EP0514609B1 - Process for hydrogen peroxide bleaching of high-yield pulps - Google Patents
Process for hydrogen peroxide bleaching of high-yield pulps Download PDFInfo
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- EP0514609B1 EP0514609B1 EP91401317A EP91401317A EP0514609B1 EP 0514609 B1 EP0514609 B1 EP 0514609B1 EP 91401317 A EP91401317 A EP 91401317A EP 91401317 A EP91401317 A EP 91401317A EP 0514609 B1 EP0514609 B1 EP 0514609B1
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- hydrogen peroxide
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- 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 present invention relates to a high-yield pulp bleaching process using hydrogen peroxide in an alkaline medium.
- high-yield pulp is meant here the pulp obtained with a yield by weight in the dry state relative to the starting lignocellulosic material, such as wood generally in the form of chips, counted in the dry state, which is greater than approximately 85% and often at least 90%.
- Such pastes are produced by defibering the starting material, wood chips most often, by means of a grinding wheel or a disc shredder, associated or not with a chemical and / or heat treatment.
- a first phase is proposed in which the alkalinity conditions are abnormally strong with a view to improving the mechanical quality of the fibers and a second phase under normal alkalinity conditions for correct the bleaching defect resulting from the first phase.
- LACHENAL also describes a two-phase process but in which an amount of sodium hydroxide is much greater than that normally accepted for a first phase is implemented in the second phase.
- FR-A-2537177 recommends the maintenance of conditions as uniform as possible throughout the laundering by proceeding in a succession of distinct phases.
- a phase is distinguished from the following in that the products which have served in the first, in particular hydrogen peroxide and alkaline agents such as sodium hydroxide, are eliminated from the pulp, at least for the most part, for example 90%, normally by washing and / or pressing said paste.
- the energy and investment costs which result from this oppose the advantage of improving the efficiency of use of hydrogen peroxide.
- the process of the present invention comprises two phases of action of hydrogen peroxide on the pulp but does not require the above intermediate operation.
- the term “paste” is understood to mean the assembly consisting of lignocellulosic material counted in the dry state and of the liquid present with it.
- the pretreatment using a metal ion complexing agent is generally carried out at a temperature normally lower than 100 ° C but higher than 20 ° C, for example between 50 ° C and 95 ° C, at a consistency, percentage of dough in the dry state, between 5% and 30% and most often between 10% and 15%, for a period which depends on the other parameters but which is most often between 5 minutes and 2 hours, at a pH between 4 and 8.
- the complexing agent is generally used at a rate of 0.1% to 1%, most often at a rate of 0.2% to 0.5% and it is most often chosen from sodium tripolyphosphate, sodium tetrapyrophosphate, sodium salts of citric acids, nitrilotriacetic, ethylenediaminetetraacetic, diethylenetriaminepentaacetic (DTPA).
- sodium tripolyphosphate sodium tetrapyrophosphate
- sodium salts of citric acids sodium tetrapyrophosphate
- DTPA diethylenetriaminepentaacetic
- washing following the pretreatment using a complexing agent means the operation which consists in eliminating more or less completely, and here as efficiently as possible, the liquid present in the dough, thanks for example to the pressing of that -this on filter or in a dilution-pressing sequence, repeated or not, in which the dilution is very generally ensured by water.
- efficiency is meant, expressed in percent, the degree of elimination of the liquid present in the dough before washing. In the process of the invention, the efficiency targeted for washing is at least 75%.
- the amount of hydrogen peroxide H2O2 engaged at the start of treatment of the pretreated paste and washed as above, can be between 0.5% and 6%, preferably between 3% and 5%.
- the additional amount of H2O2 added during treatment with H2O2 in an alkaline medium according to the process of the invention is often between 0.25% and 3% and is in any case and as already mentioned, equal to or less than the amount of H2O2 engaged at the start of treatment.
- the alkaline agent mainly chosen to accompany H2O2 is sodium hydroxide NaOH.
- the amount of NaOH added to the pulp with H2O2 at the start of treatment, as well as the additional amount of NaOH added during treatment with additional H2O2, essentially depend on the amount of H2O2 and also on the nature of the wood and other parameters of treatment.
- the first of these two amounts of NaOH can be between 0.5% and 6%, most often between 1.5% and 4%; the second can also be between 0.5% and 6% and preferably between 1% and 3%.
