JP2011231278A - Resin composition for polyamideimide resin-based seamless tubular body, and seamless tubular body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for a polyamideimide resin-based seamless tubular body for forming a coating film and a seamless tubular body excellent in tensile strength and elongation at break.SOLUTION: This resin composition for a polyamideimide resin-based seamless tubular body is obtained by reacting (a) a polycarboxylic acid component having, as an essential component, a tri- or more-basic polycarboxylic anhydride having an acid anhydride group and optionally a carboxy group or a group derived therefrom; (b) a polycarboxylic acid compound including 4,4'-biphenyldicarboxylic acid or a derivative thereof as an essential component; and (c) an aromatic polyisocyanate in a basic polar solvent.

Description

  The present invention relates to a polyamideimide resin-based resin composition for a seamless tubular body that is suitable for use for the purpose of transmitting rotational motion in various precision devices such as electrical / electronic devices and electronic copying machines using a polyamideimide resin. And a seamless tubular body obtained using the same.

  As the seamless tubular body as described above, the polyimide resin is, for example, a polyimide resin obtained from pyromellitic dianhydride and 4,4′-diaminodiphenyl ether, or 3,3′-4,4′-biphenyltetracarboxylic dianhydride. What was produced from the polyimide resin obtained from a thing and p-phenylene cyamine is known. Polyimide resin is applied as a mainstream because it has particularly excellent mechanical properties (tear strength, elastic modulus, elongation). However, in recent years, needs for cost reduction are further increasing, and polyamide imide resin has attracted attention from the viewpoint of low cost and the same imide resin system.

  In general, polyamide-imide resins are excellent in heat resistance, chemical resistance and solvent resistance. Therefore, in order to form protective coatings on various substrates as coating components of various paints for varnish for enameled wire, heat-resistant protective coatings are especially useful. It has been widely used to form films. As a conventional polyamideimide resin, for example, a polyamideimide resin obtained by a reaction of diphenylmethane-4,4'-diisocyanate and trimellitic anhydride is best known. However, the seamless tubular body using this polyamide-imide resin is extremely inferior in tensile strength and breaking elongation that greatly affect its life.

  Conventionally, as a seamless tubular body using a polyamideimide resin, those having improved tear strength and the like have been proposed (see Patent Document 2 and Patent Document 3). There are no particular proposals regarding the tensile strength and elongation at break of the membrane.

JP 2004-160729 A JP 2007-016097 A JP 2009-099891 A

  An object of the present invention is to provide a seamless tubular body excellent in tensile strength and elongation at break using a polyamideimide resin, and to provide a polyamideimide resin-based resin composition therefor. is there.

The present invention relates to the following.
1. (A) a polycarboxylic acid component having an acid anhydride group and having a carboxyl group or a tricarboxylic or higher polycarboxylic acid anhydride optionally having a carboxyl group or a group derived therefrom; and (b) 4, For polyamidoimide resin-based seamless tubular bodies obtained by reacting a polycarboxylic acid compound essentially comprising 4'-biphenyldicarboxylic acid or a derivative thereof and (c) an aromatic polyisocyanate in a basic polar solvent Resin composition.
2. Item 2. The blending ratio {(b) / (a)} of the component (a) and the component (b) used in the reaction is 0.01 / 0.99 to 0.60 / 0.40 in an equivalent ratio. Polyamideimide resin-based resin composition for seamless tubular bodies.
3. The blending ratio {(c) / [(a) + (b)]} of all isocyanate components and all polycarboxylic acid components used in the reaction is 0.8 to 1.4 in terms of equivalent ratio, and number average Item 3. The resin composition for a polyamideimide resin-based seamless tubular body according to any one of Items 1 and 2, wherein the molecular weight is 10,000 to 50,000.
4). Item 1-3, wherein the coating film formed by applying and heating the polyamide-imide resin heat-resistant resin composition has a tensile strength of 150 MPa or more and an elongation at break of 30% or more. The resin composition for polyamideimide resin-based seamless tubular bodies according to any one of the above.
5). Item 5. A seamless tubular body molded using the polyamideimide resin heat-resistant resin composition according to any one of Items 1 to 4.

