Solvent-soluble polyimide with simplified manufacturing process and method for producing the same

Abstract

The present invention provides a method for producing polyimide, comprising the steps of (a) polymerizing a dianhydride acid monomer and a diamine monomer to produce a polyamic acid, and (b) reacting the polyamic acid with carbonyl diimidazole to produce a soluble polyimide, wherein the soluble polyimide is in the form of a varnish.

Description

Technical Field

[0001] The present invention relates to a solvent-soluble polyimide and a method for producing the same. Specifically, the present invention relates to a polyimide with simplified processes and excellent thermal and mechanical properties and a method for producing the same.

Background Art

[0002] Generally, polyimide (PI) is a polymer material based on an imide ring with extremely excellent chemical stability along with a rigid aromatic main chain. Among organic materials, it has the highest level of heat resistance, chemical resistance, electrical insulation, chemical resistance, and weather resistance, and can be manufactured in various forms such as films, fibers, and membranes. Due to such properties, polyimide is widely used in a wide range of fields as a high-tech material and an insulating coating agent in the fields of electric and electronic, semiconductor, display, automobile, aviation, and space materials.

[0003] Polyimide can be produced by dissolving an acid dianhydride having two acid 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), followed by coating and drying, and heat treatment at a temperature of about 350°C for imidization. Conventionally, there have been many demands to handle polyimide in a solution state, and many developments have been made for solvent-soluble polyimide.

[0004] However, conventionally, polyimide produced by imidization through a dehydration and ring-closure reaction by a chemical method or a thermal (high-temperature) method has a problem that it is difficult to process because it has an insoluble property in a solvent. Also, in order to produce a solvent-soluble polyimide, generally, only monomers with high solubility can be used, but these monomers generally have low heat resistance, so the produced polyimide has problems of low heat resistance and chemical resistance. On the other hand, in order to use polyimide in the form of a solution while having heat resistance and chemical resistance, there is a method of forming a coating film with a polyamic acid solution, which is a polyimide precursor, and then imidizing it to produce polyimide.

[0005] However, polyamic acid solutions are susceptible to humidity, making them difficult to handle and store. Furthermore, imidizing polyamic acid requires either a high-temperature heat treatment process or a complex and lengthy processing method.

[0006] Against this backdrop, there is a need to develop a polyimide that maintains the high heat resistance and insulating properties of polyimides, is easily soluble in organic solvents, and allows for the manufacture of polyimide-based products through simple processes. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a method for producing polyimide with excellent thermal and mechanical properties, while simplifying the manufacturing process by omitting purification, filtration, and drying steps to remove by-products (impurities).

[0008] Furthermore, the present invention aims to provide a method for producing polyimide that is fully imidized and has soluble properties in organic solvents.

[0009] Furthermore, the present invention aims to provide a polyimide produced by the method for producing the polyimide described above.

[0010] Furthermore, the present invention aims to provide the polyimide in various forms, such as a separation membrane, binder, insulating coating, and coating material.

[0011] Furthermore, the present invention aims to provide a polyimide manufacturing composition that can be used in the polyimide manufacturing method described above. [Means for solving the problem]

[0012] Because the present invention can be modified in various ways and has various embodiments, specific embodiments will be illustrated and described in detail. However, this should not be understood as limiting the present invention to specific embodiments, but rather as including all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0013] The terms used in this application are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “includes” or “having” specify the presence of features, figures, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or possibility of adding one or more other features, figures, steps, actions, components, parts, or combinations thereof.

[0014] Wherever a quantity, concentration, or other value or parameter is given in this specification by enumeration of ranges, preferred ranges, preferred upper limits, and preferred lower limits, it should be understood that this specifically discloses all ranges formed by any pair of limits or preferred values ​​of any upper range and any limits or preferred values ​​of any lower range, regardless of whether the ranges are disclosed separately.

[0015] Where a range of numerical values ​​is referred to herein, unless otherwise specified, that range is intended not to be limited to the specific values ​​referred to when defining the range, including its endpoints and the models within that range.

