Method for recycling insulating layers of insulated wires and cables, and method for manufacturing insulated wires and cables

Abstract

To provide a method for recycling the insulating layers of collected insulated wires and cables without performing complicated processing or incurring excessive costs. [Solution] A method for recycling the insulating layer of an insulated electric wire or cable that solves the above-mentioned problems is a method for recycling the insulating layer of an insulated electric wire or cable that has at least a conductor and an insulating layer containing polyethylene or cross-linked polyethylene arranged around the conductor, and includes the steps of separating the conductor from the insulating layer, producing recycled naphtha from the separated insulating layer, and mixing the recycled naphtha with new naphtha to form a new insulating layer of an insulated electric wire or cable. In the recycling method, impurities are removed in the step of producing the recycled naphtha.

Description

[Technical Field]

[0001] The present invention relates to a method for recycling the insulating layer of an insulated wire or cable, and a method for producing an insulated wire or cable. [Background technology]

[0002] Cross-linked polyethylene and polyethylene (collectively referred to herein as "polyethylene-based resins") are widely used in the insulating layers of insulated wires and cables due to their excellent electrical insulation and mechanical properties. For example, in high-voltage cables used for power transmission, distribution, wiring, etc., an insulating layer made of cross-linked polyethylene is disposed around the conductor. In high-voltage cables having an insulating layer made of cross-linked polyethylene, such as CV cable, an inner semiconductive layer made of tape or extrusion molding is disposed inside the insulating layer, and an outer semiconductive layer made of tape or extrusion molding, a shielding layer, and a sheath made of polyvinyl chloride are disposed outside the insulating layer. On the other hand, insulated wires for high-voltage overhead electric lines also have an insulating layer made of polyethylene or cross-linked polyethylene disposed around the conductor. In such insulated wires, a separator tape or the like may be disposed between the conductor and the insulating layer.

[0003] Traditionally, used or old insulated wires and cables have been collected and the conductors (metals) have been recycled. However, components other than the conductors (such as insulating layers) have often been disposed of in landfills due to the difficulty and cost involved in recycling.

[0004] In recent years, from the viewpoint of environmental protection, etc., it has become desirable to recycle materials other than conductors as well. In response to such demands, for example, it has been proposed to separate the conductor from the surrounding material (resin) and use the separated resin as a reducing agent in a blast furnace (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-75094 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 does not fully utilize the resin. As mentioned above, polyethylene resins are often used in the insulating layers of insulated wires and cables, and recycling these polyethylene resins would be extremely useful. However, insulating layers often contain materials other than polyethylene resins, including separators and semiconducting layers, making it difficult to isolate the polyethylene resin alone. Furthermore, the polyethylene resin in the insulating layers of recovered insulated wires and cables may be degraded or contaminated. In such cases, even if the polyethylene resin can be isolated, quality issues remain. Furthermore, if the polyethylene resin is cross-linked polyethylene, recycling requires the application of heat and shear force to sever the cross-linked chains. However, severing the cross-linked chains requires specialized equipment and is costly.

[0007] The present invention has been made in view of these problems. A primary object of the present invention is to provide a method for recycling the insulating layer of recovered insulated wires and cables without incurring the excessive costs associated with complex processes such as separation and thermoplasticization. Another primary object of the present invention is to provide a method for manufacturing insulated wires and cables using the above-mentioned method for recycling the insulating layer of insulated wires and cables. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present invention, A method for recycling an insulating layer of an insulated wire or cable having at least a conductor and an insulating layer containing polyethylene or cross-linked polyethylene arranged around the conductor, separating the conductor from the insulating layer; generating recycled naphtha from the separated insulating layer; mixing the recycled naphtha and new naphtha to produce a material for forming new insulated wires and cables; Including, In the step of producing the recycled naphtha, a treatment for removing impurities is performed. A method for recycling the insulation layer of insulated wire and cable is provided.

