JP2012164424A - Polyester imide resin based varnish for low dielectric constant coating film - Google Patents

Abstract

The present invention provides an insulated wire whose dielectric constant is reduced by an insulating layer mainly composed of polyesterimide, and a polyesterimide resin varnish capable of forming an insulating film having a low dielectric constant.
The dielectric constant of a polyesterimide insulating film has a correlation with the weight molecular weight of the polyesterimide before heat curing. Therefore, as a polyesterimide which is the main component of the varnish, polyhydric carboxylic acid anhydrides and dicarboxylic acids and / or alkyl esters thereof (hereinafter collectively referred to as “carboxylic acids”), alcohols, and diamine compounds A polyesterimide having a weight average molecular weight (Mw) of 9000 or more is used.
[Selection] Figure 1

Description

  The present invention relates to a polyesterimide resin varnish and an insulated wire using the same, and more specifically, a varnish for forming a polyesterimide insulating coating having a high partial discharge (corona discharge) starting voltage and an insulated wire having the insulating coating. About.

  In an electric device having a high applied voltage, for example, a motor used at a high voltage, a high voltage is applied to an insulated wire constituting the electric device, and partial discharge (corona discharge) is likely to occur on the surface of the insulating coating. The generation of corona discharge causes a local temperature rise and generation of ozone and ions. As a result, there has been a problem that the insulating coating is eroded, causing dielectric breakdown at an early stage, and shortening the life of the insulated wire and thus the electrical equipment.

  The insulation film of insulated wires is required to have excellent insulation, excellent adhesion to conductors, high heat resistance, mechanical strength, etc., but for insulated wires used in electrical equipment with high applied voltage, For the above reasons, further improvement of the corona discharge start voltage is also required.

  As a device for increasing the corona discharge starting voltage, there is a reduction in dielectric constant of the insulating layer. For example, it is known that polyimide resin and fluororesin have a low dielectric constant, and the corona discharge starting voltage can be increased by forming an insulating layer with these materials. Patent Document 1 (Japanese Patent Laid-Open No. 2009-277369) discloses an insulated wire using a mixed resin of polyesterimide and polyethersulfone as an insulating layer.

JP 2009-277369 A

  The method using a low dielectric constant material for the insulating layer is effective for improving the corona discharge starting voltage, but the insulating layer needs to satisfy the requirements for insulation, adhesion to the conductor, heat resistance, and mechanical strength. is there. Material cost is also an important factor in material selection.

  Polyimide resin has a low dielectric constant and is excellent in heat resistance, mechanical strength, and the like, but is a high-cost material and causes an increase in the price of insulated wires. In addition, although the fluororesin has a low dielectric constant, its use is limited when it is used as an insulating layer because of poor heat resistance and mechanical strength. The insulating material described in Patent Document 1 has a good balance between dielectric constant and mechanical properties. However, since thermoplastic engineering plastics such as polyethersulfone are not thermally cured, they have a disadvantage of poor heat resistance. The characteristics may be insufficient.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a varnish capable of forming a low dielectric constant insulating layer mainly composed of polyesterimide and an insulated wire using the varnish. There is.

  As a result of various investigations on a combination of polyesterimide raw materials, particularly carboxylic acids and diamines, the present inventors have found that there is a correlation between the weight average molecular weight and the dielectric constant of the polyesterimide obtained as a reaction product. The present invention has been completed.

  That is, the polyesterimide resin varnish for low dielectric constant coating of the present invention comprises polyhydric carboxylic acid anhydride, dicarboxylic acid and / or alkyl ester thereof (hereinafter collectively referred to as “carboxylic acids”), alcohol And a polyesterimide resin varnish mainly composed of polyesterimide obtained by reacting a diamine compound, wherein the polyesterimide has a weight average molecular weight (Mw) of 9000 or more.

  It is preferable that the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyesterimide is 2.6 or more.

  The molar ratio (OH / COOH) of the hydroxyl group of the alcohol to the carboxyl group of the carboxylic acid is preferably 1.2 to 2.7, and the content ratio of the imido acid moiety to the ester moiety (imide / ester) Is preferably 0.2 to 1.0.

  The present invention also includes an insulated wire having an insulating coating formed by applying and baking the above-described polyesterimide resin varnish to a conductor.

  In the present invention, the weight average molecular weight and the number average molecular weight are both values measured by gel permeation chromatography.

