CA2048618C - A method of de-inking waste paper materials - Google Patents
A method of de-inking waste paper materials Download PDFInfo
- Publication number
- CA2048618C CA2048618C CA 2048618 CA2048618A CA2048618C CA 2048618 C CA2048618 C CA 2048618C CA 2048618 CA2048618 CA 2048618 CA 2048618 A CA2048618 A CA 2048618A CA 2048618 C CA2048618 C CA 2048618C
- Authority
- CA
- Canada
- Prior art keywords
- weight
- ink
- approximately
- stock
- fibrous stock
- 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 - Fee Related
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
- D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
- D21C5/02—Working-up waste paper
-
- 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
- D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
- D21C5/02—Working-up waste paper
- D21C5/025—De-inking
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/64—Paper recycling
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- Paper (AREA)
- Treatment Of Sludge (AREA)
Abstract
A method of de-inking waste paper materials consists in pulping the paper material in a hydropulper (I) to form a fibrous stack, and adding a substance in the form of a mixture of phosphated and carbonated sodium salts to the fibrous stock to dis-perse ink particles from the stock, The stock and dispersed ink particles pass through washing stages (4), (7) and (8), in a centrifu-gal cleaner (3), in order to remove the ink particles from the fibrous stock.
Description
~ , PGT/GB90/00385 _1_ METHOD OF DE-INKING WASTE PAPER MATERIALS
This invention relates to a method of de-inking waste paper materials.
In the paper and board industry, the use of second-ary fibres derived from recycling waste paper materials is well-known, and the dispersal and separation of ink parti-cles from waste paper materials and its secondary fibres is a necessary step in the recycling of the material, particu-larly in the production of paper for newsprint, tissues, and fine paper.
In known re-cycling processes, the waste paper or "furnish" is usually placed in a hydrapulper where it is mixed with water and the following chemicals:
(1) caustic soda or other de-inking chemical, (2) sodium metasilicate as a buffering agent, and (3) hydrogen peroxide or other bleaching agent.
In the hydrapulper, the "furnish" is disintegrated into a fibrous pulp, which is then de-inked and bleached by the added chemicals. From the hydrapulper the fibrous pulp or sloshed fibres, with a consistency of 15~ (as in high consistency pulping) or 5-6$ (as in Mills not using high consistency pulping), is dumped into a series of "dump" or storage chests where the sloshed fibres are diluted down to a consistency of around 1.5~
The "stock''' or diluted sloshed fibres then pass to the de-inking equipment, which either consists of flotation cells or washing screens or a combination of these, where the dispersed ink particles are removed from the sloshed f fibres .
In the method of utilising flotation cells, a "collector" soap is added to the "stock" prior to entering the de-inking cell to agglomerate the dispersed ink-_2_ particles which then float to the surface of the cell on air-bubbles which are sourced at the base of the flotation cell and which are then skimmed off.
In the washing method of de-inking the dispersed ink particles are washed out of the system by passing the stock onto a rotary decker, a sidemill screen, a screw press, or similar equipment, using large volumes of water.
These known methods of de-inking thus require the addition of a number of different de-inking chemicals.
Some chemicals are also only effective for one of the two different methods, i.e. flotation and washing methods, and cannot be used in the other method. Furthermore, caustic soda, which is most commonly used in relatively large amounts as a de-inking chemical, can attack the fibres and may not be regarded as being environmentally safe when emptied from the mill into external water sources.
It is therefore an object of the present invention to provide a method of de-inking waste paper materials which substantially removes the above-mentioned problems associated with known methods.
Accordingly, the present invention consists in a method of de-inking waste paper materials comprising the steps ofm-pulping the paper material to form a fibrous stock of a slush-like consistency;
adding a substance to the fibrous stock to disperse ink particles from the stock;
and removing the dispersed ink particles from the fibrous stock;
characterised in that the substance used to dis-perse ink particles consists of a mixture of phosphated and carbonated sodium salts.
Preferably, the substance consists of 1 to 75~
weight in weight of sodium carbonate and 25 to 99~ weight WO 90/10749 PC.T/GB90/00385 -in weight of sodium phosphate.
