Method for producing resin composition fine particles, resin composition fine particles obtained by the method, method for producing inorganic fine particles, and inorganic fine particles obtained by the method

Abstract

To provide a method for producing resin composition fine particles that enables easy control of particle diameter of resin composition fine particles and allows high recovery efficiency of the resin composition fine particles.SOLUTION: A method for producing resin composition fine particles in which a liquid fluid containing a resin composition including a resin and a solvent is sprayed and the resin composition is dried, and a method for producing inorganic fine particles in which fine particles containing a resin are subjected to heat treatment at a temperature of 200°C or more and 1500°C or less under an inert gas atmosphere in a floating state to produce inorganic fine particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing resin composition fine particles, and resin composition fine particles obtained by said method. The present invention also relates to a method for producing inorganic fine particles, and inorganic fine particles obtained by said method. [Background technology]

[0002] Resin composition microparticles obtained by dissolving or dispersing a resin or resin composition in a solvent and then removing the solvent by drying or the like are used in a variety of applications and as precursors thereof because the shape of the resulting powder particles, such as particle size, is uniform. For example, resin composition fine particles obtained by using an insulating resin or resin composition are used for an insulating coating, and resin composition fine particles obtained by using a resin or resin composition and a conductive metal or the like are used for a conductive coating.

[0003] Resin composition microparticles obtained by using a resin and a metal such as a transition metal can be used as a catalyst for various chemical reactions or decomposition reactions. The obtained resin composition microparticles can also be mixed with other materials such as other powders or compositions. By uniformly dispersing the resin composition microparticles in other materials, they can also be used as modifiers that improve the resulting physical properties.

[0004] Furthermore, the resin in the resin composition microparticles obtained can be carbonized by calcination or the like to form inorganic particles. The inorganic particles obtained in this manner have been expanded into applications such as catalysts, electronic materials, and composite fibers. For example, the use of the inorganic particles as an active material for secondary batteries such as lithium secondary batteries, which are electronic materials, has also been considered. Furthermore, inorganic particles with a particle size on the nano-order are being considered for a wide range of applications as nanoparticles.

[0005] As a method for producing such resin composition fine particles, a method called disk drying is often adopted for drying a solution or dispersion containing a resin or a resin composition (for example, Patent Document 1). Disk drying is a method in which a liquid such as a solution or dispersion containing a resin or a resin composition is applied to a disk, and the disk is heated to remove the solvent from the liquid. After the solvent is removed, the resin composition particles adhering to the disk are scraped off to recover the resin composition particles. Depending on the intended application, the recovered resin composition particles may be used as is, or may be further subjected to a process such as calcination to form inorganic particles, etc. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-241235 Summary of the Invention [Problem to be solved by the invention]

[0007] Disk drying is widely used in the production of resin composition fine particles because it allows the organic solvent in the solution to be efficiently removed and dried by applying the solution onto a disk heated to a high temperature. However, in the case of disk drying, if the amount of resin is large, the resin composition becomes sticky after drying on the disk, which may make it difficult to scrape off from the disk, resulting in a decrease in the efficiency of recovery of the resin composition.In addition, as the recovery speed decreases, the solvent is more likely to remain due to clumping. Furthermore, when the resin composition dried on the disk is scraped off, the resin composition may fuse and become lumpy. If such a lumpy resin composition is directly fired, it becomes hard lumpy inorganic particles, which may require a complicated process such as crushing, or the particle size distribution may vary and show bimodal distribution, making it difficult to control the particle size. Furthermore, in conventional methods for producing inorganic fine particles by baking a resin composition, a horizontally long baking furnace is used, and the baking is carried out while the material to be baked is packed in a container and moved through the furnace, which can lead to the progression of agglomeration due to solidification, sintering, etc. Therefore, in order to obtain inorganic fine particles having a desired average particle size, a pulverization step is required, and the amount of fine powder can increase due to the pulverization.

[0008] Therefore, there has been a demand for the development of a method for producing powder from a solution or dispersion containing a resin or resin composition, which allows for easy control of the particle size of resin composition fine particles and has excellent powder recovery efficiency. Furthermore, there has been a demand for the development of a method for producing inorganic fine particles that suppresses agglomeration due to solidification and sintering during firing and produces less fine powder due to excessive pulverization.

[0009] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, the present invention aims to provide a method for producing resin composition microparticles from a solution or dispersion containing a resin or resin composition, which method allows for easy control of the particle size of the resin composition microparticles and has excellent recovery efficiency for the resin composition microparticles. Another object of the present invention is to provide a method for producing inorganic fine particles that suppresses the occurrence of coagulation and sintering during firing and produces little fine powder. Another object of the present invention is to provide inorganic fine particles with a simplified production process and little fine powder, by combining the above-mentioned method for producing resin composition fine particles with the method for producing inorganic fine particles, and a method for producing the same. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A method for producing resin composition fine particles, comprising spraying a liquid fluid containing a resin-containing resin composition and a solvent, and drying the resin composition. [2] The method for producing resin composition microparticles according to [1] above, wherein the resin composition contains an inorganic substance. [3] The method for producing resin composition microparticles according to [1] or [2] above, wherein the shape of the resin composition is such that each particle independently maintains its shape without fusing together when dried. [4] The method for producing resin composition microparticles described in [1] to [3] above, wherein the drying is performed by contacting the resin composition with hot air such that the spray direction of the liquid fluid and the blowing direction of the hot air are opposite to each other, thereby drying the resin composition. [5] A method for producing resin composition microparticles described in any of [1] to [4], wherein the amount of the resin composition in the liquid fluid is 10% by mass or more and 90% by mass or less, with the mass of the liquid fluid being 100% by mass. [6] The method for producing resin composition microparticles according to any one of [1] to [5] above, wherein the solvent is an organic solvent having a boiling point of 40°C or higher and 180°C or lower. [7] The method for producing resin composition microparticles according to any one of [1] to [6], wherein the resin undergoes thermal decomposition mass loss of 5% by mass or more and 60% by mass or less up to 1000°C in the atmosphere. [8] The method for producing resin composition microparticles described in any one of [1] to [7], wherein the organic solvent is recovered together with the hot air, and the amount of organic solvent recovered per hour is 60 mass% or more, assuming that the content of organic solvent per hour in the sprayed liquid fluid is 100 mass%. [9] The method for producing resin composition microparticles according to any one of [1] to [8], wherein the sprayed liquid fluid becomes particulate with an average particle size D50 of 0.1 μm or more and 100 μm or less during the drying.

[0011] The present invention also has the following aspects.

[10] A method for producing inorganic fine particles by heat-treating resin-containing fine particles in a suspended state in an inert gas atmosphere at a temperature of 200°C to 1500°C.

[11] The method for producing inorganic fine particles according to

[10] above, wherein the fine particles further contain at least one of a metal and a metal oxide.

[12] The method for producing inorganic fine particles according to any one of

[10] to

[11] , wherein the content of at least one of the metal and the metal oxide in the fine particles is 99% by mass or less, with the mass of the fine particles being 100% by mass.

[13] The method for producing inorganic fine particles according to any one of

[10] to

[12] above, wherein the average particle size of the obtained inorganic fine particles is 0.1 μm or more and 100 μm or less in terms of D50.

[14] The method for producing inorganic fine particles according to any one of

[10] to

[13] , wherein the particle diameter of at least one of the metal and the metal oxide in the fine particles is 10 nm or more and 300 nm or less in terms of D50.

[15] The method for producing inorganic fine particles according to any one of

[10] to

[14] above, wherein the heat treatment is carried out in multiple batches under conditions where at least one of the temperature and the residence time is different.

[16] The method for producing inorganic fine particles according to any one of

[10] to

[15] above, wherein the fine particles are transported in a certain direction and subjected to a heat treatment.

[17] The method for producing inorganic fine particles according to any one of

[10] to

[16] above, wherein the inorganic fine particles are further heated after the heat treatment.

[0012] Furthermore, the present invention has the following aspects.

[18] A method for producing inorganic microparticles, comprising spraying a liquid fluid containing a resin-containing resin composition and a solvent, drying the resin composition to obtain resin composition microparticles, and then heat-treating the obtained resin composition microparticles in a suspended state under an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower.

[19] The method for producing inorganic fine particles according to

[18] above, wherein the shapes of the resin composition and the resin composition fine particles are not fused together during drying and heat treatment, and each particle independently maintains its shape.

[20] The method for producing resin composition microparticles according to

[18] or

[19] , wherein the drying is performed by bringing hot air into contact with the resin composition so that the spray direction of the liquid fluid and the blowing direction of the hot air are opposite to each other, thereby drying the resin composition. [twenty one] The method for producing inorganic fine particles according to any one of

[18] to

[20] above, wherein the heat treatment is continuously carried out on the resin composition fine particles. [twenty two] Resin composition fine particles obtained by spraying a liquid fluid containing a resin-containing resin composition and a solvent, and then drying the resin composition. [twenty three] Inorganic fine particles obtained by heating resin-containing fine particles in a suspended state in an inert gas atmosphere at a temperature of 200°C to 1500°C. [twenty four] Inorganic microparticles obtained by spraying a liquid fluid containing a resin composition and a solvent, drying the resin composition to obtain resin composition microparticles, and then heat-treating the obtained resin composition microparticles in a suspended state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower. [Effects of the Invention]

[0013] According to the present invention, a method for producing resin composition microparticles from a solution or dispersion containing a resin or resin composition is provided, which allows for easy control of the particle size of the resin composition microparticles and has excellent recovery efficiency for the resin composition microparticles. Furthermore, the present invention provides a method for producing inorganic fine particles that suppresses the occurrence of coagulation and sintering during firing and produces little fine powder. Furthermore, according to the present invention, by combining the method for producing resin composition fine particles and the method for producing inorganic fine particles, the production process is simplified and inorganic fine particles with less fine powder and a method for producing the same are provided. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of an apparatus for continuously producing the resin composition fine particles of the present invention and the inorganic fine particles. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Method of producing resin composition fine particles> The method for producing resin composition microparticles of the present invention (hereinafter also referred to as "the present production method I") is a method in which a liquid fluid containing a resin-containing resin composition and a solvent is sprayed, and the resin composition is dried. Examples of resins used in Production Method I include polyolefins such as polyethylene, polypropylene, polybutene, poly(4-methylpentene), and polyhexene; polystyrene; polystyrene derivatives having a substituent such as an alkyl group having from 1 to 4 carbon atoms or a halogen atom on the benzene ring; polydienes such as polybutadiene, polyisoprene, and ethylene-propylene-diene copolymer; halogenated polyolefins such as polyfluoroethylene, polytetrafluoroethylene, polyvinyl chloride, and polyvinylidene chloride; polyvinyl esters such as polyvinyl acetate and polyvinyl alcohol or saponified products thereof; polyesters, polyamides, polyimides, polyamideimides, polysilicon resins, polysiloxanes, and phenolic resins. Copolymers of the monomers that constitute these resins may also be used. Examples of phenols constituting the phenolic resin include alkylphenols such as cresol and xylenol, polyhydric phenols such as resorcinol, phenylphenol, aminophenol, etc. Examples of aldehydes constituting the phenolic resin include formaldehyde, paraformaldehyde, acetaldehyde, etc. The phenolic resin may be either a resol type in which a phenol and an aldehyde are reacted in the presence of an alkali catalyst, or a novolak type in which a phenol and an aldehyde are reacted in the presence of an acid catalyst. These resins are appropriately selected depending on the intended use of the resulting resin composition particles, and the resin may be one kind or a mixture of two or more kinds of resins. The resin composition may also consist of the above resins alone. Furthermore, the above phenols may be combined with resins such as polysilicon resins and polysiloxanes to form composite resins.

[0016] Among the above resins, in order to prevent coagulation and sintering during firing when the resin composition microparticles obtained by this manufacturing method I are fired as described below, resins whose thermal decomposition mass loss is 60% by mass or less up to 1000°C in air are preferred, and resins whose mass loss is 40% by mass or less are more preferred. The thermal decomposition mass loss is preferably 0 mass % up to 1000°C in air, that is, no thermal decomposition mass loss occurs up to 1000°C in air, but may be 0.1 mass % or more.

