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WO1994020672A1 - Procede de blanchiment de la pate a bois - Google Patents

Procede de blanchiment de la pate a bois Download PDF

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Publication number
WO1994020672A1
WO1994020672A1 PCT/US1994/002710 US9402710W WO9420672A1 WO 1994020672 A1 WO1994020672 A1 WO 1994020672A1 US 9402710 W US9402710 W US 9402710W WO 9420672 A1 WO9420672 A1 WO 9420672A1
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WIPO (PCT)
Prior art keywords
pulp
ozone
oxygen
xylanase
peroxide
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PCT/US1994/002710
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English (en)
Inventor
Karl-Erik L. Eriksson
Jan L. Yang
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University of Georgia Research Foundation Inc UGARF
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University of Georgia Research Foundation Inc UGARF
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Publication of WO1994020672A1 publication Critical patent/WO1994020672A1/fr
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • This application discloses a process for delignifying and bleaching pulp that does not use chlorine or chlorine derivatives.
  • Wood is a lignocellulosic material that is predominantly cellulose, hemicellulose, and lignin.
  • Cellulose is a saccharide polymer composed of linear D-glucose units.
  • Hemicelluloses are linear and branched saccharide homo- and heteropolymers of five and six carbon sugars such as xylose, arabinose, mannose, galactose, and glucose.
  • Lignin is a polymer composed primarily of methoxylated phenylpropane units that have been randomly linked by a variety of carbon-carbon and ether linkages, resulting in a three-dimensional matrix.
  • the linear cellulose molecules are arranged in densely packed fibril bundles, crosslinked by hemicellulose. Lignin matrices encase the cellulose fibrils, imparting strength and stability to the wood.
  • paper is a two- dimensional meshwork of randomly arranged cellulosic fibers linked by hydrogen bonds between the polysaccharide units.
  • the cellulosic fibers To make paper from wood, the cellulosic fibers must be separated from the lignin and deposited into a hydrogen-bonded tangled mat .
  • the strength of paper and paper products prepared from pulp depends on the strength of the intertwined cellulosic network, and therefore, it is important that the process that isolates the fibers from the lignin and that treats the fibers thereafter not unduly degrade, or shorten, the cellulosic polymer. Fibers are typically isolated from lignocellulosic material mechanically or chemically, or through a combination of these processes.
  • Pulps are prepared chemically by treating lignocellulosic material with chemical ox ⁇ dants, such as sulfate and sulfite, that degrade the lignin. After the lignin is oxidized, it is separated from the cellulose. A small fraction of the oxidized lignin, however, typically remains in the pulp covalently bound to hemicellulose. The oxidized lignin has a dark color that discolors the resulting pulp and products made from the pulp.
  • chemical ox ⁇ dants such as sulfate and sulfite
  • brightness reversion i.e. yellowing
  • the bleached lignin oxidizes over time in contact with air.
  • brightness reversion can be minimized.
  • the standard unit of measure for the lignin content of pulp or paper products is the kappa number.
  • the kappa number is determined by a permanganate oxidation test according to TAPPI
  • the standard unit of pulp brightness is the International Organization for Standardization (ISO) , which is evaluated by TAPPI Method T-525 OM- 86. Pulps of a brightness of 83-92% are considered fully bleached and are sometimes necessary for the production of good quality paper.
  • ISO International Organization for Standardization
  • pulp bleaching processes are multistep procedures in which the pulp is treated with a number of agents in very specific sequences.
  • the conventional method for bleaching pulp includes treatment of the pulp with chlorine or chlorine-containing compounds such as calcium hypochlorite, sodium hypochlorite, and chlorine dioxide. These processes work by removing, as opposed to bleaching, the lignin.
  • the chlorine compounds also degrade a portion of the cellulose, reducing the chain length of the polymer, and the viscosity of the pulp. Further, and importantly, the effluent from these processes constitutes a potential environmental hazard since it contains a large number of chlorinated lignin breakdown products.
  • U.S. Patent No. 4,687,745 discloses a process for enhancing the strength and brightness of mechanical pulps that includes treating the pulp with a lignolytic enzyme mixture from a Phanerochaete chrysosporium fermentation process.
