JP2010222158A - Method for producing high purity silica particle - Google Patents
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本発明は、四塩化珪素の加水分解によって高純度シリカ粒子の製造する方法において、生産性がよく、平均粒径が１００μｍ以上の高純度シリカ粒子を製造することができる製造方法に関する。 The present invention relates to a method for producing high-purity silica particles having a high productivity and an average particle size of 100 μm or more in a method for producing high-purity silica particles by hydrolysis of silicon tetrachloride.
高純度シリカ粒子の製造方法として、四塩化珪素の加水分解による製造方法が知られている。例えば、特開昭６２−２１７０８号公報（特許文献１）には、高純度の四塩化珪素を純水に攪拌しながら加えて加水分解させ、生成したゲルを予備乾燥し、これを磨砕した微細粒子を篩分けし、次いで、１４００℃まで加熱乾燥して粒度４０〜１０００μｍのシリカ粒子を製造する方法が記載されている。また、特開昭６２−３０６１３号公報（特許文献２）には、四塩化珪素を塩酸などに加えて加水分解させる方法が記載されている。 As a method for producing high-purity silica particles, a production method by hydrolysis of silicon tetrachloride is known. For example, in Japanese Patent Laid-Open No. 62-21708 (Patent Document 1), high-purity silicon tetrachloride is added to pure water with stirring and hydrolyzed, and the resulting gel is pre-dried and ground. A method is described in which fine particles are sieved and then heated to 1400 ° C. to produce silica particles having a particle size of 40 to 1000 μm. Japanese Patent Laid-Open No. 62-30613 (Patent Document 2) describes a method of hydrolyzing silicon tetrachloride by adding it to hydrochloric acid or the like.
四塩化珪素の加水分解は次式[１]に示される。反応式では、１モルの四塩化珪素に対して、４モルの水が反応し、言い換えると水１リットルに対して１４モルの四塩化珪素が反応するはずであるが、実際には、攪拌しながら、四塩化珪素を水に添加すると、水１リットルに対して１モル程度の四塩化珪素を添加した時点で生成物はゲル状になり、これより多くの四塩化珪素を添加することができなくなる。生成するゲルに含まれるシリカ含有量が低いと工業的な製造方法として適さないものになる。 Hydrolysis of silicon tetrachloride is represented by the following formula [1]. In the reaction formula, 4 mol of water should react with 1 mol of silicon tetrachloride. In other words, 14 mol of silicon tetrachloride should react with 1 liter of water. However, when silicon tetrachloride is added to water, the product becomes a gel when about 1 mole of silicon tetrachloride is added to 1 liter of water, and more silicon tetrachloride can be added. Disappear. If the silica content contained in the resulting gel is low, it is not suitable as an industrial production method.
ＳｉＣｌ4＋４Ｈ2Ｏ → ４ＨＣｌ＋ＳｉＯ2＋２Ｈ2Ｏ …[１] SiCl 4 + 4H 2 O → 4HCl + SiO 2 + 2H 2 O [1]
特許文献２に記載された四塩化珪素を塩酸などに添加する方法は、ゲルの代わりにスラリー状の微粉末の沈殿が生じるため四塩化珪素の添加は妨げられないが、その沈殿物を乾燥してできるシリカの粒子径は数μｍオーダーであり、粒径１００μｍ以上の粒子を得ることができない。 Although the method of adding silicon tetrachloride described in Patent Document 2 to hydrochloric acid or the like causes precipitation of a fine slurry powder instead of gel, addition of silicon tetrachloride is not hindered, but the precipitate is dried. The particle diameter of silica that can be obtained is on the order of several μm, and particles having a particle diameter of 100 μm or more cannot be obtained.
本発明は、高純度シリカ粒子の製造方法における従来の問題を解決したものであり、生産性がよく、平均粒径が１００μｍ以上の高純度シリカ粒子を製造することができる製造方法を提供する。 The present invention solves the conventional problems in the method for producing high-purity silica particles, and provides a production method capable of producing high-purity silica particles having good productivity and an average particle size of 100 μm or more.
