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

• the present invention relates to the treatment of chemical paper pulps with hydrogen peroxide with a view to their bleaching.
• the lignin level of the pulp translated by the profession into a KAPPA index, practically determines the overall quantity of chemical bleach to be used.
• Pretreatment mid acid as described for example in Japanese Patent Application No. 76.102103 and the French patent application published under the e No. 2,520,397 reduces this value to 15-20 but raises difficulties previously reported due to effluents as a result of the alternation of steps in acid bath and in alkaline bath implied by the proposed technique.
• the treatment according to the present invention does not imply the drawbacks of the known methods and provides pasta whose KAPPA index can range. up to being less than 10 from chemical pulp of softwoods with a very high efficiency of the chemical agent used, hydrogen peroxide.
• the chemical pulp of softwood is subjected to the action of hydrogen peroxide at a temperature between 90 ° C and 100 ° C, in two stages, the first carried out at a pH between 8, 5 and 9.5, in the presence of at least one metal ion sequestering agent chosen from nitrogen sequestering agents and sequestering agents derived from polyphosphoric and poylphosphonic acids, in an amount equal to at least 3 g / l of bath, so as to consume an amount by weight of hydrogen peroxide of between 0.3% and 2.5% by weight of the dry paste, the second carried out at a pH at least equal to 11, in the presence of at least 3 ⁇ 10 -3 gram atom of magnesium in the form of magnesium hydroxide Mg (OH) z per hundred grams of dry paste to consume hydrogen peroxide during this second stage so that the total weight consumption of hydrogen peroxide during the two stages is between 2% and 5% of the weight of the dry dough.
• the first carried out at a pH between 8, 5 and 9.5 in the presence of at least
• the nature of the chemical agent capable of reaching the pH values defined for the first step is not critical, the alkalizing chemical agent chosen, however, being neither oxidized nor reduced by hydrogen peroxide.
• Sodium hydroxide and sodium carbonate meet the above definition, as also, and preferably, sodium tripolyphosphate, sodium salt of ethylenediaminetetraacetic acid and sodium salt of diethylenetriaminepentaacetic acid .
• the pH keeps during this first stage a value as constant as possible, which is achievable by known techniques, for example the use of buffers or the continuous or intermittent introduction of one or more chemical agents as defined above.
• sodium tripolyphosphate the sodium salt of ethylenediaminetetraacetic acid and the sodium salt of diethylenetriaminepentaacetic acid are preferably used.
• the duration of the first stage is generally less than 4 hours.
• alkaline agents which may be suitable for reaching the pH chosen in the second step, sodium hydroxide and sodium carbonate are particularly suitable.
• magnesium hydroxide can be introduced as it is or formed in the treatment bath from a magnesium salt such as chloride, nitrate or sulfate, the anion of which is inert vis- with respect to hydrogen peroxide.
• a magnesium salt such as chloride, nitrate or sulfate, the anion of which is inert vis- with respect to hydrogen peroxide.
• the duration of the second stage is generally between 2 and 5 hours.
• Consistency is not a critical factor for carrying out the two stages of treatment according to the invention. For practical and economic reasons it is always preferable that the consistency is between 3% and 5% and better between 5% and 15%.
• the quantity of hydrogen peroxide used is of course at least equal to the quantity to be consumed and is at most generally equal to 5% by weight of the weight of dry pulp, preferably 3 , About 5%.
• the dough can be separated in a customary manner of the liquor from the bath and subjected in a known manner to an alkaline extraction before the second stage of the treatment.
• This alkaline extraction generally carried out at a temperature of the order of 90 ° to 120 ° C, is preferably carried out in the majority of cases. However, it remains optional and may even advantageously not be carried out in particular when the conditions chosen to perform the first step are such that the hydrogen peroxide used in it is consumed almost entirely.
