JP4192566B2 - Method for producing high whiteness bleached kraft pulp - Google Patents

Description

【０００５】
図１に示すように、プロアントシアニジンの分子構造中にはフェノール性水酸基が多数ある。このことから解るように、プロアントシアニジンは酸性の物質である。従って、プロアントシアニジンが多く含まれるシラカンバ属、カエデ属、コナラ属の樹木のチップあるいは酸性物質であるエラグ酸が多く含まれるクルミ属の樹木のチップをクラフト蒸解する場合、プロアントシアニジンあるいはエラグ酸がアルカリ性の蒸解液を消費し、本来の蒸解の目的であるリグニンの溶解反応が阻害される。また、蒸解時、リグニンと反応し難分解性の強い着色構造を生成する。その結果、蒸解後パルプのカッパー価が増大し、後続の漂白工程において漂白薬品を多く添加する必要が生じたり、漂白終了後のパルプの白色度が低下するなどの問題を引き起こす。また、プロアントシアニジンは酸性領域で反応を進める漂白段において酸分解され、着色物質であるアントシアニジンを生ずる。アントシアニジンは酸性でもアルカリ性でも発色し、酸性領域では赤色、アルカリ性領域では青色を呈する。従って、プロアントシアニジンが蒸解終了までに十分に除去されず、漂白工程に多くの量が持ち込まれると、漂白パルプが着色し、色相が変化したり、白色度が低下する問題を引き起こす。
【０００６】
シラカンバ属、カエデ属、コナラ属の難蒸解性かつ難漂白性の原因物質の一つが、プロアントシアニジンであることに着目して、これらの材からプロアントシアニジンを積極的に除去し、蒸解性や漂白性の改善を図ったパルプ製造に関する先行技術を調査したが、先願は見いだせなかった。但し、プロアントシアニジンは、食品、化粧品の酸化防止剤や脱臭剤、医薬品などの製造原料として有用であり、これらの分野でプロアントシアニジンを抽出する技術が多く報告されており、先願も多数ある。例えば、ブドウ果実の搾汁粕を原料としてプロアントシアニジンを含むポリフェノールを、例えば水、エタノールなどの溶媒で60℃以下の低温で抽出する方法が知られている(特許文献１参照。)。また、ブドウの果実の搾汁粕または種子を水にて70℃以上で抽出するに際し、前処理として70℃未満の水と接触させて水可溶性物質を除去するプロアントシアニジンの製造方法が登録されている(特許文献２参照。)。また、ブドウ抽出物等に含まれるプロアントシアニジンを有効成分とする血清リポプロテイン(a)低下剤およびコレステロール低下剤の製造において、抽出に使用する溶媒として、水、低級アルコール、アセトン、アルキルケトン、酢酸エチル等からなる群から選ばれる単独または２種以上の溶媒の混合溶剤が記載されている(特許文献３参照。)。また、ブドウ種子、搾汁粕からのプロアントシアニジンの抽出において、プロアントシアニジンの抽出効率、純度を高める目的で、ブドウ種子またはブドウ果実搾汁粕を水溶性有機溶媒または水溶性有機溶媒と水との混合物で、加熱還流させながら抽出する方法が示されている(特許文献４参照。)。また、咽喉用うがい薬の製造に関し、ブドウ種子からプロアントシアニジンを抽出する溶媒として、メタノール、エタノール、イソプロパノールなどの水溶性アルコール類、アセトン、エチルメチルケトン、N,N-ジメルホルムアミド、酢酸、水などの利用が記載され、抽出条件として、抽出温度0〜100℃、好ましくは25〜90℃、時間は10分間〜24時間、好ましくは30分間〜2時間の記載がある(特許文献５参照。)。
【０００７】
【特許文献１】
米国特許第1167006号明細書
【特許文献２】
特許第2694748号明細書
【特許文献３】
特開平8-225453号公報
【特許文献４】
特開平11-80148号公報
【特許文献５】
特開2001-39844号公報
【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シラカンバ属、カエデ属、コナラ属、クルミ属の単材あるいはこれらの混合材、あるいは該シラカンバ属、カエデ属、コナラ属、クルミ属の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シラカンバ属、カエデ属、コナラ属、クルミ属の単材チップあるいはこれらの混合材チップ、あるいは該シラカンバ属、カエデ属、コナラ属、クルミ属の材が配合された材チップに、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シラカンバ属、カエデ属、コナラ属、クルミ属の材は、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。この材は単独樹種品でも良いし、２樹種以上の混合品でも良い。また、該定義のシラカンバ属、カエデ属、コナラ属、クルミ属の材と、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シラカンバ属、カエデ属、コナラ属、クルミ属の材に含まれるプロアントシアニジン、エラグ酸などの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、シラカンバ属に関しては、Betula(以下、B.と略す) platyphylla(シラカンバ)、B.ermani(ダケカンバ)、B.globispira(ジゾウカンバ)、B.davurica(ヤエガワカンバ)、B.maximowicziana(ウダイカンバ)、B.grossa(アズサ)、B.corylifolia(ウラジロカンバ)、B.schmidtii(オノオレ)、B.papyrifera(White birch)、B.alleghaniensis(Yellow birch)などの老齢木が挙げられる。カエデ属に関しては、Acer(以下、A.と略す) palmatum(タカオモミジ、ヤマモミジ)、A.japonicum(ハウチワカエデ)、A.sieboldianum(コハウチワカエデ)、A.shirasawanum(オオイタヤメイゲツ)、A.tenuifolium(ヒナウチワカエデ)、A.argutum(アサノハカエデ)、A.ukurunduense(オガラバナ)、A.tschonoskii(ミネカエデ)、A.micranthum(コミネカエデ)、A.crataegifolium(ウリカエデ)、A.rufinerve(ウリハダカエデ)、A.capillipes(ホソエカエデ)、A.nipponicum(テツカエデ)、A.ginnala(カラコギカエデ)、A.mono(イタヤカエデ、エンコウカエデ)、A.miyabei(エゾイタヤ)、A.diabolicum(カジカエデ)、A.rubrum(ハナノキ)、A.buergerianum(トウカエデ)、A.carpinifolium(チドリノキ)、A.distylum(ヒトツバカエデ)、A.cissifolium(ミツデカエデ)、A.nikoense(メグスリノキ)、A.saccharum(Sugar maple)などの老齢木が挙げられる。コナラ属に関しては、Quercus(以下、Q.と略す)serrata(コナラ)、Q.crispula(ミズナラ)、Q.acutissima(クヌギ)、Q.variabilis(アベマキ)、Q.dentata(カシワ)、Q.aliena(ナラガシワ)、Q.phillyraeoides(ウバメガシ)、Q.myrsinaefolia(シラカシ)、Q.glauca(アラカシ、ヒリュウガシ)、Q.acuta(アカガシ)、Q.paucidentata(ツクネガシ)、Q.stenophylla(ウラジロガシ)、Q.gilva(イチイガシ)、などの老齢木が挙げられる。クルミ属に関しては、Juglans nigra(Black walnut)などの老齢木が挙げられる。
【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液と共に連続蒸解釜へ投入され、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、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広葉樹のみから成るチップを採取した。このチップは、A.saccharum(Sugar maple)、B.papyrifera(White birch)、B.alleghaniensis(Yellow birch)、他の樹種から構成されているものである。1%アルカリ抽出前後の72%硫酸不溶分の差は5.2%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3.8%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13.0、12.2、8.2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】

