EP0190723A1 - Process for improving the mechanical properties of a chemical or semi-chemical bagasse paper pulp - Google Patents

Process for improving the mechanical properties of a chemical or semi-chemical bagasse paper pulp Download PDF

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Publication number
EP0190723A1
EP0190723A1 EP86101427A EP86101427A EP0190723A1 EP 0190723 A1 EP0190723 A1 EP 0190723A1 EP 86101427 A EP86101427 A EP 86101427A EP 86101427 A EP86101427 A EP 86101427A EP 0190723 A1 EP0190723 A1 EP 0190723A1
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Prior art keywords
chemical
oxidizing agent
treatment
bagasse
acid
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EP86101427A
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German (de)
French (fr)
Inventor
Jacques Dr. Hageman
Lucien Plumet
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Solvay Chimie SA
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Interox SA
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Publication of EP0190723A1 publication Critical patent/EP0190723A1/en
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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

Definitions

  • the present invention relates to a method for improving the mechanical properties of chemical or semi-chemical bagasse pulp containing marrow.
  • Bagasse is a lignocellulosic material which generally contains a significant amount of marrow. This is made up of a cellulosic constituent, the parenchyma, which does not have the fibrous structure and cannot be used for papermaking.
  • the bagasse Before cooking for the pulping, the bagasse generally undergoes a pretreatment of mechanical purification aiming at eliminating part of the marrow which it contains.
  • Chemical and semi-chemical paper pulps made from cellulosic materials, in particular bagasse pulps are generally subjected to treatments with oxidizing agents to reduce their lignin content and improve their whiteness. These known methods are generally sequential treatments which comprise several successive bleaching stages, possibly interspersed with washing, dilution and / or concentration stages. To achieve the desired residual lignin level and whiteness, it has thus been proposed to subject the chemical and semi-chemical bagasse pastes to the oxidizing action of chlorine in an acid medium and then to follow this step with an extraction step.
  • Patent US-A-4404061 JJ CAEL, INTERNATIONAL PAPER Co discloses a process for delignification and bleaching of lignocellulosic materials using peroxymonosulfuric acid or a salt of this acid which makes it easier to separate the cellulose non-cellulosic materials (x column 1, lines 50 to 56 and lines 25 to 28 x). Bagasse is cited among the lignocellulosic raw materials (x column 2, line 61 x).
  • the invention overcomes the disadvantages of the known processes by providing a new process for improving the mechanical properties of chemical pulps and semi-chemical bagasse containing a high proportion of marrow, which achieves high brightness levels decreasing appreciably the coloring as well as the polluting load of the effluents.
  • the invention relates to a method for improving the mechanical properties of a chemical or semi-chemical bagasse dough containing at least 25% by weight of marrow, according to which the dough is subjected to a treatment by means of an oxidizing agent; according to the invention, the oxidizing agent is selected from persulfuric acids and their salts.
  • bagasse is intended to denote the fibrous vascular bundles of the stems of plants other than wood belonging to the class of monocots such as cereal straws, sugar cane and cane from EUR, bamboo, esparto, corn stalks, rushes and reeds as well as sabadilla.
  • the invention applies very particularly to crushed stems of sugar cane in the state in which they arise after the sugar extraction operation.
  • the method according to the invention is intended for all chemical or semi-chemical bagasse pastes, that is to say on the one hand chemical pastes having undergone a delignifying treatment in the presence of chemical reagents such as sodium in alkaline medium (kraft or sulphate cooking), sulfur dioxide or a metal salt of sulfurous acid in acid medium (sulphite cooking), a salt of sulfurous acid in neutral medium (semi-chemical cooking in neutral sulfite also called NSSC) and on the other hand semi-chemical pastes obtained by treatment with cold caustic soda followed by mechanical defibration.
  • chemical reagents such as sodium in alkaline medium (kraft or sulphate cooking), sulfur dioxide or a metal salt of sulfurous acid in acid medium (sulphite cooking), a salt of sulfurous acid in neutral medium (semi-chemical cooking in neutral sulfite also called NSSC) and on the other hand semi-chemical pastes obtained by treatment with cold caustic soda followed by mechanical defibration.
  • the invention is particularly intended for pasta with a high marrow content, such as those where this content is between 25 and 40% and preferably between 30 and 40%.
  • the treatment of the dough consists in subjecting it to an oxidizing agent selected from persulfuric acids and their salts.
  • an oxidizing agent selected from persulfuric acids and their salts.
  • all persulfuric acids in the liquid state or in aqueous or organic solution may be suitable, as well as all the salts of these acids.
  • Peroxymonosulfuric acid also called Caro acid, is preferred.
  • the quantity of oxidizing agent which it is advisable to use depends on a large number of parameters, among which appear in particular the nature of the selected bagasse, the purification pretreatment which it has undergone, the technique selected for pulping, the oxidizing agent selected, any subsequent steps in the bleaching sequence and the degree of whiteness sought.
  • the oxidizing agent is generally used in sufficient quantity health so that at the end of the complete whitening sequence, the dough has acquired a high final whiteness, most often greater than 80 degrees from the ISO standard.
  • Caro acid in an amount of between 0.1 and 8 g per 100 g of dry paste. Most often, it is between 0.5 and 5 g / 100 g of dry dough.
  • the temperature at which the treatment with the oxidizing agent is carried out is not critical. It is generally in the range from 298 to 343 K. The selection of an optimum temperature value depends on the possibilities of the apparatus used. Generally low temperatures in the range of 298 to 313 K are preferred.
