EP0535741A1 - Process for improving the selectivity in the delignification of a chemical pulp - Google Patents
Process for improving the selectivity in the delignification of a chemical pulp Download PDFInfo
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- EP0535741A1 EP0535741A1 EP92202952A EP92202952A EP0535741A1 EP 0535741 A1 EP0535741 A1 EP 0535741A1 EP 92202952 A EP92202952 A EP 92202952A EP 92202952 A EP92202952 A EP 92202952A EP 0535741 A1 EP0535741 A1 EP 0535741A1
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- Prior art keywords
- organic peroxyacid
- process according
- treatment
- acid
- peroxyacid
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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
- D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids
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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
- D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
Definitions
- the invention relates to a method for delignifying a chemical pulp. It particularly relates to a method for improving the selectivity of such a delignification operation.
- the invention aims to remedy the drawbacks of known methods by providing a method which achieves effective delignification of the unbleached chemical pulp with a high selectivity which makes it possible to obtain pulps having high intrinsic qualities.
- the invention relates to a process for improving the selectivity of the delignification of a chemical paper pulp by means of an organic peroxyacid according to which the unbleached pulp from the cooking operation is treated with a aqueous solution of this organic peroxyacid at a temperature between 2 and 47 ° C.
- chemical paper pulp the pulp 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 salt metal of sulfurous acid in an acid medium (cooking with sulfite).
- chemical reagents such as sodium sulfide in alkaline medium (kraft or sulfate cooking), sulfur dioxide or a salt metal of sulfurous acid in an acid medium (cooking with sulfite).
- Semi-chemical pastes such as those where cooking was carried out using a sulfurous acid salt in a neutral medium (cooking with neutral sulfite also called NSSC cooking) or even those obtained by treatment with caustic soda cold followed by mechanical defibration can also be bleached and / or delignified by the process according to the invention.
- the organic peroxyacid is selected from aliphatic carboxylic peroxyacids comprising a single percarboxylic group and a saturated linear or branched alkyl chain of less than 11 carbon atoms.
- Aliphatic carboxylic peroxyacids with a linear saturated alkyl chain having less than 6 carbon atoms are preferred. Examples of such peroxyacids are performic acid, peracetic acid, perpropanoic acid, n-perbutanoic acid and n-perpentanoic acid.
- Peracetic acid is particularly preferred because of its effectiveness and its good biodegradable properties.
- the organic peroxyacid is selected from diperoxyacarboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms and two percarboxylic groups substituted on carbon atoms situated in the alpha-omega l position 'one over the other.
- diperoxyacarboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms and two percarboxylic groups substituted on carbon atoms situated in the alpha-omega l position 'one over the other.
- Examples of such peroxyacids are 1,6-diperoxyhexanedioic acid, 1,8-diperoxyoctanedioic acid and 1,10-diperoxydecanedioic acid, and 1,12-diperoxydodecanedioic acid.
- the organic peroxyacid is selected from aromatic peroxyacids comprising at least one percarboxylic group per benzene nucleus.
- aromatic peroxyacids which have only one percarboxylic group per benzene nucleus will be chosen.
- An example of such an acid is peroxybenzoic acid.
- Another variant of the process according to the invention consists in choosing an organic peroxyacid substituted with one or more halogen atoms or by any other organic functional substituent.
- organic functional substituent is meant a functional group such as the carbonyl group (ketone, aldehyde or carboxylic acid), the alcohol group, the groups containing nitrogen such as the nitrile, nitro, amine and amide groups, groups containing sulfur such as the sulfo and mercapto groups.
- the peroxyacid can equally be used in the form of an aqueous solution of peroxyacid or alternatively in the form of an ammonium, alkali metal or alkaline earth metal salt of this peroxyacid.
- the treatment with organic peroxyacid is carried out at a temperature between 35 and 45 ° C.
- the treatment is carried out with organic peroxyacid at atmospheric pressure.
- the duration of this treatment depends on the temperature and the essence of the wood used to prepare the dough, as well as the efficiency of the preceding cooking. Times of about 120 minutes to about 240 minutes are fine, and it is even possible to exceed this limit by about 100% without risking substantial degradation of the mechanical strength properties of the dough.
- the temperature of the treatment is high, that is to say above 45 ° C., it is possible to use shorter times ranging between approximately 45 minutes to approximately 120 minutes.
- the treatment according to the invention can be carried out in any type of apparatus suitable for the treatment of paper pulp by means of acid reagents.
- the retention tank for unbleached pulp present in all bleaching installations and acting as a buffer tank between the wood cooking unit and the pulp bleaching unit is particularly suitable for carrying out the process according to the invention.
- the dough can thus be treated there during its storage without requiring the investment of an expensive specific device.
- the ability to safely exceed the normal duration of treatment is particularly well suited to the role of storage buffer for the retention tank.
