EP2128331A1 - Verfahren zum Bleichen von Papierzellstoff - Google Patents

Verfahren zum Bleichen von Papierzellstoff Download PDF

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Publication number
EP2128331A1
EP2128331A1 EP08156934A EP08156934A EP2128331A1 EP 2128331 A1 EP2128331 A1 EP 2128331A1 EP 08156934 A EP08156934 A EP 08156934A EP 08156934 A EP08156934 A EP 08156934A EP 2128331 A1 EP2128331 A1 EP 2128331A1
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EP
European Patent Office
Prior art keywords
bleaching
process according
pulp
weight
hydrogen peroxide
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.)
Withdrawn
Application number
EP08156934A
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English (en)
French (fr)
Inventor
Pierre Dournel
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 SA
Original Assignee
Solvay 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
Application filed by Solvay SA filed Critical Solvay SA
Priority to EP08156934A priority Critical patent/EP2128331A1/de
Priority to CA2723311A priority patent/CA2723311A1/en
Priority to EP09753845A priority patent/EP2286024A1/de
Priority to US12/992,316 priority patent/US20110067831A1/en
Priority to PCT/EP2009/056278 priority patent/WO2009144190A1/en
Publication of EP2128331A1 publication Critical patent/EP2128331A1/de
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1042—Use of chelating agents

