JP4222582B2

JP4222582B2 - Method for producing high purity silica sol

Info

Publication number: JP4222582B2
Application number: JP05667399A
Authority: JP
Inventors: 邦明前島
Original assignee: Nippon Chemical Industrial Co Ltd
Current assignee: Nippon Chemical Industrial Co Ltd
Priority date: 1999-03-04
Filing date: 1999-03-04
Publication date: 2009-02-12
Anticipated expiration: 2019-03-04
Also published as: JP2000247625A

Description

【０００１】
【発明の属する技術分野】
本発明は、珪酸アルカリから作られる不純物を含まないシリカゾルの製造方法に関する。特に、本発明は、３〜３００ナノメートル（ｎｍ）の大きさを有するシリカのゾルを安価に製造するのに好適である。本発明の製造方法で得られたシリカゾルは、Ａｌ、Ｆｅその他の多価金属や遊離アニオン等の不純物を含まないので、高純度シリカゲル、高純度セラミックスの原料、ブラウン管等のガラス製品用バインダー、触媒用バインダー、シリコンの研磨材や電子材料基板等の研磨材等に有用である。
【０００２】
【従来の技術】
市販のシリカゾルは水ガラスを原料とし、酸による中和もしくはイオン交換などの方法により製造されている。高純度のシリカゾルを製造するためには、この製造工程に酸処理工程を加えて金属元素を溶解しイオン交換や限外ろ過により除去する方法が知られている（特開昭６１−１５８８１０号公報、特開平４−２６０６号公報、特開平６−１６４１４号公報など）。また、特開平７−２９１６１４号公報には珪酸ナトリウム水溶液と６規定の鉱酸との反応によりシリカゲルを生成させ、次いで分離回収したシリカゲルを１規定鉱酸にて３回洗浄処理してシリカ原料を作成し、これを水酸化第四アンモニウムに溶解し、次いで加熱下に酸中和法によりシリカ粒子を折出させて、さらに水を蒸発させて濃縮しシリカの分散したスラリーを作成する方法が提案されている。
【０００３】
また、四塩化珪素の熱分解により得られる、金属等の不純物をほとんど含有しない高純度のシリカ微粉末を水に分散した高純度のシリカゾルは、研磨用途などに使用されている。また、アンモニアを含有するアルコール溶液中で、アルキルシリケートを加水分解させる方法で製造される高純度のシリカゾルも研磨用途などに使用されている。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記の特開昭６１−１５８８１０号公報、特開平４−２６０６号公報、特開平６−１６４１４号公報などに記載の、水ガラスを原料としてイオン交換してシリカゾルを得る方法では金属や遊離アニオン等の不純物を完全に除去することができない。
【０００５】
また、特開平７−２９１６１４号公報の方法では、高濃度の塩酸を大量に使用して金属の除去を行っているが、シリカからクロルイオンを洗い出す工程までには、大量の酸排水が発生し工業的に合理的な製法とは言い難い。また、硫酸中和法によってシリカ粒子を作成しているが、この方法では粒子は小さいものしかできず、凝集しているため（白濁した液になる）限外ろ過法が使用できず、蒸発濃縮という不経済な方法を行わねばならない。蒸発濃縮では第四アンモニウムと硫酸が高濃度化し、第四アンモニウムの酸化分解を防止するため窒素パージも必要となる。
【０００６】
四塩化珪素の熱分解法で得られるシリカ微紛末は高価である上、凝集粒子であり水に分散しても単分散のゾルを得ることが出来ず、Ｎａ等の含有率は低いもののＡｌやＴｉは多い。
アルキルシリケートから得られるシリカはもっとも高純度化が可能であるが、原料費のためもっとも高価である。
【０００７】
本発明は、この様な従来技術に鑑みてなされたものであり、水ガラスという安価な原材料から、高純度のシリカゾルを提供することを目的とするものである。
【００１１】
【課題を解決するための手段】
すなわち、本発明は、下記不純物の含有量がいずれの元素も全て５ｐｐｍ以下である高純度シリカゲルを水酸化第四アンモニウム水溶液に溶解する第１工程、該水酸化第四アンモニウムをイオン交換により除去して活性珪酸液を作成する第２工程、該活性珪酸液をアルカリ触媒の存在下で加熱してシリカを３〜３００ｎｍの粒子径に粒子成長させる第３工程を有することを特徴とする下記不純物の含有量がいずれの元素も全て５ｐｐｍ以下である高純度シリカゾルの製造方法である。
Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ。
【００１２】
また、本発明は、下記不純物の含有量がいずれの元素も全て５ｐｐｍ以下であるシリカゲルを水酸化第四アンモニウム水溶液に溶解する第１工程、該水酸化第四アンモニウムをイオン交換により除去して活性珪酸液を作成する第２工程、該活性珪酸液をアルカリ触媒の存在下でＡｌまたはＣａを添加して加熱してシリカを３〜３００ｎｍの粒子径に粒子成長させる第３工程を有することを特徴とする下記不純物の含有量がいずれの元素も全て５ｐｐｍ以下である高純度シリカゾルの製造方法である。
Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ。
【００１３】
上記の製造方法で用いるシリカゲルは、珪酸ナトリウム水溶液と鉱酸との反応によりシリカを生成させる方法において、キレート剤および過酸化水素が存在する酸濃度１規定以上の酸性領域中でシリカゲルの沈殿を生成させ、次いで分離回収したシリカゲルをキレート剤および過酸化水素含有の鉱酸にて洗浄処理して得られたシリカゲル、又は珪酸ナトリウム水溶液と鉱酸との反応によりシリカゲルを生成させる方法において、キレート剤が存在する酸性領域中でシリカゲルの沈殿を生成させ、次いで分離回収したシリカゲルを過酸化水素含有の鉱酸にて洗浄処理して得られたシリカゲルであるのが好ましい。
【００１４】
【発明の実施の形態】
本発明は、珪酸アルカリと鉱酸との湿式反応によって得られたシリカゲルを水酸化第四アンモニウム水溶液に溶解した後、イオン交換法または解膠法によって製造した、Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ不純物の含有量がいずれの元素も全て５ｐｐｍ以下である高純度シリカゾルを提供する。更には、ＵおよびＴｈの含有量がそれぞれｌｐｐｂ以下である高純度シリカゾルを提供する。
【００１５】
即ち、本発明に原料として用いるシリカゲルは、本出願人の先行出願である特公平４−８１５２６号公報および特公平５−５７６６号公報に開示した高純度シリカを用いるのが好ましい。このシリカゲルは、▲１▼珪酸ナトリウム水溶液と鉱酸との反応によりシリカを生成させる方法において、キレート剤および過酸化水素が存在する酸濃度１規定以上の酸性領域中でシリカの沈殿を生成させ、次いで分離回収したシリカをキレート剤および過酸化水素含有の鉱酸にて洗浄処理して得られたシリカゲル、又は▲２▼珪酸ナトリウム水溶液と鉱酸との反応によりシリカを生成させる方法において、キレート剤が存在する酸性領域中でシリカゲルの沈殿を生成させ、次いで分離回収したシリカゲルを過酸化水素含有の鉱酸にて洗浄処理して選られたシリカゲルである。このシリカゲルはＡｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ不純物の含有畳がいずれの元素も全て５ｐｐｍ以下であり、更にはｌｐｐｍ以下であり、更には、ＵおよびＴｈの含有量がそれぞれｌｐｐｂ以下である。
【００１６】
また、本発明における不純物の含有量は、シリカゲルまたはシリカゾル中のシリカ重量に対する含有濃度である。
【００１７】
本発明の高純度シリカゾルは、珪酸アルカリおよび鉱酸との湿式反応によって生成するシリカゲルを水酸化第四アンモニウム水溶液に溶解した後、イオン交換法または解膠法によって３〜３００ｎｍのシリカ粒子径に粒子成長したシリカゾルであって、Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ不純物の含有量がいずれの元素も全て５ｐｐｍ以下であり、更にはＵおよびＴｈの含有量がそれぞれｌｐｐｂ以下のものである。
【００１８】
また、本発明の高純度シリカゾルは、前記イオン交換法または解膠法による製造工程でＡｌまたはＣａを添加して修飾変成された３〜３００ｎｍのシリカ粒子径に粒子成長したシリカゾルであって、前記不純物のＡｌとＣａを除いたＢ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ不純物の含有量がいずれの元素も全て５ｐｐｍ以下であり、更にはＵおよびＴｈの含有量がそれぞれｌｐｐｂ以下のものである。
