TECHNICAL FIELD

The present invention relates to a method for producing a powder containing zirconia particles, among others.

BACKGROUND ART

A zirconia sintered body has been used for dental materials such as dental prostheses. Many of such dental prostheses are produced by forming a zirconia shaped body of a desired shape, for example, a disc or prism shape, through the process of pressing zirconia particles or shaping a composition containing zirconia particles, followed by calcination of the zirconia shaped body into a calcined body (mill blank), and subsequent sintering of the zirconia calcined body after cutting (milling) it into the shape of the desired dental prosthesis.

There are instances where a zirconia sintered body is required to have both high translucency and high strength. A possible approach to achieving this objective is to, for example, reduce the crystal grain size of a zirconia sintered body with the use of zirconia particles of small particle sizes. For example, Patent Literature 1 describes a specific semi-transparent zirconia sintered body having a primary particle size of 100 nm or less.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2010-514665 A

SUMMARY OF INVENTION

Technical Problem

Traditional zirconia sintered bodies have room for further improvement in terms of translucency and strength. Specifically, the zirconia particles tend to aggregate when dried to prepare a zirconia particle-containing powder, and the powder does not always form a compact zirconia sintered body for reasons related to manufacture, particularly when the zirconia particles have a small particle size.

It is accordingly an object of the present invention to provide a method for producing a zirconia particle-containing powder that enables easy production of a zirconia sintered body having both high translucency and high strength. Another object of the present invention is to provide a powder obtained by using such a method, a method for producing a zirconia shaped body by using the powder, a zirconia shaped body obtained by using the method thereof, a method for producing a zirconia calcined body by using the powder, a zirconia calcined body obtained by using the method thereof, a method for producing a zirconia sintered body by using the powder, and a zirconia sintered body obtained by using the method thereof.

Solution to Problem

The present inventor conducted intensive studies to achieve the foregoing objects, and found that a zirconia sintered body having both high translucency and high strength can be obtained with ease when a liquid having a specific surface tension is used as a dispersion medium contained in a zirconia particle-containing slurry being dried to produce a powder to be used to produce a zirconia sintered body, and when the slurry is dried by spray drying. The present inventor completed the present invention after further studies based on this finding.

Specifically, the present invention relates to the following [1] to [26].

[1] A method for producing a zirconia particle-containing powder, comprising a drying step of spray drying a slurry containing zirconia, particles, wherein the zirconia particles have an average primary particle diameter of 30 nm or less, and the slurry comprises a dispersion medium containing a liquid having a surface tension at 25° C. of 50 mN/m or less.

[2] The method according to [1], wherein the zirconia particles comprise 2.0 to 9.0 mol % yttria.

[3] The method according to [1] or [2], wherein the content of the liquid in the dispersion medium is 50 mass % or more.

[4] The method according to any one of [1] to [3], wherein the liquid is at least one selected from the group consisting of methanol, ethanol, 2-methoxyethanol, 1,4-dioxane, 2-ethoxyethanol, and 2-(2-ethoxyethoxy)ethanol.

[5] The method according to any one of [1] to [4], wherein the method produces a powder containing zirconia particles and a fluorescent agent.

[6] The method according to [5], wherein the fluorescent agent comprises a metallic element, and the powder comprises the fluorescent agent in an amount of 0.001 to 1 mass % in terms of an oxide of the metallic element relative to a mass of zirconia.

[7] The method according to [5] or [6], wherein the zirconia particle-containing slurry comprises a fluorescent agent.

[8] A powder obtained by the method of any one of [1] to [7].

[9] A powder comprising zirconia particles, wherein the zirconia particles have an average primary particle diameter of 30 nm or less, and a zirconia shaped body, formed by shaping the powder by uniaxial pressing and subsequently subjecting the powder to cold isostatic pressing (OP) under a pressure of 170 MPa and sintering at 1,100° C. for 2 hours under ordinary pressure, has a three-point flexural strength of 400 MPa. or more after the zirconia shaped body, and the zirconia shaped body has a transmittance of 40% or more for light of 700 nm wavelength through a thickness of 0.5 mm.

[10] A method for producing a zirconia shaped body, comprising a shaping step of shaping zirconia particles, wherein the method uses a powder obtained by the method of any one of [11] to [7], or the powder of [9].

[12] The method according to [10] wherein the shaping step is a step of pressing the powder.

[12] The method according to [10], wherein the shaping step is a step of shaping a composition comprising zirconia particles and a resin.

[13] The method according to [12], wherein the composition is obtained by mixing the powder and a resin.

[14] The method according to [10], wherein the shaping step is a step of polymerizing a composition comprising zirconia particles and a polymerizable monomer in a mold, or stereolithography using the composition.

[15] The method according to [14], wherein the composition is obtained by mixing the powder and a polymerizable composition.

[16] The method according to [14] or [15], wherein the shaping step is a stereolighography process.

[17] A zirconia shaped body obtained by the method of any one of [10] to [16].

A method for producing a zirconia calcined body, comprising a step of calcining a zirconia shaped body obtained by the method of any one of [10] to [16].

[19] The method according to [18], wherein the calcination is carried out between 300° C. or more and less than 900° C.

[20] A zirconia calcined body obtained by the method of [18] or [19].

[21] A method for producing a zirconia sintered body, comprising a step of sintering a zirconia shaped body obtained by the method of any one of [10] to [16], under ordinary pressure.

[22] The method according to [21], wherein the sintering is carried out between 900° C. or more and 1,200° C. or less.

[23] A method for producing a zirconia sintered body, comprising a step of sintering a zirconia calcined body obtained by the method of [18] or [19], under ordinary pressure.

[24] The method according to [23], wherein the sintering is carried out between 900° C. or more and 1,200° C.′ or less.

[25] The method according to any one of [21] to [24], wherein the zirconia sintered body is a dental material.

[26] A zirconia sintered body obtained by the method of any one of [21] to [25].

Advantageous Effects of Invention

According to the present invention, a method for producing a zirconia particle-containing powder is provided that enables easy production of a zirconia sintered body having both high translucency and high strength. The present invention also provides a powder obtained by using such a method, a method for producing a zirconia shaped body by using the powder, a zirconia shaped body obtained by using the method thereof, a method for producing a zirconia calcined body by using the powder, a zirconia calcined body obtained by using the method thereof, a method for producing a zirconia sintered body by using the powder, and a zirconia sintered body obtained by using the method thereof.

