EP0728238A1 - Method of bleaching chemical paper pulp - Google Patents

Method of bleaching chemical paper pulp

Info

Publication number
EP0728238A1
EP0728238A1 EP94931025A EP94931025A EP0728238A1 EP 0728238 A1 EP0728238 A1 EP 0728238A1 EP 94931025 A EP94931025 A EP 94931025A EP 94931025 A EP94931025 A EP 94931025A EP 0728238 A1 EP0728238 A1 EP 0728238A1
Authority
EP
European Patent Office
Prior art keywords
pulp
sequence
treatment
carried out
acid
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.)
Granted
Application number
EP94931025A
Other languages
German (de)
French (fr)
Other versions
EP0728238B2 (en
EP0728238B1 (en
Inventor
François Desprez
Johan Devenyns
Nicholas A. Troughton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Solvay Chimie SA
Original Assignee
Solvay Interox SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=3887547&utm_source=***_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0728238(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Solvay Interox SA filed Critical Solvay Interox SA
Publication of EP0728238A1 publication Critical patent/EP0728238A1/en
Application granted granted Critical
Publication of EP0728238B1 publication Critical patent/EP0728238B1/en
Publication of EP0728238B2 publication Critical patent/EP0728238B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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.
  • the first step of a conventional chemical pulp bleaching sequence aims to complete the delignification of the unbleached pulp as it occurs after the cooking operation.
  • This first delignifying step is traditionally carried out by treating the unbleached pulp with chlorine in an acid medium or by a chlorine-chlorine dioxide association, in mixture or in sequence, so as to react with the residual lignin of the pulp and give rise to chlorolignins which can be extracted from the pulp by dissolving these chlorolignins in an alkaline medium in a subsequent treatment step.
  • the invention remedies these drawbacks of known methods by providing a new method for delignification and / or bleaching of chemical paper pulps which makes it possible to achieve high levels of whiteness without degrading the cellulose too strongly and without using chlorinated reagents.
  • the invention relates to a process for bleaching a chemical pulp, having undergone extensive cooking, by means of a sequence of treatment steps free of chlorinated reagents, according to which the sequence comprises the steps 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.
  • All types of wood used for the production of chemical pulps are suitable for carrying out the process of the invention and, in particular those used for kraft and sulphite pulps, namely softwoods such as, for example, the various species of pine and fir and deciduous woods like, for example, beech, oak, eucalyptus and hornbeam.
  • softwoods such as, for example, the various species of pine and fir and deciduous woods like, for example, beech, oak, eucalyptus and hornbeam.
  • extended cooking is intended to denote any process for cooking chemical pulp mentioned above in which the flow and recycling of the various cooking reagents and liquors, as well as the physical parameters of the process, are regulated so as to modifying the process in order to obtain an improved delignification rate while maintaining the viscosity of the cellulose at an acceptable level.
  • the first step is a step of decontamination of 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 polyphosphate inorganic, such as, for example, an alkali metal pyrophosphate or meta-phosphate, a polycarboxylate or an organic aminopolycarboxylate such as, for example, tartaric, citric, gluconic, ethylenediaminetetraacetic, diethylene triaminepentaacetic, cyclohexanediaminetetraacetic and their salts, poly- ⁇ hydroxyacrylic acid and its salts or an organic polyphosphonate such as ethylenediaminetetramethylphosphonic acids, diethylenetriaminepenta (methylenephosphonic), cyclohexanediaminetetramethylenephosphonic acids and their salts.
  • a small amount of acid can also be added in step Q.
  • Stage Q can also, as a variant, consist of a treatment with an acid free from 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 MgS ⁇ .7H2 ⁇ / 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.
  • bisul ⁇ fite is intended to denote the acid salts of sulfurous acid corresponding to the formula Me (HS ⁇ 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 about 5 or more and preferably about 5.5 or more. Likewise, the amount of acid will often be adjusted so that the pH does not exceed 7 and, preferably, not 6.5.
  • the pH will be adjusted so as to make the medium appreciably more acidic, that is to say, not exceeding pH 5 and, preferably not 4.5. Generally, in order not to degrade the dough, we should 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 pulp. Most often, this amount does not exceed 1.0 g of sequestering agent per 100 g of dry pulp.
  • 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 of the sequestrant and, at the same time not too high so as not to degrade the cell. ⁇ lose and not 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.
  • 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 strength qualities, 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 within wide limits depending on the type of equipment used, the choice of acid, the temperature and the pressure, for example from approximately 15 minutes to several hours. Times of at least 10 minutes and preferably at least 15 minutes are generally sufficient. Likewise, the pretreatment times generally do not exceed 60 minutes and preferably not 40 minutes. A duration of about 30 minutes has given excellent results.
  • Stage Q is generally carried out at a paste consistency of at least 2% dry matter and, preferably, at least 2.5 X dry matter. In most cases, this consistency does not exceed 15% and preferably not more than 10%. The consistency of approximately 3% of dry matter has given excellent results.
  • the second treatment step 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 H2O2 / 100 g of dry paste and preferably at least 0.5 g / 100 will be used. g dry dough.
  • the amounts of hydrogen peroxide should also generally not exceed 5.0 g H2O2 100 g of dry paste and preferably not 4.0 g / 100 g of dry paste.
  • step P The temperature of step P must be adjusted so as to remain at least equal to 50 ° C. and preferably to 70 ° C. It must also not exceed 150 ° C and preferably not exceed 135 ⁇ C. Temperatures of 90 ° C and 120 ° C have given excellent results.
  • An interesting variant of the process according to the invention consists in carrying out step P of the sequence at a high temperature of at least 100 ° C.
  • the temperature of this step P is preferably at least 110 ° C. It 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 the demotion of the whiteness of the dough will be reduced. In practice, it will be set at a value of at least 60 minutes and, preferably, at least 90 minutes. She will have to also most often do 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% of dry matter. It will often not be less than 5 X and preferably not less than 8 X.
  • step P can, as a variant, be advantageously chosen from high values of 25% by weight of dry matter or more.
  • a consistency of 30 X has given excellent results.
  • the sequence can be preceded by an oxygen step (step 0).
  • This oxygen step is carried out by bringing the paste into contact with gaseous oxygen at a pressure of between 20 and 1000 kPa in the presence of an alkaline compound in an amount such as the weight of alkaline compound relative to the dry dough weight is between 0.5 and 5 X.
  • the temperature of the oxygen step should generally be above 70 ° C and preferably 80 ° C. This temperature should also usually be 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 paste to be complete. However, it cannot exceed this reaction time too strongly, otherwise it will cause deterioration 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 the soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids. Magnesium salts are preferred, in particular, magnesium sulfate heptahydrate used in an amount of 0.02 to 1% by weight relative to the dry paste.
  • the consistency of paste in step 0 is generally not less than 8 X by weight of dry matter and, preferably, not less than 10 X. This consistency usually does not exceed 30 X by weight of dry matter and preferably 25 X.
  • step 0 can also be carried out in the presence of hydrogen peroxide (step Op).
  • the quantity of hydrogen peroxide which can be incorporated in step 0 is generally not less than 0.2 g H2O2 per 100 g of dry paste and, Q most often, not less than 0, 5 g. Likewise, we will usually not exceed 2.5 g H2O2 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.
  • an additional enzymatic step consisting in treating the dough with at least one enzyme can be incorporated at any point in the sequence of treatment steps.
  • This enzymatic treatment can also be carried out before or after the optional oxygen pretreatment step.
  • enzyme is intended to denote any enzyme capable of facilitating the delignification, by the stages of treatment subsequent to the stage of treatment with the enzyme, of an unbleached chemical paper pulp originating from the cooking operation. or a chemical 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 efficiency lies in the alkaline pH zone, and very particularly 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 capable of reacting with hemicelluloses on which the lignin present in the dough 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 bonds which constitute a major part of the interface between lignin and the rest carbohydrates.
  • An example of a xylanase in accordance with the process according to the invention is 1,4- ⁇ -D-xylan xylannohydrolase, EC 3.2.1.8.
  • the xylanases preferred in the methods according to the invention can be of various origins. In particular, they may 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 else 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 polymeric cellulose chains of the pulp.
  • An interesting variant of the process according to the invention consists in carrying out the enzymatic step X in the presence of at least one sequestering agent of metal ions.
  • the metal ion sequestrants can advantageously be chosen from the sequestrants suitable for step Q which are described above. It is also possible to perform step Q in the presence at least one enzyme. In this case, an enzyme can be used which conforms to those described above. It is also possible to combine the incorporation of enzyme in step Q with the addition of an enzymatic step at any point in the sequence.