  The polyesterimide resin varnish of the present invention can provide a heat-cured film (insulating film) having a low dielectric constant based on the characteristics of polyesterimide as a main component.

It is a graph which shows the relationship between the weight average molecular weight (Mw) of a polyesterimide, and a dielectric constant. It is a graph which shows the relationship between the molecular weight ratio (Mw / Mn) of polyesterimide, and a dielectric constant. It is a figure for demonstrating the measuring method of a dielectric constant.

  Although embodiments of the present invention will be described below, it should be considered that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Polyesterimide]
First, the polyesterimide which is the main component of the polyesterimide resin varnish for low dielectric constant coating of the present invention will be described.

Polyesterimide is a resin having an ester bond and an imide bond in the molecule, an imide formed from a carboxylic acid anhydride and an amine, a polyester formed from an alcohol and a carboxylic acid or an alkyl ester thereof, and a free acid of the imide. It is formed by adding a group or an anhydride group to the ester forming reaction. Such a polyesterimide is synthesized under conditions that cause imidization, esterification, and transesterification.
The polyesterimide used in the present invention is produced by reaction using carboxylic acids, diamine compounds, and alcohols as the main raw material monomers. Gel permeation chromatography (N-methyl-2-pyrrolidone (NMP) as a developing solvent, as a standard sample) A polyesterimide having a weight average molecular weight (Mw) of 9000 or more, preferably 12000 or more, more preferably 15000 or more, as measured by polystyrene.

  The relationship between the weight average molecular weight of the polyesterimide and the dielectric constant of the polyesterimide resin film obtained by heating and curing the polyesterimide is correlated as shown in FIG. In particular, a polyesterimide having a weight average molecular weight of less than 9000 tends to increase the dielectric constant and is 3.6 or more. On the other hand, when the weight average molecular weight is 9000 or more (preferably 12000 or more, more preferably 15000 or more), the dielectric constant becomes 3.6 or less, and the dielectric constant tends to gradually decrease as the weight average molecular weight increases. It is in. Accordingly, the polyesterimide resin varnish of the present invention has a dielectric constant of an insulating film formed from a currently marketed polyesterimide resin varnish by setting the weight average molecular weight of the main component polyesterimide to 9000 or more. In general, an insulating coating having a dielectric constant lower than 3.6 to 3.9) can be provided. The large weight average molecular weight means that the ratio of hydroxyl groups at the molecular terminals that cause an increase in dielectric constant per molecule of polyesterimide is reduced, or the hydroxyl group-containing raw materials (EG, THEIC) that are usually used in excess during the polymerization reaction. This may be because there are fewer unreacted components.

Furthermore, the molecular weight ratio (Mw / Mn) of the polyesterimide is preferably 2.6 or more. The relationship between the molecular weight ratio (Mw / Mn) of the polyesterimide and the dielectric constant of the polyesterimide resin film is correlated as shown in FIG.
Here, the molecular weight ratio (Mw / Mn) of 2.6 or more means that the molecular weight distribution is wide, that is, polyesterimide molecules having various molecular weights and molecular chain lengths are included.

  Accordingly, the polyesterimide used in the present invention is a carboxylic acid which is a raw material monomer of the polyesterimide so that the weight average molecular weight is 9000 or more, and preferably the molecular weight ratio (Mw / Mn) is 2.6 or more. , A diamine compound, and alcohols are appropriately combined.

  Among the raw materials for polyesterimide, especially by using high molecular weight compounds as diamines and dicarboxylic acids, increasing the imide ratio (imide / ester), reducing the hydroxyl excess (OH / COOH), etc. It becomes possible to increase the weight average molecular weight of the polyesterimide resin.

By using a high molecular weight compound as a raw material monomer, in particular, a diamine that is an imide-forming component, a dicarboxylic acid that is an ester-forming component, or an alkyl ester thereof, a molecular weight total amount of an imide constituent unit and an ester constituent unit is obtained. Since it can increase, it is thought that there exists a tendency to reduce content of polar groups, such as an ester bond and an imide bond, per unit weight of the obtained polyesterimide. Since the ester bond and the imide bond have polarity, it is considered that the dielectric constant of the polyesterimide is decreased by decreasing the content thereof.
Hereinafter, the raw material monomers will be described in order.

