WO2023182038A1

WO2023182038A1 - Method for producing polymer, varnish, and method for producing varnish

Info

Publication number: WO2023182038A1
Application number: PCT/JP2023/009565
Authority: WO
Inventors: 舜星野; 紘二鈴木; 琢朗畠山; 孝博村谷
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2022-03-23
Filing date: 2023-03-13
Publication date: 2023-09-28
Also published as: TW202402885A

Abstract

This method for producing a polymer, the method comprising Step 1 for polymerizing diamine and tetracarboxylic dianhydride to obtain a polymer, wherein: the molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is 1.00 to 1.03 (exclusive of 1.03); Step 1 is a step for polymerizing diamine and tetracarboxylic dianhydride in the presence of tert-butanol and a solvent; and the polymer has, as a repeating unit, at least one selected from the group consisting of an amidic acid unit and an imide unit, and has a weight average molecular weight of at least 300,000.

Description

Polymer manufacturing method, varnish, and varnish manufacturing method

The present invention relates to a method for producing a polymer, a varnish, and a method for producing a varnish.

Since polyimide resin has excellent mechanical properties and heat resistance, various uses are being considered in fields such as electrical and electronic parts. For example, since it is desired to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with polyimide film substrates, polyimide resins that satisfy the performance as optical materials are being developed.
Varnish, which is a solution of polyimide or a polyimide precursor dissolved in a solvent, is used as a raw material for manufacturing polyimide molded bodies such as polyimide films. Varnishes have also been devised to improve the performance of the resulting polyimide molded bodies and to facilitate the manufacture of the molded bodies.

For example, Patent Document 1 discloses a varnish containing a specific amount of a polymer such as polyamic acid, a solvent, and a compound such as a monovalent primary amine or monovalent alcohol for the purpose of improving storage stability. There is.

Japanese Patent Application Publication No. 2021-014564

Polyimide resins have excellent properties as described above, but recently, even higher strength and heat resistance have been required. Therefore, it is necessary to increase the molecular weight of polyimide resin. Furthermore, varnishes with various resin concentrations are required depending on the shape, thickness, and purpose of the intended polyimide film. On the other hand, varnishes containing high molecular weight polyimides or polyimide precursors have a problem in that their viscosity tends to increase during storage. Furthermore, the viscosity changes greatly when the resin concentration changes, and the resin concentration required differs depending on the application. In this manner, it has been difficult to suppress changes in viscosity and maintain stability of the varnish at various resin concentrations. In particular, there has been a demand for a varnish that has excellent storage stability even though it contains a high molecular weight polyimide or a polyimide precursor.
The present invention was made in view of these circumstances, and an object of the present invention is to create a varnish that exhibits little increase in viscosity even in a wide viscosity range and has excellent storage stability despite containing a high molecular weight resin. The object of the present invention is to provide a method for producing a polymer that can be obtained, a varnish containing the polymer, and a method for producing a varnish.

The present inventors have discovered that the above problems can be solved by setting the monomer ratio in a specific range when obtaining a polymer that is a polyimide or a polyimide precursor, and polymerizing it in the presence of tert-butanol, and have completed the invention. reached.

That is, the present invention relates to the following [1] to [14].
[1] A method for producing a polymer, comprising a step 1 of polymerizing a diamine and a tetracarboxylic dianhydride to obtain a polymer, the molar ratio of the diamine to the tetracarboxylic dianhydride in the step 1 ( diamine/tetracarboxylic dianhydride) is 1.00 or more and less than 1.03, and step 1 is a step of polymerizing the diamine and the tetracarboxylic dianhydride in the presence of tert-butanol and a solvent. . A method for producing a polymer, wherein the polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units, and has a weight average molecular weight of 300,000 or more.
[2] The method for producing a polymer according to [1] above, wherein the polymer is at least one selected from the group consisting of polyamic acid, polyimide, and imido-amic acid copolymers.
[3] The above-mentioned [1], wherein the polymer is a polyamic acid, and step 1 is a step of mixing a solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol, and polymerizing the mixture. Or the method for producing a polymer according to [2].
[4] The polymer is a polyamic acid, the tetracarboxylic dianhydride contains a compound represented by the following formula (a1), and the diamine contains a compound represented by the following general formula (b1). , a method for producing the polymer according to any one of [1] to [3] above.

(In formula (b1), R ¹ , R ² , and R ³ each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
[5] The polymer is an imide-amic acid copolymer, and the tetracarboxylic dianhydride consists of a first tetracarboxylic dianhydride and a second tetracarboxylic dianhydride, The method for producing a polymer according to [1] or [2], wherein the diamine consists of a first diamine and a second diamine, and the step 1 consists of the following step 1-1 and the following step 1-2.
Step 1-1: A step of reacting the first tetracarboxylic dianhydride and the first diamine in the presence of a solvent to obtain an imide oligomer. Step 1-2: The imide oligomer obtained in Step 1-1. Step of mixing and polymerizing the second tetracarboxylic dianhydride, the second diamine, and tert-butanol [6] The polymer is an imide-amic acid copolymer, and the first tetracarboxylic dianhydride The acid dianhydride contains a compound represented by the following formula (a1), the second tetracarboxylic dianhydride contains a compound represented by the following formula (a2), and the first diamine and the first dianhydride contain a compound represented by the following formula (a2). The method for producing a polymer according to the above [5], wherein the diamine of No. 2 contains a compound represented by the following formula (b1).

(In formula (b1), R ¹ , R ² , and R ³ each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
[7] The method according to any one of [1] to [6] above, wherein the amount of tert-butanol in Step 1 is 2 mol% or more based on the total amount of tetracarboxylic dianhydride in Step 1. Method for producing polymers.
[8] A varnish containing a polymer obtained by the production method according to any one of [1] to [7] above and a solvent.
[9] A method for producing a varnish, comprising a step 1 of polymerizing a diamine and a tetracarboxylic dianhydride to obtain a polymer, the molar ratio of the diamine to the tetracarboxylic dianhydride in step 1 (diamine /tetracarboxylic dianhydride) is 1.00 or more and less than 1.03, and step 1 is a step of polymerizing diamine and tetracarboxylic dianhydride in the presence of tert-butanol and a solvent, The polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units, and has a weight average molecular weight of 300,000 or more, and the varnish contains the polymer and a solvent. Production method.
[10] A varnish obtained by the manufacturing method described in [9] above.
[11] The varnish according to [8] or [10], wherein the viscosity increase rate on the 7th day of storage at 23°C is 15% or less relative to the viscosity on the 0th day.
[12] The varnish according to [8], [10], or [11], wherein the solvent contains at least one selected from the group consisting of a cyclic amide, a chain amide, and a cyclic ester.
[13] The varnish according to any one of [8] or [10] to [12] above, wherein the solvent contains N-methylpyrrolidone.
[14] A step of casting the varnish according to any one of [8] or [10] to [13] above on a base material, and a step of drying the cast varnish to form a polymer film. A method for producing a polyimide film, including:

According to the present invention, a method for producing a polymer that can produce a varnish with little increase in viscosity and excellent storage stability despite containing a high molecular weight resin, a varnish containing the polymer, and production of the varnish method can be provided. Furthermore, a method for producing a polyimide film using the varnish can also be provided.

