JP3965270B2 - Highly dispersible high purity magnesium hydroxide powder, method for producing the same, and magnesium hydroxide slurry - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、水酸化マグネシウム粉末に関し、さらに詳しくは、特に、電子材料あるいは触媒材料として有利に用いることができる高分散性高純度水酸化マグネシウム粉末とその製造方法、及び電子材料あるいは触媒材料の製造に有利に用いることができる水酸化マグネシウムスラリーに関するものである。
【０００２】
【従来の技術】
水酸化マグネシウム［Ｍｇ（ＯＨ）2］は３５０℃以上に加熱されると、水１分子を放出して酸化マグネシウムとなる。このような水酸化マグネシウムの熱挙動を利用して、水酸化マグネシウム粉末は、電線被覆用樹脂など合成樹脂の難燃剤として使用されている。また、水酸化マグネシウム粉末は水に接触しても酸化マグネシウムのように水和しないことから、湿式混合の可能なマグネシアセラミックス原料にも利用されている。これらの難燃剤あるいはマグネシアセラミックス原料に使用する水酸化マグネシウム粉末は、水中での分散性が高いこと、及び高純度であることが必要とされている。
【０００３】
特開昭６０−１７６９１８号公報には、１０００℃で１時間焼成後の酸化マグネシウム含有量が９９．５％以上、平均結晶粒子径が１μｍ以下、１μｍ以下の二次粒子の割合が７０％以上の水酸化マグネシウム粉末、及び、塩化マグネシウム水溶液と水酸化カルシウム水溶液とを反応させる水酸化マグネシウム粉末の製造方法が提案されている。そして、この公報の実施例では、１０００℃で１時間焼成後の酸化マグネシウム含有量が、９９．９重量％、平均結晶粒子径が０．２μｍ、１μｍ以下の二次粒子が割合が８６％以上の水酸化マグネシウム粉末が示されている。
【０００４】
また、酸化マグネシウムを水中に投入して、酸化マグネシウムを水和させる高分散性水酸化マグネシウム粉末を製造する方法も提案されている。
【０００５】
特開昭６３−２７７５１０号公報では、水酸化マグネシウム種粒子及びマグネシウム塩の存在するスラリー中にて、酸化マグネシウムを水和させる水酸化マグネシウムの製造方法が提案されている。そして、この公報の実施例では、Ｘ線回折による（００１）面に垂直な方向の結晶子の大きさが７８．４ｎｍ、平均粒子径が２．３μｍ、比表面積６．１ｍ2／ｇの水酸化マグネシウム粉末が示されている。
【０００６】
特開平２−４８４１４号公報では、５０℃以上の温水中で、酸化マグネシウムの水和反応工程を３回以上繰り返す、比表面積が１０ｍ2／ｇ以下で、かつ六角板状結晶の水酸化マグネシウムの製造方法が提案されている。
【０００７】
【発明が解決しようとする課題】
近年、水酸化マグネシウム粉末は、電子材料、あるいは触媒などへの利用が検討されており、より高度な水中分散性と、より高純度（酸化マグネシウム換算の純度で９９．９５重量％以上）の水酸化マグネシウムの開発が望まれている。しかしながら、本発明者の研究によると、これまでに知られている水酸化マグネシウム粉末あるいは製造方法により得られる水酸化マグネシウム粉末では、酸化マグネシウム換算の純度が特に電子材料や触媒材料として用いるには低く、また水中分散性も不十分であるということが判明した。
【０００８】
従って、本発明の目的は、特に、電子材料あるいは触媒材料として有利に使用することができる、水中分散性が高く、かつ高純度の水酸化マグネシウム粉末、及びその製造方法を提供することにある。さらに、本発明は、特に、電子材料あるいは触媒材料の製造に有利に使用することができる高分散性高純度水酸化マグネシウムスラリーを提供することもその目的とする。
【０００９】
【課題を解決するための手段】
本発明は、比表面積が５〜２００ｍ 2 ／ｇの範囲内にあって、純度が９９．９５重量％以上の単結晶からなる酸化マグネシウム微粉末を、水蒸気に接触させることにより、水和させて得られた、比表面積が５〜２００ｍ2／ｇの範囲内にあって、酸化マグネシウム換算の純度が９９．９５重量％以上であることを特徴とする高分散性高純度水酸化マグネシウム粉末にある。
【００１０】
