CN113228202A

CN113228202A - Electrical insulating resin composition and electrical insulator

Info

Publication number: CN113228202A
Application number: CN201880100410.XA
Authority: CN
Inventors: 四家圣一; 平井友贵; 田端栞; 石井秀典; 五月女毅彦
Original assignee: Showa Denko KK
Current assignee: Resonac Holdings Corp
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2021-08-06
Also published as: JPWO2020136827A1; JP7338643B2; WO2020136827A1

Abstract

The electrical insulating resin composition of the present invention comprises a polyamideimide resin having a number average molecular weight of 17,000 to 23,000 and an acid value of 30 to 50mgKOH/g, and inorganic particles.

Description

Electrical insulating resin composition and electrical insulator

Technical Field

The present disclosure relates to an electrical insulating resin composition and an electrical insulator using the same.

Background

In recent years, from the viewpoint of energy saving and variable speed control, inverter control type electric appliances are increasingly used. In particular, in the field of hybrid vehicles and industrial engines, efficiency has been increased, and inverter driving has been applied as a variable speed device in a control system thereof, and the size reduction, weight reduction, high heat resistance, and high voltage driving of the device have been rapidly advanced.

In recent years, devices that can be switched at high speed, such as an IGBT (Insulated Gate Bipolar Transistor), have been developed as power devices for driving inverters. As a result, the frequency of surge voltage increases, and thus, the occurrence of an instance in which dielectric breakdown occurs at an early stage in an engine, an electric appliance, or the like increases. As one of the causes of insulation breakdown in the above-described element, it is pointed out that when a high voltage is applied to the coil for an engine, partial discharge is likely to occur in the insulating film of the insulated wire.

On the other hand, polyamide-imide resins are used in various applications as important electrical insulating materials because of their excellent resistance to processing, heat, chemicals, hydrolysis and the like. In particular, in the field of automobile engines (including hybrid automobile engines), in the wire winding process during the manufacture of the engine, the wire is subjected to elongation, bending, abrasion, and the like while being subjected to a strong tensile force. Therefore, excellent processing resistance is required for the winding wire. In addition, the winding wire is often provided in the presence of transmission oil. Therefore, as performance requirements for a winding wire used in an engine, there are requirements that the winding wire is not corroded by transmission oil and is resistant to hydrolysis by moisture in the oil. Furthermore, the wound wire is required to have heat resistance capable of withstanding use at high temperatures. From such a viewpoint, the polyamideimide resin is indispensable as an electrical insulating material used for a coiled wire (particularly, an insulated wire).

From these viewpoints, various studies have been made to realize an electrical insulating material that can satisfy typical performance requirements for an insulated wire such as processability resistance, heat resistance, chemical resistance, and hydrolysis resistance and can suppress deterioration of a destructive insulating film due to partial discharge.

For example, the present inventors have found that excellent dielectric breakdown voltage characteristics can be obtained by a resin composition containing a modified polyamideimide resin modified with a specific polybutadiene resin in order to suppress partial discharge degradation in an insulating film (patent document 1). Further, as an electrical insulating material capable of suppressing partial discharge degradation in an insulating film, a resin composition containing a resin such as a polyamideimide resin and inorganic particles such as silica is disclosed (patent documents 2 to 4).

However, with the recent increase in surge voltage, an electrical insulating material having higher resistance to partial discharge degradation of an insulating film than before has been desired.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication (JP 2015-84329)

Patent document 2: japanese patent laid-open publication No. 2001 + 307557

Patent document 3: japanese laid-open patent publication No. 2012 and 197367

Patent document 4: japanese patent laid-open No. 2008-251295

Disclosure of Invention

Technical problem to be solved by the invention

In general, the partial discharge degradation resistance of an insulating film formed of an electrical insulating material containing a resin such as a polyamide-imide resin and inorganic particles such as silica is improved by increasing the content of the inorganic particles. On the other hand, the flexibility, adhesion to a conductor, and dielectric breakdown voltage of an insulating film of an electrical insulating material containing inorganic particles are reduced. When the flexibility and adhesiveness of the insulating film are low, the insulated wire having such an insulating film is liable to be degraded in insulation properties due to mechanical stress at the time of winding the wire. In addition, when the dielectric breakdown voltage is low, dielectric breakdown of the insulating film is likely to occur.

In this way, in the electrical insulating material containing inorganic particles, it is desired to balance the typical required characteristics of the insulating film, such as flexibility, adhesiveness, and dielectric breakdown voltage, and the resistance to partial discharge degradation of the insulating film. In addition, an electrical insulating material having excellent withstand voltage life when a high-frequency ac voltage is applied is desired for increasing the life of an engine, an electric appliance, or the like driven by an inverter.

In view of the above circumstances, the present disclosure provides an electrical insulating resin composition capable of forming an insulating film having flexibility, excellent adhesion and dielectric breakdown voltage, and an excellent withstand voltage lifetime. Further, the present disclosure provides an electrical insulator having high insulation reliability using the electrical insulating resin composition.

