EP0511695A1 - Process for bleaching of lignocellulose-containing pulp - Google Patents
Process for bleaching of lignocellulose-containing pulp Download PDFInfo
- Publication number
- EP0511695A1 EP0511695A1 EP92201005A EP92201005A EP0511695A1 EP 0511695 A1 EP0511695 A1 EP 0511695A1 EP 92201005 A EP92201005 A EP 92201005A EP 92201005 A EP92201005 A EP 92201005A EP 0511695 A1 EP0511695 A1 EP 0511695A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pulp
- chlorine
- alkaline earth
- hydrogen peroxide
- earth metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
-
- 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
- D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
-
- 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
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
Definitions
- the present invention relates to a process for delignification and bleaching of chemically digested lignocellulose-containing pulp, wherein the pulp is acid treated at a pH of between about 1 and about 6, whereupon a water-soluble compound containing an alkaline earth metal is added at a pH of between about 1 and about 7 before the pulp is treated with a chlorine-free bleaching agent.
- the initial acidic treatment removes the trace metals of the pulp, whereas the subsequent addition of alkaline earth metal ions in aqueous solution returns the ions to the positions in the pulp where they have a particularly beneficial effect on the preservation of the cellulose chains and, consequently, on the viscosity, as well as on the consumption of bleaching agent in the subsequent bleaching step.
- the pulp may be finally bleached to the desired brightness, suitably with a chlorine-free bleaching agent, such a ozone, to completely avoid formation and discharge of AOX.
- chlorine-free bleaching agents such as hydrogen peroxide, peracetic acid or ozone
- the delignification and consumption of the bleaching agent become less effective than with chlorine-containing bleaching agents, unless the pulp is pretreated.
- a hydrogen peroxide treatment in an alkaline environment is disturbed by the presence in the pulp of ions of certain metals, such as Mn, Cu and Fe. These metal ions cause degradation of hydrogen peroxide, thereby reducing the efficiency of the peroxide treatment and increasing the consumption of peroxide.
- this can be counteracted by pretreating the pulp with an acid, such as sulphuric acid or nitric acid, whereby the concentration of all types of metal ions is reduced.
- an acid such as sulphuric acid or nitric acid
- metal ions for example Mg, which are advantageous to the peroxide treatment disappear, which ions stabilize the peroxide and increase the selectivity of the peroxide.
- CA 575,636 discloses the addition of magnesium sulphate to stabilize alkaline peroxide solutions. However, the addition is made directly to the bleaching liquor and in alkaline environment insoluble magnesium hydroxide precipitates. Furthermore, US 4,222,819 discloses the addition of magnesium ions to acidic peroxide solutions, but also in this case the addition is made directly to the bleaching liquor. None of the related methods makes possible diffusion of the magnesium ions into the pulp to such an extent, that a pulp of high brightness and strength can be obtained.
- the invention provides a process in which lignocellulose-containing pulp is treated under the conditions disclosed in the claims, whereby the metal ions harmful to the subsequent bleaching are effectively removed and the profile of alkaline earth metals is restored before the pulp is bleached in a chlorine-free bleaching step.
- the invention relates to a process for bleaching of chemically digested lignocellulose-containing pulp, wherein the pulp is acid treated at a pH in the range from about 1 up to about 6, whereupon a compound containing an alkaline earth metal is added at a pH in the range from about 1 up to about 7 and in an amount of from about 0.01 kg, suitably 0.5 kg, up to about 10 kg/ton of dry pulp, calculated as alkaline earth metal, and that the pulp subsequently is treated with a chlorine-free bleaching agent.
- Acid treatment is an effective process to eliminate metal ions from lignocellulose-containing pulps.
- ions of alkaline earth metals especially when in their original positions in the pulp, have a positive influence on the selectivity of the delignification as well as on the stability and consumption of chlorine-free bleaching agents, such as peroxides, ozone and oxygen.
- the present process presents an economic solution to the problem of creating a suitable trace-metal profile for the subsequent chlorine-free bleaching, in that non-desirable metal ions are eliminated while supplied ions of alkaline earth metals essentially recover the positions in the vicinity of the cellulose chains previously occupied by ions of alkaline earth metals.
- an advantage of the present process is that the pH adjustment between the treatment with acid and addition of alkaline earth metal ions becomes very limited or may be left out altogether, which is advantageous to process technique and economy.
- Chlorine-free bleaching agents include inorganic peroxide compounds, such as hydrogen peroxide and sodium peroxide, organic peroxide compounds, such as peracetic acid, as well as ozone, oxygen and sodium dithionite.
- hydrogen peroxide (P), oxygen (O) and ozone (Z) are used in an optional sequence or mixture.
- the sequence P-Z or (PO)-Z are especially preferred.
- pH is suitably adjusted by adding to the pulp an alkali or an alkali-containing liquid, such as sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, oxidized white liquor or magnesium hydroxide slurry.
- an alkali or an alkali-containing liquid such as sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, oxidized white liquor or magnesium hydroxide slurry.
- the magnesium hydroxide slurry is taken from the chemical handling system in the production of sulphite pulp with magnesium as base, i.e. magnefite pulp.
- the acid treatment suitably is carried out with an acid.
- the acids used are inorganic acids, suitably sulphuric acid, nitric acid, hydrochloric acid or residual acid from a chlorine dioxide reactor, either separately or in an optional mixture.
- sulphuric acid is employed.
- Compounds containing an alkaline earth metal relate to water-soluble chemicals containing magnesium or calcium, or mixtures of such chemicals.
- Use is suitably made of magnesium-containing compounds, such as magnesium sulphate or magnesium chloride, or calcium-containing compounds, such as calcium chloride or calcium oxide.
- Use is preferably made of magnesium sulphate or magnesium chloride, the use of magnesium sulphate being especially preferred.
- the combination of temperature and pH at the addition of the compound containing an alkaline earth metal is always so chosen that the compound is in aqueous solution when contacted with the pulp.
- the acid treatment is carried out at a pH of from about 1 up to about 6, suitably from 1.5 up to 5, preferably from 2 up to 4. It is especially preferred that the acid treatment is carried out at a pH of from 2 up to 3.
- the addition is made at a pH in the range from about 1 up to about 7, suitably in the range from 2 up to 6, preferably in the range from 2 up to 4. It is especially preferred that the addition of magnesium is made at a pH of from 2 up to 3.
- the chlorine-free bleaching agent is hydrogen peroxide
- the pulp is suitably treated at a pH of from about 8 up to about 12, preferably at a pH of from 10 up to 12. Treatment with the other chlorine-free bleaching agents mentioned above, is carried out within the normal pH ranges for each bleaching agent, which are well-known to the person skilled in the art.
- the treatment according to the invention is preferably carried out with a washing step between the acid treatment and addition of alkaline earth metal ions, such that the trace metals that are harmful to the treatment with a chlorine-free bleaching agent are removed from the pulp suspension.
- a compound containing an alkaline earth metal and a chlorine-free bleaching agent can be carried out at an optional position in the bleaching sequence, e.g. immediately after digestion of the pulp or after an oxygen step.
- the process according to the invention is preferably applied to pulp that has been delignified in an oxygen step prior to the treatment.
- the pulp in the acid treatment also can be subjected to bleaching and/or delignifying treatment.
- Bleaching and/or delignifying chemicals active within the pH range suitable in the acid treatment are e.g. chlorine dioxide, ozone, peracetic acid and/or an acid peroxide-containing compound.
- a combination of acid treatment and bleaching and/or delignifying treatment takes place in an ozone step.
