JP2004018336A

JP2004018336A - Method of manufacturing titanium oxide composite particle and method of manufacturing paper with filler added therein

Info

Publication number: JP2004018336A
Application number: JP2002178015A
Authority: JP
Inventors: Toshiaki Minami; 南　敏明
Original assignee: Nippon Paper Industries Co Ltd; Jujo Paper Co Ltd
Current assignee: Nippon Paper Industries Co Ltd; Jujo Paper Co Ltd
Priority date: 2002-06-19
Filing date: 2002-06-19
Publication date: 2004-01-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide paper with filler added therein which has a high optical characteristic such as whiteness or opacity, scarcely causes deterioration in paper strength due to the inclusion of filler and in which the soiling of white water due to titanium oxide in paper making is prevented to remarkably improve a yield of the filler. <P>SOLUTION: The composite particle is manufactured by aggregating calcium carbonate fine particles and titanium oxide fine particles by using a cationic polymer or an amphoteric polymer so as to have 50% volume average particle diameter of 0.5-5 μm measured by a laser diffraction/scattering method, and is added into pulp slurry as the filler. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、新規な複合填料の製造方法並びに填料を内添した紙の製造方法に関し、特に白色度、不透明度などの光学特性が高く、填料内添による紙力低下が少なく、抄造時の酸化チタンによる白水の汚れを防止し、填料歩留りを向上させた填料内添紙の製造方法に関する。
【０００２】
【従来の技術】
近年、森林資源保護、省資源問題、ゴミ問題を含む環境負荷軽減の見地から紙の軽量化が必要とされている。紙の軽量化を目指す場合、特に印刷紙、包装紙等の分野では、白色度、不透明度、印刷適性を高めるために、各種の填料を内添して製造している。従来から填料内添による紙の白色度、不透明性の向上方法として、二酸化チタンのような屈折率の大きな填料を内添して散乱効率を上げる方法並びに白土、タルク、炭酸カルシウム、有機顔料等の屈折率１．５近辺の填料を内添して、パルプ繊維間の密着を抑制し散乱表面積を増加させる方法がとられている。
【０００３】
しかしながら、酸化チタン微粒子は粒子径が０．１〜０．３ミクロンであり極めて小さいために、抄紙時に大部分が白水中に流出し、パルプ繊維への保持が非常に悪く、填料歩留りが低いという大きな問題があった。また、このような小さな填料粒子がパルプ繊維間に分布することによって繊維間の結合を阻害し紙力を低下させてしまう欠点もあった。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、白色度、不透明度などの光学特性が高く、填料内添による紙力低下が少なく、抄紙時の酸化チタンによる白水の汚れを防止し、填料歩留りを大幅に向上させた填料内添紙を提供することである。
【０００５】
【課題を解決するための手段】
上記課題は、炭酸カルシウム微粒子と酸化チタン微粒子をカチオン性ポリマーまたは両性ポリマーを使用してレーザー回折／散乱法による５０％体積平均粒子径が０．５〜５ミクロンに凝集処理した複合粒子を製造し、パルプスラリーに填料として内添することにより解決された。
【０００６】
【発明の実施の形態】
本発明では、炭酸カルシウム微粒子と酸化チタン微粒子を凝集させるためにカチオン化ポリマーまたは両性ポリマーを使用する。カチオン化ポリマーとしては、カチオン化澱粉、カチオン化ポリアクリルアミド（ポリアクリルアミドを以下、ＰＡＭと記述する）、カチオン化ＰＶＡ、カチオン化ＣＭＣなどが挙げられる。
