JP2004169194A - Method for postbleaching bleached kraft pulp - Google Patents
Method for postbleaching bleached kraft pulp Download PDFInfo
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- JP2004169194A JP2004169194A JP2002333000A JP2002333000A JP2004169194A JP 2004169194 A JP2004169194 A JP 2004169194A JP 2002333000 A JP2002333000 A JP 2002333000A JP 2002333000 A JP2002333000 A JP 2002333000A JP 2004169194 A JP2004169194 A JP 2004169194A
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- pulp
- bleaching
- bleached kraft
- whiteness
- kraft pulp
- Prior art date
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Links
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000002655 kraft paper Substances 0.000 title claims abstract description 28
- 238000004061 bleaching Methods 0.000 claims abstract description 54
- 239000007844 bleaching agent Substances 0.000 claims abstract description 12
- 238000010009 beating Methods 0.000 claims abstract description 10
- 238000002360 preparation method Methods 0.000 claims description 13
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 12
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 10
- KFSLWBXXFJQRDL-UHFFFAOYSA-N Peracetic acid Chemical compound CC(=O)OO KFSLWBXXFJQRDL-UHFFFAOYSA-N 0.000 claims description 6
- RYYXDZDBXNUPOG-UHFFFAOYSA-N 4,5,6,7-tetrahydro-1,3-benzothiazole-2,6-diamine;dihydrochloride Chemical compound Cl.Cl.C1C(N)CCC2=C1SC(N)=N2 RYYXDZDBXNUPOG-UHFFFAOYSA-N 0.000 claims description 3
- PEYVWSJAZONVQK-UHFFFAOYSA-N hydroperoxy(oxo)borane Chemical compound OOB=O PEYVWSJAZONVQK-UHFFFAOYSA-N 0.000 claims description 3
- MMCOUVMKNAHQOY-UHFFFAOYSA-N carbonoperoxoic acid Chemical compound OOC(O)=O MMCOUVMKNAHQOY-UHFFFAOYSA-N 0.000 claims description 2
- 238000004076 pulp bleaching Methods 0.000 claims 1
- 239000000123 paper Substances 0.000 abstract description 26
- 239000000126 substance Substances 0.000 abstract description 14
- 239000002994 raw material Substances 0.000 abstract description 10
