JP4192565B2 - Method for producing high whiteness bleached kraft pulp - Google Patents
Method for producing high whiteness bleached kraft pulp Download PDFInfo
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- JP4192565B2 JP4192565B2 JP2002334450A JP2002334450A JP4192565B2 JP 4192565 B2 JP4192565 B2 JP 4192565B2 JP 2002334450 A JP2002334450 A JP 2002334450A JP 2002334450 A JP2002334450 A JP 2002334450A JP 4192565 B2 JP4192565 B2 JP 4192565B2
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Description
【０００１】
【発明の属する技術分野】
難蒸解性かつ難漂白性のユーカリ属(Eucalyptus)の材から高白色度の漂白クラフトパルプを製造する方法に関するものである。
【０００２】
【従来の技術】
ユーカリ材や南方材が広葉樹クラフトパルプの主要原料になってきている。このユーカリ材は種類が多く、樹種、樹齢、産地などの違いにより、その蒸解性や漂白性が異なっている。ユーカリ材はashタイプとblood woodタイプに大別され、ashタイプは抽出成分量が少ないのでパルプ材として工業的に利用する場合には比較的問題がないとされている。一方、blood woodタイプでは酸性の抽出成分に起因する様々な問題が発生するので、その軽減策が必要である。
【０００３】
ユーカリ材には、キノと称されるポリフェノール類およびエラグ酸などの酸性の抽出成分が含まれている。キノ成分は縮合型タンニンを主成分とする樹木分泌物であり、淡黄色から濃紅色にいたる色調を持ち、樹種により特徴を異にしている。エラグ酸は木材中に遊離の状態でも存在するが、没食子酸とエラグ酸から形成されるエラグタンニン酸の形で主に存在する。このエラグタンニン酸は蒸解中に加水分解されて、エラグ酸になる。エラグ酸は強い酸性を示すと同時にアルカリ性条件下で容易に酸化され、キノン型となりパルプセルロースに強く吸着し、パルプ白色度に悪影響を及ぼす。更に、高温、高圧下では、そのフェノール性のために重合しやすく、粘着性物質となる。
【０００４】
ユーカリ材に含まれる前記の酸性の抽出成分は、その含有量が多ければパルプ収率を低下させる。また、クラフト蒸解のアルカリ性薬剤を消費する。この消費は、リグニンの溶出によるアルカリ消費よりも反応が速いため、未晒しパルプの高カッパー価(換言すれば、白色度の低下)の問題を引き起こし、後続の漂白工程の負荷を増大させ、漂白薬品の使用量増加あるいは漂白パルプの白色度低下も引き起こす。また、ウォッシャーやディフューザーなどで抽出成分由来のスケールが発生したり、濃縮黒液の粘度が著しく上昇し真空蒸発が不良になることで、回収ボイラーでの黒液の燃焼性が悪化するなどの問題を引き起こす。
【０００５】
以上のような難蒸解性の材の種々な問題は古くから認識され、その対策が検討されている。蒸解性や漂白性の改善を目的とした技術としては、例えば、アルカリ蒸解の場合、リグニン、炭水化物がアルカリを消費するが、酸性抽出成分はこれらより迅速にアルカリと反応するので、酸性抽出成分を黒液中の残アルカリとまず反応させ、次いで白液を添加して蒸解を行う二段蒸解法が考案されている(非特許文献１参照。)。また、ユーカリ材の熱水抽出により同一カッパー価で比較して、クラフトパルプの白色度が向上し、活性アルカリ添加量を削減できること、およびパルプ収率と塩素消費量には差がないことが報告されている(非特許文献２参照。)。また、ユーカリ材に含まれる酸性抽出成分はアルカリ条件下の酸素による酸化処理で容易に淡色化すること、および黒液の燃焼性を改善できることが明らかなことから、クラフト蒸解に先立つアルカリ酸化前処理により、パルプの白色度が改善できることが記載されている(非特許文献３参照。)。また、キノ物質を含む木材のアルカリ蒸解によるパルプ製造法に関し、特にキノ物質を含む木材チップを、30℃以上でアルカリリグニンの溶出温度以下でアルカリ性蒸解液で予め処理しキノ物質を滲出し、次いで蒸解を行うパルプ製造法が示されている(特許文献１参照。)。また、ユーカリチップから滲出する多量の滲出液の酸性度を合理的に中和して対金属腐食性を低減するとともにチップの蒸解性の向上と蒸解薬品および漂白薬品の節減を目的として、ユーカリチップにアルカリ性溶液を噴霧し、対チップ0.3〜1.5重量%となるように前記アルカリを付着させた後、少なくとも2週間堆積する方法が示されている(特許文献２参照。)。また、ユーカリ材チップのようなアルカリ可溶性抽出成分の多い木材チップの蒸解に際し、アルカリ可溶性抽出成分を最も効果的有利に抽出することを目的として、木材チップを、該木材の平均厚さの20〜50%間隙を有し、対向して互いに反対方向に、かつ周速比1：1.1〜1.5で回転する2本の金属ロール間に通した後、アルカリ蒸解する方法が示されている(特許文献３参照。)。
【０００６】
パルプ蒸解後の黒液の濃縮性、燃焼性を改善する技術としては、例えば、ユーカリ材のような南方材等、ポリフェノール類あるいはタンニン類等を多く含む材のクラフトパルプ廃液の溶存物質の5〜35%を必要量の加圧空気等により酸化分解し、クラフト法における薬品回収を可能とする技術が開示されている(特許文献４参照。)。また、ユーカリ材を主体としたパルプ蒸解液を濃縮、燃焼して得られる緑液を苛性化して蒸解液を再生する処理工程において、濃縮前の希廃液に緑液又は緑液を苛性化して得られる白液を添加、混合し、空気酸化した後、あるいは空気酸化後ある程度濃縮した後、苛性ソーダを添加して廃液のpHを高め、次いで所定濃度まで濃縮してから燃焼する方法が示されている(特許文献５参照。)。
