JP2003128786A - Polyimide-amic acid ester copolymer, gel film, and method for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide-amic acid ester copolymer as the precursor of a poly-p-phenylene pyromellitimide-based polyimide capable of undergoing drawing operation through preventing the hydrolysis of its molecular chain contributing to its physical property deterioration, to provide a gel film of the copolymer, and to provide respective methods for producing them. SOLUTION: This copolymer is produced from (A) an aromatic amic acid ester formed from aromatic tetracarboxylic acids with pyromellitic acid accounting for >=30 mol% thereof and aromatic diamines with p-phenylenediamine accounting for >=30 mol% thereof and (B) an aromatic imide, wherein the molar ratio A/B is (0.5:99.5) to (99.5:0.5). The gel film of the copolymer is obtained by soaking an alcohol-containing solution with a swollen form put to dehydration condensation as a result of bringing a solution of the polyamic acid formed from the diamine and the acid anhydride into a solvent containing a dehydration condensation agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyimide amic acid ester copolymer, which is a precursor of polyparaphenylenepyromellitimide polyimide, which is excellent in molding processability and which prevents hydrolysis of a molecular chain which causes deterioration of physical properties. The present invention relates to a gel film and a manufacturing method thereof.

[0002]

2. Description of the Related Art Polyimide has been extensively developed due to its heat resistance and excellent mechanical properties. In particular, wholly aromatic polyimide is expected to exhibit particularly high heat resistance and mechanical properties due to its rigid structure. However, especially in the case of wholly aromatic polyimide, it is infusible and insoluble, and it is difficult to perform molding in the polyimide state. Therefore, molding is performed in the precursor state.

For example, as the most common precursor, molding and orientation in a polyamic acid state, which is a reaction of an amine component and an acid anhydride, has been attempted. However, in the case of polyparaphenylenepyromellitimide-based polyimide, which is expected to have a high Young's modulus during orientation due to its rigid molecular structure,
The polyamic acid that is the precursor thereof is easily hydrolyzed during molding, and the resulting polyimide has low strength, and it is difficult to obtain a molded body such as a film having a strength that can be practically used.

Polymer Papers Vol. 65, No 5, p
In p282-290, a method of forming a polyamic acid solution, which is a precursor of polyparaphenylenepyromellitimide, after film formation, and uniaxially stretching the obtained polyamic acid film in a solvent and then imidizing the polyamic acid solution is reported. . However, a series of operations such as film formation, stretching, drying, and heat treatment all need to be performed in a dry atmosphere, and even with this result in mind, it is difficult to overcome brittleness while exerting a high elastic modulus by stretching. Met.

In the patent application filed by the present inventors, as another precursor, a swelled gel film of polyisoimide, which is a structural isomer of polyimide, is used as a precursor, and this is stretched to produce a polyimide with significantly improved toughness. Has been reported. However, since isoimide reacts with water to be converted to amic acid and the molecular chain is hydrolyzed, a series of operations such as film formation, stretching, drying, and heat treatment must be performed in a dry atmosphere.

As an example of using a polyamic acid ester as a precursor having higher hydrolysis resistance, (1) Polym
er 40 (1999) pp. 2681-2685, pyromellitic dianhydride is reacted with ethanol to form a 2-ester and further converted into an acid chloride, which is then reacted with para-phenylenediamine to obtain a target polyamic acid ester. It has been reported that a polyamic acid ester film is obtained by casting this from a solution and then further heat-treated to obtain an intended polyimide film. However, no attempt has been made to impart orientation by stretching or the like, and no improvement in mechanical properties has been reported.

Polymer Preprants
Japan Vol. 41, N0.9 (1992) 37
On pages 52-3754, highly oriented polyamic acid ester fibers utilizing the fact that a polyamic acid ester having a long alkyl side chain having a carbon number of 10 to 14 exhibits a liquid crystal state, and further highly oriented by thermal imidization thereof Imide fibers have been reported. However, when the liquid crystal is passed through such a liquid crystal state, the uniaxial orientation is remarkably improved, but the physical properties are balanced in the two orthogonal directions which are generally required for industrial films. Realizing a film is difficult.

