JPH11140185A - Wholly aromatic polyimide precursor powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide precursor powder comprising a polyimide precursor excellent in stability and convertible into a polyimide of a high degree of polymerization and to provide a process for producing the polyamide precursor powder inexpensively and easily without using a larger amount of a solvent. SOLUTION: This wholly aromatic polyimide precursor powder comprises a salt formed from an aromatic diamine and 3,3',4,4'-biphenyltetracarboxylic acid. An aromatic diamine is mixed with 3,3',4,4'-biphenyltetracarboxylic acid in a poor solvent for the polyimide precursor to be formed to obtain a suspension in which polyimide precursor particles are dispersed, and the polyimide precursor particles are isolated to obtain a wholly aromatic polyimide precursor powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wholly aromatic polyimide precursor powder and a method for producing the same.

[0002]

2. Description of the Related Art Polyimide resins are known to have various characteristics depending on their chemical structures. In particular, wholly aromatic polyimides have recently been used in electronic and electrical applications due to their excellent heat resistance, mechanical properties and sliding properties. It is one of the engineering plastics that has attracted attention in industries such as industry, automobile industry, space and aviation industry, and high demand is expected.

Generally, a wholly aromatic polyimide does not have a thermal softening point and is insoluble in a solvent, so that molding is often difficult. Therefore, various studies have been made to improve these problems. It has been done. For example, in many cases
A method of forming a polyamic acid (polymer) having an amide bond, which is a precursor of a polyimide, and converting this into a polyimide has been performed.

As a method of obtaining a polyimide precursor powder,
As a first method, a method in which a polyimide precursor solution (polyamic acid solution) is added to a poor solvent and mixed to precipitate a dissolved polyimide precursor is disclosed in JP-A-1-2920.
No. 35, JP-A-4-272934 or JP-A-4-272936. However, according to this method, since a difference in solubility of the polyimide precursor (polyamic acid) in the solvent is used, a large amount of poor solvent is required for polyamic acid, and the polyamic acid solution and the poor solvent are not used. Has to be strictly controlled. In addition, the degree of polymerization of polyamic acid tends to decrease due to hydrolysis, and care must be taken in its handling.

A second method is disclosed in Japanese Patent Laid-Open No.
As disclosed in JP-A-71539, JP-A-5-202763 or JP-A-5-2202764, a polyimide precursor suspended in a system using a water-soluble ketone or a water-soluble ether as a solvent is separated. There is a way to do that. According to this method, a polyimide precursor powder can be easily obtained, but the obtained polyimide precursor is a polyamic acid having a high degree of polymerization as in the above method, and the degree of polymerization tends to decrease due to hydrolysis. Some things had not improved.

Japanese Patent Publication No. 2-48571 discloses that
In the poor solvent of the resulting polyimide, the monomer component consisting of aromatic tetracaronic dianhydride and the aromatic diamine is dissolved in the poor solvent of the polyimide to form a uniform solution, and the polyimide particles are precipitated by heating and separated. A method for obtaining a polyimide powder is disclosed. However, even in this method, in a uniform solution in which the monomers are dissolved, the monomers react with each other to form polyamic acid as described above, and the polymer is dissolved in the solvent.

[0007]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a polyimide which has excellent stability, can be converted into a polyimide having a high degree of polymerization, and can be suitably used for molding polyimide. An object of the present invention is to provide a polyimide precursor powder and a method for producing a wholly aromatic polyimide precursor powder capable of easily and inexpensively producing such a polyimide precursor powder.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, when an aromatic diamine and a specific aromatic tetracarboxylic acid are mixed in a specific solvent, polyimide precursor particles are obtained. A suspension of is obtained, polyimide precursor particles are isolated from this suspension to obtain a polyimide precursor powder, and the knowledge that a polyimide powder having a high degree of polymerization can be obtained by imidizing the polyimide precursor powder, Based on such findings, the present invention has been achieved.