- the treatment of the paste with H2O2 in an alkaline medium can take place in the presence of a stabilizer of H2O2, such as for example sodium silicate, as well as an agent complexing ions metallic, such as DTPA in the form of the sodium salt.
- a stabilizer of H2O2 such as for example sodium silicate
- an agent complexing ions metallic such as DTPA in the form of the sodium salt.
- H2O2 and NaOH at the start of treatment, from 0% to 4% of said silicate solution and from 0% to 0.5% of said DTPA salt solution can be added during bleaching with the additional amounts of H2O2 and of NaOH added to the dough.
- the treatment using H2O2 in an alkaline medium is normally carried out at a temperature between 60 ° C and 90 ° C, between 65 ° C and 75 ° C most often, at the highest possible consistency, for example between 15% and 45%.
- the duration of action of H2O2 added with NaOH at the start of treatment like that of H2O2 added with NaOH during treatment according to the process of the invention, mainly depend on the temperature and the amount of H2O2; each of them is most often between 1 hour and 6 hours.
- the pulp subjected to the bleaching process is a mechanical grinding pulp formed, by weight, of 75% of softwood and 25% of hardwood, and whose degree of whiteness is equal to 63 , 2 ° ISO.
- the dough is subjected before treatment with H2O2 in an alkaline medium, to a pretreatment with a consistency of 10% using 0.5% of an aqueous solution at 40% by weight of salt sodium DTPA, at 90 ° C for 15 minutes followed by a washing efficiency of 90%.
- the treatment using H2O2 in an alkaline medium was each time carried out in the absence of complexing agent for metal ions, at a temperature equal to 70 ° C., at a consistency successively equal to 20% before the additional additions H2O2 and NaOH were made, 15% after these additions were made.
- H2O2, NaOH, sodium silicate solution of density 1.33 designated by silicate expressed as usual here in% by weight relative to the dough in the dry state are given in the single table below in which also appear the degrees of whiteness of the dough which has been subjected either to the process of the invention, or to a known process comprising, unlike the process according to the invention, a washing designated by L, of equal effectiveness at 90%, before additional addition of at least H2O2 and NaOH.
- the duration of the bleaching treatment was each 7 hours.
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Description
La présente invention concerne un procédé de blanchiment de pâtes à haut rendement à l'aide de peroxyde d'hydrogène en milieu alcalin.The present invention relates to a high-yield pulp bleaching process using hydrogen peroxide in an alkaline medium.
Par pâtes à haut rendement on entend ici les pâtes obtenues avec un rendement pondéral à l'état sec par rapport à la matière lignocellulosique de départ, comme le bois généralemnt sous forme de copeaux, comptée à l'état sec, qui est supérieur à environ 85 % et souvent égal au moins à 90 %.By high-yield pulp is meant here the pulp obtained with a yield by weight in the dry state relative to the starting lignocellulosic material, such as wood generally in the form of chips, counted in the dry state, which is greater than approximately 85% and often at least 90%.
De telles pâtes sont fabriquées par défibrage de la matière de départ, des copeaux de bois le plus souvent, au moyen d'une meule ou d'un défibreur à disques, associé ou non à un traitement chimique et/ou thermique.Such pastes are produced by defibering the starting material, wood chips most often, by means of a grinding wheel or a disc shredder, associated or not with a chemical and / or heat treatment.
Elles comprennent celles que l'industrie qualifie de mécaniques, thermomécaniques, chimicothermomécaniques.They include those that the industry describes as mechanical, thermomechanical, chemothermal mechanical.
Deux types de procédés sont aujourd'hui utilisés pour réaliser leur blanchiment :
- le premier consiste à faire agir sur la pâte un agent réducteur, classiquement l'hydrosulfite, dans des conditions douces et en milieu neutre ou légèrement acide. Il en résulte un blanchiment partiel qui pour certaines applications est néanmoins suffisant.
- le deuxième procédé consiste à faire agir sur la pâte le peroxyde d'hydrogène en milieu alcalin. Le blanchiment obtenu est plus important que dans le procédé précédent ce qui explique qu'aujourd'hui, pour satisfaire les exigences de qualités des papiers, le procédé au peroxyde soit de plus en plus utilisé.
- the first consists in causing a reducing agent, conventionally hydrosulfite, to act on the paste, under mild conditions and in a neutral or slightly acid medium. This results in partial whitening which for certain applications is nevertheless sufficient.
