EP2438235A1 - Procédé pour produire une pâte mécanique - Google Patents

Procédé pour produire une pâte mécanique

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Publication number
EP2438235A1
EP2438235A1 EP10724032A EP10724032A EP2438235A1 EP 2438235 A1 EP2438235 A1 EP 2438235A1 EP 10724032 A EP10724032 A EP 10724032A EP 10724032 A EP10724032 A EP 10724032A EP 2438235 A1 EP2438235 A1 EP 2438235A1
Authority
EP
European Patent Office
Prior art keywords
oxidant
process according
mechanical treatment
pulp
treatment stage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10724032A
Other languages
German (de)
English (en)
Inventor
Pia Hellström
Pär NILSSON
Karin Susanne Maria Walter
Patrik Johansson
Eva Linnea Elisabeth Wackerberg
Magnus Lars Paulsson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nouryon Chemicals International BV
Original Assignee
Akzo Nobel Chemicals International BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Akzo Nobel Chemicals International BV filed Critical Akzo Nobel Chemicals International BV
Priority to EP10724032A priority Critical patent/EP2438235A1/fr
Publication of EP2438235A1 publication Critical patent/EP2438235A1/fr
Withdrawn legal-status Critical Current

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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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/08—Pretreatment of the finely-divided materials before digesting with oxygen-generating compounds
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/04—Pretreatment of the finely-divided materials before digesting with acid reacting compounds
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/222—Use of compounds accelerating the pulping processes

Definitions

  • the present invention relates to a process for producing a high-yield pulp from a lignocellulose containing material.
  • the optical properties of high-yield pulps are quality parameters that are becoming increasingly important since brightness and whiteness requirements for inter alia improved newsprint and many uncoated and coated magazine paper grades, e.g. SC (Super-Calendered Paper), LWC (Low-Weight Coated Paper), MWC (Medium-Weight Coated Paper) have been raised in recent years.
  • the brightness depends on the relationship between the light absorption coefficient (k) and the light scattering coefficient (s). High values of the ratio s/k are required to attain high brightness values.
  • the s-value for pulp can only vary between about 15 and 60 m 2 /kg whereas the k-value can vary by several powers of ten (Pauler, N.
  • a further concern of the present invention is to provide such process without substantially reducing the fibre length or strength properties of the produced pulp. It is a further object to provide a process of producing a high-yield pulp which has a suitable end pH for papermaking, for example for neutral and alkaline papermaking with the benefits of lowering the furnish cost as well as reducing scaling and corrosion of equipment used in the processing of the pulp.
  • the present invention relates to a process for preparing a high-yield pulp comprising a) treating a lignocellulose containing material chemically by means of an oxidising system comprising at least one non-enzymatic oxidant and an activator and optionally an alkali at a pH from about 2 to about 6.5; and b) treating the lignocellulose containing material mechanically in at least one mechanical treatment stage for a time sufficient to produce a high-yield pulp, wherein the lignocellulose containing material is chemically treated prior to and/or during at least one mechanical treatment stage, wherein oxidant is present: i) after addition of alkali provided alkali is added to the oxidising system and/or ii) after said at least one mechanical treatment stage.
  • the present invention also relates to a process for preparing a high-yield pulp comprising a) treating a lignocellulose containing material chemically by means of an oxidising system comprising at least one non-enzymatic oxidant and an activator and optionally an alkali at a pH from about 2 to about 6.5; and b) treating the lignocellulose containing material mechanically in at least one mechanical treatment stage for a time sufficient to produce a high-yield pulp, wherein the lignocellulose containing material is chemically treated prior to and/or during at least one mechanical treatment stage, wherein the temperature of the lignocellulosic material before, during and/or after at least one mechanical treatment stage of the process ranges from about 45 0 C to about 200 0 C for a period of time ranging from about 1 second to about 5 hours and wherein oxidant is present: i) after addition of alkali provided alkali is added to the oxidising system and/or ii) after said at least one mechanical
  • the temperature of the lignocellulosic material before, during and/or after at least one mechanical treatment stage ranges from about 45°C to about 180 0 C, for example from about 50 0 C to about 180°C or from about 55°C to about 180 0 C.
