Solvent-soluble polyimide and preparation method thereof

Abstract

The present disclosure provides a polyimide comprising: a dianhydride monomer as a polymerization unit; and a diamine monomer including 4, 4 '-methylenebis (2, 6-diethylaniline) (MEDA) wherein the polyimide is a random copolymer in which polymerized units are irregularly arranged.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a solvent-soluble polyimide and a method for preparing the same. More particularly, the present disclosure relates to a polyimide having excellent thermal and mechanical properties and solubility in organic solvents and a method for preparing the same. BACKGROUND

[0002] In general, polyimides (PIs) are based on imide rings having excellent chemical stability together with a rigid aromatic main chain, and are polymer materials having the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance among organic materials, and thus are prepared in various forms such as thin films, fibers, membranes, etc. Due to these properties, polyimides are used as advanced materials and insulating coating agents in a wide range of fields such as electrical and electronic, semiconductors, displays, automobiles, aerospace, and materials.

[0003] Polyimides can be prepared by dissolving an acid dianhydride having two anhydride groups in a molecule and a diamine having two amino groups in a molecule in a solvent to synthesize a polyimide precursor called polyamic acid (PAA), and applying and drying the polyimide precursor, followed by heat treatment at about 350°C to perform imidization (or called imination). Since there is a high demand for handling polyimides in a solution state, a great deal of development has been made on solvent-soluble polyimides.

[0004] However, conventional polyimides prepared by imidization using a conventional chemical method or a high-temperature method through dehydration and ring closure reaction have insolubility in solvents, resulting in processing difficulties. In addition, in order to prepare polyimides soluble in solvents, there is usually no choice but to use highly soluble monomers, but these monomers generally have low heat resistance, and thus the prepared polyimides have problems of low heat resistance and low chemical resistance. At the same time, in order to use polyimides having heat resistance or chemical resistance in a solution form, there is a method of preparing polyimides by forming a coating film with a polyamic acid solution as a polyimide precursor, and then performing imidization.

[0005] However, the polyamic acid solution has disadvantages of being susceptible to moisture, difficult to handle and store, and requiring a heat treatment process at a high temperature to imidize the polyamic acid.

[0006] In this background, there is a need to develop a polyimide capable of maintaining its high heat resistance and insulating properties, while being easily soluble in organic solvents, and capable of preparing a product of a polyimide group only by solvent drying without an imidization process at a high temperature. SUMMARY

[0007]

Technical Problem

[0008] An object of the present disclosure is to provide a polyimide (PI) that exhibits solubility in an organic solvent and has excellent thermal and mechanical properties.

[0009] Another object of the present disclosure is to provide a polyimide that is completely imidized, capable of being simply prepared in various forms such as a thin film and a fiber, etc. by drying a solvent without an imidization process at a high temperature.

[0010] Still another object of the present disclosure is to provide a polyimide solution including a polyimide.

[0011] Further, still another object of the present disclosure is to provide a polyimide powder including a polyimide.

[0012] Further, still another object of the present disclosure is to provide a polyimide thin film including a polyimide.

[0013] Further, still another object of the present disclosure is to provide various forms of a polyimide, for example, a separator, an adhesive, an insulating coating, and a coating material including a polyimide.

[0014] Further, still another object of the present disclosure is to provide a method for preparing a polyimide.

[0015]

Technical Solution

[0016] Various modifications can be made in the present disclosure and various embodiments can be implemented, and a specific embodiment is illustrated in the accompanying drawings and described in detail. However, these embodiments are not intended to limit the present disclosure to specific embodiments, and it should be understood that all modifications, equivalents, and alternatives included in the spirit and scope of the present disclosure are included.

[0017] The terms used in the present application are used only to describe specific embodiments, and are not intended to limit the present disclosure. The singular expression includes the plural expression, unless the context clearly dictates otherwise. In the present specification, terms such as "include" or "have" are intended to mean the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification and should not be understood as excluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0018] When the amount, concentration or other value or parameter herein is given as a range, a preferred range or a list of upper preferred values and lower preferred values, it should be understood that all ranges formed by any pair of any range upper limit or preferred value and any range lower limit or preferred value are specifically disclosed, regardless of whether the range is separately disclosed.

