JP2016037421A - α-ALUMINA COMPACT AND PRODUCTION METHOD THEREOF - Google Patents

α-ALUMINA COMPACT AND PRODUCTION METHOD THEREOF Download PDF

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JP2016037421A
JP2016037421A JP2014162205A JP2014162205A JP2016037421A JP 2016037421 A JP2016037421 A JP 2016037421A JP 2014162205 A JP2014162205 A JP 2014162205A JP 2014162205 A JP2014162205 A JP 2014162205A JP 2016037421 A JP2016037421 A JP 2016037421A
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alumina
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molded body
alumina molded
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裕謙 尾崎
Hirotaka Ozaki
裕謙 尾崎
鉄 梅田
Tetsu Umeda
鉄 梅田
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Sumitomo Chemical Co Ltd
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Priority to TW104125236A priority patent/TW201619059A/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/20—Aluminium oxides

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  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
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  • Crystals, And After-Treatments Of Crystals (AREA)
  • Powder Metallurgy (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide an α-alumina compact capable of producing efficiently a sapphire single crystal, and to provide a production method thereof.SOLUTION: There is provided an α-alumina compact in which a bulk density as an aggregate of compacts is 1.0 g/cmor more and below 1.5 g/cm, which is a compact in which a volume per piece is 0.01 cmor more and 1 cmor less, a relative density is 40% or higher and below 60%, crushing strength is 80 N or more, and a specific surface area is over 1 m/g and 4 m/g or less.SELECTED DRAWING: None

Description

本発明は、αアルミナ成形体およびその製造方法に関する。 The present invention relates to an α-alumina molded body and a method for producing the same.

αアルミナはサファイア単結晶を製造するための原料として有用であり、例えば金属モリブデン製のルツボ内に充填し、加熱溶融させたのち、溶融物を引き上げる方法により、サファイア単結晶を製造することができる〔特許文献１〕。また、いったん加熱半溶融処理によってアルミナ原料をあらかじめ坩堝サイズの大きさに塊状化してからルツボ内へ充填することが行われている。 α-alumina is useful as a raw material for producing a sapphire single crystal. For example, a sapphire single crystal can be produced by filling a metal molybdenum crucible, heating and melting, and then pulling up the melt. [Patent Document 1]. In addition, once the alumina raw material has been agglomerated to a crucible size in advance by a semi-melting treatment, the crucible is filled.

一般的に、加熱半溶融処理には、装置構成上、粉末状のαアルミナ原料は不適であり、数ミリサイズに造粒されたαアルミナが好んで使用される。また、加熱半溶融処理を効率よく行うには、高密度に焼き締まったαアルミナも不適とされている。サファイア単結晶の製造方法としては多様であるが、いずれの製造方法においても、サファイア単結晶を効率よく製造しうるαアルミナが求められている。 Generally, powdery α-alumina raw material is not suitable for the heat semi-melting treatment due to the apparatus configuration, and α-alumina granulated to several millimeters size is preferably used. In addition, α-alumina baked at a high density is also unsuitable for efficient heat semi-melting treatment. Although there are various methods for producing a sapphire single crystal, α alumina that can efficiently produce a sapphire single crystal is required in any of the production methods.

このようなαアルミナとしては、例えば、αアルミナ粉末やアルミナ前駆体を出発物質として、数ミリサイズに造粒し、球状化させた物を焼成して得た球状αアルミナを用いることが出来る。 As such α-alumina, for example, spherical α-alumina obtained by calcining an alumina powder or an alumina precursor, granulated to several millimeters size, and spheroidized can be used.

特開平５−９７５６９号公報JP-A-5-97569

しかし、このような数ミリサイズの球状αアルミナであっても、低密度であると、輸送や原料充填時に、粒子同士の摺動によって微粒成分や欠片が発生し、これが、サファイア単結晶用育成装置への原料供給配管や真空脱気配管の閉塞を引き起こすなど、サファイア単結晶の生産性が悪化する恐れがあった。
また、過度に高密度であると加熱半溶融処理を効率よく行うことが出来ないことがあった。
したがって、本発明は、サファイア単結晶を効率よく生産することができるαアルミナ成形体およびその製造方法を提供することを目的とする。 However, even with such a few millimeter sized spherical α-alumina, if it is low density, fine particles and fragments are generated by sliding between particles during transportation and raw material filling, which is grown for sapphire single crystals. There was a risk that the productivity of the sapphire single crystal would be deteriorated, such as blocking the raw material supply piping and vacuum degassing piping to the apparatus.
Moreover, when the density is excessively high, the heat semi-melting process may not be performed efficiently.
Accordingly, an object of the present invention is to provide an α-alumina molded body capable of efficiently producing a sapphire single crystal and a method for producing the same.

そこで本発明者は、サファイア単結晶を効率よく製造しうるαアルミナ成形体を開発するべく鋭意検討した結果、本発明に至った。 Therefore, the present inventors have intensively studied to develop an α-alumina molded body capable of efficiently producing a sapphire single crystal, resulting in the present invention.

すなわち本発明は、以下の構成からなる。
＜１＞１個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下であり、
相対密度が４０％以上６０％未満であり、圧壊強度が８０Ｎ以上であり、比表面積が１ｍ２／ｇを超え４ｍ２／ｇ以下である成形体で、前記成形体の集合体としてのかさ密度が１．０ｇ／ｃｍ３以上１．５ｇ／ｃｍ３未満であることを特徴とするαアルミナ成形体。
＜２＞前記αアルミナ成形体の形状が円柱状からなり、断面直径を１としたとき、高さが０．５以上１．５以下である前記＜１＞に記載のαアルミナ成形体。
＜３＞粒子径１００μｍ以下の微粒成分が０．０５質量％以下である前記＜１＞または＜２＞に記載のαアルミナ成形体。
＜４＞純度が９９．９９質量％以上であり、Ｓｉ、Ｎａ、Ｃａ、Ｆｅ、ＣｕおよびＭｇの含有量がそれぞれ１０ｐｐｍ以下である、前記＜１＞〜＜３＞のいずれかに記載のαアルミナ成形体。
＜５＞工程（１）〜（４）を含むことを特徴とするαアルミナの製造方法。
工程（１）αアルミナ前駆体と水性媒体を混合して混合物を得る工程。
工程（２）前記混合物を押出圧０．１ＭＰａ以上１．５ＭＰａ以下で押出成形し、押出成形体を得る工程。
工程（３）前記押出成形体中の水分含有率が１０質量％以上６０質量％以下となるよう調整する工程。
工程（４）水分含有率を調整後の押出成形体を焼成し、αアルミナ成形体を得る工程。
＜６＞さらに、前記αアルミナ成形体から粒子径１００μｍ以下の微粒成分を０．０５質量％以下まで除去する工程を含む前記＜５＞に記載のαアルミナ成形体の製造方法。 That is, this invention consists of the following structures.
<1> The volume per piece is 0.01 cm 3 or more and 1 cm 3 or less,
A molded body having a relative density of 40% or more and less than 60%, a crushing strength of 80 N or more, and a specific surface area of more than 1 m 2 / g and 4 m 2 / g or less, and a bulk density as an aggregate of the molded bodies The α-alumina molded body is characterized by having a value of 1.0 g / cm 3 or more and less than 1.5 g / cm 3 .
<2> The α-alumina molded body according to <1>, wherein the α-alumina molded body has a columnar shape and a cross-sectional diameter of 1, the height is 0.5 or more and 1.5 or less.
<3> The α-alumina molded product according to <1> or <2>, wherein a fine particle component having a particle diameter of 100 μm or less is 0.05% by mass or less.
<4> The purity according to any one of <1> to <3>, wherein the purity is 99.99% by mass or more, and the contents of Si, Na, Ca, Fe, Cu, and Mg are each 10 ppm or less. Alumina molded body.
<5> A method for producing α-alumina, comprising steps (1) to (4).
Step (1) A step of obtaining a mixture by mixing an α-alumina precursor and an aqueous medium.
Step (2) A step of extruding the mixture at an extrusion pressure of 0.1 MPa to 1.5 MPa to obtain an extruded product.
Process (3) The process of adjusting so that the moisture content rate in the said extrusion molded object may be 10 mass% or more and 60 mass% or less.
Process (4) The process of baking the extrusion molded object after adjusting water content, and obtaining an alpha alumina molded object.
<6> The method for producing an α-alumina molded body according to <5>, further including a step of removing a fine particle component having a particle diameter of 100 μm or less from the α-alumina molded body to 0.05% by mass or less.