[0009] In order to solve the above problem, according to one aspect of the present invention, A process for separating a conductor from an insulating layer of an insulated wire / cable, the conductor including a conductor and an insulating layer containing polyethylene or cross-linked polyethylene and disposed around the conductor; generating recycled naphtha from the separated insulating layer; a step of mixing the recycled naphtha and new naphtha to form a component constituting a new insulated wire / cable; Including, In the step of producing the recycled naphtha, a treatment for removing impurities is performed. A method for making insulated wire and cable is provided. [Effects of the Invention]

[0010] According to the present invention, it is possible to recycle the insulating layers of collected insulated wires and cables without using expensive equipment or performing complicated processes. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the flow of a method for recycling an insulating layer of an insulated wire or cable according to one embodiment of the present invention. [Figure 2]FIG. 2A is a schematic cross-sectional view showing an example of a cable to which the method for recycling the insulating layer of an insulated wire / cable of the present invention can be applied, and FIG. 2B is a schematic cross-sectional view showing an example of an insulated wire to which the method for recycling the insulating layer of an insulated wire / cable of the present invention can be applied. DETAILED DESCRIPTION OF THE INVENTION

[0012] The method for recycling the insulating layer of an insulated wire or cable of the present invention relates to a method for recycling the insulating layer of an insulated wire or cable having at least a conductor and an insulating layer containing polyethylene or cross-linked polyethylene arranged around the conductor. The recycling method of the present invention makes it possible to utilize the polyethylene or cross-linked polyethylene in the insulating layer, which has traditionally been difficult to utilize, as a material for producing new insulated wires or cables. In other words, new insulated wires or cables can be produced using the recycling method of the present invention.

[0013] FIG. 1 shows the flow of a method for recycling the insulating layer of an insulated wire or cable according to one embodiment of the present invention. In this embodiment, as shown in FIG. 1, the conductor and insulating layer of a recovered insulated wire or cable are separated (S110, hereinafter also referred to as the "separation step"). Then, recycled naphtha is produced from the insulating layer separated in the separation step S110 (S120, hereinafter also referred to as the "naphtha production step"). Then, the recycled naphtha obtained in the naphtha production step S120 and new naphtha are mixed to produce materials for new insulated wires or cables (materials for forming insulating layers and sheaths) (S130, hereinafter also referred to as the "reuse step"). Note that this recycling method may include further steps other than those described above.

[0014] The recycling method will be specifically described below using the example of a CV cable 100 shown in FIG. 2A as the collected insulated wire / cable. The CV cable 100 includes a conductor 10 and, arranged around the conductor, an inner semiconductive layer 21 made of a tape or extrusion molded product, an insulating layer 22 containing cross-linked polyethylene, an outer semiconductive layer 23 made of a tape or extrusion molded product, a shielding layer 24, and a sheath 60. However, the CV cable 100 may also include other components. The CV cable 100 may be a used cable, or one that has been unused and is no longer needed. It may also be a semi-finished product or a finished product that is not used in a finished product, such as a surplus portion generated during the manufacturing process.

[0015] (separation process) In the separation step S110, the recovered CV cable 100 is separated into the conductor 10 and a portion including the insulating layer 22. In this embodiment, the CV cable 100 is separated into the conductor 10, the sheath 60, and other portions (the inner semiconductive layer 21, the insulating layer 22, the outer semiconductive layer 23, and the shielding layer 24 (hereinafter, these are also collectively referred to as the "intermediate layer 20").

[0016] The conductor 10 of the CV cable 100 contains copper and is highly recyclable. Separating the conductor 10 in advance facilitates recycling of the conductor 10 itself. Separating the conductor 10 also facilitates the naphtha production process S120, described below. Meanwhile, the sheath 60 of the CV cable 100 contains polyvinyl chloride. Polyvinyl chloride is not directly used as a raw material for naphtha in the naphtha production process S120, described below. In other types of cables besides CV cables, the sheath 60 may be made of a material other than polyvinyl chloride, such as a polyethylene-based resin. In this case, it can be treated in the same way as the insulation layer. While it is possible to perform the naphtha production process S120, described below, with the sheath 60 attached to the intermediate layer 20, in this case, chlorine-based components derived from polyvinyl chloride may affect the equipment, requiring neutralization. Therefore, separating the sheath 60 from the intermediate layer 20 allows for more efficient naphtha production.

[0017] There are no particular limitations on the method for separating the CV cable 100 into the conductor 10, intermediate layer 20, and sheath 60. For example, one method is to cut the intermediate layer 20 and the sheath 60 using a cutter or laser irradiation, and then cut open the intermediate layer 20 and the sheath 60. The direction of the cuts can be selected as appropriate. For example, the cuts may be made approximately parallel to the central axis of the CV cable 100, or may be made spirally around the central axis of the CV cable 100. This method also makes it easy to separate the intermediate layer 20 and the sheath 60. The separated conductor 10 and sheath 60 can each be recycled using a known method.

