JP3513951B2 - Polyamideimide resin and adhesive and coating agent containing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyamide-imide resin. More specifically, the present invention relates to a polyamideimide resin soluble in a general-purpose solvent having various small polarities such as ketones and nitriles and a low boiling point, and an adhesive and a coating agent containing the polyamideimide resin.

[0002]

2. Description of the Related Art Polyamideimide resins that have been developed and used in the past are soluble only in amide solvents such as N-methyl-2-pyrrolidone,
Since these solvents have extremely large polarities and high boiling points, they require a high temperature for drying, and in many cases they cannot be used for coating plastics and the like due to their strong solvent power. Furthermore, the conventional polyamide-imide resin is
When it was tried to be used as an adhesive, it had a problem in use, such as the boiling point of the solvent being dissolved was too high. The polyamide-imide resin is synthesized by direct polymerization by the isocyanate method or via a polyamic acid by the amine method. However, the conventional polyamide-imide resin is soluble only in a solvent having a large polarity and a high boiling point as described above, and in a solvent having a small polarity and a low boiling point,
There was a problem that the reaction did not proceed and only a resin with insufficient physical properties could be synthesized.

That is, an object of the present invention is to provide a polyamideimide resin soluble in a general-purpose solvent having a low polarity and a low boiling point, and also to provide an adhesive and a coating agent containing the polyamideimide resin. is there.

[0004]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventor has determined that a structural unit [A], a structural unit [B] and a structural unit [C] described below are essential structural units. The present inventors have found that the polyamide-imide resin described above is soluble in a general-purpose solvent having a low polarity and a low boiling point, and thus completed the present invention.

That is, the present invention provides (1) the general formula [I]:

[0006]

[Chemical 4]

[Wherein R is COOR¹OOC (R¹A
Rukiren), COO (R²O) _nOC (R²A
Rukilen, n represents 2 to 10), SO₂Or indicates O
A structural unit [A] and a formula [II]:

[0008]

[Chemical 5]

The structural unit [B] represented by the formula [I] and the formula [I
II]:

[0010]

[Chemical 6]

Polyamideimide resin having the structural unit [C] represented by the following as an essential structural unit, (2) 10 to 30 mol% of the structural unit [A] and 20 of the structural unit [B] in all the structural units.
To 40 mol% and the structural unit [C] is 8 to 50 mol%, and the polyamideimide resin according to (1),
(3) An adhesive containing the polyamide-imide resin according to (1),
(4) A coating agent containing the polyamide-imide resin according to (1).

In the present specification, alkylene in R ¹ is a linear or branched alkylene having 2 to 10 carbon atoms, and examples thereof include ethylene, propylene, butylene, hexamethylene, neopentylene and isopropylene. Preferred are ethylene, propylene, butylene, hexamethylene and neopentylene. Also, R ²
The alkylene in is a linear or branched alkylene having 2 to 10 carbon atoms, and examples thereof include ethylene, propylene, isopropylene, butylene, t-butylene, etc., preferably ethylene, propylene, butylene, t.
-Butylene. Moreover, n shows the integer of 2-10, Preferably it is the integer of 2-4.

In the present invention, the structural units [A] and [B]
And [C] are represented by the general formula [I ′]:

[0014]

[Chemical 7]

A tetracarboxylic acid represented by the following formula (wherein R is as defined above) (hereinafter referred to as compound [I ']) or its reactive derivative, and a trimellitic acid represented by the following formula

[0016]

[Chemical 8]

Or a reactive derivative thereof and a compound of the general formula [II
I ']:

[0018]

[Chemical 9]

(In the formula, X represents NCO or NH ₂ )
It is derived by reacting with an isocyanate or an amine represented by (hereinafter, also referred to as compound [III ′]).

Here, the reactive derivative of carboxylic acid means
The anhydride, the halide, etc. are shown.

That is, the polyamide-imide resin of the present invention comprises a compound [I '] and a carboxylic acid component consisting of trimellitic acid or a reactive derivative thereof, and a compound [II
It is obtained by reacting with an isocyanate component or an amine component consisting of I ']. Hereinafter, the carboxylic acid component includes not only carboxylic acid but also those in the form of its reactive derivative.