  • Another variant of the process according to the invention consists in interposing an oxidizing step between step Q and step P. All the oxidizing chemical reagents are suitable for carrying out this oxidizing step. Among the oxidizing reagents known and usually used for delignifying and bleaching paper pulps, it is preferred to use reagents which do not contain 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_ ⁇ -H or also an ammonium salt or any metal of this acid.
  • the peroxyacids according to the invention can indif ⁇ ferently belong to the family of inorganic or organic peroxyacids.
  • the peroxyacid is an inorganic peroxyacid.
  • the inorganic peroxyacids according to the invention can comprise one or more perhydro ⁇ xyl groups. However, inorganic peroxyacids having only one perhydroxyl group are preferred. Examples of such inorganic peroxyacids are sulfuric, selenic, telluric, phosphoric, arsenic and silicic peroxyacids. Good results have been obtained with monoperoxysulfuric acid.
  • the peroxyacid is an organic peroxyacid.
  • the 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 peroxyacids comprising from one to three percarboxylic groups.
  • Aliphatic peroxyacids comprising a single percarboxylic group generally comprise a linear or branched saturated alkyl chain of less than 11 carbon atoms and, preferably less than 6 carbon atoms.
  • peroxyacids are peroxyacetic, peroxypropanoic, peroxybutanoic and peroxypentanoic acids.
  • Peroxy ⁇ acetic acid is particularly preferred because of its efficiency and the relative simplicity of its methods of preparation.
  • the aliphatic peroxyacids comprising two and three percarboxylic groups are selected from di- and triperoxyacidic carboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms.
  • diperoxyacids it is preferred that the two percarboxylic groups substitute carbon atoms located in the alpha-omega position relative to one another.
  • diperoxyacids are 1,6-diperoxyhexanedioic acid, 1,8-diperoxyoctanedioic acid and 1,10-diperoxydecanedioic acid, and 1,12-diperoxydodecanedioic acid.
  • An example of a triperoxyacid is triperoxycitric acid.
  • the aromatic peroxyacids are selected from those which comprise at least one peroxycarboxylic group per benzene nucleus.
  • the aromatic peroxyacids which have only one peroxycarbo ⁇ xyl group per benzene nucleus will be chosen.
  • An example of such an acid is peroxybenzoic acid.
  • organic peroxyacid substituted with any organic functional substituent is intended to denote 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 as the sulfo and mercapto groups. Mixtures of different inorganic and / or organic peroxyacids are also well suited.
  • the peroxyacid can indifferently be used in the form of a solution of peroxyacid or alternatively in the form of a solution of an ammonium salt, of an alkali metal or of an alkaline earth metal of this peroxyacid.
  • solution designate a solution in water or in an organic solvent.
  • Mixtures of organic solvents are also suitable for dissolving peroxyacids in accordance with the invention, as are 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 the effectiveness of the preceding cooking and delignification treatments. In practice, a quantity of peroxyacid is generally used which is not less than 0.2 g of H2O2 equivalent per 100 g of dry paste and, preferably, not less than 0.5 g / 100 g dry paste. Equivalent to H2O2. is intended to denote the amount of hydrogen peroxide which contains an identical amount of active oxygen. Usually, an amount of peroxyacid will not exceed 3 g of H2O2 equivalent per 100 g of dry paste and, preferably, 2 g of H2O2 equivalent / 100 g dry paste.
  • the peroxyacid treatment stage can also be carried out in the presence of one or more additives compatible with peroxyacids such as, for example, surfactants, stabilizers of peroxyacid, depolymerization inhibitors of cellulosic fibers and anti-corrosion agents.
  • additives compatible with peroxyacids
  • such additives are anionic surfactants, nonionic surfactants, soluble salts of Mg and sequestrants of metal ions.
  • the amount of these additives used does not exceed 3 g per 100 g of dry paste and, preferably, does not exceed 2.5 g per 100 g of dry paste.
  • 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 60 ° C. Likewise, this temperature generally does not exceed 100 ° C and preferably not 95 ° C. A temperature of 90 ° C has 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 essence of the wood used to prepare the dough, as well as the efficiency of the cooking and the steps that preceded it. Times of about 60 minutes to about 500 minutes are fine. A duration of 120 minutes has given excellent results.
  • the pH of the peroxyacid treatment stage can be in the range of both acidic and alkaline pHs. However, moderately acidic pHs are preferred. In practice, it is preferable to fix the initial pH at a value of 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, to 30% of dry matter. It will often not be less than 5% and preferably not less than 8 X. A consistency of 10 X has given good results.
  • the ozone treatment step consists in subjecting the dough to a gas stream consisting of a mixture of ozone and oxygen coming from an electric ozone generator supplied with dry oxygen gas. In the laboratory, a generator is advantageously used whose flow rate is from 50 to 100 l / hour and, preferably, from 70 to
  • the amount of ozone used can easily be adjusted by varying the duration of sweeping of the ozone / oxygen mixture stream on 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 very suitable and preferably 1.5 to 4.
  • a pH of 2 to 3 obtained by subjecting the dough to a 30 minute pre-conditioning treatment using an H2SO solution or SO2 at a rate of 0.5 X by weight of SO2 relative to the dry pulp and with a consistency of 3% dry matter has given very good results.
  • the consistency of the ozone treatment step will be selected from the range of 0.5 to 45% of dry matter and, preferably, from 0.5 to 3% (in the case of low-consistency apparatus) or between 10 to 15 X (case of medium consistency equipment). A consistency of 35% dry matter has given excellent results on a laboratory scale.
  • the temperature of the ozone treatment stage must remain low, otherwise the mechanical properties of the treated pulp will be seriously degraded. This temperature is generally from 2 to 50 ° C and preferably from 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 for opening the dough (called “fluffing" in the English-speaking literature) intended to increase the contact surface of the paste with ozone.
  • This operation is particularly useful when the consistency of the paste during the ozone treatment is at least 15% of dry matter.
  • the process according to the invention applies to the bleaching of any kind of chemical pulp which has undergone extensive cooking. It is well suited for delignifying kraft and sulfite pastes. It is particularly well suited for processing kraft pasta.
  • 1st stage oxygen stage (stage 0): pressure, kPa: 600 NaOH content, g / lOOg dry paste: 4 0 MgS ⁇ content. 7H2 ⁇ , g / lOOg dry paste: 0.5 temperature, degrees C: 120 duration, min: 60 consistency, X by weight of dry matter: 12
  • 3rd stage hydrogen peroxide stage (stage P): Q H2O2 content »g / 100g dry paste: example 1R 5.7 example 2R 3 example 3R 3 NaOH content, g / 100g dry paste: example 1R 1, 6 example 2R 2.0 example 3R 1.3 MgSO content .7H2 ⁇ , g / 100g dry paste 1.0 temperature, degrees C: example 1R 90 example 2R 120 example 3R 120 duration, min 240 consistency,% by weight of material dryer example 1R 30 example 2R 10 example 3R 30 where DTMPANa represents the heptasodium salt of diethylene triaminepenta (methylene phosphonic) acid.
  • the dough underwent a washing with demineralized water at room temperature.
  • step Q step at EDTA
  • step Q EDTA content, g / 100g dry paste: 0.4 H2SO4 content (for pH 5): 0.34 temperature, degrees C: 70 duration, min: 45 consistency
  • step P hydrogen peroxide stage
  • step P H2O2 content, g / lOOg dry paste: 3.0 NaOH content, g / lOOg dry paste: 1.3 MgS ⁇ 4.7H2 ⁇ content, g / 100g dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg
  • the paste was washed with demineralized water at room temperature.
  • the kappa index, the whiteness of the dough and its degree of polymerization were determined.
  • step Q step with EDTA
  • step Q EDTA content
  • g / lOOg dry paste 0.4 H2SO4 content (for pH 5): 0.34 temperature
  • degrees C 70 duration
  • min 45 consistency
  • X by weight of dry matter 10
  • 2nd stage peracetic acid stage (Paa stage): CH3CO3H content, g / lOOg dry paste: example 5: 1.0 example 6: 2.0 example 7: 3.0 DTMPANay content, g / lOOg dry paste: 0.1 MgSO4.7H2 ⁇ content, g / lOOg dry paste: 0.05 temperature, degrees C: 80 duration, min: 180 consistency, X by weight of dry matter: 10 where DTMPANay represents the heptasodium salt of diethylenetriaminepenta acid (methylenephosphonic).
  • 3rd stage hydrogen peroxide stage (stage P): H2O2 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 MgS ⁇ 4-7H2 ⁇ content, g / lOOg dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg dry paste: 3.0 temperature, degrees C: 90 duration, min: 240 consistency , X by weight of dry matter: 30
  • the paste was washed with demineralized water at room temperature.
  • the kappa index, the whiteness of the dough and its degree of polymerization were determined.
  • step Q step with EDTA
  • step Q content in EDTA, g / lOOg dry paste 0.4 H2SO4 content (for pH 5) 0.34 temperature, degrees C 70 duration, min 45 consistency
  • step C A Caro acid step
  • step C A H2SO5 content, g / lOOg dry paste: example 8: 1.5 example 9: 3.0 example 10 : 4.5 NaOH content, g / lOOg dry paste: example 8: 2.86 example 9: 5.76 example 10: 8.76 content of DTMPANa, g / lOOg of dry paste: 0.1 content of MgS ⁇ 4- 7H2 ⁇ , g / lOOg dry paste: 0.05 temperature, degrees C: 80 duration, min: 180 consistency, X by weight of dry matter: 10 where DTMPANa
  • 3rd stage hydrogen peroxide stage (stage P): H2O2 content, g / lOOg dry paste: 2.0 NaOH content, g / lOOg dry paste: example 8: 1.3 example 9: 1.4 example 10: 1.7 MgS ⁇ 4.7H2 ⁇ content, g / lOOg dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg dry paste: 3.0 temperature, degrees C: 90 duration, min: 240 consistency , X by weight of dry matter: 30