[0019] When a numerical range is recited herein, unless otherwise stated, the end points and ranges of the present invention within that range are intended to be inclusive of the specific values stated when defining that range.

[0020] As used herein, "dianhydride" is intended to include precursors or derivatives thereof, which are also referred to as "dianhydride" or "acid dianhydride". These products can not be technically dianhydrides, but will still react with diamines to form polyamic acid, and the polyamic acid can be converted back to polyimide.

[0021] As used herein, "diamine" is intended to include precursors or derivatives thereof, which can not be technically diamines, but will still react with dianhydride acid to form polyamic acid, and the polyamic acid can be converted back to polyimide.

[0022] Further, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present application. Specific details of the present application will be described in the following.

[0023] The present disclosure relates to a polyimide (PI) having solubility in an organic solvent.

[0024] Polyimide

[0025] In one general aspect, there is provided a polyimide comprising: as a polymerization unit, a dianhydride monomer; and a diamine monomer comprising 4,4'-methylenebis(2,6-diethylaniline) (MEDA), wherein the polyimide is a random copolymer in which the polymerization units are irregularly arranged.

[0026] A random copolymer is a copolymer composed of three or more types of polymerization units (repeating units), in which the order of the polymerization units is randomly connected. For example, the expression "- (A)a- (B)b- (C)c- (D)d-", which is a random copolymer of polymerization units A to D, means that the polymerization units are randomly connected in various forms, such as -(A-B-A-D-A-B-A-B-C)-, -(A-A-C-C-C-B-B-D-B)-, -(A-A-D-A-B-A-D-A-B-A-C-C)-, etc., where a, b, c, and d are the proportions of polymerization units A, B, C, and D, respectively.

[0027] The dianhydride monomer can include at least one selected from the group consisting of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyl tetracarboxylic dianhydride (BPDA), and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA). More specifically, the dianhydride monomer can be any one of the above dianhydride monomers or a combination of two or more. More specifically, the dianhydride monomer is preferably composed of one type. More specifically, the dianhydride monomer preferably includes 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA).

[0028] The diamine monomer can further include at least one selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD), and p-phenylenediamine (p-PD). More specifically, the diamine monomer can further include any one of the above diamine monomers or two or more. More specifically, the diamine monomer preferably further includes one type. More specifically, the diamine monomer preferably includes 2,4-diaminotoluene (2,4-TDA).

[0029] In one embodiment, the polyimide can include, as a polymerization unit, the dianhydride monomer 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA); and the diamine monomers 4,4'-methylenebis(2,6-diethylbenzeneamine) (MEDA) and 2,4-diaminotoluene (2,4-TDA).

[0030] The amount of 4,4'-methylenebis(2,6-diethylbenzeneamine) (MEDA) in the total diamine monomers can be greater than 0 mol% and less than or equal to 15 mol%. For example, the upper limit thereof can be 15 mol% or less, 14 mol% or less, 13 mol% or less, 12 mol% or less, 11 mol% or less, and the lower limit thereof can be 0.1 mol% or more, 0.5 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more. Specifically, the amount of MEDA can be 3 to 12 mol%.

[0031] The amount of 2,4-diaminotoluene (2,4-TDA) in the total diamine monomer can be 85 mol% or higher and less than 100 mol%. For example, the lower limit can be 85 mol% or higher, 86 mol% or higher, 87 mol% or higher, 88 mol% or higher, 89 mol% or higher, and the upper limit can be 99.9 mol% or lower, 99.5 mol% or lower, 99 mol% or lower, 98 mol% or lower, 97 mol% or lower, 96 mol% or lower. Specifically, the amount can be from 88 to 97 mol%.

[0032] Polyimide may comprise 90 to 110 mol%, preferably 95 to 105 mol%, more preferably 100 mol% of a diamine monomer.

[0033] The polyimide may comprise 90 to 110 mol%, preferably 95 to 105 mol%, more preferably 100 mol% of a dianhydride monomer.

