Slurry, molded body, and sintered body

Abstract

Provided is slurry which can be sintered at a low temperature in a short time, and with which it is possible to obtain a densified sintered body. This slurry contains a zirconia powder, a glass powder, and a polymerizable monomer.

Description

Slurry, compact, and sintered body

[0001] The present disclosure relates to a slurry, a compact, and a sintered body.

[0002] Known sintering aids for zirconia powder include alumina, silica, aluminum silicate, and transition metal oxides (see, for example, Patent Document 1).

[0003] JP 2015-93813 A

[0004] Conventional zirconia powders require high temperatures and long periods of time for sintering, and the resulting sintered body contains many pores or voids.

[0005] An object of the present invention is to provide a slurry that can be sintered at a low temperature in a short time to obtain a densified sintered body.

[0006] The slurry of the present disclosure includes zirconia powder, glass powder, and a polymerizable monomer.

[0007] According to the present disclosure, it is possible to provide a slurry that can be sintered at a low temperature in a short time, and that can yield a densified sintered body.

[0008] 1A and 1B are SEM photographs of a cross section of a sintered body obtained from the slurry of the present embodiment and a comparative example, respectively.

[0009] Next, an embodiment of the present invention will be described.

[0010] <Slurry> The slurry of this embodiment contains zirconia powder, glass powder, and a polymerizable monomer.

[0011] The zirconia powder is zirconia (ZrO ２ ) granules or powder.

[0012] Zirconia (ZrO ２) is monoclinic at room temperature, but as the temperature increases, the crystal structure undergoes a phase transition to tetragonal and then cubic. This phase transition is accompanied by a change in volume, so repeated temperature increases and decreases can lead to destruction of the sintered body. Therefore, it is preferable to use partially stabilized zirconia, which is made by dissolving rare earth oxides or the like in zirconia as a stabilizer, thereby forming oxygen vacancies in the crystal structure and suppressing destruction due to temperature increases and decreases.

[0013] Such stabilizers include yttria (Y ２ O ３ ), Scandia (Sc ２ O ３ ), calcia (CaO), magnesia (MgO), ceria (CeO ２ ), praseodymium (Pr ２ O ３ ), Neodia (Nd ２ O ３ ), Tria (ThO ２ ), Urania (UO ２ ), titania (TiO ２ ), manganese oxide (MnO ２ ), strontia (SrO), baria (BaO), nickel oxide (NiO), cobalt oxide (Co ２ O ４ ), chromium oxide (Cr ２ O ３ , CrO ３ Among these, yttria (Y ２ O ３ ) is preferred as a stabilizer.

[0014] The content of the stabilizer is not particularly limited, but is preferably 1 mol % to 8 mol %, more preferably 1.5 mol % to 6 mol %, and more preferably 2 mol % to 5 mol % in the zirconia powder. By including 1 mol % to 8 mol % of the stabilizer in the zirconia powder, the resulting zirconia sintered body contains tetragonal zirconia particles and exhibits excellent toughness due to stress-induced phase transition.

[0015] The particle size of the zirconia powder is not particularly limited, but is preferably 0.01 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.9 μm or less, and even more preferably 0.2 μm or more and 0.7 μm or less. Here, particle size refers to the average particle size defined by the median diameter (d50). When the particle size of the zirconia powder is 0.01 μm or more and 1.0 μm or less, the zirconia powder is easily dispersed in the slurry, and a uniform slurry can be obtained.

[0016] The glass powder is glass granules or powder.

[0017] The type of glass is not particularly limited, and examples thereof include lithium silicate glass, lithium disilicate glass, lithium metasilicate glass, strontium glass, strontium boroaluminosilicate glass, strontium fluoroaluminosilicate glass, barium glass, barium boroaluminosilicate glass, barium fluoroaluminosilicate glass, lanthanum glass, lanthanum boroaluminosilicate glass, lanthanum fluoroaluminosilicate glass, zinc silicate glass, zinc borosilicate glass, zinc fluorosilicate glass, zinc borate glass, potassium feldspar glass, soda feldspar glass, aluminum fluoride-zirconium fluoride glass, and zirconium fluoride (ZBLAN: ZrF ４ -BaF2-LaF ３ -AlF ３ -NaF) glass, etc. These may be used alone or in combination of two or more. Among these, lithium disilicate glass, barium glass, and zinc fluorosilicate glass are preferred.