また、本発明は、比表面積が５〜２００ｍ2／ｇの範囲内にあって、純度が９９．９５重量％以上の単結晶からなる酸化マグネシウム微粉末を、水蒸気に接触させることにより、水和させることを特徴とする上記本発明の高分散性高純度水酸化マグネシウム粉末の製造方法にもある。
【００１１】
さらに、本発明は、上記の高分散性高純度水酸化マグネシウム粉末が、平均粒子径が０．１〜１．０μｍの範囲内にある高純度水酸化マグネシウム粒子凝集体を形成して分散していることを特徴とする水酸化マグネシウムスラリーにもある。
【００１２】
ここで、本発明における酸化マグネシウム換算の純度とは、水酸化マグネシウム粉末を１０００℃で焼成して得られた酸化マグネシウム粉末中の酸化マグネシウム量を意味する。水酸化マグネシウム、及び酸化マグネシウムの比表面積は、ＢＥＴ法により測定した値である。また、水酸化マグネシウム粒子凝集体の平均粒子径は、レーザ回折法により測定した値である。
【００１３】
【発明の実施の形態】
本発明の高分散性高純度水酸化マグネシウム粉末は、比表面積が５〜２００ｍ2／ｇの範囲内、好ましくは５〜１００ｍ2／ｇ、より好ましくは５〜５０ｍ2／ｇの範囲内にあること、及び酸化マグネシウム換算の純度が９９．９５重量％以上、特に９９．９８重量％以上であることに主な特徴がある。
【００１４】
本発明の高分散性高純度水酸化マグネシウム粉末は、独立した微細な水酸化マグネシウム粒子の集合体である。そして、本発明の高分散性高純度水酸化マグネシウム粉末は、水などの溶媒に分散させた状態では、水中分散性の高い水酸化マグネシウム粒子の凝集体を形成する。この水酸化マグネシウム粒子凝集体のレーザ回折法により測定される体積基準の平均粒子径は、水中分散性の観点から０．１〜１．０μｍの範囲内にあることが好ましく、０．１〜０．８μｍの範囲内にあることがより好ましい。また、水酸化マグネシウム粒子凝集体は、その形状が球形に近いものであることが水中分散性の観点から好ましい。具体的には、粒子の表面形状を表す指標として知られている比表面積形状係数（「微粒子ハンドブック」 朝倉書店 １９９１年発行 ６０頁参照）が、６〜５０の範囲内にあることが好ましく、６〜３０の範囲内にあることがより好ましい。このような水酸化マグネシウム粒子凝集体が分散されている水酸化マグネシウムスラリーは、湿式混合に適しており電子材料あるいは触媒材料の製造に有利に使用することができる。
【００１５】
本発明の高分散性高純度水酸化マグネシウム粉末は、微細な一次粒子が独立した高純度の単結晶からなる酸化マグネシウム微粒子を水和させることにより製造することができる。本発明の高分散性高純度水酸化マグネシウム粉末の製造に用いる酸化マグネシウム微粉末は、純度が９９．９５重量％以上であって、比表面積が５〜２００ｍ2／ｇの範囲内にあることが好ましい。
【００１６】
本発明の高分散性高純度水酸化マグネシウム粉末の製造に好適に用いることができる酸化マグネシウム微粒子の例としては、マグネシウム蒸気と酸素との気相酸化反応により、結晶核を成長させる気相法により製造したものを挙げることができる。さらに、具体的には、宇部マテリアルズ（株）より販売されている気相法高純度超微粉マグネシアを挙げることができる。この気相法高純度超微粉マグネシアの化学分析値は下記表１の通りである。
【００１７】
【表１】
酸化マグネシウム微粉末を水和させる方法としては、酸化マグネシウム微粉末を水蒸気に接触させる方法（以下、水蒸気接触水和法という）と、酸化マグネシウム微粉末を水中に投入する方法（以下、水中水和法という）とがある。本発明者の研究によれば、水蒸気接触水和法により酸化マグネシウム微粉末を水和させて得た水酸化マグネシウム粉末は、水中水和法により酸化マグネシウム微粉末を水和させて得た水酸化マグネシウム粉末よりも相対的に水中分散性に優れていることが判明している。これは、詳細は不明であるが、水中水和法では酸化マグネシウム微粒子の水和反応が速いために、水和により生成した水酸化マグネシウム粒子が凝集しやすくなるためと考えられる。また、水蒸気接触水和法は、通常の水中水和法で行われる、ろ過、脱水、乾燥、粉砕工程を必要としないので不純物が混入しにくく、また、工程が少なくなるので工業的観点からも有利である。
【００１９】
水蒸気接触水和法により、酸化マグネシウム微粉末を水和させる場合は、酸化マグネシウム微粉末と水蒸気との接触は室温で行っても良いが、より速やかに水和を進行させるためには、５０〜１８０℃の温度で行うことが好ましい。また、この時の湿度は６０〜１００％ＲＨの範囲内に調整されていることが好ましい。
