CA1080406A - Bleach hydrolysis of pulp with substantially reduced use of chlorine - Google Patents
Bleach hydrolysis of pulp with substantially reduced use of chlorineInfo
- Publication number
- CA1080406A CA1080406A CA245,088A CA245088A CA1080406A CA 1080406 A CA1080406 A CA 1080406A CA 245088 A CA245088 A CA 245088A CA 1080406 A CA1080406 A CA 1080406A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- peroxide
- stage
- bleaching
- hydrolysis
- 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
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides in a multistage process for fully bleaching a pulp using a minimum of chlorine, the improvement in which the first stage comprises an alkaline peroxide bleach hydrolysis in which stage the pulp is bleached with a content of alkali of 0.5 to 3% by weight, calculated as a 100% substance and relative to absolutely dry pulp, and at a temperature of the bleaching liquor of at least 65°C.
The present invention provides in a multistage process for fully bleaching a pulp using a minimum of chlorine, the improvement in which the first stage comprises an alkaline peroxide bleach hydrolysis in which stage the pulp is bleached with a content of alkali of 0.5 to 3% by weight, calculated as a 100% substance and relative to absolutely dry pulp, and at a temperature of the bleaching liquor of at least 65°C.
Description
:~8~
The present invention rela~es to the multistage bleaching o~ pulp.
Copending application No. 201,323 filed May 31, 1974 (Canadian Patent No. 1,055,656, issued June 5, 1979) discloses a multistage process for fully bleaching pulps, i.e., a process which can be carried out with substantially smaller amounts of chlorine than those used heretofore in the technical apparatus for a pulp-bleaching plant. In this process pulps can be fully bleached in several stages without the use of pressure when the bleaching se~uence, when required in combination wlth a slight partial chlorination, is initiated with a strongly alkaline peroxide bleach hydrolysis. This strongly alkaline peroxide bleaching stage (P), which simultaneously acts as a hydrolysis, replaces the conventional acid chlorination with subsequent extraction stage~
Thus, the copending application describes and claims a multistage process for fully bleaching a pulp in which the pulp is bleached in a plurality of stages by treatment with chlorine containing compounds selected from hypochlorite and chlorine dioxide, and in which in a stage of said bleaching process, prior to said bleaching stages with said chlorine containing compounds, the pulp having a consistency not above 35% is hydroly~ed with an alkaline aqueous peroxide solution, the amount of peroxide in said hydrolysis stage being from 0.2 to 10% by weight computed for a 100% hydrogen peroxide and relative to absolutely dry pulp, the amount of alkali in said hydrolysis stage being from 2 to 15% by weight, computed for a 100% substance, relative to absolutely dry pulp, the hydrolysis being carried out at a temperature ranging from 20C to the boiling point of the bleaching liquor.
As in the known bleaching processes, the bleaching ;
effect depends on the kind of wood, i.e., conifers (soft wood) ~`
,.. ~ .
:L~8~ VlE;
or hard wood or annual plants, as well as on the manner in which the pulping process is carried out and thus on the degree of hydrolysis. The possible partial chlorination is necessary only when hard pulps, i.e., pulps rich in lignin and hemicellulose, are bleached to whiteness contents of 90~ of MgO. A partial chlorination can be carried out either prior to the start of the actual bleaching operation, i.e., prior to the strongly alkaline peroxide stage, or -the strongly alkaline peroxide stage is followed directly by a partial chlorination and extraction stage. Approximately one fifth of the amount of chlorine used heretofore and approximately one half of the amount of alkali used heretofore are required.
When the multistage bleaching process of copending application No. 201,323 was further developed it was surprising-ly found that by maintaining specific conditions of reaction a substantial additional amount of alkali can be saved in the peroxide stage.
~ ~ -la-.~, . .
The present invention relates to a multistage process for fully bleaching a pulp in which the bleaching sequences according to copending application No. 201,323 - if necessary, combined with a slight partial chIorination - starts with an alkaline peroxide hydrolysis, preferably without the use of pres-sure. This process is characterized in that the pulp is bleached in the peroxide stage with a content of alkali of 0.5 to 3% by weight, calculated as a 100% substance and relative to atro pulp (atro = absolutely dry), and at a temperature of the bleaching liquor ranging from at least 65C to the boiling point.