[Production method of polymer]
The method for producing a polymer of the present invention is a method for producing a polymer, comprising a step 1 of obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride, the method comprising: obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride; The molar ratio of the diamine to the diamine (diamine/tetracarboxylic dianhydride) is 1.00 or more and less than 1.03, and in step 1, the diamine and the tetracarboxylic dianhydride are combined with tert-butanol in the presence of a solvent. A method for producing a polymer, wherein the polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units, and has a weight average molecular weight of 300,000 or more. be.

<Polymer>
First, the polymer produced by the above production method will be explained.
The polymer has at least one repeating unit selected from the group consisting of an amic acid unit and an imide unit, preferably an amic acid unit as a constituent unit, and more preferably an amide unit from the viewpoint of improving storage stability. Both acid units and imide units are repeating units.
Here, "having an amic acid unit as a repeating unit" refers to one unit having an amic acid structure in which the following tetracarboxylic dianhydride and diamine are bonded one by one, and the minimum repeating unit in the polymer is The unit of In addition, "having an imide unit as a repeating unit" refers to one unit having an imide structure in which the following tetracarboxylic dianhydride and diamine are bonded one by one, and is the smallest repeating unit in the polymer. means.
The polymer is preferably at least one selected from the group consisting of polyamic acid, polyimide, and imide-amic acid copolymer, more preferably selected from the group consisting of polyamic acid and imide-amic acid copolymer. From the viewpoint of obtaining a high molecular weight polymer, polyamic acid is more preferred, and from the viewpoint of improving storage stability, imide-amic acid copolymer is even more preferred.

The weight average molecular weight (Mw) of the polymer is 300,000 or more, preferably 400,000 or more, and more preferably 500,000 or more from the viewpoint of the mechanical strength of the resulting polyimide film. Although there is no upper limit to the upper limit, it is preferably 1,000,000 or less, more preferably 700,000 or less. Further, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. In addition, the weight average molecular weight and number average molecular weight of the said polymer can be calculated|required from the standard polystyrene (PS) conversion value by gel filtration chromatography measurement.

As mentioned above, in step 1, the diamine and the tetracarboxylic dianhydride are polymerized in the presence of tert-butanol, so the polymer has a tert-butoxy group derived from tert-butanol at a part of the end. have

(Each structural unit of the polymer)
The polymer has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine.
In addition, when the polymer is a polyamic acid, the structural unit A and the structural unit B form an amic acid structure, and when the polymer is a polyimide, the structural unit A and the structural unit B form an imide structure, When the polymer is an imide-amic acid copolymer, structural unit A and structural unit B form both an imide structure and an amic acid structure, but structural units derived from tetracarboxylic dianhydride constitute the structural unit. Unit A and the structural units derived from diamine are collectively referred to as structural unit B.

(Component unit A)
The structural unit A is a structural unit derived from a tetracarboxylic dianhydride, and is not particularly limited as long as it is a structural unit derived from a tetracarboxylic dianhydride, but is preferably an aromatic tetracarboxylic dianhydride. , and more preferably a structural unit derived from aromatic tetracarboxylic dianhydride.

Examples of aromatic tetracarboxylic dianhydrides that provide structural units derived from aromatic tetracarboxylic dianhydrides include biphenyltetracarboxylic dianhydride (BPDA), 9,9-bis(3,4-dicarboxyphenyl) ) Fluorene dianhydride (BPAF), pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfone tetra Examples include carboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenonetetracarboxylic dianhydride.
Among these, from the viewpoint of achieving high molecular weight, at least one compound selected from the group consisting of a compound represented by the following formula (a1) and a compound represented by the following formula (a2) is preferred, and more Preferably, it is a compound represented by the following formula (a1).
That is, the structural unit A is preferably selected from the group consisting of a structural unit (A1) derived from a compound represented by the following formula (a1) and a structural unit (A2) derived from a compound represented by the following formula (a2). , and more preferably a structural unit (A1) derived from a compound represented by the following formula (a1).

The compound represented by formula (a1) is biphenyltetracarboxylic dianhydride (BPDA), and a specific example thereof is 3,3',4,4'-biphenyl represented by the following formula (a1s). Tetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a1a), and the following formula (a1i) Examples include 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a1s) is preferred.

The compound represented by formula (a2) is 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

When the polymer is a polyamic acid, it preferably contains the structural unit (A1).
When the polymer is an imide-amic acid copolymer, the polyimide unit preferably contains the structural unit (A2), and the polyamic acid unit preferably contains the structural unit (A1).

The structural unit A may contain structural units other than aromatic tetracarboxylic dianhydride. Tetracarboxylic dianhydrides that provide such structural units include, but are not particularly limited to, alicyclic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides.
Examples of the alicyclic tetracarboxylic dianhydride that provides a structural unit derived from 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 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, or positional isomers thereof.
Examples of the aliphatic tetracarboxylic dianhydride that provides structural units derived from aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and the like.
The number of structural units optionally included in the structural unit A may be one, or two or more.
In addition, in this specification, aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more alicyclic rings. The term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing the above and not containing an aromatic ring, and the term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.

(Component unit B)
The structural unit B is a structural unit derived from a diamine, and is not particularly limited as long as it is a structural unit derived from a diamine, but preferably includes a structural unit derived from an aromatic diamine, and more preferably contains a structural unit derived from an aromatic diamine. It is a structural unit derived from

Examples of aromatic diamines that provide structural units derived from aromatic diamines include 4-aminophenyl-4-aminobenzoate (4-BAAB), 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 3,5 -Diaminobenzoic acid (3,5-DABA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 1,4-phenylenediamine, p-xylylenediamine, 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-1H-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.

Among the aromatic diamines, a compound represented by the following formula (b1) is preferred from the viewpoint of achieving high molecular weight.

(In formula (b1), R ¹ , R ² , and R ³ each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
That is, the structural unit B preferably includes a structural unit (B1) derived from the compound represented by the formula (b1).
R ¹ , R ² and R ³ each independently represent an organic group having 1 to 20 carbon atoms, preferably R ¹ , R ² and R ³ each independently represent a methyl group or a trifluoromethyl group. .
h, i, j, and k are integers from 0 to 4, and each of h, i, j, and k is preferably 0.
In addition, when the structural unit B contains the structural unit (B1) derived from the compound represented by the above formula (b1), the structural unit A contains the structural unit (A1) derived from the compound represented by the above formula (a1). It is preferable to include. That is, the structural unit A of the polymer includes a structural unit (A1) derived from the compound represented by the formula (a1), and the structural unit B of the polymer is represented by the formula (b1). It is preferable to include a structural unit (B1) derived from a compound. By combining the above structural units, a high molecular weight polymer with excellent film properties can be obtained, and the storage stability, which is an effect of the present invention, can be more clearly expressed.