  • the temperature of the lignocellulose containing material is maintained at the defined temperature range before, during, and/or after at least one mechanical treatment stage for from about 5 second to about 3 hours, for example from about 10 seconds to about 1 hour, or from about 1 minute to about 0.5 hours.
  • the temperature of the lignocellulosic material is maintained in the defined temperature range after at least one mechanical treatment stage.
  • the temperature of the lignocellulosic material is maintained during a period of time as defined herein after at least one mechanical treatment stage, for example after one or two mechanical treatment stages.
  • oxidant is present after i) as defined above.
  • oxidant is present after ii) as defined above.
  • one embodiment of the invention concerns presence of oxidant only after ii) as defined above
  • the non-enzymatic oxidant (calculated as 100%) is added in an amount from about 0.1 to about 5, for example from about 0.5 to about 3 or from about 0.5 to about 2 wt% based on the weight of the lignocellulose containing material
  • an activator (calculated as 100%) is added in an amount from about 0.0005 to about 0.05, for example from about 0.001 to about 0.025, or from about 0.001 to about 0.01 , or from about 0.0025 to about 0.01 wt% based on the weight of the lignocellulose containing material.
  • An activator is a component which is able to activate the oxidant of the invention, i.e. to increase its oxidative function.
  • the weight ratio of activator to oxidant ranges from about 0.0001 to about 0.5, for example from about 0.0001 to about 0.01 , or from about 0.0005 to about 0.01.
  • alkali is added in an amount from about 0.05 to about 3, from about 0.1 to about 2, for example from about 0.1 to about 1 , or from about
  • At least about 5%, for example at least about 7%, or at least about 10%, or at least about 15% of the total amount of oxidant added is present after stage i) or ii).
  • the amount of oxidant remaining after stage i) or ii) is also referred to herein as "residual oxidant", for example “residual hydrogen peroxide”.
  • up to about 60% for example up to about 40%, or up to about 25%, or up to about 10%, or up to about 5%, of the total amount of oxidant added is present after stage i) or ii).
  • oxidant is present after the first mechanical treatment stage, for example in a process comprising only one or two or three or more mechanical treatment stages.
  • oxidant is present after the last mechanical treatment stage in a series of two or three or more mechanical treatment stages.
  • oxidant is present after addition of alkali, for example prior to and/or during the first mechanical treatment stage.
  • an activator is added prior to or during any mechanical treatment stage, either separately or simultaneously with a non-enzymatic oxidant.
  • the activator may be added either before, simultaneously or after the addition of a non-enzymatic oxidant. This may be just before the addition of a non-enzymatic oxidant before a mechanical treatment stage such as a refiner, but may also be before e.g. a primary refiner whereas the non-enzymatic oxidant is added after the primary refiner but before a secondary refiner.
  • the mechanical treatment may be performed in one or two or three or more mechanical treatment stages.
  • the mechanical treatment may be performed in two stages or more including a reject mechanical treatment stage where up to 60 wt% of the lignocellulose containing material may be passed through.
  • the mechanical treatment stages usually are performed by passing the lignocellulose containing material through grinders and/or refiners.
  • other mechanical treatments may also be performed in equipments as, e.g. plug screws (e.g. impressafiner), roller mills (e.g. Szego mill), double shaft extruders (Bi-Vis screw extruder), the reciprocating apparatus, RT FiberizerTM, dispersers or in any combinations thereof.
  • the oxidising system is applied to the lignocellulose containing material at one or several stages before and/or during mechanical treatment. According to one embodiment, the oxidising system is applied as an inter-stage treatment between two mechanical treatment stages. According to one embodiment, the oxidising system is applied to at least one reject refining stage.
  • the non-enzymatic oxidant is selected from inorganic peroxy compounds such as hydrogen peroxide or hydrogen peroxide generating compounds such as salts of percarbonate, perborate, peroxysulphate, peroxyphosphate, peroxysilicate or corresponding weak acids.
  • the non-enzymatic oxidant is selected from organic peroxy compounds such as peroxy carboxylic acids, e.g. peracetic acid and perbenzoic acid.
  • the oxidising system comprises halogen containing oxidants such as chlorine dioxide, chlorite, hypochlorite, and chloro sodium salt of cyanuric acid.