【０００７】
【非特許文献１】
Sloman,A.R.,Appita,14(2),57(1960)
【非特許文献２】
Nelson,P.F.,et al.,Appita,24(2),101(1970)
【非特許文献３】
Hemingway,R.W.et al.,Appita,25(6),445(1972)
【特許文献１】
特公昭47-24162号公報
【特許文献２】
特開昭53-134903号公報
【特許文献３】
特許第1506085号明細書
【特許文献４】
特公昭48-42242号公報
【特許文献５】
特許第1021680号明細書
【０００８】
【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、高白色度の漂白クラフトパルプの製造において、難蒸解性かつ難漂白性であるユーカリ材あるいは該ユーカリ材が配合された材の蒸解性と漂白性を改善し、高白色度のTCFあるいはECF漂白パルプを提供することにある。
【０００９】
【課題を解決するための手段】
難蒸解性かつ難漂白性のユーカリ材のみから成るチップ、あるいは該ユーカリ材チップが配合されたチップに、次の工程から成る一連の処理を施すことにより、高白色度の漂白クラフトパルプを製造できる。
（ａ）木材チップにアルカリ性水溶液を含浸させる工程
（ｂ）前記アルカリ性水溶液を含浸させた木材チップを３０〜６０分間かつ温度５０〜８０℃で保持する工程
（ｃ）前記（ｂ）工程の後、アルカリ抽出液を抜き取り、木材チップを洗浄する工程
（ｄ）前記アルカリ抽出後に得られた木材チップをクラフト蒸解し、カッパー価１４〜２２の未晒しパルプを製造する工程
（ｅ）前記（ｄ）工程で得られた未晒しパルプをＴＣＦ漂白あるいはＥＣＦ漂白し、ハンター白色度８４％以上の高白色度の漂白パルプを製造する工程
【００１０】
【発明の実施の形態】
本願発明の処理対象である難蒸解性かつ難漂白性のユーカリ材は、1%アルカリ抽出前後の72%硫酸不溶分(クラーソンリグニン)の差で4%以上のものと定義される。このユーカリ材は単独樹種品でも良いし、該定義のユーカリ材のみから成る２樹種以上の混合品でも良い。また、該定義のユーカリ材と、蒸解性および漂白性が通常レベル〜易レベルである他のユーカリ属あるいは他の科・属の広葉樹材との混合品であるが、この混合品の状態で該定義内に入る難蒸解性かつ難漂白性の混合材も処理対象とすることができ、該混合材は海外のチップ積出しの段階での混合材でも良いし、国内のパルプ工場のチップヤードから連続蒸解釜への払い出しの段階での混合材でも良い。
【００１１】
難蒸解性かつ難漂白性のユーカリ材に含まれる酸性の抽出成分量は樹齢、産地(換言すれば生育環境)などで異なるので具体的な樹種を特定することは難しい面があるが、フトモモ科ユーカリ属に関しては、キノ成分を多く含む樹種としては、Eucalyptus(以下、E.と略す) calophylla、E. citriodora、E. diversicolor、E.globulus、E.grandis、E. gummifera、、E. marginata、E.nesophila、E.nitensなどの老齢木、エラグタンニン酸を多く含む樹種としては、E.amygdalina、E.camaldulensis、E.delegatensis、E. gigantea、E. muelleriana、E. obliqua、E.regnans、E. sieberiana、E. viminalisなどの老齢木、ロイコアントシアニジンを多く含む樹種としては、E. camaldulensis、E. marginataなどの老齢木を挙げることができる。
【００１２】
難蒸解性かつ難漂白性の木材チップにアルカリ性水溶液を含浸させる工程では、粗大なチップとチップダストを除去しサイズを整えたチップを処理する。このアルカリ性水溶液含浸工程は、チップスクリーニング工程以降、蒸解工程の間の任意な箇所に設置することができるが、アルカリ性水溶液の含浸を良くするためにスチーミングベッセル以降が望ましい。アルカリ性薬剤としては水酸化ナトリウムや水酸化カリウムを使用できるが、水酸化ナトリウムが好適である。
【００１３】
該含浸処理が木材チップをアルカリ性水溶液に浸漬する方法の場合には、木材チップを含浸容器に入れ、アルカリ性水溶液を添加し、チップにアルカリ性水溶液を含浸させる。この際、含浸を良くする目的で減圧下で行うことが好ましい。アルカリ性薬剤のチップ(絶乾)に対する添加率は1.0〜10.0固形分重量%が好ましく、1.0〜5.0固形分重量%が更に好ましい。アルカリ性水溶液(容積)／チップ容積の液比は4.0〜10.0が好ましく、4.0〜6.0が更に好ましい。アルカリ性水溶液の固形分濃度は、前記の添加率と液比を満足するように予め濃度調整する。
【００１４】
該含浸処理は、木材チップを圧縮し、圧縮した状態または圧解放後にアルカリ水溶液を含浸させる方法でも実施することができる。この場合のアルカリ性薬剤のチップ(絶乾)に対する添加率は1.0〜10.0固形分重量%が好ましく、1.0〜5.0固形分重量%が更に好ましい。この圧縮に用いる装置としては、木材チップを十分に圧縮できるものであれば良く、特に制限はないが、アンドリッツ(Andritz)社のインプレサファイナー(impresssfiner)や、バルメット(Valmet)社のプレックススクリュウー(Prex screw)を挙げることが出来る。圧縮比は２：１以上が好ましく、４：１以上が更に好ましい。
【００１５】
次いで、アルカリ性水溶液を含浸させた木材チップを、保持容器内で加温下、所定時間保持し、この間、酸性の抽出成分をアルカリ性水溶液で抽出・中和する。温度は５０〜８０℃が好ましく、５０〜７５℃がより好ましい。保持時間は温度にも左右されるが、３０〜６０分間が好ましい。保持終了時の終ｐＨは、８．０〜１０．０とすることが好ましい。
【００１６】
次いで、アルカリ性水溶液で抽出・中和後の液を除去し、チップを十分に水で洗浄する。不十分な洗浄では、後続の蒸解工程へ影響が出る。
【００１７】
