JP2005000762A - Cationic resin-modified silica-dispersed liquid and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic resin-modified silica-dispersed liquid which is manufactured by using wet silica as a raw material, the silica concentration of which exceeds 22 wt.%, from which a coating liquid having stable viscosity can be obtained when this silica-dispersed liquid is used as a raw material of the coating liquid for inkjet recording paper and from which a coating film layer having excellent gloss, ink absorptivity and water resistance can be obtained, and to provide a manufacturing method therefor. <P>SOLUTION: The cationic resin-modified silica-dispersed liquid is manufactured by dispersing wet silica and a cyclic ammonium salt type cationic resin (for example, a polymer of diaryl dimethyl ammonium salt) having ≤10,000 average molecular weight in a polar solvent such as water so that the silica concentration exceeds 22 wt.%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２７】
式（１）、式（２）において、Ｒ^１及びＲ^２は、水素原子又はメチル基を表す。
【００２８】
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。
【００２９】
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１，０００〜８，０００である、上記の式（１）又は式（２）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（１）又は式（２）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から選定した１種類のカチオン性樹脂、或いは２種類以上を混合したカチオン性樹脂である。
【００３０】
本発明において、カチオン性樹脂の使用量は、カチオン性樹脂変性シリカ分散液が製造途中でゲル化することなく安定に製造でき、且つ、得られたカチオン性樹脂変性シリカ分散液の粘度を低くするために、シリカ１００重量部に対して、２〜５０重量部、特に２〜１５重量部とすることが好ましい。カチオン性樹脂変性シリカ分散液の粘度が低いと、塗工液を製造するための以降に続く製造工程においてハンドリング性が良くなるので非常に好ましい。
【００３１】
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粘度は、シリカの比表面積及び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、湿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、水と上記極性溶媒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、カチオン性樹脂変性シリカ分散液中のシリカ濃度は２２重量％超である。
【００３５】
該シリカ分散液中のシリカ濃度が低くなると、前述したように、塗工液調製後の塗工工程において一回の塗工で十分な厚みの塗工層が形成することが難しくなる場合があり、また、塗工後乾燥する際のエレルギー効率の悪化や物流コストの面からも問題がある。
【００３６】
本発明のカチオン性樹脂変性シリカ分散液は、極性溶媒、湿式シリカ及び平均分子量が１万以下の環状アンモニウム塩型のカチオン性樹脂を混合・分散・微粒化することにより製造することができる。
【００３７】
カチオン性樹脂として平均分子量が１万を超える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２２重量％超のカチオン性樹脂変性シリカ分散液を製造すると、製造の途中でシリカ粒子が凝集し、シリカ分散液全体が凝集する。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のカチオン性樹脂を用いた場合、平均分子量が１万以下であっても、分散液中のシリカ濃度が２２重量％超のカチオン性樹脂変性シリカ分散液を製造すると、製造の途中でシリカ粒子が凝集し、シリカ分散液全体が凝集する。
【００３８】
極性溶媒中に湿式シリカ及びカチオン性樹脂を混合・分散・微粒化してカチオン性樹脂変性シリカ分散液を製造する好ましい方法としては、（１）極性溶媒中に湿式シリカを分散したシリカスラリーを湿式メディア型粉砕機によりシリカスラリー中のシリカ粒子の平均粒子径を０．５μｍ未満に微粒化したシリカ分散液を調製した後、カチオン性樹脂と混合して、予備混合液を調製し、更に、高圧ホモジナイザーを用いて、予備混合液中のシリカ粒子を平均粒子径０．５μｍ未満になるまで微粒化する方法、（２）極性溶媒、湿式シリカ及びカチオン性樹脂を混合・分散したシリカスラリーを、湿式メディア型分散機を用いて、該シリカスラリー中のシリカ粒子を平均粒子径０．５μｍ未満に微粒化する方法を挙げることができる。
【００３９】
尚、本発明において、シリカスラリーとは、極性溶媒中に湿式シリカを分散したもので、シリカ粒子の平均粒子径を０．５μｍ未満に微粒化する前のものを指し、カチオン性樹脂を含んだ状態であっても、微粒化する前のものはシリカスラリーと表現する。シリカ分散液とは、該シリカスラリー中のシリカ粒子の平均粒子径を０．５μｍ未満になるまで微粒化したものを指すが、カチオン性樹脂を含有するものは含まない。予備混合液とは、シリカ分散液とカチオン性樹脂とを混合したものを指す。また、カチオン性樹脂変性シリカ分散液とは、カチオン性樹脂を含んだシリカスラリー又は予備混合液を微粒化した後のものを指し、平均粒子径０．５μｍ未満のシリカ粒子とカチオン性樹脂とを含有している。
【００４０】
シリカスラリーを得る際の湿式シリカとしては、前述の湿式シリカ粉や、中和反応後に濾過や洗浄を行った後の乾燥工程を施さない湿式シリカケークを使用することができる。湿式シリカケークは乾燥工程を施した湿式シリカ粉と比較して凝集粒子が軟らかいため、分散性が良く、湿式シリカとして好ましく使用できる。しかし、湿式シリカケークは比表面積が高くなるほど湿式シリカケークの水分含有率も高くなるので、湿式シリカとして湿式シリカケークを用いる場合は、シリカ分散液中のシリカ濃度を２２重量％超に高め、且つ、分散性を良くするために、湿式シリカ粉と湿式シリカケークとを混合して湿式シリカとして使用することが好ましい。またその際は、極性溶媒に湿式シリカケークを添加した後に湿式シリカ粉を添加し、混合してシリカスラリーとすることが、高シリカ濃度のシリカスラリーを効率よく得ることができるので好ましい。
【００４１】
上記（１）の、極性溶媒中に湿式シリカを分散したシリカスラリーを湿式メディア型粉砕機によりシリカスラリー中のシリカ粒子の平均粒子径を０．５μｍ未満に微粒化したシリカ分散液を調製した後、カチオン性樹脂と混合して、予備混合液を調製し、更に、高圧ホモジナイザーを用いて、予備混合液中のシリカ粒子を平均粒子径０．５μｍ未満になるまで微粒化することにより、シリカ濃度２２重量％超のカチオン性樹脂変性シリカ分散液を得る方法においては、まず、極性溶媒中に湿式シリカを分散して、シリカ濃度が２２重量％超のシリカスラリーを得る。
【００４２】
シリカスラリーの製造途中及びその後のシリカスラリーの微粒化途中でゲル化することなく安定してシリカ濃度が２２重量％超のカチオン性樹脂変性シリカ分散液を製造するためには、得られるシリカスラリーのｐＨを５未満になるように調整することが好ましい。
【００４３】
シリカスラリーのｐＨを５未満に調整する方法としては、極性溶媒に予め硫酸等の鉱酸を添加してｐＨ調整を行った後、該極性溶媒に湿式シリカを分散する方法、又は湿式シリカと硫酸等の鉱酸を同時に添加して、ｐＨ調整を行いながら、極性溶媒に湿式シリカを分散してシリカスラリーを調製する方法が好ましい。
【００４４】
極性溶媒中に湿式シリカを分散して、ｐＨ５未満のシリカスラリーを調製する際に使用する分散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、吸引式分散機などの分散機、更に上記の高速回転せん断型撹拌機とプロペラ羽根及びパドル翼を組み合わせた複合型分散機、プラネタリーミキサーと高速回転遠心放射型撹拌機又は高速せん断型撹拌機を組み合わせた複合分散機等が挙げられる。
【００４５】
上記（１）の方法においては、次いで、得られたｐＨ５未満のシリカスラリーを、該スラリー中のシリカ粒子の平均粒子径を０．５μｍ未満に微粒化することにより、シリカ分散液を得る。
【００４６】
シリカスラリー中のシリカ粒子の平均粒子径を０．５μｍ未満に微粒化し、シリカ分散液を調製する際に使用する微粒化装置としては、湿式メディア型粉砕機を用いることが好ましい。
【００４７】
湿式メディア型粉砕機とは、平均粒径０．０５〜３ｍｍφ程度のビーズを粉砕メディアとして用いる粉砕機であり、代表例を具体的に例示すると、ニッカトー製の商品名；ポットミル、井上製作所製の商品名；マイティーミル、アイメックス製の商品名；ビスコミル、アシザワ製の商品名；アジテータミル、コトブキ技研工業製の商品名；スーパーアペックスミル、ウルトラアペックスミル及びウィリー・エ・バッコーフェン製の商品名；ダイノーミルなどを挙げることができる。
【００４８】
極性溶媒中の湿式シリカ粒子の平均粒子径を０．５μｍ未満に微粒化するのに使用できる微粒化装置としては、湿式メディア型粉砕機の他にも、超音波分散機や高圧ホモジナイザーなどがあるが、超音波分散機は大量製造には向いておらず、また、高圧ホモジナイザーは目的の粒子径になるまで微粒化処理するのに処理時間がかかり、生産性が悪くなるので好ましくない。
【００４９】
湿式シリカのように凝集粒子の硬い無機酸化物を微粒化する場合には、粉砕メディア相互と被粉砕物との衝撃作用で微粒化粉砕する原理を採用している湿式メディア型粉砕機が適している。
【００５０】
湿式メディア型粉砕機の接液部には、ジルコニア又はアルミナを主成分とするセラミック、或いはポリウレタン系又はポリエチレン系の樹脂などシリカに対して磨耗性の高い素材が好ましい。また、使用される粉砕メディアは、公知の粉砕用メディアを用いることができるが、中でも硬度の観点からジルコニアビーズが好ましい。
【００５１】
上記（１）の方法においては、次いで、上記の方法で得られたシリカ分散液を、平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂と混合・分散することにより、予備混合液を得る。
【００５２】
シリカ分散液とカチオン性樹脂との混合方法は、特に限定されないが、カチオン性樹脂の水溶液にシリカ分散液を加えて混合する方法が好ましい。シリカ分散液とカチオン性樹脂とを混合・分散して予備混合液を調製する際に使用する混合機は特に制限されないが、前述の一般撹拌機、高速回転遠心放射型撹拌機、高速回転せん断型撹拌機、コロイドミル、プラネタリーミキサー、吸引式分散機などの分散機、更に上記の分散機を組み合わせた複合型分散機が挙げられる。
【００５３】
上記方法で得られた予備混合液中のシリカ粒子はカチオン性樹脂により再凝集し、平均粒子径が０．５μｍ以上となっている。そこで、予備混合液を更に微粒化して本発明のカチオン性樹脂変性シリカ分散液を得る。
【００５４】
予備混合液を更に微粒化して、カチオン性樹脂変性シリカ分散液を調製するのに使用する分散機としては、高圧ホモジナイザーを用いる。
【００５５】
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。
【００５６】
予備混合液を、上記の高圧ホモジナイザーを用いて処理圧力３０ＭＰａ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３０ＭＰａ以上の条件でオリフィスを通過させることによって、生産性良く、平均粒子径が０．５μｍ未満のシリカ粒子を２２重量％超含有するカチオン性樹脂変性シリカ分散液を得ることができる。
【００５７】
シリカ粒子の平均粒子径が０．５μｍ未満のシリカ分散液とカチオン性樹脂とを混合・分散した予備混合液中では、前述したようにシリカ粒子の再凝集が起こっており、これを更に微粒化させようとすると急激に粘度が上昇した後に、粘度が下降する傾向がある。このように急激に粘性が変化する予備混合液、特に途中で一度粘度が急激に上昇するような予備混合液を湿式メディア式粉砕機などで更に微粒化させようとすると、運転条件の設定が非常に難しくなるので好ましくない。高圧ホモジナイザーは、このような粘性が急激に変化する予備混合液の微粒化に対して非常に適している。
【００５８】
