JP2024015908A - Polyimide precursor solution and polyimide molding - Google Patents

Abstract

To provide a polyimide precursor solution capable of yielding a polyimide molding that excels in both thermal conductivity and tensile breaking strength.SOLUTION: A polyimide precursor solution contains a polyimide precursor, a β-alkoxypropionamide solvent, an amide group-bearing tertiary amine compound, and a carbon material.SELECTED DRAWING: None

Description

The present invention relates to a polyimide precursor solution and a polyimide molded article.

Patent Document 1 states, ``A polyimide resin containing two or more types of at least one of a component derived from a tetracarboxylic dianhydride and a component derived from a diamine compound, and a urea-based solvent and an alkoxy group. An endless belt having a polyimide resin layer containing at least one solvent selected from solvent group A consisting of amide-based solvents containing amide-based solvents and ester group-containing amide-based solvents in an amount of 50 ppm to 2000 ppm. .

Patent Document 2 states, ``A process for reacting an acid component and an amine component in a solvent containing at least a β-alkoxypropionamide (b) and an amide group-containing tertiary amine compound (c). A method for producing an alkali-soluble resin solution containing oxazole, polyamideimide, a precursor thereof, and/or a copolymer selected from two or more thereof, wherein the β-alkoxypropionamide (b) and an amide group-containing A method for producing an alkali-soluble resin solution containing 10 to 1,800 ppm of an amide group-containing tertiary amine compound (c) based on β-alkoxypropionamide (b) in a solvent containing at least a tertiary amine compound (c). is disclosed.

Japanese Patent Application Publication No. 2019-172974 Patent Publication No. 6900844

Polyimide molded articles molded using conventional polyimide precursor solutions containing only a polyimide precursor and a β-alkoxypropionamide solvent tend to have low thermal conductivity and tensile strength at break.
Therefore, in the present disclosure, compared to a polyimide precursor solution containing only a polyimide precursor and a β-alkoxypropionamide solvent, when a polyimide molded body is made using this solution, thermal conductivity and tensile strength at break are improved. It is an object of the present invention to provide a polyimide precursor solution that yields a polyimide molded article that is excellent in both aspects.

Specific means for solving the above problems include the following aspects.
<1> Polyimide precursor,
β-alkoxypropionamide solvent,
an amide group-containing tertiary amine compound;
carbon material;
A polyimide precursor solution containing.
<2> The polyimide precursor solution according to <1>, wherein the β-alkoxypropionamide solvent is a compound represented by the following general formula (A).

(In the general formula (A), R ¹ represents an alkyl group having 1 to 6 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. .)
<3> The compound represented by the general formula (A) is at least one of 3-methoxy-N,N-dimethylpropionamide and 3-n-butoxy-N,N-dimethylpropionamide, ＞The polyimide precursor solution described in ＞.
<4> The polyimide precursor solution according to <1>, wherein the amide group-containing tertiary amine compound contains a compound represented by the following general formula (B).

(In the general formula (B), R ¹ and R ² each independently represent an aldehyde group or an alkyl group having 1 to 5 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom, or , represents a monovalent organic group having an alkyl group having 1 or more and 5 or less carbon atoms.)
<5> The compound represented by the general formula (B) is at least one of 3-dimethylamino-N,N-dimethylpropionamide and N-[2-(dimethylamino)ethyl]-N-methylformamide. , the polyimide precursor solution according to <4> above.
<6> The polyimide precursor solution according to <1>, wherein the amide group-containing tertiary amine compound has a content of 10 ppm or more and 2000 ppm or less based on the total amount of the polyimide precursor solution.
<7> The polyimide precursor solution according to <1>, wherein the content of the amide group-containing tertiary amine compound relative to the carbon material is 0.01% by mass or more and 2% by mass or less.
<8> The polyimide precursor solution according to <1>, wherein the carbon material includes at least one selected from the group consisting of carbon black, graphene, and carbon nanotubes.
<9> The polyimide precursor solution according to <8>, wherein the carbon material has a structure of a granular hollow aggregate or a graphene mesosponge.
<10> The polyimide precursor solution according to <1>, wherein the carbon material has a content of 5% by volume or more and 20% by volume or less with respect to the polyimide precursor.
<11> The polyimide precursor solution according to <1>, wherein the carbon material has a content of 2% by mass or more and 1000% by mass or less with respect to the amide group-containing tertiary amine compound.
<12> The β-alkoxypropionamide solvent contains a compound represented by the following general formula (A),
The polyimide precursor solution according to <1> above, wherein the amide group-containing tertiary amine compound contains a compound represented by the following general formula (B).
<13> A polyimide molded body made of a heat-cured product of the polyimide precursor solution according to <1>.
<14> The polyimide molded article according to <13>, wherein the polyimide molded article is an endless belt.

According to the invention according to <1>, <2>, <3>, <4>, <5>, or <12>, a polyimide precursor solution containing only a polyimide precursor and a β-alkoxypropionamide solvent A polyimide precursor solution is provided that yields a polyimide molded article having better thermal conductivity and tensile strength at break than in other cases.
According to the invention according to <6>, the amide group-containing tertiary amine compound has lower thermal conductivity and tensile strength at break than when the content of the tertiary amine compound is less than 10 ppm or more than 2000 ppm based on the total amount of the polyimide precursor solution. A polyimide precursor solution from which a polyimide molded article excellent in both aspects can be obtained is provided.
According to the invention according to <7>, the amide group-containing tertiary amine compound has better thermal conductivity and tensile strength than when the content of the amide group-containing tertiary amine compound is less than 0.01% by mass or more than 2% by mass with respect to the carbon material. A polyimide precursor solution from which a polyimide molded article having both excellent breaking strength can be obtained is provided.
According to the invention according to <8>, there is provided a polyimide precursor solution that allows a polyimide molded body with excellent thermal conductivity to be obtained compared to a case where the carbon material is graphite.
According to the invention according to <9>, a polyimide precursor solution is provided that allows a polyimide molded article with excellent thermal conductivity to be obtained compared to a case where the carbon material is carbon black.
According to the invention according to <10>, the carbon material has excellent both thermal conductivity and tensile strength at break compared to a case where the content of the carbon material is less than 5% by volume or more than 20% by volume with respect to the polyimide precursor. A polyimide precursor solution from which a polyimide molded article can be obtained is provided.
According to the invention according to <11>, the carbon material has better thermal conductivity and tensile strength at break than when the content of the amide group-containing tertiary amine compound is less than 2% by mass or more than 1000% by mass. Provided is a polyimide precursor solution that yields a polyimide molded article that is excellent in both.
According to the invention according to <13>, compared to a polyimide precursor solution containing only a polyimide precursor and a β-alkoxypropionamide solvent, when formed into a polyimide molded article, thermal conductivity and tensile breaking strength are improved. A polyimide molded article excellent in both is provided.

Embodiments of the present invention will be described below. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

In the numerical ranges described step by step in this specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of another numerical range described step by step. good. Furthermore, in the numerical ranges described in this disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the Examples.

In this specification, each component may contain multiple types of corresponding substances.

In this specification, when referring to the amount of each component in a composition, if there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types present in the composition means the total amount of substances.

