JPH0126372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing aromatic polyimide. More specifically, the present invention relates to a method for producing an aromatic polyimide solution with high concentration and low solution viscosity.

The method for producing aromatic polyimide involves producing an aromatic polyamic acid solution, which is a precursor of aromatic polyimide, from a tetracarboxylic acid component and a diamine component, and then imidizing the polyamic acid by heating or using a dehydrating agent. Method (two-stage method)
A method (one-step method) in which a tetracarboxylic acid component and a diamine component are polymerized and imidized at high temperature to form an aromatic polyimide solution is conventionally well known.

Of these, in the former method (two-step method), the solubility of the intermediate polyamic acid is poor, and expensive and highly hygroscopic solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide must be used. In addition, when stored at room temperature, viscosity increases and gelation occurs, so it has the disadvantage that it must be stored under cooling. Furthermore, during imidization, eliminated products such as water are generated, so for example,
When used for purposes such as covering electric wires, it has drawbacks such as a tendency to cause defects called "blisters."

On the other hand, in the latter method (one-stage method), a soluble aromatic polyimide can be obtained only when specific tetracarboxylic acids and diamines are used, so selection of these raw material components and solvents is important.

Regarding this one-step method, for example,
No. 113597 discloses that a soluble aromatic compound is produced by polymerizing and imidizing a tetracarboxylic acid component mainly composed of biphenyltetracarboxylic acids and an aromatic diamine component in an approximately equimolar organic polar solvent at high temperature. A method for producing polyimide is described. This method solves the previously known problems of soluble polyimides produced using benzophenone tetracarboxylic acids as acid components, namely, when the polymerization reaction temperature exceeds 160°C, the resin becomes cloudy or gels. The stability of the solution decreases (Tokukosho
44-9576), and because it is necessary to use a special diamine that is asymmetrical or has a side chain as a diamine component, the heat resistance and mechanical properties are low (for example, Japanese Patent Publication No. 46-17145,
No. 47-26878, Special Publication No. 18639, Special Publication No. 18639, Special Publication No. 18639-
No. 19119, Special Publication No. 49-30717, Special Publication No. 49-30718
It was intended to improve the problems described in various publications such as Japanese Patent Publication No. 49-106599).

However, in the method disclosed in JP-A-50-113597, the polymerization/imidization reaction is carried out at high temperatures, so the reaction proceeds rapidly and the resulting aromatic polyimide has an extremely high degree of polymerization. Therefore, with this method, it is difficult to produce an aromatic polyimide solution having a desired solution viscosity with good reproducibility.

Particularly when using an aromatic polyimide solution as a varnish, a high polymer concentration is desired from the viewpoint of productivity and cost. It is desired that the solution has a low viscosity of about poise/30°C. In order to obtain such a high concentration and low viscosity solution, it is necessary to suppress the degree of polymerization of polyimide produced in the polymerization/imidization reaction.

The polymerization/imidization reaction that makes it possible to suppress the degree of polymerization of polyimide is described in JP-A-56-
38324 and JP-A-57-34127, a tetracarboxylic acid component containing biphenyltetracarboxylic acid and an aromatic diamine are used in approximately equal moles,
The polymerization reaction system is made into a closed system, and if necessary, water is added to the reaction system and the water pressure of the reaction system and/or the water content of the polymerization liquid or the water content of the polymerization liquid reaches a constant value. A method for controlling solution viscosity by polymerizing at a polymerization temperature of .degree. C. is disclosed.

According to the description in the above-mentioned Japanese Patent Application Laid-open No. 56-38324,
a tetracarboxylic acid component containing 45 mol% or more of 3,3′,4,4′-biphenyltetracarboxylic acids;
It is said that a polyimide with a logarithmic viscosity of 0.7 to 6 can be obtained from an aromatic diamine whose main component is 4,4'-diaminodiphenyl ether. There is no description regarding the production of aromatic polyimide. Also, according to the description in Japanese Patent Application Laid-Open No. 57-34127, 2, 3,
It is said that a polyimide with a logarithmic viscosity of 0.2 to 6 can be obtained from a tetracarboxylic acid component containing 70 mol% or more of 3',4'-biphenyltetracarboxylic acids and an aromatic diamine; In the examples, there is no description of the production of an aromatic polyimide having a logarithmic viscosity of 1.0 or less.