[0017] The thermal decomposition mass loss measurement method involves placing a sample in a pre-measured alumina heat-resistant container, measuring the mass of each container, and using this mass as the pre-thermal decomposition mass. The heat-resistant container containing the sample is placed in an electric furnace and heated to 1000°C in an inert gas atmosphere at a rate of 5°C / min. Once the temperature reaches 1000°C, the mass of each container is measured. The temperature is maintained at a constant value for 5 hours after reaching 1000°C, after which heating is stopped and the sample is allowed to cool naturally to room temperature. The heat-resistant container containing the sample is removed, and the mass of each container is measured and used as the post-thermal decomposition mass. From these measurements, the mass of the sample before and after thermal decomposition due to heat treatment is calculated, and the thermal decomposition mass loss is calculated by ((mass before thermal decomposition - mass after thermal decomposition) / mass before thermal decomposition) x 100 (mass%).

[0018] In the present production method I, the resin composition containing the resin may contain an inorganic substance depending on the intended use of the resulting resin composition particles. Examples of inorganic substances include zero-valent metals, metal oxides, metal salts, carbon, silicon, and oxides thereof. These inorganic substances are appropriately selected depending on the application of the resin composition microparticles to be obtained, and the inorganic substance may be one type or a mixture of two or more types.

[0019] A liquid fluid containing the resin composition and the solvent is obtained by mixing the resin composition with the solvent. The liquid fluid may be a solution in which the resin composition is uniformly dissolved in the solvent, or a dispersion in which the resin composition is dispersed in the solvent. From the viewpoint of efficient atomization, which will be described later, the viscosity of the resulting liquid fluid is preferably 0.1 mPa·s or more and 300 mPa·s or less as measured by an E-type viscometer. An E-type viscometer is a cone-plate rotational viscometer, consisting of a cone-shaped rotor mounted on a plate. The sample is filled between the plate and rotor, and the cone is rotated. The shear stress is calculated from the deformation of the spiral spring at the top of the cone, and the viscosity, yield value, thixotropy, etc. of the sample can be determined from the shear rate / shear stress curve.

[0020] The solvent serves to dissolve or disperse the resin composition, and examples of the solvent include water and organic solvents. The solvent is appropriately selected depending on the combination with the resin composition or the inorganic substance. Examples of organic solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; alcohols such as ethanol, methanol, normal propyl alcohol, and isopropyl alcohol; and aromatics such as benzene, toluene, and xylene.

[0021] The boiling point of the organic solvent is preferably 40° C. or higher and 180° C. or lower from the viewpoint of drying efficiency when drying the resin composition, which will be described later.

[0022] The amount of the resin composition in the liquid fluid is preferably 10% by mass or more and 90% by mass or less, with the mass of the liquid fluid being 100% by mass. When the amount of the resin composition is within the above range, the liquid fluid can be smoothly discharged, and spherical dried particles with a uniform particle size can be obtained. From this perspective, the amount of the resin composition is more preferably 15% by mass or more and 60% by mass or less.

[0023] The resin composition containing the resin may be mixed with a solvent using a mixing device such as a stirrer equipped with a blade, a grinder equipped with a media, or a disperser equipped with another mechanism. Examples of the stirring device equipped with a blade include a Henschel mixer, a pressure kneader, a Banbury mixer, and a planetary mixer. Examples of the grinding device equipped with media include a ball mill, attritor, basket mill, sand mill, sand grinder, Dyno Mill, Dispermat, SC Mill, spike mill, and agitator mill. Examples of dispersion devices equipped with other mechanisms include a microfluidizer, a nanomizer, an ultimizer, an ultrasonic homogenizer, a dissolver, a disper, a high-speed impeller, and a thin film swirling high-speed mixer.

[0024] The resin composition and the solvent are mixed by adding the resin composition to the solvent and mixing or kneading the two to obtain a liquid fluid. The resin composition may be added all at once or in multiple portions. In the mixing of the resin composition and the solvent, the resin composition and the solvent may be kneaded in advance to obtain a kneaded mixture, and then the solvent may be added to the kneaded mixture to obtain a liquid fluid. The solvents used in the kneading and addition may be the same or different solvents.

[0025] If the resulting liquid fluid is a dispersion, a surfactant or dispersant may be added to improve dispersibility. Surfactants include cationic surfactants, anionic surfactants and amphoteric surfactants. Examples of dispersants include aqueous and non-aqueous dispersants. Non-aqueous dispersants include polymeric types such as polyethers, alcohols, polyalkylene polyamines, and polycarboxylic acid partial alkyl esters, low molecular weight types such as polyhydric alcohol esters and alkyl polyamines, and inorganic types such as polyphosphates.

[0026] The resulting liquid fluid may contain additives as appropriate depending on the intended use of the resulting resin composition particles. Examples of additives include plasticizers, crosslinking agents, antioxidants, stabilizers, lubricants, processing aids, antistatic agents, colorants, impact resistance aids, and foaming agents. These additives may be added to the resin composition in advance, to the solvent in advance, or when the resin composition and the solvent are mixed. The additives may be added all at once or in multiple portions. When added multiple times, the addition may be continuous or intermittent.

[0027] The liquid fluid obtained as described above is sprayed to form fine droplets of the liquid fluid. When spraying, the liquid fluid may be diluted with gas so that droplets of the liquid fluid are suspended in the gas and sprayed. Dilution with gas is preferred because it further reduces the droplets of the liquid fluid. Examples of spraying methods include spraying the pressurized liquid fluid from a spray hole, spraying the fluid through an orifice while causing a swirling motion by passing the fluid through a volute or screw pin, spraying the fluid while forming a liquid film, supplying the liquid onto a disk or impeller-type disk rotating at high speed and atomizing the liquid using centrifugal force, and spraying the liquid using ultrasonic waves generated by the vibration of a piezoelectric ceramic.

[0028] The spray direction may be horizontal, upward, downward, etc. However, when carrying out this manufacturing method I and the inorganic fine particles described later in succession, the inorganic fine particle manufacturing equipment is usually placed in the direction in which the spray falls, so the spray direction is preferably downward.

[0029] In this production method I, the resin composition contained in the droplets of the liquid fluid atomized by the spraying is dried to obtain fine resin composition particles. The drying method may be, for example, a method of spraying the liquid fluid into a space previously set at a high temperature, a method of contacting droplets of the sprayed liquid fluid with a gaseous fluid, a method of spraying the liquid fluid into a space previously set at a reduced pressure, etc. The space previously set at a high temperature is preferably filled with an inert gas such as helium or nitrogen, or a gas such as air. Among the above drying methods, the method of bringing the sprayed droplets of the liquid fluid into contact with the gaseous fluid is preferred from the viewpoint of drying efficiency.

[0030] When the sprayed droplets of the liquid fluid are brought into contact with a gaseous fluid, the gaseous fluid may be an inert gas such as helium or nitrogen, or air. These gaseous fluids are preferably at room temperature or higher, and the temperature of the gaseous fluid is preferably set in advance to be higher than the temperature of the liquid fluid after spraying.

[0031] It is more preferable to bring the resin composition contained in the droplets of the liquid fluid into contact with hot air, which is a fluid of an inert gas or air, the temperature of which has been set in advance to be higher than the temperature of the liquid fluid after spraying. When drying is performed using hot air, the hot air may be blown in a fixed direction or may be turbulent. From the viewpoint of drying efficiency, it is preferable to bring the resin composition contained in the liquid fluid into contact with the hot air so that the blowing direction of the hot air is opposite to the spraying direction.

[0032] When the resin composition contained in the liquid fluid is dried by contacting it with hot air, the spray volume per unit time when spraying the liquid fluid is preferably 100 L / min or more and 300 L / min or less. Furthermore, when the resin composition contained in the liquid fluid is dried by contacting it with hot air, the volume of the hot air blown per unit time is preferably equal to or greater than the spray volume per unit time when spraying the liquid fluid, and the volume of the hot air blown is more preferably 150 L / min or more and 2000 L / min or less. By these processes, the solvent vapor evaporated by the hot air is blown together with the hot air in the opposite direction to the falling direction of the particles, so that the particles and the solvent are separated efficiently, resulting in particles with higher dryness. The spray volume per unit time when spraying a liquid fluid refers to the volume per unit time of inert gas or air that is sprayed at high pressure to eject the liquid fluid from the side of the nozzle when spraying the liquid fluid from the nozzle. The volume of hot air blown per unit time is the volume of heated inert gas or air being sprayed per unit time, for example, the volume of heated inert gas or air being sprayed per unit time in the opposite direction to the spray direction of the liquid fluid. These can be appropriately set and controlled by the device used in Production Method I.

[0033] When a resin composition contained in a liquid fluid is dried by contacting the resin composition with hot air, the solvent contained in the liquid fluid is dried by being entrained in the hot air. Therefore, when an organic solvent is used as the solvent, the resin composition particles are brought into contact with hot air, and then the hot air containing the organic solvent is recovered, which improves the efficiency of separation of the solvent from the resin composition particles and the efficiency of recovery of the solvent.

[0034] When recovering organic solvent from hot air, it is desirable to recover as much organic solvent as possible from the viewpoint of reusing the dried hot air after recovery. From this viewpoint, when the content of organic solvent per unit time in the sprayed liquid fluid is taken as 100 mass%, the amount of organic solvent recovered per unit time is preferably 60 mass% or more, more preferably 80 mass% or more. From this viewpoint, it is even more preferable to recover the entire amount of organic solvent.

[0035] From the viewpoint of controlling the particle size of the resin composition microparticles obtained by this manufacturing method I and obtaining resin composition microparticles with little aggregation, it is preferable that in this manufacturing method I, a liquid fluid containing a resin-containing resin composition and a solvent is sprayed, and when the resin composition dries to become resin composition microparticles, the resin composition microparticles do not fuse together and each particle retains its independent shape. "The particles do not fuse together and each particle maintains its shape independently" means that even if the particles are somewhat sticky together, they can be easily dispersed by hot air or the like.

[0036] In order for the resin composition fine particles to maintain their individual shapes without fusing together when the resin composition is dried, the spray direction and spray speed of the resin composition and the drying temperature may be adjusted.

[0037] This production method I can be suitably carried out, for example, by the apparatus shown in FIG. A specific embodiment of the present production method I will be described below with reference to FIG. 1, but the present production method I is not limited to this embodiment. The inorganic particle production system 100 shown in FIG. 1 includes a resin composition particle production apparatus 120 used in the present production method I, and an inorganic particle production apparatus 140 for producing inorganic particles from a resin composition.

[0038] The resin composition microparticle manufacturing apparatus 120 includes a spraying section 102 that sprays a liquid fluid containing a resin-containing resin composition and a solvent, and a supplying section 104 that supplies an inert gas whose temperature is adjusted to a temperature that volatilizes the solvent contained in the liquid fluid in the direction opposite to the spraying direction of the liquid fluid so as to come into contact with the sprayed liquid fluid in order to dry the resin composition.

[0039] The resin composition microparticle manufacturing apparatus 120 includes a recovery section 106 that recovers the solvent that has evaporated from the liquid fluid that has come into contact with the inert gas by cooling, and a storage section 108 that stores the resin composition microparticles in a floating state that have been produced by the solvent being evaporated and separated from the liquid fluid that has come into contact with the inert gas.

[0040] Spraying unit 102 includes a liquid supply tank 5 that stores a liquid fluid containing a resin-containing resin composition and a solvent, a liquid feed pump 6 that feeds the liquid fluid stored in liquid supply tank 5, and a liquid temperature regulator 7 that adjusts the temperature of the liquid fluid fed by liquid feed pump 6. Spraying unit 102 also includes a gas supply device 8 that supplies a dilution gas that dilutes the liquid fluid in order to spray the liquid fluid, a valve 9 that adjusts the flow rate of the gas supplied by gas supply device 8, and a gas temperature regulator 10 that adjusts the temperature of the gas whose flow rate has been adjusted. Spraying unit 102 includes a liquid sprayer 2 that sprays the temperature-adjusted liquid fluid into spray-drying tank 1 using temperature-adjusted gas.

