JP2009195841A - Triboelectric charging apparatus, electrostatic separation apparatus, and method for producing recycled plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a triboelectric charging apparatus that efficiently removes adhering dust from the inside wall of its charging container without interrupting charging, stabilizes the state of charges on the inside wall of the container, and stably enables highly precise material sorting. <P>SOLUTION: The triboelectric charging apparatus that charges chargeable plastic particles 1a and 1b by triboelectric charging is provided with a charging container 3 into which the plastic particles 1a and 1b are fed, a cleaning section including an electroconductive brush 12, and a discharge apparatus. The cleaning section moves along the inside surface of the charging container 3 to discharge and clean the inside surface and includes an electrically grounded electroconductive material. The discharge apparatus discharges the dust removed from the inside surface of the charging container 3 when the electroconductive brush 12 sweeps the inside surface into its outside by sucking and removing the dust through a dust removal hole 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction charging device, an electrostatic sorting device, and a recycled plastic manufacturing method, and in particular, a friction charging device used in the process of recycling waste, an electrostatic sorting device including the friction charging device, and The present invention relates to a method for producing recycled plastic using an electrostatic sorting device.

  In a recycling process for home appliances, etc., after removing a single member that is generally easy to collect manually, the product is crushed with a shredder and the material is selected. In the selection of this material, a mixture of materials of different types with different triboelectric charge orders (orders with substances that tend to be positively charged when rubbing between different materials at the top and those that tend to be negatively charged at the bottom) In general, electrostatic sorting devices are known in which each material charged to the positive electrode and the negative electrode is passed through an electrostatic field generated between the electrodes and sorted in an electrostatic field using the difference in electrostatic force. ing.

  In the friction charging device, not only friction between materials but also charging due to friction between the material and the inner wall surface of the charging container occurs. If the fine dust generated during product crushing adheres to or accumulates in the inner wall of the charging container, it becomes an obstruction factor for charging of the material, and it becomes impossible to obtain the amount of charge necessary for material selection. I know.

  Therefore, conventionally, various techniques for removing dust have been proposed (see, for example, Patent Documents 1 and 2). Patent Document 1 proposes a friction charging device that includes a brush that contacts the inner wall surface of the charging container and removes the dust adhering to the inner wall surface in conjunction with the stirring blades in order to suppress a decrease in charge amount due to dust. ing. Patent Document 2 proposes a sorting technique that removes dust adhering to the mixed plastic before frictional charging in order to suppress a reduction in sorting accuracy due to dust adhesion.

In addition, as a technique for periodically removing the charge on the inner surface of the charging container and imparting a stable charge amount, charged particles are radiated from the needle-shaped discharging electrode disposed in the charging container to the inner surface of the charging container, and the inner surface of the charging container is discharged. There has been proposed an electrostatic sorting apparatus having a charge eliminating means (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 2003-31182 JP2003-103198A JP 2005-111371 A

  In the triboelectric charging device described in Patent Document 1, since only the cleaning of the inner wall surface of the charging container is performed, the effect of removing dust firmly adhered to the inner wall surface of the charging container due to electrostatic force is small. In addition, there has been a problem that the dust removed from the inner wall surface of the charging container adheres to the mixture flakes to be sorted by electrostatic force and causes charging failure and sorting failure. Furthermore, since the inner wall surface of the charging container is charged by collision and friction with the mixture during stirring, dust tends to adhere to the inner wall surface of the charging container as the charge accumulates, and the charging efficiency of the mixture due to contact with the inner wall surface is increased. There arises a problem that air discharge occurs and the charge of the mixture is neutralized.

  In addition, dust may be generated by stirring the mixed plastic in the charging container. However, as described above, if dust accumulates in the container due to static electricity, it may cause a reduction in sorting accuracy. Is necessary. However, the sorting technique described in Patent Document 2 does not disclose a technique related to cleaning of the charging container and neutralization.

  Further, in the electrostatic sorting apparatus described in Patent Document 3, since the charge is discharged by the discharge of charged particles, the material cannot be charged during the charge removal, and the processing capacity is reduced. In order to perform charging continuously, it is necessary to use a plurality of charging containers, which causes a problem of increasing costs.

  The present invention has been made in view of the above problems, and its main purpose is to efficiently remove dust adhering to the inner wall of the charging container without interrupting charging and to stabilize the charged state of the inner wall of the charging container. An object of the present invention is to provide a frictional charging device that can stably select materials with high accuracy.

  Another object of the present invention is to provide an electrostatic sorting device provided with the above-described frictional charging device, and a method for producing recycled plastic using the electrostatic sorting device.

  The frictional charging device according to the present invention is a frictional charging device that charges a mixture having charging properties by frictional charging, and includes a charging container into which the mixture is charged, a cleaning unit, and a discharging device. The cleaning unit moves along the inner wall surface of the charging container to perform charge removal and cleaning of the inner wall surface, and includes a grounded conductive material. The discharging device discharges the dust removed from the inner wall surface of the charging container by the cleaning unit to the outside of the charging container.

