CA1153161A - Method for the production of greaseproof paper - Google Patents
Method for the production of greaseproof paperInfo
- Publication number
- CA1153161A CA1153161A CA000361696A CA361696A CA1153161A CA 1153161 A CA1153161 A CA 1153161A CA 000361696 A CA000361696 A CA 000361696A CA 361696 A CA361696 A CA 361696A CA 1153161 A CA1153161 A CA 1153161A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- greaseproof
- paper
- sulphate
- alkali
- 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
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
- D21C9/14—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites
- D21C9/144—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with ClO2 or chlorites with ClO2/Cl2 and other bleaching agents in a multistage process
Abstract
"METHOD FOR THE PRODUCTION OF GREASEPROOF PAPER"
ABSTRACT OF THE DISCLOSURE
A greaseproof pulp is produced by bleaching an oxygen-alkali delignified high yield sulphate pulp with chlorine, alkali and hypochlorite and refining the bleached pulp. The bleaching in the hypochlorite stage may be conducted so that the pH value of the pulp at the end of this stage will be 7.0 to 8.5. The bleached pulp may be refined at a pH value of 7.0 to 10Ø
ABSTRACT OF THE DISCLOSURE
A greaseproof pulp is produced by bleaching an oxygen-alkali delignified high yield sulphate pulp with chlorine, alkali and hypochlorite and refining the bleached pulp. The bleaching in the hypochlorite stage may be conducted so that the pH value of the pulp at the end of this stage will be 7.0 to 8.5. The bleached pulp may be refined at a pH value of 7.0 to 10Ø
Description
BACKROVND OF THE INVENTION
Field of the invention The present invention relates to a method for the production of greaseproof paper or greaseproof pulp by refining a bleached sulphate pulp.
DESCRIPTION OF THE PRIOR ART
Greaseproof paper, which is a special paper for packing fatty products, is traditionally produced from sulphite chemical pulp. For the desired quality of the paper to be obtained, the chemical pulp must be refined until it obtains the properties required by a greaseproof pulp. The chemical pulp must therefore be easy to refine, and additionally should be pure and contain only small amounts of odourous and tasting ingredients.
As small and medium sulphite pulp factories are closed down because of pollution problems, it has been : tried to use bleached sulphate;chemical pulp in the production of greaseproof paper. Since ordinary sulphate pulp is difficult to refine, it consumes considerably more refining energy and additionally requires expensive chemical aids to obtain approximately the same greaseproof properties as sulphite pulp.
~ ~ .
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SUMMARY OF THE INVENTION
The object of the present invention is to provide a method for the production of a satisfactory greaseproof paper from a s~lphate pulp, while obtaining advantages compared with both sulphite pulps and previously used sulphate pulps.
In the method according to the invention a known oxygen-alkali delignified high yield sulphate pulp is bleached with chlorine, alkali and hypochlorite and the bleached pulp is refined. In other words, the inven-tion consists in the use of a delignified high yield sulphate pulp for the production of greaseproof paper after chlorine-alkali-hypochlorite bleaching and refi-ning of the pulp.
DETAILED DESCRIPTION OF THE INVENTION WIT~ PREFERRED
EMBODIMENTS
The sulphate pulp used as a starting material for the production of the greaseproof pulp according to the invention, is a known high yield sulphate pulp which has been delignified as described in US patent specification 4 093 Sll and TAPPI 59 (11) : 77 (1976).
This sulphate pulp is produced with a hemicellulose preserving cooking liquor, preferably a polysulphide :
liquor having a polysulphide content of 2 to 12 grams per liter and produced by the Moxy process, to a relati-vely high lignin content corresponding to a kappa number of about 60, see TAPPI 58 (8) : 172 (1972). After a partial washing, the pulp was further delignified to a kappa number of about 30 with oxygen and alkali at about 110C in a suitable reactor. The pulp was then further bleached in three stages with chlorine, alkali and sodium hypochlorite, respectively, to a brightness of 80 to 85~ SCAN. If the bleaching of the sulphite , . , ~ . . .. ~ :
~ ' ----` liS31~
pulp in the hypochlorite stage is cond~cted so that the pH value of the pulp at the end of this stage is 7.0 to 8.5, it has turned out that the obtained pulp is particularly easy to refine to greaseproof properties.
