JP6740642B2 - Insulated wire manufacturing method - Google Patents

Description

The present invention relates to an insulated wire and a method for manufacturing the same.

Windings (enamel wires), which are insulated wires used for coils of electrical equipment such as rotating electric machines and transformers, generally have a layer around a conductor that is formed into a cross-sectional shape that matches the application and shape of the coil. It has a structure in which the above insulator is formed. Among them, as the conductor, for example, in addition to a circular cross section, a rectangular cross section is often used for the purpose of reducing the volume occupied by the coil.

As a method of forming an insulator around the conductor, for example, a method of coating and baking an insulating paint obtained by dissolving a resin in an organic solvent around the conductor, or extruding a resin composition prepared in advance around the conductor. There are methods of coating and methods of using these methods in combination.

In recent years, due to the demand for miniaturization of electrical equipment, in the coil winding process of winding a winding around a core to produce a coil, the winding has become densely wound around a small-diameter core with high tension, Insulators are required to have mechanical properties (for example, adhesion and wear resistance) that can withstand severe processing stress.

Further, since a higher voltage such as an inverter surge voltage is applied to the coil in the electric device, the insulator may be deteriorated or damaged due to the occurrence of partial discharge.

In order to prevent the deterioration and damage of the insulator due to the partial discharge, the insulator having a high partial discharge inception voltage is being developed. Examples of methods for increasing the partial discharge inception voltage (PDIV) of the insulator include a method of increasing the thickness of the insulator and a method of forming the insulator with a resin having a low relative dielectric constant.

However, if the thickness of the insulator is increased, the winding becomes thick, the size of the coil increases, and the space factor decreases, which is not preferable.

On the other hand, as a resin having a low relative dielectric constant, there is a fluorine-based polyimide resin having a specific structure having a lower relative dielectric constant as compared with a conventional polyimide resin having a relative dielectric constant of about 3 to 4. Also, the relative permittivity is about 2.3 to 2.8 (see, for example, Patent Document 1), is not particularly low, and it is difficult to greatly improve the partial discharge inception voltage.

Therefore, there is a method of foaming the insulator as a means for greatly reducing the relative dielectric constant of the insulator. As a specific method, a resin containing polyphenylene sulfide (PPS) as a main material is extrusion-coated around a conductor and then held in a pressurized inert gas atmosphere so that an inert gas is contained in the resin. A method of foaming by heating under pressure is known (for example, refer to Patent Document 2).

However, after impregnation with the inert gas, the impregnated amount of the inert gas decreases with time due to leakage of the inert gas, so in order to obtain the desired degree of foaming, the time from impregnation to normal pressure heating Must be strictly controlled. Further, the impregnated amount of the inert gas also changes depending on the crystallinity of PPS and the amount of the auxiliary material added. Therefore, in order to obtain the desired foaming degree, the impregnation condition (pressure, time, temperature) of the inert gas depends on the material. Need to be adjusted.

JP, 2002-056720, A International Publication No. 2011/118717 Pamphlet

An object of the present invention is to provide an insulated wire having a foamed insulator made of polyphenylene sulfide resin formed without impregnation with an inert gas and having an increased partial discharge inception voltage.

According to one aspect of the invention,
A step of foaming a resin composition containing a polyphenylene sulfide resin and aluminum hydroxide by a dehydration reaction of the aluminum hydroxide,
A step of extruding the foamed resin composition around a conductor to form a foamed insulator having a foaming degree of 30% or more and 80% or less;
There is provided a method for manufacturing an insulated electric wire having:

According to the present invention, it is possible to provide an insulated wire including a foamed insulator made of polyphenylene sulfide resin formed without impregnation with an inert gas and having an increased partial discharge inception voltage.

1A is a schematic cross-sectional view showing an example of the structure of an insulated wire according to an embodiment of the present invention, and FIG. 1B is a schematic view showing an example of an insulated wire manufacturing apparatus according to the embodiment. It is a figure.