In this embodiment, the term "membrane" is a concept that includes not only what is generally called a "membrane" but also what is generally called a "film" and a "sheet."

<Polyimide precursor solution>
The polyimide precursor solution according to this embodiment is a polyimide precursor solution containing a polyimide precursor, a β-alkoxypropionamide solvent, an amide group-containing tertiary amine compound, and a carbon material.

Polyimide molded bodies are used for belts and the like of fixing members installed in image forming apparatuses.
A polyimide molded article can be obtained by applying a polyimide precursor solution containing a polyimide precursor onto an object to be coated and heat-treating the coating film formed.

In recent years, from the viewpoint of manufacturing with low environmental impact, β-alkoxypropionamide solvents have been used as solvents in polyimide precursor solutions. β-alkoxypropionamide solvents often contain an amide group-containing tertiary amine compound for reasons of manufacturing convenience. Conventional polyimide precursor solutions containing this β-alkoxypropionamide solvent and an amide group-containing tertiary amine compound tended to have both thermal conductivity and tensile strength at break when formed into polyimide molded products. . The reason for this is not necessarily clear, but it is inferred as follows.

The amide group-containing tertiary amine compound has the effect of promoting imidization of the polyimide precursor. Therefore, imidization progresses at a relatively early stage during film formation, and a polyimide molded body with uneven higher-order structure is likely to be obtained. As a result, there tends to be a portion where the thermal conductivity of the polyimide molded article is locally reduced. Furthermore, the tensile strength at break tends to decrease in locally brittle portions where the higher-order structure is uneven.

On the other hand, since the polyimide precursor solution according to the present embodiment has the above-mentioned structure, even when it is used to form a polyimide molded article, it has excellent both thermal conductivity and tensile strength at break. Although this mechanism of action is not necessarily clear, it is inferred as follows.

The polyimide precursor solution according to this embodiment further contains a carbon material in addition to the polyimide precursor, the β-alkoxypropionamide solvent, and the amide group-containing tertiary amine compound. As a result of intensive studies by the present inventors, we found that when a carbon material is mixed with an amide group-containing tertiary amine compound in the presence of a β-alkoxypropionamide solvent, which is an aprotic polar solvent, the carbon material becomes an amide group-containing tertiary amine compound. It was found that the affinity for amine compounds tends to be higher. Therefore, also during film formation, imidization tends to be moderately promoted by the interaction of the carbon material with the amide group-containing tertiary amine compound. Furthermore, when a polyimide molded product is formed, the presence of carbon material in the voids of the higher-order structure of the polyimide suppresses the formation of locally brittle portions. As a result, it is thought that even when formed into a polyimide molded article, it is excellent in both thermal conductivity and tensile strength at break.

(β-alkoxypropionamide solvent)
A β-alkoxypropionamide solvent is a propionamide compound having an alkoxy group at the β position (that is, *-CH ₂ -CH ₂ -C(=O)-N-R ^E1 ,R ^E2 , * is a linking site, R ^E1 and R ^E2 each independently represent a hydrogen atom or a monovalent organic group).
Since the β-alkoxypropionamide solvent has a high solubility of the polyimide precursor, it is possible to suitably adjust the concentration of the polyimide precursor contained in the polyimide precursor solution.
The β-alkoxypropionamide solvents may be used alone or in combination of two or more.

The β-alkoxypropionamide solvent is preferably a compound represented by the following general formula (A).

(In the general formula (A), R ¹ represents an alkyl group having 1 to 6 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. .)

When the β-alkoxypropionamide solvent is a compound represented by the above general formula (A), the β-alkoxypropionamide solvent has better solubility of the polyimide precursor.

In the general formula (A), the alkyl group having 1 to 6 carbon atoms represented by R ¹ includes a linear or branched alkyl group having 1 to 6 carbon atoms.
Examples of the linear alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, and n-hexyl group.
Examples of branched alkyl groups having 1 to 6 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-butyl group, -hexyl group.

In the general formula (A), R ¹ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and preferably represents a linear alkyl group having 1 to 6 carbon atoms, It is more preferable to represent a linear alkyl group having 1 to 5 carbon atoms, and even more preferably a linear alkyl group having 1 to 4 carbon atoms. In the general formula (A), when R ¹ is the above group, the solubility of the polyimide precursor is better.

In the general formula (A), the alkyl group having 1 to 6 carbon atoms represented by R ² to R ³ includes a linear or branched alkyl group having 1 to 6 carbon atoms.
Examples of the linear alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, and the like.
Examples of the branched alkyl group having 1 to 6 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, and tert-butyl group.

In the general formula (A), R ² to R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a linear or branched alkyl group having 1 to 6 carbon atoms. It is preferable to represent a linear alkyl group having 1 to 3 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and even more preferably a linear alkyl group having 1 to 2 carbon atoms. In the general formula (A), when R ² to R ³ are each independently the above groups, the solubility of the polyimide precursor is better.

The compound represented by the general formula (A) is preferably at least one of 3-methoxy-N,N-dimethylpropionamide and 3-n-butoxy-N,N-dimethylpropionamide. When the compound represented by the general formula (A) is at least one of the above two types of compounds, the solubility of the polyimide precursor is better.

Examples of compounds represented by general formula (A) are shown below, but the present disclosure is not limited thereto.

・3-methoxy-N,N-dimethylpropionamide ・3-methoxy-N,N-diethylpropionamide ・3-methoxy-N,N-di-n-propylpropionamide ・3-methoxy-N,N-di -n-Butylpropionamide/3-methoxy-N,N-di-n-butylpropionamide/3-ethoxy-N,N-diethylpropionamide/3-ethoxy-N,N-dimethylpropionamide/3-ethoxy -N,N-di-n-propylpropionamide/3-n-butoxy-N,N-dimethylpropionamide/3-n-butoxy-N,N-diethylpropionamide/3-n-butoxy-N,N -di-n-propylpropionamide, 3-n-butoxy-N,N-di-n-butylpropionamide, 3-n-propoxy-N,N-dimethylpropionamide, 3-n-propoxy-N,N -Diethylpropionamide/3-n-propoxy-N,N-monomethylmonoethylpropionamide/3-n-propoxy-N,N-di-n-propylpropionamide/3-n-propoxy-N,N-di -n-butylpropionamide/3-n-hexyloxy-N,N-dimethylpropionamide/3-n-hexyloxy-N,N-diethylpropionamide/3-tert-butoxy-N,N-di-n -Propylpropionamide/3-tert-butoxy-N,N-di-n-butylpropionamide/3-tert-butoxy-N,N-dimethylpropionamide/3-tert-butoxy-N,N-diethylpropionamide・3-iso-propoxy-N,N-dimethylpropionamide ・3-iso-propoxy-N,N-diethylpropionamide ・3-iso-propoxy-N,N-di-n-propylpropionamide ・3-iso -Propoxy-N,N-di-n-butylpropionamide/3-octoxy-N,N-dimethylpropionamide

(Other solvents)
The polyimide precursor solution according to the present embodiment may further contain a solvent other than the β-alkoxypropionamide solvent to the extent that the effects of the present embodiment are not impaired.