【００１９】
本発明の高純度シリカゾルの製造方法は、Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈ不純物の含有量がいずれの元素も全て５ｐｐｍ以下であり、更にはＵおよびＴｈの含有量がそれぞれｌｐｐｂ以下であるシリカゲルを、水酸化第四アンモニウムに溶解する第１工程、イオン交換により水酸化第四アンモニウムを除去して活性珪酸液を作成する第２工程、アルカリ触媒の存在下で加熱して３〜３００ｎｍの粒子径に粒子成長させる第３工程を行うことを特徴とする。
【００２０】
なお、本発明におけるシリカ粒子の粒子径は、シリカの窒素吸着ＢＥＴ法測定による粒子径であり、平均粒子径を示す。この時、シリカの密度を２．２ｇ／ｃｍ³として計算する。
【００２１】
本発明に使用されるシリカゲルは、珪酸ナトリウムと鉱酸との反応によって得られるものであるが、その反応に使用される珪酸ナトリウムとしては、モル比ＳｉＯ₂ ／Ｎａ₂ Ｏが１から４の市販の珪酸ナトリウム溶液（水ガラス）を使用することができ、適宜希釈して使用しても良い。
【００２２】
一方、珪酸ナトリウム溶液と反応させる鉱酸としては、塩酸、硝酸、硫酸などがあげられ、単独又は２種以上の混酸でもよく、適宜希釈して使用される。酸濃度は１規定以上が良い。
【００２３】
反応時に共存させるキレート剤としては、シュウ酸、マロン酸、コハク酸等のジカルボン酸、トリカルバリル酸等のポリカルボン酸、クエン酸、リンゴ酸等のオキシカルボン酸、ニトリルトリ酢酸、エチレンジアミンテトラ酢酸等のアミノポリカルボン酸が使用できる。
【００２４】
上記キレート剤だけでも不純物の含有量がいずれの元素も全て５ｐｐｍ以下とする事ができるが、これに加えて過酸化水素を共存させることで不純物除去が格段と向上する。
【００２５】
キレート剤および過酸化水素添加量は反応系内のシリカに対して０．１〜５重量％、好ましくは０．１〜２重量％で、鉱酸または珪酸ナトリウム、好ましくは珪酸ナトリウムに添加する。
【００２６】
反応は撹拌下の鉱酸に珪酸ナトリウムを添加して行い、反応温度は常温ないし９０℃の任意温度でよい。シリカゲルの析出後も１〜５時間撹拌熟成を行うのが好ましい。
【００２７】
次いで、生成したシリカゲルの沈殿を常法により分離し、分離したシリカゲルを鉱酸で酸処理する。鉱酸、キレート剤の種類は上記と同様であるが過酸化水素は不可欠である。処理時の酸濃度は０．１〜３規定、キレート剤および過酸化水素添加量は反応系内のシリカに対して０．０１〜５重量％、好ましくは０．１〜２重量％が良い。
【００２８】
酸処理工程は１回または必要に応じて複数回行い、処理温度も任意に選定できる。こうして不純物を除去したシリカゲルは、ろ過水洗等の方法により、酸処理剤を除き、高純度のシリカゲルとして回収する。得られたシリカゲルは、不純物Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量がいずれの元素も全て５ｐｐｍ以下のものが得られる。
上記方法で得られたシリカゲルをシリカ原料として、シリカゾルを製造することができる。
【００２９】
本発明のシリカゾルの製造方法において、第１工程では、シリカゲルを水酸化第四アンモニウム水溶液に溶解する。第四アンモニウムとしては、例えばテトラメチルアンモニウム、テトラブチルアンモニウム、β−ヒドロキシエチルトリメチルアンモニウム、テトラエタノールアンモニウム、メチルトリエタノールアンモニウム、ベンジルトリメチルアンモニウム等が単品または複数種混合して使用できる。水酸化第四アンモニウム（Ｒ₄ ＮＯＨ）とシリカのモル比（ＳｉＯ₂ ／Ｒ₄ ＮＯＨ）は１〜４がよく、１未満にするのは無意味に不経済であり、４を越えると溶解しにくい。シリカ濃度は１０〜３０ｗｔ％が良く、濃度が高いと液の粘性が高くなり３０ｗｔ％を越えると取り扱いにくい。溶解は温度が高いほど速やかであるが、常温から沸点の任意の温度でよい。
【００３０】
第２工程はシリカの溶液よりシリカゾルを製造する工程であるが、イオン交換法と解膠法の２方法があり、イオン交換法の方が作業が簡単で余分な副原料の投入もないため不純物の侵入が無く好ましい。
【００３１】
イオン交換法では、まず塩酸や硫酸によってＨ⁺ 型にしたカチオン交換樹脂のカラムを準備しておく。第１工程で製造したシリカ溶液をシリカ濃度２〜７ｗｔ％に純水で希釈して、カチオン交換樹脂のカラムに通し、第四アンモニウムイオンを除去し、「活性珪酸液」を得る。この活性珪酸液をアルカリ触媒の存在下で加熱してシリカの粒子径を３〜３００ｎｍに粒子成長させる。
【００３２】
「活性珪酸液」のシリカ濃度は２〜４ｗｔ％の範囲がよい。これよりも低いと、後工程での加熱や濃縮に過大の負担がかかり、これよりも高いと、液のゲル化が早くハンドリング性に欠ける。次いで該活性珪酸液は、アルカリ触媒を加えて加熱して珪酸を重合させ粒子成長させる。
【００３３】
係る粒子成長工程は、水ガラスを原料とするシリカゾルの製造法においても、通常行われているものであり、例えば米国特許３５３８０１５号記載の方法は水性媒体中に活性珪酸液とアルカリ水溶液を特定の添加速さで同時添加する方法、特開昭５８−１５０２２号公報の方法はアルカリ水溶液の中に活性珪酸液を特定の添加速さで添加する方法、特開昭６３−１２３８０７号公報の方法はアルミニウム化合物の存在下でアルカリ水溶液の中に活性珪酸液を添加しアニオン性の強いシリカゾルを作る方法、米国特許２６８０７２１号の方法は、１６０〜３００℃の水熱処理により非球状のシリカゾルを作る方法、特開平１−３１７１１５号公報の方法は、カルシウム塩等を添加した活性珪酸液にアルカリを加えた後、６０〜２５０℃の水熱処理により細長い形状のシリカゾルを作る方法、特開平４−１８７５１２号公報の方法は、アルミニウム塩等を添加した活性珪酸液をアルカリ珪酸塩に添加して細長い形状のシリカゾルを作る方法、特開平６−１９９５１５号公報の方法は、常法により粒子成長を終えたシリカゾルにアルミニウム塩等を添加したのち更に８０〜２５０℃の水熱処理により安定なシリカゾルを作る方法、等々があり、これら水ガラス法のあらゆる製造方法が適用できる。
【００３４】
本発明においては、具体的に使用されるアルカリは、アンモニア、アミン、水酸化第四アンモニウムなどであり、第１工程で製造したシリカの水酸化第四アンモニウム溶液も好ましい。
【００３５】
上記のように、活性珪酸液をアルカリ触媒と混合して加熱して珪酸を重合し粒子成長をさせる方法は多数あるので、どの方法を適用するかによって、アルカリ触媒の種類、量を選定しなくてはならない。
【００３６】
従って、基本的な条件としてｐＨが７以上となるようにアルカリ触媒を加え加熱して珪酸の重合を進行させることが本発明の構成要素となる。更に好ましくは、ｐＨが８以上である。
【００３７】
活性珪酸液をアルカリ性にして加熱すると珪酸の重合反応を進行させることができる。そしてこの珪酸の重合反応の進行によって反応媒体中にシリカの核粒子が生成し、更にアルカリを添加する等の方法で液のアルカリ性を保ちながら活性珪酸液を加えていくと、その粒子成長によって３〜３００ｎｍ、好ましくは５〜１００ｎｍの揃った粒子径を有するシリカゾルが生成する。
【００３８】
アルカリ触媒を全量あらかじめ反応媒体中に入れておき、そこへ活性珪酸液を添加していく方法も良い。その逆はできない。
【００３９】
市販のシリカゾルやアルミナゾル等を種粒子として反応媒体中にあらかじめ入れておき、これに活性珪酸液とアルカリ触媒をシリカ１モルに対して０．００５〜０．１モルとなる量で同時に連続添加して、種粒子を粒子成長する方法も良い。
【００４０】
市販品でなく本発明で作成したシリカゾルを種粒子に使用するのは更に良い。粒子成長の初期に反応媒体中にアルミニウム化合物やカルシウム化合物を微量添加して、成長粒子の形状を非球状にするのも良い。
【００４１】
なお、ＡｌまたはＣａを添加して修飾変成するとは、粒子の形状を非球状化したり、粒子の荷電を正又は負にしたり、その強さを調節したりする方法で、既に前記記載のイオン交換法の粒子成長方法を不純物濃度を配慮して実施すればよい。
【００４２】
この重合粒子成長反応は、減圧、常圧、加圧のいずれの圧力下でも行うことができるが、６０℃以上、好ましくは８０℃から反応混合物の沸点以下の温度で充分な撹拌下に行うのがよい。
【００４３】
活性珪酸液の添加終了後、更に７０℃以上、好ましくは８０〜２００℃で、３０分以上、好ましくは１〜６時間程度加熱熟成を行うのが好ましい。この加熱熟成の途中又は後に、アルミニウム化合物等を添加してシリカ粒子の表面に沈着させ、粒子の性状を変えることもできる。
【００４４】
本発明の方法で得られたシリカゾルは、蒸発法、限外ろ過法等の通常の方法によって濃縮することができる。この濃縮によって約４０％までの安定なシリカゾルが得られる。更には、イオン交換法により、アルカリ触媒を除去することができ、実質的にシリカ以外の成分を含まないシリカゾルを得ることができる。