  • the oxidising system comprises oxygen, ozone and/or nitrogen oxides such as NO or NO 2 .
  • the oxidizing system comprises combinations of different oxidants, which can be either added or re-used from the process steps which generate the non-enzymatic oxidants.
  • the activator is selected from metal ions, e.g. transition metal ions such as ions of Fe, Mn, Co, Cu, W or Mo; TAED (Tetra Acetyl Ethylene Diamine); cyanamide, or combinations thereof.
  • transition metal ions such as Fe ions may be used, for example in the form of acids or salts such as cupper sulphate, iron sulphate, or complexes with common organic or inorganic compounds.
  • ultraviolet radiation or other radiation is applied to the non-enzymatic oxidant or to the lignocellulose containing material being treated with the non-enzymatic oxidant.
  • equipment for monitoring the amount of oxidant for example hydrogen peroxide at various points, for example after stages i) and/or ii) in the process is employed.
  • Such equipment could be used to safeguard that oxidant is present in certain amounts after certain stages in the process in order to optimize energy reduction and optical properties of the produced pulp.
  • An example of instrument suitable for this purpose is BTG's in-line residual hydrogen peroxide analyzer RPA-5000.
  • the oxidant is substantially free from ozone which can be advantageous due to the fact that ozone does not provide a sufficient pulp yield due to low selectivity and is usually a more expensive alternative.
  • the oxidising system comprises less than 5 wt%, for example less than 2 wt% or less than 1 wt% ozone (calculated as 100%) based on the total weight of the oxidising system.
  • the oxidant is substantially free from chlorine dioxide.
  • substantially free from chlorine dioxide is meant that the oxidising system comprises less than 5 wt%, or less than 2 wt% or less than 1 wt% chlorine dioxide (calculated as 100%) based on the total weight of oxidising system.
  • the pH at which the chemical treatment is performed ranges from about 2.5 to about 6, for example from about 2.5 to about 5.5 or from about 3 to about 5.5 such as from about 3 to about 4.
  • the pH is from about 3.5 to about 5
  • the lignocellulose containing material is not chemically treated before stage a) and/or between stages a) and b) at a pH from about 7 to about 14, for example from about 8 to about 14 or from about 9 to about 14, e.g. from about 10 to about 14 or from about 10.5 to about 14 or from about 1 1 to about 14, or from about 11.5 to about 14.
  • high-yield pulp may comprise e.g. mechanical pulp (MP), refiner mechanical pulp (RMP), pressurized refiner mechanical pulp (PRMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high-temperature TMP (HT-TMP), RTS-TMP, Thermopulp, groundwood pulp (GW), stone groundwood pulp (SGW), pressure groundwood pulp (PGW), super pressure groundwood pulp (PGW-S), thermo groundwood pulp (TGW), thermo stone groundwood pulp (TSGW), chemimechanical pulp (CMP), chemirefinermechanical pulp (CRMP), chemithermomechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), sulphite-modified thermomechanical pulp (SMTMP), reject CTMP (CTMP R ), groundwood CTMP (G-CTMP), semichemical pulp (SC), neutral sulphite semi chemical pulp (NSSC), high-yield sulphite pulp (HYS), biomechanical pulp (BRMP), pulps produced according to the r
  • the high-yield pulp is mechanical pulp, refiner mechanical pulp, groundwood pulp, chemimechanical pulp, semichemical pulp, thermomechanical and/or chemithermomechanical pulp. According to one embodiment, the high-yield pulp has a yield of at least about
  • the high-yield pulp has a yield of at least about 90% such as at least about 95%.
  • the pulp may be a bleached or non-bleached pulp.
  • the lignocellulose containing material comprises non-defibrated wood.
  • the lignocellulose containing material comprises mechanically treated lignocellulose containing material.
  • the lignocellulose containing material may comprise e.g. wood logs, finely-divided raw materials, including woody materials, such as wood particles (e.g. in the form of wood chips, wood shavings, wood fibres and saw dust) and fibres of annual or perennial plants including non-wood.