本発明は、以下の手段によって上記課題を解決した高純度シリカ粒子の製造方法に関する。
〔１〕四塩化珪素の加水分解によって高純度のシリカ粒子を製造する方法において、塩酸を抽出する難水相溶性の有機溶媒を反応溶液に予め混合し、加水分解反応の進行に伴い生成する反応液中の塩酸を該有機溶媒中に抽出することを特徴とする高純度シリカ粒子の製造方法。
〔２〕塩酸抽出溶媒がトリオクチルアミン、トリブチルアミン、トリペンチルアミン、トリヘキシルアミン、またはトリヘプチルアミンである上記[１]に記載する高純度シリカ粒子の製造方法。
〔３〕反応溶液のｐＨを１.５〜２.０に保持して加水分解を進める上記[１]または上記[２]に記載する高純度シリカ粒子の製造方法。
〔４〕塩酸を抽出する難水相溶性の有機溶媒を混合した純水を攪拌しながら、冷却下、四塩化珪素を少量づつ添加して加水分解を進めた後に、攪拌を止めて静置し、層分離した有機溶媒層を除去し、静置後、生成したゲル状物質を回収して乾燥し、焼成する上記[１]〜上記[３]の何れかに記載する高純度シリカ粒子の製造方法。
〔５〕純水１リットルに対する四塩化珪素の導入量が１.５モル比以上である上記[１]〜上記[４]に記載する高純度シリカ粒子の製造方法。
〔６〕生成したゲル中のシリカ含有量が５.０質量％以上である上記[１]〜上記[５]の何れかに記載する高純度シリカ粒子の製造方法。
〔７〕製造される高純度シリカ粒子の平均粒子径が１００μｍ以上である上記[１]〜上記[６]の何れかに記載する高純度シリカ粒子の製造方法。
The present invention relates to a method for producing high-purity silica particles that solves the above-described problems by the following means.
[1] In a method for producing high-purity silica particles by hydrolysis of silicon tetrachloride, a reaction that is generated as the hydrolysis reaction proceeds by previously mixing a hardly water-compatible organic solvent for extracting hydrochloric acid into the reaction solution. A method for producing high-purity silica particles, characterized by extracting hydrochloric acid in a liquid into the organic solvent.
[2] The method for producing high-purity silica particles according to the above [1], wherein the hydrochloric acid extraction solvent is trioctylamine, tributylamine, tripentylamine, trihexylamine, or triheptylamine.
[3] The method for producing high-purity silica particles according to the above [1] or [2], wherein the hydrolysis proceeds while maintaining the pH of the reaction solution at 1.5 to 2.0.
[4] Stirring pure water mixed with a poorly water-soluble organic solvent for extracting hydrochloric acid while stirring, add silicon tetrachloride in small portions, proceed with hydrolysis, then stop stirring and let stand. The production of the high-purity silica particles according to any one of [1] to [3] above, wherein the separated organic solvent layer is removed and left standing, and then the gel-like substance produced is recovered, dried and fired Method.
[5] The method for producing high-purity silica particles according to the above [1] to [4], wherein the amount of silicon tetrachloride introduced per 1 liter of pure water is 1.5 molar ratio or more.
[6] The method for producing high-purity silica particles according to any one of [1] to [5] above, wherein the silica content in the generated gel is 5.0% by mass or more.
[7] The method for producing high-purity silica particles according to any one of [1] to [6] above, wherein an average particle diameter of the produced high-purity silica particles is 100 μm or more.
本発明の製造方法は、四塩化珪素の加水分解によって高純度のシリカ粒子を製造する方法において、塩酸を抽出する難水相溶性の有機溶媒を反応溶液に予め混合し、反応液中の塩酸を該有機溶媒中に抽出して加水分解を行うため、純水１リットルに対して１.５モル以上の四塩化珪素を加水分解してもゲル化せず、従って、シリカ含有量５.０質量％以上のゲルを得ることができる。 The production method of the present invention is a method for producing high-purity silica particles by hydrolysis of silicon tetrachloride, wherein a hardly water-compatible organic solvent for extracting hydrochloric acid is premixed in a reaction solution, and hydrochloric acid in the reaction solution is added. Since it is extracted into the organic solvent and hydrolyzed, it does not gel even when 1.5 mol or more of silicon tetrachloride is hydrolyzed with respect to 1 liter of pure water. Therefore, the silica content is 5.0 mass. % Or more of the gel can be obtained.
