JPH04142332A - Production of polyimide resin powder - Google Patents

Abstract

PURPOSE:To obtain a polyimide resin powder which has a large specific surface area and a low degree of imidization, is crystalline and can give a molding excellent mechanical properties by cyclizing a specified aromatic polyamic acid through thermal dehydration by heating. CONSTITUTION:An aromatic polyamic acid comprising repeating units of formula I (wherein R0 is a 6-30C tetravalent aromatic group; R1 is a 6-30C bivalent aromatic group; and n is a positive integer) is cyclized through thermal dehydration by heating in an organic polar solvent (e.g. N,N-dimethylacetamide) to obtain an aromatic polyimide resin powder comprising repeating units of formula II (wherein R0 and R1 are as defined above; and m is a positive integer). This powder is prepared so that it may have a specific surface area of 20m<2>/g or above and a degree of imidization of below 90%. It is very excellent in mechanical properties such as strength and toughness in addition to high heat resistance inherent in an aromatic polyimide resin and can give a molding which can be very extensively and usefully used as a machine part or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyimide resin powder. More specifically, the present invention relates to a method for producing polyimide resin powder that can produce polyimide resin molded articles with excellent mechanical properties.

[Conventional technology] Aromatic polyimide resin moldings have excellent heat resistance and
It has various properties such as wear resistance, chemical resistance, and radiation resistance, and can be used as mechanical parts such as sliding members, automobiles, office equipment, electrical/electronic equipment, aerospace, nuclear power, and general industrial machinery. It is widely used in various fields.

However, in order to further expand the use of polyimide resins, which have such excellent properties, as metal substitute materials and precision structural materials, it is essential to improve mechanical properties such as strength and toughness. Continuous efforts are being made to this day.

Such polyimide resins are insoluble in organic solvents and do not melt by heating, so the method for producing thick molded products is to compress polyimide resin powder and simultaneously and/or during compression molding. Alternatively, a method is used in which compression molding is performed and then heat treatment is performed in a non-pressure state.

The aromatic polyimide resin powder can be produced by, for example, the method disclosed in Japanese Patent Publication No. 39-30080, in which aromatic tetracarboxylic dianhydride and aromatic diamine are reacted in an organic polar solvent. There is a method of obtaining a polyimide resin powder by preparing a polyamic acid solution and then thermally dehydrating and ring-closing the solution. In addition, as disclosed in Japanese Patent Publication No. 89-9078 and Japanese Patent Application Laid-open No. 61-252228, polyamic acid is produced by reacting aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent. A method of obtaining a polyimide resin powder by preparing a solution, then contacting this solution with a poor solvent for polyamic acid such as water, toluene, hexane, etc. to obtain a polyamic acid powder, and heating this, and furthermore, As disclosed in No.-26926,
A method can be found in which a polyimide resin powder is directly obtained by reacting an aromatic tetracarboxylic acid component and an aromatic diisocyanate in an organic polar solvent.

[Problems to be Solved by the Invention] According to these conventional methods, polyimide resin powder having a large specific surface area, high imidization rate, and high crystallinity, or polyimide resin powder having a small specific surface area, low imidization rate, and low crystallinity. Resin powder can be changed.

However, the specific surface area of polyimide resin powder is closely related to the specific gravity and mechanical properties of the compression molded product, and if the specific surface area is small, the cohesiveness of the powders in the compression molded product will be insufficient, so molding The proportion of voids in the body increases,
Decrease the specific gravity and mechanical properties of the molded product. Furthermore, if the imidization rate and crystallinity of the polyimide resin powder are too high, the interaction between the powders during compression molding and heat treatment of the molded product will be insufficient, resulting in a decrease in the mechanical properties of the molded product.

That is, in order to improve the mechanical properties of a polyimide resin molded article, the objective is to develop a polyimide resin powder that has a specific surface area that is larger than a certain amount, and has an appropriate imidization rate and crystallinity.

[Means for Solving the Problems] In view of the above problems, the present inventors have conducted extensive studies and have developed a method for producing polyimide resin powder for producing polyimide resin molded articles that have both excellent heat resistance and mechanical properties. We have come to offer it. Specifically, the production of polyimide resin powder that has a specific surface area of 200,127 g or more, has an imidization rate lower than 90%, and can yield a polyimide molded product with significantly improved specific gravity and mechanical strength. This has led to the present invention.

