METHOD FOR MARKING A TEXTILE THREAD WITH A FLUORESCENT ELEMENT, TEXTILE THREAD PRODUCED BY THE MARKING METHOD, AND USE OF SAID TEXTILE THREAD FOR WEAVING AN ITEM OF CLOTHING

Abstract

A method for marking a textile thread by a fluorescent element has the following successive steps: placing a textile thread and at least one fluorescent element in a reaction chamber, introducing a fluid into the reaction chamber, increasing the temperature and pressure in the reaction chamber up to a temperature and a pressure so as to transform the fluid into a supercritical fluid and to mark the textile thread by the fluorescent element. The fluorescent element is chosen from organolanthanide complexes.

Description

BACKGROUND OF THE INVENTION

The invention relates to a method for marking a textile thread by a fluorescent element and also relates to a textile thread obtained by said method.

STATE OF THE ART

An increasing number of manufactured products are the object of fraudulent reproduction. The counterfeited products are difficult to distinguish from the original products, in particular due to the quality of the reproduction and/or on account of the fact that they can be distributed through the same distribution channels as the original products.

The textile sector is one of those that is most affected by these reproductions.

In addition to the economic losses (loss of jobs, loss of turnover for the companies), the reproductions are often manufactured under unsuitable hygiene conditions and by under-qualified manpower, which makes these products dangerous for health not only for the employees but also for consumers.

It is essential to set up actions aiming to protect these products, often copied practically identically.

To facilitate detection of copies, certain products can be marked with an authenticating element. This can involve a secured optic marking suitable for textile labels.

OBJECT OF THE INVENTION

The object of the invention is to remedy the shortcomings of the prior art, and in particular to propose a method for marking an item of clothing that is simple and easy to implement, the marking having to be difficult to copy and at the same time easily identifiable.

This object tends to be achieved by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from the following description of particular embodiments of the invention given for non-restrictive example purposes only and represented in the appended drawings, in which:

FIG. 1 represents a photograph of a textile thread, marked according to the method of the invention, and of an unmarked textile thread,

FIG. 2 represents a photograph of the two textile threads of FIG. 1, illuminated under an ultraviolet lamp,

FIG. 3 represents an emission spectrum of a textile thread marked according to the method of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The method for marking a textile thread by a fluorescent element comprises the following successive steps:

• • placing a textile thread and at least one fluorescent element in a reaction chamber,
  • introducing a fluid into the reaction chamber,
  • increasing the temperature and pressure in the reaction chamber up to a temperature Ts, higher than the critical temperature of the fluid Tc, and up to a pressure Ps, higher than the critical pressure of the fluid Pc, so as to transform the fluid into a supercritical fluid and to mark the textile thread by the fluorescent element.

In the textile field, supercritical fluids, such as carbon dioxide, can be used for colouring/impregnating textile materials such as synthetic fibres of polyester type with pigments (document EP 1,126,072 and Kikic and al., Current Opinion in Solid State and Materials Science 2003, 7, 399-405). The method enables the quantity of waste/polluted water to be significantly reduced compared with conventional dyeing methods.

The method does however require the use of a small quantity of water, in the reaction chamber, for example in the form of a relative humidity comprised between 10% and 100%, to improve the reactivity and/or accessibility of the fibres.

However, such a marking, that is only visual, is fairly easy to counterfeit.

The method for marking is a method for marking a textile thread by a fluorescent element. A distinctive fluorescent element is placed on the textile thread. The marking is a fluorescent marking.

The marking is advantageously invisible to the naked eye and therefore difficult to identify by a person not knowing the specificity of the marking.

What is meant by method for marking is a method which enables the material to be marked without impairing its properties, and in particular without colouring it.

The marking is advantageously homogeneous. The marking can be made on the surface or in the volume of the material.

Marking in the volume of the material advantageously enables marking both at the surface and in depth. Even if the molecules at the surface lose their properties or are eliminated on account of the successive washings and/or long exposure to the sun, the in-depth molecules can act as a reservoir. The lifetime of the material is thus increased.

After marking, the fluorescent element is linked to the textile thread. The fluorescent element cannot be dissociated from the textile thread by simple washing for example. The resistance of the marking also resists ethanol, acetone and water. The marking can also no longer be removed by simple rubbing of a cloth on the textile thread obtained.

What is meant by textile thread is an agglutination of textile fibres to form a long assembly. The textile threads are designed to be woven in order to form fabrics for confection of items of clothing for example.

The textile thread is a synthetic textile thread made from polymer, or from cotton or leather.

The synthetic textile thread comprises 1% to 88.5% by weight of a polymer material.

