JP3521173B2 - Method for producing hexagonal boron nitride powder - Google Patents
Method for producing hexagonal boron nitride powderInfo
- Publication number
- JP3521173B2 JP3521173B2 JP18657297A JP18657297A JP3521173B2 JP 3521173 B2 JP3521173 B2 JP 3521173B2 JP 18657297 A JP18657297 A JP 18657297A JP 18657297 A JP18657297 A JP 18657297A JP 3521173 B2 JP3521173 B2 JP 3521173B2
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- Prior art keywords
- boron nitride
- nitride powder
- hexagonal boron
- weight
- crystallization
- Prior art date
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Description
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】本発明は、樹脂、ゴム、グリ
ース等の充填材の微粒子成分として好適な含有水分量の
少ない六方晶窒化ほう素粉末の製造方法に関する。
【０００２】
【従来の技術】六方晶窒化ほう素粉末は、黒鉛類似の層
状構造を有し、熱伝導性、絶縁性、化学的安定性、固体
潤滑性、耐熱衝撃性などの特性に優れ、これらの特性を
活かして固体潤滑・離型剤、填材、耐熱性・絶縁性焼結
体の製造用原料などに応用されている。六方晶窒化ほう
素粉末を充填材として用いる場合、その充填性を向上さ
せるために、通常、粗粒子成分と微粒子成分を混ぜ合わ
せて粒子径分布の調整が行われる。
【０００３】しかしながら、例えば樹脂を１００℃以上
で硬化を行う場合に、粒子径分布の調整を行った六方晶
窒化ほう素粉末を充填材として用いた樹脂では、六方晶
窒化ほう素粉末の微粒子成分に含まれる水分が蒸発する
ために発泡し強度が低下するという問題がある。また、
硬化触媒を用いた樹脂に上記粒子径分布の調整を行った
六方晶窒化ほう素粉末を配合すると、六方晶窒化ほう素
粉末の微粒子成分に含まれる水分と硬化触媒が反応し硬
化が進まないという問題があった。充填材を粗粒子成分
主体の六方晶窒化ほう素粉末とすれば、これらの問題は
起こらないが、充填性が損なわれてしまうという問題が
あった。
【０００４】高純度かつ微細な粒子径を持つ六方晶窒化
ほう素粉末を得る方法として、特開昭６１−２５６９０
５号公報には、粗製六方晶窒化ほう素粉末に炭素質粉末
を５〜１５重量％添加し、アンモニア又はアンモニアと
非酸性ガスとの混合ガス気流中で加熱処理することが記
載されている。しかし、この方法では、副生成ガスの水
蒸気が粉体に混入し、水分量が０．２重量％程度をこえ
てしまう。
【０００５】
【発明が解決しようとする課題】本発明の目的は、 充填
材の微粒子成分として好適な含有水分量が少なく、微粉
末の六方晶窒化ほう素粉末を提供することである。
【０００６】
【課題を解決するための手段】本発明者らは、上記課題
を解決するため種々検討した結果、六方晶窒化ほう素粉
末の微粒子成分には含有水分が多いが、これを減少させ
るには非晶質窒化ほう素を原料とし、これに特定量の結
晶化触媒を添加し、実質的に水素原子を含まない非酸化
性ガスの雰囲気下、従来よりも比較的低温で焼成し結晶
化すればよいことを見いだし、本発明に至ったものであ
る。
【０００７】すなわち、本発明は、結晶化触媒５〜２０
重量％含有の非晶質窒化ほう素粉末を、脱水された窒素
ガスの雰囲気下、温度１４００℃〜１６５０℃で焼成す
ることを特徴とする、ＢＥＴ法比表面積が１５．０ｍ ２
／ｇ以上、含有水分量が０．１５重量％以下の六方晶窒
化ほう素粉末の製造方法である。
【０００８】
【発明の実施の形態】以下、更に詳しく本発明について
説明する。
【０００９】本発明で製造される六方晶窒化ほう素粉末
は、含有水分が少なくかつ微粒子であることが特徴であ
る。すなわち、従来の結晶性の高い粗粒子からなる六方
晶窒化ほう素粉末にあってはその含有水分量は０．１重
