WO2002028954A1

WO2002028954A1 - Substance containing plastic, glass, textiles or paper, provided with a nir tag and a method for identifying said substance

Info

Publication number: WO2002028954A1
Application number: PCT/EP2001/010274
Authority: WO
Inventors: Hans-Jürgen BACH; Wolfgang Holley
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2000-10-05
Filing date: 2001-09-06
Publication date: 2002-04-11
Also published as: DE10049404A1; DE10049404C2

Abstract

The invention relates to a method for identifying substances containing plastic, glass, textiles or paper using NIR spectrometry, by means of the characteristic absorption property of tagging substances, which are applied to the substances during their treatment process. The property is based on at least one dominant band in the NIR absorption spectrum, which can be spectrally identified even when superimposed with the NIR absorption spectrum of the substance and the materials associated with said substance.

Description

Plastic, glass, textile or paper-containing material provided with an NIR marker and method for identifying this material

The invention is based on a method for identifying materials with NIR spectrometry on the basis of the characteristic absorption behavior of marker substances which are added to the materials during the processing process. The characteristic is based on at least one dominant band in the NIR absorption spectrum.

Spectro etrical methods are increasingly used in process analytics as detection techniques in material flow systems and in process engineering. They often provide material parameters that serve as a signal for recognizing the presence or absence of certain materials or objects in the process or as separation criteria in sorting and separating processes. Spectral (separation) criteria In addition to conventional criteria (e.g. mass density, particle size, (electro-) magnetic properties), they are established and enable, for example, the automated separation of mixtures of substances that cannot be separated using conventional criteria or detection methods (e.g. processing in mining: detection and separation of the target mineral by dyeing - or absorption band detection on the rock particles).

Under process technology conditions, NIR spectrometers have proven to be very reliable, robust detection systems for generating process measurement, control, regulation and monitoring signals (see Converter 33 (5), (1996), 7-8). Corresponding process spectrometers and the sorting units based on them have been state of the art in plastic sorting for a few years, e.g. for the purpose of waste treatment.

Spectro etrical detection methods always find their limits where substances with a similar spectral "fingerprint" are to be distinguished quickly and with little error. The possibility of using labeling substances with dominant NIR spectral properties is known in one case from the patent literature. US 5,397,819 and US 5,461,136 describe the use of organic NIR fluorophores for marking plastics. However, the use of these NIR-active markers is limited to covalently integrating the NIR fluorophore into the polymer backbone or to distribute (i.e., dissolve) it in a molecularly dispersed manner in the polymer. In addition, the detection of the marker is limited to NIR fluorescence spectrometry.

Plastics are often components of more complex ones Mixed waste / even pure plastic waste generally consists of several types of plastic (PE, PP, PS, PVC, etc.) and almost always of different types of plastic. Plastic grades are differently borrowed additives that are made of the same polymer. Common organic-based plastic additives (such as plasticizers, lubricants, antioxidants, UV absorbers, dyes, etc.) in the amounts usually used show only low NIR spectral signals. They are generally also lacking other properties that can be determined process-analytically with reasonable effort. To make matters worse, the abundance of plastic additives available on the market and the requirement profiles for plastics mean that there is an almost unmanageable combination of additives in different proportions in the different types of plastic. For this reason, plastics can only be detected with specific diagnostic effort, if at all, with considerable diagnostic effort. No solutions are known for quick (real-time) detection in the context of process engineering or material flow processes. In particular, no marking substances or methods are known which support the desired detections for plastics in a technically applicable manner. In any case, this applies to the process-analytically important area of NIR detection in reflection or absorption mode. The NIR detection used today only leads to the detection of plastic species (with a species purity of approx. 80 to 90% in the positive sort)

Fraction), but not to differentiate between different types of plastic.

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The marking according to the invention is particularly advantageous when materials or objects are to be recognized or differentiated which do not have a characteristic or sufficiently distinguishable absorption or reflection spectrum in the NIR range. A further advantage is that materials or objects marked according to the invention can also be recognized by their NIR spectrum if this spectrum is overlaid by substances that are adhering or mixed with the materials or objects.

By using several markers according to the invention, more than one type of material or type of objects marked according to the invention can be recognized in parallel and also differentiated from one another. If more than one marker is used according to the invention on the same material or the same object, more complex information can also be stored in the material or on the object and recognized by means of NIR in the process, e.g. the date of manufacture, the intended application or the recipient of the material or object, its material composition, etc.

The detection of the marker is also possible if the base material has absorptions in the area of the marker, since the markers to be used according to the invention have much more intense signals (ie a larger absorption coefficient) than all additives / additives normally used in plastics processing. The dominant band can be clearly recognized spectrally even in the case of an overlay with the NIR absorption spectra of the material and the substances associated with the material. Preferably, the NIR marker comprises at least one dominant-NIR absorption band having a half width of each less than 400 cm ^-1, more preferably less than 150 cm ^"1, comprising.

