EP0466752B1 - A process for bleaching a fiber pulp with a chemical solution - Google Patents

A process for bleaching a fiber pulp with a chemical solution Download PDF

Info

Publication number
EP0466752B1
EP0466752B1 EP90905528A EP90905528A EP0466752B1 EP 0466752 B1 EP0466752 B1 EP 0466752B1 EP 90905528 A EP90905528 A EP 90905528A EP 90905528 A EP90905528 A EP 90905528A EP 0466752 B1 EP0466752 B1 EP 0466752B1
Authority
EP
European Patent Office
Prior art keywords
treatment
bed
liquid
chemicals
pulp
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
EP90905528A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0466752A1 (en
Inventor
Hakan ÖSTMAN
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.)
HACKMAN PROSESSI Oy AB
SALOMANS Oy
Original Assignee
HACKMAN PROSESSI Oy AB
SALOMANS Oy
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 HACKMAN PROSESSI Oy AB, SALOMANS Oy filed Critical HACKMAN PROSESSI Oy AB
Publication of EP0466752A1 publication Critical patent/EP0466752A1/en
Application granted granted Critical
Publication of EP0466752B1 publication Critical patent/EP0466752B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1031—Pulse, dynamic, displacement processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0021—Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)
    • D21C11/0028—Effluents derived from the washing or bleaching plants
    • 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
    • D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
    • D21C9/06—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents in filters ; Washing of concentrated pulp, e.g. pulp mats, on filtering surfaces

