EP0509905B1 - Process for producing high yield bleached pulp - Google Patents

Process for producing high yield bleached pulp Download PDF

Info

Publication number
EP0509905B1
EP0509905B1 EP92401044A EP92401044A EP0509905B1 EP 0509905 B1 EP0509905 B1 EP 0509905B1 EP 92401044 A EP92401044 A EP 92401044A EP 92401044 A EP92401044 A EP 92401044A EP 0509905 B1 EP0509905 B1 EP 0509905B1
Authority
EP
European Patent Office
Prior art keywords
solution
chips
hydrogen peroxide
process according
impregnated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92401044A
Other languages
German (de)
French (fr)
Other versions
EP0509905A1 (en
Inventor
Michel Devic
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Arkema France SA
Original Assignee
Elf Atochem SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Elf Atochem SA filed Critical Elf Atochem SA
Publication of EP0509905A1 publication Critical patent/EP0509905A1/en
Application granted granted Critical
Publication of EP0509905B1 publication Critical patent/EP0509905B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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
    • D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/02—Pretreatment of the raw materials by chemical or physical means
    • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
    • 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

Definitions

  • the present invention relates to a process for the production of high-yield, bleached paper pulps having good mechanical characteristics, particularly chemo-mechanical and chemo-thermal pulps.
  • the wood chips are subjected to separate or associated actions of mechanical, chemical or thermal origin.
  • Chemical pulps are obtained by chemical defibration of wood. Their yield is generally less than 50%.
  • yield is meant the weight of dough in the dry state relative to the weight of starting material in the dry state.
  • Mechanical type pulps, or high yield pulps are produced by mechanical defibration of wood chips, for example in a grindstone shredder or a disc shredder or refiner.
  • the yield is generally greater than 85%.
  • the mechanical characteristics, in particular the resistance to rupture, tearing and bursting, are poor.
  • thermomechanical doughs TMP
  • TMP thermomechanical doughs
  • the wood chips were also treated with a sodium sulfite solution at acidic or basic pH depending on the nature of the wood.
  • the pulps obtained also called chemical-mechanical pulps, have good mechanical characteristics.
  • CMP chemothermal-mechanical pastes
  • CTMP pastes are mechanical resistance and that the yield generally remains greater than 85% and, more often than not, at least equal to approximately 90% and therefore similar to that of purely mechanical origins.
  • patent EP-A-239 583 describes a process in which the wood chips, before defibration, undergo three successive treatments, a treatment with a solution of agent complexing metal ions, a treatment with a solution of a stabilizing agent of hydrogen peroxide, such as sodium silicate and magnesium salts, and treatment with an alkaline solution of peroxide.
  • the treatment, before defibration, with hydrogen peroxide, without treatment with sulphites also makes it possible to improve the mechanical strengths, but the properties are not yet high enough, in particular in the case of softwood.
  • the subject of the present invention is therefore a process which makes it possible to obtain, after defibering, high-yielding pastes having both high mechanical properties (resistance to breakage, tearing, bursting), and a high degree whiteness, particularly above 80 ° ISO for softwoods, making them suitable for use in the manufacture of paper with a high whiteness level.
  • an additional step of impregnating the chips with a solution containing a complexing or sequestering agent of metal ions can be provided before step (d), for example by using an aqueous solution at 40% of DTPA (sodium salt diethylenetriamine pentaacetic acid).
  • DTPA sodium salt diethylenetriamine pentaacetic acid
  • Lignocellulosic materials which can be treated by the process according to the invention include softwoods, such as fir, pine, spruce, etc., hardwoods, such as poplar, wood from eucalyptus, etc ... in the form of chips, as they are usually used in the pulp industry.
  • softwoods such as fir, pine, spruce, etc.
  • hardwoods such as poplar, wood from eucalyptus, etc ... in the form of chips, as they are usually used in the pulp industry.
  • these chips are first treated with a solution of one or more reducing agents (step a). This treatment is done by impregnating the chips with the solution.
  • the usual means of the paper industry can be used.
  • these, previously softened by wetting and / or steaming with water vapor are compressed by means of a screw press, to remove a part of the gases and / or liquid present in the shavings.
  • the chips are impregnated with the reducing solution.
  • the PREX system from SUNDS-DEFIBRATOR
  • the IMPRESSAFINER system from BAUER
  • the HYMAC conical screw press and all the devices for obtaining one or more several com chip pressures and expansions in the presence of the impregnating solution with, preferably, the highest possible compression ratio.
  • the expansion of the chips must be carried out in the presence of the smallest possible amount of solution with which the chips must be impregnated.
  • the reducing solution used in the process according to the invention, contains one or more reducing agents which can be chosen from sulfite or bisulfite of alkali metal or a mixture of sulfur dioxide and an alkaline agent like hydroxide of sodium. It is also possible to use sodium borohydride (NaBH 4 ) pure or in alkaline solution.
  • reducing agents which can be chosen from sulfite or bisulfite of alkali metal or a mixture of sulfur dioxide and an alkaline agent like hydroxide of sodium. It is also possible to use sodium borohydride (NaBH 4 ) pure or in alkaline solution.
  • the reducing agent is chosen from alkali sulfites, such as sodium sulfite, sodium borohydride in alkaline solution, such as the product BOROL R , sold by the company MORTON International and comprising 12% by weight of sodium borohydride and 40% by weight of sodium hydroxide, the mixtures of sodium sulfite and alkaline solution of sodium borohydride BOROL R.
  • alkali sulfites such as sodium sulfite, sodium borohydride in alkaline solution, such as the product BOROL R , sold by the company MORTON International and comprising 12% by weight of sodium borohydride and 40% by weight of sodium hydroxide, the mixtures of sodium sulfite and alkaline solution of sodium borohydride BOROL R.
  • the reducing agent is used in an amount of 0.1 to 10% by weight relative to the weight of the chips in the dry state and, more particularly, in an amount of 0.5 to 6% for sodium sulfite, from 0 , 5 to 1.5% for the alkaline sodium borohydride solution BOROL R.
  • the pH of the reducing solution is between a value greater than 7 and 13 depending on the nature of the lignocellulosic material of the shavings and, preferably, the pH is between 11 and 12.8 for the hardwood and between 9.5 and 11 for softwood.
  • An alkaline agent such as NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , MgO, CaO can be added, if necessary, to bring the pH of the reducing solution to the desired value.
  • a complexing or chelating agent for metal ions can be added to the reducing solution.
  • This agent can be, for example, sodium tripolyphosphate, sodium tetrapyrophosphate, sodium salts of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid.
  • the sodium salt of diethylenetriamine pentaacetic acid (DTPA) is preferably used in the form of a 40% aqueous solution, preferably in an amount of 0.2 to 0.5% of this solution.
  • the temperature of the reducing solution during the impregnation can be between 10 and 100 ° C. depending on the stability of the reducing agent, a high temperature favoring the impregnation speed and a low temperature favoring the good conservation of the reducing properties of the solution.
  • a temperature of 20 to 60 ° C is preferred and, in particular, a temperature of 20 to 40 ° C for the reducing solutions obtained by mixing Na 2 SO 3 and alkaline sodium borohydride solution BOROL R .
  • the chips immediately after impregnation with the reducing solution, are heated to a temperature of 60 to 160 ° C and preferably from 75 to 120 ° C (step b).
  • the duration of the heating depends on the temperature and the nature of the wood and varies from 1 minute to 3 hours.
  • the preferred duration is 15 to 60 min at 90 ° C and 5 to 30 min at 120 ° C.
  • the impregnated chips are transported and heated away from oxygen in the air, for example using an atmosphere of water vapor or an inert gas such as nitrogen or anhydride carbonic.
  • the chips are subjected to this pressing because the efficiency of the process increases with the elimination of this solution. It is particularly desirable that at least 20% of the reducing solution is removed.
  • the reducing solution can be removed in one or more pressing steps. You can also, after pressing, rinse the shavings with water.
  • Pressing can be done at a temperature between 20 and 160 ° C.
  • step (a) It is possible to recycle all or part of the reducing solution extracted during the pressing step to prepare the reducing solution useful in step (a).
  • the chips after impregnation with the solution of reducing agent (s) and after pressing, are treated by impregnation (step d) with an alkaline solution of hydrogen peroxide.
  • the oxidizing agent, hydrogen peroxide is used in an amount of 0.1 to 10% by weight relative to the weight of chips in the dry state to be treated, depending on the degree of whiteness sought; in general, the amount of hydrogen peroxide is between 1 and 5% by weight. More than 5% by weight is not generally used for economic reasons.
  • alkaline agents such as NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , MgO, CaO etc. are added to the H 2 O 2 solution so that the initial pH of this solution is understood between 8 and 12.5.
  • the preferred agent is NaOH.
  • the optimum amount of alkaline agent depends on the nature of the wood and is proportional to the amount of H 2 O 2 . This amount, expressed as NaOH, can vary from 0.5% to 10% and preferably from 0.5 to 6% by weight relative to the weight of chips in the dry state to be treated.
  • One or more stabilizers of hydrogen peroxide in an alkaline medium can be added to the alkaline solution of H 2 O 2 to reduce the decomposition of this solution and thus increase the efficiency of the treatment.
  • metal ions such as, for example, diethylenetriaminepentaacetic and ethylenediaminetetraacetic acids in the form of sodium salts. They are used in an amount of 0.1 to 1% by weight relative to the weight of chips in the dry state to be treated.
  • the temperature of the alkaline solution of hydrogen peroxide during the impregnation is between 10 and 80 ° C and, preferably, at a temperature not exceeding 40 ° C to reduce the decomposition of the peroxide.
  • the shavings are heated, during a step (e), to a temperature between 50 ° C. and 120 ° C. and preferably between 60 and 80 ° C for a period of 10 minutes to 5 hours depending on the nature of the wood, the temperature and the amount of hydrogen peroxide.
  • the duration can reach 5 hours at 60 ° C, it is 2 to 3 hours at 70 ° C and 1 to 2 hours at 90 ° C.
  • Heating is generally provided by steam in a saturated atmosphere.
  • the chips are defibrated or refined, by passing through one or more refiners at atmospheric pressure or under the pressure of a few bars of water vapor.
  • refining is carried out with two stages of refining, the first stage being under pressure and the second atmospheric.
  • the refining conditions depend on the characteristics required for the pulp.
  • Refined pulp is generally neutralized by an acid to remove the alkalinity resulting from treatment with the alkaline solution of hydrogen peroxide.
  • This neutralization is preferably carried out up to a pH of 5.5 to 6 using dilute sulfuric acid or alternatively SO 2 gas.
  • the dough is then treated in the usual way (purification, classification, recycling of refusals, etc.).
  • the amounts of reagents are expressed as a percentage by weight relative to the wood chips in the dry state.
  • softwood (fir) or hardwood (poplar) wood chips are used.
  • the shavings were taken from an industrial mechanical pulp manufacturing facility and meet industry standards.
  • sheets of paper are produced with this pulp to measure the whiteness and the mechanical characteristics, according to ISO standards of the paper industry.
  • the commercial sodium borohydride solution used comes from the company MORTON International and contains 12% NaBH 4 and 40% NaOH; it is designated under the name of BOROL R.
  • the metal ion complexing agent used in the examples is DTPA (sodium salt of diethylenetriamine pentaacetic acid) in the form of a 40% aqueous solution.
  • Softwood shavings (fir, spruce) are washed and steamed with water. These shavings are impregnated continuously with a reducing solution at 20 ° C. comprising 5.9% of sodium sulfite, 0.5% of DTPA solution at 40% and 1.5% of sodium borohydride solution BOROL R , the solution having a pH of 10.5.
  • the chips are heated at 60 ° C for 30 min.
  • the shavings are pressed at 60 ° C. to remove approximately 0.5 l of reducing solution per kg of (dry) shavings (ie approximately 50% removal). Rinse with 2 l of water per kg of dry chips.
  • the chips are impregnated, continuously, with an oxidizing solution at 20 ° C., comprising 5% of hydrogen peroxide, 2% of sodium hydroxide, 4% of solution with 40% of sodium silicate and 0.5 % 40% DTPA solution.
  • the oxidizing solution has a pH of 11.5.
  • the impregnated chips are then heated at 90 ° C for 1 hour, then refined in a double disc refiner.
  • the dough is then classified and the refusals are returned to the refiner.
  • the refined dough has a drip index of 70 ° SR.
  • the method according to the invention which comprises treatment with a reducing solution containing sodium sulfite and sodium borohydride and treatment with hydrogen peroxide makes it possible to obtain a pulp from softwood which, after defibration, has a high degree of whiteness, greater than 80 ° ISO.
  • Example 2 The procedure is as for Example 1, but the duration of heating to 90 ° C. after impregnation with the oxidizing solution is 2 hours instead of 1 hour.
  • a paste is obtained having the same mechanical characteristics and a whiteness of 83 ° ISO.
  • Example 2 The procedure is as for Example 1, except that the reducing solution is composed of 5.9% Na 2 SO 3 and 0.5% of 40% DTPA solution and has a pH of 9.6 .
  • a paste is obtained having the following characteristics: ISO whiteness 80 ° ISO Tear resistant : Break length 4400 m Burst resistance 2.2 KPa m 2 / g Tear resistance 5.4 mN m 2 / g.
  • the procedure is as in Example 1, but the chips are not treated with a reducing solution.
  • the first treatment consists of impregnating the chips with a solution containing only 0.5% of 40% DTPA solution.
  • a paste is obtained having the following characteristics: ISO whiteness 78 ° ISO Tear resistant : Break length 3200 m Burst resistance 1.6 KPa m 2 / g Tear resistance 5.2 mN m 2 / g.
  • Hardwood shavings (poplar, aspen), washed and steamed, are continuously impregnated with a reducing solution at 20 ° C, consisting of 5% Na 2 SO 3 , 1.5% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution and having a pH of 11.5.
  • a reducing solution consisting of 5% Na 2 SO 3 , 1.5% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution and having a pH of 11.5.
  • the impregnated shavings are heated at 100 ° C. for 30 min under an atmosphere of steam.
  • the chips are then pressed at 60 ° C to remove more than 50% of reducing solution. Rinse with 2 1 of water per kg of dry chips.
  • the shavings are then impregnated with an oxidizing solution at 20 ° C. comprising 5.2% of hydrogen peroxide, 4% of sodium hydroxide, 4% of solution with 40% of sodium silicate and 0.5% of solution at 40% DTPA, and having a pH of 11.4.
  • the chips are then heated at 90 ° C for 2 hours and refined in a double disc refiner at atmospheric pressure.
  • the refined dough After classification, the refined dough has a drip index of 56 ° SR.
  • the characteristics of this paste are as follows: ISO whiteness 87 ° ISO Tear resistant : Break length 3300 m Burst resistance 1.3 KPa m 2 / g Tear resistance 3.5 mN m 2 / g.
  • hardwood shavings are treated which are relatively white.
  • the method according to the invention makes it possible to obtain a paste, after defibering, the degree of white of which is very high.
  • Example 5 The procedure is as for Example 5, but the reducing solution is composed of 5% Na 2 SO 3 and 0.5% of solution 40% DTPA and has a pH of 11.
  • the dough obtained has the following characteristics: ISO whiteness 85.2 ° ISO Tear resistant : Break length 2900 m Burst resistance 1.20 KPa m 2 / g Tear resistance 3.1 mN m 2 / g.
  • Example 5 The procedure is as in Example 5, but no reducing agent is added to the first treatment: the first impregnation is carried out with a solution containing only 0.5% of 40% DTPA solution.
  • the dough obtained has the following characteristics: ISO whiteness 84 ° ISO Tear resistant : Break length 2300 m Burst resistance 0.9 KPa m 2 / g Tear resistance 2.9 mN m 2 / g.
  • Hardwood (poplar) shavings are washed and dried at 90 ° C. They are impregnated, continuously, with a reducing solution at 20 ° C consisting of 1% sodium borohydride solution (BOROL R ) and 0.5% of 40% DTPA solution.
  • the solution has a pH of 12.7.
  • the chips are heated at 90 ° C for 15 min.
  • the chips are pressed at a temperature of 60 ° C to eliminate approximately 0.5 l of reducing solution per kg of dry shavings (i.e. approximately 20% of reducing solution eliminated).
  • the chips are then impregnated with an oxidizing solution at 20 ° C. comprising 4.25% of hydrogen peroxide and 3.8% of sodium hydroxide.
  • the solution has a pH of 10.5.
  • the shavings impregnated with oxidizing solution are heated at 85 ° C for 1 h. It is refined in a first double disc refiner at atmospheric pressure, then in a second single disc refiner also at atmospheric pressure.
  • the refined paste after neutralization at pH 6 with SO 2 , has a drainage index of 62 ° SR and has the following characteristics: ISO whiteness 80.9 ° ISO Tear resistant : Break length 2800 m Burst resistance 1.25 KPa m 2 / g
  • Example 8 The procedure is exactly as for Example 8, but a reducing solution composed of 1% Na 2 SO 3 , 1% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution is used. .
  • the dough obtained has a drip index of 68 ° SR and has the following characteristics: ISO whiteness 81.1 ° ISO Tear resistant : Break length 3100 m Burst resistance 1.36 KPa m 2 / g
  • Example 8 The procedure is exactly as for Example 8, but a reducing solution composed of 2% Na 2 SO 3 , 1% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution is used. .
  • the dough obtained has a drip index of 65 ° SR and has the following characteristics: ISO whiteness 81.7 ° ISO Tear resistant : Break length 3320 m Burst resistance 1.38 KPa m 2 / g
  • the procedure is as in Example 8, but without adding a reducing agent to the first treatment: the first impregnation is carried out with a solution composed only of 0.5% of 40% DTPA solution.
  • the dough obtained has a drip index of 6 6 ° SR and has the following characteristics: ISO whiteness 79.8 ° ISO Tear resistant : Break length 2900 m Burst resistance 1.21 KPa m 2 / g
  • Examples 8 to 11 hardwood (poplar) shavings with a lower initial whiteness are used than in Examples 5 to 7.
  • the whiteness of the final pulp is therefore lower than that obtained in Examples 5 to 7 , but again, it can be seen that the treatment of the wood chips by a reducing treatment, then by an oxidizing treatment, makes it possible to obtain, after defibering the wood, a paste of very high level of whiteness and having reinforced mechanical characteristics. .

