EP0882151B1 - Verfahren zur behandlung von chemischem zellstoff - Google Patents

Verfahren zur behandlung von chemischem zellstoff Download PDF

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Publication number
EP0882151B1
EP0882151B1 EP97903408A EP97903408A EP0882151B1 EP 0882151 B1 EP0882151 B1 EP 0882151B1 EP 97903408 A EP97903408 A EP 97903408A EP 97903408 A EP97903408 A EP 97903408A EP 0882151 B1 EP0882151 B1 EP 0882151B1
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Prior art keywords
bleaching
pulp
process according
acid
chelating
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English (en)
French (fr)
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EP0882151A1 (de
Inventor
Ilkka Renvall
Reijo Aksela
Aarto Paren
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Kemira Oyj
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Kemira Chemicals Oy
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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
    • 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 or delignification of pulp, wherein, before bleaching or delignification with an oxygen chemical, the pulp is pretreated with a chelating agent in order to eliminate the adverse effects of any heavy metals present in the pulp.
  • ECF elementary chlorine free
  • TCF total chlorine free
  • Usable bleaching processes also include bleaching with peroxy compounds (such as peracetic acid, caron acid, or mixtures of peracids), a peroxide-enhanced oxygen step, and a peroxide-enhanced oxygen-alkali step.
  • peroxy compounds such as peracetic acid, caron acid, or mixtures of peracids
  • Such bleaching steps are most commonly preceded by the binding of heavy metals.
  • the metals can be removed by an acid wash. This is often disadvantageous, since at least some of the subsequent bleaching steps are carried out in alkaline conditions. If heavy metals are removed at a low pH, it is necessary first to use an acid in order to reach a low pH and in the next step an alkali to neutralize the acid. Furthermore, the acid wash removes Mg and Ca ions, which are regarded as advantageous for bleaching. The acid wash may also reduce the strength of the pulp.
  • Peroxy compounds such as peracetic acid and hydrogen peroxide are highly susceptible to the catalytic action of heavy metals.
  • heavy metals are bound by using agents which chelate metal ions, for example polyaminocarboxylic acids. These include in particular ethylene diamine tetra-acetic acid and its salts (EDTA) and diethylene triamine penta-acetic acid and its salts (DTPA).
  • EDTA ethylene diamine tetra-acetic acid and its salts
  • DTPA diethylene triamine penta-acetic acid and its salts
  • 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, both on the consumption of peroxy compounds and often on the bleaching result, by reducing, for example, the viscosity of the bleached pulp. Detrimental heavy metals originate in the pulp, the treatment waters and the pulp-treatment apparatus.
  • Effective chelating agents are often poorly biodegradable, as is DTPA, or are completely non-biodegradable, as is EDTA.
  • TCF bleaching has increased the use of the said chelating agents. Therefore interest has arisen in replacing poorly biodegradable chelating agents either in part or entirely with biodegradable chelating agents.
  • the biodegradable chelating agents be preferably phosphorus-free and also contain as small an amount of nitrogen as possible.
  • Biodegradable complexing agents have been developed for detergent 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.
  • EP patent application 556 782 discloses the use of EDDS as an iron complexer in photography chemicals.
  • Example 9 of the publication mentions that the ferric salts of EDTA, DTPA and HEDTA are not biodegradable.
  • the Fe 2+ salt of EDDS is biodegradable.
  • the biodegradabilities of the compounds were tested in the example by a generally approved testing method (301C Amendment MITI Test (I), OECD Chemical Substance Testing Guidelines, May 1981).
  • ISA 2,2'-iminodisuccinic acid
  • ISA 2,2'-iminodisuccinic 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.
  • only perborate is used. Since perborate releases hydrogen peroxide only slowly, no far-reaching conclusions can be drawn from the examples of the patent regarding the stabilization of hydrogen peroxide in similar detergent compositions.
