Amorphous silica-based composite oxide particulates, method for producing same, dental composition, and blank for dental cutting

Abstract

[Problem] To provide amorphous silica-based composite oxide particulates which are added in order to enhance strength of a dental curable composition and which, even if the added amount thereof is increased, are less likely to impair polishing properties of a cured product. [Solution] After hydrolysis of alkyl silicate, a metal alkoxide to be compounded is mixed to prepare a sol, and water is added to the obtained sol to obtain a wet gel. Then, the wet gel is dried, crushed, and sintered to obtain amorphous silica-based composite oxide particulates having an average particle size of 1-10 μm. In so doing, the conditions to prepare the sol and gel are controlled so that, in a diffraction pattern obtained by performing X-ray diffractometry, the ratio B / A of the diffraction intensity ratio B at the peak top of a peak with the highest diffraction intensity among diffraction peaks derived from a composite metal oxide to the diffraction intensity A at the peak top of a halo peak derived from amorphous silica is 0.5-0.9.

Description

Irregular silica-based composite oxide powder and its manufacturing method, dental composition, and dental cutting blank

[0001] The present invention relates to amorphous silica-based composite oxide powder and its production method, a dental composition containing the composite oxide particles, and a dental cutting blank in which at least a part of the cutting target is made of the cured product.

[0002] Dental curable compositions primarily composed of polymerizable monomers, inorganic fillers, and polymerization initiators, as well as composite materials (composed of resins and inorganic fillers), such as hybrid resins made of the cured products thereof, are widely used as materials for dental prosthetic treatment. For example, the uncured dental curable compositions are used as composite resin restorations and dental cements, and cured products such as hybrid resins are used as materials for the cutting portions of dental mill blanks used to manufacture prosthetics such as inlays and crowns using CAD / CAM systems.

[0003] In the dental curable compositions described above, from the viewpoint of the flowability of the composition and the strength of the cured product, or from the viewpoint of the strength and surface smoothness of the cured product, a filler consisting of inorganic spherical powder particles and a filler consisting of irregular inorganic powder particles are often used in combination (see Patent Documents 1 to 3). Here, the term "spherical inorganic powder particles" refers to powder particles composed of spherical or nearly spherical inorganic particles, and the term "irregular inorganic powder particles" refers to powder particles obtained by a crushing or pulverizing process in the manufacturing process, in which the individual constituent inorganic particles have a non-spherical, non-uniform shape (usually having a fracture surface resulting from crushing or pulverization, often having edges, and having an irregular shape).

[0004] For example, in relation to a dental hardenable composition intended for use as a composite resin, Patent Document 1 describes that a hardened product having high mechanical strength (bending strength) can be obtained by using a combination of amorphous inorganic powder particles, at least a part of which is amorphous and has an average particle size of 1 to 9 μm, with particles having a particle size of 1 to 10 μm accounting for 95% by weight or more, and spherical inorganic powder particles having an average particle size of 0.08 to 1 μm. Furthermore, Patent Document 2 describes that a photocurable dental restorative material containing a high concentration of a filler made of a mixture of spherical inorganic powder particles having an average particle size of 0.1 to 5 μm and (preferably) spherical inorganic powder particles having an average particle size of 0.01 to 0.1 μm is excellent in aesthetics and strength, and that if a filler further containing amorphous inorganic powder particles having an average particle size of 1 to 9 μm is used in the above mixture, these physical properties will be slightly reduced, but relatively good surface smoothness (aesthetics) will be maintained and mechanical strength can be greatly improved, making the material suitable for restorative materials for molars and the like that are subjected to high occlusal pressure.

[0005] Furthermore, with regard to the dental curable composition, which is intended to be used as a raw material for resin materials for dental cutting, Patent Document 3 describes that, from the viewpoint of the strength of the cured product, it is preferable that the inorganic filler be a combination of irregular and spherical shapes.

[0006] As the material for the particles that make up such inorganic powders and granules, silica-based composite oxides such as silica-zirconia, whose refractive index can be easily controlled by the composition, are often used because it is easy to adjust the refractive index difference of the inorganic filler so as to obtain a transparent cured product. It is known that spherical powders and granules (hereinafter also referred to as "spherical silica-based composite oxide powders") and irregular powders and granules (hereinafter also referred to as "irregular silica-based composite oxide powders") made of silica-based composite oxides can be obtained by the following methods, respectively.

[0007] That is, it is known that spherical silica-based composite oxide powder particles can be produced by a method (generally called the sol-gel method) in which a mixed solution containing a hydrolyzable organosilicon compound and an organic compound of a hydrolyzable metal (which is the metal component of the composite oxide to be composited with silica) (also called a "composite metal") is added to an alkaline solvent that dissolves the organosilicon compound and the organic compound of the composite metal but does not substantially dissolve the reaction product, thereby causing hydrolysis and precipitating the reaction product (see Patent Documents 1 and 2).

[0008] Furthermore, one method for producing amorphous silica-based composite oxide powder particles is to melt a mixture of silica and a composite metal oxide at a high temperature above the melting point to obtain a glass-like substance, which is then pulverized. However, a more common method is to dissolve an alkoxysilane compound in an organic solvent, add water to the solution to partially hydrolyze it, add an alkoxide of another metal to be composited and an alkali metal compound to hydrolyze it to produce an (agar-like) gel-like substance, dry the gel-like substance, and then pulverize and calcinate it as necessary (see Patent Documents 1 and 2). As an example of producing amorphous silica-based composite oxide powder particles by this method, Patent Document 1 describes a method in which hydrochloric acid water is added to a solution of tetraethyl silicate dissolved in isobutanol to partially hydrolyze the mixture, and then tetrabutyl zirconate (or tetrabutyl titanate) and sodium methylate are added and stirred. Water is added during stirring to further promote hydrolysis, and the resulting gel is dried, pulverized, baked at 900°C for 2 hours, and then classified, thereby obtaining a powder particle having a predetermined average particle size, which is made of amorphous inorganic particles composed of a composite oxide of zirconium (or titanium containing a small amount of anatase crystals) containing some tetragonal zirconia crystals, silicon, and sodium, at least some of which are amorphous.

[0009] Japanese Patent Publication No. 2019-132102 Japanese Patent No. 4148334 International Publication No. 2019-054507 Pamphlet

[0010] Toshihiko Abe, Kazuo Torii, "Quantitative Analysis of Amorphous Silica and Fe2O3 by X-ray Background Method," Clay Science, Vol. 14, No. 4, 109-115 (1974)

[0011] For the reasons mentioned above, it is considered preferable to use a combination of amorphous silica-based composite oxide powder and spherical silica-based composite oxide powder as the inorganic filler in a "dental cutting mill blank having a cutting portion made of hybrid resin" (hereinafter also referred to as "HR blank"), which can also be used to produce prostheses for molars, which require high strength. However, as the content of amorphous powder increases, the surface smoothness of the cured product tends to decrease. According to the studies of the present inventors, for example, when the content of amorphous powder exceeds 50 parts by mass relative to the total mass of the amorphous silica-based composite oxide powder and spherical silica-based composite oxide powder in the inorganic filler, the polishability of the cured product decreases, and it is found that polishing a prosthesis produced using the HR blank to obtain an aesthetically pleasing luster requires a considerably long time.

[0012] Therefore, the present invention aims to provide an amorphous silica-based composite oxide powder that can be blended into a dental curable composition containing a polymerizable monomer, an inorganic filler including spherical silica-based composite oxide inorganic powder and amorphous silica-based composite oxide powder, and a polymerization initiator, which can give a transparent cured product, and which is unlikely to reduce the polishability of the cured product even when the blending amount is increased to increase the strength of the cured product, and which can easily give a glossy finish with excellent aesthetics through polishing, as well as a method for producing the same. Further, an object of the present invention is to provide an HR blank that can be used to produce a prosthesis that has the characteristics of transparency, high strength, and can easily give a glossy finish with excellent aesthetics through polishing, and a dental curable composition containing a spherical and amorphous silica-based composite oxide filler that is the raw material for the same.

