JP3697335B2 - Treatment of chemical pulp with acidic bleached white water - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、化学パルプの酸性漂白白水による処理方法及び印刷用紙または塗工用原紙に関する。更に詳しくは化学パルプの漂白において、酸性漂白白水を用いて酸性高温処理を蒸解、洗浄後、酸素漂白前または後に実施し、洗浄脱水工程を経て、または経ないで、更に多段漂白を行うことによって、漂白反応を促進させると共に塩素化合物の使用量を減らしてＡＯＸを低減させる方法に関する。更に広葉樹パルプに特有の印刷において問題となるベッセルピックの発生を酸性漂白白水による処理によって減少させる方法に関するもので、かつベッセルピックの少なく、ＡＯＸの含有量の少ない印刷用紙または塗工用原紙に関するものである。
【０００２】
【従来の技術】
パルプ漂白の目的は、パルプ繊維の内部や表面に付着しているリグニンや着色物質を分解、変質させたり可溶性にして取り除き、白色度を上昇させることである。
【０００３】
従来、化学パルプの漂白は、蒸解後に、塩素、次亜塩素酸塩、過酸化水素及び二酸化水素等で段階的に処理する方法が一般的に取られてきた。近年は、排水負荷量の軽減及び漂白薬品費の削減を目的として酸素漂白を加える方法が多く採用されている。
【０００４】
一方、最近は、ダイオキシンを含む、ＡＯＸの規制や安全性の点から、塩素系薬品を使用しない、いわゆる非塩素漂白方法が開発され操業されるようになってきた。非塩素漂白方法には、塩素及び二酸化塩素等の塩素系薬品を全く使用しないＴＣＦ法、塩素のみを使用しないＥＣＦ法がある。
【０００５】
過酸化物及びオゾンによる非塩素漂白方法は、既に公知の通りである。しかしながら、過酸化物又はオゾン漂白では、パルプが前処理されていない限り、過酸化物又はオゾンがパルプスラリー中に存在するＭｎ、Ｆｅ等の微量金属によって分解され、漂白効率が低下するために漂白剤を多量に使用することとなり、コストアップにつながり、且つ分解によって生じたラジカル等活性化学種によるパルプ粘度の低下の問題がある。
【０００６】
そこで、微量金属の対策として、特開平５−１４８７８４号公報はリグノセルロース含有パルプをｐＨ１〜６の範囲で酸処理後、アルカリ土類金属含有化合物をｐＨ１〜７の範囲で処理するオゾン、過酸化物の漂白方法が、また、特開平５−１４８７８５号公報ではリグノセルロース含有パルプをｐＨ３．１〜９．０の範囲内にて窒素ポリカルボン酸の錯化剤により処理するオゾン、過酸化物の漂白方法等が提案されている。
【０００７】
しかし、これらの方法による前処理は微量金属の除去には限界があり、効果的ではないだけでなく、カッパー価低減効果はほとんど認められない。
【０００８】
一方、最近、酵素による脱リグニン方法が研究されている。酵素としては、セルラーゼ、キシラナーゼ、ペクチナーゼ、リパーゼ等が知られている。例えば、特公平２−２６４０８７号公報では、ｐＨ４〜８のキシラナーゼを含む酵素による未晒パルプの処理方法。又、特公平２−２９３４８６号公報では、ｐＨ３〜１０でヘミセルラーゼを含む酵素による未晒パルプの処理方法等が提案されている。
【０００９】
更に、酵素によるパルプの改質方法が研究されている。例えば、特公平２−２０７５６号公報では、抄紙時にセルラーゼとセロビオースを１／０．０５〜０．５の比率で添加することで叩解が促進され電力が低減する。又、特公昭６３−１３５５９７号公報では、ＦＰ活性が２０ｍｇ／酵素ｇ以上の酵素の添加によるベッセルピックの防止等が提案されている。
【００１０】
しかし、これらの方法は、脱リグニン効果、漂白性の改善とセルロースの改質等を同時に与えることができないだけでなく、パルプ収率が低下する。
【００１１】
上記のような過酸化物やオゾンの漂白における前処理として、酸処理や酸性の酵素処理等が多く報告されているが、いずれも上記に示す様な問題点が存在する。
【００１２】
そこで、過酢酸、カロ酸、混合過酸等の酸性条件下での活性過酸化物による脱リグニン効果と漂白性の改善についての研究が盛んに行われているがコスト高や品質の低下、薬品の安全性等の問題から実際に使用されていない状況にある。
【００１３】
更に、１９９６年１１月の紙パルプ技術協会主催の『オゾン漂白セミナー』においてアールストローム社がオゾンと二酸化塩素の前処理として硫酸でｐＨ３．５−４、１１０℃処理することでカッパー価が下がり、オゾンと二酸化塩素の添加量を節減できると発表している。
しかし、酸処理による白色度の向上が認められず、更にパルプ粘度とパルプ収率の低下が起こっている。更に硫酸の使用によるコスト高や高温のため密閉型装置が必要である等の問題がある。
【００１４】
【発明が解決しようとする課題】
本発明の目的は、前記の従来技術の問題点（１）高価な硫酸の使用、（２）カッパー価の低減効果が小さい、（３）漂白性の改善効果が低い、（４）セルロースの改質によるベッセルピック防止効果が低い、（５）パルプ収率の低下、（６）パルプ粘度の低下、等を解決することであり、漂白反応を促進させると共に塩素化合物の使用量を減らしてＡＯＸを低減させ、更に広葉樹パルプに特有の印刷において問題となるベッセルピックの発生を酸性漂白白水による処理によって減少させる方法である。
【００１５】
【課題を解決するための手段】
本発明者は、上記の問題点を解決すべく鋭意研究を重ねた結果、驚くべきことに漂白工程から排出される酸性白水で漂白前のパルプ（蒸解パルプ及び酸素漂白パルプ等）を処理することにより、上記問題点のほとんどを解消でき、漂白効果が高く、かつ広葉樹パルプにおいてベッセルピックの少ないパルプとＡＯＸの低減ができることを見出し、本発明の化学パルプの酸性漂白白水による処理方法を完成するに至った。
即ち、化学パルプの漂白において、酸性漂白白水を用いて酸性高温処理を蒸解、洗浄後、酸素漂白前または後に実施し、洗浄脱水工程を経て、または経ないで、更に多段漂白を行う方法である。
【００１６】
【発明の実施の形態】
本発明に使用される化学パルプは、蒸解あるいは酸素漂白された広葉樹パルプまたは針葉樹パルプである。尚、針葉樹パルプよりも南方系広葉樹パルプの方が漂白性の改善効果が大きく、更に広葉樹に特有であるベッセルピックに対しては、特に優れてた効果が認められる。
【００１７】
本発明の酸性漂白白水による酸性高温処理に使用される酸性漂白白水とは、塩素、二酸化塩素、塩素と二酸化塩素、オゾン、有機過酸、無機過酸、混合過酸類、耐酸性の酵素による処理から発生する１つ以上の白水である。
【００１８】
処理温度は、５０〜１３０℃、好ましくは６０〜１１０℃、より好ましくは７０〜１００℃である。ここで、処理温度が５０℃未満では処理効率が低く、１３０℃を超える場合は期待したほどの効果が現れないだけでなくパルプ粘度とパルプ収率の低下が起こる。
【００１９】
処理時間は、２０〜２４０分、好ましくは３０〜１８０分、より好ましくは６０〜１２０分である。ここで、処理時間が２０分未満では効果が小さく、２４００分より長い場合はそれ以上の効果が現れない。
【００２０】
処理ｐＨが１〜５、好ましくはｐＨ２〜４である。ここで、処理ｐＨが１未満では装置の腐食の問題とパルプの粘度とパルプ収率が低下し、ｐＨ５より高い場合、処理の効果が現れない。
【００２１】
パルプ濃度は１〜３０重量％、好ましくは３〜２５重量％、より好ましくは５〜２０重量％である。ここで、パルプ濃度が１重量％未満では処理効率が悪く、３０重量％より濃い場合には撹拌混合が不十分となり好ましくない。
【００２２】
後段の多段漂白としては、以下の▲１▼〜▲６▼の少なくとも一つ以上を組合せて漂白する。
▲１▼塩素、二酸化塩素、次亜塩素酸塩の１つ以上の薬品を用いて酸性水媒体中で漂白。
▲２▼オゾンを用いて酸性水媒体中で漂白。
▲３▼過酸化物又は過酸化物と酸素を用いてアルカリ性水媒体中で漂白。
▲４▼過酸化物を用いて酸性水媒体中で漂白。
▲５▼還元剤を用いてアルカリ性水媒体中で漂白。
▲６▼耐酸性の酵素による処理。
【００２３】
本発明には、酸性の漂白段からの洗浄脱離液を前段の酸性漂白の希釈水や洗浄水として戻し最終的に酸性高温処理を行った後、排出する方法、及び更にアルカリ性の漂白からの洗浄脱離液を前段の希釈水や洗浄水として戻し最終的に黒液回収工程で処理する方法を組合わせることができる。