Means for solving the problems

The present inventors have conducted intensive studies on an electrical insulating resin composition comprising a polyamideimide resin and inorganic particles. As a result, they have found that an electrical insulating resin composition having excellent partial discharge degradation resistance and excellent withstand voltage life while suppressing a decrease in flexibility and adhesiveness due to the addition of inorganic particles can be realized by using a polyamideimide resin having a specific number average molecular weight and a specific acid value, and have accomplished the present invention. That is, the present invention relates to the embodiments described below. However, the present invention is not limited to the following embodiments.

An embodiment relates to an electrical insulating resin composition comprising:

a polyamideimide resin having a number average molecular weight of 17,000 to 23,000 and an acid value of 30 to 50 mgKOH/g; and

inorganic particles.

In the electrically insulating resin composition, the inorganic particles preferably have an average primary particle diameter of 50nm or less.

In the electrical insulating resin composition, the inorganic particles are preferably contained in an amount of 5 to 50 parts by mass per 100 parts by mass of the polyamideimide resin.

In the electrically insulating resin composition, the inorganic particles preferably contain silica.

Another embodiment relates to an electrical insulator comprising:

a conductor; and

an insulating film formed using the electrical insulating resin composition of the above embodiment.

In the above electric insulator, the conductor is preferably a metal wire.

Effects of the invention

According to the present invention, it is possible to provide an electrical insulating resin composition capable of forming an insulating film that can suppress partial discharge degradation and has an excellent withstand voltage life while maintaining the typical required performance of the insulating film such as flexibility, adhesiveness, and dielectric breakdown voltage. In addition, the use of the electrically insulating resin composition can provide an electrically insulating body having high insulation reliability.

Drawings

Fig. 1 is a schematic cross-sectional view showing an embodiment of an insulated wire.

Fig. 2 is a schematic sectional view showing another embodiment of the insulated wire.

Fig. 3 is a schematic sectional view showing another embodiment of the insulated wire.

Fig. 4 is a schematic sectional view showing another embodiment of the insulated wire.

Detailed Description

The embodiments of the present invention will be described in more detail below, but the present invention is not limited to the following descriptions.

1. Electrically insulating resin composition

One embodiment relates to an electrical insulating resin composition comprising a polyamideimide resin having a number average molecular weight (Mn) of 17,000 to 23,000 and an acid value of 30 to 50mgKOH/g, and inorganic particles. The respective components are explained below.

[ Polyamide-imide resin ]

The polyamideimide resin may be 1 type of polyamideimide resin, or may contain 2 or more types of polyamideimide resins, as long as it has Mn and an acid value within the above-specified ranges.

The polyamideimide resin is a resin obtained by the reaction of an acid component containing a tricarboxylic acid anhydride or a derivative thereof (hereinafter also referred to as an acid component (a)) with a diisocyanate compound or a diamine compound (hereinafter also referred to as a component (b)).

(acid component (a))

The tricarboxylic acid anhydride used as the acid component (a) may be a tricarboxylic acid having an acid anhydride group, which reacts with an isocyanate group or an amino group in the component (b). For producing the polyamideimide resin, a tricarboxylic acid anhydride or a derivative thereof may be used without particular limitation.

In the acid component (a), the tricarboxylic anhydride preferably has a structure containing an aromatic group from the viewpoint of heat resistance. In one embodiment, the acid component (a) preferably contains a tricarboxylic anhydride represented by the following formula (I) or the following formula (II). Among them, trimellitic anhydride is particularly preferable from the viewpoint of heat resistance and cost. The tricarboxylic acid anhydride represented by the following formula (I) or the following formula (II) may be used alone or 2 or more kinds may be used in combination according to purposes.

[ chemical formula No. 1]

In the formula, X¹represents-CH₂-、-CO-、-SO₂-or-O-.

[ chemical formula No. 2]

In another embodiment, the acid component (a) may further contain an acid component different from the tricarboxylic anhydride. For example, the acid component (a) may further contain a tetracarboxylic dianhydride as needed. As concrete examples of the tetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 3,3 ', 4, 4' -benzophenonetetracarboxylic acid dianhydride, 3,3 ', 4, 4' -biphenyltetracarboxylic acid dianhydride, 1,2,5, 6-naphthalenetetracarboxylic acid dianhydride, 2,3,5, 6-pyridinetetracarboxylic acid dianhydride, 1,4,5, 8-naphthalenetetracarboxylic acid dianhydride, 3,4,9, 10-perylenetetracarboxylic acid dianhydride, 4,4 '-sulfonyldibenzoic acid dianhydride, m-terphenyl-3, 3', 4,4 '-tetracarboxylic acid dianhydride (3, 3', 4,4 '-m-terphenyltetracarboxylic acid dianhydride), 4, 4' -oxydiphthalic acid dianhydride, 1,1,1,3,3, 3-hexafluoro-2, 2-bis (2, 3-or 3, 4-dicarboxyphenyl) propane dianhydride, can be used, 2, 2-bis (2, 3-or 3, 4-dicarboxyphenyl) propane dianhydride, 2, 2-bis [4- (2, 3-or 3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride, 1,1,1,3,3, 3-hexafluoro-2, 2-bis [4- (2, 3-or 3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride, 1, 3-bis (3, 4-dicarboxyphenyl) -1,1,3, 3-tetramethyldisiloxane dianhydride, butanetetracarboxylic acid dianhydride, bicyclo- [2,2,2] -oct-7-ene-2: 3:5: 6-tetracarboxylic acid dianhydride, and the like.