Definitions

  • the present invention relates to a process for the bleaching of paper pulp, especially mechanical paper pulp, through a bleaching treatment with hydrogen peroxide and an alkali source.
  • Such bleaching treatment usually involves the use of peroxide stabilizers.
  • the US patent 6221209 of SOLVAY INTEROX relates to a process for bleaching a chemical paper pulp by first purifying the pulp so as to reduce its manganese content and then by bleaching it with hydrogen peroxide in alkaline medium, especially at a pH adjusted to at least 10 by the addition of an alkaline compound (i.e. sodium hydroxide), and in the presence of a stabilizing agent, namely sodium silicate.
  • an alkaline compound i.e. sodium hydroxide
  • magnesium hydroxide is used as alkaline source in the hydrogen peroxide bleaching of mechanical paper pulp, it is difficult to achieve a satisfactory brightness, and the consumption of hydrogen peroxide for a given brightness is high.
  • the purpose of the present invention is to provide a process which does not present the above disadvantages and which enables to obtain a higher paper pulp brightness compared to the known use of other alkaline sources than sodium hydroxide, such as magnesium hydroxide or calcium hydroxide.
  • the purpose of the present invention is also to provide a process which allows decreasing the consumption of hydrogen peroxide for a given brightness.
  • the present invention therefore relates to a process for the bleaching of paper pulp in which an aqueous suspension of paper pulp is subjected to a bleaching treatment with hydrogen peroxide in the presence of at least one alkaline earth hydroxide selected from magnesium hydroxide and calcium hydroxide and of at least one poly- ⁇ -hydroxyacrylic acid, its salt or their mixture.
  • alkaline earth hydroxides such as magnesium hydroxide and/or calcium hydroxide as alkaline source
  • sodium silicate cannot be used when using alkaline earth hydroxides such as magnesium hydroxide and/or calcium hydroxide as alkaline source, because it forms precipitates with those products, leading to scaling.
  • Such scaling creates problems in the whole production line including in the paper machine, when the mill is an integrated site.
  • alkaline earth hydroxides such as magnesium hydroxide and/or calcium hydroxide
  • the common practice is to bleach without any stabilizer, except aminopolycarboxylic acids or their salts, such as diethylene triamine penta-acetic acid (DTPA) or its sodium salt which will act as chelating agents and will therefore limit the decomposition of the hydrogen peroxide which is catalyzed by transition metals such as manganese or iron.
  • DTPA diethylene triamine penta-acetic acid
  • the conditions present during the bleaching are usually not suitable for a good efficiency of such chelating agents and therefore the
  • alkaline earth hydroxide selected from magnesium hydroxide and calcium hydroxide as alkaline source
  • PHAA poly- ⁇ -hydroxyacrylic acid, its salt or their mixtures
  • the PHAA used in the process of the invention generally has a molecular weight within a specific range. As the molecular weight is rather difficult to measure, it is inferred by measuring the viscosity, the higher the molecular weight, the higher the viscosity. Viscosity in the range of 10 to 100 mPa.s is usual but more particularly it can be in the range of 20 to 60 mPa.s. Commonly, the PHAA is used as a sodium salt of poly- ⁇ -hydroxyacrylic acid, corresponding to sodium poly- ⁇ -hydroxyacrylate (referred to as PHAS). In the invention, good results are obtained using only one PHAA. Nevertheless, more than one PHAA can be used.
  • PHAS sodium poly- ⁇ -hydroxyacrylate
  • the bleaching treatment according to the present invention is generally carried out at an initial pH of at least 8, in particular of at least 8,5, values of at least 9 being preferred.
  • the initial pH is usually at most 14, in special cases at most 13, values of at most 12 being convenient.
  • the pH of the aqueous suspension during the bleaching treatment is measured using equipment normally found in pulp mills for such a purpose.
  • the natural pH of the paper pulp suspension is adjusted to the required value by means of an alkaline compound comprising at least one alkaline earth hydroxide selected from magnesium hydroxide and calcium hydroxide.
  • the amount of alkaline earth hydroxide according to the invention, used in the bleaching step of the present invention is generally such that the pH of the suspension is maintained within the above-mentioned range. This amount is usually at least 0,1 % by weight of dry pulp, preferably at least 1% by weight of dry pulp, more preferably at least 2% by weight of dry pulp.
  • the amount of alkaline earth hydroxide according to the invention, used in the bleaching step of the present invention is generally at most 10% by weight of dry pulp, with particular preference at most 5% by weight of dry pulp.
