JP4203916B2 - Plastic identification method and identification device - Google Patents

Description

  The present invention relates to a technique for non-destructively identifying a plastic material, and more particularly to a plastic identification method and identification apparatus based on Raman scattering for identifying a plastic material at high speed.

  When processing plastics that are discarded as household waste or industrial waste, the material of the discarded plastic may be unknown. Most of such waste plastics can only be incinerated after pulverization. However, plastic has the property that it can be melted and remolded by identifying what the waste plastic material (type of raw material) is, so it can be reused for high value-added products. Is possible. Even in the case of incineration, for example, if polyvinyl chloride is present, toxic gas may be generated. Therefore, it is necessary to detect its presence in advance.

  As a method for identifying the material of such waste plastic, a method using a Raman scattering spectrum has been proposed. For example, in Patent Document 1, monochromatic laser light emitted from a laser light source is guided to a fiber head via an optical fiber, and a plastic material is irradiated with the laser light via the fiber head, so that the fiber provided in the fiber head The light scattered from the plastic material through the head objective lens is collected, and the collected light is guided to the spectroscope through the optical fiber, and the Raman scattering spectrum is determined by spectroscopic analysis, and stored in the database. It is described that the type of plastic material is identified by collating with a known band pattern.

  Further, for example, in Patent Document 2, a Raman scattering spectrum of an identified plastic whose material is unknown is measured, and the wave number of a plurality of Raman peaks and relative intensity values at the wave number are extracted from the Raman scattering spectrum. Compare the wave number of the Raman peak of a known plastic and the relative intensity value at that wave number with the wave number of the Raman peak of the measured Raman scattering spectrum and the relative intensity value at that wave number. It is described to identify.

JP 2000-356595 A Japanese Patent Laid-Open No. 10-38807

  In any of the above conventional methods, the type of the plastic to be identified is identified by directly comparing the Raman scattering spectrum obtained from the unknown plastic to be identified with the known Raman scattering spectrum. In the conventional method, in order to directly compare the Raman scattering spectra, it is necessary to measure the Raman scattering spectrum so that the SN ratio is increased. For this reason, in the measurement of the Raman scattering spectrum by a normal spectroscopic device, it is necessary to continuously irradiate the laser beam for several seconds. Therefore, in the conventional method, it takes a long time to identify one plastic.

  In addition, the mathematical process for extracting a peak from the measured Raman scattering spectrum is complicated and computationally intensive, and this operation requires a long time. Although the above Patent Documents 1 and 2 do not describe the measurement time, even if measurement is performed under the best conditions, only a few identifications can be performed per second, which is not practical. Considering that many waste plastics are crushed and processed, it is necessary to identify several tens or more per second for practical plastic sorting.

  Therefore, an object of the present invention is to provide a plastic identification method and identification apparatus based on Raman scattering that can identify a plastic material at high speed.

  The plastic identifying method of the present invention includes a Raman scattering signal acquisition step of irradiating a plastic to be identified, which is an identification target, with a laser beam, and obtaining a Raman scattered signal from the Raman scattered light scattered from the plastic to be identified. Raman scattering intensity and baseline position (hereinafter referred to as "known baseline position") of one or more peak positions (hereinafter referred to as "known peak positions") set by measuring the Raman scattering spectrum of plastic .) And the Raman scattering intensity corresponding to the known peak position and the Raman shifting wave number corresponding to the known baseline position for each plastic material to be identified obtained from the Raman scattering signal of the plastic to be identified. Plastic material to be identified based on Raman scattering intensity Identifying and an identification step.

  In addition, the plastic identifying apparatus of the present invention includes a laser irradiation system for irradiating a plastic to be identified which is an identification target with a laser beam, and a Raman scattering signal acquisition for obtaining a Raman scattered signal from the Raman scattered light scattered from the plastic to be identified. Means and a Raman scattering intensity at one or more peak positions (known peak positions) and a Raman scattering intensity at a baseline position (known baseline positions) preset by measuring a Raman scattering spectrum of a known plastic. The storage means, the Raman scattering intensity at the Raman shift wave number corresponding to the known peak position for each plastic material to be identified obtained from the Raman scattering signal of the plastic to be identified, and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position , Of the known peak position stored in the storage means Those having identifying means for identifying the material of the identified plastics on the basis of the Mann scattering intensity and Raman scattering intensity of a known baseline position.

