Polyesterimides and polyesteramic acids

Abstract

To provide a polyesterimide with excellent thermal stability and high elongation, a method for producing the same, and a polyesteramide acid that is a precursor of the polyesterimide.SOLUTION: A polyesterimide has repeating units represented by the general formula (1) in the figure. (In the formula (1), X includes a divalent group represented by the formula (X1) in the figure and a divalent group represented by the formula (X2) in the figure, where the molar ratio of the divalent group represented by the formula (X1) to the divalent group represented by Formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyesterimide and a polyesteramic acid which is a precursor of the polyesterimide. [Background technology]

[0002] Polyimide resins, polyesterimide resins, and polyamideimide resins have excellent insulating properties and durability, and are therefore being considered for a variety of uses in the fields of electrical and electronic products. In particular, high performance is required of resins used in the insulated wires that make up motor coils. This is because motors are used for a variety of purposes, including industrial applications and consumer electronics, and a variety of motors are required depending on the application, such as high output, small size, and light weight. Recently, with the spread of electric vehicles and other vehicles, high-performance motors for transportation applications have also been developed.

[0003] Among the above resins, polyesterimide resins have been further improved by taking advantage of the fact that they have both ester bonds and imide bonds, and by imparting other properties in addition to insulating properties and durability. For example, Patent Document 1 discloses a composition for forming a release layer, which contains a polyamic acid obtained by reacting an aromatic diamine containing an ester bond or an ether bond with an aromatic tetracarboxylic dianhydride containing an ester bond or an ether bond, and an organic solvent, for the purpose of forming a release layer having appropriate adhesiveness and releasability, and discloses a polyesterimide resin as the release layer formed using the composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 129546 Summary of the Invention [Problem to be solved by the invention]

[0005] Polyesterimides are used in the field of electrical and electronic products due to their insulating properties and durability. However, when they are used in electronic substrates such as those shown in Patent Document 1 or insulated wires, excellent mechanical properties, particularly flexibility, are required. In particular, as mentioned above, there is a demand for greater thermal stability in order to accommodate the recent trend toward smaller motors with higher output. Therefore, there has been a demand for polyesterimide resins that are particularly excellent in thermal stability and elongation. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyesterimide having excellent thermal stability and a high elongation percentage, a method for producing the same, and a polyesteramic acid that is a precursor of the polyesterimide. [Means for solving the problem]

[0006] The present inventors discovered that a polyesterimide containing structural units consisting of a specific carboxylic acid component and two diamine components in a specific ratio can solve the above-mentioned problems, and further discovered that a polyester amide acid having a specific structure is useful as a precursor thereof, thereby completing the present invention.

[0007] That is, the present invention relates to the following [1] to

[15] . [1] A polyesterimide having a repeating unit represented by the following general formula (1): [ka] (In formula (1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.) [2] The polyesterimide according to [1] above, wherein the repeating unit represented by the formula (1) is a repeating unit represented by the following formula (1-1): [ka] [3] The polyesterimide according to the above [1] or [2], wherein the divalent group represented by the formula (X1) is a divalent group represented by the following formula (X1-1): [ka] [4] The polyesterimide according to any one of the above [1] to [3], wherein the divalent group represented by the formula (X2) is a divalent group represented by the following formula (X2-1): [ka] [5] The polyesterimide according to any one of the above [1] to [4], which is substantially free of aliphatic hydrocarbon groups. [6] The polyesterimide according to any one of the above [1] to [5], wherein the glass transition temperature of the polyesterimide is 220 to 280°C. [7] The polyesterimide according to any one of the above [1] to [6], wherein the polyesterimide has a 10% thermal weight loss temperature in air of 470°C or higher. [8] The polyesterimide according to any one of the above [1] to [7], wherein the polyesterimide has a breaking elongation of 15% or more as measured in a longitudinal tensile test using a test piece of 30 mm × 10 mm × 0.05 mm. [9] A polyester amide acid having a repeating unit represented by the following general formula (2): [ka] (In formula (2), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[10] The polyester amide acid according to [9] above, wherein the weight average molecular weight of the polyester amide acid is 5,000 to 1,000,000.

[11] A varnish comprising the polyester amide acid according to [9] or

[10] above and an organic solvent.

[12] The varnish according to the above

[11] , wherein the concentration of the polyester amide acid in the varnish is 8 to 50 mass %.

[13] The varnish according to

[11] or

[12] above, wherein the organic solvent in the varnish contains N,N-dimethylacetamide.

[14] The varnish according to any one of the above

[11] to

[13] , wherein the viscosity of the polyester amide acid in the varnish at 25°C is 1 to 50 Pa·s.

[15] A method for producing a polyesterimide, comprising the step of heating the varnish according to any one of the above

[11] to

[14] to imidize the polyesteramic acid. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyesterimide having excellent thermal stability and high elongation, a method for producing the same, and a polyesteramic acid which is a precursor of the polyesterimide. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Polyesterimide] The polyesterimide of the present invention has a repeating unit represented by the following general formula (1). [ka] (In formula (1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0010] The reason why the polyesterimide of the present invention has excellent thermal stability and high elongation is not clear, but is thought to be as follows. The polyesterimide of the present invention is believed to have high elongation because the copolymerization of a tetracarboxylic acid component having an ester bond with two diamine components causes a disorder in the intermolecular ordered structure, making it easier for the molecular chain to follow displacements.In addition, the inclusion of a rigid biphenylene group is believed to provide excellent thermal stability.