【０００７】
両性ポリマーのとしては、アクリルアミドを主体とする水溶性共重合のマンニッヒＰＡＭ、ホフマンＰＡＭなどが知られているが、分岐状両性共重合体ＰＡＭが最も優れている。分岐状両性共重合体ＰＡＭは、モノマーとアクリルアミドとを触媒の存在下で重合反応させ同時に架橋反応も行うものである。これにより、架橋型の分岐状両性共重合体ＰＡＭが得られ、その特徴として、粘度が低く三次元的分岐構造であるためパルプ繊維への定着点が極めて多くなり、パルプ繊維上の水酸基と水素結合する確率も高くなり紙力が飛躍的に向上する。さらに、分子量１５０〜３５０万の分岐状両性共重合体ＰＡＭで被覆処理された軽質炭酸カルシウム複合粒子には、填料の表面に分岐状ＰＡＭが静電気力で結合しており、ＰＡＭのアミド基がパルプ繊維と水素結合するため、複合粒子が媒介となってパルプ繊維同士を結合し、結果として紙力が大幅に向上する。
【０００８】
本発明の分岐状両性共重合体ＰＡＭの分子量は１５０〜３５０万程度のものである。１５０万未満では、填料歩留まりが低下するとともに、紙力の向上効果が得られにくい。また３５０万を超えると所望の効果は得られない。
【０００９】
本発明で使用される炭酸カルシウムとしては、製紙用填料であればよく、カルサイトや、アラゴナイトなどの米粒状、紡錘形、針状などが使用されるが、特に、紡錘形の粒子が微凝集したロゼット型軽質炭酸カルシウムが嵩高性発現の観点から最も好ましい。粒径としては、形成される複合凝集体粒子の粒径を鑑み、０．１〜５ミクロンが望ましい。
【００１０】
本発明で使用される酸化チタンとしては、製紙用填料であればよく、結晶形はルチル型、アナターゼ型のどちらも使用可能であるが、特に、アナターゼ型が屈折率の観点から最も好ましい。粒径としては、形成される複合凝集体粒子の粒径を鑑み、０．０５〜０．５ミクロンが望ましい。
【００１１】
カチオン性ポリマーまたは両性ポリマーにより生成した炭酸カルシウムと酸化チタンから成る複合粒子の平均粒径を、０．５〜５ミクロンに設定することにより、光学特性を高め、かつ白水汚れを低減し酸化チタン填料の歩留りを高めることが可能である。
【００１２】
粒径コントロールの方法としては、次の方法が一例として挙げられる。直径１ｍｍのガラスビーズを充填したサンドグラインダーに、１０〜３０％濃度の炭酸カルシウム及び酸化チタン混合スラリーを添加し、分子量１５０〜３５０万の分岐状両性共重合体ＰＡＭの１％溶液を、強攪拌（２０００ｒｐｍ）しながら添加し２０分間攪拌を行う。この時に添加する分岐状両性共重合体ＰＡＭの填料に対する添加率を固形分で０．０１〜０．５％に調整すること、及び攪拌速度の調整により、複合粒子の平均粒径を０．５〜５ミクロン程度にコントロールできる。
【００１３】
本発明では、本発明の効果を損ねない範囲で公知の填料としてクレー、シリカ、タルク、焼成カオリン、水酸化アルミニウムなどの無機填料、あるいは塩化ビニル樹脂、ポリスチレン樹脂、尿素ホルマリン樹脂、メラミン系樹脂、スチレン／ブタジエン系共重合体系樹脂などの合成樹脂から製造される有機填料を併用することもできる。
【００１４】
また、必要に応じて、ＰＡＭ系高分子、ポリビニルアルコール系高分子、カチオン化澱粉、尿素／ホルマリン樹脂、メラミン／ホルマリン樹脂などの紙力増強剤；アクリルアミド／アミノメチルアクリルアミドの共重合物の塩、カチオン化澱粉、ポリエチレンイミン、ポリエチレンオキサイド、アクリルアミド／アクリル酸ナトリウム共重合物などのろ水性あるいは歩留まり向上剤；硫酸アルミニウム（硫酸バンド）、耐水化剤、紫外線防止剤、退色防止剤などの助剤などを含有してもよい。
【００１５】
【実施例】
以下、本発明を実施例及び比較例に従って詳細に説明するが、本発明はこれらに限定されるものではない。尚、説明中、パーセントは重量パーセントを示す。白色度、不透明度、裂断長、填料歩留り、灰分、ＴＯＰＲ（トータルワンパスリテンション）、ＡＯＰＲ（アッシュのワンパスリテンション）を以下に示す方法にて測定した。
・白色度の測定：白色度はＪＩＳ　Ｐ　８１２３に基づきハンター白色度計で測定した。・不透明度の測定：不透明度はＪＩＳ　Ｐ　８１３８に基づき、ハンター反射率計を使用して測定した。
・填料の歩留り：予め作成しておいた、填料を配合していない手抄きシート（ブランク）及び填料を配合した手抄きシートより１０×１０ｃｍの紙片１０枚を切り取り、１０５℃×３時間乾燥させた後に絶乾重量を秤りとる。次に、この絶乾紙片を電気炉にて５７５℃×２時間焼くことによりシート中に含まれる灰分を求める。填料歩留り（％）は下記の式より算出した。
填料歩留り＝｛（填料入りシート灰分重量／同絶乾重量−ブランク灰分重同絶乾重量）｝／填料配合率×１００
・裂断長：ＪＩＳ　Ｐ　８１１３により次式で求めた。
裂断長＝引張強さ／（試験片の幅×試験片の坪量）×１０００
・灰分：ＪＩＳ　Ｐ　８１２８に基づき灰化温度は５７５℃とした。