  According to these inventions, the Raman scattering intensity of one or more known peak positions and the Raman scattering intensity of a known baseline position are set in advance by measuring the Raman scattering spectrum of a known plastic, and these known peaks are set. The known peak position for each plastic material to be identified from the Raman scattering intensity at the position and the Raman scattering intensity at the known baseline position, and the Raman scattering signal obtained by irradiating the identification target plastic that is the identification target with the laser light The material of the plastic to be identified can be identified on the basis of the Raman scattering intensity at the Raman shift wave number corresponding to 1 and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position. That is, in the present invention, the Raman scattering wave number corresponding to the known peak position and the known baseline position respectively set in advance for each plastic material is obtained without accurately measuring the Raman scattering spectrum of the measured plastic and determining the peak position. Since only the Raman scattering intensity needs to be obtained from the Raman scattering signal, the plastic material can be identified at high speed.

  Here, it is desirable that the laser irradiation system is a system in which laser light is condensed by a single convex lens having a focal length of 150 mm or less and irradiated to the plastic to be identified. The working distance from the lens tip to the plastic to be identified is as high as the focal distance of 150 mm or less by condensing the laser light with a normal convex lens instead of the objective lens and irradiating the plastic to be identified. Can do. In addition, the depth of focus (in-focus range) is wider than when using an objective lens, and laser light with moderate intensity can be applied to identification plastics of various sizes and thickness without overheating. Can be collected, and Raman scattered light can be efficiently collected.

  It is desirable that the convex lens further constitutes a part of a condensing system that condenses the Raman scattered light scattered from the plastic to be identified. By forming the irradiation lens that irradiates the identified plastic with laser light and the condensing lens that condenses the scattered light with the same convex lens, Raman scattered light can be emitted regardless of the direction from which the laser is irradiated to the identified plastic. It is possible to collect light, and light irradiation and light collection can be performed efficiently.

  Further, it is desirable that the laser irradiation system guides the laser beam generated by the laser generator to the convex lens only by the reflection of the mirror. The laser light generated by the laser generator is guided to the convex lens only by the reflection of the mirror without using the optical fiber, so that the laser light can be condensed by the convex lens without irradiating the irradiated plastic.

  The Raman scattered signal acquisition means includes a spectroscope, an optical fiber that guides the light collected by the convex lens to the spectroscope, and a multi-channel photodetector that detects the light dispersed by the spectroscope and converts it into an electrical signal. It is desirable to obtain a Raman scattering signal from an electrical signal converted by a multichannel photodetector. Thereby, the spectroscope and the multi-channel photodetector, which are precision instruments, can be arranged in a place with a good working environment away from the laser irradiation system.

(1) The Raman scattering intensity of one or more known peak positions and the Raman scattering intensity of a known baseline position are set in advance by measuring the Raman scattering spectrum of a known plastic, and the Raman scattering of these known peak positions. Intensity and Raman scattering intensity corresponding to known baseline position and Raman corresponding to known peak position for each plastic material to be identified, obtained from Raman scattering signal obtained by irradiating laser light to identification target plastic as identification object By identifying the material of the plastic to be identified based on the Raman scattering intensity at the shift wave number and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position, 1 on the Raman scattering spectrum set for each plastic to be identified in advance. Known peak position above the point and known peak position Since it is possible to identify the material of the plastic to be identified simply by obtaining only the Raman scattering intensity at the Raman shift wave number corresponding to each line position from the Raman scattering signal, there is no need to measure the entire Raman scattering spectrum as in the past, It becomes possible to identify the plastic material at high speed.

(2) The laser irradiation system collects the laser beam by one convex lens having a focal length of 150 mm or less and irradiates the identified plastic, so that the working distance from the lens tip to the identified plastic is the focal point. The distance can be as high as 150 mm or less, and the material of the plastic pieces of various sizes being conveyed by a belt conveyor or the like can be identified. In addition, the depth of focus is wider than when using an objective lens, and it is possible to focus laser light with an appropriate intensity without overheating for plastics of various sizes and thicknesses, The Raman scattered light can be collected efficiently.