【００４５】
イオン交換法により、アルカリ触媒を除去したシリカゾルは、有機溶剤を加えつつ蒸発法、限外ろ過法の工程を行うことにより、水分を溜去、洗い出しする事で有機溶剤に分散したシリカゾル、すなわちオルガノゾルとすることができる。
【００４６】
次に、解膠法により、第２工程のシリカの溶液よりシリカゾルを製造する工程について説明する。
【００４７】
解膠法は、第１工程で製造したシリカ溶液を純粋でシリカ濃度４〜１０ｗｔ％まで希釈した後、水酸化第四アンモニウムとシリカのモル比（ＳｉＯ₂／Ｒ₄ＮＯＨ）を１０〜４０の範囲に調製し、８０℃〜２５０℃の温度に加熱して粒子を成長させる。モル比の調節法としては、シリカ溶液に原料のシリカゲルを加える方法、シリカ溶液に前記活性珪酸を加える方法、あるいはイオン交換法で製造したシリカゲルを加える方法などがある。また、気相法で作成されたシリカ源やエチルシリケートから作成されたシリカ源を加える方法も、それらから混入する不純物を考慮した上では充分に可能である。これ以降の第３工程の製造方法は、イオン交換と同様な方法により行うことができる。
【００４８】
【実施例】
以下に、本発明を具体的に説明する。
【００４９】
（高純度シリカゲルの製造例１）
撹拌機付き反応糟に硝酸水溶液（ＨＮＯ₃ ＝１９．３重量％）３２８５ｇをとり、７０℃に加温した。
これとは別に、珪酸ソーダＪＩＳ３号（Ｎａ₂ Ｏ＝９．２重量％、ＳｉＯ₂ ＝２８．５重量％、ＳｉＯ₂ ／Ｎａ₂ Ｏモル比＝３．２０）２１００ｇを容器に取り撹拌し、ＥＤＴＡ（エチレンジアミンテトラ酢酸）０．６ｇを小量の水に分散させたものを添加し、溶解した。更に７０℃で２時間撹拌した。
【００５０】
硝酸水溶液にこのＥＤＴＡ含有珪酸ナトリウム水溶液を約３０分かけて添加し、シリカゲルの沈殿を生成させた、この間反応糟の温度を７０〜８０℃に保持した。添加後、反応スラリーを８０℃で２時間撹拌して熟成を行った。
この反応終了スラリーからシリカゲルの沈殿をろ過分離し、これを水中にリパルプして洗浄した後、再びろ過分離した。
【００５１】
分離回収したシリカゲルを撹拌機付き酸処理槽に取り、これに水と硝酸を加えてスラリー全量５リットル、スラリー中の硝酸濃度１規定となるようにして調整し、さらに３５％過酸化水素水１７ｇを添加して撹拌しながら、９０℃で３時間加熱して酸処理した後、スラリーからシリカゲルをろ過分離し、水でリパルプ洗浄固液分離を数回繰り返し、スラリーの電気伝導度が５０μＳ以下となった時点でろ過してシリカゲルを回収した。
【００５２】
このシリカゲルは水分６３．３％で、乾燥せずに以下の実験に使用した。また、シリカ中の不純分量を第１表に記載した。
【００５３】
（高純度シリカゲルの製造例２）
撹拌機付き反応糟に硝酸水溶液（ＨＮＯ₃ ＝１９．３重量％）４０００ｇをとり、これにシュウ酸（２水塩、市販品）６ｇ、３５％過酸化水素水（市販品）１７ｇを添加して溶解した。この硝酸水溶液に珪酸ソーダＪＩＳ３号（Ｎａ₂ Ｏ＝９．２重量％、ＳｉＯ₂ ＝２８．５重量％、ＳｉＯ₂ ／Ｎａ₂ Ｏモル比＝３．２０）２１００ｇを約３０分かけて添加し、シリカゲルの沈殿を生成させた。この間反応槽の温度を７０〜８０℃に保持した。添加後、反応スラリーを８０℃で２時間撹拌して熟成を行った。
【００５４】
この反応終了スラリーからシリカゲルの沈殿をろ過、洗浄を繰り返して、分離回収した。
【００５５】
分離回収したシリカゲルを撹拌機付き酸処理槽に取り、これに水と硝酸を加えてスラリー全量５リットル、スラリー中の硝酸濃度１規定となるようにして調整し、さらにシュウ酸６ｇ、３５％過酸化水素水１７ｇを添加して撹拌しながら、９０℃で３時間加熱して酸処理した後、スラリーからシリカゲルをろ過分離し、水でリパルプ洗浄固液分離を数回繰り返し、スラリーの電気伝導度が５０μＳ以下となった時点でろ過してシリカゲルを回収した。
【００５６】
このシリカゲルは水分６１．５％で、乾燥せずに以下の実施例に使用した。また、シリカ中の不純分量を表１に記載した。
【００５７】
【表１】

【００５８】
（市販水酸化第四アンモニウムの不純物）
以下の実施例で使用した市販水酸化第四アンモニウムは、第１表記載の成分がいずれも０．０２ｐｐｍ以下であった。
【００５９】
実施例１
製造例１のシリカ含有量３６．７％の含水高純度シリカゲル３２７ｇを撹拌機付き１リットルガラス製反応容器に取り、純水５０ｇと市販水酸化テトラメチルアンモニウム２０％水溶液３６８ｇを加え、撹拌下に徐々に加熱して８０℃まで液温が上昇した後、１６時間撹拌下にこの温度を保ちシリカゲルを溶解した。水分の蒸発により、回収したシリカ溶液は６７８ｇであり、無色透明でシリカ濃度１７．７％、水酸化テトラメチルアンモニウム濃度１０．７％であった。
【００６０】
回収したシリカ溶液は６７８ｇのうち５００ｇを分取し、純水２４５０ｇを混合しシリカ濃度３．０％に希釈した。この希釈シリカ溶液は、予め塩酸によってＨ型に再生した５００ｍｌのカチオン交換樹脂（オルガノ（株）製「アンバーライトＩＲｌ２０Ｂ」）を充填したカラムを０．５時間かけて定速度で通過させ、３５００ｇのテトラメチルアンモニウムイオンを除去した活性珪酸液を得た。この活性珪酸液のｐＨは４．４であった。
【００６１】
別の撹拌機付き容器に純水１６７ｇを仕込み、上記の回収したシリカ溶液の残部３３ｇを加えて希釈し、撹拌下９５℃に加熱し、撹拌と温度を保ちながら活性珪酸液を８時間かけて定速で添加した。添加終了後、１時間撹拌と温度を保ち熟成を行った。
【００６２】
放冷後、この液はシリカコロイド特有の青味を帯びた半透明液であった。次いで、限外ろ過によりシリカ濃度１５％に濃縮し約６００ｇのシリカゾルを得た。このゾルの水酸化テトラメチルアンモニウム濃度は０．１１％であり、コロイダルシリカ粒子は１２ｎｍのＢＥＴ法粒子径を有していた。このシリカゾルのＡｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量はいずれの元素も全て５ｐｐｍ以下であり、実質的にテトラメチルアンモニウムとシリカ以外の成分を含まないシリカゾルを得た。
【００６３】
シリカ粒子の粒子径は窒素吸着ＢＥＴ法により測定した値であり、その測定法は、試料を１０ｇとり希塩酸を加えてｐＨを５とし、加熱して固化し、１５０℃で乾燥して粉末試料とし、ＭｉｃｒｏｍｅｒｉｔｉｃｓＦｌｏｗＳｏｒｂＩＩ２３００形（（株）島津製作所製）にて測定した。
【００６４】
実施例２
製造例２のシリカ含有量３８．５％の含水高純度シリカゲル５４０ｇを撹拌機付き１リットルガラス製反応容器に取り、純水３００ｇと市販水酸化β−ヒドロキシエチルトリメチルアンモニウム４８％水溶液２９ｌｇを加え、撹拌下に徐々に加熱して８０℃まで液温が上昇した後、１６時間撹拌下にこの温度を保ちシリカゲルを溶解した。水分の蒸発により、回収したシリカ溶液は１１２５ｇであり、無色透明でシリカ濃度１８．５％、水酸化β−ヒドロキシエチルトリメチルアンモニウム濃度１２．５％であった。
【００６５】
回収したシリカ溶液は１１２５ｇのうち４７６ｇを分取し、純水２４７５ｇを混合しシリカ濃度３．０％に希釈した。この希釈シリカ溶液は、予め塩酸によってＨ型に再生した５００ｍｌのカチオン交換樹脂（オルガノ（株）製「アンバーライトＩＲｌ２０Ｂ」）を充填したカラムを０．５時間かけて定速度で通過させ、３５００ｇのβ−ヒドロキシエチルトリメチルアンモニウムイオンを除去した活性珪酸液を得た。この活性珪酸液のｐＨは４．４であった。
【００６６】
別の撹拌機付き容器に純水１６９ｇを仕込み、上記の回収したシリカ溶液の残部３ｌｇを加えて希釈し、撹拌下９５℃に加熱し、撹拌と温度を保ちながら活性珪酸液を８時間かけて定速で添加した。添加終了後１時間撹拌と温度を保ち熟成を行った。
【００６７】
放冷後、この液はシリカコロイド特有の青味を帯びた半透明液であった。次いで、限外ろ過によリシリカ濃度１５％に濃縮し約６００ｇのシリカゾルを得た。このゾルのコロイダルシリカ粒子は１２ｎｍのＢＥＴ法粒子径を有していた。このシリカゾルのＡｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量はいずれの元素も全てｌｐｐｍ以下であり、実質的にβ−ヒドロキシエチルトリメチルアンモニウムとシリカ以外の成分を含まないシリカゾルを得た。
【００６８】
実施例３
製造例２のシリカ含有量３８．５％の含水高純度シリカゲル５４０ｇを撹拌機付き１リットルガラス製反応容器に取り、純水３００ｇと市販水酸化β−ヒドロキシエチルトリメチルアンモニウム４８％水溶液２９ｌｇを加え、撹拌下に徐々に加熱して８０℃まで液温が上昇した後、１６時間撹拌下にこの温度を保ちシリカゲルを溶解した。水分の蒸発により、回収したシリカ溶液は１１２５ｇであり、無色透明でシリカ濃度１８．５％、水酸化β−ヒドロキシエチルトリメチルアンモニウム濃度１２．５％であった。
