Method for producing polyimide

Abstract

A method for producing a polyimide, the method comprising: a step 1 in which a diamine solution is obtained by dissolving a diamine in an organic solvent, and a tetracarboxylic dianhydride is added to the diamine solution and mixed to form a uniform solution; and a step 2 in which the tetracarboxylic dianhydride and the diamine are polycondensed. In the step 1, the diamine solution is adjusted so that the temperature of the diamine solution does not exceed 100 DEG C from the start of the addition of the tetracarboxylic acid dianhydride until the solution becomes a uniform solution. A polyimide having excellent colourless properties and a varnish having a sufficient viscosity required for coating can be obtained.

Description

Technical Field

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

[0002] Polyimide resin has excellent mechanical properties and heat resistance, so various uses have been studied in the fields of electrical and electronic components. For example, it is expected that the glass substrate used in image display devices such as liquid crystal displays and OLED displays will be replaced with a polyimide film substrate, and the development of polyimide resins that meet the performance of optical materials is underway. In particular, recently, the development of displays that are lightweight and flexible and can be bent or rolled up is being actively carried out. In this field, it is required that resin materials with excellent mechanical properties such as toughness are also excellent on the basis of transparency and heat resistance, and research is underway.

[0003] For example, Patent Document 1 discloses a solvent-soluble alicyclic polyimide copolymer 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.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-045054 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] As a raw material for easily manufacturing a polyimide molded body represented by a polyimide film, a varnish as a polyimide solution soluble in a solvent is used. Solvent-soluble polyimide is obtained by coating and drying the polyimide film, but sufficient viscosity is required during coating. In addition, polyimide resin has excellent properties as described above, but is prone to coloring such as yellowing during manufacture. As described above, since it is also used for optical materials, higher colorlessness is required. Therefore, it is required to obtain a method for a polyimide comprising a solvent-soluble polyimide and excellent colorlessness.

[0009] 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 having no coloration and excellent colorlessness, which can obtain a varnish having a sufficient viscosity required for coating.

[0010] Solutions for solving problems

[0011] The present inventors have found that the above-mentioned problems can be solved by mixing tetracarboxylic dianhydride with a diamine solution at a specific temperature range before polycondensation in the production of a polyimide, and have completed the invention.

[0012] That is, the present invention relates to the following [1] to

[14] .

[0013] [1] A method for producing a polyimide, comprising: step 1, dissolving a diamine in an organic solvent to obtain a diamine solution, adding tetracarboxylic dianhydride to the diamine solution and mixing to obtain a uniform solution; and step 2, polycondensing the tetracarboxylic dianhydride and the diamine; in step 1, the diamine solution is adjusted so that the temperature does not exceed 100° C. from the addition of the tetracarboxylic dianhydride until the uniform solution is obtained.

[0014] [2] The method for producing a polyimide according to [1], wherein in step 1, the temperature of the diamine solution at the start of addition of tetracarboxylic dianhydride is 60 to 85°C.

[0015] [3] The method for producing a polyimide 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.

[0016] [4] The method for producing a polyimide according to any one of [1] to [3], wherein a catalyst is added after step 1 and before polycondensation.

[0017] [5] The method for producing a polyimide according to [4], wherein the catalyst is at least one selected from the group consisting of triethylamine and triethylenediamine.

[0018] [6] The method for producing a polyimide according to any one of [1] to [5], wherein the temperature of the polycondensation in step 2 is 150 to 250°C.

[0019] [7] The method for producing a polyimide according to any one of [1] to [6], wherein the tetracarboxylic dianhydride contains a compound represented by the following formula (1).

[0020]

[0021] [8] The method for producing a polyimide according to any one of [1] to [7], wherein the diamine comprises a compound represented by the following general formula (2).

[0022]

[0023] [9] The method for producing a polyimide according to any one of [1] to [8], wherein the diamine comprises a compound represented by the following formula (3).

