Solvent for resin synthesis, method for producing resin using the solvent, and composition containing these solvent and resin

Abstract

Provided are a solvent for use in synthesizing polyimide precursors, polyamideimide precursors, polyimide resins, polyamideimide resins, etc., which can synthesize high-molecular-weight polymers in a short time, does not produce a cloudy reaction solution during or after the reaction, and has high transparency and storage stability; a method for producing these resins using the solvent; and a composition containing these resins. [Solution] A solvent (C) for resin synthesis contains 10 to 99.9999 mass% of an amide solvent (A) and 0.0001 to 5 mass% of a reaction accelerator (B), wherein the reaction accelerator (B) is an aliphatic or aromatic tertiary amine compound having one or more tertiary amino groups in the molecule, and the amide solvent (A) is an alkoxy-N-substituted propanamide.

Description

Technical Field

[0001] The present invention relates to a solvent for resin synthesis such as polyimide precursors, polyamideimide precursors, polyimide resins, and polyamideimide resins, a method for producing a resin using the solvent, and a composition containing these solvents and resins.

Background Art

[0002] A group of polyimides (polyimide, polyamideimide, polyesterimide, polyetherimide, etc.) have a strong molecular structure, are not only excellent in heat resistance, but also have mechanical and chemical properties that are not found in other resins. As high-performance plastics, they are widely used in various fields such as films, coating agents, protective films, general electrical insulation materials, bearings, heat-resistant paints, heat-insulating shafts, heat-insulating trays, electronic parts, and automotive parts. In particular, aromatic polyimide is synthesized from aromatic diamine and aromatic tetracarboxylic dianhydride, and has a strong molecular structure and strong intermolecular forces, so it has the highest level of thermal, mechanical, and chemical properties among synthetic resins, and is widely known as a super engineering plastic. Since polyimide is generally insoluble and infusible, diamine or diisocyanate and acid dianhydride are reacted in an organic solvent at a low temperature of about room temperature to synthesize polyamic acid as a precursor. After processing the obtained precursor solution into a film or the like, it is synthesized by dehydration cyclization (imidization) by heating or by a chemical reaction. Also, when synthesizing polyimide soluble in an organic solvent or thermoplastic polyimide, etc., after synthesizing a polyimide precursor, imidization can be carried out by heating in the same solvent. In various polyimides, in order to obtain high-performance products, it is necessary to stably synthesize a high-molecular-weight precursor solution (varnish), and the obtained precursor solution has excellent storage stability (solution stability). Research on the synthesis of precursors has also attracted attention.

[0003] Although the type of suitable solvent (good solvent) varies depending on the chemical structure of the polyimide, organic polar solvents such as amide solvents are generally used for the synthesis of polyimide precursors. Amide solvents are known for their excellent dissolving power, high boiling points and flash points, and being thermally and chemically stable. However, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAC), which are commonly used for the synthesis of polyimide precursors, are likely to cause inflammation when they come into contact with the skin or eyes, and there are concerns about their carcinogenicity and teratogenicity. Thus, their harmfulness to the human body has become a problem. In particular, NMP also has problems in terms of the environment, toxicology, and / or administration (REACH) (Patent Documents 1 and 2).

[0004] To solve problems such as the low safety of amide solvents such as NMP and DMF, recently, N-butyl-2-pyrrolidone (NBP) and 3-methoxy-N,N-dimethylpropanamide (KJCMPA (registered trademark)), which are amide solvents with high safety and dissolving power, have attracted attention as solvents for the synthesis of a group of polyimides such as polyimide precursors (Patent Documents 3 and 4). However, since these prior arts aim to use NBP and KJCMPA merely as alternative solvents for NMP, it is only necessary to exhibit effects such as a dissolving power comparable to that of conventional NMP. Various problems of conventional NMP, such as the difficulty in increasing the molecular weight of the polyimide precursor, low solution stability of the polyimide precursor (easily becoming turbid), easy whitening during polyimide film formation, and easy occurrence of surface unevenness, have not been solved. On the other hand, to solve the problems of whitening and surface unevenness during polyimide film formation, there are reports of using KJCMPA or 3-butoxy-N,N-dimethylpropanamide (KJCBPA (registered trademark)) (Patent Documents 5 to 7). However, it was necessary to mix and use these solvents with nonpolar organic solvents, alcohols, or water at the same time. However, the introduction of a large amount of alcohol or water having active hydrogen causes side reactions such as the hydrolysis reaction of acid dianhydride and the hydrolysis of the produced polyamic acid, which is the precursor, and as a result, it becomes inevitable to avoid the turbidity of the polyimide precursor solution, and problems such as the inability to achieve high molecular weight of the polyimide precursor are likely to occur instead.

[0005] Moreover, although polyurethane is a plastic material, it is as soft as rubber and excellent in tensile strength, abrasion resistance, elasticity, and oil resistance. It is used in all kinds of industrial products, from daily necessities such as the soles of sports shoes and clothing to industrial materials such as sound insulation materials, heat insulation materials, and adhesives, and automotive materials such as bumpers and headrests. The synthesis of polyurethane can be carried out by various methods depending on its structure and use. However, since the urethanization reaction is an exothermic reaction, many thermoplastic polyurethanes are stably synthesized by the solution polymerization method. In particular, in order to increase the molecular weight, DMF and other polar solvents in which the generated polyurethane can be uniformly dissolved are often used. However, as described above, the safety issues associated with DMF still remain a concern.

[0006] As described above, there is still no known solvent that can efficiently and stably synthesize high-molecular-weight polymers, and the reaction solution does not become cloudy during or after the reaction, has high transparency and storage stability, and is excellent in adhesion to the substrate, and is preferably used for the synthesis of polyamic acids such as polyimide precursors and polyamideimide precursors, polyimides, polyamideimides, polyurethanes, etc.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to efficiently and stably synthesize a high molecular weight polymer, and to obtain a synthetic resin that does not cause the reaction solution to become turbid during or after the reaction, has high transparency and storage stability, and excellent adhesion to a substrate. The present invention provides a solvent suitable for the synthesis of polyamic acids such as polyimide precursors and polyamideimide precursors, polyimides, polyamideimides, polyurethanes, etc., and a method for producing the synthetic resin using the solvent.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found a solvent (C) for resin synthesis containing an amide-based solvent (A) and a reaction accelerator (B), and have reached the present invention.

[0010] That is, the present invention is (1) A resin synthesis solvent (C) containing 10 to 99.9999% by mass of an amide-based solvent (A) and 0.0001 to 5% by mass of a reaction accelerator (B), wherein the reaction accelerator (B) is an aliphatic or aromatic tertiary amine compound having one or more tertiary amino groups in the molecule, and the amide-based solvent (A) is an alkoxy-N-substituted propanamide represented by the general formula (1).

Chemical Formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Advantages of the Invention

[0011] The solvent for resin synthesis of the present invention contains an amide-based solvent (A) and a reaction accelerator (B). By using this synthesis solvent as a reaction solvent when synthesizing polyimide precursors, polyamide-imide precursors, etc. from acid dianhydrides, diamines, and / or diisocyanates, these reactions can proceed at a high speed with controllability, and at the same time, various high-molecular-weight precursors (polyamic acids) can be obtained. The resulting polyamic acid solution has excellent transparency, does not become cloudy even after long-term storage, and has good storage stability. From such various polyamic acid solutions, polyimide films, heat-resistant paints, etc. having high transparency, high smoothness, and excellent mechanical strength can be easily manufactured. Furthermore, the solvent for resin synthesis of the present invention can also be suitably used for the urethanization reaction of polyols and diisocyanates, and the reaction can proceed at a high speed with controllability, and at the same time, high-molecular-weight and high-performance polyurethanes can be obtained.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. An embodiment of the present invention is a solvent for resin synthesis (C) containing an amide-based solvent (A) and a reaction accelerator (B). The amide-based solvent (A) is a compound having one or more amide groups in the molecule, and its content is 10 to 99.9999% by mass based on the solvent for resin synthesis (C). The amide-based solvent (A) is preferably a compound having no active hydrogen and / or a functional group that reacts with active hydrogen in the molecule. When its content is 80% by mass or more, in order to maintain the fluidity of the solvent for resin synthesis (C) at the reaction temperature, it is more preferable that the state of A in the temperature range of 0°C to 140°C is a liquid.

[0013] The above-mentioned amide-based solvent (A) is not particularly limited, but it is preferably one with low danger and harmfulness to human health, ecology, and the environment, and more preferably a highly safe compound that has no impact on human health, ecology, and the environment. Examples of such compounds include N-alkyl (with 4 or more carbon atoms)-2-pyrrolidone (N-butyl-2-pyrrolidone, N-hexyl-2-pyrrolidone, etc.), N-alkyl (with 1 or more carbon atoms) alkane (with 2 or more carbon atoms) amide (N-ethylhexanamide, N-butylbutanamide, etc.), N,N-dialkyl (with 1 or more carbon atoms) alkane (with 2 or more carbon atoms) amide (N,N-dimethylbutanamide, N,N-diethylbutanamide, N,N-dimethyloctanamide, etc.), alkoxy (with 1 or more carbon atoms)-N-alkyl ((with 1 or more carbon atoms) alkane (with 2 or more carbon atoms) amide (ethoxy-N-methylpropanamide, hexyloxy-N-ethylbutanamide, etc.), alkoxy (with 1 or more carbon atoms)-N,N-dialkyl ((with 1 or more carbon atoms) alkane (with 2 or more carbon atoms) amide (methoxy-N,N-dimethylpropanamide, ethoxy-N,N-dimethylbutanamide, lauroxy-N,N-dimethylpropanamide, phenyloxy-N,N-methylethylpropanamide, etc.), alkanoyl (with 2 or more carbon atoms) morpholine (propanoyl morpholine, butanoyl morpholine, hexanoyl morpholine, octanoyl morpholine, etc.), alkoxy (with 1 or more carbon atoms) alkanoyl (with 2 or more carbon atoms) morpholine (methoxyethanoyl morpholine, 4-(3-methoxypropinoyl) morpholine, etc.), N,N-dialkyl (with 2 or more carbon atoms) acetamide (N,N-diethylacetamide, N,N-dipropylacetamide, N,N-diisopropylacetamide, N,N-dibutylacetamide, N,N-diisobutylacetamide, N,N-dihexylacetamide, etc.). These amide-based solvents (A) may be used alone or in combination of two or more.

[0014] The amide-based solvent (A) is preferably an alkoxy-N-substituted propanamide and an alkoxy-N,N-disubstituted propanamide represented by the following general formula (1) (wherein R1 to R3 each independently represents a linear alkyl group having 1 to 22 carbon atoms, a branched alkyl group having 3 to 22 carbon atoms, an alkyl ether group having 2 to 22 carbon atoms, an alicyclic hydrocarbon having 3 to 22 carbon atoms, or an aromatic hydrocarbon having 6 to 22 carbon atoms, and R4 represents a hydrogen atom or a methyl group. Also, R2 and R3 each independently represent a hydrogen atom (except when they are both hydrogen atoms) or, together with the nitrogen atom carrying them, form a saturated 5- to 7-membered ring (including those having an oxygen atom).). Alkoxy-N-substituted propanamides and alkoxy-N,N-disubstituted propanamides are industrially produced, and further have an ether group and an amide group simultaneously in the molecule, and are excellent in solubility in various synthetic resins and their raw materials.