Temperatures ranging from 65 to 85C are preferably used. The amount of chlorine used in the chlorination stage is only a small fraction of the amounts used for the chlorination in the processes known heretofore. The peroxide stage is carried out with an excess of alkali. The partial chlorination can also be dispensed with if the usual oxidation bleaching stages which follow the hydrolysis bleaching, such as hypochlorite, chlorine dioxide or peroxide, are increased. Of course, this partial chlorination may be omitted altogether if whiteness contents above 90% of MgO are not required and whiteness contents between 85 and 90% of MgO are sufficient.
Bleaching with chlorine and extracting with alkali (C-E stage) dissolves out organic substances. Therefore oxygen-consuming substances and compounds having a high chlorine content are taken into the waste water of the pulp mill, whereupon the waste water cannot any longer be discharged into the main water-ways.
It is a known fact that bleaching waste waters containing chlorine or chloride ions cause intense corrosion in the re~ener-ative devices. The alkaline bleach hydrolysis of the presentinvention allows the e~aporation and concentration of the sub-stances dissolved out, their combustion and the regeneration of ~ .
, - ,: . ., . , . . , , !
~08~ 6 alkali in conventional apparatus. Moreover the alkaline treat-ment showed that 85 to 90% of the substances loading the waste waters are dissolved out in this stage and thus are not discharged into the main canal.
Inorganic or organic peroxides or hydroperoxides, pre-ferably hydrogen peroxide, sodium peroxide or t-butyl hydrogen peroxide or mixtures of these components in aqueous solutions are suitable as the per-compounds~ Hydrogen peroxide and sodium peroxide are particularly suitable. The amount of peroxide used may be from 0.2 to 10% by weight, preferably from 0.6 to 6% by weight, calculated as a 100% hydrogen peroxide and relative to absolutely dry pulp.
Sodium hydroxide or even calcium hydroxide or ammonium hydroxide (NH3 or NH40H) are preferably used as alkalis, i.e., alkali or alkaline earth hydroxides, required for the alkaline peroxidic bleach hydrolysis described hereinbefore. Said hydro-xides are used in amounts from 0.5 to 3% by weight, preferably 1 to 3% by weight, computed as a 100% substance and relative to absolutely dry pulp. -The alkaline-peroxidic bleach hydrolysis is carried out in a known manner at temperatures ranging from 65C to the bleach-ing liquor. It is of course possible to carry out the bleaching operation under pressure but the advantage obtained when using the per-compounds and the bleaching sequence mentioned hereinbefore lies particularly in the fact that the operation is carried out at atmospheric pressure, i.e., without the use of additional pre-ssure and apparatus.
As mentioned hereinbefore, the bleaching process may be carried out in existing bleacheries. The pulp consistencies preferably are between 10 and 20%. By pulp consistPncy is meant percent by weight of pulp in the pulp suspension. ~owever, it is also possible to carry out the alkaline peroxidic stage at higher V~
solids contents, i.e., up to 35~, using suitable technical aids, as for example, thick-pulp pumps, kneaders and high-pressure filters. The absence of sodium tetrasilicate, which is normally used in peroxidic bleaching stages, is a further advantage.
Conventional complexing agents or stabilizers, as for example, magnesium sulphate or organic N- or P-containing complex-ing agents, as for example, ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid and nitrolotriacetic acid can be used in the bleaching liquor. It is also possible to use N- and P-free complexing agents, as for example, polyoxy-carboxylic acids (German Patent Applications P 19 04 940.2, P 19 04 941.3 and P 19 42 556.0).
Additionally to the advance in the art of the process according to the copending application - namely that pulps, in-cluding hard pulps, can be fully bleached in existing bleaching apparatus of the pulp mills and that the waste waters in which substances loading the main waterways are dissolved out in the first stage so that said waste waters are non-corrosive, the process according to the invention results in a reduction in the amount of alkali required.
The present invention will be further illustrated by -way of the following Examples. In the Examples the percentages always are percent by weight, relative to unbleached dry pulp.
In all the tests tap water of 5 German hardness was used and the operations were carried out in enamelled containers. After each stage the pulp was washed with tap water and after the last stage it was acidified with SO2. The whiteness degrees (luminance factors) were determined according to German standard methods (Zellcheming Merkblatter) with the Elrepho whiteness degree meter ~filter R 46?.
