EP0348411B1 - An improved peroxide bleaching method - Google Patents

An improved peroxide bleaching method Download PDF

Info

Publication number
EP0348411B1
EP0348411B1 EP88901957A EP88901957A EP0348411B1 EP 0348411 B1 EP0348411 B1 EP 0348411B1 EP 88901957 A EP88901957 A EP 88901957A EP 88901957 A EP88901957 A EP 88901957A EP 0348411 B1 EP0348411 B1 EP 0348411B1
Authority
EP
European Patent Office
Prior art keywords
acid
pulp
bleaching
suspension
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.)
Expired
Application number
EP88901957A
Other languages
German (de)
French (fr)
Other versions
EP0348411A1 (en
Inventor
Joseph Kubat
Lars Magnus Qvist
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.)
Kemira Kemi AB
Original Assignee
Kemira Kemi AB
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 Kemi AB filed Critical Kemira Kemi AB
Priority to AT88901957T priority Critical patent/ATE83016T1/en
Publication of EP0348411A1 publication Critical patent/EP0348411A1/en
Application granted granted Critical
Publication of EP0348411B1 publication Critical patent/EP0348411B1/en
Expired legal-status Critical Current

Links

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

Definitions

  • Combinations of hydrogen peroxide with certain organic acids stand out as an especially efficient form of the peroxide bleaching technique.
  • the treatment is carried out within the acid range of the pH-scale, facilitating the formation of peroxyacids which are the active chemical species in the bleaching process.
  • the common way, of bleaching with peroxides is carried out using slightly alkaline conditions enhancing the formation of peroxide anions HO2 ⁇ which are the active ionic species. Higher alkalinities are to be avoided since hydrogen peroxide then decomposes to oxygen.
  • the purpose of the present disclosure is to describe a simple method to enhance the bleaching efficiency of hydrogen peroxide by adding certain inexpensive organic acids to the bleaching solution.
  • the acids in question are formic, acetic, lactic, maleic acid and phtalic acid; they can be used separately or in various combinations. Contrary to similar mixtures of hydrogen peroxide with such acids which have been proposed to increase the efficiency of the bleaching process, cf. for instance Austrian Patent 203.454, the mixtures of the present disclosure are being used within the alkaline range of the pH-scale and not on its acid side.
  • This alkalinity of the treating solution is the main characteristic feature of the present invention relating to peroxide bleaching process in the presence of the organic acids enumerated above, i.e. formic, acetic, lactic, maleic acid and phtalic acid or mixtures thereof.
  • the bleaching efficiency of peroxides can be improved if the bleaching process is carried out in the presence of low concentrations of one or more of the enumerated acids while maintaining the pH-value within the alkaline range 8-13, which pH-range is provided by the addition of an alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide.
  • an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide.
  • US-A-3,193,445 discloses a two-step process for bleaching cellulosic materials, e.g. wood pulp, whereby in a first step bleaching takes place using hydrogen peroxide at an alkaline pH and in a second step a carboxylic acid anhydride is added to reduce the content of hydrogen peroxide remaining in the reaction medium.
  • the method according to the present invention allows bleaching with lower acid and peroxide concentrations than when using common peroxy acid methods while still obtaining the same bleaching effect.
  • potassium hydroxide gives a significantly higher brightness of the bleached material than does sodium hydroxide. The difference amounted to 2-8 SCAN brightness units.
  • a bleaching mixture containing 4% H2O2, 1% acetic acid, and 1% formic acid gave after bleaching carried out as described above a brightness of 78%, the brightness gain being 18 units.

Landscapes

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

Abstract

A method for bleaching wood pulp without the use of peroxy acids by means of from 0.1 to 10 %, based on the dry weight of the pulp, of hydrogen peroxide characterized in that an organic acid selected from the group formic acid, acetic acid, lactic acid, maleic acid and phtalic acid or any mixture thereof is added together with such an amount of an alkali hydroxide to the pulp suspension to be bleached as to give a pH-value of the suspension within the alkaline range of from 8.0 to 13.