強酸性白水中には重金属（マンガン、鉄等）が含まれているため、回収工程内に蓄積する、更に塩素系漂白剤の白水による装置の腐食が考えられる。そこで、本システムではアルカリ性白水のみ黒液回収工程に戻し、塩素を含む酸性白水のみ排出する方法である。
尚、塩素系漂白剤を使用しないＴＣＦの場合、例えばオゾン漂白について白水中の重金属の除去（例えばキレート処理等）を行うことで全量について黒液回収に戻すことが可能である。
【００２４】
本発明の酸性漂白白水による酸性高温処理によって製造された針葉樹または広葉樹の化学パルプは、ＰＰＣ、感熱紙、インクジェット、バブルジェット、レーザービーム等の印刷用紙または塗工用原紙に好ましく適用される。
更に、化学パルプがユーカリ類及び／またはフタバガキ科の１つ以上を含む南方系広葉樹パルプを原料として酸性漂白白水による酸性高温処理によって製造された化学パルプは、印刷用紙または塗工用原紙に好ましく適用される。
【００２５】
【実施例】
以下に実施例を挙げて本発明を具体的に説明するが、本発明は本実施例に限定されるものではない。尚、実施例において記載の部、％は全て重量部、重量％によるものである。又、白色度は、ＪＩＳ−Ｐ８１２３、パルプ粘度は、ＴＡＰＰＩ Ｔ−２３０ ｏｍ−８２、カッパー価は、ＴＡＰＰＩ Ｔ−２３６ ｈｍ−８５、濾水度は、ＪＩＳ−Ｐ８１２１、不透明度は、ＪＩＳ−Ｐ８１３８、引張強度は、ＪＩＳ−Ｐ８１１３、引裂強度は、ＪＩＳ−Ｐ８１１９、平滑度は、ＴＡＰＰＩ Ｔ−４７９、内部結合（以下ＩＢと略す）は、インターナルボンドテスター（東西精機製作所社製）、ベッセルピック（以下ＶＰと略する）は、ＲＩ試験機（石川島機械社製）にて３０ｃｍ2（ｎ＝３）あたりのベッセル数、ＣＯＤ、色度はＪＩＳ−Ｋ０１０２、ＡＯＸは全有機ハロゲン分析装置ＴＯＸ−１０型（三菱化学社製）にて測定した。
【００２６】
以下の実施例で用いて酸性漂白白水は、当社実機プラントより発生した塩素（Ｃ）／二酸化塩素（Ｄ）漂白白水（ｐＨ約２、ＣＯＤ１０００ｐｐｍ、色度１２００ｐｐｍ）、Ｄ白水（ｐＨ約４、８０ｐｐｍ、色度１６０ｐｐｍ）、ラボのオゾン（Ｚ）漂白より発生した白水（ｐＨ約２、ＣＯＤ１４０ｐｐｍ、色度１３０ｐｐｍ）の３種類を使用し、ｐＨ調整には硫酸を用いた。
【００２７】
（処理ｐＨの検討）
実施例１
広葉樹（ユーカリ系約７５％配合）の酸素漂白後の洗浄脱水したパルプ（酸素漂白パルプと略す、カッパー価９．３、粘度２２．９ｃｐ、白色度４７．８％）に、Ｃ／Ｄ白水を用いてｐＨ１に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところ、カッパー価が３．７、白色度が５２．３％、粘度が９．３ｍＰａｓのパルプを得た。
【００２８】
実施例２
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところ、カッパー価が５．２、白色度が４９．４％、粘度が１９．５ｍＰａｓのパルプを得た。
【００２９】
実施例３
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ４に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところ、カッパー価が６．９、白色度が４８．３％、粘度が２２．９ｍＰａｓのパルプを得た。
【００３０】
実施例４
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ５に調整し、パルプ濃度を１０％、９０℃、１２０分間処理したところ、カッパー価が７．８、白色度が４７．８％、粘度が２３．０ｍＰａｓのパルプを得た。
実施例１〜４までの結果について表１に示す。
ｐＨ１ではカッパー価の低下が大きく、白色度も増加するが極端にパルプ粘度が低下している。またｐＨ５ではパルプ粘度の低下は見られないが、白色度が変わらず、若干カッパー価の低下が低い傾向にある。尚、ｐＨの傾向はＤ白水、Ｚ白水でも同様の傾向が認められ、更にＣ／Ｄ白水よりもカッパー価の低下率が０．５〜１．０程度良好であった。
【００３１】
【表１】
（処理濃度の検討）
実施例５
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を５％、９０℃、９０分間処理したところ、カッパー価が５．６、白色度が４９．１％、粘度が２１．８ｍＰａｓのパルプを得た。
【００３３】
実施例６
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１５％、９０℃、９０分間処理したところ、カッパー価が５．０、白色度が４９．６％、粘度が１９．４ｍＰａｓのパルプを得た。
【００３４】
実施例７
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を２５％、９０℃、９０分間処理したところ、カッパー価が４．６、白色度が５０．１％、粘度が１９．１ｍＰａｓのパルプを得た。
実施例５〜６までの結果について表２に示す。
処理濃度が低濃度より高濃度の方がカッパー価の低下が大きく、白色度も増加する傾向にある。処理濃度が１０％と１５％ではそれほどの差が見られないこと、設備等を考慮すると中濃度でも十分である。
【００３５】
【表２】
（処理温度の検討）
実施例８
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、１３０℃、６０分間処理したところ、カッパー価が３．１、白色度が５４．９％、粘度が９．８ｍＰａｓのパルプを得た。
【００３７】
実施例９
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、１１０℃、９０分間処理したところ、カッパー価が３．３、白色度が５２．９％、粘度が１２．８ｍＰａｓのパルプを得た。
【００３８】
実施例１０
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、７０℃、９０分間処理したところ、カッパー価が７．６、白色度が４８．０％、粘度が２２．８ｍＰａｓのパルプを得た。
【００３９】
実施例１１
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、５０℃、１２０分間処理したところ、カッパー価が７．９、白色度が４７．９％、粘度が２２．９ｍＰａｓのパルプを得た。
実施例８〜１１の結果について表３に示す。
５０℃では時間を長くすることでいくらか効果が見られる。しかし、１３０℃では時間を短くした場合でもパルプ粘度の低下が大きかった。従って、物性、装置等を考慮すると圧力容器を必要としない１００℃以下が望ましい。
【００４０】
【表３】
（処理時間の検討）
実施例１２
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、３０分間処理したところ、カッパー価が８．１、白色度が４８．９％、粘度が２２．３ｍＰａｓのパルプを得た。
【００４２】
実施例１３
実施例１の酸素漂白パルプに、Ｃ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、１８０分間処理したところ、カッパー価が４．６、白色度が５０．７％、粘度が１８．３ｍＰａｓのパルプを得た。
実施例１２、１３の結果を表４に示す。
３０分では短く、１８０分では期待したほどの効果が見られなかった。従って、３０〜１８０分の間でも十分である。
【００４３】
【表４】
実施例１４
実施例１の酸素漂白パルプに、Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところ、カッパー価が４．６、白色度が５０．８％、粘度が１９．２ｍＰａｓのパルプを得た。
【００４５】
実施例１５
実施例１の酸素漂白パルプに、Ｚ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところ、カッパー価が４．５、白色度が５０．９％、粘度が１９．１ｍＰａｓのパルプを得た。
【００４６】
実施例１６
実施例１の酸素漂白パルプに、Ｐａ（Ｐａは混合過酸処理を表す）白水を用いて、ｐＨ２、パルプ濃度１０％、９０℃の条件で９０分間処理し、カッパー価が４．９、白色度５０．１％、粘度が１８．６ｍＰａｓのパルプを得た。
