JP6028420B2 - Hollow particles and method for producing the same - Google Patents

Description

The present invention relates to hollow particles and a method for producing the same. More specifically, the present invention relates to a hollow particle having an outer shell containing silica and excellent in dispersibility, and a method for producing the same.

Since hollow particles have a lower specific gravity than solid particles, they are used in various applications. In particular, silica-based hollow particles are characterized by excellent properties such as low dielectric constant, heat resistance, heat insulation, impact resistance, and pressure resistance. Therefore, it is added to various materials for the purpose of weight reduction, heat insulation performance, imparting dimensional stability, and the like. For example, for the purpose of weight reduction, it is used for resin molded parts such as molding compounds for portable electronic devices and automobiles, paints and members for moving bodies, various building materials, and the like. In addition to this, hollow particles are expected to have many fields of application.

When added to various materials as described above, it is necessary to uniformly disperse the hollow particles in the material in order to efficiently utilize the characteristics of the hollow particles. However, the hollow particles have a problem that their physical strength is lower than that of solid particles because of their structure. As a result, when dispersed in the material, the outer shell is broken and the hollow structure cannot be maintained, and the characteristics may be deteriorated. Under such circumstances, the appearance of hollow particles having high mechanical strength has been strongly demanded.

As the hollow particles and the production method thereof, there are the following reports in the prior art. In Patent Document 1, an organic silicon compound such as methoxysilicate [Si (OCH ₃ ) ₄ ] or ethoxysilicate [Si (OC ₂ H ₅ ) ₄ ] and a foaming material are mixed and atomized, and then thermally decomposed. It is described that a hollow silica powder can be obtained.

Moreover, in patent document 2, after adding alcohol, water, and an acid catalyst to tetraethyl orthosilicate (TEOS) and making it carry out partial hydrolysis, dibutyl phthalate is added and this solution contains surfactant. A method for producing spherical hollow porous silica particles by mixing and stirring and emulsifying in an aqueous ammonia solution and causing a polycondensation reaction has been proposed.

Furthermore, Patent Document 3 proposes spherical silica particles having a micron-size particle size that are synthesized by a hydrolysis reaction and a condensation polymerization reaction between tetraalkoxysilane and water. The shell constituting the silica particles is a micron-sized shell having a dense concentration gradient structure on the outside and coarser toward the inside.

In Patent Document 4, hollow silica particles composed of a dense silica shell are obtained by precipitating active silica on a support other than silica from an alkali metal silicate under specific conditions, and then removing the support. A manufacturing method has also been proposed.

Further, in Patent Document 5, highly dispersed silica nano hollow particles composed of a dense silica shell by preparing calcium carbonate coated with silica, dispersing it in water, and adding an acid to dissolve calcium carbonate. There has been proposed a method of manufacturing.

JP-A-6-91194 Japanese Patent No. 2590428 Japanese Patent Laid-Open No. 11-29318 Japanese Patent No. 3419787 JP 2005-263550 A

The silica hollow particles obtained in the above prior art documents have a weak shell and / or an insufficient shell thickness. As a result, there are problems in physical properties, mainly strength.

For example, the methods described in Patent Documents 1, 2, or 3 utilize a so-called interfacial reaction in which silica is precipitated at the gas-liquid or liquid-liquid (aqueous phase-oil phase) interface. In this case, since the pores are present in the shell of the silica hollow particles obtained, it becomes brittle.

The method described in Patent Document 4 or 5 is a method of forming silica hollow particles by depositing silica on a support other than silica and then removing the support. In such a method, the resulting hollow silica particle shell becomes dense, but it has been difficult to make the shell sufficiently thicker than the particle diameter. In particular, the tendency became more prominent as the particle size of the support increased. The reason why it becomes difficult to increase the thickness of the shell as the particle size of the support increases is considered as follows. As the particle size of the support increases, the specific surface area of the particles decreases accordingly, and the area in which the silica in the dispersion can be deposited decreases. As a result, it was considered that the silica could not be sufficiently deposited on the support and was liberated.