An example of using a polyimide amidic acid ester copolymer as a precursor is, for example, JP-A-8-231.
In JP 719, a polyamic acid ester-imide is obtained by preliminarily synthesizing a diamine containing an amide ester group, and then reacting with an acid anhydride to chemically imidize a polyamic acid ester-imide, which is molded from a solution. Obtaining films and fibers. However, this method cannot be applied to polyparaphenylenepyromellitimide polyimide because its precursor polyimide amidate ester copolymer is insoluble in general molding solvents.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a polyimide amic acid ester which is a precursor of polyparaphenylenepyromellitimide polyimide, which is capable of preventing hydrolysis of a molecular chain which causes deterioration of physical properties and is excellent in molding processability. Copolymers, films therefrom, and methods of making the same are provided.

[0010]

According to the present invention, an aromatic tetracarboxylic acid containing at least 30 mol% of pyromellitic acid and an aromatic tetracarboxylic acid is used.
Aromatic amic acid ester (A) composed of an aromatic diamine containing 0 mol% or more of paraphenylenediamine
And the aromatic imide (B), and the molar ratio of (A) and (B) is in the range of 0.5: 99.5 to 99.5: 0.5. The ester copolymer and the polyimide amic acid ester copolymer gel film which is swollen by a solvent and has a weight swelling degree of 3 to 100 times.

When the amount of pyromellitic acid and paraphenylenediamine is less than 30 mol%, the orientation property of the polyimide amidate ester copolymer gel during stretching is insufficient.
When the ratio of (A) :( B) is smaller than 0.5: 99.5, the ratio of (B) is 9 when the ratio of (B) is 9 when the ratio of (A) is less than 0.5: 99.5.
If it is less than 9.5: 0.5, the orientation property of the obtained polyimide / amic acid ester copolymer gel during stretching is insufficient. If the degree of swelling of the polyimide / amic acid ester copolymer gel is less than 3, the stretching ratio at the time of stretching is reduced, and if it exceeds 100, a large amount of solvent is used, and the economical efficiency of the process is reduced. The alcohol residue constituting the ester portion of the polyamic acid ester (A) is composed of an aliphatic or aromatic alcohol.

This method for producing a gel film is characterized in that a solution of polyamic acid is introduced into a solvent containing a dehydration condensation agent and then immersed in a solution containing alcohol.

Hereinafter, (a) preparation of a polyamic acid solution,
(A) Preparation of Swelled Molded Body by Dehydration Condensation (c) Polyimide amidate ester copolymerization will be described step by step.

(A) Preparation of Polyamic Acid Solution A polymer of polyamic acid is obtained by reacting an aromatic tetracarboxylic acid with an aromatic diamine in solution. In the present invention, mainly 30 mol% or more of pyromellitic dianhydride is used as the acid component. It is more preferable to use 50 mol% or more pyromellitic dianhydride, and it is further preferable to use 80 mol% or more pyromellitic dianhydride.

Other components include 1,2,3,4-benzenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride and 2,3,4,5-thiophenetetraanhydride. Carvone dianhydride, 2,2 ', 3,3'
-Benzophenone tetracarboxylic dianhydride, 2,
3 ', 3,4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3,3 ', 4
4'-p-terphenyltetracarboxylic dianhydride,
2,2 ', 3,3'-p-terphenyltetracarboxylic dianhydride, 2,3,3', 4'-p-terphenyltetracarboxylic dianhydride, 1,2,4,5- Naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,2,6,7-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetra Carboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,6,7-
Anthracene tetracarboxylic dianhydride, 1,2,5
6-anthracene tetracarboxylic dianhydride, 1,2,
6,7-phenanthrene tetracarboxylic acid dianhydride,
1,2,7,8-phenanthrene tetracarboxylic dianhydride, 1,2,9,10-phenanthrene tetracarboxylic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride Thing, 2,6-dichloronaphthalene-1,
4,5,8-Tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-
1,4,5,8-tetracarboxylic dianhydride, 1,4
5,8-Tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride Anhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-
Dicarboxyphenyl) sulfone dianhydride, bis (3,3
4-dicarboxyphenyl) sulfone dianhydride, 1,1
-Bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane Dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,6-bis (3,4-dicarboxyphenoxy) pyridine dianhydride, 1,1,1,3 3,3-hexafluoro-2,2
Examples thereof include, but are not limited to, bis (3,4-dicarboxyphenyl) propane dianhydride and bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride.

