CA2202445A1 - Process for the delignification and/or bleaching of a paper pulp - Google Patents
Process for the delignification and/or bleaching of a paper pulpInfo
- Publication number
- CA2202445A1 CA2202445A1 CA 2202445 CA2202445A CA2202445A1 CA 2202445 A1 CA2202445 A1 CA 2202445A1 CA 2202445 CA2202445 CA 2202445 CA 2202445 A CA2202445 A CA 2202445A CA 2202445 A1 CA2202445 A1 CA 2202445A1
- Authority
- CA
- Canada
- Prior art keywords
- acid
- process according
- pulp
- treatment
- peroxyacid
- 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.)
- Abandoned
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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
- D21C9/166—Bleaching ; Apparatus therefor with per compounds with peracids
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
Process for the improvement in the selectivity of the delignification and/or bleaching of a preferably chemical paper pulp by means of a peroxyacid, according to which the pulp is treated with an aqueous solution of this organic peroxyacid in the presence of at least one ancillary agent for viscosity protection, selected from inorganic acids of phosphorus and their alkali metal salts, preferably pyrophosphoric acid, sodium pyrophosphates and their ammonium salts.
Description
CA 0220244~ 1997-04-11 The invention relates to a process for improving the selectivity of the delignification and/or bleaching of a paper pulp comprising lignin, by means of an organic peroxyacid, in which the pulp is treated with the aid of an aqueous solution of this organic peroxyacid in the presence of an auxiliary.
It is known to apply to paper pulps, in particular chemical paper pulps obtained by cooking cellulose-based materials in the presence of chemical reactants, a succession of stages of delignifying and/or bleaching treatment, during which oxidizing chemical products are employed. The first stage of a sequence for bleaching chemical pulp is generally aimed at improving the delignification of the unbleached pulp directly originating from the cooking stage. This first delignifying stage is usually carried out on the unbleached pulp with chlorine applied in acidic medium, chlorine dioxide or with a combination of the two so as to bring about a reaction with the residual lignin in the pulp and to give rise to products which can be extracted from this pulp by solubilization during a subsequent stage of treatment.
For reasons related to the improvement of the environment, the chlorine-containing reactants are increasingly being replaced with chlorine-free reactants which are more favourable to the environment.
For example, in Japanese Patent Application 55/94811 the treatment of a kraft pulp by delignification with oxygen is described, this process comprising the use of a peracetic acid stage in the presence of additives such as diethylenetriaminepentaacetic acid (DTPA).
According to European Patent Application No.
EP-A-578 305 the paper pulp is treated with a peroxyacid in the presence of a stabilizing agent chosen from phosphonic acids and their salts, and this has the effect of improving the selectivity of the delignification.
In general, the presence of a chelating and/or stabilizing agent in the delignification stage makes it possible to avoid a considerable degradation of the CA 0220244~ 1997-04-11 cellulose chains in the pulp, this degradation being responsible for a decrease in its viscosity. Although the effect of these protective agents is undeniable, it does not reach a sufficient level, especially for the production of high-quality pulp.
After the delignifying stage the pulps are usually bleached by means of one or several oxidizing substances chosen especially from chlorine dioxide, ozone, hydrogen peroxide and peracetic acid. These bleaching operations are generally carried out in the presence of protecting agents for cellulose, in order to avoid the degradation of the latter, like, for example, magnesium sulphate.
However, the processes described in the state of the art do not make it possible to obtain paper pulps of sufficiently high quality because of a degree of degradation of the cellulose which is still too high.
The Applicant Company has therefore sought to remedy this disadvantage.
The subject-matter of the present invention is a process for delignification and/or bleaching of a paper pulp, comprising at least one stage of treatment by means of an organic peroxyacid, characterized in that the said treatment is performed in the presence of one or several ancillary agents for protecting the viscosity of the pulp, which are chosen from the inorganic acids of phosphorus and their salts.
Inorganic acids of phosphorus denote acids containing no carbon-phosphorus bonds; there may be mentioned, for example, phosphorous acid, phosphoric acid, pyrophosphoric acid and polyphosphoric acids.
A salt of an inorganic acid of phosphorus denotes an acid of phosphorus in which one or more of these acidic functional groups is (are) converted into salt, and especially alkali metal salts.
The process which is the subject-matter of the present invention can be carried out with any types of paper pulp5, regardless of whether they are chemical, CA 0220244~ 1997-04- 11 mechanical or recycled pulps like, for example, so-called "kraft" pulps.
