JPH11171990A - Wholly aromatic polyimide precursor powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject powder excellent in stability, capable of being converted into a polyimide with a high polymerization degree and useful for molding a polyimide by mixing an aromatic diamine and a diester of a specific aromatic tetracarboxylic acid. SOLUTION: This powder comprises a salt composed of (A) an aromatic diamine and (B) a salt formed out of a diester of an aromatic tetracarbocylic acid of the formula (R is a 1-5C alkyl). For example, the component A is mixed with the component B in nearly same mols in the solvent, and a poor solvent for the polyimide precursor such as water or a water-soluble alcohol of up to twice of the amount of the liquid is added to the suspension of the obtained polyimide precursor or a solution of the polyimide precursor to precipitate the polyimide precursor powder. The obtained precipitate is filtered, and dried to remove the solvent and to provide the objective powder with the particle diameter of about 5-150 μm. The powder is heated and baked to carrying out the imide cyclization and to provide a polyimide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD 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. In general, wholly aromatic polyimides do not have a thermal softening point, and are often difficult to mold due to insolubility in a solvent. For this reason, various studies have been made to improve these problems. . In many cases, a method is used in which a polyamic acid (polymer), which is a polyimide precursor having an amide bond, is molded and converted into a polyimide.

One method for obtaining a polyimide precursor powder is to mix a polyimide precursor solution (polyamic acid solution) with a poor solvent to precipitate a dissolved polyimide precursor. JP-A-292035, JP-A-4-272934 or JP-A-4-272
No. 936, and the like. 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 to be used is required for the polyamic acid, and
There was a problem that the mixing conditions of the polyamic acid solution and the poor solvent had to be strictly controlled. In addition, the degree of polymerization of polyamic acid tends to decrease due to hydrolysis, and care must be taken when handling the polyamic acid.

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.

[0005] Japanese Patent Publication No. 2-48571 discloses that
In the poor solvent of the resulting polyimide, the monomer component consisting of aromatic tetracarboxylic dianhydride and 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 by using the method 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.

[0006]

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.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, obtained by mixing an aromatic diamine and a specific aromatic tetracarboxylic acid diester in a solvent, and When the powder obtained by isolating the polyimide precursor from the suspension was heated and calcined, the imide was closed, and the finding that polyimide was formed was obtained.
Based on such findings, the present invention has been achieved.

That is, the gist of the present invention is, first, a wholly aromatic polyimide precursor powder comprising a salt formed from an aromatic diamine and an aromatic tetracarboxylic diester represented by the structural formula (1). Second, an aromatic diamine and an aromatic tetracarboxylic acid diester represented by the structural formula (1) are mixed in a solvent to form a salt, and the solvent is removed to isolate. This is a method for producing a wholly aromatic polyimide precursor powder. R represents an alkyl group having 1 to 5 carbon atoms.

[0009]

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[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 comprises a salt formed from an aromatic diamine and an aromatic tetracarboxylic acid diester represented by the structural formula (1). Produce polyimide. Here, imide ring closure refers to the formation of an imide ring by a thermal or chemical reaction.

[0011]

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R represents an alkyl group having 1 to 5 carbon atoms, preferably a methyl or ethyl group having 1 or 2 carbon atoms in terms of production. R ′ represents a divalent aromatic residue having at least one carbon 6-membered ring. In addition, polyamic acid, which is a typical polyimide precursor, is a polymer including a repeating unit having an amide bond between an acid and an amine as shown in the following general formula (2),
It is considered that the salt does not have such an amide bond and is in a form having a weak interaction (ionic bond) between the acid and the amine.

[0013]

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Therefore, even if the polyimide precursor powder obtained according to the present invention is dissolved in various solvents, it is merely a solution in which the monomer is dispersed. It does not exhibit such a property that the viscosity of the solution rapidly increases.

The aromatic diamine which is the source of R 'in the polyimide precursor according to the present invention includes those represented by the following structural formulas, and one or more kinds of mixtures selected from these may be used. it can.