【００２４】
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２に示し、カッパー価とパルプ総収率の関係を図３に示し、カッパー価と白色度の関係を図４に示した。
【００２５】
【図２】

【００２６】
【図３】

【００２７】
【図４】

【００２８】
図２の結果から、比較例１では活性アルカリ添加量が17%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３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４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3〜4%向上する。
【００２９】
【実施例２】
実施例１で製造したカッパー価18.5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20.6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５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18.3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21.3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５に示す。
【００３１】
【表２】

【００３２】
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。この化合物はプロアントシアニジン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10.0と比較例２−２のカッパー価9.8の比較)でも、白色度は3.8%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】

【００３４】
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】

【００３６】
【図５】

【００３７】
表４および図５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２−１、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シラカンバ属、カエデ属、コナラ属、クルミ属のチップあるいはシラカンバ属、カエデ属、コナラ属、クルミ属の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シラカンバ属、カエデ属、コナラ属、クルミ属の材から高白色度の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 having a high degree of whiteness from a material of the genus Birch, Maple, Quercus, and Walnut that is hardly digestible and difficult to bleach.
[0002]
[Prior art]
Hardwood growing in the temperate zone has become the main raw material for kraft pulp. This broad-leaved tree has many types, and its digestibility and bleaching properties differ depending on the species, age, and place of production. Plant pigments and ellagic acid are substances other than lignin that affect the digestibility and bleaching properties of pulp. These plant pigments are roughly classified into flavonoids, xanthones, and quinones. It is known that proanthocyanidins belonging to the flavonoid pigments and further belonging to polyphenols are contained in a large amount in broad-leaved trees of the genus Birch, Maple, and Quercus. The walnut trees are rich in ellagic acid. Especially in old-aged trees, the content increases. Therefore, in order to effectively utilize these hardly digestible and hardly bleachable materials as pulp materials, a mitigation measure is necessary.
[0003]
This proanthocyanidin is a condensed tannin present in a tree, that is, a compound in which flavan-3-ol or flavan-3,4-diol is unitized by condensation or polymerization, and these are treated with dianiline, delphinidin, This name is given because it produces anthocyanidins such as belargonidine. Accordingly, proanthocyanidins are dimer, trimer, tetramer, and even 30-mer macromolecular procyanidins, prodelphinidins, propelargonidines and the like and their stereoisomers. Is a generic term that includes Proanthocyanidins include 2-30 mer having flavan-3-ol or flavan-3,4-diol represented by the general formula of FIG. 1 as a structural unit (wherein R ₁ is hydrogen, galloyl group or A glycopyranosyl group, R ₂ represents hydrogen or a hydroxyl group, and R ₃ and R ₄ represent hydrogen, a hydroxyl group, or a methoxy group).
[0004]
[Figure 1]