- the second method consists in causing the hydrogen peroxide to act on the paste in an alkaline medium. The bleaching obtained is more important than in the previous process, which explains why today, to meet the quality requirements of the papers, the peroxide process is used more and more.
Toutefois, le peroxyde d'hydrogène est un produit cher dont la stabilité décroît à mesure que le pH augmente. S'il est admis que la zone de pH dans laquelle est normalement réalisé le blanchiment par le peroxyde d'hydrogène s'étend d'environ 9 à environ 11 comme le rappelle "The bleaching of pulp", TAPPI Press, SINGH ed., Atlanta USA, 1970, p.227, la recherche dans ce cadre d'une utilisation toujours plus efficace du peroxyde d'hydrogène est d'intérêt permanent pour l'industrie.However, hydrogen peroxide is an expensive product whose stability decreases as the pH increases. If it is accepted that the pH zone in which bleaching by hydrogen peroxide is normally carried out extends from approximately 9 to approximately 11 as recalled by "The bleaching of pulp", TAPPI Press, SINGH ed., Atlanta USA, 1970, p.227, research in this context of an ever more efficient use of hydrogen peroxide is of permanent interest for the industry.
C'est ainsi qu'il a été proposé de faire intervenir le peroxyde d'hydrogène en au moins deux phases distinctes de blanchiment.It has thus been proposed to involve hydrogen peroxide in at least two distinct bleaching phases.
Par exemple dans la demande de brevet WO-A-84.02366 il est proposé une première phase dans laquelle les conditions d'alcalinité sont anormalement fortes en vue d'améliorer la qualité mécanique des fibres et une seconde phase dans des conditions d'alcalinité normales pour corriger le défaut de blanchiment résultant de la première phase.For example, in patent application WO-A-84.02366, a first phase is proposed in which the alkalinity conditions are abnormally strong with a view to improving the mechanical quality of the fibers and a second phase under normal alkalinity conditions for correct the bleaching defect resulting from the first phase.
Dans TAPPI Journal, Mars 1987, pages 119 et suivantes. D. LACHENAL décrit aussi un procédé en deux phases mais dans lequel une quantité d'hydroxyde de sodium est très supérieure à celle normalement admise pour une première phase est mise en oeuvre dans la deuxième phase.In TAPPI Journal, March 1987, pages 119 et seq. D. LACHENAL also describes a two-phase process but in which an amount of sodium hydroxide is much greater than that normally accepted for a first phase is implemented in the second phase.
Enfin le FR-A-2537177 préconise le maintien de conditions aussi uniformes que possible tout au long du blanchiment en procédant en une succession de phases distinctes.Finally FR-A-2537177 recommends the maintenance of conditions as uniform as possible throughout the laundering by proceeding in a succession of distinct phases.
Dans chacun des procédés proposés une phase se distingue de la suivante en ce qu'intermédiairement les produits qui ont servi dans la première, en particulier le peroxyde d'hydrogène et les agents alcalins comme l'hydroxyde de sodium, sont éliminés de la pâte, au moins en majeure partie, par exemple 90 %, normalement par lavage et/ou pressage de ladite pâte. Les coûts d'énergie et d'investissement qui en découlent s'opposent à l'intérêt d'améliorer le rendement d'utilisation du peroxyde d'hydrogène.In each of the proposed processes, a phase is distinguished from the following in that the products which have served in the first, in particular hydrogen peroxide and alkaline agents such as sodium hydroxide, are eliminated from the pulp, at least for the most part, for example 90%, normally by washing and / or pressing said paste. The energy and investment costs which result from this oppose the advantage of improving the efficiency of use of hydrogen peroxide.
Le procédé de la présente invention comprend deux phases d'action du peroxyde d'hydrogène sur la pâte mais ne nécessite aucunement l'opération intermédiaire ci-dessus.The process of the present invention comprises two phases of action of hydrogen peroxide on the pulp but does not require the above intermediate operation.