  • the consistency or weight content of the mixture formed from the bagasse dough and the oxidizing agent is generally, in the process according to the invention, at least 2X and most often at least 3X. It generally does not exceed 40% and more often than not 30%.
  • the treatment of bagasse dough with the oxidizing agent can be carried out in the presence of additives such as, for example, compounds of an acidic nature or pH regulators such as buffers.
  • the acidic compounds can be sulfuric, hydrochloric, nitric or orthophosphoric acids. Sulfuric acid is preferred. Bicarbonates of alkali metals or of ammonium can be chosen alone or as a mixture with a compound with an acidic character as pH regulators.
  • the process according to the invention is generally carried out in the presence of sulfuric acid.
  • the dose of sulfuric acid is generally 0.1 to 20% of the weight of dry bagasse. It is also possible to use other additives such as sequestering and stabilizing agents, surfactants, agents capable of protecting the cellulosic chains to prevent their depolymerization, wetting agents, activating agents and anti-corrosion agents.
  • the duration of the treatment with the oxidizing agent is variable and depends on various factors, in particular the nature of the bagasse, the technique used for pulping, the oxidizing agent selected and the working temperature. In principle, there is no maximum limit to the duration of treatment with the oxidizing agent and, if care is taken to exceed a minimum required to reach the physico-chemical equilibria and often being around 50 at 80 minutes, it is safe for the dough to prolong the treatment, for example when it is imposed by the residence time in an existing apparatus. In general, the duration of the treatment with the oxidizing agent is from 15 to 150 minutes and most often from 60 to 105 minutes.
  • the oxidizing agent used is peroxymonosulfuric acid or Caro acid.
  • the Caro acid is preferably used in the form of a solution.
  • the solvent is most often water.
  • the amount of solvent is advantageously at least 0.1% and generally does not exceed 99.5% of the total weight of the mixture which essentially comprises bagasse paste, the solvent, Caro acid and any additives.
  • the solvent is water, it is used in an amount of at least 0.5X and most often at least 1% of the total weight of the mixture. In general, the amount of water used does not exceed 95%, most often not 90X and preferably not 85X of the total weight of the mixture.
  • the treatment with Caro acid is carried out under acidic or neutral pH conditions in a wide range of pH values ranging from 1 to 7.
  • the choice of a value particular pH must be done according to the type of cooking to which the dough was subjected and according to the content of it in alkali or acid.
  • Preferred pH values are between 1 and 3.
  • the treatment with the oxidizing agent can be followed by a conventional bleaching sequence using bleaching agents well known for bleaching bagasse pulp such as chlorine in an acid medium (step C), caustic soda (step E of alkaline extraction), sodium or calcium hypochlorite in alkaline medium (step H), hydrogen peroxide in alkaline medium (step P) and chlorine dioxide in acid medium (step D).
  • bleaching agents well known for bleaching bagasse pulp such as chlorine in an acid medium (step C), caustic soda (step E of alkaline extraction), sodium or calcium hypochlorite in alkaline medium (step H), hydrogen peroxide in alkaline medium (step P) and chlorine dioxide in acid medium (step D).
  • bleaching agents well known for bleaching bagasse pulp such as chlorine in an acid medium (step C), caustic soda (step E of alkaline extraction), sodium or calcium hypochlorite in alkaline medium (step H), hydrogen peroxide in alkaline medium (step P) and chlorine dioxide in acid medium (step D).
  • the application of the pretreatment, with the oxidizing agent, in accordance with the process according to the invention most often makes it possible to substantially reduce the amounts of these reagents, particularly those of chlorinated reagents. This results in the significant advantage of a reduction in the content of chloride ions and of chlorinated organic compounds in the effluents of the bleaching installation and therefore a considerable reduction in environmental pollution.
  • the method according to the invention makes it possible to obtain pasta with a better degree of whiteness than those obtained by the methods of the prior art. All other things remaining equal, it thus allows the use of bagasse whose residual marrow content is higher, which reduces the cost of the pretreatment of purification or demoelling. In general, bagasse with a residual marrow content of between 30 and 40% is suitable in most cases.
  • a chemical paste from Iraqi sugar cane bagasse which has been cooked with lime (initial whiteness 37.6 ° ISO, kappa index 39.6) and still containing 25 to 35X by weight of marrow has been subjected to a conventional whitening sequence in four stages : CEHH (example 1R) or PCEH (example 2R) under the following operating conditions. The percentages of reagents are given relative to the weight of the dry paste.
  • Table II shows the results of the evaluations carried out on the bleached pasta according to the same methods as in Examples 1R and 2R.
  • the notation C A symbolizes the treatment with Caro acid.
  • Examples 3 and 4 also show that it is possible, with a whiteness equal to that obtained with the reference CEHH sequence (example 1R), to obtain, with the process according to the invention, the elimination of the second step H, a pulp with better solidity, a reduction of 8 to 5.2% (example 3) and from 8 to 4.75% (example 4) of the total load of active chlorine and less pollution of the effluents.

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  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
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Abstract

The process consists in subjecting the chemical or semichemical bagasse pulp containing pith to a treatment with persulphuric acid or a salt of this acid. No figure.

Description

La présente invention concerne un procédé pour l'amélioration des propriétés mécaniques des pâtes à papier chimiques ou semi-chimiques de bagasse contenant de la moelle.The present invention relates to a method for improving the mechanical properties of chemical or semi-chemical bagasse pulp containing marrow.