Further, in the method described in Patent Document 4 or 5, since it is necessary to use a material other than silica as the support, there is a problem that the components of the support remain and the purity of the hollow particles is lowered. .

As described above, the conventional silica-based hollow particles have a problem that the strength is low, and when subjected to stress at the time of blending, there is a problem that the particles are broken and the hollow shape cannot be maintained.

The present invention has been completed by the present inventors for the purpose of solving the above problems. That is, the first aspect of the present invention is a spherical or substantially spherical hollow particle having an outer shell and a hollow portion present in the outer shell,
The outer shell has a single layer structure containing silica,
The hollow particles are
The average primary particle size is 0.3 to 2.0 μm,
The apparent density at 414 MPa (60000 psia) measured by the mercury intrusion method is 1.10 to 2.09 g / mL,
The present invention relates to hollow particles having a major axis / minor axis value of 1.00 to 1.03.

In a preferred embodiment of the present invention, the thickness of the outer shell is 50 to 300 nm.

In another preferred embodiment of the present invention, the single-layer structure of the outer shell consists essentially of silica.

A second aspect of the present invention is a method for producing a spherical or substantially spherical hollow particle having an outer shell and a hollow portion present inside the outer shell,
Step (1) of preparing solid particles containing silica and heat-treating the solid particles at a temperature of 600 ° C. or higher and lower than 700 ° C. to form a precursor layer of an outer shell on the outer edge of the solid particles The present invention relates to a production method comprising a step (2) and a step (3) of mixing the solid particles and an alkali solution to dissolve the inside of the solid particles to form an outer shell and a hollow portion.

In preferable embodiment of this invention, 1 or more types of lithium compounds are added in the said process (2) before heat processing.

The solid particles are preferably substantially composed only of silica.

The hollow particles of the present invention have a dense silica shell with a sufficient thickness, and have a higher physical strength than conventional silica hollow particles. Therefore, when blended in a resin composition or a coating composition, there is an advantage that a hollow structure is maintained even when subjected to a strong load during mixing or dispersion. Further, the hollow particles of the present invention are excellent in dispersibility in a matrix such as a resin and are uniformly dispersed. Due to such high strength and high dispersibility, characteristics such as low dielectric constant, heat resistance, heat insulation, impact resistance, and pressure resistance, which are characteristic of silica hollow particles, can be utilized.

It is a cross-sectional SEM (scanning electron microscope) photograph of the hollow particle of this invention.

Hereinafter, embodiments of the present invention including the best mode for carrying out the invention will be described in detail. However, the present invention is not limited thereto, and is based on the description of the claims. Needless to say, it is specified.

<Hollow particles>
The first aspect of the present invention relates to hollow particles. The hollow particles are spherical or substantially spherical hollow particles having an outer shell and a hollow portion existing inside the outer shell.

The outer shell has a single layer structure containing silica. The outer shell preferably contains 95% by mass or more of silica, more preferably 98% by mass or more, and particularly preferably consists essentially of silica. “Substantially only composed of silica” means that 99% by mass or more of the outer shell is formed of silica and does not include an amount of another component that affects the physical properties of silica. It is also preferable that the outer shell is 100% by mass silica (the outer shell is made only of silica).

The hollow particles have an average primary particle size of 0.3 to 2.0 μm. In the present specification, the “average primary particle diameter” means a value specified by a transmission electron microscope (TEM) method. Although not specifically limited, specifically, the hollow particles are observed with a TEM, and five visual fields are selected at random so that the number of primary particles is 10, and the maximum diameter is set for a total of 50 primary particles. taking measurement. The average value of the maximum diameters can be the average primary particle diameter.

The average primary particle diameter of the hollow particles is preferably 0.4 to 2.0 μm, more preferably 0.7 to 1.0 μm. Within the above range is preferable in that high porosity particles can be efficiently synthesized.

