JP2006233023A - Method for producing porous polyamic acid fine particle and porous polyimide fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a size-controlled and high quality porous polyimide fine particle and a porous polyamic acid fine particle to be a raw material for it. <P>SOLUTION: A polyamic acid and a polymer which is miscible with the polyamic acid and soluble in an organic solvent in an amount of 0.5-100 mass% to the polyamic acid are dissolved in the organic solvent to obtain a mixed solution of the polyamic acid and the polymer. The mixed solution is poured into a poor solvent of the polyamic acid miscible with the organic solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing porous polyamic acid fine particles and porous polyimide fine particles having a controlled particle size and pore size.

  Polyimide is used in many fields because it has various excellent properties such as heat resistance, solvent resistance, and electrical insulation. For example, in addition to being used as an alternative material for metals and ceramics, it is also used as a film, varnish, adhesive, bulk molding material, etc. in the electric and electronic industry fields and aerospace industry fields used under severe conditions.

  Such a material obtained by atomizing polyimide is expected to be used in various applications due to a synergistic effect due to the combination of the characteristics of the polyimide itself and its fine structure. For example, powder toner additives for image formation, additives for screen printing, etc. have been proposed. Among them, porous polyimide fine particles having pores on the surface of polyimide fine particles are low dielectric materials and It is very useful as a template for various nanodevices.

  Conventionally, porous polymer fine particles have been generally prepared by a spray drying method in which a polymer solution is sprayed and dried instantaneously. However, the spray drying method has problems that it is difficult to control production conditions and select a solvent.

In contrast, the present inventors have previously developed a completely new method for producing porous polyimide fine particles different from the spray drying method. This is because, in a reprecipitation method (Patent Document 1) for producing polyamic acid fine particles having a controlled particle size by pouring a polyamic acid solution into a poor solvent, an alkali metal halide salt is added to the polyamic acid solution to be poured. By adding, porous polyamic acid fine particles are formed, and then imidization treatment is performed (Patent Document 2).
Japanese Laid-Open Patent Publication No. 2003-252990 Japanese Laid-Open Patent Publication No. 2004-196869

  According to the production method of Patent Document 1, porous polyimide fine particles can be produced easily and with good reproducibility. However, there has been a demand for a method capable of producing fine particles having a smaller particle size and pore size and a high porosity. That is, the particle size, pore size, and porosity of the polyimide fine particles can be freely changed according to the application, and more uniform polyimide particles can be produced with a narrower particle size, pore size, and porosity distribution. A method was sought.

  Therefore, an object of the present invention is to provide a size-controlled high-quality porous polyimide fine particle and a method for producing porous polyamic acid fine particles as a raw material thereof.

  As a result of intensive studies, the present inventors dissolved a specific polymer together with polyamic acid in a good solvent in the reprecipitation method, so that the polymer became a pore source of the polyamic acid fine particles, and high-quality pores were obtained. It has been found that fine polyamic acid fine particles can be produced with good reproducibility. It has also been found that by imidizing this, it can be converted into porous polyimide fine particles while maintaining the particle size of the porous polyamic acid fine particles and the shape properties of the pores.

  That is, in the present invention, polyamic acid and 0.5 to 100% by mass of the polyamic acid, which is compatible with the polyamic acid and soluble in the organic solvent, are dissolved in the organic solvent. A method for producing porous polyamic acid fine particles, which solves the above problems by injecting a polyamic acid / polymer mixed solution into a poor solvent of the polyamic acid that is compatible with the organic solvent. It is.

  In this invention, the organic solvent is preferably a polar amide solvent, and in the polymer, the polymer repeating unit is selected from a carboxyl group, a carbonyl group, an ester group, an amino group, and a hydroxyl group. It preferably has a substituent.

  According to the present invention, it is possible to provide a method for producing high-quality porous polyamic acid fine particles in which the particle size, pore diameter, and porosity of the porous polyamic acid fine particles are controlled. Here, the porosity means the ratio (percentage) of the total area of the pores to the surface area of the fine particles.

  Further, by imidizing the porous polyamic acid fine particles obtained as described above, the produced porous polyamic acid fine particles maintain the shape properties such as the particle diameter, the pore diameter, and the porosity. Since it can be converted into porous polyimide fine particles, high-quality porous polyimide fine particles can be easily produced.