La bagasse est une matière lignocellulosique qui contient généralement une quantité non négligeable de moelle. Celle-ci est formée d'un constituant cellulosique, le parenchyme, qui ne possède pas la structure fibreuse et ne peut être utilisé pour la fabrication du papier.Bagasse is a lignocellulosic material which generally contains a significant amount of marrow. This is made up of a cellulosic constituent, the parenchyma, which does not have the fibrous structure and cannot be used for papermaking.

Avant la cuisson pour la mise en pâte, la bagasse subit généralement un prétraitement d'épuration mécanique ayant pour but d'éliminer une partie de la moelle qu'elle contient.Before cooking for the pulping, the bagasse generally undergoes a pretreatment of mechanical purification aiming at eliminating part of the marrow which it contains.

Les pâtes à papier chimiques et semi-chimiques fabriquées à partir de matières cellulosiques, en particulier les pâtes de bagasse, sont généralement soumises à des traitements avec des agents oxydants pour réduire leur teneur en lignine et améliorer leur blancheur. Ces procédés connus sont généralement des traitements séquentiels qui comportent plusieurs étapes successives de blanchiment, éventuellement entrecoupées d'étapes de lavage, de dilution et/ou de concentration. Pour parvenir au taux de lignine résiduelle et à la blancheur désirés, on a ainsi proposé de soumettre les pâtes chimiques et semi-chimiques de bagasse à l'action oxydante du chlore en milieu acide puis de faire suivre cette étape par une étape d'extraction alcaline suivie d'une étape oxydante à l'hypochlorite en milieu alcalin de façon à réaliser la séquence de blanchiment-délignification symbolisée par l'abréviation CEH (PULP AND PAPER INTERNATIONAL, juin 1975, San Francisco, HEINZ BENZINGER "Today's bagasse technology" pages 42 à 44 et page 57 * page 44, dernier paragraphe et page 57, colonne de gauche, lignes 1 à 14 *). D'autres séquences mettant en oeuvre du dioxyde de chlore (étape D) ou du peroxyde d'hydrogène (étape P) ont également été proposées (TAPPI JOURNAL, Vol. 40, août 1957, Altanta D.D. HINRICHS et al. "Sugarcane Bagasse as a Fibrous Papermaking Material VIII. Bleaching of Hawaian Bagasse Pulps", pages 637 à 645 * 1er paragraphe, lignes 3 et 4 et 10 à 18 *).Chemical and semi-chemical paper pulps made from cellulosic materials, in particular bagasse pulps, are generally subjected to treatments with oxidizing agents to reduce their lignin content and improve their whiteness. These known methods are generally sequential treatments which comprise several successive bleaching stages, possibly interspersed with washing, dilution and / or concentration stages. To achieve the desired residual lignin level and whiteness, it has thus been proposed to subject the chemical and semi-chemical bagasse pastes to the oxidizing action of chlorine in an acid medium and then to follow this step with an extraction step. alkaline followed by an oxidative step with hypochlorite in an alkaline medium so as to achieve the bleaching-delignification sequence symbolized by the abbreviation CEH (PULP AND PAPER INTERNATIONAL, June 1975, San Francisco, HEINZ BENZINGER "Today's bagasse technology" pages 42 to 44 and page 57 * page 44, last paragraph and page 57, left column, lines 1 to 14 *). Other sequences putting chlorine dioxide (step D) or hydrogen peroxide (step P) have also been proposed (TAPPI JOURNAL, Vol. 40, August 1957, Altanta DD HINRICHS et al. "Sugarcane Bagasse as a Fibrous Papermaking Material VIII . Bleaching of Hawaian Bagasse Pulps ", pages 637 to 645 * 1st paragraph, lines 3 and 4 and 10 to 18 *).

Ces procédés de blanchiment et de délignification connus ne parviennent habituellement pas à fournir des pâtes de blancheur et de propriétés mécaniques élevées. En outre, ils mettent en oeuvre des quantités importantes de réactifs chlorés qui sont responsables de la coloration intense et du caractère polluant des effluents.These known bleaching and delignification processes usually fail to provide pulps of whiteness and high mechanical properties. In addition, they use large quantities of chlorinated reagents which are responsible for the intense coloring and the polluting character of the effluents.

Le brevet US-A-4404061 (J.J. CAEL, INTERNATIONAL PAPER Co) divulgue un procédé de délignification et de blanchiment de matières ligno-cellulosiques au moyen d'acide peroxymonosulfurique ou d'un sel de cet acide qui permet de séparer plus facilement la cellulose des matériaux non cellulosiques (x colonne 1, lignes 50 à 56 et lignes 25 à 28 x). La bagasse est citée parmi les matières premières ligno-cellulosiques (x colonne 2, ligne 61 x).Patent US-A-4404061 (JJ CAEL, INTERNATIONAL PAPER Co) discloses a process for delignification and bleaching of lignocellulosic materials using peroxymonosulfuric acid or a salt of this acid which makes it easier to separate the cellulose non-cellulosic materials (x column 1, lines 50 to 56 and lines 25 to 28 x). Bagasse is cited among the lignocellulosic raw materials (x column 2, line 61 x).

L'invention remédie aux inconvénients des procédés connus, en fournissant un procédé nouveau d'amélioration des propriétés mécaniques de pâtes chimiques et semi-chimiques de bagasse contenant' une forte proportion de moelle, qui permette d'atteindre de hauts niveaux de blancheur en diminuant sensiblement la coloration ainsi que la charge polluante des effluents.The invention overcomes the disadvantages of the known processes by providing a new process for improving the mechanical properties of chemical pulps and semi-chemical bagasse containing a high proportion of marrow, which achieves high brightness levels decreasing appreciably the coloring as well as the polluting load of the effluents.

