JP4260205B1 - Raman scattering signal acquisition method, Raman scattering signal acquisition device, plastic identification method and identification device - Google Patents

Abstract

Even a transparent or translucent plastic is accurately identified.
A belt conveyor 4 for placing and conveying a plastic to be identified P on a belt 4a formed of a stainless steel plate, and irradiating laser light L on the plastic to be identified P on the belt conveyor 4; A Raman scattering discriminator 5 for obtaining the Raman scattered light R scattered from the identified plastic P and identifying the material of the identified plastic P is provided. Even if the identified plastic P is transparent or translucent, the laser light transmitted through the identified plastic P is reflected on the surface of the belt 4a, and the influence of the Raman effect by the belt 4a is reduced. A remarkable Raman scattering signal of few plastics P to be identified is obtained, and more accurate identification is possible.
[Selection] Figure 1

Description

  The present invention relates to a Raman scattering signal acquisition method and a Raman scattering signal acquisition device for acquiring a Raman scattering signal scattered from a transparent or translucent object, and a non-destructive plastic material based on the acquired Raman scattering signal. The present invention relates to a plastic identifying method and an identifying apparatus.

  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, laser light is irradiated from a laser device onto an unknown plastic whose material is carried on a belt conveyor, and a Raman scattering spectrum is measured with a spectroscope. The wave number of multiple Raman peaks and their relative intensity values at that wave number are extracted from the Raman scattering spectrum, the wave number of the Raman peak of a known plastic, the relative intensity value at that wave number, and the Raman peak of the measured Raman scattering spectrum. And the relative intensity value at the wave number are compared, and the material of the plastic to be identified is identified from the comparison result.

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

  By the way, in the case of continuously identifying the plastics to be identified, as described in Patent Document 2, the Raman scattering spectrum is measured by irradiating laser light while carrying the plastics to a predetermined position by a belt conveyor. Become. However, when the Raman scattering spectrum is measured by irradiating the plastic to be identified placed on the belt conveyor with laser light, the peak of the Raman scattering spectrum is observed when the plastic to be identified is transparent or translucent plastic. May not appear clearly and may not be accurately identified.

  Therefore, the present invention provides a Raman scattering signal acquisition method and a Raman scattering signal acquisition device capable of obtaining a clear Raman scattering signal even for a transparent or semi-transparent object, and is transparent or semi-transparent. An object of the present invention is to provide a plastic identification method and identification apparatus based on Raman scattering, which can accurately identify the material of plastic.

  The method for acquiring a Raman scattered signal of the present invention irradiates an object placed on a mounting table having a metal surface or mirror surface with a laser beam, and obtains a Raman scattered signal from the Raman scattered light scattered from the object. It is characterized by. The Raman scattering signal acquisition device of the present invention has a metal surface or a mirror surface, a mounting table on which the object is mounted, and a laser irradiation system that irradiates the object mounted on the mounting table with laser light. And a Raman scattered signal acquisition means for obtaining a Raman scattered signal from the Raman scattered light scattered from the object.

  In these inventions, the metal surface or mirror surface of the mounting table on which the object is mounted reflects the laser light, thereby reducing the influence of the Raman effect of the mounting table on the Raman scattered light scattered from the object. Therefore, even if the object is transparent or translucent, a clear Raman scattering signal with little influence of the mounting table can be obtained.

  According to the plastic identifying method of the present invention, laser light is irradiated to a plastic to be identified which is an identification target placed on a mounting table having a metal surface or a mirror surface, and the Raman scattered light scattered from the plastic to be identified. A Raman scattering signal acquisition step for obtaining a Raman scattering signal, a Raman scattering intensity of one or more peak positions (hereinafter referred to as “known peak positions”) set in advance by measuring a Raman scattering spectrum of a known plastic, and In the Raman scattering wave number corresponding to the known peak position for each plastic material to be identified obtained from the Raman scattering intensity of the baseline position (hereinafter referred to as “known baseline position”) and the Raman scattering signal of the identified plastic. At the wavenumber of the Raman shift corresponding to the Raman scattering intensity and the known baseline position Based on the Man scattering intensity comprises an identification step of identifying the material of the identified plastic.

