CA2224677C - Peroxide bleaching of pulp - Google Patents
Peroxide bleaching of pulp Download PDFInfo
- Publication number
- CA2224677C CA2224677C CA002224677A CA2224677A CA2224677C CA 2224677 C CA2224677 C CA 2224677C CA 002224677 A CA002224677 A CA 002224677A CA 2224677 A CA2224677 A CA 2224677A CA 2224677 C CA2224677 C CA 2224677C
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- peroxide
- particle size
- added
- surface area
- 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 - Fee Related
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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
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Detergent Compositions (AREA)
- Cosmetics (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
A process for peroxide bleaching of pulp using magnesium oxide as sole alkaline source wherein said pulp is bleached in the presence of hydrogen peroxide for a maximum period of 180 minutes and achievement of a target ISO
brightness of 65 in regard to freshly prepared pulp characterised in that said magnesium oxide is utilised as MgO particles having a particle size of 5-500 microns and a particle surface area (PSA) of between 20-60 m2/g. By using such parameters, a peroxide bleaching process may be carried out most efficiently on a commercial scale.
brightness of 65 in regard to freshly prepared pulp characterised in that said magnesium oxide is utilised as MgO particles having a particle size of 5-500 microns and a particle surface area (PSA) of between 20-60 m2/g. By using such parameters, a peroxide bleaching process may be carried out most efficiently on a commercial scale.
Description
TITLE
"PEROXIDE BLEACHING OF PULP"
FIELD OF THE INVENTION
THIS INVENTION relates to a process for peroxide bleaching of pulp. Pulps which may be bleached in the process of the invention include lignocellulose pulp which may be produced mechanically and chemi-mechanically with yields in the region of greater than 75% which are otherwise known as high yield pulps.
BACKGROUND OF THE INVENTION
In a conventional peroxide bleaching process, sodium hydroxide is used as an alkali source. To achieve a desired brightness with maximum efficiency, auxiliary substances are also used. Such auxiliary substances include sodium silicate, magnesium sulphate and chelating agents inclusive of DTPA (sodium salt of diethylene triamino pentaacetic acid).
Reference may be made to a prior art article by Soteland et al., 1988, TAPPI Proceedings 231-236, which describes a peroxide bleaching process which utilises magnesium oxide as a sole alkaline source. The pulp was pretreated with DTPA and magnesium oxide particles were utilised in a size range of 1.00 mm - 0.25 mm or smaller. The magnesium oxide were also used in a concentration of 2-3% based on the dry weight of the pulp. The Mg0 used in the process was light-burnt Mg0 and finely crushed. It was found that brightness levels obtained were very close to that which was achieved by conventional bleaching using NaOH. In the bleaching process, the pulp was diluted to form a pulp suspension and the amount of Mg0 was added to the suspension under vigorous stirring. Hydrogen peroxide was subsequently added to the suspension at a concentration of 3% based on the weight of the pulp. This reference also made the observation that coarse particles are less effective as an alkaline source during peroxide bleaching.
Having regard to the abovementioned reference, an observation was also made in the corresponding patent specification DE3617942 that use of Mg0 as sole alkaline source considerably simplified the bleaching process since sodium hydroxide as alkaline source and auxiliary chemicals such as sodium silicate could be omitted.
Another advantage of using Mg0 as sole alkaline source was that only a small amount of waste is produced in the bleaching plant. Thus, for example, in integrated mills which produce magnesium sulphite pulp and peroxide bleached high-yield pulps, the used bleaching liquor is combusted and the Mg0 may be recovered for re-use.
However, the use of Mg0 as sole alkaline source in a peroxide bleaching process has not as yet achieved widespread commercial acceptance because although the principle of utilising 7 5 Mg0 as sole alkaline source was described in the Soteland et al.
references, the means of reducing the principle to practice on a commercial scale has not yet been fully elucidated.