[0011] The molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5, preferably 30 / 70 to 85 / 15, and more preferably 40 / 60 to 85 / 15.

[0012] The repeating unit represented by the formula (1) is preferably a repeating unit represented by the following formula (1-1) from the viewpoints of availability of raw materials and thermal stability. [ka] (In formula (1-1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0013] The divalent group represented by the formula (X1) is preferably a divalent group represented by the following formula (X1-1) from the viewpoints of availability of raw materials and thermal stability. [ka]

[0014] The divalent group represented by the formula (X2) is a divalent group represented by the following formula (X2-1) from the viewpoints of availability of raw materials and thermal stability. [ka]

[0015] The polyesterimide has a repeating unit represented by the general formula (1), and the content of the repeating unit represented by the formula (1) is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 90 mol % or more, and still more preferably 95 mol % or more and 100 mol % or less, based on the total repeating units constituting the polyesterimide. It is even more preferable that the polyesterimide consists solely of the repeating unit represented by the general formula (1). Here, the repeating unit constituting polyesterimide refers to a unit in which one tetracarboxylic dianhydride and one diamine are bonded via an imide structure.

[0016] The polyesterimide is preferably substantially free of aliphatic hydrocarbon groups. Here, "substantially free of aliphatic hydrocarbon groups" means that the content of aliphatic hydrocarbon groups in the polyesterimide is a content that does not affect the effects of the present invention, or the polyesterimide does not contain any aliphatic hydrocarbon groups. Specifically, the content of aliphatic hydrocarbon groups in the polyesterimide is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and still more preferably 0% by mass. It is even more preferable that the polyesterimide does not contain any aliphatic hydrocarbon groups. The aliphatic hydrocarbon group is a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, or an alicyclic hydrocarbon group present in the main chain or side chain of the polyesterimide, specifically an alkyl group, an alkylene group, an alkylidene group, an alkenyl group, an alkynyl group, a cycloalkyl group, or the like.

[0017] The glass transition temperature of the polyesterimide is preferably 200 to 300°C, more preferably 220 to 285°C, even more preferably 220 to 250°C, and even more preferably 250 to 270°C. When the glass transition temperature of the polyesterimide is in the above range, the heat resistance is excellent and the thermal stability of the polyesterimide is good. The glass transition temperature of the polyesterimide can be determined by measuring the temperature dependence of the loss tangent (tanδ) in the tensile mode using a dynamic viscoelasticity measuring device (DMA) for a film sample of the polyesterimide, and determining the temperature at which tanδ reaches its peak. Specifically, the glass transition temperature can be determined by the method described in the examples.

[0018] The 10% thermal weight loss temperature of the polyesterimide in air is preferably 470°C or higher, more preferably 490°C or higher. There is no upper limit, but it is generally 800°C or lower. When the 10% thermal weight loss temperature of the polyesterimide in air is within the above range, the polyesterimide has excellent heat resistance and the insulating coating layer has good thermal stability. The 10% thermal weight loss temperature of the polyesterimide in air can be measured by TGA (thermogravimetric analysis), specifically, by the method described in the examples.

[0019] The breaking elongation measured in a longitudinal tensile test using a 30 mm × 10 mm × 0.05 mm test piece of the polyesterimide is preferably 15% or more, more preferably 17% or more, even more preferably 20% or more, even more preferably 30% or more, and even more preferably 33% or more. It is also typically 100% or less. When the breaking elongation is within the above range, the polyesterimide has excellent elongation and good flexibility. The breaking elongation is expressed as the elongation of the length of the test piece at break when a tensile test is performed in the longitudinal direction (parallel to the 30 mm side) at a rate of 1 mm / min using a film-like test piece with long sides of 30 mm, short sides of 10 mm, and thickness of 0.05 mm (however, the 30 mm long sides do not include the length of the portion fixed to the jig, and both ends of the long sides of the test piece have gripped portions fixed to the jig with a width of 10 mm and a thickness of 0.05 mm). Specifically, it can be determined by the method described in the Examples.

[0020] The dielectric constant of the polyesterimide at 1 kHz is preferably 3.1 or less, more preferably 3.0 or less, and even more preferably 2.9 or less. There is no lower limit, but it is generally 2.0 or more. When the dielectric constant of the polyesterimide at 1 kHz is within the above range, the dielectric constant of the insulating coating layer is low and the insulating properties are excellent. The dielectric constant of the polyesterimide can be measured by the automatic balancing bridge method in accordance with JIS C 2138, and specifically, it can be measured by the method described in the examples.

[0021] As described above, the polyesterimide of the present invention has excellent thermal stability and high elongation, and is therefore useful as a material for electric and electronic products, and is particularly suitable as a coating material for insulated wires.

[0022] [Polyester amide acid] The polyesterimide is not particularly limited as long as it is produced by a method that can obtain a polyesterimide having a repeating unit represented by formula (1), but it is preferably produced by imidizing a polyesteramic acid as a precursor. The polyester amide acid, which is the precursor of the polyester imide, will be described below.

