JPS5933105B2 - Method and device for manufacturing coated wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electric wire coated with crosslinked polyethylene or vulcanized rubber, and to an improvement in a crosslinked omega sign device.

Many power cables and distribution lines for electronic devices are coated and insulated with cross-linked polyethylene or vulcanized rubber, and the method for manufacturing this type of coated wire is generally to add cross-linking to the crosshead die of an extrusion molding machine for conductor coating. A continuous cross-linking device is used which is directly connected to the device, and the cross-linking device is composed of three parts made of high-pressure steel pipes: a heating section, a pre-cooling section, and a cooling section.

To explain in more detail, a conductor is coated with an uncrosslinked polyethylene resin or rubber containing an organic peroxide using an extrusion molding machine for conductor coating, and then immediately crosslinked by heating in a heating section of a crosslinking device, and then in a precooling section. The product is cooled in the cooling section. Conventionally, as a heating source in the heating section of a crosslinking device, 15 ■/c! High-pressure steam of 7 or higher has been used in

In this method, high-pressure steam is introduced into a heating section, and the coating is passed through the high-pressure steam to perform thermal crosslinking. The production rate in this case is determined by the crosslinking time in the heating section and the cooling time from the crosslinking temperature of the coating to room temperature in the precooling section and the cooling section. Increasing the heating temperature is effective in shortening the crosslinking time, and for this purpose it is necessary to further increase the pressure of high-pressure steam. However, if the coating is heated to too high a temperature, it will take a long time to cool down, resulting in a very long cross-linking device, and if the pressure becomes high, there will be problems with the pressure resistance of the cross-linking device and the structure of the insulated wire outlet. Excessive costs or problems with equipment handling and maintenance may occur. Furthermore, when high-pressure steam is used, steam enters the insulating layer during crosslinking, requiring a long drying process to remove it, and microboards may form after the steam is removed. This has become a problem. In order to improve the above-mentioned problems, a thermal crosslinking method that does not use high-pressure steam as a heating source has recently been proposed and put into practical use. For example, a method using heat radiation using an electric heater or the like, a method of circulating a heated and pressurized inert gas as a heating medium, or a method using a liquid such as silicone oil or a low melting point metal molten salt are known. However, since both of the above manufacturing methods can independently control the heating crosslinking temperature and the pressure inside the crosslinking equipment, they are highly effective in raising the heating temperature, increasing production speed, and reducing the occurrence of microboards. However, it has the following basic problems.

That is, in these methods, similar to thermal crosslinking using high-pressure steam, an uncrosslinked coating containing an organic peroxide is thermally crosslinked by heat conduction via a high-temperature heating medium, and the outer layer of the coating is Since heat is transferred to the inner layer sequentially,
The decomposition of the organic peroxide occurs at a heat transfer rate, and the crosslinking reaction progresses.

Moreover, polyethylene resin and rubber are poor conductors of heat, and it takes a considerable amount of time to heat them to the desired crosslinking temperature. Since the coating is heated to a high temperature, for example, 250°C or higher, it takes a long time to cool the coating, and in order to increase the production rate, the crosslinking equipment needs to be longer, resulting in a large-scale equipment. There is a point. The inventors previously proposed a method of crosslinking an uncrosslinked polyethylene resin containing an organic peroxide in a molten state at a relatively low temperature and in a short time by irradiating ultraviolet rays.

The present invention skillfully utilizes the advantages thereof to solve the problems of the conventional method, and provides a method and apparatus for simply, efficiently and continuously manufacturing coated electric wires.

That is, the present invention provides a method for manufacturing a covered wire using an apparatus for manufacturing a covered wire in which a crosslinking device comprising a crosslinking pipe section and a cooling pipe section is directly connected to a crosshead die of an extrusion molding machine for conductor coating. After coating the conductor with a crosslinkable rubber or polyethylene resin containing an organic peroxide, the crosslinking pipe section of the crosslinking device is heated at a temperature higher than the melting temperature of the coating and at a temperature at which heat alone will not substantially cause crosslinking. A method for producing a covered electric wire, characterized in that the wire passes through an interior heated under conditions of and time and at the same time irradiation with ultraviolet rays; The present invention relates to a covered electric wire manufacturing apparatus characterized in that it is provided with a heating medium circulation device.