  The plastic identification device of the present invention has a metal surface or a mirror surface, and irradiates a laser beam onto a placement table on which a plastic to be identified, which is an identification target, is placed, and a laser to be identified. A laser irradiation system, a Raman scattering signal acquisition means for obtaining a Raman scattering signal from Raman scattered light scattered from a plastic to be identified, and one or more peak positions set in advance by measuring a Raman scattering spectrum of a known plastic ( The storage means for storing the Raman scattering intensity at the known peak position) and the Raman scattering intensity at the baseline position (known baseline position), and the known peak position for each plastic material to be identified obtained from the Raman scattering signal of the plastic to be identified. For the Raman scattering intensity and the known baseline position at the corresponding Raman shift wavenumber Identification means for identifying the material of the plastic to be identified based on the Raman scattering intensity at the wave number of the Raman shift to be detected, the Raman scattering intensity at the known peak position and the Raman scattering intensity at the known baseline position stored in the storage means Is.

  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 based on the Raman scattering intensity at the wave number of the Raman shift corresponding to and the Raman scattering intensity at the wave number of the Raman shift corresponding to the known baseline position. That is, in the present invention, the wave number of Raman shift corresponding to each of the known peak position and the known baseline position set in advance for each plastic material without accurately measuring the Raman scattering spectrum of the plastic to be measured and obtaining the peak position. Since it is only necessary to obtain the Raman scattering intensity from the Raman scattering signal, the plastic material can be identified at high speed.

  In particular, in the present invention, the metal surface or the mirror surface of the mounting table on which the plastic to be identified is mounted reflects the laser beam, so that the influence of the Raman effect by the mounting table on the Raman scattered light scattered from the plastic to be identified is reduced. Since the number can be reduced, an outstanding Raman scattering signal of the plastic to be identified which is less affected by the mounting table can be obtained, and the plastic material can be more accurately identified. Therefore, when the plastic to be identified is a transparent or translucent plastic, even if the laser light transmitted through the transparent or translucent plastic to reach the mounting table, there is little influence of the Raman effect by the mounting table, It is possible to accurately identify the plastic material.

  Here, the metal surface of the mounting table is preferably glossy. If the surface is glossy, almost no Raman scattered light is generated from the surface of the mounting table, so that more accurate plastic identification is possible. Further, the metal constituting the metal surface of the mounting table can be, for example, stainless steel, aluminum, or copper. Since these metals are inexpensive and have good workability, the mounting table having the metal surface can be easily formed. Obtainable.

  In addition, the laser irradiation system is preferably one that condenses laser light with a single convex lens having a focal length of 150 mm or less and irradiates 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) An object placed on a mounting surface having a metal surface or a mirror surface is irradiated with laser light, and a Raman scattering signal is obtained from the Raman scattered light scattered from the object, thereby being scattered from the object. Since the influence of the Raman effect of the mounting table on the Raman scattered light can be reduced, it is possible to obtain a clear Raman scattering signal with little influence of the mounting table even if the object is transparent or translucent. Become.

(2) 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 at a known baseline position, and obtained from a Raman scattering signal obtained by irradiating a plastic to be identified, which is an identification target placed on a mounting surface having a metal surface or mirror surface, with a laser beam Configuration for identifying plastic material to be identified based on Raman scattering intensity at Raman shift wave number corresponding to known peak position for each plastic material to be identified and Raman scattering intensity at Raman shift wave number corresponding to known baseline position The Raman scattering scan set for each plastic to be identified in advance Conventionally, the material of the plastic to be identified can be identified simply by obtaining the Raman scattering intensity only from the Raman scattering signal at the wave number of the Raman shift corresponding to one or more known peak positions and known baseline positions on the kettle. Thus, it is not necessary to measure the entire Raman scattering spectrum, and the plastic material can be identified at high speed. In particular, in the present invention, the metal surface or the mirror surface of the mounting table on which the plastic to be identified is mounted reflects the laser beam, so that the influence of the Raman effect by the mounting table on the Raman scattered light scattered from the plastic to be identified is reduced. Since the number can be reduced, an outstanding Raman scattering signal of the plastic to be identified which is less affected by the mounting table can be obtained, and the plastic material can be more accurately identified. Therefore, even if the plastic to be identified is a transparent or translucent plastic, the plastic material can be accurately identified.