Chemical formula

[0015] The above-mentioned alkoxy-N-substituted propanamides and alkoxy-N,N-disubstituted propanamides are compounds composed of arbitrarily combined functional groups represented by R1, R2, and R3. For example, methoxy-N-methylpropanamide (when R1 and R2 are methyl groups and R3 is a hydrogen atom), methoxy-N,N-dimethylpropanamide (when R1, R2, and R3 are all methyl groups), 3-methoxy-N,N-diethylpropanamide (when R1 is a methyl group and R2 and R3 are ethyl groups), butoxy-N,N-dimethylpropanamide (when R1 is a butyl group and R2 and R3 are methyl groups), lauroxy-N,N-dimethylpropanamide (when R1 is a lauryl group and R2 and R3 are methyl groups), stearoxy-N-ethylpropanamide (when R1 is a stearyl group, R2 is a hydrogen atom, and R3 is an ethyl group), phenyloxy-N,N-methylethylpropanamide (when R1 is a phenyl group, R2 is a methyl group, and R3 is an ethyl group), ethoxy-N-phenylpropanamide (when R1 is an ethyl group, R2 is a hydrogen atom, and R3 is a phenyl group), methoxy-N-cyclohexylpropanamide (when R1 is a methyl group, R2 is a cyclohexyl group, and R3 is a hydrogen atom), isooctyloxy-N-ethoxyethylpropanamide (when R1 is an isooctyl group, R2 is a hydrogen atom, and R3 is an ethoxyethyl group), cyclohexyloxy-N,N-methyloleylpropanamide (when R1 is a cyclohexyl group, R2 is a methyl group, and R3 is an oleyl group), 3-isopropoxy-N,N-dimethylpropanamide (when R1 is an isopropyl group and R2 and R3 are methyl groups), 4-(3-methoxypropionyl)morpholine (when R1 is a methyl group and R2 and R3 together with the nitrogen atom carrying them form a saturated 6-membered ring having an oxygen atom), and the like. These compounds may be used alone or in combination of two or more.

[0016] Further, the alkoxy-N-substituted propanamides and alkoxy-N,N-disubstituted propanamides have the general formula (6) (wherein R 12 is a linear alkyl group having 1 to 18 carbon atoms or a branched alkyl group having 3 to 18 carbon atoms, R 13 and R 14each independently represents a hydrogen atom or a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms (except when they are simultaneously hydrogen atoms), R 15 represents a hydrogen atom or a methyl group. A compound represented by ) is preferable because it is easy to obtain inexpensive industrial raw materials and can be industrially produced in high yield due to its structure with low steric hindrance. Furthermore, methoxy-N,N-dimethylpropanamide and butoxy-N,N-dimethylpropanamide are particularly preferable because they have high safety for workers and the environment and are generally handled as industrial products. [Chemical formula]

[0017] The reaction accelerator (B) in the present invention is a compound having one or more tertiary amino groups in the molecule. The substituents of the amino group of the reaction accelerator (B) are not particularly limited and may be aliphatic or aromatic, and may be linear, cyclic, or may or may not have an unsaturated group. Also, when the reaction accelerator (B) does not have a hydrogen atom bonded to a heteroatom in the molecule, B does not cause side reactions with acid dianhydrides, isocyanate compounds, etc., which are raw materials for synthetic resins, and a high molecular weight synthetic resin can be obtained in a short time. Therefore, it is preferable. When performing the resin synthesis reaction using the resin synthesis solvent (C), it is preferable to select a compound whose boiling point is higher than the reaction temperature for the reaction accelerator (B) because it will not volatilize during the reaction and can efficiently promote the reaction. Examples of the reaction accelerator (B) include tertiary aliphatic amines such as trialkyl (having 1 or more carbon atoms, which may be the same or different) amines, dialkyl (having 1 or more carbon atoms, which may be the same or different) cyclohexylamines, tricyclohexylamines, etc., tertiary aromatic amines such as dialkyl (having 1 or more carbon atoms, which may be the same or different) anilines, dialkyl (having 1 or more carbon atoms, which may be the same or different) 2,4,6-trimethylanilines, N-methyldiphenylamine, triphenylamine, etc., and tertiary aliphatic amines having aromatic substituents such as N,N-dimethylbenzylamine, N-methyldibenzylamine, etc. These reaction accelerators (B) may be used alone or in combination of two or more.

[0018] The reaction accelerator (B) more preferably further has at least one functional group selected from an ether group, an ester group, and an amide group in the molecule. By having these functional groups, the promoting effect of the reaction by the reaction accelerator (B) (improvement of the reaction rate and / or improvement of the molecular weight of the produced polymer) tends to be improved. Although the mechanism regarding these effects is not clear, the inventors presume that it is because the polarity of the reaction accelerator (B) is enhanced by the coexistence of an ether group, an ester group, or an amide group.

[0019] The reaction accelerator (B) having an ether group in the molecule (hereinafter, also referred to as "reaction accelerator (b1)" or simply "b1") is not particularly limited as long as at least one ether group is present in any of the substituents of the tertiary amino group. Further, these ether groups may be formed in a chain structure or a cyclic structure. For example, (methoxyethyl)diethylamine, N,N-dimethyldimethoxymethanamine, (ethoxyethyl)dibutylamine, (methoxyhexyl)ethylhexylamine, (methoxyethyl)diphenylamine, di(methoxyethyl)cyclohexylamine, tri(butoxymethyl)amine, etc. may be mentioned. These reaction accelerators (b1) may be used alone or in combination of two or more.

[0020] The reaction accelerator (B) having an ester group in the molecule (hereinafter, also referred to as "reaction accelerator (b2)" or simply "b2") is not particularly limited as long as at least one ester group is present in any of the substituents of the tertiary amino group. Further, these ester groups may be formed in a chain structure or a cyclic structure. For example, methyl 3-methoxypropionate, methyl dimethylaminopropionate, butyl dimethylaminopropionate, methyl dibutylaminopropionate, butyl dibutylaminopropionate, ethyl diethylaminobutyrate, butyl ethylhexylaminoacetate, isopropyl morpholinopropionate, ethyl methylbenzylaminolaurate, etc. may be mentioned. These reaction accelerators (b2) may be used alone or in combination of two or more.

[0021] The reaction accelerator (B) having an amide group in the molecule (hereinafter, also referred to as "reaction accelerator (b3)" or simply "b3") is not particularly limited except for the amide-based solvent (A), and it suffices if one or more amide groups are present in any of the substituents of the tertiary amino group. Further, these amide groups may be formed in a chain structure or a cyclic structure. For example, dimethylamino-N,N-dimethylpropionamide, dimethyl-N,N-dibutylaminopropionamide, dibutylamino-N,N-dimethylpropionamide, dibutylamino-N,N-dibutylpropionamide, diethylamino-N,N-dimethylbutyramide, ethylhexylamino-N,N-diethylacetamide, morpholinopropionic acid morpholide, methylbenzylamino-N,N-dimethyllauramide, N,N-dimethylpropionamide, etc. may be mentioned. These reaction accelerators (b3) may be used alone or in combination of two or more.

[0022] The reaction accelerator (b1) having an ether group in the molecule, the reaction accelerator (b2) having an ester group in the molecule, and the reaction accelerator (b3) having an amide group in the molecule may be used alone, one selected from the group consisting of them, or in combination of two or more.

[0023] The solvent (C) for resin synthesis of the present embodiment contains an amide-based solvent (A), and the content of A is 10 to 99.9999% by mass based on the whole of the solvent (C) for resin synthesis. The content of A is preferably 20 to 99.99% by mass, and more preferably 30 to 99.8% by mass. When the solvent (C) for resin synthesis contains 10% by mass or more of A, it has sufficient dissolving power for various resin synthesis raw materials and the resulting synthetic resin, which is preferable. Further, when the content of A is 99.9999% by mass or less, it is possible to contain 0.0001% by mass or more of the reaction accelerator (B) which is an essential component of the solvent (C) for resin synthesis, and since the reaction accelerating effect by B can be confirmed, it is preferable.

[0024] The solvent (C) for resin synthesis in this embodiment contains a reaction accelerator (B) in addition to the amide-based solvent (A). The content of B is 0.0001 to 5% by mass based on the total amount of the solvent (C) for resin synthesis. If B is contained in the solvent (C) for resin synthesis in an amount of 0.0001% by mass or more, it can exhibit a promoting effect on the resin synthesis reaction, which is preferable. On the other hand, if the content of the reaction accelerator (B) exceeds 5% by mass based on the total amount of the synthesis solvent (C), the reaction rate may be difficult to control, which is not preferable. Since the reaction accelerator (B) has a tertiary amino group, it easily forms a neutralization salt with the carboxylic acid group generated during resin synthesis, and by protecting the carboxylic acid group of polyamic acid, which is a polyimide precursor and a polyamide-imide precursor, as a neutralization salt, the transparency and storage stability of these precursor solutions are improved. Such a neutralization salt evaporates with the heating imidization of the precursor and can obtain high-molecular-weight polyimide resin and polyamide-imide resin by the imidization reaction of the deprotected carboxylic acid group. From these viewpoints, the content of the reaction accelerator (B) is preferably 0.001 to 2% by mass, more preferably 0.01 to 1% by mass based on the total amount of the solvent (C) for resin synthesis.

[0025] In addition, the contents of the reaction accelerators (b1), (b2), and (b3) that can be contained in the reaction accelerator (B) are 0.0001 to 5% by mass for each of b1, b2, and b3 based on the total amount of the solvent (C) for resin synthesis because b1, b2, and b3 can be used alone. However, when two or more selected arbitrarily from b1, b2, and b3 are mixed and used, their total content does not exceed 5% by mass based on the total amount of the solvent (C) for resin synthesis.

[0026] The reaction accelerator (B) is preferably a reaction accelerator (b3) having an amide group in the molecule. By having one or more amino groups and one or more amide groups, the polarity of the whole molecule is improved, and the reaction acceleration effect by the amino group is improved due to the influence of the amide group. Or, it is considered that due to the interaction between the amide group and the amino group in the molecule of b3, in addition to the amino group, a reaction acceleration effect by the amide group is also produced. Further, depending on the raw materials for resin synthesis, the types of products, the charging ratios of various raw materials, reaction conditions such as reaction temperature and reaction time, and the desired molecular weight of the synthetic resin to be further produced, etc., it is possible to mix and use b3 with a reaction accelerator (b2) having an ester group in the molecule, mix and use b3 with a reaction accelerator (b1) having an ether group in the molecule, or mix and use b3 with b2 and b1.

[0027] As one embodiment of the solvent (C) for resin synthesis, it is possible to use the amide-based solvent (A) in combination with other solvents. Examples of other solvents include aromatic hydrocarbon solvents such as xylene, solvent naphtha, toluene, ethylbenzene, and tetralin; urea-based solvents having a urea group such as 1,3-dimethylurea, 1,3-diethylurea, 1,3-diphenylurea, 1,3-dicyclohexylurea, tetramethylurea, tetraethylurea, 2-imidazolidinone, propyleneurea, 1,3-dimethyl-2-imidazolidinone, and N,N-dimethylpropyleneurea; lactone solvents such as β-propiolactone, γ-butyrolactone, α-acetyl-γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone; ether solvents such as dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 1,4-dioxane, 2-methyltetrahydrofuran, cyclopentyl methyl ether, 4-methyltetrahydropyran, acetophenone, acetylacetone, butyl acetate, ethyl benzoate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, ethyl acetoacetate, isoamyl acetate, n-pentyl acetate, and ethyl propionate; ketone solvents; ester solvents; and general-purpose solvents such as 1,3-dioxolane, dimethyl sulfoxide, nitrobenzene, N-formylmorpholine, and 4-acetylmorpholine. These solvents may be used alone as other solvents or in combination of two or more.

