EP0096460B1 - Verfahren zur Verbesserung und Erhaltung der Eigenschaften einer Pulpe - Google Patents

Verfahren zur Verbesserung und Erhaltung der Eigenschaften einer Pulpe Download PDF

Info

Publication number
EP0096460B1
EP0096460B1 EP19830302424 EP83302424A EP0096460B1 EP 0096460 B1 EP0096460 B1 EP 0096460B1 EP 19830302424 EP19830302424 EP 19830302424 EP 83302424 A EP83302424 A EP 83302424A EP 0096460 B1 EP0096460 B1 EP 0096460B1
Authority
EP
European Patent Office
Prior art keywords
pulp
pulps
fibres
mechanical
consistency
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
Application number
EP19830302424
Other languages
English (en)
French (fr)
Other versions
EP0096460A2 (de
EP0096460A3 (en
Inventor
Michel Barbe
Rajinder S. Seth
Derek H. Page
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.)
Pulp and Paper Research Institute of Canada
Original Assignee
Pulp and Paper Research Institute of Canada
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
Priority claimed from US06/377,111 external-priority patent/US4431479A/en
Priority claimed from CA000402701A external-priority patent/CA1170487A/en
Application filed by Pulp and Paper Research Institute of Canada filed Critical Pulp and Paper Research Institute of Canada
Publication of EP0096460A2 publication Critical patent/EP0096460A2/de
Publication of EP0096460A3 publication Critical patent/EP0096460A3/en
Application granted granted Critical
Publication of EP0096460B1 publication Critical patent/EP0096460B1/de
Expired 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
    • D21C9/001—Modification of pulp properties
    • D21C9/007—Modification of pulp properties by mechanical or physical means

