JP7843437B2 - Method for recovering copper from enameled wire - Google Patents

Description

This invention relates to a method for recovering copper from enameled wire.

Enameled wire is known in which an insulator is formed by coating a conductor with enamel paint and drying it. In enameled wire, the high adhesion between the conductor and the insulator makes it difficult to remove the insulator and recover the copper when the enameled wire is discarded.

Patent Document 1 discloses a method for removing the insulator of an enameled wire by heating and carbonizing it, followed by applying mechanical force. Patent Document 2 discloses a method for removing the insulator by immersing the enameled wire in an alkaline solution to hydrolyze it.

Japanese Patent Publication No. 2011-174175 Japanese Patent Application Publication No. 10-25523

However, the method described in Patent Document 1 requires heating the insulator to a high temperature of 500°C or higher to carbonize it, which necessitates a huge amount of thermal energy, resulting in high processing costs. Furthermore, there is a risk that the purity of the recovered copper may decrease due to oxidation of the conductor or integration of the carbide with the conductor during heating.

The method described in Patent Document 2 requires a high-concentration alkaline solution, resulting in high chemical costs and the need for wastewater treatment, leading to significant environmental impact and high processing costs. Furthermore, heating is required to hydrolyze the insulator, further increasing processing costs.

Therefore, the present invention aims to provide a method for recovering copper from enameled wire that can reduce environmental impact and recover high-purity copper at low processing costs.

The present invention aims to solve the above problems by providing a method for recovering copper or copper alloy from an enameled wire having an insulator surrounding a conductor made of copper or a copper alloy, comprising: a stripping step of applying compression or rolling to the enameled wire to peel off the insulator from the conductor; and a removal step of peeling off and removing the insulator that has been stripped from the conductor.

According to the present invention, a method for recovering copper from enameled wire is available that can reduce environmental impact and recover high-purity copper at a low processing cost.

This is a schematic diagram of a copper recovery apparatus for enameled wire used in a copper recovery method for enameled wire according to one embodiment of the present invention. (a) and (b) are diagrams illustrating the compression process. These are photographs showing examples of enameled wire after compression processing: (a) after one press, (b) after two presses, and (c) after making cuts with a blade in (b). (a) is a photograph showing a cross-section of the enameled wire before compression, and (b) is a photograph showing a cross-section of the enameled wire after compression. This is a diagram illustrating the rolling process. This is a perspective view showing an example of a removal device. This figure shows the results of the investigation into processing conditions for compression (press working). This is a flowchart of a method for recovering copper from enameled wire according to one embodiment of the present invention.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 1 is a schematic diagram of the copper recovery device 1 (hereinafter simply referred to as copper recovery device 1) used in the copper recovery method for enameled wire according to this embodiment. As shown in Figure 1, the copper recovery device 1 is a device that removes the insulator 22 from the conductor 21 of the enameled wire 2 and recovers the copper or copper alloy that constitutes the conductor 21, and comprises a stripping device 3 and a removal device 4.

The enameled wire 2 is an electric wire used, for example, in vehicle motors, transformers, induction heating coils, etc. The enameled wire 2 may be a round wire with a circular cross-section, or a rectangular wire with a rectangular cross-section. Furthermore, the enameled wire 2 is not limited to round or rectangular wires; for example, its cross-sectional shape may be elliptical or triangular, and its cross-sectional shape is not particularly limited. The enameled wire 2 comprises a conductor 21 made of copper or a copper alloy, and an insulator 22 formed by applying and baking enamel paint around the conductor 21. The insulator 22 may be made of, for example, polyimide, polyamide-imide, polyester, polyurethane, polyester-imide, etc.

In enameled wire 2, the adhesion force of the insulator 22 to the conductor 21 is known to be high. Therefore, when disposing of enameled wire 2, removing the insulator 22 from the conductor 21 and recovering the conductor 21 (i.e., recovering the copper or copper alloy constituting the conductor 21) is not easy. The copper recovery device 1 according to this embodiment makes it possible to easily remove the insulator 22 even in enameled wire 2 where the adhesion force between the conductor 21 and the insulator 22 is high, and to easily recover the copper or copper alloy constituting the conductor 21. A detailed explanation follows below.