As the diamine component, 30 mol% or more of para-phenylenediamine is used in the amine component. Fifty
More preferably, mol% or more of paraphenylenediamine is used, and more preferably 80 mol% or more of paraphenylenediamine.

Specific examples of the other components include m-
Phenylenediamine, 1,4-diaminonaphthalene,
1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,6-diaminoanthracene, 2,7-
Diaminoanthracene, 1,8-diaminoanthracene, 2,4-diaminotoluene, 2,5-diamino (m
-Xylene), 2,5-diaminopyridine, 2,6-diaminopyridine, 3,5-diaminopyridine, 2,4-
Diaminotoluenebenzidine, 3,3′-diaminobiphenyl, 3,3′-dichlorobenzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine,
2,2'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,
4'-diaminodiphenyl ether, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylsulfone, 4,
4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl thioether, 4,4'-diamino-3,3 ', 5,5' -Tetramethyldiphenyl ether, 4,4'-diamino-
3,3 ', 5,5'-tetraethyldiphenyl ether, 4,4'-diamino-3,3', 5,5'-tetramethyldiphenylmethane, 1,3-bis (3-aminophenoxy) benzene, 1,3 -Bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy)
Benzene, 2,6-bis (3-aminophenoxy) pyridine, 1,4-bis (3-aminophenylsulfonyl)
Benzene, 1,4-bis (4-aminophenylsulfonyl) benzene, 1,4-bis (3-aminophenylthioether) benzene, 1,4-bis (4-aminophenylthioether) benzene, 4,4′-bis (3-Aminophenoxy) diphenyl sulfone, 4,4′-bis (4-aminophenoxy) diphenyl sulfone, bis (4-aminophenyl) amine bis (4-aminophenyl) -N-methylamine bis (4-aminophenyl) −
N-phenylamine bis (4-aminophenyl) phosphine oxide, 1,1-bis (3-aminophenyl) ethane, 1,1-bis (4-aminophenyl) ethane,
2,2-bis (3-aminophenyl) propane, 2,2
-Bis (4-aminophenyl) propane, 2,2-bis (4-amino-3,5-dimethylphenyl) propane,
4,4'-bis (4-aminophenoxy) biphenyl,
Bis [4- (3-aminophenoxy) phenyl] sulfone, Bis [4- (4-aminophenoxy) phenyl] sulfone, Bis [4- (4-aminophenoxy) phenyl] ether, Bis [4- (4-amino) Phenoxy) phenyl] methane, bis [3-methyl-4- (4-aminophenoxy) phenyl] methane, bis [3-chloro-4
-(4-aminophenoxy) phenyl] methane, bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-aminophenoxy) phenyl] ethane, 1 , 1-bis [3-methyl-4- (4-aminophenoxy) phenyl] ethane,
1,1-bis [3-chloro-4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] ethane,
2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3-methyl-4- (4-
Aminophenoxy) phenyl] propane, 2,2-bis [3-chloro-4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3,5-dimethyl-4-]
(4-Aminophenoxy) phenyl] propane, 2,2
-Bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3-methyl-4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3,5-dimethyl-4] -(4-Aminophenoxy) phenyl] butane, 2,2-bis [3,5-dibromo-4- (4-aminophenoxy) phenyl] butane, 1,1,1,3
3,3-hexafluoro-2,2-bis (4-aminophenyl) propane, 1,1,1,3,3,3-hexafluoro-2,2-bis [3-methyl-4- (4- Aminophenoxy) phenyl] propane and the like can be mentioned, but the invention is not limited thereto.