[0016] In this specification, “dianhydride” is intended to include its precursors or derivatives, but it may also be referred to as “dianhydric acid,” “dianhydride,” or “acidic dianhydride.” These may not be technically dianhydrides, but nevertheless react with diamines to form polyamic acids, which can also be converted to polyimides.

[0017] In this specification, “diamine” is intended to include its precursors or derivatives, which may not be technically diamines, but nevertheless react with dianhydride acids to form polyamic acids, which can also be converted to polyimides.

[0018] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally 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 the meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application. The specific details for realizing the invention are described below.

[0019] The present invention relates to a method for producing polyimide that simplifies the manufacturing process by omitting purification, filtration, and drying steps to remove by-products (impurities), and that also produces polyimide with excellent thermal and mechanical properties.

[0020] Method for producing polyimide The present invention provides a method for producing polyimide, comprising the steps of (a) polymerizing a dianhydride acid monomer and a diamine monomer to produce a polyamic acid, and (b) reacting the polyamic acid with carbonyl diimidazole to produce a soluble polyimide, wherein the soluble polyimide is in the form of a varnish.

[0021] The method for producing the polyimide may not perform a purification step including purification, filtration, and drying steps after step (b).

[0022] Conventionally, during chemical imidization, in order to remove by-products, after undergoing purification steps such as purification, washing, filtration, and drying and being obtained in powder form, it was dissolved in a polar organic solvent for use. However, in the present invention, by using an additive CDI having the functions of a catalyst and a dehydrating agent simultaneously, the purification step including the purification, filtration, and drying processes is omitted, and it can be used immediately in the form of a varnish.

[0023] In step (a), the carbonyldiimidazole can be reacted in an amount of 0.5 to 1.5 molar equivalents with respect to 1 molar equivalent of the polyamic acid. For example, the upper limit may be 1.5, 1.4, 1.3, 1.2, 1.1 molar equivalents or less, and the lower limit may be 0.5, 0.6, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 molar equivalents or more. When the carbonyldiimidazole is reacted in an amount less than 0.5 molar equivalent, the physical properties of the produced polyimide deteriorate, which is not preferable. When it is reacted in an amount exceeding 1.5 molar equivalents, a further purification step is required, which is not preferable.

[0024] The purification step may mean a series of processes such as purification, washing, filtration, and drying for removing by-products (impurities, catalysts, unreacted substances, etc.) after performing the imidization step.

[0025] Also, the purification may include a purification method usually used in polymer synthesis such as reprecipitation like the alcohol precipitation method.

[0026] Step (b) can be performed at a temperature of 20 to 60°C. For example, the upper limit may be 60°C, 58°C, 55°C, 52°C, 50°C, 48°C, 45°C, 44°C, 43°C, 42°C, 41°C or less, and the lower limit may be 20°C, 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 36°C, 37°C, 38°C or more.

[0027] Step (b) can be carried out for 0.5 to 5 hours. For example, the upper limit may be 5, 4.5, 4, 3.5, 3, 2.7 hours or less, and the lower limit may be 0.5, 0.8, 1, 1.2, 1.5, 2.0, 2.3 hours or more.

[0028] The reaction in step (b) is an imidization reaction, and the imidization rate may be 97 to 100%, preferably 98 to 100%, more preferably 99 to 100%, and most preferably 100%.

[0029] In step (a), the polymerization may be random polymerization or block polymerization.

[0030] Specifically, when polymerizing by random polymerization, a random copolymer can be produced, and a copolymer composed of two or more polymerization units (repeating units) can be produced. 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 linked 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., and a, b, c, and d represent the ratios of the polymerization units A, B, C, and D.

[0031] Also, step (a) can include (a-1) a step of adding the total amount of diamine monomers to the total amount of dianhydride acid monomers, and (a-2) a step of randomly polymerizing the total amount of diamine monomers and the total amount of dianhydride acid monomers. For example, for the random polymerization, after dissolving the total amount of diamine monomers in an organic solvent, then adding and dissolving the total amount of dianhydride monomers, and then polymerizing, a polyamic acid can be produced.