  • the amount of alkaline earth hydroxide according to the invention, used in the bleaching step of the present invention is for instance of from 2 to 5% by weight of dry pulp, for example about 3% by weight of dry pulp.
  • the amount of alkaline earth hydroxide according to the invention depends on the amount of hydrogen peroxide used and on the type of pulp.
  • the ratio alkaline earth hydroxide according to the invention / hydrogen peroxide can for example vary from 0,3 to 2,5, preferably from 0,5 to 2,0 depending on the amount of hydrogen peroxide added and on the type of pulp. For example, the ratio may be about 1.
  • the alkaline earth hydroxide according to the invention is usually added to the paper pulp suspension in the form of an aqueous slurry.
  • the particle size of the alkaline earth hydroxide according to the invention is sufficiently small for the slurry to be readily suspendible, advantageously having a mean particle size of less than about 10 ⁇ m, preferably less than 6 ⁇ m, for example about 2 ⁇ m.
  • the bleaching step of the invention is generally carried out at a consistency of at least 10 % of dry pulp based on the weight of pulp suspension.
  • the efficiency of the process increases as the consistency is increased up to a value of around 30 % by weight of dry pulp.
  • the consistency can be up to 40 % by weight of dry pulp.
  • the bleaching treatment of the invention is usually carried out using an amount of hydrogen peroxide required to achieve the final target brightness.
  • the amount of hydrogen peroxide is generally equal to or higher than 0,1 % by weight of dry pulp, preferably equal to or higher than 0,5 % by weight of dry pulp, more preferably equal to or higher than 1 % by weight of dry pulp.
  • the amount of hydrogen peroxide is usually equal to or lower than 8 % by weight of dry pulp, especially equal to or lower than 6 % by weight of dry pulp, and more particularly equal to or lower than 5 % by weight of dry pulp.
  • the amount of hydrogen peroxide may be about 2 to 4% by weight of dry pulp.
  • the bleaching treatment of the invention is usually carried out at a temperature equal to or higher than 40°C, especially equal to or higher than 60°C.
  • the temperature can be up to about 100°C.
  • the temperature is preferably less than 100°C, more preferably equal to or less than 95°C, for example equal to or less than 85°C.
  • the optimum bleach temperature depends on the wood type and pulping process but is normally in the range of 60 to 95°C.
  • the duration of the bleaching treatment of the process of the invention is usually from 10 min to 6 h, varying from mill to mill. For instance, it can vary from 30 to 300 min.
  • the bleaching treatment can be carried out at a pH of from 8 to 14, at a consistency of from 10 to 40 %, and at a temperature of from 60 to 95°C, during 1 to 4 hours.
  • the amount of PHAA, especially PHAS, used in the bleaching step of the invention is usually equal to or higher than 0,05 % by weight of dry pulp, especially equal to or higher than 0,1 % by weight of dry pulp.
  • the amount of PHAA is commonly equal to or lower than 2 % by weight of dry pulp, values of at most 1 % being suitable.
  • typical amounts of PHAA are about 0,1 to 0,5 % by weight of dry pulp.
  • the optimum amount is dependent on the amount of metallic ions in the pulp and must be optimized for each particular mill.
  • the bleaching step of the invention can be carried out in the presence of any other alkaline or alkaline earth hydroxides than the alkaline earth hydroxides according to the invention, such as in the presence of sodium hydroxide.
  • the bleaching step of the invention may also be carried out in the absence sodium hydroxide.
  • the bleaching step of the invention can also be carried out in the presence of any other additives, such as magnesium sulfate or other soluble magnesium salts.
  • the bleaching step is carried out in the absence of any other stabilizer, and especially in the absence of sodium silicate.
  • the aqueous suspension of the paper pulp may be subjected to a chelating treatment to reduce the metallic ion content of the suspension, and especially its manganese content. It is for example usual to carry out a pretreatment step (or chelating treatment), with at least one aminopolycarboxylic acid, its salt or their mixture (referred to as APCA) prior to the bleaching treatment.
  • a pretreatment step or chelating treatment
  • APCA aminopolycarboxylic acid, its salt or their mixture
  • the APCA used in the pretreatment step is generally chosen from ethylene diamine tetra-acetic acid (EDTA), diethylene triamine penta-acetic acid (DTPA), triethylene tetramine hexa-acetic acid (TTHA), cyclohexane diamine tetra-acetic acid (CDTA), methylglycine di-acetic acid (MGDA), nitrilo tri-acetic acid (NTA).
  • EDTA ethylene diamine tetra-acetic acid
  • DTPA diethylene triamine penta-acetic acid
