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
• • 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
  • D21C9/1084—Bleaching ; Apparatus therefor with reducing compounds

Definitions

• the present invention relates to a process for the preser ⁇ vation of the mechanical strength characteristics of chemical paper pulps during treatment of these pulps with a view to delignification or bleaching. It relates more particularly to a process in which the treatment for delignification or bleaching of these paper pulps comprises a sequence of two consecutive stages with a peroxygenated reagent, the first stage being carried out in an acid medium, the second in an alkaline medium.
• the invention overcomes this disadvantage of known methods, by providing a novel method of delignification and / or bleaching of chemical paper pulps which makes it possible to achieve high rates of delignification while preserving the intrinsic quality of the cellulose and the weight yield of pulp produced.
• the invention relates to a method for preserving the mechanical strength characteristics of a chemical paper pulp during a delignification and / or bleaching treatment comprising two stages of treatment using a peroxygen reagent, the first in an acid medium and the second in an alkaline medium, according to which a treatment is inserted between the two stages using a reducing compound.
• chemical paper pulp by chemical paper pulp is meant the pulp having undergone a delignifying treatment by presence of chemical reagents such as sodium sulphide in alkaline medium (kraft or sulphate cooking), sulfur dioxide or a metal salt of sulfurous acid in acid medium (sulphite cooking), a salt of sulfurous acid in a neutral environment (cooking with neutral sulfite also called NSSC cooking).
• chemical reagents such as sodium sulphide in alkaline medium (kraft or sulphate cooking), sulfur dioxide or a metal salt of sulfurous acid in acid medium (sulphite cooking), a salt of sulfurous acid in a neutral environment (cooking with neutral sulfite also called NSSC cooking).
• the invention is particularly intended for pasta which has undergone kraft cooking and whose residual lignin content after cooking is within the range of kappa indices between 15 and 35 depending on the type of wood species from which they originate and the efficiency of the cooking process.
• wood used for the production of chemical pulp are suitable for carrying out the process of the invention and, in particular those used for kraft pulp, namely softwoods such as, for example, the various species of pine and fir and hardwoods like, for example, beech, oak and hornbeam.
• peroxygenated reagent is intended to denote any inorganic or organic reagent comprising in its molecule two oxygen atoms linked to one another by a covalent bond.
• the peroxygen compounds can be chosen from hydrogen peroxide, metal peroxides and, in particular, alkali or alkaline earth metal peroxides such as sodium peroxide, inorganic persalts such as perborates, percarbonates and persulfates , inorganic peracids such as monoperoxysulfuric (Caro acid) and diperoxysulfuric acids, organic peracids and, in particular, those which contain 2 to 7 carbon atoms such as peroxyacetic and peroxypropionic acids as well as their salts and hydroperoxides and peroxides organic.
• alkali or alkaline earth metal peroxides such as sodium peroxide
• inorganic persalts such as perborates, percarbonates and persulfates
• inorganic peracids such as monoper
• the pH of the first step with a peroxygen compound according to the invention is acidic, and generally less than 5. Preferably, this pH is between 0.5 and 3.5.
• the pH of the second step with a peroxygen compound must be alkaline and, more often than not, above 9. Preferably, this pH is between 10.5 and 13.5.
• the reducing compound of the intermediate step can be any reducing product used in the pulp bleaching industry. Examples of such reducing products are formamidinesulfinic acid (FAS) and its ammonium, alkali or alkaline earth metal salts, borohydrides, hydrosulfite, ammonium sulfite or bisulfite, alkali or alkaline earth metal .
• FAS and sodium borohydride have worked well. FAS is preferred because of its higher efficiency.
• the quantity of reducing agent used in the intermediate stage is generally between 0.05 and 1.5% by weight relative to the dry paste.
• the preferred amounts are between 0.08 and 1.0 X. An amount of 0.1 X already gives good results.
• the dough can be washed with water followed by a reconcentration to a dry matter content identical to that which prevails in the first step.
• An advantageous variant of the process according to the invention is not to carry out any washing of the dough between the first step with the peroxygen compound and the intermediate step with the reducing compound.
• After the reducing intermediate step it is possible to wash and reconcentrate the dough before treating it with the alkaline peroxygen compound.
• An interesting variant here is also to not carry out any washing between the reducing intermediate step and the step with the peroxygenated alkaline compound.
• the pH of the reducing intermediate step can be either acidic or alkaline. Good results have been obtained with an alkaline pH of between 10.5 and 13.5.
• the duration, the temperature and the consistency of the reductive step are not critical. They must however be chosen carefully in each case according to various parameters such as nature of the wood and the reducing compound, level of the kappa index, etc. The choice of these conditions will be determined using systematic exploratory laboratory tests available to anyone skilled in the art wishing to optimize the parameters of the reaction. As a general rule, the duration will be between 10 and 120 minutes, the temperature between 40 and 90 ° C and the consistency between 5 and 30% by weight. Conditions of 20 minutes, 60 ° C. and 15% consistency have given good results in the case of a softwood pulp with a kappa index of 30 (untreated unbleached pulp from kraft cooking).
• An advantageous variant of the process according to the invention consists in preceding the three treatment stages: acid peroxygen compound - reducing agent - alkaline peroxygen compound with a predelignification stage.
• any delignifying reagent such as chlorine, chlorine dioxide or the mixture of these two reagents, the welded caustic and anthraquinone composition, the oxygen, the oxygen and hydrogen peroxide mixture. It is often desirable, for ecological reasons, that in this predelignification step, no chlorinated reagent is used. This is why it is generally preferred to use oxygen or the oxygen-hydrogen peroxide combination as a delignifying reagent.
• the process according to the invention is well suited to the production of semi-bleached pasta free from any organic chlorinated residue. As such, it can be used for the production of pulp used in the manufacture of wrapping paper for food use.
• Example 1R (not in accordance with the invention)
• a sample of chemical pulp from pine having undergone kraft cooking (initial whiteness 27.4 ° IS0 measured according to standard ISO 2470, kappa index 29.3 measured according to standard SCAN Cl: 59) was mixed with 1% by weight of H ⁇ O ⁇ and 1% by weight of H2SO4 relative to the dry paste.
• Demineralized water was added in an amount required to reach a consistency of 15% and the sample containing the reagents was placed in a polyethylene bag which was immersed, after having kneaded it carefully, in a thermostatic water bath at 60 ° C. After 2 hours of reaction, the paste was washed in a volume of demineralized water corresponding to 40 times its dry weight.
• the paste was replaced in another polyethylene bag and treated with 1 ⁇ by weight of H2O2 and 2% by weight of NaOH relative to the dry paste. Demineralized water was then added to adjust the consistency to 12% and the paste was kneaded to homogenize the reagents, then it was left to react for 1 hour in a thermostatic water bath at 60 ° C.
• the paste was washed in a volume of demineralized water corresponding to 40 times its dry weight and filtered through a buchner filter.
• the viscosity of the treated pulp was then determined by following the procedure described in the TAPPI T 230 standard.
• Example 1R was reproduced, intercalating between the two steps at I ⁇ 2O2 a reducing treatment step where 0.1 X by weight of formamidinesulfinic acid and 1.5 X of NaOH at 15 X of consistency have been used for 20 minutes at 60 ° C.
• the paste was washed under the same conditions as in Example IR and then the paste was treated with alkaline hydrogen peroxide.
• the amount of NaOH in the alkaline hydrogen peroxide step was however reduced to 0.5 X so as to use the same total amount of NaOH as in Example IR.
• the result of the viscosity measurement of the treated pulp was 15.1 mPa.s.
• Examples 3R (not in accordance with the invention) and 4 accordinging to the invention)
• Examples IR and 2 were reproduced with another kraft pine paste with a kappa index of 23. At the end of the treatment, the kappa (according to the SCAN Cl: 59) and tear resistance (according to the TAPPI T 414 standard).
• Examples IR and 2 were reproduced with the same kraft pulp of pine with a kappa index of 29.3 but replacing the first step with acid hydrogen peroxide with a step with acid of
• Caro in an amount of 2% by weight of Caro acid compared to the dry paste.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)
• Materials For Medical Uses (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Compounds Of Unknown Constitution (AREA)
• Medicines That Contain Protein Lipid Enzymes And Other Medicines (AREA)
• Immobilizing And Processing Of Enzymes And Microorganisms (AREA)
• Apparatus Associated With Microorganisms And Enzymes (AREA)