(component (b))

The diisocyanate compound or diamine compound is not particularly limited as long as it has 2 isocyanate groups or amino groups in the molecule. In one embodiment, the component (b) preferably contains an aromatic compound having an isocyanate group or an amino group represented by the following formulae (III), (IV) and (V).

[ chemical formula No. 3]

[ chemical formula No. 4]

[ chemical formula No. 5]

In the above formula, R¹And R²Each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a hydroxyl group. The alkyl group or alkoxy group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and still more preferably 1 to 10 carbon atoms. At least one of the hydrogen atoms of the alkyl group or the alkoxy group may be substituted with a halogen atom such as a fluorine atom. In one embodiment, R¹And R²Preferably each independently a hydrogen atom.

Y represents an isocyanate group or an amino group.

X²represents-CH₂-、-C(＝O)-、-S(＝O)-、-SO₂-, -O-, -S-, or-CR³R⁴-。R³And R⁴Each independently represents the above alkyl group or alkoxy group. The alkyl group or the alkoxy group is as described above. In one embodiment, R³And R⁴Is at least 1 substituent selected from alkyl with 1-10 carbon atoms, trifluoromethyl, trichloromethyl and phenyl. In one embodiment, X²Is preferably-CH₂-。

Specific examples of the aromatic diisocyanate compound or aromatic diamine compound represented by the above formula (III), (IV) or (V) include 4,4 '-diisocyanatodiphenylmethane, 4' -diisocyanatobiphenyl, 3 '-diisocyanatobiphenyl, 3, 4' -diisocyanatobiphenyl, 4 '-diisocyanato-3, 3' -dimethylbiphenyl, 4 '-diisocyanato-2, 2' -dimethylbiphenyl, 4 '-diisocyanato-3, 3' -diethylbiphenyl, 4 '-diisocyanato-2, 2' -diethylbiphenyl, 4 '-diisocyanato-3, 3' -dimethoxybiphenyl, 4 '-diisocyanato-3, 3' -dimethoxybiphenyl, 4,4 ' -diisocyanato-2, 2 ' -dimethoxybiphenyl, 1, 5-diisocyanatonaphthalene, 2, 6-diisocyanatonaphthalene, 4 ' -diaminodiphenylmethane, 4 ' -diaminobiphenyl, 3 ' -diaminobiphenyl, 3,4 ' -diaminobiphenyl, 4 ' -diamino-3, 3 ' -dimethylbiphenyl, 4 ' -diamino-2, 2 ' -dimethylbiphenyl, 4 ' -diamino-3, 3 ' -diethylbiphenyl, 4 ' -diamino-2, 2 ' -diethylbiphenyl, 4 ' -diamino-3, 3 ' -dimethoxybiphenyl, 4 ' -diamino-2, 2' -dimethoxybiphenyl, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, and the like. These compounds may be used alone, or 2 or more of them may be used in combination.

Examples of the diisocyanate compound or diamine compound include aromatic diisocyanate compounds or aromatic diamine compounds such as tolylene diisocyanate, xylylene diisocyanate, 4 '-diisocyanatodiphenyl ether, 2-bis [4- (4' -isocyanatophenoxy) phenyl ] propane, tolylene diamine, xylylene diamine, 4 '-diaminodiphenyl ether, and 2, 2-bis [4- (4' -aminophenoxy) phenyl ] propane.

Further, as the diisocyanate compound or diamine compound, for example, aliphatic or alicyclic diisocyanate compounds or diamine compounds such as hexamethylenediamine, 2, 4-trimethylhexamethylenediamine, diaminoisophorone, bis (4-aminocyclohexyl) methane, 1, 4-diaminotrans-cyclohexane, hydrogenated m-xylylenediamine, hexamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate, diisocyanatoisoprohorone, bis (4-isocyanatocyclohexyl) methane, 1, 4-diisocyanato-trans-cyclohexane, hydrogenated m-xylylene diisocyanate and the like can be used. However, when the above aliphatic or alicyclic compound is used, it is preferable to use the above aromatic diisocyanate compound or aromatic diamine compound in combination. The amount of the aliphatic or alicyclic compound used is preferably 50 mol% or less of the total amount of the diisocyanate compound and the diamine compound, from the viewpoint of heat resistance of the obtained resin and the like.

The diisocyanate compound or diamine compound may be used in combination with a polyisocyanate compound or polyamine compound having 3 or more functions.

In one embodiment, 4' -diphenylmethane diisocyanate is particularly preferable as the diisocyanate compound or diamine compound in view of the balance among heat resistance, solubility, mechanical properties, cost, and the like.

In order to avoid the change over time, a product in which an isocyanate group is stabilized with a blocking agent may be used as necessary. Examples of the blocking agent include alcohols, phenols, oximes, and the like, but are not particularly limited.