  • TTHA triethylene tetramine hexa-acetic acid
  • CDTA cyclohexane diamine tetra-acetic acid
  • MGDA methylglycine di-acetic acid
  • NTA nitrilo tri-acetic acid
  • the APCA may be used as the free acid, its salt or their mixtures.
  • the APCA is preferably used as its salt.
  • the most preferred APCA is the sodium salt of DTPA. Good results are generally obtained using only one APCA. Nevertheless, more than one APCA can be used.
  • the chelating pretreatment step may be conducted as described in the International patent application filed as EP2008/052056 , the text of which is incorporated herein by reference.
  • the bleaching treatment may be carried out in the presence of at least one chelating agent, in particular of at least one APCA, such as those disclosed above.
  • the amount of APCA used in the bleaching treatment of the invention is usually at least 0,05 % wt based on the weight of dry pulp.
  • the amount of APCA is commonly at most about 1 % wt based on the weight of dry pulp, values of at most 0,8 % wt being suitable.
  • the weight ratio between PHAA, especially PHAS, and APCA is usually at least 1:10, preferably at least 1:5, ratios of at least 1:3 being satisfactory.
  • the weight ratio PHAA / APCA, especially PHAS / APCA is generally at most 10:1, especially at most 5:1, values of at most 3:1 1 giving the best results.
  • the bleaching treatment is carried out in the absence of a chelating agent or of another stabilizer than PHAA.
  • the paper pulp treated in the present invention can be chosen from chemical paper pulps, mechanical paper pulps or recycled paper pulps. The best results are obtained with mechanical paper pulps.
  • mechanical paper pulps are meant paper pulps obtained by mechanical treatment. Examples of such paper pulps are pressure groundwood (PGW), stone groundwood (SGW), thermomechanical pulp (TMP), refiner mechanical pulp (RMP), chemithermomechanical pulp (CTMP) and alkaline peroxide mechanical pulp (APMP or APP).
  • PGW pressure groundwood
  • SGW stone groundwood
  • TMP thermomechanical pulp
  • RMP refiner mechanical pulp
  • CTMP chemithermomechanical pulp
  • APMP or APP alkaline peroxide mechanical pulp
  • the present invention therefore also relates to the bleaching process of the invention applied to mechanical paper pulp.
  • the process of the invention can further comprise other treatment steps such as one or more additional dilution step(s), one or more additional chelating step(s), one or more additional bleaching step(s), one or more washing step(s) and/or one or more extraction step(s).
  • the order of addition of the alkaline earth hydroxide of the invention, the PHAA and the hydrogen peroxide is either first the PHAA, then the alkaline earth hydroxide of the invention, and lastly the hydrogen peroxide or first the alkaline earth hydroxide of the invention, then the PHAA, and lastly the hydrogen peroxide.
  • Those three products may also be premixed all together or two of them can be premixed.
  • the alkaline earth of the invention is usually added as a suspension in water. Dilution water may also be added.
  • the reactants are introduced in the paper pulp suspension via a pump and a high consistency mixer, especially when the bleaching is performed at a consistency close to 30%.
  • An example of configuration is : the chemicals are added in the preheating screw of the HC mixer.
  • example 2 the same conditions as in example 1 were applied except that 0,5% of PHAS were added to the bleaching step.
  • the resulting brightness of the paper pulp was 76,6°ISO and the residual peroxide content was 17% of the initial charge.
  • example 4 the same mechanical pulp as in example 3 was bleached at 70°C during 2 hours in the presence of an amount of hydrogen peroxide of 2 % by weight of dry pulp, of magnesium hydroxide of 3 % by weight of dry pulp, and of an amount of PHAS of 0,3 % by weight of dry pulp.
  • the resulting brightness of the paper pulp was the same as in example 3 (73,8°ISO) and the residual peroxide content was 31 % of the initial charge.
  • Hydrogen peroxide was added in an amount of 3 % by weight of dry pulp.
  • Magnesium hydroxide was added in an amount of 3 % by weight of dry pulp.
  • PHAS was added in an amount of 0 to 0,5 % by weight of dry pulp.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
EP08156934A 2008-05-26 2008-05-26 Verfahren zum Bleichen von Papierzellstoff Withdrawn EP2128331A1 (de)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP08156934A EP2128331A1 (de) 2008-05-26 2008-05-26 Verfahren zum Bleichen von Papierzellstoff
CA2723311A CA2723311A1 (en) 2008-05-26 2009-05-25 Process for the bleaching of paper pulp
EP09753845A EP2286024A1 (de) 2008-05-26 2009-05-25 Verfahren zum bleichen von papierzellstoff
US12/992,316 US20110067831A1 (en) 2008-05-26 2009-05-25 Process for the bleaching of paper pulp
PCT/EP2009/056278 WO2009144190A1 (en) 2008-05-26 2009-05-25 Process for the bleaching of paper pulp