Example 1 A spruce paper pulp (kappa number 22, whiteness un-bleached 51% of MgO) producea according to calcium bisulphite process is bleached in a five-stage bleaching process to a white-ness of more than 92% of ~gO:
1 stage partial chlorination with 4% pulp consistency 1 h 1.7% of C12 2nd stage 1.3% of H2O2 13% pulp consistency 75C 2 h
The present invention rela~es to the multistage bleaching o~ pulp.
Copending application No. 201,323 filed May 31, 1974 (Canadian Patent No. 1,055,656, issued June 5, 1979) discloses a multistage process for fully bleaching pulps, i.e., a process which can be carried out with substantially smaller amounts of chlorine than those used heretofore in the technical apparatus for a pulp-bleaching plant. In this process pulps can be fully bleached in several stages without the use of pressure when the bleaching se~uence, when required in combination wlth a slight partial chlorination, is initiated with a strongly alkaline peroxide bleach hydrolysis. This strongly alkaline peroxide bleaching stage (P), which simultaneously acts as a hydrolysis, replaces the conventional acid chlorination with subsequent extraction stage~
Thus, the copending application describes and claims a multistage process for fully bleaching a pulp in which the pulp is bleached in a plurality of stages by treatment with chlorine containing compounds selected from hypochlorite and chlorine dioxide, and in which in a stage of said bleaching process, prior to said bleaching stages with said chlorine containing compounds, the pulp having a consistency not above 35% is hydroly~ed with an alkaline aqueous peroxide solution, the amount of peroxide in said hydrolysis stage being from 0.2 to 10% by weight computed for a 100% hydrogen peroxide and relative to absolutely dry pulp, the amount of alkali in said hydrolysis stage being from 2 to 15% by weight, computed for a 100% substance, relative to absolutely dry pulp, the hydrolysis being carried out at a temperature ranging from 20C to the boiling point of the bleaching liquor.
As in the known bleaching processes, the bleaching ;
effect depends on the kind of wood, i.e., conifers (soft wood) ~`
,.. ~ .
:L~8~ VlE;
or hard wood or annual plants, as well as on the manner in which the pulping process is carried out and thus on the degree of hydrolysis. The possible partial chlorination is necessary only when hard pulps, i.e., pulps rich in lignin and hemicellulose, are bleached to whiteness contents of 90~ of MgO. A partial chlorination can be carried out either prior to the start of the actual bleaching operation, i.e., prior to the strongly alkaline peroxide stage, or -the strongly alkaline peroxide stage is followed directly by a partial chlorination and extraction stage. Approximately one fifth of the amount of chlorine used heretofore and approximately one half of the amount of alkali used heretofore are required.
When the multistage bleaching process of copending application No. 201,323 was further developed it was surprising-ly found that by maintaining specific conditions of reaction a substantial additional amount of alkali can be saved in the peroxide stage.
~ ~ -la-.~, . .
The present invention relates to a multistage process for fully bleaching a pulp in which the bleaching sequences according to copending application No. 201,323 - if necessary, combined with a slight partial chIorination - starts with an alkaline peroxide hydrolysis, preferably without the use of pres-sure. This process is characterized in that the pulp is bleached in the peroxide stage with a content of alkali of 0.5 to 3% by weight, calculated as a 100% substance and relative to atro pulp (atro = absolutely dry), and at a temperature of the bleaching liquor ranging from at least 65C to the boiling point.
Temperatures ranging from 65 to 85C are preferably used. The amount of chlorine used in the chlorination stage is only a small fraction of the amounts used for the chlorination in the processes known heretofore. The peroxide stage is carried out with an excess of alkali. The partial chlorination can also be dispensed with if the usual oxidation bleaching stages which follow the hydrolysis bleaching, such as hypochlorite, chlorine dioxide or peroxide, are increased. Of course, this partial chlorination may be omitted altogether if whiteness contents above 90% of MgO are not required and whiteness contents between 85 and 90% of MgO are sufficient.
Bleaching with chlorine and extracting with alkali (C-E stage) dissolves out organic substances. Therefore oxygen-consuming substances and compounds having a high chlorine content are taken into the waste water of the pulp mill, whereupon the waste water cannot any longer be discharged into the main water-ways.
It is a known fact that bleaching waste waters containing chlorine or chloride ions cause intense corrosion in the re~ener-ative devices. The alkaline bleach hydrolysis of the presentinvention allows the e~aporation and concentration of the sub-stances dissolved out, their combustion and the regeneration of ~ .
