EP3497431A1

EP3497431A1 - Device and method for identifying substances of a material by means of spectroscopy

Info

Publication number: EP3497431A1
Application number: EP17761796.6A
Authority: EP
Inventors: Dirk Fey; Juergen Bohleber; Gunther Krieg
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-08-09
Filing date: 2017-08-02
Publication date: 2019-06-19
Also published as: DE102016214792A1; WO2018028752A1

Abstract

The invention relates to a device (1) for identifying substances of a material by means of spectroscopy, comprising a laser (2) for irradiating a sample (3) of said material with light of at least one wavelength, a detector (6) for detecting the light re-emitted by the sample, and an analysis device for the spectroscopic analysis of the detected light, said laser being a pulsed laser having a pulse duration in the picosecond range or even shorter.

Description

DEVICE AND METHOD FOR IDENTIFYING SUBSTANCES OF A MATERIAL USING SPECTROSCOPY

The present invention relates to a device for identifying substances of a material, in particular of plastics and their additives, by means of spectroscopy, comprising a laser for irradiating a sample of the material with light having at least one wavelength, a detector for detecting the light re-emitted by the sample and an analysis device for the spectroscopic analysis of the detected light.

The invention further relates to a method for the identification of substances of a material, in particular of plastics and their additives, wherein by means of a laser, a sample of the material is irradiated with light of at least one wavelength and the re-emitted light from the material is detected, wherein the detected light spectroscopically is analyzed.

Although applicable to any materials and materials, the present invention will be explained with reference to plastics.

Although applicable in any field, the present invention will be explained in terms of recycling of fabrics.

The recycling of plastics has recently become increasingly important. Plastic waste already has a significant impact on the environment, be it due to the pollution of water bodies or the ever increasing amount of plastic waste. One solution to the problem is plastic recycling, which converts existing substances, ie plastics that have been processed into products that are no longer needed, into valuable substances, ie substances that are suitable for reprocessing in products. This can then be spared the resources required for the production of plastics. For the detection and identification of plastics, various optical methods have become known, for example from EP 198 16 881 B4. Here, among other things, continuously radiating lasers were used for the irradiation. A disadvantage, however, is that a reliable identification of substances and / or their additives was only possible to a limited extent, since the resolution and selectivity of the spectra obtained by means of the irradiation of the samples with laser light was quite low. It is therefore an object of the present invention to provide a method and an apparatus for identifying substances which enables a more accurate, selective and reliable identification of substances. In addition, it is an object of the invention to provide an alternative method and an alternative apparatus for identifying substances and / or their additives.

The invention solves the above-mentioned objects in a device for the identification of substances of a material by means of spectroscopy, in particular of plastics and their additives, comprising a laser for irradiating a sample of the material with light having at least one wavelength, a detector for detecting the of the sample re-emitted light and an analyzer for spectroscopic analysis of the detected light, in that the laser is a pulsed laser having a pulse duration in the range of picoseconds or an even shorter pulse duration.

The present invention also achieves the abovementioned objects in a method for identifying substances of a material, in particular of plastics and their additives, wherein a sample of the material is irradiated with light of at least one wavelength by means of a laser and the light re-emitted by the sample is detected in which the detected light is analyzed spectroscopically by irradiating the sample with pulsed light from the laser, the pulsed light having a pulse duration in the range of picoseconds or an even shorter pulse duration. The present invention also achieves the aforementioned objects by using pulsed laser light having pulse durations in the range of picoseconds or even shorter pulse durations for irradiating material, in particular plastics and their additives, whose re-emitted light is analyzed spectroscopically.

The present invention also achieves the objects mentioned above by using pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for irradiation of material to be identified, in particular of plastics and their additives, for recycling purposes.

The present invention also achieves the abovementioned objects by using pulsed laser light having pulse durations in the range of picoseconds or even shorter pulse durations for irradiating polymers, in particular plastics and, if appropriate, their additives and / or impurities, for their identification.

The present invention also achieves the abovementioned objects by using pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for fluorescence analysis, in particular for analyzing the fluorescence decay time and / or fluorescence lifetime.