The hollow particles of the present invention have an apparent density of 1.10 to 2.09 g / mL at 414 MPa (60000 psia) as measured by mercury porosimetry. In the present specification, the “apparent density” is a value obtained by dividing the mass of the hollow particles by the value of the volume of the outer shell and the volume of the hollow portion, [(mass of the hollow particles) / (outer shell] And the total volume of the hollow portion)].

The mercury intrusion method is a kind of method for analyzing pores of a porous material. This method uses the high surface tension of mercury, applies pressure to inject mercury into the pores of the powder, and determines the pore distribution and apparent density from the applied pressure and the amount of mercury injected. Is a way that can be. Since mercury has a high surface tension and does not infiltrate the pores under normal pressure, measurement is performed under pressure. In the present invention, the apparent density is a value measured by a mercury intrusion method under a pressure of 414 MPa (60000 psia). “Psi” means pound per square inch, and psia (psi absolute) means the pressure obtained by adding the atmospheric pressure to the gauge pressure in pounds per square inch. There are things.

The density by the mercury intrusion method can be measured using a mercury intrusion porosimeter. Although it does not specifically limit as an example of a mercury intrusion type porosimeter, Autopore series (made by Shimadzu Corporation) etc. can be mentioned.

The hollow particles of the present invention have an apparent density measured as described above of 1.10 to 2.09 g / mL. The apparent density correlates with the volume of the hollow portion, and the larger the hollow portion, the smaller the ratio of the outer shell layer containing silica, and the smaller the apparent density. The apparent density is preferably more than 1.10 g / mL and preferably not more than 2.09 g / mL, more preferably more than 1.54 g / mL and not more than 1,98 g / mL.

The hollow particles of the present invention are spherical or substantially spherical particles. Specifically, the value of the major axis / minor axis of the hollow particles calculated by observing with a transmission electron microscope, the so-called aspect ratio, is in the range of 1.00 to 1.03. The closer the value of major axis / minor axis is to 1, it means that the particles have a nearly spherical shape. If the particles are spherical, the stress applied to the hollow particles is uniformly dispersed, so that the resistance to the stress is generally increased. On the other hand, when the long diameter / short diameter value is high and the particles are flat, the stress may be concentrated on a certain point. Tends to break more easily than that of spherical particles. Thus, since spherical particles are difficult to break even when blended with a resin or the like, it is advantageous that the value of major axis / minor axis is in the range of 1.00 to 1.03.

The major axis / minor axis value (aspect ratio) is not particularly limited, but can be measured, for example, as follows. First, the particles are observed with a transmission electron microscope (TEM) to obtain an image of the particles. A particle is arbitrarily selected from the image, and a minimum rectangle (usually called a circumscribed rectangle) when the particle is surrounded by a rectangle is defined. The length of the minimum rectangle and the length of the short side are measured, and the ratio (long side / short side) is calculated.

The hollow particles of the present invention preferably have a porosity of 5 vol% or more and 50 vol% or less. The porosity is more preferably 5 vol% or more and less than 50 vol%, and still more preferably 10 vol% or more and less than 30 vol%. If it is the said range, it is preferable at the point which the intensity | strength of particle | grains is enough, maintaining the advantage by a hollow structure.

The porosity represents the ratio of the volume of the hollow portion to the volume of the hollow particles. A higher porosity means that the hollow part in the particle is larger, that is, the outer shell is thinner. The porosity is
Porosity (vol%) = [1-{(apparent density) / (true density)}] × 100
It is represented by “True density” is a value obtained by dividing the mass of a substance by the original volume of the substance that does not include voids or the like, and is synonymous with “specific gravity”. Usually, the true density (specific gravity) of silica (precipitated silica) is 2.2.

Originally, hollow particles have been developed for the purpose of reducing weight by providing voids inside solid particles. From this point of view, it can be said that a higher porosity is preferable, and there are actually many hollow particles having a porosity exceeding 50 vol%. However, as described above, the conventional particles having a high porosity have a problem in terms of strength because the thickness of the outer shell is insufficient. The present invention provides a silica-based hollow particle having a higher strength than before by developing a method for suppressing the porosity to a medium level.