Ｚ白水ほどではないが、Ｃ／Ｄ白水に匹敵する効果が認められる。
【００４７】
比較例１
過酸化物の漂白前処理として行われる酸処理条件にて、実施例１の酸素漂白パルプに硫酸（３．５％）にてｐＨ２に調整し、パルプ濃度を５％、６０℃、６０分間処理したところ、カッパー価が８．１、白色度が４８．３％、粘度が２１．１ｍＰａｓのパルプを得た。
【００４８】
比較例２
次に、オゾンの低減として前処理条件にて、比較例１と同様に硫酸（２．０％）にてｐＨ４に調整し、パルプ濃度を１０％、１１０℃、１８０分間処理したところ、カッパー価が４．７、白色度が５０．７％、粘度が１３．８ｍＰａｓのパルプを得た。
実施例１４、１５及び１６と比較例１、２の結果を表５に示す。
Ｃ／Ｄ白水よりＤ白水、Ｚ白水の方が効果があることが判った。更に硫酸を使用した場合、ｐＨ２の低温ではほとんど効果が認められない。また高温ｐＨ４では白水と同等の効果が見られるがパルプ粘度の低下が大きい。
【００４９】
【表５】
実施例１７
針葉樹（国産材５０％とラジアータパイン５０％配合）の酸素漂白パルプ（カッパー価１４．３、粘度１６．１ｃｐ、白色度３０．２％）に、Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、１８０分間処理したところ、カッパー価が１１．８、白色度が３２．３％、粘度が１５．９ｍＰａｓのパルプを得た。
この結果により、針葉樹パルプに関しては非常に効果が薄いことが判った。
【００５１】
実施例１８
広葉樹（ユーカリ系約７５％配合）の蒸解パルプ（カッパー価１７．４、粘度３６．９ｃｐ）にＣ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理した後に、洗浄脱水せずに酸素漂白としてＮａＯＨ（Ｅ）０．８％（対絶乾パルプ）と約４９０ｋＰａのＯ2（酸素）を添加、１１０℃、６０分間反応したところカッパー価７．８、粘度２５．６ｍＰａｓ、白色度５１．６％のパルプを得た。
【００５２】
実施例１９
実施例１８の蒸解パルプにＣ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理し、洗浄脱水したところカッパー価が１２．９、粘度が３５．３ｃｐの化学パルプを得た。更に、酸素漂白としてＥ０．６％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応したところカッパー価７．３、粘度２５．９ｍＰａｓ、白色度５２．３％のパルプを得た。
【００５３】
実施例２０
実施例１８の蒸解パルプに、酸素漂白としてパルプ濃度１２％、Ｅ０．８％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応した。洗浄脱水せずにＣ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理したところカッパー価７．５、粘度２５．７ｍＰａｓ、白色度５１．９％のパルプを得た。
【００５４】
実施例２１
実施例１８の蒸解パルプに、酸素漂白としてパルプ濃度１２％、Ｅ０．４％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応した。次にＣ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理した後に洗浄脱水せずに、酸素漂白としてパルプ濃度１２％、Ｅ０．５％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応したところカッパー価７．３、粘度２５．８ｍＰａｓ、白色度５２．０％のパルプを得た。
【００５５】
実施例２２
実施例１８の蒸解パルプに、酸素漂白としてパルプ濃度１２％、Ｅ０．４％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応した。次にＣ／Ｄ白水を用いてｐＨ２に調整し、パルプ濃度を１０％、９０℃、９０分間処理した後に、洗浄脱水したところカッパー価が１２．６、粘度が３５．９ｍＰａｓの化学パルプを得た。酸素漂白としてパルプ濃度１２％、Ｅ０．３％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応したところカッパー価７．０、粘度２６．０ｍＰａｓ、白色度５２．６％のパルプを得た。
【００５６】
比較例３
実施例１８の蒸解パルプを酸素漂白としてＥ１．０％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応したところカッパー価９．０、粘度２３．９ｍＰａｓ、白色度４８．９％のパルプを得た。
更に、実施例２、実施例１８〜２２と比較例１のパルプを、Ｃ／Ｄ−Ｅ−Ｈ（次亜塩素酸ソーダ）−Ｄにて以下の条件で漂白を行った。
実施例２の漂白条件は、Ｃの添加率は０．６％、Ｄの添加率は０．０６％、５０℃、３０分間、パルプ濃度は３．５％にて漂白した。次いでＥの添加率は０．６％、６０℃、９０分間、パルプ濃度は１２％にて漂白した。Ｈの添加率は０．３％、６５℃、２時間、パルプ濃度は１２％にて漂白した。Ｄの添加率は０．２％、７０℃、２．５時間、パルプ濃度は１２％に漂白した。
実施例１８〜２２の条件は、全て同じとしてＣの添加率は１．０％、Ｄの添加率は０．１％、５０℃、３０分間、パルプ濃度は３．５％、次いでＥの添加率は０．６％、６０℃、９０分間、パルプ濃度は１２％にて漂白した。Ｈの添加率は０．３％、６５℃、２時間、パルプ濃度は１２％にて漂白した。Ｄの添加率は０．２％、７０℃、２．５時間、パルプ濃度は１２％に漂白した。
更に、比較例３は酸性処理せずにＣ／Ｄ−Ｅ−Ｈ−Ｄにて同様に以下の条件で漂白した。Ｃの添加率１．４％、Ｄの添加率０．１４％で５０℃、３０分間、パルプ濃度３．５％にて漂白した。Ｅの添加率０．８％で、６０℃、９０分間、パルプ濃度１２％にて漂白した。Ｈの添加率０．４％で、６５℃、２時間、パルプ濃度は１２％にて漂白した。Ｄの添加率で０．３％、７０℃、２．５時間、パルプ濃度は１２％に漂白した。
実施例１８〜２２と比較例３の結果を表６、７に示す。
蒸解と酸素漂白の間に導入した時、または酸素漂白の後に導入することでカッパー価の低下効果と白色度が向上、パルプ粘度の改善されることが判った。更に洗浄脱水を加えることでなお一層改善されることが判った。また、本発明の処理を導入することで蒸解も改善でき、収率の向上も期待できる。
【００５７】
【表６】
【表７】
実施例２３
実施例２で処理、漂白したパルプを、ＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行った、物性、排水等について評価した。
【００６０】
実施例２４
実施例１４で処理されたパルプを、Ｄ1−Ｐ（過酸化水素）−Ｄ2にて漂白、更にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。
尚、Ｄ1段は、添加率０．６％で、７０℃、１．５時間漂白した。Ｐ段は、Ｐの添加率０．５％、Ｅの添加率０．３％で、６５℃、２時間漂白した。Ｄ2は、添加率０．３％で、７５℃、２．５時間漂白した。各漂白におけるパルプ濃度は全て１２％にて行った。
【００６１】
実施例２５
実施例１５で処理されたパルプを、Ｚ−Ｐ−Ｄにて漂白、更にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。
尚、Ｚ段は、添加率０．６％で、ｐＨ２、室温、１５分間漂白した。Ｐ段は、Ｐの添加率０．５％、Ｅの添加率０．３％で、６５℃、２時間漂白した。Ｄ段は、添加率０．４％、７５℃、２．５時間漂白した。各漂白におけるパルプ濃度は全て１２％にて行った。
【００６２】
比較例４
比較例３で得られたパルプを実施例２３と同様にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。
【００６３】
比較例５
比較例１で得られたパルプをＣ／Ｄ−Ｅ−Ｈ−Ｄにて以下の条件で漂白、更にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。Ｃの添加率１．２％、Ｄの添加率０．１２％で５０℃、３０分間、パルプ濃度３．５％にて漂白した。Ｅの添加率０．８％で、６０℃、９０分間、パルプ濃度１２％にて漂白した。Ｈの添加率０．４％で、６５℃、２時間、パルプ濃度は１２％にて漂白した。Ｄの添加率で０．３％、７０℃、２．５時間、パルプ濃度は１２％にて漂白した。
