JP6265989B2 - Insulated wire and manufacturing method thereof - Google Patents

Description

The present invention relates to an insulated wire and a method for manufacturing the same. More specifically, the present invention relates to an insulated wire made of fluorinated polyimide and a method for producing the same.

Insulated wires are used in motors, coils, transformers, and the like, and are used in a wide range of fields such as automobiles, industrial machines, OA equipment, and electric / electronic equipment that use them. In recent years, in order to improve the space factor, there has been an increasing demand for thinning the coating of insulated wires and increasing the heat resistance, and fluorinated polyimide has attracted attention as such a coating material.

As an insulated wire using a fluorinated polyimide as a coating material, a winding in which a coating containing a polyimide having a fluorine group or a precursor of the polyimide is applied and baked on a conductor is disclosed (for example, Patent Document 1). reference.). Moreover, the material containing the polyimide resin which has a repeating unit of a specific structure as an insulation coating material of a coil | winding is disclosed (for example, refer patent document 2).

JP-A-6-44827 JP 2002-56720 A

In this way, development of a coating material for an insulated wire using fluorinated polyimide has been attempted. Here, the polyimide usually dissolves in a solvent such as an organic solvent when it is a polyamic acid that is a precursor of the polyimide, but when it becomes a polyimide, it does not dissolve in the solvent. Therefore, for example, in the production of the winding disclosed in Patent Document 1, imidization is performed after applying a polyimide precursor paint having a fluorine group to a conductor, and heat treatment at high temperature is performed to imidize. The process is an essential process. However, there is a problem that it takes time for the imidization reaction to sufficiently proceed in such a heat treatment step. In addition, since a process that needs to be processed at a high temperature for a long time is an essential process, the productivity is low, and further, there is a problem that oxidation of the conductor proceeds. On the other hand, in the Example disclosed in Patent Document 2, the process of winding a film on a conductor is an essential process in order to form a film of fluorine-containing polyimide and to form a coating material for the winding. However, once the film is formed and wound around the conductor, the number of processing steps is increased, and the manufacturing process is complicated, resulting in low productivity. Thus, as an insulated wire using fluorinated polyimide as a coating material, there was room for improvement to make it easier to manufacture.

This invention is made | formed in view of the said present condition, Maintaining the performance as an insulated wire, providing the insulated wire with the high uniformity of the thickness of a coating | covering material and being able to manufacture more easily. Objective.

As a result of intensive studies on an insulated wire that can be easily manufactured using fluorinated polyimide as a coating material, the present inventors have found that a polymer unit based on a fluorinated diamine having a specific structure and a fluorine having a specific structure. Fluorinated polyimide containing polymerized units based on acid anhydride and having a certain proportion or more of these polymerized units is soluble in solvents, particularly solvents mainly composed of ketones and esters, and has a low dielectric constant When such a fluorinated polyimide is used as a coating material for an insulated wire, an insulated wire is manufactured by applying a varnish containing the fluorinated polyimide and a solvent on the conductor and removing the solvent. It is possible to easily manufacture an insulated wire with a uniform coating material thickness without degrading the performance of the insulated wire. It was. Thus, it has been found that the above-mentioned problems can be solved by using a specific fluorinated polyimide as a coating material for insulated wires, and the present invention has been achieved.

That is, this invention is an insulated wire which consists of a conductor and an insulating film, Comprising: This insulating film is following formula (1):

(In the formula, R _f ¹ and R _f ² represent a substituent of an aromatic ring, and one of four substitutable sites per aromatic ring is substituted with the substituent. R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms.) And / or the following formula (2):

(Wherein R _f ³ represents a substituent of the aromatic ring, and any one of the four substitutable sites of the aromatic ring is substituted with the substituent. R _f ³ represents a fluorine atom, A polymer unit (A) based on a fluorinated diamine represented by the formula (3):

(Wherein Rf ⁴ and Rf ⁵ are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms) and a polymer unit (B) based on a fluorinated acid anhydride represented by Insulating, characterized in that the polymerized units (A) and (B) are made of fluorinated polyimide with 60 mol% or more of all polymerized units, and the film thickness tolerance of the insulating film is within ± 20% It is an electric wire.

As for the said fluorinated polyimide, it is preferable that a polymerization unit (B) is 30 mol% or more of all the polymerization units.

The fluorinated polyimide may further contain a polymerized unit (C) based on a non-fluorinated diamine.

The fluorinated polyimide may further contain polymerized units (D) based on other types of acid anhydrides.

The present invention also provides the following formula (1):

(In the formula, R _f ¹ and R _f ² represent a substituent of an aromatic ring, and one of four substitutable sites per aromatic ring is substituted with the substituent. R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms.) And / or the following formula (2):

(Wherein R _f ³ represents a substituent of the aromatic ring, and any one of the four substitutable sites of the aromatic ring is substituted with the substituent. R _f ³ represents a fluorine atom, A polymer unit (A) based on a fluorinated diamine represented by the formula (3):

(Wherein R _f ⁴ and R _f ⁵ are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms), a polymer unit based on a fluorinated acid anhydride (B And a fluorinated polyimide in which the polymerized units (A) and (B) are 60 mol% or more of the total polymerized units, and a solvent, wherein the solvent contains 40% by mass or more of the total solvent and the ketone. It is also a varnish characterized by being an ester.

