JP5633774B2 - Method for producing hollow particles - Google Patents

Description

 The present invention relates to a method for producing hollow particles, and in particular, a basic compound is allowed to act on an alkoxide to advance a condensation polymerization reaction to form a shell compound to cover the surface of the core particles, and then the core particles are formed. The present invention relates to a method for producing hollow particles by dissolution and removal.

  In recent years, as part of nanotechnology research, applied research on fine particles having a particle size of several hundred nanometers or less has been actively conducted. As an example, there is an invention of highly dispersed silica nano hollow particles described in Patent Document 1 and a method for producing the same. This silica nano hollow particle is a nano hollow particle composed of a dense silica shell, in which pores of 2 nm to 20 nm are not detected in the pore distribution. First step of preparing calcium carbonate fine particles and dispersing them in a solvent In addition, it is produced by a second step of coating silica on the dispersed calcium carbonate fine particles by a sol-gel reaction (sol-gel method) of silicon alkoxide, and a third step of dissolving calcium carbonate to form silica nano hollow particles.

Here, the “sol-gel method” is generally “a method of producing glass by heating after passing through a sol and gel state from a solution. Alkoxides are often used as starting materials. (Saburo Nagakura et al., Edited by “Iwanami Rikagaku Dictionary (5th edition)”, page 777, published by Iwanami Shoten Co., Ltd. on February 20, 1998). Here, silicon alkoxides including tetraethoxysilane (TEOS) Is reacted with water under basic conditions to form a gel-like silica shell in which SiO ₂ molecules are polycondensed. The gel-like silica shell is converted into a glass-like silica shell by heating calcium carbonate in a temperature range of 200 ° C. to 1000 ° C.

  The high-dispersion silica nano hollow particles according to Patent Document 1 are hollow and have a thin silica shell, so that they have excellent heat insulation and transparency, and have a lower density, lower thermal conductivity, and higher specific surface area than solid particles. Therefore, as shown in Patent Document 2, it is possible to obtain heat insulating paint, heat insulating film and heat insulating fiber by uniformly dispersing in paint, film and synthetic fiber, and to apply to a wide range of technical fields. Can do. In addition, the hollow particles are expected to be applied in various fields including use as a lightweight filler and use as a carrier for drug delivery in the medical field.

 In general, hollow particles composed of an inorganic oxide shell typified by silica include a method of obtaining a hollow structure by foaming such as spray pyrolysis, and a core (core) as shown in Patent Document 1. After the surface of the material is coated with a target inorganic oxide film, it is manufactured by a “template method” which is a method of removing the core material.

 In the template method, hollow particles having a shape reflecting the shape of the core substance can be obtained. Representative core (core) particles include organic fine particles such as emulsion and latex, and inorganic fine particles. When an emulsion or latex is used as the core particle, the hollow particle shape is usually limited to a spherical shape. However, as described in Patent Document 1, inorganic fine particles typified by calcium carbonate are used as the core particle. In some cases, hollow particles having various shapes reflecting the crystal shape can be obtained.

 Here, in the method for producing hollow silica particles described in Patent Document 1, the first step, the second step, and the third step are each performed by a batch (batch type) operation. In order to make the hollow particle manufacturing method by the template method including the manufacturing method suitable for mass production, it is necessary to carry out the first step, the second step, and the third step by continuous operation. As one means for that purpose, the first to third steps are performed in a circulation flow path of a wet particle dispersing device such as a wet jet mill, after the calcium carbonate fine particles, silica-coated calcium carbonate fine particles and calcium carbonate are removed. This is also extremely preferable in terms of preventing aggregation of hollow particles formed of silica shells to be formed.

JP 2005-263550 A JP 2007-070458 A

However, in the technique described in Patent Document 1, since ammonia water is used as a catalyst for hydrolysis / condensation polymerization reaction of silicon alkoxide, ammonia water is used as a reservoir part of the circulation channel of the wet particle dispersion device. From the rapid increase of the hydrolysis and polycondensation reaction of the silicon alkoxide due to the local increase in ammonia concentration and the accompanying increase in the hydrogen ion concentration (pH) of the reaction solution, the formation of coarse silica particles, The aggregation and the formation of aggregates between the silica-coated calcium carbonate fine particles occur. Therefore, it becomes impossible to obtain hollow particles made of silica shells of a desired size.
In addition, these coarse silica particles and aggregates block the ultrafine diameter (usually 0.1 mm or less inner diameter) flow path for promoting particle dispersion in the wet particle disperser, so that continuous operation is not possible. There was a problem that it became possible. That is, in the technique described in Patent Document 1, it is difficult even to continuously perform only the first step and the second step.

  Therefore, the present invention has been made to solve such problems, and in the coating step by hydrolysis / condensation polymerization of alkoxide on the surface of the core particles, the core particles are aggregated and coarse shell compound particles are generated. And the aggregation thereof, and the coarsening of the particles in which the core particles are coated with the shell compound (hereinafter also simply referred to as “shell compound-coated core particles”) and the formation of aggregates are prevented. By preventing clogging of the pore flow channel of a reaction apparatus such as a wet particle dispersion apparatus by collecting, the first step and the second step are continuously performed, and further, the first to third steps are continuously performed. It is an object of the present invention to provide a method for producing hollow particles, which can be carried out in a continuous manner, can continuously obtain shell compound-coated core particles or hollow particles of a desired size, and can mass-produce hollow particles. Do Than is.

  The method for producing hollow particles according to the invention of claim 1 is characterized in that a basic compound is allowed to act on an alkoxide to cause hydrolysis and polycondensation reaction of the alkoxide to produce a shell compound (shell compound). Covering the surface of the particles (core particles), and then dissolving and removing the core particles to produce hollow particles made of the shell compound, wherein the basic compound is converted into a basic compound precursor substance. It is generated gradually by the action of a catalyst.

 Here, the “alkoxide” is also referred to as “alcoholate”. A generic term for compounds in which the hydrogen of the hydroxy group of an alcohol is replaced by a metal M. Since it is also seen as a compound in which a metal is bonded to an alkoxy group, it is also called a metal alkoxide. ............ Metal alkoxide M (OR) n can be highly purified by distillation or recrystallization, so the sol produced by the condensation polymerization reaction is gelled, and the sol-gel method for producing bulk, membrane, fiber, etc. Excellent as a raw material. (Saburo Nagakura et al., Edited by Iwanami Dictionary of Physical and Chemical Dictionary (5th edition), p. 46, published by Iwanami Shoten Co., Ltd. on February 20, 1998).

Specific examples of the alkoxide include silicon alkoxide, lithium alkoxide, sodium alkoxide, potassium alkoxide, magnesium alkoxide, aluminum alkoxide and the like.
In particular, silicon alkoxide can be regarded as a compound in which a hydrogen atom of silane SiH ₄ is substituted with an alkoxy group, so that “XX alkoxysilane (where XX indicates the number of alkoxy groups, It is also called “di, tri, or tetra prefix”.