A cet effet, l'invention concerne un procédé pour l'amélioration des propriétés mécaniques d'une pâte chimique ou semi-chimique de bagasse contenant au moins 25 Z en poids de moelle selon lequel on soumet la pâte à un traitement au moyen d'un agent oxydant ; selon l'invention, on sélectionne l'agent oxydant parmi les acides persulfuriques et leurs sels.To this end, the invention relates to a method for improving the mechanical properties of a chemical or semi-chemical bagasse dough containing at least 25% by weight of marrow, according to which the dough is subjected to a treatment by means of an oxidizing agent; according to the invention, the oxidizing agent is selected from persulfuric acids and their salts.

Selon l'invention, par le terme bagasse on entend désigner les faisceaux vasculaires fibreux des tiges de végétaux autres que le bois appartenant à la classe des monocotylédones comme les pailles de céréales, la canne à sucre et la canne de Provence, le bambou, l'esparto, les tiges de mais, les joncs et roseaux ainsi que la sabadille. L'invention s'applique tout particulièrement aux tiges écrasées de canne à sucre dans l'état où elles se présentent après l'opération d'extraction du sucre.According to the invention, the term bagasse is intended to denote the fibrous vascular bundles of the stems of plants other than wood belonging to the class of monocots such as cereal straws, sugar cane and cane from Provence, bamboo, esparto, corn stalks, rushes and reeds as well as sabadilla. The invention applies very particularly to crushed stems of sugar cane in the state in which they arise after the sugar extraction operation.

Le procédé selon l'invention s'adresse à toutes les pâtes de bagasse chimiques ou semi-chimiques, c'est-à-dire d'une part les pâtes chimiques 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), un sel de l'acide sulfureux en milieu neutre (cuisson semi-chimique au sulfite neutre encore appelée NSSC) et d'autre part les pâtes semi-chimiques obtenues par traitement à la soude caustique à froid suivi d'une défibrage mécanique.The method according to the invention is intended for all chemical or semi-chemical bagasse pastes, that is to say on the one hand chemical pastes having undergone a delignifying treatment in the presence of chemical reagents such as sodium in alkaline medium (kraft or sulphate cooking), sulfur dioxide or a metal salt of sulfurous acid in acid medium (sulphite cooking), a salt of sulfurous acid in neutral medium (semi-chemical cooking in neutral sulfite also called NSSC) and on the other hand semi-chemical pastes obtained by treatment with cold caustic soda followed by mechanical defibration.

L'invention s'adresse particulièrement à des pâtes à teneur élevée en moelle, comme celles où cette teneur est comprise entre 25 et 40% et de préférence entre 30 et 40%.The invention is particularly intended for pasta with a high marrow content, such as those where this content is between 25 and 40% and preferably between 30 and 40%.

Selon l'invention, le traitement de la pâte consiste à la soumettre à un agent oxydant sélectionné parmi les acides persulfuriques et leurs sels. En principe, tous les acides persulfuriques à l'état liquide ou en solution aqueuse ou organique peuvent convenir, ainsi que tous les sels de ces acides. En pratique, on donne la préférence à l'acide peroxymonosulfurique et aux sels d'ammonium, des métaux alcalins et des métaux alcalino-terreux des acides persulfuriques. L'acide peroxymonosulfurique, également appelé acide de Caro, a la préférence.According to the invention, the treatment of the dough consists in subjecting it to an oxidizing agent selected from persulfuric acids and their salts. In principle, all persulfuric acids in the liquid state or in aqueous or organic solution may be suitable, as well as all the salts of these acids. In practice, preference is given to peroxymonosulfuric acid and to ammonium salts, alkali metals and alkaline earth metals of persulfuric acids. Peroxymonosulfuric acid, also called Caro acid, is preferred.

Dans le procédé selon l'invention, la quantité d'agent oxydant qu'il convient de mettre en oeuvre dépend d'un grand nombre de paramètres, parmi lesquels figurent notamment la nature de la bagasse sélectionnée, le prétraitement d'épuration qu'elle a subi, la technique sélectionnée pour la mise en pâte, l'agent oxydant sélectionné, les étapes ultérieures éventuelles de la séquence de blanchiment et le degré de blancheur recherché. L'agent oxydant est généralement mis en oeuvre en quantité suffisante pour qu'à l'issue de la séquence complète de blanchiment, la pâte ait acquis une blancheur finale élevée, le plus souvent supérieure à 80 degrés de la norme ISO. On obtient généralement de bons résultats en mettant en oeuvre de l'acide de Caro en quantité comprise entre 0,1 et 8 g pour 100 g de pâte sèche. Le plus souvent, elle se situe entre 0,5 et 5 g/100 g de pâte sèche.In the process according to the invention, the quantity of oxidizing agent which it is advisable to use depends on a large number of parameters, among which appear in particular the nature of the selected bagasse, the purification pretreatment which it has undergone, the technique selected for pulping, the oxidizing agent selected, any subsequent steps in the bleaching sequence and the degree of whiteness sought. The oxidizing agent is generally used in sufficient quantity health so that at the end of the complete whitening sequence, the dough has acquired a high final whiteness, most often greater than 80 degrees from the ISO standard. Generally good results are obtained by using Caro acid in an amount of between 0.1 and 8 g per 100 g of dry paste. Most often, it is between 0.5 and 5 g / 100 g of dry dough.