In the present invention, general formula (1); (wherein, R
o is a tetravalent aromatic group having 6 to 30 carbon atoms, R1 is a carbon number 6
- 30 divalent aromatic groups, n represents a positive integer) is heated and thermally dehydrated and ring-closed to form an aromatic polyamic acid containing the general formula (II): (in the formula , Ro is a tetravalent aromatic group having 6 to 30 carbon atoms, R1
is a divalent aromatic group having 6 to 30 carbon atoms, and excellent is a positive integer. /g or more and an imidization rate of less than 90%, and an aromatic polyamic acid is heated in the presence of a tertiary amine to thermally dehydrate and ring-close the polyimide resin powder. polyimide resin powder characterized in that the tertiary amine is pyridine; polyimide resin powder characterized in that aromatic polyamic acid is thermally dehydrated and ring-closed at a temperature of 95°C or higher and 130°C or lower; The present invention relates to a method for producing a polyimide resin powder in which R8 is at least one selected from the group consisting of υ, and a polyimide resin powder in which R is at least one selected from the group consisting of υ.

[Example] In the polyamic acid containing a repeating unit represented by the general formula (RI) and the polyimide containing a repeating unit represented by the general formula (11) of the present invention, Ro is a tetravalent aromatic group having 6 to 30 carbon atoms. Specific examples of such groups include pyromellitic acid, 8,3°,4,4-biphenyltetracarboxylic acid, 3,3',4,4-benzophenonetetracarboxylic acid, and 8.3 ', 4,4'-diphenylsulfonetetracarboxylic acid, 3.8', 4,4-diphenyl ethertetracarboxylic acid, naphthalene-1,2,
Examples include residues obtained by removing the carboxylic acid group from 5,6-tetracarboxylic acid and 2,2-hexafluoropropylidene-bisphthalic acid, and these can be used alone or in a mixture of two or more. Among these, pyromellitic acid residues are particularly preferred.

Further, R1 is preferably a divalent organic group containing an aromatic group having 6 to 30 carbon atoms, and a group in which a carbon atom forming an aromatic ring serves as a bond. Specific examples of such groups include 4,4-diaminodiphenyl ether, 3
．． 4'-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfide, 4.4-bis(4-aminophenoquine)biphenyl, 4.4-diaminodiphenyl sulfone, 3.3
'~diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 2,5-diaminobenzamide, bis (4-(4-aminophenoxy)phenyl) sulfone, bis +4-(3-aminophenoquine)phenyl)
Sulfone, bis+4-(2-aminophenoxy)phenyl)sulfone, 1,4-bis(4-aminophenoxy)
Benzene, 1.3-bis(3-aminophenoxy)benzene, 1.3-bis(4-aminophenoxy)benzene, 1.4-bis(4-aminophenyl)benzene, bis+4-(4-aminophenoxy) phenyl) ether,
4.4-diaminodiphenylmethane, bis(3-ethyl-4-aminophenyl)methane, bis(3-methyl-4
-aminophenyl)methane, bis(3-chloro-4-aminophenyl)methane, 4,4-diaminobiphenyl,
4.4°-Diaminooctafluorobiphenyl, 3°3
°-dimethoxy-4,4-diaminobiphenyl, 38-
Dimethyl-4,4-diaminobiphenyl, 3,3-dichloro-4,4'-diaminobiphenyl, 2,25.5-
Tetrachloro-4,4-diaminobiphenyl 3.8-dicarboxy-4,4-diaminobiphenyl 3.3-dihydroxy-4,4'-diaminobiphenyl 2.4-diaminotoluene, 1.3-diaminobenzene 1. 4-diaminobenzene, 2.2-bis(4-(4-aminophenoxy)phenyl)propane, 2.2'-bis(4-(
4-aminophenoxy)phenyl)hexafluoropropane, 2.2'-bis(4-aminophenyl)propane, 2.2-bis(4-aminophenyl)hexafluoropropane, 2.2'-bis(3 -Hydroxy-4-aminophenyl)propane 2.2'-bis(3-hydroxy-4-aminophenylhexafluoropropane, 9.9
Examples include -bis(4-aminophenyl)-10-hydroanthracene, a residue obtained by removing the amino group from orthotolidine sulfone, and these can be used alone or in a mixture of two or more. Among these, 4,
A residue obtained by removing the amino group from 4-diaminodiphenyl ether is preferred.