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Paper (AREA)
  • Electroluminescent Light Sources (AREA)
  • Combined Devices Of Dampers And Springs (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)

Abstract

Manufacture of high-yield paper pulp from wood chips. The process consists in successively treating the chips, before grinding, with a solution containing at least one reducing agent, and then with an alkaline hydrogen peroxide solution. Application to the manufacture of paper pulp with a high degree of whiteness and good mechanical characteristics.

Description

La présente invention concerne un procédé de fabrication de pâtes à papier à haut rendement et blanchies et présentant de bonnes caractéristiques mécaniques, particulièrement des pâtes chimicomécaniques et chimicothermomécaniques.The present invention relates to a process for the production of high-yield, bleached paper pulps having good mechanical characteristics, particularly chemo-mechanical and chemo-thermal pulps.

Pour obtenir une pâte, les copeaux de bois sont soumis à des actions séparées ou associées d'origine mécanique, chimique ou thermique.To obtain a paste, the wood chips are subjected to separate or associated actions of mechanical, chemical or thermal origin.

Les pâtes chimiques sont obtenues par défibrage chimique du bois. Leur rendement est, en général, inférieur à 50 %.Chemical pulps are obtained by chemical defibration of wood. Their yield is generally less than 50%.

Par rendement, on entend le poids de pâte à l'état sec rapporté au poids de matière de départ à l'état sec.By yield is meant the weight of dough in the dry state relative to the weight of starting material in the dry state.

