JPH1038807A - Plastic discriminating method and plastic discriminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic discriminating method and a plastic discriminating device that can discriminate sorts of waste plastic without complicated processing to obtained data. SOLUTION: When waste plastic 1 placed on a belt conveyor 2 is conveyed into a specified position, laser beams are applied from a laser device 3 and spectrally diffracted by a Raman spectroscope 4, and a Raman spectrum is recorded in a recording part 5. Data of the wave number of a plurality of Raman lines and the relative intensity value of the spectrum in that wave number is extracted from the spectrum. The extracted data is compared with standard plastic sample data, previously measured and recorded in a database recording part 7, by a comparing part 6, and the result is sent to a discriminating part 8. According to the discriminated result, an instruction is sent to a sortor 9 from the discriminating part 8, and the waste plastic 1 is sorted to specified places.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of discriminating a plastic material and a plastic material discrimination device in a plastic recycling process, and more particularly to a plastic discrimination method and a plastic discrimination device using a Raman spectrum. About.

[0002]

2. Description of the Related Art Conventionally, in the process of recycling plastics, there has been an attempt to identify materials of waste plastics by a near-infrared method utilizing a near-infrared spectrum (for example, JP-A-6-210632, JP-A-6-210632). -30802
2, JP-A-7-151603). JP-A-6-21063
No. 2 discloses a method of discriminating a functional group of a plastic material based on absorption in an infrared region or a near-infrared region based on a molecular structural formula of the plastic and classifying the type. In Japanese Unexamined Patent Publication No. Hei 6-308022, a plastic is irradiated with near-infrared light to measure an absorption spectrum, and a first-order or second-order differential spectrum is obtained. Is determined by comparing with the previously obtained differential spectrum of the standard plastic to determine its precision, and determining the material of the standard plastic sample showing the maximum precision as the material of the unknown plastic. It is shown. Further, Japanese Patent Laid-Open Publication No. Hei 7-151603 discloses a method of detecting a measurable position of a near-infrared absorption spectrum required for discrimination of a plastic to be discriminated on the plastic to be discriminated. All of these use near infrared absorption and reflection spectra.

[0003]

However, these conventional methods have the following problems.

[0004] Since the near-infrared absorption spectrum is an overtone and a combined sound of absorption based on vibrational transition of molecules, the spectrum is generally broad. Therefore, a complicated data processing technique is required in the process of determining the plastic material to be determined. When the copolymer is contained, the discrimination process is further complicated.

In the near-infrared reflection absorption spectrum, the shape of the spectrum is different from that of the transmission absorption spectrum because it is affected by the direct reflection of the plastic surface. Therefore, conditions such as differential processing are newly added to the spectrum of the plastic to be discriminated, and data processing becomes complicated.

[0006] Further, if there is a substance having strong absorption in the near infrared region on the surface of the discriminated plastic, the information of the plastic material may not be accurately obtained from the spectrum due to the influence of the substance.

Further, some types of plastic have extremely strong absorption. In this case, absorption saturation occurs in the spectrum, so that information necessary for discrimination cannot be obtained.
It interferes with the discrimination of the plastic to be discriminated.

Further, in a measurement in a bright place, since the spectrum is affected by extraneous light, the accurate shape of the spectrum of the plastic to be identified may not be measured.

Accordingly, it is an object of the present invention to determine the plastic without complicated processing of its spectrum and to be influenced by the surface of the plastic to be determined and the specific absorption when measuring the spectrum. It is an object of the present invention to provide a plastic discriminating method and a plastic discriminating apparatus which can be used even in a bright place without any problem.

[0010]

A plastic discriminating method according to the present invention comprises a measuring step of measuring a Raman spectrum of a discriminated plastic whose material is unknown, and a Raman spectrum of a plastic whose known material is measured. The method includes a comparison step of comparing the Raman spectrum and a step of discriminating a plastic material to be discriminated from a result of the comparison in the comparison step.

As described above, according to the present invention, the Raman spectrum of a plastic is measured and the material of the plastic to be determined is determined based on the measured Raman spectrum. Reflecting the state of their bonding, the characteristics of each material are more clearly shown than in the infrared absorption spectrum. In addition, the Raman spectrum is obtained not as broad as in infrared absorption but as a bright line called Raman shift to a specific wave number specific to a substance. Therefore, it is easy to specify a material even if the signal level is small. Further, since the Raman scattering phenomenon has relatively low sensitivity compared to other spectra, the influence of the dye contained in the discriminated plastic or the stain on the surface is small, and it is easy to obtain information unique to the material of the discriminated plastic.
Further, since there is no Raman spectrum having a remarkably strong absorption like an infrared absorption spectrum, no saturated absorption occurs.

