JP3922902B2 - Cationic resin-modified silica dispersion and production method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、乾式シリカを使用したインクジェット用記録紙の塗工液、新聞紙の内填剤、研磨剤、金属表面処理剤の調製に有用な新規のカチオン性樹脂変性シリカ分散液に関する。
【０００２】
【従来の技術】
インクジェット用記録紙の塗工液には、インク吸収層を形成するために微粒子のシリカやアルミナ等の無機微粉体が使用されている。上記微粒子のうち、特にシリカ、とりわけ乾式シリカは、分散性に優れており、好適に使用されている。
【０００３】
一方、インクジェット用のインクとしては、一般に、アニオン性の化合物が使われることが多く、上記インク吸収層はカチオン性を有している方が、インクジェット用記録紙の画像濃度及び耐水性向上のために有利である。
【０００４】
ところが、インク吸収層を形成する無機粉体として乾式シリカを用いた場合、粒子がアニオン性を呈するため、画像濃度や耐水性に問題があった。そのため、改善策として乾式シリカに第４級アンモニウム塩基等のカチオン性基を含むカチオン性樹脂を配合したカチオン性樹脂変性シリカ分散液が提案されており、例えば、特開平１１−３２１０７９号公報には、乾式シリカ分散液を平均分子量１０万以下のカチオン性樹脂水溶液に対して添加して混合する工程を含む、混合方法を特定したカチオン性樹脂変性シリカ分散液及びその製造方法が開示されている。
【０００５】
また、特開２００１−１９４２１号公報には、ポリジアリルアミン誘導体の構成単位を有し、且つ平均分子量が１０万以下であるカチオン性樹脂水溶液に乾式シリカ微粒子を２０℃以下で添加、混合した工程を含む混合方法を特定したカチオン性樹脂変性シリカ分散液及びその製造方法が開示されている。
【０００６】
また、金属表面処理剤としては、金属の耐食性や塗料の密着性を向上させるために、シリカ分散液にカチオン性樹脂を配合した処理剤が提案されており、例えば、特開昭５６−２４４７０号公報には、カチオン性樹脂水溶液に水分散性コロイダルシリカを攪拌下に加える方法が開示されている。
【０００７】
しかし、従来の技術により得られた前記のカチオン性樹脂変性シリカ分散液中のシリカ濃度は、いずれも２５重量％以下である。
【０００８】
【発明が解決しようとする課題】
カチオン性樹脂変性シリカ分散液は、前述したようにインクジェット用紙の塗工液等に使用されるが、該カチオン性樹脂変性シリカ分散液中のシリカ濃度が高いほど、当然塗工液中のシリカ濃度も高くできる。
【０００９】
塗工液中のシリカ濃度は、高い方が塗工工程において一回の塗工で十分な厚みの塗工層が得られたり、塗工後乾燥する際のエネルギー効率が良くなるので、該カチオン性樹脂変性シリカ分散液中のシリカ濃度は高ければ高いほど好ましい。
【００１０】
また、物流コストの面からも該カチオン性樹脂変性シリカ分散液中のシリカ濃度は高い方が非常に好ましい。
【００１１】
しかしながら、前記したように従来の技術において、カチオン性樹脂水溶液とシリカを混合及び分散処理して得られたカチオン性樹脂変性シリカ分散液中のシリカ濃度はいずれも２５重量％以下であった。また、該分散液中のシリカ濃度が１８重量％を越えたあたりから、シリカ濃度が１％でも高くなると、該分散液の粘度が急激に上昇し、場合によっては、再分散が不可能なほどゲル化する問題もあり、シリカ濃度が２５重量％以上でありながら、安定なカチオン性樹脂変性シリカ分散液を得ることが困難であった。
【００１２】
したがって、シリカ濃度が高く、且つ分散液全体がゲル化せずに安定性に優れているカチオン性樹脂変性シリカ分散液が望まれる。
【００１３】
【課題を解決するための手段】
本発明者らは、上記問題を解決すべく鋭意研究を重ねた結果、平均分子量６，０００以下であり、且つ環状アンモニウム塩型のカチオン性樹脂水溶液と乾式シリカを極性溶媒中で混合及び分散することにより、分散液中のシリカ濃度が２５重量％以上であっても、極めて安定なカチオン性樹脂変性シリカ分散液が得られることを見出し、本発明を完成するに至った。
【００１４】
即ち、本発明は、極性溶媒中に乾式シリカ及びカチオン性樹脂を分散せしめた分散液であって、該分散液中のシリカ濃度が２５重量％以上であり、且つ該カチオン性樹脂が平均分子量６，０００以下であり、環状アンモニウム塩型のカチオン性樹脂であることを特徴とするカチオン性樹脂変性シリカ分散液である。
【００１５】
【発明の実施の形態】
本発明に用いられる乾式シリカは、四塩化珪素などのシラン系ガスを酸水素炎中で燃焼させて得られる、「ヒュームドシリカ」とも称されているものが何ら制限なく使用される。
【００１６】
一般に、乾式シリカは、ＢＥＴ法による比表面積が３０〜５００ｍ２／ｇの範囲のものが入手可能であり、これらの乾式シリカは好適に使用できる。特に、比表面積が２００〜５００ｍ２／ｇの乾式シリカを用いたカチオン性樹脂変性シリカ分散液は、分散液の透明性が高くなるので好ましい。例えば、光沢性の高いインクジェット用記録紙の塗工液の原料として用いた場合、分散液の透明性が低くなると、塗工層の光の透過が妨げられ、塗工層が不透明となり、光沢が不足するといった問題が発生するので好ましくない。
【００１７】
本発明において、カチオン性樹脂変性シリカ分散液中のシリカの平均凝集粒子径は、１０〜１０００ｎｍの範囲、好ましくは５０ｎｍ〜３００ｎｍの範囲が好ましい。
【００１８】
平均凝集粒子径が１０ｎｍよりも小さい場合は、カチオン性樹脂変性シリカ分散液の粘度が高くなり、例えば、インクジェット記録紙用塗工液とした場合は、扱い難いことがある。平均凝集粒子径が１０００ｎｍよりも大きい場合は、カチオン性樹脂変性シリカ分散液中で乾式シリカが沈降して相分離し易くなる可能性がある。
【００１９】
本発明のカチオン性樹脂変性シリカ分散液において、シリカ濃度が１．５重量％となるように希釈した後の光散乱指数（以下、単にｎ値とも云う）が２．０以上に調整されたものは、乾式シリカの分散性が特に優れ、かかるカチオン性樹脂変性シリカ分散液を用いることによって、透明性の高い塗工液が製造することができるため好ましい。
【００２０】
上記したｎ値は、分散液中のシリカの分散状態を表す指標であり、分散性が向上するにつれてこの値は大きくなる。