[0018] The particle size of the glass powder is not particularly limited, but is preferably 0.01 μm to 1.0 μm, more preferably 0.1 μm to 0.9 μm, and even more preferably 0.2 μm to 0.7 μm. When the particle size of the glass powder is 0.01 μm to 1.0 μm, the glass powder is easily dispersed in the slurry, and a uniform slurry can be obtained.

[0019] The content of the glass powder in the slurry is not particularly limited, but is preferably 0.01% by mass to 5% by mass, more preferably 0.05% by mass to 3% by mass, and even more preferably 0.08% by mass to 1% by mass. By including 0.01% by mass to 5% by mass of glass powder in the slurry, the sintered body can be efficiently densified during sintering of the slurry.

[0020] The glass powder further contains silicon dioxide (SiO ２ Silicon dioxide may be present in the glass powder as a glass compound or as a glass solid solution.

[0021] The content of silicon dioxide in the glass powder is not particularly limited, but is preferably 10% by mass or more and 85% by mass or less, more preferably 15% by mass or more and 80% by mass or less, and even more preferably 20% by mass or more and 75% by mass or less. When glass powder having a silicon dioxide content of 10% by mass or more and 85% by mass or less is contained in the slurry, densification of the sintered body during sintering of the slurry can be promoted.

[0022] The polymerizable monomer is a compound that is polymerized and hardened by heat or light.

[0023] The polymerizable monomer is not particularly limited, and various polymerizable monomers used in the dental field, etc. can be used. Among them, radical polymerizable monomers can be used. The polymerizable monomer may have one functional group or two or more functional groups.

[0024] The specific substance of the polymerizable monomer is not particularly limited, but examples thereof include esters of α-cyanoacrylic acid, (meth)acrylic acid, α-haloacrylic acid, crotonic acid, cinnamic acid, sorbic acid, maleic acid, itaconic acid, etc., (meth)acrylamide, (meth)acrylamide derivatives, vinyl esters, vinyl ethers, mono-N-vinyl derivatives, styrene derivatives, etc. These polymerizable monomers may be used alone or in combination of two or more. Among them, (meth)acrylic acid esters and (meth)acrylamide derivatives can be used, and (meth)acrylic acid esters are preferably used.

[0025] Here, the (meth)acrylic acid ester refers to an acrylic acid ester (hereinafter sometimes referred to as an acrylate) or a methacrylic acid ester (hereinafter sometimes referred to as a methacrylate), and the (meth)acrylamide refers to an acrylamide or a methacrylamide.

[0026] Examples of monofunctional (meth)acrylic acid esters include methyl (meth)acrylate, isobutyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, 2,3-dibromopropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, propylene glycol mono(meth)acrylate, glycerin mono(meth)acrylate, and erythritol mono(meth)acrylate.

[0027] Examples of the monofunctional (meth)acrylamide derivatives include N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-(dihydroxyethyl) (meth)acrylamide, (meth)acryloyloxydodecylpyridinium bromide, (meth)acryloyloxydodecylpyridinium chloride, (meth)acryloyloxyhexadecylpyridinium chloride, and (meth)acryloyloxydecylammonium chloride.

[0028] Examples of the difunctional (meth)acrylic acid ester include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2,2-bis[4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl]propane, 2,2-bis[4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl]propane, and 2,2-bis[4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl]propane. Examples of such acrylates include [4-(2-(meth)acryloyloxyethoxy)phenyl]propane, 2,2-bis[4-(meth)acryloyloxypolyethoxyphenyl]propane, 1,2-bis[3-(meth)acryloyloxy-2-hydroxypropoxy]ethane, pentaerythritol di(meth)acrylate, [2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)]di(meth)acrylate, and ethoxylated bisphenol A di(meth)acrylate.

[0029] Examples of tri- or higher functional (meth)acrylic acid esters include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, N,N'-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetramethacrylate, and 1,7-diacryloyloxy-2,2,6,6-tetraacryloyloxymethyl-4-oxyheptane.