(ratio of acid component (a) to component (b))

The ratio of the amount of the component (b) (which represents the diisocyanate compound or diamine compound) to the amount of the acid component (a) blended in the production of the polyamideimide resin ((b)/(a) molar ratio) can be adjusted without any particular limitation. If the molar ratio is too small, it tends to be difficult to increase the molecular weight of the resin. On the other hand, when the molar ratio is too large, the foaming reaction becomes severe, and the amount of unreacted components remaining increases, which tends to deteriorate the stability of the resin.

In one embodiment, the molar ratio of the amount of the component (b) to 1 mole of the acid component (a) is preferably 0.6 to 1.4, more preferably 0.7 to 1.3, and particularly preferably 0.8 to 1.2, because desired Mn and acid value can be easily obtained. The molar ratio of the amount to be blended is a value calculated as a ratio of the total number of moles of isocyanate groups and amino groups of the diisocyanate compound or diamine compound in the component (b) to the total number of moles of carboxyl groups, acid anhydride groups, and optionally reactive hydroxyl groups in the acid component (a).

The polyamide-imide resin can be synthesized, for example, by the following production method.

(1) A method for synthesizing a polyamideimide resin by mixing and reacting an acid component (a) and a component (b) at once.

(2) A method of synthesizing a polyamideimide resin by reacting an excess amount of component (b) with an acid component (a) to synthesize an amide imide oligomer having an isocyanate group at the terminal, and then adding the acid component (a) to the amide imide oligomer to perform a reaction.

(3) A method of synthesizing a polyamideimide resin by reacting an excess amount of the acid component (a) with the component (b) to synthesize an amideimide oligomer having an acid or acid anhydride group at the terminal, and then adding the acid component (a) and the component (b) to the oligomer to react.

(reaction temperature, reaction time)

In any of the above methods, the reaction temperature is preferably in the range of 80 to 150 ℃. The reaction time is determined so as to obtain a desired number average molecular weight (Mn), and is preferably 1 to 10 hours.

(solvent at the time of reaction)

The solvent (synthesis solvent) used for the synthesis of the polyamideimide resin is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone, N-dimethylformamide, γ -butyrolactone, N' -dimethylpropylurea [1, 3-dimethyl-3, 4,5, 6-tetrahydropyrimidin-2 (1H) -one ], a polar solvent such as dimethyl sulfoxide, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and sulfolane, an aromatic hydrocarbon solvent such as xylene and toluene, and a ketone such as methyl ethyl ketone and methyl isobutyl ketone.

The amount of the synthetic solvent used is not particularly limited, but is preferably 50 to 180 parts by mass, more preferably 60 to 120 parts by mass, based on 100 parts by mass of the total amount of the acid component (a) and the component (b). When the amount of the synthesis solvent to be used is adjusted to the above range, the occurrence of foaming reaction during synthesis can be suppressed, and the time required for synthesis can be easily adjusted appropriately.

(molecular weight of Polyamide-imide resin)

Generally, the number average molecular weight (Mn) of the polyamideimide resin used as the insulating material is preferably 9,000 to 90,000. When Mn is too small, the film forming property tends to be poor when the coating composition is produced. When the number average molecular weight is too large, the viscosity tends to increase when the coating composition is dissolved in a solvent at an appropriate concentration, and the workability in coating tends to deteriorate. The Mn of the polyamideimide resin is preferably 10,000 to 70,000.

In contrast, the polyamideimide resin composition of the above embodiment is characterized by using a polyamideimide resin having an Mn of 17,000 to 23,000. The Mn of the polyamideimide resin is more preferably 19,000 to 23,000. The Mn of the polyamideimide resin can be adjusted by the amount of the raw material charged, the reaction time, and the like. For example, the control may be performed by sampling at the time of resin synthesis, measuring by Gel Permeation Chromatography (GPC) using a calibration curve of standard polystyrene, and continuing the reaction until the target Mn is reached.

The acid value of the polyamideimide resin in the polyamideimide resin composition is preferably 30 to 50 mgKOH/g. The acid value is more preferably 35 to 45 mgKOH/g. The acid value is the total acid value of the carboxyl group in the polyamideimide resin and the carboxyl group obtained by ring-opening the acid anhydride group.

When the polyamideimide resin has an acid value within the above range, the polyamideimide resin tends to be easily dissolved or dispersed in a mixed solvent described later. Further, the finally obtained polyamide-imide resin composition tends to be less likely to gel with the passage of time. Further, although not limited by theory, it is believed that the dispersibility of the inorganic particles is improved by the interaction between the carboxyl groups in the resin and the inorganic particles described later.

(inorganic particles)

The inorganic particles contained in the electrical insulating resin composition of the above embodiment are not particularly limited as long as they can suppress partial discharge degradation of the insulating film. Generally, an insulating film formed of an electrical insulating material in which inorganic particles are added to a resin changes in characteristics depending on the dispersibility of the inorganic particles. On the other hand, when inorganic particles having an average primary particle diameter of 50nm or less are used, although it is expected that the favorable characteristics of film-forming property of the insulating film and improvement of adhesion are exhibited, secondary aggregation tends to occur, and dispersibility tends to be easily lowered. In contrast, in the electrical insulating resin composition of the above embodiment, by using the polyamideimide resin having the specific Mn and acid value described above, even when inorganic particles having an average primary particle diameter of 50nm or less are used, excellent dispersion stability can be easily obtained.

