JP2000126649A - Method for sorting plastics and plastic sorter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct separation of waste plastic chips with high reliability at the electrostatic separation unit of a plastic sorter by adding a specified amt. of a triboelectrification assistant to the plastic chips of different kinds to give each kind of plastic chip a different polarity and amount of charge, to efficiently recover a specified kind of plastic chips and to repeatedly use the assistant by leaving behind the added assistant in the sorter. SOLUTION: When the quantity of chips of specified plastic 1 to be recovered is small, the chips 1 are added into a triboelectrification device 3 as a triboelectrification assistant 21 and agitated to prevent the plastic chips 1 of different kinds (e.g. PVC and PE) from being charged to the same polarity. Subsequently, a specified amount of triboelectric charge is imparted to ensure reliable separation of chips in the electrostatic separation unit, and the specified plastic chips 1 are recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic sorting method and a plastic sorting apparatus for sorting classified pulverized waste consisting of plastic pieces by type.

[0002]

2. Description of the Related Art In recent years, recycling of refuse has been rapidly promoted. Incidentally, plastics consumed as raw materials for plastic products include vinyl chloride resin (hereinafter referred to as “PVC”) and polyethylene resin (hereinafter “P
E "), polypropylene resin (hereinafter" PP ")
), A polystyrene-based resin (hereinafter referred to as “PS”), and a methacrylic resin [acrylic resin] (hereinafter “P”).
It is considered that the above-mentioned resins occupy most of the recovered waste plastic. In addition, polyethylene terephthalate resin (hereinafter, referred to as “PET”) used as a so-called PET bottle is being independently collected. When recycling these resins, it is important to sort (sort) each type of resin.

As a technique for sorting pulverized plastic pieces, there is a plastic sorting apparatus. A conventional plastic sorting apparatus will be described with reference to FIG. In this plastic sorting apparatus, different types of resin-based plastics 1 to be sorted and pulverized waste are put into a hopper 2 in a mixed state. Then, the plastic piece 1 is put into the friction charging device 3 from the outlet of the hopper 2. The plastic piece 1 is agitated in the friction charging device 3 and frictionally charged to the polarity and the charge amount of each plastic piece 1, and thereafter, is sprayed on the upper surface of the metal drum electrode 5. The metal drum electrode 5 is rotated around a horizontal axis in a predetermined direction and is grounded.

An arc-shaped high-voltage electrode 6 is disposed obliquely above the metal drum electrode 5 in the rotation direction. A cathode of a high-voltage power supply 7 is connected to the high-voltage electrode 6. The anode of the power supply 7 is grounded. With this connection, a rotating ground electrode is formed by the metal drum electrode 5, and a sorting electrostatic field is formed between the high-voltage electrode 6 and the metal drum electrode 5.

[0005] Below the metal drum electrode 5, a first separation container 8 and a second separation container 9 which are opened upward are arranged in this order on the upstream side in the rotation direction. A brush 10 for scraping off the plastic piece 1 attached to the peripheral surface of the metal drum electrode 5 is arranged on the outer peripheral portion of the metal drum electrode 5. The operation of the above configuration will be described. A plurality of types of plastic pieces 1 are mixed into the friction charging device 3 from the hopper 2 in a mixed state, and different types of plastic pieces 1 are agitated and rub together in the cylinder of the friction charging device 3 so that the plastic pieces 1 can be rubbed. It is frictionally charged to each polarity and charge amount. Then, the charged plastic piece 1 is sprayed on the metal drum electrode 5, and the plastic piece 1 negatively charged by the friction charging device 3 is repelled by the high voltage electrode 6 and is attracted to the metal drum electrode 5, The metal drum electrode 5 is dropped into the second separation container 9 by rotation, or is scraped off from the surface of the metal drum electrode 5 by a brush 10 and separated, and then falls into the second separation container 9. Also, a plastic piece 1 charged with a positive charge opposite to that of the metal drum electrode 5
Is adsorbed on the surface of the metal drum electrode 5 and falls into the first separation container 8 due to the centrifugal force of the metal drum electrode 5.