[0023] The polyester amide acid of the present invention, which is a precursor of the polyesterimide, has a repeating unit represented by the following general formula (2). [ka] (In formula (2), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0024] The molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5, preferably 30 / 70 to 85 / 15, and more preferably 40 / 60 to 85 / 15.

[0025] The repeating unit represented by the formula (2) is preferably a repeating unit represented by the following formula (2-1) from the viewpoints of availability of raw materials and thermal stability of polyesterimide obtained by imidization. [ka] (In formula (2-1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0026] The divalent group represented by the formula (X1) is preferably a divalent group represented by the following formula (X1-1), from the viewpoints of availability of raw materials and thermal stability of polyesterimide obtained by imidization. [ka]

[0027] The divalent group represented by the formula (X2) is a divalent group represented by the following formula (X2-1) from the viewpoints of availability of raw materials and thermal stability of polyesterimide obtained by imidization. [ka]

[0028] The polyester amide acid has a repeating unit represented by the general formula (2), and the content of the repeating unit represented by the formula (2) is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 90 mol % or more, and still more preferably 95 mol % or more and 100 mol % or less, based on the total repeating units constituting the polyester amide acid. It is even more preferable that the polyester amide acid is composed only of the repeating unit represented by the general formula (2). Here, the repeating unit constituting the polyester amide acid refers to a unit in which one tetracarboxylic dianhydride and one diamine are bonded via an amide structure.

[0029] Preferably, the polyester amide acid is substantially free of aliphatic hydrocarbon groups. Here, "substantially free of aliphatic hydrocarbon groups" means that the content of aliphatic hydrocarbon groups in the polyester amide acid is a content that does not affect the effects of the present invention, or the polyester amide acid does not contain any aliphatic hydrocarbon groups. Specifically, the content of aliphatic hydrocarbon groups in the polyester amide acid is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and still more preferably 0% by mass. It is even more preferable that the polyester amide acid does not contain any aliphatic hydrocarbon groups. The aliphatic hydrocarbon group is a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, or an alicyclic hydrocarbon group present in the main chain or side chain of the polyester amide acid, specifically an alkyl group, an alkylene group, an alkylidene group, an alkenyl group, an alkynyl group, a cycloalkyl group, or the like.

[0030] The weight-average molecular weight of the polyester amide acid is preferably 5,000 to 1,000,000, and more preferably 50,000 to 300,000. A weight-average molecular weight within this range is preferred because the polyester amide acid solution can be adjusted to a concentration and viscosity suitable for various coating processes, and the polyesterimide produced by imidization exhibits excellent mechanical properties such as elongation. The weight-average molecular weight of the polyester amide acid can be determined, for example, by gel filtration chromatography measurement using a standard polystyrene (PS) equivalent. Specifically, it can be measured by the method described in the Examples.

[0031] <Production of Polyester Amide Acid> The polyester amide acid can be produced by reacting a tetracarboxylic acid component having an ester bond and a diamine component, which will be explained below.

[0032] The tetracarboxylic acid component used in the production of polyester amide acid includes a compound represented by the following general formula (a1). Among the compounds represented by the following general formula (a1), the compound represented by the following formula (a11) is preferred. [ka] The compound represented by formula (a11) is p-biphenylene bis(trimellitate) dianhydride. By using p-biphenylene bis(trimellitate) dianhydride as the tetracarboxylic acid component, an insulating coating layer having excellent thermal stability and elongation can be formed.

[0033] The ratio of the compound represented by formula (a1) in the tetracarboxylic acid component is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 90 mol % or more, and preferably 100 mol % or less. The tetracarboxylic acid component may consist solely of the compound represented by formula (a1).

[0034] The tetracarboxylic acid component may contain a tetracarboxylic acid dianhydride other than the compound represented by formula (a1). Examples of such tetracarboxylic acid dianhydrides include, but are not limited to, aromatic tetracarboxylic acid dianhydrides other than the compound represented by formula (a1), alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides. However, in the present invention, it is preferable to use neither an alicyclic tetracarboxylic acid dianhydride nor an aliphatic tetracarboxylic acid dianhydride, and it is more preferable to use only an aromatic tetracarboxylic acid dianhydride. The tetracarboxylic acid component may optionally contain one type of tetracarboxylic acid dianhydride, or two or more types of tetracarboxylic acid dianhydrides. The tetracarboxylic acid component is not limited to tetracarboxylic dianhydride, but may be a derivative thereof. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride and an alkyl ester of the tetracarboxylic acid. Among these, tetracarboxylic dianhydride is preferred.

[0035] The diamine component used in the production of polyester amide acid includes a compound represented by formula (b1) and a compound represented by formula (b2).

[0036] The molar ratio of the compound represented by formula (b1) to the compound represented by formula (b2) [(b1) / (b2)] is 30 / 70 to 95 / 5, preferably 30 / 70 to 85 / 15, and more preferably 40 / 60 to 85 / 15. Among the compounds represented by the following general formula (b1), the compound represented by the following formula (b11) is preferred.Furthermore, among the compounds represented by the following general formula (b2), the compound represented by the following formula (b21) is preferred. [ka] The compound represented by formula (b11) is 4,4'-diaminodiphenyl ether (ODA), and the compound represented by formula (b21) is 4,4'-bis(4-aminophenoxy)biphenyl (BAPB). By using ODA or BAPB as the diamine component, a polyesterimide with excellent thermal stability and elongation can be obtained.