【００２１】
なお、ｎ値は、Ｊｏｕｒｎａｌ ｏｆ Ｃｅｒａｍｉｃ Ｓｏｃｉｅｔｙ ｏｆ Ｊａｐａｎ，１０１〔６〕，７０７−７１２（１９９３）に記載の方法に準じて測定した値である。
【００２２】
即ち、市販の分光光度計を用いて、光の波長（λ）が４６０ｎｍ〜７００ｎｍの範囲の分散液のスペクトルを測定することにより、吸光度（τ）を求め、ｌｏｇ（λ）に対してｌｏｇ（τ）をプロットし、下記式（１）を用いて直線の傾き（−ｎ）を最小二乗法で求める。
【００２３】
τ＝αλ−ｎ （１）
（ここで、τは吸光度、αは定数、λは光の波長、そしてｎは光散乱指数を示す。）
本発明に用いられるカチオン性樹脂は、平均分子量が６，０００以下の環状アンモニウム塩型のカチオン性樹脂である。カチオン性樹脂の平均分子量は５００〜５，５００の範囲であることが好ましい。
【００２４】
本発明に用いられる環状アンモニウム塩型のカチオン性樹脂は、ジアリルアンモニウム塩及びその誘導体を重合して得られるカチオン性樹脂であり、具体例としては、平均分子量が６，０００以下である下記の式（２）又は式（３）で示される繰り返し単位を有するジアリルアンモニウム塩及びその誘導体の重合体、平均分子量が６，０００以下である式（２）又は式（３）で示される繰り返し単位１０〜９０モル％とジアリルアンモニウム塩及びその誘導体と共重合可能なモノマーに基づく繰り返し単位９０〜１０モル％とを有する共重合体を挙げることができる。
【００２５】
【化１】
式（２）、（３）において、Ｒ１及びＲ２は、水素原子又はメチル基を表わす。
【００２７】
ジアリルアンモニウム塩及びその誘導体と共重合可能なモノマーに基づく繰り返し単位としては、好ましくは、アクリルアミド、モノアリルアミン塩酸塩に基づく繰り返し単位が挙げられる。
【００２８】
本発明において特に好適なカチオン性樹脂は、平均分子量５００〜５，５００である、上記（２）又は式（３）で示される繰り返し単位を有するジアリルアンモニウム塩及びその誘導体の重合体、式（２）又は式（３）で示される繰り返し単位１０〜９０モル％とアクリルアミド、モノアリルアミン塩酸塩に基づく繰り返し９０〜１０モル％とを有する共重合体から選ばれるカチオン性樹脂である。
【００２９】
平均分子量が６，０００以上の環状アンモニウム塩型のカチオン性樹脂を用いて、分散液中のシリカ濃度が２５重量％以上のカチオン性樹脂変性シリカ分散液を製造すると、シリカ粒子が凝集し、シリカ分散液全体が凝集する問題がある。また、環状アンモニウム塩型のカチオン性樹脂でない場合、例えば、メタクリル酸エステルメチルクロライド重合物やアリルアミン塩酸塩重合物、アリルアミン重合物等の１〜４級アンモニウム塩型カチオン性樹脂を用いた場合、平均分子量が６，０００以下であっても、分散液中のシリカ濃度が２５重量％以上のカチオン性樹脂変性シリカ分散液を製造しようとすると、製造途中にシリカ分散液全体が凝集する問題がある。
【００３０】
本発明において、カチオン性樹脂の使用量は、シリカ１００重量部に対して、１〜５０重量部、特に１〜１５重量部が好ましい。カチオン性樹脂変性シリカ分散液中のカチオン性樹脂の量が、乾式シリカ１００重量部に対して１重量部より少なくなるように調整した場合、乾式シリカ粒子の表面電荷のバランスが不均一となり、該シリカ粒子が強固な凝集を起こし易くなる傾向がある。また、カチオン性樹脂の量がシリカ１００重量部に対して５０重量部より多くなるように調整した場合、粘度が高くなり、分散処理が困難になる場合がある。
【００３１】
また、カチオン性樹脂変性シリカ分散液の粘度が高くなると、以降に続く製造工程においてハンドリング性が低下するので好ましくない。カチオン性樹脂の添加量に対するカチオン性樹脂変性シリカ分散液の安定性は、添加するカチオン性樹脂の種類により異なるため、予め実験により、該分散液の粘度が一番低くなる最適な添加量を前記添加量より選択することが好ましい。
【００３２】
本発明において用いられる極性溶媒は、乾式シリカ及びカチオン性樹脂が分散し易い極性溶媒であれば特に制限はない。かかる極性溶媒としては、水が最も好ましい。勿論、水以外にもメタノール、エタノール、イソプロピルアルコール等のアルコール類、エーテル類、ケトン類などの極性溶媒が使用でき、また、水と上記極性との混合溶媒も好適に使用できる。
【００３３】
尚、シリカ粒子の保存安定性や分散性を向上させるために、本発明の効果を損なわない範囲で、界面活性剤や防黴剤等を少量添加しても良い。
【００３４】
本発明において、極性溶媒中に乾式シリカとカチオン性樹脂を混合又は分散してカチオン性樹脂変性シリカ分散液を製造する方法は特に制限されないが、極性溶媒、乾式シリカ粒子及びカチオン性樹脂を予め混合して、極性溶媒中に乾式シリカとカチオン性樹脂を含有している予備混合液を調製した後に、必要に応じて予備混合液中のシリカ粒子を好適な範囲の平均凝集粒子径まで微分散するための高度な分散手段を施す方法が好適に採用される。
【００３５】
上記の極性溶媒、乾式シリカ粒子及びカチオン性樹脂を予め混合する方法は、特に制限されないが、極性溶媒中にカチオン性樹脂を混合した溶液に、乾式シリカ粒子を直接混合する方法、極性溶媒中に乾式シリカ粒子を分散した後に、カチオン性樹脂を混合する方法、乾式シリカ粒子及びカチオン性樹脂をそれぞれ極性溶媒に混合した液を混合する方法などが挙げられる。
【００３６】
上記の混合に用いる混合機は特に制限されないが、プロペラ羽根、タービン羽根、パドル翼等を有する一般攪拌機、ディスパーミキサー等の高速回転遠心放射型攪拌機、ホモジナイザー、ホモミキサー、ウルトラミキサー等の高速回転せん断型攪拌機、コロイドミル、プラネタリーミキサーなどの乳化機が挙げられる。
【００３７】
上記の混合機の中でも強力なせん断力を有する混合機が好適である。具体的には、高速回転せん断型攪拌機や、プロペラ羽根及びパドル翼に更に高速せん断型攪拌機を組み合せた複合型分散機、プラネタリーミキサーと高速回転遠心放射型攪拌機又は高速回転せん断型攪拌機を組み合わせた複合型分散機が挙げられる。
【００３８】
極性溶媒、乾式シリカ粒子及びカチオン性樹脂を予め混合するときの温度（以下、単に予備混合温度という。）は、２０℃から４０℃の温度範囲で制御することが好ましい。
【００３９】