Landscapes

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

Abstract

Method of bleaching chemical paper pulp having undergone extensive cooking, involving a sequence of processing steps carried out without chlorine reagents. The pulp is subjected to decontamination from its transition metals and then to a step using alkaline hydrogen peroxide.

Description

Procédé pour le blanchiment d'une pâte à papier chimique Process for bleaching a chemical pulp
L'invention concerne un procédé de blanchiment d'une pâte à papier chimique.The invention relates to a process for bleaching a chemical pulp.
Il est connu de traiter les pâtes à papier chimiques écrues obtenues par cuisson de matières cellulosiques en présence de réactifs chimiques au moyen d'une séquence d'étapes de traitement délignifiant et blanchissant impliquant la mise en oeuvre de produits chimiques oxydants. La première étape d'une séquence classique de blanchiment de pâte chimique a pour objectif de parfaire la délignification de la pâte écrue telle qu'elle se présente après l'opération de cuisson. Cette première étape délignifiante est traditionnellement réalisée en traitant la pâte écrue par du chlore en milieu acide ou par une association chlore - dioxyde de chlore, en mélange ou en séquence, de façon à réagir avec la lignine résiduelle de la pâte et donner naissance à des chlorolignines qui pourront être extraites de la pâte par solubi- lisation de ces chlorolignines en milieu alcalin dans une étape de traitement ultérieure.It is known to treat unbleached chemical paper pulps obtained by cooking cellulosic materials in the presence of chemical reagents by means of a sequence of delignifying and whitening treatment steps involving the use of oxidizing chemicals. The first step of a conventional chemical pulp bleaching sequence aims to complete the delignification of the unbleached pulp as it occurs after the cooking operation. This first delignifying step is traditionally carried out by treating the unbleached pulp with chlorine in an acid medium or by a chlorine-chlorine dioxide association, in mixture or in sequence, so as to react with the residual lignin of the pulp and give rise to chlorolignins which can be extracted from the pulp by dissolving these chlorolignins in an alkaline medium in a subsequent treatment step.
Pour des raisons diverses, il s'avère utile, dans certaines situations, de pouvoir remplacer cette première étape déligni- fiante par un traitement qui ne fasse plus appel à un réactif chloré.For various reasons, it is useful, in certain situations, to be able to replace this first significant step with a treatment which no longer uses a chlorinated reagent.
Depuis environ une vingtaine d'années, on a proposé de faire précéder la première étape de traitement au moyen de chlore ou de l'association chlore - dioxyde de chlore par une étape à l'oxy- gène gazeux en milieu alcalin. (KIRK-OTHMER Encyclopedia ofFor about twenty years, it has been proposed to precede the first stage of treatment by means of chlorine or the combination of chlorine and chlorine dioxide by a stage with gaseous oxygen in an alkaline medium. (KIRK-OTHMER Encyclopedia of
Chemical Technology Third Edition Vol. 19, New-York 1982, page 415, 3e paragraphe et page 416, 1er et 2e paragraphes). Le taux de délignification que l'on obtient par ce traitement à l'oxygène n'est cependant pas suffisant si l'on vise à produire des pâtes chimiques de haute blancheur dont les propriétés mécaniques ne sont pas dégradées.Chemical Technology Third Edition Vol. 19, New York 1982, page 415, 3rd paragraph and page 416, 1st and 2nd paragraphs). The delignification rate obtained by this oxygen treatment is however not sufficient if the aim is to produce chemical pulps of high whiteness whose mechanical properties do not are not degraded.
Il a été proposé (Gellerstedt G et al. , "Chemical Aspects of Hydrogen Peroxide Bleaching. Part II. The Bleaching of Kraft Pulps.", Journal of Wood Chemistry and Technology, Vol. 2, n° 3, 1982, pages 231 à 250 et demande de brevet EP-A1-0456626) de blanchir des pâtes kraft au moyen de peroxyde d'hydrogène selon une séquence Q P ou 0 Q P (le sigle Q représentant une étape avec un séquestrant des ions métalliques, le sigle P une étape au peroxyde d'hydrogène et le sigle 0 une étape à l'oxygène). Ces procédés comprennent en outre obligatoirement des étapes supplé¬ mentaires mettant en oeuvre des réactifs chlorés tels que le dio- xyde de chlore.It has been proposed (Gellerstedt G et al., "Chemical Aspects of Hydrogen Peroxide Bleaching. Part II. The Bleaching of Kraft Pulps.", Journal of Wood Chemistry and Technology, Vol. 2, No. 3, 1982, pages 231 to 250 and patent application EP-A1-0456626) to whiten kraft pastes using hydrogen peroxide according to a QP or 0 QP sequence (the acronym Q representing a step with a sequestering agent of metal ions, the acronym P a step at hydrogen peroxide and acronym 0 a step with oxygen). These methods also necessarily include additional steps using chlorinated reagents such as chlorine dioxide.
L'invention remédie à ces inconvénients des procédés connus, en fournissant un procédé nouveau de délignification et/ou de blanchiment de pâtes à papier chimiques qui permet d'atteindre des niveaux élevés de blancheur sans dégrader trop fortement la cellulose et sans mettre en oeuvre de réactifs chlorés.The invention remedies these drawbacks of known methods by providing a new method for delignification and / or bleaching of chemical paper pulps which makes it possible to achieve high levels of whiteness without degrading the cellulose too strongly and without using chlorinated reagents.
A cet effet, l'invention concerne un procédé pour le blanchiment d'une pâte à papier chimique, ayant subi une cuisson extensive, au moyen d'une séquence d'étapes de traitement exemptes de réactifs chlorés, selon lequel la séquence comprend les étapes suivantes, effectuées dans l'ordre :To this end, the invention relates to a process for bleaching a chemical pulp, having undergone extensive cooking, by means of a sequence of treatment steps free of chlorinated reagents, according to which the sequence comprises the steps following steps, carried out in order:
Q P où le sigle Q représente une étape de décontamination de la pâte en ses métaux de transition et le sigle P représente une étape avec du peroxyde d'hydrogène alcalin.Q P where the acronym Q represents a step of decontaminating the pulp into its transition metals and the acronym P represents a step with alkaline hydrogen peroxide.
Par pâte à papier chimique on entend désigner les pâtes ayant subi un traitement délignifiant en présence de réactifs chimiques tels que le sulfure de sodium en milieu alcalin (cuisson kraft ou au sulfate), l'anhydride sulfureux ou un sel métallique de l'acide sulfureux en milieu acide (cuisson au sulfite ou au bisulfite). On entend également désigner ainsi les pâtes chimico-mécaniques et les pâtes semi-chimiques, par exemple celles où la cuisson a été réalisée à l'aide d'un sel de l'acide sulfureux en milieu neutre (cuisson au sulfite neutre encore appelée cuisson NSSC) qui peuvent aussi être blanchies par le procédé selon l'invention, de même que les pâtes obtenues par des procédés utilisant des solvants, comme, par exemple, les pâtes 0RGAN0S0LV, ALCELLR, 0RGAN0CELLR et ASAM décrites dans Ullmann's Encyclopedia of Industriel Chemistry, 5th Edition, Vol. A18, 1991, pages 568 et 569.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). It is also intended to denote thus the chemical-mechanical pastes and the semi-chemical pastes, for example those where the cooking was carried out using a sulfurous acid salt in a neutral medium (cooking with neutral sulfite also called cooking NSSC) which can also be laundered by the process according to the invention, as well as the pastes obtained by processes using solvents, such as, for example, the 0RGAN0S0LV, ALCELL R , 0RGAN0CELL R and ASAM pastes described in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A18, 1991, pages 568 and 569.
L'invention s'adresse particulièrement aux pâtes ayant subi une cuisson kraft ou une cuisson au sulfite.The invention is particularly intended for pasta which has undergone kraft cooking or sulphite cooking.
Tous les types de bois utilisés pour la production de pâtes chimiques conviennent pour la mise en oeuvre du procédé de l'invention et, en particulier ceux utilisés pour les pâtes kraft et au sulfite, à savoir les bois résineux comme, par exemple, les diverses espèces de pins et de sapins et les bois feuillus comme, par exemple, le hêtre, le chêne, l'eucalyptus et le charme. Selon l'invention, il importe que la pâte ait subi une cuisson extensive. Par cuisson extensive ("extended cooking"), on entend désigner tout procédé de cuisson de pâte chimique cité plus haut dans lequel on règle les flux et le recyclage des divers réactifs et liqueurs de cuisson, ainsi que les paramètres physiques du procédé, de manière à modifier le procédé en vue d'obtenir un taux de délignification amélioré tout en maintenant la viscosité de la cellulose à un niveau acceptable. Un exemple d'un tel procédé de cuisson extensive pour les pâtes kraft est décrit dans l'ouvrage de M. J. KOCUREK "Pulp and Paper Manufac¬ ture", Vol. 5, Alkaline Pulping, 3rd Edition, McGraw-Hill, New-York, 1989, page 122, paragraphe 3 (Modifications for low lignin pulping). Les pâtes ayant subi une cuisson extensive présentent généralement un indice kappa inférieur de 30 à 50 X par rapport à celui d'une même pâte ayant subi une cuisson normale. Les pâtes kraft ayant subi une cuisson extensive présentent le plus souvent un indice kappa de 20 ou moins dans le cas de bois résineux et de 14 ou moins dans le cas de bois feuillus.All types of wood used for the production of chemical pulps are suitable for carrying out the process of the invention and, in particular those used for kraft and sulphite pulps, namely softwoods such as, for example, the various species of pine and fir and deciduous woods like, for example, beech, oak, eucalyptus and hornbeam. According to the invention, it is important that the dough has undergone extensive cooking. The term "extended cooking" is intended to denote any process for cooking chemical pulp mentioned above in which the flow and recycling of the various cooking reagents and liquors, as well as the physical parameters of the process, are regulated so as to modifying the process in order to obtain an improved delignification rate while maintaining the viscosity of the cellulose at an acceptable level. An example of such an extensive cooking process for kraft pasta is described in the work by M. J. KOCUREK "Pulp and Paper Manufac¬ ture", Vol. 5, Alkaline Pulping, 3rd Edition, McGraw-Hill, New-York, 1989, page 122, paragraph 3 (Modifications for low lignin pulping). Pasta which has undergone extensive cooking generally has a kappa index 30 to 50 X lower than that of the same pasta which has undergone normal cooking. Kraft pasta which has undergone extensive cooking most often has a kappa number of 20 or less in the case of softwoods and 14 or less in the case of hardwoods.
Selon l'invention, la première étape est une étape de décon¬ tamination de la pâte en ses métaux de transition (étape Q). Selon l'invention, l'étape Q consiste à traiter la pâte par au moins un agent séquestrant tel qu'un phosphate ou polyphosphate inorganique, comme, par exemple, un pyrophosphate ou un méta- phosphate de métal alcalin, un polycarboxylate ou un aminopoly- carboxylate organique comme, par exemple, les acides tartrique, citrique, gluconique, éthylènediaminetétraacétique, diéthylène- triaminepentaacétique, cyclohexanediaminetétraacétique et leurs sels, l'acide poly-αîhydroxyacrylique et ses sels ou un poly- phosphonate organique comme les acides éthylènediaminetétraméthy- lènephosphonique, diéthylènetriaminepenta(méthylènephosphonique), cyclohexanediaminetétraméthylènephosphonique et leurs sels. Les acides éthylènediaminetétraacétique (EDTA) et diéthylènetriamine- pentaacétique (DTPA) ont donné d'excellents résultats.According to the invention, the first step is a step of decontamination of the pulp into its transition metals (step Q). According to the invention, step Q consists in treating the pulp with at least one sequestering agent such as a phosphate or polyphosphate inorganic, such as, for example, an alkali metal pyrophosphate or meta-phosphate, a polycarboxylate or an organic aminopolycarboxylate such as, for example, tartaric, citric, gluconic, ethylenediaminetetraacetic, diethylene triaminepentaacetic, cyclohexanediaminetetraacetic and their salts, poly-αhydroxyacrylic acid and its salts or an organic polyphosphonate such as ethylenediaminetetramethylphosphonic acids, diethylenetriaminepenta (methylenephosphonic), cyclohexanediaminetetramethylenephosphonic acids and their salts. Ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine-pentacetic acid (DTPA) have given excellent results.
En plus du séquestrant, on peut aussi ajouter une faible quantité d'acide à l'étape Q.In addition to the sequestrant, a small amount of acid can also be added in step Q.