[0024]

[0025]

[10] The method for producing a polyimide according to any one of [1] to [9], wherein in step 1, the lower limit of the maximum temperature reached from the start of the addition of tetracarboxylic dianhydride until a uniform solution is obtained is 80° C. or more.

[0026]

[11] The method for producing a polyimide according to any one of [1] to

[10] , wherein in step 1, the time from the addition of tetracarboxylic dianhydride to the formation of a uniform solution is 10 minutes to 10 hours.

[0027]

[12] The method for producing a polyimide according to any one of [1] to

[11] , wherein step 2 is a step of obtaining a polyimide solution.

[0028]

[13] The method for producing a polyimide according to [1], wherein in step 1, the temperature of the diamine solution at the start of addition of tetracarboxylic dianhydride is 55° C. or higher.

[0029]

[14] The method for producing a polyimide according to

[12] , wherein the polyimide concentration (solid content) of the polyimide solution is 1 to 50% by mass, and the viscosity (25° C.) of the polyimide solution is 1 to 200 Pa·s.

[0030] Effects of the Invention

[0031] According to the present invention, a varnish having a sufficient viscosity for coating can be obtained, and a method for producing a polyimide having no coloration and excellent colorlessness can be provided. DETAILED DESCRIPTION

[0032] [Method for producing polyimide]

[0033] The method for producing a polyimide of the present invention comprises: step 1, dissolving a diamine in an organic solvent to obtain a diamine solution, adding tetracarboxylic dianhydride to the diamine solution and mixing to prepare a uniform solution; and step 2, polycondensing the tetracarboxylic dianhydride and the diamine; in step 1, the diamine solution is adjusted in such a manner that the temperature does not exceed 100° C. from the addition of the tetracarboxylic dianhydride until the uniform solution is obtained.

[0034] <Step 1 (Raw Material Dissolving Step)>

[0035] The method for producing a polyimide of the present invention first comprises the following step 1: dissolving a diamine in an organic solvent to obtain a diamine solution, adding tetracarboxylic dianhydride to the diamine solution and mixing to obtain a uniform solution, wherein in step 1, the diamine solution is adjusted so that the temperature does not exceed 100° C. from the addition of tetracarboxylic dianhydride until the uniform solution is obtained.

[0036] (Diamine)

[0037] The diamine used in the diamine solution in this step is not particularly limited, and 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 in the diamine solution in this step is preferably an aromatic diamine, more preferably a compound represented by the following general formula (2) and a compound represented by the following formula (3).

[0038] The ratio of the aromatic diamine 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 ratio of the aromatic diamine is not particularly limited, and may be 100 mol% or less.

[0039] 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.

[0040]

[0041] 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.

[0042] Among these, 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.

[0043] 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.

[0044] 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.

[0045] When both the compound represented by the above formula (2) and the compound represented by the above formula (3) are used as the diamine used 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 50 / 50, more preferably 10 / 90 to 45 / 55, and even more preferably 20 / 80 to 40 / 60.

[0046] The diamine used 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.

[0047] Examples of the alicyclic diamine include 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane.

[0048] Examples of the aliphatic diamine include ethylenediamine and hexamethylenediamine.

[0049] The diamine used in this step may be one or more types, and may be one type or two or more types.

[0050] 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.

[0051] (Organic Solvent)

[0052] The organic solvent used in the diamine solution in this step is not particularly limited, as long as it can dissolve the diamine and tetracarboxylic dianhydride as raw materials and the polyimide as the product, and examples thereof include: 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.

[0053] 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.

[0054] 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.

[0055] Examples of the cyclic amide include N-methyl-2-pyrrolidone, N-methylcaprolactam, and 1,3-dimethylimidazolidinone, and N-methyl-2-pyrrolidone is preferred.

[0056] Examples of the chain amide include N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea.

[0057] Examples of the cyclic ester include γ-butyrolactone and γ-valerolactone.