[0030] Of these, the (meth)acrylic acid ester is preferably a bifunctional (meth)acrylic acid ester, more preferably neopentyl glycol di(meth)acrylate or ethoxylated bisphenol A di(meth)acrylate, and even more preferably neopentyl glycol diacrylate or ethoxylated bisphenol A diacrylate.

[0031] The content of the polymerizable monomer in the slurry is not particularly limited, but is preferably 2% by mass to 40% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 10% by mass to 20% by mass. When the content of the polymerizable monomer is 2% by mass to 40% by mass, the kneadability of the slurry is improved, and the sintered body obtained by sintering or firing the slurry can maintain high mechanical strength.

[0032] The slurry of the present disclosure may contain other components as long as the components do not impair the object of the present invention. Examples of other components contained in the slurry include a polymerization initiator, a polymerization inhibitor, a plasticizer, a dispersant, a filler (excluding zirconia powder and glass powder), a colorant, and a fluorescent agent.

[0033] Examples of the polymerization initiator include a chemical polymerization initiator and a photopolymerization initiator.

[0034] The chemical polymerization initiator is not particularly limited, and for example, a thiourea derivative, a vanadium compound, a tertiary amine, or an organic peroxide can be used.

[0035] Thiourea derivatives function as reducing agents among chemical polymerization initiators.

[0036] The thiourea derivative is not particularly limited, and examples thereof include ethylene thiourea, N-methyl thiourea, N-ethyl thiourea, N-propyl thiourea, N-butyl thiourea, N-lauryl thiourea, N-phenyl thiourea, N-cyclohexyl thiourea, N,N-dimethyl thiourea, N,N-diethyl thiourea, N,N-dipropyl thiourea, N,N-dibutyl thiourea, N,N-dilauryl thiourea, N,N-diphenyl thiourea, N,N-dicyclohexyl thiourea, trimethyl thiourea, tetramethyl thiourea, N-acetyl thiourea, N-benzoyl thiourea, 1-allyl-3-(2-hydroxyethyl)-2-thiourea, 1-(2-tetrahydrofurfuryl)-2-thiourea, N-tert-butyl-N'-isopropyl thiourea, and 2-pyridyl thiourea. Among these, N-benzoylthiourea is preferred in terms of improving the curability of the slurry.

[0037] The vanadium compound functions as a reducing agent among chemical polymerization initiators.

[0038] The vanadium compound is not particularly limited, and examples thereof include oxovanadium oxalate, vanadyl acetylacetonate, vanadium acetylacetonate, vanadyl stearate, vanadium naphthenate, vanadium benzoylacetonate, etc. Among these, vanadyl acetylacetonate is preferred in terms of improving the curability of the slurry.

[0039] Among chemical polymerization initiators, tertiary amines function as reducing agents. The tertiary amine is not particularly limited, and examples thereof include tertiary aliphatic amines and tertiary aromatic amines.

[0040] Examples of tertiary aliphatic amines include N,N-dimethylaminoethyl methacrylate and triethanolamine.

[0041] Examples of tertiary aromatic amines include alkyl p-dialkylaminobenzoates, 7-dimethylamino-4-methylcoumarin, N,N-dimethylaniline, N,N-dibenzylaniline, N,N-dimethyl-p-toluidine, N,N-diethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine, N,N,2,4,6-pentamethylaniline, N,N,2,4-tetramethylaniline, N,N-diethyl-2,4,6-trimethylaniline, etc. Among these, the tertiary amine is preferably a tertiary aromatic amine, and more preferably an alkyl p-dialkylaminobenzoate.

[0042] Examples of alkyl p-dialkylaminobenzoates include methyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, propyl p-dimethylaminobenzoate, amyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethyl p-diethylaminobenzoate, and propyl p-diethylaminobenzoate.

[0043] Among chemical polymerization initiators, organic peroxides function as oxidizing agents.

[0044] Examples of organic peroxides include benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-amyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-di(hydroperoxy)hexane, p-diisopropylbenzene monohydroperoxide, p-methane hydroperoxide, pinane hydroperoxide, etc. Among these, cumene hydroperoxide is preferred in terms of improving the curability of the slurry.