C'est un procédé de blanchiment de pâtes à haut rendement dans lequel la pâte à blanchir est soumise à un prétraitement à l'aide d'un agent complexant des ions métalliques suivi d'un lavage, puis à un traitement à l'aide de peroxyde d'hydrogène en milieu alcalin, caractérisé en ce qu'entre le début et la fin dudit traitement il est procédé à une addition supplémentaire à la pâte de peroxyde d'hydrogène et d'agent alcalin sans interruption du traitement, à un moment où 60 % à 85 % de la quantité initiale de peroxyde d'hydrogène ont été consommés, la quantité supplémentaire de peroxyde d'hydrogène ajoutée étant égale ou inférieure a ladite quantité initiale.It is a high-yield pulp bleaching process in which the bleaching pulp is subjected to a pretreatment using a metal ion complexing agent followed by washing, then to treatment using hydrogen peroxide in an alkaline medium, characterized in that between the start and the end of said treatment there is an additional addition to the paste of hydrogen peroxide and alkaline agent without interruption of the treatment, at a time when 60% to 85% of the initial amount of hydrogen peroxide was consumed, the additional amount of hydrogen peroxide added being equal to or less than said initial amount.
Dans la définition donnée ci-dessus du procédé de l'invention, comme dans tout ce qui suit, on entend par pâte l'ensemble constitué de la matière lignocellulosique comptée à l'état sec et du liquide présent avec elle.In the definition given above of the process of the invention, as in all that follows, the term “paste” is understood to mean the assembly consisting of lignocellulosic material counted in the dry state and of the liquid present with it.
Dans tout ce qui suit, sauf précision ou évidence, les quantités de matière sont exprimées en pour cents en poids par rapport au poids de pâte prise à l'état sec.In all that follows, unless specified or obvious, the quantities of material are expressed in percent by weight relative to the weight of dough taken in the dry state.
Le prétraitement à l'aide d'un agent complexant des ions métalliques est généralement effectué à une température normalement inférieure à 100°C mais supérieure à 20°C, par exemple entre 50°C et 95°C, à une consistance, pourcentage de pâte à l'état sec, comprise entre 5 % et 30 % et le plus souvent entre 10 % et 15 %, pendant une durée qui dépend des autres paramètres mais qui est le plus souvent comprise entre 5 minutes et 2 heures, à un pH compris entre 4 et 8. L'agent complexant est mis en oeuvre à raison généralement de 0,1 % à 1 %, le plus souvent à raison de 0,2 % à 0,5 % et il est le plus souvent choisi parmi le tripolyphosphate de sodium, le tétrapyrophosphate de sodium, les sels de sodium des acides citrique, nitrilotriacétique, éthylènediaminetétraacétique, diéthylènetriaminepentaacétique (DTPA).The pretreatment using a metal ion complexing agent is generally carried out at a temperature normally lower than 100 ° C but higher than 20 ° C, for example between 50 ° C and 95 ° C, at a consistency, percentage of dough in the dry state, between 5% and 30% and most often between 10% and 15%, for a period which depends on the other parameters but which is most often between 5 minutes and 2 hours, at a pH between 4 and 8. The complexing agent is generally used at a rate of 0.1% to 1%, most often at a rate of 0.2% to 0.5% and it is most often chosen from sodium tripolyphosphate, sodium tetrapyrophosphate, sodium salts of citric acids, nitrilotriacetic, ethylenediaminetetraacetic, diethylenetriaminepentaacetic (DTPA).
Par lavage faisant suite au prétraitement à l'aide d'un agent complexant on entend l'opération qui consiste à éliminer plus ou moins complètement, et ici le plus efficacement possible, le liquide présent dans la pâte, grâce par exemple au pressage de celle-ci sur filtre ou à une séquence dilution-pressage, répétée ou non, dans laquelle la dilution est très généralement assurée par de l'eau. Par efficacité on entend, exprimée en pour cent, le degré d'élimination du liquide présent dans la pâte avant lavage. Dans le procédé de l'invention l'efficacité visée pour le lavage est égale au moins à 75 %.By washing following the pretreatment using a complexing agent means the operation which consists in eliminating more or less completely, and here as efficiently as possible, the liquid present in the dough, thanks for example to the pressing of that -this on filter or in a dilution-pressing sequence, repeated or not, in which the dilution is very generally ensured by water. By efficiency is meant, expressed in percent, the degree of elimination of the liquid present in the dough before washing. In the process of the invention, the efficiency targeted for washing is at least 75%.