  Moreover, it is related with the coating-film board which has the coating film shape | molded by apply | coating and heating one of said polyamideimide resin-type heat resistant resin compositions on the surface.

  According to the polyamideimide resin-based seamless tubular body resin composition of the present invention, it becomes possible to produce a coating film having excellent tensile strength and elongation at break, and rotation in precision equipment such as electrical / electronic equipment and electronic copying machines. Not only the seamless tubular body that is the purpose of motion transmission, it is possible to enhance the functionality of various heat-resistant coating films, which is useful for improving reliability.

  The polycarboxylic acid anhydride (a) used in the production of the polyamideimide resin-based seamless tubular body resin composition in the present invention is an acid anhydride that reacts with an isocyanate group to form an imide bond in one molecule. A compound having a group, which may have a carboxyl group (or a group derived therefrom) that reacts with an isocyanate group to form an amide bond, and has a total of two or more of these groups Or a mixture thereof, and if so, there is no particular limitation. Examples of the trivalent polycarboxylic acid anhydride having an acid anhydride group and a carboxyl group or a group derived therefrom include aromatic tricarboxylic acid anhydrides represented by the general formulas (1) and (2). In view of heat resistance, cost, etc., trimellitic anhydride is particularly preferable.

（但し、両式中Ｒ′は水素、炭素数１〜１０のアルキル基又はフェニル基等のアリール基を示し、
Ｙは−ＣＨ_２−、−ＣＯ−、−ＳＯ_２−、又は−Ｏ−を示す。）
本発明おけるポリカルボン酸成分中に含まれていてもよいカルボキシル基から誘導される基とは、一般式（１）または（２）に示されるように、アルキルオキシカルボニル基やアリールオキシカルボニル基等のエステル結合を有する基などのイソシアネート基と反応してアミド結合を形成することができる基である。

(However, in both formulas, R ′ represents hydrogen, an aryl group such as a C 1-10 alkyl group or a phenyl group,
Y represents —CH ₂ —, —CO—, —SO ₂ —, or —O—. )
The group derived from a carboxyl group which may be contained in the polycarboxylic acid component in the present invention is an alkyloxycarbonyl group, an aryloxycarbonyl group or the like as shown in the general formula (1) or (2) It is a group that can react with an isocyanate group such as a group having an ester bond to form an amide bond.

In addition to these, the polycarboxylic acid component of component (a) is pyromellitic dianhydride, 3,3′-4,4′-benzophenone tetracarboxylic dianhydride, 3; 3′-4. , 4'-biphenyltetracarboxylic dianhydride, 2,2'-3,3'-biphenyltetracarboxylic dianhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride, ethylene glycol bisandhydrotrimellitate, 2,2-bis (2,5-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethanoic dianhydride, 1,1-bis (3,4-dicarboxyphenyl) sulfonic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2 , 3, , 6-pyridinetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldi Phthalic dianhydride, m-terphenyl-3,3 ', 4,4'-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 1,1,1,3,3,3 Hexafluoro-2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 1,3-bis (3,4-dicarboxylphenyl) -1,1,3,3 -Tetracarboxylic such as tetramethyldisiloxane dianhydride, butanetetracarboxylic dianhydride, bicyclo- [2,2,2] -oct-7-ene-2: 3: 5: 6-tetracaribonic dianhydride Acid dianhydride, succinic acid, glutaric acid, azimuth Acid, azelaic acid, suberic acid, sebacic acid, decanedioic acid, dodecanedioic acid, dimer acid and other aliphatic dicarboxylic acids, isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid and other aromatic dicarboxylic acids An acid or the like can be used in combination. In addition, derivatives of these polycarboxylic acid components (having a group derived from a carboxyl group) can also be used.
The amount of acid or acid anhydride that can be used as component (a) other than the trivalent polycarboxylic acid anhydride having an acid anhydride group and a carboxyl group or a group derived therefrom is 50 equivalent% or less of the total acid component It is preferable that

  In the present invention, 4,4′-biphenyldicarboxylic acid used as the component (b) is a compound represented by the following (3).