[0041] The upper part of the spray-drying tank 1 is provided with openings for piping the liquid fluid and gas from the spraying section 102 . In Figure 1, the resin composition microparticle manufacturing apparatus 120 and the inorganic microparticle manufacturing apparatus 140 are connected by a storage section 108, and the production of inorganic microparticles is carried out subsequent to the production of resin composition microparticles. However, the two apparatuses may be separated, and after the production of the resin composition microparticles, the obtained resin composition microparticles may be temporarily recovered in a microparticle storage tank or the like.

[0042] The liquid sprayer 2 has at least one nozzle for spraying the liquid fluid. In the embodiment of Fig. 1, the liquid sprayer 2 has one nozzle.

[0043] The liquid sprayer 2 uses ultrasonic waves to spray the liquid fluid. Specifically, for example, ultrasonic waves generated by the vibration of a piezo ceramic (not shown) are transmitted to the nozzle of the liquid sprayer 2, vibrating a liquid film within the nozzle, forming fine particles from the liquid fluid and spraying them in a mist.

[0044] The gas supplied by the gas supply device 8 is, for example, air. Note that the gas may be the inert gas.

[0045] The supply unit 104 includes a gas supply device 11 that supplies an inert gas, a valve 12 that adjusts the flow rate of the inert gas supplied by the gas supply device 11, and a gas temperature regulator 13 that adjusts the temperature of the inert gas, the flow rate of which is adjusted, to a temperature that volatilizes the solvent in the liquid fluid. The supply unit 104 includes at least one, for example, a pair of gas supply devices 3L and 3R that supply the temperature-adjusted inert gas in a direction opposite to the spray direction of the liquid fluid, specifically in a direction that intersects and faces the sprayed liquid fluid, so that the inert gas comes into contact with the sprayed liquid fluid. The pair of gas supply devices 3L and 3R are arranged in a straight line.

[0046] Recovery section 106 includes a collector 14 that collects the solvent vaporized from the liquid fluid that has come into contact with the inert gas through opening 106K at the top of spray-drying tank 1, a gas cooler 15 that cools the temperature of the collected solvent so that the solvent becomes liquid, and a recovery tank 16 that collects the cooled solvent in a liquid state. The top of spray-drying tank 1 may be curved upward, and opening 106K may be provided at the highest position of the top of spray-drying tank 1.

[0047] The storage section 108 is the lower area inside the spray-drying tank 1 . The separation device 120 includes a heating section 109 provided on the upper peripheral surface of the spray-drying vessel 1 for heating the liquid fluid sprayed by the liquid atomizer 2 to a first temperature. The spray drying tank 1 is configured in a cylindrical shape. The heating section 109 includes heaters 4A1 and 4A2 provided in an annular shape on the upper peripheral surface of the spray-drying tank 1. The heaters 4A1 and 4A2 may be, for example, microwave sources. The microwave sources radiate electromagnetic waves to provide accurate and effective heating. The heaters 4A1 and 4A2 may be configured as high-frequency induction heating sources having an induction coil and a high-frequency application unit that applies high-frequency current to the induction coil. When high-frequency current is applied to the induction coil, the induction coil generates an induction magnetic field for heating.

[0048] The resin composition fine particles obtained by the present production method I have a uniform particle size, and the resin composition fine particles obtained have a smaller average particle size and less fine powder. The average particle size of the resulting resin composition particles is appropriately set depending on the intended use, but is preferably 0.1 μm or more and 100 μm or less. The average particle size is the D50 value, which is the volume average particle size value that can be measured using a laser diffraction particle size analyzer or the like. D50 can be measured by dynamic light scattering using a laser particle size analyzer or the like. The volume average particle size is the particle size at which the cumulative volume distribution curve reaches 50% of the cumulative volume when plotted from the small diameter side in the particle size distribution, and this average particle size is D50.

[0049] The sprayed liquid fluid preferably becomes particles having an average particle size D50 of 0.1 μm to 100 μm during the drying process so that the average particle size of the resin composition microparticles obtained by Production Method I falls within the above range. The average particle size of the sprayed liquid fluid can be adjusted to fall within the above range during the drying process by adjusting the diameter of the spray hole, the spray pressure, etc. when spraying the liquid fluid.

[0050] A more specific embodiment will be described below, taking as an example the case where the resin composition fine particles obtained by Production Method I are used as a precursor of an active material for a secondary battery such as a lithium battery.

[0051] When the resin composition microparticles obtained by this production method I are used as a precursor for the active material of a secondary battery such as a lithium battery, it is preferable to use a polysiloxane compound, which is a resin containing at least one of a polycarbosilane structure, a polysilazane structure, a polysilane structure, and a polysiloxane structure. The polysiloxane compound may be a resin containing only these structures, or it may be a composite resin having at least one of these structures as a segment and chemically bonded to other polymer segments. Forms of composite formation include graft copolymerization, block copolymerization, random copolymerization, and alternating copolymerization. Examples include composite resins having a graft structure in which a polysiloxane segment is chemically bonded to the side chain of a polymer segment, and composite resins having a block structure in which a polysiloxane segment is chemically bonded to the end of a polymer segment.

[0052] The resin preferably uses a polysiloxane compound in which the polysiloxane segment has a structural unit represented by the following general formula (S-1) and / or the following general formula (S-2): It is particularly preferred that the polysiloxane compound has a carboxy group, an epoxy group, an amino group, or a polyether group on a side chain or terminal of the siloxane bond (Si-O-Si) main skeleton.

[0053] [ka]

[0054] [ka] In the general formulas (S-1) and (S-2), R 1 R represents an aromatic hydrocarbon group, an alkyl group, an epoxy group, a carboxy group, or the like, which may have a substituent. 2 and R 3respectively represent an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, an epoxy group, a carboxy group, or the like.

[0055] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 1,2-dimethylpropyl group, a 1-ethylpropyl group, a hexyl group, an isohexyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 2,2-dimethylbutyl group, a 1-ethylbutyl group, a 1,1,2-trimethylpropyl group, a 1,2,2-trimethylpropyl group, a 1-ethyl-2-methylpropyl group, a 1-ethyl-1-methylpropyl group, etc. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc.

[0056] Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group, and a 3-isopropylphenyl group.

[0057] Examples of the aralkyl group include a benzyl group, a diphenylmethyl group, and a naphthylmethyl group.

[0058] Examples of polymer segments other than polysiloxane segments contained in the polysiloxane compound include vinyl polymer segments such as acrylic polymers, fluoroolefin polymers, vinyl ester polymers, aromatic vinyl polymers, and polyolefin polymers, as well as polymer segments such as polyurethane polymer segments, polyester polymer segments, and polyether polymer segments. Of these, vinyl polymer segments are preferred.

[0059] The polysiloxane compound may be a composite resin in which polysiloxane segments and the polymer segments are bonded in a structure represented by the following structural formula (S-3), or may have a three-dimensional network polysiloxane structure.

[0060] [ka] In the formula, the carbon atom is a carbon atom that constitutes a polymer segment, and the two silicon atoms are silicon atoms that constitute a polysiloxane segment.

[0061] The polysiloxane segment of the polysiloxane compound may have a functional group capable of reacting by heating, such as a polymerizable double bond, in the polysiloxane segment. By subjecting the polysiloxane compound to heat treatment, a crosslinking reaction proceeds, and the compound is solidified, which facilitates thermal decomposition treatment.

[0062] Examples of polymerizable double bonds include vinyl groups and (meth)acryloyl groups. Preferably, two or more polymerizable double bonds are present in the polysiloxane segment, more preferably 3 to 200, and even more preferably 3 to 50. Furthermore, by using a composite resin having two or more polymerizable double bonds as the polysiloxane compound, the crosslinking reaction can be easily promoted.

[0063] The polysiloxane segment may have a silanol group and / or a hydrolyzable silyl group. Examples of the hydrolyzable group in the hydrolyzable silyl group include a halogen atom, an alkoxy group, a substituted alkoxy group, an acyloxy group, a phenoxy group, a mercapto group, an amino group, an amide group, an aminooxy group, an iminoxy group, and an alkenyloxy group. When these groups are hydrolyzed, the hydrolyzable silyl group becomes a silanol group. In parallel with the crosslinking reaction by the heat treatment, a hydrolysis condensation reaction occurs between the hydroxyl groups in the silanol groups and the hydrolyzable groups in the hydrolyzable silyl groups, thereby producing a solid polysiloxane compound.

[0064] The silanol group in the present invention is a silicon-containing group having a hydroxyl group directly bonded to a silicon atom. The hydrolyzable silyl group in the present invention is a silicon-containing group having a hydrolyzable group directly bonded to a silicon atom, and specific examples thereof include groups represented by the following general formula (S-4):

[0065] [ka] In the formula, R 4 represents a monovalent organic group such as an alkyl group, an aryl group, or an aralkyl group, and R 5 is a halogen atom, an alkoxy group, an acyloxy group, an allyloxy group, a mercapto group, an amino group, an amido group, an aminooxy group, an iminoxy group, or an alkenyloxy group, and b is an integer of 0 to 2.

[0066] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 1,2-dimethylpropyl group, a 1-ethylpropyl group, a hexyl group, an isohexyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 2,2-dimethylbutyl group, a 1-ethylbutyl group, a 1,1,2-trimethylpropyl group, a 1,2,2-trimethylpropyl group, a 1-ethyl-2-methylpropyl group, and a 1-ethyl-1-methylpropyl group.

[0067] Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group, and a 3-isopropylphenyl group.

[0068] Examples of the aralkyl group include a benzyl group, a diphenylmethyl group, and a naphthylmethyl group.

[0069] Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0070] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, and a tert-butoxy group.

[0071] Examples of the acyloxy group include a formyloxy group, an acetoxy group, a propanoyloxy group, a butanoyloxy group, a pivaloyloxy group, a pentanoyloxy group, a phenylacetoxy group, an acetoacetoxy group, a benzoyloxy group, and a naphthoyloxy group.

[0072] Examples of the allyloxy group include a phenyloxy group and a naphthyloxy group.

[0073] Examples of the alkenyloxy group include a vinyloxy group, an allyloxy group, a 1-propenyloxy group, an isopropenyloxy group, a 2-butenyloxy group, a 3-butenyloxy group, a 2-pentenyloxy group, a 3-methyl-3-butenyloxy group, and a 2-hexenyloxy group.

[0074] Examples of polysiloxane segments having structural units represented by the general formula (S-1) and / or the general formula (S-2) include those having the following structures.

[0075] [ka]

[0076] [ka]

[0077] [ka]

[0078] The polymer segment may have various functional groups as needed, such as a carboxyl group, a blocked carboxyl group, a carboxylic anhydride group, a tertiary amino group, a hydroxyl group, a blocked hydroxyl group, a cyclocarbonate group, an epoxy group, a carbonyl group, a primary amide group, a secondary amide group, a carbamate group, or a functional group represented by the following structural formula (S-5).

[0079] [ka]

[0080] The polymer segment may also have a polymerizable double bond such as a vinyl group or a (meth)acryloyl group.

[0081] The polysiloxane compound is preferably produced by, for example, the following methods (i) to (iii).

[0082] (i) A method in which a polymer segment containing a silanol group and / or a hydrolyzable silyl group is prepared in advance as a raw material for the polymer segment, and this polymer segment is mixed with a silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond, followed by a hydrolysis and condensation reaction.

[0083] (ii) A method in which a polymer segment containing a silanol group and / or a hydrolyzable silyl group is prepared in advance as a raw material for the polymer segment. A polysiloxane is also prepared in advance by subjecting a silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond to a hydrolysis-condensation reaction. The polymer segment and the polysiloxane are then mixed together to carry out the hydrolysis-condensation reaction.

[0084] (iii) A method in which the polymer segment, a silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond, and a polysiloxane are mixed together, and a hydrolysis condensation reaction is carried out. A polysiloxane compound can be obtained by the above method.

[0085] Commercially available polysiloxane compounds may be used, such as the Ceranate (registered trademark) series (organic-inorganic hybrid coating resin; manufactured by DIC Corporation) and the Compoceran SQ series (silsesquioxane hybrid; manufactured by Arakawa Chemical Industries, Ltd.).