- Lignocellulose-containing pulps relate to chemical pulps of softwood and/or hardwood digested according to the sulphite, sulphate, soda or organosolv process, or modifications and/or combinations thereof.
- Use is suitably made of softwood and/or hardwood digested according to the sulphate process, preferably sulphate pulp of hardwood.
- the treatment according to the invention can be applied to lignocellulose-containing pulps having an initial kappa number within the range from about 5 up to about 40, suitably 7 up to 32, preferably from 10 up to 20.
- the kappa number is determined according to the standard method SCAN-C 1:77.
- the acid treatment is carried out at a temperature of from about 10 up to about 95°C, suitably from 20 up to 80°C and preferably from 40 up to 80°C, and for a period of time of from about 1 up to about 120 min, suitably from 10 up to 120 min and preferably from 20 up to 40 min.
- the compound containing an alkaline earth metal is added at a temperature of from about 10 up to about 95°C, preferably from 40 up to 80°C, and for a period of time of from about 1 up to about 180 min, preferably from 20 up to 180 min and preferably from 30 up to 120 min.
- the pulp is treated at a temperature of from about 30 up to about 100°C, preferably from 60 up to 90°C, and for a period of time of from about 30 up to about 300 min, suitably from 60 up to 240 min.
- the pulp concentration may be from about 3 up to about 35% by weight, preferably from 3 up to 15% by weight.
- the pulp concentration may be from about 3 up to about 50% by weight, suitably from 3 up to 35% by weight and preferably from 10 up to 25% by weight.
- Treatment with the other chlorine-free bleaching agents mentioned above is carried out within the normal ranges of temperature, time and pulp concentration for each bleaching agent, which are well-known to the person skilled in the art.
- the amount of compound containing an alkaline earth metal charged lies in the range from about 0.01 up to about 10 kg/ton of dry pulp, calculated as alkaline earth metal, suitably in the range from 0.5 up to 5 kg/ton of dry pulp, calculated as alkaline earth metal, and preferably in the range from 2 up to 4 kg/ton of dry pulp, calculated as alkaline earth metal.
- the amount of hydrogen peroxide lies in the range from about 2 up to about 50 kg/ton of dry pulp, calculated as 100% hydrogen peroxide.
- the upper limit is not critical, but has been set for reasons of economy.
- the amount of hydrogen peroxide suitably lies in the range from 3 up to 30 kg/ton of dry pulp and preferably from 4 up to 20 kg/ton of dry pulp, calculated as 100% hydrogen peroxide.
- the pulp can be used for direct production of paper with a lower demand of brightness.
- the pulp may be finally bleached to the desired higher brightness, by treatment in one or more steps.
- the final bleaching is also carried out with chlorine-free bleaching agents of the type mentioned above, optionally with intermediate alkaline extraction steps, which may be reinforced with peroxide and/or oxygen. In this way, the formation and discharge of AOX is completely eliminated.
- the final bleaching is carried out with ozone in one or more steps.
- the process according to the invention means that the brightness and kappa number of the resulting pulp is higher and lower, respectively, than with the processes in which a compound containing an alkaline earth metal is not added at all or is added at a higher pH.
- the aim is a high brightness as well as a low kappa number, the latter meaning a low content of undissolved lignin.
- the consumption of the chlorine-free bleaching agent should be as low as possible meaning lower treatment costs.
- these objects are met, as is apparent from the Examples.
- the strength of the pulp measured as viscosity, is sufficient, which means that the pulp contains cellulose chains which are long enough to give a strong product.
- Sulphate pulp of softwood having a kappa number of 17, a brightness of 35% ISO and a viscosity of 970 dm3/kg was treated with sulphuric acid at a pH of 2.0.
- the pulp was treated at a temperature of 60°C for 30 min, the pulp concentration being 10% by weight.
- magnesium was added in the form of an aqueous solution containing MgSO4, to give a concentration of magnesium in the pulp of at least 500 ppm.
- the pH at the time of the addition was varied between 2.3 and 11.5 by addition of sulphuric acid.
- the pulp was bleached with hydrogen peroxide at a temperature of 90°C, the residence time and pulp concentration being 180 min and 15% by weight, respectively.
- the final pH was 11.5, and the addition of hydrogen peroxide was 15 kg/ton of dry pulp, calculated as 100% hydrogen peroxide.
- magnesium was added directly to the hydrogen peroxide step under the conditions stated above, in accordance with the prior art.
- the pulp was also treated with only sulphuric acid and hydrogen peroxide under the conditions stated above.
- the kappa number, viscosity and brightness of the pulp were determined according to SCAN Standard Methods, and the consumption of hydrogen peroxide was determined by iodometric titration. The test results appear from the Table below.
- the treatment according to the present invention with MgSO4 at a pH in the range from about 2 up to about 6 is essential to give maximum increase in brightness and maximum reduction of the kappa number, as well as minimum decrease in viscosity and minimum consumption of hydrogen peroxide. Furthermore, the importance of the magnesium ions for the increase in brightness appears from the comparison at a pH of 2.3, where, in the final test, the peroxide treatment was preceded only by acidic treatment.
- the pulp was bleached with hydrogen peroxide at a temperature of 90°C, the residence time and pulp concentration being 240 min and 10% by weight, respectively.
- the final pH was 11.5 and the addition of hydrogen peroxide was 20 kg/ton of dry pulp calculated as 100% hydrogen peroxide.
- the pulp was also treated with only sulphuric acid and hydrogen peroxide under the conditions stated above. The kappa number, viscosity and brightness were determined according to SCAN Standard Methods. The results after bleaching with hydrogen peroxide appear from the Table below. TABLE II Amount of Mg added in step 2 (kg/ton) Amount of Mg in pulp after step 2 (ppm) Kappa no.
- step 3 Viscosity step 3 (dm3/kg) Brightness step 3 (% ISO) 0 3,7 9.6 900 51.5 0.1 130 8.2 870 61.8 0.3 250 7.8 864 65.1 0.75 370 7.7 855 65.9 1.5 480 7.6 845 67.3
- the oxygen-delignified sulphate pulp of softwood used in Example 2 was treated in the sequences D - EOP-Z - P (test 1) and D - EOP - Z - Mg - P (test 2), where the conditions in each step were equal in both sequences.
- D and EOP relate to a conventional chlorine dioxide step and a conventional alkaline extraction step reinforced with hydrogen peroxide and oxygen, respectively.
- Z relates to an ozone step with a pH of 2.3.
- Mg relates to the addition of 1 kg of magnesium/ton of dry pulp, in the form of an aqueous solution containing MgSO4. Magnesium was added at a pH of 4.1, a temperature of 50°C for 30 min, the pulp concentration being about 3% by weight.
- P relates to a hydrogen peroxide step, where the pulp was treated at a temperature of 80°C for 120 min.
- the final pH was about 11.5 and the addition of hydrogen peroxide was 5 kg/ton of dry pulp calculated as 100% hydrogen peroxide.
- the viscosity and brightness were determined according to SCAN Standard Methods. The results after bleaching with hydrogen peroxide appear from the Table below.
- Step1 relates to treatment with EDTA at a pH of 5.
- Z relates to an ozone step with a pH of 2.3, the pulp concentration being 10% by weight.
- Mg relates to the addition of 1 kg of magnesium/ton of dry pulp, in the form of an aqueous solution containing MgSO4. Magnesium was added at a pH of 4.1, a temperature of 50°C for 30 min, the pulp concentration being about 3% by weight.
