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(11) EP 2 155 630 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C06C 15/00 (2006.01) 15.02.2017 Bulletin 2017/07 (86) International application number: (21) Application number: 08741636.8 PCT/NL2008/050215

(22) Date of filing: 16.04.2008 (87) International publication number: WO 2008/127106 (23.10.2008 Gazette 2008/43)

(54) A LOW- PYROTECHNIC COMPOSITION FOR PRODUCING COLORED FLAMES RAUCHARME PYROTECHNISCHE ZUSAMMENSETZUNG ZUR ERZEUGUNG VON FARBIGEN FLAMMEN COMPOSITION PYROTECHNIQUE À FAIBLE ÉMISSION DE FUMÉE POUR PRODUIRE DES FLAMMES COLORÉES

(84) Designated Contracting States: (56) References cited: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR EP-A- 1 127 860 WO-A-03/084900 HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT WO-A2-02/084458 DE-C1- 4 022 991 RO SE SI SK TR US-A- 4 078 954 US-A- 5 917 146 US-B1- 6 214 139 (30) Priority: 16.04.2007 EP 07106229 • DATABASE WPI Week 199715 Thomson (43) Date of publication of application: Scientific, London, GB; AN 1997-163554 24.02.2010 Bulletin 2010/08 XP002368163 & RU 2 064 914 C1 (LYUBERETS SOYUZ RES PRODN ASSOC) 10 August 1996 (73) Proprietor: Clearspark, LLC (1996-08-10) Glendale, CA 91201 (US) • DASGUPTA PURNENDU K ET AL: " in the United States. Analysis of relative source (72) Inventors: contributions to the food chain" ENVIRON. SCI. • WEBB, Rutger TECHNOL.; ENVIRONMENTAL SCIENCE AND 3053 LJ Rotterdam (NL) TECHNOLOGY NOV 1 2006, vol. 40, no. 21, 1 • ZEBREGS, Martijn November 2006 (2006-11-01), pages 6608-6614, 2284 CP Rijswijk (NL) XP002461863 • ZEVENBERGEN, John Franciscus • GOLEMAN WANDA L ET AL: "Contribution of 1383 EP Weesp (NL) ammonium ions to the lethality and • VAN ROOIJEN, Murk Pieter antimetamorphic effects of ammonium 3251 AT Stellendam (NL) perchlorate" ENVIRON. TOXICOL. CHEM.; ENVIRONMENTAL TOXICOLOGY AND (74) Representative: V.O. CHEMISTRY APRIL 2006, vol. 25, no. 4, April 2006 P.O. Box 87930 (2006-04), pages 1060-1067, XP002461864 2508 DH Den Haag (NL) • DATABASE WPI Week 198117, Derwent Publications Ltd., London, GB; AN 1981-29810D & JP S5 622698 A (RADIA KOGYO KK) 03 March 1981

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 155 630 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 155 630 B1 2