  According to the present invention, by using a reprecipitation method established as a technique for producing polymer fine particles, it is possible to easily produce porous polyimide particles and a porous polyamic acid serving as a precursor thereof. In addition, the particle size, pore size, and porosity of the polyimide fine particles can be changed by changing the production conditions such as the type and concentration of the polymer that is dissolved together with the polyamide. Narrow and homogeneous polyimide fine particles can be produced with good reproducibility.

  Such an operation and a gain of the present invention will be clarified from the best mode for carrying out the invention described below.

  The present invention utilizes a polymer as a pore-forming source in order to provide pores in a method for producing polyamic acid fine particles by a reprecipitation method. Hereinafter, the present invention will be described in detail. A basic method for producing polyamide fine particles by a reprecipitation method is disclosed in Patent Document 1 described above, and can be referred to.

  The polyamic acid (also referred to as polyamic acid) to be microparticulated in the present invention is a compound having a structure represented by the following general formula (1).

  X is a tetravalent substituent, and Y is a divalent substituent. X and Y are not particularly limited, and a substituent can be appropriately selected depending on the use, but usually an aromatic substituent is used. The molecular weight of the polyamic acid can also be appropriately selected basically in relation to the intended use, but in order to stably produce fine particles having a desired particle size, the weight average molecular weight may be in the range of 8000 to 220,000. preferable.

  In the present invention, the polyamic acid is first dissolved in an organic solvent together with the polymer described below to form a polyamic acid / polymer mixed solution. As the organic solvent for dissolving the polyamic acid, the polyamic acid can be dissolved. Any organic solvent can be used. Usually, a polar organic solvent is used. Specific examples thereof include ketone solvents such as acetone and methyl ethyl ketone; cyclic ether solvents such as tetrahydrofuran and dioxane; nitrile solvents such as acetonitrile; methanol, ethanol, Alcohol solvents such as isopropanol; polar amide solvents such as N, N-dimethylacetamide, N, N-dimethylformamide and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; phenol, o-, m- Or phenolic solvents such as p-cresol, xylenol, halogenated phenol, and catechol; and aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone. These can be used alone or in combination, but from the viewpoint of solubility, polar amide solvents are preferred, and N, N-dimethylacetamide and N-methylpyrrolidone are particularly preferred.

  Since the concentration of the polyamic acid dissolved in the organic solvent is a large factor that affects the particle size of the polyamic acid fine particles to be produced, the concentration is appropriately changed according to the desired particle size. In particular, the greater the molecular weight of the polyamic acid, the greater the effect of the solution concentration. The solution concentration is usually adjusted to about 0.1 to 15% by mass, but when the molecular weight is large, a solution of about 0.5% by mass is preferably adjusted.

  The polymer dissolved together with the polyamic acid has a role of forming vacancies on the surface of the polyamic acid to be fine particles. Any polymer that is compatible with the polyamic acid and is soluble in the organic solvent can be used. Polystyrene, polyacrylic acid, polymethacrylic acid, polypropylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polymethacrylic acid ester, polyacrylic acid Common polymers such as esters and polyethylene can be exemplified, and these may be homopolymers or copolymers. Among them, a polymer having a substituent selected from a carboxyl group, a carbonyl group, an ester group, an amino group, and a hydroxyl group is preferable, and polyacrylic acid, polyalkylene glycol, and polyvinyl alcohol are particularly preferable. The amount added depends on the desired pore diameter and porosity, but is 0.5 to 100% by mass, preferably 0.5 to 80% by mass, based on the polyamic acid, based on the polyamic acid.

  The polyamic acid / polymer mixed solution is injected into a poor solvent for polyamic acid to form polyamic acid fine particles dispersed in the poor solvent. The poor solvent is a solvent in which the polyamic acid can be precipitated when the polyamic acid / polymer mixed solution is added. Examples of the poor solvent include aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as decalin and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; carbon disulfide, or two of these Although the above mixed solvent is mentioned, an alicyclic hydrocarbon and the mixed solvent of this and carbon disulfide are especially preferable.

  In the poor solvent, a surfactant may be added in order to improve the dispersion stability of the porous polyamic acid fine particles. As the surfactant, a neutral surfactant is usually used, and among them, a polymer surfactant in a polyacrylate ester type is preferable. For example, ACRICID (Dainippon Ink Chemical Co., Ltd., polyacrylic acid ester pigment surface treatment agent. “Acridic” is a registered trademark of Dainippon Ink & Chemicals, Inc.) Available. When a surfactant is used, the amount thereof is not particularly limited, but if it is too large, the formation of pores is adversely affected.