In the present specification, the term "average primary particle diameter" refers to the average particle diameter of aggregated particles, that is, not the secondary particle diameter but the average particle diameter of unagglomerated monomers. The average primary particle diameter of the inorganic particles can be typically measured by a method using a laser diffraction particle size distribution measuring apparatus or a Transmission Electron Microscope (TEM). For example, in a method using TEM, the area of an image of each particle is first measured by TEM for at least hundreds or more particles randomly selected from a composition or a dispersion. Next, the diameter of a circle having the same area as the obtained area is regarded as the particle diameter, and the average value of the particle diameters is calculated by a known statistical process, thereby obtaining the average primary particle diameter.

In one embodiment, the average primary particle diameter of the inorganic particles is preferably 40nm or less, more preferably 30nm or less, and still more preferably 20nm or less, from the viewpoint of film-forming properties and adhesion.

In one embodiment, the inorganic particles may be metal oxides. Specific examples thereof include silica (silica), alumina (alumina), titania, magnesia, zirconia, and the like. Other specific examples include clay, talc, barium sulfate, and calcium carbonate. Silica is preferably used because of its excellent dispersibility in a resin and difficulty in causing particle aggregation.

The inorganic particles may be inorganic particles treated with a typical surface treatment agent such as a coupling agent, from the viewpoint of improving dispersibility in a resin. The inorganic particles may be in the form of a sol (dispersion) or may be solvent-substituted. The dispersion medium in the sol is preferably excellent in compatibility with the polyamideimide resin. As the dispersion medium, for example, N-dimethylacetamide, methylethyl isobutyl ketone, water or methanol can be used. Further, a mixed solvent of xylene and butanol may be used.

In one embodiment, the inorganic particles are preferably silica sol, although not particularly limited. For example, a silica sol containing N, N-dimethylacetamide as a dispersion medium can be preferably used. In general, silica particles having an average primary particle diameter of 50nm or less tend to undergo secondary aggregation, but the use of a silica sol makes it possible to maintain good dispersibility and easily suppress sedimentation of particles due to aggregation.

Silica sols that are commercially available can also be used, but those skilled in the art can also prepare them according to well-known methods. For example, a general method of dispersing powder in a liquid can be applied to the production of a silica sol. More specifically, there may be mentioned a method in which silica particles, a dispersion medium, a dispersant and other components are mixed and then subjected to a dispersion treatment by an ultrasonic method, a mixer method, a triple roll method, a ball mill method and the like.

In the electrical insulating resin composition of the above embodiment, the amount of the inorganic particles added is preferably 5 to 50 parts by mass with respect to 100 parts by mass of the polyamideimide resin. The amount of the inorganic particles is more preferably 10 to 40 parts by mass, and still more preferably 20 to 30 parts by mass. When a sol of inorganic particles is used, the amount of the inorganic particles (solid content) is calculated from the content of the inorganic particles contained in the sol. By adjusting the blending amount of the inorganic particles to the above range, the partial discharge degradation resistance can be improved without lowering the characteristics of the insulating film such as flexibility.

The electrically insulating resin composition of the above embodiment is obtained by mixing the polyamide imide resin and the inorganic particles, and various dispersion techniques may be applied to improve the dispersibility of the inorganic particles in the polyamide imide resin. For example, the inorganic particles may be treated with a surface treatment agent and then added to a polyamide-imide resin to perform dispersion treatment. Further, the polyamide-imide resin and the surface treatment agent may be mixed and then the inorganic particles may be further added to perform dispersion treatment. Further, a dispersant may be used in addition to the surface treatment agent.

(Mixed solvent)

In one embodiment, the electrically insulating resin composition includes the polyamideimide resin, the inorganic particles, and a solvent for mixing these components (hereinafter referred to as a mixed solvent). The mixed solvent is preferably a solvent capable of dissolving the polyamideimide resin, and may be the same as the synthetic solvent used in the synthesis of the polyamideimide resin. Therefore, in order to produce the electrical insulating resin composition, the reaction solution obtained in the production of the polyamideimide resin may be used as it is. In one embodiment, the synthesis solvent and the mixed solvent preferably contain N-methyl-2-pyrrolidone and/or N, N-dimethylacetamide.

In the electrical insulating resin composition of the above embodiment, the amount of the synthetic solvent and/or the mixed solvent is not particularly limited. The amount of the polyamide-imide resin to be blended can be adjusted so as to obtain a viscosity suitable for a desired use by diluting the polyamide-imide resin with a synthetic solvent and/or a mixed solvent. When the electrically insulating resin composition is used as an electrically insulating coating material (varnish), the solid content is generally preferably 10 to 50% by mass, more preferably 20 to 40% by mass, based on the total mass of the varnish. By adjusting the solid content in the varnish to be within the above range, excellent coating properties can be obtained, and a thick film can be easily formed by repeating coating. The solid content may be typically the total amount of the polyamide-imide resin and the inorganic particles.

