JP2021172618A - Diamine compound and method for producing the same - Google Patents

Abstract

To provide a diamine compound that allows synthesis of a polyimide resin having high heat resistance and high transparency and a method for producing the same.SOLUTION: The present invention relates to a diamine compound represented by the formula (1) and a method for producing the same, and a polyimide precursor and a polyimide including the diamine compound as a constitutional unit.SELECTED DRAWING: None

Description

The present invention relates to an industrially useful diamine compound containing an ester group and a method for producing the same.

Diamine compounds are compounds widely used in the fields of organic chemistry and polymer chemistry, and are useful in a wide range of fields for industrial applications such as fine chemicals, agrochemical raw materials and resin raw materials, as well as electronic information materials and optical materials. It is a compound. For example, a polyimide resin obtained from a diamine compound is expected to be applied as a colorless transparent flexible substrate. In particular, recently, as the TFT device type has become LTPS (low temperature polysilicon TFT), it is desired to maintain transparency even in the thermal history more than before.

The physical characteristics of polyimide obtained by using a conventional diamine compound are not sufficient for use as a heat-resistant colorless transparent substrate. As a result of confirmation by the present inventors, it was found that the polyimide resin compositions described in Patent Documents 1 and 2 have poor heat resistance, and the yellowness is remarkably deteriorated in the heat history of the LTPS step at 400 ° C. or higher. Further, Patent Document 3 reports that polyimide having an ester structure in a molecular chain exhibits a low coefficient of linear expansion and high heat resistance because it has appropriate linearity and rigidity. As a result of confirmation by the authors, there was still room for improvement in the transparency of the polyimide described in Patent Document 3.

Special Table 2016-53 1997 Japanese Unexamined Patent Publication No. 2012-052111 JP-A-2019-70811

An object of the present invention is to solve the above-mentioned problems and to provide a diamine compound capable of synthesizing a polyimide resin having high heat resistance and high transparency, and a method for producing the same.

As a result of diligent studies in view of the current state of the prior art, the present inventors have found that a novel diamine compound in which fluorine is introduced into the side chain of an aromatic ester diamine and a method for producing the same can solve the above problems. ..

で示されるジアミン化合物。
［２］ 下記式（１）：

で示される４−アミノ−３−フルオロフェニル−４’−アミノフェニルエステルの製造方法であって、
下記式（２）：

で示される４−ニトロベンゾイルクロライドと、
下記式（３）：

で示される４−ニトロ−３−フルオロフェノールとを塩基性下でエステル化反応させて、
下記式（４）：

で示される４−ニトロベンゼン−３−フルオロ−４’−ニトロフェニルエステルを得る工程と、
前記式（４）で示される４−ニトロベンゼン−３−フルオロ−４’−ニトロフェニルエステルを還元することによって、前記（１）で示される４−アミノ−３−フルオロフェニル−４’−アミノフェニルエステルを得る工程とを含む、方法。
［３］ 前記還元を、反応圧０．１〜１０ＭＰａにて接触水素化により行う、上記態様２に記載の方法。
［４］ 前記エステル化反応を、塩基の存在下、非プロトン性極性溶媒中で行う、上記態様２又は３に記載の方法。
［５］ 前記還元に先立って、前記４−ニトロベンゼン−３−フルオロ−４’−ニトロフェニルエステルを、水、又は水及びアルコール化合物の混合物を用いて結晶として析出させる工程を含む、上記態様２〜４のいずれかに記載の方法。
［６］ 前記還元により生成した４−アミノ−３−フルオロフェニル−４’−アミノフェニルエステルを、晶析溶媒を用いて結晶として析出させる工程を含み、前記晶析溶媒が、水、非極性化合物、水及び非極性化合物の混合物、水及びアルコール化合物の混合物、並びに非極性化合物及びアルコール化合物の混合物からなる群から選ばれる少なくとも１つである、上記態様２〜５のいずれかに記載の方法。
［７］ 前記アルコール化合物が、メタノール、エタノール、及び２−プロパノールからなる群から選ばれる少なくとも１つである、上記態様５又は６に記載の方法。
［８］ ４−アミノ−３−フルオロ−４’−アミノフェニルエステルを構造単位として含む、ポリイミド前駆体。
［９］ ４−アミノ−３−フルオロ−４’−アミノフェニルエステルを構造単位として含む、ポリイミド。 That is, the present invention includes the following aspects.
[1] The following equation (1):