And this invention is also a manufacturing method of the insulated wire characterized by apply | coating the said varnish on a conductor, and baking at 80-250 degreeC.

It is preferable that the said manufacturing method manufactures an insulated wire, without heating to 300 degreeC or more for 30 minutes or more.

Since the insulated wire of this invention consists of the said structure, the uniformity of the thickness of coating | covering material is high, and it can manufacture more easily, maintaining the performance as an insulated wire.

The present invention is described in detail below.

The insulated wire of the present invention comprises a conductor and an insulating film. And the said insulating film is following formula (1):

(In the formula, R _f ¹ and R _f ² represent a substituent of an aromatic ring, and one of four substitutable sites per aromatic ring is substituted with the substituent. R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms.) And / or the following formula (2):

(Wherein R _f ³ represents a substituent of the aromatic ring, and any one of the four substitutable sites of the aromatic ring is substituted with the substituent. R _f ³ represents a fluorine atom, A polymer unit (A) based on a fluorinated diamine represented by the formula (3):

(Wherein R _f ⁴ and R _f ⁵ are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms), a polymer unit based on a fluorinated acid anhydride (B ), And the polymerized units (A) and (B) are made of fluorinated polyimide that is 60 mol% or more of the total polymerized units.

In the above formula (1), R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorinated alkyl group having 1 to 8 carbon atoms, but a fluorine atom or a fluorinated alkyl having 1 to 4 carbon atoms. Group is preferable, and a fluorine atom and a C1-C3 fluorine-containing alkyl group are more preferable. Specifically, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, HCF 2 CF 2 -, CF} 3 CF 2 -, CF 3 CH 2 -, CF 3 CF 2 CF 2 CF 2 -, CF ₃ CF ₂ CF ₂ CH ₂ - are preferred, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, CF 3 CF 2 -, HCF} 2 CF 2 - is more preferable. Particularly preferred is a trifluoromethyl group.

Specific examples of the fluorinated diamine represented by the above formula (1) include fluorinated biphenyldiamine. Among these, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl and 2,2′-bis (hexafluoroethyl) -4,4′-diaminobiphenyl are more preferable, and 2,2 '-Bis (trifluoromethyl) -4,4'-diaminobiphenyl is particularly preferred.

In the above formula (2), R _f ³ represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms, preferably a fluorine atom or a fluorine-containing alkyl group having 1 to 4 carbon atoms, and a fluorine atom or carbon number. 1-3 fluorine-containing alkyl groups are more preferable. Specifically, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, HCF 2 CF 2 -, CF} 3 CF 2 -, CF 3 CH 2 -, CF 3 CF 2 CF 2 CF 2 -, CF ₃ CF ₂ CF ₂ CH ₂ - are preferred, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, HCF 2 CF 2 -, CF} 3 CF 2 - is more preferable. Particularly preferred is a trifluoromethyl group.

Specific examples of the fluorinated diamine represented by the above formula (2) include 2-trifluoromethyldiamine and 2-hexafluoroethyldiamine. Among these, 2-trifluoromethyldiamine is particularly preferable.

In the formula (3), R _f ⁴ and R _f ⁵ are the same or different and each represents a fluorine atom or a fluorinated alkyl group having 1 to 8 carbon atoms, but a fluorine atom or a fluorinated alkyl having 1 to 4 carbon atoms. Group is preferable, and a fluorine atom and a C1-C3 fluorine-containing alkyl group are more preferable. Specifically, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, HCF 2 CF 2 -, CF} 3 CF 2 -, CF 3 CH 2 -, CF 3 CF 2 CF 2 CF 2 -, CF ₃ CF ₂ CF ₂ CH ₂ - are preferred, a fluorine atom, fluoromethyl group, difluoromethyl group, trifluoromethyl _{group, HCF 2 CF 2 -, CF} 3 CF 2 - is more preferable. Particularly preferred is a trifluoromethyl group.

Among the fluorinated acid anhydrides represented by the above formula (3), 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride is particularly preferable.

The polymerized unit (A) is a polymerized unit based on the fluorinated diamine represented by the above formula (1) and / or the fluorinated diamine represented by the above formula (2), but represented by the above formula (1). It may be based on one or more of the fluorinated diamines, or may be based on one or more of the fluorinated diamines represented by the above formula (2). One or more of the fluorinated diamines represented by the above formula (1) and one or more of the fluorinated diamines represented by the above formula (2) may be used. . Among these, it is preferable that the said polymer unit (A) is a polymer unit based on the fluorinated diamine represented by the said Formula (1) from a heat resistant and solvent solubility viewpoint.

