JP2006084350A - Type discriminating method of plastics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastics type discriminating method that can certainly discriminating the type of the plastics in an inexpensive constitution without requiring complex information processing, and can easily respond also to addition of a new type of plastics. <P>SOLUTION: The plastics type is discriminated based on the correlation between a reference spectrum obtained by radiating near infrared rays to a plurality of known plastic samples of different types, respectively, and measuring transmitted light transmitted through each plastic sample or reflected light reflected from each plastic sample with a predetermined spectral means, and a measured absorption spectrum obtained by radiating the near infrared rays to the plastic samples of which types are discriminated and measuring the transmitted light transmitted through the discriminated plastic sample or the reflected light reflected from the discriminated plastic sample with the spectral means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plastic type discriminating method, and more particularly, to a plastic type discriminating method suitable for sorting plastic wastes represented by packaging, containers, etc. of foods, etc., according to type.

  Recently, industrial products using plastic have been increasing. In particular, plastic applied products have penetrated deeply into our daily necessities, and it is no exaggeration to say that they are no longer important daily necessities. Under such circumstances, there is an increasing demand for recycling of plastics that are discarded from the viewpoint of effective use of resources and, in turn, conservation of the global environment.

By the way, the discarded plastic is discriminated by a predetermined method, and is then reused as a raw material after being optimally processed for each type of plastic and used as an alternative fuel such as oil and coal. For this reason, when plastic is reused as a raw material, quality deterioration cannot be denied if different types of plastic are mixed. Alternatively, when used as a fuel, especially when polyvinyl chloride (PVC) containing chlorine is mixed, dioxins are generated and boiler corrosion is caused. For these reasons, there is an increasing expectation for a highly accurate plastic type discrimination method.
The application of infrared spectroscopy to this type of discrimination method is well known, and in particular, the number of cases using near infrared rays has increased in recent years. Near-infrared rays are characterized by being less susceptible to water adhesion and temperature radiation, which are major disturbance factors when using mid-infrared rays. The near infrared ray generally indicates an infrared ray having a wavelength of 0.8 μm to 2.5 μm, and the mid infrared ray indicates an infrared ray having a wavelength of 2.5 μm to 22 μm.

  As a method for discriminating this type of plastic, a method for discriminating waste plastic is known (see, for example, Patent Document 1). The method for discriminating waste plastic disclosed in this patent document uses a light receiving element to reflect or transmit light when the waste plastic to which water is attached is irradiated with near infrared rays having a wavelength of 0.6 μm to 2.5 μm from a projector. Near infrared absorption peak caused by functional group based on molecular structure of specific plastic in waste plastic and near infrared absorption determined in advance for a plurality of known plastics by detecting means connected to this light receiving element Compared with the peak, waste plastic is discriminated.

In addition, the sample is irradiated with detection light having a different wavelength from the other, and the reference light having a different wavelength from each other, and the reflected or transmitted light of the detection light. There is known a plastic determination method that determines which plastic belongs based on a difference or ratio between a detected value that represents the amount of received light and a reference value that represents the amount of received or reflected reference light. (For example, refer to Patent Document 2).
Japanese Patent No. 3124142 JP 2001-108616 A

  However, in the above-mentioned waste plastic discrimination method, the absorption spectrum is used after second-order differentiation for separating the absorption peak, and when a new kind of plastic is added, the wavelength of the absorption peak is searched. There is a need to. Furthermore, the infrared rays used are 0.6 μm to 2.5 μm, which includes a part of visible light and the entire wavelength range of near infrared rays, and the wide wavelength band relates to the light receiving elements and spectroscopic means constituting the apparatus. Cost increases. In addition, near-infrared light is not easily affected by water adhesion and temperature radiation, which are major disturbance factors when using mid-infrared light, but the overtone and the combined sound derived from functional groups in plastics have a narrow wavelength range. Since this is complicated, there is a problem that information processing tends to be complicated, such as statistical methods such as multivariate analysis, and preprocessing combined with first and second derivatives of absorption spectra.

Further, in the method of Patent Document 2, as with the above-described method for discriminating waste plastic, it is unavoidable to add complexity to the addition of a new plastic type in terms of setting the wavelength and threshold level for discrimination. Scalability is poor.
The present invention has been made on the basis of such a conventional situation, and the object thereof is not to require complicated information processing, and it is possible to reliably determine the type of plastic under an inexpensive configuration. Another object of the present invention is to provide a plastic type discrimination method that can easily cope with the addition of a new type of plastic.