Preferentially, the polymer material is polyester: the textile thread comprises 1 to 88.5% by weight of polyester.

The polyester can be chosen from polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalcanoate (PHA), polyethylene adipate (PEA), polybutylene succinate (PBS), polyethylene terephtalate (PET), polybutylene terephtalate (PBT), polytrimethylene terephtalate (PTT), or polyethylene naphtalate (PEN).

According to a preferred embodiment, the polyester is polyethylene terephtalate (PET).

The rest of the percentage of weight can correspond to impurities, fixing agents, colorants, etc.

For example, for a textile thread comprising 88.5% by weight of polymer material, the rest of the percentage can correspond to 2.3% of impurities, 0.7% of pre-treatment agents (to perform whitening for example), 6.5% of colorants and colorant fixing agents, and 2% of finalisation agents (fire protection treatment, waterproofing treatment, etc.).

What is meant by fluorescent element is an element having the property of being able to absorb light and to re-emit it at a higher wavelength. The fluorescent element is formed by at least one fluorescent molecule. Advantageously, the fluorescent element is composed of a multitude of fluorescent molecules of the same nature or of different natures.

Preferentially, the fluorescent molecules are of the same nature.

The quantity of fluorescent molecules is chosen in such a way as to be sufficient to be able to impregnate the textile thread and to give it detectable fluorescent properties.

The fluorescent element is preferably chosen from phthalocyanines and organolanthanide complexes.

According to a preferred embodiment, the fluorescent element is an organolanthanide complex. Advantageously, the use of an organolanthanide complex enables the material to be marked not to be coloured. The marking is invisible to the naked eye.

Organolanthanide complexes, also called lanthanide complexes, are formed from trivalent lanthanide ions, noted Ln³⁺, and from organic molecules, called ligands. The ligands are for example β-diketonates or carboxylic acids.

Advantageously, emission of the lanthanide complexes is characterised by very thin strips positioned at well-defined wavelengths: each lanthanide complex has its own optic footprint.

It is therefore possible to specifically mark a textile thread with a particular wavelength.

Organolanthanide complexes formed from Ce³⁺ and Gd³⁺ ions emit in the near-UV spectral ranges and enable the textile thread to be marked by a fluorescent element in the near-UV; the complexes formed from Tm³⁺ ions in the blue; the complexes formed from Tb³⁺ and Er³⁺ ions in the green; the complexes formed from Dy³⁺ ions in the yellow; the complexes formed from Sm³⁺ ions in the orange; the complexes formed from Er³⁺ and Eu³⁺ ions in the red, and the complexes formed from Nd³⁺, Er³⁺, Tm³⁺, and Yb³⁺ ions in the near infrared.

It is possible to associate several lanthanide complexes to obtain more complex optic signatures.

Advantageously, the lanthanide complexes are dispersed in homogeneous manner in the textile thread and are invisible to the naked eye. The marking does not modify the appearance of the product. The marking is said to be furtive.

Subjected to a suitable luminous excitation, their fluorescence is detectable by any suitable device. This device can for example be a portable spectrometer. The presence of lanthanide complexes can in particular be detected with inexpensive detectors available on the market.

Preferentially, the organolanthanide complex is a europium complex.

According to another embodiment, the fluorescent element is a phthalocyanine. The use of phthalocyanine makes it possible to obtain both a fluorescent marking and colouring of the thread. The thread can advantageously be used to make a particular pattern, visible to the naked eye, when weaving of the item of clothing is performed.

The phthalocyanine can be a phthalocyanine or a phthalocyanine derivative. In particular, it can be 1,4,8,11,15,18,22,25-Octabutoxy-29H,31H-phthalocyanine, 5,9,14,18,23,27,32,36-Octabutoxy-2,3-naphthalocyanine, 5,9,14,18,23,27,32,36-octabutoxy-2,3-copper naphthalocyanine (II), or 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-nickel phthalocyanine (II).

The fluorescent element is advantageously inserted in the reaction chamber in the form of a powder.

The fluorescent element can be mixed with the fluid or placed beside it in the reaction chamber.

The substrate can be immersed in the fluid at the beginning of the method, or it can be placed beside it.

The fluid is transformed into a supercritical fluid when it is heated to a temperature Ts higher than its critical temperature T_c and when it is compressed at a pressure Ps higher than its critical pressure P_c.

To obtain the supercritical fluid from the fluid, the chamber is therefore heated so as to reach a pressure Ps higher than pressure P_c and a temperature Ts higher than pressure T_c.