Further, the polymerized unit (B) is a polymerized unit based on the fluorinated acid anhydride represented by the above formula (3), but one type of the fluorinated acid anhydride represented by the above formula (3) or It may be based on two or more.

In the fluorinated polyimide, the constituent ratio ((A) :( B) (molar ratio)) of the polymerization units (A) and (B) is preferably 55:45 to 45:55. When the composition ratio of the polymerization units (A) and (B) is in such a range, the dielectric constant of the fluorinated polyimide is low. The constituent ratio of the polymerization units (A) and (B) ((A) :( B) (molar ratio)) is more preferably 52:48 to 48:52, and 51:49 to 49:51. More preferably it is.

In the fluorinated polyimide, the polymerization units (A) and (B) are 60 mol% or more of the total polymerization units, but as long as the polymerization units (A) and (B) include 60 mol% or more of the total polymerization units, The polymer unit may be included. When the total proportion of the polymerized units (A) and (B) in all the polymerized units in the fluorinated polyimide is 60 mol% or more, the fluorinated polyimide becomes soluble in the solvent and the dielectric constant becomes low. . The total proportion of the polymerized units (A) and (B) is preferably 65 mol% or more, more preferably 70 mol% or more. The upper limit can be 100 mol%.

As for the said fluorinated polyimide, it is preferable that a polymerization unit (B) is 30 mol% or more of all the polymerization units. When the ratio of the polymerized units (B) in the total polymerized units of the fluorinated polyimide is within such a range, the solvent solubility particularly in ketones, esters and ethers is enhanced. More preferably, the polymerized unit (B) is 40 mol% or more of the total polymerized units, and still more preferably 50 mol% or more.

Examples of the other polymer units include polymerization based on non-fluorinated diamine, non-fluorinated acid anhydride, fluorinated acid anhydride (excluding the fluorinated acid anhydride represented by the above formula (3)). Units are listed. Among these, it is also one of the preferred embodiments of the present invention that the fluorinated polyimide further contains a polymerized unit (C) based on a non-fluorinated diamine. Further, the fluorinated polyimide is further polymerized based on non-fluorinated acid anhydrides and other types of acid anhydrides such as fluorinated acid anhydrides excluding the fluorinated acid anhydrides represented by the above formula (3). Including the unit (D) is one of the preferred embodiments of the present invention.

Examples of the non-fluorinated diamine include diaminodiphenyl ether, diaminodiphenylmethane, diaminodiphenylpropane, and diaminodiphenylsulfone.

Examples of the other acid anhydrides include pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, and phenylenebis (trimellitic acid monoester acid anhydride). Non-fluorinated acid anhydrides of the above; fluorinated acid anhydrides in which the aromatic ring of pyromellitic dianhydride or biphenyltetracarboxylic dianhydride is substituted with a trifluoromethyl group or a fluoro group;

The higher the imidation ratio of the fluorinated polyimide, the better. The upper limit is 100%. If the imidization rate is low, the relative dielectric constant may be lowered. Therefore, the lower limit is preferably 70%. The imidization rate is measured by IR analysis.

The insulating film preferably has an ammonium ion content of 100 ppm or less with respect to the insulating film. The content of ammonium ions is more preferably 80 ppm or less, further preferably 50 ppm or less, and the lower limit is not particularly limited, but may be 0.01 ppm. When the content of ammonium ions is within the above range, there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.

The content of ammonium ions is measured by ion chromatography by dissolving a certain amount of insulating coating (polyimide) in a solvent such as N-methylpyrrolidone (NMP) and dropping it into stirred water to dissolve it in water. It is a value measured by the method of converting the concentration.
Specifically, 10 g of insulating coating can be dissolved in 50 ml of NMP and dropped into 150 ml of water.

In the insulating coating, the content of colored ions other than ammonium ions is preferably 200 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less with respect to the insulating coating. If the content of the colored ions is within the above range, there is little influence on the insulation resistance, and there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.

Examples of the colored ions include transition metal cations such as Fe ²⁺ , Fe ³⁺ , and Ni ²⁺ , and strong acid anions such as Cl ⁻ and SO ₄ ²⁻ .
The content of the colored ions is obtained by dissolving a certain amount of an insulating film in a solvent such as NMP, dropping into stirred water and measuring the colored ions dissolved in the water by ion chromatography, and converting the concentration. It is a value measured by the method.
Specifically, 10 g of insulating coating can be dissolved in 50 ml of NMP and dropped into 150 ml of water.

The fluorinated polyimide in the present invention includes a fluorinated diamine represented by the above formula (1) and / or a fluorinated diamine represented by the above formula (2) and a fluorinated acid anhydride represented by the above formula (3). It can be obtained by performing a ring-opening polyaddition reaction using a product and, if necessary, other diamine or acid anhydride as a raw material monomer to produce a polyamic acid and subjecting the polyamic acid to a dehydration cyclization reaction.

The ring-opening polyaddition reaction can be performed by a commonly performed method. Examples thereof include a method in which the reaction is performed by stirring the raw material monomer in a solvent.