[0086] Furthermore, when the resin composition microparticles obtained by Production Method I are used as a precursor for the active material of a lithium secondary battery, it is preferable to use a substance capable of absorbing and desorbing lithium ions in addition to the polysiloxane compound. Examples of substances capable of absorbing and desorbing lithium ions include carbon source resins, graphite, silicon dioxide, titanium oxide, and compounds containing silicon, oxygen, and carbon. Among these, it is more preferable to use a carbon source resin as the resin used in Production Method I in addition to the polysiloxane compound.

[0087] The carbon source resin is preferably a synthetic resin or natural chemical raw material that has good miscibility with polysiloxane compounds, is carbonized by high-temperature baking in an inert atmosphere, and has an aromatic functional group.

[0088] Examples of synthetic resins include thermoplastic resins such as polyvinyl alcohol and polyacrylic acid, and thermosetting resins such as phenolic resins and furan resins. Examples of natural chemical raw materials include heavy oils, particularly tar pitches, such as coal tar, light tar oil, medium tar oil, heavy tar oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch, and heavy oil. From the viewpoints of inexpensive availability and removal of impurities, phenolic resins are more preferred.

[0089] In particular, the carbon source resin is preferably a resin containing an aromatic hydrocarbon moiety, and the resin containing an aromatic hydrocarbon moiety is preferably a phenol resin, an epoxy resin, or a thermosetting resin, and the phenol resin is preferably a resol type. Examples of phenolic resins include the Sumilite Resin series (resol-type phenolic resins, manufactured by Sumitomo Bakelite Co., Ltd.).

[0090] When the resin composition fine particles obtained by this production method I are used as a precursor for an active material for a secondary battery such as a lithium battery, it is preferable to use silicon particles as the inorganic substance from the viewpoint of the electric capacity of the resulting active material. When silicon particles are used as the inorganic material, the BET specific surface area of ​​the silicon particles is 80m 2 / g or more is preferable from the viewpoint of the electric capacity of the active material and the initial coulomb efficiency. The BET specific surface area is a value determined by the BET method, and can be determined by nitrogen gas adsorption measurement, for example, using a BET specific surface area measuring device. The BET specific surface area of ​​silicon particles is between 80 and 300 m in terms of capacitance and initial coulombic efficiency. 2 / g is more preferable, 100 to 230m 2 / g is more preferred.

[0091] When silicon particles are used as the inorganic substance, it is preferable that the particle size of the silicon particles is nano-order particles at D50, from the viewpoint of improving the cycle property of the active material of the resulting secondary battery. "D50 nano-order" refers to the D50 value in nanometer units, and D50 is typically 1 to 999 nm. If the silicon particles exceed 1000 nm, dispersibility may deteriorate when the resin composition fine particles are mixed with a liquid fluid containing a solvent in the production method I, potentially reducing productivity. From these perspectives, the D50 of the silicon particles is preferably 10 to 300 nm, more preferably 10 to 150 nm, and even more preferably 20 to 100 nm. D50 is as described above.

[0092] When silicon particles are used as the inorganic material, the silicon particles may be in the form of granules, needles, or flakes, but flakes are preferred from the viewpoint of charge / discharge performance when used as an active material. From the viewpoint of charge-discharge performance when used as an active material, the silicon particles preferably have a length in the major axis direction of 20 to 300 nm and a thickness of 1 to 60 nm. From the viewpoint of charge-discharge performance when used as a negative electrode active material, the silicon particles preferably have a needle-like or flake-like shape with an aspect ratio, which is the ratio of length to thickness, of 0.5 or less.

[0093] The morphology of silicon particles can be determined by measuring the average particle size using dynamic light scattering, but samples with the above aspect ratios can be identified more easily and precisely using analytical tools such as transmission electron microscopes (TEM) and field emission scanning electron microscopes (FE-SEM). In the case of negative electrode active materials containing silicon particles, the sample can be cut with a focused ion beam (FIB) and the cross section can be observed using FE-SEM, or the sample can be sliced ​​and the state of the silicon particles can be identified by TEM observation. The aspect ratio of the silicon particles is a calculation result based on 50 particles in the main part of the sample within the field of view of the TEM image.

[0094] A liquid fluid is obtained by mixing the polysiloxane compound, and, if necessary, the carbon source resin, desired resins such as silicon particles, and inorganic substances with a solvent. The solvent may be water or the above-mentioned organic solvents, and may also contain a dispersant and a non-aqueous solvent, if necessary.

[0095] It is preferable to use silicon particles after crushing silicon chunks to a certain particle size before mixing with the solvent. The crushing is usually carried out in an inert gas atmosphere, preferably a nitrogen atmosphere from the viewpoint of handling. Furthermore, the crushing is preferably a wet crushing method in which silicon chunks are crushed in an organic solvent. The concentration of silicon chunks etc. in the wet pulverization is about 5 to 50% by mass in the organic solvent.

[0096] When mixing the polysiloxane compound and, if necessary, the carbon source resin with silicon particles, it is preferable to use a slurry in which the silicon particles have been dispersed in a solvent in advance. The solvent may be the same as that described above, and it is preferable to use the same solvent as that contained in the liquid fluid, and methyl ethyl ketone is particularly preferable. From the viewpoint of simplifying the process, it is preferable to use the slurry of silicon particles obtained by the wet grinding as is. A dispersant may be added to the slurry to promote the dispersion of silicon particles.The type of dispersant can be aqueous or non-aqueous, and non-aqueous dispersants are preferred.The type of non-aqueous dispersant can be exemplified by polymer types such as polyethers, alcohols, polyalkylene polyamines, and polycarboxylic acid partial alkyl esters, low molecular weight types such as polyhydric alcohol esters and alkyl polyamines, and inorganic types such as polyphosphates. When the dispersant is added, its amount is preferably in the range of 5% by mass to 60% by mass, more preferably 5% by mass to 40% by mass, based on the mass of the silicon particles.

[0097] Furthermore, at least one surfactant selected from the group consisting of cationic surfactants, anionic surfactants, and amphoteric surfactants may be added to the slurry to improve the dispersibility of the silicon particles. Examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, aromatic quaternary ammonium salts, and heterocyclic quaternary ammonium salts. The amine value of the cationic surfactant is, for example, 1 to 100 mgKOH / g, preferably 5 to 80 mgKOH / g, more preferably 10 to 48 mgKOH / g, and particularly preferably 35 to 48 mgKOH / g. When the amine value is within the above range, re-agglomeration of nano-sized silicon particles by pulverization can be suppressed, thereby suppressing thickening of the slurry, resulting in excellent cycle characteristics, charge / discharge capacity, and initial coulombic efficiency in the battery. Specifically, DISPERBYK 9077 (manufactured by BYK Additives & Instruments, DISPERBYK is a registered trademark) can be used as the cationic surfactant.

[0098] Examples of anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates. The acid value of the anionic surfactant is, for example, 1 to 200 mgKOH / g, preferably 10 to 180 mgKOH / g, and more preferably 50 to 150 mgKOH / g. When the acid value is within the above range, the wettability of the silicon particles to the dispersion medium is improved, thereby suppressing thickening of the slurry, resulting in excellent cycle characteristics, charge / discharge capacity, and initial coulombic efficiency in the battery. Specifically, DISPERBYK111 (manufactured by BYK Additives & Instruments) can be used as the anionic surfactant.

[0099] The surfactant may be an amphoteric surfactant having the above-mentioned amine value and acid value, or a combination of cationic and anionic surfactants having the above-mentioned amine value and acid value may be used. Amphoteric surfactants exhibit the properties of anionic surfactants in the alkaline range and the properties of cationic surfactants in the acidic range, and examples thereof include compounds containing carboxylates, amino acids, and betaines. Specifically, ANTI-TERRA®-U100 (manufactured by BYK Additives & Instruments) can be used as an amphoteric surfactant. When the surfactant is added, the amount added is preferably 5 to 60 mass %, more preferably 5 to 40 mass %, and even more preferably 5 to 20 mass %, relative to the mass of the silicon particles.

[0100] The mixture containing the polysiloxane compound and the carbon source resin is preferably in a state in which the polysiloxane compound and the carbon source resin are uniformly mixed. The mixing is carried out using an apparatus having the functions of dispersion and mixing. Examples of the apparatus having the functions of dispersion and mixing include a stirrer, an ultrasonic mixer, and a premix disperser.

[0101] When the liquid fluid contains a resin composition having the polysiloxane compound, the carbon source resin, and silicon particles, and a solvent, it is preferable that the content of silicon particles is 99% by mass or less when the total amount of the polysiloxane compound, the carbon source resin, and the silicon particles is 100% by mass. The solid content of the polysiloxane compound is preferably 1% by mass to 70% by mass, and the solid content of the carbon source resin is preferably 1% by mass to 70% by mass, and more preferably the solid content of the silicon particles is 15% by mass to 99% by mass, the solid content of the polysiloxane compound is 30% by mass to 70% by mass, and the solid content of the carbon source resin is 30% by mass to 70% by mass.

[0102] A liquid fluid containing the polysiloxane compound prepared as described above, and optionally a resin composition having the carbon source resin and silicon particles, and a solvent is sprayed using, for example, the apparatus shown in FIG. 1, and the resin composition is dried and desolvated to obtain resin composition fine particles (hereinafter also referred to as "the active material precursor") which are an active material precursor for lithium secondary batteries.

[0103] <Method of manufacturing inorganic fine particles> The method for producing inorganic microparticles of the present invention (hereinafter also referred to as "this production method II") is a method for producing inorganic microparticles by heat-treating resin-containing microparticles in a suspended state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower. The "fine particles containing resin" used in this manufacturing method II are fine particles that become inorganic fine particles when heat-treated at a temperature of 200°C or higher and 1500°C or lower, and examples thereof include fine particles made of resin, fine particles of a resin composition containing resin and at least one of a metal and a metal oxide, etc.

[0104] The resin contained in the fine particles may be the same as the resin used in Production Method I above. Furthermore, when the microparticles are a resin composition containing a resin and at least one of a metal and a metal oxide, the resin contained in the microparticles may be the same resin as the resin used in the present manufacturing method I, and at least one of the metal and metal oxide contained in the microparticles may be the same metal or metal oxide as the metal or metal oxide used in the present manufacturing method I. When the fine particles contain at least one of the metal and metal oxide, the content of at least one of the metal and metal oxide is preferably 99% by mass or less, more preferably 95% by mass or less, based on 100% by mass of the total amount of the fine particles. When the fine particles contain both the metal and metal oxide, the total content of the metal and metal oxide is preferably 99% by mass or less, more preferably 95% by mass or less, based on 100% by mass of the total amount of the fine particles.

[0105] The method for producing the fine particles includes a method for producing fine particles by mixing an appropriately selected resin or inorganic material using a single- or double-screw mixer, a Henschel mixer, a Banbury mixer, a ball mill, a bead mill, or the like, depending on the application of the inorganic fine particles to be obtained. The average particle size of the fine particles may be adjusted by sieving or the like before use in Production Method II. The fine particles may be the fine particles of the resin composition produced by the present production method I. From the viewpoint of the uniform particle size of the fine particles and the small amount of fine powder, it is preferable to use the fine particles of the resin composition obtained by the present production method I.

[0106] The resin-containing particles are heat-treated in a suspended state in an inert gas atmosphere at a temperature of 200° C. or higher and 1500° C. or lower. The inert gas is, for example, nitrogen, helium, argon, or the like.

[0107] The suspended state is a state in which the particles remain in space without directly contacting the wall or bottom of the device or container, etc. Examples include a state in which the particles are falling in space, or a state in which the particles are transported in a certain direction, such as when flowing in an upward airflow. The heat treatment is preferably carried out in a floating state where the fine particles are being transported in a fixed direction, and more preferably in a state where the fine particles are falling freely in space, from the viewpoint of suppressing fusion of the resulting inorganic fine particles.

[0108] The particles are suspended in an inert gas at a temperature of 200° C. to 1500° C., and then heat-treated. From the viewpoint of resin heating efficiency, the heat treatment temperature is preferably 300° C. to 1100° C. The heat treatment may be carried out multiple times within the above temperature range, with the particles suspended. Preferred methods of heat treatment include a method in which the entire space in which the particles are suspended is heated using a heat source to within the above temperature range, a method in which high-frequency induction heating or microwave heating is used to directly heat the particles to within the above temperature range, or a convection heating method in which hot air is generated to heat the particles to within the above temperature range.A heating method that combines these multiple heating methods is more preferred.