SUMMARY OF THE INVENTION
Surprisingly, it has now been discovered that commercial usage of magnesium oxide as a sole alkaline source in peroxide bleaching of wood pulp may be achieved by employing Mg0 particles with a particle size of less than 500 micron and more preferably less than 75 micron and having particle surface area (PSA) of between 20 60 m2/g and more preferably between 30-50 m2/g. By using such parameters, an efficient peroxide bleaching process may be carried out most efficiently on a commercial scale which may be achieved within a maximum bleaching time of 180 minutes and achievement of a maximum target of ISO brightness of 65 in regard to freshly prepared pulp.
Utilizing Mg0 with parameters outside those stated above will result in a less efficient bleaching process leading to higher usage of chemicals and therefore higher operating costs.
"PEROXIDE BLEACHING OF PULP"
FIELD OF THE INVENTION
THIS INVENTION relates to a process for peroxide bleaching of pulp. Pulps which may be bleached in the process of the invention include lignocellulose pulp which may be produced mechanically and chemi-mechanically with yields in the region of greater than 75% which are otherwise known as high yield pulps.
BACKGROUND OF THE INVENTION
In a conventional peroxide bleaching process, sodium hydroxide is used as an alkali source. To achieve a desired brightness with maximum efficiency, auxiliary substances are also used. Such auxiliary substances include sodium silicate, magnesium sulphate and chelating agents inclusive of DTPA (sodium salt of diethylene triamino pentaacetic acid).
Reference may be made to a prior art article by Soteland et al., 1988, TAPPI Proceedings 231-236, which describes a peroxide bleaching process which utilises magnesium oxide as a sole alkaline source. The pulp was pretreated with DTPA and magnesium oxide particles were utilised in a size range of 1.00 mm - 0.25 mm or smaller. The magnesium oxide were also used in a concentration of 2-3% based on the dry weight of the pulp. The Mg0 used in the process was light-burnt Mg0 and finely crushed. It was found that brightness levels obtained were very close to that which was achieved by conventional bleaching using NaOH. In the bleaching process, the pulp was diluted to form a pulp suspension and the amount of Mg0 was added to the suspension under vigorous stirring. Hydrogen peroxide was subsequently added to the suspension at a concentration of 3% based on the weight of the pulp. This reference also made the observation that coarse particles are less effective as an alkaline source during peroxide bleaching.
Having regard to the abovementioned reference, an observation was also made in the corresponding patent specification DE3617942 that use of Mg0 as sole alkaline source considerably simplified the bleaching process since sodium hydroxide as alkaline source and auxiliary chemicals such as sodium silicate could be omitted.
Another advantage of using Mg0 as sole alkaline source was that only a small amount of waste is produced in the bleaching plant. Thus, for example, in integrated mills which produce magnesium sulphite pulp and peroxide bleached high-yield pulps, the used bleaching liquor is combusted and the Mg0 may be recovered for re-use.
However, the use of Mg0 as sole alkaline source in a peroxide bleaching process has not as yet achieved widespread commercial acceptance because although the principle of utilising 7 5 Mg0 as sole alkaline source was described in the Soteland et al.
references, the means of reducing the principle to practice on a commercial scale has not yet been fully elucidated.
SUMMARY OF THE INVENTION
Surprisingly, it has now been discovered that commercial usage of magnesium oxide as a sole alkaline source in peroxide bleaching of wood pulp may be achieved by employing Mg0 particles with a particle size of less than 500 micron and more preferably less than 75 micron and having particle surface area (PSA) of between 20 60 m2/g and more preferably between 30-50 m2/g. By using such parameters, an efficient peroxide bleaching process may be carried out most efficiently on a commercial scale which may be achieved within a maximum bleaching time of 180 minutes and achievement of a maximum target of ISO brightness of 65 in regard to freshly prepared pulp.
Utilizing Mg0 with parameters outside those stated above will result in a less efficient bleaching process leading to higher usage of chemicals and therefore higher operating costs.
'CT,~Ai) ~ 6 / 0 0 3 5 RECEIVED ~ ~ ~~R iJ~l - w The dosages of Mg0 that may be utilised in the process of the invention is 0.3-2% based on the weight of the pulp.
The amount of hydrogen peroxide that may be utilised in the process of the invention is from 1-5% based on the weight of the pulp.