[0006]

In the above-mentioned friction charging device 3, a plurality of different resin-based plastic pieces 1 charged into the hopper 2 are agitated and frictionally charged. If the difference in the amount (the difference in the surface area) is large, the polarity and charge amount (charged voltage) required for electrostatic separation may not be given to the plastic piece 1 during stirring. In such a case, the metal drum electrode 5 or the high-voltage electrode 6 that uses the electric charge of the plastic piece 1 for selection cannot sufficiently perform the selection.

Therefore, an object of the present invention is to provide a plastic sorting method and a plastic sorting apparatus which can solve the above-mentioned problems.

[0008]

Means for Solving the Problems The object of the present invention is to provide a friction charging device for stirring a plastic piece obtained by mixing a plurality of pulverized types to frictionally charge the plastic piece to the polarity and charge amount of each plastic piece. The electrostatic separation unit for separating the triboelectrically-charged plastic pieces below the drop opening of the triboelectric charging device, and the plastic pieces separated by the electrostatic separation unit are separately collected for each polarity and electrode. When a plurality of types of plastic pieces are put into the triboelectric charging device, when the amount of the specific plastic pieces is small, the specific plastic pieces or the same or mixed plastic pieces are charged in the order of charging. A predetermined amount of a plastic piece located in the middle is added as a frictional charging auxiliary material, and the plastic piece to be added is left at the dropping port of the frictional charging device. Net body is attached.

In the above construction, a plastic piece obtained by mixing a plurality of pulverized types is charged into a frictional charging device and stirred to charge the plastic piece to the polarity and charge amount of each plastic piece. In the electrostatic separation unit located below the charging device, the specific plastics to be collected are collected separately in the separation container according to the polarity and the amount of charge, and the specific plastic pieces are taken out. When the amount of the pieces is small, when the mixed plastic pieces are stirred with the triboelectric charging device, the specific plastic piece, the same kind of plastic piece, the plastic piece located in the middle of the charging sequence of the mixed plastic piece, and the predetermined plastic piece Either of the plastic pieces located on the plus or minus side in the charging sequence of And pressure is to use repeatedly by causing residual The added friction auxiliary charging member in frictional charging device.

As described above, when the amount of the specific plastic piece to be recovered is small, when the mixed plastic pieces are stirred with each other by the triboelectric charging device, the specific plastic piece, the same kind of plastic piece, and the mixed plastic pieces are mixed. The polarity of each plastic piece is added by adding a predetermined amount of a plastic piece located in the middle in the charging order of the plastic pieces and a plastic piece located on the plus or minus side in the predetermined charging order as a frictional charging auxiliary material.・
Since it is charged to the charge amount, the specific plastic piece can be separated and recovered with high purity and high recovery rate.

In particular, the weight Wt of a particular plastic piece,
The relationship between the weight Wm of the triboelectric auxiliary material to be added and the total weight Wz of the mixed plastic pieces put into the triboelectric charging device is represented by
According to the setting to satisfy the following expression (Wt + Wm) /Wz=0.1 to 0.9, even if the recovery rate of a specific plastic piece is reduced, a plurality of times of triboelectric charging and electrostatic separation work are performed. , It is possible to increase the recovery rate.

Further, a plastic piece obtained by mixing a plurality of types of pulverized materials is charged into a frictional charging device and stirred to charge the plastic piece to the polarity and charge amount of each plastic piece. A plastic sorting method in which a plastic piece is separated by an electrostatic separation unit arranged below and a specific plastic piece is taken out by separately collecting the plastic pieces in a separation container according to the polarity and charge amount. When agitated plastic pieces with a frictional charging device, the above (Wt + W)
m) / Wz = Auxiliary stirring member having a surface area corresponding to the ratio of 0.1 to 0.9.
Stirring was performed to give a charge amount.