Definitions

  • the present invention relates to a continuous-working Bleaching of a fiber pulp with a chemical solution by forming from a pulp suspension a pulp bed on a filter surface and by feeding the bed through one of several chemical treatment steps in which a chemical solution is displaced through the bed.
  • a process of this type is used for the bleaching of a cellulose material it is in general called displacement bleaching or dynamic bleaching.
  • the fiber When it is desired to produce a cellulose fiber having a high degree of brightness, the fiber has to be bleached after the actual defibration process. For example, in order to obtain a sulfate pulp with a high degree of brightness, it normally has to be bleached in five steps by using chlorine and chlorine dioxide as the bleaching chemical and sodium hydroxide as the extraction chemical.
  • the pulp bed Before the removal of the above-mentioned chemical solution, and together with it the formed reaction products, from the bed by displacing them with the chemical solution used in the subsequent step, or in the case of the last bleaching step with washing water, the pulp bed is directed through a so-called stationary step, with a sufficient retention time, in order that the concentration profile produced in the bed after the displacement should have time to level out under the effect of diffusion.
  • the retention time of the above-mentioned stationary step should be in the same order as the retention times in the conventional method.
  • the object of the present invention is to avoid the above-mentioned disadvantage by using a displacement process which requires no stationary step for achieving an even chemical treatment throughout the pulp bed.
  • the bleaching process based on the displacement method is in many respects similar to the washing process based on the displacement method, but there are between them also great differences which it is important to take into account expediently in the further development of the bleaching process.
  • both processes there occurs a similar mixing of liquids due to dispersion and to the fact that the liquid flow in the fiber bed is laminar.
  • the displacement never occurs ideally as a plug, but there always occurs mixing between the liquids, which is disadvantageous in both the washing process and the bleaching process.
  • This disadvantageous mixing can be reduced in both processes by carrying out several successive displacements according to the countercurrent principle.
  • the higher the number of displacement steps used the higher the respective equipment costs.
  • the displacement is based on the cross-flow method, in which the liquid flow through the bed during the displacement is perpendicular to the travel direction of the bed.
  • pulp fibers are compressible, the consistency of the pulp bed is not constant throughout the bed; it increases exponentially towards the filter surface. This profile is, of course, dependent on the type of the pulp concerned and on how large a pressure difference is used to produce the liquid flow. Normally it rises from a consistency value of approx. 2 % to approx. 20 %, being on average approx. 10 %.
  • this phenomenon does not have a great significance, but in bleaching, in which it is important that all the fiber layers in the bed receive a sufficient quantity of active bleaching chemicals, it is of especially great significance, in particular since, in addition, the concentration of the active chemicals in the solution decreases continuously as the solution flows toward the filter surface. This is due to the above-mentioned dispersion phenomenon and the fact that chemicals are consumed as they react with the pulp layers through which they flow.
  • the pulp layers which are at a greater distance from the filter surface are treated with a chemical solution which has a great excess of chemicals as compared with the requirement.
  • the layers close to the filter surface do not receive a sufficient amount of active chemicals, or receive no active chemicals, during the displacing, and so the bleaching of the pulp bed is quite uneven.
  • the object of the present invention is to provide this kind of pulp bed treatment, but in such a manner that through losses of active chemicals there is not caused a higher consumption of chemicals than in a normal bleaching process.
  • a pulp bed is formed from a clean washed pulp to be bleached, and the washing liquid present in it is displaced by using as the displacing liquid the first bleaching solution (which contains as the active chemicals, for example, chlorine and/or chlorine dioxide), which contains active chemicals in excess, preferably approx. double the amount required in this step for the complete chemical treatment of the whole pulp bed.
  • the first bleaching solution which contains as the active chemicals, for example, chlorine and/or chlorine dioxide
  • displacement is continued with another solution or several solutions to the degree that the solution used in the first displacement and the active chemical quantity present in it has in its entirety or almost in its entirety been displaced from the bed.
  • one bleaching step contains not only one displacement but displacements with at least two solutions. Respectively, the filtrates are divided into at least three fractions.
  • the bleaching steps described above may be included several in succession in the process.
  • the recovery of the above-mentioned active chemicals effectively displaced through the bed is important in order that as little as possible of the solution of the step, containing active chemicals, should become mixed with the active chemical solution used in the subsequent treatment step. For this reason and owing to the fact that in a treatment step it is possible to use a high total quantity coefficient without thereby increasing the losses of active chemicals, the active chemical solution of the directly subsequent treatment step is not used for displacing the active chemical solution of the step concerned, but a solution as neutral as possible with respect to both treatment steps is used, for example preferably pure water at a suitable temperature.
  • a chlorine solution is displaced directly with a sodium hydroxide solution, owing to dispersion the solutions become mixed with each other in the boundary zone. Thus they partly cancel each other's positive effect in terms of bleaching and, in addition, disadvantageous secondary reactions are produced. Owing to the drastic pH change, for example, the chlorine solution may be converted to a hypochlorite solution.
  • the filtrate which is removed from the fiber bed through the filter surface during the chemical treatment by displacing it with the active chemical solution and the neutral solution usec in the step changes with respect to its chemicals content as the pulp bed proceeds during the progress of the displacement. Its first fraction contains mainly chemicals used and spent in the previous step and the reaction products produced. The fraction then changes more slowly or faster, according to the strength of the dispersion caused by the bed, to a filtrate which mainly contains the active chemicals used in the treatment step in question, which chemicals have become non-active when reacting with the fiber material of the pulp bed, and reaction products which have been formed.