To achieve maximum efficiency, the Mg0 particles are preferably added to the pulp in the form of a powder or slurry prepared in situ.
Preferably the Mg0 is added to the pulp simultaneously 1o with the peroxide or prior to the addition of the peroxide.
Chelating agents also may be used in the process of the invention and such chelating agents may comprise DTPA, EDTA or HEDTA (hydroxy-ethylene diamine tetracetic acid). Preferably the chelating agent is added to the pulp simultaneously with addition of Mg0 particles, as well as prior to addition of Mg0 particles.
Bleaching times of 60-180 minutes may also be utilised by the process of the invention to achieve a target ISO brightness of 55-65.
BRIEF DESCRIPTION OF DRAWINGS
2o In several preferred embodiments concerning the process of the invention which are discussed hereinafter in relation to Experiments 1 and 2:-FIG. 1 is a graph showin the effect of particle size on CCS (Cold Caustic Soda) pulp and more specifically showing particle size vs brightness at different times;
FIG. 2 refers to the results of Experiment 2 whereby various samples are plotted against final brightness;
FIG. 3 also refers to the result of Experiment 2 and shows the effect of surface area on CCS pulp and more specifically showing particle size vs brightness at different times; and FIG. 4 shows the results of FIG. 3 when plotted against time.
4MEiLf3EU ~f-IEE'f Wr~,IAtS~
The amount of hydrogen peroxide that may be utilised in the process of the invention is from 1-5% based on the weight of the pulp.
To achieve maximum efficiency, the Mg0 particles are preferably added to the pulp in the form of a powder or slurry prepared in situ.
Preferably the Mg0 is added to the pulp simultaneously 1o with the peroxide or prior to the addition of the peroxide.
Chelating agents also may be used in the process of the invention and such chelating agents may comprise DTPA, EDTA or HEDTA (hydroxy-ethylene diamine tetracetic acid). Preferably the chelating agent is added to the pulp simultaneously with addition of Mg0 particles, as well as prior to addition of Mg0 particles.
Bleaching times of 60-180 minutes may also be utilised by the process of the invention to achieve a target ISO brightness of 55-65.
BRIEF DESCRIPTION OF DRAWINGS
2o In several preferred embodiments concerning the process of the invention which are discussed hereinafter in relation to Experiments 1 and 2:-FIG. 1 is a graph showin the effect of particle size on CCS (Cold Caustic Soda) pulp and more specifically showing particle size vs brightness at different times;
FIG. 2 refers to the results of Experiment 2 whereby various samples are plotted against final brightness;
FIG. 3 also refers to the result of Experiment 2 and shows the effect of surface area on CCS pulp and more specifically showing particle size vs brightness at different times; and FIG. 4 shows the results of FIG. 3 when plotted against time.
4MEiLf3EU ~f-IEE'f Wr~,IAtS~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
EFFECT OF MGO PARTICLE SIZE ON THE BLEACHABILITY
OF CCS PULP
Introduction This work was performed to establish a relationship between Mg0 particle size and alkali performance in the bleaching of CCS (Cold Caustic Soda) wood pulp. Four grades of Mg0 were trialled, each one identified by its particle size distribution. Each sample of Mg0 had approximately the same surface area. Particle size and surface area for each of the samples is given in Table 1.
Summary of bleaching work CCS (chemi-mechanical pulp), pre-treated with DTPA to remove metal ions, was retrieved from the washers in the bleach plant at the Boyer mill. An equivalent mass of 20 grams OD of pulp was weighed out and placed in a plastic breaker. DTPA was then added as 0.15 % v/w on the pulp and mixed. Mg0 as 0.4% w/w, enough water to give a stock consistency of 12% and peroxide as 1.6% v/w on pulp was added and mixed for 2 minutes. The pulp was wrapped in plastic bags and placed into a constant temperature water bath at 65°C. A 3 gram OD sample was removed from the bath at intervals of 2, 3 and 4 hours. This was then made into a brightness hand sheet using the standard Boyer pulp mill method. These inrere dried overnight in a constant temperature/humidity room and tested for ISO
brightness. This procedure was repeated for all Mg0 samples as well as with control pulp containing no Mg0 (sample J) Results The results of this study indicate that particle size is a key parameter for achieving efficient peroxide bleaching of chemic-mechanical pulp. The results shown in Table 2 and FIG. 1 of this study indicate that an Mg0 particle size of < 75 N (samples G and F, d90 - 65 and 35 respectively) is required to achieve a target r : ~...,. F .. r .. . .
brightness for a given retention time of 2, 3 or 4 hours.