- the consistency of the treatment step with organic peroxyacid will generally be chosen between 2 and 40% of dry matter and, more often, between 10 and 40%. High consistencies are preferred, for example those between 20 and 40%.
- the amount of organic peroxyacid used is chosen as a function of the level of residual lignin in the pulp as well as the average duration of the treatment. Generally, amounts of between 0.5 and 4% by weight of peroxyacid relative to the dry pulp are very suitable. Most often, an amount of peroxyacid will not be used which does not exceed 3% by weight relative to the dry paste and greater than 1% of this weight.
- a decontaminating pretreatment step using an acidic aqueous solution.
- the purpose of this step is to extract from the pulp the impurities present in the form of metal ions which are detrimental to the proper conduct of the bleaching and / or delignification operations.
- All the inorganic or organic acids used in aqueous solution, alone or as a mixture are suitable. Strong inorganic acids such as, for example, sulfuric acid or hydrochloric acid are well suited.
- the acid decontaminating pretreatment is also carried out in the presence of an agent complexing metal ions.
- mixtures of the strong inorganic acids mentioned above with organic acids from the class of aminopolycarboxylic or aminopolyphosphonic acids or their alkali metal salts are particularly suitable.
- suitable aminopolycarboxylic acids are diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid and nitrilotriacetic acid.
- Diethylenetriaminepentaacetic acid (DTPA) is preferred.
- aminopolyphosphonic acids are diethylenetriaminepentamethylene phosphonic acid (DTMPA), ethylenediaminetetra acid (methylenephosphonic), cyclohexanediamine-tetramethylenephosphonic acid (CDTMPA) and nitrilotri acid (methylenephosphonic acid). DTMPA is preferred.
- the operating conditions for the acid decontaminant pretreatment are not critical. They must be determined in each particular case according to the type of paper pulp and the equipment in which the treatment is carried out. In general, the choice of acid and the quantity used should be fixed to impose on the medium a pH of less than 7, for example between approximately 1 and approximately 6.5. Especially advantageous pHs are those between about 2.0 and about 5.0. Temperature and pressure are not critical, with room temperature and atmospheric pressure generally suitable. The duration of the pretreatment can vary within wide limits depending on the type of equipment used, the choice of acid, the temperature and the pressure, for example from about 15 minutes to several hours.
- the latter are chosen from the same complexing agents as those described above for the decontaminating kneading step.
- Example 1 R unlike the other three examples, did not include washing the dough with water between the step of treatment with peracetic acid and the step of alkaline extraction.
- the hydrogen peroxide present in the alkaline extraction step of Example 1 R also comes from the residual hydrogen peroxide of the step with peracetic acid which preceded.
- the step with peracetic acid was preceded by an acid pretreatment using diethylenetriaminepentaacetic acid or DTPA (step Q).
- peracetic acid aqueous solution of commercial quality and contained hydrogen peroxide in equilibrium with peracetic acid (2.6 b of H 2 O 2 per 100 a of dry paste).
Abstract
Description
L'invention concerne un procédé de délignification d'une pâte à papier chimique. Elle concerne particulièrement un procédé pour améliorer la sélectivité d'une telle opération de délignification.The invention relates to a method for delignifying a chemical pulp. It particularly relates to a method for improving the selectivity of such a delignification operation.
Il est connu de traiter les pâtes à papier chimiques écrues obtenues par cuisson de matières cellulosiques en présence de réactifs chimiques au moyen d'une séquence d'étapes de traitement délignifiant et blanchissant impliquant la mise en oeuvre de produits chimiques oxydants. La première étape d'une séquence classique de blanchiment de pâte chimique a pour objectif de parfaire la délignification de la pâte écrue telle qu'elle se présente après l'opération de cuisson. Cette première étape délignifiante est traditionnellement réalisée en traitant la pâte écrue par du chlore en milieu acide ou par une association chlore - dioxyde de chlore, en mélange ou en séquence, de façon à réagir avec la lignine résiduelle de la pâte et donner naissance à des chlorolignines qui pourront être extraites de la pâte par solubilisation de ces chlorolignines en milieu alcalin dans une étape de traitement ultérieure.It is known to treat unbleached chemical paper pulps obtained by cooking cellulosic materials in the presence of chemical reagents by means of a sequence of delignifying and whitening treatment steps involving the use of oxidizing chemicals. The objective of the first step of a conventional chemical pulp bleaching sequence is to complete the delignification of the unbleached pulp as it occurs after the cooking operation. This first significant step is traditionally carried out by treating the unbleached pulp with chlorine in an acid medium or by a chlorine-chlorine dioxide association, in mixture or in sequence, so as to react with the residual lignin of the pulp and give rise to chlorolignins which can be extracted from the pulp by dissolving these chlorolignins in an alkaline medium in a subsequent treatment step.