[0016]

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In the polyimide precursor powder of the present invention, the aromatic diamine and the aromatic tetracarboxylic acid diester are almost equimolar, that is, the aromatic tetracarboxylic acid diester is 0.9 to 1 mole per mole of the aromatic diamine. .1 mol. 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 diester in a solvent. When approximately equimolar amounts of the aromatic diamine and the aromatic tetracarboxylic acid diester are mixed, a suspension in which the polyimide precursor particles are dispersed or a solution of the polyimide precursor is obtained. At this time, the aromatic diamine and the aromatic tetracarboxylic acid diester may be added to the reaction system as they are, 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 diester is not particularly limited, but the addition of the aromatic diamine to a system in which the aromatic tetracarboxylic diester is dissolved or dispersed in a solvent tends to allow uniform mixing in a short time. It is in.

When approximately equimolar amounts of an aromatic diamine and an aromatic tetracarboxylic acid diester are mixed in a solvent, whether a polyimide precursor suspension or a solution is obtained depends on the solubility of the polyimide precursor in the solvent. It depends. And the dispersion concentration of the polyimide precursor particles in the solvent or the solution concentration of the polyimide precursor is, for example,
In the case of N, N-dimethylformamide, the content is preferably 15 to 60% by weight. If the amount is less than 15% by weight, the solubility of the polyimide precursor is much smaller than the solubility of the polyimide precursor, so that it becomes difficult to isolate the polyimide precursor powder from such a dilute solution, and the productivity is lacking. On the other hand, if the amount exceeds 60% by weight, the suspension becomes a suspension, but the fluidity of the suspension deteriorates, and the suspension cannot be uniformly mixed. Diamines are not sufficiently mixed, and it tends to be difficult to obtain a homogeneous polyimide precursor.

When a poor solvent for the polyimide precursor such as water or a water-soluble alcohol is added up to twice the amount of the polyimide precursor suspension or the polyimide precursor solution obtained above, the polyimide precursor Since the particles are precipitated, the solvent can be easily removed by filtration and drying.
A target polyimide precursor powder having a particle size of about 50 μm can be isolated. Further, for example, in a N, N-dimethylformamide solution in which 15 to 40% by weight of a polyimide precursor is dissolved, the polyimide precursor component dissolved in the solvent is not precipitated as described above, and is directly dried by a dryer or the like. As the concentration of the solvent is increased by evaporating only the solvent, polyimide precursor particles are precipitated from the solution, so that the target polyimide precursor powder can be isolated.

The solvent used for producing the polyimide precursor powder of the present invention is preferably a solvent capable of isolating the resulting polyimide precursor as a powder, for example, an amide solvent represented by N, N-dimethylformamide or dioxane Water-soluble ethers, water-soluble ketones represented by acetone, and water-soluble alcohols represented by methanol. Among these solvent types, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dioxane, tetrahydrofuran, acetone or methanol are preferable, and a plurality of mixed solvents composed of a combination thereof may be used. .
Furthermore, various other solvents may be mixed with the above solvents and used as a synthesis solvent, as long as the practice of the present invention is not hindered. The temperature in the reaction system does not need to be particularly controlled,
It may be performed at room temperature.

The polyimide precursor powder of the present invention is dissolved in various solvents to form a polyimide precursor solution, which is used to form a polyimide film or a polyimide coating film,
Further, it can be converted into a polyimide powder by imide ring closure and molded into a molded article. Molding is carried out in a known manner from 200 to
Under heating of about 450 ° C, 100-1500kgf / cm
It can be easily performed by heating and compressing under about ² conditions. 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 baking the polyimide precursor powder or 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 various properties of the obtained polyimide, a necessary amount of the filler can be uniformly added to the reaction system during the production of the polyimide precursor powder. Is preferable since a polyimide composition in which is dispersed is obtained.