According to this, the polarity of each plastic piece
Since it is charged to the charge amount, the specific plastic piece can be separated and recovered with high purity and high recovery rate. In addition, agitated plastic pieces mixed with multiple types of pulverized,
A frictional charging device for frictionally charging each plastic piece to the polarity and charge amount, and an electrostatic separation unit for separating the frictionally charged plastic piece below the frictional charging device,
The plastic piece separated by this electrostatic separation part is
A separation container for collecting separately for each charge amount,
(Wt + Wm) / Wz = 0.
An auxiliary stirring member having a surface area corresponding to a ratio of 1 to 0.9 is provided.

According to this structure, the auxiliary stirring member functions as a frictional charging auxiliary material and charges the plastic pieces to the polarity and the charge amount, so that the specific plastic pieces can be separated and recovered with high purity and high recovery rate. be able to.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described. This plastic sorting apparatus S includes a hopper 2 for feeding a plurality of types of plastic pieces (sorted and crushed refuse) 1 of different resin types in a mixed state, And a friction charging device 3 disposed on the side of the outlet 2a for frictionally charging each plastic piece 1 by stirring, and a plurality of types of frictionally charged plastic pieces 1 disposed below the friction charging device 3. An electrostatic separation unit G for electrostatic separation;
The plastic piece 1 electrostatically separated by the electrostatic separation unit G
A first separation container 8 and a second separation container 9 for recovering the particles by polarity and charge amount (by type).

FIG. 2 shows the details of the configuration of the frictional charging device 3. The friction charging device 3 is connected to the outlet 2 of the hopper 2.
a container 11 having a double structure connected to the
1 is an outer cylindrical outer container 12 and the outer container 12
And a cylindrical inner container 13 arranged coaxially with the outer container 12. An inlet 1 connected to the outlet 2 a of the hopper 2 is provided on one upper surface of the container 11.
4 is formed, and a drop 16 of the plastic piece 1 is formed on the other lower surface of the container 11. In this drop 16, a mesh body 17 for allowing a friction charging auxiliary material 21 described later to remain in the container 11 is formed. It is stretched.

A rotary shaft 18 is provided so as to extend along the axis 11 a of the container 11, and a plurality of types of plastic pieces 1 put into the container 11 from the hopper 2 are stirred on the peripheral surface of the rotary shaft 18. A stirring rod 19 made of metal is mounted radially on the rotating shaft 1 outside the container 11.
A drive motor 20 for rotating the motor 8 is mounted.

Next, based on FIG.
Will be described. The electrostatic separation part G includes a metal drum electrode 5 disposed below the drop port 16 of the container 11 and a high voltage electrode 6 disposed obliquely above the metal drum electrode 5.
And a brush 10 disposed below the metal drum electrode 5 for scraping off the plastic pieces 1 attached to the peripheral surface of the metal drum electrode 5. The metal drum electrode 5 is rotatable around a horizontal axis in a predetermined direction, and is grounded. The high-voltage electrode 6 is connected to the cathode of a high-voltage power supply 7, and the anode of the high-voltage power supply 7 is grounded. By this connection, a rotating ground electrode is formed by the metal drum electrode 5, and a sorting electrostatic field is formed between the high-voltage electrode 6 and the metal drum electrode 5.

The first separation container 8 and the second separation container 9 are provided below the metal drum electrode 5.
And the first separation container 8 and the second separation container 9 both open upward. Next, a plastic sorting method in the plastic sorting apparatus S having the above configuration will be described. A plurality of types of plastic pieces 1 each of which has been pulverized (approximately 3 mm in spherical shape) are put into the friction charging device 3 from the hopper 2 in a mixed state, and are driven by the drive motor 20 to be stirred by the stirring rod member 19. And the plastic piece 1 follows the charging sequence according to its type,
It is charged to either plus or minus. When a plurality of types of plastic pieces 1 are charged into the hopper 2 and frictionally charged, if the amount of the specific plastic piece 1 (for example, PVC) to be collected is small, the specific plastic piece 1 is subjected to the friction. A predetermined amount is added as the charge assisting material 21. Note that the added triboelectric auxiliary material 21 is formed in a larger area (larger diameter) than the other plastic pieces 1.

