Polyimide powder and method for producing the same

Abstract

The present invention relates to a polyimide powder and a method for producing the same. The polyimide powder and method for producing the same according to the present invention can simplify the production process to increase process efficiency, produce polyimide in powder form to facilitate molding, have a low precipitation temperature, a high intrinsic viscosity to facilitate processing, and have uniform particle size to provide excellent processability.

Description

[Technical Field]

[0001] This invention relates to polyimide powder and a method for producing the same. [Background technology]

[0002] Generally, polyimide (PI) is a polymer of imide monomers formed by solution polymerization of dianhydride and diamine or diisocyanate. Based on the chemical stability of the imide ring, it possesses excellent mechanical properties such as strength, chemical resistance, weather resistance, and heat resistance. Furthermore, polyimide is attracting attention as a high-performance polymer material applicable to a wide range of industrial fields such as electronics, communications, and optics due to its excellent electrical properties such as insulating properties and low dielectric constant.

[0003] However, due to its high heat and chemical resistance, polyimide is difficult to manufacture molded products using the thermal melting method commonly used for polymer resins. Therefore, it is generally used by first synthesizing polyamic acid, a precursor, by reacting dianhydride and diamine in a solvent, and then imidizing it after dispersion or coating, depending on the application. However, this common method is complex because the process proceeds in two stages: the polyamic acid manufacturing stage and the imidization stage of polyamic acid. Furthermore, it requires high temperatures of 300°C or higher in the imidization stage, making it difficult to obtain high molecular weight polyimide.

[0004] One known method to address this is a synthesis method in which a precursor polyamic acid is reacted in the presence of a solvent and precipitated into polyimide powder by heating. However, this method has the drawback that the precipitation temperature of the polyimide powder remains high, and the polyimide powder produced by this method has low intrinsic viscosity, uneven particle size, frequent defects during molding, and reduced processability. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to solve the problems and technical challenges of the prior art described above. The present invention can provide a polyimide powder and a method for producing polyimide powder that are easy to mold by producing polyimide in powder form, have a low precipitation temperature, high intrinsic viscosity, are easy to process, have a uniform particle size, and have excellent processability. [Means for solving the problem]

[0006] The present invention relates to polyimide powder and a method for producing polyimide powder. The method for producing the polyimide powder involves reacting a dianhydride monomer component, a diamine monomer component, and a catalyst in a solvent, and then heating the mixture to precipitate the polyimide powder.

[0007] Specifically, the present invention provides a method for producing polyimide powder, comprising a polymerization step in which a dianhydride monomer component and a diamine monomer component are dissolved in a solvent and the reaction proceeds, and an imidation step in which a catalyst is added to the reaction solution produced in the polymerization step to imidize and precipitate polyimide powder.

[0008] The dianhydride monomer is not particularly limited as long as it can react with a diamine monomer to form a polyimide. For example, the dianhydride monomer according to the present invention may include at least one selected from the group consisting of pyromeretic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), and p-phenylenebis(trimellitate anhydride) (TAHQ).

[0009] The dianhydride monomer may be, for example, pyromeretic dianhydride (PMDA), oxydiphthalic dianhydride (ODPA), or a mixture thereof. In this case, the molar ratio of pyromeretic dianhydride (PMDA) to oxydiphthalic dianhydride (ODPA) in the dianhydride monomer may be 9:1 to 1:9, for example, the molar ratio of pyromeretic dianhydride (PMDA) to oxydiphthalic dianhydride (ODPA) may be 9:1 to 7:3. The dianhydride monomer may be selectively used from the viewpoint of heat resistance and flexibility. Furthermore, when a portion of pyromeretic dianhydride (PMDA), which consists of a rigid aromatic ring, is mixed with a dianhydride monomer containing heteroatoms, such as oxydiphthalic dianhydride (ODPA), the precipitation temperature of the polyimide powder can be lowered and the color can be made brighter.

[0010] The aforementioned diamine monomer is not particularly limited as long as it can react with a dianhydride monomer to form a polyamic acid. For example, the diamine monomer according to the present invention may include at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxybenzene (TPE-Q), bisaminophenoxybenzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).

[0011] The diamine monomer can improve brightness by including a heteroatom within the monomer to de-emphasize the electron distribution of the aromatics. For example, the diamine monomer may be 4,4'-diaminodiphenyl ether (ODA).