The polyimide precursor solution according to the present embodiment further contains a solvent other than the β-alkoxypropionamide solvent (hereinafter also referred to as "other solvent") to the extent that the effects of the present embodiment are not impaired. You can stay there. However, the proportion of the β-alkoxypropionamide solvent in the total solvent is preferably 90% by mass or more, more preferably 95% by mass or more. In particular, when the other solvent is an aprotic polar solvent such as NMP described below, it is preferably within the above range from the viewpoint of safety to living organisms.

Examples of other solvents include water (eg, distilled water, ion-exchanged water, ultrafiltrated water, pure water, etc.), water-soluble organic solvents, and aprotic polar solvents. The other solvents may be used alone or in combination of two or more.

The term "water-soluble" refers to the fact that the target substance dissolves in water at 1% by mass or more at 25°C.

Examples of the water-soluble organic solvent include water-soluble ether solvents, water-soluble ketone solvents, and water-soluble alcohol solvents.

A water-soluble ether solvent is a water-soluble solvent having an ether bond in one molecule. Examples of water-soluble ether solvents include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether. Among these, tetrahydrofuran, dioxane, etc. are preferable as the water-soluble ether solvent.

A water-soluble ketone solvent is a water-soluble solvent having a ketone group in one molecule. Examples of water-soluble ketone solvents include acetone, methyl ethyl ketone, and cyclohexanone. Among these, acetone is preferred as the water-soluble ketone solvent.

A water-soluble alcoholic solvent is a water-soluble solvent having an alcoholic hydroxyl group in one molecule. Examples of water-soluble alcoholic solvents include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, monoalkyl ether of ethylene glycol, propylene glycol, monoalkyl ether of propylene glycol, diethylene glycol, and diethylene glycol. Monoalkyl ether, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene- Examples include 1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 2-ethyl-2-hydroxymethyl-1,3-propanediol, and 1,2,6-hexanetriol. Among these, preferred as the water-soluble alcoholic solvent are methanol, ethanol, 2-propanol, ethylene glycol, monoalkyl ether of ethylene glycol, propylene glycol, monoalkyl ether of propylene glycol, diethylene glycol, and monoalkyl ether of diethylene glycol.

Examples of the aprotic polar solvent include solvents with a boiling point of 150°C or more and 300°C or less and a dipole moment of 3.0D or more and 5.0D or less. Specifically, the aprotic polar solvent includes, for example, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), Hexamethylene phosphoramide (HMPA), N-methylcaprolactam, N-acetyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone (DMI), N,N'-dimethylpropylene urea, tetramethylurea, Examples include trimethyl phosphate and triethyl phosphate.

Among the above solvents, it is preferable that the other solvents include aprotic polar solvents from the viewpoint of solubility of the polyimide precursor.

When the other solvent is a water-soluble solvent, the water-soluble solvent may be used, for example, by polymerizing a tetracarboxylic dianhydride and a diamine compound in a resin particle dispersion prepared in the process of producing a polyimide precursor solution. The water-soluble solvent in the resin particle dispersion used at that time may be used as is.

When the other solvent is a water-soluble solvent, for example, when the polyimide precursor solution further contains inorganic particles as other particles, the water-soluble solvent is the water-soluble solvent in the inorganic particle dispersion prepared in the manufacturing process. may be used as is.

(Tertiary amine compound containing amide group)
The tertiary amine compound containing an amide group refers to a compound having an amide group and a tertiary amine skeleton in one molecule. The amide group-containing tertiary amine compounds may be used alone or in combination of two or more.

The number of amide groups contained in one molecule of the amide group-containing tertiary amine compound is not particularly limited, but is preferably one or more and two or less, and more preferably one.
The number of tertiary amine skeletons contained in one molecule of the amide group-containing tertiary amine compound is not particularly limited, but is preferably one or more and two or less, and more preferably one.

The type of amide group contained in one molecule of the amide group-containing tertiary amine compound is not particularly limited, and one type of group may be used alone or two or more types of groups may be used in combination.
The type of tertiary amine skeleton contained in one molecule of the amide group-containing tertiary amine compound is not particularly limited, and one type of skeleton may be used alone or two or more types of skeletons may be used in combination.

The amide group-containing tertiary amine compound preferably contains a compound represented by the following general formula (B).

(In the general formula (B), R ¹ and R ² each independently represent an aldehyde group or an alkyl group having 1 to 5 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom, or , represents a monovalent organic group having an alkyl group having 1 or more and 5 or less carbon atoms.)

When the amide group-containing tertiary amine compound contains the compound represented by the above general formula (B), the affinity with the carbon material increases during film formation, so when formed into a polyimide molded article, Excellent in both thermal conductivity and tensile strength.

In the general formula (B), the alkyl group having 1 to 5 carbon atoms represented by R ¹ to R ² includes a linear or branched alkyl group having 1 to 5 carbon atoms.
Examples of the linear alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, and n-pentyl group.
Examples of the branched alkyl group having 1 to 5 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, and tert-pentyl group.

In the general formula (B), R ¹ to R ² each independently represent an aldehyde group or an alkyl group having 1 to 5 carbon atoms; an aldehyde group or a linear alkyl group having 1 to 5 carbon atoms; It is preferable to represent an aldehyde group or a linear alkyl group having 1 or more and 3 or less carbon atoms, and even more preferably an aldehyde group or an alkyl group having 1 or more and 2 or less carbon atoms. In the general formula (B), when R ¹ to R ² are the above groups, the affinity with the carbon material increases during film formation, so that when formed into a polyimide molded product, thermal conductivity and Superior tensile strength.

In the general formula (B), the alkyl group having 1 to 5 carbon atoms represented by R ³ to R ⁴ is the same as the alkyl group having 1 to 5 carbon atoms represented by R ¹ to R ² . Examples include groups.

In the general formula (B), R ³ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and a linear alkyl group having 1 to 5 carbon atoms. It is preferable to represent a linear alkyl group having 1 or more and 3 or less carbon atoms, and even more preferably to represent an alkyl group having 1 or more and 2 or less carbon atoms. In the general formula (B), when R ³ to R ⁴ are the above groups, the affinity with the carbon material increases during film formation, so when formed into a polyimide molded product, thermal conductivity and Superior tensile strength.

The compound represented by general formula (B) is preferably at least one of 3-dimethylamino-N,N-dimethylpropionamide and N-[2-(dimethylamino)ethyl]-N-methylformamide. When the compound represented by the general formula (B) is the above compound, the affinity with the carbon material increases during film formation, so when formed into a polyimide molded product, thermal conductivity and tensile rupture are improved. Superior in both strength.

Examples of compounds represented by general formula (B) are shown below, but the present disclosure is not limited thereto.

