Particulate material, dental material, and method for producing particulate material

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

Particulate materials and dental materials

[0001] The present invention relates to a particulate material and a dental material using the particulate material.

[0002] Conventional dental materials commonly use resin compositions called composite resins, which contain inorganic particulate materials dispersed in a resin material (see, for example, Patent Document 1). Pre-hardened materials such as monomers are used as the resin material. Composite resins are polymerized and hardened by filling a missing tooth site with the resin and then irradiating it with external energy such as light. The present applicant has provided a filler to be filled into resin compositions that can be used for dental purposes.

[0003] Japanese Patent Application Publication No. 2021-155399 Japanese Patent Application Publication No. 2021-172577

[0004] Resin compositions that can be used in dental applications are applications that require aesthetics. For example, dental resin compositions are required to have high strength and excellent appearance, such as gloss when polished (hereinafter referred to as "polishability"). The inventors of the present application believed that the filler disclosed in Patent Document 2 did not achieve both polishability and filling ability. As a result of extensive research, they discovered that in order to achieve both strength and polishability, it is necessary to limit the upper limit of the specific surface area so that a large amount of filler can be filled, and to reduce the linseed oil absorption per surface area, thereby improving polishability.

[0005] Furthermore, when used as a dental material, imparting X-ray contrast 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. Metal oxides (such as zirconia) with X-ray contrast have a high refractive index, and simply adding them as a filler does not easily adjust the refractive index to around 1.50. Furthermore, adding them while maintaining the refractive index does not provide sufficient X-ray contrast. Furthermore, the exposure of metal oxides with X-ray contrast on the surface raises concerns about deterioration in polishability, reactivity with silane coupling agents, and stability.

[0006] The present invention was completed in view of the above circumstances, and an object to be achieved is to provide a particulate material that can be used as a filler in dental materials, and a dental material that uses the particulate material.

[0007] The particulate material of the present invention, which solves the above-mentioned 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 has a surface made of silica, wherein a portion of the primary particles contains a heavy element having an atomic number of 38 or more as a metal oxide, and at least a portion of the remainder of the primary particles are particles made of silica, and the specific surface area is 180 m ２ / g or less, unit volume (100 cm ３ ) linseed oil absorption per unit surface area (m ２ ) the linseed oil absorption per unit weight is 0.02 g or less, the light transmittance is more than 20%, and the mass of the heavy elements is 4% to 60% based on the total mass.

[0008] By using aggregates, it is possible to improve strength while achieving optical performance close to that of small particle sizes. Because the surface of the aggregate is made of silica, it is possible to introduce any functional group onto the surface by using a silane coupling agent, etc., and it is also possible to suppress the exposure of heavy elements, etc. to the surface.

[0009] The particulate material of the present invention having the above-mentioned configuration can achieve both polishing properties and filling properties when used in dental materials.

[0010] 1 is a SEM photograph of Filler 1 in an example.

[0011] The particulate material of the present invention and a dental material using the particulate material are described in detail below based on the following embodiments. The particulate material of this embodiment can provide a resin composition with high translucency by dispersing it in a transparent resin material. Resin compositions with high translucency are suitable for use in dental materials such as denture materials and dental filling materials. (Particle Material) The particulate material of this embodiment 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, with the surface composed of silica. A portion of the primary particles (hereinafter referred to as "first primary particles") contains a heavy element with an atomic number of 38 or higher as a metal oxide. At least a portion of the remaining 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 optionally other primary particles (hereinafter referred to as "other primary particles").

[0012] The particulate material is preferably an aggregate formed by combining or fusing the above-mentioned multiple types of primary particles together through dehydration condensation. OH groups exist on the surface of the metal oxide constituting the primary particles, and dehydration condensation occurs between adjacent primary particles, or the metal oxide melts and fuses.