本発明において、極性溶媒中に湿式シリカを分散してシリカスラリーを得るときの温度、該シリカスラリーを微粒化してシリカ分散液を得るときの温度、該シリカ分散液とカチオン性樹脂とを混合・分散して予備混合液を得るときの温度、予備混合液を微粒化するときの温度（以下、いずれも分散液製造温度ともいう）は、製造途中で増粘・ゲル化などを起こすことなく安定的に製造するために、いずれの場合も４０℃以下の温度範囲で制御することが好ましい。
【００５９】
分散液製造温度を４０℃以下の温度範囲に制御する方式は特に制限されないが、４０℃以下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。
【００６０】
上記（２）の、極性溶媒、湿式シリカ及びカチオン性樹脂を混合・分散したシリカスラリーを、湿式メディア型分散機を用いて、該シリカスラリー中のシリカ粒子を平均粒子径０．５μｍ未満になるまで微粒化することにより、カチオン性樹脂変性シリカ分散液を得る方法においては、まず極性溶媒、湿式シリカ及び平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂を混合・分散してシリカ濃度が２２重量％超のシリカスラリーを得る。
【００６１】
シリカスラリーを得る方法としては、（ｉ）極性溶媒、湿式シリカ及び平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂を混合・分散して一度で平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂を含んだシリカスラリーとする方法、（ｉｉ）湿式シリカを極性溶媒に混合・分散して一度シリカスラリーとした後、更に平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂と混合・分散して、平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂を含んだシリカスラリーとする方法を挙げることができる。
【００６２】
上記（ｉ）及び（ｉｉ）の両方法において、カチオン性樹脂の有無に関わらず、シリカの平均粒子径を０．５μｍ未満まで微粒化する前のシリカスラリーのｐＨは５未満になるように調整するのが好ましい。シリカスラリーのｐＨを５未満に調整することにより、シリカスラリーの製造途中及びその後のシリカスラリーの微粒化途中でゲル化などの現象を起こすことなく、シリカ濃度２２重量％超のカチオン性樹脂変性シリカ分散液を安定的に製造することが可能となる。
【００６３】
シリカスラリーを得る方法（ｉ）においては、シリカスラリーのｐＨを５未満に調整するための方法として、予め極性溶媒にカチオン性樹脂を添加してｐＨを５未満に調整した後、該極性溶媒に湿式シリカを分散する方法、極性溶媒に湿式シリカとカチオン性樹脂とを同時に添加して、ｐＨ調整を行いながら、極性溶媒に湿式シリカを分散する方法を挙げることができる。
【００６４】
また、シリカスラリーを得る方法（ｉｉ）においては、上記（１）のカチオン性樹脂変性シリカ分散液を製造する方法においてカチオン性樹脂を混合する前のシリカスラリーのｐＨを５未満に調整する方法として前述したように、極性溶媒に予め硫酸等の鉱酸を添加してｐＨ調整を行った後、該極性溶媒に湿式シリカを分散する方法、湿式シリカと硫酸等の鉱酸とを同時に添加して、ｐＨ調整を行いながら、極性溶媒に湿式シリカを分散する方法を挙げることができる。
【００６５】
更に、ｐＨを５未満に調整したカチオン性樹脂を含んでいないシリカスラリーとカチオン性樹脂とを混合・分散してカチオン性樹脂を含んでいるシリカスラリーを得る方法は、特に制限されないが、シリカスラリーをカチオン性樹脂水溶液に添加し、混合・分散する方法、シリカスラリーとカチオン性樹脂水溶液とを同時に添加して、混合・分散する方法などを挙げることができる。
【００６６】
シリカスラリーを調製するために使用する分散機は、カチオン性樹脂の有無に関わらず、特に制限されないが、前述の一般攪拌機、高速回転遠心放射型攪拌機、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、吸引式分散機などの分散機、更に上記の分散機を組み合わせた複合型分散機が挙げられる。
【００６７】
上記（２）のカチオン性樹脂変性シリカ分散液を製造する方法においては、次いで、上記の方法で得られたカチオン性樹脂を含むシリカスラリーを、該シリカスラリー中のシリカ粒子の平均粒子径を０．５μｍ未満に微粒化することにより、本発明のカチオン性樹脂変性シリカ分散液を得る。
【００６８】
カチオン性樹脂を含むシリカスラリーを微粒化して、カチオン性樹脂シリカ分散液を調製するために使用する微粒化装置としては、前述の湿式メディア型粉砕機を用いることができる。
【００６９】
本発明において、極性溶媒、湿式シリカ及びカチオン性樹脂を混合・分散してシリカスラリーを得るときの温度、シリカスラリー中の湿式シリカ粒子を平均粒子径０．５μｍ未満に微粒化してカチオン性樹脂変性シリカ分散液を得るときの温度（以下、この温度も分散液製造温度ともいう）は、製造途中で増粘・ゲル化などを起こすことなく安定的に製造するために、いずれの場合も４０℃以下の温度範囲で制御することが好ましい。
【００７０】
分散液製造温度を４０℃以下の温度範囲に制御する方式は特に制限されないが、４０℃以下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。
【００７１】
【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。
【００７２】
なお、以下の方法によって湿式シリカケークの調製、及びカチオン性樹脂変性シリカ分散液の物性測定及びカチオン性樹脂変性シリカ分散液を原料にして調製した塗工液の性能評価を行った。
【００７３】
（１）シリカケークの調製
（１−１）シリカケークＡの調製
市販の珪酸ソーダと純水を反応槽中に珪酸ソーダの濃度が５重量％となるように投入した。反応槽の温度を４０℃として、２２重量％硫酸を用いて中和反応（中和率５０％まで）を行った後、反応液の温度を９５℃とした。この反応液に中和率が１００％になるまで上記硫酸を加えた。生成したシリカに濾過、洗浄操作を繰り返し、シリカケークＡ（シリカ含有量１５重量％）を得た。このシリカケークＡを乾燥させたシリカの比表面積は２８０ｍ^２／ｇである。
【００７４】
（１−２）シリカケークＢの調製
市販の珪酸ソーダと純水を反応槽中に珪酸ソーダの濃度が５重量％となるように投入した。反応槽の温度を４０℃として、２２重量％硫酸を用いて中和反応（中和率２５％まで）を行った後、反応液の温度を９５℃とした。この反応液に中和率が１００％になるまで上記硫酸を加えた。生成したシリカに濾過、洗浄操作を繰り返し、シリカケークＢ（シリカ含有量１８重量％）を得た。このシリカケークＢを乾燥させたシリカの比表面積は２００ｍ^２／ｇである。
【００７５】
（２）カチオン性樹脂シリカ分散液の物性測定
（２−１）粘度測定
カチオン性樹脂変性シリカ分散液３００ｇを５００ｍｌ容器に採取し、ホモジナイザー（イカ製、ウルトラタラックスＴ−２５）を用いて、２０，０００ｒｐｍで５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。
【００７６】
（２−２）ｐＨ測定
シリカスラリー又はカチオン性樹脂変性シリカ分散液３００ｇを５００ｍｌ容器に採取し、ホモジナイザー（イカ製、ウルトラタラックスＴ−２５）を用いて、２０，０００ｒｐｍで５分間攪拌した。次に３０℃の恒温槽に１０分間つけた後、ｐＨメーター（堀場製作所、Ｆ−２２）を用いて、シリカスラリー及びカチオン性樹脂変性シリカ分散液のｐＨを測定した。
【００７７】
（２−３）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、該分散液をイオン交換水で希釈した後、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Ｄ_５０を測定し、この値を平均粒子径として採用した。
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。
【００７８】
（３）塗工液の性能評価
（３−１）塗工液の調製方法
カチオン性樹脂変性シリカ分散液をシリカ濃度が２０重量％となるようにイオン交換水で希釈した後、希釈したカチオン性樹脂変性シリカ分散液と１０重量％のポリビニルアルコール水溶液（クラレ製、ＰＶＡ１２０）をシリカ：ポリビニルアルコール固形分比＝２：１になるようにプロペラミキサーで撹拌、混合し、塗工液を得た。
【００７９】
（３−２）塗工液の粘度測定
調製直後のカチオン性樹脂変性シリカ分散液、及び該カチオン性樹脂変性シリカ分散液を保存温度２５℃の条件で７日間保存した調製７日後のカチオン性樹脂変性シリカ分散液を用いて、（３−１）の方法により塗工液を調製し、それぞれの塗工液９０ｇを１００ｍｌ容器に採取し、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の条件で塗工液の粘度を測定した。
【００８０】
（３−３）インクジェット記録用シート（塗工層）の作成方法
（３−１）で得られた塗工液をフィルムコーター（テスター産業製、ＰＩ−１２１０ Ｆｉｌｍ Ｃｏａｔｅｒ）を用いて、塗工量が２０ｇ／ｍ^２となるようにＰＥＴシート（アイ・シー・アイ・ジャパン製、メリネックス７０５）の表面に塗工した後、乾燥してＰＥＴシート上に塗工層を作成し、インクジェット記録用シートとした。
【００８１】
（３−４）塗工層の光沢性
インクジェット記録用シートの塗工層表面の８５°鏡面光沢を変角光度計（スガ試験社製、ＵＧＶ−５Ｄ）を用いて、ＪＩＳ Ｚ ８７４１の測定方法に準じて測定を行い、塗工層の光沢性を下記の基準で評価した。
◎：８５°鏡面光沢 ８０以上
○：８５°鏡面光沢 ７５〜８０
△：８５°鏡面光沢 ７０〜７５
×：８５°鏡面光沢 ７０以下
【００８２】
（３−５）塗工層のインク吸収性
インクジェットプリンタ（エプソン製、ＰＭ７００Ｃ）を用いてマゼンダインクでベタ印刷を行い、印字直後から５秒毎に印刷した印字面に市販の上質紙を貼り合わせ、上質紙にインクが転写しなくなるまでの時間の測定を行い、塗工層の吸液性を下記の基準で評価した。
◎：１０秒以内
○：１５〜２０秒
△：２５〜３０秒
×：３５秒以上
【００８３】
（３−６）塗工層の耐水性
インクジェットプリンタ（エプソン製、ＰＭ７００Ｃ）を用いてマゼンダインクで文字印刷を行い、印字面のインクが充分に乾燥したことを確認した後、印字後のインクジェット記録用シートを水中に浸漬し、３０秒後インクが流れ出すことにより発生する印刷した文字の滲んだ状態を肉眼で観察した。
○：文字の滲みがほとんど観察されない。
△：文字の滲みが観察される。
×：数１０ヶ所以上文字の滲みが観察される。
【００８４】
実施例１
イオン交換水８０ｇに、シリカスラリーのｐＨが４．５となるようにｐＨ調整剤として２Ｎ硫酸を添加した後、液温度を３０℃に維持して、シリカケークＡ１，６７０ｇを徐々に添加し、続いて比表面積が２８０ｇ／ｍ^２の湿式シリカ粉（トクヤマ製、ファインシールＸ−３７Ｂ）を２５０ｇ徐々に添加しながら、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、ｐＨが４．５のシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化処理することにより、平均粒子径が０．２５μｍのシリカ分散液を得た。
【００８５】
このシリカ分散液２，０００ｇを平均分子量４，０００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５０重量％）１００ｇ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８０ＭＰａ、液温度３０℃の条件で再分散処理を行うことにより、カチオン性樹脂変性シリカ分散液を得た。
【００８６】
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、塗工液の評価を表２に示した。
【００８７】
実施例２
イオン交換水３６０ｇに、シリカスラリーのｐＨが４．５となるようにｐＨ調整剤として２Ｎ硫酸を添加した後、液温度を３０℃に維持して、シリカケークＢ１，３９０ｇを徐々に添加し、続いて比表面積が２００ｇ／ｍ^２の湿式シリカ粉（トクヤマ製、ファインシールＴ−３２）を２５０ｇ徐々に添加しながら、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、ｐＨが４．５のシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化処理することにより、平均粒子径が０．２３μｍのシリカ分散液を得た。
【００８８】
このシリカ分散液２，０００ｇを平均分子量４，０００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５０重量％）１００ｇ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８０ＭＰａ、液温度３０℃の条件で再分散処理を行うことにより、カチオン性樹脂変性シリカ分散液を得た。
【００８９】
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、塗工液の評価を表２に示した。
【００９０】
実施例３
イオン交換水１，５００ｇに、シリカスラリーのｐＨが４．５になるようにｐＨ調整剤として２Ｎ硫酸を添加した後、比表面積が２８０ｍ^２／ｇの湿式シリカ粉（トクヤマ製、ファインシールＸ−３７Ｂ）５００ｇ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）で分散することにより、ｐＨが４．５のシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化処理することにより、平均粒子径が０．３２μｍのシリカ分散液を得た。
【００９１】