[0058] As other ester solvents, acetic acid (2-methoxy-1-methylethyl ester) and the like can be mentioned.

[0059] Examples of the phosphorus-containing amide solvent include hexamethylphosphoramide and hexamethylphosphorus triamide.

[0060] Examples of the sulfur-containing solvent include dimethyl sulfone, dimethyl sulfoxide, and sulfolane.

[0061] Examples of the ketone solvent include acetone, methyl ethyl ketone, cyclohexanone, and methylcyclohexanone.

[0062] 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.

[0063] 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.

[0064] Specific examples of the carbonate-based solvent include diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and propylene carbonate.

[0065] 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, 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, preferably γ-butyrolactone.

[0066] The above organic solvents can be used alone or in combination of two or more.

[0067] (Tetracarboxylic dianhydride)

[0068] The tetracarboxylic dianhydride added to the diamine solution 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 added to the diamine solution in this step is preferably alicyclic tetracarboxylic dianhydride, and more preferably a compound represented by the following formula (1).

[0069] The ratio of alicyclic tetracarboxylic dianhydride 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 alicyclic tetracarboxylic dianhydride is not particularly limited, and can be 100 mol% or less.

[0070] 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.

[0071]

[0072] 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.

[0073] Among them, 1,2,4,5-cyclohexanetetracarboxylic dianhydride which is a compound represented by the above formula (1) is preferred.

[0074] 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.

[0075] The tetracarboxylic dianhydride used in this step may contain 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.

[0076] 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.

[0077] As aliphatic tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride etc. are mentioned.

[0078] The tetracarboxylic dianhydride used in this step may be one or more types, and may be one or two or more types.

[0079] 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.

[0080] (Raw material dissolution method)

[0081] First, a diamine is dissolved in an organic solvent to obtain a diamine solution. The diamine solution can be obtained by mixing the diamine and the organic solvent.

[0082] The concentration of the diamine in the diamine solution is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and further preferably 30 to 45% by mass.

[0083] The temperature for dissolving the diamine in the organic solvent is not limited, but is preferably 100° C. or lower. It is preferably 55° C. or higher. It is more preferably 60 to 85° C., and even more preferably 65 to 80° C. When the temperature is within the above range, cooling or heating is not required when adding tetracarboxylic dianhydride, which is preferred.

[0084] When dissolving the diamine in the organic solvent, it is preferably carried out under an inert gas atmosphere. The inert gas 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.

[0085] Next, tetracarboxylic dianhydride is added to the diamine solution and mixed to prepare a uniform solution. At this time, the diamine solution is adjusted so that it does not exceed 100° C. from the start of the addition of tetracarboxylic dianhydride until the solution becomes uniform. By adjusting the temperature in this way, the obtained polyimide is non-colored and excellent in colorlessness, and the varnish thereof has a sufficient viscosity required for coating.

[0086] The reason why the above-mentioned polyimide is obtained by the production method of the present invention is not clear, but is considered as follows.

[0087] It is believed that if tetracarboxylic dianhydride is added at a temperature not exceeding 100°C, the imidization reaction between the added tetracarboxylic dianhydride and the diamine is suppressed until the tetracarboxylic dianhydride is completely dissolved, and condensation water is not generated. It is believed that the hydrolysis of the tetracarboxylic dianhydride is suppressed, so that the subsequent polycondensation reaction proceeds rapidly, and a polyimide solution (varnish) having a sufficient viscosity and a polyimide having excellent colorlessness and no coloration can be obtained.

[0088] The “uniform solution” is a state in which tetracarboxylic dianhydride is completely dissolved. That is, when the total amount of tetracarboxylic dianhydride is added to the diamine solution and mixed, the solution is considered to be a “uniform solution” when there is no change in the appearance of the solution.