When a plurality of types of mixed plastic pieces 1 charged into the frictional charging device 3 are agitated by the plastic pieces 1 and the agitating rod member 19 in the inner container 13 and rub against each other, the plurality of types of plastic pieces 1 The piece 1 is sufficiently friction-charged to the polarity and charge amount of each plastic piece 1 by the addition of the triboelectric charge assisting material 21, and the frictionally charged plastic piece 1 passes through the mesh of the mesh body 17. Is spread on the metal drum electrode 5. However, since the added triboelectric auxiliary material 21 is formed in a larger area than the other plastic pieces 1, it remains in the container 11 without falling off from the mesh 17.

The plastic piece 1 charged negatively by the frictional charging device 3 repels the high voltage electrode 6 and is attracted to the metal drum electrode 5, and the second drum 5 is rotated by the rotation of the metal drum electrode 5. Or is scraped off from the surface of the metal drum electrode 5 by the brush 10 and falls into the second separation container 9. Further, the plastic piece 1 charged with a positive charge opposite to that of the high voltage electrode 6 is attracted to the surface of the high voltage electrode 6 and falls into the first separation container 8 by the rotation of the metal drum electrode 5. Therefore, even when a plurality of types of plastic pieces 1 are mixed, a specific plastic piece 1 can be recovered from the mixed state.

When the plastic sorting is subsequently performed, the added triboelectric auxiliary material 21 remains in the container 11, so that it is not necessary to add the triboelectric auxiliary material 21 this time. Is reused in the frictional charging device 3, and the different types of plastic pieces 1 rub against each other in the frictional charging device 3 to charge to the polarity and charge amount (charged voltage) of each plastic piece 1 in the same manner as described above. Then, the plastic piece 1 is reliably separated in the electrostatic separation part G, and can be separated and collected in the first separation container 8 and the second separation container 9.

By the way, more specifically, P
When P, PE, PVC, PS, and PET are arranged in the order of the charging column, (+) PS → PE →
PP → PET → PVC (There is also data indicating PP → PVC → PET) (−). Here, PP located in the middle order of the charging line is selected as a reference plastic material, and when another plastic material is rubbed against the reference plastic material made of PP, many positive charges are charged in the order of PE <PS, In addition, PP is hardly charged, and PE
Many negative charges are charged in the order of T <PVC. In this way, by selecting the plastic in the middle rank of the charging train as the reference plastic material, the mixed plastic pieces 1 can be frictionally charged to the polarity and charge amount for each type.

Then, as a type of the plastic piece 1,
Using PE, PP, PS, PET, and PVC, tests of the recovery rate and the recovery purity were performed. In this test, the weight ratio of the plastic piece 1 was determined as follows: PE: PP: PS: PET: PVC = 4: 2: 2: 1:
1 and the total weight (stirring weight) W of one plastic piece 1
z was set to 100 to 500 g. The test results are as shown in the graph of FIG. This graph shows the remaining plastic piece 1 from which PVC was separated and recovered, that is, PE, P
The recovery rate and purity of P, PS, and PET. As is clear from this graph, in the above weight ratio, the purity (shown by ●) is as high as 90% or more, and the recovery rate (shown by ○) is 50%.
It turns out that the degree is low.

The charging potential of PVC and PE after frictionally charging five types of plastic pieces 1 mixed at the above weight ratio was examined. Note that PVC and PE are plastics located on the minus side and the plus side, respectively, in terms of charging sequence. As a result, as shown in FIG. 4, when the content of PVC is 20% by weight or less or 80% by weight or more, when PP is selected as the reference plastic material and another plastic material is rubbed as described above, It was found that the polarity of the positively charged PE in the charging train was the same negative as that of PVC.

