JP2009046365A - Method for producing silica-based hollow particles and method for producing core / shell particles - Google Patents

Abstract

A method for producing silica-based hollow particles and a method for producing core / shell particles capable of efficiently forming a silica-based coating film are provided.
A method for producing silica-based hollow particles according to the present invention includes the following steps (A) to (D).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment,
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer to obtain core-shell particles; and
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )
(D) A step of removing part or all of calcium carbonate from the core-shell particles on which the silica-based coating layer is formed.
[Selection figure] None

Description

  The present invention relates to a method for producing silica-based hollow particles and a method for producing core / shell particles.

  In recent years, functional hollow particles that can be used in the fields of medicine, cosmetics, and optics have been developed. Among functional hollow particles, hollow particles having a silica-based coating layer excellent in transparency and strength and having a low refractive index are attracting particular attention.

  The production method includes, for example, a method of producing basic particles by an aerosol method, heating and drying, a method of spraying, drying and baking a metal compound aqueous sol, and preparing and heating a W / O type or O / W / O type emulsion. Thus, a method for removing water and oil has been proposed. However, the hollow particles obtained by these production methods are all insufficient in strength, and tend to have a broad particle size distribution.

  Therefore, in order to solve these problems, in Patent Document 1, a silicate is deposited by acid treatment on support particles such as calcium carbonate to form a silica coating, and then separated, dried, and supported by an acid. A production method for eluting the body has been proposed.

  Patent Document 2 proposes the following manufacturing method. Calcium carbonate having a primary particle diameter of 20 to 200 nm by transmission electron microscopy is prepared in an aqueous system and aged to have a particle diameter of 20 to 700 nm by a static light scattering method. Thereafter, it is dehydrated to form a water-containing cake, and the water-containing cake is dispersed in alcohol. Ammonia water, water, silicon alkoxide, silicon alkoxide / alcohol volume ratio of 0.002 to 0.1, ammonia contained in ammonia water 4 to 15 mol of water per mol of silicon alkoxide, water A silica-coated calcium carbonate is prepared by adding 25 to 200 mol per mol of silicon alkoxide. Thereafter, washing with alcohol and water is performed to form a water-containing cake again. The water-containing cake is dispersed in water and an acid is added to adjust the acid concentration of the liquid to 0.1 to 3 mol / L and dissolve calcium carbonate. Thereby, hollow particles composed of a dense silica shell, the primary particle diameter by transmission electron microscopy is 30 to 300 nm, the particle diameter by static light scattering method is 30 to 800 nm, and measured by the mercury intrusion method. Silica nano hollow particles characterized in that pores of 2 to 20 nm are not detected in the pore distribution can be obtained.

However, in the above conventional manufacturing method, independent silica particles are inevitably produced when the silica-based coating layer is formed, and independent silica particle crystals are formed rather than forming the silica-based coating layer on the surface of the calcium carbonate particles. Since the growth proceeds preferentially, there is a problem that it takes time to form a silica-based coating layer on the surface of the calcium carbonate particles. Furthermore, there is a problem that a silica-based coating layer is hardly formed on the surface of the calcium carbonate particles.
Special Table 2000-500113 JP 2006-263550 A

  An object of the present invention is to provide a method for producing silica-based hollow particles and a method for producing core-shell particles, which can efficiently form a silica-based coating film.

The method for producing silica-based hollow particles according to the present invention includes the following steps (A) to (D).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment,
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer to obtain core-shell particles; and
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )
(D) A step of removing part or all of calcium carbonate from the core-shell particles on which the silica-based coating layer is formed.

  In the method for producing silica-based hollow particles according to the present invention, the oxo acid and salts thereof may be phosphoric acid, aluminate, silicic acid and salts thereof.

  In the method for producing silica-based hollow particles according to the present invention, the step (A) can be performed in the absence of a catalyst.

  In the method for producing silica-based hollow particles according to the present invention, the step (D) can be performed using an ultrafiltration method.

  The method for producing silica-based hollow particles according to the present invention may further include (E) a step of hydrothermally treating the silica-based hollow particles obtained in the step (D).

The manufacturing method of the core-shell particles according to the present invention includes the following steps (A) to (C).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment, and
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer;
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )

  In the method for producing core / shell particles according to the present invention, the oxo acid and salts thereof may be phosphoric acid, aluminate, silicic acid and salts thereof.

  In the method for producing core / shell particles according to the present invention, the step (A) can be performed in the absence of a catalyst.

  According to the above method for producing core / shell particles, it is possible to provide a starting point for forming a silica-based coating film on the surface thereof by modifying calcium carbonate particles by reacting calcium carbonate with phosphoric acid or the like. it can. In addition, when the silica-based coating film is formed on the surface of the calcium carbonate particles without modifying them, independent silica particles are generated as a by-product. Generation of independent silica particles can also be suppressed.

  According to the method for producing a silica-based hollow particle dispersion, since the core / shell particles obtained by the production method are used, hollow particles having a substantially uniform shell thickness can be formed. Since the silica-based hollow particle dispersion obtained by the above production method can realize a low refractive index, it is suitable for applications such as an antireflection film, for example.

  Hereinafter, a method for producing core / shell particles and a method for producing a silica-based hollow particle dispersion according to an embodiment of the present invention will be specifically described.