Paper pulp denotes any material containing cellulose-based fibres which are obtained from wood, regardless of whether they are so-called "coniferous"
species like, for example, the different varieties of pine, fir or spruce or else the so-called "deciduous~
species like, for example, the different varieties of hornbeam, aspen, beech, birch, poplar, oak or eucalyptus or mixtures thereof. These paper pulps can also be obtained from various so-called annual plants such as, for example, the different varieties of kenaf, jute, bamboo, reed, or from parts of plants such as, for example, cereal straw like wheat or rice straw or sugar cane bagasse. Paper pulps can also be obtained by reprocessing recovered papers such as newspapers, magazines, packaging cardboard, newsprint and writing paper and photocopying paper which forms, inter alia, office wastes, data processing printouts and broke from paper manufacture.
Organic peroxyacid denotes percarboxylic acids or polycarboxylic acids in which at least one carboxyl functional group is peroxidized to a carboxylic group -C(O)-O-OH. Examples of such peroxyacids which may be mentioned are in particular peralkanoic acids containing from 1 to 10 carbon atoms, mono-peroxyalkanedioic acids containing from 1 to 10 carbon atoms, monoperoxyalkenedioic acids containing from 1 to 10 carbon atoms, diperoxyalkanedioic acids containing from 1 to 10 carbon atoms, peroxyaryldicarboxylic acids or diperoxyaryl-dicarboxylic acids in which the aryl group represents a phenyl or naphthyl radical. Examples of such aromatic acids which may be mentioned are peroxybenzoic acid, monoperoxyphthalic acids, diperoxy-phthalic acids or peroxynaphthoic acids.
In a first preferred embodiment of theinvention the ancillary agent for protecting the viscosity of the pulp is pyrophosphoric acid, sodium CA 0220244~ 1997-04-11 pyrophosphate, tripolyphosphoric acid or sodium tripolyphosphate.
In a second preferred embodiment of the invention the organic peroxyacid is chosen from performic acid, peracetic acid, 1,6-diperoxyhexanedioic acid, 1,4-monoperoxybutenedioic acid, 1,4-monoperoxy-butanedioic acid and perbenzoic acid.
The peroxyacids are prepared according to methods which are known to a person skilled in the art.
In particular, peracetic acid is either obtained by reaction of an aqueous solution of hydrogen peroxide with acetic acid according to the equilibrium:
H202 + CH3C02H ~ CH3CO3H + H20 and it is then referred to by the expression peracetic acid "at equilibrium", or obtained by azeotropic distillation at reduced pressure of an aqueous mixture of hydrogen peroxide and acetic acid in the presence of an acidic catalyst, or of an aqueous solution of peracetic acid at equilibrium.
The peroxyacid employed may be either substantially pure or preferably in aqueous solution containing at least 4 ~ by weight of this peroxyacid, optionally mixed with the corresponding organic acid and/or hydrogen peroxide. Peracetic acid in aqueous solution is preferably employed, either as a mixture at equilibrium with hydrogen peroxide and acetic acid, or obtained by azeotropic distillation.
In a third preferred embodiment of the invention the organic peroxyacid is peracetic acid in aqueous solution containing at least 4 ~ by weight of the said peroxyacid and especially in aqueous solution at equilibrium, also containing hydrogen peroxide, such that the H202/peracetic acid weight ratio is higher than 0.5 and especially higher than 1.
Such solutions which are available commercially contain, for example, by weight:
.. .. . . . . .
CA 0220244~ l997-04-ll Peracetic6.2 ~ 4.2 ~ 15.2 ~ 5.2 ~ 15.6 ~ 16.5 ~ 4.4 %
acid Hydrogen22 ~28.5 ~ 23 % 14.1 ~ 14.6 ~10 ~ 37 peroxide This peroxyacid can also be generated in situ.
The solutions of peroxyacid may contain at least 0.1 % by weight of strong acid, such as, for example, sulphuric acid, nitric acid, phosphoric acid, methanesulphonic acid, or a mixture of these acids and at most approximately 3 ~ by weight. The peroxyacid may also be prepared by contact of a mixture of H2O2 and acid with a heterogeneous acid catalyst, for example a sulphonated polystyrene.
According to another embodiment of the invention sodium silicate and/or magnesium salts or magnesium compounds such as magnesia, magnesium carbonate, magnesium sulphate or magnesium chloride is (are) added to the paper pulp.
The treatment with this peroxyacid will be preferably performed in a temperature range of between 20~C and 140~C, especially between 50 and 120~C and preferably between 70~ and 90~C, but also under pressure, preferably lower than or equal to approximately 10 bars, and especially lower than 5 bars. The reactor may, in particular, be pressurized with air or with a gas containing more than 21 % of oxygen and especially at least 80 ~ of oxygen.