 In addition, “particles” are generally “fine particles constituting a substance. (Shinmura, edited by “Kojien (4th edition)”, page 2693, published by Iwanami Shoten Co., Ltd. on November 15, 1991). The term “hollow particle” means a particle having a space inside, regardless of whether or not it exists.

Furthermore, examples of the “basic compound” include ammonia (NH ₃ ), amine, amide, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) ₂ ), etc. Examples of the “compound precursor substance” include urea ((NH ₂ ) ₂ CO) that generates ammonia by the action of a catalyst.

In the constitution of the present invention, the alkoxide is silicon alkoxide, and the shell compound is silica (SiO ₂ ).
Here, as described above, the silicon alkoxide can be regarded as a compound in which the hydrogen atom of silane SiH ₄ is substituted with an alkoxy group, and therefore, “XX alkoxysilane (XX represents the number of alkoxy groups. This is also called "mono, di, tri, or tetra prefix". Specifically, there are compounds such as tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

 Further, as the silicon alkoxide for coating the surface of the core particles with the silica shell by the sol-gel method, various silicon alkoxides such as tetraethoxysilane (TEOS) as described above can be used. Specifically, for example, ethyl silicate (product name “high purity ethyl silicate”: tetraethoxysilane (TEOS)) from Tama Chemical Industries, Ltd., alkoxysilane (product name) among functional silanes from Shin-Etsu Chemical Co., Ltd. “KBE-04”: tetraethoxysilane (TEOS)) or the like can be used.

Furthermore, in the structure of this invention, the said core particle is an inorganic fine particle melt | dissolved with an acid.
Here, as the “acid”, carboxylic acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid / benzoic acid, citric acid, butyric acid, etc. can be used, and the concentration thereof is arbitrarily set according to the kind of inorganic fine particles to be dissolved can do. In addition, calcium carbonate, calcium sulfate, barium sulfate, sodium carbonate, sodium hydrogen carbonate, lithium carbonate, or the like can be used as the inorganic substance constituting the “inorganic fine particles”.

Furthermore, in the configuration of the present invention, the inorganic fine particles are calcium carbonate fine particles.
Here, as a method for producing such calcium carbonate fine particles, for example, there is a method of growing crystals in an aqueous system. The calcium carbonate crystals produced by this method are calcite and hexagonal, but by controlling the synthesis conditions, they grow into a cubic shape, that is, a “cubic shape”. be able to. Here, the “cubic form” refers to a shape similar to a cube surrounded by a face, not limited to a cube.

 The method of growing calcium carbonate fine particles in an aqueous system is not particularly limited. A method of introducing carbon dioxide into a calcium hydroxide slurry to precipitate calcium carbonate, or a soluble calcium salt such as calcium chloride. A method of precipitating calcium carbonate by adding a soluble carbonate such as sodium carbonate to the aqueous solution can be applied.

  As a method for obtaining the calcium carbonate fine particles, commercially available calcium carbonate fine particles can be purchased and used. For example, fine particle calcium carbonate of Hayashi Kasei Co., Ltd., synthetic calcium carbonate of Shiraishi Kogyo Co., Ltd., etc. can be used.

In addition, in the configuration of the present invention, the hollow particles made of the shell compound are nano hollow particles made of a silica shell whose outer diameter measured by a microscope is in the range of 30 nm to 200 nm.
Here, “microscopy” refers to a method of actually observing particles using a scanning electron microscope (SEM) or transmission electron microscope (TEM) to determine the size of each part of the particles.

 In order to produce nano hollow particles composed of a silica shell having such an outer diameter, it is preferable to use core particles having an outer diameter in the range of 8 nm to 160 nm. For example, when calcium carbonate fine particles are used as the core particles, an example of a method for producing such calcium carbonate fine particles is a method of growing crystals in an aqueous system. The calcium carbonate crystals produced by this method are calcite and hexagonal, but by controlling the synthesis conditions, they grow into a cubic shape, that is, a “cubic shape”. be able to. Here, the “cubic form” refers to a shape similar to a cube surrounded by a face, not limited to a cube.

 The method of growing calcium carbonate fine particles in an aqueous system is not particularly limited. A method of introducing carbon dioxide into a calcium hydroxide slurry to precipitate calcium carbonate, or a soluble calcium salt such as calcium chloride. A method of precipitating calcium carbonate by adding a soluble carbonate such as sodium carbonate to the aqueous solution can be applied.

 At this time, in order to obtain calcium carbonate fine particles having a target outer diameter in the range of 8 nm to 160 nm, it is desirable that the precipitation rate of calcium carbonate is increased at a relatively low temperature. For example, in the method of introducing carbon dioxide gas into the calcium hydroxide slurry, the liquid temperature when introducing the carbon dioxide gas is 30 ° C. or less, and the rate at which the carbon dioxide gas is introduced is 1.0 L / 100 g of calcium hydroxide. It is preferable to set it to min or more.

  Moreover, as a method for obtaining calcium carbonate fine particles having an outer diameter in the range of 8 nm to 160 nm, commercially available calcium carbonate fine particles can be purchased and used. For example, fine particle calcium carbonate of Hayashi Kasei Co., Ltd., synthetic calcium carbonate of Shiraishi Kogyo Co., Ltd., etc. can be used.

  According to a second aspect of the present invention, there is provided a method for producing a hollow particle, wherein a basic compound is allowed to act on an alkoxide to cause hydrolysis and polycondensation reaction of the alkoxide to produce a shell compound (shell compound). Covering the surface of the particles (core particles), and then dissolving and removing the core particles to produce hollow particles made of the shell compound, wherein the core particles are dispersed in a solvent to disperse the core particles A step of dispersing, the alkoxide in the core particle dispersion solution, a basic compound precursor material for generating the basic compound, and acting on the basic compound precursor material to gradually generate the basic compound. An addition stirring step of adding and stirring the catalyst to be carried out, and the dispersion step and the addition stirring step are carried out continuously in the reaction apparatus.

 Here, as the “solvent”, various solvents such as water, particularly distilled water, pure water, organic solvents such as methanol and ethanol can be used. In addition, the “reaction apparatus” may be an integrated reaction container such as a single container equipped with a stirring device, or a series of reaction apparatuses in which a plurality of components are continuously combined. Furthermore, “continuously performed in the reaction apparatus” means that each step is performed continuously without taking out an intermediate substance or the like from the reaction apparatus on the way.

 In the configuration of the present invention, further, dissolution removal in which the core particles are dissolved and removed by adding a compound that dissolves the core particles to the particles in which the core particles formed in the addition stirring step are coated with the shell compound. And the dispersion step, the addition stirring step and the dissolution removal step are continuously performed in a reaction apparatus.