1. Method for Producing Core / Shell Particles A method for producing core / shell particles according to an embodiment of the present invention includes the following steps (A) to (C).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment, and
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer;
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )
Hereinafter, each process of the manufacturing method of the core-shell particle which concerns on this embodiment is demonstrated.

  In addition, it is desirable that the steps (A) to (C) are not performed in the core / shell particle drying step and are all performed in the presence of a solvent. This is because once the particles of several tens of nanometers are dried and aggregated, it may be difficult to re-disperse.

1.1 Step (A)
Step (A) is a pretreatment step of heating a dispersion containing an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof. For example, the calcium carbonate particles can be modified by dispersing calcium carbonate particles as core particles in a phosphoric acid aqueous solution and stirring the mixture at a temperature of 50 to 80 ° C. for 0.5 to 3 hours.

  As the core particles, inorganic materials such as calcium carbonate, magnesium oxide, zinc oxide, aluminum and iron can be used. Considering the later steps, it is preferable to be an inorganic material that is easily decomposed by acid, has low solubility in water, is not a polymer compound, and exhibits alkali to weak alkalinity, and calcium carbonate that satisfies all these conditions. It is particularly preferred. In addition, calcium carbonate is widely used industrially and can be obtained at low cost, so that the manufacturing cost can be suppressed.

  The particle size of the calcium carbonate particles depends on the size of the target core / shell particles or hollow particles. To obtain the strength of the hollow particles, the average particle size measured by the dynamic light scattering method is 5 to 300 nm. It is preferable that the thickness is 10 to 100 nm.

  The aqueous medium used in this embodiment has no particular problem even if it contains other liquids in addition to water, but the water content is usually 50% by mass or more, preferably 75% by mass or more, and 95 The content is more preferably at least mass%, particularly preferably a medium consisting only of water.

  Examples of oxo acids include phosphoric acid, aluminate, silicic acid, iodic acid, boric acid, chloric acid, chromic acid, and antimonic acid. Among these, when phosphoric acid, aluminate, or silicic acid and calcium carbonate are reacted, the silica-based coating layer can be efficiently formed on the surface of the calcium carbonate particles in the step (C). Examples of silicic acid include orthosilicic acid, metasilicic acid, metadisilicic acid and the like. Examples of phosphoric acid include peroxophosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphoric acid, hypophosphorous acid and the like.

  Here, when silicic acid is used as the oxo acid, the step (A) is preferably performed in the absence of a catalyst in order to suppress the formation of independent silica particles. That is, once independent silica particles are formed, silicic acid is considered to preferentially contribute to crystal growth of independent silica particles rather than react with calcium carbonate particles.

1.2 Process (B)
Step (B) is a step of washing the calcium carbonate particles reacted with at least one compound selected from oxo acids and salts thereof in step (A). Unreacted oxo acid and the like can be removed by thoroughly washing the calcium carbonate particles after the reaction with, for example, water. Here, the calcium carbonate particles after washing may be dispersed in distilled water to prepare a dispersion for use in the next step.

1.3 Process (C)
Hydrolysis condensation of at least one compound selected from the compound represented by the above general formula (1) (hereinafter also referred to as “compound 1”), silicic acid and silicate in the presence of a basic catalyst. This is a step of forming core-shell particles by forming a silica-based coating layer that coats calcium carbonate particles. In the step (A), it is speculated that when calcium carbonate particles are modified by reacting calcium carbonate and phosphoric acid, a starting point for forming the silica-based coating layer can be provided. Thereby, in a process (C), formation of a silica type coating film can be performed efficiently. In the step (C), when the compound represented by the general formula (1) is used, it is preferable to perform hydrolysis condensation in an organic solvent, and when using silicic acid or silicate, an aqueous medium. Among them, it is preferable to perform hydrolysis condensation.

  The reaction temperature in the hydrolysis condensation is 0 to 100 ° C., preferably 20 to 80 ° C., and the reaction time is 30 to 1000 minutes, preferably 30 to 300 minutes.

1.3.1 Compound 1
In the general formula (1), examples of the monovalent organic group represented by R ¹ and R ² include an alkyl group, an alkenyl group, an aryl group, an allyl group, and a glycidyl group. Among these, the monovalent organic group represented by R ¹ is preferably an alkyl group or a phenyl group.

  Here, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and the like. Preferably, the alkyl group has 1 to 5 carbon atoms, and these alkyl groups may be linear or branched. Further, a hydrogen atom may be substituted with a fluorine atom or the like. Examples of the aryl group include a phenyl group, a naphthyl group, a methylphenyl group, an ethylphenyl group, a chlorophenyl group, a bromophenyl group, and a fluorophenyl group. Examples of the alkenyl group include a vinyl group, a propenyl group, a 3-butenyl group, a 3-pentenyl group, and a 3-hexenyl group.

In the general formula (1), when d = 0, the compound 1 is a compound in which the monovalent organic group represented by R ¹ does not exist.

  Specific examples of compound 1 in the case of d = 0 include, for example, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra-n-butoxysilane, and tetra-sec-butoxysilane. , Tetra-tert-butoxysilane, tetraphenoxysilane, and the like. These may be used alone or in combination of two or more.