- 238000010411 cooking Methods 0.000 abstract description 4
- 239000013055 pulp slurry Substances 0.000 description 10
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000011121 hardwood Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 239000004155 Chlorine dioxide Substances 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 235000019398 chlorine dioxide Nutrition 0.000 description 3
- 230000029087 digestion Effects 0.000 description 3
- 239000000975 dye Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 101710121765 Endo-1,4-beta-xylanase Proteins 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000011437 continuous method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- -1 etc.) Substances 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- MWNQXXOSWHCCOZ-UHFFFAOYSA-L sodium;oxido carbonate Chemical compound [Na+].[O-]OC([O-])=O MWNQXXOSWHCCOZ-UHFFFAOYSA-L 0.000 description 1
- 239000011122 softwood Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- Paper (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
製紙用漂白クラフトパルプの白色度の変更方法であって、漂白工程の処理を終えた漂白クラフトパルプを調成工程で叩解する前に、該パルプに漂白剤を添加することを特徴とする漂白クラフトパルプの後漂白方法に関するものである。
【０００２】
【従来の技術】
多くの紙パルプ工場では、数多くの品種の紙を製造しており、この紙はそれぞれ白色度の規格値あるいは目標値が異なっている。また、漂白クラフトパルプを原料とした印刷用紙や上質紙においては、紙の更なる高白色度化の要望が今も続いている。複数のパルプ蒸解・漂白プラントを有する工場では、各プラントで白色度の異なる漂白クラフトパルプを製造し、これを混合することで異なる白色度の紙を抄造することが可能である。しかし、原料の漂白クラフトパルプの製造においては、省力化、省薬品、省エネルギーなどの観点から、小規模なパルプ蒸解・漂白プラントを停止しあるいは廃棄し、大規模なプラントを新設することが多く行われている。このような１系列のパルプ蒸解・漂白プラントしか持たない工場では、最も白色度が高い紙に合わせて、蒸解および／または漂白条件を強化して高白色度の漂白クラフトパルプを製造し、高白色度紙の抄造と並行して抄造している他の通常レベルの白色度紙の製造では、紙の白色度を低下できる染料などの添加剤を加えることで対応している。従って、パルプの蒸解用薬品および／または漂白薬品のみならず、染料などの抄紙用薬品も無駄に消費している状況がある。
【０００３】
近年の高白色度の紙の原料に使用できるような、高白色度の漂白パルプを製造する従来の技術としては、例えば、セルロースを過酸化水素で漂白するに当たって、過酸化物を添加したパルプ懸濁液に紫外線を照射する方法が登録されている（特許文献１参照。）。また、漂白工程として、少なくとも１段以上の塩素系の漂白段を含むシーケンスによって漂白されたパルプを、キシラナーゼで処理し、更に次亜塩素酸塩段と二酸化塩素段の漂白シーケンスで漂白することを特徴とする高白色度パルプの製造方法が示されている（特許文献２参照。）。また、リグノセルロース物質より得られた漂白パルプを、更に高温高アルカリハイポ晒段と二酸化塩素晒段の連続したシーケンスからなる工程で漂白する高白色度パルプの製造方法において、該二酸化塩素晒段の工程が、二酸化塩素添加率１〜３重量％（対絶乾パルプ）で、かつ９１以上から１００℃未満の高温下で実施されることを特徴とする高白色度パルプの製造方法が示されている（特許文献３参照。）。しかし、これらの技術は、いずれも漂白工程における漂白方法に係わるものであり、製造するパルプ全量の白色度を高める技術である。従って、これらの技術では白色度向上のために要する漂白薬品のコストがかかり、しかも漂白条件の変更はなかなか小回りが利かないので、白色度の規格値が異なる少量・多数の紙の品種、銘柄の切り替えに逐次対応できないという問題がある。
