EP0155928A1 - Mechanical pulp hydrosulfite bleaching - Google Patents
Mechanical pulp hydrosulfite bleaching Download PDFInfo
- Publication number
- EP0155928A1 EP0155928A1 EP85890055A EP85890055A EP0155928A1 EP 0155928 A1 EP0155928 A1 EP 0155928A1 EP 85890055 A EP85890055 A EP 85890055A EP 85890055 A EP85890055 A EP 85890055A EP 0155928 A1 EP0155928 A1 EP 0155928A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pump
- pulp
- recited
- hydrosulfite
- further characterized
- 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.)
- Granted
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Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
- D21D5/26—De-aeration of paper stock
-
- 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
- D21C9/1089—Bleaching ; Apparatus therefor with reducing compounds with dithionites
Definitions
- hydrosulfite such as sodium hydrosulfite or zinc hydrosulfite.
- hydrosulfite bleaching can achieve the desired decoloration of the mechanical pulp, there are a number of drawbacks associated with its use. Hydrosulfite is oxidized extremely rapidly by air, therefore the entrainment of air in the pulp can negate the bleaching effects of the hydrosulfite. This makes hydrosulfite impractical for use with mechanical pulps having a consistency of much greater than 4 percent since as the consistency rises the pulp tends to entrain air.
- it is desirable to effect bleaching at the same consistency as for other processing of the pulp e.g. 5-25 percent, preferably 8-15 percent), although successive diluting and thickening stages are to be avoided because of the equipment costs and energy expense associated therewith.
- a method of treating mechanical pulp that allows reductive bleaching of the pulp in an effective manner at pulp consistencies of about 5-25 percent, and preferably 8-15 percent, during the entire treating procedure.
- the method comprises, or consists essentially of, the following sequential steps:
- the mixer may be eliminated, and the hydrosulfite added directly to the fluidizing pump.
- the chemical may be added to the discharge, or the suction, of the pump.
- the method according to the present invention is applicable to mechanical pulps. That term, as commonly used in the industry and as used in the instant specification and claims, encompasses refiner mechanical pulps (RMP), chemimechanical pulps (CMP), thermomechanical pulps (TMP), chemithermomechanical pulps (CTMP), and stone groundwood pulps.
- RMP refiner mechanical pulps
- CMP chemimechanical pulps
- TMP thermomechanical pulps
- CMP chemithermomechanical pulps
- stone groundwood pulps stone groundwood pulps.
- the mechanical pulp is produced utilizing any desired conventional technique, and then is fed by line 11 to a storage tower 12 or the like. According to the present invention it is preferable to mount a fluidizing centrifugal pump 13 at the bottom of the storage tower 12, to draw the mechanical pulp downwardly therefrom.
- the pulp typically has a consistency of about 5-25 percent, and a consistency of 8-15 percent is preferred.
- the fluidizing centrifugal pump 13, and an apparatus and method for controlling the head therefrom, are illustrated and described in Applicant's United States Patent No. 4,435,193 issued March 6, 1984.
- the pump 13, as illustrated in Figure 2 may comprise an inlet channel 14, a rotor 15 including a plurality of axially extending blades 16 having an interior opening 17 therebetween, and impeller blades 18.
- the blades 18 rotate in a spiral housing section 19, and gas can pass through openings 21, 22 from the housing section 19 to a gas chamber 20, the gas chamber 20 being connected up to a gas discharge line 23.
- Pulp passes from the pump 13 into the discharge line 25, with a throttling valve 26 disposed therein.
- the head of the pump 13 is controlled, by adjusting the throttling valve 26 in a manner explained in the aforementioned U.S. Patent No. 4,435,193, so that a variety of heads within a wide range may be achieved.
- the valve 26 preferably is controlled, according to the present invention, so that the pump head is maximized, to thereby maximize the degassing action of the pump (i.e. maximizing the amount of air withdrawn through conduit23).
- the pulp is immediately passed to a mixer 28.