  Specific examples of the compound 1 in the case of d = 1 to 3 include, for example, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltriisopropoxysilane, methyltri-n-butoxysilane, methyltri- sec-butoxysilane, methyltri-tert-butoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltriisopropoxysilane, ethyltri-n-butoxysilane, ethyltri-sec -Butoxysilane, ethyltri-tert-butoxysilane, ethyltriphenoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri-n-propoxysilane, -Propyltriisopropoxysilane, n-propyltri-n-butoxysilane, n-propyltri-sec-butoxysilane, n-propyltri-tert-butoxysilane, n-propyltriphenoxysilane, isopropyltrimethoxysilane, isopropyl Triethoxysilane, isopropyltri-n-propoxysilane, isopropyltriisopropoxysilane, isopropyltri-n-butoxysilane, isopropyltri-sec-butoxysilane, isopropyltri-tert-butoxysilane, isopropyltriphenoxysilane, n-butyl Trimethoxysilane, n-butyltriethoxysilane, n-butyltri-n-propoxysilane, n-butyltriisopropoxysilane, n-butyltri-n-butoxysilane, -Butyltri-sec-butoxysilane, n-butyltri-tert-butoxysilane, n-butyltriphenoxysilane, sec-butyltrimethoxysilane, sec-butylisotriethoxysilane, sec-butyltri-n-propoxysilane, sec- Butyltriisopropoxysilane, sec-butyltri-n-butoxysilane, sec-butyltri-sec-butoxysilane, sec-butyltri-tert-butoxysilane, sec-butyltriphenoxysilane, tert-butyltrimethoxysilane, tert-butyl Triethoxysilane, tert-butylto-n-propoxysilane, tert-butyltriisopropoxysilane, tert-butyltri-n-butoxysilane, tert-butyltri-sec-butoxy Sisilane, tert-butyltri-tert-butoxysilane, tert-butyltriphenoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltriisopropoxysilane, phenyltri-n-butoxysilane, Phenyltri-sec-butoxysilane, phenyltri-tert-butoxysilane, phenyltriphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldiisopropoxysilane, dimethyldi-n-butoxysilane, Dimethyldi-sec-butoxysilane, dimethyldi-tert-butoxysilane, dimethyldiphenoxysilane, diethyldimethoxysilane, diethyldiethoxysilane Diethyldi-n-propoxysilane, diethyldiisopropoxysilane, diethyldi-n-butoxysilane, diethyldi-sec-butoxysilane, diethyldi-tert-butoxysilane, diethyldiphenoxysilane, di-n-propyldimethoxysilane, di-n -Propyldiethoxysilane, di-n-propyldi-n-propoxysilane, di-n-propyldiisopropoxysilane, di-n-propyldi-n-butoxysilane, di-n-propyldi-sec-butoxysilane, di -N-propyldi-tert-butoxysilane, di-n-propyldi-phenoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, diisopropyldi-n-propoxysilane, diisopropyldiisopropoxysilane, dii Propyl di-n-butoxysilane, diisopropyldi-sec-butoxysilane, diisopropyldi-tert-butoxysilane, diisopropyldiphenoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n-butyldi -N-propoxysilane, di-n-butyldiisopropoxysilane, di-n-butyldi-n-butoxysilane, di-n-butyldi-sec-butoxysilane, di-n-butyldi-tert-butoxysilane, di -N-butyldi-phenoxysilane, di-sec-butyldimethoxysilane, di-sec-butyldiethoxysilane, di-sec-butyldi-n-propoxysilane, di-sec-butyldiisopropoxysilane, di-sec- Butyldi-n-butoxysilane, di-sec- Butyldi-sec-butoxysilane, di-sec-butyldi-tert-butoxysilane, di-sec-butyldi-phenoxysilane, di-tert-butyldimethoxysilane, di-tert-butyldiethoxysilane, di-tert-butyldi- n-propoxysilane, di-tert-butyldiisopropoxysilane, di-tert-butyldi-n-butoxysilane, di-tert-butyldi-sec-butoxysilane, di-tert-butyldi-tert-butoxysilane, di- tert-Butyldi-phenoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi-n-propoxysilane, diphenyldiisopropoxysilane, diphenyldi-n-butoxysilane, diphenyldi-sec-butoxysila , Diphenyl -tert- butoxysilane include diphenyl phenoxy silanes. These may be used alone or in combination of two or more.

  Particularly preferred compounds as Compound 1 are tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltri-iso-propoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, Examples thereof include phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane. These may be used alone or in combination of two or more.

1.3.2 Catalyst In the step (C), the point that promotes the hydrolytic condensation of the compound represented by the above general formula (1), silicic acid and silicate, and the calcium carbonate is used during the hydrolytic condensation. In view of being difficult to dissolve, it is preferable to use a basic compound as a catalyst in the hydrolytic condensation.