[0109] The suspended state is set so as to be maintained for a time period during which the resin contained in the fine particles is sufficiently carbonized, and the time during which this suspended state is maintained is referred to as the residence time. For example, when the fine particles are in a suspended state and are falling freely, the residence time is preferably maintained for several seconds to several tens of seconds, and more preferably from 1 second to 60 seconds. In the heat treatment, it is preferable to carry out the heat treatment in several separate steps under different conditions of at least one of temperature and residence time. When the heating is divided into multiple steps, for example, a method of performing a heat treatment under conditions of a heating temperature of 200°C to 1500°C and a residence time of 1 to 60 seconds, followed by a subsequent heat treatment under conditions of a heating temperature of 500°C to 1500°C and a residence time of 1 to 30 hours can be given. These heat treatments are performed in series, with the particles in a suspended state or in a suspended and then suspended state.

[0110] By the heat treatment, the resin contained in the fine particles is carbonized or oxidized to become inorganic fine particles. In this production method II, the inorganic fine particles obtained by the heat treatment may be further heated in a post-treatment. When heated in the post-treatment, the inorganic fine particles are preferably heated in a state other than the floating state. The state other than the floating state is, for example, a state in which the inorganic fine particles are deposited, stagnated, or flowing, such as a state in which the inorganic fine particles are stored in a container or the like.

[0111] By carrying out such post-treatment heating, the heating time can be extended, the state of the inorganic fine particles after heating can be precisely controlled, and particles with controlled carbonization can be more easily obtained. The heating in the post-treatment may be carried out continuously following the heating in the suspended state, or the inorganic fine particles may be temporarily collected and transferred to a separate container where they are further heated.

[0112] This production method II can be suitably carried out, for example, by an inorganic particle production apparatus 140 that produces inorganic particles from a resin composition in an inorganic particle production system 100 shown in FIG. 1, the resin composition fine particles produced in the resin composition fine particle production apparatus 120 fall freely in a storage section 108 shared with the inorganic fine particle production apparatus 140, and while free falling, are heated by a heating section 110 to become inorganic fine particles. The heating section 110 is equipped with heaters 4B1, 4B2, and 4B3 arranged in an annular shape on the lower peripheral surface of the spray-drying tank 1.

[0113] Heaters 4B1, 4B2, and 4B3 may be, for example, microwave sources. Electromagnetic waves emitted from the microwave sources provide accurate and effective heating. Alternatively, heaters 4B1, 4B2, and 4B3 may be configured as high-frequency induction heating sources having an induction coil and a high-frequency application unit that applies high-frequency current to the induction coil. When high-frequency current is applied to the induction coil, the induction coil generates an induction magnetic field for heating.

[0114] The lower side of the spray-drying tank 1 has a tapered shape. A deposition section 112 is provided on the lower side of the spray-drying tank 1.

[0115] An opening is formed on the lower side of the spray-drying tank 1. The deposition section 112 has a hollow cylindrical shape. The size of the lower opening of the spray-drying tank 1 is the same as the size of the upper opening of the deposition section 112. The lower opening of the spray-drying tank 1 and the upper opening of the deposition section 112 are connected. The size of the lower opening of deposition section 112 is smaller than the size of the upper opening of deposition section 112. The lower opening of deposition section 112 is connected to flow path 113 for discharging inorganic fine particles.

[0116] Heaters 4B1, 4B2, and 4B3 of heating unit 110 heat the resin microparticle composition, which is produced by production method I and stored in a floating state in storage unit 108, in a floating state at a temperature of 200° C. or higher and 1500° C. or lower, for example, 1000° C. At this time, the resin component contained in the resin microparticle composition is carbonized to become inorganic microparticles. The generated inorganic fine particles are naturally discharged from the deposition section 112 via the flow path 113 .

[0117] FIG. 1 shows an embodiment in which resin composition microparticles obtained by manufacturing method I are used as resin-containing microparticles, but as described above, resin-containing microparticles may be prepared separately and supplied to the inorganic microparticle manufacturing apparatus 140.

[0118] The inorganic fine particles obtained by the present production method II have a uniform particle size, and the inorganic fine particles obtained have a smaller average particle size and less fine powder. The average particle size of the resulting inorganic fine particles is appropriately set depending on the application, but is preferably 0.1 μm or more and 100 μm or less. When the inorganic fine particles contain at least one of a metal and a metal oxide, the particle size of at least one of the metal and the metal oxide in the inorganic fine particles is preferably 10 nm to 300 nm in D50. When the inorganic fine particles contain both a metal and a metal oxide, the particle size of at least one of the metal and the metal oxide in the inorganic fine particles is preferably 10 nm to 300 nm in D50, and more preferably both of the particle sizes are 10 nm to 300 nm in D50. When the average particle size of the resulting inorganic fine particles is within the above range, it is preferable to use fine particles containing a resin having an average particle size of 0.1 μm or more and 100 μm or less as a raw material. It is more preferable to use fine particles of the resin composition obtained by Production Method I as the fine particles containing a resin. The average particle size is the D50 value, which is the same as above.

[0119] A more specific embodiment will be described below, taking as an example the case where the inorganic fine particles obtained by this production method II are used as an active material for a secondary battery such as a lithium battery. The fine particles used in this production method II include, for example, a precursor of an active material obtained by mixing a slurry containing silicon particles with the mixture of the polysiloxane compound and the carbon source resin, followed by removing the solvent. Methods for removing the solvent include methods using a dryer, a reduced pressure dryer, a spray dryer, etc. From the viewpoint of particle size and the like, it is preferable to use the resin composition fine particles obtained by the present production method I as the precursor of the active material.

[0120] When the precursor of the active material is used as fine particles, the active material for the secondary battery can be obtained by heating the precursor in a suspended state at a temperature of 200° C. to 1200° C. as shown in FIG.

[0121] The BET specific surface area of ​​the obtained active material was 50 m from the viewpoint of electrical capacity and initial coulombic efficiency. 2 / g or less is preferable, and 1.0m 2 / g or more 50m 2 / g or less is more preferable. When the BET specific surface area is within this range, the amount of solvent absorbed during electrode preparation can be kept appropriate, and the amount of binder used to maintain binding properties can also be kept appropriate. Note that the BET specific surface area is a value determined by the BET method as described above, and can be determined by nitrogen gas adsorption measurement, for example, using a specific surface area measurement device.

[0122] Furthermore, when the active material is used as the negative electrode active material in a secondary battery, from the viewpoint of suppressing the generation of solid-phase interfacial electrolyte decomposition products (hereinafter also referred to as "SEI") during charge and discharge, thereby reducing the decrease in reversible charge and discharge capacity per unit volume, and from the viewpoint of suppressing peeling from the current collector during electrode film formation, the volume average particle size of the active material obtained by Production Method II is preferably 0.1 μm to 20 μm. The volume average particle size of the active material obtained by Production Method II is more preferably 2.5 μm or more, and particularly preferably 5.0 μm or more. The volume average particle size of the active material is more preferably 15 μm or less, even more preferably 12 μm or less, and particularly preferably 10 μm or less. The volume average particle size is the D50 value mentioned above.

[0123] In the XRD analysis of the active material obtained by this production method II, the crystallite diameter assigned to the (111) plane of the silicon particles in the active material is preferably 40 nm or less, more preferably 35 nm or less, and even more preferably 30 nm or less, from the viewpoints of initial Coulomb efficiency and capacity retention. The crystallite size is a value determined by the Scherrer method in XRD.

[0124] When an active material precursor obtained by mixing a slurry containing silicon particles with a mixture of a polysiloxane compound and a carbon source resin and removing the solvent is used as fine particles, the active material precursor obtained by this production method II is an active material precursor whose matrix phase contains silicon particles. When the active material obtained by this production method II is used as an active material for a secondary battery, the matrix phase is a material capable of absorbing and desorbing lithium ions. A material capable of absorbing and desorbing lithium ions is a material that can absorb lithium ions into the matrix phase during battery charging and desorb lithium ions from the matrix phase during battery discharge. In a lithium secondary battery, the above-mentioned cycle of absorption and desorption is repeated. The matrix phase of the active material obtained by Production Method II is a matrix phase composed of compounds containing silicon, oxygen, and carbon. An example of a compound containing silicon, oxygen, and carbon is silicon oxycarbide.

[0125] Silicon oxycarbide is composed of compounds containing silicon, oxygen, and carbon, and is preferably a structure containing a three-dimensional network structure of a silicon-oxygen-carbon skeleton and free carbon. Here, free carbon refers to carbon that is not contained in the three-dimensional silicon-oxygen-carbon skeleton. Free carbon includes carbon that exists as a carbon phase, carbon that is bonded to carbon atoms in the carbon phase, and carbon that is bonded to the silicon-oxygen-carbon skeleton and the carbon phase.

[0126] The silicon oxycarbide is preferably represented by the following formula (1): SiOxCy(1) In formula (1), x represents the molar ratio of oxygen to silicon, and y represents the molar ratio of carbon to silicon. When the active material obtained by this production method II is used in a secondary battery, from the viewpoint of achieving an advantageous balance between charge / discharge performance and capacity retention rate, 1≦x<2 is preferable, 1≦x≦1.9 is more preferable, and 1≦x≦1.8 is even more preferable. When the active material obtained by this production method II is used in a secondary battery, 1≦y≦20 is preferable, and 1.2≦y≦15 is more preferable, from the viewpoint of the balance between charge / discharge performance and initial coulombic efficiency.

[0127] The x and y values ​​can be determined by measuring the mass content of each element and then converting it into a molar ratio (atomic ratio). In this case, the oxygen and carbon contents can be quantified using an inorganic elemental analyzer, and the silicon content can be quantified using an inductively coupled plasma (ICP) optical emission spectrometer (ICP-OES). Although it is preferable to measure x and y by the method described above, it is also possible to perform local analysis of the active material, obtain the content ratio data obtained from many measurement points, and then infer the content ratio of the entire active material. Examples of local analysis include energy dispersive X-ray spectroscopy (SEM-EDX) and electron probe microanalyzer (EPMA).

[0128] When the matrix phase is a silicon oxycarbide phase composed of silicon oxycarbide and includes a three-dimensional network structure of a silicon-oxygen-carbon skeleton and free carbon, the silicon-oxygen-carbon skeleton in the silicon oxycarbide phase has high chemical stability and forms a composite structure with the free carbon, resulting in small volume changes upon lithium absorption and desorption. The silicon particles are tightly enclosed in the composite structure of the silicon-oxygen-carbon skeleton and free carbon, further suppressing volume changes of the silicon particles upon lithium absorption and desorption. As a result, when the active material obtained by this production method II is used as a negative electrode active material, the silicon particles in the negative electrode play a key role in exhibiting charge / discharge performance, while the silicon oxycarbide phase further suppresses particle destruction associated with volume changes of the silicon particles during charge / discharge, thereby further improving the cycleability of the lithium secondary battery.

[0129] Furthermore, when the compound that constitutes the silicon oxycarbide phase has a three-dimensional network structure of a silicon-oxygen-carbon skeleton and a structure containing free carbon, the electron distribution within the silicon-oxygen-carbon skeleton changes when lithium ions approach, forming electrostatic or coordinate bonds between the silicon-oxygen-carbon skeleton and the lithium ions. These electrostatic and coordinate bonds allow lithium ions to be stored within the silicon-oxygen-carbon skeleton. Meanwhile, because the coordinate bond energy is relatively low, lithium ion desorption reactions occur easily. This means that the silicon-oxygen-carbon skeleton is thought to be capable of reversibly inserting and extracting lithium ions during charging and discharging.