【００６９】
回収したシリカ溶液は１１２５ｇのうち４７６ｇを分取し、純水２４７５ｇを混合しシリカ濃度３．０％に希釈した。この希釈シリカ溶液は、予め塩酸によってＨ型に再生した５００ｍｌのカチオン交換樹脂（オルガノ（株）製「アンバーライトＩＲｌ２０Ｂ」）を充填したカラムを０．５時間かけて定速度で通過させ、３５００ｇのβ−ヒドロキシエチルトリメチルアンモニウムイオンを除去した活性珪酸液を得た。この活牲珪酸液のｐＨは４．４であった。
【００７０】
別の撹拌機付き容器に純水１６７ｇを仕込み、実施例１で製造したシリカ濃度１７．７％、水酸化テトラメチルアンモニウム濃度ｌ０．７％のシリカ溶液３３ｇを加えて希釈し、撹拌下９５℃に加熱し、撹拌と温度を保ちながら活牲珪酸液を８時間かけて定速で添加した。添加終了後、１時間撹拌と温度を保ち熱成を行った。
【００７１】
放冷後、この液はシリカコロイド特有の青味を帯びた半透明液であった。次いで、限外ろ過によりシリカ濃度１５％に濃縮し、約６００ｇのシリカゾルを得た。このゾルのコロイダルシリカ粒子は１２ｎｍのＢＥＴ法粒子径を有していた。このシリカゾル３００ｇを撹拌機付きオートクレーブに仕込み、撹拌下２時間で１８０℃まで加熱し、そのまま１８０℃を３時間保った後放冷した。このゾルのコロイダルシリカ粒子は１７ｎｍのＢＢＴ法粒子径を有し、Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量はいずれの元素も全て５ｐｐｍ以下であり、実質的にテトラメチルアンモニウムとシリカ以外の成分を含まないシリカゾルを得た。
【００７２】
実施例４
製造例２のシリカ含有量３８．５％の含水高純度シリカゲル５４０ｇを撹拌機付き１リットルガラス製反応容器に取り、市販水酸化メチルトリエタノールアンモニウム５０％水溶液７２２ｇを加え、撹拌下に徐々に加熱して８０℃まで液温が上昇した後１６時間撹拌下にこの温度を保ちシリカゲルを溶解した。水分の蒸発により、回収したシリカ溶液は１１２５ｇであり、無色透明でシリカ濃度１８．５％、水酸化メチルトリエタノールアンモニウム濃度３２．１％であった。
【００７３】
回収したシリカ溶液１１２５ｇに純水５８０５ｇを混合しシリカ濃度３．０％に希釈した。この希釈シリカ溶液は、予め塩酸によってＨ型に再生した２０００ｍｌのカチオン交換樹脂（オルガノ（株）製「アンバーライトＩＲｌ２０Ｂ」）を充填したカラムを０．５時間かけて定速度で通過させ、７５００ｇのメチルトリエタノールアンモニウムイオンを除去した活性珪酸液を得た。この活性珪酸液のｐＨは４．４であった。
【００７４】
実施例１で製造したシリカ濃度１５％のテトラメチルアンモニウムとシリカ以外の成分を合まない６００ｇのシリカゾルのうち１６０ｇを別の撹拌機付き容器に仕込み、純水１０００ｇを加えて希釈し、更に水酸化テトラメチルアンモニウム２０％水溶液３ｇを加えてｐＨを１０とし、撹拌下９５℃に加熱し、撹拌と温度を保ちながら７５００ｇの活性珪酸液と２２ｇの水酸化テトラメチルアンモニウム２０％水溶液を８時間かけて定速で同時に添加した。添加終了後、１時間撹拌と温度を保ち熱成を行った。
【００７５】
放冷後、この液はシリカコロイド特有の乳白半透明液であった。次いで、限外ろ過によりシリカ濃度３０％に濃縮し約７５０ｇのシリカゾルを得た。このゾルのコロイダルシリカ粒子は２４ｎｍのＢＥＴ法粒子径を有していた。このシリカゾル３００ｇを撹拌機付きオートクレーブに仕込み、撹拌下２時間で１８０℃まで加熱し、そのまま１８０℃を３時間保った後放冷した。このゾルのコロイダルシリカ粒子は３２ｎｍのＢＥＴ法粒子径を有し、Ａｌ、Ｃａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量はいずれの元素も全て５ｐｐｍ以下であり、実質的にテトラメチルアンモニウムとシリカ以外の成分を含まないシリカゾルを得た。
【００７６】
実施例５
製造例２のシリカ含有量３８．５％の含水高純度シリカゲル５４０ｇを撹拌機付き１リットルガラス製反応容器に取り、純水３００ｇと市販水酸化β−ヒドロキシエチルトリメチルアンモニウム４８％水溶液２９ｌｇを加え、撹拌下に徐々に加熱して８０℃まで液温が上昇した後１６時間撹拌下にこの温度を保ちシリカゲルを溶解した。水分の蒸発により、回収したシリカ溶液は１１２５ｇであり、無色透明でシリカ濃度１８．５％、水酸化β−ヒドロキシエチルトリメチルアンモニウム濃度１２．５％であった。
【００７７】
回収したシリカ溶液１１２５ｇは純水５８０５ｇを混合しシリカ濃度３．０％に希釈した。この希釈シリカ溶液は、予め塩酸によってＨ型に再生した２０００ｍｌのカチオン交換樹脂（オルガノ（株）製「アンバーライトＩＲｌ２０Ｂ」）を充填したカラムを０．５時間かけて定速度で通過させ、７５００ｇのβ−ヒドロキシエチルトリメチルアンモニウムイオンを除去した活性珪酸液を得た。この活性珪酸液のｐＨは４．４であった。
【００７８】
実施例１で製造したシリカ濃度１５％のテトラメチルアンモニウムとシリカ以外の成分を含まない６００ｇのシリカゾルのうち１６０ｇを別の撹拌機付き容器に仕込み、純水１０００ｇを加えて希釈し、更に撹拌下１規定塩酸を滴下してｐＨを７とした。ここに塩基性塩化アルミニウム（Ａｌ₂ （ＯＨ）₅ Ｃｌ）の０．２５％水溶液１０ｇを滴下した。滴下によって透明液がわずかに濁り、シリカ粒子が凝集したことが観察された。続いて、２０％テトラメチルアンモニウム水溶液を滴下してｐＨを１０とし、撹拌下９５℃に加熱し、撹拌と温度を保ちながら７５００ｇの活性珪酸液と２２ｇの水酸化テトラメチルアンモニウム２０％水溶液を８時間かけて定速で同時に添加した。添加終了後、１時間撹拌と温度を保ち熱成を行った。
【００７９】
放冷後、この液はシリカコロイド特有の乳白半透明液であった。次いで、限外ろ過によりシリカ濃度３０％に濃縮し約７５０ｇのシリカゾルを得た。このゾルのコロイダルシリカ粒子は２６ｎｍのＢＥＴ法粒子径を有していた。また透過型電子顕微鏡写真によると、このシリカ粒子は粒子径が２０ｎｍから４０ｎｍまであり、形状も真球状ではないものが多くて不揃いであった。このシリカゾルはＣａ、Ｂ、Ｂａ、Ｃｏ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｐｂ、Ｓｒ、Ｔｉ、Ｚｎ、Ｚｒ、ＵおよびＴｈの含有量はいずれの元素も全て５ｐｐｍ以下であり、実質的にテトラメチルアンモニウムとシリカと微量のＡｌ以外の成分を含まないシリカゾルを得た。
【００８０】
【発明の効果】
以上説明した様に、本発明によれば、水ガラスという安価な原材料から、３００ｎｍ以下、特に数ｎｍ〜１００ｎｍの粒子径を有する高純度のシリカのゾルを製造することができる。そしてこのゾルは、数十重量％のシリカ濃度まで濃縮することができ、長期にわたり安定である。また、本発明の方法で得られたシリカゾルの液状媒体を、有機溶媒で置換することにより、オルガノゾルと呼ばれる有機溶媒分散のシリカゾルを得ることができる。
【００８１】
また、本発明の方法により得られたシリカ粒子は、Ａｌ、Ｆｅ、その他多価金属やアニオン等の不純成分を含まず、シリコンウェハー用研磨材、液体クロマトグラフィー担体用高純度シリカゲル等の原料、触媒用バインダー、特殊ゼオライトの原料、電子材料用塗料に添加されるマイクロフィラー、高分子フィルム用マイクロフィラー等に有用である。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a silica sol containing no impurities and made from an alkali silicate.Manufacturing methodAbout. In particular, the present invention is suitable for inexpensively producing a silica sol having a size of 3 to 300 nanometers (nm). The silica sol obtained by the production method of the present invention does not contain impurities such as Al, Fe and other polyvalent metals and free anions. Therefore, high purity silica gel, raw materials for high purity ceramics, binders for glass products such as cathode ray tubes, catalysts It is useful for abrasives such as binders for silicon, silicon abrasives and electronic material substrates.