  Examples of basic compounds that can be used as catalysts include methanolamine, ethanolamine, propanolamine, butanolamine, N-methylmethanolamine, N-ethylmethanolamine, N-propylmethanolamine, N-butylmethanolamine, N -Methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, N-methylpropanolamine, N-ethylpropanolamine, N-propylpropanolamine, N-butylpropanolamine, N-methyl Butanolamine, N-ethylbutanolamine, N-propylbutanolamine, N-butylbutanolamine, N, N-dimethylmethanolamine, N, N-diethylmethanolamine, N, N-di Propylmethanolamine, N, N-dibutylmethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-dipropylethanolamine, N, N-dibutylethanolamine, N, N- Dimethylpropanolamine, N, N-diethylpropanolamine, N, N-dipropylpropanolamine, N, N-dibutylpropanolamine, N, N-dimethylbutanolamine, N, N-diethylbutanolamine, N, N-di Propylbutanolamine, N, N-dibutylbutanolamine, N-methyldimethanolamine, N-ethyldimethanolamine, N-propyldimethanolamine, N-butyldimethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N Propyldiethanolamine, N-butyldiethanolamine, N-methyldipropanolamine, N-ethyldipropanolamine, N-propyldipropanolamine, N-butyldipropanolamine, N-methyldibutanolamine, N-ethyldibutanolamine, N-propyldibutanolamine, N-butyldibutanolamine, N- (aminomethyl) methanolamine, N- (aminomethyl) ethanolamine, N- (aminomethyl) propanolamine, N- (aminomethyl) butanolamine, N- (aminoethyl) methanolamine, N- (aminoethyl) ethanolamine, N- (aminoethyl) propanolamine, N- (aminoethyl) butanolamine, N- (aminopropyl) methanolamine, N- (a Minopropyl) ethanolamine, N- (aminopropyl) propanolamine, N- (aminopropyl) butanolamine, N- (aminobutyl) methanolamine, N- (aminobutyl) ethanolamine, N- (aminobutyl) propanolamine, N- (aminobutyl) butanolamine, methoxymethylamine, methoxyethylamine, methoxypropylamine, methoxybutylamine, ethoxymethylamine, ethoxyethylamine, ethoxypropylamine, ethoxybutylamine, propoxymethylamine, propoxyethylamine, propoxypropylamine, propoxybutylamine , Butoxymethylamine, butoxyethylamine, butoxypropylamine, butoxybutylamine, methylamine, ethylamine, Pyramine, butylamine, N, N-dimethylamine, N, N-diethylamine, N, N-dipropylamine, N, N-dibutylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetramethylethylenediamine, tetraethylethylenediamine, tetrapropylethylenediamine, tetrabutylethylenediamine, methylaminomethylamine, methylaminoethylamine, methylaminopropylamine, methyl Aminobutylamine, ethylaminomethylamine, ethylaminoethylamine, ethylaminopro Ruamine, ethylaminobutylamine, propylaminomethylamine, propylaminoethylamine, propylaminopropylamine, propylaminobutylamine, butylaminomethylamine, butylaminoethylamine, butylaminopropylamine, butylaminobutylamine, pyridine, pyrrole, piperazine, pyrrolidine, Piperidine, picoline, morpholine, methylmorpholine, diazabicycloocrane, diazabicyclononane, diazabicycloundecene, ammonia, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, etc. More preferred is ammonia.

The basic compound may be a nitrogen-containing compound represented by the following general formula (2) (hereinafter also referred to as “compound 2”).
(X ¹ X ² X ³ X ⁴ N) _g Y (2)

In the general formula (2), X ¹ , X ² , X ³ , and X ⁴ are the same or different and are each a hydrogen atom or an alkyl group having 1 to 20 carbon atoms (preferably a methyl group, an ethyl group, a propyl group, or a butyl group). Group, hexyl group, etc.), hydroxyalkyl group (preferably hydroxyethyl group etc.), aryl group (preferably phenyl group etc.), arylalkyl group (preferably phenylmethyl group etc.), Y represents a halogen atom (preferably A fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a 1 to 4 valent anionic group (preferably a hydroxy group), and g represents an integer of 1 to 4.

  Specific examples of Compound 2 include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-iso-propylammonium hydroxide, tetra-n-butylammonium hydroxide, tetra-hydroxide iso-butylammonium hydroxide, tetra-tert-butylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, tetraheptylammonium hydroxide, tetraoctylammonium hydroxide, tetranonylammonium hydroxide, tetradecylammonium hydroxide, Tetraundecyl ammonium hydroxide, tetradodecyl ammonium hydroxide, tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, teto chloride Ethylammonium, tetra-n-propylammonium bromide, tetra-n-propylammonium chloride, tetra-n-butylammonium bromide, tetra-n-butylammonium chloride, hexadecyltrimethylammonium hydroxide, -n-hexabromide Decyltrimethylammonium hydroxide, hydroxide-n-octadecyltrimethylammonium, bromide-n-octadecyltrimethylammonium bromide, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, benzyltrimethylammonium chloride, didecyldimethylammonium chloride, distearyldimethylammonium chloride, chloride Tridecylmethylammonium, tetrabutylammonium hydrogen sulfate, tributylmethylammonium bromide, trioctyl chloride Methyl ammonium, trilauryl methyl ammonium chloride, benzyl trimethyl ammonium hydroxide, benzyl bromide triethylammonium, and the like are preferable benzyl bromide tributylammonium bromide phenyl trimethyl ammonium, choline and the like. Among these, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-n-butylammonium hydroxide, tetramethylammonium bromide, tetramethylammonium chloride, tetraethyl bromide are particularly preferable. Ammonium, tetraethylammonium chloride, tetra-n-propylammonium bromide, tetra-n-propylammonium chloride. Compound 2 may be used alone or in combination of two or more.

  The usage-amount of a basic compound is 0.00001-20 mol normally with respect to 1 mol of total amounts of the hydrolysable group in a silane compound, Preferably it is 0.00005-10 mol.

  The shell thickness of the core / shell particles obtained in this way can be controlled by the hydrolysis condensation reaction time, reaction temperature, concentration of compound 1 and the like, and can be made to have an almost uniform thickness.