(3) Since the metal surface of the mounting table is glossy, almost no Raman scattered light is generated from the surface of the mounting table, thereby enabling more accurate plastic identification.

  FIG. 1 is a schematic configuration diagram of a plastic identification device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of the Raman scattering identification device of FIG. 1, and FIG. 3 is a block diagram of the Raman scattering identification device of FIG.

  In FIG. 1, a plastic identification device 1 according to an embodiment of the present invention includes a pretreatment wind sorter 2 that sorts a crushed plastic material into foreign matters and plastic pieces, and a plastic sorted by the pretreatment wind sorter 2. A vibration alignment feeder 3 that vibrates and aligns the pieces, a belt conveyor 4 as a conveying device that places and conveys plastic pieces aligned by the vibration alignment feeder 3 on a belt 4a as a mounting table, and a belt conveyor 4 A laser scattering discriminator 5 for irradiating laser light to an upper plastic piece, that is, a plastic to be identified, which is an identification target, and obtaining Raman scattered light scattered from the plastic to be identified to identify the material of the plastic to be identified. Prepare. In the plastic identification device 1 according to this embodiment, the belt 4a is formed of a stainless steel plate, and the surface thereof is glossy.

  In addition, the plastic identification device 1 includes a sorting air gun 6 that sorts the plastic to be identified for each material by ejecting air according to the result of identification by the Raman scattering classifier 5, and an air gun that drives the sorting air gun 6. A drive device 7 and a synchronization control device 8 that controls operations of the Raman scattering discriminator 5 and the air gun drive device 7 in synchronization are provided. The plastic identification device 1 also includes a conveyor speed adjustment device 9 that adjusts the conveyance speed of the belt conveyor 4, and the synchronization control device 8 adjusts the conveyor speed together with the Raman scattering identification device 5 and the air gun driving device 7 described above. The operation of the device 9 is controlled in synchronization.

  As shown in FIG. 2, the Raman scattering discriminator 5 irradiates laser light to the identification plastic P placed on the belt 4 a and detects the Raman scattered light scattered from the identification plastic P. Head 11, multichannel spectrometer 22 connected to detector head 11 and optical fiber 21, data processing device 30 that receives and processes electrical signals output from multichannel spectrometer 22, and a semiconductor described later A semiconductor laser driving power source 40 for driving the laser generator 12.

  The detection unit head 11 includes a semiconductor laser generator 12 that constitutes a laser irradiation system 10 (see FIG. 3) that irradiates laser light to an identification plastic P that is an identification target, and a single convex lens having a focal length of 40 to 150 mm. 13, and a mirror 14 a and a dichroic mirror 14 b that reflect the laser light L generated by the semiconductor laser generator 12 and guide it to the convex lens 13. The dichroic mirror 14b reflects the laser light L and transmits the Raman scattered light R. The mirror 14 a can be omitted by adjusting the direction of the semiconductor laser generator 12. The dichroic mirror 14b 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 12 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 beam L generated by the semiconductor laser generator 12 is reflected by the mirror 14a, is further reflected by the dichroic mirror 14b, is guided to the convex lens 13, is condensed by the convex lens 13, and is applied to the identification plastic P. The detection unit head 11 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 13 and guides it to the optical fiber 21. The Raman scattered light R passes through the dichroic mirror 14 b and is collected at the entrance of the optical fiber 21.

The optical fiber 21 guides the light collected by the convex lens 13 of the detection unit head 11 to the multichannel spectrometer 22. The multi-channel spectroscope 22 is a spectroscope, a two-dimensional photo detector of 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 23 is provided on the light incident side of the multichannel spectrometer 22. The optical fiber 21, the multichannel spectroscope 22, and the excitation light removal filter 23 perform Raman scattering signals R from the plastic P to be identified by multichannel spectroscopy and convert them into electric signals, thereby obtaining Raman scattering signals. The scattered signal acquisition means 20 (refer FIG. 3) is comprised. Multichannel spectroscope 22 may not be of high resolution, can be selected by the performance of the diffraction grating and the photodetector incorporated therein, for example, 2 cm ^-1 in the range of wave numbers 400～1600Cm ^-1 Raman shift Any Raman scattering signal can be obtained.

