Particle materials and dental materials, and methods for manufacturing particle materials

Abstract

The problems to be solved are to provide a particle material that can be used as a filler of a dental material and to provide a dental material that uses the particle material.　This particle material, which overcomes the aforementioned problem, is an aggregate containing silica primary particles having a volume-average particle size of 1-20 nm, said aggregate having in the interior thereof primary particles of two or more types of metal elements, and comprising a metal oxide in which one or more of the metal elements is a heavy element having an atomic number of at least 38, the particles of the heavy-element metal oxide being composed of primary particles having a volume-average particle size of 1–20 nm, and the surface of said primary particles being composed of silica, wherein the specific surface area is 180 m2 / g or less, the amount of linseed oil absorbed per unit volume (100 cm3) is 200 g or less, the the amount of linseed oil absorbed per unit surface area (m2) is 0.02 g or less, the light transmittance exceeds 10%, and the mass of the heavy elements is 4–60% based on the total mass. By using these aggregates, it is possible to achieve optical performance similar to that achieved with a small particle size while improving strength.

Description

Technical Field

[0001] The present invention relates to particulate materials and dental materials using such particulate materials.

Background Art

[0002] Conventionally, as a dental material, a resin composition called a so-called composite resin in which inorganic particulate materials are dispersed in a resin material has been widely used (for example, Patent Document 1). As the resin material, a pre-cured material such as a monomer is adopted. After the composite resin is filled in a defective part of a tooth, external energy such as light irradiation is applied, and the resin material is polymerized and cured. The present applicant provides a filler to be filled in a resin composition that can be used for dental applications.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a resin composition that can be used for dental applications is an application that requires aesthetics. For example, a dental resin composition is required to have high strength and excellent appearance such as gloss by polishing (hereinafter referred to as "polishability"). The inventors of the present application considered that it is difficult to say that the filler disclosed in Patent Document 2 achieves both polishability and filling property. As a result of intensive studies, in order to achieve both strength and polishability, it is possible to fill a large amount of filler, so the upper limit of the specific surface area is limited, and it was found that the polishability can be improved by reducing the linseed oil absorption per unit surface area.

[0005] Furthermore, when used as a dental material, radiopaquery is a desirable physical property. Here, (meth)acrylic acid-based resin materials commonly used in dental materials have a refractive index of around 1.50. Radiopaque metal oxides (such as zirconia) have a high refractive index, and it is not easy to adjust the refractive index to around 1.50 simply by adding them as fillers. Moreover, if they are added while maintaining the refractive index, they do not exhibit sufficient radiopaquery. In addition, there were concerns that the exposure of radiopaque metal oxides to the surface would lead to deterioration of polishability, reactivity with silane coupling agents, and poor stability.

[0006] This invention was completed in view of the above circumstances, and relates to a particulate material that can be used as a filler in dental materials, and a dental material using the particulate material. and method for manufacturing particle materials The problem to be solved is to provide [the necessary solution]. [Means for solving the problem]

[0007] The particle material of the present invention, which solves the above problems, is an aggregate composed of primary particles having a volume-average particle size of 1 nm to 20 nm and containing two or more metal elements, and whose surface is silica. Some of the aforementioned primary particles contain heavy elements with atomic numbers of 38 or higher as metal oxides. At least a portion of the remainder of the primary particles is composed of silica particles. Specific surface area is 180 m² 2 / g or less, Unit volume (100 cm³) 3 ) The amount of flaxseed oil absorbed per unit is 200g or less. Unit surface area (m²) 2 ) The amount of flaxseed oil absorbed per serving is 0.02g or less. Light transmittance is over 20% The mass of the aforementioned heavy elements is between 4% and 60% of the total mass.

[0008] By employing aggregates, it is possible to improve strength while achieving optical performance close to that of smaller particle sizes. Since the surface of the aggregates is composed of silica, arbitrary functional groups can be introduced to the surface using silane coupling agents, etc., while suppressing the exposure of heavy elements to the surface. [Effects of the Invention]

[0009] The particle material of the present invention having the above configuration can achieve both abrasiveness and filling properties when used in dental materials. [Brief explanation of the drawing]

[0010] [Figure 1] This is an SEM image of filler 1 in the example. [Modes for carrying out the invention]

[0011] The particle material of the present invention and dental materials using the particle material will be described in detail below based on embodiments. The particle material of this embodiment can provide a resin composition with high light transmittance when dispersed in a transparent resin material. Resin compositions with high light transmittance can be suitably used in dental materials such as denture materials and dental fillings. (particle material) The particle material of this embodiment is an aggregate composed of primary particles with a volume-average particle size of 1 nm to 20 nm and containing two or more metal elements, with a silica surface. A portion of the primary particles (hereinafter referred to as "first primary particles") contains heavy elements with atomic number 38 or higher as metal oxides. At least a portion of the remainder of the primary particles (hereinafter referred to as "second primary particles") is composed of silica. In other words, the primary particles constituting the aggregate include first primary particles, second primary particles, and other primary particles that may be optionally present (hereinafter referred to as "other primary particles").