【００６４】
比較例６
比較例３と同様に酸性処理を行わず、Ｄ1−Ｐ−Ｄ2にて漂白、更にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。
尚、Ｄ1段は、添加率０．８％で、７０℃、１．５時間漂白した。Ｐ段は、Ｐの添加率０．７％、Ｅの添加率０．４％で、６５℃、２時間漂白した。Ｄ2段は、添加率０．４％で、７５℃、２．５時間漂白した。各漂白におけるパルプ濃度は全て１２％にて行った。
【００６５】
比較例７
比較例３と同様に酸性処理を行わず、Ｚ−Ｐ−Ｄにて漂白、更にＰＦＩミルにて叩解（４０００ｒｅｖ）し、手抄き（坪量６０ｇ／ｃｍ2）を行い、物性、排水等について評価した。
尚、Ｚ段は、添加率０．８％で、ｐＨ２、室温、１５分間漂白した。Ｐ段は、Ｐの添加率０．６％、Ｅの添加率０．３％で、６５℃、２時間漂白した。Ｄ段は、添加率０．４％で、７５℃、２．５時間漂白した。各漂白におけるパルプ濃度は全て１２％にて行った。
実施例２３〜２５と比較例４〜６の結果を表８、９に示す。
白色度が上昇し収率、粘度の低下がなく、排水負荷が半減している。更にカッパー価の低下により漂白剤の添加量が約４割程度削減できることも判った。
パルプ物性は、強度、平滑性、更にベッセルピックがかなり改善され、叩解性も良くなっていることが判った。
【００６６】
【表８】
【表９】
実施例２６
実施例２３で得られた化学パルプ（濾水度４００ｍｌ）に硫酸バンド０．７％カチオン澱粉０．６％、サイズ剤０．０２％、軽質カルシウム８％、歩留向上剤０．０３％を添加して坪量１００ｇ／ｍ2のシートを手抄きした。
【００６９】
比較例７
比較例３で得られた化学パルプ（濾水度４００ｍｌ）を実施例２５と同様に硫酸バンド０．７％カチオン澱粉０．６％、サイズ剤０．０２％、軽質カルシウム８％、歩留向上剤０．０３％を添加して坪量１００ｇ／ｍ2のシートを手抄きした。
実施例２６と比較例５を比べると実施例のパルプ強度が強く、ベッセルピックが少ない等ため印刷用紙として評価したところ、ダイヤ印刷における印刷適性、ブリスター等が比較例よりも数段良好であった。
【００７０】
実施例２７
実施例１８の蒸解パルプに実施例２４において発生した各段の漂白白水を酸素漂白にＰ白水、酸性処理にＤ1白水、Ｄ1にＤ2白水、ＰとＤ2に新水を用いて、酸素漂白の条件としては、パルプ濃度１２％、Ｅ０．６％と約４９０ｋＰａのＯ2を添加、１１０℃、６０分間反応した後、実施例２４と同様の条件（Ａ−Ｄ1−Ｐ−Ｄ2）で漂白したところ、白色度８７．６％、粘度１８．９ｍＰａｓと実施例２３よりも白色度が高く、高粘度の化学パルプを得た。
Ｐ白水の使用により酸素漂白後のカッパー価が低下し白色度も上がるため、後段の漂白性が良くなる結果となった。更にＰ白水がアルカリ源となるためアルカリの節減ができるが、若干排水の負荷が上がる傾向にあった。
【００７１】
【発明の効果】
実施例に示したように本発明の化学パルプの漂白において、酸性漂白白水を用いて酸性高温処理を蒸解、洗浄後、酸素漂白前または後に実施し、洗浄脱水工程を経て、または経ないで、更に多段漂白を行うことによって、漂白反応を促進させると共に塩素化合物の使用量を減らしてＡＯＸを低減させることができる。更に広葉樹パルプに特有の印刷において問題となるベッセルピックの発生を酸性漂白白水による処理によって減少させることができる。かつベッセルピックの少なく、ＡＯＸの含有量の少ない印刷用紙または塗工用原紙を与えることが可能となる。
従来の低温酸処理に比べ、漂白性の改善とセルロースの改質を同時に与えることができ、その結果、易叩解、高白色度、高収率の化学パルプが得られる。かつ叩解時に繊維がフィブリル化され易くなり、ベッセルピックや紙ムケの防止が可能である。また、硫酸による高温酸処理に比べ、漂白薬品の添加量が少なく済むだけでなく、漂白白水のＡＯＸ、ＣＯＤ、色度の低減が図られ、排出量の削減と白水の有効利用が可能であり、、パルプ粘度の保護も可能である。
更に、酸性の酵素処理に比べると、パルプ収率低下が少なく後段の漂白促進効果が大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating chemical pulp with acidic bleached white water and a printing paper or a base paper for coating. More specifically, in chemical pulp bleaching, acidic high temperature treatment using acid bleached white water is performed after digestion, washing, before or after oxygen bleaching, and further through multistage bleaching with or without a washing dehydration step. And a method for reducing AOX by accelerating the bleaching reaction and reducing the amount of chlorine compound used. Further, it relates to a method for reducing the occurrence of vessel pick which is a problem in printing peculiar to hardwood pulp by treatment with acidic bleaching white water, and relates to a printing paper or a base paper for coating with a low vessel pick and a low AOX content. It is.
[0002]
[Prior art]
The purpose of pulp bleaching is to increase the whiteness by decomposing, changing or solubilizing and removing lignin and coloring substances adhering to the inside and surface of the pulp fiber.
[0003]
Conventionally, chemical pulp bleaching has generally been performed in a stepwise manner with chlorine, hypochlorite, hydrogen peroxide, hydrogen dioxide or the like after cooking. In recent years, many methods of adding oxygen bleaching have been adopted for the purpose of reducing drainage load and reducing bleaching chemical costs.
[0004]
On the other hand, recently, so-called non-chlorine bleaching methods that do not use chlorinated chemicals have been developed and operated in view of AOX regulations and safety including dioxins. Non-chlorine bleaching methods include the TCF method that does not use chlorine and chlorine dioxide and other chlorine chemicals, and the ECF method that does not use only chlorine.
