EP0728238B2 - Verfahren zum bleichen von zellstoff - Google Patents

Verfahren zum bleichen von zellstoff Download PDF

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Publication number
EP0728238B2
EP0728238B2 EP94931025A EP94931025A EP0728238B2 EP 0728238 B2 EP0728238 B2 EP 0728238B2 EP 94931025 A EP94931025 A EP 94931025A EP 94931025 A EP94931025 A EP 94931025A EP 0728238 B2 EP0728238 B2 EP 0728238B2
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EP
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Prior art keywords
stage
process according
pulp
treatment
dry
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English (en)
French (fr)
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EP0728238A1 (de
EP0728238B1 (de
Inventor
François Desprez
Johan Devenyns
Nicholas A. Troughton
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Solvay Chimie SA
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Solvay Interox SA
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16

Definitions

  • the invention relates to a process for bleaching a chemical pulp.
  • Patent application EP-A-0 511 695 describes a process for the delignification and the bleaching of a dough for chemical paper according to which the pulp is treated with an acid at pH 1 to 6, it is treated with a compound containing an alkaline earth metal at a pH of 1 to 7, then with a chlorine-free bleach, for example hydrogen peroxide (claims 1 and 2).
  • Patent application EP-A-0 512 590 also describes a process for delignification and bleaching of a chemical paper pulp, According to this process the profile is modified in trace of metals in the dough by treatment with a complexing agent at a pH between 3.1 and 9.0 and bleached then the dough with a hydroene peroxide step followed by an ozone step (claim 2, page 7.)
  • a complexing agent at a pH between 3.1 and 9.0
  • bleached then the dough with a hydroene peroxide step followed by an ozone step
  • the invention overcomes these disadvantages of known methods, by providing a new delignification method. and / or bleaching of chemical pulp which allows high whiteness levels to be achieved without degrade the cellulose too much and without using chlorinated reagents.
  • the invention relates to a process for bleaching a chemical pulp of softwood or hardwood, which has undergone extensive cooking and has a kappa number of 20 or less after cooking in the case of softwoods and 14 or less in the case of hardwoods, by means of a sequence of stages of treatment free of chlorinated reagents, comprising the following steps, carried out in order:
  • chemical paper pulp 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 metal salt of sulfurous acid in an acid medium (cooking with sulfite or bisulfite).
  • chemical reagents such as sodium sulfide in alkaline medium (kraft or sulfate cooking), sulfur dioxide or a metal salt of sulfurous acid in an acid medium (cooking with sulfite or bisulfite).
  • the invention is particularly intended for pasta which has undergone kraft cooking or sulphite cooking.
  • wood used for the production of chemical pulp are suitable for the implementation of process of the invention and, in particular those used for kraft and sulfite pulps, namely resinous woods such as, for example, the various species of pine and fir and hardwoods such as, for example, beech, oak, eucalyptus and charm.
  • the dough has undergone extensive cuisso.
  • extensive cooking extended cooking
  • it is intended to denote any process for cooking chemical pulp mentioned above in which the flows and recycling are regulated. of various cooking reagents and liquors, as well as the physical parameters of the process, so as to modify the process for obtaining an improved delignification rate while maintaining the viscosity of the cellulose at a level acceptable.
  • An example of such an extensive cooking process for kraft pasta is described in the work by M. J. KOCUREK "Pulp and Paper Manufacture", Vol. 5, Alkaline Pulping, 3rd Edition, McGraw-Hill, New-York, 1989, page 122, paragraph 3 (Modifications for low lignin pulping).
  • Pasta that has undergone extensive cooking generally has a kappa index 30 to 50% lower than that of the same dough having undergone normal cooking.
  • Kraft pasta that has undergone extensive cooking has a kappa number of 20 or less in the case of wood softwood and 14 or less in the case of hardwoods.
  • the first step is a step of decontaminating the pulp into its transition metals (step Q).
  • step Q consists in treating the pulp with at least one sequestering agent such as a phosphate. or inorganic polyphosphate, such as, for example, an alkali metal pyrophosphate or metaphosphate, a polycarboxylate or an organic aminopolycarboxylate such as, for example, tartaric, citric, gluconic acids, ethylenediaminetetraacetic, diethylenetriaminepentaacetic, cyclohexanediaminetetraacetic and their salts, acid poly- ⁇ -hydroxyacrylic and its salts or an organic polyphosphonate such as ethylenediaminetetramethylenephosphonic acids, diethylenetriaminepenta (methylenephosphonic), cyclohexanediaminetetramethylenephosphonic and their salts.