- P2 relates to a hydrogen peroxide step, where the pulp was treated at a temperature of 80°C for 120 min. The final pH was about 11.5 and the addition of hydrogen peroxide was 5 kg/ton of dry pulp calculated as 100% hydrogen peroxide.
- the pulp was also treated in the sequence Step1 - P1 - z - (PMg) (test 3).
- (PMg) relates to the addition of magnesium in the second alkaline hydrogen peroxide step under the conditions stated above, in accordance with the prior art.
- the viscosity and brightness were determined according to SCAN Standard Methods, and the consumption of hydrogen peroxide was determined by iodometric titration. The results after the second hydrogen peroxide step appear from the Table below.
Landscapes
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Paper (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Materials For Medical Uses (AREA)
- Investigating Or Analysing Biological Materials (AREA)
- Diaphragms For Electromechanical Transducers (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
- Stringed Musical Instruments (AREA)
- Breeding Of Plants And Reproduction By Means Of Culturing (AREA)
- Noodles (AREA)
Abstract
Description
- The present invention relates to a process for delignification and bleaching of chemically digested lignocellulose-containing pulp, wherein the pulp is acid treated at a pH of between about 1 and about 6, whereupon a water-soluble compound containing an alkaline earth metal is added at a pH of between about 1 and about 7 before the pulp is treated with a chlorine-free bleaching agent. The initial acidic treatment removes the trace metals of the pulp, whereas the subsequent addition of alkaline earth metal ions in aqueous solution returns the ions to the positions in the pulp where they have a particularly beneficial effect on the preservation of the cellulose chains and, consequently, on the viscosity, as well as on the consumption of bleaching agent in the subsequent bleaching step. After the treatment according to the invention, the pulp may be finally bleached to the desired brightness, suitably with a chlorine-free bleaching agent, such a ozone, to completely avoid formation and discharge of AOX.
- In the production of chemical pulp of high brightness, wood chips are first cooked to separate the cellulose fibres. Part of the lignin holding the fibres together is thus degraded and modified, such that it can be removed by subsequent washing. However, in order to obtain sufficient brightness, more lignin has to be removed, together with brightness-impairing (chromophoric) groups. This is frequently effected by delignification with oxygen, followed by bleaching in several stages.
- For environmental reasons, it has become increasingly common to treat chemical pulp with chlorine-free bleaching agents already in the first bleaching steps. The big advantage is the drastic reduction in the discharges of chlorinated organic substances detrimental to the environment, owing to the combined effect of a smaller amount of chlorine-containing bleaching agents and lower content of lignin, which is the organic substance primarily reacting with the chlorine.
- It is known to use chlorine-free bleaching agents, such as hydrogen peroxide, peracetic acid or ozone, already in the prebleaching. However, the delignification and consumption of the bleaching agent become less effective than with chlorine-containing bleaching agents, unless the pulp is pretreated. Thus, a hydrogen peroxide treatment in an alkaline environment is disturbed by the presence in the pulp of ions of certain metals, such as Mn, Cu and Fe. These metal ions cause degradation of hydrogen peroxide, thereby reducing the efficiency of the peroxide treatment and increasing the consumption of peroxide. According to CA 1,206,704, this can be counteracted by pretreating the pulp with an acid, such as sulphuric acid or nitric acid, whereby the concentration of all types of metal ions is reduced. However, by this treatment also metal ions, for example Mg, which are advantageous to the peroxide treatment disappear, which ions stabilize the peroxide and increase the selectivity of the peroxide.
- CA 575,636 discloses the addition of magnesium sulphate to stabilize alkaline peroxide solutions. However, the addition is made directly to the bleaching liquor and in alkaline environment insoluble magnesium hydroxide precipitates. Furthermore, US 4,222,819 discloses the addition of magnesium ions to acidic peroxide solutions, but also in this case the addition is made directly to the bleaching liquor. None of the related methods makes possible diffusion of the magnesium ions into the pulp to such an extent, that a pulp of high brightness and strength can be obtained.
- The invention provides a process in which lignocellulose-containing pulp is treated under the conditions disclosed in the claims, whereby the metal ions harmful to the subsequent bleaching are effectively removed and the profile of alkaline earth metals is restored before the pulp is bleached in a chlorine-free bleaching step.
- The invention relates to a process for bleaching of chemically digested lignocellulose-containing pulp, wherein the pulp is acid treated at a pH in the range from about 1 up to about 6, whereupon a compound containing an alkaline earth metal is added at a pH in the range from about 1 up to about 7 and in an amount of from about 0.01 kg, suitably 0.5 kg, up to about 10 kg/ton of dry pulp, calculated as alkaline earth metal, and that the pulp subsequently is treated with a chlorine-free bleaching agent.
- Acid treatment is an effective process to eliminate metal ions from lignocellulose-containing pulps. At the same time it is known, that ions of alkaline earth metals, especially when in their original positions in the pulp, have a positive influence on the selectivity of the delignification as well as on the stability and consumption of chlorine-free bleaching agents, such as peroxides, ozone and oxygen. The present process presents an economic solution to the problem of creating a suitable trace-metal profile for the subsequent chlorine-free bleaching, in that non-desirable metal ions are eliminated while supplied ions of alkaline earth metals essentially recover the positions in the vicinity of the cellulose chains previously occupied by ions of alkaline earth metals. This is achieved by adding the compound containing an alkaline earth metal at such a pH and such a temperature that the compound is dissolved in water, thus enabling the diffusion required to obtain the intended effect. Furthermore, an advantage of the present process is that the pH adjustment between the treatment with acid and addition of alkaline earth metal ions becomes very limited or may be left out altogether, which is advantageous to process technique and economy.
- Chlorine-free bleaching agents include inorganic peroxide compounds, such as hydrogen peroxide and sodium peroxide, organic peroxide compounds, such as peracetic acid, as well as ozone, oxygen and sodium dithionite. Suitably, hydrogen peroxide (P), oxygen (O) and ozone (Z) are used in an optional sequence or mixture. Preferably, use is made of hydrogen peroxide or mixtures of hydrogen peroxide and oxygen (PO). The sequence P-Z or (PO)-Z are especially preferred.
- In the treatment with a chlorine-free bleaching agent in an alkaline environment, pH is suitably adjusted by adding to the pulp an alkali or an alkali-containing liquid, such as sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, oxidized white liquor or magnesium hydroxide slurry. Suitably, the magnesium hydroxide slurry is taken from the chemical handling system in the production of sulphite pulp with magnesium as base, i.e. magnefite pulp.
- The acid treatment suitably is carried out with an acid. The acids used are inorganic acids, suitably sulphuric acid, nitric acid, hydrochloric acid or residual acid from a chlorine dioxide reactor, either separately or in an optional mixture. Preferably, sulphuric acid is employed.
- Compounds containing an alkaline earth metal relate to water-soluble chemicals containing magnesium or calcium, or mixtures of such chemicals. Use is suitably made of magnesium-containing compounds, such as magnesium sulphate or magnesium chloride, or calcium-containing compounds, such as calcium chloride or calcium oxide. Use is preferably made of magnesium sulphate or magnesium chloride, the use of magnesium sulphate being especially preferred. The combination of temperature and pH at the addition of the compound containing an alkaline earth metal is always so chosen that the compound is in aqueous solution when contacted with the pulp.