[0012] The particulate material is preferably an aggregate formed by dehydration condensation or fusion of the above-mentioned multiple types of primary particles. OH groups are present on the surface of the metal oxide constituting the primary particles, and dehydration condensation proceeds between adjacent primary particles, or the metal oxide melts and fuses.

[0013] The particle size of the aggregate is not particularly limited. Since the primary particles are bonded and fused together, the primary particles are strongly bonded to each other, and the mechanical strength of the particulate material can be improved. Further, the shape of the aggregate is not particularly limited, but a crushed shape is preferred. The crushed shape is a shape having a surface formed by crushing. For example, as shown in FIG. 1, it refers to a shape with an angular surface when observed by SEM. By adopting the crushed shape, physical properties such as flexural strength can be improved when used in a resin composition.

[0014] The volume average particle size of the aggregate is preferably 0.1 μm or more and 10 μm or less. Examples of the lower limit values include 0.2 μm, 0.3 μm, 0.5 μm, and 1.0 μm, and examples of the upper limit values include 8.0 μm, 5.0 μm, and 3.0 μm. These lower limit values and upper limit values can be arbitrarily combined. When the particle size of the aggregate is within the range of the above lower limit value or more, the strength is improved when applied to a resin composition. Further, when it is within the range of the above upper limit value or less, the particulate material can be properly dispersed in a resin material or the like. In addition, by mixing aggregates with large and small particle sizes as individual aggregates, the filling rate of filling the resin composition with aggregates can be improved.

[0015] The specific surface area of the aggregate is 180 m 2 / g or less. In particular, examples of the upper limit value include 160 m 2 / g, 150 m 2 / g, 130 m 2 / g, 100 m 2 / g, and examples of the lower limit value include 10 m 2 / g, 15 m 2 / g, 20 m 2 / g, 30 m 2The value can be exemplified by / g. These lower and upper limits can be combined arbitrarily. The specific surface area is a value measured by the BET method using nitrogen gas.

[0016] Volume average of primary particles constituting the aggregate grain Examples of lower diameter limits include 3 nm, 5 nm, 9 nm, 11 nm, and 14 nm, while examples of upper diameter limits include 18 nm and 16 nm. These lower and upper limits can be combined arbitrarily. Furthermore, the range of volume-average particle size can be set independently for each of the primary particles, secondary particles, and other primary particles. The volume-average particle size of the primary particles of aggregated particles can be measured by embedding the aggregated particles in resin, then polishing and ion milling to expose the cross-section of the aggregated particles, and performing SEM or TEM observation and image analysis.

[0017] The primary particles are not particularly limited in their metallic elements, but those with high oxide stability are desirable. Examples include aluminum, zirconium, titanium, and silicon, which can form oxides with particularly high stability against moisture. Two or more metallic elements can exist as individual metallic oxides or as composite oxides of two or more metallic elements within the aggregate.

[0018] These two metallic elements can be incorporated as individual compounds within each primary particle constituting the aggregate, allowing for the aggregation of primary particles with multiple compositions. Furthermore, it is possible to incorporate multiple metallic elements or multiple compounds within a single primary particle.

[0019] The primary particles contain heavy elements. Heavy elements are elements with an atomic number of 38 or higher, and are not particularly limited, but are preferably selected from zirconium, barium, and titanium. The primary particles may contain other metallic elements as described above, such as composite oxides, in the same particles along with the heavy elements. The heavy element content is between 4% and 60% of the total mass of the particle material, with lower limits of 5%, 7%, 10%, and 14%, and upper limits of 55%, 50%, 40%, and 30%. These lower and upper limits can be combined arbitrarily.

[0020] The inclusion of secondary particles composed of silica improves the polishability when applied to a resin composition. Here, "composed of silica" means that 80% or more by mass is composed of silica, preferably 90% or more, more preferably 95% or more, even more preferably 99%, and particularly preferably 100% (excluding unavoidable impurities).

[0021] Secondary particles have upper limits of 95%, 90%, and 85% of the total mass. Approximately % The lower limit can be set to approximately 50%, 30%, 20%, or 10%. These upper and lower limits can be combined in any way.