【０００４】
【特許文献１】
特許第２５９３３９２号明細書
【特許文献２】
特開平６−１０１１８５号公報
【特許文献３】
特開平９−１０５０９１号公報
【０００５】
【発明が解決しようとする課題】
本願発明が解決しようとする課題は、製紙用漂白クラフトパルプの白色度の変更方法に関し、高白色度の漂白クラフトパルプを製造でき、しかも紙の品種・銘柄切り替えに伴う原料パルプに要求される白色度変化にも対応できる漂白クラフトパルプの後漂白技術の提供にあり、更には無駄に使用されている漂白薬品や抄紙薬品を節減することにある。
【０００６】
【課題を解決するための手段】
漂白工程の処理を終えた漂白クラフトパルプを調成工程で叩解する前に、該パルプに漂白剤を添加することを特徴とする漂白クラフトパルプの後漂白方法。
【０００７】
【発明の実施の形態】
本願発明の後漂白に適用されるパルプは、通常の漂白工程での処理を終了した広葉樹または針葉樹の漂白クラフトパルプである。該パルプのハンター白色度は抄紙原料パルプとして通常のレベルである８０〜９０％が好ましく、８０〜８５％が更に好ましい。ハンター白色度が８０％未満のパルプでは、高白色度のパルプを得づらく、後漂白の漂白薬品を多量に添加しなければならず、漂白処理コストの面でも高白色度の紙の製造が困難である。ハンター白色度が９０％を超えるパルプでは、本願発明の後漂白の処理を施しても白色度の向上幅が小さく、好ましくない。
【０００８】
漂白工程後、調成工程までのパルプ原料のフローは、調成工程が漂白工程につながっているかどうか、また各製紙メーカーのノウハウの面もあり、まちまちであるが、基本的なパルプ原料フローは次の通りである。漂白工程での漂白処理を終了したパルプ懸濁液（以下、パルプスラリーと称す）は、完成ＢＫＰチェストと呼ばれる貯蔵用容器に貯えられる。ここから、抜き出されたパルプスラリーは必要に応じて濃度調整され、抄紙用の各原料を処理・混合する調成工程へポンプにより移送される。調成工程に受け入れたパルプスラリーは、通常一旦チェストに貯えられる。次いで、パルプスラリーは叩解に適した濃度に調整され、叩解機で叩解され、叩解後のパルプを貯えるチェストに送られる。その後、連続ミキサーにおいて、同様に叩解処理した他のパルプや、損紙、抄紙白水、製紙用薬品（例えば、硫酸アルミニウム、サイズ剤、染料、他の添加剤など）、填料などが、紙の銘柄毎に規定された配合率で混合され、連続的にマシンチェストへ送られる。マシンチェストでは、抄紙機ヘッドボックスからの戻り原料と混合され、抄紙機のヘッドボックスへ送られ、ヘッドボックスからワイヤー上に噴き出され、抄紙される。
【０００９】
完成ＢＫＰチェストに貯えられたパルプスラリーは各抄紙機のラインに分割供給される。本願発明では、この内、高白色度の紙の抄造に必要な量のパルプを一部取り出して、特定の漂白薬品を添加して後漂白を行う。この漂白はバッチ式でも良いし、連続式でも構わない。
【００１０】
バッチ式では、漂白剤を添加混合したパルプスラリーは漂白容器に入れられ、後記の特定の固形分濃度、反応温度、反応時間で漂白処理後、ブローされる。漂白容器は複数基設置されても良い。バッチ式反応容器の設置場所は、完成ＢＫＰチェストの後から、調成工程の叩解機の前までの間である。調成工程の叩解機の前にあるチェストとは別個に、その前に設置することが好ましい。
【００１１】
連続式では、２通りの方法がある。第１の方法としては、反応塔の底部から漂白剤を添加混合したパルプスラリーを圧入し、パルプスラリーが反応塔の底部から頂部へ移動する間に、後記の特定の固形分濃度、反応温度、反応時間で漂白処理する。処理後のパルプスラリーは頂部より排出される。この方法は、本願発明で使用する全ての漂白剤に適用できるが、特に漂白反応に比較的時間を要する漂白剤に適している。この場合、連続式反応塔の設置場所は、完成ＢＫＰチェストの後から、調成工程の叩解機の前までの間である。調成工程の叩解機の前にあるチェストとは別個に、その前に設置することが好ましい。第２の方法は、漂白反応が極めて速いオゾンを漂白剤として添加する場合に適用できる方法であり、完成ＢＫＰチェストの後、調成工程叩解機前の間のパルプスラリーを移送する配管中にインラインミキサーを設置し、該インラインミキサー入り口の直前またはインラインミキサー入口部分にオゾンガスを注入し、インラインミキサーの撹拌力で混合し反応させる方法である。