[0034] Polyimide may comprise dianhydride monomers and diamine monomers in a molar ratio of 1:2 to 2:1, preferably 1:1.

[0035] Polyimide exhibits excellent solubility in organic solvents for solid contents of 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25% or higher. In one embodiment, the turbidity of the solution is visually confirmed by adding 20% ​​polyimide solids at room temperature, followed by stirring for 30 minutes.

[0036] The organic solvent may be an aprotic polar organic solvent, specifically, it may include at least one selected from the group consisting of N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropionamide (DMPA), and N,N-diethylacetamide (DEAc).

[0037] In this disclosure, the thermal decomposition temperature (Td) and the glass transition temperature (Tg) are measured, wherein the thermal decomposition temperature is primarily used as a standard for judging the thermal properties of polyimide, and the glass transition temperature can predict thermal properties as well as determine mechanical properties.

[0038] The thermal decomposition temperature (Td) of polyimide at 5% weight loss can be 485°C or higher. For example, the lower limit of the thermal decomposition temperature of polyimide can be 487±1°C, 490±1°C, 493±1°C, 495±1°C, or 496±1°C or higher. The thermal decomposition temperature can be measured using a TA thermogravimetric analyzer Q50. In a particular embodiment, polyimide can be heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere and then held isothermally for 1 hour to remove moisture. The temperature at which 5% weight loss occurs by heating to 600°C at a rate of 10°C / min can then be measured.

[0039] The glass transition temperature (Tg) of polyimide can be 300 °C or higher. For example, the lower limit of the glass transition temperature can be 305 ± 1 °C, 310 ± 1 °C, 312 ± 1 °C, 315 ± 1 °C, 317 ± 1 °C, or 318 ± 1 °C or higher. The glass transition temperature of polyimide can be measured using dynamic mechanical analysis (DMA) at a rate of 5 °C / min.

[0040] The polyimide disclosed herein is characterized by its excellent solubility in organic solvents while maintaining excellent thermal properties.

[0041] By irregularly arranging the polymerization units, the polyimide of this disclosure can achieve heat resistance and solvent solubility by reducing the amount of MEDA to 15 mol% or less. Therefore, the polyimide can be readily dissolved in organic solvents, allowing it to be easily prepared into films, fibers, etc., by drying the solvent without an imidization process at high temperatures.

[0042] Furthermore, the polyimide film can have a tensile strength of 90 MPa or higher, preferably 95 MPa or higher, and there is no particular upper limit, but it can be 400 MPa or lower. Tensile strength was measured using an Instron 5564 UTM device from INSTRON.

[0043] The polyimide film may have a modulus of 2.5 GPa or higher, preferably 3 GPa or higher. The modulus was measured using an Instron 5564 UTM device from INSTRON.

[0044] The polyimide film may have an elongation of 3.5% or higher, preferably 4.0% or higher. The elongation was measured using an Instron 5564 UTM device from INSTRON.

[0045] In another general aspect, a polyimide solution comprising a polyimide and an organic solvent is provided.

[0046] The polyimide disclosed herein has excellent solubility in organic solvents, and its advantage is that it can be readily used in polyimide films, fibers or coatings by using polyimide in solution form dissolved in organic solvents.

[0047] In this disclosure, based on 100 parts by weight of a polyimide solution, the polyimide solution may have a polyimide solids content of 15 to 50% by weight. The lower limit of the solids content by weight may be 16, 17, 18, 19, or 20% by weight or higher, and the upper limit of the solids content by weight may be 45, 40, 35, 30, 27, or 25% by weight or lower. By adjusting the solids content of the polyimide solution, the increase in viscosity can be controlled and the processing time during the curing process can be shortened.