[0005]
As shown in FIG. 1, there are many phenolic hydroxyl groups in the molecular structure of proanthocyanidins. As can be seen from this, proanthocyanidins are acidic substances. Therefore, when kraft cooking of birch, maple, and oak tree chips that are rich in proanthocyanidins or walnut tree chips that are rich in ellagic acid, an acidic substance, proanthocyanidins or ellagic acid is alkaline. The lignin dissolution reaction, which is the original purpose of cooking, is inhibited. In addition, it reacts with lignin during cooking to produce a colored structure that is difficult to decompose. As a result, the kappa number of the pulp after cooking increases, and it becomes necessary to add a large amount of bleaching chemicals in the subsequent bleaching process, and the whiteness of the pulp after bleaching is reduced. Proanthocyanidins are acid-decomposed in the bleaching stage where the reaction proceeds in the acidic region to produce anthocyanidins that are colored substances. Anthocyanidins develop color whether acidic or alkaline, and exhibit red in the acidic region and blue in the alkaline region. Therefore, if proanthocyanidins are not sufficiently removed by the end of cooking and a large amount is brought into the bleaching process, the bleached pulp is colored, causing a problem that the hue is changed or the whiteness is lowered.
[0006]
Focusing on proanthocyanidins as one of the causative and non-bleaching causative substances of birch genus, maple genus, and quercus genus, proanthocyanidins are actively removed from these materials, resulting in digestibility and bleaching. Although prior art related to pulp production with improved properties was investigated, no prior application was found. However, proanthocyanidins are useful as raw materials for producing antioxidants and deodorants for foods and cosmetics, pharmaceuticals, etc., and many techniques for extracting proanthocyanidins have been reported in these fields, and there are many prior applications. For example, a method is known in which polyphenols containing proanthocyanidins are extracted at a low temperature of 60 ° C. or less with a solvent such as water or ethanol using grape juice squeezed as a raw material (see Patent Document 1). In addition, when extracting grape juice squeezes or seeds with water at 70 ° C or higher, a method for producing proanthocyanidins that removes water-soluble substances by pre-treatment with water below 70 ° C is registered. (See Patent Document 2). In the production of serum lipoprotein (a) and cholesterol lowering agents containing proanthocyanidins contained in grape extracts as active ingredients, water, lower alcohols, acetone, alkyl ketones, acetic acid are used as solvents for extraction. A single solvent or a mixed solvent of two or more solvents selected from the group consisting of ethyl and the like is described (see Patent Document 3). In addition, in the extraction of proanthocyanidins from grape seeds and squeezed grapes, grape seeds or grape fruit squeezed potatoes are mixed with water-soluble organic solvent or water-soluble organic solvent and water for the purpose of increasing the extraction efficiency and purity of proanthocyanidins. A method of extracting with a mixture while heating under reflux is shown (see Patent Document 4). In addition, for the production of throat gargles, as solvents for extracting proanthocyanidins from grape seeds, water-soluble alcohols such as methanol, ethanol, isopropanol, acetone, ethyl methyl ketone, N, N-dimerformamide, acetic acid, water The extraction conditions include an extraction temperature of 0 to 100 ° C., preferably 25 to 90 ° C., and a time of 10 minutes to 24 hours, preferably 30 minutes to 2 hours (see Patent Document 5). ).
[0007]
[Patent Document 1]
US Patent No. 1167006 [Patent Document 2]
Patent No. 2694748 [Patent Document 3]
JP-A-8-225453 [Patent Document 4]
Japanese Patent Laid-Open No. 11-80148 [Patent Document 5]
JP 2001-39844 A [0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that, in the production of bleached kraft pulp with high whiteness, a single material of birch genus, maple genus, konara genus, walnut genus which is difficult to digest and difficult to bleach, or a mixed material thereof, Another object of the present invention is to provide a high-whiteness TCF or ECF bleached pulp by improving the digestibility and bleachability of a material containing the materials of the genus Birch, Maple, Konara, and Walnut.
[0009]
[Means for Solving the Problems]
