Method for producing polyimide varnish

Abstract

A method for producing a polyimide varnish, the method comprising: a polycondensation step for obtaining a reaction product (x) by polycondensation of one or more types of tetracarboxylic acid dianhydrides and one or more types of diamine compounds; a step for obtaining a dilution solvent (y) by bubbling an inert gas in an organic solvent; and a dilution step for mixing the reaction product (x) with a dilution solvent (y) to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less. Thus, a varnish which contains a solvent-soluble polyimide, is free from coloration, and has excellent colourlessness can be obtained.

Description

Technical Field

[0001] The invention relates to a method for preparing polyimide varnish. Background Art

[0002] Polyimide resins have excellent mechanical properties and heat resistance, and therefore various applications have been studied in the fields of electrical and electronic components. For example, it is expected that glass substrates used in image display devices such as liquid crystal displays and OLED displays will be replaced with polyimide film substrates, and polyimide resins that meet the performance requirements of optical materials have been developed.

[0003] As a raw material for easily producing a polyimide molded body represented by such a polyimide film, a varnish which is a solution of a polyimide soluble in a solvent is used. In order to improve the performance of the obtained polyimide molded body, polyimide varnishes are also studied.

[0004] For example, Patent Document 1 discloses a solvent-soluble alicyclic polyimide copolymer and a varnish obtained by imidizing a combination of 1,2,4,5-cyclohexanetetracarboxylic dianhydride, a specific dicarboxylic anhydride, and a specific alicyclic diamine at a specific charging ratio for the purpose of improving heat resistance, transparency, and toughness.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-045054 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] The varnish of the polyimide soluble in solvent is excellent in formability as mentioned above. In addition, polyimide resin has excellent property as mentioned above, but easily produces coloring such as yellowing when manufacturing. Recently, owing to also being used for optical material as mentioned above, higher colorlessness is required. Therefore, it is required to obtain the method for the varnish comprising the polyimide of solvent soluble type and excellent colorlessness.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a polyimide varnish which contains a solvent-soluble polyimide and is free of color and has excellent colorlessness.

[0011] Solutions for solving problems

[0012] The present inventors have found that the above-mentioned problems can be solved by polycondensing tetracarboxylic dianhydride and diamine and diluting the mixture with a diluting solvent obtained by bubbling an inert gas in an organic solvent in the production of a polyimide varnish, and have completed the present invention.

[0013] That is, the present invention relates to the following [1] to

[12] .

[0014] [1] A method for producing a polyimide varnish, comprising: a polycondensation step of subjecting one or more tetracarboxylic dianhydrides and one or more diamines to a polycondensation reaction to obtain a reaction product (x); a step of bubbling an inert gas in an organic solvent to obtain a dilution solvent (y); and a dilution step of mixing the reaction product (x) with the dilution solvent (y) to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less.

[0015] [2] The method for producing a polyimide varnish according to [1], wherein the inert gas is bubbled at a flow rate of 0.5 L / kg·min or more for 15 minutes or more.

[0016] [3] The method for producing a polyimide varnish according to [1] or [2], wherein the organic solvent is at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

[0017] [4] The method for producing a polyimide varnish according to any one of [1] to [3], wherein the inert gas is nitrogen gas.

[0018] [5] The method for producing a polyimide varnish according to any one of [1] to [4], wherein the temperature of the polycondensation reaction in the polycondensation step is 150 to 250°C.

[0019] [6] The method for producing a polyimide varnish according to any one of [1] to [5], wherein the polycondensation reaction in the polycondensation step is carried out in an organic solvent.

[0020] [7] The method for producing a polyimide varnish according to [6] above, wherein the dissolved oxygen concentration of the organic solvent used in the polycondensation reaction is 0.0016 mg / L or less.

[0021] [8] The method for producing a polyimide varnish according to any one of [1] to [7], wherein the tetracarboxylic dianhydride contains a compound represented by the following formula (1).

[0022]

[0023] [9] The method for producing a polyimide varnish according to any one of [1] to [8], wherein the diamine comprises a compound represented by the following general formula (2).

[0024]

[0025]

[10] The method for producing a polyimide varnish according to any one of [1] to [9], wherein the diamine comprises a compound represented by the following formula (3).

[0026]

[0027]

[11] The method for producing a polyimide varnish according to any one of [6] to

[10] , wherein the organic solvent used in the polycondensation reaction is obtained by bubbling an inert gas in the organic solvent.

[0028]

[12] The method for producing a polyimide varnish according to [9], wherein the diamine further comprises a compound represented by the following formula (3), and the molar ratio [(2) / (3)] of the compound represented by formula (2) to the compound represented by formula (3) is 5 / 95 to 40 / 60.

[0029]

[0030] Effects of the Invention

[0031] According to the present invention, there can be provided a method for producing a polyimide varnish which contains a solvent-soluble polyimide and is free of color and has excellent colorlessness. DETAILED DESCRIPTION

[0032] [Method for producing polyimide varnish]

[0033] The method for producing a polyimide varnish of the present invention comprises: a polycondensation step of subjecting one or more tetracarboxylic dianhydrides and one or more diamine compounds to a polycondensation reaction to obtain a reaction product (x); a step of bubbling an inert gas in an organic solvent to obtain a dilution solvent (y); and a dilution step of mixing the reaction product (x) with the dilution solvent (y) to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less.