  • a small amount of acid can also be added in step Q.
  • Step Q can also, as a variant, consist of a treatment with an acid free of a sequestrant, followed by the addition of soluble magnesium salt in an amount such that the weight ratio of the amount of Mg to that of Mn present. in the dough is at least 30. Generally, amounts of Mg corresponding to 1 to 4 g MgSO 4 .7H 2 O / 100 g of dry dough are sufficient.
  • the term “acid” is intended to denote the anhydrides or inorganic acids such as sulfur dioxide and sulfuric, sulfurous, hydrochloric, phosphoric and nitric acids or their acid salts, as well as organic acids such as carboxylic or phosphonic acids or their salts acids.
  • Sulfuric acid, sulfur dioxide or alkali or alkaline earth metal bisulfites are well suited.
  • bisulfite is intended to denote the acid salts of sulfurous acid corresponding to the formula Me (HSO 3 ) n, in which Me symbolizes a metal atom of valence n, n being an integer having the value 1 or 2.
  • the amount of acid to be used will depend on the type of wood and the amount of metallic impurities it contains. In general, an amount of acid will be used such that the pH of the dough is around 5 or more and, preferably about 5.5 or more. Similarly, we will often adjust the amount of acid so that the pH does not exceed not 7 and preferably not 6.5. When step Q is free of sequestering agents, the pH will be adjusted so as to make the medium substantially more acid, that is to say, not exceeding pH 5 and preferably not 4.5. Generally, we in order not to degrade the dough, avoid going below pH 1.5 and, preferably, below pH 2.0.
  • the sequestrant is generally used in step Q in an amount not exceeding 1.5 g of active material per 100 g of dry dough. Most often, this amount does not exceed 1.0 g of sequestering agent per 100 g of dough dried.
  • Stage Q is generally carried out at a pressure close to atmospheric pressure and at a temperature sufficient to ensure good efficiency of the acid and / or sequestrant and, at the same time not too high so as not to degrade the cellulose and not to burden the energy cost of the heating means used in said step.
  • a temperature of at least 40 ° C and preferably at least 50 ° C is suitable. Of even, it is advantageous that the temperature does not exceed 100 ° C and, preferably not 90 ° C.
  • step Q The duration of step Q must be sufficient to ensure a complete reaction. Although longer durations have no influence on the delignification rate of the dough as well as on its intrinsic resistance qualities, it it is not advisable to extend the reaction time beyond that necessary for the completion of the reaction. so as to limit the investment costs and the energy costs of heating the dough.
  • the duration of the pretreatment can vary widely depending on the type of equipment used, the choice of acid, the temperature and pressure, for example from about 15 minutes to several hours. Duration of at least 10 minutes and, preferably at least 15 minutes are generally sufficient. Likewise, the pretreatment times do not exceed generally not 60 minutes and preferably not 40 minutes. A duration of about 30 minutes gave excellent results.
  • Stage Q is generally carried out at a paste consistency of at least 2% of dry matter and, preferably, at least 2.5% dry matter. Most often, this consistency does not exceed 15% and, preferably not 10%. The consistency of approximately 3% dry matter has given excellent results.
  • the second treatment step represents the final step and is a step with alkaline hydrogen peroxide (step P).
  • the nature of the alkali must be such that it has good extraction efficiency for the oxidized lignin at the same time as good solubility.
  • An example of such an alkali is sodium hydroxide in aqueous solution.
  • the quantity of alkali to be used must be sufficient to maintain the pH above 10 and preferably above 11.
  • the quantity of alkali must also be adjusted to ensure sufficient consumption of the peroxide at the end of the reaction. In practice, amounts of alkali of 1 to 4 g of alkali per 100 g of dry pulp are very suitable.
  • a quantity of hydrogen peroxide of at least 0.3 g H 2 O 2/100 g of dry pulp and preferably at least 0.5 g / 100 g of dry dough. It is also that the amounts of hydrogen peroxide does not generally exceed 5.0 g H 2 O 2/100 g of dry pulp and preferably 4,0 g / 100 g of dry pulp.
  • step P The temperature of step P must be adjusted so as to remain above 110 ° C. It should also not exceed 150 ° C and preferably not exceed 135 ° C. A temperature of 120 ° C has given excellent results.
  • the temperature of this stage P generally does not exceed 140 ° C and preferably not 135 ° C.
  • step P The duration of step P must be sufficient for the bleaching reaction to be as complete as possible. However, it cannot exceed this reaction time too strongly, otherwise it will lead to a demotion of the whiteness of the dough. In practice, it will be set at a value of at least 60 minutes and, preferably, at least 90 minutes. It should also most often not exceed 600 and preferably 500 minutes.