The fact that the polarity of PE is the same (minus) as that of PVC means that the PVC, which is a specific plastic piece 1, is to be separated from another plastic piece 1 and taken out. The separation performance at the time will be reduced. Thus, in the first embodiment, the weight Wt of the specific plastic piece 1 and the added triboelectric charge assisting material 2
1 and the total weight Wz of the plastic pieces 1 put into the frictional charging device 3 are set to the following equation (2) corresponding to the above equation (1) (Wt + Wm) /Wz=0.5 (2) did. Then, as a triboelectric charge assisting material 21, 50 with respect to the total weight Wz of a plurality of types of mixed plastic pieces 1.
By adding PVC by weight, a separation test was performed with the plastic sorting apparatus S, and as a result, a PVC recovery rate and purity of 90% or more were obtained.

This is because, by adding 50% by weight of PVC as the frictional charging auxiliary material 21, the charging polarity of PVC and PE after frictionally charging by the frictional charging device 3 is clearly opposite (PVC according to the charging sequence). Is negative and PE is positive), and the polarity and charge amount required for separation are given to each of the plurality of types of plastics 1. It is conceivable that PET is negatively charged in the same manner as PVC, and falls into the second separation container 8, but this can be dealt with by changing the voltage applied to the sorting electrostatic field.

By the way, in the above experiment, (Wt + Wm)
/Wz=0.5, but from FIG.
It can be seen that the purity is as high as 90% in any range of (Wt + Wm) /Wz=0.1 to 0.9. Therefore, to obtain a high purity recovery rate, (Wt + Wm)
/Wz=0.1 to 0.9 is sufficient. However, it can be seen that the recovery rate of the specific plastic piece 1 decreases as the value departs from the value of (Wt + Wm) /Wz=0.5. For example, (Wt + Wm) / Wz = 0.
At 1,0.9, the recovery is as low as about 50%.

However, this can be solved by repeating the above-mentioned separation operation several times.
That is, the frictional charging auxiliary material 21 remaining in the frictional charging device 3 is reused as it is, and the frictional charging auxiliary material 21 is agitated again with the specific plastic piece 1 once subjected to the separating operation to frictionally charge the frictionally charged auxiliary material 21. By separating other plastic pieces 1 to be mixed with the plastic piece 1, the recovery rate can be improved.

For example, PVC obtained by performing a separation operation once
If the recovery rate of (specific plastic piece 1) is 50%,
When about 50% of the other plastic pieces 1 are mixed, the remaining triboelectric auxiliary material 21 is reused as it is,
As a result of being stirred again and frictionally charged with a specific plastic piece 1 in which about 50% of other plastic pieces 1 are mixed, 7
0% recovery was obtained. Of course, the purity in this case is also 90%
Above was high. When the frictional charge auxiliary material 21 is reused, another plastic piece 1 is put into the frictional charging device 3 in accordance with the amount of the remaining frictional charge auxiliary material 21 so that the specific plastic piece 1 Polarity and charge amount. As described above, a high recovery rate can be realized by repeating the above-mentioned electrostatic separation operation a plurality of times.

As described above, according to the first embodiment of the present invention, when a specific plastic piece 1 (for example, PVC) to be collected is small, the specific plastic piece 1 is frictionally charged in the frictional charging device 3. By adding and stirring as the charge assisting material 21, different types of plastic pieces 1 are prevented from being charged to the same polarity and different charge amounts are given, and therefore, separation in the electrostatic separation unit G is performed. And the specific plastic piece 1 can be collected.

In general, the container 11 and the stirring rod member 19 of the frictional charging device 3 are often made of metal for reasons of manufacturability, safety against charging, stability of charging characteristics of the plastic piece 1, and the like. In this case, PE and PP were negatively charged similarly to PVC, and it was difficult to recover PVC. However, according to the first embodiment of the present invention, the specific charging is performed in the frictional charging device 3. By adding the plastic piece 1 as the frictional charging auxiliary material 21 and stirring, the polarity and the charge amount of the plastic piece 1 to be recovered are different from those of the other plastic pieces.
Even when the stirring rod member 19 is made of metal, separation at the electrostatic separation unit G can be reliably performed, and a specific plastic piece 1 is reliably collected by giving the polarity and charge amount of each plastic piece 1. be able to.