In other words, these methods require the reaction system to be a closed system, and the effect of water on inhibiting the polymerization reaction is relatively small. However, there was the inconvenience that the water pressure of the reaction system and the water content of the polymerization solution had to be kept extremely high.

The present inventor has discovered that the polymerization reaction in the polymerization/imidization reaction between the tetracarboxylic dianhydride component and the diamine component can be suppressed by using a phenolic solvent in the reaction system and introducing a monohydric alcohol. The present invention was achieved by discovering that this can be achieved easily and extremely effectively.

Since the polymerization reaction suppression effect of the polymerization/imidization reaction in the present invention is extremely high, there is no need to make the reaction system a particularly closed system, and an aromatic polyimide solution with high concentration and low solution viscosity can be obtained extremely easily in a normal pressure system. be able to. Moreover, the polyimide solution obtained by the method of the present invention has better long-term viscosity stability than the aromatic polyimide solution obtained using the known reaction suppression method through the coexistence of water in the reaction system. show.

According to the present invention, the monohydric alcohol is introduced into the polymerization reaction in the polymerization/imidization reaction of the tetracarboxylic dianhydride component and the diamine component by coexisting the monohydric alcohol in the reaction system or by using a phenolic solvent. This is carried out by reacting a tetracarboxylic acid component and a monohydric alcohol in advance.

Therefore, the present invention provides 0.5 times or more mole of aromatic tetracarboxylic dianhydride, and
2.
Polymerizing and imidizing an aromatic tetracarboxylic dianhydride containing 40 mol% or more of 3,3',4'-biphenyltetracarboxylic dianhydride and a substantially equimolar amount of an aromatic diamine. 2,3,3',4'-
40 mol% biphenyltetracarboxylic dianhydride
The aromatic tetracarboxylic dianhydride containing more than
0.5 times the mole or more, and 40% by weight based on the total of the phenolic solvent and monohydric alcohol
Logarithm, characterized by reacting a monohydric alcohol in the following amount, and then reacting with aromatic diamine in a substantially equimolar amount to the aromatic tetracarboxylic dianhydride to polymerize and imidize the aromatic tetracarboxylic dianhydride. The present invention provides a method for producing an aromatic polyimide solution containing 15 to 50% by weight of aromatic polyimide having a viscosity of 0.1 to 1.0.

According to the present invention, for example, by using an inexpensive phenolic solvent such as cresol, which is a general-purpose solvent for electric wire varnish, the polymer concentration is as high as 15 to 50% by weight, but as low as several hundred poise/30°C or less. An aromatic polyimide solution having a solution viscosity can be produced extremely easily and with good reproducibility. The aromatic polyimide solution obtained is
As mentioned above, it has excellent long-term storage stability. Furthermore, when used as working wire coatings, coatings, films, etc., it has extremely excellent characteristics as a varnish, such as excellent heat resistance, electrical insulation, mechanical properties, abrasion resistance, and solvent resistance. It is.

Next, the present invention will be explained in detail.

The aromatic tetracarboxylic dianhydride used in the present invention containing 40 mol% or more of 2,3,3',4'-biphenyltetracarboxylic dianhydride is However, it does not cause turbidity or gelation and has high solubility.

In the above tetracarboxylic dianhydride component, 2,
Acid anhydrides that can be used in combination with 3,3',4'-biphenyltetracarboxylic dianhydride include 3,
3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride are preferred. However, in small amounts, pyromellitic dianhydride, bis(3,4-
dicarboxyphenyl)methane dianhydride, 2,2
-Bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, etc. Can be used. Moreover, a mixture of three or more types of acid anhydrides may be used as the acid component.

The diamine component used in the present invention is 4,4′-
Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, o-tolidine,
3,5-diaminobenzoic acid, o-dianisidine,
These are aromatic diamines such as 1,5-naphthalenediamine, 2,6-naphthalenediamine, and p-phenylenediamine, and these may be used alone or in combination.