  • step P is generally chosen to be less than or equal to 50% by weight of dry matter and, preferably 40% dry matter.
  • the sequence can be preceded by an oxygen step (step O).
  • This oxygen step is carried out by bringing the paste into contact with gaseous oxygen under a pressure between 20 and 1000 kPa in the presence of an alkaline compound in an amount such as the weight of compound alkaline relative to the weight of dry dough is between 0.5 and 5%.
  • the temperature of the oxygen step should generally be above 70 ° C and preferably 80 ° C. he it is also suitable that this temperature is usually less than 130 ° C and preferably 120 ° C.
  • the duration of the oxygen treatment must be sufficient for the reaction of the oxygen with the lignin contained in the dough is complete. However, it cannot exceed this reaction time too strongly, otherwise it will induce degradations in the structure of the cellulose chains of the pulp. In practice, it will be at least 30 minutes and preferably at least 40 minutes. Usually it will not exceed 120 minutes and preferably not 80 minutes.
  • the treatment of the pulp with oxygen can also be done in the presence of a cellulose protective agent such as soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids.
  • a cellulose protective agent such as soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids.
  • Magnesium salts are preferred, in particular, the magnesium sulfate heptahydrate used to 0.02 to 1% by weight based on the dry paste.
  • the paste consistency during step Q is generally not less than 8% by weight of dry matter and, preferably not less than 10%. This consistency usually does not exceed 30% by weight of material dry and preferably 25%.
  • step O can also be carried out in the presence of hydrogen peroxide (step Op).
  • the quantity of hydrogen peroxide which can be incorporated in stage O is generally not less than 0.2 g H 2 O 2 per 100 g of dry paste and, most often, not less than 0, 5 g. Likewise, we will usually not exceed 2.5 g H 2 O 2 per 100 g of dry paste and, most often, not 2 g.
  • step P can also be reinforced by the presence of gaseous oxygen (step Eop).
  • the oxygen pressure used will most often be at least 20 kPa and at most 1000 kPa.
  • step X it is possible to incorporate at any point before the step end of the treatment step sequence an additional enzymatic step consisting in treating the dough with at least one enzyme (step X).
  • This enzymatic treatment can also be carried out before or after the pretreatment step to possible oxygen.
  • enzyme is intended to denote any enzyme capable of facilitating delignification, through the processing steps subsequent to the step of treatment with the enzyme, of an unbleached chemical pulp from the operation of baking or chemical paper pulp that has already been subjected to an oxygen treatment step.
  • an alkalophilic enzyme will be used, that is to say an enzyme whose maximum effectiveness is in the alkaline pH zone, and especially at a pH of 7.5 and above.
  • a category of enzymes well suited to the process according to the invention are hemicellulases. These enzymes are able to react with hemicelluloses on which the lignin present in the paste is fixed.
  • the hemicellulases used in the process according to the invention are xylanases, that is to say hemicellulolytic enzymes capable of cutting the xylan links which constitute a major part of the interface between lignin and the rest of the carbohydrates.
  • xylanase in accordance with the process according to the invention is 1,4- ⁇ -D-xylane xylanohydrolase, EC 3.2.1.8.
  • the xylanases preferred in the methods according to the invention can be of various origins. They can particular to have been secreted by a wide range of bacteria and fungi.
  • Xylanases of bacterial origin are particularly interesting.
  • the xylanases secreted by bacteria of the genus Bacillus have given good results.
  • Xylanases derived from bacteria of the genus Bacillus and of the species pumilus have given excellent results. Of these, xylanases from Bacillus pumilus PRL B12 are particularly interesting.
  • the xylanases of Bacillus pumilus PRL B12 in accordance with the invention can come directly from a strain of Bacillus pumilus PRL B12 or also from a host strain of a different microorganism which has been genetically manipulated beforehand to express the genes coding for degradation xylans from Bacillus pumilus PRL B12.
  • a purified xylanase will be used which does not contain other enzymes.
  • the xylanase according to the process according to the invention does not contain cellulase so as not to destroy the chains cellulose pulp polymers.
  • An interesting variant of the process according to the invention consists in carrying out the enzymatic step X in the presence at least one sequestrant of metal ions.
  • the sequestrants of metal ions can advantageously be chosen from the sequestrants suitable for step Q which are described above.
