Solvent-soluble polyimide

Abstract

The present invention provides a polyimide containing, as polymerized units, a dianhydride acid monomer including one selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and a diamine monomer including 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

Description

[Technical Field]

[0001] The present invention relates to a solvent-soluble polyimide, and more particularly to a polyimide that is soluble in organic solvents. [Background technology]

[0002] In general, polyimide (PI) is a polymeric material based on imide rings, which have excellent chemical stability along with a rigid aromatic main chain, and has the highest levels of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials. It can be manufactured into various forms such as films, fibers, and membranes. Due to these properties, polyimides are widely used as advanced materials and insulating coating agents in the fields of electrical and electronics, semiconductors, displays, automobiles, aviation, and space materials.

[0003] Polyimide can be manufactured by dissolving an acid dianhydride, which has two acid anhydride groups in the molecule, and a diamine, which has two amino groups in the molecule, in a solvent to synthesize a polyimide precursor called polyamic acid (PAA), which is then coated and dried, and heat-treated at a temperature of around 350°C to imidize it. Traditionally, there has been a strong demand for handling polyimides in solution, and much development has been underway for solvent-soluble polyimides.

[0004] However, conventional polyimides produced by imidization through dehydration and ring-closure reactions using chemical or high-temperature methods have been difficult to process due to their solvent-insolubility. Furthermore, to produce solvent-soluble polyimides, highly soluble monomers must generally be used. However, these monomers generally have low heat resistance, resulting in poor heat and chemical resistance. Meanwhile, to use polyimides in solution while maintaining heat and chemical resistance, one method involves forming a coating film with a polyamic acid solution, which is a polyimide precursor, and then imidizing the coating film to produce polyimides.

[0005] However, polyamic acid solutions have the disadvantages of being easily affected by humidity, making them difficult to handle and store, and requiring a high-temperature heat treatment step to imidize the polyamic acid.

[0006] Under these circumstances, there is a need to develop polyimides that maintain the high heat resistance and insulating properties of polyimides, are easily soluble in organic solvents, and can be used to produce polyimide-based products by simply drying the solvent, without the need for a high-temperature imidization process. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a polyimide (PI) that is soluble in organic solvents.

[0008] Another object of the present invention is to provide a polyimide that can be produced into various forms such as films and fibers by simply drying the solvent without a high-temperature imidization process.

[0009] Another object of the present invention is to provide a polyimide solution containing the above polyimide.

[0010] Another object of the present invention is to provide a polyimide powder containing the above polyimide.

[0011] Another object of the present invention is to provide a separator containing the polyimide.

[0012] Another object of the present invention is to provide a fiber containing the polyimide.

[0013] Another object of the present invention is to provide an insulating layer containing the polyimide.

[0014] Another object of the present invention is to provide a coating layer containing the polyimide. [Means for solving the problem]

[0015] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be illustrated and described in detail, but it should be understood that this does not limit the present invention to the specific embodiments, and that the present invention includes all modifications, equivalents, and alternatives that fall within the spirit and technical scope of the present invention.

[0016] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" and the like specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and should be understood not to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0017] Whenever an amount, concentration, or other value or parameter is given herein by a list of ranges, preferred ranges, or upper preferred values ​​and lower preferred values, that should be understood to specifically disclose all ranges formed by any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are otherwise disclosed.

[0018] Where a range of numerical values ​​is recited herein, unless otherwise stated, it is intended that the endpoints of the range and any values ​​within the range be included. The scope of the invention is not limited to the specific values ​​recited when defining the range.

[0019] As used herein, "dianhydride" is intended to include precursors or derivatives thereof, but may also be referred to as "dianhydride acids," "dianhydrides," or "acid dianhydrides," which may not technically be dianhydrides but nevertheless react with diamines to form polyamic acids, which in turn can be converted to polyimides.

[0020] As used herein, "diamine" is intended to include precursors or derivatives thereof, which may not technically be diamines, but which nevertheless react with dianhydride acids to form polyamic acids, which in turn can be converted to polyimides.

[0021] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an ideal or overly formal sense unless expressly defined in this application. Specific details for realizing the above invention are described below.

[0022] The present invention relates to a polyimide (PI) that is soluble in an organic solvent.

