Polyesterimides and polyesteramic acids

Abstract

To provide: a polyesterimide with excellent thermal stability and high elongation; a polyesteramide acid capable of realizing a low-viscosity varnish; and a production method of the polyesterimide.SOLUTION: A polyesterimide has a repeating unit represented by the general formula (1) and a terminal structure represented by the general formula (2), where the molar ratio [(1) / (2)] of the repeating unit represented by the general formula (1) to the terminal structure represented by the general formula (2) is 100 / 5 to 100 / 1.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to polyesterimide and polyester amic acid which is a precursor of the polyesterimide.

Background Art

[0002] Polyimide resins, polyesterimide resins, and polyamideimide resins have excellent insulation and durability, and thus various applications are being studied in the field of electric and electronic products. In particular, high performance is required for the resin used for the insulating wire constituting the motor coil. This is because motors are used in various applications such as industrial applications and household electrical appliances, and depending on the application, various motors such as high output, small size, and light weight are required. Recently, with the spread of electric vehicles and the like, high performance motors for transportation applications have also been developed.

[0003] Among these resins, the polyesterimide resin takes advantage of having both an ester bond and an imide bond, and further improvements are being made such as imparting other properties in addition to insulation and durability. For example, Patent Document 1 discloses a polyamic acid obtained by reacting an aromatic diamine containing an ester bond or an ether bond and an aromatic tetracarboxylic dianhydride containing an ester bond or an ether bond, and a composition for forming a release layer containing an organic solvent for the purpose of forming a release layer having appropriate adhesiveness and peelability, and a polyesterimide resin is disclosed as the release layer formed using the composition.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Polyesterimide is used in the field of electrical and electronic products due to its insulating and durable properties. However, when used in electronic substrates or insulated wires, as shown in Patent Document 1, particularly excellent mechanical properties such as flexibility are required. In particular, as mentioned above, in order to cope with the miniaturization and increased power output of motors in recent years, greater thermal stability is required. Therefore, there was a need for a polyesterimide resin that was particularly stable against heat and had excellent elongation properties. Furthermore, the polyesterimide or precursor varnish (solution) used in the manufacture of electronic circuit boards and insulated wires had high viscosity, resulting in problems with thin-film formation and coating properties. This invention has been made in view of the above circumstances, and the object of this invention is to provide a polyesteramic acid that can produce a polyesterimide with excellent thermal stability and high elongation, and a varnish with low viscosity, and a method for producing a polyesterimide using the polyesteramic acid. [Means for solving the problem]

[0006] The inventors have discovered that a structural unit consisting of a specific carboxylic acid component and two diamine components, a polyesterimide having a specific terminal structure, and a polyesteramic acid having a specific structure as a precursor thereof can solve the above problems, and have completed the invention.

[0007] In other words, the present invention relates to the following [1] to

[18] . [1] A polyesterimide having repeating units represented by the following general formula (1) and terminal structures represented by the following general formula (2), wherein the molar ratio [(1) / (2)] of the repeating units represented by the following general formula (1) to the terminal structures represented by the following general formula (2) is 100 / 5 to 100 / 1. [ka] (In formula (1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2). In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.) [2] The polyesterimide according to [1] above, wherein the repeating unit represented by formula (1) is the repeating unit represented by the following formula (1-1). [ka] (In formula (1-1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2).) [3] The polyesterimide according to [1] or [2] above, wherein X contains a divalent group represented by formula (X2). [4] A polyesterimide according to any one of [1] to [3] above, wherein X comprises a divalent group represented by formula (X1) and a divalent group represented by formula (X2), and 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. [5] The polyesterimide according to any one of [1] to [4] above, wherein the polyesterimide is substantially free of aliphatic hydrocarbon groups. [6] A polyesterimide according to any one of [1] to [5] above, wherein R is a hydrogen atom. [7] The polyesterimide according to any one of [1] to [6] above, wherein the glass transition temperature of the polyesterimide is 220 to 280°C. [8] The polyesterimide according to any one of [1] to [7] above, wherein the 10% thermoweight loss temperature of the polyesterimide in air is 470°C or higher. [9] The polyesterimide according to any one of [1] to [8] above, wherein the elongation at break measured by a longitudinal tensile test using a 30 mm × 10 mm × 0.05 mm test piece of the polyesterimide is 20% or more.

[10] A polyester amide acid having repeating units represented by the following general formula (3) and terminal structures represented by the following general formula (4), wherein the molar ratio of the repeating units represented by general formula (3) to the terminal structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1. [ka] (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2). In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[11] The polyesteramide acid according to

[10] above, wherein the weight-average molecular weight of the polyesteramide acid is 135,000 to 250,000.

[12] The polyester amide acid according to

[10] or

[11] above, wherein the viscosity of a 15% by mass solution of N,N-dimethylacetamide at 25°C is 1 to 25 Pa·s.

[13] A varnish comprising a polyesteramic acid described in any one of

[10] to

[12] above and an organic solvent.

[14] The varnish according to

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

[15] A method for producing polyester imide, comprising the step of heating the varnish described in

[13] or

[14] above to imide the polyesteramic acid.

[16] A method for producing polyesteramic acid, comprising reacting a tetracarboxylic dianhydride having an ester bond, a diamine, and 0.01 to 0.05 moles of phthalic anhydride per mole of the tetracarboxylic dianhydride.

[17] A method for producing polyesteramide acid according to

[16] above, wherein the phthalic anhydride is a particle with a residue of 0.5% or less on a 75 μm sieve.

[18] The method for producing a polyester amic acid according to

[16] or

[17] above, wherein the polyester amic acid has a repeating unit represented by the following general formula (3) and a terminal structure represented by the following formula (5). [Chemical formula] (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2).) [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide a polyester imide having excellent thermal stability and a high elongation rate, a polyester amic acid capable of obtaining a varnish with a low viscosity, and a method for producing a polyester imide using the polyester amic acid. In particular, since the varnish containing the polyester amic acid has a low viscosity, it is particularly suitable for coating electric wires. [Embodiments for Carrying Out the Invention]

[0009] [Polyester Imide] The polyester imide of the present invention has a repeating unit represented by the following general formula (1) and a terminal structure represented by the following general formula (2), and the molar ratio [(1) / (2)] of the repeating unit represented by the following general formula (1) to the terminal structure represented by the general formula (2) is 100 / 5 to 100 / 1 [Chemical formula] (In formula (1), X is at least one selected from the group consisting of a divalent group represented by the above formula (X1) and a divalent group represented by the above formula (X2). In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0010] The reason why the polyester imide of the present invention has excellent thermal stability and a high elongation rate is not clear, but it is considered as follows. The polyesterimide of the present invention is thought to have excellent thermal stability because it contains rigid biphenylene groups, ester groups, and imide groups. Furthermore, it is thought to have high elongation due to the presence of flexible ether groups.