このシリカ分散液２，０００ｇを平均分子量４，０００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５０重量％）１００ｇ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８０ＭＰａ、液温度３０℃で再分散処理を行うことにより、カチオン性樹脂変性シリカ分散液を得た。
【００９２】
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、塗工液の評価を表２に示した。
【００９３】
実施例４
湿式シリカ粉として、比表面積が２００ｍ^２／ｇの湿式シリカ粉（トクヤマ製、ファインシールＴ−３２）を用いる以外は実施例３と同様にしてカチオン性樹脂変性シリカ分散液を得た。
【００９４】
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、塗工液の評価を表２に示した。
【００９５】
実施例５
カチオン性樹脂として、平均分子量７，０００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５０重量％）とする以外は、実施例１と同様にして、カチオン性樹脂変性シリカ分散液を得た。
【００９６】
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、塗工液の評価を表２に示した。
【００９７】
実施例６
カチオン性樹脂として、平均分子量４，０００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５０重量％）とする以外は、実施例１と同様にして、カチオン性樹脂変性シリカ分散液を得た。
【００９８】
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、塗工液の評価を表２に示した。
【００９９】
実施例７
シリカスラリーのｐＨが４．５で一定になるように、イオン交換水に湿式シリカ粉と２Ｎ硫酸を同時に徐々に添加する以外は、実施例３と同様にしてカチオン性樹脂変性シリカ分散液を得た。
【０１００】
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、塗工液の評価を表２に示した。
【０１０１】
実施例８
平均分子量４，０００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重量％）１，５００ｇに比表面積が２８０ｃｍ^２／ｇの湿式シリカ粉（トクヤマ製、ファインシールＸ−３７Ｂ）５００ｇ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）で分散することにより、ｐＨが４．２のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１０２】
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、塗工液の評価を表２に示した。
【０１０３】
実施例９
平均分子量４，０００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２８重量％）１８０ｇに、シリカケークＡ１，６７０ｇを徐々に添加し、続いて比表面積が２８０ｇ／ｍ^２の湿式シリカ粉（トクヤマ製、ファインシールＸ−３７Ｂ）を２５０ｇ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・分散することにより、ｐＨが４．２のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１０４】
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、塗工液の評価を表２に示した。
【０１０５】
実施例１０
実施例１と同様にして、ｐＨが４．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量４，０００のジアリルジメチルアンモニウムクロライド重合物（カチオン性樹脂濃度５０重量％）１００ｇ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、ｐＨが３．６のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１０６】
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、塗工液の評価を表２に示した。
【０１０７】
実施例１１
実施例３と同様にして、ｐＨが４．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量４，０００のジアリルジメチルアンモニウムクロライド重合物（カチオン性樹脂濃度５０重量％）１００ｇ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、ｐＨが３．５のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１０８】
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、塗工液の評価を表２に示した。
【０１０９】
実施例１２
イオン交換水１，５００ｇに、比表面積２８０ｇ／ｍ^２の湿式シリカ粉（トクヤマ製、ファインシールＸ−３７Ｂ）５００ｇと平均分子量４，０００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５０重量％）１００ｇを同時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、ｐＨ４．３のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１１０】
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、塗工液の評価を表２に示した。
【０１１１】
実施例１３
シリカスラリーのｐＨが４．５で一定になるように、イオン交換水に湿式シリカ粉と２Ｎ硫酸を同時に徐々に添加する以外は、実施例３と同様にしてｐＨが４．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量４，０００のジアリルジメチルアンモニウムクロライド重合物（カチオン性樹脂濃度５０重量％）１００ｇ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、ｐＨが３．５のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１１２】
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、塗工液の評価を表２に示した。
【０１１３】
比較例１
実施例１と同様にして、ｐＨ４．５のシリカ分散液を得た。
【０１１４】
このシリカ分散液２，０００ｇを平均分子量２０，０００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５０重量％）１００ｇ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）で混合を試みたが、混合途中に強固にゲル化し、再分散が不可能となった。
【０１１５】
比較例２
実施例１と同様にして、ｐＨ４．５のシリカ分散液を得た。
【０１１６】
このシリカ分散液２，０００ｇを平均分子量５，０００のアリルアミン塩酸塩重合物（カチオン性樹脂濃度５０重量％）１００ｇ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）で混合を試みたが、混合途中に強固にゲル化し、再分散が不可能となった。
【０１１７】
比較例３
実施例１と同様にして、ｐＨが４．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量２０，０００のジアリルジメチルアンモニウムクロライド重合物（カチオン性樹脂濃度５０重量％）１００ｇ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、ｐＨが３．５のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化処理を試みたが、滞留時間２分の時点で分散液が強固にゲル化し、微粒化処理が不可能となった。
【０１１８】
比較例４
実施例１と同様にして、ｐＨが４．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量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５０重量％）１００ｇ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、ｐＨが３．５のカチオン性樹脂を含有するシリカスラリーを得ることを試みたが、混合途中にシリカスラリーが強固にゲル化し、再分散が不可能となった。
【０１１９】
比較例５
ｐＨ調整剤を添加しない以外は、実施例１と同様にして、シリカスラリーを得た。シリカスラリーのｐＨは５．８であった。このシリカスラリーを実施例１と同じ条件で微粒化処理することを試みたが、滞留時間４分の段階で分散液が強固にゲル化し、引き続き微粒化処理を行うことが不可能となった。
【０１２０】
比較例６
イオン交換水１，５００ｇに、比表面積が３００ｍ^２／ｇの乾式シリカ粉（トクヤマ製、レオロシールＱＳ３０）５００ｇ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）で分散することにより、ｐＨが３．５のシリカスラリーを得た。このシリカスラリー２，０００ｇを分子量４，０００のジアリルジメチルアンモニウムクロライド重合物（カチオン性樹脂濃度５０重量％）１００ｇ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、ｐＨが２．３のカチオン性樹脂を含有するシリカスラリーを得た。このシリカスラリーを湿式メディア型粉砕機（コトブキ技研工業製、スーパーアペックスミルＳＡＭ−１）を用いて、ビーズ径０．３ｍｍφ、ビーズ充填率８０％、ローター周速１０ｍ／ｓｅｃ、液温度３０℃の条件で微粒化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。
【０１２１】
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、塗工液の評価を表２に示した。
【０１２２】
比較例７
乾式シリカとして、比表面積が２００ｍ^２／ｇの乾式シリカ粉（トクヤマ製、レオロシールＱＳ１０２）を用いる以外は比較例６と同様にして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、塗工液の評価を表２に示した。
【０１２３】
【表１】

【０１２４】
【表２】

【０１２５】
実施例１〜１３で得られた本発明のカチオン性樹脂変性シリカ分散液を用いて調製した塗工液は、いつ塗工液を調製しても塗工液粘度が低い値で安定しており、且つ、該塗工液を塗工した塗工層は、いずれも光沢性、インク吸収性、耐水性に優れていた。
【０１２６】
また、本発明の製造方法によれば、カチオン性樹脂として平均分子量１万以下の環状アンモニウム塩型のカチオン性樹脂を用いることで、カチオン性樹脂変性シリカ分散液中のシリカ濃度が２２重量％超であっても、製造途中にゲル化することなく、本発明のカチオン性樹脂変性シリカ分散液を得ることができ、得られた該分散液中のシリカの平均粒子径も０．５μｍ未満であることが確認された。
【０１２７】
一方、比較例１〜５では、製造途中に分散液全体がゲル化してしまい、分散液中のシリカ濃度が２２重量％超であり、シリカの平均粒子径が０．５μｍ未満であるカチオン性樹脂シリカ分散液を得ることができなかった。
【０１２８】
また、比較例６〜７で得られた乾式シリカを原料としたカチオン性樹脂変性シリカ分散液を用いて調製した塗工液は、バインダーを混合する時期によって塗工液粘度が不安定であり、且つ、該塗工液を塗工した塗工層は、湿式シリカを原料とした本発明のカチオン性樹脂変性シリカ分散液と比較して、若干インク吸収性が低かった。
【０１２９】
【発明の効果】
以上の説明からも理解されるように、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１万以下の環状アンモニウム塩型のカチオン性樹脂にすることにより、該分散液中のシリカ濃度が２２重量％超であり、湿式シリカ粒子の平均粒子径が０．５μｍ未満でありながら、製造途中にゲル化せずに安定して得られるため、光沢性、インク吸収性、耐水性に優れたインクジェット用記録紙の塗工液の原料などに好適に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention includes various coating agents, semiconductor wafers, and the like for imparting gas barrier properties, corrosion resistance, hydrophilicity, glossiness, liquid absorption, insulation, etc. to recording paper for ink jet, film, resin, glass, metal, etc. The present invention relates to a novel wet silica dispersion useful for the preparation of IC abrasives, emulsion stabilizers and the like.