[0013] The present invention solves the above-mentioned problems, and in a first aspect, the present invention provides an amorphous silica-based composite oxide powder composed of non-porous silica-based composite oxide particles containing silicon and at least one metal, wherein the molar ratio of the at least one metal to the total amount of the silicon and the at least one metal in the silica-based composite oxide particles is 0.05 or more and 0.25 or less, the amorphous silica-based composite oxide powder has an average particle size, defined as the median diameter in a volume-based particle size distribution determined by a laser diffraction-scattering method, of 1 μm or more and 10 μm or less, and in a diffraction pattern obtained by X-ray diffraction measurement of the amorphous silica-based composite oxide powder, the ratio B / A of the diffraction intensity A at the peak top of a halo peak derived from amorphous silica appearing near 2θ=22° to the diffraction intensity B at the peak top of the peak with the highest diffraction intensity among the diffraction peaks derived from oxides of the at least one metal is 0.5 or more and 0.9 or less.

[0014] In the amorphous silica-based composite oxide powder particles of the above form (hereinafter also referred to as "the amorphous silica-based composite oxide powder particles of the present invention"), the specific surface area measured by the BET method is 3 m ２ g －１ Over 8m ２ g －１ In the pore size distribution obtained by BJH method measurement, the total pore volume in the pore size range of 10 nm to 50 nm is 0.06 cm ３ g －１ It is preferable that:

[0015] It is also preferable that the at least one metal contains at least one of Zr and Ti, and optionally Na.

[0016] A second aspect of the present invention is a method for producing amorphous silica-based composite oxide powder particles comprising non-porous silica-based composite oxide particles containing silicon and at least one metal selected from the group consisting of Zr and Ti. (Hereinafter, this will also be referred to as "the amorphous silica-zirconia-based or silica-titania-based powder and granules of the present invention.") The production method includes the following steps: a hydrolysis step of preparing a silica component raw material liquid containing a hydrolyzate of an alkyl silicate and a condensate of the hydrolyzate by hydrolyzing at least a portion of the alkyl silicate in a reaction liquid containing a mixed solution of an alkyl silicate and an alcohol and an aqueous inorganic acid solution; a sol preparation step of mixing a metal source containing at least one of an alkyl zirconate and an alkyl titanate with the silica component raw material liquid to prepare a precursor sol in which silica-based composite oxide precursor particles containing silicon and at least one metal selected from Zr and Ti are dispersed; a gel formation step of mixing 100 parts by mass of the precursor sol with 5 to 10 parts by mass of water to form a precursor wet gel; a milling step of drying and then milling the precursor wet gel to obtain amorphous precursor powder and granules; and a calcination step of calcining the precursor powder and granules to produce non-porous silica-based composite oxide particles. In the hydrolysis step, hydrolysis and condensation reactions are carried out using the reaction solution in which: (a) the alcohol is a branched alkyl alcohol having 3 to 5 carbon atoms; (b) the concentration of protons contained in the aqueous inorganic acid solution relative to the reaction solution is 0.4 (mmol / L) to 0.9 (mmol / L); (c) the volume concentration of water in the reaction solution is 2 (vol%) to 4 (vol%); (d) the ratio of protons (mmol) contained in the aqueous inorganic acid solution to 1 (mmol) of the alkyl silicate is 0.02 (mol%) to 0.04 (mol%); and (e) the ratio of the amount of water (mmol) contained in the reaction solution to 1 (mmol) of the alkyl silicate is 50 (mol%) to 100 (mol%).In a gas chromatogram obtained by gas chromatographic analysis of the silica component raw material liquid prepared in the hydrolysis step, the peak area of ​​a peak attributable to an unhydrolyzed product (a1) of alkyl silicate having no hydroxyl groups, at least a part of whose functional groups may be substituted with alkoxy groups by the alcohol in the mixed solution, is designated as S. １ The peak area of ​​the hydroxysilicate monomer (a2) containing at least one hydroxyl group and one silicon atom, which is the hydrolysis product of (a1), is defined as S ２ and the peak area of ​​the silicate dimer (a3) ​​containing two silicon atoms, which is a condensate of the (a2) and / or a condensate of the (a1) and the (a2), is: S ３ In the case where S is defined as １ The peak area ratio of S2 to S2 is 0.3 or more and 0.6 or less, and S １ The peak area ratio of S3 to the total amount of silicon and metal contained in the silica-based composite oxide precursor particles is 0.03 to 0.5. In the sol preparation step, the metal raw material and the silica component raw material liquid are mixed so that the molar ratio of silicon to the total amount of silicon and metal contained in the silica-based composite oxide precursor particles is 0.05 to 0.25, and the content of silicon and metal contained in the silica-based composite oxide precursor particles relative to the precursor sol is 1.5 (mol / L) to 3 (mol / L). In the calcination step, calcination is carried out at a temperature of 700°C to 1000°C.

[0017] The metal source may include a sodium alkoxide.

[0018] A third aspect of the present invention is a dental curable composition (hereinafter also referred to as "dental curable composition of the present invention") comprising: 100 parts by mass of a polymerizable monomer; 100 to 200 parts by mass of spherical inorganic powder particles having an average particle size of 0.1 to 5 μm; 40 to 100 parts by mass of spherical inorganic powder particles having an average particle size of 0.01 to 0.1 μm; 100 to 250 parts by mass of the amorphous silica-based composite oxide powder particles of the present invention; and 0.1 to 1 part by mass of a polymerization initiator.

[0019] A fourth aspect of the present invention is a dental cutting blank having a portion to be cut, characterized in that at least a portion of the portion to be cut consists of a hardened body of the dental hardenable composition of the present invention (hereinafter also referred to as the "blank of the present invention").

[0020] The amorphous silica-based composite oxide powder of the present invention has the advantage that, when used as an amorphous silica-based composite oxide powder component in a dental curable composition containing a combined spherical-irregular silica-based composite oxide filler, it is unlikely to reduce the polishability of the cured product even when the blending amount is increased to increase the strength of the cured product, and an aesthetically excellent luster can be easily obtained by polishing. Furthermore, the production method of the present invention makes it possible to efficiently produce the amorphous silica-based composite oxide powder of the present invention having the above-mentioned excellent characteristics.

[0021] This figure shows a diffraction pattern obtained by carrying out X-ray diffraction measurement on the amorphous silica-based composite oxide powder particles of the present invention in Example 1.

[0022] Porous, amorphous silica-based composite oxide powders, which are obtained by obtaining a wet silica-based composite oxide by a wet method such as the sol-gel method and then calcining it at a low temperature, are thought to be easily polished. Therefore, the use of such amorphous powders is thought to improve the polishability of a cured dental curable composition containing a spherical-irregular silica-based composite oxide filler. However, the voids in such porous, amorphous silica-based composite oxide powders can serve as fracture origins, resulting in reduced strength when the cured product or a prosthesis made from the cured product or a molded product thereof is formed. Furthermore, if a pulverized ceramic such as silica, which has low toughness, is used instead of the amorphous silica-based composite oxide powder, the refractive index difference with the resin component in the cured product becomes large, resulting in significant light scattering and a loss of transparency.

[0023] The present inventors suspected that the polishing properties of non-porous (solid) amorphous silica-based composite oxide powder particles (specifically, a hardened dental curable composition containing a spherical-amorphous combined silica-based composite oxide filler that contains the same) would be affected by the microstructure and crystallinity of the composite oxides that make up each particle. They investigated the microstructure and crystallinity of the silica-zirconia amorphous powder particles disclosed in Patent Document 1, which are conventional amorphous silica-based composite oxide powder particles with low polishing properties, and also prepared amorphous silica-based composite oxide powder particles by changing the production conditions in various ways, and investigated the microstructure, crystallinity and polishing properties of many of the resulting amorphous silica-based composite oxide powder particles.