To achieve an equivalent brightness with samples C (d90 - 1500) or D (d90 = 3500), the chemical dosages of Mg0 and H202 ' would need to be increased.
EFFECT OF MGO PARTICLE SURFACE AREA ON THE
BLEACHABILITY OF CCS PULP
Introduction This work was performed to establish a relationship between Mg0 particle surface area and alkali performance in the bleaching of CCS (Cold Caustic Soda) wood pulp. Five grades of Mg0 were trialled, each one identifiable by its particle surface area. Each sample of Mg0 had approximately the same particle size. Particle size and surface area data for each of the samples is given in Table 3.
Summary of bleaching work CCS (chemi-mechanical) pulp, pre-treated with DTPA to remove metal ions, was retrieved from the washers in the bleach plant at the Boyer mill. For each sample, a mass of 10 g O.D. pulp was placed into a beaker and the approximate mass of chemicals added.
The pulp was mixed for 2 minutes in a bench top mixer. The pulp was then wrapped in plastic bags and placed into a constant temperature water bath at 65°C. After two hours retention, the samples were removed from the bath and divided into two. Half the sample was returned to the bath for a further hour of reaction while the other half was made into 5 gram brightness hand sheets. These were dried overnight and then tested for ISO brightness. The work was repeated with samples taken at 2, 3 and 4 hours.
Results In the previous study (Experiment 1 ), we determined that Mg0 particle size was important for peroxide bleaching efficiency. The results of this study indicate that particle surface area is also a key parameter for achieving maximum brightness for a given chemical dose. The results from these two independent studies (Tables 4 and 5, FIGS. 2 and 3) indicate that a surface area in the range 30-50 m2/g (samples B and C) is required to achieve maximum brightness for a given retention time and chemical dose. Surprisingly, when the surface area is either decreased or increased, the peroxide bleaching efficiency is reduced as indicated in FIGS. 2 and 3 by the bell shaped curves with brightness plateaus between samples B and C. To achieve an equivalent brightness to samples B and C with samples A, D or E, the chemical charges of H20 and Mg0 would need to be increased.
The results in FIG. 3, when plotted against time (FIG. 4), appear to indicate that a similar brightness will be achieved with four of the five samples when the bleaching time is extended indefinitely.
However, indefinite bleaching time is not a commercial reality and there is a clear benefit, based on these results, in employing Mg0 particles with a specific size and surface area. In fact, if Mg0 particles, with parameters outside those stated in this document are used, then the target brightness may not be achieved without increasing chemical dose rates.
TA-Sample Particle size d90 Surface area m2/g micron Sample Surface AreaBrightness m21 g 2 hr 3 hr 4 hr F < 40 61.39 62.17 62.88 G < 75 61.22 61.94 62.69 H < 2000 56.85 57.98 59.17 I < 5000 56.32 56.19 56.97 J 0 54.3 55.03 55.04 Sample Particle size d90 Surface area mzlg micron 0 15 (d90 = 70) gg Sample Surface AreaBrightness mzl 2 hr 3 hr A 1 58.5 59.1 B 35 60.2 60.5 C 43 60.1 60.6 g8 58.3 59.0 142 56.8 58.8 Sample Surface AreaBrightness mz/
2 hr 3 hr 4 hr 1 56.02 57.75 58.54 35 58.89 60.58 60.96 C 43 59.17 31.37 61.09 98 58.15 59.1 60.29 E 142 57.45 59.13 60.27 LEG-Bleaching conditions:
Mg0 % wlw on oven dry pulp = 0.4%
H202 - 1.6%
DTPA = 0.15 Temperature = 65C
Initial brightness 47.1 Bleaching conditions:
Mg0 % w/w on oven dry pulp = 0.3%
H2O2 = 1.8%
DTPA = 0.1 Temperature = 65C
Initial brightness 43.5 Bleaching conditions:
Mg0 % w/w on oven dry pulp = 0.4%
HZO2 = 1.6%
DTPA = 0.15 Temperature - 65 C
Initial brightness 47.1 FIG. 1 Effect of particle size pulp - Particle size vs brightness on CCS at different times.