  • EPO 0 406 617 A2 discloses a method to delignify lignocellulosic material that includes treating the material with a ligninase enzyme, or ligninase in combination with xylanase.
  • U.S. Patent No. 4,923,565 discloses a method for treating a paper pulp with cellulase and hemicellulase enzymes.
  • PCT WO 91/02840 discloses treating the pulp with a hemicellulose-hydrolyzing enzyme.
  • Methods to bleach pulp have also been advanced that include oxidizing the pulp with oxidants such as ozone, oxygen, and hydrogen peroxide instead of chlorine or chlorine dioxide in very specific sequences in the absence of an enzyme step in the process.
  • oxidants such as ozone, oxygen, and hydrogen peroxide instead of chlorine or chlorine dioxide in very specific sequences in the absence of an enzyme step in the process.
  • Canadian Patent No. 1 132 760 discloses a process for bleaching chemical pulp that includes, in specific sequence, a peroxide bleaching stage, wherein the peroxide is selected from the group consisting of alkaline hydrogen peroxide, acid hydrogen peroxide, and peracid; and at least one ozone bleaching stage. .An oxygen stage is optionally included as the first step.
  • PCT Publication No. WO 92/12289 discloses a chlorine-free process for bleaching lignocellulosic pulp that includes an ozone step followed by a peroxide step.
  • U.S. Patent No. 5,164,043 discloses a process for bleaching lignocellulosic material that includes, in specific sequence, an oxygen step, an ozone step, and then a chlorine-dioxide or peroxide step.
  • U.S. Patent No. 5,179,021 to du Manior, et al. discloses that chemical pulp can be bleached to an ISO brightness level of approximately 50-60% by treating the pulp with oxygen or an oxygen- containing gas in alkaline medium, followed by treatment of a sufficient amount of a substantially cellulase-free xylanase to hydrolyze xylosidic linkages in the material.
  • the patent teaches that one or more additional steps be employed selected from the group consisting of treatment in an aqueous medium with: (i) chlorine, chlorine dioxide, or mixtures thereof; (ii) chlorine dioxide alone; (iii) peroxide; (iv) hypochlorite; (v) ozone; or (vi) nitrogen dioxide.
  • the oxygen and xylanase steps are followed by steps (i) and (ii) , or steps (i) and (iii) .
  • du Manior does not disclose any specific sequences of process steps that provides a high pulp brightness level and which do not include chlorine or chlorine dioxide.
  • a method for the bleaching of hardwood and softwood pulp without chlorine or chlorine derivatives is disclosed that has a short sequence of steps and that provides a pulp with high brightness, good physical strength, and low degree of brightness reversion.
  • the specific sequence in which the treatment steps are carried out is important. It has been discovered that, for example, xylanase has little effect when used after an ozone step. Further, if ozone is used as the last step of the bleaching process, a significant amount of brightness reversion can occur, whereas if peroxide is used as the last step, brightness reversion is minimized.
  • hardwood pulp can be bleached without chlorine or chlorine derivatives to a high brightness level using a specific, optimized, sequence of process steps that includes the use of an enzyme treatment in combination with oxygen or oxygen derivative bleaching steps.
  • the specific steps are, in sequence: (i) treatment with oxygen; (ii) treatment with xylanase; and (iii) treatment with ozone; followed by (iv) treatment with peroxide.
  • This specific sequence of bleaching steps is referred to below as the OXZP process. It has been discovered that this specific combination of steps can provide a brightness level of up to 90% ISO or greater, without undue detrimental effect on the physical properties of the pulp.
  • the pulp can be subjected to alkaline extraction or enhanced alkaline extraction steps between the treatment steps to assist the removal of the lignin, as necessary.
  • softwood pulp can be bleached without chlorine or chlorine derivatives to a high brightness level also using a specific, yet different, optimized, sequence of process steps that includes the use of an enzyme treatment in combination with oxygen or oxygen derivative bleaching steps.
  • the specific steps are, in sequence: (i) treatment with oxygen; (ii) treatment with xylanase; (iii) alkaline extraction; and (iv) ozone treatment; followed by (v) treatment with peroxide.
  • This optimized sequence for the bleaching of softwood pulp is referred to below as OXE p ZP.
  • an additional ozone step is included before the alkaline extraction step (OXZ ⁇ E p Z 2 P) .