2. Manufacturing method of silica hollow particle The manufacturing method of the silica hollow particle dispersion which concerns on one Embodiment of this invention includes the following process (A)-(D).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment,
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer to obtain core-shell particles; and
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )
(D) A step of removing part or all of calcium carbonate from the core-shell particles on which the silica-based coating layer is formed.

  That is, the method for producing a silica hollow particle dispersion according to an embodiment of the present invention uses the core-shell particles generated by the steps (A) to (C) described above.

The method for producing a silica hollow particle dispersion according to an embodiment of the present invention further includes:
(E) Hydrothermal treatment of the silica-based hollow particles obtained in step (D),
(F) A step of replacing the aqueous medium with a hydrophobic organic solvent may be included.

  Hereinafter, although each process of the manufacturing method of the silica hollow particle which concerns on this embodiment is demonstrated, since process (A)-(C) is a method for manufacturing said core shell particle, description is abbreviate | omitted. .

  In addition, it is desirable that all of the steps (A) to (F) are performed in the presence of a solvent without providing a drying step. This is because once the particles of several tens of nanometer size are dried and aggregated, it may be difficult to re-disperse.

2.1 Process (D)
Step (D) is a step of removing part or all of calcium carbonate from the core-shell particles on which the silica-based coating layer produced by steps (A) to (C) is formed. In the step (D), it is preferable to remove part or all of the calcium carbonate from the core-shell particles by acidifying the dispersion using an acidic compound and eluting calcium carbonate into the dispersion.

  Specific examples of the acidic compound include inorganic acids or organic acids. Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. The inorganic acid is preferably a monovalent acid. Examples of organic acids include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oxalic acid, maleic acid, methylmalonic acid, adipic acid, sebacic acid, gallic acid Acid, butyric acid, meritic acid, arachidonic acid, shikimic acid, 2-ethylhexanoic acid, oleic acid, stearic acid, linoleic acid, linolenic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, benzenesulfone Acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, formic acid, malonic acid, sulfonic acid, phthalic acid, fumaric acid, citric acid, tartaric acid, maleic anhydride, fumaric acid, itaconic acid, succinic acid, mesaconic acid, Citraconic acid, malic acid, malonic acid, hydrolyzed glutaric acid, hydrolyzed maleic anhydride Object can include hydrolysis products of phthalic anhydride. These may be used alone or in combination of two or more.

  The amount of the acidic compound used varies depending on the amount and type of the basic compound that is the catalyst used and the treatment temperature, but is 0.1 to 50 mol, preferably 0.5 to 0.1 mol with respect to 1 mol of the total amount of calcium carbonate. 10 moles. In addition, when a basic catalyst is used in the above catalyst, the basic compound that is the catalyst and the acidic compound react with each other, so that the amount is particularly preferably 1 to 10 mol with respect to 1 mol of the total amount of calcium carbonate. . If the amount of the calcium carbonate acidic compound used is less than 0.1 mol with respect to 1 mol of the total amount of calcium carbonate, the calcium carbonate may not be removed.

  In step (D), if necessary, the calcium carbonate produced by removing part or all of the core-shell particles on which the silica-based coating layer has been formed in the above step is removed from the dispersion. The process of carrying out can be included. The method for removing calcium carbonate from the dispersion outside the system is not particularly limited, but it is preferable to apply an ultrafiltration method.

  Specifically, the silica-based hollow particles obtained in the above step (D) are put in a vessel connected with a pressure gauge, a flow meter, an ultrafiltration membrane, and a circulation pump, and a predetermined circulation flow rate or a predetermined temperature is set. Solvent replacement using an ultrafiltration membrane while circulating the dispersion at linear speed (in batch method, solvent replacement is performed by concentrating and then diluting with a predetermined amount of water, and in continuous method, a predetermined amount is added during concentration. The solvent is replaced by diluting with water.) Thus, a dispersion in which the solid content is preferably 1 to 50% by mass and silica-based hollow particles are dispersed in an aqueous medium can be prepared. . At this time, calcium carbonate is removed from the dispersion out of the system.

  In addition, the dispersion of silica-based hollow particles is preferably an aqueous medium when the hydrothermal treatment step (E) is performed after the step (D), and the water content is 75% by mass or more. It is particularly preferred. In the dispersion of the silica-based hollow particles, there is no particular limitation on the method for setting the water content to 75% by mass or more. However, in order to prevent thickening of the silica-based hollow particles, for example, water and an organic solvent are mixed with water. During the solvent replacement step, it is preferable to always maintain the water content at 75% by mass or more.

  The temperature in the solvent replacement is preferably 40 to 80 ° C. Further, the circulating flow rate of the solvent during operation is preferably 2 in terms of linear velocity with respect to the surface of the ultrafiltration membrane in order to perform efficient solvent replacement in the ultrafiltration membrane and ensure safety during operation. It is 0.0 to 4.5 m / second, more preferably 3.0 to 4.0 m / second.

  The ultrafiltration membrane used in this step is not particularly limited as long as it does not cause problems due to operating pressure, temperature, and organic solvent used, but is made of ceramic having excellent temperature, pressure, and solvent resistance. Is preferred. Further, the pore diameter of the ultrafiltration membrane is smaller than that of the silica-based hollow particles, but it is preferable when expressed as a fractional molecular weight of the ultrafiltration membrane used as a substitute value for the pore diameter in this technical field. Is 3,000 to 1,000,000, more preferably 30,000 to 500,000, particularly preferably 100,000 to 200,000. Further, the shape of the ultrafiltration membrane is not particularly limited, but a cylindrical shape is preferred because of a high permeation flow rate and a low clog.