In the structure of the present invention, the alkoxide is silicon alkoxide, and the shell compound is silica (SiO ₂ ).
Here, as described above, the silicon alkoxide can be regarded as a compound in which the hydrogen atom of silane SiH ₄ is substituted with an alkoxy group, and therefore, “XX alkoxysilane (XX represents the number of alkoxy groups. This is also called "mono, di, tri, or tetra prefix". Specifically, there are compounds such as tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

 Further, as the silicon alkoxide for coating the surface of the core particles with the silica shell by the sol-gel method, various silicon alkoxides such as tetraethoxysilane (TEOS) as described above can be used. Specifically, for example, ethyl silicate (product name “high purity ethyl silicate”: tetraethoxysilane (TEOS)) from Tama Chemical Industries, Ltd., alkoxysilane (product name) among functional silanes from Shin-Etsu Chemical Co., Ltd. “KBE-04”: tetraethoxysilane (TEOS)) or the like can be used.

Furthermore, in the structure of this invention, the said core particle is an inorganic fine particle melt | dissolved with an acid.
Here, as the “acid”, carboxylic acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid / benzoic acid, citric acid, butyric acid, etc. can be used, and the concentration thereof is arbitrarily set according to the kind of inorganic fine particles to be dissolved can do. In addition, calcium carbonate, calcium sulfate, barium sulfate, sodium carbonate, sodium hydrogen carbonate, lithium carbonate, or the like can be used as the inorganic substance constituting the “inorganic fine particles”.

Furthermore, in the configuration of the present invention, the inorganic fine particles are calcium carbonate fine particles.
Here, as a method for producing such calcium carbonate fine particles, for example, there is a method of growing crystals in an aqueous system. The calcium carbonate crystals produced by this method are calcite and hexagonal, but by controlling the synthesis conditions, they grow into a cubic shape, that is, a “cubic shape”. be able to. Here, the “cubic form” refers to a shape similar to a cube surrounded by a face, not limited to a cube.

 The method of growing calcium carbonate fine particles in an aqueous system is not particularly limited. A method of introducing carbon dioxide into a calcium hydroxide slurry to precipitate calcium carbonate, or a soluble calcium salt such as calcium chloride. A method of precipitating calcium carbonate by adding a soluble carbonate such as sodium carbonate to the aqueous solution can be applied.

  As a method for obtaining the calcium carbonate fine particles, commercially available calcium carbonate fine particles can be purchased and used. For example, fine particle calcium carbonate of Hayashi Kasei Co., Ltd., synthetic calcium carbonate of Shiraishi Kogyo Co., Ltd., etc. can be used.

In addition, in the configuration of the present invention, the hollow particles made of the shell compound are nano hollow particles made of a silica shell whose outer diameter measured by a microscope is in the range of 30 nm to 200 nm.
Here, “microscopy” refers to a method of actually observing particles using a scanning electron microscope (SEM) or transmission electron microscope (TEM) to determine the size of each part of the particles.

 In order to produce nano hollow particles composed of a silica shell having such an outer diameter, it is preferable to use core particles having an outer diameter in the range of 8 nm to 160 nm. For example, when calcium carbonate fine particles are used as the core particles, an example of a method for producing such calcium carbonate fine particles is a method of growing crystals in an aqueous system. The calcium carbonate crystals produced by this method are calcite and hexagonal, but by controlling the synthesis conditions, they grow into a cubic shape, that is, a “cubic shape”. be able to. Here, the “cubic form” refers to a shape similar to a cube surrounded by a face, not limited to a cube.

 The method of growing calcium carbonate fine particles in an aqueous system is not particularly limited. A method of introducing carbon dioxide into a calcium hydroxide slurry to precipitate calcium carbonate, or a soluble calcium salt such as calcium chloride. A method of precipitating calcium carbonate by adding a soluble carbonate such as sodium carbonate to the aqueous solution can be applied.

 At this time, in order to obtain calcium carbonate fine particles having a target outer diameter in the range of 8 nm to 160 nm, it is desirable that the precipitation rate of calcium carbonate is increased at a relatively low temperature. For example, in the method of introducing carbon dioxide gas into the calcium hydroxide slurry, the liquid temperature when introducing the carbon dioxide gas is 30 ° C. or less, and the rate at which the carbon dioxide gas is introduced is 1.0 L / 100 g of calcium hydroxide. It is preferable to set it to min or more.

  Moreover, as a method for obtaining calcium carbonate fine particles having an outer diameter in the range of 8 nm to 160 nm, commercially available calcium carbonate fine particles can be purchased and used. For example, fine particle calcium carbonate of Hayashi Kasei Co., Ltd., synthetic calcium carbonate of Shiraishi Kogyo Co., Ltd., etc. can be used.

  The method for producing hollow particles according to the invention of claim 3 is the structure of claim 1 or claim 2, wherein the basic compound precursor substance has one or more amide groups or amino groups in the molecule, Ammonia is generated by the action of the catalyst.

The basic compound precursor substance is urea, and the catalyst is urease (urea decomposing enzyme).
Here, “urea” has the chemical formula (NH ₂  ) ₂  An organic compound represented by CO 2, “urease” means “an enzyme that catalyzes the reaction of hydrolyzing urea into ammonia and carbon dioxide. (Saburo Nagakura et al., Edited by “Iwanami Physical and Chemical Dictionary (5th edition)”, page 119, published on February 20, 1998 by Iwanami Shoten).

  In the method for producing hollow particles according to the first aspect of the present invention, a basic compound is allowed to act on an alkoxide to cause hydrolysis / condensation polymerization of the alkoxide to proceed to produce a shell compound (shell compound). A hollow particle composed of a shell compound by covering the surface of the resulting particle (core particle) and then dissolving and removing the core particle, wherein the basic compound acts as a catalyst on the basic compound precursor substance. And gradually generate.

 Thus, in the method for producing hollow particles according to the present invention, since the basic compound is gradually generated by the action of the catalyst on the basic compound precursor substance, the basic compound is unevenly distributed and the alkoxide is reduced at once. Without polymerization, the basic compound is gradually generated uniformly throughout the solution in which the core particles are dispersed, and the formation of the shell compound by the hydrolysis / condensation reaction of the alkoxide is evenly distributed in the reaction medium. As it progresses, core particles agglomerate, coarse shell compound particles are produced and agglomerated, and the core particles (shell compound-coated core particles) whose surface is coated with the produced shell compound are coarsened and aggregates are formed. It can be surely prevented.