(other Components)

The electrical insulating resin composition of the above embodiment may further contain an additive such as a colorant as needed. The blending amount of the additive is preferably adjusted within a range not to degrade the film characteristics.

2. Electrical insulator

The electrical insulating resin composition of the above embodiment can be preferably used as an electrical insulating material for providing insulation properties to various conductors.

An embodiment relates to an electrical insulator having: a conductor; and an insulating film formed of the electrically insulating resin composition of the above embodiment for providing insulation to the conductor. The insulating film may be formed by applying the electrically insulating resin composition of the above embodiment to a conductor and then welding the same.

Examples of the conductor include a metal wire such as a copper wire and a structure to which another insulating property is desired. In the electrical insulator, the conductor may further have an additional insulating film made of another electrical insulating material in addition to the insulating film made of the electrical insulating resin composition.

(conductor)

Examples of the conductor include a metal wire described later and an electric/electronic component used in an inverter control device or the like. The electrical/electronic component to which the insulating film formed of the electrical insulating resin composition of the above embodiment is applied is particularly useful for high voltage applications and inverter control applications.

When the electrically insulating resin composition of the above embodiment is coated on a metal wire, an insulated wire (enameled wire) excellent in processability resistance, heat resistance, dielectric breakdown voltage characteristics and the like and high in insulation reliability can be provided. In addition, similarly, by using the electrically insulating resin composition of the above embodiment, an electric/electronic component having high resistance to dielectric breakdown can be provided.

(method for producing insulating film)

The method for applying the electrically insulating resin composition of the above embodiment is not particularly limited, and a technique known in the art can be applied. For example, when an electrical insulating resin composition prepared as an electrical insulating coating material (varnish) is applied to an electric wire (metal wire), a method such as die coating or felt coating can be applied.

The electrical insulating resin composition of the above embodiment can be coated on a conductor to be coated, and then the coating film is dried and cured to form an insulating film. The drying and curing of the coating film can be achieved by heat treatment at a temperature of 260 to 520 ℃ for a period of 2 seconds to several minutes. When the temperature during the heat treatment is low, a solvent may remain after drying and curing of the coating film, and the coating film characteristics may be degraded. In addition, when the temperature at the time of curing is not sufficiently high (for example, when the curing temperature is less than 260 ℃), the coating film may be insufficiently dried and cured. When the heating time is too short, the solvent remains in the coating film, and the coating film characteristics tend to be deteriorated. On the other hand, when the heating time is too long, time and energy are wasted, and the production efficiency is liable to be lowered.

The drying and curing method (soldering method) of the electrically insulating resin composition coated on the metal wire (electric wire) can be carried out according to a conventional method. A typical example of the method is a method in which an electrically insulating resin composition is applied to an electric wire and then passed through a heating furnace. From the viewpoint of improving the dielectric breakdown resistance of an insulating film formed of a cured film formed by the drying and curing, it is preferable to form the insulating film by repeating the application of the electrical insulating resin composition several times.

The insulating film may have a single-layer structure or a multilayer structure. Although not particularly limited, in one embodiment, the entire thickness of the insulating film is preferably 20 to 200 μm, and more preferably 40 to 150 μm. When the coating film is too thin, the insulation property becomes insufficient; when the thickness is too large, the ratio of the conductor is reduced when the coil is formed, and the electromotive force is reduced. Further, when the coating film is too thick, it is disadvantageous in terms of miniaturization and thinning.

(insulated wire (enameled wire))

Next, as an example of the electric insulator, an insulated wire will be described in more detail. Fig. 1 is a schematic cross-sectional view showing an embodiment of an insulated wire. Fig. 2 to 4 are schematic cross-sectional views showing other embodiments of the insulated wire. An insulated wire a shown in fig. 1 includes a conductor 1 and an insulating film 2 formed by applying the electrically insulating resin composition of the embodiment to the conductor 1 and welding the composition.

Specific examples of the conductor 1 include a metal wire such as a copper wire. In one embodiment, the cross-sectional shape of the wire may be circular as shown in FIG. 1. In another embodiment, the cross-sectional shape of the metal wire may be a square, a rectangular or a flat angle.

The insulating film 2 may have a multilayer structure in combination with other electrically insulating materials. In this case, the insulating film has a multilayer structure in which 2 or more layers of different electrical insulating materials are stacked. In such a multilayer structure, the insulating film formed from the electrically insulating resin composition of the above embodiment may be an innermost layer in contact with the conductor, an outermost layer in contact with the outside, or an intermediate layer. Examples of other electrical insulating materials include polyester imide resins, polyurethane resins, polyester resins, polyimide resins, and polyamide imide resins substantially free of inorganic particles.

In one embodiment, the insulated wire a may have a structure in which a primer layer 3 is provided between the conductor 1 and the insulating film 2 as shown in fig. 2. In another embodiment, the insulated wire a may have a structure including a conductor 1, an insulating coating 2, and a cap coat 4 as shown in fig. 3. In another embodiment, the insulated wire a may have a structure including a conductor 1, a primer layer 3, an insulating coating 2, and a cap coat 4.

