EP0726979B1 - Verfahren zum bleichen von zellstoff - Google Patents

Verfahren zum bleichen von zellstoff Download PDF

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Publication number
EP0726979B1
EP0726979B1 EP94931026A EP94931026A EP0726979B1 EP 0726979 B1 EP0726979 B1 EP 0726979B1 EP 94931026 A EP94931026 A EP 94931026A EP 94931026 A EP94931026 A EP 94931026A EP 0726979 B1 EP0726979 B1 EP 0726979B1
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Prior art keywords
sequence
stage
process according
steps
acid
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EP94931026A
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English (en)
French (fr)
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EP0726979A1 (de
Inventor
François Desprez
Nicholas A. Troughton
Johan Devenyns
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Solvay Chimie SA
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Solvay Interox SA
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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
    • D21C9/1057—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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents
    • 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

  • the invention relates to a process for bleaching a dough for chemical paper.
  • the first step in a sequence conventional chemical pulp bleaching aims to perfect the delignification of the unbleached dough as it is present after the cooking operation.
  • This first step delignifying is traditionally carried out by treating the dough unbleached by chlorine in an acid medium or by a chlorine association - chlorine dioxide, in mixture or in sequence, so as to react with the residual lignin from the pulp and give rise to chlorolignins which can be extracted from the pulp by solubilization of these chlorolignins in an alkaline medium in a step further processing.
  • Patent application EP-A-0 433 138 discloses sequences bleaching including the three successive stages Acid - Alkaline hydrogen peroxide - Acid (page 3, lines 35 to 37). Step P is carried out there at a temperature of 55 to 85 ° C.
  • Patent application EP-A-0 402 335 discloses sequences bleaching product with two stages: Sequestrant - Peroxide of alkaline hydrogen. Step P is carried out at a temperature from 50 to 130 ° C (page 12, claim 11). The sequence can be followed by traditional bleaching steps including chlorinated reagents (example 7, page 9).
  • the invention remedies these drawbacks of known methods, by providing a new delignification and / or bleaching of chemical pulp which achieves high whiteness levels without severely degrading the cellulose and without using chlorinated reagents.
  • the invention relates to a process for bleaching a chemical paper pulp by means of a sequence of treatment steps comprising at least the following steps, carried out in order: QPA where the acronym Q represents a step of decontaminating the pulp into its transition metals, the acronym A represents a step with a non-peroxygenated acid and the acronym P represents a step with alkaline hydrogen peroxide carried out at a temperature above 100 ° C.
  • the invention relates to a method for bleaching a chemical pulp by means of a sequence of steps according to which the processing steps are free of chlorinated reagents and the sequence comprises the following steps, carried out in the order: QPAP
  • chemical paper pulp By chemical paper pulp is meant the pulps having undergone a delignifying treatment in the presence of chemical reagents such as sodium sulfide in alkaline medium (kraft or sulfate cooking), sulfur dioxide or a metal salt of sulfurous acid in an acid medium (cooking with sulfite or bisulfite).
  • chemical reagents such as sodium sulfide in alkaline medium (kraft or sulfate cooking), sulfur dioxide or a metal salt of sulfurous acid in an acid medium (cooking with sulfite or bisulfite).
  • the invention is particularly intended for pasta which has undergone kraft or sulfite cooking.
  • All types of wood used for the production of chemical pulp is suitable for implementing the method of the invention and, in particular those used for kraft and sulfite pastes, namely softwoods such as, for example, the various species of pine and fir and hardwoods like, for example, beech, oak, eucalyptus and charm.
  • the first step is a step of decontamination of the paste into its transition metals (step Q).
  • step Q consists in treating the dough with at least one sequestering agent such than an inorganic phosphate or polyphosphate, such as, for example, an alkali metal pyrophosphate or metaphosphate, a polycarboxylate or an organic aminopolycarboxylate such as, for example, tartaric, citric, gluconic, ethylenediaminetetraacetic, diethylenetriaminepentaacetic, cyclohexanediaminetetraacetic and their salts, poly- ⁇ -hydroxyacrylic acid and its salts or an organic polyphosphonate such as ethylenediaminetetramethylenephosphonic acids, diethylenetriaminepenta (methylenephosphonic), cyclohexanediaminetetramethylenephosphonic and their salts.
  • Ethylenediaminetetraacetic acids (EDTA) and diethylenetriaminepentaacetic (DTPA) have given excellent results.
  • the sequestrant is generally used in step Q in not more than 1.5 g of sequestrant per 100 g of dry dough. Most often, this amount is at most 1.0 g of sequestering agent for 100 g of dry dough. She is often at least minus 0.01 g / 100 g of dry dough.
