Method for producing polyimide hollow particles and polyimide hollow particles

Abstract

The present invention provides a method which is capable of producing polyimide hollow particles, the method being capable of producing polyimide hollow particles having excellent heat resistance without requiring use of template particles and without requiring high temperature and high pressure. The present invention also provides polyimide hollow particles which are produced by this production method.　A method for producing polyimide hollow particles according to one embodiment of the present invention produces polyimide hollow particles, each of which has a shell part and a hollow portion that is surrounded by the shell part. This method for producing polyimide hollow particles comprises: a step for preparing an internal oil phase that contains polyamic acid fine particles and a solvent; a step for preparing an external oil phase which contains a hydrocarbon-based solvent and at least one substance that is selected from the group consisting of silicon dioxide and a compound having a siloxane bond; and a step for performing a chemical imidization reaction in an emulsion that has been prepared from the internal oil phase and the external oil phase.

Description

[Technical Field]

[0001] The present invention relates to a method for producing polyimide hollow particles and to polyimide hollow particles. More specifically, it relates to a method for producing polyimide hollow particles having a shell portion and a hollow portion surrounded by the shell portion, and to polyimide hollow particles. [Background technology]

[0002] Polyimide is a chemically and mechanically stable material with excellent heat resistance, solvent resistance, mechanical properties, and electrical insulation properties. For this reason, polyimide can be used as a coating material for electrical insulating components, a filler for molding, an electrical and electronic material, a substitute material for metals and ceramics, a film, a varnish, an adhesive, a bulk molding material, and a composite material.

[0003] Polyimide particles, which are made by pulverizing polyimide, are endowed with properties derived from their shape and structure, in addition to the polyimide-derived properties mentioned above. Furthermore, hollow particle formation is known as a means of imparting properties such as lightness and heat insulation to the particles. Therefore, if polyimide particles are hollowed out to form polyimide hollow particles, properties derived from the hollow structure will be added in addition to the polyimide-derived properties mentioned above, and improvements in performance in conventional applications and development into new applications can be expected.

[0004] Patent Document 1 discloses a method for producing polyimide microparticles by preparing a polyamic acid solution obtained by dissolving polyamic acid in an organic solvent containing at least 50% amide-based solvent, injecting the solution into a poor solvent containing a polyacrylic acid ester-based polymer surfactant under specific conditions to prepare a dispersion of polyamic acid microparticles, adding a pyridine / acetic anhydride mixed solution to the prepared dispersion of polyamic acid microparticles to chemically imideize it, preparing a dispersion of polyimide microparticles, separating the organic solvent and the poor solvent in the prepared dispersion of polyimide microparticles, agglomerating the polyimide microparticles at the liquid-liquid interface to form polyimide microparticle aggregates, and then separating and recovering the formed polyimide microparticle aggregates and drying them.

[0005] However, the polyimide microparticle aggregates obtained by the manufacturing method described in Patent Document 1 have a problem in that they contain a polyacrylic acid ester-based polymer surfactant with low heat resistance used as a dispersant, and because a large amount of this dispersant is used, it reduces the heat resistance that the polyimide can inherently exhibit.

[0006] Patent Document 2 discloses a method for producing hollow particles having a volume-average particle diameter of 0.1 μm to 1 mm, wherein the shell constituting the hollow particle consists of one or more layers, and the outermost layer of these layers is layer (A) made of polyimide (a), and the method is characterized by including the following steps 1 to 6. Step 1: A step to produce a polyamic acid solution (S1) consisting of polyamic acid and a solvent (S1). Step 2: A step to produce a dispersion (D1) by dispersing fine particles (A1) made of other materials (b) in a polyamic acid solution (S1). Step 3: A dispersion (D2) in which hydrophobic fine particles (A2) are dispersed in a solvent (s2) that is miscible with the solvent (s1) without dissolving polyamic acid, and a dispersion (D1) are mixed and stirred to produce a dispersion (D3) containing precursor particles (A3) in which polyamic acid is adsorbed on the surface of the fine particles (A1). Step 4: The process of separating and extracting precursor particles (A3) from the dispersion (D3). Step 5: Disperse precursor particles (A3) in a hydrophobic solvent (s3) having an SP value of 7 or less and a boiling point equal to or greater than the boiling points of solvents (s1) and (s2), and carry out an imidation reaction at a temperature equal to or greater than the boiling points of solvents (s1) and (s2) and less than the boiling point of hydrophobic solvent (s3) to obtain a hydrophobic solvent dispersion (D4) of imidized particles (A4). Step 6: A step to obtain imidized particles (A4) by separating, washing and drying from a hydrophobic solvent dispersion (D4), wherein if the fine particles (A1) made of other material (b) are hollow fine particles, the obtained imidized particles (A4) are obtained as the desired hollow particles; if the fine particles (A1) are solid fine particles, the obtained imidized particles (A4) are added to an aqueous medium and dispersed, and further a solvent or decomposition agent for other material (b) is added to remove material (b) and wash to obtain the desired hollow particles.

[0007] However, the manufacturing method described in Patent Document 2 is a method for producing hollow particles using a so-called template method, and the particle size of the resulting particles depends on the particle size of the template particles. Furthermore, the presence of template particles in the hollow portion surrounded by the shell affects the physical properties of the resulting hollow particles, leading to problems such as a decrease in the heat resistance that polyimide can inherently exhibit.

[0008] Patent Document 3 discloses a method for producing hollow resin particles with resin (A) as the shell, characterized by suspending a solution (E) obtained by dissolving a precursor (A1) of resin (A) and a phase separation accelerator (C) in a volatile solvent (B) in a solvent (D) that is insoluble with the precursor (A1), resin (A), and volatile solvent (B) and has a higher boiling point than the volatile solvent (B), polymerizing the solution under pressure to synthesize resin (A), and then depressurizing at a temperature above the boiling point of the volatile solvent (B). Polyimide resin is disclosed as one of the exemplary compounds of resin (A).

[0009] However, the manufacturing method described in Patent Document 3 is a manufacturing method that uses harsh conditions of high temperature and high pressure, which presents problems such as the need for special manufacturing equipment and poor production efficiency due to the time required for heating and cooling.

[0010] Patent Document 4 discloses hollow particles having a volume-average particle diameter of 0.1 μm to 1 mm, wherein the shell constituting the hollow particle consists of one or more layers, and the outermost layer of these layers is a layer (L1) made of polyimide (a).

[0011] However, the manufacturing method described in Patent Document 4 is a method for producing hollow particles using a so-called template method, and the particle size of the resulting particles depends on the particle size of the template particles. Furthermore, the presence of template particles in the hollow portion surrounded by the shell portion affects the physical properties of the resulting hollow particles, leading to problems such as a decrease in the heat resistance that polyimide can inherently exhibit. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 5429922 [Patent Document 2] Patent No. 5133107 [Patent Document 3] Patent No. 4991327 [Patent Document 4] Japanese Patent Publication No. 2009-235294 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide a method for producing polyimide hollow particles that does not require the use of template particles, does not require high temperature and high pressure conditions, and produces polyimide hollow particles with excellent heat resistance. Another objective is to provide polyimide hollow particles with excellent heat resistance. [Means for solving the problem]