The diamine compound indicated by.
[2] The following equation (1):

A method for producing 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by.
The following formula (2):

4-Nitrobenzoyl chloride indicated by
The following formula (3):

Esterification reaction with 4-nitro-3-fluorophenol represented by (1) under basic conditions,
The following formula (4):

The step of obtaining 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester represented by
By reducing the 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester represented by the above formula (4), the 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by the above (1) A method, including the steps of obtaining.
[3] The method according to the second aspect, wherein the reduction is carried out by catalytic hydrogenation at a reaction pressure of 0.1 to 10 MPa.
[4] The method according to the above aspect 2 or 3, wherein the esterification reaction is carried out in the presence of a base in an aprotic polar solvent.
[5] Aspects 2 to 2 above, which comprises a step of precipitating the 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester as crystals using water or a mixture of water and an alcohol compound prior to the reduction. The method according to any one of 4.
[6] A step of precipitating the 4-amino-3-fluorophenyl-4'-aminophenyl ester produced by the reduction as crystals using a crystallization solvent is included, and the crystallization solvent is water, a non-polar compound. The method according to any one of aspects 2 to 5, wherein the method is at least one selected from the group consisting of a mixture of water and a non-polar compound, a mixture of water and an alcohol compound, and a mixture of a non-polar compound and an alcohol compound.
[7] The method according to aspect 5 or 6, wherein the alcohol compound is at least one selected from the group consisting of methanol, ethanol, and 2-propanol.
[8] A polyimide precursor containing 4-amino-3-fluoro-4'-aminophenyl ester as a structural unit.
[9] A polyimide containing 4-amino-3-fluoro-4'-aminophenyl ester as a structural unit.

According to one aspect of the present invention, a diamine compound capable of synthesizing a polyimide resin having high heat resistance and high transparency and a method for producing the same can be provided.

^{FIG. 1 is a diagram showing a hydrogen nuclear magnetic resonance (hereinafter, also referred to as 1} H-NMR) spectrum of 4-amino-3-fluorophenyl-4'-aminophenyl ester obtained in Example 1.

Hereinafter, an exemplary embodiment of the present invention (hereinafter, abbreviated as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof. In addition, unless otherwise specified, the characteristic values described in the present disclosure are values measured by the method described in the section of [Example] or a method understood by those skilled in the art to be equivalent thereto. Intended.

で示される４−アミノ−３−フルオロフェニル−４’−アミノフェニルエステルを提供する。 << Diamine compound and its manufacturing method >>
One aspect of the present invention is a novel diamine compound, specifically, the following formula (1):

The 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by is provided.

The diamine compound shown in (1) above is a polyimide that is required to be transparent because a resin composition that is transparent and has a small haze can be provided by introducing fluorine into the side chain of the aromatic ester diamine. , Polyamide and the like are promising as raw materials. Further, since the diamine compound contains an ester group, it has excellent functions such as high solubility in a solvent, high heat resistance, high mechanical strength, low linear expansion, low thermal expansion, and low moisture absorption expansion. It is also promising as a raw material for polyimide having properties. More specifically, the diamine compound has a substituent at a specific position as shown in the above formula, so that the molecule of the diamine and the acid dianhydride in the polyimide obtained from the diamine compound and the acid dianhydride. It can cause internal twisting and suppress the CT transition in the polyimide molecule, and as a result, the coloring of the polyimide film can be suppressed. Further, the diamine compound has an electron-withdrawing substituent at the above-mentioned position to stabilize the highest occupied molecular orbital (HOMO) derived from the π orbital localized in the aromatic ring portion containing imide nitrogen. As a result, the coloring of the polyimide can be suppressed. Further, by using a diamine having a substituent at the above-mentioned position, the intermolecular orientation of the polyimide film can be suppressed, and as a result, the haze of the film can be suppressed.

In one embodiment, the 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by the above formula (1) is a yellowish white compound.