- the pulp must be passed to the mixer 28 so that substantially no air . introduction occurs, and the mixer 28 must effect mixing without air introduction.
- hydrosulfite bleaching chemical is added from line 29 to the mixer, and is thoroughly mixed with the pulp.
- the mixer 28 preferably comprises a fluidizing mixer such as shown in U.S. Patents 4,093,506 and 4,339,206,
- hydrosulfite bleaching chemical added to provide an effective charge will vary depending upon the properties of the mechanical pulp, the amount of bleaching desired, etc. Typically, however, the sodium hydrosulfite or zinc hydrosulfite would be added so that the total charge was about 0.5-1.5 percent. Buffering, sequestering, and/or chelating agents, such as sodium tripolyphophate and sodium diethylenetriaminepetaacetate, are also preferably added with the hydrosulfite.
- the pulp After mixing of the hydrosulfite bleaching chemical into the pulp using mixer 28, the pulp, still at the same consistency (i.e. 5-25 percent), is retained at predetermined pH and temperature conditions for a predetermined period of time to effect the desired bleaching.
- This retention may be merely in conduits passing the pulp onto a further processing station, or may be in a vessel particularly designed for that purpose, such as a conventional up-flow bleaching tower 31.
- Typical, although not limiting, conditions are: pH, about 4.5-6.5; temperature, about 35-80 C; retention time, about 0.25-2 hours.
- the bleaching action can be effectively controlled, and the desired amount of bleaching chemical can be added to effect the desired bleaching.
- the degassing action is accomplished, according to the present invention, in a simple and effective manner, and with a minimum amount of equipment.
- the pulp at a consistency of between 5-25 percent, and preferably 8-15 percent, is withdrawn from storage tower 12, simultaneously pumped and degassed by fluidizing centrifugal pump 13, the head of which is controlled by valve 26 to maximize degassing action, immediately passed to fluidizing mixer 28 at which the hydrosulfite bleaching chemical is added via line 29, and subsequently passed to a conventional retention tower 31, or the like, where it is retained at predetermined pH and temperature conditions for a predetermined period of time to effect desired bleaching.
- the hydrosulfite bleaching chemical is added through line 33 directly to the discharge of the pump 13.
- the pulp has been effectively degassed, and when the bleaching chemical is added through a nozzle, or like other introduction structure, due to the turbulence of the pulp at that point, it will become intermixed with the pulp, and effective bleaching will occur.
- the pump 13 is shown with the axis of rotation of the rotor thereof horizontal. This merely illustrates that the present invention may be practiced irrespective of the orientation (e.g., horizontal or vertical) of the pump rotor.
- the hydrosulfite bleaching chemical is added via line 35 at the suction of the pump 13. Again, introduction can be accomplished utilizing a suitable nozzle, or the like. While the pulp is not completely degassed at this position, adding the bleaching chemical at the suction provides for complete intermixing of the bleaching chemical with the pulp as it is pumped by the pump 13, and the time from chemical addition at the suction side of the pump, to effective degassing by the pump, is short enough that under most circumstances entrained air will not significantly negate the bleaching effects of the hydrosulfite. However, if entrained air does negate such effects for a particular pulp, then the embodiments of FIGURES 1 and 3 will be utilized instead of the embodiment of FIGURE 4.
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
- Detergent Compositions (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Catalysts (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
Description
- With shortages in raw materials for manufacture of paper pulps, mechanical pulping processes have become of more interest. Mechanical pulping processes generally have higher yields than chemical pulping processes. However, since in mechanical pulping processes (including refiner mechanical pulping (RMP), chemimechanical pulping (CMP), thermomechanical pulping (TMP), and chemithermomechanical pulping (CTMP)), most of the lignin and polysaccharides are left in the pulp, rather than being dissolved and modified as in chemical pulping, bleaching must be accomplished by' decoloration, instead of by solubilization,' as in chemical pulping.