本発明のαアルミナ成形体は、原料輸送時および原料充填時の微粉の発塵が少ないため、サファイア製造装置内の原料供給配管等での閉塞の懸念がなく、また、加熱半溶融処理を効率よく行うことが出来るので、高い生産効率でサファイア単結晶を得ることができる。
したがって、本発明によれば、サファイア単結晶原料として好適なαアルミナ成形体およびその製造方法を提供することができる。 The α-alumina molded body of the present invention has less dust generation during transportation of raw materials and during filling of raw materials, so there is no concern about blockage in the raw material supply pipes in the sapphire production apparatus, and the heat semi-melt treatment is efficient. Since it can be performed well, a sapphire single crystal can be obtained with high production efficiency.
Therefore, according to this invention, the alpha alumina molded object suitable as a sapphire single-crystal raw material and its manufacturing method can be provided.

本発明のαアルミナ成形体は、１個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下であり、相対密度が４０％以上６０％未満であり、圧壊強度が８０Ｎ以上であり、比表面積が１ｍ２／ｇを超え４ｍ２／ｇ以下である成形体で、前記成形体の集合体としてのかさ密度が１．０ｇ／ｃｍ３以上１．５ｇ／ｃｍ３未満であることを特徴とする。前記αアルミナ成形体は、例えばαアルミナ前駆体と水性媒体との混合物を押出成形し焼成して得ることができる。 The α-alumina molded body of the present invention has a volume per piece of 0.01 cm 3 or more and 1 cm 3 or less, a relative density of 40% or more and less than 60%, a crushing strength of 80 N or more, and a specific surface area of 1 m. The molded body is more than 2 / g and not more than 4 m 2 / g, and has a bulk density as an aggregate of the molded bodies of 1.0 g / cm 3 or more and less than 1.5 g / cm 3 . The α-alumina molded body can be obtained, for example, by extruding and firing a mixture of an α-alumina precursor and an aqueous medium.

前記製造方法に用いられるαアルミナ前駆体とは、焼成することによりαアルミナに転移し得る化合物であって、例えば水酸化アルミニウム、アルミニウムイソプロポキシド、アルミニウムエトキシド、アルミニウムｓ−ブトキシド、アルミニウムｔ−ブトキシド等のアルミニウムアルコキシド、γアルミナ、δアルミナ、θアルミナなどの遷移アルミナなどが挙げられ、通常は水酸化アルミニウムが用いられる。 The α-alumina precursor used in the production method is a compound that can be converted to α-alumina by firing, and for example, aluminum hydroxide, aluminum isopropoxide, aluminum ethoxide, aluminum s-butoxide, aluminum t- Examples thereof include aluminum alkoxides such as butoxide, transition aluminas such as γ alumina, δ alumina, and θ alumina, and aluminum hydroxide is usually used.

水酸化アルミニウムは、例えば加水分解性アルミニウム化合物を加水分解することにより得られるものが使用される。加水分解性アルミニウム化合物としては、例えばアルミニウムアルコキシド、塩化アルミニウムなどが挙げられるが、純度の点でアルミニウムアルコキシドが好ましく用いられる。 As the aluminum hydroxide, for example, one obtained by hydrolyzing a hydrolyzable aluminum compound is used. Examples of the hydrolyzable aluminum compound include aluminum alkoxide and aluminum chloride. Aluminum alkoxide is preferably used in terms of purity.

水酸化アルミニウムの結晶型は、不定形（アモルファス）、ギブサイト型であってもよく、特に限定されないが、結晶中に含まれる結晶水が少ないベーマイト、あるいは擬ベーマイトであると焼成前後で成形体の体積の変化を小さくすることができ、本発明のαアルミナ成形体の1個あたりの体積を制御し易いので好ましい。 The crystal form of aluminum hydroxide may be indeterminate (amorphous) or gibbsite type, and is not particularly limited. However, when the boehmite contains less crystal water or pseudo boehmite, It is preferable because the change in volume can be reduced and the volume per one α-alumina molded body of the present invention can be easily controlled.

以下、αアルミナ前駆体として、水酸化アルミニウムを使用した場合を例として説明する。 Hereinafter, the case where aluminum hydroxide is used as the α-alumina precursor will be described as an example.

水酸化アルミニウム粉末を水性媒体と混合する。ここで水性媒体としては、水単独を用いることができる。また、水と水性アルコールとの混合媒体を用いることもできる。ここで、水溶性アルコールとしては、特に限定されないが、メタノール、エタノール、プロパノール、イソプロパノール等の炭素数３以下の低沸点アルコールが好ましい。水酸化アルミニウムに加える水分量としては、水酸化アルミニウム１００重量部に対して通常１００〜２００重量部であり、好ましくは１２０〜１６０重量部である。
２００重量部を超える水分量では、混合物がスラリー化し、押出成形を行えないことがあるため好ましくなく、１００重量部未満では、混合物の流動性が極めて乏しく、押出成形に多くのエネルギーを要するため好ましくない。 Aluminum hydroxide powder is mixed with an aqueous medium. Here, water alone can be used as the aqueous medium. A mixed medium of water and aqueous alcohol can also be used. Here, the water-soluble alcohol is not particularly limited, but a low-boiling alcohol having 3 or less carbon atoms such as methanol, ethanol, propanol, and isopropanol is preferable. The amount of water added to aluminum hydroxide is usually 100 to 200 parts by weight, preferably 120 to 160 parts by weight, based on 100 parts by weight of aluminum hydroxide.
Moisture amount exceeding 200 parts by weight is not preferable because the mixture may be slurried and extrusion may not be performed, and if it is less than 100 parts by weight, the fluidity of the mixture is extremely poor, and a lot of energy is required for extrusion. Absent.

混合するに際しては、ボールミルや混合ミキサーを用いたり、超音波を照射したりすることで、分散性よく水酸化アルミニウムと純水とを混合できるが、水酸化アルミニウムに実質的に圧力を加えることなく、連続的に混合する方法が好ましい。この方法としては、回転する円盤上に、水酸化アルミニウム粉末を連続的に供給しながら、同時に、同じ回転円盤上に水性溶媒を噴射して混合する方式を用いることができ、装置としては、例えば、株式会社粉研パウテックス製のフロージェットミキサーが挙げられる。このようにすることで、焼成した際に、αアルミナ前駆体の粒子同士の焼結が均一に進行し、成形体内に生じる細孔（空隙）の大きさも均一となるため、本発明のαアルミナ成形体が得られやすい。一方で、ボールミルや混合ミキサー、転動造粒など水酸化アルミニウムに圧力が加わる方式では、混合時に水酸化アルミニウムが過度に圧密される結果、焼成したときの粒子成長が促進され、成形体内に粗大な空隙が発生しやすくなり、圧壊強度の低下につながり、本発明のαアルミナ成形体が得られない可能性があり好ましくない。 When mixing, aluminum hydroxide and pure water can be mixed with good dispersibility by using a ball mill or a mixing mixer or by irradiating ultrasonic waves, but without substantially applying pressure to the aluminum hydroxide. A continuous mixing method is preferred. As this method, while supplying aluminum hydroxide powder continuously on a rotating disk, it is possible to use a method of simultaneously jetting and mixing an aqueous solvent on the same rotating disk. And a flow jet mixer manufactured by Powder Research Powtex Co., Ltd. By doing so, the sintering of the particles of the α-alumina precursor progresses uniformly during firing, and the size of the pores (voids) generated in the molded body also becomes uniform, so the α-alumina of the present invention A molded body is easily obtained. On the other hand, in systems where pressure is applied to aluminum hydroxide, such as ball mills, mixing mixers, and rolling granulation, the aluminum hydroxide is excessively consolidated during mixing, resulting in accelerated particle growth when fired and coarse in the molded body. Undesirably, voids are likely to occur, leading to a decrease in crushing strength, and the α-alumina molded product of the present invention may not be obtained.