The pH of the stage of treatment with the peroxyacid may be acidic, neutral or alkaline ! but preferably a pH of between 5 and 9, and more preferably between 7 and 8.5, will be chosen. The duration of the treatment will be shorter than 4 hours, preferably shorter than 2 hours and, especially, shorter than 60 minutes. In a preferred alternative form of the invention the treatment with the peroxyacid is CA 0220244~ 1997-04- 11 performed firstly at a pH of between 2 and 7, especially between 4 and 6, for less than 4 hours, especially less than two hours, and preferably for one hour or less, at a temperature of between 40 and 100~C, and then the pulp is alkalified without intermediate washing to a pH of between 8 and 12, especially between 9.5 and 12, and left for less than 4 hours at a temperature of between 60 and 120~C.
In general, quantities of at least 3 kg of peroxyacid per ton of pulp, expressed as dry material and, preferably, of at least 8 kg per ton of paper pulp expressed as dry material will be employed.
The treatment may be performed in the presence of protective agents for cellulose such as magnesium salts and alkali and alkaline-earth metal silicates.
In general it is not necessary to precede the organic peroxyacid treatment with a washing or a stage of decontaminating pretreatment by means of an acidic aqueous solution. This washing or this stage are for the purpose of extracting from the pulp the impurities which are present in the form of metal ions which are usually detrimental to the good progress of the bleaching and/or delignification operations.
The delignification according to the invention with the aid of a peroxyacid is generally a complement to the usual stages of delignification and/or bleaching of a paper pulp such as, for example, the oxygen delignification with ozone or with chlorine dioxide. It is also possible to employ the peracetic acid present in the bleaching liquid (peroxyacid residue) for a treatment upstream of the bleaching, for example a delignification stage.
According to a preferred embodiment of the invention the peroxyacid originates from a washing solution in a subsequent stage of the process for treatment of the paper pulp.
The invention will be understood better-with the aid of the following examples of embodiment which are given without any limitation being implied.
CA 0220244~ 1997-04- 11 Ex~m~le 1 A kraft pulp with an initial kappa number of 24.2 and with a viscosity, expressed as degree of polymerization (Dp), of 1480 is treated with peracetic acid at equilibrium. The peracetic acid and hydrogen peroxide charges are equal to 3 ~ by weight relative to the dry pulp; the pulp is left for 2 hours at 90~C in contact with 0.5 ~ by weight, relative to the pulp, of ancillary agent for viscosity protection. After this treatment the pulp is washed with water and then treated for 1 hour at 90~ in a basic medium in contact with 3 ~ relative to the dry pulp, of soda, and this finally washed again with water. The values of the characteristics of the pulp thus obtained are the following:
Table 1 Complexant K No. Dp (degree of polymerization) - 13.8 1016 EDTA 16.1 1009 DTPA 14.5 1055 DEQUEST 2010 13.4 1350 pyrophosphate 12.9 1300 1) It is found that sodium pyrophosphate permits a better delignification of the pulp in comparison with the control test, without appreciable loss of the physical properties of the pulp, expressed as Dp.
It is known to apply to paper pulps, in particular chemical paper pulps obtained by cooking cellulose-based materials in the presence of chemical reactants, a succession of stages of delignifying and/or bleaching treatment, during which oxidizing chemical products are employed. The first stage of a sequence for bleaching chemical pulp is generally aimed at improving the delignification of the unbleached pulp directly originating from the cooking stage. This first delignifying stage is usually carried out on the unbleached pulp with chlorine applied in acidic medium, chlorine dioxide or with a combination of the two so as to bring about a reaction with the residual lignin in the pulp and to give rise to products which can be extracted from this pulp by solubilization during a subsequent stage of treatment.
For reasons related to the improvement of the environment, the chlorine-containing reactants are increasingly being replaced with chlorine-free reactants which are more favourable to the environment.
For example, in Japanese Patent Application 55/94811 the treatment of a kraft pulp by delignification with oxygen is described, this process comprising the use of a peracetic acid stage in the presence of additives such as diethylenetriaminepentaacetic acid (DTPA).
According to European Patent Application No.
EP-A-578 305 the paper pulp is treated with a peroxyacid in the presence of a stabilizing agent chosen from phosphonic acids and their salts, and this has the effect of improving the selectivity of the delignification.
In general, the presence of a chelating and/or stabilizing agent in the delignification stage makes it possible to avoid a considerable degradation of the CA 0220244~ 1997-04-11 cellulose chains in the pulp, this degradation being responsible for a decrease in its viscosity. Although the effect of these protective agents is undeniable, it does not reach a sufficient level, especially for the production of high-quality pulp.
After the delignifying stage the pulps are usually bleached by means of one or several oxidizing substances chosen especially from chlorine dioxide, ozone, hydrogen peroxide and peracetic acid. These bleaching operations are generally carried out in the presence of protecting agents for cellulose, in order to avoid the degradation of the latter, like, for example, magnesium sulphate.