  The 4,4′-biphenyldicarboxylic acid derivative is a compound in which the carboxyl group of 4,4′-biphenyldicarboxylic acid is a group derived from the carboxyl group as in the previous section.

  The blending ratio of the carboxylic acid component (b) and the polycarboxylic acid component (a) in the present invention is 0.01 / 0.99 to 0 in terms of an equivalent ratio of {(b) component / (a) component}. .60 / 0.40 is preferable, 0.1 / 0.9 to 0.5 / 0.5 is more preferable, and 0.2 / 0.8 to 0.8 / 0.2. It is particularly preferable to do this. If the equivalent ratio is less than 0.01 / 0.99, the effect of improving the tensile strength is not exhibited, and if it exceeds 0.60 / 0.40, the breaking elongation of the coating film is significantly reduced.

  There is no restriction | limiting in particular as an aromatic polyisocyanate compound of (c) component in this invention, It represents with following General formula (4).

［式中、Ｘは、炭素数１〜１８のアルキレン基又はフェニレン基等のアリーレン基（これはメチル基等の低級アルキル基を置換基として有していてもよい）を示す］で表される。

[Wherein, X represents an arylene group such as an alkylene group having 1 to 18 carbon atoms or a phenylene group (which may have a lower alkyl group such as a methyl group as a substituent)] .

  Examples of the diisocyanates represented by the general formula (4) include diphenylmethane-2,4'-diisocyanate, 3,2'-, 3,3'-, 4,2'-, 4,3'-. 5,2'-, 5,3'-, 6,2'- or 6,3v-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'-, 3,3v-, 4,2v-, 4 , 3'-, 5,2'-, 5,3'-, 6,2'- or 6,3'-diethyldiphenylmethane-2,4'-diisocyanate, 3,2'-, 3,3'-, 4,2'-, 4,3'-, 5,2'-, 5,3'-, 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4 '-Diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'- Isocyanate, diphenylsulfone-4,4′-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4, Various conventionally known diisocyanate compounds such as 4 ′-{2,2-bis (4-phenoxyphenyl) propane} diisocyanate can be mentioned. These may be used alone or in admixture of two or more. Among the above polyisocyanate compounds, diphenylmethane-4,4'-diisocyanate is most preferably used in the present invention from the viewpoint of heat resistance and mechanical properties of the coating film.

  Hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanero, 4,4'-dicyclohexylmethane diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylylene diisocyanate, lysine diisocyanate Aliphatic or cycloaliphatic isocyanates such as tri- or higher functional polyisocyanates may be used, and those stabilized with a blocking agent necessary to avoid changes over time may be used.

  In addition, it is preferable that the compounding ratio {(c) / [(a) + (b)]} of all isocyanate components and acid components is 0.8 to 1.4 in terms of equivalent ratio, and 0.9 to 1 .3 is more preferable, and 0.9 to 1.2 is particularly preferable. If this ratio is less than 0.8, it is difficult to increase the molecular weight of the polyamideimide resin, and if it exceeds 1.4, the elongation at break is significantly reduced.

  The main polymerization is carried out in an organic solvent, and a polar solvent is preferably used as the organic solvent from the viewpoint of solubility. Specifically, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, dimethylsulfoxide, hexamethylphosphoramide, tetramethylene A sulfone can be used, and can be used alone or in combination. From the viewpoint of economy and ease of polymerization, N-methyl-2-pyrrolidone or N, N-dimethylacetamide is preferably used. Moreover, although there is no restriction | limiting in particular in the usage-amount, it is preferable to set it as 100-900 weight part with respect to 100 weight part of total amounts of the said polycarboxylic acid, 4,4'-biphenyl dicarboxylic acid, and polyisocyanate, 600 is more preferable, and 150 to 400 is particularly preferable.