[0024] As a result, due to analytical limitations, no clear differences in microstructure could be found. However, it was discovered that the complex oxide in conventional amorphous silica-based complex oxide powder particles has a relatively high crystallinity (see Comparative Example 8), and that when specific conditions are adopted, amorphous silica-based complex oxide powder particles can be obtained, which are made of a complex oxide that is significantly less crystalline (significantly more amorphous) than the above-mentioned complex oxides, and that when this is used, even if the blending amount is increased, the polishing properties (of the dental curable composition containing the combined spherical and amorphous silica-based complex oxide filler) are unlikely to decrease, leading to the completion of the present invention.

[0025] Each embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, the expression "x to y" using numerical values ​​x and y means "greater than or equal to x and less than or equal to y." In such an expression, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x. Furthermore, in this specification, the term "(meth)acrylic" means both "acrylic" and "methacrylic." Similarly, the term "(meth)acrylate" means both "acrylate" and "methacrylate," and the term "(meth)acryloyl" means both "acryloyl" and "methacryloyl."

[0026] 1. Irregular Silica-Based Composite Oxide Powder of the Present Invention The irregular silica-based composite oxide powder of the present invention is an irregular powder composed of non-porous silica-based composite oxide particles containing silicon and at least one metal. Here, the term "irregular powder" refers to powder in which the individual particles constituting the powder are non-spherical (non-true spherical) and the individual particles do not have a uniform outer shape.

[0027] Here, non-porous means that the particles are solid particles that have no or substantially no pores that communicate with the outside. Specifically, the specific surface area measured by the BET method is 3 to 8 m ２ g －１ In the pore size distribution obtained by BJH method measurement, the total pore volume in the pore size range of 10 to 50 nm is 0.06 cm ３ g －１ This means that the specific surface area is 8m or less. ２ g －１ or a pore volume of 0.06 cm ３ g －１ If the density exceeds 100%, the silica-based composite oxide particles may not be sufficiently densified, and voids communicating with the outside may remain.

[0028] The amorphous silica-based composite oxide powder particles of the present invention must also satisfy the following conditions (1), (2) and (3).

[0029] (1) In the silica-based composite oxide particles, the molar ratio of the at least one metal to the total amount of silicon and the at least one metal is 0.05 or more and 0.25 or less. In other words, when the total amount (moles) of silicon atoms contained in the composite oxide that is the material for the silica-based composite oxide particles is [Si] and the total amount (moles) of the at least one metal contained in the composite oxide is [M], the ratio of [M] to the sum of [Si] and [M]: [M] / ([Si] + [M]) is 0.05 to 0.25. (2) The average particle size of the amorphous silica-based composite oxide powder, defined as the median diameter in a volume-based particle size distribution determined by a laser diffraction-scattering method, is 1 to 10 μm. (3) In a diffraction pattern obtained by subjecting the amorphous silica-based composite oxide powder to X-ray diffraction measurement, the ratio of the diffraction intensity at the peak top of the highest diffraction intensity peak among the diffraction peaks derived from oxides of the at least one metal (B) to the diffraction intensity at the peak top of the halo peak derived from amorphous silica appearing at a diffraction angle of about 2θ = 22° (A) (B / A) is 0.5 to 0.9.

[0030] The silica-based composite oxides that form the nonporous silica-based composite oxide particles that make up the amorphous silica-based composite oxide powder of the present invention are typically metal oxides that do not have an absorption band due to a dd-d transition at visible light wavelengths, and the at least one metal in the metal oxide is at least one metal selected from the group consisting of Groups 2, 3, and 4 of the periodic table. Specifically, examples of Group 2 metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Examples of Group 3 metal elements include scandium (Sc), yttrium (Y), and lanthanides. Examples of Group 4 metal elements include titanium (Ti), zirconium (Zr), and hafnium (Hf). Among these metal elements, at least one metal element selected from the group consisting of Ba, Ti, and Zr is preferred, with Zr or Ti being particularly preferred. These metals are usually oxides according to their valence, such as BaO and TiO ２ , ZrO２ and silicon oxide (silica: SiO ２ ) to form a composite oxide. That is, in the particularly preferred embodiment described above, it becomes silica zirconia or silica titania.

[0031] In addition, silica-based composite oxides are made with Na in order to suppress the influence of strong acid points on the surface and to improve the densification effect by firing. ２ It may contain O. In this case, the at least one metal contains Na in addition to the above metals.

[0032] As shown in (1) above, the composite oxide must have a composition in which [M] / ([Si]+[M]) is 0.05 to 0.25. Having such a composition makes it possible to adjust the refractive index of the composite oxide particles to 1.48 to 1.56, which is the same as or close to the refractive index of the cured product of a polymerizable monomer commonly used in dental curable compositions, and makes it possible to provide a transparent dental curable composition containing a spherical-irregular silica-based composite oxide filler. For reasons of imparting high X-ray contrast and improving the polishability of the dental curable composition cured product, [M] / ([Si]+[M]) is preferably 0.05 to 0.2, and particularly preferably 0.05 to 0.15.

[0033] Furthermore, as shown in (2) above, the average particle size, defined as the median diameter in the volume-based particle size distribution determined by the laser diffraction-scattering method, must be 1 to 10 μm. If the average particle size is less than 1 μm, the dilatancy of the dental curable composition increases, resulting in a decrease in operability, while if it exceeds 10 μm, the strength of the dental curable composition when made into a hardened product decreases. From the viewpoint of achieving both strength and operability, the average particle size is preferably 0.05 to 50 μm, and particularly preferably 0.1 to 10 μm.

[0034] Furthermore, as shown in (3) above, the diffraction pattern obtained by X-ray diffraction measurement of the amorphous silica-based composite oxide powder of the present invention must satisfy the condition that B / A = 0.5 to 0.9.

[0035] Here, as the X-ray diffraction measurement method, for example, powder X-ray diffraction measurement can be used under the conditions of X-ray output: 40 kV, 30 mA, scan axis: 2θ / θ, scan range: 5° to 120°. It is known that for amorphous silica, a halo peak derived from amorphous silica appears at a diffraction angle of approximately 2θ = 25° (see Non-Patent Document 1). In the X-ray diffraction pattern of the amorphous silica-based composite oxide powder, this halo peak and the diffraction peaks derived from each oxide of the at least one metal are observed overlapping each other. In condition (3), A refers to the diffraction intensity (cps) at the peak top of the halo peak (peak 1 appearing at approximately 2θ = 22° in Figure 1), and B refers to the peak top of the peak with the greatest diffraction intensity among the diffraction peaks derived from each oxide of the at least one metal, for example, in the case of zirconia, the diffraction intensity (cps) at the peak top of the peak (peak 2 in Figure 1) appearing at a diffraction angle of approximately 2θ = 30°. In the case of titania, it means a peak that appears at a diffraction angle of about 2θ=25°.

[0036] If B / A is less than 0.5, the bending strength of the cured dental curable composition containing the spherical-irregular silica-based composite oxide filler tends to decrease, while if it exceeds 0.9, the transparency of the cured product decreases significantly. Although the mechanism of this opacification is not entirely clear, it is believed that light scattering occurs at the silica-metal oxide interface due to the separation of the silica component and the metal oxide component of the silica-based composite oxide. B / A is preferably 0.50 to 0.85, and particularly preferably 0.50 to 0.80.

[0037] 2. Manufacturing Method of the Present Invention The manufacturing method of the present invention is a method for manufacturing the amorphous silica-based composite oxide powder of the present invention (i.e., the amorphous silica-zirconia-based or silica-titania-based powder of the present invention) in which the at least one metal contains at least one of Zr and Ti, and similarly to the manufacturing methods for non-porous amorphous silica-zirconia powder and non-porous amorphous silica-titania powder described in Patent Documents 1 and 2, the method comprises the following steps: hydrolysis step, sol preparation step, gel formation step, pulverization step, and calcination step. The at least one metal may optionally contain Na.