予備混合温度は、高いほど予備混合液の粘度が低くなるが、４０℃を超えると予備混合液内のシリカ粒子が凝集し易くなり、予備混合液の粘度が急上昇して予備混合液がゲル化する傾向にある。また、予備混合温度が２０℃未満の場合も、予備混合液の粘度が上昇する傾向にある。
【００４０】
更に本発明においては、該予備混合液に更に高度な分散処理を施してカチオン性樹脂変性シリカ分散液を得ることが好ましいが、予備混合液の粘度が高いほど、高度な分散処理をして得られたカチオン性樹脂変性シリカ分散液の粘度も高くなる傾向にある。カチオン性樹脂変性シリカ分散液粘度が高くなると、以降に続く製造工程においてハンドリング性が低下するので好ましくない。
【００４１】
予備混合温度を２０℃から４０℃の温度範囲に制御する方式は特に制限されないが、２０℃から４０℃の温度範囲において任意の一定温度となるように制御することが好ましい。
【００４２】
本発明において、上記方法で得られた予備混合液は、用途によっては予備混合液をそのままカチオン性樹脂変性シリカ分散液として用いることもできるが、予備混合に次いで、高度な分散処理を施すことにより、極めて安定性に優れ、これを使用して塗工液を調製するときにも安定性に優れたカチオン性樹脂変性シリカ分散液が得られる。
【００４３】
本発明において、上記の高度な分散処理方法は特に制限されないが、ビーズミル、サンドミル、超音波ホモジナイザー、高圧ホモジナイザー等を用いた分散処理が挙げられる。中でも高圧ホモジナイザーを用いた分散処理が好ましい。
【００４４】
高圧ホモジナイザーの代表例を具体的に例示すると、ナノマイザー製の商品名；ナノマイザー、マイクロフルイディクス製の商品名；マイクロフルイダイザー、及びスギノマシン製のアルティマイザーなどを挙げることができる。上記の高圧ホモジナイザーを用いて、極性溶媒とシリカとカチオン性樹脂とを混合した混合溶液を、処理圧力３００ｋｇｆ／ｃｍ２以上で対向衝突させるか、或いはオリフィスの入口側と出口側の差圧が３００ｋｇｆ／ｃｍ２以上の条件でオリフィスを通過させることによって好適な範囲の平均凝集粒子径を持ったカチオン性樹枝変性シリカ分散液を得ることができる。
【００４５】
上記の高度な分散処理による分散の程度は、前述したように得られるカチオン性樹脂変性シリカ分散液中のシリカの平均凝集粒子径が、１０〜１０００ｎｍの範囲、好ましくは５０〜３００ｎｍの範囲となるように行うことが好ましい。
【００４６】
【実施例】
以下、本発明の実施例を挙げて具体的に説明するが、本発明はこれら実施例によって何ら制限されるものではない。
【００４７】
なお、以下の方法によってカチオン性樹脂変性シリカ分散液の物性測定を行った。
（粘度測定）
カチオン性樹脂変性シリカ分散液３００gを５００ｃｃ容器に採取し、プロペラ羽根（羽根形状櫂十字型、羽根外径６０ｍｍφ）を用いて、３００ｒｐｍで１０分間攪拌した。次に３０℃の恒温槽に１０分間つけた後、Ｂ型粘度計（トキメック製、ＢＬ）を用いて６０ｒｐｍの条件でカチオン性樹脂変性シリカ分散液の粘度を測定した。
（ｎ値の測定）
カチオン性樹脂変性シリカ分散液の可視光吸収スペクトルを、分光光度計（日本分光製、Ｕｂｅｓｔ−３５型）を用いて測定した。まず、光路長１０ｍｍのセルを用い、参照セル及び試料セルにそれぞれイオン交換水を満たし、全波長範囲にわたってゼロ点校正を行った。次に、カチオン性樹脂変性シリカ分散液のシリカ濃度が１．５重量％となるようにイオン交換水で希釈した後、試料セルに入れて、波長（λ）４６０〜７６０ｎｍの吸光度（τ）を測定した。ｌｏｇ（λ）及びｌｏｇ（τ）をプロットし、前述した式（１）を用いて直線の傾き（−ｎ）を最小二乗法で求めた。このようにして求められたｎを光散乱指数として採用した。
（平均粒子径の測定）
カチオン性樹脂変性シリカ分散液のシリカ濃度が１０重量％となるように、イオン交換水に希釈した後、光散乱回折式の粒度分布測定装置（コールター製、コールターＬＳ−２３０）を用いて、体積基準算術平均径Ｄ５０を測定し、この値を平均径として採用した。
【００４８】
なお、測定に際しては、水（分散媒）の屈折率１．３３２及びシリカの屈折率１．４５８をパラメーターとして入力した。
（保存安定性）
カチオン性樹脂変性シリカ分散液の保存安定性は、該分散液がゲル化して流動性がなくなるまでの日数を調べた。
【００４９】
実施例１
平均分子量２，０００のジアリルジメチルアンモニウムクロライド重合物水溶液（カチオン性樹脂濃度３．９重量％）１，７３０ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６７０ｇを徐々に添加し、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液の物性を表１に示した。
【００５０】
実施例２
平均分子量４，５００のジアリルジメチルアンモニウムクロライド重合物水溶液（カチオン性樹脂濃度３．６重量％）１，７６０ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６４０ｇを徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液及の物性を表１に示した。
【００５１】
実施例３
平均分子量５，０００のジアリルジメチルアンモニウムクロライド−アクリルアミド共重合物水溶液（カチオン性樹脂濃度３．５重量％）１，７７５ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６２５ｇを徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液の物性を表１に示した。
【００５２】
実施例４
平均分子量５，０００のジアリルメチルアミン塩酸塩重合物水溶液（カチオン性樹脂濃度２．５重量％）１，７７５ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６２５ｇを徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液の物性を表１に示した。
【００５３】
実施例５
