EP2328693B1 - Process for automatic identification of an object's material - Google Patents

Description

The present invention relates to a method for the automatic identification of objects or materials, for example plastics. Identification means the extraction of information concerning the material or object, cf. GB-A-2 119 509

This method is particularly applicable to the sorting and recycling of materials from used objects.

Processes are known for the automatic identification of objects or materials consisting in including in these objects or materials low concentrations of substances having specific luminescence properties, irradiating them with the aid of a broad spectrum light beam. frequency, to perform a spectrophotometric analysis of the response of the substances included in the material and to identify them according to these responses, cf. FR-A-2 901 160 .

• l'envoi des ondes transmises ou réfléchies par l'objet ou la matière sur un élément dispersif qui les dévie de manière à obtenir un spectre lumineux de l'intensité lumineuse en différentes zones du spectre correspondant à des plages de longueurs d'ondes différentes,
• la détection de l'intensité lumineuse dans chacune desdites zones,
• la comparaison de cette intensité avec une ou plusieurs valeurs de seuil spécifiquement attribuées à cette zone et qui ont été préalablement enregistrées en mémoire,
• le résultat de cette comparaison contribuant à la détermination du code d'identité de la matière.

In their application No. 06 04578, the Applicants have for example proposed a method in which the spectrophotometric analysis comprises in particular the following steps, after irradiation of the object or the labeled material:

• sending the waves transmitted or reflected by the object or the material onto a dispersive element which deflects them so as to obtain a light spectrum of light intensity in different areas of the spectrum corresponding to different wavelength ranges,
• the detection of the luminous intensity in each of said zones,
• the comparison of this intensity with one or more threshold values specifically assigned to this zone and which have been previously stored in memory,
• the result of this comparison contributing to the determination of the identity code of the material.

However, this method is inherently limited in the ability to encode information about the material because of the uniqueness of the type of excitation. It may be useful to code several types of information concerning a material, for example its composition, its recycling path, its manufacturer.
It is also limited in the case of strongly colored or black materials, which are relatively frequent. The coloration is due to the presence within the material of colored pigments, in particular carbon black, in variable proportions. Carbon black is used as a radiation protector, mainly UV, in outdoor applications or as a stabilizing and reinforcing agent. Its action consists mainly in absorbing the radiation received by the material that can lead to degradation of the polymer chains. However, it also has the property of absorbing radiation that could be emitted in particular in the visible spectrum by the material constituting the object and / or markers included, which explains its dark or black color. As a result, the excitation by a light source does not result in spectral emission making it possible to easily extract information concerning the material with very low concentrations of markers if the latter is strongly colored or black.

The invention therefore more particularly aims to solve this problem with a method for identifying different materials regardless of their color with very low concentrations of markers.

According to the invention, this method comprises the steps according to claim 1.

The method involves subjecting a material or object to a combination of different excitation vectors and no longer just to a light excitation. The excitation vectors can be applied simultaneously or in sequence.

• une étape de sélection d'au moins une substance réagissant à au moins un desdits vecteurs d'excitation en émettant une réponse détectable à distance, lesdites substances étant prévues pour être incorporées au sein ou à la surface de matières sans modifier de façon substantielle les propriétés physiques ou chimiques desdites matières,
• une étape d'élaboration d'une table de correspondance consistant en un ensemble de relations biunivoques entre une combinaison de réponses et une information concernant ladite matière,

et d'une étape de marquage dans laquelle on incorpore sélectivement au moins une substance sélectionnée au sein ou à la surface d'une matière, de façon à rendre active ladite matière ou actifs des objets composés de ladite matière.The identification process is preceded by a phase comprising:

• a step of selecting at least one substance reacting to at least one of said excitation vectors by emitting a remotely detectable response, said substances being intended to be incorporated into the breast or surface of materials without substantially modifying the properties physical or chemical nature of the said materials,
• a step of generating a correspondence table consisting of a set of one-to-one relationships between a combination of responses and information about said subject matter,

and a labeling step in which at least one selected substance is selectively incorporated within or on the surface of a material, so as to activate said material or active objects composed of said material.