 In addition, by preventing the formation of these coarse particles and the formation of aggregates, the particles are dispersed when the reaction is performed in a circulation path in a reaction apparatus such as a wet particle disperser such as a wet jet mill. It is possible to prevent clogging of the fine-diameter channel of the part, and thereby it is possible to continuously produce the shell compound-coated core particles by continuously carrying out the reaction in the reaction apparatus. Thereafter, the hollow particles made of the shell compound can be mass-produced by dissolving and removing the core particles from the produced shell compound-coated core particles.

 By firing the hollow particles made of the shell compound, the fine through-holes of the shell compound generated when the core particle constituent material dissolved when the core particle is dissolved and removed flow out of the shell compound are blocked. Because it becomes hollow particles with strength and is not destroyed even when pressure is applied, it can be uniformly mixed and dispersed in various substances including paints, films, and synthetic fibers. Various materials including fiber can be obtained and applied to a wide range of technical fields.

In this way, in the coating step by hydrolysis / condensation polymerization of the alkoxide on the surface of the core particles, the core particles are aggregated, coarse shell compound particles are formed and aggregated, and the shell compound-coated core particles are coarsened and aggregated. While preventing the formation of aggregates and preventing clogging of pore channels in a reaction device such as a wet particle dispersion device due to these coarse particles and aggregates, shell compound-coated core particles of a desired size It becomes the manufacturing method of the hollow particle which can obtain continuously.
Therefore, the hollow particles can be mass-produced as described above, and hollow particles having a desired size can be produced at a lower cost than in the past.

In the configuration of the present invention, since the alkoxide is silicon alkoxide and the shell compound is silica (SiO ₂ ), the resulting hollow particles are hollow particles made of silica shells, and the low density of the hollow particles made of silica shells, It becomes a method for producing hollow particles that can be applied to a wide range of technical fields by utilizing low thermal conductivity, high specific surface area, light weight and the like.

 In addition, by firing the hollow particles made of the silica shell within a temperature range of 200 ° C. to 1000 ° C., the fine particles of the silica shell produced by the outflow of the dissolved core particle constituent material when the core particles are dissolved and removed. Since the through-holes are blocked and become hollow particles made of strong silica shells that are not destroyed even when pressure is applied, they should be uniformly mixed and dispersed in various materials including paints, films, and synthetic fibers. It is possible to obtain various materials including heat-insulating paints, heat-insulating films, and heat-insulating fibers, and can be applied to a wide range of technical fields.

Since the core particles having the constitution of the present invention are inorganic fine particles that are dissolved by an acid, the core particles can be obtained or produced at a relatively low cost , and hollow particles having a desired size can be obtained at a lower cost. It becomes the manufacturing method of the hollow particle which can be manufactured.

Since the inorganic fine particles having the constitution of the present invention are calcium carbonate fine particles, hollow particles having various outer shapes can be obtained by using calcium carbonate fine particles having various crystal shapes such as cubic and hexagonal as core particles. Can be manufactured.
In addition, since the calcium carbonate fine particles are relatively easy to manufacture and obtain, the hollow particles can be produced at a lower cost.

  Since the hollow particles made of the shell compound having the constitution of the present invention are nano hollow particles made of a silica shell having an outer diameter measured by microscopy of 30 nm to 200 nm, silica nano particles having an outer diameter of 30 nm to 200 nm are used. Since hollow particles can be mass-produced, for example, as described in Patent Document 2, it is possible to obtain heat insulating paint, heat insulating film, and heat insulating fiber at low cost by uniformly dispersing them in the paint, film, and synthetic fiber. In addition, it is a method for producing hollow particles that can be applied to a wide variety of technical fields.

In addition, since the basic compound precursor is urea and the catalyst is urease, by using ammonia generated by the urease enzyme reaction of urea instead of ammonia water, uniform ammonia is not unevenly distributed in the reaction medium. By realizing the concentration, core particles can be aggregated, coarse shell compound particles can be generated and aggregated, and the resulting shell compound-coated core particles can be prevented from becoming coarse and forming aggregates. It is also possible to prevent clogging of the fine-diameter channel of the part.
This makes it possible to continuously produce shell compound-coated core particles having a target size, and mass-produce hollow particles having a target size.

 In the method for producing hollow particles according to the invention of claim 2, a basic compound is allowed to act on the alkoxide to cause hydrolysis / condensation polymerization of the alkoxide to proceed to form a shell compound to cover the surface of the core particle, A method for producing hollow particles made of a shell compound by dissolving and removing core particles, wherein a dispersion step in which core particles are dispersed in a solvent to form a core particle dispersion solution, an alkoxide in the core particle dispersion solution, and a basic A dispersion step and an addition step comprising adding and stirring a basic compound precursor material that generates a compound and a catalyst that acts on the basic compound precursor material and gradually generates a basic compound. The stirring step is carried out continuously in the reactor.

 Thus, in the method for producing hollow particles according to the present invention, the core particle dispersion solution produced in the dispersion step acts on the alkoxide, the basic compound precursor material, and the basic compound precursor material in the addition stirring step. Then, a catalyst for gradually generating a basic compound is added and stirred. Therefore, the basic compound is unevenly distributed and the alkoxide is not condensed at once, and the basic compound is gradually generated uniformly throughout the core particle dispersion solution, so that the alkoxide is hydrolyzed and condensed by the condensation polymerization reaction. Since compound formation proceeds uniformly in the reaction medium, core particles are agglomerated, coarse shell compound particles are generated and agglomerated, and core particles whose surface is coated with the generated shell compound (shell compound-coated core) Particles) and formation of aggregates can be reliably prevented.

 In addition, by preventing the formation of these coarse particles and the formation of aggregates, the particles are dispersed when the reaction is performed in a circulation path in a reaction apparatus such as a wet particle disperser such as a wet jet mill. Can prevent clogging of the fine-diameter flow path of the part, and thus the dispersion step and the addition stirring step can be continuously performed in the reaction apparatus to continuously produce the shell compound-coated core particles. become. Thereafter, the hollow particles made of the shell compound can be mass-produced by dissolving and removing the core particles from the produced shell compound-coated core particles.

In this way, in the coating step by hydrolysis / condensation polymerization of the alkoxide on the surface of the core particles, the core particles are aggregated, coarse shell compound particles are formed and aggregated, and the shell compound-coated core particles are coarsened and aggregated. While preventing the formation of aggregates and preventing clogging of pore channels in a reaction device such as a wet particle dispersion device due to these coarse particles and aggregates, shell compound-coated core particles of a desired size It becomes the manufacturing method of the hollow particle which can obtain continuously.
Therefore, the hollow particles can be mass-produced as described above, and hollow particles having a desired size can be produced at a lower cost than in the past.

 In addition, a dispersion removing step for adding and dissolving the core particles by adding a compound for dissolving the core particles to the particles in which the core particles formed in the adding and stirring step are coated with the shell compound is provided. And the dissolution and removal step is carried out continuously in the reactor.

