JPH11176262A - Manufacture of foam insulated electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electric wire having an insulation layer significantly thinned by foaming at high productivity by applying a thermosetting liquid varnish containing no solvent and mixed with a photodecomposable foaming agent to a conductor, foaming the agent by ultraviolet radiation, and then hardening the liquid varnish by heating. SOLUTION: A conductor 2 (copper, aluminum, etc.), is sent out of a conductor sending apparatus 1, preheated by a preheating apparatus 3, and sent to a coating tank 34. In a coating die 5, a thermosetting liquid varnish (including polymerizable oligomer, a polymerizable monomer, and crosslinking initiating agent) containing no solvent mixed with a photodecomposable foaming agent (an azo type compound, an azide type compound) decomposed and foamed by ultraviolet ray radiation is applied to the resultant conductor 2. The obtained coated wire 6 is passed through an ultraviolet ray radiating apparatus 7 to foam the photodecomposable foaming agent and then the liquid varnish containing no solvent is thermally cured in a heated nitrogen circulating heating furnace 9 to give foam insulated electric wire 9 to be taken by a take-up apparatus 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a foamed insulated wire. More specifically, the present invention relates to a method for manufacturing a thin-diameter foam insulated wire used for high-speed signal transmission.

[0002]

2. Description of the Related Art In recent years, there has been a growing demand for smaller and lighter communication devices, higher speed transmission, lower cost, and the like in communication devices and precision electronic devices.

In such insulated wires used for communication equipment and precision electronic equipment, there is a tendency to reduce the conductor diameter to 0.5 mm or less in order to meet the demand for reduction in size and weight. In addition, there is a strong tendency to foam the insulating layer in order to meet the demand for high-speed signal transmission. Furthermore, high-speed productivity of insulated wires has been strongly demanded in order to meet demands for cost reduction.

[0004] Conventionally, insulated wires are manufactured by continuously feeding a long conductor to an extruder and continuously extruding and coating a rubber or plastic material on the conductor.

However, in the extrusion coating operation of the rubber or plastic material, it is difficult to reduce the thickness of the insulating layer and to extrude it at a higher speed because of the nature of the extrusion coating operation. For example, if the thickness of the insulating layer is further reduced, defective portions of the insulating layer frequently occur. Further, if the extrusion temperature is increased to achieve high-speed extrusion, rubber and plastic materials are thermally degraded. Further, when the pressure is increased in order to extrude at a high speed, the thin conductive wire is broken.

On the other hand, an enameled wire obtained by repeatedly applying and baking an enamel paint on a conductor can be further reduced in thickness. However, enameled wire is repeatedly applied and baked with an enamel paint, so that a large-scale printing facility is required, and it is not always effective in reducing manufacturing costs due to environmental measures and the like. In addition, enameled wires have a low dielectric constant and are difficult to foam uniformly, so that high-speed transmission is difficult.

On the other hand, an insulated wire coated with a UV-crosslinkable resin can reduce the thickness of the insulating layer and increase the production speed.

That is, since the ultraviolet-crosslinking resin-coated insulated wire is a manufacturing method in which a solvent-free ultraviolet-crosslinking resin containing an ultraviolet-curing initiator is coated on a conductor, it can be thinned, and the coated wire can be coated with ultraviolet light. Since the time for passing through the irradiation furnace and the time for clogging and curing are several seconds, the speed can be increased. In addition, the ultraviolet irradiation furnace is small and simple, and therefore does not require a large-scale printing facility or the like used for producing enameled wires.

In this insulated wire coated with a UV-crosslinked resin, the UV-crosslinked resin layer can be foamed.

The following method has been proposed as a method for producing such a foamed ultraviolet-crosslinked resin-coated insulated wire.