  • This fraction then in a corresponding manner changes to a fraction which in the main contains active chemicals used in the treatment step which have not been spent through reaction and correspond to the excess of active chemical which is used in the treatment step.
  • This fraction for its part changes, when the bed proceeds, in a corresponding manner to a fraction which in the main contains chemicals which are derived from the neutral solution which is used as a displacement solution in this step immediately after the active chemical solution.
  • this solution as is normally recommendable, is pure water
  • the above-mentioned fraction which contains active chemicals changes to nearly pure water before it again changes to a solution which contains spent chemicals used in the subsequent treatment step and the formed reaction products, unless the step in question is the last treatment step.
  • the third filtrate fraction above which contains active chemicals which have not been spent in the reactions in the treatment step, are recovered as carefully as possible and are reused together with fresh added chemicals as a chemical solution in the same treatment step.
  • the maximum recovery of active chemicals is obtained when it is possible to adjust the removal of the filtrate fractions so that the maximum concentration of active chemicals in both of the "tails" is the same, i.e. the concentration of active chemicals in the filtrate is the same at both division points of the filtrate fractions.
  • the filtrate could be divided into different fractions simply by dividing the filtrate chamber behind the screen surface by means of partitions sealing tightly to the screen. In this case it would, however, not be possible in all operating situations to achieve maximal recovery of chemicals, since the location of the chemical profile of the filtrate in the equipment used shifts when the ratio between the displacement liquid flow rate and the filter surface travel speed changes. In addition to this, the location of the chemical profile between the chemicals spent in the reaction and the still active chemicals is affected by the proportion of the used active chemicals spent in the treatment of the bed. This proportion depends, among other things, on how much residual lignin or a similar chemicals-consuming constituent is present in the pulp bed which is being treated.
  • the apparatus includes in addition to the fixed support structure 6 only two moving parts: a rotating screen mantle 7 together with the drive 8 connected with it, and the stirrer 9 for the washed pulp web.
  • the circular shape of the screen mantle is maintained by means of an upper screen support ring 10 and lower support ring 11.
  • the desired rotational velocity is provided for the screen mantle by means of a screen-mantle drawing ring 12 and a drive 8 connected to it.
  • the liquid volume between the inner and outermost support structures 13, 14, where the screen mantle also rotates is divided by means of partitions 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 in such a way that separate liquid chambers are formed for the different displacement steps.
  • the screen mantle is sealed by means of gaskets 28, 29 secured to the support rings, to enable a higher liquid level 30, 31 to be maintained inside the screen than outside the screen when there is a pulp web 32 on the screen surface.
  • the filtrate chamber is divided by means of partitions which leave a uniformly wide slit in relation to the filter surface, through which slit part of the filtrate fraction can pass into the preceding or subsequent filtrate fraction.
  • the most recommendable embodiment is that the principal variables of the process are in the same order as when the equipment is used for washing pulp.
  • the thickness of the pulp bed is 20 -100 mm, preferably approx. 50 mm.
  • the pressure difference for accomplishing the liquid displacement is 1 - 4 meters of water head.
  • the travel speed of the screen is 0,2 - 1 m/s, preferably approx. 0.5 m/s.
  • the total quantity coefficient of the displacement of one treatment step is >1.5, preferably >2.
  • the quantity coefficient of the active chemical solution is approx. one-half of these values.
  • the total retention time of the fiber bed in one treatment step will be 10 - 50 seconds, normally approx. 20 seconds.
  • the most preferred embodiment of the present invention is to use in each displacement bleaching step a high quantity coefficient, i.e. a coefficient approx. twice that in the displacement bleaching processes used so far, and in addition to divide each step into at least two partial steps, the use of this bleaching process requires that there be available a method and equipment required for implementing the method, enabling several successive displacement steps to be implemented in one and the same apparatus and that, when steps are added their marginal costs are relatively low and also the equipment costs calculated per effective screen surface are economical.
  • the surface layer of the fiber bed is treated with an approx. double amount of chemicals as compared with the bottom layer.
  • This non-uniform distribution does not, however, affect the uniform chemical treatment of the bed, since, if we examine the individual fiber layers of the bed, through each layer there flow active chemicals the amount of which approaches infinite in ratio to the amount that the fiber layer concerned spends in order to achieve a complete reaction.
  • the present process requires a maximally rapid transfer of chemicals, which is based on a forced, directed flow not only around the fibers but also through them, because the retention time is so short that no significant transfer of material can take place through diffusion. For this reason it is also necessary to aim at the system remaining a two-phase system, which requires that the pressure in the system will not be below the total equilibrium pressure of the gases an vapors. In this case a maximum proportion of the gases and vapors remains dissolved in the liquid phase, and no disturbing gas bubbles or gas phase is formed in the bed during the treatment.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
  • Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
  • Communication Cables (AREA)
  • Management, Administration, Business Operations System, And Electronic Commerce (AREA)
  • Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
EP90905528A 1989-04-07 1990-04-06 A process for bleaching a fiber pulp with a chemical solution Expired - Lifetime EP0466752B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI891662 1989-04-07
FI891662A FI85513C (fi) 1989-04-07 1989-04-07 Foerfarande foer behandling av fibermassa med kemikalieloesning.
PCT/FI1990/000095 WO1990012146A1 (en) 1989-04-07 1990-04-06 A process for treating a fiber pulp with a chemical solution