  The number average molecular weight of the polyamideimide resin thus obtained is preferably 1,000 to 50,000, more preferably 15,000 to 40,000, and particularly preferably 20,000 to 35,000. If the number average molecular weight is less than 10,000, various properties such as heat resistance and mechanical properties of the coating film tend to be reduced. If the number average molecular weight exceeds 50,000, the concentration is suitable as a coating material. When dissolved in a solvent, the viscosity increases and the workability during coating tends to be poor.

  The number average molecular weight of the polyamideimide resin is measured by sampling the reaction solution at the end of the synthesis, using a standard polystyrene calibration curve by gel permeation chromatography (GPC), and synthesizing until the target number average molecular weight is reached. By continuing the above, it is possible to adjust to a desired range.

In the present invention, after synthesizing the polyamideimide resin in the basic polar solvent, the resin concentration is adjusted by adding an organic solvent as it is or without appropriate separation of the polyamideimide resin from the basic polar solvent. As a resin composition for a resin-based seamless tubular body, it can be used for production of a seamless tubular body.
Polyamideimide resin-based seamless tubular body resin composition forms a coating film with excellent tensile strength, elongation at break, heat resistance, chemical resistance and solvent resistance by applying to a suitable substrate and heating. Can be peeled to form a seamless tubular body. This is suitable for the purpose of transmitting rotational motion in various precision devices such as electric / electronic devices and electronic copying machines that require long-term durability, and is particularly useful as a transfer belt. In addition to the transfer belt, it is useful for a fixing belt, an intermediate transfer belt, a medium transport belt, a transport belt, a cylindrical body, a transfer roll, a belt photoreceptor base, and the like in similar devices.
Moreover, the resin composition for a polyamide-imide resin-based seamless tubular body can be used as a film, fiber, or other raw material for electrical and electronic parts and mechanical parts.
By applying and heating the polyamide-imide resin heat-resistant resin composition of the present invention by the above-described method, a coating film having a tensile strength of 150 MPa or more and a breaking elongation of 60% or more (sheet) Can be used as a mules tubular body or the like.

  In the case of forming a coating film, the polyamideimide resin-based seamless tubular body resin composition of the present invention usually has a solid content of preferably 10 to 50% by weight, more preferably 20 to 40% by weight. It is preferable to adjust. As the organic solvent used for adjusting the solid content concentration, in addition to the basic solvent described above, for example, ketone solvents (methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.) ester solvents (ethyl acetate, butyl acetate, γ-butyrolactone, etc.) , Ether solvents (diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, etc.), cellosolve solvents (butyl cellosolve acetate, ethyl cellosolve acetate, methyl cellosolve acetate, etc.), aromatic hydrocarbon solvents (toluene, xylene, p-cymene, etc.), tetrahydrofuran , Dioxane, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethyl Sulfoxide, hexamethylphosphoramide, tetramethylene sulfone.

In the case of forming a seamless tubular body, the polyamideimide resin-based seamless tubular body resin composition of the present invention is injected into a base material (for example, a stainless steel cylindrical mold) and heated at 150 to 300 ° C with hot air for 30 to 30 minutes. After drying for 120 minutes, a seamless tubular body can be obtained by demolding.
As a base material for forming a coating film, for example, a plate-like base material such as a glass plate is used, and the resin composition for a polyamide-imide resin-based seamless tubular body of the present invention is applied to the surface of the base material, and then heated. It is possible to obtain a coated plate having a coating film having excellent strength, breaking elongation, heat resistance, chemical resistance and solvent resistance on the surface.
In these cases, a filler such as a conductive filler such as carbon may be further kneaded and used in the polyamideimide resin-based seamless tubular body resin composition.
In these cases, the thickness of the coating film varies depending on the application and expected value of the coating film and is not particularly limited, but is usually 20 to 120 μm, preferably 50 to 80 μm.

  In addition, the resin composition for a polyamideimide resin-based seamless tubular body may include a material other than the polyamideimide resin. For example, high heat resistance such as polyimide resin, polyethersulfone, and polysulfone of the same resin series. You may comprise the thermoplastic resin etc.