Les pâtes de type mécanique ou pâtes à haut rendement, sont fabriquées par défibrage mécanique des copeaux de bois, par exemple dans un défibreur à meule ou un défibreur ou raffineur à disques. Le rendement est généralement supérieur à 85 %. Cependant, les caractéristiques mécaniques, notamment les résistance à la rupture, à la déchirure et à l'éclatement, sont médiocres.Mechanical type pulps, or high yield pulps, are produced by mechanical defibration of wood chips, for example in a grindstone shredder or a disc shredder or refiner. The yield is generally greater than 85%. However, the mechanical characteristics, in particular the resistance to rupture, tearing and bursting, are poor.

Pour améliorer ces caractéristiques mécaniques, on a fait subir aux copeaux de bois, avant défibrage, un traitement thermique par de la vapeur d'eau à une température de 100°C à 140°C. On appelle ces pâtes des pâtes thermomécaniques (TMP). Elles présentent cependant une blancheur médiocre.To improve these mechanical characteristics, the wood chips were subjected, before defibration, to a heat treatment with steam at a temperature of 100 ° C. to 140 ° C. These doughs are called thermomechanical doughs (TMP). However, they exhibit poor whiteness.

On a aussi traité les copeaux de bois par une solution de sulfite de sodium à pH acide ou basique selon la nature du bois. Les pâtes obtenues, appelées aussi pâtes chimicomécaniques, présentent de bonnes caractéristiques mécaniques.The wood chips were also treated with a sodium sulfite solution at acidic or basic pH depending on the nature of the wood. The pulps obtained, also called chemical-mechanical pulps, have good mechanical characteristics.

On a pu aussi considérablement augmenter la résistance des pâtes mécaniques, en faisant subir, aux copeaux de bois, un traitement à l'aide d'un ou plusieurs agents chimiques combiné à des opérations de chauffage et de défibrage mécanique. Ces pâtes sont appelées pâtes chimicothermomécaniques (CTMP) (voir par exemple EP-A-0 351 330 et US-A-4 486 267). Ce traitement consiste en une cuisson non destructrice de la matière, réalisée à une température égale ou supérieure à 100°C, sous pression de vapeur d'eau saturée, en présence de sulfite, en particulier le sulfite de sodium Na2SO3, ou de bi-sulfite de sodium NaHSO3.It was also possible to considerably increase the resistance of mechanical pulps, by subjecting the wood chips to a treatment using one or more chemical agents combined with heating and mechanical defibration operations. These pastes are called chemothermal-mechanical pastes (CTMP) (see for example EP-A-0 351 330 and US-A-4 486 267). This treatment consists of a non-destructive cooking of the material, produced at a temperature equal to or greater than 100 ° C., under saturated steam pressure, in the presence of sulfite, in particular sodium sulfite Na 2 SO 3 , or sodium bi-sulfite NaHSO 3 .

L'intérêt de ces pâtes CTMP est que leur résistance mécanique est améliorée et que le rendement reste généralement supérieur à 85 % et, le plus souvent, au moins égal à 90 % environ et donc semblable à celui des pâtes d'origine purement mécanique.The advantage of these CTMP pastes is that their mechanical resistance is improved and that the yield generally remains greater than 85% and, more often than not, at least equal to approximately 90% and therefore similar to that of purely mechanical origins.

Si les pâtes ainsi traitées, particulièrement les pâtes chimicomécaniques (CMP) et les pâtes chimicothermomécaniques (CTMP), présentent des résistances mécaniques améliorées, leur blanchiment, rendu nécessaire par la qualité demandée pour le papier, reste un problème.If the pulp thus treated, particularly the chemical mechanical pulp (CMP) and the chemical thermal pulp (CTMP), have improved mechanical resistance, their bleaching, made necessary by the quality demanded for the paper, remains a problem.

Pour obtenir un meilleur blanchiment de ces pâtes, il a été proposé, dans les brevets FR 1 389 308 et EP-A-293309, de traiter des copeaux de bois par des solutions combinées de sulfite et de borohydrure de métal alcalin, à des pH acide ou alcalin.To obtain a better bleaching of these pulps, it has been proposed, in patents FR 1 389 308 and EP-A-293 309, to treat wood chips with combined solutions of sulfite and alkali metal borohydride, at pH acidic or alkaline.

Ces traitements permettent d'obtenir, après défibrage, des pâtes qui présentent de bonnes propriétés mécaniques et une blancheur améliorée. La blancheur obtenue est cependant encore insuffisante et les pâtes raffinées doivent subir un traitement de blanchiment par du peroxyde d'hydrogène. Ce problème de blanchiment insuffisant est dû notamment au traitement par le sulfite qui, s'il améliore les propriétés mécaniques des pâtes raffinées obtenues, entraîne pour ces pâtes une mauvaise réponse au blanchiment par le peroxyde d'hydrogène FR-A-2 389 712 décrit un procédé de fabrication de pâtes mécaniques où il y a un prétraitement des copeaux de bois avec un agent réducteur. Après imprégnation, on effectue un chauffage des copeaux avant le défibrage qui se produit en présence de peroxide d'hydrogène.These treatments make it possible to obtain, after defibration, pastes which have good mechanical properties and improved whiteness. The whiteness obtained is however still insufficient and the refined pastes must undergo a bleaching treatment with hydrogen peroxide. This problem of insufficient bleaching is due in particular to the treatment with sulphite which, if it improves the mechanical properties of the refined pulps obtained, causes for these pulps a poor response to bleaching by hydrogen peroxide FR-A-2,389,712 described a process for manufacturing mechanical pulps where there is a pretreatment of wood chips with a reducing agent. After impregnation, the chips are heated before defibering which occurs in the presence of hydrogen peroxide.

Il apparaît donc qu'il existe un problème pour obtenir des pâtes qui, à la fois, présentent de bonnes propriétés mécaniques et une blancheur suffisante pour être utilisable pour la fabrication de papier à haut niveau de blancheur.It therefore appears that there is a problem in obtaining pulps which, at the same time, have good mechanical properties and a whiteness sufficient to be usable for the production of paper with a high whiteness level.

Pour résoudre ce problème, le brevet EP-A-239 583 décrit un procédé dans lequel les copeaux de bois, avant défibrage, subissent trois traitements successifs, un traitement par une solution d'agent complexant des ions métalliques, un traitement par une solution d'un agent stabilisant du peroxyde d'hydrogène, comme le silicate de sodium et les sels de magnésium, et un traitement par une solution alcaline de peroxyde.To solve this problem, patent EP-A-239 583 describes a process in which the wood chips, before defibration, undergo three successive treatments, a treatment with a solution of agent complexing metal ions, a treatment with a solution of a stabilizing agent of hydrogen peroxide, such as sodium silicate and magnesium salts, and treatment with an alkaline solution of peroxide.

On obtient ainsi, après défibrage, des pâtes d'une blancheur améliorée. Cependant, cette blancheur qui reste inférieure à 80° ISO, pour les bois de résineux notamment, n'est pas encore suffisante pour convenir à tous les usages.After defibering, pulps of improved whiteness are thus obtained. However, this whiteness which remains below 80 ° ISO, in particular for softwoods, is not yet sufficient to be suitable for all uses.

Il est donc généralement nécessaire de prévoir une étape de blanchiment classique de la pâte raffinée par du peroxyde d'hydrogène, ce qui augmente les coûts de fabrication.It is therefore generally necessary to provide a conventional bleaching step for the refined pulp with hydrogen peroxide, which increases the manufacturing costs.

En outre, le traitement, avant défibrage, par du peroxyde d'hydrogène, sans traitement par des sulfites, permet aussi d'améliorer les résistances mécaniques, mais les propriétés ne sont pas encore assez élevées, notamment dans le cas du bois de résineux.In addition, the treatment, before defibration, with hydrogen peroxide, without treatment with sulphites, also makes it possible to improve the mechanical strengths, but the properties are not yet high enough, in particular in the case of softwood.

La présente invention a donc pour objet un procédé permettant d'obtenir, après défibrage, des pâtes à haut rendement présentant à la fois des propriétés mécaniques élevées (résistances à la rupture, à la déchirure, à l'éclatement), et un haut degré de blancheur, particulièrement supérieur à 80° ISO pour les bois de résineux, les rendant aptes à être utilisées pour la fabrication du papier à haut niveau de blancheur.The subject of the present invention is therefore a process which makes it possible to obtain, after defibering, high-yielding pastes having both high mechanical properties (resistance to breakage, tearing, bursting), and a high degree whiteness, particularly above 80 ° ISO for softwoods, making them suitable for use in the manufacture of paper with a high whiteness level.

Le procédé selon l'invention est un procédé de fabrication de pâte à papier à haut rendement blanchie, à partir de copeaux de bois, selon lequel on traite les copeaux par une solution alcaline de peroxyde d'hydrogène, avant de les défibrer, caractérisé en ce qu'il consiste:

  • a) à imprégner les copeaux avec une solution réductrice comprenant du sulfite de sodium et/ou du borohydrure de sodium et ayant un pH compris entre une valeur supérieure à 7 et 13,
  • b) à chauffer les copeaux imprégnés à une température comprise entre 60 et 160° C,
  • c) à presser les copeaux de façon à extraire au moins 20 % de la solution réductrice,
  • d) à imprégner les copeaux avec la solution alcaline contenant le peroxyde d'hydrogène,
  • e) à chauffer les copeaux imprégnés à l'étape (d) à une température comprise entre 50 et 120° C, et
  • f) à raffiner les copeaux ainsi traités à l'étape (e).
The process according to the invention is a process for manufacturing bleached high-yield paper pulp from wood chips, according to which the chips are treated with an alkaline solution of hydrogen peroxide, before defibrizing them, characterized in what it consists of:
  • a) impregnating the shavings with a reducing solution comprising sodium sulfite and / or sodium borohydride and having a pH of between a value greater than 7 and 13,
  • b) heating the impregnated chips to a temperature between 60 and 160 ° C,
  • c) pressing the chips so as to extract at least 20% of the reducing solution,
  • d) impregnating the shavings with the alkaline solution containing the hydrogen peroxide,
  • e) heating the impregnated chips in step (d) to a temperature between 50 and 120 ° C, and
  • f) refining the chips thus treated in step (e).

