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
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
• • 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
  • D21C9/1084—Bleaching ; Apparatus therefor with reducing compounds

Definitions

• the present invention is concerned with a single stage process for decreasing carbohydrate degradation of sulphite pulps during the O Mg0 process by the addition of a
• oxygen dehgnification technology uses sodium hydroxide as the alkaline source and the resulting effluent produced can therefore be incorporated into the chemical recovery system of the
• MgO magnesium hydroxide
• Mg OH magnesium hydroxide
• the temperature of delignification with MgO or Mg(OH) 2 must be about 30°C higher than for the same process using NaOH as the delignification agent (see Luo et al., supra).
• the temperature of delignification with MgO or Mg(OH) 2 must be about 30°C higher than for the same process using NaOH as the delignification agent (see Luo et al., supra).
• delignification rate can be increased in the O Mg0 process by the addition of a very limited amount of NaOH, since small concentrations of sodium salts can be tolerated in the recovery system of magnesium-based sulphite process.
• the risk of contamination in the long run is such that this alternative does not represent a desirable selection.
• pulp such as ozone delignified pulp
• pulp viscosity For example, it was
• a single stage bleaching process should be considered, wherein a reducing agent would be added in situ. This would represent a significant advance in pulp bleaching, and bring significant benefits to the industry, because the elimination of one
• the present invention comprises the conventional steps of oxygen delignification of pulp, namely treating a pulp slurry in a reactor under oxygen overpressure in the presence of an alkali
• alkali source examples include Ca(OH) 2 , NH 4 OH, NaOH and the like.
• Reducing agents include sodium
• the process comprises a first stage
• the single stage process is much preferred because of the elimination of washing and pressing operations required after treatment with the
• Figure 1 illustrates the strength properties of O Mg0 + R D 0 E op (DP) bleached pulp
• the two-stage process is also most advantageous for MgO delignification of
• the present invention comprises the use of a small amount of a reducing agent
• Preferred alkaU source are MgO, Mg(OH) 2 and the like.
• the key feature of the unexpected results obtained with the present single stage process is that the activity of the reducing agent is substantially not affected by the overpressure of oxygen in the reaction media.
• the reducing agent and the alkaU source may be added
• the reducing agent is added to the pulp shortly before the alkali source.
• conditions for carrying the present single stage process are as foUows: pH from 8 to 13; temperature of from 80 to 140 °C; an oxygen overpressure of from 30 to 200 psi; a pulp consistency of from 1% to 50%; an addition of from 0.01% to 10% of sodium borohydride,
• preferred conditions are: 127 °C; 1 0 psi O 2 pressure; 10% pulp consistency; an addition
• delignification stage are the same as those above.
• preferred conditions are as follows: 0.1% to 10% (by weight on pulp) of reducing agent is mixed with a pulp suspension at a pH of from 5 to 13 and maintained at a temperature of 20 to 100°C for a period of time of a few seconds up to 2 hours. The pulp is then washed
• the pulp are not as good as the single stage treated pulp, or two stage treated pulp wherein
• the pulp slurry is subsequently transferred to a Parr pressure reactor preheated at a
• O Mg0 D 0 E op (DP) bleached pulp are inferior to those of the O Mg0 + R D 0 E op (DP) bleached
• the eastern softwood sulphite pulp (kappa no. 26.0, pulp viscosity 40.1 mPa.s
• Example 1 determined on the chlorite delignified pulp
• the reactor preheated at a temperature of about 100°C.
• the 0 MgO delignification process is performed at a temperature of 127°C with an oxygen overpressure of about 100 psi for 2
• This example is provided to show the effect of sodium borohydride concentration on the pulp viscosity after the 0 MgO + R deUgnification process.
• An Eastern softwood sulphite pulp with a kappa no. of 25.2 and viscosity of 43.1 mPa-s determined on the chlorite deUgnified pulp is used.
• the sodium borohydride concentration varies from 0
• the required amount of NaBH 4 is rapidly mixed with a pulp slurry having a pulp consistency of 10% and containing about 2% MgO
• Example 1 The kappa number, viscosity and brightness of the 0 MgO + R delignified pulps
• Example 4 This example is provided to show that a two-stage RO Mg0 , i.e., treatment with
• Table 3 shows that the results obtained for a pulp treated under the RO Mg0
• This example is provided to show that a reduction with sodium borohydride in a second stage after the O ⁇ treatment of the pulp in a first stage, i.e., a O Mg0 R sequence,
• O Mg ⁇ R treated pulp is substantially lower than that of the single stage O Mg0 + R treated pulp according to the present invention.
• Example 3 The same Eastern softwood sulphite pulp as in Example 3 is used. 20 g ol pulp is subjected to a first stage O ⁇ process under the conditions of 10% pulp consistency, 2%
• deUgnification stage For obvious reasons, as mentioned above, a single stage process is most preferred.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (3)

Citations (4)

• 1998
  • 1998-01-19 CA CA002278188A patent/CA2278188C/en not_active Expired - Fee Related
  • 1998-01-19 AU AU55464/98A patent/AU5546498A/en not_active Abandoned
  • 1998-01-19 AT AT98900506T patent/ATE216741T1/de not_active IP Right Cessation
  • 1998-01-19 WO PCT/CA1998/000020 patent/WO1998031872A1/en active IP Right Grant
  • 1998-01-19 EP EP98900506A patent/EP0960235B1/de not_active Expired - Lifetime
  • 1998-01-19 DE DE69805056T patent/DE69805056T2/de not_active Expired - Fee Related

Patent Citations (4)

Non-Patent Citations (1)

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