【００２０】
一方、水中水和法により、酸化マグネシウム微粉末を水和させる場合は、酸化マグネシウム微粒子を投入する水の温度は５０〜１００℃の範囲内にあることが好ましい。また、酸化マグネシウム微粒子の水和により生成した水酸化マグネシウム粒子の凝集を起こりにくくするために、撹拌下で酸化マグネシウム微粉末を水和させることが好ましい。
【００２１】
【実施例】
（１）水蒸気接触水和法により酸化マグネシウム微粉末を水和させた水酸化マグネシウムの製造例
［実施例１］
比表面積２７ｍ2／ｇの酸化マグネシウム微粉末［気相法高純度超微粉マグネシア（グレード５００Ａ）、宇部マテリアルズ（株）製］１．３ｋｇを蓋付きステンレス容器（容量２０リットル）に入れて、その容器ごと９０℃、相対湿度７０％ＲＨに保持された恒温恒湿器内で５日間放置して酸化マグネシウム微粉末を水和させて、水酸化マグネシウム粉末を製造した。なお、恒温恒湿器の天井部に結露した水が容器内に侵入しないように、ステンレス容器の蓋を、容器との隙間を２ｃｍあけた状態で、容器の上部（開口部）に固定した。
【００２２】
［実施例２］
比表面積１４ｍ2／ｇの酸化マグネシウム微粉末［気相法高純度超微粉マグネシア（グレード１０００Ａ）、宇部マテリアルズ（株）製］１．３ｋｇを蓋付きステンレス容器（容量２０リットル）に入れて、その容器ごと９０℃、相対湿度７０％ＲＨに保持された恒温恒湿器内で６日間放置した以外は、実施例１と同様の操作を行って、水酸化マグネシウム粉末を製造した。
【００２３】
［実施例３］
比表面積７ｍ2／ｇの酸化マグネシウム微粉末［気相法高純度超微粉マグネシア（グレード２０００Ａ）、宇部マテリアルズ（株）製］１．３ｋｇを蓋付きステンレス容器（容量２０リットル）に入れて、その容器ごと９０℃、相対湿度７０％ＲＨに保持された恒温恒湿器内で７日間放置した以外は、実施例１と同様の操作を行って、水酸化マグネシウム粉末を製造した。
【００２４】
（２）水中水和法により酸化マグネシウム微粉末を水和させた水酸化マグネシウムの製造例
［比較例１］
前記実施例１で使用した酸化マグネシウム微粉末と同一の酸化マグネシウム微粉末１０ｇを、５０℃に保持された温水３００ミリリットルに投入し、５時間攪拌して酸化マグネシウム微粉末を水和させて、水酸化マグネシウムスラリーを得た。次いで、得られた水酸化マグネシウムスラリーをろ過、脱水、乾燥して水酸化マグネシウム固形物とした後、粉砕機で粉砕して、水酸化マグネシウム粉末を製造した。
【００２５】
［比較例２］
前記実施例２で使用した酸化マグネシウム微粉末と同一の酸化マグネシウム微粉末を用いた以外は、比較例１と同様の操作を行って水酸化マグネシウム粉末を製造した。
【００２６】
［比較例３］
前記実施例３で使用した酸化マグネシウム微粉末と同一の酸化マグネシウム微粉末を用いた以外は、比較例１と同様の操作を行って水酸化マグネシウム粉末を製造した。
【００２７】
［評価］
上記実施例１〜６により製造した水酸化マグネシウム粉末について、酸化マグネシウム換算純度、比表面積を測定し、電子顕微鏡により表面状態を観察した。また、水酸化マグネシウム粉末を溶媒に分散させて水酸化マグネシウム粒子凝集体の平均粒子径を測定し、比表面積形状係数も算出した。
【００２８】
（１）酸化マグネシウム換算純度の測定
水酸化マグネシウム粉末を１０００℃で３時間焼成して得た酸化マグネシウム粉末中の不純物（Ａｌ2Ｏ3、ＳｉＯ2、ＣａＯ、Ｆｅ2Ｏ3、ＺｎＯ、Ｎａ2Ｏ、ＭｎＯ、ＮｉＯ、Ｃｒ2Ｏ3、Ｂ2Ｏ3）について定量分析を行い、得られた不純物含有量の総和を１００％から差し引いた値を酸化マグネシウム換算純度とした。その結果を下記の表２に示す。
【００２９】
（２）比表面積（Ｓ）の測定
比表面積（Ｓ）は、ＢＥＴ法により測定した。その結果を下記の表２に併せて示す。
【００３０】
（３）平均粒子径（ｄv）の測定
平均粒子径（ｄv）は、水酸化マグネシウム粉末０．４５ｇを、０．２重量％のヘキサメタリン酸ナトリウム水溶液５０ミリリットルに投入し、次いで、超音波（出力３００Ｗ）により１５分間分散処理を行った後に、レーザ回折法（装置名９３２０−Ｘ１００、マイクロトラック（株）製）を用いて測定した。その結果を下記の表２に併せて示す。
【００３１】
（４）比表面積換算係数（φsv）の算出
比表面積換算係数（φsv）は、下記の式（１）により算出した。その結果を下記の表２に併せて示す。