このようにして水酸化アルミニウムと水性媒体とを混合し、その混合物を押出成形により成形し、押出成形体を得る。押出成形圧は、所望の押出成形体の形が保持できる範囲で可能な限り低いほうが好ましく、通常０．１ＭＰａ以上１．５ＭＰａ以下、好ましくは、０．３ＭＰａ以上１．０ＭＰａ以下である。０．１ＭＰａを下回ると押出成形体の形状が保持できない恐れがあり好ましくなく、１．５ＭＰａを超えると、過度の圧密により最終的に得られるαアルミナ成形体の密度が高くなり過ぎる可能性があり、さらに、押出機の材質摩耗による不純物コンタミが生じる恐れもあるため好ましくない。得られた押出成形体は、通常、円柱状や多角柱状をしているが、円柱状であることが好ましく、その断面直径を１としたとき、高さが０．５以上１．５以下であることが好ましい。最終的に得られる本発明のαアルミナ成形体は、乾燥や焼成により全体的に収縮するが、押出成形体の形状、ならびに高さ／断面直径比が踏襲される。αアルミナ成形体が、高さ／断面直径比が０．５以上１．５以下である円柱状であると、加熱半溶融処理を行う場合に、均一な密度で塊状化させることができる。さらに、流動性が良く、高温雰囲気下に維持した装置に原料を連続供給して使用しても、装置内で目詰まりを起こすことなく容易に結晶成長を行うことができる。 In this manner, aluminum hydroxide and an aqueous medium are mixed, and the mixture is molded by extrusion to obtain an extruded product. The extrusion pressure is preferably as low as possible as long as the desired shape of the extruded product can be maintained, and is usually from 0.1 MPa to 1.5 MPa, and preferably from 0.3 MPa to 1.0 MPa. If the pressure is less than 0.1 MPa, the shape of the extruded molded body may not be maintained, which is not preferable. If the pressure exceeds 1.5 MPa, the density of the finally obtained α-alumina molded body may be too high. Furthermore, it is not preferable because impurity contamination due to material wear of the extruder may occur. The obtained extrusion-molded body usually has a columnar shape or a polygonal columnar shape, but preferably has a columnar shape. When the cross-sectional diameter is 1, the height is 0.5 to 1.5. Preferably there is. The finally obtained α-alumina molded product of the present invention shrinks as a whole by drying or firing, but the shape of the extruded product and the height / cross-sectional diameter ratio are followed. When the α-alumina molded body has a columnar shape with a height / cross-sectional diameter ratio of 0.5 or more and 1.5 or less, it can be agglomerated at a uniform density when performing the heat semi-melting treatment. Furthermore, even if the raw material is continuously supplied to an apparatus maintained in a high temperature atmosphere with good fluidity, crystal growth can be easily performed without causing clogging in the apparatus.

押出成形体の大きさは、焼成後の1個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下となる様にすればよい。目安としてαアルミナ前駆体としてベーマイトまたは擬ベーマイトを用いた場合、焼成前の押出成形体1個あたりの体積が０．０２ｃｍ３以上２０ｃｍ３以下、好ましくは０．０４ｃｍ３以上１０ｃｍ３以下であると、焼成後の成形体１個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下と成り易い。焼成後の1個あたりの体積が０．０１ｃｍ３未満の大きさでは、乾燥や焼成の工程で押出成形体同士が固着することがあるため、好ましくない。焼成後の1個あたりの体積が１ｃｍ３を超える大きさでは、充填した際に個々のαアルミナ成形体同士の隙間が過度に大きいため、加熱半溶融処理により坩堝サイズに塊状化させた際に、その隙間が空隙として残ってしまい、塊状物の密度が所望のレベルまで上がらないことがあり好ましくない。 The size of the extruded product may be such that the volume per piece after firing is 0.01 cm 3 or more and 1 cm 3 or less. When using boehmite or pseudo-boehmite as α-alumina precursor as a guide, volume per extruded body before firing is 0.02 cm 3 or more 20 cm 3 or less, and preferably is 0.04 cm 3 or more 10 cm 3 or less The volume per one molded body after firing tends to be 0.01 cm 3 or more and 1 cm 3 or less. When the volume per piece after firing is less than 0.01 cm 3 , the extrusion-molded bodies may stick together in the drying or firing step, which is not preferable. When the volume per piece after firing exceeds 1 cm 3 , the gaps between the individual α-alumina compacts are excessively large when filled, so that when they are agglomerated into a crucible size by heating semi-melting treatment The gaps remain as voids, and the density of the lump may not increase to a desired level, which is not preferable.

押出成形体は、焼成工程への搬送時の変形や潰れを防ぐために、含まれる水分量を適度に調整することが好ましい。調整後の水分含有率は、通常１０質量％以上６０質量％以下、好ましくは、２０質量％以上４０質量％以下である。調整後の水分含有率が１０質量％未満では、押出成形体の弾性が過度に低下し、搬送時の外部衝撃でヒビや割れが生じやすく、焼成後に得られるαアルミナ成形体の圧壊強度を低下させ、本発明のαアルミナ成形体が得られない可能性がある。調整後の水分含有率が６０質量％を超えると、押出成形体の剛性が過度に低下し、搬送時の外部衝撃で変形が生じやすくなり、変形箇所は焼成後に得られるαアルミナ成形体の圧壊強度の低下につながるため、本発明のαアルミナ成形体が得られない可能性がある。押出成形体中に含まれる水分量の調整方法としては、例えばオーブン中で乾燥させてもよいし、高周波乾燥機で乾燥させてもよいが、乾燥後水分含有率の制御が容易な点で、コンベア式乾燥機で乾燥させることが好ましい。乾燥させる際の温度は通常６０℃以上１２０℃以下、好ましくは、８０℃以上１００℃以下である。乾燥温度が１２０℃を超えると、乾燥速度が過度に速まり、押出成形体表面とその内部の乾燥速度差が大きくなるため、乾燥後の押出成形体にクラックが生じやすくなり、得られるαアルミナ成形体の圧壊強度が低下する恐れがある。６０℃未満では、乾燥速度が遅く生産効率が悪くなるため好ましくない。コンベア式乾燥機で乾燥させる際、熱風風速は、コンベア上に乗せる成形体の層厚にもよるが、通常０．３ｍ／ｓ以上１．２ｍ／ｓ以下、好ましくは、０．５ｍ／ｓ以上１．０ｍ／ｓ以下である。熱風風速が１．２ｍ／ｓを超えると、乾燥速度が過度に速まり、押出成形体表面とその内部の乾燥速度差が大きくなるため、乾燥後に押出成形体にクラックが生じ、得られるαアルミナ成形体の圧壊強度が低下する恐れがある。熱風風速が０．３ｍ／ｓ未満では、乾燥速度が遅く生産効率が悪くなるため好ましくない。また、必要に応じ、湿潤雰囲気下で加湿することにより押出成形体中の水分量を調整してもよい。 In order to prevent deformation and crushing of the extruded product during conveyance to the firing step, it is preferable to appropriately adjust the amount of water contained. The moisture content after adjustment is usually 10% by mass to 60% by mass, and preferably 20% by mass to 40% by mass. When the moisture content after adjustment is less than 10% by mass, the elasticity of the extruded molded product is excessively reduced, cracks and cracks are likely to occur due to external impact during conveyance, and the crushing strength of the α-alumina molded product obtained after firing is reduced. Therefore, there is a possibility that the α-alumina molded body of the present invention cannot be obtained. When the moisture content after adjustment exceeds 60% by mass, the rigidity of the extruded molded body is excessively reduced, and deformation is likely to occur due to external impact during transportation, and the deformed portion is crushed by the α-alumina molded body obtained after firing. Since it leads to a decrease in strength, the α-alumina molded body of the present invention may not be obtained. As a method for adjusting the amount of water contained in the extruded product, for example, it may be dried in an oven or may be dried with a high-frequency dryer, but in terms of easy control of the moisture content after drying, It is preferable to dry with a conveyor dryer. The temperature for drying is usually 60 ° C. or higher and 120 ° C. or lower, and preferably 80 ° C. or higher and 100 ° C. or lower. When the drying temperature exceeds 120 ° C., the drying speed is excessively increased, and the difference in the drying speed between the surface of the extruded molded body and the inside thereof is increased. There is a possibility that the crushing strength of the molded body may be reduced. If it is less than 60 degreeC, since a drying rate is slow and production efficiency worsens, it is unpreferable. When drying with a conveyor-type dryer, the hot air speed is usually 0.3 m / s or more and 1.2 m / s or less, preferably 0.5 m / s or more, although it depends on the layer thickness of the molded product placed on the conveyor. 1.0 m / s or less. When the hot air speed exceeds 1.2 m / s, the drying speed becomes excessively high, and the difference in the drying speed between the surface of the extruded product and the inside thereof increases, so that cracks occur in the extruded product after drying, and the resulting α alumina There is a possibility that the crushing strength of the molded body may be reduced. If the hot air speed is less than 0.3 m / s, the drying speed is slow and the production efficiency is deteriorated, which is not preferable. Moreover, you may adjust the moisture content in an extrusion molded object by humidifying in a humid atmosphere as needed.