That is, the gist of the present invention is to provide a wholly aromatic polyimide precursor powder comprising a salt formed of an aromatic diamine and 3,3 ', 4,4'-biphenyltetracarboxylic acid. It is. Second, aromatic diamine and 3,3 ', 4,4
4′-biphenyltetracarboxylic acid is mixed to obtain a suspension in which the polyimide precursor particles are dispersed, and the polyimide precursor particles are isolated to obtain a wholly aromatic polyimide precursor powder. It is a manufacturing method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyimide precursor powder of the present invention is a powder comprising a salt formed from an aromatic diamine and 3,3 ′, 4,4′-biphenyltetracarboxylic acid (hereinafter sometimes referred to as aromatic tetracarboxylic acid). Body. The polyimide precursor in the present invention produces a polyimide comprising a repeating unit represented by the following formula (1) upon imide ring closure. Here, imide ring closure refers to the formation of an imide ring by a thermal or chemical reaction.

[0011]

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In the above formula (1), R is at least 1
A divalent aromatic residue having two carbon 6-membered rings is shown. Examples of the aromatic diamine as a source of R include those shown in the following structural formula group, and one of these or one of these A plurality of types selected from among them can be used.

[0013]

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The polyamic acid, which is a typical polyimide precursor, is a polymer comprising a repeating unit having an amide bond between an acid and an amine as shown in the following general formula (2). The polyimide precursor in the present invention is a salt having no amide bond and having a weak interaction (ionic bond) between an acid and an amine.

[0015]

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Therefore, even if the wholly aromatic polyimide precursor powder of the present invention is dissolved in various solvents for dissolving the wholly aromatic polyimide precursor powder of the present invention, the monomer simply forms a salt, Since this is a liquid in a dispersed state, the viscosity of the solution does not suddenly increase as the concentration or the degree of polymerization increases unlike a polymer solution.

In the polyimide precursor powder of the present invention, the aromatic diamine and the aromatic tetracarboxylic acid are substantially equimolar, that is, 0.9 to 1.1 moles of the aromatic tetracarboxylic acid per mole of the aromatic diamine. It is preferably formed from moles. When the polyimide precursor powder is formed from a composition that is not approximately equimolar, when the imide is closed and converted into polyimide, an excess of monomer components in equimolar remains in the polyimide or the degree of polymerization of the polyimide is reduced. This is not preferable because it tends to greatly decrease and lose the inherent properties of polyimide.

The polyimide precursor powder of the present invention is produced by mixing approximately equimolar amounts of an aromatic diamine and an aromatic tetracarboxylic acid in a poor solvent for the resulting polyimide precursor.
When approximately equimolar amounts of an aromatic diamine and an aromatic tetracarboxylic acid are mixed, a suspension in which polyimide precursor particles are dispersed is obtained. At this time, the aromatic diamine and the aromatic tetracarboxylic acid may be directly added to the reaction system, or one or both of them may be dissolved in a solvent and the solution may be added to the reaction system. The order of addition of the aromatic diamine and the aromatic tetracarboxylic acid is not particularly limited, but it is preferable to add the aromatic diamine to a system in which the aromatic tetracarboxylic acid is dissolved or dispersed in a solvent, because the mixture can be uniformly mixed in a short time.
At this time, it is preferable that the dispersion concentration of the polyimide precursor particles in the suspension is 5 to 50% by weight. If the amount of the polyimide precursor particles in the suspension is less than 5% by weight, the productivity is poor, and if it exceeds 50% by weight, the fluidity of the suspension is deteriorated, and the suspension tends to be inferior in handling, such as being unable to mix uniformly.

In the present invention, any solvent may be used as a solvent for producing the polyimide precursor powder, as long as it is a poor solvent for the polyimide precursor to be produced. Preferred examples include N, N-dimethylformamide, Alcohols and the like, and these solvents are used alone,
Alternatively, these solvents can be used in combination. Furthermore, various other solvents may be mixed with the above solvents and used as a reaction solvent within a range not to hinder the practice of the present invention.

Examples of the water-soluble alcohol include, for example,
Methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, , 3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-
2,4-pentanediol, glycerin, 2-ethyl-
2- (hydroxymethyl) -1,3-propanediol, 1,2,6-hexanetriol and the like. Among these solvents, methyl alcohol is particularly preferred.

The temperature in the reaction system does not need to be particularly controlled, and may be room temperature. When N, N-dimethylformamide is used as a poor solvent, the temperature of the reaction system is preferably 50 ° C. or lower, particularly preferably 30 ° C. or lower. If the temperature of the reaction system exceeds 50 ° C., the yield of the polyimide precursor to be produced is remarkably reduced, and the yield tends to deteriorate, which is not preferable.