The polyamic acid containing the repeating unit represented by the general formula (1) is produced by a known method.

For example, it is produced by reacting an aromatic tetracarboxylic dianhydride component and an aromatic diamine component in an organic polar solvent at a temperature of 100° C. or lower, but it may be produced by other methods. Further, the logarithmic viscosity of the polyamic acid obtained here is preferably at least 0.1 when measured at 30° C. at a concentration of 0.5 g/100 ml as a solution of N,N-dimethylacetamide, for example.

As a method for producing a polyimide resin powder containing a repeating unit represented by the general formula (I An example is a method of thermally dehydrating and ring-closing by heating under certain conditions in a solvent.

Examples of the organic polar solvent used for producing the polyimide resin powder of the present invention from polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide;

Formamide solvents such as N-dimethylformamide and N,N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-acetyl-2- pyrrolidone solvents such as pyrrolidone, N-vinyl-2-pyrrolidone, phenol, 0-cresol, m
- Phenolic solvents such as cresol, p-cresol, xylenol, halogenated phenol, and catechol, hexamethylphosphoramide, and γ-butyrolactone can be used, and these can be used alone or in a mixture of two or more. . Among these, formamide-based, acetamide-based, and pyrrolidone-based amide solvents are preferred from the viewpoint of solubility of polyamic acid.

Furthermore, hydrocarbon solvents such as n-hexane, cyclohexane, n-octane, benzene, toluene, and xylene, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ether solvents such as diethyl ether, methylene chloride, chloroform, Some halogenated hydrocarbons such as trichlorotrifluoroethane can also be used.

Furthermore, it is important that the conversion reaction from polyamic acid to polyimide resin powder is carried out in the presence of a tertiary amine.

Tertiary amines are known to have the effect of preventing cleavage of the polymer main chain due to hydrolysis of polyamic acid and increasing the reaction rate of the dehydration ring closure reaction to form polyimide.

Tertiary amines that bring about such effects include all aliphatic, aromatic, and heterocyclic compounds, and specific examples include trimethylamine, triethylamine, N,N-dimethylbenzylamine, N,N-dimethyldodecylamine, triethylenediamine, N,N-dimethylaniline,
3.4-lutidine, 3゜5-lutidine, 2,4.6-collidine, 2,6-lutidine, pyridine, 4-benzylpyridine, 2-methylpyridine, 3-methylpyridine, 4
-Methylpyridine, 2-ethylpyridine, quinoline, inquinoline, etc., and these can be used alone or in a mixture of two or more. Among these, pyridine is preferred because it can dissolve polyamic acid and can also be used as a solvent for the conversion reaction into polyimide.

The amount of these tertiary amines to be used depends on the basic strength of the tertiary amine used and the solubility of the polyamic acid, so it is difficult to specify it uniformly, but in general, it is per mole of carboxylic acid residue of the polyamic acid. 0.1 equivalent or more, preferably 0.5 equivalent or more, more preferably 1.0 equivalent or more, particularly preferably 2.0 equivalent or more.

Further, these tertiary amines and amines may be added all at once or in portions during the heating step for converting polyamic acid into polyimide or during any step before heating. for example,
It may be added before the synthesis of polyamic acid, during the synthesis process, or after the synthesis of polyamic acid is completed and before heating is started.

The polyamic acid is dissolved in the mixed liquid of the organic polar solvent and tertiary amine at a concentration of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 15% by weight.

In the method for producing polyimide resin powder of the present invention, in which the polyamic acid solution is heated to cause a thermal dehydration ring-closing reaction to precipitate polyimide powder and convert it into polyimide resin powder, heating conditions are extremely important. The heating temperature depends on the type and amount of the solvent and tertiary amine used and is difficult to uniformly define, but is generally 95°C or higher and 140°C or lower, preferably 95°C or higher and 130°C or lower.