Description smoke, it has the advantages that it has a high extruda- bility, a well-controlled burning rate, and generates at- [0001] The present invention relates to a -con- tractive colour patterns. taining pyrotechnic composition for producing colored [0010] The chlorine-containing pyrotechnic composi- flames. 5 tions according to the present invention are substantially [0002] Conventional colourful contain signif- free of perchlorate. In the context of the present invention icant amounts of salts and perchlorate to generate this means that they will contain not more then typical the desired colour(s). Such fireworks affect the environ- impuritylevel ( i.e.trace amounts) of perchlorate. So, pref- ment since a small percentage of unburned stars or erably, the present pyrotechnic compositions contain contain perchlorate and eventually may end up in drink- 10 less than 0.05% (m/m) (mass percentage), based on total ing water. Another problem associated with known fire- pyrotechnic composition. works is the generation of a lot of smoke which causes [0011] In the pyrotechnic composition according to the major problems in enclosed venues as for instance sport present invention the is present in an stadiums inside cities. amount in the range of from 85 -95 wt%, based on total [0003] In US 6,214,139 and US 5,917,146 metal salts 15 pyrotechnic composition. of several high nitrogen, low content energetic [0012] Preferably, the nitrocellulose to be used in ac- materials are presented as viable ingredients for low- cordance with the present invention has a nitrogen con- smoke fireworks compositions. tent of less than 14 wt%. More preferably, the nitrocellu- [0004] JP-S-5 622 698 describes compositions for fire- lose has a nitrogen content in the range of from 12 to works that consist for more than 60 wt.% of nitrocellulose 20 13.5 wt%. (having 8-13.5 wt.% N content), 0-1 wt.% conventional [0013] 3-80 wt% of the fibrous nitrocellulose starting colouring agent. 0-1 wt.% conventional spark generating material has been dissolved during the process of pre- agent and 0-10 wt.% adhesive agent. paring the pyrotechnic composition. [0005] The high nitrogen, low carbon content energetic [0014] Suitably, the fibrous nitrocellulose starting ma- materials mentioned in these documents are, however, 25 terial is at least partly dissolved using a mixture of organic not readily available compounds. In order to prepare solvents. Suitable solvents include acetone, ethanol, these compounds multi-step syntheses are required. ethyl acetate, butyl acetate, isopropanol butanol, methyl Furthermore, in some of these syntheses environmental ethyl ketone, and methyl isobutyl ketone. Preferred sol- unfriendly, toxic or hazardous chemical precursors are vents include acetone and ethanol. Preferably, a mixture required. These two issues increase the price of the metal 30 is used of acetone and ethanol. salts of a high nitrogen, low-carbon content considerably. [0015] Preferably, the colourant is present in an [0006] Object of the present invention is to reduce the amount in the range of from 1-10 wt%, based on total environmental impact of fireworks by providing a low- pyrotechnic composition. smoke, perchlorate-free pyrotechnic compositions that [0016] Preferably, the colourant is selected from the can be used in fireworks, and which compositions include 35 group consisting of aminotetrazole, a high-nitrogen content, low-carbon content material that aminotetrazole,strontium ,, and bar- is widely available in the chemical industry (a so-called ium . bulk product). [0017] Preferably, the colourant comprises strontium [0007] Surprisingly, it has now been found that this ob- aminotetrazole or barium aminotetrazole. ject can be realised when use is made of a chlorine-con- 40 [0018] Suitably, the present pyrotechnic composition taining pyrotechnic composition comprising a colourant comprises in addition an oxidator in an amount in the and a particular nitrocellulose. range of from 1-80 wt%, based on total pyrotechnic com- [0008] Accordingly, the present invention relates to a position. chlorine-containing pyrotechnic composition for produc- [0019] Preferably, the oxidator is chosen from the 45 ing colored flames which is substantially free of perchlo- group consisting of KClO3, KNO3, NH4NO3, Sr(NO3)2, rate which composition comprises a nitrocellulose which Ba(NO3)2, and Ba(ClO3)2. is derived from a fibrous nitrocellulose starting material [0020] More preferably, the oxidator comprises that has partially been NH4NO3, Sr(NO3)2 or Ba(NO3)2. dissolved during the process of preparing the pyrotechnic [0021] The present invention also relates to a firework composition and a colourant, 50 article comprising the pyrotechnic composition according wherein the nitrocellulose is present in an amount of to the present invention. 85-95 wt.%, based on total pyrotechnic composition, and [0022] In addition, the present invention also provides wherein 3-80 wit.% of the fibrous nitrocellulose starting a method for preparing the pyrotechnic composition ac- material has been dissolved during the process of pre- cording to the invention, which method comprises mixing paring the pyrotechnic composition. 55 the nitrocellulose starting material, the colourant and the [0009] Apart from the fact that the chlorine-containing chlorine donor and mixing the mixture so obtained with pyrotechnic composition according to the present inven- a mixture of organic solvents, extruding the material thus tion is substantially free of perchlorate and generates little obtained, and evaporating the solvent present in the ex-