Among the compounds represented by formula (b1) above, the compound represented by formula (b11) (4-aminophenyl-4-aminobenzoate (4-BAAB)) is particularly preferred.
That is, the structural unit B particularly preferably includes a structural unit (B11) derived from the compound represented by the above formula (b11).
In addition, when the structural unit B contains the structural unit (B11) derived from the compound represented by the above formula (b11), the structural unit A contains the structural unit (A1) derived from the compound represented by the above formula (a1). It is preferable to include. That is, the structural unit A of the polymer includes a structural unit (A1) derived from the compound represented by the formula (a1), and the structural unit B of the polymer is represented by the formula (b11). It is preferable to include a structural unit (B11) derived from a compound. By combining the above structural units, a high molecular weight polymer with excellent film properties can be obtained, and the storage stability, which is an effect of the present invention, can be particularly clearly expressed.

Structural unit B may also contain structural units other than aromatic diamine. Diamines that provide such structural units include, but are not particularly limited to, alicyclic diamines and aliphatic diamines.
Examples of the alicyclic diamine that provides a structural unit derived from an alicyclic diamine include 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane.
Examples of aliphatic diamines that provide structural units derived from aliphatic diamines include ethylene diamine and hexamethylene diamine.
The number of structural units optionally included in the structural unit B may be one, or two or more.
In addition, in this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings and no aromatic ring, Group diamine means a diamine containing neither aromatic ring nor alicyclic ring.

(Polymer manufacturing method and varnish manufacturing method)
As described above, the method for producing the polymer includes Step 1 of obtaining a polymer by polymerizing diamine and tetracarboxylic dianhydride, and the molar ratio of the diamine to the tetracarboxylic dianhydride in Step 1 is The ratio (diamine/tetracarboxylic dianhydride) is 1.00 or more and less than 1.03, and step 1 is a step of polymerizing diamine and tetracarboxylic dianhydride in the presence of tert-butanol and a solvent. However, it is preferable to use the following method.
The polymer contains either or both of imide units and amic acid units, but these can be controlled by changing the manufacturing method.
Specifically, in a production method containing both imide units and amic acid units (method for producing an imide-amic acid copolymer), only the step of producing a part (polyimide part) mainly containing imide units is used. By doing this, a polymer (polyimide) consisting essentially of imide units can be obtained, and by using only the process of producing a part (polyamic acid part) mainly containing amic acid units, a polymer consisting essentially of amic acid units can be obtained. (polyamic acid) can be obtained.

According to the above method, a polymer solution containing a polymer dissolved in a solvent is obtained. The varnish of the present invention may be obtained by adding a solvent to the above-mentioned polymer solution, or may be obtained by concentrating the solution to reduce the amount of solvent. Therefore, the method for producing the varnish of the present invention includes the method for producing the polymer.
That is, the method for producing a varnish of the present invention is a method for producing a varnish, which includes step 1 of obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride, and the method includes a step 1 of obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride. The molar ratio of the diamine to the diamine (diamine/tetracarboxylic dianhydride) is 1.00 or more and less than 1.03, and in step 1, the diamine and the tetracarboxylic dianhydride are combined with tert-butanol in the presence of a solvent. In this step, the polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units and has a weight average molecular weight of 300,000 or more, and the varnish has a repeating unit of at least one selected from the group consisting of amic acid units and imide units, and the varnish has A method for producing varnish, including coalescence and solvent.
The varnish may be the polymer solution itself obtained by the above-mentioned method for producing a polymer, may have a solvent added thereto, or may have a reduced amount of solvent by concentration or the like. That is, the method for producing the varnish is any one of a method having only the step 1, a method having a step of adding a solvent after the step 1, or a method having a step of reducing the solvent after the step 1. It's okay.

As mentioned above, the preferred conditions for Step 1 differ depending on whether the polymer obtained by the production method of the present invention is an imide-amic acid copolymer, polyimide, or polyamic acid. The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in No. 1 is 1.00 or more and less than 1.03. The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is preferably 1.005 or more, more preferably 1.010 or more. Further, it is preferably 1.025 or less, more preferably 1.020 or less. By setting the molar ratio of the diamine to the tetracarboxylic dianhydride in the above range in Step 1, a high molecular weight polymer can be obtained, and even though it contains a high molecular weight polymer, the viscosity does not increase. A varnish with excellent storage stability can be obtained.
Further, the amount of tert-butanol used in Step 1 is preferably 2 mol% or more, more preferably 2.5 mol% or more, based on the total amount of tetracarboxylic dianhydride in Step 1, and Preferably it is 3 mol% or more. Moreover, it is preferably 5 mol% or less, more preferably 4 mol% or less, and still more preferably 3.5 mol% or less. By setting the amount of tert-butanol in Step 1 within the above range, it is possible to obtain a varnish with little increase in viscosity and excellent storage stability despite containing a high molecular weight polymer.

By setting the molar ratio of the diamine to the tetracarboxylic dianhydride in the above range and using tert-butanol, a varnish with little increase in viscosity and excellent storage stability despite containing a high molecular weight polymer is obtained. The reason why this is possible is not clear, but it is thought that the reaction between the diamine and the acid dianhydride is suppressed by the reaction between the acid dianhydride and tert-butanol.
Below, cases in which the polymer obtained by the above production method is an imide-amic acid copolymer, a polyimide, and a polyamic acid will be explained in detail.

(Method for producing imide-amic acid copolymer)
In the case of a polymer containing both imide units and amic acid units (hereinafter also referred to as an imide-amic acid copolymer), a preferred production method is such that the tetracarboxylic dianhydride is a first tetracarboxylic dianhydride. and a second tetracarboxylic dianhydride, the diamine consists of a first diamine and a second diamine, and Step 1 consists of the following Step 1-1 and the following Step 1-2.
Step 1-1: A step of reacting the first tetracarboxylic dianhydride and the first diamine in the presence of a solvent to obtain an imide oligomer. Step 1-2: The imide oligomer obtained in Step 1-1. A step of mixing and polymerizing a second tetracarboxylic dianhydride, a second diamine, and tert-butanol

Preferred tetracarboxylic dianhydrides and diamines used in each step will be described in the description of each step, but when the polymer obtained by the production method of the present invention is an imide-amic acid copolymer, preferably The first tetracarboxylic dianhydride contains a compound represented by the following formula (a1), the second tetracarboxylic dianhydride contains a compound represented by the following formula (a2), and the first tetracarboxylic dianhydride contains a compound represented by the following formula (a2), The first diamine and the second diamine include a compound represented by the following formula (b1).

(In formula (b1), R ¹ , R ² , and R ³ each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
R ¹ , R ² and R ³ each independently represent an organic group having 1 to 20 carbon atoms, preferably R ¹ , R ² and R ³ each independently represent a methyl group or a trifluoromethyl group. .
h, i, j, and k are integers from 0 to 4, and each of h, i, j, and k is preferably 0.

[Step 1-1]
Step 1-1 is a step in which the first tetracarboxylic dianhydride constituting the imide moiety and the first diamine are reacted in the presence of a solvent to obtain an imide oligomer.
The first tetracarboxylic dianhydride used in step 1-1 preferably includes aromatic tetracarboxylic dianhydride, more preferably aromatic tetracarboxylic dianhydride. Further, it preferably contains a compound represented by the above formula (a2). The first tetracarboxylic dianhydride may contain a tetracarboxylic dianhydride other than the aromatic tetracarboxylic dianhydride.
The first diamine used in step 1-1 preferably includes an aromatic diamine, more preferably an aromatic diamine. Further, it preferably contains a compound represented by the above formula (b1), and more preferably contains a compound represented by the above formula (b11). The first diamine may contain diamines other than aromatic diamines.
In step 1-1, the amount of diamine relative to the tetracarboxylic dianhydride is preferably 1.01 to 2 mol, more preferably 1.05 to 1.9 mol, and 1.1 to 1.7 mol. More preferably, it is in moles.