[0032] Specifically, when polymerization is carried out by block polymerization, block copolymers can be produced, which are copolymers composed of two or more polymerization units (repeating units). For example, the expression "-(A)a-(B)b-(C)c-(D)d-", which is a block copolymer of polymerization units A to D, means that the same polymerization units are linked together in the form of -(AAABBBBBCCCCDDD)-, and a, b, c, and d represent the ratios of polymerization units A, B, C, and D.

[0033] Furthermore, step (a) includes (a-1) adding one dianhydride acid monomer to one diamine monomer, and (a-2) performing block polymerization of the one diamine monomer and one dianhydride acid monomer, and steps (a-1) and (a-2) can be repeated multiple times. For example, the block polymerization can be carried out by dissolving one diamine monomer in an organic solvent, then adding one dianhydride monomer and polymerizing it, adding another diamine monomer and polymerizing it, and repeating the steps of adding another dianhydride monomer and polymerizing it to produce polyamic acid.

[0034] The dianhydride monomer may include one or more selected from the group consisting of pyromeretic dianehydride (PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianehydride (BTDA), oxydiphthalic dianehydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianehydride (DSDA), and 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propanedianehydride. More specifically, it may be any one or more of the dianhydride acid monomers mentioned above. More specifically, the dianhydride acid monomer preferably consists of one type, and more specifically, it is preferable to include 3,3',4,4'-benzophenone tetracarboxylic dianehydride (BTDA).

[0035] The diamine monomer may include one or more selected from the group consisting of 4,4'-methylenebis(2,6-diethylaniline) (MEDA), 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD), p-phenylenediamine (p-PD), 3,3''-diaminodiphenylsulfone (3,3''-DDS), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP), 3,5-diethyltoluene-2,6-diamine, 3,5-diethyltoluene-2,4-diamine, and 4,4'-methylenebis(2-ethyl-6-methylaniline) (MEMA). More specifically, it may be a combination containing one or more of the diamine monomers mentioned above. More specifically, the diamine monomer preferably contains one or more types, and more specifically, preferably contains 4,4'-methylenebis(2,6-diethylaniline) (MEDA) and 2,4-diaminotoluene (2,4-TDA).

[0036] In one embodiment, the polyamic acid may be obtained by polymerizing the dianhydride monomer 3,3',4,4'-benzophenone tetracarboxylic dianehydride (BTDA) and the diamine monomers 4,4'-methylenebis(2,6-diethylaniline) (MEDA) and 2,4-diaminotoluene (2,4-TDA).

[0037] The content of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in the total diamine monomer may be greater than 0 mol% and 50 mol% or less. For example, the upper limit may be 50 mol%, 40 mol%, 30 mol%, 20 mol%, 18 mol%, 17 mol%, 15 mol%, 13 mol%, or 12 mol%, and the lower limit may be 0.1 mol%, 1 mol%, 2 mol%, 3 mol%, or 4 mol% or more.

[0038] The content of 2,4-diaminotoluene (2,4-TDA) in the total diamine monomer may be less than 100 mol% or 50 mol% or more. For example, the upper limit may be 99.9 mol%, 99 mol%, 98 mol%, 97 mol%, or 96 mol%, and the lower limit may be 50 mol%, 60 mol%, 70 mol%, 80 mol%, 72 mol%, 73 mol%, 75 mol%, or 78 mol% or more.

[0039] The polyimide may contain 90 to 110 mol% of the diamine monomer, preferably 95 to 105 mol%, and more preferably 100 mol%.

[0040] The polyimide may contain 90 to 110 mol% of the dianhydride acid monomer, preferably 95 to 105 mol%, and more preferably 100 mol%.

[0041] The polyimide may contain the dianhydride monomer and the diamine monomer in a molar ratio of 1:2 to 2:1, preferably in a molar ratio of 1:1.