Definitions

  • This invention relates to a process for treating lignocellulosic pulp fibres of either softwoods or hardwoods to provide pulps of improved properties.
  • this invention is directed to the treatment of mechanical pulps and high-yield chemical pulps to improve and retain the properties of such pulps.
  • Newsprint traditionally has been manufactured from a furnish consisting of a mixture of a mechanical pulp and a chemical pulp.
  • Mechanical pulp is used because it imparts certain desired properties to the furnish: namely, its high light scattering coefficient contributes to paper opacity and allows the use of a thinner sheet; its high oil absorbency improves ink acceptance during printing.
  • Runnability refers to properties which allow the wet web to be transported at high speed through the forming, pressing and drying sections of a paper-machine and allows the dried paper sheet to be reeled and printed in an acceptable manner. Runnability contributes to papermachine and pressroom efficiency.
  • Mechanical pulps including stone groundwood (SG) and pressurized stone groundwood (PSG) can be made to provide wet stretch but only at the expense of poor drainage.
  • Higher quality mechanical pulps are obtained by manufacture in open discharge refiners, to produce refiner mechanical pulp (RMP) and in pressurized thermomechanical pulp (TMP).
  • RMP refiner mechanical pulp
  • TMP pressurized thermomechanical pulp
  • Still further upgraded mechanical pulps were provided by chemical pretreatment of the wood chips prior to refining to provide chemimechanical pulp (CMP or CTMP).
  • U.S. Patent 4,116,758 issued Sept. 26, 1978 to M. J. Ford provided a process for producing high-yield chemimechanical pulps from woody lignocellulose material by treatment with an aqueous solution of a mixture of sulfite and bisulfite, to provide a pulp which can be readily defibered by customary mechanical means to provide a pulp having excellent strength characteristics.
  • the fibres of low-yield chemical pulps are known for their desirable dry- and wet-web strength properties. Observations of low-yield chemical fibres in a formed paper sheet indicate that these tend to have a kink and curl which is said to contribute, in an advantageous way, to the papermachine runnability and to certain physical properties.
  • Mechanical pulps lack the desirable strength properties to replace, in whole or in part, low-yield chemical pulps, e.g. kraft or sulphite pulps, in linerboard, newsprint, tissue, printing grades and coated-base grade of paper. Consequently, it has been an aim of the art to improve the physical properties of mechanical and high-yield chemical pulps, so that such improved pulps would be used to replace low-yield chemical pulps.
  • High-yield and ultra-high yield sulphite pulps are used as reinforcing pulps for manufacture of newsprint and other groundwood-containing papers. Although they may be subjected to high-consistency refining, their fibres are in practice substantially straight because the curl introduced in high-consistency refining is lost in subsequent handling.
  • Another example, described below, of a method of the invention, is to render permanent, by non-chemical means, the curl imparted to the fibres of high-consistency mechanically treated, mechanical and high-yield chemical pulps.
  • the mechanical pulps or high-yield chemical pulps of the examples described below can be produced by either mechanical defibration of wood, e.g. in stone groundwood (SG), pressurized stone groundwood (PSG), refiner mechanical pulp (RMP) and thermomechanical pulp (TMP) production or by mechanical defibration, at high consistency, followed or preceded by a chemical treatment of wood chips and pulps e.g.
  • UHYS ultra-high-yield sulphite pulps
  • HAS high-yield sulphite pulps
  • CMP chemi-thermomechanical
  • CMP high-yield chemimechanical
  • MPC interstage thermomechanical and chemically post-treated mechanical pulp
  • TMPC thermomechanical pulps
  • a method for treating pulps, that have already been curled comprises: subjecting the pulp to a heat treatment while the pulp is at a high consistency in the form of nodules or entangled mass, thereby to render the curl permanent to subsequent mechanical action.
  • a method for treating high-yield or mechanical pulps, that have already been curled by a mechanical action at high consistency comprises: subjecting the pulp to a heat treatment at a temperature of at least 100°C, while the pulp is at a high consistency of at least 15% thereby to render the curl permanent to subsequent mechanical action.
  • a method for treating high-yield or mechanical pulps, that have already been curled by a high-consistency action comprises: subjecting the pulp to a heat treatment at a temperature of 100°C-170°C for a time varying between 60 minutes and 2 minutes, while the pulp is at a high consistency of 15% to 35%, thereby to render the curl permanent to subsequent mechanical action.
  • the examples disclose a method which follows the mechanical action that has already made the fibres curly in either mechanical, ultra high-yield or high-yield pulps.