The supercritical fluid generally presents a volumetric mass density close to that of the liquid and a viscosity close to that of the gas. The supercritical fluid enables a better diffusion than the corresponding liquid phase. It also enables surface tensions to be reduced.

Preferentially, the fluid is inserted in the chamber in liquid form. According to an alternative it could be inserted in gaseous form.

Otherwise, the fluid could be inserted in the reaction chamber in supercritical state.

The supercritical fluid is advantageously inert with respect to the textile thread.

Preferentially, the fluid inserted into the reaction chamber is carbon dioxide. Even more preferentially it is liquid carbon dioxide.

This is a solvent referred to as “environment-friendly solvent”, i.e. it is non-polluting for the environment. The method involving the use of carbon dioxide does not generate aqueous or organic polluting rejects, which are harmful for the environment.

Preferentially, pressure Ps and temperature Ts are maintained for a duration of at least 15 minutes. This duration enables a homogeneous and continuous coating to be achieved, at least at the surface of the textile thread.

Advantageously, the duration is comprised between 15 minutes and 10 hours. The choice of the duration enables the quantity of fluorescent molecules penetrating into and being fixed in the textile thread to be defined.

Preferentially, pressure Ps is comprised between 100 bars and 400 bars, and even more preferentially between 300 bars and 350 bars.

Preferentially, temperature Ts is comprised between 50° C. and 200° C., and even more preferentially temperature Ts is comprised between 110° C. and 150° C.

These pressure and temperature ranges make it possible to be positioned beyond the critical point of the fluid and to transform the carbon dioxide into supercritical carbon dioxide. Pressure Pc and temperature Tc of the critical point are, for carbon dioxide, respectively 31° C. and 74 bars.

The supercritical fluid is then absorbed by the textile thread: the supercritical fluid penetrates into the fibres of the textile thread. The fluorescent element is drawn into the textile thread by the supercritical fluid.

The supercritical fluid enables the fluorescent element to be trapped in the textile thread: the textile thread is impregnated, marked by the fluorescent element.

Once the textile thread has been impregnated, the pressure and/or temperature are dropped back below the critical fluid point so as to eliminate the fluid absorbed by the textile thread. The pressure and temperature are then reduced until an ambient temperature and pressure are reached.

A textile thread marked by a fluorescent element is obtained. The fluorescent molecules are trapped in the textile thread under ambient temperature and pressure conditions (i.e. around 20-25° C. and 1 bar).

According to a particular embodiment, a solvent is placed in the reaction chamber. Advantageously, the solvent is placed in the reaction chamber before the supercritical fluid is inserted.

The solvent enables the fluorescent element be more easily solubilised. A larger quantity of fluorescent element can be used, which advantageously enables the reaction time necessary for obtaining marking of the textile thread to be limited.

The solvent is preferably an organic solvent. The fluorescent element advantageously presents a better solubility in an organic solvent.

The solvent is advantageously chosen from dichloromethane, ethanol, acetone, tetrahydrofurane and trichloromethane.

The method requires little or no solvents, depending on the embodiments. There are therefore less fluorescent elements lost in the solvent circuit. The effluents do not need to be treated. This point is particularly advantageous as one of the main problems of industries specialised in textiles is processing of residues (Directive 2008/1/EC).

In one embodiment, the method does not require the use of water. The fluid does not contain any water and the solvent does not contain any water.

The method will be described by means of the following examples given for non-illustrative and non-restrictive example purposes only.

For each of the following examples, a textile thread is placed in a tubular reaction chamber equipped with a pressure gauge and a thermometer. The marker, i.e. the fluorescent element, is also inserted in the reaction chamber.

The weight ratio between the textile thread and fluorescent element is comprised between 1% by weight and 20% by weight. Preferentially the weight ratio between the textile thread and fluorescent element is 10%±1%.

At this stage of the method, an organic solvent can also be inserted. It can be inserted by means of a graduated syringe.

The solvent volume is comprised between 0.5 mL and 1 mL.

The reactor is then loaded with liquid CO₂ until a first pressure of 80 bars±20 bars is obtained, i.e. 60 bars to 100 bars.

The reactor is then heated by means of heating element up to a temperature Ts comprised between 50° C. and 200° C. The temperature is chosen according to the required pressure Ps, pressure Ps being comprised between 100 bars and 400 bars.

The CO₂ is then in its supercritical state, i.e. at a higher temperature than the temperature of the critical point Tc of 31° C. and at a higher pressure than the pressure of the critical point Pc of 74 bars, which enables transfer of the fluorescent molecule at the surface and/or in the volume of the textile thread.

