JP2001085223A - Method for demolishing magnetic field generating device and method for recycling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide methods for demolishing and recycling a magnetic field generating device by which the device can be demolished and recycled safely and inexpensively. SOLUTION: A magnetic field generating device 10 incorporates a pair of platy yokes 12a and 12b which are connected to each other through a columnar yoke 24. On the surfaces of the yokes 12a and 12b facing each other, permanent magnets 14a and 14b respectively containing pluralities of neodymium magnets (22) are provided. In a method in which the neodymium magnets (22) are degaussed and an adhesive is shaved, the neodymium magnets (22) are recovered from the generator 10 by eliminating the adhesive after the magnets (22) are degaussed by heating the generator 10 to 200-350 deg.C. In a method in which the adhesive is carbonized, the magnets (22) are recovered after the adhesive is carbonized by heating the generator 10 to 350-1,000 deg.C. The recovered neodymium magnets (22) are reused by polishing the surfaces of the magnets (22). Alternatively, the recovered magnets (22) are reused by aging the magnets (22) again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for disassembling and recycling a magnetic field generator, and more particularly, to a method for disassembling a magnetic field generator.
Large M that can be used for diagnosis of human body using neodymium magnet
The present invention relates to a disassembly method and a recycling method of a magnetic field generator for RI.

2. Description of the Related Art In a large-sized magnetic field generator of this kind, since the size of a neodymium magnet as a sintered body is limited, a plurality of neodymium magnets are usually fixed to one plate yoke with an adhesive. I was The following can be considered as a method for disassembling such a magnetic field generator. First, after loosening the screw connecting the plate yoke and the column yoke, the magnetic field generator is lifted by a crane and disassembled. Then, the plate yoke is immersed in a tank filled with a solvent for melting the adhesive, and the neodymium magnet fixed to the plate yoke is taken out.

[0002]

However, since the magnetized neodymium magnet has a very strong magnetic force, in this method, the neodymium magnet is removed from the tank by the repulsive force between the neodymium magnets at the moment when the adhesive comes off. It is dangerous to jump out. Also, when taking out the detached neodymium magnet, the hand may be pinched by a strong attractive force. In addition, since the neodymium magnet is a sintered body and is easily broken, if the adhesive comes off at any moment due to repulsion between the neodymium magnets, it will be chipped. Further, when the neodymium magnets or the neodymium magnets collide with the plate-like yoke, sparks are generated, and there is a problem that there is a risk of fire or explosion. A method of demagnetizing a neodymium magnet by applying a demagnetizing magnetic field when disassembling the magnetic field generator is also conceivable. However, since a magnetic field generator for MRI is large, a strong magnetic field must be generated over a wide range to demagnetize it. Such demagnetization must be difficult, and large demagnetizing devices are expensive and impractical.

[0003] In Japanese Patent Publication No. 3-20045, each permanent magnet is magnetized and its magnetic properties are measured, and then each permanent magnet is demagnetized by heating. A method of magnetizing and assembling a magnet body is disclosed. However, this method is for properly disposing permanent magnets, and does not disclose or disassemble a large-sized magnetic field generator. Therefore, a main object of the present invention is to provide a disassembly method and a recycling method of a magnetic field generator that can be disassembled and recycled at a safe and low cost.

[0004]

According to a first aspect of the present invention, there is provided a method for disassembling a magnetic field generator, comprising: a plate yoke; and a plurality of neodymium magnets connected by an adhesive. A method for disassembling a magnetic field generator having a permanent magnet provided on a plate yoke, comprising:
Heating is performed at 0 ° C to 1000 ° C. Claim 2
The disassembly method of the magnetic field generator according to the first aspect of the present invention is the disassembly method of the magnetic field generator according to the first aspect, wherein the magnetic field generator further includes a columnar yoke connected to the plate yoke.
According to a third aspect of the present invention, there is provided a method for disassembling a magnetic field generator.
Alternatively, in the disassembling method of the magnetic field generator described in 2, the heating temperature of the magnetic field generator is 200 ° C. to 400 ° C.