- In the process according to the invention, the acid treatment is carried out at a pH of from about 1 up to about 6, suitably from 1.5 up to 5, preferably from 2 up to 4. It is especially preferred that the acid treatment is carried out at a pH of from 2 up to 3. When magnesium is the alkaline earth metal in the compound containing an alkaline earth metal, the addition is made at a pH in the range from about 1 up to about 7, suitably in the range from 2 up to 6, preferably in the range from 2 up to 4. It is especially preferred that the addition of magnesium is made at a pH of from 2 up to 3. When the chlorine-free bleaching agent is hydrogen peroxide, the pulp is suitably treated at a pH of from about 8 up to about 12, preferably at a pH of from 10 up to 12. Treatment with the other chlorine-free bleaching agents mentioned above, is carried out within the normal pH ranges for each bleaching agent, which are well-known to the person skilled in the art.
- The treatment according to the invention is preferably carried out with a washing step between the acid treatment and addition of alkaline earth metal ions, such that the trace metals that are harmful to the treatment with a chlorine-free bleaching agent are removed from the pulp suspension.
- The realization of the acid treatment, a compound containing an alkaline earth metal and a chlorine-free bleaching agent, can be carried out at an optional position in the bleaching sequence, e.g. immediately after digestion of the pulp or after an oxygen step. The process according to the invention is preferably applied to pulp that has been delignified in an oxygen step prior to the treatment.
- It is also within the scope of the invention, that the pulp in the acid treatment also can be subjected to bleaching and/or delignifying treatment. Bleaching and/or delignifying chemicals active within the pH range suitable in the acid treatment, are e.g. chlorine dioxide, ozone, peracetic acid and/or an acid peroxide-containing compound. Suitably, a combination of acid treatment and bleaching and/or delignifying treatment takes place in an ozone step.
- Lignocellulose-containing pulps relate to chemical pulps of softwood and/or hardwood digested according to the sulphite, sulphate, soda or organosolv process, or modifications and/or combinations thereof. Use is suitably made of softwood and/or hardwood digested according to the sulphate process, preferably sulphate pulp of hardwood.
- The treatment according to the invention can be applied to lignocellulose-containing pulps having an initial kappa number within the range from about 5 up to about 40, suitably 7 up to 32, preferably from 10 up to 20. Here, the kappa number is determined according to the standard method SCAN-C 1:77.
- In the process according to the invention, the acid treatment is carried out at a temperature of from about 10 up to about 95°C, suitably from 20 up to 80°C and preferably from 40 up to 80°C, and for a period of time of from about 1 up to about 120 min, suitably from 10 up to 120 min and preferably from 20 up to 40 min. The compound containing an alkaline earth metal is added at a temperature of from about 10 up to about 95°C, preferably from 40 up to 80°C, and for a period of time of from about 1 up to about 180 min, preferably from 20 up to 180 min and preferably from 30 up to 120 min. When the chlorine-free bleaching agent is hydrogen peroxide, the pulp is treated at a temperature of from about 30 up to about 100°C, preferably from 60 up to 90°C, and for a period of time of from about 30 up to about 300 min, suitably from 60 up to 240 min. In the acid treatment and in the addition of alkaline earth metal ions, the pulp concentration may be from about 3 up to about 35% by weight, preferably from 3 up to 15% by weight. When the chlorine-free bleaching agent is hydrogen peroxide, the pulp concentration may be from about 3 up to about 50% by weight, suitably from 3 up to 35% by weight and preferably from 10 up to 25% by weight. Treatment with the other chlorine-free bleaching agents mentioned above, is carried out within the normal ranges of temperature, time and pulp concentration for each bleaching agent, which are well-known to the person skilled in the art.
- The amount of compound containing an alkaline earth metal charged, lies in the range from about 0.01 up to about 10 kg/ton of dry pulp, calculated as alkaline earth metal, suitably in the range from 0.5 up to 5 kg/ton of dry pulp, calculated as alkaline earth metal, and preferably in the range from 2 up to 4 kg/ton of dry pulp, calculated as alkaline earth metal.
- In preferred embodiments employing hydrogen peroxide as the chlorine-free bleaching agent, the amount of hydrogen peroxide, lies in the range from about 2 up to about 50 kg/ton of dry pulp, calculated as 100% hydrogen peroxide. The upper limit is not critical, but has been set for reasons of economy. The amount of hydrogen peroxide suitably lies in the range from 3 up to 30 kg/ton of dry pulp and preferably from 4 up to 20 kg/ton of dry pulp, calculated as 100% hydrogen peroxide.
- After the acid treatment, a compound containing an alkaline earth metal and a chlorine-free bleaching agent, the pulp can be used for direct production of paper with a lower demand of brightness. Alternatively, the pulp may be finally bleached to the desired higher brightness, by treatment in one or more steps. Suitably, the final bleaching is also carried out with chlorine-free bleaching agents of the type mentioned above, optionally with intermediate alkaline extraction steps, which may be reinforced with peroxide and/or oxygen. In this way, the formation and discharge of AOX is completely eliminated. Suitably, the final bleaching is carried out with ozone in one or more steps. By the treatment according to the invention, the lignin content has been reduced to a sufficiently low level before any chlorine-containing bleaching agents are used. Therefore, chlorine dioxide and/or hypochlorite may well be used in one or more final bleaching steps without causing formation of large amounts of AOX.
- Moreover, use of the process according to the invention means that the brightness and kappa number of the resulting pulp is higher and lower, respectively, than with the processes in which a compound containing an alkaline earth metal is not added at all or is added at a higher pH. In a process for bleaching chemical pulps, the aim is a high brightness as well as a low kappa number, the latter meaning a low content of undissolved lignin. At the same time, the consumption of the chlorine-free bleaching agent should be as low as possible meaning lower treatment costs. In the process according to the invention, these objects are met, as is apparent from the Examples. Furthermore, the strength of the pulp, measured as viscosity, is sufficient, which means that the pulp contains cellulose chains which are long enough to give a strong product.
- The invention and its advantages are illustrated in more detail by the Examples below which, however, are only intended to illustrate the invention and are not intended to limit the same. The percentages and parts stated in the description, claims and examples, refer to percent by weight and parts by weight, respectively, unless anything else is stated.
- Sulphate pulp of softwood having a kappa number of 17, a brightness of 35% ISO and a viscosity of 970 dm³/kg was treated with sulphuric acid at a pH of 2.0. The pulp was treated at a temperature of 60°C for 30 min, the pulp concentration being 10% by weight. After washing the pulp with water, magnesium was added in the form of an aqueous solution containing MgSO₄, to give a concentration of magnesium in the pulp of at least 500 ppm. In the tests, the pH at the time of the addition was varied between 2.3 and 11.5 by addition of sulphuric acid. Then, the pulp was bleached with hydrogen peroxide at a temperature of 90°C, the residence time and pulp concentration being 180 min and 15% by weight, respectively. The final pH was 11.5, and the addition of hydrogen peroxide was 15 kg/ton of dry pulp, calculated as 100% hydrogen peroxide. For comparative purposes, magnesium was added directly to the hydrogen peroxide step under the conditions stated above, in accordance with the prior art. To provide a further comparison, the pulp was also treated with only sulphuric acid and hydrogen peroxide under the conditions stated above. The kappa number, viscosity and brightness of the pulp were determined according to SCAN Standard Methods, and the consumption of hydrogen peroxide was determined by iodometric titration. The test results appear from the Table below.