[0023] Solvent-soluble polyimide

[0024] The present invention provides a polyimide containing, as polymerized units, a dianhydride acid monomer including one selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and a diamine monomer including 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

[0025] The diamine monomer may further include one or more diamine monomers selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4′-methylenedianiline (MDA), and phenylenediamine (PD).

[0026] Specifically, the diamine monomer may include 4,4'-methylenebis(2,6-diethylaniline) (MEDA) alone, or may include 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in combination with one or more diamine monomers selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4'-methylenedianiline (MDA), and phenylenediamine (PD).

[0027] In one embodiment, the polyimide can include the dianhydride monomer 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine monomer 4,4'-methylenebis(2,6-diethylaniline) (MEDA) as polymerized units.

[0028] In one embodiment, the polyimide can include, as polymerized units, the dianhydride monomer 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine monomers 4,4'-methylenedianiline (MDA) and 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

[0029] In one embodiment, the polyimide can include, as polymerized units, the dianhydride monomer 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine monomers 4,4'-methylenedianiline (MDA), phenylenediamine (PD), and 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

[0030] In one embodiment, the polyimide can include, as polymerized units, the dianhydride monomer 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine monomers phenylenediamine (PD) and 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

[0031] In one embodiment, the polyimide can include, as polymerized units, the dianhydride monomer 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and the diamine monomers 2,4-diaminotoluene (TDA) and 4,4'-methylenebis(2,6-diethylaniline) (MEDA).

[0032] The phenylenediamine (PD) may include one or more selected from the group consisting of o-phenylenediamine (o-PD) and m-phenylenediamine (m-PD), and preferably includes m-phenylenediamine (m-PD).

[0033] The content of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in the total diamine monomers may be 60 mol% or more, preferably 60 to 110 mol%, and more preferably 60 to 100 mol%. For example, the lower limit may be 61 mol%, 62 mol%, 63 mol%, 64 mol%, or 65 mol% or more.

[0034] If the content of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) is less than 60 mol %, the solubility in organic solvents cannot be ensured, which is undesirable.

[0035] Of the total diamine monomers, the content of one or more diamine monomers selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4'-methylenedianiline (MDA), and phenylenediamine (PD) may be 40 mol% or less, specifically, 0 to 40 mol%. For example, the upper limit may be 39 mol%, 38 mol%, 37 mol%, 36 mol%, or 35 mol%. 0 mol% means that none of the following diamine monomers is contained in the total diamine monomers: 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4'-methylenedianiline (MDA), and phenylenediamine (PD).

[0036] The polyimide may contain the diamine monomer in an amount of 90 to 110 mol %, preferably 95 to 105 mol %, and more preferably 100 mol %.

[0037] The polyimide may contain the dianhydride acid monomer in an amount of 90 to 110 mol %, preferably 95 to 105 mol %, and more preferably 100 mol %.

[0038] The polyimide may contain the dianhydride acid monomer and the diamine monomer in a molar ratio of 6:4 to 4:6, preferably 5:5.

[0039] The polyimide has excellent solubility in organic solvents when the solid content is 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 25 wt% or more. In one embodiment, a polyimide solid content of 20 to 25 wt% was added at room temperature, followed by stirring for 30 minutes, and the turbidity of the solution was visually confirmed.

[0040] The organic solvent may be an aprotic polar organic solvent, and specifically may include one or more selected from the group consisting of N-methyl-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc).

[0041] In the present invention, the thermal decomposition temperature (Td), which is mainly used as a criterion for determining the thermal properties of the polyimide, and the glass transition temperature (Tg), which can predict the thermal properties and determine the mechanical properties, were confirmed.

[0042] The glass transition temperature (Tg) of the polyimide may be 250° C. or higher, and for example, the lower limit of the glass transition temperature may be 255° C., 260° C., 265° C., 270° C., or 275° C. or higher. The glass transition temperature of the polyimide can be measured using DMA at a rate of 10° C. / min.