[0022] Furthermore, primary particles composed of compounds made of elements other than the metal element may also be included. The amount of elements other than the metal element can be included up to the amount of the metal element as the main component. Here, the amount of the metal element as the main component means that it is present in an amount of 50% by mass or more, preferably 70% or more, and more preferably 90% or more.

[0023] Other primary particles may be included that do not contain heavy elements and are not composed of silica. Examples of other primary particles include those containing the metallic elements mentioned above.

[0024] Metallic elements can exist not only as metal oxides, but also as nitrides, carbides, and other forms. Specific internal compositions include aluminum oxide, zirconia, titania, silica, and their composite oxides. For aluminum oxides, gamma-alumina or boehmite can be used.

[0025] The surface of the aggregate is composed of silica. In other words, for the primary particles (and any other primary particles present), the primary particles are used as the interior (referred to as the "core"), and their surface is coated with silica. The silica coating can be done after the aggregate is formed or while the primary particles are still in the process of being coated.

[0026] Here, the statement that the surface of the aggregate is composed of silica means that the lower limit of the area of ​​the silica-covered portion of the aggregate's surface (hereinafter sometimes referred to as the "silica portion" or "coating layer") is 50% or more, preferably 70%, 75%, 80%, 85%, 90%, 95%, or 99%, and even more preferably 100% (completely covered with silica without any exposure).

[0027] To completely cover a surface with silica without any exposure, it is effective to coat it with a layer formed by a chemical reaction. For example, a silica coating can be formed by hydrolyzing and dehydrating condensing tetraethoxysilane. On the other hand, if the silica coating layer required to produce a filler with a refractive index suitable for dental materials is formed solely by the aforementioned chemical bonding layer, the bonds between the silica coating layers become strong, worsening polishability and transparency. The area of ​​the silica-covered portion can be calculated by directly measuring the silica content through direct observation with an electron microscope, or indirectly by measuring the amount of metallic elements other than silica.

[0028] The particulate material has a light transmittance of 20% or more, and it is particularly preferable that it has a transmittance of 25% or more, 30% or more, 35% or more, 40% or more, or 50% or more.

[0029] Light transmittance was measured as follows. First, each test sample was placed in a test solution with a refractive index adjusted in increments of 0.005. The OD value was measured in five test solutions: the one with the highest transparency (the refractive index of this test solution was taken as the refractive index of the test sample), and test solutions with refractive indices of 0.005 and 0.01 above and below that value. The refractive index of the obtained test solutions and their OD values ​​were plotted, and the light transmittance was calculated from the OD value at the peak of the quadratic curve when an approximate quadratic curve was used. The OD value was measured using a light ray with a wavelength of 589 nm in a sample suspension (0.1 g of the test sample suspended in 2 mL of the test solution) in a 15 mm diameter pore.

[0030] The silica covering the surface can be calculated as SiO2, with lower limits of 40%, 50%, and 60% relative to the total mass of the particle material, and upper limits of 95%, 90%, and 85% relative to the total mass. These lower and upper limits can be combined in any way.

[0031] The silica portion formed on the surface is a layer present on the surface of the aggregate. The thickness of the coating layer is not particularly limited, but it is preferable to cover the surface of the aggregate almost without gaps. When a coating layer is present, it is possible to coat the surface of the aggregated primary particles so that the primary particles are directly aggregated together (i.e., the coating layer is formed after the primary particles are aggregated), or it can be interposed between the aggregated primary particles (i.e., the coating layer is formed on the surface of the primary particles before they are aggregated to form the aggregate). It is desirable that the coating layer is either covalently bonded to the surface of the primary particles or physically bonded by intermolecular forces. By having a silica coating layer, it is possible to suppress the surface exposure of highly active zirconia, which can suppress the degradation of the resin when used dispersed in a resin, and can also suppress the change over time of the organic components of the surface modification. The organic material constituting the coating layer is preferably a condensate of a silane compound. If the silane compound is a compound having two or more OSIOR groups, a coating layer consisting of a condensate can be formed. One method for producing silane compound condensates is to condense the aforementioned silane compound in contact with the surface of primary particles (whether before or after aggregate formation). Primary particles are composed of inorganic materials and typically have OH groups on their surface. Therefore, the aforementioned silane compound can react with the OH groups present on the surface of the primary particles to form covalent bonds.

[0032] Functional groups may be introduced to the surface of the silica portion. While there are no particular limitations on the functional groups to be introduced, when dispersed in a resin material, it is preferable to introduce functional groups that have high affinity with the resin material. Examples include acrylic acid and its esters, methacrylic acid and its esters, and epoxy. Kishi When using resins as resin materials, introducing acrylic groups, methacrylic groups, epoxy groups, etc., allows them to react with the resin material and form strong bonds.