An insulated wire (foamed wire) 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1A is a schematic cross-sectional view showing an example of the structure of the insulated wire 10. The insulated wire 10 includes a conductor 20 and a foam insulator 30.

As the conductor 20, for example, a rectangular copper wire is used. It should be noted that the conductor 20 is not limited to the rectangular copper wire, and other shapes and materials may be used.

The foamed insulator 30 is formed around the conductor 20 and has a foamed region (foamed portion) 31. The foamed insulator 30 is made of a resin composition containing a polyphenylene sulfide (PPS) resin and alumina. Further, as will be understood from the manufacturing process of the foamed insulation 30 described below, the foamed insulation 30 is a resin composition obtained by foaming a resin composition containing a PPS resin and aluminum hydroxide by a dehydration reaction of aluminum hydroxide. It can also be said to consist of things.

The resin composition forming the foamed insulation 30 may contain a resin other than the PPS resin, various additives, and the like, if necessary.

In order to sufficiently increase the partial discharge inception voltage, the foamed insulator 30 preferably has a foaming degree of 30% or more. Further, in order to stabilize the insulation thickness of the foamed insulation 30, the foamed insulation 30 preferably has a foaming degree of 80% or less. The definition of the degree of foaming will be described later in the description of Examples and Comparative Examples.

Next, a method of manufacturing the insulated wire 10 will be described with reference to FIG. FIG. 1B is a schematic diagram showing an example of an apparatus 100 for manufacturing the insulated wire 10.

The conductor 20 is fed from the feeder 101 and introduced into the preheating furnace 103 via the pulley 102. The preheating furnace 103 preheats the conductor 20 in an inert gas atmosphere. Nitrogen gas, which is a low-cost general-purpose gas, and helium gas, which has excellent thermal conductivity, are effective as the inert gas, but the inert gas is not limited to these.

Since the surface of the conductor 20 is exposed to a high temperature environment inside the preheating furnace 103, the surface of the conductor 20 may be oxidized. However, the atmosphere inside the preheating furnace 103 should be replaced with an inert gas atmosphere. Thereby, the surface of the conductor 20 can be suppressed from being oxidized. By suppressing the oxidation of the surface of the conductor 20, it is possible to prevent the adhesion between the conductor 20 and the foamed insulation 30 from decreasing.

The preheating temperature of the conductor 20 in the preheating furnace 103 is preferably equal to or higher than the melting point of the PPS resin, specifically, for example, 280° C. or higher, and more preferably 300° C. or higher and 320° C. or lower. As a result, the adhesion between the conductor 20 and the foam insulation 30 can be improved.

Next, around the conductor 20 preheated in the preheating furnace 103, the resin composition containing the PPS resin and aluminum hydroxide is foamed by the dehydration reaction of aluminum hydroxide by the extruder 104. Are extrusion coated to form the foamed insulation 30.

The step of forming the foamed insulation 30 will be described in more detail. PPS resin and aluminum hydroxide are put into the extruder 104. The extrusion temperature in the extruder 104 is slightly higher than the preheating temperature, and is preferably a temperature at which a dehydration reaction of aluminum hydroxide sufficiently occurs, for example, more than 300° C., and 310° C. or more and 330° C. or less. Is more preferable.

The particle size of aluminum hydroxide is preferably 1 μm or less. Here, the “particle size” is an average particle size calculated from a particle size distribution obtained by measurement based on a laser diffraction/scattering method (JIS Z 8825:2013). The peak temperature of the dehydration reaction of aluminum hydroxide is generally 245° C., 320° C., and 550° C. However, by setting the particle size of aluminum hydroxide to 1 μm or less, the dehydration reaction peaking at 320° C. Can be selectively generated.