・3-dimethylamino-N,N-dimethylpropionamide ・3-diethylamino-N,N-dimethylpropionamide ・3-dipropylamino-N,N-dimethylpropionamide ・3-dibutylamino-N,N-dimethyl Propionamide/3-dipentylamino-N,N-dimethylpropionamide/3-methylethylamino-N,N-dimethylpropionamide/3-ethylpropylamino-N,N-dimethylpropionamide/3-dimethylamino-N , N-diethylpropionamide, 3-dimethylamino-N,N-dipropylpropionamide, 3-dimethylamino-N,N-dibutylpropionamide, 3-dimethylamino-N,N-dipentylpropionamide, 3-dimethyl Amino-N,N-methylethylpropionamide/N-[2-(dimethylamino)ethyl]-N-methylformamide

The content of the amide group-containing tertiary amine compound relative to the total amount of the polyimide precursor solution is preferably 10 ppm or more and 2000 ppm or less, more preferably 20 ppm or more and 1800 ppm or less, and even more preferably 50 ppm or more and 1500 ppm or less. .
When the content of the amide group-containing tertiary amine compound is 10 ppm or more with respect to the total amount of the polyimide precursor solution, the affinity with the carbon material increases and imidization becomes more efficient during film formation. Therefore, when formed into a polyimide molded article, it has better thermal conductivity and tensile strength at break.
If the content of the amide group-containing tertiary amine compound is 2000 ppm or less based on the total amount of the polyimide precursor solution, imidization will be excessively promoted during film formation, resulting in polyimide molding with uneven higher order structure. It is easy to suppress the formation of a solid body, and has excellent tensile strength at break.

The content of the amide group-containing tertiary amine compound relative to the carbon material is preferably 0.001% by mass or more and 2.50% by mass or less, and preferably 0.01% by mass or more and 2.00% by mass or less. More preferably, it is 0.015% by mass or more and 1.50% by mass or less.
In particular, when the content of the amide group-containing tertiary amine compound is 0.01% by mass or more based on the carbon material, the affinity with the carbon material increases and imidization is improved during film formation. Since it is more likely to be promoted efficiently, when it is made into a polyimide molded article, it is superior in both thermal conductivity and tensile strength at break.
If the content of the amide group-containing tertiary amine compound is less than 2.00% by mass based on the carbon material, imidization will be excessively promoted during film formation, resulting in polyimide molding with uneven higher order structure. The carbon material is more likely to be inhibited from forming a body, and the gaps in the higher-order structure are more easily filled with the carbon material more efficiently, resulting in superior tensile strength at break.

(carbon material)
Examples of the carbon material include carbon black such as Ketjen black, oil furnace black, channel black, and acetylene black; pyrolytic carbon; graphite; single-layer or multi-layer graphene; short or long carbon nanotubes; single-wall or multi-layer. carbon nanotubes; fullerenes and derivatives thereof; carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers; and the like. The carbon materials may be used alone or in combination of two or more.

Among the above, the carbon material preferably contains at least one selected from the group consisting of carbon black, graphene, and carbon nanotubes, and more preferably contains at least one of graphene and carbon nanotubes.
When the carbon material is at least one selected from the above group, the affinity between the amide group-containing tertiary amine compound and the carbon material is more likely to increase during film formation, so when formed into a polyimide molded article. Furthermore, it has excellent thermal conductivity and tensile strength at break.

The carbon material preferably has a structure of a granular hollow aggregate or a graphene mesosponge.
When the carbon material has the structure of the above-mentioned granular hollow aggregates or graphene mesosponges, the affinity between the amide group-containing tertiary amine compound and the carbon material is more likely to increase during film formation. When this happens, both thermal conductivity and tensile strength at break are superior. Moreover, elasticity is easily imparted to the polyimide molded body by filling the voids in the higher-order structure of the polyimide with the carbon material.

・Graphene mesosponge Graphene mesosponge is a porous carbon material that has mesopores. The International Union of Pure and Applied Chemistry (IUPAC) defines pores with a diameter of 2 nm or less as micropores, pores with a diameter of 2 nm or more and 50 nm or less as mesopores, and pores with a diameter of 50 nm or more as macropores. Materials having mesopores are collectively referred to as mesoporous materials.

Graphene meso-sponge is, for example, a porous carbon material composed of graphene sheets that are three-dimensionally continuous along the shape of mesopores, and in which the number of laminated graphene sheets is several layers or less, and is preferably , a porous carbon material composed only of a single layer of graphene without defects.

The basic skeleton of graphene mesosponges is graphene. In graphene mesosponges, each graphene sheet is large in size, and the number of stacked graphene layers is small. Therefore, graphene mesosponges have high elasticity as well as thermal conductivity, and also have high electrical conductivity.

- Granular hollow aggregate A granular hollow aggregate of carbon material is a granular aggregate formed by combining carbon materials with each other, and in the granular hollow aggregate, there are carbon materials and voids between the carbon materials. (that is, a void forming a hollow state). Examples of the carbon material include carbon fiber, graphene, and fullerene. If the carbon material is carbon fiber, the granular hollow aggregate of the carbon material is preferably a granular hollow aggregate formed by a plurality of fibrous carbons intertwined with each other. In addition, if the carbon fiber is graphene, it is a granular hollow aggregate made up of a plurality of sheet-like structures (i.e., graphene) consisting of a single layer in which carbon atoms bonded by sp2 bonds are arranged in a plane. is preferred.

The granular hollow aggregate may be, for example, spherical, ellipsoidal, or irregularly shaped.

The granular hollow aggregate of the carbon material is preferably a granular hollow aggregate formed by a plurality of fibrous carbons intertwined with each other, or a granular hollow aggregate formed by a combination of a plurality of graphenes, from the viewpoint of availability, From the viewpoint of obtaining high thermal conductivity, it is more preferable to use a granular hollow aggregate (hereinafter also referred to as a "fiber aggregate") in which a plurality of fibrous carbons are entangled with each other. Note that the number of fibrous carbons contained in the fiber aggregate is not particularly limited as long as it is plural (ie, two or more). The fibrous carbon contained in the fiber aggregate is preferably carbon nanotubes from the viewpoint of availability, thermal conductivity, and the like.

The content of the carbon material relative to the polyimide precursor (carbon material/polyimide precursor) is preferably 5% by volume or more and 20% by volume or less, more preferably 7% by volume or more and 18% by volume or less, and 10% by volume or less. % or more and 16 volume % or less is more preferable.
In particular, when the carbon material is graphene meso-sponge, the content of the carbon material with respect to the total amount of the polyimide precursor solution is 8% by volume or more and 18% by volume or less from the viewpoint of improving thermal conductivity, electrical conductivity, and flexibility. The content is preferably 10% by volume or more and 15% by volume or less.

When the content of the carbon material is 5% by volume or more based on the polyimide precursor, a certain amount or more of the carbon material is present in the polyimide molded body, so that unevenness in thermal conductivity is easily suppressed. Furthermore, since the carbon material is more likely to be filled into the gaps in the higher-order structure of the polyimide molded body more efficiently, the tensile strength at break is more excellent.
If the content of the carbon material is 20% by volume or less based on the polyimide precursor, the hardness of the polyimide molded body will be prevented from becoming too high and brittle during film formation, so that the tensile strength at break will increase. Excellent.

The content of the carbon material relative to the amide group-containing tertiary amine compound (carbon material/amide group-containing tertiary amine compound) is preferably 2% by mass or more and 1000% by mass or less, and 5% by mass or more and 500% by mass or less. More preferably, it is 10% by mass or more and 100% by mass or less.