  • Such a mechanical action generally takes place at high consistency (15%-35%), and may typically be a high-consistency disc refining action, e.g. as is generally used in pulp manufacture.
  • the method disclosed in the examples thus consists of a simple heat treatment of the pulp in the presence of water while it is retained in the form of nodules or entangled mass at high consistency.
  • the process may involve temperatures above 100°C in which case a pressure vessel is required.
  • the method sets the curl in place either by relief of stresses in the fibre or by a cross-linking mechanism, so that upon subsequent processing during papermaking, the fibres retain their curled form.
  • This curled form has particular advantages for the properties of the wet web, so that the runnability of the papermachine is improved. In addition, the toughness of the finished product is increased.
  • the method begins with a pulp that has been converted to the curly state by mechanical action at high consistency, and in which the fibres are held in a curly state in the form of nodules or entangled mass.
  • the pulp may be either purely mechanical e.g. stone groundwood, pressurized stone groundwood, refiner mechanical, thermomechanical, or a chemimechanical pulp such as ultra high-yield sulphite pulp or high-yield sulphite pulp. Conversion to a curly state is generally achieved naturally in the high-consistency refining action that is normally used for refiner mechanical, thermomechanical and ultra high-yield sulphite pulp.
  • the pulp fibres may be lignocellulosic fibres produced by mechanical defibration, or by refining, or by refining in a disc refiner at high consistency, or by mechanical defibration at high consistency of wood chips, or by mechanical defibration at high consistency of wood chips followed or preceded by a chemical treatment, or by a single stage refining, or after two successive refinings, or between two successive refinings.
  • They may alternatively be pulp fibres commercially produced under the designation of refiner mechanical pulp, pressurized refiner mechanical pulp and thermomechanical pulp either from a single stage or two-stage refining, or commercially produced under the designation of ultra high-yield pulps, high-yield pulps, high-yield chemimechanical pulps, interstage thermomechanical pulps and chemically post-treated mechanical or thermomechanical pulps, or may be part of the furnish, e.g. the refined rejects in mechanical pulp production or may be whole pulps.
  • the method disclosed in the examples comprises of taking the curled pulp at high consistency (say 15-35%) in the form of nodules or entangled mass and subjecting it to heat treatment without appreciable drying of the pulp.
  • the temperature and duration of the heat treatment controls the extent to which the curl in the fibres is rendered permanent, and this may be adjusted to match the advantages sought.
  • This method may be carried out as a batch method in a digester or as a continuous method through a steaming tube maintained at high pressure.
  • the method may also include the step of incorporating a brightening agent during heat treatment, to upgrade the brightness while retaining the improved pulp properties; or the subsequent steps of brightening or bleaching sequences to upgrade the brightness of the pulps while maintaining the improved pulp properties; or indeed may be carried out in brightened pulps thereby also to maintain adequate brightness after heat treatment.
  • the method is to take a pulp that has been made curly by high-consistency (20-35%) refining, and to set in the curl (and perhaps microcompressions) by subjecting it at a high consistency to an elevated temperature (e.g. 110°C-160°C) for a brief time (e.g. 1 minute to 1 hour).
  • an elevated temperature e.g. 110°C-160°C
  • This set-in curl is resistant to removal by the hot disintegration experienced during papermaking.
  • the advantages of such a pulp are: 1. higher wet-web stretch; 2. higher tearing strength; and 3. better drainage.
  • the method may be a batch process, i.e. if the pulp is placed in a pressure vessel e.g. a closed reaction vessel or digester, or it may be a continuous process e.g. through a steaming tube maintaining high pressures.
  • a pressure vessel e.g. a closed reaction vessel or digester
  • a continuous process e.g. through a steaming tube maintaining high pressures.
  • the temperature and duration of the heat treatment controls the extent to which the curl in the fibres is rendered permanent, and this may be adjusted to match the advantages sought.
  • Preferred conditions are as follows: temperatures of from above 100° to 170° with corresponding steam pressures of 5 psig to 105 psig and for periods from 2 minutes to 60 minutes.
  • the treatment disclosed in the examples has been observed to render fibre curl permanent including fibre twists, kinks and microcompressions.
  • the pulp may then be brightened in accordance with any of the well-known conventional brightening sequences.