  According to the present invention, dust on the inner wall of the charging container can be efficiently removed without interrupting frictional charging by allowing the inner wall surface of the charging container to be cleaned and neutralized simultaneously with the charging of the mixture. In addition, by stabilizing the charged state of the inner wall of the charging container, the mixture can be stably charged, so that highly accurate selection of the mixture having chargeability can be stably performed.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic diagram showing an electrostatic sorting device according to Embodiment 1 of the present invention. The plastic particles 1a and 1b that are fed into the electrostatic sorting apparatus as a mixture to be sorted are charged plastics, for example, a mixed plastic after a used product is crushed with a shredder in a recycling process for home appliances and the like. It is a mixture of certain materials. The plastic particles 1a and 1b have a property of being charged, that is, easily charged with static electricity. For example, the plastic particles 1a and 1b have such properties that the plastic particles 1a are positively charged and the plastic particles 1b are negatively charged by friction with each other.

  As shown in FIG. 1, the electrostatic sorting device includes a friction charging device that charges the plastic particles 1a and 1b by friction charging. In addition, the electrostatic sorting device uses a plurality of types of synthetic resin materials in an electrostatic field depending on the charged state of the plastic particles 1a and 1b charged in the friction charging device, utilizing the fact that the charging characteristics of each plastic type are different from each other. A sorting device is provided for sorting certain plastic particles 1a and 1b by type.

  The friction charging device includes a charging container 3 in which the plastic particles 1a and 1b are frictionally charged. The charging container 3 is formed in a cylindrical shape. Disc-shaped input side lid 4a and discharge side lid 4d are provided on two cylindrical bottom surfaces of charging container 3 so as to be parallel to each other. An opening is formed in the charging side lid 4a. The opening is formed so as to include the center of the circle of the charging side lid 4a.

  The inner wall surface of the charging container 3 is formed of a charged material. The entire charging container 3 may be formed of a chargeable material. As a material for forming the inner wall surface of the charging container 3, a material that is on the minus side of the plastic particles 1a and on the plus side of the plastic particles 1b in the charging sequence can be selected. If the material is selected in this way, the plastic particles 1a are positively charged by the collision with the inner wall surface of the charging container 3, and the plastic particles 1b are negatively charged by the collision with the inner wall surface of the charging container 3. More preferable.

  A rotating shaft 5 is connected to the outer surface of the charging container 3 of the discharge side lid 4d. The rotary shaft 5 is connected to the drive motor 6 with a drive belt 6a interposed therebetween. When the drive motor 6 is operated, the rotary shaft 5 rotates. A dust suction machine 11 having a negative pressure source is installed outside the charging container 3. The dust suction machine 11 is connected to the rotary shaft 5 with a communication member 11a interposed therebetween. An air passage (not shown) is formed inside the communication member 11a. The communication member 11a is formed so that the internal space of the charging container 3 and the negative pressure source of the dust suction machine 11 are communicated with each other via this ventilation path.

  In the charging container 3, a plurality of stirring blades 4 b as stirring members are formed so as to intersect the circumferential direction of a circle that is a radial cross section of the cylindrical charging container 3. If the stirring blade 4b is formed so as to be along the radial direction (typically extending in a direction parallel to the radial direction) of a circle that is a radial cross section of the cylindrical charging container 3, More preferred.

  In addition, a plurality of disk-shaped guides 4 c in the container are provided in the charging container 3. The in-container guide 4c is disposed along the radial cross section of the charging container 3. That is, the stirring blade 4b and the in-container guide 4c are disposed so as to be substantially orthogonal.

  Inside the charging container 3, the charging side lid 4a, the stirring blade 4b, the in-container guide 4c, and the discharging side lid 4d are connected. Therefore, the charging side cover 4a, the stirring blade 4b, the in-container guide 4c, and the discharging side cover 4d are integrated in the charging container 3 by the rotation shaft 5 connected to the discharging side cover 4d being rotated by the drive motor 6. Rotating motion. The charging-side lid 4a, the container guide 4c, and the discharge-side lid 4d are arranged so as to slide on the inner wall surface of the side wall of the charging container 3. With such a structure, it is possible to hold the stirring blade 4 b and maintain the proximity distance between the stirring blade 4 b and the inner wall surface of the charging container 3.

  A mixture discharge port 7 that is an outlet through which the plastic particles 1a and 1b are discharged from the charging container 3 is formed on the lower side wall of the charging container 3 on the side where the discharge side lid 4d is provided. ing. A sorting device is installed below the mixture discharge port 7. The sorting device is divided into a transfer device 8, an electric field forming unit having a ground electrode 9a that is grounded and a high voltage applying electrode 9b that is electrically connected to a high voltage power source 9c, and a plurality of sorting and collecting units 10a and 10b. A recovery container 10.

