JP2012059588A - Polyester imide resin varnish for low dielectric constant coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polyester imide based varnish capable of forming a low dielectric constant insulation layer and an insulation wire which uses the varnish to achieve a low dielectric constant.SOLUTION: The polyester imide resin varnish consists mainly of polyester imide resin obtained by reacting carboxylic acid which contains dicarboxylate in molecular weight of 167 or more or its anhydride or alkyl ester (kind of carboxylic acid), alcohols, and a diamine compound. Furthermore, it is preferable that the diamine compound should contain a diamine compound in molecular weight of 250 or more. For an imide group having a large polarizability, it is possible to reduce an imide group percentage content per polyester imide molecular chain of a unit quantity by increasing the molecular weight of a raw material monomer and, hence, to lower a dielectric constant.

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 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 of using a low dielectric constant material for the insulating layer is effective in improving the corona discharge starting voltage, but the insulating layer must also satisfy the requirements for insulation, adhesion to conductors, heat resistance, and mechanical strength. There is. 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, it is soft and inferior in heat resistance and mechanical strength, so its use is limited when used as an insulating layer. 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. The object of the present invention is to reduce the dielectric constant by using a varnish capable of forming a low dielectric constant insulating layer mainly composed of polyesterimide and the varnish. It is in providing the insulated wire which aimed at.

The present inventors have found that the dielectric constant of the polyesterimide resin film can be lowered by reducing the content ratio in the polyesterimide molecular chain with respect to the imide group having a large polarization, and completed the present invention.
The present inventors have found that a dielectric constant of a polyesterimide resin film can be lowered by using a diamine having a large molecular weight among diamine raw material monomers, and has already filed an application (Japanese Patent Application No. 2010-195481). ). Furthermore, as for dicarboxylic acid, it was found that the dielectric constant of the polyesterimide resin film can be reduced by using dicarboxylic acid having a large molecular weight, and the present invention has been completed.

  That is, the polyesterimide resin varnish for low dielectric constant coating of the present invention comprises a carboxylic acid containing a dicarboxylic acid having a molecular weight of 167 or more, or an anhydride or an alkyl ester thereof (hereinafter collectively referred to as “carboxylic acids”), an alcohol, The main component is a polyesterimide resin obtained by reacting a diamine compound. The dicarboxylic acid is preferably naphthalenedicarboxylic acid or cyclohexanedicarboxylic acid.

  The diamine compound preferably contains a diamine compound having a molecular weight of 250 or more, and more preferably is a diamine compound not containing a fluorine atom.

  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 imide acid part to the ester part (imide / ester) Is preferably 0.2 to 1.0.

  The polyesterimide resin varnish for a low dielectric constant film of the present invention preferably further contains phenolic resins.

  The present invention also includes an insulated wire having an insulating coating formed by applying and baking the polyesterimide resin varnish for a low dielectric constant coating of the present invention to a conductor.

  By increasing the molecular weight of the raw material monomer dicarboxylic acid, the imide group content per polyester imide molecular chain can be lowered, and the imide group content with high polarizability is reduced, thereby lowering the dielectric constant of the polyester imide resin film. be able to.

It is a figure for demonstrating the measuring method of a dielectric constant. It is a graph which shows the relationship between the molecular weight of diamine, and a dielectric constant. It is a graph which shows the relationship between the molecular weight of the dicarboxylic acid used in the Example, and a dielectric constant. It is a graph which shows the relationship between the total molecular weight of diamine and the dicarboxylic acid which were used in the Example, and 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 resin varnish and its production method]
First, the synthesis of the polyesterimide resin used in the polyesterimide varnish of the present invention will be described.

<Polyesterimide resin>
The polyesterimide resin is a resin having an ester bond and an imide bond in the molecule, an imide formed from a polycarboxylic acid or its anhydride and an amine, a polyester formed from an alcohol and a carboxylic acid, and liberation of the imide. It is formed by adding an acid group or an anhydride group to the ester forming reaction. Such a polyesterimide resin is synthesized under conditions that cause imidization, esterification, and transesterification.

  The polyesterimide resin used in the present invention is characterized in that a carboxylic acid containing a dicarboxylic acid having a molecular weight of 167 or more, a diamine, or an alcohol is used as a polyesterimide raw material monomer, and further a diamine having a molecular weight of 250 or more is used as a diamine. is there. Hereinafter, each component will be described.