2 3 EP 2 155 630 B1 4 truded material so as to obtain a porous material. lon, Pergut, Alloprene, (tradenames), [0023] The metal salt can be obtained by reacting a (PVC), polyvinylidine chloride, hexachlorethane or hex- corresponding metal compound with 5-aminotetrazole. achlorobenzene (C6Cl6), or chlorinated waxes or chlo- Preferably, the metal salt is obtained by reacting the cor- rinated paraffin. responding metal hydroxide, metal sulphate, metal chlo- 5 [0038] More preferably, the chlorine is provided by am- ride or metal nitrate with 5-aminotetrazole. More prefer- monium chloride. ably, the metal salt is obtained by reacting the corre- [0039] The pyrotechnic composition to be used in ac- sponding metal hydroxide or metal nitrate with 5-ami- cordance with the present invention may include other notetrazole. Most preferably, the metal salt is obtained conventional components (burn rate modifier, stabilizer, by reacting the corresponding metal hydroxide with 5- 10 processing additives, flegmatizer, etc.) which are com- aminotetrazole. mon for those skilled in the art. If present, these compo- [0024] The 5-aminotetrazole can either be in anhy- nents will be present in an amount of less than 10 wt%, drous form or containing crystal water. based on total pyrotechnic composition. [0025] Suitably, the metal to be used in the metal salt [0040] The present invention also relates to a firework is selected from the group consisting of , stron- 15 article comprising the pyrotechnic composition in accord- tium, barium, , potassium, , , lith- ance with the present invention. ium, , , and . [0041] In addition, the present invention relates to the [0026] Preferably, the metal is strontium, barium or use of a metal salt of 5-aminotetrazole as described here- copper. inabove in a firework article. [0027] Mixtures of various metal salts can suitably be 20 used to yield desired colours. Examples [0028] Suitably, the metal salt to be used can be pro- tonated by means of an acid. Example 1 [0029] Suitably, the acid is selected from the group consisting of hydrogen chloride, hydrogen bromide, hy- 25 [0042] A pyrotechnic composition in accordance of the drogen iodide, hydrogen fluoride, nitric acid, chloric acid present invention and in the form of Red Ultra Low smoke and perchloric acid. perchlorate-free stars (codename MZ5A) was prepared [0030] Preferably, the acid is hydrogen chloride, chlo- having the following composition: 100 gram (94.79 wt%) ric acid or perchloric acid. nitrocellulose (NC) fibers, 13.5 wt% N from Bergerac; [0031] Suitably, the oxidator is selected from the group 30 5.27 gram (5 wt%) strontium aminotetrazole (Sr-AT) as consisting of , barium nitrate, barium synthesized by the inventors; 0.22 gram (0.21 wt%) chlorate, , and . NH4Cl, pro analyse, Merck KGaG, catalogue number [0032] Preferably, the oxidator comprises ammonium 1.01145.1000. nitrate. [0043] The NC was dried for two days at 45° Celsius [0033] The pyrotechnic fuel is selected from the group 35 in a Heraeus stove to remove all water. Both the Sr-AT consisting of nitrocellulose, cellulose, 5-amino-1H-tetra- and the NH4Cl crystals were ground to a fine powder zole (CH3N5), guanidinium nitrate, Arabic gum, red gum using a mortar and pestle to ensure an intimate mixture. and . An Erlenmeyer flask was filled with 35.14 g acetone and [0034] Preferably, the pyrotechnic fuel comprises ni- 50 g ethanol. This mixture was stirred until homogenously trocellulose or cellulose. 40 mixed. This mixture of solvent was used to yield a ratio [0035] The pyrotechnic fuel to be used in accordance of NC:acetone of 74:26. with the invention may be applied in liquid form as well [0044] To start, half of the solvent mixture was added as in powder form. Apart from nitrocellulose and cellulose to 50 g of the NC, in a small scale S-blader mixer (IKA also a different compound can be used as pyrotechnic mixer). After 10 minutes the mixing blades were scraped fuel such as for instance 5 amino 1H tetrazole. 45 freefrom lumps,after which the mixerwas restarted. After [0036] The pyrotechnic composition according to the 15 minutes another 25 g of NC was added after which present invention contains chlorine. Suitably, the present the mixer was restarted. After 20 minutes the finely pow- pyrotechnic compositions comprise chlorine in an dered NH4Cl and Sr-AT were added to the mixer. After amount in the range of from 1-20 wt%, preferably in the 35 minutes the remaining NC and solvent were added. range of from 0.2-5 wt%, based on total pyrotechnic com- 50 After continued mixing at 60 minutes after start the mixer position. The chlorine can be provided by the colourant was emptied. This mixture was inserted in the Rosand or by a separate chlorine donor. Such a chlorine donor Double Barrel Capillary Rheometer. Under the barrels of is suitably present in an amount of from 1 to 20 wt%, this Rosand Rheometer, an extrusion nozzle of 10mm based on total pyrotechnic composition. was installed. After filling the pistons are lowered at a [0037] The chlorine is preferably provided by ammo- 55 speed of 100mm/min, while pressures remain between nium chloride. Other chlorine donors may be used, such 2.5 en 3.2 MPa (25-32 bar). Underneath the Rosand Rh- as those that have been described in prior art of pyro- eometer the extrudate was collected and cut manually technics, for example chlorinated rubbers such as Par- to cylinders 1 cm long. These cylindrical stars were dried