[0012] The catalyst is a tertiary amine. Generally, in methods for producing polyimide via polyamic acid, amines are used to imidize the polyamic acid. Specifically, the amine catalyst can promote the dehydration reaction and produce polyimide through the ring-closing reaction of the polyamic acid. However, there are no reported methods for using a tertiary amine in the process of producing polyimide powder. Nevertheless, the inventors have found that using a tertiary amine in the method for producing polyimide powder can lower the precipitation temperature of the polyimide powder. Furthermore, the polyimide powder produced using the catalyst has a high intrinsic viscosity, making it easy to process during molding, significantly reducing the occurrence of cracks, and improving the yield.

[0013] Specifically, the catalyst may be pyridine, β-picoline, 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine (TEA), isoquinoline, or a mixture thereof. In particular, when the tertiary amine contains a lone pair of electrons, it is more effective in lowering the deposition temperature of the polyimide powder and increasing its intrinsic viscosity. For example, the catalyst may be pyridine, β-picoline, or isoquinoline.

[0014] The catalyst may be included in an amount of 0.1 to 500 moles based on 100 moles of the diamine monomer component. For example, the amount of the catalyst may be 0.1 moles or more, 0.5 moles or more, 1 mole or more, 5 moles or more, 10 moles or more, 50 moles or more, or 100 moles or more relative to the diamine monomer, and there is no particular upper limit, but it may be 400 moles or less, 300 moles or less, or 200 moles or less. If the amount of catalyst is less than the above range, the effect of lowering the precipitation temperature of the polyimide powder and increasing its intrinsic viscosity cannot be expected, and if it exceeds the above range, the rate of change of the above effect due to the catalyst will be small, leading to an increase in cost. When the above range is met, the intrinsic viscosity can be increased and the polyimide precipitation temperature can be lowered without degrading the physical properties of the polyimide powder.

[0015] The aforementioned solvents are benzene, toluene, xylene, acetone, hexane, heptane, chlorobenzene, methanol, ethanol, n-propanol, isopropanol, N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylcaprolactam, hexamethylphosphoramide, tetramethylene sulfone, dimethyl sulfoxide, o-cresol, m-c Resol, p-cresol, phenol, p-chlorophenol, 2-chloro-4-hydroxytoluene, diglyme, triglyceride, tetraglyceride, dioxane, γ-butyrolactone, dioxolane, cyclohexanone, cyclopentanone, dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, dibromomethane, tribromomethane, 1,2-dibromoethane, or 1,1,2-tribromoethane may be used alone or in combination.

[0016] From the viewpoint of compatibility with the catalyst and lowering the polyimide precipitation temperature, the solvent is preferably a solvent containing at least one nitrogen element. For example, suitable solvents for the present invention may be N-methyl-2-pyrrolidone (NMP), xylene, or m-cresol, either alone or in combination.

[0017] Alternatively, the solvent according to the present invention may be a composite solvent including a first solvent containing at least one nitrogen element and a second solvent having at least one hydroxy group (-OH). For example, the first solvent may be N-methyl-2-pyrrolidone (NMP), and the second solvent may be m-cresol.

[0018] At this time, the weight ratio of the first solvent to the second solvent is 5:5 to 9:1. For example, the weight ratio of the first solvent to the second solvent may be 6:4 to 9:1, 7:3 to 9:1, 7:3 to 8:2, 3:7 to 10:0, 4:6 to 9:1, or 5:5 to 8:2. When the weight ratio of the first solvent is higher than the above range, the precipitation temperature of the polyimide powder becomes higher. When it is lower than the above range, polymerization close to suspension polymerization is carried out, making it difficult to obtain powder, and the brightness of the produced powder may become darker.

[0019] By including the composite solvent as described above, the present invention can uniformly dissolve the dianhydride monomer and the diamine monomer, and thus the precipitated polyimide powder can form uniform particles with less aggregation.

[0020] Also, for the composite solvent according to the present invention, the difference between the boiling point of the first solvent and the boiling point of the second solvent may be 10°C or less. For example, the difference between the boiling point of the first solvent and the boiling point of the second solvent may be 5°C or less, 4°C or less, 3°C or less, 2°C or less, or 1°C or less.

[0021] By minimizing the difference in boiling points between the mixed solvents as described above, the precipitation temperature of the polyimide powder can be lowered when heating the polymer, and the intrinsic viscosity of the produced polyimide powder can be increased.

[0022] The polymerization step may be to disperse or dissolve the dianhydride monomer component together with the diamine monomer component in a solvent, or to produce a solution in which the dianhydride monomer component is dispersed in a solvent and a solution in which the diamine monomer component is dispersed in a solvent, and then add a catalyst to the polymer obtained by mixing these. Also, among the dianhydride monomer component and the diamine monomer component, one component may be first dissolved in a solvent, and then the remaining component may be dissolved in the solution.