[0042] The polyimide may be a soluble polyimide with excellent solubility in organic solvents at a solid content of 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, or 25 wt% or more. The upper limit is not particularly limited, but may be 50 wt% or less.

[0043] The organic solvent may be an aprotic polar organic solvent, and specifically, it may contain one or more selected from the group consisting of N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropanamide (DMPA), and N,N-diethylacetamide (DEAc).

[0044] In this invention, we confirmed 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 also ensure mechanical properties.

[0045] The 5% wt% thermal decomposition temperature (Td) of the polyimide may be 485°C or higher. For example, the lower limit of the thermal decomposition temperature may be 487±1°C, 490±1°C, 493±1°C, or 495±1°C or higher, and the upper limit is not particularly limited, but may be 600°C or lower. The thermal decomposition temperature can be measured using a TA-Q50 thermogravimetric analysis model. In a specific example, the polyimide is heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere, and then the temperature at which a 5% weight loss occurs can be measured.

[0046] The glass transition temperature (Tg) of the polyimide may be 300°C or higher. For example, the lower limit of the glass transition temperature may be 305±1°C, 310±1°C, 312±1°C, 315±1°C, 317±1°C, or 318±1°C or higher, and the upper limit is not particularly limited, but may be 500°C or lower. The glass transition temperature can be measured for the polyimide using DMA at a rate of 5°C / min.

[0047] Furthermore, the polyimide has a modulus of 3.0 GPa or higher, preferably 3.3 GPa or higher, and there is no particular upper limit, although it may be 30.0 GPa or lower. The modulus was measured using an Instron 5564 UTM instrument manufactured by INSTRON.

[0048] The polyimide has a tensile strength of 110 MPa or more, preferably 115 MPa or more, and there is no particular upper limit, but it may be 400 MPa or less. The tensile strength was measured using an Instron 5564 UTM instrument manufactured by INSTRON.

[0049] The polyimide has an elongation of 5% or more, preferably 5.2% or more, and there is no particular upper limit, although it may be 30% or less. The elongation was measured using an Instron 5564 UTM instrument manufactured by INSTRON.

[0050] Generally, to imidize polyamic acid, a dehydrating agent and catalyst are used to remove impurities, followed by purification, filtration, and drying. However, the polyimide production method according to the present invention simplifies the production process by using the additive CDI, thereby omitting purification steps such as purification, filtration, and drying to remove by-products (impurities). Furthermore, it is possible to produce a polyimide with excellent thermal and mechanical properties as well as excellent solubility in solvents.

[0051] In another aspect, the present invention provides a polyimide produced by the method for producing the polyimide described above. Here, the polyimide may be a solvent-soluble polyimide.

[0052] The polyimide may also be in the form of a varnish, and the polyimide has the advantage of being readily usable in polyimide films, fibers, or coatings by being used immediately in the form of a varnish without a purification process including purification, filtration, and drying steps.

[0053] In another aspect, the present invention provides a polyimide film containing the aforementioned polyimide.

[0054] The thickness of the polyimide film can be appropriately selected considering the application, usage environment, and physical properties of the polyimide film. For example, the thickness of the polyimide film may be 1 to 100 μm, 5 to 50 μm, 10 to 40 μm, or 15 to 25 μm, but is not limited thereto.

[0055] In another aspect, the present invention provides a part that includes a molded body formed from the polyimide.

[0056] Specifically, the components may be, but are not limited to, electronic circuit board components, semiconductor devices, lithium-ion battery components, solar cell components, fuel cell components, motor windings, engine peripheral components, paints, optical components, heat dissipation materials, electromagnetic shielding materials, surge components, dental materials, slide coatings, and electrostatic chucks.

[0057] In another aspect, the present invention provides a separation membrane, fiber, insulating layer, or coating layer containing the polyimide described above.