The substance may also include 1 to 2$ weight in weight of metas~:licates and/or 0.5 to 2~ weight in weight of caustic soda.
The substance may also include hygroscopic salts, together with a non-caustic booster, and may include a sanitiser.
If desirf~d, a bleaching chemical may be added, for example 0.25 to 5~ weight in weight of hydrogen peroxide or any other suitable bleaching agent.
The invention will now be further described by way of example with reference to the accompanying drawing, which illustrates schematically one embodiment of the present invention.
Referring now to the drawing, there is shown a flow diagram of a washing method of de-inking, the steps of which are well-known to those skilled in the art, except for the replacement of known de-inking substances by the substance as used in accordance with the present invention.
In the illustrated method, waste paper is fed into a hydrapulper 1, in which it is disintegrated into a fi-brous pulp or fibrous stock of a sloshed consistency.
Water is added to the stock, together with a substance to disperse ink particles from the stock. From there, the stock and dispersed ink particles pass into a centrifugal cleaner 2 to remove grit, pins, clips, etc, and through a screen 3 to remove oversized particles.
The stock: then passes to a first washing stage 4 consisting of a thickener 5 and a fine deflaker or dispers-er 6, which produces a well defibered stock, which is rea-sonably clean and free from ink specks but still contains very small ink peirticles. From there, the stock passes to second and third washing stages, 7 and 8 respectively, each including a vert~_cal screen 9 and in which dilution water WO 90/10749 ~ ~ ~ PCT/GB90/00385 _4_ is added to the stock. A fourth washing stage 10 consists of another thickener 11, and the clean stock is then passed from the thickener 11 to refiners and paper-making machin-ery.
In accordance with an embodiment of the present invention, the substance added to disperse the ink parti-cles consists of a mixture of 1 to 75~ weight in weight of sodium carbonate and 25 to 99~ weight in weight of sodium phosphate, with a typical composition being 8~ weight in weight of sodium carbonate and 92~ weight in weight of sodium phosphate.
The substance may also include small quantities of metasilicates (for example 1 to2~ weight in weight) and/or caustic soda (for example 0.5 to 2~ weight in weight). The composition may be further enhanced by using hygroscopic salts, together with a non-caustic booster, and may include a sanitiser. A bleaching agent, for example 0.25 to 5~
hydrogen peroxide, may also be added.
As an alternative to the above-described washing method of de-inking, the substance may be utilised to disperse ink particles in known flotation methods.
The use of this substance in de-inking methods has advantages over the use of the chemicals generally used as follows:-(1) It is an effective ink dispersant in both tradi-tional methods of de-inking (i.e. Flotation and Washing), unlike other de-inking products which are only effective in one or other of the traditional methods but not both.
(2) By virtue of its formulation, it can be used as a "one-shot" ink dispersant in the hydrapulper, without the need for the addition of buffering agent or any other chemical in the hydrapulper.
(3) It is effective as an ink dispersant at low temper-atures (eg. 9°C), and therefore saves the power required to heat the hydrapulper contents to 50°-60°C, as is necessary in known methods usi~ig'o~.her de-inking chemicals.
This invention relates to a method of de-inking waste paper materials.
In the paper and board industry, the use of second-ary fibres derived from recycling waste paper materials is well-known, and the dispersal and separation of ink parti-cles from waste paper materials and its secondary fibres is a necessary step in the recycling of the material, particu-larly in the production of paper for newsprint, tissues, and fine paper.
In known re-cycling processes, the waste paper or "furnish" is usually placed in a hydrapulper where it is mixed with water and the following chemicals:
(1) caustic soda or other de-inking chemical, (2) sodium metasilicate as a buffering agent, and (3) hydrogen peroxide or other bleaching agent.
In the hydrapulper, the "furnish" is disintegrated into a fibrous pulp, which is then de-inked and bleached by the added chemicals. From the hydrapulper the fibrous pulp or sloshed fibres, with a consistency of 15~ (as in high consistency pulping) or 5-6$ (as in Mills not using high consistency pulping), is dumped into a series of "dump" or storage chests where the sloshed fibres are diluted down to a consistency of around 1.5~
The "stock''' or diluted sloshed fibres then pass to the de-inking equipment, which either consists of flotation cells or washing screens or a combination of these, where the dispersed ink particles are removed from the sloshed f fibres .
In the method of utilising flotation cells, a "collector" soap is added to the "stock" prior to entering the de-inking cell to agglomerate the dispersed ink-_2_ particles which then float to the surface of the cell on air-bubbles which are sourced at the base of the flotation cell and which are then skimmed off.
In the washing method of de-inking the dispersed ink particles are washed out of the system by passing the stock onto a rotary decker, a sidemill screen, a screw press, or similar equipment, using large volumes of water.
These known methods of de-inking thus require the addition of a number of different de-inking chemicals.
Some chemicals are also only effective for one of the two different methods, i.e. flotation and washing methods, and cannot be used in the other method. Furthermore, caustic soda, which is most commonly used in relatively large amounts as a de-inking chemical, can attack the fibres and may not be regarded as being environmentally safe when emptied from the mill into external water sources.
It is therefore an object of the present invention to provide a method of de-inking waste paper materials which substantially removes the above-mentioned problems associated with known methods.
Accordingly, the present invention consists in a method of de-inking waste paper materials comprising the steps ofm-pulping the paper material to form a fibrous stock of a slush-like consistency;
adding a substance to the fibrous stock to disperse ink particles from the stock;
and removing the dispersed ink particles from the fibrous stock;
characterised in that the substance used to dis-perse ink particles consists of a mixture of phosphated and carbonated sodium salts.
Preferably, the substance consists of 1 to 75~
weight in weight of sodium carbonate and 25 to 99~ weight WO 90/10749 PC.T/GB90/00385 -in weight of sodium phosphate.
The substance may also include 1 to 2$ weight in weight of metas~:licates and/or 0.5 to 2~ weight in weight of caustic soda.
The substance may also include hygroscopic salts, together with a non-caustic booster, and may include a sanitiser.
If desirf~d, a bleaching chemical may be added, for example 0.25 to 5~ weight in weight of hydrogen peroxide or any other suitable bleaching agent.
The invention will now be further described by way of example with reference to the accompanying drawing, which illustrates schematically one embodiment of the present invention.
Referring now to the drawing, there is shown a flow diagram of a washing method of de-inking, the steps of which are well-known to those skilled in the art, except for the replacement of known de-inking substances by the substance as used in accordance with the present invention.
In the illustrated method, waste paper is fed into a hydrapulper 1, in which it is disintegrated into a fi-brous pulp or fibrous stock of a sloshed consistency.
Water is added to the stock, together with a substance to disperse ink particles from the stock. From there, the stock and dispersed ink particles pass into a centrifugal cleaner 2 to remove grit, pins, clips, etc, and through a screen 3 to remove oversized particles.
The stock: then passes to a first washing stage 4 consisting of a thickener 5 and a fine deflaker or dispers-er 6, which produces a well defibered stock, which is rea-sonably clean and free from ink specks but still contains very small ink peirticles. From there, the stock passes to second and third washing stages, 7 and 8 respectively, each including a vert~_cal screen 9 and in which dilution water WO 90/10749 ~ ~ ~ PCT/GB90/00385 _4_ is added to the stock. A fourth washing stage 10 consists of another thickener 11, and the clean stock is then passed from the thickener 11 to refiners and paper-making machin-ery.
In accordance with an embodiment of the present invention, the substance added to disperse the ink parti-cles consists of a mixture of 1 to 75~ weight in weight of sodium carbonate and 25 to 99~ weight in weight of sodium phosphate, with a typical composition being 8~ weight in weight of sodium carbonate and 92~ weight in weight of sodium phosphate.
The substance may also include small quantities of metasilicates (for example 1 to2~ weight in weight) and/or caustic soda (for example 0.5 to 2~ weight in weight). The composition may be further enhanced by using hygroscopic salts, together with a non-caustic booster, and may include a sanitiser. A bleaching agent, for example 0.25 to 5~
hydrogen peroxide, may also be added.
As an alternative to the above-described washing method of de-inking, the substance may be utilised to disperse ink particles in known flotation methods.