[0089] When tetracarboxylic dianhydride is added to the aforementioned diamine solution, an organic solvent may also be added on the basis of tetracarboxylic dianhydride. By adding an organic solvent, a more uniform solution can be made. In addition, tetracarboxylic dianhydride may also be dissolved or dispersed in an organic solvent and added to the aforementioned diamine solution in the form of a tetracarboxylic dianhydride solution or dispersion. The organic solvent used herein is preferably an organic solvent described in the above-mentioned (organic solvent), more preferably an organic solvent contained in the diamine solution.

[0090] In step 1, the temperature of the diamine solution at the start of the addition of tetracarboxylic dianhydride is preferably 100° C. or lower so as not to exceed 100° C. during dissolution. In addition, from the viewpoint of improving the solubility of tetracarboxylic dianhydride, it is preferably 55° C. or higher. The temperature of the diamine solution at the start of the addition of tetracarboxylic dianhydride is more preferably 60 to 85° C., and even more preferably 65 to 80° C.

[0091] In this step, the amount of tetracarboxylic dianhydride added is preferably 0.9 to 1.1 mol per 1 mol of the diamine in the diamine solution.

[0092] In step 1, after adding tetracarboxylic dianhydride, the diamine solution is stirred until a uniform solution is obtained. By stirring the diamine solution, the time until a uniform solution is obtained can be shortened, and the coloring of the obtained polyimide can be further reduced.

[0093] In this step, from the addition of tetracarboxylic dianhydride until a uniform solution is obtained, that is, during the dissolution of tetracarboxylic dianhydride, the diamine solution is adjusted so that it does not exceed 100° C., and the highest reached temperature may be 100° C. or lower, preferably 99° C. or lower, more preferably 98° C. or lower, further preferably 97° C. or lower, and further preferably 96° C. or lower. There is no limitation on the lower limit of the highest reached temperature, but it is preferably 80° C. or higher from the perspective of the time taken for the precipitation and dissolution of tetracarboxylic dianhydride.

[0094] The time from the addition of tetracarboxylic dianhydride to the formation of a uniform solution, that is, the dissolution time of tetracarboxylic dianhydride may be appropriately adjusted depending on the amount of the solution, etc., and is preferably 10 minutes to 10 hours, more preferably 20 minutes to 5 hours, and even more preferably 30 minutes to 2 hours.

[0095] In this process, the diamine solution is adjusted so that it does not exceed 100°C from the addition of tetracarboxylic dianhydride until it becomes a uniform solution, but the case where it exceeds 100°C for a very short time is also included in the scope of the present invention. This is because if it is a very short time, the effect of the present invention will not be damaged. The time that does not damage the effect of the present invention varies depending on the maximum reached temperature, etc., and it can be less than 1 / 100 (less than 1%) of the time from the addition of tetracarboxylic dianhydride until it becomes a uniform solution.

[0096] In addition, from the addition of tetracarboxylic dianhydride until a uniform solution is formed, the dissolution of tetracarboxylic dianhydride is preferably carried out under an inert gas atmosphere. As the inert gas, at least one selected from the group consisting of nitrogen and a rare gas is preferred, and nitrogen is more preferred. Among the rare gases, argon is preferred.

[0097] <Step 2 (Polycondensation Step)>

[0098] The method for producing a polyimide of the present invention comprises a step 2 of polycondensing the tetracarboxylic dianhydride and the diamine, following the step 1. The polycondensation reaction is performed to obtain a polyimide. In this step, the polycondensation reaction is performed in the presence of an organic solvent, so the polyimide is obtained as a polyimide solution.

[0099] It is preferred to add the catalyst after step 1 and before polycondensation. By adding the catalyst after step 1, the imidization reaction can be carried out using a raw material solution in which tetracarboxylic dianhydride is completely dissolved, so that the target polyimide can be obtained.

[0100] Examples of the catalyst (imidation catalyst) used here include a base catalyst and an acid catalyst.

[0101] 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.

[0102] 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.