[0023] In one embodiment, the polymerization step may include a step of heating a solvent, a step of dissolving a diamine monomer component in the heated solvent, and a step of reacting a dianhydride monomer component with the solution in which the diamine is dissolved.

[0024] The step of heating the solvent may be carried out at a temperature of 50 to 100°C. For example, the temperature may be 60 to 90°C or 60 to 80°C. The step of dissolving the diamine monomer component in the heated solvent may be carried out at a temperature of 50 to 100°C for 1 to 60 minutes. In this case, the temperature may be, for example, 60 to 90°C or 60 to 80°C, and the time may be 1 to 30 minutes.

[0025] Also, the step of reacting the dianhydride monomer component with the solution in which the diamine is dissolved may be carried out at a temperature of 50 to 100°C for 1 to 6 hours. At this time, in the step of reacting the dianhydride monomer component with the solvent in which the diamine is dissolved, the dianhydride monomer component may be introduced at a rate of 0.01 mol / s to 10 mol / s. For example, it may be introduced at a rate of 0.05 mol / s to 10 mol / s, 0.1 mol / s to 10 mol / s, 1 mol / s to 10 mol / s, 1 mol / s to 5 mol / s, or 1 mol / s to 3 mol / s.

[0026] By producing a polymer by the method as described above, side reactions can be suppressed and the yield of the product can be increased, and by reducing the content of residual dianhydride or diamine, the color of the polyimide powder can be brightened.

[0027] Furthermore, by adding dianhydride at the rate described above, side reactions can be suppressed and the yield of the product can be increased, and the color of the polyimide powder can be brightened by reducing the content of residual dianhydride or diamine.

[0028] In the polymerization step, the content of dianhydride monomer and diamine monomer is 1 to 30% by weight based on the total volume of the solution. For example, the content of dianhydride monomer and diamine monomer in the solution may be 1 to 20% by weight, 1 to 15% by weight, 3 to 15% by weight, 5 to 15% by weight, or 5 to 10% by weight based on the total volume of the solution. If the solid content exceeds the above range, stirring may be difficult, the yield may decrease, or the quality may deteriorate. If the solid content is lower than the above range, the manufacturing cost may increase.

[0029] The polymerization step involves polymerizing the dianhydride monomer and the diamine monomer by heating. The heating temperature in the polymerization step is 30 to 100°C, and for example, the heating temperature in the polymerization step may be 40 to 100°C, 50 to 90°C, or 60 to 80°C.

[0030] If the heating temperature is lower than the range, the reaction proceeds too slowly, and the yield of polyimide powder decreases. If the heating temperature is higher than the range, the particle size may increase.

[0031] In the polymerization step, the reaction time may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours.

[0032] If the reaction time is shorter than the range, the reaction yield may decrease, and the mechanical properties of the powder, such as elongation and tensile strength, may decline. If the reaction time is longer than the range, the powder may become darker in color and the particle size may increase.

[0033] The imidation step is a step of imidizing the polymer polymerized by heating and pressurizing. The heating temperature in the imidation step is 150 to 300°C, and for example, the heating temperature in the imidation step may be 160 to 200°C, 170 to 200°C, or 180 to 200°C.

[0034] If the heating temperature is lower than the range, the reaction proceeds too slowly, and the yield of polyimide powder decreases. If the heating temperature is higher than the range, the particle size may increase.

[0035] In the imidization step, the reaction time may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours.

[0036] If the reaction time is shorter than the range, the reaction yield may decrease, and mechanical properties such as elongation and tensile strength may decrease. If the reaction time is longer than the range, the powder may become darker in color and the particle size may increase.

[0037] The present invention allows for the precipitation of polyimide powder through the imidation step. In this case, the polyimide powder may be precipitated at a precipitation temperature of 100 to 200°C. For example, the lower limit of the precipitation temperature may be 105°C or higher, 110°C or higher, 115°C or higher, 120°C or higher, 125°C or higher, or 130°C or higher, and the upper limit of the precipitation temperature may be 195°C or lower, 190°C or lower, 185°C or lower, 180°C or lower, 175°C or lower, 170°C or lower, 165°C or lower, 160°C or lower, 155°C or lower, 150°C or lower, 145°C or lower, 140°C or lower, or 135°C or lower. The precipitation temperature is affected by the composition of the dianhydride monomer and diamine, the type and content of the catalyst, and the solvent.