[0024]

The present invention will be described below in detail with reference to examples. In the examples, the Tg was measured using a DSC
This was performed in a nitrogen atmosphere using SC-7 (manufactured by Perkin-Elmer). In addition, the thermal decomposition starting temperature is determined by a TGA measuring device TG.
It measured in nitrogen atmosphere using A-7 (made 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 1 100 g of N, N-dimethylformamide in 100 g
(0.279 mol) of biphenyltetracarboxylic acid dimethyl ester was dissolved, and 55.9 g (0.279 mol) was dissolved.
Of 4,4′-oxydianiline was added and stirred at 25 ° C. for 12 hours to obtain a milky white suspension. This was dried under reduced pressure at 100 ° C. for 12 hours and pulverized on a 300 μm mesh to obtain 148 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 was 285 ° C., and the thermal decomposition onset temperature was 588 ° C.

Example 2 100 g (0.279 mol) in 400 g of methanol
Was dissolved, 55.9 g (0.279 mol) of 4,4′-oxydianiline was added, and the mixture was stirred at 20 ° C. for 18 hours to obtain a milky white suspension. This was separated by filtration, dried under reduced pressure at 60 ° C. for 12 hours, pulverized on a mesh of 300 μm,
152 g of a white polyimide precursor powder of about 0 μm was obtained. Mw of the obtained powder was 1,000 or less. When the obtained polyimide precursor powder was heated under reduced pressure at 200 ° C. for 16 hours, a yellow polyimide powder was obtained. The Tg of this polyimide powder was 282 ° C., and the thermal decomposition onset temperature was 578 ° C.

Example 3 100 g of N, N-dimethylformamide and 200 g
100 g (0.2 g) in a mixed solution of methanol
79 mol) of biphenyltetracarboxylic acid dimethyl ester was dissolved, and 55.9 g (0.279 mol) of 4,4′-oxydianiline was further added thereto, followed by stirring at 20 ° C. for 18 hours to obtain a white suspension. Was. This was separated by filtration, dried under reduced pressure at 60 ° C. for 12 hours, and pulverized on a 300 μm mesh to obtain 147 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 was 284 ° C., and the thermal decomposition onset temperature was 578 ° C.

Comparative Example 1 155.11 g (0.5 mol) of biphenyltetracarboxylic dianhydride and 100.12 g (0.5 mol) of 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 slowly added with stirring,
The whole system was stirred at 140 ° C. for 15 hours to obtain a yellow suspension. This was separated by filtration and dried under reduced pressure at 200 ° C. for 12 hours.
A polyimide powder was obtained. Tg was 284 ° C., and thermal decomposition onset temperature was 578 ° C.

Comparative Example 2 100 g in 300 g of N, N-dimethylformamide
(0.3 mol) of biphenyltetracarboxylic acid was dissolved, 60.6 g (0.3 mol) of 4,4-oxydianiline was added, and the mixture was stirred at 20 ° C. for 30 minutes to obtain 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 154 g of a white polyimide precursor powder having an average particle diameter of about 100 μm. Mw of the obtained powder was 1,000 or less. This is filtered off at 200 ° C. for 12 hours.
After drying under reduced pressure for a time, a polyimide powder was obtained. The Tg of the obtained polyimide powder was 284 ° C., and the thermal decomposition onset temperature was 585 ° C.

Examples 1 to 3 and Comparative Examples 1 and 2 show that the polyimide powder obtained from the polyimide precursor powder according to the present invention is exactly the same as the polyimide powder obtained by the conventional method. Was. That is, it was found that the polyimide powder obtained from the polyimide precursor powder according to the present invention was composed of polyimide having a high degree of polymerization.

[0031]

As described above, since the wholly aromatic polyimide precursor powder of the present invention is composed of a low molecular weight polyimide precursor, it does not easily undergo hydrolysis and the like, is excellent in stability, and has high polymerization. Degree of polyimide powder. Further, according to the production method of the present invention, the polyimide precursor powder can be easily obtained at low cost.

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

Claims (2)

[Claims] 1. A wholly aromatic polyimide precursor powder comprising a salt formed from an aromatic diamine and an aromatic tetracarboxylic acid diester represented by the structural formula (1). Embedded image Here, R represents an alkyl group having 1 to 5 carbon atoms. 2. A method comprising mixing an aromatic diamine and an aromatic tetracarboxylic acid diester represented by the structural formula (1) in a solvent to form a salt, removing the solvent and isolating the salt. A method for producing an aromatic polyimide precursor powder. Embedded image