According to a fourth aspect of the present invention, there is provided a method for disassembling a magnetic field generator according to the first or second aspect, wherein the heating temperature of the magnetic field generator is 200 ° C. to 35 ° C.
The temperature is 0 ° C, and after the neodymium magnet is demagnetized, the adhesive is removed and the neodymium magnet is recovered. Claim 5
The disassembling method of the magnetic field generating device according to claim 1 or 2,
Wherein the heating temperature of the magnetic field generator is 350 ° C. to 1000 ° C., and the neodymium magnet is recovered by carbonizing the adhesive. According to a sixth aspect of the present invention, in the method of disassembling the magnetic field generator according to the first aspect, the adhesive is an acrylic adhesive.

According to a seventh aspect of the present invention, there is provided a method of disassembling a magnetic field generator according to the first aspect, wherein the neodymium magnet is an R-Fe-B ternary neodymium magnet. . The disassembly method of the magnetic field generator according to claim 8 is the disassembly method of the magnetic field generator according to claim 1, wherein a plurality of neodymium magnets are arranged such that the same pole is arranged in a direction parallel to the main surface of the plate-like yoke. Is to be placed. A method for recycling a magnetic field generator according to claim 9, wherein the magnetic field generator includes a plate yoke and a permanent magnet including a plurality of neodymium magnets bonded by an adhesive and provided on the plate yoke. A recycling method, comprising:
The neodymium magnet is recovered after heating at 00 ° C. to 1000 ° C., and the surface of the recovered neodymium magnet is polished to reuse the neodymium magnet.

A method for recycling a magnetic field generator according to a tenth aspect is the method for recycling a magnetic field generator according to the ninth aspect, wherein the recovered neodymium magnet is subjected to aging treatment again. A method of recycling a magnetic field generator according to claim 11, wherein the magnetic field generator includes a plate yoke and a permanent magnet including a plurality of neodymium magnets bonded by an adhesive and provided on the plate yoke. In a recycling method, a neodymium magnet is recovered after heating a magnetic field generator at 200 ° C. to 1000 ° C., and the recovered neodymium magnet is re-aged and reused.

If the heating temperature of the magnetic field generator is lower than 200 ° C., the neodymium magnet cannot be sufficiently demagnetized and cannot be safely taken out. Further, since the adhesive is reversible up to 200 ° C., if the heating temperature is lower than 200 ° C., when the adhesive is cooled thereafter, the adhesive recovers the adhesive strength again. On the other hand, if the heating temperature exceeds 1000 ° C., the structure of the neodymium magnet itself changes and the magnetic properties deteriorate, so that
Even if the neodymium magnet is collected, it is difficult to reuse it. Therefore, in the disassembly method of the magnetic field generator according to claim 1,
By heating the magnetic field generator at 200 ° C. to 1000 ° C., the neodymium magnet is sufficiently demagnetized and the adhesive strength of the adhesive is reduced. As a result, the neodymium magnet can be safely taken out, and the magnetic field generator can be safely disassembled. Further, since heating may be performed, cost can be reduced.

[0009] Neodymium magnets that are magnetized are extremely dangerous, but by heating the magnetic field generator with the column-shaped yoke connected to the plate-shaped yoke as described in claim 2. In addition, handling of the magnetic field generator during disassembly is further facilitated. Due to the characteristics of the neodymium magnet, aging treatment is required when the heating temperature exceeds 400 ° C. However, in the disassembly method of the magnetic field generator according to claim 3, the magnetic field generator is heated at 400 ° C. or less. The neodymium magnet can be reused simply by re-magnetizing the heated neodymium magnet without aging.

In the method for disassembling the magnetic field generator according to the present invention, the neodymium magnet is demagnetized by heating the magnetic field generator at 200 ° C. to 350 ° C., and the adhesive is altered to reduce the adhesive force. Weaken. Therefore, the neodymium magnet can be safely taken out only by removing the deteriorated adhesive. Further, since the surface of the neodymium magnet is less deteriorated, it is easy to reuse the neodymium magnet. In the disassembly method of the magnetic field generating device according to the fifth aspect, the magnetic field generating device is set to 35
By heating at 0 ° C. or higher, the adhesive carbonizes and loses adhesive strength, and the neodymium magnet loses almost all magnetic force. Therefore, collection and handling of the neodymium magnet is facilitated.