The use of this substance in de-inking methods has advantages over the use of the chemicals generally used as follows:-(1) It is an effective ink dispersant in both tradi-tional methods of de-inking (i.e. Flotation and Washing), unlike other de-inking products which are only effective in one or other of the traditional methods but not both.
(2) By virtue of its formulation, it can be used as a "one-shot" ink dispersant in the hydrapulper, without the need for the addition of buffering agent or any other chemical in the hydrapulper.
(3) It is effective as an ink dispersant at low temper-atures (eg. 9°C), and therefore saves the power required to heat the hydrapulper contents to 50°-60°C, as is necessary in known methods usi~ig'o~.her de-inking chemicals.
(4) Unlike caustic soda, it does not attack the fibres, and therefore gives a stronger paper end product, and may be used as a caustic soda replacement in the hydrapulper.
(5) As an ink dispersant, it does not necessarily require a collector soap in Flotation de-inking, nor the high temperature (60°C) necessary when a collector soap is used, this giving further economies in use.
(5) Tt is sa:Eer to the environment, i.e. it is much less toxic to aquatic wildlife, and has lower and more acceptable Biological Oxygen Demand (B.O.D.) and Chemical Oxygen Demand (C.O.D.) when emptied from the mill into external water sources than other de-inking products at the present time e.g. caustic soda or bleach.
(7) In mill trials, it has been found to have excellent "former" properties in that it gives a uniform distribution of fibres in the finished paper which results in a better quality end product.
Furthermore, mill machine runs and further experi-mental procedures utilising this substance in de-inking methods have revealed the following additional advantages:-( a ) str:i.king increases in the strength of the recycled products of between 5 to 30~, depending on the waste mix in the furnish used;
(b) production of a better, less speckled product when used to de-i.nk better grade, office-type waste paper, hitherto known as "difficult to de-ink" grade (i.e. wood-free waste);
(c) successful attacks on laser print, xero-graphic print, hitherto known as "difficult to remove"
inks, and on the new FLOXO inks, as well as producing a higher brightness than standard de-inking products; and {d) enabling up to 85~ of "stickies" or gums to -, _6-be passed out, thus removing the bulk of a major problem of the paper recycling industry, which can account for expen-sive "down-time" of the machines.
Whilst particular embodiments of the present inven-tion have been described, various modifications will be envisaged without departure from the scope of the inven-tion, as defined in the appended claims.
(5) Tt is sa:Eer to the environment, i.e. it is much less toxic to aquatic wildlife, and has lower and more acceptable Biological Oxygen Demand (B.O.D.) and Chemical Oxygen Demand (C.O.D.) when emptied from the mill into external water sources than other de-inking products at the present time e.g. caustic soda or bleach.
(7) In mill trials, it has been found to have excellent "former" properties in that it gives a uniform distribution of fibres in the finished paper which results in a better quality end product.
Furthermore, mill machine runs and further experi-mental procedures utilising this substance in de-inking methods have revealed the following additional advantages:-( a ) str:i.king increases in the strength of the recycled products of between 5 to 30~, depending on the waste mix in the furnish used;
(b) production of a better, less speckled product when used to de-i.nk better grade, office-type waste paper, hitherto known as "difficult to de-ink" grade (i.e. wood-free waste);
(c) successful attacks on laser print, xero-graphic print, hitherto known as "difficult to remove"
inks, and on the new FLOXO inks, as well as producing a higher brightness than standard de-inking products; and {d) enabling up to 85~ of "stickies" or gums to -, _6-be passed out, thus removing the bulk of a major problem of the paper recycling industry, which can account for expen-sive "down-time" of the machines.
Whilst particular embodiments of the present inven-tion have been described, various modifications will be envisaged without departure from the scope of the inven-tion, as defined in the appended claims.
