阅读说明：本技术 包覆电线的处理方法 (Method for processing coated electric wire ) 是由 高桥宪史 村冈秀 林浩志 于 2019-10-18 设计创作，主要内容包括：本发明涉及一种包覆电线的处理方法,其中,对于在金属线上包覆有树脂的包覆电线,在碱共存下,且在非燃烧气氛下,将包覆电线进行低温加热而使包覆树脂脆化,再将脆化的包覆树脂破碎,分离包覆树脂与金属线。(The present invention relates to a method for treating a coated electric wire in which a resin is coated on a metal wire, the coated electric wire is subjected to low-temperature heating in the presence of an alkali and in a non-combustion atmosphere to embrittle a coating resin, and the embrittled coating resin is crushed to separate the coating resin from the metal wire.)

1. A method for processing a covered electric wire,

in a coated electric wire in which a metal wire is coated with a resin, the coated electric wire is heated at a low temperature in the presence of an alkali and in a non-combustion atmosphere to embrittle the coated resin, the embrittled coated resin is crushed, and the coated resin and the metal wire are separated.

2. The method of processing a covered electric wire according to claim 1,

the non-combustion atmosphere is superheated steam atmosphere, nitrogen atmosphere, carbonic acid gas atmosphere, or the mixture of the two atmospheres, and the low-temperature heating temperature is 180-270 ℃.

3. The method of processing a covered electric wire according to claim 1 or 2,

and simultaneously carrying out low-temperature heating and crushing on the coated electric wire.

4. The method of processing a covered electric wire according to any one of claims 1 to 3,

the coated electric wire is heated at a low temperature of 180 to 270 ℃ in a non-combustion atmosphere using a heating furnace having a crushing medium in the furnace, and the coated resin is embrittled and crushed at the same time.

Technical Field

The present invention relates to a method for efficiently separating a metal wire and a coating resin from a coated electric wire. More specifically, the present invention relates to a method for making a coating resin brittle and easily separating the resin from a metal wire when the coated wire is heat-treated under relatively mild conditions of about 200 ℃.

The present application claims priority based on patent application No. 2018-197748 filed in japan on 19.10.2018, and the contents thereof are incorporated herein by reference.

Background

The coated wire has a shape in which a metal wire as a conductor is coated with an insulating resin coating material such as a vinyl chloride resin, and is widely used as a basic component of various electric devices such as an electric part of an automobile, a home electric appliance, a communication device, and a computer. A large amount of waste coated electric wires are produced along with the disposal of such various electric devices. Since the coated electric wire uses a metal wire as a conductor such as a copper wire, the metal wire such as a copper wire is recovered from the waste coated electric wire and recycled. However, in the coated electric wire, since the resin coating material is closely coated around the metal wire, the metal wire needs to be separated from the coating resin in order to recover the metal wire for recycling.

As a method for processing a coated electric wire, the following methods have been known.

The coated electric wire is finely cut and the coating resin is peeled from the copper wire, and then the cut ultra-fine copper wire and the coating resin are subjected to wet specific gravity separation to recover the copper wire (patent document 1).

The coating resin is burned, and the burned residue is mechanically removed to recover the copper wire (patent document 2).

A method of carbonizing a coating resin by heat treatment of a coated electric wire in a non-oxidizing atmosphere and separating the carbide to recover a copper wire (patent document 3).

Patent document 1: japanese laid-open patent publication No. 2012-089358

Patent document 2: japanese laid-open patent publication No. 61-143529

Patent document 3: japanese patent No. 05134719

In the processing method of patent document 1, after the coated wire is finely cut, the metal wire and the coating resin are separated by wet specific gravity. This method is a method of physically peeling off the coating resin from the metal wire by a mechanical pressure at the time of cutting the coated electric wire, and therefore, it is necessary to cut the coated electric wire very finely. Further, since the resin-coated fine pieces are likely to remain in the metal wire, there is a problem that the quality of the metal is reduced. Further, since it is necessary to finely cut the metal wire to reliably separate the metal wire from the coating resin, there is a problem that the blade of the crusher is easily damaged, the crushing time is long, and the treatment efficiency is poor.