  • DE patent application 4 216 363 discloses the use of ISA as a stabilizer of tensides. There is no mention of the use of a peroxide compound.
  • EP patent application 513 948 mentions the use of the substance in detergents which are intended for hard surfaces and contain an organic solvent boiling at approx. 90 °C. There is no mention of the use of a peroxide compound.
  • DE patent application 4 340 043 discloses the use of ISA as a bleaching agent in the bleaching of groundwood pulp.
  • 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 than DTPA.
  • the object of the present invention is to eliminate the adverse effects of heavy metals in the bleaching and delignification of chemical pulp. It is also an object to obtain a biodegradable effective chelating agent which yields a good bleaching result.
  • DTPA which is commonly used in the bleaching of pulp, chelates heavy metals best at a pH of approx. 5.
  • Suitable pH values in the use of the compounds in accordance with the invention for the pretreatment of pulp are pH 4-8, preferably pH 5.0-7.5 and most preferably pH 6.5-7.5. If the compounds are also used in the actual bleaching or delignification step, the suitable pH values are respectively pH 4-8, preferably pH 4-6 and most preferably pH 4-5. Since chelating can be carried out at a higher pH value, the consumption of alkali in the subsequent step is not as high as when the chelating is carried out at a lower pH. This is a clear advantage over, for example, DTPA.
  • the process according to the invention can be used for all known chemical pulps. These include alkaline and neutral sulfite pulps, soda pulps, sulfate pulps (kraft pulps) and oxygen-delignified (oxygen cooking) sulfate pulps. Furthermore, the process can be used in the bleaching of so-called organosolv pulps in which alcohols or organic acids have been used as the cooking solvent, for example Milox cooking in formic acid.
  • the chelating process according to the invention may also be used when polysulfides or, for example, anthraquinone, have/has been used in sulfate cooking.
  • the treatment can be carried out on pulp cooked from different fiber raw materials, such as softwood, hardwood or reed, straw or other raw material of vegetable origin.
  • the chelating process according to the invention with compounds of Formula I is used as a pretreatment before bleaching or delignification with oxygen chemicals.
  • Chelating agents according to Formula I such as EDDS and ISA, can also be used as a chelating agent in bleaching or delignification with oxygen chemicals.
  • bleaching with peracetic acid bleaching with mixtures of peracids, bleaching with hydrogen peroxide, bleaching with mixtures of hydrogen peroxide and peracids, transition-metal catalyzed hydrogen peroxide bleaching within the acid pH range, developed by the applicant, alkaline peroxide bleaching, and combinations of all these, as well as oxygen delignification, peroxide-enhanced oxygen-alkali steps and pressurized peroxide steps and, in conjunction with these, optional treatments with enzymes, ozone or chlorine dioxide.
  • the chelating process according to the invention can be used as a pretreatment for pulp bleaching or delignification in acid conditions and possibly also in the bleaching or delignification step itself.
  • the pH control of an 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.
  • an especially suitable chelating agent according to Formula I may be ethylenediamine-N,N'-disuccinic acid, 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. It is also possible to use ethylenediamine-N,N'-disuccinic acid together with calcium sulfate and/or magnesium sulfate.
  • Another particularly suitable chelating agent is 2,2'-iminodisuccinic acid, 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. It is also possible to use 2,2'-iminodisuccinic acid together with calcium sulfate and/or magnesium sulfate.
  • Usable chelating agents also include N-(1,2-dicarboxyethyl)-N-(2-hydroxyethyl)aspartamic acid, its various isomers and its alkali metal salts and earth-alkali metal salts.
  • the acid may also be used together with potassium sulfate or magnesium sulfate.
  • the chelating agent may be added in an amount of 0.1-5 kg, preferably 0.5-2 kg per metric ton of dry pulp.