(Peeling device 3)
The stripping device 3 is a device that performs a stripping process in which the enamel wire 2 is subjected to compression (pressing) or rolling to separate the insulator 22 from the conductor 21.

Figures 2(a) and 2(b) illustrate the compression process (pressing). When compression is performed using the peeling device 3, the peeling device 3 is a press machine 31 for performing the compression. In the compression process, the enamel wire 2 is crushed in a direction perpendicular to its longitudinal direction. In particular, it is preferable to move the enamel wire 2 along its longitudinal direction and continuously compress it along its longitudinal direction. In this embodiment, a flat rectangular wire is used as the enamel wire 2, and in the peeling process, compression is performed by pressing the enamel wire 2 in the direction of its short axis. At this time, by placing a gauge block 311 between the press machines 31, the enamel wire 2 is formed to the same thickness as the gauge block 311.

When compression is applied, as shown in Figure 2(b), the enameled wire 2 deforms so as to be pushed outward in the direction perpendicular to the pressing direction. This results in compressive stress acting in the pressing direction (the direction of the short axis of the enameled wire 2) and tensile stress acting perpendicular to the pressing direction (the direction of the long axis of the enameled wire 2). As a result, the enameled wire 2 is stretched along its long axis, and due to the difference in elasticity between the conductor 21 and the insulator 22, shear stress is generated at the interface between the conductor 21 and the insulator 22, causing partial delamination between them. By making a cut 22a in this delaminate portion (compressed surface) with the blade 41 of the removal device 4 described later, the insulator 22 can be removed from the conductor 21.

In the compression process, multiple presses may be applied to any point along the longitudinal direction of the enameled wire 2. Applying multiple presses makes it easier for partial delamination to occur between the conductor 21 and the insulator 22. Furthermore, in the compression process, it is preferable to repeatedly run the enameled wire 2 through the compression process and press it again, thereby sequentially applying pressure to the entire length of the enameled wire 2.

Figure 3 shows a photograph of an example of enameled wire 2 after compression processing. Figure 3(a) shows the wire after one press, (b) after two presses, and (c) after two presses with a cut made with a blade. Figure 4(a) shows a cross-section of enameled wire 2 before compression processing, and Figure 4(b) shows a cross-section of enameled wire 2 after compression processing. Figure 4(b) shows the state after a cut 22a has been made in the insulator 22 with a blade. As shown in Figures 3 and 4, it was confirmed that the insulator 22 can be separated from the conductor 21 by compression processing. Optimal processing conditions for compression processing will be described later.

Figure 5 illustrates the rolling process. When rolling is performed during the delamination process, a rolling mill 32 is used as the delamination device 3. The rolling mill 32 compresses and stretches the enameled wire 2 by passing it between a pair of rollers 321. In the rolling mill 321, the rollers 321 are rotated so that their outer surfaces move in the same direction as the enameled wire 2's travel direction at the point of contact with the enameled wire 2. In the rolling process, similar to the compression process described above, the enameled wire 2 is stretched perpendicular to the compression direction (the opposing direction of the rollers 321). Due to the difference in elasticity between the conductor 21 and the insulator 22, shear stress is generated at the interface between the conductor 21 and the insulator 22, resulting in a partial delamination between the conductor 21 and the insulator 22.

(Removal device 4)
The removal device 4 is a device that performs a removal process in which the insulator 22 that has been peeled off from the conductor 21 by the peeling device 3 is peeled off and removed. Figure 6 is a diagram showing an example of the removal device 4. As shown in Figure 6, the removal device 4 makes continuous cuts 22a along the longitudinal direction of the insulator 22 after the peeling process with a blade 41, and removes the insulator 22 from the conductor 21 by continuously peeling off the insulator 22 that has been divided by the cuts 22a.