When the content of the carbon material is 2% by mass or more and 50 times that of the amide group-containing tertiary amine compound, the affinity with the amide group-containing tertiary amine compound is more likely to increase during film formation. Therefore, when made into a polyimide molded article, it has excellent both thermal conductivity and tensile strength at break.
If the content of the carbon material is 1000% by mass or less and 50 times that of the amide group-containing tertiary amine compound, imidization will be excessively promoted during film formation, resulting in polyimide molding with uneven higher-order structure. The carbon material is more likely to be inhibited from forming a body, and the gaps in the higher-order structure are more easily filled with the carbon material more efficiently, resulting in superior tensile strength at break.

(Polyimide precursor)
The polyimide precursor is, for example, a polymer of tetracarboxylic dianhydride and a diamine compound. The polyimide precursor may be, for example, a resin (polyimide precursor) having a repeating unit represented by general formula (I).

(In general formula (I), A represents a tetravalent organic group, and B represents a divalent organic group.)
Here, in the general formula (I), the tetravalent organic group represented by A is the residue obtained by removing four carboxyl groups from the raw material tetracarboxylic dianhydride.

On the other hand, the divalent organic group represented by B is a residue obtained by removing two amino groups from a diamine compound as a raw material.

That is, the polyimide precursor having a repeating unit represented by the general formula (I) is a polymer of a tetracarboxylic dianhydride and a diamine compound.

Examples of the tetracarboxylic dianhydride include aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic dianhydride, but aromatic tetracarboxylic dianhydride is preferable. That is, in general formula (I), the tetravalent organic group represented by A is preferably an aromatic organic group.
Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride. Anhydride, 4,4'-oxydiphthalic dianhydride, 3,4'-oxydiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3, 4-dicarboxyphenyl)methane dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride, p -Phenylenebis(trimelitate anhydride), m-phenylenebis(trimelitate anhydride), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, naphthalene-1,4,5 , 8-tetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 4,4' -diphenyl ether bis(trimellitate anhydride), 4,4'-diphenylmethane bis(trimellitate anhydride), 4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4'-bis( 3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy) diphenyl ether dianhydride, 2,2-bis(4-hydroxyphenyl)propane bis(trimellitate anhydride) p-terphenyltetracarboxylic dianhydride, m-terphenyltetracarboxylic dianhydride, and the like.

Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4 -Cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentyl acetic acid dianhydride, 3,5,6-tricarboxynorbonane -2-acetic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarvone Acid dianhydride, aliphatic or alicyclic tetracarboxylic dianhydride such as bicyclo[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; 1 ,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, 1,3,3a ,4,5,9b-hexahydro-5-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, 1,3,3a , 4,5,9b-hexahydro-8-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, etc. Examples include aliphatic tetracarboxylic dianhydride.

Among these, aromatic tetracarboxylic dianhydrides are preferred as tetracarboxylic dianhydrides, specifically pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, is preferred, and further preferred are pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride, Particularly preferred is 3,3',4,4'-biphenyltetracarboxylic dianhydride.

In addition, one type of tetracarboxylic dianhydride may be used alone, or two or more types may be used in combination.

In addition, when using two or more types in combination, even if aromatic tetracarboxylic dianhydride or aliphatic tetracarboxylic acid is used in combination, aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic dianhydride You can also combine things.

On the other hand, a diamine compound is a diamine compound having two amino groups in its molecular structure. Examples of the diamine compound include aromatic diamine compounds and aliphatic diamine compounds, but aromatic diamine compounds are preferable. That is, in general formula (I), the divalent organic group represented by B is preferably an aromatic organic group.

Examples of diamine compounds include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl sulfide. , 4,4'-diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, 5-amino-1-(4'-aminophenyl)-1,3,3 -Trimethylindane, 6-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide , 3,5-diamino-4'-trifluoromethylbenzanilide, 3,4'-diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4' -Methylene-bis(2-chloroaniline), 2,2',5,5'-tetrachloro-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5' -dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 2,2-bis[4-(4- aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-amino phenoxy)-biphenyl, 1,3'-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-(p-phenyleneisopropylidene)bisaniline, 4,4' -(m-phenyleneisopropylidene)bisaniline, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino) Aromatic diamines such as -2-trifluoromethyl)phenoxy]-octafluorobiphenyl; aromatic compounds having two amino groups bonded to an aromatic ring such as diaminotetraphenylthiophene and a heteroatom other than the nitrogen atom of the amino group Group diamine; 1,1-methaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane , isophorone diamine, tetrahydrodicyclopentadienyl diamine, hexahydro-4,7-methanoindani dimethylene diamine, tricyclo[6,2,1,0 ^2.7 ]-undecylene dimethyl diamine, 4,4'- Examples include aliphatic diamines such as methylenebis(cyclohexylamine) and alicyclic diamines.

Among these, aromatic diamine compounds are preferable as diamine compounds, and specifically, for example, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3 , 4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenylsulfone are preferred, and 4,4'-diaminodiphenyl ether and p-phenylenediamine are particularly preferred.

Note that the diamine compounds may be used alone or in combination of two or more. Moreover, when using a combination of two or more types, an aromatic diamine compound or an aliphatic diamine compound may be used in combination, or an aromatic diamine compound and an aliphatic diamine compound may be combined.

Furthermore, in order to adjust the handling properties and mechanical properties of the obtained polyimide, it may be preferable to copolymerize two or more types of tetracarboxylic dianhydride and/or diamine compounds.

As a combination of copolymerization, for example, a tetracarboxylic dianhydride and/or diamine compound having one aromatic ring in its chemical structure, and a tetracarboxylic dianhydride and/or diamine compound having two or more aromatic rings in its chemical structure. Copolymerization with diamine compounds, aromatic tetracarboxylic dianhydrides and/or diamine compounds, and carboxylic dianhydrides and/or having flexible linking groups such as alkylene groups, alkyleneoxy groups, and siloxane groups. Alternatively, copolymerization with a diamine compound, etc. may be mentioned.

The number average molecular weight of the polyimide precursor is preferably 5,000 or more and 300,000 or less, more preferably 10,000 or more and 150,000 or less.

When the number average molecular weight of the polyimide precursor is within the above range, a decrease in the solubility of the polyimide precursor in a solvent is suppressed, and film formability is easily ensured.

The number average molecular weight of the polyimide precursor is measured by gel permeation chromatography (GPC) under the following measurement conditions.
・Column: Tosoh TSKgelα-M (7.8mm I.D x 30cm)
・Eluent: DMF (dimethylformamide)/30mMLiBr/60mM phosphoric acid ・Flow rate: 0.6mL/min
・Injection volume: 60μL
・Detector: RI (differential refractive index detector)

The content (that is, concentration) of the polyimide precursor is preferably 0.1% by mass or more and 40% by mass or less, more preferably 0.5% by mass or more and 25% by mass, based on the entire polyimide precursor solution. The content is preferably 1% by mass or more and 20% by mass or less.

(Other additives)
The polyimide precursor solution according to this embodiment may contain a polyimide precursor, a β-alkoxypropionamide solvent, an amide group-containing tertiary amine compound, and other additives other than the carbon material. Other additives include, for example, catalysts for promoting imidization reactions and leveling materials for improving film forming quality.

As a catalyst for promoting the imidization reaction, a dehydrating agent such as an acid anhydride, an acid catalyst such as a phenol derivative, a sulfonic acid derivative, a benzoic acid derivative, etc. may be used.