L'étape Q peut aussi, en variante, consister en un traitement par un acide exempt d'un séquestrant, suivi d'une addition de sel soluble de magnésium en quantité telle que le rapport pondéral de la quantité de Mg à celle de Mn présent dans la pâte soit d'au moins 30. Généralement, des quantités de Mg correspondant à 1 à 4 g MgSθ .7H2θ / 100 g de pâte sèche sont suffisantes. Par acide, on entend désigner les anhydrides ou les acides inorganiques tels que l'anhydride sulfureux et les acides sulfurique, sulfureux, chlorhydrique, phosphorique et nitrique ou leurs sels acides, ainsi que les acides organiques tels que les acides carboxyliques ou phosphoniques ou leurs sels acides. L'acide sulfurique, l'anhydride sulfureux ou les bisulfites de métal alcalin ou alcalino-terreux conviennent bien. Par bisul¬ fite on entend désigner les sels acides de l'acide sulfureux répondant à la formule Me(HSθ3)n, dans laquelle Me symbolise un atome de métal de valence n, n étant un nombre entier valant 1 ou 2.Stage Q can also, as a variant, consist of a treatment with an acid free from 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 MgSθ .7H2θ / 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. By bisul¬ fite is intended to denote the acid salts of sulfurous acid corresponding to the formula Me (HSθ3) n, in which Me symbolizes a metal atom of valence n, n being an integer having the value 1 or 2.
La quantité d'acide à mettre en oeuvre dépendra du type de bois et de la quantité d'impuretés métalliques qu'il contient. En général, on mettra en oeuvre une quantité d'acide telle que le pH de la pâte soit d'environ 5 ou plus et, de préférence, d'environ 5,5 ou plus. De même, on ajustera souvent la quantité d'acide pour que le pH ne dépasse pas 7 et, de préférence, pas 6,5. Lorsque l'étape Q est exempte de séquestrant, le pH sera réglé de manière à rendre le milieu sensiblement plus acide, c'est-à-dire, ne dépassant pas pH 5 et, de préférence pas 4,5. Généralement, on évitera, afin de ne pas dégrader la pâte, de descendre en dessous de pH 1,5 et, de préférence, en dessous de pH 2,0.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 about 5 or more and preferably about 5.5 or more. Likewise, the amount of acid will often be adjusted so that the pH does not exceed 7 and, preferably, not 6.5. When step Q is free of sequestering agent, the pH will be adjusted so as to make the medium appreciably more acidic, that is to say, not exceeding pH 5 and, preferably not 4.5. Generally, in order not to degrade the dough, we should avoid going below pH 1.5 and, preferably, below pH 2.0.
Le séquestrant est généralement mis en oeuvre à l'étape Q en quantité ne dépassant pas 1,5 g de matière active pour 100 g de pâte sèche. Le plus souvent, cette quantité ne dépasse pas 1,0 g de séquestrant pour 100 g de pâte sèche.The sequestrant is generally used in step Q in an amount not exceeding 1.5 g of active material per 100 g of dry pulp. Most often, this amount does not exceed 1.0 g of sequestering agent per 100 g of dry pulp.
L'étape Q s'effectue généralement à une pression voisine de la pression atmosphérique et à une température suffisante pour assurer une bonne efficacité de l'acide et/ou du séquestrant et, dans le même temps pas trop élevée pour ne pas dégrader la cellu¬ lose et ne pas grever le coût énergétique des moyens de chauffage mis en oeuvre dans ladite étape. En pratique, une température d'au moins 40 °C et, de préférence, d'au moins 50 °C convient bien. De même, il est avantageux que la température ne dépasse pas 100 °C et, de préférence pas 90 °C.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 of the sequestrant and, at the same time not too high so as not to degrade the cell. ¬ lose and not burden the energy cost of the heating means used in said step. In practice, a temperature of at least 40 ° C and preferably at least 50 ° C is suitable. Likewise, it is advantageous that the temperature does not exceed 100 ° C and preferably not 90 ° C.
La durée de l'étape Q doit être suffisante pour assurer une réaction complète. Bien que des durées plus longues soient sans influence sur le taux de délignification de la pâte ainsi que sur ses qualités de résistance intrinsèques, il n'est pas conseillé de prolonger la durée de la réaction au-delà de celle nécessaire à l'achèvement de la réaction de façon à limiter les coûts d'investissement et les coûts énergétiques de chauffage de la pâte. En pratique, la durée du prétraitement peut varier dans de larges proportions selon le type d'équipement utilisé, le choix de l'acide, la température et la pression, par exemple de 15 minutes environ à plusieurs heures. Des durées d'au moins 10 minutes et, de préférence, d'au moins 15 minutes sont en général suffisantes. De même, les durées de prétraitement ne dépassent généralement pas 60 minutes et, de préférence pas 40 minutes. Une durée d'environ 30 minutes a donné d'excellents résultats.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 strength qualities, 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. In practice, the duration of the pretreatment can vary within wide limits depending on the type of equipment used, the choice of acid, the temperature and the pressure, for example from approximately 15 minutes to several hours. Times of at least 10 minutes and preferably at least 15 minutes are generally sufficient. Likewise, the pretreatment times generally do not exceed 60 minutes and preferably not 40 minutes. A duration of about 30 minutes has given excellent results.
L'étape Q s'effectue généralement à une consistance en pâte d'au moins 2 % de matières sèches et, de préférence, d'au moins 2,5 X de matières sèches. Le plus souvent, cette consistance ne dépasse pas 15 % et, de préférence pas 10 X. La consistance d'environ 3 % de matières sèches a donné d'excellents résultats.Stage Q is generally carried out at a paste consistency of at least 2% dry matter and, preferably, at least 2.5 X dry matter. In most cases, this consistency does not exceed 15% and preferably not more than 10%. The consistency of approximately 3% of dry matter has given excellent results.
Selon l'invention, la deuxième étape de traitement est une étape au peroxyde d'hydrogène alcalin (étape P). La nature de l'alcali doit être telle que celui-ci présente une bonne effica¬ cité d'extraction de la lignine oxydée en même temps qu'une bonne solubilité. Un exemple d'un tel alcali est l'hydroxyde de sodium en solution aqueuse. La quantité d'alcali à mettre en oeuvre doit être suffisante pour maintenir le pH au-dessus de 10 et, de préférence au-dessus de 11. La quantité d'alcali doit aussi être ajustée pour assurer une consommation suffisante du peroxyde à la fin de la réaction. En pratique, des quantités d'alcali de 1 à 4 g d'alcali pour 100 g de pâte sèche conviennent bien. On uti- lisera, en plus de ces quantités d'alcali une quantité de peroxyde d'hydrogène d'au moins 0,3 g H2O2/IOO g de pâte sèche et, de préférence, d'au moins 0,5 g/100 g de pâte sèche. Il convient aussi que les quantités de peroxyde d'hydrogène ne dépassent généralement pas 5,0 g H2O2 IOO g de pâte sèche et, de préférence, pas 4,0 g/100 g de pâte sèche.According to the invention, the second treatment step 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. In addition to these amounts of alkali, a quantity of hydrogen peroxide of at least 0.3 g H2O2 / 100 g of dry paste and preferably at least 0.5 g / 100 will be used. g dry dough. The amounts of hydrogen peroxide should also generally not exceed 5.0 g H2O2 100 g of dry paste and preferably not 4.0 g / 100 g of dry paste.
La température de l'étape P doit être ajustée de façon à rester au moins égale à 50 °C et, de préférence à 70 °C. Elle doit aussi ne pas dépasser 150 °C et, de préférence, ne pas dépasser 135 βC. Des températures de 90 °C et de 120 °C ont donné d'excellents résultats.The temperature of step P must be adjusted so as to remain at least equal to 50 ° C. and preferably to 70 ° C. It must also not exceed 150 ° C and preferably not exceed 135 β C. Temperatures of 90 ° C and 120 ° C have given excellent results.
Une variante intéressante du procédé selon l'invention consiste à effectuer l'étape P de la séquence à une température élevée d'au moins 100 °C. Selon cette variante, la température de cette étape P est de préférence d'au moins 110 °C. Elle ne dépasse généralement pas 140 °C et, de préférence, pas 135 °C.An interesting variant of the process according to the invention consists in carrying out step P of the sequence at a high temperature of at least 100 ° C. According to this variant, the temperature of this step P is preferably at least 110 ° C. It generally does not exceed 140 ° C and preferably not 135 ° C.
La durée de l'étape P doit être suffisante pour que la réaction de blanchiment soit aussi complète que possible. Elle ne peut cependant pas excéder trop fortement ce temps de réaction sous peine d'induire une rétrogradation de la blancheur de la pâte. En pratique, elle sera fixée à une valeur d'au moins 60 minutes et, de préférence, d'au moins 90 minutes. Elle devra aussi le plus souvent ne pas dépasser 600 et, de préférence, 500 minutes.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 the demotion of the whiteness of the dough will be reduced. In practice, it will be set at a value of at least 60 minutes and, preferably, at least 90 minutes. She will have to also most often do not exceed 600 and preferably 500 minutes.
La consistance de l'étape P est généralement choisie infé¬ rieure ou égale à 50 % en poids de matières sèches et, de préfé- rence, à 40 % de matières sèches. Elle ne sera souvent pas infé¬ rieure à 5 X et, de préférence, pas inférieure à 8 X.The consistency of step P is generally chosen to be less than or equal to 50% by weight of dry matter and, preferably, 40% of dry matter. It will often not be less than 5 X and preferably not less than 8 X.
La consistance de l'étape P peut, en variante, être avanta¬ geusement choisie parmi les valeurs élevées de 25 X en poids de matières sèches ou plus. Une consistance de 30 X a donné d'excellents résultats.The consistency of step P can, as a variant, be advantageously chosen from high values of 25% by weight of dry matter or more. A consistency of 30 X has given excellent results.
Dans une autre variante au procédé selon l'invention, on peut faire précéder la séquence par une étape à l'oxygène (étape 0). Cette étape à l'oxygène s'effectue par mise en contact de la pâte avec de l'oxygène gazeux sous une pression comprise entre 20 et 1000 kPa en présence d'un composé alcalin en quantité telle que le poids de composé alcalin par rapport au poids de pâte sèche soit compris entre 0,5 et 5 X.In another variant of the process according to the invention, the sequence can be preceded by an oxygen step (step 0). This oxygen step is carried out by bringing the paste into contact with gaseous oxygen at a pressure of between 20 and 1000 kPa in the presence of an alkaline compound in an amount such as the weight of alkaline compound relative to the dry dough weight is between 0.5 and 5 X.
La température de l'étape à l'oxygène doit généralement être supérieure à 70 °C et, de préférence, à 80 °C. Il convient aussi que cette température soit habituellement inférieure à 130 °C et, de préférence, à 120 °C.The temperature of the oxygen step should generally be above 70 ° C and preferably 80 ° C. This temperature should also usually be less than 130 ° C and preferably 120 ° C.
La durée du traitement par l'oxygène doit être suffisante pour que la réaction de l'oxygène avec la lignine contenue dans la pâte soit complète. Elle ne peut cependant pas excéder trop fortement ce temps de réaction sous peine d'induire des dégra¬ dations dans la structure des chaînes cellulosiques de la pâte. En pratique, elle sera d'au moins 30 minutes et, de préférence, d'au moins 40 minutes. Habituellement, elle ne dépassera pas 120 minutes et, de préférence, pas 80 minutes. Le traitement de la pâte par l'oxygène peut aussi se faire en présence d'un agent protecteur de la cellulose tel que les sels solubles de magnésium, les agents séquestrants organiques comme les acides polycarboxyliques ou phosphoniques. Les sels de magnésium sont préférés, en particulier, le sulfate de magnésium heptahydraté employé à raison de 0,02 à 1 X en poids par rapport à la pâte sèche. La consistance en pâte lors de l'étape 0 n'est généralement pas inférieure à 8 X en poids de matières sèches et, de préfé¬ rence, pas inférieure à 10 X. Cette consistance ne dépasse habi¬ tuellement pas 30 X en poids de matières sèches et, de préfé- 5 rence, 25 X.The duration of the oxygen treatment must be sufficient for the reaction of the oxygen with the lignin contained in the paste to be complete. However, it cannot exceed this reaction time too strongly, otherwise it will cause deterioration 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 the soluble magnesium salts, organic sequestering agents such as polycarboxylic or phosphonic acids. Magnesium salts are preferred, in particular, magnesium sulfate heptahydrate used in an amount of 0.02 to 1% by weight relative to the dry paste. The consistency of paste in step 0 is generally not less than 8 X by weight of dry matter and, preferably, not less than 10 X. This consistency usually does not exceed 30 X by weight of dry matter and preferably 25 X.
