JP3264555B2 - Polyimide precursor fibrids, polyimide paper obtained therefrom, polyimide composite paper, polyimide composite board, and methods for producing them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide precursor fibrid containing no aprotic polar organic solvent, a polyimide paper obtained therefrom, a polyimide composite paper, a polyimide composite board and a method for producing them.

[0002]

2. Description of the Related Art Polyimide is known to have excellent heat resistance, mechanical properties, electrical properties, weather resistance, etc., and is useful as a raw material for films and molded articles. For example,
Polyimides prepared from 4,4'-diaminodiphenyl ether and pyromellitic dianhydride can be used to obtain films and molded articles having excellent heat resistance, which are widely used for electrical insulation and the like.

[0003] On the other hand, in the field of heat-resistant synthetic paper, aramid synthetic paper is known and widely used, but those having higher heat resistance have recently been developed due to the sophistication of advanced materials for space and aircraft applications. There is a growing demand for synthetic papers having better heat resistance and strength than aramid. Attempts have been made to obtain polyimide paper by making polyimide fibrids.
Japanese Patent Application Laid-Open No. 2-297330 discloses a method for producing a polyimide fibride, which comprises injecting a polyamic acid solution using an aprotic polar organic solvent into a coagulant containing acetic acid and / or acetic anhydride under high-speed stirring. JP-A-64-26718 discloses a process for producing a polyimide fibrid in which a polyamic acid solution is injected under high shear into a coagulation bath comprising a mixture of a chemical cyclizing agent and a cyclizing catalyst. ing. However, the paper obtained by making the polyimide fibrids obtained by these methods has low strength,
There were practical problems.

Further, Japanese Patent Publication No. Sho 60-1402 discloses that
There is disclosed a method for producing pulp-like particles by dispersing a polymer solution obtained by a solution polymerization method in the presence of short fibers in a precipitant. According to this method, pulp-like particles of polyamic acid containing short fibers are obtained, but an aprotic polar solvent remains in the pulp-like particles, and the polyamic acid contains an aprotic polar solvent. If it remains, there is a problem that the hydrolysis reaction is easily promoted and the degree of polymerization is lowered. In addition, since a large amount of aprotic polar solvent remains in the pulp-like particles, a high-purity polyimide paper cannot be obtained by paper-making and imidization. The aprotic polar solvent remaining in the ooze out, dissolves the pulp-like particles,
Since the particles adhere to each other, there is also a problem that the shape of the pulp-like particles is not seen, resulting in a film-like paper.

In recent years, there has been an increasing demand for a material having higher mechanical properties and heat resistance, and attention has been paid to compounding a polyimide resin with another material. A method of mixing and manufacturing in the same manner as a polyimide molded article has been studied. The polyimide molded body is obtained by press-molding and heat-treating a powdery polyimide resin (JP-A-2-18420, JP-B-49-5).
737, JP-A-61-250030, JP-A-1-292035, etc.). However, it was difficult to uniformly mix and disperse the powdery resin and the short fibers, and it was difficult to obtain a composite having high strength.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to firstly provide a polyimide precursor fibrid containing no aprotic polar organic solvent and a method for producing the same. To provide a polyimide paper excellent in strength consisting of a polyimide fibrid obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid and a method for producing the same, and thirdly, a polyimide precursor constituting the polyimide precursor fibrid A polyimide composite paper comprising a ring-closing polyimide fibrid and other short fibers, in which these components are uniformly dispersed, and having excellent strength, and a method for producing the same, are provided. Fourth, the polyimide precursor fibrid is constituted. Consists of polyimide fibrid and other short fibers obtained by ring-closing the polyimide precursor,
An object of the present invention is to provide a polyimide composite board in which these components are uniformly dispersed and have excellent strength and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve such problems, and as a result, have found that a mixed solvent of a polyimide precursor and a solvent in which the polyimide precursor and the solvent do not strongly solvate or When a polyimide precursor solution consisting of a single solvent is injected into a coagulation bath and subjected to a shearing force, a polyimide precursor fibride containing no aprotic polar organic solvent can be produced. The papermaking, polyimide paper, polyimide composite paper and polyimide composite board obtained from this papermaking have been found to solve the above-mentioned problems, and the present invention has been achieved.