[0037] The total ratio of the compound represented by formula (b1) and the compound represented by formula (b2) in the diamine component is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less.

[0038] The diamine component may contain a diamine other than the compound represented by formula (b1) or the compound represented by formula (b2). Examples of such diamines include, but are not limited to, aromatic diamines other than the compound represented by formula (b1) or the compound represented by formula (b2), alicyclic diamines, and aliphatic diamines. However, in the present invention, it is preferable to use substantially neither alicyclic diamines nor aliphatic diamines, and it is more preferable to use only aromatic diamines. The diamine component may optionally contain one kind of diamine or two or more kinds of diamines. The diamine component is not limited to diamine, but may be a derivative thereof. Examples of the derivative include a diisocyanate corresponding to the diamine. Among these, diamine is preferred.

[0039] The polyester amide acid produced using the above raw materials has structural units derived from the tetracarboxylic dianhydride and structural units derived from the diamine. Furthermore, the polyester imide produced using the polyester amide acid produced using the above raw materials as a precursor has structural units derived from the tetracarboxylic dianhydride and structural units derived from the diamine. That is, the polyester amide acid of the present invention preferably has structural units derived from the tetracarboxylic dianhydride and structural units derived from the diamine. Furthermore, the polyester imide of the present invention preferably has structural units derived from the tetracarboxylic dianhydride and structural units derived from the diamine.

[0040] The polyester amide acid can be produced by reacting a tetracarboxylic acid component containing a compound represented by the formula (a1) with a diamine component containing a compound represented by the formula (b1) or a compound represented by the formula (b2). The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0041] In the present production method, the method for reacting the tetracarboxylic acid component with the diamine component is not particularly limited, and any known method can be used. Specific examples of the reaction method include a method in which a tetracarboxylic acid component, a diamine component, a solvent, and, if necessary, an end-capping agent are charged into a reactor and stirred at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out at 80°C or less, the molecular weight of the polyester amide acid does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so that polyester amide acid can be produced stably.

[0042] The terminal blocking agent is preferably a monoamine or a dicarboxylic acid. The amount of the terminal blocking agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Examples of the monoamine terminal blocking agent include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, 3-phenoxyaniline, 4-phenoxyaniline, m-anisidine, and p-anisidine. Of these, aniline, 4-phenoxyaniline, and p-anisidine are preferred. The dicarboxylic acid terminal blocking agent is preferably a dicarboxylic acid, and a portion of the dicarboxylic acid may be ring-closed. Examples include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. Of these, phthalic acid and phthalic anhydride are more preferred.

[0043] The solvent used in the production of polyester amide acid may be any solvent capable of dissolving the polyester amide acid produced, such as aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, and aromatic hydrocarbon solvents, with aprotic solvents being preferred.

[0044] Specific examples of aprotic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone; and ester solvents such as 2-methoxy-1-methylethyl acetate. Preferred are amide or lactone solvents, more preferred are amide solvents, and even more preferred is N,N-dimethylacetamide.

[0045] Specific examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N,N-dimethylacetamide is even more preferred. Specific examples of aromatic hydrocarbon solvents include toluene, xylene, and ethylbenzene. The above solvents may be used alone or in combination of two or more.

[0046] By the above method, a solution of polyester amide acid dissolved in a solvent is obtained. The concentration of polyester amide acid in the resulting solution is preferably 1 to 80% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 30% by mass.

[0047] [varnish] When the polyesterimide is produced by imidizing the polyesteramic acid as a precursor, the polyesteramic acid is preferably used as a varnish for the production of the polyesterimide. By using the varnish, polyesterimides of various shapes can be easily produced.

[0048] The varnish of the present invention contains the polyester amide acid and an organic solvent, and the polyester amide acid is dissolved in the organic solvent. That is, the varnish of the present invention contains a polyester amide acid having a repeating unit represented by the following general formula (2) and an organic solvent, and the polyester amide acid is dissolved in the organic solvent. [ka] (In formula (2), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0049] The organic solvent contained in the varnish is not particularly limited as long as it dissolves polyester amide acid, but the compounds described above as solvents used in the production of polyester amide acid are preferred. Specifically, the organic solvent contained in the varnish preferably contains the amide solvent or the lactone solvent, more preferably contains an amide solvent, and even more preferably contains N,N-dimethylacetamide. Furthermore, the organic solvent contained in the varnish is preferably the amide solvent or the lactone solvent, more preferably contains an amide solvent, and even more preferably contains N,N-dimethylacetamide. The above solvents may be used alone or in combination.

[0050] The varnish may further contain a dehydration catalyst. Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; etc. These may be used alone or in combination of two or more.

