Waste plastic sorting device and waste plastic sorting method

Abstract

To provide sorting equipment which sorts waste plastics by material with high accuracy.SOLUTION: Sorting equipment of waste plastics includes: a surface treatment part which treats surfaces of a waste plastic pieces including black waste plastic pieces; an irradiation part which irradiates the surface-treated waste plastic pieces with light; a reflection spectrum detection part which receives reflected light of the irradiated light and detects a spectrum of the reflected light; a determination part which determines the material of the waste plastic pieces on the basis of the spectrum of the reflected light; and a sorting part which sorts at least the black waste plastic pieces by material on the basis of the result of determination.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a waste plastic sorting device and a waste plastic sorting method. [Background technology]

[0002] Material recycling, in which new materials or products are produced using waste plastics, is known as the main method for reusing waste plastics derived from discarded home appliances, discarded automobiles, etc. Since collected waste plastics usually contain various types (materials) of plastics, in material recycling, the waste plastics must be sorted by material according to the regenerated products to be produced.

[0003] As a means for sorting waste plastics, for example, a method is known in which pieces of waste plastic are irradiated with light such as infrared light and the material of the plastic is determined by utilizing the spectrum of the reflected light obtained by the irradiation (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-100903 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to produce high-quality products in material recycling, it is necessary to sort waste plastics with high accuracy. However, in conventional waste plastic sorting using reflection of infrared light or the like, halation may occur depending on the intensity of the irradiated light, the irradiation distance, etc., and there are cases where reflected light capable of generating a reflection spectrum effective for determining the material cannot be obtained sufficiently. Therefore, there is a demand for improved sorting accuracy in a waste plastic sorting device or sorting method using light reflection.

[0006] Therefore, an object of one aspect of the present invention is to provide a sorting device that sorts waste plastics based on their material with high accuracy. [Means for solving the problem]

[0007] A waste plastic sorting device according to one embodiment of the present invention comprises a surface treatment unit that treats the surfaces of waste plastic pieces including black waste plastic pieces, an irradiation unit that irradiates light onto the surface-treated waste plastic pieces, a reflection spectrum detection unit that receives reflected light of the light irradiated by the irradiation unit and detects the spectrum of the reflected light, a judgment unit that judges the material of the waste plastic pieces based on the spectrum of the reflected light, and a sorting unit that sorts at least the black waste plastic pieces by material based on the result of the judgment. Effect of the Invention

[0008] According to the present disclosure, a sorting device can be provided that can sort waste plastic based on its material with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a waste plastic sorting device according to an embodiment; [Diagram 2] A side view of the waste plastic sorting device shown in Figure 1. [Diagram 3] Plan view of the waste plastic sorting device shown in Figure 1. [Figure 4] Schematic diagram showing an example of a surface treatment unit [Diagram 5] Functional block diagram of the sorting device [Figure 6] Flowchart of waste plastic material discrimination process according to the embodiment [Figure 7] Diagram showing the method of extracting spectra for correction [Figure 8] FIG. 13 is a diagram showing an example of a process for extracting a characteristic wavelength region from a reflected wave spectrum. [Figure 9] A diagram showing an example of feature data extraction [Figure 10] An example of material discrimination using a decision tree [Figure 11] FIG. 2 is a plan view showing a first material sorting method using the sorting device of the present embodiment; [Figure 12] FIG. 11 is a plan view showing a second material sorting method using the sorting device of the present embodiment. [Figure 13] FIG. 11 is a plan view showing a third material sorting method using the sorting device of the present embodiment. [Figure 14] FIG. 11 is a plan view showing a fourth material sorting method using the sorting device of the present embodiment. [Figure 15] FIG. 11 is a plan view showing a fifth material sorting method using the sorting device of the present embodiment. [Figure 16] FIG. 13 is a diagram showing an example of an operation screen of the sorting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0011] In the following description, the x, y, and z directions are perpendicular to each other. The x and y directions are horizontal, and the z direction is vertical. The x direction is the conveying direction of the conveying path 3 of the conveyor 2. The y direction is the width direction of the conveying path 3 of the conveyor 2. For convenience of explanation, the positive z direction side may be referred to as the upper side, and the negative z direction side as the lower side. Also, the negative x direction side may be referred to as the upstream side, and the positive x direction side as the downstream side.

[0012] The schematic configuration of a waste plastic sorting device 1 according to one embodiment of the present invention will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view showing the schematic configuration of the waste plastic sorting device 1 according to this embodiment. Fig. 2 is a side view of the waste plastic sorting device 1 shown in Fig. 1. Fig. 3 is a plan view of the waste plastic sorting device 1 shown in Fig. 1. As shown in Figs. 1 to 3, the waste plastic sorting device 1 is equipped with a surface treatment section 20 upstream of the device.

[0013] The waste plastics sorted by the sorting device 1 according to this embodiment are aggregates of waste plastic pieces (a group of waste plastic pieces) obtained by crushing waste home appliances, discarded automobiles, etc. Each waste plastic piece may have a plate-like or layer-like shape, and may have an average maximum length of 5 to 50 mm and an average area in a plan view of 20 to 2500 mm. 2 In this embodiment, waste plastic pieces of a predetermined material are selected from a collection of waste plastic pieces (a group of waste plastic pieces) including black waste plastic pieces, preferably from a collection of black waste plastic pieces (a group of black waste plastic pieces). In addition, the waste plastic pieces selected by this embodiment may contain colored waste plastic pieces of another color, such as blue or red, in addition to the black waste plastic pieces.

[0014] In this specification, black refers to a color with a brightness of 6 or less, expressed in Munsell notation according to JIS 8721. The black color of black waste plastic pieces usually comes from the carbon black (carbon filler) contained in the black waste plastic pieces.

[0015] 1 to 3 show, as an example, an apparatus for determining and separating waste plastic pieces of one material from a group of waste plastic pieces S1 made of one type of material and waste plastic pieces S2 made of a different type of material from the waste plastic pieces. In the following, the waste plastic pieces S1 and S2 may be collectively represented by the symbol S. The number of materials (types) of the waste plastic pieces separated from the group of waste plastic pieces is not particularly limited, and may be 2 to 10 types. Specific examples of plastic materials include polyethylene (PE), polypropylene (PP), polycarbonate / acrylonitrile-butadiene-styrene (PCABS), acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polyphenylene ether / polystyrene (PPEPS), polyamide (PA), polycarbonate (PC), polyacetal (POM), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), etc.

[0016] In the waste plastic sorting device 1 according to this embodiment, the material of the waste plastic is determined based on the reflection spectrum detected from the reflected light obtained by irradiating the waste plastic with infrared light or the like, and the material is identified (details on the determination will be described later). In the conventional configuration, when light is applied, strong regular reflection (specular reflection) occurs depending on the intensity of the irradiated light, the irradiation distance, etc., and there are cases where the reflected light (diffuse reflected light) effective for determining the material is not obtained sufficiently. In contrast, the sorting device 1 according to this embodiment has a surface treatment section 20, which processes the surface of the waste plastic pieces, making it possible to obtain appropriate reflected light.

[0017] In particular, black plastics have a weaker level (strength) of the absorption region specific to the material than plastics of other colors, and are therefore more affected by the surface condition. In particular, when the glossiness of the plastic surface is relatively high, the influence of infrared reflection on the plastic surface, especially the influence of regular reflection (specular reflection), becomes large, making it difficult to see the absorption level and to distinguish the material. Therefore, by performing a surface treatment to roughen the surface to a specified roughness, the influence of regular reflection of infrared rays on the plastic surface can be suppressed, the spectral intensity of the reflected light spectrum can be increased, and the difference in reflection spectrum intensity due to the material can be properly observed. As a result, the accuracy of sorting black plastic pieces can be improved.

[0018] The surface treatment by the surface treatment unit 20 may be a treatment that changes the surface state to such an extent that a reflection spectrum effective for identifying the material can be obtained when light is irradiated. For example, the surface treatment according to this embodiment may be a treatment that changes the surface state of the waste plastic pieces so that the glossiness (specular glossiness) (Gs60(%)) at an incident angle of 60° measured in accordance with JIS Z 8741 is 10 or less. The glossiness at an incident angle of 60° may be preferably 8 or less, more preferably 6 or less, and even more preferably 1.5 or less. The glossiness at the incident angle of 60° may be 0.1 or more. Furthermore, the surface treatment according to this embodiment may be a treatment that changes the surface state so that the glossiness (specular glossiness) (Gs75(%)) at an incident angle of 75° measured in accordance with JIS Z 8741 is 25 or less. The glossiness at an incident angle of 75° may be preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less. The glossiness at the incident angle of 75° may be 0.1 or more. The surface treatment in this embodiment is preferably carried out so as to have a glossiness at an incidence angle of 60° within the above range, and also a glossiness at an incidence angle of 75° within the above range. By having the above glossiness, particularly a glossiness at an incidence angle of 60° and / or a glossiness at an incidence angle of 75°, it is possible to impart an appropriate rough surface state to the plastic surface, thereby improving the sorting accuracy even when the waste plastic pieces are black plastic pieces.

[0019] The surface treatment according to the present embodiment may be a treatment for changing the surface condition of the waste plastic pieces so that the surface roughness mean deviation (SMD) is 1 μm or more. The surface roughness mean deviation may be preferably 1.1 μm or more, more preferably 1.2 μm or more. The surface roughness mean deviation may be preferably 6 μm or less, preferably 3 μm or less, more preferably 2.5 μm or less. By performing the surface treatment so that the surface roughness mean deviation (SMD) is in the above range, the plastic surface can be given an appropriate rough surface condition. Therefore, even if the waste plastic pieces are black plastic pieces, the reflection spectrum can be appropriately obtained, and the sorting accuracy can be improved.

[0020] In addition, by making 50% or more, and preferably 80% or more, of the total surface area of ​​the waste plastic pieces satisfy one or more of the following conditions: gloss (specular gloss (%)) at an incident angle of 60° measured in accordance with JIS Z 8741 is 10 or less, gloss (specular gloss (%)) at an incident angle of 75° measured in accordance with JIS Z 8741 is 25 or less, and surface roughness mean deviation (SMD) is 1 μm or more, the sorting accuracy of waste plastic pieces using infrared rays can be improved.

[0021] The surface treatment in this embodiment may be a roughening treatment or a smoothening treatment depending on the surface condition of the original waste plastic pieces. The surface treatment may be a wet treatment using a liquid or a dry treatment not using a liquid. Specific examples of surface treatment include polishing (or grinding) using an abrasive tool such as a wire brush or sandpaper and / or an abrasive, and surface treatment using chemicals. Of these, polishing is preferred because the amount of waste that may be generated by the treatment is relatively small and the disposal of the waste is easy.

[0022] FIG. 4 is a schematic diagram of an example of the surface treatment section 20. The surface treatment section 20 shown in FIG. 4 is equipped with a plurality of rollers having a rough surface. By passing the waste plastic pieces S' before surface treatment between the plurality of rollers, the surface of the waste plastic pieces S' is scraped, forming fine irregularities and / or eliminating excessively large irregularities, thereby obtaining waste plastic pieces S with appropriate irregularities. The surface of the waste plastic pieces with appropriate irregularities has the above-mentioned predetermined glossiness, and the plastic type can be determined with higher accuracy by using light irradiation in the sorting device 1.

[0023] In the surface treatment section 20 shown in FIG. 4, a large roller 21 that rotates in the direction of transport of the waste plastic pieces and small-diameter rough-surface rollers 23, 23, 23 that face the large roller 21 and rotate in the opposite direction to the large roller 21 are arranged. The rough-surface rollers 23, 23, 23 have brushes or sandpaper attached to their surfaces. The waste plastic pieces S' before surface treatment supplied from the supply section 28 are supplied between the large roller 21 and the rough-surface rollers 23, 23, 23, and are transported in the transport direction, while the surface facing the rough-surface rollers 23, 23, 23 is roughened. In the surface treatment section 20, downstream of the large roller 21 and the rough-surface rollers 23, 23, 23, another large roller 22 that rotates in the direction of transport of the waste plastic pieces and small-diameter rough-surface rollers 25, 25, 25 that face the large roller 22 and rotate at high speed in the opposite direction to the large roller 22 are arranged. The rough-surface rollers 25, 25, 25 are fitted with brushes or sandpaper, similar to the rough-surface rollers 23, 23, 23. The large roller 22 and the rough-surface rollers 25, 25, 25 are arranged so that the surface of the waste plastic pieces S' opposite to the surface roughened by the rough-surface rollers 23, 23, 23 is roughened. With this configuration, both sides of the waste plastic pieces S' have a surface condition appropriate for the material determination in the sorting device 1, allowing for highly accurate sorting by material. The rotation speeds of the rough-surface rollers 23, 23, 23 and the rough-surface rollers 25, 25, 25 can be set according to the desired surface condition of the waste plastic pieces. The appropriate surface condition can be one that satisfies one or more of the following conditions: gloss (specular gloss (%)) at an incidence angle of 60° measured in accordance with JIS Z 8741 is 10 or less, gloss (specular gloss (%)) at an incidence angle of 75° measured in accordance with JIS Z 8741 is 25 or less, and the mean deviation of surface roughness (SMD) is 1 μm or more. In the case of waste plastic pieces that contain or consist of black plastic pieces, the above surface condition can improve the sorting accuracy.

[0024] The waste plastic pieces are obtained by removing plastic parts from discarded home appliances, discarded automobiles, etc., and then crushing them to reduce their size so as to facilitate recycling. The surface treatment in this embodiment may be incorporated into the crushing step.

[0025] Referring again to Figs. 1 to 3, the processing of the waste plastic pieces S after surface treatment in the sorting device 1 will be described. The main components include a vibration feeder 8 as an example of a supply unit that sequentially supplies the waste plastic pieces S1 and S2 after surface treatment obtained from the surface treatment unit 20, and a conveyor 2 as an example of a transport unit that transports the waste plastic pieces S1 and S2 supplied by the vibration feeder 8. The crushed (surface-treated) waste plastic pieces S1 and S2 are supplied to the vibration feeder 8 via, for example, an input hopper. The vibration feeder 8 vibrates the placement surface on which the waste plastic pieces S1 and S2 are placed, thereby supplying the waste plastic pieces S1 and S2 to the conveyor 2 while preventing them from overlapping with each other. The conveyor 2 has a conveying path 3 on its upper surface, and transports the waste plastic pieces S1 and S2 on the conveying path 3 in a direction away from the vibration feeder 8.

[0026] The sorting device 1 also includes a light 10 as an example of an irradiation unit that irradiates infrared rays onto the waste plastic pieces S1 and S2, a mid-infrared camera 4 as an example of a reflection spectrum detection unit that detects the reflection spectrum from the waste plastic pieces S1 and S2, and a discrimination device 5 that determines or identifies the material of the waste plastic pieces S1 and S2 based on the reflection spectrum detected by the mid-infrared camera 4.

[0027] The lighting 10 has a lamp 10A (see FIG. 7) that is an infrared light source such as a halogen tungsten lamp, and irradiates (emits) infrared rays from the lamp 10A toward the waste plastic pieces S1, S2. The lighting 10 is also installed so that reflected light from the waste plastic pieces S1, S2 enters the mid-infrared camera 4, and is installed on both upper sides (or one upper side) of the conveyor 2 in the flow direction relative to the mid-infrared camera 4.

[0028] The light irradiated to the waste plastic pieces may include infrared rays of 2 to 8 μm, preferably mid-infrared rays of more than 3 μm, more specifically infrared rays of more than 3 μm and 8 μm or less. The mid-infrared rays in the above wavelength range include a region where the light absorption rate of black plastic is relatively low, so that even for black waste plastic, a reflected light spectrum effective for determining the material of the plastic (a reflected light spectrum in which a significant difference can be observed depending on the material) can be obtained.

[0029] As shown in FIG. 1, for example, one mid-infrared camera 4 can measure the entire width direction (y direction) of the conveyor 2, divide the conveyor 2 into a plurality of (e.g., 318) regions along the width direction, receive near-infrared reflected light from the black waste plastic pieces S1 and S2, and measure the spectrum of the reflected light for each region. The mid-infrared camera 4 may be, for example, a camera equipped with a spectrometer for an infrared wavelength region of 3 μm or more or more than 3 μm. The mid-infrared camera 4 performs measurements at a scan frequency of, for example, 230 Hz, and transmits 318 pieces of spectrum data to the discrimination device 5 for each scan. The discrimination device 5 outputs the material judgment results for each of the 318 regions based on the 318 pieces of spectrum data received from the mid-infrared camera 4 to the injection control unit 6 described below.

[0030] The reflected light received by the mid-infrared camera 4 may preferably include infrared rays in a wavelength region of more than 3 μm, more preferably more than 3 μm and 8 μm or less, and even more preferably more than 3 μm and 5 μm or less. By receiving reflected light in the above wavelength region, data useful for determining the material of black waste plastic can be obtained. In other words, a significant difference due to the material can be observed in the spectral intensity of reflected light in the above wavelength region.

[0031] Furthermore, the sorting device 1 is equipped with an injection nozzle row 7 that injects air laterally or obliquely in a direction intersecting the conveying direction (x direction) downstream of the conveying direction of the conveyor 2. The injection nozzle row 7 is composed of a plurality of injection nozzles (e.g., 318) arranged in the width direction (y direction) of the conveyor 2, and the operation of each injection nozzle is controlled by the injection control unit 6. The injection control unit 6 can inject air from the injection nozzles of the injection nozzle row 7 or not inject air according to the material judgment result received from the discrimination device 5. That is, it is possible to select the target waste plastic pieces and blow air onto them (selective blowing). Then, for example, the black waste plastic pieces S1 and S2 are sorted and dropped into a plurality of areas (e.g., a collection hopper or container) divided by a partition plate 9 (FIG. 2), and the waste plastics of the desired material are separated and collected. In other words, in this embodiment, the injection control unit 6 and the injection nozzle row 7 function as a sorting unit 12 that collects waste plastic pieces of a desired material from those flowing on the conveying path 3 of the conveyor 2 based on the material determination result by the discrimination device 5.

[0032] 1 to 3, the sorting unit 12 uses a jet of air or a predetermined gas to selectively blow or not blow away the waste plastic pieces S on the conveyor 2, but the sorting form is not limited to that shown in the figures. For example, information on the material determination result by the discrimination device 5 may be sent to a robot arm, and the robot arm may sort the waste plastic pieces by their material, thereby separating the waste plastic pieces.

[0033] The operation of the sorting device 1, that is, the processing of the waste plastic pieces supplied from the surface treatment unit 20, will be described. For example, when the crushed waste plastic pieces S1, S2 are supplied to the vibrating feeder 8 via an input hopper or the like, the vibrating feeder 8 vibrates the supplied waste plastic pieces S1, S2 to prevent them from overlapping, transports them downstream, and supplies them to the conveyor 2.

[0034] The waste plastic pieces S1 and S2 supplied to the transport path 3 on the upper surface of the conveyor 2 are irradiated with infrared light from the lighting 10 at a position where they can be imaged by the mid-infrared camera 4 while being transported in the transport direction on the x-positive side. The mid-infrared camera 4 receives the infrared light emitted from the lighting 10 and reflected by the waste plastic pieces S1 and S2, and outputs the light reception result (data of the received light spectrum) to the discrimination device 5.

[0035] The discrimination device 5 identifies the material of the waste plastic pieces S1, S2 based on the light reception result input from the mid-infrared camera 4. The material determination method by the discrimination device 5 will be described in detail later with reference to Figs. 5 to 10. The discrimination device 5 outputs the material identification result to the injection control unit 6.

[0036] The injection control unit 6 selects an injection nozzle corresponding to the material from among the multiple injection nozzles arranged in the injection nozzle row 7, and transmits a control signal at the appropriate timing. Each injection nozzle in the injection nozzle row 7 that receives the control signal opens its nozzle opening and injects air. By injecting air from the injection nozzle at an appropriate timing according to the discrimination result of the discrimination device 5, the material to be sorted can be separated from other materials and collected.

[0037] In the example shown in Figures 1 to 3, the waste plastic pieces S1 on the conveyor 2 receive air from the air injection nozzle that has received the control signal, are blown off, fall, and are collected in a collection container or the like. Also, the black waste plastic pieces S2 on the conveyor 2 do not receive air from the injection nozzle, so are collected in a collection container or the like different from the black waste plastic pieces S1. In this way, by individually injecting and stopping the injection nozzles included in the injection nozzle row 7, it is possible to separate and collect waste plastic pieces of a predetermined material from a group of waste plastic pieces of multiple materials.

[0038] According to this embodiment, the waste plastic pieces to be sorted are surface-treated and have a predetermined surface roughness, preferably on both sides, so that they can have an appropriate friction coefficient against the conveyor 2. Therefore, in the sorting section 12, the targeted waste plastic pieces are reliably blown away, and the non-targeted waste plastic pieces are reliably not blown away, which also contributes to improving the sorting accuracy.

[0039] 5 to 10, the material determination and discrimination of waste plastics by the discrimination device 5 will be described. FIG.

[0040] As shown in FIG. 5, the discrimination device 5 has a preprocessing section 51, and further has a first judgment section 52, a second judgment section 53, and a third judgment section 54 (collectively referred to as judgment sections).

[0041] The pre-processing unit 51 performs pre-processing such as correction and processing of the reflection spectrum of the black waste plastic pieces S1, S2 detected by the mid-infrared camera 4. For example, the pre-processing unit 51 corrects the detected reflection spectrum using a spectrum measured under conditions where the reflected light is bright and a spectrum measured under conditions where the reflected light is dark. "Dark conditions (dark conditions)" refers to conditions that are relatively darker than the above-mentioned "bright conditions (light conditions)." In addition, the pre-processing unit 51 performs processing to cut out a predetermined frequency range from the corrected reflection spectrum.

[0042] The first determination unit 52 determines whether the spectrum detected by the mid-infrared camera 4 is from the waste plastic pieces S1, S2 or the conveying path 3 of the conveyor 2. The first determination unit 52 makes the determination using a trained One Class SVM (Support Vector Machine).

[0043] One Class SVM is a type of SVM, which is a type of machine learning classification algorithm. In SVM, the support vectors of each class (the ones closest to other classes in the training data) are used as the basis, and the classification boundary is set to maximize the Euclidean distance between them. In addition, if the features are nonlinear, a kernel is used to map the data into the feature space. By appropriately selecting the kernel, it is possible to draw the classification boundary even with complex data arrangements.

[0044] In One Class SVM, a method called the kernel trick is used to map one type of training data into a high-dimensional feature space. At this time, the training data is mapped so that it is placed far away from the origin, so data that is not similar to the original training data is gathered near the origin. This property is used to distinguish between normal data (conveyor 2) and abnormal data (objects (waste plastic pieces S1, S2)).

[0045] By using One Class SVM, which has excellent pattern recognition ability, in the first determination unit 52, it is possible to accurately determine whether the reflection spectrum is reflected by the waste plastic pieces S1, S2 or the transport path 3 of the conveyor 2. Note that the first determination unit 52 may apply a classification method of supervised learning of machine learning other than One Class SVM.

[0046] The second judgment unit 53 extracts feature data Score1 and Score2 (feature amount) from the spectrum judged to be a waste plastic piece by the first judgment unit 52. The feature amount may be, for example, the maximum value, average value, integral value, etc. of the spectral intensity in a predetermined wavelength region, but it is preferable to extract the feature amount using a trained PLS (Partial Least Squares) method.

[0047] PLS is a type of regression algorithm for supervised learning in machine learning, and performs regression analysis between only a small number of principal components calculated from explanatory variables and the objective variable. In PLS, the principal components are calculated so that the covariance with the objective variable is large. In this embodiment, two types of feature data Score1 and Score2 are calculated using PLS based on the explanatory variables of the reflection spectra determined to be reflected by the waste plastic pieces S1 and S2.

[0048] By using PLS in the second judgment unit 53, it is possible to reduce the multidimensional explanatory variables of the reflectance spectrum to a small number of feature quantities, and therefore it is possible to extract more easily distinguishable appropriate feature data Score1 and Score2. Note that the second judgment unit 53 may apply a machine learning multivariate analysis method other than PLS.

[0049] The third judgment unit 54 judges the material of the waste plastic pieces S1, S2 corresponding to the spectrum based on the two feature values ​​Score1 and Score2 of the reflection spectrum extracted by the second judgment unit 53. The third judgment unit 54 makes the judgment using a trained decision tree. A decision tree is a type of classification algorithm for supervised learning. A decision tree represents the rules for classifying the objective variables in a tree structure, and is frequently used in classification problems.

[0050] By using a decision tree in the third judgment unit 54, the materials of the waste plastic pieces S1 and S2 can be accurately determined from the two feature amounts Score1 and Score2 of the reflection spectrum. Note that a classification method of supervised learning of machine learning other than the decision tree may be applied to the third judgment unit 54.

[0051] The discrimination device 5 can be physically configured as a computer system including a CPU (Central Processing Unit), a RAM (Random Access Memory) and a ROM (Read Only Memory) as main storage devices, a communication module, an auxiliary storage device, and the like. Each function of the discrimination device 5 shown in Fig. 5 is realized by loading a predetermined computer software (material determination program) into the CPU, RAM, and the like, thereby operating various hardware under the control of the CPU and reading and writing data in the RAM. That is, by executing the material determination program according to this embodiment on a computer, the discrimination device 5 functions as a pre-processing unit 51, a first determination unit 52, a second determination unit 53, and a third determination unit 54 in Fig. 5.

[0052] The material discrimination program of this embodiment is stored, for example, in a storage device provided in a computer. Note that the material discrimination program may be configured so that a part or all of it is transmitted via a transmission medium such as a communication line, and is received and recorded (including installed) by a communication module or the like provided in the computer. Also, the material discrimination program may be configured so that a part or all of it is recorded (including installed) in the computer from a state in which it is stored in a portable storage medium such as a CD-ROM, DVD-ROM, or flash memory.

[0053] The discrimination device 5 may be a circuit configured with an analog circuit, a digital circuit, or an analog-digital mixed circuit. It may also include a control circuit that controls each function of the discrimination device 5. Each circuit may be implemented using an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like.

[0054] Similarly, the injection control unit 6 can also be physically configured as a computer system including a CPU, RAM and ROM, a communication module, an auxiliary storage device, etc., and its functions are realized by loading predetermined computer software into the CPU, RAM, etc.

[0055] 6 is a flowchart of a process for determining the material of waste plastic according to the embodiment. Each process in the flowchart shown in FIG.

[0056] In step S01, the pre-processing unit 51 processes the spectrum S org (n, w) is acquired. Here, n is the number of sensors (the number of spectrum detection areas divided in the width direction of the conveyor 2 by the mid-infrared camera 4), and when the number of sensors is 318, an integer from 0 to 317 corresponding to each detection area is used. w is the wavelength of the spectrum, and in this embodiment, a total of 131 wavelengths are set at intervals of 20 (nm) between 2700 (nm) and 5300 (nm), and an integer from 0 to 130 corresponding to each wavelength is used. In other words, S org (n, w) represents the numerical value of the spectral intensity of wavelength w in the nth spectral detection region along the width direction of the conveyor 2.

[0057] In step S02, the preprocessing unit 51 processes the spectrum S obtained in step S01. org (n,w) is corrected to obtain the corrected spectrum S cor (n, w) is calculated. This correction absorbs the difference in the spectral intensity characteristics due to the influence of the concentration changes of water vapor and carbon dioxide in the measurement space, the temperature of the black waste plastic pieces S1 and S2 to be measured, the aging of the lighting 10 and the mid-infrared camera 4, the position on the conveyor 2, etc. The corrected spectrum S cor (n, w) can be calculated, for example, by the following formula (1).

[0058]

number

[0059] Figure 7 shows the correction spectrum W ref (n,w), D ref 7 is a diagram showing a method for extracting (n, w). As shown in FIG. 7, a calibration plate 11 for acquiring a correction spectrum is placed in the imaging area of ​​the mid-infrared camera 4 on the conveying path 3 of the conveyor 2, and the spectrum of reflected light is detected by the mid-infrared camera 4, thereby obtaining the correction spectrum W ref (n,w), D ref (n,w) can be obtained.

[0060] The first correction spectrum W measured under bright reflected light conditions ref In the case of (n, w), a calibration plate 11 (aluminum, stainless steel, etc.) that reflects all wavelengths in the mid-infrared region is placed, and with the light 10 turned on, data is acquired for all wavelengths (w = 0 (2700), 2 (2720), ..., 130 (5300)) for all sensors (n = 0, 1, 2, ..., 317).

[0061] Second correction spectrum D measured under low reflected light conditions ref In the case of (n, w), a calibration plate 11 (aluminum, stainless steel, etc.) that reflects all wavelengths in the mid-infrared region is placed, and with the lighting 10 turned off (or the camera shutter closed), data is acquired for all wavelengths (w = 0 (2700), 2 (2720), ..., 130 (5300)) for all sensors (n = 0, 1, 2, ..., 317).

[0062] The calibration plate 11 is, for example, as shown by the dotted arrow in FIG. ref (n,w), D refIt is preferable that the calibration plate 11 is installed so as to be movable between the position of the imaging area of ​​the mid-infrared camera 4 on the transport path 3 of the conveyor 2, where the calibration plate 11 is placed when acquiring (n, w), and a standby position that is outside the imaging area of ​​the mid-infrared camera 4 and the irradiation range of the illumination light 10. In other words, it is preferable that the calibration plate 11 can be fixed to a predetermined position within the field of view of the mid-infrared camera 4 and a predetermined position outside the field of view, and can be moved between these two predetermined positions. It is preferable that the calibration plate 11 is processed so that the main surface that receives the light from the illumination light 10 has a large surface roughness that is rough. This makes it possible to suppress the occurrence of halation of reflected light on the calibration plate 11.

[0063] Furthermore, the conveyor 2 may be stopped when the correction spectrum is acquired. In this case, if the calibration plate 11 is not correctly positioned in the imaging area of ​​the mid-infrared camera 4 due to some malfunction in the operation of the calibration plate 11, the temperature of the portion of the conveyor 2 on the transport path 3 irradiated with the infrared rays from the lighting 10 will rise, which may cause burning or fire. For this reason, if the calibration plate 11 is not fixed within the field of view of the mid-infrared camera 4, it is preferable to provide an interlock so that the lighting 10 does not irradiate infrared rays.

[0064] As shown in FIG. 7, the lighting 10 has a lamp 10A (sheath heater, carbon lamp, Kanthal lamp, etc.) which is a light source of infrared rays, and a reflector 10B which collects heat from the lamp 10A. The lamp 10A is formed so as to extend along the width direction (y direction) of the conveyor 2, and is arranged so as to radiate infrared rays in all directions around the axis along the y axis. The reflector 10B is arranged on the opposite side of the conveyor 2 from the conveying path 3 with respect to the lamp 10A, and is formed so as to be curved along the circumferential direction around the axis of the lamp 10A, so that it can collect infrared rays radiated from the lamp 10A to the opposite side of the conveyor 2, and reflect and send them to the conveyor 2 side. The reflector 10B is made of, for example, aluminum, stainless steel, or aluminum-plated material.

[0065] Returning to FIG. 6, in step S03, the preprocessing unit 51 generates a corrected spectrum S corA characteristic wavelength region is extracted from (n, w). FIG. 8 is a diagram showing an example of a process for extracting a characteristic wavelength region from a reflected wave spectrum obtained when infrared rays are irradiated onto black waste plastic pieces. The horizontal axis of FIG. 8 indicates the wavelength (nm) of the spectrum, and the vertical axis indicates the intensity of the spectrum at each wavelength. FIG. 8 shows an example of the spectrum of each material, acrylonitrile-butadiene-styrene (ABS), high impact polystyrene (HIPS), polypropylene (PP), and polyethylene (PE). In the example of FIG. 8, the spectra of the wavelength regions of 3250 to 3750 (nm) and 4400 to 4600 (nm) are extracted. Therefore, when sorting black plastics by material, the spectrum of at least one of the wavelength regions in the above ranges can be used.

[0066] 6, in step S04, the first determination unit 52 uses the spectrum corrected in step S02 and from which a characteristic wavelength region has been extracted in step S03 to determine whether each spectrum is the belt (conveyance path 3) of the conveyor 2 or an object (waste plastic) on the conveyance path 3. In this embodiment, the first determination unit 52 makes the determination by using a trained One Class SVM.

[0067] In step S05, the second judgment unit 53 extracts two types of feature data Score1 and Score2 from the spectrum judged to be an object (waste plastic) in step S04 using the trained PLS. FIG. 9 is a diagram showing an example of extracted feature data. The horizontal axis of FIG. 9 indicates the first feature data (Score1), and the vertical axis indicates the second feature data (Score2). FIG. 9 shows an example of extraction of four types of materials, ABS, HIPS, PP, and PE, as exemplified in FIG. 8. As shown in FIG. 9, it can be seen that the areas plotted for each material can be divided in a two-dimensional space using the two types of feature data Score1 and Score2. The number of types of feature data may be other than two.

[0068] Returning to FIG. 6, in step S06, the third judgment unit 54 discriminates the material using a trained decision tree based on the two types of feature data Score1 and Score2 extracted in step S5. FIG. 10 is a diagram showing an example of material discrimination using a decision tree. In this embodiment, in order to ultimately discriminate four types of materials (PE, PP, ABS, HIPS), the decision tree has two levels of conditional branching as shown in FIG. 10. In the first level, a set of feature data Score1 and Score2 is divided into two groups G1 and G2 using a conditional branching function f1 (Score1, Score2). In the second level, one group G1 is further divided into two groups G11 and G12 using a conditional branching function f2 (Score1, Score2). In the second level, the other group G2 is further divided into two groups G21 and G22 using a conditional branching function f3 (Score1, Score2). As a result, the pairs of feature data Score1 and Score2 are classified into four groups G11, G12, G21, and G22, and the materials of each group are determined to be PE, PP, ABS, and HIPS, respectively.

[0069] As such, the discrimination device 5 of the waste plastic material discrimination and sorting apparatus 1 in this embodiment is equipped with a first judgment unit 52 that judges whether the spectrum of reflected light of light irradiated by the lighting 10 onto the conveying path 3 of the conveyor 2, detected by the mid-infrared camera 4, is from either the waste plastic piece S or the conveying path 3, a second judgment unit 53 that extracts two types of feature data Score1 and Score2 from the spectrum judged to be the waste plastic piece S by the first judgment unit 52, and a third judgment unit 54 that discriminates the materials S1 and S2 of the waste plastic piece S based on the feature data Score1 and Score2 extracted by the second judgment unit 53.

[0070] With this configuration, output information on the material of waste plastic can be obtained from the input information of the reflection spectrum through three stages of judgment processing and data narrowing: narrowing down to the spectrum of black waste plastic pieces S by object discrimination in the first judgment unit 52, dimensional compression from the spectrum information to feature data by feature amount extraction in the second judgment unit 53, and classification processing in the third judgment unit 54. Therefore, the waste plastic sorting device 1 of this embodiment can judge the material of waste plastic taking into account various conditions, and can perform detailed judgment over multiple stages, improving the accuracy of judging the material of waste plastic.

[0071] In addition, the discrimination device 5 of the waste plastic sorting device 1 according to this embodiment detects the reflection spectrum S org (n, w) is the first correction spectrum W measured under bright reflected light conditions. ref (n,w) and the second correction spectrum D measured under relatively darker conditions. ref A pre-processing unit 51 is provided for performing correction using (n, w).

[0072] Thus, the reflectance spectrum S org (n, w) is, for example, calculated using equation (1) as the correction spectrum W ref (n,w), D ref By correcting using (n, w), it is possible to suppress differences in the characteristics of the spectral intensity due to the influence of the temperature of the black waste plastic pieces S1 and S2 to be measured, the aging of the mid-infrared camera 4, the position on the conveyor 2, etc. cor By using (n, w) to perform learning and judgment in the first judgment unit 52, the second judgment unit 53, and the third judgment unit 54, it is possible to further improve the accuracy of judgment of the material of the waste plastic.

[0073] The preprocessing unit 51 further processes the corrected spectrum S cor A predetermined frequency range is cut out from (n, w) and the processed spectrum is output to the first determination unit 52.

[0074] With this configuration, parts of the spectrum that are closely related to the material of the waste plastic can be extracted and used for learning and judgment by the first judgment unit 52, the second judgment unit 53, and the third judgment unit 54, thereby reducing the inclusion of noise that hinders learning and judgment, and further improving the accuracy of determining the material of the waste plastic.

[0075] In this embodiment, the pre-processing unit 51 detects the reflection spectrum S org Two processes are performed: a correction process for (n, w) and a process for extracting a predetermined frequency range. However, a configuration may be adopted in which only one of the two processes is performed.

[0076] Furthermore, a method for sorting waste plastics of a desired material using the sorting device 1 of this embodiment will be described with reference to Figs. 11 to 15. Fig. 11 is a plan view showing a first material sorting method using the sorting device 1 of this embodiment. Fig. 11 shows a simplified diagram corresponding to the plan view of the sorting device 1 shown in Fig. 3. From Fig. 11 onwards, an example will be described in which a plastic mix containing waste plastic pieces of five different materials (1), (2), (3), (4), and (5) is to be sorted, as an example of the sorting method.

[0077] In the example of FIG. 11, the conveyor 2 and the sorting section 12 are configured to form a single transport path that is not divided in the width direction (y direction) of the conveyor 2. In the sorting section 12, the waste plastics are separated into two major types by the jetting and stopping of each jet nozzle of the jet nozzle row 7, with the partition plate 9 shown in FIG. 2 and the like as a boundary. For this reason, in order to separate the plastic mix containing five types of materials to be sorted into each individual material, it is necessary to repeat the process of separating each type into one of the sorting sections 12-1 (for example, a device that collects waste plastics sprayed with air from the jet nozzle 7) of the sorting section 12. That is, as shown in FIG. 11, first, only waste plastic pieces of material (1) are selected from the plastic mix and collected in the sorting section 12-1. At this time, the remaining plastic mix collected in the other sorting section 12-2 contains the other four types of materials (2) to (5). Next, the remaining plastic mix containing the four types is again fed into the sorting device 1, and one of the materials (2) to (5) is selected. By repeating this procedure four times, the five types of waste plastic pieces of materials (1) to (5) can be separated by material.

[0078] FIG. 12 is a plan view showing a second material sorting method by the sorting device 1A of this embodiment. In FIG. 12 and subsequent figures, the conveying path 3 of the conveyor 2 is divided into two systems, a first system and a second system, in the width direction. More specifically, the inlet (vibration feeder 8), the conveyor 2, and the sorting section 12 are each divided into two systems in the width direction. Note that the inlet 8 and the conveyor 2 are not divided into two components, but rather a single element is provided with a partition or the like to prevent mixing between the systems. For example, the conveying path 3 of the conveyor 2 can be divided into two systems by providing a partition wall along the conveying direction at approximately the center position in the width direction.

[0079] In the following description, the first system is denoted by the suffix A, and the second system is denoted by the suffix B. Additionally, elements corresponding to sorting unit 12-1 in Fig. 11 are denoted as "sorting unit A1" and "sorting unit B1," and elements corresponding to sorting unit 12-2 in Fig. 11 are denoted as "sorting unit A2" and "sorting unit B2."

[0080] In the example of Fig. 12, waste plastic pieces of the same material are collected in the first and second systems. For example, as shown in Fig. 12, a plastic mix containing waste plastic pieces of five types of materials (1) to (5) is supplied to the inlets A and B of the first and second systems, respectively, and material determination is performed in each system, and waste plastic pieces of the same material (1) are collected in the sorting section A1 and sorting section B1. In addition, waste plastic pieces containing the remaining materials (2) to (5) other than material (1) are collected in the sorting section A2 and sorting section B2.

[0081] Fig. 13 is a plan view showing a third material sorting method by the sorting device 1B of this embodiment. In the example of Fig. 13, the first system collects waste plastic pieces of a first material, and supplies the remaining waste plastic pieces to a second system, and the second system collects waste plastic pieces of a second material from the remaining waste plastic pieces. In the example of Fig. 13, multiple types of mixed materials can be separated into three types: the first material, the second material, and other materials.

[0082] In the example of Fig. 13, a plastic mix containing five types of waste plastic pieces of materials (1) to (5) is fed to the first line inlet A, the materials are determined on the first line conveyor A, and the waste plastic pieces of material (1) are collected in the sorting section A1. The remaining waste plastic pieces containing materials (2) to (5) are collected in the sorting section A2.

[0083] Next, the remaining waste plastics collected in sorting section A2, which are a mixture of materials (2) to (5), are transported by conveying device 13 to inlet B of the second system and supplied to inlet B. The material is determined in conveyor B of the second system, and waste plastic pieces of material (2) are collected in sorting section B1. In sorting section B2, the remaining waste plastic pieces, which are a mixture of materials (3) to (5), are collected.

[0084] Fig. 14 is a plan view showing a fourth material sorting method by the sorting device 1C of this embodiment. In the example of Fig. 14, the first system collects waste plastic pieces of the first material and a small amount of other materials, and supplies the collected waste plastic pieces to the second system, and the second system collects waste plastic pieces of the first material from the waste plastic pieces of the first material and a small amount of other materials. In the example of Fig. 14, plastic pieces of a specific type of material can be sorted to a high purity.

[0085] In the example of Fig. 14, a plastic mix containing five types of materials (1) to (5) is fed to the first system inlet A, the materials are determined on the first system conveyor A, and the waste plastic pieces of material (1) and trace amounts of materials (2) to (5) are collected in the sorting section A1. In addition, the remaining waste plastics containing materials (2) to (5) and trace amounts of material (1) are collected in the sorting section A2.

[0086] Next, the waste plastics collected in the sorting section A1, which are a mixture of material (1) and trace amounts of (2) to (5), are transported by the transport device 13 to the second line of inlet B and supplied to the inlet B. The material is determined by the second line of conveyor B, and material (1) is sorted again in the sorting section B1, and waste plastic pieces of material (1) are collected. The material (1) collected in this sorting section B1 has a higher purity of material (1) than the material collected in the sorting section A1. In the sorting section B2, the remaining waste plastics mixed with materials (1) to (5) are collected.

[0087] Fig. 15 is a plan view showing a fifth material sorting method by the sorting device 1D of this embodiment. In the example of Fig. 15, in the first system, waste plastic pieces of the first material and trace amounts of other materials are removed, and the remaining removed waste plastic pieces are supplied to the second system, and in the second system, waste plastic pieces of the first material and trace amounts of other materials are further removed from the other waste plastic pieces, and waste plastic pieces not containing the first material are collected. In the example of Fig. 15, plastic pieces of a specific type of material can be more reliably sorted out from mixed materials.

[0088] In the example of Fig. 15, a plastic mix containing five types of materials (1) to (5) is fed into the first system inlet A, the materials are determined on the first system conveyor A, and waste plastic pieces of material (1) and small amounts of materials (2) to (5) are collected in the sorting section A1. In addition, waste plastics containing the remaining materials (2) to (5) and a small amount of (1) are collected in the sorting section A2.

[0089] Next, the waste plastics collected in the sorting section A2, which are a mixture of materials (2) to (5) and a small amount of (1), are transported by the transport device 13 to the second line of inlet B and supplied to inlet B. The material is determined by the second line of conveyor B, and the material (1) is again sorted in the sorting section B1, and waste plastic pieces containing a mixture of material (1) and trace amounts of materials (2) to (5) are collected. In the sorting section B2, the remaining waste plastics containing a mixture of materials (2) to (5) and a trace amount of (1) are collected.

[0090] FIG. 16 is a diagram showing an example of an operation screen of the sorting device 1. The operation screen shown in FIG. 16 is displayed on a display device installed in the material sorting device 1, for example. As shown in FIG. 16, the operation screen lists the names of plastic materials to be sorted, and allows the material to be sprayed and sorted for each of the first system ("primary" in FIG. 16 and the second system ("secondary" in FIG. 15) to be individually selected. The display device on which the operation screen is displayed is, for example, a touch panel, and by switching the "OFF" display in the "JET SELECTION" field to "ON" display by pressing the "OFF" display, it is possible to set the injection nozzles of the injection nozzle row 7 to inject air and separate the material in the sorting section in the case of the material (ABS in FIG. 16). In addition, the operation screen also has a "Raw Material Input Area Ratio" field, which allows the ratio of each material to be mixed into the material to be displayed according to the result of the material determination process.

[0091] In the above, the waste plastic sorting device has been mainly described as including a surface treatment section 20 that treats the surface of the waste plastic pieces, but the sorting device may be in a form that does not include the surface treatment section 20. That is, another embodiment of the present invention is a waste plastic sorting device that includes an irradiation section that irradiates light onto waste plastic pieces including black waste plastic pieces that have been surface-treated, a reflection spectrum detection section that receives reflected light of the light irradiated by the irradiation section and detects the spectrum of the reflected light, a judgment section that judges the material of the waste plastic pieces based on the spectrum of the reflected light, and a sorting section that sorts at least the black waste plastic pieces by material based on the result of the judgment. That is, the sorting device may be in a form that allows the input of waste plastic pieces that have already been surface-treated. In this case, the surface-treated waste plastic pieces may be treated so that their surfaces satisfy one or more of the following conditions: a glossiness (specular glossiness (%)) at an incident angle of 60° measured in accordance with JIS Z 8741 is 10 or less, a glossiness (specular glossiness (%)) at an incident angle of 75° measured in accordance with JIS Z 8741 is 25 or less, and a surface roughness mean deviation (SMD) is 1 μm or more.

[0092] Another embodiment of the present invention may be a method for sorting waste plastic, which includes an irradiation step of irradiating light onto surface-treated waste plastic pieces, including black waste plastic pieces, a determination step of receiving reflected light of the light irradiated by the irradiation unit, detecting the spectrum of the reflected light, and determining the material of the waste plastic pieces based on the spectrum of the reflected light, and a sorting step of sorting at least the black waste plastic pieces by material based on the result of the determination. EXAMPLES

[0093] (Example 1) In this embodiment, a group of black waste plastic pieces (plastic mix) was used as the target of sorting. The size of each plastic piece was about 5 to 30 mm in average diameter in plan view. The group of black waste plastic pieces used was a group of plastic pieces containing at least seven types of plastic pieces, namely polyethylene (PE), polypropylene (PP), polycarbonate / acrylonitrile-butadiene-styrene (PCABS), acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polyphenylene ether / polystyrene (PPEPS), and polyamide (PA), but also contained plastics other than the above seven types of plastics. Such a group of black waste plastic pieces was sorted by material using a sorting device similar to the sorting device 1 shown in Figures 1 to 3. The weight of the group of black waste plastic pieces used in one trial was 2.35 kg. The conveyor speed of the sorting device was 120 to 150 m / min.

[0094] In the sorting device, infrared rays of 3 to 5 μm were irradiated and the reflected light spectrum was detected. From the reflected light spectrum obtained, spectra in the wavelength ranges of 3250 to 3750 nm and 4400 to 4600 nm were extracted, and characteristic quantities were calculated. Based on the characteristic quantities, the plastic material was determined.

[0095] In the sorting device used in this embodiment, a nozzle row in which 318 nozzles are arranged in a direction perpendicular to the conveying direction is provided. The discrimination device in the sorting device was capable of registering seven types of plastics: polyethylene (PE), polypropylene (PP), polycarbonate / acrylonitrile-butadiene-styrene (PCABS), acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polyphenylene ether / polystyrene (PPEPS), and polyamide (PA). In addition, for each trial, one or more types of plastics could be selected to be blown off by injecting air from the nozzle (selectively blown).

[0096] Waste plastics were sorted by selective spraying in Trials 1-A and 1-1 to 1-7 shown below.

[0097] Trial 1-A: Selective spraying of all seven types of plastic Trial 1-1: Selective spraying of PE only Trial 1-2: Selective spraying of PP only Trial 1-3: Selective spraying of only PCABS Trial 1-4: Selective spraying of ABS only Trial 1-5: PS only sprayed Trial 1-6: Selective spraying of PPEPS only Trial 1-7: Selective spraying of PA only

[0098] <Measurement and Evaluation> To evaluate the accuracy of sorting, the recovery rate R of all seven types of plastics in the collected material obtained in Trial 1-A was A (%), recovery rate R of various plastics in the collected materials obtained in trials 1-1 to 1-7 PE , R PP , ...(%), and the purity R of various plastics in the recovered materials obtained in Trials 1-1 to 1-7. PE , R PP The results are shown in Table 1.

[0099] (Recovery rate R A (Calculation of Recovery rate R of all seven types of plastics in Trial 1-A A (%) was calculated as follows:

[0100] R A (%)=W A / W L ×100 ·W L (kg): Amount of waste plastic pieces (plastic mix) input ·W A (kg): Amount of all 7 types of waste plastic pieces collected (amount of plastic pieces blown away by selective spraying)

[0101] (Recovery rate R PE , RPP , ...) Recovery rate R of various plastics in trials 1-1 to 1-7 PE , R PP , ... (%) was calculated as follows: First, a group of waste plastic pieces with the content ratio and amount of each material shown in Table 2 was prepared and each trial was carried out, and the recovery rate for each type of plastic was calculated based on the actually recovered amount.

[0102] For example, R in trial 1-1 PE was calculated from the following formula: R PE (%)=W1 PE / sWA PE ×100 W1 PE (kg): Actual recovery amount of PE from Trial 1-1 ·sWA PE (kg): PE content (Table 2) The recovery rates of the other plastics in Trials 1-2 to 1-7 were similarly determined.

[0103] (Purity R PE , R PP , …) Purity of the recovered material from Trials 1-1 to 1-7 P PE , P PP , ...(%) are the content ratios of various plastics in each collected material in each trial. These purities were obtained by feeding the plastic pieces collected in each trial of the sorting device back into the sorting device and using the plastic ratio determination function of the sorting device. For example, the purity P in Trial 1-1 was PE was the PE content measured by the plastic ratio determination function. The same was true for the other plastics in Trials 1-2 to 1-7.

[0104] (Measurement of surface properties) As a surface characteristic of the plastic pieces after the surface treatment, the glossiness (specular glossiness (%)) was measured according to JIS Z 8741. A glossmeter "VG 7000" manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measurement, and the glossiness (specular glossiness (%)) was measured at an incidence angle of 60° and an incidence angle of 75°. In addition, the mean deviation of the surface roughness (SMD) of the plastic pieces after the surface treatment was measured using an automated surface tester "KES-FB4-A" manufactured by Kato Tech Co., Ltd. Table 3 shows the measurement results of the surface characteristics of PCABS and PS as representative examples.

[0105] (Example 2) Except for not carrying out surface treatment, the plastic pieces were sorted by material in the same manner as in Example 1. As in Example 1, selective spraying was carried out in Trials 2-A and 2-1 to 2-7 shown below.

[0106] Trial 2-A: Selective spraying of all seven types of plastic Trial 2-1: Selective spraying of PE only Trial 2-2: Selective spraying of PP only Trial 2-3: Selective spraying of only PCABS Trial 2-4: Selective spraying of ABS only Trial 2-5: PS only sprayed Trial 2-6: Selective spraying of PPEPS only Trial 2-7: Selective spraying of PA only

[0107] The content ratio, content, recovery rate, and purity were determined in the same manner as in Example 1. The results are shown in Tables 1 and 2. In addition, the surface properties of the plastic pieces before sorting were determined in the same manner as in Example 1. The results are shown in Table 3.

[0108] [Table 1]

[0109] [Table 2]

[0110] [Table 3]

[0111] Table 1 shows the results of the selective spraying trials of all seven types of plastics (Trial 1-A in Example 1 and Trial 2-A in Example 2) and the selective spraying trials of various representative plastics (Trials 1-3 to 1-6 in Example 1 and Trials 2-3 to 2-6 in Example 2), comparing Example 1 (with surface treatment) with Example 2 (without surface treatment). From these results, it was found that the recovery rate and purity of the plastic pieces were improved by performing surface treatment before sorting the waste plastic pieces. In particular, it was found that the recovery rate and purity of the plastic pieces were improved by performing surface treatment so that the gloss (specular gloss (%)) at an incident angle of 60° measured in accordance with JIS Z 8741 was 10 or less, the gloss (specular gloss (%)) at an incident angle of 75° measured in accordance with JIS Z 8741 was 25 or less, or the surface roughness mean deviation (SMD) was 1 μm or more.

[0112] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0113] 1, 1A, 1B, 1C, 1D Waste plastic sorting equipment 2. Conveyor 3. Transport Path 4. Mid-infrared camera (reflection spectrum detection section) 5 Discrimination device 6 Injection control section 7 Injection nozzle row 8. Vibration feeder 12, 12-1, 12-2, A1, A2, B1, B2 Sorting Section 20 Surface treatment section 21, 22 Large Lola 23, 25 Rough surface roller 28 Supply section 51 Pretreatment section 52 1st Judgment Section 53 Second Judgment Section 54 Third Judgment Section S, S1, S2 Waste plastic pieces (black waste plastic pieces) S' Waste plastic pieces before surface treatment

Claims

1. A waste plastic sorting device, comprising: A surface treatment section for treating the surfaces of the waste plastic pieces including the black waste plastic pieces; An irradiation unit that irradiates the surface-treated waste plastic pieces with light; a reflection spectrum detection unit that receives reflected light of the irradiated light and detects a spectrum of the reflected light; a pre-processing unit that corrects the spectrum of the detected reflected light using a first correction spectrum and a second correction spectrum obtained by measuring a calibration plate that is irradiated with light from the irradiation unit, the first correction spectrum being obtained by measuring reflected light of light irradiated onto the calibration plate under bright conditions, and the second correction spectrum being obtained by measuring under dark conditions that are darker than the bright conditions; A determination unit that determines the material of the waste plastic pieces based on the corrected spectrum of the reflected light; A waste plastic sorting device comprising a sorting section that sorts at least black waste plastic pieces by material based on the results of the judgment.

2. A waste plastic sorting device, comprising: A surface treatment section for treating the surfaces of the waste plastic pieces including the black waste plastic pieces; An irradiation unit that irradiates the surface-treated waste plastic pieces with light; a reflection spectrum detection unit that receives reflected light of the irradiated light and detects a spectrum of the reflected light; A determination unit for determining the material of the waste plastic pieces based on the spectrum of the reflected light; A sorting unit that sorts at least black waste plastic pieces by material based on the result of the judgment, In the surface treatment section, the surface of the waste plastic pieces is (a) A specular gloss at an incident angle of 60° measured in accordance with JIS Z 8741 is 10% or less; (b) A specular gloss at an incident angle of 75° measured in accordance with JIS Z 8741 is 25% or less; and (c) Surface roughness mean deviation (SMD) is 1 μm or more A waste plastic sorting device that processes the waste plastic so as to satisfy one or more of the above conditions.

3. The waste plastic sorting device according to claim 1 or 2, wherein the irradiated light includes mid-infrared light having a wavelength of more than 3 μm.

4. The waste plastic pieces are transported on a transport path, The determination unit is A first determination unit that determines whether the spectrum of the reflected light is the spectrum of the waste plastic pieces or the spectrum of the transport path; A second determination unit that extracts a feature amount from the spectrum determined to be the spectrum of the waste plastic pieces; A third determination unit that determines the material of the waste plastic pieces based on the feature amount; The waste plastic sorting device according to any one of claims 1 to 3, further comprising a sorting section that sorts at least black waste plastic pieces by material based on the results obtained in the third judgment section.

5. The pre-processing unit performs processing to extract a predetermined frequency range from the corrected spectrum, The waste plastic sorting device according to claim 4 , which cites claim 1 , wherein the first determination unit determines the material of the waste plastic pieces using the extracted spectrum.

6. The waste plastic pieces are transported on a transport path, The waste plastic sorting device according to claim 1 , wherein the transport path is divided into two systems, a first system and a second system, in a width direction of the transport path.

7. The waste plastic sorting device according to claim 6, wherein the first system and the second system collect waste plastic pieces of the same material.

8. In the first system, waste plastic pieces of a first material are collected, and the remaining waste plastic pieces are supplied to the second system; The waste plastic sorting device according to claim 6, wherein in the second system, waste plastic pieces of a second material are collected from the remaining waste plastic pieces.

9. In the first system, waste plastic pieces of a first material and a small amount of other materials are collected, and the collected waste plastic pieces are supplied to the second system; 7. The waste plastic sorting device according to claim 6, wherein in the second system, waste plastic pieces of a first material are collected from among the first material and trace amounts of waste plastic pieces of other materials.

10. In the first system, the first material and a small amount of other waste plastic pieces are removed, and the remaining waste plastic pieces are supplied to the second system. The waste plastic sorting device described in claim 6, wherein in the second system, waste plastic pieces containing the first material and trace amounts of other materials are further removed from the remaining waste plastic pieces, and waste plastic pieces not containing the first material are collected.

11. A method for sorting waste plastics, comprising the steps of: A surface treatment step of treating the surfaces of the waste plastic pieces including black waste plastic pieces; An irradiation step of irradiating the surface-treated waste plastic pieces with light from an irradiation unit; a reflection spectrum detection step of receiving reflected light of the irradiated light and detecting a spectrum of the reflected light; a pre-processing step of correcting the spectrum of the detected reflected light using a first correction spectrum and a second correction spectrum obtained by measuring a calibration plate on which light from the irradiation unit is irradiated, the first correction spectrum being obtained by measuring reflected light of light irradiated onto the calibration plate under bright conditions, and the second correction spectrum being obtained by measuring under dark conditions that are darker than the bright conditions; A determination step of determining the material of the waste plastic pieces based on the corrected spectrum of the reflected light; A method for sorting waste plastic, comprising a sorting step of sorting at least black waste plastic pieces by material based on the results of the judgment.

12. A waste plastic sorting device, comprising: An irradiation unit that irradiates light onto the surface-treated waste plastic pieces, including the black waste plastic pieces; a reflection spectrum detection unit that receives reflected light of the light irradiated by the irradiation unit and detects a spectrum of the reflected light; a pre-processing unit that corrects the spectrum of the detected reflected light using a first correction spectrum and a second correction spectrum obtained by measuring a calibration plate that is irradiated with light from the irradiation unit, the first correction spectrum being obtained by measuring reflected light of light irradiated onto the calibration plate under bright conditions, and the second correction spectrum being obtained by measuring under dark conditions that are darker than the bright conditions; A determination unit that determines the material of the waste plastic pieces based on the corrected spectrum of the reflected light; A waste plastic sorting device comprising a sorting section that sorts at least black waste plastic pieces by material based on the results of the judgment.

13. A waste plastic sorting device, comprising: An irradiation unit that irradiates light onto the surface-treated waste plastic pieces, including the black waste plastic pieces; a reflection spectrum detection unit that receives reflected light of the light irradiated by the irradiation unit and detects a spectrum of the reflected light; A determination unit for determining the material of the waste plastic pieces based on the spectrum of the reflected light; A sorting unit that sorts at least black waste plastic pieces by material based on the result of the judgment, The surface of the waste plastic piece is (a) A specular gloss at an incident angle of 60° measured in accordance with JIS Z 8741 is 10% or less; (b) A specular gloss at an incident angle of 75° measured in accordance with JIS Z 8741 is 25% or less; and (c) Surface roughness mean deviation (SMD) is 1 μm or more A waste plastic sorting device that is processed to meet one or more of the above conditions.

14. A method for sorting waste plastics, comprising the steps of: An irradiation step of irradiating light from an irradiation unit onto the surface-treated waste plastic pieces including the black waste plastic pieces; a reflection spectrum detection step of receiving reflected light of the irradiated light and detecting a spectrum of the reflected light; a pre-processing step of correcting the spectrum of the detected reflected light using a first correction spectrum and a second correction spectrum obtained by measuring a calibration plate on which light from the irradiation unit is irradiated, the first correction spectrum being obtained by measuring reflected light of light irradiated onto the calibration plate under bright conditions, and the second correction spectrum being obtained by measuring under dark conditions that are darker than the bright conditions; A determination step of determining the material of the waste plastic pieces based on the corrected spectrum of the reflected light; A method for sorting waste plastic, comprising a sorting step of sorting at least black waste plastic pieces by material based on the results of the judgment.

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