JP5109374B2 - Polyamideimide resin solution and production method thereof, resin composition and coating composition - Google Patents

Description

  The present invention relates to a polyamideimide resin solution, a method for producing the same, a resin composition, and a coating composition.

  Polyamideimide resins are excellent in heat resistance, chemical resistance and solvent resistance, and are therefore widely used as coating agents for various substrates, for example, enameled wire varnishes and heat resistant paints. However, these polyamide-imide resins and paints use N-methyl-2-pyrrolidone as a main solvent, so that they absorb moisture when applied, so that workability is poor. As an improvement, a varnish synthesized with γ-butyrolactone having a lower hygroscopicity by introducing a flexible structure into the resin structure to improve the solubility was produced. However, the introduction of a flexible structure has a problem that mechanical properties and heat resistance are lowered.

  Polyamideimide resin can be obtained by one-step synthesis with trimellitic acid and diphenylmethane diisocyanate. Usually synthesized in a polar solvent such as N-methyl-2-pyrrolidone. Since N-methyl-2-pyrrolidone absorbs moisture in the air, it has a problem of gelation unless it is quickly transferred to a drying process after coating. Solvents that can be used for synthesis are dimethylformamide, dimethylacetamide, γ-butyrolactone, etc., but when synthesized with a solvent other than N-methyl-2-pyrrolidone, the molecular weight does not increase or is not soluble. It is difficult to synthesize due to turbidity and gelation. As this improvement method, introduction of toluene diisocyanate or an aliphatic structure having good solubility in the resin structure is performed. However, this method tends to lower the heat resistance and film strength of the polyamide-imide resin due to the introduction of a structure having good solubility. Further, turbidity and gelation can be prevented by reducing the resin concentration to about 15%, but there is a problem that the resin film is thin when applied because the resin concentration is low. Furthermore, when synthesizing using γ-butyrolactone, it was necessary to raise the synthesis temperature to 170 ° C.

JP 2006-137794 A

  The present invention is a method for producing a polyamide-imide resin solution containing a polyamide-imide resin capable of stably synthesizing a high-molecular-weight polyamide-imide resin and maintaining the heat resistance and film strength of the polyamide-imide resin, and The present invention provides a method for producing a polyamide-imide resin solution capable of producing a polyamide-imide resin solution with reduced hygroscopicity and excellent stability. Moreover, this invention provides the polyamideimide resin solution obtained by this manufacturing method, and the resin composition and coating composition containing it.

The present invention relates to the following.
1. A derivative of a trivalent carboxylic acid having an acid anhydride group (a) and a compound having a divalent amino group or an isocyanate group (b) are mixed in a mixed solvent of γ-butyrolactone and N-methyl-2-pyrrolidone. A process for producing a polyamide-imide resin solution, characterized by reacting.

2. The component (a) is a derivative of a trivalent aromatic carboxylic acid having an acid anhydride group, the component (b) is an aromatic compound having a divalent amino group or an isocyanate group, and the polyamideimide resin is Item 2. The method for producing a polyamideimide resin solution according to Item 1, which is an aromatic polyamideimide resin.

3. The component (a) is a derivative of a trivalent aromatic carboxylic acid having an acid anhydride group represented by the following general formula (I) or (II), and the component (b) is represented by the following general formula (III), The production of a polyamideimide resin solution according to item 1 or 2, which is an aromatic compound having a divalent amino group or an isocyanate group represented by (IV) or (V), and the polyamideimide resin is an aromatic polyamideimide resin. Method.

（Ｙは−ＣＨ_２−、−ＣＯ−、−ＳＯ_２−又は−Ｏ−を示す。）

(Y represents —CH ₂ —, —CO—, —SO ₂ — or —O—)

［式中、Ｒ^２はアルキル基、水酸基又はアルコキシ基であり、Ｒ^３はアミノ基またはイソシアネート基である。］

[Wherein R ² represents an alkyl group, a hydroxyl group or an alkoxy group, and R ³ represents an amino group or an isocyanate group. ]

4). Item 4. The method for producing a polyamideimide resin solution according to any one of Items 1 to 3, wherein the polyamideimide resin has a number average molecular weight of 9000 to 50000.
5. Item 5. The method for producing a polyamideimide resin solution according to any one of Items 1 to 4, wherein the polyamideimide resin film has a tensile strength of 90 MPa or more at room temperature (25 ° C).
6). Item 6. A polyamideimide resin solution produced by the method according to any one of Items 1 to 5.