(1) Carboxylic acids As the carboxylic acids, there are used polyhydric carboxylic acid anhydrides mainly involved in imidization reactions, dicarboxylic acids involved in esterification and transesterification reactions, and / or alkyl esters thereof.

(1-1) Polyhydric Carboxylic Anhydride Polyhydric Carboxylic Anhydride is a compound in which one molecule of water is lost from two carboxyl groups and two acyl groups share one oxygen atom. In addition, compounds in which one or more free carboxyl groups remain are preferably used. Therefore, in addition to the tetracarboxylic anhydride, a compound in which two carboxyl groups of a polyvalent carboxylic acid having three or more carboxyl groups are converted into acid anhydrides by a dehydration reaction is included.

  Examples of the trivalent or higher polyhydric carboxylic acid anhydride include trimellitic acid anhydride, 3,4,4′-benzophenone tricarboxylic acid anhydride, 3,4,4′-biphenyltricarboxylic acid anhydride, biphenyltetracarboxylic acid Dianhydride, benzophenone tetracarboxylic dianhydride, diphenylsulfone tetracarboxylic dianhydride, oxydiphthalic dianhydride (OPDA), pyromellitic dianhydride (PMDA), 4,4 '-(2,2- And aromatic tetracarboxylic dianhydrides such as hexafluoroisopropylidene) diphthalic dianhydride (6FDA). Of these, trimellitic anhydride (TMA) is preferably used. These can be used alone or in combination.

(1-2) Dicarboxylic acid and / or alkyl ester thereof As the dicarboxylic acid, not only monocyclic aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid conventionally used as polyesterimide raw material monomers, but also 2-methyl Alkyl group-containing phthalic acids such as -1,4-benzenedicarboxylic acid, polynuclear aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexyldicarboxylic acid can be used.

  Examples of the polynuclear aromatic dicarboxylic acid include 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, , 7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and the like; anthracene dicarboxylic acid; phenanthrene dicarboxylic acid An acid etc. are mentioned. The alicyclic hydrocarbon dicarboxylic acid includes 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,3-dicarboxylnorbornane and the like. Examples include the above alicyclic hydrocarbon dicarboxylic acids.

  Since the weight average molecular weight of the polyesterimide as the reaction product tends to increase as the molecular weight of the dicarboxylic acid as the raw material monomer increases, a dicarboxylic acid having a molecular weight of 167 or more (preferably 200 or more), specifically, It is preferable to use the polynuclear aromatic hydrocarbon dicarboxylic acid or the alicyclic hydrocarbon dicarboxylic acid.

  The dicarboxylic acid may be used as an alkyl ester. Alkyl esters of dicarboxylic acids are incorporated into polyesterimide molecular chains in the same manner as dicarboxylic acids by participating in polyesterimide resin synthesis reactions, particularly esterification reactions and transesterification reactions, as with dicarboxylic acids. The above dicarboxylic acids and alkyl esters thereof can be used alone or in combination.

(2) Diamine As a diamine, a diamine conventionally used in the field of polyesterimide resin varnish, specifically, 4,4′-methylenediphenyldiamine (MDA), 4,4′-diaminodiphenyl ether, p In addition to -phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, hexamethylenediamine, and diaminodiphenylsulfone, aromatic diamines having a high molecular weight (specifically, a molecular weight of 250 or more) can be used.

  Examples of the aromatic diamine compound having a molecular weight of 250 or more include 1,3-bis (4-aminophenoxy) benzene (Mw = 292.33), 4,4′-bis (4-aminophenoxy) biphenyl (Mw = 368). .43), 1,1-bis {4- (4-aminophenoxy) phenyl} cyclohexane (Mw = 450.59), 1,4-bis (4-aminophenoxy) naphthalene (Mw = 342.40), 1 , 3-bis (4-aminophenoxy) adamantane (Mw = 350.45), 2,2-bis {4- (4-aminophenoxy) phenyl} propane (Mw = 410.51), 2,2-bis { 4- (4-aminophenoxy) phenyl} hexafluoropropane (Mw = 518.45), bis {4- (4-aminophenoxy) phenyl} sulfone (M = 432.49), 4,4'-diamino-2,2'-bis (trifluoromethyl) diphenyl ether (Mw = 336.23), bis {4- (4-aminophenoxy) phenyl} ketone (Mw = 396) .44), 1,4-bis (4-aminophenoxy) 2,3,5-trimethylbenzene (Mw = 334.41), 1,4-bis (4-aminophenoxy) 2,5-di-t- Butylbenzene (Mw = 404.54), 1,4-bis {4-amino-2- (trifluoromethyl) phenoxy} benzene (Mw = 428.33), 2,2-bis [4- {4-amino -2- (trifluoromethyl) phenoxy} phenyl] hexafluoropropane (Mw = 654.45), 4,4′-diamino-2- (trifluoromethyl) diphenyl ether (Mw = 68.23), 1,3-bis (4-aminophenoxy) neopentane (Mw = 286.37), 2,5-bis (4-aminophenoxy) biphenyl (Mw = 368.43), 9,9′- And bis (4-aminophenyl) fluorene (Mw = 348.44).