[0011] In formula (1), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2), preferably including a divalent group represented by formula (X2), more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2), and even more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2).

[0012] When X contains a divalent group represented by formula (X1) and a divalent group represented by formula (X2), the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is preferably 30 / 70 to 95 / 5, more preferably 30 / 70 to 85 / 15, even more preferably 40 / 60 to 85 / 15, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is within the above range, the product exhibits excellent thermal stability and high elongation, and is particularly excellent in terms of thermal stability. This is thought to be because the copolymerization of the tetracarboxylic acid component having an ester bond and the two types of diamine components causes disorder in the intermolecular ordered structure, making it easier for the molecular chains to follow displacement, resulting in high elongation. Furthermore, the inclusion of a rigid biphenylene group is thought to contribute to its excellent thermal stability.

[0013] The repeating unit represented by formula (1) is preferably the repeating unit represented by the following formula (1-1) from the viewpoint of raw material availability and thermal stability. [ka] (In formula (1-1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2).)

[0014] The divalent group represented by the above formula (X1) is preferably a divalent group represented by the following formula (X1-1) from the viewpoint of raw material availability and thermal stability. [ka]

[0015] The divalent group represented by the above formula (X2) is preferably a divalent group represented by the following formula (X2-1) from the viewpoint of raw material availability and thermal stability. [ka]

[0016] The polyesterimide has repeating units represented by the general formula (1), wherein the content of the repeating units represented by formula (1) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less, relative to the total repeating units constituting the polyesterimide. It is even more preferable that the polyesterimide consists only of repeating units represented by the general formula (1). Here, the repeating units that make up polyesterimide refer to units in which one tetracarboxylic dianhydride and one diamine are bonded via an imide structure.

[0017] The polyesterimide of the present invention has a terminal structure represented by the following general formula (2), and the molar ratio [(1) / (2)] of the repeating unit represented by the general formula (1) to the terminal structure represented by the following general formula (2) is 100 / 5 to 100 / 1. [ka] (In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0018] R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group, and preferably R is a hydrogen atom. The fact that R is a hydrogen atom improves the storage stability of the varnish and further improves the thermal stability of the resulting polyesterimide.

[0019] The molar ratio [(1) / (2)] between the repeating unit represented by the general formula (1) and the terminal structure represented by the general formula (2) is 100 / 5 to 100 / 1, preferably 100 / 4.5 to 100 / 1.5, more preferably 100 / 4.5 to 100 / 2.5, and even more preferably 100 / 3.5 to 100 / 2.5. When the molar ratio between the repeating unit represented by the general formula (1) and the terminal structure represented by the general formula (2) is within the above range, thermal stability and elongation are excellent.

[0020] 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 such that it does not affect the effects of the present invention, or that the polyesterimide contains no 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 even more preferably 0% by mass. It is even more preferable that the polyesterimide does not contain aliphatic hydrocarbon groups. The aliphatic hydrocarbon groups mentioned above are saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, and alicyclic hydrocarbon groups present in the main chain or side chain of the polyesterimide. Specifically, these include alkyl groups, alkylene groups, alkylidene groups, alkenyl groups, alkynyl groups, cycloalkyl groups, and the like.

[0021] 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, even more preferably 240 to 280°C, even more preferably 245 to 280°C, even more preferably 250 to 280°C, and even more preferably 250 to 270°C. When the glass transition temperature of the polyesterimide is within the above range, it exhibits excellent heat resistance and good thermal stability. The glass transition temperature of the polyesterimide can be determined by measuring the temperature dependence of the loss tangent (tanδ) in the tensile mode on a film-like sample of polyesterimide using a dynamic viscoelasticity analyzer (DMA), and finding the temperature at which tanδ peaks. Specifically, it can be measured by the method described in the examples.

[0022] The 10% thermoweight loss temperature of the polyesterimide in air is preferably 470°C or higher, and more preferably 490°C or higher. There is no upper limit, but it is generally 800°C or lower. When the 10% thermoweight loss temperature of the polyesterimide in air is within the above range, it exhibits excellent heat resistance and good thermal stability of the insulating coating layer. The 10% thermoweight loss temperature of the polyesterimide in air can be measured by the TGA (thermogravimetric analysis) method, specifically by the method described in the examples.

[0023] The elongation at break 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, even more preferably 33% or more, and even more preferably 40% or more. It is also usually 100% or less. When the elongation at break is within the above range, the stretchability is excellent and the flexibility of the polyesterimide is good. The elongation at break 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 speed of 1 mm / min using a film-like test piece with a long side of 30 mm × short side of 10 mm × thickness of 0.05 mm (however, the 30 mm of the long side does not include the length of the part fixed to the jig, and the test piece has gripping parts fixed to a jig with a width of 10 mm × thickness of 0.05 mm at both ends of the long side). Specifically, it can be determined by the method described in the examples.

[0024] As described above, the polyesterimide of the present invention has excellent thermal stability and high elongation, making it useful as a material for electrical and electronic products, and in particular suitable as a coating material for insulated wires.

[0025] [Polyesteramide acid] The polyesterimide is not particularly limited as long as it is produced by a method that yields a polyesterimide having repeating units represented by formula (1), but it is preferable to produce it by imidizing a polyesteramic acid as a precursor. The following describes polyesteramic acid, which is a precursor of the aforementioned polyesterimide.

[0026] The polyesteramic acid of the present invention, which is a precursor of the polyesterimide, preferably has repeating units represented by the following general formula (3) and terminal structures represented by the following general formula (4), and the molar ratio of the repeating units represented by general formula (3) to the terminal structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1. [ka] (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2). In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0027] In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2), preferably including a divalent group represented by formula (X2), more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2), and even more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2).