, - ,: . ., . , . . , , !
~08~ 6 alkali in conventional apparatus. Moreover the alkaline treat-ment showed that 85 to 90% of the substances loading the waste waters are dissolved out in this stage and thus are not discharged into the main canal.
Inorganic or organic peroxides or hydroperoxides, pre-ferably hydrogen peroxide, sodium peroxide or t-butyl hydrogen peroxide or mixtures of these components in aqueous solutions are suitable as the per-compounds~ Hydrogen peroxide and sodium peroxide are particularly suitable. The amount of peroxide used may be from 0.2 to 10% by weight, preferably from 0.6 to 6% by weight, calculated as a 100% hydrogen peroxide and relative to absolutely dry pulp.
Sodium hydroxide or even calcium hydroxide or ammonium hydroxide (NH3 or NH40H) are preferably used as alkalis, i.e., alkali or alkaline earth hydroxides, required for the alkaline peroxidic bleach hydrolysis described hereinbefore. Said hydro-xides are used in amounts from 0.5 to 3% by weight, preferably 1 to 3% by weight, computed as a 100% substance and relative to absolutely dry pulp. -The alkaline-peroxidic bleach hydrolysis is carried out in a known manner at temperatures ranging from 65C to the bleach-ing liquor. It is of course possible to carry out the bleaching operation under pressure but the advantage obtained when using the per-compounds and the bleaching sequence mentioned hereinbefore lies particularly in the fact that the operation is carried out at atmospheric pressure, i.e., without the use of additional pre-ssure and apparatus.
As mentioned hereinbefore, the bleaching process may be carried out in existing bleacheries. The pulp consistencies preferably are between 10 and 20%. By pulp consistPncy is meant percent by weight of pulp in the pulp suspension. ~owever, it is also possible to carry out the alkaline peroxidic stage at higher V~
solids contents, i.e., up to 35~, using suitable technical aids, as for example, thick-pulp pumps, kneaders and high-pressure filters. The absence of sodium tetrasilicate, which is normally used in peroxidic bleaching stages, is a further advantage.
Conventional complexing agents or stabilizers, as for example, magnesium sulphate or organic N- or P-containing complex-ing agents, as for example, ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid and nitrolotriacetic acid can be used in the bleaching liquor. It is also possible to use N- and P-free complexing agents, as for example, polyoxy-carboxylic acids (German Patent Applications P 19 04 940.2, P 19 04 941.3 and P 19 42 556.0).
Additionally to the advance in the art of the process according to the copending application - namely that pulps, in-cluding hard pulps, can be fully bleached in existing bleaching apparatus of the pulp mills and that the waste waters in which substances loading the main waterways are dissolved out in the first stage so that said waste waters are non-corrosive, the process according to the invention results in a reduction in the amount of alkali required.
The present invention will be further illustrated by -way of the following Examples. In the Examples the percentages always are percent by weight, relative to unbleached dry pulp.
In all the tests tap water of 5 German hardness was used and the operations were carried out in enamelled containers. After each stage the pulp was washed with tap water and after the last stage it was acidified with SO2. The whiteness degrees (luminance factors) were determined according to German standard methods (Zellcheming Merkblatter) with the Elrepho whiteness degree meter ~filter R 46?.
Example 1 A spruce paper pulp (kappa number 22, whiteness un-bleached 51% of MgO) producea according to calcium bisulphite process is bleached in a five-stage bleaching process to a white-ness of more than 92% of ~gO:
1 stage partial chlorination with 4% pulp consistency 1 h 1.7% of C12 2nd stage 1.3% of H2O2 13% pulp consistency 75C 2 h
2.8% of NaOH
3rd stage 0.6% of NaOCl 12% pulp consistency 54C 2 h 4th stage 0.30 of C1O2 14% pulp consistency 75C 1.5 h 5th stage 0.3% of NaOCl 12~ pulp consistency 50C 2 h 0.2% of NaOH
As this Example shows, even in hard spruce paper pulps the content of chlorine can be reduced substantially, i.e., from a conventional value of 5.5 to 6.5% of C12 to 1.7% of C12. The strength properties attained are of the order of those of pulps bleached according to the conventional method. Further the purity of the pulps was particularly high and the pulps had a lower con-tent of rind, bast and bark. More than 90% of the organic sub-stance in the waste water is from the first two bleaching sequen-ces and can thus be passed on for thickening and combustion.