(1) Carboxylic acids The carboxylic acids include dicarboxylic acids having a molecular weight of 167 or more. Specifically, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalene Polynuclear compounds such as dicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid such as 2,7-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, phenanthenedicarboxylic acid, etc. Aromatic hydrocarbon dicarboxylic acid; alkyl group-containing phthalic acid such as 2-methyl-1,4-benzenedicarboxylic acid; 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, Carbon number such as 2,3-dicarboxyl norbornane Such as dicarboxylic acids or alicyclic hydrocarbons. Of these, naphthalenedicarboxylic acid is preferably used from the viewpoint of reactivity, and 2,6-naphthalenedicarboxylic acid is more preferable. In addition, these dicarboxylic acids may be used as alkyl esters or acid anhydrides.

  All of the above dicarboxylic acids have a molecular weight greater than that of phthalic acid (molecular weight 166). Therefore, by using these dicarboxylic acids instead of phthalic acid (including terephthalic acid and isophthalic acid), the ratio of imide groups contained per unit molecular weight of the polyesterimide molecular chain to be synthesized can be reduced. Since the imide group has a high polarizability, the dielectric constant of the polyesterimide film can be lowered by reducing the imide group content in the polyesterimide.

  The carboxylic acids used in the present invention may include other polycarboxylic acid anhydrides, dicarboxylic acids having a molecular weight of 166 or less, or alkyl esters thereof, in addition to dicarboxylic acids having a molecular weight of 167 or more.

  As other polycarboxylic anhydrides, one molecule of water is lost from two carboxyl groups, two acyl groups share one oxygen atom, and one or more free carboxyl groups The remaining compounds can be used, for example, trimellitic anhydride, 3,4,4′-benzophenone tricarboxylic anhydride, 3,4,4′-biphenyltricarboxylic anhydride, biphenyltetracarboxylic dianhydride , Benzophenone tetracarboxylic dianhydride, diphenylsulfone tetracarboxylic dianhydride, oxydiphthalic dianhydride (OPDA), pyromellitic dianhydride (PMDA), 4,4 '-(2,2-hexafluoro And aromatic tetracarboxylic dianhydrides such as isopropylidene) diphthalic dianhydride (6FDA). Of these, trimellitic anhydride (TMA) is preferably used.

  The content ratio of the dicarboxylic acid having a molecular weight of 167 or more in the carboxylic acids is not particularly limited, but it is preferably 10 to 100 mol% of the dicarboxylic acids, and trimellitic anhydride is preferably included as the other carboxylic acids.

(2) Diamine As a diamine, a diamine conventionally used in the field of polyesterimide resin varnish, specifically, 4,4′-methylenediphenyldiamine (MDA) (Mw = 198.26), 4, 4'-diaminodiphenyl ether (Mw = 200.24), p-phenylenediamine (Mw = 108.14), etc. can be used.

  However, it is preferable to use a diamine compound having at least a part of the diamine, preferably 50 mol% or more, more preferably 80 mol% or more, further preferably 100 mol%, and a molecular weight of 250 or more. As with dicarboxylic acids, diamines having a high molecular weight are used in at least a part of the polyesterimide raw material monomer to lower the content of imide groups per unit molecular weight of the synthesized polyesterimide molecular chain. be able to. By using a high-molecular-weight diamine for the diamine that is an imide group-forming component, it is possible to obtain a greater effect on the imide group content reduction effect per polyesterimide molecular chain than that obtained with a high-molecular-weight dicarboxylic acid alone. Become.

  The diamine compound having a molecular weight of 250 or more is not particularly limited, but an aromatic diamine is preferably used. Specifically, 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-amino) Phenoxy) 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 (Mw = 432.49), 4,4′-diamino-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 = 268.23), 1,3-bis (4-aminophenol) Xyl) neopentane (Mw = 286.37), 2,5-bis (4-aminophenoxy) biphenyl (Mw = 3688.43), 9,9′-bis (4-aminophenyl) fluorene (Mw = 348.44) Etc.) can be used, and these can be used alone or in combination of two or more. Of these, from the viewpoint of cost and availability, a compound containing no fluorine atom is preferred. Diamine compounds containing fluorine atoms tend to have a greater effect on reducing the dielectric constant than diamine compounds of the same molecular weight, but they are used as polyesterimide resin varnish materials because of their cost and availability. There are circumstances that are difficult. In this regard, the combined use with a high molecular weight dicarboxylic acid makes it possible to reduce the dielectric constant to the same extent as when a fluorine atom-containing diamine is used.