[0014] [1] The method for producing polyimide hollow particles according to an embodiment of the present invention is a method for producing polyimide hollow particles having a shell portion and a hollow portion surrounded by the shell portion, the method including: a step of preparing an internal oil phase containing polyamic acid fine particles and a solvent; a step of preparing an external oil phase containing at least one selected from the group consisting of a compound having a siloxane bond and silicon dioxide and a hydrocarbon-based solvent; and a step of performing a chemical imidization reaction in an emulsion prepared from the internal oil phase and the external oil phase. [2] In the method for producing polyimide hollow particles according to [1] above, the compound having a siloxane bond may be polysiloxane. [3] In the method for producing polyimide hollow particles according to [1] above, the compound having a siloxane bond may have an azo group. [4] In the method for producing polyimide hollow particles according to [1] above, the silicon dioxide may be hydrophobic silica particles having a specific surface area of 10 m 2 / g or more. [5] In the method for producing polyimide hollow particles according to any one of [1] to [4] above, the reaction temperature of the chemical imidization reaction may be 100°C or lower. [6] In the method for producing polyimide hollow particles according to any one of [1] to [5] above, the solvent contained in the internal oil phase may be an amide-based solvent. [7] In the method for producing polyimide hollow particles according to any one of [1] to [6] above, the concentration of the polyamic acid fine particles in the emulsion may be 0.1% by weight or more. [8] The polyimide hollow particles according to an embodiment of the present invention are polyimide hollow particles having a shell portion and a hollow portion surrounded by the shell portion, and have a volume average particle diameter of 0.1 μm to 100 μm. [9] In the polyimide hollow particles according to [8] above, the coefficient of variation (CV value) of the particle diameter of the polyimide hollow particles may be 80% or less.

[10] In the polyimide hollow particles according to [8] or [9] above, the 5% thermogravimetric weight loss temperature when the polyimide hollow particles are heated at 10°C / min in an air atmosphere may be 330°C or higher.

[11] In the polyimide hollow particles described in any one of [8] to

[10] above, when the relative dielectric constant of the film F1 formed by blending 20 parts by weight of the polyimide hollow particles and 80 parts by weight of polyimide is defined as Dk1, and the relative dielectric constant of the film F0 composed only of polyimide is defined as Dk0, the relative dielectric constant reduction rate calculated by (Dk1 / Dk0) × 100 (%) may be 20% or more.

[12] The polyimide hollow particles described in any one of [8] to

[11] above may be the polyimide hollow particles obtained by the production method described in any one of [1] to [7] above. [Effect of the Invention]

[0015] According to an embodiment of the present invention, there is provided a method capable of manufacturing polyimide hollow particles, which does not require the use of template particles, does not require high-temperature and high-pressure conditions, and can manufacture polyimide hollow particles having excellent heat resistance. Further, polyimide hollow particles having excellent heat resistance can be provided. [Brief Description of the Drawings]

[0016] [Figure 1] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (1) obtained in Example 1. [Figure 2] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (2) obtained in Example 2. [Figure 3] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (3) obtained in Example 3. [Figure 4] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (4) obtained in Example 4. [Figure 5] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (5) obtained in Example 5. [Figure 6] It is a scanning electron microscope photograph of the particle cross-section of the polyimide hollow particles (6) obtained in Example 6. [Figure 7]This is a scanning electron microscope image of the particle cross-section of the polyimide hollow particle (7) obtained in Example 7. [Figure 8] This is a scanning electron microscope image of a cross-sectional view of the polyimide hollow particles (8) obtained in Example 8. [Figure 9] This is a scanning electron microscope image of a cross-sectional view of the polyimide hollow particle (9) obtained in Example 9. [Figure 10] This is a scanning electron microscope image of a cross-sectional view of the polyimide hollow particles (10) obtained in Example 10. [Modes for carrying out the invention]

[0017] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0018] ≪≪1. Method for producing polyimide hollow particles≫≫ A method for producing polyimide hollow particles according to an embodiment of the present invention is a method for producing polyimide hollow particles having a shell portion and a hollow portion surrounded by the shell portion.

[0019] In this invention, "hollow" refers to a state in which the interior is filled with a substance other than resin, such as a gas or liquid, and preferably, in order to better exhibit the effects of this invention, it refers to a state in which the interior is filled with gas.

[0020] The shell portion and the hollow portion enclosed by the shell portion may consist of one hollow region or multiple hollow regions (porous structure).

[0021] A method for producing polyimide hollow particles according to an embodiment of the present invention includes the steps of: preparing an inner oil phase containing polyamic acid fine particles and a solvent (hereinafter, for convenience, this may be referred to as step I); preparing an outer oil phase containing at least one selected from the group consisting of compounds having siloxane bonds and silicon dioxide and a hydrocarbon solvent (hereinafter, for convenience, this may be referred to as step II); and carrying out a chemical imidation reaction in an emulsion prepared from the inner oil phase and the outer oil phase (hereinafter, for convenience, this may be referred to as step III).

[0022] The method for producing polyimide hollow particles according to embodiments of the present invention may include any suitable steps other than steps I, II, and III, as long as they do not impair the effects of the present invention.

[0023] The method for producing polyimide hollow particles according to the embodiment of the present invention has the advantage that the particle size of the resulting polyimide hollow particles does not depend on the particle size of the template particles, because it does not use a so-called template method that uses template particles. Furthermore, the method for producing polyimide hollow particles according to the embodiment of the present invention has the advantage that, because it does not use a so-called template method that uses template particles, no template particles remain in the hollow portion surrounded by the shell portion, and therefore the physical properties of the template particles do not affect the physical properties of the resulting polyimide hollow particles. In particular, it has the advantage that the heat resistance that polyimide can inherently exhibit can be fully expressed.

[0024] The method for producing polyimide hollow particles according to the embodiment of the present invention does not require high temperature and high pressure conditions, thus eliminating the need for special manufacturing equipment for high temperature and high pressure reactions, and reducing factors that worsen production efficiency, such as the time required for heating and cooling.

[0025] ≪1-1. Process I≫ In step I, an inner oil phase containing polyamic acid fine particles and a solvent is prepared.

[0026] Polyamic acid nanoparticles can be prepared by any suitable method, provided that the effects of the present invention are not impaired. Such a method may involve mixing a solution of tetracarboxylic anhydride dissolved in a solvent with a solution of diamine dissolved in a solvent and reacting the mixture.

[0027] As the tetracarboxylic anhydride, any suitable tetracarboxylic anhydride can be used as long as it does not impair the effects of the present invention. There may be only one tetracarboxylic anhydride or two or more. Examples of such tetracarboxylic anhydrides include 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 1,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-biphenyltetracarboxylic Examples include aromatic tetracarboxylic acid anhydrides such as rubonic acid dianhydride, 2,2',6,6'-biphenyltetracarboxylic acid dianhydride, naphthalene-1,2,4,5-tetracarboxylic acid dianhydride, anthracene-2,3,6,7-tetracarboxylic acid dianhydride, and phenanthrene-1,8,9,10-tetracarboxylic acid dianhydride; aliphatic tetracarboxylic acid anhydrides such as butane-1,2,3,4-tetracarboxylic acid dianhydride; alicyclic tetracarboxylic acid anhydrides such as cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride; and heterocyclic tetracarboxylic acid anhydrides such as pyridine-2,3,5,6-tetracarboxylic acid anhydride. From the viewpoint of being able to better express the effects of the present invention, among these tetracarboxylic anhydrides, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) and pyromellitic acid dianhydride are preferred.

[0028] As the tetracarboxylic anhydride, a tetracarboxylic anhydride in which a portion is substituted with an acid chloride may be used. By substituting a portion of the tetracarboxylic anhydride with an acid chloride, effects such as increasing the reaction rate or further reducing the particle size of the resulting polyamic acid nanoparticles can be obtained depending on the conditions. Examples of acid chlorides include diethyl pyromelitate diacyl chloride.