That is, the gist of the present invention is to firstly provide a polyimide precursor which comprises a polyimide precursor which forms a non-thermoplastic polyimide by ring closure and which does not substantially contain an aprotic polar organic solvent. Body fibrid and a method for producing the same, and secondly, a polyimide paper comprising a polyimide fibrid obtained by ring-closing a polyimide precursor constituting the polyimide precursor fibrid, and a method for producing the same. A polyimide composite paper and a method for producing the same, comprising a polyimide fibrid and a short fiber obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid,
Fourth, there is provided a polyimide composite board comprising a polyimide fibrid obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid and short fibers, and a method for producing the same.

Hereinafter, the present invention will be described in detail for each item. 1. Polyimide Precursor Fiber and Method for Producing the Same In the present invention, the polyimide precursor may be any one as long as it becomes a non-thermoplastic polyimide by ring closure, and preferred is a wholly aromatic polyimide precursor. And a polyamic acid homopolymer or copolymer having a repeating unit represented by the following general formula (1) is particularly preferred.

[0010]

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Here, R represents a tetravalent aromatic residue containing at least one carbon 6-membered ring. Each of the two valences of the four valences is bonded to an adjacent carbon atom in the six-membered ring.
Specific examples of R include the following.

[0012]

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In particular, R is preferably the following.

[0014]

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Here, R 'represents a divalent aromatic residue having 1 to 4 carbon 6-membered rings. The following are preferred as specific examples of R '.

[0016]

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[0017]

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The following are particularly preferred as R '.

[0019]

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Among the polyamic acids comprising the above combinations, the polyimide obtained by ring-closing the polyamic acid derived from diaminodiphenyl ether as the acid anhydride component is pyromellitic dianhydride and the diamine component is poly (4,4)
4'-oxydiphenylenepyromellitimide). In the present invention, the polyimide precursor preferably has an intrinsic viscosity [η] of 0.1 or more, particularly 0.5 or more. [Η] is a value directly related to the molecular weight of the polymer, and can be measured as described later. In the present invention, the aprotic polar organic solvent is N, N
-Dimethylformamide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N-methylcaprolactam, N-acetyl-2-pyrrolidone, dimethylsulfoxide, hexamethylphosphoramide, etc., which are inherent properties of a solvent. A solvent having a dipole moment with a polarity greater than about 3.0 Debye.

Conventionally, a solution of a polyimide precursor is prepared by subjecting a diamine such as diaminodiphenyl ether and a tetracarboxylic dianhydride such as pyromellitic dianhydride to a polymerization reaction in an aprotic polar organic solvent as described above. It has been manufactured by a solution polymerization method. Therefore, when the polyimide precursor solution prepared in such a solvent is poured into an aqueous coagulation bath to obtain a polyimide precursor fibrid or a polyimide fibrid, the aprotic polar organic solvent remains in the fibrid. It was.

In the present invention, a polyimide precursor fibrid is produced by using a polyimide precursor solution comprising a mixed solvent of a solvent in which the polyimide precursor and the solvent are not solvated strongly or a single solvent as described below. The precursor fibrids do not substantially contain an aprotic polar organic solvent, and a decrease in the degree of polymerization of the polyimide precursor can be suppressed. The polyimide precursor solution is obtained by polymerizing a diamine and tetracarboxylic dianhydride in a mixed solvent of a solvent in which the polyimide precursor and the solvent are not solvated strongly or in a solvent composed of a single solvent. The polymerization reaction temperature is preferably −30 to 60 ° C.,
-20 to 40 ° C is more preferable. Polymerization reaction time is 1-2
00 minutes is preferable, and 5 to 100 minutes is more preferable. The polyimide precursor solution may be prepared by dissolving a polyimide precursor produced by another method in these solvents.