The present invention also achieves the above-mentioned objects by using a pulse laser with pulse durations in the range of picoseconds or even shorter pulse durations for irradiating material whose re-emitted light is analyzed spectroscopically to identify the material, in particular by means of a fluorescence lifetime analysis. One of the advantages achieved with this is that, when irradiated with pulsed light, in particular in the picosecond range, a better spectral resolution of the spectrum of the light re-emitted by the sample can be achieved, thus, for example, for subsequent Raman spectroscopy or fluorescence spectroscopy, which results in reliability and selectivity of identification also of significantly improved chemically similar substances. In addition, the flexibility in terms of the applicability of the device or the method in various areas are substantially increased. A further advantage is that in this way the duration of the excitation hardly influences the subsequent detection of the re-emitted light of a sample.

A detector is to be understood in particular in the description, preferably in the claims also a Dektorarray or the like. Pulse durations in the range of femtoseconds, attoseconds, etc. are to be understood as being even shorter pulse durations with regard to the picosecond range, in particular in the claims, preferably in the description. In particular in the claims, preferably in description, the femtosecond range is understood to mean the range between 0.1 fs and 500 fs, in particular the range between 1 fs and 100 fs, preferably the range between 2.5 fs and 50 fs , in particular the range between 4 fs and 10 fs, preferably the range between 5 fs and 8 fs, for example 5, 6, 7 and / or 8 fs. In particular in the claims, preferably in description, the range of the atto seconds is to be understood as meaning the range between 0.1 as and 500 as, in particular the range between 1 as and 100 as, preferably the range between 2.5 as and 50 as , in particular the range between 4 as and 10 as, preferably the range between 5 as and 8 as, for example 5, 6, 7 and / or 8 as. The term "material" is given in particular in the claims, preferably in the description or to understand more than one substance.

The term "substance" is to be understood in particular in the claims, preferably in the description, as any kind of solid, liquid or gaseous substance. In particular, the term "substance" is understood to mean any type of polymer or polymer, in particular plastics, for example

any type of silicone or silicone polymer, in particular silicon tectosilane granulate, silicone tectosil film, silicone adhesive Sn, silicone adhesive Pt, any type of silicone hose, etc., any type of polyethylene PE, such as LDPE, HDPE and UHDPE,

Polymethylmethacrylate PMMA,

- polystyrene PS,

- polyvinyl chloride and its derivatives,

- polycarbonate PC,

- polyethylene terephthalate PET.

The term "additive" is to be understood in particular in the claims, preferably in the description, any intentional or undesired additions to a substance or substances, in particular flame retardants, preferably halogenated, in particular brominated and / or chlorinated flame retardants, for example comprising

- polybrominated diphenyl ether PDBE,

- polybrominated biphenyl PBB,

decabrominated diphenyl ether,

- pentabrominated diphenyl ether,

octabrominated diphenyl ether,

- hexabromocyclododecane,

Tetrabromobisphenol A TBBP-A,

- tetrabromophthalic anhydride,

- brominated polystyrenes,

- brominated phenols,

- reactive flame retardants,

- antimony trioxide,

- antimony pentoxide,

Ammonium sulfate,

The term "additive" is to be understood in particular in the claims, preferably in the description, not marking substances, so-called "markers" which are added to a polymer, for example a plastic for its identification and in particular later, for example by means of fluorescence analysis to identify the plastic provided therewith. Further features, advantages and further embodiments of the invention are described below or disclosed by the following:

Preferably, the time interval between two pulses of the laser is substantially at least one order of magnitude, preferably at least two orders of magnitude, in particular three orders of magnitude above the pulse duration. Thus, in a most efficient manner, re-emitted light from a sample can be measured after excitation for a significantly longer time than the excitation time, for example, a factor of 100, 1,000 to 10,000, etc., for a longer time. Thereby, the reliability for the identification can be further increased by the spectroscopic analysis of re-emitted light of the sample. For example, if the laser provides a pulse duration in the range of picoseconds, the time interval between two pulses in the nanosecond range is selected. Conveniently, the re-emitted light is substantially detectable between two pulses of the laser. This makes it possible to easily realize a plurality of sequential excitations and measurements of the re-emitted light of a sample. This also further increases the reliability of the spectroscopic analysis, as it allows several measurements to be carried out in a very short time. These may then be averaged, for example, to produce a less erroneous spectroscopic analysis result, e.g. by increasing the signal-to-noise ratio.