[0005]
Non-chlorine bleaching methods using peroxide and ozone are already known. However, in peroxide or ozone bleaching, unless the pulp is pretreated, the peroxide or ozone is decomposed by trace metals such as Mn and Fe present in the pulp slurry, and bleaching efficiency is reduced. A large amount of the agent is used, leading to an increase in cost and a problem of a decrease in pulp viscosity due to active chemical species such as radicals generated by decomposition.
[0006]
Therefore, as a countermeasure for trace metals, Japanese Patent Application Laid-Open No. 5-148784 discloses ozone and peroxidation in which lignocellulose-containing pulp is acid-treated in a pH range of 1 to 6 and then an alkaline earth metal-containing compound is treated in a pH range of 1 to 7. In addition, JP-A-5-148785 discloses a method of bleaching lignocellulose-containing pulp with a complexing agent of nitrogen polycarboxylic acid within a pH range of 3.1 to 9.0. A bleaching method has been proposed.
[0007]
However, the pretreatment by these methods has a limitation in removing trace metals and is not only effective, but almost no kappa number reduction effect is observed.
[0008]
Recently, enzymatic delignification methods have been studied. As the enzyme, cellulase, xylanase, pectinase, lipase and the like are known. For example, in Japanese Examined Patent Publication No. 2-264087, a method for treating unbleached pulp with an enzyme containing xylanase having a pH of 4-8. Japanese Patent Publication No. 2-293486 proposes a method for treating unbleached pulp with an enzyme containing hemicellulase at pH 3-10.
[0009]
Furthermore, methods for modifying pulp with enzymes have been studied. For example, in Japanese Patent Publication No. 2-20756, cellulase and cellobiose are added at a ratio of 1 / 0.05 to 0.5 at the time of paper making to promote beating and reduce power. Japanese Patent Publication No. 63-135597 proposes prevention of vessel picking by addition of an enzyme having an FP activity of 20 mg / g or more.
[0010]
However, these methods can not only provide a delignification effect, improved bleachability and modification of cellulose, but also reduce the pulp yield.
[0011]
As a pretreatment in the bleaching of peroxides and ozone as described above, many acid treatments and acidic enzyme treatments have been reported, but there are problems as described above.
[0012]
Therefore, research on delignification effect and bleaching property improvement by active peroxide under acidic conditions such as peracetic acid, caroic acid, mixed peracid, etc. has been actively conducted. It is in a situation where it is not actually used due to safety issues.
[0013]
Furthermore, at the “Ozone Bleaching Seminar” sponsored by the Paper and Pulp Technology Association in November 1996, ARL STROM was treated with sulfuric acid at pH 3.5-4 and 110 ° C. as a pretreatment of ozone and chlorine dioxide. Announced that the amount of ozone and chlorine dioxide added can be reduced.
However, the whiteness improvement by acid treatment is not recognized, and the pulp viscosity and pulp yield are further reduced. Further, there are problems such as the need for a closed type apparatus due to high cost and high temperature due to the use of sulfuric acid.
[0014]
[Problems to be solved by the invention]
The objects of the present invention are the above-mentioned problems of the prior art (1) use of expensive sulfuric acid, (2) small effect of reducing the kappa number, (3) low effect of improving bleachability, and (4) modification of cellulose. The effect of preventing vessel picking due to the quality is to solve (5) lower pulp yield, (6) lower pulp viscosity, etc., and promote bleaching reaction and reduce the amount of chlorine compound used to reduce AOX Reduce,Furthermore, it is a method to reduce the occurrence of vessel pick which is a problem in printing peculiar to hardwood pulp by treatment with acidic bleached white water.Ru.
[0015]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors surprisingly treated pulp before bleaching (such as digested pulp and oxygen bleached pulp) with acidic white water discharged from the bleaching process. Finds that most of the above problems can be eliminated, the bleaching effect is high, and pulp with less vessel pick in hardwood pulp and AOX can be reduced.,Process for treating chemical pulp of the present invention with acidic bleached white waterIt came to complete.
That is, in chemical pulp bleaching, acidic high temperature treatment using acid bleached white water is performed after cooking, washing, and before or after oxygen bleaching, and further performing multistage bleaching with or without a washing dehydration step.The
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The chemical pulp used in the present invention is a hardwood pulp or softwood pulp that has been digested or oxygen bleached. It should be noted that the southern hardwood pulp has a greater effect of improving bleachability than the softwood pulp, and a particularly excellent effect is observed for the vessel pick that is peculiar to hardwood.
[0017]
The acidic bleaching white water used for the acidic high temperature treatment with the acidic bleached white water of the present invention is a treatment with chlorine, chlorine dioxide, chlorine and chlorine dioxide, ozone, organic peracid, inorganic peracid, mixed peracid, acid-resistant enzyme. One or more white waters generated from
[0018]
Processing temperature is 50-130 degreeC, Preferably it is 60-110 degreeC, More preferably, it is 70-100 degreeC. Here, when the treatment temperature is less than 50 ° C., the treatment efficiency is low, and when it exceeds 130 ° C., not only the expected effect does not appear but also the pulp viscosity and the pulp yield decrease.
[0019]
The treatment time is 20 to 240 minutes, preferably 30 to 180 minutes, more preferably 60 to 120 minutes. Here, the effect is small when the treatment time is less than 20 minutes, and no further effect is exhibited when the treatment time is longer than 2400 minutes.
[0020]
The treatment pH is 1 to 5, preferably pH 2 to 4. Here, when the treatment pH is less than 1, the problem of corrosion of the apparatus, the viscosity of the pulp and the pulp yield are lowered, and when the treatment pH is higher than 5, the effect of the treatment does not appear.
[0021]
The pulp concentration is 1 to 30% by weight, preferably 3 to 25% by weight, more preferably 5 to 20% by weight. Here, when the pulp concentration is less than 1% by weight, the treatment efficiency is poor, and when the pulp concentration is more than 30% by weight, the stirring and mixing is not preferable.
[0022]
As the subsequent multistage bleaching, at least one of the following (1) to (6) is combined and bleached.
(1) Bleaching in an acidic aqueous medium using one or more chemicals of chlorine, chlorine dioxide and hypochlorite.
(2) Bleaching in an acidic aqueous medium using ozone.
(3) Bleaching in an alkaline aqueous medium using peroxide or peroxide and oxygen.
(4) Bleaching in an acidic aqueous medium using peroxide.
(5) Bleaching in an alkaline aqueous medium using a reducing agent.
(6) Treatment with acid-resistant enzyme.
[0023]
In the present invention, the washing detachment liquid from the acidic bleaching stage is returned as diluted water or washing water of the acidic bleaching stage in the previous stage, and finally discharged after the acidic high temperature treatment, and further from the alkaline bleaching. It is possible to combine a method in which the washing desorption liquid is returned to the previous dilution water or washing water and finally processed in the black liquor recovery step.
Since strongly acidic white water contains heavy metals (manganese, iron, etc.), the corrosion of the apparatus due to white water of chlorine bleach that accumulates in the recovery process is considered. Therefore, in this system, only alkaline white water is returned to the black liquor recovery step, and only acidic white water containing chlorine is discharged.
In the case of TCF that does not use a chlorine bleach, for example, by removing heavy metals in white water (for example, chelate treatment) for ozone bleaching, the entire amount can be returned to black liquor recovery.
[0024]
Coniferous or hardwood chemical pulp produced by acidic high temperature treatment with acidic bleached white water of the present inventionIsPPC, thermal paper, ink jet, bubble jet, laser beam, etc. printing paper or coating base paperPreferably applied to.