However, the processes described in the state of the art do not make it possible to obtain paper pulps of sufficiently high quality because of a degree of degradation of the cellulose which is still too high.
The Applicant Company has therefore sought to remedy this disadvantage.
The subject-matter of the present invention is a process for delignification and/or bleaching of a paper pulp, comprising at least one stage of treatment by means of an organic peroxyacid, characterized in that the said treatment is performed in the presence of one or several ancillary agents for protecting the viscosity of the pulp, which are chosen from the inorganic acids of phosphorus and their salts.
Inorganic acids of phosphorus denote acids containing no carbon-phosphorus bonds; there may be mentioned, for example, phosphorous acid, phosphoric acid, pyrophosphoric acid and polyphosphoric acids.
A salt of an inorganic acid of phosphorus denotes an acid of phosphorus in which one or more of these acidic functional groups is (are) converted into salt, and especially alkali metal salts.
The process which is the subject-matter of the present invention can be carried out with any types of paper pulp5, regardless of whether they are chemical, CA 0220244~ 1997-04- 11 mechanical or recycled pulps like, for example, so-called "kraft" pulps.
Paper pulp denotes any material containing cellulose-based fibres which are obtained from wood, regardless of whether they are so-called "coniferous"
species like, for example, the different varieties of pine, fir or spruce or else the so-called "deciduous~
species like, for example, the different varieties of hornbeam, aspen, beech, birch, poplar, oak or eucalyptus or mixtures thereof. These paper pulps can also be obtained from various so-called annual plants such as, for example, the different varieties of kenaf, jute, bamboo, reed, or from parts of plants such as, for example, cereal straw like wheat or rice straw or sugar cane bagasse. Paper pulps can also be obtained by reprocessing recovered papers such as newspapers, magazines, packaging cardboard, newsprint and writing paper and photocopying paper which forms, inter alia, office wastes, data processing printouts and broke from paper manufacture.
Organic peroxyacid denotes percarboxylic acids or polycarboxylic acids in which at least one carboxyl functional group is peroxidized to a carboxylic group -C(O)-O-OH. Examples of such peroxyacids which may be mentioned are in particular peralkanoic acids containing from 1 to 10 carbon atoms, mono-peroxyalkanedioic acids containing from 1 to 10 carbon atoms, monoperoxyalkenedioic acids containing from 1 to 10 carbon atoms, diperoxyalkanedioic acids containing from 1 to 10 carbon atoms, peroxyaryldicarboxylic acids or diperoxyaryl-dicarboxylic acids in which the aryl group represents a phenyl or naphthyl radical. Examples of such aromatic acids which may be mentioned are peroxybenzoic acid, monoperoxyphthalic acids, diperoxy-phthalic acids or peroxynaphthoic acids.
In a first preferred embodiment of theinvention the ancillary agent for protecting the viscosity of the pulp is pyrophosphoric acid, sodium CA 0220244~ 1997-04-11 pyrophosphate, tripolyphosphoric acid or sodium tripolyphosphate.
In a second preferred embodiment of the invention the organic peroxyacid is chosen from performic acid, peracetic acid, 1,6-diperoxyhexanedioic acid, 1,4-monoperoxybutenedioic acid, 1,4-monoperoxy-butanedioic acid and perbenzoic acid.
The peroxyacids are prepared according to methods which are known to a person skilled in the art.
In particular, peracetic acid is either obtained by reaction of an aqueous solution of hydrogen peroxide with acetic acid according to the equilibrium:
H202 + CH3C02H ~ CH3CO3H + H20 and it is then referred to by the expression peracetic acid "at equilibrium", or obtained by azeotropic distillation at reduced pressure of an aqueous mixture of hydrogen peroxide and acetic acid in the presence of an acidic catalyst, or of an aqueous solution of peracetic acid at equilibrium.
The peroxyacid employed may be either substantially pure or preferably in aqueous solution containing at least 4 ~ by weight of this peroxyacid, optionally mixed with the corresponding organic acid and/or hydrogen peroxide. Peracetic acid in aqueous solution is preferably employed, either as a mixture at equilibrium with hydrogen peroxide and acetic acid, or obtained by azeotropic distillation.
In a third preferred embodiment of the invention the organic peroxyacid is peracetic acid in aqueous solution containing at least 4 ~ by weight of the said peroxyacid and especially in aqueous solution at equilibrium, also containing hydrogen peroxide, such that the H202/peracetic acid weight ratio is higher than 0.5 and especially higher than 1.
Such solutions which are available commercially contain, for example, by weight:
.. .. . . . . .
