CA1122358A - Process for the full bleaching of pulp - Google Patents
Process for the full bleaching of pulpInfo
- Publication number
- CA1122358A CA1122358A CA335,412A CA335412A CA1122358A CA 1122358 A CA1122358 A CA 1122358A CA 335412 A CA335412 A CA 335412A CA 1122358 A CA1122358 A CA 1122358A
- Authority
- CA
- Canada
- Prior art keywords
- stage
- pulp
- process according
- minutes
- temperature
- 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
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
- D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Detergent Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a multistage process for the full bleaching of pulp having at least three-stages in which the pulp, when required after a pre-treatment with at least one of magnesium salts and organic complexing agents, is treated with a per compound in a first stage, with chlorite in a second stage and bleached with a per compound in a third stage.
The present invention provides a multistage process for the full bleaching of pulp having at least three-stages in which the pulp, when required after a pre-treatment with at least one of magnesium salts and organic complexing agents, is treated with a per compound in a first stage, with chlorite in a second stage and bleached with a per compound in a third stage.
Description
11'~,~3S8 I'he present invention rela-tes to a multistage, process for the full bleaching of pulp having at least three-stages.
The bleaching of pulp with peroxides is disclosed in laid-open German Specifications Nos. 2,327,900 and 2,219,504. In the process according to the laid-open German Specification
The bleaching of pulp with peroxides is disclosed in laid-open German Specifications Nos. 2,327,900 and 2,219,504. In the process according to the laid-open German Specification
2,219,504 which comprises a stage sequence of P-D-P substantial corrosion problems may be encountered.
The present invention is a multistage process for the full bleaching of pulp having at least three-stages. In the process the pulp, if required after a pre-treatment with magnesium salts and/or organic complexing agents, is treated with a per compound in a first stage, with chlorite in a second stage and bleached with chlorite in a third stage. For difficultly bleach-able pulps or for attaining a desired degree of polymerization further known bleaching stages can be added. These bleaching stages are described in Ullmann's Enzyklopadie der technischen Chemie, third edition, volume 18, page 778 (1967). The process according to the invention can be carried out, for example, in bleaching devices such as those described in Ullmann's Enzyklo-padie der technischen Chemie, third edition, volume 18, page 755.
Washing with water can be carried out between the individual bleaching stages in a conventional manner. However, in a preferred embodiment the washing between the second and third stage can be dispensed with without disadvantage to the quality of the product.
The process according to the invention can be used for all the conventional pulp types. These pulps can be from any conifer or they can be hardwood-sulphite pulps, as for example, spruce-sulphite pulp or beechwood-sulphite pulp. The process according to the invention can be used with special advantage for the bleaching of spruce, paper and viscose sulphite pulp or of beechwood sulphite-viscose pulp. The process can also be used ~l~ZZ358 for the bleaching of any long- or short-fibered pulps such as those of poplar and birch.
The pre-treatment of the pulp may be carried out in aqueous solution at a pulp consistency of 2 -to 15% by weight, (relative to atro pulp), preferably from 3 to 5O by weight. The temperature may be between 5 and 80C, preferably between 5 and 20C. The time of pre--treatment may be between 5 and 10 minutes.
The concentration of magnesium salt may be from 0.005 to 0.6% by weight, preferably from 0.1 to 0.4% by weight (relative to atro pulp and MgSO4). MgSO4, MgC12, Mg(NO3)2, Mg EDTA (ethylene diamine tetraacetic acid) or magnesium salts of polyoxy-carboxylic acid are suitable as magnesium salts. These polyoxy-carboxylic acids are described, for example, in laid-open German Specifica-tions 1,904,940, 1,904,941 and 1,942,556.
The first bleaching stage may be carried out with a per compound at a pulp consistency of 5 to 10% by weight, preferably 8 to 12~ by weight (relative to atro pulp) in an aqueous solution.
An organic or inorganic peroxide, such as hydrogen peroxide, sodium peroxide or t-butyl hydro-peroxide, can be used as the per compound. In a preferred embodiment hydrogen peroxide is used.