En variante, l'étape 0 peut aussi être effectuée en présence de peroxyde d'hydrogène (étape Op). La quantité de peroxyde d'hydrogène que l'on peut incorporer à l'étape 0 n'est généra¬ lement pas inférieure à 0,2 g H2O2 pour 100 g de pâte sèche et, Q le plus souvent, pas inférieure à 0,5 g. De même on ne dépassera habituellement pas 2,5 g H2O2 pour 100 g de pâte sèche et, le plus souvent, pas 2 g.Alternatively, step 0 can also be carried out in the presence of hydrogen peroxide (step Op). The quantity of hydrogen peroxide which can be incorporated in step 0 is generally not less than 0.2 g H2O2 per 100 g of dry paste and, Q most often, not less than 0, 5 g. Likewise, we will usually not exceed 2.5 g H2O2 per 100 g of dry paste and, most often, not 2 g.
D'une manière analogue, l'étape P peut aussi être renforcée par la présence d'oxygène gazeux (étape Eop). Dans ce cas, la pression d'oxygène mise en oeuvre sera le plus souvent d'au moins 20 kPa et d'au plus 1000 kPa.Similarly, step P can also be reinforced by the presence of gaseous oxygen (step Eop). In this case, the oxygen pressure used will most often be at least 20 kPa and at most 1000 kPa.
Dans une autre variante du procédé selon l'invention, on peut incorporer en un point quelconque de la séquence d'étapes de traitement une étape supplémentaire enzymatique consistant à traiter la pâte avec au moins une enzyme (étape X). Ce traitement enzymatique peut aussi être réalisé avant ou après l'étape de prétraitement à l'oxygène éventuelle.In another variant of the process according to the invention, an additional enzymatic step consisting in treating the dough with at least one enzyme (step X) can be incorporated at any point in the sequence of treatment steps. This enzymatic treatment can also be carried out before or after the optional oxygen pretreatment step.
Par enzyme, on entend désigner toute enzyme capable de faci¬ liter la délignification, par les étapes de traitement ulté- rieures à l'étape de traitement avec l'enzyme, d'une pâte à papier chimique écrue provenant de l'opération de cuisson ou d'une pâte à papier chimique ayant déjà été soumise à une étape de traitement par de l'oxygène.The term “enzyme” is intended to denote any enzyme capable of facilitating the delignification, by the stages of treatment subsequent to the stage of treatment with the enzyme, of an unbleached chemical paper pulp originating from the cooking operation. or a chemical pulp that has already been subjected to an oxygen treatment step.
De préférence, on utilisera une enzyme alcalophile, c'est-à-dire une enzyme dont l'efficacité maximale se situe dans la zone de pH alcalins, et tout particulièrement à un pH de 7.5 et plus.Preferably, an alkalophilic enzyme will be used, that is to say an enzyme whose maximum efficiency lies in the alkaline pH zone, and very particularly at a pH of 7.5 and above.
Une catégorie d'enzymes bien adaptées au procédé selon l'invention sont les hémicellulases. Ces enzymes sont aptes à réagir avec les hémicelluloses sur lesquelles est fixée la lignine présente dans la pâte. De préférence, les hémicellulases mises en oeuvre dans le procédé selon l'invention sont des xylanases, c'est-à-dire des enzymes hémicellulolytiques capables de couper les liens xylane qui constituent une partie majeure de l'interface entre la lignine et le reste des carbohydrates. Un exemple de xylanase conforme au procédé selon l'invention est la 1,4-β-D-xylane xyla- nohydrolase, EC 3.2.1.8.A category of enzymes well suited to the process according to the invention are hemicellulases. These enzymes are capable of reacting with hemicelluloses on which the lignin present in the dough is fixed. Preferably, the hemicellulases used in the process according to the invention are xylanases, that is to say hemicellulolytic enzymes capable of cutting the xylan bonds which constitute a major part of the interface between lignin and the rest carbohydrates. An example of a xylanase in accordance with the process according to the invention is 1,4-β-D-xylan xylannohydrolase, EC 3.2.1.8.
Les xylanases préférées dans les procédés selon l'invention peuvent être d'origines diverses. Elles peuvent en particulier avoir été sécrétées par une large gamme de bactéries et de champignons.The xylanases preferred in the methods according to the invention can be of various origins. In particular, they may have been secreted by a wide range of bacteria and fungi.
Les xylanases d'origine bactérienne sont particulièrement intéressantes. Parmi les xylanases d'origine bactérienne, les xylanases sécrétées par les bactéries du genre Bacillus ont donné de bons résultats.Xylanases of bacterial origin are particularly interesting. Among the xylanases of bacterial origin, the xylanases secreted by bacteria of the genus Bacillus have given good results.
Les xylanases dérivées de bactéries du genre Bacillus et de l'espèce pumilus ont donné d'excellents résultats. Parmi celles-ci, les xylanases provenant de Bacillus pumilus PRL B12 sont tout particulièrement intéressantes. Les xylanases de Bacillus pumilus PRL B12 conformes à l'invention peuvent provenir directement d'une souche de Bacillus pumilus PRL B12 ou encore d'une souche hôte d'un microorganisme différent qui a préalablement été manipulé génétiquement pour exprimer les gènes codant pour la dégradation des xylanes du Bacillus pumilus PRL B12.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 else 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.
De préférence, on utilisera une xylanase purifiée qui ne contient pas d'autres enzymes. En particulier, il est préféré que la xylanase conforme au procédé selon l'invention ne contienne pas de cellulase afin de ne pas détruire les chaînes polymériques de cellulose de la pâte.Preferably, a purified xylanase will be used which does not contain other enzymes. In particular, it is preferred that the xylanase according to the process according to the invention does not contain cellulase so as not to destroy the polymeric cellulose chains of the pulp.
Une variante intéressante du procédé selon l'invention consiste à effectuer l'étape enzymatique X en présence d'au moins un séquestrant des ions métalliques. Les séquestrants des ions métalliques peuvent avantageusement être choisis parmi les séquestrants convenant pour l'étape Q qui sont décrits plus haut. Il est également possible d'effectuer l'étape Q en présence d'au moins une enzyme. Dans ce cas, on peut utiliser une enzyme conforme à celles décrites plus haut. On peut aussi combiner l'incorporation d'enzyme dans l'étape Q avec l'addition d'une étape enzymatique en un point quelconque de la séquence. Une autre variante au procédé selon l'invention consiste à intercaler une étape oxydante entre l'étape Q et l'étape P. Tous les réactifs chimiques oxydants conviennent pour réaliser cette étape oxydante. Parmi les réactifs oxydants connus et utilisés habituellement pour délignifier et blanchir les pâtes à papier, on préfère utiliser les réactifs qui ne contiennent pas de chlore. Les peroxyacides et l'ozone sont particulièrement préférés.An interesting variant of the process according to the invention consists in carrying out the enzymatic step X in the presence of at least one sequestering agent of metal ions. The metal ion sequestrants can advantageously be chosen from the sequestrants suitable for step Q which are described above. It is also possible to perform step Q in the presence at least one enzyme. In this case, an enzyme can be used which conforms to those described above. It is also possible to combine the incorporation of enzyme in step Q with the addition of an enzymatic step at any point in the sequence. Another variant of the process according to the invention consists in interposing an oxidizing step between step Q and step P. All the oxidizing chemical reagents are suitable for carrying out this oxidizing step. Among the oxidizing reagents known and usually used for delignifying and bleaching paper pulps, it is preferred to use reagents which do not contain chlorine. Peroxyacids and ozone are particularly preferred.
Par peroxyacides, on entend désigner tous les acides comportant dans leur molécule au moins un groupe perhydroxyle _o_θ-H ou encore un sel d'ammonium ou d'un métal quelconque de cet acide. Les peroxyacides selon l'invention peuvent indif¬ féremment appartenir à la famille des peroxyacides inorganiques ou organiques.The term “peroxyacids” is intended to denote all the acids comprising in their molecule at least one perhydroxyl group _o_θ-H or also an ammonium salt or any metal of this acid. The peroxyacids according to the invention can indif¬ ferently belong to the family of inorganic or organic peroxyacids.
Selon une variante de l'invention, le peroxyacide est un peroxyacide inorganique. Les peroxyacides inorganiques conformes à l'invention peuvent comporter un ou plusieurs groupes perhydro¬ xyle. Les peroxyacides inorganiques comportant un seul groupe perhydroxyle sont cependant préférés. Des exemples de tels peroxyacides inorganiques sont les peroxyacides sulfurique, sélé- nique, tellurique, phosphoriques, arsénique et silicique. De bons résultats ont été obtenus avec l'acide monoperoxysulfurique. Selon une autre variante de l'invention, le peroxyacide est un peroxyacide organique. Les peroxyacides organiques conformes à l'invention sont sélectionnés parmi l'acide performique et les peroxyacides aliphatiques ou aromatiques.According to a variant of the invention, the peroxyacid is an inorganic peroxyacid. The inorganic peroxyacids according to the invention can comprise one or more perhydro¬ xyl groups. However, inorganic peroxyacids having only one perhydroxyl group are preferred. Examples of such inorganic peroxyacids are sulfuric, selenic, telluric, phosphoric, arsenic and silicic peroxyacids. Good results have been obtained with monoperoxysulfuric acid. According to another variant of the invention, the peroxyacid is an organic peroxyacid. The organic peroxyacids in accordance with the invention are selected from performic acid and aliphatic or aromatic peroxyacids.
Lorsque le peroxyacide organique est un peroxyacide alipha- tique, il est sélectionné parmi les peroxyacides comportant de un à trois groupes percarboxyliques.When the organic peroxyacid is an aliphatic peroxyacid, it is selected from peroxyacids comprising from one to three percarboxylic groups.
Les peroxyacides aliphatiques comportant un seul groupe percarboxylique comprennent généralement une chaîne alkyle saturée linéaire ou ramifiée de moins de 11 atomes de carbone et, de préférence, de moins de 6 atomes de carbone. Des exemples de tels peroxyacides sont les acides peroxyacétique, peroxypropa- noïque, peroxybutanoïques et peroxypentanoïques. L'acide peroxy¬ acétique est particulièrement préféré en raison de son efficacité et de la relative simplicité de ses méthodes de préparation. Les peroxyacides aliphatiques comportant deux et trois groupes percarboxyliques sont sélectionnés parmi les di- et triperoxyacides carboxyliques comportant une chaîne alkyle liné¬ aire ou ramifiée de moins de 16 atomes de carbone. Dans le cas des diperoxyacides, on préfère que les deux groupements percar¬ boxyliques substituent des atomes de carbone situés en position alpha-omega l'un par rapport à l'autre. Des exemples de tels diperoxyacides sont l'acide 1,6-diperoxyhexanedioïque, l'acide 1,8-diperoxyoctanedioïque et l'acide 1,10-diperoxydécanedioïque, et l'acide 1,12-diperoxydodécanedioïque. Un exemple de triper- oxyacide est l'acide triperoxycitrique.Aliphatic peroxyacids comprising a single percarboxylic group generally comprise a linear or branched saturated alkyl chain of less than 11 carbon atoms and, preferably less than 6 carbon atoms. Examples of such peroxyacids are peroxyacetic, peroxypropanoic, peroxybutanoic and peroxypentanoic acids. Peroxy¬ acetic acid is particularly preferred because of its efficiency and the relative simplicity of its methods of preparation. The aliphatic peroxyacids comprising two and three percarboxylic groups are selected from di- and triperoxyacidic carboxylic acids comprising a linear or branched alkyl chain of less than 16 carbon atoms. In the case of diperoxyacids, it is preferred that the two percarboxylic groups substitute carbon atoms located in the alpha-omega position relative to one another. Examples of such diperoxyacids are 1,6-diperoxyhexanedioic acid, 1,8-diperoxyoctanedioic acid and 1,10-diperoxydecanedioic acid, and 1,12-diperoxydodecanedioic acid. An example of a triperoxyacid is triperoxycitric acid.
Les peroxyacides aromatiques sont sélectionnés parmi ceux qui comportent au moins un groupement peroxycarboxylique par noyau benzénique. De préférence, on choisira les peroxyacides aromatiques qui ne comportent qu'un seul groupement peroxycarbo¬ xylique par noyau benzénique. Un exemple d'un tel acide est l'acide peroxybenzoïque.The aromatic peroxyacids are selected from those which comprise at least one peroxycarboxylic group per benzene nucleus. Preferably, the aromatic peroxyacids which have only one peroxycarbo¬ xyl group per benzene nucleus will be chosen. An example of such an acid is peroxybenzoic acid.