[0130] The silicon oxycarbide may contain nitrogen in addition to silicon, oxygen, and carbon. In this production method II, nitrogen atoms contained in the raw materials used, such as phenolic resins, polysiloxane compounds, other nitrogen compounds such as dispersants, and nitrogen gas used in the firing process, can be introduced into the silicon oxycarbide phase as atomic groups containing nitrogen atoms as functional groups within the molecule. When the silicon oxycarbide phase contains nitrogen, the active material obtained by this production method II tends to have excellent charge / discharge performance and capacity retention when used as a negative electrode active material. When the compound constituting the silicon oxycarbide phase is a compound containing silicon, oxygen, carbon and nitrogen, the silicon oxycarbide phase preferably contains a compound represented by the following formula (2). SiOaCbNc(2) In formula (2), a represents the molar ratio of oxygen to silicon, b represents the molar ratio of carbon to silicon, and c represents the molar ratio of nitrogen to silicon. When the silicon oxycarbide phase contains the compound represented by the above formula (2), from the viewpoints of charge-discharge performance and capacity retention rate when using an active material containing silicon particles in a secondary battery, 1≦a≦2, 1≦b≦20, 0<c≦0.5 are preferable, and 1≦a≦1.9, 1.2≦b≦15, 0<c≦0.4 are more preferable.

[0131] Similar to the above-mentioned x and y, the a, b and c can be obtained by measuring the mass content of the elements and then converting them into molar ratios (atomic ratios). Similar to the above-mentioned x and y, the measurement of a, b and c is preferably carried out by the method described above. However, it is also possible to perform a local analysis of the active material obtained by this production method II, obtain a large number of measurement points of the content ratio data obtained thereby, and infer the content ratio of the entire active material obtained by this production method II. Examples of local analysis include energy dispersive X-ray spectroscopy (SEM-EDX) and electron probe microanalyzer (EPMA).

[0132] In the case of the active material obtained by this production method II, the silicon oxycarbide preferably has free carbon composed only of carbon element together with the silicon-oxygen-carbon skeleton structure. When the silicon oxycarbide has free carbon, in the Raman spectrum of the active material, 1590 cm attributed to the G band of the graphite long-period carbon lattice structure -1 and 1330 cm attributed to the D band of the graphite short-period carbon lattice structure with disorder and defects -1A scattering peak around this range is observed. The intensity ratio of the scattering peak intensity of the D band, I(D band), to the scattering peak intensity of the D band, I(G band), I(G band) / I(D band), is preferably 0.7 or more and 2 or less. The scattering peak intensity ratio, I(G band) / I(D band), is more preferably 0.7 or more and 1.8 or less. The fact that the scattering peak intensity ratio, I(G band) / I(D band), is in the above range means the following about free carbon in the matrix.

[0133] Some carbon atoms in the free carbon are bonded to some silicon atoms in the silicon-oxygen-carbon skeleton. This free carbon is an important component that influences charge-discharge characteristics. Free carbon is primarily found in the silicon-oxygen-carbon skeleton, which is composed of SiO2C2, SiO3C, and SiO4. Because it is bonded to some silicon atoms in the silicon-oxygen-carbon skeleton, electron transfer between the silicon atoms inside and on the surface of the silicon-oxygen-carbon skeleton and the free carbon is facilitated. Therefore, when an active material with a matrix phase containing silicon particles is used as an anode active material in a secondary battery, the lithium ion insertion and deintercalation reactions during charge and discharge proceed rapidly, improving charge-discharge characteristics. Furthermore, while the lithium ion insertion and deintercalation reactions can cause the active material to expand and contract, the presence of free carbon in its vicinity is thought to mitigate this expansion and contraction of the entire active material, significantly improving capacity retention.

[0134] The free carbon is formed during the thermal decomposition of the silicon-containing compound and the carbon source resin in an inert gas atmosphere during the production of the silicon oxycarbide phase. Specifically, carbonizable moieties in the molecular structures of the silicon-containing compound and the carbon source resin are converted into carbon components by high-temperature thermal decomposition in an inert atmosphere, and some of these carbons bond to part of the silicon-oxygen-carbon skeleton. The carbonizable component is preferably a hydrocarbon, more preferably an alkyl, alkylene, alkene, alkyne, or aromatic compound, and even more preferably an aromatic compound.

[0135] Furthermore, the presence of free carbon is expected to reduce the resistance of the active material, and when the active material is used as the negative electrode of a secondary battery, it is thought that the reaction inside the active material will occur uniformly and smoothly, resulting in an active material for secondary batteries that has an excellent balance between charge / discharge performance and capacity retention. While free carbon can be introduced solely from silicon-containing compounds, the use of a carbon source resin in combination is expected to increase the amount of free carbon present and its effects. The type of carbon source resin is not particularly limited, but a carbon compound containing a six-membered carbon ring is preferred.

[0136] The state of free carbon can be identified not only by Raman spectroscopy but also by thermogravimetric differential thermal analysis (TG-DTA). Unlike carbon atoms in a silicon-oxygen-carbon skeleton, free carbon is easily thermally decomposed in the atmosphere, and the amount of carbon present can be determined from the amount of thermal weight loss measured in the presence of air. In other words, the amount of carbon can be quantified using TG-DTA. Furthermore, the thermal weight loss behavior can easily reveal changes in thermal decomposition temperature behavior, such as the decomposition reaction onset temperature, decomposition reaction termination temperature, the number of thermal decomposition species, and the temperature at which each species experiences maximum weight loss. The temperature values ​​of these behaviors can be used to determine the state of carbon. Meanwhile, the carbon atoms in the silicon-oxygen-carbon skeleton, i.e., the carbon atoms bonded to the silicon atoms that make up the SiO2C2, SiO3C, and SiO4, possess extremely strong chemical bonds, making them highly thermally stable and unlikely to undergo thermal decomposition in air within the temperature range of thermal analysis. Furthermore, carbon in the silicon oxycarbide phase of the active material has properties similar to amorphous carbon and therefore undergoes thermal decomposition in air at temperatures between approximately 550°C and 900°C. This results in rapid weight loss. While the maximum temperature for TG-DTA measurement is not particularly limited, it is preferable to perform TG-DTA measurements in air at temperatures between approximately 25°C and approximately 1000°C or higher in order to completely complete the carbon pyrolysis reaction.

[0137] The active material (inorganic fine particles) obtained by this production method II may be coated on the surface with a coating material, which is preferably a material that is expected to have electron conductivity, lithium ion conductivity, and the effect of inhibiting decomposition of the electrolyte. Examples of the coating material include electron-conductive materials such as carbon, titanium, nickel, etc. Among these, carbon is preferred, and low-crystalline carbon is more preferred, from the viewpoint of improving the chemical stability and thermal stability of the active material.

[0138] When the coating material is low-crystalline carbon, the average thickness of the coating layer is preferably 10 nm to 300 nm, and the content of low-crystalline carbon is preferably 1 to 30 mass % relative to the total mass of the active material obtained by Production Method II, taken as 100 mass %. When the coating material is carbon, the carbon coating is preferably formed on the surface of the active material by vapor deposition. The amount of the carbon coating is preferably 1% by mass to 10% by mass, where the total mass of the active material and the carbon coating is 100% by mass, from the viewpoint of improving the chemical stability and thermal stability of the active material. The mass of the active material obtained by this manufacturing method II refers to the mass of the silicon particles when the active material is composed only of silicon particles, and refers to the total mass of both when the active material is composed of silicon particles and a matrix phase. For example, when the matrix phase is silicon oxycarbide, it refers to the total mass of the silicon particles and silicon oxycarbide. When the silicon oxycarbide contains nitrogen, it refers to the total mass including the nitrogen. When the active material contains another third component described below, it refers to the total mass including the third component.

[0139] It is preferable to produce inorganic fine particles by combining the present production method I and the present production method II, from the viewpoint of suppressing adhesion of inorganic fine particles to the container wall during recovery, storage, and transportation, and improving the recoverability of inorganic fine particles. Also, it is preferable to carry out both methods simultaneously, from the viewpoint of sharing utilities and reducing equipment costs. That is, a manufacturing method that combines the present manufacturing method I and the present manufacturing method II (hereinafter also referred to as "the present manufacturing method III") is a method in which a liquid fluid containing a resin-containing resin composition and a solvent is sprayed, the resin composition is dried to obtain resin composition microparticles, and the obtained resin composition microparticles are heat-treated in a suspended state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower.

[0140] It is preferable that the present manufacturing method I and the present manufacturing method II are carried out continuously, and the present manufacturing method III involves spraying a liquid fluid containing a resin-containing resin composition and a solvent, drying the resin composition, and then preferably heat-treating the resin composition fine particles obtained by drying the resin composition fine particles in a suspended state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower, without removing them from the system or recovering them, even if the resin composition fine particles may be temporarily retained in a separate container or the like. When manufacturing method I and manufacturing method II are carried out continuously, for example, the area for drying the resin composition and the area for baking the resulting resin composition microparticles are located in an integrated container, or the area for drying the resin composition and the area for baking the resulting resin composition microparticles are located in separate containers, and the two containers are connected by a flow path to carry out the drying and baking processes continuously. This allows manufacturing method I and manufacturing method II to be carried out continuously. In this production method III, the resin, solvent, etc. are the same as those in the production method I, and the preferred ranges are also the same. In this production method III, the inert gas, floating state, heat treatment, etc. are the same as those in the production method II, and the preferred ranges are also the same.

[0141] When manufacturing method I and manufacturing method II are carried out consecutively, manufacturing method III is carried out by connecting the resin composition microparticle manufacturing apparatus 120 and the inorganic microparticle manufacturing apparatus 140 by sharing the storage section 108, as shown in Figure 1 above. 1, and for example, the resin composition microparticle production apparatus 120 and the inorganic microparticle production apparatus 140 may be connected by piping or the like, and the resin composition microparticles produced in the resin composition microparticle production apparatus 120 may be transferred by a pump or the like to the inorganic microparticle production apparatus 140. Alternatively, for example, the resin composition microparticle production apparatus 120 may be disposed at the top and the inorganic microparticle production apparatus 140 may be disposed at the bottom, and the two may be connected by piping or the like, and the resin composition microparticles produced in the resin composition microparticle production apparatus 120 may be transferred by free fall to the inorganic microparticle production apparatus 140.

[0142] From the viewpoint of controlling the particle size of the inorganic microparticles obtained by this production method III and obtaining inorganic microparticles with little aggregation, it is preferable that in this production method III, a liquid fluid containing a resin-containing resin composition and a solvent is sprayed, and when the resin composition is dried to form resin composition microparticles, the resin composition microparticles do not fuse together and each particle maintains its individual shape. Furthermore, in this production method III, it is preferable that during the heat treatment of the obtained resin composition microparticles in a suspended state under an inert gas atmosphere at a temperature of 200°C to 1500°C, the resin composition microparticles do not fuse together and each particle maintains its individual shape. The phrase "particles do not fuse together and each particle maintains its individual shape" is the same as above.

[0143] In order to prevent the resin composition particles from fusing together and each particle retaining its shape independently when the resin composition is dried, the spray direction, spray speed, and drying temperature of the resin composition may be adjusted in the same manner as in Production Method I.

[0144] Furthermore, while the obtained resin composition microparticles are heated in a floating state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower, the spray direction and spray speed of the resin composition and the drying temperature can be adjusted so that the resin composition microparticles do not fuse together and each particle maintains its independent shape.

[0145] When the inorganic microparticles obtained by this manufacturing method III are used as an active material for a secondary battery such as a lithium battery, the inorganic microparticles obtained by continuously carrying out this manufacturing method II using the active material precursor obtained by the above-mentioned manufacturing method I can be used as an active material for a secondary battery such as a lithium battery, particularly as a negative electrode active material (hereinafter also referred to as "this active material").

[0146] The present active material has excellent cycle properties and is suitable for use as a negative electrode active material for secondary batteries containing the present active material. Specifically, a slurry containing the active material, an organic binder, and, if necessary, other components such as a conductive additive, is applied to a copper foil current collector in the form of a thin film to form a negative electrode. A carbon material such as graphite can also be added to the slurry to prepare a negative electrode. Examples of carbon materials include natural graphite, artificial graphite, and amorphous carbon such as hard carbon or soft carbon.

[0147] For example, the active material and a binder, which is an organic binding material, are mixed together with a solvent using a dispersing device such as a stirrer, ball mill, super sand mill, or pressure kneader to prepare a negative electrode material slurry, which is then applied to a current collector to form a negative electrode layer. Alternatively, the negative electrode material can be obtained by forming the paste-like negative electrode material slurry into a shape such as a sheet or pellet and integrating it with a current collector.