[0018] On the other hand, of the intermediate layer 20 (the internal semiconductive layer 21, the insulating layer 22, the external semiconductive layer 23, and the shielding layer 24), the internal semiconductive layer 21, the insulating layer 22, and the external semiconductive layer 23 are often difficult to separate individually, and may be directly subjected to the naphtha production step S120 described below. On the other hand, the shielding layer 24 in the intermediate layer 20 is formed of copper-containing tape, copper wire, or the like. Therefore, the shielding layer 24 may be further separated from the intermediate layer 20, and the copper in the shielding layer 24 may be recycled. The method for separating the shielding layer 24 is not particularly limited. For example, the intermediate layer 20 may be crushed to the order of millimeters by a known method, and the crushed material may be separated by a sorting method using specific gravity, or the like.

[0019] (Naphtha production process) In the naphtha production step S120, recycled naphtha is produced from the portion containing the insulating layer 22 separated in the separation step S110 (specifically, the intermediate layer 20, or the intermediate layer 20 from which the shielding layer 24 has been removed). At this time, by crushing the intermediate layer 20 (or the intermediate layer 20 from which the shielding layer 24 has been removed) to an appropriate size, recycled naphtha can be produced efficiently in a short time. Crushing may be performed in the process line of the naphtha production step 120, or may be performed separately between the separation step S110 and the naphtha production step 120.

[0020] The recycled naphtha can be produced by a conventional method. For example, the intermediate layer 20 (or the intermediate layer 20 after removing the shielding layer 24) can be heated in an inert atmosphere. Examples of the inert atmosphere include a nitrogen atmosphere and an argon atmosphere. The heating temperature is appropriately selected depending on the desired properties of the recycled naphtha (such as the average carbon number of hydrocarbons), but is usually preferably 250°C or higher and 550°C or lower. A heating temperature within this range enables efficient decomposition of the crosslinked structure of the crosslinked polyethylene contained in the insulating layer 22 and decomposition of the polyethylene chains. Meanwhile, the heating time can be appropriately adjusted depending on the heating temperature and the desired properties of the recycled naphtha. The boiling point of the recycled naphtha produced in the naphtha production step S120 is not particularly limited, as long as it is similar to the boiling point of ordinary naphtha. However, it is particularly preferably about 35 to 80°C, which is the same as the boiling point of light naphtha containing a large amount of ethylene.

[0021] Here, in the naphtha generation step S120, a process is performed to separate impurities (residues) present in the reaction system during or after the production of the recycled naphtha. Examples of impurities include components derived from the inner semiconductive layer 21 and the outer semiconductive layer 23. Furthermore, when the naphtha generation step S120 is performed on the intermediate layer 20 including the shielding layer 24, components derived from the shielding layer 24 also become impurities.

[0022] The method for removing impurities is not particularly limited as long as it can extract the recycled naphtha with high purity. For example, the composition obtained after the heating step can be centrifuged to separate the oily component (recycled naphtha) from the solid component (impurities), or the composition obtained after the heating step can be filtered to remove the solid component (impurities). To remove liquid impurities, differences in boiling points can be exploited to separate only recycled naphtha with a predetermined boiling point. By performing such impurity removal processing, the quality of the recycled naphtha can be improved. By using the material produced in the recycling step S130 (described below) to form new insulated wire and cable components, it becomes possible to manufacture high-quality insulated wire and cable.

[0023] (Reuse process) In the recycling step S130, the recycled naphtha obtained in the naphtha production step S120 is mixed with new naphtha to produce a material for forming a new insulated wire / cable. The type of new insulated wire / cable produced in this embodiment may be the CV cable described above, or may be a cable or insulated wire other than the CV cable, such as an insulated wire for a high-voltage overhead wire (such as an OE wire or an OC wire).

[0024] When naphtha (recycled naphtha and new naphtha) is used as a raw material to form new insulated wire and cable components, ethylene is first purified from the naphtha using a known method. When ethylene is purified, components other than ethylene (impurities) are removed. Therefore, even if recycled naphtha is used as part of the raw material, deterioration in quality, which is typical of recycled products, is unlikely to occur. Furthermore, since a large amount of naphtha is typically used when refining ethylene from naphtha, recycled naphtha and new naphtha may be mixed. Mixing recycled naphtha and new naphtha in this way has the advantage of lowering the concentration of recycled naphtha in the raw material, thereby making it less likely to deteriorate the properties typical of recycled products. The blending ratio of recycled naphtha to new naphtha is not particularly limited and can be any ratio.