[0028] The content of other solvents is 89.9999% by mass or less, preferably 5 to 50% by mass, more preferably 10 to 30% by mass, based on the total amount of the solvent (C) for resin synthesis. When other solvents are contained at 89.9999% by mass or less, an amide solvent (A) which is an essential component of the solvent (C) for resin synthesis can be contained at 10% by mass or more, and a reaction accelerator (B) can be contained at 0.0001% by mass or more. Since a high dissolving power of various raw materials for resin synthesis by A with respect to the obtained synthetic resin and a reaction accelerating effect by B can be confirmed, it is preferable.

[0029] In one embodiment, the boiling points of the amide solvent (A) and other solvents are preferably 80°C to 400°C at normal pressure. Further, the boiling points of these solvents are more preferably 100°C to 350°C at normal pressure, and particularly preferably 180°C to 280°C at normal pressure. If the boiling point of the solvent is less than 80°C, when the reaction is carried out at a temperature of 80°C or higher in the manufacturing process of the synthetic resin, the concentration of the reaction solution changes due to the evaporation of the solvent, and it becomes difficult to reproduce the molecular weight and solution viscosity of the resin precursor and synthetic resin obtained. On the other hand, when the boiling point of the solvent exceeds 400°C, in the manufacturing process of forming a film of a polyamic acid solution on a substrate such as metal and subjecting it to stepwise imidization at a temperature of 100°C to 500°C, the solvent may not evaporate completely, and may remain in a large amount in products such as the obtained polyimide film, or may carbonize in the product, resulting in problems such as a decrease in the transparency, strength, elongation, heat resistance, chemical resistance, etc. of the product.

[0030] As one embodiment of the solvent (C) for resin synthesis, it is possible to use an amide-based solvent (A) and an ionic liquid in combination. Also, as the solvent (C) for resin synthesis, an amide-based solvent (A), other solvents, and an ionic liquid can be used in combination. In the present invention, the ionic liquid is a salt composed of an anion and a cation, and its state in the temperature range of 0°C to 150°C is liquid. Since the ionic liquid has high polarity and excellent dissolving power for poorly soluble synthetic resins, by containing the ionic liquid, a polyamic acid solution with higher transparency and stability can be obtained. Also, the ionic liquid is hardly volatile and hardly flammable, has high thermal stability and chemical stability, and has high ionic conductivity and excellent electrochemical properties. Therefore, it does not have an adverse effect even in the high-temperature imidization reaction of polyamic acid. By containing a trace amount of the ionic liquid in products such as polyimide films, flexibility can be imparted to the products, the imidization reaction can proceed at a temperature above the glass transition temperature, and the heat resistance is further improved.

[0031] When classified according to the cation of the basic skeleton constituting the ionic liquid, examples include imidazolium salts, pyrrolidinium salts, pyridinium salts, piperidinium salts, ammonium salts, and phosphonium salts. Also, various ionic liquids can be selected by changing the anion species of these salts or the substituents such as the alkyl groups of the cation and the anion. Among them, imidazolium salts, pyrrolidinium salts, pyridinium salts, piperidinium salts, and ammonium salts are preferred because they have a nitrogen atom and exhibit basicity. This is considered to be because many of the amide-based solvents contained in the solvent (C) for resin synthesis are neutral to weakly basic, and the ionic liquids exhibiting basicity have good compatibility with the amide-based solvents. Also, imidazolium salts and ammonium salts are more preferred because high-purity industrial products are easily available. These ionic liquids may be used alone or in combination of two or more.

[0032] The content of the ionic liquid is 20% by mass or less, preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, based on the total amount of the solvent (C) for resin synthesis. When the content of the ionic liquid exceeds 20% by mass, a large amount of the ionic liquid remains in the final product such as a polyimide film obtained by directly heating the polyamic acid solution. Also, even if the polyamic acid solution is once subjected to precipitation treatment and then imidized, a small amount of the ionic liquid remains in the final product, which may adversely affect the quality of the product. On the other hand, it is preferable to contain 0.001% by mass or more of the ionic liquid because it can provide flexibility, elongation, and electrochemical properties to the final product such as a polyimide film.

[0033] The solvent (C) for resin synthesis of this embodiment may further contain a stabilizer (D). The stabilizer (D) in this specification is a compound having active hydrogen in the molecule, and specifically includes water, alcohol, amine, etc. Since the stabilizer (D) has active hydrogen in the molecule, it reacts with acid dianhydride or diisocyanate, which are raw materials of the synthetic resin, and protects the reactive groups of these compounds, thereby relaxing the reaction rate of resin synthesis as needed and preventing cloudiness of the reaction solution and generation of insoluble matter (gelation). The rate control of the resin synthesis reaction, the molecular weight control of the resin, and the stability control of the resin solution can be performed more precisely. Particularly in a multi-stage reaction in which the reaction is carried out while changing reaction conditions such as temperature, by using the reaction accelerator (B) and the stabilizer (D) in combination, the reaction can proceed smoothly over a wide range of temperatures, and a high molecular weight resin or a resin solution having high transparency and storage stability can be obtained.

[0034] From the viewpoint of being easily deprotected, the stabilizer (D) is preferably water, an alcohol having a boiling point of less than 140°C, or an amine (excluding (B)) having a boiling point of less than 140°C. Further, from the viewpoint of being easily removed from the reaction solution by distillation, the stabilizer (D) is more preferably water, an alcohol having a boiling point of 120°C or lower, or an amine (excluding (B)) having a boiling point of 120°C or lower, and particularly preferably an alcohol having a boiling point of 100°C or lower or an amine (excluding (B)) having a boiling point of 100°C or lower. The stabilizer (D) may be used alone or in combination of two or more kinds.

[0035] The alcohol as the stabilizer (D) is not particularly limited as long as it has a hydroxyl group in the molecule. As the alcohol, a monofunctional alcohol having only one hydroxyl group in the molecule, a difunctional alcohol having two hydroxyl groups in the molecule, or a polyfunctional alcohol having three or more hydroxyl groups in the molecule can be used. Among them, monofunctional alcohols are preferred because both the protection reaction and the deprotection reaction proceed relatively easily. Examples of monofunctional alcohols include monofunctional alcohols having one primary or secondary hydroxyl group in the molecule, such as methyl alcohol, ethyl alcohol, isopropanol, t-butyl alcohol, 9-decen-1-ol, 1-octacosanol, diethylene glycol monomethyl ether, propylene glycol-1-monomethyl ether, 4-dimethylamino-1-butanol, cyclohexanol, benzyl alcohol, etc. Among them, methyl alcohol, ethyl alcohol, n-propanol, isopropanol, n-butyl alcohol, and t-butyl alcohol have a boiling point of 120°C or lower under normal pressure and can be deprotected at low temperature, so they are more preferred. These alcohols may be used alone or in combination of two or more kinds.

[0036] The amine as the stabilizer (D) is not particularly limited as long as it is a primary amine or a secondary amine having an amino group in the molecule, excluding the reactive accelerator (B). Among them, secondary amines are preferred because both the protection reaction and the deprotection reaction proceed relatively easily. Examples of secondary amines include dimethylamine, ethylmethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, dicyclohexylamine, diallylamine, piperidine, pyrrolidine, morpholine, N-methylbenzylamine, and dibenzylamine. Among them, dimethylamine, ethylmethylamine, diethylamine, dipropylamine, diisopropylamine, diallylamine, piperidine, and pyrrolidine are more preferred because their boiling points are 120°C or lower under normal pressure and can be deprotected at low temperatures. These amines may be used alone or in combination of two or more.

[0037] The stabilizer (D) may be used alone as any one selected from the group consisting of water, the various alcohols described above, and the various amines described above, or may be used in combination of two or more.

[0038] When using stabilizer (D), it is presumed that the mechanism of action varies depending on the type of D and the types of raw materials for the resin synthesis reaction. For example, in the synthesis of polyimide precursors and polyimide resins from acid dianhydrides and diamines, first, the acid dianhydride and diamine are subjected to a ring-opening polyaddition reaction in a solvent to obtain a polyamic acid (having carboxylic acid groups and amides) as a polyimide precursor. Subsequently, by heating, an intramolecular dehydration cyclization reaction of the polyamic acid (formation of imide groups by dehydration of carboxylic acid groups and amide groups) occurs, yielding polyimide. If water is present in this reaction system, one carboxylic acid anhydride group of the acid dianhydride is hydrolyzed to form two carboxylic acid groups, increasing the number of functional groups reacting with amino groups, disrupting the stoichiometry of the charged diamine and acid dianhydride, preventing the degree of polymerization of the polyamic acid from increasing, and ultimately not obtaining a high molecular weight polyimide resin. Therefore, it is not preferable to add water as a stabilizer. On the other hand, if alcohol or amine is present in this reaction system, one carboxylic acid anhydride group reacts with alcohol to form one carboxylic acid group and one carboxylic acid ester group, or one carboxylic acid anhydride group reacts with amine to form one carboxylic acid group and one carboxylic acid amide group, without changing the number of functional groups reacting with amino groups, and a polyamic acid with a high degree of polymerization and partially substituted with amide acid ester groups or a polyamic acid partially substituted with amide acid amide groups can be obtained. Polyamic acid esters and polyamic acid amides have higher solution stability compared to the corresponding polyamic acids. Therefore, by adding alcohol or amine as a stabilizer to the resin synthesis solvent, a polyimide precursor solution with high transparency and high stability can be obtained. Also, polyamic acid esters and polyamic acid amides are imidized by heating with the elimination of alcohol or amine, ultimately yielding a high molecular weight polyimide resin. For this reason, when synthesizing polyimide precursors and polyimide resins from acid dianhydrides and diamines, it is preferable to add alcohol or amine as a stabilizer to the solvent.

[0039] Also, when synthesizing a polyamideimide precursor and a polyamideimide resin from an acid dianhydride and a diisocyanate using a stabilizer (D), by containing a small amount of water in the reaction system, the acid anhydride group is hydrolyzed to obtain a carboxylic acid group. The obtained carboxylic acid group reacts with the isocyanate group of the diisocyanate to form an amide group, and the degree of polymerization of the polyamic acid, which is the polyamideimide precursor, does not decrease. On the contrary, an improvement in the reaction rate and an improvement in the molecular weight (degree of polymerization) are observed. Also, when alcohol or amine is present in this reaction system, the same effect as in the reaction system of the polyimide precursor is observed. At the same time, since alcohol and amine have a protective effect on the isocyanate group, by performing protection and deprotection as necessary, a polyimide precursor solution with higher transparency, higher stability, and high molecular weight and a high molecular weight polyamideimide resin can be obtained. Therefore, when synthesizing a polyamideimide precursor and a polyamideimide resin from an acid dianhydride and a diisocyanate, it is preferable to add water, alcohol, or amine as a stabilizer to the solvent.