TABLE I pH at the addition of Mg Kappa number step 2 Viscosity step 2 (dm³/kg) Brightness step 2 (% ISO) Residual H₂O step 2 (kg/ton) 2.3 9.1 903 61.0 1.5 4.7 9.2 910 60.0 1.0 9.5 9.8 930 56.1 0.9 11.5 10.0 940 52.2 0.2 ---- * 9.8 890 54.1 0.5 2.3 ** 9.9 875 48.2 0.0 * Magnesium added directly to the alkaline hydrogen peroxide step. ** No magnesium added. - As is apparent from the Table, the treatment according to the present invention with MgSO₄ at a pH in the range from about 2 up to about 6 is essential to give maximum increase in brightness and maximum reduction of the kappa number, as well as minimum decrease in viscosity and minimum consumption of hydrogen peroxide. Furthermore, the importance of the magnesium ions for the increase in brightness appears from the comparison at a pH of 2.3, where, in the final test, the peroxide treatment was preceded only by acidic treatment.
- Oxygen-delignified sulphate pulp of softwood having a kappa number of 13.7, a brightness of 37.1% ISO and a viscosity of 1057 dm³/kg, was treated in a first step with 15 kg of sulphuric acid/ton of dry pulp at a pH of 1.9. The pulp was treated at a temperature of 50°C for 60 min, the pulp concentration being 10% by weight. After washing the pulp with water, in a second step between 0.1 and 1.5 kg of magnesium/ton of dry pulp was added in the form of an aqueous solution containing MgSO₄. Magnesium was added at a pH of 4.1, a temperature of 50°C for 60 min and with a pulp concentration of 3.5% by weight. Then, the pulp was bleached with hydrogen peroxide at a temperature of 90°C, the residence time and pulp concentration being 240 min and 10% by weight, respectively. The final pH was 11.5 and the addition of hydrogen peroxide was 20 kg/ton of dry pulp calculated as 100% hydrogen peroxide. For comparative purposes, the pulp was also treated with only sulphuric acid and hydrogen peroxide under the conditions stated above. The kappa number, viscosity and brightness were determined according to SCAN Standard Methods. The results after bleaching with hydrogen peroxide appear from the Table below.
TABLE II Amount of Mg added in step 2 (kg/ton) Amount of Mg in pulp after step 2 (ppm) Kappa no. step 3 Viscosity step 3 (dm³/kg) Brightness step 3 (% ISO) 0 3,7 9.6 900 51.5 0.1 130 8.2 870 61.8 0.3 250 7.8 864 65.1 0.75 370 7.7 855 65.9 1.5 480 7.6 845 67.3 - As is apparent from the Table, acid treatment followed by addition of dissolved magnesium and bleaching with hydrogen peroxide according to the present invention, positively influence the pulp as regards kappa number, viscosity and brightness.
- The oxygen-delignified sulphate pulp of softwood used in Example 2, was treated in the sequences D - EOP-Z - P (test 1) and D - EOP - Z - Mg - P (test 2), where the conditions in each step were equal in both sequences. D and EOP relate to a conventional chlorine dioxide step and a conventional alkaline extraction step reinforced with hydrogen peroxide and oxygen, respectively. Z relates to an ozone step with a pH of 2.3. Mg relates to the addition of 1 kg of magnesium/ton of dry pulp, in the form of an aqueous solution containing MgSO₄. Magnesium was added at a pH of 4.1, a temperature of 50°C for 30 min, the pulp concentration being about 3% by weight. P relates to a hydrogen peroxide step, where the pulp was treated at a temperature of 80°C for 120 min. The final pH was about 11.5 and the addition of hydrogen peroxide was 5 kg/ton of dry pulp calculated as 100% hydrogen peroxide. The viscosity and brightness were determined according to SCAN Standard Methods. The results after bleaching with hydrogen peroxide appear from the Table below.
TABLE III Test Amount of Mg added (kg/ton) Amount of Mg in pulp after addition (ppm) Viscosity (dm³/kg) Brightness (% ISO) 1 0 16 820 86.3 2 1.0 255 872 88.4 - As is apparent from the Table, addition of dissolved magnesium after an initial acid treatment with ozone and bleaching with hydrogen peroxide according to the present invention, positively influence the pulp as regards viscosity and brightness.
- The oxygen-delignified sulphate pulp of softwood used in Example 2, was treated in the sequences Step1 - P₁ - Z - P₂ (test 1) and Step1 - P₁ - Z - Mg - P₂ (test 2), where the conditions in each step were equal in both sequences. Step1 relates to treatment with EDTA at a pH of 5. Z relates to an ozone step with a pH of 2.3, the pulp concentration being 10% by weight. Mg relates to the addition of 1 kg of magnesium/ton of dry pulp, in the form of an aqueous solution containing MgSO₄. Magnesium was added at a pH of 4.1, a temperature of 50°C for 30 min, the pulp concentration being about 3% by weight. P₂ relates to a hydrogen peroxide step, where the pulp was treated at a temperature of 80°C for 120 min. The final pH was about 11.5 and the addition of hydrogen peroxide was 5 kg/ton of dry pulp calculated as 100% hydrogen peroxide. For comparative purposes, the pulp was also treated in the sequence Step1 - P₁ - z - (PMg) (test 3). (PMg) relates to the addition of magnesium in the second alkaline hydrogen peroxide step under the conditions stated above, in accordance with the prior art. The viscosity and brightness were determined according to SCAN Standard Methods, and the consumption of hydrogen peroxide was determined by iodometric titration. The results after the second hydrogen peroxide step appear from the Table below.
TABLE IV Test Amount of Mg added (kg/ton) Amount of Mg in pulp (ppm) Viscosity (dm³/kg) Bright-ness (% ISO) H₂O₂ consumed in P₂ (% of added) 1 0 9 794 80.9 76 2 1.0 300 856 83.9 28 3 1.0 120 809 81.6 60 - As is apparent from the Table, addition of magnesium within the present pH range before bleaching with hydrogen peroxide, positively influence the pulp as regards viscosity and brightness and reduces the consumption of hydrogen peroxide.
Claims (10)
- A process for delignification and bleaching of chemically digested lignocellulose-containing pulp, characterised in that the pulp is acid treated at a pH in the range from about 1 up to about 6, whereupon a compound containing an alkaline earth metal is added at a pH in the range from about 1 up to about 7 and in an amount of from about 0.01 up to about 10 kg/ton of dry pulp, calculated as alkaline earth metal, and that the pulp subsequently is treated with a chlorine-free bleaching agent.
- A process according to claim 1, characterised in that the chlorine-free bleaching agent consists of hydrogen peroxide, oxygen and ozone in an optional sequence or mixture.
- A process according to claim 2, characterised in that the chlorine-free bleaching agent consists of hydrogen peroxide or a mixture of hydrogen peroxide and oxygen.
- A process according to claim 1, characterised in that the compound containing an alkaline earth metal is added at a pH of from 2 up to 6.
- A process according to claim 1, characterised in that the compound containing an alkaline earth metal consists of a water-soluble magnesium compound.
- A process according to claim 1 or 5, characterised in that the compound containing an alkaline earth metal consists of magnesium sulphate or magnesium chloride.
- A process according to claim 1, characterised in that the pulp is washed after the acid treatment.
- A process according to claim 1, characterised in that the pulp, after the treatment, is finally bleached with a chlorine-free bleaching agent, optionally with intermediate alkaline extraction steps.
- A process according to claim 8, characterised in that the pulp, after the treatment, is finally bleached with ozone in one or more steps.