  The data processing device 30 is a personal computer, a CPU board, or the like, and the multi-channel spectrometer 22 is connected by, for example, a PCI (Peripheral Component Interconnect) interface. As shown in FIG. 3, the data processing device 30 selects the material of the plastic P to be identified based on the storage unit 31 that stores preset reference values and the Raman scattering signal acquired by the Raman scattering signal acquisition unit 20. Identification means 32 for identifying, and output means 33 for outputting a result (identification signal) identified by the identification means.

  The reference values stored in the storage means 31 are plastics to be identified, such as PC (polycarbonate), PS (polystyrene), PP (polypropylene), PET (polyethylene terephthalate), PVC (polyvinyl chloride), ABS resin (acrylonitrile. Raman scattering of one or more known peak positions and known baseline positions set in advance for each known plastic material such as butadiene / styrene copolymer resin (LDPE), LDPE (low density polyethylene), and HDPE (high density polyethylene). It is strength.

FIG. 4 shows each of known plastics (acrylic (clear color), PC (white), ABS (white), PS (clear color), PVC (clear color))) as a reference sample by the plastic identification device in this embodiment. The result which acquired the Raman scattering spectrum is shown. The horizontal axis in FIG. 4 represents the wave number (cm ⁻¹ ) of the Raman shift, and the vertical axis represents the Raman scattering intensity (arbitrary intensity).

4, 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 discriminating means 32 has a 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 discriminated from the Raman scattered signal acquired by the Raman scattered signal acquiring means 20. The Raman scattering intensity at the wave number of the Raman shift corresponding to the scattering intensity and the known baseline position (point B in the example of PS) is obtained, and the obtained Raman scattering intensity and the reference value stored in the storage means 31 are obtained. Based on this, the material of the plastic to be identified is identified.

For example, the discriminating means 32 uses the Raman scattering intensities R _A1 and R _{A2 at} the wave number of the Raman shift corresponding to the known peak positions (two points A ₁ and A ₂ ) for each plastic material to be identified, and the known baseline position (point B). each of the difference between the Raman scattering intensity R _B at a wave number of the corresponding Raman shift _{in) (R A1 -R B),} ( and R _A2 -R _B), the Raman scattering of the known peak positions of the known plastic as a reference value The difference (R _A10 -R _B0 ) and (R _A20 -R _B0 ) between the intensities R _A10 , 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 comparing with / (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 31 in advance.

FIG. 5 shows an example of PS identification by the identification means 32. As shown in FIG. 5, the Raman scattering intensities R _A1 and R _{A2 at} the wave number of the Raman shift corresponding to the known peak positions at the two points A ₁ and A ₂ of PS and the Raman shift corresponding to the known baseline position at the point B are shown. The ratio (R _A1 -R _B ) / (R _A2 -R _B ) of the difference (R _A1 -R _B ) and (R _A2 -R _B ) from the Raman scattering intensity R _B at the wave number is the same as that of other materials. It is very different from the thing. 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. 6 shows an example of PP identification by the identification means 32. As shown in FIG. 6, 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 X 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. 6, not all PPs can be extracted under the above conditions, but those extracted by the identification means 32 do not include anything other than PP. Can be used without problems.

Further, the identification means 32 has 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 at the Raman shift wave number corresponding to the known baseline position. the ratio R _A1 / R _B of the _B, R _A2 / calculates R _B, the ratio R between the Raman scattering intensity R _B0 of the Raman scattering intensity R _A10, R _A20 and known baseline position of the known peak position of the known plastic 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 _A10 / R _B0 and R _A20 / R _B0 .

FIG. 7 shows an example of PS identification by the identification means 32. As shown in FIG. 7, the Raman scattering intensity R _{A1 at} the wave number of Raman shift corresponding to the known peak position at one point A ₁ of PS and the Raman scattering intensity R _{B at} the wave number of Raman shift corresponding to the known baseline position The ratio R _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. 8 shows an example of PP identification by the identification means 32. As shown in FIGS. 8A and 8B, the Raman scattering intensity at the wave number of Raman shift corresponding to two known peak positions of PP and the Raman scattering intensity at the wave number of Raman shift corresponding to the known baseline position. The ratio X is different from those 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 32 determines the difference between the Raman scattering intensities R _A1 and R _A2 (R _A1 −R _A2 ) and the known baseline position at the wave number of the Raman shift 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 wave number of the Raman shift corresponding to is calculated, and the Raman scattering intensities R _A10 and R _A20 at two known peak positions of the known plastic are calculated. The ratio of the difference (R _A10 −R _A20 ) to the Raman scattering intensity R _B0 at the known baseline position (R _A10 −R _A20 ) / the material of the plastic to be identified by comparing with a threshold value as a reference value set from R _B0 It can be set as the structure which identifies.

