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
  • 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)
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
  • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

• the present invention relates to a method in bleaching of lignocellulosic material (cellulose pulp) with ozone.
• the cellulose pulp can be produced both chemically and chemimechanically.
• Chemical cellulose pulps are a clearly defined category of cellulose pulps and are comprised, for instance, of sulphite pulp, sulphate pulp and polysulphide pulp.
• Particularly suitable chemical cellulose pulps are those that have a high viscosity at relatively low Kappa numbers.
• Belonging to this group of cellulose pulps are sulphate pulps which have been cooked or digested at a high sulphidity, and modified sulphate pulps that have been cooked or digested in accordance with a counterflow method in which white liquor is added also during an advanced stage of the cooking process, and alkaline cellulose pulps which are cooked in the presence of one or more catalysts, for instance in the presence of a quinone compound, such as anthraquinone.
• Suitable cellulose pulps are those having the designations MSS-AQ (mini - sulphide sulphite - anthraquinone), Si-Sa-Si (sulphite-sulphate-sulphite) and PS-Si (polysulphide-sulphite), all of which are referred to in the journal "Paperi ja Puu H , 5/1989, pp. 509-513.
• Particularly suitable chemimechanical pulps are those in which the digestion or cooking process is relatively far reaching and is followed by a mechanical defibering process.
• the ozone bleaching process can be applied to unbleached cellulose pulp or cellulose pulp which has been delignified/ bleached in one or more stages.
• waste liquors deriving from the final pulp bleaching stage have hitherto not generally been returned to the chemical recovery system, but they have been discharged to the recipient.
• the ever increasing demands placed on emissions to the environment have meant that the release of these liquors to the recipient must be reduced to a minimum. This also applies to relatively harmless compounds in the form, for instance, of non chlorinated but oxygen consuming substances.
• the present Invention solves this problem partially and relates to a method in bleaching with ozone lignocellulosic material (celiulose pulp) which has been produced at least partially by chemical processes, in the presence of water and at an acidity, expressed as pH, of 2-5.
• the method is characterized in that the acidity is sustained during the ozone bleaching process by adding to the system either a sulphuric acid solution or an acid sodium sulphate solution prepared by electrolysis (or electrodialysis) of a substan ⁇ tially -neutral sodium sulphate solution obtained by recyc ⁇ ling chemicals in a system to which rest solution (waste liquor) derived from the ozone bleaching process is passed.
• sodium sulphate is taken from "the chemical recovery system at some appropriate loca ⁇ tion.
• An example of an appropriate location is the electric precipitator in the recovery boiler included in the chemical recovery system, where the separated dust contains essen- tially sodium sulphate and minor quantities of sodium car ⁇ bonate and sodium chloride.
• the waste liquor from the ozone bleaching process is mixed with other waste liquor from the pulp manufacturing process, this waste liquor being recovered and 'returned to the evapo ⁇ ration and combustion plant (the recovery boiler) of the chemical system.
• the evapo ⁇ ration and combustion plant the recovery boiler
• Part of the sodium sulphate collected in the electric precipitator is removed therefrom and dissolved in water and the subsequent solution is then subjected to an electrolysis or an electrodialysis process.
• ozone bleaching waste liquor is mixed with waste liquor from an alkaline treatment stage, for instance in the bleaching department, so as to obtain an essentially neutral solution, which is then cooled so that sodium sulphate (Na-SO.) is precipitated, this sodium sulphate precipi ⁇ tate being separated and led away and dissolved in water and the resulting solution is then subjected to an electrolysis or an electrodialysis process.
• an alkaline treatment stage for instance in the bleaching department
• the remaining mother liquor which contains essentially organic materials, is transferred to the chemical recovery system.
• the sodium sulphate solution contains metals, such as calcium, magnesium or manganese, in harmful quanti ⁇ ties, it is appropriate to treat the solution with a hydro ⁇ gen saturated cation exchanger prior to the electrolysis or electrodialysis stage.
• the sodium sulphate solutions obtained, for instance, in the aforedescribed manner, are subjected to electrolysis or electrodialysis in a cell which is provided with anode, cathode and one or more membranes.
