JP2011162733A - Heat-resistant resin composition and coating using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant resin composition curable at low temperature and having excellent heat resistance, and a coating using the heat-resistant resin composition, curable at low temperature and capable of forming a coating film having low shrinkage percentage upon curing and excellent mechanical properties, such as high elongation percentage, and heat resistance. <P>SOLUTION: The heat-resistant resin composition is obtained by blending 5-100 pts.wt. of a polyamideimide resin having a number-average molecular weight of 2,000-40,000 with 100 pts.wt. of polyamic acid having a number-average molecular weight of 15,000-50,000. The coating using the heat-resistant resin composition is also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat resistant resin composition and a paint using the same. Specifically, the present invention relates to the heat-resistant resin composition used for sliding members, belts, various protective coatings, and a paint using the same.

  Paints using polyimide resins such as polyamic acid and polyimide resin are widely used as electrical insulation paints, coating materials for various substrates, binder resins for sliding parts, and belts because of their good heat resistance and solvent resistance. It has been. However, in general, polyimide resins often require high-temperature treatment for a long time for heating during coating film formation. Therefore, in order to prevent deterioration of the coating film performance and damage to the coated object due to high-temperature long-time curing, the curing of the polyimide-based resin is promoted at a low temperature by adding an epoxy resin or a melamine resin to the polyimide-based resin. In addition, a method for improving the coating and curing workability by increasing the meltability at a low temperature is known (see, for example, Patent Document 1). By using these epoxy resins and melamine resins, there is a drawback that the heat resistance of the resulting cured product is lowered even though a cured coating film can be obtained by heating at a relatively low temperature for a short time. Patent Document 2 and Patent Document 3 describe polyamic acid and resin compositions obtained by blending polyamide, polyetherimide, or polyethersulfone with polyamic acid. However, these resin compositions have the disadvantage that they need to be cured at high temperatures if they take a long time to cure.

JP-A-10-219108 JP 2006-108175 A JP-A-8-239645

As mentioned above, when an epoxy resin, a melamine resin, etc. are mix | blended with a polyimide resin and a coating film is hardened, there existed a fault that the heat resistance of the hardened | cured material obtained fell.
The present invention solves these problems, and provides a heat-resistant resin composition that can be cured at a low temperature and has excellent heat resistance. In addition, the present invention is a coating using this heat-resistant resin composition, which can be cured at low temperature, has a low shrinkage ratio upon curing, and has excellent mechanical properties such as high elongation ratio and heat resistance. The present invention provides a paint capable of forming a film.

The present invention relates to the following heat-resistant resin composition and paint.
(1) A heat resistant resin composition comprising 5 to 100 parts by weight of a polyamideimide resin having a number average molecular weight of 2,000 to 40,000 and 100 parts by weight of a polyamic acid having a number average molecular weight of 15,000 to 50,000. object.

  The heat resistant resin composition according to (1), wherein the ratio of the total number of amide groups to the total number of imide groups in the polyamide-imide resin is 37/63 to 70/30.

  The polyamic acid is obtained by polyaddition reaction of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and the polyamideimide resin is an aromatic tricarboxylic acid anhydride and an aromatic diisocyanate or aromatic diamine. Polycondensation reaction product, polycondensation reaction product of aromatic tricarboxylic acid anhydride and dicarboxylic acid with aromatic diisocyanate or aromatic diamine, or aromatic tricarboxylic acid anhydride and tetracarboxylic acid dianhydride and aromatic diisocyanate or aromatic The heat resistant resin composition according to (1) or (2), which is a polycondensation reaction product with a group diamine.

  (1)-The coating material using the heat resistant resin composition in any one of (3).

  The paint according to (4), comprising 100 parts by weight of the polyamic acid, 5 to 100 parts by weight of the polyamideimide resin, and an organic solvent.

  The heat-resistant resin composition of the present invention is a heat-resistant resin composition that can be cured at a low temperature and provides a cured product having excellent heat resistance. In addition, the paint using the heat-resistant resin composition of the present invention can be cured at a low temperature, and forms a coating film excellent in mechanical properties and heat resistance such as a low shrinkage ratio at the time of curing and a high elongation ratio. It can be.