洗浄後のチップは蒸解工程へ送られ、通常の条件(活性アルカリ添加量、硫化度、液比、最高温度、保持時間、Ｈファクターなど)でクラフト蒸解に供する。また、MCC、EMCC、ITC、Lo-solidなどの修正クラフト法の蒸解に供しても良い。また、1ベッセル液相型、１ベッセル液相／気相型、2ベッセル液相／気相型、2ベッセル液相型などの蒸解型式なども特に限定はない。すなわち、本願のアルカリ性水溶液を含浸し、これを保持する工程は、従来の蒸解液の浸透処理を目的とした装置や部位とは別個に設置されるものである。蒸解を終えた未晒しパルプは蒸解液を抽出後、ディフュージョンウォッシャーなどの装置で洗浄する。洗浄後の未晒しパルプのカッパー価は14〜22にすることが好ましい。15〜18が更に好ましい。
【００１８】
次いで、所定のカッパー価の未晒しパルプをTCF漂白あるいはECF漂白で漂白処理を行う。TCF漂白、ECF漂白は公知のシーケンスで行えば良く、特に限定はない。具体的には、TCF漂白シーケンスとしては、Z-E-P、Z-E/O-P、E/OP-POなどが挙げられ、ECF漂白シーケンスとしては、D-E-D、D-E/O-D、E/O-D、E-O-D、Z-Dなどが挙げられる。本願発明の処理対象である難蒸解性かつ難漂白性の材は、通常の蒸解条件かつ通常のTCF、ECF漂白シーケンスでは、ハンター白色度84%以上の漂白パルプを得ることが困難であるが、本願発明の前記（a）〜（ｄ）工程の処理により、ハンター白色度84%以上の高白色度の漂白パルプを容易の製造できる。
【００１９】
【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。
【実施例１】と【比較例１】でクラフト蒸解性を比較し、【実施例２】と【比較例２】で二酸化塩素によるECF(D-ECFと略す)漂白性を比較した。
【００２０】
下記のチップを実施例、比較例に供した。
１．チップの産地、樹種
日本製紙株式会社のチップヤードからユーカリのチップを採取した。1%アルカリ抽出前後の72%硫酸不溶分の差は4.5%であった。
２．チップサイズの調整
前記チップをジャイロシフタを用いて篩い分け、粗大チップとチップダストを除去し、9.5〜25.4mmφのチップとした。このチップを以下の実施例、比較例で使用した。
【００２１】
【実施例１】
前記のチップサイズを調整したチップに、真空下で水酸化ナトリウム水溶液を15分間浸透させた後、下記に示す条件で2.4Ｌ容回転型オートクレーブを用いてアルカリ抽出を行った。アルカリ抽出物量は約3%であり、抽出前、浸透後、抽出後におけるアルカリ抽出液のpHは、それぞれ12.9、12.7、9.3であった。抽出処理後チップを十分に水洗し、下記に示す条件で、2.4Ｌ容回転型オートクレーブを用いてクラフト蒸解を行った。蒸解終了後、蒸解液を抽出し、残有効アルカリ濃度とpHを測定した。パルプは十分に洗浄後、フラットスクリーンで粕を除去し、精選収率、粕率、総収率を求め、カッパー価とハンター白色度を測定した。結果を表１に示す。
アルカリ抽出条件：チップ300ｇ(絶乾)、水酸化ナトリウム添加量2.0%、液比5.0L/kg、最高温度80℃、保持時間60分間、昇温時間30分間
クラフト蒸解条件：チップ300g(絶乾)、活性アルカリ添加量12〜17%、硫化度25%、液比2.5L/kg、最高温度160℃、保持時間94分間、Ｈファクター830
【００２２】
【比較例１】
前記のチップサイズを調整したチップを、前記の条件で、2.4Ｌ容回転型オートクレーブを用いてクラフト蒸解を行った。以下、実施例１と同様な処理と測定を行った。結果を表１に示す。
【００２３】
【表１】
表１の結果から、活性アルカリ添加量とカッパー価の関係を図１に示し、カッパー価とパルプ総収率の関係を図２に示し、カッパー価と白色度の関係を図３に示した。
【００２５】
【図１】
【図２】
【図３】
図１の結果から、比較例１では活性アルカリ添加量が15%以下になると急激にカッパー価が上昇し、難蒸解性を示すのに対し、実施例のアルカリ抽出処理した場合は、易蒸解性となり、活性アルカリ添加量の削減が可能である。図２の結果から、同一カッパー価で比較した場合、実施例１と比較例１で収率の差は認められない。図３の結果から、同一カッパー価における白色度はアルカリ抽出することで約2〜4%向上する。
【００２９】
【実施例２】
実施例１で製造したカッパー価15.0のクラフト蒸解後のパルプを、酸素脱リグニンした後、ECF漂白としてD0(初段二酸化塩素)−E/P(過酸化水素を併用したアルカリ処理)−D1(２段目二酸化塩素)のシーケンスで漂白処理した。これを実施例２−１とした。実施例１で製造したカッパー価17.1のクラフト蒸解後のパルプを同様に処理した。これを実施例２−２とした。酸素脱リグニン、D0、E/P、D1の反応条件は下記の通り。酸素脱リグニンは、Quantum high intensity mini mixerを用いて行い、反応後、パルプを十分に洗浄し、次の漂白に供した。漂白はすべてプラスチックパックにパルプスラリー(パルプ濃度10%)を入れてウォーターバス中で行った。漂白後、パルプ濃度1.5%まで清水で希釈し、搾水を用いて数回洗浄した。続く漂白段では前段の搾水を用いてパルプ濃度15%とした後、パルプ濃度が10%となるように漂白薬品を所定量添加して漂白した。但し、D0段に限り、前段の酸素脱リグニンの排水は持ち込んでいない。酸素脱リグニン後P後のKN価と白色度を表２に、D0後、E/P後のKN価と白色度を表３に、また、D1後の白色度の結果を表４と図４に示す。
酸素脱リグニン：パルプ濃度10%、水酸化ナトリウム添加量2.0%、反応時間60分間、反応温度96℃、酸素初期圧6.0kg/cm2
D0：パルプ濃度10%、二酸化塩素添加量4.0kg/ADTP、反応温度60℃、反応時間20分間
E/P：パルプ濃度10%、水酸化ナトリウム添加量6.0kg/ADTP、過酸化水素添加量3.6kg/ADTP、反応温度70℃、反応時間75分間
D1：パルプ濃度10%、二酸化塩素添加量1.0,3.0,5.0kg/ADTP、反応温度70℃、反応時間150分間
【００３０】
【比較例２】