  Since the weight average molecular weight of the polyesterimide as the reaction product tends to increase as the molecular weight of the diamine as the raw material monomer increases, it is preferable to use a diamine having a molecular weight of 250 or more.

(3) Alcohols Examples of alcohols include dihydric alcohols such as ethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and 1,6-cyclohexanedimethanol; Examples include trihydric or higher alcohols such as methylolpropane and pentaerythritol; alcohols having an isocyanurate ring. Examples of the alcohol having an isocyanurate ring include tris (hydroxymethyl) isocyanurate, tris (2-hydroxyethyl) isocyanurate (THEIC), and tris (3-hydroxypropyl) isocyanurate. These polyhydric alcohols may be used alone or in combination of two or more. However, from the viewpoint of imparting heat resistance, it is preferable to use a combination of an alcohol having an isocyanurate ring and a lower alcohol. More preferred is a combination of THEIC and ethylene glycol. More preferably, the combination is in a ratio such that the OH group molar ratio (THEIC / EG) of THEIC to ethylene glycol (EG) is 0.5 to 4.0.

The polyesterimide raw material monomer as described above is appropriately selected and used so that the weight average molecular weight of the obtained polyesterimide is 9000 or more.
The combination having a weight average molecular weight of 9000 or more is not particularly limited, but it is preferable to select a high molecular weight compound for each of the diamine that is an imide-forming component and the carboxylic acid that is an ester-forming component. Specifically, by using a carboxylic acid having a molecular weight of 167 or more as the carboxylic acid and a diamine compound having a molecular weight of 250 or more as the diamine, it becomes easy to increase the weight average molecular weight of the polyesterimide as the reaction product. Either a diamine or a dicarboxylic acid may be used, but the weight average molecular weight of the polyesterimide can be further increased by using a combination of high molecular weights for both the dicarboxylic acid and the diamine.

Furthermore, the weight average molecular weight of the polyesterimide varies depending on the blend composition of the raw material monomers as described above.
In the blended composition of the polyesterimide forming component, the molar ratio of hydroxyl group to carboxyl group (OH / COOH) (hereinafter, this ratio may be referred to as “hydroxyl excess”) ranges from 1.2 to 2.7. It is preferable to mix | blend with, More preferably, it is 1.2-2.0, More preferably, it is 1.5-1.9. As the value of OH / COOH is decreased, the weight average molecular weight of the polyesterimide as a reaction product tends to increase, and as a result, the dielectric constant of the cured film obtained using the polyesterimide can be reduced. It becomes possible. However, when the hydroxyl excess is too low, particularly when it is 1 or less, there is a problem that the reaction liquid is strongly solidified (thickened), and stirring is practically impossible. Although it is possible to solve these problems by using a solvent, the molecular weight is less likely to increase. Further, when the acid becomes excessive, unreacted acid remains, which causes a problem that the appearance is deteriorated. For these reasons, it is preferable that the hydroxyl excess is more than 1, preferably within the above range.

The amount of hydroxyl groups referred to here is the amount of hydroxyl groups contained in the alcohol, and is determined as an amount obtained by multiplying the blending amount (mol) by the number of functional groups. For example, ethylene glycol is calculated as 2 moles because it has 2 OH groups in one molecule, and THEIC is calculated as 3 moles because it has 3 OH groups in one molecule.
The amount of carboxyl groups refers to the amount of carboxyl groups that form an ester. Specifically, the amount of dicarboxylic acid or its alkyl ester, which is a carboxylic acid, and the free amount contained in the polyvalent carboxylic acid anhydride. Refers to the amount of carboxyl groups. It is obtained as an amount obtained by multiplying the blending amount (mol) by the number of functional groups. The dicarboxylic acid is calculated by 2 mol, and even if the carboxyl group is an ester, it is calculated by treating it as equivalent to the dicarboxylic acid. In the case of an acid anhydride, only the amount of free carboxyl groups is calculated as an acid in the molar ratio of the carboxyl groups. For example, in the case of trimellitic anhydride, it is calculated as 1 mole.