[0029] As a solvent for dissolving tetracarboxylic anhydride, any suitable solvent can be used, provided that it substantially dissolves tetracarboxylic anhydride and does not dissolve the resulting polyamic acid nanoparticles, as long as it does not impair the effects of the present invention. Such a solvent may be one type or two or more types. Examples of such solvents include 2-propanone, 3-pentanone, tetrahydropyrene, epichlorohydrin, acetone, methyl ethyl ketone (MEK), tetrahydrofuran (THF), ethyl acetate, acetanilide, methanol, ethanol, isopropanol, toluene, and xylene. Furthermore, even solvents that dissolve polyamic acid nanoparticles, such as amide solvents like N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP), can be used if they are mixed with the above-mentioned poor solvents for polyamic acid nanoparticles to adjust the mixture so that the polyamic acid nanoparticles do not dissolve (for example, precipitate). Furthermore, in order to adjust the molecular weight of the resulting polyamic acid nanoparticles, water may be used in combination with the above-mentioned solvents as a solvent for dissolving tetracarboxylic anhydride.

[0030] The concentration of tetracarboxylic anhydride in the solution obtained by dissolving tetracarboxylic anhydride in a solvent can be any appropriate concentration as long as it does not impair the effects of the present invention. From the viewpoint of preparing good spherical polyamic acid fine particles, such a concentration is preferably 0.01% to 20% by weight, more preferably 0.1% to 10% by weight, even more preferably 0.3% to 7.0% by weight, and particularly preferably 0.5% to 5.0% by weight.

[0031] Any suitable diamine can be used as the diamine, as long as it does not impair the effects of the present invention. There may be only one diamine or two or more diamines. Examples of such diamines include 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl ether (DPE), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 1,4'-bis(4-aminophenoxy)benzene (TPE-Q), 1,3'-bis(4-aminophenoxy)benzene (TPE-R), o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-methylene-bis(2-chloroaniline), 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl sulfide, and 2,6'-diaminotoluene. Examples include aromatic diamines such as 2,4-diaminochlorobenzene, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 3,3'-diaminobenzophenone, 3,4-diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4'-diaminobibenzyl, R(+)-2,2'-diamino-1,1'-binaphthalene, and S(+)-2,2'-diamino-1,1'-binaphthalene; aliphatic diamines such as 1,2-diaminomethane, 1,4-diaminobutane, tetramethylenediamine, and 1,10-diaminododecane; alicyclic diamines such as 1,4-diaminocyclohexane, 1,2-diaminocyclohexane, bis(4-aminocyclohexyl)methane, and 4,4'-diaminodicyclohexylmethane; 3,4-diaminopyridine; and 1,4-diamino-2-butanone. Blocked diamines may also be used as diamines. From the viewpoint of better exhibiting the effects of the present invention, among these diamines, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl ether (DPE), and 1,3'-bis(4-aminophenoxy)benzene (TPE-R) are preferred.

[0032] For the purpose of modifying the resulting polyamic acid nanoparticles, diamines may be used in combination with other amine compounds (monoamine compounds, polyhydric amine compounds, etc.).

[0033] As a solvent for dissolving the diamine, any suitable solvent can be used, provided that it substantially dissolves the diamine but does not dissolve the resulting polyamic acid nanoparticles, as long as it does not impair the effects of the present invention. Such a solvent may be one type or two or more types. Examples of such solvents include 2-propanone, 3-pentanone, tetrahydropyrene, epichlorohydrin, acetone, methyl ethyl ketone (MEK), tetrahydrofuran (THF), ethyl acetate, acetanilide, methanol, ethanol, isopropanol, toluene, and xylene. Furthermore, even solvents that dissolve polyamic acid nanoparticles, such as amide solvents like N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP), can be used if they are mixed with the above-mentioned poor solvents for polyamic acid nanoparticles to adjust the mixture so that the polyamic acid nanoparticles do not dissolve (for example, precipitate).

[0034] The concentration of diamine in the solution obtained by dissolving the diamine in a solvent can be any appropriate concentration as long as it does not impair the effects of the present invention. From the viewpoint of preparing good spherical polyamic acid fine particles, such a concentration is preferably 0.01% to 20% by weight, more preferably 0.1% to 10% by weight, even more preferably 0.3% to 7.0% by weight, and particularly preferably 0.5% to 5.0% by weight.

[0035] As a method for reacting a solution of tetracarboxylic anhydride dissolved in a solvent with a solution of diamine dissolved in a solvent, any suitable method can be used as long as it does not impair the effects of the present invention. From the viewpoint of better exhibiting the effects of the present invention, a method of mixing and reacting a solution of tetracarboxylic anhydride dissolved in a solvent with a solution of diamine dissolved in a solvent is more preferable than a method of stirring with ultrasound. By stirring with ultrasound, it is possible to refine the average particle size by about 50% compared to a conventional stirring method. For ultrasonic stirring, any suitable ultrasonic device and conditions can be used, such as an ultrasonic emulsifier such as an ultrasonic homogenizer (manufactured by Branson, etc.). The frequency of the ultrasound can be set appropriately according to the desired particle size, etc., and is usually around 10kHz to 100kHz, preferably 15kHz to 45kHz.

[0036] The temperature at which the solution of tetracarboxylic anhydride dissolved in a solvent and the solution of diamine dissolved in a solvent are mixed and reacted can be any suitable temperature within a range that does not impair the effects of the present invention. From the viewpoint of preparing good spherical polyamic acid fine particles, such a temperature is preferably 0°C to 130°C, more preferably 5°C to 80°C, even more preferably 10°C to 50°C, particularly preferably 15°C to 40°C, and most preferably 20°C to 30°C.

[0037] The reaction time for mixing the solution of tetracarboxylic anhydride dissolved in a solvent with the solution of diamine dissolved in a solvent can be any appropriate time within a range that does not impair the effects of the present invention. From the viewpoint of preparing good spherical polyamic acid fine particles, such a time is preferably 10 seconds to 24 hours, more preferably 10 seconds to 12 hours, even more preferably 10 seconds to 6 hours, and particularly preferably 10 seconds to 1 hour.

[0038] The molar ratio of tetracarboxylic anhydride to diamine can be any appropriate molar ratio as long as it does not impair the effects of the present invention. From the viewpoint of preparing good spherical polyamic acid fine particles, such a molar ratio is preferably 1:0.5 to 1:1.5, more preferably 1:0.8 to 1:1.2, and even more preferably 1:0.9 to 1:1.1.

[0039] In a method involving mixing a solution of tetracarboxylic anhydride dissolved in a solvent with a solution of diamine dissolved in a solvent and reacting the mixture, polyamic acid nanoparticles typically precipitate as fine particles in the solvent. Therefore, the polyamic acid nanoparticles precipitated in the solvent can be isolated by solid-liquid separation using any appropriate method, washed if necessary using any appropriate method, and dried if necessary using any appropriate method.

[0040] Any suitable method can be used for solid-liquid separation, as long as it does not impair the effects of the present invention. For example, centrifugation is one such method of solid-liquid separation.

[0041] Any suitable solvent can be used as the solvent for preparing the inner oil phase, as long as it does not impair the effects of the present invention. Such solvents may be one type or two or more types. From the viewpoint of being able to better express the effects of the present invention, amide solvents are preferably used as the solvent for preparing the inner oil phase. Examples of amide solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone, and acetanilide.

[0042] The inner oil phase may contain any other suitable components as long as they do not impair the effects of the present invention, provided that they contain polyamic acid fine particles and a solvent. From the viewpoint of better exhibiting the effects of the present invention, the total content of polyamic acid fine particles and solvent in the inner oil phase is preferably 80% to 100% by weight, more preferably 90% to 100% by weight, even more preferably 95% to 100% by weight, and particularly preferably 98% to 100% by weight.

[0043] The inner oil phase may contain, as other components, at least one non-crosslinkable polymer selected from the group consisting of polyolefins, styrene polymers, (meth)acrylic polymers, styrene-(meth)acrylic polymers, polycarbonates, and styrene-maleic anhydride copolymers. Such non-crosslinkable polymers may be one type or two or more types.