・ＴＯＰＲ：ＤＤＪ（ダイナミックドレネージジャーテスター）にて測定した総歩留り（％）
・ＡＯＰＲ：　ＤＤＪにて測定した灰分歩留り（％）
【００１６】
＜複合粒子の合成例１＞
軽質炭酸カルシウム（奥多摩工業製　ＴＰ−１２１　平均粒径１ミクロン）の粉体４５ｇ及び酸化チタン（古河機械金属工業製　ＦＡ−５０　平均粒径０．３ミクロン）の粉体５ｇを水４５０ｇに添加して、ホモミキサーを使用して回転数３０００ｒｐｍで２０分間、分散処理を行い１０％炭酸カルシウム・酸化チタン（９０：１０）スラリーを調製した。次にこのスラリー１００ｇをビーカーに入れ、スリーワンモーターで攪拌しながら、分岐状両性共重合体ＰＡＭ（ＰＳ４６２　荒川化学製　分子量　２５０万）の１　％溶液を０．３ｇ添加し、そのまま１０分間攪拌を続け、ＴＰ１２１・ＦＡ５０・ＰＳ４６２複合粒子が得られた。粒度分布測定装置マスターサイザーＳ（マルバーン社製）を使用して、レーザー回折／散乱法により５０％体積平均粒子径を測定したところ３．１ミクロンであった。
【００１７】
＜複合粒子の合成例２＞
ロゼット型軽質炭酸カルシウム（ファイザー社製　ファイカーブＨ　平均粒径３ミクロン　略してＦＣＨ）の粉体４５ｇ及び酸化チタン（古河機械金属工業製　ＦＡ−５０平均粒径０．３ミクロン）の粉体５ｇを水４５０ｇに添加して、ホモミキサーを使用して回転数３０００ｒｐｍで２０分間、分散処理を行い１０％炭酸カルシウム・酸化チタン（９０：１０）スラリーを調製した。次にこのスラリー１００ｇをビーカーに入れ、スリーワンモーターで攪拌しながら、分岐状両性共重合体ＰＡＭ（ＰＳ４６２　荒川化学製　分子量　２５０万）の１％溶液を０．３ｇ添加し、そのまま１０分間攪拌を続け、ＦＣＨ・ＦＡ５０・ＰＳ４６２複合粒子が得られた。粒度分布測定装置マスターサイザーＳ（マルバーン社製）を使用して、レーザー回折／散乱法により５０％体積平均粒子径を測定したところ５．１ミクロンであった。
【００１８】
［実施例１］
広葉樹晒パルプ（ＬＢＫＰ　ＣＳＦ４０７ｍｌ）のスラリー（濃度　０．５０％）に、合成例１の複合凝集体粒子スラリーをパルプ絶乾重量当り２０％となるように添加し、３分間攪拌後、硫酸バンドを絶乾重量当り０．５％添加した。さらに、１分間攪拌後、紙力剤として、ＰＳ４６２をパルプの絶乾重量当り０．３％添加攪拌し、ｐＨが８．７になるように硫酸バンドを微量添加した。この調成したパルプスラリーを用いて、丸型手抄き器で目標坪量が６４ｇ／ｍ^２、紙中灰分が１３重量％となるように抄造し、プレスにより脱水後、送風乾燥機（５０℃、１時間）にて乾燥しシートサンプルを作製した。このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００１９】
［実施例２］
実施例１において、合成例１の複合凝集体粒子スラリーをパルプ絶乾重量当り４０％となるように添加した以外は実施例１と同様にシートサンプルを作製し、このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２０】
［比較例１］
広葉樹晒パルプ（ＬＢＫＰ　ＣＳＦ４０７ｍｌ）のスラリー（濃度　０．５０％）に、軽質炭酸カルシウム（奥多摩工業製　ＴＰ−１２１　平均粒径１ミクロン）の１０％スラリー及び酸化チタン（古河機械金属工業製　ＦＡ−５０　平均粒径０．３ミクロン）の１０％スラリー（ＴＰ１２１：ＦＡ５０＝９０：１０）をパルプ絶乾重量当り２０％となるように添加し、３分間攪拌後、硫酸バンドを絶乾重量当り０．５％添加した。さらに、１分間攪拌後、紙力剤として、ＰＳ４６２をパルプの絶乾重量当り０．３％添加攪拌し、ｐＨが８．７になるように硫酸バンドを微量添加した。この調成したパルプスラリーを用いて、丸型手抄き器で目標坪量が６４ｇ／ｍ^２、紙中灰分が１３重量％となるように抄造し、プレスにより脱水後、送風乾燥機（５０℃、１時間）にて乾燥しシートサンプルを作製した。このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２１】
［比較例２］
比較例１において、軽質炭酸カルシウム（奥多摩工業製　ＴＰ−１２１　平均粒径１ミクロン）スラリー及び酸化チタン（古河機械金属工業製　ＦＡ−５０　平均粒径０．３ミクロン）スラリー（ＴＰ１２１：ＦＡ５０＝９０：１０）をパルプ絶乾重量当り４０％となるように添加した以外は比較例１と同様にシートサンプルを作製し、このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２２】
［実施例３］
広葉樹晒パルプ（ＬＢＫＰ　ＣＳＦ４０７ｍｌ）のスラリー（濃度　０．５０％）に、合成例２の複合凝集体粒子スラリーをパルプ絶乾重量当り２０％となるように添加し、３分間攪拌後、硫酸バンドを絶乾重量当り０．５％添加した。さらに、１分間攪拌後、紙力剤として、ＰＳ４６２をパルプの絶乾重量当り０．３％添加攪拌し、ｐＨが８．７になるように硫酸バンドを微量添加した。この調成したパルプスラリーを用いて、丸型手抄き器で目標坪量が６４ｇ／ｍ^２、紙中灰分が１３重量％となるように抄造し、プレスにより脱水後、送風乾燥機（５０℃、１時間）にて乾燥しシートサンプルを作製した。このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２３】