There is no particular restriction on the method of reacting the first tetracarboxylic dianhydride and the first diamine to obtain the imide oligomer in step 1-1, and any known method can be used.
The specific reaction method is as follows: (1) Tetracarboxylic dianhydride, diamine, and solvent are charged into a reactor, stirred at 10 to 110°C for 0.5 to 30 hours, and then heated to imidize. Method for carrying out the reaction, (2) After charging the diamine and the solvent into a reactor and dissolving them, charging the tetracarboxylic dianhydride, stirring at 10 to 110°C for 0.5 to 30 hours as necessary, and then (3) A method in which tetracarboxylic dianhydride, diamine, and a solvent are charged into a reactor, and the temperature is immediately raised to carry out an imidization reaction.

In the imidization reaction, it is preferable to use a Dean-Stark apparatus or the like to conduct the reaction while removing water generated during production. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

In the above imidization reaction, a known imidization catalyst can be used. Examples of imidization catalysts include base catalysts and acid catalysts.
Base catalysts include pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N Examples include organic base catalysts such as -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.
In addition, examples of acid catalysts include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, etc. can be mentioned. The above imidization catalysts may be used alone or in combination of two or more.
Among the above, from the viewpoint of ease of handling, base catalysts are preferred, organic base catalysts are more preferred, one or more selected from triethylamine and triethylenediamine are still more preferred, and triethylamine is even more preferred.

The temperature of the imidization reaction is preferably 120 to 250°C, more preferably 160 to 200°C from the viewpoint of reaction rate and suppression of gelation and the like. Further, the reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

By the above method, a solution containing an imide oligomer dissolved in a solvent is obtained. The solution containing the imide oligomer obtained in Step 1-1 contains the components used as the first tetracarboxylic dianhydride and the first diamine in Step 1-1 to the extent that the effects of the present invention are not impaired. At least a portion may be contained as an unreacted monomer.

[Step 1-2]
Step 1-2 in the production method of the present invention is a step in which the imide oligomer obtained in Step 1-1, the second tetracarboxylic dianhydride, the second diamine, and tert-butanol are mixed and polymerized. .

The second tetracarboxylic dianhydride used in step 1-2 preferably includes aromatic tetracarboxylic dianhydride, more preferably aromatic tetracarboxylic dianhydride. Further, it preferably contains a compound represented by the above formula (a1). The second tetracarboxylic dianhydride may contain a tetracarboxylic dianhydride other than the aromatic tetracarboxylic dianhydride.
The second diamine used in step 1-2 preferably includes an aromatic diamine, more preferably an aromatic diamine. Further, it preferably contains a compound represented by the above formula (b1), and more preferably contains a compound represented by the above formula (b11). The second diamine may contain diamines other than aromatic diamines.
Since the molar ratio of diamine to tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1-1 and Step 1-2 as a whole is 1.00 or more and less than 1.03, Step 1-2 The molar ratio of diamine to tetracarboxylic dianhydride in Step 1-1 and Step 1-2 as a whole is 1.00 or more, taking into account the respective amounts used in Step 1-1. It is determined to be less than .03. Among these, the molar ratio of diamine to tetracarboxylic dianhydride in step 1-2 is preferably 0.70 to 1.00 mol, more preferably 0.80 to 0.95 mol. , more preferably 0.85 to 0.90 mol.

In step 1-2, tert-butanol is mixed in addition to the imide oligomer, the second tetracarboxylic dianhydride, and the second diamine. There is no limit to the amount of tert-butanol used in Step 1-2, but it is preferably 2 mol% or more based on the total amount of tetracarboxylic dianhydride in Step 1-1 and Step 1-2. More preferably it is 2.5 mol% or more, and still more preferably 3 mol% or more. Moreover, it is preferably 5 mol% or less, more preferably 4 mol% or less, and still more preferably 3.5 mol% or less. By setting the amount of tert-butanol in step 1-2 within the above range, it is possible to obtain a varnish with little increase in viscosity and excellent storage stability despite containing a high molecular weight polymer.

In Step 1-2, the method for polymerizing the imide oligomer obtained in Step 1-1, the second tetracarboxylic dianhydride, and the second diamine is not particularly limited, and any known method can be used. .
As a specific reaction method, (1) the imide oligomer, the second tetracarboxylic dianhydride, the second diamine, and tert-butanol are charged into a reactor, and the temperature is heated at 0 to 120°C, preferably 5 to 80°C. (2) After charging the imide oligomer and the solvent into a reactor and dissolving them, charging the second tetracarboxylic dianhydride, second diamine and tert-butanol, Examples include a method of stirring at a temperature of 1 to 120°C, preferably 5 to 80°C for 1 to 72 hours.
In either method, it is preferable that the diamine be dissolved in a solvent in advance.
When the reaction is carried out at 80°C or lower, the molecular weight of the copolymer obtained in step 1-2 does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed. Polymers can be produced stably.

The concentration of the copolymer in the resulting solution is usually 1 to 50% by weight, preferably 3 to 35% by weight, and more preferably 5 to 30% by weight.

The weight average molecular weight (Mw) of the imide-amic acid copolymer obtained by the above production method is 300,000 or more, preferably 400,000 or more, from the viewpoint of the mechanical strength of the obtained polyimide film, More preferably, it is 500,000 or more. Although there is no upper limit to the upper limit, it is preferably 1,000,000 or less, more preferably 700,000 or less. Further, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. Note that the weight average molecular weight and number average molecular weight of the copolymer can be determined from standard polystyrene (PS) equivalent values determined by gel filtration chromatography measurement.

(Method for producing polyamic acid)
In the case of a polymer containing an amic acid unit (also referred to as a polyamic acid), a preferred manufacturing method is such that step 1 mixes a solution containing a diamine and a solvent, a tetracarboxylic dianhydride and tert-butanol, This is a polymerization step.

As described above, the tetracarboxylic dianhydride used in Step 1 preferably includes aromatic tetracarboxylic dianhydride, more preferably aromatic tetracarboxylic dianhydride. Further, it preferably contains a compound represented by the above formula (a1). The tetracarboxylic dianhydride may contain a tetracarboxylic dianhydride other than the aromatic tetracarboxylic dianhydride.
As mentioned above, the diamine used in Step 1 preferably includes an aromatic diamine, and more preferably an aromatic diamine. Further, it preferably contains a compound represented by the above formula (b1), and more preferably contains a compound represented by the above formula (b11). The diamine may include diamines other than aromatic diamines.

That is, when the polymer obtained by the production method of the present invention is a polyamic acid, preferably the tetracarboxylic dianhydride contains a compound represented by the following formula (a1), and the diamine contains a compound represented by the following general formula (b1). ).