【００１２】
本願発明で添加する漂白薬品は、オゾン、過酸化水素、過酢酸、過炭酸、過硼酸、二酸化チオ尿素の中から選ばれる１種類である。
【００１３】
後漂白の反応条件は、パルプ固形分重量濃度１〜６％、好ましくは２〜５％、反応温度３０〜６０℃、好ましくは３０〜５０℃、反応時間３秒間〜１０時間、好ましくは３秒間〜５時間である。尚、反応時間の最短時間３秒間は、漂白剤がオゾンの場合である。
【００１４】
本願発明の後漂白処理を終えた漂白クラフトパルプのハンター白色度は、８３〜９５％、好ましくは８５〜９５％、より好ましくは８７〜９５％、更に好ましくは９０〜９５％である。反応時および／または反応終了後のｐＨは、オゾン、過酸化水素、過酢酸、過炭酸、過硼酸、二酸化チオ尿素の各漂白剤の公知の最適なｐＨ範囲に入るように、アルカリ性薬剤または酸性薬剤を添加することが好ましい。この場合、後漂白反応が終了した後、ｐＨを５．５〜７．０に調整することが好ましい。
【００１５】
【実施例】
次に実施例に基づき、本願発明を更に詳細に説明するが、本願発明はこれらに限定されるものではない。
【００１６】
【実施例１】
日本製紙株式会社Ａ工場の完成ＢＫＰチェストから採取した、ハンター白色度８４．８％の広葉樹漂白クラフトパルプを、清水でパルプ固形分重量濃度３．０％に希釈し、ｐＨを調整することなく、中濃度ミキサーに入れた。これを約４０℃に加温した後、５００ｒｐｍあるいは２，２００ｒｐｍで撹拌しながらオゾンガスを風乾パルプＴ当たり、１．０、２．０ｋｇ添加した。添加後直ちにパルプを取り出して白色度を測定した。結果を表１に示す。オゾンによる後漂白処理により、白色度が０．９〜１．５％向上した。
【００１７】
【表１】
【実施例２】
日本製紙株式会社Ｂ工場の完成ＢＫＰチェストから採取した、ハンター白色度８４．８％の広葉樹漂白クラフトパルプを、清水でパルプ固形分重量濃度３．０％に希釈し、ｐＨを調整することなく、中濃度ミキサーに入れた。これを約４０℃に加温した後、２，２００ｒｐｍで撹拌しながらオゾンガスを風乾パルプＴ当たり、１．０、２．０ｋｇ添加した。添加後直ちにパルプを取り出して白色度を測定した。結果を表２に示す。オゾンによる後漂白処理により、白色度が１．１〜１．４％向上した。
【００１９】
【表２】
【実施例３】
日本製紙株式会社Ａ工場の完成ＢＫＰチェストから採取した、ハンター白色度８４．８％の広葉樹漂白クラフトパルプを、清水でパルプ固形分重量濃度３．０％に希釈し、水酸化ナトリウムを添加してｐＨ＝１０．５に調整した後、中濃度ミキサーに入れた。これを５０℃に加温した後、撹拌しながら過酸化水素を風乾パルプＴ当たり、３．０、５．０ｋｇ添加した。９０分間反応させた後、白色度を測定した。反応終了後、パルプを取り出してｐＨ無調整とｐＨ＝７．０に中和したものについてハンター白色度を測定した。結果を表３に示す。過酸化水素による後漂白処理により、白色度が０．６〜１．７％向上した。
【００２１】
【表３】
【発明の効果】
漂白工程の処理を終えた漂白クラフトパルプを調成工程で叩解する前に、該パルプに漂白剤を添加するという漂白クラフトパルプの後漂白方法により、高白色度の紙の原料である高白色度の漂白クラフトパルプを製造でき、しかも紙の品種・銘柄切り替えに伴う原料パルプに要求される白色度変化にも対応できる。更に、無駄に使用されている蒸解薬品および／または漂白薬品と抄紙薬品を節減することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
A method for changing the whiteness of a bleached kraft pulp for papermaking, comprising adding a bleaching agent to the pulp before beating the bleached kraft pulp having undergone the bleaching step in the preparation step. It relates to a method of post-bleaching pulp.