7). Item 7. A resin composition comprising the polyamideimide resin solution according to Item 6.
8). Item 8. The resin composition according to Item 7, further comprising 1 to 40 parts by weight of at least one selected from the group consisting of a polyfunctional epoxy resin, a polyisocyanate compound, and a melamine compound with respect to 100 parts by weight of the polyamideimide resin.
9. Item 9. A coating composition using the resin composition according to Item 7 or 8 as a binder.

  By the method for producing a polyamide-imide resin solution of the present invention, a polyamide-imide resin solution having lower hygroscopicity and better workability than a polyamide-imide resin varnish using N-methyl-2-pyrrolidone can be obtained. Moreover, according to the method of the present invention, a polyamideimide resin having mechanical properties equal to or higher than that of a polyamideimide resin obtained by a conventional production method can be obtained. In addition, the obtained γ-butyrolactone-based resin solution has better workability than conventional polyamide-imide resin varnishes, and should be suitably used as a binder resin for coating applications and various protective / coating materials. Can do.

  The trivalent carboxylic acid derivative (a) having an acid anhydride group and the compound (b) having a divalent amino group or isocyanate group used in the method of the present invention react with each other to form a polyamideimide resin. There is no particular limitation as long as it does. However, the method of the present invention is particularly suitable for the synthesis of an aromatic polyamideimide resin having a relatively low solubility in γ-butyrolactone having a low hygroscopic property, and from the viewpoint of the mechanical strength of the synthesized polyamideimide resin. As a component (a), a trivalent aromatic carboxylic acid derivative (aromatic tricarboxylic acid anhydride) having an acid anhydride group is used, and as a component (b) an aromatic having a divalent amino group or an isocyanate group. It is preferable to use a compound (aromatic diamine compound or aromatic diisocyanate compound).

  The polyamideimide resin of the present invention comprises (a) a derivative of a trivalent carboxylic acid having an acid anhydride group represented by the following general formula (I) or (II), (b) the following general formula (III), ( It is preferable that it consists of an aromatic resin obtained by making it react with at least 1 sort (s) of the compound which has a bivalent amino group or isocyanate group shown by IV) and (V).

  As an example of the component (a), as a derivative of a trivalent aromatic carboxylic acid having an acid anhydride group, for example, compounds represented by the general formulas (I) and (II) may be mentioned, which react with an isocyanate group or an amino group. There is no particular limitation as long as it is a derivative of a trivalent carboxylic acid having an acid anhydride group. In view of heat resistance, cost, etc., trimellitic anhydride is particularly preferable. These trivalent aromatic carboxylic acid derivatives having an acid anhydride group are used alone or in combination depending on the purpose.

（Ｙは−ＣＨ_２−、−ＣＯ−、−ＳＯ_２−又は−Ｏ−を示す。）

(Y represents —CH ₂ —, —CO—, —SO ₂ — or —O—)

  In addition to these, if necessary, tetracarboxylic dianhydride (pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4, 4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 1,4,5,8 -Naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldiphthalic 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, 2,2 Bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 1 , 1,1,3,3,3-hexafluoro-2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 1,3-bis (3 , 4-Dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, butanetetracarboxylic dianhydride, bicyclo- [2,2,2] -oct-7-ene-2: 3: 5: 6-tetracarboxylic dianhydride etc.) etc. can be used.