By configuring this invention as described above, it has the following advantages.

(1) Since the decomposition of the organic peroxide does not depend on the temperature of the coating, there is no need to raise the heating temperature of the coating, especially the surface temperature, higher than necessary.

(2) The crosslinking reaction saves energy because it occurs due to the synergistic effect of thermal energy and ultraviolet energy.
Furthermore, crosslinking can be efficiently achieved even at low temperatures where heat alone would not substantially cause crosslinking.

(3) The time required for cooling is shortened because the coating is crosslinked at a relatively lower temperature than the crosslinking temperature caused by heat alone, and the production rate is significantly improved due to (2) the excellent crosslinking efficiency. (4) Compared to conventional continuous crosslinking equipment, the lengths of the crosslinking pipe section and the cooling pipe section can be significantly shortened, making the entire crosslinking equipment smaller and reducing equipment costs.

(5) Equipment such as an ultraviolet light generation source and a heating medium circulation device in the cross-linked pipe section are relatively simple, and the heating cross-linked pipe section in a conventional continuous cross-linking apparatus can be easily replaced or modified. (6)
Since high-pressure steam is not used, there is no generation of microboards due to steam, and a coated wire with excellent quality can be obtained.
etc.

The rubber or polyethylene resin crosslinkable with an organic peroxide used in this invention includes copolymers mainly composed of ethylene such as polyethylene, ethylene monovinyl acetate copolymer, ethylene-propylene copolymer, etc. Alternatively, it means butyl rubber, chloroprene, polyisoprene, ethylene-propylene-diene copolymer, etc.

The organic peroxide used in this invention has a decomposition temperature higher than the melting temperature of rubber or polyethylene resin, and also absorbs ultraviolet rays to generate radicals, which can effectively crosslink rubber or polyethylene resin. Preferred organic peroxides include 1,1-bis(t-butylperoxy)3,3,5
-Trimethylcyclohexane, n-butyl 4,4-bis(t-butylperoxy)valerate, 2,5 dimethylhexane 2,5-dihydroperoxide, di-t-butylperoxide, 2,5-dimethyl 2,5 -ji(t
-butylperoxy)hexane, 2,5-dimethyl 2,
5-di(t-butylperoxy)hexyne-3,1,3
-bis(t-butylperoxyisopropyl)benzene,
These include dicumyl peroxide, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, and cumene hydroperoxide.

The amount of organic peroxide used is 5 parts or less per 100 parts of rubber or polyethylene resin.
From the viewpoint of efficiency, the amount is preferably about 0.5 to 2 parts. Therefore, in addition to the organic peroxide, antioxidants, crosslinking retarders, crosslinking accelerators, crosslinking auxiliaries, voltage stabilizers, etc. are added to the rubber or polyethylene resin to be coated and crosslinked to substantially effect the crosslinking reaction. It may be added to the extent that it does not affect.

Examples of such antioxidants include 2,2'-methylenebis(4methyl-6t-butylphenol) and 2-mercaptobenzimidazole, and examples of crosslinking retarders include:
Hydroquinone, 2,6-di-t-butyl-4-methylphenol, 4,47-butylidene bis(3-methyl 6-
t-butylphenol), etc.; polyfunctional monomers such as ethylene glycol dimethacrylate and triallyl isocyanurate are used as crosslinking accelerators and crosslinking coagents.
Polyfunctional polymers such as 1,2-polybutadiene, 2-
Photosensitizing compounds such as methyl 1,4-naphthoquinone and β-methylanthraquinone, and tetramethylthyuram disulfite are used as voltage stabilizers.Anthracene, diphenyl disulfide, copper N,N'-dialkyl dithiocarbamate etc. Methods for incorporating organic peroxide into rubber or polyethylene resin include methods such as melting the organic peroxide or dissolving it in an appropriate solvent and impregnating it in contact with the solution, or kneading it in advance using an extruder, etc. .