  • step Q it is also possible to carry out step Q in the presence of at least one enzyme.
  • Another variant of the process according to the invention consists in interposing an oxidizing step between step Q and the step P.
  • All oxidizing chemical reagents are suitable for carrying out this oxidizing step.
  • reagents known and usually used for delignifying and bleaching paper pulps, it is preferred to use reagents which do not contain no chlorine. Peroxyacids and ozone are particularly preferred.
  • peroxyacids is intended to denote all the acids comprising in their molecule at least one perhydroxyl group -O-O-H or an ammonium salt or any metal of this acid.
  • Peroxyacids according to the invention can either belong to the family of inorganic or organic peroxyacids.
  • the peroxyacid is an inorganic peroxyacid.
  • Inorganic peroxyacids in accordance with the invention may contain one or more perhydroxyl groups. Inorganic peroxyacids having only one perhydroxyl group are however preferred. Examples of such inorganic peroxyacids are sulfuric, selenic, telluric, phosphoric, arsenic and silicic peroxyacids. Good results have have been obtained with monoperoxysulfuric acid.
  • the peroxyacid is an organic peroxyacid.
  • Organic peroxyacids in accordance with the invention are selected from performic acid and aliphatic or aromatic peroxyacids.
  • organic peroxyacid is an aliphatic peroxyacid
  • it is selected from the peroxyacids comprising from one to three percarboxylic groups.
  • Aliphatic peroxyacids comprising a single percarboxylic group generally comprise a chain saturated linear or branched alkyl of less than 11 carbon atoms and preferably less than 6 carbon atoms carbon.
  • peroxyacids are peroxyacetic, peroxypropanoic, peroxybutanoic acids and peroxypentanoic.
  • Peroxyacetic acid is particularly preferred because of its effectiveness and the relative simplicity of its preparation methods.
  • the aliphatic peroxyacids comprising two and three percarboxylic groups are selected from the di- and triperoxycarboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms.
  • diperoxyacids it is preferred that the two percarboxylic groups substitute atoms of carbon located in alpha-omega position relative to each other.
  • diperoxyacids are acid 1,6-diperoxyhexanedioic acid, 1,8-diperoxyoctanedioic acid and 1,10-diperoxydecanedioic acid, and acid 1.12-diperoxydodecanedioic.
  • An example of a triperoxyacid is triperoxycitric acid.
  • aromatic peroxyacids are selected from those which comprise at least one peroxycarboxylic group by benzene nucleus. Preferably, we will choose aromatic peroxyacids which contain only one only peroxycarboxylic group per benzene nucleus.
  • An example of such an acid is peroxybenzoic acid.
  • 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, the groups containing sulfur such than the sulfo and mercapto groups.
  • the peroxyacid can indifferently be used in the form of a peroxyacid solution or alternatively under form of a solution of an ammonium salt, an alkali metal or an alkaline earth metal of this peroxyacid.
  • solution is intended to denote a solution in water or in an organic solvent.
  • Mixtures of organic solvents also suitable for dissolving peroxyacids in accordance with the invention, as well as mixtures of water with one or more organic solvents miscible with water.
  • Aqueous solutions are preferred.
  • the amount of peroxyacid to be used in the oxidizing step can vary over a wide range. It depends on the type of wood used and on the effectiveness of the preceding cooking and delignification treatments. In practice, an amount of peroxyacid is generally used which is not less than 0.2 g of H 2 O 2 equivalent per 100 g of dry pulp and, preferably, not less than 0.5 g / 100 g dry paste.
  • H 2 O 2 equivalent is intended to denote the amount of hydrogen peroxide which contains an identical amount of active oxygen. Usually, a quantity of peroxyacid will not exceed 3 g of H 2 O 2 equivalent per 100 g of dry pulp and, preferably, 2 g of H 2 O 2 equivalent / 100 g of dry pulp.
  • the peroxyacid treatment step can also be carried out in the presence of one or more compatible additives with peroxyacids such as, for example, surfactants, peroxyacid stabilizers, inhibitors of depolymerization of cellulosic fibers and anti-corrosion agents.
  • suitable additives include surfactants anionics, nonionic surfactants, soluble salts of Mg and sequestrants of metal ions.
  • the quantity of these additives used does not exceed 3 g per 100 g of dry dough and preferably not more than 2.5 g per 100 g of dry dough.
  • the peroxyacid treatment step according to the invention can be carried out over a wide range of temperatures.
  • the peroxyacid treatment will be carried out at a temperature of at least 40 ° C and, preferably at least minus 60 ° C.
  • this temperature generally does not exceed 100 ° C and preferably not 95 ° C.
  • a temperature of 90 ° C led to good results.
  • the treatment is carried out with organic peroxyacid at atmospheric pressure.