These aromatic tetracarboxylic dianhydrides and
The aromatic diamine and the aromatic diamine are used in substantially equimolar amounts, and the aromatic polyimide concentration in the resulting aromatic polyimide solution is 15 to 50% by weight. If the aromatic polyimide concentration in the aromatic polyimide solution that is produced exceeds 50% by weight, the aromatic polyimide solution will have too high a viscosity and will be difficult to use, for example, in varnishes for coating electrical materials. It cannot be used for any purpose,
It is also difficult to use it practically in various other applications. Further, when the aromatic polyimide concentration in the aromatic polyimide solution is less than 15% by weight, the solution viscosity becomes sufficiently low, but such a dilute solution has low practical value.

Preferred examples of the phenolic solvent used in the present invention include cresol and xylenol, which can be used alone or in combination. Further, a portion of other phenolic solvents such as phenol and halogenated phenol may be mixed with cresol, xylenol, and the like.

The monohydric alcohol introduced into the reaction system of the present invention has the effect of suppressing excessive progress of the polymerization reaction (increasing the molecular weight). Monohydric alcohols that can be used in the present invention include lower aliphatic monohydric alcohols,
Aromatic monohydric alcohol, alicyclic monohydric alcohol,
and monohydric alcohols having an ether group. Among these, examples of lower aliphatic alcohols include methanol, ethanol, propanol, and butanol, and examples of aromatic monohydric alcohols include benzyl alcohol and α-(or β-)phenethyl alcohol. Examples of the alicyclic monohydric alcohol include cyclohexanol, and examples of the monohydric alcohol having an ether group include methyl cellosolve and ethyl cellosolve.

The amount of monohydric alcohol introduced into the polymerization/imidization reaction system of the present invention is 0.5 times or more, preferably 1 times or more in mole relative to the tetracarboxylic dianhydride, and the amount of monohydric alcohol introduced into the polymerization/imidization reaction system of the present invention is 0.5 times or more, preferably 1 times or more in mole, and The content should be 40% by weight or less based on the total amount. If the amount of monohydric alcohol used relative to the tetracarboxylic dianhydride is small, the effect of suppressing polymerization will not be sufficient, and if the amount used is too large, it will adversely affect the solubility of the aromatic polyimide produced (Comparative Example 2).

In the present invention, the monohydric alcohol is reacted with an aromatic tetracarboxylic dianhydride in a phenolic solvent in advance, and then subjected to a polymerization/imidization reaction; or It is used in any of the embodiments in which it is allowed to coexist in the reaction system.

When a monohydric alcohol is reacted with a tetracarboxylic dianhydride in advance, in order to achieve the reaction quickly, it is preferable to heat the reaction system to completely dissolve the acid anhydride. However, the heating temperature is preferably below the boiling point of the phenolic solvent used in the reaction system.

The polymerization and imidization reactions in the present invention can be carried out by conventionally known methods. The reaction temperature is usually selected from the range of 100°C to 300°C, particularly preferably from 130°C to 250°C.

Note that if a large amount of free monohydric alcohol is present in the aromatic polyimide solution produced, it will cause polymer precipitation and decrease in long-term storage stability. Therefore, when a large amount of monohydric alcohol is introduced into the reaction system, it is preferable to remove free alcohol during or after the reaction is completed.

Next, Examples and Comparative Examples of the present invention will be shown.

However, in each of the following examples, the solution viscosity was measured as rotational viscosity using an E-type viscometer manufactured by Tokyo Keiki Co., Ltd. In addition, the logarithmic viscosity of polyimide is 0.5
g/100ml (solvent: m-cresol) using a Canon Fuenske viscometer at 30°C.

[Example 1] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 5.88 g (0.02 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3.69 g (0.08 mol) of ethyl alcohol, and 75.51 g of m-cresol. The mixture was placed in a 180°C oil bath and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

After adding 8.01 g (0.04 mol) of 4,4'-diaminodiphenyl ether to this solution, the mixture was heated and stirred for an additional 2 hours in an oil bath at 180°C to effect polymerization and imidization. After the reaction was completed, nitrogen was introduced into the reaction system for several minutes to remove free ethyl alcohol. The resulting reaction solution was a uniform aromatic polyimide solution containing about 20% by weight of aromatic polyimide (logarithmic viscosity 0.42) and having a solution viscosity of 58 poise/30°C.

When this solution was stored at 50°C for 40 days, the solution viscosity was 135 poise/30°C. Also, 90 at 30℃
When stored for several days, the solution viscosity was 94 poise/30°C. That is, no gelation or polymer precipitation occurred under any of the storage conditions.

