber refers to any cellulosic fiber and its derivatives or textile of vegetable, animal and artificial origin. Such as, but not limited to, cellulose acetate, cotton, hemp, linen, wool, cashmere, Rayon, Lyocell, Nylon, polyester, polyamide, among others.

The present invention thus relates to a copolymer with good affinity for cellulosic substrates and with sensory and chromogenic properties. The matrix of this copolymer contains units such that, when applied, the coating of the paper or textile material is successful and, at the same time, does not allow its elution by water. Examples: methylmethacrylate, <NUM>-hydroxyethylmethacrylate, <NUM>-vinyl-<NUM>-pyrrolidone. The sum of these monomers constitutes more than <NUM>% of the monomeric units of the copolymer. A radical polymerization is carried out involving the matrix units and two sensor and chromogenic monomers (><NUM>%, mol/mol). One of them has a primary amino group (unit A); the other monomer contains an activated aromatic ring (B unit). Once polymerization is complete, the polymer can be precipitated with a non-polar organic solvent.

The invention also relates to a method of preparing paper or textile materials that involves the application of the copolymer described above, these materials used for packaging, documents or any other related products (<FIG>). The copolymer can be dissolved in a polar organic solvent of appropriate volatility, in such a way that this solution is incorporated, as a liquid product, ink or coating, in and/or on any paper or textile material, consisting mainly of cellulose, such as packaging, printing and writing paper and cardboard. Depending on the combination, the paper turns white or yellow, but changes color immediately after contact with an acidic nitrite solution and, then, with a sodium hydroxide solution (<FIG>, <FIG>, <FIG>). Alternatively, without hydroxide, the reaction kinetics with chromogenic groups is slower.

Equimolar combinations between three different A-units and four different B-units lead to different colors.

The polymer matrix consists of a combination of monomers forming a polymer with good affinity for cellulose and is insoluble in water, so that it does not elute from the paper sample when it comes into contact with water or aqueous solutions, including the solution of nitrite (<FIG> and <FIG>).

In one of the examples of this invention, the polymer matrix is constituted, for example, by <NUM>-vinyl-<NUM>-pyrrolidone and methylmethacrylate. The sensor or chromogenic copolymer is prepared by mixing equimolar or different amounts of these compounds together with amounts (at least <NUM>% mol/mol) of the chromogenic units. The polymer matrix consists of any two of these monomers, such as, for example: <NUM>-vinyl-<NUM>-pyrrolidone, methylmethacrylate, <NUM>-hydroxyethylmethacrylate, (<NUM>-dimethylaminoethyl) methacrylate, acrylic acid, sodium acrylate, vinyl acetate, vinylsilane, diacetate of allylidene, terephthalic acid, terephthaloyl chloride, methacrylamide, <NUM>-hydroxyethyl methacrylate, glycidyl methacrylate, dodecyl methacrylate, butyl acrylate (<FIG>).

The A unit is a compound with at least one primary amino group (-NH<NUM>), such as for example <NUM>-vinylaniline, and the B unit is a monomer with at least one activated aromatic ring (example: with hydroxyl groups and/or tertiary amino).

In one of the examples of this invention the A unit is <NUM>-vinylaniline ("A1" in <FIG>), commercially available (<NPL>).

In one of the examples of this invention, unit A is synthesized from <NUM>-aminophenol (<NPL>), obtaining a poly-heterocyclic compound with a secondary amide group and a primary amino group ("A2" in <FIG>).

In one of the examples of this invention, unit A is synthesized from <NUM>-amino-<NUM>,<NUM>-naphthalic anhydride (<NPL>), obtaining a poly-heterocyclic hydrazine ("A3" in <FIG>).

In one of the examples of this invention the B unit is <NUM>-acetamidophenol ("B1" in <FIG>), commercially available (<NPL>).

In one example of this invention the B unit is N-(<NUM>-hydroxyphenyl)methacrylamide ("B2" in <FIG>), commercially available (<NPL>).

In one of the examples of this invention, unit B is synthesized from <NUM>-aminobenzyl alcohol (<NPL>), obtaining a polycyclic amide with a tertiary amino group ("B3" in <FIG>).

In one of the examples of this invention the B unit is synthesized from two commercially available compounds: N-hydroxysuccinimide (<NPL>) and <NUM>-hydroxyquinoline (<NPL>). The resulting poly- and heterocyclic compound is "B4" in <FIG>.