The solvent for polymerizing the polyamic acid may be any solvent which does not react with a dehydrating condensing agent such as DCC (N, N'-dicyclohexylcarbodiimide) / acetic anhydride and amine and which dissolves the polyamic acid. .

Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone hexamethylphosphoramide, 1,3-dimethylimidazolidinone, tetramethylurea and 1,3-dipropyl. Imidazolidinone, N-methylcaprolactam,
Aprotic polar solvents such as dimethyl sulfoxide, dimethyl sulfone, tetramethyl sulfone, ethylene glycol, pyridine, 2-picoline, 3-picoline, 4
-Picoline, 2,3-lutidine, 2,4-lutidine,
Heteroaromatic compounds such as 2,5-lutidine, 2,6-lutidine, 3,4-lutidine, 3,5-lutidine, and 2,6-lutidine, cresols, and the like can be given.

These solvents are carbon tetrachloride, chloroform, dichloromethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-
To be used in admixture with other organic solvents such as tetrachloroethane, 1,1,2,2-tetrachloroethane, trichlorethylene, tetrachloroethylene, and other organic halides, benzene, toluene, benzonitrile, xylene, solvent naphtha, and dioxane. It is possible, but not limited to this.

In order to obtain the polyamic acid in the present invention, the amount of diamine used in the above organic solvent is preferably 0.90 to 1.1 as a ratio to the number of moles of acid anhydride.
It is preferable to react it as 0, more preferably 0.95 to 1.05 to obtain a polyamic acid.

In order to block the ends of the polymer in this polymer, phthalic anhydride and its substitution product, hexahydrophthalic anhydride and its substitution product, succinic anhydride and its substitution product, and aniline and its substitution product as the amine component. However, the present invention is not limited to this. The reaction temperature is preferably -10 to 100 ° C, more preferably -10 to 80 ° C. Further, it is more preferable that the obtained polyamic acid solution is filtered under a nitrogen atmosphere to remove the solid matter so that a film can be formed later. The higher the inherent viscosity of the obtained polymer is, the more preferable it is, and it is particularly preferable that it is 3 or more.

(B) Preparation of a dehydrated condensation-swelled molded product, and a dehydrated condensation-swelled molded product of a polyamic acid is obtained by directly introducing a polyamic acid solution as a film into a condensing agent solution. At this time, as the condensing agent, acid anhydrides such as acetic anhydride, benzoic anhydride, and trifluoroacetic acid dianhydride; chlorides such as phosgene, thionyl chloride, tosyl chloride, and nicotyl chloride; phosphorus trichloride, triphenyl phosphite , Phosphorus compounds such as cyanide diethylphosphate; N, N
N-N such as'-dicyclohexylcarbodiimide-
Condensing agents such as disubstituted carbodiimides are included. In order to obtain a gel film having high stretchability, acetic anhydride, N, N'-dicyclohexylcarbodiimide and the like are more preferable, but the present invention is not limited thereto.

In order to further facilitate the condensation reaction, tertiary aliphatic amines such as trimethylamine, triethylamine, tributylamine, diisopropylethylamine and triethylenediamine; N, N-dimethylaniline, 1,8-bis (N, Aromatic amines such as N-dimethylamino) naphthalene, pyridine, lutidine, quinoline, isoquinoline, 1,8-diazabicyclo [5.
4.0] Heterocyclic compounds such as undecene and N, N-dimethylaminopyridine may be used as a reaction accelerator.

At this time, the amount of the reaction catalyst with respect to the dehydration condensing agent is not particularly limited, but is 1 mol% or more, preferably 10 mol% or more.

Further, the condensing agent may be a solution using the following solvents. The solvent constituting the solution may be a general organic solvent in which the condensing agent dissolves and does not react, and the condensing agent solution does not substantially dissolve the gel film. Particularly preferably, by using a condensing agent solution that does not dissolve the gel body but swells, the subsequent esterification proceeds rapidly and the resulting polyimide-polyamic acid ester swells sufficiently and the subsequent stretching operation. Is possible. The degree of swelling is defined as the degree of swelling = the weight of the swollen gel body / the weight after drying, which is not particularly specified but is 2 to 10
It is preferably 0.