［実施例４］
実施例３において、合成例２の複合凝集体粒子スラリーをパルプ絶乾重量当り４０％となるように添加した以外は実施例３と同様にシートサンプルを作製し、このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２４】
［比較例３］
広葉樹晒パルプ（ＬＢＫＰ　ＣＳＦ４０７ｍｌ）のスラリー（濃度　０．５０％）に、ロゼット型軽質炭酸カルシウム（ファイザー社製　ファイカーブＨ　平均粒径３ミクロン）の１０％スラリー及び酸化チタン（古河機械金属工業製　ＦＡ−５０　平均粒径０．３ミクロン）スラリー（ＦＣＨ：ＦＡ５０＝９０：１０）をパルプ絶乾重量当り２０％となるように添加し、３分間攪拌後、硫酸バンドを絶乾重量当り０．５％添加した。さらに、１分間攪拌後、紙力剤として、ＰＳ４６２をパルプの絶乾重量当り０．３％添加攪拌し、ｐＨが８．７になるように硫酸バンドを微量添加した。この調成したパルプスラリーを用いて、丸型手抄き器で目標坪量が６４ｇ／ｍ^２、紙中灰分が１３重量％となるように抄造しプレスにより脱水後、送風乾燥機（５０℃、１時間）にて乾燥しシートサンプルを作製した。このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２５】
［比較例４］
比較例３において、ロゼット型軽質炭酸カルシウム（ファイザー社製　ファイカーブＨ　平均粒径３ミクロン）の１０％スラリー及び酸化チタン（古河機械金属工業製　ＦＡ−５０　平均粒径０．３ミクロン）１０％スラリー（ＦＣＨ：ＦＡ５０＝９０：１０）をパルプ絶乾重量当り４０％となるように添加した以外は比較例３と同様にシートサンプルを作製し、このシートの裂断長、紙中灰分、さらに、調成したパルプスラリーを使用してＤＤＪによる総歩留り（ＴＯＰＲ）、灰分歩留り（ＡＯＰＲ）を測定し表１に示した。
【００２６】
【表１】

【００２７】
表１に示すように、実施例１及び実施例２の軽質炭酸カルシウム及び酸化チタンを分子量２５０万の分岐状両性共重合体であるＰＳ４６２で被覆処理したＴＰ１２１・ＦＡ５０・ＰＳ４６２複合粒子では、裂断長が３．７０、２．５１であり、比較例１及び比較例２のＴＰ１２１、ＦＡ５０の混合粒子の裂断長３．５０、２．３９に比較して、５．０２〜５．７１％紙力が向上した。一方、実施例３及び実施例４のロゼット型軽質炭酸カルシウムを分子量３００万の分岐状両性共重合体であるＰＳ４６２で被覆処理したＦＣＨ・ＦＡ５０・ＰＳ４６３複合粒子では、裂断長が３．５０、２．３１であり、比較例１及び比較例２のＦＣＨ、ＦＡ５０混合粒子の裂断長３．３１、２．２１に比較して、４．５２〜５．７４％紙力が向上した。
【００２８】
また、ＤＤＪによる灰分歩留り及び総歩留りも、ＴＰ１２１・ＦＡ５０・ＰＳ４６２複合粒子及びＦＣＨ・ＦＡ５０・ＰＳ４６２複合粒子では１０％前後高かった。また、ＴＰ１２１・ＦＡ５０・ＰＳ４６２複合粒子はＴＰ１２１、ＦＡ５０混合粒子に比較して、白色度は１．１ポイント程度向上し、不透明度は０．７〜１ポイント程度向上した。さらに、ＦＣＨ・ＦＡ５０・ＰＳ４６３複合粒子はＦＣＨ、ＦＡ５０混合粒子に比較して、白色度は２ポイント程度向上し、不透明度は２ポイント程度向上した。
【００２９】
【発明の効果】
炭酸カルシウム微粒子及び酸化チタン微粒子を分子量１５０〜３５０万の分岐状両性共重合体ポリアクリルアミドで被覆処理した複合粒子を製造し、紙に内添することにより以下の特性を備えた填料内添紙が得られた。
１）　白色度、不透明度などの光学特性が優れている
２）　紙力（裂断長、引裂強度）が優れている
３）抄紙時における白水汚れが防止できる
４）酸化チタン填料の歩留りが高い[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a novel composite filler and a method for producing a paper internally containing a filler. In particular, the optical properties such as whiteness and opacity are high, the decrease in paper strength due to the internal addition of the filler is small, and oxidation during papermaking is performed. The present invention relates to a method for producing a filler-filled paper that prevents contamination of white water by titanium and improves the filler yield.