The acrylic adhesive has a strong adhesive strength at room temperature, but when heated at 200 ° C. or higher, it undergoes thermal denaturation or carbonization, and the adhesive strength is weakened. Therefore, claim 6
When an acrylic adhesive is used as the adhesive as in the disassembly method of the magnetic field generator described in (1), the recovery of the neodymium magnet becomes easy. Compared with a quaternary system containing Co, a ternary neodymium magnet has a small magnetic flux density and a low coercive force at a high temperature, thermal demagnetization occurs from a low temperature, and a large demagnetization rate. Therefore, R-Fe-B (R is a rare earth element) as in the disassembly method of the magnetic field generator according to claim 7.
When the ternary neodymium magnet is used, desired demagnetization can be easily performed on the neodymium magnet, and the neodymium magnet is suitable for recycling by heating.

When a plurality of neodymium magnets are arranged so that the same poles are arranged in a direction parallel to the main surface of the plate-like yoke, if the magnetic field generator is to be dismantled without demagnetization, repulsion between the neodymium magnets is caused. The disassembly work is dangerous due to the force, but according to the disassembly method of the magnetic field generator according to claim 8, the neodymium magnet can be safely recovered even in such a case. In the method for recycling a magnetic field generator according to claim 9, the surface of the recovered neodymium magnet is polished, whereby the surface is purified and the adhesive force when the neodymium magnet is bonded again can be recovered. Can be recycled. In the method for recycling a magnetic field generator according to claims 10 and 11, the properties of the neodymium magnet can be reliably restored by aging the collected neodymium magnet again, and the neodymium magnet can be recycled well. .

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an example of a magnetic field generator 10 for MRI to which the present invention is applied. The magnetic field generator 10 is obtained by removing an electric circuit part from an MRI apparatus, and is substantially composed of only a magnetic circuit part. The magnetic field generator 10 includes a pair of plate yokes 12a and 12b which are arranged to face each other with a gap. On the surfaces of the plate yokes 12a and 12b facing each other,
Permanent magnets 14a and 14b are arranged, respectively, and pole pieces 16a and 16b are arranged on the surface thereof.
The pole pieces 16a and 16b each have a plate yoke 12a.
Pole piece fixing bolts 18 penetrating through
a and 18b, the permanent magnets 14a and 14b
Fixed on top.

Each of the permanent magnets 14a and 14b is composed of a plurality of magnet blocks 20. Magnet block 2
0 is, for example, 55 × 50 × 50 m as shown in FIG.
It is formed by fixing a plurality of neodymium magnets 22 in a cubic shape with the magnetic poles facing in the same direction. By using the neodymium magnet 22 having such a size that it can be homogeneously sintered, the permanent magnets 14a and 14b with little variation in magnetic properties can be obtained. Further, by fixing the neodymium magnets 22 with the magnetic poles facing in the same direction, 0.2T or less is applied between the pole pieces 16a and 16b.
A strong magnetic field of 0.3T is obtained. As can be seen from FIG. 3, the neodymium magnets 22 attract each other in the vertical direction, but repel each other because the same poles are arranged in the horizontal direction.

As the neodymium magnet 22, for example, R-F described in US Pat. No. 4,770,723 is used.
Uses a ternary neodymium magnet composed of e-B (composition Nd: 31 wt%, B: 1.0 wt%, and the balance Fe contains elements such as Al and Cu at 0.3 wt% or less). Is done. The thermal demagnetization curve of this ternary neodymium magnet is shown in FIG.
Is shown by line A in FIG. A thermal demagnetization curve of a quaternary neodymium magnet further containing Co at 0.9 wt% is shown by a line B in FIG. As can be seen by comparing the line A and the line B, the ternary neodymium magnet has lower heat resistance than the quaternary neodymium magnet, and thermal demagnetization (reduction in magnetic flux density and coercive force) occurs from a low temperature. The demagnetization rate also increases. Therefore, if a ternary neodymium magnet is used, desired demagnetization of the neodymium magnet 22 can be easily performed. For example, if a ternary neodymium magnet is heated to 200 ° C., the demagnetization rate becomes 7
0%.