  Moreover, in the composition of the polyesterimide raw material monomer, the molar ratio (imide / ester) of the imide bond to the ester bond of the polyesterimide to be obtained is 0.2 in the range of the imide / ester ratio in the conventional polyesterimide. Although what is necessary is just to mix | blend in the range of about -1.0, Preferably it is 0.32-1.0. If the imide / ester ratio is increased, the weight average molecular weight of the resulting polyesterimide resin tends to increase, and consequently the dielectric constant tends to decrease. Therefore, the imide / ester ratio is set to 0.32 to 1.0. It is preferable.

Here, the imide amount is a molar ratio of the imide acid synthesized from the acid anhydride and the diamine, and is obtained as an amount obtained by multiplying the blending amount of diamine (number of moles) by the number of functional groups (2).
The ester amount is calculated as the amount of carboxylic acid. Therefore, it is equal to the carboxyl group amount calculated by the hydroxyl group excess rate described above.

(4) Other components For the synthesis of the polyesterimide, in addition to the raw material monomers (carboxylic acids, diamines, alcohols) listed above, diisocyanates may be used as long as they do not impair the effects of the present invention. .
Examples of the diisocyanate include diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-3,3′-diisocyanate, diphenylmethane-3,4′-diisocyanate, diphenylether-4,4′-diisocyanate, and benzophenone-4,4. '-Diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, naphthylene-1,5-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, etc. Aromatic diisocyanates can be used. Such a diisocyanate can react with a carboxylic acid and participate in an amide or imide formation reaction.

(5) Synthesis of polyesterimide The method for producing polyesterimide is not particularly limited. For example, (1) a method in which polyesterimide raw material monomers (for example, carboxylic acids, diamines, alcohols) are added all at once and imidization and esterification are performed simultaneously; (2) an imide acid component (carboxylic anhydride, diamine, and Examples include a method in which a polyester-forming component (polyvalent carboxylic acid, monocarboxylic acid or alkyl ester thereof, and alcohols) other than these reactants is reacted in advance and then imidized by adding an imido acid component. It is done.

  In the above production method, a titanium system such as tetrabutyl titanate (TBT) or tetrapropyl titanate (TPT) is used as a catalyst. It is preferable to use titanium alkoxides such as tetrapropyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetrabutyl titanate, and tetrahexyl titanate. The catalyst is preferably blended in an amount of 0.01 to 0.5 parts by mass (0.01 to 0.5% by mass of the synthesized resin) per 100 parts by mass of the polyesterimide raw material monomer.

  Of the above production methods, the method (1) is preferably used from the viewpoint of ease of synthesis. Specifically, a polyesterimide raw material monomer is charged into the system, heated, and reacted at 80 to 250 ° C. Completion of the reaction can be known by confirming the coincidence with the calculated values of the distilled water and the resin amount calculated from the monomer blending amount. After the reaction is completed, the polyesterimide can have a high molecular weight by maintaining the high temperature.

  The reaction of the raw material monomer may be performed in the presence or absence of a solvent. When imidodicarboxylic acid is produced, the viscosity of the synthesis system increases, and therefore, synthesis in the presence of a solvent is preferable in terms of easy control in the system. On the other hand, according to the synthesis of the polyesterimide resin without a solvent, the polyesterimide raw material monomer in the system is present at a high concentration, so that it is possible to expect a higher reaction rate and higher molecular weight.

  The polyesterimide used as the main component of the varnish of the present invention is a polyesterimide synthesized as described above, and has a weight average molecular weight (Mw) of 9000 or more. As described above, the weight average molecular weight of the polyesterimide can be adjusted by the reaction temperature and the reaction time in addition to the kind of raw material monomer to be used and the blending composition.

[Polyesterimide resin varnish for low dielectric constant coating]
The polyesterimide resin varnish of the present invention contains the above polyesterimide as a main component. Specifically, the polyesterimide is dissolved in a solvent and further contains a curing agent, other resins, and additives as necessary.