[0045] The photopolymerization initiator is not particularly limited, and examples thereof include camphorquinone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzil ketal, diacetyl ketal, benzil dimethyl ketal, benzil diethyl ketal, benzil bis(2-methoxyethyl)ketal, 4,4'-dimethyl(benzyl dimethyl ketal), anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 1,2-benzanthraquinone, 1-hydroxyanthraquinone, 1-methylanthraquinone, 2-ethylanthraquinone, and 1-bromoanthraquinone. Examples of suitable thioxanthone include thiaquinone, thioxanthone, 2-isopropylthioxanthone, 2-nitrothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chloro-7-trifluoromethylthioxanthone, thioxanthone-10,10-dioxide, thioxanthone-10-oxide, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, bis(4-dimethylaminophenyl)ketone, and 4,4'-bis(diethylamino)benzophenone. Among these, camphorquinone and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide are preferred in terms of improving the curability of the molded product of the slurry.

[0046] These polymerization initiators may be used alone or in combination of two or more.

[0047] The content of the polymerization initiator in the slurry is not particularly limited, but is, for example, 0.001% by mass or more and 10% by mass or less, preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.01% by mass or more and 0.1% by mass or less. When the content of the polymerization initiator in the slurry is 0.001% by mass or more, the curability of the slurry is further improved, and when it is 10% by mass or less, the storage stability of the slurry is improved and the polymerization efficiency when the slurry is cured is improved.

[0048] Examples of polymerization inhibitors include dibutylhydroxytoluene (2,6-di-tert-butyl-p-cresol), 6-tert-butyl-2,4-xylenol, hydroquinone, 4-methoxyphenol, 4-tert-butylpyrocatechol, and tert-butylhydroquinone. These polymerization inhibitors may be used alone or in combination of two or more. Among these, dibutylhydroxytoluene is preferred in terms of improving the curability of the slurry.

[0049] The content of the polymerization inhibitor in the slurry is not particularly limited, but when contained, it is 0.0005% by mass or more and 5% by mass or less, preferably 0.001% by mass or more and 1% by mass or less, and more preferably 0.005% by mass or more and 0.1% by mass or less. When the content of the polymerization inhibitor in the slurry is 0.0005% by mass or more and 5% by mass or less, the storage stability of the slurry is improved.

[0050] Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, polypropylene glycol, dimethyl phthalate, diethyl phthalate, di-2-ethylhexyl phthalate, and dibutyl phthalate.

[0051] Among these, polypropylene glycol is preferred as the plasticizer. The average molecular weight of the polypropylene glycol is preferably 200 or more and 600 or less, more preferably 300 or more and 500 or less, and even more preferably 380 to 420.

[0052] Examples of dispersants include polyacrylic acid, sodium polyacrylate, ammonium polyacrylate, formalin condensed naphthalene sulfonic acid, partially alkyl esterified polycarboxylic acid, polyether, polyalkylene polyamine, sodium polyphosphate, polycarboxylic acid alkylamine salt, linear alkylbenzene sulfonic acid, α-sulfofatty acid methyl ester salt, α-olefin sulfonic acid, dialkyl sulfosuccinic acid, alkyl sulfate ester salt, polyoxyethylene alkyl acid ester salt, and commercially available dispersants such as Disperbyk-110, 162, and 180 (all of which are wetting dispersants manufactured by BYK-Chemie; "Disperbyk" is a registered trademark).

[0053] Examples of fillers include zirconia powder, inorganic fillers other than glass powder, organic-inorganic composite fillers, and cluster fillers. Fillers that have been hydrophobized may be used. For example, a silane coupling agent such as γ-methacryloyloxypropyltrimethoxysilane can be used to hydrophobize the filler.

[0054] Examples of colorants include ZrSiO ４ -Fe ２ O ３ , ZrSiO ４ -V ２ O ５ , ZrSiO ４ -NiO-CoO, CoO-ZnO-Al ２ O ３ , MnO—SiO ２ -Al ２ O ３ , NiO, CoO, iron oxide, neodymium oxide, erbium oxide, praseodymium oxide, titanium oxide, alumina, silica, and the like.

[0055] Examples of the fluorescent agent include europium oxide, gallium oxide, gadolinium oxide, neodymium oxide, thulium oxide, and bismuth oxide.