From the suspension in which the polyimide precursor particles are dispersed, the solvent can be easily removed by filtration or drying, and a polyimide precursor powder having a particle size of 5 to 150 μm can be isolated. Further, by adding the suspension to, for example, 0.5 to 3 times the amount of water, toluene, hexamethylene, etc., and precipitating a polyimide precursor partially dissolved in a poor solvent, a higher yield of polyimide is obtained. A precursor powder can be obtained.

The polyimide precursor powder of the present invention is dissolved in various solvents for dissolving the polyimide precursor to form a polyimide precursor solution, from which a polyimide film or a polyimide coating film is formed. The body powder can be converted into a polyimide powder by imide ring closure and then molded to form a compact. Molding conditions are known conditions, for example, 200 to 450 ° C., 100 to 1500 kgf /
It can be easily molded by heating and compressing at cm ² . In this case, it is preferable to use polyimide powder which has been sufficiently preliminarily fired at about 300 ° C. in order to eliminate generation of volatile components during molding.

The imide ring closure proceeds by heating and firing the polyimide precursor powder or by chemically treating it with a dehydrating agent represented by acetic anhydride. For example, when the firing is performed at a temperature of 120 ° C. to 250 ° C. in air, in an inert atmosphere such as nitrogen, or in a vacuum, the polyimide precursor powder undergoes imide ring closure to be converted into a polyimide having a high degree of polymerization.

When an inorganic or organic filler is blended for the purpose of improving the various properties of the obtained polyimide, a necessary amount of the filler is uniformly added to the reaction system at the time of producing the polyimide precursor powder. Is preferable since a polyimide composition in which is dispersed is obtained.

[0026]

The present invention will be described below in detail with reference to examples. In the examples, the Tg was measured using a DSC
It carried out in nitrogen atmosphere using SC-7 (made by Perkin-Elmer). In addition, the thermal decomposition onset temperature
The measurement was performed in a nitrogen atmosphere using a measuring device TTGA-7 (manufactured by Perkin-Elmer). The degree of polymerization of the polyimide precursor was measured using a GPC measuring device, and evaluated by weight average molecular weight (Mw) in terms of polystyrene.

Example 1 495.3 g dissolved in 2500 g of methanol
(1.5 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic acid was added to 300.4 g (1.5 mol) of 4,
4′-Oxydianiline was added and the mixture was stirred at 25 ° C. for 12 hours to obtain a white suspension. This is filtered off at 60 ° C. for 1 hour.
Dry under reduced pressure for 2 hours, pulverize on a 150 μm mesh,
725 g of a white polyimide precursor powder having an average particle diameter of about 80 μm was obtained. Mw of the obtained powder was 1,000 or less. The obtained polyimide precursor powder is heated at 200 ° C. for 1 hour.
After heating under reduced pressure for 6 hours, a yellow polyimide powder was obtained. The Tg of this polyimide powder was 285 ° C., and the thermal decomposition onset temperature was 592 ° C., which proved to be exactly the same as the polyimide powder obtained by the conventional method. That is, it is understood that the polyimide powder obtained from the polyimide precursor powder of the present invention is composed of a polyimide having a high degree of polymerization.

Example 2 495.3 g (1.5 mol) of 3,3 ', 4,4'- dissolved in 1500 g of N, N-dimethylformamide
To biphenyltetracarboxylic acid, 300.4 g (1.5
Mol) of 44'-oxydianiline, and
After stirring for an hour, a white suspension was obtained. This was added to 500 g of pure water, further stirred at 20 ° C. for 3 hours, filtered, dried at 60 ° C. under reduced pressure for 12 hours, pulverized on a 150 μm mesh, and a white polyimide precursor having an average particle diameter of about 80 μm. 730 g of powder was obtained. Mw of the obtained powder is 10
00 or less. The obtained polyimide precursor powder was mixed with 2
When heated under reduced pressure at 00 ° C. for 16 hours, a yellow polyimide powder was obtained. The Tg of this polyimide powder was 278 ° C., and the thermal decomposition onset temperature was 579 ° C., which proved to be exactly the same as the polyimide powder obtained by the conventional method. That is, it is understood that the polyimide powder obtained from the polyimide precursor powder of the present invention is composed of a polyimide having a high degree of polymerization.