[0103] 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 the group consisting of triethylamine and triethylenediamine is further preferred, and addition of both triethylamine and triethylenediamine is further preferred.

[0104] The polycondensation reaction in this step is preferably carried out as follows.

[0105] The polycondensation reaction in the present polycondensation step is preferably carried out in an organic solvent.

[0106] The organic solvent used in the polycondensation reaction is preferably the organic solvent described in the above (Organic Solvent), and more preferably the organic solvent used in the above diamine solution. The organic solvent may be added during the polycondensation reaction, or the polycondensation reaction may be carried out using only the organic solvent used when dissolving the above diamine solution and tetracarboxylic dianhydride.

[0107] 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.

[0108] 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.

[0109] The polycondensation step is preferably carried out in an inert gas atmosphere. The inert gas is preferably at least one selected from the group consisting of nitrogen and rare gases, more preferably nitrogen. Among the rare gases, argon is preferred.

[0110] 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.

[0111] In this polycondensation step, a terminal blocking agent may be used in addition to the above-mentioned tetracarboxylic dianhydride and diamine.

[0112] 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 the 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.

[0113] The polyimide solution obtained in this step has polyimide uniformly dissolved therein, and the concentration (solid content) of the polyimide is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and further preferably 10 to 30% by mass. The viscosity (25° C.) of the polyimide solution is preferably 1 to 200 Pa·s, and more preferably 1 to 100 Pa·s.

[0114] 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. Using the polyimide solution or polyimide varnish as a raw material, and removing the organic solvent to form a formed product such as a polyimide film can be obtained.

[0115] The polyimide obtained by the production method of the present invention is suitable 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 as a raw material for image display devices such as liquid crystal displays and OLED displays.

[0116] (Polyimide)

[0117] 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.

[0118] Specifically, the polyimide preferably includes a structural unit derived from an alicyclic tetracarboxylic dianhydride, and more preferably includes a structural unit derived from a compound represented by the following formula (1).

[0119] Among the structural units derived from tetracarboxylic dianhydride, the ratio of the structural units derived from alicyclic 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 units derived from alicyclic tetracarboxylic dianhydride is not particularly limited, and can be 100 mol% or less.

[0120] Among the structural units derived from tetracarboxylic dianhydride, the ratio of the structural units derived from the compound represented by the following formula (1) 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 units derived from the compound represented by the following formula (1) is not particularly limited, and can be 100 mol% or less.

[0121]

[0122] 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.

[0123] 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.

[0124] The structural unit derived from tetracarboxylic dianhydride may be one or more types, and may be one type or two or more types.

[0125] 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 general 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 general formula (2) and a structural unit derived from a compound represented by the following formula (3).

[0126] Among the structural units derived from diamines, the ratio of structural units derived from aromatic diamines 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 structural units derived from aromatic diamines is not particularly limited, and may be 100 mol% or less.

[0127] Among the structural units derived from diamine, the total ratio of the structural units derived from the compound represented by the following formula (2) and the structural units derived from the compound represented by the following formula (3) 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 units derived from the compound represented by the following formula (2) and the structural units derived from the compound represented by the following formula (3) is not particularly limited, and may be 100 mol% or less.

[0128]

[0129] 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.

[0130] 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 50 / 50, more preferably 10 / 90 to 45 / 55, and further preferably 20 / 80 to 40 / 60.

[0131] 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.

[0132] The structural unit derived from diamine may be one or more types, and may be one type or two or more types.

[0133] 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.

[0134] <Polyimide varnish>

[0135] Since the polyimide obtained in the polycondensation step is obtained in the form of a polyimide solution containing an organic solvent, it can be directly used as a polyimide varnish, and the organic solvent can be added or removed to adjust the polyimide concentration (solid content) suitable for the polyimide varnish. Since the polyimide varnish contains a solvent-soluble polyimide obtained by the production method of the present invention, it has a sufficient viscosity required for coating, and the varnish is also non-colored and excellent in colorlessness.

