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EP0479319B1 - Process poor in chlorine for the bleaching and delignification of cellulosic pulp - Google Patents

Process poor in chlorine for the bleaching and delignification of cellulosic pulp Download PDF

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Publication number
EP0479319B1
EP0479319B1 EP91116992A EP91116992A EP0479319B1 EP 0479319 B1 EP0479319 B1 EP 0479319B1 EP 91116992 A EP91116992 A EP 91116992A EP 91116992 A EP91116992 A EP 91116992A EP 0479319 B1 EP0479319 B1 EP 0479319B1
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EP
European Patent Office
Prior art keywords
bleaching
weight
chlorine
hydrogen peroxide
solution
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP91116992A
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German (de)
French (fr)
Other versions
EP0479319A1 (en
Inventor
Werner Dr. Sturm
Ludwig Eibl
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Evonik Operations GmbH
Original Assignee
SKW Trostberg AG
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Publication of EP0479319A1 publication Critical patent/EP0479319A1/en
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • the present invention relates to a process for low-chlorine bleaching and delignification of pulp in several stages.
  • Lignin-free cellulose is largely required to produce white-stable and / or high-strength paper products.
  • the pulp which is made from vegetable raw materials such as wood, reeds, straw, bagasse or similar. is obtained by chemical digestion (sulfate, sulfite or organosolve digestion), subjected to a delignifying bleach.
  • the present invention is therefore based on the object of providing a process for chlorine-free final bleaching of cellulose pretreated with chlorine-free or with a sequence of chlorine-free and chlorine-containing chemicals or elemental chlorine, which does not have the disadvantages of the prior art mentioned, but rather with little effort and, if possible without the use of chlorine-containing treatment agents, enables the production of pulps with high whiteness.
  • This object is achieved in that one is pre-bleached with an at least two-stage bleaching sequence
  • An aqueous cyanamide solution and an alkaline hydrogen peroxide solution are added to the pulp in an extractive final bleach, the last stage of the pre-bleaching sequence comprising a peroxide-reinforced alkaline extraction and the cyanamide solution and the alkaline hydrogen peroxide solution being added separately in the final bleach.
  • the pre-bleached pulp can be a material blended with chlorine-free bleaches or a sequence of chlorine-containing and chlorine-free bleaches, e.g. Oxygen-chlorine-hydrogen peroxide, oxygen / peroxide-chlorine dioxide-peroxide etc. has been treated.
  • the process according to the present invention comprises an extractive bleaching step with two treatment agents which are added in any order but separately.
  • a pulp which is usually pre-bleached with an at least two-stage bleaching sequence and usually has a whiteness of about 70 to 80%, is kappa values from 1.5 to 3.0 and material densities from 5 to 30 wt .-% (preferably 10 to 15 wt .-%) treated with the first treatment agent, namely an aqueous cyanamide solution.
  • the amount of the cyanamide to be used depends on the weight of the pulp and is 0.01 to 1.0% by weight, preferably 0.1 to 0.5% by weight, based on the dry weight of the pulp.
  • the concentration of the cyanamide used in the aqueous solution can be varied within wide limits and is 0.1 to 60% by weight, preferably 1 to 10% by weight.
  • alkaline hydrogen peroxide solution is added to the pulp as a second treatment agent.
  • treatment agents are already known from the prior art and usually contain sodium hydroxide, soda or magnesium oxide as the alkalizing agent.
  • the amount of alkali compound (such as NaOH) depends on the pulp used and is preferably 0.1 to 2.5% by weight, in particular 0.5 to 1.5% by weight, based on the dry weight of the pulp.
  • the amount of hydrogen peroxide which is usually 0.1 to 3.0% by weight, in particular 0.5 to 1.5% by weight, is also used, depending on the dry weight of the pulp.
  • the time interval between separate mixing of cyanamide and alkaline hydrogen peroxide solution can be relatively short, i.e. 10 to 20 seconds.
  • a simultaneous but spatially separate addition of the treatment agents can also take place if there is an intensively acting mixing unit at the addition point.
  • reaction temperatures for the extractive bleaching stage can also be varied within wide limits.
  • the bleaching is carried out at 20 to 90 ° C., preferably 40 to 80 ° C.
  • the bleaching process according to the invention is generally carried out in a pH range from 8 to 13, preferably from 10 to 12.
  • the process according to the invention is particularly well suited for the technical field, since it also requires very little chlorine-containing treatment agents.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)
  • Medicines Containing Material From Animals Or Micro-Organisms (AREA)
  • General Preparation And Processing Of Foods (AREA)
  • Cereal-Derived Products (AREA)
  • Jellies, Jams, And Syrups (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Detergent Compositions (AREA)