The spectroscopic analysis expediently comprises a fluorescence spectral analysis and / or a fluorescence lifetime analysis. By means of a fluorescence spectral analysis or a fluorescence lifetime analysis, in particular, plastics can be distinguished simply and reliably.

Advantageously, the sample can be irradiated with light of a fundamental frequency and / or one or more integer multiples thereof by means of the laser. Thus, the material sample can be irradiated in a simple manner, for example, with multiple wavelengths or frequencies. If the laser has a fundamental frequency, simple frequency doubling, tripling, etc. can also cover a very large wavelength range for irradiation, which means flexibility significantly increased in terms of identification of chemically different substances.

Expediently, the fundamental frequency and / or the frequency multiplication correspond to wavelengths in the range between 233 nm and 300 nm, in particular between 250 nm and 280 nm, preferably at 266 nm and wavelength doubling at 532 nm. This enables a particularly reliable identification of plastics by means of a spectroscopic analysis and any added foreign substances or additives such as flame retardants or impurities of the plastic such as oil, gasoline, etc.

Advantageously, the picosecond range refers to the range between 0.5 ps and 500 ps, more particularly the range between 1 ps and 100 ps, preferably the range between 2.5 ps and 50 ps, more preferably between 4 ps and 10 ps, preferably between 5 ps and 8 ps, for example 5, 6, 7 and / or 8 ps. This can reliably achieve a short excitation time for a sample of the material.

Conveniently, the sample is illuminable by the laser in a first direction, the re-emitted light being detectable in a second direction by the detector, the first direction and the second direction being substantially opposite. This makes it possible to achieve an extremely compact design of the device. Further important features and advantages of the invention will become apparent from the subclaims, from the drawings, and from associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention. Preferred embodiments and embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components or elements.

It shows

Fig. 1 in schematic form an apparatus according to an embodiment of the present invention;

Fig. 2 partial spectra of different plastics when excited with a

Nanosecond laser; and

Fig. 3 partial spectra for plastics when excited with a picosecond laser.

Fig. 1 shows in schematic form a device according to an embodiment of the present invention.

In Fig. 1, a device 1 for the identification of plastic and / or optionally one or more of its additives is shown. In this case, the device 1 comprises a pulsed light source 2, here in the form of a picosecond laser, with which a sample 3 of the plastic to be identified is irradiated. The pulse duration of the laser is 7.5 ps. Of course, the pulse duration may be as low as 1 ps or 100 ps or so. The re-emitted light from the sample 3 is detected via a filter 4 and a lens 5 by means of a sensor 6. The raw signal obtained by the sensor 6 is processed by means of a signal processing 7 and by means of a differentiator 8 also a differentiated signal is generated.

A trigger is likewise generated by means of a trigger generation 9, which then triggers a first timer integrator 12a and via a delay 10 a second timer integrator 12b. By means of the two integrators 12a and 12b, the signal is integrated at different non-overlapping time periods on the falling edge of the processed signal. By means of a quotation 13, the two values which are provided by the two integrators 12a and 12b are related to each other, here supplied by means of quotient formation and the number thus obtained to an evaluation 14.

The evaluation 14 can u.a. consist in that in a memory of the device, a plurality of reference key figures for various. Combinations of plastics and their additives has been deposited and based on a comparison between these ratios and the determined index by the measurement then the plastic and / or its additives are identified , For the storage of such values / characteristic numbers, it is possible, for example, to carry out repeated measurements of the same plastic with the same additives and then to store these in the memory, for example with an average value and a corresponding deviation. In the case of ambiguous identification, such a result can be displayed to a user accordingly and the plastic, if the method is used in recycling, can be sorted out separately and then possibly fed to a further identification method.

Fig. 2 shows partial spectra of various plastics taken at excitation with a nanosecond laser and Fig. 3 shows partial spectra for plastics when excited with a picosecond laser.