[0038] Hydrolysis step: A step of using an alkyl silicate as a silicon source, adding an inorganic acid aqueous solution to a mixed solution of the alkyl silicate and alcohol to hydrolyze at least a portion of the alkyl silicate, and preparing a silica component raw material solution containing a hydrolyzate of the alkyl silicate and a condensate of the hydrolyzate. In the hydrolysis step, at least a portion of the alkyl silicate is hydrolyzed in a reaction solution containing a mixed solution of the alkyl silicate and alcohol and an inorganic acid aqueous solution under specific conditions described below, thereby preparing a silica component raw material solution containing a hydrolyzate of the alkyl silicate and a condensate of the hydrolyzate. The silica component raw material solution prepared in this manner does not precipitate solid particles. Furthermore, in a gas chromatogram obtained by gas chromatography analysis of the silica component raw material solution, specific peak area ratios for the unhydrolyzed product, hydrolyzed product, and condensate, as described below, are obtained.

[0039] Sol preparation step: A step of preparing a silica-based composite oxide precursor sol (also simply referred to as "precursor sol") by using a metal source containing at least one of alkyl zirconate and alkyl titanate as the metal source of the at least one metal, and mixing the silica component source liquid containing Si in an amount corresponding to the [Si] with the metal source in an amount corresponding to [M] such that the [M] / ([Si] + [M]) is 0.05 to 0.25. In the sol preparation step, the metal source and the silica component source liquid are mixed so that the molar ratio of silicon to the total amount of silicon and metal contained in the silica-based composite oxide precursor particles is 0.05 to 0.25. This results in the preparation of a precursor sol in which silica-based composite oxide precursor particles containing silicon and at least one metal selected from Zr and Ti in the molar ratio are dispersed. Furthermore, the silica-based composite oxide particles finally produced thereby also have the [M] / ([Si] + [M]) being 0.05 to 0.25.

[0040] Gel Forming Step: A step of mixing 100 parts by mass of the silica-based composite oxide precursor sol with 5 to 10 parts by mass of water to form a silica-based composite oxide precursor wet gel (also simply referred to as "precursor wet gel").

[0041] Pulverization step: This is a step of drying the silica-based composite oxide precursor wet gel and then pulverizing it to obtain amorphous silica-based composite oxide precursor granules (also simply referred to as "precursor granules").

[0042] Calcination step: A step of calcining the silica-based composite oxide precursor powder. In the calcination step, the precursor powder containing the silica-based composite oxide precursor particles is calcined at a specific temperature described below, thereby producing non-porous silica-based composite oxide particles.

[0043] In the manufacturing method of the present invention, the amorphous silica-zirconia-based or silica-titania-based powder particles of the present invention can be efficiently manufactured by carrying out the hydrolysis step, the sol preparation step, and the firing step under specific conditions.

[0044] It is obvious from the conditions of the sol preparation step that the amorphous silica-based composite oxide powder obtained by the production method of the present invention satisfies the above-mentioned condition (1) that the amorphous silica-based composite oxide powder of the present invention must satisfy, and the above-mentioned condition (2) can also be easily satisfied by carrying out an operation such as classification, if necessary, after the pulverization step or the calcination step. Furthermore, by carrying out the above-mentioned hydrolysis step and gel formation step so as to satisfy the above-mentioned conditions, it becomes possible to satisfy the above-mentioned condition (3).

[0045] Each step of the production method of the present invention will be described in detail below.

[0046] 2-1. Hydrolysis Step In the hydrolysis step, an alkyl silicate is used as a silicon source, and an aqueous inorganic acid solution is added to a mixed solution of the alkyl silicate and alcohol to hydrolyze at least a portion of the alkyl silicate, thereby preparing a silica component raw material liquid containing a hydrolyzate of the alkyl silicate and a condensate of the hydrolyzate. In this process, in the production method of the present invention, the hydrolysis and condensation reactions are carried out so as to satisfy the following conditions (a) to (e), thereby preparing a silica component raw material liquid of a specific composition that satisfies the following condition (f) without precipitating solid particles:

[0047] (a) A branched alkyl alcohol having 3 to 5 carbon atoms (hereinafter also referred to as a "specific alcohol") is used as the alcohol. (b) The concentration of protons contained in the aqueous inorganic acid solution relative to the reaction solution (i.e., the proton concentration obtained by dividing the amount of protons contained in the aqueous inorganic acid solution by the total volume (L) of the reaction solution): [H ＋ ] is 0.4 to 0.9 (mmol / L). (c) The water volume concentration in the reaction solution (i.e., the water volume concentration obtained by dividing the amount of water (L) contained during hydrolysis by the total volume of the reaction solution) is 2 to 4 (vol%). (d) The ratio of protons (mmol) contained in the aqueous inorganic acid solution to 1 (mmol) of alkyl silicate (i.e., the amount of protons (mmol) relative to 1 (mmol) of alkyl silicate): {([H ＋] / [Si])×100} is set to 0.02 to 0.04 (mol %). (e) The ratio of the amount of water (mmol) contained in the reaction solution to 1 (mmol) of alkyl silicate (i.e., the amount of water (mmol) to 1 (mmol) of the alkyl silicate): {([H ２ O] / [Si] × 100} is set to 50 to 100 (mol %).

[0048] (f) In the gas chromatogram obtained by gas chromatographic analysis of the silica component raw material solution prepared under the above conditions, the peak area of ​​the peak attributable to the unhydrolyzed alkyl silicate (a1) having no hydroxyl group, at least a part of whose functional groups may be substituted with an alkoxy group by the alcohol in the mixed solution, is expressed as S １ The peak area of ​​the hydroxysilicate monomer (a2) containing at least one hydroxyl group and one silicon atom, which is the hydrolysis product of (a1), is S ２ and the peak area of ​​the silicate dimer (a3) ​​containing two silicon atoms, which is a condensate of the (a2) and / or a condensate of the (a1) and the (a2), is: S ３ In the case where S is defined as １ The peak area ratio of S2 to S is 0.3 to 0.6, and S １ The peak area ratio of S3 to S4 is 0.03 to 0.5. In the condensation product of (a2), the two (a2)s may be the same or different. The alkoxy group is derived from the alcohol (solvent) in the mixed solution.

[0049] In other words, the (a1) is an unhydrolyzed product of the unreacted alkyl silicate and alkyl silicate in which at least one functional group has been substituted with a solvent alcohol, but which does not have a hydroxyl group. The (a2) is a hydroxysilicate monomer consisting of a compound containing one silicon atom, in which at least one alkoxy group in the unreacted alkyl silicate and alkyl silicate in which at least one functional group has been substituted with a solvent alcohol has been substituted with a hydroxyl group. The (a3) ​​is a silicate dimer consisting of a compound containing two silicon atoms, in which the hydroxysilicate monomer (a2) is condensed with another hydroxysilicate monomer (a2) or the alkyl silicate used as a raw material to form a siloxane bond.

[0050] Regarding (f), gas chromatography analysis can be suitably performed using a stationary phase containing dimethylpolysiloxane, a mobile phase containing helium, and a flame ionization detector (FID). The following peaks derived from (a1) to (a3) ​​can be identified by GC-MS analysis.

[0051] By using such a silica component raw material solution and performing the calcination in the calcination step at a temperature in the range of 700 to 1000°C as described below, the resulting solution will have the crystallinity specified in the above condition (3). The reason for this is not entirely clear, but is presumed to be as follows. That is, in a reaction solution using a branched alkyl alcohol having 3 to 5 carbon atoms (specific alcohol), the alkyl silicate concentration and the water content relative to the alkyl silicate are relatively high, and the proton concentration is relatively low to carry out hydrolysis and the resulting condensation reaction. This causes the alkoxide bonded to the silicon atom in the raw silicate to undergo a transesterification reaction with the specific alcohol, resulting in a silicate bonded with an alkoxide derived from the specific alcohol. Because the alkoxide derived from the specific alcohol is bulky, it is thought to be less susceptible to hydrolysis than the raw silicate. Therefore, the condensation reaction to form these oligomers proceeds slowly, making it possible to prepare a silica component raw material solution containing a relatively high concentration of hydroxysilicate monomer (a2) and silicate dimer (a3) ​​without producing a high level of condensation product that precipitates as a solid. It is believed that in the sol preparation step, the formation of bonds (M-O-M) between metal atoms via oxygen atoms is suppressed, facilitating the formation of metallosiloxane bonds (Si-O-M; M is a metal atom), and complexes in which metal atoms are encapsulated in silicate oligomers condense to form a silica-based composite oxide precursor sol. This makes it difficult for oxides of metal atoms to separate in the firing step, and the amorphous silica also interferes with the periodic arrangement of metal elements, thereby enhancing the amorphous nature.