La température à laquelle on effectue le traitement avec l'agent oxydant n'est pas critique. Elle se situe généralement dans la plage allant de 298 à 343 K. La sélection d'une valeur optimum de la température dépend des possibilités de l'appareillage utilisé. On préfère généralement des températures peu élevées situées dans la plage de 298 à 313 K.The temperature at which the treatment with the oxidizing agent is carried out is not critical. It is generally in the range from 298 to 343 K. The selection of an optimum temperature value depends on the possibilities of the apparatus used. Generally low temperatures in the range of 298 to 313 K are preferred.

La consistance ou teneur pondérale du mélange formé de la pâte de bagasse et de l'agent oxydant est en général, dans le procédé selon l'invention, d'au moins 2X et le plus souvent d'au moins 3X. Elle ne dépasse en général pas 40% et le plus souvent pas 30%.The consistency or weight content of the mixture formed from the bagasse dough and the oxidizing agent is generally, in the process according to the invention, at least 2X and most often at least 3X. It generally does not exceed 40% and more often than not 30%.

Dans le procédé selon l'invention, le traitement de la pâte de bagasse avec l'agent oxydant peut être opéré en présence d'additifs tels que, par exemple, des composés à caractère acide ou des régulateurs de pH tels que des tampons. Les composés à caractère acide peuvent être les acides sulfurique, chlorhydrique, nitrique ou orthophosphorique. L'acide sulfurique est préféré. Des bicarbonates de métaux alcalins ou d'ammonium peuvent être choisis seuls ou en mélange avec un composé à caractère acide comme régulateurs de pH. Le procédé selon l'invention est en général réalisé en présence d'acide sulfurique. La dose d'acide sulfurique est en général de 0,1 à 20% du poids de bagasse sèche. On peut également mettre en oeuvre d'autres additifs tels que des agents séquestrants et stabilisants, des agents tensioactifs, des agents capables de protéger les chaînes cellulosiques pour éviter leur dépolymérisation, des agents mouillants, des agents activants et des agents anti-corrosion.In the process according to the invention, the treatment of bagasse dough with the oxidizing agent can be carried out in the presence of additives such as, for example, compounds of an acidic nature or pH regulators such as buffers. The acidic compounds can be sulfuric, hydrochloric, nitric or orthophosphoric acids. Sulfuric acid is preferred. Bicarbonates of alkali metals or of ammonium can be chosen alone or as a mixture with a compound with an acidic character as pH regulators. The process according to the invention is generally carried out in the presence of sulfuric acid. The dose of sulfuric acid is generally 0.1 to 20% of the weight of dry bagasse. It is also possible to use other additives such as sequestering and stabilizing agents, surfactants, agents capable of protecting the cellulosic chains to prevent their depolymerization, wetting agents, activating agents and anti-corrosion agents.

La durée du traitement avec l'agent oxydant est variable et dépend de divers facteurs, notamment de la nature de la bagasse, de la technique utilisée pour la mise en pâte, de l'agent oxydant sélectionné et de la température de travail. En principe, il n'y a pas de limite maximum à la durée du traitement avec l'agent oxydant et, si l'on prend soin de dépasser un minimum requis pour atteindre les équilibres physico-chimiques et se situant souvent aux environs de 50 à 80 minutes, on peut sans danger pour la pâte prolonger le traitement, par exemple lorsqu'il est imposé par le temps de séjour dans un appareillage existant. En général, la durée du traitement avec l'agent oxydant est de 15 à 150 minutes et le plus souvent de 60 à 105 minutes.The duration of the treatment with the oxidizing agent is variable and depends on various factors, in particular the nature of the bagasse, the technique used for pulping, the oxidizing agent selected and the working temperature. In principle, there is no maximum limit to the duration of treatment with the oxidizing agent and, if care is taken to exceed a minimum required to reach the physico-chemical equilibria and often being around 50 at 80 minutes, it is safe for the dough to prolong the treatment, for example when it is imposed by the residence time in an existing apparatus. In general, the duration of the treatment with the oxidizing agent is from 15 to 150 minutes and most often from 60 to 105 minutes.

Dans une forme de réalisation préférée du procédé selon l'invention, l'agent oxydant mis en oeuvre est de l'acide peroxymonosulfurique ou acide de Caro. Dans cette forme de réalisation du procédé selon l'invention, l'acide de Caro est de préférence mis en oeuvre à l'état d'une solution.In a preferred embodiment of the process according to the invention, the oxidizing agent used is peroxymonosulfuric acid or Caro acid. In this embodiment of the process according to the invention, the Caro acid is preferably used in the form of a solution.

Le solvant est le plus souvent l'eau. La quantité de solvant est avantageusement d'au moins 0,1% et ne dépasse en général pas 99,5% du poids total du mélange qui comprend essentiellement la pâte de bagasse, le solvant, l'acide de Caro et les additifs éventuels. Lorsque le solvant est l'eau, il est mis en oeuvre en quantité d'au moins 0,5X et le plus souvent d'au moins 1% du poids total du mélange. En général, la quantité d'eau mise en oeuvre ne dépasse pas 95%, le plus souvent pas 90X et de préférence pas 85X du poids total du mélange.The solvent is most often water. The amount of solvent is advantageously at least 0.1% and generally does not exceed 99.5% of the total weight of the mixture which essentially comprises bagasse paste, the solvent, Caro acid and any additives. When the solvent is water, it is used in an amount of at least 0.5X and most often at least 1% of the total weight of the mixture. In general, the amount of water used does not exceed 95%, most often not 90X and preferably not 85X of the total weight of the mixture.