[0002]
[Prior art]
Inkjet recording paper has a coating layer that is an ink absorption layer for absorbing ink on one or both sides of a base paper. As a coating liquid raw material for forming the coating layer, wet silica and Dry silica or the like is used (see, for example, Patent Documents 1, 2, and 3).
[0003]
On the other hand, in general, anionic compounds are often used as inks for ink jets, and the above-mentioned coating layer has a cationic property to improve image density and water resistance of ink jet recording paper. Is advantageous.
[0004]
However, silica used as a coating liquid raw material has a problem in image density and water resistance because particles exhibit anionic properties. Therefore, as an improvement measure, a coating layer for applying a coating liquid containing silica and a cationic resin containing a cationic group such as a quaternary ammonium base has been proposed (see, for example, Patent Documents 4 and 5).
[0005]
However, in recent years, since there is a demand for inkjet recording paper that can obtain image quality similar to photographs, it is possible to obtain a coating layer that is excellent in glossiness in addition to the aforementioned water resistance and ink absorbability. A coating solution is desired.
[0006]
Among the silicas used as coating liquid raw materials, dry silica obtained by burning a silane-based gas such as silicon tetrachloride in an oxyhydrogen flame is excellent in dispersibility in a polar solvent. It is easy to atomize the average particle size of dry silica to submicron order even in the working fluid. The surface of the coating layer to which the coating liquid containing silica is applied has excellent smoothness and glossiness as the average particle diameter of the silica particles in the coating liquid is smaller. Therefore, the coating liquid containing dry silica has the advantage of high gloss. The average particle size refers to the average aggregated particle size of silica aggregated particles formed by collecting primary silica particles.
[0007]
However, dry silica has a problem that ink absorbency is lower than that of wet silica and image quality similar to that of photographs cannot be printed at high speed.
[0008]
Moreover, although the coating liquid containing a silica is obtained by mixing the silica slurry which disperse | distributed the silica in the polar solvent, and binders, such as polyvinyl alcohol aqueous solution (for example, refer patent document 6), the coating liquid containing dry-type silica is obtained. In this case, the viscosity of the coating liquid obtained by mixing the silica slurry immediately after the dry silica is dispersed in the polar solvent and the binder, and the silica slurry several days after the dry silica is dispersed in the polar solvent. This causes a phenomenon that the viscosities of the coating liquids obtained by mixing the binder and the binder are remarkably different (for example, see Patent Document 7). When the coating solution viscosities are extremely different as described above, the conditions for coating on the base paper by the coating machine, that is, the coating conditions cannot be made constant, causing a big problem in manufacturing process management.
[0009]
On the other hand, silica slurry in which wet silica obtained by precipitation by reaction of sodium silicate and mineral acid is dispersed in a polar solvent has a low viscosity of the coating solution obtained whenever it is mixed with a binder and is stable. It has the advantage of being.
[0010]
Further, as described above, wet silica has an advantage that ink absorbency is higher than that of dry silica.
[0011]
However, since wet silica particles have a strong cohesiveness between primary particles, there is a problem that large aggregated particles are easily formed in the coating liquid, the average particle diameter is large, and gloss is low.
[0012]
As a measure to solve the above problem, a silica slurry in which wet silica is dispersed in a polar solvent and a cationic resin are mixed, and the silica particle surface is cationized with a cationic resin, and then the wet silica agglomerated particles in the dispersion are mixed. There has been proposed a method of producing a cationic resin-modified silica dispersion having a small average particle diameter by mechanically atomizing to submicron order (see, for example, Patent Documents 8, 9, and 10).
[0013]
However, the silica concentration in the above-mentioned cationic resin-modified silica dispersion using wet silica obtained by the prior art as a raw material cannot exceed 22% by weight, and a sufficient thickness can be obtained by one coating. The coating layer is not obtained, a great amount of energy is consumed to dry after coating, and the distribution cost is increased. Therefore, the wet silica concentration in the silica dispersion is increased. It was anxious to do.
[0014]
However, using conventional technology, a cationic resin-modified silica dispersion having a silica concentration of more than 22% by weight and an average particle size of silica in the dispersion of the order of submicron is manufactured using wet silica as a raw material. Even when trying to do so, phenomena such as aggregation and gelation occurred during the production, and a satisfactory cationic resin-modified silica dispersion could not be obtained.
[0015]
[Patent Document 1]
JP-A-55-51583
[Patent Document 2]
JP 56-144853 A
[Patent Document 3]
JP 60-204390 A
[Patent Document 4]
JP-A 61-43593
[Patent Document 5]
Japanese Patent Laid-Open No. 62-268682
[Patent Document 6]
JP 59-185690 A
[Patent Document 7]
Japanese Patent Laid-Open No. 2003-94796
[Patent Document 8]
JP-A-10-181190
[Patent Document 9]
JP 2000-239536 A
[Patent Document 10]
JP 2002-47454 A
[0016]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to prepare wet coating silica as a raw material, when the silica concentration is more than 22% by weight, and when used as a raw material for an inkjet recording paper coating liquid, any time a coating liquid is prepared. To provide a cationic resin-modified silica dispersion capable of obtaining a coating liquid having a stable viscosity and capable of obtaining a coating layer having excellent water resistance, ink absorbability, and gloss, and a method for producing the same. It is in.
[0017]
[Means for Solving the Problems]
As a result of intensive research to solve the above problems, the present inventors have mixed and dispersed an average molecular weight of 10,000 or less and a cyclic ammonium salt type cationic resin and wet silica in a polar solvent. Even when the silica concentration is more than 22% by weight, a coating solution having a stable viscosity can be obtained even when a binder is mixed without causing a phenomenon such as gelation during the production. The coating layer obtained by coating has found that a cationic resin-modified silica dispersion having excellent water resistance, ink absorbability, and glossiness can be obtained, and the present invention has been completed.
[0018]
That is, the present invention is a dispersion in which wet silica and a cationic resin are dispersed in a polar solvent, the silica concentration in the dispersion is more than 22% by weight, and the silica particles in the dispersion A cationic resin-modified silica dispersion, wherein the cationic resin is a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less, and a polar solvent In addition, a silica concentration exceeding 22% by weight obtained by mixing, dispersing, and atomizing a wet type silica and a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less, and the average particle size of the silica particles is 0.00. This is a method for producing a cationic resin-modified silica dispersion having a size of less than 5 μm.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The wet silica used in the present invention is a wet silica powder also called “white carbon” obtained by precipitating silica in a solution by neutralizing sodium silicate with a mineral acid. In addition, wet silica cake that does not undergo a drying step after filtration or washing after the neutralization reaction is softer than the wet silica powder that has undergone the drying step, and therefore has good dispersibility and is preferably used as wet silica. Is done. However, since the wet silica cake has a higher moisture content as the specific surface area increases, the wet silica powder and wet silica cake are mixed to increase the silica concentration in the silica dispersion and to improve the dispersibility. Then, it may be used as wet silica.
[0020]
In the present invention, the average particle diameter of silica in the cationic resin-modified silica dispersion is required to be less than 0.5 μm. When the average particle diameter of silica is 0.5 μm or more, there is a problem that when the raw material of the coating liquid for inkjet recording paper is used, the smoothness of the surface of the coating layer cannot be obtained and the gloss is insufficient. When a cationic resin-modified silica dispersion having an average particle diameter of silica of less than 0.5 μm is used as a raw material for a coating liquid for inkjet recording paper, smoothness of the coating layer surface is obtained and glossiness is increased. The average particle size of silica in the cationic resin-modified silica dispersion is preferably 0.05 μm to 0.4 μm, more preferably 0.05 μm to 0.2 μm, in order to achieve both glossiness and ink absorbability at a high level. It is.