At a temperature lower than this, the conversion reaction to polyimide is extremely slow, making it difficult to obtain a homogeneous polyimide powder, and at a temperature higher than this, the imidization rate of the polyimide powder obtained becomes too high, which is not preferable. For example, N,N-dimethylacetamide/pyridine (weight ratio, ■=1) as an organic polar solvent/tertiary amine, a solution concentration of 10% by weight of polyamic acid (that is, pyridine is added to 1 mole of carboxylic acid residue of polyamic acid) (approximately 12 equivalents are used), 100-120℃
It is important to do this within the range of

The heating time should be longer as the heating temperature is lower and shorter as the heating temperature is higher; it is generally 0.1 to 50 hours, preferably 0.1 to 30 hours.

By heating the polyamic acid solution under the above-mentioned specific conditions, the imide ring closure reaction proceeds, and the polyimide becomes insolubilized and precipitated as a powder.

The thus obtained slurry solution of polyimide powder is cooled, filtered, washed and dried to obtain a polyimide resin powder having the characteristics of the present invention.

However, the drying temperature must be 300°C or lower, preferably 250°C or lower. If the drying temperature is higher than this for several hours, the imidization rate of the polyimide resin powder becomes too high, which is not preferable.

The polyimide resin powder obtained by the production method of the present invention has a specific surface area of at least 1lI2/g or more,
Preferably 10m2/g or more, particularly preferably 20m2/g or more
The essential requirements are that the imidization rate is less than 95%, preferably less than 90%, and the logarithmic viscosity is, for example, 0.5 g/m as a solution of concentrated sulfuric acid. When measured at 80° C. at a concentration of 100+nl, it generally has a value of 0.1 to 2.0, but preferably at least 0.1. Even if a polyimide resin powder having a value of less than 0.1 is used, the polyimide resin molded article obtained therefrom will not exhibit sufficient mechanical strength. The imidization rate referred to here refers to the rate of ring closure of amic acid to imide, and is calculated, for example, by measurement of Fourier transform infrared absorption spectrum. In detail, first of all, based on the imide ring < 720 c+n-1
<8800ffl- based on nearby absorption and benzene ring
The ratio of the absorbance of the absorption around 1 (hereinafter, this ratio can be specifically claimed).Next, the imidization rate of the polyamic acid is set to 0%, and the method as disclosed in Japanese Patent Publication No. 39-30080,
That is, a polyimide resin powder produced by a method of reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic polar solvent to obtain a solution of polyamic acid, and then thermally dehydrating and ring-closing this, was The imidization rate of the powder obtained by heat treatment at ℃ for 5 hours was 10
It is given as a relative value proportional to the magnitude of r, assuming 0%.

That is, the present invention imidizes a polyimide resin powder, which has both a large specific surface area and a low imidization rate necessary for producing a molded article with excellent mechanical properties, by thermally dehydrating and ring-closing a polyamic acid solution. It is characterized by being manufactured by an extremely simple method.

The polyimide resin molded product obtained by compression molding the polyimide resin powder obtained by this manufacturing method has excellent heat resistance, as well as high specific gravity, high tensile strength, high tensile elongation at break, and high impact strength. It has excellent mechanical properties.

Further, the present invention will be specifically explained with reference to the following examples, but the present invention is not limited only to these examples.

Example 1 Under a nitrogen stream, 20.02 g (0.10 mol) of 4,4-diaminodiphenyl ether (hereinafter referred to as ODA)
) with N,N-dimethylacetamide (hereinafter referred to as DMAc) 2501 and pyridine (hereinafter referred to as py) 25
After dissolving in the mixed solution of 01, 21.81 g of pyromellitic dianhydride (hereinafter referred to as PMDA) was added under water cooling.
0.10 mol) was gradually added as a powder over about 30 minutes. After the addition was completed, stirring was continued for 60 minutes to obtain a polyamic acid concentration of about 5001.

Subsequently, the obtained polyamic acid solution was heated and continued to be heated and stirred. The internal temperature at this time was 110°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with DMAc and methanol in this order, and the filtration was repeated.

Further, the powder was dried under reduced pressure at 150° C. for several hours, and then treated in a perfect oven at 200° C. to obtain 38 g of the polyimide resin powder of the present invention.

A part of the polyimide resin powder obtained by the above treatment was taken, and its specific surface area and imidization rate were determined as B, E,
It was calculated by measuring the specific surface area using the T, method and measuring the infrared absorption spectrum.

Furthermore, in order to evaluate the crystallinity of this polyimide resin powder, the diffraction intensity was measured using a wide-angle X-ray diffractometer. As shown in the diffraction intensity curve of FIG. 1, peaks were observed near 2θ of 11° (peak 1), 14° (peak 2), 23° (peak 3), and 27° (peak 4). This indicates that this polyimide resin powder is essentially crystalline.