(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 manufacturing method of polyesterimide using the above polyesterimide raw material monomer is not particularly limited. For example, (1) A method in which polyesterimide raw material monomers (carboxylic acids, diamines, alcohols) are added all at once and imidization and esterification are performed simultaneously; (2) After reacting in advance with a polyester component other than the imide acid component, Examples thereof include a method of imidizing by adding an imidic acid component.

Of the above production methods, the method (1) is preferably used from the viewpoint of ease of synthesis.
The polyesterimide synthesis reaction may be performed in the presence of an organic solvent such as cresol, or may be performed in the 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.

  In the composition of the polyesterimide raw material monomer, the molar ratio of hydroxyl group to carboxyl group (OH / COOH) (hereinafter, this ratio may be referred to as “hydroxyl excess”) is not particularly limited and is 1.2 to It can mix | blend in the range of 2.7. Preferably it is 1.2 or more and less than 2, more preferably 1.2 to 1.9. According to the viewpoint of the present inventors, as the OH / COOH increases, the dielectric constant tends to increase, and by making the OH / COOH 1.9 or less, ε ( (Dielectric constant) can be a dielectric constant lower than about 3.8 (see Japanese Patent Application No. 2010-186880). By setting the hydroxyl excess to 1.9 or less, a polyesterimide having a lower dielectric constant can be obtained. It becomes possible.

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 contained in dicarboxylic acids that are carboxylic acids or their alkyl esters and carboxylic anhydrides. 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 not particularly limited, and is within the range of the imide / ester ratio in the conventional polyesterimide. Although what is necessary is just to mix | blend in the range of a certain 0.2-1.0, Preferably it is 0.32-1.0. According to the viewpoint of the present inventors, when the imide / ester ratio is increased, the dielectric constant tends to decrease (see Japanese Patent Application No. 2010-186880), and therefore the imide / ester ratio is 0.32 or more to 1.0. Thus, the dielectric constant can be further reduced.

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.

  In the synthesis of the polyesterimide resin used in the present invention, a titanium system such as tetrabutyl titanate (TBT) or tetrapropyl titanate (TPT) is further used as a catalyst. Titanium alkoxides such as tetrapropyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetrabutyl titanate, and tetrahexyl titanate are preferably used. The catalyst is preferably blended in an amount of 0.01 to 0.5 parts by mass (0.01 to 0.5% by weight of the synthesized resin) per 100 parts by mass of the polyesterimide raw material monomer.

  As described above, the polyesterimide raw material monomer is charged into the system, heated, and reacted at 80 to 250 ° C. The blending order of the polyesterimide raw material monomer is not particularly limited, and may be charged all at once into the system. The reaction of the raw material monomer may be carried out in the presence or absence of a solvent. When the reaction is carried out in the presence of a solvent, the reaction may be carried out at 80 to 250 ° C. after dilution with the solvent.

  Completion of the reaction can be known by confirming the coincidence with the calculated values of the distilled water and resin amount calculated from the blended monomers.

  The polyesterimide resin synthesized as described above is diluted with an organic solvent, and a curing agent and other additives are added to produce a polyesterimide varnish.

<Organic solvent>
As a solvent for dilution, the well-known organic solvent conventionally used for the polyesterimide 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.

<Curing agent>
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.

<Other ingredients>
In the production of the polyesterimide resin varnish of the present invention, in order to further improve the properties required of the varnish, for example, heat resistance, flexibility, etc., as resins other than the polyesterimide resin, phenol resin, xylene resin, Phenol resins such as phenol-modified xylene resins, phenoxy resins, polyamide resins, polyamideimide resins, and the like may be added.
Furthermore, you may add various additives, such as a pigment, dye, an inorganic or organic filler, and a lubricant, as needed. You may further heat after addition of these additives.

[Insulated wire]
The insulated wire of the present invention uses the polyesterimide 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 the above-mentioned cured body of the polyesterimide resin varnish of the present invention as an insulating coating, and uses a higher molecular weight compound than conventional carboxylic acids as a polyesterimide raw material monomer. Thus, it is possible to reduce the imide group content contained per unit molecular weight of the polyesterimide molecular chain, and thus the dielectric constant of the polyesterimide film alone can be 3.5 or less. Furthermore, with regard to the diamine compound as well, it is possible to further reduce the imide group content contained per unit molecular weight of the polyesterimide molecular chain by using a higher molecular weight compound than before. It is possible to reduce the dielectric constant, which is difficult in the case of a dicarboxylic acid alone or a diamine compound containing no fluorine, such as .3 or less.
In addition, in Japanese Patent Application No. 2010-195481, it is disclosed that a dielectric constant of 3.3 or less can be achieved by using a high molecular weight diamine. However, an easily available dicarboxylic acid such as naphthalenedicarboxylic acid or cyclohexanedicarboxylic acid can be used. By using in combination, it becomes possible to efficiently reduce the imide group content by using an easily available diamine. As a result, a dielectric constant of 3.2 or less, which has been difficult to manufacture by increasing the molecular weight of the diamine monomer alone, is obtained. It can also be achieved.