We have so far found markers with the properties necessary for carrying out the invention in some mineral substances. Certain minerals have very characteristic NIR spectral properties, which can also be superimposed on the NIR

The spectra of many other substances dominate. Their dominant NIR spectral fingerprint is based on signals that originate from water molecules that are firmly bound components of the mineral and that only vibrate in preferred spatial directions when excited with NIR light; this corresponds to the fact that such a substance has a very high absorption signal (= large molar absorption coefficient) in the NIR over a narrow wave number range.

Examples of minerals with a NIR spectrum suitable for the use according to the invention are talc, kaolin and basic magnesium carbonate. Additional selection criteria for a marker substance are the heat resistance / physicochemical stability including structural stability of the marker with regard to the processing conditions when doping a material or when applying the marker to an object, as well as physical properties of the powders that can be produced from such minerals (agglomeration behavior, dispersing agent - hold in carriers, compatibility with materials, etc.).

In particular, the marking according to the invention can be used as a dopant on various materials, preferably on all types of synthetic thermoplastics, thermosets, elastomers and composite materials and articles made therefrom, by including the NIR marker in the matrix formed from the material. However, this is not a covalent attachment of the marker to the polymer. It is also applicable to biopolymers such as starch, proteins, cellulose and their chemical modifications, polylactic acid, polycaprolactone and other biodegradable polymers of native or synthetic origin.

The NIR marker is preferably applied to the material in the form of a coating, the coating e.g. can be applied in the form of a varnish, an adhesive or other adhesion promoter.

The marker substance according to the invention can also be part of one or more layers in a composite structure (e.g. composite foil, object made from composite foil) or it can be introduced between the layers of a composite.

The marking according to the invention is applicable to all objects on the surface of which the marker according to the invention can be applied by means of a suitable carrier.

The method according to the invention is based on using dominant NIR spectral properties of certain NIR-active substances in order to use it to mark materials made of plastic, glass or paper-containing materials or composite materials therefrom

NIR spectrometric methods to recognize tral. The purpose of the recognition is to distinguish materials or objects marked according to the invention from materials or objects not marked or otherwise marked or to be able to automatically detect the presence or absence of the material or object marked according to the invention in process engineering processes or in material flow systems.

The procedure according to the invention is such that a substance is added to the material during the processing process which has at least one dominant band in the NIR absorption spectrum, which also overlaps with the NIR absorption spectra of the material and that associated with the material

Substances is spectrally recognizable, or after the processing is completed, this substance is attached to the material. This material can then e.g. in separation or sorting processes based on the characteristic absorption behavior of the NIR marker can later be identified with NIR spectrometry.

The detection by an “NIR eye” serves in particular to generate an (electrical or other) signal which indicates the presence or absence of a specific material or a specific type of objects in a process or at a specific point in the process. Such signals can be used, for example, for the solution of monitoring, control and regulating tasks in the context of process control technology. In particular, such signals provide control and regulating criteria for sorting and separating processes in process engineering. This is a clear advantage over the current state of the technique. ω cυ t \ _> t \) ono Cn O n

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the, e.g. marking plastics in the course of the production of granules,

The application of the powdery marker in at least one layer in the case of layered composite materials or objects constructed from a composite, including the insertion of the marker between at least two layers of the composite,

The surface treatment of the material in the form of a coating containing the marker or consisting of the marker, which e.g. is applied by means of PVD or CVD processes, it also being possible to coat on a carrier material which is subsequently connected to the material,

• the application of the powdered marker. in the course of painting, printing or labeling processes,

The application of the marker together with a coated or uncoated flat carrier, e.g. a label that is applied to the material or object to be marked.

The spectrometric principle to be used in accordance with the invention to detect this property is based on the recording and evaluation of the specific absorption and / or the reflection of non-absorbed radiation in the wavelength range of the near infrared. Detection is usually carried out in reflection mode. NIR process spectrometers required for this are state of the art.

The uses of the method according to the invention can be illustrated using the following exemplary cases: 1) A material doped by manufacturer A according to the invention can be distinguished according to its origin compared to the same materials that come from other manufacturers. 2) A material compound that differs chemically only structurally or in terms of minor components in its additives from other compounds of the same material can be identified with the aid of the marking according to the invention and separated by sorting from mixtures according to this. This is the most important prerequisite for the production of high-quality recyclate from the corresponding material waste. 3) The bottler A uses a marker according to the invention for the plastic beverage bottles he uses (for example as a component of the printing ink for barcode printing, with which each bottle is provided in the course of the filling process) in order to “his” bottles in the course of the retribution be able to identify and sort them in returnable packaging or for bottler-specific recycling measures in the one-way packaging area. The marking according to the invention could be used in the future when sorting out certain qualities of the packaging plastic polyethylene terephthalate (PET) from post-consumer packaging waste: Here, a "high quality" recycling pool could be formed, the bottlers subject to disposal under certain conditions (bottle material Criteria) (keyword: "marking license"). PET is predicted to have a large market potential for plastic beverage bottles - however, consumer acceptance of the material will be high Dimensions depend on a recognized high quality recycling of PET.