[0028] When X includes a divalent group represented by formula (X1) and a divalent group represented by formula (X2), the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is preferably 30 / 70 to 95 / 5, more preferably 30 / 70 to 85 / 15, even more preferably 40 / 60 to 85 / 15, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is within the above range, the thermal stability is particularly excellent.

[0029] The repeating unit represented by formula (3) above is preferably the repeating unit represented by the following formula (3-1) from the viewpoint of raw material availability and the thermal stability of the polyesterimide obtained by imidization. [ka] (In equation (3-1), X is at least one selected from the group consisting of the divalent group represented by equation (X1) and the divalent group represented by equation (X2).)

[0030] The divalent group represented by formula (X1) is preferably a divalent group represented by the following formula (X1-1) from the viewpoint of raw material availability and the thermal stability of the polyesterimide obtained by imidization. [ka]

[0031] The divalent group represented by the above formula (X2) is preferably the divalent group represented by the following formula (X2-1) from the viewpoint of raw material availability and the thermal stability of the polyesterimide obtained by imidization. [ka]

[0032] The polyesteramic acid has repeating units represented by the general formula (3), wherein the content of the repeating units represented by formula (3) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less, relative to the total repeating units constituting the polyesteramic acid. It is even more preferable that the polyesteramic acid consists only of repeating units represented by the general formula (3). Here, the repeating unit that constitutes a polyesteramic acid refers to a unit in which one tetracarboxylic dianhydride and one diamine are bonded via an amide structure.

[0033] The polyesteramic acid has a terminal structure represented by the following general formula (4), and preferably the molar ratio [(3) / (4)] of the repeating unit represented by the following general formula (3) to the terminal structure represented by the following general formula (4) is 100 / 5 to 100 / 1. [ka] (In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0034] R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group, and preferably R is a hydrogen atom. The fact that R is a hydrogen atom is preferable because it provides good storage stability for the varnish and good thermal stability for the resulting polyesterimide. The terminal structure represented by the general formula (4) is preferably the terminal structure represented by the following formula (5). In other words, the polyesteramic acid of the present invention more preferably has a repeating unit represented by the following general formula (3) and a terminal structure represented by the following formula (5). [ka] (In equation (3), X is at least one selected from the group consisting of the divalent group represented by equation (X1) and the divalent group represented by equation (X2).)

[0035] The molar ratio [(3) / (4)] between the repeating unit represented by the general formula (3) and the terminal structure represented by the general formula (4) is preferably 100 / 5 to 100 / 1, more preferably 100 / 4.5 to 100 / 1.5, even more preferably 100 / 4.5 to 100 / 2.5, and even more preferably 100 / 3.5 to 100 / 2.5. When the molar ratio between the repeating unit represented by the general formula (3) and the terminal structure represented by the general formula (4) is within the above range, a varnish with high concentration and low viscosity can be obtained, and a polyester imide with high thermal stability and elongation can be obtained.

[0036] Furthermore, the polyesteramic acid preferably contains substantially no aliphatic hydrocarbon groups. Here, "substantially free of aliphatic hydrocarbon groups" means that the content of aliphatic hydrocarbon groups in the polyesteramic acid is such that it does not affect the effects of the present invention, or that the polyesteramic acid does not contain any aliphatic hydrocarbon groups. Specifically, the content of aliphatic hydrocarbon groups in the polyesteramic 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 even more preferably 0% by mass. It is even more preferable that the polyesteramic acid does not contain any aliphatic hydrocarbon groups. The aliphatic hydrocarbon groups mentioned above are saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, and alicyclic hydrocarbon groups present in the main chain or side chain of the polyesteramic acid. Specifically, these include alkyl groups, alkylene groups, alkylidene groups, alkenyl groups, alkynyl groups, cycloalkyl groups, etc.

[0037] The weight-average molecular weight of the polyesteramic acid is preferably 5,000 to 1,000,000, more preferably 135,000 to 250,000, even more preferably 135,000 to 240,000, even more preferably 145,000 to 240,000, even more preferably 145,000 to 190,000, and even more preferably 145,000 to 170,000. When the weight-average molecular weight is within the above range, the polyesteramic acid varnish can be adjusted to a concentration suitable for various coating processes. Furthermore, a low-viscosity varnish is obtained, and the polyesterimide produced by imidation exhibits excellent mechanical properties such as elongation. The weight-average molecular weight of the polyesteramic acid can be determined, for example, by gel filtration chromatography to obtain a value equivalent to standard polystyrene (PS). Specifically, it can be measured by the method described in the examples.

[0038] The viscosity of a 15% by mass N,N-dimethylacetamide solution of the polyesteramic acid at 25°C is preferably 1 to 25 Pa·s, more preferably 1 to 20 Pa·s, even more preferably 1 to 15 Pa·s, and even more preferably 1 to 10 Pa·s. When the viscosity of the N,N-dimethylacetamide solution of the polyesteramic acid is within this range, a low-viscosity varnish suitable for coating electric wires can be obtained.

[0039] <Production of Polyesteramic Acid> The aforementioned polyesteramic acid has repeating units represented by the following general formula (3) and terminal structures represented by the following general formula (4), as described above, and can be manufactured by any method as long as the molar ratio of the repeating units represented by general formula (3) to the terminal structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1. A preferred manufacturing method is described below.

[0040] A preferred method for producing polyesteramic acid in the present invention is to react a tetracarboxylic dianhydride having an ester bond, a diamine, and 0.01 to 0.05 moles of phthalic anhydride with 1 mole of the tetracarboxylic dianhydride, as described below. The polyesteramic acid produced by this method has a repeating unit represented by the following general formula (3) and a terminal structure represented by the following formula (5). [ka] (In equation (3), X is at least one selected from the group consisting of the divalent group represented by equation (X1) and the divalent group represented by equation (X2).)

[0041] Examples of tetracarboxylic acid components used in the production of polyesteramic acid include compounds 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-biphenylenebis(trimellitate) dianhydride. By using p-biphenylenebis(trimellitate) dianhydride as the tetracarboxylic acid component, an insulating coating layer with excellent thermal stability and elongation can be formed.