In the first bleaching stage the temperature may be between 40 and 95C, preferably between 50 and 75C. The time of the first bleaching stage may be between 30 and 240 minutes, preferably between 60 and 180 minutes. The concentration of the per compound may be from 0.5 to 5~ by weight, preferably from 0.8 to 1.2% by weight (relative to atro pulp and 100~ of H2O2). The concentra-tion of alkali, preferably sodium hydroxide, may be 1.5 to 10%
by weight, preferably 2.0 to 4.0% by weight (relative to atro pulp and 100% of NaOH).
In the second stage an alkali chlorite, preferably sodium chlorite, can be used as chlorite in the aqueous solution.
The pulp consistency in the second stage may be 5 to 15o by weight preferably 8 to 12% by weight (relative to atro pulp). The temp-erature may be from 20 to 80C, preferably from 25 to 60C. The time of the second stage may be between 30 and 240 minu-tes, pre-ferably between 60 and 180 minutes. The concentration ~f the alkali chlorite may be from 0.05 to 1.0% by weight, preferably 0.1 to 0.3% by weight(relative to atro pulp and 100% of sodium chlorite). The pH value of the second stage may be 2.5 to 5.0, preferably 3.0 to 4. The pH value can be adjusted by adding an organic acid, for example, formic acid or acetic acid or a mineral acid. In a preferred embodiment nitric acid (NHO3) is used.
The third stage can be carried out with a per compound in an aqueous solution at a pulp consistency of 5 to 15% by weight, preferably 8 to 12% by weight (relative to atro pulp). Inorganic or organic peroxides, as for example, hydrogen peroxide, sodium peroxide or t-butyl hydro-peroxide, can be used as the per com-pound, hydrogen peroxide being the preferred per compound. The temperature may be from 40 to 95C, preferably from 50 to 65C.
The time of the third bleaching stage may be from 30 to 240 min-utes, preferably from 60 to 120 minutes. The concentration of per compound, preferably hydrogen peroxide, may be from 0.2 to 2.0% by weight, preferably 0.4 to 0.8% by weight (relative to atro pulp and 100% of H2O2). The concentration of alkali can be from 0.5 to 3.0% by weight, preferably 0.8 to 1.2% by weight (relative to atro pulp and 100% of NaOH). Sodium hydroxide is preferably used as alkali.
The process according to the invention has the advantage that because of the combination and sequence of the bleaching ` stages per compound, chlorite and per compound and by operating the chlorite bleaching stage at a pH value between 3 and 5 the amount of chlorite used can be maintained so low that the amounts of chlorine getting into the waste water disposal system are insignificant. This means that the process according to the . . ~
~l~Z358 invention operates alr,lost chlorine--free.
The white conten-t of the final product as compa-ed with that of the final products of the conventional processes is improved. More over the yield can also be increased by 2 to
The present invention is a multistage process for the full bleaching of pulp having at least three-stages. In the process the pulp, if required after a pre-treatment with magnesium salts and/or organic complexing agents, is treated with a per compound in a first stage, with chlorite in a second stage and bleached with chlorite in a third stage. For difficultly bleach-able pulps or for attaining a desired degree of polymerization further known bleaching stages can be added. These bleaching stages are described in Ullmann's Enzyklopadie der technischen Chemie, third edition, volume 18, page 778 (1967). The process according to the invention can be carried out, for example, in bleaching devices such as those described in Ullmann's Enzyklo-padie der technischen Chemie, third edition, volume 18, page 755.
Washing with water can be carried out between the individual bleaching stages in a conventional manner. However, in a preferred embodiment the washing between the second and third stage can be dispensed with without disadvantage to the quality of the product.
The process according to the invention can be used for all the conventional pulp types. These pulps can be from any conifer or they can be hardwood-sulphite pulps, as for example, spruce-sulphite pulp or beechwood-sulphite pulp. The process according to the invention can be used with special advantage for the bleaching of spruce, paper and viscose sulphite pulp or of beechwood sulphite-viscose pulp. The process can also be used ~l~ZZ358 for the bleaching of any long- or short-fibered pulps such as those of poplar and birch.
The pre-treatment of the pulp may be carried out in aqueous solution at a pulp consistency of 2 -to 15% by weight, (relative to atro pulp), preferably from 3 to 5O by weight. The temperature may be between 5 and 80C, preferably between 5 and 20C. The time of pre--treatment may be between 5 and 10 minutes.