Examples of the solvent include amides such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide; sulfoxides such as dimethyl sulfoxide; esters such as γ-butyrolactone, butyl acetate, ethyl acetate, and ethyl lactate; methyl ethyl ketone, methyl isobutyl Ketones such as ketone, acetone, cyclohexanone, etc. can be used. Among these, a solvent in which the total of ketones and / or esters accounts for 40% by mass or more of the total solvent is preferable, and a solvent in which the total of ketones and / or esters accounts for 50% by mass or more of the total solvent is more preferable. More preferably, the total amount of ketones and / or esters occupies 75% by mass or more of the total solvent.

The ring-closing polyaddition reaction using the monomer may be carried out while substituting with an inert gas, preferably nitrogen gas, during the reaction. Moreover, although reaction temperature and reaction time can be set suitably, for example, 0-150 degreeC, Preferably it is room temperature (25 degreeC) -100 degreeC, and 2-24 hours, Preferably, it is 2-12. It can be time.

The dehydration cyclization reaction can be performed by a commonly performed method. For example, a method of heat-treating the polyamic acid obtained by the ring-opening polyaddition reaction, a polyamic acid obtained by the ring-opening polyaddition reaction, or the like. And a method of chemically treating them.

Specifically, the polyamic acid is heat-treated in an inert gas atmosphere at a reaction temperature of 20 to 300 ° C., preferably 50 to 200 ° C. for 1 to 48 hours, preferably 2 The method of heating for -24 hours is mentioned.
Examples of the inert gas include argon gas, helium gas, nitrogen gas, and the like. At this time, a dehydrating agent such as phosphoric acid may be used.

Specific examples of the method of chemically treating the polyamic acid include a method of treating the polyamic acid with a dehydrating agent or an imidizing agent. The treatment method using the imidizing agent can be performed by a commonly performed method.
Examples of the treatment method include a method using acetic anhydride as a dehydrating agent and pyridine as an imidizing agent.

The higher the imidization rate, the better. The upper limit is 100%. If the imidization rate is low, the relative dielectric constant may be lowered. Therefore, the lower limit is preferably 70%. The imidization rate is measured by IR analysis.

The insulated wire of the present invention is composed of a conductor and an insulating film, but the insulating film may be formed on the outer periphery of the conductor so that the conductor and the insulating film are in contact with each other. An insulating film may be formed on the outer periphery of the conductor via another layer, for example, another resin layer. The insulating film is preferably in contact with the conductor, and in that case, an insulated wire with strong adhesion between the conductor and the insulating film can be obtained.

Although the film thickness of the said insulating film is not restrict | limited in particular, For example, it is preferable that it is 1-200 micrometers. More preferably, it is 2-120 micrometers, More preferably, it is 3-60 micrometers. Moreover, it can also be thinned to 30 μm or less. Reducing the thickness of the insulating film is advantageous in terms of excellent heat dissipation performance.
The film thickness of the insulating film can be measured by a laser outer diameter measuring machine, an eddy current displacement system, or a combination thereof.

The insulating film has a film thickness tolerance within ± 20%. The insulated wire of the present invention has a film thickness tolerance of the insulating film in such a range, so that the film thickness of the coating material is high and the partial discharge start voltage is high. The thickness tolerance of the insulating film is preferably within ± 15%, more preferably within ± 10%.
The film thickness tolerance can be calculated from the difference between the average value and the upper and lower limit values by continuously measuring the film thickness of the insulating film.

The said insulation film can be obtained by forming the varnish containing the fluorinated polyimide and solvent in this invention in the outer periphery of a conductor, and the insulated wire of this invention manufactures the fluorinated polyimide in this invention mentioned above, for example. The varnish containing a process and this fluorinated polyimide and a solvent is prepared, this varnish is apply | coated on a conductor, and it can manufacture by the manufacturing method including baking at 80-250 degreeC.
That is, the manufacturing method of the insulated wire which apply | coats the varnish containing the fluorinated polyimide and solvent in this invention on a conductor, and bakes at 80-250 degreeC is also one of this invention.
Moreover, the said varnish containing the fluorinated polyimide and solvent in this invention is also one of this invention.

As the solvent contained in the varnish, the same solvent as used in the above-described ring-opening polyaddition reaction can be used, but the same solvent as that used in the ring-opening polyaddition reaction may be used. Different solvents may be used. That is, the fluorinated polyimide obtained in the fluorinated polyimide production process is obtained in the form of a solution dissolved in a solvent, but the solution may be used as it is as a varnish, or the same solvent may be added to the solution. It may be used as a varnish after removing the partial solvent to adjust the fluorinated polyimide concentration, or may be used as a varnish by adding a different solvent to the solution.
Among these, the form in which the solvent contained in the varnish is 40% by mass or more of the whole solvent is a ketone and / or an ester is also one of the preferred embodiments of the present invention.