  • step Q In addition to the sequestrant, we can also, according to this first variant, add a small amount of acid in step Q.
  • the amount of acid used to do this will generally set to impose a pH of around 5 on the medium.
  • Step Q can also, according to a second variant, consist of a treatment with an acid free of a sequestrant, followed by the addition of soluble magnesium salt in an amount such that the weight ratio of the amount of Mg to that of Mn present in the dough is at least 30. It is also generally not useful for the amount of Mg to exceed that for which the weight ratio Mg / Mn is equal to 10 4 .
  • the term “acid” is intended to denote the anhydrides or inorganic acids such as sulfur dioxide and sulfuric, sulfurous, hydrochloric, phosphoric and nitric acids or their acid salts, as well as organic acids such as carboxylic or phosphonic acids or their salts acids.
  • Sulfur dioxide or alkali or alkaline earth metal bisulfites are well suited.
  • bisulfite is intended to denote the acid salts of sulfurous acid corresponding to the formula Me (HS0 3 ) n, in which Me symbolizes a metal atom of valence n, n being an integer having the value 1 or 2.
  • the amount of acid to be put will depend on the type of wood and the amount of impurities that it contains.
  • the pH will be adjusted so as to make the medium substantially more acidic, that is to say, with a pH at most equal to 5 and, preferably at most 4.5.
  • Stage Q is generally carried out at a pressure close to atmospheric pressure and at a temperature sufficient to ensure efficient consumption of acid and / or sequestrant and at the same time not too high so as not to degrade the cellulose and not burden the energy cost of the means of heating implemented in said step.
  • a temperature of at least 40 ° C and preferably at least 50 ° C is fine.
  • the temperature does not not exceed 100 ° C and preferably not 95 ° C. The best results were obtained at 50-55 ° C.
  • the duration of stage Q must be sufficient to ensure a complete reaction. Although longer durations are without influence on the delignification rate of the dough as well as on its intrinsic resistance qualities, it is not recommended to extend the reaction time beyond that necessary upon completion of the reaction so as to limit costs investment and heating energy costs of the dough.
  • the duration of the pretreatment can vary within large proportions depending on the type of equipment used, the choice acid, temperature and pressure, for example 15 minutes approximately to several hours. Duration of at least 10 minutes and preferably at least 15 minutes are generally sufficient. Likewise, the pretreatment times do not exceed generally not 90 minutes and preferably not 60 minutes. A duration of about 30 minutes has given excellent results.
  • Stage Q is generally carried out at a paste consistency at least 2% dry matter and preferably at least 2.5% dry matter. Most often, this consistency does not not more than 15% and preferably not more than 10%. Consistency about 3% dry matter has given excellent results.
  • the preferred sequence is a sequence QPAP.
  • the symbols P denote steps with alkaline hydrogen peroxide.
  • the nature of the alkali must be such as this exhibits good extraction efficiency of lignin oxidized together with good solubility.
  • a example of such an alkali is sodium hydroxide in aqueous solution.
  • the quantity of alkali to be used must be sufficient to maintain the pH at a value of at least 10 and, from preferably at least 11.
  • the amount of alkali should also be adjusted to ensure sufficient consumption of peroxide at the end of reaction.
  • step P when step P is carried out in the absence of stabilizer, or when sodium silicate is present as a stabilizer, quantities of alkali of at least 1 and at most 3 g of alkali per 100 g of dry paste are suitable good.
  • quantities of alkali to maintain a pH of at least 10.
  • quantities of alkali up to a maximum of 8 g / 100 g dry paste can be used.
  • steps P must be adjusted so that remain at least 50 ° C and preferably 70 ° C. She should also not exceed 150 ° C and preferably not exceed 135 ° C. A temperature of 90 ° C gave excellent results.
  • At least one of the steps P of the sequence to a temperature above 100 ° C.
  • the temperature of this step P is preferably at least 110 ° C. It generally does not exceed 140 ° C and, from preferably not 135 ° C.
  • steps P must be sufficient for the bleaching reaction is as complete as possible. She cannot, however, exceed this reaction time too strongly under penalty of inducing a demotion of the whiteness of the dough. In practice, it will be set at a value of at least 60 minutes and preferably at least 90 minutes. She will have to also most often do not exceed 600 and preferably 500 minutes.
  • steps P is generally chosen to be lower or equal to 50% by weight of dry matter and, preferably, 40% dry matter. She will often not less than 5% and preferably not less than 8%. A consistency of 10% has given good results.
  • the consistency of the last step P may, alternatively, advantageously be chosen from high values of at least 25% by weight of dry matter and preferably 30% or more.
  • the consistency of the other steps P will generally be at most 20%. It will also suit, the most often, that the consistency of the other steps P is at least 8%.
  • step A is a processing step with a non-peroxygenated acid.
