WO1997030210A1 - Procede de blanchiment de pate haut rendement - Google Patents

Procede de blanchiment de pate haut rendement Download PDF

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Publication number
WO1997030210A1
WO1997030210A1 PCT/FI1997/000108 FI9700108W WO9730210A1 WO 1997030210 A1 WO1997030210 A1 WO 1997030210A1 FI 9700108 W FI9700108 W FI 9700108W WO 9730210 A1 WO9730210 A1 WO 9730210A1
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WO
WIPO (PCT)
Prior art keywords
bleaching
pulp
process according
peroxide
terized
Prior art date
Application number
PCT/FI1997/000108
Other languages
English (en)
Inventor
Ilkka Renvall
Elias Suokas
Reijo Aksela
Aarto Paren
Original Assignee
Kemira Chemicals Oy
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 Kemira Chemicals Oy filed Critical Kemira Chemicals Oy
Priority to AU17975/97A priority Critical patent/AU1797597A/en
Publication of WO1997030210A1 publication Critical patent/WO1997030210A1/fr

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Classifications

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

Definitions

  • the invention relates to a process for the bleaching of a high yield pulp, wherein the pulp is pretreated before peroxide bleaching and/or is treated in connection with peroxide bleach ⁇ ing with a chelating agent in order to bind into a chelate complex the heavy metals present in the pulp.
  • high yield pulps are meant above all mechanical pulps the bleaching of which differs from the bleaching of chemical pulps in that the aim is to avoid delignification.
  • the yield of pulp is maintained at a high level.
  • the aim in bleaching is to ren ⁇ der colorless the color-producing components (chromophoric groups) present in lignin.
  • the chelating carried out in connec ⁇ tion with the bleaching of mechanical pulps differs from the pretreatment carried out in connection with the bleaching of chemical pulps. In the latter case the complexes formed in the chelating are removed by a wash.
  • no wash is carried out in the pretreatment; instead, the pretreated pulp is compressed to the consistency used in bleaching, in which case only a small proportion of the metal complexes are removed from the pulp.
  • mechanical pulps also com ⁇ prise recycled fibers, from which only printing ink is removed, not lignin.
  • Mechanical pulps can be divided into two principal categories, pure mechanical pulps and chemi-mechanical pulps. These pulps can further be divided into subcategories so that mechanical pulps include stone groundwood (SGW), pressure groundwood (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP) and others such as TRMP and PRMP. Respectively, the chemi-mechanical pulps include low-sulfonated pulps (chemi- thermomechanical pulp CTMP and BCTMP), chemically modified pulps (OPCO) and high-sulfonated pulps (CMP, UHYS).
  • Mechanical pulps are used in the making of, for example, news ⁇ print, magazine paper and porous paper grades (tissue papers). Certain highly bleached chemi-mechanical pulps (BCTMP grades) are also used in bleached printing papers to replace chemical pulp.
  • BCTMP grades highly bleached chemi-mechanical pulps
  • Hydrogen peroxide is used for the bleaching of mechanical pulps and of recycled fiber which contains paper fiber made from mechanical pulps.
  • the bleaching conditions must be rendered such that the hydro ⁇ gen peroxide will not dissociate.
  • Heavy metals catalyze the dissociation of hydrogen peroxide and peroxy compounds.
  • the ions the most detrimental in terms of bleaching are manganese (Mn) , iron (Fe) and copper (Cu).
  • other heavy metals such as chromium ions (Cr), etc., have a detrimental effect on the consumption of peroxy compounds.
  • Detrimental heavy metals originate in the pulp, the treatment waters and the pulp-treatment apparatus.
  • heavy metals are bound by using agents which chelate metal ions, for example poly- aminocarboxylic acids.
  • agents which chelate metal ions for example poly- aminocarboxylic acids.
  • EDTA ethylene diamine tetra-acetic acid and its salts
  • DTPA diethylene triamine penta-acetic acid and its salts
  • DTMPA diethylene triamine pentame hylenephosphonic acid
  • the bleaching of mechanical pulps and recycled fiber is common ⁇ ly carried out with hydrogen peroxide at a high pH.
  • Magnesium sulfate and waterglass are added during the bleaching step in order to stabilize the peroxide.
  • Many hypotheses have been presented regarding the stabilizing effect of the above- mentioned compounds.
  • the stabilizing effect of waterglass is probably based on waterglass surrounding the hydroxides, oxy- hydroxides and oxides formed under alkaline conditions when iron precipitates, thus inactivating the catalytic surfaces of these solids.