[0013] The particle size of the aggregate is not particularly limited. The primary particles are bonded and fused together, which results in a strong bond between the primary particles and improves the mechanical strength of the particulate material. The shape of the aggregate is not particularly limited, but a crushed shape is preferred. A crushed shape refers to a shape with a surface formed by crushing, and refers to an angular surface shape when observed with an SEM, as shown in Figure 1, for example. By adopting a crushed shape, physical properties such as bending strength can be improved when the aggregate is used in a resin composition.

[0014] The volume average particle size of the aggregates is preferably 0.1 μm or more and 10 μm or less, with examples of lower limits being 0.2 μm, 0.3 μm, 0.5 μm, and 1.0 μm, and examples of upper limits being 8.0 μm, 5.0 μm, and 3.0 μm. These lower and upper limits can be arbitrarily combined. When the particle size of the aggregates is in the range equal to or greater than the above-mentioned lower limit, strength is improved when applied to a resin composition. Furthermore, when the particle size is in the range equal to or less than the above-mentioned upper limit, the particulate material can be properly dispersed in the resin material, etc. Note that by mixing large and small particle size aggregates as individual aggregates, the filling rate at which the aggregates can be filled into the resin composition can be improved.

[0015] The specific surface area of ​​the aggregate is 180 m ２ / g or less. In particular, the upper limit is 160m ２ / g, 150m ２ / g, 130m ２ / g, 100m ２ / g can be exemplified, with a lower limit of 10m ２ / g, 15m ２ / g, 20m ２ / g, 30m ２ / g is an example. 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] The volume average diameter of the primary particles constituting the aggregates can be exemplified by lower limits of 3 nm, 5 nm, 9 nm, 11 nm, and 14 nm, and upper limits of 18 nm and 16 nm. These lower and upper limits can be combined arbitrarily. Furthermore, it is also possible to set a volume average diameter range independently for each of the first primary particles, the second primary particles, and the other primary particles. The volume average diameter of the primary particles of the aggregated particles can be measured by embedding the aggregated particles in a resin, polishing and ion milling the aggregated particle cross section, and then performing SEM or TEM observation and image analysis.

[0017] The metal element contained in the primary particles is not particularly limited, but is preferably one whose oxide has high stability. Examples include aluminum, zirconium, titanium, and silicon, which can form oxides that are particularly stable against moisture. Two or more metal elements can exist within the aggregates as a single metal oxide or as a composite oxide of two or more metal elements.

[0018] These two metal elements can be contained as a single compound in each of the primary particles constituting the aggregate to aggregate primary particles having a plurality of compositions, and it is also possible to contain a plurality of metal elements or a plurality of compounds in one primary particle.

[0019] The first primary particles contain a heavy element. The heavy element is an element with an atomic number of 38 or higher, and is preferably selected from the group consisting of zirconium, barium, and titanium, although not limited thereto. The first primary particles may contain the heavy element and other metal elements, such as those mentioned above, in the form of a composite oxide or the like within the same particle. The content of the heavy element is 4% or more and 60% or less based on the total mass of the particle material, with lower limits of 5%, 7%, 10%, and 14% being acceptable, and upper limits of 55%, 50%, 40%, and 30% being acceptable. These lower and upper limits can be combined in any desired manner.

[0020] The second primary particles contain silica, which improves the abrasiveness when applied to a resin composition. Here, "composed of silica" means that the second primary particles are composed of 80% or more by mass of silica, preferably 90% or more, more preferably 95% or more, even more preferably 99%, and particularly preferably 100% (excluding inevitable impurities).

[0021] The second primary particles may have an upper limit of about 95%, 90%, or 85% and a lower limit of about 50%, 30%, 20%, or 10% based on the total mass. These upper and lower limits can be combined in any way.

[0022] Furthermore, primary particles composed of a compound of an element other than the metal element to be contained may also be contained. The element other than the metal element may be contained 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 the metal element is contained in an amount of 50 mass% or more, preferably 70% or more, and more preferably 90% or more.