[0002]
[Prior art]
In recent years, paper has been required to be lighter from the viewpoint of protection of forest resources, resource saving, and reduction of environmental load including garbage. When aiming to reduce the weight of paper, particularly in the fields of printing paper, wrapping paper, etc., various fillers are added internally in order to increase whiteness, opacity and printability. Conventionally, as a method of improving the whiteness and opacity of paper by adding a filler, there is a method of increasing the scattering efficiency by internally adding a filler having a large refractive index such as titanium dioxide, and a method of improving clay, talc, calcium carbonate, organic pigments, and the like. A method has been adopted in which a filler having a refractive index of around 1.5 is internally added to suppress adhesion between pulp fibers and increase the scattering surface area.
[0003]
However, since the titanium oxide fine particles have an extremely small particle diameter of 0.1 to 0.3 micron, most of them flow out into white water during papermaking, have very poor retention in pulp fibers, and have a low filler yield. There was a big problem. There is also a disadvantage that such small filler particles are distributed between the pulp fibers, thereby inhibiting the bonding between the fibers and reducing the paper strength.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a filler having high optical properties such as whiteness and opacity, a small decrease in paper strength due to internal addition of the filler, prevention of white water contamination by titanium oxide during papermaking, and a significant improvement in the filler yield. It is to provide internal paper.
[0005]
[Means for Solving the Problems]
The object is to produce composite particles obtained by agglomerating calcium carbonate fine particles and titanium oxide fine particles to a 50% volume average particle diameter of 0.5 to 5 microns by a laser diffraction / scattering method using a cationic polymer or an amphoteric polymer. The problem was solved by internally adding the pulp slurry as a filler.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, a cationized polymer or an amphoteric polymer is used to aggregate the calcium carbonate fine particles and the titanium oxide fine particles. Examples of the cationized polymer include cationized starch, cationized polyacrylamide (hereinafter, polyacrylamide is referred to as PAM), cationized PVA, and cationized CMC.
[0007]
As the amphoteric polymer, Mannich PAM and Hoffman PAM which are water-soluble copolymers mainly composed of acrylamide are known, but the branched amphoteric copolymer PAM is the most excellent. The branched amphoteric copolymer PAM is obtained by polymerizing a monomer and acrylamide in the presence of a catalyst and simultaneously performing a crosslinking reaction. As a result, a cross-linked branched amphoteric copolymer PAM is obtained, which is characterized in that it has a low viscosity and has a three-dimensional branched structure, so that the number of fixing points on the pulp fiber becomes extremely large, and the hydroxyl groups on the pulp fiber and hydrogen The probability of joining is increased, and the paper strength is dramatically improved. Further, to the calcium carbonate composite particles coated with the branched amphoteric copolymer PAM having a molecular weight of 1.5 to 3.5 million, the branched PAM is electrostatically bound to the surface of the filler, and the amide group of the PAM is pulp-free. Due to hydrogen bonding with the fibers, the composite particles serve as a medium to bond the pulp fibers together, and as a result, the paper strength is greatly improved.
[0008]
The molecular weight of the branched amphoteric copolymer PAM of the present invention is about 1.5 to 3.5 million. If it is less than 1.5 million, the yield of the filler decreases and the effect of improving the paper strength is hardly obtained. If it exceeds 3.5 million, desired effects cannot be obtained.
[0009]
As the calcium carbonate used in the present invention, any filler for papermaking may be used, and calcite, rice grains such as aragonite, spindle-shaped, needle-shaped and the like are used, and particularly, rosettes in which spindle-shaped particles are finely aggregated. Light calcium carbonate is most preferred from the viewpoint of expressing bulkiness. The particle size is preferably 0.1 to 5 microns in view of the particle size of the formed composite aggregate particles.
[0010]
As the titanium oxide used in the present invention, any filler may be used as long as it is a paper-making filler, and any of rutile-type and anatase-type crystal forms can be used. In particular, anatase-type is most preferable from the viewpoint of the refractive index. The particle size is desirably 0.05 to 0.5 microns in view of the particle size of the formed composite aggregate particles.