また、本発明の製造方法によれば、平均粒子径１００μｍ以上、好ましくは、平均粒子径１５０μｍ以上の高純度シリカ粒子を得ることができる。電子材料として使用される高純度な石英ガラスは、一般に平均粒子径１５０μｍ〜４２５μｍ程度の高純度シリカ粒子を原料として製造されており、本発明の方法によって製造される高純度シリカ粒子は上記電子材料用石英ガラスの原料として好適である。 In addition, according to the production method of the present invention, high-purity silica particles having an average particle diameter of 100 μm or more, and preferably an average particle diameter of 150 μm or more can be obtained. High-purity quartz glass used as an electronic material is generally manufactured using high-purity silica particles having an average particle diameter of about 150 μm to 425 μm as raw materials. The high-purity silica particles manufactured by the method of the present invention are the above-mentioned electronic materials. It is suitable as a raw material for quartz glass.
以下、本発明を実施形態に基づいて説明する。
本発明の製造方法は、四塩化珪素の加水分解によって高純度のシリカ粒子を製造する方法において、塩酸を抽出する難水相溶性の有機溶媒を反応溶液に予め混合し、反応液中の塩酸を該有機溶媒中に抽出して加水分解を行うことを特徴とする高純度シリカ粒子の製造方法である。
Hereinafter, the present invention will be described based on embodiments.
The production method of the present invention is a method for producing high-purity silica particles by hydrolysis of silicon tetrachloride, wherein a hardly water-compatible organic solvent for extracting hydrochloric acid is premixed in a reaction solution, and hydrochloric acid in the reaction solution is added. A method for producing high-purity silica particles, wherein the hydrolysis is performed by extraction into the organic solvent.
四塩化珪素の加水分解によってゲルを生成させるには、例えば、純水を攪拌しながら反応容器を冷却して四塩化珪素を少量づつ添加すればよい。加水分解が進むと溶液がゲル化する。本発明の製造方法は、塩酸を抽出する難水相溶性の有機溶媒を、四塩化珪素を添加する純水に予め混合しておく。 In order to generate a gel by hydrolysis of silicon tetrachloride, for example, the reaction vessel is cooled while stirring pure water, and silicon tetrachloride is added little by little. As hydrolysis proceeds, the solution gels. In the production method of the present invention, a hardly water-compatible organic solvent for extracting hydrochloric acid is mixed in advance with pure water to which silicon tetrachloride is added.
塩酸を抽出する作用を有し、かつ水に対する溶解度が小さい有機溶媒（難水相溶性と云う）としては、トリブチルアミン、トリペンチルアミン、トリヘキシルアミン、トリヘプチルアミン、トリヘオクチルアミンなどのアルキルアミン類を用いることができる。 Organic solvents that extract hydrochloric acid and have low solubility in water (referred to as poorly water-compatible) include alkylamines such as tributylamine, tripentylamine, trihexylamine, triheptylamine, and triheoctylamine. Can be used.
四塩化珪素の加水分解によってシリカと共に塩酸が生じる。本発明の製造方法は、塩酸を抽出する難水相溶性の有機溶媒を反応溶液中に存在させることによって、上記塩酸を有機溶媒中に抽出し、この有機溶媒は水に溶解し難いので、反応溶液から塩酸が除去された状態で四塩化珪素の加水分解が進行する。従って、有機溶媒を加えない場合よりもゲル化するまでにより多くの四塩化珪素を加水分解することができ、シリカの生成量を増加させることができる。 Hydrolysis of silicon tetrachloride produces hydrochloric acid along with silica. In the production method of the present invention, the above-mentioned hydrochloric acid is extracted into an organic solvent by allowing a hardly water-compatible organic solvent for extracting hydrochloric acid to be present in the reaction solution, and this organic solvent is difficult to dissolve in water. Hydrolysis of silicon tetrachloride proceeds with hydrochloric acid removed from the solution. Therefore, more silicon tetrachloride can be hydrolyzed until gelation than when no organic solvent is added, and the amount of silica produced can be increased.
四塩化珪素の加水分解によって塩酸が生じるので、反応溶液のｐＨは酸性になるが、塩酸を有機溶媒に抽出することによって反応溶液のｐＨは一定範囲を保つようになる。有機溶媒の添加量は反応溶液のｐＨが１.５〜２.５の範囲を維持する量が好ましい。 Hydrochloric acid is generated by the hydrolysis of silicon tetrachloride, so that the pH of the reaction solution becomes acidic, but by extracting hydrochloric acid into an organic solvent, the pH of the reaction solution is kept within a certain range. The addition amount of the organic solvent is preferably an amount that maintains the pH of the reaction solution in the range of 1.5 to 2.5.