で示される４−ニトロベンゾイルクロライドと、下記式（３）：

で示される４−ニトロ−３−フルオロフェノールとを塩基性下（すなわち、ｐＨ７．０超の条件下）で反応（すなわちエステル化反応）させることにより、中間体である下記式（４）：

で示される４−ニトロベンゼン−３−フルオロ−４’−ニトロフェニルエステルを製造することができる。 In one embodiment, the compound represented by the above formula (1) can be produced by the following method. First, the following formula (2):

4-Nitrobenzoyl chloride represented by and the following formula (3):

The following formula (4):

4-Nitrobenzene-3-fluoro-4'-nitrophenyl ester represented by (1) can be produced.

In one embodiment, the above esterification reaction of the compound represented by the formula (2) and the compound represented by the formula (3) is carried out in the presence of a base, preferably in an aprotic polar solvent.

Examples of the aprotonic polar solvent preferably used in this esterification reaction include sulfoxide compounds, sulfolane compounds, amide compounds, nitrile compounds, ether compounds and the like.

Examples of the sulfoxide compound include dimethyl sulfoxide (DMSO) and diethyl sulfoxide.

Examples of the sulfolane compound include sulfolane and methyl sulfolane.

Examples of the amide compound include N, N-dimethylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide (DMF), 2-pyrrolidone, and N-methyl-2-pyrrolidone (NMP). ), Hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolinodine and the like.

Examples of the nitrile compound include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile and the like.

Examples of the ether compound include monoglime, diglime, triglime, tetraglime, diethyl ether, diisopropyl ether, di-n-butyl ether, t-butyl methyl ether, cyclopentyl methyl ether, tetrahydrofuran (THF), tetrahydropyran, 1,4-dioxane, and the like. Examples thereof include 1,3-dioxolane, anisole and morpholine.

Among these, tetrahydrofuran and N, N-dimethylformamide (DMF) are preferable because they have a low boiling point and are easy to remove.

The aprotic polar solvent may be used alone or in combination of two or more.

The amount of the aprotic polar solvent used is usually in the range of 0.1 to 20 times by mass with respect to the compound represented by the formula (2).

Examples of the base preferably used in this esterification reaction include alkali metal hydride, alkaline earth metal hydride, alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal carbonate, and alkaline earth metal. Examples thereof include carbonates, alkali metal hydrogen carbonates, alkali metal alkoxides, alkaline earth metal alkoxides, alkali metal fluorides and amines.

Examples of the alkali metal hydride include lithium hydride, sodium hydride, potassium hydride and the like.
Examples of the alkaline earth metal hydride include beryllium hydride, magnesium hydride, calcium hydride and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like.
Examples of the alkaline earth metal hydroxide include beryllium hydroxide, magnesium hydroxide, calcium hydroxide and the like.

Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, potassium carbonate and the like.
Examples of the alkaline earth metal carbonate include beryllium carbonate, magnesium carbonate, calcium carbonate and the like.
Examples of the alkali metal bicarbonate include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate and the like.

Examples of the alkali metal alkoxide include sodium methoxide, sodium ethoxide, sodium t-butoxide, potassium methoxide, potassium ethoxide, potassium t-butoxide and the like.
Examples of the alkaline earth metal alkoxide include magnesium diethoxydo and magnesium dimethoxyde.

Examples of the alkali metal fluoride include sodium fluoride, potassium fluoride, cesium fluoride and the like.

Examples of amines include tertiary amines such as trimethylamine, triethylamine, tributylamine, N, N-dimethylaniline, dimethylbenzylamine, N, N, N', N'-tetramethyl-1,8-naphthalenediamine, pyridine, and pyrrol. , Urasyl, Collidine, Rutidine and other heteroaromatic amines, 1,8-diaza-bicyclo [5.4.0] -7-undecene, 1,5-diaza-bicyclo [4.3.0] -5-nonen And the like, cyclic amidine and the like.

These bases may be used alone or in combination of two or more. Of these bases, triethylamine and pyridine are particularly preferable because they are liquid and easy to handle, and because they have a low boiling point, they are easy to remove.