  • non-peroxygenated acid designate any inorganic or organic acid whose molecule does not does not contain the peroxy group -0-0-. All inorganic acids or usual organic materials used in aqueous solution, alone or in mixture are suitable. Strong inorganic acids such as, for example, sulfuric, phosphoric, nitric or acid hydrochloric acid are suitable. Sulfuric acid, solution aqueous has given excellent results.
  • step A The operating conditions of step A must be determined in each particular case according to the type of pulp and wood essence used.
  • the choice of acid and the quantity should be fixed implemented to impose a pH on the medium substantially less than 7, for example from at least about 1 to at most about 6.5.
  • Especially advantageous pHs are those of at least about 2.5 and at most about 5.5.
  • the temperature and pressure do not are not critical, atmospheric pressure and temperatures from at least 10 ° C to at most 100 ° C generally suitable.
  • the Pretreatment time can vary widely depending on the type of equipment used, the choice of acid, the temperature and pressure, for example from about 30 minutes to many hours.
  • step A it is possible to introduce, in addition to the acid, a magnesium salt soluble in aqueous acid medium.
  • the amount of magnesium that can be added does not exceed 0.4 g magnesium per 100 g of dry paste and preferably 0.1 g / 100 g dry paste.
  • an Mg salt When an Mg salt is introduced, its quantity is at least 0.005 g / 100 g of dry paste.
  • step A can consist of a simple washing of the dough using a solution acidic aqueous.
  • this acid wash can be inserted between the two stages P.
  • Another variant of the process according to the invention consists in repeat steps P and A a second time to achieve the complete sequence Q P A P A P.
  • step 0 it is can precede the sequence with an oxygen step (step 0).
  • This oxygen step is carried out by bringing the dough with gaseous oxygen at a pressure of at least 20 kPa and at most 1000 kPa in the presence of an alkaline compound in amount such as the weight of alkaline compound relative to the dry dough weight is at least 0.5 and at most 5%.
  • a particular embodiment of the method consists in recycle all or part of the effluents from the second and / or the third stage P towards a stage P located earlier in the sequence.
  • a similar recycling of the effluents from the second acid step, when present, to the first step sequence acid can also be achieved.
  • the oxygen step temperature should generally be 70 ° C or more and preferably at least 80 ° C. he this temperature should also not exceed 130 ° C and, from preferably does not exceed 120 ° C.
  • the duration of the oxygen treatment must be sufficient so that the reaction of oxygen with the lignin contained in the dough is complete. However, it cannot exceed too much strongly this reaction time under penalty of inducing degradations in the structure of the cellulose chains of the pulp. In practice, it will be 30 minutes or more and, preferably, at least 40 minutes. Usually it will not exceed 120 minutes and preferably not more than 80 minutes.
  • Treatment of the dough with oxygen can also be done in the presence of a cellulose protective agent such as soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids.
  • a cellulose protective agent such as soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids.
  • the salts of magnesium are preferred, in particular, magnesium sulfate heptahydrate used at a rate of 0.02 to 1% by weight relative to dry dough.
  • the consistency of the paste in step 0 is generally not not less than 8% by weight of dry matter and, preferably, not less than 10%. This consistency does not usually exceed not 30% by weight of dry matter and, preferably, 25%.
  • step 0 can also be carried out in the presence of hydrogen peroxide (step 0p).
  • the quantity of hydrogen peroxide which can be incorporated in step 0 is generally not less than 0.2 g H 2 0 2 per 100 g of dry paste and, most often, not less than 0, 5 g. Likewise, we will usually not exceed 2.5 g H 2 0 2 per 100 g of dry paste and, most often, not 2 g.
  • the first step P can also be reinforced by the presence of gaseous oxygen (step Eop).
  • the oxygen pressure used will most often at least 20 kPa and at most 1000 kPa.
  • step X it is can incorporate at any point in the sequence of stages of treatment an additional enzymatic step consisting of treat the dough with at least one enzyme (step X).
  • This treatment enzymatic can also be carried out before or after the stage of oxygen pretreatment.
  • enzyme is intended to denote any enzyme capable of facilitate delignification, through the processing steps subsequent to the step of treatment with the enzyme, from a paste to unbleached chemical paper from the cooking operation or chemical paper pulp that has already been subjected to a step treatment with oxygen.
  • an alkalophilic enzyme will be used, that is to say an enzyme whose maximum efficiency lies in the alkaline pH zone, and especially at a pH of 7.5 and more.
  • a category of enzymes well suited to the process according to the invention are hemicellulases. These enzymes are able to react with the hemicelluloses on which the lignin present in the dough.
  • the hemicellulases used in the process according to the invention are xylanases, i.e. hemicellulolytic enzymes capable of cutting xylan bonds which constitute a major part of the interface between the lignin and the rest of the carbohydrates.