The PPS resin is melted in the extruder 104, and the melted PPS resin and aluminum hydroxide are kneaded. At this time, since the temperature inside the extruder 104 is, for example, 310° C. to 330° C., a dehydration reaction occurs in which aluminum hydroxide is decomposed into alumina (Al ₂ O ₃ ) and water (H ₂ O). By setting the particle size of aluminum hydroxide to 1 μm or less, the dehydration reaction that peaks at 245° C. can be suppressed, and the dehydration reaction can be prevented from proceeding before the aluminum hydroxide is sufficiently kneaded with the PPS resin. it can. That is, it is possible to cause a dehydration reaction in a state where aluminum hydroxide is sufficiently kneaded with the PPS resin to efficiently foam the resin composition.

The foamed region 31 is formed by volatilization of the water generated by the dehydration reaction, and the foamed insulator 30 is formed around the conductor 20 in a state where alumina is contained in the PPS resin.

The particle size of alumina contained in the foamed insulator 30 is considered to be 1 μm or less corresponding to the particle size of aluminum hydroxide before the dehydration reaction being 1 μm or less.

The foaming degree of the foamed insulation 30 is preferably 30% or more and 80% or less. The content (addition amount) of aluminum hydroxide before the dehydration reaction is, for example, 0.3 wt% or more and 1 wt% or less with respect to the PPS resin in order to set the foaming degree of the foamed insulator 30 to 30% or more and 80% or less. Can be It should be noted that this condition can be said to be such that the content of alumina in the foamed insulator 30 is 0.3 wt% or more and 1 wt% or less with respect to the PPS resin in terms of aluminum hydroxide.

In this way, the step of forming the foamed insulation 30 (the step of manufacturing the insulated wire 10) includes the step of foaming the resin composition containing the PPS resin and aluminum hydroxide by the dehydration reaction of aluminum hydroxide, The step of extruding the foamed resin composition around the conductor 20 to form the foamed insulator 30 having a foaming degree of 30% or more and 80% or less.

After that, the conductor 20 on which the foamed insulator 30 is formed is cooled by the water tank 105 and wound by the winder 107 through the take-up machine 106. In this way, the insulated wire 10 can be manufactured.

With the above-described embodiment, for example, the following effects can be obtained.

The foamed insulator 30 can be obtained by foaming the resin composition containing the PPS resin by the dehydration reaction of aluminum hydroxide. Since the dehydration reaction of aluminum hydroxide is used here, the foamed insulation 30 is formed (configured) from a resin composition containing a PPS resin and alumina.

By using the foamed insulation 30 that is foamed, the partial discharge inception voltage of the insulated wire 10 can be increased. The degree of foaming of the foamed insulation 30 is preferably 30% or more and 80% or less.

In this way, the foamed insulation 30 using the PPS resin can be obtained without impregnating with the inert gas, and the partial discharge inception voltage of the insulated wire 10 can be increased.

By setting the particle size of aluminum hydroxide to 1 μm or less, a dehydration reaction that peaks at 320° C. can be selectively caused, and foaming in extrusion of a resin composition containing a PPS resin having a melting point of about 280° C. Can be efficiently performed. By performing the foaming efficiently, the amount of aluminum hydroxide added can be reduced.

Further, as will be described later, by using aluminum hydroxide having a particle size of 1 μm or less, good adhesion between the conductor 20 and the foamed insulation 30 can be obtained.

Next, examples and comparative examples will be described. Here, a rectangular copper wire having a long side of about 3 mm and a short side of about 2 mm is used as the conductor 20, and the foamed insulator 30 is formed by using a resin composition containing a PPS resin and aluminum hydroxide. As shown in Table 1, six types of insulated electric wires (foamed windings) 10 of Examples 1 and 2 and Comparative Examples 1 to 4 were manufactured. Then, the effects of the examples were verified by evaluating these insulated electric wires 10.

Regarding Examples 1-2 and Comparative Examples 1-4, the conductor 20 was introduced into the preheating furnace 103 and preheated to about 300° C. in a nitrogen atmosphere, and the extruder 104 foamed the conductor 20 at a thickness of 150 μm. The insulator 30 was formed. After forming the foamed insulation 30, the conductor 20 was cooled to room temperature together with the foamed insulation 30 in the water tank 105, and the insulated wire 10 was wound up by the winder 107 through the winder 106.