[0023] Particles that do not contain heavy elements and are not composed of silica may be contained as other primary particles, such as those containing metal elements as described above.

[0024] Metal elements may exist as metal oxides or may contain nitrides, carbides, etc. Specific internal compositions include aluminum oxide, zirconia, titania, silica, and composite oxides thereof. Examples of aluminum oxide include gamma alumina and boehmite.

[0025] The surface of the aggregate is composed of silica. That is, the first primary particles (and other primary particles, if any) are used as the interior (appropriately referred to as the "core"), and the surfaces of these primary particles are coated with silica. The silica coating can be performed after the aggregate is formed, or the primary particles can be coated.

[0026] Here, the expression "the surface of the aggregate is composed of silica" means that the lower limit of the area of ​​the portion of the surface of the aggregate that is covered with silica (hereinafter, sometimes referred to as "silica portion" or "coating layer") is 50% or more, preferably 70%, 75%, 80%, 85%, 90%, 95%, or 99%, and more preferably completely covered with silica (100%).

[0027] To cover the surface with silica without exposing it to light, 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 condensation of tetraethoxysilane. On the other hand, if the silica coating layer with the amount of silica required to produce a filler with a refractive index suitable for dental materials is formed only with the above-mentioned chemically bonded layer, the bonds between the silica coating layers will be strong, resulting in poor polishability and poor transparency. The area of ​​the silica-covered portion can be calculated by directly measuring the silica through direct observation with an electron microscope, or indirectly by measuring the amount of metal elements other than silica.

[0028] The particulate material preferably has a light transmittance of 20% or more, more preferably 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 whose refractive index was adjusted in 0.005 increments. The OD values ​​were measured for five test solutions: the test solution with the highest visual transparency (the refractive index of this test solution was designated the refractive index of the test sample), and test solutions with refractive indices 0.005, 0.01, and 5. The refractive indexes of the obtained test solutions and their OD values ​​in the test solutions were plotted, and the light transmittance was calculated from the OD value at the apex of a quadratic curve approximated by a quadratic curve. The OD value was measured using a sample suspension (0.1 g of test sample suspended in 2 mL of test solution) in a 15 mm diameter hole using light with a wavelength of 589 nm.

[0030] The silica covering the surface is SiO ２ When converted to the total mass of the particulate material, the lower limit can be 40%, 50%, or 60%, and the upper limit can be 95%, 90%, or 85%. 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 aggregates. The thickness of the coating layer is not particularly limited, but it is preferable to coat the surface of the aggregates with almost no gaps. When a coating layer is present, it can be formed by coating the surfaces of the aggregated primary particles, resulting in direct aggregation of the primary particles (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 surfaces of the primary particles and then aggregated to form aggregates). The coating layer is preferably either covalently bonded to the surface of the primary particles or physically bonded via intermolecular bonding or the like. The silica coating layer can suppress surface exposure of highly active zirconia, thereby suppressing deterioration of the resin when dispersed in a resin and used, and suppressing changes over time in the organic components of the surface modification. The organic substance constituting the coating layer is preferably a condensation product of a silane compound. If the silane compound is a compound having two or more SiOR groups, a coating layer composed of the condensation product can be formed. The silane compound condensate can be produced by condensing the silane compound in contact with the surfaces of primary particles (before or after forming aggregates). Primary particles are typically made of inorganic materials and have OH groups on their surfaces. Therefore, the silane compound can react with the OH groups present on the surfaces of the primary particles to form covalent bonds.

[0032] A functional group may be introduced onto the surface of the silica portion. There are no particular limitations on the type of functional group to be introduced, but when dispersing in a resin material, it is preferable to introduce a functional group that has a high affinity with the resin material. For example, when acrylic acid and its esters, methacrylic acid and its esters, or epoxy resins are used as the resin material, introducing an acrylic group, a methacrylic group, an epoxy group, or the like can react with the resin material to form a strong bond.

