JPH09106712A - Insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal characteristics, electrical characteristics, and chemical resistance of an insulated wire. SOLUTION: An insulated wire is constituted by a structure having a cover formed by applying and burning polyimide precursor body vanish composed of a polyimide precursor body and solvent onto a conductor. Thereby, the dielectric loss rate in 250 deg.C is 15% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated wire having polyimide as an insulating film.

[0002]

BACKGROUND OF THE INVENTION Conventionally, N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N, A polyimide precursor varnish using an aprotic polar solvent such as N-dimethylformamide (DMF) as a solvent has been generally used. It is known that a polyimide precursor, that is, these solvents used for varnishing a polyamic acid has a high dipole moment of 3.0 debye or more and is strongly associated with the polyamic acid. (Journal of
Polymer Science, A-1, 4, 2607 (196)
6), the same magazine A, 25, 2005 (1987), the same magazine A, 2
5, 2479 (1987)). That is, in the manufacturing process of an insulated wire in which a polyimide precursor varnish is applied on a conductor and baked to cure it as a polyimide film, in order to remove the solvent from the film, the strong association between the polyamic acid and the aprotic polar solvent is cut off. It was necessary to add high heat energy.

[0003]

In recent years, in order to use a polyimide insulated wire under more severe electrical conditions and more severe environments, the thermal and electrical characteristics of the insulated wire,
It is desired to improve chemical resistance. Conventionally, when a polyimide insulated wire is manufactured, N-methyl-2-pyrrolidone (N
MP), N, N-dimethylacetamide (DMAc), N, N
A polyimide precursor varnish using an aprotic polar solvent such as dimethylformamide (DMF) as a solvent has been generally used. Since these solvents form a strong association with the polyamic acid which is the polyimide precursor, it is difficult to completely remove the solvent from the insulated wire coating and often remain inside the coating. The residual solvent remaining inside the film acts as a plasticizer to reduce the thermal softening property and solvent resistance of the film of the insulated wire. Further, the OFM characteristic, which is one of the electrical characteristics of the insulated wire, is deteriorated. As described above, the solvent remaining inside the insulating film has a problem of deteriorating the characteristics of the insulated wire.

[0004]

The present invention comprises a structure having a coating formed by coating and baking a polyimide precursor varnish consisting of a polyimide precursor and a solvent on a conductor. The dielectric loss factor at 250 ° C. Is 15% or less. Further, the present invention provides an insulated electric wire comprising a polyimide precursor varnish composed of a polyimide precursor and a solvent, the polyimide precursor and the solvent being strongly unsolvated, and applied and baked onto a conductor.

The present invention relates to the production of a polyimide insulated wire,
In order to realize the removal of the residual solvent from the insulating film, an aprotic solvent having a strong association force with the resin in the varnish is not used as a solvent for the conventional polyimide precursor varnish.

As a solvent for varnish, a solvent having a weak association force,
For example, a protic solvent (for example, a water-soluble solvent) is used. The solvent may be water soluble. Examples of the solvent are a mixed solvent of a water-soluble solvent having weak association with the resin component in the varnish and water, a compound having an ether group and an alcoholic hydroxyl group in the same molecule, or glycol ethers. The water-soluble solvent is, for example, an ether compound, a water-soluble alcohol compound, or a water-soluble ketone compound.

Examples of the water-soluble ether compounds include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol diethyl ether and the like, and THF is particularly preferable. As the water-soluble alcohol compound, for example, methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol,
Ethylene glycol, 1,2-propanediol, 1,3
-Propanediol, 1,3-butanediol, 1,4-
Butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 2-ethyl-2-hydroxymethyl-1 1,3-propanediol, 1,2,6-hexanetriol and the like can be mentioned, with particular preference given to methanol, ethanol and ethylene glycol. Examples of the water-soluble ketone compound include acetone and methyl ethyl ketone, with acetone being particularly preferred.

As a solvent having an ether group and an alcoholic hydroxyl group in the same molecule, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol. , Tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-
Methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, polyethylene glycol, polypropylene glycol, among these, 2-Methoxyethanol and tetrahydrofurfuryl alcohol are particularly preferable.