[0033] Furthermore, on the surface of the silica portion, formula (1):-OSiX 1 X 2 X 3A functional group represented by formula (2):-OSiY 1 Y 2 Y 3 A functional group represented by can be introduced. Here, in formulas (1) and (2), X 1 X is a phenyl group, vinyl group, epoxy group, methacrylic group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group; 2 , X 3 -OSiR3 and -OSiY 4 Y 5 Y 6 They are selected more independently of each other; Y 1 is R; Y 2 , Y 3 R and -OSiY 4 Y 5 Y 6 They are selected more independently of each other. 4 is R; Y 5 and Y 6 R and -OSiR3 are independently selected; R is independently selected from alkyl groups having 1 to 3 carbon atoms. Note that X 2 , X 3 , Y 2 , Y 3 , Y 5 , and Y 6 Either of these is the X of the adjacent functional group 2 , X 3 , Y 2 , Y 3 , Y 5 , and Y 6 It may be joined with any of the following using -O-.

[0034] The refractive index of the particle material can be controlled by adjusting the ratio of silica to other metal oxides, or by introducing functional groups into the silica portion. Because the particle size of the coated particles is small, the refractive index can be adjusted while maintaining transparency. When used in dental materials (described later), it is preferable that the refractive index of the particle material differs from that of the transparent resin material used by -0.1 to 0.1.

[0035] Particle materials have a unit volume (100 cm³). 3The amount of linseed oil absorbed per unit is 200g or less, with 170g, 160g, and 150g being particularly noteworthy upper limits. To reduce this value, the packing density of the particle material can be improved, or the sphericity can be improved. The unit volume is calculated as (apparent volume) × (1 - porosity).

[0036] Furthermore, the unit surface area (m²) is calculated from the surface area of ​​the particle material (value measured by the BET method using nitrogen gas). 2 The amount of linseed oil absorbed per gram is 0.02 g or less, with 0.018 g, 0.016 g, and 0.014 g being particularly noteworthy upper limits. To reduce this value, the packing density of the particle material can be improved, or the sphericity can be improved.

[0037] The particle material may contain inorganic particle material with a volume-average particle size of 1 nm to 200 nm, dispersed down to the primary particle level. The amount of inorganic particle material can be between 0% and 90% of the total mass of the particle material. Examples of lower limits for the inorganic particle material content include 2%, 5%, and 10%, while examples of upper limits include 60%, 50%, and 40%. These lower and upper limits can be combined arbitrarily. By including the inorganic particle material within the above ranges, it is possible to reduce the viscosity of the resin composition and improve the toughness of the cured resin product containing it.

[0038] Inorganic particle materials are given by formula (1):-OSiX 1 X 2 X 3 A functional group represented by formula (2):-OSiY 1 Y 2 Y 3 It is preferable that the functional group represented by is bonded to the surface of the silica particles. Since formulas (1) and (2) are the same as those described above, their explanation is omitted. (Method of manufacturing particle materials) The method for producing the particle material of this embodiment is a method that can suitably produce the above-mentioned particle material. The method for producing the particle material of this embodiment comprises a dispersion step, a coating step, and other steps that can be selected as needed. Other steps include an aggregation step, a modification step, and a particle size distribution adjustment step.

[0039] The dispersion process involves dispersing particles with an internal composition (core particles: which become primary particles and other primary particles, if present, after going through the coating process described later) in a liquid dispersion medium to form a dispersion. Core particles can be obtained by conventional methods. For example, they can be produced by reacting compounds that serve as precursors to the internal composition. For example, if zirconia is used as the internal composition, a zirconia sol can be used, and if boehmite is used, aluminum hydroxide with an appropriate particle size can be used as a precursor by grinding, and core particles made of boehmite can be obtained by hydrothermal treatment.

[0040] Furthermore, core particles can be obtained by using aluminum oxide with an appropriate particle size as a precursor and heating it in an acidic or alkaline aqueous solution. Colloidal silica can be described as coated particles in which the surface of core particles, which are made up of silica as a whole, is coated with a surface composition made of silica, so adding colloidal silica is also included in the dispersion process. In addition to using a mixture of multiple types of materials as core particles, core particles made up of multiple types of materials can also be added sequentially.