After that, the remaining polyimide resin powder was filled into the mold, and a hydraulic compression molding machine was used to produce 5,000 kg/mold at room temperature.
Pressure was applied for 3 minutes at ca+2 pressure. Further, heat treatment was performed at 450° C. for 30 minutes under a nitrogen stream in a non-pressure state to obtain a polyimide resin molded body.

Regarding the polyimide resin molding thus obtained, specific gravity (method of JIS K 7112), bending strength and flexural modulus (method of JIS K 7203), tensile strength at break and tensile elongation at break (method of JIS K 8911) were measured. , (2) Notched Izot impact strength (method of JIS K 7110) was measured. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

Example 2 Under nitrogen flow, ODA 20.02g (0,1Omol)
was dissolved in a mixed solution of N,N-dimethylformamide (hereinafter referred to as DMP) 2001 and Py 200+nl, and then 21.81 g of PMDA (0.1 Oio
1) was gradually added as a powder over about 30 minutes. After the addition was completed, stirring was continued for 60 minutes, and the polyamic acid solution 4001
I got it.

Subsequently, the obtained polyamic acid solution was heated and continued to be heated and stirred. The internal temperature at this time was 107°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with DMF and then methanol, and the filtration was repeated.

Further, the powder was dried under reduced pressure at 150° C. for several hours, and then treated in a perfect oven at 200° C. to obtain 36 g of the polyimide resin powder of the present invention.

A portion of the obtained polyimide resin powder was also taken, and its specific surface area and imidization rate were calculated in the same manner as in Example 1. Furthermore, in order to evaluate the crystallinity of this polyimide resin powder, the diffraction intensity was measured using a wide-angle X-ray diffractometer, and the same peaks as in Example 1 were observed. This indicates that this polyimide resin powder is essentially crystalline.

Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body.

Regarding the polyimide resin molded article thus obtained, specific gravity, bending strength, bending modulus, tensile strength at break, tensile elongation at break, and notched isot impact strength were measured in the same manner as in Example 1. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

Example 3 Under nitrogen flow, ODA 20.02g (0.10io1)
After dissolving in DMAC2501, PMDA was added under ice cooling.
21.81 g (0.1 Omol) was gradually added as a powder over about 30 minutes. Continue stirring for 60 minutes after the addition is complete.
Polyamic acid solution 2501 was obtained. Next Py 20
0ml was added and stirred for 30 minutes.

Subsequently, the obtained polyamic acid solution was heated and continued to be heated and stirred. The internal temperature at this time was 115°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with DMAc and methanol in this order, and the filtration was repeated.

Further, the powder was dried under reduced pressure at 150°C for several hours, and then treated in a perfect oven at 200°C to obtain 38 g of polyimide resin powder of the present invention.

A portion of the obtained polyimide resin powder was also removed, and its specific surface area and imidization rate were calculated in the same manner as in Example 1. Furthermore, in order to evaluate the crystallinity of this polyimide resin powder, the diffraction intensity was measured using a wide-angle X-ray diffractometer, and the same peaks as in Example 1 were observed. This indicates that this polyimide resin powder is essentially crystalline.

Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body.

The specific gravity, bending strength, bending modulus, tensile strength at break, tensile elongation at break, and V-notched Izo impact strength of the polyimide resin molded article thus obtained were measured in the same manner as in Example 1. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

Comparative Example 1 A polyamic acid solution obtained in the same manner as in Example 1 was heated and continued to be heated and stirred. The internal temperature at this time was 132°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with DM^c1 methanol and filtered repeatedly.

Further, the powder was dried under reduced pressure at 150°C for several hours, and then treated in a perfect oven at 200°C to obtain 37 g of polyimide resin powder.

A portion of the obtained polyimide resin powder was also taken, and its specific surface area and imidization rate were calculated in the same manner as in Example 1.

Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body.

Regarding the polyimide resin molded article thus obtained, specific gravity, bending strength, bending modulus, tensile strength at break, tensile elongation at break, and notched isot impact strength were measured in the same manner as in Example 1. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

Comparative Example 2 Under nitrogen flow, ODA 20.02g (0.10nol)
is N-methyl-2-pyrrolidone (hereinafter referred to as NMP)
After dissolving in 400ml, PMD^21.
81 g (0.10 sol) was gradually added as a powder over about 30 minutes.