比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６７０ｇを純水１，３９５ｇに徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で分散することにより、乾式シリカ分散液を得た。この乾式シリカ分散液を分子量２，０００のジアリルジメチルアンモニウムクロライド重合物水溶液（カチオン性樹脂濃度２０重量％）３３５ｇに徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液の物性を表１に示した。
【００５４】
実施例６
比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６４０ｇを純水１，４４０ｇに徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で分散することにより、乾式シリカ分散液を得た。この乾式シリカ分散液を分子量４，５００のジアリルジメチルアンモニウムクロライド重合物水溶液（カチオン性樹脂濃度２０重量％）３２０ｇに徐々に添加しながら、液温度を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合することにより予備混合液を得た。この予備混合液を高圧ホモジナイザー（ナノマイザー製、ナノマイザー、ＬＡ−３１）を用いて処理圧力８００ｋｇｆ／ｃｍ２で、オリフィスを１回通過させて分散処理することによりカチオン性樹脂変性シリカ分散液を得た。得られたカチオン性樹脂変性シリカ分散液の物性を表１に示した。
【００５５】
比較例１
平均分子量３０，０００のジアリルジメチルアンモニウムクロライド重合物水溶液（カチオン性樹脂濃度１．７重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、予備混合液全体が乾式シリカ添加中にゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は４８０ｇであった。
【００５６】
比較例２
平均分子量２００，０００のジアリルジメチルアンモニウムクロライド−アクリルアミド共重合物水溶液（カチオン性樹脂濃度１．７重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、乾式シリカ添加中に予備混合液全体がゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は４００ｇであった。
【００５７】
比較例３
平均分子量２０，０００のジアリルメチルアミン塩酸塩重合物水溶液（カチオン性樹脂濃度１．７重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、乾式シリカ添加中に予備混合液全体がゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は４８０ｇであった。
【００５８】
比較例４
平均分子量５，０００のアリルアミン塩酸塩重合物水溶液（カチオン性樹脂濃度３．３重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、乾式シリカ添加中に予備混合液全体がゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は４６０ｇであった。
【００５９】
比較例５
平均分子量５，０００のアリルアミン重合物水溶液（カチオン性樹脂濃度２．３重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、乾式シリカ添加中に分散液全体がゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は２８０ｇであった。
【００６０】
比較例６
平均分子量４，０００のメタクリル酸エステルメチルクロライド重合物水溶液（カチオン性樹脂濃度１．７重量％）１，８００ｇに、比表面積が３００ｍ２／ｇの乾式シリカ（トクヤマ製、レオロシールＱＳ−３０）６００ｇを徐々に添加しながら、液温を３０℃に維持して、ウルトラミキサー（みづほ工業製、ウルトラミキサーＬＲ−２）で混合したところ、予備混合液全体が乾式シリカ添加中にゲル化し、分散不可能となった。ゲル化した時点までに添加した乾式シリカの量は３２０ｇであった。
【００６１】
【表１】
実施例１〜６で得られたカチオン性樹脂変性シリカ分散液は、分散液中のシリカ濃度が２５重量％以上であっても、凝集すること無く、極めて安定であることが確認された。
【００６３】
一方、比較例１〜６では、製造途中に分散液全体がゲル化してしまい、シリカ濃度が２５重量％以上のカチオン性樹脂変性シリカ分散液を得ることができなかった。
【００６４】
【発明の効果】
以上の説明で理解されるように、本発明のカチオン性樹脂変性シリカ分散液は、カチオン性樹脂を平均分子量６，０００以下の環状アンモニウム塩型のカチオン性樹脂とすることにより、該分散液中のシリカ濃度が２５重量％以上であるにも関わらず、製造時においてゲル化せず、更に安定性に優れているため、インクジェット用記録紙の塗工液、新聞紙の内填剤、研磨剤、金属表面処理剤等にも好適に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel cationic resin-modified silica dispersion which is useful for the preparation of a coating liquid for ink jet recording paper using dry silica, a filler for newspapers, an abrasive and a metal surface treatment agent.
[0002]
[Prior art]
In order to form an ink absorbing layer, inorganic fine powders such as fine-particle silica and alumina are used in a coating liquid for inkjet recording paper. Of the fine particles, silica, especially dry silica, is excellent in dispersibility and is preferably used.