As described above, the molar ratio of diamine to tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is 1.00 or more and less than 1.03. The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is preferably 1.005 or more, more preferably 1.010 or more. Further, it is preferably 1.025 or less, more preferably 1.020 or less. By setting the molar ratio of the diamine to the tetracarboxylic dianhydride in the above range in Step 1, a high molecular weight polymer can be obtained, and even though it contains a high molecular weight polymer, the viscosity does not increase. A varnish with excellent storage stability can be obtained.

In step 1, a solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol are mixed and polymerized. There is no limit to the amount of tert-butanol used in Step 1, but as described above, it is preferably 2 mol% or more, more preferably 2.5% by mole, based on the total amount of tetracarboxylic dianhydride in Step 1. It is mol% or more, more preferably 3 mol% or more. Moreover, it is preferably 5 mol% or less, more preferably 4 mol% or less, and still more preferably 3.5 mol% or less. By setting the amount of tert-butanol in Step 1 within the above range, it is possible to obtain a varnish with little increase in viscosity and excellent storage stability despite containing a high molecular weight polymer.

In Step 1, the method for polymerizing the tetracarboxylic dianhydride and diamine is not particularly limited, and any known method can be used.
A specific reaction method is to charge a solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol into a reactor, and heat the mixture at a temperature of 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. Examples include a method of stirring.
When the reaction is carried out at 80°C or lower, the molecular weight of the polyamic acid obtained in step 1 does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so the polyamic acid is stabilized. It can be manufactured by

The concentration of polyamic acid in the resulting solution is usually 1 to 50% by weight, preferably 3 to 35% by weight, and more preferably 5 to 30% by weight.

The weight average molecular weight (Mw) of the polyamic acid obtained by the above production method is 300,000 or more, preferably 400,000 or more, more preferably 500,000 or more, from the viewpoint of the mechanical strength of the obtained polyimide film. 000 or more. Although there is no upper limit to the upper limit, it is preferably 1,000,000 or less, more preferably 700,000 or less. Further, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. The weight average molecular weight and number average molecular weight of the polyamic acid can be determined from standard polystyrene (PS) equivalent values determined by gel filtration chromatography.

(Method for manufacturing polyimide)
In the case of a polymer containing imide units (also referred to as polyimide), a preferred manufacturing method is such that step 1 mixes a solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol, and polymerizes the mixture. It is a process.

As described above, the tetracarboxylic dianhydride used in Step 1 preferably includes aromatic tetracarboxylic dianhydride, more preferably aromatic tetracarboxylic dianhydride. Further, it preferably contains a compound represented by the above formula (a1). The tetracarboxylic dianhydride may contain a tetracarboxylic dianhydride other than the aromatic tetracarboxylic dianhydride.
As mentioned above, the diamine used in Step 1 preferably includes an aromatic diamine, and more preferably an aromatic diamine. Further, it preferably contains a compound represented by the above formula (b1), and more preferably contains a compound represented by the above formula (b11). The diamine may include diamines other than aromatic diamines.
The molar ratio of diamine to tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is 1.00 or more and less than 1.03, as described above. The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is preferably 1.005 or more, more preferably 1.010 or more. Further, it is preferably 1.025 or less, more preferably 1.020 or less. By setting the molar ratio of the diamine to the tetracarboxylic dianhydride in the above range in Step 1, a high molecular weight polymer can be obtained, and even though it contains a high molecular weight polymer, the viscosity does not increase. A varnish with excellent storage stability can be obtained.

In Step 1, the method for polymerizing the tetracarboxylic dianhydride and diamine is not particularly limited, and any known method can be used.
A specific reaction method is as follows: (1) A solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol are charged into a reactor, and the reaction is carried out at 10 to 110°C for 0.5 to 30 hours as necessary. A method of stirring and then raising the temperature to perform an imidization reaction, (2) A solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol are charged into a reactor, and the temperature is immediately raised to imidize. Examples include methods for conducting the reaction.

The concentration of polyimide in the resulting solution is usually in the range of 1 to 50% by weight, preferably in the range of 3 to 35% by weight, and more preferably in the range of 5 to 30% by weight.

The weight average molecular weight (Mw) of the polyimide obtained by the above production method is 300,000 or more, preferably 400,000 or more, and more Preferably it is 500,000 or more. Although there is no upper limit to the upper limit, it is preferably 1,000,000 or less, more preferably 700,000 or less. Further, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. Note that the weight average molecular weight and number average molecular weight of the polyimide can be determined from standard polystyrene (PS) equivalent values determined by gel filtration chromatography measurement.
Next, the raw materials used in the method for producing the polymer (imide-amic acid copolymer, polyamic acid, polyimide) and the method for producing the varnish of the present invention will be explained.

[Tetracarboxylic dianhydride]
The tetracarboxylic dianhydride used as a raw material in the present production method is not particularly limited as long as it is a tetracarboxylic dianhydride, but preferably contains an aromatic tetracarboxylic dianhydride, more preferably an aromatic tetracarboxylic dianhydride. It is a tetracarboxylic dianhydride.
Among these, from the viewpoint of achieving high molecular weight, at least one compound selected from the group consisting of the compound represented by the formula (a1) and the compound represented by the formula (a2) is preferable, and more Preferably it is a compound represented by the above formula (a1).
When the polymer is a polyamic acid, it preferably contains a compound represented by the formula (a1).
When the polymer is an imide-amic acid copolymer, the raw material for the polyimide unit contains a compound represented by the formula (a2), and the raw material for the polyamic acid unit contains a compound represented by the formula (a1). It is preferable that the compound contains a compound.
Examples of the tetracarboxylic dianhydride include acid dianhydrides, but the invention is not limited thereto, and derivatives thereof may be used as long as they provide the structural unit A in the polymer. Such derivatives include tetracarboxylic acids (free acids) and alkyl esters of the tetracarboxylic acids. Among these, acid dianhydrides are preferred.

[Diamine]
The diamine used as a raw material in this production method is not particularly limited as long as it is a diamine, but preferably contains an aromatic diamine, more preferably an aromatic diamine, and even more preferably a diamine represented by the above formula (b1). It further preferably includes a compound represented by the above formula (b11).
Examples of the diamine include diamine, but the diamine is not limited thereto, and derivatives thereof may be used as long as they provide the structural unit B in the polymer. Examples of such derivatives include diisocyanates corresponding to diamines. Among these, diamines are preferred.

[Terminal sealing agent]
Furthermore, in addition to the above-mentioned tetracarboxylic dianhydride, diamine, and tert-butanol, a terminal capping agent may be used in the production of the polymer. The terminal capping agent is preferably used in step 1-2 in the production of the imide-amic acid copolymer.
As the terminal capping agent, monoamines or dicarboxylic acids are preferable. The amount of the terminal capping agent to be introduced is preferably 0.0001 to 0.1 mol, particularly preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Examples of monoamine terminal capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3- Ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are recommended. Among these, benzylamine and aniline can be preferably used. As the dicarboxylic acid terminal capping agent, dicarboxylic acids are preferred, and a portion thereof may be ring-closed. 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 these, phthalic acid and phthalic anhydride can be preferably used.