  The mixture of the plastic particles 1a and 1b is charged into the charging container 3 by the charging device 2 through the opening formed in the charging side lid 4a. The mixture of the plastic particles 1a and 1b charged into the charging container 3 is stirred in the charging container 3 according to the rotation of the stirring blade 4b as a stirring member. By this stirring, the plastic particles 1 a and 1 b are frictionally charged by being rubbed against each other by the collision between the plastic particles and the collision between the plastic particle and the inner wall surface of the charging container 3. The plastic particles 1a and 1b are charged by frictional charging so as to have a charge polarity and a charge amount corresponding to the type of plastic.

  The charging container 3 is arranged such that its axial direction is inclined with respect to the horizontal direction. When the charging container 3 is tilted, the plastic particles 1a and 1b move toward the mixture discharge port 7 from the opening of the charging side lid 4a by the action of gravity. That is, no power is required to move the plastic particles 1a and 1b in the axial direction in the charging container 3. However, if the inclination angle is too large, the plastic particles 1a and 1b freely fall within the charging container 3 and between the plastic particles 1a and 1b or between the plastic particles 1a and 1b and the inner wall surface of the charging container 3. Since friction does not occur, the plastic particles 1a and 1b cannot be charged. Therefore, for example, the charging container 3 can be inclined and arranged so that the axial direction of the charging container 3 forms an angle of more than 0 ° and not more than 30 ° with respect to the horizontal direction.

  On the other hand, the container is arranged so as to follow the circular radial cross section of the charging container 3, that is, so as to intersect (typically orthogonal) the flow of the plastic particles 1a and 1b toward the mixture discharge port 7. An inner guide 4c is provided. The in-container guide 4c forms a structure that blocks the plastic particles 1a and 1b moving toward the mixture discharge port 7. Therefore, since the residence time of the plastic particles 1a and 1b in the charging container 3 can be increased, the plastic particles 1a and 1b can be reliably frictionally charged in the charging container 3.

  The charged plastic particles 1a and 1b are discharged from the mixture discharge port 7 and supplied to the sorting device. The plastic particles 1a and 1b fall from the mixture discharge port 7 to the transfer device 8, and are further charged into an electric field generated between the ground electrode 9a and the high voltage application electrode 9b. In this electric field, the plastic particles 1a and 1b are sorted by electrostatic force based on the state of charge, that is, the difference in charge polarity and charge strength (charge amount). For example, the positively charged plastic particles 1 a are attracted to the ground electrode 9 a side and collected in the sorting and collecting unit 10 a of the collecting container 10. Further, the negatively charged plastic particles 1 b are attracted to the high voltage application electrode 9 b side and are collected in the sorting and collecting unit 10 b of the collecting container 10.

  2 is a cross-sectional view of the charging container in a cross section taken along line II-II shown in FIG. As shown in FIG. 2, the charging container 3 rotates at an angular velocity ω1 by a power source such as a motor (not shown). Further, the agitating blade 4b is rotated by the drive motor 6 shown in FIG. 1 around the rotation axis extending in the axial direction of the charging container 3 at an angular speed ω2 different from the angular speed ω1 of the charging container 3. That is, the stirring blade 4 b has a relative speed with respect to the charging container 3. For this reason, the stirring blade 4 b relatively moves along the inner wall surface of the charging container 3.

  A neutralization cleaning portion 4e is provided at the end of the agitating blade 4b that is in close proximity to the inner wall surface of the charging container 3. The static elimination cleaning part 4e moves along the inner wall surface of the charging container 3 with the rotational movement of the stirring blade 4b. The neutralization cleaning unit 4e moves along the side wall surface of the cylindrical charging container 3 in accordance with the rotational movement of the stirring blade 4b having a relative speed with respect to the side wall surface of the charging container 3. And cleaning.

  The shape of the stirring blade 4b is not limited to the shape shown in FIGS. 1 and 2, and for example, as long as the plastic particles 1a and 1b can be stirred in the charging container 3, the shape of a stirring screw, the shape of a turbine blade, etc. , It may be formed in any shape.

  3 is an enlarged cross-sectional view showing the vicinity of region III shown in FIG. As shown in FIG. 3, the static elimination cleaning unit 4 e of the present embodiment specifically includes a conductive brush 12. The stirring blade 4b is made of metal in order to ground the conductive brush 12. That is, the static elimination cleaning unit 4e includes a grounded conductive material. When the stirring blade 4b formed of a conductive material comes into contact with the plastic particles 1a and 1b, the charged plastic particles 1a and 1b are neutralized. Therefore, the stirring blade 4b is covered with the insulating cover 13 in order to suppress contact between the stirring blade 4b and the plastic particles 1a and 1b. The insulating cover 13 as a cover member that covers the stirring blade 4b is formed of an insulating material.