水酸化アルミニウムと水性媒体との混合物を押出成形した押出成形体を焼成する。焼成温度は、本願発明で規定する純度、比表面積、相対密度およびかさ密度のαアルミナ成形体が容易に得られる点で、通常１２００〜１４５０℃、好ましくは１２５０〜１４００℃である。１４５０℃を越える場合では、焼成炉からの不純物汚染などが起こり易く、さらに、比表面積が過度に小さくなり、一方相対密度およびかさ密度は過度に大きくなり、本発明のαアルミナ成形体が得られない可能性がある。また、１２００℃未満では、水酸化アルミニウムのα化が不十分で、比表面積が過度に大きくなり、一方相対密度およびかさ密度は過度に小さくなることがある。 An extruded product obtained by extruding a mixture of aluminum hydroxide and an aqueous medium is fired. The firing temperature is usually 1200 to 1450 ° C., preferably 1250 to 1400 ° C., in that an α-alumina molded product having the purity, specific surface area, relative density and bulk density specified in the present invention can be easily obtained. When the temperature exceeds 1450 ° C., impurity contamination from the firing furnace tends to occur, and the specific surface area becomes excessively small, while the relative density and bulk density become excessively large, and the α-alumina molded body of the present invention is obtained. There is no possibility. If it is less than 1200 ° C., the aluminum hydroxide is not sufficiently α-ized and the specific surface area becomes excessively large, while the relative density and the bulk density may be excessively decreased.

押出成形体は、例えば３０〜５００℃／時間の昇温速度で焼成温度まで昇温する。焼成時間は水酸化アルミニウムが十分にα化するに十分な時間であればよく、焼成炉の形式、焼成温度、焼成雰囲気などにより異なるが、例えば３０分以上２４時間以下、好ましくは１〜１０時間である。 The extrudate is heated to the firing temperature at a temperature increase rate of 30 to 500 ° C./hour, for example. The firing time may be a time sufficient for the aluminum hydroxide to be fully alphatized, and varies depending on the type of firing furnace, firing temperature, firing atmosphere, etc., for example, 30 minutes to 24 hours, preferably 1 to 10 hours. It is.

押出成形体は、大気中で焼成してもよいし、窒素ガス、アルゴンガスなどの不活性ガス中で焼成してもよい。また、水蒸気分圧が高い湿潤雰囲気中で焼成してもよい。 The extruded product may be fired in the air or in an inert gas such as nitrogen gas or argon gas. Moreover, you may bake in the humid atmosphere with high water vapor partial pressure.

押出成形体を焼成する際には、例えば管状電気炉、箱型電気炉、トンネル炉、遠赤外線炉、マイクロ波加熱炉、シャフト炉、反射炉、ロータリー炉、ローラーハース炉などの通常の焼成炉を用いることができる。混合物は回分式で焼成してもよいし、連続式で焼成してもよい。また静止式で焼成してもよいし、流動式で焼成してもよい。 When firing an extruded body, for example, a tubular electric furnace, a box-type electric furnace, a tunnel furnace, a far-infrared furnace, a microwave heating furnace, a shaft furnace, a reflection furnace, a rotary furnace, a roller hearth furnace, etc. Can be used. The mixture may be fired batchwise or continuously. Further, it may be fired in a static manner or may be fired in a fluid manner.

押出成形体を焼成することによって得られたαアルミナ成形体の相対密度は、好ましくは４０％以上６０％未満、より好ましくは、４５％以上５５％未満である。αアルミナ成形体の相対密度が、４０％未満であると、加熱溶融装置の容積効率が過度に低くなり生産性が低下するため好ましくない。αアルミナ成形体の相対密度が６０％以上であると、加熱半溶融処理を正常に行うことができないため好ましくない。
また、得られたαアルミナ成形体の圧壊強度は、好ましくは８０Ｎ以上、より好ましくは、１００Ｎ以上であり、通常３５０Ｎ以下である。圧壊強度が８０Ｎ未満では、輸送時や原料充填時の粒子同士の摺動によって微粒成分や欠片が発生しやすくなり、これが、サファイア単結晶用育成装置への原料供給配管や真空脱気配管の閉塞を引き起こすなど、サファイア単結晶の生産性が悪化する恐れがあり好ましくない。 The relative density of the α-alumina molded body obtained by firing the extruded molded body is preferably 40% or more and less than 60%, more preferably 45% or more and less than 55%. If the relative density of the α-alumina molded body is less than 40%, the volume efficiency of the heating and melting apparatus becomes excessively low and the productivity is lowered, which is not preferable. If the relative density of the α-alumina molded body is 60% or more, the heat semi-melting treatment cannot be performed normally, such being undesirable.
Moreover, the crushing strength of the obtained α-alumina molded body is preferably 80 N or more, more preferably 100 N or more, and usually 350 N or less. If the crushing strength is less than 80N, fine particles and fragments are likely to be generated due to the sliding of particles during transportation and filling of raw materials, and this is a blockage of the raw material supply piping and vacuum deaeration piping to the sapphire single crystal growth device. This is not preferable because the productivity of the sapphire single crystal may deteriorate.