[0136] The polyimide varnish contains polyimide and an organic solvent.

[0137] The polyimide is preferably the above-mentioned polyimide.

[0138] The organic solvent contained in the polyimide varnish is preferably the same as the organic solvent used in the polycondensation step, more preferably the organic solvent described in the above section (Organic Solvent), and further preferably the organic solvent used in the above diamine solution.

[0139] The polyimide varnish is a solution in which polyimide is uniformly dissolved, and the 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 varnish is preferably 1 to 200 Pa·s, more preferably 1 to 100 Pa·s, and further preferably 40 to 100 Pa·s.

[0140] 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.

[0141] Example

[0142] The present invention is specifically described below by way of examples. However, the present invention is not limited by these examples.

[0143] The polyimides (varnishes) obtained in Examples and Comparative Examples were evaluated by the methods shown below.

[0144] (1) Viscosity of varnish

[0145] The viscosity of the polyimide varnish obtained in each example and each comparative example was measured using an E-type viscometer TPE-100 (manufactured by Toki Sangyo Co., Ltd.). The measurement conditions were a temperature of 25° C. and a shear rate of 10 seconds. -1 .

[0146] (2) Yellowness Index (Yellowness, YI)

[0147] 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), γ-butyrolactone was added as a diluting solvent, and after confirming that it became uniform, the polyimide varnish was stored at room temperature (25°C) for 16 hours.

[0148] The tetracarboxylic acid component and the diamine component used in the Examples and Comparative Examples, and their abbreviations and the like are as follows.

[0149] <Diamine component>

[0150] BisAP: α,α′-bis(4-aminophenyl)-1,3-diisopropylbenzene (compound represented by formula (3), manufactured by MITSUIFINE CHEMICALS, INC Co., Ltd.)

[0151] TMDA: 1-(4-aminophenyl)-1,3,3-trimethylphenylindan-6-amine / 1-(4-aminophenyl)-1,3,3-trimethylphenylindan-5-amine mixture (compound represented by formula (2), manufactured by Japan Junryo Pharmaceutical Co., Ltd.)

[0152] <Tetracarboxylic acid component>

[0153] HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (compound represented by formula (1), manufactured by Mitsubishi Gas Chemical Co., Ltd.)

[0154] <Manufacturing of polyimide>

[0155] Example 1

[0156] (Process 1: Raw material dissolving process)

[0157] Into a reaction vessel equipped with a stainless steel Maxblend stirring blade, a nitrogen inlet pipe, and a cooler as a reaction apparatus, 28.415 kg (82.48 mol) of BisAP, 9.417 kg (35.35 mol) of TMDA, and 61.6 kg of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were charged, and the temperature was raised to 75° C. while stirring at 60 rpm in a nitrogen atmosphere to obtain a uniform diamine solution.

[0158] After adding 26.415 kg (117.83 mol) of HPMDA and 10.0 kg of γ-butyrolactone to the diamine solution at a solution temperature of 75°C, the solution was stirred while controlling the solution temperature to 100°C or less (maximum temperature 97°C) to obtain a uniform raw material solution.

[0159] (Step 2: Polycondensation Step)

[0160] 5.962 kg of triethylamine (manufactured by Daicel Corporation), 0.026 kg of triethylenediamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 7.0 kg of γ-butyrolactone were added to the raw material solution, and the solution temperature was raised to 180° C. over about 100 minutes. The mixture was stirred at a temperature of 180° C. in the reaction system for 5 hours while collecting the components removed by distillation, thereby obtaining a polyimide solution containing polyimide.

[0161] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0162] Examples 2 and 3

[0163] A polyimide solution containing polyimide was obtained in the same manner as in Example 1 except that the temperature of the diamine solution before adding tetracarboxylic dianhydride in step 1 was changed to the temperature shown in Table 1. The maximum temperature reached by the solution in step 1 is shown in Table 1.