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• 1990
  • 1990-10-17 BE BE9000985A patent/BE1004630A3/fr not_active IP Right Cessation
• 1991
  • 1991-10-04 CA CA002094268A patent/CA2094268A1/fr not_active Abandoned
  • 1991-10-04 EP EP91917649A patent/EP0553141B1/de not_active Expired - Lifetime
  • 1991-10-04 DE DE69104374T patent/DE69104374D1/de not_active Expired - Lifetime
  • 1991-10-04 WO PCT/EP1991/001906 patent/WO1992007139A1/fr active IP Right Grant
  • 1991-10-04 AU AU86371/91A patent/AU648115B2/en not_active Ceased
  • 1991-10-04 US US08/039,146 patent/US5534115A/en not_active Expired - Fee Related
  • 1991-10-04 BR BR919107000A patent/BR9107000A/pt not_active Application Discontinuation
  • 1991-10-04 AT AT91917649T patent/ATE112340T1/de not_active IP Right Cessation
  • 1991-10-15 ZA ZA918219A patent/ZA918219B/xx unknown
  • 1991-10-16 PT PT99243A patent/PT99243B/pt not_active IP Right Cessation
• 1993
  • 1993-04-14 FI FI931664A patent/FI931664A0/fi unknown
  • 1993-04-16 NO NO931419A patent/NO300901B1/no unknown

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