１２００℃を超えるような高温条件下の焼成では、焼成容器に起因した不純物コンタミが生じることがあり、特に、焼成容器と接している表面積の大きな微粒成分では、不純物コンタミが生じやすい。そのような、汚染された微粒成分が、αアルミナ成形体の表面に残留すると、アルミナを高温で溶かして融液化した際に、融液中の不純物濃度が局所的に高まることがあり、それが起点となって育成するサファイア単結晶の欠陥原因となる恐れがあるため、αアルミナ成形体の表面から微粒成分を除去することが好ましい。特に、粒子径が１００μｍ以下の微粒成分は、焼成容器の底部に堆積しやすく、また比較的大きな比表面積を有していることから不純物を多く含みやすい。そのため、除去すべき対象とする微粒成分は、粒子径が１００μｍ以下とすることが好ましい。微粒成分の除去方法としては、一般的な分級処理による方法が用いられ、湿式法または乾式法で行うことが出来るが、微粒成分除去後のαアルミナ成形体から乾燥等により溶媒除去が不要な乾式法で行うことが好ましい。乾式分級による微粒分の除去方法としては、気流式分級機や振動型篩別機を用いることが出来る。αアルミナ成形体は、圧壊強度が８０Ｎ以上と高いため微粒成分の除去の際に割れや欠片が生じにくいが、過度な衝撃や磨耗による破損や微粉化を防止する上で振動型篩別機を用いることが好ましく、集塵式による微粒成分の除去と篩別機を組み合わせて使用するとさらに好ましい。篩別の目開きは、効率的に微粒成分を分離除去する観点から、好ましくは、０．２ｍｍ以上２．０ｍｍ以下、さらに好ましくは、０．５ｍｍ以上１．５ｍｍ以下である。微粒成分の含有量は、粒子径１００μｍ以下の微粒成分が、好ましくは０．０５質量％以下であり、さらに好ましくは０．０１質量％以下である。粒子径１００μｍ以下の微粒成分０．０５質量％を超えると、アルミナ融液中の局所的不純物濃度が高まり、サファイア単結晶の欠陥原因となる可能性があり好ましくない。微粒成分を必要十分に除去するためには、篩別処理を複数回繰り返し行ってもよい。しかし、過度の篩別処理は生産効率の低下につながるため、篩別処理は２回以上７回以下が好ましい。 When firing under a high temperature condition exceeding 1200 ° C., impurity contamination due to the firing container may occur. In particular, impurity contamination tends to occur with a fine particle component having a large surface area in contact with the firing container. When such contaminated fine particle components remain on the surface of the α-alumina molded body, when the alumina is melted at a high temperature and melted, the concentration of impurities in the melt may increase locally. Since there is a risk of causing defects in the sapphire single crystal grown as a starting point, it is preferable to remove the fine particle component from the surface of the α-alumina molded body. In particular, a fine particle component having a particle size of 100 μm or less is likely to be deposited on the bottom of the baking container and has a relatively large specific surface area, and thus tends to contain a large amount of impurities. Therefore, it is preferable that the fine particle component to be removed has a particle diameter of 100 μm or less. As a method for removing the fine particle component, a general classification method is used, which can be performed by a wet method or a dry method. However, a dry method that does not require solvent removal by drying or the like from the α-alumina molded body after the fine particle component is removed. It is preferable to carry out by the method. As a method for removing fine particles by dry classification, an airflow classifier or a vibration type sieving machine can be used. The α-alumina molded body has a high crushing strength of 80 N or more, so it is difficult for cracks and fragments to occur when removing fine components, but a vibration-type sieving machine is used to prevent damage and pulverization due to excessive impact and wear. It is preferable to use it, and it is more preferable to use it in combination with the removal of the fine particle component by a dust collection type and a sieving machine. The sieve opening is preferably 0.2 mm or more and 2.0 mm or less, and more preferably 0.5 mm or more and 1.5 mm or less, from the viewpoint of efficiently separating and removing fine particle components. The content of the fine particle component is preferably 0.05% by mass or less, and more preferably 0.01% by mass or less, with respect to the fine particle component having a particle size of 100 μm or less. If the fine particle component having a particle diameter of 100 μm or less exceeds 0.05% by mass, the local impurity concentration in the alumina melt is increased, which may cause defects in the sapphire single crystal, which is not preferable. In order to remove the fine particle component sufficiently and sufficiently, the sieving process may be repeated a plurality of times. However, since excessive sieving treatment leads to a decrease in production efficiency, the sieving treatment is preferably performed 2 times or more and 7 times or less.

この様にして得られた本発明のαアルミナ成形体は、１個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下であり、相対密度が４０％以上６０％未満、より好ましくは、４５％以上５５％未満であり、圧壊強度が８０Ｎ以上、より好ましくは、１００Ｎ以上であり、比表面積が１ｍ２／ｇを超え４ｍ２／ｇ以下であり、集合体としてのかさ密度が１．０ｇ／ｃｍ３以上１．５ｇ／ｃｍ３未満である。相対密度が４０％以上６０％未満であるため、加熱半溶融処理による塊状化が容易であり、前記塊状物を加熱溶融したのち冷却することにより容易にこれを単結晶化させてサファイア単結晶を製造することができる。また、圧壊強度が８０Ｎ以上であるため、原料輸送時の摺動による微粉の発生および原料充填時の微粉の発塵が少なく、原料供給配管での閉塞の懸念がなくなり、高い生産効率でサファイア単結晶を得ることができる。さらに、比表面積が１ｍ２／ｇを超え４ｍ２／ｇ以下であることから、表面への吸着水分によるルツボを酸化させるおそれがなく、さらにサファイア単結晶に形成されるボイドを抑制することができる。また、得られたαアルミナ成形体の閉気孔率が１％以下であると閉気孔内に取り込まれていた水分を減らすことができ、ボイド生成を抑制する上でさらに好ましい。 The α-alumina molded body of the present invention thus obtained has a volume of 0.01 cm 3 or more and 1 cm 3 or less, and a relative density of 40% or more and less than 60%, more preferably 45% or more. Less than 55%, crushing strength is 80 N or more, more preferably 100 N or more, the specific surface area is more than 1 m 2 / g and 4 m 2 / g or less, and the bulk density as an aggregate is 1.0 g / cm 3 or more and less than 1.5 g / cm 3 . Since the relative density is 40% or more and less than 60%, it is easy to agglomerate by heating and semi-melting treatment, and the agglomerated material is easily melted and then cooled to be single crystallized to obtain a sapphire single crystal. Can be manufactured. In addition, since the crushing strength is 80 N or more, the generation of fine powder due to sliding during raw material transportation and the generation of fine powder during filling of raw materials are small, and there is no concern of clogging in the raw material supply piping, and sapphire unit is highly efficient. Crystals can be obtained. Furthermore, since the specific surface area exceeds 1 m 2 / g and is 4 m 2 / g or less, there is no possibility of oxidizing the crucible due to moisture adsorbed on the surface, and voids formed in the sapphire single crystal can be suppressed. . Moreover, when the closed porosity of the obtained α-alumina molded body is 1% or less, the moisture taken into the closed pores can be reduced, which is more preferable in suppressing void formation.

本発明のαアルミナ成形体においては、形状が円柱状からなり、断面直径を１としたとき、高さが０．５以上１．５以下であることが好ましい。形状が断面直径を１としたとき、高さが０．５以上１．５以下である円柱状であるため、加熱半溶融処理を行う際に、均一な密度で塊状化させることができる。また、高温雰囲気下に維持した装置に原料を連続供給して使用しても、流動性がよいため装置内で目詰まりを起こすことなく容易に結晶成長を行うことができる。 In the α-alumina molded body of the present invention, the shape is a columnar shape, and when the cross-sectional diameter is 1, it is preferable that the height is 0.5 or more and 1.5 or less. When the cross section diameter is 1, the shape is a columnar shape having a height of 0.5 or more and 1.5 or less, so that it can be agglomerated at a uniform density when performing the heat semi-melting treatment. Even if the raw material is continuously supplied to an apparatus maintained in a high-temperature atmosphere and used, crystal growth can be easily performed without causing clogging in the apparatus due to good fluidity.

本発明のαアルミナ成形体においては、粒子径１００μｍ以下の微粒成分が０．０５質量％以下であることが好ましい。粒子径１００μｍ以下の微粒成分が０．０５質量％以下であるため、アルミナ融液の中に、結晶欠陥の起点となる局所的不純物濃度の高まりが生じる懸念がなくなり、結晶欠陥のないサファイア単結晶を得ることができる。 In the α-alumina molded body of the present invention, the fine particle component having a particle diameter of 100 μm or less is preferably 0.05% by mass or less. Since the fine particle component having a particle diameter of 100 μm or less is 0.05% by mass or less, there is no concern that the local impurity concentration that is the starting point of crystal defects will increase in the alumina melt, and there is no crystal defect. Can be obtained.

本発明のαアルミナ成形体においては、純度が９９．９９質量％以上であって、Ｓｉ、Ｎａ、Ｃａ、Ｆｅ、ＣｕおよびＭｇの含有量がそれぞれ１０ｐｐｍ以下であることが好ましい。これをサファイア単結晶製造用アルミナ原料として用いることで、着色やクラック等の少ない良質なサファイア単結晶が得られる。 In the α-alumina molded body of the present invention, the purity is preferably 99.99% by mass or more, and the contents of Si, Na, Ca, Fe, Cu and Mg are each preferably 10 ppm or less. By using this as an alumina raw material for sapphire single crystal production, a high-quality sapphire single crystal with little coloring and cracks can be obtained.