Since the Raman spectrum has these characteristics, it is hardly affected by, for example, the effects of direct reflection on the surface, irregular reflection from unevenness on the surface, and the shape of the discriminated plastic. These are advantageous features for discriminating waste plastic. In the actual discrimination process, a Raman spectrum of a plastic whose material is sufficiently known to prepare a sufficiently good sample can be measured as a spectrum that well represents the characteristics of the material. On the other hand, the discriminated plastic whose material is unknown may generally have various stains attached to the surface, but when the Raman spectrum is measured, the characteristic of the material is not affected by the attached matter such as the stain. Is obtained. Therefore, by comparing the Raman spectrum of the plastic whose material is unknown and the Raman spectrum of the plastic whose material is known, the material of the plastic to be determined can be identified. If this discrimination method is applied to the separation of waste plastic, the material of waste plastic can be discriminated.

Further, the plastic discriminating method according to the present invention comprises a measuring step of measuring the Raman spectrum of the plastic to be discriminated whose material is unknown, a wave number of the Raman line based on the Raman spectrum measured in the measuring step, and the wave number of the Raman line. The extraction step of extracting the relative intensity value, the wave number of the Raman line of the plastic whose material is known, the relative intensity value at that wave number, and the Raman line wave number of the Raman spectrum measured in the measurement step and the relative intensity value at that wave number And a step of discriminating the material of the discriminated plastic from the comparison result of the comparison step.

The Raman spectrum is not broad as in the case of the infrared absorption spectrum, but is obtained as a bright line called a Raman shift at a specific wave number specific to a substance. As a representative parameter, the characteristic of the Raman spectrum is represented by the bright line (Raman line). ) And the relative intensity value at that wave number. The Raman spectrum of a plastic whose material is known to provide a sufficiently good sample has a Raman shift that well characterizes the material, and as a result,
The wave number and the relative intensity value at that wave number well represent the characteristics of the material. In addition, the discriminated plastic whose material is unknown may generally have various stains attached to the surface.However, when the Raman spectrum is measured from the characteristics of the Raman spectrum described above, the influence of the attached matter such as the stain can be found. A Raman shift that clearly shows the characteristics of the material can be obtained without receiving it. The wave number and the relative intensity value at the wave number well represent characteristics of the material. Therefore, when the wave number of the Raman line and the relative intensity value at that wave number are extracted from the measured Raman spectrum, and this extracted data is compared with the wave number of the Raman line of a plastic whose material is known and the relative intensity value at that wave number, respectively, The material of the discriminated plastic can be identified without performing complicated data processing. If this discrimination method is applied to the separation of waste plastic, the material of waste plastic can be discriminated.

The plastic discriminating apparatus according to the present invention comprises: a spectrum measuring means for measuring a Raman spectrum of a plastic to be discriminated whose material is unknown; a recording means for storing a Raman spectrum of a plastic whose material is known; A spectrum comparing means for comparing the Raman spectrum measured by the means with the Raman spectrum recorded in the recording means; and a discriminating means for discriminating the material of the plastic to be discriminated from the comparison result by the spectrum comparing means.

Since the spectrum measuring means for measuring the spectrum of the discriminated plastic whose material is unknown based on the Raman spectrum having the above-mentioned characteristics is provided, it is possible to obtain a spectrum that well represents the characteristics of the discriminated plastic material. it can. In addition, recording means for storing the Raman spectrum of a plastic whose material is known, and spectrum comparing means for comparing the Raman spectrum measured by the spectrum measuring means with the Raman spectrum recorded in the recording means are provided. The spectra can be compared immediately after measuring the spectra of the plastic. Since the discriminating means for discriminating the plastic material to be discriminated from the comparison result by the spectrum comparing means is provided, the plastic material to be discriminated can be immediately identified from the comparison result. If this discriminating apparatus is applied to the separation of waste plastic, the material of waste plastic can be determined.

In the plastic discriminating apparatus according to the present invention, the recording means records the wave number of the Raman line of the Raman spectrum of the plastic whose material is known and the relative intensity value at the wave number. Extraction means for extracting the wave number of the Raman line and the relative intensity value at that wave number from the Raman spectrum of the plastic to be discriminated measured by the spectrum measurement means, and the wave number and relative intensity value extracted by the extraction means and stored in the recording means Means for comparing the wave number of the Raman line and the relative intensity value at the wave number may be provided.

The Raman spectrum is obtained as an emission line called a Raman shift to a specific wave number specific to a substance, and the wave number of this emission line (Raman line) and the relative intensity value at the wave number are taken as typical parameters of the Raman spectrum. Can be For a plastic whose raw material is sufficiently known to prepare a sample, a Raman shift that well represents the characteristics of the raw material can be obtained. In addition, the plastic to be identified whose material is unknown may have various stains or the like generally adhered to the surface, but due to the above-described characteristics of the Raman spectrum,
When the Raman spectrum is measured, a Raman shift that clearly shows the characteristics of the material can be obtained without being affected by extraneous matter such as dirt. Therefore, an extraction means for extracting the wave number of the Raman line and the relative intensity value at the wave number from this spectrum is provided, and the recording means is provided for the Raman wave number of the Raman spectrum of a plastic whose material is known and the relative number at the wave number. Since the intensity data is recorded, comparing the extracted data with the wave number of the Raman ray recorded in the recording means and the relative intensity value at that wave number, the discrimination can be performed without complicated data processing. Plastic materials can be identified. If this discriminating apparatus is applied to the separation of waste plastic, the material of waste plastic can be determined.