Further, chemical pulp produced by acidic high-temperature treatment with acidic bleached white water using southern hardwood pulp containing eucalyptus and / or one or more of the dipterocarpaceae as raw materialsIsPrinting paper or coating paperPreferably applied to.
[0025]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In the examples, all parts and% are based on parts by weight and% by weight. Further, the whiteness is JIS-P813, the pulp viscosity is TAPPI T-230 om-82, the kappa number is TAPPI T-236 hm-85, the freeness is JIS-P8121, and the opacity is JIS-P8138. The tensile strength is JIS-P8113, the tear strength is JIS-P8119, the smoothness is TAPPI T-479, the internal bond (hereinafter abbreviated as IB) is an internal bond tester (manufactured by Tozai Seiki Seisakusyo), Vessel pick (Hereinafter abbreviated as VP) is 30 cm with an RI testing machine (Ishikawajima Machine Co., Ltd.).2The number of vessels per (n = 3), COD, and chromaticity were measured with JIS-K0102, and AOX was measured with a total organic halogen analyzer TOX-10 (manufactured by Mitsubishi Chemical Corporation).
[0026]
The acid bleached white water used in the following examples is chlorine (C) / chlorine dioxide (D) bleached white water (pH about 2, COD 1000 ppm, chromaticity 1200 ppm), D white water (pH about 4, 80 ppm) generated from our actual plant. , Chromaticity 160 ppm), white water (pH about 2, COD 140 ppm, chromaticity 130 ppm) generated from laboratory ozone (Z) bleaching, and sulfuric acid was used for pH adjustment.
[0027]
(Examination of treatment pH)
Example 1
Washed and dehydrated pulp after broad-leaved tree (containing about 75% eucalyptus) (abbreviated as oxygen-bleached pulp, kappa number 9.3, viscosity 22.9 cp, whiteness 47.8%) with C / D white water The pH was adjusted to 1 using a pulp concentration of 10% and 90 ° C. for 90 minutes, and a pulp having a copper number of 3.7, a whiteness of 52.3%, and a viscosity of 9.3 mPas was obtained.
[0028]
Example 2
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated with a pulp concentration of 10%, 90 ° C. for 90 minutes, the copper number was 5.2 and the whiteness was 49.4%. A pulp with a viscosity of 19.5 mPas was obtained.
[0029]
Example 3
When the oxygen bleached pulp of Example 1 was adjusted to pH 4 using C / D white water and treated with a pulp concentration of 10%, 90 ° C. for 90 minutes, the kappa number was 6.9 and the whiteness was 48.3%. A pulp with a viscosity of 22.9 mPas was obtained.
[0030]
Example 4
When the oxygen bleached pulp of Example 1 was adjusted to pH 5 using C / D white water and treated with a pulp concentration of 10%, 90 ° C. for 120 minutes, the kappa number was 7.8 and the whiteness was 47.8%. A pulp with a viscosity of 23.0 mPas was obtained.
The results of Examples 1 to 4 are shown in Table 1.
At pH 1, the Kappa number is greatly decreased and the whiteness is increased, but the pulp viscosity is extremely decreased. Moreover, although the fall of a pulp viscosity is not seen at pH 5, whiteness does not change and it exists in the tendency for the fall of a kappa number to be a little low. In addition, the tendency of pH was similar in D white water and Z white water, and the decrease rate of the kappa number was about 0.5 to 1.0 better than that of C / D white water.
[0031]
[Table 1]
(Examination of treatment concentration)
Example 5
The oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 5%, 90 ° C. for 90 minutes, resulting in a kappa number of 5.6 and a whiteness of 49.1%. A pulp with a viscosity of 21.8 mPas was obtained.
[0033]
Example 6
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated with a pulp concentration of 15% and 90 ° C. for 90 minutes, the copper number was 5.0 and the whiteness was 49.6%. A pulp with a viscosity of 19.4 mPas was obtained.
[0034]
Example 7
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 25% and 90 ° C. for 90 minutes, the copper number was 4.6 and the whiteness was 50.1%. A pulp having a viscosity of 19.1 mPas was obtained.
The results of Examples 5 to 6 are shown in Table 2.
When the treatment concentration is higher than the lower concentration, the kappa number decreases more and the whiteness tends to increase. In view of the fact that there is no significant difference between the treatment concentrations of 10% and 15%, and facilities are considered, the intermediate concentration is sufficient.
[0035]
[Table 2]
(Examination of processing temperature)
Example 8
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 10% and 130 ° C. for 60 minutes, the copper number was 3.1 and the whiteness was 54.9%. A pulp with a viscosity of 9.8 mPas was obtained.
[0037]
Example 9
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 10% and 110 ° C. for 90 minutes, the copper number was 3.3 and the whiteness was 52.9%. A pulp with a viscosity of 12.8 mPas was obtained.
[0038]
Example 10
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 10% and 70 ° C. for 90 minutes, the copper number was 7.6 and the whiteness was 48.0%. A pulp with a viscosity of 22.8 mPas was obtained.
[0039]
Example 11
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated at a pulp concentration of 10%, 50 ° C. for 120 minutes, the kappa number was 7.9 and the whiteness was 47.9%. A pulp with a viscosity of 22.9 mPas was obtained.
The results of Examples 8 to 11 are shown in Table 3.
At 50 ° C, some effect can be seen by increasing the time. However, at 130 ° C., the pulp viscosity was greatly reduced even when the time was shortened. Accordingly, in consideration of physical properties, equipment, etc., it is desirable that the temperature is 100 ° C. or lower, which does not require a pressure vessel.
[0040]
[Table 3]
(Examination of processing time)
Example 12
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated with a pulp concentration of 10% and 90 ° C. for 30 minutes, the copper number was 8.1 and the whiteness was 48.9%. A pulp with a viscosity of 22.3 mPas was obtained.
[0042]
Example 13
When the oxygen bleached pulp of Example 1 was adjusted to pH 2 using C / D white water and treated with a pulp concentration of 10%, 90 ° C. for 180 minutes, the copper number was 4.6 and the whiteness was 50.7%. A pulp having a viscosity of 18.3 mPas was obtained.
The results of Examples 12 and 13 are shown in Table 4.
It was short at 30 minutes and did not show the expected effect at 180 minutes. Therefore, even between 30 and 180 minutes is sufficient.
[0043]
[Table 4]
Example 14
The oxygen bleached pulp of Example 1 was adjusted to pH 2 using D white water and treated at a pulp concentration of 10%, 90 ° C. for 90 minutes. As a result, the copper number was 4.6, the whiteness was 50.8%, and the viscosity was Yielded 19.2 mPas pulp.
[0045]
Example 15
The oxygen bleached pulp of Example 1 was adjusted to pH 2 using Z white water and treated at a pulp concentration of 10%, 90 ° C. for 90 minutes. As a result, the copper number was 4.5, the whiteness was 50.9%, and the viscosity was Obtained a pulp of 19.1 mPas.
[0046]
Example 16
The oxygen bleached pulp of Example 1 was treated for 90 minutes under the conditions of pH 2, pulp concentration 10%, 90 ° C. using Pa (Pa represents mixed peracid treatment) white water, kappa number 4.9, white A pulp having a degree of 50.1% and a viscosity of 18.6 mPas was obtained.
Although not as good as Z white water, an effect comparable to C / D white water is observed.
[0047]
Comparative Example 1
Under acid treatment conditions performed as a pre-bleaching treatment for peroxide, the oxygen bleached pulp of Example 1 was adjusted to pH 2 with sulfuric acid (3.5%), and the pulp concentration was treated at 5%, 60 ° C. for 60 minutes. As a result, a pulp having a kappa number of 8.1, a whiteness of 48.3%, and a viscosity of 21.1 mPas was obtained.