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP08156934A EP2128331A1 (de) 2008-05-26 2008-05-26 Verfahren zum Bleichen von Papierzellstoff

Publications (1)

Publication Number Publication Date
EP2128331A1 true EP2128331A1 (de) 2009-12-02

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EP08156934A Withdrawn EP2128331A1 (de) 2008-05-26 2008-05-26 Verfahren zum Bleichen von Papierzellstoff
EP09753845A Withdrawn EP2286024A1 (de) 2008-05-26 2009-05-25 Verfahren zum bleichen von papierzellstoff

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EP09753845A Withdrawn EP2286024A1 (de) 2008-05-26 2009-05-25 Verfahren zum bleichen von papierzellstoff

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US (1) US20110067831A1 (de)
EP (2) EP2128331A1 (de)
CA (1) CA2723311A1 (de)
WO (1) WO2009144190A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010136550A1 (en) * 2009-05-29 2010-12-02 Solvay Sa Process for the bleaching of mechanical paper pulp

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0801169A1 (de) * 1996-04-12 1997-10-15 Elf Atochem S.A. Verfahren zur Delignifizierung und Bleichen von chemischen Papierzellstoffen
DE19614587A1 (de) * 1996-04-13 1997-10-16 Jaschinski Thomas Dipl Holzw Verfahren und Bleichlösung zum Bleichen von cellulosischen Faserstoffen
EP0814193A2 (de) * 1996-06-21 1997-12-29 Nippon Peroxide Co., Ltd. Stabilisierungsmittel für Peroxidbleichen und Verfahren zum Bleichen eines faserigen Materials unter Verwendung desselben
US6221209B1 (en) 1992-07-06 2001-04-24 Solvay Interox (Société Anonyme) Multi-stage bleaching process having a final stabilized peroxide stage
US20010050153A1 (en) * 2000-01-28 2001-12-13 Wajer Mark T. Process employing magnesium hydroxide in peroxide bleaching of mechanical pulp
US20050217813A1 (en) * 2004-03-31 2005-10-06 Shevchenko Sergey M Methods to enhance brightness of pulp and optimize use of bleaching chemicals
WO2005108673A1 (en) * 2004-05-12 2005-11-17 Kemira Oyj New composition and process for the treatment of fibre material

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1978129B (zh) * 2005-12-02 2010-11-10 鸿富锦精密工业（深圳）有限公司 滚圆设备
FI119375B (fi) * 2007-02-02 2008-10-31 Kemira Oyj Uusi koostumus ja menetelmä kuitumateriaalin käsittelemiseksi

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6221209B1 (en) 1992-07-06 2001-04-24 Solvay Interox (Société Anonyme) Multi-stage bleaching process having a final stabilized peroxide stage
EP0801169A1 (de) * 1996-04-12 1997-10-15 Elf Atochem S.A. Verfahren zur Delignifizierung und Bleichen von chemischen Papierzellstoffen
DE19614587A1 (de) * 1996-04-13 1997-10-16 Jaschinski Thomas Dipl Holzw Verfahren und Bleichlösung zum Bleichen von cellulosischen Faserstoffen
EP0814193A2 (de) * 1996-06-21 1997-12-29 Nippon Peroxide Co., Ltd. Stabilisierungsmittel für Peroxidbleichen und Verfahren zum Bleichen eines faserigen Materials unter Verwendung desselben
US20010050153A1 (en) * 2000-01-28 2001-12-13 Wajer Mark T. Process employing magnesium hydroxide in peroxide bleaching of mechanical pulp
US7052578B2 (en) 2000-01-28 2006-05-30 Martin Marietta Magnesia Specialties, Inc. Process employing magnesium hydroxide in peroxide bleaching of mechanical pulp
US20050217813A1 (en) * 2004-03-31 2005-10-06 Shevchenko Sergey M Methods to enhance brightness of pulp and optimize use of bleaching chemicals
WO2005108673A1 (en) * 2004-05-12 2005-11-17 Kemira Oyj New composition and process for the treatment of fibre material

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010136550A1 (en) * 2009-05-29 2010-12-02 Solvay Sa Process for the bleaching of mechanical paper pulp

Also Published As

Publication number Publication date
EP2286024A1 (de) 2011-02-23
US20110067831A1 (en) 2011-03-24
WO2009144190A1 (en) 2009-12-03
CA2723311A1 (en) 2009-12-03

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