  • biodegradable chelating agents At least in part with biodegradable chelating agents which do not contain nitrogen.
  • the bleaching of recycled fibers can often also be carried out using reducing agents such as dithionite, and peroxide bleach ⁇ ing is not always necessary. Hydrogen peroxide is used more in the slushing of recycled pulp than in actual bleaching. For this reason the treatment of recycled fiber involves the same problems as regards the stability of hydrogen peroxide.
  • EDTA and DTMPA are regarded as non-biodegradable.
  • DTPA is poor ⁇ ly biodegradable.
  • Biodegradable complexing agents have been developed for deter ⁇ gent builders. They must at the same time have softening action on water, i.e. they must bind calcium ions and magnesium ions.
  • One such sequestering agent is ethylenediamine disuccinic acid (EDDS). This compound has three stereoisomers.
  • ISA 2,2'-imino- disuccinic acid
  • ISA 2,2'-imino- disuccinic acid
  • the use of this compound in alkaline detergents is disclosed in EP patent application 509 382.
  • the patent application mentions the use of 2,2'-iminodisuccinic acid as a stabilizer of peroxide compounds, in particular in alkaline detergent compositions which contain hydrogen peroxide and its derivatives.
  • DE patent application 4 340 043 discloses the use of ISA as a bleaching agent in the bleaching of groundwood.
  • the purpose of ISA is the stabilization of hydrogen peroxide, and the examples show that at a pH of 10 it is a better stabilizer of hydrogen peroxide than is DTPA.
  • biodegradable ethylenediamine disuccinic acid (EDDS) or 2,2'-iminodisuccinic acid (ISA), and their alkali metal salts can be used successfully as a chelat ⁇ ing agent.
  • the object of the present invention is to eliminate the adverse effects of heavy metals in the bleaching of high yield pulps.
  • the aim is to provide for use a biodegradable chelating agent which yields a good bleaching result.
  • hydroxy ⁇ carboxylic acids can be used successfully as chelating agents together with nitrogen-containing chelating agents in bleach ⁇ ing.
  • Hydroxycarboxylic acids are not efficient binders of heavy metals.
  • they chelate well calcium and mag ⁇ nesium.
  • Citric acid for example, has been used instead of phosphates in phosphate-free detergents and cleansing agents, which are required to bind calcium and magnesium.
  • the usability of the chelating process according to the invention is based specifically on the joint effect of chelating agents of dif ⁇ ferent types.
  • the pH the most preferable in terms of bleaching is approx. 5-5.5.
  • aminopolycarboxylic acids are replaced with the above-mentioned hydroxycarboxylic acids, the chelating can be carried out at a higher pH.
  • the usable pH range is 6-8, most preferably pH 6.5-7.5.
  • the procedure according to the invention is advantageous, since the nitrogen-containing chelating agent can in part be replaced with a biodegradable chelating agent which does not contain nitrogen.
  • the characteristics of the invention are given in the accom ⁇ panying claims.
  • nitrogen-containing chelating agents can be replaced with compounds, known per se, having the general formula I
  • n 1-8, is 0-2n, p is 0-n, q is 0-2,
  • R- ⁇ is COOH
  • R 2 is H, CH 2 OH or COOH.
  • carboxylic acids, hydroxycarboxylic acids, polyhydroxycarboxylic acids and hydroxypolycarboxylic acids according to Formula I such as citric acid, tartaric acid, lactic acid, pimelic acid, glutamic acid, glucoheptonic acid, ascorbic acid, glycolic acid, glutaric acid, adipic acid, succinic acid or malonic acid, can be used as replacement che ⁇ lating agents.
  • the process according to the invention can be used in the pre ⁇ treatment of mechanical pulps and/or in the actual bleaching.
  • the process is suitable for the treatment of all mechanical pulps, such as stone groundwood, pressure groundwood, refiner mechanical pulp, thermomechanical pulp, chemi-mechanical refiner pulp and chemi-mechanical pulp.
  • the process is also suitable for the bleaching of recycled fiber and textile fiber.
  • the process can be used both in single-step and in two-step peroxide bleaching of mechanical pulp.
  • the treatment is also suitable for mechanical pulp bleaching in which dithionite or formadine sulfinic acid bleaching is used instead of peroxide in some step.
  • the compounds according to Formula I may be added already to the impregnation liquor, whereby the efficacy of the bleaching can be improved.
  • the treatment may be performed on pulps obtained from various fiber raw materials, such as softwood or hardwood.
  • the pH control of the acid chelating step can be carried out using conventional mineral acids, such as sulfuric acid, sulfur dioxide or an aqueous solution thereof, carbon dioxide, or organic acids such as formic acid and acetic acid.