F1G. 2 Sample number vs final final brightness.
FIG. 3 Effect of surface area on pulp - Surface area vs brightness CCS at different FIG. 4 Effect of surface area on CCS pulp - Time vs brightness for different surface areas
EFFECT OF MGO PARTICLE SIZE ON THE BLEACHABILITY
OF CCS PULP
Introduction This work was performed to establish a relationship between Mg0 particle size and alkali performance in the bleaching of CCS (Cold Caustic Soda) wood pulp. Four grades of Mg0 were trialled, each one identified by its particle size distribution. Each sample of Mg0 had approximately the same surface area. Particle size and surface area for each of the samples is given in Table 1.
Summary of bleaching work CCS (chemi-mechanical pulp), pre-treated with DTPA to remove metal ions, was retrieved from the washers in the bleach plant at the Boyer mill. An equivalent mass of 20 grams OD of pulp was weighed out and placed in a plastic breaker. DTPA was then added as 0.15 % v/w on the pulp and mixed. Mg0 as 0.4% w/w, enough water to give a stock consistency of 12% and peroxide as 1.6% v/w on pulp was added and mixed for 2 minutes. The pulp was wrapped in plastic bags and placed into a constant temperature water bath at 65°C. A 3 gram OD sample was removed from the bath at intervals of 2, 3 and 4 hours. This was then made into a brightness hand sheet using the standard Boyer pulp mill method. These inrere dried overnight in a constant temperature/humidity room and tested for ISO
brightness. This procedure was repeated for all Mg0 samples as well as with control pulp containing no Mg0 (sample J) Results The results of this study indicate that particle size is a key parameter for achieving efficient peroxide bleaching of chemic-mechanical pulp. The results shown in Table 2 and FIG. 1 of this study indicate that an Mg0 particle size of < 75 N (samples G and F, d90 - 65 and 35 respectively) is required to achieve a target r : ~...,. F .. r .. . .
brightness for a given retention time of 2, 3 or 4 hours.
To achieve an equivalent brightness with samples C (d90 - 1500) or D (d90 = 3500), the chemical dosages of Mg0 and H202 ' would need to be increased.
EFFECT OF MGO PARTICLE SURFACE AREA ON THE
BLEACHABILITY OF CCS PULP
Introduction This work was performed to establish a relationship between Mg0 particle surface area and alkali performance in the bleaching of CCS (Cold Caustic Soda) wood pulp. Five grades of Mg0 were trialled, each one identifiable by its particle surface area. Each sample of Mg0 had approximately the same particle size. Particle size and surface area data for each of the samples is given in Table 3.
Summary of bleaching work CCS (chemi-mechanical) pulp, pre-treated with DTPA to remove metal ions, was retrieved from the washers in the bleach plant at the Boyer mill. For each sample, a mass of 10 g O.D. pulp was placed into a beaker and the approximate mass of chemicals added.
The pulp was mixed for 2 minutes in a bench top mixer. The pulp was then wrapped in plastic bags and placed into a constant temperature water bath at 65°C. After two hours retention, the samples were removed from the bath and divided into two. Half the sample was returned to the bath for a further hour of reaction while the other half was made into 5 gram brightness hand sheets. These were dried overnight and then tested for ISO brightness. The work was repeated with samples taken at 2, 3 and 4 hours.