La quantité de peroxyde d'hydrogène H₂O₂engagée en début de traitement de la pâte prétraitée et lavée comme ci-dessus, peut être comprise entre 0,5 % et 6 %, de préférence entre 3 % et 5 %.The amount of hydrogen peroxide H₂O₂ engaged at the start of treatment of the pretreated paste and washed as above, can be between 0.5% and 6%, preferably between 3% and 5%.
La quantité supplémentaire de H₂O₂ ajoutée au cours du traitement par H₂O₂ en milieu alcalin selon le procédé de l'invention est souvent comprise entre 0,25 % et 3 % et est en tous cas et comme déjà mentionné, égale ou inférieure à la quantité de H₂O₂ engagé en début de traitement.The additional amount of H₂O₂ added during treatment with H₂O₂ in an alkaline medium according to the process of the invention is often between 0.25% and 3% and is in any case and as already mentioned, equal to or less than the amount of H₂O₂ engaged at the start of treatment.
L'agent alcalin principalement choisi pour accompagner H₂O₂ est l'hydroxyde de sodium NaOH.The alkaline agent mainly chosen to accompany H₂O₂ is sodium hydroxide NaOH.
La quantité de NaOH ajoutée à la pâte avec H₂O₂ en début de traitement, de même que la quantité supplémentaire de NaOH ajoutée en cours de traitement avec H₂O₂ additionnel, dépendent essentiellement de la quantité de H₂O₂ et aussi de la nature du bois et des autres paramètres du traitement. La première de ces deux quantités de NaOH peut être comprise entre 0,5 % et 6 %, le plus souvent entre 1,5 % et 4 % ; la seconde peut être comprise aussi entre 0,5 % et 6 % et de préférence entre 1 % et 3 %.The amount of NaOH added to the pulp with H₂O₂ at the start of treatment, as well as the additional amount of NaOH added during treatment with additional H₂O₂, essentially depend on the amount of H₂O₂ and also on the nature of the wood and other parameters of treatment. The first of these two amounts of NaOH can be between 0.5% and 6%, most often between 1.5% and 4%; the second can also be between 0.5% and 6% and preferably between 1% and 3%.
Comme dans les procédés connus, le traitement de la pâte à l'aide de H₂O₂ en milieu alcalin peut avoir lieu en présence d'un stabilisant de H₂O₂, comme par exemple le silicate de sodium, de même que d'un agent complexant des ions métalliques, comme par exemple le DTPA sous forme de sel de sodium. Par exemple de 1 % à 4 % d'une solution aqueuse de silicate de sodium de densité 1,33 et de 0 % à 0,5 % d'une solution aqueuse à 40 % en poids de sel de sodium de DTPA peuvent être ajoutés avec H₂O₂ et NaOH en début de traitement, de 0 % à 4 % de ladite solution de silicate et de 0 % à 0,5 % de ladite solution de sel de DTPA peuvent être ajoutés en cours de blanchiment avec les quantités supplémentaires de H₂O₂ et de NaOH ajoutées à la pâte.As in the known methods, the treatment of the paste with H₂O₂ in an alkaline medium can take place in the presence of a stabilizer of H₂O₂, such as for example sodium silicate, as well as an agent complexing ions metallic, such as DTPA in the form of the sodium salt. For example, from 1% to 4% of an aqueous sodium silicate solution of density 1.33 and from 0% to 0.5% of an aqueous solution at 40% by weight of sodium salt of DTPA can be added. with H₂O₂ and NaOH at the start of treatment, from 0% to 4% of said silicate solution and from 0% to 0.5% of said DTPA salt solution can be added during bleaching with the additional amounts of H₂O₂ and of NaOH added to the dough.
Le traitement à l'aide de H₂O₂ en milieu alcalin est normalement réalisé à une température comprise entre 60°C et 90°C, entre 65°C et 75°C le plus souvent, à une consistance la plus élevée possible, comprise par exemple entre 15 % et 45 %. La durée d'action de H₂O₂ ajouté avec NaOH en début de traitement, comme celle de H₂O₂ ajouté avec NaOH en cours de traitement selon le procédé de l'invention, dépendent principalement de la température et de la quantité de H₂O₂ ; chacune d'elle est le plus souvent comprise entre 1 heure et 6 heures.The treatment using H₂O₂ in an alkaline medium is normally carried out at a temperature between 60 ° C and 90 ° C, between 65 ° C and 75 ° C most often, at the highest possible consistency, for example between 15% and 45%. The duration of action of H₂O₂ added with NaOH at the start of treatment, like that of H₂O₂ added with NaOH during treatment according to the process of the invention, mainly depend on the temperature and the amount of H₂O₂; each of them is most often between 1 hour and 6 hours.