In the first embodiment, in order to improve the recovery rate, the frictional charging auxiliary material 21 remaining in the frictional charging device 3 is reused as it is, and the plastic pieces 1 are repeatedly stirred. Was charged by friction.
However, the present invention is not limited to this.
When stirring each other, the polarities of each plastic piece 1 can also be taken out by taking out from the frictional charging device 3 once, throwing it into the hopper 2 together with the other plastic pieces 1 and stirring and frictionally charging with the frictional charging device 3. Since the charge amount is provided, the same operation and effect as in the first embodiment can be obtained.

Further, in the first embodiment, when a plurality of types of plastic pieces 1 are put into the hopper 2 and subjected to frictional charging, if the amount of the specific plastic pieces 1 to be collected is small, the specific plastic pieces 1 are specified. Is added as a triboelectric charge assisting material 21 in a predetermined amount, but the present invention is not limited to this. A plastic piece 1 of the same kind as the specific plastic piece 1 to be collected or a mixed plastic piece Even if the plastic piece 1 positioned in the middle in the charging sequence 1 or the plastic piece positioned on the plus or minus side in the predetermined charging sequence is added as a friction charging auxiliary material 21 by a predetermined amount, The same operation and effect as those of the first embodiment can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the plastic sorting device S according to the second embodiment of the present invention, the frictional charging device 3 includes:
Double-structure container 1 connected to outlet 2a of hopper 2
1, the container 11 comprises an external cylindrical external container 12
And a cylindrical internal container 13 disposed inside the external container 12 and coaxially with the external container 12. An intake port 14 connected to the outlet 2 a of the hopper 2 is provided on one upper surface of the container 11. On the other lower surface of the container 11, a drop port 16 of the plastic piece 1 is configured to be openable and closable by a shutter 25, and an opening / closing cylinder device 26 for opening and closing the shutter 25 is provided.

The rotating shaft 18 extends along the axis of the container 11.
A metal agitating rod member 19 for agitating the plurality of types of plastic pieces 1 put into the container 11 from the hopper 2 is radially attached to a peripheral surface of the rotating shaft 18, and is provided outside the container 11. A drive motor 20 for rotating the rotary shaft 18 is mounted on the inner container 13, and an auxiliary stirring member 27 is extended toward the rotary shaft 18 on the inner surface of the inner container 13.

The auxiliary stirring member 27 replaces the frictional charging auxiliary material 21 added at the time of frictional charging in the first embodiment, and the total surface area of the auxiliary stirring member 27 is equal to that of the first embodiment. (Wt + Wm) / Wz
= 0.1 to 0.9 is set so as to have a surface area corresponding to the ratio.

The frictional charging device 3 includes a vibrator 28 attached to the lower surface of the container 11 for applying vibration to the container 11.
It has. Another configuration of the plastic sorting device S is as follows.
The description is omitted because it is the same as the first embodiment. Here, a plastic sorting method by the plastic sorting apparatus S according to the second embodiment of the present invention will be described. As in the first embodiment, a plurality of types of pulverized plastic pieces 1 are mixed with each other by a
And stirred by the drive of the drive motor 20.
Then, the different types of plastic pieces 1 charged into the triboelectric charging device 3 are mixed in the inner container 13 with the plastic pieces 1.
The particles are agitated by the agitating rod member 19 and the auxiliary agitating member 27 and frictionally charged with each other.