The solvent is not particularly limited, but N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N'-diethylacetamide,
Can be selected from amide solvents such as and general organic solvents such as aromatic hydrocarbons, alcohols, ketones, esters, ethers, etc., especially N-methyl-2-pyrrolidone, N, N ',-dimethylacetamide, etc. A highly polar solvent is preferably used when a gel body that gives a polyimide having high rigidity after imidization is used.

These organic solvents may be used alone,
Alternatively, two or more kinds may be used in combination. Further, when the polyisoimide and amic acid components contained in the obtained gel body react with water, the physical properties of the finally obtained polyimide film will be deteriorated, so that the solution is preferably dehydrated.

The concentration of the condensing agent in the condensation solution is not specified, but it is preferably 0.5% or more and 100% or less in order to allow the reaction to proceed sufficiently. The reaction temperature for reacting the condensing agent and the polyamic acid is not particularly limited, but a temperature not lower than the freezing point of the condensing agent solution and not higher than the boiling point of the solvent can be used.

The method of introducing the polyamic acid solution into the condensing agent solution in the method of obtaining the gel film by casting the polyamic acid solution as a film and directly introducing it into the condensation solution is a generally known wet or dry wet molding method. Any method such as a method may be used. Examples of the film forming method include, but are not limited to, a die extrusion method, a casting method using an applicator, and a method using a coater. Further, in order to prevent the deactivating of the condensing agent, it is preferable to carry out these steps in a low humidity atmosphere.

(C) Polyimide amidate ester copolymerization By dipping the partially isoimidated and swollen shaped article obtained by the above-mentioned method in a solution containing alcohol, the isoimide moiety is converted to an imide or amidate ester. The desired polyimide-amide esterification reaction is performed.

The alcohol is a compound represented by the general formula (1) R—OH (1) (R is an alkyl chain having 1 to 30 carbon atoms and an aromatic hydrocarbon) and is not particularly limited.

The alcohol-containing solution preferably contains 2 to 100% of alcohol, and it is preferably carried out under dry conditions in order to prevent amide oxidation of isoimide.

Other solutions are not particularly limited. In particular, a solution that swells the resulting polyimide amidate ester copolymer and the partially isoimidated and swollen molded body without dissolving them is preferable. In addition, a reagent that traps water may be mixed to prevent hydrolysis. The reaction temperature is not limited as long as the solution containing alcohol does not volatilize. The reaction time is not limited as long as polyisoimide is sufficiently converted into a polyamic acid ester or polyimide having high hydrolysis resistance.

In the amic acid component of the polyimide amic acid ester copolymer thus obtained, the cis form
The trans form is not particularly limited.

The degree of swelling by weight of the polyimide / amic acid ester copolymer gel film is not particularly specified, but it is preferably 3 to 100 times, and more preferably 5 times or more in consideration of the improvement of the stretchability thereafter. This gel film was stretchable even at room temperature.

[0037]

EXAMPLES The method of the present invention will be described in more detail below with reference to examples. However, these examples do not limit the scope of the present invention. The polyamic acid has an inherent viscosity of 0.5 g in NMP / 100 ml.
At 35 ° C. Further, the imidization ratio is a peak at 1500 cm ^-1 attributable to skeletal vibration and 720c.
It was calculated from the peak intensity ratio of m ⁻¹ .

(A) Preparation of Polyamic Acid Solution In a reaction vessel equipped with a thermometer, a stirrer and a raw material inlet,
1500 ml of N-methyl-2-pyrrolidone (NMP) dehydrated with molecular sieves in a nitrogen atmosphere was added, and 21.4 g of paraphenyldiamine was further added and completely dissolved, followed by cooling to 0 ° C. in an ice bath. 43.2 g of pyromellitic dianhydride was added to the cooled diamine solution and reacted. The reaction temperature was raised to 25 ° C., and the reaction was continued for 1 hour in a cooled state. After reacting for 2 hours at room temperature, 0.011 g of aniline was added and further reacted for 30 minutes. After completion of the reaction, the mixture was filtered under a nitrogen atmosphere and then defoamed to obtain a polyamic acid solution. The logarithmic viscosity of this solution was 4.12, and the final polymer concentration was 4 wt%.