[0040] The content of the stabilizer (D) can be appropriately changed depending on the type of resin synthesis reaction, the reaction accelerator (B) used, or the type of stabilizer (D). However, it is preferably 10 to 500% by mass based on the total amount of B. Within this range, the synthesis of precursors such as polyamideimide precursors and polyimide precursors, as well as the synthesis of polyurethane, can easily control the reaction rate within a predetermined temperature range. Also, the content of D is more preferably 20 to 300% by mass with respect to B, and particularly preferably 50 to 200% by mass.

[0041] The solvent (C) for resin synthesis of the present embodiment can be suitably used for the synthesis of polyimide copolymers, polyamide resins, polyurethane resins, polyester resins, polyacrylic resins, and fluororesins composed of any two or more selected from polyimide precursors, polyamideimide precursors, polyesterimide precursors, polyetherimide precursors, polyimide resins, polyamideimide resins, polyesterimide resins, polyetherimide resins, and the various resin precursors.

[0042] The acid dianhydrides used as raw materials for polyimide resins, polyamideimide resins, polyesterimide resins, polyetherimide resins, and precursors thereof include, for example, pyromellitic dianhydride, 3,3’,4,4’-biphenyltetracarboxylic dianhydride, 2,3,3’,4’-biphenyltetracarboxylic dianhydride, 2,2’,3,3’-biphenyltetracarboxylic dianhydride, 3,3’,4,4’-benzophenonetetracarboxylic dianhydride, 2,2’,3,3’-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4’-oxydiphthalic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis(4-(3,4-dicarboxyphenoxy)phenyl)fluorene dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, aliphatic tetracarboxylic dianhydrides such as butanetetracarboxylic dianhydride, and aliphatic tetracarboxylic dianhydrides containing an alicyclic group such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride. These acid dianhydrides may be used alone or in combination of two or more.

[0043] Diamine compounds used as raw materials for polyimide resins, polyamideimide resins, polyesterimide resins, polyetherimide resins, and precursors thereof include, for example, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl methane, 1,4-bis(4-aminophenoxy)benzene, benzidine, m-phenylenediamine, p-phenylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)ether, 1,4-bis(4-aminophenoxy)benzene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4'-diaminobiphenyl, 2,2',3,3'-tetramethyl-4,4'-diaminobiphenyl, 3,3',4,4'-tetramethyl-4,4'-diaminobiphenyl, 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl, 9,9-bis(4-aminophenyl)fluorene, 2,2'-bis(trifluoromethyl)-5,5'-dihydroxybenzidine, 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, aromatic diamines such as compounds in which at least a part of the hydrogen atoms of these aromatic rings are substituted with alkyl groups or halogen atoms, and aliphatic diamines containing cycloaliphatic groups such as cyclohexyldiamine and methylenebiscyclohexylamine. These diamine compounds may be used alone or in combination of two or more.

[0044] Diisocyanates used as raw materials for polyamideimide resins and their precursors, and raw materials for polyurethane resins include, for example, aliphatic diisocyanates, aromatic diisocyanates, and araliphatic diisocyanates. These diisocyanate compounds may be used alone or in combination of two or more.

[0045] Examples of aliphatic diisocyanates include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, 2,2'-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 1,6,11-undecamethylene triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 2,5,7-trimethyl-1,8-diisocyanate-5-isocyanatomethyloctane, bis(isocyanatoethyl) carbonate, bis(isocyanatoethyl) ether, 1,4-butylene glycol dipropyl ether-ω,ω'-diisocyanate, lysine isocyanatomethyl ester, lysine triisocyanate, 2-isocyanatoethyl-2,6-diisocyanate hexanoate, 2-isocyanatopropyl-2,6-diisocyanate hexanoate, bis(4-isocyanate-n-butylidene) pentaerythritol, 2,6-diisocyanate methyl caproate, and other aliphatic diisocyanates.

[0046] In addition, examples of alicyclic diisocyanates having a cyclic structure in aliphatic diisocyanates include isophorone diisocyanate (IPDI), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof (bis(isocyanatomethyl)cyclohexane (H6XDI)), 4,4’-, 2,4’- or 2,2’-dicyclohexylmethane diisocyanate or a mixture thereof (H12MDI), 1,3- or 1,4-cyclohexane diisocyanate or a mixture thereof, 1,3- or 1,4-bis(isocyanatoethyl)cyclohexane, methylcyclohexane diisocyanate, 2,2’-dimethyl dicyclohexylmethane diisocyanate, dimer acid diisocyanate, 2,5- or 2,6-diisocyanatomethylbicyclo[2,2,1]-heptane (NBDI), 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethylbicyclo-[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethylbicyclo-[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo-[2,2,1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo-[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo-[2,2,1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo-[2,2,1]-heptane and other alicyclic diisocyanates.

[0047] Examples of the aromatic diisocyanate include aromatic diisocyanates such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and isomer mixtures (TDI) of these tolylene diisocyanates, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, and any isomer mixture (MDI) of these diphenylmethane diisocyanates, toluidine diisocyanate (TODI), paraphenylene diisocyanate, naphthalene diisocyanate (NDI).

[0048] Examples of the aromatic aliphatic diisocyanate include aromatic aliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or a mixture thereof (XDI), 1,3- or 1,4-tetramethylxylylene diisocyanate or a mixture thereof (TMXDI).

[0049] Specific examples of the polyol used as a raw material of the polyurethane resin include polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, epoxy polyol, vegetable oil polyol, polyolefin polyol, acrylic polyol, silicone polyol, fluorine polyol, and vinyl monomer-modified polyol. These polyols may be used alone or in combination of two or more.

[0050] Since the resin synthesis solvent (C) of the present embodiment is excellent in solubility in polyimide resin, polyamideimide resin, polyesterimide resin, polyetherimide resin and their precursors, and polyurethane resin, polyamide resin, polyacrylic resin, fluororesin, etc., it can be suitably used as a solvent used for the production and dissolution of various resins. Further, by using the resin synthesis solvent (C) of the present embodiment, the synthesis reaction of the various resins can be completed in a short time, the reaction easily proceeds even at low temperature and can be easily controlled even at high temperature, and a resin having high molecular weight, high transparency, good heat resistance and mechanical properties can be obtained.

[0051] When synthesizing various resins using the solvent (C) for resin synthesis, it can be carried out under known reaction conditions. That is, the reaction apparatus, raw materials and raw material charging ratio, raw material charging method, reaction temperature, reaction time, purification method, etc. are the same as before. Also, in terms of the reaction temperature, when synthesizing a polyimide precursor, a polyamide-imide precursor (hereinafter also collectively referred to as polyamic acid), and polyurethane, the reaction can be completed at a lower temperature compared to the prior art. On the other hand, the dehydration imidization reaction of various precursors can be carried out at a higher temperature compared to the prior art, and resin products such as polyimide and polyamide-imide with higher heat resistance and chemical resistance can be obtained.

[0052] In the reaction for synthesizing a polyimide precursor from an acid dianhydride and a diamine using the solvent (C) for resin synthesis in one embodiment, the reaction temperature is -20°C to 80°C, preferably 0°C to 70°C, and more preferably 10°C to 60°C. In the reaction for synthesizing a polyamide-imide precursor from an acid dianhydride and a diisocyanate, the reaction temperature is 40°C to 140°C, preferably 60°C to 130°C, and more preferably 80°C to 120°C. For the synthesis of these precursors, if the reaction temperature is above the respective lower limit temperatures, the reaction can proceed at a sufficient rate and be completed in a short time, so the productivity is good. Also, when the reaction temperature is below the respective upper limit temperatures, the progress of the intramolecular imidization reaction of the generated polyamic acid is suppressed, the transparency of the polyamic acid solution is good, and there is no precipitation of turbidity or gel-like insoluble matter over time, and the storage stability is good. Incidentally, the reaction time for these reactions varies depending on the reaction temperature, but is usually in the range of 1 hour to 24 hours.

[0053] In the reaction of synthesizing polyurethane from polyol and diisocyanate using the solvent (C) for resin synthesis in one embodiment, the reaction temperature is usually 20°C to 150°C, preferably 30°C to 120°C, and more preferably 40°C to 110°C. Due to the presence of the reaction accelerator (B), the urethanization reaction can proceed even at a low temperature of about 20°C, and a high molecular weight polyurethane can be obtained. Also, when alcohol or amine is present as a stabilizer, the isocyanate groups of diisocyanate are protected, and self-polymerization of diisocyanate by heating (uretidionation, isocyanuration, etc.) and side reactions between diisocyanate and amide-based solvents at high temperatures can be suppressed, and a high molecular weight polyurethane solution that does not gel can be obtained. The viscosity of the polyurethane solution thus obtained is low and can be suitably used as a binder resin for coating agents, inks, adhesives, etc.

[0054] Using a polyurethane resin solution containing a synthetic solvent (C) produced in one embodiment, this is added to water, and the polyurethane resin is dispersed in water to produce a polyurethane dispersion (PUDs). PUDs are widely used in environmentally friendly low-VOC type water-based paints, adhesives, ink binders, coating agents, etc. Since the organic solvent contained in PUDs is required to have excellent water solubility and safety, the resin synthesis solvent (C) is considered to be optimal as a solvent for synthesizing polyurethane resins for PUDs. PUDs containing the resin synthesis solvent (C) have excellent storage stability because the isocyanate groups are protected by a stabilizer (D), and even after long-term storage, no two-layer separation or generation of insoluble matter (gelation) occurs in the dispersion liquid, and it can be stored in a wide temperature range of -20 to 80°C. Also, since the amide groups of the amide-based solvent (A) in the resin synthesis solvent (C) have good adhesion to various base materials from rubber, plastic to metal, PUDs are used in steel plate treatment agents for various steel plates such as hot-dip galvanized steel plates, electro-galvanized steel plates, hot-rolled steel plates, cold-rolled steel plates, etc., rubber coating agents, and coating agents and primers for films and substrates such as polyethylene terephthalate, polycarbonate, polyacrylic, polyvinyl chloride, polyamide, etc. The polyurethane resin produced in the present invention can be made into a high molecular weight, and the viscosity of the PUDs prepared therefrom can be arbitrarily adjusted according to the purpose, and it is applicable to various printing styles such as inkjet printing, screen printing, flexographic printing, gravure printing, etc., and can be used as a binder for printing ink on textiles (dyeing), films, sheets, etc.

[0055] The polyimide precursor solution (also referred to as polyamic acid solution or resin varnish) produced using the resin synthesis solvent (C) of the present embodiment has good stability during long-term storage (transportation and storage) and during use (manufacture of polyimide molded articles). The polyimide precursor solution obtained using the resin synthesis solvent (C) can be used as a coating liquid for forming polyimide molded articles or polyamide-imide molded articles, ink, insulating protective film, conductive ink, photosensitive resin, heat-resistant paint, etc. as a binder resin. Further, as the coating liquid for forming a polyimide molded article, for example, after forming a coating film having a desired thickness on a metal or glass substrate by a normal film-forming method (spin coating method, dip coating method, solvent casting method, slot die coating method, spray coating method, roll coating method, etc.), stepwise heating imidization is performed to form a polyimide film, polyimide sheet, polyamide-imide heat-resistant coating film, lubricating coating film, adhesive film for metal bonding, liquid crystal alignment film, etc. It can be used for the molding of molded articles.