At this time, the frictional charging device 3 is provided with the auxiliary stirring member 27 having a surface area corresponding to the total surface area of the frictional charging auxiliary material 21 in the first embodiment. 1 is frictionally charged to the polarity and charge amount of each plastic piece 1. And
The frictionally charged plastic piece 1 drops from the drop opening 16 to the electrostatic separation portion G by driving the vibrator 28 (or the container 11 may be inclined instead of attaching the vibrator), and the frictionally charged plastic piece 1 is frictionally charged. The plastic piece 1 charged with a negative charge in the device 3 is repelled by the high-voltage electrode 6 and sucked by the metal drum electrode 5, and falls into the second separation container 9 due to the centrifugal force, or the brush 10 It is scraped off from the surface of the metal drum electrode 5 and separated, and falls into the second separation container 9. The plastic piece 1 charged with a positive charge by the friction charging device 3 is a plastic piece 1 charged with a positive charge opposite to the metal drum electrode 5.
Is sucked by the high-voltage electrode 6, falls into the first separation container 8 by the rotation of the metal drum electrode 5, and is separated and collected.

As described above, according to the second embodiment of the present invention, (Wt + Wm) / Wz =
Since the auxiliary stirring member 27 having a surface area corresponding to the total surface area of the frictional charging auxiliary material 21 in the first embodiment at a ratio of 0.1 to 0.9 is provided, each plastic piece 1 By the stirring of the auxiliary stirring member 27, the plastic piece 1 is frictionally charged to the polarity and charge amount of each plastic piece 1. Therefore, the specific plastic piece 1 and the other plastic piece 1 are collected at a high recovery rate and high purity in the electrostatic separation section G. Can be separated. Other functions and effects are the same as those of the first embodiment.

[0041]

As is apparent from the above description, the present invention can be applied to a case where a plurality of types of plastic pieces are charged into a triboelectric charging device when the amount of the specific plastic pieces to be recovered is small. Any one of a plastic piece of the same type, a plastic piece of the same type, a plastic piece positioned in the middle in the charging sequence of a mixed plastic piece, and a plastic piece positioned on the plus or minus side in the predetermined charging sequence as a triboelectric charging auxiliary by a predetermined amount. By adding, different types of plastic pieces can be charged to the polarity and charge amount of each plastic piece, thereby ensuring separation at the electrostatic separation unit and ensuring the specific plastic piece. It can be collected, and the added triboelectric auxiliary material is left in the triboelectric charging device, so that it can be used repeatedly It can be.

In particular, the weight Wt of a particular piece of plastic,
The relationship between the weight Wm of the triboelectric auxiliary material to be added and the total weight Wz of the mixed plastic pieces put into the triboelectric charging device is represented by
According to the setting that satisfies (Wt + Wm) /Wz=0.1 to 0.9, even if the recovery rate of a specific plastic piece becomes low, a plurality of times of triboelectric charging and electrostatic separation are performed. As a result, the recovery rate can be increased.

In addition, the above formula (W
(t + Wm) / Wz = Auxiliary stirring member having a surface area corresponding to the ratio of 0.1 to 0.9, which is agitated so as to give a polarity and a charge amount to each plastic piece. Since each piece is charged to the polarity and charge amount, the specific plastic piece can be separated and recovered with high purity and high recovery rate.

Further, the above formula (W
According to the provision of the auxiliary stirrer having a surface area corresponding to the ratio of (t + Wm) /Wz=0.1 to 0.9, the auxiliary stirrer functions as a frictional charge auxiliary material, and each plastic piece is , The specific plastic pieces can be separated and recovered with high purity and high recovery rate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a plastic sorting device according to a first embodiment of the present invention.

FIG. 2 is a cutaway view showing a configuration of the frictional charging device.

FIG. 3 is a graph showing the relationship between the stirring weight of a plastic piece and the recovery rate / purity.

FIG. 4 is a graph showing a relationship between a PVC content and a charging potential per unit weight.

FIG. 5 is a graph showing the relationship between the content of a specific plastic piece and the recovery rate / purity.

FIG. 6 is a side sectional view of a frictional charging device according to a second embodiment of the present invention.