[0042] The proportion 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 also preferably 100 mol% or less. The tetracarboxylic acid component may consist only of the compound represented by formula (a1).

[0043] The tetracarboxylic acid component may include tetracarboxylic dianhydrides other than the compound represented by formula (a1). Such tetracarboxylic dianhydrides are not particularly limited, but include aromatic tetracarboxylic dianhydrides other than the compound represented by formula (a1), alicyclic tetracarboxylic dianhydrides, and aliphatic tetracarboxylic dianhydrides. However, in the present invention, it is preferable not to use alicyclic tetracarboxylic dianhydrides or aliphatic tetracarboxylic dianhydrides substantially, and it is more preferable to use only aromatic tetracarboxylic dianhydrides. The tetracarboxylic acid component may optionally contain one or more tetracarboxylic dianhydrides. The tetracarboxylic acid component is not limited to tetracarboxylic dianhydride, but may also be a derivative thereof. Examples of such derivatives include the tetracarboxylic acid corresponding to the tetracarboxylic dianhydride and the alkyl ester of the tetracarboxylic acid. Among these, tetracarboxylic dianhydride is preferred.

[0044] Examples of diamine components used in the production of polyesteramic acid include the compound represented by the following general formula (b1) and the compound represented by the following general formula (b2). The diamine component used in the production of polyesteramic acid includes at least one selected from the group consisting of the compound represented by formula (b1) and the compound represented by formula (b2), preferably including the compound represented by formula (b2), and more preferably including the compound represented by formula (b1) and the compound represented by formula (b2).

[0045] When the diamine component includes a compound represented by formula (b1) and a compound represented by formula (b2), the molar ratio of the compound represented by formula (b1) to the compound represented by formula (b2) [(b1) / (b2)] is preferably 30 / 70 to 95 / 5, more preferably 30 / 70 to 85 / 15, even more preferably 40 / 60 to 85 / 15, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the compound represented by formula (b1) to the compound represented by formula (b2) [(b1) / (b2)] is within the above range, the thermal stability is particularly excellent. Among the compounds represented by the following general formula (b1), the compound represented by formula (b11) is preferred. Furthermore, among the compounds represented by the following general formula (b2), the compound represented by 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.

[0046] 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 also preferably 100 mol% or less.

[0047] The diamine component may include diamines other than the compound represented by formula (b1) or the compound represented by formula (b2). Such diamines are not particularly limited, but include aromatic diamines, alicyclic diamines, and aliphatic diamines other than the compound represented by formula (b1) or the compound represented by formula (b2). However, in the present invention, it is preferable not to use alicyclic diamines or aliphatic diamines substantially, and it is more preferable to use only aromatic diamines. The diamine component may consist of one type of diamine or two or more types. The diamine component is not limited to diamines, but may also be a derivative thereof. Examples of such derivatives include diisocyanates corresponding to diamines. Among these, diamines are preferred.

[0048] In the method for producing polyesteramic acid of the present invention, 0.01 to 0.05 moles of phthalic anhydride are reacted with 1 mole of tetracarboxylic dianhydride. In the method for producing polyesteramic acid of the present invention, phthalic anhydride is introduced as a terminal encapsulant. The amount of phthalic anhydride used is preferably 0.01 to 0.05 moles, more preferably 0.015 to 0.045 moles, more preferably 0.025 to 0.045 moles, and even more preferably 0.025 to 0.035 moles per mole of tetracarboxylic dianhydride. When the amount of phthalic anhydride used is within the above range, a varnish with low viscosity despite high concentration can be obtained, and a polyester imide with high thermal stability and elongation can be obtained. The phthalic anhydride can be obtained in particulate form (e.g., powder), flake form, lump form, etc., and any form may be used, but the phthalic anhydride used in this invention is preferably in particulate form. Being in particulate form allows for the acquisition of a varnish with lower viscosity. The phthalic anhydride is preferably fine particles. More preferably, the phthalic anhydride is composed of particles with a residue of 0.5% or less on a 75 μm sieve.

[0049] The polyesteramic acid produced using the above raw materials has constituent units derived from the tetracarboxylic dianhydride, constituent units derived from the diamine, and terminal structures derived from phthalic anhydride. Furthermore, the polyesterimide produced using the polyesteramic acid produced using the above raw materials as a precursor has constituent units derived from the tetracarboxylic dianhydride, constituent units derived from the diamine, and terminal structures derived from phthalic anhydride. In other words, the polyesteramic acid of the present invention preferably has constituent units derived from the tetracarboxylic dianhydride, constituent units derived from the diamine, and terminal structures derived from phthalic anhydride. Furthermore, the polyesterimide of the present invention preferably has constituent units derived from the tetracarboxylic dianhydride, constituent units derived from the diamine, and terminal structures derived from phthalic anhydride.

[0050] The polyesteramic acid can be produced by reacting a tetracarboxylic acid component containing the compound represented by formula (a1) with a diamine component containing the compound represented by formula (b1) or formula (b2) with 0.01 to 0.05 moles of phthalic anhydride per mole of tetracarboxylic dianhydride. The amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 moles.

[0051] There are no particular restrictions on the method used to react the tetracarboxylic acid component, the diamine component, and phthalic anhydride in this manufacturing method; known methods can be used. Specific reaction methods include charging the tetracarboxylic acid component, diamine component, phthalic anhydride, and solvent into a reactor and stirring at a temperature of 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. When the reaction is carried out at temperatures below 80°C, the molecular weight of the polyesteramic acid does not fluctuate depending on the temperature history during polymerization, and the progression of thermal imidization can also be suppressed, thus enabling the stable production of polyesteramic acid.

[0052] The solvent used in the production of polyesteramic acid can be any solvent capable of dissolving the resulting polyesteramic acid. Examples include aprotic solvents, phenolic solvents, etheric solvents, carbonate solvents, aromatic hydrocarbon solvents, etc., with aprotic solvents being preferred.

[0053] 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 hexamethylphosphoricamide and hexamethylphosphinetriamide; sulfur-containing solvents such as dimethylsulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone; and ester solvents such as acetic acid (2-methoxy-1-methylethyl). Preferably, the solvent is an amide or lactone solvent, more preferably an amide solvent, and even more preferably N,N-dimethylacetamide.