  As an example of the component (b), as an aromatic compound having a divalent amino group (aromatic diamine compound) and an aromatic compound having a divalent isocyanate group (aromatic diisocyanate compound), for example, the following general formula (III ), Compounds represented by (IV) and (V), and these aromatic compounds having a divalent amino group (aromatic diamine compounds) and aromatic compounds having a divalent isocyanate group (aromatic diisocyanate compounds). Are used alone or in combination depending on the purpose.

［式中、Ｒ^２はアルキル基（例えば、炭素数１〜２０のアルキル基）、水酸基又はアルコキシ基（例えば炭素数１〜２０のアルコキシ基）であり、Ｒ^３はアミノ基またはイソシアネート基である。］

[Wherein R ² is an alkyl group (for example, an alkyl group having 1 to 20 carbon atoms), a hydroxyl group or an alkoxy group (for example, an alkoxy group having 1 to 20 carbon atoms), and R ³ is an amino group or an isocyanate group. . ]

  Examples of aromatic diamine compounds and aromatic diisocyanate compounds represented by the general formulas (III), (IV), and (V) include 4,4'-diaminodiphenylmethane, 4,4'-diaminobiphenyl, 3,3'- Diaminobiphenyl, 3,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3, 3'-diethylbiphenyl, 4,4'-diamino-2,2'-diethylbiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatobi Phenyl, 3,3'-diisocyanatobiphenyl, 3,4'-diisocyanatobiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 4,4'-diisocyanato-2,2'-dimethyl Biphenyl, 4,4'-diisocyanato-3,3'-diethylbiphenyl, 4,4'-diisocyanato-2,2'-diethylbiphenyl, 4,4'-diisocyanato-3,3'-dimethoxybiphenyl, 4,4 '-Diisocyanato-2,2'-dimethoxybiphenyl, 1,5-diisocyanatonaphthalene, 2,6-diisocyanatonaphthalene and the like can be used. These can be used alone or in combination.

  Other aromatic diamine compounds and aromatic diisocyanate compounds include, for example, tolylenediamine, xylylenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis [4- (4'-aminophenoxy) phenyl. Propane, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diisocyanatodiphenyl ether, 2,2-bis [4- (4'-isocyanatophenoxy) phenyl] propane and the like.

  If necessary, as part of component (b), hexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, diaminoisophorone, bis (4-aminocyclohexyl) methane, 1,4-diaminotranscyclohexane, hydrogenated m-xylylenediamine, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, diisocyanatoisophorone, bis (4-isocyanatocyclohexyl) methane, 1,4-diisocyanatotranscyclohexane, hydrogenated m- Aliphatic, such as xylylene diisocyanate, alicyclic isocyanate, and trifunctional or higher polyisocyanate can also be used.

  In order to improve the hardness of the coating, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 1,5-diisocyanatonaphthalene, 2,6-diisocyanatonaphthalene and the like containing a naphthalene ring should be added. In the case of blending, the blending amount is preferably 5 to 30 mol%, more preferably 10 to 20 mol% in the total amount of component (b). If it is less than 10 mol%, the coating film hardness tends to be insufficiently improved, and if it exceeds 30 mol%, flexibility and adhesion tend to decrease.

  From the mechanical properties, 4,4′-diamino-3,3′-dimethylbiphenyl, 4,4′-diamino-2,2′-dimethylbiphenyl having a biphenyl derivative structure, 4,4′-diamino- 3,3'-diethylbiphenyl, 4,4'-diamino-2,2'-diethylbiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diamino-2,2'- Aromatic diamine compounds such as dimethoxybiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 4,4'-diisocyanato-2,2'-dimethylbiphenyl, 4,4'-diisocyanato-3,3 ' -Diethylbiphenyl, 4,4'-diisocyanato-2,2'-diethylbiphenyl, 4,4'-diisocyanato-3,3'-dimethoxybiphenyl, 4, It is preferable to use an aromatic diisocyanate compound such as' -diisocyanato-2,2'-dimethoxybiphenyl. When blended, the blending amount is preferably 10 to 85 mol% in the total amount of component (b). 10 to 30% is preferable. If it is 30% or more, the mechanical properties are improved, but the varnish tends to become cloudy or gel.