  • This alternative sequence can be used to bleach those pulps with significantly higher initial lignin content, within one ozone step may be inadequate alone to achieve sufficient delignification without impairing pulp physical strength.
  • softwood RDH (rapid displacement of heat) pulp is bleached with the sequence XE p ZP.
  • softwood pulp can be also subjected to alkaline extraction or enhanced alkaline extraction steps between the treatment steps to assist the removal of the lignin, as necessary.
  • Eucalyptus, pine, and pine RDH kraft pulps delignified with the specified combination of xylanase and oxygen or oxygen derivative steps set out above, were found to have consistently lower kappa numbers and higher brightness at the same level of ozone charge as compared to control pulps without the enzyme step.
  • a brightness of 90.0% ISO was readily obtained compared to a brightness of 84.7% for the control, OZP pulp.
  • pulps were also bleached to the same brightness levels using the conventional sequence DEDED.
  • the pulps bleached with the specific enzyme and oxygen-based chemical steps have good brightness stability, similar tensile index and slightly lower tear index than the reference DEDED pulps.
  • the oxygen step is removed from the OXZP, OXE P ZP and OXZ ⁇ E p Z 2 P processes for bleaching hardwood and softwood pulps that have very low initial lignin contents such as pulps from the RDH cooking process.
  • Figure 1 is a graph illustrating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and kappa number of the oxygen- bleached eucalyptus Kraft pulp with and without xylanase treatment.
  • the open triangles indicate the brightness level (% ISO) of the oxygen- bleached, ozone treated eucalyptus Kraft pulp.
  • the solid triangles indicate the brightness level (% ISO) of an oxygen-bleached, xylanase and ozone treated eucalyptus Kraft pulp.
  • the open circles indicate the kappa number of an oxygen-bleached, ozone treated eucalyptus Kraft pulp.
  • the solid circles indicate the kappa number of an oxygen- bleached, xylanase and ozone treated eucalyptus Kraft pulp.
  • Figure 2 is a graph illustrating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and viscosity (mPa.s) of an oxygen-bleached eucalyptus Kraft pulp with or without xylanase treatment.
  • the open triangles indicate the brightness level (% ISO) of the oxygen-bleached, ozone treated eucalyptus Kraft pulp.
  • the solid triangles indicate the brightness level (% ISO) of the oxygen-bleached, xylanase and ozone treated eucalyptus Kraft pulp.
  • the open circles indicate the kappa number of an oxygen- bleached, ozone treated eucalyptus Kraft pulp.
  • the solid circles indicate the kappa number of an oxygen-bleached, xylanase and ozone treated eucalyptus Kraft pulp.
  • Figure 3 is a graph indicating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and kappa number of an oxygen- bleached pine Kraft pulp with or without xylanase treatment.
  • the open triangle indicates the brightness of the oxygen-bleached and ozone treated pine Kraft pulp.
  • the solid triangle indicates the brightness of the oxygen-bleached and ozone treated pine Kraft pulp that has also been treated with xylanase.
  • the open circle indicates the viscosity of the oxygen-bleached and ozone treated pine Kraft pulp.
  • the solid circle indicates the viscosity of the oxygen-bleached and ozone treated pine Kraft pulp that has also been treated with xylanase.
  • Figure 4 is a graph indicating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and viscosity of an oxygen- bleached pine Kraft pulp with or without xylanase treatment.
  • the open triangle indicates the brightness (% ISO) of the oxygen-bleached pine Kraft pulp treated without xylanase.
  • the solid triangle indicates the brightness (% ISO) of an oxygen-bleached pine Kraft pulp treated with xylanase.
  • the open circle indicates the viscosity (mPa.s) of an oxygen-bleached pine Kraft pulp treated without xylanase.
  • the solid circle refers to the viscosity of an oxygen-bleached pine Kraft pulp treated with xylanase.
  • Figure 5 is a graph showing the effect of ozone consumption on brightness and kappa number of a RDH pine Kraft pulp pre-treated with XE p or E p stages.
  • the open triangle indicates the brightness (% ISO) of the RDH pine Kraft pulp treated with enhanced alkaline extraction, ozone, and peroxide.