3 5 EP 2 155 630 B1 6 in a Heraeus stove at 40° C for 12 hours, in order to sisting of strontium aminotetrazole, barium aminote- remove all solvents, and the stars were then dried in a trazole, strontium nitrate, barium nitrate, and barium Gallenkamp vacuumstove at 40° C for 5 hours. chlorate.

Example 2 5 6. A composition according to any one of claims 1-5, wherein chlorine is present in an amount of from 1 [0045] A pyrotechnic composition in accordance of the to 20 wt.%, based on total pyrotechnic composition. present invention and in the form of Green Ultra Low smoke perchlorate-free stars (codename MZ6) was pre- 7. A composition according to any one of claims 1-6, pared having the following composition: 100 gram (93.35 10 wherein the chlorine is provided by ammonium chlo- wt%) nitrocellulose fibers, 13.5 wt% N from Bergerac; ride, chlorinated rubbers, polyvinyl chloride, polyvi- 5.26 gram (4.91 wt%) barium aminotetrazole, as synthe- nylidine chloride, hexachlorethane, hexachloroben- sized by the inventors; 1.86 gram (1.74 wt%) NH 4Cl, pro zene, chlorinated waxes, or chlorinated paraffin. analyse, Merck KGaG. Said composition was prepared in the same way as the Red ultra-low smoke perchlorate- 15 8. A composition according to any one of claims 1-7, free star mixture described in Example 1. which in addition comprises an oxidiser in an amount [0046] It will be clear to those skilled in the art that the in the range of from 1-80 wt.%, based on total pyro- Rosand Rheometer was used to produce stars on a lab- technic composition. oratory scale (i.e. typically small scale batches), while at the same time it allows the users to measure important 20 9. A composition according to claim 8, wherein the ox- rheometric parameters which are crucial for large scale idiser is chosen from the group consisting of KNO 3, extrusion processes. The Theyson Twin Screw Extruder NH4NO3, Sr(NO3)2, and Ba(NO3)2. (co-rotating, self wiping, 45mm, 1305 screw length, 29 L/D) is a suitable and attractive option for large scale 10. A composition according to any one of claims 1-9, productionof the pyrotechnic stars described inthis spec- 25 which in addition comprises a metal salt of (5-ami- ification. notetrazole) in an amount in the range of from 1-10 wt.%, based on total pyrotechnic composition.

Claims 11. A composition according to claim 10, wherein the 30 metal comprises barium, strontium or copper. 1. A chlorine-containing pyrotechnic composition for producing colored flames which is substantially free 12. A method for preparing a chlorine-containing pyro- of perchlorate which composition comprises a nitro- technic composition for producing colored flames ac- cellulose which is derived from a fibrous nitrocellu- cording to any one of claims 1-11, comprising lose starting material that has partially been dis-35 solved during the process of preparing the pyrotech- - mixing the nitrocellulose starting material, the nic composition, and a colorant, wherein the nitro- colorant and a chlorine donor, cellulose is present in an amount of 85-95 wt.%, - mixing the mixture so obtained with a mixture based on total pyrotechnic composition, and of organic solvents, wherein 3-80 wt.% of the fibrous nitrocellulose start- 40 - extruding the material thus obtained, and ing material has been dissolved during the process - evaporating the solvent present in the extruded of preparing the pyrotechnic composition. material so as to obtain a porous material.

2. A composition according to claim 1, wherein the ni- 13. A firework article comprising the pyrotechnic com- trocellulose has a nitrogen content of less than 14 45 position as described in any one of claims 1-11. wt.%.