• elle garantit que l'incorporation des substances ne modifiera pas les propriétés physiques ou chimiques des matières dans lesquelles elles seront incorporées,
• elle dispense des tests de non toxicité,
• les substances utilisées seront difficilement détectables et notamment invisibles à l'oeil nu,
• le surcoût sera faible.

Les substances pourront être de nature différente :

• des composés chimiques,
• des particules, notamment des nanoparticules, c'est-à-dire des particules ou des structures dont la taille se mesure en nanomètres.

Les substances pourront être noyées dans la masse ou disposés en surface, par exemple par imprégnation (par exemple dans un textile, une teinture...), par enduction (dépôt de vernis, peinture, pulvérisation) sur différents supports, par exemple des pièces métalliques d'aviation, que ce soit sur l'ensemble de la surface ou ponctuellement (sérigraphie, dépôt au tampon), ou sous forme d'étiquettes marquées en partie visible ou non.
Avantageusement, ce revêtement pourra comprendre une zone réfléchissante recouverte d'une couche transparente contenant des marqueurs. Cette technique permet ainsi d'effectuer une spectrophotométrie par réflexion qui réduit considérablement les pertes énergétiques.In this preliminary phase, at least one substance that can be incorporated in materials, for example plastics, is selected at a very low concentration, each substance S _i having a response R _{i, j} at a excitation vector V _j . Each substance does not need to respond to each excitation vector, it is sufficient that it responds to at least one excitation vector.
In the most common case, a substance S _i responds to the excitation vector V _i and there are as many substances as excitation vectors. However, two substances can respond to the same excitation vector provided that their responses are distinct, for example in fluorescence, at different wavelengths. The number of substances used in a material may therefore be greater than the number of excitation vectors. Conversely, the number of substances may be less than the number of excitation vectors in the case where one or more substances would respond to different excitation vectors. The multiplication of the excitation vectors has the advantage of making it possible to appeal to larger families of substances and thus to widen the coding.
The very low concentration used for the substances is essential:

• it ensures that the incorporation of substances will not alter the physical or chemical properties of the materials into which they will be incorporated,
• it provides non-toxicity tests,
• the substances used will be difficult to detect and in particular invisible to the naked eye,
• the extra cost will be low.

The substances may be of a different nature:

• chemical compounds,
• particles, especially nanoparticles, that is to say particles or structures whose size is measured in nanometers.

The substances may be embedded in the mass or placed on the surface, for example by impregnation (for example in a textile, a dye, etc.), by coating (deposition of varnish, paint, spraying) on various supports, for example parts aviation metals, whether on the whole of the surface or punctually (silkscreen, buffer deposit), or in the form of labels marked partly visible or not.
Advantageously, this coating may comprise a reflective zone covered with a transparent layer containing markers. This technique makes it possible to carry out a reflection spectrophotometry which considerably reduces the energy losses.

• la substance S₁ fournit une réponse R_1,1 à l'excitation V₁,
• la substance S₂ fournit une réponse R_2,1 à l'excitation V₁,
• la substance S₃ fournit une réponse R_3,2 à l'excitation V₂,

on obtient 2³ - 1 = 7 combinaisons de réponses possibles, et donc une table de correspondance à 7 entrées.
Plus généralement, l'emploi de n substances de marquage dans une matière (n ≥ 1), soumis à p vecteurs d'excitation (p ≥ 2), en vue d'obtenir r réponses (r ≤ n * p) permet de bâtir une table de correspondance à 2^r - 1 entrées, et donc de coder pour autant d'informations concernant la matière.
On peut donc aboutir à une grande possibilité de codage d'informations concernant une matière ou d'un objet incorporant ces matières en multipliant les vecteurs d'excitation et les substances.Since the responses of the substances to the different excitation vectors are known, it is possible to draw up a correspondence table between combinations of substances and thus of responses to the excitations and the information provided for the materials into which they will be incorporated. For example, if three substances S ₁ , S ₂ and S ₃ and two excitation vectors V ₁ and V _{2 are used} and if:

• the substance S ₁ provides a response R _1,1 to the excitation V ₁ ,
• the substance S ₂ provides a response R _2.1 to the excitation V ₁ ,
• the substance S ₃ provides a response R _3.2 to the excitation V ₂ ,

we obtain 2 ³ - 1 = 7 combinations of possible answers, and thus a 7-input correspondence table.
More generally, the use of n marking substances in a material (n ≥ 1), subject to p excitation vectors (p ≥ 2), in order to obtain r responses (r ≤ n * p) makes it possible to construct a table of correspondence with 2 ^r - 1 entries, and thus to encode for as much information concerning the matter.
It can therefore lead to a great possibility of coding information about a material or an object incorporating these materials by multiplying the excitation vectors and substances.

• on compare lesdites réponses obtenues aux combinaisons de réponses présentes dans ladite table de correspondance,
• on attribue ladite information lorsque ladite comparaison révèle une identité.

In the step of determining information about said material or said object:

• comparing said responses obtained with the response combinations present in said correspondence table,
• said information is attributed when said comparison reveals an identity.

The excitations to which matter is subjected cause one or more responses. These answers are compared with the table of correspondence between expected answers and information on the subject, which allows for example to identify this subject. If no answer is obtained, or if the answer obtained is not in the correspondence table, it will not be possible to assign information about the subject.

In the correspondence table development step, only the presence or absence of a substance response to the excitation vectors and / or the intensity of a response can be taken into account. of substance, for example in the form of a plurality of response thresholds.

It is also possible to take into account the spontaneous emission of a selected substance in the absence of an excitation vector, for example in the form of spontaneous emission of electromagnetic radiation or of particles, neutral or charged, in particular in the case of the radioactivity, or emission of molecules, including odoriferous.

Advantageously, it is possible, in the detection step, to take into account the emission of the material under the effect of the excitation vectors, in particular to correct the responses obtained, for example to subtract the background noise.

• excitation électromagnétique, notamment une excitation optique, par exemple un faisceau lumineux à large spectre de fréquence, dans l'infra-rouge ou les UV, les rayons X,
• excitation électrique, par exemple sous la forme de l'application d'un champ électrique,
• excitation magnétique, par exemple sous la forme de l'application d'un champ magnétique,
• excitation thermique,
• excitation par flux de particules, notamment d'électrons.

A large number of excitation vectors can be envisaged:

• electromagnetic excitation, in particular an optical excitation, for example a light beam with a broad frequency spectrum, in the infra-red or the UV, the X-rays,
• electrical excitation, for example in the form of the application of an electric field,
• magnetic excitation, for example in the form of the application of a magnetic field,
• thermal excitation,
• excitation by flow of particles, in particular electrons.

• émission électromagnétique, notamment une émission lumineuse, fluorescence (visible, X, UV) ou phosphorescence,
• variation de champ magnétique,
• variation de champ électrique.

Comme indiqué plus haut, ces réponses sont détectables à distance.Advantageously, the expected responses from the substances and the responses obtained are chosen from the list comprising:

• electromagnetic emission, in particular light emission, fluorescence (visible, X, UV) or phosphorescence,
• magnetic field variation,
• electric field variation.

As noted above, these responses are detectable remotely.

• dans l'étape de marquage, on marque les matériaux ou objets avec un marqueur comportant du vanadate d'Yttrium dopé Europium, à une concentration inférieure à 200 ppm, voire inférieure à 100 ppm,
• dans l'étape d'excitation, on applique à la matière ou l'objet une excitation électromagnétique dans la gamme comprise entre 230 et 390 nm, préférentiellement 330-340 nm,
• dans l'étape de détection, on effectue une détection dudit marqueur dans une bande centrée sur 610-620 nm et une mesure de l'intensité du pic correspondant.