比較例１で製造したカッパー価15.6のクラフト蒸解後のパルプを使用した以外は実施例２と同様に酸素脱リグニンと漂白を行った。これを比較例２−１とした。比較例１で製造したカッパー価19.6のクラフト蒸解後のパルプを使用した以外は実施例２と同様に酸素脱リグニンと漂白を行った。これを比較例２−２とした。酸素脱リグニン後P後のKN価と白色度を表２に、D0後、E/P後のKN価と白色度を表３に、また、D1後の白色度の結果を表４と図４に示す。
【００３１】
【表２】
表２の結果から、比較例２は実施例２に比較してΔカッパー価は大きいにもかかわらず、Δ白色度は両者でほとんど差が認められない。このことから、比較例２の未晒しパルプ中には、白色度にはほとんど寄与せず、過マンガン酸カリウムを無駄に消費する化合物が存在していることがわかる。この化合物はキノ、エラグ酸などの酸性の抽出成分と考えられる。また、酸素脱リグニン後のカッパー価がほぼ同等(実施例２−２のカッパー価9.3と比較例２−２のカッパー価9.6の比較)でも、白色度は5.3%という顕著な差があることから、比較例２の未晒しパルプ中には強い着色構造が存在すると考えられる。
【００３３】
【表３】
表３に示す結果のD0段後のパルプのΔカッパー価とΔ白色度について実施例２と比較例２を比較すると、比較例２の場合、Δカッパー価が実施例２と同じレベルでもΔ白色度が高いことから、過マンガン酸カリウムの消費が同じレベルでも強く着色した構造が比較例２のパルプ中に存在すると考えられる。
【００３５】
【表４】
【図４】
表４および図４の結果から、二酸化塩素添加量3.0kg/ADTPにおけるD-ECF漂白性は実施例２−１が最も優れ、次いで実施例２−２、比較例２−１、比較例２−２の順であり、酸性の抽出成分をアルカリ抽出した未晒しパルプのほうがD-ECF漂白性が優れていることがわかる。また、比較例２−２では二酸化塩素添加量5.0kg/ADTPでも84%の白色度を得られなかった。
【００３８】
【発明の効果】
難蒸解性かつ難漂白性のユーカリ材チップあるいは該ユーカリ材が配合されたチップを、アルカリ性水溶液含浸工程−温度５０〜８０℃、保持時間３０〜６０分間の保持工程−アルカリ抽出液の抽出、洗浄工程−カッパー価１４〜２２の未晒しパルプを製造する蒸解工程−白色度８４％以上の漂白パルプを製造するＴＣＦ漂白あるいはＥＣＦ漂白から成る一連の処理を施すことにより、難蒸解性かつ難漂白性であるユーカリ材から高白色度のＴＣＦあるいはＥＣＦ漂白パルプを製造でき、森林資源の有効活用を促進できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing bleached kraft pulp of high whiteness from a material of Eucalyptus which is hardly digestible and difficult to bleach.
[0002]
[Prior art]
Eucalyptus wood and southern wood are becoming the main raw materials for hardwood kraft pulp. There are many types of eucalyptus wood, and their digestibility and bleaching properties differ depending on the species, age, and location of production. Eucalyptus wood is broadly divided into ash type and blood wood type, and the ash type has a relatively small problem when used industrially as a pulp material because the amount of extracted components is small. On the other hand, in the blood wood type, various problems due to the acidic extract components occur, and a mitigation measure is necessary.
[0003]
Eucalyptus wood contains polyphenols called quino and acidic extraction components such as ellagic acid. The kino component is a secretion of a tree mainly composed of condensed tannin, has a color tone from light yellow to deep red, and has different characteristics depending on the tree species. Ellagic acid is present in the wood in a free state, but is mainly present in the form of ellagitannic acid formed from gallic acid and ellagic acid. This ellagitannic acid is hydrolyzed during cooking to ellagic acid. Ellagic acid exhibits strong acidity and is easily oxidized under alkaline conditions, becomes a quinone type, strongly adsorbs to pulp cellulose, and adversely affects pulp whiteness. Furthermore, at high temperature and high pressure, it is easy to polymerize due to its phenolic property, and becomes a sticky substance.