〔solvent〕
The solvent used in the method for producing a polymer may be any solvent as long as it can dissolve the produced polymer. Examples include aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, etc., and at least one selected from the group consisting of aprotic solvents, phenol solvents, ether solvents, and carbonate solvents is preferred. .

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 containing cyclic esters.
Among these, the solvent preferably contains at least one selected from the group consisting of a cyclic amide, a chain amide, and a cyclic ester, and more preferably a cyclic amide.
Examples of the cyclic amide include N-methylpyrrolidone, N-methylcaprolactam, and 1,3-dimethylimidazolidinone, with N-methylpyrrolidone being preferred.
Examples of the chain amide include N,N-dimethylformamide, N,N-dimethylacetamide, and tetramethylurea.
Examples of the cyclic ester include γ-butyrolactone and γ-valerolactone.
Other ester solvents include acetic acid (2-methoxy-1-methylethyl) and the like.
Examples of the phosphorus-containing amide solvent include hexamethylphosphoric amide, hexamethylphosphine triamide, and the like.
Examples of the sulfur-containing solvent include dimethylsulfone, dimethylsulfoxide, and sulfolane.
Examples of the ketone solvent include acetone, methyl ethyl ketone, cyclohexanone, methyl cyclohexanone, and the like.

Specific examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4 -xylenol, 3,5-xylenol, etc.
Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, and bis[2-(2-methoxyethoxy)ethyl]. Examples include ether, tetrahydrofuran, 1,4-dioxane and the like.
Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and the like.
Among the above solvents, it preferably contains at least one selected from the group consisting of cyclic amides, chain amides, and cyclic esters, more preferably contains cyclic amides, and still more preferably contains N-methylpyrrolidone. The above solvents may be used alone or in combination of two or more.

[varnish]
The varnish of the present invention contains the polymer obtained by the above manufacturing method and a solvent.
The solvent is not particularly limited as long as it dissolves the polymer, but it is preferable to use the above-mentioned compounds alone or in a mixture of two or more as the solvent used for producing the polymer. Among the above solvents, it preferably contains at least one selected from the group consisting of cyclic amides, chain amides, and cyclic esters, more preferably contains cyclic amides, and still more preferably contains N-methylpyrrolidone.
The varnish of the present invention may be the polymer solution itself obtained by the above-mentioned polymer production method, may have a solvent added thereto, or may have a reduced amount of solvent by concentration or the like. .

When the polymer contained in the varnish of the present invention is a polyamic acid or an imide-amic acid copolymer and contains an amic acid moiety, the varnish of the present invention may further contain an imidization catalyst and a dehydration catalyst. The imidization catalyst may be any imidization catalyst having a boiling point of 40° C. or higher and 180° C. or lower, and amine compounds having a boiling point of 180° C. or lower are preferred. If the imidization catalyst has a boiling point of 180° C. or lower, there is no risk that the film will be colored during drying at a high temperature after film formation and the appearance will be impaired. Moreover, if the imidization catalyst has a boiling point of 40° C. or higher, it is possible to avoid the possibility of volatilization before imidization sufficiently progresses.
An amine compound suitably used as an imidization catalyst includes pyridine or picoline. The above imidization catalysts may be used alone or in combination of two or more.
Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; and the like. These may be used alone or in combination of two or more.

Since the polymer contained in the varnish of the present invention has solvent solubility, it can be made into a highly concentrated varnish. The varnish of the present invention preferably contains 3 to 40% by mass of the polymer, more preferably 5 to 40% by mass, and even more preferably 10 to 30% by mass. The viscosity of the varnish is preferably 1 to 200 Pa·s, more preferably 2 to 20 Pa·s. The viscosity of the varnish is a value measured at 25°C using an E-type viscometer.
In addition, the varnish of the present invention may contain inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, antifoaming agents, optical brighteners, within the range that does not impair the required properties of the polyimide film. It may also contain various additives such as a cross-linking agent, a polymerization initiator, and a photosensitizer.

Although the varnish of the present invention contains a high molecular weight resin, there is little increase in viscosity even in a wide viscosity range, and it has excellent storage stability. Therefore, the rate of increase in viscosity on the 7th day of storage at 23°C is preferably 20% or less, more preferably 15% or less, and still more preferably 12% or less, with respect to the viscosity on day 0. Even more preferably, it is 9% or less.

[Method for manufacturing polyimide film]
A polyimide film can be manufactured using the varnish. Since the varnish contains a high molecular weight resin, a high strength film can be produced. In addition, even though the varnish contains a high molecular weight resin, there is little increase in viscosity even in a wide viscosity range, and it has excellent storage stability, so it is possible to stably produce a high-strength film even after long-term storage. .

Although there are no particular limitations on the method for producing a polyimide film using the varnish of the present invention, the following method is preferred.
That is, a suitable method for producing a polyimide film includes the steps of casting the above-mentioned varnish onto a substrate, and drying the cast varnish to form a polymer film.

Examples of the base material include smooth plate-like objects, such as smooth glass plates, metal plates, and plastic plates.
"Cast on a base material" means "to apply on a base material" and refers to pouring varnish onto a base material and forming it into a film.
After the varnish is cast onto a substrate, the solvent contained in the varnish is removed by heating and dried to form a polymer film. Furthermore, it is preferable to produce a polyimide film by a step of drying the polymer film at a temperature higher than the boiling point of the solvent.
A polyimide film may be obtained by peeling the polymer film from the base material and then drying it at a temperature higher than the boiling point of the solvent, or by drying the polymer film at a temperature higher than the boiling point of the solvent before peeling it from the base material. A polyimide film may be obtained by peeling the polyimide film from the base material. Furthermore, even if the polymer in the polymer film has an amic acid moiety, it can be imidized (dehydration ring closed) by heating at a temperature equal to or higher than the boiling point of the solvent to obtain a polyimide film.
The weight average molecular weight (Mw) of the polyimide contained in the polyimide film obtained by the above manufacturing method is 300,000 or more, preferably 400,000 or more, especially from the viewpoint of elongation among the mechanical strength of the polyimide film. Yes, more preferably 500,000 or more. Although there is no upper limit to the upper limit, it is preferably 1,000,000 or less, more preferably 700,000 or less. Further, from the same viewpoint, the number average molecular weight is preferably 50,000 to 500,000. Note that the weight average molecular weight and number average molecular weight of the polyimide can be determined from standard polystyrene (PS) equivalent values determined by gel filtration chromatography measurement.

The heating temperature when drying the varnish of the present invention to obtain a polymer film is preferably 50 to 150°C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, more preferably 15 minutes to 1 hour.