  A minute dust 15 exists in the charging container 3. Dust 15 is generated when the used product is pulverized, and dust 15 may also be generated due to wear of the plastic particles 1a and 1b accompanying stirring in the charging container 3. The individual plastic particles 1 a and 1 b are charged by the collision of the plastic particles accompanying the stirring in the charging container 3 and the collision with the inner wall surface of the charging container 3. On the other hand, the inner wall of the charging container 3 is also charged by the collision with the plastic particles 1a and 1b. When the charging container 3 is charged, the dust 15 adheres to the inner wall of the charging container 3 by electrostatic force.

  When the dust 15 adheres to the inner wall of the charging container 3, there is a problem that the effect of charging the plastic particles 1a and 1b due to the collision with the inner wall of the charging container 3 is lost. In addition, when the potential of the inner wall of the charging container 3 exceeds 30 kV, which is the dielectric breakdown strength of air, there is an adverse effect that air discharge occurs and the charging of the plastic particles 1a and 1b is neutralized.

  In the present embodiment, as shown in FIG. 3, a conductive brush 12 is provided at the end of the stirring blade 4 b that is in close proximity to the inner wall surface of the charging container 3. The conductive brush 12 is made of a conductive material such as metal, and is grounded via a stirring blade 4b made of metal. The tip of the conductive brush 12 is in contact with the inner wall surface of the charging container 3. Therefore, with the rotational movement of the stirring blade 4b, the conductive brush 12 slides on the inner wall surface of the charging container 3 and continuously neutralizes the inner wall surface of the charging container 3. The inner wall surface of the charging container 3 is neutralized by contact with the conductive brush 12, so that no charge is accumulated in the charging container 3, and the charging state of the charging container 3 is stabilized.

  Further, the conductive brush 12 sweeps the inner wall surface of the charging container 3 along with the rotational movement of the stirring blade 4b, and cleans the dust 15 attached to the inner wall surface of the charging container 3 by electrostatic force. That is, the static elimination cleaning unit 4 e includes the conductive brush 12 as a wiping member that slides on the inner wall surface of the charging container 3. The conductive brush 12 can continuously remove and clean the inner wall surface of the charging container 3 as the stirring blade 4b rotates. Since the inner wall of the charging container 3 is neutralized by contact with the conductive brush 12, charges are not accumulated on the inner wall of the charging container 3, and the charged state is stabilized. Therefore, in the frictional charging device of the first embodiment, the efficiency of the frictional charging device is always improved without requiring the operation of discharging and cleaning the charging container 3 by interrupting the charging of the plastic particles 1a and 1b that are objects to be electrostatically selected. Charging can be performed stably.

  The inner wall surface of the charging container 3 is cleaned by the conductive brush 12, and the dust 15 is swept up. In order to stably and continuously charge the plastic particles 1a and 1b, it is necessary to continuously discharge the collected dust 15 to the outside of the charging container 3. Therefore, the friction charging device according to the present embodiment is a dust discharging device that discharges the dust 15 removed from the inner wall surface of the charging container 3 by the static eliminating cleaning unit 4e including the conductive brush 12 to the outside of the charging container 3. A suction device for sucking 15 out of the charging container is included.

  The suction device has a dust suction machine 11 and a communication member 11a shown in FIG. The air passage formed inside the communicating member 11a communicates with the dust removing hole 14 formed inside the stirring blade 4b shown in FIG. The dust removal hole 14 communicates with an opening formed on the end surface of the stirring blade 4 b that is in close proximity to the inner wall surface of the charging container 3. That is, the suction device has a dust suction path, and the dust suction path includes an opening formed on the surface of the stirring blade 4b inside the charging container 3 and the dust suction machine 11, and a dust removal hole. 14 and the communication member 11a. The ventilation path and the dust removal hole 14 inside the communication member 11a constitute a part of the dust suction path. The opening formed on the end face of the stirring blade 4 b is the opening end of the dust suction path formed inside the charging container 3.

  When a negative pressure source such as a vacuum pump installed inside the dust suction machine 11 is operated, the inside of the dust suction path is depressurized. Therefore, the dust 15 removed from the inner wall surface of the charging container 3 by the conductive brush 12 passes through the opening formed in the end face of the stirring blade 4b as shown by the arrow in FIG. 14 is sucked into the interior. The dust 15 sucked into the dust removing hole 14 is further sucked out of the charging container 3 through the dust suction path.

  Here, as shown in FIG. 3, the closest distance d where the distance of the gap between the stirring blade 4b and the inner wall surface of the charging container 3 is the smallest is the minimum diameter of the plastic particles 1a and 1b to be selected. It is formed so as to be smaller than the minimum particle diameter which is a value. Further, the closest distance d is formed to be larger than the maximum dust diameter which is the maximum value of the diameter of the dust 15 to be removed from the inside of the charging container 3. By disposing the stirring blade 4b in the charging container 3 in this manner, the dust 15 that has been neutralized and removed by the conductive brush 12 is selectively selected by the dust suction machine 11 to which the dust removal hole 14 is connected. Removed by suction. That is, it is possible to suck and discharge only the dust 15 to the outside of the charging container 3 without sucking the plastic particles 1 a and 1 b to the outside of the charging container 3.