【００３２】
【数１】
式（１）
φsv＝ｄv×Ｓ×ρ
［ただし、Ｓは上記（２）で測定した比表面積（ｍ2／ｇ）、ｄvは上記（３）で測定した平均粒子径（μｍ）、ρは水酸化マグネシウムの密度で２．３９（ｇ／ｃｍ3）である］
【００３３】
【表２】
表２
────────────────────────────────────
ヘキサメタリン酸ナトリウム水溶液
中の水酸化マグネシウム粒子凝集体
ＭｇＯ換算純度 比表面積 平均粒子径 比表面積形状係数
（重量％） （ｍ2／ｇ） （μｍ）
────────────────────────────────────
実施例１ ９９．９８以上 ４１．４ ０．２９ ２９
比較例１ ９９．９８以上 ６３．６ ７．４４ １１３１
────────────────────────────────────
実施例２ ９９．９８以上 １６．３ ０．７３ ２８
比較例２ ９９．９８以上 ７３．５ １１．４３ ２００８
────────────────────────────────────
実施例３ ９９．９８以上 ８．０ ０．９３ １８
比較例３ ９９．９８以上 １７．７ １．２１ ５１
────────────────────────────────────
【００３４】
水蒸気接触水和法により酸化マグネシウム微粉末を水和させて製造した水酸化マグネシウム粉末（実施例１〜３）は、水酸化マグネシウム粒子凝集体の平均粒子径が１μｍ以下、比表面積形状係数が１０〜３０の範囲内にあることから、水中水和法により酸化マグネシウム微粉末を水和させて製造した水酸化マグネシウム粉末（比較例１〜３）と比較して水中分散性が高いことがわかる。
【００３５】
（５）電子顕微鏡による表面観察
電子顕微鏡により表面観察した結果、実施例１〜３及び比較例１〜３により得られた水酸化マグネシウムはいずれも独立した微細な水酸化マグネシウム粒子の集合体であることが確認できた。添付図面の図１に、実施例１で製造した水酸化マグネシウム粉末の電子顕微鏡写真を示す。図１から明らかに、実施例１で製造した水酸化マグネシウム粉末は、独立した微細な水酸化マグネシウム粒子の集合体であることがわかる。
【００３６】
【発明の効果】
本発明の水酸化マグネシウム粉末は、水中分散性が高く、酸化マグネシウム換算の純度が高い。従って、本発明の水酸化マグネシウム粉末は、誘電体用原料などの電子材料や触媒材料として有利に用いることができる。
また、酸化マグネシウム微粒子を水蒸気に接触させることにより水和させる本発明の高分散性高純度水酸化マグネシウム粉末の製造方法により得られる水酸化マグネシウムは、酸化マグネシウム微粒子を水中で水和させて得られる水酸化マグネシウムと比較して水中分散性に優れている。さらに、本発明の高分散性高純度水酸化マグネシウム粉末の製造方法は、酸化マグネシウム微粒子を水中で水和させる場合に必要となるろ過、脱水、乾燥、粉砕工程を必要としないので不純物が混入しにくく、また、工程が少なくなるので工業的にも有利である。
さらに、本発明の水酸化マグネシウムスラリーは、高純度の水酸化マグネシウム粒子凝集体が分散されているので、特に、誘電体用原料などの電子材料あるいは触媒材料の製造に有利に使用することができる。
【図面の簡単な説明】
【図１】実施例１により製造した水酸化マグネシウム粉末の電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates hydroxide magnesium U beam powder, more particularly, in particular, highly dispersed high purity hydroxide magnesium U beam powder and a manufacturing method thereof which can advantageously be used as an electronic material or the catalyst material, and an electronic material or The present invention relates to a magnesium hydroxide slurry that can be advantageously used in the production of a catalyst material.