Description

  • The bleaching of wood pulp with peroxides is an established technique in the manufacture of bleached pulp grades, hydrogen peroxides being the by far the most common reagent used for such purposes. In a large number of patents and reports various details of this technique and its numerous ramifications are described.
  • Combinations of hydrogen peroxide with certain organic acids stand out as an especially efficient form of the peroxide bleaching technique. The treatment is carried out within the acid range of the pH-scale, facilitating the formation of peroxyacids which are the active chemical species in the bleaching process. Contrary to this, the common way, of bleaching with peroxides is carried out using slightly alkaline conditions enhancing the formation of peroxide anions HO₂⁻ which are the active ionic species. Higher alkalinities are to be avoided since hydrogen peroxide then decomposes to oxygen.
  • The purpose of the present disclosure is to describe a simple method to enhance the bleaching efficiency of hydrogen peroxide by adding certain inexpensive organic acids to the bleaching solution. The acids in question are formic, acetic, lactic, maleic acid and phtalic acid; they can be used separately or in various combinations. Contrary to similar mixtures of hydrogen peroxide with such acids which have been proposed to increase the efficiency of the bleaching process, cf. for instance Austrian Patent 203.454, the mixtures of the present disclosure are being used within the alkaline range of the pH-scale and not on its acid side. This alkalinity of the treating solution is the main characteristic feature of the present invention relating to peroxide bleaching process in the presence of the organic acids enumerated above, i.e. formic, acetic, lactic, maleic acid and phtalic acid or mixtures thereof.
  • Disclosures similar to those of the Austrian Patent 203.454, relating to the use of hydrogen peroxide containing certain organic acids at acidic conditions, can also be found in a number of other patents, cf. for instance US 2.720.441, FR 1.565.397, Japan 77.120.104. It is therefore even more surprising that a significant enhancement of the bleaching efficiency of hydrogen peroxide can be attained in the alkaline range of the pH-scale, where such an enhancement normally would not be expected. The increased bleaching efficiency of hydrogen peroxide in the presence of certain organic acids under acidic conditions can be related to the formation of peroxy acids. However, under the conditions specified in the present invention peroxy acids cannot be of any importance since the alkaline environment does not favor recations leading to such peroxy acids.
  • It has according to the present invention been found that the bleaching efficiency of peroxides can be improved if the bleaching process is carried out in the presence of low concentrations of one or more of the enumerated acids while maintaining the pH-value within the alkaline range 8-13, which pH-range is provided by the addition of an alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide.
  • When using peroxide and alkali metal hydroxide for bleaching of pulp with the addition of low concentrations of the enumerated acids a considerably improved bleaching is attained as compared to bleaching carried out with peroxide and the alkali metal hydroxide without the use of said acids.
  • US-A-3,193,445 discloses a two-step process for bleaching cellulosic materials, e.g. wood pulp, whereby in a first step bleaching takes place using hydrogen peroxide at an alkaline pH and in a second step a carboxylic acid anhydride is added to reduce the content of hydrogen peroxide remaining in the reaction medium.
  • The method according to the present invention allows bleaching with lower acid and peroxide concentrations than when using common peroxy acid methods while still obtaining the same bleaching effect.
  • Furthermore by using the method according to the present invention problems associated with the use of common peroxide stabilizers are avoided. Among these primarily silicates may be mentioned which when utilizing bleaching processes based on such methods in a technical scale may give rise to undesirable deposits (scaling).
  • Another surprising finding according to the present invention is the fact that potassium hydroxide gives a significantly higher brightness of the bleached material than does sodium hydroxide. The difference amounted to 2-8 SCAN brightness units.
  • The enhancement of the bleaching efficiency of hydrogen peroxide by the acids listed above, using KOH to adjust the pH-value, will now be illustrated by some examples. The experiments were carried out with unbleached mechanical pulp (pine). The chemicals (peroxide and acid) were added simultaneously to a 2% suspension of the pulp in water, whereafter the pH-value was immediately adjusted to 9-10 by KOH at 60°C, 1 h stirring. After completing the treatment, the pulp was formed into laboratory sheets using standardized procedures (SCAN C11:75). The measurement of brightness was carried out according to SCAN C11:75, the brightness being expressed in ISO-units. The brightness value of the unbleached pulp was 57-60.
  • The invention is illustrated by means of the following examples.
    • Example 1
  • A bleaching mixture containing 4% H₂O₂, 1% acetic acid, and 1% formic acid (based on the weight of the quantity of pulp present in the system) gave after bleaching carried out as described above a brightness of 78%, the brightness gain being 18 units.
    • Example 2
  • When carrying out the bleaching operation at lower peroxide and acid concentrations, namely 1.5% H₂O₂, 0.75% acetic acid, and 0.75% formic acid a brightness of 72% (gain 15 units) was recorded. Again, the concentration figures are percentages of the amount of pulp used in the reaction. In all other respects, the conditions were similar to those used in Example 1.
    • Example 3
  • With a reaction mixture of 4% H₂O₂ and 4% lactic acid a brightness value of 78% was obtained. This value was increased to 81.4 when adding a magnesium compound (0.4% Mg²⁺ = 4% MgSO₄x7H₂O). Reducing the peroxide and lactic acid concentrations to 1.5% resulted in a brightness reading of 72% which could be increased to 75 in the presence of 0.4% Mg²⁺ (= 4% MgsO₄x7H₂O).
  • With H₂O₂/maleic acid mixtures similar results were obtained.
    With H₂O₂/phtalic acid mixtures similar results were obtained.
  • The above results have been optimized with regard to the pH-value of the reaction mixture, the pH-value being adjusted using KOH. As already mentioned, the use of NaOH at the same pH resulted in lower brightness values. No optimization was, however, carried out with regard to the pulp concentrations. Using higher pulp concentrations, the brightness gain can be expected to increase by at least 6 units (cf. "The Bleaching of Pulp", L.A. Beeman and J.S. Reichert, Tappi Monograph No. 10, 210 (1953)). The efficiency of the present method thus appears to have been demonstrated with sufficient clarity.
  • It may be mentioned that experiments where the acid was added to the pulp suspension after the addition of alkali and peroxide produced similar results.