The boiling point of the solvent is preferably 100 ° C to 250 ° C. When the boiling point of the solvent of the varnish is 100 ° C. or lower, the solvent is vaporized in the varnish reservoir of the device for applying the varnish on the conductor, and the resin component is solidified, so that continuous production of electric wires cannot be performed. When the boiling point of the solvent is 250 ° C. or higher, the boiling point is higher than that of the existing solvent system, which is disadvantageous because it does not contribute to the improvement of productivity.

The polyimide precursor may be a polyamic acid obtained from an aromatic tetracarboxylic dianhydride and an aromatic diamine. Preferred polyimide precursors include wholly aromatic polyimide precursors, and particularly homopolymers or copolymers of polyamic acid having a repeating unit represented by the general formula (1), or homopolymers of partially imidized polyamic acid. Alternatively, copolymers are preferred.

[0011]

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[0012] Here, R represents a tetravalent aromatic residue containing at least one 6-membered carbon ring, and each of the 4 valents forms a pair, and each of the 4 valences forms a pair. It is characterized by being connected to. Specific examples of R include the following.

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In particular, R is preferably the following.

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R'represents a divalent aromatic residue having 1 to 4 carbon 6-membered rings. Specific examples of R ′ include the following.

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[0015]

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The following are particularly preferred as R '.

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The most preferable polyamic acid having a repeating unit represented by the above general formula (1) is pyromellitic dianhydride (PMDA) or 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride (B
It is a polyamic acid derived from PDA) and diaminodiphenyl ether (DADE). The former is poly (4,4'-oxydiphenylenepyromellitimide), and the latter is poly (4,4'-oxydiphenylene). -3,
3 ', 4,4'-biphenyltetracarboximide).

The molecular weight of the polyimide precursor (measured by gel permeation chromatography in terms of polystyrene) is preferably 50,000 or more. More preferably, the molecular weight is desired to be 70,000 or more. When the molecular weight is less than 50,000, a good insulating film cannot be formed because the film is cracked or the film is separated from the conductor during the production of the insulated wire.

In the present invention, the dipole moment is used as an index for measuring the association force between the solvent and the solute. In the present invention, a solvent having a dipole moment value of 3.0 debye or more is a solvent having a strong association force, and a solvent having a dipole moment value of less than 3.0 debye is a solvent having a weak association force. Define.

Conventionally, when manufacturing a polyimide insulated wire,
A typical solvent of the polyimide precursor varnish that has been generally used as a material for forming a polyimide film,
These are N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc) and N, N-dimethylformamide (DMF). The dipole moment values of these solvents are 4.1, 3.7, and 3.9, respectively, and all have a high polarity of 3.0 debye or more, and thus are strongly associated with the polyamic acid. On the other hand, typical solvents used in the present invention are THF, acetone, 2-methoxyethanol, and tetrahydrofurfuryl alcohol, and the dipole moment values of these solvents are 1.
7, 2.7, 2.0 and 2.1, each having a low polarity of less than 3.0 debye and weakly associated with a polyamic acid.

The varnish contains a polyimide precursor and a solvent. In the varnish, the content of the polyimide precursor may be, for example, 10 to 50% by weight. The conductor may be metal. Examples of conductors are copper, nickel plated copper, gold, gold plated copper and the like. The thickness of the conductor is not limited, but is usually 0.02 to 3 mm. The thickness of the coating formed by the polyimide precursor is, for example, 1 to
It may be 50 μm.

The insulated wire of the present invention can be manufactured by applying a polyimide precursor varnish to a conductor and baking it. Baking is, for example, 300 to 600 ° C.
It can be done depending on the temperature.

According to the present invention, the solvent remaining in the insulating film is reduced. The amount of solvent remaining in the insulating film of the polyimide electric wire can be evaluated by dielectric relaxation measurement. It can be considered that the smaller the value of DF (dielectric loss rate) of the insulated wire evaluated by the dielectric relaxation measurement, the smaller the amount of solvent remaining in the insulating film.

The conventional polyimide electric wire has a dielectric loss rate of 15% or more at 250 ° C. measured by dielectric relaxation measurement, whereas the polyimide electric wire of the present invention has a dielectric loss rate of 250 ° C.
The dielectric loss rate is 15% or less, particularly 10% or less, and the amount of solvent remaining in the insulating film is smaller than that of the conventional polyimide electric wire. The polyimide-insulated electric wire of the present invention has a smaller amount of solvent remaining in the insulating film as compared with the conventional polyimide-insulated electric wire, and the thermal characteristics, electrical characteristics, and chemical resistance of the insulated wire are improved.