[0011]
By setting the average particle size of the composite particles composed of calcium carbonate and titanium oxide formed by a cationic polymer or an amphoteric polymer to 0.5 to 5 microns, the optical characteristics are enhanced, and white water stain is reduced, and the titanium oxide filler is reduced. It is possible to increase the yield.
[0012]
As a method for controlling the particle size, the following method is mentioned as an example. A mixed slurry of calcium carbonate and titanium oxide having a concentration of 10 to 30% is added to a sand grinder filled with glass beads having a diameter of 1 mm, and a 1% solution of a branched amphoteric copolymer PAM having a molecular weight of 1.5 to 3.5 million is vigorously stirred. (2000 rpm) and stirring for 20 minutes. At this time, the average particle size of the composite particles is adjusted to 0.5 to 0.5% by adjusting the addition ratio of the branched amphoteric copolymer PAM to the filler to 0.01 to 0.5% in terms of solid content, and adjusting the stirring speed. It can be controlled to about 5 microns.
[0013]
In the present invention, clay, silica, talc, calcined kaolin, inorganic fillers such as aluminum hydroxide, or vinyl chloride resin, polystyrene resin, urea formalin resin, melamine-based resin, as well-known fillers as long as the effects of the present invention are not impaired, An organic filler produced from a synthetic resin such as a styrene / butadiene copolymer resin can also be used in combination.
[0014]
If necessary, a PAM-based polymer, a polyvinyl alcohol-based polymer, a cationized starch, a paper strength enhancer such as a urea / formalin resin, a melamine / formalin resin; a salt of a copolymer of acrylamide / aminomethylacrylamide; Drainage or retention improvers such as cationized starch, polyethyleneimine, polyethylene oxide, acrylamide / sodium acrylate copolymer; assistants such as aluminum sulfate (sulfate band), water resistant agent, ultraviolet ray inhibitor, anti-fading agent, etc. May be contained.
[0015]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the description, percentages indicate weight percentages. The whiteness, opacity, tear length, filler retention, ash, TOPR (total one-pass retention), and AOPR (ash one-pass retention) were measured by the following methods.
-Measurement of whiteness: Whiteness was measured by a Hunter whiteness meter based on JIS P 8123. Opacity measurement: Opacity was measured using a Hunter reflectometer based on JIS P 8138.
Filler Yield: Cut out 10 pieces of 10 × 10 cm pieces of paper from a hand-made sheet (blank) without filler and a hand-made sheet with filler, which have been prepared in advance, and 105 ° C. × 3 hours After drying, weigh the absolute dry weight. Next, the ash contained in the sheet is obtained by baking this absolutely dried paper piece in an electric furnace at 575 ° C. for 2 hours. Filler yield (%) was calculated from the following equation.
Filler yield = {(weight of sheet ash with filler / identical dry weight−blank ash weight / identical dry weight)} / filler mixing ratio × 100
-Break length: It was determined by the following equation according to JIS P 8113.
Breaking length = tensile strength / (width of test piece × basis weight of test piece) × 1000
Ash content: The ash temperature was 575 ° C. based on JIS P 8128.
・ TOPR: Total yield (%) measured by DDJ (Dynamic Drainage Jar Tester)
-AOPR: Ash yield measured by DDJ (%)
[0016]
<Synthesis example 1 of composite particles>
45 g of powder of light calcium carbonate (TP-121 manufactured by Okutama Kogyo Co., Ltd., average particle size 1 micron) and 5 g of powder of titanium oxide (FA-50, manufactured by Furukawa Kikai Kinzoku Kogyo Kogyo Co., Ltd., 0.3 micron) were added to 450 g of water. Using a homomixer, a dispersion treatment was performed at 3000 rpm for 20 minutes to prepare a 10% calcium carbonate / titanium oxide (90:10) slurry. Next, 100 g of this slurry was put in a beaker, and 0.3 g of a 1% solution of a branched amphoteric copolymer PAM (PS462, Arakawa Chemical Co., Ltd., molecular weight 2.5 million) was added while stirring with a three-one motor, and stirring was continued for 10 minutes. , TP121 / FA50 / PS462 composite particles were obtained. When the 50% volume average particle diameter was measured by a laser diffraction / scattering method using a particle size distribution analyzer Mastersizer S (manufactured by Malvern), it was 3.1 microns.
[0017]
<Synthesis example 2 of composite particles>
45 g of powder of rosette-type light calcium carbonate (Phibeur H, manufactured by Pfizer Inc., average particle diameter of 3 μm, FCH for short) and 5 g of powder of titanium oxide (FA-50, manufactured by Furukawa Kikinzoku Kogyo Kogyo with an average particle diameter of 0.3 μm) The mixture was added to 450 g of water and subjected to a dispersion treatment at 3000 rpm for 20 minutes using a homomixer to prepare a 10% calcium carbonate / titanium oxide (90:10) slurry. Next, 100 g of this slurry was placed in a beaker, and while stirring with a three-one motor, 0.3 g of a 1% solution of a branched amphoteric copolymer PAM (PS462, Arakawa Chemical Co., Ltd., molecular weight 2.5 million) was added, and stirring was continued for 10 minutes. And FCH / FA50 / PS462 composite particles. Using a particle size distribution analyzer Mastersizer S (manufactured by Malvern), the 50% volume average particle diameter was measured by a laser diffraction / scattering method and found to be 5.1 microns.