After the addition was completed, stirring was continued for 60 minutes to obtain a polyamic acid solution. Next, N,N-dimethylbenzylamine 27.0
g and stirred for 30 minutes.

Subsequently, the obtained polyamic acid solution was heated and continued to be heated and stirred. At this time, the internal temperature was 170°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with NMP and methanol in that order, and the filtration was repeated.

Further, the powder was dried under reduced pressure at 150° C. for several hours, and then treated in Perfect Open at 250° C. to obtain 37 g of polyimide resin powder.

A portion of the obtained polyimide resin powder was also taken, and its specific surface area and imidization rate were calculated in the same manner as in Example 1.

After that, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body.

Regarding the polyimide resin molded article thus obtained, specific gravity, bending strength, bending modulus, tensile strength at break, tensile elongation at break, and notched isot impact strength were measured in the same manner as in Example 1. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

Comparative Example 3 Under nitrogen flow, ODA 20.02g (0.10io1)
After dissolving in Py 5001, under ice cooling, PMD^2
1.81 g (0.10 nol) was gradually added as a powder over about 30 minutes.

After the addition was completed, stirring was continued for 60 minutes to obtain a polyamic acid solution.

Subsequently, the obtained polyamic acid solution was heated to reflux, and heating and stirring were continued. The internal temperature at this time was 110°C. During this time, the polyimide became insolubilized and precipitated as a powder. After cooling, the filtered powder was washed with DM^C1 methanol and filtered repeatedly.

Further, the powder was dried under reduced pressure at 150° C. for several hours, and then treated in a perfect oven at 200° C. to obtain 82 g of polyimide resin powder.

A portion of the obtained polyimide resin powder was also taken, and its specific surface area and imidization rate were calculated in the same manner as in Example 1.

Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body.

The specific gravity, bending strength, bending modulus, tensile strength at break, tensile elongation at break, and V-notched Izo impact strength of the polyimide resin molded article thus obtained were measured in the same manner as in Example 1. These results are shown in Table 1 together with the results of specific surface area and imidization rate.

[Effects of the Invention] The present invention provides a method for producing essentially crystalline polyimide resin powder having a large specific surface area and a low imidization rate. In addition to the high heat resistance, which is the original property of aromatic polyimide resins, it also has extremely excellent mechanical properties such as strength and toughness, producing polyimide resin molded products that can be used extremely widely and usefully in machine parts. It has become possible to produce polyimide resin powder for

[Brief explanation of drawings]

FIG. 1 is a wide-angle X-ray diffraction intensity curve of the polyimide resin powder of the present invention obtained according to Example 1. patent

Claims (1)

[Claims] 1 General formula (I) in an organic polar solvent: ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_0 is a tetravalent aromatic group having 6 to 30 carbon atoms, R
_1 is a divalent aromatic group having 6 to 30 carbon atoms, and n is a positive integer). ): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R_0 is a tetravalent aromatic group having 6 to 30 carbon atoms, R
_1 is a divalent aromatic group having 6 to 30 carbon atoms, m is a positive integer) In the method for producing an aromatic polyimide resin powder containing a repeating unit represented by 20 m^2/g or more and an imidization rate of less than 90%, a method for producing polyimide resin powder. 2. The method for producing a polyimide resin powder according to claim 1, wherein the aromatic polyamic acid is heated in the presence of a tertiary amine to thermally dehydrate and ring-close it. 3. The method for producing polyimide resin powder according to claim 2, wherein the tertiary amine is pyridine. 4. The method for producing polyimide resin powder according to claim 1, wherein the aromatic polyamic acid is thermally dehydrated and ring-closed at a temperature of 95° C. or higher and 130° C. or lower. 5 The above R_0 has ▲a mathematical formula, a chemical formula, a table, etc.▼, ▲a mathematical formula, a chemical formula,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Claim 1
A method for producing the polyimide resin powder described above. 6 The above R_1 has ▲a mathematical formula, a chemical formula, a table, etc.▼, ▲a mathematical formula, a chemical formula,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
Claim 1 is at least one selected from the group consisting of ▼
A method for producing the polyimide resin powder described above.