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
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
• • 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
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
  • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
  • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

• the invention aims to remedy the drawbacks of known methods by providing a method which makes it possible to obtain new bleaching sequences which generate high levels of whiteness while preserving the intrinsic qualities of the dough.
• a sequence which has given good results in treatments free of chlorinated reagents of TCF type is the OQPZP sequence comprising a step X.
• This step X can precede the sequence so as to carry out the complete sequence XOQPZ P. It can also be inserted between two step any of the sequence, such as, for example, the complete sequences OXQPZP and OQPXZ P.
• the acronym / signifies that the step immediately preceding the acronym and that following the acronym may possibly be combined in a single step.
• steps X are followed by a step Q and steps P are preceded by a step Q.
• the method is particularly suitable for the treatment of chemical paper pulps.
• 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.
• step Q When a sequestrant is present, a small amount of acid can also be added in step Q.
• the amount of acid to be used in step Q according to the invention depends 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 paste is greater than about 5 and, preferably, about 5.5. 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, less than pH 5 and, preferably, 4.0. Generally, in order not to degrade the dough, we should avoid going below pH 1.0 and, preferably, below pH 1.5.
• the sequestrant is generally used in step Q in an amount less than 1.5 g of sequestrant per 100 g of dry pulp. Most often, this amount is less than 1.0 g of sequestrant 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 efficient consumption of the acid and / or of the sequestrant and, at the same time not too high so as not to degrade the cellulose. 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.
• it is advantageous that the temperature does not exceed 100 ° C and preferably not 90 ° C. The best results have been obtained at around 50 ° C.
• step Q The duration of step Q must be sufficient to ensure a complete reaction. Although longer durations have no influence on the delignification rate of the dough as well as on its intrinsic resistance qualities, it is not recommended 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, it is important that the pretreatment times do not exceed 60 minutes and preferably not 40 minutes. The duration of approximately 30 minutes has given excellent results.
• the treatment stage P is a stage with alkaline hydrogen peroxide.
• 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 between 1 and 3 g of alkali per 100 g of dry pulp are very suitable.
• step P The duration of step P must be sufficient for the bleaching reaction to be complete. 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. It should also most often not exceed 300 and, preferably, 200 minutes. A combination of the temperature and time conditions of about 70 ° C and about 120 minutes has given good results.
• step P is generally chosen to be less than or equal to 40% of dry matter and, preferably, to 30% of dry matter. It will often not be less than 5% and preferably not less than 8%. A consistency of 12% has given good results.
• step Z of the treatment sequence is an ozone step. It 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 gaseous oxygen.
• a generator is advantageously used whose flow rate is between 50 and 100 l / hour and, preferably, between 70 and 90 l / 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 1 minute to 10 minutes are sufficient to use an amount of ozone of between 0.2 and 1 g per 100 g of dry paste.
• the ozone treatment is preferably carried out in an acid medium.
• a pH of 0.5 to 5 is suitable and preferably 1.5 to 4.
• a pH of 3 has given very good results.
• the consistency of the ozone treatment step will be chosen to be at least 2% dry matter and preferably at least 10%. It will generally not exceed 50% dry matter and preferably not 45%. A consistency of 40% has given excellent results.
• the temperature of the ozone treatment stage must remain low, otherwise the mechanical strength properties of the treated pulp will be seriously degraded.
• This temperature generally does not exceed 50 ° C and preferably not 35 ° C. However, it will be at least 2 ° C and, most often, at least 10 ° C.
• the ambient temperature of 22 ° C has given good results.
• An interesting variant of the process according to the invention consists in making the ozone treatment precede a mechanical treatment for opening the dough (called “fluffing” in the English literature) intended to increase the contact surface of the dough with ozone. This operation is particularly useful when the consistency of the dough during the ozone treatment is at least 15% dry matter.
• step P is meant to designate steps with hydrogen peroxide in an alkaline medium as described above, but also steps of alkaline extraction reinforced with a small amount of hydrogen peroxide (steps Ep) and steps involving the use of oxygen mixed with hydrogen peroxide (steps Eop).
• step X of treatment with at least one enzyme consists in treating the dough with a composition containing at least one enzyme.
• enzyme is intended to denote any enzyme capable of facilitating the delignification, by the treatment steps subsequent to the treatment step with the enzyme, of an unbleached chemical paper pulp originating from the cooking operation or from a chemical paper pulp that has already been subjected to one or more steps of bleaching with oxidizing reagents such as oxygen, hydrogen peroxide and ozone.
• 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.
• 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.
• stage X stage with the xylanase enzyme
• stage O oxygen stage
• pressure, bar 6 NaOH content
• g / 100g dry paste 0.5 temperature, degrees C: 120 duration
• 3rd stage stage at DTPA
• stage Q DTPA content
• g / 100g dry paste 0.2 temperature
• degrees C 50 duration
• g / 100g dry paste 1.5 NaOH content
• g / 100g dry paste 1.8 content of Na silicate 38 ° Be

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Chemical & Material Sciences (AREA)
• Biochemistry (AREA)
• Microbiology (AREA)
• Paper (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)

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• 1993
  • 1993-07-15 BE BE9300745A patent/BE1007272A3/fr not_active IP Right Cessation
• 1994
  • 1994-07-07 CA CA002127582A patent/CA2127582A1/fr not_active Abandoned
  • 1994-07-11 EP EP94202003A patent/EP0634520A1/fr not_active Withdrawn
  • 1994-07-12 NZ NZ260982A patent/NZ260982A/en unknown
  • 1994-07-13 AU AU67431/94A patent/AU682363B2/en not_active Ceased
  • 1994-07-13 ZA ZA945110A patent/ZA945110B/xx unknown
  • 1994-07-14 NO NO942651A patent/NO942651L/no unknown
  • 1994-07-15 FI FI943388A patent/FI943388A/fi not_active Application Discontinuation
  • 1994-07-15 JP JP6163768A patent/JPH0748792A/ja active Pending
  • 1994-07-15 YU YU45394A patent/YU45394A/sh unknown
  • 1994-07-15 BR BR9402833A patent/BR9402833A/pt not_active Application Discontinuation

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