The carboxylic acid component used in the present invention comprises the compound [I '] and trimellitic acid. Specific examples of the compound [I ′] include ethylene glycol ditrimellitate, propylene glycol ditrimellitate,
Alkylene glycol ditrimellitates such as 1,4-butanediol ditrimellitate, hexamethylene glycol ditrimellitate, neopentyl glycol ditrimellitate, and polyalkylene glycol ditrimellitates such as polyethylene glycol ditrimellitate and polypropylene glycol ditrimellitate. , 3, 3 ',
4,4'-diphenylsulfone tetracarboxylic acid, 4,
4'-oxydiphthalic acid and the like can be mentioned. You may use these 2 or more types together.

The isocyanate component or amine component used in the present invention comprises compound [II '], that is, 2,4-tolylene diisocyanate or 2,4-tolylene diamine, respectively.

In order to obtain the polyamide-imide resin of the present invention, a carboxylic acid component consisting of the compound [I '] and trimellitic acid and an isocyanate component or amine component consisting of the compound [II'] are reacted as desired. The composition may be appropriately selected and subjected to polymerization. The ratio of the reaction composition at the time of polymerizing the carboxylic acid component (that is, the compound [I ′] and trimellitic acid) and the isocyanate component or the amine component is from the viewpoint of the polymerization degree and the side reaction suppression, the isocyanate component or the amine. The carboxylic acid component is preferably 0.9 to 1.3 mol, and more preferably 0.95 to 1.2 mol, relative to 1 mol of the component.

The production of the polyamide-imide resin of the present invention is
It may be carried out according to a conventional method, for example, solution polymerization, melt polymerization,
Interfacial polymerization and the like are mentioned, and from the viewpoint of operability and side reaction suppression,
Solution polymerization is preferred.

In the case of solution polymerization, the solvent used is
It is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include cyclohexanone, acetonitrile, butyronitrile, cyclopentanone, methyl ethyl ketone,
1,4-dioxane, methoxybenzene, 2-methyltetrahydrofuran, N-methyl-2-pyrrolidone and the like can be mentioned. Among them, cyclohexanone, acetonitrile, butyronitrile, cyclopentanone, methyl ethyl ketone, 1,4-
General-purpose solvents such as dioxane, methoxybenzene and 2-methyltetrahydrofuran are preferred. Here, the general-purpose solvent is a solvent having a small polarity and a low boiling point, preferably a solvent having a dielectric constant of 37 or less and a boiling point of 160 ° C. or less.

In the case of solution polymerization using an isocyanate, for example, a carboxylic acid component in the form of a carboxylic acid or an anhydride thereof and an isocyanate component are heated in a solvent as described above at a reaction temperature of 100 ° C. or lower for 4 to 6 hours. The reaction is carried out at around the boiling point of the solvent for 3 to 6 hours to remove the solvent to obtain a polyamide-imide resin.

In the case of solution polymerization using an amine, for example, a carboxylic acid component in the form of a carboxylic acid, an anhydride thereof or a halide thereof and an amine component are reacted in a solvent as described above at a reaction temperature of 50 ° C. Below, preferably 20
The reaction is carried out at a temperature of not higher than 0 ° C. for a reaction time of 3 to 12 hours, preferably 4 to 6 hours, to give a polyamic acid, and dehydration ring closure to obtain a polyamideimide resin. Alternatively, the polyamide-imide resin may be obtained by performing a dehydration ring closure after molding in the state of polyamic acid.

In order to shorten the polymerization time and increase the degree of polymerization, tertiary amines (eg, triethylamine, tripropylamine, tributylamine, N-ethylmorpholine, N, N-diethylaniline, N, N) are used. -Dimethylaniline, etc.), a metal catalyst (for example, tri-n-butyltitanium acetate, di-n-butyltitanium diacetate, etc.) and the like may be added to perform polymerization.