  • EDDS and ISA can be used together with hydroxycarboxylic acids without the bleaching result being worsened.
  • EDDS and ISA may in part be replaced with chelating agents which do not contain nitrogen, such as hydroxycarboxylic acids having the general formula II R 1 C n H m (OH) p (COOH) q R 2 where
  • carboxylic acids, hydroxycarboxylic acids, polyhydroxycarboxylic acids and hydroxypolycarboxylic acids according to Formula II 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 chelating agents.
  • hydroxy acids can be used as chelating agents in bleaching.
  • the said substances are quite poor binders of heavy metals, but bind well calcium and magnesium.
  • citric acid has been used as a replacement for phosphates in phosphate-free detergents and cleansing agents, in which the substances are required to bind calcium and magnesium.
  • Especially the binding of magnesium should be disadvantageous in terms of bleaching.
  • CS stands for consistency
  • PAA for a peracetic acid treatment
  • mP for a molybdate-activated peroxide treatment
  • O for an oxygen treatment
  • P for an alkaline peroxide treatment
  • Q for a chelating step.
  • the doses in the tables are indicated in kilograms per metric ton of pulp (kg/tp).
  • Na 5 DTPA stands for the pentasodium salt of DTPA
  • Na 4 EDTA stands for the tetrasodium salt of EDTA
  • H 4 EDDS stands for the acid form of EDDS.
  • the pH used will determine how the chelating agents are dissociated, i.e. in which form they actually appear in the treatment.
  • the H 4 EDDS (reaction mixture) mentioned in the table refers to experiments in which the chelating agent used was an unpurified reaction product directly from the process for the preparation of EDDS.
  • Table 2 shows the results of washing experiments similar to those described in Example 1, when EDDS was diluted with certain hydroxy acids.
  • Softwood sulfate pulp Chelating conditions Kappa number 16.9 Time (t) 60 min Viscosity 963 dm 3 /kg Temperature (T) 70 °c Brightness 39.6 % ISO Consistency (CS) 12 % Chelate Dose pH Metal contents in the filtrate (ppm) kg/tp Fe Mn Mg Ca Na 5 DTPA 1 6.7 1.2 2.9 4 17 Na 5 DTPA 2 6.5 2.0 2.8 17 48 Na 5 DTPA 2 5.7 2.0 3.3 13 52 Na 5 DTPA 0.5 6.6 0.8 1.5 5 26 Na 4 EDTA 2 6.5 1.8 3.3 5 49 Water wash 6.0 0.3 0.3 6 22 Water wash 7.0 0.3 0.3 14 66 Na 3 citrate 1 6.3 0.0 0.6 9 26 H 4 EDDS + Na 3 citrate 0.5+1 7.5 1.3 2.4 8 18 H 4 EDDS + Na 3 citrate 0.75
  • DTPA is usually dosed into a softwood pulp at a rate of approx. 2 kg/tp.
  • Table 2 the effect of the DTPA dose on the chelating of metals was first investigated. Chelating was clearly less when the dose of EDDS was reduced from a rate of 2.0 kg/tp to a rate of 1.0 kg/tp or 0.5 kg/tp. In the previous series of experiments (Table 1) it was observed that when Na 4 EDDS was used at a rate of 1.5 kg/tp, chelating was as complete as when Na 5 DTPA was used at a rate of 2.0 kg/tp.
  • the nitrogen load in the effluents from the chelating step can be reduced significantly, while the chelating of the metals is still sufficiently complete for bleaching.
  • An oxygen-delignified pulp was chelated and bleached with an alkaline hydrogen peroxide.
  • the chelating agent used was EDDS or DTPA.
  • the results are compiled in Table 3.
  • the bleaching result can be evaluated on the basis of the consumption of peroxide, the brightness achieved, and the viscosity of the pulp.
  • Na 5 DTPA stands for the pentasodium salt of DTPA
  • Na 4 EDTA stands for the tetrasodium salt of EDTA
  • ISA stands for the acid form of iminodisuccinic acid of ISA.
  • pH it is the pH used that determines how the chelating agents are dissociated, i.e. in which form they actually are present in the treatment.
  • Chelating with a mixture of ISA and the sodium salt of citric acid was also successful, considering that the chelating was carried out at a pH of 7.7.
  • An oxygen-delignified pulp pretreated with a molybdate-catalyzed peroxide was chelated and bleached with an alkaline hydrogen peroxide.
  • the chelating agent used was ISA or DTPA.
  • the results are compiled in Table 9.
  • the bleaching result can be assessed on the basis of peroxide consumption and the achieved brightness and pulp viscosity.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)
  • Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
  • Treatment Of Fiber Materials (AREA)