[0044] The content of the non-crosslinkable polymer in the internal oil phase is preferably 0% to 20% by weight, more preferably 0% to 10% by weight, even more preferably 0% to 5% by weight, and particularly preferably 0% to 2% by weight, in order to better exhibit the effects of the present invention.

[0045] From the viewpoint of enabling the effects of the present invention to be more fully expressed, the internal oil phase is preferably prepared by dissolving polyamic acid fine particles in a solvent. Furthermore, if the internal oil phase contains a non-crosslinkable polymer, the internal oil phase is preferably prepared by dissolving polyamic acid fine particles and the non-crosslinkable polymer in a solvent.

[0046] The concentration of polyamic acid fine particles in the inner oil phase can be any appropriate concentration as long as it does not impair the effects of the present invention. From the viewpoint of better exhibiting the effects of the present invention, such a concentration is preferably 0.1% to 50% by weight, more preferably 1% to 40% by weight, even more preferably 5% to 35% by weight, and particularly preferably 10% to 30% by weight.

[0047] ≪1-2. Process II≫ In step II, an outer oil phase is prepared containing at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide, and a hydrocarbon solvent. The at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide preferably functions as a dispersant. The compounds having siloxane bonds may be one or two or more. The silicon dioxide may be one or two or more.

[0048] By employing at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide as a dispersant, unlike polyacrylic acid ester-based polymer surfactants which have low heat resistance, the dispersant itself has high heat resistance, thus not reducing the heat resistance that the polyimide in the target polyimide fine particles can inherently exhibit. Furthermore, by employing at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide as a dispersant, a good emulsion can be obtained even with a small amount of dispersant used, and the chemical imidation reaction to convert polyamic acid fine particles into polyimide fine particles can be carried out in a relatively high-concentration system, resulting in excellent manufacturing efficiency.

[0049] Compounds having a siloxane bond are compounds having a Si-O-Si bond, and preferably compounds having the structure shown in formula (1). [ka]

[0050] In formula (1), R 1 , R 2 R is either the same or different, and each is either a hydrogen atom or an alkyl group. The number of carbon atoms in this alkyl group is preferably 1 to 10, more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 2, and most preferably 1, from the viewpoint of being able to better express the effects of the present invention. In formula (1), R 1 , R 2From the viewpoint of being able to better express the effects of the present invention, these are preferably alkyl groups, and more preferably methyl groups.

[0051] The compound having a siloxane bond is more preferably a compound having a polysiloxane structure in which the structure shown in formula (1) is a repeating unit, and even more preferably a compound having the structure shown in formula (1) (where R 1 is a methyl group, R 2 It is a compound having a polysiloxane structure (polydimethylsiloxane structure) in which methyl groups are repeated as units.

[0052] One embodiment of a compound having a siloxane bond is a polysiloxane. By using a polysiloxane, the effects of the present invention can be more fully expressed. One preferred embodiment of the polysiloxane is a self-emulsified high-degree-of-polymerization polysiloxane, and a commercially available example is "KM-9787" manufactured by Shin-Etsu Chemical Co., Ltd.

[0053] Another embodiment of a compound having a siloxane bond is a compound having the structure shown in formula (1), which is compound (A) having an azo group (-N=N-). By employing such compound (A), the effects of the present invention can be more fully expressed.

[0054] The number-average molecular weight Mn of compound (A) is preferably 5,000 to 1,000,000, more preferably 10,000 to 800,000, even more preferably 30,000 to 500,000, particularly preferably 40,000 to 300,000, and most preferably 50,000 to 200,000, from the viewpoint of being able to better express the effects of the present invention.

[0055] Compound (A) preferably has an amide bond (-NH-CO-) from the viewpoint of being able to better express the effects of the present invention. By having an amide bond in addition to the azo group (-N=N-), the effects of the present invention can be better expressed through electronic and steric effects derived from the azo group and the amide group.

[0056] As the compound (A), from the viewpoint of further expressing the effects of the present invention, etc., it preferably has a cyano group. By having an amide bond and a cyano group in addition to the azo group (-N=N-), the effects of the present invention can be further expressed by the electronic and steric effects derived from the azo group, amide group, and cyano group.

[0057] As the compound (A), from the viewpoint of particularly further expressing the effects of the present invention, etc., it is a compound having a polydimethylsiloxane structure, an azo group, an amide group, and a cyano group. As such a compound, any appropriate compound can be adopted as long as the effects of the present invention are not impaired. Specific examples of such compounds include, for example, the products named "VPS-1001" and "VPS-1001N" manufactured by Fujifilm Wako Pure Chemical Corporation, which are known as polydimethylsiloxane unit-containing polymer azo polymerization initiators.

[0058] One embodiment of silicon dioxide is the compound (B) which is hydrophobic silica particles having a specific surface area of 10 m 2 / g or more. By adopting such a compound (B), the effects of the present invention can be more expressed.

[0059] From the viewpoint of further expressing the effects of the present invention, etc., the specific surface area of the compound (B) is preferably 10 m 2 / g to 1000 m 2 / g, more preferably 30 m 2 / g to 500 m 2 / g, and even more preferably 50 m 2 / g to 300 m 2 / g.

[0060] As the compound (B), having a specific surface area of 10 m 2Any suitable compound can be used as long as it does not impair the effects of the present invention, as long as it contains hydrophobic silica particles of 1 / g or more.Specific examples of such compounds include the trade names "Aerosil R972", "Aerosil R972CF", "Aerosil R972V", "Aerosil R974", "Aerosil R976", "Aerosil R976S", and "Aerosil R9200" manufactured by Nippon Aerosil Co., Ltd.

[0061] As the hydrocarbon solvent, any suitable hydrocarbon solvent can be used as long as it does not impair the effects of the present invention. Such hydrocarbon solvents may be one type or two or more types. Examples of such hydrocarbon solvents include pentane, hexane, cyclohexane, heptane, octane, benzene, toluene, xylene, and ethylbenzene.

[0062] The outer oil phase may contain any other suitable components as long as they do not impair the effects of the present invention, provided that they do not impair the effects of the present invention, as long as they contain at least one selected from the group consisting of compounds having siloxane bonds and silicon dioxide and a hydrocarbon solvent. From the viewpoint of better exhibiting the effects of the present invention, the total content of at least one selected from the group consisting of compounds having siloxane bonds and silicon dioxide and the hydrocarbon solvent in the outer oil phase is preferably 80% to 100% by weight, more preferably 90% to 100% by weight, even more preferably 95% to 100% by weight, particularly preferably 98% to 100% by weight, and most preferably substantially 100% by weight. Note that "substantially 100% by weight" means that although there are no other components intentionally added, it may include the presence of trace amounts of impurities (e.g., less than 1% by weight) that do not affect the effects of the present invention.

[0063] From the viewpoint of enabling the effects of the present invention to be more fully expressed, the outer oil phase is preferably prepared by dissolving at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide in a hydrocarbon solvent.

[0064] The concentration of at least one compound selected from the group consisting of siloxane-bonded compounds and silicon dioxide in the outer oil phase can be any appropriate concentration within a range that does not impair the effects of the present invention. From the viewpoint of better exhibiting the effects of the present invention, such a concentration is preferably 0.001% to 10% by weight, more preferably 0.005% to 5.0% by weight, and even more preferably 0.01% to 3.0% by weight.

[0065] ≪1-3. Process III≫ In step III, a chemical imidation reaction is carried out in an emulsion prepared from the inner oil phase prepared in step I and the outer oil phase prepared in step II.

[0066] In step III, preferably, an emulsion is prepared from the inner oil phase and the outer oil phase, and a chemical imidizing agent is added to the emulsion to carry out a chemical imidization reaction.