In a preferred embodiment of the present invention, the thickness of the outer shell is 50 to 300 nm. However, the thickness of the outer shell is smaller than a value of 1/2 of the average primary particle diameter (that is, particle radius). Since the outer shell exists symmetrically about the diameter direction of the particle, the particle whose outer shell thickness is ½ means a solid particle having no void inside, and the thickness of the outer shell. Is exceeding 1/2. This means that the thickness is larger than the particle radius, which is theoretically impossible. In the present specification, the thickness of the outer shell of the hollow particle is not particularly limited. For example, the hollow particle is cut to form a cross section for observation, and the cross section is observed using an observation means such as a scanning electron microscope. It can be measured by observing. As a method for forming a cross section, a method using a focused ion beam processing observation apparatus (FIB) (FIB method), an embedded polishing method in which a sample is embedded in a resin or the like and polished to form a cross section of the sample, a cross section polisher (CP) A method using a device (CP method) is known. In particular, in the present invention, it is preferable to form the cross section using the CP method, which is relatively less affected by the skill level of the operator when forming the cross section.

Examples of the cross section polisher include a cross-section sample preparation device (manufactured by JEOL Ltd., product numbers: IB09010, IB09020).

The hollow particles may be further subjected to surface treatment. Examples of the surface treatment include surface treatment with a silane coupling agent. Although not particularly limited, examples of the silane coupling agent include vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3 Epoxy group-containing silane coupling agents such as glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane A styryl group-containing silane coupling agent such as p-styryltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methyl Methacrylic group-containing silane coupling agents such as acryloxypropyltriethoxysilane; Acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane; N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N- (vinylbenzyl) -2-aminoethyl-3-aminopropyl Containing amino groups such as hydrochloride of trimethoxysilane Silane coupling agents; ureido group-containing silane coupling agents such as 3-ureidopropyltriethoxysilane; mercapto group-containing silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and -mercaptopropyltrimethoxysilane; bis (triethoxy (Silylpropyl) sulfide group-containing silane coupling agents such as tetrasulfide; and isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane.

(Method for producing hollow particles)
The second aspect of the present invention relates to a method for producing hollow particles. This manufacturing method
A method of producing a spherical or substantially spherical hollow particle having an outer shell and a hollow portion present inside the outer shell,
A step (1) of preparing solid silica particles containing silica and a step of forming a precursor layer of an outer shell on the outer edge of the particles by heat-treating the solid silica particles at a temperature of 600 ° C. or higher and lower than 700 ° C. (2), the solid silica particles, and the alkali solution are mixed to dissolve only the inside of the particles to form an outer shell and a hollow portion (3).

-Step (1) Step (1) is a step of preparing solid particles containing silica. The solid particles preferably contain 95% by mass or more of silica, more preferably contain 98% by mass or more, and particularly preferably consist essentially of silica. “Substantially only composed of silica” means that 99% by mass or more of the solid particles are formed of silica and do not contain an amount of another component that affects the physical properties of silica. It is also preferable that the solid particles are 100% by mass silica (the solid particles are composed only of silica).

The method for preparing the solid particles is not particularly limited, and ready-made products may be used or synthesized. Although not particularly limited, a typical method for synthesizing solid silica particles includes a wet method. In the wet method, silica is synthesized by hydrolyzing a silicate ester or neutralizing a silicate with a mineral acid. As the wet method, a precipitation (precipitation) method and a sol-gel method are known, but any method may be adopted depending on the desired properties.

-Step (2) Step (2) is a step (temporary firing step) in which the solid particles prepared in (1) above are heat-treated at a predetermined temperature. By this preliminary firing, a crystalline silica layer is formed on the outer edge of the solid particles, which later becomes the outer shell of the above-mentioned hollow particles. On the other hand, the inside of the particles is amorphous silica. The amorphous silica inside the particles is then dissolved in step (3) to form a hollow part. On the other hand, the crystalline silica layer at the outer edge remains without being removed even in the step (3) and forms the outer shell of the hollow particles.

The heat treatment is performed at a temperature of 600 ° C. or higher and lower than 700 ° C. If the temperature is less than 600 ° C., the crystalline silica phase is not formed at the outer edge of the solid particles, or the region of the crystalline silica phase is narrow, and the outer shell is not formed at all in the step (3). A thick shell is not formed. On the other hand, if it is 700 ° C. or higher, only the crystalline silica phase or the region of the crystalline silica phase is wide, and in the step (3), hollow silica particles having a predetermined porosity cannot be obtained.

In a preferred embodiment of the step (2), one or more lithium compounds are added to the solid particles before the heat treatment. The lithium compound functions as a crystallization aid. Examples of the lithium compound include, but are not limited to, metal lithium, lithium carbonate, lithium acetate, lithium benzoate, lithium bromide, lithium chloride, lithium fluoride, lithium dihydrogen phosphate, lithium hexafluorophosphate, water Lithium oxide, lithium iodide, lithium metasilicate, lithium nitrate, lithium nitride, lithium orthosilicate, lithium oxalate, lithium oxide, lithium salicylate, lithium stearate, lithium sulfate, lithium sulfide, lithium tartrate, lithium tetraborate, etc. It is done. Among these, lithium carbonate is preferable in that the carbonate ions are evaporated by heating, so that no anion-derived residue is generated in the system.

Lithium is removed by passing through the following step (3) after acting as a crystallization aid in step (2), and hardly remains in the hollow particles. Therefore, a lithium compound is a preferred crystallizing agent in that it has an excellent effect as a crystallization aid and has little influence on the purity of silica in the finally obtained hollow particles.

-Step (3) Next, step (3) will be described. In the step (3), the solid particles temporarily calcined in the step (2) are brought into contact with an alkaline solution to selectively dissolve only the amorphous silica-containing sites inside the particles while leaving the outer shell. In this step, the outer shell and the hollow part are formed to obtain hollow particles.

Examples of the alkali include, but are not limited to, hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide, lithium carbonate, Examples thereof include carbonates such as sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and potassium potassium carbonate, and bicarbonates such as sodium bicarbonate and potassium bicarbonate.

As the solvent contained in the alkaline solution, water is preferable. In addition to water, there is no particular limitation as long as it is a solvent that dissolves the alkali, and an organic solvent or a mixture of water and an organic solvent can also be used as the solvent. Examples of the organic solvent include methanol, ethanol, isopropanol, butanol, 1-propanol, pentanol, alcohols such as ethylene glycol, and ketones such as acetone.

The amount of the alkali depends on the porosity of the desired hollow particles and the temperature at which the solid particles are brought into contact with the alkali solution, but it is generally preferable to use 0.1 to 10 mol with respect to 1 mol of SiO ₂ . The temperature at which the solid particles are brought into contact with the alkaline solution is preferably 50 ° C to 90 ° C.

If desired, the hollow particles obtained in the step (3) can be obtained as a powdery substance by separating, washing and drying according to a known method.

<Uses of hollow particles>
The hollow particles thus obtained can be used for various applications. Although not particularly limited, for example, various film anti-blocking agents and slipperiness-imparting agents, various spacers for liquid crystal display devices, sealing agents for various electronic components such as semiconductor sealing materials and liquid crystal sealing agents, light diffusing agents, It can be applied to cosmetic additives, dental materials, toner external additives, column fillers, and the like.

Hereinafter, the present invention will be described with reference to comparative examples together with examples, but the present invention is not limited to these examples. In addition, in the following, the primary particle diameter, outer shell thickness, apparent density, porosity, and major axis / minor axis of the obtained hollow particles were measured as follows.

