US3716448A - Single stage delignification and bleaching of chemical pulp with oxygen in the presence of a protector - Google Patents

Single stage delignification and bleaching of chemical pulp with oxygen in the presence of a protector Download PDF

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Publication number
US3716448A
US3716448A US00040429A US3716448DA US3716448A US 3716448 A US3716448 A US 3716448A US 00040429 A US00040429 A US 00040429A US 3716448D A US3716448D A US 3716448DA US 3716448 A US3716448 A US 3716448A
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United States
Prior art keywords
pulp
percent
protector
bleaching
reaction
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Expired - Lifetime
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US00040429A
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English (en)
Inventor
S Roymoulik
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International Paper Co
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International Paper Co
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Publication of US3716448A publication Critical patent/US3716448A/en
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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
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
    • D06M11/77—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with silicon or compounds thereof
    • D06M11/79—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with silicon or compounds thereof with silicon dioxide, silicic acids or their salts

Definitions

  • the commercial bleaching sequences used in modern-day pulp mills have anywhere from three to six stages. In these sequences chlorine, in one form or another, represents a major constituent. Some of the chlorine-containing compounds which are used are chlorine gas, chlorine dioxide and sodium hypochlorite. While these bleaching sequences are effective, they have certain disadvantages. A major disadvantage in the multiple-stage chlorine-containing bleaching sequences is the liberation of objectionable chlorine-containing effluent materials. Today, when intensive efforts are being made to abate pollution of our air and water, a chlorine-free bleaching sequence is most desirable. Another disadvantage is that when five or six stages are employed in a bleaching sequence, the cost of the chemicals necessarily becomes quite expensive. Another problem created by these chlorine-containing compounds is that they degrade the cellulosic portion of the pulp with consequent impairment and diminution in its physical properties.
  • Watanabe US. Pat. No. 3,251,730, discloses treating a substantially chlorine-free pulp in aqueous alkaline solution followed by treatment with oxygen under pressure at an elevated temperature.
  • the Watanabe patent discloses that by following his process the reduction in pulp viscosity is minimized. It has been found, however, that this oxygen-alkali sequence, like most of the other oxidative bleaching agents, is not specific.
  • the treatment not only attacks the chromophoric groups derived from the chemically modified lignin, but also the carbohydrate portion of the molecule, i.e., cellulose and hemicellulose, resulting in degradation of the pulp, as manifested by loss in the degree of polymerization. As a result, there is a loss in pulp strength, yield and viscosity.
  • protector compound selected from the group consisting of polysulfides having the formula Na S wherein x is an integer from I to 4 and Na S O
  • protector throughout this application shall mean either an oxidizing or a reducing agent which is capable of preventing the degradation and depolymerization of the cellulosic portion of the pulp by reacting with the carbonyl end groups to convert them into either hydroxyl groups, when a reducing agent is used, or carboxyl groups, when an oxidizing agent is used.
  • the process of the present invention be carried out at a temperature of from about C. to about 110C. and even more preferably at a temperature of from about C. to about 105C. and most preferably at C. It is preferred that the pressure during the reaction be maintained at from about 90 p.s.i. to about 1 10 p.s.i. and even more preferably at about 100 p.s.i. Naturally, however, the time of reaction, the temperature and pressure of reaction are all interdependent, as well as being dependent upon the nature of the pulp that is employed, the end use of the pulp, and the necessity for striking a compromise between the sought for delignification and the prevention of cellulose degradation.
  • sodium hydrosulfite When sodium hydrosulfite is used as the protector, since it is a reducing agent, it protects the carbonyl end groups of the cellulose against degradation by converting them to alcohol groups.
  • a sodium polysulfide When a sodium polysulfide is used as the protector, since it is an oxidizing agent, it stabilizes the cellulose against degradation by converting the carbonyl end groups to carboxyl groups.
  • Na S is the preferred polysulfide.
  • the concentration of either sodium hydrosulfite or sodium polysulfide should be at least about 0.2 percent, based upon the weight of the pulp. Preferably, however, the concentration should be from about 2 percent to about l0 percent.
  • the 10 percent figure represents an economical upper limit. Concentrations in excess of 10 percent can be used, but no additional benefits are obtained. 7
  • An important advantage of the process is that since the protectors contain only sodium and sulfur ions, both of which are used in conventional sulfite or sulfate pulping operations, the effluent from the process can be fed back into the chemical recovery system thereby preventing stream pollution which would otherwise occur if the effluent was emptied into the water as is conventionally practiced.
  • sodium hydroxidein concentrations of from about 1 percent to about 5 percent can be employed in the present process.
  • Sodium hydroxide can be used advantageously when pulps having high lignin contents, for example 5 percent or above, are employed, to speed up the rate of reaction, or when low concentrations of Na S Or, or Na S namely, 2 percent or less are employed.
  • concentration of the protector is 2 percent or above, it is unnecessary to use sodium hydroxide.
  • a process for delignifying and bleaching a chemical pulp while minimizing cellulose degradation which comprises:
  • a protector at a concentration of from about 0.2 percent to about 10 percent based on the weight of the pulp, said protector being selected from the group consisting of Na S O and Na S wherein x is an integer from 1 to 4.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
US00040429A 1970-05-25 1970-05-25 Single stage delignification and bleaching of chemical pulp with oxygen in the presence of a protector Expired - Lifetime US3716448A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US4042970A 1970-05-25 1970-05-25

Publications (1)

Publication Number Publication Date
US3716448A true US3716448A (en) 1973-02-13

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Family Applications (1)

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US00040429A Expired - Lifetime US3716448A (en) 1970-05-25 1970-05-25 Single stage delignification and bleaching of chemical pulp with oxygen in the presence of a protector

Country Status (7)

Country Link
US (1) US3716448A (enrdf_load_stackoverflow)
JP (1) JPS563477B1 (enrdf_load_stackoverflow)
CA (1) CA937357A (enrdf_load_stackoverflow)
DE (1) DE2122804A1 (enrdf_load_stackoverflow)
FI (1) FI56713C (enrdf_load_stackoverflow)
FR (1) FR2093716A5 (enrdf_load_stackoverflow)
SE (1) SE375566C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4338158A (en) * 1976-04-09 1982-07-06 Weyerhaeuser Company Pulping in the presence of a protector

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61161791U (enrdf_load_stackoverflow) * 1985-03-29 1986-10-07
SE8704041L (sv) * 1987-10-16 1989-04-17 Sca Development Ab Saett vid blekning av cellulosamassa

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3384533A (en) * 1963-09-19 1968-05-21 Air Liquide Delignification and bleaching of chemical and semichemical cellulose pulps with oxygen and catalyst

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3384533A (en) * 1963-09-19 1968-05-21 Air Liquide Delignification and bleaching of chemical and semichemical cellulose pulps with oxygen and catalyst

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4338158A (en) * 1976-04-09 1982-07-06 Weyerhaeuser Company Pulping in the presence of a protector

Also Published As

Publication number Publication date
SE375566B (enrdf_load_stackoverflow) 1975-04-21
FI56713C (fi) 1981-11-09
FI56713B (fi) 1979-11-30
CA937357A (en) 1973-11-27
FR2093716A5 (enrdf_load_stackoverflow) 1972-01-28
DE2122804A1 (de) 1971-12-02
SE375566C (sv) 1984-07-16
JPS563477B1 (enrdf_load_stackoverflow) 1981-01-24

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