CA 0220244~ l997-04-ll Peracetic6.2 ~ 4.2 ~ 15.2 ~ 5.2 ~ 15.6 ~ 16.5 ~ 4.4 %
acid Hydrogen22 ~28.5 ~ 23 % 14.1 ~ 14.6 ~10 ~ 37 peroxide This peroxyacid can also be generated in situ.
The solutions of peroxyacid may contain at least 0.1 % by weight of strong acid, such as, for example, sulphuric acid, nitric acid, phosphoric acid, methanesulphonic acid, or a mixture of these acids and at most approximately 3 ~ by weight. The peroxyacid may also be prepared by contact of a mixture of H2O2 and acid with a heterogeneous acid catalyst, for example a sulphonated polystyrene.
According to another embodiment of the invention sodium silicate and/or magnesium salts or magnesium compounds such as magnesia, magnesium carbonate, magnesium sulphate or magnesium chloride is (are) added to the paper pulp.
The treatment with this peroxyacid will be preferably performed in a temperature range of between 20~C and 140~C, especially between 50 and 120~C and preferably between 70~ and 90~C, but also under pressure, preferably lower than or equal to approximately 10 bars, and especially lower than 5 bars. The reactor may, in particular, be pressurized with air or with a gas containing more than 21 % of oxygen and especially at least 80 ~ of oxygen.
The pH of the stage of treatment with the peroxyacid may be acidic, neutral or alkaline ! but preferably a pH of between 5 and 9, and more preferably between 7 and 8.5, will be chosen. The duration of the treatment will be shorter than 4 hours, preferably shorter than 2 hours and, especially, shorter than 60 minutes. In a preferred alternative form of the invention the treatment with the peroxyacid is CA 0220244~ 1997-04- 11 performed firstly at a pH of between 2 and 7, especially between 4 and 6, for less than 4 hours, especially less than two hours, and preferably for one hour or less, at a temperature of between 40 and 100~C, and then the pulp is alkalified without intermediate washing to a pH of between 8 and 12, especially between 9.5 and 12, and left for less than 4 hours at a temperature of between 60 and 120~C.
In general, quantities of at least 3 kg of peroxyacid per ton of pulp, expressed as dry material and, preferably, of at least 8 kg per ton of paper pulp expressed as dry material will be employed.
The treatment may be performed in the presence of protective agents for cellulose such as magnesium salts and alkali and alkaline-earth metal silicates.
In general it is not necessary to precede the organic peroxyacid treatment with a washing or a stage of decontaminating pretreatment by means of an acidic aqueous solution. This washing or this stage are for the purpose of extracting from the pulp the impurities which are present in the form of metal ions which are usually detrimental to the good progress of the bleaching and/or delignification operations.
The delignification according to the invention with the aid of a peroxyacid is generally a complement to the usual stages of delignification and/or bleaching of a paper pulp such as, for example, the oxygen delignification with ozone or with chlorine dioxide. It is also possible to employ the peracetic acid present in the bleaching liquid (peroxyacid residue) for a treatment upstream of the bleaching, for example a delignification stage.
According to a preferred embodiment of the invention the peroxyacid originates from a washing solution in a subsequent stage of the process for treatment of the paper pulp.
The invention will be understood better-with the aid of the following examples of embodiment which are given without any limitation being implied.
CA 0220244~ 1997-04- 11 Ex~m~le 1 A kraft pulp with an initial kappa number of 24.2 and with a viscosity, expressed as degree of polymerization (Dp), of 1480 is treated with peracetic acid at equilibrium. The peracetic acid and hydrogen peroxide charges are equal to 3 ~ by weight relative to the dry pulp; the pulp is left for 2 hours at 90~C in contact with 0.5 ~ by weight, relative to the pulp, of ancillary agent for viscosity protection. After this treatment the pulp is washed with water and then treated for 1 hour at 90~ in a basic medium in contact with 3 ~ relative to the dry pulp, of soda, and this finally washed again with water. The values of the characteristics of the pulp thus obtained are the following:
Table 1 Complexant K No. Dp (degree of polymerization) - 13.8 1016 EDTA 16.1 1009 DTPA 14.5 1055 DEQUEST 2010 13.4 1350 pyrophosphate 12.9 1300 1) It is found that sodium pyrophosphate permits a better delignification of the pulp in comparison with the control test, without appreciable loss of the physical properties of the pulp, expressed as Dp.
2) It is also found that the chelating agents for the metal cations which have an aminocarboxylic structure and are conventionally employed in the treatments with hydrogen peroxide, such as EDTA (ethylenediaminetetraacetic acid) and DTPA
CA 0220244~ 1997-04-11 (diethylenetriaminepentaacetic acid) have an unfavourable effect on delignification.
CA 0220244~ 1997-04-11 (diethylenetriaminepentaacetic acid) have an unfavourable effect on delignification.