[0002]
[Prior art]
Commercially available silica sol is produced from water glass as a raw material by a method such as neutralization with an acid or ion exchange. In order to produce a high-purity silica sol, a method is known in which an acid treatment step is added to this production step to dissolve the metal element and remove it by ion exchange or ultrafiltration (Japanese Patent Laid-Open No. 61-158810). JP-A-4-2606, JP-A-6-16414, etc.). Japanese Patent Laid-Open No. 7-291614 discloses that silica gel is produced by a reaction between an aqueous sodium silicate solution and 6N mineral acid, and then the separated silica gel is washed with 1N mineral acid three times to obtain a silica raw material. A method is proposed in which this is dissolved in quaternary ammonium hydroxide, and then silica particles are folded out by heating with an acid neutralization method, followed by evaporation of water and concentration to create a silica-dispersed slurry. Has been.
[0003]
Further, a high-purity silica sol obtained by thermal decomposition of silicon tetrachloride, in which a high-purity silica fine powder containing almost no impurities such as metals is dispersed in water is used for polishing. Further, high-purity silica sol produced by a method of hydrolyzing an alkyl silicate in an alcohol solution containing ammonia is also used for polishing.
[0004]
[Problems to be solved by the invention]
However, in the method described in JP-A-61-158810, JP-A-4-2606, JP-A-6-16414, etc., a silica sol is obtained by ion exchange using water glass as a raw material. Impurities such as anions cannot be completely removed.
[0005]
In addition, in the method of JP-A-7-291614, a large amount of high-concentration hydrochloric acid is used to remove the metal, but a large amount of acid waste water is generated before the step of washing out chloro ions from silica. It is hard to say that it is an industrially rational manufacturing method. In addition, silica particles are prepared by the sulfuric acid neutralization method, but this method can only produce small particles, and because they are agglomerated (becomes a cloudy solution), ultrafiltration cannot be used, and evaporative concentration This is an uneconomical process. In evaporative concentration, the concentration of quaternary ammonium and sulfuric acid is increased, and a nitrogen purge is required to prevent oxidative decomposition of quaternary ammonium.
[0006]
Silica fine powder powder obtained by the thermal decomposition method of silicon tetrachloride is expensive, and is agglomerated particles. Even when dispersed in water, a monodisperse sol cannot be obtained. There are many Ti and Ti.
Silica obtained from alkyl silicate can be most highly purified, but is most expensive due to raw material costs.
[0007]
The present invention has been made in view of such a conventional technique, and an object thereof is to provide a high-purity silica sol from an inexpensive raw material such as water glass.
[0011]
[Means for Solving the Problems]
  That is,The present invention is a first step in which high-purity silica gel containing all the following impurities in an amount of 5 ppm or less is dissolved in a quaternary ammonium hydroxide aqueous solution, the quaternary ammonium hydroxide is removed by ion exchange and activated. Content of the following impurities characterized by comprising a second step of creating a silicic acid solution, a third step of growing the silica to a particle size of 3 to 300 nm by heating the active silicic acid solution in the presence of an alkali catalyst. Is a method for producing a high purity silica sol in which all the elements are all 5 ppm or less.
    Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th.
[0012]
Further, the present invention provides a first step of dissolving silica gel in which all of the following impurities are all 5 ppm or less in a quaternary ammonium hydroxide aqueous solution, and the quaternary ammonium hydroxide is removed by ion exchange to be active. A second step of creating a silicic acid solution, and a third step of growing the silica to a particle diameter of 3 to 300 nm by adding Al or Ca in the presence of an alkali catalyst and heating the activated silicic acid solution. The content of the following impurities is a method for producing a high purity silica sol in which all the elements are all 5 ppm or less.
B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th.
[0013]
Silica gel used in the above production method is a method in which silica is produced by a reaction between an aqueous sodium silicate solution and a mineral acid. In this method, silica gel precipitates are produced in an acidic region having a chelating agent and hydrogen peroxide in an acid concentration of 1 N or more. And then separating and recovering the silica gel obtained by washing with a chelating agent and a mineral acid containing hydrogen peroxide, or a method of producing silica gel by a reaction between an aqueous sodium silicate solution and a mineral acid. The silica gel is preferably obtained by forming a silica gel precipitate in the existing acidic region and then washing the separated and recovered silica gel with a mineral acid containing hydrogen peroxide.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, silica gel obtained by wet reaction of alkali silicate and mineral acid is dissolved in a quaternary ammonium hydroxide aqueous solution, and then manufactured by an ion exchange method or a peptization method. Al, Ca, B, Ba, Co , Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th Impurities of high purity silica sol in which all elements are all 5 ppm or less. Furthermore, a high-purity silica sol in which the contents of U and Th are each lppb or less is provided.
[0015]
That is, as the silica gel used as a raw material in the present invention, it is preferable to use the high-purity silica disclosed in Japanese Patent Publication No. 4-81526 and Japanese Patent Publication No. 5-5766, which are prior applications of the present applicant. This silica gel is produced in the method of producing silica by the reaction of (1) an aqueous sodium silicate solution and a mineral acid, in which a silica precipitate is produced in an acidic region having an acid concentration of 1 N or more in the presence of a chelating agent and hydrogen peroxide, Next, silica gel obtained by washing the separated and recovered silica with a chelating agent and a mineral acid containing hydrogen peroxide, or (2) a method of producing silica by reacting an aqueous sodium silicate solution with a mineral acid, Is a silica gel selected by forming a silica gel precipitate in an acidic region in which is present, and then washing the separated and recovered silica gel with a mineral acid containing hydrogen peroxide. This silica gel contains Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th impurities. 5 ppm or less, further 1 ppm or less, and U and Th contents are each lppb or less.
[0016]
Further, the content of impurities in the present invention is a content concentration relative to the weight of silica in silica gel or silica sol.
[0017]
The high-purity silica sol of the present invention is obtained by dissolving silica gel produced by a wet reaction with an alkali silicate and a mineral acid in an aqueous solution of quaternary ammonium hydroxide, and then adjusting the particle size to 3 to 300 nm by an ion exchange method or a peptization method. Grown silica sol with Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th impurities. These elements are all 5 ppm or less, and the contents of U and Th are each 1 ppb or less.
[0018]
The high-purity silica sol of the present invention is a silica sol having a particle size grown to a silica particle diameter of 3 to 300 nm modified and modified by adding Al or Ca in the production process by the ion exchange method or the peptization method, Except for the impurities Al and Ca, the contents of B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th impurities are all elements. All are 5 ppm or less, and the contents of U and Th are each 1 ppb or less.
[0019]
The high purity silica sol production method of the present invention comprises Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th impurities. The first step of dissolving silica gel in which all the elements are all 5 ppm or less and the U and Th contents are each 1 ppb or less in quaternary ammonium hydroxide, quaternary ammonium hydroxide by ion exchange It is characterized by performing a second step of removing activated carbon to produce an active silicic acid solution and a third step of heating in the presence of an alkali catalyst to grow particles to a particle size of 3 to 300 nm.
[0020]
In addition, the particle diameter of the silica particle in this invention is a particle diameter by the nitrogen adsorption BET method measurement of a silica, and shows an average particle diameter. At this time, the density of silica is 2.2 g / cm.^ThreeCalculate as
[0021]
The silica gel used in the present invention is obtained by the reaction of sodium silicate and mineral acid, but the sodium silicate used in the reaction has a molar ratio of SiO.₂ / Na₂ A commercially available sodium silicate solution (water glass) with O of 1 to 4 can be used, and it may be diluted as appropriate.