[0054] Specific examples of phenolic 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-based 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-based solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above solvents, amide solvents or lactone solvents are preferred, amide 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 individually or in combination of two or more.

[0055] By the above method, a polyester amide acid solution dissolved in a solvent is obtained. The concentration of polyesteramide 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.

[0056] [varnish] When producing polyesterimide by imidizing the polyesteramic acid, which is used as a precursor, it is preferable to use the polyesteramic acid as a varnish in the production of polyesterimide. By using a varnish, polyesterimide of any shape can be easily produced.

[0057] The varnish of the present invention comprises the polyesteramic acid and an organic solvent, wherein the polyesteramic acid is dissolved in the organic solvent. In other words, the varnish of the present invention contains a polyesteramic acid and an organic solvent, wherein the repeating unit represented by the following general formula (3) and the terminal structure represented by the following general formula (4) have a molar ratio [(3) / (4)] of 100 / 5 to 100 / 1, and the polyesteramic acid is dissolved in the organic solvent. [ka] (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2). In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0058] The organic solvent contained in the varnish can be any solvent that dissolves polyesteramic acid and is not particularly limited, but the compounds mentioned above are preferred as solvents used in the production of polyesteramic acid. Specifically, the organic solvent contained in the varnish preferably contains the amide solvent or the lactone solvent, more preferably contains the amide solvent, and even more preferably contains N,N-dimethylacetamide. Furthermore, the organic solvent contained in the varnish preferably contains the amide solvent or the lactone solvent, more preferably contains the amide solvent, and even more preferably contains N,N-dimethylacetamide. In other words, it is even more preferable that the organic solvent in the varnish contains N,N-dimethylacetamide, and even more preferable that the organic solvent in the varnish substantially contains N,N-dimethylacetamide. The above solvents may be used individually or in combination of two or more.

[0059] The varnish may further contain a dehydration catalyst. Examples of dehydration catalysts include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may be used individually or in combination of two or more.

[0060] The polyesteramic acid contained in the varnish is solvent-soluble, and as described above, a low-viscosity solution can be obtained, making it possible to obtain a high-concentration varnish that is stable at room temperature. The concentration of the polyesteramide 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 polyesteramide acid in the varnish may be adjusted by diluting the polyesteramide acid solution immediately after its production with an organic solvent, or the polyesteramide acid solution may be used as is as a varnish if the concentration of polyesteramide acid in the solution is within the above range and is suitable for the production of polyesterimide. The viscosity of the varnish at 25°C is preferably 1 to 50 Pa·s, more preferably 1 to 30 Pa·s, even more preferably 1 to 25 Pa·s, even more preferably 1 to 20 Pa·s, even more preferably 1 to 15 Pa·s, and even more preferably 1 to 10 Pa·s. Because the varnish of the present invention contains the polyesteramic acid, it has a high concentration yet low viscosity, making it suitable for coating electric wires. The viscosity of the varnish can be measured, for example, using an E-type (cone-plate type) viscometer. Specifically, it can be measured by the method described in the examples.

[0061] Furthermore, the varnish may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent whitening agents, crosslinking agents, polymerization initiators, and photosensitive agents, to the extent that they do not impair the desired properties of the resulting polyesterimide. The method for producing the varnish is not particularly limited, and known methods can be applied. For example, it can be obtained by adjusting the concentration of the polyesteramic acid solution obtained by the above-described production method by mixing in additional solvents as needed.

[0062] [Method for producing polyesterimide] The method for producing polyesterimide according to the present invention is not particularly limited, but it is preferable to produce it using the aforementioned polyesteramic acid, and more preferably to produce it using the aforementioned varnish. Specifically, the method for producing polyesterimide of the present invention preferably includes the step of heating the varnish to imide the polyesteramic acid. That is, the method for producing polyesterimide of the present invention includes the step of heating a varnish containing a polyesteramic acid having repeating units represented by the following general formula (3) and terminal structures represented by the following general formula (4), wherein the molar ratio of the repeating units represented by general formula (3) to the terminal structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1, and an organic solvent, to imide the polyesteramic acid. [ka] (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2). In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0063] There are no particular restrictions on the method for producing polyesterimide using the aforementioned varnish, and known methods can be used. For example, when manufacturing a film-shaped polyesterimide, i.e., a polyesterimide film, the varnish is applied to a smooth support such as a glass plate, metal plate, or plastic, or formed into a film. Then, organic solvents such as reaction solvents and diluent solvents contained in the varnish are removed by heating to obtain a polyesteramic acid film. Finally, the polyesteramic acid in the polyesteramic acid film is imidized (dehydrated and ring-closed) by heating to produce the polyesterimide film. Thus, the preferred method for producing a film-shaped polyesterimide, i.e., a polyesterimide film, is to apply the aforementioned varnish onto a support and then heat it.

[0064] First, it is preferable to obtain a polyester amide acid film by drying the varnish and removing the solvent. The drying temperature is preferably 50 to 150°C. The heating temperature for imidizing the polyester amide acid in film form 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 these temperatures and times, the resulting polyester imide film will have good physical properties. Examples of heating atmospheres include air, nitrogen, oxygen, hydrogen, and nitrogen / hydrogen mixtures. Furthermore, the imidation method is not limited to thermal imidation; chemical imidation can also be applied.

[0065] The polyesterimide obtained in this way has repeating units represented by formula (1) and terminal structures represented by formula (2), as described above, and the molar ratio of the repeating units represented by formula (1) to the terminal structures represented by formula (2) [(1) / (2)] is 100 / 5 to 100 / 1, exhibiting 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.

[0066] <Insulated wire> As described above, the polyesterimide of the present invention has excellent properties and is therefore useful as an insulating coating layer for insulated wires. A suitable insulated wire using the polyesterimide of the present invention will be described below. In other words, the insulated wire using polyesterimide of the present invention is an insulated wire having a conductor and an insulating coating layer covering the conductor, Preferably, the insulating coating layer is an insulated wire containing polyesterimide, having repeating units represented by the following general formula (1) and end structures represented by the following general formula (2), and the molar ratio [(1) / (2)] of the repeating units represented by the following general formula (1) to the end structures represented by the following general formula (2) is 100 / 5 to 100 / 1. [ka] (In formula (1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2). In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0067] The insulating coating layer of the insulated wire covers the conductor and contains polyesterimide having repeating units represented by general formula (1) and end structures represented by general formula (2), with a molar ratio [(1) / (2)] of 100 / 5 to 100 / 1. The polyesterimide used in the insulating coating layer is preferably the polyesterimide described in the [Polyesterimide] section above. Specifically, it is preferably one of the polyesterimides shown below.