[0041] The coating step involves adding a precursor compound, which reacts to form the surface composition (silica), to the obtained dispersion to create the surface composition, thereby coating and forming coated particles on the surface of the core particles. When silica particles such as colloidal silica (corresponding to secondary particles) are added in the dispersion step, the colloidal silica acts as coated particles even without a coating step, as it is equivalent to coated particles where the surface of the silica core particles is coated with a silica surface.

[0042] The coating process can be performed in one step or in multiple steps. Furthermore, if the dispersion process is performed in multiple steps, the coating process can be carried out in between steps. The ratio of the internal composition to the surface composition can be controlled by adjusting the amount of core particles and the amount of added precursor.

[0043] Any compound can be used as a precursor. For example, tetraethoxysilane can be used as a precursor. Tetraethoxysilane readily produces silica in the presence of water. The so-called sol-gel method, in which tetraethoxysilane is hydrolyzed in an acidic or basic atmosphere, can be employed.

[0044] The agglomeration process is performed after the coating process and involves heating the coated particles obtained in the coating process to cause agglomeration. This process forms aggregates. The coated particles correspond to the primary particles of the aggregates. The resulting aggregates can be subjected to grinding or classification operations to achieve the desired particle size distribution. The heating temperature in the agglomeration process is the temperature at which dehydration condensation and softening occur between the coated particles. Examples include temperatures above 250°C, above 450°C, and above 500°C. Heating within this temperature range can improve the strength of the resulting particle material.

[0045] The modification step is performed after the coating step and involves modifying the coated particles obtained in the coating step by bringing a silane compound into contact with the surface. When combined with the aggregation step, it can be performed either before or after the modification step.

[0046] (Dental materials) The dental material of this embodiment comprises the above-described particle material and a transparent resin material that disperses the particle material. The content of the particle material is 10% to 80% of the total volume.

[0047] As the particle materials that can be used are as described above, further explanation will be omitted. Transparent resin materials can be selected from ordinary resin materials such as thermoplastic resins and thermosetting resins. Examples include acrylic acid or acrylic acid esters and their derivatives, epoxy resins, polyimide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, vinyl chloride, polypropylene, and polyethylene. The concept of transparent resin materials includes not only polymer materials but also precursors such as monomers before polymerization.

[0048] The method for dispersing the particulate material in the transparent resin material is not particularly limited. For example, when a thermoplastic resin is used as the transparent resin material, a transparent resin composition can be obtained by mixing and kneading the heated and melted transparent resin material with the particulate material, or by mixing a precursor of the transparent resin material (transparent resin precursor material: monomer, prepolymer, etc.) with the particulate material and then carrying out a polymerization reaction. When the transparent resin material is a thermosetting resin, it can be cured after mixing the transparent resin precursor and the particulate material. Note that a mixture of the transparent resin precursor and the particulate material before polymerization is also included in the dental material of this embodiment. By using a photopolymerizable material as the transparent resin precursor material, a photopolymerizable transparent resin composition can be provided. The resin composition after polymerization can be expected to have high transparency, a low coefficient of thermal expansion (CTE), and a high modulus of elasticity. [Examples]

[0049] The particle material of the present invention will be described in detail below based on the following examples. First, the manufacturing of the fillers used in the test will be described. Fillers 1 to 8 are the particle material of the present invention (examples), and fillers 9 to 17 are Book This is a particle material that deviates from the invention (a comparative example).

[0050] (Sample preparation) · Filler 1 300g of isopropyl alcohol (IPA) and 50g of tetraethoxysilane (Colcoat Co., Ltd.: Ethyl Silicate 28) were mixed, then 500g of zirconium sol (particle size 14nm, solid content 20%, Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was added and stirred, and then left to stand at 44°C for 72 hours (dispersion step, coating step).

[0051] Subsequently, 2150g of Snowtex OS (colloidal silica acidic sol, particle size 9nm, solid content 20% by mass: Nissan Chemical Corporation) was added, stirred, and allowed to stand at 44°C for 24 hours. 5% aqueous ammonia was added to adjust the pH to 8-9. The resulting liquid was a fluid sol (dispersion step). The resulting sol was dried in a hot air dryer at 140°C for 14 hours (aggregation step).

[0052] The dried material was adjusted using a mixer and a dry jet mill so that the D50 was 2 μm (particle size distribution adjustment process) (it was in a crushed shape; Figure 1), and then calcined in an electric furnace at 1010°C for 6 hours (calcination process). The BET specific surface area of ​​the powder obtained by calcination was 102 m². 2 It was / g.