[0004]
The said acidic extraction component contained in a eucalyptus material will reduce a pulp yield, if there is much content. It also consumes kraft cooking alkaline chemicals. This consumption is faster than alkali consumption due to elution of lignin, causing the problem of high kappa value of unbleached pulp (in other words, decreased whiteness), increasing the load of the subsequent bleaching process, It also causes an increase in chemical usage or a decrease in the whiteness of bleached pulp. In addition, problems such as generation of scale derived from extracted components in washer, diffuser, etc., or the viscosity of concentrated black liquor significantly increases and the vacuum evaporation becomes poor, which deteriorates the flammability of black liquor in the recovery boiler. cause.
[0005]
Various problems of the above hard-to-cook materials are recognized for a long time, and countermeasures are being studied. For example, in the case of alkaline cooking, lignin and carbohydrates consume alkali, but acidic extract components react with alkali more quickly than these. A two-stage cooking method has been devised, in which the reaction is first performed with the remaining alkali in the black liquor and then the white liquor is added for cooking (see Non-Patent Document 1). In addition, it is reported that the whiteness of kraft pulp can be improved and the amount of active alkali added can be reduced by hot water extraction of eucalyptus wood, and that there is no difference in pulp yield and chlorine consumption. (See Non-Patent Document 2). In addition, it is clear that acidic extract components contained in eucalyptus wood can be easily lightened by oxidation with oxygen under alkaline conditions, and it is clear that black liquor combustion can be improved, so alkali oxidation pretreatment prior to kraft cooking Describes that the whiteness of the pulp can be improved (see Non-Patent Document 3). In addition, it relates to a pulp production method by alkali cooking of wood containing quino substances, and in particular, wood chips containing quino substances are pretreated with alkaline cooking liquor at 30 ° C. or more and below the elution temperature of alkali lignin, A pulp production method for cooking is shown (see Patent Document 1). Also, eucalyptus chips are used to rationally neutralize the acidity of a large amount of exudate that exudes from eucalyptus chips to reduce corrosion resistance to metals and to improve the digestibility of chips and to reduce cooking chemicals and bleaching chemicals. A method is described in which an alkali solution is sprayed on the substrate and the alkali is deposited so as to be 0.3 to 1.5% by weight with respect to the chip, and then deposited for at least two weeks (see Patent Document 2). In addition, when cooking wood chips having a high amount of alkali-soluble extract components such as eucalyptus wood chips, the purpose of extracting the alkali-soluble extract components most effectively and advantageously is to remove the wood chips from 20 to the average thickness of the wood. A method is described in which alkali digestion is performed after passing between two metal rolls that have a 50% gap, face each other in opposite directions and rotate at a peripheral speed ratio of 1: 1.1 to 1.5 (Patent Document) 3).
[0006]
Examples of techniques for improving the concentration and flammability of black liquor after pulp digestion include 5 to 5% of dissolved substances in kraft pulp waste liquid of materials containing a large amount of polyphenols or tannins, such as southern materials such as eucalyptus. A technique is disclosed in which 35% is oxidatively decomposed with a required amount of pressurized air or the like to enable chemical recovery in the kraft method (see Patent Document 4). Also obtained by causticizing the green liquor or green liquor into the dilute waste liquid before concentration in the process of regenerating the liquor by causticizing the green liquor obtained by concentrating and burning the pulp cooking liquor mainly composed of eucalyptus wood After adding the white liquor to be mixed, air-oxidized, or after being air-oxidized or concentrated to some extent after air-oxidization, caustic soda is added to increase the pH of the waste liquid, and then it is concentrated to a predetermined concentration before burning. (See Patent Document 5).
[0007]
[Non-Patent Document 1]
Sloman, AR, Appita, 14 (2), 57 (1960)
[Non-Patent Document 2]
Nelson, PF, et al., Appita, 24 (2), 101 (1970)
[Non-Patent Document 3]
Hemingway, RWet al., Appita, 25 (6), 445 (1972)
[Patent Document 1]
Japanese Patent Publication No. 47-24162 [Patent Document 2]
Japanese Patent Laid-Open No. 53-134903 [Patent Document 3]
Patent No. 1506085 [Patent Document 4]
Japanese Patent Publication No. 48-42242 [Patent Document 5]
Patent No. 1021680 Specification [0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to improve the digestibility and bleachability of eucalyptus materials that are difficult to digest and difficult to bleach in the production of bleached kraft pulp with a high degree of whiteness, or materials containing the eucalyptus materials. It is to provide high whiteness TCF or ECF bleached pulp.
[0009]
[Means for Solving the Problems]
High-whiteness bleached kraft pulp can be produced by applying a series of treatments consisting of the following steps to chips made of only eucalyptus wood that is hardly digestible and difficult to bleach, or chips containing the eucalyptus wood chips. .
(A) Step of impregnating wood chip with alkaline aqueous solution (b) Step of holding wood chip impregnated with alkaline aqueous solution for 30 to 60 minutes and at a temperature of 50 to 80 ° C. (c) After the step (b), (D) A step of kraft cooking the wood chips obtained after the alkali extraction to produce unbleached pulp having a copper number of 14 to 22 (e) The step (d) A process for producing bleached pulp having a high whiteness with a Hunter whiteness of 84% or more by performing TCF bleaching or ECF bleaching on the unbleached pulp obtained in Step 1.