Pour des raisons diverses, il s'avère utile, dans certaines situations, de pouvoir remplacer cette première étape délignifiante par un traitement qui ne fasse plus appel à un réactif chloré.For various reasons, it is useful, in certain situations, to be able to replace this first significant step with a treatment which no longer uses a chlorinated reagent.
On a déjà proposé de traiter les pâtes chimiques par une première étape à l'acide peracétique à des températures supérieures à 50° C et des pH compris entre 3 et 9 (Bailey C.W. et Dence C.W., "Peroxyacetic Acid Bleaching of Chemical Pulps", Tappi, Janvier 1966, Vol. 49, No. 1, pages 9 à 15). Dans ce procédé connu, il apparaît toutefois que le traitement à l'acide peracétique donne lieu à des pâtes de viscosité et de propriétés mécaniques moins bonnes que les pâtes délignifiées par une étape traditionnelle au chlore en milieu acide par suite d'une sélectivité de délignification moins élevée qui se traduit par une attaque plus marquée des chaînes de la cellulose.It has already been proposed to treat chemical pulps by a first step with peracetic acid at temperatures above 50 ° C and pH between 3 and 9 (Bailey CW and Dence CW, "Peroxyacetic Acid Bleaching of Chemical Pulps", Tappi, January 1966, Vol. 49, No. 1, pages 9 to 15). In this known process, however, it appears that the treatment with peracetic acid gives rise to pastes of viscosity and less good mechanical properties than pastes delignified by a traditional chlorine step in an acid medium as a result of delignification selectivity. lower which results in a more marked attack on the cellulose chains.
L'invention vise à remédier aux inconvénients des procédés connus en fournissant un procédé qui réalise une délignification efficace de la pâte chimique écrue assortie d'une sélectivité élevée qui permette l'obtention de pâtes présentant de hautes qualités intrinsèques.The invention aims to remedy the drawbacks of known methods by providing a method which achieves effective delignification of the unbleached chemical pulp with a high selectivity which makes it possible to obtain pulps having high intrinsic qualities.
A cet effet, l'invention concerne un procédé pour l'amélioration de la sélectivité de la délignification d'une pâte à papier chimique au moyen d'un peroxyacide organique selon lequel on traite la pâte écrue provenant de l'opération de cuisson par une solution aqueuse de ce peroxyacide organique à une température comprise entre 2 et 47° C.To this end, the invention relates to a process for improving the selectivity of the delignification of a chemical paper pulp by means of an organic peroxyacid according to which the unbleached pulp from the cooking operation is treated with a aqueous solution of this organic peroxyacid at a temperature between 2 and 47 ° C.
Selon l'invention, par pâte à papier chimique, on entend désigner les pâtes ayant subi un traitement délignifiant en présence de réactifs chimiques tels que le sulfure de sodium en milieu alcalin (cuisson kraft ou au sulfate), l'anhydride sulfureux ou un sel métallique de l'acide sulfureux en milieu acide (cuisson au sulfite). Les pâtes semi-chimiques telles que celles où la cuisson a été réalisée à l'aide d'un sel de l'acide sulfureux en milieu neutre (cuisson au sulfite neutre encore appelée cuisson NSSC) ou encore celles obtenues par traitement à la soude caustique à froid suivi d'un défibrage mécanique peuvent aussi être blanchies et/ou délignifiées par le procédé selon l'invention.According to the invention, by chemical paper pulp is meant the pulp 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 salt metal of sulfurous acid in an acid medium (cooking with sulfite). Semi-chemical pastes such as those where cooking was carried out using a sulfurous acid salt in a neutral medium (cooking with neutral sulfite also called NSSC cooking) or even those obtained by treatment with caustic soda cold followed by mechanical defibration can also be bleached and / or delignified by the process according to the invention.
Celle-ci s'adresse particulièrement aux pâtes ayant subi une cuisson kraft et dont la teneur en lignine résiduelle après cuisson se situe dans la plage d'indices kappa compris entre 8 et 40 (ou encore ayant un nombre permanganate compris entre 5 et 30) selon le type d'essence de bois dont elles proviennent et l'efficacité du processus de cuisson. Tous les types de bois utilisés pour la production de pâtes chimiques conviennent pour la mise en oeuvre du procédé de l'invention et, en particulier ceux utilisés pour les pâtes kraft, à savoir les bois résineux comme, par exemple, les diverses espèces de pins et de sapins et les bois feuillus comme, par exemple, l'eucalyptus, le hêtre, le chêne et le charme.This is particularly intended for pasta which has undergone kraft cooking and whose residual lignin content after cooking is within the range of kappa indices between 8 and 40 (or even having a permanganate number between 5 and 30) depending on the type of wood from which they come and the efficiency of the cooking process. All types of wood used for the production of chemical pulp are suitable for implementing the process of the invention and, in particular those used for kraft pulp, namely resinous woods, for example, the various species of pine and fir and hardwoods like, for example, eucalyptus, beech, oak and hornbeam.