(B) Preparation of dehydrated condensation-formed and swollen molded body DC in a container equipped with a temperature controller and an agitator
A N-methyl-2-pyrrolidone solution having a C (N, N′-dicyclohexylcarbodiimide) concentration of 28 wt% was added, and the mixture was heated to 40 ° C., D
A CC bath was created. The polyamic acid solution prepared in (a) above was cast on a glass substrate using a doctor blade having a thickness of 1.0 mm. This was introduced into the above-mentioned DCC bath to be solidified by reaction, and then peeled off from the glass substrate,
This was further immersed in NMP at 40 ° C. for solvent replacement to obtain a sheet. The degree of weight swelling was 17 times.

(C) Polyimide amidate ester copolymerization The dehydration-condensed and swollen molded article produced in (a) above was dehydrated under dry conditions such as dehydrated methanol, NMP, DCC (N, N).
A polyimide amidate ester copolymer gel film was obtained by immersing in a solution containing'-dicyclohexylcarbodiimide) for 24 hours. When confirmed by IR spectrum, the reaction proceeded completely, and the broad peaks at around 1660 cm ^-1 and 3000 cm ^-1 attributed to the polyamic acid disappeared and were attributed to the polyamic acid ester 1.
670 cm ⁻¹ , 1605 cm ⁻¹ peaks and 1780 cm ⁻¹ , 1370 cm ⁻¹ , 72 assigned to polyimide
A peak at 0 cm ^-1 was observed (Fig. 1). The imidization ratio was 60%. The degree of weight swelling was 7 times.

This gel film can be stretched even at room temperature, and it is also possible to finally obtain the intended oriented polyparaphenylenepyromellitimide by subjecting it to frame fixing and heat treatment after stretching.

[0042]

By using the method of the present invention, it is possible to produce a stretchable polyimide precursor while preventing hydrolysis of polyamic acid, and to obtain an oriented polyimide film by thermal imidization of the polyimide precursor.

[Brief description of drawings]

FIG. 1 is an IR spectrum of a polyimide amic acid ester copolymer gel film obtained in an example.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA60 AF14 AF45 BA02 BB02                       BB07 BC01 BC02                 4J043 PA02 PA04 PA05 QB15 QB31                       SA06 SB01 SB02 TA14 TA22                       TB01 TB02 UA121 UA122                       VA011 VA022 ZA12 ZA31

Claims (4)

[Claims] 1. An aromatic amic acid ester (A) composed of an aromatic tetracarboxylic acid containing 30 mol% or more of pyromellitic acid and an aromatic diamine containing 30 mol% or more of paraphenylenediamine, and an aromatic compound. It is composed of imide (B) and the molar ratio of (A) and (B) is 0.5: 99.5.
The polyimide amidate ester copolymer is characterized by being in the range of ˜99.5: 0.5. 2. A copolymer gel film comprising a polyimide amidate ester copolymer according to claim 1, which is swollen by a solvent and has a weight swelling degree of 3 to 100 times. 3. A solution of a polyamic acid obtained by a reaction of an aromatic tetracarboxylic acid and an aromatic diamine is introduced into a solvent containing a dehydration condensation agent, and then immersed in a solution containing alcohol. The method for producing the polyimide / amide ester copolymer according to claim 1, wherein 4. A solution of a polyamic acid obtained by a reaction of an aromatic tetracarboxylic acid and an aromatic diamine is introduced into a solvent containing a dehydration condensation agent, and then immersed in a solution containing alcohol. A method for producing a gel film comprising the polyimide / amic acid ester copolymer according to claim 2.