  • mineral acids such as sulfuric acid, sulfur dioxide or an aqueous solution thereof, carbon dioxide, or organic acids such as formic acid and acetic acid.
  • nitrogen-containing, phosphorus-free chelating agents are preferably used, whereby environmental problems due to phosphorus are avoided.
  • chelating agents include ethylenediamine-N,N'-disuccinic acid (EDDS), its various isomers and its alkali metal salts such as sodium and potassium salts, and its earth-alkali metal salts such as calcium and magnesium salts, 2,2'-iminodisuccinic acid (ISA), its various isomers and its alkali metal salts such as sodium and potassium salts, and its earth-alkali metal salts such as calcium and magnesium salts.
  • EDDS ethylenediamine-N,N'-disuccinic acid
  • ISA 2,2'-iminodisuccinic acid
  • ISA 2,2'-iminodisuccinic acid
  • its various isomers and its alkali metal salts such as sodium and potassium salts
  • earth-alkali metal salts such as calcium and magnesium salts.
  • Usable chelating agents also include, among polyaminocarboxylic acids, ethylenediamine tetra-acetic acid (EDTA) and its salts, and diethylenetriamine penta-acetic acid (DTPA) and its salts.
  • EDTA ethylenediamine tetra-acetic acid
  • DTPA diethylenetriamine penta-acetic acid
  • Chelating agents within the scope of the invention are those which in addition to nitrogen also contain phosphorus, such as polyaminomethylene phosphonic acids or biodegradable aminoalkane diphosphonic acids, the use of which in the bleaching of pulp is known per se from WO applica ⁇ tion publication 95/12029.
  • Some specific examples of these chelating agents are, among aminoalkane phosphonic acids, 4- morpholinomethylene-1,1-diphosphonic acid (MMDPA) and its salts, among alkane diphosphonic acids, 1-hydroxyethylene di ⁇ phosphonic acid (HEDPA) and its salts, and, among aminopoly- methylene phosphonic acids, aminotrimethylene phosphonic acid and its salts, ethylene diamine tetramethylene phosphonic acid and its salts, and diethylene triamine pentamethylene phos ⁇ phonic acid (DTMPA) and its salts.
  • MMDPA 4- morpholinomethylene-1,1-diphosphonic acid
  • HEDPA 1-hydroxyethylene di ⁇ phosphonic acid
  • DTMPA diethylene triamine pentamethylene phos ⁇ phonic acid
  • washing experi ⁇ ments were first performed on a chemical pulp.
  • the success of bleaching is not dependent solely on the efficacy of the che ⁇ lating of heavy metals, but the chelating results can be re ⁇ lodged as giving a guideline.
  • the best pH range for metal removal can be sought by means of washing experiments. With the help of washing experiments carried out on the same pulp at the same pH it is possible to compare the efficacies in the chelat ⁇ ing of metal ions by different chelating agents.
  • Table 1 shows that a water wash is without effect as regards the chelating of metals.
  • citric acid used alone does not remove heavy metals.
  • Citric acid chelates only earth-alkali metals, which is not desirable in terms of bleaching. This indicates that a good chelating result is achieved through the joint effect of nitrogen-containing chelating agents and, for example, citric acid.
  • a commercial TMP having an initial brightness of 55 % ISO was bleached with peroxide by pretreating it first with chelates for 30 minutes at a consistency of 10 % and a temperature of 60 °C.
  • the dose of chelates was 1.5 kg/metric ton of pulp.
  • the pH in the pretreatment was 6.5.
  • the peroxide bleaching was carried out at a temperature of 70 °C and a consistency of 15 % for 60 minutes.
  • the doses of waterglass and alkali are shown in accompanying Table 2. Table 2
  • Refiner mechanical pulp was bleached by pretreating it first at the same consistency, at the same temperature and for the same time as in Example 2.
  • the dose of the chelating agents was 2 kg/metric ton of pulp.
  • the pH in the pretreatment was approx. 6-6.5.
  • the conditions of the peroxide bleaching are shown in Table 3.
  • the final pH of the bleaching was approx. 8.5 in all the experiments. Residual peroxide was determined from the bleaching filtrate.
  • Refiner mechanical pulp was bleached with hydrogen peroxide by pretreating it fir ⁇ t at a consistency of 10 % at 60 °C.
  • the chelating agents were dosed at a rate of 2 kg/metric ton of pulp, both in the pretreatment and in the bleaching.
  • the pH was 6-6.5.
  • the peroxide bleaching was carried out at 70 °C, at a consistency of 15 %, for 60 min. The results of the experiments are shown in Table 4.
  • Citric acid kg/tp 1
  • Citric acid kg/tp 1
  • Refiner mechanical pulp was bleached with hydrogen peroxide at 70 °C, at a consistency of 15 %, for 60 min.
  • the results of the experiments are shown in Table 5.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Abstract