The method of removing the solvent from the solution-polymerized polyamideimide resin as described above may be heating drying, vacuum drying, or drying under an inert gas (eg, nitrogen, argon, etc.). Drying is carried out in the presence of oxygen at 20
If the temperature exceeds 0 ° C, the resin may gel.
The above results in gelation. Therefore, the drying is 200
It is preferably carried out at a temperature of not higher than 0 ° C, more preferably not higher than 150 ° C. In addition, even in a vacuum or under an inert gas, 200
Drying is preferably performed at a temperature of not more than 0 ° C, more preferably not more than 150 ° C.

A poor solvent may be added to control the evaporation rate of the solvent. Examples of the poor solvent include aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents such as hexane and octane, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ketone solvents such as isophorone, dioxane, and the like. Examples thereof include ether solvents such as ethylene glycol dimethyl ether and tetrahydrofuran, and ester solvents such as methyl acetate, ethyl acetate, -n-butyl acetate and cellosolve acetate. Of these, aromatic hydrocarbon solvents such as toluene and xylene, and aliphatic hydrocarbon solvents such as hexane and octane are preferable. However, a solvent having active hydrogen such as an alcohol solvent such as methanol or ethanol is not suitable.

After removing the solvent, a heat treatment for imparting strength to the polyamide-imide resin can be carried out. This treatment is preferably carried out under vacuum or in an atmosphere of an inert gas such as nitrogen, and the heat treatment temperature is from 200 to 400 degreeC is preferable and 250-350 degreeC is more preferable. The heat treatment time is preferably 3 to 72 hours, more preferably 3 to 12 hours. The physical properties of the polyamide-imide resin can also be adjusted by the above heat treatment conditions and the like.

In the above-mentioned polymerization using amine, dehydration ring closure of polyamic acid may be carried out simultaneously with the heat treatment for imparting the above-mentioned strength, or may be carried out using a chemical ring closure agent such as acetic anhydride. In addition, in order to prevent the molecular weight of the polyamic acid from decreasing, a phosphorus compound such as triphenyl phosphite may be used in combination.

As described above, the polyamideimide resin of the present invention is prepared by reacting the carboxylic acid component consisting of the compound [I '] and trimellitic acid with the isocyanate component or amine component consisting of the compound [III']. Although obtained, a polyamide-imide resin obtained by adding and reacting a carboxylic acid, an isocyanate, or an amine other than those shown below is also included in the scope of the present invention.

The carboxylic acid component used in the present invention may contain the following carboxylic acid in addition to the above compound [I '] and trimellitic acid. Other carboxylic acid components include, for example, pyromellitic acid, 3,
3 ', 4,4'-benzophenone tetracarboxylic acid,
Tetracarboxylic acids such as 3,3 ′, 4,4′-diphenyltetracarboxylic acid, terephthalic acid, isophthalic acid, 4,
4'-biphenyl dicarboxylic acid, 4,4'-biphenyl ether dicarboxylic acid, 4,4'-biphenyl sulfone dicarboxylic acid, 4,4'-benzophenone dicarboxylic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, dimer acid And dicarboxylic acids such as stilbene dicarboxylic acid. You may use these 2 or more types together.

The isocyanate component used in the present invention may contain the following isocyanates in addition to 2,4-tolylene diisocyanate. Other isocyanate components include, for example, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyldiphenylmethane-
4,4'-diisocyanate, 3,3'-diethyldiphenylmethane-4,4'-diisocyanate, 3,3 '
-Dichlorodiphenylmethane-4,4'-diisocyanate, 3,3'-dichlorodiphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenyl-4,
4'-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, orthochloroparaphenylene diisocyanate, paraphenylene diisocyanate, metaphenylene diisocyanate, 4,4 '
-Diphenyl ether diisocyanate, 3,4'-diphenyl ether diisocyanate, 3,4'-diphenylmethane diisocyanate, 4,4'-diphenyl sulfone diisocyanate, 3,4'-diphenyl sulfone diisocyanate, 4,4'-benzophenone diisocyanate, 3,4 ' -Benzophenone diisocyanate, 2,2'-diphenylpropane diisocyanate,
Paraxylylene diisocyanate etc. are mentioned. You may use these 2 or more types together.