The concentration of magnesium salt may be from 0.005 to 0.6% by weight, preferably from 0.1 to 0.4% by weight (relative to atro pulp and MgSO4). MgSO4, MgC12, Mg(NO3)2, Mg EDTA (ethylene diamine tetraacetic acid) or magnesium salts of polyoxy-carboxylic acid are suitable as magnesium salts. These polyoxy-carboxylic acids are described, for example, in laid-open German Specifica-tions 1,904,940, 1,904,941 and 1,942,556.
The first bleaching stage may be carried out with a per compound at a pulp consistency of 5 to 10% by weight, preferably 8 to 12~ by weight (relative to atro pulp) in an aqueous solution.
An organic or inorganic peroxide, such as hydrogen peroxide, sodium peroxide or t-butyl hydro-peroxide, can be used as the per compound. In a preferred embodiment hydrogen peroxide is used.
In the first bleaching stage the temperature may be between 40 and 95C, preferably between 50 and 75C. The time of the first bleaching stage may be between 30 and 240 minutes, preferably between 60 and 180 minutes. The concentration of the per compound may be from 0.5 to 5~ by weight, preferably from 0.8 to 1.2% by weight (relative to atro pulp and 100~ of H2O2). The concentra-tion of alkali, preferably sodium hydroxide, may be 1.5 to 10%
by weight, preferably 2.0 to 4.0% by weight (relative to atro pulp and 100% of NaOH).
In the second stage an alkali chlorite, preferably sodium chlorite, can be used as chlorite in the aqueous solution.
The pulp consistency in the second stage may be 5 to 15o by weight preferably 8 to 12% by weight (relative to atro pulp). The temp-erature may be from 20 to 80C, preferably from 25 to 60C. The time of the second stage may be between 30 and 240 minu-tes, pre-ferably between 60 and 180 minutes. The concentration ~f the alkali chlorite may be from 0.05 to 1.0% by weight, preferably 0.1 to 0.3% by weight(relative to atro pulp and 100% of sodium chlorite). The pH value of the second stage may be 2.5 to 5.0, preferably 3.0 to 4. The pH value can be adjusted by adding an organic acid, for example, formic acid or acetic acid or a mineral acid. In a preferred embodiment nitric acid (NHO3) is used.
The third stage can be carried out with a per compound in an aqueous solution at a pulp consistency of 5 to 15% by weight, preferably 8 to 12% by weight (relative to atro pulp). Inorganic or organic peroxides, as for example, hydrogen peroxide, sodium peroxide or t-butyl hydro-peroxide, can be used as the per com-pound, hydrogen peroxide being the preferred per compound. The temperature may be from 40 to 95C, preferably from 50 to 65C.
The time of the third bleaching stage may be from 30 to 240 min-utes, preferably from 60 to 120 minutes. The concentration of per compound, preferably hydrogen peroxide, may be from 0.2 to 2.0% by weight, preferably 0.4 to 0.8% by weight (relative to atro pulp and 100% of H2O2). The concentration of alkali can be from 0.5 to 3.0% by weight, preferably 0.8 to 1.2% by weight (relative to atro pulp and 100% of NaOH). Sodium hydroxide is preferably used as alkali.
The process according to the invention has the advantage that because of the combination and sequence of the bleaching ` stages per compound, chlorite and per compound and by operating the chlorite bleaching stage at a pH value between 3 and 5 the amount of chlorite used can be maintained so low that the amounts of chlorine getting into the waste water disposal system are insignificant. This means that the process according to the . . ~
~l~Z358 invention operates alr,lost chlorine--free.
The white conten-t of the final product as compa-ed with that of the final products of the conventional processes is improved. More over the yield can also be increased by 2 to
3%. Furthermore, the washing between the second and third l~leach-ing stage can be dispensed with, whereby an improved hcat cconomy is attained.
The temperature in the second stage can be reduced to 20C, whereby the corrosion problems are also substantially reduced; these problems can be encountered, for example, in the chlorine dioxide stage (D) in the process according to the German Patent No. 2,219,504.