Une autre variante du procédé selon l'invention consiste à choisir un peroxyacide organique substitué par tout substituant fonctionnel organique. Par substituant fonctionnel organique, on entend désigner un groupement fonctionnel tel que le groupement carbonyle (cétone, aldéhyde ou acide carboxylique), le groupement alcool, les groupements contenant de l'azote tels que les groupements nitrile, nitro, aminé et amide, les groupements contenant du soufre tels que les groupements sulfo et mercapto. Des mélanges de différents peroxyacides inorganiques et/ou organiques sont également bien adaptés.Another variant of the process according to the invention consists in choosing an organic peroxyacid substituted with any organic functional substituent. The term “organic functional substituent” is intended to denote 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 as the sulfo and mercapto groups. Mixtures of different inorganic and / or organic peroxyacids are also well suited.
Le peroxyacide peut indifféremment être mis en oeuvre à l'état d'une solution de peroxyacide ou encore sous forme d'une solution d'un sel d'ammonium, de métal alcalin ou de métal alcalino-terreux de ce peroxyacide. Par solution on entend désigner une solution dans l'eau ou dans un solvant organique. Les mélanges de solvants organiques conviennent églement pour la mise en solution des peroxyacides conformément à l'invention, de même que les mélanges d'eau avec un ou de plusieurs solvants organiques miscibles à l'eau. Les solutions aqueuses sont préférées.The peroxyacid can indifferently be used in the form of a solution of peroxyacid or alternatively in the form of a solution of an ammonium salt, of an alkali metal or of an alkaline earth metal of this peroxyacid. By solution is meant designate a solution in water or in an organic solvent. Mixtures of organic solvents are also suitable for dissolving peroxyacids in accordance with the invention, as are mixtures of water with one or more organic solvents miscible with water. Aqueous solutions are preferred.
La quantité de peroxyacide à mettre en oeuvre dans l'étape oxydante peut varier dans une large gamme. Elle dépend du type de bois utilisé et de l'efficacité des traitements de cuisson et de délignification qui ont précédé. En pratique, on met généra¬ lement en oeuvre une quantité de peroxyacide qui n'est pas infé¬ rieure à 0,2 g d'équivalent H2O2 pour 100 g de pâte sèche et, de préférence, pas inférieure à 0,5 g/100 g pâte sèche. Par équi¬ valent H2O2. on entend désigner la quantité de peroxyde d'hydro¬ gène qui contient une quantité identique d'oxygène actif. Habi¬ tuellement, on ne dépassera pas une quantité de peroxyacide de 3 g d'équivalent H2O2 pour 100 g de pâte sèche et, de préférence, 2 g d'équivalent H2O2/IOO g pâte sèche.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 the effectiveness of the preceding cooking and delignification treatments. In practice, a quantity of peroxyacid is generally used which is not less than 0.2 g of H2O2 equivalent per 100 g of dry paste and, preferably, not less than 0.5 g / 100 g dry paste. Equivalent to H2O2. is intended to denote the amount of hydrogen peroxide which contains an identical amount of active oxygen. Usually, an amount of peroxyacid will not exceed 3 g of H2O2 equivalent per 100 g of dry paste and, preferably, 2 g of H2O2 equivalent / 100 g dry paste.
L'étape de traitement au peroxyacide peut aussi être réa¬ lisée en présence d'un ou plusieurs additifs compatibles avec les peroxyacides tels que, par exemple, des tensioactifs, des stabi¬ lisants du peroxyacide, des inhibiteurs de dépolymérisation des fibres cellulosiques et des agents anti-corrosion. Des exemples de tels additifs sont les tensio-actifs anioniques, les tensio- actifs non-ioniques, les sels solubles de Mg et les séquestrants des ions métalliques. En règle générale, lorsqu'ils sont présents, la quantité de ces additifs mise en oeuvre ne dépasse pas 3 g pour 100 g de pâte sèche et, de préférence, ne dépasse pas 2,5 g pour 100 g de pâte sèche. L'étape de traitement au peroxyacide selon l'invention peut s'effectuer dans une large gamme de températures. En général, on effectuera le traitement au peroxyacide à une température d'au moins 40 °C et, de préférence d'au moins 60 °C. De même, cette température ne dépasse généralement pas 100 °C et, de préférence, pas 95 °C. Une température de 90 °C a conduit à de bons résultats. Généralement, on effectue le traitement avec le peroxyacide organique à pression atmosphérique. La durée de ce traitement dépend de la température et de l'essence du bois ayant servi à préparer la pâte, ainsi que de l'efficacité de la cuisson et des étapes qui ont précédé. Des durées d'environ 60 minutes à environ 500 minutes conviennent bien. Une durée de 120 minutes a donné d'excellents résultats.The peroxyacid treatment stage can also be carried out in the presence of one or more additives compatible with peroxyacids such as, for example, surfactants, stabilizers of peroxyacid, depolymerization inhibitors of cellulosic fibers and anti-corrosion agents. Examples of such additives are anionic surfactants, nonionic surfactants, soluble salts of Mg and sequestrants of metal ions. As a general rule, when they are present, the amount of these additives used does not exceed 3 g per 100 g of dry paste and, preferably, does not exceed 2.5 g per 100 g of dry paste. The peroxyacid treatment step according to the invention can be carried out over a wide range of temperatures. In general, the peroxyacid treatment will be carried out at a temperature of at least 40 ° C and preferably at least 60 ° C. Likewise, this temperature generally does not exceed 100 ° C and preferably not 95 ° C. A temperature of 90 ° C has led to good results. Generally, the treatment is carried out with organic peroxyacid at atmospheric pressure. The duration of this treatment depends on the temperature and the essence of the wood used to prepare the dough, as well as the efficiency of the cooking and the steps that preceded it. Times of about 60 minutes to about 500 minutes are fine. A duration of 120 minutes has given excellent results.
Le pH de l'étape de traitement au peroxyacide peut se situer aussi bien dans la gamme des pH acides que des pH alcalins. On préfère cependant les pH modérément acides. En pratique, on préfère fixer le pH initial à une valeur d'au moins 3,5. On ne dépassera généralement pas un pH initial de 5. Un pH initial de 4 a conduit à de bons résultats.The pH of the peroxyacid treatment stage can be in the range of both acidic and alkaline pHs. However, moderately acidic pHs are preferred. In practice, it is preferable to fix the initial pH at a value of at least 3.5. An initial pH of 5 will generally not be exceeded. An initial pH of 4 has led to good results.
La consistance en pâte de l'étape de traitement au peroxy- acide est généralement choisie inférieure ou égale à 40 % en poids de matières sèches et, de préférence, à 30 % de matières sèches. Elle ne sera souvent pas inférieure à 5 % et, de préfé¬ rence, pas inférieure à 8 X. Une consistance de 10 X a donné de bons résultats. Selon une autre variante de l'invention, l'étape de traitement à l'ozone consiste à soumettre la pâte à un courant gazeux constitué d'un mélange d'ozone et d'oxygène provenant d'un générateur électrique d'ozone alimenté en oxygène gazeux sec. En laboratoire, on utilise avantageusement un générateur dont le débit est de 50 à 100 1/heure et, de préférence, de 70 àThe 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, to 30% of dry matter. It will often not be less than 5% and preferably not less than 8 X. A consistency of 10 X has given good results. According to another variant of the invention, the ozone treatment step consists in subjecting the dough to a gas stream consisting of a mixture of ozone and oxygen coming from an electric ozone generator supplied with dry oxygen gas. In the laboratory, a generator is advantageously used whose flow rate is from 50 to 100 l / hour and, preferably, from 70 to
90 1/heure. La quantité d'ozone mise en oeuvre peut facilement être ajustée en faisant varier la durée de balayage du courant de mélange ozone/oxygène sur la pâte. Généralement, des durées de 20 à 80 minutes suffisent pour mettre en oeuvre une quantité d'ozone de 0,4 à 2 g pour 100 g de pâte sèche. A l'échelle industrielle, on s'arrangera pour régler le débit des générateurs d'ozone et la durée du traitement pour fixer la quantité d'ozone mise en oeuvre sur la pâte à des valeurs semblables à celles que l'on réalise en laboratoire. Grâce à la technique de travail en continu, il sera possible en milieu industriel, de réduire de manière substantielle la durée du traitement jusqu'à descendre à des durées de l'ordre de 1 minute.90 1 / hour. The amount of ozone used can easily be adjusted by varying the duration of sweeping of the ozone / oxygen mixture stream on 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. On an industrial scale, we will manage to regulate the flow rate of the ozone generators and the duration of the treatment to fix the quantity of ozone used on the dough at values similar to those which we realize in the laboratory. . Thanks to the technique of continuous work, it will be possible in an industrial environment, to substantially reduce the duration of treatment until it drops to durations of the order of 1 minute.
Le traitement à l'ozone se réalise de préférence en milieu acide. Des pH de 0,5 à 5 conviennent bien et, de préférence, de 1,5 à 4. Un pH de 2 à 3 obtenu en soumettant la pâte à un traitement de conditionnement préalable de 30 minutes au moyen d'une solution de H2SO ou de SO2 à raison de 0,5 X en poids de SO2 par rapport à la pâte sèche et avec une consistance de 3 % de matières sèches a donné de très bons résultats.The ozone treatment is preferably carried out in an acid medium. A pH of 0.5 to 5 is very suitable and preferably 1.5 to 4. A pH of 2 to 3 obtained by subjecting the dough to a 30 minute pre-conditioning treatment using an H2SO solution or SO2 at a rate of 0.5 X by weight of SO2 relative to the dry pulp and with a consistency of 3% dry matter has given very good results.
La consistance de l'étape de traitement à l'ozone sera sélectionnée dans la gamme de 0,5 à 45 % de matières sèches et, de préférence de 0,5 à 3 % (cas des appareillages à basse consis¬ tance) ou entre 10 à 15 X (cas des appareillages à consistance moyenne). Une consistance de 35 X de matières sèches a donné d'excellents résultats à l'échelle du laboratoire. La température de l'étape de traitement à l'ozone doit rester peu élevée sous peine de conduire à des dégradations importantes des propriétés mécaniques de la pâte traitée. Cette température est généralement de 2 à 50 °C et, de préférence de 10 à 35 °C. Le plus souvent, on réalise simplement le traitement à l'ozone à température ambiante.The consistency of the ozone treatment step will be selected from the range of 0.5 to 45% of dry matter and, preferably, from 0.5 to 3% (in the case of low-consistency apparatus) or between 10 to 15 X (case of medium consistency equipment). A consistency of 35% dry matter has given excellent results on a laboratory scale. The temperature of the ozone treatment stage must remain low, otherwise the mechanical properties of the treated pulp will be seriously degraded. This temperature is generally from 2 to 50 ° C and preferably from 10 to 35 ° C. Most often, the ozone treatment is simply carried out at room temperature.
Une variante intéressante du procédé selon l'invention consiste à faire précéder le traitement à l'ozone par un traitement mécanique d'ouverture de la pâte (appelé "fluffing" dans la littérature anglo-saxonne) destiné à accroître la surface de contact de la pâte avec l'ozone. Cette opération est particu¬ lièrement utile lorsque la consistance de la pâte lors du traitement à l'ozone est d'au moins 15 X de matières sèches.An interesting variant of the process according to the invention consists in preceeding the ozone treatment by a mechanical treatment for opening the dough (called "fluffing" in the English-speaking literature) intended to increase the contact surface of the paste with ozone. This operation is particularly useful when the consistency of the paste during the ozone treatment is at least 15% of dry matter.
Le procédé conforme à l'invention s'applique au blanchiment de toute espèce de pâte chimique ayant subi une cuisson exten- sive. Il convient bien pour délignifier les pâtes kraft et au sulfite. Il est particulièrement bien adapté au traitement des pâtes kraft.The process according to the invention applies to the bleaching of any kind of chemical pulp which has undergone extensive cooking. It is well suited for delignifying kraft and sulfite pastes. It is particularly well suited for processing kraft pasta.