  For example, consider a case of electrostatically sorting a mixture of plastic raw materials pulverized to a particle size of 8 mm or less and screened with 2 mm, and removing dust having a diameter of less than 0.3 mm. In this case, the distance between the end of the agitating blade 4b that is in close proximity to the inner wall surface of the charging container 3 and the inner wall surface of the charging container 3 is rotated within the range of 0.3 mm to 2.0 mm. The stirring blade 4b can be disposed in the charging container 3 so as to perform the movement. In this way, it is possible to efficiently remove dust, which is an impediment to charging of the plastic raw material, and to remove the static electricity by touching the static elimination part containing the conductive material to the plastic raw material mixture flakes to be selected. Can be suppressed.

  FIG. 4 is a schematic diagram showing the shape of the dust removal hole. The dust removing hole 14 is formed so as to include a small-diameter portion 14a having a relatively small diameter and a large-diameter portion 14b having a relatively large diameter in the cross section of the stirring blade 4b shown in FIG. One end of the small diameter portion 14a is open to the surface of the stirring blade 4b, and the small diameter portion 14a has an open end. When the diameter W1 of the small diameter portion 14a shown in FIG. 4 is compared with the diameter W2 of the large diameter portion 14b, there is a relationship represented by the formula W1 <W2. The cross-sectional area of the radial cross section of the small diameter portion 14a is formed to be relatively small with respect to the radial cross section of the large diameter portion 14b.

  For example, the large-diameter portion 14b is formed so as to extend along the longitudinal direction of the stirring blade 4b (typically parallel to the longitudinal direction), and the direction intersecting the direction in which the large-diameter portion 14b extends (typically A plurality of small-diameter portions 14a may be formed so as to extend along the direction perpendicular to the direction. When the dust removal hole 14 is formed in this way, the total volume of the plurality of small diameter portions 14a is smaller than the volume of the large diameter portion 14b. Therefore, considering the flow of the gas discharged to the outside of the charging container 3 through the dust removal hole 14, the flow velocity of the gas flowing through the small diameter portion 14a is higher than the flow velocity of the gas flowing through the large diameter portion 14b. growing. Therefore, since the suction force for sucking the dust 15 is further increased, the dust 15 can be sucked out of the charging container 3 more efficiently.

  Next, a method for producing recycled plastic using the electrostatic sorting apparatus according to Embodiment 1 in the process of recycling waste that recovers valuable resources such as plastic from discarded products will be described. FIG. 5 is a flowchart showing a method for producing recycled plastic.

  First, as shown in step (S10), used products such as discarded home appliances and office machines are prepared. In the recycling of discarded products such as discarded home appliances and office machines, first, metal and parts that are easy to disassemble and are valuable are collected by manual disassembly shown in the step (S20). The remaining part is a complex of metals and plastics that are difficult to disassemble / recover. Generally, as shown in the step (S30), these are largely divided into a mixture of crushed metal particles and a mixture of crushed particles of plastics as shown in step (S30). Separated. Further, each mixture subjected to the mixing and crushing process is subjected to a separation and recovery process for each component and recycled.

  The electrostatic sorting apparatus of the present embodiment uses a mixture of pulverized particles of a plurality of types of plastic members that are close to each other in specific gravity and difficult to separate and collect by the specific gravity sorting method, because the charging characteristics for each type of plastic are different from each other. It can be applied to a process of electrostatic sorting for each plastic type. For example, waste home appliances are crushed and sorted after manual disassembly to obtain a plastic mixed raw material (step (S40)). The mixture of the plurality of types of plastic members mainly contains polypropylene (PP) resin, acrylonitrile-butadiene-styrene (ABS) resin, and polystyrene (PS) resin. From this mixed plastic, PP resin having a small specific gravity is first selected by the specific gravity selection method shown in the step (S50).

  The ABS resin and the PS resin are recovered from the plastic mixed raw material including the ABS resin, the PS resin and the residual PP resin remaining after the recovery of the PP resin by the electrostatic sorting method shown in the step (S60). Specifically, in order to extract the main two components (ABS, PS) from the three component system (ABS, PS, PP) by the electrostatic sorting method, for example, the electrostatic sorting process can be combined in two stages. That is, when ABS, PS, PP are arranged in the order of charging, there is a property that charging is easily performed in the order of ABS, PS, PP. Therefore, in the first stage electrostatic sorting process, the ABS / PS / PP mixture is first triboelectrically charged, and the positively charged ABS resin is sorted and collected, and then in the second stage electrostatic sorting process, PS / PP The mixture is triboelectrically charged and the positively charged PS resin is selected and collected.