Advantageously:

• in the marking step, the materials or articles are marked with a label comprising Europium doped yttrium vanadate, at a concentration of less than 200 ppm, or even less than 100 ppm,
• in the excitation step, an electromagnetic excitation is applied to the material or the object in the range between 230 and 390 nm, preferably 330-340 nm,
• in the detecting step, detecting said marker in a band centered at 610-620 nm and measuring the intensity of the corresponding peak.

Europium-doped Yttrium vanadate excited between 230 and 390 nm, that is to say in the near UV, used alone or in combination with other markers, provides a response centered on 610-620 nm exploitable in the materials. black or strongly colored.
When a dark or strongly colored material is excited in the near UV, a relatively large background noise is observed which requires signal processing, for example to form a baseline, so as to extract and quantify the responses. When Europium-doped Yttrium vanadate is used in combination with another marker, one of them can be used as calibration, then one works in differential.

The method makes it possible to collect one or more information concerning a substance or an object, for example a chemical property, in particular its chemical composition and thus to identify the substance under examination or its quality (type, grade). The information may also concern the manufacture of the material or the object, for example the identity of its manufacturer, its place or date of manufacture ...
We thus go from the simple identification of a subject or an object to its authentication, ie to be able to distinguish an authentic object from an unauthorized copy, for example in the fight against counterfeiting .

Due to its general nature, the process is applicable to all types of materials, especially black or highly colored materials, which absorb a wide range of radiation.

In the case of excitation by light beam, the identification data may comprise the combination of selected markers, the wavelengths of the characteristic lines, their intensity, the duration of a possible fluorescence ...
Thus, it is not necessary to observe all the wavelengths emitted by the material, it is sufficient to analyze the ranges of values corresponding to the lines provided in the correspondence table, previously stored in memory, in order to verify their presence or absence without worrying about areas outside these rays.

The identification code may result from a combination of markers and may consist of a binary number whose binary digits each correspond to the presence or absence of a marker.

• sur la voie de valorisation, de recyclage, de rejet ou élimination, cette voie pouvant être commune pour des matériaux de compositions différentes et pouvant évoluer dans le temps,
• sur le fait de savoir si la matière possède une propriété particulière, par exemple s'il s'agit d'une matière première secondaire, c'est-à-dire déjà recyclée.

In the case of identification for material recycling, it may be possible to use this combination of markers to code the type or grade of materials, eg plastics, which can be sorted by type or grade. once the identification is made. The code can also carry:

• on the way of recovery, recycling, rejection or elimination, this way being able to be common for materials of different compositions and being able to evolve in the time,
• on whether the material has a particular property, for example if it is a secondary raw material, that is to say, already recycled.

By extension, the combination of several excitation vectors and markers can make it possible to obtain several pieces of information of different natures on a material, for example the authentication of one or more actors in the life cycle of a material or material. an object (manufacturer, distributor, owner ...); for this purpose, it suffices that the material incorporated in the object has been previously marked according to one or more actors involved in the life cycle of a material or an object and not only of its composition.

• au tri de matériaux ou d'objets,
• au recyclage de matériaux ou d'objets,
• à la traçabilité de matériaux ou d'objets,
• au contrôle qualité, par exemple la vérification qu'un lot de matériaux déjà triés correspond bien à la composition annoncée, de façon à optimiser les opérations de recyclage.

The method is therefore applicable:

• sorting materials or objects,
• recycling materials or objects,
• traceability of materials or objects,
• the quality control, for example the verification that a batch of already sorted materials corresponds to the composition announced, so as to optimize the recycling operations.

The method is applicable to the identification of any type of material, especially materials of any color, more or less dark; it is particularly applicable to the identification of colored or black materials.

• La figure 1 représente des courbes de fluorescence naturelle de trois composés plastiques ;
• La figure 2 représente des courbes de fluorescence de polypropylène noir, avec différentes concentrations de marqueur.