[0052] From the viewpoint of effectiveness, [H ＋ ] is preferably 0.45 to 0.85 (mmol / L), and 100×[H ２ It is preferable that the ratio of [O] / [Si] is 60 to 90 (mol %). ２ / S １ is preferably 0.3 to 0.55, and S ３ / S １ is preferably 0.03 to 0.2.

[0053] As the alkyl silicate serving as the silicon source, ethyl silicate, methyl silicate, butyl silicate, etc. can be used.

[0054] As the branched alkyl alcohol having 3 to 5 carbon atoms (specific alcohol), alcohols such as 2-propanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-1-butanol can be suitably used. In this step, it is sufficient that at least one type of the specific alcohol is contained, and a mixture of two or more types may also be used.

[0055] As the aqueous inorganic acid solution used in this step, any aqueous solution using an inorganic acid can be used without any limitation, but from the viewpoint of industrial availability, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, and an aqueous sulfuric acid solution are preferred.

[0056] The temperature at which the hydrolysis is carried out may be any temperature at which the various raw materials are compatible in a liquid state, and the hydrolysis is preferably carried out at 30 to 50°C.

[0057] In the sol preparation step, a metal raw material containing at least one of alkyl zirconate and alkyl titanate, and optionally sodium alkoxide, is used as a metal source for the at least one metal, and a silica-based composite oxide precursor sol is prepared by mixing the silica component raw material liquid containing Si in an amount corresponding to the above [Si], the metal raw material in an amount corresponding to [M] such that the above [M] / ([Si]+[M]) is 0.05 to 0.25, and an appropriate base, depending on the desired composition of the amorphous silica-zirconia or silica-titania powder or granules of the present invention.

[0058] As the alkyl zirconate used as the metal raw material, tetrapropyl zirconate, tetrabutyl zirconate, etc. can be used, but tetra-n-butyl zirconate is particularly preferred because it is more stable, easier to handle, and less expensive. As the alkyl titanate, tetrapropyl titanate, tetrabutyl titanate, etc. can be used, but tetraisopropyl titanate is particularly preferred because it is less expensive.

[0059] The sodium alkoxide, which is the metal raw material, is used as needed to adjust the acidity of the composite oxide powder and prevent discoloration, coloring, and strength reduction of the resulting hardened body. As the sodium alkoxide, sodium methoxide and / or sodium ethoxide are preferably used. Sodium alkoxide is not necessarily used, but if used, it is preferably used in an amount such that [Na] / ([Si]+[Zr]+[Na]) or [Na] / ([Si]+[Ti]+[Na]) is 0.01 to 0.1, particularly 0.02 to 0.05. Sodium alkoxides are used in the presence of water to form OH groups. － Since the silica component raw material liquid functions as a base by generating a compound represented by the formula (a1), the compound represented by the formula (a3) ​​and the metal raw material are condensed (by hydrolysis and dehydration) to form a silica-based composite oxide precursor sol (also simply referred to as "precursor sol") in which silica-based composite oxide precursor particles are dispersed in a dispersion medium.

[0060] The silica component raw material liquid and the metal raw material can be suitably mixed at room temperature of about 15 to 45° C. by stirring with a stirrer and a stirring bar.

[0061] In the production method of the present invention, in order to efficiently obtain a uniform gel, the content of silica-based composite oxide precursor particles in the silica-based composite oxide precursor sol must be 1.5 to 3.0 (mol / L) in the sol preparation step. That is, the content of silica-based composite oxide precursor particles, calculated by dividing the sum of the total amounts (moles) of silicon and metal contained in the silica-based composite oxide by the volume (L) of the silica-based composite oxide precursor sol, is adjusted to be 1.5 to 3 (mol / L). Here, the silica-based composite oxide precursor particles refer to the silica and each inorganic component contained in the composite oxide raw material, and the number of moles can be determined by the amount and concentration of the raw material input and the molecular weight of each component. A content of less than 1.5 (mol / L) is undesirable because it significantly prolongs the gelation time and reduces productivity. Furthermore, a content of more than 3.0 (mol / L) is undesirable because it does not form a uniform agar-like gel, but rather an opaque glassy solid precipitates non-uniformly from the sol. The above content can be adjusted by adjusting the amount of raw material input, adding a solvent or water, or removing the solvent or water by drying.

[0062] 2-3. Gel Formation Step This step involves mixing 100 parts by mass of the silica-based composite oxide precursor sol with 5 to 10 parts by mass of water to form a silica-based composite oxide precursor wet gel. By mixing the silica-based composite oxide precursor sol with water, hydrolysis and condensation of the dispersoids in the sol proceed, causing the molecular structure to become entangled, increasing the viscosity and forming a solid gel that incorporates the dispersion medium and water inside.

[0063] From the viewpoint of obtaining a uniform gel, when mixing the silica-based composite oxide precursor sol with water, stirring with a stirrer and a stirring bar is more preferable to prevent local gelation due to non-uniformity of the concentration. If the amount of water is less than 5 parts by mass, gelation does not occur, and if it exceeds 10 parts by mass, solid silica particles will precipitate and settle, making it impossible to obtain a gel, which is not preferable.

[0064] 2-4. Pulverization Step In this step, the wet gel formed in the previous step is recovered and dried to obtain a dry gel, which is then pulverized to roughly adjust the particle size. Any known drying method can be used to dry the wet gel without any restrictions. However, from the perspective of obtaining denser silica-based composite oxide particles, it is preferable to set the residual ratio of the dispersion medium and water incorporated inside to 40 mass % or less. Because a gel with such a residual ratio is easily obtained, the drying conditions are preferably a drying temperature of 80 to 150°C and a drying time of 1 to 18 hours.

[0065] As a pulverization method, for example, ball mill pulverization using a pot and balls made of yttria-reinforced zirconia can be suitably used. By pulverizing before firing, pulverization and particle size control after the firing step can be easily performed.

[0066] Since the average particle size of the amorphous silica-zirconia powder or silica-titania of the present invention, which is the target, is 1 to 10 μm, it is sufficient to pulverize the powder so that the average particle size is larger than the target average particle size within the above range, but it is preferable to pulverize the powder so that the average particle size is about 100% larger than the target average particle size within the above range. After pulverization, classification using a sieve or classification by elutriation may be carried out as necessary.

[0067] 2-5. Calcination Step In this step, the powder obtained in the previous step is calcined. Any known calcination method can be used without limitation. The calcination temperature is set to 700 to 1000°C, preferably 800 to 950°C, from the viewpoint of removing the liquid component and obtaining a powder having a B / A ratio of 0.5 to 0.9, and from the viewpoint of preventing fusion between particles.

[0068] 2-6. Other Steps As another step, further classification may be performed to narrow the particle size distribution. Furthermore, the obtained silica-based composite oxide particles may be subjected to a silane coupling treatment to improve their affinity with the organic matrix when blended into a dental composition. Any known silane coupling agent may be used in the silane coupling treatment without any restrictions.

[0069] 3. Dental curable composition of the present invention and blank of the present invention The dental curable composition of the present invention contains 100 parts by mass of a polymerizable monomer, 100 to 200 parts by mass (preferably 100 to 150 parts by mass) of spherical inorganic powder particles having an average particle size of 0.1 to 5 μm, 40 to 100 parts by mass (preferably 40 to 80 parts by mass) of spherical inorganic powder particles having an average particle size of 0.01 to 0.1 μm, 100 to 250 parts by mass (preferably 150 to 250 parts by mass) of the amorphous silica-based composite oxide powder particles of the present invention, and 0.1 to 1 part by mass of a polymerization initiator.