  The polyamic acid having a number average molecular weight of 15,000 to 50,000 used in the present invention can generally be produced by polyaddition reaction of tetracarboxylic dianhydride and diamine.

  As the tetracarboxylic dianhydride, an aromatic tetracarboxylic dianhydride is preferable, and as the aromatic tetracarboxylic dianhydride, a conventionally known one can be used. For example, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic acid 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 Anhydride, 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 is preferably used. . In terms of cost, pyromellitic dianhydride is preferable, and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is preferable in terms of mechanical strength.

  As tetracarboxylic dianhydride, aromatic tetracarboxylic dianhydride is preferably used, butane tetracarboxylic dianhydride, bicyclo- [2,2,2] -oct-7-ene-2: Aliphatic tetracarboxylic dianhydrides such as 3: 5: 6-tetracarboxylic dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane Other tetracarboxylic dianhydrides such as polysiloxane tetracarboxylic dianhydrides having a polysiloxane structure in the main chain such as dianhydrides may be used in place of a part of the aromatic tetracarboxylic dianhydrides. Good. When these other tetracarboxylic dianhydrides are used, the amount used is preferably 20 mol% or less in the total amount of tetracarboxylic dianhydrides. If it exceeds 20 mol%, the mechanical strength and heat resistance of the cured resin composition may be reduced.

  As the diamine, an aromatic diamine is preferable. As the aromatic diamine, conventionally known diamines can be used. For example, paraphenylene diamine, orthophenylene diamine, orthotolidine, metatolidine, 4,4-diaminodiphenyl ether, 3,4 -Diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, xylylenediamine, phenylenediamine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl -4,4'-diaminobiphenyl, 4,4'-diaminodiphenylmethane, 3,4-diaminodiphenyl, 2,4-diaminobiphenyl, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-tri Range amine, 2,6-tolyre Diamine, m- xylylenediamine, etc. 3,3' hydroxyl-4,4'-diaminobiphenyl is preferably used. Diaminodiphenyl ether is preferred from the standpoint of elongation of mechanical properties. From the viewpoint of strength, metatrizine and paraphenylenediamine are preferable.

  As the diamine, it is preferable to use an aromatic tetracarboxylic dianhydride. However, an aliphatic diamine and another diamine having a polysiloxane structure in the main chain are replaced with a part of the aromatic diamine. It may be used. When using these other diamines, the amount used is preferably 30 mol% or less in the total amount of diamines. If it exceeds 30 mol%, the mechanical strength, heat resistance, etc. of the cured resin composition may be reduced.

  These tetracarboxylic dianhydrides and diamines may be used alone or in combination of several kinds.

  In the synthesis of polyamic acid, the mixing ratio of tetracarboxylic dianhydride and diamine is preferably 0.8 to 1.1 in terms of a molar ratio of tetracarboxylic dianhydride / diamine, and 0.9 to 1. 1 is more preferable, and 0.95 to 1.05 is most preferable for curing with the polyamideimide resin. When the molar ratio deviates from the range of 0.8 to 1.1, a uniform coating film is not formed when the polyamideimide resin is mixed, and there is a tendency to separate even in a solution state.

  The polyaddition reaction of the tetracarboxylic dianhydride and diamine is performed in a solvent, and a basic polar solvent is preferably used as the solvent from the viewpoint of solubility. Specifically, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, dimethyl sulfoxide, hexamethylphosphoramide, Examples include tetramethylene sulfone, which can be used alone or in combination. From the viewpoint of economy and ease of polymerization, it is preferable to use N-methyl-2-pyrrolidone or N, N-dimethylacetamide.

  Although there is no restriction | limiting in particular in the usage-amount of a solvent, It is preferable to set it as 300-450 weight part with respect to 100 weight part of total amounts of tetracarboxylic dianhydride and diamine, and it is more preferable to set it as 375-400 weight part. .