  In order to achieve the above-described object, the plastic type discrimination method according to the present invention is a method of transmitting transmitted light that passes through each plastic sample or each plastic sample when a plurality of different types of known plastic samples are each irradiated with near infrared rays. A reference absorption spectrum obtained by measuring the reflected light reflected from each of them by a predetermined spectroscopic means, and the transmitted light transmitted through the plastic sample to be discriminated by irradiating the plastic sample to be discriminated with the near infrared ray It is characterized in that the type of plastic is discriminated from the correlation with the measured absorption spectrum obtained by measuring the reflected light reflected from the plastic sample to be discriminated by a predetermined spectroscopic means. In particular, near infrared rays of 1.6 μm to 1.9 μm are used as the target wavelengths of the respective absorption spectra or the correlation.

  In the plastic type discrimination method described above, a pure plastic sample serving as a criterion for judgment is irradiated with near infrared rays having a wavelength of 1.6 μm to 1.9 μm, and the light transmitted through the plastic sample or reflected by the plastic sample is reflected. The light is dispersed by a predetermined spectroscopic means to obtain an absorption spectrum (reference absorption spectrum) of the plastic sample. On the other hand, the near-infrared ray having the same wavelength is also irradiated to the plastic to be judged, and the transmitted light transmitted through the plastic sample or the reflected light reflected from the plastic sample is absorbed by a predetermined spectroscopic means. (Measurement absorption spectrum) is obtained. At this time, an absorption spectrum having a high correlation with the measured absorption spectrum is found out of the reference class absorption spectra described above, and the type of plastic is determined.

Finding an absorption spectrum with high correlation is performed as follows.
(1) A phase between a measured absorption spectrum and a reference absorption spectrum at a predetermined wavelength pitch and wavelength range with a pair of an absorption amount (absorbance) in a measured absorption spectrum at the same wavelength and an absorption amount (absorbance) in one reference absorption spectrum. Calculate the number of relationships.
(2) This is performed for all combinations with reference absorption spectra, and a correlation coefficient for each reference absorption spectrum is calculated.
(3) A combination with the reference absorption spectrum having the largest correlation coefficient and close to [1] is searched, and the plastic of the reference absorption spectrum is set as the type of plastic to be determined.

The correlation coefficient is calculated by a single correlation analysis that is a general statistical method.
That is, if the correlation coefficient between the measured absorption spectrum and a plurality of reference absorption spectra is obtained, and the plastic having the largest correlation coefficient and the reference absorption spectrum close to [1] is obtained, the plastic type to be determined is determined. be able to.
Preferably, the spectroscopic means is composed of a diffraction grating and a linear array type light receiving element.

  As described above, according to the plastic type discriminating method according to the present invention, a plurality of known plastic samples of different types are each irradiated with near-infrared rays and transmitted light or each plastic sample is transmitted through each plastic sample. The reference absorption spectrum obtained by measuring the reflected light reflected from each by a predetermined spectroscopic means, and the near-infrared light applied to the plastic sample to be subjected to type discrimination, or the transmitted light transmitted through the plastic sample to be discriminated or the discrimination target Since the correlation between the reflected light reflected from the plastic sample and the measured absorption spectrum measured by a predetermined spectroscopic means is obtained, the type of plastic can be appropriately determined.

  In particular, since the wavelength targeted for the absorption spectrum or the correlation can be limited to the near-infrared region of 1.6 μm to 1.9 μm, the cost applied to the optical system can be suppressed. In other words, when the plastic type discriminating apparatus is configured by applying the plastic type discriminating method according to the present invention, the cost can be reduced.