An example of the method is shown in the following example.

Example 1:

10 to 50% by weight of talc are stirred into a quantity of acrylic-based clearcoat to the point of optical homogeneity. A small amount of the paint formulation thus obtained is applied with a brush to the outer surface of a commercially available 1.51 PET bottle. After the lacquer has dried at room temperature, detection is carried out using an FT-NIR spectrometer in reflection mode using a quartz glass fiber probe. It will be a flash of light

(1 scan) is radiated onto the marking and the spectral composition of the reflected light is analyzed. The result, a "1-scan spectrum", is shown in FIG. 1. This is the NIR spectrum of a PET bottle marked with talc-containing acrylic lacquer

(a) compared to the individual NIR spectra of acrylic paint (b), PET (c) and talc (d). The result of the measurement can be converted into a standardized signal by the spectrometer computer and fed into the control of a sorting system via an I / O card.

2 shows a section of the NIR spectra of three suitable markers: talc (a), basic magnesium carbonate (b) and kaolin (c)

Claims

claims

1. A plastic, glass, textile or paper-containing material or composite material provided with an NIR marker, containing at least one component with at least one dominant band in the NIR absorption spectrum, which can also be superimposed on the NIR

Absorption spectra of the material and the substances associated with the material can be detected spectrally.

2. Material according to at least one of the preceding claims, characterized in that the

NIR marker has at least one dominant absorption band with a half width of less than 400 cm ^-1 each.

3. Material according to at least one of the preceding claims, characterized in that the

NIR marker has at least one dominant absorption band with a half width of less than 150 cm ^-1 each.

4. Material according to at least one of the preceding claims, characterized in that the

NIR marker is mineral.

5. Material according to at least one of the preceding claims, characterized in that the NIR marker is selected from the group kaolin, talc and basic magnesium carbonate or mixtures thereof.

6. Material according to at least one of the preceding claims, characterized in that the NIR marker is enclosed in a matrix formed by the material.

7. Material according to at least one of the preceding claims, characterized in that the NIR marker is applied as a coating on the material.

8. Material according to claim 7, characterized in that the coating has the function of

Lacquer, an adhesive, a printing ink, a primer or an adhesion promoter.

9. Material according to at least one of the preceding claims, characterized in that the material is constructed as a layer-like composite and the NIR marker is contained in at least one layer.

10. Material according to claim 9, characterized in that the NIR marker is contained in at least one space between two layers.

11. Material according to at least one of the preceding claims, characterized in that a carrier containing the NIR marker can be fastened to the material.

12. A method for identifying plastic, glass or paper-containing materials or composite materials thereof with NIR spectrometry, where

a) during the processing process, the material as NIR marker at least one component nente with at least one dominant band in the NIR absorption spectrum, which is spectrally recognizable even when superimposed with the NIR absorption spectra of the material and the substances associated with the material, is added or is attached to the material after completion of the processing process and

b) the material based on the characteristic absorption behavior of the NIR marker with the

NIR spectrometry is identified.

13. The method according to claim 12, characterized in that a mineral component is added as the NIR marker.

14. The method according to at least one of claims 12 or 13, characterized in that the NIR marker is added in powdery consistency.

15. The method according to at least one of claims 12 to 14, characterized in that the NIR marker is built into the material matrix.

16. The method according to at least one of claims 12 to 15, characterized in that as a material

Plastic is used and the NIR marker is added to it in the molten state.

17. The method according to at least one of claims 12 to 16, characterized in that a composite material with a layer structure of is selected in which the marker is added in at least one layer.

18. The method according to at least one of claims 12 to 17, characterized in that as a material

Composite material with a layer structure is selected in which the marker is added in at least one space between two layers.

19. The method according to at least one of claims 12 to 18, characterized in that the material is completely or partially coated by surface treatment, the coating containing the marker substance.

20. The method according to at least one of claims 12 to 19, characterized in that the surface treatment is carried out by means of CVD or PVD.

21. The method according to at least one of claims 12 to 20, characterized in that the surface treatment is carried out by means of painting or printing processes.

22. The method according to at least one of claims 10 to 18, characterized in that a carrier containing the NIR marker is attached to the material by means of an adhesive or adhesion promoter.

23. The method according to at least one of claims 12 to 22, characterized in that the NIR marker is attached to the material with a label as a carrier.

24. Use of the method according to at least one of claims 12 to 23 for the identification of

Materials in separation and sorting processes.

25. Use of the method according to at least one of claims 12 to 23 for the detection of a material in a process engineering process or in a material flow system.

26. Use of the method according to at least one of claims 12 to 23 for identifying the authenticity or originality of documents, banknotes or objects or for demonstrating copyright infringement or unlawful

Taking possession.