[0148] Examples of the organic binder include styrene-butadiene rubber copolymers (hereinafter also referred to as "SBR"); unsaturated carboxylic acid copolymers such as ethylenically unsaturated carboxylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylonitrile, and hydroxyethyl (meth)acrylate, and (meth)acrylic copolymers composed of ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid; and polymer compounds such as polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polyimide, polyamideimide, and carboxymethyl cellulose (hereinafter also referred to as "CMC").

[0149] Depending on their physical properties, these organic binders may be dispersed or dissolved in water, or dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP). The content of the organic binder in the negative electrode layer of the lithium ion secondary battery negative electrode is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 3 to 15% by mass.

[0150] When the content of the organic binder is 1% by mass or more, adhesion is improved and destruction of the negative electrode structure due to expansion and contraction during charge and discharge is further suppressed, while when the content is 30% by mass or less, an increase in electrode resistance is further suppressed. Within this range, the active material has high chemical stability and can be used with an aqueous binder, making it easy to handle in practical applications.

[0151] The negative electrode material slurry may contain a conductive additive, if necessary. Examples of the conductive additive include carbon black, graphite, acetylene black, and conductive oxides and nitrides. The amount of the conductive additive used may be about 1% by mass to 15% by mass of the negative electrode active material of the present invention.

[0152] The current collector may be made of copper, nickel, titanium, stainless steel, or the like in the form of a foil, perforated foil, mesh, or other strip. Porous materials such as porous metal (foamed metal) and carbon paper may also be used.

[0153] Examples of methods for applying the negative electrode material slurry to the current collector include metal mask printing, electrostatic coating, dip coating, spray coating, roll coating, doctor blade coating, gravure coating, screen printing, etc. After application, it is preferable to perform a rolling treatment using a flat plate press, a calendar roll, or the like, as necessary.

[0154] The negative electrode material slurry can be formed into a sheet or pellet form, and the sheet or pellet can be integrated with the current collector by, for example, rolling, pressing, or a combination thereof.

[0155] The negative electrode layer formed on the current collector or the negative electrode layer integrated with the current collector is preferably heat-treated depending on the organic binder used. For example, when an aqueous styrene-butadiene rubber copolymer (SBR) or the like is used, the heat treatment may be performed at 100 to 130°C, and when an organic binder having a polyimide or polyamideimide as the main skeleton is used, the heat treatment is preferably performed at 150 to 450°C.

[0156] This heat treatment removes the solvent and hardens the binder, increasing strength and improving adhesion between particles and between the particles and the current collector. These heat treatments are preferably carried out in an inert atmosphere such as helium, argon, or nitrogen, or in a vacuum atmosphere, to prevent oxidation of the current collector during treatment.

[0157] After the heat treatment, the negative electrode is preferably subjected to pressure treatment. In the negative electrode using this active material, the electrode density is 1 g / cm 3 to 1.8 g / cm 3 and preferably 1.1 g / cm 3 to 1.7 g / cm 3More preferably, it is 1.2 g / cm 3 to 1.6 g / cm 3 It is more preferable that the electrode density is higher. The higher the electrode density, the better the adhesion and volumetric capacity density of the electrode tend to be. On the other hand, if the electrode density is too high, the voids in the electrode are reduced, which weakens the effect of suppressing the volume expansion of silicon, etc., and may result in a decrease in the capacity retention rate. Therefore, an optimal range of electrode density is selected.

[0158] In addition to this active material, an active material obtained by a method other than this manufacturing method II using the active material precursor obtained by this manufacturing method I, and inorganic fine particles obtained by this manufacturing method II using the active material precursor obtained by a method other than this manufacturing method I, can also be suitably used as a negative electrode active material for lithium secondary batteries in the same manner as described above.

[0159] When the lithium secondary battery is used as a wet electrolyte secondary battery, for example, it can be constructed by disposing a positive electrode and a negative electrode containing an active material opposite each other with a separator interposed therebetween and injecting an electrolyte solution.

[0160] The positive electrode can be obtained by forming a positive electrode layer on the surface of a current collector in the same manner as the negative electrode. In this case, the current collector can be a strip-shaped current collector made of a metal or alloy such as aluminum, titanium, or stainless steel, in the form of a foil, perforated foil, mesh, or the like.

[0161] The positive electrode material used in the positive electrode layer is not particularly limited. When manufacturing a lithium ion secondary battery among nonaqueous electrolyte secondary batteries, for example, a metal compound, metal oxide, metal sulfide, or conductive polymer material capable of doping or intercalating lithium ions may be used. Examples include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2), and their composite oxides (LiCoxNiyMnzO2, x+y+z=1), lithium manganese spinel (LiMn2O4), lithium vanadium compounds, VO5, VO 13, VO2, MnO2, TiO2, MoV2O8, TiS2, V2S5, VS2, MoS2, MoS3, Cr3O8, Cr2O5, olivine-type LiMPO4 (wherein M is Co, Ni, Mn, or Fe), conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyacene, porous carbon, etc., can be used alone or in combination.

[0162] The separator may be, for example, a nonwoven fabric, cloth, or microporous film primarily composed of a polyolefin such as polyethylene or polypropylene, or a combination thereof. Note that if the nonaqueous electrolyte secondary battery to be fabricated has a structure in which the positive electrode and the negative electrode are not in direct contact with each other, it is not necessary to use a separator.

[0163] As the electrolyte, for example, a so-called organic electrolyte can be used, which is obtained by dissolving a lithium salt such as LiClO4, LiPF6, LiAsF6, LiBF4, or LiSO3CF3 in a non-aqueous solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, cyclopentanone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3-methyl-1,3-oxazolidin-2-one, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, butyl ethyl carbonate, dipropyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, or ethyl acetate, either alone or as a mixture of two or more components.

[0164] The structure of the secondary battery is not particularly limited, but typically, a positive electrode, a negative electrode, and a separator, which is provided as needed, are wound into a flat spiral shape to form a wound electrode plate group, or these are stacked in flat plates to form a stacked electrode plate group, and these electrode plate groups are enclosed in an exterior housing. The half-cells used in the examples of the present invention are configured so that the negative electrode is mainly made of the active material of the present invention, and a simple evaluation is performed using metallic lithium as the counter electrode. This is to more clearly compare the cycle properties of the active material itself.

[0165] The secondary battery is not particularly limited, and may be used as a paper battery, a button battery, a coin battery, a laminated battery, a cylindrical battery, a prismatic battery, etc. The above-described negative electrode active material of the present invention can also be applied to general electrochemical devices that use the insertion and desorption of lithium ions as a charge / discharge mechanism, such as hybrid capacitors and solid-state lithium secondary batteries.

[0166] The resin composition microparticles obtained by Production Method I, the inorganic microparticles obtained by Production Method II, and the inorganic microparticles obtained by Production Method III are easy to control in particle size and contain little fine powder, and therefore, by appropriately selecting the resin and inorganic compound, they can be suitably used not only as the active material for the lithium secondary battery, but also for various applications such as catalysts, conductive coatings, insulating coatings, modifiers, and precursors thereof.

[0167] Furthermore, the resin composition microparticles obtained by this manufacturing method I can be used as the raw material for this manufacturing method II, and the inorganic microparticles obtained by this manufacturing method III are inorganic microparticles that are inhibited from forming agglomerates due to coagulation and sintering during firing, and contain little fine powder generated by excessive pulverization. Furthermore, when Production Method III is a continuous process of Production Method I and Production Method II, agglomeration due to solidification and sintering during firing can be suppressed, and inorganic fine particles with little fine powder resulting from excessive pulverization can be obtained in a single step.

[0168] Although the present manufacturing method I, the present manufacturing method II, and the present manufacturing method III have been described above, the present invention is not limited to the configurations of the above-described embodiments. In the configurations of the above-described embodiments, Production Method I, Production Method II, and Production Method III may have any other steps added thereto, or may be replaced with any other steps that exhibit the same function. Furthermore, the present invention is not limited to the configurations of the above-described embodiments with respect to the resin composition particles obtained by Production Method I, the inorganic particles obtained by Production Method II, and the inorganic particles obtained by Production Method III. The resin composition microparticles obtained by Production Method I, the inorganic microparticles obtained by Production Method II, and the inorganic microparticles obtained by Production Method III may contain any other components in the configuration of the above-mentioned embodiment, or may be substituted with any component that exhibits a similar function. [Example]

[0169] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The resin compositions used in the examples and comparative examples are as follows. Resin composition: A polysiloxane compound was prepared by the method of Synthesis Example 1 below, and a curable resin composition was produced by the method of Synthesis Example 2 below.

[0170] Synthesis Example 1: Preparation of polysiloxane compound A reaction vessel equipped with a stirrer, thermometer, dropping funnel, condenser, and nitrogen gas inlet was charged with 1,421 parts by mass of methyltrimethoxysilane (hereinafter referred to as "MTMS") and heated to 60°C. Next, a mixture of 0.17 parts by mass of isopropyl acid phosphate ("Phoslex A-3" manufactured by SC Organic Chemical Co., Ltd.) and 207 parts by mass of deionized water was added dropwise to the reaction vessel over 5 minutes, and the mixture was stirred at 80°C for 4 hours to carry out the hydrolysis and condensation reaction of MTMS.

[0171] The condensate obtained by the hydrolysis-condensation reaction was distilled at a temperature of 40 to 60°C under a reduced pressure of 40 to 1.3 kPa. Note that "under a reduced pressure of 40 to 1.3 kPa" means that the reduced pressure was 40 kPa at the start of methanol distillation and was continued until it finally reached 1.3 kPa. This also applies to the following descriptions. By removing the methanol and water produced during the reaction, 1,000 parts by mass of a liquid containing an MTMS condensate (hereinafter also referred to as "a1") having a number-average molecular weight of 1,000 to 5,000 was obtained. The active ingredient content of the obtained liquid was 70% by mass. The effective component is calculated by dividing the theoretical yield (parts by mass) when all methoxy groups of a silane monomer such as MTMS undergo a condensation reaction by the actual yield (parts by mass) after the condensation reaction, i.e., [theoretical yield (parts by mass) when all methoxy groups of a silane monomer undergo a condensation reaction / actual yield (parts by mass) after the condensation reaction].

[0172] Synthesis Example 2: Production of curable resin composition A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, a condenser, and a nitrogen gas inlet was charged with 150 parts by mass of butanol (hereinafter also referred to as "BuOH"), 105 parts by mass of phenyltrimethoxysilane (hereinafter also referred to as "PTMS"), and 277 parts by mass of dimethyldimethoxysilane (hereinafter also referred to as "DMDMS"), and the temperature was raised to 80°C. Next, at the same temperature, a mixture containing 21 parts by weight of methyl methacrylate (hereinafter also referred to as "MMA"), 4 parts by weight of butyl methacrylate (hereinafter also referred to as "BMA"), 3 parts by weight of butyric acid (hereinafter also referred to as "BA"), 2 parts by weight of methacryloyloxypropyltrimethoxysilane (hereinafter also referred to as "MPTS"), 3 parts by weight of BuOH, and 0.6 parts by weight of butylperoxy-2-ethylhexanoate (hereinafter also referred to as "TBPEH") was added dropwise to the reaction vessel over 6 hours. After completion of the addition, the mixture was allowed to react at the same temperature for a further 20 hours to obtain an organic solvent solution of a vinyl polymer (a2) having a number average molecular weight of 10,000 and having hydrolyzable silyl groups. Next, a mixture of 0.04 parts by mass of isopropyl acid phosphate ("Phoslex A-3" manufactured by SC Organic Chemical Co., Ltd.) and 112 parts by mass of deionized water was added dropwise over 5 minutes, and the mixture was stirred at the same temperature for a further 10 hours to cause a hydrolysis and condensation reaction, thereby obtaining a liquid containing a composite resin in which the hydrolyzable silyl group of the vinyl polymer (a2) was bonded to the hydrolyzable silyl group and silanol group of the polysiloxane derived from the PTMS and DMDMS. Next, 472 parts by mass of the MTMS condensate (a1) obtained in Synthesis Example 1 and 80 parts by mass of deionized water were added to this liquid, and the mixture was stirred at the same temperature for 10 hours to cause a hydrolysis and condensation reaction, and the produced methanol and water were removed by distillation under the same conditions as in Synthesis Example 1. Next, 250 parts by mass of BuOH was added, and 1,000 parts by mass of a curable resin composition with a nonvolatile content of 60.1% by mass was obtained.