[0002]
[Prior art]
When magnesium hydroxide [Mg (OH) 2 ] is heated to 350 ° C. or higher, one molecule of water is released to become magnesium oxide. Utilizing such thermal behavior of magnesium hydroxide, magnesium hydroxide powder has been used as a flame retardant for synthetic resins such as resin for covering electric wires. Further, since magnesium hydroxide powder does not hydrate like magnesium oxide even when it comes into contact with water, it is also used as a magnesia ceramic raw material that can be wet-mixed. Magnesium hydroxide powder used for these flame retardants or magnesia ceramic materials is required to have high dispersibility in water and high purity.
[0003]
In JP-A-60-176918, the content of magnesium oxide after firing for 1 hour at 1000 ° C. is 99.5% or more, the average crystal particle size is 1 μm or less, and the proportion of secondary particles of 1 μm or less is 70%. A magnesium hydroxide powder and a method for producing a magnesium hydroxide powder in which a magnesium chloride aqueous solution and a calcium hydroxide aqueous solution are reacted have been proposed. In the example of this publication, the content of magnesium oxide after firing at 1000 ° C. for 1 hour is 99.9% by weight, the average crystal particle diameter is 0.2 μm, and the proportion of secondary particles of 1 μm or less is 86%. The above magnesium hydroxide powder is shown.
[0004]
There has also been proposed a method for producing highly dispersible magnesium hydroxide powder in which magnesium oxide is introduced into water to hydrate the magnesium oxide.
[0005]
Japanese Patent Application Laid-Open No. 63-277510 proposes a method for producing magnesium hydroxide in which magnesium oxide is hydrated in a slurry containing magnesium hydroxide seed particles and a magnesium salt. Then, in the embodiment of this publication, the size of the X-ray diffraction (001) perpendicular to the direction of crystallites surface 78.4Nm, average particle child size 2.3 .mu.m, a specific surface area of 6.1 m 2 / g Magnesium hydroxide powder is shown.
[0006]
In JP-A-2-48414, magnesium hydroxide hydration reaction step is repeated three times or more in warm water at 50 ° C. or higher, the specific surface area is 10 m 2 / g or less, and hexagonal plate-like magnesium hydroxide Manufacturing methods have been proposed.
[0007]
[Problems to be solved by the invention]
In recent years, magnesium hydroxide powder has been studied for use in electronic materials or catalysts, and has higher dispersibility in water and higher purity (more than 99.95% by weight in terms of magnesium oxide). Development of magnesium oxide is desired. However, according to the research of the present inventors, the magnesium hydroxide powder obtained by the conventionally known magnesium hydroxide powder or the production method has a low magnesium oxide purity especially for use as an electronic material or a catalyst material. It was also found that the dispersibility in water was insufficient.
[0008]
Accordingly, an object of the present invention is to provide a magnesium hydroxide powder having high dispersibility in water and high purity that can be advantageously used as an electronic material or a catalyst material, and a method for producing the same. Furthermore, an object of the present invention is to provide a highly dispersible high-purity magnesium hydroxide slurry that can be advantageously used particularly for the production of electronic materials or catalyst materials.
[0009]
[Means for Solving the Problems]
In the present invention, a magnesium oxide fine powder comprising a single crystal having a specific surface area within a range of 5 to 200 m 2 / g and a purity of 99.95% by weight or more is hydrated by contacting with water vapor. The obtained high-dispersion high-purity magnesium hydroxide powder has a specific surface area in the range of 5 to 200 m 2 / g and a magnesium oxide equivalent purity of 99.95% by weight or more. .
[0010]
The present invention also provides a hydration method by bringing magnesium oxide fine powder comprising a single crystal having a specific surface area within a range of 5 to 200 m 2 / g and a purity of 99.95 wt% or more into contact with water vapor. There is also a method for producing a highly dispersible high purity magnesium hydroxide powder according to the present invention .
[0011]
Furthermore, the present invention provides a dispersion of the high-dispersion high-purity magnesium hydroxide powder that forms a high-purity magnesium hydroxide particle aggregate having an average particle diameter in the range of 0.1 to 1.0 μm. There is also a magnesium hydroxide slurry characterized by the fact that
[0012]
Here, the purity in terms of magnesium oxide in the present invention means the amount of magnesium oxide in the magnesium oxide powder obtained by firing the magnesium hydroxide powder at 1000 ° C. The specific surface areas of magnesium hydroxide and magnesium oxide are values measured by the BET method. The average particle diameter of the magnesium hydroxide particle aggregate is a value measured by a laser diffraction method.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The highly dispersible high purity magnesium hydroxide powder of the present invention has a specific surface area of 5 to 200 m 2 / g, preferably 5 to 100 m 2 / g, more preferably 5 to 50 m 2 / g. And the purity in terms of magnesium oxide is 99.95% by weight or more, particularly 99.98% by weight or more.