  There is no particular limitation on the method of polyaddition reaction of tetracarboxylic dianhydride and diamine in a solvent, but it is preferably performed in an inert atmosphere such as nitrogen. For example, when preparing the reaction mixture, it is preferable to prepare a reaction solution by mixing the diamine and the solvent, then raising the temperature, and gradually adding and dissolving the tetracarboxylic dianhydride. At that time, it is preferable to cool the liquid temperature so as not to generate heat and keep the liquid temperature at 50 ° C. or lower. Thereafter, the reaction solution is heated and reacted, and at this time, it is preferable to keep the reaction temperature at 100 ° C. or lower.

  The polyamic acid used in the present invention has a number average molecular weight of 15,000 to 50,000, preferably 18,000 to 40,000. When the number average molecular weight of the polyamic acid is less than 15,000, the coating film after curing of the heat-resistant resin composition becomes brittle and hardly forms a film. If it exceeds 50,000, it tends to phase separate from the polyamide-imide resin, and it is difficult to develop uniform characteristics. Furthermore, the storage stability tends to be significantly impaired. In the present invention, the number average molecular weight of the polyamic acid is measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

  In the above polyamic acid synthesis reaction, the number average molecular weight of the polyamic acid obtained is measured using a standard polystyrene calibration curve by gel permeation chromatography (GPC) by sampling the reaction solution during the synthesis reaction, By continuing the synthesis until the target number average molecular weight is reached, the above range is maintained (the same applies to the examples).

  As the polyamideimide resin (hereinafter sometimes referred to as PAI resin) used in the present invention, those obtained by polycondensation reaction of tricarboxylic acid anhydride and diisocyanate or diamine can be used.

  As the tricarboxylic acid anhydride component, aromatic tricarboxylic acid is preferably used, and trimellitic acid anhydride is preferable in terms of flexibility, storage stability and cost. Not only aromatic tricarboxylic acids but also other tricarboxylic anhydrides such as aliphatic tricarboxylic anhydrides that react with isocyanate groups or amino groups may be used, but in combination with aromatic tricarboxylic acids such as trimellitic anhydride It is preferable to do. When an aromatic tricarboxylic acid anhydride and another tricarboxylic acid anhydride are used in combination, the amount of the other tricarboxylic acid anhydride used is preferably 30 mol% or less in the total amount of the tricarboxylic acid anhydride component. If the amount of other tricarboxylic acid anhydride used exceeds 30 mol%, gelation or molecular weight tends to be difficult during synthesis.

  The diisocyanate or diamine used for the synthesis of the polyamideimide resin is preferably an aromatic diisocyanate or an aromatic diamine, and particularly preferably an aromatic diisocyanate or diamine having a diphenylmethane structure, a biphenyl structure or a naphthalene structure is used as an essential component. By using these as essential components, there is an effect of improving the dimensional stability, the strength of mechanical properties, and the elastic modulus. Examples of such aromatic diisocyanates include 4,4′-diphenylmethane diisocyanate, 3,3′-diphenylmethane diisocyanate, 2,4-diphenylmethane isocyanate, 3,3′-dimethyl-4,4′-biphenyl diisocyanate, and naphthalene. -1,5-diisocyanate, naphthalene-2,6-diisocyanate and the like, and other aromatic diisocyanate components include xylylene diisocyanate and paraphenylene diisocyanate. 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,4-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminobiphenyl, naphthalene-1, - diamines, include naphthalene-2,6-diamine, and the like xylylenediamine, p-phenylenediamine as other aromatic diisocyanate component.

When an aromatic diisocyanate or diamine having a diphenylmethane structure, a biphenyl structure or a naphthalene structure is an essential component and another aromatic diisocyanate or aromatic diamine is used in combination, the amount of the other aromatic diisocyanate or aromatic diamine used is aromatic. The total amount of diisocyanate or aromatic diamine is preferably 20 mol% or less.
Moreover, although other diamines, such as aliphatic diamines other than aromatic diamine, may be used, when using these together, it is preferable that the usage-amount of other diamine shall be 10 mol% or less in the total amount of diamine. If the amount of other diamine used exceeds 10 mol%, the reaction is difficult and the molecular weight tends not to increase.

  Each of the above tricarboxylic acid anhydrides, diisocyanates, and diamines may be used alone or in combination.