[0058] In another aspect, the present invention provides a composition for producing soluble polyimides, comprising a polyamic acid containing a dianhydride monomer and a diamine monomer as polymerization units, and carbonyl diimidazole. [Effects of the Invention]

[0059] The method for producing polyimide according to the present invention simplifies the manufacturing process by omitting the purification, filtration, and drying steps for removing by-products (impurities), and enables the production of polyimide with excellent thermal and mechanical properties.

[0060] Furthermore, it is possible to produce polyimides that are fully imidized and possess soluble properties in organic solvents.

[0061] Furthermore, the polyimide according to the present invention has the effect of being applicable to various fields such as separation membranes, binders, insulating coatings, coating materials, and fibers. [Brief explanation of the drawing]

[0062] [Figure 1] These are optical images of the polyimide films produced by Example 5-1 and Comparative Examples 9 and 10. [Modes for carrying out the invention]

[0063] To aid in understanding the present invention, examples are provided below. The following examples are provided to facilitate understanding of the present invention and do not limit the scope of the invention.

[0064] <Examples> Example 1: Production of polyimide (random copolymer) Example 1-1 Under 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 dianehydride (BTDA) was added, and the MEDA, 2,4-TDA, and BTDA were randomly polymerized for 1 hour to obtain a polyamic acid composition.

[0065] To the obtained polyamic acid composition, 1.0 molar equivalent of carbonyl diimidazole (CDI) was added, and a chemical imidation process was carried out by a continuous batch polymerization process at 40°C for 2.5 hours to produce a soluble polyimide (20 wt% solids content). This was used in the form of a varnish without purification, filtration, or drying. This means that it has solubility in organic solvents (DMF).

[0066] Examples 1-2 Soluble polyimide was prepared in the same manner as in Example 1-1, except that 0.9 molar equivalents of carbonyldiimidazole (CDI) were added instead of 1.0 molar equivalent of carbonyldiimidazole (CDI) as in Example 1-1.

[0067] Examples 1-3 A soluble polyimide was prepared in the same manner as in Example 1-1, except that instead of using 5 mol% methylenebis(2,6-diethylaniline) (MEDA) and 95 mol% 2,4-diaminotoluene (2,4-TDA) as in Example 1-1, 10 mol% methylenebis(2,6-diethylaniline) (MEDA) and 90 mol% 2,4-diaminotoluene (2,4-TDA) were used.

[0068] Example 2: Production of polyimide (block copolymer) Example 2-1 Under a nitrogen / room temperature atmosphere, 10 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 dianehydride (BTDA) was added and block polymerization was carried out for 1 hour. Next, 90 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.

[0069] To the obtained polyamic acid composition, 1.0 molar equivalent of carbonyl diimidazole (CDI) was added, and a chemical imidation process was carried out by a continuous batch polymerization process at 40°C for 2.5 hours to produce a soluble polyimide (20 wt% solids content). This was then used in the form of a varnish without purification, filtration, or drying.

[0070] Example 2-2 Soluble polyimide was produced in the same manner as in Example 2-1, except that instead of adding 10 mol% of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) and 90 mol% of 2,4-diaminotoluene (2,4-TDA) as in Example 2-1, 20 mol% of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) and 80 mol% of 2,4-diaminotoluene (2,4-TDA) were added.

[0071] Example 3: Production of polyimide (random copolymer) Examples 3-1 to 3-3 As shown in Table 1 below, soluble polyimides were produced using the same method as in Example 1-1, but with different types and contents of monomers and additives.

[0072] Example 4: Production of polyimide (block copolymer) Examples 4-1 to 4-3 As shown in Table 1 below, soluble polyimides were produced using the same method as in Example 2-1, but with different types and contents of monomers and additives.

[0073] Comparative Example 1: Production of polyimide (using catalyst and dehydrating agent) Under 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 dianehydride (BTDA) was added, and the MEDA, 2,4-TDA, and BTDA were randomly polymerized for 1 hour to obtain a polyamic acid composition.