The concentration of the varnish is not particularly limited as long as the fluorinated polyimide is uniformly dispersed in the solvent. The solid content concentration is 1 to 40 mol%, more preferably 5 to 30 mol%. It is desirable that

The characteristic of the fluorinated polyimide in the present invention is its solvent solubility. Usually, the polyimide is insoluble in the solvent after the ring closure, and the solvent-soluble polyimide which is soluble in the solvent after the ring closure also has an amide as the main solvent.

However, since amides may have poor wettability with conductors such as copper wire, a large film thickness difference may appear when a ring-closed polyimide dissolved in amide is applied to the conductor, and when the film thickness difference is large, Many undesirable effects such as variations in withstand voltage, variations in partial discharge start voltage, variations in winding shape, and improvement in the coefficient of friction between conductors may appear. On the other hand, when the polyimide is processed into a coating material, the difference in film thickness is increased because the films are overlapped.
On the other hand, since the fluorinated polyimide in the present invention contains the specific polymerization units described above in a specific ratio, the total of ketone and / or ester accounts for 40% by mass or more of the total solvent as a solvent for the varnish. A solvent can be used. As a result, the varnish does not repel a conductor such as a copper wire, and can be applied without any film thickness tolerance, thereby providing a highly uniform coating. It becomes possible to suppress.

The varnish may contain other components as long as it contains the fluorinated polyimide and the solvent. For example, additives such as pigments, dyes, inorganic fillers, organic fillers, lubricants, adhesion improvers, and the like have low reactivity. It may contain molecules, compatibilizers, and the like. Furthermore, other resins may be included as long as the effects of the present invention are not impaired.

The varnish preferably has an ammonium ion content of 100 ppm or less. The content of ammonium ions is more preferably 80 ppm or less, further preferably 50 ppm or less, and the lower limit is not particularly limited, but may be 0.01 ppm. When the content of ammonium ions is within the above range, there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.

The content of ammonium ions is a value measured by a method in which a certain amount of varnish is dropped into stirred water and ammonium ion dissolved in water is measured by ion chromatography and the concentration is converted. .
Specifically, after the concentration of the fluorinated polyimide in the varnish is adjusted to 20% by mass, 100 ml of varnish can be added to 150 ml of water.
A varnish with a small content of ammonium ions can be suitably produced by a method for producing a varnish described later.

The content of colored ions other than ammonium ions is preferably 200 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. When the content of the colored ions is within the above range, there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.
Examples of the colored ions include transition metal cations such as Fe ²⁺ , Fe ³⁺ , and Ni ²⁺ , and strong acid anions such as Cl ⁻ and SO ₄ ²⁻ .
The content of the colored ions is a value measured by a method in which a certain amount of varnish is dropped into stirred water and the concentration of the colored ions dissolved in the water is measured by ion chromatography. is there.
Specifically, after the concentration of the fluorinated polyimide in the varnish is adjusted to 20% by mass, 100 ml of varnish can be added to 150 ml of water.
A varnish with a small content of colored ions other than ammonium ions can be suitably produced by a method for producing a varnish described later.

In the present invention, an insulating film is formed on the conductor by applying the varnish directly on the conductor or through another layer and baking it. Unlike the prior art, the present invention applies and bakes a varnish containing polyimide, and it is not necessary to imidize polyamic acid in the baking process to obtain polyimide. Therefore, the baking temperature does not need to be high enough to perform imidization and can be set to 80 to 250 ° C. Therefore, the method for manufacturing an insulated wire according to the present invention is more effective than the conventional manufacturing method. The adverse effect on the conductor such as the progress of oxidation is low and the productivity is high.
From these things, it is one of the preferable characteristics of the manufacturing method of the insulated wire of this invention that an insulated wire can be manufactured, for example, without heating to 300 degreeC or more for 30 minutes or more.

As a specific form of the step of applying the varnish on the conductor and baking it at 80 to 250 ° C., for example, after applying the varnish directly or through another layer on the conductor, the set temperature is 80 to The form which forms the insulating film by repeating the operation | work which passes through the inside of the furnace set to 250 degreeC for 5 to 10 second per baking, and is baked several times is mentioned.

The other layers are different from the insulating film. The other layer is, for example, a layer made of at least one resin selected from the group consisting of aromatic polyetherketone resin, fluororesin, polyamideimide, polyetherimide, polyethersulfone, and polyphenylene sulfide. It is preferable.

The material for forming the conductor is not particularly limited as long as the material has good conductivity, and examples thereof include copper, copper alloy, copper clad aluminum, aluminum, silver, gold, and galvanized iron.

The shape of the conductor is not particularly limited, and may be circular or flat. In the case of a circular conductor, the diameter of the conductor may be 0.3 to 2.5 mm.

One of the characteristics of the fluorinated polyimide in the present invention is its transparency. Since the fluorinated polyimide in the present invention contains the above-mentioned specific polymerization units in a specific ratio, it becomes a transparent coating material when used as an insulating film of an insulated wire. Thus, when the insulation film of an insulated wire is transparent, it becomes easy to inspect the covered conductor. That is, the insulated wire of the present invention is also suitable for the present invention in that the difference in reflectance between the conductor before being coated with the insulating film and the insulated wire after being coated with the insulating film is within 20%. It is one of the embodiments. The difference in reflectance is more preferably within 15%, further preferably within 10%.