The amount of the base used is preferably 1.0 to 3.0 mol times, more preferably 1.0 to 1.5 mol times, the amount of the compound represented by the formula (2). By increasing the amount of base to 1.0 mol times or more, it is possible to prevent a decrease in yield due to unachieved reaction, and by setting the amount to 3.0 mol times or less, the energy required for base removal is reduced and waste is also generated. It is preferable because it reduces the amount.

This esterification reaction is preferably carried out in a nitrogen atmosphere. By carrying out in a nitrogen atmosphere, it is possible to suppress a decrease in purity by preventing oxygen from being mixed into the system.

The reaction temperature of this esterification reaction is usually preferably 0 to 100 ° C, more preferably 0 to 50 ° C. When the temperature is 0 ° C. or higher, the reaction proceeds rapidly, and when the temperature is 100 ° C. or lower, side reactions can be suppressed and a decrease in yield can be prevented.

The reaction time of this esterification reaction is usually in the range of 0.5 to 20 hours.

After completion of this esterification reaction, crystals are precipitated by adding a crystallization solvent to the reaction mixture, and by isolating this, the intermediate 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester is obtained. can get. The obtained intermediate may be recrystallized from, for example, the same type of crystallization solvent as that used for the above-mentioned precipitation.

Examples of the crystallization solvent preferably used in this esterification reaction include water and alcohol compounds. In a preferred embodiment, the crystallization solvent is water or a mixture of water and an alcohol compound. Examples of the alcohol compound include methanol, ethanol, 2-propanol and the like. These crystallization solvents may be used alone or in combination of two or more. Of these crystallization solvents, water and methanol are particularly preferable because they can be obtained at low cost.

で示される４−アミノ−３−フルオロフェニル−４’−アミノフェニルエステルを製造することが出来る。 Next, by reducing the 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester of the formula (4) obtained above, the following formula (1):

4-Amino-3-fluorophenyl-4'-aminophenyl ester represented by can be produced.

As a reduction method, there are a metal reduction method using zinc powder, iron powder, tin, stannous chloride, etc. and a catalytic hydrogenation method using a hydrogenation catalyst, but the method for isolating the target product is simple. Contact hydrogenation is most preferable from the viewpoints of less waste requiring treatment and good economic efficiency.

Examples of suitable hydrogenation catalysts used in this catalytic hydrogenation reaction include noble metal catalysts and Raney nickel catalysts.
Examples of the noble metal catalyst include those containing at least one noble metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, and iridium.
Examples of the form of the catalyst include a form supported on activated carbon, graphene, fibroin, zeolite, diatomaceous earth, alumina and the like.
Among these, platinum carbon and palladium carbon catalysts are particularly preferable from the viewpoint of economy and operability.

The amount of the noble metal catalyst is usually preferably an amount corresponding to 0.001 to 0.5 mass times as much as the noble metal content with respect to the compound represented by the formula (4), and more preferably 0.01 as the noble metal content. It is ~ 0.2 mass times. By setting the noble metal content of the catalyst to 0.001 times by mass or more, the hydrogenation reaction proceeds rapidly, and by setting it to 0.5 by mass or less, the ratio of the catalyst cost to the product cost can be reduced, and the catalyst cost can be reduced. The burden of filtering work is reduced.

Examples of the solvent preferably used for this catalytic hydrogenation include alcohol compounds, ester compounds, ether compounds, and amide compounds.

Examples of the alcohol compound include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, methoxyethanol, ethoxyethanol, 1-methoxy-2-propanol and the like.

Examples of the ester compound include ethyl acetate, propyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate and the like.

Examples of the ether compound include grime, diglyme, tetrahydrofuran, dioxane and the like.

Examples of the amide compound include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like.

Among these, tetrahydrofuran and N, N-dimethylformamide (DMF) are preferable because they have a low boiling point and are easy to remove.

The solvent may be used alone or in combination of two or more. The amount of the solvent used in the catalytic hydrogenation reaction is usually in the range of 0.1 to 20 times by mass with respect to the compound represented by the formula (4).

The reaction temperature of this catalytic hydrogenation is usually preferably 0 to 150 ° C, more preferably 50 to 120 ° C. By setting the temperature to 0 ° C. or higher, the reaction proceeds rapidly, and by setting the temperature to 150 ° C. or lower, side reactions can be suppressed and a decrease in yield can be prevented.