[0034] <Polycondensation process>

[0035] The method for producing a polyimide varnish of the present invention firstly causes one or more tetracarboxylic dianhydrides and one or more diamine compounds to undergo a polycondensation reaction to obtain a reaction product (x).

[0036] The reaction product (x) contains the polyimide after polycondensation. By mixing with the dilution solvent (y) obtained in the next step, a polyimide varnish containing the polyimide obtained in this step can be obtained.

[0037] (Tetracarboxylic dianhydride)

[0038] The tetracarboxylic dianhydride used for polycondensation in this step is not particularly limited, but preferably contains alicyclic tetracarboxylic dianhydride, and more preferably contains a compound represented by the following formula (1). In addition, the tetracarboxylic dianhydride used for polycondensation in this step is preferably alicyclic tetracarboxylic dianhydride, and more preferably a compound represented by the following formula (1).

[0039] The ratio of the compound represented by the following formula (1) in the tetracarboxylic dianhydride used in this step is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 95 mol% or more. The upper limit of the ratio of the compound represented by the following formula (1) is not particularly limited, and can be 100 mol% or less.

[0040]

[0041] Examples of the alicyclic tetracarboxylic dianhydride include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyltetracarboxylic dianhydride, 5,5'-(1,4-phenylene)-bis[hexahydro-4,7-methanoisobenzofuran-1,3-dione], 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid-5,5',6,6'-dianhydride, and positional isomers thereof.

[0042] Among them, 1,2,4,5-cyclohexanetetracarboxylic dianhydride which is a compound represented by the above formula (1) is preferred.

[0043] By using alicyclic tetracarboxylic dianhydride, the obtained polyimide is soluble in solvent, has no coloration, and has excellent colorlessness. In particular, by using the compound represented by the above formula (1), the obtained polyimide is soluble in solvent, has no coloration, and has extremely excellent colorlessness.

[0044] The tetracarboxylic dianhydride used for polycondensation in this step may include tetracarboxylic dianhydride other than alicyclic tetracarboxylic dianhydride. Such tetracarboxylic dianhydride is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic dianhydride.

[0045] Examples of the aromatic tetracarboxylic dianhydride include biphenyltetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenonetetracarboxylic dianhydride.

[0046] As aliphatic tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride etc. are mentioned.

[0047] In this step, the tetracarboxylic dianhydride to be subjected to polycondensation may be one or more types, and may be one or two or more types.

[0048] It should be noted that, in the present specification, aromatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing one or more alicyclic rings and no aromatic ring, and aliphatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.

[0049] (Diamine)

[0050] The diamine used for polycondensation in this step is not particularly limited, but preferably contains an aromatic diamine, more preferably contains at least one selected from the group consisting of a compound represented by the following general formula (2) and a compound represented by the following formula (3), and further preferably contains a compound represented by the following general formula (2) and a compound represented by the following formula (3). In addition, the diamine used for polycondensation in this step is preferably an aromatic diamine, more preferably a compound represented by the following formula (2) and a compound represented by the following formula (3).

[0051] The total ratio of the compound represented by the following formula (2) and the compound represented by the following formula (3) in the diamine used in this step is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 95 mol% or more. The upper limit of the total ratio of the compound represented by the following formula (2) and the compound represented by the following formula (3) is not particularly limited, and can be 100 mol% or less.

[0052]

[0053] Examples of the aromatic diamine include 1-(4-aminophenyl)-1,3,3-trimethylphenylindaneamine, α,α'-bis(4-aminophenyl)-1,3-diisopropylbenzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4-aminophenyl-4-aminobenzoate, 2,2'-bis(trifluoromethyl)benzidine, 3,5-diaminobenzoic acid, 9,9-bis(4-aminophenyl)fluorene, 1,4-phenylenediamine, p-phenylenediamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'- Diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 1,4-bis(4-aminophenoxy)benzene, etc.

[0054] Among them, at least one selected from the group consisting of 1-(4-aminophenyl)-1,3,3-trimethylphenylindanamine as the compound represented by the above formula (2) and α,α′-bis(4-aminophenyl)-1,3-diisopropylbenzene as the compound represented by the above formula (3) is preferred.

[0055] By using an aromatic diamine, the obtained polyimide is soluble in a solvent, has no coloration, and has excellent colorlessness. In particular, by using any one or both of the compound represented by the aforementioned formula (2) and the compound represented by the aforementioned formula (3), the obtained polyimide is soluble in a solvent, has no coloration, and has extremely excellent colorlessness.