The insulated wire of the present invention can be suitably used for wrapping wires, automotive wires, robot wires, and the like. Moreover, it can be used suitably also as a coil winding (magnet wire), and if the insulated wire of the present invention is used, it is difficult to cause damage in winding processing. The above winding is suitable for motors, rotating electrical machines, compressors, transformers, etc., requires high voltage, high current and high thermal conductivity, requires high-density winding processing, and is downsized. -It has the characteristics that it can sufficiently withstand the use with high output motors. Moreover, it is suitable also as an electric wire for power distribution, power transmission, or communication.

The varnish is
A step of polyaddition reaction of a fluorinated diamine and a fluorinated acid anhydride to obtain a polyamic acid solution (1),
A step (2) of obtaining a solution of fluorinated polyimide by dehydration cyclization reaction from the obtained polyamic acid solution,
Dropping the obtained solution into a poor solvent to precipitate the fluorinated polyimide, and recovering the powdered fluorinated polyimide (3);
After the powdered fluorinated polyimide is dissolved in a good solvent, the obtained solution is dropped into a poor solvent to precipitate the fluorinated polyimide, and a purification step for recovering the purified powdered fluorinated polyimide ( 4) and
Step (5) for obtaining a varnish by dissolving the fluorinated polyimide in a solvent
It can manufacture suitably also by the manufacturing method characterized by including.

According to this production method, a varnish containing almost no ammonium ions can be produced. Moreover, according to this manufacturing method, the varnish which hardly contains coloring ions other than an ammonium ion can be manufactured.

The polyaddition reaction in step (1) and the dehydration cyclization reaction in step (2) are as described above.

In step (3), the solution obtained in step (2) is dropped into a poor solvent to precipitate the fluorinated polyimide, and the powdered fluorinated polyimide is recovered. Examples of the poor solvent include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, toluene, and the like.

In the step (4), the powdered fluorinated polyimide obtained in the step (3) is dissolved in a good solvent, and then the obtained solution is dropped into a poor solvent to precipitate the fluorinated polyimide, followed by purification. The powdered fluorinated polyimide is recovered.
Examples of the good solvent include amides such as N-methylpyrrolidone (NMP), dimethylacetamide, and dimethylformamide; sulfoxides such as dimethyl sulfoxide; esters such as γ-butyrolactone, butyl acetate, ethyl acetate, and ethyl lactate; And ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetone and cyclohexanone; Among these, a solvent in which the total of ketones and / or esters accounts for 40% by mass or more of the total solvent is preferable, and a solvent in which the total of ketones and / or esters accounts for 50% by mass or more of the total solvent is more preferable. More preferably, the total amount of ketones and / or esters occupies 75% by mass or more of the total solvent.
Examples of the poor solvent include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, toluene, and the like.

Step (4) is one of the important steps in the production method. Since the said manufacturing method includes the process (4) for refine | purifying a fluorinated polyimide, it can adjust the ammonium ion contained in the varnish finally obtained to desired content. Moreover, since the said manufacturing method includes the process (4) for refine | purifying a fluorinated polyimide, colored ions other than the ammonium ion contained in the varnish finally obtained can be adjusted to desired content. .

Step (4) can be repeated any number of times, and is preferably repeated until ammonium ions can be reduced to a desired amount, more preferably 3 times or more, and even more preferably 5 times or more. The obtained powdery fluorinated polyimide may be dried.
The powdery fluorinated polyimide preferably has an ammonium ion content of 100 ppm or less with respect to the fluorinated polyimide. The content of ammonium ions is more preferably 80 ppm or less, further preferably 50 ppm or less, and the lower limit is not particularly limited, but may be 0.01 ppm. When the content of ammonium ions is within the above range, there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.
The content of ammonium ions is measured by ion chromatography by dissolving a certain amount of powdered fluorinated polyimide in a solvent such as N-methylpyrrolidone (NMP), dropping it into stirred water and dissolving it in water. Then, the value is measured by the method of converting the density.
Specifically, 10 g of powdery fluorinated polyimide can be dissolved in 50 ml of NMP and dropped into 150 ml of water.
The powdered fluorinated polyimide preferably has a content of colored ions other than ammonium ions of 200 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. When the content of the colored ions is within the above range, there is an advantage that there is little adverse effect on the partial discharge start voltage and withstand voltage.
Examples of the colored ions include transition metal cations such as Fe ²⁺ , Fe ³⁺ , and Ni ²⁺ , and strong acid anions such as Cl ⁻ and SO ₄ ²⁻ .
The content of the colored ions is determined by dissolving a certain amount of powdered fluorinated polyimide in a solvent such as NMP, dropping into stirred water and measuring the colored ions dissolved in water by ion chromatography. It is a value measured by the method of converting.
Specifically, 10 g of powdery fluorinated polyimide can be dissolved in 50 ml of NMP and dropped into 150 ml of water.