  The plastic type discrimination method of the present invention will be described below with reference to the drawings. Fig. 1 shows the wavelength of near infrared rays on the horizontal axis when near infrared rays having a wavelength of 1.0 µm to 2.5 µm are radiated to the material of various plastics (hereinafter referred to as reference plastics) that serve as a basis for discriminating the type of plastic. It is a graph which shows the light-absorption spectrum which took the light absorbency of the infrared rays absorbed by each reference | standard plastics on a vertical axis | shaft on the vertical axis | shaft. In this figure, the solid line is polyethylene (PE) with a thickness of 0.8 mm, the alternate long and short dash line is polyethylene terephthalate (PET) with a thickness of 0.5 mm, and the solid line with a circle is polypropylene with a thickness of 1.0 mm (PP ), A solid line with a triangle mark indicates polystyrene (PS) with a thickness of 1.0 mm, and a solid line with a mark x indicates polyvinyl chloride (PVC) with a thickness of 0.75 μm. FIG. 2 shows the absorbance in the wavelength range of 1.6 μm to 1.9 μm. As shown in FIGS. 1 and 2, the absorbance (absorption) tends to increase in the wavelength range of 1.6 μm to 1.9 μm and the wavelength range of 2.1 μm to 2.5 μm. The pattern is different. The difference in pattern for each type reflects the difference in molecular structure unique to plastics. By the way, this absorbance is obtained by measuring transmitted light using Shimadzu UV3100PC under the spectral condition of slit 20 nm and wavelength pitch 2 nm.

  FIG. 3 is a graph obtained by normalizing the absorbance characteristics shown in FIG. 2 with a peak value of 1 for each reference plastic material. As shown in these figures, the absorbance peaks of each reference plastic are as follows. PET has a wavelength of 1.662 μm, PS has a wavelength of 1.682 μm, PVC has a wavelength of 1.716 μm, PP has a wavelength of 1.724 μm, and PE has a wavelength of 1. A result of 728 μm was obtained.

  Next, the inventor prepared six samples (A, B, C, D, E, and F) to verify whether or not the type of plastic can be determined from these absorbance spectra. The thickness of each sample is 0.3 mm for sample A, 0.15 mm for sample B, 0.25 mm for sample C, 1.20 mm for sample D, 0.10 mm for sample E, and 1.40 mm for sample F. . When these samples are irradiated with near infrared rays having a wavelength of 1.0 μm to 2.5 μm, the horizontal axis represents the wavelength of the near infrared rays, and the vertical axis represents the absorbance of the infrared rays absorbed by each plastic material. Drawing the graph showing the spectrum gives FIG. 4 and FIG. Note that FIG. 5 is a graph drawn by extracting only the wavelength range of 1.6 μm to 1.9 μm from the absorbance spectrum shown in FIG. 4. With respect to the absorbance spectrum of each sample thus obtained, a scatter diagram was prepared in order to obtain the absorbance spectrum and correlation coefficient of each reference plastic material obtained as described above. In addition, the scatter diagrams shown in FIGS. 6 to 11 depict the locus of the plotted points as lines for easy understanding of the correlation. Therefore, the marks on the lines such as ◯ and Δ are different from the actual plot.

  First, the absorbance of each reference plastic is plotted on the horizontal axis and the absorbance of sample A is plotted on the vertical axis. The absorbance of each reference plastic and the absorbance of sample A at the same wavelength are matched and plotted under a predetermined wavelength pitch and wavelength range. The scatter diagram shown in FIG. 6 was created. Then, it can be read that the sample A and the PE of the reference plastic draw a flat circle as shown by the solid line and the correlation is not strong. In addition, it can be seen that Sample A and PET have a locus protruding upward in the graph as shown by a one-dot chain line, and there is no correlation. Next, samples A and PP tend to rise to the right as shown by the circled circles, and although there is some correlation with sample A, it shows that the correlation is not strong because it draws a meandering locus. . In addition, it can be seen that Samples A and PS have a triangular trace as indicated by the straight line marked with Δ, and have no correlation. Next, it can be seen that Sample A and PVC become straight lines that rise to the right and have a very strong correlation. From these things, it can be discriminate | determined that the sample A is PVC. In fact, this sample A is PVC.

  Next, for Sample B, a scatter diagram similar to Sample A described above is drawn as shown in FIG. Then, it can be seen that the sample B and the PE of the reference plastic draw a flat semicircle as shown by a solid line, and the correlation is not strong. In addition, it can be seen that Sample B and PET have a locus protruding upward in the graph as indicated by a one-dot chain line, and there is no correlation. Next, it can be seen that Samples B and PP are straight ascending as shown by the circled circles and are extremely correlated. In addition, it can be seen that Samples B and PS have a trace that draws a triangle with one side meandering slightly, as shown by the straight line with a Δ mark. Next, it can be seen that Sample B and PVC are slightly deformed semicircles as shown by the straight line with a cross, and that the correlation is strong. From these facts, it can be determined that the sample B is PP. In fact, this sample B is PP.