Publications (2)

Publication Number Publication Date
EP0466752A1 EP0466752A1 (en) 1992-01-22
EP0466752B1 true EP0466752B1 (en) 1996-07-10

Family

ID=8528196

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90905528A Expired - Lifetime EP0466752B1 (en) 1989-04-07 1990-04-06 A process for bleaching a fiber pulp with a chemical solution

Country Status (13)

Country Link
EP (1) EP0466752B1 (xx)
JP (1) JPH05500835A (xx)
AT (1) ATE140282T1 (xx)
AU (1) AU647020B2 (xx)
BR (1) BR9007276A (xx)
CA (1) CA2049951A1 (xx)
DE (1) DE69027770T2 (xx)
ES (1) ES2091240T3 (xx)
FI (1) FI85513C (xx)
NO (1) NO176485C (xx)
NZ (1) NZ233237A (xx)
WO (1) WO1990012146A1 (xx)
ZA (1) ZA902703B (xx)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6423183B1 (en) 1997-12-24 2002-07-23 Kimberly-Clark Worldwide, Inc. Paper products and a method for applying a dye to cellulosic fibers
US6749721B2 (en) 2000-12-22 2004-06-15 Kimberly-Clark Worldwide, Inc. Process for incorporating poorly substantive paper modifying agents into a paper sheet via wet end addition
US7749356B2 (en) 2001-03-07 2010-07-06 Kimberly-Clark Worldwide, Inc. Method for using water insoluble chemical additives with pulp and products made by said method
US6582560B2 (en) 2001-03-07 2003-06-24 Kimberly-Clark Worldwide, Inc. Method for using water insoluble chemical additives with pulp and products made by said method
US7670459B2 (en) 2004-12-29 2010-03-02 Kimberly-Clark Worldwide, Inc. Soft and durable tissue products containing a softening agent

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA783483A (en) * 1964-08-13 1968-04-23 Electric Reduction Company Of Canada Processes for bleaching cellulosic pulps
NO141172B (no) * 1970-06-25 Keskuslaboratorio-Centrallaboratorium Ab, Oy, Fremgangsmaate ved dynamisk bleking av fibermasse
FI67894C (fi) * 1982-05-21 1985-06-10 Rauma Repola Oy Foerfarande och anordning foer blekning av fibermassa
FI86895C (fi) * 1990-01-11 1997-01-15 Poeyry Jaakko & Co Oy Foerfarande foer motstroemstvaettning och blekning av massa fraon cellulosakok

Also Published As

Publication number Publication date
ZA902703B (en) 1994-10-07
ES2091240T3 (es) 1996-11-01
BR9007276A (pt) 1992-03-17
FI85513B (fi) 1992-01-15
AU647020B2 (en) 1994-03-17
FI891662A0 (fi) 1989-04-07
DE69027770D1 (de) 1996-08-14
EP0466752A1 (en) 1992-01-22
CA2049951A1 (en) 1990-10-08
NO176485C (no) 1995-04-12
FI891662A (fi) 1990-10-08
DE69027770T2 (de) 1996-11-28
ATE140282T1 (de) 1996-07-15
NO913904L (no) 1991-10-04
JPH05500835A (ja) 1993-02-18
WO1990012146A1 (en) 1990-10-18
NO176485B (no) 1995-01-02
NO913904D0 (no) 1991-10-04
AU5420190A (en) 1990-11-05
FI85513C (fi) 1992-04-27
NZ233237A (en) 1993-02-25

Similar Documents

Publication Publication Date Title
CA1122756A (en) Oxygen delignification of wood pulp
FI59434B (fi) Delignifiering och blekning av cellulosa med syre
US4806203A (en) Method for alkaline delignification of lignocellulosic fibrous material at a consistency which is raised during reaction
US4298426A (en) Method and apparatus for treating pulp with oxygen in a multi-stage bleaching sequence
US4295926A (en) Method and apparatus for treating pulp with oxygen
DE69028797D1 (de) Verfahren zum Bleichen von Zellstoff mit Ozon
EP0281273A1 (en) Cellulosic pulp
US4298427A (en) Method and apparatus for intimately mixing oxygen and pulp while using an alkali to extract bleaching by-products
US4310384A (en) Reducing chemical transfer between treatment stages
US3258391A (en) Chemical recovery in pulp manufacture
EP0466752B1 (en) A process for bleaching a fiber pulp with a chemical solution
CA1225267A (en) Method and apparatus for washing paper pulp
US4295927A (en) Method and apparatus for treating pulp with oxygen and storing the treated pulp
EP0420860B1 (en) Process and apparatus for the manufacture of pulp for paper, board, fiberboard and similar products
EP0106609A1 (en) Apparatus and method for oxygen extraction of lower consistency pulp
US4608122A (en) Method for washing a paper fiber on a belt washer using a sonic frequency disturbance
US1683262A (en) Process of chemically treating and washing pulp
US5227075A (en) Process and apparatus for continuous filtering and liquid displacement of a liquid suspension of a fibrous or finely-divided material
US3575795A (en) Rapid high consistency bleaching with continuous diffusion
CA1096591A (en) Displacement of a liquid a by a liquid b in a suspension
KR960006125B1 (ko) 향상된 산소 탈리그닌화 선택성의 펄프를 얻는 방법
US3587257A (en) Bleaching system including a single,triple-deck table washer
FI91896C (fi) Menetelmä happivalkaisun yhteydessä
CA1230205A (en) Process and apparatus for bleaching of pulp
CA1246304A (en) Process and apparatus for bleaching of pulp

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: 19911001

AK Designated contracting states

Kind code of ref document: A1

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

17Q First examination report despatched

Effective date: 19921210

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 IT LI LU NL SE

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

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 19960710

Ref country code: DK

Effective date: 19960710

Ref country code: BE

Effective date: 19960710

Ref country code: LI

Effective date: 19960710

Ref country code: CH

Effective date: 19960710

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 Corresponds to:

Ref document number: 140282

Country of ref document: AT

Date of ref document: 19960715

Kind code of ref document: T

REF Corresponds to:

Ref document number: 69027770

Country of ref document: DE

Date of ref document: 19960814

ET Fr: translation filed
REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2091240

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
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

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

Ref country code: GB

Effective date: 19970406

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

Ref country code: ES

Payment date: 19970414

Year of fee payment: 8

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

Ref country code: DE

Payment date: 19970421

Year of fee payment: 8

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

Ref country code: SE

Payment date: 19970425

Year of fee payment: 8

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

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

Ref country code: FR

Payment date: 19970430

Year of fee payment: 8

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

Effective date: 19970406

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

Ref country code: AT

Payment date: 19980324

Year of fee payment: 9

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

Ref country code: ES

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 19980407

Ref country code: SE

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

Effective date: 19980407

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

Ref country code: FR

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19980430

EUG Se: european patent has lapsed

Ref document number: 90905528.7

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: 19990202

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

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

Ref country code: AT

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

Effective date: 19990406

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 20000301