3. A composition according to claim 1 or 2, wherein the Patentansprüche nitrocellulose has a nitrogen content in the range of from 12 to 13.5 wt.%. 50 1. Chlorhaltige pyrotechnische Zusammensetzung zur Herstellung farbiger Flammen, die im Wesentlichen 4. A composition according to any one of claims 1-3, frei von Perchlorat ist, wobei die Zusammensetzung wherein the colorant is present in an amount in the eine Nitrozellulose, welche von einem faserigen Ni- range of from 1-10 wt.%, based on total pyrotechnic trozellulose-Ausgangsmaterial gewonnen ist, das composition. 55 teilweise während des Verfahrens der Herstellung der pyrotechnischen Zusammensetzung aufgelöst 5. A composition according to any one of claims 1-4, wurde, und einen Farbstoff umfasst, wobei die Ni- wherein the colorant is chosen from the group con- trozellulose in einer Menge von 85-95 Gew.-%, ba-

4 7 EP 2 155 630 B1 8

sierend auf der gesamten pyrotechnischen Zusam- technischen Zusammensetzung zur Herstellung far- mensetzung, vorhanden ist, und biger Flammen nach einem der Ansprüche 1-11, um- wobei 3-80 Gew.-% des faserigen Nitrozellulose- fassend Ausgangsmaterials während des Verfahrens der Herstellung der pyrotechnischen Zusammenset-5 - Mischen des Nitrozellulose-Ausgangsmateri- zung aufgelöst worden sind. als, des Farbstoffs und eines Chlordonors, - Mischen des so erhaltenen Gemischs mit ei- 2. Zusammensetzung nach Anspruch 1, wobei die Ni- nem Gemisch organischer Lösungsmittel, trozellulose einen Stickstoffgehalt von weniger als - Extrudieren des so erhaltenen Materials und 14 Gew.-% hat. 10 - Verdampfen des in dem extrudierten Material vorhandenen Lösungsmittels, um ein poröses 3. Zusammensetzung nach Anspruch 1 oder 2, wobei Material zu erhalten. die Nitrozellulose einen Stickstoffgehalt in dem Be- reich von 12 bis 13,5 Gew.-% hat. 13. Feuerwerksartikel, umfassend die pyrotechnische 15 Zusammensetzung wie in einem der Ansprüche 4. Zusammensetzung nach einem der Ansprüche 1-3, 1-11 beschrieben. wobei der Farbstoff in einer Menge in dem Bereich von 1-10 Gew.-%, basierend auf der gesamten py- rotechnischen Zusammensetzung, vorhanden ist. Revendications 20 5. Zusammensetzung nach einem der Ansprüche 1-4, 1. Composition pyrotechnique contenant du chlore, wobei der Farbstoff ausgewählt ist aus der Gruppe, destinée à produire des flammes colorées, qui est bestehend aus Strontiumaminotetrazol, Bariumami- sensiblement exempte de perchlorate, laquelle com- notetrazol, Strontiumnitrat, Bariumnitrat und Bari- position comprend une nitrocellulose qui est dérivée umchlorat. 25 d’une matière première de nitrocellulose fibreuse qui a été dissoute en partie au cours d’un processus 6. Zusammensetzung nach einem der Ansprüche 1-5, consistant à préparer la composition pyrotechnique, wobei Chlor in einer Menge von 1 bis 20 Gew.-%, et un colorant, dans laquelle la nitrocellulose est pré- basierend auf der gesamten pyrotechnischen Zu- sente en une quantité comprise entre 85 % et 95 % sammensetzung, vorhanden ist. 30 du poids total, sur la base de la composition pyro- technique totale ; et 7. Zusammensetzung nach einem der Ansprüche 1-6, dans laquelle entre 3 % et 80 % du poids total de la wobei das Chlor bereitgestellt wird durch Ammoni- matière première de nitrocellulose fibreuse, ont été umchlorid, chlorierte Gummis, Polyvinylchlorid, Po- dissous au cours du processus consistant à préparer lyvinylidinchlorid, Hexachlorethan, Hexachlorben- 35 la composition pyrotechnique. zen, chlorierte Wachse oder chloriertes Paraffin. 2. Composition selon la revendication 1, dans laquelle 8. Zusammensetzung nach einem der Ansprüche 1-7, la nitrocellulose présente une teneur en azote infé- die zusätzlich ein Oxidationsmittel in einer Menge in rieure à 14 % du poids total. dem Bereich von 1-80 Gew.-%, basierend auf der 40 gesamten pyrotechnischen Zusammensetzung, 3. Composition selon la revendication 1 ou la revendi- umfasst. cation 2, dans laquelle la nitrocellulose présente une teneuren azote qui se situedans une plagecomprise 9. Zusammensetzung nach Anspruch 8, wobei das entre 12 % du poids total et 13,5 % du poids total. Oxidationsmittel ausgewählt ist aus der Gruppe, be- 45 stehend aus KNO3, NH4NO3, Sr(NO3)2 und 4. Composition selon l’une quelconque des revendica- Ba(NO3)2. tions 1 à 3, dans laquelle le colorant est présent en une quantité qui se situe dans une plage comprise 10. Zusammensetzung nach einem der Ansprüche 1-9, entre 1 % du poids total et 10 % du poids total, sur die zusätzlich ein Metallsalz von (5-Aminotetrazol) 50 la base de la composition pyrotechnique totale. in einer Menge in dem Bereich von 1-10 Gew.-%, basierend auf der gesamten pyrotechnischen Zu- 5. Composition selon l’une quelconque des revendica- sammensetzung, umfasst. tions 1 à 4, dans laquelle le colorant est sélectionné dans le groupe constitué par un aminotétrazole de 11. Zusammensetzung nach Anspruch 10, wobei das 55 strontium, un aminotétrazole de baryum, un nitrate Metall Barium, Strontium oder Kupfer umfasst. de strontium, un nitrate de baryum, et un chlorate de baryum. 12. Verfahren zur Herstellung einer chlorhaltigen pyro-