[0014]
The highly dispersible high purity magnesium hydroxide powder of the present invention is an aggregate of independent fine magnesium hydroxide particles. And the highly dispersible highly purified magnesium hydroxide powder of this invention forms the aggregate of magnesium hydroxide particle | grains with high dispersibility in water in the state disperse | distributed to solvents, such as water. The volume-based average particle diameter of the magnesium hydroxide particle aggregate measured by the laser diffraction method is preferably in the range of 0.1 to 1.0 μm from the viewpoint of dispersibility in water. More preferably, it is in the range of 8 μm. Moreover, it is preferable from a viewpoint of dispersibility in water that the shape of the magnesium hydroxide particle aggregate is close to a spherical shape. Specifically, it is preferable that the specific surface area shape factor (see “Particle Handbook”, Asakura Shoten, 1991, page 60), which is known as an index representing the surface shape of particles, is in the range of 6-50. More preferably, it is in the range of ˜30. The magnesium hydroxide slurry in which such magnesium hydroxide particle aggregates are dispersed is suitable for wet mixing and can be advantageously used for the production of electronic materials or catalyst materials.
[0015]
The highly dispersible high purity magnesium hydroxide powder of the present invention can be produced by hydrating magnesium oxide fine particles comprising a high purity single crystal in which fine primary particles are independent. The magnesium oxide fine powder used for the production of the highly dispersible high purity magnesium hydroxide powder of the present invention has a purity of 99.95% by weight or more and a specific surface area of 5 to 200 m 2 / g. preferable.
[0016]
Examples of magnesium oxide particles which can be suitably used for the production of finely divided high purity magnesium hydroxide powder of the present invention, the gas phase oxidation reaction of the magnesium U beam vapor and oxygen, the gas phase of growing crystal nuclei What was manufactured by the method can be mentioned. More specifically, vapor phase high purity ultrafine powder magnesia sold by Ube Materials Co., Ltd. can be mentioned. The chemical analysis values of this gas phase high purity ultrafine magnesia are shown in Table 1 below.
[0017]
[Table 1]
As a method of hydrating the magnesium oxide fine powder, a method of bringing the magnesium oxide fine powder into contact with water vapor (hereinafter referred to as a water vapor contact hydration method) and a method of adding the magnesium oxide fine powder into water (hereinafter referred to as hydration in water). law that) and there is. According to the inventor's research, magnesium hydroxide powder obtained by hydrating magnesium oxide fine powder by a water vapor contact hydration method is obtained by hydrating magnesium oxide fine powder by water hydration method. It has been found that it is relatively better in water dispersibility than magnesium powder. Although the details are unknown, it is considered that the magnesium hydroxide particles produced by hydration easily aggregate because the hydration reaction of the magnesium oxide fine particles is fast in the underwater hydration method. In addition, the water vapor contact hydration method does not require filtration, dehydration, drying, and pulverization steps, which are performed in a normal water hydration method, so that impurities are hardly mixed in, and the number of steps is reduced, so that from an industrial viewpoint. It is advantageous.
[0019]
When the magnesium oxide fine powder is hydrated by the water vapor contact hydration method, the contact between the magnesium oxide fine powder and the water vapor may be performed at room temperature, but in order to promote hydration more rapidly, 50 to It is preferable to carry out at a temperature of 180 ° C. Moreover, it is preferable that the humidity at this time is adjusted in the range of 60 to 100% RH.
[0020]
On the other hand, when the magnesium oxide fine powder is hydrated by the underwater hydration method, the temperature of the water into which the magnesium oxide fine particles are charged is preferably in the range of 50 to 100 ° C. Further, in order to make it difficult for the magnesium hydroxide particles produced by hydration of the magnesium oxide fine particles to aggregate, it is preferable to hydrate the magnesium oxide fine powder with stirring.
[0021]
【Example】
(1) Production Example of Magnesium Hydroxide by Hydrating Magnesium Oxide Fine Powder by Steam Contact Hydration [Example 1]
Put 1.3 kg of magnesium oxide fine powder [gas phase high purity ultrafine magnesia (grade 500A), manufactured by Ube Materials Co., Ltd.] with a specific surface area of 27 m 2 / g into a stainless steel container with a lid (capacity 20 liters). The container was allowed to stand for 5 days in a constant temperature and humidity chamber maintained at 90 ° C. and a relative humidity of 70% RH to hydrate the magnesium oxide fine powder to produce a magnesium hydroxide powder. Note that the lid of the stainless steel container was fixed to the upper part (opening) of the container with a gap of 2 cm between the container and the container so that water condensed on the ceiling of the constant temperature and humidity chamber did not enter the container.