In the treatment method of patent document 2, the coating resin is removed by burning, and therefore the coating resin can be almost completely removed, but heating in an oxidizing atmosphere causes a problem that a part of the conductive metal is oxidized and the quality of the metal is degraded. Further, the thermal decomposition of the resin-coated vinyl chloride resin generates corrosive hydrogen chloride gas, which causes problems that the processing apparatus and piping are easily corroded, and the processing of the exhaust gas is complicated. Furthermore, harmful dioxins may be generated.

In the treatment method of patent document 3, in order to suppress the generation of dioxin, the coated electric wire is heated in oil or under non-oxygen conditions to carbonize the coating resin. The metal wire covering the electric wire can be prevented from being oxidized.

However, when the coated electric wire is heated in oil, there is a problem that the oil adheres to the surface of the metal wire and the quality of the metal is degraded, and there is a problem that the coating resin is not sufficiently carbonized by heating under non-oxygen conditions. Further, the treatment method of patent document 3 shows that the residual chlorine concentration is reduced and the heating time is shortened by removing the generated hydrogen chloride or the like by allowing an alkaline substance to coexist in the oil, but the above-mentioned problem in heating in the oil is not solved. Further, when the coated electric wire is heated in oil or under non-oxygen conditions to carbonize the coating resin, the process is often prolonged, which results in a loss of economic efficiency.

Disclosure of Invention

The present invention solves the above problems of the conventional processing methods and provides a method for separating a metal wire and a coating resin in a short time more efficiently than the conventional method, in which the metal wire and the coating resin are not peeled off by shearing of the coated wire and the coating resin is not burned by performing a heat treatment in a non-combustion atmosphere.

The present invention is a method for processing a coated electric wire having the following characteristics.

(1) A method for processing a coated electric wire, characterized in that a coated electric wire in which a metal wire is coated with a resin is subjected to low-temperature heating in the presence of an alkali and in a non-combustion atmosphere to embrittle the coated resin, and the embrittled coated resin is crushed to separate the coated resin from the metal wire.

(2) The method for processing a covered electric wire according to item (1), wherein the non-combustion atmosphere is a superheated steam atmosphere, a nitrogen atmosphere, a carbonic acid gas atmosphere, a mixed atmosphere thereof, or an atmosphere, and the temperature of the low-temperature heating is 180 ℃ to 270 ℃.

(3) The method for processing a covered electric wire according to the above (1) or (2), wherein the low-temperature heating and the crushing of the covered electric wire are performed simultaneously.

(4) The method for processing a coated electric wire according to any one of the above (1) to (3), wherein the coated electric wire is heated at a low temperature of 180 to 270 ℃ in a non-combustion atmosphere using a heating furnace having a crushing medium in the furnace, and the embrittlement and crushing of the coating resin are simultaneously performed.

The method for treating a coated electric wire according to the present invention can effectively embrittle the coating resin by heat treatment in the presence of an alkali, and can suppress the generation of corrosive hydrogen chloride gas or dioxins.

Further, in the treatment method of the present invention, since the low-temperature heating treatment is performed in a non-combustion atmosphere, the metal such as copper used as the metal wire of the covered electric wire can be recovered without oxidizing the metal, and the quality of the recovered metal can be improved.

In the treatment method of the present invention, since low-temperature heat treatment is used, the amount of gas generated is small, the treatment of exhaust gas is easy, and the combustion cost can be reduced. Also, the recovered coating resin can be effectively used in alternative fuels and the like.

In addition, in the method of heating at a low temperature while applying physical impact by crushing the medium, the treatment can be performed in a shorter time and at a low cost.

Drawings

Fig. 1 is a schematic process diagram of a method of processing a coated electric wire according to the present embodiment.

Fig. 2 is a schematic process diagram of the method for treating the coated electric wire according to the present embodiment in which heating and crushing are performed simultaneously.

Detailed Description

The embodiment of the method for treating a coated electric wire according to the present invention will be specifically described below.

The method for processing a coated electric wire according to the present embodiment is characterized by comprising: in a coated electric wire in which a resin is coated on a metal wire, the coated electric wire is heated at a low temperature in the presence of an alkali and in a non-combustion atmosphere to embrittle a coating resin, and the embrittled coating resin is crushed to separate the coating resin from the metal wire. Fig. 1 schematically shows a processing method according to the present embodiment.