  As a solvent for dilution, the well-known organic solvent conventionally used for the polyesterimide resin varnish can be used. Specifically, an organic solvent capable of dissolving a polyesterimide resin such as N-methylpyrrolidone, cresolic acid, m-cresol, p-cresol, phenol, xylenol, xylene, cellosolves and the like is used. Dilution with an organic solvent is performed so that the nonvolatile content (solid content) is 40 to 50% by mass.

As the curing agent, a titanium-based curing agent, a blocked isocyanate, or the like can be used.
Examples of the titanium curing agent include tetrapropyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetrabutyl titanate, and tetrahexyl titanate. These titanium-based curing agents may be used alone, or may be blended as a mixed solution preliminarily mixed with an organic solvent used in a paint.

  Examples of the blocked isocyanate include diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-3,3′-diisocyanate, diphenylmethane-3,4′-diisocyanate, diphenylether-4,4′-diisocyanate, and benzophenone-4,4 ′. -Diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, naphthylene-1,5-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, etc. Illustrated. Of these, compounds having an isocyanuric ring that can impart heat resistance are preferably used. Specifically, Sumitomo Biurethane's CT table, BL-3175, TPLS-2759, BL-4165, etc. can be used. From the viewpoint of lowering the dielectric constant of the polyesterimide resin film, the amount of blocked isocyanate added is preferably small.

  Resins other than the polyesterimide resin may be added within a range that does not impair other characteristics in order to improve characteristics required for the varnish, such as heat resistance and flexibility. Examples of the resin other than the polyesterimide resin include phenol resins such as phenol resin, xylene resin, and phenol-modified xylene resin, phenoxy resin, polyamide resin, and polyamideimide resin.

  Furthermore, examples of additives that can be added as necessary include pigments, dyes, inorganic or organic fillers, and lubricants.

[Insulated wire]
The insulated wire of the present invention uses the polyesterimide resin varnish of the present invention as an insulating coating.
As the conductor, a metal conductor such as copper, a copper alloy wire, or an aluminum wire is used. The diameter of the conductor and the cross-sectional shape thereof are not particularly limited, but those having a conductor diameter of 0.4 mm to 3.0 mm can be generally used.

  The polyesterimide resin varnish of the present invention is applied to the surface of a conductor, and an insulating film is formed by baking. Application | coating and baking can be performed by the method and conditions similar to formation of the insulation film of the conventional insulated wire. The coating and baking process may be repeated twice or more. Further, the polyesterimide resin varnish of the present invention can be used by blending with other resin paints within a range not impairing the gist of the present invention.

  Baking of the polyesterimide resin varnish is preferably performed by passing through a furnace at about 300 to 500 ° C. for 2 to 4 minutes.

  From the viewpoint of protecting the conductor, the thickness of the insulating film is preferably 1 to 100 μm, more preferably 10 to 50 μm. This is because if the insulating coating becomes too thick, the outer diameter of the insulated wire increases, and as a result, the space factor of the coil in which the insulated wire is wound tends to decrease.

The insulating film of the polyesterimide resin varnish may be formed directly on the conductor, or a base layer may first be formed on the conductor surface, and an insulating film of polyesterimide resin may be formed thereon.
Examples of the underlayer include insulating films formed by applying and baking various conventionally known insulating paints such as polyurethane, polyester, polyesterimide, polyesteramideimide, polyamideimide, polyimide, and the like.

  Furthermore, you may provide an overcoat layer in the upper layer of the polyesterimide film formed using the varnish of this invention. In particular, by providing a surface lubrication layer for imparting lubricity to the outer surface of an insulated wire, the stress generated by the friction between the wires during coil winding and compression processing to increase the space factor, and by this stress This is preferable because damage to the insulating film can be reduced. The resin that constitutes the topcoat layer may be any resin that has lubricity, for example, paraffins such as liquid paraffin and solid plasticine, various waxes, polyethylene, fluororesin, silicone resin and other lubricants with a binder resin. There may be mentioned a bound one. Preferably, an amidoimide resin imparted with lubricity by adding paraffin or wax is used.

  The insulated wire of the present invention uses a cured body of the polyesterimide resin varnish of the present invention as an insulating coating, and the weight average molecular weight of the polyester resin constituting the main component of the insulating coating is 9000 or more, preferably Furthermore, because the molecular weight ratio (Mw / Mn) is 2.6 or more, an insulating film having a lower dielectric constant than that of an insulating film obtained using a conventional polyesterimide resin varnish is formed.