量％以下であるが、比表面積が１５．０ｍ２／ｇ以上で
ある微粒子の窒化ほう素粉末においては、その含有水分
量は０．１５重量％よりも多いものであった。これに対
し、本発明で製造される六方晶窒化ほう素粉末は、ＢＥ
Ｔ法比表面積が１５．０ｍ２／ｇ以上、含有水分量が
０．１５重量％以下である。
【００１０】本発明で製造された微粒子の六方晶窒化ほ
う素粉末は、含有水分量が少ないため、樹脂やグリース
等に充填してもその加水分解を抑えることができる。
【００１１】含有水分量は、１００℃以上の一定温度中
に被測定物を恒量になるまで放置し、その重量減少を調
べることによって便宜的に知ることができるが、より精
度良く測定するには、 以下のカールフィッシャー滴定法
によることが望ましい。
【００１２】カールフィッシャー滴定法とは、カールフ
ィッシャー試薬を用いた含有水分測定法であり、Ｉ2 ＋
ＳＯ2 ＋Ｈ2 Ｏ→２ＨＩ＋ＳＯ3 、の反応を利用したも
のである。その手順は、 まず系内を１００℃以上の一定
温度に保ち系内の水分を完全に除去した後、被測定物を
投入し、被測定物中の水分とカールフィッシャー試薬と
を上式により反応させる。被測定物中の水分が完全に放
出されるまで系内は一定温度に保たれる。六方晶窒化ほ
う素は結晶水を持たないので、測定温度は１００℃以
上、窒化ほう素が分解する６００℃程度以下で行われ
る。次いで、滴定を行い、その終点から含有水分量を算
出する。滴定の終点は、過剰よう素による着色、電位差
滴定又は電流滴定により知ることができる。
【００１３】また、本発明においては、微粒子の多い六
方晶窒化ほう素粉末であるかどうかの評価は表面積値を
用いて行われる。レーザー回折・散乱法によってもおよ
その評価はできるが、一般にサブミクロン以下の粒子を
多く含む粉末では凝集が起きていることが多く、この凝
集の解砕が効果的に行われたかどうかによって測定値が
異なるため、本発明においては適切な方法とはいえな
い。
【００１４】本発明の六方晶窒化ほう素粉末の製造方法
は、原料として、結晶化触媒５〜２０重量％含有する非
晶質窒化ほう素粉末を用い、しかも窒化ほう素の結晶化
温度を比較的低温である１４００℃〜１６５０℃とする
ことによって製造することができる。
【００１５】非晶質窒化ほう素粉末に結晶化触媒を混合
するには、非晶質窒化ほう素粉末に結晶化触媒を機械的
に混合する方法、非晶質窒化ほう素粉末の合成原料に結
晶化触媒及び／又は結晶化触媒の前駆物質を混合してお
き、非晶質窒化ほう素粉末の合成と同時に結晶化触媒を
混入させる方法のいずれかが用いられる。後者の場合に
は、非晶質窒化ほう素粉末の合成の際に前駆物質である
ほう酸等が揮発するのでその揮発量を見越して各原料成
分の割合を調整することが必要となる。なお、混合に際
しては、ボールミル、リボンブレンダー、ヘンシェルミ
キサーなどの一般的な混合機が使用される。
【００１６】本発明で使用される結晶化触媒は、酸化ほ
う素（Ｂ2 Ｏ3 ）、アルカリ金属のほう酸塩、アルカリ
土類金属のほう酸塩などである。また、結晶化触媒の前
駆物質とは、非晶質窒化ほう素粉末の結晶化温度ないし
は合成温度において上記結晶化触媒を生成する物質であ
る。例えば、酸化ほう素の前駆物質はほう酸であり、ア
ルカリ金属ほう酸塩のそれはアルカリ金属の炭酸塩、水
酸化物及び／又は酸化物とほう酸との混合物であり、更
にはアルカリ土類金属ほう酸塩のそれはアルカリ土類金
属の炭酸塩、水酸化物及び／又は酸化物とほう酸との混
合物である。
【００１７】結晶化触媒の量は生成する六方晶窒化ほう
素粉末に対し内割で５〜２０重量％である。５重量％よ
りも少ないと結晶化が不十分となり、 また２０重量％よ
りも多いと結晶化が進み過ぎて結晶性が高くなり、ＢＥ
Ｔ比表面積が小さくなる。
【００１８】本発明で採用される結晶化温度は１４００
〜１６５０℃である。焼成温度が１４００℃よりも低い
と非晶質窒化ほう素粉末が十分に結晶化しない。一方、
焼成温度が１６５０℃よりも高いと粒成長が進みすぎ、
ＢＥＴ比表面積が小さくなる。
【００１９】本発明における焼成（結晶化）は、脱水さ
れた窒素ガスの雰囲気下で行われる。酸化性ガス雰囲気
下であると、非晶質六方晶窒化ほう素粉末又は生成した
六方晶窒化ほう素粉末が酸化されてしまう。また、水素
ガス、アンモニアガス等のように分子中に水素原子を持
つガスでは、焼成時に水素原子が非晶質六方晶窒化ほう
素粉末に不純物として取り込まれた酸素原子と反応して
水蒸気を発生するので本発明には適さない。
【００２０】焼成炉としては、マッフル炉、管状炉、雰