In addition, materials other than inorganic particles having a volume average particle diameter of 0.001 μm or more and 0.2 μm or less may be added to the polyimide precursor solution depending on the purpose of use, such as a conductive material added to impart conductivity. (Electroconductivity (for example, volume resistivity less than 10 ⁷ Ω·cm) or semiconductivity (for example, volume resistivity 10 ⁷ Ω·cm or more and 10 ¹³ Ω·cm or less)) may be contained.

Examples of conductive materials include carbon black (for example, acidic carbon black with a pH of 5.0 or lower); metals (for example, aluminum and nickel); metal oxides (for example, yttrium oxide, tin oxide, etc.); ionic conductive substances (for example, titanium potassium acid, LiCl, etc.); These conductive materials may be used alone or in combination of two or more.

(Polyimide molded body)
The polyimide molded article according to this embodiment is a molded article made of a heat-cured product of the polyimide precursor solution according to this embodiment. In other words, the polyimide molded body is composed of a cured product obtained by heating a polyimide precursor solution. Specifically, the polyimide molded article according to the present embodiment is a molded article in which a coating film of the polyimide precursor solution according to the present embodiment is dried and imidized by heat treatment.
According to this embodiment, a polyimide molded body having excellent both thermal conductivity and tensile strength at break can be obtained.

The film thickness of the polyimide molded body may be determined depending on the application. The lower limit of the film thickness is, for example, 5 m or more. In addition, when the film thickness of the polyimide molded body is in the range of 5 μm or more and 300 μm or less, a molded product with good in-plane uniformity, film thickness uniformity, uniformity of physical properties in the film thickness direction, etc. can be easily obtained.

Examples of the polyimide film as the polyimide molded product include a flexible electronic board film, a copper-clad laminate film, a laminate film, an electrical insulation film, a porous film for fuel cells, and a separation film.
In addition, polyimide coatings as polyimide molded products include insulating coatings, heat-resistant coatings, IC packages, adhesive films, liquid crystal alignment films, resist films, flattening films, microlens array films, electric wire coatings, optical fiber coatings, etc. is exemplified.
Other polyimide molded bodies include belt members. Examples of belt members include drive belts (for example, endless belts of drive belts), belts for electrophotographic image forming apparatuses (for example, endless belts such as intermediate transfer belts, transfer belts, fixing belts, conveyance belts, etc.). be done.

・Method for manufacturing polyimide molded object The method for manufacturing the polyimide molded object according to this embodiment is not particularly limited as long as it is a method of molding using the polyimide precursor solution according to this embodiment, but for example, the method for manufacturing the polyimide molded object according to this embodiment is An example of this method is to apply a polyimide precursor solution onto a base material to form a coating film, and then heat-treat the film to obtain a polyimide molded body. Note that the polyimide molded article manufactured using the polyimide precursor solution is not particularly limited.

Hereinafter, a method for manufacturing an endless belt will be described in detail as an example of a method for manufacturing a polyimide molded body according to the present embodiment.

The method for producing an endless belt includes, for example, a process of applying a polyimide precursor solution onto a cylindrical base material to form a coating film, and a process of drying the coating film formed on the base material to form a dry film. , a step of imidizing the dry film (heating treatment) and imidizing the polyimide precursor to form a polyimide resin layer, and a step of removing the polyimide resin layer from the base material to form an endless belt. include. Specifically, for example, it is as follows.

First, a polyimide precursor solution is applied to the inner or outer surface of a cylindrical base material to form a coating film. As the cylindrical base material, for example, a cylindrical metal base material is suitably used. Instead of metal, a base material made of other materials such as resin, glass, ceramic, etc. may be used. Further, a glass coat, a ceramic coat, etc. may be provided on the surface of the base material, and a silicone-based, fluorine-based, etc. release agent may be applied.

Here, in order to accurately apply the polyimide precursor solution, it is preferable to perform a step of defoaming the polyimide precursor solution before applying the polyimide precursor solution. By defoaming the polyimide precursor solution, bubble formation and defects in the coating film during coating are suppressed.
Examples of methods for defoaming the polyimide precursor solution include a method of reducing the pressure, a method of centrifugation, and the like. Defoaming by reducing the pressure is convenient and has a high defoaming ability, so it is suitable.

Next, the cylindrical base material on which the coating film of the polyimide precursor solution has been formed is placed in a heated or vacuum environment to dry the coating film and form a dry film. At least 30% by mass, preferably at least 50% by mass of the contained solvent is evaporated.

Next, the dried film is subjected to imidization treatment (heat treatment). This forms a polyimide resin layer.
The heating conditions for the imidization treatment are, for example, heating at 150°C or higher and 400°C or lower (preferably 200°C or higher and 300°C or lower) for 20 minutes or more and 60 minutes or less to cause an imidization reaction and form a polyimide resin layer. be done. During the heating reaction, the temperature may be gradually increased in steps or at a constant rate before the final heating temperature is reached. The imidization temperature varies depending on, for example, the type of tetracarboxylic dianhydride and diamine used as raw materials, and if the imidization is insufficient, the mechanical and electrical properties will be poor. Set.
Thereafter, the polyimide resin layer is removed from the cylindrical base material to obtain an endless belt.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples below. The materials, amounts used, proportions, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Note that unless otherwise specified, "parts" means "parts by mass."

<Example 1>
(Preparation of polyimide precursor solution 1)
A flask equipped with a stirring bar and a thermometer was filled with 82 parts of 3-methoxy-N,N-dimethylpropionamide, which is a β-alkoxypropionamide solvent. Here, 10 parts of p-phenylenediamine (hereinafter also referred to as "PDA"), which is a diamine compound, and 3,3',4,4'-biphenyltetracarboxylic dianhydride, which is tetracarboxylic dianhydride. (hereinafter also referred to as "BPDA"): 10 parts were added, and the mixture was reacted with stirring for 15 hours while maintaining the reaction temperature at 50°C. Thereafter, 0.1 part of 3-dimethylamino-N,N-dimethylpropionamide, which is an amide group-containing tertiary amine compound, and 5 parts of carbon black, which is a carbon material, are further added to the polyimide precursor solution. I got 1.

In the obtained polyimide precursor solution, the proportion of the polyimide precursor was 13 parts by mass based on the entire polyimide precursor solution. Moreover, the weight average molecular weight of the polyimide precursor contained in the polyimide precursor solution was 40,000.

<Examples 2 to 20, Comparative Examples 1 to 3>
The same method as in Example 1 was used, except that the β-alkoxypropionamide solvent, the amide group-containing tertiary amine compound, the type and amount of carbon material, and the type and amount of other solvents were as shown in Table 1. An example polyimide precursor solution was obtained.