In this invention, the rubber or polyethylene resin containing an organic peroxide is easily coated onto a conductor by melting it at a temperature at which substantially no crosslinking reaction occurs using a known extrusion molding machine for conductor coating. can be coated on conductors.

For example, an organic peroxide may be attached to the surface of rubber or polyethylene resin particles and the organic peroxide may be fed to the extruder, or the organic peroxide may be fed while the rubber or polyethylene resin is in a molten state within the extruder. The conductor is cross-dispersed at a temperature below the decomposition temperature of the oxide, and the conductor is coated continuously using a crosshead die installed at the tip of the extruder. At this time, if even a small amount of crosslinking occurs in the extruder or crosshead die, the surface of the coating will become rough and a good product cannot be obtained. It is preferable to suppress. The ultraviolet light used in this invention has a wavelength of 1000λ to 400λ.
Ultraviolet rays of 1850A to 4000A are particularly preferred.

As such an ultraviolet radiation source, a low pressure, high pressure, ultra-high pressure mercury lamp, xenon lamp, etc. are used. In this invention, the heating temperature of the crosslinking part of the crosslinking device and the passing time of the coating are above the melting temperature of the coating, and the temperature and time conditions are such that heat alone does not substantially cause crosslinking, and the rubber or polyethylene resin used is , depending on the organic peroxide.

As an example of this, a 2 mm thick sheet of a composition containing 2 parts of dicumyl peroxide in 100 parts of low density polyethylene with a melting temperature of 103°C, at 140°C,
The time required for substantially no crosslinking at 160°C was determined to be 12 minutes and 1.5 minutes, respectively. Note that the time is the time from the time when the sample is placed in a hot air circulation heating oven set at the crosslinking temperature and the sample becomes molten. In this invention, the heating medium introduced into the bridged pipe section is gas,
Any liquid may be used, but it must have good UV transmittance.
It is desirable to have a function to prevent oxidative deterioration of the coating. In particular, when irradiating far ultraviolet rays with a wavelength of 2000 Å or less, the presence of oxygen causes oxidative decomposition of the coating, resulting in significant deterioration. An atmosphere of inert gas such as carbon is preferable.

Further, specific heating methods include heater heating, infrared rays, heat rays emitted from high-pressure mercury lamps, and the like. When a high-pressure mercury lamp or an ultra-high-pressure mercury lamp is used as a source of ultraviolet light, it can be used as a heating source at the same time, and the surrounding medium is heated and the heating medium accompanies the method of the present invention. This is an advantage when implementing When ultraviolet rays are irradiated at a temperature higher than the melting temperature of a coating containing organic peroxide, the transparency of the ultraviolet rays increases due to the absence of crystalline parts, and the dispersion of the organic peroxide increases. Because of its good properties, a coated wire with uniform crosslinking can be obtained.

Further, by irradiating ultraviolet rays at a temperature and time that are above the melting temperature of the coating and at a time when heat alone will not substantially cause crosslinking, the crosslinking reaction of the coating can be significantly accelerated. This is due to the decomposition and crosslinking reaction of organic peroxides.
This is due to the synergistic effect of using thermal energy and ultraviolet energy at the same time. In the present invention, it is desirable that the crosslinking pipe section of the crosslinking device be in a pressurized state in order to suppress the generation of bubbles due to the gas generated during the crosslinking reaction of the coating, and the method of pressurizing the heating medium is used. .

Normally, the gauge pressure is 1K'/Ci! ? A method of continuously supplying the heating medium pressurized above is used. moreover,
In order to remove moisture mixed into the cross-linked pipe section and volatile matter generated by decomposition of organic peroxide, a heating medium is circulated,
A condenser can be provided if necessary. However,
By circulating the heating medium that is continuously supplied under pressure, the heating temperature of the crosslinked pipe section can be easily controlled. The duration of UV irradiation is determined by the desired degree of crosslinking and is highly dependent on the UV source and its intensity, the resin temperature of the coating, and the content and type of organic peroxide. .