DETAILED DESCRIPTION OF THE INVENTION
The hard-to-digest and hard-to-bleach eucalyptus material to be treated according to the present invention is defined as 4% or more due to the difference of 72% sulfuric acid insoluble matter (Klarson lignin) before and after 1% alkali extraction. This eucalyptus material may be a single tree species, or a mixture of two or more tree species composed solely of the defined eucalyptus material. Further, it is a mixture of the eucalyptus wood of the above definition and other eucalyptus genus or other family / genus broadleaf wood having normal to easy digestibility and bleachability. Non-digestible and hard-to-bleach mixed materials that fall within the definition can also be treated, and the mixed materials may be mixed materials at the overseas chip loading stage or continuously from the chip yard of domestic pulp mills. A mixed material at the stage of discharging to the digester may be used.
[0011]
Although the amount of acidic extractables contained in refractory and hard-to-bleach eucalyptus wood varies depending on the age of the tree, the place of production (in other words, the growth environment), etc., it is difficult to specify the specific tree species. Regarding the Eucalyptus genus, as a tree species containing a lot of mushroom components, Eucalyptus (hereinafter abbreviated as E.) calophylla, E. citriodora, E. diversicolor, E. globulus, E. grandis, E. gummifera, E. marginata, Old tree such as E. nesophila, E. nitens, tree species rich in ellagitannic acid, E. amygdalina, E. camaldulensis, E. delegatensis, E. gigantea, E. muelleriana, E. obliqua, E. regnans, Old tree such as E. sieberiana and E. viminalis, and tree species rich in leucoanthocyanidins include old trees such as E. camaldulensis and E. marginata.
[0012]
In the step of impregnating a hard-to-digest and hard-to-bleach wood chip with an alkaline aqueous solution, coarse chips and chip dust are removed to process chips having a uniform size. The alkaline aqueous solution impregnation step can be installed at any location between the chip screening step and the cooking step, but in order to improve the impregnation of the alkaline aqueous solution, the steaming vessel and the subsequent steps are desirable. Sodium hydroxide or potassium hydroxide can be used as the alkaline agent, but sodium hydroxide is preferred.
[0013]
In the case where the impregnation treatment is a method of immersing wood chips in an alkaline aqueous solution, the wood chips are placed in an impregnation container, an alkaline aqueous solution is added, and the chips are impregnated with the alkaline aqueous solution. At this time, it is preferable to carry out under reduced pressure for the purpose of improving the impregnation. The addition rate of the alkaline drug to the chip (absolutely dry) is preferably from 1.0 to 10.0 solids by weight, more preferably from 1.0 to 5.0 solids by weight. The liquid ratio of alkaline aqueous solution (volume) / chip volume is preferably 4.0 to 10.0, and more preferably 4.0 to 6.0. The solid content concentration of the alkaline aqueous solution is adjusted in advance so as to satisfy the addition ratio and the liquid ratio.
[0014]
The impregnation treatment can also be performed by compressing the wood chips and impregnating with an alkaline aqueous solution after being compressed or released. In this case, the addition ratio of the alkaline chemical to the chip (absolutely dry) is preferably from 1.0 to 10.0% by solid weight, more preferably from 1.0 to 5.0 solids by weight. Any device can be used for the compression as long as it can sufficiently compress the wood chips, and there is no particular limitation. However, Andritz's Impresssfiner and Valmet's plex screw (Prex screw). The compression ratio is preferably 2: 1 or more, more preferably 4: 1 or more.
[0015]
Next, the wood chip impregnated with the alkaline aqueous solution is kept in the holding container while being heated for a predetermined time, and during this time, the acidic extraction component is extracted and neutralized with the alkaline aqueous solution. Temperature is preferably 50~ 80 ℃, 50~ 75 ℃ is not more preferable. The retention time also depends on the temperature, have preferably 30 to 60 minutes. The final pH at the end of holding is preferably 8.0 to 10.0.
[0016]
Next, the solution after extraction / neutralization is removed with an alkaline aqueous solution, and the chip is sufficiently washed with water. Insufficient cleaning will affect the subsequent cooking process.
[0017]
The washed chips are sent to the cooking process and subjected to kraft cooking under normal conditions (active alkali addition amount, sulfidity, liquid ratio, maximum temperature, holding time, H factor, etc.). Moreover, you may use for cooking of correction craft methods, such as MCC, EMCC, ITC, and Lo-solid. There are also no particular limitations on the cooking type such as 1 vessel liquid phase type, 1 vessel liquid phase / gas phase type, 2 vessel liquid phase / gas phase type, and 2 vessel liquid phase type. That is, the step of impregnating and holding the alkaline aqueous solution of the present application is installed separately from the conventional apparatus or part for the purpose of permeating the cooking liquid. The unbleached pulp that has been cooked is washed with a device such as a diffusion washer after extracting the cooking liquor. It is preferable to set the kappa number of unbleached pulp after washing to 14-22. 15-18 are more preferable.
[0018]
Next, unbleached pulp having a predetermined kappa number is subjected to bleaching treatment by TCF bleaching or ECF bleaching. TCF bleaching and ECF bleaching may be performed by a known sequence, and are not particularly limited. Specifically, TCF bleaching sequences include ZEP, ZE / OP, E / OP-PO, etc., and ECF bleaching sequences include DED, DE / OD, E / OD, EOD, ZD, etc. . The hard-to-cook and hard-to-bleach material that is the subject of the present invention is difficult to obtain bleached pulp with a hunter whiteness of 84% or more under normal cooking conditions and normal TCF and ECF bleaching sequences. By the processes of the steps (a) to (d) of the present invention, bleached pulp having a high whiteness with a Hunter whiteness of 84% or more can be easily produced.