It is preferable to further include a step of drying the polymer film after removing the solvent contained in the varnish by heating at a temperature equal to or higher than the boiling point of the solvent used. If the polymer in the polymer film has an amic acid moiety, it may be imidized by chemical imidization or the like and then dried at a temperature higher than the boiling point of the solvent, but thermal imidization (dehydration ring closure) may occur in the main drying step. It is preferable to prepare a polyimide film.
The heating temperature for further drying the polymer film is preferably 100 to 500°C, more preferably 200 to 450°C, and even more preferably 300 to 430°C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, more preferably 15 minutes to 1 hour.
When drying the polymer film at a temperature higher than the boiling point of the solvent, heating can be divided into two or more stages. When heating is divided into two or more stages, it is preferably two or more stages. Although there is no upper limit, it is preferably 5 or less.
Although not particularly limited, for example, when dividing into two or more stages, the heating temperature in the first stage is preferably 100 to 300°C, and the heating time is preferably 1 minute to 6 hours. The heating temperature in the final stage is preferably 300 to 500°C, and the heating time is preferably 1 minute to 6 hours. When dividing into two stages, the heating temperature in the first stage is preferably 100 to 300°C, and the heating time is preferably 1 minute to 6 hours. The heating temperature in the second stage is preferably 300 to 500°C, and the heating time is preferably 1 minute to 6 hours.
The atmosphere for further drying the polymer film includes air gas, nitrogen gas, oxygen gas, hydrogen gas, nitrogen/hydrogen mixed gas, etc., but in order to suppress the coloring of the resulting polyimide film, the oxygen concentration must be Preferred are nitrogen gas having a concentration of 100 ppm or less, and a nitrogen/hydrogen mixed gas containing hydrogen at a hydrogen concentration of 0.5% or less.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the intended use, but is preferably 1 to 250 μm, more preferably 5 to 100 μm, and still more preferably 5 to 50 μm. A thickness of 1 to 250 μm allows practical use as a self-supporting film.
The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the varnish, and the amount of varnish used during casting.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays.

The present invention will be specifically explained below using Examples. However, the present invention is not limited to these Examples in any way.
The varnishes obtained in Examples and Comparative Examples were evaluated by the method shown below.

(1) Content of polymer Approximately 3 g of the varnishes obtained in Examples and Comparative Examples were taken and their mass was precisely weighed. Next, the varnish was sufficiently dried in a dryer at 320° C. under nitrogen, and the mass of the dried varnish (polymer) was precisely weighed. The mass of the varnish before drying was designated as (A), and the mass of the varnish (polymer) after drying was designated as (B). The content (%) of the polymer in the varnish was calculated using the formula below.
Polymer content (%) = (B)/(A) x 100
The content of the polymer in the varnish of each Example and each Comparative Example is shown in Table 1-1 and Table 1-2.

(2) Weight average molecular weight of polymer The weight average molecular weight of the polymer contained in the varnish obtained in each Example and each Comparative Example was determined by standard polystyrene (manufactured by Tosoh Corporation) converted value by gel filtration chromatography measurement. Ta. The eluent was 24.8mM LiBr H ₂ O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.5%) and DMF (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for high-performance liquid chromatography). The one to which 63.2 mM phosphoric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., for high performance liquid chromatography) was added was used. The apparatus was Shodex 101 (manufactured by Showa Denko KK), the column was KD-806M (manufactured by Showa Denko KK), the flow rate was 1.0 mL/min, and the column temperature was 40°C.
The molecular weight of the polymer contained in the varnish of each Example and each Comparative Example is shown in Table 1-1 and Table 1-2.

(3) Storage stability evaluation The varnish obtained in each example and each comparative example was treated with NMP ( diluted with N-methyl-2-pyrrolidone). The viscosity of the solution immediately after dilution (before storage) was defined as the viscosity (A) on day 0 of storage. The diluted solution was put into a glass screw tube, purged with nitrogen, and then stored at 23° C. and 50% humidity. The viscosity was measured again on the 7th day of storage, and was defined as the viscosity (B) on the 7th day of storage. The viscosity increase rate was calculated using the following formula.
Thickening rate (%) = [(B) - (A)] / (A) x 100
The results of the storage stability evaluation of the varnishes of each Example and each Comparative Example are shown in Table 1-1 and Table 1-2. The smaller the value of the thickening rate, the better the storage stability.

(4) Tensile elongation evaluation Tensile elongation, which is a film physical property, was evaluated using polyimide films obtained from the varnishes obtained in Examples and Comparative Examples by the method described in the production of polyimide films below.
The tensile elongation rate was measured in accordance with JIS K7127:1999 using a tensile tester "Strograph VG-1E" (manufactured by Toyo Seiki Co., Ltd.). The distance between the chucks was 50 mm, the test piece size was 10 mm x 70 mm, the test speed was 20 mm/min, and the number of tests was 5 times. Those with an average elongation rate of 10% or more were rated A, and those less than 10% were rated B. The larger the average value of elongation, the better the tensile elongation and the better the physical properties of the film.
The evaluation results are shown in Table 1-1 and Table 1-2.

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, and their abbreviations are as follows.
<Tetracarboxylic dianhydride>
BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (manufactured by JFE Chemical Co., Ltd.; compound represented by formula (a2))
s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, compound represented by formula (a1s))
<Diamine>
4-BAAB: 4-aminophenyl-4-aminobenzoate (manufactured by Nihon Junryo Pharmaceutical Co., Ltd.; compound represented by formula (b11))

The abbreviations of solvents and catalysts used in Examples and Comparative Examples are as follows.
NMP: N-methyl-2-pyrrolidone (manufactured by Tokyo Pure Chemical Industries, Ltd.)
TEA: Triethylamine (manufactured by Kanto Kagaku Co., Ltd.)

<Example 1: Production of polyamic acid varnish>
26.101 g (0.114 mol) of 4-BAAB was placed in a 500 mL 5-necked round-bottomed flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean Stark fitted with a cooling tube, a thermometer, and a glass end cap. ) and 192.000 g of NMP were added, the system temperature was set to 70° C. under a nitrogen atmosphere, and the mixture was stirred at a rotational speed of 200 rpm to obtain a solution.
To this solution, 0.254 g (0.003 mol) of tert-butanol and 24.000 g of NMP were added, and further 33.645 g (0.114 mol) of s-BPDA and 24.000 g of NMP were added, and the mixture was heated at 70°C. A solution containing polyamic acid was obtained by stirring for 4 hours. NMP was added to this to give a viscosity of 3 Pa·s at 25° C., thereby preparing a varnish for storage stability evaluation.

<Example 2: Production of imide-amic acid copolymer varnish>
7.449 g (0.033 mol) of 4-BAAB was placed in a 500 mL 5-necked round-bottomed flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean Stark fitted with a cooling tube, a thermometer, and a glass end cap. ) and 49.695 g of NMP were added, the system temperature was set to 70° C. under a nitrogen atmosphere, and the mixture was stirred at a rotational speed of 200 rpm to obtain a solution.
After adding 9.974 g (0.022 mol) of BPAF and 15.000 g of NMP in one batch to this solution, 0.110 g of TEA as an imidization catalyst and 5.000 g of NMP were added, and heated with a mantle heater. The temperature inside the reaction system was raised to 190°C over about 20 minutes. While collecting the components to be distilled off, the temperature inside the reaction system was maintained at 190°C and refluxed for 1 hour. Thereafter, 135.065 g of NMP was added and the temperature inside the reaction system was cooled to 50° C. to obtain a solution containing an oligomer having an imide repeating structural unit.
To the resulting solution were added 17.754 g (0.078 mol) of 4-BAAB and 15.000 g of NMP, then 0.242 g (0.003 mol) of tert-butanol and 5.000 g of NMP, and then A solution containing an imido-amic acid copolymer was obtained by adding 25.606 g (0.087 mol) of s-BPDA and 15.000 g of NMP and stirring at 70° C. for 4 hours. NMP was added to this to give a viscosity of 3 Pa·s at 25° C., thereby preparing a varnish for storage stability evaluation.

