GB1596045A - Fire extinguishants - Google Patents

Fire extinguishants Download PDF

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Publication number
GB1596045A
GB1596045A GB16438/77A GB1643877A GB1596045A GB 1596045 A GB1596045 A GB 1596045A GB 16438/77 A GB16438/77 A GB 16438/77A GB 1643877 A GB1643877 A GB 1643877A GB 1596045 A GB1596045 A GB 1596045A
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GB
United Kingdom
Prior art keywords
solid composite
composite particle
fire
particle according
core
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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
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GB16438/77A
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Dunlop Ltd
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Dunlop Ltd
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Filing date
Publication date
Application filed by Dunlop Ltd filed Critical Dunlop Ltd
Priority to GB16438/77A priority Critical patent/GB1596045A/en
Priority to IT7822466A priority patent/IT7822466A0/en
Priority to FR7811657A priority patent/FR2387666A1/en
Priority to BE186981A priority patent/BE866213A/en
Priority to DE19782817316 priority patent/DE2817316A1/en
Publication of GB1596045A publication Critical patent/GB1596045A/en
Expired legal-status Critical Current

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Classifications

    • AHUMAN NECESSITIES
    • A62LIFE-SAVING; FIRE-FIGHTING
    • A62DCHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
    • A62D1/00Fire-extinguishing compositions; Use of chemical substances in extinguishing fires
    • A62D1/0007Solid extinguishing substances
    • A62D1/0014Powders; Granules

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Fire-Extinguishing Compositions (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Description