  • the solid triangle indicates the brightness (% ISO) of * the RDH pine Kraft pulp treated with xylanase, enhanced alkaline extraction and ozone.
  • the open circle indicates the kappa number of a RDH pine Kraft pulp treated with enhanced alkaline extraction and ozone.
  • the solid circle refers to the kappa number of a RDH pine Kraft pulp treated with xylanase, enhanced alkaline extraction and ozone.
  • Figure 6 is a graph showing the effect of ozone consumption on brightness and viscosity of the RDH pine Kraft pulp pre-treated with XE p or E p stages.
  • the open triangle indicate the brightness (% ISO) of the RDH pine Kraft pulp treated with enhanced alkaline extraction and ozone.
  • the solid triangle indicates the brightness (% ISO) of a RDH pine Kraft pulp treated with xylanase, enhanced alkaline extraction and ozone.
  • the open circle indicates the kappa number of the RDH pine Kraft pulp treated with enhanced alkaline extraction and ozone.
  • the solid circle indicates the kappa number of an RDH pine Kraft pulp treated with xylanase, enhanced alkaline extraction and ozone.
  • Figure 7 is a graph indicating the tear and tensile relationship of eucalyptus Kraft pulps bleached in the sequences of OXZP and ODEDED.
  • the open circle refers to eucalyptus Kraft pulp treated in sequence with oxygen, xylanase, ozone, and peroxide (OXZP) .
  • the solid circle refers to eucalyptus Kraft pulp treated in sequence with oxygen, chlorine dioxide, alkaline extraction, chlorine dioxide, alkaline extraction, and chlorine dioxide (ODEDED) .
  • hardwood refers to angiosper s.
  • hardwoods include eucalyptus, birch, oak, beech, aspen, gum, maple, poplar and sycamore.
  • softwood refers to gymnosperms. Examples of softwoods include pine, spruce, hemlock, Douglas-fir, larch and redwood.
  • the Beloit Rapid Displacement of Heat (RDH) process used to produce the pine RDH pulp is reported in TAPPI, Vol. 66 (3) , 120 (1983) .
  • oxygen (0) oxygen (0) , ozone (Z) , alkaline or sodium hydroxide extraction (E) , enhanced alkaline extraction (sodium hydroxide extraction combined with peroxide or oxygen) (E p or E 0 ) , chelation of metal ions (Q) , hydrogen peroxide (P) , hypochlorites (H) , sodium hydrosulfite (Y) , chlorine (C) , mixtures of chlorine and chlorine dioxide (C10 2 ) (C/D) , chlorine dioxide (C10 2 ) (D) , and xylanase (X) .
  • ISO refers to International Organization for Standardization which is a basic brightness unit.
  • DTPA refers to diethylene triamine pentaacetic acid.
  • the invention as described herein is an optimized process for the delignification and bleaching of hardwood and softwood chemical pulps that uses no elemental chlorine or other chlorine containing chemicals, and results in pulp with good strength and high brightness levels.
  • the specific steps for the bleaching of hardwood pulp are, in sequence: (i) treatment with oxygen; (ii) treatment with xylanase; and (iii) treatment with ozone; followed by (iv) treatment with peroxide.
  • This specific sequence of bleaching steps is referred to below as the OXZP process.
  • the specific steps for ' the treatment of softwood pulp are, in sequence: (i) treatment with oxygen; (ii) treatment with xylanase; (iii) alkaline extraction; and (iv) ozone treatment; followed by (v) treatment with peroxide.
  • This optimized sequence for the bleaching of softwood pulp is referred to below as OXEZP.
  • an additional ozone step is included before the alkaline extraction step (OXZ ⁇ P) .
  • Softwood RDH (rapid displacement of heat) pulp is bleached with the sequence XE p ZP.
  • both the hardwood and softwood pulps can be subjected to alkaline extraction or enhanced alkaline extraction steps between the treatment steps as necessary to assist the removal of the lignin.
  • Chelation of metal ions in the pulp solution prior to the peroxide bleaching step results in pulp with higher brightness levels than when the peroxide stage is performed without prior chelation of the metal ions.
  • Performing the ozone step before the peroxide step also generally results in significantly higher brightness levels and less brightness reversion than pulp bleached with these steps reversed.