The reaction pressure (that is, hydrogen pressure) in this catalytic hydrogenation reaction is preferably 0.1 to 10 MPa, more preferably 0.1 to 5 MPa. When it is 0.1 MPa or more, the catalytic hydrogenation reaction proceeds satisfactorily, and when it is 10 MPa or less, side reactions can be suppressed and a decrease in yield can be prevented.

After completion of the catalytic hydrogenation reaction, the catalyst is filtered off by a conventional method, and crystals are precipitated by adding a crystallization solvent to the filtrate. By isolating this, 4-amino represented by the formula (1) is used. -3-Fluorophenyl-4'-aminophenyl ester is obtained. The obtained compound may be recrystallized, for example, with the same type of crystallization solvent as that used for the above-mentioned precipitation.

As the crystallization solvent preferably used in this catalytic hydrogenation reaction, for example, water, an alcohol compound, a non-polar compound and the like can be preferably used, and more specifically, water, a non-polar compound, water and a non-polar compound can be used. At least one selected from the group consisting of a mixture of polar compounds, a mixture of water and alcohol compounds, and a mixture of non-polar compounds and alcohol compounds is preferred.

Examples of the alcohol compound include methanol, ethanol, 2-propanol and the like.

Examples of the non-polar compound include n-hexane, n-heptane, cyclohexane, toluene, xylene and the like.

These crystallization solvents may be used alone or in combination of two or more. Of these crystallization solvents, water and ethanol are particularly preferable because they give high-purity 4-amino-3-fluorophenyl-4'-aminophenyl ester.

After recrystallization, purification by sublimation may be performed to further increase the purity. As a result, yellowish white crystals are obtained from the grayish white powder. The temperature during sublimation purification is preferably 150 to 250 ° C, more preferably 150 to 200 ° C. By setting the temperature to 150 ° C. or higher, the target product can be sublimated, and by setting the temperature to 250 ° C. or lower, side reactions can be suppressed and a decrease in yield can be prevented.

The diamine compound represented by the formula (1) obtained above can exhibit high transparency by introducing fluorine into the compound.

This diamine compound is promising as a raw material for polyimides, polyamide resins, etc., which are required to have transparency. In addition, since this compound contains an ester group, it has excellent functionality such as high solubility in a solvent, high heat resistance, high mechanical strength, low linear expansion, low thermal expansion, and low moisture absorption expansion. It is also promising as a raw material for polyimide having the above.

One aspect of the present invention also provides a polyimide precursor obtained by using the diamine compound represented by the formula (1). In one aspect, the polyimide precursor has a structural unit derived from the diamine compound represented by the formula (1) and a structural unit derived from the tetracarboxylic dianhydride. Examples of the tetracarboxylic acid dianhydride include aromatic tetracarboxylic acid dianhydride, aliphatic tetracarboxylic acid dianhydride and alicyclic tetracarboxylic acid dianhydride, and from the viewpoint of yellowness in a high temperature region, Aromatic tetracarboxylic acid dianhydride having 8 to 36 carbon atoms is preferable. The number of carbons referred to here also includes the number of carbons contained in the carboxyl group. The polyimide precursor may have a structural unit derived from a diamine other than the diamine compound represented by the formula (1), but in a typical embodiment, the diamine-derived structural unit is represented by the formula (1). It consists of structural units derived from diamine compounds. The polyimide precursor (more specifically, polyamic acid) can be synthesized by subjecting a diamine to a tetracarboxylic acid dianhydride by a polycondensation reaction. The polycondensation reaction may be carried out in a solvent. A part of the polyimide precursor may be imidized.

The weight average molecular weight (Mw) of the polyimide precursor may be preferably 10,000 to 300,000, or 30,000 to 200,000. When the weight average molecular weight is 10,000 or more, the mechanical properties such as elongation and breaking strength are excellent, the residual stress is low, and the YI is low. When the weight average molecular weight is 300,000 or less, the weight average molecular weight can be easily controlled during the synthesis of the polyamic acid, and a polyimide precursor having an appropriate viscosity can be obtained, which is preferable in terms of coatability and the like. In the present disclosure, the weight average molecular weight is a value obtained as a standard polystyrene-equivalent value using gel permeation chromatography (hereinafter, also referred to as GPC).