  The remaining compounding monomer is preferably compounded with 4,4'-diiaminodiphenylmethane or 4,4'-diisocyanatodiphenylmethane from the viewpoint of improvement in cost and elongation of mechanical properties. The amount of 4,4'-diaminodiphenylmethane or 4,4'-diisocyanatodiphenylmethane is preferably 5 to 90 mol%, more preferably 10 to 80 mol%, based on the total amount of component (b).

  Moreover, you may use what stabilized the isocyanate group with the blocking agent as needed in order to avoid a change over time. The blocking agent includes alcohol, phenol, oxime, etc., but there is no particular limitation.

  The blending ratio of the component (b) is preferably such that the ratio of the total number of isocyanate groups to the total number of carboxyl groups and acid anhydride groups of the component (a) is 0.6 to 1.4. -1.3 is more preferable, and 0.8-1.2 is particularly preferable. If it is less than 0.6 or exceeds 1.4, it tends to be difficult to increase the molecular weight of the resin.

  In the present invention, when the component (a) and the component (b) are reacted, a mixed solvent of γ-butyrolactone and N-methyl-2-pyrrolidone is used as a solvent. The blending amount of γ-butyrolactone and N-methyl-2-pyrrolidone is preferably 0.1 to 60 parts by weight of N-methyl-2-pyrrolidone per 100 parts by weight of γ-butyrolactone during the reaction. It is more preferable to set it as 2-50 weight part, and it is still more preferable to set it as 0.2-40 weight part. When the amount of N-methyl-2-pyrrolidone in the mixed solvent during the reaction is less than 0.1 parts by weight per 100 parts by weight of γ-butyrolactone, the synthesis temperature may have to be 160 ° C. or higher. The viscosity of the varnish tends to be unstable, and if it exceeds 60 parts by weight, the amount of N-methyl-2-pyrrolidone can be synthesized in the same manner as 100 parts by weight. Sometimes it tends to take longer to dry.

The amount of the mixed solvent used during the reaction is preferably 200 to 300 parts by weight, more preferably 210 to 250 parts by weight, per 100 parts by weight of the total amount of the component (a) and the component (b). preferable. When the amount of the mixed solvent used is less than 200 parts by weight, the foaming reaction becomes violent and tends to be blown out from the synthesis container. When the amount exceeds 300 parts by weight, the synthesis time tends to be long, and the resin concentration is low. Since it becomes low, it tends to become difficult to thicken the film when it is made into a paint.
In addition, after confirming the synthesis of the polyamideimide resin having a predetermined number average molecular weight and stopping the heating, if necessary, γ-butyrolactone is added to the reaction solution, and the mixed solvent in the resulting polyamideimide resin solution The amount may be adjusted to be 260 to 330 parts by weight, preferably 265 to 325 parts by weight, per 100 parts by weight of the total amount of the components (a) and (b). When the amount of the mixed solvent in the obtained polyamideimide resin solution is less than 260 parts by weight per 100 parts by weight of the total amount of the component (a) and the component (b), the resin solution is gelled and the stability is poor. When the amount exceeds 330 parts by weight, it tends to be difficult to increase the thickness when forming a coating film.
In the polyamideimide resin solution with the concentration adjusted in this way, the blending ratio of γ-butyrolactone and N-methyl-2-pyrrolidone in the mixed solvent was 0.1% of N-methyl-2-pyrrolidone per 100 parts by weight of γ-butyrolactone. It is preferable to set it as 1-60 weight part, and it is more preferable to set it as 0.2-50 weight part. If the amount of N-methyl-2-pyrrolidone is less than 0.1 parts by weight, the stability of the resin solution tends to be poor, and the cured resin film tends to be brittle. When it exceeds, in order to eliminate a residual solvent, when it hardens | cures, 250 degreeC or more and the heating for 30 minutes or more are needed, and there exists a tendency for the necessity to dry-harden for a long time to arise.