Results In the previous study (Experiment 1 ), we determined that Mg0 particle size was important for peroxide bleaching efficiency. The results of this study indicate that particle surface area is also a key parameter for achieving maximum brightness for a given chemical dose. The results from these two independent studies (Tables 4 and 5, FIGS. 2 and 3) indicate that a surface area in the range 30-50 m2/g (samples B and C) is required to achieve maximum brightness for a given retention time and chemical dose. Surprisingly, when the surface area is either decreased or increased, the peroxide bleaching efficiency is reduced as indicated in FIGS. 2 and 3 by the bell shaped curves with brightness plateaus between samples B and C. To achieve an equivalent brightness to samples B and C with samples A, D or E, the chemical charges of H20 and Mg0 would need to be increased.
The results in FIG. 3, when plotted against time (FIG. 4), appear to indicate that a similar brightness will be achieved with four of the five samples when the bleaching time is extended indefinitely.
However, indefinite bleaching time is not a commercial reality and there is a clear benefit, based on these results, in employing Mg0 particles with a specific size and surface area. In fact, if Mg0 particles, with parameters outside those stated in this document are used, then the target brightness may not be achieved without increasing chemical dose rates.
TA-Sample Particle size d90 Surface area m2/g micron Sample Surface AreaBrightness m21 g 2 hr 3 hr 4 hr F < 40 61.39 62.17 62.88 G < 75 61.22 61.94 62.69 H < 2000 56.85 57.98 59.17 I < 5000 56.32 56.19 56.97 J 0 54.3 55.03 55.04 Sample Particle size d90 Surface area mzlg micron 0 15 (d90 = 70) gg Sample Surface AreaBrightness mzl 2 hr 3 hr A 1 58.5 59.1 B 35 60.2 60.5 C 43 60.1 60.6 g8 58.3 59.0 142 56.8 58.8 Sample Surface AreaBrightness mz/
2 hr 3 hr 4 hr 1 56.02 57.75 58.54 35 58.89 60.58 60.96 C 43 59.17 31.37 61.09 98 58.15 59.1 60.29 E 142 57.45 59.13 60.27 LEG-Bleaching conditions:
Mg0 % wlw on oven dry pulp = 0.4%
H202 - 1.6%
DTPA = 0.15 Temperature = 65C
Initial brightness 47.1 Bleaching conditions:
Mg0 % w/w on oven dry pulp = 0.3%
H2O2 = 1.8%
DTPA = 0.1 Temperature = 65C
Initial brightness 43.5 Bleaching conditions:
Mg0 % w/w on oven dry pulp = 0.4%
HZO2 = 1.6%
DTPA = 0.15 Temperature - 65 C
Initial brightness 47.1 FIG. 1 Effect of particle size pulp - Particle size vs brightness on CCS at different times.
F1G. 2 Sample number vs final final brightness.
FIG. 3 Effect of surface area on pulp - Surface area vs brightness CCS at different FIG. 4 Effect of surface area on CCS pulp - Time vs brightness for different surface areas
Claims (11)
1. A process for peroxide bleaching of pulp using magnesium oxide as sole alkaline source wherein said pulp is bleached in the presence of hydrogen peroxide for a maximum period of 180 minutes and achievement of a maximum target ISO brightness of 65 in regard to freshly prepared pulp characterized in that said magnesium oxide is utilized as Mg0 particles having a particle size of 5-500 microns and a particle surface area (PSA) of between 20-60 m2/g.
2. A process as claimed in Claim 1 wherein said MgO
particles have a particle size of less than 75 microns.
particles have a particle size of less than 75 microns.
3. A process as claimed in Claim 1 wherein the MgO
particles have a particle size surface area of between 30-50 m2/g.
particles have a particle size surface area of between 30-50 m2/g.
4. A process as claimed in Claim 1 which utilizes a dosage of MgO which is 0.3-2% based on the weight of the pulp.
5. A process as claimed in Claim 1 wherein the amount of hydrogen peroxide utilized comprises 1-5% based on the weight of the pulp.
6. A process as claimed in Claim 1 wherein the MgO
particles are added to the pulp in the form of a powder or slurry prepared in situ.
particles are added to the pulp in the form of a powder or slurry prepared in situ.
7. A process as claimed in Claim 1 wherein the MgO
particles are added to the pulp simultaneously with the addition of peroxide.
particles are added to the pulp simultaneously with the addition of peroxide.