  The amount of the poor solvent into which the polyamic acid / polymer mixed solution is injected is usually 10 times or more based on the volume of the polyamic acid / polymer mixed solution. Although there is no particular upper limit, it is preferable that the upper limit is not too large from the viewpoint of workability and economical efficiency of fine particle recovery. From the viewpoint of fine particle precipitation and workability, it is generally used about 100 times.

  At the time of injection, the poor solvent is preferably stirred in order to make the generated porous polyamic acid fine particles uniform. The stirring speed is not particularly limited, but is preferably 100 to 3000 rpm.

  The temperature of the poor solvent at the time of injection is not particularly limited as long as the solvent remains in a liquid state, but the particle size also changes when the temperature of the poor solvent is changed, so by keeping the temperature of the poor solvent constant, The particle size of the resulting porous polyamic acid fine particles can be controlled. For example, when a poor solvent having a temperature lower than 30 ° C. is used, the particle size of the porous polyamic acid fine particles tends to increase. Usually, the temperature is controlled in the range of −20 ° C. to 60 ° C. according to the desired particle size.

  The injection is preferably performed in a short time at a stretch in order to prevent variation in particle characteristics. In the laboratory, a syringe is usually used.

  The porous polyamic acid fine particles thus obtained usually have a particle diameter of 50 to 10,000 nm by controlling the temperature of the poor solvent, the type of polymer dissolved with the polyamic acid, the amount added, etc. It becomes a porous polyamic acid fine particle having a porosity of 500 nm and 0.1 to 30%.

  The porous polyamic acid fine particles produced as described above become porous polyimide fine particles by imidization treatment. The imidization can be performed by any known method. In general, there are two types of imidization: thermal imidation that thermally dehydrates and chemical imidization using a dehydrating agent. Either method may be used, thermal imidization or chemical imidization. You may use together. For example, in order to quantitatively convert polyamic acid into polyimide, it is also preferable to perform thermal imidization after chemical imidization. Thermal imidization is usually performed by heating to about 80 ° C to 300 ° C. Although the heating time depends on the heating temperature, it is usually about several minutes to several tens of hours. Chemical imidation usually promotes chemical imidization of pyridine, picoline, imidazole, isoquinoline, triethylamine, and other dehydrating agents such as acetic anhydride and trifluoroacetic anhydride in the reaction solution in a temperature range from room temperature to about 150 ° C. It is preferably carried out using an acetic anhydride / pyridine mixed solvent or an acetic anhydride / triethylamine mixed solvent. The imidization may be carried out in a state of being dispersed in a poor solvent or may be carried out after isolating the porous polyamic acid fine particles. It is done in the state.

  As described above, when the porous polyamic acid fine particles obtained by the reprecipitation method are imidized, the shape properties of the polyamic acid fine particles such as the particle size of the polyamic acid fine particles, the dispersion thereof, the pore size and the porosity are retained. Since it is converted into polyimide fine particles as it is, high-quality polyimide fine particles can be produced.

Examples will be shown below, but the present invention is not limited thereto.
Example 1
Polyamic acid obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4′-diaminodiphenyl ether ( (Molecular weight: 68650) was dissolved in N-methylpyrrolidone at a concentration of 1.5% by mass. Polyvinyl alcohol (molecular weight: 500) was added to the polyamic acid so that the blending amounts were (a) 20% by mass, (b) 50% by mass, and (c) 70% by mass, respectively. The solution of was prepared. Each 0.1 ml of these solutions was 0.1% by mass of a neutral polymer surfactant (Acridic, manufactured by Dainippon Ink & Chemicals, Inc.) using a microsyringe at room temperature under a stirring condition of 1500 rpm. Poured into 10 ml of contained cyclohexane. Then, a dispersion of polyamic acid fine particles having pores formed on the surface of each particle could be obtained.
To each of the porous polyamic acid fine particle dispersions thus obtained, 0.1 ml of a mixed solution having a pyridine / acetic anhydride molar ratio of 1/1 was added with stirring, and the chemical imidation was completed by holding for about 2 hours. As a result, porous polyimide fine particles maintaining the porosity of the porous polyamic acid fine particles were obtained.
The porosity (pore diameter, particle size, porosity) of the porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