  The plastic material collected by electrostatic sorting is heated and kneaded for each type to be re-pelletized (step (S70)), thereby becoming a recycled plastic that can be used as a raw material for plastic products used for home appliances and the like ( Step (S80)).

  As described above, in the frictional charging device of the present embodiment, the conductive brush 12 slides on the inner wall surface of the charging container 3 during the frictional charging of the plastic particles 1 a and 1 b, and the inner wall surface of the charging container 3. Is continuously removed, and dust 15 adhering to the inner wall surface of the charging container 3 by electrostatic force is cleaned. The cleaned dust 15 is sucked out of the charging container 3 by the suction device and discharged to the outside. That is, the plastic particles 1a and 1b can be charged, and the charging container 3 can be cleaned and discharged at the same time.

  Therefore, the dust 15 adhering to the inner wall surface of the charging container 3 can be efficiently removed without interrupting the charging of the plastic particles 1a and 1b, so that the processing capacity of the friction charging device can be increased. In addition, since the charged state of the inner wall surface of the charging container 3 can be stabilized, it is possible to always give a stable charge amount to the plastic particles 1a and 1b.

  Further, since the plastic particles 1a and 1b are stirred and frictionally charged by the stirring blade 4b that rotates in the cylindrical charging container 3, the plastic particles 1a and 1b can be efficiently frictionally charged with a simple configuration. . In addition, a conductive brush 12 is provided at the end of the stirring blade 4 b that is in close proximity to the inner wall surface of the charging container 3, and the conductive brush 12 moves along the inner wall surface of the charging container 3 as the stirring blade 4 b rotates. Move along. Therefore, the neutralization and cleaning of the inner wall surface of the charging container 3 by the conductive brush 12 can be reliably performed with low power.

  Moreover, in the electrostatic sorting apparatus provided with the above-described friction charging device, the plastic particles 1a and 1b to be sorted can be stably triboelectrically charged, so that highly accurate electrostatic sorting of the mixture can be stably performed. Become. Furthermore, according to the manufacturing method of the recycled plastic which uses this electrostatic sorting apparatus, a high quality plastic raw material can be manufactured from the mixed plastic which crushed used products.

(Embodiment 2)
FIG. 6 is a partial cross-sectional view of the charging container of the frictional charging device of the second embodiment. In the frictional charging device of the second embodiment, the static elimination cleaning unit 4e (see FIG. 2) sprays a fluid containing ionized gas on the inner wall surface of the charging container 3 instead of the conductive brush 12 of the first embodiment. It is different from the first embodiment in that a fluid ejecting mechanism is included. In the second embodiment, the static elimination cleaning unit 4e is disposed so as to be close to the inner wall surface of the charging container 3 in a non-contact state. FIG. 7 is a block diagram of the fluid ejection mechanism.

  Specifically, as shown in FIGS. 6 and 7, the fluid ejecting mechanism includes a positive pressure source such as a compressor installed outside the charging container 3. The fluid ejection mechanism includes a nozzle having an ion gas ejection hole 16 formed inside the stirring blade 4b, and an ion gas ejection hole 16 opened on the surface where the stirring blade 4b is close to and opposed to the inner wall surface of the charging container 3. Part 16a. The positive pressure source and the ion gas ejection hole 16 communicate with each other through an air passage, and the ionized gas generated by the ion gas generator is supplied into the air passage.

  Pressurized gas such as compressed air supplied from the positive pressure source includes ionized gas generated in the ion gas generator, flows through the inside of the air passage, and is supplied to the ion gas ejection hole 16. For example, ionized gas can be generated by applying a high pressure to the needle electrode and ionizing air by corona discharge. The ion gas generator may generate a gas in which positive ions and negative ions are mixed, or the generation of positive ions and the generation of negative ions are alternately repeated in a short time. You may do it. Pressurized gas, which is a fluid containing ionized gas, is ejected from the nozzle portion 16 a and sprayed onto the inner wall surface of the charging container 3 as indicated by an arrow in FIG. 6.

  For example, the negatively charged dust 15 is firmly attached to the inner wall surface of the positively charged charging container 3 by electrostatic force. The dust 15 charged to the positive polarity is firmly attached to the inner wall surface charged to the negative polarity. By supplying an ionized gas having a polarity opposite to the charging polarity of the dust 15, the charging of the dust 15 is neutralized, the electrostatic force is eliminated, and the dust 15 can be easily removed from the inner wall surface. In this way, the dust 15 adhering to the inner wall surface of the charging container 3 is blown away by the jet of pressurized gas, and is sucked by the dust suction machine 11 (see FIG. 1) connected to the dust removing hole 14 to be charged. It is sucked out of the container 3 and removed.