In addition, the non-combustion atmosphere may be referred to as a non-combustion condition.

Generally, a coated electric wire is formed by coating a metal wire such as a copper wire with an insulating resin such as vinyl chloride resin or polyethylene resin. The processing method of the present embodiment can be widely applied to general coated electric wires. The coated electric wire may be roughly crushed for disposal.

In the rough crushing, the coated electric wire may be crushed by a biaxial crusher or the like so that the long side of the coated electric wire is 10cm or less.

In the treatment method of the present embodiment, the coated electric wire is heated at a low temperature in a non-combustion atmosphere while being made to coexist with an alkali, thereby embrittling the coated resin. The base coexists in the coated electric wire, whereby the coating resin can be effectively embrittled. It is considered that this is because the plasticizer contained in the coating resin is decomposed by the alkali to promote embrittlement of the resin. Further, the alkali can capture hydrogen chloride (HCl) generated by thermal decomposition of vinyl chloride resin or the like as a coating resin, and can greatly reduce the amount of hydrogen chloride contained in the exhaust gas. Further, the alkali physically adsorbs tar generated by the deterioration of the resin, and thus, clogging of piping or blocking of a treated product due to tar can be suppressed.

As the base, for example, a hydroxide, an oxide, or a carbonate of an alkaline earth metal, or a mixture of these can be used. Specifically, calcium hydroxide, calcium oxide, calcium carbonate, or the like can be used. Furthermore, fly ash generated by burning municipal waste, smoke generated by burning industrial waste, or hydride obtained by dechlorinating and washing dust collected in a chlorine bypass system of a cement plant by water washing or the like can be used, and a mixture of these can be used.

The most preferable alkali is calcium hydroxide having a good resin embrittlement and hydrogen chloride gas trapping effect, and when a mixture is used, an alkali containing calcium hydroxide in a large amount is preferable.

The base may be in the form of a powder, a suspension or an aqueous solution. The amount of the alkali to be added may be about 1/5 to about 2/3 weight of the coated electric wire, and is more preferably 1/5 to 1/3 weight.

Since the treatment method of the present embodiment is a method of embrittling the coating resin without burning it, the coated electric wire is heated at a low temperature in a non-burning atmosphere in the coexistence of alkali. The non-combustion atmosphere is a superheated steam atmosphere, a nitrogen atmosphere, a carbonic acid gas atmosphere, or a mixed atmosphere thereof, and may be performed under the atmosphere if the coating resin does not combust at the heating temperature.

The superheated steam atmosphere, nitrogen atmosphere, carbonic acid gas atmosphere, and mixed atmosphere thereof are preferably non-oxidizing atmospheres because oxidation of the metal wire can be suppressed.

Superheated steam is most effective for resin embrittlement. And the specific heat of the superheated steam is large, and temperature control is easy, so that it is preferable.

In the treatment method of the present embodiment, the temperature for low-temperature heating is preferably 180 ℃ to 270 ℃, and more preferably 200 ℃ to 250 ℃. Embrittlement of the coating resin does not proceed sufficiently at a heating temperature of less than 180 ℃. On the other hand, if the heating temperature exceeds 270 ℃, the amount of thermal decomposition gas generated from the coating resin increases, which is not preferable because the waste gas treatment becomes complicated and the operation cost increases.

In the treatment method of the present embodiment, since low-temperature heating in the above temperature range is used, the vinyl chloride resin and the like are not decomposed. Also, oxidation of the metal hardly proceeds. In addition, the heating temperature is low, and the operation cost can be reduced. As the heat source, waste heat of the plant can be utilized.

As the heating device, a batch type fixed furnace, a continuous type heating furnace such as a rotary kiln, or the like can be used. The heating time may be, for example, about 50 minutes to 90 minutes for a treatment amount (coated wire + alkali) of 2 kg.

The heated treatment was cooled to room temperature and crushed. The coating resin is solidified by cooling after the heat treatment, and therefore can be easily broken. The crushing method may be shear crushing, impact crushing, or both. As the crusher, a shear crusher (single shaft crusher, twin shaft crusher, chopper), an impact crusher (vertical crusher, ball mill, rod mill), or the like can be used. By this crushing treatment, the brittle resin is finely crushed, and therefore can be easily separated from the metal wire.