The pH value at the end of the hypochlorite bleaching stage,should preferably be within the range 7.0 to 8.0 and particularly between 7.0 and 7.5. These are exeptio-nally low values. On the other hand it is preferred to refine the pulp in alkaline surroundings, i.e. at a pH value of at least 7.0 and possibly as high as 10Ø
A testing of this pulp in the laboratory showed that it was considerably better suited for the production of greaseproof paper than ordinary sulphate pulp marketed for this purpose. Compared with greaseproof paper from sulphite pulp, the high yield sulphate pulp produced a more pure product having satisfactory greaseproof properties. The paper further had better wet strength properties than the sulphite pulp, and thus produced fewer breaks in the paper machine with a correspondingly higher paper production. The refining energy demand was approximately as for sulphite pulp, i.e. substan-tially lower than for the sulphate pulp presently marke-ted for greaseproof purposes.
Also the strength properties of the finished product were considerably better than what is usual with a sul-phite pulp as a starting material. The high strength resulted in a better convertability of the paper produced in the pilot period. Convertability is a property which becomes more and more important due to present demands for advanced pressures and high speed packing machines.
The content of odourous and tasting ingredients and resin in the sulphate pulp used is at such a low level compared with sulphite pulp that no problems are to be expected. On the contrary, sulphite pulp from pine wood may give inconveniences with respect to taste and odour in the product and also acute resin problems, .~ . .
.
.
"~: , llS3161 but also sulphite pulp from fir wood may give problems in this respect.
Further features of the invention will be apparent from the following description and the claims. The inven-tion will be further illustrated by means of examples.
Example 1 A high yield sulphate pulp was produced in a conti-nuous vapour phase Kamyr digester from a mixture of fir and pine chips. The production was approximately 350 tons per day. 19.5~ effective alkali calculated as NaOH was added per ton dry chips. The white liquor had a content of about 6 to 8 grams polysulfide sulphur per liter and was produced by the Moxy process. The white liquor sulfidity was about 40% before the oxyda-tion in the Moxy reactor. For a more detailed descrip-tion of the Moxy process, see US patent specification 4 308 313. The temperature in the cooking zone was about 160C and the cooking time was about 2.5 hours.
From the blowing conduit of the digester a pulp flow of about 70 tons per day was branched out and passed to a reactor through an in-line refiner. In the refiner liquor, oxygen and steam were admixed. The addition of oxygen and alkali corresponded to 35 kg 2 and 50 kg NaOH, respectively, for each ton of pulp. The steam demand corresponded to a temperature increase from about 85C to 110C at 10% pulp consistency. The residence time of the pulp in the reactor was about 30 minutes at 5 at pressure before the pulp was diluted and blown to a tank.
The oxygen-alkali delignification res~lted in a reduction of the kappa number of the pulp from about 60 to about 30. A sample of this pulp was further bleached in the laboratory in three stages with chlorine, alkali and sodium hypochlorite (6.5% chlorine, 2.5% NaOH and
Field of the invention The present invention relates to a method for the production of greaseproof paper or greaseproof pulp by refining a bleached sulphate pulp.
DESCRIPTION OF THE PRIOR ART
Greaseproof paper, which is a special paper for packing fatty products, is traditionally produced from sulphite chemical pulp. For the desired quality of the paper to be obtained, the chemical pulp must be refined until it obtains the properties required by a greaseproof pulp. The chemical pulp must therefore be easy to refine, and additionally should be pure and contain only small amounts of odourous and tasting ingredients.
As small and medium sulphite pulp factories are closed down because of pollution problems, it has been : tried to use bleached sulphate;chemical pulp in the production of greaseproof paper. Since ordinary sulphate pulp is difficult to refine, it consumes considerably more refining energy and additionally requires expensive chemical aids to obtain approximately the same greaseproof properties as sulphite pulp.
~ ~ .