上記有機溶媒を混合した純水を攪拌しながら、４５℃以下に冷却し、四塩化珪素を少量づつ添加して加水分解を進めた後に、攪拌を止めて静置すると、有機溶媒は水に溶け難いので反応溶液の液面に分離する。この分離した有機溶媒層を取り除く。 While stirring pure water mixed with the above organic solvent, cool to 45 ° C or lower, add silicon tetrachloride in small portions, proceed with hydrolysis, stop stirring and let stand, and the organic solvent will dissolve in water. Since it is difficult, it separates into the liquid level of the reaction solution. The separated organic solvent layer is removed.
有機溶媒層を除去した反応溶液は、放置しておくとゲル化する。このゲルを回収して乾燥し、焼成する。乾燥に好適な温度は約１５０℃〜約２００℃である。乾燥したゲルには水分が抜けた微細な気孔が存在し、またその粒子表面には多くのＯＨ基が付着している。このため、必要に応じ、気孔を塞ぐための処理やＯＨ基を除去する処理を施すことができる。気孔を塞ぐ、あるいは、ＯＨ基を除去するための手段としては、焼成が有効である。焼成に好適な温度はシリカの融点付近（１０００〜１５００℃）である。この乾燥・焼成処理によってゲル中の水分が除去されてシリカ粒子になる。 The reaction solution from which the organic solvent layer has been removed gels if allowed to stand. The gel is collected, dried and baked. A suitable temperature for drying is from about 150 ° C to about 200 ° C. The dried gel has fine pores from which moisture has been removed, and many OH groups are attached to the particle surface. For this reason, the process for plugging pores and the process for removing OH groups can be performed as necessary. As a means for closing the pores or removing OH groups, firing is effective. A suitable temperature for firing is around the melting point of silica (1000 to 1500 ° C.). The moisture in the gel is removed by this drying / firing treatment to form silica particles.
本発明の製造方法によれば、副生した塩酸が有機溶媒で抽出されるので、ゲル化するまでにより多くの四塩化珪素を加水分解することができる。例えば、有機溶媒を用いない従来の製造方法では、四塩化珪素の添加量は純水１リットルに対して１モル程度が限界であるのに対して、本発明の製造方法では、純水１リットルに対して１.５モル以上、好ましくは２.０モル以上の四塩化珪素を加水分解することができる。従って、シリカ含有量７.０質量％以上、好ましくは９.０質量％程度のゲルを得ることができる。なお、ゲル中のシリカ含有量は次式[２]に示される。
（乾燥焼成処理後のシリカ重量／乾燥焼成処理前のゲル重量）×１００ …[２]
According to the production method of the present invention, by-produced hydrochloric acid is extracted with an organic solvent, more silicon tetrachloride can be hydrolyzed until gelation occurs. For example, in a conventional production method that does not use an organic solvent, the amount of silicon tetrachloride added is limited to about 1 mole per 1 liter of pure water, whereas in the production method of the present invention, 1 liter of pure water is used. In contrast, 1.5 mol or more, preferably 2.0 mol or more of silicon tetrachloride can be hydrolyzed. Therefore, a gel having a silica content of 7.0% by mass or more, preferably about 9.0% by mass can be obtained. The silica content in the gel is represented by the following formula [2].
(Silica weight after dry baking process / gel weight before dry baking process) × 100 [2]
また、本発明の製造方法では、反応溶液から塩酸が有機溶媒に抽出され、ゲルを乾燥したときに得られるシリカ粒子の粒径が大きくなる。具体的には、平均粒子径１００μｍ以上のシリカ粒子を得ることができる。従って、電子材料用石英ガラスの原料粉末として好適である。 Moreover, in the manufacturing method of this invention, hydrochloric acid is extracted from the reaction solution by the organic solvent, and the particle size of the silica particle obtained when a gel is dried becomes large. Specifically, silica particles having an average particle diameter of 100 μm or more can be obtained. Therefore, it is suitable as a raw material powder for quartz glass for electronic materials.
なお、上記電子材料用石英ガラスの原料粉末として用いるシリカ粒子を製造するには、純度９９.９９％以上の四塩化珪素と比抵抗１７.５ＭΩ・cm以上（２５℃）の超純水を用いるとよい。 In order to produce silica particles used as a raw material powder for quartz glass for electronic materials, silicon tetrachloride having a purity of 99.99% or more and ultrapure water having a specific resistance of 17.5 MΩ · cm or more (25 ° C.) are used. Good.