  • the duration of this treatment depends on the temperature and the type of wood used to prepare the pulp, as well as on the efficiency of the cooking and the preceding stages. Times of approximately 60 minutes to approximately 500 minutes are suitable well. A duration of 120 minutes has given excellent results.
  • the pH of the peroxyacid treatment stage can be in the range of acid pH as well as alkaline pH. However, moderately acidic pHs are preferred. In practice, we prefer to set the initial pH at a value at least 3.5. An initial pH of 5 will generally not be exceeded. An initial pH of 4 has led to good results.
  • the paste consistency of the peroxyacid treatment step is generally chosen to be less than or equal to 40 % by weight of dry matter and preferably 30% of dry matter. It will often not be less than 5% and preferably not less than 8%. A consistency of 10% has given good results.
  • the ozone treatment step consists in subjecting the dough to a current gas consisting of a mixture of ozone and oxygen from an oxygen-powered electric ozone generator dry gas.
  • a generator is advantageously used, the flow rate of which is 50 to 100 l / hour and, preferably from 70 to 90 l / hour.
  • the amount of ozone used can easily be adjusted by varying the duration of the ozone / oxygen mixture stream sweeping over the dough. Generally, durations of 20 to 80 minutes are sufficient to use an amount of ozone of 0.4 to 2 g per 100 g of dry paste.
  • the ozone treatment is preferably carried out in an acid medium.
  • a pH of 0.5 to 5 is suitable and preferably 1.5 to 4.
  • a pH of 2 to 3 obtained by subjecting the dough to a 30-minute conditioning treatment using a solution of H 2 SO 4 or SO 2 at a rate of 0.5% by weight of SO 2 relative to the dry paste and with a consistency of 3% of dry matter has given very good results.
  • the consistency of the ozone treatment step will be selected in the range of 0.5 to 45% of materials dry and preferably from 0.5 to 3% (in the case of low consistency apparatus) or between 10 to 15% (in the case of medium consistency equipment). 35% dry matter consistency gave excellent results at the laboratory scale.
  • the temperature of the ozone treatment stage must remain low, otherwise it will lead to degradation important mechanical properties of the treated pulp. This temperature is generally from 2 to 50 ° C and, from preferably 10 to 35 ° C. Most often, the ozone treatment is simply carried out at room temperature.
  • An interesting variant of the process according to the invention consists in preceeding the ozone treatment by a mechanical treatment of opening the dough (called “fluffing” in Anglo-Saxon literature) intended to increase the contact surface of the paste with ozone. This operation is particularly useful when the consistency of the dough when treated with ozone is at least 15% dry matter.
  • the process according to the invention applies to the bleaching of any kind of chemical pulp which has undergone a extensive cooking. It is well suited for delignifying kraft and sulfite pastes. It is particularly well suited to processing of kraft pasta.
  • a sample of coniferous pulp having undergone normal kraft cooking (initial whiteness 27.9 ° ISO measured according to standard ISO 2470-1977 (F), kappa index 26.7 measured according to standard SCAN C1-59 and degree of polymerization 1680 expressed in number of glucosic units and measured according to the SCAN C15-62 standard) was treated according to a sequence of 3 OQP steps under the following conditions: 1st stage: oxygen stage (stage O): pressure, kPa 600 NaOH content, g / 100g dry paste 4 MgSO 4 .7H 2 O content, g / 100g dry paste 0.5 temperature, degrees C 120 duration, min 60 consistency,% by weight of dry matter 12 2nd stage: stage at EDTA (stage Q): EDTA content, g / 100g dry paste 0.4 temperature, degrees C 70 duration, min 45 consistency,% by weight of dry matter 10 3rd stage: hydrogen peroxide stage (stage P): H 2 O 2 content , g / 100g dry paste
  • the paste was washed with demineralized water at room temperature.
  • the paste was washed with demineralized water at room temperature.
  • 3rd stage hydrogen peroxide stage (stage P): H 2 O 2 content , g / 100g dry paste 2.0 NaOH content, g / 100g dry paste: example 5 1.0 example 6 1.2 example 7 1.6 MgSO 4 .7H 2 O content, g / 100g dry paste 1.0 Na silicate content 38 ° Be, g / 100g dry paste 3.0 temperature, degrees C 90 duration, min 240 consistency,% by weight of dry matter 30
  • the paste was washed with demineralized water at room temperature.
  • 3rd stage hydrogen peroxide stage (stage P): H 2 O 2 content , g / 100g dry paste 2.0 NaOH content, g / 100g dry paste: example 8 1.3 example 9 1.4 example 10 1.7 MgSO 4 .7H 2 O content, g / 100g dry paste 1.0 Na silicate content 38 ° Be, g / 100g dry paste 3.0 temperature, degrees C 90 duration, min 240 consistency,% by weight of dry matter 30
  • the paste was washed with demineralized water at room temperature.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Claims (10)