(Example 2)
Polyamic acid obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4′-diaminodiphenyl ether ( (Molecular weight: 68650) was dissolved in N-methylpyrrolidone at a concentration of 1.5% by mass. To this, polyacrylic acid (molecular weight: 2000) was added to the polyamic acid so that the blending amounts were (a) 20 mass%, (b) 40 mass%, and (c) 60 mass%, respectively. A seed solution was prepared. Each 0.1 ml of these solutions was 0.1% by mass of a neutral polymer surfactant (Acridic, manufactured by Dainippon Ink & Chemicals, Inc.) using a microsyringe under stirring conditions of 1000 rpm at room temperature. Each was poured into 10 ml of cyclohexane. Then, a dispersion of polyamic acid fine particles having pores formed on the surface of each particle could be obtained.
To each of the porous polyamic acid fine particle dispersions thus obtained, 0.1 ml of a mixed solution having a pyridine / acetic anhydride molar ratio of 1/1 was added with stirring, and chemical imidization was carried out by holding for about 2 hours. Then, thermal imidation was performed by holding at 270 ° C. for 3 hours to allow the imidization to proceed quantitatively. Thereby, the porous polyimide fine particle which maintained the porosity of the porous polyamic-acid fine particle was able to be obtained.
The porosity (pore size, particle size, porosity) of the obtained porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

(Example 3)
A polyamic acid (molecular weight: 40000) obtained by polymerization of 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride and tetrafluoro-m-phenylenediamine is used as a neutral polymer. A surfactant (Acridic, manufactured by Dainippon Ink & Chemicals, Inc.) was dissolved in N, N-dimethylacetamide containing 0.1% by mass at a concentration of 1.5% by mass. To this, polyacrylic acid (molecular weight: 2000) was added to the polyamic acid so that the blending amounts were (a) 20 mass%, (b) 40 mass%, and (c) 60 mass%, respectively. A seed solution was prepared. 0.1 ml of each of these solutions was injected into 10 ml of cyclohexane using a microsyringe at room temperature under a stirring condition of 1500 rpm. Then, a dispersion of polyamic acid fine particles having pores formed on the surface of each particle could be obtained.
To each of the porous polyamic acid fine particle dispersions thus obtained, 0.1 ml of a mixed solution having a pyridine / acetic anhydride molar ratio of 1/1 was added with stirring, and the chemical imidation was completed by holding for about 2 hours. As a result, porous polyimide fine particles maintaining the porosity of the porous polyamic acid fine particles were obtained.
The porosity (pore diameter, particle size, porosity) of the porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

Example 4
Polyamic acid (molecular weight: 90000) obtained by polymerization of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine was added to N-methylpyrrolidone at a concentration of 1.5% by mass. Dissolved. Polyacrylic acid (molecular weight: 450,000) was added to the polyamic acid so that the blending amounts were (a) 10 mass%, (b) 20 mass% and (c) 30 mass%, respectively. A seed solution was prepared. Each 0.1 ml of these solutions was 0.1% by mass of a neutral polymer surfactant (Acridic, manufactured by Dainippon Ink & Chemicals, Inc.) using a microsyringe at room temperature under a stirring condition of 1500 rpm. Poured into 10 ml of contained cyclohexane. Then, a dispersion of polyamic acid fine particles having pores formed on the surface of each particle could be obtained.
To each of the porous polyamic acid fine particle dispersions thus obtained, 0.1 ml of a mixed solution having a pyridine / acetic anhydride molar ratio of 1/1 was added with stirring, and the chemical imidation was completed by holding for about 2 hours. As a result, porous polyimide fine particles maintaining the porosity of the porous polyamic acid fine particles were obtained.
The porosity (pore diameter, particle size, porosity) of the porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