2.2 Process (E)
Step (E) is a step of hydrothermally treating the silica-based hollow particles obtained in step (D).

  As the hydrothermal treatment, specifically, an alkaline aqueous solution is added to the dispersion obtained in the step (D) as necessary to make the dispersion basic (preferably in the range of pH 8 to 13). It can be adjusted and heat treated. At this time, the heat treatment temperature is in the range of 50 to 350 ° C, preferably in the range of 100 to 300 ° C. In the heat treatment, the concentration of the dispersion obtained in the step (D) can be diluted in advance or concentrated. By heating, it is repeated that the bonds between molecules are cut or tied, and silica-based hollow particles in which the silica-based coating layer is densified (high density) can be obtained.

2.3 Step (F)
Step (F) is a step of replacing the aqueous medium with a hydrophobic organic solvent.

2.3.1 Hydrophobic Organic Solvent The hydrophobic organic solvent in this embodiment is water in the organic layer when it is mixed with water at 20 ° C. to form two layers without being uniformly mixed with water. Means an organic solvent having a content of 12% by mass or less, for example, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; butyl acrylate, methyl methacrylate, hexamethylene Examples thereof include unsaturated acrylic ester solvents such as diacrylate and trimethylolpropane triacrylate; aromatic hydrocarbons such as toluene and xylene; ethers such as dibutyl ether. Among these, ketones are preferable, and methyl ethyl ketone and methyl isobutyl ketone are more preferable. These hydrophobic organic solvents can be used alone or in combination of two or more.

2.3.2 Solvent replacement method In order to replace the aqueous medium with a hydrophobic organic solvent, the replacement may be performed after passing through an organic solvent such as methanol or ethanol. This is because if the water-based medium is directly replaced with the hydrophobic organic solvent, the silica-based hollow particles may be aggregated, and once aggregated, it is difficult to re-disperse. A method for replacing the aqueous medium with an organic solvent such as methanol is not particularly limited, but an ultrafiltration method can be preferably applied.

  Specifically, the silica-based hollow particles that have been densified are dispersed, and the dispersion containing the aqueous medium is placed in a container to which a pressure gauge, a flow meter, an ultrafiltration membrane, and a circulation pump are connected. The solvent is replaced using an ultrafiltration membrane while circulating the dispersion at a predetermined circulation flow rate or linear velocity (in the batch method, the solvent is replaced by diluting with a predetermined amount of the first organic solvent after concentration, In the continuous method, the solvent is replaced by diluting with a predetermined amount of the first organic solvent during the concentration.), So that the solid concentration is preferably 20 to 50% by mass and the silica-based hollow particles are methanol. A dispersion dispersed in an organic solvent such as can be prepared.

In this silica-based hollow particle dispersion, the water content is preferably 5% by mass or less, more preferably 2% by mass or less. If the water content exceeds 5% by mass, the viscosity may increase during storage. The concentration of the silanol group on the surface of the silica-based hollow particles is preferably 3.0 × 10 ⁻⁵ mol / g or less, more preferably 2.0 × 10 ⁻⁵ mol / g or less. If the concentration of silanol groups on the surface of the silica-based hollow particles exceeds 3.0 × 10 ⁻⁵ mol / g, the dispersion may thicken during storage.

  It is preferable that the temperature in solvent substitution is below the boiling point of an aqueous medium, More preferably, it is 40-80 degreeC. Further, the circulating flow rate of the solvent during operation is preferably 2 in terms of linear velocity with respect to the surface of the ultrafiltration membrane in order to perform efficient solvent replacement in the ultrafiltration membrane and ensure safety during operation. It is 0.0 to 4.5 m / second, more preferably 3.0 to 4.0 m / second.

  The ultrafiltration membrane used in this step is not particularly limited as long as it does not cause problems due to operating pressure, temperature, and organic solvent used, but is made of ceramic having excellent temperature, pressure, and solvent resistance. Is preferred. Further, the pore diameter of the ultrafiltration membrane is smaller than that of the silica-based hollow particles, but when expressed as a fractional molecular weight of the ultrafiltration membrane used as a substitute value for the pore diameter in this technical field, it is preferable. Is 3000 to 1,000,000, more preferably 30,000 to 500,000, and particularly preferably 100,000 to 200,000. Further, the shape of the ultrafiltration membrane is not particularly limited, but a cylindrical shape is preferred because of a high permeation flow rate and a low clog.

  When replacing water in the dispersion with an organic solvent such as methanol using an ultrafiltration membrane, as described above, due to differences in operation methods (for example, differences between batch method and continuous method), concentration and dilution operations are performed. Or a method of diluting at the same time as concentration (during concentration), but in the method for producing a silica-based hollow particle dispersion according to this embodiment, the amount of diluted solvent is small. Therefore, a method of diluting simultaneously with concentration is preferable. The amount of the organic solvent used for dilution is preferably 1 to 10 kg with respect to 1 kg of water in the dispersion.