[0051] The polyester amide acid contained in the varnish has solvent solubility, and therefore can be used to form a highly concentrated varnish that is stable at room temperature. The concentration of the polyester amide acid in the varnish is preferably 5 to 70% by mass, more preferably 8 to 50% by mass, and even more preferably 10 to 30% by mass. The concentration of polyester amide acid in the varnish may be adjusted by diluting the polyester amide acid solution immediately after the production of the polyester amide acid with an organic solvent, or, if the concentration of polyester amide acid in the polyester amide acid solution is within the above range and is a concentration suitable for producing a polyesterimide, the polyester amide acid solution may be used as a varnish as is. The viscosity of the varnish at 25°C is preferably 1 to 50 Pa·s, and more preferably 5 to 30 Pa·s. The viscosity of the varnish can be measured, for example, using an E-type (cone-plate) viscometer. Specifically, it can be measured by the method described in the examples.

[0052] The varnish may also contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, antifoaming agents, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, within limits that do not impair the required properties of the resulting polyesterimide. The method for producing the varnish is not particularly limited, and any known method can be applied. For example, the varnish can be obtained by mixing an additional solvent, as necessary, with the polyester amide acid solution obtained by the above-mentioned production method to adjust the concentration.

[0053] [Method of producing polyesterimide] The method for producing the polyesterimide of the present invention is not particularly limited, but it is preferable to produce it using the above-mentioned polyester amide acid, and it is more preferable to produce it using the above-mentioned varnish. Specifically, the method for producing a polyesterimide of the present invention includes a step of heating the varnish to imidize the polyesteramic acid. That is, the method for producing a polyesterimide of the present invention includes a step of heating a varnish containing a polyesteramic acid having a repeating unit represented by the following general formula (2) and an organic solvent to imidize the polyesteramic acid. [ka] (In formula (2), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0054] There are no particular limitations on the method for producing polyesterimide using the varnish, and any known method can be used. For example, when producing a polyesterimide in the form of a film, i.e., a polyesterimide film, the varnish is applied to a smooth support such as a glass plate, a metal plate, or plastic, or formed into a film, and then organic solvents such as reaction solvents and dilution solvents contained in the varnish are removed by heating to obtain a polyesteramic acid film, and the polyesteramic acid in the polyesteramic acid film is imidized (dehydration ring-closure) by heating to produce a polyesterimide film. Thus, a preferred method for producing a polyesterimide film is to apply the above-mentioned varnish to a support and then heat it.

[0055] First, the varnish is dried to remove the solvent, thereby obtaining a polyester amide acid film. The drying temperature is preferably 50 to 150°C. The heating temperature when imidizing the polyesteramic acid in a film state by heating is preferably 200 to 400° C., more preferably 220 to 350° C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, more preferably 15 minutes to 1 hour. By using such a temperature and time, the physical properties of the resulting polyesterimide film are improved. The heating atmosphere may be air gas, nitrogen gas, oxygen gas, hydrogen gas, or a nitrogen / hydrogen mixed gas. The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[0056] The polyesterimide thus obtained has the repeating unit represented by formula (1) as described above, and has excellent thermal stability and high elongation. Therefore, it is useful as a material for electrical and electronic products, and is particularly suitable as a coating material for insulated wires.

[0057] [Insulated wire] The polyesterimide of the present invention has the above-mentioned excellent properties and is therefore useful as an insulating coating layer for an insulated wire. In the following, a preferred insulated wire using the polyesterimide of the present invention will be described. That is, the insulated wire using the polyesterimide of the present invention is an insulated wire having a conductor and an insulating coating layer that coats the conductor, The insulated wire preferably has an insulating coating layer containing a polyesterimide having a repeating unit represented by the following general formula (1). [ka] (In formula (1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

[0058] The insulating coating layer of the insulated wire coats the conductor and contains polyesterimide having a repeating unit represented by the general formula (1). The polyesterimide used in the insulating coating layer is preferably the polyesterimide described above in the section [Polyesterimide]. Specifically, the polyesterimide shown below is preferred.

[0059] The molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5, preferably 30 / 70 to 85 / 15, and more preferably 40 / 60 to 85 / 15.

[0060] The repeating unit represented by the formula (1) is preferably a repeating unit represented by the formula (1-1) from the viewpoints of availability of raw materials and thermal stability. The divalent group represented by the formula (X1) is preferably a divalent group represented by the formula (X1-1) from the viewpoints of availability of raw materials and thermal stability. The divalent group represented by the formula (X2) is a divalent group represented by the formula (X2-1) from the viewpoints of availability of raw materials and thermal stability.

[0061] The polyesterimide has a repeating unit represented by the general formula (1), and the content of the repeating unit represented by the formula (1) is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 90 mol % or more, and still more preferably 95 mol % or more and 100 mol % or less, based on the total repeating units constituting the polyesterimide. It is even more preferable that the polyesterimide consists solely of the repeating unit represented by the general formula (1). Here, the repeating unit constituting polyesterimide refers to a unit in which one tetracarboxylic dianhydride and one diamine are bonded via an imide structure.

[0062] The polyesterimide is preferably substantially free of aliphatic hydrocarbon groups. Here, "substantially free of aliphatic hydrocarbon groups" means that the content of aliphatic hydrocarbon groups in the polyesterimide is a content that does not affect the effects of the present invention, or the polyesterimide does not contain any aliphatic hydrocarbon groups. Specifically, the content of aliphatic hydrocarbon groups in the polyesterimide is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and still more preferably 0% by mass. It is even more preferable that the polyesterimide does not contain any aliphatic hydrocarbon groups. The aliphatic hydrocarbon group is a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, or an alicyclic hydrocarbon group present in the main chain or side chain of the polyesterimide, specifically an alkyl group, an alkylene group, an alkylidene group, an alkenyl group, an alkynyl group, a cycloalkyl group, or the like.