  • the oxygen bleaching of pulp is typically carried out in.an alkaline aqueous media with a pH above 7, and preferably above 11, a pulp consistency of approximately 10-15%, a partial pressure of oxygen of between approximately 80 and 120 psi, and a temperature between approximately 80 and 110 °C.
  • the oxygen treatment step generally takes between approximately 30 and 90 minutes.
  • the oxygen containing gas can be air, or can be purified oxygen.
  • the xylanase treatment is typically carried out at a temperature ranging between 30 and 70'C, preferably 50°C, a pulp consistency of between approximately 5 and 20%, preferably 10%, with a xylanase concentration of 0.1-5 U/g o.d. (oven dried) pulp, preferably 2.0 U/g o.d. pulp, for approximately 30 minutes to 4 hours, preferably 90 minutes.
  • the pH of the xylanase treatment typically ranges between 3-7, and preferably 5.
  • xylanase is derived from the fungus Aureobasidiu pullulans .
  • Xylanase from this source is essentially free of cellulase activity, which weakens the strength of the wood pulp.
  • Other xylanases which do not show appreciable cellulase activity can also be used in this process, such as xylanases from thermophilic and alkalophidic bacteria.
  • the ozone bleaching step is typically carried out at a temperature ranging between 15 and 60 °C, preferably 25 ° C, a pulp consistency of 30-45%, with an ozone concentration of 0.1-5.0%, typically 0.1- 0.5% for approximately 3 to 15 minutes.
  • the pH of pulps during ozone treatment is generally between 2 and 4, and more typically, around 3.
  • the enhanced alkaline extraction is typically carried out at a temperature ranging between 30 and 90°C, and preferably approximately 70 ⁇ C, at a basic pH, preferably greater than 11; and at a pulp consistency of 5-20%, preferably 10-15%, for a time period ranging between 30 and 120 minutes, and generally approximately 90 minutes.
  • the charge of sodium hydroxide is usually between 0.5 and 2.0%, and contains hydrogen peroxide ranging between 0.2 and 1.0, preferably 0.5%, or oxygen gas with a partial pressure 50-100 psi.
  • the optional chelation step is usually carried out at a temperature ranging between 40 and 100°C, preferably approximately 80'C, a pulp consistency of between 5 and 20%, preferably 10%, with a chelating agent concentration of 0.1-0.5%, preferably 0.2%, and with the addition of 1-5% sodium bisulfite, preferably 3% as S0 2 on o.d. pulp.
  • This step is typically carried out for between approximately 5 and 90 minutes, and generally, for approximately 15 minutes.
  • the chelation stage can be performed before the enhanced alkaline extraction as well as before the peroxide stage.
  • Chelating agents that can be used in the process include, but are not limited to DTPA, EDTA (ethylenediamine tetra acetate) and NTA (nitrilotri acetic) .
  • the peroxide step is typically carried out at a temperature ranging between 50 and 90'C, preferably i 70°C, a pulp consistency of between 5 and 20%, typically 12%, with a peroxide concentration of between 1.0 and 3.0%, and a sodium hydroxide concentration of between 1.0 and 2.0%, for between approximately 1 and 5 hours, preferably 3 hours.
  • the pH of the solution used for the peroxide treatment step is basic, and typically greater than
  • the xylanase was produced in batch fermentation by the fungus, Aureobasidium pullulans . The cultivation and subsequent preparation of the culture filtrate has been described previously. Yang, J. and Eriksson, K-E., Hotzaba, 46(6) :481 (1992) . Evaluation of the enzyme against birchwood xylan, mannan, carboxylmethylcellulose and arabinogalactan indicated that the hydrolytic activity of this culture filtrate consists solely of endo-xylanase activity (480 units/ml) . One unit of xylanase activity was defined as the amount of enzyme releasing one ⁇ mol of xylose equivalent per minute at ambient defined (30°C) temperature. Pulp Bleaching Procedure
  • Pulps were disintegrated by 10,000 revolutions in a disintegrator (Noram, PQ, Canada) at room temperature before bleaching.
  • the pulp suspensions were filtered on a Buchner funnel and then placed in double-layer polyester bags.