  • pulp fibres obtained after refining at high consistency are very curly.
  • the fibres retain substantially their curliness so as to produce wet webs with high wet-web stretch, work-to-rupture and fast drainage.
  • pulps receive mechanical action at high temperatures and low consistencies so that their curliness is lost. It is believed that pulps which are given standard hot disintegration treatment in the laboratory at low consistency experience similar conditions during which the curliness is lost and the wet-web properties deteriorate.
  • the percent stretch-to-break was obtained for wet-webs pressed so as to give a breaking length of 100 meters. It is considered that this value is a measure of the "toughness" of the wet-web and is an indication of the runnability of the pulp on a papermachine.
  • Hot disintegration was done according to the procedure of C. W. Skeet and R. S. Allan in Pulp Paper Mag. Canada, Vol. 69, No. 8, pp. T222-224, April 19, 1968.
  • the advantage of this new pulp has been determined in terms of the extensibility (percent stretch-to-break) of wet webs prepared from the pulp pressed so as to give a breaking length of 100 metres. It is considered that this value is a measure of the "toughness" of the wet sheet, and is an indication of the runnability of the pulp on a papermachine.
  • pulp fibres were treated in a digester at 150°C and at about 22% consistency for approximately 60 minutes.
  • the heat treatment produces the desired effects, on wet-web stretch and drainage, for all the lignocellulosic pulp fibres, e.g., mechanical pulp and high-yield sulphite pulp fibres.
  • the treatment has no effect on cellulosic pulp fibres which contain little or no lignin.
  • This example illustrates the effect of the temperature of the treatment.
  • Lignocellulosic pulp fibres were treated in a digester at temperatures of 110,130,150 and 170°C for 60 minutes and at approximately 22% consistency. The results reproduced in Table II were obtained after a standard hot disintegration.
  • This example illustrates the effect of the time for the treatment.
  • Lignocellulosic pulp fibres at approximately 22% consistency were treated in a digester at 150°C for 2, 10 and 60 minutes respectively.
  • the results reproduced in Table III were obtained after a standard hot disintegration.
  • This example illustrates the effect of the consistency of the pulp fibres when submitted to heat treatment.
  • Lignocellulosic pulp fibres were treated in a digester at 150°C for 60 minutes at consistencies of 5, 10, 20, and 25%.
  • % consistency means the percentage of oven-dried weight of pulp fibres to the total weight of pulp fibres plus water.
  • the effect of the treatment is greater, the higher the consistency of the pulp fibres.
  • the treatment has no effect on pulp fibres at low consistency, typically lower than 5%.
  • This example illustrates the effect of the heat treatment on the wet-web and dry-handsheet properties of high-yield pulps.
  • the lignocellulosic pulp fibres were heat treated in a digester at 150°C and at about 20% consistency for approximately 60 minutes.
  • the heat treatment improves, in addition to the wet-web stretch and work to rupture, the dry handsheet tear strength and stretch (Table V).
  • This example illustrates the effect of the pH of the pulp fibres during the heat treatment.
  • a 70% yield sulphite pulp at a pH of 3.2 was heat treated in a digester at 150°C and at about 20% consistency for approximately 60 minutes.
  • Another sample of the same pulp was sprayed with a solution of sodium carbonate to increase its pH to 10.0 and was also given a heat treatment at the same conditions.
  • This example illustrates the effect of pulp bleaching or brightening agents on the wet-web and dry-handsheet strength of heat treated pulps.
  • pulps have been heat treated in the way described earlier, with the addition of a brightening agent during the heat treatment stage.
  • thermomechanical pulp and a 70%-yield sulphite pulp at about 30% consistency were sprayed with a solution of 2% H 2 0 2 , 0.4% EDTA, 3% Na 2 S i O 3 , 0.005% MgS0 4 , to bring it to 19% consistency.
  • the pulps were treated at 150°C for 10 minutes.
  • This example illustrates the effect of the heat treatment on bleached or brightened pulps.
  • a 70% yield sulphite pulp and a thermomechanical pulp at about 30% consistency were sprayed with a solution of 2% H 2 O 2 , 0.4% EDTA, 3% Na 2 Si0 3 and 0.005% MgS0 4 to bring it to 19% consistency.
  • the pulps reacted with the chemicals for one hour at 60°C. Afterwards, the pulps were heat treated at 150°C for 10 minutes.
  • Results are given in Table IX for the original pulps before heat treatment, the brightened pulps and for both pulps after heat treatment.
  • the heat treatment, done under the conditions disclosed herein on the brightened pulp compared to the original pulp gave similar properties while it had higher visual efficiency.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Claims (20)