[0070] The dental curable composition of the present invention corresponds to the photocurable dental restorative material disclosed in Patent Document 2, which contains a mixture of spherical inorganic powder particles having an average particle size of 0.1 to 5 μm, spherical inorganic powder particles having an average particle size of 0.01 to 0.1 μm, and irregular inorganic powder particles having an average particle size of 1 to 9 μm, except that the amorphous inorganic powder particles are replaced with the amorphous silica-based composite oxide powder particles of the present invention, and the amounts of each powder particle are within the above-mentioned ranges. Therefore, as each component other than the amorphous silica-based composite oxide powder particles of the present invention, any component that can be used in the photocurable dental restorative material disclosed in Patent Document 2 can be used without particular limitation. However, the dental curable composition of the present invention is not limited to use as a photocurable dental restorative material, and can also be suitably used as a raw material composition for so-called hybrid resins, which form the cutting portion of dental cutting blanks.

[0071] To briefly explain each component other than the amorphous silica-based composite oxide powder particles of the present invention in the dental curable composition of the present invention, suitable polymerizable monomers include 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane, 1,6-bis(methacrylethyloxycarbonylamino)-2,2-4-trimethylhexane, neopentyl glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and butylene glycol dimethacrylate.

[0072] As the spherical inorganic powder or particle, any generally suitable material can be used without any limitation as long as the average particle diameter is within the above range. Specifically, suitable materials include composite inorganic oxides such as silica-zirconia, silica-titania, and silica-alumina, borosilicate glass, soda glass, glass containing heavy metals (e.g., barium, strontium, and zirconium), aluminosilicate, fluoroaluminosilicate, glass ceramics, and silica.

[0073] Furthermore, as the polymerization initiator, not only can photopolymerization initiators such as bisacylphosphine oxides disclosed in Patent Document 2 be suitably used, but also thermal polymerization initiators such as benzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxydicarbonate, etc. be suitably used. When the dental curable composition of the present invention is used as a raw material composition for a hybrid resin that will be used as a cutting target, it is preferable to use a thermal polymerization catalyst as the polymerization catalyst, because when used as a resin material for dental cutting, it is necessary to obtain a thick, toned cured product, which can make it difficult to transmit light to the inside of the curable composition.

[0074] The dental curable composition of the present invention can be obtained by thoroughly kneading the above-mentioned essential components and optional components added as needed in predetermined amounts, and then defoaming the resulting paste to remove air bubbles.

[0075] As described above, the dental curable composition of the present invention is suitable as a raw material composition for so-called hybrid resin, which becomes the cutting portion of a dental cutting blank, and the blank of the present invention made of the cured product thereof has the advantage of being high strength and easily polished to obtain an aesthetically excellent luster. When the dental curable composition of the present invention is used to produce the blank of the present invention, a cast polymerization method using a mold is preferably used, as described in JP 2019-178105 A, for example.

[0076] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0077] 1. Production and Evaluation of Irregular Silica-Based Composite Oxide Powder and Granules The abbreviations for the compounds used in the production of the composite oxide particles are shown below. <Silicon Source (Alkyl Silicate)> TES: Tetraethyl silicate (manufactured by Colcoat Co., Ltd.) <Metal Raw Materials> TBZ: 87 mass% tetra(n-butoxy)zirconate n-butyl alcohol solution (manufactured by Hokko Chemical Co., Ltd.) TPT: Tetraisopropyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) NaOMe: 28 mass% sodium methoxide methanol solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Example 1 [Hydrolysis Step] 60 g of a 0.11 mass% aqueous sulfuric acid solution and 1,056 g of TES were dissolved in 0.9 L of 2-methyl-1-propanol (isobutyl alcohol), and the solution was mixed at room temperature for 2 hours and 30 minutes to hydrolyze, thereby preparing a silica component raw material liquid. At this time, the proton concentration obtained by dividing the amount of protons contained in the sulfuric acid aqueous solution by the total volume (L) of the reaction solution is: [H ＋ ] (also referred to as "proton concentration relative to the reaction solution") is 0.63 (mmol / L), and the water volume concentration (also referred to as "water concentration relative to the reaction solution") obtained by dividing the amount of water (L) contained during hydrolysis by the total volume of the reaction solution is 2.8 (vol%), which is the "amount of protons relative to alkyl silicate", the above amount of protons (mmol) relative to TES: 1 (mmol): 100 × [H ＋ ] / [Si] is 0.026 (mol%), which is the "amount of water relative to alkyl silicate." The amount of water (mmol) relative to TES: 1 (mmol): 100 × [H ２ For reference, the proton concentration in the reaction solution: [H ＋ ] and the water concentration in the reaction solution, converted into a concentration based on the volume (L) of the silica-based composite oxide precursor sol obtained in the sol preparation step described below, ＋ ]=0.53 (mmol / L), and the water concentration=2.4 (vol %).

[0078] The silica component raw material solution thus obtained was subjected to GC-MS analysis under the following conditions, and the observed peaks were identified and classified into unhydrolyzed product (a1), hydroxysilicate monomer (a2), and silicate dimer (a3). The peak area of ​​the peak assigned to (a1) was calculated from the sum of the intensities of the classified peaks: S １ , the peak area of ​​(a2) above: S ２ , the peak area of ​​(a3) ​​above: S ３ Search for S ２ / S １ and S ３ / S １ The results are shown in Table 2. In Table 2, S ２ / S １ and S ３ / S １ The values ​​are shown as a percentage (100 times the value). Analysis conditions and peak identification results: Apparatus: 7890A (Agilent Technologies), column: DB-5; Initial temperature: 60°C, retention time: 1 min, heating rate: 5°C / min; Final temperature: 260°C, retention time: 4 min, injection port temperature: 260°C; Sample injection amount: 1 μL, split ratio: 20:1; Each classification and the retention time (rt, unit: min.) of the detected peaks belonging to it are shown below. Classification: rt (min.) of each peak (a1): 7.7, 11.4, 14.5, 17.6, 20.5 (total of 5 peaks) (a2): 8.5, 12.3, 15.7, 18.7 (total of 4 peaks) (a3): 20.3, 23.0, 25.3, 27.2 (total of 4 peaks).

[0079] [Sol Preparation Step] Subsequently, 190 g of TBZ and 50 g of NaOMe were added to the silica component raw material liquid and stirred for 10 minutes to obtain a silica-based composite oxide precursor sol. [M] / ([Si]+[M]) was 0.12. The silica-based composite oxide precursor content (also referred to as "precursor content") calculated by dividing the sum of the total amount (moles) of silicon atoms and the total amount (moles) of the at least one metal contained in the composite oxide by the volume (L) of the silica-based composite oxide precursor sol was 2.3 (mol / L).

[0080] [Gel Preparation Step] Then, 150 g of water (7 parts by mass per 100 parts by mass of the silica-based composite oxide precursor sol) was added to the silica-based composite oxide precursor sol while stirring, to obtain a silica-based composite oxide precursor wet gel.

[0081] [Pulverization step and calcination step] The obtained wet gel was left to stand at room temperature for 4 hours, and after solidification was confirmed, it was recovered and further dried by air drying at 120°C for 15 hours to solidify. The dried gel was pulverized in a vibration ball mill to an average particle size of 4 μm to obtain a white powder. The powder was then calcined at 900°C for 4 hours to obtain amorphous silica-based composite oxide powder F1, which corresponds to the amorphous silica-based composite oxide powder of the present invention.

[0082] The obtained F1 was subjected to powder X-ray diffraction measurement to determine the crystallinity, specifically, the halo peak intensity of amorphous silica appearing at a diffraction angle (2θ) of 22°: A and the halo peak intensity of ZrO appearing at a diffraction angle (2θ) of 30°: B. ２ The ratio of the main peak intensity of A to B, B / A, was determined, and various analyses were carried out to determine the average particle size, specific surface area, pore volume, etc. The obtained X-ray diffraction pattern is shown in Figure 1, and the results of various analyses are shown in Table 2. The various analyses were carried out as follows.

[0083] (1) Powder X-ray Diffraction Measurement Powder X-ray diffraction measurement for evaluating the crystallinity of the amorphous silica-based composite oxide powder particles was performed using an X-ray diffractometer (manufactured by Rigaku Corporation) with an X-ray output of 40 kV, 30 mA, a detector of D / teX Ultra, a scan axis of 2θ / θ, and a scan range of 5 deg to 120 deg.