[Example 1]
In Example 1, as the resin composition forming the foamed insulation 30, a resin composition containing PPS resin and 1 wt% aluminum hydroxide having a particle size of 0.9 μm with respect to the PPS resin was used, and the extrusion temperature was 330. ℃ was made.

[Example 2]
In Example 2, as the resin composition forming the foamed insulation 30, a resin composition containing PPS resin and aluminum hydroxide having a particle size of 0.9 μm and 0.3 wt% with respect to the PPS resin was used. Was set to 330°C.

[Comparative Example 1]
In Comparative Example 1, as the resin composition forming the foamed insulator 30, a resin composition containing PPS resin and 1 wt% aluminum hydroxide with a particle size of 3.0 μm with respect to the PPS resin was used, and the extrusion temperature was 330. ℃ was made.

[Comparative Example 2]
In Comparative Example 2, as the resin composition forming the foamed insulator 30, a resin composition containing PPS resin and 1 wt% of aluminum hydroxide having a particle size of 0.9 μm with respect to the PPS resin was used, and the extrusion temperature was 300. ℃ was made.

[Comparative Example 3]
In Comparative Example 3, as the resin composition for forming the foamed insulation 30, a resin composition containing PPS resin and aluminum hydroxide having a particle size of 0.9 μm and 3 wt% with respect to the PPS resin was used, and the extrusion temperature was 330. ℃ was made.

[Comparative Example 4]
In Comparative Example 4, as the resin composition forming the foamed insulation 30, a resin composition containing PPS resin and aluminum hydroxide having a particle size of 0.9 μm and 0.2 wt% with respect to the PPS resin was used. Was set to 330°C.

The degree of foaming of the foamed insulation 30, the adhesion between the conductor 20 and the foamed insulation 30, and the partial discharge inception voltage (PDIV) were evaluated as follows. The appearance was also evaluated.

[Evaluation method of foaming degree]
The foamed insulation 30 cut out from the insulated wire 10 has a density ρ1 measured by a liquid weighing method, and contains a PPS resin in a state where aluminum hydroxide is not added to the resin composition forming the foamed insulation 30. From the density ρ2 of the resin composition measured by the liquid weighing method, the foaming degree α was determined as follows.
α=(1-ρ1/ρ2)×100
At this time, the specific gravity of aluminum hydroxide was extremely small and was ignored. The degree of foaming of 30% or more and 80% or less was evaluated as passing “◯”. If the foaming degree is less than 30%, the height of the partial discharge inception voltage is insufficient, and therefore the result is “Fail”, and if the foaming degree is more than 80%, the insulation thickness is unstable. ..

[Adhesion evaluation method]
The insulated wire 10 having a length of about 500 mm was rapidly stretched and disconnected by a rapid extension test apparatus with a target line distance of 200 mm, and the total length of cracks in the foamed insulation 30, exposure of the conductor 20, and coating floating. Of less than 7 mm was evaluated as passing “◯”, and those of 7 mm or more were evaluated as unacceptable “x”.

[Evaluation method of partial discharge inception voltage]
An alternating current having a frequency of 50 Hz was applied between the two conductors 20 to the sample in which the long-side surfaces of the two insulated wires 10 were adhered to each other over a length of 150 mm so that no gap was formed. While increasing the voltage at 10 V per second, the voltage at which 50 pC partial discharge is generated 50 times or more is measured, and if the voltage is 1550 V or more, the result is “OK”, and if it is less than 1550 V, the result is “Fail”. X".

[result]
Example 1 and Example 2 passed all the evaluation items, and were excellent in foaming degree, adhesiveness, and partial discharge inception voltage. Specifically, the degree of foaming was good, the partial discharge inception voltage was high, and the particle size of aluminum hydroxide was as small as 0.9 μm, so the adhesion between the conductor 20 and the foamed insulator 30 was also good.