[0068] In formula (1), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2), preferably including a divalent group represented by formula (X2), more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2), and even more preferably including a divalent group represented by formula (X1) and a divalent group represented by formula (X2).

[0069] When X includes a divalent group represented by formula (X1) and a divalent group represented by formula (X2), the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is preferably 30 / 70 to 95 / 5, more preferably 30 / 70 to 85 / 15, even more preferably 40 / 60 to 85 / 15, even more preferably 40 / 60 to 70 / 30, and even more preferably 40 / 60 to 60 / 40. When the molar ratio of the group represented by formula (X1) to the group represented by formula (X2) [(X1) / (X2)] is within the above range, the thermal stability is particularly excellent.

[0070] The repeating unit represented by formula (1) is preferably the repeating unit represented by formula (1-1) from the viewpoint of raw material availability and thermal stability. The divalent group represented by formula (X1) is preferably the divalent group represented by formula (X1-1) from the viewpoint of raw material availability and thermal stability. The divalent group represented by formula (X2) is, from the viewpoint of raw material availability and thermal stability, the divalent group represented by formula (X2-1).

[0071] The polyesterimide has repeating units represented by the general formula (1), wherein the content of the repeating units represented by formula (1) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less, relative to the total repeating units constituting the polyesterimide. It is even more preferable that the polyesterimide consists only of repeating units represented by the general formula (1). Here, the repeating units that make up polyesterimide refer to units in which one tetracarboxylic dianhydride and one diamine are bonded via an imide structure.

[0072] The polyesterimide has a terminal structure represented by the following general formula (2), and the molar ratio [(1) / (2)] of the repeating unit represented by the following general formula (1) to the terminal structure represented by the following general formula (2) is 100 / 5 to 100 / 1. [ka] (In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

[0073] R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group, and preferably R is a hydrogen atom. The fact that R is a hydrogen atom improves the storage stability of the varnish and further improves the thermal stability of the resulting polyesterimide.

[0074] The molar ratio [(1) / (2)] between the repeating unit represented by the general formula (1) and the terminal structure represented by the general formula (2) is 100 / 5 to 100 / 1, preferably 100 / 4.5 to 100 / 1.5, more preferably 100 / 4.5 to 100 / 2.5, and even more preferably 100 / 3.5 to 100 / 2.5. When the molar ratio between the repeating unit represented by the general formula (1) and the terminal structure represented by the general formula (2) is within the above range, thermal stability and elongation are excellent.

[0075] 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 such that it does not affect the effects of the present invention, or that the polyesterimide contains no 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 even more preferably 0% by mass. It is even more preferable that the polyesterimide does not contain aliphatic hydrocarbon groups. The aliphatic hydrocarbon groups mentioned above are saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, and alicyclic hydrocarbon groups present in the main chain or side chain of the polyesterimide. Specifically, these include alkyl groups, alkylene groups, alkylidene groups, alkenyl groups, alkynyl groups, cycloalkyl groups, and the like.

[0076] 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, even more preferably 250 to 280°C, and even more preferably 250 to 270°C. When the glass transition temperature of the polyesterimide is within this range, it exhibits excellent heat resistance and good thermal stability. The glass transition temperature of the polyesterimide can be determined by measuring the temperature dependence of the loss tangent (tanδ) in the tensile mode on a film-like sample of polyesterimide using a dynamic viscoelasticity analyzer (DMA), and finding the temperature at which tanδ peaks. Specifically, it can be measured by the method described in the examples.

[0077] The 10% thermoweight loss temperature of the polyesterimide in air is preferably 470°C or higher, and more preferably 490°C or higher. There is no upper limit, but it is generally 800°C or lower. When the 10% thermoweight loss temperature of the polyesterimide in air is within the above range, it exhibits excellent heat resistance and good thermal stability of the insulating coating layer. The 10% thermoweight loss temperature of the polyesterimide in air can be measured by the TGA (thermogravimetric analysis) method, specifically by the method described in the examples.

[0078] The elongation at break 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, even more preferably 33% or more, and even more preferably 40% or more. It is also usually 100% or less. When the elongation at break is within the above range, the stretchability is excellent and the flexibility of the polyesterimide is good. The elongation at break 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 speed of 1 mm / min using a film-like test piece with a long side of 30 mm × short side of 10 mm × thickness of 0.05 mm (however, the 30 mm of the long side does not include the length of the part fixed to the jig, and the test piece has gripping parts fixed to a jig with a width of 10 mm × thickness of 0.05 mm at both ends of the long side). Specifically, it can be determined by the method described in the examples.

[0079] The method for manufacturing the insulated wire is not particularly limited, but it is preferable to manufacture it using the varnish described above. Specifically, a preferred method for manufacturing the insulated wire is a method for manufacturing the insulated wire, comprising applying a varnish containing a polyesteramic acid and an organic solvent to a conductor, wherein the varnish has repeating units represented by general formula (3) and end structures represented by general formula (4), and the molar ratio of the repeating units represented by general formula (3) to the end structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1, and baking it to form an insulating coating layer. The insulating coating layer of the insulated wire obtained in this way is obtained by imidizing the aforementioned polyesteramic acid, and therefore contains a polyesterimide having repeating units represented by general formula (1) and terminal structures represented by general formula (2), with a molar ratio [(1) / (2)] of 100 / 5 to 100 / 1.

[0080] 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 appropriate thickness can be formed. The curing temperature is preferably 180 to 600°C, more preferably 200 to 600°C, and even more preferably 250 to 500°C. The curing 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 curing temperature is low, a longer curing time is preferable, and when the temperature is high, a shorter curing time is preferable. The baking process is performed to remove the organic solvent contained in the varnish, imide the polyesteramic acid, and fix the insulating coating layer on the conductor. However, if chemical imidation is used instead of thermal imidation for the imidation reaction, baking may be performed at a lower temperature. The insulated wire obtained as described above has an insulating coating layer containing polyesterimide, which provides excellent thermal stability, high elongation, and a low dielectric constant. For these reasons, the insulated wire is particularly suitable as an insulated wire for motor coils. [Examples]

[0081] The present invention will be specifically described below with reference to examples. However, the present invention is not limited in any way by these examples.