[0043] The 5 wt % thermal decomposition temperature (Td) of the polyimide may be 400°C or higher. For example, the lower limit of the thermal decomposition temperature may be 410°C, 415°C, 420°C, 425°C, 430°C, or 435°C or higher. The thermal decomposition temperature can be measured using a thermogravimetric analyzer (Model Q50) manufactured by TA Corporation. In a specific example, the polyimide is heated to 100°C at a rate of 10°C / min in a nitrogen atmosphere, and then maintained at the same temperature for 30 minutes to remove moisture. Next, the temperature is raised to 600°C at a rate of 10°C / min, and the temperature at which a 5% weight loss occurs can be measured.

[0044] The polyimide of the present invention is characterized by maintaining excellent thermal properties and having excellent solubility in organic solvents.

[0045] The polyimide of the present invention contains 60 mol % or more of MEDA and is combined with a specific dianhydride monomer and diamine monomer to ensure solubility. This makes it easy to dissolve in organic solvents, and films, fibers, etc. can be produced by simply drying the solvent without a high-temperature imidization process.

[0046] In another aspect, there is provided a polyimide solution comprising the polyimide of the present invention and an organic solvent.

[0047] The polyimide of the present invention has excellent solubility in organic solvents, and therefore has the advantage that it can be easily used for polyimide film, fiberization, or coating when used in the form of a solution dissolved in an organic solvent.

[0048] In the present invention, the polyimide solution may have a polyimide solids content of 15 to 60 wt % based on 100 parts by weight of the polyimide solution. The lower wt % solids content limit may be 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 wt % or more, and the upper wt % solids content limit may be 55, 50, 45, 40, 37, or 35 wt % or less. By adjusting the solids content of the polyimide solution, it is possible to control the increase in viscosity and shorten the process time during the curing process.

[0049] In one embodiment, the polyimide solution of the present invention is prepared at a temperature of 23° C. and 1 s -1 The viscosity measured under the shear rate condition may be in the range of 200 to 50,000 cP. Specifically, the lower limit of the viscosity of the polyimide solution is 500 cP or more, 1,000 cP or more, 1,200 cP or more, 1,500 cP or more, 1,600 cP or more, 1,700 cP or more, 2,000 cP or more, 2,200 cP or more, 2,500 cP or more, 2,600 cP or more, 2,700 cP or more, 5,500 cP or more, 5,900 cP or more, 5,980 cP or more, 6,500 cP or more, 7,000 cP or more, 8,000 cP or more, 10,000 cP or more, 11,000 cP or more, 12,200 cP or more, 13,000 cP or more, 14,000 cP or more. The viscosity may be 14,350 cP or more, 14,400 cP or more, 14,500 cP or more, 15,000 cP or more, or 15,500 cP or more, and the upper limit may be 49,000 cP or less, 45,000 cP or less, 40,000 cP or less, 30,000 cP or less, 25,000 cP or less, 20,000 cP or less, 18,000 cP or less, 16,000 cP or less, 15,500 cP or less, 15,000 cP or less, 14,500 cP or less, 8,000 cP or less, 5,000 cP or less, 3,500 cP or less, or 2,900 cP or less. By adjusting the viscosity range of the polyimide solution, the present application can produce a cured polyimide having excellent processability and desired physical properties.

[0050] In yet another aspect, there is provided a polyimide powder comprising the polyimide of the present invention.

[0051] In yet another aspect, there is provided a polyimide film comprising the polyimide of the present invention.

[0052] In yet another aspect, a part is provided that includes a molded article formed from the polyimide.

[0053] Specifically, the parts may be, but are not limited to, electronic circuit board parts, semiconductor devices, lithium ion battery parts, solar cell parts, fuel cell parts, motor windings, engine peripheral parts, paints, optical parts, heat dissipation materials, electromagnetic wave shielding materials, surge parts, dental materials, slide coatings, and electrostatic chucks.

[0054] The present invention also provides a separator comprising the polyimide.

[0055] The present invention also provides a fiber comprising the polyimide described above.

[0056] The present invention also provides an insulating layer comprising the polyimide described above.

[0057] The present invention also provides a coating layer comprising the polyimide. [Effects of the Invention]

[0058] The polyimide according to the present invention is soluble in organic solvents and can be produced into various forms such as films and fibers by simply drying the solvent without the need for a high-temperature imidization process, thereby improving the ease of processing.

[0059] Furthermore, the polyimide of the present invention has the effect of exhibiting excellent solubility in organic solvents and excellent thermal properties.