The concentration of the polyimide precursor in the polyimide precursor solution is preferably 0.1 to 60% by weight,
25% by weight is more preferred. As a mixed solvent of a solvent in which the polyimide precursor and the solvent are not strongly solvated, a mixed solvent selected from a water-soluble ether compound, a water-soluble alcohol compound, a water-soluble ketone compound and water is used.
As the sole solvent, a water-soluble compound having an ether group and an alcoholic hydroxyl group in the same molecule is preferably used.

Examples of the water-soluble ether compound include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and the like, with THF being particularly preferred. Examples of the water-soluble alcohol compound include, for example, methanol, ethanol, 1-propanol, 2-
Propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentane Diol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 2-ethyl-2- (hydroxymethyl) -1,3-propanediol, 1,2,6-hexa Triol and the like.
Particularly preferred are methanol, ethanol and ethylene glycol. Examples of the water-soluble ketone compound include acetone, methyl ethyl ketone, and the like. Particularly preferred is acetone.

In the case of a mixed solvent, a combination of a water-soluble ether compound and water, a water-soluble ether compound and a water-soluble alcohol compound, and a water-soluble ketone compound and water are particularly preferable. The mixing ratio of the solvent in the mixed solvent is 96: 4-79: 21 for the water-soluble ether compound and water, and 9 for the water-soluble ether compound and the water-soluble alcohol compound in weight ratio.
0:10 to 56:44, and preferably 90:10 to 65:35 for a water-soluble ketone compound and water. In the case of a single solvent, a water-soluble compound having an ether group and an alcoholic hydroxyl group in the same molecule is used. Examples of such a solvent include 2-methoxyethanol, 2-ethoxyethanol, and 2- (methoxymethoxy) ethoxyethanol. , 2
-Isopropoxyethanol, 2-butoxyethanol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether,
Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, Examples thereof include dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, polyethylene glycol, and polypropylene glycol. Particularly preferred are 2-methoxyethanol and tetrahydrofurfuryl alcohol. Further, a water-soluble compound having an ether group and an alcoholic hydroxyl group in the same molecule and a poor solvent can be used in combination.

In the present invention, solvation means
It means that the solvent and the solute are associated (association). In the polyimide precursor solution, an essential interaction (interaction) between the solute polyimide precursor and the solvent
Means The degree of solvation can be determined, for example, by a solvation index measured by the following method. That is, 5000 mg of a solution containing 6% by weight of a polyimide precursor is uniformly poured onto a standard glass plate having an inner diameter of 86 mm and a height of 18 mm, air-dried at room temperature, and loses fluidity.
If the weight of the polyimide precursor on the plate after the solvent is distilled off at 40 ° C. for 40 hours is Amg, the solvation index can be expressed by the following equation.

[0027]

(Equation 1)

In the present invention, the solvent used preferably has a solvation index of less than 0.35, particularly preferably 0.3 or less, and a solvent having a dipole moment, which is a characteristic property of the solvent, of 3 Debyes or less is preferably used. Can be The polyimide precursor fibrids of the present invention can be produced by injecting the above-described polyimide precursor solution into a coagulation bath and applying a shearing force to form fibrides, and recovering the fibrids. As a device for that purpose, a mixer, a Waring mixer, a flow path stirring device combining a rotor and a stator can be applied.

As the coagulation bath, any solvent may be used as long as it is a poor solvent for the polyimide precursor. Usually, water, which is a typical poor solvent for the polyimide precursor, or
A mixed solvent containing 70% by weight or more of water is used. As the solvent in the mixed solvent containing water, any solvent having water solubility may be used, but a water-soluble ether, a water-soluble alcohol, and a water-soluble ketone are preferably used. The volume ratio of the coagulation bath to the polyimide precursor solution is preferably 5 to 100. The temperature at the time of fibrid formation is suitably from 10 to 60 ° C.
Seconds to 10 minutes are appropriate. In the present invention, the polyimide precursor fibrid refers to fibrous or film-like particles, and two of the three dimensions are on the order of microns.