3) Finally, it is found that sodium pyrophosphate can be advantageously employed instead of a solution containing 40 ~ of l-hydroxyethylideneamino-1-dimethylenephosphonic acid HEDP (such as, for example, the product sold under the trade name Dequest 2010).
Examples 2 to 5 The following various inorganic polyphosphates were employed in the examples below:
- sodium polyphosphate, pyrophosphoric acid, pentasodium tripolyphosphate and sodium hexa-metaphosphate.
The pulp treated had the following characteristic:
- Kappa number: 24.2 - Degree of polymerization: 1510.
The treatment was carried out in the following manner with the following solution:
- 3 ~ by weight of peracetic acid, - 3.4 ~ by weight of hydrogen peroxide.
This solution was heated to a temperature of 90~C, the treatment taking place for 3 hours with a pulp consistency of 10 ~. Table 2 below summarizes the various values obtained as a function of the percentage of ancillary agent for viscosity protection by volume, of the kappa number, of the degree of polymerization, of the percentage of hydrogen peroxide consumed, and of the percentage of peracetic acid consumed.
CA 0220244~ 1997-04- 11 g T~hle 2 Additive ~ ~nri 1 1 ~ry Kappa Dpv ~ ~2o2 ~ PAA
agent No. cons.cons.
Control 0 10.1 504 1.7 3 Example 2 Na pyroph~sph~te 0.1 10.3 984 1.6 3 Na pyrophosphate 0.2 10.4 1228 1.1 3 Na pyrophosphate 0.4 10.6 1367 0.9 3 Na pyrophosphate 0.5 10.6 1324 1.2 3 Na pyroph~sph~te 0.7 10.3 1318 1.1 3 Example 3 Pyrophosphoric acid 0.5 9.1 1165 1.4 3 Example 4 Na tripolyphosphate 0.5 10.5 1327 1 3 Example 5 Na hexamet~ph~sph~te 0.5 9 1240 1.2 3 ~xample 6 A treatment is carried out the conditions of which are summarized in Table 3 below. The treatment is carried out with a charge of 3 ~ by weight of peracetic acid and 3.3 ~ of hydrogen peroxide relative to the dry 10 pulp.
Table 3 Conditions Treatment with 0.5 ~ Control (without Na pyrophosphate pyrophosphate) Kappa No. Dpv Kappa No. Dpv soo, 3 hours10.3 1324 10.1 504 90~, 2 hours12.8 1300 13.8 1000 110~, 1 hour14.9 1244 15.6 1127 In the examples shown above it will be noted that all the. polyphosphates tested and which are soluble in the bleaching solution give good results.
Where sodium pyrophosphate is concerned, the optimum quantity of this material lies between 0.2 ~ and 0.5 by weight relative to the dry pulp.
CA 0220244~ 1997-04-11 Example 7 A chemical pulp of initial kappa number (KNo.) equal to 24 and with a degree of polymerization (Dp) equal to 1510 is treated at 90~C for l hour at pH = 4 in the presence of sodium pyrophosphate with an aqueous solution at equilibrium of peracetic acid and of hydrogen peroxide; the peracetic acid and hydrogen peroxide charges are 3 % and 3.3 ~ by weight relative to the dry pulp, respectively; the sodium pyrophosphate charge is 0.5 ~.
The pulp is then divided into two portions.
The first portion is treated with approximately ~ of soda so that the pH rises to 10.-5 and the reaction is then continued for 2 hours.
The second portion (control) is washed with water and then treated with soda for 1 hour at 90~C.
The following results are obtained:
Table 4 Pulp before First portion Second portion treatment(test) after (control) after treatment treatment KNo. 24 6.2 14.4 Dp 1510 1124 1487 Example 8 When the procedure followed is analogous to Example 7 and when the stage of treatment of the first (test) part is modified by the extra addition of 0.2 ~
of magnesium sulphate the following results are obtained:
CA 0220244~ 1997-04-11 Table 5 Pulp before First portion Second portion treatment (test) after (control) after treatment treatment KNo.24.8 8.6 16.7 Dp1450 1195 1409 The results of Examples 7 and 8 show the additional advantage in treating with the peroxyacid firstly at acidic pH and in then raising the pH without any intermediate washing. This increases the delignification while preserving an acceptable degree of polymerization.
Examples 2 to 5 The following various inorganic polyphosphates were employed in the examples below:
- sodium polyphosphate, pyrophosphoric acid, pentasodium tripolyphosphate and sodium hexa-metaphosphate.
The pulp treated had the following characteristic:
- Kappa number: 24.2 - Degree of polymerization: 1510.
The treatment was carried out in the following manner with the following solution:
- 3 ~ by weight of peracetic acid, - 3.4 ~ by weight of hydrogen peroxide.