  • the xylanase treatment (X) was carried out at a pulp consistency of 10% in 50 mM sodium acetate buffer with a pH 5.0 and a xylanase charge of 2 units/g pulp at 50'C for 90 minutes. After the enzyme treatment, the pulps were washed with water. Treatment of pulp in the control sequence was carried out under identical conditions as the treated pulp but without enzyme.
  • Ozone delignification was carried out batchwise at high consistency conditions. Pulp samples were first acidified with sulfuric acid to a pH range of 2-3 and then dewatered with a handpresser to a pulp consistency of approximately 40%. The pulps were subsequently fluffed in a hammer mill prior to the ozone treatment.
  • the ozone generator used in this study had a production capacity of 80-200 g ozone/hr, yielding ozone concentrations of 1-5% (w/w) .
  • a typical batch ozone treatment was carried out with 50 g o.d. (oven dry) pulp, and an ozone charge of between 0.1 to 3.0% (w/w) for 3-15 minutes at ambient temperature and pressure. Ozone concentration was determined by iodometric titration.
  • pulps were pretreated with 0.2% diethylene triamine pentaacetic acid (DTPA) and 3.0% NaHS0 3 calculated as S0 2 on o.d. pulp at a consistency of 10%, pH 4.5 for 15 minutes at 80°C (Q) .
  • DTPA diethylene triamine pentaacetic acid
  • Ep H2O2 0.5 180 70 > 1 1 10
  • the chemical and physical properties of the pulps were analyzed according to the following Tappi test methods: T205 om-88 (forming handsheets for physical tests of pulp) , T227 om-85 (freeness of pulp) , T230 om-89 (viscosity of pulp) , T236 cm- 85 (kappa number of pulp) , T238 cm-85 (laboratory beating of pulp) , and T525 om-86 (brightness of pulp) .
  • the physical properties of the bleached kraft pulps were evaluated at the Institute of Paper Science and Technology (IPST) , Atlanta, Georgia. RESULTS Bleaching of Eucalyptus Kraft Pulp
  • the mill produced oxygen-bleached eucalyptus pulp was treated with Aureobasidium xylanase. This treatment decreased the kappa number from 8.4 to 7.5, increased the viscosity from 23.1 to 25.1 mPa.s and brightness from 53.2 to 55.4% (ISO) .
  • Xylanase treatment of unbleached eucalyptus pulp decreased the kappa number from 12.1 to 10.9, increased the viscosity from 29.5 to 31.0 and brightness from 34.0 to 36.6% (ISO) .
  • Figure 1 is a graph illustrating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and kappa number of an oxygen-bleached eucalyptus Kraft pulp with and without xylanase treatment.
  • Figure 2 is a graph illustrating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and viscosity (mPa.s) of an oxygen- bleached eucalyptus Kraft pulp treated with or without xylanase.
  • the mill produced, oxygen bleached pine kraft pulp was also treated with Aureobasidium xylanase.
  • Xylanase treatment of this pulp decreased the kappa number from 19.3 to 18.0, increased viscosity from 22.2 to 23.4 and brightness from 28.7 to 30.0% (ISO) .
  • Xylanase treatment of unbleached pine kraft pulp decreased the kappa number from 28.6 to 26.8, increased viscosity from 34.0 to 34.2 and brightness from 23.8 to 26.1% (ISO) .
  • Figure 3 is a graph indicating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and kappa number of an oxygen- bleached pine Kraft pulp with or without xylanase treatment.
  • Figure 4 is a graph indicating the effect of ozone consumption as a function of pulp percentage (w/w) on brightness and viscosity of an oxygen-bleached pine Kraft pulp treated with or without xylanase.
  • the kappa number of the xylanase treated pulp was reduced from 18 to 6. As indicated in Figure 3, when xylanase was not used in pulp treatment, the kappa number decreased from 19 to 8 with gradually increased ozone charges up to approximately 2.5%. As indicated in Figure 4, however, the viscosity of the pulp declined initially and then stabilized at approximately 10 mPa. s. Pulp bleached with the OXZ sequence has consistently higher brightness than OZ bleached pulp at the same levels of ozone charges. Brightness of the xylanase treated pulp developed much faster and the brightness ceiling was higher than the OZ pulp.