(Average primary particle diameter of hollow particles)
Observed with a transmission electron microscope (TEM), randomly select 5 fields of view where the number of primary particles is 10, measure the maximum diameter for a total of 50 primary particles, find the average value, and calculate the average primary The particle diameter was taken.

(Outer shell thickness)
Approximately the same volume of hollow particles and epoxy resin (epoxy G2) are mixed on a glass plate, applied to a silicone plate, vacuum defoamed at 80 ° C. for 10 minutes, and then heated at 120 ° C. for 30 minutes. The epoxy resin was cured to obtain a composite of hollow particles and a cured epoxy resin. Using the cross section polisher SM-09010 manufactured by JEOL Ltd., the composite was processed for 20 hours at an ion acceleration voltage of 4.0 kV to prepare a cross-sectional observation sample.

The sample for cross-sectional observation is observed with a scanning electron microscope (SEM), and five visual fields are selected at random so that the number of cut primary particles is 3. Each of the cut primary particles has a total of 15 primary particles. The thickness of the thinnest part of the particle shell was measured, and the average value was obtained as the thickness of the outer shell.

(Apparent density)
A sample dried at 120 ° C. for 1 hour was weighed into a cell and measured using an Autopore IV9510 manufactured by Shimadzu Corporation.

(Porosity)
The apparent density was determined by the method described above. Thereafter, the porosity of the hollow particles was determined by the following formula. Note that 2.20 is a generally known true density (specific gravity) of precipitated silica.
Porosity (vol%) = [1-{(apparent density of hollow particles) / (2.20)}] × 100

(Long diameter / short diameter of hollow particles)
Observe with a transmission electron microscope (TEM), randomly select 5 fields of view where the number of primary particles is 10, and measure the maximum diameter (major axis) and minimum diameter (minor axis) of a total of 50 primary particles. The value obtained by dividing the major axis by the minor axis was defined as the major axis / minor axis of the silica hollow particles.

Example 1
204 g of 25% aqueous ammonia solution, 85.5 g of ethanol, and 184 g of water were put into a container and the temperature was adjusted to 25 ° C. Then, while stirring, normal ethyl silicate (tetraethoxysilane) manufactured by Tama Chemical Industries The slurry was dropped for 45 minutes at a rate of 9.36 g / min to obtain a slurry containing solid silica particles. The slurry was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain solid silica particles.

After adding 150 g of water and 0.7 g of lithium carbonate to 30 g of the solid silica particles and stirring at room temperature for 1 hour, the obtained mixed slurry was dried at 130 ° C. Of mixed powder was obtained.

The mixed powder was fired at 630 ° C. for 30 minutes to obtain a fired powder.

When the fired powder was observed with a transmission electron microscope, the average primary particle size was 0.39 μm, and the value of major axis / minor axis was 1.00. The apparent density measured by the above method was 2.18 g / mL.

150 g of water and 5 g of sodium hydroxide were added to 15 g of the calcined powder containing solid particles, and the mixture was stirred at 60 ° C. for 1 hour. The mixture was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle size was 0.32 μm, and the value of major axis / minor axis was 1.01. Furthermore, the thickness of the outer shell measured by the above method was 56 nm. Moreover, the apparent density measured by the said method was 1.59 g / mL, and the porosity was 27.1 vol%.

(Example 2)
102 g of 25% aqueous ammonia solution, 65.5 g of ethanol, and 92 g of water were put into a container and the temperature was adjusted to 25 ° C., and then 4.67 g / ethyl silicate (tetraethoxysilane) manufactured by Tama Chemical Industries, Ltd. was used. Drops were added for 45 minutes at a rate of minutes to obtain a slurry containing solid silica particles. The slurry was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain solid silica particles.

After adding 150 g of water and 0.7 g of lithium carbonate to 30 g of the solid silica particles and stirring at room temperature for 1 hour, the obtained mixed slurry was dried at 130 ° C. Of mixed powder was obtained.

The mixed powder was fired at 630 ° C. for 30 minutes to obtain a fired powder.