(3) Since the convex lens further constitutes a part of a condensing system that condenses the Raman scattered light scattered from the plastic to be identified, it is possible to irradiate the plastic to be identified from any direction. Raman scattered light can be collected, and irradiation and collection of light can be performed efficiently. As a result, there is no restriction on the irradiation direction of the laser beam, and even general users as well as specialists can easily use it. In addition, the material can be identified by condensing the Raman scattered light regardless of the direction in which the laser beam is irradiated from various directions on the plastic pieces of various shapes conveyed by a belt conveyor or the like. .

(4) Since the laser irradiation system guides the laser beam generated by the laser generator to the convex lens only by the reflection of the mirror, the laser beam is condensed by the convex lens without dropping the output of the laser beam and irradiated to the plastic to be identified. can do.

(5) Raman scattering signal acquisition means includes a spectroscope, an optical fiber that guides the light collected by the convex lens to the spectroscope, a multichannel photodetector that detects the light split by the spectroscope and converts it into an electrical signal, And a Raman scattering signal is obtained from the electrical signal converted by the multichannel photodetector, so that the spectroscope and the multichannel photodetector, which are precision instruments, are separated from the laser irradiation system and the working environment is good. Can be placed in place.

  FIG. 1 is a plastic identification device according to an embodiment of the present invention, and FIG. 2 is a block diagram of the plastic identification device of FIG.

  In FIG. 1, a plastic identification device 1 according to an embodiment of the present invention irradiates a laser beam to an identification plastic that is an identification target and collects Raman scattered light scattered from the identification plastic. 2, a multichannel spectrometer 4 connected by the detector head 2 and the optical fiber 3, a data processing device 5 for inputting and processing an electric signal output from the multichannel spectrometer 4, and generation of a semiconductor laser to be described later And a semiconductor laser driving power source 6 for driving the apparatus 20.

  The detection unit head 2 includes a semiconductor laser generator 20 that constitutes a laser irradiation system 10 (see FIG. 2) that irradiates laser light to an identification plastic P that is an identification target, and one piece of a focal length of 40 to 150 mm. A convex lens 21, and a mirror 22 a and a dichroic mirror 22 b that reflect the laser light L generated by the semiconductor laser generator 20 and guide it to the convex lens 21 are provided. The dichroic mirror 22b reflects the laser light L and transmits the Raman scattered light R. The mirror 22a can be omitted by adjusting the direction of the semiconductor laser generator 20. The dichroic mirror 22b can be replaced with a half mirror that reflects the laser light L and transmits the Raman scattered light R.

  For example, a semiconductor laser generator 20 having a high output capable of obtaining an output of 100 mW or more in a wavelength range of 600 to 900 nm is used. The laser light L generated by the semiconductor laser generator 20 is reflected by the mirror 22a, is further reflected by the dichroic mirror 22b, is guided to the convex lens 21, is condensed by the convex lens 21, and is irradiated onto the identification plastic P. The detection unit head 2 also serves as a condensing system that condenses the Raman scattered light R scattered from the plastic P to be identified by the convex lens 21 and guides it to the optical fiber 3. The Raman scattered light R passes through the dichroic mirror 22b and is collected at the entrance of the optical fiber 3.

The optical fiber 3 guides the light collected by the convex lens 21 of the detection unit head 2 to the multichannel spectrometer 4. The multi-channel spectroscope 4 includes a spectroscope, a two-dimensional photo detector having 1024 pixels or less such as a CCD (Charge Coupled Device) or a linear array photodiode that detects light converted by the spectroscope and converts it into an electric signal. It is a small spectroscope composed of An excitation light removal filter 7 is provided on the light incident side of the multichannel spectrometer 4. The optical fiber 3, the multichannel spectroscope 4 and the excitation light removal filter 7 are Raman which obtains a Raman scattered signal by performing multichannel spectroscopy on the Raman scattered light R scattered from the identification plastic P and converting it into an electric signal. The scattered signal acquisition means 11 (refer FIG. 2) is comprised. Multichannel spectrometer 4 may not be of high resolution, it can be selected by the performance of the diffraction grating and the photodetector incorporated therein, for example, of 2 cm ^-1 in the range of the Raman shift wavenumber 400～1600Cm ^-1 Any device capable of obtaining a Raman scattering signal may be used.