[0022]
On the other hand, examples of the mineral acid to be reacted with the sodium silicate solution include hydrochloric acid, nitric acid, sulfuric acid and the like, and they may be used alone or as a mixture of two or more kinds, and are appropriately diluted for use. The acid concentration is preferably 1 N or more.
[0023]
Examples of chelating agents that coexist during the reaction include dicarboxylic acids such as oxalic acid, malonic acid, and succinic acid, polycarboxylic acids such as tricarballylic acid, oxycarboxylic acids such as citric acid and malic acid, nitrile triacetic acid, and ethylenediaminetetraacetic acid. Aminopolycarboxylic acids can be used.
[0024]
Even with the above chelating agent alone, the content of impurities can be reduced to 5 ppm or less for all elements, but in addition to this, the removal of impurities can be remarkably improved by the coexistence of hydrogen peroxide.
[0025]
The amount of the chelating agent and hydrogen peroxide added is 0.1 to 5% by weight, preferably 0.1 to 2% by weight, based on silica in the reaction system, and is added to mineral acid or sodium silicate, preferably sodium silicate.
[0026]
The reaction is carried out by adding sodium silicate to the stirring mineral acid, and the reaction temperature may be any temperature ranging from room temperature to 90 ° C. It is preferable to carry out stirring and aging for 1 to 5 hours after the precipitation of silica gel.
[0027]
Subsequently, the produced silica gel precipitate is separated by a conventional method, and the separated silica gel is acid-treated with a mineral acid. The types of mineral acids and chelating agents are the same as above, but hydrogen peroxide is essential. The acid concentration during the treatment is 0.1 to 3 N, and the addition amount of the chelating agent and hydrogen peroxide is 0.01 to 5% by weight, preferably 0.1 to 2% by weight, based on the silica in the reaction system.
[0028]
The acid treatment step is performed once or a plurality of times as necessary, and the treatment temperature can be arbitrarily selected. The silica gel from which impurities have been removed in this manner is recovered as high-purity silica gel by removing the acid treatment agent by a method such as filtration water washing. The obtained silica gel has any content of impurities Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th. All elements can be obtained at 5 ppm or less.
A silica sol can be produced using the silica gel obtained by the above method as a silica raw material.
[0029]
In the silica sol production method of the present invention, in the first step, silica gel is dissolved in a quaternary ammonium hydroxide aqueous solution. As the quaternary ammonium, for example, tetramethylammonium, tetrabutylammonium, β-hydroxyethyltrimethylammonium, tetraethanolammonium, methyltriethanolammonium, benzyltrimethylammonium and the like can be used alone or in combination. Quaternary ammonium hydroxide (R_Four NOH) to silica molar ratio (SiO₂ / R_Four NOH) is preferably 1 to 4, and less than 1 is meaninglessly uneconomical and exceeding 4 is difficult to dissolve. The silica concentration is preferably 10 to 30 wt%. If the concentration is high, the viscosity of the liquid increases, and if it exceeds 30 wt%, it is difficult to handle. Dissolution is quicker as the temperature is higher, but may be any temperature from room temperature to boiling point.
[0030]
The second process is a process for producing silica sol from a silica solution. There are two methods, the ion exchange method and the peptization method. The ion exchange method is simpler and requires no extra auxiliary materials to be introduced. No intrusion is preferable.
[0031]
In the ion exchange method, first, H or H with hydrochloric acid or sulfuric acid.⁺ Prepare a cast cation exchange resin column. The silica solution produced in the first step is diluted with pure water to a silica concentration of 2 to 7 wt% and passed through a cation exchange resin column to remove quaternary ammonium ions to obtain an “active silicic acid solution”. This active silicic acid solution is heated in the presence of an alkali catalyst to grow the particle diameter of silica to 3 to 300 nm.
[0032]
The silica concentration of the “active silicic acid solution” is preferably in the range of 2 to 4 wt%. If it is lower than this, an excessive burden will be imposed on heating and concentration in the post-process, and if it is higher than this, gelation of the liquid will occur quickly and handling properties will be lacking. Next, the activated silicic acid solution is heated by adding an alkali catalyst to polymerize silicic acid to grow particles.
[0033]
Such a particle growth step is usually performed also in a method for producing silica sol using water glass as a raw material. For example, the method described in US Pat. No. 3,580,015 specifies an active silicic acid solution and an alkaline aqueous solution in an aqueous medium. A method of simultaneous addition at an addition rate, a method of Japanese Patent Application Laid-Open No. 58-15022 is a method of adding an active silicic acid solution to an alkaline aqueous solution at a specific addition rate, and a method of Japanese Patent Application Laid-Open No. 63-123807 is A method of making an anionic silica sol by adding an active silicic acid solution in an alkaline aqueous solution in the presence of an aluminum compound, a method of US Pat. No. 2,680,721 is a method of making an aspherical silica sol by hydrothermal treatment at 160 to 300 ° C., In the method of JP-A-1-317115, an alkali is added to an active silicic acid solution to which calcium salt or the like is added, and then a hydrothermal treatment at 60 to 250 ° C. A method for producing an elongated silica sol, a method disclosed in JP-A-4-187512 is a method for producing an elongated silica sol by adding an active silicate solution to which an aluminum salt or the like is added to an alkali silicate, and JP-A-6-199515. The method of No. 1 has a method of making a stable silica sol by hydrothermal treatment at 80 to 250 ° C. after adding an aluminum salt or the like to a silica sol that has finished particle growth by a conventional method. The method is applicable.
[0034]
In the present invention, the alkali specifically used is ammonia, amine, quaternary ammonium hydroxide or the like, and the quaternary ammonium hydroxide solution of silica produced in the first step is also preferable.
[0035]
As described above, there are many methods for mixing active silica solution with an alkali catalyst and heating to polymerize silicic acid to cause particle growth, so it is not necessary to select the type and amount of the alkali catalyst depending on which method is applied. must not.
[0036]
Therefore, as a basic condition, it is a constituent of the present invention that an alkali catalyst is added and heated so that the pH is 7 or more to advance the polymerization of silicic acid. More preferably, the pH is 8 or more.
[0037]
When the activated silicic acid solution is made alkaline and heated, the polymerization reaction of silicic acid can proceed. Then, by the progress of the polymerization reaction of silicic acid, silica core particles are generated in the reaction medium, and when the active silicic acid solution is added while maintaining the alkalinity of the solution by a method such as addition of alkali, the particle growth causes 3 A silica sol having a uniform particle size of ˜300 nm, preferably 5˜100 nm, is produced.
[0038]
A method in which the entire amount of the alkali catalyst is put in the reaction medium in advance and the active silicic acid solution is added thereto may be used. The reverse is not possible.
[0039]
Commercially available silica sol, alumina sol, etc. are put in the reaction medium in advance as seed particles, and an active silicic acid solution and an alkali catalyst are simultaneously added thereto in an amount of 0.005 to 0.1 mol per mol of silica. Thus, a method of growing seed particles is also good.
[0040]
It is better to use the silica sol prepared in the present invention as a seed particle instead of a commercial product. It is also possible to make the growth particles non-spherical by adding a small amount of an aluminum compound or calcium compound to the reaction medium at the initial stage of particle growth.
[0041]
The modification by adding Al or Ca is a method in which the shape of the particles is made non-spherical, the charge of the particles is made positive or negative, or the strength thereof is adjusted. The grain growth method of the method may be carried out in consideration of the impurity concentration.
[0042]
This polymerization particle growth reaction can be carried out under reduced pressure, normal pressure, or pressurized pressure, but is carried out with sufficient stirring at a temperature of 60 ° C. or higher, preferably 80 ° C. to the boiling point of the reaction mixture. Is good.
[0043]
After completion of the addition of the active silicic acid solution, it is preferable to carry out heat aging at 70 ° C. or more, preferably 80 to 200 ° C. for 30 minutes or more, preferably about 1 to 6 hours. During or after the heat aging, an aluminum compound or the like can be added and deposited on the surface of the silica particles to change the properties of the particles.
[0044]
The silica sol obtained by the method of the present invention can be concentrated by an ordinary method such as an evaporation method or an ultrafiltration method. This concentration results in a stable silica sol up to about 40%. Furthermore, an alkali catalyst can be removed by an ion exchange method, and a silica sol substantially free of components other than silica can be obtained.
[0045]
The silica sol from which the alkali catalyst has been removed by the ion exchange method is a silica sol dispersed in the organic solvent by collecting and washing out the water by performing the steps of the evaporation method and ultrafiltration method while adding the organic solvent, that is, the organo sol It can be.
[0046]
Next, a process for producing a silica sol from the silica solution in the second process by the peptization method will be described.