 Therefore, the basic compound is unevenly distributed and the alkoxide is not condensed at once, and the basic compound is gradually generated uniformly throughout the core particle dispersion solution. Since compound formation proceeds uniformly in the reaction medium, core particles are agglomerated, coarse shell compound particles are generated and agglomerated, and core particles whose surface is coated with the generated shell compound (shell compound-coated core) Particles) and formation of aggregates can be reliably prevented.

 In addition, by preventing the formation of these coarse particles and the formation of aggregates, the particles are dispersed when the reaction is performed in a circulation path in a reaction apparatus such as a wet particle disperser such as a wet jet mill. Blockage of the fine-diameter channel of the part can be prevented, whereby the dispersion step, the addition stirring step and the dissolution removal step can be continuously carried out in the reaction apparatus to continuously produce hollow particles. It becomes possible. That is, in addition to the effect of the invention according to claim 2, the process up to the dissolution and removal step is continuously carried out in the reaction apparatus, so that the hollow particle manufacturing method is more excellent in mass productivity.

Since the alkoxide having the constitution of the present invention is silicon alkoxide and the shell compound is silica (SiO ₂ ), the hollow particles obtained are hollow particles made of silica shells, and the low density and low thermal conductivity of the hollow particles made of silica shells. It becomes a method for producing hollow particles that can be applied to a wide range of technical fields by utilizing the rate, the high specific surface area, the light weight and the like.

 In addition, by firing the hollow particles made of the silica shell within a temperature range of 200 ° C. to 1000 ° C., the fine particles of the silica shell produced by the outflow of the dissolved core particle constituent material when the core particles are dissolved and removed. Since the through-holes are blocked and become hollow particles made of strong silica shells that are not destroyed even when pressure is applied, they should be uniformly mixed and dispersed in various materials including paints, films, and synthetic fibers. It is possible to obtain various materials including heat-insulating paints, heat-insulating films, and heat-insulating fibers, and can be applied to a wide range of technical fields.

  Since the core particle having the constitution of the present invention is an inorganic fine particle dissolved by an acid, the core particle can be obtained or manufactured at a relatively low cost, and a hollow particle having a desired size can be manufactured at a much lower cost. It becomes the manufacturing method of the hollow particle which can be performed.

Since the inorganic fine particles having the constitution of the present invention are calcium carbonate fine particles, hollow particles having various outer shapes can be obtained by using calcium carbonate fine particles having various crystal shapes such as cubic and hexagonal as core particles. Can be manufactured.
In addition, since the calcium carbonate fine particles are relatively easy to manufacture and obtain, the hollow particles can be produced at a lower cost.

  In the configuration of the present invention, the hollow particles made of the shell compound are nano hollow particles made of a silica shell having an outer diameter measured by microscopy of 30 nm to 200 nm, so that the outer diameter is 30 nm to 200 nm. Since some silica nano hollow particles can be mass-produced, for example, as described in Patent Document 2 above, by uniformly dispersing in paint, film, and synthetic fiber, heat insulating paint, heat insulating film, and heat insulating fiber can be obtained at low cost. Therefore, the hollow particle production method can be applied to a wide variety of technical fields.

In addition, since the basic compound precursor is urea and the catalyst is urease, by using ammonia generated by the urease enzyme reaction of urea instead of ammonia water, uniform ammonia is not unevenly distributed in the reaction medium. By realizing the concentration, core particles can be aggregated, coarse shell compound particles can be generated and aggregated, and the resulting shell compound-coated core particles can be prevented from becoming coarse and forming aggregates. It is also possible to prevent clogging of the fine-diameter channel of the part.
This makes it possible to continuously produce shell compound-coated core particles having a target size, and a hollow particle manufacturing method capable of mass-producing hollow particles having a target size.

In the method for producing hollow particles according to the invention of claim 3, the basic compound precursor substance has at least one amide group or amino group in the molecule and generates ammonia by the action of the catalyst. In addition to the effect of the invention according to claim 1 or claim 2, by using ammonia generated by the action of a catalyst instead of ammonia water, a uniform ammonia concentration can be realized without uneven distribution in the reaction medium. Aggregation of particles, formation of coarse shell compound particles and their aggregation, coarsening of the formed shell compound-coated core particles, formation of aggregates, etc. can be reliably prevented. Occlusion can also be prevented.
This makes it possible to continuously produce shell compound-coated core particles having a target size, and a hollow particle manufacturing method capable of mass-producing hollow particles having a target size.

It is a flowchart which shows the manufacturing method of the hollow particle which concerns on Embodiment 1 of this invention. It is a transmission electron microscope (TEM) photograph which expands and shows the hollow particle which consists of a silica shell manufactured by the manufacturing method of the hollow particle which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the mode of adsorption | suction of the nitrogen molecule in the specific surface area measurement by BET method using nitrogen. When the specific surface area measurement by the BET method is performed on the solid particles of silica having the same particle size and the hollow particles composed of the silica shells produced by the method for producing hollow particles according to Embodiment 1 of the present invention. It is a graph which shows adsorption amount. (A) is a schematic diagram for demonstrating how to obtain the specific surface area of the hollow particle which consists of a silica shell manufactured by the manufacturing method of the hollow particle which concerns on Embodiment 1 of this invention, (b) is a value of a specific surface area. 2 is a graph for determining the density of silica shells of hollow particles made of silica shells manufactured by the method for manufacturing hollow particles according to Embodiment 1 of the present invention. It is a flowchart which shows the manufacturing method of the hollow particle which concerns on Embodiment 2 of this invention.

In order to carry out the method for producing hollow particles according to the present invention, a reaction apparatus is required, and the production can be carried out using a reaction vessel equipped with a stirrer (stirring blade), but has a circulation channel. It is more preferable to carry out the production using a wet particle dispersing apparatus. As the wet particle disperser, a wet jet mill, a pressure homogenizer, a wet atomizer, or the like can be used.
More specifically, for example, a wet atomization device “Nanomizer (registered trademark)” manufactured by Yoshida Kikai Kogyo Co., Ltd., a wet jet mill “NanoJet Pal (registered trademark)” manufactured by Joko Co., Ltd. SMT pressure homogenizers “LAB1000”, “LAB2000”, “15MR”, “Starburst (registered trademark) minilab machine”, “Starburst (registered trademark) Lab”, “Star” manufactured by Sugino Machine Co., Ltd. There are wet particle dispersers such as Burst® 40 ”.

 In the method for producing hollow particles according to the present invention, the alkoxide is hydrolyzed / condensed to produce a shell compound, and any type of alkoxide can be used depending on the intended use of the hollow particles. it can. Specific examples of the alkoxide include silicon alkoxide, lithium alkoxide, sodium alkoxide, potassium alkoxide, magnesium alkoxide, aluminum alkoxide and the like.