  The best mode for carrying out the present invention will be described with reference to examples. The examples are not intended to limit the scope of the invention.

[Measurement and calculation method]
First, the measurement and calculation methods performed in this example will be described.
(1) Weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight ratio (Mw / Mn) of polyesterimide
Measurement was carried out by gel permeation chromatography (GPC) at a column temperature of 40 ° C. and a flow rate of 0.5 mL / min using HPC-GEL 8220GPC (a column is TSK-GEL GMHHR × 2 in series) manufactured by Tosoh Corporation. In addition, N-methylpyrrolidone (phosphoric acid 30 mM, LiBr 30 mM solution) was used as a developing solvent, and polystyrene was used as a standard sample.

(2) Measurement of dielectric constant About each obtained insulated wire, the dielectric constant of the insulating layer was measured. The measurement was performed as shown in FIG. That is, a measurement sample was prepared by applying a silver paste to three surfaces of an insulated wire (applying width is 10 mm at two ends and 100 mm at the center), and between the conductor and the silver paste. The dielectric constant was calculated from the measured capacitance value and the thickness of the coating.

(3) Hydroxyl excess (OH / COOH)
Based on the compounding amount of the monomer, the OH amount and the COOH amount were calculated by the following formula, and the OH amount / COOH amount was calculated.
OH amount = number of moles of ethylene glycol × 2 + number of moles of THEIC × 3
COOH amount = number of moles of dicarboxylic acid (TPA or NDCA) × 2 + number of moles of TMA × 1

(4) Imide / ester ratio Based on the compounding quantity of a monomer, the imide quantity and ester quantity were computed by the following formula, and the imide / ester ratio was computed.
Amount of imide = number of moles of diamine compound × 2
Ester amount = number of moles of dicarboxylic acid (TPA or NDCA) × 2 + number of moles of TMA × 1

[Synthesis of polyesterimide]
As a raw material monomer for polyesterimide, the following compounds are combined as shown in Tables 1 and 2, and 1.2 g of tetrapropyl titanate (TPT) is added as a catalyst. The temperature was raised to 180 ° C. over 1 hour, further raised to 235 ° C. over 4 hours from 180 ° C., and further maintained at 235 ° C. for 3 hours. During this holding time (3 hours), the reaction was complete. Completion of the reaction is based on the fact that water is generated in the process of esterification reaction between carboxylic acid and hydroxyl group, and imidation reaction between diamine and carboxylic acid anhydride. It was confirmed that the amount of water produced by the synthesis of was consistent. Even when the reaction was completed in less than 3 hours, the molecular weight was increased by continuing the reaction after taking out the theoretical amount of distilled water.
The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight ratio (Mw / Mn) of the obtained polyesterimide were measured based on the measurement method. In Table 1, the numerical value in parentheses of the raw material monomer indicates the molecular weight.

a) Carboxylic acids Trimellitic anhydride (TMA)
Terephthalic acid (TPA)
Naphthalenedicarboxylic acid (NDCA)

b) Alcohols Ethylene glycol (EG)
Tris (2-hydroxyethyl) cyanurate (THEIC))

c) Diamines 4,4′-Methylenediphenyldiamine (MDA)
2,2′-dimethyl-4,4′-diaminobiphenyl (mTBHG)
9,9'-bis (4-aminophenyl) fluorene (BAPF)
Norbornanediamine (NBDA)
2,2-bis {4- (4-aminophenoxy) phenyl} propane (BAPP)
1,3-bis (4-aminophenoxy) benzene (APB)
4,4'-Oxydianiline (ODA)
3,5-diethyltoluene-2,4-diamine (DETDA)

  THEIC / EG (OH group molar ratio), hydroxyl group excess (OH / COOH) in compounded monomer, imide bond and ester bond content molar ratio (imide / ester) of synthesized polyesterimide, weight of synthesized polyesterimide The average molecular weight (Mw), the number average molecular weight (Mn), and the molecular weight ratio (Mw / Mn) are shown in Tables 1 and 2 together.