  1. Verfahren zum Bleichen eines chemischen Papierzellstoffs aus Nadelhölzern oder Laubhölzern, der einem extensiven Kochen unterzogen wurde und der nach dem Kochen eine Kappa-Zahl von 20 oder weniger im Fall von Nadelhölzern und von 14 oder weniger im Fall von Laubhölzern aufweist, mittels einer Folge von Behandlungsschritten, die frei von chlorhaltigen Reagentien sind, die die folgenden Schritte, die in der Reihenfolge :
       Q P
    ausgeführt werden, umfaßt, worin das Kürze Q einen Schritt zur Dekontaminierung des Zellstoffs von seinen Übergangsmetallen darstellt und das Kürzel P den Endschritt mit alkalischem Wasserstoffperoxid darstellt, der bei einer Temperatur von 110 °C oder mehr und einer Stoffdichte an Zellstoff von wenigstens 25 Gew.-% Trockensubstanzen durchgeführt wird.
  2. Verfahren gemäß Anspruch 1, bei dem der Schritt P in Gegenwart von gasförmigem Sauerstoff durchgeführt wird.
  3. Verfahren gemäß Anspruch 1 oder 2, bei dem die Temperatur des Schrittes P 150 °C nicht überbesteigt.
  4. Verfahren gemäß einem der Ansprüche 1 bis 3, bei dem der Folge ein Schritt mit gasförmigem Sauerstoff vorausgeht.
  5. Verfahren gemäß einem der Ansprüche 1 bis 4, in dem der Schritt P bei einer Stoffdichte an Zellstoff von wenigstens 30 Gew.-% Trockensubstanzen und höchstens 50 Gew.-% Trockensubstanzen durchgeführt wird.
  6. Verfahren gemäß einem der Ansprüche 1 bis 5, bei dem der Schritt Q aus einer Behandlung mit einer Säure besteht, die frei von einem Sequestrierungsmittel ist, der eine Zugabe von löslichem Mg-Salz in einer solchen Menge folgt, daß das Gewichtsverhältnis der Menge and Mg zu derjenigen an in dem Zellstoff vorhandenem Mn 30 oder mehr ist.
  7. Verfahren gemäß einem der Ansprüche 1 bis 6, bei dem man zwischen den Schritt Q und den Schritt P einen oxidierenden Schritt mit einem Reagens einschiebt, das unter den Peroxysäuren und Ozon ausgewählt ist.
  8. Verfahren gemäß einem der Ansprüche 1 bis 7, bei dem der Schritt Q in Gegenwart eines Enzyms ausgeführt wird.
  9. Verfahren gemäß einem der Ansprüche 1 bis 8, bei dem man an einem beliebigen Punkt einen zusätzlichen Schritt mit einem Enzym einfügt.
  10. Anwendung des Verfahrens gemäß einem der Ansprüchen 1 bis 9 auf das Bleichen von Kraft- oder Sulfit-Zellstoffen.
EP94931025A 1993-11-10 1994-10-28 Verfahren zum bleichen von zellstoff Expired - Lifetime EP0728238B2 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
BE9301251A BE1007757A3 (fr) 1993-11-10 1993-11-10 Procede pour le blanchiment d'une pate a papier chimique.
BE9301251 1993-11-10
PCT/EP1994/003590 WO1995013420A1 (fr) 1993-11-10 1994-10-28 Procede pour le blanchiment d'une pate a papier chimique