  For Sample C, a scatter diagram similar to Sample A and Sample B described above is shown in FIG. It can be seen that the sample C and the PE of the reference plastic draw a flat and horizontally long triangle as shown by the solid line, and the correlation is not strong. On the other hand, it can be seen that Sample C and PET are straight ascending as shown by the alternate long and short dash line and have a strong correlation. Next, it can be seen that Samples C and PP are triangles with two sides slightly collapsed as indicated by the circled circles, and there is no correlation. Samples C and PS have a shape in which one side of the triangle is extended as indicated by a straight line with a Δ mark, and it can be seen that there is no correlation at all. Next, it can be read that Sample C and PVC are triangles whose two sides are largely crushed, as indicated by the straight line with a cross, and there is no correlation. From these, it can be determined that the sample C is PET. In fact, this sample C is PET.

  Further, for Sample D, a scatter diagram similar to Samples A, B, and C described above is shown in FIG. First, it can be seen that the sample D and the PE of the reference plastic are triangles with two sides slightly crushed as shown by the solid line, and there is no correlation. Next, it can be seen that Sample D and PET are flat ellipses protruding upward as shown by the alternate long and short dash line and have no correlation. In addition, it can be seen that the samples D and PP have a slightly distorted triangle at the bottom as shown by the line marked with a circle, and have no correlation. Further, it can be seen that Samples D and PS are straight ascending as shown by the straight line marked with Δ, and have a strong correlation. Next, it can be read that the sample D and PVC are triangles with two sides slightly crushed as shown by the straight line with a cross, and there is no correlation. From these, it can be determined that the sample D is PS. In fact, this sample D is PS.

  Next, for Sample E, a scatter diagram similar to Samples A, B, C, and D described above is drawn as shown in FIG. First, it can be seen that the sample E and the PE of the reference plastic have a strong correlation as shown by the solid line and rise upward. Next, it can be seen that Sample E and PET draw a triangular shape protruding upward as shown by the alternate long and short dash line and have no correlation. Samples E and PP draw a flat semicircle with a circle on the lower side as indicated by the circled circle, and it can be seen that there is no correlation. Further, it can be seen that the samples E and PS are triangular and have no correlation as indicated by the straight line marked with Δ. Next, it can be seen that the sample E and the PVC have a cloud shape like rising smoke as indicated by the straight line with a cross, and there is no correlation. From these facts, it can be determined that the sample E is PE. In fact, this sample E is PE.

  Finally, for Sample F, a scatter diagram similar to Samples A, B, C, D, and Sample E described above is shown in FIG. As shown in this figure, sample E and the reference plastics PE, PP, and PVC draw a triangle as shown by the solid line, the line marked with ○, and the line marked with x, respectively, and there should be no correlation Can be read. In addition, it can be read that the samples E and PET are flat ellipses protruding upward and have no correlation. Further, it can be seen that Samples E and PS are slightly flat semicircles with the upper side being the circumference as shown by the line with Δ mark, and there is no correlation. Thus, sample E is found to have a low correlation with any reference plastic. In fact, this sample is PC (polycarbonate). This sample F was evaluated with a material other than the reference plastic in order to confirm the usefulness of the plastic type discrimination method of the present invention.

  The evaluation test described above was carried out at a wavelength range of 1.6 μm to 1.9 μm. Table 1 shows the results of analysis of the correlation coefficient for each sample, including other wavelength ranges.

この表に示す波長範囲は、ａが波長１.０μｍ〜２.５μｍ、ｂが前述した波長１.６μｍ〜１.９μｍ、ｃが波長２.１μｍ〜２.５μｍを示す。この表に示すように、試料Ａについては、全ての波長範囲において、ＰＶＣに対する（対ＰＶＣ）相関係数が最も大きく、０.９９９と極めて［１］に近い値が得られた。また、他の基準プラスチック（ＰＥ，ＰＥＴ，ＰＰ，ＰＳ）については、いずれも相関係数が［１］から離れた値となった。このようなことからいずれの波長範囲においても、各試料の材質は、基準プラスチックとの相関が強く出ているとき、すなわち相関係数が最も大きく、かつ［１］に近い値となるものが試料の種別を示すと判定することができる。同様に他の試料Ｂ，Ｃ，Ｄ，Ｅについても、それぞれ対ＰＰ，対ＰＥＴ，対ＰＳ，対ＰＥの相関係数が、いずれも最も大きく、かつ［１］に近い値になり、各試料の種別を判定できる。