Claims (4)

  1. A method for bleaching wood pulp without the use of peroxy acids by means of from 0.1 to 10%, based on the dry weight of the pulp, of hydrogen peroxide wherein an organic acid selected from the group formic acid, acetic acid, lactic acid, maleic acid and phtalic acid or any mixture thereof is added together with such an amount of an alkali hydroxide to the pulp suspension to be bleached as to give a pH-value of the suspension within the alkaline range of from 8.0 to 13.
  2. A method according to claim 1, characterized in that the acid is used in an amount of from 0.25 to 10 % based on the dry weight of the pulp.
  3. A method according to claim 1 or 2, characterized in that the alkali metal hydroxide used is potassium hydroxide.
  4. A method according to any of the preceding claims, characterized in that the alkaline pH-range used is 9-10.
EP88901957A 1987-02-12 1988-02-12 An improved peroxide bleaching method Expired EP0348411B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88901957T ATE83016T1 (en) 1987-02-12 1988-02-12 PEROXIDE BLEACHING PROCESS.

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE8700569 1987-02-12
SE8700569A SE8700569D0 (en) 1987-02-12 1987-02-12 AN IMPROVED PEROXIDE BLEACHING METHOD
CA000612006A CA1333650C (en) 1987-02-12 1989-09-19 Peroxide bleaching method

Publications (2)

Publication Number Publication Date
EP0348411A1 EP0348411A1 (en) 1990-01-03
EP0348411B1 true EP0348411B1 (en) 1992-12-02

Family

ID=25673050

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88901957A Expired EP0348411B1 (en) 1987-02-12 1988-02-12 An improved peroxide bleaching method

Country Status (7)

Country Link
EP (1) EP0348411B1 (en)
AT (1) ATE83016T1 (en)
CA (1) CA1333650C (en)
DE (1) DE3876429T2 (en)
FI (1) FI91545C (en)
SE (1) SE8700569D0 (en)
WO (1) WO1988006202A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE505980C2 (en) * 1993-12-23 1997-10-27 Bim Kemi Ab Ways to prevent peroxide-degrading enzymes by bleaching with hydrogen peroxide
DE19516151A1 (en) * 1995-05-03 1996-11-07 Sven Siegle Process for the production of a pulp from cellulosic material, the pulp itself and its use
FI115641B (en) * 1996-02-19 2005-06-15 Kemira Oyj Bleaching process for high yields
FI115470B (en) * 1996-02-19 2005-05-13 Kemira Oyj Process for the treatment of chemical cellulose material