Eventuellement, une étape supplémentaire d'imprégnation des copeaux par une solution contenant un agent complexant ou séquestrant des ions métalliques, peut être prévue avant l'étape (d), par exemple en utilisant une solution aqueuse à 40 % de DTPA (sel de sodium de l'acide diéthylènetriamine pentaacétique).Optionally, an additional step of impregnating the chips with a solution containing a complexing or sequestering agent of metal ions, can be provided before step (d), for example by using an aqueous solution at 40% of DTPA (sodium salt diethylenetriamine pentaacetic acid).

Les matières lignocellulosiques que l'on peut traiter par le procédé selon l'invention, comprennent les bois de résineux, comme le sapin, le pin, l'épicéa, etc, les bois de feuillus, comme le peuplier, le bois de l'eucalyptus, etc... sous forme de copeaux, tels qu'ils sont utilisés habituellement dans l'industrie de la pâte à papier. On peut aussi traiter des plantes annuelles, comme la bagasse, la paille, etc... coupées en morceaux de quelque centimètres.Lignocellulosic materials which can be treated by the process according to the invention include softwoods, such as fir, pine, spruce, etc., hardwoods, such as poplar, wood from eucalyptus, etc ... in the form of chips, as they are usually used in the pulp industry. One can also treat annual plants, like bagasse, straw, etc ... cut into pieces of a few centimeters.

Ces copeaux subissent les traitements préparatoires habituellement utilisés dans l'industrie de la pâte à papier, par exemple, lavage, triage, préchauffage par de la vapeur d'eau, etc...These shavings undergo the preparatory treatments usually used in the pulp industry, for example, washing, sorting, preheating with steam, etc.

Selon le procédé de l'invention, on traite d'abord ces copeaux par une solution d'un ou plusieurs agents réducteurs (étape a). Ce traitement se fait par imprégnation des copeaux par la solution. Pour cette imprégnation, on peut utiliser les moyens habituels de l'industrie papetière. Avant l'imprégnation proprement dite des copeaux, ceux-ci, préalablement ramollis par mouillage et/ou étuvage à la vapeur d'eau, sont comprimés au moyen d'une presse à vis, pour éliminer une partie des gaz et/ou de liquide présents dans les copeaux. Lors de l'expansion des copeaux, après la compression, les copeaux sont imprégnés de la solution réductrice.According to the method of the invention, these chips are first treated with a solution of one or more reducing agents (step a). This treatment is done by impregnating the chips with the solution. For this impregnation, the usual means of the paper industry can be used. Before the actual impregnation of the shavings, these, previously softened by wetting and / or steaming with water vapor, are compressed by means of a screw press, to remove a part of the gases and / or liquid present in the shavings. During the expansion of the chips, after compression, the chips are impregnated with the reducing solution.

Comme appareil convenant particulièrement bien à l'imprégnation industrielle en continu des copeaux, on peut citer le système PREX de SUNDS-DEFIBRATOR, le système IMPRESSAFINER de BAUER, la presse à vis conique HYMAC, ainsi que tous les appareils permettant d'obtenir une ou plusieurs com pressions et expansions des copeaux, en présence de la solution d'imprégnation avec, d'une manière préférée, un rapport de compression le plus élevé possible.As a particularly suitable device for continuous industrial impregnation of shavings, the PREX system from SUNDS-DEFIBRATOR, the IMPRESSAFINER system from BAUER, the HYMAC conical screw press and all the devices for obtaining one or more several com chip pressures and expansions in the presence of the impregnating solution with, preferably, the highest possible compression ratio.

Selon l'invention, l'expansion des copeaux doit être réalisée en présence d'une quantité la plus faible possible de solution dont les copeaux doivent être imprégnés.According to the invention, the expansion of the chips must be carried out in the presence of the smallest possible amount of solution with which the chips must be impregnated.

La solution réductrice, utilisée dans le procédé selon l'invention, contient un ou plusieurs agents réducteurs qui peuvent être choisis parmi le sulfite ou le bisulfite de métal alcalin ou un mélange de dioxyde de soufre et d'un agent alcalin comme l'hydroxyde de sodium. On peut aussi utiliser le borohydrure de sodium (NaBH4) pur ou en solution alcaline.The reducing solution, used in the process according to the invention, contains one or more reducing agents which can be chosen from sulfite or bisulfite of alkali metal or a mixture of sulfur dioxide and an alkaline agent like hydroxide of sodium. It is also possible to use sodium borohydride (NaBH 4 ) pure or in alkaline solution.

D'une manière préférée et pour des raisons économiques, l'agent réducteur est choisi parmi les sulfites alcalins, comme le sulfite de sodium, le borohydrure de sodium en solution alcaline, comme le produit BOROLR, commercialisé par la Société MORTON International et comprenant 12 % en poids de borohydrure de sodium et 40 % en poids d'hydroxyde de sodium, les mélanges de sulfite de sodium et de solution alcaline de borohydrure de sodium BOROLR.In a preferred manner and for economic reasons, the reducing agent is chosen from alkali sulfites, such as sodium sulfite, sodium borohydride in alkaline solution, such as the product BOROL R , sold by the company MORTON International and comprising 12% by weight of sodium borohydride and 40% by weight of sodium hydroxide, the mixtures of sodium sulfite and alkaline solution of sodium borohydride BOROL R.

L'agent réducteur est utilisé à raison de 0,1 à 10 % en poids par rapport au poids des copeaux à l'état sec et, plus particulièrement, à raison de 0,5 à 6 % pour le sulfite de sodium, de 0,5 à 1,5 % pour la solution alcaline de borohydrure de sodium BOROLR.The reducing agent is used in an amount of 0.1 to 10% by weight relative to the weight of the chips in the dry state and, more particularly, in an amount of 0.5 to 6% for sodium sulfite, from 0 , 5 to 1.5% for the alkaline sodium borohydride solution BOROL R.

Selon l'invention, le pH de la solution réductrice est compris entre une valeur supérieure à 7 et 13 selon la nature de la matière lignocellulosique des copeaux et, d'une manière préférée, le pH est compris entre 11 et 12,8 pour le bois de feuillu et entre 9,5 et 11 pour le bois de résineux.According to the invention, the pH of the reducing solution is between a value greater than 7 and 13 depending on the nature of the lignocellulosic material of the shavings and, preferably, the pH is between 11 and 12.8 for the hardwood and between 9.5 and 11 for softwood.

Un agent alcalin comme NaOH, KOH, Na2CO3, K2CO3, MgO, CaO peut être ajouté, si nécessaire, pour amener le pH de la solution réductrice à la valeur souhaitée.An alkaline agent such as NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , MgO, CaO can be added, if necessary, to bring the pH of the reducing solution to the desired value.

Selon l'invention, un agent complexant ou chelatant des ions métalliques peut être ajouté à la solution réductrice. Cet agent peut être, par exemple, le tripolyphosphate de sodium, le tétrapyrophosphate de sodium, les sels de sodium des acides nitrilotriacétique, éthylénediaminetétraacétique, diéthylènetriamine pentaacétique. On utilise de préférence le sel de sodium de l'acide diéthylènetriamine pentaacétique (DTPA) sous forme de solution aqueuse à 40 %, de préférence en quantité de 0,2 à 0,5 % de cette solution.According to the invention, a complexing or chelating agent for metal ions can be added to the reducing solution. This agent can be, for example, sodium tripolyphosphate, sodium tetrapyrophosphate, sodium salts of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid. The sodium salt of diethylenetriamine pentaacetic acid (DTPA) is preferably used in the form of a 40% aqueous solution, preferably in an amount of 0.2 to 0.5% of this solution.

La température de la solution réductrice pendant l'imprégnation peut être comprise entre 10 et 100°C selon la stabilité de l'agent réducteur, une température élevée favorisant la vitesse d'imprégnation et une température basse favorisant la bonne conservation des propriétés réductrices de la solution.The temperature of the reducing solution during the impregnation can be between 10 and 100 ° C. depending on the stability of the reducing agent, a high temperature favoring the impregnation speed and a low temperature favoring the good conservation of the reducing properties of the solution.

Dans la plupart des cas, une température de 20 à 60°C est préférée et, particulièrement, une température de 20 à 40°C pour les solutions réductrices obtenues par mélange de Na2SO3 et de solution alcaline de borohydrure de sodium BOROLR.In most cases, a temperature of 20 to 60 ° C is preferred and, in particular, a temperature of 20 to 40 ° C for the reducing solutions obtained by mixing Na 2 SO 3 and alkaline sodium borohydride solution BOROL R .

Les copeaux, aussitôt après imprégnation par la solution réductrice, sont chauffés à une température de 60 à 160°C et de préférence de 75 à 120°C (étape b).The chips, immediately after impregnation with the reducing solution, are heated to a temperature of 60 to 160 ° C and preferably from 75 to 120 ° C (step b).

La durée du chauffage dépend de la température et de la nature du bois et varie de 1 mn à 3 heures. La durée préférée est 15 à 60 mn à 90°C et de 5 à 30 mn à 120°C.The duration of the heating depends on the temperature and the nature of the wood and varies from 1 minute to 3 hours. The preferred duration is 15 to 60 min at 90 ° C and 5 to 30 min at 120 ° C.

De préférence, les copeaux imprégnés sont transportés et chauffés à l'abri de l'oxygène de l'air, en utilisant par exemple, une atmosphère de vapeur d'eau ou d'un gaz inerte comme l'azote ou de l'anhydride carbonique.Preferably, the impregnated chips are transported and heated away from oxygen in the air, for example using an atmosphere of water vapor or an inert gas such as nitrogen or anhydride carbonic.