Among these, the generated shell compound is silica (SiO ₂ ) or alumina (Al ₂ O ₃ ), which is chemically stable and has high hardness, strength and heat resistance, and can produce useful hollow particles. It is particularly preferable to use silicon alkoxide or aluminum alkoxide. As the silicon alkoxide, any silicon alkoxide such as a so-called silane coupling agent can be used. In particular, tetraethyl silicate (tetraethoxysilane, TEOS) is preferably used.

 In the method for producing hollow particles according to the present invention, first, a colloidal dispersion of core particles or a dry powder is mixed with a solvent such as water or alcohol and dispersed by ultrasonic irradiation or the like. Then, a reaction liquid in which the alkoxide as the shell compound source is well mixed at a predetermined concentration is prepared. Here, as the core particle, it is preferable to use various inorganic fine particles that are dissolved by an acid. In particular, since the manufacture and acquisition are relatively easy and hollow particles having various outer shapes can be manufactured, calcium carbonate It is more preferable to use fine particles.

  Then, the reaction liquid prepared as described above is put into a reaction vessel equipped with a stirring device (stirring blade) or a wet particle dispersion device equipped with a circulation channel such as a wet jet mill as a “reaction device”. The basic compound precursor substance is added and stirred or circulated to obtain a uniform concentration, and then added with a catalyst that causes a decomposition reaction of the basic compound precursor substance. The compound precursor material is decomposed to sequentially generate a basic compound, and the surface of the core particle is coated on the surface of the core particle by hydrolysis / condensation polymerization reaction of alkoxide.

The shell compound-coated core particles thus produced are separated and recovered by solid-liquid separation from a reaction vessel, a wet particle dispersion device, etc., dried, then redispersed in a solvent, and an acid such as hydrochloric acid is added to the interior. Hollow particles can be obtained by dissolving and removing the core particles.
In addition, a reaction containing shell compound-coated core particles generated in a reaction vessel equipped with a stirring device (stirring blade) or a wet particle dispersing device equipped with a circulation channel such as a wet jet mill as a “reaction device” Hollow particles can also be obtained by dissolving and removing the inner core particles by adding an acid such as hydrochloric acid to the liquid.

  Below, the specific manufacturing method of the hollow particle which concerns on embodiment of this invention is demonstrated, referring drawings.

[Embodiment 1]
Initially, the manufacturing method of the hollow particle which concerns on Embodiment 1 of this invention is demonstrated with reference to the flowchart of FIG. As shown in FIG. 1, first, calcium carbonate fine particles 2 as core particles are mixed with ethanol 3 and distilled water 4 as a solvent, and a dispersion treatment is performed by ultrasonic waves (step S10). This step corresponds to the “dispersing step” in the present invention. Subsequently, tetraethoxysilane (TEOS) 5, urea 6 and urease 7 are added and stirred at 25 ° C. (step S11). This step corresponds to the “addition stirring step” in the present invention.

  In addition, the shaking stirring process in step S11 is performed for 2 hours in the method for producing hollow particles according to Example 1 of the first embodiment, and is performed for 4 hours in the method for producing hollow particles according to Example 2. In the manufacturing method of the hollow particle which concerns on 3, it performed for 6 hours.

 In step S11, the reaction shown in [Chemical Formula 1] occurs in which tetraethoxysilane 5 is hydrolyzed to tetrahydroxysilane 5A, and this tetrahydroxysilane 5A is dehydrated and polycondensed to become silica 1A.

The reaction shown in [Chemical Formula 1] is catalyzed by the hydrolysis reaction shown in [Chemical Formula 2], that is, urea 6 converts ammonia (NH ₃ ) 6A and carbon dioxide (CO ₂ ) 6B by the action of urease 7. It is ammonia 6A which is gradually generated by the generated reaction.

 Thereafter, the shake-stirred solution is filtered under pressure through an amphiphilic filter (pore size: 0.1 μm) (step S12) to separate the solid particles from the solid, remove solid particles generated as impurities, and wash with ethanol. (Step S13), excess tetraethoxysilane 5, urea 6 and urease 7 were washed away. And it dried at 25 degreeC for 24 hours (step S14), and the calcium carbonate fine particle (silica shell covering calcium carbonate fine particle) 8 coat | covered with the silica shell was obtained.

 The obtained silica shell-coated calcium carbonate fine particles 8 are redispersed in distilled water 4 (step S15), and by performing an acid treatment in which dilute hydrochloric acid (3 mol / L) is added, calcium carbonate fine particles 2 as core particles are obtained. It dissolves and flows out of the silica shell while making fine through holes in the silica shell, thereby removing calcium carbonate (step S16). This was washed with distilled water (step S17), filtered again (step S18), and dried at 90 ° C. for 16 hours (step S19), whereby hollow particles 1 composed of silica shells were obtained.

Here, the amount of each component used in the method for producing hollow particles according to Embodiment 1 will be described. First, in step S10, 12 ml of ethanol 3 and 3 ml of distilled water 4 were mixed, and 1.63 g of substantially cubic calcium carbonate fine particles 2 having an average particle diameter of 60 nm measured by a microscopic method was added thereto. In Step S11, 1 mL of tetraethoxysilane (TEOS) 5, 0.450 g of urea 6 and 0.050 g of urease 7 were added.
About these compounding quantities, it shows in Table 1 collectively.

  These blending amounts are common to the hollow particle production method according to Example 1 of the first embodiment, the hollow particle production method according to Example 2, and the hollow particle production method according to Example 3. It is.

  Among the obtained hollow particles 1 made of silica shells, the particles were actually observed using a transmission electron microscope (TEM) for the hollow particle production method according to Example 3. A TEM photograph of the hollow particles according to Example 3 is shown in FIG. As can be seen from the TEM image in FIG. 2, the hollow particles 1 made of the obtained silica shell have an inner diameter of about 60 nm, which is the same as the outer diameter (average particle diameter) of the calcium carbonate fine particles 2 used as the core particles. It was a hollow particle made of a silica shell having an outer diameter of about 80 nm provided with a silica shell having a thickness of.

  That is, since the hollow particles 1 made of the silica shell produced by the method for producing hollow particles according to Example 3 of Embodiment 1 have not produced coarse particles or formed aggregates in the production process, It is a hollow particle having an outer diameter and a silica shell thickness which are the target size. And in the manufacturing method of the hollow particle which concerns on this Embodiment 1, step S10 and step S11 in the flowchart of FIG. 1 are performed continuously in the reaction container with a stirrer (stirring blade) as a reaction apparatus. .

  Therefore, in the method for producing hollow particles according to the first embodiment, the core particles are agglomerated, coarse shell compound particles are formed and agglomerated in the coating step by hydrolysis / condensation polymerization of the alkoxide on the surface of the core particles. And preventing the coarsening of the shell compound-coated core particles and the formation of aggregates, and the blockage of the pore channels in the reaction apparatus such as a wet particle dispersing device by these coarse particles and aggregates. Thus, shell compound-coated core particles having a desired size can be continuously obtained.