[0056] The 1-(4-aminophenyl)-1,3,3-trimethylphenylindaneamine as the compound represented by the aforementioned formula (2) is preferably at least one selected from the group consisting of 1-(4-aminophenyl)-1,3,3-trimethylphenylindane-6-amine and 1-(4-aminophenyl)-1,3,3-trimethylphenylindane-5-amine, and more preferably both 1-(4-aminophenyl)-1,3,3-trimethylphenylindane-6-amine and 1-(4-aminophenyl)-1,3,3-trimethylphenylindane-5-amine are used.

[0057] When both the compound represented by the above formula (2) and the compound represented by the above formula (3) are used as the diamine for polycondensation in this step, the molar ratio of the compound represented by the above formula (2) to the compound represented by the above formula (3) [(2) / (3)] is preferably 5 / 95 to 40 / 60, more preferably 5 / 95 to 30 / 70, and even more preferably 10 / 90 to 20 / 80.

[0058] The diamine used for polycondensation in this step may contain diamines other than aromatic diamines. Such diamines are not particularly limited, and examples thereof include alicyclic diamines and aliphatic diamines.

[0059] Examples of the alicyclic diamine include 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane.

[0060] Examples of the aliphatic diamine include ethylenediamine and hexamethylenediamine.

[0061] In this step, the diamine to be subjected to polycondensation may be one or more types, and may be one type or two or more types.

[0062] In the present specification, aromatic diamine refers to a diamine containing one or more aromatic rings, alicyclic diamine refers to a diamine containing one or more alicyclic rings and no aromatic ring, and aliphatic diamine refers to a diamine containing neither an aromatic ring nor an alicyclic ring.

[0063] (Polycondensation reaction)

[0064] The polycondensation step is a step of subjecting one or more tetracarboxylic dianhydrides and one or more diamines to a polycondensation reaction to obtain a reaction product (x). The polycondensation reaction in this step is preferably performed as follows.

[0065] The polycondensation reaction in the present polycondensation step is preferably carried out in an organic solvent.

[0066] The organic solvent used in the polycondensation reaction may be any solvent that can dissolve the generated polyimide, and examples thereof include aprotic solvents, phenolic solvents, etheric solvents, carbonate solvents, etc., and preferably at least one selected from the group consisting of aprotic solvents, phenolic solvents, etheric solvents and carbonate solvents.

[0067] Specific examples of the aprotic solvent include amide solvents such as cyclic amides and chain amides, phosphorus-containing amide solvents, sulfur-containing solvents, ketone solvents, and ester solvents including cyclic esters.

[0068] Among these, the organic solvent preferably comprises at least one selected from the group consisting of cyclic amides, chain amides and cyclic esters, more preferably comprises at least one selected from the group consisting of chain amides and cyclic esters, preferably comprises cyclic esters. In addition, the organic solvent is preferably selected from at least one selected from the group consisting of cyclic amides, chain amides and cyclic esters, more preferably selected from at least one selected from the group consisting of chain amides and cyclic esters, preferably cyclic esters.

[0069] Examples of the cyclic amide include N-methyl-2-pyrrolidone, N-methylcaprolactam, and 1,3-dimethylimidazolidinone, and N-methyl-2-pyrrolidone is preferred.

[0070] Examples of the chain amide include N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea.

[0071] Examples of the cyclic ester include γ-butyrolactone and γ-valerolactone.

[0072] As other ester solvents, acetic acid (2-methoxy-1-methylethyl ester) and the like can be mentioned.

[0073] Examples of the phosphorus-containing amide solvent include hexamethylphosphoramide and hexamethylphosphorus triamide.

[0074] Examples of the sulfur-containing solvent include dimethyl sulfone, dimethyl sulfoxide, and sulfolane.

[0075] Examples of the ketone solvent include acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone.

[0076] Specific examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol.

[0077] Specific examples of the ether solvent include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane.

[0078] Specific examples of the carbonate-based solvent include diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and propylene carbonate.

[0079] Among these specific organic solvents, the organic solvent preferably contains at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone, more preferably contains at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide, and further preferably contains γ-butyrolactone. In addition, the organic solvent is preferably at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone, more preferably at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide, and further preferably γ-butyrolactone.

[0080] The above organic solvents can be used alone or in combination of two or more.

[0081] The dissolved oxygen concentration of the organic solvent used in the polycondensation reaction is preferably 0.019 mg / L or less, more preferably 0.008 mg / L or less, further preferably 0.0016 mg / L or less, and further preferably less than 0.0016 mg / L. There is no restriction on the lower limit value, and it is preferred that the aforementioned organic solvent does not contain dissolved oxygen. There is no restriction on the method for reducing the dissolved oxygen concentration of the organic solvent, and it is preferred that the method for obtaining the dilution solvent (y) described later is the same as the method for bubbling an inert gas in the aforementioned organic solvent to obtain the organic solvent used in the polycondensation reaction.

[0082] The inert gas is preferably at least one selected from the group consisting of nitrogen gas and rare gases, more preferably nitrogen gas. Among the rare gases, argon gas is preferred.