A method for blending hollow spheres (Japanese Patent Laid-Open No. 3-6741)
No. 7, JP-A-3-71521, etc.) Method of blending thermally inflatable balloons (JP-A-4-22014) Bubble blowing method of nitrogen, air, etc. (JP-A-3-267)
No. 172) Method of blending a thermal decomposition foaming agent (JP-A-4-264316) Method of blending a photolytic blowing agent (JP-A-7-45145)

[0012]

However, the above-mentioned method for producing an insulated electric wire coated with a foamed ultraviolet-crosslinked resin has the following problems.

In this method, it is difficult to uniformly disperse the hollow spheres in the ultraviolet-crosslinking resin and to maintain the state from a liquid state to a cured state, and as a result, it is difficult to achieve uniform foaming.

[0014] In this method, when the thermal expansion balloon is heated to foam the thermal expansion balloon, the viscosity of the ultraviolet cross-linking resin is reduced, and as a result, there are many failures of dripping from the conductor.

[0015] In this method, bubbles such as nitrogen and air blow out with time, and as a result, uniform foaming is difficult.

[0016] In this method, when the thermal decomposition foaming agent is heated to foam it, the viscosity of the ultraviolet-crosslinked resin is reduced, and as a result, there are many failures of dripping from the conductor.

In this method, the photolytic blowing agent foams upon irradiation with ultraviolet light, and at the same time, the ultraviolet-crosslinked resin cures. Therefore, the foamed ultraviolet-crosslinked resin insulating layer obtained by this method can achieve uniform foaming without gas release.

For this reason, in the method for producing the insulated electric wire coated with the foamed ultraviolet-crosslinking resin, the above-mentioned method of blending the photolytic foaming agent has been frequently used.

However, it has been found that the following problems also occur in the method of blending the photolytic foaming agent.

(A) Decrease in cross-linking efficiency of ultraviolet-crosslinked resin In this method, since the absorption wavelength of the photolytic foaming agent and the absorption wavelength of the ultraviolet-curing initiator compounded in the ultraviolet-crosslinked resin are close to each other, irradiation was performed. Most of the UV light is eaten by the photolytic blowing agent, thereby reducing the cross-linking efficiency of the UV cross-linked resin. In particular, azide-based photo-decomposition and foaming agents and diazo-based photo-decomposition and foaming agents have a large absorption of ultraviolet rays.

(B) Irregular foaming of the foamed ultraviolet-crosslinked resin layer near the conductor As shown in (a) above, the crosslinked resin of the foamed ultraviolet-crosslinked resin obtained because of the poor crosslinking efficiency of the ultraviolet-crosslinked resin cures closer to the conductor side. Becomes insufficient. For this reason, the bubbles are concentrated near the conductor side to generate large open cells, and as a result, there are problems such as uneven foaming and separation from the conductor.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art, to achieve a remarkable thinning and an improvement in productivity. Moreover, it is an object of the present invention to provide a novel method for producing a foamed insulated wire capable of uniformly foaming the insulating layer of the obtained insulated wire.

[0023]

The gist of the present invention is to provide a thermosetting liquid non-solvent varnish containing a photo-decomposing and foaming agent which is decomposed and foamed by ultraviolet irradiation on a conductor. A method for producing a foamed insulated wire, characterized in that, after forming a mold liquid non-solvent varnish application line, the thermosetting liquid non-solvent varnish application line is irradiated with ultraviolet rays and subsequently heated and cured.

As described above, by adding a photo-decomposing foaming agent that decomposes and foams to a thermosetting liquid solventless varnish by ultraviolet irradiation, the foaming step and the curing step can be controlled independently.
As a result, the thermosetting liquid solventless varnish containing the photodecomposition foaming agent can be foamed at an arbitrary viscosity, and then completely heat-cured in that state.

[0025] Thus, the thickness of the insulating layer of the insulated wire can be remarkably reduced by the solventless varnish coating production method, and the foaming step and the curing step can be controlled independently, so that the degree of foaming of the insulating layer can be uniform. Adhesion with the conductor can be significantly improved.