  Since the nozzle portion 16 a is opened on the surface of the stirring blade 4 b, the nozzle portion 16 a moves along the inner wall surface of the charging container 3 as the stirring blade 4 b rotates in the charging container 3. Therefore, the charge container 3 can be discharged and cleaned by sequentially ejecting a fluid containing ionized gas over the entire side wall surface of the charge container 3.

  By the fluid ejecting mechanism described above, the neutralization and cleaning of the inner wall surface of the charging container 3 is performed without interrupting the charging of the plastic particles 1a and 1b, similarly to the neutralization and cleaning of the dust 15 by the conductive brush 12 of the first embodiment. Is possible.

(Embodiment 3)
FIG. 8 is a partial cross-sectional view of the charging container of the frictional charging device of the third embodiment. In the frictional charging device of the third embodiment, the dust removing hole 14 is formed on the wall surface of the charging container 3, and the opening end of the dust suction path for sucking and discharging the dust to the outside of the charging container 3 is inside the charging container 3. It is different from the first embodiment in that it is formed on the wall surface.

  Since the stirring blade 4b is a thin plate-like member, when the dust removing hole 14 is formed inside the stirring blade 4b, there may be a problem in workability and strength of the stirring blade 4b. On the other hand, if it is the structure which forms the dust removal hole 14 in the charging container 3 side shown in FIG. 8, the dust removal hole 14 can be processed more easily, and the intensity | strength of the stirring blade 4b which rotates is improved. Therefore, the reliability of the friction charging device can be improved.

(Embodiment 4)
FIG. 9 is a partial cross-sectional view of the charging container of the frictional charging device of the fourth embodiment. The friction charging device according to the fourth embodiment is different from the third embodiment in that the dust receiving portion 17 is formed outside the charging container 3 and the charging container 3 is formed as a double container. .

  In the friction charging device of the fourth embodiment, a slit 18 is formed in the lower portion of the charging container 3. The dust removed from the inner wall surface of the charging container 3 by the conductive brush 12 falls into the internal space 19 of the dust receiving portion 17 via the slit 18. According to this configuration, in order to discharge dust to the outside of the charging container 3, it is not necessary to form the dust removal hole as a pore in the stirring blade 4 b or the charging container 3, and the discharging device is formed with a simpler structure. Therefore, the manufacturing cost of the friction charging device can be reduced. If the suction device is configured to communicate with the internal space 19 to reduce the pressure in the internal space 19, in addition to the free fall of dust, the suction device sucks dust from the inside of the charging container 3 to the dust receiver 17. Therefore, dust can be discharged to the outside of the charging container 3 more efficiently.

  In order to make the charging container 3 a double container, in addition to the structure for forming the dust receiving portion 17 shown in FIG. 9, for example, a structure in which a partition wall is formed inside the charging container 3 may be used.

  In the description of the first to fourth embodiments, the agitation blade 4b rotates and moves inside the charging container 3, so that the electrostatically selected plastic particles 1a and 1b are frictionally charged. The configuration is not limited to this. For example, the charging container 3 may be vibrated and the plastic particles 1a and 1b and the inner wall surface of the charging container 3 rub against each other in the charging container 3, whereby the electrostatically selected mixture may be frictionally charged.

  Examples of the present invention will be described below. First, a test was conducted to examine the influence of dust adhering to the surface of a plastic material having chargeability on the chargeability of the plastic material. The test results are shown in Table 1.

  According to the test results in the second row in Table 1, the chargeability of the raw material from which only fine particles of 0.3 mm or more were removed with a sieve was poor. At this time, the content of dust of 0.3 mm or less and the content of particles of 2 mm or less + dust are almost equal, and the diameter of the dust adhered to the raw material is considered to be about 0.3 mm or less. That is, accumulation of dust having a particle diameter of 0.3 mm or less in a plastic raw material has been a cause of poor charging of the plastic raw material. As described above, if the plastic raw material is poorly charged, it becomes impossible to select the plastic raw material with a purity of 99% or higher, which is necessary to apply the recycled plastic to the home appliance again.

  Then, next, it is a mixture of plastic raw materials recovered from discarded home appliances, pulverized to a particle size of 8 mm or less and screened with 2 mm, ABS content 35%, PS content 55%, residual PP content 10% An experiment was conducted in which the mixture was electrostatically sorted using the electrostatic sorting apparatus of the first embodiment. The proximity distance between the stirring blade 4b and the inner wall of the charging container 3 is 1.5 mm, which is smaller than the diameter of the plastic material, so that the plastic material is not discharged to the outside of the charging container 3.

  In this case, ABS is charged positively due to friction of the mixture, and PS and residual PP are negatively charged. If the material of the charging container 3 is ABS, the charging container 3 is also charged to +. When charge removal and cleaning of the charging container are not performed, the surface potential of the inner wall of the charging container 3 rises to 20 kV 30 minutes after the start of charging, and dust adheres to the entire inner wall of the charging container 3 due to the resulting electrostatic force.