[0056] Using the resin synthesis solvent (C) of the present embodiment, a polyimide film can be produced. The production method is not particularly limited, but using a polyimide varnish (polyimide precursor solution, partially imidized polyimide precursor solution) or polyimide resin solution (solution of soluble polyimide resin) synthesized using the resin synthesis solvent (C), after forming a coating film on a metal or glass substrate, a method of imidizing by stepwise heat treatment at a temperature of 100°C to 500°C in a high-temperature convection oven or the like can be mentioned. The heat treatment is performed in an inert gas atmosphere such as nitrogen for 10 to 60 minutes at 100°C to 300°C, 30 to 60 minutes at 300°C to 400°C, and 5 to 30 minutes at 400°C to 500°C, preferably 10 to 30 minutes at 100°C to 150°C, 10 to 30 minutes at 220°C to 250°C, 30 minutes at 350°C, and 10 minutes at 450°C. The polyimide film heat-treated at such a temperature and time can remove the solvent stepwise and completely, and has high transparency and high heat resistance.

[0057] Polyimide particles can be produced using the solvent (C) for resin synthesis of this embodiment. The production method is not particularly limited, but while stirring the polyimide varnish (polyimide precursor solution, partially imidized polyimide precursor solution) synthesized using the solvent (C) for resin synthesis, it is heated stepwise at a temperature of 50°C to 300°C to imidize and insolubilize the polyimide particles for dispersion and precipitation, and adding the polyimide varnish synthesized using the solvent (C) for resin synthesis into a high-boiling nonpolar solvent (poor solvent), and heating stepwise at a temperature of 50°C to 300°C while irradiating with ultrasonic waves or while stirring to imidize and insolubilize the polyimide particles for dispersion and precipitation. Examples of the high-boiling nonpolar solvent include xylene, acetophenone, ethyl benzoate, benzyl benzoate, tetralin, etc. Here, the stepwise heating at 50°C to 300°C means heating at 50°C to 200°C for 30 to 120 minutes and at 200°C to 300°C for 10 to 60 minutes, preferably heating at 70°C for 60 minutes, at 120°C for 60 minutes, and at 240°C for 30 minutes. The polyimide particles produced by these methods are preferably heat-treated at 350°C for 120 minutes after being obtained as a powder by centrifugation or vacuum drying treatment.

[0058] The polyimide particles obtained by the production method of the present invention have characteristics such as high heat resistance, solvent resistance (chemical resistance), and excellent electrical insulation similar to the polyimide resin, and are widely used in high-tech industries such as the electric and electronic industry technology field and the aerospace technology field. For example, application development to composite materials such as powder toner additives for image formation, coating materials for electrical insulation parts, molding fillers, electric and electronic materials such as liquid crystal spacers, and additives for heat-resistant paints and lubricants is expected.

[0059] By using the solvent (C) for resin synthesis of the present invention, high-quality polyimide varnish, polyamideimide varnish, polyesterimide varnish, polyetherimide varnish, polyurethane resin varnish, polyamide resin varnish, polyacrylic resin varnish, and fluororesin varnish can be obtained. Further, by appropriately heat-treating and molding these varnishes, high-quality polyimide-based, polyamideimide-based, polyesterimide-based, polyetherimide-based, polyurethane-based, polyamide-based, polyacrylic-based, and fluorine-based resins, films, particles, etc. can be obtained. Molded articles such as these resins, films, and particles are polyimide films and polyimide sheets such as flexible electronic substrate films, copper-clad laminated films, laminate films, electrical insulation films, porous films for fuel cells, separation films, etc., insulating coatings, heat-resistant coatings, IC packages, adhesive films, liquid crystal alignment films, resist films, planarization films, microlens array films, wire coating films, optical fiber coating films, etc. polyimide coatings, drive belts, belt members such as belts for electrophotographic image forming apparatuses (for example, intermediate transfer belts, transfer belts, fixing belts, conveying belts), etc. can be suitably used.

Examples

[0060] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, "parts", "%", and " / " are all based on mass unless otherwise specified.

[0061] The materials used in the Examples and Comparative Examples are as follows. (A) Amide-based solvent A-1: N-Butyl-2-pyrrolidone A-2: 3-Methoxy-N,N-dimethylpropanamide (manufactured by KJ Chemicals, registered trademark "KJCMPA") A-3: 3-Butoxy-N,N-dimethylpropanamide (manufactured by KJ Chemicals, registered trademark "KJCBPA") A-4: 3-Lauroxy-N,N-dimethylpropanamide A-5: 3-Methoxy-N,N-diethylpropanamide A-6: 3-Ethoxy-N-phenylpropanamide A-7: 3-Methoxy-N-cyclohexylpropanamide A-8: N,N-Diethylbutanamide A-9: N-Propanoylmorpholine A-10: 4-(3-Methoxypropionyl)morpholine A-11: N,N-Diisopropylacetamide A-12: 3-Isopropoxy-N,N-dimethylpropanamide (B) Reaction accelerator B-1: Tributylamine B-2: Triethylenediamine b1-1: (Methoxyethyl)diphenylamine b1-2: N,N-Dimethyldimethoxymethanamine b2-1: Methyl dimethylaminopropionate b2-2: Butyl dibutylaminopropionate b2-3: Methyl 3-methoxypropionate b3-1: Dibutylamino-N,N-dimethylpropionamide b3-2: Morpholinopropyl morpholide b3-3: Dibutylamino-N,N-dimethylpropionamide b3-4: N,N-Dimethylpropionamide (D) Stabilizer D-1: Water D-2: Methanol D-3: Isopropyl alcohol D-4: Diethylamine D-5: Pyrrolidine (E) Ionic liquid E-1: Tetrabutylammonium trifluoromethanesulfonate E-2: 1-Methyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide (F) Other solvents F-1: 1,3-Dimethyl-2-imidazolidinone F-2: Dimethyl sulfoxide F-3: γ-Valerolactone F-4: γ-Butyrolactone F-5: N-Formylmorpholine F-6: 4-Acetylmorpholine F-7: Dipropylene glycol dimethyl ether F-8: 4-Methyltetrahydropyran F-9: Cyclopentyl methyl ether F-10: Xylene

[0062] Example 1 (Synthesis and Evaluation of Polyimide Precursor Solution) Into a 1000 mL four-necked flask equipped with a stir bar, thermometer, dropping funnel, and nitrogen gas inlet tube, 350 g of C-1 (shown in Table 1) as a solvent and 25.0 g (125 mmol) of 4,4'-diaminodiphenyl ether (ODA) as a diamine compound were charged. After stirring at room temperature for 30 minutes while passing nitrogen gas to obtain a colorless, transparent solution, the temperature of the solution was raised to 80 °C, and 37.8 g (128 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as an acid dianhydride was slowly added while maintaining 80 °C. After continuing stirring at 80 °C for another 1 hour, it was cooled to room temperature, and 5 g of solvent C-1 was added so that the solid content concentration became 15% by mass, obtaining a colorless, transparent, viscous polyimide precursor solution (varnish). The transparency and presence or absence of coloring of the obtained varnish were visually observed, viscosity measurement and number average molecular weight analysis of the polyimide precursor were performed by the following methods, and the results are shown in Table 1. Also, after storing the obtained varnish at 40 °C for 30 days, its viscosity was measured, the viscosity change rate over time was calculated by the following formula, and the viscosity after storage and the viscosity change rate over time are shown in Table 1. Viscosity change rate over time (%) = (Viscosity after 30 days - Initial viscosity) / Initial viscosity × 100%

[0063] (Viscosity Measurement) Using a cone and plate viscometer (manufactured by Toki Sangyo Co., Ltd., RE550 type viscometer), the viscosity of the varnish was measured at 25 °C according to JIS K5600-2-3.

[0064] (Number Average Molecular Weight) Using the Hitachi High-Speed Liquid Chromatograph L6000 and the Hitachi Data Analyzer ATT-8, Gelpack GL-S300MDT-5 (two columns) was used as the column, and a solvent prepared by dissolving phosphoric acid (0.06 M) and lithium bromide (0.06 M) in a mixture of DMF / THF = 1 / 1 (L / L) was used as the mobile phase. Measurements were carried out under the conditions of a sample concentration of 0.2% and a flow rate of 1.0 ml / min, and the number average molecular weight was calculated using a calibration curve with polystyrene standard samples.

[0065] Preparation and Evaluation of Polyimide Film The obtained polyimide precursor solution (varnish) was applied to a glass substrate and heat-treated at 120°C for 10 minutes, 250°C for 10 minutes, and 350°C for 30 minutes under a nitrogen stream using a hot air dryer. The laminate of the polyimide film and the glass substrate was immersed in water for 10 minutes, the polyimide film was peeled off from the glass substrate, and dried at 80°C for 10 minutes using a hot air dryer to obtain a colorless and transparent polyimide film with a film thickness of about 10 μm. The appearance, light transmittance, strength, elongation, and linear thermal expansion coefficient of the obtained polyimide film were evaluated by the following methods, and the results are shown in Table 1.

[0066] (Appearance of Polyimide Film) Using the obtained polyimide film, visual observation was carried out to confirm the occurrence of defects such as foaming and cracking, and evaluation was performed according to the following criteria. ◎: Pale yellow, transparent, without foaming or cracking. 〇: Pale yellow to yellow, transparent, with slight foaming or cracking. △: Yellow or translucent, with several foaming or cracking. ×: Yellow to brown or opaque, with many foaming or cracking.

[0067] (Transparency) Under the conditions of a temperature of 23°C and a relative humidity of 50%, after the obtained polyimide film was allowed to stand overnight, the light transmittance was measured. The measurement was carried out in accordance with JIS K7105 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-2000). The higher the light transmittance, the better the transparency of the polyimide film.

[0068] (Tensile strength and elongation at break) The obtained polyimide film was cut into test pieces with a length of 100 mm and a width of 10 mm, and after standing for 24 hours under the conditions of a temperature of 23°C and a relative humidity of 50%, a tensile testing machine (manufactured by ORIENTEC, Tensilon RTA-100) was used, and the test was carried out with a gauge length of 50 mm, a tensile speed of 50 mm / min, and n = 5. The higher the tensile strength, the higher the strength of the polyimide film. Also, the higher the elongation at break, the higher the elongation of the polyimide film.

[0069] (Coefficient of linear thermal expansion) The obtained polyimide film was cut into test pieces with a length of 20 mm and a width of 2 mm, and after standing overnight under the conditions of a temperature of 23°C and a relative humidity of 50%, a thermomechanical analyzer (manufactured by SII NanoTechnology Inc., EXSTAR6000) was used to carry out the measurement under a nitrogen gas flow. The measurement method was to heat from room temperature to 220°C at a rate of 5°C / min, cool from 220°C to room temperature, and then heat for the second time at a rate of 5°C / min, and measure the average coefficient of linear expansion at 50°C to 200°C. The lower the average coefficient of linear expansion, the higher the heat resistance and dimensional stability.