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE633420A (en) * 1962-07-16
DE2219505C3 (en) * 1972-04-21 1974-10-17 Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt Chlorine-free multi-stage bleaching of cellulose

Also Published As

Publication number Publication date
CA1333650C (en) 1994-12-27
FI91545C (en) 1994-07-11
SE8700569D0 (en) 1987-02-12
DE3876429D1 (en) 1993-01-14
FI91545B (en) 1994-03-31
FI893742A0 (en) 1989-08-08
ATE83016T1 (en) 1992-12-15
DE3876429T2 (en) 1993-07-01
WO1988006202A1 (en) 1988-08-25
EP0348411A1 (en) 1990-01-03

Similar Documents

Publication Publication Date Title
Gould Studies on the mechanism of alkaline peroxide delignification of agricultural residues
US5552018A (en) A process for delignifying pulp with organic peroxyacid in the presence of phosphonic acids and their salts
JP2504400B2 (en) Bleaching of mechanical pulp with hydrogen peroxide
CA2155124C (en) Inhibition of hydrogen peroxide decomposing enzymes, e.g. catalase and peroxidase during bleaching of cellulose fibers
US5618386A (en) Enzymatic bleaching of chemical lignocellulose pulp
EP0348411B1 (en) An improved peroxide bleaching method
RU2189412C2 (en) Method of bleaching paper pulp
US5607544A (en) Process and agent for the oxidative bleaching of wood pulp and for deinking waste paper
CA1122358A (en) Process for the full bleaching of pulp
JPS63256786A (en) Pulp bleaching method
JPH06505063A (en) Method for exposing chemical paper pulp and application of this method to bleaching kraft pulp
CA2149649C (en) Process for bleaching of lignocellulose-containing pulp
HUT64119A (en) Method for enzyme-bleaching cellulose
US4912791A (en) Pretreatment of textile materials: alkaline scour or bleach with organo-phosphorus compound
US3709779A (en) Bleaching of mechanical pulps with hydrosulfite in the presence of an alkali metal silikate
US2687943A (en) Bleaching of mechanical wood pulp
CA1282911C (en) Delignification process for ligno-cellulosic materials
RU2200155C2 (en) Method of preparing peracids' solution for delignification and bleaching
US3966698A (en) Recovery of tall oil soaps
JP2779197B2 (en) Plant fiber bleaching method
SU870538A1 (en) Wood pulp bleaching method
JP3265036B2 (en) Bleaching method of alkaline pulp
SU861444A1 (en) Cooking liquor for producing fibrous semiproduct
US3733247A (en) Bleching of cellulose fibers with an aqueous solution of a water-soluble hydroperoxypentacyanocobaltate salt
JPH0748792A (en) Method for bleaching paper pulp

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19891016

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT CH DE FR GB IT LI SE

R17P Request for examination filed (corrected)

Effective date: 19890731

DIN1 Information on inventor provided before grant (deleted)
RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: KEMIRA KEMI AKTIEBOLAG

17Q First examination report despatched

Effective date: 19910618

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT CH DE FR GB IT LI SE

REF Corresponds to:

Ref document number: 83016

Country of ref document: AT

Date of ref document: 19921215

Kind code of ref document: T

REF Corresponds to:

Ref document number: 3876429

Country of ref document: DE

Date of ref document: 19930114

ET Fr: translation filed
ITF It: translation for a ep patent filed

Owner name: BARZANO' E ZANARDO ROMA S.P.A.

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19930222

Year of fee payment: 6

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19940213

EUG Se: european patent has lapsed

Ref document number: 88901957.6

Effective date: 19940910

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19950810

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19950811

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19950828

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19950831

Year of fee payment: 8

Ref country code: CH

Payment date: 19950831

Year of fee payment: 8

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19960212

Ref country code: AT

Effective date: 19960212

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19960229

Ref country code: CH

Effective date: 19960229

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19960212

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19961031

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19961101

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050212