(54) FIRE EXTINGUISHANTS (71) We, DUNLOP LIMITED, a British Company of Dunlop House, Ryder Street, St.
James's, London S.W.1, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to fire extinguishing material comprising solid particles for use in preventing or extinguishing fires.
It is known to extinguish a fire, especially the burning of an inflammable liquid hydrocarbon, by applying solid particles of inorganic or organic material to the combustion zone. Such particles are generally useful for Class B fires such as those of inflammable gases or vapours or of liquids giving off inflammable gases or vapours. The activity of the particles is a result of chemical and/or physical action. The chemical action may be by the particle surface adsorbing radicals involved in the combustion process, and the physical action is a smothering effect either by the particles themselves or by their heat-decomposition product e.g. a non-flammable gas.
Usually when these particles are applied the proportion actually utilised in preventing or extinguishing a fire is significantly small. In particular, when applied from conventional extinguishers only about 20% of the particles reach the combustion zone, the rest going elsewhere as a result of, for example, convection currents and inaccurate aiming. Also, of the particles which land accurately, usually only the particle surfaces are effective, i.e. only about 5% of the particle bulk. Thus, often only about 1% of the total bulk of particles emitted from the extinguisher is actually utilised in preventing or extinguishing the fire.
Generally the fire extinguishing properties improve as the total particle surface area (surface area per gram) increases and consequently as the particle size decreases, but if the particles are too small and light their efficiency is too low because of their tendency to be carried away by convection currents, their low projectability and their tendency to cake on storage.
In accordance with the present invention there is provided a means by which the utilisation and efficiency of particulate fire extinguishing material can be improved.
According to the present invention there is provided the use as a fire extinguishant of solid composite particles each having a unitary solid core and, attached to the surface of the core, a solid material having chemical or chemical and physical fire extinguishing properties and which is present in an amount of at least 5 per cent by weight of the core.
By means of the present invention it is possible to utilise a relatively dense core material having a surface of lighter material which is more effective in extinguishing fires, thereby optimising the fire fighting properties. Also by means of the present invention it is possible to utilise small particles of material which otherwise would be carried away by convection currents and therefore could not be used satisfactorily on their own; this can be achieved by attaching these small particles to larger particles, if desired of the same material. Further, it is possible to employ a core of relatively cheap material having an attached surface of relatively expensive but more effective fire extinguishing material.
The core may be a particle of a material which itself has chemical or chemical and physical fire extinguishing properties or it may be of a material which is merely a carrier for the active material attached to its surface.
The core material and the surface material may be the same or different (preferably different) and they may be attached by a physical or chemical process. When the core and surface are of the same material e.g. both of sodium bicarbonate, the particle size of the surface material is smaller than that of the core.
The preferred materials having the required fire extinguishing properties and which are suitable for the core and/or the attached surface are ionic salts, particularly ionic salts of alkali metals or ammonia.
Preferably the material having fire extinguishing properties is one which will decompose or decrepitate on heating to product smaller particles, thus increasing the total particle surface area. Salts which decompose are generally effective if their decomposition temperatures are below 250"C. Salts which decrepitate on heating in the temperature range 100-2500C. may be used with advantage.
Preferably the material having fire extinguishing properties should decompose on heating to produce a metal carbonate, particularly an alkali metal carbonate such as sodium carbonate. Examples of suitable materials are the alkali metal salts of carboxylic acids which may be mono-,di- or tri-carboxylic acids such as formic, acetic, oxalic, citric or tartaric acid. Alternatively, it may be possible to use an alkali metal salt of a substituted mono-, di- or tri-carboxylic acid. Other suitable salts are sodium, potassium and ammonium salts e.g. (NH4)2HPO4, Na2CO3, NaHCO3, KHCO3, (NH4)2SO4, K3AlF6, KCI and Nail.
Examples of suitable particles having both core and surface of fire extinguishing materials are particles having a core of sodium bicarbonate and an attached surface of sodium bicarbonate or a salt (e.g. an alkali metal salt) of either an inorganic acid such as HYPO4 HCl or H2SO4 or a carboxylic acid such as formic, acetic, oxalic, citric or tartaric acid. Such an attached surface material is usually in the form of relatively small particles which may be chemically or physically linked to the core. Alternatively the core may be of a material which is not usually regarded as having fire extinguishing properties (except as a result of mere resistance to burning) for example sand, glass, carbon black and fly ash.The attachment of the surface material to such cores will usually be by physical means rather than as a result of chemical reaction. The amount of surface material attached to the core will depend on the core material employed. A suitable range of amounts of surface material is 5 to 5()'T by weight of the core preferably 5 to 40% by weight of the core and advantageously 10 to 20% by weight of the core. The composite particle size may be in a verv wide range but a preferred composite particle size is in the range 10 to 300 microns.
The core particle size may be at least 5 times that of the surface material.
A suitable chemical method for making the particles of the invention comprises thoroughly mixing particles of the core material with a solution of a material which reacts with the core surface to produce the attached surface material. If desired the particles of core material may be pre-dispersed in a suitable liquid medium. Preferably the dispersing medium of the core material is compatible with the solvent for the surface-producing material and if desired they may be the same liquid. Preferably also the dispersing medium should not react with the surface-producing material.For the preparation of particles having a core of an inorganic salt such as sodium bicarbonate and a surface of a carboxylic acid salt such as sodium acetate, oxalate, citrate or tartrate, a suitable dispersing medium for the core material is cyclohexane, carbon tetrachloride or an alcohol and a suitable solvent for the material used to produce the surface. i.e. the carboxylic acid. is a polar solvent such as ethanol or propanol. The reaction may be achieved at room temperature or at elevated temperatures in order to achieve production in a short time. If a bicarbonate e.g. sodium bicarbonate is used as the core and/or surface-forming material and the reaction is carried out at an elevated temperature (e.g. at least 50"C). the sodium bicarbonate is likely to decompose to sodium carbonate during the react ion.One guide as to the completion of reaction between the particles of an inorganic salt such as sodium bicarbonate and a carboxylic acid is the cessation of CO2 evolution.