8. A process as claimed in Claim 1 wherein the MgO
particles are added to the pulp prior to the addition of peroxide.
particles are added to the pulp prior to the addition of peroxide.
9. A process as claimed in Claim 1 further comprising the step of adding to the pulp a chelating agent selected from DTPA, EDTA
or HEDTA.
or HEDTA.
10. A process as claimed in Claim 9 wherein the chelating agent is added to the pulp simultaneously with the addition of MgO
particles.
particles.
11. A process as claimed in Claim 9 wherein the chelating agent is added to the pulp prior to the addition of MgO particles.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPN3520A AUPN352095A0 (en) | 1995-06-13 | 1995-06-13 | Peroxide bleaching of pulp |
| AUPN3520 | 1995-06-13 | ||
| PCT/AU1996/000354 WO1996041917A1 (en) | 1995-06-13 | 1996-06-13 | Peroxide bleaching of pulp |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2224677A1 CA2224677A1 (en) | 1996-12-27 |
| CA2224677C true CA2224677C (en) | 2003-12-02 |
Family
ID=3787861
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002224677A Expired - Fee Related CA2224677C (en) | 1995-06-13 | 1996-06-13 | Peroxide bleaching of pulp |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0832323B1 (en) |
| KR (1) | KR19990022875A (en) |
| AT (1) | ATE197825T1 (en) |
| AU (1) | AUPN352095A0 (en) |
| CA (1) | CA2224677C (en) |
| DE (1) | DE69611091D1 (en) |
| WO (1) | WO1996041917A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7052578B2 (en) * | 2000-01-28 | 2006-05-30 | Martin Marietta Magnesia Specialties, Inc. | Process employing magnesium hydroxide in peroxide bleaching of mechanical pulp |
| US6743332B2 (en) | 2001-05-16 | 2004-06-01 | Weyerhaeuser Company | High temperature peroxide bleaching of mechanical pulps |
| US6881299B2 (en) | 2001-05-16 | 2005-04-19 | North American Paper Corporation | Refiner bleaching with magnesium oxide and hydrogen peroxide |
| US8845860B2 (en) | 2010-09-16 | 2014-09-30 | Georgia-Pacific Consumer Products Lp | High brightness pulps from lignin rich waste papers |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI52877B (en) * | 1972-11-16 | 1977-08-31 | Ahlstroem Oy | |
| NO852330L (en) * | 1985-06-10 | 1986-12-11 | Papirind Forskningsinst | PROCEDURES FOR PEROXIDE BLACKING OF CELLULOSE-CONTAINING Masses. |
| DE4400954B4 (en) * | 1994-01-14 | 2007-03-01 | Stefan Kürzeder | Process for increasing the brightness of bleaching wood pulp with hydrogen peroxide |
-
1995
- 1995-06-13 AU AUPN3520A patent/AUPN352095A0/en not_active Abandoned
-
1996
- 1996-06-13 DE DE69611091T patent/DE69611091D1/en not_active Expired - Lifetime
- 1996-06-13 CA CA002224677A patent/CA2224677C/en not_active Expired - Fee Related
- 1996-06-13 EP EP96917277A patent/EP0832323B1/en not_active Expired - Lifetime
- 1996-06-13 KR KR1019970709344A patent/KR19990022875A/en not_active Application Discontinuation
- 1996-06-13 AT AT96917277T patent/ATE197825T1/en active
- 1996-06-13 WO PCT/AU1996/000354 patent/WO1996041917A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1996041917A1 (en) | 1996-12-27 |
| ATE197825T1 (en) | 2000-12-15 |
| AUPN352095A0 (en) | 1995-07-06 |
| EP0832323B1 (en) | 2000-11-29 |
| CA2224677A1 (en) | 1996-12-27 |
| KR19990022875A (en) | 1999-03-25 |
| EP0832323A4 (en) | 1998-09-09 |
| DE69611091D1 (en) | 2001-01-04 |
| EP0832323A1 (en) | 1998-04-01 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20150615 |