Examples of markers suitable for new plastics will be described below, by way of non-limiting examples with reference to the accompanying drawings in which:

• The figure 1 represents natural fluorescence curves of three plastic compounds;
• The figure 2 represents fluorescence curves of black polypropylene, with different concentrations of marker.

The figure 1 represents the fluorescence intensity curves of three unmarked plastic compounds, Acrylonitrile Butadiene Styrene (ABS, Curve 1), Polypropylene (PP, Curve 2) and Pigmented Polypropylene Black (Curve 3), ABS and PP being two commonly used materials. The illumination is produced by means of a UV-TOP light emitting diode (LED) operating at about 330 nm, i.e., in the near UV, with a nominal output power of 1 mW and the spectra are obtained with FluoroMax ® fluorescence spectrometer.

• que l'intensité de fluorescence naturelle de l'ABS et du PP diminue dans la région du rouge et du proche infra-rouge (λ > 500 nm),
• que l'intensité de fluorescence du PP pigmenté de noir est constante dans le domaine entier visible et proche IR, mais avec une intensité de plus de deux ordres de grandeur inférieure à celle des échantillons non pigmentés.

We aknowledge :

• that the natural fluorescence intensity of ABS and PP decreases in the region of red and near infra-red (λ> 500 nm),
• that the fluorescence intensity of the black pigmented PP is constant in the entire visible and near-IR domain, but with an intensity of more than two orders of magnitude lower than that of the unpigmented samples.

• marqueur H : deux pics d'émission à 614 et 618 nm,
• marqueur I : un pic d'émission à 515 nm.

In view of this weak intrinsic response of these materials in the red and near-IR range on the one hand, and the uniformly weak response of the black pigmented material, it is deduced that it may be advantageous to use markers which , after irradiation of the marked object or material, emit radiation in a frequency band corresponding to the red - near infrared.
Advantageously, one will choose markers that have a response in the range of 500 to 650 nm.
Given the Stokes shift, the irradiation must take place in a range of lower wavelengths, for example in the near UV, in the range 220 to 380 nm.
The markers used may be chemical, organic or mineral, or composed of nanoparticles. These may be made-to-order products or commercial products.
It is possible, for example, to use markers sold by "Phosphor Technology Dyes" (registered trademark), the characteristics of which are as follows:

• H marker: two emission peaks at 614 and 618 nm,
• marker I: an emission peak at 515 nm.

These markers also have the advantage of having good thermal and chemical stability, as well as good UV resistance.

• on utilisera une source d'excitation de forte puissance, typiquement une lampe à arc au Xénon, une LED UV ou un laser ;
• on procédera à l'amplification du signal correspondant auxdites intensités lumineuses transmises ou réfléchies ;
• on effectuera un traitement du signal correspondant auxdits rayonnement émis en vue de réduire le bruit de fond, en particulier par l'exploitation du niveau des pics caractéristiques du ou des marqueurs.

To obtain a signal that identifies the material:

• a high power excitation source will be used, typically a Xenon arc lamp, a UV LED or a laser;
• the signal corresponding to said transmitted or reflected light intensities will be amplified;
• the signal corresponding to said emitted radiation will be processed in order to reduce the background noise, in particular by exploiting the level of the characteristic peaks of the marker or markers.

The figure 2 illustrates the results obtained with a Xenon arc lamp and a FluoroMax ® fluorescence spectrometer, in the case of black polypropylene marked with the H marker, at two different concentrations, 200 ppm (curve 1) and 100 ppm (curves 2 and 3 ). It is found that the two characteristic peaks of the H marker clearly stand out from the background noise at 614 and 618 nm, thus allowing its identification and thereby the identification of the material in which it is included, even when it is black.