[Example 2] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 5.88 g (0.02 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 7.37 g (0.16 mol) of ethyl alcohol, and 29.67 g of m-cresol. The mixture was placed in a 140°C oil bath and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

After adding 8.01 g (0.04 mol) of 4,4'-diaminodiphenyl ether to this solution, the polymerization was carried out by heating and stirring for an additional 1 hour and 30 minutes in an oil bath at 140°C.
Imidization was performed. After the reaction was completed, nitrogen was flowed into the reaction system for several minutes to remove free ethyl alcohol.

The resulting reaction solution was an aromatic polyimide (logarithmic viscosity
It was a homogeneous aromatic polyimide solution containing about 40% by weight of 0.13) and a solution viscosity of 195 poise/30°C.

[Example 3] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 8.83g
(0.03 mol), 3,3',4,4'-biphenyltetracarboxylic dianhydride 2.94 g (0.01 mol), 4,4'-
Diaminodiphenyl ether 8.01g (0.04mol),
10.81 g (0.10 mol) of benzyl alcohol and 68.34 g of m-cresol were placed in an oil bath at 170°C, and the mixture was heated and stirred for 2 hours to effect polymerization and imidization.

The resulting reaction solution was an aromatic polyimide (logarithmic viscosity
0.39) containing approximately 20% by weight, the viscosity of the solution is 50 poise/
It was a homogeneous aromatic polyimide solution at 30°C.

When this solution was stored at 30°C for 90 days, the solution viscosity was 79 poise/30°C, and no gelation or polymer precipitation occurred at all.

[Example 4] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 5.88 g (0.02 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 5.13 g (0.16 mol) of methyl alcohol, and 45.96 g of m-cresol. The mixture was placed in a 150°C oil bath and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

Add 4,4'-diaminodiphenylmethane to this solution.
After adding 7.93 g (0.04 mol), the mixture was heated and stirred for an additional 2 hours in an oil bath at 150°C to effect polymerization and imidization. After the reaction was completed, nitrogen was flowed into the reaction system for several minutes to remove free methyl alcohol. The resulting reaction solution had a solution viscosity of 398% containing about 30% by weight of aromatic polyimide (logarithmic viscosity 0.33).
It was a homogeneous aromatic polyimide solution at 30°C.

[Example 5] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 6.44 g (0.02 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3.69 g (0.08 mol) of ethyl alcohol, and m-
81.35 g of cresol was added, placed in an oil bath at 180°C, and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

8.01 g (0.04 mol) of 4,4'-diaminodiphenyl ether was added to this solution, and the mixture was stirred for an additional 2 hours in an oil bath at 180°C to effect polymerization and imidization. After the reaction was completed, nitrogen was introduced into the reaction system for several minutes to remove free ethyl alcohol.
The resulting reaction solution was an aromatic polyimide (logarithmic viscosity
0.38) containing approximately 20% by weight, the viscosity of the solution is 42 poise/
It was a homogeneous aromatic polyimide solution at 30°C.

When this solution was stored at 50°C for 40 days, the solution viscosity was 45 poise/30°C, and no gelation or polymer precipitation occurred.

[Example 6] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol) and 5.88 g (0.02 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-
Diaminodiphenyl ether 8.01g (0.04mol)
Add 12.98 g (0.12 mol) of benzyl alcohol and 66.13 g of 2,4-xylenol,
The mixture was placed in an oil bath at 0.degree. C. and heated and stirred for 2 hours to effect polymerization and imidization.

The resulting reaction solution was an aromatic polyimide (logarithmic viscosity
0.37) containing approximately 20% by weight, the viscosity of the solution is 41 poise/
It was a homogeneous aromatic polyimide solution at 30°C.

When this solution was stored at 50°C for 40 days, the solution viscosity was 98 poise/30°C, and no gelation or polymer precipitation occurred at all.