  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) Measurement of dielectric constant (ε) The prepared ester imide resin varnish was applied to a copper wire (diameter: 1.0 mm), baked at a furnace temperature of 450 ° C., and insulated with an ester imide resin layer having a film thickness of 35 μm. An insulated wire was created. About each obtained insulated wire, the dielectric constant of the insulating layer was measured. As shown in FIG. 1, silver paste was applied to three places on the surface of the insulated wire to prepare a measurement sample (the width of application was 10 mm at two ends and 100 mm at the center). The capacitance between the conductor and the silver paste was measured with an LCR meter, and the dielectric constant was calculated from the measured capacitance value and the film thickness.

(2) 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 × 2 + number of moles of TMA × 1

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

<Relationship between molecular weight of diamine compound and dielectric constant of insulating coating>
As polyesterimide raw material monomers, carboxylic acids (trimellitic anhydride (TMA) and terephthalic acid (TPA)), alcohols (ethylene glycol (EG) and tris (2-hydroxyethyl) cyanurate (THEIC)), and Table 2 No. Diamines having different molecular weights as shown in A1-A21 are blended in the amounts (g) shown in Table 1, respectively, and 1.2 g of tetrapropyl titanate (TPT) is added as a catalyst (0. 16 weight%) and the temperature was raised to 80 ° C., then the temperature was raised from 80 ° C. to 180 ° C. over 1 hour, further raised from 180 ° C. to 235 ° C. over 4 hours, and further 235 Hold at 3 ° C. for 3 hours.

  In addition, the compounding quantity of each component shown in Table 1 is the quantity for synthesize | combining 750 g of polyesterimide resin. As shown in Table 1, the THEIC / EG (OH group molar ratio), hydroxyl excess (OH / COOH), and the imide bond / ester bond content molar ratio (imide / ester) of the synthesized polyesterimide resin in the blended monomer It calculated so that it might become.

  Based on the formation of water in the process of esterification reaction of carboxylic acid and hydroxyl group and imidation reaction of diamine and anhydride group, it was generated by the theoretical water amount calculated from the blended monomer amount and the synthesis of the above polyesterimide resin Completion of the reaction was confirmed by matching the amount of water.

  The polyesterimide resin synthesized as described above was prepared using SCX-1 (trade name of Neochemical Co., Ltd., which is a mixed solvent of phenol and cresol) and Swazol # 1000 (trade name of Maruzen Petroleum Co., Ltd., Solvent Naphtha). Was added at a ratio of SCX-1 / Swazole = 80/20, and diluted to a polyesterimide resin concentration of 50% by weight.

(2) Preparation of ester imide resin varnish (A series), production of insulated wire, measurement evaluation of dielectric constant TPT (tetrapropyl titanate) was dissolved in cresol as a curing agent in the polyesterimide resin solution synthesized above. A TPT / cresol solution (TPT concentration 63%) was added in the amount shown in Table 1 (60 g), and then mixed at 120 ° C. for 2 hours. Next, as other resins, a solution in which phenol-modified xylene formaldehyde resin P100 is dissolved in an organic solvent SCX-1 (trade name of Neochemical Co., Ltd., which is a mixed solvent of phenol and cresol) with a solid content is shown in Table 1. After adding the amount shown in (60 g), the mixture was stirred at 70 ° C. for about 1 hour, whereby the blended diamine compound No. Each ester imide resin varnish No. A1-A21 A1-A21 was prepared and manufactured. About A1-A21, the dielectric constant was measured based on the said measuring method. The measurement results are shown in Table 2 together with the type of amine added. The relationship between the molecular weight of the amine used and the dielectric constant is shown in FIG.

  As can be seen from FIG. 2, the dielectric constant tends to decrease as the molecular weight of the diamine compound used for the synthesis of the polyesterimide resin increases.