[0025] Next, the ethylene obtained by the above purification is used to prepare materials for new insulated wires and cables, such as olefins such as polyethylene and polypropylene, or polyvinyl chloride. The preparation method for these materials is not particularly limited and can be carried out by conventional methods. For example, in the case of polyethylene, it can be a method in which ethylene is polymerized in the presence of a known catalyst. The prepared materials are usually processed into pellets or the like.

[0026] The resulting material is then used to form new insulated wire and cable components (e.g., insulating layers, sheaths, semiconducting layers, and pressure tapes) using known methods. The forming method and materials for each component are appropriately selected depending on the desired type of insulated wire or cable. For example, when forming an insulating layer made of polyethylene around a conductor (e.g., the insulating layer of an OE wire), the polyethylene can be extruded around the conductor to form the insulating layer. Furthermore, when forming a polyethylene sheath as the outermost layer of a cable (e.g., a CV cable in which the sheath is made of polyethylene rather than polyvinyl chloride; also known as a CE cable), the polyethylene can be extruded around the shielding layer (or the insulating layer for lower voltage classes) to form the polyethylene sheath. The resulting polyvinyl chloride can also be used to form a sheath instead of polyethylene. In this case, a new CV cable can be formed. Furthermore, when the resulting material is used for a sheath, additives can be added to satisfy the required cable properties. These additives can be the same as conventional materials that do not use recycled materials, or they can be blended specifically for recycled materials. However, when a small amount of naphtha produced by recycling is mixed with a considerable amount of new naphtha, it can be handled in the same way as new material.

[0027] Furthermore, when forming an insulating layer made of cross-linked polyethylene around a conductor (e.g., the insulating layer of an OC cable or a CV cable), the insulating layer can be formed by extrusion coating a composition containing polyethylene and a cross-linking agent around the conductor, with a separator on the conductor (in the case of an electric wire) or an internal semiconductive layer (in the case of a cable), and chemically cross-linking the layer with the cross-linking agent. Alternatively, the insulating layer can be formed by extrusion coating polyethylene around the conductor or the internal semiconductive layer, and then irradiating the polyethylene with energy such as ultraviolet light or an electron beam. The resulting material can be used to form new insulating layers and sheaths for insulated wires and cables, as well as new holding tapes (made of resin) and semiconductive layers for insulated wires and cables. Holding tapes are also called pressure tapes.

[0028] (Variation) The above describes a method for recycling the insulation layer of a single-core CV cable or the sheath of a CE cable. However, the same recycling method can also be used for cables in which multiple single-core cables are twisted together (for example, CVT cables, CET cables, etc.).

[0029] Furthermore, the above-described recycling method can also be applied to the insulating layer of an insulated wire. For example, as shown in Fig. 2B, a similar recycling method can be performed on an insulated wire (such as an OE wire or an OC wire) 200 having an insulating layer 32 made of polyethylene or cross-linked polyethylene around a conductor 15. Note that in the insulated wire (such as an OE wire or an OC wire) 200, a separator tape (not shown) or the like may be placed between the conductor 15 and the insulating layer 32.

[0030] When the recycling method is performed on the insulated wire (OE wire, OC wire, or the like) 200, the same steps as above are performed: a separation step S110 for separating the conductor 15 from the insulating layer 32; a naphtha production step S120 for producing recycled naphtha from the insulating layer separated in the separation step S110; and a reuse step S130 for mixing the recycled naphtha obtained in the naphtha production step S120 with new naphtha to produce a material for forming a new insulated wire / cable.

[0031] However, the insulated wire (such as an OE wire or an OC wire) 200 often has a smaller diameter than the above-mentioned CV cable 100. Therefore, it can be difficult to separate the conductor 15 from the insulating layer 32 in the separation step S110. Therefore, when performing the separation step S110 on an insulated wire (such as an OE wire or an OC wire) 200, one method is to cut the insulated wire 200 at a length of 50 millimeters or less in the longitudinal direction and apply vibrations using a vibrator or the like to efficiently separate the conductor 15 from the insulating layer 32. In order to reliably separate the insulating layer 32 from the conductor 15, it is also possible to pass the wire through water or the like after vibration, thereby separating them due to the difference in specific gravity.