本発明のαアルミナ成形体は、ＥＦＧ法、チョクラルスキー法、カイロポーラス法等のサファイア単結晶成長方法の原料として適用することができ、好ましくは、連続的に原料を供給する必要があるＥＦＧ法、ならびに原料を加熱半溶融処理することを前提としたチョクラルスキー法、カイロポーラス法に用いられる。 The α-alumina molded body of the present invention can be applied as a raw material for a sapphire single crystal growth method such as an EFG method, a Czochralski method, or a Cairo porous method, and preferably an EFG that needs to be supplied continuously. And the Czochralski method and the Cairoporous method, which are premised on heat and semi-melt treatment of the raw material.

以下、実施例によって本発明をより詳細に説明するが、本発明はこれら実施例によって限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

なお、実施例における評価方法は下記のとおりである。
（１）相対密度
得られたαアルミナ成形体の相対密度は、細孔容積（開気孔体積）と粒子密度から算出した閉気孔体積から算出した焼結密度を用いた。細孔容積は試料を１２０℃で４時間乾燥後、オートポアＩＩＩ９４２０装置（ＭＩＣＲＯＭＥＲＩＴＩＣＳ社製）を用いて水銀圧入法により細孔半径１μｍ以下の範囲の細孔容積として求めた。
相対密度（％）＝（焼結密度／３．９８）×１００
焼結密度（ｇ／ｃｍ３）＝１／{（１／３．９８）＋細孔容積＋閉気孔体積}
閉気孔体積 （ｃｍ３／ｇ）＝（１／粒子密度）−（１／３．９８）
（２）閉気孔率
閉気孔率は粒子密度から、下記の式で算出した。また粒子密度は、ＪＩＳ Ｒ７２２２の真比重測定方法に基づき算出した。
閉気孔率（％）＝〔（閉気孔体積）／{（１／３．９８）＋細孔容積＋閉気孔体積}〕×１ ００
（３）体積
前記焼結密度と前記αアルミナ成形体１個あたりの質量から、下記式を用いることで算出した。
体積（ｃｍ３／個）＝質量〔ｇ／個〕／焼結密度〔ｇ／ｃｍ３〕
（４）圧壊強度
ＪＩＳ Ｚ ８８４１：１９９３に準じて、加圧速度＝１ｍｍ／ｓの条件で無作為に抽出した計２０個を測定し、その平均により圧壊強度を算出した。なお、円柱状αアルミナ成形体の場合、荷重方向は、断面の直径方向とした。
（５）落下強度
落下高さを５ｍとした以外は、ＪＩＳ Ｚ ８８４１：１９９３に準じた方法により測定した。落下操作５回後の試料を目開き１ｍｍのふるい分け、ふるい上に残った試料の質量（ｍ）と全試料の質量（ｍ0）とから、下式により算出した。
落下強度＝ｍ／ｍ0×１００
（６）押出成形体及びαアルミナ成形体の寸法
円柱状に成形された押出成形体又はその押出成形体を焼成して得られたαアルミナ成形体から無作為に抽出した計１２０個について、その断面の直径とその二つの断面の距離を押出成形体又はαアルミナ成形体の高さとしてデジタルノギスを用いて測定し、平均高さと平均断面直径を算出した。
（７）αアルミナ成形体中に存在する粒子径１００μｍ以下の微粒成分の計量
目開き１００μｍの篩に、１回あたり試料５００ｇを投入し、ＪＩＳ Ｋ ００６９：１９９２に準じて、１分間に篩を通過する微粒成分が投入した試料質量の０．１％以下となった時を終点とした。
上記篩別処理を２０回実施し、篩下の回収微粒成分の２０回分の合計質量（ｗ）と篩に投入した試料の２０回分の合計質量（ｗ０）とから、下式によりαアルミナ成形体中の含有率を算出した。
粒子径１００μｍ以下の微粒成分の含有率（質量％）＝ｗ／ｗ０×１００
（８）不純物濃度、純度
Ｓｉ、Ｎａ、Ｍｇ、Ｃｕ、Ｆｅ、Ｃａの含有量は、固体発光分光法にて測定した。
純度としては、前記αアルミナ成形体中に含まれるＳｉ，Ｎａ，Ｍｇ，Ｃｕ，Ｆｅ，Ｃａの質量の総和（質量％）を上記測定結果から算出し、これを１００から差し引いたものを用いた。算出式は以下のとおりである。
純度（質量％）＝１００−不純物の質量の総和（質量％）
（９）かさ密度
試料を内径３７ｍｍ、高さ１８５ｍｍのシリンダーに充填した後、その試料質量を測定容器の容積で除してかさ密度を算出した。
（１０）比表面積
比表面積は、ＢＥＴ比表面積測定装置〔島津製作所社製「２３００−ＰＣ−１Ａ」〕を用いて窒素吸着法により測定した。
（１１）押出成形体の水分含有率
試料約１０ｇを秤量し、赤外線水分計〔株式会社ケット科学研究所「ＦＤ−８００」〕にて、加熱温度を１２０℃、測定終点を３０秒あたりの質量減少率が、投入した試料質量に対し０．０５％以下となった時点とし、湿潤基準にて試料の水分含有率（質量％）を測定した。 In addition, the evaluation method in an Example is as follows.
(1) Relative density
As the relative density of the obtained α-alumina compact, the sintered density calculated from the closed pore volume calculated from the pore volume (open pore volume) and the particle density was used. The pore volume was determined as a pore volume within a pore radius of 1 μm or less by mercury porosimetry using an Autopore III9420 apparatus (MICROMERITICS) after drying the sample at 120 ° C. for 4 hours.
Relative density (%) = (sintering density / 3.98) × 100
Sintering density (g / cm 3 ) = 1 / {(1 / 3.98) + pore volume + closed pore volume}
Closed pore volume (cm 3 / g) = (1 / particle density) − (1 / 3.98)
(2) Closed porosity
The closed porosity was calculated from the particle density according to the following formula. The particle density was calculated based on the true specific gravity measurement method of JIS R7222.
Closed porosity (%) = [(closed pore volume) / {(1 / 3.98) + pore volume + closed pore volume}] × 100
(3) The volume was calculated by using the following formula from the sintered density and the mass per one α-alumina compact.
Volume (cm 3 / piece) = mass [g / piece] / sintering density [g / cm 3 ]
(4) Crushing strength According to JIS Z 8841: 1993, a total of 20 samples extracted at random under the condition of pressurization speed = 1 mm / s were measured, and the crushing strength was calculated from the average. In the case of a cylindrical α-alumina molded body, the load direction was the diameter direction of the cross section.
(5) Drop strength The drop strength was measured by a method according to JIS Z 8841: 1993 except that the drop height was 5 m. The sample after 5 drops was sieved with a 1 mm aperture, and the mass was calculated from the mass (m) of the sample remaining on the sieve and the mass (m 0 ) of all the samples.
Drop strength = m / m 0 × 100
(6) Dimensions of Extruded Molded Body and α-Alumina Molded Body About a total of 120 extrusion-molded bodies molded into a cylindrical shape or a total of 120 randomly extracted from α-alumina molded bodies obtained by firing the extruded molded body, The cross-sectional diameter and the distance between the two cross-sections were measured using a digital caliper as the height of the extruded or α-alumina compact, and the average height and average cross-sectional diameter were calculated.
(7) A 500 g sample per time is put into a sieve having a measuring aperture of 100 μm and a fine particle component having a particle diameter of 100 μm or less present in the α-alumina compact, and the sieve is passed in 1 minute in accordance with JIS K 0069: 1992. The end point was set when the passing fine particle component became 0.1% or less of the charged sample mass.
The above sieving process is carried out 20 times, and the total mass (w) of 20 collected fine particle components under the sieve and the total mass (w 0 ) of 20 samples of the sample put on the sieve are used to form α alumina according to the following formula: The content in the body was calculated.
Content (% by mass) of fine particle component having a particle diameter of 100 μm or less = w / w 0 × 100
(8) Impurity concentration and purity Si, Na, Mg, Cu, Fe, and Ca content were measured by solid-state emission spectroscopy.
As the purity, the total mass (% by mass) of Si, Na, Mg, Cu, Fe, and Ca contained in the α-alumina molded body was calculated from the above measurement results, and the value obtained by subtracting this from 100 was used. . The calculation formula is as follows.
Purity (mass%) = 100-total mass of impurities (mass%)
(9) After the bulk density sample was filled into a cylinder having an inner diameter of 37 mm and a height of 185 mm, the bulk density was calculated by dividing the sample mass by the volume of the measurement container.
(10) Specific surface area The specific surface area was measured by a nitrogen adsorption method using a BET specific surface area measuring device [“2300-PC-1A” manufactured by Shimadzu Corporation].
(11) About 10 g of the moisture content sample of the extruded product was weighed and measured by an infrared moisture meter (Kett Science Laboratory "FD-800") at a heating temperature of 120 ° C and a measurement end point of 30 seconds. The moisture content (% by mass) of the sample was measured on a wet basis when the decrease rate was 0.05% or less with respect to the sample mass charged.