Selon l'invention, le peroxyacide organique est sélectionné parmi les peroxyacides aliphatiques carboxyliques comportant un seul groupement percarboxylique et une channe alkyle saturée linéaire ou ramifiée de moins de 11 atomes de carbone. Les peroxyacides carboxyliques aliphatiques à chaîne alkyle saturée linéaire comportant moins de 6 atomes de carbone sont préférés. Des exemples de tels peroxyacides sont l'acide per- formique, l'acide peracétique, l'acide perpropanoïque, l'acide n-perbutanoïque et l'acide n-perpentanoïque. L'acide peracétique est particulièrement préféré en raison de son efficacité et de ses bonnes propriétés biodégradables.According to the invention, the organic peroxyacid is selected from aliphatic carboxylic peroxyacids comprising a single percarboxylic group and a saturated linear or branched alkyl chain of less than 11 carbon atoms. Aliphatic carboxylic peroxyacids with a linear saturated alkyl chain having less than 6 carbon atoms are preferred. Examples of such peroxyacids are performic acid, peracetic acid, perpropanoic acid, n-perbutanoic acid and n-perpentanoic acid. Peracetic acid is particularly preferred because of its effectiveness and its good biodegradable properties.
Dans une variante au procédé selon l'invention, le peroxyacide organique est sélectionné parmi les diperoxyacides carboxyliques comportant une chaîne alkyle linéaire ou ramifiée de moins de 16 atomes de carbone et deux groupements percarboxyliques substitués sur des atomes de carbone situés en position alpha-omega l'un par rapport à l'autre. Des exemples de tels peroxyacides sont l'acide 1,6-diperoxyhexanedioïque, l'acide 1,8-diperoxyoctanedioïque et l'acide 1,10-diperoxydécanedioïque, et l'acide 1,12-diperoxydodécanedioïque.In a variant of the process according to the invention, the organic peroxyacid is selected from diperoxyacarboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms and two percarboxylic groups substituted on carbon atoms situated in the alpha-omega l position 'one over the other. Examples of such peroxyacids are 1,6-diperoxyhexanedioic acid, 1,8-diperoxyoctanedioic acid and 1,10-diperoxydecanedioic acid, and 1,12-diperoxydodecanedioic acid.
Dans une autre variante au procédé selon l'invention, le peroxyacide organique est sélectionné parmi les peroxyacides aromatiques comportant au moins un groupement percarboxylique par noyau benzénique. De préférence, on choisira les peroxyacides aromatiques qui ne comportent qu'un seul groupement percarboxylique par noyau benzénique. Un exemple d'un tel acide est l'acide peroxybenzoïque.In another variant of the process according to the invention, the organic peroxyacid is selected from aromatic peroxyacids comprising at least one percarboxylic group per benzene nucleus. Preferably, aromatic peroxyacids which have only one percarboxylic group per benzene nucleus will be chosen. An example of such an acid is peroxybenzoic acid.
Une autre variante au procédé selon l'invention consiste à choisir un peroxyacide organique substitué par un ou plusieurs atomes d'halogène ou par tout autre substituant fonctionnel organique. Par tout autre substituant fonctionnel organique, on entend désigner un groupement fonctionnel tel que le groupement carbonyle (cétone, aldéhyde ou acide carboxylique), le groupement alcool, les groupements contenant de l'azote tels que les groupements nitrile, nitro, amine et amide, les groupements contenant du soufre tels que les groupements sulfo et mercapto.Another variant of the process according to the invention consists in choosing an organic peroxyacid substituted with one or more halogen atoms or by any other organic functional substituent. By any other organic functional substituent, is meant a functional group such as the carbonyl group (ketone, aldehyde or carboxylic acid), the alcohol group, the groups containing nitrogen such as the nitrile, nitro, amine and amide groups, groups containing sulfur such as the sulfo and mercapto groups.
Le peroxyacide peut indifféremment être mis en oeuvre à l'état d'une solution aqueuse de peroxyacide ou encore sous forme d'un sel d'ammonium, de métal alcalin ou de métal alcalino-terreux de ce peroxyacide.The peroxyacid can equally be used in the form of an aqueous solution of peroxyacid or alternatively in the form of an ammonium, alkali metal or alkaline earth metal salt of this peroxyacid.