[0070] Examples 2 to 12 and Comparative Examples 1 to 6 In Examples 2 to 12, a polyimide precursor solution (varnish) with a solid content concentration of 15% by mass was synthesized and further a polyimide film was produced in the same manner as in Example 1, except that the diamine component, acid dianhydride component, solvent (C-2 to C-12), and other components described in Tables 1 and 2 were used. The obtained varnish and film were evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2. Also, in Comparative Examples 1 to 6, a polyimide precursor solution (varnish) was synthesized and a polyimide film was produced in the same manner as in Example 1, using the diamine component, acid dianhydride component, solvent, and other components described in Table 3. The obtained varnish and film were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

[0071]

Table 1

[0072]

Table 2

[0073]

Table 3

[0074] As can be seen from the results of the examples and comparative examples shown in Tables 1 to 3, the solvent (C) for resin synthesis according to the embodiment of the present invention contains an amide solvent (A) and a reaction accelerator (B), thereby enabling the reaction between a diamine compound and an acid dianhydride to proceed quickly and stably, and a polyimide precursor solution (varnish) with high transparency, colorlessness, and low viscosity can be produced. Also, the rate of change over time of the viscosity of the obtained varnish is extremely low, and it can cope with long-term storage and transportation. Furthermore, it can be seen that the polyimide film obtained using these varnishes has high transparency, high light transmittance, low colorability, and is excellent in strength, elongation, heat resistance, and dimensional stability. The effect of the present invention is due to the synergistic effect of the excellent dissolving power of the amide solvent (A) which is a constituent component of the solvent (C) for resin synthesis and the reaction acceleration by the reaction accelerator (B), and it cannot be obtained by using only the amide solvent (A) or a combination of the reaction accelerator (B) and other solvents.

[0075] Example 13 (Synthesis of polyamideimide precursor solution) Into a 3 L four-necked flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen gas inlet tube, 117.6 g (0.6 mol) of trimellitic anhydride (TMA), 128.8 g (0.4 mol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 250.2 g (1.0 mol) of 4,4'-diphenylmethane diisocyanate (MDI), and 500 g of Solvent C-13 (shown in Table 4) were charged, and the temperature was raised to 120 °C with stirring and reacted at 120 °C for 6 hours. After completion of the reaction, the reaction solution was cooled to 80 °C and diluted with Solvent C-13 (660 g) so that the solid content concentration became 30% by mass to obtain a colorless and transparent polyamideimide precursor solution (varnish). The viscosity of the obtained precursor solution and the number average molecular weight of the precursor were measured by the same method as described above, and the results are shown in Table 4.

[0076] Examples 14 to 24 and Comparative Examples 7 to 12 In Examples 14 to 24, a polyamide-imide precursor solution was synthesized in the same manner as in Example 13, except that the acid dianhydride component, diisocyanate component, solvent (C-14 to C-24), and other components described in Tables 4 and 5 were used. Also, in Comparative Examples 7 to 12, a polyamide-imide precursor solution was synthesized in the same manner as in Example 13 using the acid dianhydride component, diisocyanate component, solvent, and other components described in Table 6. The viscosities of the obtained various precursor solutions and the number-average molecular weights of the precursors were measured by the same method as described above, and the results are shown in Tables 4 to 6.

[0077] Preparation and Evaluation of Coating Films The obtained polyamide-imide precursor solution (varnish) was used as a test paint and applied onto an aluminum substrate or copper foil with a thickness of 1.0 mm so that the dry film thickness was approximately 5 μm, followed by pre-drying at 80°C for 20 minutes and firing at 400°C for 10 minutes to obtain a coating film. Using the obtained coating film, the adhesion, flex resistance, acid resistance, alkali resistance, and steam resistance were evaluated, and the results are shown in Tables 4 to 6.

[0078] (Adhesion) According to JIS-K5600, 100 squares of 1 mm were made on the coating film, and a peel test was performed using an adhesive tape. The number of remaining squares was counted, and the adhesion was evaluated according to the following criteria. ◎: No peeling for 100 squares 〇: No peeling for 95 - 99 squares △: No peeling for 70 - 94 squares ×: No peeling for 0 - 69 squares

[0079] (Flex Resistance) When bending the coating film (with an aluminum plate) with the coated surface facing outward, the aluminum plate used for coating was sandwiched at the bending part, and the flex resistance was evaluated according to the following criteria based on the number of plates sandwiched when cracks appeared in the bending part. ◎: 0 plates 〇: 1 - 2 plates △: 3 - 5 plates ×: 6 or more plates

[0080] (Acid Resistance) A test piece with the non-coated surface of the coating film (with an aluminum plate) protected by an adhesive tape was immersed in a 5% sulfuric acid solution, left standing at room temperature for 1 week, and then the state of the coating film was visually observed, and the acid resistance was evaluated according to the following criteria. ○: No change △: Blisters are visible ×: The coating film peels off

[0081] (Alkali resistance) A test piece with the non-coated surface of the coating film (with an aluminum plate) protected by an adhesive tape was immersed in a 5% sodium hydroxide solution, left standing at room temperature for 1 week, and then the state of the coating film was visually observed, and the alkali resistance was evaluated according to the following criteria. ○: No change △: Blisters are visible ×: The coating film peels off

[0082] (Steam resistance) The coating film (with an aluminum plate) was brought into contact with steam at 120 °C pressurized to 2 atm in an autoclave for 100 hours, and then the adhesion was evaluated in the same manner as above. The higher the adhesion, the higher the steam resistance was evaluated.

[0083]

Table 4

[0084]

Table 5

[0085]

Table 6

[0086] As can be seen from the results of the examples and comparative examples shown in Tables 4 to 6, the solvent (C) for resin synthesis, which is an embodiment of the present invention, contains an amide-based solvent (A) and a reaction accelerator (B). When the diisocyanate compound reacts with the acid dianhydride, the reaction can proceed stably, and the reaction rate is high. A polyamide-imide precursor solution (varnish) with high transparency, colorless, and low viscosity can be produced. Also, the rate of change over time of the viscosity of the obtained varnish is extremely low, and it can cope with long-term storage and transportation. Furthermore, by applying these varnishes onto a metal substrate and performing a baking operation at a high temperature of 300°C to 550°C, a high-performance coating film having excellent adhesion, flexural resistance, acid resistance, alkali resistance, and steam resistance can be obtained. The effect of the present invention is due to the synergistic effect of the excellent dissolving power of the amide-based solvent (A), which is a constituent component of the solvent (C) for resin synthesis, and the reaction acceleration by the reaction accelerator (B), and cannot be obtained by using only the amide-based solvent (A) or a combination of the reaction accelerator (B) and other solvents. Since the coating film thus obtained has heat resistance above the baking temperature, the various polyamide-imide precursor solutions (varnishes) obtained in the present invention can be suitably used as heat-resistant paints.

[0087] Example 25 (Synthesis of Polyurethane Resin Solution) Into a 2 L four-necked flask equipped with a stirrer, a condenser, and a thermometer, 150.0 g (0.05 mol) of polypropylene glycol (PPG), 100.0 g (0.05 mol) of polyester polyol (PEs), 62.6 g (0.25 mol) of 4,4'-diphenylmethane diisocyanate (MDI), and 800 g of Solvent C-25 (shown in Table 7) were charged. The temperature was raised to 70°C with stirring and reacted at 70°C for 2 hours to obtain a prepolymer. Next, 9.3 g (0.15 mol) of ethylene glycol (EG) was added and reacted at 60°C for 3 hours. The reaction solution was cooled to room temperature and diluted with Solvent C-25 (490 g) so that the solid content (polyurethane resin) concentration became 25.0 mass% to obtain a polyurethane resin solution as a colorless and transparent solution. The viscosity of the obtained resin solution and the number average molecular weight of the resin were measured by the same method as described above and are shown in Table 7.

[0088] Examples 26 to 36 and Comparative Examples 13 to 18 Except for changing to the conditions described in Tables 7 to 9, the polyurethane resins in Examples 26 to 36 and Comparative Examples 13 to 18 were synthesized in the same manner as in Example 25. The viscosities of the obtained various resin solutions and the number average molecular weights of the resins were measured by the same method as described above and are shown in Tables 7 to 9.

[0089] Using the obtained polyurethane resin solution, a coating film was prepared by the following method. The tensile strength (breaking strength) and tensile elongation (breaking elongation) of the coating film were measured by the same tensile test as described above and are shown in Tables 7 to 9.

[0090] (Water vapor permeability test and water pressure resistance test) Using the obtained polyurethane resin solution, it was applied onto nylon taffeta subjected to water repellent treatment with a roll-on knife coater so that the thickness after drying was 40 μm, and coagulated in water for 2 minutes. Further, it was immersed in warm water at 50 °C for 3 minutes for washing, and dried at 150 °C for 1 minute to obtain a moisture permeable and waterproof fabric having a polyurethane resin film. Using the obtained moisture permeable and waterproof fabric, the water vapor permeability was measured based on JIS L-1099 (Method A-1), and the water pressure resistance was measured based on JIS L-1092. These measurement results are shown in Tables 7 to 9.

[0091]

Table 7

[0092]

Table 8

[0093]

Table 9

[0094] As can be seen from the results shown in Tables 7 to 9, the solvent (C) for resin synthesis according to the embodiment of the present invention contains an amide solvent (A) and a reaction accelerator (B), thereby enabling the reaction between a polyol and a diisocyanate to proceed stably, and a polyurethane resin having a high molecular weight can be obtained, and a highly transparent and colorless polyurethane resin solution can be produced. Further, the rate of change of the viscosity of the obtained polyurethane resin solution with time is extremely low, and it can cope with long-term storage and transportation. Furthermore, by applying these polyurethane resin solutions onto a release paper or a plastic sheet, a coating film having high strength and high elongation can be obtained, and by applying it onto nylon taffeta, a water-resistant product such as a moisture-permeable waterproof fabric having both moisture permeability and water resistance can be produced. The effect of the present invention is due to the synergistic effect of the excellent dissolving power of the amide solvent (A) which is a constituent component of the solvent (C) for resin synthesis and the reaction acceleration by the reaction accelerator (B), and it cannot be obtained by using only the amide solvent (A) or a combination of the reaction accelerator (B) and other solvents. In addition, since the polyurethane resin obtained in the present invention has excellent water resistance, various polyurethane dispersions (PUDs) can be produced by dispersing it in water.

[0095] Examples 37 to 46 (lubricating paint) and Comparative Examples 19 to 24 Using various varnishes (polyimide precursor solutions, polyimide amide precursor solutions) obtained in Examples 1 to 24 and Comparative Examples 1 to 12, they were mixed with the solid lubricants and additives shown in Tables 10 and 11, and diluted with the solvents used in each varnish so that the solid content concentration became 15% by mass, and a lubricating paint was prepared. Using the prepared lubricating paint, the paintability and coatability were evaluated by the following methods, and the results are shown in Table 10. Further, a lubricating coating film was prepared from the lubricating paint by the following method, and the abrasion resistance and adhesion were evaluated, and the results are shown in Tables 10 and 11. In the table, "MoS2" is molybdenum disulfide (manufactured by Sumitomo Lubricant Co., Ltd., Molypowder PS, density 4.8 g / cm 3 )), "PTFE" is polytetrafluoroethylene (manufactured by Central Glass Co., Ltd., Cefralube), and "graphite" is flaky graphite W-5 (manufactured by Ito Graphite Industry Co., Ltd., density 2.2 g / cm 3) The "epoxy resin" refers to a novolac-type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., Epicoat 152).