[0047]
In the peptization method, the silica solution produced in the first step is pure and diluted to a silica concentration of 4 to 10 wt%, and then the molar ratio of quaternary ammonium hydroxide to silica (SiO 2).₂/ R_FourNOH) is prepared in the range of 10 to 40 and heated to a temperature of 80 ° C. to 250 ° C. to grow the particles. As a method for adjusting the molar ratio, there are a method of adding silica gel as a raw material to a silica solution, a method of adding the above active silicic acid to a silica solution, and a method of adding silica gel produced by an ion exchange method. In addition, a method of adding a silica source prepared by a vapor phase method or a silica source prepared from ethyl silicate is sufficiently possible in consideration of impurities mixed in from them. The manufacturing method of the 3rd process after this can be performed by the method similar to ion exchange.
[0048]
【Example】
The present invention will be specifically described below.
[0049]
(Production Example 1 of high-purity silica gel)
Nitric acid aqueous solution (HNO_Three = 19.3 wt%) 3285 g was taken and heated to 70 ° C.
Separately, sodium silicate JIS3 (Na₂ O = 9.2 wt%, SiO₂ = 28.5 wt%, SiO₂ / Na₂ 2100 g of O molar ratio = 3.20) was placed in a container and stirred, and 0.6 g of EDTA (ethylenediaminetetraacetic acid) dispersed in a small amount of water was added and dissolved. The mixture was further stirred at 70 ° C. for 2 hours.
[0050]
This sodium silicate aqueous solution containing EDTA was added to the aqueous nitric acid solution over about 30 minutes to form a silica gel precipitate. During this time, the temperature of the reaction vessel was maintained at 70 to 80 ° C. After the addition, the reaction slurry was aged by stirring at 80 ° C. for 2 hours.
A silica gel precipitate was separated from the reaction-finished slurry by filtration, repulped into water, washed, and then separated again by filtration.
[0051]
The separated and collected silica gel is placed in an acid treatment tank equipped with a stirrer, and water and nitric acid are added thereto to adjust the total amount of the slurry to 5 liters and the concentration of nitric acid in the slurry to 1 N. Further, 17 g of 35% hydrogen peroxide solution The mixture was stirred and heated at 90 ° C. for 3 hours for acid treatment, and then the silica gel was separated from the slurry by filtration, and the repulp washing and solid-liquid separation with water was repeated several times. The electrical conductivity of the slurry was 50 μS or less. At that time, the silica gel was recovered by filtration.
[0052]
This silica gel had a moisture content of 63.3% and was used for the following experiments without drying. Moreover, the amount of impurities in silica is shown in Table 1.
[0053]
(Production Example 2 of High-Purity Silica Gel)
Nitric acid aqueous solution (HNO_Three = 19.3 wt%) 4000 g was added, and 6 g of oxalic acid (dihydrate, commercially available product) and 17 g of 35% hydrogen peroxide solution (commercially available product) were added and dissolved therein. Sodium silicate JIS3 (Na₂ O = 9.2 wt%, SiO₂ = 28.5 wt%, SiO₂ / Na₂ (O molar ratio = 3.20) 2100 g was added over about 30 minutes to form a silica gel precipitate. During this period, the temperature of the reaction vessel was maintained at 70 to 80 ° C. After the addition, the reaction slurry was aged by stirring at 80 ° C. for 2 hours.
[0054]
The silica gel precipitate was repeatedly filtered and washed from the reaction-terminated slurry, and separated and recovered.
[0055]
The separated and collected silica gel is placed in an acid treatment tank equipped with a stirrer, and water and nitric acid are added thereto to adjust the total amount of the slurry to 5 liters and the concentration of nitric acid in the slurry to 1 N. Further, oxalic acid 6 g, 35% excess After adding 17 g of hydrogen oxide water and stirring, heating at 90 ° C. for 3 hours for acid treatment, the silica gel is separated from the slurry by filtration, and repulp washing and solid-liquid separation with water is repeated several times. The silica gel was recovered by filtration at a time when became less than 50 μS.
[0056]
This silica gel had a moisture content of 61.5% and was used in the following examples without drying. Further, Table 1 shows the amount of impurities in silica.
[0057]
[Table 1]

[0058]
(Impurity of commercially available quaternary ammonium hydroxide)
Commercially available quaternary ammonium hydroxides used in the following examples had 0.02 ppm or less of all the components listed in Table 1.
[0059]
Example 1
327 g of water-containing high-purity silica gel having a silica content of 36.7% in Production Example 1 was placed in a 1-liter glass reaction vessel equipped with a stirrer, and 50 g of pure water and 368 g of a commercially available tetramethylammonium hydroxide 20% aqueous solution were added. After gradually heating and the liquid temperature rose to 80 ° C., this temperature was maintained with stirring for 16 hours to dissolve the silica gel. The recovered silica solution was 678 g by evaporation of water, was colorless and transparent and had a silica concentration of 17.7% and a tetramethylammonium hydroxide concentration of 10.7%.
[0060]
Of the 678 g of recovered silica solution, 500 g was collected, mixed with 2450 g of pure water, and diluted to a silica concentration of 3.0%. This diluted silica solution was passed through a column packed with 500 ml of a cation exchange resin (“Amberlite IR120B” manufactured by Organo Co., Ltd.) previously regenerated into H-type with hydrochloric acid at a constant rate over 0.5 hours, and 3500 g An active silicic acid solution from which tetramethylammonium ions were removed was obtained. The pH of this active silicic acid solution was 4.4.
[0061]
  167 g of pure water is charged into another container with a stirrer,The remainder of the recovered silica solutionThe mixture was diluted with 33 g, heated to 95 ° C. with stirring, and the active silicic acid solution was added at a constant rate over 8 hours while maintaining stirring and temperature. AdditionFinishThereafter, the mixture was aged while maintaining stirring and temperature for 1 hour.
[0062]
  After standing to cool, this liquid was a translucent liquid with a bluish color characteristic of silica colloid. Subsequently, it was concentrated to a silica concentration of 15% by ultrafiltration to obtain about 600 g of silica sol. The sol had a tetramethylammonium hydroxide concentration of 0.11%, and the colloidal silica particles had a BET particle diameter of 12 nm. The content of Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th in this silica sol is 5 ppm for all elements. Is substantially less than tetramethylammonium and silica.Not includedA silica sol was obtained.
[0063]
The particle diameter of the silica particles is a value measured by the nitrogen adsorption BET method. In this measurement method, 10 g of a sample is taken, pH is adjusted to 5 by adding dilute hydrochloric acid, solidified by heating, and dried at 150 ° C. to obtain a powder sample. , Micromeritics Flow Sorb II 2300 (manufactured by Shimadzu Corporation).
[0064]
Example 2
540 g of water-containing high-purity silica gel having a silica content of 38.5% in Production Example 2 was placed in a 1 liter glass reaction vessel equipped with a stirrer, and 300 g of pure water and 29 lg of a commercially available 48% aqueous solution of β-hydroxyethyltrimethylammonium hydroxide were added, After gradually heating with stirring and the liquid temperature rose to 80 ° C., this temperature was maintained with stirring for 16 hours to dissolve the silica gel. The recovered silica solution was 1125 g due to evaporation of water, was colorless and transparent, had a silica concentration of 18.5%, and a β-hydroxyethyltrimethylammonium hydroxide concentration of 12.5%.
[0065]
The recovered silica solution was 476 g out of 1125 g, mixed with 2475 g of pure water and diluted to a silica concentration of 3.0%. This diluted silica solution was passed through a column packed with 500 ml of a cation exchange resin (“Amberlite IR120B” manufactured by Organo Co., Ltd.) previously regenerated into H-type with hydrochloric acid at a constant rate over 0.5 hours, and 3500 g An active silicic acid solution from which β-hydroxyethyltrimethylammonium ions were removed was obtained. The pH of this active silicic acid solution was 4.4.
[0066]
  169 g of pure water was charged into another container with a stirrer,The remainder of the recovered silica solution3 lg was added for dilution, and the mixture was heated to 95 ° C. with stirring, and the active silicic acid solution was added at a constant rate over 8 hours while maintaining stirring and temperature. After completion of the addition, the mixture was aged while maintaining stirring and temperature for 1 hour.
[0067]
After standing to cool, this liquid was a translucent liquid with a bluish color characteristic of silica colloid. Subsequently, the silica was concentrated to 15% by ultrafiltration to obtain about 600 g of silica sol. The sol colloidal silica particles had a BET particle size of 12 nm. The content of Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th in this silica sol is 1 ppm for all elements. A silica sol which is substantially the same as the following and does not contain any components other than β-hydroxyethyltrimethylammonium and silica was obtained.
[0068]
Example 3
540 g of water-containing high-purity silica gel having a silica content of 38.5% in Production Example 2 was placed in a 1 liter glass reaction vessel equipped with a stirrer, and 300 g of pure water and 29 lg of a commercially available 48% aqueous solution of β-hydroxyethyltrimethylammonium hydroxide were added, After gradually heating with stirring and the liquid temperature rose to 80 ° C., this temperature was maintained with stirring for 16 hours to dissolve the silica gel. The recovered silica solution was 1125 g due to evaporation of water, was colorless and transparent, had a silica concentration of 18.5%, and a β-hydroxyethyltrimethylammonium hydroxide concentration of 12.5%.