The primer layer and the cap coat layer are not particularly limited, and are preferably made of a polyamide-imide resin substantially free of inorganic particles from the viewpoint of compatibility with the resin of the insulating film 2. The primer layer and the cap coat layer may contain less than 5 parts by mass of inorganic particles per 100 parts by mass of the polyamideimide resin, but are preferably composed of only the polyamideimide resin. The polyamideimide resin used for forming the primer layer may be the same as the specific polyamideimide resin constituting the electrical insulating resin composition of the above embodiment, but is not particularly limited thereto, and other polyamideimide resins having a larger Mn may be used. For example, in one embodiment, the polyamideimide resin used to form the primer layer and the cap layer may have an Mn of 23,000 to 29,000.

As described above, the insulated wire a is excellent in processability resistance, heat resistance, dielectric breakdown voltage characteristics, and the like, and has high insulation reliability by covering the conductor 1 with the insulating film 2 formed of the electrical insulating resin composition of the above embodiment. Therefore, the insulated wire of the above embodiment can be preferably used in a coil of a stator or a rotor. Such a stator or rotor is equipped into an inverter drive motor or other high-voltage drive motor or the like. Examples of the inverter-driven engine include an engine for a hybrid vehicle, an engine for an electric vehicle, an engine for a hybrid diesel engine, an engine for an electric motorcycle, an engine for an elevator, and an engine used in construction machinery.

The coil formed using the insulated wire according to the above embodiment can provide high insulation reliability in the above applications, and can achieve a long life of an electric appliance or an engine. This effect is effective particularly in inverter control to which a higher voltage is applied. Further, the electrical insulating resin composition can provide sufficient dielectric breakdown voltage characteristics even with a thin insulating film, and thus can contribute to downsizing and weight saving of electric appliances, motors, and the like.

Examples

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples described below, and various modifications can be made without departing from the scope of the present invention.

1. Preparation of electrically insulating resin composition

The number average molecular weight and acid value of the polyamide-imide resins prepared in the following examples and comparative examples were measured as follows.

(number average molecular weight (Mn))

The conditions for measurement are as follows.

GPC type: hitachi L6000

A detector: hitachi L4000 type UV

Wavelength: 270nm

A data processor: ATT 8

A chromatographic column: gelpack GL-S300MDT-5(× 2)

Column size: 8mm phi x 300mm

Solvent: DMF/THF-1/1 (l) + phosphoric acid 0.06M + lithium bromide 0.06M

Sample concentration: 5mg/1ml

Injection amount: 5 μ l

Pressure: 49kgf/cm²(4.8×10⁶Pa)

Flow rate: 1.0 ml/min

(acid value)

0.5g of the polyamideimide resin composition was collected, 0.15g of 1, 4-diazabicyclo [2,2,2] octane was added thereto, and 60g of N-methyl-2-pyrrolidone and 1mL of ion-exchanged water were further added thereto, followed by stirring until the polyamideimide resin was completely dissolved. The solution thus obtained was titrated with a potential difference titrator using 0.05 mol/L alcoholic potassium hydroxide solution.

(example 1)

192.1g (1.00 mol) of trimellitic anhydride, 250.3g (1.00 mol) of 4, 4' -diphenylmethane diisocyanate and 362.0g of N-methyl-2-pyrrolidone were placed in a flask equipped with a thermometer, a stirrer and a cooling tube. Subsequently, the mixture was slowly heated to 130 ℃ over about 6 hours while paying attention to rapid foaming of carbon dioxide gas generated by the reaction in a dry nitrogen gas flow, and further, the temperature was maintained at 130 ℃ for 4 hours, thereby obtaining a polyamideimide resin solution. The polyamideimide resin solution was diluted with N, N-dimethylacetamide and then incubated at 200 ℃ for 2 hours to prepare a polyamideimide resin solution having a resin concentration (solid content) of 40%. The polyamideimide resin in the obtained solution was analyzed, and as a result, the number average molecular weight was 21,000 and the acid value was 40 mgKOH/g.

Then, 100 parts by mass of the polyamideimide resin solution and 33.3 parts by mass of the silica sol were mixed and stirred at 60 to 70 ℃ for 1 hour to obtain a resin composition for electrical insulation. The silica sol had an average primary particle diameter of silica of 11nm, a silica content of 30 mass%, and a content of N, N-dimethylacetamide as a dispersion medium of 70 mass%. In the resin composition for electrical insulation, the amount of silica particles added is 25 parts by mass per 100 parts by mass of the polyamideimide resin.

Comparative example 1

192.1g (1.00 mol) of trimellitic anhydride, 250.3g (1.00 mol) of 4, 4' -diphenylmethane diisocyanate and 362.0g of N-methyl-2-pyrrolidone were placed in a flask equipped with a thermometer, a stirrer and a cooling tube. Subsequently, the mixture was slowly heated to 130 ℃ over about 6 hours while paying attention to rapid foaming of carbon dioxide gas generated by the reaction in a dry nitrogen gas flow, and further, the temperature was maintained at 130 ℃ for 2 hours, thereby obtaining a polyamideimide resin solution. The polyamideimide resin solution was diluted with N, N-dimethylacetamide and then incubated at 200 ℃ for 2 hours to prepare a polyamideimide resin solution having a resin concentration (solid content) of 40%. The polyamideimide resin in the obtained solution was analyzed, and as a result, the number average molecular weight was 16,000 and the acid value was 55 mgKOH/g.