- One major process for bleaching of mechanical pulps is a reductive bleaching process utilizing hydrosulfite, such as sodium hydrosulfite or zinc hydrosulfite. While hydrosulfite bleaching can achieve the desired decoloration of the mechanical pulp, there are a number of drawbacks associated with its use. Hydrosulfite is oxidized extremely rapidly by air, therefore the entrainment of air in the pulp can negate the bleaching effects of the hydrosulfite. This makes hydrosulfite impractical for use with mechanical pulps having a consistency of much greater than 4 percent since as the consistency rises the pulp tends to entrain air. However, it is desirable to effect bleaching at the same consistency as for other processing of the pulp (e.g. 5-25 percent, preferably 8-15 percent), although successive diluting and thickening stages are to be avoided because of the equipment costs and energy expense associated therewith.
- According to the present invention, a method of treating mechanical pulp is provided that allows reductive bleaching of the pulp in an effective manner at pulp consistencies of about 5-25 percent, and preferably 8-15 percent, during the entire treating procedure. According to one aspect of the present invention, the method comprises, or consists essentially of, the following sequential steps:
- (a) Simultaneous pumping and degassing the mechanical pulp. This is preferably accomplished utilizing a fluidizing centrifugal pump. (b) Immediately after after (a), mixing, substantially without air introduction, the mechanical pulp with an effective charge of hydrosulfite bleaching chemical. The mixing preferably is accomplished in a fluidizing mixer, and the hydrosulfite bleaching chemical includes sequestering, chelating, and buffering agents. A typical charge is 0.5-1.5 percent hydrosulfite. And (c) retaining the pulp at predetermined pH (e.g. about 4.5-6.5) and temperature (e.g. about 35-80°C) conditions for a predetermined period of time (e.g. about 0.25-2 hours) to effect the desired bleaching. By practicing the invention oxidation of the reductive bleaching agent is avoided, a minimal amount of equipment is utilized, and the processing can be done at the desired consistency range of 8-15 percent.
- Alternatively, the mixer may be eliminated, and the hydrosulfite added directly to the fluidizing pump. For instance, the chemical may be added to the discharge, or the suction, of the pump.
- It is the primary object of the present invention to provide a method for treating mechanical pulp to provide efficient reductive bleaching thereof. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.
-
- FIGURE 1 is a schematic view illustrating exemplary apparatus utilized in practicing the method according to the present invention;
- FIGURE 2 is a schematic detail cross- sectional view of the exemplary fluidizing centrifugal pump illustrated in FIGURE 1; and
- FIGURES 3 and 4 are schematic views of two different alternative embodiments of apparatus for practicing the method of the invention.
- The method according to the present invention is applicable to mechanical pulps. That term, as commonly used in the industry and as used in the instant specification and claims, encompasses refiner mechanical pulps (RMP), chemimechanical pulps (CMP), thermomechanical pulps (TMP), chemithermomechanical pulps (CTMP), and stone groundwood pulps.