,. , , ,~
, -llS316~
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method for the production of a satisfactory greaseproof paper from a s~lphate pulp, while obtaining advantages compared with both sulphite pulps and previously used sulphate pulps.
In the method according to the invention a known oxygen-alkali delignified high yield sulphate pulp is bleached with chlorine, alkali and hypochlorite and the bleached pulp is refined. In other words, the inven-tion consists in the use of a delignified high yield sulphate pulp for the production of greaseproof paper after chlorine-alkali-hypochlorite bleaching and refi-ning of the pulp.
DETAILED DESCRIPTION OF THE INVENTION WIT~ PREFERRED
EMBODIMENTS
The sulphate pulp used as a starting material for the production of the greaseproof pulp according to the invention, is a known high yield sulphate pulp which has been delignified as described in US patent specification 4 093 Sll and TAPPI 59 (11) : 77 (1976).
This sulphate pulp is produced with a hemicellulose preserving cooking liquor, preferably a polysulphide :
liquor having a polysulphide content of 2 to 12 grams per liter and produced by the Moxy process, to a relati-vely high lignin content corresponding to a kappa number of about 60, see TAPPI 58 (8) : 172 (1972). After a partial washing, the pulp was further delignified to a kappa number of about 30 with oxygen and alkali at about 110C in a suitable reactor. The pulp was then further bleached in three stages with chlorine, alkali and sodium hypochlorite, respectively, to a brightness of 80 to 85~ SCAN. If the bleaching of the sulphite , . , ~ . . .. ~ :
~ ' ----` liS31~
pulp in the hypochlorite stage is cond~cted so that the pH value of the pulp at the end of this stage is 7.0 to 8.5, it has turned out that the obtained pulp is particularly easy to refine to greaseproof properties.
The pH value at the end of the hypochlorite bleaching stage,should preferably be within the range 7.0 to 8.0 and particularly between 7.0 and 7.5. These are exeptio-nally low values. On the other hand it is preferred to refine the pulp in alkaline surroundings, i.e. at a pH value of at least 7.0 and possibly as high as 10Ø
A testing of this pulp in the laboratory showed that it was considerably better suited for the production of greaseproof paper than ordinary sulphate pulp marketed for this purpose. Compared with greaseproof paper from sulphite pulp, the high yield sulphate pulp produced a more pure product having satisfactory greaseproof properties. The paper further had better wet strength properties than the sulphite pulp, and thus produced fewer breaks in the paper machine with a correspondingly higher paper production. The refining energy demand was approximately as for sulphite pulp, i.e. substan-tially lower than for the sulphate pulp presently marke-ted for greaseproof purposes.
Also the strength properties of the finished product were considerably better than what is usual with a sul-phite pulp as a starting material. The high strength resulted in a better convertability of the paper produced in the pilot period. Convertability is a property which becomes more and more important due to present demands for advanced pressures and high speed packing machines.
The content of odourous and tasting ingredients and resin in the sulphate pulp used is at such a low level compared with sulphite pulp that no problems are to be expected. On the contrary, sulphite pulp from pine wood may give inconveniences with respect to taste and odour in the product and also acute resin problems, .~ . .
.
.
"~: , llS3161 but also sulphite pulp from fir wood may give problems in this respect.
Further features of the invention will be apparent from the following description and the claims. The inven-tion will be further illustrated by means of examples.
Example 1 A high yield sulphate pulp was produced in a conti-nuous vapour phase Kamyr digester from a mixture of fir and pine chips. The production was approximately 350 tons per day. 19.5~ effective alkali calculated as NaOH was added per ton dry chips. The white liquor had a content of about 6 to 8 grams polysulfide sulphur per liter and was produced by the Moxy process. The white liquor sulfidity was about 40% before the oxyda-tion in the Moxy reactor. For a more detailed descrip-tion of the Moxy process, see US patent specification 4 308 313. The temperature in the cooking zone was about 160C and the cooking time was about 2.5 hours.