In the present invention, it is preferable that the conductor is preheated before applying the thermosetting liquid solventless varnish, or is heated after application.

[0027]

Next, an embodiment of a method for manufacturing a foamed insulated wire according to the present invention will be described.

In the present invention, the conductive metal is a conductive metal such as copper, aluminum, nickel, chromium, silver, platinum,
There are gold and iron alone or alloys based on these.

The shape of the conductor may be a single wire or a stranded wire. Further, these conductors may be plated with other metals.

In the present invention, the basic constitution of the thermosetting liquid solventless varnish contains a polymerizable oligomer, a polymerizable monomer and a crosslinking initiator.

Here, the polymerizable oligomer is a polymer having two or more functional groups having an unsaturated bond, for example, an acryloyl group, a methacryloyl group, an acryl group, and a vinyl group. These may be those in which some elements are substituted with fluorine.

Such polymerizable oligomers include epoxy acrylate oligomers, epoxidized oil acrylate oligomers, urethane acrylate oligomers, polyester urethane acrylate oligomers, polyether urethane acrylate oligomers, polyester acrylate oligomers, and polyether acrylate oligomers. There are oligomers, vinyl acrylate oligomers, silicone acrylate oligomers, polybutadiene acrylate oligomers, polystyrene ethyl methacrylate oligomers, polycarbonate dicarbonate oligomers, unsaturated polyester oligomers, and polyene / thiol oligomers.

These polymerizable oligomers can be used alone or in a blend.

In the present invention, the polymerizable monomer is a polymerizable monomer having two or more acryloyl groups, methacryloyl groups, acryl groups, vinyl groups and the like.

In the present invention, the crosslinking initiator is decomposed by heat to generate free radicals, and the free radical has a function of initiating the curing of polymerizable oligomers and polymerizable monomers. Examples of such a crosslinking initiator include benzoin ether compounds, ketal compounds, acetophenone compounds, benzophenone compounds, thioxanthone compounds, and azobis compounds.

In the present invention, the foaming agent is a compound that generates bubbles by visible light or ultraviolet light, and examples thereof include azo compounds, azide compounds, and diazo compounds.

In the present invention, other than the above, the following compounds can be appropriately compounded as required.

That is, such a compound includes a starting aid, an antiadhesive, a thixotropic agent, a filler, a plasticizer, a non-reactive polymer, a coloring agent, a flame retardant, a flame retardant auxiliary, a softening inhibitor, Release agents, desiccants, dispersants, wetting agents, anti-settling agents, thickeners, anti-static agents, anti-static agents, fungicides, rodents, termites, matting agents, anti-blocking agents, Anti-skinning agent,
Surfactants and the like.

In the present invention, the UV irradiation source includes a low-pressure mercury lamp, a metal halide lamp and the like. It is preferable to add a device for cutting off the heat of the ultraviolet irradiation source, for example, an infrared absorption filter, a cold mirror, a pure reflux system, or the like. This is for decomposing only the photo-decomposition foaming agent at the time of ultraviolet irradiation, and completely preventing the start of curing of the thermosetting liquid solventless varnish.

In the present invention, examples of the heating device include an induction heating device, a hot air circulation furnace, an electric furnace, and an infrared lamp.

In the present invention, if temperature control is possible, an apparatus in which an ultraviolet irradiation source and a heating device are combined and integrated may be used.

[0042]

Next, examples of the method for producing a foamed insulated wire of the present invention will be described together with comparative examples.

(Base Composition of Thermosetting Liquid Solventless Varnish) The base compositions of the thermosetting liquid solventless varnish used in Examples and Comparative Examples are as follows.

A) Polymerizable oligomer: urethane acrylate oligomer: 80.0 parts by weight b) Polymerizable monomer: monomer having an acryloyl group: 20.0 parts by weight c) Crosslinking initiator: azide-based photofoaming agent 4 parts by weight (Example) First, 5 parts by weight of an azobis-based thermal polymerization initiator was added to the base composition of the above-mentioned thermosetting liquid non-solvent varnish, whereby the thermosetting liquid containing the thermal polymerization initiator of one example was added. A solventless varnish was obtained.