[Example 7] In a 300 ml separable flask, add 2, 3, 3,
4′-biphenyltetracarboxylic dianhydride 2.35g
(0.008 mol) and 9.41 g (0.032) mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,
Add 4.01 g (0.020 mol) of 4'-diaminodiphenyl ether, 4.24 g (0.020 mol) of o-tolidine, 5.56 g (0.08 mol) of ethyl alcohol, and 80.22 g of m-cresol, and place this in an oil bath at 170°C. The polymerization and imidization were carried out by heating and stirring for 2 hours. After the reaction was completed, nitrogen was introduced into the reaction system for several minutes to remove free ethyl alcohol. The resulting reaction solution contained aromatic It was an aromatic polyimide solution containing about 20% by weight of polyimide (logarithmic viscosity 0.46) and having a solution viscosity of 93 poise/30°C and about unity.

When this solution was stored at 50°C for 40 days, the solution viscosity was 178 poise/30°C, and no gelation or polymer precipitation occurred at all.

[Comparative Example 1] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 3,3',4,4'-biphenyltetracarboxylic dianhydride 5.88 g (0.02 mol), 4,4'-
Diaminodiphenyl ether 8.01g (0.04mol),
Add 79.11g of m-cresol and add 170g of m-cresol.
The mixture was placed in an oil bath at 0.degree. C. and heated and stirred for 2 hours to effect polymerization and imidization.

As described above, the aromatic polyimide solution obtained by the reaction without using monohydric alcohol was a homogeneous polyimide solution containing about 20% by weight of polyimide, but the solution was extremely high at over 10,000 poise/30°C. It showed the viscosity.

[Comparative Example 2] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 3,3',4,4'-biphenyltetracarboxylic dianhydride 5.88 g (0.02 mol), 4,4'-
Diaminodiphenyl ether 8.01g (0.04mol),
44.50 g (0.41 mol) of benzyl alcohol and 54.39 g of m-cresol were placed in an oil bath at 180° C. and heated and stirred for 2 hours to effect polymerization and imidization.

As mentioned above, the aromatic polyimide solution obtained by the reaction using an excess amount of monohydric alcohol had a uniform solution viscosity of 8 poise/30°C, but when stored at room temperature, the polymer disappeared on the third day. It precipitated.

[Comparative Example 3] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 3,3',4,4'-biphenyltetracarboxylic dianhydride 5.88 g (0.02 mol), water 2.89 g
(0.16 mol) and 76.46 g of m-cresol were placed in an oil bath at 180°C and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

8.01 g (0.04 mol) of 4,4'-diaminodiphenyl ether was added to this solution, and the mixture was heated and stirred for an additional 2 hours in an oil bath at 180°C to effect polymerization and imidization.

As described above, the aromatic polyimide solution obtained by reacting with water instead of monohydric alcohol was a homogeneous polyimide solution containing about 20% by weight of polyimide, but it was extremely high at over 10,000 poise/30°C. showed high solution viscosity.

[Comparative Example 4] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 5.88g
(0.02 mol), 3,3',4,4'-biphenyltetracarboxylic dianhydride 5.88 g (0.02 mol), water 2.90 g
(0.16 mol) and 76.58 g of m-cresol were placed in an oil bath at 140°C and heated and stirred for 30 minutes. The acid anhydride was completely dissolved.

8.01 g (0.04 mol) of 4,4'-diaminodiphenyl ether was added to this solution, and the mixture was heated and stirred for an additional 2 hours in an oil bath at 140°C to effect polymerization and imidization.

As described above, the aromatic polyimide solution obtained by reacting with water instead of monohydric alcohol is a homogeneous polyimide solution containing about 20% by weight of polyimide, and the solution viscosity is 70 poise/30°C. Ta.

However, this aromatic polyimide solution was heated to 40°C at 50℃.
When stored for several days, the viscosity of this solution increased to over 1000 poise/30°C.

[Comparative Example 5] Glass coating autoclave (inner diameter 4.5
cm, depth 17 cm), 5.88 g (0.02 mol) of 2,3,3',4'-biphenyltetracarboxylic dianhydride,
3,3',4,4'-biphenyltetracarboxylic dianhydride 5.88g (0.02 mol), 4,4'-diaminodiphenyl ether 8.01g (0.04 mol), water 5.77g
(0.32 mol) and 76.32 g of m-cresol were added, and the gas inside the autoclave was replaced with nitrogen gas.The autoclave was then sealed and heated at 140°C for 2 hours to carry out a polymerization/imidization reaction.