Non-digestible and hard-to-bleach white birch, maple, white oak, walnut genus chips or a mixture of these chips, or a material mixed with birch, maple, oak, walnut High whiteness bleached kraft pulp can be produced by subjecting the chips to a series of treatments comprising the following steps. (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-cook and hard-bleached birch, maple, quercus, and walnut materials that are the subject of the present invention are 4% difference in 72% sulfuric acid insoluble matter (Klarson lignin) before and after 1% alkali extraction. It is defined as more than%. This material may be a single tree species or a mixture of two or more species. In addition, it is a mixed product of the material of the genus Birch, Maple, Quercus, and Walnut with the definition, and other hardwoods having a normal level to an easy level of digestibility and bleachability. It is also possible to treat non-digestible and non-bleachable mixed materials that fall within the definition in this definition, and the mixed materials may be mixed materials at the overseas chip loading stage, or chip yards of domestic pulp mills. It may be a mixed material at the stage of discharge from the continuous digester.
[0011]
The amount of acidic extractables such as proanthocyanidins and ellagic acid contained in hard-to-digest and hard-bleached birch, maple, oak, and walnut varieties varies depending on the age of the tree and the place of production (in other words, the growth environment). Therefore, it is difficult to specify a specific tree species, but Betula (hereinafter abbreviated as B.) platyphylla, B.ermani, B. globispira, B. globispira, B. .davurica (Yaegawa birch), B.maximowicziana (Udai bimamba), B.grossa (Azusa), B.corylifolia (Vulture birch), B.schmidtii (Ononore), B.papyrifera (White birch), B. alleghaniensis (Yellow birch) An old tree such as As for the genus Maple, Acer (hereinafter abbreviated as A.) palmatum (Takamomimomi, Yamamomiji), A.japonicum (Akasaka maple), A. sieboldianum (Akasaka maple), A. shirasawanum (Aoi tenaefokae), A. tenuifolium , A.argutum, A.ukurunduense, A.tschonoskii, A.micranthum, A.crataegifolium, A.rufinerve, A.capillipes, A.capillipes , A. nipponicum, A. ginnala, A. mono, A. miyabei, A. diabolicum, A. rubrum, A. buergerianum ( Aged trees such as A. carpinifolium, A. distylum, A. cissifolium, A. nikoense, A. saccharum (Sugar maple). Quercus (hereinafter abbreviated as Q.) serrata, Q. crispula, Q. acutissima, Q. variabilis (Abemak), Q. dentata, Q. aliena (Naragasiwa), Q.phillyraeoides (Umegamegashi), Q.myrsinaefolia (Shirakashi), Q.glauca (Arakasi, Hirugashi), Q.acuta (Akagashi), Q.paucidentata (Tsukunegashi), Q.stenophylla (Vulture) Aged trees such as gilva are known. For the genus Walnut, examples include old-aged trees such as Juglans nigra (Black walnut).
[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. The temperature is 50 ~ 80
℃ is preferred, 50~ 75 ℃ is not more preferable. Holding time depends on temperature, but 30 ~
60 minutes have preferred. 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 chips after washing are put together with the cooking liquor into a continuous digester 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, as TCF bleaching sequences, TCF bleaching sequences include ZEP, ZE / OP, E / OP-PO, etc., and ECF bleaching sequences include DED, DE / OD, E / OD, EOD. , ZD and the like. 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. A bleached pulp having a high whiteness with a Hunter whiteness of 84% or more can be produced by the treatment in the steps (a) to (d) of the present invention.
[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 made from broad-leaved trees were collected from the chip yard of Nippon Paper Industries Co., Ltd. This chip is composed of A. saccharum (Sugar maple), B. papyrifera (White birch), B. alleghaniensis (Yellow birch), and other tree species. The difference in 72% sulfuric acid insoluble content before and after 1% alkali extraction was 5.2%.
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 3.8%, and the pH of the alkaline extract before extraction, after infiltration and after extraction was 13.0, 12.2, and 8.2, 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: Chip 300g (absolutely dry), sodium hydroxide addition 2.0%, liquid ratio 5.0L / kg, maximum temperature 80 ° C, holding time 60 minutes, heating time 30 minutes Kraft cooking conditions: chip 300g (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]