<Example 3: Production of imide-amic acid copolymer varnish>
A solution containing an imide-amic acid copolymer was obtained in the same manner as in Example 2, except that the amount of 4-BAAB was changed as shown in Table 1-1. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Examples 4 and 5: Production of imide-amic acid copolymer varnish>
In the same manner as in Example 3, a solution containing an imide-amic acid copolymer was obtained. NMP was added to this so that the solid content (concentration of the polymer in the varnish) was 15% by mass and 20% by mass, respectively, to prepare a varnish for storage stability evaluation.

<Comparative Example 1: Production of polyamic acid varnish>
A solution containing polyamic acid was obtained in the same manner as in Example 1, except that tert-butanol was not used. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Comparative Example 2: Production of polyamic acid varnish>
A solution containing polyamic acid was obtained in the same manner as in Comparative Example 1. NMP was added to this so that the solid content (concentration of the polymer in the varnish) was 15% by mass to prepare a varnish for storage stability evaluation.

<Comparative Examples 3 and 4: Production of polyamic acid varnish>
A solution containing polyamic acid was obtained in the same manner as in Example 1, except that methanol or ethanol was used instead of tert-butanol. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Comparative Example 5: Production of imide-amic acid copolymer varnish>
A solution containing an imide-amic acid copolymer was obtained in the same manner as in Example 2, except that tert-butanol was not used. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Comparative Examples 6 and 7: Production of imide-amic acid copolymer varnish>
In the same manner as in Comparative Example 5, a solution containing an imide-amic acid copolymer was obtained. NMP was added to this so that the solid content (concentration of the polymer in the varnish) was 15% by mass and 20% by mass, respectively, to prepare a varnish for storage stability evaluation.

<Comparative Example 8: Production of imide-amic acid copolymer varnish>
A solution containing an imide-amic acid copolymer was obtained in the same manner as in Comparative Example 5, except that the amount of s-BPDA was changed as shown in Table 1-2. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Comparative Example 9: Production of imide-amic acid copolymer varnish>
A solution containing an imido-amic acid copolymer was obtained in the same manner as in Example 3, except that tert-butanol was not used. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Comparative Example 10: Production of imide-amic acid copolymer varnish>
A solution containing an imide-amic acid copolymer was obtained in the same manner as in Comparative Example 5, except that the amount of 4-BAAB was changed as shown in Table 1-2. NMP was added to this so that the viscosity at 25° C. was 3 Pa·s to obtain a varnish for storage stability evaluation.

<Production of polyimide film>
The polyimide film used in the tensile elongation evaluation was manufactured as follows.
The varnishes produced in the above Examples and Comparative Examples were applied onto a glass plate by spin coating, held at 80°C for 20 minutes on a hot plate, then transferred to a hot air dryer, and heated at a temperature increase rate of 5°C under a nitrogen atmosphere. The temperature was raised to 420° C./min at 420° C. in a hot air dryer under a nitrogen atmosphere for 60 minutes to evaporate the solvent and thermally imidize the mixture to obtain a polyimide film.

As shown in Tables 1-1 and 1-2, the varnish containing the polymer obtained by the production method of the present invention has a wide viscosity range despite containing a high molecular weight resin (polyimide precursor). It can be seen that a varnish with little increase in viscosity and excellent storage stability can be obtained. In addition, in Comparative Examples 8 and 10, the molecular weight of the resin is low.

Claims

A method for producing a polymer, comprising Step 1 of obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride,
The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is 1.00 or more and less than 1.03,
The step 1 is a step of polymerizing diamine and tetracarboxylic dianhydride in the presence of tert-butanol and a solvent,
A method for producing a polymer, wherein the polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units, and has a weight average molecular weight of 300,000 or more.
The method for producing a polymer according to claim 1, wherein the polymer is at least one selected from the group consisting of polyamic acid, polyimide, and imido-amic acid copolymers.
3. The polymer is a polyamic acid, and step 1 is a step of mixing a solution containing a diamine and a solvent, a tetracarboxylic dianhydride, and tert-butanol, and polymerizing the mixture. A method for producing a polymer.
A claim in which the polymer is a polyamic acid, the tetracarboxylic dianhydride contains a compound represented by the following formula (a1), and the diamine contains a compound represented by the following general formula (b1). A method for producing a polymer according to any one of 1 to 3.

(In formula (b1), R 1 , R 2 , and R 3 each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
The polymer is an imide-amic acid copolymer, the tetracarboxylic dianhydride is composed of a first tetracarboxylic dianhydride and a second tetracarboxylic dianhydride, and the diamine is The method for producing a polymer according to claim 1 or 2, comprising a first diamine and a second diamine, and wherein the step 1 comprises the following step 1-1 and the following step 1-2.
Step 1-1: A step of reacting the first tetracarboxylic dianhydride and the first diamine in the presence of a solvent to obtain an imide oligomer. Step 1-2: The imide oligomer obtained in Step 1-1. A step of mixing and polymerizing the second tetracarboxylic dianhydride, the second diamine, and tert-butanol
The polymer is an imide-amic acid copolymer, the first tetracarboxylic dianhydride contains a compound represented by the following formula (a1), and the second tetracarboxylic dianhydride contains a compound represented by the following formula (a2), and the first diamine and the second diamine contain a compound represented by the following formula (b1), the method for producing a polymer according to claim 5. .

(In formula (b1), R 1 , R 2 , and R 3 each independently represent an organic group having 1 to 20 carbon atoms. h, i, j, and k are integers of 0 to 4.)
The method for producing a polymer according to any one of claims 1 to 6, wherein the amount of tert-butanol in step 1 is 2 mol% or more based on the total amount of tetracarboxylic dianhydride in step 1.
A varnish containing a polymer obtained by the production method according to any one of claims 1 to 7 and a solvent.
A method for producing a varnish comprising Step 1 of obtaining a polymer by polymerizing a diamine and a tetracarboxylic dianhydride,
The molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) in Step 1 is 1.00 or more and less than 1.03,
The step 1 is a step of polymerizing diamine and tetracarboxylic dianhydride in the presence of tert-butanol and a solvent,
The polymer has at least one repeating unit selected from the group consisting of amic acid units and imide units, and has a weight average molecular weight of 300,000 or more,
A method for producing a varnish, wherein the varnish contains the polymer and a solvent.
A varnish obtained by the manufacturing method according to claim 9.
The varnish according to claim 8 or 10, wherein the viscosity increase rate on the 7th day of storage at 23°C is 15% or less relative to the viscosity on the 0th day.
The varnish according to claim 8, 10, or 11, wherein the solvent contains at least one selected from the group consisting of a cyclic amide, a chain amide, and a cyclic ester.
The varnish according to any one of claims 8 or 10 to 12, wherein the solvent contains N-methylpyrrolidone.
A method for producing a polyimide film, comprising the steps of casting the varnish according to any one of claims 8 or 10 to 13 on a base material, and drying the cast varnish to form a polymer film.