  The data processing device 5 is a personal computer, a CPU board, or the like, and the multichannel spectrometer 4 is connected by, for example, a PCI (Peripheral Component Interconnect) interface. As shown in FIG. 2, the data processing device 5 stores the material of the identified plastic P based on the Raman scattering signal acquired by the storage unit 12 that stores a preset reference value and the Raman scattering signal acquisition unit 11. Identification means 13 for identifying and output means 14 for outputting a result (identification signal) identified by the identifying means.

  The reference values stored in the storage means 12 are known plastics such as PS (polystyrene), PP (polypropylene), PET (polyethylene terephthalate), LDPE (low density polyethylene) and HDPE (high density polyethylene). The Raman scattering intensities at one or more known peak positions and known baseline positions set in advance for each material.

FIG. 3 shows the result of acquiring the Raman scattering spectrum of each of known plastics (PS, PP, PET, LDPE, HDPE) as a reference sample by the plastic identification device in the present embodiment. The horizontal axis in FIG. 3 is the Raman shift wave number (cm ⁻¹ ), and the vertical axis is the Raman scattering intensity (arbitrary intensity). 3, when describing the PS as an example, there is a peak at a position of the PS at the point A ₁ and the point A _2, these two points A _1, A ₂ or near the peak position for the PS identification. Since there is a point B on the baseline between these peak positions A ₁ and A ₂ , this point B is set as a baseline position for PS identification. For the baseline position and intensity, it is desirable to use the value of the bottom portion because the Raman scattering intensity that is not so far from the peak position is weak. In calculating the intensity, the average value of the measurement points in the vicinity including the peak position and the baseline position is calculated, and this can be used to improve the SN ratio.

The identification unit 13 performs Raman scattering at the Raman shift wave number corresponding to a known peak position (two points A ₁ and A _{2 in} the example of PS) for each plastic material to be identified from the Raman scattering signal acquired by the Raman scattering signal acquisition unit 11. The Raman scattering intensity at the Raman shift wave number corresponding to the intensity and the known baseline position (point B in the PS example) is obtained, and based on the obtained Raman scattering intensity and the reference value stored in the storage means 12 It identifies the material of the plastic to be identified.

For example, the discriminating means 13 uses the Raman scattering intensities R _A1 and R _A2 and the known baseline position (point B) at the Raman shift wave number corresponding to the known peak positions (two points A ₁ and A ₂ ) for each plastic material to be identified. each of the difference between the Raman scattering intensity R _B in the Raman shift wave number corresponding to (R _A1 -R _B), and (R _A2 -R _B), the Raman scattering intensity of a known peak positions of the known plastic as the reference value R The difference (R _A10 −R _B0 ) and (R _A20 −R _B0 ) between _A10 and R _A20 and the Raman scattering intensity R _B0 at the known baseline position are directly or each ratio (R _A1 −R _B ) / ( The material of the plastic to be identified is identified by comparison by (R _A2 -R _B ), (R _A10 -R _B0 ) / (R _A20 -R _B0 ). The reference value for comparing directly _{(R A10 -R B0), (} R A20 -R B0), or, the reference value for comparing the ratio _{(R A10 -R B0) / (} R A20 -R B0) Is stored in the storage means 12 in advance.

FIG. 4 shows an example of PS identification by the identification means 13. As shown in FIG. 4, the Raman scattering intensities R _A1 and R _{A2 at} the Raman shift wave numbers corresponding to the known peak positions at the two points A ₁ and A ₂ of PS and the Raman shift wave number corresponding to the known baseline position at the point B The ratios (R _A1 -R _B ) / (R _A2 -R _B ) of the differences (R _A1 -R _B ) and (R _A2 -R _B ) from the Raman scattering intensity R _B are different from those of other materials. Are very different. Therefore, the ratio (R _A10 ) of the difference (R _A10 −R _B0 ) and (R _A20 −R _B0 ) between the Raman scattering intensities R _A10 and R _{A20 at} the known peak position of PS and the Raman scattering intensity R _B0 at the known baseline position. -R _B0) / (filtered by thresholds S _PS as a reference value set from R _A20 -R _B0) (in the illustrated example _{(R A10 -R B0) / (} R A20 -R B0)> S PS = 2.5 By extracting only PS), it is possible to identify and extract only PS from a sample in which PS, PP, PET, LDPE, and HDPE are mixed.