[0082] [Physical property measurement and evaluation] The physical properties of the polyesteramidic acid, varnish, and polyesterimide obtained in the examples and comparative examples were measured and evaluated by the methods described below.

[0083] (1) Weight-average molecular weight of polyesteramic acid The weight-average molecular weight of the polyesteramic acids obtained in the examples and comparative examples was measured as follows. The varnish containing the aforementioned polyesteramic acid was diluted with the mobile phase solvent shown below to a polyesteramic acid concentration of 0.2% by mass to prepare the measurement solution. Using the measurement solution, gel filtration chromatography was performed under the following conditions to determine the weight-average molecular weight of the polyesteramic acid in terms of polystyrene equivalent. 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 (30mM), H3PO4 (30mM)) Mobile phase flow rate: 0.7mL / min Molecular weight standard material: Polystyrene (Shodex M-6.8,63,955)

[0084] (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. Varnishes with a viscosity exceeding 50 Pa·s were marked as ">50" in Table 1. Equipment: Type E (cone plate type) viscometer HAAKE RheoStress 6000 (manufactured by Thermo Scientific) Measurement temperature: 25℃ Shear rate: 3s -1

[0085] (3) Glass transition temperature (Tg) The films obtained in the test example and comparative test example were dried under vacuum at 100°C for 16 hours, cut into strips 10 mm wide and 30 mm long, and used as measurement samples. Using the aforementioned sample, the glass transition temperature (Tg) was measured under the following conditions using a dynamic viscoelasticity analyzer DMA7100 (manufactured by Hitachi High-Tech Science Corporation). Tg is the temperature at the peak top of the loss tangent (tanδ). Measurement mode: Tensile mode Heating conditions: Heat from 30°C to 320°C at a rate of 10°C / min, hold for 5 minutes. Frequency: 1Hz Amplitude: 10μm

[0086] (4) Thermogravimetric temperature (Td), evaluation of thermal stability The polyesterimide films obtained in the examples and comparative examples were powdered using a freeze-drying machine, dried under vacuum at 100°C for 16 hours, and prepared as samples for measurement. Using the aforementioned sample, the 10% mass thermogravimetric loss temperature (Td10%) was measured by TGA (thermogravimetric analysis) under the following conditions using a differential thermogravimetric analyzer STA7200 (manufactured by Hitachi High-Tech Science Co., Ltd.). Td10% was defined as the temperature at which the mass of the sample decreased by 10% compared to the mass at the start of the measurement. A higher thermogravimetric loss temperature indicates superior thermal stability. Samples that did not reach a Td of 10% even after heating to 500°C were considered to have a measurement value exceeding the upper limit of 490°C and were marked as ">490" in Table 1. Heating conditions: Heat from 30°C to 500°C at a rate of 10°C / min, hold for 5 minutes. Measurement environment: Under an air atmosphere

[0087] (5) Elongation at break (evaluation of elongation) The polyesterimide films obtained in the examples and comparative examples were cut into 10 mm x 60 mm sections to prepare test specimens. Using the aforementioned test specimens, tensile tests were conducted under the following conditions using a precision universal testing machine, Autograph AGX-plus (manufactured by Shimadzu Corporation). The length of the test specimen at fracture was measured from the displacement of the load cell at the time of fracture, and the elongation at fracture was calculated using the following formula. Elongation at break (%) = (Length of specimen at break - Length of initial specimen) / (Length of initial specimen) × 100 Distance between gripping parts: 30mm Load cell (tensile force): 50N Tensile speed: 1 mm / min (Tensile direction: Longitudinal direction of the test specimen)

[0088] [Raw materials] The raw materials used in the examples and comparative examples, along with their abbreviations, are as follows. <Raw materials for polyesterimide and polyesteramic acid> TA-BP: p-biphenylene bis(trimellitate) dianhydride (BP-TME, manufactured by Honshu Chemical Industry Co., Ltd.; compound represented by formula (a11). Purity 98.6%. For the production of polyesteramic acid, a compound dried under vacuum at 100°C for approximately 2 hours was used.) ODA: 4,4'-Diaminodiphenyl ether (manufactured by Seika Co., Ltd.; compound represented by formula (b11). Purity 99.98%) BAPB: 4,4'-Bis(4-aminophenoxy)biphenyl (manufactured by Seika Co., Ltd.; compound represented by formula (b21); purity 99.94%) Phthalic anhydride (flake form) (manufactured by Tokyo Chemical Industry Co., Ltd.; purity 99.0%) Phthalic anhydride (particulate): Sconoch 7 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) (residue 0.02% after 75 μm sieve, fine powder)

[0089] <Solvent> DMAc: N,N-dimethylacetamide

[0090] [Manufacturing of polyesteramic acid (varnish)] Example 1 A 300 mL separable flask equipped with a mechanical stirrer featuring a nitrogen inlet tube, exhaust tube, and stirring blades was circulated with nitrogen to create a nitrogen atmosphere. Next, 1.676 g (8.32 mmol) of ODA and 0.766 g (2.08 mmol) of BAPB were added to the separable flask. Then, DMAc was added to achieve a concentration of 20% by mass of the resulting polyesteramic acid. Next, 5.420 g (10.0 mmol) of TA-BP and 0.060 g (0.4 mmol) of phthalic anhydride (flake form) were added. The reaction was carried out at 25°C with stirring, and after confirming the start of viscosity increase, DMAc was added to obtain a reaction mixture with a polyesteramic acid concentration of 15% by mass. The reaction mixture was further reacted at 25°C for 20 hours with stirring to obtain a polyesteramic acid solution (varnish).

[0091] Example 2 In Production Example 1, a polyesteramic acid solution (varnish) was obtained in the same manner as in Example 1, except that the amounts (ratios) of ODA, BAPB, phthalic anhydride (flake form), and TA-BP were changed to the amounts (ratios) shown in Table 1.