[0056] <Method for Producing Slurry> The method for producing the slurry is not particularly limited, and for example, the slurry of the present disclosure can be obtained by mixing and uniformly dispersing zirconia powder, glass powder, and a polymerizable monomer.

[0057] <Molded body> The molded body of the present disclosure can be obtained using the slurry of the present disclosure. The molding method for the molded body is not particularly limited, and for example, a method of pouring the slurry into a mold and solidifying it (slip casting method, gel casting method, etc.), or an additive manufacturing method (active manufacturing, 3D printing, etc.) can be used. Among these, it is preferable to use 3D printing, which allows for precise molding.

[0058] For 3D printing, a known 3D printer can be used. Examples of 3D printer methods include stereolithography (SLA) and digital light processing (DLP), with the DLP method being preferred. Examples of commercially available DLP 3D printers include the MAX UV (manufactured by Asiga).

[0059] Examples of methods for stacking by 3D printing include a method in which a container containing stacked molded bodies is irradiated with light from above (free liquid level method), a method in which light is irradiated from below (regulated liquid level method), etc. Among these, the regulated liquid level method is preferred.

[0060] When a molded article is produced using the controlled liquid level method, the bottom surface of the container is optically transparent, and light emitted from below the container passes through the bottom surface of the container and is irradiated onto the molded article. Examples of the light to be irradiated include ultraviolet light and visible light having a wavelength of 380 to 450 nm. Examples of light sources for the irradiated light include LED lasers, LED lamps, and LED projectors.

[0061] The method for producing the molded body may further include a step of washing the molded body, a step of post-polymerizing the molded body, and the like.

[0062] <Sintered body> The sintered body of the present disclosure can be obtained by sintering or firing the molded body of the present disclosure. The sintering conditions for the sintered body are not particularly limited. For example, the heating temperature during sintering is 700°C or higher and 2500°C or lower, preferably 900°C or higher and 2000°C or lower, and more preferably 1100°C or higher and 1700°C or lower. By setting the heating temperature during sintering to 700°C or higher and 2500°C or lower, a sintered body that is sufficiently degreased and sintered can be obtained.

[0063] The heating temperature during sintering may be increased stepwise. For example, the compact may be sintered while increasing the temperature from 1000°C to 1500°C at a rate of 100°C / min. When increasing the temperature during sintering, each temperature may or may not be maintained.

[0064] The heating time during sintering is not particularly limited. For example, the heating time during sintering is 10 seconds to 2 hours, preferably 30 seconds to 1 hour, and more preferably 1 minute to 30 minutes. By setting the heating time during sintering to 10 seconds to 2 hours, a sintered body that is sufficiently degreased and sintered can be obtained.

[0065] As described above, the slurry of the present disclosure contains zirconia powder, glass powder, and a polymerizable monomer, allowing the slurry in which the zirconia powder and the glass powder are uniformly mixed to be molded and cured. Furthermore, the resulting molded body can be sintered by liquid phase sintering. Therefore, the slurry of the present disclosure can be sintered at a low temperature in a short time. Furthermore, sintering the slurry of the present disclosure can produce a sintered body that is dense.

[0066] As described above, the slurry of the present disclosure allows sintering at a lower temperature and in a shorter time because the glass powder becomes liquid during sintering. In addition, the wettability of zirconia to the glass that becomes liquid during sintering is improved, and the compact is more likely to shrink due to capillary force, resulting in a more dense sintered compact.

[0067] As described above, the molded body of the present disclosure is obtained using the slurry of the present disclosure, and thus the effects of the slurry of the present disclosure can be obtained.

[0068] That is, the molded body of the present disclosure can be obtained by using a slurry containing zirconia powder, glass powder, and a polymerizable monomer, molding and curing a slurry in which the zirconia powder and the glass powder are uniformly mixed. Furthermore, the molded body of the present disclosure can be sintered by liquid phase sintering. Therefore, the molded body of the present disclosure can be sintered at a low temperature in a short time. Furthermore, by sintering the molded body of the present disclosure, a sintered body that is densified while maintaining the shape of the molded body can be obtained.

[0069] As described above, the sintered body of the present disclosure is obtained by further sintering a molded body obtained using the slurry of the present disclosure, thereby achieving the effects of the slurry of the present disclosure.