[0021]
In the present invention, the average particle diameter refers to the average particle diameter of the silica aggregate particles in the cationic resin-modified silica dispersion, and is a volume-based arithmetic average diameter D as measured by a light scattering diffraction type particle size distribution meter. ₅₀ That is.
[0022]
The cationic resin used in the present invention is a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less. Using a cyclic ammonium salt type cationic resin with an average molecular weight exceeding 10,000, when a cationic resin-modified silica dispersion having a silica concentration in the dispersion of more than 22% by weight is produced, silica particles are aggregated during the production. Then, the entire silica dispersion is agglomerated. In addition, when it is not a cyclic ammonium salt type cationic resin, for example, when using a quaternary ammonium salt type cationic resin such as a methacrylic acid ester methyl chloride polymer, an allylamine hydrochloride polymer, an allylamine polymer, Even if the average molecular weight is 10,000 or less, when a cationic resin-modified silica dispersion having a silica concentration of more than 22% by weight in the dispersion is produced, the silica particles are aggregated during the production, and the entire silica dispersion is aggregated. To do.
[0023]
That is, by using a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less, a cationic resin-modified silica having a silica concentration of more than 22% by weight without causing a phenomenon such as gelation during the production. It becomes possible to produce the dispersion stably. The average molecular weight of the cyclic ammonium salt type cationic resin is preferably 1,000 to 8,000.
[0024]
In the present invention, the average molecular weight is a polyethylene conversion value determined from gel permeation chromatography.
[0025]
The cyclic ammonium salt type cationic resin used in the present invention is a cyclic ammonium salt type cationic resin obtained by polymerizing a diallylammonium salt and a derivative thereof, and specific examples thereof include the following formula (1) or Polymer of diallylammonium salt having a repeating unit represented by formula (2) and a derivative thereof, copolymer of 10 to 90 mol% of a repeating unit represented by formula (1) or formula (2), and diallylammonium salt and a derivative thereof Mention may be made of copolymers having 90 to 10 mol% of repeating units based on possible monomers.
[0026]
[Chemical 1]

[0027]
In Formula (1) and Formula (2), R ¹ And R ² Represents a hydrogen atom or a methyl group.
[0028]
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.
[0029]
In the present invention, a particularly preferred cationic resin is a compound having an average molecular weight of 1,000 to 8,000 and having a repeating unit represented by the above formula (1) or (2) and a derivative thereof. From a copolymer, a copolymer having 10 to 90 mol% of repeating units represented by formula (1) or formula (2) and 90 to 10 mol% of repeating units based on a monomer copolymerizable with diallylammonium salt and derivatives thereof One kind of selected cationic resin or a mixture of two or more kinds of cationic resins.
[0030]
In the present invention, the amount of the cationic resin used is such that the cationic resin-modified silica dispersion can be stably produced without gelation during the production, and the viscosity of the obtained cationic resin-modified silica dispersion is lowered. Therefore, it is preferable to set it as 2-50 weight part with respect to 100 weight part of silica, especially 2-15 weight part. When the viscosity of the cationic resin-modified silica dispersion is low, it is very preferable because the handling property is improved in the subsequent production process for producing the coating liquid.
[0031]
The viscosity of the cationic resin-modified silica dispersion with respect to the addition amount of the cationic resin varies depending on the specific surface area of the silica and the type of the cationic resin to be added. It is preferable to select the addition amount 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 wet 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-mentioned polar solvent 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 silica concentration in the cationic resin-modified silica dispersion is more than 22% by weight.
[0035]
When the silica concentration in the silica dispersion is lowered, as described above, it may be difficult to form a coating layer having a sufficient thickness by a single coating in the coating process after the coating liquid is prepared. Also, there are problems in terms of deterioration of energy efficiency and distribution cost when drying after coating.
[0036]
The cationic resin-modified silica dispersion of the present invention can be produced by mixing, dispersing and atomizing a polar solvent, wet silica and a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less.
[0037]
Using a cyclic ammonium salt type cationic resin having an average molecular weight exceeding 10,000 as the cationic resin, and producing a cationic resin-modified silica dispersion having a silica concentration of more than 22% by weight, Silica particles agglomerate and the entire silica dispersion agglomerates. In addition, when it is not a cyclic ammonium salt type cationic resin, for example, when using a quaternary ammonium salt type cationic resin such as a methacrylic acid ester methyl chloride polymer, an allylamine hydrochloride polymer, an allylamine polymer, Even if the average molecular weight is 10,000 or less, when a cationic resin-modified silica dispersion having a silica concentration of more than 22% by weight in the dispersion is produced, the silica particles are aggregated during the production, and the entire silica dispersion is aggregated. To do.
[0038]
As a preferred method for producing a cationic resin-modified silica dispersion by mixing, dispersing, and atomizing wet silica and a cationic resin in a polar solvent, (1) a silica slurry in which wet silica is dispersed in a polar solvent is used as a wet medium. After preparing a silica dispersion in which the average particle size of the silica particles in the silica slurry is atomized to less than 0.5 μm using a mold grinder, the mixture is mixed with a cationic resin to prepare a premixed solution, and a high-pressure homogenizer A method of atomizing silica particles in a premixed liquid until the average particle size is less than 0.5 μm, (2) silica slurry in which polar solvent, wet silica and cationic resin are mixed and dispersed, A method of atomizing the silica particles in the silica slurry to an average particle size of less than 0.5 μm using a mold disperser can be mentioned.
[0039]
In the present invention, the silica slurry is a dispersion of wet silica in a polar solvent, and refers to the one before the average particle size of the silica particles is atomized to less than 0.5 μm, including a cationic resin. Even in the state, the material before atomization is expressed as silica slurry. The silica dispersion refers to those obtained by atomization until the average particle size of the silica particles in the silica slurry is less than 0.5 μm, but does not include those containing a cationic resin. The premixed liquid refers to a mixture of a silica dispersion and a cationic resin. Further, the cationic resin-modified silica dispersion refers to a silica slurry containing a cationic resin or a premixed liquid after atomization, and silica particles having an average particle diameter of less than 0.5 μm and a cationic resin. Contains.
[0040]
As the wet silica for obtaining the silica slurry, the above-mentioned wet silica powder or a wet silica cake that is not subjected to a drying step after filtration or washing after the neutralization reaction can be used. Since the wet silica cake has softer aggregated particles than the wet silica powder subjected to the drying step, it has good dispersibility and can be preferably used as wet silica. However, since the wet silica cake has a higher moisture content as the specific surface area becomes higher, when the wet silica cake is used as the wet silica, the silica concentration in the silica dispersion is increased to more than 22% by weight, and the dispersibility is increased. In order to improve the quality, it is preferable to mix wet silica powder and wet silica cake and use them as wet silica. Moreover, in that case, it is preferable to add wet silica powder to a polar solvent and then add wet silica powder and mix to obtain a silica slurry, because a silica slurry with a high silica concentration can be obtained efficiently.
[0041]
After preparing the silica dispersion in which the silica slurry in which the wet silica is dispersed in the polar solvent of (1) above is atomized to less than 0.5 μm in average particle diameter of the silica particles in the silica slurry by a wet media type pulverizer By mixing with a cationic resin to prepare a premixed liquid, and further using a high-pressure homogenizer, the silica concentration in the premixed liquid is atomized until the average particle diameter is less than 0.5 μm, thereby obtaining a silica concentration. In the method of obtaining a cationic resin-modified silica dispersion of more than 22% by weight, first, wet silica is dispersed in a polar solvent to obtain a silica slurry having a silica concentration of more than 22% by weight.
[0042]
In order to stably produce a cationic resin-modified silica dispersion having a silica concentration of more than 22% by weight without gelation during the production of the silica slurry and during the subsequent atomization of the silica slurry, It is preferable to adjust the pH to be less than 5.
[0043]
As a method for adjusting the pH of the silica slurry to less than 5, after adjusting the pH by previously adding a mineral acid such as sulfuric acid to a polar solvent, wet silica is dispersed in the polar solvent, or wet silica and sulfuric acid. A method of preparing a silica slurry by dispersing wet silica in a polar solvent while simultaneously adjusting pH by adding a mineral acid such as the above.
[0044]
A disperser used when preparing a silica slurry having a pH of less than 5 by dispersing wet silica in a polar solvent is not particularly limited, but a high speed such as a general stirrer having a propeller blade, a turbine blade, a paddle blade, a disper mixer, etc. High-speed rotary shear type stirrers such as rotary centrifugal radiation type stirrers, homogenizers, homomixers, ultra mixers, dispersers such as colloid mills, planetary mixers, suction type dispersers, and the above high-speed rotary shear type stirrers and propeller blades Examples thereof include a composite disperser combining paddle blades, a composite disperser combining a planetary mixer and a high-speed rotating centrifugal radiation stirrer, or a high-speed shear stirrer.
[0045]
In the above method (1), the silica slurry having a pH of less than 5 is then atomized to an average particle size of silica particles of less than 0.5 μm to obtain a silica dispersion.
[0046]
It is preferable to use a wet media type pulverizer as the atomizer used when preparing the silica dispersion by atomizing the average particle diameter of the silica particles in the silica slurry to less than 0.5 μm.
[0047]
The wet media type pulverizer is a pulverizer using beads having an average particle diameter of about 0.05 to 3 mmφ as a pulverization medium. Specifically, a representative example is a product name manufactured by Nikkato; Pot Mill, manufactured by Inoue Seisakusho. Product name: Product name made by Mighty Mill, Aimex; Product name made by Viscomil, Ashizawa; Product name made by Agitator Mill, Kotobuki Giken Kogyo; Product name made by Super Apex Mill, Ultra Apex Mill and Willie et Bacchofen; And so on.
[0048]
As the atomization apparatus that can be used for atomizing the average particle diameter of wet silica particles in a polar solvent to less than 0.5 μm, there are an ultrasonic disperser and a high-pressure homogenizer in addition to a wet media type pulverizer. However, an ultrasonic disperser is not suitable for mass production, and a high-pressure homogenizer is not preferable because it takes a long time to atomize until the target particle size is reached, resulting in poor productivity.
[0049]
When atomizing hard oxides with hard agglomerated particles such as wet silica, a wet media type pulverizer that employs the principle of pulverization and pulverization by the impact action between the pulverization media and the object to be crushed is suitable. Yes.