Returning to FIG. 2, each magnet block 20 of the permanent magnet 14a is disposed in close contact with the same magnetic pole (eg, N pole) facing the upper surface, and each magnet block 20 of the permanent magnet 14b is A magnetic pole (for example, S-pole) different from that of 14a is closely attached to the lower surface. As described above, since the permanent magnets 14a and 14b face different magnetic pole surfaces, a uniform magnetic field is formed.
The permanent magnets 14a and 14b are respectively bonded between the side surfaces of each magnet block 20 with an adhesive.

Here, an acrylic adhesive is used as an adhesive used for bonding the neodymium magnets 22 and the magnet blocks 20 respectively. For example, an epoxy-based adhesive needs to be heated to be quickly cured, whereas an acrylic-based adhesive is quickly cured at room temperature, and is suitable for bonding the neodymium magnet 22. Therefore, by using an acrylic adhesive, the neodymium magnets 22 having a strong magnetic force and repelling each other can be converted to the plate-like yoke 1.
It can be easily fixed on 2a, 12b. On the other hand, the acrylic adhesive undergoes thermal denaturation when heated at 200 ° C. or higher, further carbonizes at 350 ° C. or higher, ignites at 420 ° C. or higher, and weakens the adhesive force. It will be easier. As an acrylic adhesive, for example,
Hard Rock C-323-03 manufactured by Denki Kagaku Kogyo Co., Ltd., which has a tensile shear strength under heat as shown in FIG. 5, is used.

A pair of plate yokes 12a and 12a
b is magnetically connected and supported by four columnar yokes 24 having a circular cross section so as to face each other at a predetermined interval. In this manner, the magnetic field generator 10 includes the pair of pole pieces 16a.
It is configured such that a uniform magnetic field is formed in a space between the first and second electrodes 16b. The plate-shaped yokes 12 a and 12 b and the column-shaped yoke 24 are connected by screws 26. The size of the magnetic field generator 10 is 220 cm long and 120 c wide.
m, height 170 cm. The distance between the pole pieces 16a, 16b is between 40 cm and 50 cm. The cubic neodymium magnet 22 shown in FIG.
Pole piece 1 by stacking two or three
A spherical uniform magnetic field space having a diameter of 30 cm to 40 cm is formed between 6a and 16b. The strength of the magnetic field space is 0.2T to 0.2T.
3T.

A process of disassembling the magnetic field generator 10 thus configured and recycling the neodymium magnet 22 will be described. First, the MRI apparatus is collected from a hospital or the like, and is carried into a factory having a heating furnace 28 as shown in FIG. Next, electrical components such as a heat insulating material and a wiring material, that is, non-metal members are removed, and only the magnetic field generator 10 is used. The magnetic field generator 10 is mounted on a cart 30 as shown in FIG. The heating furnace 28 needs to be large enough to accommodate the entire magnetic field generator 10 as assembled. When the dimensions of the magnetic field generator 10 are, for example, length × width × height = about 1.9 × 1.1 × 1.5 m, the dimensions of the heating furnace 28 are set to about 2 × 2 m in frontage and about 5 m in depth. Is desirable. As the heating furnace 28, an electric furnace or a heavy oil furnace is used, but the electric furnace facilitates temperature adjustment.

Then, as described later, a heat treatment is performed based on the heat pattern, and after the heat treatment is completed, it is naturally cooled.
Thereafter, the bolts 18a and 18b of the magnetic field generator 10 are loosened, and the neodymium magnet 22 is taken out. Plate yoke 12 first
The neodymium magnet 22 may be taken out after the a, 12b and the columnar yoke 24 are separated. At this time, the recovered neodymium magnet 22 is finished on the outer peripheral surface. Then, if necessary, aging heat treatment is performed in a tempering furnace (not shown) at, for example, 450 ° C. to 600 ° C. for 3 hours or more to recover magnetic properties.
Check the dimensions and magnetic properties of the neodymium magnet 22,
The neodymium magnet 22 is reused.