  Further, as the diisocyanate, those obtained by stabilizing an isocyanate group with a blocking agent may be used. Examples of the blocking agent include aliphatic alcohols, phenols, and oximes, but there is no particular limitation.

  In the synthesis of the polyamideimide resin used in the present invention, the following compounds can be used in order to change the ratio of the amide group to the imide group.

  When increasing the amide group, instead of a part of the tricarboxylic acid anhydride, dicarboxylic acid such as aromatic dicarboxylic acid (isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, etc.) or the like Dicarboxylic acids (succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, sebacic acid, decanedioic acid, dodecanedioic acid, dimer acid, etc.) and modified dicarboxylic acids such as acrylic-modified terminal dicarboxylic acid compounds, etc. Can be used.

  When increasing the imide group, instead of a part of the tricarboxylic acid anhydride, a tetracarboxylic acid dianhydride such as pyromellitic acid dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid diacid is used. Anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic acid Anhydride, 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-dicarbo Cyphenyl) propane dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis [4- (2,3- or 3,4-di Carboxyphenoxy) phenyl] propane dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] propane The main chain of aromatic tetracarboxylic dianhydride such as dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride Tetracarboxylic dianhydride having a siloxane structure, butanetetracarboxylic dianhydride, bicyclo- [2,2,2] -oct-7-ene-2: 3: 5: 6-tetracarboxylic dianhydride, etc. Aliphatic tetracarboxylic acid Or the like can be used things.

  Said dicarboxylic acid and tetracarboxylic dianhydride may each be used individually by 1 type, and may use 2 or more types together.

  The blending ratio of the acid component having a tricarboxylic anhydride as an essential component used for the synthesis of the polyamideimide resin and the diisocyanate or diamine is the total number of isocyanate groups or amino groups relative to the total number of carboxyl groups and acid anhydride groups of the acid component. The ratio of (total number of isocyanate groups or amino groups) / (total number of carboxyl groups and acid anhydride groups) is preferably 0.6 to 1.3, and 0.7 to 1.3. It is more preferable to set it as 0.8, and it is especially preferable to set it as 0.8-1.2. If this ratio is less than 0.6 or exceeds 1.3, it tends to be difficult to increase the molecular weight of the resin.

  The polycondensation reaction between the acid component containing the above tricarboxylic acid anhydride as an essential component and diisocyanate or diamine diamine is performed in a solvent, and a basic polar solvent is preferably used as the solvent from the viewpoint of solubility. Specifically, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, dimethyl sulfoxide, hexamethylphosphoramide, Tetramethylene sulfone, 1,2-dimethylimidazole, N, N′-dimethylpropyleneurea and the like can be mentioned, and each can be used alone or in combination. From the viewpoint of economy and ease of polymerization, N-methyl- It is preferable to use 2-pyrrolidone or N, N-dimethylacetamide.

  Although there is no restriction | limiting in particular in the usage-amount of a solvent, It is preferable to set it as 100-300 weight part with respect to 100 weight part of the total amount of the acid component and diisocyanate or diamine which have a tricarboxylic acid anhydride as an essential component, 150-275 weight More preferably, it is a part.

  Although the reaction conditions of the polycondensation reaction in the solvent of the acid component having tricarboxylic anhydride as an essential component and diisocyanate or diamine diamine cannot be specified in general, it is usually 100 to 140 under an inert atmosphere such as nitrogen. Performed at a temperature of ° C.

  In the synthesis of the polyamide-imide resin, tricarboxylic acid anhydride monochloride may be used as an acid component instead of tricarboxylic acid anhydride. In this case, the reaction is performed at a temperature lower than the above reaction temperature for several hours. Polyamideimide resin can also be obtained.

  The ratio of the amide group / imide group of the polyamideimide resin having a number average molecular weight of 2,000 to 40,000 used in the present invention (total number of amide groups / total number of imide groups in the polyamideimide resin) is 30/70 to 75. / 25 is preferable, and 37/63 to 70/30 is most preferable. This ratio of amide group to imide group is very effective for increasing the amide group when improving the stretchability and flexibility of the film, and when improving the heat resistance from reducing the heated weight of the film or the glass transition. In the case of improving the temperature, increasing the imide group has a great effect. If the ratio of amide group / imide group is less than 30/70, it is difficult to synthesize, and the film formability is poor and the film tends to become brittle. If it exceeds 75/25, cracks occur during film molding. It tends to be easy to do.