  • the woody raw material can be derived from hardwood or softwood species, such as birch, beech, aspen such as European aspen, alder, eucalyptus, maple, acacia, mixed tropical hardwood, pine such as loblolly pine, fir, hemlock, larch, spruce such as Black spruce or Norway spruce, and mixtures thereof.
  • Non-wood plant raw material can be provided from e.g. straws of grain crops, reed canary grass, reeds, flax, hemp, kenaf, jute, ramie, sisal, abaca, coir, bamboo, bagasse or combinations thereof.
  • the lignocellulose containing material comprises hardwood and/or softwood species.
  • the lignocellulose containing material is substantially free from non-wood.
  • the lignocellulose containing material contains less than 5 wt%, for example less than 1 wt% non-wood based on the total weight of lignocellulose containing material.
  • the lignocellulose containing material is treated with the oxidising system for from about one second to about ten hours, for example from about five seconds to about five hours, or from about ten seconds to about three hours.
  • the lignocellulose containing material is chemically and/or mechanically treated at a temperature from about 30 to about 200 0 C, for example from about 50 to about 180 0 C, or from about 80 to about 180°C.
  • the lignocellulose containing material is preheated before the chemical treatment is initiated.
  • Such pre-treatment may be performed at a temperature from about 30 to about 200 0 C, for example from about 50 to about 180°C, or from about 50 to about 140°C, for example for a period of time ranging from about 1 second to about 5 hours, such as from about 10 seconds to about 1 hour, or from about 1 minute to about 0.5 hour.
  • the oxidising system comprises an enhancer that facilitates/controls the oxidation depending on the amount thereof added.
  • An enhancer may be selected from for example complexing agents, chelating agents and/or ligands.
  • the enhancer is selected from nitrogen-containing polycarboxylic acids, nitrogen-containing polyphosphonic acids, nitrogen-containing polyalcohols, oxalic acid, oxalate, glycolate, ascorbic acid, citric acid, nitrilo acetate, gallic acid, fulvic acid, itaconic acid, haemoglobin, hydroxybenzenes, catecholates (e.g.
  • quinolines such as hydroxyquinoline (e.g. 8- hydroxyquinoline), dimethoxybenzoic acids, dihydroxybenzoic acids, dimethoxybenzylalcohols, pyridine, histidylglycine, phthalocyanine, acetonitrile, 18-crown- 6-ether, mercaptosuccinic acid, cyclohexadienes, polyoxomethalates, and combinations thereof.
  • the enhancer is selected from nitrogen-containing organic compounds, such as nitrogen-containing polycarboxylic acids, nitrogen- containing polyphosphonic acids, nitrogen-containing polyalcohols, and mixtures thereof.
  • the enhancer is selected from diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and mixtures thereof.
  • the enhancer is selected from compounds based on other aminopolycarboxylic acids, polyphosphates or polyphosphonic acids, hydroxycarboxylates, hydrocarboxylic acids, dithiocarbamate, iminodisuccinic acid, [S, S ' ]- etylenediaminedisuccinic acid.
  • the enhancer is selected from dihydroxybenzene (e.g. hydroquinone), trihydroxybenzene, dihydroxybenzoic acid (e.g. 3,4- dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid), 3,4-dimethoxybenzylalcohol, 3,4- dimethoxybenzoic acid, 3,4-dimethoxy toluene, 1 ,3-cyclohexadiene, polyoxomethalates.
  • the oxidising system comprises as an enhancer also at least one enzyme.
  • an enhancer is added prior to or during any mechanical treatment stage, either separately or simultaneously with a non-enzymatic oxidant and optionally an activator.
  • the enhancer may thus be added either before, simultaneously or after the addition of a non-enzymatic oxidant. This may be just before the addition of the non-enzymatic oxidant, for example before a mechanical treatment stage such as a refiner, but may also be before e.g. a primary refiner whereas the non- enzymatic oxidant is added after the primary refiner but before a secondary refiner.
  • an enhancer (calculated as 100%) is added in an amount from about 0.01 to about 2, for example from about 0.05 to about 0.5, or from about 0.05 to about 0.3 wt% based on the weight of the lignocellulose containing material.
  • the weight ratio of enhancer to oxidant ranges from about 0.001 to about 2, for example from about 0.01 to about 1 , or from about 0.025 to about 1.