[0074] To the obtained polyamic acid composition, 0.3 molar equivalents of pyridine (catalyst, Py) and 1.0 molar equivalent of acetate anhydride (dehydrating agent, AA) were added, and a chemical imidation process was carried out by a continuous batch polymerization process at 60°C. Next, after the reaction was complete, the polymer was precipitated in an ethanol-free solvent to remove impurities (unreacted material, catalyst, AA, etc.), and this was purified by drying in a vacuum oven at a temperature of less than 150°C for 24 hours to produce polyimide powder (solid content 20 wt%).

[0075] Comparative Example 2: Production of polyimide (including purification process) The soluble polyimide produced in Example 1-1 was precipitated in an ethanol-free solvent to remove impurities (unreacted material, catalyst, AA, etc.), and then further purified by drying in a vacuum oven at a temperature of less than 150°C for 24 hours to produce polyimide powder.

[0076] Comparative Examples 3 and 4: Production of Polyimide As shown in Table 1 below, polyimide powders were produced using the same method as in Comparative Example 1, but with different types and contents of monomers and additives, and different polymerization methods.

[0077] Comparative Examples 5-8: Production of Polyimide As shown in Table 1 below, polyimide powders were produced using the same method as in Comparative Example 2, but with different types and contents of monomers and additives, and different polymerization methods.

[0078] Table 1 below lists the type and content of monomers, polymerization method, type and content of additives, whether or not a purification step was performed, and whether or not solubility was present for the examples and comparative examples. To evaluate solubility, the polyimide powder of the comparative example was added to the organic solvent N,N'-dimethylformamide (DMF) and stirred for 30 minutes, after which the degree of turbidity of the solution was visually checked.

[0079] [Table 1]

[0080] Example 5: Production of polyimide (random copolymer) film Example 5-1 The polyimide varnish produced in Example 1-1 was 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 is not particularly limited. After cooling at 25°C, it was separated from the glass substrate to produce a polyimide film with a thickness of approximately 20 μm.

[0081] Examples 5-2 and 5-3 A polyimide film was produced in the same manner as in Example 5-1, except that in Example 5-1, the polyimide varnishes produced in Examples 1-2 and 1-3 were used instead of the polyimide varnish produced in Example 1-1.

[0082] Example 6: Production of polyimide (block copolymer) film Examples 6-1 and 6-2 A polyimide film was produced in the same manner as in Example 5-1, except that in Example 5-1, the polyimide varnishes produced in Examples 2-1 and 2-2 were used instead of the polyimide varnish produced in Example 1-1.

[0083] Example 7: Production of polyimide (random copolymer) film Examples 7-1 to 7-3 A polyimide film was produced in the same manner as in Example 5-1, except that in Example 5-1, the polyimide varnishes produced in Examples 3-1 to 3-3 were used instead of the polyimide varnish produced in Example 1-1.

[0084] Example 8: Production of polyimide (block copolymer) film Examples 8-1 to 8-3 A polyimide film was produced in the same manner as in Example 5-1, except that in Example 5-1, the polyimide varnishes produced in Examples 4-1 to 4-3 were used instead of the polyimide varnish produced in Example 1-1.

[0085] Comparative Example 9: Manufacturing of Polyimide Film The polyimide powder produced in Comparative Example 1 was dissolved in an organic solvent (DMF) to obtain a 20 wt% solids solution. 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 is not particularly limited. After cooling to 25°C, the solution was separated from the glass substrate to produce a polyimide film with a thickness of approximately 20 μm.

[0086] Comparative Examples 10-16: Manufacturing of Polyimide Films A polyimide film was manufactured in the same manner as in Comparative Example 9, except that instead of using the polyimide powder manufactured in Comparative Example 1, the polyimide powders manufactured in Comparative Examples 2 to 8 were used, respectively.

[0087] <Example of experiment> Experimental Example 1: Comparison of the appearance of polyimides Figure 1 shows optical images of the polyimide films produced by Example 5-1 and Comparative Examples 9 and 10.