<FIG> show the spectroscopic (infrared and nuclear magnetic resonance) characterization of the synthesized monomers: A2, A3, B3, B4.

The synthesis of the copolymer is carried out by radical polymerization, using an appropriate initiator and a polar organic solvent.

In one of the examples of this invention, the different monomeric units, i.e., the units that form the polymer matrix and the chromogenic units A and B, were dissolved in N,N-dimethylformamide (DMF), in a molar ratio <NUM>:<NUM>:<NUM>:<NUM>, respectively. The initiator, e.g., azo-bisisobutyronitrile (AIBN) was then added. The solution was sonicated, heated and held at <NUM>-<NUM> for about <NUM> hours without stirring.

The polymer, in each case, was precipitated with diethyl ether or another non-polar organic solvent. All polymers generated were purified by means of a Soxhlet extractor. The yield was <NUM>-<NUM>%. Twelve combinations of A and B unities were prepared for the same polymer matrix (<NUM>-vinyl-<NUM>-pyrrolidone and methylmethacrylate) , resulting in <NUM> different polymers with the same matrix, each with a different response, in terms of color, on contact with a nitrite solution.

<FIG> contain the spectroscopic (visible, infrared, and nuclear magnetic resonance region) characterization of four of the possible chromogenic copolymers, which show clearly different colors when forming the azo dye.

For the constitution of liquid products, paints and coatings that incorporate the copolymers described in this invention, the polymers obtained can be dissolved in different organic solvents with appropriate volatility, including acetonitrile and short-chain alcohols. Dissolving in DMF, dimethylsulfoxide or other high-boiling solvents is not recommended as it requires long drying times for the coated paper.

The coating can be done by dipping, deposition, bar/roll, knife, curtain, or any other way of dispensing a liquid onto the surface of a paper or textile material.

Coated papers, depending on the combination of A and B units, retain the original paper color or turn slightly yellow. Only when an acidic nitrite solution is sprayed is one of the different colors revealed. <NUM> of this acidic solution contains at least <NUM> of sodium nitrite (<FIG>). Alternatively, other nitrite salts can be used, such as potassium nitrite or ammonium nitrite. Acidity can be achieved by adding <NUM>-<NUM> of <NUM>% HCl (w/w) per <NUM> of solution.

The color change takes place <NUM>-<NUM> after applying the acidic nitrite solution, or immediately after spraying with an alkaline solution such as sodium hydroxide.

The acidic nitrite solution was sprayed onto twelve paper discs, each containing a different combination of A and B units. Subsequently, a sodium hydroxide "spray" was applied, immediately observing a different color on each paper disc, including yellow, orange, green, purple, reddish, pink, gray, and some intermediate colors (<FIG>).

Let the A unit be "A1", i.e., <NUM>-vinylaniline. Let the B unit be "B2", i.e., N-(<NUM>-hydroxyphenyl)methacrylamide.

<NUM> mmol of <NUM>-vinyl-<NUM>-pyrrolidone, <NUM> mmol of methylmethacrylate, <NUM> mmol of A unit and <NUM> mmol of B unit were dissolved in <NUM> of DMF. Then azo-bisisobutyronitrile (AIBN) as initiator was added in an amount of <NUM> mmol. The solution was sonicated for <NUM>. Then, it was kept at <NUM> for <NUM>, without stirring and under an inert atmosphere (nitrogen). The abovementioned amount of AIBN guarantees a molecular weight distribution of approximately <NUM> Da (measured by time-of-flight mass spectrometry ), which favors solubility and does not reach excessive viscosity.

The solution was allowed to cool up to room temperature. Then, it was added, drop by drop, to diethyl ether (<NUM>) under strong stirring. The polymer obtained was then purified by means of a Soxhlet extractor.

<NUM> of chromogenic copolymer was dissolved in <NUM> of acetonitrile. <NUM> microliters of this solution was deposited on the surface of a paper disk with <NUM> in diameter, and the solvent was evaporated at <NUM> for <NUM>. The resulting paper was white in color, just like the original paper.

Claim 1:
A chromogenic copolymer, comprising at least two monomeric units, of general formula I:
<CHM>
wherein at least one of the R1-R5 groups is an NH<NUM> group or contains an aromatic ring with an NH<NUM> group, and wherein at least one of the R6-R10 groups is an aromatic ring activating group, and in which the proportion of any of the monomeric units represents at least <NUM>% of the total number of monomer units.