[0024]
From the results shown in Table 1, the relationship between the active alkali addition amount and the kappa number is shown in FIG. 2, the relationship between the kappa number and the total pulp yield is shown in FIG. 3, and the relationship between the kappa number and the whiteness is shown in FIG.
[0025]
[Figure 2]

[0026]
[Fig. 3]

[0027]
[Fig. 4]

[0028]
From the results shown in FIG. 2, in Comparative Example 1, when the amount of active alkali added is 17% or less, the kappa number increases rapidly and shows poor digestibility. Thus, the amount of active alkali added can be reduced. From the results of FIG. 3, when compared with the same kappa number, no difference in yield is observed between Example 1 and Comparative Example 1. From the result of FIG. 4, the whiteness at the same kappa number is improved by about 3 to 4% by alkali extraction.
[0029]
[Example 2]
The pulp after kraft cooking with a kappa value of 18.5 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 kappa number of 20.6 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 18.3 produced in Comparative Example 1 was used. This was designated as Comparative Example 2-1. Oxygen delignification and bleaching were carried out in the same manner as in Example 2 except that the pulp after kraft cooking with a copper number of 21.3 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 Table 2, after D _0, in Table 3 the KN number and whiteness after E / P, also, a table 4 the results of whiteness after D ₁ As shown in FIG.
[0031]
[Table 2]

[0032]
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 proanthocyanidins. In addition, even when the kappa number after oxygen delignification is almost the same (comparation between the kappa number 10.0 of Example 2-2 and the kappa number 9.8 of Comparative Example 2-2), the whiteness has a remarkable difference of 3.8%. It is considered that a strong colored structure is present in the unbleached pulp of Comparative Example 2.
[0033]
[Table 3]

[0034]
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]

[0036]
[Figure 5]

[0037]
From the results shown in Table 4 and FIG. 5, 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 Examples 2-1 and 2-2, 84% whiteness could not be obtained even with a chlorine dioxide addition amount of 5.0 kg / ADTP.
[0038]
【The invention's effect】
Hardly digestible and hard-bleaching white birch, maple, white oak, walnut chips or chips mixed with white birch, maple, white oak, walnut genus, alkaline aqueous solution impregnation step-temperature 50 ~ 80 ° C., holding time of 30 to 60 minutes holding step-extraction of alkaline extract, washing step-cooking step for producing unbleached pulp with a copper number of 14-22-TCF bleaching for producing bleached pulp with a whiteness of 84% or more Alternatively, by applying a series of treatments consisting of ECF bleaching, high-whiteness TCF or ECF-bleached pulp can be produced from birch, maple, Quercus, and walnut materials that are difficult to digest and bleach. Promote effective use of resources.

Claims (4)

Highly white bleached kraft pulp that is difficult to digest and hard to bleach from materials of the genus Betula, Maple genus (Acer), Quercus genus (Quercus), walnut genus (Juglans) A method of manufacturing
(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. The hard-to-digest and hard-bleaching materials of birch genus, maple genus, quercus genus and walnut genus are 4% or more in terms of the difference in 72% sulfuric acid insoluble content before and after 1% alkali extraction. A method for producing bleached kraft pulp with high whiteness as described in 1. In the step of impregnating and holding the wood chips with an alkaline aqueous solution, the treatment is performed by immersing the wood chips in the alkaline aqueous solution, and the liquid ratio is 4.0 to 10.0 and / or the final pH is 8.0 to 10.0. A method for producing bleached kraft pulp having high whiteness according to claim 1 or 2. 3. The step of impregnating wood chips with an alkaline aqueous solution, wherein the treatment is performed by a method in which the wood chips are compressed and impregnated with an alkaline aqueous solution after being compressed or released from pressure. A method for producing bleached kraft pulp with high whiteness.