  • xylanases i.e. 1,4- ⁇ -D-xylan xylanohydrolase, EC 3.2.1.8.
  • Preferred xylanases in the methods according to the invention can be of various origins. They can in particular have been secreted by a wide range of bacteria and mushrooms.
  • Xylanases of bacterial origin are particularly interesting.
  • the xylanases secreted by bacteria of the genus Bacillus have given good results.
  • Xylanases derived from bacteria of the genus Bacillus and of the species pumilus have given excellent results. Of these, xylanases from Bacillus pumilus PRL B12 are particularly interesting.
  • the xylanases of Bacillus pumilus PRL B12 in accordance with the invention can come directly from a strain of Bacillus pumilus PRL B12 or else from a host strain of a different microorganism which has been genetically manipulated beforehand to express the genes coding for degradation xylans from Bacillus pumilus PRL B12.
  • a purified xylanase will be used which does not contains no other enzymes.
  • the xylanase according to the process according to the invention does not contain no cellulase so as not to destroy the polymer chains pulp cellulose.
  • An interesting variant of the method according to the invention consists in carrying out the enzymatic step X in the presence of at least a sequestrant of metal ions.
  • Ion sequestrants metal can advantageously be chosen from sequestrants suitable for step Q which are described above.
  • the process according to the invention applies to bleaching of all kinds of chemical pulp. It is well suited for delignifying kraft and sulfite pastes. It is particularly well suited for processing kraft pasta.
  • a sample of softwood pulp having undergone kraft cooking (initial whiteness 27.9 ° ISO measured according to ISO 2470-1977 (F), kappa index 26.7 measured according to SCAN C1-59 and degree of polymerization 1680 expressed in number of glucosic units and measured according to standard SCAN C15-62) was treated according to a sequence of 2 steps 0 P under the following conditions: 1st stage: stage at DTPA (stage Q): DTPA content, g / 100g dry paste 0.2 temperature, degrees C 90 duration, min 60 consistency,% by weight of dry matter 4 2nd stage: hydrogen peroxide stage (stage P): H 2 0 2 content , g / 100g dry paste 5 NaOH content, g / 100g dry paste 4 DTMPANa 7 content, g / 100g of dry paste 0 to 1 MgS0 content 4 .7H 2 0, g / 100g dry paste 0.5 temperature, degrees C 90 and 120 duration, min 120 consistency,% by weight of dry matter 10 where
  • Example No. DTMPANa 7 g / 100g ms Stage temperature P ° C 1R 0 90 2R 0.25 90 3R 0.50 90 4R 1.00 90 5R 0 120 6R 0.25 120 7R 0.50 120 8R 1.00 120
  • the dough underwent a washing with demineralized water at room temperature.
  • the dough underwent a washing with demineralized water at room temperature.
  • stage P hydrogen peroxide stage (stage P): H 2 0 2 content , g / 100g dry paste 1 NaOH content, g / 100g dry paste 1.5 MgS0 content 4 .7H 2 0, g / 100g dry paste 1 temperature, degrees C 120 duration, min 180 consistency,% by weight of dry matter 30
  • the dough underwent a washing with demineralized water at room temperature.
  • step A step with an acid (step A): H 2 S0 4 content , g / 100g dry paste Ex. 11: 1.08 (pH 3) Ex. 12: 0.52 (pH 5) Ex. 13 and 14: 0 S0 2 content, g / 100g dry paste Ex. 11 and 12: 0 Ex. 13: 1.06 (pH 3) Ex.
  • stage P hydrogen peroxide stage (stage P): H 2 0 2 content , g / 100g dry paste 1 NaOH content, g / 100g dry paste 1.5 Na silicate content 38 ° Be, g / 100g of dry paste 3 MgS0 content 4 .7H 2 0, g / 100g dry paste 1 temperature, degrees C 120 duration, min 180 consistency,% by weight of dry matter 30
  • the dough underwent a washing with demineralized water at room temperature.
  • the same pulp sample as in Examples 1R to 14 was bleached using the sequence 0 XQPAP by using in step X an amount of xylanase derived from Bacillus pumilus PRL B12 corresponding to 10 XU / g of dry pulp .
  • the XU Xylanase Unit
  • the XU is defined as the quantity of xylanase which, under the conditions of the test, catalyzes the release of reducing sugars equivalent, in reducing power, to 1 micromole of glucose per minute.
  • stage O oxygen stage
  • stage O pressure, bar 6 NaOH content
  • stage X enzyme stage
  • stage X H 2 S0 4 for pH 7 xylanase content
  • XU enzyme stage
  • stage Q H 2 S0 4 for pH 5 EDTA content
  • % by weight of dry matter 3 4th stage hydrogen peroxide stage (stage P): H 2 0 2 content , g / 100g dry paste 4 NaOH content, g / 100g dry paste 4 DTMPANa 7 content, g / 100g of dry paste 0.25 MgS
  • stage 4th stage sulfuric acid stage (stage A): H 2 S0 4 , for pH 3 temperature, degrees C 90 duration, min 120 consistency,% by weight of dry matter 10
  • stage P hydrogen peroxide stage (stage P): H 2 0 2 content , g / 100g dry paste 1 (Ex. 15) and 2 (Ex. 16) NaOH content, g / 100g dry paste 1.5 Na silicate content 38 ° Be, g / 100g of dry paste 3 MgS0 content 4 .7H 2 0, g / 100g dry paste 1 temperature, degrees C 120 duration, min 180 consistency,% by weight of dry matter 30
  • the dough underwent a washing with demineralized water at room temperature, except between stages X and Q which were carried out by simple acidification at pH 5 by means of sulfuric acid and by incorporation EDTA to the pulp harvested at the end of stage X, without dilution nor reconcentration.