Les copeaux ayant été imprégnés par la solution réductrice, puis chauffés, sont pressés au moyen d'une presse à vis ou d'un autre moyen, afin d'extraire une partie de la solution réductrice après réaction. Les copeaux sont soumis à ce pressage car l'efficacité du procédé augmente avec l'élimination de cette solution. Il est en particulier souhaitable qu'au moins 20 % de la solution réductrice soit éliminée.The shavings having been impregnated with the reducing solution, then heated, are pressed by means of a screw press or by other means, in order to extract a part of the reducing solution after reaction. The chips are subjected to this pressing because the efficiency of the process increases with the elimination of this solution. It is particularly desirable that at least 20% of the reducing solution is removed.

On peut éliminer la solution réductrice en une ou plusieurs étapes de pressage. On peut aussi, après le pressage, rincer les copeaux avec de l'eau.The reducing solution can be removed in one or more pressing steps. You can also, after pressing, rinse the shavings with water.

Le pressage peut se faire à une température comprise entre 20 et 160°C.Pressing can be done at a temperature between 20 and 160 ° C.

Il est possible de recycler tout ou partie de la solution réductrice extraite au cours de l'étape de pressage pour préparer la solution réductrice utile à l'étape (a).It is possible to recycle all or part of the reducing solution extracted during the pressing step to prepare the reducing solution useful in step (a).

Les copeaux, après imprégnation par la solution d'agent(s) réducteur(s) et après pressage, sont traités par imprégnation (étape d) par une solution alcaline de peroxyde d'hydrogène.The chips, after impregnation with the solution of reducing agent (s) and after pressing, are treated by impregnation (step d) with an alkaline solution of hydrogen peroxide.

L'agent oxydant, le peroxyde d'hydrogène, est utilisé à raison de 0,1 à 10 % en poids par rapport au poids de copeaux à l'état sec à traiter, en fonction du degré de blancheur recherché ; en général, la quantité de peroxyde d'hydrogène est comprise entre 1 et 5 % en poids. Une quantité supérieure à 5 % en poids n'est pas utilisée en général pour des raisons économiques.The oxidizing agent, hydrogen peroxide, is used in an amount of 0.1 to 10% by weight relative to the weight of chips in the dry state to be treated, depending on the degree of whiteness sought; in general, the amount of hydrogen peroxide is between 1 and 5% by weight. More than 5% by weight is not generally used for economic reasons.

Un ou plusieurs agents alcalins, tels que NaOH, KOH, Na2CO3, K2CO3, MgO, CaO etc.. sont ajoutés à la solution d'H2O2 de manière que le pH initial de cette solution soit compris entre 8 et 12, 5. L'agent préféré est NaOH. La quantité optimum d'agent alcalin dépend de la nature du bois et est proportionnelle à la quantité d'H2O2. Cette quantité, exprimée en NaOH, peut varier de 0, 5 % à 10 % et de préférence de 0, 5 à 6 %, en poids par rapport au poids de copeaux à l'état sec à traiter.One or more alkaline agents, such as NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , MgO, CaO etc. are added to the H 2 O 2 solution so that the initial pH of this solution is understood between 8 and 12.5. The preferred agent is NaOH. The optimum amount of alkaline agent depends on the nature of the wood and is proportional to the amount of H 2 O 2 . This amount, expressed as NaOH, can vary from 0.5% to 10% and preferably from 0.5 to 6% by weight relative to the weight of chips in the dry state to be treated.

Un ou plusieurs agents stabilisants du peroxyde d'hydrogène en milieu alcalin peuvent être ajoutés à la solution alcaline d'H2O2 pour diminuer la décomposition de cette solution et accroître ainsi l'efficacité du traitement. On peut citer comme agent stabilisant, le silicate de sodium, généralement sous forme de solution à 40 % et utilisé à raison de 0,5 à à 5 %, en poids par rapport au poids de copeaux sec, les sels de magnésium comme le chlorure, le nitrate, le carbonate et les sels mixtes à raison de 0,01 à 1 % de magnésium, et les polylactones de l'acide poly(alpha-hydroxy acrylique) et utilisées à raison de 0,02 à 2 % en poids.One or more stabilizers of hydrogen peroxide in an alkaline medium can be added to the alkaline solution of H 2 O 2 to reduce the decomposition of this solution and thus increase the efficiency of the treatment. Mention may be made, as stabilizing agent, of sodium silicate, generally in the form of a 40% solution and used in an amount of 0.5 to 5%, by weight relative to the weight of dry chips, magnesium salts such as chloride, nitrate, carbonate and mixed salts at 0.01 to 1% magnesium, and poly (alpha-hydroxy acrylic) acid polylactones and used at 0.02 at 2% by weight.

On peut aussi ajouter à la solution de peroxyde d'hydrogène un ou plusieurs agents complexants ou séquestrants des ions métalliques comme, par exemple, les acides diéthylènetriaminepentaacétique et éthylènediaminetétraacétique sous forme de sels de sodium. On les utilise à raison de 0,1 à 1 % en poids par rapport au poids de copeaux à l'état sec à traiter.It is also possible to add to the hydrogen peroxide solution one or more complexing or sequestering agents of metal ions such as, for example, diethylenetriaminepentaacetic and ethylenediaminetetraacetic acids in the form of sodium salts. They are used in an amount of 0.1 to 1% by weight relative to the weight of chips in the dry state to be treated.

La température de la solution alcaline de peroxyde d'hydrogène pendant l'imprégnation est comprise entre 10 et 80°C et, de préférence, à une température n'excédant pas 40°C pour diminuer la décomposition du peroxyde.The temperature of the alkaline solution of hydrogen peroxide during the impregnation is between 10 and 80 ° C and, preferably, at a temperature not exceeding 40 ° C to reduce the decomposition of the peroxide.

Après l'étape d'imprégnation des copeaux par la solution alcaline de peroxyde d'hydrogène, on chauffe les copeaux, lors d'une étape (e), à une température comprise entre 50°C et 120°C et de préférence comprise entre 60 et 80°C pendant une durée de 10 mn à 5 heures selon la nature du bois, la température et la quantité de peroxyde d'hydrogène. En général, la durée peut atteindre 5 heures à 60°C, elle est de 2 à 3 heures à 70°C et de 1 à 2 heures à 90°C. Le chauffage est, généralement, assuré par de la vapeur en atmosphère saturée.After the step of impregnating the shavings with the alkaline hydrogen peroxide solution, the shavings are heated, during a step (e), to a temperature between 50 ° C. and 120 ° C. and preferably between 60 and 80 ° C for a period of 10 minutes to 5 hours depending on the nature of the wood, the temperature and the amount of hydrogen peroxide. In general, the duration can reach 5 hours at 60 ° C, it is 2 to 3 hours at 70 ° C and 1 to 2 hours at 90 ° C. Heating is generally provided by steam in a saturated atmosphere.

A l'issue des deux traitements par les solutions réductrice et oxydante, les copeaux sont défibrés ou raffinés, par passage dans un ou plusieurs raffineurs à pression atmosphérique ou sous pression de quelques bars de vapeur d'eau.At the end of the two treatments with the reducing and oxidizing solutions, the chips are defibrated or refined, by passing through one or more refiners at atmospheric pressure or under the pressure of a few bars of water vapor.

Généralement, le raffinage s'effectue avec deux stades de raffinage, le premier stade étant sous pression et le second atmosphérique. Les conditions de raffinage dépendent des caractéristiques requises pour la pâte à papier.Generally, refining is carried out with two stages of refining, the first stage being under pressure and the second atmospheric. The refining conditions depend on the characteristics required for the pulp.

La pâte raffinée est généralement neutralisée par un acide pour éliminer l'alcalinité résultant du traitement par la solution alcaline de peroxyde d'hydrogène. Cette neutralisation est, de manière préférentielle, effectuée jusqu'à un pH de 5,5 à 6 au moyen d'acide sulfurique dilué ou bien de SO2 gazeux.Refined pulp is generally neutralized by an acid to remove the alkalinity resulting from treatment with the alkaline solution of hydrogen peroxide. This neutralization is preferably carried out up to a pH of 5.5 to 6 using dilute sulfuric acid or alternatively SO 2 gas.

La pâte est ensuite traitée de manière habituelle (épuration, classage, recyclage des refus, etc..).The dough is then treated in the usual way (purification, classification, recycling of refusals, etc.).

Les exemples suivants, donnés à titre indicatif, mais non limitatif, permettent de juger de l'invention et de ses avantages. Dans ces exemples, les quantités de réactifs sont exprimées en pourcentage en poids par rapport aux copeaux de bois à l'état sec. On utilise dans les exemples des copeaux de bois de résineux (sapin) ou de feuillu (peuplier). Les copeaux ont été prélevés sur une installation industrielle de fabrication de pâte à papier mécanique et sont conformes aux standards de cette industrie.The following examples, given as an indication, but not limiting, make it possible to judge of the invention and of its advantages. In these examples, the amounts of reagents are expressed as a percentage by weight relative to the wood chips in the dry state. In the examples, softwood (fir) or hardwood (poplar) wood chips are used. The shavings were taken from an industrial mechanical pulp manufacturing facility and meet industry standards.

Les exemples ont été réalisés sur une installation pilote de fabrication de pâte mécanique à haut rendement.The examples were carried out on a pilot installation for manufacturing high-yield mechanical pulp.