実施例１
αアルミナ前駆体として、アルミニウムアルコキシドの加水分解法により得られた高純度水酸化アルミニウム（擬ベーマイト）を用いた。前記水酸化アルミニウム１００重量部と水性媒体として水１６０部とを内部に混合用回転円盤を有する連続噴射混合機（株式会社粉研パウテックス製フロージェットミキサー）を用いて混合し、湿潤水酸化アルミニウムを得た。
得られた湿潤水酸化アルミニウムを、直径４ｍｍの円柱状に押出成形し、４ｍｍ間隔で切断した。そのときの押出成形圧力は、０．６ＭＰａであった。得られた押出成形体の平均断面直径が４．０ｍｍ、平均高さが４．０ｍｍで、断面直径を１としたときの高さは、１．０であった。この押出成形体を、コンベア式乾燥機中、熱風温度１００℃、熱風風速０．６ｍ／ｓ、層厚３０ｍｍで乾燥させ、乾燥後水分含有率３０質量％まで水分を揮発させた後に、昇温速度１００℃／ｈｒ、焼成温度１３５０℃で４時間焼成した。次いで、目開き１．４ｍｍの樹脂製の網を備えた振動型篩別機を用いて、微粒成分の篩別除去を２回行い、αアルミナ成形体Ａを得た。 Example 1
As the α-alumina precursor, high-purity aluminum hydroxide (pseudo boehmite) obtained by a hydrolysis method of aluminum alkoxide was used. 100 parts by weight of the above aluminum hydroxide and 160 parts of water as an aqueous medium were mixed using a continuous jet mixer having a rotating disk for mixing inside (flow jet mixer manufactured by Powder Research Co., Ltd.), and wet aluminum hydroxide was mixed. Obtained.
The obtained wet aluminum hydroxide was extruded into a cylindrical shape having a diameter of 4 mm and cut at intervals of 4 mm. The extrusion pressure at that time was 0.6 MPa. The obtained extruded product had an average cross-sectional diameter of 4.0 mm, an average height of 4.0 mm, and a height of 1.0 when the cross-sectional diameter was 1. The extruded product was dried in a conveyor dryer at a hot air temperature of 100 ° C., a hot air wind speed of 0.6 m / s, and a layer thickness of 30 mm. After drying, the water content was volatilized to 30% by mass, and then the temperature was raised. Firing was performed at a rate of 100 ° C./hr and a firing temperature of 1350 ° C. for 4 hours. Subsequently, using a vibration-type sieving machine equipped with a resin mesh having a mesh size of 1.4 mm, the fine component was removed twice to obtain an α-alumina compact A.

前記αアルミナ成形体Ａは円柱状で、平均断面直径が２．３ｍｍ、平均高さが２．３ｍｍで、断面直径を１としたときの高さが１．０であり、相対密度は５１％、体積は０．０１ｃｍ３、圧壊強度は１２７Ｎ、閉気孔率は０％、かさ密度は１．１ｇ／ｃｍ３、比表面積は２．５ｍ２／ｇであった。また、前記αアルミナＡ成形体中のＳｉは４ｐｐｍ、Ｎａは５ｐｐｍ以下、Ｍｇは１ｐｐｍ以下、Ｃｕは１ｐｐｍ以下、Ｆｅは４ｐｐｍ、Ｃａは１ｐｐｍ以下であり、アルミナ純度は９９．９９質量％で、粒子径１００μｍ以下の微粒成分が０．００３質量％であった。このαアルミナ成形体Ａは、圧壊強度が十分に高いため、落下強度が９９．６と高く、サファイア単結晶製造に用いると原料輸送時や原料充填時の摺動に起因する微粉発塵が少なく、供給配管等の閉塞を抑制できる。また、相対密度も５１％であることから、加熱半溶融処理を正常に行うことができる。さらに微粒成分含有量も極めて少ないため、サファイア単結晶育成時に結晶欠陥の発生を抑制できる。 The α-alumina compact A is cylindrical, has an average cross-sectional diameter of 2.3 mm, an average height of 2.3 mm, a cross-sectional diameter of 1, and a relative density of 51%. The volume was 0.01 cm 3 , the crushing strength was 127 N, the closed porosity was 0%, the bulk density was 1.1 g / cm 3 , and the specific surface area was 2.5 m 2 / g. In the α-alumina A molded body, Si is 4 ppm, Na is 5 ppm or less, Mg is 1 ppm or less, Cu is 1 ppm or less, Fe is 4 ppm, Ca is 1 ppm or less, and the alumina purity is 99.99 mass%. The fine particle component having a particle diameter of 100 μm or less was 0.003% by mass. Since this α-alumina compact A has a sufficiently high crushing strength, the drop strength is as high as 99.6, and when used in the production of sapphire single crystals, there is little dust generation due to sliding during transportation of raw materials or filling of raw materials. , Blockage of supply piping and the like can be suppressed. Moreover, since a relative density is also 51%, a heating semi-melt process can be performed normally. Furthermore, since the content of the fine particle component is extremely small, the occurrence of crystal defects can be suppressed during the growth of the sapphire single crystal.

実施例２
焼成後の微粒成分の篩別除去を行わなかった以外は、実施例１と同様にしてαアルミナ成形体Ｂを得た。 Example 2
An α-alumina molded body B was obtained in the same manner as in Example 1 except that the fine particle component after calcination was not removed by sieving.

前記αアルミナ成形体Ｂは円柱状で、平均断面直径が２．３ｍｍ、平均高さが２．３ｍｍで、断面直径を１としたときの高さが１．０であり、相対密度は５１％、体積は０．０１ｃｍ３、圧壊強度は１２７Ｎ、落下強度は９９．６、閉気孔率は０％、かさ密度は１．１ｇ／ｃｍ3、比表面積は２．５ｍ２／ｇであった。また、前記αアルミナＢ成形体中のＳｉは７ｐｐｍ、Ｎａは６ｐｐｍ、Ｍｇは１ｐｐｍ以下、Ｃｕは１ｐｐｍ以下、Ｆｅは４ｐｐｍ、Ｃａは２ｐｐｍであり、アルミナ純度は９９．９９質量％で、粒子径１００μｍ以下の微粒成分を０．４質量％であった。このαアルミナ成形体Ｂは、圧壊強度が十分に高いため、落下強度も９９．６と高く、サファイア単結晶製造に用いると原料輸送時や原料充填時の摺動に起因する微粉発塵が少なく、供給配管等の閉塞を抑制できる。また相対密度が５１％であることから加熱半溶融処理を正常に行うことができる。 The α-alumina compact B is cylindrical, has an average cross-sectional diameter of 2.3 mm, an average height of 2.3 mm, a height of 1.0 when the cross-sectional diameter is 1, and a relative density of 51%. The volume was 0.01 cm 3 , the crushing strength was 127 N, the drop strength was 99.6, the closed porosity was 0%, the bulk density was 1.1 g / cm 3 , and the specific surface area was 2.5 m 2 / g. In the α-alumina B molded body, Si was 7 ppm, Na was 6 ppm, Mg was 1 ppm or less, Cu was 1 ppm or less, Fe was 4 ppm, Ca was 2 ppm, alumina purity was 99.99 mass%, particle size The fine particle component of 100 μm or less was 0.4% by mass. Since this α-alumina compact B has a sufficiently high crushing strength, it has a high drop strength of 99.6, and when used in the production of sapphire single crystals, there is little dust generation due to sliding during transportation of raw materials or filling of raw materials. , Blockage of supply piping and the like can be suppressed. Further, since the relative density is 51%, the heating semi-melting process can be normally performed.

