JP3893823B2 - Method for producing low soda alumina - Google Patents
Method for producing low soda alumina Download PDFInfo
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- JP3893823B2 JP3893823B2 JP36698699A JP36698699A JP3893823B2 JP 3893823 B2 JP3893823 B2 JP 3893823B2 JP 36698699 A JP36698699 A JP 36698699A JP 36698699 A JP36698699 A JP 36698699A JP 3893823 B2 JP3893823 B2 JP 3893823B2
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- soda
- alumina
- silica
- producing low
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Description
【０００１】
【発明の属する技術分野】
本発明は低ソーダアルミナの製造方法に関する。
【０００２】
【従来の技術】
低ソーダアルミナは、内燃機関のスパークプラグ碍子、電子部品用セラミックス、耐熱性・耐摩耗性セラミックス等の原料として多量に使用されている。
【０００３】
低ソーダアルミナの工業的な製造方法として、アルミン酸ナトリウム溶液を加水分解して得られるソーダを含有する水酸化アルミニウム又は遷移アルミナにシリカ系物質を添加し、鉱化剤の存在下で焼成した後、シリカ系物質を分離する方法が知られている。
【０００４】
【発明が解決しようとする課題】
しかしながら、前記方法ではシリカ系物質として、十分に水洗し、かつ微粒成分を除去したシリカ系物質を用いる場合にも低ソーダアルミナはＳｉＯ2含有量が高くなることがあった。
【０００５】
【発明を解決するための手段】
本発明者等は、ソーダを含有する水酸化アルミニウム又は遷移アルミナから低ソーダアルミナを製造するための方法について鋭意検討した結果、シリカ系物質をアルミナ粒子を用いて被覆してなるシリカ系脱ソーダ剤を用いることによりＳｉＯ2含有量を低減し得ることを見出し、本発明を完成するに至った。すなわち、本発明は、（１）ソーダを含有する水酸化アルミニウム又は遷移アルミナに、シリカ系物質をアルミナ粒子を用いて被覆してなるシリカ系脱ソーダ剤を添加し、鉱化剤の存在下で焼成した後、該脱ソーダ剤とアルミナを分離してなる低ソーダアルミナの製造方法であり、
【０００６】
（２）アルミナ粒子の平均粒子径が１０〜２００μｍであることを特徴とする（１）記載の低ソーダアルミナの製造方法であり、
【０００７】
（３）シリカ系物質が珪石、石英、珪砂であることを特徴とする（１）又は（２）に記載の低ソーダアルミナの製造方法であり、
【０００８】
（４）脱ソーダ剤のＳｉＯ2含有量が５０重量％以上であることを特徴とする（１）〜（３）の何れか１つに記載の低ソーダアルミナの製造方法であり、
【０００９】
（５）鉱化剤がフッ素系物質であることを特徴とする（１）〜（４）の何れか１つに記載の低ソーダアルミナの製造方法である。
【００１０】
【発明の実施の形態】
以下本発明を詳細に説明する。
本発明は、シリカ系物質をアルミナ粒子を用いて被覆してなるシリカ系脱ソーダ剤を用いることを特徴とする。前記シリカ系脱ソーダ剤を用いる場合には、ＳｉＯ2含有量の低い低ソーダアルミナを製造することができる。更に、同一焼成炉を使って繰り返し焼成した時でも、ＳｉＯ2含有量が低い低ソーダアルミナを得ることが可能となる。
【００１１】
シリカ系物質としては、例えば、珪石、石英、珪砂、シャモット、ムライト、シリマナイト、マグネシウムシリケート、アルミナシリケート等が挙げられる。就中、脱ソーダ性能が高いことから、珪石、石英、珪砂の適用が推奨される。前記シリカ系物質は、通常、平均粒子径が０．３ｍｍ〜２ｍｍであることが好ましい。
【００１２】
シリカ系物質を被覆するために用いるアルミナ粒子しては、そのアルミナ粒子の平均粒子径は好ましくは２〜２００μｍ、より好ましくは２０〜１００μｍである。平均粒子径が前記範囲内である場合には、シリカ系物質に由来する低ソーダアルミナのＳｉＯ2汚染を一層低減し、かつ低ソーダアルミナの脱ソーダ化を促進できる。理由は詳らかではないが、ＳｉＯ2汚染についてはシリカ系物質と水酸化アルミニウム、遷移アルミナ若しくは低ソーダアルミナとが接触することを避けられることが関係し、脱ソーダ化についてはアルミナに含まれるソーダが気体となって拡散しシリカ系物質に捕捉されることが関係していると考えられる。また、得られる低ソーダアルミナの不純物汚染を低減するできることから、前記アルミナ粒子はＡｌ2Ｏ3純度が９９重量％以上であることが好ましい。
【００１３】
シリカ系脱ソーダ剤の調製方法としては、例えば、シリカ系物質とアルミナ粒子とを混合し、次いで得られた混合物をロータリーキルン、ローラーハースキルン又は電気炉等の焼成炉を用い温度１０００℃以上、好ましくは１１００℃〜１３００℃で焼成する方法が挙げられる。脱ソーダ剤の調製に際しては、前記混合物をフッ素系物質又は塩素系物質の存在下で焼成を行ってもよい。シリカ系脱ソーダ剤はＳｉＯ2含有量が好ましくは５０重量％以上、より好ましくは７０重量％〜９０重量％である。