• the treatment process can be carried out in at least three ways.
• the electrolysis is carried out in a cell that is provided with anode, cathode, and a cation selective membrane, wherein sodium sulphate solution is delivered to the anode chamber and water is delivered to the cathode chamber so that an acid solution is formed and oxygen gas is generated at the anode and so that a sodium hydroxide solution is formed and hydrogen gas is generated at the cathode.
• the electrolysis is carried out in a cell that is provided with anode, cathode an anion selective and a cation selective membrane, wherein sodium sulphate solution is introduced between the two membranes and water is introduced to the anode chamber and the cathode chamber respectively, so that. a sulphuric acid solution is formed and oxygen gas generated at the anode and so that a sodium hydroxide solution is formed and hydrogen gas generated at the cathode.
• the treatment is carried out in a multi chamber cell that is provided with anode, cathode and anion selective, cation selective and bipolar membranes, wherein the anode chamber is delimited by an anion selective membrane and the cathode chamber is delimited by a cation selective membrane, and wherein bipolar membranes are disposed between said membranes, and wherein sodium sulphate solution is delivered to those chambers that are delimited by bipolar membranes, so that a sulphuric acid solution is formed in at least the membrane chamber -which is placed nearest the cathode and hydrogen gas is generated at said cathode, and so that a sodium hydroxide solution is formed at least in the membrane chamber which' is placed nearest the anode, and oxygen gas is generated at said anode.
• oxygen gas and hydrogen gas are formed in smaller quantities than in the two preceding alternatives, since these electrode reactions do not take place at the bipolar membranes.
• This third method is referred to as electrodialysis.
• the first and the second alternative methods i.e. the methods which describe conventional electrolysis, are parti ⁇ cularly preferred because of their simplicity.
• the acid solution (sulphuric acid solution) and the sodium hydroxide solution respectively formed in the afore ⁇ said cells are removed from the cell individually and the acid solution (the sulphuric acid solution) is delivered to the cellulose pulp so as to obtain the acidity required and desired for the ozone bleaching process.
• Sodium hydroxide is also a valuable chemical which can be used, for instance, in the alkaline stage of the cellulose pulp treatment process, this stage often following the ozone bleaching stage. If desired, the intrinsically valuable chemicals oxygen and hydrogen can also be collected.
• the invention enables the consumption of externally produced purchased) acid and externally produced (pur ⁇ chased) alkali to be greatly reduced in the manufacture of cellulose pulp that is bleached with ozone.
• the secondary products oxygen gas and hydrogen gas can be used in the cellulose pulp manufacturing process, for example for oxygen g as bleaching and steam generation respectively.
• the inven ⁇ tion primarily leads to the possibility of mastering the environmental problems in a practically complete closing of the pulp manufacturing process, i.e. also including final bleaching waste liquors.
• Figure 1 is a flow sheet which illustrates a pulp manu ⁇ facturing process in which a first embodiment of the inven ⁇ tion is included and described, this embodiment including mixing together ozone bleaching waste liquor and some other alkaline waste liquor.
• Figure 2 illustrates a flow sheet for a pulp manufactur ⁇ ing process in which a second embodiment of the invention is included and described, this embodiment including returning ozone bleaching waste liquor to the chemical recover system of the pulp mill.
• Figures 3, 4 and 5 illustrate in detail a partial stage of the invention, namely in Figures 3 and 4 the electrolysis of the sodium sulphate solution produced, and in Figure 5, the electrodialysis of the sodium sulphate solution produced.
• pine chips are delivered through the conduit 1 to the digester 2, which contains a cooking liquor composed essentially of sodium hydroxide and sodium sulphide. Subsequent to digesting the wood and exposing the fibres thereof, the exposed fibres - the pulp - is transpor- ted through the pulp conduit 3 (which extends through the entire pulp mill) to the washing section 4, where the major part of the consumed cooking liquor (the cooking waste liquor or the black liquor) is extracted from the pulp.
• the cooking waste liquor is transported through conduits 5 and 6 to the chemical recovery system of the mill, this system including, among other things, an evaporation plant 7 and a combustion plant (recovery boiler) 8, which is provided with an electric precipitator 9.