[0053] Ten parts by mass of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM503) were added to the powder obtained by calcination and stirred with a mixer to uniformly adhere it to the surface of the calcined powder. Note that the filler shown in this example 1 is , 3-methacryloxypropyltrimethoxysilane on a surface area of ​​1 m² 2A reaction of 4 μmol was carried out. After that, the mixture was left to stand at 44°C for 24 hours, and then dried in a hot air dryer at 105°C for 6 hours to obtain Filler 1, the test sample for this experiment (modification step). The obtained Filler 1 is an aggregate in which coated particles, in which core particles made of zirconia are coated with silica, and silica particles (corresponding to coated particles in which silica is used as the core particle and coated with silica) are aggregated and sintered, and 3-methacryloxypropyl groups are introduced to the surface. The introduction of 3-methacryloxypropyl groups is to increase the affinity with the adjusted resin described later, and the type of functional group that is preferable to introduce differs depending on the type of resin to be mixed, and should be appropriately selected.

[0054] · Filler 2 The calcination process involved using an electric furnace to calcinate the powder at 1020°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 63 m²). 2 Filler 2, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 6 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0055] · Filler 3 The calcination process involved calcining in an electric furnace at 1040°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 25 m²). 2 Filler 3, the test sample for this study, was obtained using the same process as for Filler 1, except that 3 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0056] · Filler 4 The calcination process involved using an electric furnace to calcinate the powder at 850°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 159 m²). 2 Filler 4, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 16 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step.

[0057] • Filler 5 The dispersion process involved using 1525g of Snowtex OS, and the calcination process involved calcining in an electric furnace at 850°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 155m²). 2 Filler 5, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 15 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step.

[0058] · Filler 6 The dispersion process involved using 2750g of Snowtex OS, and the calcination process involved calcining in an electric furnace at 1010°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 47m²). 2 Filler 6, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 5 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0059] · Filler 7 The dispersion process involved using 3660g of Snowtex OS, and the calcination process involved calcining in an electric furnace at 1010°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 43m²). 2 Filler 7 for this test was obtained using the same process as for Filler 1, except that 4 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0060] · Filler 8 The dispersion process involved using 415g of Snowtex OS, and the calcination process involved calcining in an electric furnace at 850°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 150m²). 2 Filler 8, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 15 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step.

[0061] · Filler 9 The calcination process involved firing in an electric furnace at 1080°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 12 m²). 2 Filler 9, the test sample for this test, was obtained using the same procedure as for Filler 1, except that 1 part by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step.

[0062] · Filler 10 In the dispersion and coating processes, the amount of tetraethoxysilane was 105 g, and zirconia sol was replaced with 500 g of aluminum sol 10A (particle size 10 nm, solid content 10% by mass, manufactured by Kawaken Fine Chemicals Co., Ltd., crystal form: pseudo-boehmite). In the dispersion process, the amount of Snowtex OS was 500 g. In the calcination process, calcination was performed using an electric furnace at 1090°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 100 m²). 2 Filler 10, the test sample for this test, was obtained using the same procedure as for Filler 1, except that 10 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step.

[0063] · Filler 11 The calcination process involved using an electric furnace to calcinate the powder at 1100°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 50 m²). 2 Filler 11 for this test was obtained using the same process as for filler 10, except that 5 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0064] • Filler 12 100 parts by mass of silica particulate material (volume average particle size 2 μm, manufactured by Admatex Co., Ltd., SO-C6) was mixed with 0.4 parts by mass of 3-methacryloxypropyltrimethoxysilane and stirred with a mixer. After standing at 25°C for 72 hours, the mixture was dried in a hot air dryer at 105°C for 6 hours to obtain surface-treated filler 12.

[0065] · Filler 13 100 parts by mass of hydrophilic fumed silica (AEROSIL200, manufactured by Nippon Aerosil Co., Ltd.) was mixed with 20 parts by mass of 3-methacryloxypropyltrimethoxysilane and stirred with a mixer. After standing at 25°C for 72 hours, the mixture was dried in a hot air dryer at 105°C for 6 hours to obtain surface-treated filler 13.

[0066] • Filler 14 In the dispersion and coating processes, zirconia sol with a particle size of 14 nm was converted to zirconia sol with a particle size of 25 nm (particle size 25 nm, solid content 20%, Daiichi Kigenso Kagaku Kogyo Co., Ltd.). In the calcination process, the material was calcined in an electric furnace at 850°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 243 m²). 2 Filler 14 for this test was obtained using the same procedure as for Filler 1, except that 24 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0067] • Filler 15 In the dispersion and coating processes, zirconia sol with a particle size of 14 nm was converted to zirconia sol with a particle size of 25 nm (particle size 25 nm, solid content 20%, Daiichi Kigenso Kagaku Kogyo Co., Ltd.). In the calcination process, the mixture was calcined in an electric furnace at 1020°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 68 m²). 2 Filler 15, the test sample for this study, was obtained using the same procedure as for Filler 1, except that 7 parts by mass of 3-methacryloxypropyltrimethoxysilane were added to the calcined powder as a modification step.