囲気炉などのバッチ式炉や、ロータリーキルン、スクリ
ューコンベヤ炉、トンネル炉、ベルト炉、プッシャー
炉、竪型連続炉などの連続式炉が用いられる。これらは
目的に応じて使い分けられ、例えば多くの品種の窒化ほ
う素粉末を少量ずつ製造するときはバッチ式炉を、一定
の品種を多量製造するときは連続式炉が採用される。
【００２１】以上のようにして製造された六方晶窒化ほ
う素粉末は、必要に応じて粉砕、分級、酸処理による残
留触媒の除去（精製）、洗浄、乾燥などの後処理工程を
経た後、実用に供される。
【００２２】本発明の方法で製造された六方晶窒化ほう
素粉末は、ＢＥＴ法比表面積が１５．０ｍ2 ／ｇ以上で
あり、含有水分量が０．１５重量％以下となる理由は、
次のように考えられる。すなわち、通常、比表面積の大
きな六方晶窒化ほう素粉末は、窒素源原料とほう素源原
料との混合物、又は分子内中に窒素源とほう素源をもつ
物質を、１４００℃〜１８００℃で反応及び結晶化する
ことによって製造される。この場合において、窒素源と
してアミノ基を分子内に持つ物質やアンモニアが用いら
れるが、このような分子中に水素原子を持つ物質を原料
としたのでは焼成の際に反応の副生成ガスとして水蒸気
が発生し、水分含有量の多い六方晶窒化ほう素粉末とな
る。これに対し、本発明の製造法によれば、非晶質窒化
ほう素粉末と結晶化触媒の混合物を原料に用いて１４０
０℃〜１６５０℃という低温度領域で結晶化が行われる
ため、焼成時に水蒸気等の反応の副生成ガスは発生せず
に、窒化ほう素の結晶化のみが緩やかに進行する。この
ため比表面積が大きいにもかかわらず、含有水分量の少
ない六方晶窒化ほう素粉末となる。
【００２３】
【実施例】以下、実施例、比較例、参考例をあげて更に
具体的に本発明を説明する。
【００２４】実施例１
結晶化触媒としてＢ2 Ｏ3 を１２重量％含有した非晶質
窒化ほう素粉末１０ｋｇをバッチ雰囲気炉にて、脱水さ
れた窒素ガス雰囲気下、１６００℃で焼成した。得られ
た焼成物を粉砕し、硝酸にて残留触媒の除去・洗浄・乾
燥を行い六方晶窒化ほう素粉末を得た。この六方晶窒化
ほう素粉末のＢＥＴ一点法による比表面積を「ＱＵＮＴ
ＡＳＯＲＢ−Ｊｒ ＯＳ Ｊｒ−１」（ＱＵＮＴＡＣＨ
ＲＯＭＥ社製）にて測定したところ、２０．６ｍ2 ／ｇ
であった。また、カールフィッシャー法で１２０℃にお
ける含有水分量を水分気化装置「ＭｏｄｅｌＶＡ−２
２」及び「ＣＡ−０５」（三菱化学社製）にて測定した
ところ、０．０６重量％であった。
【００２５】この六方晶窒化ほう素の粉末をシリコーン
樹脂（東レ・ダウ・シリコーン社製「ＳＥ１８８０」）
に２０体積％充填し、真空乾燥機中で３０分間脱泡した
後、１５０℃で３時間硬化させ、その表面及び内部の肉
眼観察を行ったが、異状は認められなかった。
【００２６】実施例２
結晶化触媒としてＣａＯ・Ｂ2 Ｏ3 を８重量％含有した
非晶質窒化ほう素粉末１０ｋｇをバッチ雰囲気炉にて、
脱水された窒素ガス雰囲気下、１５００℃で焼成した
後、実施例１と同様の処理を行ったところ、ＢＥＴ比表
面積及び含有水分量がそれぞれ２９．４ｍ2 ／ｇ及び
０．１３重量％の六方晶窒化ほう素粉末であった。これ
を実施例１と同様の方法でシリコーン樹脂に充填し脱泡
後硬化させ、その表面及び内部の肉眼観察を行ったが、
異状は認められなかった。
【００２７】比較例１
ほう酸５．５ｋｇ、メラミン４．５ｋｇ、炭酸カルシウ
ム１．０ｋｇの混合物をバッチ雰囲気炉にて、アンモニ
ア雰囲気下、１５５０℃で焼成した後、実施例１と同様
の処理を行ったところ、ＢＥＴ比表面積及び１２０℃で
の含有水分量がそれぞれ２６．７ｍ2 ／ｇ及び０．２９
重量％の六方晶窒化ほう素粉末が得られた。これを実施
例１と同様の方法でシリコーン樹脂に充填し脱泡後硬化
させ、その表面及び内部観察を行ったところ、気泡跡が
観察された。
【００２８】比較例２
結晶化触媒としてＢ2 Ｏ3 を１２重量％含有した非晶質
窒化ほう素１０ｋｇをバッチ雰囲気炉にて、脱水された
窒素ガス雰囲気下、１７５０℃で焼成した後、実施例１
と同様の処理を行ったところ、ＢＥＴ比表面積及び含有
水分量がそれぞれ５．７ｍ2 ／ｇ及び０．０７重量％の
六方晶窒化ほう素粉末が得られた。
【００２９】参考例１
市販の微粉グレードである電気化学工業社製六方晶窒化
ほう素粉末「ＳＰ−２」のＢＥＴ比表面積は３１．７ｍ
2 ／ｇであり、１２０℃における含有水分量は０．４１
重量％である。この粉末を実施例１と同様の方法でシリ
コーン樹脂に充填し脱泡後硬化させると、その表面及び