Il a été constaté qu'il est souvent avantageux de procéder à l'addition des quantités supplémentaires de H₂O₂ et de NaOH en cours du traitement quand sont consommés environ 70 % à 80 % de la quantité de H₂O₂ initialement engagée.It has been found that it is often advantageous to add additional quantities of H supplémentairesO₂ and NaOH during the treatment when about 70% to 80% of the quantity of H₂O₂ initially used is consumed.
Les exemples suivants, donnés à titre indicatif mais non limitatif, soit illustrent l'invention, soit sont donnés à titre comparatif.The following examples, given as an indication but not limiting, either illustrate the invention or are given for comparison.
Dans chacun de ces exemples, la pâte soumise au procédé de blanchiment est une pâte mécanique de meule formée, en poids, de 75 % de bois de résineux et de 25 % de bois de feuillu, et dont le degré de blancheur est égal à 63,2°ISO. Dans chacun de ces exemples encore, la pâte est soumise avant le traitement par H₂O₂ en milieu alcalin, à un prétraitement à la consistance de 10 % à l'aide de 0,5 % d'une solution aqueuse à 40 % en poids de sel de sodium du DTPA, à 90°C durant 15 minutes suivi d'un lavage d'efficacité égale à 90 %.In each of these examples, the pulp subjected to the bleaching process is a mechanical grinding pulp formed, by weight, of 75% of softwood and 25% of hardwood, and whose degree of whiteness is equal to 63 , 2 ° ISO. In each of these examples again, the dough is subjected before treatment with H₂O₂ in an alkaline medium, to a pretreatment with a consistency of 10% using 0.5% of an aqueous solution at 40% by weight of salt sodium DTPA, at 90 ° C for 15 minutes followed by a washing efficiency of 90%.
Le traitement à l'aide de H₂O₂ en milieu alcalin a chaque fois été réalisé en l'absence d'agent complexant des ions métalliques, à une température égale à 70°C, à une consistance successivement égale à 20 % avant que les additions supplémentaires de H₂O₂ et de NaOH aient été faites, à 15 % après que ces additions aient été faites.The treatment using H₂O₂ in an alkaline medium was each time carried out in the absence of complexing agent for metal ions, at a temperature equal to 70 ° C., at a consistency successively equal to 20% before the additional additions H₂O₂ and NaOH were made, 15% after these additions were made.
Les quantités de H₂O₂, NaOH, solution de silicate de sodium de densité 1,33 désignée par silicate, exprimées comme à l'ordinaire ici en % pondéral par rapport à la pâte à l'état sec sont données dans le tableau unique ci-après dans lequel figurent aussi les degrés de blancheur de la pâte qui a été soumise soit au procédé de l'invention, soit à un procédé connu comportant, au contraire du procédé conforme à l'invention, un lavage désigné par L, d'efficacité égale à 90 %, avant addition supplémentaire d'au moins H₂O₂ et NaOH.The amounts of H₂O₂, NaOH, sodium silicate solution of density 1.33 designated by silicate, expressed as usual here in% by weight relative to the dough in the dry state are given in the single table below in which also appear the degrees of whiteness of the dough which has been subjected either to the process of the invention, or to a known process comprising, unlike the process according to the invention, a washing designated by L, of equal effectiveness at 90%, before additional addition of at least H₂O₂ and NaOH.
La durée du traitement de blanchiment a été chaque fois égale à 7 heures.
Claims (8)
- Process for bleaching paper pulp in high yield in which the pulp to be bleached is subjected to a pretreatment using a complexing agent for metal ions, followed by a washing, and then to a treatment using hydrogen peroxide in an alkaline medium, characterized in that between the start and the end of the treatment a supplementary addition of hydrogen peroxide and alkaline agent is made to the pulp without interruption of the treatment, at a moment when 60 % to 85 % of the initial amount of hydrogen peroxide has been consumed, the supplementary amount of hydrogen peroxide added being equal to or less than the said initial amount.
- Process according to Claim 1, characterized in that the supplementary addition of hydrogen peroxide and alkaline agent takes place when 70 % to 80 % of the initial amount of hydrogen peroxide has been consumed.