[0063] The glass transition temperature of the polyesterimide is preferably 200 to 300°C, more preferably 220 to 285°C, even more preferably 220 to 280°C, and even more preferably 250 to 270°C. When the glass transition temperature of the polyesterimide is within the above range, the heat resistance and thermal stability of the polyesterimide are excellent. The glass transition temperature of the polyesterimide can be determined by measuring the temperature dependence of the loss tangent (tanδ) in a tensile mode using a dynamic viscoelasticity measuring device (DMA) on a film sample of the polyesterimide, and determining the temperature at which tanδ reaches its peak. Specifically, the glass transition temperature can be determined by the method described in the examples.

[0064] The 10% thermal weight loss temperature of the polyesterimide in air is preferably 470°C or higher, more preferably 490°C or higher. There is no upper limit, but it is generally 800°C or lower. When the 10% thermal weight loss temperature of the polyesterimide in air is within the above range, the polyesterimide has excellent heat resistance and the insulating coating layer has good thermal stability. The 10% thermal weight loss temperature of the polyesterimide in air can be measured by TGA (thermogravimetric analysis), specifically, by the method described in the examples.

[0065] The breaking elongation measured in a longitudinal tensile test using a 30 mm × 10 mm × 0.05 mm test piece of the polyesterimide is preferably 15% or more, more preferably 17% or more, even more preferably 20% or more, even more preferably 30% or more, and even more preferably 33% or more. It is also typically 100% or less. When the breaking elongation is within the above range, the polyesterimide has excellent elongation and good flexibility. The breaking elongation is expressed as the elongation of the length of the test piece at break when a tensile test is performed in the longitudinal direction (parallel to the 30 mm side) at a rate of 1 mm / min using a film-like test piece with long sides of 30 mm, short sides of 10 mm, and thickness of 0.05 mm (however, the 30 mm long sides do not include the length of the portion fixed to the jig, and both ends of the long sides of the test piece have gripped portions fixed to the jig with a width of 10 mm and a thickness of 0.05 mm). Specifically, it can be determined by the method described in the Examples.

[0066] The dielectric constant of the polyesterimide at 1 kHz is preferably 3.1 or less, more preferably 3.0 or less, and even more preferably 2.9 or less. There is no lower limit, but it is generally 2.0 or more. When the dielectric constant of the polyesterimide at 1 kHz is within the above range, the dielectric constant of the insulating coating layer is low and the insulating properties are excellent. The dielectric constant of the polyesterimide can be measured by the automatic balancing bridge method in accordance with JIS C 2138, and specifically, it can be measured by the method described in the examples.

[0067] The method for producing the insulated wire is not particularly limited, but it is preferable to produce the insulated wire using the varnish described above. Specifically, a preferred method for producing an insulated wire is a method for producing an insulated wire, which comprises applying a varnish containing a polyester amide acid having a repeating unit represented by the general formula (2) and an organic solvent onto a conductor and baking the varnish to form an insulating coating layer. The insulating coating layer of the insulated wire obtained in this manner is obtained by imidizing the polyester amide acid described above, and therefore contains a polyesterimide containing a repeating unit represented by general formula (1).

[0068] According to this manufacturing method, the varnish is applied to a conductor and baked to form an insulating coating layer, thereby obtaining an insulated wire. By repeating the application and baking process, an insulating coating layer of an appropriate thickness can be formed. The baking temperature is preferably 180 to 600°C, more preferably 200 to 600°C, and even more preferably 250 to 500°C. The baking time is preferably 1 minute to 10 hours, more preferably 5 minutes to 3 hours, and even more preferably 5 minutes to 1 hour. When the temperature is low, a longer baking time is preferable, and when the temperature is high, a shorter baking time is preferable. The baking is carried out to remove the organic solvent contained in the varnish, imidize the polyester amide acid, and fix the insulating coating layer on the conductor. However, if chemical imidization is used for the imidization reaction instead of thermal imidization, baking may be carried out at a lower temperature. The insulated wire obtained as described above has an insulating coating layer containing polyesterimide, which has excellent thermal stability, high elongation, and a low dielectric constant, making the insulated wire particularly suitable as an insulated wire for forming a motor coil. [Example]

[0069] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples in any way.

[0070] [Physical property measurement and evaluation] The physical properties of the polyester amide acids, varnishes and polyesterimides obtained in the examples and comparative examples were measured and evaluated by the methods described below.