内部には気泡跡が観察された。
【００３０】
【発明の効果】本発明によれば、ＢＥＴ比表面積が１
５．０ｍ2 ／ｇ以上、含有水分量が０．１５重量％以下
である、充填材の微粒子成分として好適な六方晶窒化ほ
う素粉末を得ることができる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hexagonal boron nitride powder having a low water content and suitable as a fine particle component of a filler such as resin, rubber and grease. about the. [0002] Hexagonal boron nitride powder has a layered structure similar to graphite, and has excellent properties such as thermal conductivity, insulation, chemical stability, solid lubrication, and thermal shock resistance. Utilizing these properties, it is applied to solid lubricating / release agents, fillers, and raw materials for producing heat-resistant / insulating sintered bodies. When a hexagonal boron nitride powder is used as a filler, the particle size distribution is usually adjusted by mixing a coarse particle component and a fine particle component in order to improve the filling property. However, for example, when a resin is cured at a temperature of 100 ° C. or more, a resin using a hexagonal boron nitride powder whose particle size distribution is adjusted as a filler is not suitable for the fine particle component of the hexagonal boron nitride powder. There is a problem that the water content contained in the water vaporizes and foams to reduce the strength. Also,
When the hexagonal boron nitride powder whose particle size distribution is adjusted is blended with the resin using the curing catalyst, the moisture contained in the fine particle component of the hexagonal boron nitride powder reacts with the curing catalyst, and the curing does not proceed. There was a problem. If the filler is hexagonal boron nitride powder mainly composed of coarse particles, these problems do not occur, but there is a problem that the filling property is impaired. As a method for obtaining hexagonal boron nitride powder having high purity and a fine particle diameter, Japanese Patent Application Laid-Open No. 61-25690 is known.