[0083] As the bubbling condition, the inert gas is preferably bubbled at a flow rate of 0.5 L / kg·min or more, and more preferably at a flow rate of 0.6 L / kg·min or more. It should be noted that 0.5 L / kg·min means that 0.5 L of inert gas is bubbled in 1 minute relative to 1 kg of the organic solvent. There is no upper limit to the flow rate, but it is preferably bubbled at a flow rate of 1.0 L / kg·min or less.

[0084] In addition, preferably bubbling at a flow rate of 0.5L / kg·minute or more for 15 minutes or more, more preferably bubbling at a flow rate of 0.5L / kg·minute or more for 20 minutes or more, further preferably bubbling at a flow rate of 0.5L / kg·minute or more for 30 minutes or more, and further preferably bubbling at a flow rate of 0.5L / kg·minute or more for 50 minutes or more. There is no upper limit to the bubbling time, but from the viewpoint of efficiency, it is preferably bubbling for less than 10 hours, more preferably bubbling for less than 3 hours.

[0085] In addition, it is more preferred to bubble for more than 15 minutes at a flow rate of 0.6L / kg·minute, further preferably for more than 20 minutes at a flow rate of 0.6L / kg·minute, further preferably for more than 30 minutes at a flow rate of 0.6L / kg·minute, and further preferably for more than 50 minutes at a flow rate of 0.6L / kg·minute. There is no upper limit to the bubbling time, but from the viewpoint of efficiency, it is preferably bubbled for less than 10 hours, more preferably for less than 3 hours.

[0086] In this step, the method for polycondensing tetracarboxylic dianhydride and diamine is not particularly limited, and a known method can be used.

[0087] Specific reaction methods include: (1) a method in which a solution containing a diamine and an organic solvent and tetracarboxylic dianhydride are added to a reactor, stirred at 10 to 110° C. for 0.5 to 30 hours as required, and then the temperature is raised to carry out a polycondensation reaction; (2) a method in which a solution containing a diamine and an organic solvent and tetracarboxylic dianhydride are added to a reactor, and the temperature is immediately raised to carry out a polycondensation reaction.

[0088] In this step, the charging amount ratio of tetracarboxylic dianhydride and diamine used for producing the polyimide resin is preferably 0.9 to 1.1 mol of diamine per 1 mol of tetracarboxylic dianhydride.

[0089] In the polycondensation reaction, water is generated by imidization, so it is preferable to carry out the reaction while removing the water generated during the production using a Dean-Stark apparatus, etc. By carrying out such an operation, the degree of polymerization and the imidization ratio can be further increased.

[0090] In the above-mentioned imidization reaction, a known imidization catalyst can be used. Examples of the imidization catalyst include a base catalyst and an acid catalyst.

[0091] Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-methylpyridine, β-methylpyridine, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogen carbonate, and sodium hydrogen carbonate.

[0092] Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. The imidization catalysts may be used alone or in combination of two or more.

[0093] Among the above, from the viewpoint of operability, a base catalyst is preferred, an organic base catalyst is more preferred, at least one selected from triethylamine and triethylenediamine is further preferred, and addition of both triethylamine and triethylenediamine is further preferred.

[0094] From the viewpoint of reaction rate and gelation suppression, the temperature of the polycondensation reaction in the polycondensation step is preferably 120 to 250° C., more preferably 150 to 250° C., and even more preferably 160 to 200° C. The reaction time is preferably 0.5 to 10 hours after the start of distillation of generated water.

[0095] In addition, the present polycondensation step is preferably performed under the aforementioned inert gas atmosphere.

[0096] The concentration of the polyimide in the obtained reaction product (x) is usually in the range of 1 to 50% by mass, preferably 3 to 35% by mass, and more preferably 5 to 30% by mass.

[0097] From the viewpoint of the mechanical properties of the obtained polyimide, the weight average molecular weight (Mw) of the polyimide obtained in this process is 200,000 or more, preferably 300,000 or more, and more preferably 400,000 or more. In addition, there is no upper limit, preferably 1,000,000 or less, more preferably 700,000 or less. In addition, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. It should be noted that the weight average molecular weight and number average molecular weight of the polyimide can be obtained by using the standard polystyrene (PS) conversion value measured based on gel filtration chromatography.

[0098] In this polycondensation step, a terminal blocking agent may be used in addition to the above-mentioned tetracarboxylic dianhydride and diamine.

[0099] As the end-capping agent, monoamines or dicarboxylic acids are preferred. The amount of the end-capping agent introduced is preferably 0.0001 to 0.1 moles, particularly preferably 0.001 to 0.06 moles, relative to 1 mole of the tetracarboxylic acid component. As the monoamine end-capping agent, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are preferred. Among them, benzylamine and aniline can be used appropriately. As a dicarboxylic acid end-capping agent, dicarboxylic acids are preferred, and a part of them can also be closed-loop. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are recommended. Among them, phthalic acid and phthalic anhydride can be used appropriately.

[0100] <Step of Obtaining a Dilution Solvent (y)>

[0101] The method for producing a polyimide varnish of the present invention comprises: the polycondensation step, a step of bubbling an inert gas in an organic solvent to obtain a dilution solvent (y), and a dilution step of mixing the reaction product (x) and the dilution solvent (y) to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less.