1. Verfahren zur Beibehaltung der Faserkräuselung von Zellstoffasern, die schon durch Einwirkung bei hoher Konsistenz gekräuselt worden sind, dadurch gekennzeichnet, daß man diese Zellstoffasern einer Wärmebehandlung bei einer Temperatur von 170°C oder weniger für eine Zeitspanne von wenigstens 2 Minuten unterzieht, während dieser Zellstoff in Form von Knötchen oder verfilzter Masse sich bei einer Konsistenz von wenigstens 5% befindet.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Wärmebehandlungsstufe bei einer Temperatur von 100 bis 170°C durchgeführt wird.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Konsistenz des Zellstoffs während der Wärmebehandlung 15 % oder mehr beträgt.
4. Verfahren nach einem der Ansprüche 1, 2 oder 3, dadurch gekennzeichnet, daß die Wärmebehandlungsstufe als ansatzweise Methode in einem Kocher durchgeführt wird.
5. Verfahren nach einem der Ansprüche 1, 2 oder 3, dadurch gekennzeichnet, daß die Wärmebehandlungsstufe als kontinuierliche Methode durch ein bei hohem Druck gehaltenes Dämpfrohr durchgeführt wird.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Zellstofffasern Holzstoff-Zellstoffasern sind, die durch mechanische Zerfaserung hergestellt sind.
7. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Zellstoffasern Holzstoff-Zellstoffasern sind, die durch Refinern hergestellt sind.
8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß die Fasern durch Refinern in einem Scheibenrefiner bei hoher Konsistenzt und/oder in einer Vorrichtung, wie einem "Curlator"@ oder einem "Frotopulper"@, der Kräuselung und Krümmung in die Fasern einführt, erzeugt sind.
9. Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß die Fasern durch mechanisches Zerfasern von Holzschnitzeln bei hoher Knosistenz erzeugt sind.
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, daß von oder nach der mechanischen Zerfaserung eine chemische Behandlung durchgeführt wird.
11. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß die Fasern nach einstufigem Refinern oder nach 2 aufeinanderfolgenden Refiningstufen oder zwischen 2 aufeinanderfolgenden Refiningstufen erhalten sind.
12. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Holzstoff-Zellstoffasern sich bei einem neutralen oder alkalischen pH-Wert befinden.
13. Verahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Zellstoffasern solche Zellstoffasern sind, die unter der Bezeichnung mechanischer Holzstoff bzw. RMP, mechanischer Druckrefiner Holzstoff bzw. PRMP oder mechanischer Holzstoff mit Thermo-Vorbehandlung bzw. TMP entweder durch einstufiges oder 2-stufiges Refinern erzeugt sind.
14. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Zellstoffasern solche Zellstoffasern sind, die unter der Bezeichnung Höchstausbeute-Zellstoffe, Hochausbeute-Zellstoffe, Hochausbeute-mechanische Holzstoffe mit Chemo-thermo-Vorbehandlung bzw. CTMP, chemomechanische Stoffe bzw. CMP, Zwischenstufen-mechanischer-Holzstoff mit Thermo-Vorbehandlung bzw. interstage TMP und chemisch nachbehaldelte mechanischer oder thermomechanische Stoffe erzeugt sind.
15. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Zellstofffasern Teil des Mahlguts einer Papier- oder Plattenproduktes ist.
16. Verfahren nach einem der vorhergenden Ansprüche, dadurch gekennzeichnet, daß die Zellstoffasern der gemahlene Grobstoff bei der Erzeugung von mechanischem oder Hochausbeute-Zellstoff ist.
17. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Zellstoffasern der ganze Stoff des Mahlguts eines Papier- oder Platenproduktes sind.
18. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß ein Aufhellungsmittel während der Wärmebehandlung eingebracht wird.
19. Verfahren nach einem der Ansprüche 1 bis 17, dadurch gekennzeichnet, daß anschließend eine Aufhellungsstufe oder Bleichsequenzen angewandt werden.
20. Verfahren nach einem der Ansprüche 1 bis 17, dadurch gekennzeichnet, daß die Zellstoffe aufgehellte bzw. gebleichte Zellstoffe sind.
EP19830302424 1982-05-11 1983-04-29 Verfahren zur Verbesserung und Erhaltung der Eigenschaften einer Pulpe Expired EP0096460B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US06/377,111 US4431479A (en) 1982-05-11 1982-05-11 Process for improving and retaining pulp properties
US377111 1982-05-11
CA000402701A CA1170487A (en) 1981-05-07 1982-05-11 Process for improving and retaining pulp properties