In the plastic discriminating apparatus according to the present invention, the recording means may be configured to record the Raman spectrum of the plastic whose material measured by the spectrum measuring means is known.

When the Raman spectrum recorded in the recording means and the Raman spectrum of the plastic to be discriminated are measured by the same apparatus, the spectral sensitivity of the detector, the diffraction efficiency of the spectrometer, and the like are determined by the Raman shift and relative intensity of the Raman line. Can be identified without affecting.

In the plastic discriminating apparatus according to the present invention, the spectrum measuring means may have an excitation light source for outputting near-infrared laser light for obtaining a Raman spectrum.

When a Raman spectrum is obtained using an excitation light source that emits near-infrared laser light as described above, the influence of fluorescence from fluorescent impurities, coloring materials, stains, oxides, and the like can be avoided. Many samples can be distinguished by the device.

In the plastic discriminating apparatus according to the present invention, the spectrum measuring means has an excitation light source for outputting a pulse laser beam for obtaining a Raman spectrum, and means for measuring a Raman spectrum in synchronization with the excitation light source. It may be.

When the Raman spectrum is acquired using the pumping light source that outputs the pulsed laser light in synchronization with the pumping light source, the device can be operated in a bright place without being affected by extraneous light.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a schematic diagram of a plastic waste discrimination system to which the present invention is applied. In the waste discrimination system of FIG. 1, when a waste plastic (unknown sample) 1 is carried on a belt conveyor 2 and brought to a predetermined position, a laser beam is emitted from a laser device 3 and a Raman The spectrum is measured and recorded in the recording unit 5. This spectrum is compared with the spectrum of the standard plastic sample recorded in the database recording unit 7 by the comparison unit 6, and the comparison result is sent to the determination unit 8. Based on the result of this determination, an instruction is issued from the determination unit 8 to the separator 9 so that the waste plastic 1 is separated to a predetermined place.

Next, the procedure for measuring the Raman spectrum of a plastic sample using this waste discrimination system will be described. The laser device 3 uses a semiconductor-excited pulse oscillation YAG laser, for example, having a wavelength of 1.064 μm, a pulse width of 10 nm, a repetition frequency of 12 kHz, and an average output of 13 m.
W. The sample 1 is irradiated with the laser light as excitation light, the backscattered light is separated by a Raman spectroscope 4 via a notch filter (not shown), and a near-infrared photomultiplier tube (not shown) is used as a detector. ) Was used to measure the scattered light intensity.
For the measurement of the scattered light intensity, the Raman spectroscope 4 was scanned and the photons were sequentially counted by using the synchronous photon counting method in which the gate of the detector was opened in synchronization with the irradiation of the pulsed laser light, and the Raman spectrum was measured.

As described above, when the gate system for performing measurement in synchronization with the pulse of the pulse laser device is employed, the device can be operated in a bright place without being affected by extraneous light.

When a Raman spectrum is acquired by near-infrared excitation in this way, the influence of competing fluorescence can be avoided. Therefore, since the influence of fluorescence from fluorescent impurities, coloring materials, stains, oxides, and the like can be avoided, many samples can be distinguished with a simple measuring device. In the present embodiment, 1.064 μm near-infrared light is used as excitation light for acquiring a Raman spectrum. However, the present invention is not limited to this, and 0.7 μm to 1.6 μm near-infrared light is used. The excitation light in the outer region can be used.

The results of measuring the Raman spectra of the six unknown samples as described above are shown in FIGS.
(A). FIGS. 2 (b) to 7 (b) show the results of measuring Raman spectra of standard plastic samples corresponding to the respective materials shown in FIGS. 2 (a) to 7 (a).
Shown in These FIGS. 2 (a) to 7 (a) and FIGS. 2 (b) to
In FIG. 7B, the horizontal axis indicates the Raman shift in units of cm ^-1 , and the vertical axis indicates the relative intensity value of the scattered light. Less than,
Each of FIGS. 2 to 7 will be described.

FIG. 2A shows the result of measuring the Raman spectrum of the floppy case as the unknown sample S1,
FIG. 2B shows the result of measuring the Raman spectrum of polystyrene (PST) as a standard plastic sample. In FIG. 2A, A ′, B ′, C ′, D ′,
Raman lines are observed at wave numbers indicated by E ', F', G ', and H'. FIG. 2 shows a Raman spectrum of PST.
In (b), there are Raman lines at the wave numbers A, B, C, D, E, F, G, and H in the figure. FIG. 2 (a) and FIG.
Comparing A and A 'from H and H' in (b) in correspondence with each other, the wave numbers at the peaks are almost equal, and the relative intensity values of the peaks show good agreement. Therefore, S1 is P
It is determined to be ST.