- Typically, the mechanical pulp is produced utilizing any desired conventional technique, and then is fed by line 11 to a
storage tower 12 or the like. According to the present invention it is preferable to mount a fluidizingcentrifugal pump 13 at the bottom of thestorage tower 12, to draw the mechanical pulp downwardly therefrom. The pulp typically has a consistency of about 5-25 percent, and a consistency of 8-15 percent is preferred. - The fluidizing
centrifugal pump 13, and an apparatus and method for controlling the head therefrom, are illustrated and described in Applicant's United States Patent No. 4,435,193 issued March 6, 1984. Thepump 13, as illustrated in Figure 2, may comprise aninlet channel 14, arotor 15 including a plurality of axially extendingblades 16 having an interior opening 17 therebetween, andimpeller blades 18. Theblades 18 rotate in aspiral housing section 19, and gas can pass throughopenings housing section 19 to agas chamber 20, thegas chamber 20 being connected up to agas discharge line 23. - Pulp passes from the
pump 13 into thedischarge line 25, with athrottling valve 26 disposed therein. The head of thepump 13 is controlled, by adjusting thethrottling valve 26 in a manner explained in the aforementioned U.S. Patent No. 4,435,193, so that a variety of heads within a wide range may be achieved. Thevalve 26 preferably is controlled, according to the present invention, so that the pump head is maximized, to thereby maximize the degassing action of the pump (i.e. maximizing the amount of air withdrawn through conduit23). - After simultaneous pumping and degassing of the mechanical pulp in the
pump 13, the pulp is immediately passed to amixer 28. The pulp must be passed to themixer 28 so that substantially no air . introduction occurs, and themixer 28 must effect mixing without air introduction. At the mixer, hydrosulfite bleaching chemical is added from line 29 to the mixer, and is thoroughly mixed with the pulp. For the practice of the present invention, themixer 28 preferably comprises a fluidizing mixer such as shown in U.S. Patents 4,093,506 and 4,339,206, - The amount of hydrosulfite bleaching chemical added to provide an effective charge will vary depending upon the properties of the mechanical pulp, the amount of bleaching desired, etc. Typically, however, the sodium hydrosulfite or zinc hydrosulfite would be added so that the total charge was about 0.5-1.5 percent. Buffering, sequestering, and/or chelating agents, such as sodium tripolyphophate and sodium diethylenetriaminepetaacetate, are also preferably added with the hydrosulfite.
- After mixing of the hydrosulfite bleaching chemical into the
pulp using mixer 28, the pulp, still at the same consistency (i.e. 5-25 percent), is retained at predetermined pH and temperature conditions for a predetermined period of time to effect the desired bleaching. This retention may be merely in conduits passing the pulp onto a further processing station, or may be in a vessel particularly designed for that purpose, such as a conventional up-flow bleaching tower 31. Typical, although not limiting, conditions are: pH, about 4.5-6.5; temperature, about 35-80 C; retention time, about 0.25-2 hours. - Since the pulp is essentially completely degassed before mixing with the hydrosulfite bleaching chemical, the bleaching action can be effectively controlled, and the desired amount of bleaching chemical can be added to effect the desired bleaching. The degassing action is accomplished, according to the present invention, in a simple and effective manner, and with a minimum amount of equipment. The pulp, at a consistency of between 5-25 percent, and preferably 8-15 percent, is withdrawn from
storage tower 12, simultaneously pumped and degassed by fluidizingcentrifugal pump 13, the head of which is controlled byvalve 26 to maximize degassing action, immediately passed to fluidizingmixer 28 at which the hydrosulfite bleaching chemical is added via line 29, and subsequently passed to aconventional retention tower 31, or the like, where it is retained at predetermined pH and temperature conditions for a predetermined period of time to effect desired bleaching. - In the exemplary embodiments of the present invention illustrated schematically in FIGURES 3 and 4, the
mixer 28 is eliminated, and instead the hydrosulfite is added directly to the pulp within thepump 13. In the FIGURES 3 and 4 embodiments, the control mechanisms for thepump 13 have not been shown, for clarity of illustration. - In the FIGURE 3 embodiment, the hydrosulfite bleaching chemical is added through
line 33 directly to the discharge of thepump 13. At the discharge of thepump 13, the pulp has been effectively degassed, and when the bleaching chemical is added through a nozzle, or like other introduction structure, due to the turbulence of the pulp at that point, it will become intermixed with the pulp, and effective bleaching will occur. - In the embodiment illustrated in FIGURE 4, the
pump 13 is shown with the axis of rotation of the rotor thereof horizontal. This merely illustrates that the present invention may be practiced irrespective of the orientation (e.g., horizontal or vertical) of the pump rotor. - In the FIGURE 4 embodiment, the hydrosulfite bleaching chemical is added via
line 35 at the suction of thepump 13. Again, introduction can be accomplished utilizing a suitable nozzle, or the like. While the pulp is not completely degassed at this position, adding the bleaching chemical at the suction provides for complete intermixing of the bleaching chemical with the pulp as it is pumped by thepump 13, and the time from chemical addition at the suction side of the pump, to effective degassing by the pump, is short enough that under most circumstances entrained air will not significantly negate the bleaching effects of the hydrosulfite. However, if entrained air does negate such effects for a particular pulp, then the embodiments of FIGURES 1 and 3 will be utilized instead of the embodiment of FIGURE 4. - While the invention has been herein shown and described in what is presently conceived to be the most practical and preferred embodiment thereof, it will be apparent to those of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims so as to encompass all equivalent methods and procedures.