[0003]
On the other hand, in general, anionic compounds are often used as inkjet inks, and the ink absorbing layer has a cationic property in order to improve image density and water resistance of inkjet recording paper. Is advantageous.
[0004]
However, when dry silica is used as the inorganic powder for forming the ink absorbing layer, the particles exhibit an anionic property, which causes a problem in image density and water resistance. Therefore, as an improvement measure, a cationic resin-modified silica dispersion in which a dry resin is mixed with a cationic resin containing a cationic group such as a quaternary ammonium base has been proposed. For example, JP-A-11-321079 discloses In addition, a cationic resin-modified silica dispersion having a specified mixing method and a method for producing the same are disclosed, including a step of adding and mixing a dry silica dispersion to an aqueous cationic resin solution having an average molecular weight of 100,000 or less.
[0005]
Japanese Patent Application Laid-Open No. 2001-19421 discloses a process in which dry silica fine particles are added to a cationic resin aqueous solution having a structural unit of a polydiallylamine derivative and having an average molecular weight of 100,000 or less and mixed at 20 ° C. or less. A cationic resin-modified silica dispersion having a specified mixing method and a method for producing the same are disclosed.
[0006]
Further, as a metal surface treatment agent, a treatment agent in which a cationic resin is blended with a silica dispersion in order to improve the corrosion resistance of a metal and the adhesion of a paint has been proposed. For example, Japanese Patent Application Laid-Open No. 56-24470. The publication discloses a method of adding water-dispersible colloidal silica to an aqueous cationic resin solution with stirring.
[0007]
However, the silica concentration in the cationic resin-modified silica dispersion obtained by the conventional technique is 25% by weight or less.
[0008]
[Problems to be solved by the invention]
As described above, the cationic resin-modified silica dispersion is used as a coating liquid for inkjet paper, but naturally, the higher the silica concentration in the cationic resin-modified silica dispersion, the higher the silica concentration in the coating liquid. Can also be higher.
[0009]
When the silica concentration in the coating solution is higher, a coating layer having a sufficient thickness can be obtained by a single coating in the coating process, or energy efficiency when drying after coating is improved. The silica concentration in the functional resin-modified silica dispersion is preferably as high as possible.
[0010]
From the viewpoint of physical distribution cost, it is very preferable that the silica concentration in the cationic resin-modified silica dispersion is high.
[0011]
However, as described above, in the conventional technique, the silica concentration in the cationic resin-modified silica dispersion obtained by mixing and dispersing the cationic resin aqueous solution and silica was 25% by weight or less. Also, when the silica concentration in the dispersion exceeds 18% by weight and the silica concentration increases even at 1%, the viscosity of the dispersion rapidly increases, and in some cases, redispersion is impossible. There was also a problem of gelation, and it was difficult to obtain a stable cationic resin-modified silica dispersion while the silica concentration was 25% by weight or more.
[0012]
Therefore, a cationic resin-modified silica dispersion having a high silica concentration and excellent stability without causing gelation of the entire dispersion is desired.
[0013]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors mix and disperse a cyclic ammonium salt type cationic resin aqueous solution and dry silica in a polar solvent having an average molecular weight of 6,000 or less. Thus, even when the silica concentration in the dispersion was 25% by weight or more, it was found that an extremely stable cationic resin-modified silica dispersion can be obtained, and the present invention has been completed.
[0014]
That is, the present invention is a dispersion in which dry silica and a cationic resin are dispersed in a polar solvent, the silica concentration in the dispersion is 25% by weight or more, and the cationic resin has an average molecular weight of 6 It is a cationic resin-modified silica dispersion characterized by being a cyclic ammonium salt type cationic resin.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
As the dry silica used in the present invention, what is also called “fumed silica” obtained by burning a silane-based gas such as silicon tetrachloride in an oxyhydrogen flame is used without any limitation.
[0016]
Generally, dry silica having a specific surface area in the range of 30 to 500 m 2 / g by the BET method is available, and these dry silicas can be suitably used. In particular, a cationic resin-modified silica dispersion using dry silica having a specific surface area of 200 to 500 m 2 / g is preferable because the transparency of the dispersion is increased. For example, when used as a raw material for a coating liquid for inkjet recording paper with high glossiness, if the transparency of the dispersion liquid becomes low, the light transmission of the coating layer is hindered, the coating layer becomes opaque, and the gloss is high. This is not preferable because a problem such as shortage occurs.
[0017]
In the present invention, the average aggregate particle diameter of silica in the cationic resin-modified silica dispersion is in the range of 10 to 1000 nm, preferably in the range of 50 nm to 300 nm.
[0018]
When the average agglomerated particle diameter is smaller than 10 nm, the viscosity of the cationic resin-modified silica dispersion increases. For example, when it is used as a coating liquid for inkjet recording paper, it may be difficult to handle. When the average aggregated particle size is larger than 1000 nm, dry silica may settle in the cationic resin-modified silica dispersion to facilitate phase separation.
[0019]
In the cationic resin-modified silica dispersion of the present invention, the light scattering index (hereinafter also simply referred to as n value) after dilution so that the silica concentration is 1.5% by weight is adjusted to 2.0 or more. Is particularly preferable because the dispersibility of dry silica is particularly excellent, and by using such a cationic resin-modified silica dispersion, a highly transparent coating solution can be produced.
[0020]
The above-mentioned n value is an index representing the dispersion state of silica in the dispersion, and this value increases as the dispersibility improves.
[0021]
The n value is a value measured according to the method described in Journal of Ceramic Society of Japan, 101 [6], 707-712 (1993).
[0022]
That is, using a commercially available spectrophotometer, the absorbance (τ) is obtained by measuring the spectrum of the dispersion having a light wavelength (λ) in the range of 460 nm to 700 nm, and log (λ) τ) is plotted, and the slope (−n) of the straight line is obtained by the least square method using the following formula (1).
[0023]
τ = αλ− n (1)
(Where τ is absorbance, α is a constant, λ is the wavelength of light, and n is the light scattering index.)