FIGS. 2 and 3 each show a section of a recorded spectrum (intensity versus wavelength) for two different plastics, which are represented by the broken and uninterrupted lines, respectively. In Fig. 2, the solid lines indicate the plastic polystyrene PS, the broken lines the plastic acrylonitrile-butadiene-styrene ABS. In Fig. 3, the solid line indicate the plastic polystyrene PS, the broken lines the plastic polypropylene PP. In this case, the plastics were each irradiated several times and their spectrum was recorded. In Fig. 2, the two plastics were each multiply with a Nanosecond laser, so laser light with pulse durations in the nanosecond range, irradiated, and Fig. 3 with a picosecond laser, ie with laser light with pulse durations in the picosecond range. As can be seen, the recorded spectra in the overlapping wavelength ranges between 290nm and 340nm in FIG. 2 have a much less pronounced characteristic compared to the course of the spectra of FIG. 3. Moreover, the respective maxima in In summary, the use of a pico-seconds laser, a femtosecond laser, etc. for the identification of substances in a material sample allows their simple and reliable as well as cost-effective identification. Although the present invention has been described in terms of preferred embodiments, it is not limited thereto, but modifiable in a variety of ways.

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LIST OF REFERENCE NUMBERS

1 device

2 pulse light source

3 sample

4 filters

5 lens

6 sensor

7 signal conditioning

8 differentiators

9 trigger generation

10 retarders

12a, 12b integrator

13 quotation

14 evaluation

Claims

1. Device for the identification of substances of a material, in particular of plastics and their additives, by means of spectroscopy,

full

a laser for irradiating a sample of the material with light having at least one wavelength,

a detector for detecting the light reemitierten by the sample and an analysis device for spectroscopic analysis of the detected light, characterized in that

the laser is a pulsed laser having a pulse duration in the range of picoseconds or an even shorter pulse duration.

2. Device according to claim 1, wherein the time interval between two pulses of the laser is substantially at least an order of magnitude, preferably at least two orders of magnitude, in particular three orders of magnitude above the pulse duration.

A device according to claim 2, wherein the re-emitted light is substantially detectable between two pulses of the laser.

4. Device according to one of claims 1 -3, wherein the spectroscopic analysis comprises a fluorescence spectral analysis and / or a fluorescence lifetime analysis.

5. Device according to one of claims 1 -4, wherein the sample with light of a fundamental frequency and / or one or more integer frequency multiples thereof can be irradiated by means of the laser.

6. The device according to claim 5, wherein the wavelength in the range between 233nm and 300nm, in particular between 250nm and 280nm, preferably 266nm corresponds and wherein at least one other Frequency length is the corresponding frequency doubling of a fundamental frequency.

7. The device of claim 1, wherein the sample is illuminable by the laser in a first direction, and wherein the remitted light is detectable in a second direction by the detector, wherein the first direction and the second direction are substantially opposite ,

8. The device according to one of claims 1-7, wherein the picosecond region designates the range between 0.5 ps and 500 ps, in particular the ranges between 1 ps and 100 ps, preferably the range between 2.5 ps and 5.0 ps, in particular between 4 ps and 10 ps, preferably between 5 ps and 8 ps, for example 5, 6, 7, or 8 ps.

9. A method for the identification of substances of a material, in particular of plastics and their additives, wherein a sample of the material is irradiated with light of at least one wavelength by means of a laser and the light reemitierte by the sample is detected, wherein the detected light is analyzed spectroscopically,

characterized in that

the sample is irradiated with pulsed light from the laser, the pulsed light having a pulse duration in the range of picoseconds or a shorter pulse duration.

A method according to claim 9, wherein the picosecond range designates the range between 0.5 ps and 500 ps, in particular the ranges between 1 ps and 100 ps, preferably the range between 2.5 ps and 5.0 ps, in particular between 4 ps and 10 ps, preferably between 5 ps and 8 ps, for example 5, 6, 7, or 8 ps.

1 1. Use of pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for irradiation of material, in particular of plastics and their additives, the re-emitted light is analyzed spectroscopically.

12. Use of pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for the irradiation of material to be identified, in particular of plastics and their additives, for recycling purposes.

13. Use of pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for the irradiation of polymers, in particular plastics and / or their additives, for their identification.

14. Use of pulsed laser light with pulse durations in the range of picoseconds or even shorter pulse durations for fluorescence analysis, in particular for the analysis of the fluorescence decay time and / or fluorescence lifetime.

15. Use of a pulse laser with pulse durations in the range of picoseconds or even shorter pulse durations for irradiation of material, in particular of plastics and their additives, whose re-emitted light is analyzed spectroscopically for identifying the material, in particular by means of a fluorescence lifetime analysis.