2. Polyimide Paper and Method for Producing the Same Since the polyimide paper of the present invention is produced by making a polyimide precursor fibrid substantially not containing an aprotic polar organic solvent, and then closing the polyimide precursor constituting the fibrid, it is produced. Substantially no aprotic polar organic solvent. That is, the polyimide precursor fibrids obtained as described above, in an aqueous medium such as water, uniformly dispersed by a method such as stirring, as in the case of conventionally known natural pulp papermaking, a long wire or The paper is made using a paper-mesh type paper making device, and then the water content is 50 to
A pressure of 1 to 200 kg / cm ² is applied to depressurize and dehydrate to 90% by weight to obtain a wet paper made of polyimide precursor fibrids. Next, the obtained wet paper is treated as it is or is dried and chemically or thermally treated to close the polyimide precursor constituting the fibrids, thereby producing a polyimide paper. For chemical ring closure, it may be immersed in a conventionally known ring closure catalyst solution such as acetic anhydride and pyridine, acetic anhydride and picoline, acetic anhydride and 2,6-lutidine at room temperature for 1 to 20 hours. To thermally close the ring, 150 to 3
The heating may be performed at a temperature of 00 ° C. for 0.5 to 5 hours, but it is preferable to sufficiently dry the ring before closing. Polyimide paper obtained in this way, to perform ring closure after papermaking,
In the process of ring closure, entanglement between fibrids is strengthened, and polyimide paper having excellent strength is obtained.

3. Polyimide composite paper and its manufacturing method The non-thermoplastic polyimide composite paper of the present invention is a mixed suspension obtained by dispersing the polyimide precursor fibrid and short fiber obtained as described above in an aqueous medium, It is obtained by making paper in the same manner, pressing and dewatering to obtain a wet paper, and then closing the polyimide precursor constituting the polyimide precursor fibrids. In other words, in the above-described polyimide paper manufacturing process, a polyimide composite paper can be obtained by mixing short fibers at the time of papermaking, and the polyimide precursor fibrids are dispersed in an aqueous medium.
A polyimide composite paper having good uniformity is obtained.

Examples of the short fibers include glass fibers, carbon fibers, organic fibers, and ceramic fibers. Short fibers having good dispersibility in an aqueous medium are used for producing the composite paper of the present invention. Among these, a para-aramid short fiber produced from para-phenylenediamine and terephthalic acid chloride, a meta-aramid short fiber produced from meta-phenylenediamine and isophthalic acid chloride, or a copolymerized aramid short fiber thereof is preferable. Short fiber length is 1-2
0 mm and a fiber diameter of 5 to 20 μm are preferred. The mixing ratio between the polyimide precursor fibrids and the short fibers is such that the weight ratio between the polyimide fibrids and the short fibers after conversion to imide is 5:95 to
It is preferable to set 99.5: 0.5.

4. Polyimide composite board and method for producing the same The polyimide composite board of the present invention is, like the composite paper described above, made of a polyimide precursor fibrid and short fibers, and squeezed and dewatered composite wet paper, or dried composite paper. Any number of layers are laminated, pressed to integrate the respective layers, the polyimide precursor constituting the fibrids is closed, and the non-thermoplastic polyimide fibrids and short fibers substantially containing no aprotic polar organic solvent are contained. To obtain a polyimide composite board consisting of The pressing pressure at this time can control the density of the composite board. The pressing pressure is preferably from 1 to 5000 kg / cm ² . When laminating the dried paper, it is preferable to heat at the time of pressing in order to enhance the interlayer adhesion. Press surface temperature is 80
~ 300 ° C is preferred.

The composite board pressed by lamination can be made into a polyimide composite board by closing the polyimide precursor using the same method as in the case of composite paper. Part or all of the rings may be closed. In the polyimide composite board of the present invention, a polyimide precursor fibrid and papermaking in which short fibers are uniformly dispersed are laminated, so that the obtained polyimide composite board has excellent uniformity.