FIG. 9 shows an example of PS identification by the identification means 32. As shown in FIG. 9, the difference between the Raman scattering intensities R _A1 and R _A2 (R _A1 −R _A2 ) and the known baseline position at the wave number of the Raman shift corresponding to the known peak positions at the two points A ₁ and A ₂ of PS. the ratio of the Raman scattering intensity R _B at a wave number of the corresponding Raman shifted _{(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.

Thus, the difference (R _A1 −R _A2 ) between the Raman scattering intensities R _A1 and R _A2 at the wave number of the Raman shift corresponding to the known peak positions at the two points A ₁ and A ₂ of PS corresponds to the known baseline position. By taking the ratio (R _A1 −R _A2 ) / R _B to the Raman scattering intensity R _{B at} the wave number of the Raman shift, 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. 10 shows an example of PP identification by the identification means 32. As shown in FIG. 10, the ratio X of the difference in Raman scattering intensity at the wave number of Raman shift corresponding to two known peak positions of PP and the Raman scattering intensity at the wave number of Raman shift corresponding to the known baseline position is The range is different from other materials. 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 32 has the Raman scattering intensity and the known baseline at the wave number of the Raman shift 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 20. The plastic is identified based on the Raman scattering intensity at the wave number of the Raman shift corresponding to the position and the reference value stored in the storage means 31, and the entire Raman scattering spectrum is measured as in the prior art. The plastic is identified by a simple calculation process without performing a complicated calculation process such as extracting a peak from the Raman scattering spectrum. Note that the identification means 32 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 crushed plastic (which may contain foreign matter) is sorted into the foreign matter and the plastic piece by the pretreatment wind sorter 2, and the sorted plastic piece is separated. Vibrating and aligning is performed by the vibration alignment feeder 3 and conveyed by the belt conveyor 4. Then, the Raman scattering discriminator 5 irradiates the plastic P to be identified on the belt 4a of the belt conveyor 4 with a laser beam to identify the material of the plastic, and sorts the plastic by the sorting air gun 6 according to the discrimination result. to recover.

  At this time, the Raman scattering discriminator 5 uses the semiconductor laser generator 12 that generates a powerful laser beam as a light source, and condenses and irradiates the laser beam on the surface of the plastic P to be identified as a sample by the convex lens 13. The Raman scattered light contained in the light is condensed coaxially by the same convex lens 13 used for condensing the laser light, guided to the multichannel spectrometer 22 by the optical fiber 21, 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 scattering signal obtained by the 512-channel multi-channel spectrometer 22 can be measured at a high speed with a sufficient SN ratio. FIG. 11 shows an example in which the Raman scattering signal of PP is measured at 50 ms and 10 ms, respectively. As shown in FIG. 11, the SN ratio sufficient for discrimination even when 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 such as finding the Raman scattering intensity at one or two points of the wave number and the Raman scattering intensity of the wave number of the Raman shift 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 processing and comparing the value with the reference value determined for the plastic of the reference sample. In this embodiment, one or two Raman shift wave numbers corresponding to the peak positions are used, but three or more points may be used.

  In particular, in the plastic identification device 1 according to the present embodiment, the belt 4a of the belt conveyor 4 is formed of stainless steel. Therefore, even if the plastic to be identified is transparent or translucent such as a clear color, the plastic is transmitted. Since the laser beam thus reflected is reflected by the surface of the belt 4a, the Raman scattered light of the belt 4a is not generated. Thereby, since the influence of the Raman effect by the belt 4a on the Raman scattered light scattered from the plastic to be identified on the belt 4a is reduced, a conspicuous Raman scattering signal with little influence of the belt 4a is obtained, and more accurate. Plastics can be identified.