[0025]

Preferred embodiments of the present invention will be described below with reference to examples.

Example 1 Using 2-methoxyethanol (boiling point: 125 ° C.) as a solvent,
A polyimide precursor varnish containing a polyimide precursor (molecular weight 88000), which is a polyamic acid composed of pyromellitic dianhydride (PMDA) and diaminodiphenyl ether (DADE) (polyimide precursor content: 15
% By weight) on a conductor with a diameter of 1.00 mm and a film thickness of 0.030
The coating was applied so that the thickness became mm, and baking was performed in a baking furnace at a furnace temperature of 400 ° C. Table 1 shows the wire characteristics of the insulated wire of this example. The amount of residual solvent in the insulating film is evaluated by dielectric relaxation measurement. It can be considered that the smaller the value of DF (dielectric loss factor) of the insulated wire evaluated by the dielectric relaxation measurement, the smaller the amount of solvent remaining in the insulating film.

Example 2 The solvent of the polyimide precursor varnish was a THF / MeOH mixed solvent (THF boiling point: 66 ° C., MeOH boiling point: 65 ° C.)
And an insulated wire was obtained in the same manner as in Example 1 except that the molecular weight of the polyimide precursor was changed to 107,000. Table 1 shows the wire characteristics of the insulated wire of this example. When the winding was manufactured using this varnish for a long time, the varnish thickened due to the evaporation of the solvent of the varnish, and the winding could not be manufactured.

Examples 3 and 4 The procedure of Example 1 was repeated except that the solvent for the polyimide precursor varnish was 2-methoxyethanol and the molecular weights of the polyimide precursors were 23000 (Example 3) and 47000 (Example 4). I got an insulated wire. Table 1 shows the wire characteristics of the insulated wire of this example.

Comparative Example 1 N-methyl-2-pyrrolidone (boiling point: 202 ° C.), which is an aprotic polar solvent, was used as a solvent, and the polyimide precursor Wannispirer ML (manufactured by DuPont) in which the molecular weight of the polyimide precursor was 90,000. ) Is coated on a conductor with a diameter of 1.00 mm so that the film thickness is 0.030 mm, and the furnace temperature is 400
It was baked in a baking oven at ℃. The electric wire characteristics of the insulated electric wire of this comparative example are shown in Table 1.

[0030]

[Table 1]

Note): (1) DF is the dielectric loss rate measured in the molten metal bath. (2) OFM was measured according to the NEMA standard overload test method. (3) Flexibility, adhesion, heat shock, one-way wear,
Dielectric breakdown voltage, NaOH resistance and H ₂ SO ₄ resistance are JIS C3
It was measured according to the 003 enamel copper wire and enamel aluminum wire test methods.

[0032]

The solvent of the varnish of the present invention has a weaker association force with the resin than the solvent of the conventional varnish. In the present invention, the solvent can be easily removed in the electric wire manufacturing process, and the effect that the solvent remaining in the insulating film is reduced to improve the thermal characteristics, electric characteristics, and chemical resistance of the insulated electric wire To do.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuuo Ueoka 1-3-3 Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Electric Industries, Ltd. (72) Inventor Toshihiko Tanaka Kikuzumiichi, Minami-ku, Nagoya-shi, Aichi Prefecture 7-10 Sumitomo Electric Industries, Ltd. Nagoya Works (72) Inventor Isao Tomioka 23 Uji Kozakura, Uji City, Kyoto Prefecture Central Research Institute of Unitika Ltd. (72) Inventor Shoji Okamoto 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. A structure having a coating formed by coating and baking a polyimide precursor varnish consisting of a polyimide precursor and a solvent on a conductor, and having a dielectric loss rate at 250 ° C. of 15% or less. Characterized insulated wire. 2. An insulated wire comprising a polyimide precursor varnish composed of a polyimide precursor and a solvent, wherein the polyimide precursor and the solvent are not strongly solvated and applied and baked onto a conductor.