De préférence, le traitement avec le peroxyacide organique s'effectue à une température comprise entre 35 et 45° C. Généralement, on effectue le traitement avec le peroxyacide organique à pression atmosphérique. La durée de ce traitement dépend de la température et de l'essence du bois ayant servi à préparer la pâte, ainsi que de l'efficacité de la cuisson qui a précédé. Des durées d'environ 120 minutes à environ 240 minutes conviennent bien, et il est même possible de dépasser cette limite d'environ 100 % sans risquer de dégradation substantielle des propriétés de résistance mécanique de la pâte. Lorsque la température du traitement est élevée, c'est-à-dire supérieure à 45° C, il est possible d'utiliser des durées plus courtes comprises entre environ 45 minutes à environ 120 minutes. Le traitement selon l'invention peut se faire dans tout type d'appareillage approprié pour le traitement de pâte à papier au moyen de réactifs acides. La cuve de rétention de la pâte écrue présente dans toutes les installations de blanchiment et jouant le rôle de réservoir tampon entre l'unité de cuisson du bois et l'unité de blanchiment de la pâte convient particulièrement bien pour la réalisation du procédé selon l'invention. La pâte peut ainsi y être traitée pendant son stockage sans nécessiter l'investissement d'un appareil spécifique onéreux. La faculté de pouvoir dépasser sans danger la durée normale du traitement est particulièrement bien adaptée au rôle de tampon de stockage de la cuve de rétention.Preferably, the treatment with organic peroxyacid is carried out at a temperature between 35 and 45 ° C. Generally, the treatment is carried out with organic peroxyacid at atmospheric pressure. The duration of this treatment depends on the temperature and the essence of the wood used to prepare the dough, as well as the efficiency of the preceding cooking. Times of about 120 minutes to about 240 minutes are fine, and it is even possible to exceed this limit by about 100% without risking substantial degradation of the mechanical strength properties of the dough. When the temperature of the treatment is high, that is to say above 45 ° C., it is possible to use shorter times ranging between approximately 45 minutes to approximately 120 minutes. The treatment according to the invention can be carried out in any type of apparatus suitable for the treatment of paper pulp by means of acid reagents. The retention tank for unbleached pulp present in all bleaching installations and acting as a buffer tank between the wood cooking unit and the pulp bleaching unit is particularly suitable for carrying out the process according to the invention. The dough can thus be treated there during its storage without requiring the investment of an expensive specific device. The ability to safely exceed the normal duration of treatment is particularly well suited to the role of storage buffer for the retention tank.
La consistance de l'étape de traitement par le peroxyacide organique sera généralement choisie entre 2 et 40 % de matières sèches et, le plus souvent, entre 10 et 40 %. On préfère les consistances élevées, par exemple celles comprises entre 20 et 40 %.The consistency of the treatment step with organic peroxyacid will generally be chosen between 2 and 40% of dry matter and, more often, between 10 and 40%. High consistencies are preferred, for example those between 20 and 40%.
Dans le procédé selon l'invention, la quantité de peroxyacide organique utilisée est choisie en fonction du taux de lignine résiduelle dans la pâte ainsi que de la durée moyenne du traitement. Généralement, des quantités comprises entre 0,5 et 4 % en poids de peroxyacide par rapport à la pâte sèche conviennent bien. Le plus souvent, on utilisera une quantité de peroxyacide ne dépassant pas 3 % en poids par rapport à la pâte sèche et supérieure à 1 % de ce poids.In the process according to the invention, the amount of organic peroxyacid used is chosen as a function of the level of residual lignin in the pulp as well as the average duration of the treatment. Generally, amounts of between 0.5 and 4% by weight of peroxyacid relative to the dry pulp are very suitable. Most often, an amount of peroxyacid will not be used which does not exceed 3% by weight relative to the dry paste and greater than 1% of this weight.
Il peut être intéressant, en variante, de faire précéder le traitement par le peroxyacide organique par une étape de prétraitement décontaminant au moyen d'une solution aqueuse acide. Cette étape a pour but d'extraire de la pâte les impuretés présentes sous forme d'ions métalliques qui sont nuisibles au bon déroulement des opérations de blanchiment et/ou de délignification. Tous les acides inorganiques ou organiques utilisés en solution aqueuse, seuls ou en mélange conviennent. Les acides forts inorganiques tels que, par exemple, l'acide sulfurique ou l'acide chlorhydrique conviennent bien.It may alternatively be advantageous to precede the treatment with organic peroxyacid by a decontaminating pretreatment step using an acidic aqueous solution. The purpose of this step is to extract from the pulp the impurities present in the form of metal ions which are detrimental to the proper conduct of the bleaching and / or delignification operations. All the inorganic or organic acids used in aqueous solution, alone or as a mixture are suitable. Strong inorganic acids such as, for example, sulfuric acid or hydrochloric acid are well suited.