- Process according to either of Claims 1 and 2, characterized in that the initial amount of hydrogen peroxide is between 0.5 % and 6 % by weight relative to the pulp in the dry state.
- Process according to Claim 3, characterized in that the initial amount of hydrogen peroxide is betweeen 3 % and 5 %.
- Process according to one of Claims 1 to 4, characterized in that the supplementary amount of hydrogen peroxide added is between 0.25 % and 3 % by weight relative to the pulp in the dry state.
- Process according to one of Claims 1 to 5, characterized in that the alkaline agent which accompanies the hydrogen peroxide is sodium hydroxide, which is employed in a proportion of between 0.5 % and 6 % by weight relative to the pulp in the dry state, both at the start of the treatment as the initial amount employed and during the treatment as the supplementary amount added.
- Process according to Claim 6, characterized in that the amount of sodium hydroxide employed at the start of this treatment is between 1.5 % and 4 %.
- Process according to either of Claims 6 and 7, characterized in that the supplementary amount of sodium hydroxide added is between 1 % and 3 % by weight relative to the pulp in the dry state.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT91401317T ATE109529T1 (en) | 1991-05-22 | 1991-05-22 | PROCESS FOR HYDROGEN PEROXIDE BLEACHING OF HIGH-YIELD PULP. |
| DE1991603259 DE69103259T2 (en) | 1991-05-22 | 1991-05-22 | Process for hydrogen peroxide bleaching of high-yield pulps. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9005749A FR2661431B1 (en) | 1990-04-30 | 1990-04-30 | HIGH-YIELD PAPER PULP HYDROGEN PEROXIDE BLEACHING PROCESS. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0514609A1 EP0514609A1 (en) | 1992-11-25 |
| EP0514609B1 true EP0514609B1 (en) | 1994-08-03 |
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ID=9396411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91401317A Expired - Lifetime EP0514609B1 (en) | 1990-04-30 | 1991-05-22 | Process for hydrogen peroxide bleaching of high-yield pulps |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US5296100A (en) |
| EP (1) | EP0514609B1 (en) |
| JP (1) | JPH0726351B2 (en) |
| AU (1) | AU642007B2 (en) |
| CA (1) | CA2041389A1 (en) |
| ES (1) | ES2057805T3 (en) |
| FI (1) | FI99154C (en) |
| FR (1) | FR2661431B1 (en) |
| NO (1) | NO178936C (en) |
| NZ (1) | NZ237980A (en) |
| PT (1) | PT97514B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2661431B1 (en) * | 1990-04-30 | 1992-07-17 | Atochem | HIGH-YIELD PAPER PULP HYDROGEN PEROXIDE BLEACHING PROCESS. |
| SE9301960L (en) * | 1993-06-08 | 1994-07-25 | Kvaerner Pulping Tech | Bleaching of chemical pulp with peroxide at overpressure |
| US5620563A (en) * | 1994-10-31 | 1997-04-15 | Pulp Paper Res Inst | Process for delignification and bleaching of chemical wood pulps with hydrogen peroxide and a dicyandiamide activator |
| US5562740A (en) * | 1995-06-15 | 1996-10-08 | The Procter & Gamble Company | Process for preparing reduced odor and improved brightness individualized, polycarboxylic acid crosslinked fibers |
| AU1357097A (en) * | 1996-02-27 | 1997-09-16 | Tetra Laval Holdings & Finance Sa | Process for sanitizing post-consumer paper fibers and product formed therefrom |
| US6899790B2 (en) * | 2000-03-06 | 2005-05-31 | Georgia-Pacific Corporation | Method of providing papermaking fibers with durable curl |
| US6627041B2 (en) * | 2000-03-06 | 2003-09-30 | Georgia-Pacific Corporation | Method of bleaching and providing papermaking fibers with durable curl |