【００１４】
アルミナ粒子の平均粒子径により異なり一義的ではないが、通常、シリカ系脱ソーダ剤を構成するシリカ系物質に対してアルミナ粒子の割合が増えると、シリカ系脱ソーダ剤の脱ソーダ性能が低下する傾向にあるので、アルミナ粒子の割合を適宜調整することが好ましい。
【００１５】
本発明の低ソーダアルミナの製造方法を行うに際しては、前述したシリカ系脱ソーダ剤を用いて以下の工程▲１▼ソーダを含有する水酸化アルミニウム又は遷移アルミナにシリカ系脱ソーダ剤を添加し、▲２▼鉱化剤の存在下で焼成した後、▲３▼脱ソーダ剤とアルミナを分離してなる、を順に行えばよい。
【００１６】
ソーダを含有する水酸化アルミニウム又は遷移アルミナとしては、例えば、アルミン酸ナトリウム溶液を加水分解して得られる水酸化アルミニウム又はその水酸化アルミニウムを仮焼して得られる遷移アルミナ等が挙げられる。また、これらを混合したものでもよい。
【００１７】
鉱化剤としては、例えばフッ素系物質、塩素系物質、ホウ素系物質が挙げられる。就中、焼成炉の腐食が比較的起り難いことからフッ素系物質の適用が推奨される。フッ素系物質の具体例としては、例えば、フッ化水素、フッ化アルミニウム、フッ化マグネシウム、フッ化アンモニウム等が挙げられる。フッ素系物質の最適な存在量は、焼成温度、時間に応じて適宜選択すればよい。
【００１８】
前記工程▲１▼を行うに際しては、例えば、焼成炉に水酸化アルミニウム又は遷移アルミナ（以下、水酸化アルミニウム等とする。）を添加し、シリカ系脱ソーダ剤を添加する方法、焼成炉に水酸化アルミニウム等とシリカ系脱ソーダ剤とを同時に添加する方法、又は水酸化アルミニウム等とシリカ系脱ソーダ剤とを水平円筒型混合機等の容器回転式混合機を用いて混合した後、得られた混合物を焼成炉に添加する方法等で行えばよい。
【００１９】
前記工程▲２▼を行うに際しては、例えば、ロータリーキルン、ローラハースキルン又は電気炉等の焼成炉を用いて工程（１）で得られた水酸化アルミニウム等とシリカ系脱ソーダ剤との混合物をフッ素系物質の存在下で焼成すればよい。焼成条件は、使用する焼成炉により異なり一義的ではないが通常温度が１０００℃以上、好ましくは１１００℃〜１４００℃であり、時間が数分以上、好ましくは１０分〜１０時間である。
【００２０】
前記工程▲３▼を行うに際しては、例えば、篩い分け機等の乾式分級機を用いて脱ソーダ剤とアルミナを分離すればよい。
【００２１】
【実施例】
以下実施例により更に詳細には説明するが、本発明は実施例により制限されるものではない。
Ｎａ2Ｏ含有量（重量％）；蛍光Ｘ線分析により測定した。
ＳｉＯ2含有量（重量％）；蛍光Ｘ線分析により測定した。
【００２２】
実施例１
シリカ系脱ソーダ剤の調製：
平均粒子径１ｍｍの珪砂１００重量部と平均粒子径５０μｍの遷移アルミナ粒子７００重量部とを混合し、次いで得られた混合物を焼成炉を用いて温度１３００℃で焼成した。得られた焼成物を冷却後、１４９μｍの目開きの篩で遷移アルミナ粒子を除去して、ＳｉＯ2含有量７５重量％のシリカ系脱ソーダ剤を得た。
【００２３】
低ソーダアルミナの焼成：
バイヤー法により得られた水酸化アルミニウム（Ｎａ2Ｏ含有量０．２重量％、ＳｉＯ2含有量０．０１重量％未満）１００重量部と前記脱ソーダ剤５重量部との混合物を、フッ素系物質の存在下、連続焼成炉（焼成帯域の温度が１３００℃である。）を用いて焼成し、低ソーダアルミナと脱ソーダ剤との混合物を得た。得られた混合物を冷却後、１４９μｍの目開きの篩を用いて脱ソーダ剤と低ソーダアルミナとに分離した。得られた低ソーダアルミナはＮａ2Ｏ含有量が０．１重量％未満であり、ＳｉＯ2含有量が０．０２７重量％であり、結晶構造がα型であった。
【００２４】
比較例１
実施例１において、前記脱ソーダ剤に変えて、水洗し、かつ微粒成分を除去しして得られた平均粒子径１ｍｍの珪砂を用いた以外は同様にして行った。得られた低ソーダアルミナはＮａ2Ｏ含有量が０．１重量％未満であり、ＳｉＯ2含有量が０．０４４重量％であり、結晶構造がα型であった。
【００２５】
【発明の効果】
以上詳述した様に、本発明はソーダを含有する水酸化アルミニウム又は遷移アルミナからＳｉＯ2含有量が低い低ソーダアルミナを製造し得る方法であり、産業上の利用価値は大である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing low soda alumina.
[0002]
[Prior art]
Low soda alumina is used in large quantities as a raw material for spark plug insulators for internal combustion engines, ceramics for electronic parts, heat-resistant and wear-resistant ceramics, and the like.
[0003]