[0071] (1) Weight-average molecular weight of polyester amide acid The weight average molecular weight of the polyester amide acids obtained in the examples and comparative examples was measured as follows. The varnish containing the polyester amide acid was diluted with the mobile phase solvent shown below to prepare a measurement solution so that the polyester amide acid concentration was 0.2% by mass. Using the measurement solution, gel filtration chromatography was performed under the following conditions to determine the weight average molecular weight of the polyester amide acid in terms of polystyrene. Equipment: CBM-20A, SIL-10ADvp, LC-10ADvp, DGU-12A, SPD-10Avp, CTO-10Avp, RID-10A, FRC-10A (all manufactured by Shimadzu Corporation) Column: Shodex GPC K-804 Column temperature: 50℃ Mobile phase: N-methylpyrrolidone (LiBr (30 mM), H3PO4 (30 mM)) Mobile phase flow rate: 0.7mL / min Molecular weight standard: Polystyrene (Shodex M-6.8,63,955)

[0072] (2) Viscosity of the varnish The viscosity of the varnishes obtained in the examples and comparative examples was measured using the following viscometer under the following conditions. Apparatus: E-type (cone-plate) viscometer HAAKE RheoStress 6000 (manufactured by Thermo Scientific) Measurement temperature: 25℃ Shear rate: 3s -1

[0073] (3) Glass transition temperature (Tg) The films obtained in the test examples and comparative test examples were dried in a vacuum at 100° C. for 16 hours and cut into strips 10 mm wide and 30 mm long to prepare measurement samples. Using the measurement sample, the glass transition temperature (Tg) was measured under the following conditions using a dynamic viscoelasticity measuring device DMA7100 (manufactured by Hitachi High-Tech Science Corporation). Tg is the temperature at the peak top of the loss tangent (tan δ). Measurement mode: Tensile mode Temperature rise conditions: 30℃ to 320℃ at 10℃ / min, hold for 5 minutes Frequency: 1Hz Amplitude: 10μm

[0074] (4) Thermal Gravity Loss Temperature (Td, evaluation of thermal stability) The polyesterimide films obtained in the examples and comparative examples were powdered using a freeze-pulverizer, and dried in a vacuum at 100° C. for 16 hours to prepare measurement samples. Using the measurement sample, the 10% mass loss temperature (Td10%) was measured by TGA (thermogravimetric analysis) under the following conditions using a thermogravimetric and differential thermal analyzer STA7200 (manufactured by Hitachi High-Tech Science Corporation). Td10% was defined as the temperature at which the mass of the measurement sample decreased by 10% compared to the mass at the start of the measurement. The higher the thermal weight loss temperature, the better the thermal stability. Note that the measured value of a sample that did not reach Td10% even when heated to 500°C was deemed to exceed the upper measurement temperature limit of 490°C, and is indicated in Table 1 as ">490". Temperature rise conditions: 30℃ to 500℃ at 10℃ / min, hold for 5 minutes Measurement environment: Air atmosphere

[0075] (5) Breaking elongation (evaluation of elongation) The polyesterimide films obtained in the examples and comparative examples were cut into 10 mm x 60 mm test pieces. Using the test specimen, a tensile test was carried out under the following conditions using a precision universal testing machine Autograph AGX-plus (manufactured by Shimadzu Corporation). The length of the test specimen at break was measured from the displacement of the load cell at break, and the breaking elongation was calculated using the following formula. Breaking elongation (%) = (length of test piece at break - initial length of test piece) / (initial length of test piece) × 100 Grip distance: 30 mm Load cell (tensile force): 50N Tensile speed: 1 mm / min (tensile direction: longitudinal direction of test piece)

[0076] (6) Dielectric constant (relative permittivity) The films obtained in the Production Examples and Comparative Production Examples were cut into 60 mm x 60 mm pieces and dried in a vacuum at 100°C for 18 hours to prepare test pieces. The dielectric constant (relative permittivity) of the test piece was measured using a Precision LCR Meter E4980A (manufactured by Agilent Technologies) under the following conditions: The measurement frequency was 1 kHz. Measurement environment: 23°C ± 2°C, 50% RH ± 5% RH Electrode dimensions: Main electrode φ36mm, ring electrode inner diameter φ38mm Electrode material: conductive silver paste

[0077] [Raw materials] The raw materials and their abbreviations used in the examples and comparative examples are as follows: <Raw material for polyesterimide and polyesteramide acid> TA-BP: p-biphenylenebis(trimellitate)dianhydride (BP-TME manufactured by Honshu Chemical Industry Co., Ltd.; a compound represented by formula (a11). Purity: 98.6%. For the production of polyester amide acid, the compound was dried under vacuum at 100°C for about 2 hours.) TA-BPZ: p-(cyclohexylidenebisphenylene)bis(trimellitate)dianhydride (BPZ-TME manufactured by Honshu Chemical Industry Co., Ltd.; compound represented by the following formula; purity 99.2%) [ka] TA-HMBP: p-(2,2',3,3',5,5'-hexamethylbiphenylene)-bis(trimellitate) dianhydride (TMPBP-TME manufactured by Honshu Chemical Industry Co., Ltd.; compound represented by the following formula; purity 99.5%) [ka] ODA: 4,4'-diaminodiphenyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b11); purity 99.4%) BAPB: 4,4'-bis(4-aminophenoxy)biphenyl (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b21); purity 100%) BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by the formula below; purity 99.4%) [ka]

[0078] <Solvent> DMAc: N,N-dimethylacetamide

[0079] [Production of polyester amide acid (varnish)] Example 1 Nitrogen was passed through a 300 mL separable flask equipped with a nitrogen inlet pipe, an exhaust pipe, and a mechanical stirrer equipped with a stirring blade, to create a nitrogen atmosphere. Next, 1.007 g (5.0 mmol) of ODA and 1.842 g (5.0 mmol) of BAPB were placed in the separable flask, and then DMAc was added so that the concentration of the resulting polyester amide acid became 12.5% ​​by mass. Subsequently, 5.420 g (10.0 mmol) of TA-BP was added. The mixture was allowed to react at 25°C with stirring. After confirming that the viscosity had begun to increase, DMAc was added so that the concentration of the resulting polyester amide acid was 10% by mass, forming a reaction mixture. The reaction mixture was further allowed to react at 25°C for 20 hours with stirring to obtain a polyester amide acid solution (varnish).