<Relationship between type of dicarboxylic acid and dielectric constant of insulating coating>
(1) Synthesis of polyesterimide resin As polyesterimide raw material monomers, carboxylic acids (trimellitic anhydride (TMA) and dicarboxylic acid), alcohols (ethylene glycol (EG) and tris (2-hydroxyethyl) cyanurate (THEIC)) And diamine (4,4-methylenediphenyldiamine (MDA)) in an amount (g) shown in Table 3, respectively, and 1.2 g of tetrapropyl titanate (TPT) as a catalyst. Then, the temperature was raised from 80 ° C. to 180 ° C. over 1 hour, further raised from 180 ° C. to 235 ° C. over 4 hours, and further maintained at 235 ° C. for 3 hours.

  Examples of the dicarboxylic acid include terephthalic acid (molecular weight 166: manufactured by Mitsubishi Gas Chemical Co., Ltd.), 2,6-naphthalenedicarboxylic acid (molecular weight 216: manufactured by Sumikin Air Water Co., Ltd.), 1,4-cyclohexanedicarboxylic acid (molecular weight 172: Nikko). Any one of Rika Co., Ltd.) was used. These blending amounts are 750 g of resin finally obtained, THEIC / EG (OH group molar ratio) in the blended monomer, hydroxyl excess (OH / COOH), imide bond and ester of the polyesterimide resin to be synthesized The amount at which the bond molar ratio (imide / ester) was the value shown in Table 3 was calculated and blended.

  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 anhydride group, the theoretical water amount calculated from the blended monomer amount and the synthesis of the above polyesterimide resin Completion of the reaction was confirmed by agreement with the amount of water produced.

  The polyesterimide resin synthesized as described above was prepared using SCX-1 (trade name of Neochemical Co., Ltd., which is a mixed solvent of phenol and cresol) and Swazol # 1000 (trade name of Maruzen Petroleum Co., Ltd., Solvent Naphtha). Was added at a ratio of SCX-1 / Swazole = 80/20, and diluted to a polyesterimide resin concentration of 50% by weight.

(2) Preparation of polyesterimide resin varnish (C series), production of insulated wires and measurement evaluation of dielectric constant In the polyesterimide resin solution synthesized above, TPT (tetrapropyl titanate) was dissolved in cresol as a curing agent. After adding 60 g of a TPT / cresol solution (TPT concentration 63%), the mixture was mixed at 120 ° C. for 2 hours. Next, as another resin, 60 g of a solution obtained by dissolving phenol-modified xylene formaldehyde resin P100 in a solid content in an organic solvent SCX-1 (trade name of Neochemical Co., Ltd., which is a mixed solvent of phenol and cresol) is added. After that, by stirring for about 1 hour at 70 ° C., polyesterimide resin varnish Nos. With different types of the mixed dicarboxylic acid were used. C1-C3 was prepared, using this, the insulated wire was produced by the above-mentioned method, and the dielectric constant was measured. The measurement results are shown in Table 3 together with the composition. The relationship between the molecular weight of the dicarboxylic acid used and the dielectric constant is shown in FIG.

  No. C1 is a conventional polyesterimide resin varnish using terphthalic acid as the dicarboxylic acid and MDA as the diamine. As can be seen from Table 3 and FIG. 3, the dielectric constant decreased as the molecular weight of the dicarboxylic acid increased. By using a dicarboxylic acid having a large molecular weight, it is considered that the dielectric constant can be lowered as in the case of diamine.

<Relationship between type of polyesterimide raw material monomer and dielectric constant of insulating coating>
(1) Synthesis of polyesterimide resin As dicarboxylic acid, terephthalic acid (molecular weight 166: manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 2,6-naphthalenedicarboxylic acid (molecular weight 216: manufactured by Sumikin Airwater Co., Ltd.) used in the C series. , 1,4-cyclohexanedicarboxylic acid (molecular weight 172: manufactured by Nikko Rica Co., Ltd.), as diamine, MDA (Mw = 198.26), 2,2-bis (4 (4-aminophenoxy) phenyl Propane) (Mw = 410.51), 9,9′-bis (4-aminophenyl) fluorene (Mw = 348.44), and other raw material monomers (trimellitic anhydride, ethylene glycol) , THEIC) and the amount (g) shown in Table 4 respectively. After adding 1.2 g of Nate (TPT) and raising the temperature to 80 ° C., the temperature was raised from 80 ° C. to 180 ° C. over 1 hour, further raised from 180 ° C. to 235 ° C. over 4 hours, Hold at 235 ° C. for 3 hours.