No. 5 describes that a carbonaceous powder is added to a crude hexagonal boron nitride powder in an amount of 5 to 15% by weight and heat-treated in a gaseous stream of ammonia or a mixed gas of ammonia and a non-acidic gas. However, in this method, the water vapor of the by-product gas is mixed into the powder, and the water content exceeds about 0.2% by weight. An object of the present invention is to provide a fine hexagonal boron nitride powder having a low water content and suitable as a fine particle component of a filler. The present inventors have conducted various studies to solve the above-mentioned problems. As a result, the fine particle component of the hexagonal boron nitride powder contains a large amount of water, but this is reduced. Amorphous boron nitride is used as a raw material, a specific amount of a crystallization catalyst is added thereto, and calcined at a relatively lower temperature than before in a non-oxidizing gas atmosphere containing substantially no hydrogen atoms. The present invention has been found to be achieved by the present invention. That is, the present invention provides a crystallization catalyst of 5 to 20
The amorphous boron nitride powder weight% containing, dehydrated nitrogen
Under an atmosphere of gas, to calcination at a temperature 1400 ° C. to 1650 ° C.
A BET specific surface area of 15.0 m 2
/ G or more and a water content of 0.15% by weight or less
This is a method for producing boron nitride powder . Hereinafter, the present invention will be described in more detail. [0009] The hexagonal boron nitride powder produced by the present invention is characterized in that it contains a small amount of water and is fine. That is, conventional hexagonal boron nitride powder composed of coarse particles having high crystallinity has a water content of 0.1% by weight or less, but has a specific surface area of 15.0 m 2 / g or more. In the above boron nitride powder, the water content was more than 0.15% by weight. On the other hand, the hexagonal boron nitride powder produced in the present invention is BE
The T method specific surface area is 15.0 m 2 / g or more, and the water content is 0.15% by weight or less. [0010] The fine hexagonal boron nitride powder produced by the present invention has a low water content, so that the hydrolysis can be suppressed even when the powder is filled in a resin or grease. The moisture content can be conveniently determined by leaving the object to be measured at a constant temperature of 100 ° C. or higher until it reaches a constant weight and examining its weight loss. It is desirable to use the following Karl Fischer titration method. The Karl Fischer titration method is a method for measuring water content using a Karl Fischer reagent, and comprises I 2 +
It utilizes the reaction of SO 2 + H 2 O → 2HI + SO 3 . The procedure is as follows: First, keep the inside of the system at a constant temperature of 100 ° C or higher to completely remove the water in the system, then put in the object to be measured, and react the water in the object with the Karl Fischer reagent according to the above formula. Let it. The inside of the system is kept at a constant temperature until the moisture in the object is completely released. Since hexagonal boron nitride does not have water of crystallization, the measurement is performed at a temperature of 100 ° C. or more and about 600 ° C. or less at which boron nitride is decomposed. Next, titration is performed, and the water content is calculated from the end point. The end point of the titration can be determined by coloring with excess iodine, potentiometric titration or amperometric titration. In the present invention, the evaluation as to whether the powder is hexagonal boron nitride powder having a large number of fine particles is performed by using the surface area value. Approximate evaluations can be made by the laser diffraction / scattering method.However, in general, powders containing a lot of sub-micron particles often cause agglomeration, and the measured value depends on whether or not this agglomeration has been effectively broken. Therefore, it is not an appropriate method in the present invention. According to the method for producing hexagonal boron nitride powder of the present invention, an amorphous boron nitride powder containing 5 to 20% by weight of a crystallization catalyst is used as a raw material. It can be produced by setting the crystallization temperature to a relatively low temperature of 1400 ° C. to 1650 ° C. In order to mix the crystallization catalyst with the amorphous boron nitride powder, a method of mechanically mixing the crystallization catalyst with the amorphous boron nitride powder is used. One of the methods is to mix the crystallization catalyst and / or the precursor of the crystallization catalyst and mix the crystallization catalyst simultaneously with the synthesis of the amorphous boron nitride powder. In the latter case, the precursor boronic acid or the like volatilizes during the synthesis of the amorphous boron nitride powder, so that it is necessary to adjust the ratio of each raw material component in anticipation of the volatilization amount. When mixing, a general mixer such as a ball mill, a ribbon blender, and a Henschel mixer is used. The crystallization catalyst used in the present invention is boron oxide (B 2 O 3 ), an alkali metal borate, an alkaline earth metal borate, or the like. The precursor of the crystallization catalyst is a substance that produces the crystallization catalyst at the crystallization temperature or the synthesis temperature of the amorphous boron nitride powder. For example, the precursor of boron oxide is boric acid, that of alkali metal borates is that of alkali metal carbonates, hydroxides and / or mixtures of oxides and boric acid, and also that of alkaline earth metal borates. It is a mixture of alkaline earth metal carbonates, hydroxides and / or oxides and boric acid. The amount of the crystallization catalyst is 5 to 20% by weight based on the hexagonal boron nitride powder produced. If it is less than 5% by weight, crystallization is insufficient, and if it is more than 20% by weight, crystallization proceeds excessively and the crystallinity becomes high.