[0022]
[Example 2]
Put 1.3 kg of magnesium oxide fine powder [gas phase high purity ultrafine magnesia (grade 1000A), manufactured by Ube Materials Co., Ltd.] with a specific surface area of 14 m 2 / g into a stainless steel container with a lid (capacity 20 liters). Magnesium hydroxide powder was manufactured in the same manner as in Example 1 except that the container was left in a constant temperature and humidity chamber maintained at 90 ° C. and a relative humidity of 70% RH for 6 days.
[0023]
[Example 3]
Put 1.3 kg of magnesium oxide fine powder with a specific surface area of 7 m 2 / g [gas phase method high purity ultrafine powder magnesia (grade 2000A), manufactured by Ube Materials Co., Ltd.] into a stainless steel container with a lid (capacity 20 liters). Magnesium hydroxide powder was produced in the same manner as in Example 1 except that the container was left in a constant temperature and humidity chamber maintained at 90 ° C. and a relative humidity of 70% RH for 7 days.
[0024]
(2) Manufacture example of magnesium hydroxide in which magnesium oxide fine powder is hydrated by hydration method in water [ Comparative Example 1 ]
10 g of the same magnesium oxide fine powder as that used in Example 1 was put into 300 ml of warm water maintained at 50 ° C. and stirred for 5 hours to hydrate the magnesium oxide fine powder, A magnesium oxide slurry was obtained. Next, the obtained magnesium hydroxide slurry was filtered, dehydrated and dried to obtain a magnesium hydroxide solid, and then pulverized with a pulverizer to produce a magnesium hydroxide powder.
[0025]
[ Comparative Example 2 ]
Magnesium hydroxide powder was manufactured in the same manner as in Comparative Example 1 except that the same magnesium oxide fine powder as that used in Example 2 was used.
[0026]
[ Comparative Example 3 ]
Magnesium hydroxide powder was manufactured in the same manner as in Comparative Example 1 except that the same magnesium oxide fine powder as that used in Example 3 was used.
[0027]
[Evaluation]
About the magnesium hydroxide powder manufactured by the said Examples 1-6, the magnesium oxide conversion purity and the specific surface area were measured, and the surface state was observed with the electron microscope. Further, magnesium hydroxide powder was dispersed in a solvent, the average particle diameter of the magnesium hydroxide particle aggregate was measured, and the specific surface area shape factor was also calculated.
[0028]
(1) Measurement of magnesium oxide equivalent purity Impurities (Al 2 O 3 , SiO 2 , CaO, Fe 2 O 3 , ZnO, Na 2) in magnesium oxide powder obtained by firing magnesium hydroxide powder at 1000 ° C. for 3 hours. O, MnO, NiO, Cr 2 O 3 , B 2 O 3 ) were quantitatively analyzed, and a value obtained by subtracting the total impurity content obtained from 100% was defined as magnesium oxide equivalent purity. The results are shown in Table 2 below.
[0029]
(2) Measurement of specific surface area (S) The specific surface area (S) was measured by the BET method. The results are also shown in Table 2 below.
[0030]
(3) Measurement average particle diameter of the average particle diameter (d v) (d v) is a magnesium hydroxide powder 0.45 g, was added to 0.2 wt% of sodium hexametaphosphate aqueous solution 50 ml, and then, ultrasonic After carrying out a dispersion treatment for 15 minutes with an output of 300 W, measurement was performed using a laser diffraction method (device name: 9320-X100, manufactured by Microtrac Co., Ltd.). The results are also shown in Table 2 below.
[0031]
(4) Calculation of specific surface area conversion coefficient (φ sv ) The specific surface area conversion coefficient (φ sv ) was calculated by the following formula (1). The results are also shown in Table 2 below.