[0048]
Comparative Example 2
Next, as a reduction of ozone, the pH value was adjusted to 4 with sulfuric acid (2.0%) in the same pretreatment conditions as in Comparative Example 1, and the pulp concentration was 10% at 110 ° C. for 180 minutes. Of 4.7, whiteness 50.7%, and viscosity 13.8 mPas.
Table 5 shows the results of Examples 14, 15 and 16 and Comparative Examples 1 and 2.
It was found that D white water and Z white water were more effective than C / D white water. Furthermore, when sulfuric acid is used, the effect is hardly recognized at a low temperature of pH 2. Moreover, although the effect equivalent to white water is seen at high temperature pH 4, the fall of pulp viscosity is large.
[0049]
[Table 5]
Example 17
Oxygen bleached pulp (copper number 14.3, viscosity 16.1 cp, whiteness 30.2%) of conifer (50% domestic wood and 50% radiata pine), adjusted to pH 2 using D white water, pulp concentration Was treated for 10 minutes at 90 ° C. for 180 minutes to obtain a pulp having a kappa number of 11.8, a whiteness of 32.3%, and a viscosity of 15.9 mPas.
From this result, it was found that the effect was very weak with respect to softwood pulp.
[0051]
Example 18
A hardwood (containing about 75% eucalyptus) digested pulp (kappa number 17.4, viscosity 36.9 cp) was adjusted to pH 2 using C / D white water, and the pulp concentration was treated at 10%, 90 ° C. for 90 minutes. Later, NaOH (E) 0.8% (absolute dry pulp) and about 490 kPa O as oxygen bleaching without washing and dewatering2When (oxygen) was added and reacted at 110 ° C. for 60 minutes, a pulp having a kappa number of 7.8, a viscosity of 25.6 mPas, and a whiteness of 51.6% was obtained.
[0052]
Example 19
The digested pulp of Example 18 was adjusted to pH 2 using C / D white water, treated with a pulp concentration of 10%, 90 ° C. for 90 minutes, washed and dehydrated to have a kappa number of 12.9 and a viscosity of 35.3 cp. Chemical pulp was obtained. Furthermore, as oxygen bleaching, E0.6% and O of about 490 kPa2Was added and reacted at 110 ° C. for 60 minutes to obtain a pulp having a kappa number of 7.3, a viscosity of 25.9 mPas and a whiteness of 52.3%.
[0053]
Example 20
The digested pulp of Example 18 was subjected to oxygen bleaching as a pulp concentration of 12%, E0.8% and O of about 490 kPa.2And reacted at 110 ° C. for 60 minutes. Pulp having a kappa number of 7.5, a viscosity of 25.7 mPas, and a whiteness of 51.9% when adjusted to pH 2 using C / D white water without washing and dewatering and treated at a pulp concentration of 10%, 90 ° C. for 90 minutes. Got.
[0054]
Example 21
The digested pulp of Example 18 was subjected to oxygen bleaching at a pulp concentration of 12%, E0.4% and O of about 490 kPa.2And reacted at 110 ° C. for 60 minutes. Next, the pH was adjusted to 2 using C / D white water, and the pulp concentration was 10% at 90 ° C. for 90 minutes, and was not washed and dehydrated. O2Was added and reacted at 110 ° C. for 60 minutes to obtain a pulp having a kappa number of 7.3, a viscosity of 25.8 mPas and a whiteness of 52.0%.
[0055]
Example 22
The digested pulp of Example 18 was subjected to oxygen bleaching at a pulp concentration of 12%, E0.4% and O of about 490 kPa.2And reacted at 110 ° C. for 60 minutes. Next, it was adjusted to pH 2 using C / D white water, treated with a pulp concentration of 10%, 90 ° C. for 90 minutes, and then washed and dehydrated to obtain a kappa number of 12.6 and a viscosity of 35.9 mP.agot chemical pulp of s. acidAs a plain bleaching, pulp concentration 12%, E0.3% and O of about 490 kPa2Was added and reacted at 110 ° C. for 60 minutes to obtain a pulp having a kappa number of 7.0, a viscosity of 26.0 mPas, and a whiteness of 52.6%.
[0056]
Comparative Example 3
The digested pulp of Example 18 was oxygen bleached and E 1.0% and O of about 490 kPa.2Was added and reacted at 110 ° C. for 60 minutes to obtain a pulp having a kappa number of 9.0, a viscosity of 23.9 mPas, and a whiteness of 48.9%.
Further, the pulps of Example 2, Examples 18 to 22 and Comparative Example 1 were bleached with C / D-EH (sodium hypochlorite) -D under the following conditions.
The bleaching conditions of Example 2 were bleaching at a C addition rate of 0.6%, a D addition rate of 0.06%, 50 ° C. for 30 minutes, and a pulp concentration of 3.5%. Subsequently, bleaching was performed at an addition rate of E of 0.6%, 60 ° C., 90 minutes, and a pulp concentration of 12%. Bleaching was performed at an addition rate of H of 0.3%, 65 ° C., 2 hours, and a pulp concentration of 12%. The addition rate of D was bleached to 0.2%, 70 ° C., 2.5 hours, and the pulp concentration was 12%.
The conditions of Examples 18 to 22 are all the same. The addition rate of C is 1.0%, the addition rate of D is 0.1%, 50 ° C., 30 minutes, the pulp concentration is 3.5%, and then E is added. The bleaching was performed at a rate of 0.6%, 60 ° C. for 90 minutes, and a pulp concentration of 12%. Bleaching was performed at an addition rate of H of 0.3%, 65 ° C., 2 hours, and a pulp concentration of 12%. The addition rate of D was bleached to 0.2%, 70 ° C., 2.5 hours, and the pulp concentration was 12%.
Further, Comparative Example 3 was similarly bleached with C / D-E-H-D without the acid treatment under the following conditions. Bleaching was performed at an addition rate of C of 1.4% and an addition rate of D of 0.14% at 50 ° C. for 30 minutes and a pulp concentration of 3.5%. Bleaching was performed at 60 ° C. for 90 minutes with a pulp concentration of 12% at an addition rate of E of 0.8%. Bleaching was performed at an addition ratio of H of 0.4%, 65 ° C., 2 hours, and a pulp concentration of 12%. The addition rate of D was 0.3%, 70 ° C., 2.5 hours, and the pulp concentration was bleached to 12%.
The results of Examples 18 to 22 and Comparative Example 3 are shown in Tables 6 and 7.
It was found that when introduced between cooking and oxygen bleaching or after oxygen bleaching, the effect of lowering the kappa number and whiteness are improved, and the pulp viscosity is improved. Further, it has been found that further improvement can be achieved by adding washing and dehydration. Moreover, cooking can be improved by introducing the treatment of the present invention, and an increase in yield can be expected.
[0057]
[Table 6]
[Table 7]
Example 23
The pulp treated and bleached in Example 2 was beaten (4000 rev) with a PFI mill and hand-made (basis weight 60 g / cm).2The physical properties, drainage, etc. were evaluated.
[0060]
Example 24
The pulp treated in Example 14 was bleached with D1-P (hydrogen peroxide) -D2, beaten with a PFI mill (4000 rev), and hand-made (basis weight 60 g / cm).2) And physical properties, drainage, etc. were evaluated.
The D1 stage was bleached at 70 ° C. for 1.5 hours at an addition rate of 0.6%. The P stage was bleached at 65 ° C. for 2 hours at an addition rate of P of 0.5% and an addition rate of E of 0.3%. D2 was bleached at 75 ° C. for 2.5 hours at an addition rate of 0.3%. The pulp concentration in each bleaching was 12%.