[0096] (Paintability) Regarding the prepared lubricating paint, the dispersion state of the solid lubricant and the presence or absence of aggregation of the resin varnish (polyimide varnish, polyamide-imide varnish) were visually confirmed, and evaluation was performed according to the following criteria. ◎: No aggregates were observed in the lubricating paint during the mixing process and after preparation, the resin varnish was dissolved, and it was homogeneous (practical level). ○: The solid lubricant was not uniformly dispersed during the mixing process, but finally there were no aggregates in the lubricating paint, the varnish resin was dissolved, and it was homogeneous (practical level). ×: The varnish resin in the lubricating paint during the mixing process or after preparation caused gelation due to aggregation.

[0097] (Coatability) Using the prepared lubricating paint, a 10-μm-thick film was applied to the surface of a SUS316 disk (diameter 100 mm, thickness 5 mm) by spray coating. The state of the coated surface was visually confirmed, and evaluation was performed according to the following criteria. ○: The coated surface was uniform and good (practical level). ×: The coated surface was non-uniform, with undulations and unevenness.

[0098] (Sliding characteristics (wear resistance)) Using the prepared lubricating paint, spray coating was performed on the surface of a SUS316 disk (diameter 100 mm, thickness 5 mm) preheated to 90 °C so that the thickness of the coating film was 10 μm. Then, it was dried at 100 °C for 10 minutes, at 200 °C for 10 minutes, and further heated at 400 °C for 1 hour to obtain a coating film test piece, and a reciprocating sliding wear test was performed using a steel ball (SUJ2) as the counter material. The sliding test conditions were 15 mm / s for 100 cycles. After the sliding test, the wear depth of the coating film was measured, and evaluation was performed according to the following criteria. ◎: The wear depth of the most worn part was 3 μm or less (practical level). ○: The wear depth of the most worn part exceeded 3 μm and was 5 μm or less (practical level). △: The wear depth of the most worn part exceeds 5 μm and is 7 μm or less (practical level). ×: The wear depth of the most worn part is 7 μm or more.

[0099] (Adhesion) The prepared lubricating paint was spray-coated on the surface of a SUS316 plate (diameter 50 mm × 50 mm, thickness 5 mm) with the coating conditions fixed so that the coating thickness was 10 μm. The coated surface was dried at 100 °C for 10 minutes, at 200 °C for 10 minutes, and further heated at 400 °C for 1 hour to form a coating film. According to JIS-K5600, 100 squares of 1 mm were made on the coating film, and a peeling test was carried out with an adhesive tape. The number of remaining squares was counted, and the adhesion was evaluated according to the following criteria. ◎: No peeling among 100 〇: No peeling among 95 - 99 △: No peeling among 70 - 94 ×: No peeling among 0 - 69

[0100]

Table 10

[0101]

Table 11

[0102] Examples 47 - 52 (adhesive) and Comparative Examples 25 - 28 Using a tabletop coater (Coater TC-1, manufactured by Mitsui Electric Precision Co., Ltd.), various varnishes (polyimide precursor solution, polyimide amide precursor solution) obtained in Examples 1 to 24 and Comparative Examples 1 to 12 were applied to one side of a polyimide film (manufactured by DuPont, Kapton ENS, length × width × thickness = 200 mm × 300 mm × 25 μm) with a bar coater (RDS #15) so that the thickness after drying was 35 μm, and dried at 100°C for 10 minutes and then at 200°C for 10 minutes to obtain a coverlay film with an adhesive layer thickness of 35 μm. The obtained coverlay film (adhesive layer side) was placed on a copper foil from which the surface rust-preventive metal layer had been removed (polyimide film / adhesive layer / copper foil), pressed under the conditions of a temperature of 400°C, a pressure of 1 MPa, and a time of 1 minute, and then heated in an oven at a temperature of 400°C for 24 hours to obtain a laminate having a three-layer structure of polyimide film / adhesive layer / copper foil.

[0103] A polyimide copper-clad laminate (manufactured by Nippon Steel Chemical Co., Ltd., Espanex MC18-25-00FRM) was circuit-processed to prepare a printed circuit board on which a circuit with a wiring width / wiring pitch (L / S) = 1 mm / 1 mm was formed. The above coverlay film (adhesive layer side) was placed on the circuit surface of the printed circuit board (polyimide film / adhesive layer / printed circuit board / adhesive layer / polyimide film), pressed under the conditions of a temperature of 400°C, a pressure of 1 MPa, and a time of 1 minute, and then heated in an oven at a temperature of 400°C for 24 hours to obtain a wiring board provided with a coverlay film (a laminate having a five-layer structure of polyimide film / adhesive layer / printed circuit board / adhesive layer / polyimide film).

[0104] The adhesive strength of the obtained laminate was measured by the following method, evaluated according to the following criteria, and the results are shown in Table 12. Also, the solder heat resistance (dry and moisture-resistant) of the obtained wiring board was evaluated by the following method, and the results are shown in Table 12.

[0105] (Adhesive strength) The laminate was cut into test pieces with a width of 10 mm and a length of 100 mm. Using a tensile testing machine (manufactured by Toyo Seiki Co., Ltd., Strograph-M1), the polyimide film and the copper foil were peeled off at a speed of 50 mm / min in the 180° direction, and the peel strength was taken as the adhesive strength and evaluated according to the following criteria. ◎: Above 0.35 kN / m ○: Above 0.2 kN / m and less than 0.35 kN / m ×: Less than 0.2 kN / m

[0106] (Solder heat resistance (dry)) After leaving the obtained wiring board in a thermo-hygrostat chamber at a temperature of 105 °C and a relative humidity of 50% for 1 hour, it was immersed in a heated solder bath for 10 seconds, and the adhesion state was observed to check for defects such as foaming, swelling, and peeling, and evaluated according to the following criteria. ○: No defects such as foaming, swelling, and peeling even at a solder bath temperature of 300 °C. ×: Defects such as foaming, swelling, and peeling are present at a solder bath temperature of less than 300 °C.

[0107] (Solder heat resistance (humidity-resistant)) After leaving the obtained wiring board in a thermo-hygrostat chamber at a temperature of 85 °C and a relative humidity of 85% for 24 hours, it was immersed in a heated solder bath for 10 seconds, and the adhesion state was observed to check for defects such as foaming, swelling, and peeling. ○: No defects such as foaming, swelling, and peeling even at a solder bath temperature of 280 °C. ×: Defects such as foaming, swelling, and peeling are present at a solder bath temperature of less than 280 °C.

[0108]

Table 12

[0109] Examples 53 to 58 (photosensitive resin) and Comparative Examples 29 to 32 Each of the various varnishes (polyimide precursor solutions) obtained in Examples 1 to 12 and Comparative Examples 1 to 6 was weighed to a solid content of 10 g, and 1.6 g of 1,2-naphthoquinonediazide-5-sulfonic acid ester of α,α,α'-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene (TS150-A, manufactured by Toyo Gosei Co., Ltd.) as a quinonediazide compound and 0.42 g of WPAG-567 (manufactured by Fuji Film Wako Pure Chemical Corporation) as a photoacid generator were added to obtain a photosensitive polyimide precursor composition. The obtained photosensitive polyimide precursor composition was applied onto a 6-inch silicon wafer so that the film thickness after pre-baking would be 14 to 16 μm, and pre-baked at 120 °C for 2 minutes using a hot plate (coating and developing apparatus Mark-7 manufactured by Tokyo Electron Limited) to obtain a photosensitive resin film. Next, a reticle with a pattern was set in an exposure machine (i-line stepper DSW-8000 manufactured by GCA), and the obtained photosensitive resin film with the exposure time changed at an intensity of 365 nm was exposed with i-line (365 nm) of a mercury lamp. Using a developing apparatus Mark-7 manufactured by Tokyo Electron Limited, a 2.38% aqueous solution of tetramethylammonium hydroxide was sprayed onto the exposed film for 10 seconds at 50 rotations, then left standing for 40 seconds at 0 rotations, sprayed again for 10 seconds, left standing for 40 seconds, then rinsed with water at 400 rotations and spin-dried at 3000 rotations for 10 seconds to obtain a developed photosensitive resin film. The developed photosensitive resin film was heat-treated at 140 °C for 30 minutes under a nitrogen stream (oxygen concentration 20 ppm or less) using an inert oven INH-21CD manufactured by Koyo Thermo System Co., Ltd., then heated up to 350 °C over 1 hour and heat-treated at 350 °C for 1 hour to produce a cured film.

[0110] The storage stability, sensitivity and resolution in pattern processing, shrinkage rate of the film thickness before and after heat treatment, and adhesion characteristics of the cured film of the obtained photosensitive polyimide precursor composition were evaluated by the following methods, and the results are shown in Table 13.

[0111] (Storage stability) After preparing the photosensitive polyimide precursor composition, the absolute value of the difference between the optimum exposure time of the one immediately pattern-processed and the optimum exposure time of the one pattern-processed after being left standing at 23 °C for 2 weeks was calculated and evaluated according to the following criteria. ◎: The absolute value of the difference is 100 msec or less ○: The absolute value of the difference is more than 100 msec and 200 msec or less ×: The absolute value of the difference is more than 200 msec

[0112] (Sensitivity) After exposure and development, the exposure time (optimal exposure time) at which a 50-μm line-and-space pattern (1L / 1S) is formed with a 1:1 width was determined and evaluated according to the following criteria. The shorter the optimal exposure time, the higher the sensitivity. ◎: The optimal exposure time is 700 msec or less ○: The optimal exposure time is more than 700 msec and 800 msec or less ×: The optimal exposure time is more than 800 msec

[0113] (Resolution) After exposure and development, the minimum pattern dimension at the optimal exposure time was measured and evaluated according to the following criteria. The smaller the minimum pattern dimension, the higher the resolution. ◎: The minimum pattern dimension is 5 μm or less ○: The minimum pattern dimension is more than 5 μm and 10 μm or less ×: The minimum pattern dimension is more than 10 μm

[0114] (Shrinkage rate) Using Lambda Ace STM-602 manufactured by Dainippon Screen Mfg. Co., Ltd., the film thickness of the photosensitive resin film after development (refractive index 1.629) and the film thickness of the cured film (refractive index 1.773) were measured, and the shrinkage rate of the film thickness was calculated according to the following formula and evaluated according to the following criteria. Shrinkage rate (%) = (film thickness after development - film thickness after curing) ÷ film thickness after development × 100 ◎: The shrinkage rate is 25% or less ○: The shrinkage rate is more than 25% and 30% or less ×: The shrinkage rate is more than 30%

[0115] (Adhesion property) A photosensitive polyimide precursor composition was applied onto a silicon substrate so that the film thickness after pre-baking was 10 μm, and then pre-baked at 120 °C for 2 minutes using a hot plate (coating and developing apparatus Mark-7 manufactured by Tokyo Electron Limited). Thereafter, heat treatment was performed at 170 °C for 30 minutes and at 350 °C for 1 hour in an air atmosphere to obtain a polyimide film. After performing a pressure cooker test (PCT) treatment on the polyimide film under saturated conditions at 120 °C and 2 atmospheres for 400 hours, 100 2-mm square grids were prepared, and a peel test was performed using an adhesive tape. The number of peeled square grids was counted, and the adhesion characteristics were evaluated according to the following criteria. ○: The number of peeled pieces is less than 30 ×: The number of peeled pieces is 30 or more

[0116]

Table 13

[0117] Examples 59 to 64 (ink compositions) and Comparative Examples 33 to 36 Various varnishes (polyimide precursor solutions, polyimide amide precursor solutions) obtained in Examples 1 to 24 and Comparative Examples 1 to 12 were used as ink compositions as they were, and the warpage, solvent resistance, plating resistance, flame retardancy, and printability after printing (coating, drying) were evaluated by the following methods and are shown in Table 14.