Abstract

A process for low-chlorine bleaching and delignification of pulp is described, a pulp prebleached in an at least two-stage bleaching sequence being treated in an extractive final bleach separately with an aqueous solution of cyanamide and an alkaline solution of hydrogen peroxide. In this way, pulps of high degrees of whiteness can be produced in a chlorine-free final bleach.

Description

Die vorliegende Erfindung betrifft ein Verfahren zur chlorarmen Bleiche und Delignifizierung von Zellstoff in mehreren Stufen.The present invention relates to a process for low-chlorine bleaching and delignification of pulp in several stages.

Zur Herstellung weißestabiler und/oder hochfester Papiererzeugnisse wird weitgehend ligninfreier Zellstoff benötigt. Zu diesem Zweck wird der Zellstoff, der aus pflanzlichen Rohstoffen wie Holz, Schilf, Stroh, Bagasse o.ä. durch einen chemischen Aufschluß (Sulfat-, Sulfit- oder Organosolvaufschluß) gewonnen wird, einer delignifizierenden Bleiche unterworfen. Bei diesen üblicherweise mehrstufigen Bleichverfahren wurden früher im wesentlichen elementares Chlor (C) und Hypochlorit (H) als Behandlungsmittel verwendet, wobei beispielsweise für Sulfitzellstoff folgende Bleichsequenz gängig war:



        (C) - (E) - (H) - (H)



(C) = Chlorbleiche, (E) = Extraktion der Chlorlignine mit wäßriger Natronlauge, (H) = Hypochloritbehandlung.Lignin-free cellulose is largely required to produce white-stable and / or high-strength paper products. For this purpose, the pulp, which is made from vegetable raw materials such as wood, reeds, straw, bagasse or similar. is obtained by chemical digestion (sulfate, sulfite or organosolve digestion), subjected to a delignifying bleach. In these usually multistage bleaching processes, elemental chlorine (C) and hypochlorite (H) were previously used as treatment agents, the following bleaching sequence being common for sulfite pulp, for example:



(C) - (E) - (H) - (H)



(C) = chlorine bleach, (E) = extraction of the chlorine lignins with aqueous sodium hydroxide solution, (H) = hypochlorite treatment.

Zur Verringerung des umweltbelastenden Einsatzes von elementarem Chlor wurde die Extraktionsstufe zunehmend mit Peroxid durchgeführt, wobei eine deutliche Reduzierung des Einsatzes von Elementarchlor erreicht werden konnte.In order to reduce the environmentally harmful use of elemental chlorine, the extraction stage was increasingly carried out with peroxide, with a significant reduction in the use of elemental chlorine being achieved.

Weitere Verringerungen des Gebrauches von Elementarchlor gelangen durch den Einsatz von Chlordioxid und/oder die Vorschaltung einer Sauerstoffstufe (EO) bzw. einer mit Sauerstoff und Wasserstoffperoxid unterstützten Extraktionsstufe (EOP), wobei folgende Vorbleichsequenzen im Laufe der Zeit entwickelt wurden:



        C - EP




        EO(P) - C - EP




        C/D - EP




        EO(P) - D - EP




        EOP - H - EP


EOP
= Extraktion mit Unterstützung von Sauerstoff/Wasserstoffperoxid
EP
= Extraktion mit Wasserstoffperoxid und NaOH
C
= Behandlung mit Chlor
C/D
= Behandlung mit Chlor/Chlordioxid
D
= Behandlung mit Chlordioxid
EO
= Extraktion mit Unterstützung von Sauerstoff
H
= Behandlung von Hypochlorit
Zellstoffe, die nach den oben genannten Bleichsequenzen behandelt wurden, weisen jedoch in der Regel einen für hohe Ansprüche zu geringen Weißgrad auf. Da aber eine Endbleiche mit chlorhaltigen Bleichmitteln wie Hypochlorit und Chlordioxid mit Belastungen für Abwasser und Abluft sowie eventuell Organochlor-Rückständen im Zellstoff verbunden ist, wird zunehmend eine absolut chlorfreie Lösung angestrebt. Der Ersatz einer Fertigbleiche mit Hypochlorit oder Chlordioxid durch eine weitere Bleichstufe mit Wasserstoffperoxid führt in vielen Fällen nicht zum gewünschten Weißgradniveau.Further reductions in the use of elemental chlorine are achieved through the use of chlorine dioxide and / or the addition of an oxygen stage (EO) or an extraction stage supported by oxygen and hydrogen peroxide (EOP), the following pre-bleaching sequences being developed over time:



C - EP




EO (P) - C - EP




C / D - EP




EO (P) - D - EP




EOP-H-EP


EOP
= Extraction with the support of oxygen / hydrogen peroxide
EP
= Extraction with hydrogen peroxide and NaOH
C.
= Treatment with chlorine
CD
= Treatment with chlorine / chlorine dioxide
D
= Treatment with chlorine dioxide
EO
= Extraction with the support of oxygen
H
= Treatment of hypochlorite
However, pulps that have been treated according to the bleaching sequences mentioned above generally have a degree of whiteness that is too low for high demands. However, since final bleaching with chlorine-containing bleaches such as hypochlorite and chlorine dioxide is associated with pollution of waste water and exhaust air and possibly organochlorine residues in the pulp, an absolutely chlorine-free solution is increasingly being sought. Replacing a finished bleach with hypochlorite or chlorine dioxide with a further bleaching stage with hydrogen peroxide in many cases does not lead to the desired level of whiteness.

Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zur chlorfreien Endbleiche von mit chlorfreien oder mit einer Sequenz von chlorfreien und chlorhaltigen Chemikalien bzw. elementarem Chlor vorbehandelten Zellstoffen zu schaffen, welches die genannten Nachteile des Standes der Technik nicht aufweist, sondern mit geringem Aufwand und möglichst ohne Zuhilfenahme von chlorhaltigen Behandlungsmitteln die Herstellung von Zellstoffen mit hohen Weißgraden ermöglicht.The present invention is therefore based on the object of providing a process for chlorine-free final bleaching of cellulose pretreated with chlorine-free or with a sequence of chlorine-free and chlorine-containing chemicals or elemental chlorine, which does not have the disadvantages of the prior art mentioned, but rather with little effort and, if possible without the use of chlorine-containing treatment agents, enables the production of pulps with high whiteness.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß man einen mit einer mindestens zweistufigen Bleichsequenz vorgebleichten Zellstoff in einer extraktiven Endbleiche mit einer wäßrigen Cyanamidlösung und einer alkalischen Wasserstoffperoxid-Lösung versetzt, wobei die letzte Stufe der Vorbleichsequenz eine peroxidverstärkte alkalische Extraktion umfaßt und in der Endbleiche die Cyanamidlösung und die alkalische Wasserstoffperoxidlösung getrennt zugesetzt werden.This object is achieved in that one is pre-bleached with an at least two-stage bleaching sequence An aqueous cyanamide solution and an alkaline hydrogen peroxide solution are added to the pulp in an extractive final bleach, the last stage of the pre-bleaching sequence comprising a peroxide-reinforced alkaline extraction and the cyanamide solution and the alkaline hydrogen peroxide solution being added separately in the final bleach.

Es hat sich überraschenderweise gezeigt, daß man auf diese Weise den Einsatz von chlorhaltigen Chemikalien deutlich reduzieren kann, ohne Abstriche bei der Erzielung hoher Weißgrade hinnehmen zu müssen.Surprisingly, it has been shown that the use of chlorine-containing chemicals can be significantly reduced in this way without having to accept compromises in achieving high degrees of whiteness.

Die Aktivierung von Peroxid mittels Cyanamidderivaten ist zwar beispielsweise aus der DE-A-35 44 398 bekannt. Dort wird aber im Gegensatz zur vorliegenden Erfindung die Behandlung von ungebleichtem oder nur vorbehandeltem Material beschrieben. Gemäß vorliegender Erfindung wird hingegen zur Erreichung höherer Endweißgrade den Vorbleichen, deren letzte Stufe eine EP-Behandlung umfaßt, anstatt der üblichen extraktiven Stufe mit Natronlauge eine mit der Kombination aus Wasserstoffperoxid und Cyanamid verstärkte extraktive Stufe zur Entfernung der die folgende aktivierte Bleichstufe störenden Bestandteile nachgeschaltet.The activation of peroxide by means of cyanamide derivatives is known, for example, from DE-A-35 44 398. In contrast to the present invention, however, the treatment of unbleached or only pretreated material is described there. According to the present invention, however, in order to achieve higher final whiteness levels, the bleaching, the last stage of which comprises EP treatment, is followed by an extractive stage reinforced with the combination of hydrogen peroxide and cyanamide instead of the usual extractive stage with sodium hydroxide solution in order to remove the constituents which interfere with the following activated bleaching stage.

Bei dem vorgebleichten Zellstoff kann es sich um ein Material handeln, das mit chlorfreien Bleichmitteln oder einer Sequenz von chlorhaltigen und chlorfreien Bleichmitteln, z.B. Sauerstoff-Chlor-Wasserstoffperoxid, Sauerstoff/Peroxid-Chlordioxid-Peroxid etc. behandelt worden ist.The pre-bleached pulp can be a material blended with chlorine-free bleaches or a sequence of chlorine-containing and chlorine-free bleaches, e.g. Oxygen-chlorine-hydrogen peroxide, oxygen / peroxide-chlorine dioxide-peroxide etc. has been treated.

Das Verfahren entsprechend der vorliegenden Erfindung umfaßt eine extraktive Bleichstufe mit zwei Behandlungsmitteln, die in beliebiger Reihenfolge, aber getrennt zugegeben werden.The process according to the present invention comprises an extractive bleaching step with two treatment agents which are added in any order but separately.

Für diese extraktive Bleichstufe wird ein mit einer mindestens zweistufigen Bleichsequenz vorgebleichter Zellstoff, der üblicherweise Weißgrade von ca. 70 bis 80 %, Kappawerte von 1,5 bis 3,0 sowie Stoffdichten von 5 bis 30 Gew.-% (vorzugsweise 10 bis 15 Gew.-%) aufweist, mit dem ersten Behandlungsmittel, nämlich einer wäßrigen Cyanamidlösung behandelt. Die Menge des zu verwendenden Cyanamids richtet sich nach dem Gewicht des Zellstoffs und beträgt 0,01 bis 1,0 Gew.-%, vorzugsweise 0,1 bis 0,5 Gew.-%, bezogen auf das Trockengewicht des Zellstoffs.For this extractive bleaching stage, a pulp, which is usually pre-bleached with an at least two-stage bleaching sequence and usually has a whiteness of about 70 to 80%, is kappa values from 1.5 to 3.0 and material densities from 5 to 30 wt .-% (preferably 10 to 15 wt .-%) treated with the first treatment agent, namely an aqueous cyanamide solution. The amount of the cyanamide to be used depends on the weight of the pulp and is 0.01 to 1.0% by weight, preferably 0.1 to 0.5% by weight, based on the dry weight of the pulp.

Die Konzentration des verwendeten Cyanamids in der wäßrigen Lösung kann in weiten Grenzen variiert werden und beträgt 0,1 bis 60 Gew.-%, vorzugsweise 1 bis 10 Gew.-%.The concentration of the cyanamide used in the aqueous solution can be varied within wide limits and is 0.1 to 60% by weight, preferably 1 to 10% by weight.

Als zweites Behandlungsmittel wird eine alkalische Wasserstoffperoxid-Lösung dem Zellstoff zugesetzt. Solche Behandlungsmittel sind aus dem Stand der Technik bereits bekannt und enthalten üblicherweise als Alkalisierungsmittel Natriumhydroxid, Soda bzw. Magnesiumoxid. Die Menge an Alkaliverbindung (wie z.B. NaOH) richtet sich nach dem eingesetzten Zellstoff und beträgt vorzugsweise 0,1 bis 2,5 Gew.-%, insbesondere 0,5 bis 1,5 Gew.-%, bezogen auf das Trockengewicht des Zellstoffs.An alkaline hydrogen peroxide solution is added to the pulp as a second treatment agent. Such treatment agents are already known from the prior art and usually contain sodium hydroxide, soda or magnesium oxide as the alkalizing agent. The amount of alkali compound (such as NaOH) depends on the pulp used and is preferably 0.1 to 2.5% by weight, in particular 0.5 to 1.5% by weight, based on the dry weight of the pulp.

Ebenfalls in Abhängigkeit vom Trockengewicht des Zellstoffs wird die Menge an Wasserstoffperoxid eingesetzt, die üblicherweise bei 0,1 bis 3,0 Gew.-%, insbesondere 0,5 bis 1,5 Gew.-%, liegt.The amount of hydrogen peroxide, which is usually 0.1 to 3.0% by weight, in particular 0.5 to 1.5% by weight, is also used, depending on the dry weight of the pulp.

Der Wasserstoffperoxid-Zusatz verstärkt die alkalische Lösung in ihrer Wirkung, die bei der Bleiche störenden Bestandteile zu extrahieren.The addition of hydrogen peroxide increases the effectiveness of the alkaline solution in extracting the constituents which interfere with bleaching.

Es ist erfindungswesentlich, daß beide erfindungsgemäßen Behandlungsmittel nicht gleichzeitig, sondern getrennt dem Zellstoff zugegeben werden, wobei es - wie bereits dargelegt - nicht entscheidend auf die Reihenfolge der Zugabe ankommt.It is essential to the invention that the two treatment agents according to the invention are not added to the pulp simultaneously, but separately, and - as already explained - the order of addition is not critical.

Es hat sich jedoch in den meisten Fällen als besonders vorteilhaft herausgestellt, zuerst die wäßrige Cyanamidlösung und daran anschließend die alkalische Wasserstoffperoxid-Lösung in den Zellstoff einzuarbeiten. Der zeitliche Abstand der getrennten Einmischung von Cyanamid und alkalischer Wasserstoffperoxidlösung kann relativ kurz, d.h. 10 bis 20 Sekunden sein. Ferner kann auch eine gleichzeitige, aber örtlich getrennte Zugabe der Behandlungsmittel erfolgen, wenn sich an der Zugabestelle ein intensiv wirkendes Mischaggregat befindet.In most cases, however, it has proven particularly advantageous to first incorporate the aqueous cyanamide solution and then the alkaline hydrogen peroxide solution into the pulp. The time interval between separate mixing of cyanamide and alkaline hydrogen peroxide solution can be relatively short, i.e. 10 to 20 seconds. Furthermore, a simultaneous but spatially separate addition of the treatment agents can also take place if there is an intensively acting mixing unit at the addition point.

Die Reaktionstemperaturen für die extraktive Bleichstufe können ebenfalls in weiten Grenzen variiert werden. Aus Gründen der Wirtschaftlichkeit wird die Bleiche bei 20 bis 90°C, vorzugsweise 40 bis 80°C, durchgeführt.The reaction temperatures for the extractive bleaching stage can also be varied within wide limits. For reasons of economy, the bleaching is carried out at 20 to 90 ° C., preferably 40 to 80 ° C.

In der Regel resultieren hierbei Bleichzeiten von 15 bis 420 Minuten, vorzugsweise 60 bis 240 Minuten. Nach der üblichen Aufarbeitung des Zellstoffs wie Verdünnen mit Brauchwasser, pH-Werteinstellung auf neutralen Bereich und Nachwaschen erhält man einen Zellstoff mit einem Weißgrad von ca. 85 bis 89 %.As a rule, this results in bleaching times of 15 to 420 minutes, preferably 60 to 240 minutes. After the usual processing of the pulp, such as dilution with process water, pH adjustment to a neutral range and washing, a pulp with a whiteness of approx. 85 to 89% is obtained.

Das erfindungsgemäße Bleichverfahren wird im allgemeinen in einem pH-Bereich von 8 bis 13, vorzugsweise von 10 bis 12 durchgeführt.The bleaching process according to the invention is generally carried out in a pH range from 8 to 13, preferably from 10 to 12.

Aufgrund dieser hohen Weißgrade und der niedrigen Ligningehalte der erzeugten Zellstoffe eignet sich das erfindungsgemäße Verfahren besonders gut für den technischen Bereich, da es gleichzeitig mit sehr wenig chlorhaltigen Behandlungsmitteln auskommt.Because of these high degrees of whiteness and the low lignin content of the cellulose produced, the process according to the invention is particularly well suited for the technical field, since it also requires very little chlorine-containing treatment agents.

Die nachfolgenden Beispiele sollen die Erfindung näher erläutern.The following examples are intended to explain the invention in more detail.

BeispieleExamples

Alle Bleichstufen wurden in Polyethylenbeuteln durchgeführt.All bleaching stages were carried out in polyethylene bags.

Bestimmungen:

- Weißgrad:
Vom gewaschenen Zellstoff wurden am Blattbildner (nach Rapid Köthen) normgerechte Weißeblätter gebildet und mit einem Meßgerät der Marke Elrepho 2000 (Datacolor) der Weißgrad in % nach der Iso-Norm 2470 ermittelt.
- Kappazahl:
Die Bestimmung dieser Kenngröße, welche ein Maß für den Ligningehalt im Zellstoff ist, erfolgte nach Iso-Norm 302.
Regulations:
- whiteness:
Standard white sheets were formed from the washed pulp on the sheet former (according to Rapid Köthen) and the whiteness in% according to the ISO standard 2470 was determined using a measuring device from Elrepho 2000 (Datacolor).
- Kappa number:
This parameter, which is a measure of the lignin content in the pulp, was determined in accordance with ISO standard 302.

Beispiel 1 (Vergleich) Example 1 (comparison)

In 67,11 g Fichten-Magnesiumbisulfit-Zellstoff (20 g otro) nach einer C-EP-Vorbehandlung mit 77,0 % Weißgrad und Kappa 2,3 wurden 132,89 g einer wäßrigen Lösung, die 3,0 g 10 %ige NaOH-Lösung (d.h. 0,3 g NaOH) und 0,67 g 30 %ige Wasserstoffperoxidlösung (d.h. 0,20 g H₂O₂) enthielt, intensiv eingeknetet. Zum Ausreagieren wurde die 10 %ige Zellstoffaufschlämmung in ein etwa 50°C warmes Wasserbad gegeben. Nach 240 Minuten Bleichdauer wurde die Suspension mit Brauchwasser verdünnt, auf pH 6,0 eingestellt, abgesaugt und nachgewaschen. Es wurde ein Weißgrad von 81,9 und ein Kappawert von 1,6 erhalten.In 67.11 g of spruce magnesium bisulphite pulp (20 g otro) after a C-EP pretreatment with 77.0% whiteness and Kappa 2.3, 132.89 g of an aqueous solution containing 3.0 g of 10% strength NaOH solution (ie 0.3 g NaOH) and 0.67 g 30% hydrogen peroxide solution (ie 0.20 g H₂O₂), kneaded intensively. To react, the 10% pulp slurry was placed in a water bath at about 50 ° C. After 240 minutes of bleaching, the suspension was diluted with process water, adjusted to pH 6.0, suction filtered and washed. A whiteness of 81.9 and a kappa value of 1.6 were obtained.

Beispiel 2Example 2

In 67,11 g Fichten-Magnesiumbisulfit-Zellstoff (20 g otro) nach einer C-EP-Vorbehandlung mit 77,0 % Weißgrad und Kappa 2,3 wurden 51,89 g einer wäßrigen Lösung, die 0,34 g einer 10 %igen Cyanamidlösung (d.h. 0,034 g Cyanamid) enthielt, eingearbeitet. Nach 2 bis 5 Minuten wurden 80,99 g einer wäßrigen Lösung, die 3,0 g 10 %iges NaOH und 0,67 g 30 %iges Wasserstoffperoxid enthielt, zugegeben und ebenfalls intensiv eingemischt. Bleichbedingungen und Aufarbeitung entsprachen Beispiel 1. Es wurde ein Weißgrad von 85,7 % und ein Kappawert von 1,3 erhalten.In 67.11 g of spruce magnesium bisulfite pulp (20 g otro) after a C-EP pretreatment with 77.0% whiteness and Kappa 2.3, 51.89 g of an aqueous solution containing 0.34 g of a 10% Contained cyanamide solution (ie 0.034 g cyanamide) incorporated. After 2 to 5 minutes, 80.99 g of an aqueous solution, the 3.0 g of 10% NaOH and 0.67 g of 30% Contained hydrogen peroxide, added and also mixed intensively. Bleaching conditions and working up corresponded to Example 1. A whiteness of 85.7% and a kappa value of 1.3 were obtained.

Beispiel 3 (Vergleich) Example 3 (comparison)

In 100 g Fichten-Magnesiumbisulfit-Zellstoff (20 g otro) nach einer EOP-D-EP-Behandlungs-Sequenz mit 80,2 % Weißgrad und 1,8 Kappa wurden 100 g einer wäßrigen Lösung, die 1 g 10 %iges NaOH und 0,33 g 30 %iges Wasserstoffperoxid enthielt, intensiv eingearbeitet. Zum Ausreagieren wurde die 10 %ige Stoffsuspension in ein etwa 70°C warmes Wasserbad gegeben. Nach 120 Minuten Bleichdauer wurde die Fasersuspension mit Brauchwasser verdünnt, auf pH 6,0 eingestellt, abgesaugt und nachgewaschen. Weißgrad 86,0 %.In 100 g of spruce magnesium bisulfite pulp (20 g otro) after an EOP-D-EP treatment sequence with 80.2% whiteness and 1.8 kappa were 100 g of an aqueous solution containing 1 g of 10% NaOH and Contained 0.33 g of 30% hydrogen peroxide, intensively incorporated. To react, the 10% stock suspension was placed in a water bath at about 70 ° C. After a bleaching period of 120 minutes, the fiber suspension was diluted with process water, adjusted to pH 6.0, suction filtered and washed. Whiteness 86.0%.

Beispiel 4Example 4

In 100 g Fichten-Magnesiumbisulfit-Zellstoff (20 g otro) nach einer EOP-D-EP-Behandlungs-Sequenz mit 80,2 % Weißgrad und 1,8 Kappa wurden 39,57 g einer wäßrigen Lösung, die 0,18 g 10 %iges Cyanamid enthielt, 2 bis 5 Minuten intensiv eingearbeitet. Anschließend wurden 60,43 g einer wäßrigen Lösung, die 1 g 10 %iges NaOH und 0,33 g 30 %iges Wasserstoffperoxid enthielt, zugesetzt und eingeknetet. Bleichbedingungen und Aufarbeitung wie Beispiel 3. Weißgrad 89,3 %.In 100 g of spruce magnesium bisulfite pulp (20 g otro) after an EOP-D-EP treatment sequence with 80.2% whiteness and 1.8 kappa, 39.57 g of an aqueous solution containing 0.18 g of 10 Contained% cyanamide, worked intensively for 2 to 5 minutes. Then 60.43 g of an aqueous solution containing 1 g of 10% NaOH and 0.33 g of 30% hydrogen peroxide were added and kneaded. Bleaching conditions and processing as in Example 3. Whiteness 89.3%.

Claims (9)

  1. Process for the low chlorine bleaching and delignification of cellulose with an at least two-step bleaching sequence as a pre-bleach and an extractive end bleach with an aqueous solution of cyanamide and an alkaline solution of hydrogen peroxide,
    wherein the last step of the pre-bleaching sequence comprises a peroxide-strengthened alkaline extraction (EP) and the cyanamide solution and the alkaline hydrogen peroxide solution are separately added in the end bleach.
  2. Process according to claim 1,
    wherein the amount of cyanamide is 0.01 to 1% by weight, preferably 0.1 to 0.5% by weight, referred to the dry weight of the cellulose.
  3. Process according to claims 1 and 2,
    wherein the concentration of the cyanamide in the aqueous solution is adjusted to 0.1 to 60% by weight, preferably 1 to 10% by weight.
  4. Process according to claims 1 to 3,
    wherein the hydrogen peroxide solution is adjusted alkaline with sodium hydroxide.
  5. Process according to claim 4,
    wherein 0.1 to 2.5% by weight, preferably 0.5 to 1.5% by weight of sodium hydroxide, referred to the dry weight of the cellulose, is used.
  6. Process according to one of claims 1 to 5,
    wherein the amount of hydrogen peroxide is 0.1 to 3.0% by weight, preferably 0.5 to 1.5% by weight, referred to the dry weight of the cellulose.
  7. Process according to one of claims 1 to 6,
    wherein the aqueous cyanamide solution is first added to the cellulose and subsequently the alkaline hydrogen peroxide solution.
  8. Process according to one of claims 1 to 7,
    wherein the extractive bleaching step is carried out at a temperature of 20 to 90°C, preferably 40 to 80°C.
  9. Process according to one of claims 1 to 8,
    wherein the reaction is carried out at a pH value of 8 to 13, preferably 10 to 12.
EP91116992A 1990-10-05 1991-10-04 Process poor in chlorine for the bleaching and delignification of cellulosic pulp Expired - Lifetime EP0479319B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4031597A DE4031597A1 (en) 1990-10-05 1990-10-05 METHOD FOR LOW-CHLORINE BLEACHING AND DELIGNIFICATION OF CELLULAR
DE4031597 1990-10-05

Publications (2)

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EP0479319A1 EP0479319A1 (en) 1992-04-08
EP0479319B1 true EP0479319B1 (en) 1995-04-05

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EP91116992A Expired - Lifetime EP0479319B1 (en) 1990-10-05 1991-10-04 Process poor in chlorine for the bleaching and delignification of cellulosic pulp

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EP (1) EP0479319B1 (en)
AT (1) ATE120815T1 (en)
CA (1) CA2052758A1 (en)
DE (2) DE4031597A1 (en)
ES (1) ES2070388T3 (en)
FI (1) FI914694A (en)
NO (1) NO913848L (en)

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Publication number Priority date Publication date Assignee Title
DE102009045628A1 (en) 2009-10-13 2011-04-14 Henkel Ag & Co. Kgaa Bleach activators for processes for bleaching cellulosic fibers

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE664257C (en) * 1929-09-11 1938-08-25 Degussa Process for upgrading cellulose
AT167849B (en) * 1945-01-10 1951-03-10 Buffalo Electro Chem Co Process for bleaching wood pulp
AT183646B (en) * 1950-06-30 1955-10-25 Buffalo Electro Chem Co Process for bleaching sulphate or sulphite pulp
DE2742262C2 (en) * 1977-09-20 1982-06-09 Degussa Ag, 6000 Frankfurt Process for the production of a medium to high viscosity softwood sulphite pulp
US4568420B1 (en) * 1984-12-03 1999-03-02 Int Paper Co Multi-stage bleaching process including an enhanced oxidative extraction stage
FR2589494B1 (en) * 1985-10-30 1988-07-29 Atochem PROCESS FOR BLEACHING CHEMICAL PAPER PULP
DE3544398A1 (en) * 1985-12-16 1987-06-19 Sueddeutsche Kalkstickstoff METHOD FOR THE BLEACHING AND DELIGNIFICATION OF CELLULAR-BASED PRODUCTS
DE4004364A1 (en) * 1990-02-13 1991-08-14 Sueddeutsche Kalkstickstoff Bleaching and delignifying pre-balanced cellulose - in two stages with peroxide activated with cyanamide or cyanamide salt, avoiding agents contg. chlorine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
J.P. Casey "Pulp and paper; Chemistry and Chemical Technology" dritte Auflage, Band 1, 1980, John Wiley & Sons, New York, Seiten 663, 669, 677, 678, 694-696. *

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DE59105105D1 (en) 1995-05-11
FI914694A (en) 1992-04-06
ES2070388T3 (en) 1995-06-01
ATE120815T1 (en) 1995-04-15
CA2052758A1 (en) 1992-04-06
DE4031597A1 (en) 1992-04-09
NO913848L (en) 1992-04-06
NO913848D0 (en) 1991-10-01
EP0479319A1 (en) 1992-04-08
FI914694A0 (en) 1991-10-04

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