5 9 EP 2 155 630 B1 10

6. Composition selon l’une quelconque des revendica- tions 1 à 5, dans laquelle le chlore est présent en une quantité qui se situe dans une plage comprise entre 1 % du poids total et 20 % du poids total, sur la base de la composition pyrotechnique totale. 5

7. Composition selon l’une quelconque des revendica- tions 1 à 6, dans laquelle le chlore est fourni par un chlorure d’ammonium, des caoutchoucs chlorés, un polychlorure de vinyle, un polychlorure de vinylidè- 10 ne, un hexachloréthane, un hexachlorobenzène, des cires chlorées, ou une paraffine chlorée.

8. Composition selon l’une quelconque des revendica- tions 1 à 7, qui comprend en outre un agent oxydant 15 enune quantité qui sesitue dans uneplage comprise entre 1 % du poids total et 80 % du poids total, sur la base de la composition pyrotechnique totale.

9. Composition selon la revendication 8, dans laquelle 20 l’agent oxydant est sélectionné dans le groupe cons- titué par : KNO3, NH4NO3, Sr(NO3)2, et Ba(NO3)2.

10. Composition selon l’une quelconque des revendica- tions 1 à 9, qui comprend en outre un sel métallique 25 de (5 - aminotétrazole) en une quantité qui se situe dans une plage comprise entre 1 % du poids total et 10 % du poids total, sur la base de la composition pyrotechnique totale. 30 11. Compositionselon la revendication 10, danslaquelle le métal comprend le baryum, le strontium ou le cui- vre.

12. Procédé destiné à préparer une composition pyro- 35 technique qui contient du chlore, destinée à produire des flammes colorées selon l’une quelconque des revendications 1 à 11, comprenant les étapes con- sistant à : 40 - mélangerla matièrepremière de nitrocellulose, le colorant et un donneur de chlore ; - mélanger le mélange ainsi obtenu et un mé- lange de solvants organiques ; - extruder le matériau ainsi obtenu ; et 45 - faire évaporer le solvant présent dans le ma- tériau extrudé de façon à obtenir un matériau poreux.

13. Article de feu d’artifice comprenant la composition 50 pyrotechnique selon l’une quelconque des revendi- cations 1 à 11.

55

6 EP 2 155 630 B1

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 6214139 B [0003] • JP 5622698 B [0004] • US 5917146 A [0003]

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