[0033] The surface of the silica portion is provided with a compound represented by the formula (1): -OSiX １ X ２ X ３ and a functional group represented by formula (2): -OSiY１ Y ２ Y ３ In the formulas (1) and (2), X1 is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acryl group; ２ , X ３ Ha-OSiR ３ and -OSiY ４ Y ５ Y ６ are each independently selected from the group consisting of: Y １ is R; Y ２ , Y ３ is R and -OSiY ４ Y ５ Y ６ are independently selected from the following: ４ is R; Y ５ and Y ６ is R and -OSiR ３ and R is independently selected from alkyl groups having 1 to 3 carbon atoms. ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ Any of the adjacent functional groups X ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ may be bonded to either of the above via —O—.

[0034] The refractive index of the particulate material can be controlled by adjusting the ratio of the silica portion to the amount of 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), the difference in refractive index between the particulate material and the transparent resin material employed is preferably between -0.1 and 0.1.

[0035] The particulate material is packed into a unit volume (100 cm ３The linseed oil absorption per unit area is 200 g or less, with particular upper limits of 170 g, 160 g, and 150 g being examples. This value can be reduced by increasing the packing rate of the particulate material or improving the sphericity. The unit volume is calculated by multiplying the apparent volume by 1 - porosity.

[0036] The unit surface area (m) calculated from the surface area of ​​the particulate material (measured by the BET method using nitrogen gas) ２ The linseed oil absorption per gram of the powder is 0.02 g or less, and examples of upper limits include 0.018 g, 0.016 g, and 0.014 g. This value can be reduced by increasing the packing density of the particulate material or by improving the sphericity.

[0037] The particulate material may contain an inorganic particulate material having a volume average particle size of 1 nm to 200 nm and dispersed down to primary particles. The inorganic particulate material may be contained in an amount greater than 0% and not greater than 90% based on the total mass of the particulate material. Examples of lower limits for the content of the inorganic particulate material include 2%, 5%, and 10%, and examples of upper limits include 60%, 50%, and 40%. These lower and upper limits can be combined arbitrarily. By containing the inorganic particulate material in the above range, it is possible to reduce the viscosity of the resin composition and improve the toughness of the cured resin containing the inorganic particulate material.

[0038] The inorganic particle material is represented by the formula (1): —OSiX １ X ２ X ３ and a functional group represented by formula (2): -OSiY １ Y ２ Y ３ and a functional group represented by the formula (1) are bonded to the surface of the silica particles. Formulas (1) and (2) are the same as those described above, and therefore description thereof will be omitted. (Method for producing particulate material) The method for producing particulate material of this embodiment is a method that can suitably produce the particulate material described above. The method for producing particulate material of this embodiment includes a dispersion step, a coating step, and other steps that can be selected as necessary. Examples of other steps include an aggregation step, a modification step, and a particle size distribution adjustment step.

[0039] The dispersion process is a process in which particles having the internal composition (core particles: particles corresponding to first primary particles and other primary particles, if present, after passing through the coating process described below) are dispersed in a liquid dispersion medium to form a dispersion. Core particles can be obtained by a conventional method. For example, they can be produced by reacting a compound that serves as a precursor to the internal composition. For example, when zirconia is used as the internal composition, zirconia sol can be used. When boehmite is used, aluminum hydroxide pulverized to an appropriate particle size by milling or the like can be used as a precursor, and core particles made of boehmite can be obtained by hydrothermal treatment.

[0040] Furthermore, aluminum oxide with an appropriate particle size can be used as a precursor and heated in an acid or alkaline aqueous solution to obtain core particles. Colloidal silica can be considered as coated particles in which the surfaces of core particles made entirely of silica are coated with a surface composition made of silica, so adding colloidal silica is also included in the dispersion process. A mixture of multiple materials can be used as the core particles, or core particles made of multiple materials can be added sequentially.