[0070] That is, the sintered body of the present disclosure can be obtained by further sintering a molded body obtained using a slurry containing zirconia powder, glass powder, and a polymerizable monomer, and then molding and hardening the slurry in which the zirconia powder and glass powder are uniformly mixed. The molded body can be sintered by liquid phase sintering. Therefore, the sintered body of the present disclosure can be obtained by sintering at a low temperature and for a short time. Furthermore, the sintered body and molded body of the present disclosure are densified while maintaining their shapes.

[0071] As described above, the sintered body of the present disclosure can be obtained by sintering the slurry of the present disclosure at a low temperature for a short time, and furthermore, the slurries of the present disclosure from which such sintered bodies are obtained can be used for various dental materials, such as dental prostheses, orthodontic appliances, dental surgical guides, dental implants, etc.

[0072] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0073] <Preparation of Glass Powder> Glass raw materials were thoroughly mixed and stirred using a mortar or a nylon ball mill. The resulting mixture was placed in a platinum crucible and placed in an electric furnace. The electric furnace was heated to 1300°C, melted, and homogenized, and then poured into water to form glass blocks. The resulting glass blocks were pulverized for 20 hours using an alumina ball mill and then passed through a 120-mesh sieve to obtain glass powder. The glass powder was further wet-pulverized for 50 to 70 hours using an alumina ball mill to obtain barium glass powder and zinc fluorosilicate glass powder with a median diameter of 0.4 μm. Upon confirming the composition, the zinc fluorosilicate glass powder was found to be 26.4 mass% zinc oxide, 6.5 mass% fluorine, 24.7 mass% silicon dioxide, 9.6 mass% calcium oxide, and 32.5 mass% lanthanum oxide, while the barium glass was 45.0 mass% silicon dioxide, 12.0 mass% boron oxide, 8.9 mass% aluminum oxide, 1.8 mass% fluorine, and 32.3 mass% barium oxide.

[0074] The lithium disilicate glass ceramic was prepared by heating a bulk glass at 650°C for 60 minutes and then at 850°C for 10 minutes. The composition was determined to be 69.8% by mass of silicon dioxide, 11.7% by mass of lithium oxide, 5.6% by mass of aluminum oxide, 5.6% by mass of diphosphorus pentoxide, 2.4% by mass of potassium oxide, 1.2% by mass of sodium oxide, 1.9% by mass of zirconium oxide, 1.4% by mass of strontium oxide, and 0.4% by mass of titanium oxide. The resulting glass ceramic was wet-ground for 15 hours using an alumina ball mill with zirconia media to obtain a glass ceramic powder. The glass powder was further elutriated to obtain a lithium disilicate glass ceramic powder with a median diameter of 0.4 μm.

[0075] <Slurry Preparation> Using a planetary / revolutionary mixer, 3 mol% yttria-containing zirconia powder was mixed with neopentyl glycol diacrylate and ethoxylated bisphenol A diacrylate as photopolymerizable monomers, polypropylene 400 (polypropylene with an average molecular weight of approximately 400) as a plasticizer, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator to obtain a uniform slurry. To this was added 0.2 mass% of the above-mentioned glass powder (lithium disilicate glass ceramic powder, barium glass powder, or zinc fluorosilicate glass powder), and the mixture was mixed in a mortar to obtain a uniformly dispersed slurry. Examples and comparative examples of the resulting slurries are shown in Tables 1 to 3.

[0076] <Preparation of Molded Article> The obtained slurry was cut into a thin layer of 50 micrometers using a film applicator, and this was laminated under light irradiation to prepare a cured body of 1.5 mm in thickness. The cured body was cut using a precision cutter to obtain a molded body of 5 mm in length, 5 mm in width, and 1.5 mm in thickness.

[0077] The obtained compacts were placed in a furnace, degreased, and sintered to obtain sintered bodies. The heating rate after the degreasing process was 100°C / min, and the temperatures were raised to 1300°C (without holding), 1400°C (without holding), 1500°C (without holding), and 1500°C (held for 2 hours), and then the compacts were allowed to cool.