Il est avantageux que le prétraitement décontaminant acide soit en outre réalisé en présence d'un agent complexant des ions métalliques. A cette fin, des mélanges des acides forts inorganiques cités plus haut avec des acides organiques de la classe des acides aminopolycarboxyliques ou aminopolyphosphoniques ou leurs sels de métaux alcalins conviennent particulièrement bien. Des exemples d'acides aminopolycarboxyliques adéquats sont l'acide diéthylènetriaminepentaacétique, l'acide éthylènediaminetétraacétique, l'acide cyclo- hexanediaminetétraacétique et l'acide nitrilotriacétique. L'acide diéthylènetriaminepentaacétique (DTPA) est préféré. Des exemples d'acides aminopolyphosphoniques sont l'acide diéthylènetriaminepentaméthylène- phosphonique (DTMPA), l'acide éthylènediaminetétra(méthylènephosphonique), l'acide cyclohexanediamine- tétraméthylènephosphonique (CDTMPA) et l'acide nitrilotri(méthylènephosphonique). Le DTMPA est préféré.It is advantageous that the acid decontaminating pretreatment is also carried out in the presence of an agent complexing metal ions. To this end, mixtures of the strong inorganic acids mentioned above with organic acids from the class of aminopolycarboxylic or aminopolyphosphonic acids or their alkali metal salts are particularly suitable. Examples of suitable aminopolycarboxylic acids are diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid and nitrilotriacetic acid. Diethylenetriaminepentaacetic acid (DTPA) is preferred. Examples of aminopolyphosphonic acids are diethylenetriaminepentamethylene phosphonic acid (DTMPA), ethylenediaminetetra acid (methylenephosphonic), cyclohexanediamine-tetramethylenephosphonic acid (CDTMPA) and nitrilotri acid (methylenephosphonic acid). DTMPA is preferred.
Les conditions opératoires du prétraitement décontaminant acide ne sont pas critiques. Elles doivent être déterminées dans chaque cas particulier en fonction du type de pâte à papier et de l'appareillage dans lequel s'effectue le traitement. D'une manière générale, il convient de fixer le choix de l'acide et la quantité mise en oeuvre pour imposer au milieu un pH inférieur à 7, par exemple compris entre environ 1 et environ 6,5. Des pH spécialement avantageux sont ceux compris entre environ 2,0 et environ 5,0. La température et la pression ne sont pas critiques, la température ambiante et la pression atmosphérique convenant généralement bien. La durée du prétraitement peut varier dans de larges proportions selon le type d'équipement utilisé, le choix de l'acide, la température et la pression, par exemple de 15 minutes environ à plusieurs heures.The operating conditions for the acid decontaminant pretreatment are not critical. They must be determined in each particular case according to the type of paper pulp and the equipment in which the treatment is carried out. In general, the choice of acid and the quantity used should be fixed to impose on the medium a pH of less than 7, for example between approximately 1 and approximately 6.5. Especially advantageous pHs are those between about 2.0 and about 5.0. Temperature and pressure are not critical, with room temperature and atmospheric pressure generally suitable. The duration of the pretreatment can vary within wide limits depending on the type of equipment used, the choice of acid, the temperature and the pressure, for example from about 15 minutes to several hours.
On peut aussi remplacer le prétraitement décontaminant par l'incorporation dans l'étape de délignification au peroxyacide elle-même d'un ou plusieurs agents complexants des ions métalliques. Ces derniers sont choisis parmis les mêmes agents complexants que ceux décrits plus haut pour l'étape de pétraitement décontaminant.One can also replace the decontaminating pretreatment by the incorporation in the delignification step with peroxyacid itself of one or more complexing agents of metal ions. The latter are chosen from the same complexing agents as those described above for the decontaminating kneading step.
Dans une autre variante au procédé selon l'invention, on peut, si l'on désire obtenir de hauts niveaux de blancheur, faire suivre le traitement avec un peroxyacide par une séquence d'étapes de blanchiment traditionnelles impliquant ou non des réactifs chlorés. Des exemples de telles étapes sont les suivantes: étapes à l'oxygène gazeux ou à l'ozone, étapes au peroxyde d'hydrogène alcalin en présence ou non d'oxygène gazeux, étapes au dioxyde de chlore ou à l'hypochlorite de sodium, extractions alcalines à la soude caustique.In another variant of the process according to the invention, it is possible, if it is desired to obtain high levels of whiteness, to follow the treatment with a peroxyacid by a sequence of traditional bleaching steps. with or without chlorine reagents. Examples of such steps are as follows: steps with gaseous oxygen or ozone, steps with alkaline hydrogen peroxide in the presence or absence of gaseous oxygen, steps with chlorine dioxide or sodium hypochlorite, alkaline extractions with caustic soda.
Les exemples qui suivent sont donnés dans le but d'illustrer l'invention, sans pour autant en limiter sa portée.The examples which follow are given for the purpose of illustrating the invention, without however limiting its scope.
Les mesures effectuées dans les exemples décrits ci-après ont été effectuées selon les normes qui suivent :
- - Indice kappa : TAPPI Method T236, CM85.