The process according to the invention is illustrated and described in greater detail by means of the following Examples.
Example 1 Bleaching of a beechwood-sulphite-rayon pulp according to the prior art first stage = 2.2~ of C12 1 hour pulp consistency 3% 15C
washing second stage = 3.6% of NaOH 3 hours pulp consistency 10% 75C
washing third stage = 0.4% of active chlorine 4 hours pulp consistency 10% 40C
washing (Ca hypochlorite) Example 2 Bleaching of a beechwood-sulphite-rayon pulp according to the invention first stage = 1.0% of H2O2 3 hours pulp consistency 10% 75C
3% of NaOH
l~Z35~3 washing second stage = 0.15% of NaClO2 12 hours pulp consistency 10% 30C
0.4% of HNO3 no washing third stage = 0.4% of H2O2 2 hours pulp consistency 10% 65C
1.0% of NaOH
Results Example 1 Example 2 white content bleached (Elrepho) 92.0 94.6 yield % 93.3 96.6 ~-cellulose % 90.6 90.4 Rl9 % 94.2 93.8 viscosity (SKV) 178 214 For a beechwood-sulphite-rayon pulp the two examples show that better bleaching can be attained with the process according to the invention. The pulp yield, which is higher by 3.3%, is obtained with an almost unchanged content of ~-cellulose.
The Rl9 value, which has only slightly decreased, indicates that the gain in yield is largely maintained with the pulp alkaliza-tion and viscose production. The higher viscosity indicates that the process is extremely easy on the fibres.
In the known bleaching process according to Example 1 the total consumption of chlorine was 2.6%, relative to pulp, and in the bleaching operation according to the invention 0.06r.
Example 3 Bleaching of a spruce-sulphite pulp according to the prior art ~: first stage = 4% of C12 1 hour pulp consistency 3% 15C
washing I
35~
second stage = 3.5~ of NaOi~ 1 hour pulp consistency 10-~ 70C
washing third stage = 1.0% of active chlorine 3 hours : pulp consistency 10% 40C
washing fourth stage = 1.0 of active chlorine 3 hours pulp consistency 10% 40C
Example 4 Bleaching of a spruce-sulphite pulp for paper according to the invention first stage = 1.5% of H2O2 3.0% of NaOH 1 hour pulp consistency 10% 70C
washing second stage = 0.4~ of NaClO2 0.5% of HNO3 3 hours pulp consistency 10% 50C
no washing third stage = 1.0~ of H2O2 1.5% of NaOH 3 hours pulp consistency 10% 60C
` washing Results Example 3Example ~
(invention) white content (bleached) 90.3 90.7 yield ~ 92.5 93.1 At a slightly higher white content and a slightly better yield the chlorine content in the effluent is reduced by the pro-cess according to the invention from 6~o to O.16% relative to pulp applied.
llZZ35~, Example 5 Bleaching of a spruce-sulphite pulp according to the invention pre-treatment = 0.3% of MgSO4 10 minutes pulp consistency 5% 15C
concentrating to a pulp consistency of 10%
first stage = 1.3% of H2O2 3.0% of NaOH l hour pulp consistency 10% 70C
washing second stage = 0.4% of NaClO2 3 hours pulp consistency 10% 30C
third stage = 1% of H2O2 1.5% of NaOH 3 hours pulp consistency 10% 60C
The bleached pulp attained a white content of 91.0%.
By pre-treatment with MgSO4 the use of peroxide in the first stage could be reduced to 1.3% of H2O2.
,
The temperature in the second stage can be reduced to 20C, whereby the corrosion problems are also substantially reduced; these problems can be encountered, for example, in the chlorine dioxide stage (D) in the process according to the German Patent No. 2,219,504.
The process according to the invention is illustrated and described in greater detail by means of the following Examples.