[0032] The separated insulating layer 32 is then subjected to the naphtha production step S120 in the same manner as described above, to produce recycled naphtha from the polyethylene or cross-linked polyethylene contained in the insulating layer 32. In this case, the impurity removal process described above is also performed. The insulated wire 200 is often used outdoors and may be contaminated with dust and dirt from the atmosphere. Furthermore, as described above, separator tape may be included, and resin derived from the separator tape may be mixed in with the insulating layer 32. Therefore, by removing the impurities (residue) in the naphtha production step S120, an excellent recycled naphtha can be obtained.

[0033] After the recycled naphtha is produced, a recycling step S130 is carried out in which the recycled naphtha is mixed with new naphtha in the same manner as described above to produce a material for forming a new insulated wire or cable. The produced material can be used to form new insulated wire or cable components. In this case, too, the type of the newly produced insulated wire or cable is not particularly limited, and may be, for example, the insulated wire for the high-voltage overhead electric wire described above (such as an original equipment manufacturer (OE) or overcurrent (OC) electric wire).

[0034] (Effects of the recycling method of the present invention) Conventional material recycling is premised on the ability to separate the insulating layer to be recycled from an insulating layer (semiconductor + insulator) made up of multiple different components, and in order to do this with long insulated wires and cables, it is necessary to build facilities to do this efficiently, and the corresponding costs and labor required make it extremely difficult to carry out commercially. A method of mixing and processing multiple components without separating them is also possible, but when used in composite materials, the initial performance cannot be guaranteed, and the uses are limited or even non-existent, making it impossible to use even if recycled. With the recycling method of the present invention, even in cases where the insulated wire or cable is composed of multiple layers, such as a semiconductive layer and an insulating layer, and where separating the insulating layer alone is difficult or would incur considerable costs, it is possible to recover an amount of naphtha equivalent to the polyethylene resin contained in the insulating layer of the insulated wire or cable without complex processing and recycle it into material for another insulated wire or cable. Furthermore, when the insulating layer is made of cross-linked polyethylene, after the separation step, it is necessary to carry out a thermoplasticization step using large-scale thermoplasticization equipment, which requires a considerable amount of energy, to cut the cross-linked chains of the cross-linked polyethylene. However, this method does not require these steps. Furthermore, in the recycling method of the present invention, polyethylene resin is returned to the state of naphtha, which is then mixed with new naphtha and used as a resin material for new insulated wire and cable components (for example, insulating layers, sheaths, etc.). Therefore, there is almost no performance degradation specific to recycled products, or an increase in mass due to the addition of additives or new materials to satisfy performance, and the resin can be reborn as a resin that satisfies the properties of new products for use in insulators, sheaths, etc., making it possible to maintain a high rate of improvement as a recycled product. [Industrial Applicability]

[0035] The method for recycling the insulating layer of an insulated wire or cable and the method for manufacturing an insulated wire or cable of the present invention make it possible to recycle the insulating layer without complex processing or excessive costs, and are therefore extremely useful in the field of insulated wire or cable manufacturing. [Explanation of symbols]

[0036] 10, 15 conductors 20 Middle Class 21 Internal semiconducting layer 22, 32 Insulation layer 23 Outer semiconductive layer 24 Shielding layer 60 Sheath 100 CV cable 200 Insulated wire (OE wire or OC wire, etc.)

Claims

1. A method for recycling an insulating layer of an insulated wire or cable having at least a conductor and an insulating layer containing polyethylene or cross-linked polyethylene arranged around the conductor, separating the conductor from the insulating layer; generating recycled naphtha from the separated insulating layer; a step of mixing the recycled naphtha and new naphtha to produce a material for forming a new insulated wire / cable; Including, In the step of producing the recycled naphtha, a treatment for removing impurities is performed. How to recycle the insulation layer of insulated wire and cable.

2. A process for separating a conductor from an insulating layer of an insulated wire / cable, the conductor including a conductor and an insulating layer containing polyethylene or cross-linked polyethylene and disposed around the conductor; generating recycled naphtha from the separated insulating layer; a step of mixing the recycled naphtha and new naphtha to form a component constituting a new insulated wire / cable; Including, In the step of producing the recycled naphtha, a treatment for removing impurities is performed. Manufacturing method for insulated wire and cable.

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