  These blending amounts are 750 g of resin finally obtained, THEIC / EG (OH group molar ratio) in the blended monomer, hydroxyl excess (OH / COOH), imide bond and ester of the polyesterimide resin to be synthesized The bond molar ratio (imide / ester) was calculated and blended in such amounts as shown in Table 4.

  In addition, completion of reaction was confirmed when the theoretical water amount calculated from the amount of compounding monomers and the water amount produced | generated by the synthesis | combination of the said polyesterimide resin corresponded like the said varnish C series.

(2) Preparation of polyester resin varnish (AC series), production of insulated wires and measurement evaluation of dielectric constant The polyesterimide resin synthesized as described above was diluted in the same manner as the varnish C series, and further a curing agent (TPT / Cresol solution (TPT concentration 63%)), phenol-modified xylene formaldehyde resin P100, and stirring at 70 ° C. for about 1 hour, AC series polyesterimide resin varnish with different types of dicarboxylic acid and diamine compounded No. AC1-AC8 was prepared. Varnish No. AC1 and AC2 correspond to conventional polyesterimide resin varnishes using terephthalic acid as the dicarboxylic acid and MDA as the diamine.

  The prepared varnish no. Using AC1-8, an insulated wire was produced by the method described above, and the dielectric constant was measured. The measurement results are shown in Table 4 together with the composition. In Table 4, “(diamine + dicarboxylic acid) molecular weight” is the total molecular weight of the molecular weight of the diamine used and the molecular weight of the dicarboxylic acid. The relationship between the total molecular weight and the dielectric constant is shown in FIG.

  As can be seen from Table 4 and FIG. 4, it can be seen that the dielectric constant decreases as the total molecular weight increases. Therefore, for both diamine and dicarboxylic acid, the imide group content per polyester imide molecular chain can be reduced by using a molecular weight compound larger than that of terephthalic acid and MDA which are generally used. The dielectric constant can be lowered. Regarding the effect of reducing the dielectric constant, diamine and dicarboxylic acid can contribute to reducing the imide group content per polyesterimide molecular chain by increasing the molecular weight without interfering with each other. Furthermore, when AC3 is compared with AC7 and AC6, all have the same molecular weight (diamine + dicarboxylic acid), the effect of reducing the dielectric constant of AC3 is smaller than that of AC6 and AC7. From this, it can be seen that using a compound having a large molecular weight for both dicarboxylic acid and diamine increases the dielectric constant reduction effect rather than increasing the molecular weight of diamine alone.

  Therefore, for both diamines and dicarboxylic acids, it is usually difficult to achieve with only one of dicarboxylic acids and diamines not containing fluorine atoms by using a molecular weight compound larger than terephthalic acid and MDA that are generally used. It is also possible to achieve a dielectric constant of 3.3 or lower, and further 3.2 or lower.

  Further, from comparison between AC1 and AC2, it can be seen that the dielectric constant can be lowered by lowering the hydroxyl excess.

  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 (8)

Low dielectric constant mainly composed of a polyesterimide resin obtained by reacting a carboxylic acid containing a dicarboxylic acid having a molecular weight of 167 or more, an anhydride or an alkyl ester thereof (hereinafter collectively referred to as “carboxylic acids”), an alcohol, and a diamine compound. Polyesterimide resin varnish for rate coating. The polyesterimide resin varnish for a low dielectric constant film according to claim 1, wherein the dicarboxylic acid is naphthalenedicarboxylic acid or cyclohexanedicarboxylic acid. The polyesterimide resin varnish for a low dielectric constant film according to claim 1, wherein the diamine compound includes a diamine compound having a molecular weight of 250 or more. The polyesterimide resin varnish for a low dielectric constant film according to claim 3, wherein the diamine compound is a diamine compound containing no fluorine atom. The polyesterimide for a low dielectric constant film according to any one of claims 1 to 4, 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. Resin varnish. The polyesterimide resin varnish for a low dielectric constant film according to any one of claims 1 to 5, wherein a content ratio (imide / ester) of the imide acid portion to the ester portion is 0.2 to 1.0. . Furthermore, the polyesterimide resin varnish for a low dielectric constant film according to any one of claims 1 to 6, further comprising a phenol resin. The insulated wire which has an insulating film formed by apply | coating and baking the varnish of any one of Claims 1-7 on a conductor.

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