FIG. 3A shows a result of measuring a Raman spectrum of a ruler as the unknown sample S2, and FIG.
Is an MMA resin (PMM) as a standard plastic sample.
It is the result of measuring the Raman spectrum of A). FIG.
In (a), A ', B', C ', D', E ',
Raman lines are observed at wave numbers indicated by F ', G', H ', and J'. FIG. 3 shows a Raman spectrum of the MMA resin.
In (b), A, B, C, D, E, F, G, H,
There is a Raman line at the wave number indicated by J. FIG. 3 (a) and FIG.
Comparing A and A 'to J and J' in (b) in correspondence with each other, the wave numbers at the peaks are almost equal, and the relative intensity values of the peaks also show good agreement. Therefore, S2 is P
MMA is determined.

FIG. 4A shows the result of measuring the Raman spectrum of a white translucent tube as an unknown sample S3, and FIG. 4B shows the result of measuring the Raman spectrum of polyethylene (PE) as a standard plastic sample. The result. In FIG. 4A, Raman lines are observed at wave numbers indicated by A ', B', C ', and D' in the figure. In FIG. 4B showing the Raman spectrum of PE, A, B, C, and
There is a Raman line at the wave number indicated by D. FIG. 4 (a) and FIG.
Comparing A and A 'from D and D' in (b) in correspondence with each other, the wave numbers of the peaks are almost equal, and the relative intensities at the respective peaks show good agreement. Therefore, S3 is PE
Is determined.

FIG. 5A shows the result of measuring the Raman spectrum of a plastic screw as an unknown sample S4.
FIG. 5B shows a result of measuring a Raman spectrum of polycarbonate (PC) as a standard plastic sample. In FIG. 5A, A ′, B ′, C ′, D ′,
E ', F', G ', H', J ', K', L ', M',
A Raman line is seen at the wave number indicated by N '. Also, in FIG. 5B showing the Raman spectrum of PC, A, A in FIG.
There are Raman lines at wave numbers B, C, D, E, F, G, H, J, K, L, M, and N. FIG. 5 (a) and FIG. 5 (b)
Comparing A and A 'from N to N' in
The wave numbers of the peaks are almost equal, and the relative intensities at each peak also show good agreement. Therefore, S4 is determined to be a PC.

FIG. 6A shows the result of measuring the Raman spectrum of a vinyl tape as an unknown sample S5, and FIG. 6B shows the result of measuring the Raman spectrum of a vinyl chloride resin (PVC) as a standard plastic sample. It is. In FIG. 6A, A ′, B ′, C ′, D ′,
Raman lines are observed at the wave numbers indicated by E 'and F'. Also, P
In FIG. 6B showing a Raman spectrum of VC, Raman lines are present at wave numbers indicated by A, B, C, D, E, and F in the figure. 6 (a) and 6 (b), the wave numbers of the peaks are almost equal, and the relative intensities of the peaks show good agreement. Therefore, S5 is determined to be PVC.

FIG. 7A shows the result of measuring the Raman spectrum of a white tube as the unknown sample S6, and FIG. 7B shows the result of measuring Teflon (P) as a standard plastic sample.
It is the result of measuring the Raman spectrum of TFE). In FIG. 7A, A ′, B ′, C ′, D ′, E ′,
A Raman line is seen at the wave number indicated by F '. Also, PTFE
In FIG. 7B showing the Raman spectrum of, the wave numbers indicated by A, B, C, D, E, and F in the figure have Raman lines.
7 (a) and 7 (b), when A and A 'to F and F' are compared with each other, the wave numbers of the peaks are almost equal, and the relative intensities of the respective peaks show good agreement. Therefore, S6 is determined to be PTFE.

As described above, from the specific examples of FIGS.
The Raman spectrum reveals the state of atomic groups and their bonds from the spectrum, and more clearly shows the characteristics of each material as compared with the near-infrared absorption spectrum. Therefore, by comparing the Raman spectrum of a plastic with an unknown material with the spectrum of a sample with a known material, the plastic material with an unknown material can be identified. If this is used for discriminating waste plastic, the material of waste plastic can be discriminated in a non-contact manner.

Next, a description will be given of a database creation procedure and a comparison procedure and a discrimination procedure when a method based on peak detection and intensity comparison is used for these data.