[0067] Mixing the inner oil phase and the outer oil phase typically involves adding the inner oil phase to the outer oil phase.

[0068] From the viewpoint of enabling the effects of the present invention to be more fully realized, the mixing ratio of the inner oil phase to the outer oil phase is preferably 1:10 to 1:500 by weight, more preferably 1:30 to 1:300, and even more preferably 1:50 to 1:100.

[0069] As a method for preparing an emulsion from the inner oil phase and the outer oil phase, any suitable method can be adopted as long as it does not impair the effects of the present invention. From the viewpoint of being able to better express the effects of the present invention, a preferred method for preparing an emulsion from the inner oil phase and the outer oil phase is to add the inner oil phase to the outer oil phase and perform emulsification using an emulsifier or disperser. Examples of emulsifiers and dispersers include batch-type emulsifiers such as homogenizers (manufactured by IKA, etc.), Polytron homogenizers (manufactured by Central Science Trading Co., Ltd. or Kinetica, etc.), and Homomixer MARK II (manufactured by Primix, Inc.); Ebara Milder (manufactured by Arihara Seisakusho Co., Ltd.), Filmix (manufactured by Primix, Inc.), Colloid Mill (manufactured by Shinko Pantech Co., Ltd., etc.), Slasher (manufactured by Mitsui Miike Chemical Machinery Co., Ltd., etc.), Trigonal wet pulverizer (manufactured by Mitsui Miike Chemical Machinery Co., Ltd., etc.), Capy Examples include continuous emulsifiers such as TRON (manufactured by Eurotech, etc.) and Fine Flow Mill (manufactured by Taiheiyo Kiko Co., Ltd.); high-pressure emulsifiers such as microfluidizers (manufactured by Powrec, Inc.), nanomizers (manufactured by Nanomizer, Inc.), nanovata (manufactured by Yoshida Machinery Industry Co., Ltd.), and APV Gaurin (manufactured by Gaurin, Inc.); membrane emulsifiers such as membrane emulsifiers (manufactured by Reika Kogyo Co., Ltd., etc.); vibratory emulsifiers such as vibromixers (manufactured by Reika Kogyo Co., Ltd., etc.); and ultrasonic emulsifiers such as ultrasonic homogenizers (manufactured by Branson, Inc., etc.).

[0070] When preparing the emulsion from the inner oil phase and the outer oil phase, any other suitable component may be added, as long as it does not impair the effects of the present invention.

[0071] The concentration of polyamic acid fine particles in the emulsion prepared from the inner oil phase and the outer oil phase can be any appropriate concentration as long as it does not impair the effects of the present invention. From the viewpoint of further exhibiting the effects of the present invention, the concentration of polyamic acid fine particles in the emulsion prepared from the inner oil phase and the outer oil phase is preferably 0.1% by weight or more, more preferably 0.15% to 5.0% by weight, and even more preferably 0.2% to 1.0% by weight.

[0072] As the chemical imidizing agent, any suitable chemical imidizing agent can be used as long as it does not impair the effects of the present invention. There may be only one chemical imidizing agent or two or more chemical imidizing agents. For example, a combination of pyridine and acetic anhydride can be used as such. From the viewpoint of being able to better express the effects of the present invention, the weight ratio of pyridine to acetic anhydride is preferably 1:0.1 to 1:10, more preferably 1:0.3 to 1:3, even more preferably 1:0.5 to 1:2, and particularly preferably 1:0.8 to 1:1.2.

[0073] The amount of chemical imidizing agent used can be any appropriate amount, as long as it does not impair the effects of the present invention. From the viewpoint of better exhibiting the effects of the present invention, the amount of chemical imidizing agent used is preferably 50 to 1200 parts by weight, and more preferably 100 to 800 parts by weight, per 100 parts by weight of polyamic acid fine particles in the internal oil phase.

[0074] The reaction temperature for the chemical imidation reaction can be set to any appropriate temperature within a range that does not impair the effects of the present invention, depending on the boiling point of the hydrocarbon solvent in the outer oil phase. From the viewpoint of better exhibiting the effects of the present invention, the reaction temperature for the chemical imidation reaction is preferably 100°C or lower, more preferably 0°C to 90°C, and more preferably 20°C to 80°C.

[0075] The reaction time for the chemical imidation reaction can be any appropriate time within a range that does not impair the effects of the present invention. From the viewpoint of better exhibiting the effects of the present invention, the reaction time for the chemical imidation reaction is preferably 0.1 hours to 50 hours, and more preferably 1.0 hour to 24 hours.

[0076] By carrying out a chemical imidation reaction, polyimide hollow particles are formed in the reaction solution. The resulting polyimide hollow particles can be isolated by solid-liquid separation using any suitable method, washed if necessary using any suitable method, and dried if necessary using any suitable method.

[0077] Any suitable method can be used for solid-liquid separation, as long as it does not impair the effects of the present invention. For example, centrifugation is one such method of solid-liquid separation.

[0078] ≪≪2. Polyimide Hollow Particles≫≫ The polyimide hollow particles according to the embodiment of the present invention have a shell portion and a hollow portion surrounded by the shell portion. As mentioned above, the term "hollow" in the present invention means a state in which the interior is filled with a substance other than resin, such as a gas or liquid, and preferably means a state in which it is filled with gas, in order to better exhibit the effects of the present invention. Also, as mentioned above, the shell portion and the hollow portion surrounded by the shell portion may consist of one hollow region or may consist of multiple hollow regions (porous structure).

[0079] The polyimide hollow particles according to the embodiments of the present invention preferably have a volume-average particle diameter of 0.1 μm to 100 μm, more preferably 0.5 μm to 80 μm, and even more preferably 1.0 μm to 50 μm. If the volume-average particle diameter of the polyimide hollow particles according to the embodiments of the present invention is too small and outside the above range, the thickness of the shell portion will be relatively thin, which may result in polyimide hollow particles that do not have sufficient strength. If the average particle diameter of the polyimide hollow particles according to the embodiments of the present invention is too large and outside the above range, the chemical imidation reaction may not proceed sufficiently, which may result in reduced heat resistance.

[0080] The polyimide hollow particles according to the embodiments of the present invention preferably have a coefficient of variation (CV) of particle size of 80% or less, more preferably 1% to 80%, even more preferably 2% to 75%, particularly preferably 3% to 70%, and most preferably 5% to 65%. If the coefficient of variation (CV) of particle size of the polyimide hollow particles according to the embodiments of the present invention is within the above range, the effects of the present invention can be more fully realized. If the coefficient of variation (CV) of particle size of the polyimide hollow particles according to the embodiments of the present invention is too large and outside the above range, the amount of coarse particles will increase, which may lead to difficulties in forming thin films or variations in thickness when, for example, a resin layer is formed from a resin composition. The smaller the coefficient of variation (CV) of particle size of the polyimide hollow particles according to the embodiments of the present invention, the more uniform the particle size is, which is preferable. However, considering factors such as the feasibility of practical production, the lower limit may be as described above.

[0081] The polyimide hollow particles according to the embodiments of the present invention have a 5% thermoweight loss temperature of preferably 330°C or higher, more preferably 350°C or higher, even more preferably 370°C or higher, and particularly preferably 400°C or higher when heated at a rate of 10°C / min in an air atmosphere. In practice, the upper limit of the 5% thermoweight loss temperature is preferably 600°C or lower. If the 5% thermoweight loss temperature is within the above range, the polyimide hollow particles according to the embodiments of the present invention can exhibit excellent heat resistance. If the 5% thermoweight loss temperature is too low and falls outside the above range, for example, when the polyimide hollow particles are kneaded with a thermosetting resin, the polyimide hollow particles may deform due to heating for the curing reaction, and the hollow portion may be lost, which may reduce the low dielectric effect and the low dielectric loss tangent effect.