- - Viscosité : TAPPI Method T230, OM89.
- - Kappa index: TAPPI Method T236, CM85.
- - Viscosity: TAPPI Method T230, OM89.
Un échantillon de pâte kraft de pin Ponderosa d'indice kappa de 28,4 et de viscosité de 32,1 mPs a été soumis à une étape de délignification au moyen d'une solution aqueuse d'acide peracétique suivie d'une étape d'extraction alcaline en présence de peroxyde d'hydrogène (séquence Paa Ep).A sample of Ponderosa pine kraft pulp with a kappa index of 28.4 and a viscosity of 32.1 mPs was subjected to a delignification step using an aqueous solution of peracetic acid followed by a step of alkaline extraction in the presence of hydrogen peroxide (Paa Ep sequence).
Quatre essais ont été réalisés, deux dans les conditions de température et durée de l'art antérieur, notés exemples 1 R et 2R, et deux dans les conditions de l'invention (notés exemples 3 et 4). L'exemple 1 R, contrairement aux trois autres exemples, n'a pas comporté de lavage à l'eau de la pâte entre l'étape de traitement à l'acide peracétique et l'étape d'extraction alcaline. Le peroxyde d'hydrogène présent dans l'étape d'extraction alcaline de l'exemple 1 R provient par ailleurs du peroxyde d'hydrogène résiduaire de l'étape à l'acide peracétique qui a précédé. Dans l'exemple 4, on a, selon l'invention, fait précéder l'étape à l'acide peracétique par un prétraitement acide au moyen d'acide diéthylènetriaminepentaacétique ou DTPA (étape Q).Four tests were carried out, two under the temperature and duration conditions of the prior art, noted examples 1 R and 2R, and two under the conditions of the invention (noted examples 3 and 4). Example 1 R, unlike the other three examples, did not include washing the dough with water between the step of treatment with peracetic acid and the step of alkaline extraction. The hydrogen peroxide present in the alkaline extraction step of Example 1 R also comes from the residual hydrogen peroxide of the step with peracetic acid which preceded. In Example 4, according to the invention, the step with peracetic acid was preceded by an acid pretreatment using diethylenetriaminepentaacetic acid or DTPA (step Q).
Dans chacun de ces essais, on a mis en oeuvre 2,0 g d'acide peracétique pour 100 g de pâte sèche. L'acide peracétique employé était une solution aqueuse de qualité commerciale et contenait du peroxyde d'hydrogène à l'équilibre avec l'acide peracétique (2,6 b d'H202 pour 100 a de pâte sèche).In each of these tests, 2.0 g of peracetic acid were used per 100 g of dry paste. The peracetic acid employed was an aqueous solution of commercial quality and contained hydrogen peroxide in equilibrium with peracetic acid (2.6 b of H 2 O 2 per 100 a of dry paste).
Les conditions opératoires et les résultats obtenus figurent au tableau qui suit.
Par rapport à la pâte écrue, les résultats de délignification et de perte de viscosité après l'étape d'extraction alcaline sont les suivants :
Claims (10)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP97122629A EP0844328A3 (en) | 1991-10-04 | 1992-09-25 | Process for improving the selectivity in the delignification of a chemical pulp |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US77085991A | 1991-10-04 | 1991-10-04 | |
| US770859 | 1991-10-04 | ||
| US94283892A | 1992-09-10 | 1992-09-10 | |
| US942838 | 1997-10-02 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97122629A Division EP0844328A3 (en) | 1991-10-04 | 1992-09-25 | Process for improving the selectivity in the delignification of a chemical pulp |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0535741A1 true EP0535741A1 (en) | 1993-04-07 |
| EP0535741B1 EP0535741B1 (en) | 1998-07-08 |
Family
ID=27118364
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97122629A Withdrawn EP0844328A3 (en) | 1991-10-04 | 1992-09-25 | Process for improving the selectivity in the delignification of a chemical pulp |
| EP92202952A Revoked EP0535741B1 (en) | 1991-10-04 | 1992-09-25 | Process for improving the selectivity in the delignification of a chemical pulp |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97122629A Withdrawn EP0844328A3 (en) | 1991-10-04 | 1992-09-25 | Process for improving the selectivity in the delignification of a chemical pulp |
Country Status (9)
| Country | Link |
|---|---|
| EP (2) | EP0844328A3 (en) |