Similarly, FIG. 5 shows an example of PP identification by the identification means 13. As shown in FIG. 5, the ratio X of the difference between the Raman scattering intensity at the Raman shift wave number corresponding to the two known peak positions of PP and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position is Positive and negative are different from those of other materials. Therefore, by filtering (extracting only X> 0 in the illustrated example) by the threshold value _SPP as a reference value set from the ratio of the difference between the Raman scattering intensity at the known peak position of PP and the Raman scattering intensity at the known baseline position. , PS, PP, PET, LDPE, HDPE can be identified and extracted only from PP. As shown in FIG. 5, not all PPs can be extracted under the above conditions. However, since the one extracted by the identification means 13 does not include anything other than PP, Can be used without problems.

Further, the identification means 13 includes Raman scattering intensities R _A1 and R _{A2 at} the Raman shift wave number corresponding to the known peak position for each plastic material to be identified, and the Raman scattering intensity R _{B at} the Raman shift wave number corresponding to the known baseline position. R _A1 / R _B , R _A2 / R _B are calculated, and the ratio R _A10 / R _A0 between the Raman scattering intensities R _A10 and R _A20 at known peak positions of the known plastic and the Raman scattering intensity R _{B0 at} known baseline positions is calculated. It is also possible to adopt a configuration in which the material of the plastic to be identified is identified by comparing with a threshold value as a reference value set from R _B0 and R _A20 / R _B0 .

FIG. 6 shows an example of PS identification by the identification means 13. As shown in FIG. 6, the ratio R between the Raman scattering intensity R _{A1 at} the Raman shift wave number corresponding to the known peak position at one point A ₁ of PS and the Raman scattering intensity R _B at the Raman shift wave number corresponding to the known baseline position. _A1 / R _B is different from that of other materials. Therefore, in this example, filtering is performed by the threshold value S _PS1 as a reference value set from the ratio R _A10 / R _B0 between the Raman scattering intensity R _{A10 at} the known peak position of PS and the Raman scattering intensity R _B0 at the known baseline position. , by the condition that satisfies the threshold S _PS1, it is possible to extract and identify PS, PP, PET, LDPE, from HDPE are mixed sample PS only.

Similarly, FIG. 7 shows an example of PP identification by the identification means 13. As shown in FIGS. 7A and 7B, the Raman scattering intensity at the Raman shift wave number corresponding to the two known peak positions of PP and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position The ratio X is different from that of other materials. Therefore, in this example, filtering is performed by the threshold values S _PP1 and S _PP2 as reference values set from the ratio of the Raman scattering intensity at the known peak position of PP and the Raman scattering intensity at the known baseline position, and both threshold values are satisfied. As a condition, it is possible to identify and extract only PP from a sample in which PS, PP, PET, LDPE, and HDPE are mixed.

Alternatively, the discriminating means 13 sets the difference between the Raman scattering intensities R _A1 and R _A2 (R _A1 −R _A2 ) and the known baseline position at the Raman shift wave numbers corresponding to two known peak positions for each plastic material to be discriminated. The ratio (R _A1 −R _A2 ) / R _B with the Raman scattering intensity R _B at the corresponding Raman shift wavenumber is calculated, and the difference between the Raman scattering intensities R _A10 and R _A20 at two known peak positions of the known plastic ( R _A10 -R _A20 ) and the Raman scattering intensity R _B0 at the known baseline position (R _A10 -R _A20 ) / R _B0 is compared with a threshold value as a reference value set to identify the material of the identified plastic It can be set as the structure to do.