The method for producing the polyamideimide resin solution of the present invention can be carried out, for example, by the following procedure.
(1) A method of synthesizing a polyamideimide resin by using (a) component (acid component) and (b) component (diamine compound or diisocyanate compound component) at a time and reacting them.
(2) A method of synthesizing a polyamideimide resin by reacting (a) component with an excessive amount of (b) to synthesize an amideimide oligomer having an isocyanate group at the end and then reacting by adding component (a). .
(3) After reacting the excess of component (a) with component (b) to synthesize an amide-imide oligomer having an acid or acid anhydride group at the terminal, reaction is performed by adding component (a) and component (b). To synthesize a polyamide-imide resin.

  The reaction temperature is preferably 90 to 150 ° C, more preferably 100 to 145 ° C. The reaction time varies depending on the molecular weight of the polyamideimide resin in the target polyamideimide resin solution, but is usually preferably 5 to 20 hours, more preferably 6 to 15 hours.

  The polyamideimide resin in the polyamideimide resin solution obtained by the production method of the present invention preferably has a number average molecular weight of 9,000 to 50,000, more preferably 14,000 to 25,000. If the number average molecular weight is less than 9,000, the film formability when used as a paint tends to deteriorate, and if it exceeds 50,000, the viscosity increases when dissolved in a solvent at an appropriate concentration as a paint. The workability at the time of painting tends to be inferior, and the paint and varnish tend to be hygroscopically whitened, resulting in poor workability. For this reason, the number average molecular weight of the polyamideimide resin is more preferably 14,000 to 25,000. The number average molecular weight of the polyamideimide resin is sampled at the time of resin synthesis, measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve, and the synthesis is continued until the target number average molecular weight is reached. By doing so, it is managed within the above range.

  The polyamideimide resin in the polyamideimide resin solution obtained by the production method of the present invention preferably has a tensile strength of 90 MPa or more at room temperature (25 ° C.) when formed into a film, and is 95 MPa or more. More preferred.

  It is preferable that the resin composition of this invention contains at least 1 sort (s) chosen from the group which consists of a polyfunctional epoxy resin compound, a polyisocyanate compound, and a melamine compound with the said polyamideimide resin solution. The blending amount is preferably 1 to 40 parts by weight and more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the polyamideimide resin. When this amount is less than 1 part by weight, the effect of improving the adhesion is reduced, and when it exceeds 40 parts by weight, the heat resistance of the coating film tends to be remarkably reduced, and the coating strength is further reduced.

  Examples of the polyfunctional epoxy resin compound include bisphenol A type epoxy compound, glycerin triglycidyl type epoxy compound, aromatic polyglycidyl (tetraglycidoxytetraphenylethane type, phenol type epoxy, novolac type epoxy compound) and the like. Examples of the polyisocyanate compound include isocyanate compounds such as hexamethylene diisocyanate, reactants of two or more alcohol compounds such as hexamethylene glycol, and polyisocyanate compounds synthesized from an isocyanate compound and water or an amine compound. Examples of the melamine compound include Cymel 300, Cymel 303, Cymel 327, and the like manufactured by Mitsui Cytec.

  The resin composition of the present invention is used as a binder component, and additives such as a fluororesin compound and a colorant are added as necessary, and N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N ′ -It can be dissolved in solvents such as aromatic hydrocarbon solvents such as dimethylformamide, xylene and toluene, and ketones such as methyl ethyl ketone and methyl isobutyl ketone, and adjusted to an appropriate viscosity to obtain a coating composition. In the case of a paint, the solid content is generally 10 to 50% by weight.