(Example 5)
Polyamic acid obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4′-diaminodiphenyl ether ( (Molecular weight: 68650) was dissolved in N-methylpyrrolidone at a concentration of 1.5% by mass, and 40% by mass of polyacrylic acid (molecular weight: 2000) was added to the polyamic acid. Using 0.1 ml of this solution under stirring conditions of 1000 rpm at room temperature, 10 ml of cyclohexane and (b) 20 vol% of CS ₂ were added to 10 ml of cyclohexane. Each was injected into a cyclohexane / CS ₂ mixture. Then, a dispersion of polyamic acid fine particles having pores formed on the surface of each particle could be obtained.
To each of the porous polyamic acid fine particle dispersions thus obtained, 0.1 ml of a mixed solution having a molar ratio of pyridine / acetic anhydride of 1/1 was added with stirring, and chemical imidization was carried out by maintaining for about 2 hours. Then, thermal imidization was performed by holding at 270 ° C. for 3 hours, and imidization was quantitatively advanced. Thereby, the porous polyimide fine particle which maintained the porosity of the porous polyamic acid fine particle was able to be obtained.
The porosity (pore diameter, particle size, porosity) of the obtained porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

(Example 6)
Polyamic acid obtained by polymerization of 2,2- (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride and 4,4′-diaminodiphenyl ether ( (Molecular weight: 68650) is dissolved in N-methylpyrrolidone at a concentration of 1.5% by mass, and 20% by mass of polypropylene glycol-2,4-diisocyanate (molecular weight: 4000) is added to polyamic acid. did. 0.1 ml of this solution contains 0.1% by mass of a neutral polymer surfactant (Acridic, manufactured by Dainippon Ink & Chemicals, Inc.) using a microsyringe under stirring conditions of 1000 rpm at room temperature. Pour into 10 ml cyclohexane. Then, a dispersion of polyamic acid fine particles having pores formed on the particle surface could be obtained.
To the porous polyamic acid fine particle dispersion thus obtained, 0.1 ml of a mixed solution having a molar ratio of pyridine / acetic anhydride of 1/1 was added with stirring, followed by chemical imidization by holding for about 2 hours. Thermal imidization was carried out by holding at 270 ° C. for 3 hours to allow the imidization to proceed quantitatively. Thereby, the porous polyimide fine particle which maintained the porosity of the porous polyamic acid fine particle was able to be obtained.
The porosity (pore diameter, particle size, porosity) of the obtained porous polyimide fine particles was observed with a scanning electron microscope (SEM). The results are shown in FIG.

(result)
From the photographs of the scanning electron microscopes of Examples 1 to 6, although the size varies depending on the experimental conditions, the porous polyimide is homogeneous with a narrow particle size, pore size, and porosity distribution each having a particle size of about 50 nm to 1000 nm. It can be seen that fine particles are obtained. In Examples 1 to 4 in which the amount of the polymer added together with the polyamic acid was changed, the porosity and pore diameter of the formed porous polyamic acid fine particles were increased as the blending amount of the polymer was increased. Further, in Example 5 in which the blending of the poor solvent was changed, the particle size and the porosity of the formed porous polyamic acid fine particles were smaller as the blending amount of CS ₂ was larger. From these facts, it is understood that porous polyimide acid fine particles having various particle diameters, pore diameters, and porosity can be prepared by changing the poor solvent, the kind of polymer, and the blending amount of the polymer.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the invention can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a manufacturing method involving such a change is also included in the technical scope of the present invention. Must be understood.

2 is a SEM photograph of porous polyimide fine particles obtained in Example 1. 2 is a SEM photograph of porous polyimide fine particles obtained in Example 2. 4 is a SEM photograph of porous polyimide fine particles obtained in Example 3. 4 is a SEM photograph of porous polyimide fine particles obtained in Example 4. 4 is a SEM photograph of porous polyimide fine particles obtained in Example 5. 4 is a SEM photograph of porous polyimide fine particles obtained in Example 6.

Claims (4)

A polyamic acid / polymer mixed solution in which a polyamic acid and 0.5 to 100% by mass of the polyamic acid and a polymer compatible with the polyamic acid and soluble in the organic solvent are dissolved in an organic solvent. Is injected into a poor solvent of the polyamic acid that is compatible with the organic solvent. The method for producing porous polyamic acid fine particles according to claim 1, wherein the organic solvent is a polar amide solvent. 2. The porous property according to claim 1, wherein the polymer has a repeating unit selected from a carboxyl group, a carbonyl group, an ester group, an amino group, and a hydroxyl group. A method for producing polyamic acid fine particles. A method for producing porous polyimide fine particles, wherein the porous polyamic acid fine particles prepared by the production method according to any one of claims 1 to 3 are further subjected to imidization treatment.

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