Normally, it is desirable to control the irradiation so that the molten coating is crosslinked within several tens of seconds. Next, the present invention will be specifically explained based on the attached drawings.

The drawing is an explanatory diagram of a crosslinking device in the ultraviolet crosslinking method of the present invention, in which 1 is a crosshead die, the crosslinking device is directly connected to the crosshead die 1, and is composed of a crosslinking pipe section 2 and a cooling pipe section 3, each of which is pressurized. Made from high pressure steel pipes.

The inner surface of the bridged pipe portion 2 preferably has a structure that enhances the reflection efficiency of ultraviolet rays, and for example, a structure in which a hard aluminum plate is attached to the inner surface of a steel pipe or metal plating is used is used. Next, several high-pressure mercury lamps 5 and the like protected by transparent quartz tubes 4 are placed inside the bridge tube as a source of ultraviolet light and a source of medium heating. A supply port 6 and a discharge port 7 for cooling inert gas (nitrogen) were provided in the transparent quartz tube to prevent the high-pressure mercury lamp from overheating and to maintain a good lighting condition. The cross-linked pipe section 2 is heated by using heat rays emitted from a high-pressure mercury lamp 5, by pressurizing nitrogen, which is an inert gas, as a heating medium through a supply port 8, and by providing a circulation device 9, a condenser 10, etc. The heating temperature inside the cross-linked pipe is controlled by circulating nitrogen while removing moisture and volatile matter mixed in the nitrogen gas sealed inside the cross-linked pipe. The cooling pipe section 3 is connected to the bridging pipe section 2, and cooling water is press-fitted from the water supply port 11 and discharged from the tongue outlet 12. 13
The circulating water supply is controlled by a cooling water level adjustment device.

When producing a covered electric wire using the above-mentioned crosslinking apparatus, the preheated conductor W is melt-coated with rubber or polyethylene resin containing an organic peroxide using the crosshead die 1, and immediately introduced into the crosslinking apparatus. The electric wire introduced into the crosslinked pipe section is irradiated with ultraviolet rays at the same time as it passes through a heating medium heated at a temperature and time that is above the melting temperature of the coating and at a temperature and time at which heat alone does not substantially cause crosslinking. Perform crosslinking. The covered wire, which has been completely crosslinked in the crosslinked pipe section 2, is
Subsequently, it passes through water in the cooling pipe section 3, where it is cooled and carried outside to become a product. The degree of crosslinking in this invention is defined as rubber or polyethylene resin placed in a 200-mesh wire mesh basket and refluxed in boiling toluene for 7 hours. perform the extraction,
Defined by the proportion of resin insoluble in toluene after drying, the term "substantially non-crosslinked coating" as used in the present invention means one in which the degree of crosslinking is zero. Furthermore, the melting temperature of rubber or polyethylene resin is the temperature when the crystal part of the coating is in a molten state, and specifically, in the case of rubber, the softening temperature measured according to JIS-K253l. In the case of polyethylene resin, it refers to the peak temperature when the melting curve is measured using a differential scanning calorimeter at a heating rate of 8° C./min.

The present invention will be explained below with reference to Examples.

Example low density polyethylene (density 0.917ff/CC
, Mll. Of! /10: A composition consisting of 100 parts by weight (melting temperature: 103°C) and 1.0 parts by weight of 1,3-bis(t-butylperoxyisopropyl)benzene was supplied to an extrusion molding machine for conductor coating, and heated at 125°C. After coating uncrosslinked polyethylene with a thickness of 411 on the copper wire, which was melt-extruded at extrusion temperature and gluing 7 strands per piece, it was immediately introduced into the crosslinking equipment shown in the drawing and coated at a speed of 3 m/min. Manufactured electric wire.