Here, the generation process of Raman scattered light will be described in detail with reference to FIG. As shown in FIG. 12, a transparent or translucent object Q such as a plastic P to be identified is placed on a mounting table 100 having a metal surface such as a belt 4a made of stainless steel, and laser light is applied to the object Q. Is transmitted from the convex lens 13 of the laser irradiation system 10 through the Raman scattered light R ₁ generated by the laser light L ₁ traveling from the convex lens 13 toward the object Q and the transparent or translucent object Q, and the mounting table 100. The Raman scattered light R ₂ generated by the laser light L ₂ reflected by the metal surface is condensed by the convex lens 13. That is, since the laser light passes through the transparent or semi-transparent object Q and is reflected by the metal surface of the mounting table 100, twice the Raman scattered light R ₁ and R ₂ are collected. A clear Raman scattering signal can be obtained by the Raman scattering signal acquisition means 20 from the collected Raman scattered light R ₁ and R ₂ .

  In the present embodiment, the belt 4a is a stainless steel plate, but the rubber belt may be covered with an aluminum foil. Alternatively, it can be formed of copper or aluminum which is a metal other than stainless steel. In short, the belt 4a has only to have a metal surface, and more preferably has a gloss. Alternatively, the surface of the belt 4a may be a mirror surface, and similarly, a clear Raman scattering signal is obtained by reflecting the laser light transmitted through a transparent or translucent object on the mirror surface of the mounting table. The influence on the Raman scattering spectrum due to the difference in the material of the belt 4a will be described later.

  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. Therefore, it is possible to identify and sort a large amount of waste plastic that is actually discharged while being conveyed by the belt conveyor 4 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 13 having a focal length of 150 mm or less and irradiated to the identification plastic P. Therefore, the operation from the lens tip to the identification plastic P is performed. The distance can be secured to the same extent as the focal length of 150 mm or less, and the material of the plastic pieces of various sizes conveyed by the belt conveyor 4 can be identified.

  Further, since the convex lens 13 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 with 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 in which the laser light L is irradiated on the plastic pieces of various shapes conveyed by the belt conveyor 4. Can do.

  In the plastic identification device 1 according to the present embodiment, the laser irradiation system 10 guides the laser light L generated by the semiconductor laser generator 12 to the convex lens 13 only by the reflection of the mirror 14a and the dichroic mirror 14b. It is possible to condense the light with the convex lens 13 without irradiating the output of the laser light L and irradiate 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 the belt conveyor 4. . 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 11 incorporating the semiconductor laser generator 12 and the multi-channel spectrometer 22 are connected only by the general-purpose optical fiber 21, precise parts such as the multi-channel spectrometer 22 and the data processing device 30 are operated. It can be installed in a remote location with good environment.

  As described with reference to FIG. 12, the mounting table 100 having a metal surface such as the stainless steel belt 4 a in this embodiment, the laser irradiation system 10, and the Raman scattering signal acquisition unit 20 are used as a Raman scattering signal acquisition device. If applied to Patent Documents 1 and 2, a clear Raman scattering signal can be obtained even for a transparent or translucent object Q. Therefore, a clearer Raman scattering spectrum can be obtained to identify a plastic to be identified. It becomes possible to carry out more accurately.

  An experiment was conducted on the influence on the Raman scattering spectrum due to the difference in the material of the belt 4a of the plastic identification device 1. FIG. 13 shows the results of acquiring Raman scattering spectra of acrylic (clear color) placed on various metal plates and rubber belts. Table 1 shows the various metals used for the experiment.

  As is clear from FIG. 13, the peak positions of the Raman scattering spectrum are conspicuous in the various metal plates as compared with the rubber belt, and based on this, it is possible to more accurately identify the clear plastic. On the other hand, in the rubber belt, the peak position of the Raman scattering spectrum is unclear, so it is impossible to identify the clear plastic. This is presumed to be affected by the Raman scattered light of rubber.

  In addition, Table 2 shows the transmittance of clear and white acrylic laser light. Laser light transmittance is measured by placing a laser irradiation system 10 and a Spectra-Physics laser power meter (Model 407A) on both sides of a clear and white acrylic plate (2 mm thick). The ratio of the intensity value (W) of the laser power meter when it passed through each acrylic plate and the intensity value (W) of the laser power meter when the acrylic plate was removed was determined. The results are shown in Table 2.