[0035]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. In addition,
In the present invention, each characteristic value was obtained as follows. Break length: It was determined by the following equation based on JIS P8113.

[0036]

(Equation 2)

Intrinsic viscosity [η]: The time required for a polymer solution having a polyimide precursor concentration of 0.5% by weight in an N, N-dimethylacetamide solvent to flow at 30 ° C. through a capillary of a fixed volume of a standard viscometer and the solvent. The time during which only the gas flowed was measured and determined by the following equation.

[0038]

(Equation 3)

Water retention: JAPAN TAPPI paper pulp test method No. 26-78. Tensile strength: Measured based on JIS K6911. Flexural strength: Measured according to JIS K6911. Flexural modulus: Measured based on JIS K6911.

Example 1 2.00 g of diaminodiphenyl ether was dissolved in 33.5 g of THF containing 4.5% by weight of water and kept at 30.degree. To this, 2.19 g of pyromellitic dianhydride was added at a time, and stirring was continued for 1 hour to obtain a polyamic acid solution in which [η] of the polyamic acid was 2.5. The solvation index of this solution system was 0.28. This solution was mixed with 11.1 g of water and 230.6 g of THF.
(Solid content: 1.5% by weight). Put 1.2 liters of water in a home mixer, stir vigorously,
80 g of the diluted polyamic acid solution was poured into the mixture for 2 minutes, and the mixture was further stirred for 1 minute to produce polyamic acid fibrids. The generated polyamic acid fibrids were separated by filtration, 1 liter of water was added, and the mixture was stirred and filtered three times. [Η] of the polyamic acid constituting the obtained fibrids was 2.0, and the water retention was 240. Since this fibrid has not been conventionally produced using an aprotic polar organic solvent, it is clear that it does not substantially contain an aprotic polar organic solvent.

Example 2 4.00 g of diaminodiphenyl ether was added to THF 59.
2. dissolved in a mixed solution of 6 g and 15.9 g of methanol;
It was kept at 8 ° C. 3. Add pyromellitic dianhydride to this solution.
When 40 g was added at a time and stirring was continued for 1 hour, a polyamic acid solution in which [η] of polyamic acid was 1.0 was obtained. The solvation index of this solution system was 0.30. This was diluted with THF / methanol (weight ratio 4/1) so that the solid content concentration became 7.5%. The rotational viscosity was 74 cps. A continuous homomixer equipped with a coagulant, stock solution supply port and coagulated fibrid slurry discharge port (capacity 500 ml, turbine speed 8
500r. p. m. ), Add the above-mentioned polyamic acid solution to 2
4 ml / min and 960 ml / min of water were simultaneously supplied, and fibrid slurry was continuously taken out from the outlet. The generated polyamic acid fibrids were separated by filtration, 1 liter of water was added, and the mixture was stirred and filtered three times. [Η] of the polyamic acid constituting the obtained fibrid was 0.8, and the water retention was 460. Since this fibrid has not been conventionally produced using an aprotic polar organic solvent, it is clear that it does not substantially contain an aprotic polar organic solvent.

Example 3 1.2 g of the fibrid obtained in Example 1 was dispersed in 2 liters of water, and paper was made to a size of 10 cm × 10 cm.
This was pressed and dehydrated at a pressure of 10 kg / cm ² and then immersed in a mixed solution of acetic anhydride / pyridine (volume ratio: 7/3) at room temperature for 20 hours to imidize. After the imidized paper was washed with toluene, it was dried at 80 ° C. for 1 hour. The breaking length of the obtained polyimide paper was 1.6 km.

Example 4 A polyamide acid wet paper web made and pressed and dehydrated in the same manner as in Example 3 was heat-treated at 200 ° C. for 10 minutes and subsequently at 300 ° C. for 1 hour to be imidized. The breaking length of the obtained polyimide paper was 1.8 km.