  EXAMPLES Next, examples of the present invention will be described, but it is needless to say that the present invention is not limited to these examples and includes many other embodiments based on the spirit of the invention.

115.3 g (0.70 mol) of trimellitic anhydride as component (a), 4,4′-biphenyldicarboxylic acid [trade name: 4BPA] (manufactured by Toray Fine Chemical Co.) as component (b) 72.7 g (0 (3 mol), diphenylmethane-4,4′-diisocyanate 256.5 (1.025 mol) and N-methyl-2-pyrrolidone 825.5 g as a component (c) flask equipped with a thermometer, stirrer and condenser The mixture was heated to 140 ° C. over a period of about 6 hours in a dry nitrogen stream, paying attention to the sudden bubbling of carbon dioxide gas generated by the reaction, and then reacted for 11 hours. Thus, a resin composition solution containing a polyamideimide resin having a number average molecular weight of 28900 was obtained.
The blending ratios of component (a), component (b), and component (c) used in this reaction are as follows in terms of equivalent ratio.
{(B) / (a)} = 0.30 / 0.70
{(C) + / [(a) + (b)]} = 1.025
The obtained resin composition solution was diluted with xylene to obtain a resin composition for a polyamideimide resin-based seamless tubular body having a resin concentration of 24% by weight.

(A) Trimellitic anhydride 172.9 g (0.90 mol) as component, pyromellitic anhydride 32.7 g (0.15 mol) (b) 4,4′-biphenyldicarboxylic acid [trade name: 4BPA] (manufactured by Toray Fine Chemical Co., Ltd.) 36.3 g (0.15 mol), diphenylmethane-4,4′-diisocyanate 256.5 (1.05 mol), N-methyl-2-pyrrolidone 925 as component (c) .6 g was charged into a flask equipped with a thermometer, stirrer, and condenser, and this mixture was gradually heated in a dry nitrogen stream over about 6 hours, paying attention to the sudden foaming of carbon dioxide generated by the reaction. Then, the temperature was raised to 145 ° C., followed by reaction for 13 hours to obtain a solution of a polyamideimide resin heat-resistant resin composition having a number average molecular weight of 31300.
The blending ratios of component (a), component (b), and component (c) used in this reaction are as follows in terms of equivalent ratio.
{(B) / (a)} = 0.15 / 0.85
{(C) + / [(a) + (b)]} = 1.05
The obtained solution was diluted with N, N-dimethylacetamide to obtain a heat resistant paint (resin concentration: 27% by weight).

As component (a) trimellitic anhydride 134.5 g (0.70 mol), sebacic acid 20.2 g (0.10 mol) (b) As component 4,4'-biphenyldicarboxylic acid [trade name: 4BPA] ( Toray Fine Chemical Co., Ltd.) 48.4 g (0.20 mol), (d) component diphenylmethane-4,4′-diisocyanate 270.3 (1.08 mol), N-methyl-2-pyrrolidone 1105.5 g A flask equipped with a thermometer, a stirrer, and a cooling tube was charged, and the mixture was gradually heated to about 145 hours over about 6 hours in a dry nitrogen stream while paying attention to the sudden foaming of carbon dioxide generated by the reaction. After heating up to 0 degreeC, it was made to react for 16 hours and the solution of the polyamidoimide resin-type heat resistant resin composition whose number average molecular weight is 25800 was obtained.
The blending ratios of component (a), component (b), and component (c) used in this reaction are as follows in terms of equivalent ratio.
{(B) / (a)} = 0.20 / 0.80
{(C) + / [(a) + (b)]} = 1.08
The obtained solution was diluted with N, N-dimethylacetamide to obtain a heat resistant paint (resin concentration: 27% by weight).