[0068] • Filler 16 In the dispersion and coating processes, 1000g of isopropyl alcohol and 1500g of tetraethoxysilane were used, Snowtex OS was not added, and the calcination process involved calcination in an electric furnace at 850°C for 6 hours (the BET specific surface area of ​​the powder obtained by calcination was 2m²). 2Filler 16, the test sample for this test, was obtained using the same process as for Filler 1, except that 0.2 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step. As a result, a particle material was obtained that did not contain primary particles (secondary primary particles) made of silica.

[0069] · Filler 17 After mixing 100g of deionized water and 100g of Snowtex OS, 75g of zirconyl nitrate solution (20% solids, Taiyo Kogyo Co., Ltd.) was added and stirred, then 152g of 1% aqueous ammonia was added and left to stand at room temperature for 72 hours (dispersion step, coating step).

[0070] Subsequently, 230g of Snowtex OS was added, stirred, and allowed to stand at 44°C for 24 hours. 5% aqueous ammonia was added to adjust the pH to 8-9. The resulting liquid was a fluid sol (dispersion step). The resulting sol was dried in a hot air dryer at 140°C for 14 hours (aggregation step). From this point onward, the process was the same as for filler 1, except that 19 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the calcined powder as a modification step, to obtain filler 17, the test sample for this experiment. As a result, a particulate material was obtained that did not contain zirconia (corresponding to a heavy element) as primary particles (first-order particles). (Flaxseed oil absorption and specific surface area) Each test sample was weighed out in quantities of 5-10 g and measured. Linseed oil was added in small amounts while the mixture was heated at 2000 rpm and atmospheric pressure for 1 minute using a foam remover / mixer, followed by 2000 rpm and 7.5 kPa for 1 minute. This process was repeated until the mixture became paste-like, and the amount of linseed oil absorbed was calculated using the following formula based on the amount of linseed oil required just before it became paste-like. Specific gravity was 2.38 g / cm³ (silica). 3 Zirconia 6.00g / cm³ 3 Alumina 3.36 g / cm³ 3 The values ​​used were calculated according to the composition ratio using [a specific method]. The specific surface area was measured by the BET method using nitrogen gas. (Amount of linseed oil absorbed [g / 100g]) = (Total mass of added linseed oil) / (Mass of filler used) × 100 (Flaxseed oil absorption [g / 100cm 3])=(linseed oil absorption amount [g / 100g])×specific gravity [g / cm 3 ], (Flaxseed oil absorption [g / m 2 ]) = (Linseed oil absorption amount [g / 100g]) / (Specific surface area [m²] 2 / g] × 100), (abrasive) Using a foam remover, 10g of each test sample and 10g of the prepared resin were mixed by first running the mixture at 2000 rpm and atmospheric pressure for 1 minute, and then at 2000 rpm and 3kPa for 3 minutes. The resulting slurry-like resin composition was poured into a 2.6cm square, 6mm high mold and cured in a UV oven. Filler 10 and 13 The slurry-like resin composition is prepared Made I couldn't do it.

[0071] The resulting hardened material was polished for 2 minutes using #400 grit sandpaper on a pressure polishing machine (Marutoh, Doctor-lap) under the following conditions: LOAD ADJUST 0.35, BALANCER 0.35, HEAD SPEED 3.2, SPEED 20.

[0072] Afterward, polishing was performed under the same conditions, except that the abrasive paper was replaced with #2000 grit. The sample was checked every 10 seconds, and the time until gloss was observed across the entire polished surface was measured.

[0073] The prepared resin was a mixture of 60 parts by mass of urethane dimethacrylate (SigmaAldrich), 40 parts by mass of triethylene glycol dimethacrylate (Shin Nakamura Chemical Industry Co., Ltd.), 0.3 parts by mass of camphorquinone (SigmaAldrich), and 1 part by mass of ethyl 4-dimethylaminobenzoate (Tokyo Chemical Industries, Ltd.). (Refractive index and light transmittance) The refractive index and light transmittance are measured using the method described in the embodiment. Below, the above procedure will be specifically explained using a filler adjusted to a refractive index of 1.51 as an example.

[0074] Since the filler adjusted to a refractive index of 1.51 exhibits the highest transparency when immersed in a test solution with a refractive index of 1.51, test solutions with refractive indices around 1.51, specifically 0.005 and 0.010, were prepared using cyclohexane, toluene, and bromonaphthalene, respectively.