In this embodiment, a pair of blades 41 are positioned opposite each other, one above the center of the enameled wire 2. Each blade 41 forms a cut 22a along the longitudinal direction of the enameled wire 2, thereby continuously dividing the insulator 22 into two halves, left and right. The divided insulator 22 is then opened to the left and right, and each insulator 22 is guided to the winding roller 43 via the guide roller 42. As the enameled wire 2 is moved along the wire, the insulator 22 is wound onto the winding roller 43, causing it to be pulled to the left and right, and continuously stripped from the conductor 21. Note that the up/down and left/right directions here are relative and are not limited to the vertical and horizontal directions.

The winding tension of the insulator 22 by the winding roller 43 should be between 5% and 90% of the breaking strength of the insulator 22. The breaking strength of the insulator 22 is the value measured by performing a tensile test using an autograph after cutting the insulator 22 from the enameled wire 2 into strips with a width of 1 mm, at a gauge length of 30 mm and a tensile speed of 10 mm/min. This allows the insulator 22 to be peeled off stably without causing deflection or breakage of the insulator 22. Furthermore, the angle θ between the direction in which the insulator 22 is pulled when peeling it from the conductor 21 and the direction in which the enameled wire 2 runs should be between 30 degrees and 160 degrees, preferably between 90 degrees and 160 degrees. This makes it easier to peel the insulator 22 from the conductor 21 and also suppresses breakage of the insulator 22 during winding. Note that the removal device 4 shown in Figure 6 is merely an example, and the specific structure of the removal device 4 can be modified as appropriate.

(Regarding suitable processing conditions for the peeling process)
Compression processing (pressing) was performed while changing the processing conditions, and it was confirmed whether the insulator 22 could be easily peeled off the enameled wire 2 after processing. The results are shown in Figure 7. In Figure 7, the areas from which the insulator 22 could be easily peeled off are indicated by hatching. A flat rectangular wire was used as the enameled wire 2, and the press was applied in the direction of its short axis.

As shown in Figure 7, when performing compression processing, it is desirable to perform the processing so that the rate of change in thickness is 54.5% or more. The rate of change in thickness can be obtained by the following formula, where A is the thickness of the enameled wire 2 before processing (for example, the thickness in the short axis direction of a rectangular wire) and B is the thickness of the enameled wire 2 after processing.
Change in thickness (%) = {(A - B) / A} × 100

Furthermore, as shown in Figure 7, when performing compression processing, it is desirable to perform the processing so that the rate of change in Vickers hardness is 105.5% or more. The rate of change in Vickers hardness can be obtained by the following formula, where C is the Vickers hardness before processing and D is the Vickers hardness after processing. The Vickers hardness was measured according to the method described in JIS Z2244 (2009). The measurement conditions were a load of 200g and a holding time of 15 seconds. The cross-section of the sample was mirror-polished, and the average value of the values measured at two locations near the center of the conductor 21 was used.
Change in Vickers hardness (%) = {(D - C) / C} × 100

Figure 7 shows an example of compression processing, but it is desirable to apply similar conditions to rolling processing as well. That is, when rolling is performed in the peeling process, it is desirable to perform the processing so that the change in thickness is 54.5% or more and the change in Vickers hardness is 105.5% or more, just as in the case of compression processing.

(Method for recovering copper from enameled wire)
Figure 8 is a flowchart of the copper recovery method for enameled wire according to this embodiment. As shown in Figure 8, in the copper recovery method for enameled wire according to this embodiment, the peeling step S1 and the removal step S2 are repeated in succession to recover the copper or copper alloy that constitutes the conductor 21 of the enameled wire 2.

In step S1, the stripping process, the stripping device 3 is used to compress or roll the enameled wire 2 to strip the insulator 22 from the conductor 21. It is preferable to perform this process so that the change in thickness is 54.5% or more and the change in Vickers hardness is 105.5% or more. Note that in the stripping process, it is not necessary for the entire insulator 22 to be stripped from the conductor 21; it is sufficient for stripping to occur only in a portion of the insulator 22 to serve as a starting point for the stripping process.