[0102] The dilution solvent (y) used in the subsequent dilution step can be obtained by bubbling an inert gas in an organic solvent.

[0103] The organic solvent used as the dilution solvent (y) is preferably the same as the organic solvent used in the aforementioned polycondensation step. The organic solvent used as the dilution solvent (y) is capable of dissolving the polyimide obtained in the aforementioned polycondensation step, and includes: aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, etc., preferably at least one selected from the group consisting of aprotic solvents, phenolic solvents, ether solvents and carbonate solvents.

[0104] Specific examples of the aprotic solvent include amide solvents such as cyclic amides and chain amides, phosphorus-containing amide solvents, sulfur-containing solvents, ketone solvents, and ester solvents including cyclic esters.

[0105] Among these, the organic solvent preferably comprises at least one selected from the group consisting of cyclic amides, chain amides and cyclic esters, more preferably comprises at least one selected from the group consisting of chain amides and cyclic esters, preferably comprises cyclic esters. In addition, the organic solvent is preferably selected from at least one selected from the group consisting of cyclic amides, chain amides and cyclic esters, more preferably selected from at least one selected from the group consisting of chain amides and cyclic esters, preferably cyclic esters.

[0106] Examples of the cyclic amide include N-methyl-2-pyrrolidone, N-methylcaprolactam, and 1,3-dimethylimidazolidinone, and N-methyl-2-pyrrolidone is preferred.

[0107] Examples of the chain amide include N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea.

[0108] Examples of the cyclic ester include γ-butyrolactone and γ-valerolactone.

[0109] As other ester solvents, acetic acid (2-methoxy-1-methylethyl ester) and the like can be mentioned.

[0110] Examples of the phosphorus-containing amide solvent include hexamethylphosphoramide and hexamethylphosphorus triamide.

[0111] Examples of the sulfur-containing solvent include dimethyl sulfone, dimethyl sulfoxide, and sulfolane.

[0112] Examples of the ketone solvent include acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone.

[0113] Specific examples of the phenolic solvent include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol.

[0114] Specific examples of the ether solvent include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane.

[0115] Specific examples of the carbonate-based solvent include diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and propylene carbonate.

[0116] Among these specific organic solvents, the organic solvent preferably contains at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone, more preferably contains at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide, and further preferably contains γ-butyrolactone. In addition, the organic solvent is preferably at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide and N-methyl-2-pyrrolidone, more preferably at least one selected from the group consisting of γ-butyrolactone and N,N-dimethylacetamide, and further preferably γ-butyrolactone.

[0117] The above organic solvents can be used alone or in combination of two or more.

[0118] The inert gas used when bubbling the inert gas in the organic solvent is preferably at least one selected from the group consisting of nitrogen gas and rare gases, more preferably nitrogen gas. Among the rare gases, argon gas is preferred.

[0119] As the bubbling condition, the inert gas is preferably bubbled at a flow rate of 0.5 L / kg·min or more, and more preferably at a flow rate of 0.6 L / kg·min or more. It should be noted that 0.5 L / kg·min means that 0.5 L of inert gas is bubbled in 1 minute relative to 1 kg of the organic solvent. There is no upper limit to the flow rate, but it is preferably bubbled at a flow rate of 1.0 L / kg·min or less.

[0120] In addition, preferably bubbling at a flow rate of 0.5L / kg·minute or more for 15 minutes or more, more preferably bubbling at a flow rate of 0.5L / kg·minute or more for 20 minutes or more, further preferably bubbling at a flow rate of 0.5L / kg·minute or more for 30 minutes or more, and further preferably bubbling at a flow rate of 0.5L / kg·minute or more for 50 minutes or more. There is no upper limit to the bubbling time, but from the viewpoint of efficiency, it is preferably bubbling for less than 10 hours, more preferably bubbling for less than 3 hours.

[0121] In addition, it is more preferred to bubble for more than 15 minutes at a flow rate of 0.6L / kg·minute, further preferably for more than 20 minutes at a flow rate of 0.6L / kg·minute, further preferably for more than 30 minutes at a flow rate of 0.6L / kg·minute, and further preferably for more than 50 minutes at a flow rate of 0.6L / kg·minute. The upper limit of the bubbling time is not particularly limited, but from the viewpoint of efficiency, it is preferably bubbled for less than 10 hours, and more preferably for less than 3 hours.

[0122] The dilution solvent (y) obtained as described above is an organic solvent with a reduced dissolved oxygen concentration, and the dissolved oxygen concentration of the dilution solvent (y) is preferably 0.019 mg / L or less, more preferably 0.008 mg / L or less, further preferably 0.0016 mg / L or less, and further preferably less than 0.0016 mg / L. The lower limit is not limited, and the dilution solvent (y) preferably does not contain dissolved oxygen.

[0123] When producing the polyimide varnish, by using a diluting solvent (y) obtained by bubbling an inert gas in an organic solvent, a varnish containing a solvent-soluble polyimide and having no color and excellent colorlessness can be obtained.