From the blowing conduit of the digester a pulp flow of about 70 tons per day was branched out and passed to a reactor through an in-line refiner. In the refiner liquor, oxygen and steam were admixed. The addition of oxygen and alkali corresponded to 35 kg 2 and 50 kg NaOH, respectively, for each ton of pulp. The steam demand corresponded to a temperature increase from about 85C to 110C at 10% pulp consistency. The residence time of the pulp in the reactor was about 30 minutes at 5 at pressure before the pulp was diluted and blown to a tank.
The oxygen-alkali delignification res~lted in a reduction of the kappa number of the pulp from about 60 to about 30. A sample of this pulp was further bleached in the laboratory in three stages with chlorine, alkali and sodium hypochlorite (6.5% chlorine, 2.5% NaOH and
2.7% hypochlorite ~ 0.2% NaOH, the pH value being about ~153161 7.0 at the end of the hypochlorite stage) to a bright-ness of 83% SCAN. The pulp thus obtained was compared with a conventional sulphate pulp for the produc tion of greaseproof. The result of the comparison is shown in table 1.
It appears from table 1 that the oxygen-alkali delignified high yield sulphate pulp was considerably easier to refine to a low freeness and greaseproof proper-ties than the conventional sulphate pulp sold to various producers of greaseproof paper. The conventional sulphate pulp is so difficult to refine that the paper requires an addition of expensive chemicals such as carboxy methyl cellulose in order to give satisfactory greaseproof properties.
Example 2 From the blowing conduit of a continuous Kamyr digester in which a high yield sulphate pulp as described in example 1 was produced, a flow of about 50 tons per day was branched from the pulp. In total about 400 tons such pulp were bleached in the oxygen reactor at the same conditions as described in example 1, and then pressed in a screw press to about 27% dry matter. The pulp entering the reactor had an average kappa number of 51.1, whereas the kappa number in the outlet from the reactor was 30.7. The pulp was then shipped to a sulphite factory. Here the chemical pulp production was interrupted, and both the bleaching plant and the paper factory were fed with the supplied oxygen bleached pulp for about 5 days.
In the bleaching plant about 6.5% chlorine was added to the pulp in the first stage, about 2.5% NaOH
was added in the second stage, and about 3% active chlo-rine as sodium hypochlorite was added in the third stage at 40 to 42C. The pH value was about 7.0 at the end of the third stage.
' ' ` '~
~15316~
Table 1 Pulp acc. to Conventional sulphate Example 1 pulp (bleached) Refining time, rev. on PFI
refiner 7000 9000105001050013500 15000 Freeness, s74 118 244 17 37 47 Wear index, Nm/g 120.5 124.5121.5123.5122.5 125.5 Air perme-ability, nm/Pa14.6 4.6 0.94 206 45.4 37-9 Blister formation Trace Trace Heavy NoNo No Prior to refining the pùlp was buffered with a mixture of sodium bicarbonate and NaOH, so that the pulp after refining still had a pH value of at least 7Ø
The ordinary greaseproof products of the factory were produced with excellent quantitative and qualitative results. As an example of the results obtained, table 2 states results for the greaseproof pulp according to the invention compared with the demands made to a greaseproof pulp having a base weight of 34 (55 g/m2) and high quality.
The paper described in example 2 has been examined for odour and taste at Sentralinstitutt for industriell forskning, Oslo, and Verpackungslabor fur Lebensmittel und Getranke, Vienna. At SI the paper was analysed on a gas chromatograph and compared with a corresponding analysis of ordinary greaseproof paper from sulphate pulp. The analysis showed a substantially smaller area below the chromatographic curve for the product accor-.
.
ii5~
Table 2 Demands to greaseproof Analysis data forpulp having a base 2 greaseproof pulp weight of 34 (55 g/m ) having a base weight and high quality of 34, produced in accordance with the invention Opacity, phV ~ 60 61 Tappi number, s ~21800 1800 Air permeability ~ 0 Burst strength ~ 26 31 Longitudinal tear strength ~ 19 22 Transverse tear strength ~ 22 25 Bentzen ~ 300 500 Wet strength, % ~ 30 34 Number of spots ~ 20 4 Area of spots, mm ~ 1 0,18 . , _ . . _ ding to the invention, which means that there should be no danger of odour and taste problems. At the said laboratory in Vienna, a taste panel compared a vegetable parchment paper and a greaseproof paper produced accor-ding to the invention. The conclusion was that after covering of a butter surface with the two types of paper, no difference in taste of the butter could be established, so that both papers could be regarded as equivalent with respect to transferring taste to fatty products.