FIG. 8 shows an example of PS identification by the identification means 13. As shown in FIG. 8, the difference (R _A1 −R _A2 ) between the Raman scattering intensities R _A1 and R _{A2 at} the Raman shift wave numbers corresponding to the known peak positions at the two points A ₁ and A ₂ of PS and the known baseline position. the ratio of the Raman scattering intensity R _B at the corresponding Raman shift wavenumber _{(R A1 -R A2) / R} B are largely different from those of other materials. Therefore, the ratio of the difference (R _A10 -R _A20 ) between the Raman scattering intensities R _A10 and R _A20 at the two known peak positions of PS and the Raman scattering intensity R _B0 at the known baseline position (R _A10 -R _A20 ) / by filtering by the threshold S _PS as a reference set from R _B0 value, it is possible to extract and identify PS, PP, PET, LDPE, from HDPE are mixed sample PS only.

As described above, the difference (R _A1 −R _A2 ) between the Raman scattering intensities R _A1 and R _{A2 at} the Raman shift wave number corresponding to the known peak positions at the two points A ₁ and A ₂ of PS and the Raman corresponding to the known baseline position. By taking the ratio (R _A1 −R _A2 ) / R _B with the Raman scattering intensity R _B at the shift wave number, it is possible to further improve the identification accuracy. In addition, since sufficient identification accuracy can be obtained from only the three values of Raman scattering intensities R _A1 , R _A2 , and R _B , the time required for calculation processing is extremely small, and a large amount of waste plastic can be identified in a short time. Can do.

Similarly, FIG. 9 shows an example of PP identification by the identification means 13. As shown in FIG. 9, the ratio X between the Raman scattering intensity at the Raman shift wave number corresponding to the two known peak positions of PP and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position is The range is different from that of the material. Therefore, filtering is performed using threshold values S _PPH and S _PPL as reference values set from the ratio between the difference in Raman scattering intensity at the two known peak positions of PP and the Raman scattering intensity at the known baseline position (in the example shown, S _PPH > By extracting only those in the range of X> S _PPL ), it is possible to identify and extract only PP from a sample in which PS, PP, PET, LDPE, and HDPE are mixed.

  As described above, the discriminating means 13 has the Raman scattering intensity and the known baseline position at the Raman shift wave number corresponding to the known peak position for each plastic material to be discriminated obtained from the Raman scattering signal obtained by the Raman scattering signal obtaining means 11. The plastic is identified on the basis of the Raman scattering intensity at the Raman shift wave number corresponding to and the reference value stored in the storage means 12, and the entire Raman scattering spectrum is measured as in the prior art, and this measured Raman is measured. Plastics are identified by simple arithmetic processing without performing complicated arithmetic processing such as extracting a peak from a scattered spectrum. The identification means 13 according to the present invention is not limited to the above-described specific calculation example, and can be adopted as long as it is a simple calculation process in which only a specific plastic stands out.

  In the plastic identification device 1 having the above-described configuration, the semiconductor laser generator 20 that generates a powerful laser beam is used as a light source, and this laser beam is condensed and irradiated onto the surface of the identification plastic P that is a sample by the convex lens 21, and the scattered light. Is scattered coaxially by the same convex lens 21 used for condensing the laser light, guided to the multichannel spectrometer 4 by the optical fiber 3, and subjected to multichannel spectroscopy to obtain a Raman scattered signal. Since the Raman scattering signal obtained here only needs to obtain only the preset peak position and baseline position, it is not necessary to accurately measure the entire Raman scattering spectrum as in the prior art. In addition, if measurement is performed with as few pixels as possible, the light intensity per pixel increases, so that a large electrical signal can be extracted. Therefore, for example, even a Raman scattered signal obtained by the 512-channel multi-channel spectrometer 4 can be measured at a high speed with a sufficient S / N ratio. FIG. 10 shows an example in which the Raman scattering signal of PP is measured at 50 ms and 10 ms, respectively. As shown in FIG. 10, the SN ratio sufficient for identification even if high-speed processing of about 10 ms is performed for one measurement. Necessary Raman scattering signal is obtained with low noise.

Further, in the plastic identification device 1 according to the present embodiment, the Raman shift corresponding to the peak position (for example, A ₁ and A _{2 in} the case of PS) determined in advance for each plastic to be identified from the Raman scattering signal thus obtained. Simple calculation processing such as finding the Raman scattering intensity of one or two wave numbers and the Raman scattering intensity of the Raman shift wave number corresponding to the baseline position (for example, B in the case of PS) and calculating the ratio It is possible to identify 50 or more plastics per second by a simple method of performing and comparing the value with the reference value determined for the plastic of the reference sample. In the present embodiment, one or two Raman shift wave numbers corresponding to the peak position are used, but three or more points may be used.