[0041] The coating step is a step in which a precursor, which is a compound that becomes the surface composition (silica) by reaction, is added to the obtained dispersion to generate the surface composition, thereby coating and forming the surface of the core particles with the surface composition, thereby forming coated particles. When silica particles (corresponding to the second primary particles) such as colloidal silica are added in the dispersion step, the colloidal silica acts as coated particles even without the coating step, because it is equivalent to coated particles in which the surface of the core particles made of silica is coated with a surface made of silica.

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

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

[0044] The aggregation process is a process carried out after the coating process, in which the coated particles obtained in the coating process are heated to aggregate. Aggregates are formed in this process. The coated particles correspond to the primary particles of the aggregates. The obtained aggregates can be subjected to pulverization and classification to achieve the required particle size distribution. The heating temperature in the aggregation process is a temperature at which dehydration condensation and softening occur between the coated particles. Examples include temperatures above 250°C, 450°C or higher, and 500°C or higher. Heating within this temperature range can improve the strength of the obtained particulate material.

[0045] The modification step is a step carried out after the coating step, in which a silane compound is brought into contact with the surface of the coated particles obtained by the coating step to modify them. When combined with the aggregation step, the modification step can be carried out either before or after the aggregation step.

[0046] (Dental Material) The dental material of this embodiment includes the above-described particulate material and a transparent resin material that disperses the particulate material. The content of the particulate material is 10% or more and 80% or less by volume of the total material.

[0047] The particle materials that can be used are as described above, and further explanation will be omitted. The transparent resin material 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, polyimides, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, vinyl chloride, polypropylene, and polyethylene. The transparent resin material is a concept that includes not only polymeric 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 a heated and melted transparent resin material with a particulate material, or by mixing a precursor of the transparent resin material (transparent resin precursor material: monomer, prepolymer, etc.) with a particulate material and then polymerizing the mixture. When the transparent resin material is a thermosetting resin, the transparent resin precursor and the particulate material can be mixed and then cured. Note that a mixture of a transparent resin precursor and a 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 polymerized resin composition can be expected to have high transparency, a low coefficient of thermal expansion (CTE), and a high modulus of elasticity.

[0049] The particulate material of the present invention will be described in detail below based on examples. First, the production of the fillers used in the tests will be described. Fillers 1 to 8 are particulate materials of the present invention (Examples), and Fillers 9 to 17 are particulate materials outside the method of the present invention (Comparative Examples).

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

[0051] Thereafter, 2150 g of Snowtex OS (colloidal silica acidic sol, particle size 9 nm, solid content 20% by mass: Nissan Chemical Industries, Ltd.) 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 sol with good fluidity (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 form; see Figure 1), and then calcined in an electric furnace at 1010 °C for 6 hours (calcination process). The BET specific surface area of ​​the calcined powder was 102 m ２ / g.

[0053] 10 parts by mass of 3-methacryloxypropyltrimethoxysilane (KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the powder obtained by firing and stirred with a mixer, thereby uniformly adhering the silane to the surface of the fired powder. Note that Fillers 1 to 11 shown in this example were prepared by adding 3-methacryloxypropyltrimethoxysilane to a powder having a surface area of ​​1 m. ２ 4 μmol per 1000g of zirconia was reacted. The mixture was then left to stand at 44°C for 24 hours, and then dried in a hot air dryer at 105°C for 6 hours to perform a surface treatment, yielding Filler 1, the test sample for this test (modification step). The resulting Filler 1 is an aggregate formed by sintering together coated particles in which zirconia core particles are coated with silica and silica particles (corresponding to coated particles in which silica core particles are coated with silica), with 3-methacryloxypropyl groups introduced onto the surface. The purpose of introducing the 3-methacryloxypropyl groups is to increase affinity with the modifying resin described below, and the type of functional group that is preferably introduced varies depending on the type of resin to be mixed, and is selected appropriately.

[0054] Filler 2: The firing process was carried out at 1020°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 63 m ２ / g), and Filler 2, a test sample for this test, was obtained in the same manner as Filler 1, except that 6 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step.