Ce pilote, d'une capacité d'environ 200 kg/h, fonctionne en continu et comprend :

  • Une chaîne de préparation des copeaux : stockage, lavage à l'eau et étuvage à la vapeur d'eau à une température de 90°C,
  • Un premier imprégnateur à vis comprenant une zone de compression avec filtration et une zone d'expansion où le réactif est injecté par une pompe doseuse,
  • Une capacité tampon permettant d'assurer une durée de séjour de 5 à 60 mm à une température de 40 à 100°C,
  • Un deuxième imprégnateur à vis comprenant une zone de compression munie d'un filtre et d'un dispositif d'injection d'eau de lavage et une zone d'imprégnation où le deuxième réactif est injecté au moyen d'une pompe doseuse,
  • Une capacité tampon permettant d'assurer une durée de séjour de 15 à 120 mn à une température de 40 à 100°C,
  • Un raffineur à double disque (40 pouces),
  • Un classeur HOOPER à fentes et un cuvier de stockage et de neutralisation de la pâte par du SO2 gazeux.
This pilot, with a capacity of around 200 kg / h, operates continuously and includes:
  • A chain of chip preparation: storage, washing with water and steaming with water at a temperature of 90 ° C,
  • A first screw impregnator comprising a compression zone with filtration and an expansion zone where the reagent is injected by a metering pump,
  • A buffer capacity enabling a residence time of 5 to 60 mm to be ensured at a temperature of 40 to 100 ° C,
  • A second screw impregnator comprising a compression zone provided with a filter and a device for injecting washing water and an impregnation zone into which the second reagent is injected by means of a metering pump,
  • A buffer capacity enabling a residence time of 15 to 120 minutes to be ensured at a temperature of 40 to 100 ° C,
  • A double disc refiner (40 inches),
  • A HOOPER filing cabinet with slits and a vat for storage and neutralization of the pulp by gaseous SO 2 .

Après fabrication de la pâte, des feuilles de papier sont réalisées avec cette pâte pour mesurer la blancheur et les caractéristiques mécaniques, selon les normes ISO de l'industrie papetière.After manufacturing the pulp, sheets of paper are produced with this pulp to measure the whiteness and the mechanical characteristics, according to ISO standards of the paper industry.

La solution commerciale de borohydrure de sodium utilisée provient de la Société MORTON International et contient 12 % de NaBH4 et 40 % de NaOH ; elle est désignée sous le nom de BOROLR.The commercial sodium borohydride solution used comes from the company MORTON International and contains 12% NaBH 4 and 40% NaOH; it is designated under the name of BOROL R.

L'agent complexant des ions métalliques, utilisé dans les exemples, est du DTPA (sel de sodium de l'acide diéthylènetriamine pentaacétique) sous forme de solution aqueuse à 40 %.The metal ion complexing agent used in the examples is DTPA (sodium salt of diethylenetriamine pentaacetic acid) in the form of a 40% aqueous solution.

EXEMPLE 1EXAMPLE 1

Des copeaux de résineux (sapin, épicéa) sont lavés et étuvés à la vapeur d'eau. On imprègne ces copeaux, en continu, avec une solution réductrice à 20°C comprenant 5,9 % de sulfite de sodium, 0,5 % de solution de DTPA à 40 % et 1,5 % de solution de borohydrure de sodium BOROLR, la solution ayant un pH de 10,5.Softwood shavings (fir, spruce) are washed and steamed with water. These shavings are impregnated continuously with a reducing solution at 20 ° C. comprising 5.9% of sodium sulfite, 0.5% of DTPA solution at 40% and 1.5% of sodium borohydride solution BOROL R , the solution having a pH of 10.5.

On chauffe les copeaux à 60°C pendant 30 mn. On presse les copeaux à 60°C pour éliminer environ 0,5 l de solution réductrice par kg de copeaux (secs) (soit environ 50 % d'élimination). On rince avec 2 l d'eau par kg de copeaux secs.The chips are heated at 60 ° C for 30 min. The shavings are pressed at 60 ° C. to remove approximately 0.5 l of reducing solution per kg of (dry) shavings (ie approximately 50% removal). Rinse with 2 l of water per kg of dry chips.

Puis on imprègne les copeaux, en continu, avec une solution oxydante à 20°C, comprenant 5 % de peroxyde d'hydrogène, 2 % d'hydroxyde de sodium, 4 % de solution à 40 % de silicate de sodium et 0,5 % de solution à 40 % de DTPA. La solution oxydante a un pH de 11,5.Then the chips are impregnated, continuously, with an oxidizing solution at 20 ° C., comprising 5% of hydrogen peroxide, 2% of sodium hydroxide, 4% of solution with 40% of sodium silicate and 0.5 % 40% DTPA solution. The oxidizing solution has a pH of 11.5.

On chauffe alors les copeaux imprégnés à 90°C pendant 1 heure, puis on les raffine dans un raffineur double disque. La pâte est alors classée et les refus sont renvoyés au raffineur.The impregnated chips are then heated at 90 ° C for 1 hour, then refined in a double disc refiner. The dough is then classified and the refusals are returned to the refiner.

La pâte raffinée a un indice d'égouttage de 70°SR.The refined dough has a drip index of 70 ° SR.

Après neutralisation de la pâte à pH 6 par du SO2, les caractéristiques suivantes sont obtenues : Blancheur ISO 82° Résistance à la rupture :    Longueur de rupture 4500 m Résistance à l'éclatement 2,3 KPa m2/g Résistance à la déchirure 5,1 mN m2/g. After neutralization of the paste at pH 6 with SO 2 , the following characteristics are obtained: ISO whiteness 82 ° Tear resistant : Break length 4500 m Burst resistance 2.3 KPa m 2 / g Tear resistance 5.1 mN m 2 / g.

On peut noter que le procédé selon l'invention, qui comprend un traitement par une solution réductrice contenant du sulfite de sodium et du borohydrure de sodium et un traitement par du peroxyde d'hydrogène permet d'obtenir une pâte à partir de bois de résineux qui, après défibrage, présente un degré de blancheur élevé, supérieur à 80° ISO.It can be noted that the method according to the invention, which comprises treatment with a reducing solution containing sodium sulfite and sodium borohydride and treatment with hydrogen peroxide makes it possible to obtain a pulp from softwood which, after defibration, has a high degree of whiteness, greater than 80 ° ISO.

EXEMPLE 2EXAMPLE 2

On procède comme pour l'exemple 1, mais la durée du chauffage à 90°C après imprégnation par la solution oxydante, est de 2 heures au lieu d'1 heure.The procedure is as for Example 1, but the duration of heating to 90 ° C. after impregnation with the oxidizing solution is 2 hours instead of 1 hour.

On obtient une pâte ayant les mêmes caractéristiques mécaniques et une blancheur de 83° ISO.A paste is obtained having the same mechanical characteristics and a whiteness of 83 ° ISO.

EXEMPLE 3EXAMPLE 3

On procède comme pour l'exemple 1, à l'exception que la solution réductrice est composée de 5,9 % de Na2SO3 et de 0,5 % de solution à 40 % de DTPA et a un pH de 9,6. On obtient une pâte ayant les caractéristiques suivantes : Blancheur ISO 80° ISO Résistance à la rupture :    Longueur de rupture 4400 m Résistance à l'éclatement 2,2 KPa m2/g Résistance à la déchirure 5,4 mN m2/g. The procedure is as for Example 1, except that the reducing solution is composed of 5.9% Na 2 SO 3 and 0.5% of 40% DTPA solution and has a pH of 9.6 . A paste is obtained having the following characteristics: ISO whiteness 80 ° ISO Tear resistant : Break length 4400 m Burst resistance 2.2 KPa m 2 / g Tear resistance 5.4 mN m 2 / g.

EXEMPLE 4EXAMPLE 4 (comparatif)(comparative)

On procède comme à l'exemple 1, mais on ne traite pas les copeaux par une solution réductrice. Le premier traitement consiste en une imprégnation des copeaux par une solution contenant uniquement 0,5 % de solution à 40 % de DTPA.The procedure is as in Example 1, but the chips are not treated with a reducing solution. The first treatment consists of impregnating the chips with a solution containing only 0.5% of 40% DTPA solution.

On obtient une pâte ayant les caractéristiques suivantes : Blancheur ISO 78° ISO Résistance à la rupture :    Longueur de rupture 3200 m Résistance à l'éclatement 1,6 KPa m2/g Résistance à la déchirure 5,2 mN m2/g. A paste is obtained having the following characteristics: ISO whiteness 78 ° ISO Tear resistant : Break length 3200 m Burst resistance 1.6 KPa m 2 / g Tear resistance 5.2 mN m 2 / g.

On peut constater que le traitement des copeaux, avant défibrage, par une solution de peroxyde d'hydrogène, comme décrit dans le brevet EP-A-239 583, et donc sans traitement réducteur,ne permet pas d'obtenir une pâte ayant un degré de blancheur et des résistances mécaniques, analogues à celles obtenues avec le procédé selon l'invention.It can be seen that the treatment of the chips, before defibering, with a solution of hydrogen peroxide, as described in patent EP-A-239 583, and therefore without treatment reducing, does not make it possible to obtain a paste having a degree of whiteness and mechanical strengths, similar to those obtained with the process according to the invention.

EXEMPLE 5EXAMPLE 5

Des copeaux de feuillu (peuplier, tremble) lavés et étuvés, sont imprégnés en continu avec une solution réductrice à 20°C, constituée de 5 % de Na2SO3, de 1,5 % de solution de borohydrure de sodium (BOROLR) et 0,5 % de solution à 40 % de DTPA et ayant un pH de 11,5.Hardwood shavings (poplar, aspen), washed and steamed, are continuously impregnated with a reducing solution at 20 ° C, consisting of 5% Na 2 SO 3 , 1.5% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution and having a pH of 11.5.

On chauffe les copeaux imprégnés à 100°C pendant 30 mn sous atmosphère de vapeur d'eau. On presse alors les copeaux à 60°C pour éliminer plus de 50 % de solution réductrice. On rince avec 2 1 d'eau par kg de copeaux secs.The impregnated shavings are heated at 100 ° C. for 30 min under an atmosphere of steam. The chips are then pressed at 60 ° C to remove more than 50% of reducing solution. Rinse with 2 1 of water per kg of dry chips.