One aspect of the present invention also provides a polyamide obtained using the diamine compound represented by the formula (1). The polyamide can be produced by imidization of the above-mentioned polyimide precursor (for example, thermal imidization in a nitrogen atmosphere).

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Various evaluations in the examples were performed as follows.

<Measurement of hydrogen nuclear magnetic resonance ( ¹ H-NMR) spectrum>
^{In Example 1, the 1} H-NMR spectrum of 4-amino-3-fluorophenyl-4'-aminophenyl ester was analyzed under the following analytical conditions. The chemical purity of 4-amino-3-fluorophenyl-4'-aminophenyl ester was determined from the peak area ratio of the compound spectrum obtained from the following measurements.
Measuring device: ECS400 manufactured by JEOL Ltd.
Resonance frequency: 400MHz
Measuring solvent: DMSO-d ₆
Chemical shift criteria: DMSO-d ₆ (2.50 ppm)
Measurement temperature: Room temperature integration frequency: 16 times

<Measurement of weight average molecular weight and number average molecular weight>
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions.
As a solvent, N, N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for high performance liquid chromatography, 24.8 mmol / L lithium bromide monohydrate immediately before measurement (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity) 99.5%) and 63.2 mmol / L phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for high performance liquid chromatography) were added and dissolved). The calibration curve for calculating the weight average molecular weight was prepared using standard polystyrene (Easic Type PS-1, Agilent Technologies, Inc.).

Equipment: HLC-8220GPC (manufactured by Tosoh)
Column: Tsk gel Super HM-H (manufactured by Tosoh)
Flow rate: 0.5 mL / min Column temperature: 40 ° C
Detector: UV-8220 (UV-Vis: UV-Visible Absorber, manufactured by Tosoh Corporation)

<Example 1>
[Synthesis of Fluorine-Containing Aromatic Ester Diamine]
A stirring blade, a reflux tube, a dropping funnel, an argon introduction line, and a thermometer were attached to a 1.0 L four-necked flask, and 20.0 g (0.13 mol) of 3-fluoro-4-nitrophenol and 19.9 mL (0) of triethylamine were attached. .14 mol) and 255 mL of tetrahydrofuran were added and dissolved, and the inside of the system was replaced with argon gas. A solution prepared by dissolving 23.62 g (0.13 mol) of 4-nitrobenzoyl chloride in 51 mL of tetrahydrofuran was added dropwise thereto at around 0 ° C. The mixture was reacted at room temperature for 2 hours. After completion of the reaction, 3.0 L of ion-exchanged water was added to precipitate crystals, which were recovered by filtration. The recovered solid was suspended and washed with 1.0 L of ion-exchanged water, and the solid was recovered by filtration. The obtained solid was washed with methanol and then dried under reduced pressure at 40 ° C. for 14 hours to obtain 37.56 g (pale yellow solid, 0.12 mL) of the intermediate dinitro compound.

8.00 g (0.026 mol) of the dinitro compound, 0.80 g of 5% Pd / C (STD type, manufactured by N.E. Chemcat), and 40.0 mL of N, N-dimethylformamide were put into a 50 mL autoclave container. After replacing the inside of the autoclave with hydrogen three times, hydrogen was filled so as to have a hydrogen pressure of 4 MPa, and the mixture was immersed in an oil bath at 100 ° C. After reacting for 2 hours, the mixture was cooled to room temperature and Pd / C was removed by filtration. The filtrate was poured into ion-exchanged water, and the precipitated solid was recovered. The recovered solid was dried under reduced pressure at 80 ° C. for 2 days to obtain 5.68 g (0.023 mL) of 4-amino-3-fluorophenyl-4'-aminophenyl ester as the target grayish white solid. ^{The purity obtained by 1 1} H-NMR measurement was 98%.