First, the procedure for creating a database of plastic standard samples recorded in the database recording section 7 is shown in FIG.
This will be described with reference to FIG. Standard plastic sample A
Was measured by the apparatus shown in FIG.
1) Recording is performed on the recording unit 5 (22). Fig. 8 shows the measurement results.
(A). Next, an offset due to the dark output of the detector is subtracted from this data because it becomes an obstacle when comparing spectra in the case of a Raman spectrum having a low SN ratio (24). As a subtraction method, generally, it is preferable to use, as an offset value, the spectrum intensity in the wave number region where the Raman line of the organic substance is not present. For example, 1900cm ^-1 ~ 200
It is preferable that the spectral intensity in the 0 cm ^-1 region be the offset value. The offset value is indicated by a broken line (3) in FIG.
0), and the subsequent analysis is performed on a portion equal to or larger than this value. Thereafter, a peak is detected from the Raman spectrum to find the position of the Raman line (25). This peak is shown as v ₁ to v ₁₂ in FIG. The number of peaks to be detected is preferably about 6 to 10 points. The relative intensity values of these peaks are weighted in four steps of very strong (ss), strong (s), normal (m), and weak (w) (26). FIG. 8 (a)
The result of weighting the spectrum of is the peak v ₂ (3
1) is a weight ss, and peaks v ₁ (32), v ₆
(33), v ₁₀ (34) are weights s, v
₈ (35), v ₁₂ (36) are the weights m, and the remaining peaks v ₃ , v ₄ , v ₅ , v ₇ , v ₉ , v ₁₁ are:
Weighting w. The results of the weighting of these Raman lines are compiled into a list as shown in FIG. 8B for each standard plastic sample, and recorded in the database recording unit 7. The list may include, for example, the relative intensity value at the peak in addition to the weighting. In this way, a database is created for the necessary standard plastic samples. In the above description, these procedures (24, 24,
25, 26) are performed by the comparison unit 6 of FIG.

Next, the procedure of comparison and determination will be described with reference to FIGS. The Raman spectrum of the unknown sample plastic S was measured using the apparatus shown in FIG.
1) Recording is performed on the recording unit 5 (42). FIG. 11 shows the measurement results.
Shown in This data is subjected to an offset subtraction with an offset value (50) in the same manner as in the database creation procedure (44), peaks s _{1 to} s ₉ are detected (45), and weighting (46) is performed. The wave number of the Raman line to be compared with and the weighting data at the wave number are extracted from the spectrum. FIG. 11 shows the results of peak detection and weighting performed on the data. As a result, s ₇ (51) is the weight ss, and s ₁ (52), s ₄ (53), s ₆ (54), s
₈ (55) and s ₉ (56) are weights m, s ₂ ,
s ₃ and s ₅ are weightings w. Thereafter, the database is sequentially read from the database recording unit 7 (48),
The data is compared with the data of the unknown sample S (47), and the result is sent to the determination unit 8. In the above description, these procedures (44, 45, 46, 47) surrounded by the broken line 43 in FIG. 10 are performed by the comparison unit 6 in FIG. After receiving all of the comparison results of the data of the unknown sample S and the data of each standard plastic sample, the discriminating unit 8 selects those having a high degree of peak coincidence from these comparison results (49), and To By this method, the Raman spectra of the unknown samples S1 to S6 shown in FIGS. 2A to 7A can be determined.

The above-described database creation procedure, comparison and determination procedure can be easily realized by using a computer or the like.

Since the Raman spectrum is not broad like the infrared absorption spectrum, it is obtained as an emission line called a Raman shift at a specific wave number specific to a substance, and the characteristics of the Raman spectrum are represented by the emission line (Raman shift) as a representative parameter. Line) and the relative intensity value at that wave number. Therefore, a method based on peak detection and intensity comparison can be used. Then, the wave number of the Raman line and the relative intensity value at the wave number are extracted from the Raman spectrum of the unknown sample, and the extracted data is compared with the relative intensity value at the wave number of the Raman line of the plastic whose material is known and the wave number, Identification of the plastic material to be identified can be performed without complicated data processing.

As described above, waste plastic can be separated without contact by such a method. In addition, Raman scattering is a kind of light emission phenomenon, and the absolute value of the signal intensity may be weak in order to determine how many signals are present at the wave number of interest. Therefore, FIGS.
In the measurement of (a), as compared with the measurement of FIGS. 2 (b) to 7 (b), identification can be performed similarly even when the intensity of the excitation laser beam is reduced to 1/20 and the SN ratio is reduced. In addition, FIG.
The SN of about 1/50 of the spectrum of the unknown sample in FIG.
The ratio can also be determined by the method shown in FIG.

If the purpose is only to discriminate the waste plastic as a sample, it is not necessary to acquire a spectrum over the entire wave number range, and only the characteristic part of the Raman spectrum of the sample may be measured. In this case, a bandpass filter that transmits one or more wavelengths may be used instead of the spectroscope. In this way, the speed of the determination is increased and the apparatus is simplified. In addition, if a higher output pump laser beam is used, the speed of the discrimination can be further increased. For example, a discrimination of about 0.1 second per sample is possible. Further, a plurality of samples may be simultaneously measured in parallel using an optical fiber or the like. In this way, the speed of determination can be improved.