  The polyamideimide resin solution, the resin composition, and the coating composition of the present invention can be dried and cured by heat treatment at 160 to 380 ° C. for 10 to 60 minutes. When cured at a low temperature, the solvent remains, and the coating properties that protect the substrate may be inferior. Further, when the curing temperature is lower than 160 ° C., the coating film is not sufficiently cured and may be dissolved or swollen in a polar solvent. When the heating time is less than 10 minutes, the residual solvent remains on the coating film, and the characteristics of the coating film applied to the substrate may be inferior. When the heating time exceeds 60 minutes, it is solid as a paint by applying heat for a long time. When a lubricant or the like is added, a side reaction may occur and the properties of the coating film may be deteriorated.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

Example 1
192.1 g (1.0 mol) trimellitic anhydride, 4,4'-diisocyanato-3,3'-dimethylbiphenyl in a 2 liter four-necked flask equipped with a stirrer, condenser, nitrogen inlet tube and thermometer 26.4 g (0.1 mol), 1,5-diisocyanatonaphthalene 21.0 g (0.1 mol), 4,4′-diisocyanatodiphenylmethane 200.2 g (0.8 mol), γ-butyrolactone 970 g is charged, 3.1 g of N-methyl-2-pyrrolidone is added, the temperature is raised to 120 ° C., and the mixture is reacted for about 6 hours. When the molecular weight reached 19300, heating was stopped, and 277 g of γ-butyrolactone was charged to obtain a polyamideimide resin solution having a nonvolatile content of 25% by weight.

Example 2
In a 2 liter four-necked flask equipped with a stirrer, condenser, nitrogen inlet tube and thermometer, trimellitic anhydride 192.1 g (1.0 mol) 4,4'-diphenylmethane diisocyanate 250.3 g (1.0 mol) ), 1032 g of γ-butyrolactone is added, 3.1 g of N-methyl-2-pyrrolidone is added, the temperature is raised to 120 ° C., and the mixture is reacted for about 6 hours. When the molecular weight reached 17600, heating was stopped, and 295 g of γ-butyrolactone was charged to obtain a polyamideimide resin solution having a nonvolatile content of 25% by weight.

Example 3
192.1 g (1.0 mol) trimellitic anhydride, 4,4'-diisocyanato-3,3'-dimethylbiphenyl in a 2 liter four-necked flask equipped with a stirrer, condenser, nitrogen inlet tube and thermometer 54.9 g (0.2 mol) 4,4′-diisocyanatodiphenylmethane 200.2 g (0.8 mol) and γ-butyrolactone 1043 g were charged, and N-methyl-2-pyrrolidone 3.1 g was added. The temperature is raised to about 6 hours. When the molecular weight reached 14500, the heating was stopped, and 299 g of γ-butyrolactone was charged to obtain a polyamideimide resin solution having a nonvolatile content of 25% by weight.

Example 4
In a 2-liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, 192.1 g (1.0 mol) of trimellitic anhydride, 34.8 g of 2,4-tolylene diisocyanate (TDI) ( 0.2 mol) 200.2 g (0.8 mol) of 4,4'-diisocyanatodiphenylmethane and 1043 g of γ-butyrolactone were added, 3.1 g of N-methyl-2-pyrrolidone was added, and the temperature was raised to 145 ° C. For about 6 hours. When the molecular weight reached 14500, the heating was stopped, and 299 g of γ-butyrolactone was charged to obtain a polyamideimide resin solution having a nonvolatile content of 25% by weight.

Comparative Example 1
In a 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, 192.1 g (1.00 mol) of trimellitic anhydride and 255.3 g of 1,4'-diisocyanatodiphenylmethane (1 .02 mol) and 1043.9 g of N-methyl-2-pyrrolidone were charged, heated to 130 ° C., and reacted for 4 hours to obtain a polyamideimide resin solution having a molecular weight of 20000 and a nonvolatile content of 30% by weight.

Comparative Example 2
In a 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, trimellitic anhydride 153.7 g (0.8 mol), sebacic acid 33.2 g (0.2 mol), 4, 250.3 g (1.0 mol) of 4′-diisocyanatodiphenylmethane and 1035 g of γ-butyrolactone were charged, heated to 130 ° C., and reacted for 4 hours to obtain a polyamideimide resin solution having a molecular weight of 16,500.