  Next, an organic solvent such as methanol is replaced with a hydrophobic organic solvent. A method for replacing an organic solvent such as methanol with a hydrophobic organic solvent is not particularly limited, but an ultrafiltration method can be preferably applied. The specific method of the ultrafiltration method is the same as the method of replacing the aqueous medium with an organic solvent such as methanol.

  If all the ultrafiltration methods are applied in steps (D) and (F), the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In addition to the ultrafiltration method, a distillation method can also be applied as a method for replacing the first solvent with the second solvent. The distillation method can be applied when replacing with a second solvent having a boiling point higher than that of the first solvent. The distillation method is often carried out by reducing the vapor pressure by reducing the pressure, but it is preferably carried out at normal pressure to prevent foaming and drying of the liquid surface.

2.4 Silica-based hollow particles and silica-based hollow particle dispersion The silica-based hollow particles according to an embodiment of the present invention are at least selected from the compound represented by the general formula (1), silicic acid, and silicate. It has an outer shell layer obtained by hydrolytic condensation of one compound. And the silica type hollow particle dispersion which concerns on one Embodiment of this invention contains the silica type hollow particle obtained by the manufacturing method of the said silica type hollow particle dispersion, and an organic solvent. Here, as described above, the organic solvent is preferably a hydrophobic organic solvent.

  The content of silica-based hollow particles contained in the silica-based hollow particle dispersion obtained by the production method according to this embodiment is usually 0.1 to 50% by mass, and preferably 10 to 40% by mass.

  In the silica-based hollow particles contained in the silica-based hollow particle dispersion obtained by the production method according to this embodiment, the average particle diameter of the silica-based coating layer is preferably 5 to 300 nm, and preferably 10 to 100 nm. Is more preferable.

  Further, in the silica-based hollow particles contained in the silica-based hollow particle dispersion obtained by the production method according to the present embodiment, the average thickness of the silica-based coating layer is preferably 1 nm or more, and is 1 to 50 nm. More preferably. This is because the refractive index of the resulting hollow particles increases when the average thickness of the silica-based coating layer is 50 nm or more.

3. EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

3.1 Example 1
Add 2.3 kg of phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) adjusted to a 10 mass% aqueous solution to 27.6 kg (calcium carbonate concentration: 4.8 mass%) of colloidal calcium carbonate (Maruo Calcium Co., Ltd.) The mixture was stirred at a temperature of 60 ° C. for 1 hour. After the stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 5.8% by mass. To 6.5 kg of the obtained water sol, 47.7 kg of distilled water and 8.0 kg of a 28% by mass ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) was added dropwise a solution (SiO ₂ concentration of 2.0 wt%) 25.6 kg, was stirred for 3 hours maintaining the temperature of the reaction solution to 80 ° C.. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  To 20 kg of the obtained methanol-dispersed hollow silica sol, 6.1 g of trimethylmethoxysilane was added, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and 14 kg 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 60 nm and an average shell thickness of 10 nm was obtained.

3.2 Example 2
2. Colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 46.1 kg (calcium carbonate concentration 4.8% by mass) and trisodium phosphate adjusted to a 10% by mass aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) 9 kg was added and stirred at a temperature of 60 ° C. for 1 hour. After completion of the stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 1.5% by mass. To 25.8 kg of the obtained water sol, 29.9 kg of distilled water and 8.0 kg of a 28% by mass ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) 24.8 kg of a liquid (SiO ₂ concentration 2.1 mass%) was added dropwise, and the reaction liquid was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  23.1 g of trimethylmethoxysilane was added to 20 kg of the obtained methanol-dispersed hollow silica sol, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and 14 kg 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 100 nm and an average shell thickness of 10 nm was obtained.

3.3 Example 3
1. Colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 48.8 kg (calcium carbonate concentration 4.8% by mass) and trisodium phosphate adjusted to a 10% by mass aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) 3 kg was added and stirred at a temperature of 60 ° C. for 1 hour. After completion of the stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 1.7% by mass. To 23.4 kg of the obtained water sol, 31.8 kg of distilled water and 8.0 kg of a 28% by mass ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) 24.8 kg of a liquid (SiO ₂ concentration 2.1 mass%) was added dropwise, and the reaction liquid was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  23.1 g of trimethylmethoxysilane was added to 20 kg of the obtained methanol-dispersed hollow silica sol, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and 14 kg 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 100 nm and an average shell thickness of 10 nm was obtained.

3.4 Example 4
2.3 kg of colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) and sodium metasilicate (made by Asahi Glass S-Tech Co., Ltd.) adjusted to a 10 mass% aqueous solution are added to 27.7 kg (calcium carbonate concentration 4.8 mass%) The mixture was stirred at a temperature of 60 ° C. for 1 hour. After completion of the stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 5.5% by mass. To 6.9 kg of the obtained water sol, 47.4 kg of distilled water and 8.0 kg of 28 mass% ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) 25.7 kg of a liquid (SiO ₂ concentration of 2.0% by mass) was added dropwise, and the temperature of the reaction liquid was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  23.1 g of trimethylmethoxysilane was added to 20 kg of the obtained methanol-dispersed hollow silica sol, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and 14 kg 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 100 nm and an average shell thickness of 10 nm was obtained.