[0173] (Silicon crushing method) 5000 g of silicon powder (manufactured by Kojundo Chemical) with a silicon purity of 99.9% by mass and a volume average particle size of 3.2 μm, 2000 g of DISPERBYK9077 (manufactured by BYK Additives & Instruments; DISPERBYK is a registered trademark), and 20,000 g of methyl ethyl ketone (hereinafter also referred to as "MEK") were mixed in a stirring vessel and stirred well. The stirring vessel was covered with a lid and nitrogen gas was supplied to create an inert gas atmosphere inside the vessel. This mixture was wet-milled for 8 hours using a bead mill (MSC Mill MSC220 manufactured by Nippon Coke & Engineering Co., Ltd.) to obtain a nanosilicon-containing slurry in which silicon was uniformly dispersed in the dispersion medium. The diameter of the beads in the bead mill was 0.2 mm, and the true density of the beads was 6.0 g / cm. 3 The peripheral speed of the bead mill was set to 12 m / s. The degree of orientation f(111) of the (111) plane of silicon contained in the obtained nanosilicon-containing slurry was 0.35. The nanosilicon-containing slurry was dried at room temperature under vacuum for 10 hours to obtain dried nanosilicon.

[0174] This nanosilicon dry product 29Si-NMR measurements revealed that the ratio (i) of the area of ​​the peak in the range of -75 to -85 ppm, which indicates Si-Si bonds, to the area (ii) of other peaks containing at least SiO4, SiO3C, SiO2C2, SiOC3, SiC4, etc. [(i) / (ii) ratio] was 0.63.

[0175] Six drops of nanosilicon-containing slurry were placed on a glass plate for XRD measurement, and the plate was dried by spinning it at 2000 rpm for 10 seconds using a spin coater to obtain a nanosilicon coating. Crystal structure analysis was performed using this sample using X-ray diffraction. The orientation of the silicon (111) plane, f(111), based on the Lotgering method, was found to be 0.35.

[0176] (Preparation of Resin Composition Solution) The nanosilicon-containing slurry and the resin composition (hereinafter also referred to as SiOC-C) were mixed so that the ratio of SiOC-C / Si was 50 / 50, calculated based on the composition after firing, to prepare a resin composition solution.

[0177] [Examples 1 to 3] The resin composition solution obtained in the preparation of the resin composition solution was dried by the spraying method shown in Table 1 (corresponding to Production Method I) to obtain resin composition microparticles. The obtained resin composition microparticles were subjected to the heating method 1 shown in Table 1 to obtain inorganic microparticles (Production Method II). The obtained resin composition microparticles were subjected to Production Method II without separation (corresponding to Production Method III). In Table 1, countercurrent spraying refers to the discharge of hot air in a direction opposite to the spraying direction of the resin composition solution, while parallel spraying refers to the supply of hot air in the same direction as the spraying direction of the resin composition solution. An inert gas with a temperature of 200 to 1500°C was used as the hot air. In Table 1, floating heating refers to heating in a state where the sprayed resin composition solution exists in space without coming into direct contact with the wall or bottom of the container into which it was sprayed. The obtained inorganic fine particles were further heated by the method described in Heating 2 to obtain a powder of inorganic fine particles. Note that in Table 1, "stagnant" means that the inorganic fine particles were heated in a stationary state without moving. The obtained powder was evaluated for carbonization by the following carbonization evaluation, and for fusion and fine powder. The results are shown in Table 1.

[0178] [Comparative Examples 1 to 3] The resin composition solution obtained in the preparation of the resin composition solution was dried by the drying method shown in Table 1 to obtain resin composition microparticles. The obtained resin composition microparticles were subjected to heating method 1 shown in Table 1 to obtain inorganic microparticles. The obtained resin composition microparticles were heated by heating method 1 without being separated. Next, the inorganic microparticles were further heated by the method shown in heating method 2. In Table 1, "disk" refers to a disk dryer. In addition, in Table 1, "floating type" is the same as above. In heating method 2, "retention" is the same as above. The obtained inorganic fine particles were crushed in a crusher (corresponding to crushing 1 in Table 1), and further finely crushed in a ball mill (corresponding to crushing 2 in Table 1) to obtain a powder. The obtained powder was subjected to the carbonization evaluation described below to confirm carbonization, and was evaluated for fusion and fine powder. The results are shown in Table 1.

[0179] (Carbonization evaluation of powder after firing) The fired products obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to Raman measurement (using a Raman microscope spectrometer manufactured by RENISHAW) to obtain a 1593 cm -1 and 1335 cm -1 A peak was observed at this point, confirming carbonization (mineralization).

[0180] (Evaluation of fusion) Fusion and clumping were confirmed by SEM observation of the powders obtained in Examples 1 to 3 and Comparative Examples 1 to 3. Regarding fusion, a state in which each particle was independent and not fused together was marked with a circle in the SEM image, while a state in which the particles were fused together, i.e., the outlines of the particles were mostly connected, was marked with an X.

[0181] (Fine powder evaluation) The method for evaluating the fine particles in the powders obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was as follows: in the particle size distribution obtained by dynamic light scattering measurement using the laser particle size analyzer (Malvern Panalytical, Mastersizer 3000), when a cumulative volume distribution curve was drawn from the small diameter side, if the cumulative volume percentage of particles of 1 μm or less was less than 10%, there was little fine powder, and the result was judged as "Good", and if it was 10% or more, there was a lot of fine powder, and the result was judged as "Poor".

[0182] [Table 1]

[0183] 29 The measurement conditions for Si-NMR and XRD are as follows. [ 29 Si-NMR] Using a JNM-ECA600 manufactured by JEOL RESONANCE, the negative electrode active materials obtained in each example and comparative example were collected in a solid-state NMR sample tube (made of ZrO, φ3.2 mm) and measured under the conditions below. The peak attributed to Si (peak A with a chemical shift value of approximately −80 ppm) and the peak attributed to SiO (peak B with a chemical shift value of approximately −110 ppm) were measured, and the ratio R of peak A to peak B was calculated. [Measurement conditions] Probe: S60HX32 / AM (3.2 mm) MAS rate: 5kHz, 29 Si(119MHz) single_pulse_solid, flip 30deg., RD ​​60s x_offset:0 ppm x_sweep:500ppm x_points:2k scans 1024 ca. 17hr

[0184] [XRD] The dried nanosilicon was packed into a 0.5 mm deep glass sample plate manufactured by Rigaku Corporation, and measurements were carried out using a wide-angle X-ray diffraction (XRD) device (Rigaku Corporation's "Ultima IV") under the following conditions. Optical system: Parallel beam method + scintillation counter detector on the incident side Cu / Kα rays: 40kV / 40mA Scan speed: 2° / min Step: 0.02° Scanning range: 5° to 70°

[0185] The results in Table 1 show that the powders obtained by Production Method I and Production Method II have little fine powder and fusion, and are inhibited from coagulating or sintering during firing, resulting in inorganic fine particles with little fine powder. Production Method I and Production Method II can also be suitably carried out continuously. Production Method III, in which the resin composition fine particles obtained by Production Method I are used as the raw material for Production Method II, also produces little fine powder and fusion, and is inhibited from coagulating or sintering during firing, resulting in inorganic fine particles with little fine powder. [Explanation of symbols]

[0186] 100 Inorganic fine particle manufacturing system 120 Resin composition fine particle manufacturing equipment 140 Inorganic fine particle production equipment 102 Spray section 104 Supply section 106 Collection Department 108 Storage Unit 110 Heating section 112 Deposition part

Claims

1. A method for producing resin composition fine particles, comprising spraying a liquid fluid containing a resin-containing resin composition and a solvent, and drying the resin composition.

2. The method for producing resin composition fine particles according to claim 1 , wherein the resin composition contains an inorganic substance.

3. 3. The method for producing resin composition fine particles according to claim 1, wherein the shape of the resin composition is such that each particle independently maintains its shape without fusing together when dried.

4. The method for producing resin composition microparticles described in claim 1 or 2, wherein the drying is performed by contacting the hot air with the resin composition so that the spraying direction of the liquid fluid and the blowing direction of the hot air are opposite to each other, thereby drying the resin composition.

5. 3. The method for producing resin composition microparticles according to claim 1, wherein the amount of the resin composition in the liquid fluid is 10% by mass or more and 90% by mass or less, with the mass of the liquid fluid being 100% by mass.

6. 3. The method for producing resin composition fine particles according to claim 1, wherein the solvent is an organic solvent having a boiling point of 40° C. or higher and 180° C. or lower.

7. 3. The method for producing resin composition fine particles according to claim 1, wherein the resin undergoes thermal decomposition mass loss of 60% by mass or less at temperatures up to 1000°C in the atmosphere.

8. A method for producing resin composition microparticles as described in claim 6, wherein the organic solvent is recovered together with the hot air, and the amount of organic solvent recovered per hour is 60 mass% or more, assuming that the content of the organic solvent in the sprayed liquid fluid per hour is 100 mass%.

9. 3. The method for producing resin composition microparticles according to claim 1, wherein the sprayed liquid fluid becomes particles having an average particle size D50 of 0.1 μm or more and 100 μm or less during the drying.

10. A method for producing inorganic fine particles, comprising heating resin-containing fine particles in a suspended state in an inert gas atmosphere at a temperature of 200° C. to 1500° C. to produce inorganic fine particles.

11. The method for producing inorganic fine particles according to claim 10, wherein the fine particles further contain at least one of a metal and a metal oxide.

12. 12. The method for producing inorganic fine particles according to claim 11, wherein the content of at least one of the metal and the metal oxide in the fine particles is 99% by mass or less, with the mass of the fine particles being 100% by mass.

13. 12. The method for producing inorganic fine particles according to claim 10, wherein the average particle size of the obtained inorganic fine particles is 0.1 μm or more and 100 μm or less in terms of D50.

14. 13. The method for producing inorganic fine particles according to claim 11, wherein the particle diameter D50 of at least one of the metal and the metal oxide in the fine particles is 10 nm or more and 300 nm or less.

15. 12. The method for producing inorganic fine particles according to claim 10, wherein the heat treatment is carried out in a plurality of steps under different conditions, such as different temperatures or different residence times.

16. The method for producing inorganic fine particles according to claim 10 or 11, wherein the fine particles are transported in a certain direction and subjected to the heat treatment.

17. The method for producing inorganic fine particles according to claim 10 or 11, wherein the inorganic fine particles are further heated after the heat treatment.

18. A method for producing inorganic microparticles, comprising spraying a liquid fluid containing a resin-containing resin composition and a solvent, drying the resin composition to obtain resin composition microparticles, and heat-treating the obtained resin composition microparticles in a suspended state under an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower.

19. The method for producing inorganic fine particles according to claim 18, wherein the resin composition and the resin composition fine particles are not fused together during drying and heat treatment, and each particle independently maintains its shape.

20. 20. The method for producing inorganic microparticles according to claim 18 or 19, wherein the drying comprises bringing hot air into contact with the resin composition so that the spraying direction of the liquid fluid and the blowing direction of the hot air are opposite to each other, thereby drying the resin composition.

21. 20. The method for producing inorganic fine particles according to claim 18, wherein the heat treatment is carried out continuously on the resin composition fine particles.

22. Resin composition fine particles obtained by spraying a liquid fluid containing a resin-containing resin composition and a solvent, and then drying the resin composition.

23. These inorganic fine particles are obtained by heat treating resin-containing fine particles in a suspended state in an inert gas atmosphere at a temperature of 200°C to 1500°C.

24. Inorganic microparticles are obtained by spraying a liquid fluid containing a resin-containing resin composition and a solvent, drying the resin composition to obtain resin composition microparticles, and then heat-treating the obtained resin composition microparticles in a suspended state in an inert gas atmosphere at a temperature of 200°C or higher and 1500°C or lower.

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