Vegetable parchment paper is the material which is at present used as a packing paper for butter in most coun-tries.
, .:
: ~ :, ~15;31~
The paper according to the invention described in this example was also sent to three different custo-mers for conversion on the paper machines of their factories.
All the customers found the paper to be easily convertable.
It will thus be seen that according to the invention a greaseproof paper having a very high quality can be produced from sulphate pulp with a substantially reduced energy demand for the refining operation compared with previously used sulphate pulps, and without addition of expensive chemicals.
It appears from table 1 that the oxygen-alkali delignified high yield sulphate pulp was considerably easier to refine to a low freeness and greaseproof proper-ties than the conventional sulphate pulp sold to various producers of greaseproof paper. The conventional sulphate pulp is so difficult to refine that the paper requires an addition of expensive chemicals such as carboxy methyl cellulose in order to give satisfactory greaseproof properties.
Example 2 From the blowing conduit of a continuous Kamyr digester in which a high yield sulphate pulp as described in example 1 was produced, a flow of about 50 tons per day was branched from the pulp. In total about 400 tons such pulp were bleached in the oxygen reactor at the same conditions as described in example 1, and then pressed in a screw press to about 27% dry matter. The pulp entering the reactor had an average kappa number of 51.1, whereas the kappa number in the outlet from the reactor was 30.7. The pulp was then shipped to a sulphite factory. Here the chemical pulp production was interrupted, and both the bleaching plant and the paper factory were fed with the supplied oxygen bleached pulp for about 5 days.
In the bleaching plant about 6.5% chlorine was added to the pulp in the first stage, about 2.5% NaOH
was added in the second stage, and about 3% active chlo-rine as sodium hypochlorite was added in the third stage at 40 to 42C. The pH value was about 7.0 at the end of the third stage.
' ' ` '~
~15316~
Table 1 Pulp acc. to Conventional sulphate Example 1 pulp (bleached) Refining time, rev. on PFI
refiner 7000 9000105001050013500 15000 Freeness, s74 118 244 17 37 47 Wear index, Nm/g 120.5 124.5121.5123.5122.5 125.5 Air perme-ability, nm/Pa14.6 4.6 0.94 206 45.4 37-9 Blister formation Trace Trace Heavy NoNo No Prior to refining the pùlp was buffered with a mixture of sodium bicarbonate and NaOH, so that the pulp after refining still had a pH value of at least 7Ø
The ordinary greaseproof products of the factory were produced with excellent quantitative and qualitative results. As an example of the results obtained, table 2 states results for the greaseproof pulp according to the invention compared with the demands made to a greaseproof pulp having a base weight of 34 (55 g/m2) and high quality.
The paper described in example 2 has been examined for odour and taste at Sentralinstitutt for industriell forskning, Oslo, and Verpackungslabor fur Lebensmittel und Getranke, Vienna. At SI the paper was analysed on a gas chromatograph and compared with a corresponding analysis of ordinary greaseproof paper from sulphate pulp. The analysis showed a substantially smaller area below the chromatographic curve for the product accor-.
.
ii5~
Table 2 Demands to greaseproof Analysis data forpulp having a base 2 greaseproof pulp weight of 34 (55 g/m ) having a base weight and high quality of 34, produced in accordance with the invention Opacity, phV ~ 60 61 Tappi number, s ~21800 1800 Air permeability ~ 0 Burst strength ~ 26 31 Longitudinal tear strength ~ 19 22 Transverse tear strength ~ 22 25 Bentzen ~ 300 500 Wet strength, % ~ 30 34 Number of spots ~ 20 4 Area of spots, mm ~ 1 0,18 . , _ . . _ ding to the invention, which means that there should be no danger of odour and taste problems. At the said laboratory in Vienna, a taste panel compared a vegetable parchment paper and a greaseproof paper produced accor-ding to the invention. The conclusion was that after covering of a butter surface with the two types of paper, no difference in taste of the butter could be established, so that both papers could be regarded as equivalent with respect to transferring taste to fatty products.