[0002]
[Prior art]
Many pulp and paper mills produce many types of paper, each of which has different whiteness specifications or target values. Further, in printing paper and high-quality paper made from bleached kraft pulp, there is a continuing demand for higher whiteness of the paper. In a plant having a plurality of pulp digestion and bleaching plants, it is possible to produce bleached kraft pulp having different whiteness in each plant and to mix these to produce paper having different whiteness. However, in the production of bleached kraft pulp as a raw material, small-scale pulp digestion and bleaching plants are often shut down or disposed of and new large-scale plants are installed from the viewpoints of labor saving, chemical saving, and energy saving. Has been done. Mills with only one series of pulp cooking and bleaching plants produce bleached kraft pulp with high whiteness by strengthening the digestion and / or bleaching conditions for the paper with the highest whiteness. In the production of other ordinary levels of whiteness paper, which is made in parallel with the papermaking of the paper, it is necessary to add an additive such as a dye capable of reducing the whiteness of the paper. Therefore, there are situations in which not only pulp cooking and / or bleaching chemicals but also papermaking chemicals such as dyes are wasted.
[0003]
As a conventional technique for producing bleached pulp having high whiteness, which can be used as a raw material for paper having high whiteness in recent years, for example, in bleaching cellulose with hydrogen peroxide, pulp pulp added with peroxide is used. A method of irradiating the suspension with ultraviolet light is registered (see Patent Document 1). In the bleaching step, pulp bleached by a sequence including at least one or more chlorine-based bleaching stages is treated with xylanase, and further bleached in a bleaching sequence of a hypochlorite stage and a chlorine dioxide stage. A method for producing a characteristic high-whiteness pulp is disclosed (see Patent Document 2). Further, in the method for producing a high-brightness pulp in which the bleached pulp obtained from the lignocellulose material is further bleached in a process comprising a continuous sequence of a high-temperature high-alkali hypo bleaching stage and a chlorine dioxide bleaching stage, A process for producing a high whiteness pulp characterized in that the process is carried out at a chlorine dioxide addition rate of 1 to 3% by weight (based on absolutely dry pulp) and at a high temperature of from 91 to less than 100 ° C. (See Patent Document 3). However, these techniques are all related to the bleaching method in the bleaching step, and are techniques for increasing the whiteness of the whole pulp to be produced. Therefore, these technologies require the cost of bleaching chemicals required to improve the whiteness, and since it is difficult to change the bleaching conditions, it is difficult to change the bleaching conditions easily. There is a problem that switching cannot be performed sequentially.
[0004]
[Patent Document 1]
Patent No. 2593392 [Patent Document 2]
JP-A-6-101185 [Patent Document 3]
JP-A-9-105091
[Problems to be solved by the invention]
The problem to be solved by the present invention relates to a method for changing the whiteness of bleached kraft pulp for papermaking, which enables the manufacture of bleached kraft pulp with high whiteness, and the whiteness required for the raw material pulp accompanying the paper type / brand change. Another object of the present invention is to provide a post-bleaching technique for bleached kraft pulp that can cope with changes in the degree of bleaching, and also to reduce wasteful bleaching chemicals and papermaking chemicals.
[0006]
[Means for Solving the Problems]
A post-bleaching method for bleached kraft pulp, which comprises adding a bleaching agent to the bleached kraft pulp that has been subjected to the bleaching step before beating in the preparation step.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The pulp applied to the bleaching after the present invention is bleached kraft pulp of hardwood or softwood which has been subjected to the treatment in the usual bleaching step. The hunter whiteness of the pulp is preferably 80 to 90%, more preferably 80 to 85%, which is an ordinary level as a raw pulp for papermaking. In the case of pulp having a Hunter brightness of less than 80%, it is difficult to obtain a high brightness pulp, a large amount of post-bleaching bleaching chemicals must be added, and it is difficult to produce high brightness paper in terms of the bleaching cost. It is. In a pulp having a Hunter brightness of more than 90%, even if the bleaching treatment is performed after the present invention, the improvement in the brightness is small, which is not preferable.