[0048] In one exemplary embodiment, the polyimide solution of this disclosure may have a viscosity in the range of 200 to 30,000 cP, with the viscosity at a temperature of 23°C and a viscosity of 1 s. -1 The viscosity is measured at a shear rate. Specifically, the lower limit of the viscosity of the polyimide solution can be 300 cP or higher, 400 cP or higher, 500 cP or higher, 600 cP or higher, 700 cP or higher, or 800 cP or higher. Its upper limit can be 20,000 cP or lower, 15,000 cP or lower, 10,000 cP or lower, 9,000 cP or lower, 8,000 cP or lower, 7,000 cP or lower, 6,500 cP or lower, 6,300 cP or lower, or 6,100 cP or lower. By adjusting the viscosity range of the polyimide solution, cured polyimide products with excellent processability and desired physical properties can be prepared. Viscosity is the viscosity of polyimide with a solids content of 20% by weight that is redissolved in an organic solvent.

[0049] In another aspect, a polyimide powder comprising the polyimide disclosed herein is provided.

[0050] In another aspect, a polyimide film comprising the polyimide of this disclosure is provided.

[0051] The thickness of the polyimide film can be appropriately selected considering the application, environment, and physical properties of the polyimide film. For example, polyimide films can have thicknesses of 1 to 100 μm, 5 to 50 μm, 10 to 40 μm, or 15 to 25 μm, but are not limited to these.

[0052] Furthermore, in another aspect, an assembly comprising a molded body formed of polyimide is provided.

[0053] Specifically, the component may include, but is not limited to, electronic circuit board components, semiconductor devices, lithium-ion battery components, solar cell components, fuel cell components, motor windings, engine peripheral components, coatings, optical components, thermal insulators, electromagnetic shielding materials, surge protection components, dental materials, sliding coatings, and electrostatic chucks.

[0054] In addition, in another aspect, a separator (membrane) comprising polyimide as described above is provided.

[0055] Furthermore, in another aspect, a fiber comprising the polyimide described above is provided.

[0056] In another aspect, an insulating layer comprising the polyimide described above is provided.

[0057] Furthermore, in another aspect, a coating comprising the polyimide described above is provided.

[0058] Process for preparing a polyimide

[0059] A method for preparing a polyimide is provided, comprising: (a) adding a dianhydride monomer to a diamine monomer comprising 4,4'-methylenebis(2,6-diethylaniline) (MEDA); and (b) random polymerization of the diamine monomer and the dianhydride monomer.

[0060] The dianhydride monomer may include at least one selected from the group consisting of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyl tetracarboxylic dianhydride (BPDA), and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA).

[0061] The diamine monomer may also include at least one selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD), and p-phenylenediamine (p-PD).

[0062] Step (a) may include: (a-1) dissolving a diamine monomer comprising 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in an organic solvent; and (a-2) adding a dianhydride monomer to the dissolved diamine monomer.

[0063] Specifically, step (a) may be a step of dissolving all the diamine monomer in an organic solvent, followed by adding and dissolving all the dianhydride monomer.

[0064] The random polymerization in step (b) can be carried out for 10 to 120 minutes, preferably 30 to 100 minutes, and more preferably 50 to 70 minutes.

[0065] In one embodiment, polyamic acid (PAA) can be prepared by random polymerization of a diamine monomer and a dianhydride monomer, wherein the polyamic acid can have a viscosity in the range of 200 to 30,000 cP, and the viscosity is measured at a temperature of 23°C and a viscosity of 1 s. -1 The viscosity was measured at a shear rate. Specifically, the lower limit of the viscosity of the polyimide solution can be 300 cP or higher, 400 cP or higher, 500 cP or higher, 600 cP or higher, 700 cP or higher, or 800 cP or higher. Its upper limit can be 20,000 cP or lower, 15,000 cP or lower, 10,000 cP or lower, 9,000 cP or lower, 8,000 cP or lower, 7,000 cP or lower, 6,500 cP or lower, 6,300 cP or lower, or 6,100 cP or lower. By adjusting the viscosity range of the polyamic acid, polyimide solutions and / or cured polyimide products with excellent processability and desired physical properties can be prepared.

[0066] In step (b), polyamic acid can be prepared by polymerizing a diamine monomer and a dianhydride monomer, and the method may further include step (c) after step (b) imidizing polyamic acid to prepare polyimide.