Next, the heat-curable liquid solventless varnish blended with the thermal polymerization initiator of one example obtained above was applied and cured on a conductor having a conductor size of 42 AWG by the production line shown in FIG.

FIG. 1 is an explanatory view of a production line showing an embodiment of the method for producing a foamed insulated wire according to the present invention.

In FIG. 1, 1 is a conductor sending device, 2 is a conductor, 3 is a conductor preheating device, 4 is a coating tank, 5 is a coating die, 6 is a coating wire, 7 is an ultraviolet irradiation device, and 8 is a hot nitrogen circulation heating furnace. Reference numeral 9 denotes a foamed insulated electric wire, and reference numeral 10 denotes a foamed insulated electric wire winding device.

As can be seen from FIG. 1, in one embodiment of the method for manufacturing a foamed insulated wire according to the present invention, first, a conductor 2 is fed from a conductor sending device 1 at a speed of 10 m / min, and then this conductor 2 is fed to a conductor preheating device. 3, the preheated conductor 2 is fed into a coating tank 4 and then passed through a coating die 5 to form a coating wire 6 drawn down to a thickness of 50 μm.

Next, the coating wire 6 is foamed by passing it through an ultraviolet irradiation device 7 having a metal halide lamp with an ultraviolet output of 6 kW.

Next, the foamed coated wire 6 is fed into a hot nitrogen circulating heating furnace 8 at 250 ° C. and thermally cured to form a foamed insulated wire 9. The finally obtained foamed insulated wire 9 is taken up by a foaming insulated wire winding device. 10 and wound up.

FIG. 3 is a partially enlarged perspective explanatory view of an integrated device of the ultraviolet irradiation device and the hot nitrogen circulating heating furnace shown in FIG.

In FIG. 3, reference numeral 71 denotes a furnace body cover, 72 denotes a metal halide lamp, 73 denotes an infrared ray absorbing filter,
4 is a cold mirror, and 75 is a 60 cm long quartz tube.

That is, the ultraviolet irradiation device 7 of the integrated device comprises a quartz tube 75 through which the conductor 2 passes, a metal halide lamp 72 capable of irradiating ultraviolet rays into the quartz tube 75, and an infrared absorption filter for absorbing infrared rays from the metal halide lamp 72. 73, a cold mirror 74 for returning ultraviolet rays, and the like.

In FIG. 3, reference numeral 81 denotes a hot nitrogen circulating heating furnace main body, 82 denotes a nitrogen source, 83 denotes a branch pipe, 84 denotes an electric furnace,
85 is a solenoid valve, 86 is a thermistor, 87 is a flow meter, 88
Is a control device.

That is, the thermal nitrogen circulating heating furnace 8 of the integrated apparatus includes a nitrogen source 82, a branch pipe 83 for the nitrogen sent from the nitrogen source 82, an electric furnace 84 for heating the nitrogen sent from the nitrogen source 82, Solenoid valve 8 that can control the mixing ratio and flow rate of hot nitrogen heated in electric furnace 84 and nitrogen not heated
5. Consisting of a thermistor 86 for measuring the temperature, a flow meter 87 for measuring the flow rate, and a control device 88 for controlling the whole.

The integrated apparatus of the ultraviolet irradiation device 7 and the hot nitrogen circulating heating furnace 8 as shown in FIG. 2 can make the production line compact.

In the heating of this embodiment, hot nitrogen of 250 ° C. was supplied at a rate of 15 L / min.

The foamed insulated wire 9 obtained by one embodiment of the method for producing a foamed insulated wire of the present invention has a high foaming degree of 58% while having a thin wall thickness of 90 μm, and the entire insulating layer has a uniform foamed state. there were. Further, the productivity of the foamed insulated wire 9 was significantly improved.