[0055] Filler 3: The firing process was carried out at 1040°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 25m ２ / g), and 3 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 3 of this test was obtained in the same manner as Filler 1.

[0056] Filler 4: The firing process was carried out at 850°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 159 m ２ / g), and 16 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 4 of this test was obtained in the same manner as Filler 1.

[0057] Filler 5: In the dispersion process, the amount of Snowtex OS was 1525 g, and in the firing process, the powder was fired at 850 ° C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 155 m ２ / g), and 15 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 5 of this test was obtained in the same manner as Filler 1.

[0058] Filler 6: In the dispersion process, the amount of Snowtex OS was 2750 g, and in the firing process, the powder was fired at 1010 ° C. for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 47 m ２ / g), and 5 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 6 of this test was obtained in the same manner as Filler 1.

[0059] Filler 7: In the dispersion process, the amount of Snowtex OS was 3660 g, and in the firing process, the powder was fired at 1010 ° C. for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 43 m ２ / g), and 4 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 7 of this test was obtained in the same manner as Filler 1.

[0060] Filler 8: In the dispersion process, the amount of Snowtex OS was 415 g, and in the firing process, the powder was fired at 850 ° C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 150 m ２ / g), and 15 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 8 of this test was obtained in the same manner as Filler 1.

[0061] Filler 9: The firing process was carried out at 1080°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 12 m ２ / g), and 1 part by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 9 of this test was obtained in the same manner as Filler 1.

[0062] Filler 10: In the dispersion process and coating process, the amount of tetraethoxysilane was 105 g, and zirconia sol was replaced with 500 g of Aluminum Sol 10A (particle diameter 10 nm, solid content 10 mass%, manufactured by Kawaken Fine Chemical Co., Ltd., crystalline form: pseudo-boehmite). In the dispersion process, the amount of Snowtex OS was 500 g. In the firing process, the powder was fired at 1090 ° C. for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 100 m). ２ / g), and 10 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 10 for this test was obtained in the same manner as Filler 1.

[0063] Filler 11: The firing process was carried out at 1100°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 50 m ２ / g), and 5 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 11 for this test was obtained in the same process as Filler 10.

[0064] Filler 12: 0.4 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to 100 parts by mass of a particulate material made of silica (volume average particle size 2 μm, manufactured by Admatechs Co., Ltd., SO-C6), and the mixture was stirred in a mixer. The mixture was then left to stand at 25°C for 72 hours and then dried in a hot air dryer at 105°C for 6 hours to obtain surface-treated Filler 12.

[0065] Filler 13: 20 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to 100 parts by mass of hydrophilic fumed silica (AEROSIL 200, manufactured by Nippon Aerosil Co., Ltd.) and stirred with a mixer. The mixture was then allowed to stand at 25°C for 72 hours and then dried in a hot air dryer at 105°C for 6 hours to obtain surface-treated Filler 13.

[0066] Filler 14: In the dispersion process and coating process, zirconia sol having a particle diameter of 14 nm was replaced with zirconia sol having a particle diameter of 25 nm (particle diameter 25 nm, solid content 20%, Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and in the firing process, the powder was fired at 850°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 243 m). ２ / g), and 24 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 14 of this test was obtained in the same manner as Filler 1.

[0067] Filler 15: In the dispersion process and coating process, zirconia sol with a particle diameter of 14 nm was replaced with zirconia sol with a particle diameter of 25 nm (particle diameter 25 nm, solid content 20%, Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and in the firing process, the powder was fired at 1020°C for 6 hours using an electric furnace (the BET specific surface area of ​​the powder obtained by firing was 68 m). ２ / g), and 7 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification step, and the test sample Filler 15 for this test was obtained in the same manner as Filler 1.