This solution was heated to a temperature of 90~C, the treatment taking place for 3 hours with a pulp consistency of 10 ~. Table 2 below summarizes the various values obtained as a function of the percentage of ancillary agent for viscosity protection by volume, of the kappa number, of the degree of polymerization, of the percentage of hydrogen peroxide consumed, and of the percentage of peracetic acid consumed.
CA 0220244~ 1997-04- 11 g T~hle 2 Additive ~ ~nri 1 1 ~ry Kappa Dpv ~ ~2o2 ~ PAA
agent No. cons.cons.
Control 0 10.1 504 1.7 3 Example 2 Na pyroph~sph~te 0.1 10.3 984 1.6 3 Na pyrophosphate 0.2 10.4 1228 1.1 3 Na pyrophosphate 0.4 10.6 1367 0.9 3 Na pyrophosphate 0.5 10.6 1324 1.2 3 Na pyroph~sph~te 0.7 10.3 1318 1.1 3 Example 3 Pyrophosphoric acid 0.5 9.1 1165 1.4 3 Example 4 Na tripolyphosphate 0.5 10.5 1327 1 3 Example 5 Na hexamet~ph~sph~te 0.5 9 1240 1.2 3 ~xample 6 A treatment is carried out the conditions of which are summarized in Table 3 below. The treatment is carried out with a charge of 3 ~ by weight of peracetic acid and 3.3 ~ of hydrogen peroxide relative to the dry 10 pulp.
Table 3 Conditions Treatment with 0.5 ~ Control (without Na pyrophosphate pyrophosphate) Kappa No. Dpv Kappa No. Dpv soo, 3 hours10.3 1324 10.1 504 90~, 2 hours12.8 1300 13.8 1000 110~, 1 hour14.9 1244 15.6 1127 In the examples shown above it will be noted that all the. polyphosphates tested and which are soluble in the bleaching solution give good results.
Where sodium pyrophosphate is concerned, the optimum quantity of this material lies between 0.2 ~ and 0.5 by weight relative to the dry pulp.
CA 0220244~ 1997-04-11 Example 7 A chemical pulp of initial kappa number (KNo.) equal to 24 and with a degree of polymerization (Dp) equal to 1510 is treated at 90~C for l hour at pH = 4 in the presence of sodium pyrophosphate with an aqueous solution at equilibrium of peracetic acid and of hydrogen peroxide; the peracetic acid and hydrogen peroxide charges are 3 % and 3.3 ~ by weight relative to the dry pulp, respectively; the sodium pyrophosphate charge is 0.5 ~.
The pulp is then divided into two portions.
The first portion is treated with approximately ~ of soda so that the pH rises to 10.-5 and the reaction is then continued for 2 hours.
The second portion (control) is washed with water and then treated with soda for 1 hour at 90~C.
The following results are obtained:
Table 4 Pulp before First portion Second portion treatment(test) after (control) after treatment treatment KNo. 24 6.2 14.4 Dp 1510 1124 1487 Example 8 When the procedure followed is analogous to Example 7 and when the stage of treatment of the first (test) part is modified by the extra addition of 0.2 ~
of magnesium sulphate the following results are obtained:
CA 0220244~ 1997-04-11 Table 5 Pulp before First portion Second portion treatment (test) after (control) after treatment treatment KNo.24.8 8.6 16.7 Dp1450 1195 1409 The results of Examples 7 and 8 show the additional advantage in treating with the peroxyacid firstly at acidic pH and in then raising the pH without any intermediate washing. This increases the delignification while preserving an acceptable degree of polymerization.
Claims (11)
1. Process for delignification and/or bleaching of a paper pulp, comprising at least one stage of treatment by means of an organic peroxyacid, characterized in that the said treatment is performed in the presence of one or several ancillary agents for protecting the viscosity of the pulp, which are chosen from the inorganic acids of phosphorus and their salts.
2. Process according to Claim 1, in which the ancillary agent for protecting the viscosity of the pulp is pyrophosphoric acid, sodium pyrophosphate, tripolyphosphoric acid or sodium tripolyphosphate.
3. Process according to either of Claims 1 and 2, in which the organic peroxyacid is chosen from performic acid, peracetic acid, 1,6-diperoxyhexanedioic acid, 1,4-monoperoxybutenedioic acid, 1,4-monoperoxy-butanedioic acid and perbenzoic acid.
4. Process according to Claim 3, in which the organic peroxyacid is peracetic acid in aqueous solution containing at least 4 % by weight of the said peroxyacid and especially in aqueous solution at equilibrium, also containing hydrogen peroxide, such that the H2O2/peracetic acid weight ratio is higher than 0.5 and especially higher than 1.