Example 1 Bleaching of a beechwood-sulphite-rayon pulp according to the prior art first stage = 2.2~ of C12 1 hour pulp consistency 3% 15C
washing second stage = 3.6% of NaOH 3 hours pulp consistency 10% 75C
washing third stage = 0.4% of active chlorine 4 hours pulp consistency 10% 40C
washing (Ca hypochlorite) Example 2 Bleaching of a beechwood-sulphite-rayon pulp according to the invention first stage = 1.0% of H2O2 3 hours pulp consistency 10% 75C
3% of NaOH
l~Z35~3 washing second stage = 0.15% of NaClO2 12 hours pulp consistency 10% 30C
0.4% of HNO3 no washing third stage = 0.4% of H2O2 2 hours pulp consistency 10% 65C
1.0% of NaOH
Results Example 1 Example 2 white content bleached (Elrepho) 92.0 94.6 yield % 93.3 96.6 ~-cellulose % 90.6 90.4 Rl9 % 94.2 93.8 viscosity (SKV) 178 214 For a beechwood-sulphite-rayon pulp the two examples show that better bleaching can be attained with the process according to the invention. The pulp yield, which is higher by 3.3%, is obtained with an almost unchanged content of ~-cellulose.
The Rl9 value, which has only slightly decreased, indicates that the gain in yield is largely maintained with the pulp alkaliza-tion and viscose production. The higher viscosity indicates that the process is extremely easy on the fibres.
In the known bleaching process according to Example 1 the total consumption of chlorine was 2.6%, relative to pulp, and in the bleaching operation according to the invention 0.06r.
Example 3 Bleaching of a spruce-sulphite pulp according to the prior art ~: first stage = 4% of C12 1 hour pulp consistency 3% 15C
washing I
35~
second stage = 3.5~ of NaOi~ 1 hour pulp consistency 10-~ 70C
washing third stage = 1.0% of active chlorine 3 hours : pulp consistency 10% 40C
washing fourth stage = 1.0 of active chlorine 3 hours pulp consistency 10% 40C
Example 4 Bleaching of a spruce-sulphite pulp for paper according to the invention first stage = 1.5% of H2O2 3.0% of NaOH 1 hour pulp consistency 10% 70C
washing second stage = 0.4~ of NaClO2 0.5% of HNO3 3 hours pulp consistency 10% 50C
no washing third stage = 1.0~ of H2O2 1.5% of NaOH 3 hours pulp consistency 10% 60C
` washing Results Example 3Example ~
(invention) white content (bleached) 90.3 90.7 yield ~ 92.5 93.1 At a slightly higher white content and a slightly better yield the chlorine content in the effluent is reduced by the pro-cess according to the invention from 6~o to O.16% relative to pulp applied.
llZZ35~, Example 5 Bleaching of a spruce-sulphite pulp according to the invention pre-treatment = 0.3% of MgSO4 10 minutes pulp consistency 5% 15C
concentrating to a pulp consistency of 10%
first stage = 1.3% of H2O2 3.0% of NaOH l hour pulp consistency 10% 70C
washing second stage = 0.4% of NaClO2 3 hours pulp consistency 10% 30C
third stage = 1% of H2O2 1.5% of NaOH 3 hours pulp consistency 10% 60C
The bleached pulp attained a white content of 91.0%.
By pre-treatment with MgSO4 the use of peroxide in the first stage could be reduced to 1.3% of H2O2.
,
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A multistage process for the full bleaching of pulp having at least three-stages in which the pulp, when required after a pre-treatment with at least one of magnesium salts and organic complexing agents, is treated with a per compound in a first stage, with chlorite in a second stage and bleached with a per compound in a third stage.
2. A process according to claim 1, in which further conventional bleaching stages follow.
3. A process according to claim 1 in which washing with water is carried out between the bleaching stages.
4. A process according to the claim 1, 2 or 3 in which the pulp is passed from the second to the third stage with-out washing.
5. A process according to claim 1, 2 or 3 in which the pretreatment is carried out with a pulp consistency from 2-15% at a temperature from 5-80°C, for a time from 5-60 minutes, with an Mg salt corresponding to 0.05-0.6% Mg, and a complexing agent corresponding to 0.05-0.6% Mg.
6. A process according to claim 1, 2 or 3 in which the pretreatment is carried out with a pulp consistency from 3-5% at a temperature from 5-20°C, for a time from 5-60 minutes, with an Mg salt corresponding to 0.1 to 0.4% Mg, and a complexing agent corresponding to 0.1 to 0.3% Mg.