Dans cette forme de réalisation de l'invention, le traitement à l'acide de Caro est effectué dans des conditions acides ou neutres de pH dans une large gamme de valeurs de pH allant de 1 jusqu'à 7. Le choix d'une valeur particulière de pH doit se faire en fonction du type de cuisson à laquelle la pâte a été soumise et en fonction de la teneur de celle-ci en alcali ou en acide. Les valeurs préférées de pH se situent entre 1 et 3.In this embodiment of the invention, the treatment with Caro acid is carried out under acidic or neutral pH conditions in a wide range of pH values ranging from 1 to 7. The choice of a value particular pH must be done according to the type of cooking to which the dough was subjected and according to the content of it in alkali or acid. Preferred pH values are between 1 and 3.

Dans le procédé selon l'invention, le traitement avec l'agent oxydant peut être suivi par une séquence classique de blanchiment mettant en oeuvre des agents de blanchiment bien connus pour blanchir la pâte de bagasse comme le chlore en milieu acide (étape C), la soude caustique (étape E d'extraction alcaline), l'hypochlorite de sodium ou de calcium en milieu alcalin (étape H), le peroxyde d'hydrogène en milieu alcalin (étape P) et le dioxyde de chlore en milieu acide (étape D). Les séquences CEH ou CEHH sont en général préférées. Les quantités de réactifs utilisées à chacune de ces étapes sont variables. Elles doivent être ajustées soigneusement en fonction de l'essence de bagasse utilisée et de l'objectif de blancheur visé.In the method according to the invention, the treatment with the oxidizing agent can be followed by a conventional bleaching sequence using bleaching agents well known for bleaching bagasse pulp such as chlorine in an acid medium (step C), caustic soda (step E of alkaline extraction), sodium or calcium hypochlorite in alkaline medium (step H), hydrogen peroxide in alkaline medium (step P) and chlorine dioxide in acid medium (step D). The CEH or CEHH sequences are generally preferred. The quantities of reagents used in each of these stages are variable. They must be carefully adjusted according to the type of bagasse used and the target whiteness.

L'application du traitement préalable, avec l'agent oxydant, conformément au procédé selon l'invention permet le plus souvent de réduire sensiblement les quantités de ces réactifs, particulièrement celles des réactifs chlorés. Il en résulte l'avantage important d'une diminution de la teneur en ions chlorure et en composés organiques chlorés des effluents de l'installation de blanchiment et partant une réduction considérable de la pollution de l'environnement.The application of the pretreatment, with the oxidizing agent, in accordance with the process according to the invention most often makes it possible to substantially reduce the amounts of these reagents, particularly those of chlorinated reagents. This results in the significant advantage of a reduction in the content of chloride ions and of chlorinated organic compounds in the effluents of the bleaching installation and therefore a considerable reduction in environmental pollution.

Par ailleurs, le procédé selon l'invention permet l'obtention de pâtes d'un meilleur degré de blancheur que celles obtenues par les procédés de l'art antérieur. Toutes autres choses restant égales, il permet ainsi la mise en oeuvre de bagasses dont la teneur résiduelle en moelle est plus élevée, ce qui réduit le coût du prétraitement d'épuration ou de démoellage. D'une manière générale, des bagasses dont la teneur résiduelle en moelle est comprise entre 30 et 40% conviennent bien dans la majorité des cas.Furthermore, the method according to the invention makes it possible to obtain pasta with a better degree of whiteness than those obtained by the methods of the prior art. All other things remaining equal, it thus allows the use of bagasse whose residual marrow content is higher, which reduces the cost of the pretreatment of purification or demoelling. In general, bagasse with a residual marrow content of between 30 and 40% is suitable in most cases.

Les exemples de réalisation pratique qui suivent ont pour but d'illustrer l'invention sans pour autant en limiter la portée.The purpose of the examples of practical embodiment which follow is to illustrate the invention without however limiting its scope.

Exemples 1R et 2R non conformes à l'inventionExamples 1R and 2R not in accordance with the invention

Une pâte chimique de bagasse de canne à sucre d'Irak ayant subi une cuisson à la chaux (blancheur initiale 37,6° ISO, indice kappa 39,6) et contenant encore 25 à 35X en poids de moelle a été soumise à une séquence de blanchiment classique en quatre étapes : CEHH (exemple 1R) ou PCEH (exemple 2R) dans les conditions opératoires suivantes. Les pourcentages de réactifs sont donnés par rapport au poids de la pâte sèche.

Figure imgb0001
A chemical paste from Iraqi sugar cane bagasse which has been cooked with lime (initial whiteness 37.6 ° ISO, kappa index 39.6) and still containing 25 to 35X by weight of marrow has been subjected to a conventional whitening sequence in four stages : CEHH (example 1R) or PCEH (example 2R) under the following operating conditions. The percentages of reagents are given relative to the weight of the dry paste.
Figure imgb0001

A l'issue de chacune des deux séquences de blanchiment, on a soumis la pâte aux évaluations qui suivent :

  • - blancheur : selon norme ISO 2470
  • - viscosité : selon norme TAPPI T230
  • - taux de lignine : indice kappa selon norme SCAN Cl:59
  • - égouttabilité : selon norme NF Q 50-003
  • - résistance à la traction et longueur de rupture : selon norme ISO 1924
  • - résistance au déchirement : selon norme ISO 1974
  • - résistance à l'éclatement : selon norme ISO 2758
  • - résistance au pliage : selon norme ASTM D643
  • - couleur des effluents : selon méthode NCASI (National Council of Air and Stream Improvement, Gainsville, Florida, USA)
  • - demande chimique en oxygène des effluents (DCO) : selon méthode HACH (Hach Reactor Digestion COD).
At the end of each of the two bleaching sequences, the pulp was subjected to the following evaluations:
  • - whiteness: according to ISO 2470 standard
  • - viscosity: according to TAPPI T230 standard
  • - lignin level: kappa index according to SCAN Cl standard: 59
  • - drainability: according to standard NF Q 50-003
  • - tensile strength and breaking length: according to ISO 1924 standard
  • - tear resistance: according to ISO 1974 standard
  • - burst strength: according to ISO 2758 standard
  • - folding resistance: according to ASTM D643 standard
  • - effluent color: according to NCASI method (National Council of Air and Stream Improvement, Gainsville, Florida, USA)
  • - chemical oxygen demand of effluents (COD): according to the HACH method (Hach Reactor Digestion COD).