5. Process according to one of Claims 1 to 4, in which sodium silicate and/or magnesium salts or magnesium compounds such as magnesia, magnesium carbonate, magnesium sulphate or magnesium chloride is (are) added to the paper pulp during the said stage of treatment.
6. Process according to one of Claims 1 to 5, implemented at a temperature of between 20°C and 140°C
and especially between 50°C and 120°C and, preferably, between 70°C and 90°C.
and especially between 50°C and 120°C and, preferably, between 70°C and 90°C.
7. Process according to Claim 6, implemented at a pressure lower than or equal to 10 bars and, preferably, lower than 5 bars.
8. Process according to Claim 7, implemented in a reactor pressurized with air or with a gas containing more than 21 % of oxygen and especially at least 80 %
of oxygen.
of oxygen.
9. Process according to either of Claims 7 and 8, implemented at a pH of between 5 and 9 and especially between 7 and 8.5.
10. Process according to either of Claims 7 and 8, in which the treatment with the peroxyacid is performed firstly at a pH of between 2 and 7, especially between 4 and 6, for less than 4 hours, especially less than two hours, and preferably one hour or less, at a temperature of between 40 and 100°C, and then the pulp is alkalified, without intermediate washing, to a pH of between 8 and 12 and especially between 9.5 and 12 and left for less than 4 hours at a temperature of between 60 and 120°C.
11. Process according to one of Claims 1 to 10, characterized in that the peroxyacid originates from a washing solution in a subsequent stage of the process for treatment of the paper pulp.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9604628 | 1996-04-12 | ||
| FR9604628A FR2747408B1 (en) | 1996-04-12 | 1996-04-12 | PROCESS FOR THE DELIGNIFICATION AND / OR BLEACHING OF A PULP |
| FR9612568 | 1996-10-15 | ||
| FR9612568A FR2754550B1 (en) | 1996-10-15 | 1996-10-15 | PROCESS FOR THE DELIGNIFICATION AND / OR BLEACHING OF A PULP |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2202445A1 true CA2202445A1 (en) | 1997-10-12 |
Family
ID=26232649
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2202445 Abandoned CA2202445A1 (en) | 1996-04-12 | 1997-04-11 | Process for the delignification and/or bleaching of a paper pulp |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0801170A1 (en) |
| JP (1) | JPH1037089A (en) |
| CN (1) | CN1166553A (en) |
| CA (1) | CA2202445A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI112958B (en) * | 1997-12-19 | 2004-02-13 | Kemira Oyj | Method for bleaching chemical pulp and use of bleaching solution |
| FR2776312B1 (en) * | 1998-03-18 | 2000-05-05 | Air Liquide | PROCESS FOR DESTRUCTION OF FLUORESCENT AGENTS CONTAINED IN OLD PAPER BY PERACETIC ACID |
| CN100427676C (en) * | 2004-09-01 | 2008-10-22 | 曾繁寿 | Method of preparing paper pulp utilizing microwave technique |
| CN101265678B (en) * | 2008-04-30 | 2010-12-01 | 江西科技师范学院 | Hydrogen peroxide stabilizer composition in paper pulp bleaching |
| CN103145228A (en) * | 2013-03-06 | 2013-06-12 | 青岛大学 | Method for decoloring wastewater dyed by active dye |
| CN109736119B (en) * | 2019-02-27 | 2021-09-21 | 华南理工大学 | Paper pulp bleaching method |
| CA3122786A1 (en) * | 2021-06-18 | 2022-12-18 | Sixring Inc. | Temperature-controlled delignification of biomass |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL50696C (en) * | 1938-09-14 | |||
| FR1553704A (en) * | 1966-05-31 | 1969-01-17 | ||
| JP3046628B2 (en) * | 1991-01-23 | 2000-05-29 | 日本パーオキサイド株式会社 | Method for producing peracetic acid composition |
| BE1006057A3 (en) * | 1992-07-06 | 1994-05-03 | Solvay Interox | Method for delignification of chemical pulp. |
| RU2046869C1 (en) * | 1993-05-31 | 1995-10-27 | Акционерное общество открытого типа "Всероссийский научно-исследовательский институт целлюлозно-бумажной промышленности" | Method of bleached cellulose production |
-
1997
- 1997-04-08 EP EP97400799A patent/EP0801170A1/en not_active Withdrawn
- 1997-04-11 CA CA 2202445 patent/CA2202445A1/en not_active Abandoned
- 1997-04-11 CN CN 97110725 patent/CN1166553A/en active Pending
- 1997-04-11 JP JP9415497A patent/JPH1037089A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1037089A (en) | 1998-02-10 |
| EP0801170A1 (en) | 1997-10-15 |
| CN1166553A (en) | 1997-12-03 |
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