Here, the heat treatment will be described in detail. First, a heat treatment method for demagnetizing the neodymium magnet 22 and scraping the adhesive will be described. An electric furnace is suitable as the heating furnace 28 used in this method. In this method, the neodymium magnet 22 is demagnetized to such an extent that the magnetic properties do not deteriorate, and is heated at a temperature at which the adhesive is not carbonized. The adhesive is altered by heat and becomes brittle, but the neodymium magnet 22 cannot be taken out as it is, so it is necessary to scrape the adhesive. Specifically, the temperature is raised to 200 ° C. to 350 ° C., preferably to 300 ° C. as shown by a line C in FIG. 7, and kept at this temperature for 5 hours. As can be seen from FIG. 4, the magnetic force of the neodymium magnet 22 becomes 0.07T or less at this time.
After natural cooling, the columnar yoke 24 converts the plate yoke 12a, 12b
After removing the pole pieces 16a and 16b from the plate-shaped yokes 12a and 12b, respectively, the adhesive is scraped to take out the neodymium magnet 22. A surface grinder can be used as a machine for scraping the adhesive.

According to this method, the neodymium magnet 22 can be safely removed only by physically removing the deteriorated adhesive, and the magnetic field generator 10 can be safely disassembled.
Further, since the surface of the neodymium magnet 22 does not deteriorate, the neodymium magnet 22 can be easily reused only by cleaning and re-magnetizing the surface of the neodymium magnet 22. Further, since the heating is performed at 400 ° C. or less, the aging heat treatment does not need to be performed on the neodymium magnet 22 after the heating. Furthermore, since the heating furnace 28 can be used for heating the magnetic field generator 10, the disassembly cost can be reduced as compared with the related art described in the section of "Prior Art".

If the adhesive is soluble in a solvent even if it is thermally denatured, the adhesive may be dissolved in a solvent-containing tank. Ethyl acetate, methyl ethyl ketone, acetone and the like are used as the solvent, but since these have low permeability, it is necessary to soak the neodymium magnet 22 for about one week. On the other hand, when a highly permeable solvent such as methylene chloride or ethylene chloride is used, the neodymium magnet 22 can be recovered in about 24 hours. However, since the solvent volatilizes violently, large-scale equipment such as exhaust equipment is required.

Next, a heat treatment method for carbonizing the adhesive will be described. A heavy oil furnace is suitable as the heating furnace 28 used in this method. If a heavy oil furnace is used, the cost required for heating can be reduced. In this method, the magnetic field generator 10
Is heated to a Curie temperature (340 ° C.) or higher and the adhesive is carbonized, whereby the magnetic field generator 1 is heated.
0 is disassembled.

First, the entire magnetic field generator 10 is placed in the heating furnace 28 and, as shown by a line D in FIG.
Raise the temperature to 50 ° C. Thereafter, the magnetic field generator 10 is kept at that temperature for 5 hours, cooled naturally, and the magnetic field generator 10 is taken out. After natural cooling, the plate yokes 12a and 12b are removed from the columnar yoke 24, and the pole pieces 1 are respectively removed from the plate yokes 12a and 12b.
6a and 16b are removed, and the neodymium magnet 22 is taken out. Since carbon is attached to the surface of the taken out neodymium magnet 22 and the surface of the neodymium magnet 22 is carbonized and oxidized, it is difficult for the neodymium magnet 22 to adhere again as it is. Therefore, the surface of the neodymium magnet 22 is polished by about 0.1 mm to 0.5 mm to remove carbon and oxidized portions. After polishing, again at 500 ° C
For 1 hour to restore the properties of the neodymium magnet 22. If the temperature of the heating furnace 28 is too high, the tetragonal compound such as Nd2Fe14B causes grain growth, and the coercive force of the neodymium magnet 22 decreases. Therefore, the heating temperature needs to be 1000 ° C. or lower.

According to this method, since the adhesive carbonizes and loses the adhesive force, and the neodymium magnet 22 loses almost no magnetic force, the recovery and handling of the neodymium magnet 22 becomes easy, and the magnetic field generator 10 can be safely used. Can be dismantled. Further, by polishing the surface of the recovered neodymium magnet 22, the adhesive force when the neodymium magnet 22 is bonded again can be recovered. Further, by aging the neodymium magnet 22 again, the properties of the neodymium magnet 22 can be reliably restored.