[0078] <Relative Density of Sintered Body> The relative density of the obtained sintered body was measured by Archimedes' method. The actual measured value of the density of the sintered body obtained by Archimedes' method and the density of zirconia containing 3 mol% yttria, 6.09 g / cm ３ , and the density of each sintering aid, lithium disilicate glass ceramics 2.50 g / cm ３ , barium glass 2.95 g / cm ３ , zinc fluorosilicate glass 3.60 g / cm ３ The relative density of each sintered body is shown in Tables 1 to 3.

[0079] <Fracture toughness value> The fracture toughness value was measured using a Vickers hardness tester (FV-700, manufactured by Futuretec Co., Ltd.) in accordance with the IF method described in JIS R1607 "Testing method for fracture toughness of fine ceramics." The unit of fracture toughness value is MPa m １／２ The fracture toughness values ​​of each sintered body are shown in Tables 1 to 3.

[0080] <SEM Observation of Material Structure> The obtained sintered body was polished using polymond (final polishing grit number 1000), thermally etched, and then observed with a scanning electron microscope (SEM). A field emission scanning electron microscope (FE-SEM SU-70, manufactured by Hitachi, Ltd.) was used as the SEM. Note that FIG. 1 shows an SEM photograph of a cross section of the sintered body of Example 19, which is a sintered body obtained from the slurry of this embodiment, and FIG. 2 shows an SEM photograph of a cross section of the sintered body of Comparative Example 4, which is a comparative example.

[0081]

[0082]

[0083]

[0084] As can be seen from Tables 1 to 3, the slurries of Examples 1 to 21 gave sintered bodies with higher relative densities than the corresponding slurries of Comparative Examples 1 to 3. Furthermore, the results of SEM observation shown in Figures 1 and 2 show that the sintered body of Example 19 was denser than the sintered body of Comparative Example 4. These findings demonstrate that slurries containing glass powder in addition to zirconia powder and polymerizable monomers can give sintered bodies with higher densities.

[0085] Furthermore, the slurries of Examples 3, 6, 9, 12, 15, and 18 gave sintered bodies with higher relative densities than the slurries of Examples 2, 5, 8, 11, 14, and 17. This indicates that slurries containing zinc fluorosilicate glass powder, which has a low melting point, as the glass powder are more effective in promoting the densification of the resulting sintered bodies than slurries containing barium glass powder, which has a high melting point as the glass powder.

[0086] Furthermore, as can be seen from Tables 2 and 3, the sintered bodies obtained without tethering in Examples 16 to 18 had the same relative density as the sintered body obtained with tethering in Comparative Example 4. This indicates that a slurry containing zirconia powder and a polymerizable monomer, as well as glass powder, can shorten the sintering time at the same sintering temperature.

[0087] Furthermore, the sintered bodies obtained without tethering in Examples 16 to 18 had the same relative density as the sintered bodies obtained with tethering in Examples 19 to 21. This demonstrates that a densified sintered body can be obtained from a slurry containing zirconia powder, glass powder, and polymerizable monomer, even without providing a tethering time during sintering.

[0088] Furthermore, the sintered bodies in Examples 16 to 18 had fracture toughness values ​​equivalent to that of the sintered body in Comparative Example 4. This indicates that the slurry containing zirconia powder, glass powder, and polymerizable monomer can produce sintered bodies that are dense and maintain high mechanical strength even when the sintering time is shortened.

[0089] The above-disclosed embodiment is further noted as follows.

[0090] <1> A slurry containing zirconia powder, glass powder, and a polymerizable monomer.

[0091] <2> The slurry according to <1> above, wherein the glass powder contains silicon dioxide.

[0092] <3> The slurry according to <1> or <2> above, which is for dental use.

[0093] <4> A molded body obtained by using the slurry according to any one of <1> to <3> above.

[0094] <5> A sintered body obtained by sintering the molded body according to <4> above.

[0095] Although the embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the invention described in the claims.

[0096] This application claims priority based on Japanese Patent Application No. 2023-213435, filed on December 19, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A slurry comprising zirconia powder, glass powder, and a polymerizable monomer.

2. The slurry of claim 1, wherein the glass powder comprises silicon dioxide.

3. The slurry of claim 1, which is for dental use.

4. A molded body obtained by using the slurry according to any one of claims 1 to 3.

5. A sintered body obtained by sintering the molded body according to claim 4.

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