As for the wavelength range shown in this table, a represents a wavelength of 1.0 μm to 2.5 μm, b represents a wavelength of 1.6 μm to 1.9 μm, and c represents a wavelength of 2.1 μm to 2.5 μm. As shown in this table, for sample A, the correlation coefficient for PVC (vs. PVC) was the largest in all wavelength ranges, and 0.999 was obtained, a value very close to [1]. In addition, for the other reference plastics (PE, PET, PP, PS), the correlation coefficient was a value away from [1]. Therefore, in any wavelength range, the material of each sample has a strong correlation with the reference plastic, that is, the sample with the largest correlation coefficient and a value close to [1]. It can be determined that it indicates the type. Similarly, for the other samples B, C, D, and E, the correlation coefficients of the pair PP, the pair PET, the pair PS, and the pair PE are all the largest and close to [1]. Can be determined.

  However, for sample F, there is no reference plastic whose correlation coefficient is very close to [1]. The largest correlation coefficient for sample F is 0.965 (wavelength range: a), 0.919 (wavelength range: b), and 0.864 (wavelength range: c) for PET. In this case, it is possible to determine that the sample F is of a type other than the reference plastic by providing a certain threshold value for the correlation coefficient (for example, 0.970) and considering that the correlation coefficient is equal to or less than the threshold value.

  In addition, if the value obtained by subtracting the minimum value from the maximum value of the correlation coefficient, which is defined as the width of the correlation coefficient, this width is the largest for any sample having a wavelength of 1.6 μm to 1.9 μm. Near infrared. For example, referring to Table 1 for the sample A, in the wavelength range a (1.0 μm to 2.5 μm), the maximum value of the correlation coefficient is 0.999, and the minimum value is 0.747. The difference is 0.252. Similarly, for the sample A, in the wavelength range b (1.6 μm to 1.9 μm), the maximum value of the correlation coefficient is 0.999 and the minimum value is −0.105. 1.104. Similarly, for sample A, in the wavelength range c (2.1 μm to 2.5 μm), the maximum value of the correlation coefficient is 0.999 and the minimum value is 0.499, so the difference is , 0.500.

Hereinafter, the width of the correlation coefficient is the widest for all samples in the wavelength range b (1.6 μm to 1.9 μm). Therefore, if the sample is determined using near infrared rays having a wavelength range of 1.6 μm to 1.9 μm, the width of the correlation coefficient, that is, the dynamic range can be widened, and the type of plastic can be determined with high accuracy. it can.
In the evaluation test described above, the thicknesses of the reference plastic and the evaluation target plastics (A to E) can be correctly discriminated despite being completely different as shown in Table 2. In addition, the evaluation object plastic of this table | surface is the same kind as the reference | standard plastics described in the left column of each sample.

さらに、基準プラスチックの内、厚さ０.７５ｍｍのポリ塩化ビニルと、評価対象プラスチックの内、厚さ０.３mmのポリ塩化ビニル（試料Ａ）について、波長範囲１.０μｍ〜２.５μｍの吸光度スペクトルを比較したものが図１２である。この図が示すように板厚の厚い基準プラスチックの吸光度は、板厚の薄い評価対象プラスチックに対し、概略、厚さに比例する形で増加しているのみで相似形をなしている。このように、吸光度が厚さに概略比例することは、分光分析の分野では一般的な事実である（ここで、概略としたのは、試料表面での正反射にともなう吸光度増加が、厚さとは無関係に存在するためである）。

Furthermore, the absorbance in the wavelength range of 1.0 μm to 2.5 μm for polyvinyl chloride with a thickness of 0.75 mm among the reference plastics and polyvinyl chloride with a thickness of 0.3 mm (sample A) among the plastics to be evaluated. A comparison of the spectra is shown in FIG. As shown in this figure, the absorbance of the reference plastic having a thick plate thickness is similar to that of the evaluation target plastic having a thin plate thickness, generally increasing in proportion to the thickness. Thus, the fact that the absorbance is roughly proportional to the thickness is a general fact in the field of spectroscopic analysis (here, the outline shows that the increase in absorbance due to specular reflection on the sample surface is the thickness and thickness). Because it exists unrelatedly).