As an industrial production method of low soda alumina, after adding a silica-based material to aluminum hydroxide or transition alumina containing soda obtained by hydrolyzing a sodium aluminate solution, and calcining in the presence of a mineralizer A method for separating a silica-based material is known.
[0004]
[Problems to be solved by the invention]
However, in the above-described method, when using a silica-based material that has been sufficiently washed with water and from which fine particle components have been removed, the low soda alumina may have a high SiO 2 content.
[0005]
[Means for Solving the Invention]
As a result of intensive studies on a method for producing low-soda alumina from soda-containing aluminum hydroxide or transition alumina, the present inventors have obtained a silica-based soda removal agent obtained by coating a silica-based material with alumina particles. As a result, it was found that the SiO 2 content can be reduced by using the present invention, and the present invention has been completed. That is, the present invention adds (1) a silica-based soda removing agent obtained by coating a silica-based material with alumina particles to aluminum hydroxide or transition alumina containing soda, and in the presence of a mineralizer. It is a method for producing low soda alumina, which is obtained by separating the soda remover and alumina after firing.
[0006]
(2) The method for producing low-soda alumina according to (1), wherein the average particle diameter of the alumina particles is 10 to 200 μm,
[0007]
(3) The method for producing low-soda alumina according to (1) or (2), wherein the silica-based material is silica, quartz, or silica sand,
[0008]
(4) The method for producing low-soda alumina according to any one of (1) to (3), wherein the content of SiO 2 in the soda removal agent is 50% by weight or more,
[0009]
(5) The method for producing low-soda alumina according to any one of (1) to (4), wherein the mineralizer is a fluorine-based substance.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The present invention is characterized by using a silica-based soda removing agent obtained by coating a silica-based material with alumina particles. When the silica-based soda removing agent is used, low soda alumina having a low SiO 2 content can be produced. Furthermore, even when repeatedly fired using the same firing furnace, low soda alumina having a low SiO 2 content can be obtained.