Claims (16)

  1. Verfahren zum Bleichen oder Delignifizieren eines chemischen. Zellstoffs, bei welchem Verfahren der Zellstoff vor dem Bleichen oder Delignifizieren mittels einer Sauerstoff-Chemikalie mit einem Chelatbildner vorbehandelt wird, um die in dem Zellstoff vorhandenen Schwermetalle in einen Chelatkomplex zu binden,
    dadurch gekennzeichnet, dass
    der verwendete Chelatbildner eine Verbindung mit der Formel (I) ist:
    Figure 00320001
    wobei:
    n
    1 - 3 ist,
    m
    0 - 3 ist,
    p
    1 - 3 ist,
    R1, R2, R3 und R4
    H, Na, K, Ca oder Mg sind,
    R5 und R6
    H, CH2OH, CH2CH2OH oder CH2O(CH2CH2O)1-10CH2CH2OH sind.
  2. Verfahren nach Anspruch 1,
    dadurch gekennzeichnet, dass
    der Chelatbildner Ethylendiamin-N,N'-dibernsteinsäure und /oder ein Alkalimetallsalz oder Erdalkalimetallsalz derselben ist.
  3. Verfahren nach Anspruch 1 oder 2,
    dadurch gekennzeichnet, dass
    der verwendete Chelatbildner ein Natrium-, Calcium- oder Magnesiumsalz der Ethylendiamin-N,N'-dibernsteinsäure oder Ethylendiamin-N,N'-dibernsteinsäure und Calciumsulfat und/oder Magnesiumsulfat ist.
  4. Verfahren nach Anspruch 1,
    dadurch gekennzeichnet, dass
    der verwendete Chelatbildner 2,2'-Iminodibernsteinsäure und/oder ein Alkalimetallsalz und/oder Erdalkalimetallsalz derselben ist.
  5. Verfahren nach Anspruch 1 oder 4,
    dadurch gekennzeichnet, dass
    der verwendete Chelatbildner ein Natrium-, Calcium- oder Magnesiumsalz der 2,2'-Iminodibernsteinsäure oder 2,2'-Iminodibernsteinsäure und Calciumsulfat und/oder Magnesiumsulfat ist.
  6. Verfahren nach Anspruch 1,
    dadurch gekennzeichnet, dass
    die Vorbehandlung des Zellstoffs bei einem pH-Wert von 4 - 8, vorzugsweise bei einem pH-Wert von 5,0 - 7,5 und am bevorzugtesten bei einem pH-Wert von 6,5 - 7,5 ausgeführt wird.
  7. Verfahren nach Anspruch 1 oder 6,
    dadurch gekennzeichnet, dass
    die Vorbehandlung mit einem Chelatbildner einen Schritt darstellt, der dem Bleichen oder Delignifizieren mittels einer Sauerstoff-Chemikalie unmittelbar vorausgeht.
  8. Verfahren nach einem der Ansprüche 1, 6 und 7,
    dadurch gekennzeichnet, dass
    die Vorbehandlung einmal oder mehrmals ausgeführt wird.
  9. Verfahren nach Anspruch 1 oder 7,
    dadurch gekennzeichnet, dass
    das Bleichen oder Delignifizieren mittels einer Sauerstoff-Chemikalie umfasst: Bleichen mit Peressigsäure, Bleichen mit einer Persäure-Mischung, Bleichen mit Peroxiden an sich oder als Mischungen, entweder allein oder als eine Mischung mit Persäuren, durch ein Übergangsmetall katalysiertes Wasserstoffperoxid-Bleichen im sauren pH-Bereich, ein alkalisches Peroxid-Bleichen sowie Kombinationen all dieser als auch eine Sauerstoff-Delignifizierung, einen Peroxid-verstärkten Sauerstoff-Alkali-Schritt und Peroxidschritte unter Überdruck, und kombiniert mit diesen optionale Behandlungen mit Enzymen, Ozon oder Chlordioxid.
  10. Verfahren nach Anspruch 1 oder 9,
    dadurch gekennzeichnet, dass
    die Chelatbildungs-Behandlung ebenfalls in dem Schritt des Bleichens oder Delignifizierens mittels einer Sauerstoff-Chemikalie ausgeführt wird.
  11. Verfahren nach einem der Ansprüche 1, 9 oder 10,
    dadurch gekennzeichnet, dass
    das Bleichen oder Delignifizieren mittels einer Sauerstoff-Chemikalie bei einem pH-Wert von 4 - 8, vorzugsweise bei einem pH-Wert von 4 - 6 und am bevorzugtesten bei einem pH-Wert von 4 -5 ausgeführt wird.
  12. Verfahren nach einem der Ansprüche 1 und 9 - 11,
    dadurch gekennzeichnet, dass
    die Behandlung mit einer Sauerstoff-Chemikalie einmal oder mehrmals ausgeführt wird.
  13. Verfahren nach einem der Ansprüche 1 und 9 - 12,
    dadurch gekennzeichnet, dass
    die Behandlung des Zellstoffs mittels einer Sauerstoff-Chemikalie gleichzeitig mit einem Peroxid und einer Persäure ausgeführt wird.
  14. Verfahren nach einem der Ansprüche 1 und 9 - 13,
    dadurch gekennzeichnet, dass
    die Peroxid-Behandlung des Zellstoffs mit Wasserstoffperoxid, mit einer Mischung aus Wasserstoffperoxid und Sauerstoffgas oder mit organischen Peroxyverbindungen ausgeführt wird.
  15. Verfahren nach einem der Ansprüche 1 und 9 - 14,
    dadurch gekennzeichnet, dass
    die Persäure-Behandlung des Zellstoffs mit Peressigsäure, Perameisensäure, Perpropionsäure oder Caroscher Säure oder mit mittels eines Übergangsmetalls aktivierter Peressigsäure, Perameisensäure, Perpropionsäure oder Caroscher Säure oder einer Kombination dieser erfolgt.
  16. Verfahren nach einem der Ansprüche 1 - 15,
    dadurch gekennzeichnet, dass
    der Chelatbildner in einem Verhältnis von 0,1 - 5 kg pro Tonne trockenen Zellstoffs verwendet wird.
EP97903408A 1996-02-19 1997-02-19 Verfahren zur behandlung von chemischem zellstoff Expired - Lifetime EP0882151B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI960756 1996-02-19
FI960756A FI115469B (fi) 1996-02-19 1996-02-19 Menetelmä kemiallisen selluloosamateriaalin käsittelemiseksi
PCT/FI1997/000106 WO1997030208A1 (en) 1996-02-19 1997-02-19 Process for the treatment of chemical pulp

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EP0882151A1 EP0882151A1 (de) 1998-12-09
EP0882151B1 true EP0882151B1 (de) 2003-10-15

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EP (1) EP0882151B1 (de)
AT (1) ATE252176T1 (de)
AU (1) AU1797397A (de)
DE (1) DE69725558T2 (de)
FI (1) FI115469B (de)
WO (1) WO1997030208A1 (de)

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BE1011784A3 (fr) * 1998-03-10 2000-01-11 Solvay Procede de blanchiment de pate a papier.
EP1095184B1 (de) * 1998-04-17 2003-10-15 Alberta Research Council, Inc. Verfahren zur herstellung lignocellulosehaltiger pulpe aus nicht holzartigem material
FI991241A (fi) * 1999-06-01 2000-12-02 Aga Ab Ligniinin valkaisu ja menetelmä paperin valmistamiseksi
GB2391011A (en) * 2002-07-19 2004-01-28 Crosmill Ltd Bleaching cellulose suspensions
GB0901207D0 (en) 2009-01-26 2009-03-11 Innospec Ltd Chelating agents and methods relating thereto
BRPI1012052A2 (pt) 2009-05-28 2017-12-26 Gp Cellulose Gmbh fibras kraft hidrolisadas e quimicamente modificadas e métodos de produção e de branqueamento de fibras kraft
US9511167B2 (en) 2009-05-28 2016-12-06 Gp Cellulose Gmbh Modified cellulose from chemical kraft fiber and methods of making and using the same
US9512237B2 (en) 2009-05-28 2016-12-06 Gp Cellulose Gmbh Method for inhibiting the growth of microbes with a modified cellulose fiber
US9512563B2 (en) 2009-05-28 2016-12-06 Gp Cellulose Gmbh Surface treated modified cellulose from chemical kraft fiber and methods of making and using same
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BR112015019882A2 (pt) 2013-03-14 2017-07-18 Gp Cellulose Gmbh fibra kraft clareada oxidada e métodos para fazer polpa kraft e fibra kraft de madeira macia e para clarear polpa kraft de celulose em sequência de branqueamento de multi-estágios
BR112015020000A2 (pt) 2013-03-15 2017-07-18 Gp Cellulose Gmbh fibra kraft quimicamente modificada e métodos de fabricação da mesma
WO2015138335A1 (en) * 2014-03-12 2015-09-17 Gp Cellulose Gmbh A low viscosity kraft fiber having an enhanced carboxyl content and methods of making and using the same
EP3541849B1 (de) 2016-11-16 2023-11-15 GP Cellulose GmbH Modifizierte cellulose aus chemischen fasern und methoden zu deren herstellung und verwendung
CZ309643B6 (cs) * 2021-07-21 2023-06-07 Univerzita Pardubice Hořečnaté sole derivátů asparagové kyseliny a jejich použití jako stabilizátorů peroxidu vodíku

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DE4340043A1 (de) * 1993-11-24 1995-06-01 Henkel Kgaa Verwendung Stickstoff-haltiger Komplexbildner bei der Holzstoffbleiche
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8361571B2 (en) 2008-06-20 2013-01-29 International Paper Company Composition and recording sheet with improved optical properties
US8906476B2 (en) 2008-06-20 2014-12-09 International Paper Company Composition and recording sheet with improved optical properties

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DE69725558T2 (de) 2004-08-05
AU1797397A (en) 1997-09-02
ATE252176T1 (de) 2003-11-15
DE69725558D1 (de) 2003-11-20
FI115469B (fi) 2005-05-13
WO1997030208A1 (en) 1997-08-21
FI960756A0 (fi) 1996-02-19
FI960756A (fi) 1997-08-20
EP0882151A1 (de) 1998-12-09

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