[0018]
[Example 1]
To a slurry (concentration: 0.50%) of bleached hardwood pulp (LBKP CSF407 ml), the composite aggregate particle slurry of Synthesis Example 1 was added so as to be 20% based on the absolute dry weight of the pulp. After stirring for 3 minutes, the sulfate band was removed. 0.5% was added per absolute dry weight. Furthermore, after stirring for 1 minute, PS462 was added as a paper strengthening agent at 0.3% based on the absolute dry weight of the pulp, and the mixture was stirred. Using the prepared pulp slurry, papermaking was performed using a round hand-making machine so that the target basis weight was 64 g / m ² and the ash content in paper was 13% by weight. C. for 1 hour) to prepare a sheet sample. The tear length of the sheet, the ash content in the paper, and the total yield (TOPR) and ash yield (AOPR) by DDJ using the prepared pulp slurry were measured and are shown in Table 1.
[0019]
[Example 2]
A sheet sample was prepared in the same manner as in Example 1 except that the composite aggregate particle slurry of Synthesis Example 1 was added so as to be 40% based on the absolute dry weight of the pulp. Using the medium ash content and the prepared pulp slurry, the total yield (TOPR) and the ash yield (AOPR) were measured by DDJ, and are shown in Table 1.
[0020]
[Comparative Example 1]
A 10% slurry of light calcium carbonate (TP-121 manufactured by Okutama Kogyo Kogyo Co., Ltd., average particle size 1 micron) and a titanium oxide (FA-50 manufactured by Furukawa Kikai Kogyo Kogyo) were added to a slurry (concentration 0.50%) of bleached hardwood pulp (LBKP CSF407ml). A 10% slurry (average particle size: 0.3 micron) (TP121: FA50 = 90: 10) was added so as to have a concentration of 20% based on the absolute dry weight of the pulp, and after stirring for 3 minutes, the sulfate band was added at a concentration of 0.1% based on the absolute dry weight. 5% was added. Further, after stirring for 1 minute, PS462 was added as a paper strengthening agent at 0.3% based on the absolute dry weight of the pulp, and the mixture was stirred, and a small amount of a sulfate band was added so that the pH became 8.7. Using the prepared pulp slurry, papermaking was performed using a round hand-making machine so that the target basis weight was 64 g / m ² and the ash content in paper was 13% by weight. C. for 1 hour) to prepare a sheet sample. The tear length of the sheet, the ash content in the paper, and the total yield (TOPR) and ash yield (AOPR) by DDJ using the prepared pulp slurry were measured and are shown in Table 1.
[0021]
[Comparative Example 2]
In Comparative Example 1, a slurry of light calcium carbonate (TP-121 manufactured by Okutama Kogyo Kogyo Co., Ltd. with an average particle size of 1 micron) and a slurry of titanium oxide (FA-50 manufactured by Furukawa Kikai Kogyo Kogyo with an average particle size of 0.3 micron) (TP121: FA50 = 90: A sheet sample was prepared in the same manner as in Comparative Example 1 except that 10) was added so as to be 40% based on the absolute dry weight of the pulp, and the breaking length of the sheet, the ash content in paper, and the prepared pulp slurry were used. The total yield (TOPR) and the ash yield (AOPR) were measured by DDJ, and are shown in Table 1.
[0022]
[Example 3]
To the slurry (concentration 0.50%) of bleached hardwood pulp (LBKP CSF 407 ml), the composite aggregate particle slurry of Synthesis Example 2 was added so as to be 20% based on the absolute dry weight of the pulp. After stirring for 3 minutes, the sulfate band was removed. 0.5% was added per absolute dry weight. Furthermore, after stirring for 1 minute, PS462 was added as a paper strengthening agent at 0.3% based on the absolute dry weight of the pulp, and the mixture was stirred. Using the prepared pulp slurry, papermaking was performed using a round hand-making machine so that the target basis weight was 64 g / m ² and the ash content in paper was 13% by weight. C. for 1 hour) to prepare a sheet sample. The tear length of the sheet, the ash content in the paper, and the total yield (TOPR) and ash yield (AOPR) by DDJ using the prepared pulp slurry were measured and are shown in Table 1.