(Comparative Example) First, 5 parts by weight of benzyl methyl ketal, which is a photoinitiator, was added to the base composition of the above-mentioned thermosetting liquid solventless varnish. A solventless varnish was obtained.

Next, the thermosetting liquid solventless varnish containing the photoinitiator of the comparative example obtained above was applied and cured on a conductor having a conductor size of 42 AWG by the production line shown in FIG.

FIG. 2 is an explanatory view of a production line showing a method of producing a foamed insulated wire of a comparative example.

In FIG. 2, 1 is a conductor sending device, 2 is a conductor, 3 is a conductor preheating device, 4 is a coating tank, 5 is a coating die, 6 is a coating wire, 7 is an ultraviolet irradiation device, 9 is a foam insulated wire, Is a foam insulated wire winding device.

As can be seen from FIG. 2, in the method of manufacturing the foamed insulated electric wire of the comparative example, first, the conductor 2 is connected to the conductor sending device 1 by one.
Then, the conductor 2 is preheated to 90 ° C. in a conductor preheating device 3, and then the preheated conductor is fed into a coating tank 4 and then passed through a coating die 5. The coated line 6 is drawn down to a thickness of 50 μm.

Next, the coating wire 6 was foamed and cured by passing it through an ultraviolet irradiation device having a metal halide lamp with an ultraviolet output of 6 kW.

The foamed insulated wire obtained by the method of manufacturing the foamed insulated wire of the comparative example had an insulating layer thickness of 70 μm due to foaming.
m, the foaming degree was as low as 38%, and the foaming state of the insulating layer was non-uniform. Furthermore, the productivity of the foam insulated wire was low.

[0066]

According to the method for producing a foamed insulated wire of the present invention, the foamed wire has a high degree of foaming and a uniform foaming state even though it is a thin insulating layer, and the productivity of the foamed insulated wire is remarkably high. Yes, industrially useful.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a production line showing one embodiment of a method for producing a foamed insulated electric wire of the present invention.

FIG. 2 is an explanatory view of a production line showing a method of producing a foamed insulated wire of a comparative example.

FIG. 3 is a partially enlarged perspective explanatory view of an integrated device of the ultraviolet irradiation device and the thermal nitrogen circulation heating furnace shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor sending device 2 Conductor 3 Conductor preheating device 4 Painting tank 5 Coating die 6 Coating wire 7 Ultraviolet irradiation device 8 Thermal nitrogen circulation heating furnace 9 Foaming insulated wire 10 Foaming insulated wire winding device 71 Furnace body cover 72 Metal halide lamp 73 Infrared absorption Filter 74 Cold mirror 75 Quartz tube 81 Hot nitrogen circulation heating furnace main body 82 Nitrogen source 83 Branch tube 84 Electric furnace 85 Solenoid valve 86 Thermistor 87 Flow meter 88 Controller

Claims (4)

[Claims] 1. A thermosetting liquid solventless varnish containing a photodecomposable foaming agent which decomposes and foams upon irradiation with ultraviolet light is applied to a conductor to form a thermosetting liquid solventless varnish coating line. A method for producing a foamed insulated wire, comprising irradiating a curable liquid solventless varnish application wire with ultraviolet rays, followed by heat curing. 2. The method for producing a foamed insulated wire according to claim 1, wherein the conductor before applying the thermosetting liquid solventless varnish containing a photolytic foaming agent is preheated. 3. The method for producing a foamed insulated wire according to claim 1, wherein the conductor is subjected to high frequency induction heating after applying a thermosetting liquid non-solvent varnish containing a photolytic foaming agent. 4. The method for producing a foamed insulated wire according to claim 1, wherein the steps of applying a thermosetting liquid non-solvent varnish containing a photolytic foaming agent, irradiating ultraviolet rays and heat curing are performed under an inert gas.