Claims (14)

1. Method for identifying and/or authenticating a material or an object, particularly with a view to sorting materials or objects, comprising:

   - an excitation step comprising the application to a material or to an object of a plurality of excitation vectors (V_j, j = 1 to p),

   - a step for detecting the responses (R1, R2, R3, etc.) of the materials or objects subject to said excitation vectors (V_j, j = 1 to p),

   - a step for determining at least one item of information relating to said material or said object on the basis of said responses obtained (R1, R2, R3, etc.) and a predefined correspondence table, characterised in that it comprises:

   - a preliminary phase comprising:

   - a step for selecting at least one substance (S_i, i = 1 to n) reacting to at least one of said excitation vectors (V_j, j = 1 to p) by transmitting a remotely detectable response (R_i,j, i = 1 to n, j = 1 to p), said at least one substance being envisaged for being incorporated within or on the surface of materials without substantially modifying the physical or chemical properties of said materials,

   - a step for preparing a correspondence table consisting of a set of biunivocal relations between a combination of responses (R_i,j, i = 1 to n, j = 1 to p) and an item of information relating to said material,

   - a labelling step wherein at least one selected substance (S_i, i = 1 to n) is incorporated selectively within or on the surface of a material, so as to render said material or the objects consisting of said material active,

   and wherein, in the step for determining a information relating to said material or said object:

   - said responses obtained (R1, R2, R3, etc.) are compared to the combinations of responses (R_i,j, i = 1 to n, j = 1 to p) found in said correspondence table,

   - said information is assigned when said comparison reveals an identity.
2. Method according to claim 1, characterised in that, in the step for preparing a correspondence table,
   account is taken of only the presence or absence of a response of substance (S_i, i = 1 to n) to said excitation vectors (V_j, j = 1 to p),
   or,
   account is taken of the intensity of a response of substance (S_i, i = 1 to n) to said excitation vectors (V_j, j = 1 to p)
   and/or
   the spontaneous emission of a selected substance (S_i, i = 1 to n).
3. Method according to any of claims 1 or 2, characterised in that the step for detecting responses, the response of the material under the effect of said excitation vectors (V_j, j = 1 to p) is taken into account, particularly for correcting the responses obtained (R1, R2, R3, etc.).
4. Method according to any of claims 1 to 3, characterised in that:

   - in the labelling step, the materials or objects are labelled with a marker comprising Europium-doped Yttrium vanadate, at a concentration less than 200 ppm,

   - in the excitation step, an electromagnetic excitation in the range between 230 and 390 nm is applied to the material or object,

   - in the detection step, said marker is detected in a band centred on 610-620 nm and the corresponding peak intensity is measured.
5. Method according to any of the above claims, characterised in that the information relating to said material is a chemical property, particularly the chemical composition thereof.
6. Method according to any of the above claims, characterised in that the information relating to said material relates to the production thereof.
7. Method according to any of the above claims, characterised in that said material is black or has a strong colour.
8. Method according to any of the above claims, characterised in that the substance incorporated during the labelling step is a chemical marker which, after irradiating the labelled object or material, emits radiation in a frequency band corresponding to the red-near-infra-red band, preferably such that said marker emits radiation in the range from 500 to 650 nm and/or that the labelled object or material is irradiated in the range from 220 to 380 nm.
9. Method according to claim 8, characterised that said spectrophotometric analysis further comprises the following steps:

   - amplifying the signal corresponding to said transmitted or reflected light intensities,

   - processing the signal corresponding to said emitted radiation with a view to reducing the background noise.
10. Method according to any of the above claims, characterised in that it further comprises, prior to the excitation step, a step for grinding the objects in particle form and in that it is applied to said particles.
11. Application of the method according to any of the above claims, for sorting materials or objects.
12. Application of the method according to any of claims 1 to 10 for recycling materials or objects.
13. Application of the method according to any of claims 1 to 10 for authenticating at least one participant in the life cycle of a material or an object.
14. Application of the method according to any of claims 1 to 10 to the traceability of materials or objects, and/or to the quality control of materials or objects.

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