In Comparative Example 1, since the particle size of aluminum hydroxide was as large as 3.0 μm, the adhesion was poor, and it is considered that the dehydration reaction occurred at 245° C., but the degree of foaming was low and the partial discharge inception voltage was The condition was not met.

In Comparative Example 2, since the extrusion temperature was low, the foaming did not occur sufficiently and the condition of the partial discharge inception voltage was not satisfied.

In Comparative Example 3, since the amount of aluminum hydroxide added was as large as 3 wt %, the degree of foaming exceeded 80%, the film thickness of the foamed insulator 30 varied, and the partial discharge inception voltage could not be measured.

In Comparative Example 4, the addition amount of aluminum hydroxide was as small as 0.2 wt %, the degree of foaming was insufficient, and the condition of the partial discharge inception voltage was not satisfied.

In Comparative Example 2, Comparative Example 3, and Comparative Example 4, since the particle size of aluminum hydroxide was as small as 0.9 μm, good adhesion was obtained. By making the particle size of aluminum hydroxide small, for example, 1 μm or less, good adhesion between the conductor 20 and the foamed insulator 30 can be obtained.

According to Example 1 and Example 2, the content (addition amount) of aluminum hydroxide for adjusting the foaming degree to 30% or more and 80% or less is 0.3 wt% or more and 1 wt% with respect to the PPS resin. It can be:

Further, the particle size of aluminum hydroxide for adjusting the foaming degree to 30% or more and 80% or less can be 1 μm or less.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

Hereinafter, the preferred embodiments of the present invention will be additionally described.

(Appendix 1)
A conductor,
A foamed insulator formed around the conductor and having a foamed region,
Equipped with
The foamed insulation is made of a resin composition containing a polyphenylene sulfide resin and alumina, and the foamed insulation has a foaming degree of 30% or more and 80% or less.

(Appendix 2)
The insulated wire according to Appendix 1, wherein the content of the alumina is 0.3 wt% or more and 1 wt% or less with respect to the polyphenylene sulfide resin in terms of aluminum hydroxide.

(Appendix 3)
The insulated wire according to appendix 1 or 2, wherein the particle size of the alumina is 1 μm or less.

(Appendix 4)
A conductor,
A foamed insulator formed around the conductor and having a foamed region,
Equipped with
The foamed insulation comprises a resin composition obtained by foaming a resin composition containing a polyphenylene sulfide resin and aluminum hydroxide by a dehydration reaction of the aluminum hydroxide, and the foamed insulation has a foaming degree of 30% or more. Insulated wire with 80% or less.

(Appendix 5)
A step of foaming a resin composition containing a polyphenylene sulfide resin and aluminum hydroxide by a dehydration reaction of the aluminum hydroxide,
A step of extruding the foamed resin composition around a conductor to form a foamed insulator having a foaming degree of 30% or more and 80% or less;
And a method for manufacturing an insulated electric wire.

(Appendix 6)
6. The method for manufacturing an insulated wire according to appendix 5, wherein the content of the aluminum hydroxide is 0.3 wt% or more and 1 wt% or less with respect to the polyphenylene sulfide resin.

(Appendix 7)
The method for producing an insulated wire according to appendix 5 or 6, wherein the particle diameter of the aluminum hydroxide is 1 μm or less.

10 insulated wire (foamed wire)
20 Conductor 30 Foam Insulator 31 Foam Region (Foam Part)

Claims (3)

A step of foaming a resin composition containing a polyphenylene sulfide resin and aluminum hydroxide by a dehydration reaction of the aluminum hydroxide,
A step of extruding the foamed resin composition around a conductor to form a foamed insulator having a foaming degree of 30% or more and 80% or less;
And a method for manufacturing an insulated electric wire. The content of the aluminum hydroxide, the production method of the insulated wire according to the polyphenylene sulfide claim 1 or less 0.3 wt% or more 1 wt% based on the resin. The particle size of the aluminum hydroxide, the production method of the insulated wire according to claim 1 or 2 is 1μm or less.

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