La présente invention concerne un procédé de blanchiment de pâte mécanique avec des peroxydes. Ce procédé consiste à traiter la pâte avec un chélateur de façon à fixer dans un complexe de type chélate les métaux lourds présents dans la pâte. Pour mener à bien la chélation on utilise un mélange constitué, d'une part d'un chélateur contenant de l'azote, et d'autre part d'un ou plusieurs composés représentés par la formule générale (I): R1CnHm(OH)p(COOH)qR2 dans laquelle, n = 1 à 8, m = 0 à 2n, p = 0 à n, q = 0 à 2, R1 est COOH et R2 est H, CH2OH ou COOH.
PCT/FI1997/000108 1996-02-19 1997-02-19 Procede de blanchiment de pate haut rendement WO1997030210A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU17975/97A AU1797597A (en) 1996-02-19 1997-02-19 Process for bleaching of a high yield pulp

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI960758A FI115641B (fi) 1996-02-19 1996-02-19 Korkeasaantomassojen valkaisumenetelmä
FI960758 1996-02-19

Publications (1)

Publication Number Publication Date
WO1997030210A1 true WO1997030210A1 (fr) 1997-08-21

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AU (1) AU1797597A (fr)
FI (1) FI115641B (fr)
WO (1) WO1997030210A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0892040A2 (fr) * 1997-07-16 1999-01-20 Nippon Shokubai Co., Ltd. Compositions chélatantes
US6590120B1 (en) 1998-03-09 2003-07-08 Kemira Chemicals Oy Methods for the preparation of an N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]amine derivative and products of the methods and their uses

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0141355A1 (fr) * 1983-10-21 1985-05-15 Benckiser-Knapsack GmbH Procédé pour blanchir une pulpe de bois broyé
WO1988006202A1 (fr) * 1987-02-12 1988-08-25 Kubat Josef Methode amelioree de decoloration au peroxyde
GB2206903A (en) * 1987-06-26 1989-01-18 Sandoz Ltd Stabilisers for peroxide-containing bleaching liquors
WO1994003553A1 (fr) * 1992-08-01 1994-02-17 The Procter & Gamble Company Composition de blanchiment peroxy stabilisee a l'acide ethylenediamine-n,n'-disuccinique
DE19528843A1 (de) * 1995-08-04 1997-02-06 Cht R Beitlich Gmbh Verfahren zur Stabilisierung von alkalischen peroxidenthaltenden Bleichflotten für die Bleiche von Zellstoffen und anderen Faserstoffen

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0141355A1 (fr) * 1983-10-21 1985-05-15 Benckiser-Knapsack GmbH Procédé pour blanchir une pulpe de bois broyé
WO1988006202A1 (fr) * 1987-02-12 1988-08-25 Kubat Josef Methode amelioree de decoloration au peroxyde
GB2206903A (en) * 1987-06-26 1989-01-18 Sandoz Ltd Stabilisers for peroxide-containing bleaching liquors
WO1994003553A1 (fr) * 1992-08-01 1994-02-17 The Procter & Gamble Company Composition de blanchiment peroxy stabilisee a l'acide ethylenediamine-n,n'-disuccinique
DE19528843A1 (de) * 1995-08-04 1997-02-06 Cht R Beitlich Gmbh Verfahren zur Stabilisierung von alkalischen peroxidenthaltenden Bleichflotten für die Bleiche von Zellstoffen und anderen Faserstoffen
WO1997006303A1 (fr) * 1995-08-04 1997-02-20 Cht R. Beitlich Gmbh Procede de stabilisation de bains de blanchiment alcalins contenant des peroxydes pour le blanchiment de pates de cellulose et d'autres substances fibreuses

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0892040A2 (fr) * 1997-07-16 1999-01-20 Nippon Shokubai Co., Ltd. Compositions chélatantes
US6103686A (en) * 1997-07-16 2000-08-15 Nippon Shokubai Co. Ltd. Chelating composition
EP0892040A3 (fr) * 1997-07-16 2001-01-03 Nippon Shokubai Co., Ltd. Compositions chélatantes
US6590120B1 (en) 1998-03-09 2003-07-08 Kemira Chemicals Oy Methods for the preparation of an N-bis-[2-(1,2-dicarboxy-ethoxy)-ethyl]amine derivative and products of the methods and their uses

Also Published As

Publication number Publication date
AU1797597A (en) 1997-09-02
FI960758A0 (fi) 1996-02-19
FI960758A (fi) 1997-08-20
FI115641B (fi) 2005-06-15

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