Comparative Example 1
192.1 g (1.0 mol) of trimellitic anhydride, 262.8 g (1.05 mol) of 4,4′-diphenylmethane diisocyanate, 556.0 g of N-methyl-2-pyrrolidone were added to a thermometer, stirrer and condenser. The mixture was placed in a flask, and the mixture was gradually heated up to 140 ° C. over about 5 hours in a dry nitrogen stream while paying attention to sudden foaming of carbon dioxide gas generated by the reaction. The solution was kept warm for a period of time to obtain a polyamideimide resin solution having a number average molecular weight of 30,700.
This solution was diluted with N-methyl-2-pyrrolidone to obtain a paint (resin concentration: 23%).

Comparative Example 2
Trimellitic anhydride 134.5 (0.70 mol), sebacic acid 60.7 g (0.30 mol), 4,4'-diphenylmethane diisocyanate 262.8 g (1.01 mol), N-methyl-2-pyrrolidone 687.0g Put in a flask equipped with a thermometer, stirrer, and condenser, and gradually warm the mixture over a period of about 5 hours in a dry nitrogen stream, paying attention to the sudden foaming of carbon dioxide generated by the reaction. The temperature was raised to 130 ° C., and the temperature was kept for 8 hours to obtain a polyamideimide resin solution having a number average molecular weight of 22,700.
This solution was diluted with N-methyl-2-pyrrolidone to obtain a paint (resin concentration: 30%).

Comparative Example 3
200.24 g (1.0 mol) of 4,4′-diaminodiphenyl ether and 1673.4 g of N-methyl-2-pyrrolidone as a reaction solvent were charged into a flask equipped with a thermometer, a stirrer, and a condenser. The mixture was stirred and dissolved in a dried nitrogen stream at room temperature, and 294.22 g (1.0 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added, and the mixture was heated at 30 ° C. or lower for 7 hours. The reaction was performed to obtain a polyamic acid solution (solid content concentration: 20% by weight) having a number average molecular weight of 25,100. This is used as a paint.

Tensile test A coating material was prepared under the coating film preparation conditions shown in Table 1, and the cured coating film was peeled off from the substrate and subjected to the test. In the test, a tensile test was performed under the measurement conditions shown in Table 2, and the tensile strength and elongation at break when the coating film was broken were measured. These results are shown in Table 3.

１）比較例３のみ３５０℃−３０分の硬化を行った。

1) Only Comparative Example 3 was cured at 350 ° C. for 30 minutes.

  From Table 3, the coating films obtained from the polyamide-imide resin heat-resistant resin compositions of Examples 1 to 3 were compared with the coating films obtained from the conventional polyamide-imide resins of Comparative Examples 1 and 2, and the tensile strength and It can be seen that the elongation at break is excellent, and that the tensile strength and the elongation at break are almost the same as those of the coating film obtained from the polyimide resin of Comparative Example 3.

Claims (5)

(A) a polycarboxylic acid component having an acid anhydride group and having a carboxyl group or a tricarboxylic or higher polycarboxylic acid anhydride optionally having a carboxyl group or a group derived therefrom; and (b) 4, For polyamidoimide resin-based seamless tubular bodies obtained by reacting a polycarboxylic acid compound essentially comprising 4'-biphenyldicarboxylic acid or a derivative thereof and (c) an aromatic polyisocyanate in a basic polar solvent Resin composition.   The blending ratio {(b) / (a)} of the component (a) and the component (b) used in the reaction is 0.01 / 0.99 to 0.60 / 0.40 in an equivalent ratio. Polyamideimide resin-based seamless tubular resin composition.   The blending ratio {(c) / [(a) + (b)]} of all isocyanate components and all polycarboxylic acid components used in the reaction is 0.8 to 1.4 in terms of equivalent ratio, and number average 3. The resin composition for a polyamideimide resin-based seamless tubular body according to claim 1, having a molecular weight of 10,000 to 50,000.   The tensile strength of a coating film formed by applying and heating a polyamide-imide resin heat-resistant resin composition is 150 MPa or more, and the elongation at break is 30% or more. 4. The resin composition for a polyamideimide resin-based seamless tubular body according to any one of 3 above.   A seamless tubular body molded using the polyamide-imide resin heat-resistant resin composition according to any one of claims 1 to 4.