- A process according to claims 1-9, characterised in that the acid treatment is carried out at a temperature of from about 10 up to about 95°C for about 1 up to about 120 min, that the compound containing an alkaline earth metal is added at a temperature of from about 10 up to about 95°C for about 1 up to about 180 min and in an amount of from 0.5 up to 5 kg/ton of dry pulp, calculated as alkaline earth metal, the treated pulp having a concentration of from about 3 up to about 35% by weight, and that the pulp is treated with hydrogen peroxide at a pH of from about 8 up to about 12.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP94203640A EP0679760B1 (en) | 1991-04-30 | 1992-04-08 | Process for bleaching of lignocellulose-containing pulp |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9101301 | 1991-04-30 | ||
SE9101301A SE470065C (en) | 1991-04-30 | 1991-04-30 | Treatment of chemical pulp with an acid and then a magnesium and calcium compound in chlorine-free bleaching |
Related Child Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94203640.1 Division-Into | 1992-04-08 | ||
EP94203640A Division EP0679760B1 (en) | 1991-04-30 | 1992-04-08 | Process for bleaching of lignocellulose-containing pulp |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0511695A1 true EP0511695A1 (en) | 1992-11-04 |
EP0511695B1 EP0511695B1 (en) | 1996-08-28 |
EP0511695B2 EP0511695B2 (en) | 2004-06-02 |
Family
ID=20382601
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94203640A Expired - Lifetime EP0679760B1 (en) | 1991-04-30 | 1992-04-08 | Process for bleaching of lignocellulose-containing pulp |
EP92201005A Expired - Lifetime EP0511695B2 (en) | 1991-04-30 | 1992-04-08 | Process for bleaching of lignocellulose-containing pulp |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94203640A Expired - Lifetime EP0679760B1 (en) | 1991-04-30 | 1992-04-08 | Process for bleaching of lignocellulose-containing pulp |
Country Status (14)
Country | Link |
---|---|
EP (2) | EP0679760B1 (en) |
JP (1) | JP2592747B2 (en) |
AT (2) | ATE141971T1 (en) |
BR (1) | BR9201554A (en) |
CA (1) | CA2067296C (en) |
DE (2) | DE69227640T2 (en) |
ES (1) | ES2091395T3 (en) |
FI (1) | FI111964B (en) |
MX (1) | MX9201966A (en) |
NO (1) | NO180495C (en) |
NZ (1) | NZ242465A (en) |
RU (1) | RU2039141C1 (en) |
SE (1) | SE470065C (en) |
ZA (1) | ZA923073B (en) |
Cited By (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0595386A1 (en) * | 1992-10-29 | 1994-05-04 | Eka Nobel Ab | Process for bleaching of lignocellulose-containing pulp |
WO1994010374A1 (en) * | 1992-10-26 | 1994-05-11 | Sca-Wifsta-Östrand Ab | Method for peroxide bleaching of sulphate pulp |
WO1994011569A1 (en) * | 1992-11-11 | 1994-05-26 | Mo Och Domsjö Aktiebolag | A method in delignifying and/or bleaching of cellulose pulp |
EP0622491A2 (en) * | 1993-04-20 | 1994-11-02 | Eka Nobel Ab | Method for bleaching lignocellulose-containing pulp |
WO1995013420A1 (en) * | 1993-11-10 | 1995-05-18 | Solvay Interox (Société Anonyme) | Method of bleaching chemical paper pulp |
WO1996012063A1 (en) * | 1994-10-13 | 1996-04-25 | Ahlstrom Machinery Oy | Method for removal of hexenuronic acid groups in cellulose pulp by heat treatment |
US5571377A (en) * | 1993-06-08 | 1996-11-05 | Kvaerner Pulping Technologies Ab | Process for peroxide bleaching of chemical pulp in a pressurized bleach vessel |
DE19516151A1 (en) * | 1995-05-03 | 1996-11-07 | Sven Siegle | Process for the production of a pulp from cellulosic material, the pulp itself and its use |
WO1997015713A1 (en) * | 1995-10-20 | 1997-05-01 | Ahlstrom Machinery Oy | Acid treatment of pulp at high temperature in connection with bleaching |
EP0905307A1 (en) * | 1997-08-25 | 1999-03-31 | Praxair Technology, Inc. | Method for applying ozone in ECF bleaching |
US6007678A (en) * | 1992-11-27 | 1999-12-28 | Eka Nobel Ab | Process for delignification of lignocellulose-containing pulp with an organic peracid or salts thereof |
US6120556A (en) * | 1996-06-21 | 2000-09-19 | Nippon Peroxide Co., Ltd. | Stabilizing agent for peroxide-bleaching procedure and methods of bleaching a fiber material by using same |
US6398908B1 (en) | 1991-04-30 | 2002-06-04 | Eka Nobel Ab | Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound |
US6547923B1 (en) | 1989-05-10 | 2003-04-15 | Andritz Oy | Process for bleaching medium consistency pulp with ozone using a pressurized fluidizing mixer |
US6605181B1 (en) * | 1993-10-01 | 2003-08-12 | Kvaerner Pulping Aktiebolag | Peroxide bleach sequence including an acidic bleach stage and including a wash stage |
US6776876B1 (en) | 1994-10-13 | 2004-08-17 | Andritz Oy | Method of treating cellulosic pulp to remove hexenuronic acid |
WO2017055504A1 (en) * | 2015-09-30 | 2017-04-06 | Imerys Minerals Limited | Methods for bleaching aqueous pulps and compositions for use in these methods |
US9617686B2 (en) | 2012-04-18 | 2017-04-11 | Gp Cellulose Gmbh | Use of surfactant to treat pulp and improve the incorporation of kraft pulp into fiber for the production of viscose and other secondary fiber products |
US9719208B2 (en) | 2011-05-23 | 2017-08-01 | Gp Cellulose Gmbh | Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same |
US9777432B2 (en) | 2009-05-28 | 2017-10-03 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US9951470B2 (en) | 2013-03-15 | 2018-04-24 | Gp Cellulose Gmbh | Low viscosity kraft fiber having an enhanced carboxyl content and methods of making and using the same |
US10597819B2 (en) | 2012-01-12 | 2020-03-24 | Gp Cellulose Gmbh | Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same |
US10865519B2 (en) | 2016-11-16 | 2020-12-15 | Gp Cellulose Gmbh | Modified cellulose from chemical fiber and methods of making and using the same |
WO2021209586A1 (en) * | 2020-04-16 | 2021-10-21 | Bim Kemi Ab | Delignification process |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE1010679A3 (en) * | 1996-10-11 | 1998-11-03 | Solvay Interox | Delignification process and laundering pulp chemicals. |
JP2002266272A (en) * | 2001-03-12 | 2002-09-18 | Nippon Paper Industries Co Ltd | Method for bleaching cellulosic fibrous material pulp |
US6743332B2 (en) * | 2001-05-16 | 2004-06-01 | Weyerhaeuser Company | High temperature peroxide bleaching of mechanical pulps |
KR100547491B1 (en) * | 2005-04-27 | 2006-01-31 | 이권혁 | The production method and pulp maked bamboos |
US9512563B2 (en) | 2009-05-28 | 2016-12-06 | Gp Cellulose Gmbh | Surface treated modified cellulose from chemical kraft fiber and methods of making and using same |
US9511167B2 (en) | 2009-05-28 | 2016-12-06 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US9512237B2 (en) | 2009-05-28 | 2016-12-06 | Gp Cellulose Gmbh | Method for inhibiting the growth of microbes with a modified cellulose fiber |
MY182098A (en) * | 2012-09-27 | 2021-01-18 | Andritz Inc | Chemical treatment of lignocellulosic fiber bundle material,and methods and systems relating thereto |
US10151064B2 (en) | 2013-02-08 | 2018-12-11 | Gp Cellulose Gmbh | Softwood kraft fiber having an improved α-cellulose content and its use in the production of chemical cellulose products |