[0060] Furthermore, the polyimide according to the present invention has an effect of being applicable to various fields such as insulating coating, fibers, and membranes. DETAILED DESCRIPTION OF THE INVENTION

[0061] Examples are presented below to aid in understanding the present invention. The following examples are provided to facilitate understanding of the present invention, and are not intended to limit the scope of the present invention.

[0062] <Example>

[0063] Example 1: Preparation of polyimide

[0064] In a nitrogen / room temperature atmosphere, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-methylenebis(2,6-diethylaniline) (MEDA) were added to a dimethylformamide (DMF) organic solvent, stirred, and reacted to obtain a polyamic acid (PAA) composition. The organic solvent may be one or more selected from, but is not limited to, dimethylformamide (DMF), methylpyrrolidone (NMP), and dimethylacetamide (DMAc).

[0065] A tertiary catalyst (BP, β-picoline) and a dehydrating agent (acetic anhydride, AA) were added to the obtained polyamic acid composition, and a chemical imidization process was carried out in a continuous batch polymerization process at 60°C.

[0066] After the reaction was completed, the polymer was precipitated in an ethanol non-solvent, and impurities (unreacted materials, tertiary catalyst, AA, etc.) were removed to obtain a powdery product. The tertiary catalyst can be any tertiary amine catalyst, including, but not limited to, pyridine, β-picoline (BP), and isoquinoline (IQ). The non-solvent, intended for precipitation, can be one or more selected from the group consisting of water, methanol, ethanol, n-propanol, isopropanol, butanol, butanediol, ethylene glycol, glycerol, γ-butyrolactone, and mixtures thereof, but is not limited to these.

[0067] Then, it was dried in a vacuum oven at 60° C. for 24 hours to obtain a polyimide powder.

[0068] Examples 2 to 6

[0069] Polyimide powder was prepared in the same manner as in Example 1, except that the monomer components and content ratios were adjusted as shown in Table 1 below.

[0070] Example 7

[0071] In a nitrogen / room temperature atmosphere, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-methylenebis(2,6-diethylaniline) (MEDA) were added to an organic solvent, N-methyl-pyrrolidone (NMP), and the mixture was stirred and reacted to obtain a polyamic acid (PAA) composition. The components and amounts of the polyamic acid (PAA) composition were added in the same manner as in Example 1.

[0072] The resulting polyamic acid composition was then heated to 180°C and stirred at that temperature for 2 to 4 hours to obtain a polyimide solution through a thermal imidization process. After the reaction was completed, impurities were removed and the mixture was dried in a vacuum oven at 60°C for 24 hours to obtain a polyimide powder.

[0073] Examples 8 to 12

[0074] The components and contents of the polyamic acid (PAA) composition were added in the same manner as in Examples 2 to 6, respectively, and polyimide powder was produced in the same manner as in Example 7, except that the components and contents were adjusted.

[0075] Comparative Examples 1 to 4

[0076] Polyimide was prepared in the same manner as in Example 1, except that the monomer components and content ratios were adjusted as shown in Table 1 below.

[0077] [Table 1]

[0078] The abbreviations for the substances used in Table 1 above are as follows:

[0079] PMDA: Pyromeric dianhydride

[0080] BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride

[0081] TDA: 2,4-diaminotoluene

[0082] MDA: 4,4'-methylenedianiline

[0083] MPD: m-phenylenediamine

[0084] ODA: 4,4'-oxydianiline

[0085] MEDA: 4,4'-methylenebis(2,6-diethylaniline)

[0086] <Experimental Example>

[0087] Experimental Example 1: Evaluation of solubility

[0088] The solubility of the polyimide in an organic solvent was evaluated by adding 20 g of the polyimide powder produced in Examples 1 to 6 and Comparative Examples 1 to 4 to 80 g of the organic solvent N,N'-dimethylformamide (DMF) and visually inspecting the solubility.

[0089] Specifically, 20 wt% or 25 wt% of polyimide solids were added at room temperature, followed by stirring for 30 minutes, and the turbidity of the solution was visually confirmed. As a result of the test, the solubility was judged as "soluble" for a transparent solution with no suspended matter and a transparent color, and otherwise it was judged as "insoluble." The solubility analysis results are shown in Table 2 below.