1.00 g of the obtained grayish white 4-amino-3-fluorophenyl-4'-aminophenyl ester was placed in a sublimation purification apparatus, the ^{pressure was reduced to 1.6 × 10 -4} Pa, and the raw material portion was heated to 180 ° C. Then, it was sublimated to obtain 0.80 g of yellowish white crystals. ^{The purity obtained by 1 1} H-NMR measurement was 99.9% or more.

FIG. 1 shows a hydrogen nuclear magnetic resonance ( ¹ H-NMR) spectrum chart of the diamine compound obtained in Example 1. From ^{the measurement result of 1} H-NMR, the obtained diamine compound was identified as 4-amino-3-fluorophenyl-4'-aminophenyl ester.

<Example 2>
[Synthesis of Fluorine-Containing Aromatic Polyimide Precursor]
In a nitrogen-substituted 50 ml three-necked flask, 4.00 g of N-methyl-2-pyrrolidone (NMP) and 1.95 g (7.92 mmol) of 4-amino-3-fluorophenyl-4'-aminophenyl ester were placed. The mixture was stirred to dissolve 4-amino-3-fluorophenyl-4'-aminophenyl ester. Then, 2.35 g (8.00 mmol) of 3,3', 4,4'-biphenyltetracarboxylic dianhydride and 3.99 g of N-methyl-2-pyrrolidone (NMP) were added to adjust the concentration of polyamic acid. The polymerization reaction was adjusted to 35% by mass, and the polymerization reaction was carried out under stirring at 60 ° C. for 3 hours under a nitrogen flow. Then, 8.10 g of N-methyl-2-pyrrolidone (NMP) was added and cooled to room temperature to obtain an NMP solution of polyamic acid (hereinafter, also referred to as varnish). The weight average molecular weight (Mw) of the obtained polyamic acid was about 67,000, and Mw / Mn was 2.1.

<Example 3>
[Preparation of Fluorine-Containing Aromatic Polyimide Film]
The polyimide precursor prepared in Example 2 was coated on a glass substrate (thickness 0.7 mm) so as to have a film thickness of 10 μm after curing, and was roughly dried at 80 ° C. for 30 minutes. Then, using a drying oven, the oxygen concentration in the refrigerator was adjusted to 200 mass ppm or less under a nitrogen atmosphere, and heat-cured at 400 ° C. for 1 hour to obtain a transparent polyimide film. Was done.

<Reference example 1>
In Example 1, the hydrogen pressure was changed to normal pressure during the reduction reaction, and the reaction was carried out at 80 ° C. for 24 hours. There wasn't.

Claims (9)

The following formula (1):

The diamine compound indicated by. The following formula (1):

A method for producing 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by.
The following formula (2):

4-Nitrobenzoyl chloride indicated by
The following formula (3):

Esterification reaction with 4-nitro-3-fluorophenol represented by (1) under basic conditions,
The following formula (4):

The step of obtaining 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester represented by
By reducing the 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester represented by the above formula (4), the 4-amino-3-fluorophenyl-4'-aminophenyl ester represented by the above (1) A method, including the steps of obtaining. The method according to claim 2, wherein the reduction is carried out by catalytic hydrogenation at a reaction pressure of 0.1 to 10 MPa. The method according to claim 2 or 3, wherein the esterification reaction is carried out in the presence of a base in an aprotic polar solvent. Any of claims 2-4, comprising the step of precipitating the 4-nitrobenzene-3-fluoro-4'-nitrophenyl ester as crystals using water or a mixture of water and an alcohol compound prior to the reduction. The method described in item 1. The step of precipitating the 4-amino-3-fluorophenyl-4'-aminophenyl ester produced by the reduction as crystals using a crystallization solvent is included, and the crystallization solvent is water, a non-polar compound, water and the like. The method according to any one of claims 2 to 5, which is at least one selected from the group consisting of a mixture of non-polar compounds, a mixture of water and alcohol compounds, and a mixture of non-polar compounds and alcohol compounds. The method of claim 5 or 6, wherein the alcohol compound is at least one selected from the group consisting of methanol, ethanol, and 2-propanol. A polyimide precursor containing 4-amino-3-fluoro-4'-aminophenyl ester as a structural unit. A polyimide containing 4-amino-3-fluoro-4'-aminophenyl ester as a structural unit.

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