  Since the conventional plastic identification method based on Raman scattering requires accurate measurement of the Raman scattering spectrum, the measurement time is long and the analysis method is complicated. However, in the plastic identification device 1 of the present embodiment, Since it is only necessary to obtain the Raman scattering signal obtained by measuring only the Raman scattering intensities at the preset peak position and the baseline position without accurately measuring the Raman scattering spectrum to obtain the peak position, at least 50 high-speeds per second. It is possible to identify the plastic material. Accordingly, it is possible to identify and sort a large amount of waste plastic that is actually discharged while conveying it with a belt conveyor or the like, and obtain a recycled material with high purity for plastic recycling.

  Further, in the plastic identification device 1 according to the present embodiment, the laser light L is collected by the single convex lens 21 having a focal length of 150 mm or less and is irradiated to the identification plastic P. Therefore, the operation from the lens tip to the identification plastic P is performed. The distance can be ensured to the same extent as the focal distance of 150 mm or less, and the material of the plastic pieces of various sizes being conveyed by a belt conveyor or the like can be identified.

  Further, since the convex lens 21 constitutes a part of a condensing system for condensing the Raman scattered light scattered from the identified plastic P, the Raman light is irradiated from any direction to the identified plastic P by the laser light L. Scattered light R can be collected, and light irradiation and light collection can be performed efficiently. Thereby, there is no restriction on the irradiation direction of the laser beam L, and it is possible to use it easily even by a general user as well as an expert. In addition, the material is identified by condensing the Raman scattered light R, regardless of the direction from which the laser light L is irradiated to plastic pieces of various shapes conveyed by a belt conveyor or the like. Can do.

  Further, in the plastic identification device 1 in the present embodiment, the laser irradiation system 10 guides the laser light L generated by the semiconductor laser generator 20 to the convex lens 21 only by the reflection of the mirror 22a and the dichroic mirror 22b. The laser light L can be condensed by the convex lens 21 without losing the output of the laser light L and irradiated to the plastic to be identified.

  In addition, since the plastic identifying apparatus 1 in the present embodiment can identify the plastic to be identified at high speed, it is possible to identify the sample while it is constantly moving on a belt conveyor or the like. . For this reason, the laser beam L only needs to be continuously oscillated, and the synchronous pulse oscillation of the laser is unnecessary, so that the structure is simple.

  Since the detection unit head 2 incorporating the semiconductor laser generator 20 and the multichannel spectrometer 4 are connected only by the general-purpose optical fiber 3, the precise parts such as the multichannel spectrometer 4 and the data processing device 5 are operated. It can be installed in a remote location with good environment.

  The plastic identification device of the present invention is a device for identifying plastic materials by measuring a scattering phenomenon called Raman scattering, and for identifying various plastics discarded as household waste or industrial waste for recycling. Useful.

It is a plastic identification device in an embodiment of the present invention. It is a block diagram of the plastic identification device of FIG. It is a figure which shows the result of having acquired each Raman scattering signal of the known plastic as a reference sample with the plastic identification device in this embodiment. It is a figure which shows the example of identification of PS by an identification means. It is a figure which shows the example of identification of PP by an identification means. It is a figure which shows the example of identification of PS by an identification means. It is a figure which shows the example of identification of PP by an identification means. It is a figure which shows the example of identification of PS by an identification means. It is a figure which shows the example of identification of PP by an identification means. It is a figure which shows the example which measured the Raman scattering signal of PP at 50 ms and 10 ms, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plastic identification apparatus 2 Detection part head 3 Optical fiber 4 Multichannel spectrometer 5 Data processing apparatus 6 Semiconductor laser drive power supply 7 Excitation light removal filter 10 Laser irradiation system 11 Raman scattered signal acquisition means 12 Storage means 13 Identification means 14 Output means 20 Semiconductor laser generator 21 Convex lens 22a Mirror 22b Dichroic mirror

Claims (9)