The cationic resin used in the present invention is a cyclic ammonium salt type cationic resin having an average molecular weight of 6,000 or less. The average molecular weight of the cationic resin is preferably in the range of 500 to 5,500.
[0024]
The cyclic ammonium salt type cationic resin used in the present invention is a cationic resin obtained by polymerizing a diallylammonium salt and a derivative thereof. As a specific example, the following formula having an average molecular weight of 6,000 or less is used. A polymer of a diallylammonium salt having a repeating unit represented by (2) or formula (3) and a derivative thereof, a repeating unit 10 represented by formula (2) or formula (3) having an average molecular weight of 6,000 or less Mention may be made of copolymers having 90 mol% and 90 to 10 mol% of repeating units based on monomers copolymerizable with diallylammonium salts and derivatives thereof.
[0025]
[Chemical 1]
In the formulas (2) and (3), R1 and R2 represent a hydrogen atom or a methyl group.
[0027]
As the repeating unit based on a monomer copolymerizable with a diallylammonium salt and a derivative thereof, a repeating unit based on acrylamide or monoallylamine hydrochloride is preferable.
[0028]
A particularly preferred cationic resin in the present invention is a polymer of a diallylammonium salt having an average molecular weight of 500 to 5,500 and a repeating unit represented by the above (2) or formula (3) and a derivative thereof, formula (2) ) Or a cationic resin selected from a copolymer having 10 to 90 mol% of repeating units represented by formula (3) and 90 to 10 mol% of repeating units based on acrylamide and monoallylamine hydrochloride.
[0029]
When a cationic resin-modified silica dispersion having a silica concentration of 25% by weight or more is produced using a cyclic ammonium salt type cationic resin having an average molecular weight of 6,000 or more, silica particles are aggregated and silica There is a problem that the whole dispersion is aggregated. In addition, when it is not a cyclic ammonium salt type cationic resin, for example, when a quaternary ammonium salt type cationic resin such as a methacrylic acid ester methyl chloride polymer, an allylamine hydrochloride polymer, or an allylamine polymer is used, the average Even if the molecular weight is 6,000 or less, if an attempt is made to produce a cationic resin-modified silica dispersion having a silica concentration of 25% by weight or more in the dispersion, there is a problem that the entire silica dispersion is aggregated during the production.
[0030]
In this invention, the usage-amount of a cationic resin is 1-50 weight part with respect to 100 weight part of silica, Especially 1-15 weight part is preferable. When the amount of the cationic resin in the cationic resin-modified silica dispersion is adjusted to be less than 1 part by weight with respect to 100 parts by weight of the dry silica, the balance of the surface charge of the dry silica particles becomes non-uniform, There is a tendency that silica particles tend to cause strong aggregation. Moreover, when it adjusts so that the quantity of cationic resin may be more than 50 weight part with respect to 100 weight part of silica, a viscosity may become high and a dispersion process may become difficult.
[0031]
Moreover, it is not preferable that the viscosity of the cationic resin-modified silica dispersion increases because the handling property is lowered in the subsequent manufacturing process. Since the stability of the cationic resin-modified silica dispersion with respect to the addition amount of the cationic resin varies depending on the kind of the cationic resin to be added, the optimum addition amount that gives the lowest viscosity of the dispersion is determined by experiment in advance. It is preferable to select from the addition amount.
[0032]
The polar solvent used in the present invention is not particularly limited as long as it is a polar solvent in which dry silica and a cationic resin are easily dispersed. As such a polar solvent, water is most preferable. Of course, in addition to water, polar solvents such as alcohols such as methanol, ethanol and isopropyl alcohol, ethers and ketones can be used, and a mixed solvent of water and the above polarities can also be suitably used.
[0033]
In order to improve the storage stability and dispersibility of the silica particles, a small amount of a surfactant, an antifungal agent or the like may be added within a range not impairing the effects of the present invention.
[0034]
In the present invention, the method for producing a cationic resin-modified silica dispersion by mixing or dispersing dry silica and cationic resin in a polar solvent is not particularly limited, but the polar solvent, dry silica particles and cationic resin are mixed in advance. Then, after preparing a premixed solution containing dry silica and cationic resin in a polar solvent, if necessary, finely disperse the silica particles in the premixed solution to an average aggregate particle size in a suitable range For this purpose, a method of applying an advanced dispersion means is preferably employed.
[0035]
The method of mixing the polar solvent, the dry silica particles and the cationic resin in advance is not particularly limited, but the method of directly mixing the dry silica particles into the solution obtained by mixing the cationic resin in the polar solvent, the polar solvent Examples thereof include a method of mixing a cationic resin after dispersing the dry silica particles, a method of mixing a liquid obtained by mixing the dry silica particles and the cationic resin in a polar solvent, and the like.
[0036]
The mixer used for the above mixing is not particularly limited, but is a general stirrer having a propeller blade, a turbine blade, a paddle blade, etc., a high-speed rotary radial stirrer such as a disper mixer, a high-speed rotational shear such as a homogenizer, a homomixer, and an ultra mixer. And emulsifiers such as a mold stirrer, colloid mill, and planetary mixer.
[0037]
Among the above mixers, a mixer having a strong shearing force is suitable. Specifically, a high-speed rotary shear type agitator, a composite type disperser in which a propeller blade and a paddle blade are further combined with a high-speed shear type agitator, a planetary mixer and a high-speed rotary centrifugal radiation type agitator or a high-speed rotary shear type agitator are combined. A composite type disperser is mentioned.
[0038]
The temperature at which the polar solvent, the dry silica particles and the cationic resin are preliminarily mixed (hereinafter simply referred to as premixing temperature) is preferably controlled within a temperature range of 20 ° C to 40 ° C.
[0039]
The higher the premixing temperature, the lower the viscosity of the premixed solution. However, when the premixed temperature exceeds 40 ° C, the silica particles in the premixed solution tend to aggregate, and the viscosity of the premixed solution rises rapidly, causing the premixed solution to gel. Tend to. Also, when the premixing temperature is less than 20 ° C., the viscosity of the premixed liquid tends to increase.