  By sweeping the inner wall of the charging container 3 with the conductive brush 12, the surface potential of the inner wall of the charging container 3 is reduced to 1 kV or less, and the attached dust is removed. As a result, the chargeability of the ABS particles is improved, and ABS is recovered with high purity by electrostatic sorting. In other words, since the charging of the plastic raw material and the cleaning and discharging of the charging container can be performed at the same time, it is possible to maintain the selection of the ABS particles with a purity of 99% or more without interrupting charging and cleaning work. It becomes possible.

  By heating and kneading the ABS particles selected with a purity of 99% or more and pelletizing them, it becomes possible to obtain recycled ABS pellets having the same physical properties as the new ABS, which can be applied to household appliances again. It has been shown.

  Although the embodiments of the present invention have been described above, the configurations of the embodiments may be appropriately combined. In addition, it should be considered that the embodiments and examples disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic diagram illustrating an electrostatic sorting device according to Embodiment 1. FIG. It is sectional drawing of the charging container in the cross section which follows the II-II line | wire shown in FIG. FIG. 3 is an enlarged cross-sectional view showing the vicinity of a region III shown in FIG. 2. It is a schematic diagram shown about the shape of a dust removal hole. It is a flowchart which shows the manufacturing method of a recycled plastic. FIG. 6 is a partial cross-sectional view of a charging container of a frictional charging device according to a second embodiment. It is a block diagram of a fluid ejecting mechanism. FIG. 6 is a partial cross-sectional view of a charging container of a frictional charging device according to a third embodiment. FIG. 6 is a partial cross-sectional view of a charging container of a frictional charging device according to a fourth embodiment.

Explanation of symbols

  1a, 1b Plastic particles, 2 charging device, 3 charging container, 4a charging side lid, 4b stirring blade, 4c container guide, 4d discharging side lid, 4e static elimination cleaning unit, 5 rotating shaft, 6 drive motor, 6a driving belt, 7 Mixing outlet, 8 Conveying device, 9a Ground electrode, 9b High voltage applying electrode, 9c High voltage power source, 10 Collection container, 10a, 10b Sorting and collecting unit, 11 Dust suction machine, 11a Communication member, 12 Conductive brush, 13 Insulating cover , 14 Dust removal hole, 14a Small diameter part, 14b Large diameter part, 15 Dust, 16a Nozzle part, 16 Ion gas ejection hole, 17 Dust receiving part, 18 Slit, 19 Internal space.

Claims (8)

A triboelectric charging device for charging a mixture having charging properties by triboelectric charging,
A charged container into which the mixture is charged;
A cleaning unit including a grounded conductive material that moves along the inner wall surface of the charging container and performs charge removal and cleaning of the inner wall surface;
A friction charging device comprising: a discharging device that discharges the dust removed from the inner wall surface of the charging container by the cleaning unit to the outside of the charging container. A triboelectric charging device for charging a mixture having charging properties by triboelectric charging,
A charged container into which the mixture is charged;
A cleaning unit that moves along the inner wall surface of the charging container, blows a fluid containing ionized gas on the inner wall surface of the charging container, and performs static elimination and cleaning of the inner wall surface;
A friction charging device comprising: a discharging device that discharges the dust removed from the inner wall surface of the charging container by the cleaning unit to the outside of the charging container. The discharge device includes a suction device,
The suction device has a dust suction path in which an opening end is formed in the inner wall surface of the charging container or in the charging container, and is removed from the inner wall surface of the charging container by the cleaning unit. The frictional charging device according to claim 1, wherein the dust is sucked out of the charging container via the dust suction path.   The frictional charging device according to claim 1, further comprising a stirring member that stirs the mixture in the charging container. The charging container is formed in a cylindrical shape,
The stirring member includes a stirring blade that performs a rotating motion in the charging container around a rotating shaft extending in an axial direction of the charging container;
The frictional charging device according to claim 4, wherein the cleaning unit is provided at an end of the stirring blade that is close to and opposed to the inner wall surface of the charging container.   The stirring member is disposed in the charging container so as to perform a rotational motion while maintaining a distance between the end of the stirring blade and the inner wall surface of the charging container in a range of 0.3 mm or more and 2.0 mm or less. The frictional charging device according to claim 5, which is disposed in A frictional charging device according to any one of claims 1 to 6,
An electrostatic sorting device comprising: a sorting device that sorts the mixture according to a charged state of the mixture charged in the friction charging device.   A plurality of types of plastic members contained in a used product are mixed and crushed, and the mixture of the plurality of types of plastic members is electrostatically sorted for each plastic type using the electrostatic sorting apparatus according to claim 7, A method for producing recycled plastic, comprising a step of recycling the plastic member subjected to electro-sorting as a raw material for plastic products.

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