Example 5 3 g of the fibrids obtained in Example 2 were dispersed in 1.5 liters of water, and paper was made to have a size of 15 cm × 15 cm. This was squeezed and dehydrated at a pressure of 10 kg / cm ² , and then acetic anhydride /
It was immersed in a pyridine (7/3 volume ratio) mixed solution at room temperature for 20 hours. After washing with toluene, it was dried under reduced pressure at 80 ° C. for 1 hour and hot-pressed at 100 ° C. and 10 kg / cm ² for 5 minutes. The breaking length of the obtained polyimide paper was 3.0 km.

Example 6 The pressed and dehydrated polyamide acid wet paper obtained in the same manner as in Example 5 was dried at 60 ° C. for 1 hour. Shrinkage of 15% by drying. The obtained polyamic acid dried paper was fixed on a SUS frame and imidized by heating at 150 ° C. for 1 hour and subsequently at 300 ° C. for 1 hour. The breaking length of the obtained polyimide paper was 4.9 km.

Comparative Example 1 6.01 g of diaminodiphenyl ether was added to N-methyl-
It was dissolved in 112 g of 2-pyrrolidone (NMP) and kept at 30 ° C. 6.54 g of pyromellitic dianhydride was added thereto at a time, and stirring was continued for 1 hour to obtain a polyamic acid solution in which [η] of the polyamic acid was 2.3. The solvation index of this solution system was 0.66. This solution was treated with N-methyl-2-pyrrolidone 306.
g (solids concentration 3%). 500 ml of water was put into a household mixer, stirred vigorously, and 70 g of the diluted polyamic acid solution was poured therein. One minute later, the generated polyamic acid fibrids were separated by filtration, 1 liter of water was added, and the mixture was stirred and filtered three times. [Η] of the polyamic acid constituting the obtained fibrids was 0.5, and the water retention was 440. This fibrid 1.2
g was dispersed in 1 liter of water and paper-made to 10 cmφ. This was pressed and dewatered at a pressure of 10 kg / cm ² to obtain a translucent film-like substance having an NMP odor. When this was dried at 60 ° C. for 1 hour, it shrank by 30% and was very brittle.

Example 7 0.7 g of polyamic acid fibrids and short fibers of para-aramid (1.5 d, 6 mm) obtained in the same manner as in Example 2
0.7g dispersed in 2 liters of water 15cm x 15cm
Paper size. Squeezed and dehydrated at 10 kg / cm ² ,
After drying at 60 ° C, 1 hour at 150 ° C and 1 hour at 300 ° C
It was heat-treated for an hour to imidize. As a result, the thickness 213μ
m, a composite paper having a density of 0.32 g / cm ³ was obtained. The elongation was 2% and the breaking length was 3.9 km.

Example 8 0.6 g of polyamic acid fibrids obtained by the same operation as in Example 2 and staple meta-aramid fibers (1.5 d, 5 mm)
When 0.6 g was made and imidized in the same manner as in Example 7, a composite paper having a thickness of 134 μm and a density of 0.42 g / cm ³ was obtained. The elongation was 6% and the breaking length was 4.2 km.

Example 9 1.0 g of polyamic acid fibrids and para-aramid short fibers (1.5 d, 6 mm) obtained in the same manner as in Example 2
1.0 g of paper was made in the same manner as in Example 7, and 150 kg / cm
After squeezing and dehydrating in ² , drying was performed at 60 ° C. 170 ° C, 10
After hot-pressing at kg / cm ² for 10 minutes and heat-treating at 300 ° C. for 1 hour to imidize, a composite paper having a thickness of 162 μm and a density of 0.59 g / cm ³ was obtained. 3% elongation,
The breaking length was 5.9 km.