On imprègne alors les copeaux avec une solution oxydante à 20°C comprenant 5,2 % de peroxyde d'hydrogène, 4 % d'hydroxyde de sodium, 4 % de solution à 40 % de silicate de sodium et 0,5 % de solution à 40 % de DTPA, et ayant un pH de 11,4.The shavings are then impregnated with an oxidizing solution at 20 ° C. comprising 5.2% of hydrogen peroxide, 4% of sodium hydroxide, 4% of solution with 40% of sodium silicate and 0.5% of solution at 40% DTPA, and having a pH of 11.4.

Les copeaux sont alors chauffés à 90°C pendant 2 heures et raffinés dans un raffineur double disque à pression atmosphérique.The chips are then heated at 90 ° C for 2 hours and refined in a double disc refiner at atmospheric pressure.

Après classage, la pâte raffinée présente un indice d'égouttage de 56° SR. Les caractéristiques de cette pâte sont les suivantes : Blancheur ISO 87° ISO Résistance à la rupture :    Longueur de rupture 3300 m Résistance à l'éclatement 1,3 KPa m2/g Résistance à la déchirure 3,5 mN m2/g. After classification, the refined dough has a drip index of 56 ° SR. The characteristics of this paste are as follows: ISO whiteness 87 ° ISO Tear resistant : Break length 3300 m Burst resistance 1.3 KPa m 2 / g Tear resistance 3.5 mN m 2 / g.

On traite dans cet exemple des copeaux de feuillu qui sont relativement blancs. Le procédé selon l'invention permet d'obtenir une pâte, après défibrage, dont le degré de blanc est très élevé.In this example, hardwood shavings are treated which are relatively white. The method according to the invention makes it possible to obtain a paste, after defibering, the degree of white of which is very high.

EXEMPLE 6EXAMPLE 6

On procède comme pour l'exemple 5, mais la solution réductrice est composée de 5 % de Na2SO3 et 0,5 % de solution à 40 % de DTPA et a un pH de 11.The procedure is as for Example 5, but the reducing solution is composed of 5% Na 2 SO 3 and 0.5% of solution 40% DTPA and has a pH of 11.

La pâte obtenue présente les caractéristiques suivantes : Blancheur ISO 85,2° ISO Résistance à la rupture :    Longueur de rupture 2900 m Résistance à l'éclatement 1,20 KPa m2/g Résistance à la déchirure 3,1 mN m2/g. The dough obtained has the following characteristics: ISO whiteness 85.2 ° ISO Tear resistant : Break length 2900 m Burst resistance 1.20 KPa m 2 / g Tear resistance 3.1 mN m 2 / g.

EXEMPLE 7EXAMPLE 7 (comparatif)(comparative)

On procède comme à l'exemple 5, mais on n'ajoute pas d'agent réducteur au premier traitement : la première imprégnation est effectuée avec une solution contenant uniquement 0,5 % de solution à 40 % de DTPA.The procedure is as in Example 5, but no reducing agent is added to the first treatment: the first impregnation is carried out with a solution containing only 0.5% of 40% DTPA solution.

La pâte obtenue présente les caractéristiques suivantes : Blancheur ISO 84° ISO Résistance à la rupture :    Longueur de rupture 2300 m Résistance à l'éclatement 0,9 KPa m2/g Résistance à la déchirure 2,9 mN m2/g. The dough obtained has the following characteristics: ISO whiteness 84 ° ISO Tear resistant : Break length 2300 m Burst resistance 0.9 KPa m 2 / g Tear resistance 2.9 mN m 2 / g.

On peut constater que des copeaux de bois de feuillu traités dans cet exemple comparatif donnent, après défibrage, une pâte de blancheur nettement inférieure à celle obtenue avec les mêmes copeaux, à l'exemple 5 utilisant le procédé selon l'invention.It can be seen that the hardwood chips treated in this comparative example give, after defibering, a pulp of whiteness significantly less than that obtained with the same chips, in Example 5 using the method according to the invention.

EXEMPLE 8EXAMPLE 8

On lave et on étuve à 90°C des copeaux de feuillu (peupliers). On les imprègne, en continu, avec une solution réductrice à 20°C constituée de 1 % de solution de borohydrure de sodium (BOROLR) et de 0,5 % de solution à 40 % de DTPA. La solution a un pH de 12,7.Hardwood (poplar) shavings are washed and dried at 90 ° C. They are impregnated, continuously, with a reducing solution at 20 ° C consisting of 1% sodium borohydride solution (BOROL R ) and 0.5% of 40% DTPA solution. The solution has a pH of 12.7.

On chauffe les copeaux à 90°C pendant 15 mn.The chips are heated at 90 ° C for 15 min.

On presse les copeaux, à une température de 60°C, pour éliminer environ 0,5 l de solution réductrice par kg de copeaux secs (soit environ 20 % de solution réductrice éliminée).The chips are pressed at a temperature of 60 ° C to eliminate approximately 0.5 l of reducing solution per kg of dry shavings (i.e. approximately 20% of reducing solution eliminated).

On imprègne alors les copeaux avec une solution oxydante à 20°C comprenant 4,25 % de peroxyde d'hydrogène et 3,8 % d'hydroxyde de sodium. La solution a un pH de 10,5.The chips are then impregnated with an oxidizing solution at 20 ° C. comprising 4.25% of hydrogen peroxide and 3.8% of sodium hydroxide. The solution has a pH of 10.5.

On chauffe les copeaux imprégnés de solution oxydante à 85°C pendant 1 h. On raffine dans un premier raffineur double disque à pression atmosphérique, puis dans un deuxième raffineur simple disque aussi à pression atmosphérique.The shavings impregnated with oxidizing solution are heated at 85 ° C for 1 h. It is refined in a first double disc refiner at atmospheric pressure, then in a second single disc refiner also at atmospheric pressure.

La pâte raffinée, après neutralisation à pH 6 par SO2, a un indice d'égouttage de 62°SR et présente les caractéristiques suivantes : Blancheur ISO 80,9° ISO Résistance à la rupture :    Longueur de rupture 2800 m Résistance à l'éclatement 1,25 KPa m2/g The refined paste, after neutralization at pH 6 with SO 2 , has a drainage index of 62 ° SR and has the following characteristics: ISO whiteness 80.9 ° ISO Tear resistant : Break length 2800 m Burst resistance 1.25 KPa m 2 / g

EXEMPLE 9EXAMPLE 9

On procède exactement comme pour l'exemple 8, mais on utilise une solution réductrice composée de 1 % de Na2SO3, 1 % de solution de borohydrure de sodium (BOROLR) et 0,5 % de solution à 40 % de DTPA.The procedure is exactly as for Example 8, but a reducing solution composed of 1% Na 2 SO 3 , 1% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution is used. .

La pâte obtenue a un indice d'égouttage de 68 ° SR et présente les caractéristiques suivantes : Blancheur ISO 81,1° ISO Résistance à la rupture :    Longueur de rupture 3100 m Résistance à l'éclatement 1,36 KPa m2/g The dough obtained has a drip index of 68 ° SR and has the following characteristics: ISO whiteness 81.1 ° ISO Tear resistant : Break length 3100 m Burst resistance 1.36 KPa m 2 / g

EXEMPLE 10EXAMPLE 10

On procède exactement comme pour l'exemple 8, mais on utilise une solution réductrice composée de 2 % de Na2SO3, 1 % de solution de borohydrure de sodium (BOROLR) et 0,5 % de solution à 40 % de DTPA.The procedure is exactly as for Example 8, but a reducing solution composed of 2% Na 2 SO 3 , 1% sodium borohydride solution (BOROL R ) and 0.5% 40% DTPA solution is used. .

La pâte obtenue a un indice d'égouttage de 65°SR et présente les caractéristiques suivantes : Blancheur ISO 81,7° ISO Résistance à la rupture :    Longueur de rupture 3320 m Résistance à l'éclatement 1,38 KPa m2/g The dough obtained has a drip index of 65 ° SR and has the following characteristics: ISO whiteness 81.7 ° ISO Tear resistant : Break length 3320 m Burst resistance 1.38 KPa m 2 / g

EXEMPLE 11EXAMPLE 11 (comparatif)(comparative)

On procède comme pour l'exemple 8, mais sans ajouter d'agent réducteur au premier traitement : la première imprégnation est réalisée avec une solution composée uniquement de 0,5 % de solution à 40 % de DTPA.The procedure is as in Example 8, but without adding a reducing agent to the first treatment: the first impregnation is carried out with a solution composed only of 0.5% of 40% DTPA solution.

La pâte obtenue a un indice d'égouttage de 6 6 ° SR et présente les caractéristiques suivantes : Blancheur ISO 79,8° ISO Résistance à la rupture :    Longueur de rupture 2900 m Résistance à l'éclatement 1,21 KPa m2/g The dough obtained has a drip index of 6 6 ° SR and has the following characteristics: ISO whiteness 79.8 ° ISO Tear resistant : Break length 2900 m Burst resistance 1.21 KPa m 2 / g

Dans les exemples 8 à 11, on utilise des copeaux de bois de feuillu (peuplier) d'une blancheur initiale moindre que dans les exemples 5 à 7. La blancheur de la pâte finale est donc plus faible que celle obtenue aux exemples 5 à 7, mais on constate, là encore, que le traitement des copeaux de bois par un traitement réducteur, puis par un traitement oxydant, permet d'obtenir, après défibrage du bois, une pâte de très haut niveau de blancheur et présentant des caractéristiques mécaniques renforcées.In Examples 8 to 11, hardwood (poplar) shavings with a lower initial whiteness are used than in Examples 5 to 7. The whiteness of the final pulp is therefore lower than that obtained in Examples 5 to 7 , but again, it can be seen that the treatment of the wood chips by a reducing treatment, then by an oxidizing treatment, makes it possible to obtain, after defibering the wood, a paste of very high level of whiteness and having reinforced mechanical characteristics. .