[0050]
For the wetted part of the wet media type pulverizer, a material having high wear resistance with respect to silica such as a ceramic mainly composed of zirconia or alumina, or a polyurethane or polyethylene resin is preferable. The pulverization media used may be known pulverization media. Among them, zirconia beads are preferable from the viewpoint of hardness.
[0051]
In the method (1), the silica dispersion obtained by the above method is then mixed and dispersed with a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less to obtain a premixed solution. .
[0052]
The method of mixing the silica dispersion and the cationic resin is not particularly limited, but a method of adding the silica dispersion to the aqueous solution of the cationic resin and mixing is preferable. The mixer used to prepare the pre-mixed liquid by mixing and dispersing the silica dispersion and the cationic resin is not particularly limited, but the above-mentioned general stirrer, high-speed centrifugal centrifugal type stirrer, high-speed rotary shear type Examples thereof include a disperser such as a stirrer, a colloid mill, a planetary mixer, and a suction disperser, and a composite disperser in which the above dispersers are combined.
[0053]
The silica particles in the premixed solution obtained by the above method are re-agglomerated by the cationic resin, and the average particle size is 0.5 μm or more. Therefore, the premixed liquid is further atomized to obtain the cationic resin-modified silica dispersion of the present invention.
[0054]
A high-pressure homogenizer is used as a disperser used for preparing a cationic resin-modified silica dispersion by further atomizing the premixed solution.
[0055]
Specific examples of high-pressure homogenizers include nanomizer product names; nanomizer, microfluidics product names; microfluidizers, and Sugino Machine optimizers.
[0056]
By making the preliminary mixed solution collide with each other at a processing pressure of 30 MPa or more using the above-described high-pressure homogenizer, or by passing the orifice under a condition where the differential pressure between the inlet side and the outlet side of the orifice is 30 MPa or more, the productivity is improved. A cationic resin-modified silica dispersion containing more than 22% by weight of silica particles having an average particle size of less than 0.5 μm can be obtained.
[0057]
In the premixed liquid obtained by mixing and dispersing the silica dispersion having an average particle diameter of less than 0.5 μm and a cationic resin, reaggregation of the silica particles occurs as described above, and this is further atomized. When trying to make it, there exists a tendency for a viscosity to fall, after a viscosity rises rapidly. If you try to further atomize a premixed liquid whose viscosity changes suddenly in this way, especially a premixed liquid whose viscosity suddenly rises once in the middle with a wet media type pulverizer, the operating conditions are very It is not preferable because it becomes difficult. The high-pressure homogenizer is very suitable for atomization of the premixed liquid whose viscosity changes rapidly.
[0058]
In the present invention, a temperature at which wet silica is dispersed in a polar solvent to obtain a silica slurry, a temperature at which the silica slurry is atomized to obtain a silica dispersion, the silica dispersion and the cationic resin are mixed. The temperature at which the premixed liquid is obtained by dispersion and the temperature at which the premixed liquid is atomized (hereinafter also referred to as the dispersion manufacturing temperature) are stable without causing thickening or gelation during the manufacturing process. Therefore, in any case, it is preferable to control in a temperature range of 40 ° C. or lower.
[0059]
The method for controlling the dispersion production temperature within the temperature range of 40 ° C. or lower is not particularly limited, but it is preferable to control the dispersion liquid production temperature to be an arbitrary constant temperature within the temperature range of 40 ° C. or lower.
[0060]
The silica slurry obtained by mixing and dispersing the polar solvent, wet silica and cationic resin in (2) above is used with a wet media type disperser so that the silica particles in the silica slurry have an average particle size of less than 0.5 μm. In the method of obtaining a cationic resin-modified silica dispersion by atomizing to a low molecular weight, first, a polar solvent, wet silica and a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less are mixed and dispersed to obtain a silica concentration. A silica slurry of more than 22% by weight is obtained.
[0061]
As a method of obtaining a silica slurry, (i) a cyclic ammonium salt type having an average molecular weight of 10,000 or less by mixing and dispersing a polar solvent, wet silica and a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less at a time. A method of preparing a silica slurry containing a cationic resin, (ii) mixing and dispersing wet silica in a polar solvent to form a silica slurry, and then mixing with a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less A method of dispersing and preparing a silica slurry containing a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less can be mentioned.
[0062]
In both methods (i) and (ii), the pH of the silica slurry before the atomization of the silica to an average particle size of less than 0.5 μm is adjusted to less than 5 regardless of the presence or absence of a cationic resin. It is preferable to do this. By adjusting the pH of the silica slurry to less than 5, the cationic resin-modified silica having a silica concentration of more than 22% by weight without causing a phenomenon such as gelation during the production of the silica slurry and during the subsequent atomization of the silica slurry. It becomes possible to produce the dispersion stably.
[0063]
In the method (i) for obtaining the silica slurry, as a method for adjusting the pH of the silica slurry to less than 5, after adding a cationic resin to the polar solvent in advance to adjust the pH to less than 5, Examples thereof include a method of dispersing wet silica and a method of simultaneously adding wet silica and a cationic resin to a polar solvent and adjusting the pH while dispersing the wet silica in the polar solvent.
[0064]
In the method (ii) for obtaining a silica slurry, as a method for adjusting the pH of the silica slurry before mixing the cationic resin to less than 5 in the method for producing the cationic resin-modified silica dispersion of (1) above. As described above, after adjusting the pH by adding a mineral acid such as sulfuric acid to a polar solvent in advance, a method of dispersing wet silica in the polar solvent, adding wet silica and a mineral acid such as sulfuric acid simultaneously. A method of dispersing wet silica in a polar solvent while adjusting the pH can be mentioned.
[0065]
Furthermore, the method of obtaining a silica slurry containing a cationic resin by mixing and dispersing a silica slurry not containing a cationic resin having a pH adjusted to less than 5 and a cationic resin is not particularly limited. Can be added to the cationic resin aqueous solution and mixed / dispersed, and the silica slurry and the cationic resin aqueous solution can be added simultaneously and mixed / dispersed.
[0066]
The disperser used for preparing the silica slurry is not particularly limited regardless of the presence or absence of the cationic resin. However, the above-mentioned general stirrer, high-speed rotating centrifugal radiation stirrer, high-speed rotating shear stirrer, colloid mill, planetary Examples thereof include a disperser such as a mixer and a suction disperser, and a composite disperser in which the above dispersers are combined.
[0067]
In the method for producing the cationic resin-modified silica dispersion of (2) above, the silica slurry containing the cationic resin obtained by the above method is then treated with an average particle size of 0 in the silica slurry. The cationic resin-modified silica dispersion of the present invention is obtained by atomizing to less than 5 μm.
[0068]
As the atomizing device used for atomizing the silica slurry containing the cationic resin to prepare the cationic resin silica dispersion, the above-mentioned wet media type pulverizer can be used.
[0069]
In the present invention, the temperature at which a polar solvent, wet silica and a cationic resin are mixed and dispersed to obtain a silica slurry, and the wet silica particles in the silica slurry are atomized to an average particle size of less than 0.5 μm to modify the cationic resin. The temperature at which the silica dispersion is obtained (hereinafter also referred to as the dispersion production temperature) is 40 ° C. in any case in order to produce it stably without causing thickening or gelation during the production. It is preferable to control in the following temperature range.
[0070]
The method for controlling the dispersion production temperature within the temperature range of 40 ° C. or lower is not particularly limited, but it is preferable to control the dispersion liquid production temperature to be an arbitrary constant temperature within the temperature range of 40 ° C. or lower.
[0071]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0072]
The wet silica cake was prepared by the following method, the physical properties of the cationic resin-modified silica dispersion were measured, and the performance of the coating solution prepared from the cationic resin-modified silica dispersion was evaluated.
[0073]
(1) Preparation of silica cake
(1-1) Preparation of silica cake A
Commercially available sodium silicate and pure water were charged into the reaction vessel so that the concentration of sodium silicate was 5% by weight. The temperature of the reaction vessel was set to 40 ° C., neutralization reaction (up to a neutralization rate of 50%) was performed using 22 wt% sulfuric acid, and then the temperature of the reaction solution was set to 95 ° C. The sulfuric acid was added to the reaction solution until the neutralization rate reached 100%. Filtration and washing operations were repeated on the produced silica to obtain silica cake A (silica content 15% by weight). The specific surface area of the silica obtained by drying the silica cake A is 280 m. ² / G.
[0074]
(1-2) Preparation of silica cake B
Commercially available sodium silicate and pure water were charged into the reaction vessel so that the concentration of sodium silicate was 5% by weight. The temperature of the reaction vessel was set to 40 ° C., neutralization reaction (up to a neutralization rate of 25%) was performed using 22% by weight sulfuric acid, and then the temperature of the reaction solution was set to 95 ° C. The sulfuric acid was added to the reaction solution until the neutralization rate reached 100%. Filtration and washing operations were repeated on the produced silica to obtain silica cake B (silica content 18% by weight). The specific surface area of the silica obtained by drying the silica cake B is 200 m. ² / G.
[0075]
(2) Physical property measurement of cationic resin silica dispersion
(2-1) Viscosity measurement
300 g of the cationic resin-modified silica dispersion was collected in a 500 ml container, and stirred at 20,000 rpm for 5 minutes using a homogenizer (manufactured by Squid, Ultra Tarrax T-25). 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).
[0076]
(2-2) pH measurement
A silica slurry or 300 g of a cationic resin-modified silica dispersion was collected in a 500 ml container, and stirred at 20,000 rpm for 5 minutes using a homogenizer (manufactured by Squid, Ultra Turrax T-25). Next, after putting in a 30 degreeC thermostat for 10 minutes, the pH of a silica slurry and a cationic resin modified silica dispersion was measured using the pH meter (Horiba, F-22).
[0077]
(2-3) Measurement of average particle diameter
After the dispersion was diluted with ion-exchanged water so that the silica concentration of the cationic resin-modified silica dispersion was 10% by weight, a light scattering diffraction type particle size distribution analyzer (Coulter, Coulter LS-230) was used. Use volume-based arithmetic mean diameter D ₅₀ And this value was adopted as the average particle size.
In the measurement, the refractive index of water (dispersion medium) 1.332 and the refractive index of silica 1.458 were input as parameters.