Example 3 500 g of N, N-dimethylformamide and 1000 g
495 dissolved in a mixed solution consisting of methanol.
To 3 g (1.5 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 300.4 g (1.5 mol) of 4,4′-oxydianiline was added and stirred at 20 ° C. for 18 hours. To give a white suspension. This was filtered, dried under reduced pressure at 60 ° C. for 12 hours, and pulverized on a 150 μm mesh to obtain 750 g of a white polyimide precursor powder having an average particle diameter of about 80 μm. Mw of the obtained powder was 1,000 or less. The obtained polyimide precursor powder was heated at 200 ° C.
After heating under reduced pressure for 16 hours, a yellow polyimide powder was obtained. The Tg of this polyimide powder is 285 ° C.,
The thermal decomposition onset temperature was 581 ° C., which was found to be exactly the same as the polyimide powder obtained by the conventional method.
That is, it is understood that the polyimide powder obtained from the polyimide precursor powder of the present invention is composed of a polyimide having a high degree of polymerization.

Example 4 60.6 g (0.10 g) was added to 100.0 g (0.3 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic acid dissolved in 300 g of N, N-dimethylformamide. 3 mol) of 4,4'-oxydianiline and added at 20 ° C.
Stirring between the powders gave a yellow solution. This was cast on a tray and allowed to stand for 3 hours, whereupon a white precipitate was gradually observed, and finally a suspension was obtained. This was dried under reduced pressure at 80 ° C. for 4 hours and pulverized on a 150 μm mesh to obtain a white polyimide precursor powder 15 having an average particle diameter of about 100 μm.
4 g were obtained. Mw of the obtained powder was 1,000 or less.

Comparative Example 1 155.11 g (0.5 mol) of 4,4'-oxydiphthalic dianhydride and 100.12 g (0.5 mol) of 3,4
The 4'-oxydianiline was stirred in 1500 g of N-methylpyrrolidone at 25 ° C. for 3 hours to obtain a viscous brown solution. Mw of the obtained solution was 150,000. To this solution, 150 g of acetic anhydride was gradually added under stirring,
The whole system was stirred at 140 ° C. for 15 hours to obtain a tan suspension. This was separated by filtration and dried under reduced pressure at 200 ° C. for 12 hours to obtain a polyimide powder. The Tg of the obtained polyimide powder was 280 ° C. The thermal decomposition onset temperature is 5
85 ° C.

Reference Example 300 g of the polyimide powder obtained in Examples 1, 3 and 4 was filled in a mold of 12 × 12 cm.
After reducing the pressure at 0 ° C. for 3 hours, the mold temperature was raised to 400 ° C., a pressure of 200 kgf / cm ² was applied to the filled polyimide powder, the heating and pressurizing was maintained for 1 hour, and then cooling was performed. A molded article was obtained. The obtained molded body was cut into a predetermined shape to obtain each characteristic value shown in the table. In addition, each characteristic value was measured according to JIS standard.

[0033]

[Table 1]

[0034]

As described above, the polyimide precursor powder of the present invention has excellent stability and can be converted to a polyimide having a high degree of polymerization. Moreover, according to the production method of the present invention, such a polyimide precursor powder can be easily provided at low cost without using a large amount of solvent.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiaki Echigo 23 Uji Kozakura, Uji City, Kyoto Prefecture Inside Unitika Central Research Laboratory

Claims (5)

[Claims] 1. An aromatic diamine and 3,3 ′, 4,4′-
A wholly aromatic polyimide precursor powder comprising a salt formed with biphenyltetracarboxylic acid. 2. An aromatic diamine and 3,3 ′, 4,4′-biphenyltetracarboxylic acid are mixed in a poor solvent for a wholly aromatic polyimide precursor to be produced to disperse polyimide precursor particles. A method for producing a wholly aromatic polyimide precursor powder, comprising obtaining a suspension and isolating polyimide precursor particles. 3. The method for producing a wholly aromatic polyimide precursor powder according to claim 2, wherein the poor solvent is N, N-dimethylformamide. 4. The method for producing a wholly aromatic polyimide precursor powder according to claim 2, wherein the poor solvent is a water-soluble alcohol. 5. The method for producing a wholly aromatic polyimide precursor powder according to claim 2, wherein the poor solvent is a mixed solution of N, N-dimethylformamide and a water-soluble alcohol.