An alternative technique of manufacture which may be employed is a spray-drying method in which a dispersion of core particles in a solution of the surface-producing material is sprayed into a drying oven using, for example, a rotating spray head or an atomiser.
A further method of making the composite particles is by adding a non-solvent to a solution of the surface-producing material containing insoluble or undissolved particles of the core material to slowly precipitate the surface material on to the core particles. This is a suitable method for attaching a core material to a surface material by physical means.
For producing composite particles in which both the surface material and the core material are NaHCOS, a non-solvent such as isopropanol may be added to a saturated solution of NaHCO3 thereby causing precipitation of the dissolved NaHCO3 on to the undissolved NaHCÒS particles.
Yet another possible method of making the composite particles is by grinding. e.g. in a ball mill, the core material and the surface material.
For some combinations of core and surface materials it might be desirable to treat the surface of the core to promote attachment of the surface material, especially when the attachment is physical.
Other ingredients may be mixed with the particles of the invention in order to confer desired properties. Examples of additional ingredients are flow-improving ingredients e.g.
talc, magnesium carbonate, siliconised silicas and metal stearates, and surfactants to improve flotation on an inflammable liquid and thereby reduce the risk of re-ignition.
The particles may be applied to a fire or an inflammable material by methods known for applying solid particles for such purposes. Their application may be employed in conjunction with a fire-fighting foam for example those based on hydrolysed proteins and/or fluorocarbon surfactants.
Apart from the previously-mentioned advantages which are possible from this invention, it is possible to product particles in accordance with the invention which have a critical application rate which is lower than that of unitary particles of the same fire extinguishant.
By "critical application rate" there is meant the minimum rate of application of the particles to the fire area (e.g. kg/second/unit area of fire) to achieve fire extinction.
The invention is illustrated in the following Examples.
Example I A Commercially available sodium bicarbonate was sieved and 100 g of the fraction which passed an 80 mesh BS sieve was dispersed with mechanical stirring in 300 ml cyclohexane in a 3-necked flask fitted with a condenser and dropping funnel. A solution of 5 g oxalic acid in 75 ml ethanol was added dropwise from the funnel at a rate of about 10 drops per second. At the end of the addition the mixture was heated under reflux for about 1 hour. The mixture was cooled and the powder was filtered off, dried at 50"C and passed through an 80 mesh BS sieve.
The product was examined by electron microscopy and photographs were obtained. An attenuated reflectance infra-red spectroscopy technique was used to compare the concentration of sodium oxalate on the surface with that in the bulk of the powder. In was found that the particles of the product had a core of sodium carbonate the surface of which, when viewed by electron microscopy, was shown to have gained a rough coating of oxalate crystals. The spectroscopic technique showed a much greater concentration of oxalate at the surface of the powder than in the bulk of a sample of crushed powder.
Other experiments were performed using exactly the same procedure as above except for the following modifications B Tartaric acid was employed in place of the oxalic acid.
C Acetic acid was employed in place of the oxalic acid.
D Citric acid was employed in place of the oxalic acid.
E Carbon tetrachloride was employed in place of the cyclohexane, and a mixture of equal volumes of methanol and ethanol was employed in place of the ethanol.
F Ethanol was employed in place of the cyclohexane.
G Isopropanol was employed in place of the cyclohexane.
H Aqueous alcohols (95% alcohol: 5% water) methanol, ethanol, isopropanol and n-propanol were each employed in turn in place of the cyclohexane.
The products in all cases were composite particles having a core of sodium carbonate and a securely attached coating of the sodium salt of the carboxylic acid employed.
Had the reactions been carried out at room temperature the products would have been composite particles having a core of sodium bicarbonate and a securely attached coating of the sodium salt of the carboxylic acid employed.
Example II The efficiencies of various solid powder fire extinguishants were compared by recording the minimum application rates at which they extinguished a methane/air flame. The extinguishants were administered to the flame jet along the gas flow-path, which was vertically downwards. The following figures are the Critical Application Rates (CAR). The lower the CAR, the more efficient is the extinguishant.
Powder C.A.R.
"Monnex" 50 Sodium bicarbonate 95 Sodium carbonate coated with 5 28 weight% sodium oxalate Sodium carbonate coated with 5 55 weight% sodium tartrate Potassium chloride 84 Potassium tartrate 41 "Monnex" (a reaction product of urea and an alkali metal carbonate or bicarbonate, available from I.C.I.) and sodium bicarbonate are commonly used as fire extinguishants; "Monnex" is usually preferred. The sodium oxalate and tartrate coated particles were made by the same procedure as described in Example I except that ethanol was employed in place of the cyclohexane and, in the case of the sodium tartrate coating, tartaric acid was employed in place of the oxalic acid. All of the powders, except for the "Monnex", had passed an 80 mesh BS sieve.
It can be seen that the oxalate- and tartrate-coated sodium carbonate powders are significantly more efficient than the uncoated sodium bicarbonate powder.
Example III This example illustrates the coating of inert particles with a material having fire extinguishing properties.
20 g sodium bicarbonate were dissolved in 250 ml water and then 100 g sand particles (approximately 80 mesh) were dispersed into the solutions by mechanical stirring.
Isopropanol was then added slowly until precipitation of sodium bicarbonate began.
The mixture was then stirred overnight and the product (sand particles coated with sodium bicarbonate) was collected by filtration and dried at room temperature.
Example IV 250 g finely divided sodium bicarbonate of a particle size which just passed a BS 80 mesh sieve were dispersed by mechanical stirring into a saturated aqueous solution of sodium bicarbonate made by dissolving 50 g sodium bicarbonate in the minimum amount of water.
To this mixture was slowly added isopropanol until the point was reached at which sodium bicarbonate began to precipitate from solution. The mixture was then stirred until all the bicarbonate had precipitated and then the product was filtered off and dried at 40"C.
Examination of the product under a microscope showed it to be largely composed of sodium bicarbonate particles coated with very fine sodium bicarbonate particles.
"Monnex" is a registered Trade Mark.
WHAT WE CLAIM IS: 1. The use as a fire extinguishant of solid composite particles. each having a unitary solid core and, attached to the surface of the core. a solid material having chemical or chemical and physical fire extinguishing properties and which is present in an amount of at least 5% by weight of the core.
2. The use as a fire extinguishant of a solid composite particle according to claim 1 wherein the core comprises an inert material.
3. The use as a fire extinguishant of a solid composite particle according to claim 1 wherein the core comprises a material having chemical or chemical and physical fire extinguishing properties.
4. The use as a fire extinguishant of a solid composite particle according to claim 3 wherein the core and the solid material attached to its surface are of the same material.
5. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the particle size of the solid material attached to the surface of the core is smaller than that of the core.
6. The use as a fire extinguishant of a solid composite particle accordinvo claim 5 wherein the core is at least five times the size of that of the particles of solid material attached to the surface thereof.
7. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the particles of the solid material attached to the surface of the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (25)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    Powder C.A.R.
    "Monnex" 50 Sodium bicarbonate 95 Sodium carbonate coated with 5 28 weight% sodium oxalate Sodium carbonate coated with 5 55 weight% sodium tartrate Potassium chloride 84 Potassium tartrate 41 "Monnex" (a reaction product of urea and an alkali metal carbonate or bicarbonate, available from I.C.I.) and sodium bicarbonate are commonly used as fire extinguishants; "Monnex" is usually preferred. The sodium oxalate and tartrate coated particles were made by the same procedure as described in Example I except that ethanol was employed in place of the cyclohexane and, in the case of the sodium tartrate coating, tartaric acid was employed in place of the oxalic acid. All of the powders, except for the "Monnex", had passed an 80 mesh BS sieve.
    It can be seen that the oxalate- and tartrate-coated sodium carbonate powders are significantly more efficient than the uncoated sodium bicarbonate powder.
    Example III This example illustrates the coating of inert particles with a material having fire extinguishing properties.
    20 g sodium bicarbonate were dissolved in 250 ml water and then 100 g sand particles (approximately 80 mesh) were dispersed into the solutions by mechanical stirring.
    Isopropanol was then added slowly until precipitation of sodium bicarbonate began.
    The mixture was then stirred overnight and the product (sand particles coated with sodium bicarbonate) was collected by filtration and dried at room temperature.
    Example IV 250 g finely divided sodium bicarbonate of a particle size which just passed a BS 80 mesh sieve were dispersed by mechanical stirring into a saturated aqueous solution of sodium bicarbonate made by dissolving 50 g sodium bicarbonate in the minimum amount of water.
    To this mixture was slowly added isopropanol until the point was reached at which sodium bicarbonate began to precipitate from solution. The mixture was then stirred until all the bicarbonate had precipitated and then the product was filtered off and dried at 40"C.
    Examination of the product under a microscope showed it to be largely composed of sodium bicarbonate particles coated with very fine sodium bicarbonate particles.
    "Monnex" is a registered Trade Mark.
    WHAT WE CLAIM IS: 1. The use as a fire extinguishant of solid composite particles. each having a unitary solid core and, attached to the surface of the core. a solid material having chemical or chemical and physical fire extinguishing properties and which is present in an amount of at least 5% by weight of the core.
  2. 2. The use as a fire extinguishant of a solid composite particle according to claim 1 wherein the core comprises an inert material.
  3. 3. The use as a fire extinguishant of a solid composite particle according to claim 1 wherein the core comprises a material having chemical or chemical and physical fire extinguishing properties.
  4. 4. The use as a fire extinguishant of a solid composite particle according to claim 3 wherein the core and the solid material attached to its surface are of the same material.
  5. 5. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the particle size of the solid material attached to the surface of the core is smaller than that of the core.
  6. 6. The use as a fire extinguishant of a solid composite particle accordinvo claim 5 wherein the core is at least five times the size of that of the particles of solid material attached to the surface thereof.
  7. 7. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the particles of the solid material attached to the surface of the
    core are each lighter than the core.
  8. 8. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the material having fire extinguishing properties will decompose or decrepitate on heating to produce smaller particles.
  9. 9. The use as a fire extinguishant of a solid composite particle according to claim 8 wherein the material having fire extinguishing properties will decompose below 250"C.
  10. 10. The use as a fire extinguishant of a solid composite particle according to claim 8 wherein the material having fire extinguishing properties will decrepitate in the temperature range 100 to 250"C.
  11. 11. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the material having fire extinguishing properties comprises an ionic salt.
  12. 12. The use as a fire extinguishant of a solid composite particle according to claim 11 wherein the ionic salt comprises an alkali metal salt or an ammonium salt.
  13. 13. The use as a fire extinguishant of a solid composite particle according to claim 12 wherein the ionic salt comprises a sodium or potassium salt.
  14. 14. The use as a fire extinguishant of a solid composite particle according to claim 11, 12 or 13 wherein the ionic salt comprises a salt of an inorganic acid.
  15. 15. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the material having fire extinguishing properties comprises a salt which will decompose on heating to yield a metal carbonate.
  16. 16. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the material having fire extinguishing properties comprises a bicarbonate or a salt of a mono- di- or tri-carboxylic acid.
  17. 17. The use as a fire extinguishant of a solid composite particle according to claim 16 wherein the material having fire extinguishing properties comprises a salt of acetic acid, formic acid, oxalic acid, citric acid or tartaric acid.
  18. 18. The use as a fire extinguishant of a solid composite material according to any preceding claim wherein the material having fire extinguishing properties is selected from (NH4)2HPO4, Na2CO3, (NH4)2SO4, KX AIR6, KCI and NaCl.
  19. 19. The use as a fire extinguishant of a solid composite particle according to any preceding claim which is of a size in the range 10 to 300 microns.
  20. 20. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the surface material is present in an amount in the range 5 to 50% by weight of the core.
  21. 21. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the surface material is present in an amount in the range 5 to 40% by weight of the core.
  22. 22. The use as a fire extinguishant of a solid composite particle according to any preceding claim wherein the surface material is present in an amount in the range 10 to 20% by weight of the core.
  23. 23. The use as a fire extinguishant of a solid composite particle according to claim 1 and substantially as described in Example I or II.
  24. 24. The use as a fire extinguishant of a solid composite particle according to claim 1 and substantially as described in Example III or IV.
  25. 25. The use as a fire extinguishant of a solid composite particle according to claim 1 and substantially as herein described.
GB16438/77A 1977-04-20 1977-04-20 Fire extinguishants Expired GB1596045A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
GB16438/77A GB1596045A (en) 1977-04-20 1977-04-20 Fire extinguishants
IT7822466A IT7822466A0 (en) 1977-04-20 1978-04-19 FIRE EXTINGUISHING SUBSTANCE INCLUDING SOLID PARTICLES.
FR7811657A FR2387666A1 (en) 1977-04-20 1978-04-20 EXTINGUISHING PRODUCTS AGAINST FIRES, INCLUDING FOR EXAMPLE ALKALINE METAL SALTS
BE186981A BE866213A (en) 1977-04-20 1978-04-20 EXTINGUISHING COMPOSITIONS PRESSURE AGENT CARTRIDGE AT THE CENTER OF THE DISCHARGE TUBE
DE19782817316 DE2817316A1 (en) 1977-04-20 1978-04-20 FIRE EXTINGUISHERS