In this way, the used magnetic field generator 10 that generates a strong magnetic field is disassembled and recycled, so that resources can be used effectively. In addition, danger caused by leaving the magnetic field generator 10 unresolved can be eliminated, and safety can be ensured. Further, although the neodymium magnet 22 which is magnetized is very dangerous, at least the columnar yoke 24 is connected to the plate-like yoke 12a or 12b, and FIG.
By heating the magnetic field generator 10 in the heating furnace 28 as it is, the dismantling operation can be performed more safely.
The plate yoke to which the permanent magnet is attached is replaced with a columnar yoke 2
Needless to say, it may be placed in a heating furnace 28 while being separated from the heating furnace 4 and heated to be dismantled.

[0028]

According to the present invention, since the neodymium magnet is sufficiently demagnetized and the adhesive force of the adhesive is reduced, the neodymium magnet can be taken out safely and the magnetic field generator can be safely dismantled. Further, since heating may be performed, cost can be reduced. In addition, by polishing the surface of the recovered neodymium magnet, the surface is purified and the adhesive force when the neodymium magnet is bonded again can be recovered, and the neodymium magnet can be recycled. Further, by aging the collected neodymium magnet again, the characteristics of the neodymium magnet can be surely restored, and the neodymium magnet can be satisfactorily recycled.

[Brief description of the drawings]

FIG. 1 is a partially omitted perspective view showing an example of a magnetic field generator to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating an example of a magnetic field generator.

FIG. 3 is a perspective view showing an example of a magnet block.

FIG. 4 is a graph showing a thermal demagnetization curve of a neodymium magnet.

FIG. 5 is a graph showing the hot tensile shear strength of the adhesive.

FIG. 6 is an illustrative view showing a heating furnace and a bogie;

FIG. 7 is a graph showing an example of a heat pattern when heating the magnetic field generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnetic field generator 12a, 12b Plate yoke 14a, 14b Permanent magnet 16a, 16b Magnetic pole piece 20 Magnet block 22 Neodymium magnet 24 Columnar yoke 28 Heating furnace

Claims (11)

[Claims] 1. A disassembly method for a magnetic field generator comprising: a plate yoke; and a permanent magnet including a plurality of neodymium magnets bonded by an adhesive and provided on the plate yoke. A method for disassembling a magnetic field generator, wherein the generator is heated at 200 ° C. to 1000 ° C. 2. The method according to claim 1, wherein the magnetic field generator further includes a columnar yoke connected to the plate yoke. 3. The disassembly method for a magnetic field generator according to claim 1, wherein the heating temperature of the magnetic field generator is 200 ° C. to 400 ° C. 4. The method according to claim 1, wherein the heating temperature of the magnetic field generator is 200 ° C. to 350 ° C., and after the neodymium magnet is demagnetized, the adhesive is removed to recover the neodymium magnet. Or the disassembly method of the magnetic field generator according to 2. 5. The disassembly of the magnetic field generator according to claim 1, wherein the heating temperature of the magnetic field generator is 350 ° C. to 1000 ° C., and the neodymium magnet is recovered by carbonizing the adhesive. Method. 6. The adhesive according to claim 1, wherein the adhesive is an acrylic adhesive.
A disassembly method for the magnetic field generator according to claim 1. 7. The disassembly method for a magnetic field generator according to claim 1, wherein the neodymium magnet is an R—Fe—B ternary neodymium magnet. 8. The disassembly method for a magnetic field generator according to claim 1, wherein the plurality of neodymium magnets are arranged such that the same pole is arranged in a direction parallel to a main surface of the plate-like yoke. 9. A method for recycling a magnetic field generator having a plate yoke and a permanent magnet including a plurality of neodymium magnets bonded by an adhesive and provided on the plate yoke, the method comprising: A method for recycling a magnetic field generator, wherein the neodymium magnet is recovered after heating the generator at 200 ° C. to 1000 ° C., and the surface of the recovered neodymium magnet is polished to reuse the neodymium magnet. 10. The method for recycling a magnetic field generator according to claim 9, wherein the recovered neodymium magnet is subjected to aging treatment again. 11. A method for recycling a magnetic field generator comprising a plate yoke and a permanent magnet including a plurality of neodymium magnets bonded by an adhesive and provided on the plate yoke, wherein: A method for recycling a magnetic field generator, wherein the neodymium magnet is collected after heating the generator at 200 ° C. to 1000 ° C., and the collected neodymium magnet is re-aged and reused.