[0088] As shown in Figure 1, it was confirmed that the polyimide film of Example 5-1 exhibited a darker color compared to Comparative Examples 9 and 10. Conventional soluble polyimides achieve solubility by either giving flexibility to the molecular chain to reduce the CTC (charge transfer complex) of the imide group, or by introducing bulky substituents to the side chains to increase the steric effect. In this case, the film is transparent and exhibits reduced mechanical properties. However, the darker color of the polyimide film according to the present invention indicates that imidazole is present between the polyimide polymer chains, and that the intermolecular attractive forces are improved by hydrogen bonding, resulting in improved mechanical properties compared to conventional soluble polyimides due to CTC.

[0089] Therefore, it has been found that the present invention allows for the production of polyimide films with excellent physical properties using CDI without the need for purification, filtration, and drying steps.

[0090] Experimental Example 2: Evaluation of the physical properties of polyimide (1) Glass transition temperature (Tg) For the polyimide films produced according to the examples and comparative examples, the point at which rapid expansion occurred was measured using DMA at a temperature of 5°C / min, and this point was defined as the on-set point. The results are shown in Table 2.

[0091] (2) Thermal decomposition temperature (Td) of 5% by weight Using a TA-manufactured thermogravimetric analysis (Q50 model), the polyimide films produced in the examples and comparative examples were heated to 100°C at a rate of 10°C / min under a nitrogen atmosphere, and then kept isothermal for 1 hour to remove moisture. Next, the temperature was increased 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.

[0092] (3) Modulus (Young's modulus) Polyimide films produced according to the examples and comparative examples were prepared using an Instron 5564 UTM instrument manufactured by INSTRON. Samples measuring 400 mm in length and 10 mm in width were prepared, and the modulus was measured at a speed of 20 mm / min. The average of 10 samples was calculated. The results are shown in Table 3 below.

[0093] (4) Tensile strength Using an Instron 5564 UTM instrument manufactured by INSTRON, samples measuring 400 mm in length and 10 mm in width were prepared. The tensile strength of the polyimide films produced according to the examples and comparative examples was measured at a speed of 20 mm / min, and the average of 10 samples was calculated. The results are shown in Table 3 below.

[0094] (5) Elongation The elongation of polyimide films in the examples and comparative examples was measured under room temperature conditions using an Instron 5564 UTM instrument manufactured by INSTRON Corporation, in accordance with the ASTM D882 method. The results are shown in Table 3 below.

[0095] [Table 2]

[0096] [Table 3]

[0097] According to Table 2, the polyimide films produced by Examples 5-1 to 7-2 and 8-2 showed similar or improved glass transition temperatures (Tg 310°C or higher) and thermal decomposition temperatures (Td 5wt% 495°C or higher) compared to Comparative Examples 9, 10, and 12 to 16.

[0098] Specifically, the polyimide film produced in Example 5-1 exhibited the best heat resistance, indicating that it is preferable to add the additive CDI in a substantially equimolar manner with the polyamic acid. Furthermore, while both Examples 5-1 to 5-3, which were randomly polymerized, and Examples 6-1 to 6-2, which were block polymerized, exhibited excellent heat resistance, Examples 5-1 to 5-3, in which the polymerization units were randomly arranged, showed even better heat resistance. In other words, the present invention has confirmed that, using CDI, excellent heat resistance (Tg and Td 5wt%) can be achieved without purification, filtration, or drying steps.

[0099] Furthermore, as shown in Table 3, the polyimide films produced by Examples 5-1 to 7-2 and 8-2 were found to have similar or improved modulus (3.03 GPa or higher), tensile strength (110 MPa), and elongation (4.2% or higher) compared to Comparative Examples 9, 10, 12, and 16.

[0100] Specifically, it was confirmed that the polyimide film of Example 5-1 exhibited improved mechanical properties such as Young's modulus, strength, and elongation compared to Comparative Examples 9 and 10. In other words, as mentioned in Experimental Example 1, the present invention demonstrates that a polyimide film with excellent mechanical properties can be produced using CDI without the need for purification, filtration, and drying steps.