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB16438/77A GB1596045A (en) 1977-04-20 1977-04-20 Fire extinguishants

Publications (1)

Publication Number Publication Date
GB1596045A true GB1596045A (en) 1981-08-19

Family

ID=10077334

Family Applications (1)

Application Number Title Priority Date Filing Date
GB16438/77A Expired GB1596045A (en) 1977-04-20 1977-04-20 Fire extinguishants

Country Status (5)

Country Link
BE (1) BE866213A (en)
DE (1) DE2817316A1 (en)
FR (1) FR2387666A1 (en)
GB (1) GB1596045A (en)
IT (1) IT7822466A0 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2291590A (en) * 1994-07-25 1996-01-31 Graviner Ltd Kidde Dry fire or explosion suppressants
GB2345849A (en) * 1999-01-12 2000-07-26 Chubb Fire Ltd Fire Extinguishant
WO2003097171A1 (en) * 2002-05-15 2003-11-27 Kemira Oyj Extinguishing system, extinguisher and method for extinguishing fires

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2291590A (en) * 1994-07-25 1996-01-31 Graviner Ltd Kidde Dry fire or explosion suppressants
GB2345849A (en) * 1999-01-12 2000-07-26 Chubb Fire Ltd Fire Extinguishant
GB2345849B (en) * 1999-01-12 2003-02-12 Chubb Fire Ltd Fire extinguishant
WO2003097171A1 (en) * 2002-05-15 2003-11-27 Kemira Oyj Extinguishing system, extinguisher and method for extinguishing fires

Also Published As

Publication number Publication date
BE866213A (en) 1978-08-14
FR2387666A1 (en) 1978-11-17
IT7822466A0 (en) 1978-04-19
FR2387666B1 (en) 1980-08-29
DE2817316A1 (en) 1978-11-02

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PS Patent sealed [section 19, patents act 1949]
PCNP Patent ceased through non-payment of renewal fee