In particular, when a Raman spectrum is obtained by near-infrared excitation, the influence of competing fluorescence can be avoided. Therefore, in the plastic determination method and the plastic determination device of the present invention, the influence of fluorescence from fluorescent impurities, coloring materials, stains, oxides, and the like can be avoided, so that many samples can be determined with a simple measuring device.

(Second Embodiment) In a second embodiment, a case will be described in which the spectrum of an unknown sample is compared with a standard plastic sample using a correlation function. The Raman spectrum can be measured by the apparatus shown in FIG. 1 in the same manner as in the first embodiment. Therefore, the detailed description is omitted. Note that the correlation function f (X) is

[0047]

(Equation 1) Say. Here, X is a wave number, the function of the Raman spectrum of the standard plastic sample is S (X), and the function of the Raman spectrum of the unknown sample is D (X).

First, the procedure for creating a database of plastic standard samples recorded in the database recording section 7 is shown in FIG.
This will be described with reference to FIG. The Raman spectrum of the standard plastic sample A is measured by the apparatus shown in FIG. 1 (61), and this is recorded in the recording unit 5 (62). FIG. 8A shows the measurement results. As in the first embodiment,
An offset due to the dark output of the detector is subtracted from this data (64). The offset value is indicated by a broken line (3) in FIG.
0), and the subsequent analysis is performed on a portion equal to or larger than this value. Thereafter, in order to find the position of the Raman line, a peak is detected from the Raman spectrum in the same manner as in the first embodiment (65). This peak is shown in FIG.
(A) shown in v ₁ to v ₁₂ in. The number of peaks to detect
About 6 to 10 points are preferable. Then, the relative intensity values of the spectrum centered on these peaks are converted into data discretized at predetermined wavenumber intervals (66). All values of a given measurement area may be recorded in the database, but in order to reduce the data to be recorded in the database, the data to be discretized should be in the range of the wave number from the peak value to the offset value of the spectrum. Is preferred. The results of the discretization of these Raman spectra are recorded in the database recording unit 7 in pairs of (wave number, relative intensity value) for each standard plastic sample (67). In this way, a database is created for the necessary standard plastic samples. These procedures (64, 65, 66) surrounded by a broken line 63 in FIG.
Is performed by the comparison unit 6 in FIG. Note that the relative intensity values of all wave numbers may be discretized and recorded without performing peak detection.

Next, the procedure of comparison and determination will be described with reference to FIGS. The Raman spectrum of the unknown sample plastic S was measured with the apparatus shown in FIG.
1) Recording is performed on the recording unit 5 (72). FIG. 11 shows the measurement results.
Shown in This data is subjected to offset subtraction with an offset value (50) in the same manner as in the database creation procedure (74), peaks s _{1 to} s ₉ are detected (75), and further discretization (76) is performed. , And extract the discretized data to be compared with the database from the spectrum. Thereafter, the database is sequentially read from the database recording unit 7 (7
8) The correlation function with the data of the unknown sample S is sequentially calculated (77), and the calculation result is sent to the determination unit 8. The correlation function can be obtained by numerical integration by a computer. In the above description, these procedures (74, 75, 76, 77) surrounded by the broken line 73 in FIG. 13 are performed by the comparison unit 6 in FIG. After receiving all the calculation results of the correlation function between the data of the unknown sample S and the data of each standard plastic sample, the discriminating unit 8 calculates X of the correlation function based on these calculation results.
A behavior having a high degree of correlation is selected from behaviors near = 0 and an instruction is issued to the classifier 9. Also in this method, FIGS.
The Raman spectra of the unknown samples S1 to S6 shown in FIG.

As described above, the plastic material can also be identified by measuring the Raman spectrum of the plastic sample whose material is unknown and calculating the correlation function with the data of the standard plastic sample. Therefore,
Waste plastic can be identified. Also,
The respective composition ratios are also known from the values of the correlation functions calculated for a plurality of standard plastic samples.

Third Embodiment In the first and second embodiments, near-infrared laser light is used as excitation light for Raman spectrum measurement, but visible light is used as excitation light. It can also be used. When using visible light,
In the apparatus used in the first embodiment shown in FIG. 1, an excitation laser device 3 capable of oscillating visible laser light is provided with a Raman spectroscope 4 capable of dispersing a visible light region and a photomultiplier for visible light as a detector. A tube (not shown) is used. Raman spectra measured by such an apparatus are compared by a method based on peak detection and intensity comparison as in the first embodiment.