The conditions are kept constant during a time t comprised between 15 minutes and 10 h.

After the heating has been stopped, the temperature of the reaction chamber will be progressively reduced to ambient temperature, and the residual pressure is then broken, the pressure being stabilised at ambient pressure, i.e. around 1 bar.

The table below sets out different tests performed.

no	Ts (° C.)	Ps (bar)	Time (h)	Element	PET weight (mg)
1	130	300	0.5	Eu complex	500
2	150	300	2	Eu complex	190
3	110	350	8	Phthalocyanine	300

The phthalocyanine of example no 3 is 1,4,8,11,15,18,22,25-Octabutoxy-29H,31H-phthalocyanine.

Marking of the polymer substrates by the fluorescent element was observed with the naked eye, under an ultraviolet (UV) lamp and by confocal optical microscopy.

FIG. 2 represents a textile thread marked by a europium complex and an unmarked textile thread under daylight and FIG. 3 represents the same textile thread under ultra-violet lighting (UV at 365 nm).

Under ultra-violet lighting, the marked thread is red. The fluorescence in the red is clearly visible. The control sample is not fluorescent.

The emission spectrum of the thread marked by the europium complex was measured with an Ocean Optics portable spectrometer—FIG. 3.

The method enables a textile thread marked by at least one fluorescent element to be obtained.

The fluorescent element is preferentially chosen from phtalocyanines and organolanthanide complexes.

The fluorescent element is advantageously a europium complex.

The textile thread can be marked by several fluorescent elements.

The textile thread comprises between 1% and 88.5% by weight of polyester.

The textile thread is used to weave at least a part of an item of clothing.

The item of clothing comprises at least one textile thread obtained according to the method described in the foregoing.

Advantageously, the marking is incorporated in the item of clothing: it is incorporated in the product and is therefore resistant to tearing and/or to friction, unlike markings made on clothing labels.

This type of marking is also resistant to washing and rinsing. The fluorescent marking enables an authentication throughout the life cycle of the product.

One or more markings can be included in the same item of clothing, thereby enhancing protection of the products.

This type of marking, due to these specificities, is highly secured and particularly difficult to copy. Detection of the marking is easy and it is therefore easy to detect imitations.

Claims

1-17. (canceled)

18. Method for marking a textile thread by a fluorescent element comprising the following successive steps:

placing a textile thread and at least one fluorescent element in a reaction chamber,

introducing a fluid into the reaction chamber,

increasing the temperature and pressure in the reaction chamber up to a temperature, higher than the critical temperature of the fluid, and up to a pressure, higher than the critical pressure of the fluid, so as to transform the fluid into a supercritical fluid and to mark the textile thread by the fluorescent element,

wherein the fluorescent element is chosen from organolanthanide complexes.

19. Method according to claim 18, wherein the supercritical fluid introduced into the reaction chamber is liquid carbon dioxide.

20. Method according to claim 18, wherein the textile thread comprises from 1% to 88.5% by weight of polyester.

21. Method according to claim 20, wherein the polyester is ethylene polyterephtalate.

22. Method according to claim 18, wherein the fluorescent element is a europium complex.

23. Method according to claim 18, wherein the weight ratio between the textile thread and the fluorescent element is comprised between 1% and 20% by weight.

24. Method according to claim 18, wherein the pressure and temperature are maintained during a period of at least 15 minutes.

25. Method according to claim 24, wherein the pressure and temperature are maintained during a period comprised between 15 minutes and 10 hours.

26. Method according to claim 18, wherein the pressure is comprised between 100 bars and 400 bars.

27. Method according to claim 26, wherein the pressure is comprised between 300 bars and 350 bars.

28. Method according to claim 18, wherein the temperature is comprised between 50° C. and 200° C.

29. Method according to claim 28, wherein the temperature is comprised between 110° C. and 150° C.

30. Method according to claim 18, wherein a solvent is placed in the reaction chamber before the fluid is introduced.

31. Method according to claim 18, wherein several fluorescent elements are arranged in the reaction chamber.

32. Textile thread, obtained by means of the method according to claim 18, said textile thread being marked by at least one fluorescent element chosen from organolanthanide complexes.

33. Textile thread according to claim 32, wherein the thread comprises between 1% and 88.5% by weight of polyester.

34. Textile thread according to claim 32, wherein the fluorescent element is a europium complex.

35. Textile thread according to claim 32, wherein the textile thread is marked by several fluorescent elements.

36. A method comprising:

weaving at least part of an item of clothing with a textile thread according to claim 32.

37. Item of clothing comprising at least one textile thread according to claim 32.