[0124] <Dilution process>

[0125] In the dilution step, the reaction product (x) obtained in the polycondensation step is mixed with the dilution solvent (y) obtained by bubbling an inert gas in an organic solvent in the previous step to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less.

[0126] In this step, the method of mixing the reaction product (x) and the diluting solvent (y) is not limited, and it is preferably carried out under an inert atmosphere. As the inert gas used in this step, it is preferably at least one selected from the group consisting of nitrogen and rare gases, and more preferably nitrogen. Among the rare gases, argon is preferred.

[0127] The dissolved oxygen concentration of the polyimide solution obtained in this process is 0.23 mg / L or less. From the viewpoint of obtaining a non-colored, colorless varnish, the dissolved oxygen concentration of the polyimide solution is preferably 0.12 mg / L or less, more preferably 0.08 mg / L or less, further preferably 0.07 mg / L or less, and further preferably less than 0.07 mg / L. There is no lower limit, and from the viewpoint of efficiency, the dissolved oxygen concentration of the polyimide solution is preferably 0.007 mg / L or more. The dissolved oxygen concentration can be measured by the method described in the examples.

[0128] The polyimide solution obtained in this step has polyimide uniformly dissolved therein, and its polyimide concentration (solid content) is preferably 5 to 40% by mass, more preferably 10 to 30% by mass. The viscosity (25° C.) of the polyimide solution is preferably 1 to 200 Pa·s, more preferably 1 to 100 Pa·s.

[0129] The polyimide solution obtained in this step can be used directly as a polyimide varnish, and the concentration can be adjusted by adding or removing an organic solvent. However, from the viewpoint of the colorlessness of the obtained polyimide varnish, the concentration is preferably adjusted under an inert atmosphere, and the organic solvent preferably used for further dilution is an organic solvent with a low dissolved oxygen concentration.

[0130] (Polyimide)

[0131] The polyimide solution obtained in this step contains a polyimide. The polyimide contains a structural unit derived from the above-mentioned tetracarboxylic dianhydride and a structural unit derived from the above-mentioned diamine.

[0132] Specifically, the polyimide preferably comprises a structural unit derived from an alicyclic tetracarboxylic dianhydride, and more preferably comprises a structural unit derived from a compound represented by the following formula (1). The ratio of the structural unit derived from the compound represented by the following formula (1) in the structural unit derived from the tetracarboxylic dianhydride is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 95 mol% or more. The upper limit of the ratio of the structural unit derived from the compound represented by the following formula (1) is not particularly limited, and can be 100 mol% or less.

[0133]

[0134] By including the compound represented by the above formula (1), the obtained polyimide is soluble in a solvent and has no coloration and is extremely excellent in colorlessness.

[0135] As the structural unit derived from tetracarboxylic dianhydride, the structural unit derived from tetracarboxylic dianhydride other than the structural unit derived from alicyclic tetracarboxylic dianhydride may also be included. As such a structural unit derived from tetracarboxylic dianhydride, there is no particular limitation, and the structural unit derived from aromatic tetracarboxylic dianhydride and the structural unit derived from aliphatic tetracarboxylic dianhydride can be listed.

[0136] The structural unit derived from tetracarboxylic dianhydride may be one or more types, and may be one type or two or more types.

[0137] The polyimide preferably contains a structural unit derived from an aromatic diamine, more preferably contains at least one selected from the group consisting of a structural unit derived from a compound represented by the following formula (2) and a structural unit derived from a compound represented by the following formula (3), and further preferably contains a structural unit derived from a compound represented by the following formula (2) and a structural unit derived from a compound represented by the following formula (3). The total ratio of the structural unit derived from the compound represented by the following formula (2) and the structural unit derived from the compound represented by the following formula (3) in the structural unit derived from the diamine is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 95 mol% or more. The upper limit of the total ratio of the structural unit derived from the compound represented by the following formula (2) and the structural unit derived from the compound represented by the following formula (3) is not particularly limited, and it can be 100 mol% or less.

[0138]

[0139] By containing either or both of the structural unit derived from the compound represented by the above formula (2) and the structural unit derived from the compound represented by the above formula (3), the polyimide is soluble in a solvent and has no color and is extremely excellent in colorlessness.

[0140] When the compound comprises both structural units derived from the compound represented by the aforementioned formula (2) and structural units derived from the compound represented by the aforementioned formula (3), the molar ratio of the structural units derived from the compound represented by the aforementioned formula (2) to the structural units derived from the compound represented by the aforementioned formula (3) [(2) / (3)] is preferably 5 / 95 to 40 / 60, more preferably 5 / 95 to 30 / 70, and further preferably 10 / 90 to 20 / 80.

[0141] The structural unit derived from diamine may contain a structural unit derived from diamine other than the structural unit derived from aromatic diamine. Such a structural unit derived from diamine is not particularly limited, and examples thereof include a structural unit derived from alicyclic diamine and a structural unit derived from aliphatic diamine.

[0142] The structural unit derived from diamine may be one or more types, and may be one type or two or more types.