Information such as abbreviations and compound names written in the column of each material in Table 1 is as follows.
・MdMPA: 3-methoxy-N,N-dimethylpropionamide ・BdMPA: 3-n-butoxy-N,N-dimethylpropionamide ・OdMPA: 3-octoxy-N,N-dimethylpropionamide ・EdMPA: 3-ethoxy -N,N-dimethylpropionamide

・2MAEFA: N-[2-(dimethylamino)ethyl]-N-methylformamide ・3dMAdPA: 3-dimethylamino-N,N-dimethylpropionamide ・CB: Carbon black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) , average secondary particle diameter = 200 μm)
・Short CNT: Short carbon nanotube (manufactured by Kouki Gas Kogyo Co., Ltd., average length = 3.0 μm, average diameter = 10 nm)
・Long CNT: Long carbon nanotube (manufactured by Kouki Gas Kogyo Co., Ltd., average length = 5.0 μm, average diameter = 10 nm)
- Granular hollow aggregate (granular hollow aggregate made up of a plurality of carbon nanotubes, which are fibrous carbon, intertwined with each other and having a spherical shape: cotton spherical CNT): Created by the following manufacturing method.
・Graphene meso sponge: Created by the following manufacturing method.

(Manufacture of cotton ball-shaped CNTs)
After generating and depositing carbon nanotubes using a CVD device (Ishikawa Sangyo Co., Ltd.) in a mold with a particle size of 20 μm using the template material CaCO ₃ (Shiraishi Industries Co., Ltd.), the template was removed by washing with hydrochloric acid. , cotton ball-shaped carbon nanotubes were obtained.

(Manufacture of graphene meso sponge)
(1) Preparation of carbon-coated alumina nanoparticles by CVD (Chemical Vapor Depositio) method Alumina nanoparticles (TM300 manufactured by Daimei Kagaku Kogyo Co., Ltd., crystal phase: γ-alumina, average particle size: 7 nm, specific surface area: 220 m ² /g) ) and quartz sand (manufactured by Sendai Wako Pure Chemical Industries, Ltd.) as a spacer were mixed at a weight ratio of 3:10 (alumina nanoparticles: quartz sand). At this time, the quartz sand used was one that had been soaked in 1M hydrochloric acid for 12 hours, heated in air at 800° C. for 2 hours in a muffle furnace, and sieved at 180 μm intervals. The mixture of alumina nanoparticles and quartz sand prepared above was placed in a reaction tube (inner diameter 57 mm), and CVD using methane as a carbon source (hereinafter referred to as "methane CVD") was performed.

In the methane CVD, the alumina nanoparticles were heated from room temperature to 900°C at a temperature increase rate of 10°C/min under conditions where the flow rate of N ₂ gas was adjusted to 400ml/min, and the temperature was held at 900°C for 30 minutes. Thereafter, using N2 gas as a carrier gas, 20% by volume of methane based on the total amount of carrier gas and methane was introduced into the reaction tube, and chemical vapor deposition (CVD) treatment was performed at 900°C for 4 hours. Ta. At this time, the flow rate of methane gas was adjusted to 80 ml/min, and the flow rate of N ₂ gas was adjusted to 320 ml/min. Thereafter, the introduction of methane gas was stopped and the flow rate of N ₂ gas was adjusted to 400 ml/min, and the temperature was maintained at 900° C. for 30 minutes, followed by cooling to obtain carbon-coated alumina nanoparticles.

(2) Dissolving and removing the template The alumina nanoparticles (that is, the template) were removed from the carbon-coated alumina nanoparticles obtained in (1) above.
Hydrogen fluoride (HF) was used to remove the template from the carbon-coated alumina nanoparticles. Carbon-coated alumina nanoparticles and a concentration of 46% by mass were placed in a Teflon (registered trademark) beaker.
HF aqueous solution was added thereto, and the mixture was kept at room temperature for 6 hours while stirring with a Teflon (registered trademark) stirring bar. After that, it was naturally cooled. The sample was collected by filtration and dried by vacuum heating at 150° C. for 6 hours to obtain a porous carbon material.

(3) Heat treatment of porous carbon material The porous carbon material obtained in (2) above was crushed, several pieces were collected, placed in a graphite container, and set in a high-temperature furnace. The pressure in the high temperature part was reduced to 10 Pa using an oil pump, and heat treatment was performed while flowing a small amount of Ar to obtain a porous carbon material.
As for the heat treatment conditions, the temperature was first raised from room temperature to 1800° C. over 120 minutes. Then, it was heat-treated at 1800° C. for 60 minutes, and then naturally cooled to room temperature. The porous carbon material thus obtained was a graphene mesosponge in which the hydrogen-terminated edges of the CMS were fused by heat treatment at a high temperature of 1800°C, forming a more continuous three-dimensional graphene skeleton. .

In Table 1, [Content (vs. polyimide precursor solution)] in the item of amide group-containing tertiary amine compound refers to the content of the amide group-containing tertiary amine compound relative to the total amount of the polyimide precursor solution.
In Table 1, [content (relative to carbon material)] in the item of amide group-containing tertiary amine compound refers to the content of the amide group-containing tertiary amine compound relative to the carbon material.
In Table 1, [Content (vs. polyimide precursor)] in the carbon material section refers to the content of the carbon material relative to the polyimide precursor.
In Table 1, [content (versus tertiary amine compound)] in the carbon material section refers to the content of the carbon material relative to the amide group-containing tertiary amine compound.
In Table 1, "-" in each item indicates that each material is not included.

<Evaluation of thermal conductivity>
The polyimide precursor solution obtained in each example was applied onto a 1.0 mm thick glass substrate in an area of 10 cm x 10 cm using an applicator, and a film was obtained by drying in an oven at 80°C for 30 minutes. Ta. The gap of the applicator was adjusted so that the average thickness of the film after drying was 30 μm. The glass substrate on which the film has been formed is baked by leaving it in an oven heated to 250°C for 30 minutes, then immersed in ion-exchanged water, peeled off from the glass substrate, and dried to form polyimide. A molded body was obtained.
The thermal conductivity of the obtained polyimide molded body was measured using a temperature wave analysis method using ai-phase (manufactured by Ai-phase Co., Ltd.) under a load of 50 g, and the thermal conductivity was evaluated using the following evaluation criteria. did. The results are shown in the table.
-Evaluation criteria-
A+: 1.3 W/m・K or more A: 0.8 or more and less than 1.3 W/m・K B: 0.5 or more and less than 0.8 W/m・K C: Less than 0.5 W/m・K

<Evaluation of tensile breaking strength>
Using the polyimide precursor solution of each example, a polyimide molded body was obtained in the same manner as in the evaluation of thermal conductivity. The obtained polyimide molded body was pulled through a strip-shaped test piece (width 15 mm, length 50 mm) at a speed of 200 mm/min using a tensile testing machine (strograph manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the test piece was The tensile strength (MPa) at the time of breakage was determined as the tensile strength at break. The measurement is performed in a first direction (e.g. MD direction) and a second direction perpendicular to the first direction (e.g. TD direction), and the value of the lower strength is calculated as the tensile breaking strength. shall be.
-Evaluation criteria-
A+: 230 MPa or more A: 200 or more and less than 230 MPa B: 170 or more and less than 200 MPa C: less than 170 MPa

From the results shown in Table 1, the polyimide molded body produced using the polyimide precursor solution of the example has a higher thermal conductivity than the polyimide molded body produced using the polyimide precursor solution of the comparative example. It was found to be excellent in both tensile strength and tensile strength.

(((1))) Polyimide precursor,
β-alkoxypropionamide solvent,
an amide group-containing tertiary amine compound;
carbon material;
A polyimide precursor solution containing.
(((2))) The polyimide precursor solution according to the above (((1))), wherein the β-alkoxypropionamide solvent is a compound represented by the following general formula (A).