  • the mill produced unbleached pine RDH pulp was also treated with Aureobasidium xylanase. Enzyme treatment of this pulp decreased the kappa number from 11.3 to 10.6, increased the viscosity from
  • Figure 5 is a graph showing the effect of ozone consumption on brightness and Kappa number of the RDH pine Kraft pulp pre-treated with XE p or E p stages.
  • Figure 6 is a graph showing the effect of ozone consumption on brightness and viscosity of the RDH pine Kraft pulp pre-treated with XE p or E p stages.
  • the kappa number of the pulp decreased from 8.2 to approximately 2 for the XE p treated pulp while a decrease in kappa number from 9 to approximately 3 was obtained for the E p treated pulp with gradually increased ozone charges up to approximately 1%.
  • the viscosity of the pulp was reduced from 7.5 to 5.3 and from 7.5 to 4.8 for the XE p Z and E p Z bleached pulps respectively.
  • the XE p Z bleached pulp had a considerably higher brightness than the E p Z pulp at the same level of ozone charge.
  • the brightness of the XE p Z bleached pulp was approximately 77 while it was only approximately 67 for the E p Z bleached pulp.
  • Figure 7 is a graph indicating the tear and tensile relationship of eucalyptus Kraft pulps bleached with these sequences.
  • the freeness which development (a measurement of drainability or water holding capacity of a given pulp) during the beating of the OXZP bleached pulp is very similar to that of the
  • transition metal ions such as Mn + and Fe + in pulp is known in general to have a detrimental effect on the efficiency of an alkaline peroxide bleaching step.
  • the peroxide step was carried out with 1% H 2 0 2 , 1% NaOH, and 2% Na 2 Si0 3 for 180 minutes on 10% pulp consistency.
  • the acid wash was carried out by acidifying the pulp to pH 2.0 with 10 mM of sulfuric acid, and then washing the pulp with water.
  • the chelation step was carried out with 0.2% DTPA and 3.0% NaHS0 3 calculated as S0 2 on o.d. pulp at a consistency of 10%, and pH of 4.5 for 15 minutes at 80°C.
  • a comparison of the brightness, viscosity, and ozone consumed on w/w of eucalyptus pine and pine RDH kraft pulps bleached with different sequences of enzymes and oxygen-based chemicals is presented in Table 5.
  • the eucalyptus pulp was bleached to a brightness range of 83 to 92% ISO with sequences of OXZP and OXPZ.
  • the eucalyptus pulp was also bleached using a sequence of ODEDED to a ' brightness of 90.2%.
  • the pulp bleached in the OXZP sequence has the highest brightness compared to the OXPZ and OZP at the same level of ozone charge.
  • the viscosity of the bleached pulps were generally low, ranging from 9.2 to 12.4 mPa.s compared to the viscosity of the reference pulp (ODEDED, 24.6 mPa.s) .
  • the effect of xylanase on the brightness of the pulp was significant. Similar results were also obtained with softwood kraft pulps. When pine and pine RDH pulps were fully bleached, the most noticeable effect is that brightness level is consistently higher when the enzyme stage is used.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Biochemistry (AREA)
  • Microbiology (AREA)
  • Paper (AREA)

Abstract

Procédé de blanchiment de la pâte de bois dur ou tendre sans chlore ou dérivés chlorés et qui fournit une pâte de haute blancheur de bonne résistance mécanique et à faible degré de réversion de blancheur. La pâte de bois dur peut être blanchie à un haut degré de blancheur sans chlore ni dérivés chlorés selon la séquence spécifique OXZP. Optionnellement la pâte peut être soumise entre les phases du traitement à des phases d'extraction alcaline ou d'extraction alcaline améliorée afin de favoriser si nécessaire l'élimination de la lignine. La pâte de bois tendre peut être blanchie sans chlore ni dérivés chlorés à un haut degré de blancheur en utilisant également la séquence, différente et optimisée, des phases de processus OXEpZP ou OXZ1EpZ2P. La pâte de bois tendre obtenue par DRC (déplacement rapide de chaleur) est blanchie selon la séquence XEpZP.