[0143] [Polyimide varnish]

[0144] Provided is a method for producing a polyimide varnish, wherein the polyimide varnish obtained by the above-mentioned production method contains a solvent-soluble polyimide, and the production method can obtain a varnish with no coloration and excellent colorlessness.

[0145] The polyimide varnish contains polyimide and an organic solvent.

[0146] As the polyimide, the above-mentioned polyimide is preferable.

[0147] The organic solvent contained in the polyimide varnish is the same as the organic solvent used in the aforementioned dilution step. The polyimide solution obtained in the aforementioned dilution step can be used directly as the polyimide varnish, and the polyimide solution obtained in the aforementioned dilution step can be used directly as the polyimide varnish by adjusting the polyimide concentration (solid content) suitable for the polyimide varnish in the dilution step.

[0148] The dissolved oxygen concentration of the polyimide varnish is preferably 0.23 mg / L or less, more preferably 0.12 mg / L or less, further preferably 0.08 mg / L or less, further preferably 0.07 mg / L or less, and particularly preferably less than 0.07 mg / L from the viewpoint of colorlessness. The lower limit is not limited, but from the viewpoint of efficiency, the dissolved oxygen concentration of the polyimide varnish is preferably 0.007 mg / L or more. The dissolved oxygen concentration can be measured by the method described in the Examples.

[0149] The polyimide varnish has polyimide uniformly dissolved therein, and the polyimide concentration (solid content) thereof is preferably 5 to 40% by mass, more preferably 10 to 30% by mass. The viscosity (25° C.) of the polyimide varnish is preferably 1 to 200 Pa·s, more preferably 1 to 100 Pa·s.

[0150] In addition, the polyimide varnish may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, defoamers, fluorescent brighteners, crosslinking agents, polymerization initiators, and photosensitizers within a range that does not impair the effects of the present invention.

[0151] The polyimide varnish obtained by the production method of the present invention is suitable for use as a raw material for various components such as color filters, flexible displays, semiconductor components, optical components, etc. The polyimide varnish obtained by the production method of the present invention is particularly suitable for use as a raw material for image display devices such as liquid crystal displays and OLED displays.

[0152] Example

[0153] The present invention is specifically described below by way of examples. However, the present invention is not limited by these examples.

[0154] Evaluation of the varnishes obtained in Examples and Comparative Examples was performed by the following methods.

[0155] (1) Dissolved oxygen concentration

[0156] The dissolved oxygen concentration of the polyimide varnish obtained in each Example and each Comparative Example and the organic solvent used for the polycondensation reaction was measured using a dissolved oxygen meter "DO Meter B-506" (manufactured by Iijima Electronics Industry Co., Ltd.).

[0157] (2) Yellowness Index (Yellowness, YI)

[0158] For the yellowness (YI) of the polyimide varnish obtained in the examples and comparative examples, the polyimide varnish was put into a measuring unit with a unit length (measurement thickness) of 10 mm, and measured using a color / turbidity simultaneous measuring device "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd. The smaller the yellowness (YI), the better the colorlessness. For the polyimide varnish used for the measurement of the yellowness (YI), a polyimide varnish was used that was added with a diluting solvent and confirmed to be uniform and then stored at room temperature (25°C) for 16 hours.

[0159] <Manufacturing of polyimide varnish>

[0160] Example 1

[0161] In a 2 L 5-necked glass round-bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, 156.748 g (0.455 mol) of α,α'-bis(4-aminophenyl)-1,3-diisopropylbenzene (a compound represented by the formula (3), manufactured by MITSUI CHEMICALS, INC.), 25.972 g (0.0975 mol) of a mixture of 1-(4-aminophenyl)-1,3,3-trimethylphenylindan-6-amine / 1-(4-aminophenyl)-1,3,3-trimethylphenylindan-5-amine (a compound represented by the formula (2), manufactured by Nippon Junryo Chemical Co., Ltd.), and 346.526 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were stirred at 100 rpm at a temperature of 70°C in a nitrogen atmosphere to obtain a solution. 145.711 g (0.650 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (a compound represented by formula (1), manufactured by Mitsubishi Gas Chemical Co., Ltd.), 86.632 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation), 32.887 g of triethylamine (manufactured by Kanto Chemical Co., Ltd.) as a catalyst, and 0.146 g of triethylenediamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added thereto, and then heated in an oil bath to raise the temperature in the reaction system to 180° C. The components removed by distillation were collected, and the temperature in the reaction system was maintained at 180° C. for 5 hours to carry out a polycondensation reaction, thereby obtaining a reaction product (x1).

[0162] It should be noted that the dissolved oxygen concentration of γ-butyrolactone as the organic solvent used in the polycondensation reaction was less than 0.05%.

[0163] Nitrogen gas was bubbled into γ-butyrolactone at a flow rate of 0.625 L / kg·min for 60 minutes to obtain a dilution solvent (y1) having a reduced dissolved oxygen concentration.