Similarly, the amine component used in the present invention may contain the following amines in addition to 2,4-tolylenediamine. Other amine components include, for example, orthochloroparaphenylenediamine, paraphenylenediamine, metaphenylenediamine, 4,
4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,
4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 2,2'-
Bis (aminophenyl) propane, 2,6-tolylenediamine, paraxylylenediamine, isophoronediamine, hexamethylenediamine, 3,3′-dimethyldiphenylmethane-4,4′-diamine, 3,3′-diethyldiphenylmethane- 4,4'-diamine, 3,3'-
Dichlorodiphenylmethane-4,4'-diamine, 3,
3'-dichlorodiphenyl-4,4'-diamine, 3,
3'-dimethyldiphenyl-4,4'-diamine etc. are mentioned. You may use these 2 or more types together.

In the polyamide-imide resin of the present invention,
The proportion of the structural unit [A] is preferably 10 to 30 mol% and more preferably 15 to 25 mol% based on all structural units. The ratio of the structural unit [B] is 20 to 40 in all structural units.
Mol% is preferable and 25-35 mol% is more preferable.
Further, the ratio of the structural unit [C] is 8 to 5 in all structural units.
0 mol% is preferable, and 15 to 50 mol% is more preferable. If it is out of the above range, the dope tends to be unstable, and precipitation is likely to occur due to rapid cooling.

The molecular weight of the polyamide-imide resin of the present invention varies depending on the purpose of use, but normally, the molecular weight determined by polystyrene conversion by gel permeation chromatography (GPC) is 6,000 to 30,
It is preferably in the range of 8,000, and 8,000 to 2
More preferably, it is in the range of 10,000.

The logarithmic viscosity of the polyamide-imide resin of the present invention varies depending on the purpose for which it is used.
Methyl-2-pyrrolidone has a logarithmic viscosity of 0.2 to 1.0 obtained by holding at 30 ° C. in an Ubbelohde type viscosity tube.
It is preferably in the range of dl · g ⁻¹ , and 0.3 to 0.
More preferably, it is in the range of 7 dl · g ⁻¹ .

To the polyamide-imide resin of the present invention, known additives such as inorganic fine particles, plasticizers, curing accelerators, curing inhibitors, toning agents and coloring materials are added according to the purpose of adjusting physical properties and the like. It can also be used.

The polyamide-imide resin of the present invention can also be used as an adhesive. The adhesive containing the polyamide-imide resin of the present invention is not particularly limited, and examples thereof include solvent-based adhesives. For example, in the case of a solvent-type adhesive, it can be obtained by dissolving the polyamide-imide resin in a general-purpose solvent. In addition to the polyamide-imide resin, an epoxy resin, an acrylic resin or the like can be blended if necessary. The general-purpose solvent may be the same as the above-mentioned reaction solvent.

The adhesive may be produced by a conventional method. For example, in the case of a solvent type adhesive, a solid resin may be dissolved in a solvent to prepare the adhesive, or the solvent may be used as a solvent type adhesive. Solution polymerization may be carried out using the same solvent to prepare the adhesive without removing the solvent.

The polyamide-imide resin of the present invention is
It can also be used as a coating agent. The coating agent containing the polyamideimide resin of the present invention is not particularly limited as long as it is known per se, for example, paints and the like, from the viewpoint of heat resistance, chemical resistance, etc.,
It is preferably used as a chemical resistant coating for electronic materials. For example, when it is used as a paint, it can be obtained by dissolving the polyamide-imide resin in a general-purpose solvent. Also,
In addition to the polyamide-imide resin, an epoxy resin, an acrylic resin or the like can be blended as needed. In addition,
Examples of the general-purpose solvent include the same as the above-mentioned reaction solvent.

The coating agent may be produced according to a conventional method. For example, in the case of a paint, a solid resin may be dissolved in a solvent to prepare the same as in the case of an adhesive, or a solvent used as a paint may be used. Perform solution polymerization using the same solvent,
The coating agent may be prepared without removing the solvent.

[0046]

The present invention will be described in detail below with reference to specific examples, but the present invention is not limited thereto.

In the examples, the logarithmic viscosity was measured by the following method. 0.5 g of sample was added to 100 ml of N-methyl-
The solution dissolved in 2-pyrrolidone was measured at 30 ° C. using an Ubbelohde viscous tube.