[0067] In step (c), a dehydrating agent and a catalyst may be added to the polyamic acid to imidize it. The dehydrating agent may be, but is not particularly limited to, any reagent capable of promoting the ring-closing reaction by dehydrating the polyamic acid. Examples of dehydrating agents may include acetic anhydride, etc. The catalyst may be, but is not particularly limited to, any catalyst capable of catalyzing the ring-closing reaction of the polyamic acid. Examples of catalysts may include tertiary amines, such as quinoline, isoquinoline (IQ), β-methylpyridine (BP), etc.

[0068] The imidization reaction carried out in step (c) has an imidization rate of 97 to 100%, preferably 98 to 100%, more preferably 99 to 100%, and most preferably 100%.

[0069] Following step (c), the method may further include steps (d) of purifying, filtering, and drying the polyimide.

[0070] To purify the polyimide in step (d), it may be precipitated in a non-solvent to remove impurities. Examples of non-solvents may include, but are not limited to, water, methanol, ethanol, n-propanol, isopropanol, butanol, butanediol, ethylene glycol, glycerol, γ-butyrolactone, or mixtures thereof.

[0071] Furthermore, filtration can be carried out by selecting one or a combination of two or more of the following methods: gravity filtration, pressure filtration, vacuum filtration, pressure filtration, squeeze filtration, centrifugal filtration, microfiltration, ultrafiltration, and reverse osmosis.

[0072] In addition, drying can be carried out by selecting one or a combination of two or more of the following methods: natural drying, pressure drying, hot air drying, spray drying, film drying, vacuum drying, freeze drying, spray freeze drying, electromagnetic wave drying, and rapid drying.

[0073] [Beneficial Effects]

[0074] The polyimide disclosed herein exhibits excellent solubility in organic solvents, as well as excellent thermal and mechanical properties.

[0075] Furthermore, the polyimide according to this disclosure can be fully imidized and can be prepared in various ways (such as films and fibers) simply by drying the solvent without an imidization process at high temperatures, thereby improving the ease of processing.

[0076] Furthermore, the polyimide according to this disclosure is applicable to various fields, such as separators (membranes), adhesives, insulating coatings, coating materials, fibers, etc. Attached Figure Description

[0077] Figure 1 The results of the solubility evaluation of the polyimides prepared according to Examples 1, 2 and Comparative Example 1 in organic solvents are shown. Detailed Implementation

[0078] The following embodiments are provided to aid in understanding this disclosure. These embodiments are provided merely to facilitate a better understanding of this disclosure, but the content of this disclosure is not limited to these embodiments.

[0079] <Example>

[0080] Example 1: Preparation of polyimide

[0081] In a nitrogen / room temperature atmosphere, 5 mol% of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) and 95 mol% of 2,4-diaminotoluene (2,4-TDA) were dissolved in dimethylformamide (DMF) organic solvent. Then, 100 mol% of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added, followed by random polymerization with MEDA, 2,4-TDA, and BTDA for 1 hour to obtain a polyamic acid composition.

[0082] A tertiary catalyst (β-methylpyridine, BP) and a dehydrating agent (acetic anhydride, AA) were added to the obtained polyamic acid composition, and the resulting mixture was subjected to a chemical imidization process at 60 °C using a continuous polymerization batch process. Next, after the reaction was complete, the polymer was precipitated in an ethanol-free solvent to remove impurities (unreacted products, tertiary catalyst, AA, etc.) and dried in a vacuum oven at a temperature below 150 °C for 24 hours to prepare polyimide powder (20% by weight solids).

[0083] Example 2: Preparation of polyimide

[0084] The polyimide powder was prepared in the same manner as in Example 1, except that 10 mol% of methylene bis(2,6-diethylaniline) (MEDA) and 90 mol% of 2,4-diaminotoluene (2,4-TDA) were used instead of 5 mol% of methylene bis(2,6-diethylaniline) (MEDA) and 95 mol% of 2,4-diaminotoluene (2,4-TDA) used in Example 1.