[0101] Therefore, by using the additive CDI, the present invention has achieved process simplification by omitting the purification, filtration, and drying steps, and has made it possible to produce a polyimide film with excellent heat resistance (Tg and Td 5wt%) and mechanical properties.

[0102] In this specification, details of matters that can be easily understood and inferred by a person with ordinary skill in the art of the present invention have been omitted. Beyond the specific examples described herein, a wide variety of modifications are possible without altering the technical concept or essential configuration of the present invention. Therefore, the present invention can be implemented in ways different from those specifically described and illustrated herein, and this is something that a person with ordinary skill in the art of the present invention can understand.

Claims

1. (a) A step of polymerizing a dianhydride monomer and a diamine monomer to produce a polyamic acid, (b) The process includes the step of reacting the polyamic acid with carbonyl diimidazole to produce a soluble polyimide, The soluble polyimide is in the form of a varnish, and the method for producing polyimide.

2. The method for producing polyimide according to claim 1, wherein after step (b), the purification, filtration, and drying steps are omitted.

3. A method for producing polyimide according to claim 1, wherein carbonyldiimidazole is reacted with 0.5 to 1.5 molar equivalents of the polyamic acid in an amount equal to 1 molar equivalent.

4. The method for producing polyimide according to claim 1, wherein step (b) is a step performed at a temperature of 20 to 60°C.

5. The method for producing polyimide according to claim 1, wherein step (b) is a step performed for 0.5 to 5 hours.

6. The method for producing polyimide according to claim 1, wherein the polymerization in step (a) is random polymerization or block polymerization.

7. The method for producing polyimide according to claim 1, wherein the dianhydride monomer comprises one or more selected from the group consisting of pyromeretic dianehydride (PMDA), 3,3',4,4'-benzophenone tetracarboxylic dianehydride (BTDA), oxydiphthalic dianehydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianehydride (DSDA), and 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propanedianehydride.

8. The method for producing polyimide according to claim 1, wherein the diamine monomer comprises one or more selected from the group consisting of 4,4'-methylenebis(2,6-diethylaniline) (MEDA), 2,4-diaminotoluene (2,4-TDA), 2,6-diaminotoluene (2,6-TDA), m-phenylenediamine (m-PD), p-phenylenediamine (p-PD), 3,3''-diaminodiphenylsulfone (3,3''-DDS), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP), 3,5-diethyltoluene-2,6-diamine, 3,5-diethyltoluene-2,4-diamine, and 4,4'-methylenebis(2-ethyl-6-methylaniline) (MEMA).

9. The method for producing polyimide according to claim 8, wherein the content of 4,4'-methylenebis(2,6-diethylaniline) (MEDA) in the total diamine monomer is greater than 0 mol% and 50 mol% or less.

10. The method for producing polyimide according to claim 8, wherein the content of 2,4-diaminotoluene (2,4-TDA) in the total diamine monomer is 50 mol% or more and less than 100 mol%.

11. The method for producing the polyimide according to claim 1, wherein the soluble polyimide exhibits solubility in an organic solvent when the solid content is 15 wt% or more.

12. The method for producing polyimide according to claim 1, wherein the soluble polyimide has a 5% by weight thermal decomposition temperature (Td) of 485°C or higher.

13. The method for producing a polyimide according to claim 1, wherein the soluble polyimide has a glass transition temperature (Tg) of 300°C or higher.

14. The aforementioned soluble polyimide is The modulus is 3.0 GPa or higher. The tensile strength is 110 MPa or higher. A method for producing a polyimide according to claim 1, wherein the elongation is 5% or more.

15. A soluble polyimide produced by the method for producing polyimide according to any one of claims 1 to 14.

16. Polyamic acids containing dianhydride monomers and diamine monomers as polymerization units, A composition for producing soluble polyimide, comprising carbonyl diimidazole.

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