Raman scattering intensity and baseline position (hereinafter referred to as “known base position”) of one or more peak positions (hereinafter referred to as “known peak positions”) set by measuring a Raman scattering spectrum of a known plastic in advance. Storing the Raman scattering intensity of the line position in the storage means;
The laser beam was irradiated to the identification plastic is the identification object, in the Raman scattering signal acquisition step of obtaining a Raman scattering signal from the Raman scattered light scattered from the object to be identified plastics, Raman scattering signal or we identify the identification target plastic Obtain only the Raman scattering intensity at the Raman shift wave number corresponding to the one or more known peak positions for each plastic material to be separated and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position. one point only Raman scattering intensity in the Raman shift wavenumber, which is pre-stored in the storage means corresponding to the Raman scattering intensity and a known base line position in the Raman shift wave number corresponding to the known peak positions of several points over one point, which is The Raman scattering intensities at the known peak positions and the Identification method for a plastic comprising an identification step of identifying the material of the object to be identified plastic on the basis of the Raman scattering intensity of the line position.   The identifying step includes a difference between a Raman scattering intensity at a Raman shift wave number corresponding to a known peak position for each plastic material to be identified and a Raman scattering intensity at a Raman shift wave number corresponding to a known baseline position, and the known plastic. 2. The plastic identifying method according to claim 1, wherein a material of the identified plastic is identified by comparing a difference between a Raman scattering intensity at a known peak position and a Raman scattering intensity at a known baseline position. .   The identification step calculates a ratio between the Raman scattering intensity at the Raman shift wave number corresponding to the known peak position for each plastic material to be identified and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position, and 2. The material of the plastic to be identified is identified by comparing with a threshold value set based on a ratio of a Raman scattering intensity at a known peak position and a Raman scattering intensity at a known baseline position of the plastic. Plastic identification method.   In the identifying step, a ratio between a Raman scattering intensity at a Raman shift wave number corresponding to two known peak positions for each plastic material to be identified and a Raman scattering intensity at a Raman shift wave number corresponding to a known baseline position is calculated. The material of the identified plastic is identified by calculating and comparing it with a threshold set from the ratio of the Raman scattering intensity at the two known peak positions of the known plastic and the Raman scattering intensity at the known baseline position. The plastic identifying method according to claim 1, wherein: A laser irradiation system for irradiating a plastic to be identified, which is an identification object, with laser light;
Raman scattering signal acquisition means for obtaining a Raman scattering signal from the Raman scattered light scattered from the plastic to be identified;
Raman scattering intensity and baseline position (hereinafter referred to as “known base position”) of one or more peak positions (hereinafter referred to as “known peak positions”) set by measuring a Raman scattering spectrum of a known plastic in advance. Storage means for storing the Raman scattering intensity of the "line position"),
Raman shift wave number corresponding to the Raman scattering intensity and a known base line position in the Raman shift wave number corresponding to the known peak positions of the one or more points at several points per material of Raman scattering signal or al identifies want plastic of the object to be identified plastic to give only the Raman scattering intensity at only the Raman scattering intensity in the Raman shift wave number corresponding to the Raman scattering intensity and a known base line position in the Raman shift wave number corresponding to the known peak position of the obtained 1 or more points several points and And identifying means for identifying the material of the plastic to be identified based on the Raman scattering intensities at one or more known peak positions and the Raman scattering intensities at known baseline positions stored in advance in the storage means. Plastic identification device.   6. The plastic identifying apparatus according to claim 5, wherein the laser irradiation system collects laser light by a single convex lens having a focal length of 150 mm or less and irradiates the plastic to be identified.   7. The plastic identifying apparatus according to claim 6, wherein the convex lens further constitutes a part of a condensing system for condensing Raman scattered light scattered from the plastic to be identified.   8. The plastic identification device according to claim 6, wherein the laser irradiation system guides laser light generated by a laser generator to the convex lens only by reflection of a mirror.   The Raman scattering signal acquisition means includes a spectroscope, an optical fiber that guides the light collected by the convex lens to the spectroscope, and a multichannel photodetector that detects the light split by the spectroscope and converts it into an electrical signal. 9. The plastic identification device according to claim 6, wherein a Raman scattering signal is obtained from an electrical signal converted by the multichannel photodetector.

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