3.5 Example 5
Metasilicate solution (SiO ₂ ) obtained by dissolving sodium metasilicate (manufactured by Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 equivalents or more of a cation exchange resin (manufactured by Organo Corporation). 8.6 kg (concentration 2.0 mass%) was added to colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 21.4 kg (calcium carbonate concentration 4.8 mass%), and the mixture was stirred at a temperature of 60 ° C. for 1 hour. After stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 6.3% by mass. To the obtained water sol (6.1 kg), distilled water (48.4 kg) and 28 mass% ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) (8.0 kg) were added and stirred. To this solution, 25.7 kg of a metasilicate solution (SiO ₂ concentration 2.0 mass%) obtained by dissolving sodium metasilicate in distilled water and dealkalizing with a cation exchange resin of 1.5 equivalents or more was dropped. Then, the temperature of the reaction solution was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  23.1 g of trimethylmethoxysilane was added to 20 kg of the obtained methanol-dispersed hollow silica sol, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and 14 kg 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 100 nm and an average shell thickness of 10 nm was obtained.

3.6 Example 6
2.0 kg of colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 28.0 kg (calcium carbonate concentration 4.8 mass%) adjusted to a 12 mass% aqueous solution of sodium aluminate (manufactured by Wako Pure Chemical Industries, Ltd.) In addition, the mixture was stirred at a temperature of 60 ° C. for 1 hour. After stirring, the particles were washed with distilled water, and the obtained calcium carbonate particles were dispersed in distilled water to prepare a water sol having a calcium carbonate concentration of 6.0% by mass. To 6.4 kg of the obtained water sol, 48.1 kg of distilled water and 8.0 kg of a 28% by mass ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) 25.7 kg of a liquid (SiO ₂ concentration 2.1 mass%) was added dropwise, and the reaction liquid was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 96.8 kg of 10 mass% nitric acid was added thereto, followed by stirring for 1 hour.

After the above process is completed, the process of adding 14 kg of methanol, concentrating using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ² , and discharging 14 kg of filtrate is repeated 6 times. Thus, 20 kg of methanol-dispersed hollow silica sol was prepared. The average permeation flow rate of 6 times was 60 kg / m ² / hour, and the required time was 6 hours.

  23.1 g of trimethylmethoxysilane was added to 20 kg of the obtained methanol-dispersed hollow silica sol, and the mixture was heated and stirred at 60 ° C. for 3 hours.

After completion of the above steps, 14 kg of methyl isobutyl ketone (MIBK) is added to the obtained reaction solution, and concentrated using an ultrafiltration membrane at 50 ° C., a circulation flow rate of 50 liters / minute, and a pressure of 1 kg / cm ^2. 20 kg of MIBK-dispersed hollow silica sol was prepared by repeating the operation of discharging the filtrate 5 times. The average permeation flow rate for 5 times was 70 kg / m ² / hour, and the required time was 4 hours. When observed with a transmission electron microscope, a hollow silica particle dispersion having an average particle diameter of 100 nm and an average shell thickness of 10 nm was obtained.

3.7 Comparative Example 1
5. Colloidal calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 11.1 kg (calcium carbonate concentration 4.8% by mass) and distilled water 42.3 kg, 28% by mass ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) 0 kg was added and stirred. To this solution, metasilicate obtained by dissolving sodium metasilicate (Asahi Glass S-Tech Co., Ltd.) in distilled water and dealkalizing with 1.5 or more equivalents of cation exchange resin (organo Co., Ltd.) 6.6 kg of a liquid (SiO ₂ concentration 2.0 mass%) was added dropwise, and the reaction liquid was kept at 80 ° C. and stirred for 3 hours. After completion of the stirring, the reaction solution was brought to room temperature, and 72.6 kg of 10% by mass nitric acid was added thereto, followed by stirring for 1 hour. When observed with a transmission electron microscope, formation of a shell could not be confirmed.

Claims (8)

A method for producing silica-based hollow particles, comprising the following steps (A) to (D).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment,
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer to obtain core-shell particles; and
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. )
(D) A step of removing part or all of calcium carbonate from the core-shell particles on which the silica-based coating layer is formed. In claim 1,
The method for producing silica-based hollow particles, wherein the oxo acid and salts thereof are phosphoric acid, aluminate, silicic acid and salts thereof. In claim 1 or 2,
The said process (A) is a manufacturing method of the silica type hollow particle performed in the absence of a catalyst. In any of claims 1 to 3,
The said process (D) is a manufacturing method of a silica type hollow particle performed using an ultrafiltration method. In any of claims 1 to 4,
Furthermore, (E) The manufacturing method of a silica type hollow particle including the process of carrying out the hydrothermal treatment of the silica type hollow particle obtained at the said process (D). A method for producing core-shell particles, comprising the following steps (A) to (C).
(A) a step of heat-treating an aqueous medium containing calcium carbonate particles and at least one compound selected from oxo acids and salts thereof;
(B) a step of washing the calcium carbonate particles after the heat treatment, and
(C) Hydrolyzing and condensing at least one compound selected from the compound represented by the following general formula (1), silicic acid and silicate in the presence of a basic catalyst to coat the calcium carbonate particles Forming a silica-based coating layer;
R ¹ Si (OR ² ) _4-d (1)
(In the formula, R ¹ and R ² independently represent a monovalent organic group, and d represents an integer of 0 to ^3. ) In claim 6,
The method for producing core-shell particles, wherein the oxo acid and salts thereof are phosphoric acid, aluminate, silicic acid and salts thereof. In claim 6 or 7,
The step (A) is a method for producing core / shell particles, which is performed in the absence of a catalyst.