Claims (10)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT85890055T ATE38258T1 (en) | 1984-03-05 | 1985-03-04 | HYDROSULPHITE BLEACHING OF MECHANICAL PULP. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US58593884A | 1984-03-05 | 1984-03-05 | |
US585938 | 1984-03-05 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0155928A1 true EP0155928A1 (en) | 1985-09-25 |
EP0155928B1 EP0155928B1 (en) | 1988-10-26 |
Family
ID=24343611
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85890055A Expired EP0155928B1 (en) | 1984-03-05 | 1985-03-04 | Mechanical pulp hydrosulfite bleaching |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP0155928B1 (en) |
JP (1) | JPS60209088A (en) |
AT (1) | ATE38258T1 (en) |
BR (1) | BR8500938A (en) |
DE (1) | DE3565870D1 (en) |
FI (1) | FI77905C (en) |
NO (1) | NO164310C (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0330387A2 (en) * | 1988-02-26 | 1989-08-30 | A. Ahlstrom Corporation | Improved method and apparatus for processing pulp |
US5234480A (en) * | 1990-08-14 | 1993-08-10 | A. Ahlstrom Corporation | Method and apparatus for decreasing problems caused by residual or reaction gases or gases harmful to a process |
WO2000053844A1 (en) * | 1999-03-08 | 2000-09-14 | Holmen Aktiebolag | Method for manufacturing bleached mechanical and chemithermomechanical pulp |
EP1375735A1 (en) * | 2002-06-28 | 2004-01-02 | Rohm And Haas Company | Method for brightening pulp with hydrosulfite solution |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4877368A (en) * | 1988-11-08 | 1989-10-31 | A. Ahlstrom Corporation | Fluidizing centrifugal pump |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2071307A (en) * | 1936-08-11 | 1937-02-16 | Great Western Electro Chemical Co | Bleaching |
US2707146A (en) * | 1951-08-08 | 1955-04-26 | Scott Paper Co | Method of bleaching mechanically disintegrated wood pulp |
US2963395A (en) * | 1958-03-31 | 1960-12-06 | Crown Zellerbach Corp | Process of bleaching lignocellulosic pulps |
US3313678A (en) * | 1962-02-14 | 1967-04-11 | Svenska Cellulose Aktiebolaget | Bleaching of cellulose pulp in towers in completely filled and closed system |
US4030969A (en) * | 1972-06-13 | 1977-06-21 | Defibrator Ab | Method of dispersing a bleaching agent into a stream of fibrous cellulosic pulp material in a throttling nozzle |
US4093506A (en) * | 1975-03-14 | 1978-06-06 | Kamyr Aktiebolag | Method and apparatus for effecting even distribution and mixing of high consistency pulp and treatment fluid |
US4410337A (en) * | 1980-04-07 | 1983-10-18 | A. Ahlstrom Osakeyhtio | Method and an apparatus for separating a gas from a fibre suspension |
US4435193A (en) * | 1980-04-07 | 1984-03-06 | Kamyr Ab | Controlling operation of a centrifugal pump |
-
1985
- 1985-02-22 NO NO850720A patent/NO164310C/en unknown
- 1985-03-01 BR BR8500938A patent/BR8500938A/en not_active IP Right Cessation
- 1985-03-01 FI FI850854A patent/FI77905C/en not_active IP Right Cessation
- 1985-03-04 AT AT85890055T patent/ATE38258T1/en not_active IP Right Cessation
- 1985-03-04 EP EP85890055A patent/EP0155928B1/en not_active Expired
- 1985-03-04 DE DE8585890055T patent/DE3565870D1/en not_active Expired