[0084] (2) Measurement of Average Particle Size The particle size distribution for evaluating the average particle size of the amorphous silica-based composite oxide powder was measured using a particle size distribution analyzer (Beckman Coulter, Inc.) with a dispersoid refractive index of 1.36, a dispersion medium refractive index of 1.55, and a dispersion solvent of ethanol.

[0085] (3) Measurement of Specific Surface Area and Pore Volume The specific surface area and pore volume of the amorphous silica-based composite oxide powder were measured by nitrogen adsorption at 77 K (Kelvin) using a specific surface area / pore distribution measuring device (manufactured by Microtrac MRB).

[0086] (4) Refractive Index Measurement The refractive index of the amorphous silica-based composite oxide powder was measured by the immersion method using an Abbe refractometer (manufactured by Atago Co., Ltd.) (measurement wavelength: 589 nm). That is, in a thermostatic chamber at 25°C, 1 g of composite oxide particles was dispersed in 50 mL of anhydrous toluene in a 100 mL sample bottle. While stirring this dispersion with a stirrer, 1-bromotoluene was added dropwise little by little, and the refractive index of the dispersion was measured at the point when the dispersion became most transparent, and the obtained value was taken as the refractive index of the composite oxide particles.

[0087] Examples 2 to 4 and Comparative Examples 1 to 5 Amorphous silica-zirconia-based powder particles F2 to F4, which correspond to the amorphous silica-based composite oxide powder particles of the present invention, and amorphous silica-zirconia-based powder particles F5 to F9, which do not correspond to the amorphous silica-based composite oxide powder particles of the present invention, were obtained in the same manner as in Example 1, except that the raw materials and their amounts used were changed as shown in Table 1. The numerical values ​​in the raw material column in Table 1 represent the amount of each raw material used (unit: g (grams)). In addition, in the "Proton concentration relative to reaction liquid" and "Water concentration relative to reaction liquid" columns of Table 1, values ​​converted to concentrations based on the volume (L) of the silica-based composite oxide precursor sol are shown in brackets [ ] for reference. For F2 to F9 obtained in each Example and Comparative Example, B / A, average particle size, specific surface area, pore volume, etc. were determined in the same manner as in Example 1. The results are shown in Table 2.

[0088] Comparative Example 6 The hydrolysis step was carried out in the same manner as in Example 1 except that the raw materials and the amounts used were changed as shown in Table 1, but a glassy solid precipitated during the hydrolysis.

[0089] Comparative Example 7 The hydrolysis step to the gel preparation step were carried out in the same manner as in Example 1 except that the raw materials and their amounts were changed as shown in Table 1, but gelation of the sol did not occur.

[0090] Comparative Example 8: With reference to the manufacturing method described in Patent Document 1, amorphous silica-based composite oxide powder F10 was synthesized by the following method. That is, 5.4 g of 0.05% by mass hydrochloric acid and 160 g of TES were dissolved in 0.2 L of 2-methyl-1-propanol (isobutyl alcohol), and mixed at room temperature for 5 hours to hydrolyze. 67 g of TBZ and 7.7 g of NaOMe were added to the resulting alkyl silicate hydrolyzed liquid and stirred for 1 hour to obtain a sol. 30 g of water was then added to the sol with stirring to obtain a wet gel. The resulting wet gel was allowed to stand at room temperature for 4 hours, and after solidification was confirmed, it was recovered as a composite oxide gel. Next, the composite oxide gel was subjected to air drying at 100 ° C. for 15 hours, dried, and then pulverized using a vibrating ball mill to an average particle size of 4 μm. The pulverized product (powder) was then calcined at 900 ° C. for 2 hours to obtain amorphous silica-based composite oxide powder F10. The F10 thus obtained was subjected to the same analysis as in Example 1. The results are shown in Table 2.

[0091] Example 5 and Comparative Examples 9 and 10: Amorphous silica-titania-based powder F11, which corresponds to the amorphous silica-based composite oxide powder of the present invention, and amorphous silica-titania-based powders F12 and F13, which do not correspond to the amorphous silica-based composite oxide powder of the present invention, were obtained in the same manner as in Example 1, except that TPT was used instead of TBZ as the metal raw material and the raw materials and their amounts used were changed as shown in Table 1. The numerical values ​​in the raw material column in Table 1 represent the amount of each raw material used (unit: g (grams)). Furthermore, for the obtained F11, the B / A, average particle size, specific surface area, pore volume, etc. were determined in the same manner as in Example 1. The results are shown in Table 2.

[0092]

[0093]

[0094] 2. Preparation and Evaluation of Dental Hardenable Compositions Containing Irregular Silica-Based Complex Oxide Powder and Particles The abbreviations of the compounds used in the preparation of the hardenable compositions are shown below.

[0095] <Polymerizable monomers> UDMA: 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane D-2.6E: 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane NPG: Neopentyl glycol dimethacrylate <Thermal polymerization initiator> BPO: Benzoyl peroxide <Spherical inorganic powder and granules having an average particle size of 0.1 to 5 μm> PF1: Gamma-methacryloyloxypropyltrimethoxysilane-treated spherical silica zirconia having an average particle size of 0.5 μm <Spherical inorganic powder and granules having an average particle size of 0.01 to 0.1 μm> PF2: Gamma-methacryloyloxypropyltrimethoxysilane-treated spherical silica titania having an average particle size of 0.07 μm <Irregular silica-based composite oxide powder and granules> FS1 to FS13: γ-methacryloyloxypropyltrimethoxysilane-treated products of amorphous silica-based composite oxide particles F1 to F13 produced in Examples 1 to 5 and Comparative Examples 1 to 5, 8, 9 and 10.

[0096] Example 6 A curable polymerizable monomer composition was prepared by mixing 15 parts by mass of UDMA, 70 parts by mass of D-2.6E, 15 parts by mass of NPG, and 1.0 part by mass of BPO. Also, an inorganic powder / granular composition was prepared by mixing 60 parts by mass of FS1, 28 parts by mass of PF1, and 12 parts by mass of PF2. The inorganic powder / granular composition and the curable polymerizable monomer composition were mixed so that the inorganic powder / granular composition was 81% by mass and the curable polymerizable monomer composition was 19% by mass, and a uniform paste-like composition was obtained, which was then vacuum degassed to prepare a (dental) curable composition.

[0097] The resulting curable composition was then filled into a 14.5 mm x 14.5 mm x 18 mm mold, pressurized to 0.4 MPa with nitrogen, and heated in a 90°C heating device for 15 hours to polymerize and harden. The cured product was then cooled to room temperature and removed from the mold. The resulting cured product was then repressurized to 0.4 MPa with nitrogen and heated in a 175°C heating device for 48 hours. The cured product was then cooled to room temperature to obtain a dental cutting resin material. The following abrasion evaluation and bending strength measurements were performed. The results are shown in Table 3.

[0098] (1) Evaluation of Polishability The outer surface of the obtained dental resin material for cutting was manually polished using P1500 waterproof abrasive paper to create a test piece, which was then set on a laboratory table and polished in three stages using three types of polishing tools. The gloss of the polished surface after each polishing stage was measured. Each polishing stage was performed at a rotation speed of 10,000 rpm for 30 seconds. The gloss was measured using a gloss meter (TC108D, manufactured by Tokyo Denshoku Co., Ltd.). The polishing tools used for each stage are shown below. - Polishing tool used for the first polishing stage (brown silicone point polishing): ``Silicon Point M Type 2 / HP / 13'', manufactured by Shofu Co., Ltd. - Polishing tool used for the second polishing stage (blue silicone point polishing): ``Silicon Point M Type 2 / HP / 13'', manufactured by Shofu Co., Ltd. - Polishing tool used for the third polishing stage (buffing): ``Abrasive: Superstar V'', manufactured by Nippon Dental Industry Co., Ltd.