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  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
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Claims (11)

  1. Verfahren zum Bleichen eines chemischen Papierzellstoffs mittels einer Folge von Behandlungsschritten, die wenigstens die folgenden Schritte umfaßt, die in der Reihenfolge
       Q P A ausgeführt werden, worin das Zeichen Q einen Schritt zur Dekontaminierung des Zellstoffs von seinen Übergangsmetallen darstellt, das Zeichen A einen Schritt mit einer Säure, die keine Peroxysäure ist, darstellt und das Zeichen P einen Schritt mit alkalischem Wasserstoffperoxid, der bei einer Temperatur höher 100 °C ausgeführt wird, darstellt.
  2. Verfahren zum Bleichen eines chemischen Papierzellstoffs mittels einer Folge von Schritten gemäß Anspruch 1, dadurch gekennzeichnet, daß die Behandlungsschritte frei von chlorhaltigen Reagenzien sind und die Folge die folgenden Schritte umfaßt, die in der Reihenfolge:
       Q P A P ausgeführt werden.
  3. Verfahren gemäß einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß der Schritt Q aus einer Behandlung durch eine Säure, die frei von einem Sequestrierungsmittel ist, und einer anschließenden Zugabe von löslichem Magnesiumsalz in einer solchen Menge, daß das Gewichtsverhältnis der Menge an Mg zu derjenigen an Mn, die in dem Zellstoff vorhanden sind, wenigstens 30 ist, besteht.
  4. Verfahren gemäß einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß der Schritt Q aus einer Behandlung durch ein Sequestrierungsmittel besteht.
  5. Verfahren gemäß einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Folge ein Schritt mit gasförmigem Sauerstoff vorausgeht.
  6. Verfahren gemaß einem der Ansprüche 2 bis 5, dadurch gekennzeichnet, daß der letzte Schritt P bei einer Stoffdichte an Zellstoff von wenigstens 25 Gew.-% Trockenmasse durchgeführt wird.
  7. Verfahren gemäß einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, daß die beiden letzten Schritte A P am Ende der Folge ein zweites Mal wiederholt werden.
  8. Verfahren gemäß einem der Ansprüche 2 bis 7, dadurch gekennzeichnet, daß der Schritt A ein einfaches saures Waschen ist, das die Schritte P trennt.
  9. Verfahren gemäß einem der Ansprüche 2 bis 8, dadurch gekennzeichnet, daß man die Abwässer von wenigstens einem Schritt P oder A ganz oder teilweise in einen Schritt zurückführt, der das gleiche Reagenz verwendet und der in der Folge vorher liegt.
  10. Verfahren gemäß einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß man an einem beliebigen Punkt der Folge einen zusätzlichen Schritt mit einem Enzym einfügt.
  11. Verfahren gemäß einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, daß der erste Schritt P durch Sauerstoff verstärkt wird.
EP94931026A 1993-11-04 1994-10-28 Verfahren zum bleichen von zellstoff Revoked EP0726979B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
BE9301215A BE1007700A3 (fr) 1993-11-04 1993-11-04 Procede pour le blanchiment d'une pate a papier chimique.
BE9301215 1993-11-04
PCT/EP1994/003591 WO1995012709A1 (fr) 1993-11-04 1994-10-28 Procede pour le blanchiment d'une pate a papier chimique