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

[0069] Filler 17: 100 g of ion-exchanged water and 100 g of Snowtex OS were mixed, and then 75 g of a zirconyl nitrate solution (solid content 20%, Taiyo Koko Co., Ltd.) was added and stirred, and then 152 g of 1% ammonia water was added and the mixture was allowed to stand at room temperature for 72 hours (dispersion step, coating step).

[0070] Then, 230 g 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 process). The resulting sol was dried in a hot air dryer at 140°C for 14 hours (aggregation process). From this point on, the test sample Filler 17 for this test was obtained using the same process as Filler 1, except that 19 parts by mass of 3-methacryloxypropyltrimethoxysilane was added to the fired powder as a modification process. As a result, a particulate material was obtained that did not contain zirconia (corresponding to a heavy element) as primary particles (first primary particles). (Linseed oil absorption and specific surface area) 5-10 g of each test sample was weighed out and measured. The mixture was stirred in a foam mixer at 2000 rpm and normal pressure for 1 minute while adding linseed oil little by little, and then at 2000 rpm and 7.5 kPa for 1 minute, and this operation was repeated until the mixture became a paste.The linseed oil absorption was calculated from the amount of linseed oil required just before the mixture became a paste, according to the following formula.The specific gravity was 2.38 g / cm of silica. ３ , zirconia 6.00 g / cm ３ , alumina 3.36 g / cm ３ The specific surface area was measured by the BET method using nitrogen gas. (linseed oil absorption [g / 100g]) = (total mass of added linseed oil) / (mass of filler used) × 100, (linseed oil absorption [g / 100cm ３ ]) = (linseed oil absorption [g / 100g]) x specific gravity [g / cm ３ ], (linseed oil absorption [g / m ２]) = (linseed oil absorption [g / 100g]) / (specific surface area [m ２ / g] × 100), (Abrasiveness) 10 g of each test sample and 10 g of the prepared resin were mixed in a foam mixing mixer at 2000 rpm at normal pressure for 1 minute, and then at 2000 rpm at 3 kPa for 3 minutes. The resulting slurry-like resin composition was poured into a mold measuring 2.6 cm square and 6 mm high, and cured in a UV oven. For Fillers 6 and 9, a slurry-like resin composition could not be prepared.

[0071] The resulting cured product was polished for 2 minutes with #400 polishing paper using a pressure polishing machine (Doctor-lap, manufactured by Maruto) under the polishing conditions of LOAD ADJUST 0.35, BALANCER 0.35, HEAD SPEED 3.2, SPEED 20.

[0072] Thereafter, polishing was carried out under the same polishing conditions except that the polishing paper was replaced with #2000, and the sample was checked every 10 seconds to measure the time until gloss was observed on the entire polished surface.

[0073] The adjusting resin used was a mixture of 60 parts by mass of urethane dimethacrylate (Sigma-Aldrich), 40 parts by mass of triethylene glycol dimethacrylate (Shin-Nakamura Chemical Co., Ltd.), 0.3 parts by mass of camphorquinone (Sigma-Aldrich), and 1 part by mass of ethyl 4-dimethylaminobenzoate (Tokyo Chemical Industry Co., Ltd.). (Refractive Index and Light Transmittance) The refractive index and light transmittance are measured by the methods described in the embodiments. Hereinafter, the above operations will be specifically explained using a filler adjusted to a refractive index of 1.51 as an example.

[0074] The filler adjusted to a refractive index of 1.51 has the highest transparency when immersed in a test liquid with a refractive index of 1.51, so test liquids with refractive indices of around 1.51, 0.005, 0.010, and 1.500, 1.505, 1.510, 1.515, and 1.520 were prepared using cyclohexane, toluene, and bromonaphthalene.

[0075] 0.1 g of test sample was placed in 2 mL of this test solution and placed in a 15 mm diameter hole, and the optical density (OD value) was measured in the vertical direction at a wavelength of 589 nm. The OD value and refractive index in each test solution were plotted and approximated to a quadratic curve, and the light transmittance was calculated from the OD value at the apex (the point with the lowest OD value). (Results) The refractive index, specific surface area, linseed oil absorption, zirconium (element with 38 or more elements) content, zirconia content (converted to simple Zr), light transmittance, and polishability are shown in Table 1.