[0040]
Furthermore, in the present invention, it is preferable to obtain a cationic resin-modified silica dispersion by subjecting the preliminary mixture to a further advanced dispersion treatment. However, the higher the viscosity of the preliminary mixture, the higher the dispersion treatment. The viscosity of the obtained cationic resin-modified silica dispersion tends to be high. An increase in the viscosity of the cationic resin-modified silica dispersion is not preferable because the handling property is lowered in the subsequent production process.
[0041]
The method for controlling the premixing temperature in the temperature range of 20 ° C. to 40 ° C. is not particularly limited, but it is preferable to control the pre-mixing temperature so as to be an arbitrary constant temperature in the temperature range of 20 ° C. to 40 ° C.
[0042]
In the present invention, the premixed solution obtained by the above method can be used as it is as a cationic resin-modified silica dispersion as it is depending on the application, but by performing advanced dispersion treatment after premixing. Thus, a cationic resin-modified silica dispersion having excellent stability and excellent stability even when a coating solution is prepared using the same can be obtained.
[0043]
In the present invention, the above-described advanced dispersion treatment method is not particularly limited, and examples thereof include dispersion treatment using a bead mill, a sand mill, an ultrasonic homogenizer, a high-pressure homogenizer, and the like. Among these, a dispersion treatment using a high-pressure homogenizer is preferable.
[0044]
Specific examples of high-pressure homogenizers include nanomizer product names; nanomizer, microfluidics product names; microfluidizers, and Sugino Machine optimizers. Using the above-described high-pressure homogenizer, a mixed solution in which a polar solvent, silica, and a cationic resin are mixed is allowed to collide at a treatment pressure of 300 kgf / cm 2 or more, or the differential pressure between the inlet side and the outlet side of the orifice is 300 kgf. A cationic dendritic modified silica dispersion having an average aggregated particle diameter in a suitable range can be obtained by passing through an orifice under conditions of / cm 2 or more.
[0045]
The degree of dispersion by the above advanced dispersion treatment is such that the average aggregate particle diameter of silica in the cationic resin-modified silica dispersion obtained as described above is in the range of 10 to 1000 nm, preferably in the range of 50 to 300 nm. It is preferable to do so.
[0046]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0047]
The physical properties of the cationic resin-modified silica dispersion were measured by the following method.
(Viscosity measurement)
300 g of the cationic resin-modified silica dispersion was collected in a 500 cc container, and stirred for 10 minutes at 300 rpm using a propeller blade (blade-shaped cruciform, blade outer diameter 60 mmφ). Next, after putting in a 30 degreeC thermostat for 10 minutes, the viscosity of the cationic resin modified silica dispersion liquid was measured on condition of 60 rpm using the B-type viscosity meter (made by Tokimec, BL).
(Measurement of n value)
The visible light absorption spectrum of the cationic resin-modified silica dispersion was measured using a spectrophotometer (manufactured by JASCO Corporation, Ubest-35 type). First, using a cell having an optical path length of 10 mm, the reference cell and the sample cell were each filled with ion-exchanged water, and zero point calibration was performed over the entire wavelength range. Next, after diluting with ion-exchanged water so that the silica concentration of the cationic resin-modified silica dispersion is 1.5% by weight, it is placed in a sample cell and the absorbance (τ) at a wavelength (λ) of 460 to 760 nm is obtained. It was measured. Log (λ) and log (τ) were plotted, and the slope (−n) of the straight line was obtained by the least square method using the above-described equation (1). N thus obtained was adopted as the light scattering index.
(Measurement of average particle size)
After diluting in ion-exchanged water so that the silica concentration of the cationic resin-modified silica dispersion is 10% by weight, the volume is measured using a light scattering diffraction type particle size distribution measuring device (Coulter, Coulter LS-230). the reference arithmetic mean diameter D 50 was measured, employing this value as an average diameter.
[0048]
In the measurement, the refractive index of water (dispersion medium) 1.332 and the refractive index of silica 1.458 were input as parameters.
(Storage stability)
The storage stability of the cationic resin-modified silica dispersion was determined by examining the number of days until the dispersion gelled and lost its fluidity.
[0049]
Example 1
To 1,730 g of an aqueous solution of diallyldimethylammonium chloride polymer having an average molecular weight of 2,000 (cationic resin concentration of 3.9% by weight), 670 g of dry silica (manufactured by Tokuyama, Leolosil QS-30) having a specific surface area of 300 m 2 / g It added gradually, the liquid temperature was maintained at 30 degreeC, and the preliminary mixed liquid was obtained by mixing with an ultra mixer (the product made by Mizuho Kogyo, ultra mixer LR-2). A cationic resin-modified silica dispersion was obtained by subjecting this premixed solution to a dispersion treatment by passing it once through an orifice at a treatment pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . The physical properties of the obtained cationic resin-modified silica dispersion are shown in Table 1.
[0050]
Example 2
1,760 g of diallyldimethylammonium chloride polymer aqueous solution having an average molecular weight of 4,500 (cationic resin concentration 3.6% by weight) and 640 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) The liquid temperature was maintained at 30 ° C. while gradually adding, and a premixed liquid was obtained by mixing with an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd., Ultra Mixer LR-2). A cationic resin-modified silica dispersion was obtained by subjecting this premixed solution to a dispersion treatment by passing it once through an orifice at a treatment pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . Table 1 shows the properties of the resulting cationic resin-modified silica dispersion.
[0051]
Example 3
1,775 g of diallyldimethylammonium chloride-acrylamide copolymer aqueous solution having an average molecular weight of 5,000 (cationic resin concentration 3.5% by weight) and dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leoroseal QS-30) ) While gradually adding 625 g, the liquid temperature was maintained at 30 ° C., and the mixture was mixed with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2) to obtain a premixed liquid. A cationic resin-modified silica dispersion was obtained by subjecting this premixed solution to a dispersion treatment by passing it once through an orifice at a treatment pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . The physical properties of the obtained cationic resin-modified silica dispersion are shown in Table 1.