[0011]
Examples of the silica-based material include silica, quartz, silica sand, chamotte, mullite, sillimanite, magnesium silicate, alumina silicate, and the like. In particular, silica stone, quartz, and silica sand are recommended because of their high soda removal performance. In general, the silica-based material preferably has an average particle diameter of 0.3 mm to 2 mm.
[0012]
The alumina particles used for coating the silica-based material preferably have an average particle diameter of 2 to 200 μm, more preferably 20 to 100 μm. When the average particle diameter is within the above range, it is possible to further reduce the SiO 2 contamination of low soda alumina derived from the silica-based material and promote the soda removal of low soda alumina. The reason is not clear, but for SiO 2 contamination, it is related to avoiding contact between the silica-based material and aluminum hydroxide, transition alumina or low soda alumina. It is considered to be related to diffusion as a gas and trapped by a silica-based material. Moreover, since the impurity contamination of the low-soda alumina obtained can be reduced, the alumina particles preferably have an Al 2 O 3 purity of 99% by weight or more.
[0013]
As a method for preparing a silica-based soda remover, for example, a silica-based material and alumina particles are mixed, and the resulting mixture is then used in a kiln such as a rotary kiln, roller hearth kiln or electric furnace, and the temperature is preferably 1000 ° C. or higher. The method of baking at 1100 degreeC-1300 degreeC is mentioned. When preparing the soda removal agent, the mixture may be calcined in the presence of a fluorine-based material or a chlorine-based material. The silica-based soda remover has a SiO 2 content of preferably 50% by weight or more, more preferably 70% by weight to 90% by weight.
[0014]
Although it varies depending on the average particle diameter of the alumina particles and is not unambiguous, usually, when the ratio of the alumina particles to the silica-based material constituting the silica-based soda remover increases, the desoder performance of the silica-based soda remover decreases. Since there is a tendency, it is preferable to appropriately adjust the proportion of alumina particles.
[0015]
When performing the method for producing low-soda alumina of the present invention, the silica-based soda remover is added to the aluminum hydroxide or transition alumina containing the following steps (1) using the silica-based soda remover described above, (2) After firing in the presence of a mineralizer, (3) separating the soda agent and alumina may be performed in order.
[0016]
Examples of aluminum hydroxide or transition alumina containing soda include aluminum hydroxide obtained by hydrolyzing a sodium aluminate solution or transition alumina obtained by calcining the aluminum hydroxide. Moreover, what mixed these may be used.
[0017]
Examples of the mineralizer include a fluorine-based material, a chlorine-based material, and a boron-based material. In particular, the application of fluorine-based materials is recommended because corrosion of the firing furnace is relatively difficult to occur. Specific examples of the fluorine-based substance include hydrogen fluoride, aluminum fluoride, magnesium fluoride, ammonium fluoride, and the like. What is necessary is just to select the optimal amount of a fluorine-type substance suitably according to baking temperature and time.
[0018]
In carrying out the step (1), for example, a method of adding aluminum hydroxide or transition alumina (hereinafter referred to as aluminum hydroxide) to a firing furnace and adding a silica-based soda remover, water is added to the firing furnace. Obtained after mixing aluminum oxide or the like and silica-based soda remover at the same time, or mixing aluminum hydroxide or the like and silica-based soda remover using a container rotary mixer such as a horizontal cylindrical mixer. What is necessary is just to carry out by the method etc. which add the mixed mixture to a baking furnace.
[0019]
In performing the step (2), for example, the mixture of the aluminum hydroxide obtained in the step (1) and the silica-based soda remover using a baking kiln such as a rotary kiln, a roller hearth kiln or an electric furnace is fluorinated. It may be fired in the presence of a system material. The firing conditions vary depending on the firing furnace used and are not unambiguous, but the normal temperature is 1000 ° C. or higher, preferably 1100 ° C. to 1400 ° C., and the time is several minutes or longer, preferably 10 minutes to 10 hours.
[0020]
In carrying out the step (3), for example, the soda removing agent and alumina may be separated using a dry classifier such as a sieving machine.
[0021]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples.