The elongated metal wires and the fine resin particles are obtained by the crushing treatment, and therefore, these can be easily separated into the metal wires and the resin by physical sorting such as sieving or specific gravity sorting. As the specific gravity separator, a dry specific gravity separator (an air separator, an air separation table) or a wet specific gravity separator (a thin fraction separator, a sink-float separator, or the like) can be used.

In the processing method of the present embodiment, low-temperature heating (embrittlement of the resin) of the coated electric wire and crushing can be performed simultaneously. For example, when the coated electric wire is heated at a low temperature of 180 to 270 ℃ in a non-combustion atmosphere using a heating furnace having a crushing medium in the furnace, the coated electric wire is heated while being subjected to mechanical impact. In such a treatment method, embrittlement and crushing of the coating resin are performed simultaneously, and therefore, the treatment can be performed in a short time at low cost.

As a method of applying an impact to the coated electric wire, for example, a crushing medium such as a ball or a rod may be put into a furnace of a heating furnace such as a rotary kiln. As the material of the crushing medium, a metal such as ceramic, iron, or SUS may be used. Such a crushing medium promotes heat conduction to the coated electric wire, and therefore embrittlement of the coating resin can be effectively performed. Further, it is more preferable to provide a tappet or a stirring blade in a retort of the rotary kiln because the crushing medium flows more easily to promote the crushing. In addition, when the coated electric wire is rotated together with the retort of the rotary kiln and repeatedly dropped by its own weight to be crushed, the impact due to dropping is increased, and thus the crushing medium does not need to be put into the furnace.

As shown in fig. 2, the crushed material that has been heated and crushed at the same time may be taken out of the furnace, cooled, subjected to primary sorting such as screening to remove alkali residues, further crushed again, and subjected to secondary sorting such as specific gravity sorting to separate the crushed material into a resin component and a metal component. By performing such secondary crushing and secondary sorting, the effect of classification can be improved. Further, since the heating and the crushing are performed simultaneously, the secondary crushing can be performed in a short time. The crushing method may be shear crushing, impact crushing, or both. As the crusher, a shear crusher (single shaft crusher, twin shaft crusher, chopper), an impact crusher (vertical crusher, impact crusher), or the like can be used.

In the treatment method of the present embodiment, the coated electric wire is heated at a low temperature in the presence of alkali, and thus embrittlement of the resin is promoted by the alkali without burning the coated resin, so that exhaust gas is not generated or the amount of exhaust gas is greatly reduced, and the exhaust gas treatment in the subsequent stage is facilitated. Specifically, according to the treatment method of the present embodiment, the volatilization rate of the resin after the heat treatment can be suppressed to, for example, 10% or less.

The volatilization rate (X) of the resin is the weight ratio of the difference (A-B) between the weight (B) of the resin recovered after the heat treatment and the weight (A) of the resin before the heat treatment to the weight (A) of the resin in the covered wire before the heat treatment, as shown in the following formula [1 ].

X＝{(A-B)/A}×100％……[1]

In addition, since the metal coating the electric wire does not volatilize during low-temperature heating, the volatilization rate of the resin can be grasped from the weight reduction rate of the coated electric wire. Specifically, as shown in the following formula [2], the weight loss rate (Z) of the coated electric wire is a weight ratio of the difference (C-D) between the weight (D) of the heat-treated material recovered after the heat treatment and the weight (C) before the heat treatment to the weight (C) of the coated electric wire before the heat treatment, and is equal to the volatilization rate (X) of the resin.

Z＝{(C-D)/C}×100％……[2]

According to the treatment method of the present embodiment, for example, the resin peeling rate can be improved to 80% or more. As shown in the following formula [3], the resin peeling rate (Y) is a weight ratio of the weight (M) of the resin recovered after physical sorting to the weight (L) of the resin of the coated electric wire after heat treatment.

Y＝(M/L)×100％……[3]

In order to obtain a sufficient resin peeling effect, the resin peeling rate is preferably 80% or more, and more preferably 85% or more.