[0069]
The recovered silica solution was 476 g out of 1125 g, mixed with 2475 g of pure water and diluted to a silica concentration of 3.0%. This diluted silica solution was passed through a column packed with 500 ml of a cation exchange resin (“Amberlite IR120B” manufactured by Organo Co., Ltd.) previously regenerated into H-type with hydrochloric acid at a constant rate over 0.5 hours, and 3500 g An active silicic acid solution from which β-hydroxyethyltrimethylammonium ions were removed was obtained. The pH of this active silicic acid solution was 4.4.
[0070]
In a separate vessel equipped with a stirrer, 167 g of pure water was charged and diluted by adding 33 g of a silica solution having a silica concentration of 17.7% and a tetramethylammonium hydroxide concentration of 0.7% prepared in Example 1 and stirring at 95 ° C. The active silicic acid solution was added at a constant rate over 8 hours while maintaining stirring and temperature. After completion of the addition, the mixture was heated for 1 hour with stirring and temperature.
[0071]
After standing to cool, this liquid was a translucent liquid with a bluish color characteristic of silica colloid. Subsequently, it was concentrated to a silica concentration of 15% by ultrafiltration to obtain about 600 g of silica sol. The sol colloidal silica particles had a BET particle size of 12 nm. 300 g of this silica sol was charged into an autoclave equipped with a stirrer, heated to 180 ° C. with stirring for 2 hours, kept at 180 ° C. for 3 hours, and then allowed to cool. The colloidal silica particles of this sol have a BBT method particle diameter of 17 nm, Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr. The contents of U and Th were all 5 ppm or less for all elements, and a silica sol containing substantially no components other than tetramethylammonium and silica was obtained.
[0072]
Example 4
Take 540 g of water-containing high-purity silica gel with a silica content of 38.5% in Production Example 2 in a 1-liter glass reaction vessel equipped with a stirrer, add 722 g of a commercially available 50% aqueous solution of methyltriethanolammonium hydroxide, and gradually heat with stirring. Then, after the liquid temperature rose to 80 ° C., this temperature was kept under stirring for 16 hours to dissolve the silica gel. The recovered silica solution was 1125 g by evaporation of water, was colorless and transparent, had a silica concentration of 18.5%, and a methyltriethanolammonium hydroxide concentration of 32.1%.
[0073]
1805 g of the recovered silica solution was mixed with 5805 g of pure water and diluted to a silica concentration of 3.0%. This diluted silica solution was passed through a column packed with 2000 ml of a cation exchange resin (“Amberlite IR120B” manufactured by Organo Co., Ltd.) previously regenerated into H-type with hydrochloric acid at a constant rate over 0.5 hours. An active silicic acid solution from which methyltriethanolammonium ions were removed was obtained. The pH of this active silicic acid solution was 4.4.
[0074]
160 g of 600 g silica sol that does not combine components other than silica with tetramethylammonium having a silica concentration of 15% produced in Example 1 was charged into another vessel equipped with a stirrer, diluted with 1000 g of pure water, 3 g of 20% aqueous solution of tetramethylammonium oxide was added to adjust the pH to 10, heated to 95 ° C. with stirring, and 7500 g of active silicic acid solution and 22 g of 20% aqueous solution of tetramethylammonium hydroxide were added over 8 hours while maintaining stirring and temperature. At a constant speed. After completion of the addition, the mixture was heated for 1 hour with stirring and temperature.
[0075]
After cooling, this solution was a milky white translucent solution unique to silica colloids. Subsequently, the silica concentration was 30% by ultrafiltration to obtain about 750 g of silica sol. The sol colloidal silica particles had a BET particle size of 24 nm. 300 g of this silica sol was charged into an autoclave equipped with a stirrer, heated to 180 ° C. with stirring for 2 hours, kept at 180 ° C. for 3 hours, and then allowed to cool. The colloidal silica particles of this sol have a BET particle size of 32 nm and are Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr. The contents of U and Th were all 5 ppm or less for all elements, and a silica sol containing substantially no components other than tetramethylammonium and silica was obtained.
[0076]
Example 5
540 g of water-containing high-purity silica gel having a silica content of 38.5% in Production Example 2 was placed in a 1 liter glass reaction vessel equipped with a stirrer, and 300 g of pure water and 29 lg of a commercially available 48% aqueous solution of β-hydroxyethyltrimethylammonium hydroxide were added, After gradually heating with stirring and the liquid temperature rose to 80 ° C., this temperature was kept under stirring for 16 hours to dissolve the silica gel. The recovered silica solution was 1125 g due to evaporation of water, was colorless and transparent, had a silica concentration of 18.5%, and a β-hydroxyethyltrimethylammonium hydroxide concentration of 12.5%.
[0077]
1125 g of the recovered silica solution was mixed with 5805 g of pure water and diluted to a silica concentration of 3.0%. This diluted silica solution was passed through a column packed with 2000 ml of a cation exchange resin (“Amberlite IR120B” manufactured by Organo Co., Ltd.) previously regenerated into H-type with hydrochloric acid at a constant rate over 0.5 hours. An active silicic acid solution from which β-hydroxyethyltrimethylammonium ions were removed was obtained. The pH of this active silicic acid solution was 4.4.
[0078]
160 g of 600 g silica sol containing no components other than tetramethylammonium having a silica concentration of 15% and silica produced in Example 1 was charged into another vessel with a stirrer, diluted with 1000 g of pure water, and further stirred. 1N hydrochloric acid was added dropwise to adjust the pH to 7. Basic aluminum chloride (Al₂ (OH)_Five 10 g of a 0.25% aqueous solution of Cl) was added dropwise. It was observed that the clear liquid became slightly turbid by dripping and the silica particles were aggregated. Subsequently, 20% tetramethylammonium aqueous solution was added dropwise to adjust the pH to 10, and the mixture was heated to 95 ° C. with stirring. While maintaining the stirring and temperature, 7500 g of active silicic acid solution and 22 g of tetramethylammonium hydroxide 20% aqueous solution were added. It was added simultaneously at a constant speed over time. After completion of the addition, the mixture was heated for 1 hour with stirring and temperature.
[0079]
After cooling, this solution was a milky white translucent solution unique to silica colloids. Subsequently, the silica concentration was 30% by ultrafiltration to obtain about 750 g of silica sol. The sol colloidal silica particles had a BET particle size of 26 nm. Further, according to a transmission electron micrograph, the silica particles had a particle size of 20 nm to 40 nm, and many of them were not spherical, and were irregular. This silica sol contains Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U, and Th. There was obtained a silica sol substantially free of components other than tetramethylammonium, silica, and a trace amount of Al.
[0080]
【The invention's effect】
As described above, according to the present invention, a high-purity silica sol having a particle size of 300 nm or less, particularly several nm to 100 nm, can be produced from an inexpensive raw material such as water glass. This sol can be concentrated to a silica concentration of several tens of weight percent and is stable over a long period of time. Further, by replacing the liquid medium of the silica sol obtained by the method of the present invention with an organic solvent, an organic solvent-dispersed silica sol called an organosol can be obtained.
[0081]
Further, the silica particles obtained by the method of the present invention do not contain impurities such as Al, Fe, other polyvalent metals and anions, raw materials such as abrasives for silicon wafers, high-purity silica gel for liquid chromatography carriers, It is useful for binders for catalysts, raw materials for special zeolites, microfillers added to paints for electronic materials, microfillers for polymer films, and the like.

Claims

The first step of dissolving high-purity silica gel containing 5 ppm or less of all of the following impurities in a quaternary ammonium hydroxide solution, removing the quaternary ammonium hydroxide by ion exchange to create an active silicic acid solution And a second step of heating the activated silicic acid solution in the presence of an alkali catalyst to grow silica to a particle diameter of 3 to 300 nm. Is a method for producing a high-purity silica sol that is 5 ppm or less.
Al, Ca, B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th.

The first step of dissolving silica gel in which all of the following impurities are all 5 ppm or less in a quaternary ammonium hydroxide aqueous solution, removing the quaternary ammonium hydroxide by ion exchange to produce an active silicic acid solution 2 steps, containing the following impurities characterized in that the activated silicic acid solution has a third step of adding Al or Ca in the presence of an alkali catalyst and heating to grow silica to a particle size of 3 to 300 nm. A method for producing a high-purity silica sol in which the amount of any element is 5 ppm or less.
B, Ba, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr, Ti, Zn, Zr, U and Th.

Silica gel is a method in which silica is produced by a reaction between an aqueous sodium silicate solution and a mineral acid. In this method, a silica gel precipitate is produced in an acidic region having an acid concentration of 1 N or more in the presence of a chelating agent and hydrogen peroxide, and then separated and recovered. Silica gel obtained by washing silica gel with a mineral acid containing a chelating agent and hydrogen peroxide, or a method of producing silica gel by reacting an aqueous sodium silicate solution with a mineral acid, in an acidic region where the chelating agent is present The method for producing a high-purity silica sol according to claim 1 or 2 , which is a silica gel obtained by forming a silica gel precipitate and then washing the separated and recovered silica gel with a mineral acid containing hydrogen peroxide.