7. A process according to claim 1, 2 or 3 in which the first stage is effected using hydrogen peroxide as the per compound under the following conditions: pulp consistency from 5-20%, temperature from 40-95°C, time from 30-240 minutes, H2O2%
from 0.5-5%, and NaOH from 1.5-10%.
from 0.5-5%, and NaOH from 1.5-10%.
8. A process according to claim 1, 2 or 3 in which the first stage is effected using hydrogen peroxide as the per compound under the following conditions: pulp consistency from 8-12%, temperature from 50-75°C, time from 60-180 minutes, H2O2%
from 0.8 to 1.2%, and NaOH from 2.0 to 4Ø
from 0.8 to 1.2%, and NaOH from 2.0 to 4Ø
9. A process according to claim 1, 2 or 3 in which the second stage is effected with sodium chlorite as chlorite and under the following conditions: pulp consistency from 5-15%, temperature from 20-80°C, time from 30-240 minutes, sodium chlorite from 0.05-1.0, and initial pH from 2.5-5Ø
10. A process according to claim 1, 2 or 3 in which the second stage is effected with sodium chlorite as chlorite and under the following conditions: pulp consistency from 8-12%, temperature from 25 to 60°C, time from 60 to 180 minutes, sodium chlorite from 0.1 to 0.3, and initial pH from 3.5 to 4.
11. A process according to claim 1, 2 or 3 in which the third stage is effected with hydrogen peroxide as the per compound under the following conditions: pulp consistency from 5-15%, temperature from 40-95°C, time from 30-240 minutes, H2O2%
from 0.2-2.0%, and NaOH from 0.5-3.0%.
from 0.2-2.0%, and NaOH from 0.5-3.0%.
12. A process according to claim 1, 2 or 3 in which the third stage is effected with hydrogen peroxide as the per compound under the following conditions: pulp consistency from 8-12%, temperature from 50-65°C, time from 60 to 120 minutes, H2O2% from 0.4 to 0.8%, and NaOH from 0.8 to 1.2%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2841013A DE2841013C2 (en) | 1978-09-21 | 1978-09-21 | Process for full bleaching of pulp |
| DEP2841013.1 | 1978-09-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1122358A true CA1122358A (en) | 1982-04-27 |
Family
ID=6049994
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA335,412A Expired CA1122358A (en) | 1978-09-21 | 1979-09-11 | Process for the full bleaching of pulp |
Country Status (11)
| Country | Link |
|---|---|
| AT (1) | AT372426B (en) |
| BE (1) | BE878841A (en) |
| BR (1) | BR7905860A (en) |
| CA (1) | CA1122358A (en) |
| CH (1) | CH641515A5 (en) |
| DE (1) | DE2841013C2 (en) |
| FI (1) | FI68681C (en) |
| FR (1) | FR2436846A1 (en) |
| IT (1) | IT1119314B (en) |
| NO (1) | NO153342C (en) |
| SE (1) | SE445366B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991012366A1 (en) * | 1990-02-19 | 1991-08-22 | Amcor Limited | Bleaching of paper pulp |
| AU642971B2 (en) * | 1990-02-19 | 1993-11-04 | Paper Australia Pty Ltd | Bleaching of paper pulp |
| US5607546A (en) * | 1990-02-13 | 1997-03-04 | Molnlycke Ab | CTMP-process |
| US6398908B1 (en) | 1991-04-30 | 2002-06-04 | Eka Nobel Ab | Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound |
| US6458245B1 (en) | 1990-02-13 | 2002-10-01 | Sca Research Ab | CTMP-process |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3937932A1 (en) * | 1989-11-15 | 1991-05-16 | Holtzmann & Cie Ag E | Delignification and bleaching of pulp with alkali chlorite - by adding chlorite before acidification to produce nascent reagent, minimising pollution |
| SE500353C2 (en) * | 1992-10-26 | 1994-06-06 | Sca Wifsta Oestrand Ab | Peroxide bleaching of sulfate pulp with the addition of magnesium before bleaching |