T specific surface area decreases. The crystallization temperature employed in the present invention is 1400
１６1650 ° C. If the firing temperature is lower than 1400 ° C., the amorphous boron nitride powder does not sufficiently crystallize. on the other hand,
If the firing temperature is higher than 1650 ° C., the grain growth proceeds too much,
The BET specific surface area decreases. In the present invention, the calcination (crystallization) is carried out by dehydration.
This is performed in an atmosphere of nitrogen gas . In an oxidizing gas atmosphere, the amorphous hexagonal boron nitride powder or the generated hexagonal boron nitride powder is oxidized. In the case of gas containing hydrogen atoms in the molecule, such as hydrogen gas and ammonia gas, the hydrogen atoms react with the oxygen atoms incorporated as impurities in the amorphous hexagonal boron nitride powder during firing to generate water vapor. Therefore, it is not suitable for the present invention. As the firing furnace, a batch furnace such as a muffle furnace, a tubular furnace, and an atmosphere furnace, and a continuous furnace such as a rotary kiln, a screw conveyor furnace, a tunnel furnace, a belt furnace, a pusher furnace, and a vertical continuous furnace are used. . These can be used depending on the purpose. For example, a batch furnace is used when a large number of types of boron nitride powder are manufactured little by little, and a continuous furnace is used when a certain type is manufactured in large quantities. The hexagonal boron nitride powder produced as described above undergoes post-treatment steps such as pulverization, classification, removal (purification) of residual catalyst by acid treatment, washing and drying, if necessary. Provided for practical use. The reason why the hexagonal boron nitride powder produced by the method of the present invention has a BET specific surface area of 15.0 m 2 / g or more and a water content of 0.15% by weight or less is as follows.
It is considered as follows. That is, a hexagonal boron nitride powder having a large specific surface area is usually a mixture of a nitrogen source material and a boron source material, or a substance having a nitrogen source and a boron source in a molecule at 1400 ° C. to 1800 ° C. Manufactured by reaction and crystallization. In this case, a substance having an amino group in the molecule or ammonia is used as a nitrogen source. However, if a substance having a hydrogen atom in the molecule is used as a raw material, steam is used as a by-product gas of the reaction during firing. Are generated, and a hexagonal boron nitride powder having a high water content is obtained. On the other hand, according to the production method of the present invention, a mixture of amorphous boron nitride powder and a crystallization catalyst is used
Since crystallization is performed in a low temperature range of 0 ° C. to 1650 ° C., only by-product crystallization of boron nitride progresses slowly without generating by-product gases such as water vapor during firing. For this reason, a hexagonal boron nitride powder having a small water content is obtained despite the large specific surface area. The present invention will be described more specifically with reference to examples, comparative examples and reference examples. Example 1 10 kg of amorphous boron nitride powder containing 12% by weight of B 2 O 3 as a crystallization catalyst was fired in a batch atmosphere furnace at 1600 ° C. in a dehydrated nitrogen gas atmosphere. The obtained fired product was pulverized, and the remaining catalyst was removed, washed and dried with nitric acid to obtain hexagonal boron nitride powder. The specific surface area of this hexagonal boron nitride powder determined by the BET
ASORB-Jr OS Jr-1 "(QUANTACH
20.6 m 2 / g
Met. Further, the water content at 120 ° C. was determined by the Karl Fischer method using a water vaporizer “Model VA-2”.