• the liquors of the baths of the two stages are separated from the dough, they can respectively be advantageously used to contribute to the constitution of each of these baths in their initial composition.
• the pulp treated according to the invention can be bleached according to usual methods, the economy and efficiency of which are improved.
• the conditions defined for carrying out the first step are those which make it possible to obtain, after the second step, chemical pulps with a KAPPA index most generally less than 15 when the chemical pulp to be treated is chemical pulp of softwoods, and a particularly advantageous overall saving in treatment which is reflected, for example, in the high efficiency of hydrogen peroxide.
• Ef This is designated in the following by the term Ef defined as being equal to: H 2 O 2 consumed being the overall quantity of hydrogen peroxide consumed in% by weight of the weight of dry pulp, A KAPPA the difference between the value of the KAPPA index of the untreated pulp and the value of the KAPPA index of the pulp treated according to the invention.
• the conditions are such that, as defined above, the pH in the first step is between 8.5 and 9.5, the pH in the second step as elsewhere in the comparative example is at least equal to 11.
• a chemical pulp of resinous wood with a KAPPA index equal to 28.5 is treated for 2 h at 90 ° C. at the consistency of 5% in the presence of 3.4% of hydrogen peroxide H 2 O 2 and of 41, 4% sodium tripolyphosphate TPP.
• the dough After alkaline extraction carried out for 1 hour at 90 ° C in the presence of 20% sodium hydroxide NaOH, the dough, with the consistency of 5%, is subjected to 90 ° C and for 2 hours, to the action of 2 , 7% H 2 O 2 in the presence of 3.2% NaOH and 0.5% magnesium hydroxide Mg (OH) 2 .
• Example 2 The same paste as in Example 1 is subjected, at 90 ° C and for 2 hours, to the action of 3.4% H 2 O 2 in the presence of 4% NaOH and 0.6% Mg ( OH) 2 , the consistency being 5%.
• a chemical pulp of resinous wood with a KAPPA index equal to 33 is treated at the consistency of 5%, at 90 ° and for 1 hour in the presence of 0.6% H 2 O 2 and 17.2% TPP.
• the paste is subjected in a second step to the action of 2.7% of H 2 O 2 in the presence of 4% of NaOH and of 0.25% of Mg (OH) z , at 90 ° C for 5 h.
• the KAPPA index of the treated pulp is 3 times lower than before treatment and Ef. is around 7.
• the KAPPA index of the treated pulp is 10.5 with an overall H 2 O 2 consumption of 2.0%. Ef. is then close to 9.0.
• the consumption of H 2 O 2 in the first stage is 0.3%, it is total in the second stage.
• Example 4 is repeated, but the pH in the first step is reached by means of ethylenediaminetetraacetic acid and sodium hydroxide and is maintained at 9.5 by addition of NaOH.
• Example 4 The results of Example 4 are practically found.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)
• Measuring Leads Or Probes (AREA)
• Ultra Sonic Daignosis Equipment (AREA)
• Stereophonic System (AREA)
• Treatment Of Fiber Materials (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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ID=9319780

Family Applications (1)

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• 1985
  • 1985-05-29 FR FR8508291A patent/FR2582692B1/fr not_active Expired
• 1986
  • 1986-04-07 US US06/849,157 patent/US4734161A/en not_active Expired - Fee Related
  • 1986-05-05 CA CA000508344A patent/CA1273756A/fr not_active Expired - Lifetime
  • 1986-05-27 AT AT86420138T patent/ATE32534T1/de not_active IP Right Cessation
  • 1986-05-27 AU AU57944/86A patent/AU5794486A/en not_active Abandoned
  • 1986-05-27 DE DE8686420138T patent/DE3660024D1/de not_active Expired
  • 1986-05-27 EP EP86420138A patent/EP0208625B1/fr not_active Expired
  • 1986-05-28 ES ES555395A patent/ES8802336A1/es not_active Expired
  • 1986-05-28 FI FI862257A patent/FI83239C/fi not_active IP Right Cessation
  • 1986-05-29 JP JP61124600A patent/JPS61275491A/ja active Granted

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