Furthermore, the specific surface area of the hollow particles 1 made of the obtained silica shell was measured by the BET method. For comparison, in Step S11 of FIG. 1, instead of urea 6 and urease 7, hollow particles composed of silica shells obtained by the method for producing hollow particles of Comparative Example 1 using conventional ammonia water are also used. The specific surface area was measured by the BET method.
Here, the BET (Brunauer-Emmett-Teller) method is a method of adsorbing a molecule whose adsorption occupation area is known on the particle surface at the temperature of liquid nitrogen, and obtaining the specific surface area of the sample from the amount, such as nitrogen This is due to the low temperature physical adsorption of the inert gas.

  Moreover, the value of the specific surface area of the calcium carbonate fine particles 2 used as the core particles was obtained by calculation. The specific surface area of the hollow particles 1 made of silica shells obtained by the method for producing hollow particles according to Example 1 to Example 3 of Embodiment 1 calculated from the nitrogen adsorption isotherm by the BET method, and Comparative Example 1 Table 2 shows the specific surface area of the hollow particles made of the silica shell obtained by the method for producing hollow particles and the calculated value of the specific surface area of the calcium carbonate fine particles 2.

  As shown in Table 2, the hollow particles composed of silica shells were produced by the hollow particle production method according to Examples 1 to 3, the hollow particle production method of Comparative Example 1, and the calcium carbonate fine particles. Therefore, it is suggested that the produced hollow particles composed of the silica shell have a hollow structure, and that the formed silica shell is porous. Further, as apparent from comparison between Examples 1 to 3, the specific surface area increases as the reaction time decreases.

This is because, when the reaction time is short, the fine silica particles generated by the reaction shown in the above [Chemical Formula 1] have fine irregularities due to the deposition on the surface of the calcium carbonate fine particles as the core particles. It is considered that the specific surface area became large.
On the other hand, when the reaction time is long, the silica particles generated by the reaction shown in the above [Chemical Formula 1] grow, and the silica particles are closely adhered to each other to form a smooth surface. It is thought that it became small.

 And as shown in Table 2, the hollow particles composed of silica shells obtained by the method for producing hollow particles of Comparative Example 1 using conventional ammonia water were produced in the same 4 hours reaction time. Compared with the hollow particles 1 made of silica shells obtained by the method for producing hollow particles according to Example 2 of Form 1, the specific surface area is small. Therefore, in the method for producing hollow particles of Comparative Example 1, due to the localization of ammonia and the like, particle growth (coarseness) of silica shell-coated calcium carbonate fine particles, formation of aggregates, and the like are occurring. Conceivable.

 Next, a method for calculating the density of the silica shells of the hollow particles 1 made of the silica shells manufactured by the hollow particle manufacturing method according to Embodiment 1 will be described with reference to FIGS. As will be described later, in the hollow particle 1 composed of the silica shell according to the first embodiment, the pores into which the calcium carbonate dissolved by baking at 400 ° C. has flowed out are blocked. There are no pores, but there are micropores having a size of 2 nm or less.

 Here, “micropore” means a micropore having a pore diameter of 2 nm or less and a size through which nitrogen molecules can pass. This fact was confirmed in the specific surface area measurement by the BET method for the solid particles of silica and the hollow particles 1 made of silica shell, as shown in FIGS.

 That is, in the measurement of the specific surface area by the BET method using nitrogen molecules, as shown in FIG. 3, since the nitrogen molecules pass through the micropores 1b having a size of 2 nm or less, the hollow particles 1 made of silica shells The silica shell 1a is adsorbed on both the outer surface and the inner surface, and as a result, more than twice as many nitrogen molecules are adsorbed as compared with solid particles of the same size.

 Therefore, as shown in FIG. 4, the amount of nitrogen adsorbed on solid particles of silica is taken on the X axis, the amount of nitrogen adsorbed on hollow particles 1 made of silica shell is taken on the Y axis, and the relative pressure (P / P0) is changed. When plotting, a straight line of Y = 2.71X + 3.63 was obtained, and it was found that 2.71 times as many nitrogen molecules were adsorbed as compared with solid particles. Then, “3.63”, which is an intercept of this straight line with the Y axis, confirms the existence of micropores 1b having a size of 2 nm or less through which nitrogen molecules pass, as shown in FIG. That is, the amount of adsorption of nitrogen molecules for filling the micropores 1b appears as an intercept with the Y axis.

Therefore, the density ρ of the silica shell 1a is calculated using the phenomenon that the nitrogen molecules are adsorbed on the outer surface and the inner surface. As shown in FIG. 5 (a), when the hollow particles 1 made of a silica shell having a cubic shape are approximated by a hollow cube having an inner diameter L and a silica shell thickness d, the outer surface area of the cube is 6 × (L + 2d). ² and the internal surface area is 6 × L ² , the total surface area is 6 × {(L + 2d) ² + L ² }.

On the other hand, since the volume of the silica shell 1a is obtained by subtracting the volume of the hollow portion from the volume of the hollow cube, {(L + 2d) ³ −L ³ } is obtained. Therefore, when the density ρ of the silica shell 1a is used, the mass of the hollow particle 1 made of the silica shell is ρ × {(L + 2d) ³ −L ³ }. Therefore, the specific surface area is represented by surface area / particle mass = 6 × {(L + 2d) ² + L ² } / ρ {(L + 2d) ³ −L ³ }.

Thus, since the specific surface area is a function of the silica shell thickness d, plotting the calculated values with the density ρ as a parameter, the silica shell thickness d on the horizontal axis, and the specific surface area on the vertical axis. When the density ρ = 2.2 g / cm ³ and ρ = 1.1 g / cm ³ , the inverse proportional curves shown in FIG. 5B are obtained.

When the measured values of the specific surface area of the hollow particles 1 made of silica shells having different silica shell thicknesses d by the BET method using nitrogen are applied to this graph, as shown in FIG. It was found that this is true between the curve of ρ = 2.2 g / cm ³ , which is the density of γ, and the curve of ρ = 1.1 g / cm ³ , which is half that density. Moreover, it turned out that the density (rho) shifts to the smaller one as the silica shell thickness d becomes small. The density of the silica shell 1a of the hollow particle 1 according to Example 3 was measured by this method and found to be 1.57 g / cm ³ .