Example 2 A beech-rayon pulp (kappa number 5.5 r whiteness degree unbleached 60.7% of MgO) produced according to the calcium bi-sulphite process was bleached in a three-stage sequence on an ' operational scale under the following conditions:
1st stage 1.2 - 1.5% of H2O2 12% pulp consistency 85C 1.5 h 2.6 - 3.0% of NaOH
2nd stage 0.3 of C1O2 14% pulp consistency 65C 4 h 3Q 3rd stage 0.2 - 0.8% of NaOCl 12% pulp consistency 55C 2 h ~, The scope of the process with respect to the amount of H2O2 and NaOCl added is evident from the technical procedure for 1~1 3al41~
~etermining the viscosity values for the rayon pulp. The white-ness content obtained is 95.8% of MgO. Corresponding to the characteristics of the alkaline-peroxidic bleach hydrolysis the content of hemicellulose decreases from 13% to 8O6%. The des-ire~ ~-cellulose content of 91 to 92~ is attained. The pulp has an excellent filter value and a smaller volume o~ gel part-icles. The rate of rise of li~uor level and the swell factor of the thick pulp were within the scope of the conventional values for beech pulps.
Example 3 `
`
~ beech paper pulp (kappa number 14, whiteness degree `~ -unbleached 53% of MgO) produced according to the calcium bisul-phite process was bleached on an operational scale in a four- -~
stage process to a final whiteness of 95 to 96% of MgO.
1st stage 1-1.6% of chlorine 4% pulp consistency 1 h 2nd stage 1.3 - 1.6% of H2O2 1.3 - 1.5% of NaOH 12% pulp consistency 65C 2 h ;
3rd stage 0.2% of ClO2 14% pulp consis-tency 70C 4 h 4th stage 0.1% of C1O2 12% pulp consistency 65C 2 h The strength properties of the beech-paper pulps bleach-ed according to this sequence were higher than the values obtained in conventional bleaching operations. This is due to -the fact that the hypochlorite stage was dispensed with. Moreover, a four-stage process naturally results in an economical advantage as compared with the conventional five-stage bleaching process.
3rd stage 0.6% of NaOCl 12% pulp consistency 54C 2 h 4th stage 0.30 of C1O2 14% pulp consistency 75C 1.5 h 5th stage 0.3% of NaOCl 12~ pulp consistency 50C 2 h 0.2% of NaOH
As this Example shows, even in hard spruce paper pulps the content of chlorine can be reduced substantially, i.e., from a conventional value of 5.5 to 6.5% of C12 to 1.7% of C12. The strength properties attained are of the order of those of pulps bleached according to the conventional method. Further the purity of the pulps was particularly high and the pulps had a lower con-tent of rind, bast and bark. More than 90% of the organic sub-stance in the waste water is from the first two bleaching sequen-ces and can thus be passed on for thickening and combustion.
Example 2 A beech-rayon pulp (kappa number 5.5 r whiteness degree unbleached 60.7% of MgO) produced according to the calcium bi-sulphite process was bleached in a three-stage sequence on an ' operational scale under the following conditions:
1st stage 1.2 - 1.5% of H2O2 12% pulp consistency 85C 1.5 h 2.6 - 3.0% of NaOH
2nd stage 0.3 of C1O2 14% pulp consistency 65C 4 h 3Q 3rd stage 0.2 - 0.8% of NaOCl 12% pulp consistency 55C 2 h ~, The scope of the process with respect to the amount of H2O2 and NaOCl added is evident from the technical procedure for 1~1 3al41~
~etermining the viscosity values for the rayon pulp. The white-ness content obtained is 95.8% of MgO. Corresponding to the characteristics of the alkaline-peroxidic bleach hydrolysis the content of hemicellulose decreases from 13% to 8O6%. The des-ire~ ~-cellulose content of 91 to 92~ is attained. The pulp has an excellent filter value and a smaller volume o~ gel part-icles. The rate of rise of li~uor level and the swell factor of the thick pulp were within the scope of the conventional values for beech pulps.
Example 3 `
`
~ beech paper pulp (kappa number 14, whiteness degree `~ -unbleached 53% of MgO) produced according to the calcium bisul-phite process was bleached on an operational scale in a four- -~
stage process to a final whiteness of 95 to 96% of MgO.
1st stage 1-1.6% of chlorine 4% pulp consistency 1 h 2nd stage 1.3 - 1.6% of H2O2 1.3 - 1.5% of NaOH 12% pulp consistency 65C 2 h ;
3rd stage 0.2% of ClO2 14% pulp consis-tency 70C 4 h 4th stage 0.1% of C1O2 12% pulp consistency 65C 2 h The strength properties of the beech-paper pulps bleach-ed according to this sequence were higher than the values obtained in conventional bleaching operations. This is due to -the fact that the hypochlorite stage was dispensed with. Moreover, a four-stage process naturally results in an economical advantage as compared with the conventional five-stage bleaching process.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a multistage process for fully bleaching a pulp in which the pulp is bleached in a plurality of stages by treatment with chlorine containing compounds selected from hydrochlorite and chlorine dioxide and in which in a stage of said bleaching process, prior to said bleaching stages with said chlorine containing compounds, the pulp having a consistency not above 35% is hydrolyzed with an alkaline aqeuous peroxide solution, the amount of peroxide in said hydrolysis stage being from 0.2 to 10% by weight computed for a 100% hydrogen peroxide and relative to absolutely dry pulp, the amount of alkali in said hydrolysis stage being from 2 to 15% by weight, computed for a 100% substance, relative to absolutely dry pulp, the hydrolysis being carried out at a temperature ranging from 20°C to the boiling point of the bleaching liquor, the improve-ment in which in the alkaline peroxide bleach hydrolysis stage the pulp is bleached with a content of alkali of 0.5 to 3% by weight, calculated as a 100% substance and relative to absolutely dry pulp, and at a temperature of the bleaching liquor of at least 65°C, whereby a minimum of chlorine containing compounds is used in said process.
2. A process as claimed in claim 1 in which the said stage is effected at atmospheric pressure.
3. A process as claimed in claim 1 in which the alkaline peroxide bleach hydrolysis is used in combination with a slight partial chlorination.
4. A process according to claim 1, 2 or 3 in which the bleaching in the said stage is carried out with alkali in amounts from 1 to 3% by weight, as a 100% substance and relative to absolutely dry pulp, and at temperatures from 65 to 35°C.
5. A process as claimed in claim 1, 2 or 3, in which the peroxide is sodium peroxide or hydrogen peroxide and the alkali is sodium, calcium or ammonium hydroxide.
6. A process as claimed in claim 1, 2 or 3, in which the peroxide is present in an amount from 0.2 to 10% by weight calculated as hydrogen peroxide and relative to absolutely dry pulp.
7. A process as claimed in claim 1, 2 or 3, in which the peroxide is present in an amount from 0.6 to 6% by weight calculated as hydrogen peroxide and relative to absolutely dry pulp.
8. A process as claimed in claim 1, 2 or 3, in which the pulp consistency is from 10 to 20%.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2538673A DE2538673C2 (en) | 1975-08-30 | 1975-08-30 | Bleaching of cellulose with considerably reduced use of chlorine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080406A true CA1080406A (en) | 1980-07-01 |
Family
ID=5955230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,088A Expired CA1080406A (en) | 1975-08-30 | 1976-02-05 | Bleach hydrolysis of pulp with substantially reduced use of chlorine |
Country Status (17)
| Country | Link |
|---|---|
| AR (1) | AR221678A1 (en) |
| AT (1) | AT340765B (en) |
| BE (1) | BE836462R (en) |
| BR (1) | BR7603006A (en) |
| CA (1) | CA1080406A (en) |
| CH (1) | CH620002A5 (en) |
| DE (1) | DE2538673C2 (en) |
| ES (1) | ES443318A1 (en) |
| FI (1) | FI62869C (en) |
| FR (1) | FR2322235A1 (en) |
| GB (1) | GB1544216A (en) |
| IT (1) | IT1055792B (en) |
| NL (1) | NL7513942A (en) |