2 "and" CA-05 "(manufactured by Mitsubishi Chemical Corporation) and found to be 0.06% by weight. The hexagonal boron nitride powder is converted into a silicone resin (“SE1880” manufactured by Dow Silicone Toray).
The mixture was defoamed in a vacuum dryer for 30 minutes, cured at 150 ° C. for 3 hours, and visually observed on the surface and inside, but no abnormality was found. Example 2 10 kg of amorphous boron nitride powder containing 8% by weight of CaO.B 2 O 3 as a crystallization catalyst was placed in a batch atmosphere furnace.
After calcination at 1500 ° C. in a dehydrated nitrogen gas atmosphere, the same treatment as in Example 1 was performed, and the BET specific surface area and the water content were 29.4 m 2 / g and 0.13 wt%, respectively. It was a crystalline boron nitride powder. This was filled in a silicone resin in the same manner as in Example 1, cured after defoaming, and the surface and inside thereof were visually observed.
No abnormality was found. Comparative Example 1 A mixture of 5.5 kg of boric acid, 4.5 kg of melamine and 1.0 kg of calcium carbonate was fired in a batch furnace at 1550 ° C. in an ammonia atmosphere, and the same treatment as in Example 1 was performed. As a result, the BET specific surface area and the water content at 120 ° C. were 26.7 m 2 / g and 0.29 m 2 / g, respectively.
By weight, hexagonal boron nitride powder was obtained. This was filled in a silicone resin in the same manner as in Example 1, cured after defoaming, and the surface and inside were observed. As a result, traces of bubbles were observed. COMPARATIVE EXAMPLE 2 10 kg of amorphous boron nitride containing 12% by weight of B 2 O 3 as a crystallization catalyst was calcined in a batch atmosphere furnace at 1750 ° C. in a dehydrated nitrogen gas atmosphere. Example 1
As a result, hexagonal boron nitride powders having a BET specific surface area and a water content of 5.7 m 2 / g and 0.07% by weight, respectively, were obtained. Reference Example 1 A commercially available fine powder grade of hexagonal boron nitride powder "SP-2" manufactured by Denki Kagaku Kogyo KK has a BET specific surface area of 31.7 m.
2 / g, and the water content at 120 ° C. is 0.41
% By weight. When this powder was filled in a silicone resin in the same manner as in Example 1 and then cured after defoaming, traces of bubbles were observed on the surface and inside. According to the present invention, the BET specific surface area is 1
A hexagonal boron nitride powder having a water content of not less than 5.0 m 2 / g and a content of not more than 0.15% by weight and suitable as a fine particle component of a filler can be obtained.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭61−256905（ＪＰ，Ａ) 特開 平７−41311（ＪＰ，Ａ) 特開 平９−295801（ＪＰ，Ａ) 特開 平10−324509（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C01B 21/064 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-256905 (JP, A) JP-A-7-41311 (JP, A) JP-A-9-295801 (JP, A) JP-A-10- 324509 (JP, A) (58) Field surveyed (Int. Cl. 7 , DB name) C01B 21/064
Claims (1)
窒化ほう素粉末を、脱水された窒素ガスの雰囲気下、温
度１４００℃〜１６５０℃で焼成することを特徴とす
る、ＢＥＴ法比表面積が１５．０ｍ ２ ／ｇ以上、含有水
分量が０．１５重量％以下の六方晶窒化ほう素粉末の製
造方法。 (57) Claims 1. An amorphous boron nitride powder containing 5 to 20% by weight of a crystallization catalyst is calcined at a temperature of 1400 ° C to 1650 ° C in an atmosphere of dehydrated nitrogen gas. Characterized by
Having a BET specific surface area of 15.0 m 2 / g or more, containing water
Production of hexagonal boron nitride powder with an amount of 0.15% by weight or less
Construction method.
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| JP18657297A JP3521173B2 (en) | 1997-07-11 | 1997-07-11 | Method for producing hexagonal boron nitride powder |
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| CN102899659A (en) * | 2012-10-16 | 2013-01-30 | 哈尔滨工业大学 | Preparation method of boron nitride nanotube hydrophobic membrane |
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