Publications (3)

Publication Number Publication Date
EP0096460A2 EP0096460A2 (de) 1983-12-21
EP0096460A3 EP0096460A3 (en) 1984-02-29
EP0096460B1 true EP0096460B1 (de) 1986-09-03

Family

ID=25669674

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830302424 Expired EP0096460B1 (de) 1982-05-11 1983-04-29 Verfahren zur Verbesserung und Erhaltung der Eigenschaften einer Pulpe

Country Status (3)

Country Link
EP (1) EP0096460B1 (de)
FI (1) FI74052C (de)
NZ (1) NZ204019A (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4976819A (en) * 1988-04-28 1990-12-11 Potlatch Corporation Pulp treatment methods
US6627041B2 (en) 2000-03-06 2003-09-30 Georgia-Pacific Corporation Method of bleaching and providing papermaking fibers with durable curl
US6899790B2 (en) 2000-03-06 2005-05-31 Georgia-Pacific Corporation Method of providing papermaking fibers with durable curl
US6837970B2 (en) * 2001-12-18 2005-01-04 Kimberly-Clark Worldwide, Inc. Wood pulp fiber morphology modifications through thermal drying

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1791248A (en) * 1928-09-22 1931-02-03 Du Pont Felted-cellulose-fiber product
US1857100A (en) * 1931-08-25 1932-05-03 Celastic Corp Absorbent paper
US3011327A (en) * 1961-05-22 1961-12-05 Turbo Machine Co Apparatus for setting textile fibers
FR2049840A5 (de) * 1969-06-04 1971-03-26 Polymer Processing Res Inst
US4036679A (en) * 1975-12-29 1977-07-19 Crown Zellerbach Corporation Process for producing convoluted, fiberized, cellulose fibers and sheet products therefrom
FI773597A (fi) * 1976-12-01 1978-06-02 New Zealand Dev Finance Foerfarande foer behandling av lignocellulosa-eller cellulosafibermassa sao att behandlingen fraemjar kroekning av massans fibrer och foerbaettrar papprets rivhaollfasthet

Also Published As

Publication number Publication date
EP0096460A2 (de) 1983-12-21
FI74052B (fi) 1987-08-31
FI74052C (fi) 1987-12-10
EP0096460A3 (en) 1984-02-29
NZ204019A (en) 1986-09-10
FI831626L (fi) 1983-11-12
FI831626A0 (fi) 1983-05-10

Similar Documents

Publication Publication Date Title
US4431479A (en) Process for improving and retaining pulp properties
US8277606B2 (en) Method of providing paper-making fibers with durable curl and absorbent products incorporating same
US3707436A (en) Exploding of ammonia impregnated wood chips
US4869783A (en) High-yield chemical pulping
CA1080911A (en) Process for making high-strength, high-yield sulfite-modified thermomechanical pulp and a linerboard composition produced therefrom
EP3002365A1 (de) Modifizierte kraftfasern
US6267841B1 (en) Low energy thermomechanical pulping process using an enzyme treatment between refining zones
US4502918A (en) Two-stage chemical treatment of mechanical wood pulp with sodium sulfite
CA2634202C (en) Wood-based lignocellulosic fibrous material
US20080295986A1 (en) Method of Producing Paper and Cardboard
US6627041B2 (en) Method of bleaching and providing papermaking fibers with durable curl
US3919041A (en) Multi-stage chlorine dioxide delignification of wood pulp
US3829357A (en) Oxidative manufacture of pulp with chlorine dioxide
EP0096460B1 (de) Verfahren zur Verbesserung und Erhaltung der Eigenschaften einer Pulpe
EP0030778B1 (de) Verfahren zur Herstellung raffinierter Pulpe
CA1170487A (en) Process for improving and retaining pulp properties
USRE28777E (en) Refining of vegetable matter and delignification of the refined matter with chlorine dioxide
US4978426A (en) Production of high strength linerboard with oxygen and alkali
El‐Taraboulsi et al. A modified method of nitric acid pulping of bagasse
US4836892A (en) Pulp blends for linerboards
AU671159B2 (en) Improved bleaching of high consistency lignocellulosic pulp
US20220074139A1 (en) Pulping Methods, Methods for Manufacturing Paperboard, and Paperboard Structures
JPS6247999B2 (de)
CA1145106A (en) Procedure for improving properties of mechanical wood pulps
CA1309562C (en) Chemimechanical pulping process employing sodium carbonate and sodium sulphite

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

AK Designated contracting states

Designated state(s): DE FR IT SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Designated state(s): DE FR IT SE

ITCL It: translation for ep claims filed

Representative=s name: SOCIETA' ITALIANA BREVETTI S.P.A.

EL Fr: translation of claims filed
17P Request for examination filed

Effective date: 19840328

DET De: translation of patent claims
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR IT SE

REF Corresponds to:

Ref document number: 3365811

Country of ref document: DE

Date of ref document: 19861009

ET Fr: translation filed
ITF It: translation for a ep patent filed
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
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19890410

Year of fee payment: 7

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

Ref country code: FR

Payment date: 19890412

Year of fee payment: 7

ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19890531

Year of fee payment: 7

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

Ref country code: SE

Effective date: 19900430

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

Ref country code: FR

Effective date: 19901228

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

Ref country code: DE

Effective date: 19910101

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

EUG Se: european patent has lapsed

Ref document number: 83302424.3

Effective date: 19910115