[0008]
After the bleaching process, the flow of the pulp raw material up to the preparation process varies depending on whether the preparation process is connected to the bleaching process and the know-how of each paper maker, but the basic pulp raw material flow is It is as follows. The pulp suspension (hereinafter, referred to as pulp slurry) that has been subjected to the bleaching treatment in the bleaching step is stored in a storage container called a finished BKP chest. From this, the extracted pulp slurry is adjusted in concentration as necessary, and is transferred by a pump to a preparation step for processing and mixing each raw material for papermaking. The pulp slurry received in the preparation step is usually once stored in a chest. Next, the pulp slurry is adjusted to a concentration suitable for beating, beaten with a beater, and sent to a chest for storing the beaten pulp. Then, in a continuous mixer, other pulp, beaten paper, papermaking white water, papermaking chemicals (eg, aluminum sulfate, sizing agents, dyes, other additives, etc.), fillers, and fillers are similarly beaten in a continuous mixer. They are mixed at a prescribed mixing ratio for each case and are continuously sent to a machine chest. In the machine chest, the raw material is mixed with the returned raw material from the paper machine head box, sent to the paper machine head box, ejected from the head box onto a wire, and made into paper.
[0009]
The pulp slurry stored in the finished BKP chest is divided and supplied to each paper machine line. In the present invention, a part of the pulp necessary for papermaking of high whiteness paper is partially taken out, and a specific bleaching chemical is added to perform post-bleaching. This bleaching may be a batch type or a continuous type.
[0010]
In the batch method, a pulp slurry to which a bleaching agent is added and mixed is put into a bleaching container, and bleached at a specific solid content concentration, a reaction temperature and a reaction time described later, and then blown. A plurality of bleaching containers may be provided. The installation location of the batch type reaction vessel is from after the completed BKP chest to before the beating machine in the preparation process. It is preferable to install it separately from the chest in front of the beating machine in the preparation step.
[0011]
In the continuous method, there are two methods. As a first method, a pulp slurry to which a bleaching agent is added and mixed is injected from the bottom of the reaction tower, and while the pulp slurry moves from the bottom to the top of the reaction tower, a specific solid content concentration, a reaction temperature, Bleach for reaction time. The pulp slurry after the treatment is discharged from the top. This method is applicable to all bleaches used in the present invention, but is particularly suitable for bleaches requiring a relatively long bleaching reaction. In this case, the installation location of the continuous reaction tower is from after the completed BKP chest to before the beating machine in the preparation process. It is preferable to install it separately from the chest in front of the beating machine in the preparation step. The second method is a method which can be applied to a case where ozone, which has a very fast bleaching reaction, is added as a bleaching agent, and is provided in-line in a pipe for transferring pulp slurry after a completed BKP chest and before a preparation process beating machine. This is a method in which a mixer is installed, and ozone gas is injected just before the inlet of the inline mixer or into the inlet of the inline mixer, and mixed and reacted by the stirring power of the inline mixer.
[0012]
The bleaching chemical added in the present invention is one selected from ozone, hydrogen peroxide, peracetic acid, percarbonic acid, perboric acid, and thiourea dioxide.
[0013]
The post-bleaching reaction conditions are as follows: pulp solid content weight concentration of 1 to 6%, preferably 2 to 5%, reaction temperature of 30 to 60 ° C, preferably 30 to 50 ° C, reaction time of 3 seconds to 10 hours, preferably 3 seconds. ~ 5 hours. The minimum reaction time of 3 seconds is the case where the bleach is ozone.
[0014]
The Hunter whiteness of the bleached kraft pulp that has been subjected to the post-bleaching treatment of the present invention is 83 to 95%, preferably 85 to 95%, more preferably 87 to 95%, and still more preferably 90 to 95%. The pH at the time of the reaction and / or after the end of the reaction is set to fall within the known optimum pH range of the ozone, hydrogen peroxide, peracetic acid, percarbonate, perboric acid, and thiourea dioxide bleaching agents. Preferably, a drug is added. In this case, it is preferable to adjust the pH to 5.5 to 7.0 after the completion of the post-bleaching reaction.