Publications (3)

Publication Number Publication Date
EP0728238A1 EP0728238A1 (de) 1996-08-28
EP0728238B1 EP0728238B1 (de) 1999-01-13
EP0728238B2 true EP0728238B2 (de) 2004-08-11

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EP94931025A Expired - Lifetime EP0728238B2 (de) 1993-11-10 1994-10-28 Verfahren zum bleichen von zellstoff

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EP (1) EP0728238B2 (de)
JP (1) JPH10500178A (de)
AT (1) ATE175738T1 (de)
AU (1) AU7993994A (de)
BE (1) BE1007757A3 (de)
BR (1) BR9408027A (de)
CA (1) CA2176246A1 (de)
DE (1) DE69416000D1 (de)
ES (1) ES2129142T5 (de)
FI (1) FI961975A (de)
MA (1) MA23369A1 (de)
NO (1) NO961889D0 (de)
WO (1) WO1995013420A1 (de)
ZA (1) ZA948563B (de)

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Publication number Priority date Publication date Assignee Title
JP4967451B2 (ja) 2006-05-17 2012-07-04 三菱瓦斯化学株式会社 漂白パルプの製造方法
WO2009081714A1 (ja) 2007-12-20 2009-07-02 Mitsubishi Gas Chemical Company, Inc. 漂白パルプの製造方法

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK0402335T4 (da) * 1989-06-06 2001-06-25 Eka Chemicals Ab Fremgangsmåde til blegning af lignocelluloseholdigpulp
SE468355B (sv) * 1991-04-30 1992-12-21 Eka Nobel Ab Blekning av kemisk massa genom behandling med komplexbildare och ozon
SE470065C (sv) * 1991-04-30 1995-10-12 Eka Nobel Ab Behandling av kemisk massa med en syra och därefter en magnesium- och kalciumförening vid klorfri blekning
SE469842C (sv) * 1992-01-21 1995-09-22 Sunds Defibrator Ind Ab Blekning av kemisk massa med peroxid
SE9201477L (sv) * 1992-05-11 1993-06-28 Kamyr Ab Saett vid blekning av massa utan anvaendning av klorkemikalier
BE1006056A3 (fr) * 1992-07-06 1994-05-03 Solvay Interox Procede pour le blanchiment d'une pate a papier chimique.
CZ285246B6 (cs) * 1992-11-27 1999-06-16 Eka Nobel Ab Způsob bělení buničiny obsahující lignocelulozu
BE1007700A3 (fr) * 1993-11-04 1995-10-03 Solvay Interox Procede pour le blanchiment d'une pate a papier chimique.

Also Published As

Publication number Publication date
NO961889L (no) 1996-05-09
JPH10500178A (ja) 1998-01-06
ES2129142T3 (es) 1999-06-01
FI961975A0 (fi) 1996-05-09
EP0728238A1 (de) 1996-08-28
DE69416000D1 (de) 1999-02-25
WO1995013420A1 (fr) 1995-05-18
NO961889D0 (no) 1996-05-09
FI961975A (fi) 1996-07-09
ZA948563B (en) 1995-06-30
ATE175738T1 (de) 1999-01-15
BE1007757A3 (fr) 1995-10-17
AU7993994A (en) 1995-05-29
MA23369A1 (fr) 1995-07-01
CA2176246A1 (fr) 1995-05-18
EP0728238B1 (de) 1999-01-13
BR9408027A (pt) 1996-12-17
ES2129142T5 (es) 2005-04-01

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