[0082] The polyimide hollow particles according to the embodiment of the present invention have a relative permittivity reduction rate calculated as (Dk1 / Dk0) × 100 (%), where Dk1 is the relative permittivity of a film F1 made by blending 20 parts by weight of the polyimide hollow particles and 80 parts by weight of polyimide, and Dk0 is the relative permittivity of a film F0 made only of polyimide. This reduction rate is preferably 10% or more, more preferably 15% or more, even more preferably 18% or more, and particularly preferably 20% or more. In practice, the upper limit of the relative permittivity reduction rate is preferably 50% or less. If the relative permittivity reduction rate is within the above range, the polyimide hollow particles according to the embodiment of the present invention can exhibit an excellent low dielectric effect when added to a resin, for example, because of their low relative permittivity.

[0083] The polyimide hollow particles according to the embodiment of the present invention have a dielectric loss tangent reduction rate calculated as (Df1 / Df0) × 100 (%), where Df1 is the dielectric loss tangent of a film F1 made by blending 20 parts by weight of the polyimide hollow particles and 80 parts by weight of polyimide, and Df0 is the dielectric loss tangent of a film F0 made only of polyimide. This reduction rate is preferably 4% or more, more preferably 7% or more, even more preferably 10% or more, and particularly preferably 12% or more. In practice, the upper limit of the dielectric loss tangent reduction rate is preferably 50% or less. If the dielectric loss tangent reduction rate is within the above range, the polyimide hollow particles according to the embodiment of the present invention have a low dielectric loss tangent, and therefore, when added to a resin, for example, an excellent low dielectric loss tangent effect can be achieved.

[0084] Polyimide hollow particles according to embodiments of the present invention are preferably obtained by a method for producing polyimide hollow particles according to embodiments of the present invention.

[0085] ≪≪3. Applications of Polyimide Hollow Particles≫≫ Polyimide hollow particles according to embodiments of the present invention can be used in a variety of applications. In terms of making better use of the effects of the present invention, polyimide hollow particles according to embodiments of the present invention can be applied to semiconductor materials (typically resin compositions for semiconductor materials), paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, light diffusing films, etc., and are particularly suitable for resin compositions for semiconductor materials and paint compositions.

[0086] ≪3-1. Resin Compositions for Semiconductor Materials≫ The polyimide hollow particles according to the embodiments of the present invention can achieve low dielectric strength and low dielectric loss tangent, and exhibit excellent heat resistance, making them suitable for use in resin compositions for semiconductor components.

[0087] A resin composition for semiconductor components according to an embodiment of the present invention includes hollow resin particles according to an embodiment of the present invention.

[0088] Semiconductor components refer to the components that make up a semiconductor, such as semiconductor packages and semiconductor modules. In this specification, a resin composition for semiconductor components refers to a resin composition used in semiconductor components.

[0089] A semiconductor package is a component in which an IC chip is an essential component, and is constructed using at least one material selected from molding resin, underfill material, molded underfill material, die bonding material, prepreg for semiconductor package substrates, metal-clad laminate for semiconductor package substrates, and build-up material for printed circuit boards for semiconductor packages.

[0090] A semiconductor module is a component in which a semiconductor package is an essential component, and which is composed of at least one component selected from prepregs for printed circuit boards, metal-clad laminates for printed circuit boards, build-up materials for printed circuit boards, solder resist materials, coverlay films, electromagnetic shielding films, and adhesive sheets for printed circuit boards.

[0091] ≪3-2. Paint composition≫ The polyimide hollow particles according to the embodiments of the present invention can impart an excellent appearance to the coating film containing them, and are therefore suitable for use in coating compositions.

[0092] A coating composition according to an embodiment of the present invention contains polyimide hollow particles according to an embodiment of the present invention.

[0093] The paint composition according to the embodiments of the present invention preferably comprises at least one selected from a binder resin and a UV-curable resin. The binder resin may be one type or two or more types. The UV-curable resin may be one type or two or more types.

[0094] Any suitable binder resin can be used as the binder resin, as long as it does not impair the effects of the present invention. Examples of such binder resins include resins soluble in organic solvents or water, and emulsion-type aqueous resins that can be dispersed in water. Specifically, examples of binder resins include acrylic resins, alkyd resins, polyester resins, polyurethane resins, chlorinated polyolefin resins, and amorphous polyolefin resins.

[0095] As the UV-curable resin, any suitable UV-curable resin can be used as long as it does not impair the effects of the present invention. Examples of such UV-curable resins include polyfunctional (meth)acrylate resins and polyfunctional urethane acrylate resins, with polyfunctional (meth)acrylate resins being preferred, and polyfunctional (meth)acrylate resins having three or more (meth)acryloyl groups in one molecule being more preferred. Specific examples of polyfunctional (meth)acrylate resins having three or more (meth)acryloyl groups in one molecule include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexanetetra(meth)acrylate, pentaglycerol triacrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol triacrylate, and tripentaerythritol hexaacrylate.

[0096] When a paint composition according to an embodiment of the present invention contains at least one selected from a binder resin and a UV-curable resin, the proportion of these components can be any appropriate proportion depending on the purpose. Typically, the amount of hollow resin particles according to an embodiment of the present invention is preferably 5% to 50% by weight, more preferably 10% to 50% by weight, and even more preferably 20% to 40% by weight, relative to the total amount of the binder resin (in terms of solid content in the case of an emulsion-type aqueous resin) and at least one selected from a UV-curable resin and the hollow resin particles according to an embodiment of the present invention.

[0097] When UV-curable resins are used, a photopolymerization initiator is preferably used in combination. Any suitable photopolymerization initiator can be used as the photopolymerization initiator, as long as it does not impair the effects of the present invention. Examples of such photopolymerization initiators include acetophenones, benzoins, phosphine oxides, ketals, α-hydroxyalkylphenones, α-aminoalkylphenones, anthraquinones, thioxanthones, azo compounds, peroxides (as described in Japanese Patent Publication No. 2001-139663, etc.), 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfoniums, onium salts, borate salts, activated halogen compounds, and α-acyloxime esters.

[0098] The paint composition according to the embodiment of the present invention may contain a solvent. The solvent may be one type or two or more types. When the paint composition according to the embodiment of the present invention contains a solvent, any appropriate proportion can be adopted depending on the purpose.

[0099] As the solvent, any suitable solvent can be used as long as it does not impair the effects of the present invention. Preferably, such a solvent is one that can dissolve or disperse the binder resin or UV-curable resin. Examples of such solvents for oil-based paints include hydrocarbon solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; and ether solvents such as dioxane, ethylene glycol diethyl ether, and ethylene glycol monobutyl ether. Examples of solvents for water-based paints include water and alcohols.

[0100] The paint compositions according to embodiments of the present invention may be diluted to adjust the viscosity as needed. Any suitable diluent can be used as the diluent, depending on the purpose. Examples of such diluents include the solvents mentioned above. There may be one diluent or two or more diluents.

[0101] The coating compositions according to embodiments of the present invention may optionally contain other components, such as surface modifiers, flow modifiers, ultraviolet absorbers, light stabilizers, curing catalysts, extender pigments, coloring pigments, metal pigments, mica powder pigments, and dyes.

[0102] When forming a coating film using a coating composition according to an embodiment of the present invention, any suitable coating method can be adopted depending on the purpose. Examples of such coating methods include spray coating, roll coating, brush coating, coating reverse roll coating, gravure coating, die coating, comma coating, and spray coating.