FIG. 7 is a front sectional view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plastic piece 2 Hopper 3 Friction charging device 5 Metal drum electrode 6 High voltage electrode 8 First separation container 9 Second separation container 11 Container 17 Net 19 Stirring rod member 20 Drive motor 21 Friction charging auxiliary material G Electrostatic separation unit S plastic sorting device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daisuke Tamakoshi 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Hidehiko Maebata 1-chome, Minami-Kohita, Suminoe-ku, Osaka-shi, Osaka 7-89 Inside Hitachi Zosen Corporation (72) Inventor Hironari Arai 1-7-89 Inside Hitachi Zosen Corporation (72) Ken-ichi Nagai Minami Kohoku, Suminoe-ku, Osaka-shi Osaka 1-chome 1-chome 7-89 Hitachi Zosen Corporation

Claims (5)

[Claims] 1. A plastic piece in which a plurality of crushed types are mixed is charged into a frictional charging device and stirred to be charged to the polarity and charge amount of each plastic piece, and the charged plastic pieces are frictionally charged. A plastic sorting method in which a specific plastic piece is taken out by collecting separately in a separation container according to the polarity and the amount of charge in an electrostatic separation unit disposed below the If the amount of plastic pieces is small, when mixing the mixed plastic pieces with a triboelectric charging device, the specific plastic piece, the same type of plastic piece,
Either a plastic piece positioned in the middle in the charging sequence of the mixed plastic pieces or a plastic piece positioned on the plus or minus side in the predetermined charging sequence is added by a predetermined amount as a frictional charging auxiliary material, and the added frictional charging is performed. A plastic sorting method, wherein an auxiliary material is repeatedly used by remaining in a triboelectric charging device. 2. The relationship between the weight Wt of a specific plastic piece, the weight Wm of a triboelectric auxiliary material to be added, and the total weight Wz of a mixed plastic piece put into a triboelectric charging device is expressed by the following equation (Wt + Wm) / Wz = 0. The plastic sorting method according to claim 1, wherein the method is set so as to satisfy 0.1 to 0.9 (1). 3. A plastic piece in which a plurality of crushed types are mixed is charged into a frictional charging device and stirred to charge the plastic piece to the polarity and charge amount of each plastic piece. A plastic sorting method in which a plastic piece is separated by an electrostatic separation unit arranged below and a specific plastic piece is taken out by separately collecting the plastic pieces in a separation container according to the polarity and charge amount. When stirring the plastic pieces with a frictional charging device, an auxiliary stirring member having a surface area corresponding to the ratio of the formula (1) in the friction charging device is used for each plastic piece. A plastic sorting method characterized by stirring to give polarity and charge. 4. A friction charging device for stirring a plastic piece obtained by mixing a plurality of crushed types to frictionally charge the plastic piece to the polarity and charge amount of each plastic piece, and An electrostatic separation unit for separating the triboelectrically charged plastic pieces, and a separation container for separately collecting the plastic pieces separated by the electrostatic separation unit for each polarity / electrode are provided. When the amount of a specific plastic piece is small when the plastic piece is put into the triboelectric charging device, the specific plastic piece or the plastic piece located in the middle of the charging sequence of the same or mixed plastic pieces is used as a frictional charging auxiliary material. What is claimed is: 1. A plastic sorting apparatus in which a predetermined amount is added, wherein a net for attaching a plastic piece to be added is attached to a drop port of the frictional charging device. A plastic sorting device characterized by the following. 5. A friction charging device for stirring a plastic piece obtained by mixing a plurality of crushed types to frictionally charge the plastic piece to the polarity and charge amount of each plastic piece, and a frictionally charging device below the friction charging device. An electrostatic separation unit for separating the separated plastic pieces, and a separation container for separately collecting the plastic pieces separated by the electrostatic separation unit for each polarity and charge amount, the frictional charging device 3. A plastic sorting apparatus, wherein an auxiliary stirring member having a surface area corresponding to the ratio of the expression (1) in claim 1 is provided inside the plastic sorting apparatus.