| SE9203366L (en) * | 1992-11-11 | 1994-05-12 | Mo Och Domsjoe Ab | Process for delignification and / or bleaching of cellulose pulp |
| SE501325E (en) * | 1993-01-29 | 1999-09-20 | Kvaerner Pulping Tech | Process for chlorine-free bleaching of pulp, wherein the pulp is acidified with acetic acid in the treatment with complexing agents |
| SE502706E (en) * | 1994-04-05 | 1999-09-27 | Mo Och Domsjoe Ab | Preparation of bleached cellulose pulp by bleaching with chlorine dioxide and treatment of complexing agents in the same step |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE582239C (en) * | 1929-03-16 | 1933-09-14 | I G Farbenindustrie Akt Ges | Process for bleaching bast fibers, in particular linen and hemp, in the form of yarns and fabrics as well as in the form of raw fibers using superoxide and hypochlorite balls |
| FR1010501A (en) * | 1948-08-31 | 1952-06-12 | Papiers Abadie Sa Des | Cellulose pulp bleaching process |
| SE335053B (en) * | 1969-05-13 | 1971-05-10 | Mo Och Domsjoe Ab | |
| DE2219504C2 (en) * | 1972-04-21 | 1974-10-03 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler, 6000 Frankfurt | Multi-stage bleaching of cellulose with significantly reduced use of chlorine |
| DE2327900C3 (en) * | 1973-06-01 | 1985-02-07 | Degussa Ag, 6000 Frankfurt | Bleaching of cellulose with considerably reduced use of chlorine |
| DE2721402C2 (en) * | 1977-05-12 | 1984-04-12 | Degussa Ag, 6000 Frankfurt | Process for bleaching pulp |
-
1978
- 1978-09-21 DE DE2841013A patent/DE2841013C2/en not_active Expired
-
1979
- 1979-06-20 NO NO792067A patent/NO153342C/en unknown
- 1979-06-29 IT IT68380/79A patent/IT1119314B/en active
- 1979-07-04 FI FI792115A patent/FI68681C/en not_active IP Right Cessation
- 1979-07-10 FR FR7917876A patent/FR2436846A1/en active Granted
- 1979-09-11 CA CA335,412A patent/CA1122358A/en not_active Expired
- 1979-09-13 BR BR7905860A patent/BR7905860A/en unknown
- 1979-09-17 BE BE6/46946A patent/BE878841A/en not_active IP Right Cessation
- 1979-09-20 AT AT0620579A patent/AT372426B/en not_active IP Right Cessation
- 1979-09-20 CH CH849479A patent/CH641515A5/en not_active IP Right Cessation
- 1979-09-21 SE SE7907850A patent/SE445366B/en not_active IP Right Cessation
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5607546A (en) * | 1990-02-13 | 1997-03-04 | Molnlycke Ab | CTMP-process |
| US6458245B1 (en) | 1990-02-13 | 2002-10-01 | Sca Research Ab | CTMP-process |
| WO1991012366A1 (en) * | 1990-02-19 | 1991-08-22 | Amcor Limited | Bleaching of paper pulp |
| AU642971B2 (en) * | 1990-02-19 | 1993-11-04 | Paper Australia Pty Ltd | Bleaching of paper pulp |
| US6398908B1 (en) | 1991-04-30 | 2002-06-04 | Eka Nobel Ab | Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound |
Also Published As
| Publication number | Publication date |
|---|---|
| SE445366B (en) | 1986-06-16 |
| CH641515A5 (en) | 1984-02-29 |
| DE2841013C2 (en) | 1984-06-07 |
| AT372426B (en) | 1983-10-10 |
| FI68681B (en) | 1985-06-28 |
| ATA620579A (en) | 1983-02-15 |
| NO792067L (en) | 1980-03-24 |
| IT1119314B (en) | 1986-03-10 |
| SE7907850L (en) | 1980-03-22 |
| IT7968380A0 (en) | 1979-06-29 |
| FI792115A (en) | 1980-03-22 |
| DE2841013A1 (en) | 1980-04-03 |
| BR7905860A (en) | 1980-05-20 |
| FI68681C (en) | 1985-10-10 |
| FR2436846A1 (en) | 1980-04-18 |
| BE878841A (en) | 1980-03-17 |
| FR2436846B1 (en) | 1982-08-27 |
| NO153342C (en) | 1986-02-26 |
| NO153342B (en) | 1985-11-18 |
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