When the fired powder was observed with a transmission electron microscope, the average primary particle size was 0.72 μm, and the value of major axis / minor axis was 1.00. The apparent density measured by the above method was 2.19 g / mL.

150 g of water and 5 g of sodium hydroxide were added to 15 g of the calcined powder containing solid particles and stirred at 70 ° C. for 1 hour. The mixture was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle size was 0.69 μm, and the value of major axis / minor axis was 1.01. Furthermore, the thickness of the outer shell measured by the above method was 139 nm. Moreover, the apparent density measured by the said method was 1.76 g / mL, and the porosity was 20.0 vol%.

(Example 3)
102 g of 25% aqueous ammonia solution, 171 g of ethanol, and 92 g of water were put into a container and the temperature was adjusted to 25 ° C. Then, while stirring, normal ethyl silicate (tetraethoxysilane) manufactured by Tama Chemical Industries Ltd. The slurry was added dropwise at a rate of 36 g / min for 22.5 minutes to obtain a slurry containing solid silica particles. The slurry was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain solid silica particles.

After adding 150 g of water and 0.7 g of lithium carbonate to 30 g of the solid silica particles and stirring at room temperature for 1 hour, the obtained mixed slurry was dried at 130 ° C. Of mixed powder was obtained.

The mixed powder was fired at 640 ° C. for 30 minutes to obtain a fired powder.

When the fired powder was observed with a transmission electron microscope, the average primary particle size was 1.04 μm, and the value of major axis / minor axis was 1.00. The apparent density measured by the above method was 2.17 g / mL.

To 15 g of the calcined powder containing solid silica particles, 150 g of water and 5 g of sodium hydroxide were added and stirred at 60 ° C. for 1 hour. The mixture was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle diameter was 0.94 μm, and the value of major axis / minor axis was 1.00. Further, the thickness of the outer shell measured by the above method was 288 nm. Moreover, the apparent density measured by the said method was 2.08 g / mL, and the porosity was 5.5 vol%.

Example 4
287.75 g of the solid silica particle-containing slurry obtained in Example 1, 51 g of a 25% aqueous ammonia solution, 85.5 g of ethanol, and 46 g of water were put into a container, and the temperature was adjusted to 25 ° C., followed by stirring. While, Tama Chemical Industry Co., Ltd. make, normal ethyl silicate (tetraethoxysilane) was dripped at a rate of 9.36 g / min for 22.5 minutes to obtain a slurry containing solid silica particles. The slurry was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain solid silica particles.

After adding 150 g of water and 0.7 g of lithium carbonate to 30 g of the obtained solid silica particles and stirring at room temperature for 1 hour, the obtained mixed slurry was dried at 130 ° C. to obtain solid silica particles and A mixed powder of lithium was obtained.

The mixed powder was fired at 630 ° C. for 30 minutes to obtain a fired powder.

When the fired powder was observed with a transmission electron microscope, the average primary particle size was 1.97 μm, and the value of major axis / minor axis was 1.00. The apparent density measured by the above method was 2.15 g / mL.

150 g of water and 5 g of sodium hydroxide were added to 15 g of the calcined powder containing solid particles and stirred at 60 ° C. for 1 hour. The mixture was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle size was 1.96 μm, and the value of major axis / minor axis was 1.00. Further, the thickness of the outer shell measured by the above method was 293 nm. Moreover, the apparent density measured by the said method was 1.45 g / mL, and the porosity was 34.1 vol%.

(Example 5)
102 g of 25% aqueous ammonia solution, 65.5 g of ethanol, and 92 g of water were put in a container to a temperature of 25 ° C. Was added dropwise at a speed of 45 minutes to obtain a slurry containing solid silica particles. Lithium carbonate 1.4g was thrown into this slurry, and it stirred at room temperature for 1 hour. The obtained mixed slurry was dried at 130 ° C. to obtain a mixed powder of solid silica particles and lithium.

The mixed powder was fired at 650 ° C. for 30 minutes to obtain a fired powder.