In step (5), the fluorinated polyimide obtained in step (4) is dissolved in a solvent to obtain a varnish.

About the solvent for obtaining the said varnish, what was mentioned above as a solvent contained in a varnish can be used.

It is also possible to manufacture an insulated wire by a manufacturing method including a step of applying the varnish obtained by the above manufacturing method onto a conductor and baking it at 80 to 250 ° C. With this manufacturing method, an insulated wire made of an insulating coating with a low ammonium ion content can be manufactured. Moreover, this manufacturing method can manufacture the insulated wire which consists of an insulating film with little content of coloring ions other than an ammonium ion.

Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Example 1
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl were added to a dropping funnel, a stirrer, To a 1 L four-necked flask equipped with a reflux tube and a thermometer, a solid content concentration of 20% by weight in an N-methylpyrrolidone (NMP) solution was obtained in a nitrogen stream so that the composition ratio was 50/50 (mole% ratio). I was able to. Next, 3 mol equivalent of trifluoroacetic anhydride was added dropwise to the monomer amount in a water bath. Simultaneously with the dropwise addition, generation of reaction heat was observed, and the reaction heat rose to 60 ° C. After the exothermic reaction had subsided, 1.5 mole equivalent of pyridine was added dropwise. Then, the temperature was raised to 80 ° C., heated at 100 ° C. for 1 hour, and further heated for 3 hours. After cooling, the reaction solution was dropped into ethanol to obtain a powder. The operation of dissolving the powder again in NMP and reprecipitation with ethanol was repeated three times. The powdery white polymer thus obtained was dried in a hot air drying oven at 80 ° C. for 1 hour to obtain a powdery polymer. The obtained ring-closing polymer was dissolved in methyl ethyl ketone at a solid content concentration of 10 mol%. Then, the electric wire was coat | covered using the said solution using the electric wire coating apparatus (paste extrusion electric wire molding machine).
Covering the wire using a wire coating device (paste extrusion wire forming machine) passes a copper wire having a diameter of 7 mm through the solution containing the ring-closing polymer at 2 m / min, and then the copper wire is passed at 80 ° C. and 120 ° C. , 150 ° C., and 150 ° C., respectively, are sequentially placed in a drying furnace and dried.
About the obtained coated wire, the coating film thickness, the film thickness tolerance, and the partial discharge start voltage were measured and calculated by the following method. As a result, the coating film thickness was 10 μm, the film thickness tolerance was ± 8%, and the partial discharge. The starting voltage was 350V.

(Coating thickness)
The outer diameter of the coated electric wire was measured using a laser outer diameter measuring machine, and the coated film thickness was calculated by subtracting the outer diameter of the electric wire itself from there.

(Thickness tolerance)
The average of the coating thickness was calculated, and the upper and lower limits were subtracted therefrom.

(Partial discharge start voltage)
A coil was prepared by combining two of the produced covered wires. Next, the voltage was increased at 10 V / s with a partial discharge tester, and the voltage at 10 pC was taken as the partial discharge start voltage.

(Examples 2-4, Comparative Examples 1-2)
A coated electric wire was obtained in the same manner as in Example 1 except that the type and concentration of the solvent for dissolving the ring-closing polymer were changed as shown in Table 1 below.
The obtained coated wire was measured and calculated in the same manner as in Example 1 for the coating film thickness, film thickness tolerance, and partial discharge start voltage.

In Table 1, abbreviations are as follows.
MEK: methyl ethyl ketone MIBK: methyl isobutyl ketone γ-BL: γ-butyrolactone NMP / MEK (3/7): mixed solvent of N-methylpyrrolidone and methyl ethyl ketone in a mass ratio of 3: 7 NMP: N-methylpyrrolidone NMP / MEK ( 7/3): Mixed solvent of N-methylpyrrolidone and methyl ethyl ketone in a mass ratio of 7: 3

From the results of Table 1, it is understood that the coating material applied using a solvent in which the total of ketones and / or esters occupies 40% by mass or more of the total solvent has a small film thickness tolerance and can increase the partial discharge start voltage. It was.

(Comparative Example 3)
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl in a 50/50 molar ratio A polyamic acid solution was obtained by dissolving in methylpyrrolidone (NMP) at a solid content concentration of 20 mol% and stirring. Thereafter, the solution was applied onto a SUS plate and heated at 200 ° C. for 1 hour, and then heated at 350 ° C. for 1 hour to close the ring to form a film having a thickness of 12 μm.
The film was peeled off from the SUS plate, and the film was wound around a copper wire to obtain a covered electric wire. The obtained coated wire was measured and calculated in the same manner as in Example 1 for the coating film thickness, film thickness tolerance, and partial discharge start voltage.