FIGS. 14A and 14B show the results obtained by measuring the Raman spectra of the floppy case and the white foamed styrene using 532 nm visible light as excitation light, respectively. For comparison, FIG.
14 (a) and 14 (b) are measured by exciting with near-infrared laser light next to FIG. 14 (c) and FIG.
(D). When set to a value showing the offset value by a broken line (80) in FIG. 14 (a), t ₁ as a peak,
t ₂ and t ₃ are detected. These peaks are shown in FIG.
(C) corresponds to t ₁ ′, t ₂ ′, and t ₃ ′. When set to a value showing the offset value by a broken line (90) in FIG. 14 (b) In the same _{manner, u 1, u 2, u} 3 is detected as a peak. These peaks are represented by u ₁ ′, u ₂ ′,
Corresponds to u ₃ '. Therefore, it can be seen from the description of the first embodiment that the unknown sample can also be determined from the Raman spectrum measured using visible light as the excitation light by the procedure shown in FIGS. In this embodiment, the offset value is determined regardless of the wave number.
Depending on the offset, the offset value may have a wave number dependency.

As described above, the present invention is applicable even when visible light is used as excitation light. The obtained Raman spectrum has an offset due to the influence of fluorescence as compared with the case where near-infrared light is used as excitation light. However, this effect can be avoided by using a picosecond laser device with an excitation light source and a detector with picosecond gates.

In the first and third embodiments, waste plastic is determined by a method based on peak detection and intensity comparison, and in the second embodiment, waste plastic is determined by a method of calculating a correlation function. Plastic was determined. The present invention is not limited to these discriminating methods. In addition, a discriminating method based on a threshold value, a method of performing a non-linear pattern matching using a neural network, and the like can be used.

Further, in the first to third embodiments, the explanation has been given as to which of the plurality of standard plastic samples corresponds to the unknown sample, but this method selects only a single substance. It is especially effective when you want to. However, if all of the comparison results in the comparison unit 6 are sent to the determination unit 8, the correspondence with a plurality of standard plastic samples can also be determined. Furthermore, even when a large amount of plasticizer is contained or a copolymer, new data is created by adding multiple databases of standard plastic samples, and this is compared with an unknown sample. The composition ratio of standard plastic samples can be analyzed. Furthermore, in the case where the spectrum of an unknown sample and the spectrum of a standard plastic sample are measured by the same device, the Raman wave numbers of the plurality of standard plastic samples recorded in the database are the same as those of the plastic to be determined. When a part of the wave number of the line coincides, the relative intensity values of the corresponding Raman lines of each standard plastic sample and the plastic to be determined are compared, and when the relative ratio is obtained, the standard plastic samples are compared. The composition ratio of the sample can also be determined. Further, the spectrum recorded in the database may include not only a plastic made of a single material but also a plastic made of a plurality of materials. In this way, a plastic having a specific composition can be identified.

In the first to third embodiments, a method of scanning a spectroscope using a single-channel detector is used to obtain a Raman spectrum. A multi-channel detector having sensitivity in the light region or near-infrared light region may be used. This eliminates the need to scan the spectroscope, thereby reducing the measurement time.

In the first to third embodiments, the Raman spectrum of the standard plastic sample for creating the database is measured by the same measuring device as the Raman spectrum of the unknown sample. Since the Raman shift value inherent to the substance is invariable when the measurement devices are different, these spectra may be based on data measured by different devices, but are preferably measured by the same measurement device. This is because the intensity of the Raman line is affected by the spectral sensitivity of the detector, the diffraction efficiency of the spectrometer, and the wavelength transmittance dependency when an optical fiber is used.

It should be noted that the database is generally created once when the apparatus is started up, and can be used continuously for subsequent discrimination. It can also be applied to plastics synthesized in the future.

[0059]

As described above, the plastic discriminating method and the plastic discriminating apparatus according to the present invention acquire a Raman spectrum, which represents the characteristics of each material more than the near-infrared absorption, for the waste plastic.
The spectrum shows the atomic groups and their bonding.
By comparing this with the spectrum of the known sample, the material of the waste plastic can be easily determined without contact. Also,
The configuration of the device can be simplified.

In general, since the sensitivity of the Raman scattering phenomenon is relatively low, the influence of impurities such as dyes, pigments, and stains contained in the unknown sample is small. Therefore, according to the plastic discriminating method and the plastic discriminating device of the present invention, since the information unique to the waste plastic material can be obtained regardless of these effects, the discrimination of the waste plastic material can be easily performed.

In the plastic discriminating method and the plastic discriminating apparatus according to the present invention, since the Raman shift is unique to the substance, the substance can be specified by the number of signals at the wave number of interest. Therefore, if there is a signal that is slightly higher than the noise level, the material of the waste plastic can be determined without performing complicated data processing.

Further, the plastic discriminating method and the plastic discriminating apparatus of the present invention can be operated in a bright place without being affected by extraneous light, especially when a pulse laser device and a gate system for performing measurement in synchronization with the pulse are adopted. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a plastic waste discrimination system to which the present invention is applied.