  The polyamideimide resin used in the present invention has a number average molecular weight of 2,000 to 40,000, preferably 10,000 to 40,000, and preferably 15,000 to 30,000. More preferred. When the number average molecular weight of the polyamideimide resin is less than 2,000, the storage stability tends to be remarkably lowered, and when it exceeds 40,000, the polyimide and the polyamideimide tend to phase-separate after curing. In the present invention, the number average molecular weight of the polyamic acid is measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

  In the synthesis reaction of the above polyamideimide resin, the number average molecular weight of the obtained polyamideimide resin is determined by sampling the reaction solution during the synthesis reaction and using a standard polystyrene calibration curve by gel permeation chromatography (GPC). By measuring and continuing the synthesis until the target number average molecular weight is reached, the above range is maintained (the same applies to the examples).

  In the heat resistant resin composition of the present invention, the polyamic acid and the polyamideimide resin are preferably blended in an amount of 5 to 100 parts by weight of the polyamideimide resin in 100 parts by weight of the polyamic acid. When the blending amount of the polyamideimide resin is less than 5 parts by weight, the curability is almost the same as that of the polyimide, and the effect tends to be difficult to obtain. When it exceeds 100 parts by weight, the mechanical properties are deteriorated and the heat resistance is reduced. Tend to be similar to polyimide. As for the compounding quantity which does not change the characteristic of the polyimide after hardening, it is preferable to mix | blend 5-10 weight part polyamideimide resin. In order to reduce the curing shrinkage of the cured polyimide resin, it is preferable to blend 15 to 50 parts by weight of polyamideimide resin. It is particularly preferable to blend 20 to 40 parts by weight of the polyamideimide resin from the viewpoint of the balance of the characteristics.

  The coating material of the present invention is formed by using the heat resistant resin composition of the present invention, and usually contains the above polyamic acid and polyamideimide resin, and a solvent capable of dissolving these resin components.

  The coating material may be prepared by mixing the resin solution containing each resin obtained at the time of synthesizing the polyamic acid and the polyamideimide resin as it is, and adding a solvent to each or either one in advance to increase the viscosity. It may be mixed after preparation, or a solvent may be further added at the time of mixing the resin solution. Examples of the solvent to be added include ketone solvents (methyl ethyl ketone, ethyl 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, p-cymene, etc.), tetrahydrofuran, dioxane, N-methyl-2-pyrrolidone, N, N -Dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, tetramethyl Sulfone, 1,3-dimethyl-2-imidazolidinone, N, N'-dimethyl propylene urea, and the like.

  When the polyamic acid solution and the polyamideimide resin solution are mixed, the viscosity of each solution (viscosity at 25 ° C., the same applies to the examples) is preferably 2.0 to 20.0 Pa · s, preferably 3.0 to More preferably, it is 15.0 Pa · s. If the viscosity is less than 2.0 Pa · s, it tends to flow due to heat during film formation, causing a repelling phenomenon and tends to be difficult to apply, and if it exceeds 20.0 Pa · s, it tends to be difficult to perform spray coating. .

  The content of non-volatile components (solid components such as polyamic acid and polyamideimide resin) in the paint is preferably 15 to 30% by weight, and more preferably 15 to 25% by weight. If this content is less than 15% by weight, the reaction between the amino group or acid anhydride group of the polyamic acid and the isocyanate or amino group or acid anhydride group of the polyamideimide tends to hardly occur, and if it exceeds 30% by weight, There is a tendency that the stability of the polyamic acid is deteriorated and the working efficiency is deteriorated.

  When applying the paint of the present invention, the paint may be preliminarily heated at 40 to 80 ° C. for 10 minutes to 1 hour and used as a varnish prepared to have a viscosity suitable for application. If the heating temperature at this time exceeds 80 ° C., the film may be broken at the final curing temperature due to a decrease in molecular weight, which is not preferable.