Claims (11)

  1. Process for producing high-yield, bleached paper pulp from wood chips, according to which the chips are treated, before being ground, with an alkaline hydrogen peroxide solution, characterized in that it consists in:
    (a) impregnating the chips with a reducing solution including sodium sulphite and/or sodium borohydride having a pH of between a value greater than 7 and 13,
    (b) heating the impregnated chips at a temperature of between 60 and 160°C,
    (c) pressing the chips so as to extract at least 20 % of the reducing solution,
    (d) impregnating the chips with the alkaline solution containing hydrogen peroxide,
    (e) heating the chips which have been impregnated in step (d) at a temperature of between 50 and 120°C, and
    (f) beating the chips which have been treated in this manner in step (e).
  2. Process according to Claim 1, characterized in that sodium sulphite or sodium borohydride is used, each in a proportion of 0.1 to 10 % by weight relative to the weight of dry chips.
  3. Process according to Claim 1 or 2, characterized in that the reducing solution contains a complexing or sequestering agent for metal ions.
  4. Process according to one of Claims 1 to 3, characterized in that the temperature of the reducing solution is between 10 and 100°C.
  5. Process according to one of Claims 1 to 4, characterized in that, after being impregnated with the reducing solution, the chips are heated for 1 min to 3 hours at a temperature of between 60 and 160°C.
  6. Process according to one of Claims 1 to 5, characterized in that the chips are impregnated with alkaline hydrogen peroxide solution in a proportion of 0.1 to 10 % by weight of hydrogen peroxide relative to the weight of dry chips.
  7. Process according to one of Claims 1 to 6, characterized in that the hydrogen peroxide solution has a pH of between 8 and 12.5.
  8. Process according to one of Claims 1 to 7, characterized in that the hydrogen peroxide solution contains one or more peroxide-stabilizing agents.
  9. Process according to one of Claims 1 to 8, characterized in that the temperature of the hydrogen peroxide solution is between 10 and 80°C.
  10. Process according to one of Claims 1 to 9, characterized in that the chips which have been impregnated with the hydrogen peroxide solution are heated for 10 min to 5 hours at a temperature of between 50 and 120°C.
  11. Process according to one of Claims 1 to 10, characterized in that the wood chips are impregnated with a solution of a complexing agent for metal ions, and then pressed before being treated with the solution containing hydrogen peroxide.
EP92401044A 1991-04-17 1992-04-14 Process for producing high yield bleached pulp Expired - Lifetime EP0509905B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9104737 1991-04-17
FR9104737A FR2675518B1 (en) 1991-04-17 1991-04-17 PROCESS FOR THE PREPARATION OF HIGH YIELD AND BLEACHED PAPER PULP FROM WOOD CHIPS.

Publications (2)

Publication Number Publication Date
EP0509905A1 EP0509905A1 (en) 1992-10-21
EP0509905B1 true EP0509905B1 (en) 1996-07-10

Family

ID=9411959

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92401044A Expired - Lifetime EP0509905B1 (en) 1991-04-17 1992-04-14 Process for producing high yield bleached pulp

Country Status (12)

Country Link
EP (1) EP0509905B1 (en)
JP (1) JP2588495B2 (en)
AT (1) ATE140283T1 (en)
AU (1) AU650962B2 (en)
CA (1) CA2066316C (en)
DE (1) DE69212051T2 (en)
ES (1) ES2089436T3 (en)
FI (1) FI921671A (en)
FR (1) FR2675518B1 (en)
IE (1) IE75202B1 (en)
NO (1) NO300225B1 (en)
NZ (1) NZ242356A (en)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69912128T2 (en) 1998-04-17 2004-06-17 Alberta Research Council, Inc., Edmonton METHOD FOR PRODUCING LIGNOCELLULOSE-CONTAINING PULP FROM NON-WOODY MATERIAL
JP4738662B2 (en) * 2001-08-03 2011-08-03 日本製紙株式会社 Newspaper
JP4799774B2 (en) * 2001-08-03 2011-10-26 日本製紙株式会社 Printing paper
JP4501329B2 (en) * 2002-03-29 2010-07-14 日本製紙株式会社 Coated paper for gravure printing
JP2006123982A (en) * 2004-10-29 2006-05-18 Kyoraku Co Ltd Thin pulp molded product
CN100357517C (en) * 2005-10-14 2007-12-26 山东轻工业学院 Pretreatment liquid of cotton rod boiling
KR20110123184A (en) 2010-05-06 2011-11-14 바히아 스페셜티 셀룰로스 에스에이 Method and system for high alpha dissolving pulp production
CN103334328A (en) * 2013-06-17 2013-10-02 中国林业科学研究院林产化学工业研究所 Method for preparing bleached pulp by using eucalyptus wood chips
CN103422380B (en) * 2013-08-15 2015-11-18 齐鲁工业大学 A kind of method of needlebush high yield cooking
EP2924166A1 (en) * 2014-03-25 2015-09-30 Basf Se Method for the manufacture of bleached wood fibre
CN103978533B (en) * 2014-06-09 2016-04-06 山东轻工职业学院 A kind of bleaching process of raffia
CN109183495B (en) * 2018-09-26 2020-12-25 湖北夷盟包装材料有限公司 Preparation method of high-transparency transparent paper using bismuth-containing material

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE416481B (en) * 1977-05-02 1981-01-05 Mo Och Domsjoe Ab METHOD AND DEVICE FOR TREATMENT OF WOOD TIP FOR REMOVAL OF HEAVY METALS AND RESIN
JPS5917240B2 (en) * 1980-05-30 1984-04-20 三菱瓦斯化学株式会社 Peroxide labeling method for mechanical pulp
AU545847B2 (en) * 1981-02-11 1985-08-01 Mead Corporation, The Production of chemimechanical pump
US4486267A (en) * 1983-11-14 1984-12-04 Mead Corporation Chemithermomechanical pulping process employing separate alkali and sulfite treatments
US5002635A (en) * 1985-09-20 1991-03-26 Scott Paper Company Method for producing pulp using pre-treatment with stabilizers and refining
FR2634233B1 (en) * 1988-07-12 1995-04-14 Atochem PROCESS FOR PRODUCING BLANCHED CHEMICOTHERMOMECHANICAL PASTES
FR2659363B1 (en) * 1990-03-07 1996-04-19 Atochem PROCESS FOR THE PREPARATION OF HIGHLY YIELDED PASTA.

Also Published As

Publication number Publication date
NO921335D0 (en) 1992-04-06
DE69212051T2 (en) 1997-01-23
FR2675518A1 (en) 1992-10-23
EP0509905A1 (en) 1992-10-21
FR2675518B1 (en) 1996-10-18
JPH06220788A (en) 1994-08-09
FI921671A0 (en) 1992-04-14
IE921176A1 (en) 1992-10-21
NO300225B1 (en) 1997-04-28
ES2089436T3 (en) 1996-10-01
JP2588495B2 (en) 1997-03-05
FI921671A (en) 1992-10-18
DE69212051D1 (en) 1996-08-14
NO921335L (en) 1992-10-19
CA2066316C (en) 1999-09-28
IE75202B1 (en) 1997-08-27
AU650962B2 (en) 1994-07-07
ATE140283T1 (en) 1996-07-15
CA2066316A1 (en) 1992-10-18
NZ242356A (en) 1994-06-27
AU1489792A (en) 1992-10-22

Similar Documents

Publication Publication Date Title
EP0509905B1 (en) Process for producing high yield bleached pulp
FI61055C (en) FOERFARANDE FOER PEROXIDBLEKNING AV HOEGUTBYTESMASSA
NO147037B (en) PROCEDURE FOR PREPARING CELLULOSMASS
CA2422610C (en) Method for bleaching paper pulp
NO140535B (en) PROCEDURE FOR THE PREPARATION OF CELLULOSE PULP BY CONNECTION WITH THE OXYGEN
US5338402A (en) Process for preparing a bleached chemithermomechanical pulp
US6752904B2 (en) Process for removal of lignin from lignocellulosic material
EP0293309B1 (en) Process for producing chemithermomechanical pulps
EP0351330A1 (en) Process for manufacturing bleached chemithermomechanical pulps
JP2007521404A (en) Multi-stage mechanical pulping method using alkaline peroxide with refiner blow line treatment
AU778689B2 (en) Pulping process
EP0213376B1 (en) Process for the delignification of cellulosic materials
JP2002302888A (en) Method of production for bleached pulp
FR2618811A1 (en) Process for the manufacture of bleached chemimechanical or chemithermal mechanical pulps
CA1042160A (en) Alkali/oxygen gas digestion of wood
BE656601A (en)
SU787517A1 (en) Method of obtaining fibrous mass
JP2000273782A (en) Production of bleached pulp
FR2514382A1 (en) PROCESS AND INSTALLATION FOR THE BLEACHING OF CELLULOSIC TISSUES OF CHEMICAL MANUFACTURE

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: 19920421

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IT LI LU NL PT SE

17Q First examination report despatched

Effective date: 19940711

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

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 DK ES FR GB GR IT LI LU NL PT SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

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: 19960710

Ref country code: GR

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: 19960710

Ref country code: DK

Effective date: 19960710

REF Corresponds to:

Ref document number: 140283

Country of ref document: AT

Date of ref document: 19960715

Kind code of ref document: T

REF Corresponds to:

Ref document number: 69212051

Country of ref document: DE

Date of ref document: 19960814

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

Effective date: 19960819

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2089436

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: PT

Effective date: 19961010

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2089436

Country of ref document: ES

Kind code of ref document: T3

NLV1 Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19970430

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19970430

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19970430

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 20010322

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20010404

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20010409

Year of fee payment: 10

Ref country code: DE

Payment date: 20010409

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20010411

Year of fee payment: 10

Ref country code: AT

Payment date: 20010411

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 20010621

Year of fee payment: 10

REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20020414

Ref country code: AT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20020414

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: 20020415

Ref country code: ES

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20020415

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 NON-PAYMENT OF DUE FEES

Effective date: 20020430

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20021101

EUG Se: european patent has lapsed

Ref document number: 92401044.0

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20020414

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20021231

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 20030514

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 NON-PAYMENT OF DUE FEES;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: 20050414