(Comparative Example 4)
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl in a 50/50 molar ratio A polyamic acid solution was obtained by dissolving in methylpyrrolidone (NMP) at a solid content concentration of 20 mol% and stirring. Then, after covering an electric wire using the said solution (precursor coating material) using an electric wire coating apparatus similarly to Example 1, it carried out the heat ring closure at 350 degreeC for 1 hour, and obtained the covered electric wire. The obtained coated wire was measured and calculated in the same manner as in Example 1 for the coating film thickness, film thickness tolerance, and partial discharge start voltage, and the results were as shown in Table 2 below.

From the results of Table 2, it was found that in Comparative Example 3 in which the film was adhered, it was difficult to suppress the gap between the film and the copper wire, and thus the partial discharge start voltage was lowered. In Comparative Example 4 using the precursor paint, the copper wire was repelled due to the amide solvent at the time of coating, and the film thickness tolerance was increased by the gas when the ring was closed after coating, and partial discharge was started. I found that the voltage dropped.

(Examples 5 and 6)
The ring-opening polymer (powdered polymer) prepared in Example 1 (Example 5) and the ring-opening polymer obtained in Example 1 by performing reprecipitation into ethanol only once (Example 6) ) Was dissolved in methyl ethyl ketone at a solid content of 5% by mass, and a coil was prepared under the same test conditions as in Example 1. The film thickness was 4 μm.
A part of aluminum was vapor-deposited here, the core copper wire was connected to the ground, and a withstand voltage test was conducted.

From the results in Table 3, it was confirmed that by suppressing the content of ammonium ions, the decrease in withstand voltage and partial discharge start voltage was suppressed.

(Example 7)
A similar test was conducted by adding 250 ppm of an FeCl ₃ aqueous solution to the same polymer solution as in Example 5 with respect to the polymer. The coating polymer containing a large amount of Fe ions showed a light red color.

From the results in Table 4, it was confirmed that the reduction of the withstand voltage and the partial discharge start voltage was suppressed by suppressing the content of the colored ions.

(Ammonium ion content)
The content of ammonium ions was measured by ion chromatography. Specifically, after the polymer was put into water and treated with ultrasonic waves for about 2 hours, the polymer was filtered, and ammonium ions dissolved in the filtrate were measured by ion chromatography. As the ion chromatograph, DX500 manufactured by Dionex Co., Ltd. was used.

(Withstand voltage)
Using a withstand voltage measuring device (TOS9201 manufactured by Kikusui Electronics Co., Ltd.), the voltage was increased at 10 V / s, and the voltage with a leakage current exceeding 10 mA was defined as the withstand voltage.

Claims (7)

An insulated wire consisting of a conductor and an insulating film,
The insulating film has the following formula (1):

(In the formula, R _f ¹ and R _f ² represent a substituent of an aromatic ring, and one of four substitutable sites per aromatic ring is substituted with the substituent. R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms.) And / or the following formula (2):

(Wherein R _f ³ represents a substituent of the aromatic ring, and any one of the four substitutable sites of the aromatic ring is substituted with the substituent. R _f ³ represents a fluorine atom, A polymer unit (A) based on a fluorinated diamine represented by a fluorinated alkyl group having 1 to 8 carbon atoms),
Following formula (3):

(Wherein R _f ⁴ and R _f ⁵ are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms), a polymer unit based on a fluorinated acid anhydride (B )When,
Comprising polymerized units (A) and (B) of fluorinated polyimide that is 60 mol% or more of the total polymerized units,
An insulated wire having a thickness tolerance of the insulating film within ± 15% . The insulated wire according to claim 1, wherein the fluorinated polyimide has a polymerization unit (B) of 30 mol% or more of all polymerization units. The insulated wire according to claim 1 or 2, wherein the fluorinated polyimide further comprises a polymerized unit (C) based on a non-fluorinated diamine. The insulated wire according to any one of claims 1 to 3, wherein the fluorinated polyimide further contains a polymerization unit (D) based on another type of acid anhydride. Following formula (1):

(In the formula, R _f ¹ and R _f ² represent a substituent of an aromatic ring, and one of four substitutable sites per aromatic ring is substituted with the substituent. R _f ¹ and R _f ² are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms.) And / or the following formula (2):

(Wherein R _f ³ represents a substituent of the aromatic ring, and any one of the four substitutable sites of the aromatic ring is substituted with the substituent. R _f ³ represents a fluorine atom, A polymer unit (A) based on a fluorinated diamine represented by a fluorinated alkyl group having 1 to 8 carbon atoms),
Following formula (3):

(Wherein R _f ⁴ and R _f ⁵ are the same or different and each represents a fluorine atom or a fluorine-containing alkyl group having 1 to 8 carbon atoms), a polymer unit based on a fluorinated acid anhydride (B )When,
A fluorinated polyimide in which the polymerization units (A) and (B) are 60 mol% or more of the total polymerization units, and a solvent,
The solvent is a varnish characterized in that 40% by mass or more of the whole solvent is a ketone and / or an ester. A method for producing an insulated wire, wherein the varnish according to claim 5 is applied onto a conductor and baked at 80 to 250 ° C. The manufacturing method of the insulated wire of Claim 6 which manufactures an insulated wire, without heating for 30 minutes or more to 300 degreeC or more.