  The substrate for forming the coating film with the paint of the present invention is not particularly limited. For example, a glass substrate, a metal such as aluminum and stainless steel, a plate-like substrate such as an alloy, a cylindrical substrate inside and outside, and wear resistance. Examples include machine parts that require slipperiness. In particular, a base material such as an aluminum alloy or an iron-based alloy is suitable for the paint of the present invention from the viewpoint of adhesion.

  A coating film is formed by applying the paint of the present invention to a substrate and then heat-curing it. Usually, the heat curing is preferably performed by heating at a temperature of 30 to 100 ° C. for 10 to 30 minutes to remove the solvent and then heating and curing at a temperature of 250 to 300 ° C. for 10 to 60 minutes. When the heat curing temperature is less than 250 ° C., the film forming property of the film is remarkably lowered due to the hydrolysis reaction of polyamic acid, and there is a tendency that the film does not become a film. Deterioration tends to make the film brittle.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
Synthesis Example 1 [Synthesis of polyamic acid having a number average molecular weight of 15,000 to 50,000]

(Synthesis Example 1-1)
A 2 liter four-necked flask equipped with a stirrer, a condenser, a nitrogen inlet tube and a thermometer was charged with 200.2 (1.00 mol) of 4,4'-diaminodiphenyl ether and 1673 g of N-methyl-2-pyrrolidone. The temperature is raised to 30 ° C., 218.1 g (1.00 mol) of pyromellitic anhydride is gradually added, and the mixture is stirred and completely dissolved. At that time, it is cooled so as not to generate heat and kept at 50 ° C. or lower. This dissolved solution was reacted at 90 ° C. for 4 hours to obtain a polyamic acid resin solution having a number average molecular weight of 27,000, a viscosity of 8.6 Pa · s, and a nonvolatile content of 19.9% by weight. This resin solution is designated as resin 1.

(Synthesis Example 1-2)
A 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer was charged with 200.2 g (1.00 mol) of 4,4′-diaminodiphenyl ether and 1858 g of N-methyl-2-pyrrolidone. The temperature is raised to 30 ° C., and 264.2 g (0.82 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride is slowly added, and the mixture is stirred and completely dissolved. At that time, it is cooled so as not to generate heat and kept at 50 ° C. or lower. This dissolved solution was reacted at 90 ° C. for 5 hours to obtain a polyamic acid resin solution having a number average molecular weight of 33,000, a viscosity of 9.2 Pa · s, and a nonvolatile content of 20.1% by weight. This resin solution is designated as resin 2.

(Synthesis Example 1-3)
A 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer was charged with 200.2 g (1.00 mol) of 4,4′-diaminodiphenyl ether and 1717 g of N-methyl-2-pyrrolidone. The temperature is raised to 30 ° C., 229.1 g (1.05 mol) of pyromellitic anhydride is slowly added, and the mixture is stirred and completely dissolved. At that time, it is cooled so as not to generate heat and kept at 50 ° C. or lower. This dissolved solution was reacted at 90 ° C. for 1 hour to obtain a polyamic acid resin solution having a number average molecular weight of 26,000, a viscosity of 7.4 Pa · s, and a nonvolatile content of 19.5% by weight. This resin solution is designated as resin 3.

(Synthesis Example 1-4)
Into a 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, was charged 190.2 g (0.95 mol) of 4,4'-diaminodiphenyl ether and 1633 g of N-methyl-2-pyrrolidone. The temperature is raised to 30 ° C., 218.1 g (1.00 mol) of pyromellitic anhydride is slowly added, and the mixture is stirred and completely dissolved. At that time, it is cooled so as not to generate heat and kept at 50 ° C. or lower. This dissolved solution was reacted at 90 ° C. for 1 hour to obtain a polyamic acid resin solution having a number average molecular weight of 18,000, a viscosity of 4.6 Pa · s, and a nonvolatile content of 20.1 wt%. This resin solution is designated as resin 4.