[0164] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0165] Comparative Example 1

[0166] (Process 1: Raw material dissolving process)

[0167] Into a reaction vessel equipped with a stainless steel Maxblend stirring blade, a nitrogen inlet pipe, and a cooler as a reaction apparatus, 28.415 kg (82.48 mol) of BisAP, 9.417 kg (35.35 mol) of TMDA, and 61.6 kg of γ-butyrolactone were charged, and the mixture was heated to 92° C. while stirring at 60 rpm in a nitrogen atmosphere to obtain a uniform diamine solution.

[0168] After adding 26.415 kg (117.83 mol) of HPMDA and 10.0 kg of γ-butyrolactone to the diamine solution at a solution temperature of 92° C., the solution was stirred while controlling the solution temperature to 100 to 110° C. (maximum reaching temperature 110° C.) to obtain a uniform raw material solution. The solution temperature was kept at 100° C. or higher for 48 minutes.

[0169] (Step 2: Polycondensation Step)

[0170] 5.962 kg of triethylamine, 0.026 kg of triethylenediamine, and 7.0 kg of γ-butyrolactone were added to the raw material solution, and the solution temperature was raised to 180° C. over about 100 minutes. The reaction system was stirred at 180° C. for 5 hours while collecting the components removed by distillation, thereby obtaining a polyimide solution containing polyimide.

[0171] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0172] Comparative Example 2

[0173] A polyimide solution containing polyimide was obtained in the same manner as in Comparative Example 1 except that the temperature of the diamine solution before adding tetracarboxylic dianhydride in Step 1 was changed to the temperature shown in Table 1. The maximum temperature reached by the solution in Step 1 and the like are shown in Table 1.

[0174] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0175] Comparative Example 3

[0176] (Process 1: Raw material dissolving process)

[0177] Into a 0.3 L 5-necked glass round-bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark apparatus equipped with a cooling tube, a thermometer and a glass end cap as a reaction apparatus, 28.937 g (0.084 mol) of BisAP, 9.590 g (0.036 mol) of TMDA and 56.2 g of γ-butyrolactone were added, and the temperature was raised to 120° C. while stirring at 150 rpm in a nitrogen atmosphere to obtain a uniform diamine solution.

[0178] After adding 26.900 g (0.120 mol) of HPMDA and 13.9 g of γ-butyrolactone to the diamine solution at a solution temperature of 120° C., the solution was stirred while controlling the solution temperature to 100 to 135° C. (maximum temperature 135° C.) to obtain a uniform raw material solution. The solution temperature was kept at 100° C. or higher for 45 minutes.

[0179] (Step 2: Polycondensation Step)

[0180] 6.07 g of triethylamine, 0.027 g of triethylenediamine, and 9.9 g of γ-butyrolactone were added to the raw material solution, and the solution temperature was raised to 180° C. over about 20 minutes. The reaction system was stirred at 180° C. for 5 hours while collecting the components removed by distillation, thereby obtaining a polyimide solution containing polyimide.

[0181] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0182] Comparative Example 4

[0183] (Process 1: Raw material dissolving process)

[0184] In a 0.3 L 5-necked glass round-bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark apparatus equipped with a cooling tube, a thermometer and a glass end cap as a reaction apparatus, 28.937 g (0.084 mol) of BisAP, 9.590 g (0.036 mol) of TMDA and 56.2 g of γ-butyrolactone were added, and the temperature was raised to 50° C. while stirring at 150 rpm in a nitrogen atmosphere to obtain a uniform diamine solution.

[0185] After adding 26.900 g (0.120 mol) of HPMDA and 13.9 g of γ-butyrolactone to the diamine solution at a solution temperature of 50° C. and stirring, solid components were precipitated, and step 2 (polycondensation step) could not be performed.