• the pulp is passed to an oxygen bleaching stage where the pulp is supplied with oxygen gas, through the conduit 11, and also with alkali, normally sodium hydroxide, and optionally also with a protector.
• the oxygen bleached pulp is passed to a washing stage 12 in which the pulp is freed from the major part of the waste liquor deriving from the oxygen bleaching stage.
• the afore ⁇ said treatment process is carried out advantageously in a conventional press or in a washing press to which washing liquid is added.
• the pulp is brought to the desired con- sistency for the following ozone bleaching process of the pulp, by adjusting the pressure at which the pulp is pressed.
• the oxygen bleaching waste liquor pressed from the pulp is passed through the conduits 13 and 6 to the tradi ⁇ tional chemical recovery system. Part of the oxygen bleach- ing waste liquor can be returned to the bottom of the oxygen bleaching reactor 10 through the conduit 14.
• the pulp, which has a comparatively high pulp consistency is then delivered to the mixer 15 in which an acid sodium sulphate solution is added to the still alkaline pulp, this sodium sulphate solu- tion being prepared in the electrolysis cell 16 and tran ⁇ sported through the conduit 17.
• the acid solution is added in a quantity which will ensure that the pH value of the pulp/water mixture will be suitable for the ozone bleaching of the pulp, i.e. within the range 2-5.
• the pulp When the pulp leaves the mixer 15, it may, for instance, have a medium pulp consistency (10-15%) or a high pulp consistency (30-35%), depending on requirements.
• the pulp is then delivered to the ozone bleaching reactor 18 to which oxygen gas containing a given low ozone content is deliver ⁇ ed, in addition to pulp, through the conduit 19.
• the ozone bleaching stage is maintained at a comparatively low tem ⁇ perature, for instance a temperature within the range of 40-60°C.
• the pulp reacts completely with the ozone in this stage, and residual oxygen gas is led from the reactor through the conduit 20, for transportation to an apparatus for generating fresh ozone (not shown in the Figure).
• the pulp is then transported to a further washing stage 21, for instance in the form of a washing press.
• the ozone bleaching waste liquor recovered is passed back to the system, through the conduit 22.
• the waste liquor is divided into two flows, of which one flow is passed through the conduit 23 back to the ozone bleaching reactor 18 for the purpose of flushing pulp from the reactor.
• the other flow is passed to a mixing and crystallizing vessel 25, through the conduit 24.
• the pulp is then passed to a mixer 26 in which alkali, essentially sodium hydroxide, is added to the pulp.
• alkali essentially sodium hydroxide
• a signi ⁇ ficant part of the alkali is recovered in the form of a sodium hydroxide solution in the electrolysis cell 16, and the solution is added to the pulp in the mixer 26 through the conduit 27.
• the remainder of the sodium hydroxide required is supplied externally (purchased alkali) through the conduit 43.
• the pulp is then passed to an alkalizing or extraction tower 28. In addition to using a plain alkali stage in this stage of the process, it is possible, and even advantageous, to supply also oxygen or peroxide or both of these chemicals. Finally, the pulp is washed in the washing stage 29.
• the remaining quantity of waste liquor is passed through the conduit 31 to the pulp washer 4, imme ⁇ diately downstream of the digester 2.
• the waste liquor mixture in the vessel 25 is cooled to a temperature of, e.g., 15°C or therebelow.
• a major part of the sodium sulphate present in the waste liquor will then precipitate in the form of crystals, which settle on the bottom of the vessel 25.
• the crystals are then passed through the conduit 34 to a washing filter 35, with the aid of an appropriate feeding out device.
• the waste liquor - mother liquor - freed from the sodium sulphate crystals in the vessel 25 is discharged through the conduit 36 and mixed with oxygen bleaching waste liquor and cooking waste liquor (black liquor) for transportation into the evaporator plant 7.
• the sodium sulphate crystals are washed and cleaned on the filter 35 with a small quantity of liquid, and are thereafter passed to the dissolving vessel 38 through the conduit 37.
• the liquid removed from the sodium sulphate crystals on the filter 35 may, for instance, be introduced in the conduit 36 (not shown in the Figure).