Claims (12)
1. A method of de-inking waste paper materials comprising the steps of:
pulping the paper material to form a fibrous stock of a slush-like consistency;
dispersing ink particles from the fibrous stock by the addition of an ink dispersant composition;
and removing the dispersed ink particles from the fibrous stock;
characterized in that the ink dispersant composition consists solely of a mixture of phosphated and carbonated sodium salts or of a mixture of phosphated and carbonated sodium salts including small amounts of material selected solely from the group consisting of metasilicates and/or caustic soda.
pulping the paper material to form a fibrous stock of a slush-like consistency;
dispersing ink particles from the fibrous stock by the addition of an ink dispersant composition;
and removing the dispersed ink particles from the fibrous stock;
characterized in that the ink dispersant composition consists solely of a mixture of phosphated and carbonated sodium salts or of a mixture of phosphated and carbonated sodium salts including small amounts of material selected solely from the group consisting of metasilicates and/or caustic soda.
2. A method as claimed in claim 1, wherein said ink dispersant composition is used to disperse ink particles at low temperatures.
3. A method as claimed in claim 1 or 2 , wherein said ink dispersant composition is used as a "one-shot"
composition in a hydropulper containing said fibrous stock without addition to the hydropulper of a buffering agent or any other chemical apart from the ink dispersant composition.
composition in a hydropulper containing said fibrous stock without addition to the hydropulper of a buffering agent or any other chemical apart from the ink dispersant composition.
4. A method as claimed in claim 1, 2 or 3, wherein said mixture of phosphated and carbonated sodium salts is the sole component of said ink dispersant composition which consists of approximately 8% weight in weight of sodium carbonate and approximately 92% weight in weight of sodium phosphate.
5. A method as claimed in any one of claims 1 to 3, wherein the amount of metasilicates used is approximately 1 to 2% weight in weight.
6. A method as claimed in claim 1, 2 or 3, wherein the amount of caustic soda used is approximately 0.5% to 2%
weight in weight.
weight in weight.
7. A method of de-inking waste paper material comprising the steps of:
pulping the paper material to form a fibrous stock of a slush-like consistency;
adding an ink dispersing agent having a composition whereby ink particles are dispersed from the fibrous stock; and removing said dispersed ink particles from the stock;
wherein the composition of said ink dispersing agent is selected from the group consisting of:
(i) a mixture consisting solely of approximately 92% weight in weight of a sodium phosphate and approximately 8% weight in weight of sodium carbonate;
(ii) a mixture consisting solely of phosphated and carbonated sodium salts and approximately 1 to 2% weight in weight of metasilicates;
(iii) a mixture consisting solely of phosphated and carbonated sodium salts and approximately 0.5%
to 2% weight in weight of caustic soda; and (iv) a mixture consisting solely of phosphated and carbonated sodium salts, approximately 1% to 2%
weight by weight of metasilicates, and 0.5% to 2% weight in weight of caustic soda.
pulping the paper material to form a fibrous stock of a slush-like consistency;
adding an ink dispersing agent having a composition whereby ink particles are dispersed from the fibrous stock; and removing said dispersed ink particles from the stock;
wherein the composition of said ink dispersing agent is selected from the group consisting of:
(i) a mixture consisting solely of approximately 92% weight in weight of a sodium phosphate and approximately 8% weight in weight of sodium carbonate;
(ii) a mixture consisting solely of phosphated and carbonated sodium salts and approximately 1 to 2% weight in weight of metasilicates;
(iii) a mixture consisting solely of phosphated and carbonated sodium salts and approximately 0.5%
to 2% weight in weight of caustic soda; and (iv) a mixture consisting solely of phosphated and carbonated sodium salts, approximately 1% to 2%
weight by weight of metasilicates, and 0.5% to 2% weight in weight of caustic soda.
8. A method as claimed in claim 7, wherein said ink dispersing agent is added to the fibrous stock at ambient temperatures without applying heat thereto.
9. A method as claimed in claim 7, wherein the paper material is pulped in a hydropulper and the ink dispersing agent is added to the fibrous stock in the hydropulper as a one-shot product without adding any other chemical to the hydropulper.
10. A method as claimed in claim 9, wherein the stock is passed from the hydropulper to flotation cells in which a flotation technique is used to remove the dispersed ink particles from the fibrous stock, and the one-shot product also replaces collector soaps conventionally used in the flotation cells.
11. A method as claimed in claim 7, wherein the ink dispersing agent is added to the fibrous stock at a dosage of up to approximately 1% on stock.