[0015]
【Example】
Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
[0016]
Embodiment 1
A hardwood bleached kraft pulp with a hunter whiteness of 84.8% collected from a completed BKP chest of Nippon Paper Industries Co., Ltd. A factory was diluted with clear water to a pulp solid content concentration of 3.0%, and without adjusting the pH. Placed in medium concentration mixer. After heating this to about 40 ° C., 1.0 and 2.0 kg of ozone gas was added per air-dried pulp T while stirring at 500 rpm or 2,200 rpm. Immediately after the addition, the pulp was taken out and measured for whiteness. Table 1 shows the results. The post-bleaching treatment with ozone improved the whiteness by 0.9 to 1.5%.
[0017]
[Table 1]
Embodiment 2
A hardwood bleached kraft pulp with a hunter whiteness of 84.8%, collected from a completed BKP chest of Nippon Paper Industries B Mill, was diluted with fresh water to a pulp solids weight concentration of 3.0%, without adjusting the pH. Placed in medium concentration mixer. After heating this to about 40 ° C., 1.0 and 2.0 kg of ozone gas was added per air-dried pulp T while stirring at 2,200 rpm. Immediately after the addition, the pulp was taken out and measured for whiteness. Table 2 shows the results. Post-bleaching treatment with ozone improved the whiteness by 1.1 to 1.4%.
[0019]
[Table 2]
Embodiment 3
A hardwood bleached kraft pulp having a hunter brightness of 84.8%, which was collected from a completed BKP chest of Nippon Paper Industries Co. A mill, was diluted with clear water to a pulp solid content concentration of 3.0%, and sodium hydroxide was added. After adjusting the pH to 10.5, the mixture was placed in a medium concentration mixer. After heating to 50 ° C., 3.0 and 5.0 kg of hydrogen peroxide per air-dried pulp T was added with stirring. After reacting for 90 minutes, the whiteness was measured. After the completion of the reaction, the pulp was taken out, and the Hunter whiteness was measured for the one without pH adjustment and the one neutralized to pH = 7.0. Table 3 shows the results. Post-bleaching treatment with hydrogen peroxide improved the whiteness by 0.6-1.7%.
[0021]
[Table 3]
【The invention's effect】
Before the bleached kraft pulp that has been processed in the bleaching process is beaten in the preparation process, a bleaching kraft pulp in which a bleaching agent is added to the pulp is used as a raw material for high-brightness paper. Can produce bleached kraft pulp, and can respond to the change in whiteness required for raw pulp due to the change of paper type and brand. In addition, waste cooking and / or bleaching and papermaking chemicals can be saved.
Claims (2)
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| JP2002333000A JP4192564B2 (en) | 2002-11-18 | 2002-11-18 | Bleaching kraft pulp after bleaching method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007132836A1 (en) | 2006-05-17 | 2007-11-22 | Mitsubishi Gas Chemical Company, Inc. | Process for producing bleached pulp |
| WO2009081714A1 (en) | 2007-12-20 | 2009-07-02 | Mitsubishi Gas Chemical Company, Inc. | Process for production of bleached pulp |
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2002
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007132836A1 (en) | 2006-05-17 | 2007-11-22 | Mitsubishi Gas Chemical Company, Inc. | Process for producing bleached pulp |
| US8268123B2 (en) | 2006-05-17 | 2012-09-18 | Mitsubishi Gas Chemical Company, Inc. | Process for producing bleached pulp |
| US8864942B2 (en) | 2006-05-17 | 2014-10-21 | Mitsubishi Gas Chemical Company, Inc. | Process for producing bleached pulp |
| WO2009081714A1 (en) | 2007-12-20 | 2009-07-02 | Mitsubishi Gas Chemical Company, Inc. | Process for production of bleached pulp |
| US8900408B2 (en) | 2007-12-20 | 2014-12-02 | Mitsubishi Gas Chemical Company, Inc. | Process for production of bleached pulp |
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| JP4192564B2 (en) | 2008-12-10 |
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