• clean water is passed through the conduit 39 to the dissolv ⁇ ing vessel 38 in a quantity such that essentially all sodium sulphate crystals are dissolved.
• the dissolving process is facilitated by using a temperature which Is slightly higher than room temperature and which, for instance, reaches 35°C.
• the solution containing a large quantity of dissolved sodium sulphate is transported through the-conduit 39 to the anode chamber of the electrolysis cell 16.
• Preferably clean water is delivered to the cathode chamber in the electrolysis cell 16 through the conduit 40.
• an acid solution which is recovered in the manner earlier described
• a sodium hydroxide solution which is recovered in the aforedescrlbed manner.
• Oxygen gas is also generated in the anode chamber, this gas being led away through the conduit 41, while hydrogen gas is generated in the cathode chamber and led away through the conduit 42.
• Figure 2 is a flow sheet shown, which coincides totally with the flow sheet of Figure 1 with regard to the pulp manufacturing (and pulp refining) process. A large part of the liquid and waste liquor transportation is also effected in direct agreement with the two flow sheets. Consequently, those reference signs used in Figure 2 that are in agreement with the Figure 1 illustration are used with the addition of +50 except with respect to those few deviations which exist when making a comparison between the two embodiments of the invention.
• the waste liquor is conducted from the washing stage 71, which is located immediately downstream of the ozone bleaching stage 68, through the conduits 72 and 74 to the conduit 63, where the mentioned ozone bleaching waste liquor is mixed with oxygen bleaching waste liquor from the washing (press) stage 62.
• the mixture concerned is transported to the evaporation plant 57 through the conduit 56.
• the waste liquor concentra ⁇ ted by evaporation, the thick liquor is then passed to the recovery boiler 58 in which it is burned.
• the organic material content of the thick liquor is now converted to carbon dioxide and water, whereas its inorganic content is essentially recovered as sodium carbonate and sodium sulphide in the bottom part of the recovery boiler.
• the inorganic material accompanies the flue gases and is separated as sodium sulphate in the electric precipitator 59.
• All or a part of the sodium sulphate recovered is passed in powder form to the dissolv ⁇ ing tank 83, through the conduit 75.
• clean water is added through the conduit 84 in an amount such that all sodium sulphate will be dissolved. If it is necessary to purify the solution from foreign chemicals, this can be effected in a following treatment stage (not shown in the Figure).
• the resultant sodium sulphate solution is transpor ⁇ ted through the conduit 85 to the anode chamber of the elec ⁇ trolysis " cell 66.
• Preferably clean water is Introduced to the cathode chamber of the electrolysis cell 66, through the conduit 86.
• Oxygen gas formed in the anode chamber Is led away through the conduit 87 and hydrogen gas formed in the cathode chamber is led away through the conduit 88.
• the acid solution generated in the process of electrolysis is tran ⁇ sported through the conduit 67 to the mixer 65, for necessary acidification of the pulp prior to the pulp coming into contact with ozone in the bleaching stage 68.
• the sodium hydroxide solution produced in the process of electrolysis is transported through the conduit 77 to the mixer ' 76, in which the pulp is made alkaline.
• an oxygen bleaching stage in the mentioned position there can be applied a plain alkali stage, or a peroxide reinforced alkali stage, or an alkali stage which is reinforced with both peroxide and oxygen.
• an acid treatment stage for in- stance in accordance with the PRENOX method, it may be beneficial to treat (bleach) the pulp with chlorine dioxide, with or without intermediate washing of the pulp, immediately prior to the ozone bleaching stage.
• the inventive method is in no way limited to the ozone bleaching of sulphate pulp, but can be applied to the ozone bleaching of any chemical pulp what ⁇ soever and also to the ozone bleaching of chemimechanical pulp.
• the bleaching sequences can be quite different to the aforedescribed and mentioned bleaching sequences.
• this pulp will have after the digestion stage a much lower lignin content and a much higher brightness than sulphate pulp, which means that only two bleaching stages and at most three bleaching stages, of which one is an ozone bleaching stage, are required in order to obtain a highly clean and bright pulp.
• figure 3 shows in more detail the construction of an electrolysis cell similar to that shown in figures 1 and 2 and illustrates how decomposition of the sodium sulphate takes place.