[0023]
[Example 4]
A sheet sample was prepared in the same manner as in Example 3 except that the composite aggregate particle slurry of Synthesis Example 2 was added so as to be 40% based on the absolute dry weight of the pulp. Using the medium ash content and the prepared pulp slurry, the total yield (TOPR) and the ash yield (AOPR) were measured by DDJ, and are shown in Table 1.
[0024]
[Comparative Example 3]
Hardwood bleached pulp (LBKP CSF407ml) slurry (concentration 0.50%), rosette-type light calcium carbonate (Pfizer Co., Ltd., Ficarb H, average particle size 3 microns) 10% slurry and titanium oxide (Furukawa Machinery Metal Industry FA) A slurry (FCH: FA50 = 90: 10) was added so as to have a concentration of 20% based on the absolute dry weight of the pulp, and after stirring for 3 minutes, a sulfate band was added at a rate of 0.5% based on the absolute dry weight. % Was added. Further, after stirring for 1 minute, PS462 was added as a paper strengthening agent at 0.3% based on the absolute dry weight of the pulp, and the mixture was stirred, and a small amount of a sulfate band was added so that the pH became 8.7. Using the prepared pulp slurry, papermaking was performed using a round-shaped hand-making machine so that the target basis weight was 64 g / m ² and the ash content in paper was 13% by weight. (1 hour) to produce a sheet sample. The tear length of the sheet, the ash content in the paper, and the total yield (TOPR) and ash yield (AOPR) by DDJ using the prepared pulp slurry were measured and are shown in Table 1.
[0025]
[Comparative Example 4]
In Comparative Example 3, a 10% slurry of rosette-type light calcium carbonate (Phibah, Ficarb H, average particle size of 3 microns) and a 10% slurry of titanium oxide (Furukawa Kikai Kogyo Kogyo FA-50, average particle size of 0.3 microns) A sheet sample was prepared in the same manner as in Comparative Example 3 except that (FCH: FA50 = 90: 10) was added so as to be 40% based on the absolute dry weight of the pulp, and the tear length of this sheet, ash content in paper, and Using the prepared pulp slurry, the total yield (TOPR) and the ash yield (AOPR) were measured by DDJ and are shown in Table 1.
[0026]
[Table 1]

[0027]
As shown in Table 1, the TP121 / FA50 / PS462 composite particles obtained by coating the light calcium carbonate and titanium oxide of Examples 1 and 2 with PS462 which is a branched amphoteric copolymer having a molecular weight of 2.5 million were broken. The length is 3.70, 2.51, which is 5.02 to 5.71% as compared with the breaking length of the mixed particles of TP121 and FA50 of Comparative Example 1 and Comparative Example 2 of 3.50 and 2.39. Paper strength improved. On the other hand, in the FCH • FA50 • PS463 composite particles obtained by coating the rosette-type light calcium carbonate of Examples 3 and 4 with PS462 which is a branched amphoteric copolymer having a molecular weight of 3,000,000, the breaking length is 3.50, As a result, the paper strength was improved by 4.52 to 5.74% compared to the breaking lengths of 3.31 and 2.21 of the mixed particles of FCH and FA50 in Comparative Examples 1 and 2.
[0028]
The ash yield and total yield by DDJ were also higher by about 10% for the TP121 / FA50 / PS462 composite particles and the FCH / FA50 / PS462 composite particles. The TP121 / FA50 / PS462 composite particles improved the whiteness by about 1.1 points and the opacity by about 0.7 to 1 point compared to the TP121 and FA50 mixed particles. Further, the FCH / FA50 / PS463 composite particles have improved whiteness by about 2 points and opacity by about 2 points as compared with FCH and FA50 mixed particles.
[0029]
【The invention's effect】
Composite particles obtained by coating calcium carbonate fine particles and titanium oxide fine particles with a branched amphoteric copolymer polyacrylamide having a molecular weight of 1.5 to 3.5 million are produced and internally added to paper to obtain a filler-inner paper having the following characteristics. Obtained.
1) Excellent optical properties such as whiteness and opacity 2) Excellent paper strength (tear length, tear strength) 3) Prevents white water staining during papermaking 4) High yield of titanium oxide filler

Claims

A method for producing composite particles in which calcium carbonate fine particles and titanium oxide fine particles are subjected to agglomeration treatment to a 50% volume average particle diameter of 0.5 to 5 microns by a laser diffraction / scattering method using a cationic polymer or an amphoteric polymer.

The method for producing composite particles according to claim 1, wherein the amphoteric polymer is a branched amphoteric copolymer polyacrylamide having a molecular weight of 1.5 to 3.5 million.

The method for producing composite particles according to claim 1 or 2, wherein the calcium carbonate is rosette-type light calcium carbonate in which spindle-shaped particles are aggregated.

A method for producing a filler-filled paper by adding a filler to a pulp slurry to form a paper, wherein the filler contains any one of the composite particles according to claims 1 to 3. Production method.