Comparative example 2

192.1g (1.00 mol) of trimellitic anhydride, 250.3g (1.00 mol) of 4, 4' -diphenylmethane diisocyanate and 362.0g of N-methyl-2-pyrrolidone were placed in a flask equipped with a thermometer, a stirrer and a cooling tube. Subsequently, the mixture was slowly heated to 130 ℃ over about 6 hours while paying attention to rapid foaming of carbon dioxide generated by the reaction in a dry nitrogen gas flow, and further, the temperature was maintained at 130 ℃ for 7 hours, thereby obtaining a polyamideimide resin solution. The polyamideimide resin solution was diluted with N, N-dimethylacetamide and then incubated at 200 ℃ for 2 hours to prepare a polyamideimide resin solution having a resin concentration (solid content) of 40%. The polyamideimide resin in the obtained solution was analyzed, and as a result, the number average molecular weight was 25,000 and the acid value was 28.

Comparative example 3

A resin composition for electrical insulation having the same structure as in example 1 was prepared, except that the silica sol was not added. That is, a resin composition for electrical insulation containing no silica sol, which was composed only of a polyamideimide resin solution (resin concentration: 40 mass%) prepared in the same manner as in example 1, was prepared.

2. Production and evaluation of insulated wire

The resin compositions for electrical insulation obtained in example 1 and comparative examples 1 to 3 were applied to a copper wire having a diameter of 1.0mm, and then, they were subjected to soldering to produce an insulated wire. The conditions for the production were as follows.

(conditions for coating and baking)

A welding furnace: hot-air type shaft furnace (furnace length 5m)

Coating times: extruding the mixture 8 times (coating and welding are repeated for 8 times)

Furnace temperature: inlet (evaporation zone)/outlet (solidification zone) 320 ℃/430 DEG C

Linear speed: 16 m/min

The properties of the insulating film in the obtained insulated electric wire were tested and evaluated by the following methods. The results are shown in table 1.

(1) Thickness of the skin

The film thickness of the insulated wire is determined as follows: the diameter of the insulated wire was measured using a micrometer (D1), and then the diameter of the conductor wire after the film was burned off and removed (D2), and the difference was 1/2 to obtain the difference. That is, the film thickness shown in Table 1 corresponds to the value of (D1-D2)/2.

(2) Withstand voltage life

2 twisted samples defined in JIS C3216-5 were prepared. Next, a rectangular AC voltage of 20kHz was applied to the sample at a measurement temperature of 155. + -. 3 ℃ and a pulse voltage of 3000V, and the time until dielectric breakdown of the sample occurred was measured.

(3) Breakdown voltage of insulation

Measured according to JIS C3216-5.

(4) Flexibility

Measured according to JIS C3216-3.

(5) Adhesion Property

The insulating film left for 1 day or more after welding was twisted at a rotation speed of 100 times/min in accordance with JIS C3216-3, and the rotation speed until peeling of the film occurred was measured.

(6) Wear resistance

Measured according to JIS C3216-3.

(7) Softening resistance

Measured according to JIS C3216-6.

TABLE 1

As is clear from the results shown in table 1, the insulated wires obtained in example 1 are excellent in withstand voltage life in comparison with the insulated wires obtained in comparative examples 1 to 3, and further excellent in other typical required characteristics for the insulating film. In particular, as is clear from comparison with comparative example 3 containing no inorganic particles (silica), in example 1 corresponding to the embodiment of the present invention, by using a specific polyamideimide resin having a specific range of Mn and an acid value, even in an electrical insulating material to which inorganic particles such as silica are added, the withstand voltage life can be improved without deteriorating typical required characteristics of the insulating film such as adhesiveness, flexibility, and dielectric breakdown voltage.

As described above, according to the present invention, an electrical insulating resin composition suitable as an electrical insulating material for forming an insulating film can be provided, and an electrical insulator having excellent withstand voltage life can be provided by using such an electrical insulating resin composition. In particular, the electrically insulating resin composition of the present invention is useful for improving the long-term reliability of inverter-driven motors that are increasing in frequency and voltage.

Claims

1. An electrically insulating resin composition comprising:

inorganic particles.

2. The electrical insulating resin composition according to claim 1, wherein the inorganic particles have an average primary particle diameter of 50nm or less.

3. The electrical insulating resin composition according to claim 1 or 2, wherein the inorganic particles are contained in an amount of 5 to 50 parts by mass per 100 parts by mass of the polyamideimide resin.

4. An electrical insulating resin composition according to any one of claims 1 to 3, wherein the inorganic particles comprise silica.

5. An electrical insulator, comprising:

a conductor; and

an insulating film formed using the electrically insulating resin composition according to any one of claims 1 to 4.

6. An electrical insulator as claimed in claim 5, in which the conductor is a metal wire.