[0076] As is clear from Table 1, the unit volume (100 cm ３ It was found that Fillers 10 and 13, which have a linseed oil absorption per unit mass (m) of more than 200 g, do not form a slurry even when mixed with the adjusting resin at a mass ratio of 1:1, and are unable to exhibit sufficient filling properties in the resin material. ２ When the polishing properties of Fillers 9 and 12, which have a linseed oil absorption of more than 0.02 g per particle, were examined, it was found that Filler 9 required 120 seconds, which was longer than the other fillers, until gloss appeared, while Filler 12 did not appear glossy after polishing.

[0077] Fillers 1, 2, 3, 4, and 9 were produced by almost the same procedure except that the temperature in the firing process was changed. It was found that the specific surface area decreased as the firing temperature increased. As the specific surface area decreased, the linseed oil absorption per surface area increased to 0.02 g / m. ２ It was found that the filler 9 exceeding this value had a reduced light transmittance and abrasiveness.

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

[0079] Filler 16 is a particle that does not have a silica component as the second primary particle, and filler 17 is a particle that does not have a zirconia component as the first primary particle, and it was found that the transparency and polishability were significantly reduced.

Claims

1. An aggregate of primary particles having a volume average particle size of 1 nm to 20 nm and containing two or more metal elements, the surface of which is made of silica, a portion of the primary particles has a core particle containing a heavy element having an atomic number of 38 or more as a metal oxide and a coating layer made of silica; at least a portion of the remainder of the primary particles are particles composed of silica, Specific surface area is 180m ２ / g or less, Unit volume (100 cm ３ ) Linseed oil absorption per 200g or less, Unit surface area (m ２ ) Linseed oil absorption per unit of paper is 0.02g or less, light transmittance is more than 20%, The mass of the heavy element is 4% to 60% based on the total mass; particle material.

2. A volume average particle size of 0.1 μm to 10 μm, The primary particles are bonded or fused together by dehydration condensation. The particulate material of claim 1 .

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

4. The inorganic particle material is represented by the formula (1): —OSiX １ X ２ X ３ and a functional group represented by formula (2): -OSiY １ Y ２ Y ３ The particle material according to claim 3, wherein a functional group represented by the following formula (1) or (2) is bonded to the surface of the silica particle: X1 is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; and X ２ , X ３ Ha-OSiR ３ and -OSiY ４ Y ５ Y ６ are each independently selected from the group consisting of: Y １ is R; Y ２ , Y ３ is R and -OSiY ４ Y ５ Y ６ are independently selected from the following: ４ is R; Y ５ and Y ６ is R and -OSiR ３ and R is independently selected from alkyl groups having 1 to 3 carbon atoms. ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ Any of the adjacent functional groups X ２ , X ３ , Y ２ , Y ３ , Y ５ , and Y ６ may be bonded to either of the above via —O—.)

5. 2. The particulate material according to claim 1, which is dispersed in a transparent resin material and used as a dental material.

6. 6. The particulate material according to claim 5, wherein the difference in refractive index between the particulate material and the transparent resin material is −0.01 to 0.

01.

7. A particulate material according to any one of claims 1 to 6; a transparent resin material in which the particulate material is dispersed; and The dental material has a content of the particulate material of 10% to 80% based on the total volume.

8. A method for producing a particulate material according to claim 1, comprising: a dispersing step of dispersing the heavy element particle material in a liquid dispersion medium to form a dispersion; a coating step of adding a silica precursor to the dispersion liquid to coat the surfaces of the heavy element particle material with silica to form coated particles; an aggregating step of heating the coated particles to aggregate them; A method for producing a particulate material having the following structure:

Images