• the electrolysis cell 100 is comprised of two chambers, the anode chamber 101 and the cathode chamber 102.
• An anode 103 is arranged in the first mentioned chamber and a cathode 104 is arranged in the other chamber.
• the two chambers are mutually separated by a cation selective membrane 105, which will only allow sodium ions to pass through.
• Sodium sulphate solution is added to the anode chamber 101 through the con ⁇ duit 106 and water is added to the cathode chamber 102 through the conduit 107.
• hydrogen ions are formed at the anode 103 while generating oxygen gas at the same time, this gas being led away from the cell through the conduit 108.
• Hydroxide ions are formed at the cathode 104 at the same time as hydrogen gas is generated, this gas being led away from the cell through the conduit 109.
• an electro ⁇ lysis cell 120 having three chambers can be used, as shown i Figure 4.
• This cell also includes an anode chamber 121 and a cathode chamber 122.
• An anode 123 is arranged in the anode chamber while a cathode 124 is arranged in the cathode
• a further chamber 125 which is encircled by a cation selective membrane 126 which allows sodium ions to pass through, and an anion selective membrane 127 which allows sulphate ions to pass through.
• Sodium sulphate solution is delivered to the cell through the conduit 128 and is recycled back to the conduit (in a lower concentration) through the conduit 129.
• Water is delivered to the cell through the conduit 130, to both the cathode chamber 122 and the anode chamber 121.
• a cell 140 of the type illustrated in Figure 5 can be used.
• This cell also has an anode chamber 141 and ci cathode chamber 142 having respectively an anode 143 and a cathode 144.
• the anode chamber 141 is delimited on one side by an anion selective membrane 145, while the cathode chamber 142 is delimited on one side by a cation selective membrane 146.
• Arranged between these two membranes are two bipolar mem ⁇ branes 147 and between these a further cation selective mem ⁇ brane 146 and an anion selective membrane 145 are arranged.
• Sodium sulphate solution is added to the anode chamber 141 and the cathode chamber 142 respectively through the conduit 148, and also to each third chamber between the bipolar mem ⁇ branes, which can be included in a greater or smaller number. Water is added to remaining cell chambers through the conduit 149. When an electric voltage is applied across the cell, oxygen gas is generated at the anode 143 and led away through the conduit 150, and hydrogen gas is generated at the cathode 144 and led away through the conduit 151. Furthermore, sodium ions migrate in a direction towards the cathode 144 and sulphate ions migrate in a direction towards the anode 143. The water is dissociated to hydrogen ions and hydroxide ions at the same time. Sulphuric acid (H Constant.
• the experiment was carried out with a pine sulphate pulp having a Kappa number of 29.0 and a viscosity of 1,250
• the pulp was fluffed and introduced into an ozone bleaching reactor, where the pulp was allowed to react with ozone added in a quantity of 0.4 kg/min in a flow of 5.7 kg/min oxygen gas.
• the temperature was 50°C and the treat- ment time 30 minutes.
• the oxygen gas freed from ozone was removed from the reactor.
• liquid was added so as to flush away the pulp.
• Dilution liquid in the form of water was added in an amount of 540 1/min.
• the pulp was then pressed to a pulp consistency of 30%.
• the resultant ozone bleaching waste liquor was thereby recovered.
• the pulp was then transferred to a mixer, to which 2.7 kg of sodium hydroxide/min were added.
• the pulp was allowed to react with the alkali for 120 minutes at a temperature of 65°C and a pulp concentration of 14%.
• the pulp was then washed with clean water so as to obtain an alkaline waste liquor.
• the Kappa number of the pulp after this treatment stage was 7.3, its viscosity 903 kg/dm and its brightness 53% ISO.
• the Kappa numbers, viscosities and brightnesses recited in this patent application have been determined in accor ⁇ dance -with SCAN-C 1:77, SCAN-CM 15:88 and SCAN-C 11:75 respectively.
• the mixture was transferred to a crystallization vessel, In which the mixture was cooled to 10°C.