[0085] Comparative Example 1: Preparation of Polyimide

[0086] In a nitrogen / room temperature atmosphere, 5 mol% of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) was dissolved in dimethylformamide (DMF) organic solvent. Then, 100 mol% of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added, followed by block polymerization for 1 hour. Then, 95 mol% of 2,4-diaminotoluene (2,4-TDA) was added and block polymerization was carried out for 1 hour to obtain a polyamic acid composition.

[0087] A tertiary catalyst (β-methylpyridine, BP) and a dehydrating agent (acetic anhydride, AA) were added to the obtained polyamic acid composition, and the resulting mixture was subjected to a chemical imidization process using a continuous batch polymerization method at 60 °C. Next, after the reaction was complete, the polymer was precipitated in an ethanol-free solvent to remove impurities (unreacted products, tertiary catalyst, AA, etc.) and dried in a vacuum oven at a temperature below 150 °C for 24 hours to prepare polyimide powder (20% by weight solids).

[0088] The monomer components, amounts, polymerization methods, etc. of Examples 1, 2, and Comparative Example 1 are listed in Table 1 below. In Table 1 below, the polymerization methods are specified at a temperature of 23°C and a polymerization time of 1 second. -1Viscosity was measured at a shear rate of [value missing], and molecular weight was determined using gel permeation chromatography (GPC). In Table 1 below, the polymerization viscosity of PAA refers to the viscosity of the polyamic acid composition, the molecular weight of PAA refers to the molecular weight of the polyamic acid composition, the 20% wt% redissolved viscosity refers to the viscosity of the polyimide powder (20% wt% solids content) redissolved in an organic solvent, and the redissolved PI molecular weight refers to the molecular weight of the polyimide powder (20% wt% solids content) redissolved in an organic solvent.

[0089] [Table 1]

[0090]

[0091] Example 3: Preparation of polyimide film

[0092] The polyimide powder prepared according to Example 1 was dissolved in an organic solvent (DMF) to obtain a solution containing 20% ​​by weight of solids. This solution was then coated onto a glass substrate to a thickness of 20 μm using a spin coater (MS-B200, Mikasa) and dried at 250°C for 20 minutes. The coating method was not particularly limited. The resulting product was then cooled at 25°C and separated from the glass substrate to prepare a polyimide film with a thickness of approximately 20 μm.

[0093] Example 4: Preparation of polyimide film

[0094] Except that the polyimide powder prepared according to Example 2 was used instead of the polyimide powder prepared according to Example 1, the polyimide film was prepared in the same manner as in Example 3.

[0095] Comparative Example 3: Preparation of Polyimide Film

[0096] Except that the polyimide powder prepared according to Comparative Example 1 was used instead of the polyimide powder prepared according to Example 1, the polyimide film was prepared in the same manner as in Example 3.

[0097] <Experimental Example>

[0098] Experimental Example 1: Evaluation of Solubility

[0099] The solubility of polyimide in organic solvents was evaluated by adding 20 g of polyimide powder prepared according to Examples 1 and 2 and Comparative Example 1 to 80 g of the organic solvent N,N'-dimethylformamide (DMF) and visually confirming the solution. Specifically, 20% by weight of the polyimide solids content was added to the solution at room temperature, the solution was stirred for 30 minutes, and the turbidity of the solution was visually confirmed. The results are as follows. Figure 1 As shown.

[0100] like Figure 1 As shown, in Examples 1 and 2, it can be confirmed that polyimide has good solubility in organic solvents, with no floating matter, and is soluble. On the other hand, Comparative Example 1 shows floating matter and poor solubility in organic solvents.

[0101] In other words, the polyimides according to Example 1 and Comparative Example 1 have the same composition; however, it is understood that, unlike Comparative Example 1 which has regularly arranged polymeric units, the solubility of Example 1 can be achieved by randomly arranging the polymeric units. Therefore, according to this disclosure, solubility can be achieved by randomly arranging the polymeric units while reducing MEDA to at least 5 mol%.