| WO2001083881A2 (en) * | 2000-05-04 | 2001-11-08 | University Of New Brunswick | Peroxide bleaching of wood pulp |
| US7297225B2 (en) * | 2004-06-22 | 2007-11-20 | Georgia-Pacific Consumer Products Lp | Process for high temperature peroxide bleaching of pulp with cool discharge |
| US8138106B2 (en) | 2005-09-30 | 2012-03-20 | Rayonier Trs Holdings Inc. | Cellulosic fibers with odor control characteristics |
| FR2937656B1 (en) * | 2008-10-24 | 2010-11-19 | Arkema France | PROCESS FOR PRODUCING PAPER PULP |
| US8845860B2 (en) | 2010-09-16 | 2014-09-30 | Georgia-Pacific Consumer Products Lp | High brightness pulps from lignin rich waste papers |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE387977B (en) * | 1975-01-27 | 1976-09-20 | Elektrokemiska Ab | WAY TO PRODUCE BLEACH, MECHANICAL PULP WITH HIGH STRENGTH AND BRIGHTNESS |
| JPS5725492A (en) * | 1980-07-16 | 1982-02-10 | Mitsubishi Gas Chemical Co | Hydrogen peroxide refiner bleaching of high yield pulp |
| SE451606B (en) * | 1982-09-14 | 1987-10-19 | Sca Development Ab | VIEW WHITENING OF HOG REPLACEMENT MASSES AVERAGE PEROXIDES |
| FR2582692B1 (en) * | 1985-05-29 | 1987-12-11 | Atochem | TREATMENT OF CHEMICAL PAPER PULP WITH HYDROGEN PEROXIDE FOR BLEACHING |
| US4732650A (en) * | 1986-09-15 | 1988-03-22 | The Dow Chemical Company | Bleaching of cellulosic pulps using hydrogen peroxide |
| SE455203B (en) * | 1986-10-20 | 1988-06-27 | Eka Nobel Ab | PROCEDURE FOR THE CONTROL OF PEROXID WHEATING OF MASS |
| FR2613388B1 (en) * | 1987-04-02 | 1990-05-04 | Atochem | PROCESS FOR BLEACHING PASTA |
| JPH076148B2 (en) * | 1989-06-27 | 1995-01-30 | 新王子製紙株式会社 | Bleaching method for lignocellulosic material |
| FR2661430B1 (en) * | 1990-04-30 | 1992-07-17 | Atochem | HIGH-YIELD PAPER PULP HYDROGEN PEROXIDE BLEACHING PROCESS. |
| FR2661431B1 (en) * | 1990-04-30 | 1992-07-17 | Atochem | HIGH-YIELD PAPER PULP HYDROGEN PEROXIDE BLEACHING PROCESS. |
-
1990
- 1990-04-30 FR FR9005749A patent/FR2661431B1/en not_active Expired - Lifetime
-
1991
- 1991-04-16 NO NO911491A patent/NO178936C/en unknown
- 1991-04-25 JP JP3095600A patent/JPH0726351B2/en not_active Expired - Lifetime
- 1991-04-29 PT PT97514A patent/PT97514B/en not_active IP Right Cessation
- 1991-04-29 CA CA002041389A patent/CA2041389A1/en not_active Abandoned
- 1991-04-29 AU AU76056/91A patent/AU642007B2/en not_active Ceased
- 1991-04-29 NZ NZ237980A patent/NZ237980A/en unknown
- 1991-04-29 FI FI912074A patent/FI99154C/en not_active IP Right Cessation
- 1991-04-30 US US07/693,800 patent/US5296100A/en not_active Expired - Fee Related
- 1991-05-22 ES ES91401317T patent/ES2057805T3/en not_active Expired - Lifetime
- 1991-05-22 EP EP91401317A patent/EP0514609B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04228691A (en) | 1992-08-18 |
| FR2661431A1 (en) | 1991-10-31 |
| US5296100A (en) | 1994-03-22 |
| PT97514B (en) | 1999-02-26 |
| FI912074A0 (en) | 1991-04-29 |
| NO911491D0 (en) | 1991-04-16 |
| CA2041389A1 (en) | 1991-10-31 |
| NZ237980A (en) | 1993-04-28 |
| PT97514A (en) | 1992-01-31 |
| EP0514609A1 (en) | 1992-11-25 |
| FI99154C (en) | 1997-10-10 |
| NO178936C (en) | 1996-07-03 |
| AU642007B2 (en) | 1993-10-07 |
| JPH0726351B2 (en) | 1995-03-22 |
| AU7605691A (en) | 1991-11-07 |
| NO178936B (en) | 1996-03-25 |
| FR2661431B1 (en) | 1992-07-17 |
| FI912074A (en) | 1991-10-31 |
| FI99154B (en) | 1997-06-30 |
| ES2057805T3 (en) | 1994-10-16 |
| NO911491L (en) | 1991-10-31 |
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