[0078]
(3) Performance evaluation of coating liquid
(3-1) Preparation method of coating liquid
After diluting the cationic resin-modified silica dispersion with ion-exchanged water so that the silica concentration is 20% by weight, the diluted cationic resin-modified silica dispersion and a 10% by weight polyvinyl alcohol aqueous solution (manufactured by Kuraray, PVA120) The mixture was stirred and mixed with a propeller mixer so that the silica: polyvinyl alcohol solid content ratio = 2: 1 was obtained.
[0079]
(3-2) Viscosity measurement of coating liquid
Using the cationic resin-modified silica dispersion immediately after the preparation, and the cationic resin-modified silica dispersion 7 days after the preparation in which the cationic resin-modified silica dispersion was stored for 7 days at a storage temperature of 25 ° C., (3- Prepare coating solutions by the method of 1), collect 90 g of each coating solution in a 100 ml container, put it in a thermostatic bath at 30 ° C. for 10 minutes, and then use a B-type viscometer (manufactured by Tokimec, BL). The viscosity of the coating solution was measured under the condition of 60 rpm.
[0080]
(3-3) Method for creating inkjet recording sheet (coating layer)
Using the film coater (PI-1210 Film Coater made by Tester Sangyo), the coating amount obtained in (3-1) was 20 g / m. ² After coating on the surface of a PET sheet (MELINEX 705, manufactured by ICI Japan), a coating layer was formed on the PET sheet to obtain an inkjet recording sheet.
[0081]
(3-4) Gloss of coating layer
The 85 ° specular gloss of the coating layer surface of the inkjet recording sheet is measured using a goniophotometer (UGV-5D, manufactured by Suga Test Co., Ltd.) according to the measurement method of JIS Z 8741. The gloss was evaluated according to the following criteria.
A: 85 ° specular gloss 80 or more
○: 85 ° specular gloss 75-80
Δ: 85 ° specular gloss 70-75
×: 85 ° specular gloss 70 or less
[0082]
(3-5) Ink absorbability of coating layer
Time required to perform solid printing with magenta ink using an ink jet printer (manufactured by Epson, PM700C), paste a commercially available high quality paper on the printed surface every 5 seconds immediately after printing, and the ink does not transfer to the high quality paper The liquid absorption of the coating layer was evaluated according to the following criteria.
: Within 10 seconds
○: 15-20 seconds
Δ: 25-30 seconds
×: 35 seconds or more
[0083]
(3-6) Water resistance of coating layer
After printing characters with magenta ink using an inkjet printer (manufactured by Epson, PM700C) and confirming that the ink on the printing surface was sufficiently dried, the inkjet recording sheet after printing was immersed in water, and after 30 seconds The blurred state of the printed characters generated by the ink flowing out was observed with the naked eye.
○: Almost no bleeding of characters is observed.
Δ: Character bleeding is observed.
X: Bleeding of characters is observed in several tens of places.
[0084]
Example 1
After adding 2N sulfuric acid as a pH adjuster to 80 g of ion-exchanged water so that the pH of the silica slurry is 4.5, the solution temperature is maintained at 30 ° C., and 1,670 g of silica cake A is gradually added. Specific surface area of 280 g / m ² The silica slurry having a pH of 4.5 was dispersed by gradually adding 250 g of the wet silica powder (manufactured by Tokuyama, Fine Seal X-37B) with an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd., Ultra Mixer LR-2). Obtained. This silica slurry was subjected to a wet media type pulverizer (manufactured by Kotobuki Giken, Super Apex Mill SAM-1) with a bead diameter of 0.3 mmφ, a bead filling rate of 80%, a rotor peripheral speed of 10 m / sec, and a liquid temperature of 30 ° C. By carrying out atomization treatment under conditions, a silica dispersion having an average particle diameter of 0.25 μm was obtained.
[0085]
While gradually adding 2,000 g of this silica dispersion to 100 g of an aqueous diallyldimethylammonium chloride polymer solution having an average molecular weight of 4,000 (cationic resin concentration of 50% by weight), the liquid temperature was maintained at 30 ° C. (Preliminary liquid mixture was obtained by mixing with (Mizuho Kogyo make, Ultramixer LR-2). A cationic resin-modified silica dispersion was obtained by redispersing the premixed liquid using a high pressure homogenizer (manufactured by Nanomizer, Nanomizer LA-31) under the conditions of a treatment pressure of 80 MPa and a liquid temperature of 30 ° C.
[0086]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0087]
Example 2
After adding 2N sulfuric acid as a pH adjusting agent to 360 g of ion-exchanged water so that the pH of the silica slurry becomes 4.5, the liquid temperature is maintained at 30 ° C., and 1,390 g of silica cake B is gradually added. Specific surface area of 200 g / m ² The silica slurry having a pH of 4.5 was dispersed by gradually adding 250 g of wet silica powder (manufactured by Tokuyama, Fine Seal T-32) with an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd., Ultra Mixer LR-2). Obtained. This silica slurry was subjected to a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) with a bead diameter of 0.3 mmφ, a bead filling rate of 80%, a rotor peripheral speed of 10 m / sec, and a liquid temperature of 30 ° C. By carrying out atomization treatment under conditions, a silica dispersion having an average particle size of 0.23 μm was obtained.
[0088]
While gradually adding 2,000 g of this silica dispersion to 100 g of an aqueous diallyldimethylammonium chloride polymer solution having an average molecular weight of 4,000 (cationic resin concentration of 50% by weight), the liquid temperature was maintained at 30 ° C. (Preliminary liquid mixture was obtained by mixing with (Mizuho Kogyo make, Ultramixer LR-2). A cationic resin-modified silica dispersion was obtained by redispersing the premixed liquid using a high pressure homogenizer (manufactured by Nanomizer, Nanomizer LA-31) under the conditions of a treatment pressure of 80 MPa and a liquid temperature of 30 ° C.
[0089]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0090]
Example 3
After adding 2N sulfuric acid as a pH adjusting agent to 1,500 g of ion-exchanged water so that the pH of the silica slurry is 4.5, the specific surface area is 280 m. ² / G wet silica powder (manufactured by Tokuyama, Fine Seal X-37B) is gradually added while maintaining the liquid temperature at 30 ° C. and dispersed with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2). As a result, a silica slurry having a pH of 4.5 was obtained. This silica slurry was subjected to a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) with a bead diameter of 0.3 mmφ, a bead filling rate of 80%, a rotor peripheral speed of 10 m / sec, and a liquid temperature of 30 ° C. By carrying out atomization treatment under conditions, a silica dispersion having an average particle size of 0.32 μm was obtained.
[0091]
While gradually adding 2,000 g of this silica dispersion to 100 g of an aqueous diallyldimethylammonium chloride polymer solution having an average molecular weight of 4,000 (cationic resin concentration of 50% by weight), the liquid temperature was maintained at 30 ° C. (Preliminary liquid mixture was obtained by mixing with (Mizuho Kogyo make, Ultramixer LR-2). A cationic resin-modified silica dispersion was obtained by redispersing the premixed liquid using a high-pressure homogenizer (Nanomizer LA-31, manufactured by Nanomizer) at a treatment pressure of 80 MPa and a liquid temperature of 30 ° C.
[0092]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0093]
Example 4
Specific surface area of 200m as wet silica powder ² / G wet silica powder (manufactured by Tokuyama, Fine Seal T-32) was used in the same manner as in Example 3 to obtain a cationic resin-modified silica dispersion.
[0094]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0095]
Example 5
A cationic resin-modified silica dispersion was obtained in the same manner as in Example 1 except that the aqueous solution of diallyldimethylammonium chloride polymer having an average molecular weight of 7,000 (cationic resin concentration: 50% by weight) was used as the cationic resin. .
[0096]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0097]
Example 6
Cationic resin-modified silica dispersion as in Example 1 except that the cationic resin is a diallyldimethylammonium chloride-acrylamide copolymer aqueous solution having an average molecular weight of 4,000 (cationic resin concentration: 50% by weight). Got.
[0098]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0099]
Example 7
A cationic resin-modified silica dispersion is obtained in the same manner as in Example 3 except that wet silica powder and 2N sulfuric acid are gradually added simultaneously to ion-exchanged water so that the pH of the silica slurry is constant at 4.5. It was.
[0100]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0101]
Example 8
The specific surface area is 280 cm on 1,500 g of diallyldimethylammonium chloride polymer aqueous solution (cationic resin concentration 3% by weight) having an average molecular weight of 4,000. ² / G wet silica powder (manufactured by Tokuyama, Fine Seal X-37B) is gradually added while maintaining the liquid temperature at 30 ° C., and dispersed with an ultramixer (manufactured by Mizuho Kogyo Co., Ltd., Ultramixer LR-2). As a result, a silica slurry containing a cationic resin having a pH of 4.2 was obtained. This silica slurry was subjected to a wet media type pulverizer (manufactured by Kotobuki Giken, Super Apex Mill SAM-1) with a bead diameter of 0.3 mmφ, a bead filling rate of 80%, a rotor peripheral speed of 10 m / sec, and a liquid temperature of 30 ° C. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0102]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0103]
Example 9
Silica cake A 1,670 g was gradually added to 180 g of diallyldimethylammonium chloride polymer aqueous solution (cationic resin concentration 28% by weight) having an average molecular weight of 4,000, followed by a specific surface area of 280 g / m. ² While gradually adding 250 g of wet silica powder (manufactured by Tokuyama, Fine Seal X-37B), the liquid temperature is maintained at 30 ° C., and mixing and dispersing is performed with an ultra mixer (manufactured by Mizuho Kogyo Co., Ltd., Ultra Mixer LR-2). As a result, a silica slurry containing a cationic resin having a pH of 4.2 was obtained. Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0104]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0105]
Example 10
In the same manner as in Example 1, a silica slurry having a pH of 4.5 was obtained. While gradually adding 2,000 g of this silica slurry to 100 g of diallyldimethylammonium chloride polymer having a molecular weight of 4,000 (cationic resin concentration 50% by weight), the liquid temperature was maintained at 30 ° C. A silica slurry containing a cationic resin having a pH of 3.6 was obtained by mixing with an ultra mixer LR-2). Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0106]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0107]
Example 11
In the same manner as in Example 3, a silica slurry having a pH of 4.5 was obtained. While gradually adding 2,000 g of this silica slurry to 100 g of diallyldimethylammonium chloride polymer having a molecular weight of 4,000 (cationic resin concentration 50% by weight), the liquid temperature was maintained at 30 ° C. A silica slurry containing a cationic resin having a pH of 3.5 was obtained by mixing with an ultra mixer LR-2). Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0108]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0109]
Example 12
Specific surface area of 280 g / m for 1,500 g of ion-exchanged water ² While gradually adding 500 g of wet silica powder (Fukuseal X-37B, manufactured by Tokuyama) and 100 g of diallyldimethylammonium chloride polymer aqueous solution (cationic resin concentration 50% by weight) having an average molecular weight of 4,000, the liquid temperature was adjusted. By maintaining at 30 ° C. and mixing with an ultra mixer (manufactured by Mizuho Kogyo, Ultra Mixer LR-2), a silica slurry containing a cationic resin having a pH of 4.3 was obtained. Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0110]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0111]
Example 13
A silica slurry having a pH of 4.5 was prepared in the same manner as in Example 3 except that wet silica powder and 2N sulfuric acid were gradually added simultaneously to ion-exchanged water so that the pH of the silica slurry was constant at 4.5. Obtained. While gradually adding 2,000 g of this silica slurry to 100 g of diallyldimethylammonium chloride polymer having a molecular weight of 4,000 (cationic resin concentration 50% by weight), the liquid temperature was maintained at 30 ° C. A silica slurry containing a cationic resin having a pH of 3.5 was obtained by mixing with an ultra mixer LR-2). Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0112]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0113]
Comparative Example 1
In the same manner as in Example 1, a silica dispersion having a pH of 4.5 was obtained.