[0118] (Warpage) Various varnishes were applied onto a copper foil with a size of length × width × thickness = 50 mm × 50 mm × 13 μm so that the film thickness after drying was 10 μm. Thereafter, heat drying was performed in an oven under the conditions of a temperature of 400 °C and a time of 30 minutes to obtain a laminate in which a polyimide resin layer or a polyamideimide resin layer was laminated on the copper foil (substrate). The average value of the warpage amounts at the four corners of the laminate was determined and evaluated according to the following criteria. ◎: The average value of the warpage amount is 1 mm or less ○: The average value of the warpage amount is more than 1 mm and 2 mm or less ×: The average value of the warpage amount exceeds 2 mm

[0119] (Solvent resistance test) Each of the laminates (base material: copper foil) obtained in the above (warp) test was immersed in the solvents shown in Table 14 at room temperature for 5 minutes, and the state of the surface (resin layer) was visually observed and evaluated according to the following criteria. ◎: No change ○: Roughness or dissolution is observed on a part of the surface ×: Dissolution

[0120] (Plating resistance) Each of the laminates (base material: copper foil) obtained in the above (warp) test was subjected to electroless gold plating treatment in the following steps to obtain test specimens. Specifically, the laminate was sequentially immersed in the tanks of each step and then dried. The surface state of the obtained test specimen was visually observed and evaluated according to the following criteria. (Electroless gold plating treatment process) Degreasing treatment (acid degreasing = acid treatment), water washing, soft etching, water washing, desmear treatment, Palladium chloride catalysis, nickel (nickel nitrate) plating, Gold (potassium cyanide gold) plating, water washing, drying (Evaluation criteria) ◎: No change ○: Damage near the end ×: Granular plating adheres to the surface

[0121] (Flame retardancy) Various varnishes were applied onto a polyimide film (manufactured by Toray DuPont, Kapton 100H, thickness 25 μm) so that the film thickness after drying would be 10 μm. Thereafter, heating and drying were performed in an oven under the conditions of a temperature of 400 °C and a time of 30 minutes to obtain a laminate (base material: polyimide film) in which a polyimide resin layer or a polyamideimide resin layer was laminated on the polyimide film (base material). Regarding the obtained laminate, the flame retardancy was evaluated according to the following flammability classification in accordance with the vertical burning test (VTM) of UL94 film materials. ◎: V-0 ○: V-1 ×: V-2

[0122] (Printability) Various varnishes were printed on a polyimide film (manufactured by Toray DuPont, Kapton 100H, thickness 25 μm) through a stainless-steel metal mask with a thickness of 100 μm to form a line-and-space pattern with a line width of 500 μm and a space of 500 μm. Specifically, the metal mask was placed on the polyimide film and adhered closely. Various varnishes were spread thereon. After filling the liquid into the openings of the metal mask with a fluororesin spatula, the excess liquid was scraped off, and then the metal mask was slowly removed for printing. After printing, it was immediately held in a thermo-hygrostat at a humidity of about 100% and a temperature of 50 °C for 8 minutes. Further, it was heated in an oven under the conditions of a temperature of 400 °C and a time of 30 minutes to obtain a laminate (substrate: polyimide film) with a polyimide resin layer or a polyamide-imide resin layer having a thickness of 15 - 20 μm laminated on the polyimide film (substrate). The printability of the obtained laminate was evaluated according to the following criteria. ◎: No bleeding or smearing in the pattern. ○: The pattern can be recognized, but there is slight bleeding or smearing. ×: There is bleeding or smearing to the extent that the pattern cannot be confirmed.

[0123]

Table 14

[0124] As can be seen from the results of the examples and comparative examples shown in Tables 10 - 14, the polyimide precursor and the polyamide-imide precursor synthesized using the resin synthesis solvent (C) containing the amide-based solvent (A) and the reaction accelerator (B), which are embodiments of the present invention, can obtain these precursor solutions (resin varnishes) with low viscosity, high transparency, and high stability while having a high molecular weight. Such resin varnishes can be suitably used as various binder resins, lubricating coating films (lubricating paints), adhesives, photosensitive resins, and ink compositions.

Industrial Applicability

[0125] As described above, the solvent (C) for resin synthesis according to the embodiment of the present invention contains an amide-based solvent (A) and a reaction accelerator (B), and is suitable for the synthesis of polyimide, polyamideimide, polyesterimide, a polyimide-based copolymer composed of any one of their precursors and / or two or more precursors selected therefrom, and polyurethane resin. Resin varnishes such as polyimide varnish, polyamideimide varnish, and polyurethane resin varnish produced using the solvent for resin synthesis according to the embodiment of the present invention are suitably used as binder resins for various applications. The polyimide film obtained by molding also exhibits excellent physical properties and is used as a surface protection film or interlayer insulating film for semiconductor elements, an insulating layer or spacer layer for organic EL elements, a planarization film for thin film transistor substrates, an insulating film for organic transistors, a flexible printed circuit board, a substrate for flexible devices or liquid crystal display devices, a substrate for organic EL display devices, a substrate for electronic paper, a substrate for light receiving devices such as thin film solar cell substrates, etc. Furthermore, it can be suitably used as a binder for electrodes of lithium ion secondary batteries, an adhesive for semiconductors, etc. Also, since the polyimide precursor produced using the solvent for resin synthesis according to the embodiment of the present invention has excellent solubility in soluble polyimide, it is suitably used for the production of liquid crystal alignment agents.

Claims

1. A solvent (C) for resin synthesis containing 10 to 99.9999% by mass of an amide-based solvent (A) and 0.0001 to 5% by mass of a reaction accelerator (B), wherein the reaction accelerator (B) is an aliphatic or aromatic tertiary amine compound having one or more tertiary amino groups and one or more functional groups selected from an ether group, an ester group, and an amide group in the molecule, the amide-based solvent (A) is an alkoxy-N-substituted propanamide represented by the general formula (1), and the resin is any one resin selected from a polyimide precursor, a polyamideimide precursor, a polyimide resin, and a polyamideimide resin, the solvent (C) for resin synthesis. 【Chemical Formula 1】 (In the formula, R １ ~R ３ each independently represents a linear alkyl group having 1 to 22 carbon atoms, a branched alkyl group having 3 to 22 carbon atoms, an alkyl ether group having 2 to 22 carbon atoms, an alicyclic hydrocarbon having 3 to 22 carbon atoms, and an aromatic hydrocarbon having 6 to 22 carbon atoms, and R ４ represents a hydrogen atom or a methyl group. Further, R ２ and R ３ each independently represent a hydrogen atom (except when they are both hydrogen atoms), or together with the nitrogen atom carrying them, form a saturated 5- to 7-membered ring (including those having an oxygen atom).)

2. The solvent (C) for resin synthesis according to claim 1, wherein the reaction accelerator (B) is an aliphatic or aromatic tertiary amine compound represented by the general formula (2), having one or more tertiary amino groups in the molecule and further having one or more functional groups selected from an ether group, an ester group, and an amide group in the molecule. (In the formula, A, B, and C are each independently a linear alkyl group having 1 to 22 carbon atoms, a branched alkyl group or alkyl ether group having 3 to 22 carbon atoms, an alkyl ester group, an alkyl amide group, an alicyclic hydrocarbon having 3 to 22 carbon atoms, and an aromatic hydrocarbon having 6 to 22 carbon atoms, a substituent having an ether group represented by the general formula (3), a substituent having an ester group represented by the general formula (4), a substituent having an amide group represented by the general formula (5) (R in the formula ５ , R ７ and R ９ each represent a linear alkylene having 1 to 22 carbon atoms, a branched alkylene group or alkylene ether group having 3 to 22 carbon atoms, an alicyclic hydrocarbon having 3 to 22 carbon atoms, and an aromatic hydrocarbon having 6 to 22 carbon atoms. R ６ , R ８ , R １０ and R １１ represent a linear alkyl group having 1 to 22 carbon atoms, a branched alkyl group or alkyl ether group having 3 to 22 carbon atoms, an alkyl ester group, an alkyl amide group, an alicyclic hydrocarbon having 3 to 22 carbon atoms, and an aromatic hydrocarbon having 6 to 22 carbon atoms. Further, R １０ and R １１ may each independently be a hydrogen atom, and R １０ and R １１ may together with the nitrogen atom carrying them form a saturated 5- to 7-membered ring (including those having an oxygen atom).).). 【Chemical 2】 【Chemical Formula 3】 【Chemical Formula 4】 【Chemical Formula 5】

3. The solvent (C) for resin synthesis according to claim 1 or 2, further containing one or more solvents selected from the group consisting of an aromatic hydrocarbon-based solvent, a urea-based solvent, a lactone-based solvent, an ether-based solvent, a ketone solvent, an ester-based solvent, dimethyl sulfoxide, N-formylmorpholine, and 4-acetylmorpholine.

4. The solvent (C) for resin synthesis according to any one of claims 1 to 3, further containing one or more solvents selected from the group consisting of xylene, toluene, tetramethylurea, tetraethylurea, N,N-dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, α-acetyl-γ-butyrolactone, γ-valerolactone, δ-valerolactone, ethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, cyclopentyl methyl ether, 4-methyltetrahydropyran, acetophenone, acetylacetone, butyl acetate, ethyl benzoate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, ethyl acetoacetate, isoamyl acetate, n-pentyl acetate, ethyl propionate, 1,3-dioxolane, dimethyl sulfoxide, N-formylmorpholine, and 4-acetylmorpholine.

5. A method for producing a polyimide precursor or a polyamideimide precursor, which uses the solvent (C) for resin synthesis according to any one of claims 1 to 4, and mixes and polymerizes an acid dianhydride with a diamine and / or a diisocyanate, and a method for producing a polyimide or a polyamideimide by subjecting these precursors to thermal imidization.

6. Any one kind of resin varnish selected from a polyimide varnish and a polyamideimide varnish, which contains the solvent (C) for resin synthesis according to any one of claims 1 to 4.

7. A binder resin containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

8. An ink composition containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

9. A photosensitive resin composition containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

10. An adhesive resin composition containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

11. A resin composition for a lubricating coating film containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

12. A heat-resistant paint containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and one or more kinds of resin varnishes selected from a polyimide varnish and a polyamideimide varnish.

13. A method for producing a polyimide film, which uses a coating liquid containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and a polyimide varnish or a polyimide resin solution, forms a coating film on a substrate, and then performs stepwise thermal imidization.

14. A polyimide film obtained by heating a coating film containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and a polyimide varnish or a polyimide resin solution.

15. Polyimide particles obtained by heating a composition containing the solvent (C) for resin synthesis according to any one of claims 1 to 4 and a polyimide varnish.

16. A metal laminate comprising a coating film formed from the resin varnish according to claim 6 or the binder resin according to claim 7 and a metal substrate.

17. A metal laminate comprising the polyimide film according to claim 14 or the polyimide particles according to claim 15 and a metal substrate.

18. A wiring board containing the metal laminate according to claim 16 or 17.

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