[0164] 1323.904 g of the dilution solvent (y1) was added to the reaction product (x1) to obtain a polyimide varnish having a solid content concentration of 20% by mass in which polyimide was uniformly dissolved.

[0165] The dissolved oxygen concentration of the obtained polyimide varnish was 0.0586 mg / L. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0166] Example 2

[0167] A polycondensation reaction was carried out in the same manner as in Example 1 to obtain a reaction product (x1).

[0168] Nitrogen gas was bubbled into γ-butyrolactone at a flow rate of 0.625 L / kg·min for 20 minutes to obtain a dilution solvent (y2) having a reduced dissolved oxygen concentration.

[0169] 1323.904 g of the diluting solvent (y2) was added to the reaction product (x1) to obtain a polyimide varnish having a solid content concentration of 20% by mass in which polyimide was uniformly dissolved.

[0170] The dissolved oxygen concentration of the obtained polyimide varnish was 0.0970 mg / L. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0171] Example 3

[0172] A polycondensation reaction was carried out in the same manner as in Example 1 to obtain a reaction product (x1).

[0173] Nitrogen gas was bubbled into γ-butyrolactone at a flow rate of 0.625 L / kg·min for 15 minutes to obtain a dilution solvent (y3) having a reduced dissolved oxygen concentration.

[0174] 1323.904 g of the diluting solvent (y3) was added to the reaction product (x1) to obtain a polyimide varnish having a solid content concentration of 20% by mass in which polyimide was uniformly dissolved.

[0175] The dissolved oxygen concentration of the obtained polyimide varnish was 0.2215 mg / L. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0176] Comparative Example 1

[0177] A polycondensation reaction was carried out in the same manner as in Example 1 to obtain a reaction product (x1).

[0178] Nitrogen gas was bubbled in γ-butyrolactone at a flow rate of 0.625 L / kg·min for 10 minutes to obtain a dilution solvent (y4) having a reduced dissolved oxygen concentration.

[0179] 1323.904 g of the diluting solvent (y4) was added to the reaction product (x1) to obtain a polyimide varnish having a solid content concentration of 20% by mass in which polyimide was uniformly dissolved.

[0180] The dissolved oxygen concentration of the obtained polyimide varnish was 0.3228 mg / L. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0181] Comparative Example 2

[0182] A polycondensation reaction was carried out in the same manner as in Example 1 to obtain a reaction product (x1).

[0183] γ-Butyrolactone was used as the diluting solvent (y5) without bubbling with nitrogen gas.

[0184] 1323.904 g of the diluting solvent (y5) was added to the reaction product (x1) to obtain a polyimide varnish having a solid content concentration of 20% by mass in which polyimide was uniformly dissolved.

[0185] The dissolved oxygen concentration of the obtained polyimide varnish was 0.7139 mg / L. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0186] [Table 1]

[0187] Table 1

[0188]

[0189] *) The dissolved oxygen concentration of the organic solvent in the polycondensation reaction is less than 0.0015 mg / L.

[0190] As shown in Table 1, it can be seen that the polyimide varnish obtained by the production method of the present invention is uniform and has low yellowness, so it contains a solvent-soluble polyimide, is non-colored, and has excellent colorlessness. Therefore, the polyimide varnish obtained by the production method of the present invention can be used for materials of image display devices and the like.

Claims

1. A method for producing a polyimide varnish, comprising: a polycondensation step of subjecting one or more tetracarboxylic dianhydrides and one or more diamines to a polycondensation reaction to obtain a reaction product (x); A step of bubbling an inert gas in an organic solvent to obtain a dilution solvent (y); and In the dilution step, the reaction product (x) is mixed with a dilution solvent (y) to obtain a polyimide solution having a dissolved oxygen concentration of 0.23 mg / L or less.

2. The method for producing a polyimide varnish according to claim 1, wherein: The inert gas is bubbled at a flow rate of 0.5 L / kg·min or more for 15 minutes or more.

3. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The organic solvent is at least one selected from the group consisting of γ-butyrolactone, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

4. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The inert gas is nitrogen.

5. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The temperature of the polycondensation reaction in the polycondensation step is 150 to 250°C.

6. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The polycondensation reaction in the polycondensation step is carried out in an organic solvent.

7. The method for producing a polyimide varnish according to claim 6, wherein: The dissolved oxygen concentration of the organic solvent used in the polycondensation reaction is 0.0016 mg / L or less.

8. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The tetracarboxylic dianhydride comprises a compound represented by the following formula (1):

9. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The diamine comprises a compound represented by the following general formula (2):

10. The method for producing a polyimide varnish according to claim 1 or 2, wherein: The diamine comprises a compound represented by the following formula (3):

11. The method for producing a polyimide varnish according to claim 6, wherein: The organic solvent used in the polycondensation reaction is obtained by bubbling an inert gas in the organic solvent.

12. The method for producing a polyimide varnish according to claim 9, wherein: The diamine further comprises a compound represented by the following formula (3), and the molar ratio [(2) / (3)] of the compound represented by formula (2) to the compound represented by formula (3) is 5 / 95 to 40 / 60,

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