[ example 1]

A coated electric wire (a copper wire coated with vinyl chloride resin: about 0.2mm to 0.3mm in diameter and about 1.0mm to 3.0mm in diameter) was roughly crushed in a biaxial crusher to a length of about 5cm or less. Calcium hydroxide [ Ca (OH) ] is added as an alkali to the roughly crushed coated wire₂]And putting the mixture into a heating furnace, and heating the mixture for 60 minutes at 180-250 ℃ in the atmosphere of superheated water vapor. Heating, taking out from the furnace, cooling to room temperature, placing into a ball mill, pulverizingThe crushed material is separated into copper wires and resin particles by sieving and specific gravity separation. The results are shown in table 1.

The resin peeling rate (Y) in the table is a value obtained by the above formula [3 ].

The resin weight (L) of the coated electric wire after the heat treatment is obtained by the following procedure: the weight of the copper wire obtained from the diameter of the copper wire was subtracted from the weight of the coated electric wire after heat treatment measured using an electronic balance.

With respect to the weight (M) of the resin recovered after physical sorting, measurement was performed using an electronic balance.

The resin volatility (X) in the table is a value obtained by the above formula [1 ].

The resin weight (a) of the coated electric wire before the heat treatment was determined by the following procedure: the weight of the copper wire determined from the diameter of the copper wire was subtracted from the weight of the coated wire before heat treatment measured using an electronic balance.

The weight (B) of the resin recovered after the heat treatment is the same as the weight (L) of the resin of the coated electric wire after the heat treatment.

As shown in nos. 1 to 6 of table 1, when the coated electric wire added with calcium hydroxide is subjected to heat treatment at 180 to 250 ℃ in a non-combustion atmosphere, the resin peeling rate is 81 to 98%, and most of the coating resin can be peeled. Further, the volatilization rate of the resin is 10% or less, and the loss of the resin due to the generation of the thermal decomposition gas is small. The resin peeling rate is preferably 80% or more in order to obtain a sufficient peeling effect of the resin, and the volatilization rate of the resin is preferably 10% or less in order to suppress the amount of thermally decomposed gas of the resin.

As shown in nos. 4 to 5 of table 1, the coated electric wire can be sufficiently separated from the coating resin by adding 1/5 to 2/3 parts by weight of calcium hydroxide. Further, as shown in No.6, even when heating is performed in a nitrogen atmosphere, the coating resin can be sufficiently separated.

On the other hand, as shown in No.7 of Table 1, when the heating temperature was 150 ℃, the resin peeling rate was very low at 12%, and the resin was not sufficiently peeled. Further, as shown in No.8, when the heating temperature was 300 ℃, the volatilization rate of the resin was 15%, and the amount of the thermally decomposed gas generated was large, so that the loss of the resin was large.

On the other hand, as shown in No.9, when heating was performed under superheated steam without adding calcium hydroxide, the resin peeling rate was 53%, and the resin was not sufficiently peeled.

In this way, the resin peeling ratios of nos. 1 to 6 were about 1.5 times to about 1.8 times as high as that of No.9, and peeling of the coating resin could be greatly promoted by allowing an alkali to coexist when heating at a low temperature.

[ Table 1]

(Note) Nos. 1 to 6 are examples of the present invention, and Nos. 7 to 9 are comparative samples

[ example 2]

As the coated electric wire, a coated electric wire in which an automobile wire harness (copper wire diameter: about 0.2mm to 0.3mm, wire diameter of automobile wire harness: about 1.0mm to 3.0 mm) (hereinafter referred to as WH) is roughly crushed with a biaxial crusher to a length of about 5cm or less is used.

WH1.5kg, calcium hydroxide [ Ca (OH) ] as a base₂]0.5kg of SUS spheres as a crushing medium60 pieces) were charged into the batch rotary kiln, and then heat-treated at a heating temperature of 220 ℃ in a superheated steam atmosphere. After heating for a predetermined time (60min), the resultant was cooled to 80 ℃ or less and the heat-treated product was taken out. The heat-treated material was separated into a heat-treated material (oversize) and a powder (mainly calcium hydroxide: undersize) by primary separation using a sieve having a mesh size of 0.5 mm.

The heat-treated material (oversize) was crushed by a chopper equipped with a screen having a mesh of 8 mm. The crushed material was separated into copper wires and resin particles by air classification and sieving (mesh size: W0.8mm. times.L 10 mm).

The results are shown in table 2 (sample 11). The weight reduction rate (Z) in the table is a value obtained by the above formula [2 ].