PCT/US1994/002710 1993-03-12 1994-03-14 Procede de blanchiment de la pate a bois Ceased WO1994020672A1 (fr)

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US08/030,790 1993-03-12

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995027100A1 (fr) * 1994-04-05 1995-10-12 Mo Och Domsjö Aktiebolag Procede de traitement complexe de pate a papier combine a une etape de dioxyde de chlore
EP1039020A1 (fr) * 1999-03-23 2000-09-27 Oji Paper Co., Ltd. Procede de blanchiment de pate lignocellulosique
WO2003048449A1 (fr) * 2001-12-03 2003-06-12 Iogen Bio-Products Corporation Etape de blanchiment comprenant l'utilisation de xylanase en association avec du peroxyde d'hydrogene, des peracides ou une combinaison de ces derniers
US6824646B2 (en) 1999-03-23 2004-11-30 Oji Paper Co., Ltd. Process for oxygen bleaching and enzyme treating lignocellulosic pulp with liquid treatment and recovery
US6942754B2 (en) 1999-03-23 2005-09-13 Oji Paper Co., Ltd. Process for producing xylooligosaccharide from lignocellulose pulp
EP3399100A4 (fr) * 2015-12-29 2019-08-14 Fibria Celulose S.A. Procédé de production de pulpe de cellulose, pulpe de cellulose et son utilisation, papier
US12305332B2 (en) 2015-12-29 2025-05-20 Suzano S.A. Method for producing cellulose pulp, cellulose pulp and use thereof, paper

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4372812A (en) * 1978-04-07 1983-02-08 International Paper Company Chlorine free process for bleaching lignocellulosic pulp
US4619733A (en) * 1983-11-30 1986-10-28 Kooi Boon Lam Pollution free pulping process using recycled wash effluent from multiple bleach stages to remove black liquor and recovering sodium hydroxide from the black liquor
US4732650A (en) * 1986-09-15 1988-03-22 The Dow Chemical Company Bleaching of cellulosic pulps using hydrogen peroxide
EP0386888A2 (fr) * 1989-02-10 1990-09-12 ICI Canada Inc. Délignification à l'oxygène et traitement enzymatique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4372812A (en) * 1978-04-07 1983-02-08 International Paper Company Chlorine free process for bleaching lignocellulosic pulp
US4619733A (en) * 1983-11-30 1986-10-28 Kooi Boon Lam Pollution free pulping process using recycled wash effluent from multiple bleach stages to remove black liquor and recovering sodium hydroxide from the black liquor
US4732650A (en) * 1986-09-15 1988-03-22 The Dow Chemical Company Bleaching of cellulosic pulps using hydrogen peroxide
EP0386888A2 (fr) * 1989-02-10 1990-09-12 ICI Canada Inc. Délignification à l'oxygène et traitement enzymatique

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995027100A1 (fr) * 1994-04-05 1995-10-12 Mo Och Domsjö Aktiebolag Procede de traitement complexe de pate a papier combine a une etape de dioxyde de chlore
AU690254B2 (en) * 1994-04-05 1998-04-23 Mo Och Domsjo Aktiebolag Method for complex treatment of pulp in conjunction with a chlorine dioxide stage
US6258208B1 (en) 1994-04-05 2001-07-10 Mo Och Domsjo Aktiebolag Method for complex treatment of pulp in conjunction with a chlorine dioxide stage
EP1039020A1 (fr) * 1999-03-23 2000-09-27 Oji Paper Co., Ltd. Procede de blanchiment de pate lignocellulosique
US6824646B2 (en) 1999-03-23 2004-11-30 Oji Paper Co., Ltd. Process for oxygen bleaching and enzyme treating lignocellulosic pulp with liquid treatment and recovery
US6942754B2 (en) 1999-03-23 2005-09-13 Oji Paper Co., Ltd. Process for producing xylooligosaccharide from lignocellulose pulp
WO2003048449A1 (fr) * 2001-12-03 2003-06-12 Iogen Bio-Products Corporation Etape de blanchiment comprenant l'utilisation de xylanase en association avec du peroxyde d'hydrogene, des peracides ou une combinaison de ces derniers
EP3399100A4 (fr) * 2015-12-29 2019-08-14 Fibria Celulose S.A. Procédé de production de pulpe de cellulose, pulpe de cellulose et son utilisation, papier
US12305332B2 (en) 2015-12-29 2025-05-20 Suzano S.A. Method for producing cellulose pulp, cellulose pulp and use thereof, paper

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