比較例１
αアルミナ前駆物質として、アルミニウムアルコキシドの加水分解法により得られた高純度水酸化アルミニウム（擬ベーマイト）を用いた。該水酸化アルミニウム１００重量部と水性媒体として水１５０部とを混合しながら転動造粒させ、平均径が４ｍｍの球状の湿潤水酸化アルミニウム造粒物を得た。
得られた該水酸化アルミニウム造粒物を、コンベア式乾燥機中、熱風温度１００℃、熱風風速０．６ｍ／ｓ、層厚１０ｍｍで乾燥させ、乾燥後水分含有率３０質量％まで水分を揮発させた後に、昇温速度１００℃／ｈｒ、焼成温度１３５０℃で４時間焼成した。次いで、目開き１．４ｍｍの樹脂製の網を備えた振動型篩別機を用いて、微粒成分の篩別除去を２回行い、球状αアルミナＣを得た。 Comparative Example 1
As the α-alumina precursor, high-purity aluminum hydroxide (pseudoboehmite) obtained by a hydrolysis method of aluminum alkoxide was used. Rolling granulation was performed while mixing 100 parts by weight of the aluminum hydroxide and 150 parts of water as an aqueous medium to obtain a spherical wet aluminum hydroxide granulated product having an average diameter of 4 mm.
The obtained aluminum hydroxide granulated product is dried at a hot air temperature of 100 ° C., a hot air wind speed of 0.6 m / s, and a layer thickness of 10 mm in a conveyor dryer, and after drying, the water content is volatilized to 30% by mass. Then, it was baked for 4 hours at a heating rate of 100 ° C./hr and a baking temperature of 1350 ° C. Next, using a vibration-type sieving machine equipped with a resin mesh having a mesh size of 1.4 mm, the fine component was removed twice to obtain spherical α-alumina C.

前記球状αアルミナＣは、平均径が１．９ｍｍ、相対密度は４９％で、体積は０．００４ｃｍ３、圧壊強度は３９Ｎ、閉気孔率は０％、かさ密度は１．２ｇ／ｃｍ３、比表面積は２．８ｍ２／ｇであった。また、前記αアルミナＣ中の含まれるＳｉは６ｐｐｍ、Ｎａは５ｐｐｍ以下、Ｍｇは１ｐｐｍ、Ｃｕは１ｐｐｍ以下、Ｆｅは５ｐｐｍ、Ｃａは１ｐｐｍ以下であり、アルミナ純度は９９．９９質量％で、粒子径１００μｍ以下の微粒成分を０．００３質量％であった。この球状アルミナＣは、圧壊強度が低いため、落下強度が９６．５と低く、サファイア単結晶製造に用いると原料輸送時や原料充填時の摺動に起因する微粉発塵が起こるためサファイア単結晶を効率よく生産できない。 The spherical α-alumina C has an average diameter of 1.9 mm, a relative density of 49%, a volume of 0.004 cm 3 , a crushing strength of 39 N, a closed porosity of 0%, a bulk density of 1.2 g / cm 3 , The specific surface area was 2.8 m 2 / g. Further, Si contained in the α-alumina C is 6 ppm, Na is 5 ppm or less, Mg is 1 ppm, Cu is 1 ppm or less, Fe is 5 ppm, Ca is 1 ppm or less, and the alumina purity is 99.99% by mass. The content of fine particles having a diameter of 100 μm or less was 0.003% by mass. Since this spherical alumina C has a low crushing strength, its drop strength is as low as 96.5, and when used in the production of a sapphire single crystal, fine powder dust is generated due to sliding during transportation of the raw material or filling of the raw material. Cannot be produced efficiently.

Claims (6)

１個あたりの体積が０．０１ｃｍ３以上１ｃｍ３以下であり、
相対密度が４０％以上６０％未満であり、
圧壊強度が８０Ｎ以上であり、
比表面積が１ｍ２／ｇを超え４ｍ２／ｇ以下である成形体で、
前記成形体の集合体としてのかさ密度が１．０ｇ／ｃｍ３以上１．５ｇ／ｃｍ３未満であることを特徴とするαアルミナ成形体。 The volume per piece is 0.01 cm 3 or more and 1 cm 3 or less,
The relative density is 40% or more and less than 60%,
Crushing strength is 80 N or more,
A molded body having a specific surface area of more than 1 m 2 / g and 4 m 2 / g or less,
Α-alumina formed body, wherein the bulk density of the aggregate of the compact is less than 1.0 g / cm 3 or more 1.5 g / cm 3. 前記αアルミナ成形体の形状が円柱状からなり、断面直径を１としたとき、高さが０．５以上１．５以下である請求項１に記載のαアルミナ成形体。 2. The α-alumina molded body according to claim 1, wherein the shape of the α-alumina molded body is a columnar shape, and the height is 0.5 or more and 1.5 or less when the cross-sectional diameter is 1. 粒子径１００μｍ以下の微粒成分が０．０５質量％以下である請求項１または２に記載のαアルミナ成形体。 The α-alumina molded body according to claim 1 or 2, wherein a fine particle component having a particle diameter of 100 µm or less is 0.05 mass% or less. 純度が９９．９９質量％以上であり、Ｓｉ、Ｎａ、Ｃａ、Ｆｅ、ＣｕおよびＭｇの含有量がそれぞれ１０ｐｐｍ以下である、請求項１〜３のいずれかに記載のαアルミナ成形体。 The alpha alumina molded object according to any one of claims 1 to 3, wherein the purity is 99.99 mass% or more, and the contents of Si, Na, Ca, Fe, Cu, and Mg are each 10 ppm or less. 工程（１）〜（４）を含むことを特徴とするαアルミナの製造方法。
工程（１）αアルミナ前駆体と水性媒体を混合して混合物を得る工程。
工程（２）前記混合物を押出圧０．１ＭＰａ以上１．５ＭＰａ以下で押出成形し、押出成形体を得る工程。
工程（３）前記押出成形体中の水分含有率が１０質量％以上６０質量％以下となるよう調整する工程。
工程（４）水分含有率を調整後の押出成形体を焼成し、αアルミナ成形体を得る工程。 The manufacturing method of alpha alumina characterized by including process (1)-(4).
Step (1) A step of obtaining a mixture by mixing an α-alumina precursor and an aqueous medium.
Step (2) A step of extruding the mixture at an extrusion pressure of 0.1 MPa to 1.5 MPa to obtain an extruded product.
Process (3) The process of adjusting so that the moisture content rate in the said extrusion molded object may be 10 mass% or more and 60 mass% or less.
Process (4) The process of baking the extrusion molded object after adjusting water content, and obtaining an alpha alumina molded object. さらに、前記αアルミナ成形体から粒子径１００μｍ以下の微粒成分を０．０５質量％以下まで除去する工程を含む請求項５に記載のαアルミナ成形体の製造方法。 Furthermore, the manufacturing method of the alpha alumina molded object of Claim 5 including the process of removing the fine particle component of a particle diameter of 100 micrometers or less from the said alpha alumina molded object to 0.05 mass% or less.
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