• oxygen gas was generat- ed in the anode chamber in an amount of 190 1/min (0.27 kg/min) at the same time as an acid sodium sulphate solution was formed in which the hydrogen ions, calculated as sulphuric acid, rose to 1.7 kg/min (75% conversion) .
• Hydro- gen gas developed in the cathode chamber in an amount of 380 1/min (0.034 kg/min) at the same time as a sodium hydroxide solution was formed in an amount of 14 1/min at a concentra ⁇ tion of 10%.
• the resultant acid sodium sulphate solution contained 80 j/1 sodium sulphate and hydrogen ions, expressed as sulphuric acid, in an amount of 160 g/1.
• the solution concerned was used fully to acidify the pulp prior to the ' ozone bleaching stage, as earlier described, so that the pulp had a pH of 2.5.
• the resultant sodium hydroxide solution vas added to the pulp, as earlier mentioned. In the mixer prior to the alkalization treatment process. The sodium hydroxide content of this solution covered 50% of the sodium hydroxide addition to the pulp.
• the oxygen gas can be used in an alklaline treatment stage, for instance in an introductory oxygen bleaching stage.
• the pulp was bleached with oxygen gas at a pulp consistency of 12% and at an oxygen gas pressure of 6 kp/cm . 1.5% sodium hydroxide and 0.3% magnesium in the form of magnesium sulphate (MgSO.) had earlier been added to the pulp. Upon completion of the oxygen bleaching pro ⁇ cess, the pulp had a Kappa number of 13.0 and a viscosity of
• Precipitator dust from the sulphate mill from which the experiment pulp was taken was dissolved in an amount of 1.8 kg/min in clean water.
• the amount of water used was such that the resultant solution had a sodium sulphate content of 360 g/1.
• the dissolving took place at a temperature of 55°C.
• an electrolysis cell which had three chambers of the type illustrated in Figure 4. The cell included two membranes.
• the sodium sulphate solution was added to the centre chamber, i.e. the chamber located between the two membranes. Clean water was added to the anode chamber and the cathode chamber respectively.
• the cell temperature was 55 ⁇ C, the voltage 4.2 V, the current
• Hydrogen gas was developed in the cathode chamber in an amount of 270 1/min (0.024 kg/min) at the same time as a sodium hydroxide solu ⁇ tion was formed in an amount of 1.0 kg/min at a concentra- tion of 10%.
• the electrolyzed sodium sulphate solution was removed from the bottom of the centre chamber and was found to still contain a given content of sodium sulphate, this solution being recycled and mixed with fresh sodium sulphate solution, which was added to the cell at the upper part of the centre chamber.
• the sulphuric acid solution obtained was used fully to acidify the pulp prior to he ozone bleaching stage, as pre ⁇ viously mentioned, such that the pH of the pulp was 2.7.
• the sodium hydroxide solution obtained was added to the pulp in the mixer, as earlier described, prior to the alkalizing treatment stage.
• the sodium hydroxide solution obtained was added to the pulp in the mixer, as earlier described, prior to the alkalizing treatment stage.
• the sodium hydroxide content of this solution covered 40% of the sodium hydroxide charged to the pulp.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Detergent Compositions (AREA)

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Cited By (4)

Citations (2)

• 1991
  • 1991-09-17 SE SE9102693A patent/SE500053C2/sv unknown
• 1992
  • 1992-09-16 EP EP92920388A patent/EP0605565B1/en not_active Expired - Lifetime
  • 1992-09-16 PT PT100870A patent/PT100870B/pt not_active IP Right Cessation
  • 1992-09-16 ES ES92920388T patent/ES2089567T3/es not_active Expired - Lifetime
  • 1992-09-16 AT AT92920388T patent/ATE138989T1/de active
  • 1992-09-16 AU AU26631/92A patent/AU657003B2/en not_active Ceased
  • 1992-09-16 WO PCT/SE1992/000635 patent/WO1993006297A1/en active IP Right Grant
  • 1992-09-16 DE DE69211351T patent/DE69211351T2/de not_active Expired - Fee Related
  • 1992-09-16 CA CA002116974A patent/CA2116974A1/en not_active Abandoned
• 1994
  • 1994-03-16 FI FI941238A patent/FI941238A0/fi unknown

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