[0019]
【Example】
EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.
[Example 1] and [Comparative Example 1] compared kraft cooking properties, and [Example 2] and [Comparative Example 2] compared ECF bleaching properties with chlorine dioxide (abbreviated as D-ECF).
[0020]
The following chips were used for Examples and Comparative Examples.
1. Chips of eucalyptus were collected from the chip yard of Nippon Paper Industries Co., Ltd. The difference in 72% sulfuric acid insoluble content before and after 1% alkali extraction was 4.5%.
2. Adjustment of chip size The chips were sieved using a gyro shifter to remove coarse chips and chip dust, thereby obtaining chips of 9.5 to 25.4 mmφ. This chip was used in the following examples and comparative examples.
[0021]
[Example 1]
The chip having the adjusted chip size was infiltrated with a sodium hydroxide aqueous solution for 15 minutes under vacuum, and then subjected to alkali extraction using a 2.4 L rotary autoclave under the following conditions. The amount of the alkaline extract was about 3%, and the pH of the alkaline extract before extraction, after permeation, and after extraction was 12.9, 12.7, and 9.3, respectively. After the extraction treatment, the chip was sufficiently washed with water, and kraft cooking was performed using a 2.4 L rotary autoclave under the conditions shown below. After cooking, the cooking liquor was extracted and the residual effective alkali concentration and pH were measured. After sufficiently washing the pulp, the koji was removed with a flat screen, and the yield, the koji rate and the total yield were determined, and the kappa number and the hunter whiteness were measured. The results are shown in Table 1.
Alkali extraction conditions: 300 g of chips (absolutely dry), 2.0% sodium hydroxide addition, liquid ratio 5.0 L / kg, maximum temperature 80 ° C., holding time 60 minutes, heating time 30 minutes Kraft cooking conditions: 300 g of chips (absolutely dry) ), Active alkali addition amount 12-17%, sulfidity 25%, liquid ratio 2.5L / kg, maximum temperature 160 ° C, holding time 94 minutes, H factor 830
[0022]
[Comparative Example 1]
The chips adjusted for the chip size were subjected to kraft cooking under the above conditions using a 2.4 L rotary autoclave. Hereinafter, the same treatment and measurement as in Example 1 were performed. The results are shown in Table 1.
[0023]
[Table 1]
From the results in Table 1, the relationship between the amount of active alkali added and the kappa number is shown in FIG. 1, the relationship between the kappa number and the total pulp yield is shown in FIG. 2, and the relationship between the kappa number and the whiteness is shown in FIG.
[0025]
[Figure 1]
[Figure 2]
[Fig. 3]
From the results shown in FIG. 1, in Comparative Example 1, when the amount of active alkali added was 15% or less, the kappa number increased rapidly and showed poor digestibility. Thus, the amount of active alkali added can be reduced. From the results shown in FIG. 2, no difference in yield is observed between Example 1 and Comparative Example 1 when compared with the same kappa number. From the result of FIG. 3, the whiteness at the same kappa number is improved by about 2 to 4% by alkali extraction.
[0029]
[Example 2]
The pulp after kraft cooking with a kappa value of 15.0 produced in Example 1 was subjected to oxygen delignification and then subjected to ECF bleaching as D 0 (first stage chlorine dioxide) -E / P (alkali treatment using hydrogen peroxide in combination) -D 1 Bleaching was performed using the (second stage chlorine dioxide) sequence. This was designated as Example 2-1. The pulp after kraft cooking with a copper number of 17.1 produced in Example 1 was treated in the same manner. This was designated Example 2-2. The reaction conditions for oxygen delignification, D 0 , E / P, and D 1 are as follows. Oxygen delignification was performed using a Quantum high intensity mini mixer. After the reaction, the pulp was thoroughly washed and subjected to the next bleaching. All bleaching was performed in a water bath with pulp slurry (pulp concentration 10%) in a plastic pack. After bleaching, it was diluted with fresh water to a pulp concentration of 1.5% and washed several times with squeezed water. In the subsequent bleaching stage, the pre-squeezed water was used to adjust the pulp concentration to 15%, and then bleaching was performed by adding a predetermined amount of bleaching chemicals so that the pulp concentration would be 10%. However, only D 0 stage, drainage of the preceding oxygen delignification does not introduce. The KN value and whiteness after oxygen delignification after P in Table 2, after D 0, in Table 3 the KN value and whiteness after E / P, also, a table 4 the results of whiteness after D 1 As shown in FIG.
Oxygen delignification: pulp concentration 10%, sodium hydroxide addition 2.0%, reaction time 60 minutes, reaction temperature 96 ° C, oxygen initial pressure 6.0kg / cm 2
D 0 : Pulp concentration 10%, chlorine dioxide addition 4.0kg / ADTP, reaction temperature 60 ° C, reaction time 20 minutes
E / P: Pulp concentration 10%, sodium hydroxide addition amount 6.0kg / ADTP, hydrogen peroxide addition amount 3.6kg / ADTP, reaction temperature 70 ° C, reaction time 75 minutes
D 1 : Pulp concentration 10%, chlorine dioxide addition 1.0,3.0,5.0kg / ADTP, reaction temperature 70 ° C, reaction time 150 minutes [0030]
[Comparative Example 2]
Oxygen delignification and bleaching were performed in the same manner as in Example 2 except that the pulp after kraft cooking with a copper number of 15.6 produced in Comparative Example 1 was used. This was designated as Comparative Example 2-1. Oxygen delignification and bleaching were performed in the same manner as in Example 2 except that the pulp after kraft cooking with a copper number of 19.6 produced in Comparative Example 1 was used. This was designated as Comparative Example 2-2. The KN value and whiteness after oxygen delignification after P in Table 2, after D 0, in Table 3 the KN value and whiteness after E / P, also, a table 4 the results of whiteness after D 1 As shown in FIG.