- 1985-03-05 JP JP60042015A patent/JPS60209088A/en active Pending
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2071307A (en) * | 1936-08-11 | 1937-02-16 | Great Western Electro Chemical Co | Bleaching |
US2707146A (en) * | 1951-08-08 | 1955-04-26 | Scott Paper Co | Method of bleaching mechanically disintegrated wood pulp |
US2963395A (en) * | 1958-03-31 | 1960-12-06 | Crown Zellerbach Corp | Process of bleaching lignocellulosic pulps |
US3313678A (en) * | 1962-02-14 | 1967-04-11 | Svenska Cellulose Aktiebolaget | Bleaching of cellulose pulp in towers in completely filled and closed system |
US4030969A (en) * | 1972-06-13 | 1977-06-21 | Defibrator Ab | Method of dispersing a bleaching agent into a stream of fibrous cellulosic pulp material in a throttling nozzle |
US4093506A (en) * | 1975-03-14 | 1978-06-06 | Kamyr Aktiebolag | Method and apparatus for effecting even distribution and mixing of high consistency pulp and treatment fluid |
US4410337A (en) * | 1980-04-07 | 1983-10-18 | A. Ahlstrom Osakeyhtio | Method and an apparatus for separating a gas from a fibre suspension |
US4435193A (en) * | 1980-04-07 | 1984-03-06 | Kamyr Ab | Controlling operation of a centrifugal pump |
Non-Patent Citations (1)
Title |
---|
TAPPI, vol. 64, no. 9, September 1981, pages 113-116, Atlanta, Georgia, US; J. GULLICHSEN et al.: "Medium-consistency technology II. Storage dischargers and centrifugal pumps" * |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0330387A2 (en) * | 1988-02-26 | 1989-08-30 | A. Ahlstrom Corporation | Improved method and apparatus for processing pulp |
EP0330387A3 (en) * | 1988-02-26 | 1991-07-17 | A. Ahlstrom Corporation | Improved method and apparatus for processing pulp |
US5403442A (en) * | 1988-02-26 | 1995-04-04 | A. Ahlstrom A Corporation Of Finland | Method of deaerating and pumping a fiber suspension prior to washing |
US5234480A (en) * | 1990-08-14 | 1993-08-10 | A. Ahlstrom Corporation | Method and apparatus for decreasing problems caused by residual or reaction gases or gases harmful to a process |
WO2000053844A1 (en) * | 1999-03-08 | 2000-09-14 | Holmen Aktiebolag | Method for manufacturing bleached mechanical and chemithermomechanical pulp |
US7736463B1 (en) | 1999-03-08 | 2010-06-15 | Holmen Aktiebolag | Method for manufacturing bleached mechanical and chemithermomechanical pulp |
EP1375735A1 (en) * | 2002-06-28 | 2004-01-02 | Rohm And Haas Company | Method for brightening pulp with hydrosulfite solution |
US7029554B2 (en) | 2002-06-28 | 2006-04-18 | Rohm And Haas Company | Method for brightening pulp with hydrosulfite solution generated from borohydride and bisulfite |
Also Published As
Publication number | Publication date |
---|---|
NO850720L (en) | 1985-09-06 |
FI850854A0 (en) | 1985-03-01 |
JPS60209088A (en) | 1985-10-21 |
EP0155928B1 (en) | 1988-10-26 |
FI77905C (en) | 1989-05-10 |
FI77905B (en) | 1989-01-31 |
FI850854L (en) | 1985-09-06 |
ATE38258T1 (en) | 1988-11-15 |
NO164310B (en) | 1990-06-11 |
NO164310C (en) | 1990-09-19 |
BR8500938A (en) | 1985-10-22 |
DE3565870D1 (en) | 1988-12-01 |
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