[0052]
Example 4
1,775 g of an aqueous solution of a diallylmethylamine hydrochloride polymer having an average molecular weight of 5,000 (cationic resin concentration of 2.5% by weight) and 625 g of dry silica having a specific surface area of 300 m 2 / g (Leosil QS-30, manufactured by Tokuyama) The liquid temperature was maintained at 30 ° C. while gradually adding and a premixed solution was obtained by mixing with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2). A cationic resin-modified silica dispersion was obtained by subjecting this premixed solution to a dispersion treatment by passing it once through an orifice at a treatment pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . The physical properties of the obtained cationic resin-modified silica dispersion are shown in Table 1.
[0053]
Example 5
While gradually adding 670 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leoroseal QS-30) to 1,395 g of pure water, the liquid temperature was maintained at 30 ° C., and an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd.) By dispersing with an ultramixer LR-2), a dry silica dispersion was obtained. While this dry silica dispersion was gradually added to 335 g of a diallyldimethylammonium chloride polymer aqueous solution having a molecular weight of 2,000 (cationic resin concentration 20% by weight), the liquid temperature was maintained at 30 ° C. A premixed solution was obtained by mixing with an ultra mixer LR-2). A cationic resin-modified silica dispersion was obtained by subjecting this premixed solution to a dispersion treatment by passing it once through an orifice at a treatment pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . The physical properties of the obtained cationic resin-modified silica dispersion are shown in Table 1.
[0054]
Example 6
While gradually adding 640 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) to 1,440 g of pure water, the liquid temperature was maintained at 30 ° C., and an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd.) By dispersing with an ultramixer LR-2), a dry silica dispersion was obtained. While gradually adding this dry silica dispersion to 320 g of an aqueous diallyldimethylammonium chloride polymer solution having a molecular weight of 4,500 (cationic resin concentration 20% by weight), the liquid temperature was maintained at 30 ° C. A premixed solution was obtained by mixing with an ultra mixer LR-2). A cationic resin-modified silica dispersion was obtained by subjecting this pre-mixed liquid to a dispersion treatment by passing it once through an orifice at a processing pressure of 800 kgf / cm 2 using a high-pressure homogenizer (Nanomizer, Nanomizer, LA-31). . The physical properties of the obtained cationic resin-modified silica dispersion are shown in Table 1.
[0055]
Comparative Example 1
1,800 g of diallyldimethylammonium chloride aqueous polymer solution having an average molecular weight of 30,000 (cationic resin concentration of 1.7% by weight) and 600 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) While gradually adding, maintaining the liquid temperature at 30 ° C. and mixing with an ultramixer (Ultramix LR-2, manufactured by Mizuho Kogyo), the entire premixed solution gelled during the addition of dry silica and was not dispersible. It became. The amount of dry silica added up to the time of gelation was 480 g.
[0056]
Comparative Example 2
1,800 g of diallyldimethylammonium chloride-acrylamide copolymer aqueous solution having an average molecular weight of 200,000 (cationic resin concentration 1.7% by weight) and dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) ) While gradually adding 600 g, maintaining the liquid temperature at 30 ° C. and mixing with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2), the entire premixed solution gelled during the addition of dry silica, It became impossible to disperse. The amount of dry silica added up to the time of gelation was 400 g.
[0057]
Comparative Example 3
1,800 g of diallylmethylamine hydrochloride aqueous polymer solution having an average molecular weight of 20,000 (cationic resin concentration of 1.7% by weight) and 600 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) The liquid temperature was maintained at 30 ° C. while gradually adding and mixed with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2). It has become possible. The amount of dry silica added up to the time of gelation was 480 g.
[0058]
Comparative Example 4
To 1,800 g of an allylamine hydrochloride polymer aqueous solution (cationic resin concentration: 3.3 wt%) having an average molecular weight of 5,000, 600 g of dry silica (Reokusil QS-30, manufactured by Tokuyama) with a specific surface area of 300 m 2 / g is gradually added. The mixture was mixed with an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd., Ultra Mixer LR-2) while being added to the mixture. became. The amount of dry silica added up to the time of gelation was 460 g.
[0059]
Comparative Example 5
To 1,800 g of an allylamine polymer aqueous solution having an average molecular weight of 5,000 (cationic resin concentration 2.3 wt%), 600 g of dry silica (Rokuro QS-30, manufactured by Tokuyama) having a specific surface area of 300 m 2 / g is gradually added. While maintaining the liquid temperature at 30 ° C. and mixing with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2), the whole dispersion gelled during the addition of dry silica and became impossible to disperse. The amount of dry silica added up to the time of gelation was 280 g.
[0060]
Comparative Example 6
1,800 g of methacrylic acid ester methyl chloride polymer aqueous solution having an average molecular weight of 4,000 (cationic resin concentration of 1.7% by weight) and 600 g of dry silica having a specific surface area of 300 m 2 / g (manufactured by Tokuyama, Leolosil QS-30) The liquid temperature was kept at 30 ° C. while gradually mixing and mixing with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2). It has become possible. The amount of dry silica added up to the time of gelation was 320 g.
[0061]
[Table 1]
The cationic resin-modified silica dispersions obtained in Examples 1 to 6 were confirmed to be extremely stable without agglomeration even when the silica concentration in the dispersion was 25% by weight or more.
[0063]
On the other hand, in Comparative Examples 1-6, the whole dispersion gelled during production, and a cationic resin-modified silica dispersion having a silica concentration of 25% by weight or more could not be obtained.
[0064]
【The invention's effect】
As understood from the above description, the cationic resin-modified silica dispersion of the present invention is obtained by making the cationic resin into a cyclic ammonium salt type cationic resin having an average molecular weight of 6,000 or less. In spite of the silica concentration of 25% by weight or more, it does not gel at the time of manufacture, and is further excellent in stability, so that it is a coating liquid for inkjet recording paper, a filler for newspapers, an abrasive, It can be suitably used for a metal surface treatment agent or the like.
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