[0031]
[Table 2]
From the results of Table 2, although Comparative Example 2 has a larger ΔKappa number than that of Example 2, there is almost no difference in Δwhiteness. From this, it can be seen that the unbleached pulp of Comparative Example 2 contains a compound that hardly contributes to whiteness and consumes potassium permanganate wastefully. This compound is considered to be an acidic extraction component such as quino or ellagic acid. In addition, even when the kappa number after oxygen delignification is almost the same (comparation between the kappa number 9.3 of Example 2-2 and the kappa number 9.6 of Comparative Example 2-2), the whiteness has a remarkable difference of 5.3%. It is considered that a strong colored structure is present in the unbleached pulp of Comparative Example 2.
[0033]
[Table 3]
When Example 2 and Comparative Example 2 are compared for Δkappa number and Δwhiteness of the pulp after D 0 of the results shown in Table 3, in the case of Comparative Example 2, Δkappa number is the same level as Example 2 and Δ Since the whiteness is high, it is considered that a strongly colored structure exists in the pulp of Comparative Example 2 even when the consumption of potassium permanganate is the same level.
[0035]
[Table 4]
[Fig. 4]
From the results of Table 4 and FIG. 4, the D-ECF bleaching property at the chlorine dioxide addition amount of 3.0 kg / ADTP is the best in Example 2-1, followed by Example 2-2, Comparative Example 2-1, and Comparative Example 2- It can be seen that the unbleached pulp obtained by alkali extraction of the acidic extract component is superior in D-ECF bleachability. In Comparative Example 2-2, 84% whiteness could not be obtained even with a chlorine dioxide addition of 5.0 kg / ADTP.
[0038]
【The invention's effect】
A hard-to-digest and hard-to-bleach eucalyptus chip or a chip containing the eucalyptus material is impregnated with an alkaline aqueous solution-temperature holding step of 50 to 80 ° C, holding time of 30 to 60 minutes-extraction and washing of alkaline extract Process-Cooking process for producing unbleached pulp with a copper number of 14-22-Non-digestion and bleaching resistance by applying a series of treatments consisting of TCF bleaching or ECF bleaching to produce bleached pulp with a whiteness of 84% or more High whiteness TCF or ECF bleached pulp can be produced from eucalyptus wood, which can promote effective utilization of forest resources.
Claims (4)
（ａ）木材チップにアルカリ性水溶液を含浸させる工程
（ｂ）前記アルカリ性水溶液を含浸させた木材チップを３０〜６０分間かつ温度５０〜８０℃で保持する工程
（ｃ）前記（ｂ）工程の後、アルカリ抽出液を抜き取り、木材チップを洗浄する工程
（ｄ）前記アルカリ抽出後に得られた木材チップをクラフト蒸解し、カッパー価１４〜２２の未晒しパルプを製造する工程
（ｅ）前記（ｄ）工程で得られた未晒しパルプをＴＣＦ漂白あるいはＥＣＦ漂白し、ハンター白色度８４％以上の高白色度の漂白パルプを製造する工程
から成る一連の工程を経て処理されることを特徴とする高白色度の漂白クラフトパルプの製造方法。A method of producing bleached kraft pulp with high whiteness from a material of genus Eucalyptus which is hardly digestible and difficult to bleach, or a material containing the material,
(A) Step of impregnating wood chip with alkaline aqueous solution (b) Step of holding wood chip impregnated with alkaline aqueous solution for 30 to 60 minutes and at a temperature of 50 to 80 ° C. (c) After the step (b), (D) A step of kraft cooking the wood chips obtained after the alkali extraction to produce unbleached pulp having a copper number of 14 to 22 (e) The step (d) Unbleached pulp obtained in 1) is processed through a series of steps consisting of TCF bleaching or ECF bleaching to produce bleached pulp with high whiteness of Hunter whiteness of 84% or higher. Of making bleached kraft pulp.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101525954B1 (en) * | 2012-03-30 | 2015-06-09 | 산동 타이양즈예 컴퍼니 리미티드 | Preparation process for eucalyptus dissolving pulp |
| CN108867130A (en) * | 2018-04-26 | 2018-11-23 | 天津科技大学 | The pulping process of high yield pulp1 needlebush dissolving pulp and its dissolving pulp of preparation |
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| US8268124B2 (en) | 2007-01-15 | 2012-09-18 | Nihon Cellulose Co., Ltd. | Method for production of pulp |
| JP2010106398A (en) * | 2008-10-30 | 2010-05-13 | Dynapac Co Ltd | Corrugated board and method for producing the same |
| JP6358771B2 (en) * | 2012-06-15 | 2018-07-18 | 日本製紙株式会社 | Method for producing dissolved kraft pulp |
| AU2015286229B2 (en) * | 2014-07-10 | 2018-11-08 | Leaf Sciences Pty Ltd | Methods for treating lignocellulosic material |
| JP6581137B2 (en) * | 2017-03-24 | 2019-09-25 | 日本製紙株式会社 | Method for producing dissolved kraft pulp |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101525954B1 (en) * | 2012-03-30 | 2015-06-09 | 산동 타이양즈예 컴퍼니 리미티드 | Preparation process for eucalyptus dissolving pulp |
| CN108867130A (en) * | 2018-04-26 | 2018-11-23 | 天津科技大学 | The pulping process of high yield pulp1 needlebush dissolving pulp and its dissolving pulp of preparation |
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