[0038] The method for producing polyimide powder according to the present invention may further include a filtration and drying step after the imidation step. The filtration and drying method is not particularly limited, and the drying method may be, for example, vacuum drying or drying in a high-temperature oven. Specifically, the drying step may be drying in an oven at 100°C or higher for 24 hours or more.

[0039] Furthermore, the present invention provides polyimide powder produced by the method for producing polyimide powder described above.

[0040] The polyimide powder, produced by the manufacturing method described above, has the advantages of high intrinsic viscosity, ease of processing, uniform particle size, and excellent processability.

[0041] For example, the polyimide powder may have an intrinsic viscosity of 0.9 dl / g or more, 0.95 dl / g or more, 1.0 dl / g or more, 1.05 dl / g or more, 1.1 dl / g or more, 1.15 dl / g or more, 1.2 dl / g or more, 1.25 dl / g or more, 1.3 dl / g or more, 1.35 dl / g or more, 1.4 dl / g or more, 1.45 dl / g or more, 1.5 dl / g or more, 1.55 dl / g or more, 1.6 dl / g or more, 1.65 dl / g or more, 1.7 dl / g or more, or 1.75 dl / g or more. The intrinsic viscosity may be measured by dissolving 50 mg of polyimide powder in a vial in 10 g of concentrated sulfuric acid and then measuring it with an Ubbelohde viscometer at 30°C.

[0042] The polyimide powder according to the present invention is D 50 The particle size may be 150 μm or less. For example, the polyimide powder according to the present invention is D 50 The upper limit of 0 may be 120 μm or less, 110 μm or less, 105 μm or less, 100 μm or less, 95 μm or less, 90 μm or less, 80 μm or less, or 60 μm or less, D 50 The lower limit may be 10 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more.

[0043] The polyimide powder according to the present invention is D 99.9may also be 500 μm or less. For example, the polyimide powder according to the present invention has an upper limit of D 99.9 of 300 μm or less, 250 μm or less, 210 μm or less, or 200 μm or less, and the lower limit of D 99.9 may be 10 μm or more, 50 μm or more, or 100 μm or more.

[0044] Here, "D n " means the size of the particles when the cumulative percentage of the particle size distribution reaches n volume%. Therefore, the above "D 99.9 " means the size of the particles when the cumulative percentage of the particle size distribution reaches 99.9 volume%, and the above "D 50 " means the size of the particles when the cumulative percentage of the particle size distribution reaches 50 volume%. The particle size distribution means the particle size distribution graph of the polyimide powder analyzed using a laser particle size analyzer. Specifically, the particle size distribution may be measured using a laser diffraction light scattering type particle size distribution measuring device (for example, Malvern Mastersizer 3000).

[0045] When the above D 50 and D satisfy the above range, it is easy to set appropriate molding conditions when molding the polyimide powder, and cracks and breakage during molding can be effectively prevented, and the processability is excellent.

[0046] In addition, the polyimide powder according to the present invention may have D 99.9 / D 50 of 15 or less. For example, the polyimide powder according to the present invention has an upper limit of D 99.9 / D 50 of 14 or less, 13 or less, 12 or less, or 11 or less, and the lower limit of D 99.9 / D 50 may be 5 or more, 7 or more, or 10 or more.

[0047] The polyimide powder according to the present invention can provide a powder with small variation in particle size and uniform as described above, thereby reducing the defect rate during powder molding and increasing the yield.

[0048] Furthermore, the present invention provides molded articles containing polyimide powder. The polyimide powder produced by the present invention may be manufactured as molded articles by various molding methods, for example, compression molding, injection molding, slush molding, hollow molding, extrusion molding, or spinning methods can be used to produce the required molded articles. The molded articles may be plates, rods, films, sheets, pellets, belts, or tubes.

[0049] The polyimide powder produced by the present invention may be used in various fields such as electrical / electronics, semiconductors, displays, automobiles, medical equipment, batteries, and aerospace. [Effects of the Invention]

[0050] The polyimide powder and method for producing the same according to the present invention can simplify the manufacturing process and improve process efficiency, and because the polyimide is produced in powder form, it is easy to mold, has a low precipitation temperature, high intrinsic viscosity and is easy to process, and has uniform particle size and excellent processability. [Modes for carrying out the invention]

[0051] The present invention will be described in more detail below through examples and comparative examples that do not conform to the present invention, but the scope of the present invention is not limited to the examples presented below.