  Therefore, regarding the wavelength range of 1.6 μm to 1.9 μm, the horizontal axis represents the standard plastic absorbance, and the horizontal axis represents the absorbance of the sample to be evaluated. As shown in FIG. It can be seen that there is a strong correlation. Note that FIG. 13 is extracted from the scatter diagram regarding the sample A of FIG. 6 described above for the case of PVC in order to make it easy to understand the influence of the thickness of the sample. Further, the correlation coefficient corresponding to the scatter diagram of FIG. 13 is 0.999 described in the column of the sample A in Table 1 and the wavelength range b versus PVC.

  Thus, in the plastic type discrimination method of the present invention described above, an absorption (absorbance) spectrum obtained by irradiating a near-infrared ray to a plastic sample subject to type discrimination and measured by spectroscopic means based on transmitted light or reflected light from the sample, For a plurality of different known plastic samples, the correlation with the absorption (absorbance) spectrum measured in advance by the same method is obtained. When the correlation is strong, that is, the known plastic having the largest correlation coefficient and close to [1] It is determined that the type of plastic is a type discrimination target. For this reason, it is possible to determine the type of plastic without being affected by the plate thickness.

In the plastic type discrimination method of the present invention described above, all of absorption spectrum data in a predetermined wavelength range is used instead of discrimination by point data such as comparison of absorption peak wavelengths or comparison of received light amounts at specific wavelengths. Since the determination is made based on the correlation, the stable determination that is hardly affected by noise on the absorption spectrum is possible.
In particular, since the wavelength range of the absorption spectrum can be limited to the near infrared region of 1.6 μm to 1.9 μm, it is possible to reduce the cost associated with the spectroscopic means for obtaining the absorption spectrum and to shorten the time required for discrimination.

Furthermore, when adding a new plastic to be discriminated, only the absorption spectrum of the plastic to be added is measured and registered as a reference pattern, and no new wavelength setting or addition of discriminating logic is required. The work cost when adding plastic is greatly reduced.
It should be noted that the plastic type discrimination method of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

The graph which shows the light absorbency spectrum absorbed by these each plastic board when near infrared rays are irradiated to various plastic boards. The graph which shows the light-absorption spectrum which took out only the range of wavelength 1.6micrometer-1.9micrometer among the light-absorption spectra shown in FIG. The graph which shows the absorbance spectrum which normalized the absorbance spectrum shown in FIG. 2 by making the peak absorbance of each plastic plate into 1. FIG. The graph which shows the light absorbency spectrum absorbed by these each plastic board when near infrared rays are irradiated to the plastic board used as each sample. FIG. 5 is a graph showing an absorbance spectrum extracted from the absorbance spectrum shown in FIG. 4 only in the wavelength range of 1.6 μm to 1.9 μm. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample A and a reference | standard plastic board. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample B and a reference | standard plastic board. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample C and a reference | standard plastic board. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample D and a reference | standard plastic board. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample E and a reference | standard plastic board. The scatter diagram which shows the correlation of the light absorbency characteristic in the sample F and a reference | standard plastic board. The graph which shows the light absorbency spectrum absorbed by these plastic plates when near infrared rays are irradiated to the plastic plate of the same kind from which thickness differs. The scatter diagram which shows the correlation of the light absorbency characteristic in the reference | standard plastics shown in FIG. 12, and an unknown sample.

Explanation of symbols

A, B, C, D, E Sample PC Polycarbonate PE Polyethylene PET Polyethylene terephthalate PP Polypropylene PS Polystyrene PVC Polyvinyl chloride

Claims (3)

A reference absorption spectrum in which a plurality of different types of known plastic samples are each irradiated with near-infrared rays, and transmitted light transmitted through each plastic sample or reflected light reflected from each plastic sample is measured by a predetermined spectroscopic means,
Irradiating the plastic sample of type discrimination with the near infrared ray, and the measured absorption spectrum obtained by measuring the transmitted light transmitted through the plastic sample of discrimination type or the reflected light reflected from the plastic sample of discrimination type with the spectroscopic means A plastic type discrimination method characterized by discriminating a plastic type from a correlation.   2. The plastic type discrimination method according to claim 1, wherein a target wavelength of each absorption spectrum or the correlation is 1.6 [mu] m to 1.9 [mu] m.   2. The plastic type discrimination method according to claim 1, wherein the spectroscopic means is composed of a diffraction grating and a linear array type light receiving element.

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