[0090] Experimental Example 2: Glass transition temperature (Tg)

[0091] The polyimides produced in Examples 1 to 6 and Comparative Examples 1 to 4 were measured using DMA at a rate of 10°C / min to determine the on-set point, which was the point at which they suddenly expanded. The results are shown in Table 2.

[0092] Experimental Example: Thermal decomposition temperature (Td) of 3.5% by weight

[0093] Using a TA Thermogravimetric Analyzer Q50 model, the polyimides prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were heated to 100°C at a rate of 10°C / min in a nitrogen atmosphere, and then maintained at the same temperature for 30 minutes to remove moisture. The samples were then heated to 600°C at a rate of 10°C / min, and the temperature at which a 5% weight loss occurred was measured. The results are shown in Table 2 below.

[0094] Table 2 below shows the results of the solubility, glass transition temperature (Tg) and 5 wt % thermal decomposition temperature (Td) of the polyimides produced in Examples 1 to 6 and Comparative Examples 1 to 4.

[0095] [Table 2]

[0096] Table 2 confirms that the polyimides of Examples 1 to 6 not only exhibited excellent solubility in DMF, an aprotic polar organic solvent, but also maintained excellent thermal properties. On the other hand, the polyimides of Comparative Examples 2 and 3, which contained less than 60 mol% MEDA, did not exhibit solubility in DMF and also did not exhibit thermal properties.

[0097] Furthermore, the polyimide of Comparative Example 4, which further contained PMDA as a dianhydride monomer, and the polyimide of Comparative Example 1, which further contained ODA as a diamine monomer, did not exhibit solubility in DMF or thermal properties.

[0098] These results confirm that polyimides containing 60 mol% or more of MEDA in combination with specific dianhydride and diamine monomers are soluble in aprotic polar organic solvents (e.g., DMF) and can maintain the excellent thermal properties unique to polyimides.

[0099] This specification omits detailed descriptions of content that can be fully recognized and inferred by a person having ordinary skill in the technical field of the present invention, and various modifications are possible within the scope of the specific examples described in this specification without changing the technical idea or essential configuration of the present invention. Therefore, the present invention can be implemented in ways different from those specifically explained and exemplified in this specification, and this is something that can be understood by a person having ordinary skill in the technical field of the present invention.

Claims

1. a dianhydride acid monomer comprising one selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride; and a diamine monomer containing 4,4'-methylenebis(2,6-diethylaniline) (MEDA) as polymerized units.

2. 2. The polyimide of claim 1, wherein the diamine monomer further comprises one or more diamine monomers selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4′-methylenedianiline (MDA), and phenylenediamine (PD).

3. 3. The polyimide according to claim 2, wherein the phenylenediamine (PD) comprises at least one selected from the group consisting of o-phenylenediamine (o-PD) and m-phenylenediamine (m-PD).

4. 2. The polyimide according to claim 1, wherein the content of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in the total diamine monomers is 60 mol % or more.

5. 3. The polyimide according to claim 2, wherein the content of one or more diamine monomers selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethylbenzene-1,4-diamine, 4,4'-methylenedianiline (MDA), and phenylenediamine (PD) is 40 mol% or less of all diamine monomers.

6. The polyimide according to claim 1 , wherein the polyimide exhibits a property of being soluble in an organic solvent when the polyimide has a solid content of 15 wt % or more.

7. 7. The polyimide according to claim 6, wherein the organic solvent comprises one or more selected from the group consisting of N-methyl-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc).

8. 2. The polyimide according to claim 1, wherein the polyimide has a glass transition temperature (Tg) of 250° C. or higher.

9. 2. The polyimide according to claim 1, wherein the 5 wt % thermal decomposition temperature (Td) of the polyimide is 400° C. or higher.

10. A polyimide solution comprising the polyimide according to claim 1 and an organic solvent.

11. 11. The polyimide solution according to claim 10, wherein the polyimide solids content is 15 to 60% by weight.

12. 11. The polyimide solution according to claim 10, wherein the organic solvent comprises one or more selected from the group consisting of N-methyl-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc).

13. A polyimide powder comprising the polyimide according to any one of claims 1 to 9.

14. A polyimide film comprising the polyimide according to any one of claims 1 to 9.

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