(In the general formula (A), R ¹ represents an alkyl group having 1 to 6 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. .)
(((3))) The compound represented by the general formula (A) is at least one of 3-methoxy-N,N-dimethylpropionamide and 3-n-butoxy-N,N-dimethylpropionamide. , the polyimide precursor solution described in (((2))) above.
(((4))) The amide group-containing tertiary amine compound is any of the above (((1))) to (((3))) containing a compound represented by the following general formula (B). The polyimide precursor solution according to any one of the above.

(In the general formula (B), R ¹ and R ² each independently represent an aldehyde group or an alkyl group having 1 to 5 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom, or , represents a monovalent organic group having an alkyl group having 1 or more and 5 or less carbon atoms.)
(((5))) The compound represented by the general formula (B) is a compound of 3-dimethylamino-N,N-dimethylpropionamide and N-[2-(dimethylamino)ethyl]-N-methylformamide. The polyimide precursor solution according to ((4)) above, which is at least one of the polyimide precursor solutions.
(((6))) The amide group-containing tertiary amine compound has a content of 10 ppm or more and 2000 ppm or less based on the total amount of the polyimide precursor solution, (((1))) to (((5))) The polyimide precursor solution according to any one of .
(((7))) The amide group-containing tertiary amine compound has a content of 0.01% by mass or more and 2% by mass or less with respect to the carbon material, (((1))) to (((6) The polyimide precursor solution according to any one of ))).
(((8))) The carbon material is any one of the above ((1)) to ((7))) containing at least one selected from the group consisting of carbon black, graphene, and carbon nanotubes. The polyimide precursor solution according to any one of the above.
(((9))) The polyimide precursor solution according to ((8)) above, wherein the carbon material has a structure of a granular hollow aggregate or a graphene meso-sponge.
(((10))) The carbon material has a content of 5% by volume or more and 20% by volume or less with respect to the polyimide precursor, any one of the above ((1)) to ((9))). 1. The polyimide precursor solution according to claim 1.
(((11))) The carbon material has a content of 2% by mass or more and 1000% by mass or less with respect to the amide group-containing tertiary amine compound, (((1))) to (((10)) ) The polyimide precursor solution according to any one of the above.
(((12))) The β-alkoxypropionamide solvent contains a compound represented by the following general formula (A),
The amide group-containing tertiary amine compound is a polyimide according to any one of (((1))) to (((11))) containing a compound represented by the following general formula (B). Precursor solution.
(((13))) A polyimide molded article comprising a heat-cured product of the polyimide precursor solution according to any one of the above (((1))) to (((12))).
(((14))) The polyimide molded article according to (((13))), wherein the polyimide molded article is an endless belt.

(((1))), (((2))), (((3))), (((4))), (((5))), or (((12))) According to the invention, there is provided a polyimide precursor that allows a polyimide molded article to be obtained that is superior in both thermal conductivity and tensile strength at break compared to a polyimide precursor solution containing only a polyimide precursor and a β-alkoxypropionamide solvent. A body solution is provided.
According to the invention according to ((6))), the thermal conductivity and A polyimide precursor solution from which a polyimide molded article having both excellent tensile strength at break can be obtained is provided.
According to the invention according to ((7))), the amide group-containing tertiary amine compound has a higher thermal resistance than when the content of the amide group-containing tertiary amine compound is less than 0.01% by mass or more than 2% by mass with respect to the carbon material. A polyimide precursor solution from which a polyimide molded article having both excellent conductivity and tensile strength at break is obtained is provided.
According to the invention according to ((8))), there is provided a polyimide precursor solution that provides a polyimide molded body with excellent thermal conductivity compared to when the carbon material is graphite.
According to the invention according to ((9))), there is provided a polyimide precursor solution that provides a polyimide molded body with better thermal conductivity than when the carbon material is carbon black.
According to the invention according to ((10))), the carbon material has better thermal conductivity and tensile strength at break than when the content of the carbon material is less than 5% by volume or more than 20% by volume with respect to the polyimide precursor. Provided is a polyimide precursor solution that yields a polyimide molded article that is excellent in both.
According to the invention according to ((11))), the carbon material has a higher thermal conductivity than when the content of the amide group-containing tertiary amine compound is less than 2% by mass or more than 1000% by mass. Provided is a polyimide precursor solution from which a polyimide molded article having both excellent properties and tensile strength at break can be obtained.
According to the invention according to ((13))), when formed into a polyimide molded article, it has a higher thermal conductivity than a polyimide precursor solution containing only a polyimide precursor and a β-alkoxypropionamide solvent. A polyimide molded article having excellent both of strength and tensile strength at break is provided.

Claims (14)

a polyimide precursor;
β-alkoxypropionamide solvent,
an amide group-containing tertiary amine compound;
carbon material;
A polyimide precursor solution containing. The polyimide precursor solution according to claim 1, wherein the β-alkoxypropionamide solvent is a compound represented by the following general formula (A).

(In the general formula (A), R ¹ represents an alkyl group having 1 to 6 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. .) The compound represented by the general formula (A) is at least one of 3-methoxy-N,N-dimethylpropionamide and 3-n-butoxy-N,N-dimethylpropionamide, according to claim 2. Polyimide precursor solution. The polyimide precursor solution according to claim 1, wherein the amide group-containing tertiary amine compound contains a compound represented by the following general formula (B).

(In the general formula (B), R ¹ and R ² each independently represent an aldehyde group or an alkyl group having 1 to 5 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom, or , represents a monovalent organic group having an alkyl group having 1 or more and 5 or less carbon atoms.) The compound represented by the general formula (B) is at least one of 3-dimethylamino-N,N-dimethylpropionamide and N-[2-(dimethylamino)ethyl]-N-methylformamide. 4. The polyimide precursor solution according to 4. The polyimide precursor solution according to claim 1, wherein the content of the amide group-containing tertiary amine compound is 10 ppm or more and 2000 ppm or less based on the total amount of the polyimide precursor solution. The polyimide precursor solution according to claim 1, wherein the content of the amide group-containing tertiary amine compound relative to the carbon material is 0.01% by mass or more and 2% by mass or less. The polyimide precursor solution according to claim 1, wherein the carbon material includes at least one selected from the group consisting of carbon black, graphene, and carbon nanotubes. The polyimide precursor solution according to claim 8, wherein the carbon material has a structure of a granular hollow aggregate or a graphene meso-sponge. The polyimide precursor solution according to claim 1, wherein the content of the carbon material relative to the polyimide precursor is 5% by volume or more and 20% by volume or less. The polyimide precursor solution according to claim 1, wherein the carbon material has a content of 2% by mass or more and 1000% by mass or less with respect to the amide group-containing tertiary amine compound. The β-alkoxypropionamide solvent contains a compound represented by the following general formula (A),
The polyimide precursor solution according to claim 1, wherein the amide group-containing tertiary amine compound contains a compound represented by the following general formula (B). A polyimide molded article comprising a heat-cured product of the polyimide precursor solution according to claim 1. The polyimide molded article according to claim 13, wherein the polyimide molded article is an endless belt.