Example 1 22.96 g of ethylene glycol dianhydrotrimellitate (TMEG) as a carboxylic acid component was placed in a reaction vessel.
And 10.76 g of trimellitic anhydride (TMA),
As an isocyanate component, 3.90 g of 2,4-tolylene diisocyanate (TDI) and 22.42 g of 4,4′-diphenylmethane diisocyanate (MDI) and 60 g of solvent cyclohexanone were charged, and the mixture was charged under a nitrogen atmosphere at 10
React at 0 ℃ for 5 hours, and then cyclohexanone 80g
Was added and reacted at 150 ° C. for 5 hours. The dope solution was slightly blackish brown and transparent. The dope solution was put into alcohol for precipitation, and the solvent was removed by filtration to obtain a polyamide-imide resin (logarithmic viscosity of 0.25 dl · g ⁻¹ ). In all the structural units, the structural units [A], [B] and [C] were 25, 25 and 10 mol%, respectively.

Example 2 4,4'-diphenylsulfone tetracarboxylic acid dianhydride (DSDA) 1 as a carboxylic acid component was placed in a reaction vessel.
2.42 g and TMA 17.28 g, TDI 4.48 g and MDI 25.73 as isocyanate component
g, and 90 g of cyclohexanone as a solvent were charged, and the mixture was reacted at 100 ° C. for 5 hours in a nitrogen atmosphere. Further, 50 g of cyclohexanone was added and reacted at 150 ° C. for 5 hours. The dope was blackish brown and transparent. The dope solution was put into alcohol for precipitation, and the solvent was removed by filtration to obtain a polyamide-imide resin (logarithmic viscosity of 0.23 dl · g ⁻¹ ). In all the structural units, the structural units [A], [B] and [C] are
It was 15, 35 and 10 mol% respectively.

Example 3 TMEG 18.59 as a carboxylic acid component was placed in a reaction vessel.
g and TMA20.31g, TDI as an isocyanate component 10.52g and 4,4'-diisocyanate-3,3'-dimethylbiphenyl (TODI) 23.
94 g and 90 g of cyclohexanone as a solvent were charged and reacted at 100 ° C. for 5 hours in a nitrogen atmosphere. Further, 50 g of cyclohexanone was added and reacted at 150 ° C. for 5 hours. The dope solution was slightly blackish brown and transparent. The dope solution was put into ethanol to cause precipitation, and the solvent was removed by filtration to obtain a polyamide-imide resin (logarithmic viscosity 0.28 dl · g).
^-1 ). In all the structural units, the structural units [A], [B] and [C] were 15, 35 and 20 mol%, respectively.

Example 4 In a reaction vessel, 19.39 g of 4,4'-oxydiphthalic acid dianhydride (ODPA) as a carboxylic acid component and TM
A12.01g, TDI6.
53 g of TODI, 21.90 g of TODI, and 102 g of cyclohexanone as a solvent were charged, and the mixture was reacted at 100 ° C. for 5 hours under a nitrogen atmosphere.
The reaction was performed at 0 ° C for 5 hours. The dope was slightly brown and transparent. The dope solution was put into ethanol for precipitation, and the solvent was removed by filtration to obtain a polyamide-imide resin (logarithmic viscosity 0.21 dl · g ⁻¹ ). In all the structural units, the structural units [A], [B] and [C] are 25 and 2, respectively.
5 and 15 mol%.

Comparative Example 1 TMA81.27 as a carboxylic acid component was placed in a reaction vessel.
g, MDI 105.85 g as an isocyanate component,
When 150 g of the solvent cyclohexanone was charged and reacted at 100 ° C. for 5 hours and 150 ° C. for 2 hours in a nitrogen atmosphere, the occurrence of precipitation was confirmed.

Comparative Example 2 TMA32.565 as a carboxylic acid component was placed in a reaction vessel.
g, MDI 42.420 g as an isocyanate component,
Charge 140 g of solvent N, N-dimethylacetamide,
The reaction was performed under a nitrogen atmosphere at 100 ° C. for 5 hours and 150 ° C. for 3 hours. The dope was brown and transparent. The dope solution was put in alcohol to cause precipitation, and the solvent was removed by filtration to obtain a polyamide-imide resin (logarithmic viscosity 0.61d).
l · g ⁻¹ ). The structural unit [B] was 50 mol% in all the structural units.

The following comparative experiments were conducted using the polyamide-imide resins obtained in the above Examples and Comparative Examples.

[Solubility Experiment] Solubility in the following solvents was confirmed using the polyamideimide resins obtained in Examples 1 to 4 and Comparative Example 2. Table 1 shows the solubility of the solvent and each sample.

[0056]

[Table 1]

As can be seen from Table 1, the polyamide-imide resins of Examples are soluble in general-purpose solvents having a low polarity and a low boiling point, whereas the polyamide-imide resins of Comparative Example 2 are insoluble in these solvents. .

[Adhesion Experiment] Epoxy resin (EP828,
The adhesive strength when using Yuka Shell Co., Ltd. with the dope of Example 1 and Comparative Example 2 was measured. The base material is aluminum foil (50 μm), the adhesive thickness is 15/15 μm, and the drying conditions are 80 ° C. × 5 minutes, 160 ° C. × 20 minutes, press 280
A sample was prepared at 200 ° C. for 5 minutes at 200 kg / cm ² and measured by T peeling. Table 2 shows the measurement results.

[0059]

[Table 2]

As a result of the above experiment, the adhesive using the polyamide-imide resin of Example 1 showed excellent adhesive strength, while Comparative Example 2 had weak adhesive strength. Further, the polyamide-imide resin of the present invention was excellent in workability because the solvent could be distilled off at the curing temperature or lower even when it was used as a mixed adhesive such as epoxy.

[Plastic Coating Experiment] The dope of Example 1 was mixed with cyclohexanone to give a solid content of 1
Polyethylene terephthalate (PET) diluted to 0%
The film (thickness 10 μm) was applied with a bar coater.
This was dried with a hot air drier at 80 ° C. for 30 minutes to obtain a uniform coating film having a film thickness of 0.2 μm. Similarly, the dope of Comparative Example 2 was treated with cyclohexanone / dimethylformamide (50/50 (volume ratio)) to obtain a solid content concentration of 10%.
And was applied to a PET film (thickness 10 μm) with a bar coater. When this was dried with a hot air drier at 180 ° C. for 3 minutes, cracks and white turbidity were generated, and a uniform coating film could not be obtained.

[0062]

As described above, in the present invention, a polyamideimide resin having a low boiling point and soluble in a general-purpose solvent having a small polarity is obtained. Further, the polyamide-imide resin of the present invention is different from the conventional polyamide-imide resin, by using by dissolving in these general-purpose solvents, it is possible to lower the removal temperature of the solvent, excellent adhesive workability Was obtained. Further, since it is not necessary to use a solvent having a large polarity and a high boiling point as in the conventional case, a coating agent capable of coating without damaging the plastic was obtained due to the solubility of the solvent.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Uno 2-1-1 Katata, Otsu City, Shiga Prefecture, Toyo Spinning Co., Ltd. (56) Reference JP-A-4-318026 (JP, A) Japanese Patent Laid-Open No. 5-148361 (JP, A) Japanese Patent Laid-Open No. 5-331444 (JP, A) Japanese Patent Laid-Open No. 7-228697 (JP, A) Japanese Patent Laid-Open No. 7-292245 (JP, A) Japanese Patent Laid-Open No. 7-292319 (JP , A) JP-A-7-300527 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 73/00-73/26 CAPLUS (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. In all structural units, a compound represented by the general formula [I]: [In the formula, R represents COOR ¹ OOC (R ¹ represents alkylene), COO (R ² O) _n OC (R ² represents alkylene, n
Represents 2 to 10), SO ₂ or O], and 10 to 30 mol% of the structural unit [A] represented by the formula [II]: 20 to 40 mol% of the structural unit [B] represented by the following formula , and a compound of the formula [III]: Containing the structural unit [C] represented by
Polyamide-imide resin. 2. An adhesive containing the polyamideimide resin according to claim 1. 3. A coating agent containing the polyamide-imide resin according to claim 1.