FIG. 2A is a Raman spectrum diagram of a floppy case. FIG. 2B shows polystyrene (PST).
3 is a Raman spectrum diagram of FIG.

FIG. 3A is a Raman spectrum diagram of a ruler. FIG. 3B is a Raman spectrum diagram of the MMA resin (PMMA).

FIG. 4 (a) is a Raman spectrum diagram of a white translucent tube. FIG. 4B shows polyethylene (PE).
3 is a Raman spectrum diagram of FIG.

FIG. 5A is a Raman spectrum diagram of a plastic screw. FIG. 5 (b) shows polycarbonate (PC).
3 is a Raman spectrum diagram of FIG.

FIG. 6 (a) is a Raman spectrum diagram of a vinyl tape. FIG. 6B shows a vinyl chloride resin (PVC).
3 is a Raman spectrum diagram of FIG.

FIG. 7 (a) is a Raman spectrum diagram of a white tube. FIG. 7B is a Raman spectrum diagram of Teflon (PTFE).

FIG. 8A is a Raman spectrum diagram of a standard plastic sample A for which a database is created in the first embodiment. FIG. 8B is a conceptual diagram showing the structure of the created database.

FIG. 9 is a flowchart showing a procedure for creating a database in the first embodiment.

FIG. 10 is a flowchart showing a procedure for determining an unknown sample in the first embodiment.

FIG. 11 is a Raman spectrum diagram of the unknown sample S in the first embodiment.

FIG. 12 is a flowchart showing a procedure for creating a database in the second embodiment.

FIG. 13 is a flowchart illustrating a procedure for determining an unknown sample in the second embodiment.

FIG. 14 (a) is a Raman spectrum diagram of a certain floppy case obtained by exciting with visible light. FIG. 14B is a Raman spectrum diagram of white styrene foam obtained by excitation with visible light. FIG. 14 (c)
FIG. 15 is a spectrum diagram of the same floppy case as FIG. 14A obtained by excitation with near-infrared light. FIG. 14 (d)
FIG. 15 is a Raman spectrum diagram of the same white styrofoam as in FIG. 14B obtained by excitation with near-infrared light.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Waste plastic, 2 ... Belt conveyor, 3 ... Laser device, 4 ... Raman spectrometer, 5 ... Recording part, 6 ... Comparison part, 7 ... Database recording part, 8 ... Discrimination part, 9 ... Sorting device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroo Hamaguchi 5-10-7-407 Koyodai, Inagi-shi, Tokyo

Claims (7)

[Claims] A measuring step of measuring a Raman spectrum of a plastic whose material is unknown; a comparing step of comparing a Raman spectrum of a plastic whose material is known with a Raman spectrum measured in the measuring step; Determining the plastic material to be determined from the result of the comparison in the steps. 2. A measuring step of measuring a Raman spectrum of a discriminated plastic whose material is unknown, and an extracting step of extracting a wave number of a Raman line and a relative intensity value at the wave number from the Raman spectrum measured in the measuring step. A comparison step of comparing the wave number of the Raman line of the known plastic material and the relative intensity value at the wave number and the relative intensity value at the wave number of the Raman line and the wave number of the Raman spectrum measured in the measurement step, Determining the material of the plastic to be determined from the comparison result of the comparing step. 3. A spectrum measuring means for measuring a Raman spectrum of a discriminated plastic whose material is unknown, a recording means for storing a Raman spectrum of a plastic whose material is known, and a Raman spectrum measured by the spectrum measuring means. A plastic discriminating apparatus comprising: a spectrum comparing unit that compares Raman spectra recorded in the recording unit; and a discriminating unit that discriminates a material of the plastic to be discriminated from a result of the comparison by the spectrum comparing unit. 4. The recording means records the wave number of a Raman line of a Raman spectrum of a plastic whose material is known and a relative intensity value at the wave number, and the spectrum comparing means measures the spectrum by the spectrum measuring means. Extracting means for extracting the wave number of the Raman line and the relative intensity value at that wave number from the Raman spectrum of the plastic to be discriminated, and the wave number and the relative intensity value extracted by the extracting means and the Raman line stored in the recording means. 4. The plastic discriminating apparatus according to claim 3, further comprising means for comparing the wave number and a relative intensity value at the wave number. 5. The plastic discriminating apparatus according to claim 3, wherein said recording means records a Raman spectrum of a plastic whose material is known by said spectrum measuring means. 6. The plastic discriminating apparatus according to claim 3, wherein said spectrum measuring means has an excitation light source for outputting near-infrared laser light for Raman spectrum acquisition. 7. The apparatus according to claim 1, wherein the spectrum measuring unit includes: an excitation light source that outputs a pulsed laser beam for acquiring a Raman spectrum; and a unit that measures a Raman spectrum in synchronization with the excitation light source. Item 3. A plastic discriminating apparatus according to Item 3.