Comparative Example 3
In a 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, 192.1 g (1.0 mol) of trimellitic anhydride and 250.3 g (1 mol) of 4,4′-diisocyanatodiphenylmethane 0.02 mol) and 1023 g of γ-butyrolactone were charged, heated to 130 ° C. and reacted for 4 hours, but gelled during the reaction and polymerization did not proceed.

Test Example To the polyamideimide resin solutions obtained in Examples 1 to 4 and Comparative Examples 1 and 2, bisphenol A type epoxy resin (Epicoat 828, manufactured by Japan Epoxy Resin Co., Ltd., trade name) with respect to 100 parts by weight of the polyamideimide resin. ) Was added to obtain a resin composition varnish.

Using the above-mentioned resin composition varnish obtained by adding the bisphenol A type epoxy resin to the polyamideimide resin solutions obtained in Examples and Comparative Examples, the measurement is performed by the following method, and the characteristics are evaluated. Are shown in Table 1.
In the following tests (1), (2), and (3), the resin composition varnish was applied to an aluminum plate (A1050P, thickness 1 mm, 5 cm × 15 cm), and the heating condition for coating film curing was 180 ° C. 30 minutes.
(1) Appearance: The appearance of the resin composition varnish, the turbidity of the coating film, and the roughness of the surface were visually examined.
(2) Adhesiveness (cross cut test): A test was conducted in accordance with JIS D0202 using a resin composition varnish.
(3) Pencil hardness: Measured according to JIS K5400 using a resin composition varnish.
(4) Extraction rate: The above resin composition varnish obtained by adding an epoxy resin to a polyamide-imide resin solution was applied on a 20 × 50 mm steel plate so as to have a film thickness of 20 μm, and then heat-treated at 180 ° C. for 30 minutes. . After immersing this in N-methyl-2-pyrrolidone for 1 hour, the extraction rate was calculated from the following formula. Extraction rate = [1- (Dry film after immersion / Dry film before immersion)] × 100%
(5) Mechanical properties: A film obtained by applying a polyamideimide resin solution to a glass plate and subjecting it to a heat treatment at 180 ° C. for 30 minutes was adjusted to a film thickness of 20 μm, a width of 10 mm, and a gap between chucks of 20 mm. C.), a tensile test was performed at a tensile speed of 5 mm / min, and tensile strength and elongation were measured.
(6) Stability: the area of about 28cm ² metal dish the resin composition varnish was placed 3.0 g, spread the varnish on the entire dish. This was left in a horizontal place at a temperature of 25 ° C. and a humidity of 80%, and the generation time of the gelled product was measured.

  From the results shown in Table 1, the stability of the polyamideimide resin solution obtained in the examples of the present invention is better than that of Comparative Example 1 which is a normal polyamideimide varnish. Moreover, the strength of mechanical properties is improved as compared with Comparative Example 2 in which a flexible group is introduced. Moreover, since the resin concentration of the obtained polyamideimide resin solution is 25% by weight, a thick film is likely to be produced when it is applied.

Claims (4)

A trivalent aromatic carboxylic acid derivative (a) having an acid anhydride group represented by the following general formula (I) or (II) and 2 represented by the following general formula (III), (IV) or (V) An aromatic polyamideimide resin solution obtained by reacting an aromatic compound (b) having a valent amino group or an isocyanate group in a mixed solvent of γ-butyrolactone and N-methyl-2-pyrrolidone; A resin composition containing 1 to 40 parts by weight of a polyfunctional epoxy resin with respect to 100 parts by weight of the aromatic polyamideimide resin.

(Y represents —CH ₂ —, —CO—, —SO ₂ — or —O—)

[Wherein R ² represents an alkyl group, a hydroxyl group or an alkoxy group, and R ³ represents an amino group or an isocyanate group. ] The resin composition according to claim 1 , wherein the aromatic polyamideimide resin has a number average molecular weight of 9000 to 50000. The resin composition according to claim 1 or 2, wherein the film of the aromatic polyamideimide resin has a tensile strength of 90 MPa or more at room temperature (25 ° C). The coating composition using the resin composition in any one of Claims 1-3 as a binder.