Na 2 O content (% by weight); measured by fluorescent X-ray analysis.
SiO 2 content (% by weight); measured by fluorescent X-ray analysis.
[0022]
Example 1
Preparation of silica-based soda remover:
100 parts by weight of silica sand having an average particle diameter of 1 mm and 700 parts by weight of transition alumina particles having an average particle diameter of 50 μm were mixed, and then the resulting mixture was fired at a temperature of 1300 ° C. using a firing furnace. After the obtained fired product was cooled, the transition alumina particles were removed with a sieve having an opening of 149 μm to obtain a silica-based soda remover having a SiO 2 content of 75% by weight.
[0023]
Low soda alumina firing:
A mixture of 100 parts by weight of aluminum hydroxide (Na 2 O content 0.2% by weight, SiO 2 content less than 0.01% by weight) obtained by the Bayer method and 5 parts by weight of the above-mentioned soda remover Firing was performed in the presence of the substance using a continuous firing furnace (the temperature of the firing zone was 1300 ° C.) to obtain a mixture of low soda alumina and a soda removal agent. After cooling the obtained mixture, it was separated into a soda-removing agent and low-soda alumina using a sieve having an opening of 149 μm. The obtained low soda alumina had an Na 2 O content of less than 0.1% by weight, an SiO 2 content of 0.027% by weight, and a crystal structure of α type.
[0024]
Comparative Example 1
In Example 1, it replaced with the said soda removal agent, and it carried out similarly except having used the quartz sand with an average particle diameter of 1 mm obtained by washing with water and removing a fine particle component. The obtained low soda alumina had an Na 2 O content of less than 0.1% by weight, an SiO 2 content of 0.044% by weight, and an α-type crystal structure.
[0025]
【The invention's effect】
As described above in detail, the present invention is a method capable of producing low soda alumina having a low SiO 2 content from aluminum hydroxide or transition alumina containing soda, and its industrial utility value is great.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36698699A JP3893823B2 (en) | 1999-12-24 | 1999-12-24 | Method for producing low soda alumina |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP36698699A JP3893823B2 (en) | 1999-12-24 | 1999-12-24 | Method for producing low soda alumina |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001180931A JP2001180931A (en) | 2001-07-03 |
| JP3893823B2 true JP3893823B2 (en) | 2007-03-14 |
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| JP36698699A Expired - Fee Related JP3893823B2 (en) | 1999-12-24 | 1999-12-24 | Method for producing low soda alumina |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP5103700B2 (en) * | 2001-06-26 | 2012-12-19 | 住友化学株式会社 | Method for producing low soda alumina |
| JP2006199568A (en) * | 2004-06-16 | 2006-08-03 | Showa Denko Kk | Process for producing low-soda alumina, apparatus therefor, and alumina |
| JP4932148B2 (en) | 2004-10-18 | 2012-05-16 | 株式会社フジミインコーポレーテッド | Method for producing aluminum oxide powder |
| JP2007051037A (en) * | 2005-08-19 | 2007-03-01 | Asahi Kagaku Kogyo Co Ltd | METHOD FOR PRODUCING FLAKY alpha-ALUMINA PARTICLE |
| JP2013212684A (en) * | 2012-03-05 | 2013-10-17 | Aica Kogyo Co Ltd | Scratch resistance decorative sheet |
| KR101548633B1 (en) * | 2013-12-30 | 2015-09-01 | 한국알루미나 주식회사 | Preparation method of low soda-containing alumina using quartz |
| CN112794701A (en) * | 2021-01-11 | 2021-05-14 | 中铝山东新材料有限公司 | Alpha alumina with low sodium oxide content and preparation method thereof |
| CN112678854A (en) * | 2021-01-29 | 2021-04-20 | 中铝山东有限公司 | Preparation method of low-sodium microcrystalline alpha-alumina |
| CN114455619B (en) * | 2022-01-12 | 2024-05-07 | 中铝山东新材料有限公司 | Low-sodium small primary crystal alpha alumina and preparation method thereof |
-
1999
- 1999-12-24 JP JP36698699A patent/JP3893823B2/en not_active Expired - Fee Related
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| JP2001180931A (en) | 2001-07-03 |
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