Example 10 3.0 g of polyamic acid fibrids and para-aramid short fibers (1.5 d, 6 mm) obtained in the same manner as in Example 2
3.0 g is dispersed in 3 liters of water and 15 cm × 15 cm
Paper size. Four wet paper webs pressed and dehydrated at ² kg / cm ² were stacked and further pressed and dewatered at 150 kg / cm ² . After drying at 60 ° C, 170 ° C, 100kg / cm
^The mixture was hot-pressed at ² for 10 minutes and heat-treated at 300 ° C. for 1 hour for imidization. 1.38mm thickness, 0.74g / c density
A composite board having m ³ (porosity of 49%) was obtained. The elongation was 6% and the tensile strength was 5.7 kg / mm ² .

Example 11 3.0 g of polyamic acid fibrids and para-aramid short fibers (1.5 d, 6 mm) obtained in the same manner as in Example 2
3.0 g is dispersed in 3 liters of water and 15 cm × 15 cm
Paper size. After pressing and dewatering at 10 kg / cm ² , the product was dried at 60 ° C. Laminated 14 dried papers, 500k
g / cm ² at 170 ° C. for 10 minutes and 250 ° C. for 10 minutes.
And then heat treated at 300 ° C. for 1 hour. Thickness 2.54 mm, density 1.35 g / cm ³ (porosity 6%)
A composite board was obtained. Bending strength is 1200kg / c
m ² , and the flexural modulus was 59000 kg / cm ² .

[0052]

As described above, the polyimide precursor fibrids of the present invention do not contain an aprotic polar organic solvent. Is further obtained from the polyimide precursor fibrids and other short fibers, so that a polyimide composite paper and a polyimide composite board having excellent strength can be obtained in which the components are uniformly dispersed. It should be noted that the polyimide paper, the polyimide composite paper, and the polyimide composite board obtained from the polyimide precursor fibrids containing no aprotic polar organic solvent do not contain the aprotic polar organic solvent. Further, according to each production method of the present invention, it is possible to easily produce a polyimide precursor fibrid, a polyimide paper, a polyimide composite paper, and a polyimide composite board.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshiaki Echigo 23 Uji Kozakura, Uji-city, Kyoto Unitika Investigator, Central Research Institute, Ltd. Yoko Nakajima (56) References JP-A-62-297330 (JP, A) JP-A-64-26718 (JP, A) JP-A-2-259199 (JP, A) JP-A-52-99306 (JP, A) JP-A-52-42917 (JP, A) JP-A-61-12912 (JP, A) , A) JP 601402 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) D01F 6/74 D21H 13/26

Claims (8)

(57) [Claims] 1. A polyimide precursor fibrid comprising a polyimide precursor that forms a non-thermoplastic polyimide by ring closure and substantially does not contain an aprotic polar organic solvent. 2. A coagulation bath comprising a polyimide precursor solution comprising a polyimide precursor for forming a non-thermoplastic polyimide by ring closure, and a mixed solvent or a single solvent of a solvent in which the polyimide precursor and the solvent do not strongly solvate. 2. A method for producing a polyimide precursor fibrid according to claim 1, wherein the fibrid is formed by injecting the fibrid into the fibrid by applying a shear force. 3. A polyimide paper comprising a polyimide fibrid obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid according to claim 1. 4. The method for producing a polyimide paper according to claim 3, wherein the polyimide precursor fibrid according to claim 1 is made, and then the polyimide precursor constituting the fibrid is closed. 5. A polyimide composite paper comprising a polyimide fibrid obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid according to claim 1 and short fibers. 6. The polyimide according to claim 5, wherein the polyimide precursor fibrid according to claim 1 and short fibers are made to form a composite paper, and then the polyimide precursor constituting the fibrid is closed. Manufacturing method of composite paper. 7. A polyimide composite board comprising a polyimide fibrid obtained by ring-closing the polyimide precursor constituting the polyimide precursor fibrid according to claim 1 and short fibers. 8. A composite paper is formed by paper-making the polyimide precursor fibrid according to claim 1 and short fibers, the composite paper is laminated, and then the polyimide precursor constituting the fibrid is closed. The method for producing a polyimide composite board according to claim 7.