Synthesis Example 2 [Synthesis of polyamideimide resin having a number average molecular weight of 2,000 to 40,000]
(Synthesis Example 2-1)
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 as an acid component and 3,3′-dimethyl-4 as a diisocyanate component , 4′-diisocyanate biphenyl 105.7 g (0.40 mol), 4,4′-diphenylmethane diisocyanate 75.1 g (0.31 mol), naphthalene-1,5-diisocyanate 63.1 g (0.31 mol), N-methyl-2-pyrrolidone (785.2 g) was charged, heated to 130 ° C., and reacted for about 6 hours to obtain a PAI having a number average molecular weight of 31,000. This PAI resin solution was diluted with N-methyl-2-pyrrolidone to obtain a PAI resin solution having a viscosity of 8.7 Pa · s and a nonvolatile content of 22.1% by weight. This PAI resin solution is designated as Resin 5.

(Synthesis Example 2-2)
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 as an acid component and 3,3′-dimethyl-4 as a diisocyanate component , 4'-diisocyanate biphenyl (105.7 g, 0.40 mol), 4,4'-diphenylmethane diisocyanate (150.2 g, 0.62 mol), N-methyl-2-pyrrolidone (785.2 g) Warm and react for about 6 hours to obtain a PAI with a number average molecular weight of 31,000. This PAI resin solution was diluted with N-methyl-2-pyrrolidone to obtain a PAI resin solution having a viscosity of 7.4 Pa · s and a nonvolatile content of 20.1 wt%. This PAI resin solution is designated as Resin 6.

(Synthesis Example 2-3)
Trimellitic anhydride 153.7 g (0.80 mol) and sebacic acid 60.7 g (0.30 mol) as acid components in a 2 liter four-necked flask equipped with a stirrer, condenser, nitrogen inlet tube and thermometer As a diisocyanate component, 250.3 g (1.03 mol) of 4,4′-diphenylmethane diisocyanate and 785.2 g of N-methyl-2-pyrrolidone were charged, heated to 130 ° C., reacted for about 6 hours, and number averaged. A PAI having a molecular weight of 24,000 (amide group / imide group = 63.6 / 36.4, calculated value) was obtained. This PAI resin solution was diluted with N-methyl-2-pyrrolidone to obtain a PAI resin solution having a viscosity of 3.3 Pa · s and a nonvolatile content of 23.0% by weight. This PAI resin solution is designated as Resin 7.

(Synthesis Example 2-4)
In a 2 liter four-necked flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, 192.1 g (1.00 mol) of trimellitic anhydride as an acid component and 4,4′-diphenylmethane diisocyanate as a diisocyanate component 262.8 g (1.09 mol) and N-methyl-2-pyrrolidone 785.2 g were charged, heated to 130 ° C., and reacted for about 6 hours to obtain a PAI having a number average molecular weight of 20,000. This PAI resin solution was diluted with N-methyl-2-pyrrolidone to obtain a PAI resin solution having a viscosity of 0.9 Pa · s and a nonvolatile content of 23.0% by weight. This PAI resin solution is designated as Resin 8.

[Test method]
Adjustment of varnish: Synthesized resins 1 to 4 and resins 5 to 8 were weighed in specified amounts and mixed at 50 ° C. to 80 ° C. for 2 to 6 hours to obtain a varnish-like mixture.
Coating film curing conditions: After applying the varnish to the object to be coated, it is heated and dried on a hot plate at 80 ° C. for 30 minutes, and cured at 250 ° C. for 60 minutes in a hot air box dryer.
As a comparative example, a comparative example in which no polyamideimide resin was added was used as a comparative example 1, and an epoxy resin: Epicoat 806 (trade name, nonvolatile content: 100% by weight, manufactured by Japan Epoxy Resin Co., Ltd.) was used as a curing agent. 2. The case where resin 1 was cured at 80 ° C. for 30 minutes (hot plate), 150 ° C./15 minutes, 250 ° C./15 minutes, and 320 ° C./30 minutes was designated as Comparative Example 3.