[0052] <Manufacturing of polyamic acid solution> Example 1 A Dean-Stark trap was placed in a 1000 ml reactor equipped with a stirrer and a nitrogen injection / discharge pipe. A solvent mixture of N-methyl-2-pyrrolidone (NMP) and m-cresol in a 5:5 weight ratio was heated to 70°C while injecting nitrogen, and 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in the heated solvent. Then, pyromeretic dianhydride (PMDA) was completely dissolved in the solvent and the reaction was carried out at 75°C for 2 hours. Pyridine (PR) was added to the reaction mixture as a catalyst at a ratio of 200 moles per 100 moles of ODA, and the mixture was heated to 200°C while stirring, and then heated for a further 2 hours to precipitate polyimide powder.

[0053] For reference, the boiling point of N-methyl-2-pyrrolidone (NMP) is 202°C, and the boiling point of m-cresol is 202.2°C.

[0054] Examples 2-14 Polyimide powder was produced in the same manner as in Example 1, except that the monomer components, solvent, and catalyst were adjusted as shown in Table 1 below.

[0055] Comparative Examples 1-3 Polyimide powder was produced in the same manner as in Example 1, except that the monomer components, solvent, and catalyst were adjusted as shown in Table 1 below.

[0056] [Table 1]

[0057] Experimental example The physical properties of the manufactured polymerization product and polyimide powder were measured using the following method, and the results are shown in Table 2 below.

[0058] Experimental Example 1 - Intrinsic Viscosity The viscosity was measured at 30°C using an Ubbelohde viscometer. Specifically, 50 mg of polyimide powder was placed in a vial, dissolved in 10 g of concentrated sulfuric acid, and then measured using an Ubbelohde viscometer.

[0059] Experimental Example 2 - Precipitation Temperature After the polymerization reaction, the temperature was measured at the point when the clear solution became blurred due to imidization.

[0060] Experimental Example 3 - Particle Size Distribution of Polyimide Powder Particle size distribution of manufactured polyimide powder (D 50 The particle size distribution was measured using a laser diffraction light scattering particle size analyzer (Malvern Mastersizer 3000).

[0061] [Table 2]

Claims

1. Polymerization step in which dianhydride monomer components and diamine monomer components are reacted with a solvent. The process includes an imidation step in which a catalyst is added to the reaction solution produced in the polymerization step, and imidization is performed to precipitate polyimide powder. The solvent is a composite solvent comprising a first solvent containing at least one nitrogen element and a second solvent having at least one hydroxyl group (-OH), The difference between the boiling point of the first solvent and the boiling point of the second solvent is 10°C or less. A method for producing polyimide powder, wherein the catalyst is pyridine, β-picoline, 1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine (TEA), or a mixture thereof.

2. The method for producing polyimide powder according to claim 1, wherein the catalyst is included in an amount of 0.1 to 500 moles based on 100 moles of the diamine monomer component.

3. The polymerization step is, The step of heating the solvent, The steps include dissolving the diamine monomer component in a heated solvent, A method for producing polyimide powder according to claim 1, comprising the step of reacting a dianhydride monomer component with a solution in which a diamine is dissolved.

4. The method for producing polyimide powder according to claim 3, wherein the step of heating the solvent is performed at a temperature of 50 to 100°C.

5. The method for producing polyimide powder according to claim 3, wherein the step of dissolving the diamine monomer component in a heated solvent is carried out at a temperature of 50 to 100°C for 1 to 60 minutes.

6. The method for producing polyimide powder according to claim 3, wherein the step of reacting a dianhydride monomer component with a solvent in which a diamine is dissolved is carried out at a temperature of 50 to 100°C for 1 to 6 hours.

7. The method for producing polyimide powder according to claim 3, wherein the step of reacting the dianhydride monomer component with the solvent in which the diamine is dissolved is to add the dianhydride monomer component at a rate of 0.01 mol / s to 10 mol / s.

8. The method for producing polyimide powder according to claim 1, wherein the imidation step is carried out at a temperature of 150 to 300°C for 1 to 10 hours.

9. A method for producing polyimide powder according to claim 1, wherein the dianhydride monomer comprises at least one selected from the group consisting of pyromeretic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), and p-phenylenebis(trimellitate anhydride) (TAHQ).

10. Diamine monomers include 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenedianiline (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine ( A method for producing polyimide powder according to claim 1, comprising at least one selected from the group consisting of M-TOLDINE, 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxybenzene (TPE-Q), bisaminophenoxybenzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).

11. Polyimide powder produced by the method for producing polyimide powder described in claim 1.

12. The polyimide molded article according to claim 11, wherein the intrinsic viscosity of the polyimide powder is 0.9 dl / g or more.

13. D of polyimide powder ５０ The polyimide powder according to claim 11, wherein the particle size is 100 μm or less.

14. A polyimide molded article containing the polyimide powder described in claim 11.

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