[0061]
Example 25
The pulp treated in Example 15 was bleached with ZP-D, beaten with a PFI mill (4000 rev), and hand-made (basis weight 60 g / cm).2) And physical properties, drainage, etc. were evaluated.
The Z stage was bleached at an addition rate of 0.6% at pH 2, room temperature for 15 minutes. The P stage was bleached at 65 ° C. for 2 hours at an addition rate of P of 0.5% and an addition rate of E of 0.3%. Stage D was bleached at an addition rate of 0.4% at 75 ° C. for 2.5 hours. The pulp concentration in each bleaching was 12%.
[0062]
Comparative Example 4
The pulp obtained in Comparative Example 3 was beaten with a PFI mill (4000 rev) in the same manner as in Example 23 and hand-made (basis weight 60 g / cm).2) And physical properties, drainage, etc. were evaluated.
[0063]
Comparative Example 5
The pulp obtained in Comparative Example 1 was bleached with C / D-E-H-D under the following conditions, beaten with a PFI mill (4000 rev), and handmade (basis weight 60 g / cm2) And physical properties, drainage, etc. were evaluated. Bleaching was performed at an addition rate of C of 1.2% and an addition rate of D of 0.12% at 50 ° C. for 30 minutes and a pulp concentration of 3.5%. Bleaching was performed at 60 ° C. for 90 minutes with a pulp concentration of 12% at an addition rate of E of 0.8%. Bleaching was performed at an addition ratio of H of 0.4%, 65 ° C., 2 hours, and a pulp concentration of 12%. Bleaching was performed at an addition rate of D of 0.3%, 70 ° C., 2.5 hours, and a pulp concentration of 12%.
[0064]
Comparative Example 6
In the same manner as in Comparative Example 3, acid treatment was not performed, bleaching with D1-P-D2, and beating (4000 rev) with a PFI mill, hand-drawing (basis weight 60 g / cm)2) And physical properties, drainage, etc. were evaluated.
The D1 stage was bleached at 70 ° C. for 1.5 hours at an addition rate of 0.8%. The P stage was bleached at 65 ° C. for 2 hours at an addition rate of 0.7% and an addition rate of E of 0.4%. Stage D2 was bleached at 75 ° C. for 2.5 hours at an addition rate of 0.4%. The pulp concentration in each bleaching was 12%.
[0065]
Comparative Example 7
In the same manner as in Comparative Example 3, acid treatment was not performed, bleaching with ZPD, and beating with a PFI mill (4000 rev) and hand-drawing (basis weight 60 g / cm)2) And physical properties, drainage, etc. were evaluated.
The Z stage was bleached at an addition rate of 0.8%, pH 2, and room temperature for 15 minutes. The P stage was bleached at 65 ° C. for 2 hours at an addition rate of P of 0.6% and an addition rate of E of 0.3%. Stage D was bleached at 75 ° C. for 2.5 hours at an addition rate of 0.4%. The pulp concentration in each bleaching was 12%.
The results of Examples 23 to 25 and Comparative Examples 4 to 6 are shown in Tables 8 and 9.
Whiteness increases, yield and viscosity do not decrease, and drainage load is halved. Furthermore, it was also found that the amount of bleaching agent can be reduced by about 40% by lowering the kappa number.
As for the physical properties of the pulp, it was found that strength, smoothness, vessel picking were considerably improved, and beating properties were also improved.
[0066]
[Table 8]
[Table 9]
Example 26
Chemical pulp obtained in Example 23 (freezing degree 400 ml) was mixed with 0.7% sulfate band 0.6% cationic starch, 0.02% sizing agent, 8% light calcium, 0.03% yield improver. Add basis weight 100g / m2Hand-sheeted.
[0069]
Comparative Example 7
Chemical pulp (freeness 400 ml) obtained in Comparative Example 3 was the same as in Example 25, sulfate band 0.7% cationic starch 0.6%, sizing agent 0.02%, light calcium 8%, yield improvement 0.03% of agent is added and basis weight is 100 g / m2Hand-sheeted.
When Example 26 and Comparative Example 5 were compared, the pulp strength of the Example was strong and the vessel pick was small, and as a result, it was evaluated as a printing paper. .
[0070]
Example 27
The bleached white water produced in Example 24 was used in the digested pulp of Example 18 for oxygen bleaching using P white water for oxygen bleaching, D1 white water for acid treatment, D2 white water for D1, and fresh water for P and D2. As for the pulp concentration 12%, E0.6% and O of about 490 kPa2After reacting at 110 ° C. for 60 minutes and bleaching under the same conditions (A-D1-P-D2) as in Example 24, the whiteness was 87.6% and the viscosity was 18.9 mPas. Chemical pulp with high whiteness and high viscosity was obtained.
The use of P white water decreased the copper number after oxygen bleaching and increased the whiteness, resulting in improved subsequent bleaching. Further, since P white water becomes an alkali source, alkali can be saved, but the drainage load tends to increase slightly.
[0071]
【The invention's effect】
As shown in the examples, in the bleaching of the chemical pulp of the present invention, acidic high temperature treatment is carried out using acid bleached white water, after digestion, washing, before or after oxygen bleaching, with or without washing dehydration step, Furthermore, by performing multi-stage bleaching, the bleaching reaction can be accelerated and the amount of chlorine compound used can be reduced to reduce AOX. Furthermore, the occurrence of vessel picks, which is a problem in printing specific to hardwood pulp, can be reduced by treatment with acidic bleached white water. In addition, it is possible to provide a printing paper or a base paper for coating with a small vessel pick and a low AOX content.
Compared with the conventional low-temperature acid treatment, the bleaching property can be improved and the cellulose can be modified at the same time. As a result, easy pulping, high whiteness and high yield of chemical pulp can be obtained. In addition, the fibers are easily fibrillated at the time of beating, and vessel picking and paper smearing can be prevented. Compared with high-temperature acid treatment with sulfuric acid, not only the amount of bleaching chemical added is reduced, but also AOX, COD, and chromaticity of bleached white water can be reduced, reducing discharge and making effective use of white water. The pulp viscosity can be protected.
Furthermore, compared with an acidic enzyme treatment, the pulp yield decrease is small and the subsequent bleaching acceleration effect is large.
Claims (10)
(1)塩素、二酸化塩素、次亜塩素酸塩の１つ以上の薬品を用いて酸性水媒体中で漂白。
(2)オゾンを用いて酸性水媒体中で漂白。
(3)過酸化物又は過酸化物と酸素を用いてアルカリ性水媒体中で漂白。
(4)過酸化物を用いて酸性水媒体中で漂白。
(5)還元剤を用いてアルカリ性水媒体中で漂白。
(6)耐酸性の酵素による処理。The chemical reaction according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the subsequent multi-stage bleaching comprises bleaching in combination of at least one of the following (1) to (6): A method of treating pulp with acidic bleached white water.
(1) Bleaching in an acidic aqueous medium using one or more chemicals of chlorine, chlorine dioxide and hypochlorite.
(2) Bleaching in an acidic aqueous medium using ozone.
(3) Bleaching in an alkaline aqueous medium using peroxide or peroxide and oxygen.
(4) Bleaching in acidic aqueous medium using peroxide.
(5) Bleaching in an alkaline aqueous medium using a reducing agent.
(6) Treatment with acid-resistant enzyme.
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| JP07167797A JP3697335B2 (en) | 1997-03-25 | 1997-03-25 | Treatment of chemical pulp with acidic bleached white water |
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| JP07167797A JP3697335B2 (en) | 1997-03-25 | 1997-03-25 | Treatment of chemical pulp with acidic bleached white water |
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| JP3697335B2 true JP3697335B2 (en) | 2005-09-21 |
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