本発明の実施例を比較例と共に以下に示す。なお、実施例および比較例により得られたシリカ粒子は、微粉末（比較例２）とミリオーダーの塊（比較例２以外）であった。シリカ粒子の平均粒子径については次のような評価を行った。まず、１００μｍの篩で分級した。その結果、比較例２を除いた全ての場合において、１００μｍの篩を通過する粒子はなかった。比較例２の場合は、ほぼ全てのシリカ粒子が１００μｍの篩を通過したため、堀場製作所のレーザ回折／散乱式粒子径分布測定装置（ＬＡ−９５０）を用いて平均粒子径を測定した。 Examples of the present invention are shown below together with comparative examples. The silica particles obtained in Examples and Comparative Examples were fine powder (Comparative Example 2) and milli-order lump (other than Comparative Example 2). The average particle diameter of the silica particles was evaluated as follows. First, classification was performed with a 100 μm sieve. As a result, in all cases except Comparative Example 2, no particles passed through the 100 μm sieve. In Comparative Example 2, since almost all silica particles passed through a 100 μm sieve, the average particle size was measured using a laser diffraction / scattering particle size distribution measuring device (LA-950) manufactured by Horiba.
〔実施例１〕
純水５００ｇにトリオクチルアミンを５００ｇ入れた。該溶液を攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。ここで撹拌は、純水と四塩化珪素がよく触れ合うようにするため、かつ加水分解によって生成した塩酸とトリオクチルアミンがよく触れ合うようにするために行った。四塩化珪素を添加している間は反応容器を４５℃以下に冷却した。反応溶液のｐＨは１.９であった。四塩化珪素を１９０ｇ添加した時点で撹拌を止めて静置し、反応溶液の上側に分離したトリオクチルアミンの層を除去した。残った溶液を放置しておくと３０分後にゲル化した。生成したゲルを２００℃で５時間加熱して乾燥した後に、１３００℃で４８時間加熱して焼成し、シリカ粒子を回収した。ゲル中のシリカ含有量は９.５重量％であった。この結果を表１に示した。
[Example 1]
500 g of trioctylamine was added to 500 g of pure water. While stirring the solution, silicon tetrachloride was added at a flow rate of 2 g / min. Here, stirring was performed so that pure water and silicon tetrachloride were in good contact with each other, and hydrochloric acid and trioctylamine produced by hydrolysis were in good contact with each other. While the silicon tetrachloride was added, the reaction vessel was cooled to 45 ° C. or lower. The pH of the reaction solution was 1.9. When 190 g of silicon tetrachloride was added, the stirring was stopped and the mixture was allowed to stand, and the trioctylamine layer separated on the upper side of the reaction solution was removed. If the remaining solution was allowed to stand, it gelled after 30 minutes. The produced gel was dried by heating at 200 ° C. for 5 hours, and then heated and fired at 1300 ° C. for 48 hours to recover silica particles. The silica content in the gel was 9.5% by weight. The results are shown in Table 1.
〔実施例２〕
純水５００ｇにトリブチルアミンを５００ｇ入れた。該溶液を攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。ここで撹拌は、純水と四塩化珪素がよく触れ合うようにするため、かつ加水分解によって生成した塩酸とトリブチルアミンがよく触れ合うようにするために行った。四塩化珪素を添加している間は反応容器を４５℃以下に冷却した。反応溶液のｐＨは１.７であった。四塩化珪素を１９０ｇ添加した時点で撹拌を止めて静置し、反応溶液の上側に分離したトリオクチルアミンの層を除去した。残った溶液を放置しておくと３０分後にゲル化した。生成したゲルを２００℃で５時間加熱して乾燥した後に、１３００℃で４８時間加熱して焼成し、シリカ粒子を回収した。ゲル中のシリカ含有量は８.５重量％であった。この結果を表１に示した。
[Example 2]
500 g of tributylamine was added to 500 g of pure water. While stirring the solution, silicon tetrachloride was added at a flow rate of 2 g / min. Here, the stirring was performed so that pure water and silicon tetrachloride were in good contact with each other, and hydrochloric acid generated by hydrolysis and tributylamine were in good contact with each other. While the silicon tetrachloride was added, the reaction vessel was cooled to 45 ° C. or lower. The pH of the reaction solution was 1.7. When 190 g of silicon tetrachloride was added, the stirring was stopped and the mixture was allowed to stand, and the trioctylamine layer separated on the upper side of the reaction solution was removed. If the remaining solution was allowed to stand, it gelled after 30 minutes. The produced gel was dried by heating at 200 ° C. for 5 hours, and then heated and fired at 1300 ° C. for 48 hours to recover silica particles. The silica content in the gel was 8.5% by weight. The results are shown in Table 1.