As described above, the aromatic polyimide solution obtained by reacting with water instead of monohydric alcohol is a homogeneous polyimide solution containing about 20% by weight of polyimide, and the solution viscosity is 105 poise/30°C. Ta.

However, this aromatic polyimide solution was
When stored for several days, the solution viscosity increased to over 1000 poise/30°C.

[Comparative Example 6] Except that 3,3',4,4'-biphenyltetracarboxylic dianhydride was used instead of 2,3,3',4'-biphenyltetracarboxylic dianhydride. Polymerization and imidization were carried out in the same manner as in Example 1, but the polymer gelled while the reaction solution was heated in an oil bath at 180°C, making it impossible to produce a uniform polyimide solution. Nakatsuta.

[Comparative Example 7] A uniform polyimide solution was produced by polymerization and imidization in the same manner as in Example 1, except that ethylene glycol was used instead of ethyl alcohol.

The polyimide solution has a solution viscosity of 30 at 30°C.
It was poise.

When the polyimide solution was stored at 50°C for 6 days, the polymer gelled and precipitated, and
By day 15, the solution was no longer fluid.

[Comparative Example 8] In a 300 ml separable flask, 2, 3, 3',
4′-biphenyltetracarboxylic dianhydride 3.54g
(0.012 mol), 3,3',4,4'-benzophenonetetracarboxylic dianhydride 9.02 g (0.028 mol), benzyl alcohol 8.65 g (0.08 mol) and m-
73.60 g of cresol was added and stirred for 30 minutes in an oil bath at 180°C. The acid anhydride was completely dissolved. Add 8.01 g of 4,4'-diaminodiphenyl ether to this solution.
(0.04 mol) was added and heated and stirred in an oil bath at 180°C for 2 hours to form a solution, but a gel-like substance was formed after one week.

Claims (1)

[Claims] 1. Regarding aromatic tetracarboxylic dianhydride
0.5 times the mole or more, and 40% by weight based on the total of the phenolic solvent and monohydric alcohol
2,3,3',4'-
40 mol% biphenyltetracarboxylic dianhydride
The aromatic tetracarboxylic dianhydride containing the above and substantially equimolar aromatic diamine are polymerized.
Characterized by imidization, logarithmic viscosity is 0.1
A method for producing an aromatic polyimide solution containing 15 to 50% by weight of ~1.0 aromatic polyimide. 2 Aromatic tetracarboxylic dianhydride is 2,
Contains 40% or more of 3,3',4'-biphenyltetracarboxylic dianhydride, and the remainder is substantially 3,3',4'-biphenyltetracarboxylic dianhydride.
Claim 1 characterized in that it consists of 3',4,4'-biphenyltetracarboxylic dianhydride.
A method for producing an aromatic polyimide solution as described in Section 1. 3. The method for producing an aromatic polyimide solution according to claim 1, wherein the aromatic diamine is 4,4'-diaminodiphenyl ether. 4. The method for producing an aromatic polyimide solution according to claim 1, wherein the monohydric alcohol is a lower aliphatic alcohol or an aromatic alcohol. 5 In a phenolic solvent, 2,3,3',4'-
40 mol% biphenyltetracarboxylic dianhydride
The aromatic tetracarboxylic dianhydride containing more than
0.5 times the mole or more, and 40% by weight based on the total of the phenolic solvent and monohydric alcohol
Logarithm, characterized by reacting monohydric alcohol in the following amount, and then reacting with aromatic diamine in a substantially equimolar amount to the aromatic tetracarboxylic dianhydride to polymerize and imidize it. A method for producing an aromatic polyimide solution containing 15 to 50% by weight of aromatic polyimide having a viscosity of 0.1 to 1.0. 6 Aromatic tetracarboxylic dianhydride is 2,
Contains 40 mol% or more of 3,3',4'-biphenyltetracarboxylic dianhydride, and the remainder consists essentially of 3,3',4,4'-biphenyltetracarboxylic dianhydride The method for producing an aromatic polyimide solution according to claim 5, characterized in that: 7. The method for producing an aromatic polyimide solution according to claim 5, wherein the aromatic diamine is 4,4'-diaminodiphenyl ether. 8. The method for producing an aromatic polyimide solution according to claim 5, wherein the monohydric alcohol is a lower aliphatic alcohol or an aromatic alcohol.