[Embodiment 2]
Next, the manufacturing method of the hollow particle which concerns on Embodiment 2 of this invention is demonstrated with reference to the flowchart of FIG. As shown in FIG. 6, first, calcium carbonate fine particles 2 as core particles are mixed with ethanol 3 and distilled water 4 as a solvent, and a dispersion treatment is performed by ultrasonic waves (step S20). This step corresponds to the “dispersing step” in the present invention. Subsequently, tetraethoxysilane (TEOS) 5, urea 6 and urease 7 are added and stirred at 25 ° C. (step S21). This step corresponds to the “addition stirring step” in the present invention.

  As a result, a mixed liquid in which calcium carbonate fine particles (silica shell-coated calcium carbonate fine particles) 8 coated with silica shells 8 were dispersed was obtained. By performing an acid treatment in which dilute hydrochloric acid (3 mol / L) is added to this mixed solution, the calcium carbonate fine particles 2 as the core particles are dissolved and flow out of the silica shell while opening fine through holes in the silica shell. Thus, the calcium carbonate is removed (step S22). This step corresponds to the “dissolution removal step” in the present invention.

  Thereafter, the mixed liquid is subjected to pressure filtration (step S23), solid-liquid separation is performed, solid particles generated as impurities are removed, and the silica is washed with ethanol (step S24). Urea 6 and urease 7 were washed away. Further, it was washed with distilled water (step S25) and dried at 90 ° C. for 16 hours (step S26), whereby hollow particles 1 made of silica shells were obtained.

  Here, the amount of each component used in the method for producing hollow particles according to the second embodiment is the same as that in the first embodiment shown in Table 1 above.

  As described above, the hollow particles 1 made of the silica shell produced by the method for producing hollow particles according to Embodiment 2 are free from the generation of coarse particles and the formation of aggregates in the production process. It is a hollow particle having an outer diameter and a silica shell thickness. And in the manufacturing method of the hollow particle which concerns on this Embodiment 2, each process of step S20, step S21, and step S22 in the flowchart of FIG. 6 is continuously performed in the wet jet mill as a reaction apparatus. Yes.

  Therefore, in the method for producing hollow particles according to the second embodiment, the core particles are agglomerated, coarse shell compound particles are generated and agglomerated in the coating step by hydrolysis / condensation polymerization of the alkoxide on the surface of the core particles. And preventing the coarsening of the shell compound-coated core particles and the formation of aggregates, and the blockage of the pore channels in the reaction apparatus such as a wet particle dispersing device by these coarse particles and aggregates. In addition to continuously obtaining shell compound-coated core particles having a desired size, hollow particles having a desired size can also be continuously obtained.

In each of the above embodiments, the case where tetraethoxysilane (TEOS) 5 which is silicon alkoxide is used as the alkoxide has been described. However, the alkoxide is not limited to this, and other than that, lithium alkoxide, sodium alkoxide, Potassium alkoxide, magnesium alkoxide, aluminum alkoxide, or the like can be used.
Further, the silicon alkoxide is not limited to tetraethoxysilane, and other compounds such as tetramethoxysilane, trimethoxysilane, triethoxysilane, tetrapropoxysilane, and tetrabutoxysilane can be used.

 Further, in each of the above embodiments, examples in which calcium carbonate fine particles having an average particle diameter of 60 nm as a core particle are used have been described. However, the size of the calcium carbonate fine particles is not limited to this. Alternatively, fine calcium carbonate particles having an average particle diameter of less than 60 nm by microscopy may be used, and fine calcium carbonate particles having an average particle diameter of more than 60 nm by microscopy can also be used.

Further, in each of the above-described embodiments, examples in which ammonia (NH ₃ ) is applied as a basic compound have been described. However, the basic compound is not limited to ammonia, and other than that, amine, amide, hydroxide Various basic compounds such as sodium (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca (OH) ₂ ) can be used.

In each of the above embodiments, urea ((NH ₂ ) ₂ CO), which generates ammonia by the action of urease as a catalyst, has been described as the basic compound precursor material. Various compounds can be used as long as they are compounds that generate a basic compound by the action of a catalyst.

Further, in each of the above-described embodiments, an example in which hydrochloric acid (dilute hydrochloric acid) is used to dissolve and remove the core particles has been described. However, in order to dissolve and remove the core particles, depending on the substance constituting the core particles In addition to acids, any suitable substance can be used regardless of whether it is an inorganic compound or an organic compound.
Further, the acid is not limited to hydrochloric acid, and carboxylic acids such as sulfuric acid, nitric acid, acetic acid / benzoic acid, citric acid, butyric acid, etc. can be used, and the concentration thereof is arbitrary depending on the type of core particles to be dissolved. Can be set to

In carrying out the present invention, the amount of each component in the hollow particle production method, the compounding ratio, the reaction time, the reaction temperature, etc., as well as the other steps of the hollow particle production method, It is not limited to each example.
Note that the numerical values given in the embodiment of the present invention are not all critical values, and certain numerical values indicate suitable values suitable for implementation, so even if the numerical values are slightly changed. The implementation is not denied.

DESCRIPTION OF SYMBOLS 1 Hollow particle which consists of silica shells 2 Calcium carbonate fine particle 3 Ethanol 4 Distilled water 5 Tetraethoxysilane 6 Urea 7 Urease

Claims (3)

By causing a basic compound to act on the silicon alkoxide, the silicon alkoxide undergoes hydrolysis / condensation polymerization reaction to form a shell compound silica (SiO ₂ ) to cover the surface of the core calcium carbonate fine particles. Then, by dissolving and removing the calcium carbonate core particles with an acid, a method for producing nano hollow particles composed of silica shells having an outer diameter measured by a microscopic method within a range of 30 nm to 200 nm,
The said basic compound is the manufacturing method of the nano hollow particle characterized by making urea as a catalyst act on urea as a basic compound precursor substance . By causing a basic compound to act on the silicon alkoxide, the silicon alkoxide undergoes hydrolysis / condensation polymerization reaction to form a shell compound silica (SiO ₂ ) to cover the surface of the core calcium carbonate fine particles. Then, by dissolving and removing the calcium carbonate core particles with an acid, a method for producing nano hollow particles composed of silica shells having an outer diameter measured by a microscopic method within a range of 30 nm to 200 nm,
A dispersion step of dispersing the core particles in a solvent to obtain a core particle dispersion solution;
The silicon alkoxide in the core particle dispersion solution, and a basic compound precursor material for generating the basic compound;
An addition stirring step in which urea as a catalyst is allowed to act on urea as the basic compound precursor substance and stirring;
A dissolution removal step of dissolving and removing the core particles by adding a compound that dissolves the core particles to the particles in which the core particles formed in the addition stirring step are coated with the shell compound;
The method for producing nano hollow particles, wherein the dispersion step, the addition stirring step, and the dissolution removal step are continuously performed in a reaction apparatus.  The nano hollow according to claim 1 or 2, wherein the basic compound precursor substance has one or more amide groups or amino groups in a molecule, and generates ammonia by the action of the catalyst. Particle production method.