[0080] Examples 2 to 3 and Comparative Examples 1 to 3 A polyester amide acid solution (varnish) was obtained in the same manner as in Production Example 1, except that the amounts (ratios) of ODA, BAPB, and TA-BP in Example 1 were changed to the amounts (ratios) shown in Table 1.

[0081] Comparative Examples 4 to 6 A polyester amide acid solution (varnish) was obtained in the same manner as in Production Example 1, except that ODA, BAPB, and TA-BP were changed to the raw materials shown in Table 1.

[0082] [Production of polyesterimide (film)] Examples 4 to 6 and Comparative Examples 7 to 12 A glass plate was prepared, and the polyester amide acid solution (varnish) was applied to the glass plate using a coating machine to a film thickness of 0.04 to 0.05 mm. The varnish-coated glass plate was placed on a hot plate and heated at 100°C for 2 hours to remove the solvent. The glass plate was then heated at 200°C for 1 hour using a hot air dryer, and then further heated at 250°C for 30 minutes to thermally imidize the polyester amide acid, yielding a polyesterimide (film, thickness 0.04 to 0.05 mm).

[0083] Table 1 shows the physical properties of the polyester amide acids, varnishes, and polyesterimides obtained in the examples and comparative examples, as well as the evaluation results.

[0084] [Table 1]

[0085] As shown in Table 1, the polyesterimide of the present invention has excellent thermal stability and a high elongation. Furthermore, as shown in the Examples, since the polyesterimide can be obtained by imidizing a polyesteramic acid, the polyesteramic acid of the present invention is useful as a precursor of the polyesterimide. Furthermore, a varnish containing the polyesteramic acid is also useful as a raw material for producing the polyesterimide.

Claims

1. A polyesterimide having a repeating unit represented by the following general formula (1): 【Chemistry 1】 (In formula (1), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.)

2. The polyesterimide according to claim 1, wherein the repeating unit represented by formula (1) is a repeating unit represented by the following formula (1-1): 【Chemistry 2】

3. The polyesterimide according to claim 1 or 2, wherein the divalent group represented by formula (X1) is a divalent group represented by the following formula (X1-1): 【Transformation 3】

4. The polyesterimide according to any one of claims 1 to 3, wherein the divalent group represented by formula (X2) is a divalent group represented by the following formula (X2-1): 【Chemistry 4】

5. 5. The polyesterimide according to claim 1, wherein the content of aliphatic hydrocarbon groups in the polyesterimide is 5% by mass or less.

6. The polyesterimide according to any one of claims 1 to 5, wherein the glass transition temperature of the polyesterimide is 220 to 280°C.

7. A polyesterimide described in any one of claims 1 to 6, wherein the 10 mass % thermal weight loss temperature of the polyesterimide in air, measured by the method described below, is 470°C or higher. (method) The polyesterimide is dried in vacuum at 100° C. for 16 hours to prepare a sample for measurement. Using a thermogravimetric and differential thermal analyzer, the measurement sample is heated in an air atmosphere from 30° C. to 500° C. at a rate of 10° C. / min, and then held at 500° C. for 5 minutes. The 10% by mass thermal weight loss temperature is defined as the temperature at which the mass of the measurement sample is reduced by 10% by mass compared to the mass at the start of measurement.

8. 8. The polyesterimide according to claim 1, wherein the polyesterimide has a breaking elongation of 15% or more as measured in a longitudinal tensile test using a test piece of 30 mm x 10 mm x 0.05 mm.

9. A polyester amide acid having a repeating unit represented by the following general formula (2): 【Transformation 5】 (In formula (2), X includes a divalent group represented by formula (X1) above and a divalent group represented by formula (X2) above, and the molar ratio of the divalent group represented by formula (X1) to the divalent group represented by formula (X2) [(X1) / (X2)] is 30 / 70 to 95 / 5.) 10. The polyester amide acid of claim 9, wherein the weight average molecular weight of the polyester amide acid is 5,000 to 1,000,000.

11. A varnish comprising the polyester amide acid according to claim 9 or 10 and an organic solvent.

12. The varnish according to claim 11, wherein the concentration of the polyester amide acid in the varnish is 8 to 50% by mass.

13. 13. The varnish according to claim 11 or 12, wherein the organic solvent in the varnish comprises N,N-dimethylacetamide.

14. The varnish according to any one of claims 11 to 13, wherein the viscosity of the polyester amide acid in the varnish at 25°C is 1 to 50 Pa·s.

15. A method for producing a polyesterimide, comprising the step of heating the varnish according to any one of claims 11 to 14 to imidize the polyesteramic acid.

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