In step S2, the removal process, the removal device 4 is used to peel off and remove the insulator 22 that has been detached from the conductor 21. Here, as shown in Figure 6, cuts 22a are made continuously along the longitudinal direction of the insulator 22 after the peeling process using the blade 41. The insulator 22 is then removed from the conductor 21 by continuously peeling off the insulator 22 divided by the cuts 22a. The area where the cuts 22a are made is preferably a compressed surface that has undergone compression or rolling. However, the method is not limited to this; any method that can peel off and remove the insulator 22 may be used. The conductor 21 from which the insulator 22 has been removed is recovered, for example, by being wound onto a winding drum.

(Operation and effects of the embodiment)
As described above, the copper recovery method for enameled wire according to this embodiment includes a peeling step of applying compression or rolling to the enameled wire 2 to peel off the insulator 22 from the conductor 21, and a removal step of peeling off and removing the insulator 22 that has been peeled off from the conductor 21.

By performing compression or rolling processes, the difference in the elasticity of the conductor 21 and the insulator 22 can be utilized to separate the insulator 22 from the conductor 21, making it possible to easily peel and remove the insulator 22 from the conductor 21. This embodiment has a low environmental impact because it does not use chemicals that require wastewater treatment. Furthermore, because heat treatment is unnecessary, the conductor 21 does not oxidize, and the carbonized insulator 22 does not integrate with the conductor 21, allowing for the recovery of high-purity copper. Moreover, this embodiment does not require treatment using expensive chemicals, and general compression or rolling equipment can be used, resulting in very low equipment and processing costs, and enabling the recovery of copper or copper alloys at a low cost.

(Variant)
In the above embodiment, a case was described in which the peeling process and the removal process are performed on a single manufacturing line. However, the manufacturing line may be divided into separate processes, such as winding the enameled wire 2 once after the peeling process and then performing the removal process on the wound enameled wire 2. In addition, both compression and rolling processes may be performed in the peeling process to make the insulator 22 easier to peel off.

(Summary of the embodiments)
Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[1] A method for recovering copper from an enameled wire (2) having an insulator (22) surrounding a conductor (21) made of copper or a copper alloy, comprising: a peeling step of applying compression or rolling to the enameled wire (2) to peel the insulator (22) from the conductor (21); and a removal step of peeling off and removing the insulator (22) that has been peeled off from the conductor (21).

[2] The copper recovery method for enameled wire according to [1], wherein the enameled wire (2) is a flat rectangular wire, and in the stripping step, the compression process is performed by pressing the enameled wire (2) in the direction of its short axis, and in the compression process, the thickness change rate in the direction of the short axis is 54.5% or more.

[3] The method for recovering copper from enameled wire according to [1], wherein the compression process is performed in the stripping step such that the rate of change in Vickers hardness is 105.5% or more.

[4] The method for recovering copper from enameled wire according to [1], wherein in the removal step, cuts (22a) are made continuously along the longitudinal direction of the insulator (22) after the peeling step using a blade (41), and the insulator (22) separated by the cuts (22a) is continuously peeled off to remove the insulator (22).

(Note)
Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. In addition, the present invention can be implemented with appropriate modifications without departing from its spirit.

1... Copper recovery device for enameled wire 2... Enameled wire 21... Conductor 22... Insulator 3... Stripping device 31... Swaging machine 32... Die drawing machine 33... Nozzle machine 4... Removal device 41... Blade

Claims (2)

A method for recovering the copper or copper alloy constituting the conductor by removing the insulator from an enameled wire having an insulator around a conductor made of copper or a copper alloy,
A stripping step in which the enameled wire is subjected to compression or rolling to remove the insulator from the conductor,
The process includes a removal step of peeling off and removing the insulator that has been removed from the conductor,
The aforementioned enameled wire is a flat rectangular wire,
In the peeling step, the compression process is performed by pressing the enamel wire in the direction of its short axis, and in the compression process, the rate of change in thickness in the direction of the short axis is 54.5% or more, and the rate of change in Vickers hardness is 105.5% or more.
Methods for recovering copper from enameled wire. In the removal step, the insulator after the peeling step is continuously cut with a blade along the longitudinal direction, and the insulator divided by the cuts is continuously peeled off to remove the insulator.
A method for recovering copper from enameled wire according to claim 1.