[0102] Experimental Example 2: Evaluation of Glass Transition Temperature (Tg)

[0103] For each polyimide film prepared according to Examples 3 and 4 and Comparative Example 3, the point at which the polyimide rapidly expands at 5°C / min was measured using dynamic mechanical analysis (DMA) as the starting point. The results are shown in Table 2.

[0104] Experimental Example 3: Evaluation of the thermal decomposition temperature (Td) at 5% weight loss

[0105] Using a TA thermogravimetric analyzer Q50, the polyimides prepared according to Examples 3 and 4 and Comparative Example 3 were heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere, and then held isothermally for 1 hour to remove moisture. The temperature at which a 5% weight loss occurred after heating to 600°C at a rate of 10°C / min was then measured. The results are shown in Table 2 below.

[0106] Table 2 below shows the results for solubility, glass transition temperature (Tg), and thermal decomposition temperature (Td) of the polyimides prepared according to Examples 3 and 4 and Comparative Example 3 at 5% weight loss.

[0107] [Table 2]

[0108]

[0109] As can be confirmed from Table 2, the polyimide films (random polymerization) according to Examples 3 and 4 not only exhibit excellent solubility in DMF (aprotic polar organic solvent) but also maintain excellent thermal properties. On the other hand, Comparative Example 3 could not be film-formed because the polyimide powder (block polymerization) of Comparative Example 1 was insoluble in organic solvents.

[0110] These results show that by randomly arranging the polymerization units and reducing the amount of MEDA to 10 mol% and 5 mol%, solubility in aprotic polar organic solvents (such as DMF) can be achieved, and heat resistance (Tg and Td 5 wt%) can also be improved.

[0111] In this specification, details that are readily apparent and inferred by one of skill in the art have been omitted, and various modifications may be made without altering the technical spirit or essential configuration of this disclosure, other than the specific embodiments described herein. Therefore, this disclosure may be practiced in ways other than those specifically described and exemplified herein, as will be understood by one of skill in the art.

Claims

1. A polyimide, comprising: As an aggregation unit, Dihydride monomer; as well as Including diamine monomers of 4,4'-methylenebis(2,6-diethylaniline) (MEDA), The polyimide therein is a random copolymer in which the polymer units are irregularly arranged.

2. The polyimide according to claim 1, wherein the dianhydride monomer comprises at least one selected from the group consisting of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyl tetracarboxylic dianhydride (BPDA), and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA).

3. The polyimide according to claim 1, wherein the diamine monomer further comprises at least one selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD) and p-phenylenediamine (p-PD).

4. The polyimide according to claim 1, wherein the amount of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in the total diamine monomer is greater than 0 mol% and less than or equal to 15 mol%.

5. The polyimide according to claim 3, wherein the amount of 2,4-diaminotoluene (2,4-TDA) in the total diamine monomer is 85 mol% or higher and less than 100 mol%.

6. The polyimide of claim 1, wherein the polyimide is soluble in an organic solvent for a solid content of 15% by weight or higher.

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

8. The polyimide according to claim 1, wherein the polyimide has a thermal decomposition temperature (Td) of 485°C or higher at 5% weight loss.

9. The polyimide according to claim 1, wherein the glass transition temperature (Tg) of the polyimide is 300°C or higher.

10. A polyimide solution comprising the polyimide according to any one of claims 1 to 9 and an organic solvent.

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

12. A method for preparing polyimide, comprising: (a) Adding a dianhydride monomer to a diamine monomer comprising 4,4'-methylenebis(2,6-diethylaniline) (MEDA); as well as (b) Random polymerization of the diamine monomer and the dianhydride monomer.

13. The method of claim 12, wherein the dianhydride monomer comprises at least one selected from the group consisting of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyl tetracarboxylic dianhydride (BPDA), and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA).

14. The method of claim 12, wherein the diamine monomer further comprises at least one selected from the group consisting of 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD), and p-phenylenediamine (p-PD).

15. The method of claim 12, wherein step (a) comprises: (a-1) The diamine monomer comprising 4,4'-methylenebis(2,6-diethylaniline) (MEDA) is dissolved in an organic solvent; as well as (a-2) Add the dianhydride monomer to the dissolved diamine monomer.

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