12. A method as claimed in claim 7, wherein the ink dispersing agent is added to the fibrous stock at substantially neutral. pH conditions of approximately 6.8 to 7.8.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8905942.2 | 1989-03-15 | ||
| GB8905942A GB8905942D0 (en) | 1989-03-15 | 1989-03-15 | A method of de-inking waste paper materials |
| PCT/GB1990/000385 WO1990010749A1 (en) | 1989-03-15 | 1990-03-14 | Method of de-inking waste paper materials |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2048618A1 CA2048618A1 (en) | 1990-09-16 |
| CA2048618C true CA2048618C (en) | 2002-04-23 |
Family
ID=10653370
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2048618 Expired - Fee Related CA2048618C (en) | 1989-03-15 | 1990-03-14 | A method of de-inking waste paper materials |
Country Status (16)
| Country | Link |
|---|---|
| KR (1) | KR0151110B1 (en) |
| BG (1) | BG95308A (en) |
| BR (1) | BR9007224A (en) |
| CA (1) | CA2048618C (en) |
| DE (1) | DE69017205T2 (en) |
| FI (1) | FI914276A7 (en) |
| GB (1) | GB8905942D0 (en) |
| IN (1) | IN174412B (en) |
| LT (1) | LTIP1852A (en) |
| MC (1) | MC2179A1 (en) |
| MW (1) | MW5091A1 (en) |
| MY (1) | MY107139A (en) |
| NZ (1) | NZ232892A (en) |
| PH (1) | PH27030A (en) |
| PT (1) | PT93425B (en) |
| ZA (1) | ZA901713B (en) |
-
1989
- 1989-03-15 GB GB8905942A patent/GB8905942D0/en active Pending
-
1990
- 1990-03-06 ZA ZA901713A patent/ZA901713B/en unknown
- 1990-03-09 MY MYPI90000373A patent/MY107139A/en unknown
- 1990-03-12 IN IN205CA1990 patent/IN174412B/en unknown
- 1990-03-13 NZ NZ23289290A patent/NZ232892A/en unknown
- 1990-03-13 PH PH40180A patent/PH27030A/en unknown
- 1990-03-14 FI FI914276A patent/FI914276A7/en not_active Application Discontinuation
- 1990-03-14 BR BR9007224A patent/BR9007224A/en not_active IP Right Cessation
- 1990-03-14 KR KR1019910701116A patent/KR0151110B1/en not_active Expired - Fee Related
- 1990-03-14 PT PT93425A patent/PT93425B/en not_active IP Right Cessation
- 1990-03-14 DE DE69017205T patent/DE69017205T2/en not_active Expired - Fee Related
- 1990-03-14 MC MC90@@D patent/MC2179A1/en unknown
- 1990-03-14 CA CA 2048618 patent/CA2048618C/en not_active Expired - Fee Related
-
1991
- 1991-09-13 MW MW5091A patent/MW5091A1/en unknown
- 1991-10-10 BG BG095308A patent/BG95308A/en unknown
-
1994
- 1994-01-31 LT LTIP1852A patent/LTIP1852A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| ZA901713B (en) | 1990-12-28 |
| BR9007224A (en) | 1992-02-18 |
| DE69017205T2 (en) | 1995-10-19 |
| NZ232892A (en) | 1991-11-26 |
| FI914276A0 (en) | 1991-09-11 |
| PT93425A (en) | 1990-11-07 |
| LTIP1852A (en) | 1995-08-25 |
| PH27030A (en) | 1993-02-01 |
| BG95308A (en) | 1993-12-24 |
| IN174412B (en) | 1994-12-03 |
| DE69017205D1 (en) | 1995-03-30 |
| GB8905942D0 (en) | 1989-04-26 |
| MW5091A1 (en) | 1993-02-10 |
| PT93425B (en) | 1996-09-30 |
| KR0151110B1 (en) | 1999-05-15 |
| CA2048618A1 (en) | 1990-09-16 |
| KR920701565A (en) | 1992-08-12 |
| MC2179A1 (en) | 1992-05-22 |
| MY107139A (en) | 1995-09-30 |
| FI914276A7 (en) | 1991-09-11 |
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