| NO (1) | NO145344B (en) |
| SE (1) | SE7602842L (en) |
| YU (1) | YU37370B (en) |
| ZA (1) | ZA757822B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5143580A (en) * | 1990-04-23 | 1992-09-01 | Eka Nobel Ab | Process for reducing the amount of halogenated organic compounds in spent liquor from a peroxide-halogen bleaching sequence |
| US5149442A (en) * | 1990-04-23 | 1992-09-22 | Eka Nobel Ab | Reduction of halogenated organic compounds in spent bleach liquor |
| US5310458A (en) * | 1989-06-06 | 1994-05-10 | Eka Nobel Ab | Process for bleaching lignocellulose-containing pulps |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2416297A1 (en) * | 1978-01-31 | 1979-08-31 | Europeen Cellulose | Three-stage paper pulp bleaching - giving high whiteness level, by treating with chlorine, hypochlorite or peroxide oxidant and chlorine di:oxide |
| FR2432574A1 (en) * | 1978-08-01 | 1980-02-29 | Europeen Cellulose | PROCESS FOR BLEACHING PAPER PULP |
| FR2572431B1 (en) * | 1984-10-25 | 1987-12-04 | Centre Tech Ind Papier | PROCESS FOR THE PREPARATION OF CHEMICAL PAPER PULP FOR BLEACHING. |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE753531C (en) * | 1938-11-09 | 1953-05-18 | Degussa | Process for bleaching pulp |
| DE2327900C3 (en) * | 1973-06-01 | 1985-02-07 | Degussa Ag, 6000 Frankfurt | Bleaching of cellulose with considerably reduced use of chlorine |
-
1975
- 1975-08-30 DE DE2538673A patent/DE2538673C2/en not_active Expired
- 1975-11-12 AT AT861075A patent/AT340765B/en not_active IP Right Cessation
- 1975-11-25 FI FI753314A patent/FI62869C/en not_active IP Right Cessation
- 1975-11-28 NL NL7513942A patent/NL7513942A/en not_active Application Discontinuation
- 1975-11-28 YU YU3012/75A patent/YU37370B/en unknown
- 1975-12-03 NO NO754077A patent/NO145344B/en unknown
- 1975-12-09 ES ES443318A patent/ES443318A1/en not_active Expired
- 1975-12-09 BE BE6045289A patent/BE836462R/en not_active IP Right Cessation
- 1975-12-15 ZA ZA757822A patent/ZA757822B/en unknown
-
1976
- 1976-01-05 AR AR261846A patent/AR221678A1/en active
- 1976-01-14 IT IT67078/76A patent/IT1055792B/en active
- 1976-02-05 CA CA245,088A patent/CA1080406A/en not_active Expired
- 1976-02-25 FR FR7605307A patent/FR2322235A1/en active Granted
- 1976-02-27 SE SE7602842A patent/SE7602842L/en unknown
- 1976-04-22 GB GB16311/76A patent/GB1544216A/en not_active Expired
- 1976-05-13 BR BR7603006A patent/BR7603006A/en unknown
- 1976-08-26 CH CH1084076A patent/CH620002A5/en not_active IP Right Cessation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5310458A (en) * | 1989-06-06 | 1994-05-10 | Eka Nobel Ab | Process for bleaching lignocellulose-containing pulps |
| US5143580A (en) * | 1990-04-23 | 1992-09-01 | Eka Nobel Ab | Process for reducing the amount of halogenated organic compounds in spent liquor from a peroxide-halogen bleaching sequence |
| US5149442A (en) * | 1990-04-23 | 1992-09-22 | Eka Nobel Ab | Reduction of halogenated organic compounds in spent bleach liquor |
Also Published As
| Publication number | Publication date |
|---|---|
| NL7513942A (en) | 1977-03-02 |
| FI753314A (en) | 1977-03-01 |
| YU301275A (en) | 1983-04-27 |
| AR221678A1 (en) | 1981-03-13 |
| GB1544216A (en) | 1979-04-19 |
| BE836462R (en) | 1976-06-09 |
| BR7603006A (en) | 1977-05-31 |
| AT340765B (en) | 1978-01-10 |
| FI62869B (en) | 1982-11-30 |
| FR2322235B1 (en) | 1979-04-06 |
| FI62869C (en) | 1983-03-10 |
| SE7602842L (en) | 1977-03-01 |
| DE2538673C2 (en) | 1986-01-16 |
| DE2538673A1 (en) | 1977-03-03 |
| ZA757822B (en) | 1976-11-24 |
| ATA861075A (en) | 1977-04-15 |
| IT1055792B (en) | 1982-01-11 |
| NO145344B (en) | 1981-11-23 |
| NO754077L (en) | 1977-03-01 |
| FR2322235A1 (en) | 1977-03-25 |
| YU37370B (en) | 1984-08-31 |
| ES443318A1 (en) | 1977-05-01 |
| CH620002A5 (en) | 1980-10-31 |
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