In the configuration of the crosslinking device shown in the drawings, the length of the crosslinking pipe section 2 is 0.6 m and the length of the cooling pipe section 3 is 2 m. A hard aluminum plate is attached to the inner surface of the bridging pipe section 2, and a high-pressure mercury lamp manufactured by Ushio Inc. (model UM-45) is installed inside the bridge pipe section 2.
2) were installed in 2 stages of 4 each, and the quartz purity was 9.
The high-pressure mercury lamp was protected with a transparent quartz tube of 9.99% or higher. To prevent the high-pressure mercury lamp from overheating, the lamp was cooled using nitrogen. The inside of the cross-linked pipe is heated by utilizing the heat dissipation of high-pressure mercury, etc. Nitrogen with a gauge pressure of 5 Kf/d is sealed as a heating medium, and the nitrogen is circulated appropriately to maintain the heating temperature at 170°C to 180°C. The temperature was adjusted to ℃. When the coating layer of the coated wire obtained by passing through heating conditions and simultaneously irradiating ultraviolet rays was scraped off and the degree of crosslinking was measured, it was found to be uniformly crosslinked at 75%. When the coating layer was sliced and observed, it was completely transparent with no white cloud-like band called a cloudy ring seen because no steam was used for heating. Comparative Example A conductor was coated with uncrosslinked polyethylene containing an organic peroxide under the same conditions as in the example, and immediately introduced into the crosslinking apparatus described below to produce a coated wire at a speed of 3 m/min.

The crosslinking device used in the comparative example circulated purified water at 30°C as a heating medium in the crosslinking pipe section of the crosslinking device used in the example.
An electric heater was installed in place of the high-pressure mercury lamp in the cross-linking pipe section of the cross-linking apparatus used in the example, and an electric heater was installed in place of the high-pressure mercury lamp, and an electric heater was installed in place of the high-pressure mercury lamp. This is a crosslinking device in which nitrogen is pressurized and the inside of the crosslinked pipe section is heated to 170°C to 180°C.

When the degree of crosslinking of the obtained covered wire was measured,
The outer layer of the insulating layer of the coated wire obtained by passing it through purified water at 30°C and simultaneously irradiating it with ultraviolet rays is 5%, and the inner layer is 0%.
The insulating layer of the covered wire obtained by crosslinking only by passing through nitrogen heated to 170° C. to 180° C. without ultraviolet irradiation was 0% for both the inner and outer layers. As is clear from the above results, according to the present invention, the crosslinking reaction of the insulating layer of a covered electric wire is significantly promoted, and even a covered electric wire having a considerably thick insulating layer can be crosslinked uniformly with a high degree of crosslinking. It is possible to obtain a high-quality coated wire without microboards caused by water vapor.

In addition, the crosslinking device according to the present invention is simple, and the heating crosslinking pipe section in the conventional continuous crosslinking device can be easily replaced or modified, and since the crosslinking reaction is carried out at a relatively low temperature, the length of the cooling pipe section can be significantly reduced. This makes it possible to shorten the length of the cable, which has a great effect in terms of equipment.

[Brief explanation of the drawing]

The drawings are explanatory diagrams schematically showing an example of an apparatus used to carry out the present invention. 1...Crosshead die, 2...Bridged pipe section, 3...Cooling pipe section, 4...Transparent quartz tube, 5... - Ultraviolet light source, 9... Heating medium circulation device, W... Conductor.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a covered electric wire using an apparatus for manufacturing a covered electric wire in which a cross-linking device is directly connected to a cross-head die of an extrusion molding machine for conductor coating, in which organic peroxide-crosslinkable rubber or polyethylene resin is used. After containing peroxide and coating the conductor, the crosslinking pipe section of the crosslinking device is heated to a temperature and time that is higher than the melting temperature of the coating and does not substantially cause crosslinking with heat alone. A method for manufacturing a covered electric wire, characterized by irradiating it with ultraviolet rays at the same time. 2. In a covered electric wire manufacturing device in which a crosslinking device consisting of a crosslinking pipe section and a cooling pipe section is directly connected to a crosshead die,
An apparatus for manufacturing a covered electric wire, characterized in that an ultraviolet light generation source protected by a transparent quartz tube is provided inside the cross-linked pipe portion, and a heating medium circulation device is provided in the cross-linked pipe portion.