Vegetable parchment paper is the material which is at present used as a packing paper for butter in most coun-tries.
, .:
: ~ :, ~15;31~
The paper according to the invention described in this example was also sent to three different custo-mers for conversion on the paper machines of their factories.
All the customers found the paper to be easily convertable.
It will thus be seen that according to the invention a greaseproof paper having a very high quality can be produced from sulphate pulp with a substantially reduced energy demand for the refining operation compared with previously used sulphate pulps, and without addition of expensive chemicals.
Claims (7)
1. A method of producing a greaseproof pulp, characterized by bleaching an oxygen-alkali delignified high yield sulphate pulp with chlorine, alkali and hypochlorite and refining the bleached pulp.
2. A method according to Claim 1, wherein the sulphate pulp is produced by pulping with a hemicellulose-preserving cooking liquor.
3. A method according to Claim 2, wherein the hemicellulose-preserving cooking liquor is a poly-sulphide liquor having a polysulphide content of 2 to 12 grams per liter.
4. A method according to Claim 3, wherein the polysulphide liquor is produced by the Moxy process.
5. A process according to Claim 1, wherein the sulphate pulp has been digested to a kappa number of 40 to 100 and oxygen-alkali delignified to a kappa number of 15 to 40.
6. A method according to Claim 1, wherein the bleaching of the sulphate pulp in the hypochlorite stage is conducted so that the pH value of the bleached sul-phate pulp at the end of this stage will be 7.0 to 8.5.
7. A method according to Claim 6, wherein the bleached sulphate pulp is refined at a pH value of 7.0 to 10Ø
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO793250A NO145477C (en) | 1979-10-10 | 1979-10-10 | PROCEDURE FOR THE PREPARATION OF GREASE PREPARATION RES. GREASE PROOF-PAPER |
| NO793250 | 1979-10-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1153161A true CA1153161A (en) | 1983-09-06 |
Family
ID=19885080
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000361696A Expired CA1153161A (en) | 1979-10-10 | 1980-10-07 | Method for the production of greaseproof paper |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5696982A (en) |
| CA (1) | CA1153161A (en) |
| FI (1) | FI66944C (en) |
| FR (1) | FR2467259A1 (en) |
| NO (1) | NO145477C (en) |
| SE (1) | SE439509B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE9403857L (en) * | 1994-11-10 | 1996-05-11 | Peterson Seffle Ab | Fat-dense and fat-resistant cover material |
| SE511651C2 (en) * | 1998-03-04 | 1999-11-01 | Peterson Scanproof Ab | Food forms or packaging materials |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2566130A (en) * | 1944-06-10 | 1951-08-28 | Riegel Paper Corp | Manufacture of glassine paper |
-
1979
- 1979-10-10 NO NO793250A patent/NO145477C/en unknown
-
1980
- 1980-09-26 SE SE8006737A patent/SE439509B/en not_active IP Right Cessation
- 1980-10-07 CA CA000361696A patent/CA1153161A/en not_active Expired
- 1980-10-08 FI FI803186A patent/FI66944C/en not_active IP Right Cessation
- 1980-10-09 JP JP14065280A patent/JPS5696982A/en active Pending
- 1980-10-09 FR FR8021622A patent/FR2467259A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NO145477B (en) | 1981-12-21 |
| FI803186L (en) | 1981-04-11 |
| NO793250L (en) | 1981-04-13 |
| FR2467259B1 (en) | 1984-08-17 |
| FI66944B (en) | 1984-08-31 |
| JPS5696982A (en) | 1981-08-05 |
| SE439509B (en) | 1985-06-17 |
| NO145477C (en) | 1982-03-31 |
| SE8006737L (en) | 1981-04-11 |
| FI66944C (en) | 1984-12-10 |
| FR2467259A1 (en) | 1981-04-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |