JP5229204B2 - Plastic identification device and identification method thereof - Google Patents

Description

  The present invention relates to an apparatus for identifying reusable plastic from a crushed mixed resin obtained from waste home appliances and the like, and a method thereof.

  In the recycling of resins in waste home appliances, the parts that can be dismantled by hand are limited. Therefore, small parts and parts with complicated structures are mechanically crushed to select metals or resins. It is necessary to use recycled materials.

  In this case, since it is required to separate each material from the pulverized and mixed state, an advanced sorting technique is required. Here, in the process of selecting and separating the mixed crushed pieces mixed with metal pieces and plastic pieces for each material, the plastic pieces are polypropylene (hereinafter referred to as PP), polystyrene (hereinafter referred to as PS) or acrylonitrile-butadiene-styrene resin (hereinafter referred to as ABS). ) Etc. are mixed with plastic pieces mainly composed of various polymers.

  Among these, metals are selected by specific gravity or electrical or magnetic force, but polymers (including, for example, polymers and resins described in JP-A No. 2002-323450, paragraph No. [0004]) are: Since selection by electric or magnetic force is not possible, the polymer conveyed by the conveying means is irradiated with light, and the type is identified based on the spectrum obtained from the reflected light or scattered light from the polymer. There is a way. In order to reuse the plastic piece, it is necessary to sort by the type of these polymers, to separate and collect them. In addition, the shape of the crushed plastic piece is often a small piece of several mm square and several mm thick.

  In addition to the polymer, the plastic piece contains various additives, one of which is a carbon filler such as carbon black. The appearance of the plastic piece containing this carbon filler is black, and the color of the plastic piece, from the light transmittance, ranges from a transparent color that transmits light to a black color that does not transmit at all. There are also various. In order to reuse plastic pieces, it is necessary to sort them according to the type of polymer and sort them into a single material regardless of the color of the plastic pieces.

  As a method for identifying the material of such a plastic piece, a method using a Raman scattering spectrum has been proposed. A single-color laser beam emitted from a laser light source is irradiated onto a plastic material, the light scattered from the plastic material is collected, and the collected light is spectroscopically analyzed. In the band pattern and database of the measured Raman scattering spectrum, There is a method for identifying the material of a plastic piece by comparing it with a stored known band pattern.

  As an example of a method using this Raman scattering spectrum, a laser irradiation system for irradiating a plastic to be identified, which is an identification target, with a laser beam, and a Raman scattering signal for obtaining a Raman scattered signal from the Raman scattered light scattered from the plastic to be identified The acquisition means and the Raman scattering intensity at one or more peak positions (known peak positions) and the Raman scattering intensity at the baseline position (known baseline positions) set by measuring the Raman scattering spectrum of a known plastic in advance are stored. And the Raman scattering intensity at the Raman shift wave number corresponding to the known peak position and the Raman scattering intensity at the Raman shift wave number corresponding to the known baseline position for each plastic material to be identified obtained from the Raman scattering signal of the plastic to be identified And the known stored in the storage means There is a method of identifying a material of the plastic at high speed on the basis of the Raman scattering intensity and Raman scattering intensity of a known baseline position over click position (e.g., Patent Document 1).

Japanese Patent No. 4203916

  However, when a Raman scattering spectrum is measured, if a black plastic containing a carbon filler is irradiated with strong laser light, the plastic melts due to heat generated by absorption of the carbon filler, and the Raman scattering spectrum cannot be measured. In order to prevent melting of the plastic, when weak laser light is irradiated, the signal intensity is insufficient, and it is necessary to irradiate for a long time for signal integration. The problem is that the baseline of the Raman scattering spectrum rises or is distorted due to the influence of color, additives, etc., so that it is impossible to detect the Raman scattering spectrum having a large S / N ratio that can identify the plastic material. There is.

  The present invention has been made to solve the above-described problems, and it is possible to measure a Raman scattering spectrum having a large S / N ratio without melting the plastic even if the plastic is black or colored. It is an object of the present invention to provide a plastic identification device and method.

  The plastic identification device according to the present invention irradiates the crushed mixed plastic conveyed by the conveying means with laser light, detects reflected light or scattered light from the crushed mixed plastic with a detection element, and based on the detection result In the plastic identification device for identifying the type of plastic and its additive, a liquid is dropped on the surface of the crushed mixed plastic.

  Since the present invention makes it possible to measure a Raman scattering spectrum having a large S / N ratio in a short time without melting black or colored plastic, and to identify the type of polymer of black or colored plastic. The recovery rate of a single material in the process can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the plastic identification device in Embodiment 1 of this invention. It is a flowchart which shows the identification process using the plastic identification device in Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the data processing part in Embodiment 1 of this invention. It is an example of the block diagram which showed the internal structure of the data processing part in Embodiment 1 of this invention using concrete data. It is the figure which compared the data which concern on the case where a liquid is dripped at the surface of a plastic piece, and the case where it is not dripped, and which concerns on the Raman scattering spectrum obtained from each. It is a block diagram which shows the internal structure of the data processing part in Embodiment 2 of this invention. It is the figure which showed the Raman scattering spectrum of PS and ABS. It is the figure which showed the differential spectrum of the Raman scattering spectrum of PS and ABS. It is a block diagram of the plastic identification device in Embodiment 3 of this invention. It is a block diagram of the plastic identification device in Embodiment 4 of this invention. It is a block diagram of the plastic identification device in Embodiment 5 of this invention.

Embodiment 1.
Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  FIG. 1 is a configuration diagram of a plastic identification device according to Embodiment 1 of the present invention. FIG. 2 is a flowchart showing an identification process using the plastic identification device according to Embodiment 1 of the present invention. Hereinafter, description will be made with reference to these drawings. In the figure, the plastic piece 2 supplied from the plastic supply unit 1 for supplying the crushed mixed plastic is detected by the position sensor 4 in the process of being transferred by the transfer unit 3, and the detected position data 41 is It is sent to the data processing unit 5. Here, the transport unit 3 may be, for example, a belt conveyor, a disk-shaped rotating plate, or the like, and only needs to have a function of transporting the plastic piece 2 to a desired position. As the position sensor 4, for example, a laser position detection sensor, an ultrasonic displacement sensor, a PSD (Position Sensitive Device) displacement sensor, an optical fiber sensor, a photoelectric sensor, or the like can be used. Note that a light-emitting diode is used as the light source element used in the photoelectric sensor, and a photodiode, a phototransistor, a photo IC, or the like is used as the light-receiving element.

  The plastic piece 2 whose position has been confirmed by the position sensor 4 is further transported by the transport unit 3 and receives the instruction data 42 from the data processing unit 5 based on the position data 41 or drops the liquid 7 on the surface of the plastic piece 2 or It is conveyed to the lower part of the liquid supply part 6 to be sprayed. Here, the dropped liquid 7 is preferably an aqueous solution or organic solvent having a low boiling point, and the boiling point is selected to be lower than the melting point of the plastic to be identified. Further, it is preferable that the dropped liquid 7 is not repelled by the plastic piece 2. As the liquid satisfying such conditions, for example, a surfactant-added aqueous solution or the like is applied.

  The liquid 7 is dropped by the liquid supply unit 6, and the liquid 7 is not a predetermined portion of the surface (at least the laser irradiation portion, not necessarily the entire surface. In the case of the transport system shown in FIG. 1, the upper surface of the plastic piece 2. The plastic piece 2 adhering to the second portion is further transported by the transport unit 3, and based on the position data 41, the irradiated portion that irradiates the plastic piece 2 with the laser light 9 and the Raman scattered light 10 from the plastic piece 2 are detected. Data 43 relating to the Raman scattering spectrum is obtained by the laser irradiation detection unit 8 including the detection portion, and the obtained data is sent to the data processing unit 5. FIG. 3 is a block diagram showing an internal configuration of the data processing unit in the first embodiment of the present invention. In the figure, the data 43 relating to the Raman scattering spectrum obtained from the plastic piece 2 to be identified is recorded in the recording unit 51, and the data of the Raman scattering spectrum of a known plastic material previously stored in the storage unit 52. And the calculation unit 53, and based on the calculation result, the identification unit 54 identifies the material of the plastic piece 2 to be identified.

  FIG. 4 is an example of a block diagram illustrating the internal configuration of the data processing unit using specific data. Based on the identification result of the identification unit 54, it is possible to identify what kind of plastic polymer and what kind of additive is.

  Here, the laser beam 9 to be irradiated is preferably a long-wavelength laser beam, for example, a 1064 nm laser beam can be used in order to suppress fluorescence during laser irradiation and reduce damage during heat generation. . As the plastic piece 2 to be identified, a plastic piece 2 crushed into 2 to 30 mm squares can be considered. However, the plastic piece 2 can be transported by the transport unit 3 and can be irradiated with the laser light 9 generated from the laser irradiation detection unit 8 to generate Raman Anything can be used as long as the scattered light 10 can be obtained.

FIG. 5 is a diagram comparing the data 43 related to the Raman scattering spectrum obtained from the case where the liquid 7 is dropped on the surface of the plastic piece 2 and the case where the liquid 7 is not dropped. In the figure, the horizontal axis indicates Raman shift (cm ⁻¹ ), and the vertical axis indicates Raman scattering intensity (arbitrary intensity). In the case of no dripping, almost no Raman scattering spectrum data was obtained as the plastic piece 2 melted, whereas in the case of dripping, the melting of the plastic piece 2 was suppressed by dripping, resulting in good Raman. It can be seen that the data of the scattering spectrum is obtained.

  As described above, in the plastic identifying apparatus according to the first embodiment, even in a colored plastic containing carbon black, the liquid is vaporized even by heat generated by the absorption of the laser beam during the laser beam irradiation. The plastic piece (laser light irradiation part) is cooled by the heat of vaporization, so that the plastic can be prevented from melting and a Raman scattering spectrum capable of identifying the material can be obtained.

  Further, although plastic has been described as the resin that is the object to be identified according to Embodiment 1 of the present invention, the material of the object to be identified can be identified based on the spectrum of reflected light or scattered light from the object to be identified. Any resin may be used. Examples of such resins include those described in JP 2002-323450 A, paragraph [0004], and polymers and additives in polymer materials.

  Needless to say, it is also important to identify a rubber-based resin or sponge mixed in a plastic piece, particularly when recycling resin in a waste home appliance. In addition, although it does not correspond to resin, it is clear that carbon fiber and metal fiber cannot be distinguished, and these substances can be sorted by different sorting methods such as specific gravity sorting and electrostatic sorting.

  In addition, as a method for identifying the material of the identification target based on the spectrum of reflected light or scattered light from the identification target, a known method based on Raman spectrum analysis can be used. For example, a technique based on Raman spectrum analysis is described in Japanese Patent Laid-Open No. 10-38807.

Embodiment 2.
In the first embodiment, the data 43 related to the Raman scattering spectrum obtained by the laser irradiation detector 8 is data indicating the relationship between the Raman shift (cm ⁻¹ ) and the Raman scattering intensity, and the obtained data Is sent to the data processing unit 5, recorded in the recording unit 51, and previously stored in the storage unit 52 with the material of the Raman scattering spectrum of a known plastic and compared with the calculation unit 53. Although the identification unit 54 identifies the material of the plastic piece 2 to be identified, it may be identified using the differential spectrum of the Raman scattering spectrum. FIG. 6 is a block diagram showing the internal configuration of the data processing unit in the second embodiment of the present invention. In the figure, the parts denoted by the same reference numerals as those in the first embodiment have the same configuration, and thus the description thereof is omitted. Here, different configurations will be described.

  The Raman scattering spectrum data (data indicating the relationship between the Raman shift and the Raman scattering intensity) is recorded in the recording unit 51, differentiated by the differential operation unit 55, and the material previously stored in the storage unit 52 is known. It is compared with the differential data of the Raman scattering spectrum of plastic. Based on the comparison result, the identification unit 54 identifies the material of the plastic piece 2 to be identified.

FIG. 7 is a diagram showing Raman scattering spectra of PS and ABS. In the figure, the horizontal axis indicates Raman shift (cm ⁻¹ ), and the vertical axis indicates Raman scattering intensity (arbitrary intensity). In the Raman scattering spectrum, the baseline is inclined, and the effect of the baseline cannot be excluded when comparing the data stored in advance with the data of the Raman scattering spectrum of a known plastic. Therefore, as shown in FIG. 8, by taking the differential spectrum of the Raman scattering spectrum, the influence of the baseline can be eliminated, and the differential waveform has a steep change compared to the original waveform, so that it is short. Accurate comparison in time is possible. In FIG. 8, it can be seen that the peak position and peak intensity of the CN stretching peak near 2250 (cm ⁻¹ ), which is a Raman scattering peak characteristic of ABS, are clear.

  As described above, the data processing unit according to the second embodiment of the present invention can reduce the rise and distortion of the baseline of the Raman scattering spectrum caused by the influence of plastic color, additives, etc., and the identification accuracy of the material can be reduced. improves.

Embodiment 3 FIG.
In the first embodiment, the transport position of the plastic piece is detected by the position sensor, and the liquid is dropped or ejected on the surface of all the plastic pieces based on the detected position data. Thus, the liquid can be dropped or jetted only on the surface of the colored plastic piece that needs to be dropped or jetted on the surface of the plastic piece. FIG. 9 is a configuration diagram of a plastic identifying device according to Embodiment 3 of the present invention. In the figure, the parts denoted by the same reference numerals as those in the first embodiment have the same configuration, and thus the description thereof is omitted. Here, different configurations will be described.

  The difference from the first embodiment is that the position sensor 4 is replaced with the image recognition unit 11. The image recognition unit 11 acquires color data together with the position data 41. With this configuration, the identification device according to this embodiment can accurately drop or spray a liquid only on the surface of a colored plastic piece containing carbon black, so that the surface of the plastic piece is melted. In addition, the material can be identified by using less liquid efficiently in a shorter time than when the liquid is dropped or jetted on the surface of all the plastic pieces.

Embodiment 4 FIG.
In the first embodiment, the liquid is dropped or jetted on the surface of the plastic piece to be identified. However, the cooling piece may be jetted onto the surface of the plastic piece to cool the surface of the plastic piece. FIG. 10 is a configuration diagram of a plastic identifying device according to Embodiment 4 of the present invention. In the figure, the parts denoted by the same reference numerals as those in the first embodiment have the same configuration, and thus the description thereof is omitted. Here, different configurations will be described.

  The difference from the first embodiment is that a low-temperature air generator 12 and an aspirator 13 are provided instead of the liquid supply unit 6, and as shown in the figure, at the lower part of the laser irradiation detection unit 8. The plastic piece 2 is held by the suction device 13, and the generated cooling air 14 discharged from the low temperature air generator 12 is jetted onto the surface of the plastic piece 2. The ultra-low temperature air generator utilizes the vortex effect and can discharge cooling air at −60 ° C. With this configuration, the identification device according to this embodiment can cool the plastic piece to about −60 ° C. by instantly cooling the surface of the plastic piece with cooling air, and the plastic melts. In addition to being able to suppress this, the belt conveyor does not get wet as compared with the case where liquid is dropped or jetted, and it can be introduced into facilities that hate humidity.

Embodiment 5 FIG.
In the fourth embodiment, the low-temperature cooling gas is jetted onto the surface of the plastic piece to cool the surface of the plastic piece. However, the plastic piece is conveyed in the ultra-low temperature freezer and the entire plastic piece is cooled. It may be. FIG. 11 is a configuration diagram of a plastic identifying device according to Embodiment 5 of the present invention. In the figure, the parts denoted by the same reference numerals as those in the first embodiment have the same configuration, and thus the description thereof is omitted. Here, different configurations will be described.

  The difference from the fourth embodiment is that the plastic piece 2 is held by the suction unit 13 below the laser irradiation detection unit 8 and the generated cooling air 14 discharged from the low temperature air generator 12 is jetted onto the surface of the plastic piece 2. Instead, the plastic piece 2 is transported in the ultra-low temperature freezer 15, and as shown in the figure, the ultra-low temperature freezer 15 is filled with the cooling air 16 and the plastic piece 2 is being transported. The temperature drops. Although the cooling air 16 can be cooled to about −85 ° C., since the melting of the plastic piece 2 can be suppressed at about −60 ° C., the cooling air 16 may be cooled to about −60 ° C.

  The ultra-low temperature freezer 15 is provided with a window 17 so that the laser light 9 from the laser irradiation detector 8 and the Raman scattered light 10 generated from the plastic piece 2 can pass through. The material of the window is a material that transmits the wavelength region of the laser light 9 and the Raman scattered light 10, and for example, quartz glass, borosilicate glass, or the like is preferable. Since the inside of the ultra-low temperature freezer 15 is very low in temperature, there is a possibility that condensation will occur in the contact portion with the outside air. Therefore, as shown in the figure, an outer frame 19 that surrounds the outer periphery of the ultra-low temperature freezer 15 with dry air 18 may be provided.

  The identification device according to this embodiment can cool the plastic piece to about −60 ° C. by instantaneously cooling the surface of the plastic piece with cooling air, and can suppress the melting of the plastic. Compared with the case where liquid is dropped or jetted, the belt conveyor does not get wet and can be introduced into facilities that hate humidity.

  DESCRIPTION OF SYMBOLS 1 Plastic supply part, 2 Plastic piece, 3 Conveyance part, 4 Position sensor, 5 Data processing part, 6 Liquid supply part, 7 Liquid, 8 Laser irradiation detection part, 9 Laser light, 10 Raman scattered light, 11 Image recognition part, 12 cold air generator, 13 suction device, 14 cooling air, 15 ultra-low temperature freezer, 16 cooling air, 17 window, 18 dry air, 19 outer frame, 51 recording unit, 52 storage unit, 53 calculation unit, 54 identification unit, 55 Differential operation section

Claims (6)

  The crushing and mixing plastic conveyed by the conveying means is irradiated with laser light, the reflected light or scattered light from the crushing and mixing plastic is detected by a detection element, and the type of the plastic and its additive is identified based on the detection result. In the plastic identification device, a liquid is dropped on the surface of the crushed mixed plastic.   2. The plastic identifying apparatus according to claim 1, wherein a liquid is dropped only on the surface of the crushed mixed plastic having a predetermined color.   3. The plastic identification device according to claim 1, wherein the liquid is an aqueous solution to which a surfactant is added.   4. The plastic identifying apparatus according to claim 1, wherein the plastic and the additive type are identified based on a differential waveform obtained from the detection result.   A step of irradiating the crushed mixed plastic with laser light, a step of dropping a liquid on the surface of the crushed mixed plastic, a step of detecting a Raman scattering spectrum obtained from reflected light or scattered light from the crushed mixed plastic, and A method for identifying plastic, comprising: comparing detected data with other data to identify a material of the crushed mixed plastic.   6. The plastic identifying method according to claim 5, wherein the step of comparing the detected data with other data and identifying the material of the crushed mixed plastic uses differential data of the detected data.

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