  • thermomechanical pulp TMP
  • the wood logs were debarked and chipped and washed prior to pre-steaming (90 0 C, 10 minutes retention time), pre-heating (125°C, 2 minutes retention time) and refining operations.
  • pre-steaming 90 0 C, 10 minutes retention time
  • pre-heating 125°C, 2 minutes retention time
  • refining operations A two-stage refining setup was used and the energy input was varied in the second refining stage to obtain pulps with different freeness (refining) levels.
  • a single disc 20" pressurized refiner (Sunds Defibrator OVP- MEC with 5811 refining plates run at 1500 rpm, housing pressure of 140 kPa) was used in the first refining stage and a single disc 20" atmospheric refiner (Sunds Defibrator ROP-20 with 5811 refining plates run at 1500 rpm) in the second refining stage.
  • the energy input in the primary refiner was about 550 kWh/bone dry metric ton.
  • the chemicals hydroogen peroxide, iron sulphate, ethylenediaminetetraacetic acid
  • the pulp from the primary refiner was then stored for about 30 minutes at about 60 0 C before further mechanical treatment in the atmospheric refiner. All trials were run at constant conditions which mean that the variation in specific energy consumption and pulp and paper properties is a result of the chemicals added during the trials.
  • TMP reference was produced without addition of chemicals.
  • the pulp is denoted TMPREF in table 1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.015 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.4 wt% H 2 O 2 and 0.34 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry wood to the primary refiner.
  • the pH of the resulting pulp was 3.0.
  • the pulp is denoted TMPAP1 in table 1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.014 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.4 wt% H 2 O 2 and 0.13 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry wood to the primary refiner.
  • the pH of the resulting pulp was 3.2.
  • the pulp is denoted TMPAP2 in table 1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.0044 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.3 wt% H 2 O 2 and 0.22 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry wood to the primary refiner.
  • the pH of the resulting pulp was 3.1.
  • the pulp is denoted TMPAP3 in table 1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.0044 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.3 wt% H 2 O 2 and 0.22 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry wood to the primary refiner.
  • the pH of the resulting pulp was 3.2.
  • the pulp is denoted TMPAP4 in table 1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.014 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.4 wt% H 2 O 2 , 0.13 wt% sulphuric acid (H 2 SO 4 ) and 0.10 wt% ethylenediaminetetraacetic acid (EDTA) based on the weight of bone dry wood to the primary refiner.
  • the pH of the resulting pulp was 3.4.
  • the pulp is denoted TMPAPEDTA in table 1.
  • the process according to the invention i.e., to have an oxidant present after refining of pulps treated with at least one non- enzymatic oxidant and an activator and optionally an alkali at a pH from about 2 to about 6.5, makes it possible to produce pulps with improved optical properties.
  • Example 2
  • thermomechanical pulp TMP
  • the wood logs were debarked and chipped and washed prior to pre-heating and refining operations.
  • a 20" pressurized refiner (model OVP-MEC run at 1500 rpm) was used to produce a high-freeness pulp (about 540 ml CSF).
  • the energy input in the refiner was about 1160 kWh/bone dry metric ton.
  • the activator was then added to the defibrated pulp followed by the addition of the oxidant.
  • a mixer (Moulinex Type 843) was used to thoroughly mix in the chemicals in the pulp at room temperature. The mixing time was 30 seconds and the pulp consistency 25%.
  • the pulp was then transferred to a plastic bag that was sealed and placed in a water bath (90 0 C) for 30, 35 or 40 minutes (see below).
  • TMP reference was produced without addition of chemicals.
  • the reaction time at 90 0 C was 35 minutes.
  • the pH of the resulting pulp was 5.5.
  • the pulp is denoted TMPREF1.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.005 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.0 wt% H 2 O 2 and 0.13 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry pulp.
  • the reaction time at 90 0 C was 40 minutes.
  • the pH of the resulting pulp was 3.2.
  • the residual H 2 O 2 content was 0.08 wt% based on the lignocellulose containing material.
  • the pulp is denoted TMPX.