Les exemples qui suivent sont donnés dans le but d'illustrer l'invention, sans pour autant en limiter la portée. Exemples 1R à 3R (non conformes à l'invention)The examples which follow are given for the purpose of illustrating the invention, without however limiting its scope. Examples 1R to 3R (not in accordance with the invention)
Un échantillon de pâte de résineux ayant subi une cuisson kraft normale (blancheur initiale 27,9 °IS0 mesurée selon la norme ISO 2470-1977(F), indice kappa 26,7 mesuré selon la normeA sample of baked softwood pulp normal kraft (initial whiteness 27.9 ° IS0 measured according to ISO 2470-1977 (F), kappa index 26.7 measured according to standard
SCAN Cl-59 et degré de polymérisation 1680 exprimé en nombre d'unités glucosiques et mesuré selon la norme SCAN C15-62) a été traité suivant une séquence de 3 étapes 0 Q P dans les conditions suivantes :SCAN Cl-59 and degree of polymerization 1680 expressed in number of glucosic units and measured according to standard SCAN C15-62) was treated according to a sequence of 3 steps 0 Q P under the following conditions:
Ire étape : étape à l'oxygène (étape 0) : pression, kPa : 600 teneur en NaOH, g/lOOg pâte sèche : 4 0 teneur en MgSθ .7H2θ, g/lOOg pâte sèche : 0,5 température, degrés C : 120 durée, min : 60 consistance, X en poids de matière sèche : 121st stage: oxygen stage (stage 0): pressure, kPa: 600 NaOH content, g / lOOg dry paste: 4 0 MgSθ content. 7H2θ, g / lOOg dry paste: 0.5 temperature, degrees C: 120 duration, min: 60 consistency, X by weight of dry matter: 12
2e étape : étape à l'EDTA (étape Q) : 5 teneur en EDTA, g/lOOg pâte sèche : 0,4 température, degrés C : 70 durée, min : 45 consistance, X en poids de matière sèche : 102nd stage: EDTA stage (stage Q): 5 EDTA content, g / lOOg dry paste: 0.4 temperature, degrees C: 70 duration, min: 45 consistency, X by weight of dry matter: 10
3e étape : étape au peroxyde d'hydrogène (étape P) : Q teneur en H2O2» g/lOOg pâte sèche : exemple 1R 5,7 exemple 2R 3 exemple 3R 3 teneur en NaOH, g/100g pâte sèche : exemple 1R 1,6 exemple 2R 2,0 exemple 3R 1,3 teneur en MgSÛ .7H2θ, g/100g pâte sèche 1,0 température, degrés C : exemple 1R 90 exemple 2R 120 exemple 3R 120 durée, min 240 consistance, % en poids de matière sèche exemple 1R 30 exemple 2R 10 exemple 3R 30 où DTMPANa représente le sel heptasodique de l'acide diéthylène- triaminepenta(méthylènephosphonique).3rd stage: hydrogen peroxide stage (stage P): Q H2O2 content »g / 100g dry paste: example 1R 5.7 example 2R 3 example 3R 3 NaOH content, g / 100g dry paste: example 1R 1, 6 example 2R 2.0 example 3R 1.3 MgSO content .7H2θ, g / 100g dry paste 1.0 temperature, degrees C: example 1R 90 example 2R 120 example 3R 120 duration, min 240 consistency,% by weight of material dryer example 1R 30 example 2R 10 example 3R 30 where DTMPANa represents the heptasodium salt of diethylene triaminepenta (methylene phosphonic) acid.
A l'issue de chaque étape de traitement, la pâte a subi un lavage à l'eau déminéralisée à température ambiante.At the end of each processing step, the dough underwent a washing with demineralized water at room temperature.
Après traitement, on a déterminé l'indice kappa, la blancheur de la pâte et son degré de polymérisation. Les résultats figurent au tableau qui suit.After treatment, the kappa number, the whiteness of the dough and its degree of polymerization were determined. The results are shown in the table below.
Exemple Blancheur Indice Degré deExample Whiteness Degree Index
No. finale kappa polymérisationKappa polymerization final number
°IS0 final° IS0 final
1R 85,0 4,91 9701R 85.0 4.91 970
2R 77,1 5,99 11302R 77.1 5.99 1130
3R 84,7 4,76 8503R 84.7 4.76 850
On voit que malgré la quantité importante de peroxyde d'hydrogène mise en oeuvre, il n'a pas été possible de dépasserWe see that despite the large amount of hydrogen peroxide used, it was not possible to exceed
85 °IS0 de blancheur.85 ° IS0 whiteness.
Exemple 4 : (conforme à l'invention)Example 4: (according to the invention)
Un autre échantillon de pâte de résineux ayant subi une cuisson kraft extensive et un traitement industriel de blanchiment par l'oxygène (blancheur initiale 58,5 °IS0 mesurée selon la norme ISO 2470-1977(F), indice kappa 3,7 mesuré selon la norme SCAN Cl-59 et degré de polymérisation 800 exprimé en nombre d'unités glucosiques et mesuré selon la norme SCAN C15-62) a été traité suivant une séquence de 2 étapes Q P dans les conditions suivantes : le étape : étape à l'EDTA (étape Q) : teneur en EDTA, g/100g pâte sèche : 0,4 teneur en H2SO4 (pour pH 5) : 0,34 température, degrés C : 70 durée, min : 45 consistance, X en poids de matière sèche : 10 2e étape : étape au peroxyde d'hydrogène (étape P) : teneur en H2O2, g/lOOg pâte sèche : 3,0 teneur en NaOH, g/lOOg pâte sèche : 1,3 teneur en MgSθ4.7H2θ, g/100g pâte sèche : 1,0 teneur en silicate de Na 38 °Bé, g/lOOg pâte sèche : 3,0 température, degrés C : 120 durée, min : 240 consistance, X en poids de matière sèche : 30Another softwood pulp sample having undergone extensive kraft cooking and industrial oxygen bleaching treatment (initial whiteness 58.5 ° IS0 measured according to ISO 2470-1977 (F), kappa index 3.7 measured according to SCAN standard Cl-59 and degree of polymerization 800 expressed in number of glucosic units and measured according to standard SCAN C15-62) was treated according to a sequence of 2 steps QP under the following conditions: step: step at EDTA (step Q): EDTA content, g / 100g dry paste: 0.4 H2SO4 content (for pH 5): 0.34 temperature, degrees C: 70 duration, min: 45 consistency, X by weight of dry matter : 10 2nd stage: hydrogen peroxide stage (stage P): H2O2 content, g / lOOg dry paste: 3.0 NaOH content, g / lOOg dry paste: 1.3 MgSθ4.7H2θ content, g / 100g dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg dry paste: 3.0 temperature, degrees C: 120 duration, min: 240 consistency, X by weight of dry matter: 30
A l'issue de chaque étape de traitement, la pâte a subi un lavage à l'eau déminéralisée à température ambiante.At the end of each treatment step, the paste was washed with demineralized water at room temperature.
En fin de séquence, après traitement, on a déterminé l'indice kappa, la blancheur de la pâte et son degré de polyméri¬ sation.At the end of the sequence, after treatment, the kappa index, the whiteness of the dough and its degree of polymerization were determined.
Les résultats obtenus ont été :The results obtained were:
Exemple Blancheur Indice Degré de No. finale kappa polymérisationExample Whiteness Index Degree of final No. kappa polymerization
°IS0 final° IS0 final
4 88,0 1,6 7104 88.0 1.6 710
Exemples 5 à 7 : (conformes à l'invention)Examples 5 to 7: (in accordance with the invention)
Le même échantillon de pâte préblanchi à l'oxygène qu'à l'exemple 4 a été blanchi selon la séquence Q Paa P, le sigle Paa désignant une étape à l'acide peracetique. Les conditions opératoires réalisées ont été les suivantes : le étape : étape à l'EDTA (étape Q) : teneur en EDTA, g/lOOg pâte sèche : 0,4 teneur en H2SO4 (pour pH 5) : 0,34 température, degrés C : 70 durée, min : 45 consistance, X en poids de matière sèche : 10The same sample of pulp prebleached with oxygen as in Example 4 was bleached according to the Q Paa P sequence, the acronym Paa denoting a step with peracetic acid. The operating conditions carried out were as follows: step: step with EDTA (step Q): EDTA content, g / lOOg dry paste: 0.4 H2SO4 content (for pH 5): 0.34 temperature, degrees C: 70 duration, min: 45 consistency, X by weight of dry matter: 10
2e étape : étape à l'acide peracetique (étape Paa) : teneur en CH3CO3H, g/lOOg pâte sèche : exemple 5 : 1,0 exemple 6 : 2,0 exemple 7 : 3,0 teneur en DTMPANay, g/lOOg de pâte sèche : 0,1 teneur en MgSÛ4.7H2θ, g/lOOg pâte sèche : 0,05 température, degrés C : 80 durée, min : 180 consistance, X en poids de matière sèche : 10 où DTMPANay représente le sel heptasodique de l'acide diéthylènetriaminepenta(méthylènephosphonique). 3e étape : étape au peroxyde d'hydrogène (étape P) : teneur en H2O2, g/100g pâte sèche : 2,0 teneur en NaOH, g/lOOg pâte sèche : exemple 5 : 1,0 exemple 6 : 1,2 exemple 7 : 1,6 teneur en MgSθ4-7H2θ, g/lOOg pâte sèche : 1,0 teneur en silicate de Na 38 °Bé, g/lOOg pâte sèche : 3,0 température, degrés C : 90 durée, min : 240 consistance, X en poids de matière sèche : 302nd stage: peracetic acid stage (Paa stage): CH3CO3H content, g / lOOg dry paste: example 5: 1.0 example 6: 2.0 example 7: 3.0 DTMPANay content, g / lOOg dry paste: 0.1 MgSO4.7H2θ content, g / lOOg dry paste: 0.05 temperature, degrees C: 80 duration, min: 180 consistency, X by weight of dry matter: 10 where DTMPANay represents the heptasodium salt of diethylenetriaminepenta acid (methylenephosphonic). 3rd stage: hydrogen peroxide stage (stage P): H2O2 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 MgSθ4-7H2θ content, g / lOOg dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg dry paste: 3.0 temperature, degrees C: 90 duration, min: 240 consistency , X by weight of dry matter: 30
A l'issue de chaque étape de traitement, la pâte a subi un lavage à l'eau déminéralisée à température ambiante.At the end of each treatment step, the paste was washed with demineralized water at room temperature.
En fin de séquence, après traitement, on a déterminé l'indice kappa, la blancheur de la pâte et son degré de polyméri¬ sation.At the end of the sequence, after treatment, the kappa index, the whiteness of the dough and its degree of polymerization were determined.
Les résultats obtenus ont été les suivants :The results obtained were as follows:
Exemple Blancheur Indice Degré deExample Whiteness Degree Index
No. finale kappa polymérisationKappa polymerization final number
°IS0 final° IS0 final
5 86,4 1,7 7605 86.4 1.7 760
6 90,5 0,9 6906 90.5 0.9 690
7 91,4 0,7 6807 91.4 0.7 680
Exemples 8 à 10 : (conformes à l'invention)Examples 8 to 10: (in accordance with the invention)
Le même échantillon de pâte préblanchie à l'oxygène qu'aux exemples 5 à 8 a été blanchi selon la séquence Q C^ P. Les conditions opératoires réalisées ont été les suivantes : le étape : étape à l'EDTA (étape Q) : teneur en EDTA, g/lOOg pâte sèche 0,4 teneur en H2SO4 (pour pH 5) 0,34 température, degrés C 70 durée, min 45 consistance, X en poids de matière sèche : 10 2e étape : étape à l'acide de Caro (étape CA) : teneur en H2SO5, g/lOOg pâte sèche : exemple 8 : 1,5 exemple 9 : 3,0 exemple 10 : 4,5 teneur en NaOH, g/lOOg pâte sèche : exemple 8 : 2,86 exemple 9 : 5,76 exemple 10 : 8,76 teneur en DTMPANa , g/lOOg de pâte sèche : 0,1 teneur en MgSθ4-7H2θ, g/lOOg pâte sèche : 0,05 température, degrés C : 80 durée, min : 180 consistance, X en poids de matière sèche : 10 où DTMPANa représente le sel heptasodique de l'acide diéthylène- triaminepenta(méthylènephosphonique). 3e étape : étape au peroxyde d'hydrogène (étape P) : teneur en H2O2, g/lOOg pâte sèche : 2,0 teneur en NaOH, g/lOOg pâte sèche : exemple 8 : 1,3 exemple 9 : 1,4 exemple 10 : 1,7 teneur en MgSθ4.7H2θ, g/lOOg pâte sèche : 1,0 teneur en silicate de Na 38 °Bé, g/lOOg pâte sèche : 3,0 température, degrés C : 90 durée, min : 240 consistance, X en poids de matière sèche : 30The same sample of pulp prebleached with oxygen as in Examples 5 to 8 was bleached according to the sequence QC ^ P. The operating conditions carried out were as follows: step: step with EDTA (step Q): content in EDTA, g / lOOg dry paste 0.4 H2SO4 content (for pH 5) 0.34 temperature, degrees C 70 duration, min 45 consistency, X by weight of dry matter: 10 2nd step: Caro acid step (step C A ): H2SO5 content, g / lOOg dry paste: example 8: 1.5 example 9: 3.0 example 10 : 4.5 NaOH content, g / lOOg dry paste: example 8: 2.86 example 9: 5.76 example 10: 8.76 content of DTMPANa, g / lOOg of dry paste: 0.1 content of MgSθ4- 7H2θ, g / lOOg dry paste: 0.05 temperature, degrees C: 80 duration, min: 180 consistency, X by weight of dry matter: 10 where DTMPANa represents the heptasodium salt of diethylene-triaminepenta acid (methylenephosphonic acid). 3rd stage: hydrogen peroxide stage (stage P): H2O2 content, g / lOOg dry paste: 2.0 NaOH content, g / lOOg dry paste: example 8: 1.3 example 9: 1.4 example 10: 1.7 MgSθ4.7H2θ content, g / lOOg dry paste: 1.0 Na silicate content 38 ° Bé, g / lOOg dry paste: 3.0 temperature, degrees C: 90 duration, min: 240 consistency , X by weight of dry matter: 30
A l'issue de chaque étape de traitement, la pâte a subi un lavage à l'eau l'eau déminéralisée à température ambiante. En fin de séquence, après traitement, on a déterminé l'indice kappa, la blancheur de la pâte et son degré de polyméri¬ sation. Les résultats obtenus ont été les suivants : Exemple Blancheur Indice Degré deAt the end of each processing step, the paste was washed with demineralized water at room temperature. At the end of the sequence, after treatment, the kappa index, the whiteness of the dough and its degree of polymerization were determined. The results obtained were as follows: Example Whiteness Degree Index
No. finale kappa polymérisationKappa polymerization final number
°IS0 final° IS0 final
8 89,4 1,0 7008 89.4 1.0 700
9 90,6 0,9 7109 90.6 0.9 710
10 91,6 0,7 690 10 91.6 0.7 690