[0114]
While gradually adding 2,000 g of this silica dispersion to 100 g of an aqueous solution of diallyldimethylammonium chloride polymer having an average molecular weight of 20,000 (cationic resin concentration of 50% by weight), the liquid temperature is maintained at 30 ° C. Mixing was attempted with (Mizuho Kogyo's Ultramixer LR-2), but gelation occurred strongly during mixing, making redispersion impossible.
[0115]
Comparative Example 2
In the same manner as in Example 1, a silica dispersion having a pH of 4.5 was obtained.
[0116]
While gradually adding 2,000 g of this silica dispersion to 100 g of an allylamine hydrochloride polymer having an average molecular weight of 5,000 (cationic resin concentration of 50% by weight), the liquid temperature was maintained at 30 ° C. Mixing was attempted with an ultra mixer LR-2) manufactured by Kogyo, but it gelled strongly during mixing, making it impossible to redisperse.
[0117]
Comparative Example 3
In the same manner as in Example 1, a silica slurry having a pH of 4.5 was obtained. While gradually adding 2,000 g of this silica slurry to 100 g of diallyldimethylammonium chloride polymer having a molecular weight of 20,000 (cationic resin concentration 50% by weight), the liquid temperature was maintained at 30 ° C. A silica slurry containing a cationic resin having a pH of 3.5 was obtained by mixing with an ultra mixer LR-2). This silica slurry was subjected to a wet media type pulverizer (manufactured by Kotobuki Giken, Super Apex Mill SAM-1) with a bead diameter of 0.3 mmφ, a bead filling rate of 80%, a rotor peripheral speed of 10 m / sec, and a liquid temperature of 30 ° C. Although the atomization treatment was tried under the conditions, the dispersion liquid gelled strongly at the point of residence time of 2 minutes, and the atomization treatment became impossible.
[0118]
Comparative Example 4
In the same manner as in Example 1, a silica slurry having a pH of 4.5 was obtained. While gradually adding 2,000 g of this silica slurry to 100 g of an allylamine hydrochloride polymer aqueous solution having a molecular weight of 5,000 (cationic resin concentration of 50% by weight), the liquid temperature was maintained at 30 ° C. Manufactured by Ultramixer LR-2), and attempted to obtain a silica slurry containing a cationic resin having a pH of 3.5. It became impossible.
[0119]
Comparative Example 5
A silica slurry was obtained in the same manner as in Example 1 except that no pH adjuster was added. The pH of the silica slurry was 5.8. Attempts were made to atomize this silica slurry under the same conditions as in Example 1, but the dispersion gelled strongly at a stage where the residence time was 4 minutes, making it impossible to carry out atomization.
[0120]
Comparative Example 6
The specific surface area is 300m to 1,500g of ion-exchanged water. ² / G of dry silica powder (manufactured by Tokuyama, Leoroseal QS30) is gradually added while maintaining the liquid temperature at 30 ° C. and dispersed with an ultramixer (manufactured by Mizuho Kogyo, Ultramixer LR-2). A silica slurry with a pH of 3.5 was obtained. While gradually adding 2,000 g of this silica slurry to 100 g of diallyldimethylammonium chloride polymer having a molecular weight of 4,000 (cationic resin concentration 50% by weight), the liquid temperature was maintained at 30 ° C. A silica slurry containing a cationic resin having a pH of 2.3 was obtained by mixing with an ultra mixer LR-2). Using this silica slurry, a wet media type pulverizer (manufactured by Kotobuki Giken Co., Ltd., Super Apex Mill SAM-1) was used. By carrying out atomization treatment under conditions, a cationic resin-modified silica dispersion was obtained.
[0121]
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0122]
Comparative Example 7
Specific surface area of 200m as dry silica ² / G dry silica powder (manufactured by Tokuyama, Leolosil QS102) was used in the same manner as in Comparative Example 6 to obtain a cationic resin-modified silica dispersion.
Table 1 shows the physical properties of the obtained cationic resin-modified silica dispersion, and Table 2 shows the evaluation of the coating solution.
[0123]
[Table 1]

[0124]
[Table 2]

[0125]
The coating liquid prepared by using the cationic resin-modified silica dispersion of the present invention obtained in Examples 1 to 13 is stable at a low viscosity of the coating liquid whenever the coating liquid is prepared. And all the coating layers which apply | coated this coating liquid were excellent in glossiness, ink absorptivity, and water resistance.
[0126]
Further, according to the production method of the present invention, by using a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less as the cationic resin, the silica concentration in the cationic resin-modified silica dispersion exceeds 22% by weight. Even so, the cationic resin-modified silica dispersion of the present invention can be obtained without gelation during the production, and the average particle size of silica in the obtained dispersion is also less than 0.5 μm. It was confirmed.
[0127]
On the other hand, in Comparative Examples 1 to 5, the entire dispersion was gelated during production, the silica concentration in the dispersion was more than 22% by weight, and the average particle diameter of silica was less than 0.5 μm. A silica dispersion could not be obtained.
[0128]
Moreover, the coating liquid prepared using the cationic resin-modified silica dispersion using dry silica obtained in Comparative Examples 6 to 7 as a raw material has an unstable coating liquid viscosity depending on the timing of mixing the binder, In addition, the coating layer coated with the coating solution had a slightly lower ink absorbability than the cationic resin-modified silica dispersion of the present invention using wet silica as a raw material.
[0129]
【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 10,000 or less. The silica concentration is over 22% by weight, and the average particle size of the wet silica particles is less than 0.5 μm, and can be stably obtained without gelation during production, so that the glossiness, ink absorbability, water resistance It can be suitably used as a raw material for a coating liquid for ink jet recording paper having excellent properties.

Claims (11)

A dispersion in which wet silica and a cationic resin are dispersed in a polar solvent, the silica concentration in the dispersion is more than 22% by weight, and the average particle size of the silica particles in the dispersion is 0 Cationic resin-modified silica dispersion, wherein the cationic resin is a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less. A silica concentration exceeding 22% by weight obtained by mixing, dispersing, and atomizing a polar solvent, wet silica and a cyclic ammonium salt type cationic resin having an average molecular weight of 10,000 or less, and the average particle size of the silica particles A method for producing a cationic resin-modified silica dispersion having a size of less than 0.5 μm. 3. The silica slurry in which wet silica is dispersed in a polar solvent is atomized by a wet media type pulverizer, then mixed and dispersed with a cationic resin, and further atomized by a high-pressure homogenizer. A method for producing a cationic resin-modified silica dispersion. The cationic resin modification according to claim 3, wherein the pH of the silica slurry is adjusted beforehand with a mineral acid so that the pH of the silica slurry is less than 5, and then wet silica is dispersed in a polar solvent to form a silica slurry. A method for producing a silica dispersion. It is characterized in that wet silica and mineral acid are simultaneously added to a polar solvent so that the pH of the silica slurry is less than 5 and the wet silica is dispersed in the polar solvent while adjusting the pH to obtain a silica slurry. The method for producing a cationic resin-modified silica dispersion according to claim 3. The method for producing a cationic resin-modified silica dispersion according to claim 2, wherein the silica slurry obtained by mixing and dispersing the polar solvent, the wet silica and the cationic resin is subjected to atomization using a wet media type pulverizer. A cationic slurry is added in advance to a polar solvent to adjust the pH so that the silica slurry has a pH of less than 5, and then wet silica is dispersed in the polar solvent to form a silica slurry. 6. A process for producing a cationic resin-modified silica dispersion according to 6. The wet slurry and the cationic resin are simultaneously added to the polar solvent so that the pH of the silica slurry is less than 5, and while adjusting the pH, the wet silica is dispersed in the polar solvent to form a silica slurry. A method for producing a cationic resin-modified silica dispersion according to claim 6. After adjusting the pH with a mineral acid in advance so that the silica slurry has a pH of less than 5, wet silica is dispersed in a polar solvent to obtain a silica slurry, and then the silica slurry and the cationic resin are mixed. The method for producing a cationic resin-modified silica dispersion according to claim 6, wherein the slurry is dispersed to obtain a silica slurry containing a cationic resin. The wet silica and the mineral acid are simultaneously added to the polar solvent so that the pH of the silica slurry is less than 5, and while adjusting the pH, the wet silica is dispersed in the polar solvent to obtain a silica slurry. The method for producing a cationic resin-modified silica dispersion according to claim 6, wherein the silica slurry and the cationic resin are mixed and dispersed to form a silica slurry containing the cationic resin. The method for producing a cationic resin-modified silica dispersion according to claim 3 or 6, wherein a wet silica cake is added to a polar solvent, and then wet silica powder is added and mixed to form a silica slurry.