  • a TMP using acid hydrogen peroxide (H 2 O 2 ) was produced by adding 0.005 wt% iron (added as iron sulphate, FeSO 4 x 7 H 2 O), 1.5 wt% H 2 O 2 and 0.12 wt% sulphuric acid (H 2 SO 4 ) based on the weight of bone dry pulp.
  • the reaction time at 90 0 C was 30 minutes.
  • the pH of the resulting pulp was 3.3.
  • the residual H 2 O 2 content was 0.5 wt% based on the lignocellulose containing material.
  • the pulp is denoted TMPY.
  • TMPREF1 , TMPX, TMPY The three pulps above (TMPREF1 , TMPX, TMPY) were then divided into two portions, diluted to a pulp consistency of 4%, transferred to a plastic bag that was sealed and placed in a water bath (80 0 C) for 120 minutes in order to simulate a latency treatment of the pulp. Additional chemicals, sodium hydroxide (NaOH) and diethylenetriaminepentaacetic acid (DTPA), were added in some cases prior to the 120 minutes heat-treatment. Two different conditions were employed; A) Addition of 0.2 wt% DTPA based on the weight of bone dry pulp prior to heat-treatment at 80°C for 120 minutes.
  • NaOH sodium hydroxide
  • DTPA diethylenetriaminepentaacetic acid
  • Table 2 The amount of chemicals added and pH, residual H 2 O 2 and brightness before and after heat-treatment (80°C, 120 minutes)
  • TMPY (34% remaining H 2 O 2 ) had about 2.1 ISO units higher brightness compared to TMPX (8% remaining H 2 O 2 ). It is also beneficial to have hydrogen peroxide remaining after addition of alkali (condition B) to a chemically treated pulp; the brightness of TMPY was in this case about 3.4 ISO brightness units higher than TMPX and about 6.6 ISO brightness units higher than TMPX heat-treated at an acidic pH without any chemical addition (i.e., condition NO in table 2).
  • a chelating agent will also improve the brightness regardless of pH value of the pulp or amount of remaining hydrogen peroxide (conditions A and B in table 2).
  • the method according to the invention i.e., to have an oxidant present after addition of alkali to pulps treated with at least one non-enzymatic oxidant and an activator at a pH from about 2 to about 6.5, makes it possible to produce pulps with improved optical properties.

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Abstract

La présente invention porte sur un procédé pour préparer une pâte de haut rendement, lequel procédé comprend a) le traitement chimique d'un matériau contenant de la lignocellulose à l'aide d'un système d'oxydation comprenant au moins un oxydant non enzymatique et un activateur et, facultativement, un alcalin à un pH d'environ 2 à environ 6,5 ; et b) le traitement mécanique du matériau contenant de la lignocellulose dans au moins une étape de traitement mécanique, pendant un temps suffisant pour produire une pâte à haut rendement, le matériau contenant de la lignocellulose étant chimiquement traité avant et/ou pendant au moins une étape de traitement mécanique, la température du matériau lignocellulosique avant, pendant et/ou après au moins une étape de traitement mécanique du procédé étant comprise entre environ 45 °C et environ 200 °C pendant une période de temps comprise entre environ 1 seconde et environ 5 heures, un oxydant étant présent : (i) après l'ajout d'alcalin, pourvu qu'un alcalin soit additionné au système oxydant et/ou (ii) après ladite étape de traitement mécanique.
EP10724032A 2009-06-02 2010-05-27 Procédé pour produire une pâte mécanique Withdrawn EP2438235A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP10724032A EP2438235A1 (fr) 2009-06-02 2010-05-27 Procédé pour produire une pâte mécanique

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US18327509P 2009-06-02 2009-06-02
EP09161636 2009-06-02
EP10724032A EP2438235A1 (fr) 2009-06-02 2010-05-27 Procédé pour produire une pâte mécanique
PCT/EP2010/057288 WO2010139589A1 (fr) 2009-06-02 2010-05-27 Procédé pour produire une pâte mécanique

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EP2438235A1 true EP2438235A1 (fr) 2012-04-11

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CA2057231A1 (fr) * 1991-01-07 1992-07-08 Ulrike Tschirner Methode pour le pretraitement de matieres lignocellulosiques avant le depulpage alkalin a haut rendement au peroxyde
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