[0092] Examples 3-5 In Production Example 1, a polyesteramic acid solution (varnish) was obtained in the same manner as in Example 1, except that phthalic anhydride (flake form) was changed to phthalic anhydride (particulate form), and the amounts (ratios) of ODA, BAPB, phthalic anhydride (particulate form), and TA-BP were changed to the amounts (ratios) shown in Table 1.

[0093] Comparative Examples 1-4 In Production Example 1, a polyesteramic acid solution (varnish) was obtained in the same manner as in Example 1, except that phthalic anhydride (flake form) was not used, and ODA, BAPB, and TA-BP were replaced with the raw materials shown in Table 1.

[0094] [Manufacturing of polyesterimide (film)] Examples 6-10 and Comparative Examples 5-8 A glass plate was prepared, and the polyesteramic acid solution (varnish) obtained in each of the above examples and comparative examples was applied to the glass plate using a coating machine so that the film thickness was 0.04 to 0.05 mm. The varnished glass plate was placed on a hot plate and heated at 100°C for 2 hours to remove the solvent. Then, using a hot air dryer, it was heated at 200°C for 1 hour, and then at 250°C for 30 minutes to thermally imide the polyesteramic acid and obtain polyesterimide (film, thickness 0.04 to 0.05 mm).

[0095] Table 1 shows the physical properties of the polyesteramic acid, varnish, and polyesterimide obtained in the examples and comparative examples, as well as the evaluation results.

[0096] [Table 1]

[0097] As shown in Table 1, the polyesterimide of the present invention exhibits excellent thermal stability and high elongation. Furthermore, as shown in the examples, the polyesteramic acid of the present invention can produce a low-viscosity varnish, and by imidizing it, a polyesterimide with excellent thermal stability and high elongation can be obtained. Therefore, the polyesteramic acid of the present invention is useful as a precursor for the polyesterimide. Moreover, the varnish containing the polyesteramic acid is also useful as a raw material for producing the polyesterimide. From the above, it can be seen that the polyesterimide of the present invention is useful as a coating material for insulated wires, and the polyesteramic acid and its varnish of the present invention are suitable as raw materials for coating materials for insulated wires.

Claims

1. A polyester imide having repeating units represented by the following general formula (1) and terminal structures represented by the following general formula (2), wherein the molar ratio [(1) / (2)] of the repeating units represented by the following general formula (1) to the terminal structures represented by the following general formula (2) is 100 / 5 to 100 / 1, The content of the repeating units represented by the following general formula (1) in the polyesterimide is 50 mol% or more and 100 mol% or less relative to the total repeating units constituting the polyesterimide. The aforementioned polyesterimide is used in the insulating coating layer of an insulated electric wire. 【Chemistry 1】 (In formula (1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2). In formula (2), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

2. The polyesterimide according to claim 1, wherein the repeating unit represented by formula (1) is the repeating unit represented by the following formula (1-1). 【Chemistry 2】 (In formula (1-1), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2).)

3. The polyesterimide according to claim 1, wherein X contains a divalent group represented by formula (X2).

4. The polyesterimide according to claim 1 or 3, wherein X comprises a divalent group represented by formula (X1) and a divalent group represented by formula (X2), and 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.

5. The polyesterimide according to claim 1 or 3, wherein the polyesterimide is substantially free of aliphatic hydrocarbon groups.

6. The polyesterimide according to claim 1 or 3, wherein R is a hydrogen atom.

7. The polyesterimide according to claim 1 or 3, wherein the glass transition temperature of the polyesterimide is 220 to 280°C.

8. The polyesterimide according to claim 1 or 3, wherein the 10% thermoweight loss temperature of the polyesterimide in air is 470°C or higher.

9. The polyesterimide according to claim 1 or 3, wherein the elongation at break measured in a longitudinal tensile test using a 30 mm × 10 mm × 0.05 mm test piece of the polyesterimide is 20% or more.

10. A polyesteramic acid having repeating units represented by the following general formula (3) and terminal structures represented by the following general formula (4), wherein the molar ratio of the repeating units represented by general formula (3) to the terminal structures represented by general formula (4) [(3) / (4)] is 100 / 5 to 100 / 1, The content of the repeating units represented by the following general formula (3) in the polyesteramic acid is 50 mol% or more and 100 mol% or less relative to the total repeating units constituting the polyesteramic acid. The aforementioned polyesteramic acid is used for forming the insulating coating layer of an insulated electric wire. 【Transformation 5】 (In formula (3), X is at least one selected from the group consisting of a divalent group represented by formula (X1) and a divalent group represented by formula (X2). In formula (4), R is at least one selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.)

11. The polyesteramide acid according to claim 10, wherein the weight-average molecular weight of the polyesteramide acid is 135,000 to 250,000.

12. The polyester amide acid according to claim 10 or 11, wherein the viscosity of a 15% by mass N,N-dimethylacetamide solution at 25°C is 1 to 25 Pa·s.

13. A varnish comprising the polyesteramic acid according to claim 10 or 11 and an organic solvent.

14. The varnish according to claim 13, wherein the organic solvent in the varnish contains N,N-dimethylacetamide.

15. A method for producing polyester imide, comprising the step of heating the varnish described in claim 13 to imide the polyesteramic acid.

16. A method for producing polyesteramidic acid, comprising reacting a tetracarboxylic dianhydride having an ester bond with a diamine and phthalic anhydride, The amount of phthalic anhydride used is 0.01 to 0.05 moles per mole of tetracarboxylic dianhydride. The aforementioned polyesteramic acid has repeating units represented by the following general formula (3) and terminal structures represented by the following formula (5), The content of the repeating units represented by the following general formula (3) in the polyesteramic acid is 50 mol% or more and 100 mol% or less relative to the total repeating units constituting the polyesteramic acid. A method for producing polyesteramic acid, wherein the polyesteramic acid is used to form an insulating coating layer on an insulated electric wire. 【Transformation 6】 (In formula (3), X is at least one selected from the group consisting of the divalent group represented by formula (X1) and the divalent group represented by formula (X2).)

17. A method for producing polyesteramic acid according to claim 16, wherein the phthalic anhydride is a particle with a residue of 0.5% or less on a 75 μm sieve.

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