〔実施例３〕
純水５００ｇにトリペンチルアミンを５００ｇ入れた。該溶液を攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。ここで撹拌は、純水と四塩化珪素がよく触れ合うようにするため、かつ加水分解によって生成した塩酸とトリペンチルアミンがよく触れ合うようにするために行った。四塩化珪素を添加している間は反応容器を４５℃以下に冷却した。反応溶液のｐＨは１.８であった。四塩化珪素を１９０ｇ添加した時点で撹拌を止めて静置し、反応溶液の上側に分離したトリペンチルアミンの層を除去した。残った溶液を放置しておくと３０分後にゲル化した。生成したゲルを２００℃で５時間加熱して乾燥した後に、１３００℃で４８時間加熱して焼成し、シリカ粒子を回収した。ゲル中のシリカ含有量は８.７重量％であった。この結果を表１に示した。
Example 3
500 g of tripentylamine was added to 500 g of pure water. While stirring the solution, silicon tetrachloride was added at a flow rate of 2 g / min. Here, stirring was performed so that pure water and silicon tetrachloride were in good contact with each other, and hydrochloric acid generated by hydrolysis and tripentylamine were in good contact with each other. While the silicon tetrachloride was added, the reaction vessel was cooled to 45 ° C. or lower. The pH of the reaction solution was 1.8. When 190 g of silicon tetrachloride was added, stirring was stopped and the mixture was allowed to stand, and the tripentylamine layer separated on the upper side of the reaction solution was removed. If the remaining solution was allowed to stand, it gelled after 30 minutes. The produced gel was dried by heating at 200 ° C. for 5 hours, and then heated and fired at 1300 ° C. for 48 hours to recover silica particles. The silica content in the gel was 8.7% by weight. The results are shown in Table 1.
〔実施例４〕
純水５００ｇにトリヘキシルアミンを５００ｇ入れた。該溶液を攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。ここで撹拌は、純水と四塩化珪素がよく触れ合うようにするため、かつ加水分解によって生成した塩酸とトリヘキシルアミンがよく触れ合うようにするために行った。四塩化珪素を添加している間は反応容器を４５℃以下に冷却した。反応溶液のｐＨは１.６であった。四塩化珪素を１９０ｇ添加した時点で撹拌を止めて静置し、反応溶液の上側に分離したトリヘキシルアミンの層を除去した。残った溶液を放置しておくと３０分後にゲル化した。生成したゲルを２００℃で５時間加熱して乾燥した後に、１３００℃で４８時間加熱して焼成し、シリカ粒子を回収した。ゲル中のシリカ含有量は９.０重量％であった。この結果を表１に示した。
Example 4
500 g of trihexylamine was added to 500 g of pure water. While stirring the solution, silicon tetrachloride was added at a flow rate of 2 g / min. Here, stirring was performed so that pure water and silicon tetrachloride were in good contact with each other, and hydrochloric acid and trihexylamine produced by hydrolysis were in good contact with each other. While the silicon tetrachloride was added, the reaction vessel was cooled to 45 ° C. or lower. The pH of the reaction solution was 1.6. When 190 g of silicon tetrachloride was added, the stirring was stopped and the mixture was allowed to stand, and the trihexylamine layer separated on the upper side of the reaction solution was removed. If the remaining solution was allowed to stand, it gelled after 30 minutes. The produced gel was dried by heating at 200 ° C. for 5 hours, and then heated and fired at 1300 ° C. for 48 hours to recover silica particles. The silica content in the gel was 9.0% by weight. The results are shown in Table 1.
〔比較例１〕
トリオクチルアミンを添加せず、純水５００ｇを攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。四塩化珪素を添加している間は反応容器を４５℃以下に冷却した。四塩化珪素を９７ｇ添加した時点で溶液がゲル化し、四塩化珪素をこれ以上添加することができなかった。生成したゲルを実施例１と同様に乾燥し、焼成してシリカ粒子を回収した。ゲル中のシリカ含有量は４.９重量％であった。この結果を表１に示した。
[Comparative Example 1]
Without adding trioctylamine, silicon tetrachloride was added at a flow rate of 2 g / min while stirring 500 g of pure water. While the silicon tetrachloride was added, the reaction vessel was cooled to 45 ° C. or lower. When 97 g of silicon tetrachloride was added, the solution gelled and no further silicon tetrachloride could be added. The generated gel was dried in the same manner as in Example 1 and baked to recover silica particles. The silica content in the gel was 4.9% by weight. The results are shown in Table 1.