[0103] When forming a coating film using a coating composition according to an embodiment of the present invention, any suitable method of formation can be adopted depending on the purpose. For example, such a method involves applying the coating to any coated surface of a substrate to create a coating film, drying the coating film, and then curing the coating film as necessary to form the coating film. Examples of substrates include metals, wood, glass, and plastics (PET (polyethylene terephthalate), PC (polycarbonate), acrylic resin, TAC (triacetylcellulose), etc.). [Examples]

[0104] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "percent by weight".

[0105] <<Measurement of volume-average particle size and coefficient of variation>> The volume-average particle diameter of the particles was measured using the Coulter method as follows. The volume-average particle size of the particles was measured using a Coulter Multisizer® 3 (a measuring device manufactured by Beckman Coulter). The measurements were performed using an aperture calibrated according to the Multisizer® 3 User's Manual issued by Beckman Coulter. The aperture used for measurement was selected appropriately depending on the size of the particles being measured. For example, a 50 μm aperture was selected if the assumed volume-average particle size of the particles being measured was between 1 μm and 10 μm; a 100 μm aperture was selected if the assumed volume-average particle size of the particles was greater than 10 μm but 30 μm or less; a 280 μm aperture was selected if the assumed volume-average particle size of the particles was greater than 30 μm but 90 μm or less; and a 400 μm aperture was selected if the assumed volume-average particle size of the particles was greater than 90 μm but 150 μm or less. If the volume-average particle diameter after measurement differed from the expected volume-average particle diameter, the aperture was changed to one of the appropriate size, and the measurement was repeated. The Current (aperture current) and Gain were set appropriately according to the size of the selected aperture. For example, when an aperture with a size of 50 μm was selected, the Current (aperture current) was set to -800 and the Gain to 4; when an aperture with a size of 100 μm was selected, the Current (aperture current) was set to -1600 and the Gain to 2; and when apertures with sizes of 280 μm and 400 μm were selected, the Current (aperture current) was set to -3200 and the Gain to 1. For the measurement sample, 0.1 g of particles were dispersed in 10 ml of a 0.1 wt% nonionic surfactant aqueous solution using a touch mixer (Yamato Scientific Co., Ltd., "TOUCHMIXER MT-31") and an ultrasonic cleaner (Velvo-Clear Co., Ltd., "ULTRASONIC CLEANER VS-150") to obtain a dispersion. During the measurement, the beaker was gently stirred to prevent the introduction of air bubbles, and the measurement was terminated when 100,000 particles had been measured. The volume-average particle diameter was calculated as the arithmetic mean of the volume-based particle size distribution of the 100,000 particles. The coefficient of variation (CV value) of the particle size was calculated using the following formula. Coefficient of variation (CV value) (%) of particle size = (Standard deviation of particle size distribution based on particle volume ÷ Volume-average particle size) × 100 (%)

[0106] ≪Cross-sectional observation≫ Dried particles were mixed with the photocurable resin "D-800" (manufactured by JEOL Ltd.), and a cured product was obtained by irradiation with ultraviolet light. The cured product was then cut with nippers, the cross-section was smoothed using a cutter, and the sample was coated using a sputtering device, "Auto Fine Coater JFC-1300" (manufactured by JEOL Ltd.). Next, the cross-section of the sample was photographed using the secondary electron detector of a scanning electron microscope, "SU1510" (manufactured by Hitachi High-Technologies Corporation).

[0107] <Measurement of the 5% weight loss temperature when the temperature is raised at 10°C / min in an air atmosphere> The 5% thermogravimetric loss temperature was measured using a Hitachi High-Tech Science "NEXTA STA200RV" differential thermogravimetric analyzer. The sampling method and temperature conditions were as follows. A platinum measuring container was filled with 10.5 ± 0.5 mg of the sample, ensuring there were no gaps at the bottom, to prepare the sample for measurement. The 5% thermogravimetric loss temperature was measured using alumina as the reference material under an air gas flow rate of 200 mL / min. The TG / DTA curve was obtained by heating the sample from 30°C to 800°C at a heating rate of 10°C / min. Using the analysis software provided with the instrument, the temperature at which a 5% weight loss occurred was calculated from this curve and defined as the 5% thermogravimetric loss temperature.

[0108] [Manufacturing Example 1]: Synthesis of polyamic acid microparticles A As the first solution, 0.64 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) was dissolved in 39.4 g of acetone, and as the second solution, 0.40 g of 4,4'-diaminodiphenyl ether (DPE) was dissolved in 39.4 g of acetone to prepare each solution. Next, the two solutions were mixed at 25°C and reacted using an ultrasonic homogenizer for 5 minutes to precipitate polyamic acid nanoparticles. Subsequently, the solid-liquid separation was performed using a centrifuge, followed by several washing steps with acetone and drying to obtain polyamic acid nanoparticles A. The obtained particles were observed using a scanning electron microscope and confirmed to be monodisperse spherical particles.

[0109] [Manufacturing Example 2]: Synthesis of Polyamic Acid Microparticles B Following the same procedure as in Production Example 1, the first and second solutions were prepared. Then, 5g of deionized water was mixed into the first solution and stirred at 25°C for 30 minutes. Next, both solutions were mixed at 25°C and stirred for 10 minutes to allow the reaction to precipitate polyamic acid nanoparticles. Subsequently, solid-liquid separation was performed using a centrifuge, followed by several washing steps with acetone, and drying to obtain polyamic acid nanoparticles B. The obtained particles were observed using a scanning electron microscope and confirmed to be monodisperse spherical particles.

[0110] [Example 1] The inner oil phase was prepared by mixing and dissolving 0.2 g of polyamic acid fine particles A obtained in Production Example 1 with 0.8 g of N,N-dimethylformamide (DMF) as a solvent. Furthermore, 0.56 g of azo group-containing polydimethylsiloxane (trade name "VPS-1001", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 56 g of hexane as a solvent were mixed and dissolved to prepare the outer oil phase. The inner oil phase was added to the outer oil phase, and the mixture was emulsified and dispersed for 2 minutes at 3000 rpm using a Polytron homogenizer PT10-35 (manufactured by Central Science Trading Co., Ltd.). To the resulting emulsion, 0.4 g of acetic anhydride and 0.4 g of pyridine were added as chemical imidizing agents, and the chemical imidation reaction was carried out by heating at 60°C for 3 hours while stirring. After that, the reaction system was cooled to room temperature, and the entire slurry obtained after the reaction was completed was passed through a JIS test sieve (mesh size: 33 μm) (JIS standard number: Z 8801-1:2019) to remove coarse particles. After the particles were settled by centrifugation, the supernatant was removed, washed with cyclohexane and 2-propanol, and dried to obtain polyimide hollow particles (1). The volume-average particle size of the obtained polyimide hollow particles (1) was 20.7 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (1) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 1 shows a scanning electron microscope image of the particle cross-section of the obtained polyimide hollow particle (1).

[0111] [Example 2] Polyimide hollow particles (2) were obtained in the same manner as in Example 1, except that the solvent for the outer oil phase was cyclohexane: 66.4 g. The volume-average particle size of the obtained polyimide hollow particles (2) was 19.9 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (2) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 2 shows scanning electron microscope images of the particle cross-section of the obtained polyimide hollow particles (2).

[0112] [Example 3] Instead of 0.56g of azo group-containing polydimethylsiloxane (product name "VPS-1001", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), hydrophobic silica particles (product name "AEROSIL® R972", specific surface area = 110 ± 20 m²) are used. 2Polyimide hollow particles (3) were obtained in the same manner as in Example 2, except that 0.04 g of (manufactured by Nippon Aerosil Co., Ltd.) was used. The volume-average particle diameter of the obtained polyimide hollow particles (3) was 19.2 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (3) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 3 shows scanning electron microscope images of the particle cross-section of the obtained polyimide hollow particles (3).