The resin peeling rate (Y) in the table is a value obtained by the above formula [3 ].

The weight (C) of the WH before the heat treatment and the weight (D) of the heat-treated material recovered after the heat treatment were measured using an electronic balance.

The resin weight (L) of the WH after the heat treatment was determined by the following procedure: the weight of the copper wire as determined from the diameter of the copper wire was subtracted from the weight of the heat-treated WH measured using an electronic balance.

The weight (M) of the resin recovered after physical sorting was measured using an electronic balance.

Sample 12 in table 2 was subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that the heating atmosphere was nitrogen. The results are shown in Table 2.

Sample 13 in table 2 was subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that the heating atmosphere was set to be under the air. The results are shown in Table 2.

Sample 14 in table 2 was subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that the amount of calcium hydroxide was changed to the amount shown in table 2. The results are shown in Table 2.

Samples 15 to 16 in table 2 were subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that the heating time was changed to the time shown in table 2. The results are shown in Table 2.

Samples 17 to 19 in table 2 were subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that the heating temperature was set to the temperature shown in table 2. The results are shown in Table 2.

In sample 20 of Table 2, calcium carbonate (CaCO) was used as the alkali powder₃) Except for this, heat treatment, crushing treatment, and physical sorting were performed in the same manner as in sample 11. The results are shown in Table 2.

Samples B1 and B2 in table 2 were subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11, except that the heating temperature was set to the temperature shown in table 2. The results are shown in Table 2.

Sample B3 in table 2 was subjected to heat treatment, crushing treatment, and physical sorting in the same manner as sample 11 except that no alkali was added. The results are shown in Table 2. In sample B3, the softened and melted resin adhered to the inner wall of the rotary kiln, and it was difficult to recover the heat-treated product.

As shown in samples 11 to 20, when the coated electric wire is subjected to heat treatment at 200 to 250 ℃ in the presence of alkali (calcium hydroxide or calcium carbonate), the resin peeling rate is 93.4 to 99.5%, and most of the coating resin can be peeled. The weight loss rate was 6.7% or less, and there was almost no resin loss due to thermal decomposition gas.

Further, as shown in samples 11 to 13, the coating resin can be sufficiently separated in any atmosphere of superheated steam, a nitrogen atmosphere, and an atmospheric atmosphere. Further, as shown in samples 11 to 14, the coated resin can be sufficiently separated by adding 1/5 to 1/3 parts by weight of calcium hydroxide to the coated electric wire. As shown in samples 11 to 19, the coated resin can be sufficiently separated by heating at a heating temperature of 200 to 250 ℃ for 30 to 120 minutes. Further, as shown in sample 20, even when calcium carbonate is used as the alkali, the coated resin can be more sufficiently separated.

On the other hand, as shown in sample B1, when the heating temperature was 170 ℃, the resin peeling rate was low, 78.1%, and the resin was not sufficiently peeled. Further, as shown in sample B2, when the heating temperature is 300 ℃, the weight loss rate is 13.9%, and the amount of thermally decomposed gas generated is large, so that the loss of resin is large. Further, as shown in sample B3, when the coated electric wire was heated without adding an alkali, the resin peeling rate was low, 78.4%, and the resin was not sufficiently peeled. Further, there is a problem that the softened and melted resin adheres to the inner wall of the rotary kiln.

In this way, peeling of the coating resin can be greatly promoted by heating the coating resin at a temperature of 200 to 250 ℃ in the presence of an alkali while applying a physical impact.

[ comparative example 1]

The same WH as in sample 11 was not subjected to heat treatment, but was crushed by a chopper equipped with a screen having a mesh size of 8 mm. The crushed material was separated into copper wires and resin particles by air classification and sieving (mesh size: W0.8mm. times.L 10 mm). As a result, the resin peel ratio was 79.8%, and the resin was not sufficiently peeled.

[ Table 2]

Samples 11 to 20 are examples, and samples B1 to B3 are comparative samples

Industrial applicability

In the method for processing a covered electric wire according to the present invention, not only can a metal such as copper used as a metal wire of a covered electric wire be recovered without oxidation, but also the amount of gas generated during the processing can be reduced, and the metal wire of the covered electric wire can be efficiently recovered.