BR112015019882A2 (en) | 2013-03-14 | 2017-07-18 | Gp Cellulose Gmbh | oxidized bleached kraft fiber and methods for making kraft pulp and softwood kraft fiber and for bleaching multi-stage bleaching cellulose kraft pulp |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3507744A (en) * | 1966-04-01 | 1970-04-21 | Kimberly Clark Co | Wood pulp bleaching process utilizing peroxide pyrophosphate high concentration compositions |
DE2022866A1 (en) * | 1969-05-13 | 1970-12-23 | Mo Och Domsjoe Ab | Method of treating cellulosic material |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2742262C2 (en) * | 1977-09-20 | 1982-06-09 | Degussa Ag, 6000 Frankfurt | Process for the production of a medium to high viscosity softwood sulphite pulp |
FR2520397A1 (en) * | 1982-01-28 | 1983-07-29 | Centre Tech Ind Papier | PROCESS FOR TREATING CHEMICAL PAPER PASTES |
FR2557605B1 (en) * | 1983-12-29 | 1987-12-11 | Atochem | PROCESS FOR BLEACHING PAPER PULP BY HYDROGEN PEROXIDE |
JPH0364589A (en) * | 1989-07-28 | 1991-03-19 | Mitsubishi Gas Chem Co Inc | Bleaching of chemical pulp |
-
1991
- 1991-04-30 SE SE9101301A patent/SE470065C/en not_active IP Right Cessation
-
1992
- 1992-04-08 EP EP94203640A patent/EP0679760B1/en not_active Expired - Lifetime
- 1992-04-08 EP EP92201005A patent/EP0511695B2/en not_active Expired - Lifetime
- 1992-04-08 ES ES92201005T patent/ES2091395T3/en not_active Expired - Lifetime
- 1992-04-08 AT AT92201005T patent/ATE141971T1/en not_active IP Right Cessation
- 1992-04-08 DE DE69227640T patent/DE69227640T2/en not_active Expired - Fee Related
- 1992-04-08 DE DE69213080T patent/DE69213080D1/en not_active Expired - Lifetime
- 1992-04-08 AT AT94203640T patent/ATE173518T1/en not_active IP Right Cessation
- 1992-04-23 NZ NZ242465A patent/NZ242465A/en unknown
- 1992-04-27 FI FI921886A patent/FI111964B/en active
- 1992-04-27 CA CA002067296A patent/CA2067296C/en not_active Expired - Fee Related
- 1992-04-28 MX MX9201966A patent/MX9201966A/en unknown
- 1992-04-28 BR BR929201554A patent/BR9201554A/en not_active IP Right Cessation
- 1992-04-28 JP JP4134325A patent/JP2592747B2/en not_active Expired - Fee Related
- 1992-04-28 ZA ZA923073A patent/ZA923073B/en unknown
- 1992-04-29 NO NO19921671A patent/NO180495C/en not_active IP Right Cessation
- 1992-04-29 RU SU925011770A patent/RU2039141C1/en not_active IP Right Cessation
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3507744A (en) * | 1966-04-01 | 1970-04-21 | Kimberly Clark Co | Wood pulp bleaching process utilizing peroxide pyrophosphate high concentration compositions |
DE2022866A1 (en) * | 1969-05-13 | 1970-12-23 | Mo Och Domsjoe Ab | Method of treating cellulosic material |
Non-Patent Citations (1)
Title |
---|
WORLD PATENTS INDEX LATEST Week 9118, Derwent Publications Ltd., London, GB; AN 91-127527 & JP-A-3 064 589 (MITSUBISHI GAS CHEM KK) 19 March 1991 * |
Cited By (36)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6547923B1 (en) | 1989-05-10 | 2003-04-15 | Andritz Oy | Process for bleaching medium consistency pulp with ozone using a pressurized fluidizing mixer |
US6398908B1 (en) | 1991-04-30 | 2002-06-04 | Eka Nobel Ab | Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound |
WO1994010374A1 (en) * | 1992-10-26 | 1994-05-11 | Sca-Wifsta-Östrand Ab | Method for peroxide bleaching of sulphate pulp |
EP0595386A1 (en) * | 1992-10-29 | 1994-05-04 | Eka Nobel Ab | Process for bleaching of lignocellulose-containing pulp |
WO1994011569A1 (en) * | 1992-11-11 | 1994-05-26 | Mo Och Domsjö Aktiebolag | A method in delignifying and/or bleaching of cellulose pulp |
US6007678A (en) * | 1992-11-27 | 1999-12-28 | Eka Nobel Ab | Process for delignification of lignocellulose-containing pulp with an organic peracid or salts thereof |
EP0622491A2 (en) * | 1993-04-20 | 1994-11-02 | Eka Nobel Ab | Method for bleaching lignocellulose-containing pulp |
EP0622491A3 (en) * | 1993-04-20 | 1995-04-12 | Eka Nobel Ab | Method for bleaching lignocellulose-containing pulp. |
US5571377A (en) * | 1993-06-08 | 1996-11-05 | Kvaerner Pulping Technologies Ab | Process for peroxide bleaching of chemical pulp in a pressurized bleach vessel |
US6605181B1 (en) * | 1993-10-01 | 2003-08-12 | Kvaerner Pulping Aktiebolag | Peroxide bleach sequence including an acidic bleach stage and including a wash stage |
BE1007757A3 (en) * | 1993-11-10 | 1995-10-17 | Solvay Interox | Method of laundering of chemical pulp. |
WO1995013420A1 (en) * | 1993-11-10 | 1995-05-18 | Solvay Interox (Société Anonyme) | Method of bleaching chemical paper pulp |
WO1996012063A1 (en) * | 1994-10-13 | 1996-04-25 | Ahlstrom Machinery Oy | Method for removal of hexenuronic acid groups in cellulose pulp by heat treatment |
US6776876B1 (en) | 1994-10-13 | 2004-08-17 | Andritz Oy | Method of treating cellulosic pulp to remove hexenuronic acid |
DE19516151A1 (en) * | 1995-05-03 | 1996-11-07 | Sven Siegle | Process for the production of a pulp from cellulosic material, the pulp itself and its use |
US6183597B1 (en) | 1995-05-03 | 2001-02-06 | Natural Pulping Ag | Method of producing a pulp from cellulosic material using formic acid and hydrogen peroxide |
US6306253B2 (en) | 1995-10-20 | 2001-10-23 | Andritz-Ahlstrom Oy | Acid treatment of pulp at high temperature prior to chlorine dioxide bleaching |
WO1997015713A1 (en) * | 1995-10-20 | 1997-05-01 | Ahlstrom Machinery Oy | Acid treatment of pulp at high temperature in connection with bleaching |
US6120556A (en) * | 1996-06-21 | 2000-09-19 | Nippon Peroxide Co., Ltd. | Stabilizing agent for peroxide-bleaching procedure and methods of bleaching a fiber material by using same |
EP0905307A1 (en) * | 1997-08-25 | 1999-03-31 | Praxair Technology, Inc. | Method for applying ozone in ECF bleaching |
US9909257B2 (en) | 2009-05-28 | 2018-03-06 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US9777432B2 (en) | 2009-05-28 | 2017-10-03 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
USRE49570E1 (en) | 2009-05-28 | 2023-07-04 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US9926666B2 (en) | 2009-05-28 | 2018-03-27 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US11111628B2 (en) | 2009-05-28 | 2021-09-07 | Gp Cellulose Gmbh | Modified cellulose from chemical kraft fiber and methods of making and using the same |
US9719208B2 (en) | 2011-05-23 | 2017-08-01 | Gp Cellulose Gmbh | Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same |
US10995453B2 (en) | 2012-01-12 | 2021-05-04 | Gp Cellulose Gmbh | Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same |
US10597819B2 (en) | 2012-01-12 | 2020-03-24 | Gp Cellulose Gmbh | Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same |
US9617686B2 (en) | 2012-04-18 | 2017-04-11 | Gp Cellulose Gmbh | Use of surfactant to treat pulp and improve the incorporation of kraft pulp into fiber for the production of viscose and other secondary fiber products |
