JP2023182993A - Resin determination method - Google Patents

Abstract

To provide a resin determination method for accurately determining resin in which carbon black is contained.SOLUTION: Based on reflected light 4 received from resin 2 of a selection target irradiated with infrared light 3, a reflection or absorption spectrum of the resin is calculated. Maximum intensity of the calculated spectrum is obtained, and when it is equal to or more than a first threshold value of maximum obtainable intensity, it is determined that carbon black is not contained and a resin type is determined after normalization. When the maximum intensity is less than the first threshold value, it is determined that the carbon black is contained as a pseudo-containment, and the resin type is determined.SELECTED DRAWING: Figure 5

Description

The present invention relates to a resin determination method for determining the resin type in a sorting target in which a plurality of types of small pieces are collected in a non-contact manner.

Economic activities that involve mass consumption and mass waste are causing environmental problems on a global scale, such as global warming and resource depletion.

Under these circumstances, the Home Appliance Recycling Law has been enforced in Japan since April 2001, with the aim of building a resource recycling society. The Home Appliance Recycling Law requires recycling of used home appliances (air conditioners, televisions, refrigerators, freezers, washing machines, clothes dryers, etc.). As a result, used home appliances are crushed into small pieces at a home appliance recycling factory, then sorted and collected by material type using magnetism, wind power, or vibration, and recycled as recycled materials. . Among resin materials, polypropylene (hereinafter referred to as PP), polystyrene (hereinafter referred to as PS), and acrylonitrile butadiene styrene (hereinafter referred to as ABS) are often used in home appliances, and are described in patent documents. As proposed in No. 1, resins are sorted and collected by type using a sorting device that utilizes the light absorption characteristics in the near-infrared region (wavelength range of 1 to 3 μm) due to the molecular structure of the resin.

This sorting device irradiates small pieces conveyed by a conveyor with light including near-infrared light, detects the reflection or absorption spectrum from the resin without contact, and can determine the type of resin, so it can sort a large number of small pieces. can be processed.

However, black resins containing carbon black (fine particles mainly composed of carbon) used in small home appliances and automobiles absorb light in the near-infrared region, so a sufficient reflection or absorption spectrum cannot be obtained. However, the inability to sort them is a major issue.

Therefore, Patent Document 1 proposes an apparatus that takes into account the above-mentioned problems regarding the recycling of resin materials. In the technology described in Patent Document 1, in a material identification device 101 for black waste plastic as shown in FIG. 105 and obtains the reflection spectrum in the mid-infrared region (wavelength range 3 to 5 μm) where the influence of carbon black is reduced, it is possible to detect not only white resin that does not contain carbon black but also difficult to detect in the near-infrared region. It also makes it possible to judge black resins.

Furthermore, in recent years, a black pigment that does not contain carbon black has been developed and proposed in Patent Document 2. While carbon black absorbs infrared rays, this black pigment has the property of reflecting infrared rays, making it possible to recover black resins that have conventionally been difficult to sort in the near-infrared region.

Patent No. 5367145 Patent No. 5932464

In the future, black resins that contain carbon black and black resins that do not contain carbon black will be popularized in the market, so the resins collected from the market will be black resins that contain carbon black. It is assumed that the resin will be recycled in a mixed state with a black resin that does not contain carbon black. In this case, if these different black pigments cannot be sorted and recovered and are unintentionally mixed together, resin functions such as color adjustment and heat resistance during recycling will be affected. Therefore, it is necessary to determine with high precision whether carbon black is contained.

However, in the mid-infrared region, the inclusion of carbon black does not cause a large difference in absorption or reflection spectra from the resin, so it has been difficult to determine whether carbon black is contained. In addition, in the near-infrared region, the inclusion of carbon black causes a large difference in the absorption or reflection spectrum from the resin, but in a resin toned like gray with a concentration of less than 1% carbon black, the absorption or reflection spectrum is Because the attenuation of the reflection spectrum was slight, the spectrum was very similar to that of white resin, making it difficult to judge.

The present invention solves the above-mentioned problems, and utilizes the attenuating effect of reflected light due to the inclusion of carbon black when evaluating resins using reflection or absorption spectra in the near-infrared region. It is an object of the present invention to provide a resin determination method that accurately determines resins containing black.

In order to achieve the above object, the present invention is configured as follows.

According to one aspect of the present invention, a reflection or absorption spectrum obtained by reflected light received from an object to be sorted that has been irradiated with infrared light is set to a preset intensity of the reflection or absorption spectrum as a first threshold value. , if the first similarity is greater than or equal to the first threshold, it is normalized and the first similarity with the spectral data of one or more resin species obtained in advance is determined, and if the first similarity is greater than or equal to the second threshold of the preset first similarity and the Determining the one with the highest degree of similarity as the resin type of the sorting target,
If the reflection or absorption spectrum obtained by the reflected light is less than the first threshold, a second degree of similarity with the spectrum data of one or more types of resin obtained in advance is determined, and a second degree of similarity is calculated based on the preset second degree of similarity. The resin type that is equal to or higher than the third threshold and has the highest second similarity is determined as the resin type of the object to be sorted.

As described above, according to the resin determination method according to the aspect of the present invention, the reflection or absorption spectrum of the resin is calculated based on the reflected light received from the resin of the sorting target irradiated with infrared light, Among the calculated spectra, the maximum intensity of the spectrum is determined, and if it is greater than or equal to the first threshold of the maximum obtainable intensity, it is determined that carbon black is not contained, and after normalization, the resin type is determined, and if it is less than the first threshold. For example, it is determined whether the resin contains carbon black as pseudo-containment, and the resin type is determined. As a result, when determining and sorting resins using the reflection or absorption spectrum of the target object, the presence of carbon black can be determined with high accuracy.

Schematic diagram of a resin determination device according to an embodiment of the present invention Schematic diagram showing the effect of contamination of carbon black-containing resin by conventional mid-infrared sorting Schematic diagram showing the effect of contamination of carbon black-containing resin by conventional near-infrared sorting A spectrum graph for conventional resin determination in the near-infrared region, where the horizontal axis is wavelength and the vertical axis is absorbance. A flowchart showing a flow in which the resin determination device determines resin in an embodiment of the present invention. A graph of the spectrum of a resin sample in the near-infrared region, where the horizontal axis is wavelength and the vertical axis is absorbance. Diagram showing the determination results of the conventional method Diagram showing determination results according to an embodiment of the present invention A schematic diagram showing the influence of carbon black-containing resin contamination by near-infrared sorting according to an embodiment of the present invention Schematic diagram of a conventional apparatus for resin determination described in Patent Document 1

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

(Embodiment)
FIG. 1 is a schematic diagram of a resin determination apparatus 1 that can implement a resin determination method according to an embodiment.

Resin 2 is a material to be sorted of resins of unknown resin type, such as black resin containing carbon black (i.e., carbon-based fine particles), black resin not containing carbon black, white resin, translucent colored resin, or gray resin. be. Therefore, the resin 2 means the resin sorting object 2. The resin type means the resin type of the object to be sorted.

The configuration of a resin determination device 1 that accurately determines the type of resin based on whether carbon black is contained in the resin 2 will be described with reference to FIG.

The resin determination device 1 includes an infrared detection unit 8, a digital data conversion device 9, and an arithmetic processing device 10.

The infrared detection unit 8 has a function of irradiating the resin 2 with infrared rays and a function of receiving reflected light 4 of the infrared irradiation light 3 from the resin 2. Infrared rays have absorption characteristics in the near-infrared region (effective wavelength region 1 to 3 μm).

The digital data converter 9 converts the electrical signal output by the infrared detection unit 8 according to the reflected light 4 into digital data.

The arithmetic processing device 10 calculates the reflection spectrum of the resin 2 based on the digital data output from the digital data conversion device 9.

In FIG. 1, a belt conveyor 5 is moving at a constant speed and is an example of a transfer section that transfers the resin 2. The belt conveyor 5 transports the resin 2 along the length of the belt conveyor 5 from the input area 6 to the detection area 7 .

Further, an infrared detection unit 8 is arranged above the detection area 7 of the belt conveyor 5.

The arithmetic processing device 10 analyzes the information output from the digital data conversion device 9 and obtains the reflection spectrum of the resin 2 (ie, has a reflection spectrum acquisition function). Further, the arithmetic processing device 10 performs processing such as normalization to make it easier to judge the obtained reflection spectrum (that is, a normalization processing function). Furthermore, the arithmetic processing unit 10 compares the reflection spectrum data of the resin registered in advance (i.e. sample spectrum data) with the detected reflection spectrum data and determines the resin type (i.e. resin type determination function). It is.

Here, the method by which the arithmetic processing device 10 calculates a reflection spectrum from input digital data (ie, the reflection spectrum acquisition function) will be briefly described. The electrical signal photoelectrically converted by the infrared detection unit 8 in response to the reflected light 4 depends on the intensity of the received light. Therefore, it is possible to obtain information on the intensity of the reflected light 4 from the resin 2 from the digital data converted by the digital data converter 9.

Here, before explaining the resin type determination method (i.e. resin type determination function) according to the first embodiment, we will explain how resins containing carbon black are classified when resins are sorted using a conventional determination method. Explain the effects of contamination.

First, when sorting in the mid-infrared region of the conventional method, the spectrum is not affected by the inclusion of carbon black, so even if the resins have different colors, the same spectra will be obtained if they are the same type of resin. For example, if resins with different colors such as white, translucent, gray (with or without carbon black), or black (with or without carbon black) are transported, all Since the resins are sorted and collected as the same resin type, all the resins containing carbon black are mixed into the resins that do not contain carbon black.

In addition, when sorting in the near-infrared region of the conventional example, when resins with different colors similar to those described above are transported, as shown in Figure 3, resins that do not contain carbon black do not have spectral attenuation. Therefore, if gray without carbon black and black are the same resin type, the same spectrum will be obtained, and they will be recovered as the same resin type. Among the resins containing carbon black, the black resin, which contains about a few percent, has a large attenuation effect and is therefore collected on the non-recovery side. On the other hand, gray resin containing less than 1% carbon black has a spectrum that is very similar to that of white resin as shown in Figure 4, so it is sorted and collected as the same resin type, and carbon black is added to resin that does not contain carbon black. The resin that contains this will be mixed in.

Therefore, the present inventor has developed a method for accurately determining a resin containing carbon black by utilizing the attenuating effect of reflected light due to the inclusion of carbon black. I found a way to determine.

Next, a resin determination method based on carbon black content using the resin determination device 1 will be described.

The light source in the infrared detection unit 8 is one having a broad wavelength range, such as a black body light source or a halogen lamp, or two or more single wavelength light sources having an absorption wavelength range of the resin to be determined. Moreover, the light receiving element in the infrared detection unit 8 shall be provided with a light receiving element that receives reflected light of each wavelength from the above-mentioned light source.

It is assumed that the digital data conversion device 9 converts analog data from the light receiving element into digital data and sends it to the arithmetic processing device 10.

The arithmetic processing unit 10 calculates the reflection or absorption intensity of each wavelength, that is, the spectrum, based on the digital data output from the sent light receiving element, and determines the resin type by evaluating the spectrum.

A specific resin determination method will be described in detail based on a determination flowchart as shown in FIG. First, in step S1, from the spectrum obtained from the arithmetic processing unit 10, it is determined whether the maximum intensity of the obtained spectrum is greater than or equal to the first threshold, using an arbitrary percentage of the maximum obtainable intensity, for example 55%, as the first threshold. judge. If the maximum intensity of the obtained spectrum is greater than or equal to the first threshold value, the resin is determined to contain no carbon black, that is, the resin does not contain carbon black, and the process proceeds to step S2.

Next, in step S2, the spectrum is normalized.

Next, in step S3, the resin type is determined based on Euclidean distance as an example of the first similarity. That is, the first degree of similarity between the normalized spectral data and the spectral data of one or more types of resin obtained in advance is determined, and the first degree of similarity is greater than or equal to the second threshold of the first degree of similarity set in advance and the first degree of similarity is the highest. The higher value is determined as the resin type of resin 2, for example, resin A and resin B.

On the other hand, in step S1, if the maximum intensity of the obtained spectrum is less than the first threshold, it is determined that the resin may contain carbon black, that is, the resin pseudo-contains carbon black, and the process proceeds to step S4.

Next, in step S4, the resin containing carbon rack is determined based on Euclidean distance as an example of the second similarity. That is, the second degree of similarity between the detected and acquired spectrum data and the spectrum data of one or more types of resin acquired in advance is determined, and the degree of second similarity is determined to be equal to or higher than a preset third threshold of the second degree of similarity and the second degree of similarity The one with the highest value is determined as the resin type of resin 2, for example, resin A or resin B that does not contain carbon black, and resin A' or resin B' that contains carbon black.

In steps S3 and S4, for resin determination, a sample spectrum, that is, a sample spectrum, is obtained in advance from a resin whose physical properties are known, and the Euclidean distance d between the spectrum obtained from the resin to be determined and the sample spectrum is calculated. The resin type is determined by a determination algorithm that is calculated using the following equation (1) and compares the result with a preset second or third threshold of Euclidean distance.

For example, the first similarity is determined by Euclidean distance, and the first similarity that is equal to or higher than the second threshold and has the highest first similarity is determined as the resin type of the resin 2, for example, resin A and resin B.

The second degree of similarity is determined by the Euclidean distance, and the second degree of similarity that is equal to or higher than the third threshold and has the highest second degree of similarity is the resin type of resin 2, the resin type of resin 2, for example, resin A or resin B. , resin A' or resin B'.

Note that the second threshold value and the third threshold value are respectively set to threshold values that allow accurate determination based on the degree of similarity between spectrum data of one or more resin types acquired in advance.

Here, x _i : spectrum intensity of the object to be determined, x' _i : sample spectrum intensity, i : variable on the horizontal axis (wavelength) as shown in FIG. 4 and the like.

Next, an experiment to confirm the effectiveness of the method for accurately determining resin containing carbon black according to the first embodiment will be described.

As shown in Figure 6, the experiment used five samples of resin 2: white, translucent, gray (containing carbon black), black (containing carbon black), and black (not containing carbon black). and obtained the spectrum. The results obtained when PP was used as the resin base material in FIG. 6 are shown. The reason for excluding gray (containing no carbon black) is that black (containing no carbon black) is so similar that no difference can be seen, and gray (containing no carbon black) is excluded because it overlaps. Therefore, the gray (carbon black-free) results are treated as the same results as the black (carbon black-free) results shown below.

The Euclidean distance was determined using the resin spectrum obtained above, and the effectiveness of the conventional method and the embodiment of the present invention was verified.

Regarding the sample spectrum of equation (1), the resin spectrum obtained in FIG. 6 was used as the sample.

First, in the conventional method, the obtained spectrum is normalized and the Euclidean distance is calculated using equation (1). The calculation results are shown in FIG. The value calculated by formula (1) approaches 0 as the degree of match with the sample spectrum increases, so when looking at the value when gray (containing carbon black) is targeted, white is 0.40, semi-transparent The color shows a value close to 0.45. This is because the spectra become similar as shown in FIG. 4 by standardization. In this case, it is difficult to determine whether the resin contains carbon black or not, as there is a possibility that it will be mistakenly recognized as white or translucent if the spectral variation of the resin actually generated during recycling is taken into account. .

Next, FIG. 8 shows the results calculated based on the determination flowchart shown in FIG. 5 using the resin determination method based on the carbon black content of the embodiment of the present invention. The maximum acquired intensity was less than the first threshold for three colors: translucent color, gray (containing carbon black), and black (containing carbon black), and the agreement was obtained when gray (containing carbon black) was targeted. Looking at the degree of similarity, the value was 0.63 for translucent color and 1.25 for black color (containing carbon black). Comparing the results with the conventional method, the 40% value is large for semi-transparent colors, indicating that the risk of misrecognition has been reduced. Furthermore, regarding the risk of misjudgment with white, white becomes equal to or higher than the first threshold at the first threshold of maximum intensity and is excluded from the judgment candidates, so there is no risk of misjudgment. In addition, by setting the third threshold value to 0.5 when determining the resin containing carbon rack after it has been determined that the resin contains carbon black pseudo-containing resin, determination can be made without erroneous determination, as shown in FIG. 9. In this way, it is possible to accurately determine whether carbon black is contained, and to recover resin that does not contain carbon black.

Here, we have explained a method using Euclidean distance as an example of similarity as a judgment algorithm, but in addition, regression analysis or correlation coefficients may be used as other examples of similarity, which may be selected as appropriate, and strength judgment or resin The threshold value for determination is similarly selected appropriately.

In addition, although the above explanation was given using the case of PP as the base material resin, the resin determination method according to the embodiment of the present invention deals only with the influence of carbon black content, so other resins such as ABS or PS can be used. Even in the case of the base material, the presence of carbon black can be accurately determined in the same way as with PP, and the resin that does not contain carbon black can be recovered.

As described above, according to the resin determination method according to the embodiment, when determining the resin 2 using the reflection or absorption spectrum in the near-infrared region, the reflected light 4 is attenuated due to the inclusion of carbon black. Use influence. That is, the reflection or absorption spectrum of the resin 2 is calculated based on the reflected light 4 received from the resin 2 of the object to be sorted that has been irradiated with the infrared light 3, and the maximum intensity of the spectrum is determined among the calculated spectra. If the maximum obtainable strength is greater than or equal to the first threshold value, it is determined that carbon black is not contained, and after normalization, the resin type is determined. If it is less than the first threshold value, it is determined that carbon black is contained in the resin. The type of resin is determined. As a result, it is possible to accurately determine which resin contains carbon black.

Note that by appropriately combining any of the various embodiments or modifications described above, the effects of each can be achieved. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features in different embodiments or examples are also possible.

From the above, the resin determination method according to the above aspect of the present invention can quickly determine whether carbon black is contained even in black resin etc. containing carbon black (fine particles mainly composed of carbon). Therefore, it can be used in a recycling process, etc. in which multiple objects to be sorted are quickly sorted.

1 Resin determination device 2 Resin 3 Irradiation light 4 Reflected light 5 Belt conveyor 6 Input area 7 Detection area 8 Infrared detection unit 9 Digital data conversion device 10 Arithmetic processing unit

Claims (2)

If the reflection or absorption spectrum obtained by the reflected light received from the object to be sorted that has been irradiated with infrared light is equal to or greater than the first threshold, with the intensity of the reflection or absorption spectrum set in advance as the first threshold, The first similarity is determined by normalization with the spectrum data of one or more resin species obtained in advance, and the one having the highest first similarity that is equal to or higher than a second threshold of the first similarity set in advance is selected. Determine the resin type of the object,
If the reflection or absorption spectrum obtained by the reflected light is less than the first threshold, a second degree of similarity with the spectrum data of one or more types of resin obtained in advance is determined, and a second degree of similarity is calculated based on the preset second degree of similarity. A resin determination method, wherein a resin type that is equal to or higher than a third threshold value and has the highest second similarity is determined as the resin type of the object to be sorted. The resin determination method according to claim 1, wherein the effective wavelength range of the infrared light is 1 μm or more and 3 μm or less.

Images