[0099] (2) Measurement of Flexural Strength Test pieces measuring 1.2 mm x 4.0 mm x 18 mm were cut out from the obtained dental cutting resin material, and each surface of the test piece was polished with P2000 waterproof abrasive paper. The prepared test pieces were immersed in purified water and stored in an incubator at 37°C for 7 days to prepare measurement test pieces. A three-point bending test was performed on the 4.0 mm x 18 mm surface of the measurement test pieces using a universal testing machine autograph (manufactured by Shimadzu Corporation) at room temperature in air, with a support distance of 12.0 mm and a crosshead speed of 1.0 mm / min. The bending strength [MPa] was calculated for each of 10 test pieces using the following formula, and the average value was evaluated as the bending strength. Bending strength [MPa] = 3FS / (2bh ２ where F is the maximum load applied to the test piece [N], S is the distance between the supports [mm], b is the width of the test piece measured immediately before the test [mm], and h is the thickness of the test piece measured immediately before the test [mm].

[0100] Examples 7 to 10 and Comparative Examples 11 to 18 Preparation of curable compositions and production of dental cutting resin materials were carried out in the same manner as in Example 5, except that the composition of the inorganic powder / granule composition was changed as shown in Table 3. Furthermore, abrasion evaluation and bending strength measurement were carried out for each of the obtained dental cutting resin materials in the same manner as in Example 6. The results are shown in Table 3.

[0101]

[0102] As shown in Table 3, the dental compositions of Examples 6 to 9 containing the amorphous silica-zirconia powder of the present invention had high gloss and high bending strength at each stage of polishing. Also, as shown in Example 10, the amorphous silica-titania powder of the present invention using TPT as the metal raw material also had high bending strength and a hardened product with high gloss when polished was obtained.

[0103] On the other hand, Comparative Examples 11 to 14 showed high bending strength, but had inferior glossiness compared to the Examples. Similarly, Comparative Example 17 showed bending strength comparable to that of Example 10, but had a lower glossiness during polishing. Furthermore, in Comparative Example 15, the pore volume of the amorphous silica-based composite oxide powder F9 used was 0.151 cm ３ / g, which is considered to be composed of porous particles, improved gloss was observed, but bending strength was reduced. In Comparative Example 18, similarly to Comparative Example 15, high gloss was obtained, but bending strength was reduced, which is considered to be composed of porous particles.

[0104] As shown in Comparative Example 16, when the amorphous silica-zirconia particles described in Patent Document 1 were used, high bending strength was exhibited, but gloss was inferior to that of the Examples.

[0105] 1...Halo peak derived from amorphous silica 2...The peak with the highest diffraction intensity among the diffraction peaks derived from zirconia

Claims

1. An amorphous silica-based composite oxide powder composed of non-porous silica-based composite oxide particles containing silicon and at least one metal, In the silica-based composite oxide particles, the molar ratio of the at least one metal to the total amount of silicon and the at least one metal is 0.05 or more and 0.25 or less. The average particle diameter, defined as the median diameter in the volume-based particle size distribution of the amorphous silica-based composite oxide powder, determined by laser diffraction-scattering, is 1 μm or more and 10 μm or less. In the diffraction pattern obtained by X-ray diffraction measurement of the amorphous silica-based composite oxide powder, the ratio B / A of the diffraction intensity at the peak top of the peak with the highest diffraction intensity among the diffraction peaks derived from each oxide of at least one of the metals to the diffraction intensity at the peak top of the halo peak originating from amorphous silica that appears around 2θ = 22° is 0.5 or more and 0.9 or less. An amorphous silica-based composite oxide powder granule characterized by the following features.

2. The specific surface area measured by the BET method was 3 m². ２ g －１ Above arm m ２ g －１ The following is observed: In the pore distribution obtained by BJH method measurement, the total pore volume of pores with a diameter between 10 nm and 50 nm is 0.06 cm³. ３ g －１ The amorphous silica-based composite oxide powder granules described in claim 1 are as follows:

3. The amorphous silica-based composite oxide powder granules according to claim 1, wherein the at least one metal comprises at least one of Zr and Ti, and optionally Na.

4. A method for producing amorphous silica-based composite oxide powder granules composed of non-porous silica-based composite oxide particles containing silicon and a metal containing at least one of Zr and Ti, A hydrolysis step is performed in which, in a reaction solution containing a mixed solution of alkyl silicate and alcohol and an aqueous solution of inorganic acid, at least a portion of the alkyl silicate is hydrolyzed to prepare a silica component raw material solution containing the alkyl silicate hydrolysate and a condensate of the hydrolysate, A sol preparation step involves mixing a metal raw material containing at least one alkyl zirconate and alkyl titanate with the silica component raw material liquid to prepare a precursor sol in which silica-based composite oxide precursor particles containing silicon and at least one metal containing Zr and Ti are dispersed; A gel formation step is performed by mixing 100 parts by mass of the precursor sol with 5 to 10 parts by mass of water to form a precursor wet gel. A grinding step to obtain amorphous precursor powders by drying the aforementioned wet precursor gel and then grinding it, A calcination process is performed to produce non-porous silica-based composite oxide particles by calcining the aforementioned precursor powder, Includes, In the aforementioned hydrolysis step, (a) The alcohol is a branched alkyl alcohol having 3 to 5 carbon atoms, (b) The concentration of protons contained in the aqueous solution of the inorganic acid relative to the reaction solution is 0.4 mmol / L or more and 0.9 mmol / L or less. (c) The volume concentration of water in the reaction solution is 2 (vol%) or more and 4 (vol%) or less. (d) The ratio of protons (mol) contained in the inorganic acid aqueous solution to 1 (mol) of alkyl silicate is 0.02 (mol%) or more and 0.04 (mol%) or less. (e) The ratio of the amount of water (mol) in the reaction solution to 1 (mol) of alkyl silicate is 50 (mol%) or more and 100 (mol%) or less. Using the aforementioned reaction solution, hydrolysis and condensation reactions are carried out. In the gas chromatogram obtained by gas chromatography analysis of the silica component raw material liquid prepared in the hydrolysis step, the peak area of the peak attributed to the unhydrolyzed product (a1) of an alkyl silicate having no hydroxyl group, in which at least some of the functional groups may be substituted with alkoxy groups by the alcohol in the mixed solution, is S １ is defined as, and the peak area of the hydroxy silicate monomer (a2) containing at least one hydroxyl group and one silicon atom, which is the hydrolyzate of (a1), is S ２ is defined as, and the peak area of the silicate dimer (a3) containing two silicon atoms, which is the condensate of (a2) and / or the condensate of (a1) and (a2): S ３ When defined as, S １ The peak area ratio of S ２ to S １ is 0.3 or more and 0.6 or less, and the peak area ratio of S to S ３ is 0.03 or more and 0.5 or less, In the sol preparation step, the metal raw material and the silica component raw material liquid are mixed such that the molar ratio of metal to the total amount of silicon and metal contained in the silica-based composite oxide precursor particles is 0.05 or more and 0.25 or less, and the content of silicon and metal contained in the silica-based composite oxide precursor particles in the precursor sol is 1.5 (mol / L) or more and 3 (mol / L) or less. The firing process described above is carried out in a range of 700°C to 1000°C. A method for producing amorphous silica-based composite oxide powder granules, characterized by the following features.

5. The aforementioned metal raw material contains sodium alcoside. A method for producing amorphous silica-based composite oxide powder granules as described in claim 4.

6. Polymerizable monomer: 100 parts by mass, The average particle size is 0. Spherical inorganic powder particles of 1 μm to 5 μm in size: 100 parts by mass to 200 parts by mass, Spherical inorganic powders with an average particle size of 0.01 μm or more and 0.1 μm or less: 40 parts by mass or more and 100 parts by mass or less, The amorphous silica-based composite oxide powder granules described in claim 1: 100 parts by mass or more and 250 parts by mass or less, and Polymerization initiator: 0.1 parts by mass or more and 1 part by mass or less, A dental hardening composition containing [a specific ingredient].

7. A dental cutting blank having a part to be cut, characterized in that at least a portion of the part to be cut is made of a hardened body of the dental hardening composition described in claim 6.