[Preparation of polyesterimide resin varnish]
The polyesterimide synthesized above was prepared by using SCX-1 (trade name of Neochemical Co., Ltd., a mixed solvent of phenol and cresol) and Swazol # 1000 (trade name of Maruzen Petroleum Co., Ltd., Solvent Naphtha). SCX-1 / Swazole = 80/20 mixed solution was added to dilute the polyesterimide resin concentration to 50% by weight. After adding 60 g of a TPT / cresol solution (TPT concentration 63%) in which TPT (tetrapropyl titanate) was dissolved in cresol as a curing agent, this polyesterimide resin solution was mixed at 120 ° C. for 2 hours. Polyesterimide resin varnish no. 1-20 was prepared.

[Production of insulated wires and measurement evaluation of dielectric constant]
Polyesterimide resin varnish No. prepared above. 1-20 was applied to a copper wire (diameter 1.0 mm) and baked at a furnace temperature of 450 ° C. to produce an insulated wire that was insulated with an ester imide resin layer having a coating thickness of 35 μm.
The produced insulated wire No. For 1-20, the dielectric constant was measured based on the above measurement method. The results are shown in Tables 1 and 2 together with the measurement results. FIG. 1 shows the relationship between the weight average molecular weight (Mw) of polyesterimide and the dielectric constant, and FIG. 2 shows the relationship between the molecular weight ratio (Mw / Mn) of polyesterimide and the dielectric constant.

  As can be seen from FIG. 1, the dielectric constant tends to decrease as the weight average molecular weight of the polyesterimide increases. At a weight average molecular weight of 9000 or more (the region on the right side of the dotted line in the figure), the dielectric constant is 3.6 or less. became. In addition, as can be seen from FIG. 2, as the molecular weight ratio (Mw / Mn) of the polyesterimide resin increases, the dielectric constant tends to decrease. At a molecular weight ratio of 2.6 or more (the region on the right side from the dotted line in the figure), The dielectric constant was 3.6 or less.

  In Table 2, no. It can be seen that the weight average molecular weight of the synthesized polyesterimide tends to decrease as the hydroxyl excess increases from 10-13, and the dielectric constant tends to increase. No. It can be seen from 14-16 that as the imide / ester ratio increases, the weight-average molecular weight of the synthesized polyesterimide tends to increase, and the dielectric constant tends to decrease.

  Furthermore, no. Comparison between No. 15 and 19; From comparison of 16, 18 and 20, rather than changing the hydroxyl excess and the imide / ester ratio, the raw material monomers are high molecular weight diamine (BAPP) or dicarboxylic acid (NDCA), or high molecular weight diamine and carboxylic acid. It can be seen that the combined use has a higher dielectric constant reduction effect. It seems that the weight average molecular weight of the obtained polyesterimide resin is increased by using a high molecular weight raw material monomer.

  In Table 1, there is no significant correlation between the molecular weight of the raw material monomers (diamine, dicarboxylic acid) used and the weight average molecular weight (Mw) of the obtained polyesterimide, but this is a reaction. It seems to be due to the difference in the high molecular weight due to the heating time still held after completion.

  Since the polyesterimide resin varnish of the present invention can form a polyesterimide film having a low dielectric constant, it can be suitably used for forming an insulating film of an insulated wire having a high applied voltage.

Claims (5)

The main component is an anhydride of a polycarboxylic acid and a dicarboxylic acid and / or an alkyl ester thereof (hereinafter collectively referred to as “carboxylic acids”), an alcohol, and a polyesterimide obtained by reacting a diamine compound. A polyesterimide resin varnish,
A polyesterimide resin varnish for a low dielectric constant film, wherein the polyesterimide has a weight average molecular weight (Mw) of 9000 or more. 2. The polyesterimide resin varnish for a low dielectric constant film according to claim 1, wherein a ratio (Mw / Mn) of a weight average molecular weight (Mw) and a number average molecular weight (Mn) of the polyesterimide resin is 2.6 or more. 3. The polyesterimide resin varnish for a low dielectric constant film according to claim 1, wherein a molar ratio (OH / COOH) of a hydroxyl group of the alcohol to a carboxyl group of the carboxylic acid is 1.2 to 2.7. The polyesterimide resin varnish for a low dielectric constant film according to any one of claims 1 to 3, wherein a content ratio (imide / ester) of the imide acid portion to the ester portion is 0.2 to 1.0. . The insulated wire which has an insulating film formed by apply | coating and baking the polyesterimide resin-type varnish of any one of Claims 1-4 to a conductor.

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