Claims

R E V E N D I C A T I O N SR E V E N D I C A T I O N S
1 - Procédé pour le blanchiment d'une pâte à papier chimique, ayant subi une cuisson extensive, au moyen d'une séquence d'étapes de traitement exemptes de réactifs chlorés, caractérisé en ce que la séquence comprend les étapes suivantes, effectuées dans l'ordre :1 - Process for bleaching a chemical paper pulp, having undergone extensive cooking, by means of a sequence of treatment steps free of chlorinated reagents, characterized in that the sequence comprises the following steps, carried out in the 'order:
Q P où le sigle Q représente une étape de décontamination de la pâte en ses métaux de transition et le sigle P représente une étape avec du peroxyde d'hydrogène alcalin.Q P where the acronym Q represents a step of decontaminating the pulp into its transition metals and the acronym P represents a step with alkaline hydrogen peroxide.
2 - Procédé selon la revendication 1, caractérisé en ce la pâte soumise à la séquence d'étapes de traitement est sélec¬ tionnée parmi les pâtes kraft de bois résineux d'indice kappa de 20 ou moins et les pâtes kraft de bois feuillus d'indice kappa de 14 ou moins.2 - Method according to claim 1, characterized in that the pulp subjected to the sequence of treatment steps is selected from kraft pulp of resinous wood with kappa index of 20 or less and kraft pulp of hardwood kappa index of 14 or less.
3 - Procédé selon la revendication 1 ou 2, caractérisé en ce que l'étape P de la séquence est réalisée à une température de 100 °C ou plus.3 - Process according to claim 1 or 2, characterized in that step P of the sequence is carried out at a temperature of 100 ° C or more.
4 - Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'une étape à l'oxygène gazeux précède la séquence.4 - Method according to any one of claims 1 to 3, characterized in that a step with gaseous oxygen precedes the sequence.
5 - Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que l'étape P est réalisée à une consistance en pâte d'au moins 25 X en poids de matières sèches.5 - Method according to any one of claims 1 to 4, characterized in that step P is carried out at a paste consistency of at least 25 X by weight of dry matter.
6 - Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que l'étape Q consiste en un traitement par un acide exempt d'un séquestrant, suivi d'une addition de sel soluble de Mg en quantité telle que le rapport pondéral de la quantité de Mg à celle de Mn présent dans la pâte soit de 30 ou plus.6 - Method according to any one of claims 1 to 5, characterized in that step Q consists of a treatment with an acid free of a sequestrant, followed by the addition of soluble salt of Mg in an amount such that the weight ratio of the amount of Mg to that of Mn present in the dough either 30 or more.
7 - Procédé selon l'une quelconque des revendications 1 à 6, caractérisé en ce que l'on intercale entre l'étape Q et l'étape P une étape oxydante au moyen d'un réactif sélectionné parmi les peroxyacides et l'ozone.7 - Method according to any one of claims 1 to 6, characterized in that one interposes between step Q and step P an oxidizing step using a reagent selected from peroxyacids and ozone.
8 - Procédé selon l'une quelconque des revendications 1 à 7, caractérisé en ce que l'étape Q est effectuée en présence d'une enzyme.8 - Process according to any one of claims 1 to 7, characterized in that step Q is carried out in the presence of an enzyme.
9 - Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce que l'on incorpore une étape supplémentaire avec une enzyme en un point quelconque de la séquence.9 - Process according to any one of claims 1 to 8, characterized in that an additional step is incorporated with an enzyme at any point of the sequence.
10 - Application du procédé selon l'une quelconque des revendications 1 à 9 au blanchiment des pâtes kraft ou au sulfite. 10 - Application of the method according to any one of claims 1 to 9 to the bleaching of kraft pulp or sulfite.
EP94931025A 1993-11-10 1994-10-28 Method of bleaching chemical paper pulp Expired - Lifetime EP0728238B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
BE9301251A BE1007757A3 (en) 1993-11-10 1993-11-10 Method of laundering of chemical pulp.
BE9301251 1993-11-10
PCT/EP1994/003590 WO1995013420A1 (en) 1993-11-10 1994-10-28 Method of bleaching chemical paper pulp

Publications (3)

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

Family

ID=3887547

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94931025A Expired - Lifetime EP0728238B2 (en) 1993-11-10 1994-10-28 Method of bleaching chemical paper pulp

Country Status (14)

Country Link
EP (1) EP0728238B2 (en)
JP (1) JPH10500178A (en)
AT (1) ATE175738T1 (en)
AU (1) AU7993994A (en)
BE (1) BE1007757A3 (en)
BR (1) BR9408027A (en)
CA (1) CA2176246A1 (en)
DE (1) DE69416000D1 (en)
ES (1) ES2129142T5 (en)
FI (1) FI961975A (en)
MA (1) MA23369A1 (en)
NO (1) NO961889L (en)
WO (1) WO1995013420A1 (en)
ZA (1) ZA948563B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4967451B2 (en) 2006-05-17 2012-07-04 三菱瓦斯化学株式会社 Method for producing bleached pulp
WO2009081714A1 (en) 2007-12-20 2009-07-02 Mitsubishi Gas Chemical Company, Inc. Process for production of bleached pulp

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE402335T1 (en) * 1989-06-06 1992-04-09 Eka Nobel Ab, Surte METHOD FOR BLEACHING LIGNOCELLULOSE-CONTAINING CELLS.
SE470065C (en) * 1991-04-30 1996-01-15 Eka Nobel Ab Treatment of chemical pulp with an acid and then a magnesium and calcium compound in chlorine-free bleaching
SE468355B (en) * 1991-04-30 1992-12-21 Eka Nobel Ab CHEMISTRY OF CHEMICAL MASS THROUGH TREATMENT WITH COMPLEX PICTURES AND OZONE
SE469842C (en) * 1992-01-21 1996-01-15 Sunds Defibrator Ind Ab Bleaching of chemical pulp with peroxide
SE469387B (en) * 1992-05-11 1993-06-28 Kamyr Ab SEATING WHITE PILLOW WITHOUT USING CHLORIC CHEMICALS
BE1006056A3 (en) * 1992-07-06 1994-05-03 Solvay Interox Method of laundering of chemical pulp.
JPH08503749A (en) * 1992-11-27 1996-04-23 エカ ノーベル アクチェボラーグ Method for bleaching lignocellulose-containing pulp
BE1007700A3 (en) * 1993-11-04 1995-10-03 Solvay Interox Method of laundering of chemical pulp.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9513420A1 *

Also Published As

Publication number Publication date
CA2176246A1 (en) 1995-05-18
NO961889D0 (en) 1996-05-09
NO961889L (en) 1996-05-09
EP0728238B2 (en) 2004-08-11
BR9408027A (en) 1996-12-17
DE69416000D1 (en) 1999-02-25
ZA948563B (en) 1995-06-30
MA23369A1 (en) 1995-07-01
AU7993994A (en) 1995-05-29
FI961975A0 (en) 1996-05-09
BE1007757A3 (en) 1995-10-17
ATE175738T1 (en) 1999-01-15
FI961975A (en) 1996-07-09
ES2129142T3 (en) 1999-06-01
EP0728238B1 (en) 1999-01-13
ES2129142T5 (en) 2005-04-01
JPH10500178A (en) 1998-01-06
WO1995013420A1 (en) 1995-05-18

Similar Documents

Publication Publication Date Title
EP0578305B1 (en) Process of delignification of a chemical pulp
EP0578304B1 (en) Process for bleaching a chemical paper pulp
BE1007651A3 (en) Method of laundering of chemical pulp.
EP0019963B1 (en) Process for the delignification and bleaching of chemical and semichemical cellulose pulps
EP0578303B1 (en) Process for the delignification of a chemical paper pulp
BE1004630A3 (en) Method for preservation of strength characteristics of paper pulp chemicals.
BE1004674A3 (en) Method of laundering of chemical pulp and application of the method of laundering pulp kraft.
BE1006881A3 (en) Method for delignification of chemical pulp.
BE1007757A3 (en) Method of laundering of chemical pulp.
EP0535741B1 (en) Process for improving the selectivity in the delignification of a chemical pulp
BE1007700A3 (en) Method of laundering of chemical pulp.
EP0587822B1 (en) Process for bleaching and delignifying chemical paper pulp
BE1007272A3 (en) Method of a pulp bleach.
EP0190723A1 (en) Process for improving the mechanical properties of a chemical or semi-chemical bagasse paper pulp
BE1005800A3 (en) Method for the delignification and bleaching of a chemical paper pulp
CA2079730A1 (en) Process for improving delignification selectivity of a chemical papermaking pulp

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19960610

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE ES FR LI PT SE

17Q First examination report despatched

Effective date: 19961031

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE ES FR LI PT SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19990113

REF Corresponds to:

Ref document number: 175738

Country of ref document: AT

Date of ref document: 19990115

Kind code of ref document: T

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REF Corresponds to:

Ref document number: 69416000

Country of ref document: DE

Date of ref document: 19990225

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19990414

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2129142

Country of ref document: ES

Kind code of ref document: T3

PLBI Opposition filed

Free format text: ORIGINAL CODE: 0009260

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19991031

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19991031

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19991031

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

26 Opposition filed

Opponent name: EKA CHEMICALS AB PATENT DEPARTMENT

Effective date: 19991006

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

BERE Be: lapsed

Owner name: S.A. SOLVAY INTEROX

Effective date: 19991031

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000630

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PLAW Interlocutory decision in opposition

Free format text: ORIGINAL CODE: EPIDOS IDOP

APAC Appeal dossier modified

Free format text: ORIGINAL CODE: EPIDOS NOAPO

APAE Appeal reference modified

Free format text: ORIGINAL CODE: EPIDOS REFNO

APAC Appeal dossier modified

Free format text: ORIGINAL CODE: EPIDOS NOAPO

APBU Appeal procedure closed

Free format text: ORIGINAL CODE: EPIDOSNNOA9O

PUAH Patent maintained in amended form

Free format text: ORIGINAL CODE: 0009272

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: PATENT MAINTAINED AS AMENDED

27A Patent maintained in amended form

Effective date: 20040811

AK Designated contracting states

Kind code of ref document: B2

Designated state(s): AT BE CH DE ES FR LI PT SE

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20041006

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: PT

Payment date: 20041015

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 20041116

Year of fee payment: 11

REG Reference to a national code

Ref country code: SE

Ref legal event code: RPEO

REG Reference to a national code

Ref country code: ES

Ref legal event code: DC2A

Date of ref document: 20041111

Kind code of ref document: T5

APAH Appeal reference modified

Free format text: ORIGINAL CODE: EPIDOSCREFNO

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20051029

Ref country code: ES

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20051029

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: PT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20060428

EUG Se: european patent has lapsed
REG Reference to a national code

Ref country code: PT

Ref legal event code: MM4A

Effective date: 20060428

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 20051029