[0032]
[Expression 1]
Formula (1)
φ sv = d v × S × ρ
[However, S is the specific surface area (m 2 / g) measured in (2), d v is the average particle size (μm) measured in (3), and ρ is the density of magnesium hydroxide, 2.39 ( g / cm 3 )]
[0033]
[Table 2]
Table 2
────────────────────────────────────
Sodium hexametaphosphate aqueous solution
Magnesium hydroxide particle aggregate
MgO equivalent purity Specific surface area Average particle diameter Specific surface area shape factor
(% By weight) (m 2 / g) (μm)
────────────────────────────────────
Example 1 99.98 or more 41.4 0.29 29
Comparative Example 1 99.98 or more 63.6 7.44 1131
────────────────────────────────────
Example 2 99.98 or more 16.3 0.73 28
Comparative Example 2 99.98 or higher 73.5 11.43 2008
────────────────────────────────────
Example 3 99.98 or more 8.0 0.93 18
Comparative Example 3 99.98 or more 17.7 1.21 51
────────────────────────────────────
[0034]
Magnesium hydroxide powders (Examples 1 to 3) produced by hydrating magnesium oxide fine powder by the water vapor contact hydration method have an average particle diameter of magnesium hydroxide particle aggregate of 1 μm or less and a specific surface area shape factor of 10. Since it exists in the range of -30, it turns out that dispersibility in water is high compared with the magnesium hydroxide powder ( Comparative Examples 1-3 ) manufactured by hydrating a magnesium oxide fine powder by the underwater hydration method.
[0035]
(5) Surface observation with an electron microscope As a result of surface observation with an electron microscope, the magnesium hydroxides obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are all aggregates of independent fine magnesium hydroxide particles. I was able to confirm. FIG. 1 of the accompanying drawings shows an electron micrograph of the magnesium hydroxide powder produced in Example 1. 1 clearly shows that the magnesium hydroxide powder produced in Example 1 is an aggregate of independent fine magnesium hydroxide particles.
[0036]
【The invention's effect】
The magnesium hydroxide powder of the present invention has high dispersibility in water and high purity in terms of magnesium oxide. Therefore, the magnesium hydroxide powder of the present invention can be advantageously used as an electronic material such as a dielectric material or a catalyst material.
Further, magnesium hydroxide obtained by the method for producing a highly dispersible high purity magnesium hydroxide powder of the present invention in which magnesium oxide fine particles are hydrated by contacting with water vapor is obtained by hydrating magnesium oxide fine particles in water. Excellent dispersibility in water compared to magnesium hydroxide. Furthermore, the manufacturing method of the highly dispersible high purity magnesium hydroxide powder of the present invention does not require filtration, dehydration, drying, and pulverization steps required when hydrated magnesium oxide fine particles in water. It is difficult, and the number of processes is reduced, which is industrially advantageous.
Furthermore, since the magnesium hydroxide slurry of the present invention has high-purity magnesium hydroxide particle aggregates dispersed therein, it can be advantageously used particularly for the production of electronic materials such as dielectric materials or catalyst materials. .
[Brief description of the drawings]
1 is an electron micrograph of magnesium hydroxide powder produced according to Example 1. FIG.
Claims (8)
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| CN101119931B (en) * | 2005-02-23 | 2011-12-14 | 株式会社野泽 | Production method of magnesium hydroxide |
| JP4603958B2 (en) * | 2005-08-31 | 2010-12-22 | キヤノン株式会社 | toner |
| JP5052780B2 (en) * | 2005-11-15 | 2012-10-17 | 宇部マテリアルズ株式会社 | Method for producing magnesium hydroxide fine particle dispersion |
| WO2007097795A2 (en) * | 2005-11-28 | 2007-08-30 | Martin Marietta Materials, Inc. | Flame-retardant magnesium hydroxide compositions and associated methods of manufacture and use |
| JP5069865B2 (en) * | 2006-03-27 | 2012-11-07 | タテホ化学工業株式会社 | High purity magnesium hydroxide powder and method for producing the same |
| KR101369121B1 (en) * | 2007-03-30 | 2014-03-04 | 우베 마테리알즈 가부시키가이샤 | Magnesium hydroxide powder and method for producing the same |
| JP5016993B2 (en) | 2007-06-27 | 2012-09-05 | タテホ化学工業株式会社 | Magnesium oxide particle aggregate and method for producing the same |
| JP5571875B2 (en) * | 2007-09-28 | 2014-08-13 | Ｎｔｎ株式会社 | High frequency electronic component materials |
| JP2010097857A (en) * | 2008-10-17 | 2010-04-30 | Panasonic Corp | Plasma display panel |
| JP5604789B2 (en) * | 2009-01-29 | 2014-10-15 | 株式会社オートネットワーク技術研究所 | Flame retardant, flame retardant resin composition and insulated wire |
| JP5686563B2 (en) * | 2010-09-28 | 2015-03-18 | タテホ化学工業株式会社 | Magnesium hydroxide fine particles and magnesium oxide fine particles, and methods for producing them |
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