(1) Scratch strength (pencil method)
After coating the PAI resin composition on an aluminum plate A1050P (dimensions: 1 mm × 50 mm × 150 mm), the PAI resin composition was cured on an 80 ° C. hot plate for 30 minutes, and then heated and cured at 250 ° C. for 60 minutes in a hot air box dryer. A coating film having a thickness of about 20 μm is formed. A scratch strength test with a pencil (former JIS K-5400) was performed using the obtained coating film plate, and the pencil hardness at which the coating film was not damaged was described.
(2) Adhesion test (cross cut test)
Each varnish was applied on an aluminum plate A1050P (dimensions: 1 mm × 50 mm × 150 mm), then cured on a hot plate at 80 ° C. for 30 minutes, and then cured by heating at 250 ° C. for 60 minutes in a hot air box dryer. Forms a coating of about 20 μm. 100 1-mm grids (10 × 10) were made with a cutter, and the peel test was performed 5 times with a cellophane tape, and the ratio of cross-cut grids (cross cut residual ratio:%) was examined.
(3) Mechanical properties (measurement of mechanical strength, elastic modulus and elongation)
Each varnish is heat-cured at 200 ° C. for 30 minutes to form a coating film having a thickness of about 20 μm, a width of 10 mm, and a length of 60 mm. The obtained coating film was subjected to a tensile test (JIS K-7113) using a tensile tester under conditions of a length between chucks of 20 mm and a tensile speed of 5 mm / min, and mechanical characteristics were obtained.
(4) Thermal characteristics 5 wt% weight reduction temperature: The temperature was increased by 10 ° C / min in an air stream using a TG-DTA measuring device manufactured by SEIKO, and the temperature at which the weight was reduced by 5% was measured from the initial stage.
Glass transition temperature: The glass transition temperature was measured by heating at 10 ° C./min in the extension mode of TMA measurement.
(5) Curing shrinkage A varnish-like mixed solution is applied to a glass plate by a casting method, cured on a hot plate at 80 ° C. for 30 minutes, and cured in a hot air box dryer at 250 ° C. for 60 minutes. A film with a thickness of 30 μm is cut off and peeled off at a size of 15 cm × 10 cm in a state of being attached to a glass plate, and then the area of the film after the cut-off is measured, and the area of the film in a state of being attached to the glass plate The shrinkage ratio of the area of the film after cutting and peeling was calculated.

  From the results of Table 1, it can be seen that in Comparative Example 1 using a varnish not blended with a polyamideimide resin, coating film cracking occurred during curing. Compared with Comparative Example 2 in which an epoxy resin is blended instead of a polyamideimide resin, in Examples 1 to 5 in which polyamideimide is blended with polyamic acid, a coating film excellent in tensile strength, elastic modulus and heat resistance is obtained. It can be seen that it is formed. Moreover, in Examples 1-5 in which polyamideimide is blended in polyamic acid, mechanical properties are compared with Comparative Example 3 in which varnish not blended with polyamideimide is cured at a temperature higher than that in Examples. Was found to be substantially declining and the film could be cured without shrinking. It is also possible to raise or lower the glass transition temperature by mixing polyamic acid or polyamideimide with different glass transition temperatures and mechanical properties, and the mechanical properties can be increased or decreased. It turns out that there exists an effect in controlling the characteristic of resin.

Claims (5)

  A heat resistant resin composition comprising 5 to 100 parts by weight of a polyamideimide resin having a number average molecular weight of 2,000 to 40,000 and 100 parts by weight of a polyamic acid having a number average molecular weight of 15,000 to 50,000.   The heat-resistant resin composition according to claim 1, wherein an amide group / imide group, which is a ratio of the total number of amide groups and the total number of imide groups of the polyamide-imide resin, is 37/63 to 70/30.   The polyamic acid is obtained by polyaddition reaction of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and the polyamideimide resin is an aromatic tricarboxylic acid anhydride and an aromatic diisocyanate or aromatic diamine. Polycondensation reaction product, polycondensation reaction product of aromatic tricarboxylic acid anhydride and dicarboxylic acid with aromatic diisocyanate or aromatic diamine, or aromatic tricarboxylic acid anhydride and tetracarboxylic acid dianhydride and aromatic diisocyanate or aromatic The heat-resistant resin composition according to claim 1, which is a polycondensation reaction product with an aliphatic diamine.   The coating material using the heat resistant resin composition in any one of Claims 1-3.   The paint according to claim 4, comprising 100 parts by weight of the polyamic acid, 5 to 100 parts by weight of the polyamideimide resin, and an organic solvent.