[0186] Comparative Example 5

[0187] (Process 1: Raw material dissolving process)

[0188] Into a 0.3 L 5-necked glass round-bottom flask equipped with a stainless steel half-moon-shaped stirring blade, a nitrogen inlet pipe, a Dean-Stark apparatus equipped with a cooling tube, a thermometer and a glass end cap as a reaction apparatus, 28.937 g (0.084 mol) of BisAP, 9.590 g (0.036 mol) of TMDA and 56.2 g of γ-butyrolactone were added, and the temperature was raised to 80° C. while stirring at 150 rpm in a nitrogen atmosphere to obtain a uniform diamine solution.

[0189] After adding 26.900 g (0.120 mol) of HPMDA and 13.9 g of γ-butyrolactone to the diamine solution at a solution temperature of 80° C., the solution was stirred while controlling the solution temperature to 100 to 105° C. (maximum temperature 105° C.) to obtain a uniform raw material solution. The solution temperature was kept at 100° C. or higher for 45 minutes.

[0190] (Step 2: Polycondensation Step)

[0191] 6.07 g of triethylamine, 0.027 g of triethylenediamine, and 9.9 g of γ-butyrolactone were added to the raw material solution, and the solution temperature was raised to 180° C. over about 20 minutes. The reaction system was stirred at 180° C. for 5 hours while collecting the components removed by distillation, thereby obtaining a polyimide solution containing polyimide.

[0192] The polyimide solution was diluted with γ-butyrolactone and mixed until uniform, thereby obtaining a polyimide varnish having a solid content concentration of 20% by mass. Table 1 shows the evaluation results of the obtained polyimide varnish.

[0193] [Table 1]

[0194] Table 1

[0195]

[0196] *)GBL is γ-butyrolactone

[0197] As shown in Table 1, it can be seen that the polyimide obtained by the production method of the present invention is soluble in a solvent, has a sufficient viscosity of the varnish, and has a low yellowness. Therefore, it can be seen that the polyimide obtained by the production method of the present invention can obtain a varnish having a sufficient viscosity required for coating, is non-colored, has excellent colorlessness, and can be used for applications such as materials for image display devices.

Claims

1. A method for producing a polyimide, comprising: step 1, dissolving a diamine in an organic solvent to obtain a diamine solution, adding tetracarboxylic dianhydride to the diamine solution and mixing to obtain a uniform solution; and step 2, polycondensing the tetracarboxylic dianhydride and the diamine. In step 1, from the start of the addition of tetracarboxylic dianhydride until a uniform solution is obtained, the diamine solution is adjusted so as not to exceed 100°C.

2. The method for producing a polyimide according to claim 1, wherein: In step 1, the temperature of the diamine solution at the start of addition of tetracarboxylic dianhydride is 60 to 85°C.

3. The method for producing a polyimide 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 according to claim 1 or 2, wherein: The catalyst is added after step 1 and before polycondensation.

5. The method for producing a polyimide according to claim 4, wherein: The catalyst is at least one selected from the group consisting of triethylamine and triethylenediamine.

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

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

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

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

10. The method for producing a polyimide according to claim 1 or 2, wherein: In step 1, the lower limit of the maximum temperature reached from the start of the addition of tetracarboxylic dianhydride until a uniform solution is obtained is 80° C. or more.

11. The method for producing a polyimide according to claim 1 or 2, wherein: In step 1, the time from the start of the addition of tetracarboxylic dianhydride until a uniform solution is obtained is 10 minutes to 10 hours.

12. The method for producing a polyimide according to claim 1 or 2, wherein: Step 2 is a step of obtaining a polyimide solution.

13. The method for producing a polyimide according to claim 1, wherein In step 1, the temperature of the diamine solution at the start of addition of tetracarboxylic dianhydride is 55° C. or higher.

14. The method for producing a polyimide according to claim 12, wherein: The polyimide concentration (solid content) of the polyimide solution is 1 to 50% by mass, and the viscosity (25° C.) of the polyimide solution is 1 to 200 Pa·s.

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