  From Table 2, it can be seen that the white acrylic plate hardly transmits laser light. On the other hand, it can be seen that the clear acrylic plate transmits laser light and is translucent or transparent. In other words, the Raman scattering spectrum of each plastic of acrylic (clear color), PS (clear color), and PVC (clear color) shown in FIG. 5 is a PC that hardly transmits laser light regardless of whether it is translucent or transparent. It can be seen that an outstanding Raman scattering signal comparable to (white) and ABS (white) is obtained.

  A Raman scattering signal acquisition method and a Raman scattering signal acquisition apparatus according to the present invention acquire a Raman scattering signal scattered from a transparent or translucent object, and non-destructively use a plastic material based on the acquired Raman scattering signal. The present invention is useful for a plastic identifying method and an identifying apparatus. The plastic identifying device and the identifying device of the present invention are a method and device for identifying a plastic material by measuring a scattering phenomenon called Raman scattering, and are variously discarded as household waste or industrial waste for recycling. It is useful as a method and apparatus for identifying a new plastic.

It is a schematic block diagram of the plastic identification device in embodiment of this invention. It is a block diagram of the Raman scattering discriminator of FIG. It is a block diagram of the Raman scattering classifier 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. It is sectional drawing explaining the generation | occurrence | production process of a Raman scattered light. It is a figure which shows the result of having acquired the Raman scattering spectrum of the acryl (clear color) arrange | positioned on various metal plates and a rubber belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plastic identification apparatus 2 Pre-processing wind selector 3 Vibration alignment feeder 4 Belt conveyor 4a Belt 5 Raman scattering identification machine 6 Sorting air gun 7 Air gun drive device 8 Synchronous control device 9 Conveyor speed adjustment device 10 Laser irradiation system 11 Detector head 12 Semiconductor laser generator 13 Convex lens 14a Mirror 14b Dichroic mirror 20 Raman scattering signal acquisition means 21 Optical fiber 22 Multichannel spectrometer 23 Excitation light removal filter 30 Data processing device 31 Storage means 32 Identification means 33 Output means 40 Semiconductor laser drive power supply

Claims (6)

The laser beam is irradiated to the transparent or translucent plastic of a object placed on the mounting table having a metal surface or specular reflecting the laser beam, the plastic from the Raman scattered light scattered from the object A method for obtaining a Raman scattering signal, comprising obtaining a Raman scattering signal for identifying a material . The laser beam is irradiated to the transparent or translucent identification target plastic is the identification object placed on the mounting table having a metal surface or specular reflecting the laser beam, the Raman scattered light scattered from the object to be identified plastic Obtaining a Raman scattered signal from the Raman scattered signal obtaining step;
Raman scattering intensity and baseline position (hereinafter, “known baseline 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. Corresponding to the Raman scattering intensity and the known baseline position at the wave number of the Raman shift 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. An identification step of identifying the material of the plastic to be identified based on the Raman scattering intensity at the wave number of the Raman shift. A mounting table having a metal surface or a mirror surface that reflects laser light and on which a transparent or translucent plastic as an object is mounted;
A laser irradiation system for irradiating an object placed on the mounting table with a laser;
A Raman scattered signal acquisition device comprising: a Raman scattered signal acquiring means for acquiring a Raman scattered signal for identifying the plastic material from the Raman scattered light scattered from the object. A mounting table having a metal surface or a mirror surface that reflects laser light and on which a transparent or semi-transparent plastic to be identified is placed;
A laser irradiation system for irradiating the identification target plastic mounted on the mounting table with a laser;
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, “known baseline 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
A Raman scattering intensity at a Raman shift wave number corresponding to a known peak position for each plastic material to be identified obtained from a Raman scattering signal of the identified plastic, and a Raman scattering intensity at a Raman shift wave number corresponding to a known baseline position; A plastic identification device comprising: identification means for identifying the material of the plastic to be identified based on the Raman scattering intensity at the known peak position and the Raman scattering intensity at the known baseline position stored in the storage means. 5. The plastic identifying apparatus according to claim 4 , wherein the metal surface of the mounting table is glossy. Metal constituting the metal surface of the mounting table is a plastic identification device according to claim 4 or 5 stainless steel, aluminum or copper.