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Publication Number Publication Date
EP0726979A1 EP0726979A1 (de) 1996-08-21
EP0726979B1 true EP0726979B1 (de) 1998-05-13

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EP94931026A Revoked EP0726979B1 (de) 1993-11-04 1994-10-28 Verfahren zum bleichen von zellstoff

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EP (1) EP0726979B1 (de)
JP (1) JPH09507096A (de)
AT (1) ATE166118T1 (de)
AU (1) AU7994094A (de)
BE (1) BE1007700A3 (de)
BR (1) BR9407976A (de)
CA (1) CA2175817A1 (de)
DE (1) DE69410286T2 (de)
ES (1) ES2119234T3 (de)
FI (1) FI961895A0 (de)
MA (1) MA23365A1 (de)
NO (1) NO961817L (de)
NZ (1) NZ274852A (de)
WO (1) WO1995012709A1 (de)
ZA (1) ZA948562B (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE1007757A3 (fr) * 1993-11-10 1995-10-17 Solvay Interox Procede pour le blanchiment d'une pate a papier chimique.
FI105701B (fi) * 1995-10-20 2000-09-29 Ahlstrom Machinery Oy Menetelmä ja laitteisto massan käsittelemiseksi

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2582692B1 (fr) * 1985-05-29 1987-12-11 Atochem Traitement de pates papetieres chimiques par le peroxyde d'hydrogene en vue de leur blanchiment
DE402335T1 (de) * 1989-06-06 1992-04-09 Eka Nobel Ab, Surte Verfahren zum bleichen von lignocellulose enthaltenden zellstoffen.
FR2655668B1 (fr) * 1989-12-11 1995-06-09 Du Pin Cellulose Procede de blanchiment de pates cellulosiques chimiques.

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BE1007700A3 (fr) 1995-10-03
ES2119234T3 (es) 1998-10-01
WO1995012709A1 (fr) 1995-05-11
MA23365A1 (fr) 1995-07-01
FI961895A (fi) 1996-05-03
JPH09507096A (ja) 1997-07-15
CA2175817A1 (fr) 1995-05-11
BR9407976A (pt) 1996-12-03
ATE166118T1 (de) 1998-05-15
EP0726979A1 (de) 1996-08-21
DE69410286D1 (de) 1998-06-18
NZ274852A (en) 1997-04-24
AU7994094A (en) 1995-05-23
DE69410286T2 (de) 1998-12-10
NO961817D0 (no) 1996-05-03
NO961817L (no) 1996-05-03
ZA948562B (en) 1995-06-30
FI961895A0 (fi) 1996-05-03

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