[0113] [Example 4] Polyimide hollow particles (4) were obtained by the same procedure as in Example 3, except that the solvent for the inner oil phase was dimethylacetamide. The volume-average particle size of the obtained polyimide hollow particles (4) was 16.3 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (4) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 4 shows scanning electron microscope images of the particle cross-section of the obtained polyimide hollow particles (4).

[0114] [Example 5] Polyimide hollow particles (5) were obtained by following the same procedure as in Example 3, except that the solvent for the inner oil phase was N-methyl-2-pyrrolidone. The volume-average particle size of the obtained polyimide hollow particles (5) was 14.9 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (5) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 5 shows a scanning electron microscope image of the particle cross-section of the obtained polyimide hollow particles (5).

[0115] [Example 6] The reaction was carried out in the same manner as in Example 3, except that the reaction conditions after adding the chemical imidizing agent were changed to heating at 70°C for 1 hour while stirring, to obtain polyimide hollow particles (6). The volume-average particle size of the obtained polyimide hollow particles (6) was 14.0 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (6) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 6 shows scanning electron microscope images of the particle cross-section of the obtained polyimide hollow particles (6).

[0116] [Example 7] Polyimide hollow particles (7) were obtained in the same manner as in Example 3, except that the polyamic acid fine particles used were polyamic acid fine particles B obtained in Production Example 2. The volume-average particle size of the obtained polyimide hollow particles (7) was 14.6 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (7) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 7 shows a scanning electron microscope image of the particle cross-section of the obtained polyimide hollow particles (7).

[0117] [Example 8] Hydrophobic silica particles (product name "AEROSIL(registered trademark) R972", specific surface area = 110 ± 20 m²) 2 Polyimide hollow particles (8) were obtained in the same manner as in Example 3, except that 0.56 g of polysiloxane (trade name "KM-9787", manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of 0.04 g of polysiloxane ( / g, manufactured by Nippon Aerosil Co., Ltd.). The volume-average particle diameter of the obtained polyimide hollow particles (8) was 21.2 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (8) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 8 shows scanning electron microscope images of the particle cross-section of the obtained polyimide hollow particles (8).

[0118] [Example 9] Polyimide hollow particles (9) were obtained in the same manner as in Example 8, except that the polyamic acid fine particles used were polyamic acid fine particles B obtained in Production Example 2. The volume-average particle diameter of the obtained polyimide hollow particles (9) was 19.2 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (9) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 9 shows a scanning electron microscope image of the particle cross-section of the obtained polyimide hollow particles (9).

[0119] [Example 10] Polyimide hollow particles (10) were obtained in the same manner as in Example 2, except that 0.1 g of polyamic acid fine particles B obtained in Production Example 2, 0.01 g of polybutyl methacrylate (PBMA) (Mw=100,000) as another non-crosslinkable polymer, and 0.9 g of N,N-dimethylformamide (DMF) as a solvent were mixed and dissolved to prepare the inner oil phase. The volume-average particle diameter of the obtained polyimide hollow particles (10) was 15.3 μm. Furthermore, when the particle cross-section of the obtained polyimide hollow particles (10) was observed using a scanning electron microscope, the presence of a hollow structure with one or more air spaces covered by a shell was confirmed. The results are shown in Table 1. Figure 10 shows a scanning electron microscope image of the particle cross-section of the obtained polyimide hollow particle (10).

[0120] [Comparative Example 1] Emulsification and dispersion treatment was carried out in the same manner as in Example 1, except that 0.56 g of acrylic resin (product name "Macromonomer AB-6", manufactured by Toagosei Co., Ltd.) was used instead of 0.56 g of azo group-containing polydimethylsiloxane (product name "VPS-1001", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). However, the emulsion stability was extremely low, oil droplet coalescence occurred, and an emulsion could not be obtained.

[0121] [Comparative Example 2] Except for using polyamic acid microparticles B obtained in Production Example 2, the emulsification and dispersion treatment was carried out in the same manner as in Comparative Example 1. However, the emulsion stability was extremely low, oil droplet coalescence occurred, and it was not possible to obtain an emulsion.

[0122] [Table 1]

[0123] ≪Performance Evaluation: Evaluation of Relative Permittivity and Dielectric Loss Tangent≫ 0.425 g of hollow polyimide particles were collected, and 8.3 g of ethyl acetate and 1.7 g of solvent-soluble polyimide KPI-MX300F (manufactured by Kawamura Sangyo Co., Ltd.) were defoamed and stirred using a planetary stirring defoamer (KURABO Co., Ltd., "Mazelstar KK-250") to prepare a resin composition. The resin composition was coated onto a 5 mm thick glass plate using an applicator set to a wet thickness of 250 μm. The ethyl acetate was removed by heating at 60°C for 30 minutes, 90°C for 10 minutes, 150°C for 30 minutes, and 200°C for 30 minutes, and then cooled to room temperature to obtain a film containing polyimide hollow particles. The relative permittivity and dielectric loss tangent of the obtained film were evaluated using the cavity resonance method (measurement frequency: 10 GHz). Separately, the relative permittivity and dielectric loss tangent of a film that does not contain polyimide hollow particles (a film consisting solely of polyimide) were evaluated in the same manner. When the relative permittivity of the film containing the polyimide hollow particles obtained above is set to Dk1 and the relative permittivity loss tangent to Df1, and the relative permittivity of the film consisting only of polyimide is set to Dk0 and the relative permittivity loss tangent to Df0, the relative permittivity reduction rate calculated as (Dk1 / Dk0) × 100 (%) and the dielectric loss tangent reduction rate calculated as (Df1 / Df0) × 100 (%) were determined. The polyimide hollow particles (2), (3), and (7) obtained in Examples 2, 3, and 7 were evaluated. The results are shown in Table 2.

[0124] [Table 2]

[0125] These results confirm that the polyimide hollow particles provided by the present invention have the effect of lowering the relative permittivity and dielectric loss tangent of the substrate, and are effective for the purpose of lowering the permittivity and dielectric loss tangent of semiconductor materials. [Industrial applicability]

[0126] Polyimide hollow particles according to embodiments of the present invention can be used in a variety of applications. In terms of making better use of the effects of the present invention, polyimide hollow particles according to embodiments of the present invention can be applied to semiconductor materials (typically resin compositions for semiconductor materials), paint compositions, cosmetics, paper coating compositions, heat insulating compositions, light diffusing compositions, light diffusing films, etc., and are particularly suitable for resin compositions for semiconductor materials and paint compositions.

Claims

1. A method for producing polyimide hollow particles having a shell portion and a hollow portion surrounded by the shell portion, A step of preparing an inner oil phase containing polyamic acid fine particles and a solvent, A step of preparing an outer oil phase containing at least one compound selected from the group consisting of compounds having siloxane bonds and silicon dioxide, and a hydrocarbon solvent, A step of carrying out a chemical imidation reaction in an emulsified liquid prepared from the inner oil phase and the outer oil phase, including, A method for producing hollow polyimide particles.

2. The method for producing polyimide hollow particles according to claim 1, wherein the compound having the siloxane bond is a polysiloxane.

3. The method for producing polyimide hollow particles according to claim 1, wherein the compound having the siloxane bond has an azo group.

4. The silicon dioxide has a specific surface area of ​​10 m². 2 A method for producing polyimide hollow particles according to claim 1, wherein the particles are hydrophobic silica particles of 1g or more.

5. A method for producing polyimide hollow particles according to claim 1, wherein the reaction temperature of the chemical imidation reaction is 100°C or lower.

6. The method for producing polyimide hollow particles according to claim 1, wherein the solvent contained in the internal oil phase is an amide-based solvent.

7. The method for producing polyimide hollow particles according to claim 1, wherein the concentration of the polyamic acid fine particles in the emulsion is 0.1% by weight or more.

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