| JP (1) | JPH05195467A (en) |
| AT (1) | ATE168149T1 (en) |
| AU (1) | AU660326B2 (en) |
| DE (1) | DE69226143T2 (en) |
| ES (1) | ES2120984T3 (en) |
| FI (1) | FI924448A (en) |
| NZ (1) | NZ244592A (en) |
| PL (1) | PL171990B1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2269191A (en) * | 1992-07-29 | 1994-02-02 | Solvay Interox Ltd | Method of treating aqueous process liquors |
| WO1994012722A1 (en) * | 1992-11-27 | 1994-06-09 | Eka Nobel Ab | Process for bleaching of lignocellulose-containing pulp |
| DE19516151A1 (en) * | 1995-05-03 | 1996-11-07 | Sven Siegle | Process for the production of a pulp from cellulosic material, the pulp itself and its use |
| EP0794245B1 (en) * | 1996-03-04 | 2003-07-09 | The Procter & Gamble Company | Laundry pretreatment process and bleaching compositions |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69306974T3 (en) * | 1992-11-27 | 2004-01-08 | Eka Chemicals Ab | METHOD FOR THE DELIGRIFICATION OF LIGNOCELLULOSE-CONTAINING PULP |
| US6007678A (en) * | 1992-11-27 | 1999-12-28 | Eka Nobel Ab | Process for delignification of lignocellulose-containing pulp with an organic peracid or salts thereof |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1014536A (en) * | 1940-04-01 | 1952-08-18 | Du Pont | Wood pulp bleaching improvements |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1014536A (en) * | 1910-05-24 | 1912-01-09 | Minosaku Takahashi | Vessel-closure. |
| SE420430B (en) * | 1978-02-17 | 1981-10-05 | Mo Och Domsjoe Ab | PROCEDURE FOR WHEATING AND EXTRACTION OF LIGNOCELLULOSALLY MATERIALS WITH PEROXID CONTAINING BLACKS |
| DE3005947B1 (en) * | 1980-02-16 | 1981-01-29 | Degussa | Process for bleaching pulp using organic peracid |
| US4793898A (en) * | 1985-02-22 | 1988-12-27 | Oy Keskuslaboratorio - Centrallaboratorium Ab | Process for bleaching organic peroxyacid cooked material with an alkaline solution of hydrogen peroxide |
-
1992
- 1992-09-25 DE DE69226143T patent/DE69226143T2/en not_active Expired - Fee Related
- 1992-09-25 EP EP97122629A patent/EP0844328A3/en not_active Withdrawn
- 1992-09-25 ES ES92202952T patent/ES2120984T3/en not_active Expired - Lifetime
- 1992-09-25 EP EP92202952A patent/EP0535741B1/en not_active Revoked
- 1992-09-25 AT AT92202952T patent/ATE168149T1/en not_active IP Right Cessation
- 1992-09-28 AU AU25382/92A patent/AU660326B2/en not_active Ceased
- 1992-10-01 PL PL92296122A patent/PL171990B1/en unknown
- 1992-10-02 NZ NZ244592A patent/NZ244592A/en unknown
- 1992-10-02 FI FI924448A patent/FI924448A/en not_active Application Discontinuation
- 1992-10-05 JP JP4266321A patent/JPH05195467A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1014536A (en) * | 1940-04-01 | 1952-08-18 | Du Pont | Wood pulp bleaching improvements |
Non-Patent Citations (1)
| Title |
|---|
| ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY, vol. 53, no. 4, Octobre 1982, APPLETON (US) page 499, YOTSUYA, M. et al.: "Bleaching of pulp with peroxide" * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2269191A (en) * | 1992-07-29 | 1994-02-02 | Solvay Interox Ltd | Method of treating aqueous process liquors |
| WO1994012722A1 (en) * | 1992-11-27 | 1994-06-09 | Eka Nobel Ab | Process for bleaching of lignocellulose-containing pulp |
| DE19516151A1 (en) * | 1995-05-03 | 1996-11-07 | Sven Siegle | Process for the production of a pulp from cellulosic material, the pulp itself and its use |
| US6183597B1 (en) | 1995-05-03 | 2001-02-06 | Natural Pulping Ag | Method of producing a pulp from cellulosic material using formic acid and hydrogen peroxide |
| EP0794245B1 (en) * | 1996-03-04 | 2003-07-09 | The Procter & Gamble Company | Laundry pretreatment process and bleaching compositions |
Also Published As
| Publication number | Publication date |
|---|---|
| NZ244592A (en) | 1994-02-25 |
| FI924448A (en) | 1993-04-05 |
| EP0844328A2 (en) | 1998-05-27 |
| JPH05195467A (en) | 1993-08-03 |
| FI924448A0 (en) | 1992-10-02 |
| DE69226143D1 (en) | 1998-08-13 |
| PL171990B1 (en) | 1997-07-31 |
| AU2538292A (en) | 1993-04-22 |
| PL296122A1 (en) | 1993-06-28 |
| AU660326B2 (en) | 1995-06-22 |
| ES2120984T3 (en) | 1998-11-16 |
| DE69226143T2 (en) | 1999-02-25 |
| EP0535741B1 (en) | 1998-07-08 |
| EP0844328A3 (en) | 1998-07-15 |
| ATE168149T1 (en) | 1998-07-15 |
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