When the fired powder was observed with a transmission electron microscope, the average primary particle size was 0.71 μm, and the value of major axis / minor axis was 1.00. The apparent density measured by the above method was 2.18 g / mL.

150 g of water and 5 g of sodium hydroxide were added to 15 g of the obtained solid silica particle fired powder and stirred at 60 ° C. for 1 hour. The mixture was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle size was 0.67 μm, and the value of major axis / minor axis was 1.00. Furthermore, the thickness of the outer shell measured by the above method was 151 nm. Moreover, the apparent density measured by the said method was 1.81 g / mL, and the porosity was 17.7 vol%.

(Comparative Example 1)
30 g of CWS-50 (calcium carbonate) manufactured by Sakai Chemical Industry, 500 g of water, and 87 g of 25% aqueous ammonia solution were put into a reaction vessel, and the temperature was adjusted to 25 ° C. By dropping normal ethyl silicate (tetraethoxysilane) at a rate of 2.5 g / min for 12.8 minutes, CWS-50 (calcium carbonate) is used as a support, and silica derived from normal ethyl silicate is laminated on the surface. A slurry containing the multilayer particles was obtained. Thereafter, 2.4M hydrochloric acid was added dropwise at a rate of 7 ml / min for 71.4 minutes to obtain a slurry containing hollow silica particles from which calcium carbonate had been removed. The slurry was filtered, and the solid content separated by filtration was washed with water and dried at 130 ° C. to obtain hollow silica particles.

When the hollow silica particles were observed with a transmission electron microscope, the average primary particle diameter was 53 nm, and the value of major axis / minor axis was 1.12. Furthermore, the thickness of the outer shell measured by the above method was 4 nm. Moreover, the apparent density measured by the said method was 1.00 g / mL, and the porosity was 54.5 vol%.

The results of Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

As can be seen from Table 1, it is clear that the hollow particles belonging to the scope of the present invention of Examples 1 to 5 have a relatively low porosity and that the outer shell is 10 times or more thicker than the particles of the comparative example. became. Further, since the value of the major axis / minor axis is approximately 1, it can be seen that the hollow particles belonging to the scope of the present invention are spherical or almost spherical particles. In contrast, it can be seen that the hollow particles obtained in Comparative Example 1 have a porosity of more than 50 vol% and a thin outer shell. Further, the value of the major axis / minor axis is high, and it can be seen that the particles are elliptical.

Claims (7)

A spherical or substantially spherical hollow particle having an outer shell and a hollow portion existing inside the outer shell,
The outer shell has a single layer structure containing silica,
The hollow particles are
The average primary particle size is 0.7 to 2.0 μm,
The apparent density at 414 MPa measured by the mercury intrusion method is 1.10 to 2.09 g / mL,
Hollow particles having a major axis / minor axis value of 1.00 to 1.03. The outer shell has a thickness of 50 to 300 nm.
The hollow particle according to claim 1. The hollow particle according to claim 1 or 2, wherein 99% by mass or more of the single-layer structure of the outer shell is formed from silica. Following formula:
Porosity (vol%) = [1-{(apparent density) / (true density)}] × 100
The hollow particle according to any one of claims 1 to 3, wherein the porosity represented by the formula is 5 vol% or more and 50 vol% or less. A method of producing a spherical or substantially spherical hollow particle having an outer shell and a hollow portion present inside the outer shell,
Step (1) of preparing solid particles containing silica and heat-treating the solid particles at a temperature of 600 ° C. or higher and lower than 700 ° C. to form a precursor layer of an outer shell on the outer edge of the solid particles A production method comprising a step (2) and a step (3) of mixing the solid particles and an alkaline solution to dissolve the inside of the solid particles to form an outer shell and a hollow portion. The manufacturing method according to claim 5 , wherein in the step (2), at least one lithium compound is added before the heat treatment. The manufacturing method according to claim 5 or 6 , wherein the solid particles contain 99 mass% or more of silica.