〔比較例２〕
濃度３６質量％の塩酸水溶液５００ｇを攪拌しながら四塩化珪素を２ｇ/minの流量で添加した。四塩化珪素を添加している間、反応溶液の温度は上昇しなかったので反応容器を冷却しなかった。反応溶液はゲル化せず、四塩化珪素を４２５ｇ添加した時点で四塩化珪素の添加を終了した。生成したスラリー状の沈殿物を実施例１と同様に乾燥し、焼成してシリカ粒子を回収した。反応生成物（液分＋スラリー状沈殿物）中のシリカ含有量は１０重量％であった。この結果を表１に示した。
[Comparative Example 2]
Silicon tetrachloride was added at a flow rate of 2 g / min while stirring 500 g of a hydrochloric acid aqueous solution having a concentration of 36% by mass. During the addition of silicon tetrachloride, the temperature of the reaction solution did not increase, so the reaction vessel was not cooled. The reaction solution did not gel, and the addition of silicon tetrachloride was terminated when 425 g of silicon tetrachloride was added. The produced slurry-like precipitate was dried in the same manner as in Example 1 and baked to collect silica particles. The silica content in the reaction product (liquid component + slurry precipitate) was 10% by weight. The results are shown in Table 1.
表１に示すように、本発明の製造方法（実施例１〜４）によれば、純水１リットルに対する四塩化珪素のモル量が高く、水１リットルに対する添加量は２.５モルであり、シリカ含有量の高いシリカ粒子を得ることができる。一方、比較例１における水１リットルに対する添加量は１.１モルであり、本発明よりも大幅に低い。また、本発明のシリカ粒子の平均粒子径はミリオーダーであり、焼成後に粉砕することにより電子材料用石英ガラスの原料として使用可能であるが、比較例２のシリカ粒子の平均粒子径は１０μｍであり、上記電子材料用石英ガラスの原料としては粒子径が小さ過ぎる。 As shown in Table 1, according to the production method of the present invention (Examples 1 to 4), the molar amount of silicon tetrachloride with respect to 1 liter of pure water is high, and the addition amount with respect to 1 liter of water is 2.5 mol. Silica particles having a high silica content can be obtained. On the other hand, the amount added to 1 liter of water in Comparative Example 1 is 1.1 mol, which is significantly lower than that of the present invention. The average particle size of the silica particles of the present invention is on the order of millimeters and can be used as a raw material for quartz glass for electronic materials by pulverization after firing. The average particle size of the silica particles of Comparative Example 2 is 10 μm. The particle diameter is too small as a raw material for the quartz glass for electronic materials.
Claims (7)
In the method for producing high-purity silica particles by hydrolysis of silicon tetrachloride, a hardly water-compatible organic solvent for extracting hydrochloric acid is mixed with the reaction solution in advance, and hydrochloric acid in the reaction solution is extracted into the organic solvent. And a method for producing high-purity silica particles, wherein hydrolysis is performed.
The method for producing high-purity silica particles according to claim 1, wherein the hydrochloric acid extraction solvent is trioctylamine, tributylamine, tripentylamine, trihexylamine, or triheptylamine.
The method for producing high-purity silica particles according to claim 1 or 2, wherein hydrolysis is carried out while maintaining the pH of the reaction solution at 1.5 to 2.0.
While stirring pure water mixed with a poorly water-compatible organic solvent to extract hydrochloric acid, under cooling, silicon tetrachloride was added in small portions, followed by hydrolysis. The method for producing high-purity silica particles according to any one of claims 1 to 3, wherein the organic solvent layer is removed and allowed to stand, and then the gel-like substance produced is recovered, dried and fired.
The method for producing high-purity silica particles according to claim 1, wherein the introduced amount of silicon tetrachloride with respect to 1 liter of pure water is 1.5 molar ratio or more.
The method for producing high-purity silica particles according to any one of claims 1 to 5, wherein a silica content in the generated gel is 5.0% by mass or more.
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