[0075] 0.1 g of the test sample was placed in 2 mL of this test solution and inserted into a 15 mm diameter hole. The optical density (OD value) in the vertical direction was measured at a wavelength of 589 nm. The OD value and refractive index in each test solution were plotted, approximated as a quadratic curve, and the light transmittance was calculated from the OD value at the peak of the curve (the point with the lowest OD value). (result) Refractive index, specific surface area, linseed oil absorption capacity, zirconium ( atomic number Table 1 shows the content ratio of 38 or more elements, zirconia content (calculated as Zr element only), light transmittance, and polishability.

[0076] [Table 1] As is clear from Table 1, the unit volume (100 cm³) 3 It was found that fillers 10 and 13, which absorb more than 200g of linseed oil per unit area, did not form a slurry when mixed with the adjusted resin in a 1:1 mass ratio and could not adequately fill the resin material. 2 When examining the polishability of fillers 9 and 12, which absorb more than 0.02g of linseed oil per unit area, it was found that filler 9 required 120 seconds, a longer time than the other fillers, to produce a gloss, while filler 12 did not produce a gloss through polishing.

[0077] Fillers 1, 2, 3, 4, and 9 were manufactured using almost identical procedures, except for variations in the firing temperature. It was found that increasing the firing temperature resulted in a decrease in specific surface area. This decrease in specific surface area led to a higher linseed oil absorption rate per unit surface area, reaching 0.02 g / m². 2It was found that when filler 9 exceeds a certain value, the light transmittance decreases and the polishability also decreases.

[0078] Fillers 14 and 15 were manufactured using the same procedure as fillers 1 and 2, except that the primary zirconia particles in the aggregated particles were 25 nm in size. It was found that transparency decreased significantly when the primary particle size exceeded 20 nm.

[0079] It was found that filler 16 lacks silica as a secondary particle, and filler 17 lacks zirconia as a primary particle, resulting in a significant decrease in transparency and polishability.

Claims

1. An aggregate composed of primary particles having a volume-average particle size of 1 nm to 20 nm and containing two or more metal elements, with a silica surface, Some of the primary particles have a core particle containing a heavy element with atomic number 38 or higher as a metal oxide, and a coating layer made of silica. At least a portion of the remainder of the primary particles is composed of silica particles. Specific surface area is 180 m² ２ / g or less, Unit volume (100 cm³) ３ ) The amount of flaxseed oil absorbed per unit is 200g or less. Unit surface area (m²) ２ ) The amount of linseed oil absorbed per unit is 0.02g or less, and the light transmittance is more than 20%. The mass of the aforementioned heavy element is between 4% and 60% of the total mass. particle material.

2. The volume-average particle size is 0.1 μm to 10 μm. The primary particles are bonded together by dehydration condensation or fused together. The particle material according to claim 1.

3. The particle material according to claim 1, comprising an inorganic particle material having a volume-average particle size of 1 nm to 200 nm and dispersed down to primary particles.

4. The inorganic particle material has a functional group represented by the formula (1): -OSiX １ X ２ X ３ and a functional group represented by the formula (2): -OSiY １ Y ２ Y ３ bonded to the surface of the silica particles. (In the above formulas (1) and (2); X1 is a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group; X ２ and X ３ are each independently selected from -OSiR ３ and -OSiY ４ Y ５ Y ６ ; Y １ is R; Y ２ and Y ３ are each independently selected from R and -OSiY ４ Y ５ Y ６ ; Y ４ is R; Y ５ and Y ６ are each independently selected from R and -OSiR ３ ; R is independently selected from alkyl groups having 1 to 3 carbon atoms. Note that any one of X ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ may be bonded to -O- of any one of the adjacent functional groups X ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ .)

5. The particle material according to claim 1, which is dispersed in a transparent resin material and used in dental materials.

6. The particle material according to claim 5, wherein the difference in refractive index with respect to the transparent resin material is -0.01 to 0.

01.

7. A particle material according to any one of claims 1 to 6, A transparent resin material in which the aforementioned particle material is dispersed, It has, A dental material in which the content of the aforementioned particulate material is 10% to 80% based on the total volume.

8. A method for producing a particle material according to any one of claims 1 to 6, A dispersion step of dispersing the heavy element particle material in a liquid dispersion medium to form a dispersion, A coating step is to add a silica precursor to the dispersion and coat the surface of the heavy element particle material with silica to form coated particles. A coagulation step in which the coated particles are heated and coagulated, A method for producing particle materials having the following characteristics.

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