US10407830B2 (en) | 2012-04-18 | 2019-09-10 | Gp Cellulose Gmbh | Use of surfactant to treat pulp and improve the incorporation of kraft pulp into fiber for the production of viscose and other secondary fiber products |
US10753043B2 (en) | 2013-03-15 | 2020-08-25 | Gp Cellulose Gmbh | Low viscosity kraft fiber having an enhanced carboxyl content and methods of making and using the same |
US10550516B2 (en) | 2013-03-15 | 2020-02-04 | Gp Cellulose Gmbh | Low viscosity kraft fiber having an enhanced carboxyl content and methods of making and using the same |
US9951470B2 (en) | 2013-03-15 | 2018-04-24 | Gp Cellulose Gmbh | Low viscosity kraft fiber having an enhanced carboxyl content and methods of making and using the same |
WO2017055504A1 (en) * | 2015-09-30 | 2017-04-06 | Imerys Minerals Limited | Methods for bleaching aqueous pulps and compositions for use in these methods |
US10865519B2 (en) | 2016-11-16 | 2020-12-15 | Gp Cellulose Gmbh | Modified cellulose from chemical fiber and methods of making and using the same |
WO2021209586A1 (en) * | 2020-04-16 | 2021-10-21 | Bim Kemi Ab | Delignification process |
Also Published As
Publication number | Publication date |
---|---|
NO180495B (en) | 1997-01-20 |
AU1514992A (en) | 1993-03-11 |
CA2067296C (en) | 1997-03-04 |
CA2067296A1 (en) | 1992-10-31 |
FI921886A (en) | 1992-10-31 |
NO921671L (en) | 1992-11-02 |
ES2091395T3 (en) | 1996-11-01 |
SE470065B (en) | 1993-11-01 |
RU2039141C1 (en) | 1995-07-09 |
DE69213080D1 (en) | 1996-10-02 |
DE69227640T2 (en) | 1999-05-06 |
SE470065C (en) | 1996-01-15 |
JP2592747B2 (en) | 1997-03-19 |
ZA923073B (en) | 1992-12-30 |
MX9201966A (en) | 1992-11-01 |
DE69227640D1 (en) | 1998-12-24 |
NO180495C (en) | 2003-06-06 |
EP0511695B2 (en) | 2004-06-02 |
EP0511695B1 (en) | 1996-08-28 |
SE9101301L (en) | 1992-10-31 |
BR9201554A (en) | 1992-12-01 |
JPH05148784A (en) | 1993-06-15 |
EP0679760B1 (en) | 1998-11-18 |
FI111964B (en) | 2003-10-15 |
AU651192B2 (en) | 1994-07-14 |
ATE141971T1 (en) | 1996-09-15 |
NZ242465A (en) | 1993-12-23 |
FI921886A0 (en) | 1992-04-27 |
SE9101301D0 (en) | 1991-04-30 |
NO921671D0 (en) | 1992-04-29 |
ATE173518T1 (en) | 1998-12-15 |
EP0679760A1 (en) | 1995-11-02 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0511695B1 (en) | Process for bleaching of lignocellulose-containing pulp | |
US6398908B1 (en) | Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound | |
EP0512590B1 (en) | Process for bleaching of lignocellulose-containing material | |
US5310458A (en) | Process for bleaching lignocellulose-containing pulps | |
JP2864167B2 (en) | Delignification method of pulp containing lignocellulose. | |
EP0456626B1 (en) | Process for bleaching of lignocellulose-containing material | |
EP0622491B2 (en) | Method for bleaching lignocellulose-containing pulp | |
CA1070909A (en) | Nitrogen dioxide-oxygen delignification | |
EP0670929B2 (en) | Process for bleaching of lignocellulose-containing pulp | |
EP0595386B1 (en) | Process for bleaching of chemically digested lignocellulose-containing pulp | |
CA2139246A1 (en) | Process for bleaching of lignocellulose-containing pulp | |
JP3697335B2 (en) | Treatment of chemical pulp with acidic bleached white water |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19920408 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE ES FR IT LI PT SE |
|
17Q | First examination report despatched |
Effective date: 19921204 |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: EKA CHEMICALS AB |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AT BE CH DE ES FR IT LI PT SE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED. Effective date: 19960828 Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19960828 Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 19960828 Ref country code: LI Effective date: 19960828 Ref country code: CH Effective date: 19960828 |
|
REF | Corresponds to: |
Ref document number: 141971 Country of ref document: AT Date of ref document: 19960915 Kind code of ref document: T |
|
XX | Miscellaneous (additional remarks) |
Free format text: TEILANMELDUNG 94203640.1 EINGEREICHT AM 08/04/92. |
|
ET | Fr: translation filed | ||
REF | Corresponds to: |
Ref document number: 69213080 Country of ref document: DE Date of ref document: 19961002 |
|
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FG2A Ref document number: 2091395 Country of ref document: ES Kind code of ref document: T3 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19961129 |
|
SC4A | Pt: translation is available |
Free format text: 960829 AVAILABILITY OF NATIONAL TRANSLATION |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
PLBQ | Unpublished change to opponent data |
Free format text: ORIGINAL CODE: EPIDOS OPPO |
|
PLBI | Opposition filed |
Free format text: ORIGINAL CODE: 0009260 |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
26 | Opposition filed |
Opponent name: KEMIRA CHEMICALS OY Effective date: 19970527 |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBO | Opposition rejected |
Free format text: ORIGINAL CODE: EPIDOS REJO |
|
APAC | Appeal dossier modified |
Free format text: ORIGINAL CODE: EPIDOS NOAPO |
|
APAE | Appeal reference modified |
Free format text: ORIGINAL CODE: EPIDOS REFNO |
|
APAC | Appeal dossier modified |
Free format text: ORIGINAL CODE: EPIDOS NOAPO |
|
APAC | Appeal dossier modified |
Free format text: ORIGINAL CODE: EPIDOS NOAPO |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: PT Payment date: 20030402 Year of fee payment: 12 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20030408 Year of fee payment: 12 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: AT Payment date: 20030411 Year of fee payment: 12 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: ES Payment date: 20030429 Year of fee payment: 12 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: BE Payment date: 20030619 Year of fee payment: 12 |
|
PUAH | Patent maintained in amended form |
Free format text: ORIGINAL CODE: 0009272 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: PATENT MAINTAINED AS AMENDED |
|
27A | Patent maintained in amended form |
Effective date: 20040602 |
|
AK | Designated contracting states |
Kind code of ref document: B2 Designated state(s): AT BE CH DE ES FR IT LI PT SE |
|
XX | Miscellaneous (additional remarks) |
Free format text: TEILANMELDUNG 94203640.1 EINGEREICHT AM 08/04/92. |
|
REG | Reference to a national code |
Ref country code: SE Ref legal event code: RPEO |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20040913 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: PT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20041015 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
EN | Fr: translation not filed | ||
APAH | Appeal reference modified |
Free format text: ORIGINAL CODE: EPIDOSCREFNO |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: BE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20040430 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: SE Payment date: 20090429 Year of fee payment: 18 |
|
EUG | Se: european patent has lapsed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20100409 |