Les résultats ont été portés au tableau I.

Figure imgb0002
The results are shown in Table I.
Figure imgb0002

L'indice de qualité (IQ) a été calculé comme suit :

  • IQ = (ID.IE)0'5 où ID et IE sont respectivement les indices de déchirement et d'éclatement.
The quality index (QI) was calculated as follows:
  • IQ = (ID.IE) 0 ' 5 where ID and IE are respectively the indices of tearing and bursting.

Exemples 3 à 6 selon l'inventionExamples 3 to 6 according to the invention

La même pâte de bagasse que celle utilisée aux exemples 1R et 2R a été traitée conformément au procédé selon l'invention par une solution aqueuse d'acide de Caro puis soumise à une séquence de blanchiment identique en trois étapes CEH analogues à celles des exemples 1R et 2R.The same bagasse paste as that used in Examples 1R and 2R was treated in accordance with the method according to the invention with an aqueous solution of Caro acid and then subjected to an identical bleaching sequence in three CEH steps similar to those of Examples 1R and 2R.

Les conditions opératoires ont été les suivantes :

Figure imgb0003
The operating conditions were as follows:
Figure imgb0003

Le tableau II reprend les résultats des évaluations effectuées sur les pâtes blanchies selon les mêmes méthodes qu'aux exemples 1R et 2R. La notation CA symbolise le traitement à l'acide de Caro.

Figure imgb0004
Table II shows the results of the evaluations carried out on the bleached pasta according to the same methods as in Examples 1R and 2R. The notation C A symbolizes the treatment with Caro acid.
Figure imgb0004

La comparaison des résultats d'évaluation des propriétés mécaniques des pâtes blanchies au moyen du procédé selon l'invention (Exemples 3 à 6) avec ceux des pâtes blanchies selon les séquences de l'art antérieur (Exemples 1R et 2R) fait apparaître l'avantage du procédé selon l'invention. De plus, si l'on compare l'exemple 6 à l'exemple 1R de référence, on voit que le traitement préalable avec de l'acide de Caro conformément au procédé selon l'invention a permis de supprimer la dernière étape à l'hypochlorite en milieu alcalin, d'obtenir une blancheur de 6,5° ISO plus élevée et de ramener la charge totale en chlore actif de la séquence de blanchiment de 8 à 6,6%, ce qui représente une diminution de 17,5%. Les exemples 3 et 4 montrent par ailleurs qu'il est possible, à blancheur égale à celle obtenue avec la séquence CEHH de référence (exemple 1R) d'obtenir avec le procédé selon l'invention, la suppression de la deuxième étape H, une pâte de meilleure solidité, une réduction de 8 à 5,2% (exemple 3) et de 8 à 4,75% (exemple 4) de la charge totale en chlore actif et une moindre pollution des effluents.The comparison of the results of evaluation of the mechanical properties of pulp bleached by means of the process according to the invention (Examples 3 to 6) with those of pulp bleached according to the sequences of the prior art (Examples 1R and 2R) reveals the advantage of the process according to the invention. In addition, if we compare Example 6 with Reference Example 1R, we see that the preliminary treatment with Caro acid in accordance with the process according to the invention made it possible to suppress the last stage with hypochlorite in an alkaline medium, to obtain a whiteness of 6.5 ° higher ISO and to reduce the total charge in active chlorine of the bleaching sequence from 8 to 6.6%, which represents a decrease of 17.5%. Examples 3 and 4 also show that it is possible, with a whiteness equal to that obtained with the reference CEHH sequence (example 1R), to obtain, with the process according to the invention, the elimination of the second step H, a pulp with better solidity, a reduction of 8 to 5.2% (example 3) and from 8 to 4.75% (example 4) of the total load of active chlorine and less pollution of the effluents.

Claims (8)

1 - Procédé pour améliorer les propriétés mécaniques d'une pâte à papier chimique ou semi-chimique de bagasse contenant au moins 25 X en poids de moelle caractérisé en ce qu'on la traite avec un agent oxydant sélectionné parmi les acides persulfuriques et leurs sels.1 - Process for improving the mechanical properties of a chemical or semi-chemical bagasse pulp containing at least 25% by weight of marrow, characterized in that it is treated with an oxidizing agent selected from persulfuric acids and their salts . 2 - Procédé selon la revendication 1 caractérisé en ce que l'agent oxydant est l'acide peroxymonosulfurique.2 - Process according to claim 1 characterized in that the oxidizing agent is peroxymonosulfuric acid. 3 - Procédé selon la revendication 1 ou 2 caractérisé en ce qu'on sélectionne une pâte chimique de bagasse, cuite à la chaux.3 - Method according to claim 1 or 2 characterized in that one selects a bagasse chemical paste, cooked with lime. 4 - Procédé selon une quelconque des revendications 1 à 3 caractérisé en ce qu'on fait suivre le traitement avec l'agent oxydant par un traitement au chlore en milieu acide.4 - Process according to any one of claims 1 to 3 characterized in that the treatment with the oxidizing agent is followed by a treatment with chlorine in an acid medium. 5 - Procédé selon la revendication 4 caractérisé en ce qu'on fait suivre le traitement au chlore par une extraction alcaline au moyen d'hydroxyde de sodium et un traitement ultérieur à l'hypochlorite de sodium en milieu alcalin.5 - Process according to claim 4 characterized in that the chlorine treatment is followed by an alkaline extraction by means of sodium hydroxide and a subsequent treatment with sodium hypochlorite in an alkaline medium. 6 - Procédé selon l'une quelconque des revendications 1 à 5 caractérisé en ce que le traitement avec l'agent oxydant est effectué à un pH compris entre 1 et 7 et à une température comprise entre 298 et 343 K.6 - Method according to any one of claims 1 to 5 characterized in that the treatment with the oxidizing agent is carried out at a pH between 1 and 7 and at a temperature between 298 and 343 K. 7 - Procédé selon l'une quelconque des revendications à 6 caractérisé en ce que le traitement avec l'agent oxydant est effectué sur une pâte présentant une consistance comprise entre 3 et 30%.7 - Method according to any one of claims to 6 characterized in that the treatment with the oxidizing agent is carried out on a paste having a consistency between 3 and 30%. 8 - Procédé selon l'une quelconque des revendications 1 à 7 caractérisé en ce que le traitement avec l'agent oxydant est effectué avec une quantité d'agent oxydant comprise entre 0,5 et 5 g/100 g de pâte sèche.8 - Method according to any one of claims 1 to 7 characterized in that the treatment with the oxidizing agent is carried out with an amount of oxidizing agent between 0.5 and 5 g / 100 g of dry paste.
EP86101427A 1985-02-04 1986-02-04 Process for improving the mechanical properties of a chemical or semi-chemical bagasse paper pulp Withdrawn EP0190723A1 (en)

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FR8501608A FR2576930B1 (en) 1985-02-04 1985-02-04 PROCESS FOR THE DELIGNIFICATION AND BLEACHING OF CHEMICAL OR SEMI-CHEMICAL PAPER PULP
FR8501608 1985-02-04

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0415149A2 (en) * 1989-08-18 1991-03-06 Degussa Aktiengesellschaft Process for bleaching and delignification of lignocellulosic materials
WO1992015752A1 (en) * 1991-03-11 1992-09-17 Interox International S.A. Method for bleaching a chemical pulp and application of such method to the bleaching of a kraft pulp
EP0560421A1 (en) * 1992-03-09 1993-09-15 SOLVAY INTEROX (Société Anonyme) Process for the discolouration and bleaching of waste paper
US5246543A (en) * 1989-08-18 1993-09-21 Degussa Corporation Process for bleaching and delignification of lignocellulosic materials

Families Citing this family (1)

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WO2009015555A1 (en) * 2007-07-27 2009-02-05 Shandong Tralin Paper Co., Ltd Grass paper pulp used by papermaking and preparation method thereof

Citations (1)

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Publication number Priority date Publication date Assignee Title
US4404061A (en) * 1981-08-17 1983-09-13 International Paper Company Bleaching of lignocellulosic materials with monopersulfuric acid or its salts

Patent Citations (1)

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Publication number Priority date Publication date Assignee Title
US4404061A (en) * 1981-08-17 1983-09-13 International Paper Company Bleaching of lignocellulosic materials with monopersulfuric acid or its salts

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0415149A2 (en) * 1989-08-18 1991-03-06 Degussa Aktiengesellschaft Process for bleaching and delignification of lignocellulosic materials
EP0415149A3 (en) * 1989-08-18 1992-01-29 Degussa Aktiengesellschaft Process for bleaching and delignification of lignocellulosic materials
US5091054A (en) * 1989-08-18 1992-02-25 Degussa Corporation Process for bleaching and delignification of lignocellulosic
US5246543A (en) * 1989-08-18 1993-09-21 Degussa Corporation Process for bleaching and delignification of lignocellulosic materials
WO1992015752A1 (en) * 1991-03-11 1992-09-17 Interox International S.A. Method for bleaching a chemical pulp and application of such method to the bleaching of a kraft pulp
BE1004674A3 (en) * 1991-03-11 1993-01-12 Interox Internat Sa Method of laundering of chemical pulp and application of the method of laundering pulp kraft.
AU660301B2 (en) * 1991-03-11 1995-06-22 Solvay Interox Process for bleaching a chemical paper pulp
US5698075A (en) * 1991-03-11 1997-12-16 Solvay Interox (Societe Anonyme) Process for bleaching a chemical paper pulp in an oxygen-peroxymonosulfuric acid-hydrogen peroxide sequence
EP0560421A1 (en) * 1992-03-09 1993-09-15 SOLVAY INTEROX (Société Anonyme) Process for the discolouration and bleaching of waste paper

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JPS61179390A (en) 1986-08-12
ZA86598B (en) 1987-01-28
AU5293886A (en) 1986-08-07
FR2576930B1 (en) 1988-08-12
FR2576930A1 (en) 1986-08-08
ES8802335A1 (en) 1987-04-16
EG17850A (en) 1991-11-30
CN86101158A (en) 1986-07-30
PT81909B (en) 1987-05-13
PT81909A (en) 1986-02-01
PH21180A (en) 1987-08-07

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