AU2013257394B2

AU2013257394B2 - Use of dinitromethane salt

Info

Publication number: AU2013257394B2
Application number: AU2013257394A
Authority: AU
Inventors: Arno Hahma; Oliver Pham-Schonwetter
Original assignee: Diehl Defence GmbH and Co KG
Current assignee: Diehl Defence GmbH and Co KG
Priority date: 2012-11-28
Filing date: 2013-11-11
Publication date: 2017-09-28
Anticipated expiration: 2033-11-11
Also published as: DE102012023549B4; EP2738150B1; ZA201308872B; IL229411B; AU2013257394A1; EP2738150A3; IL229411A0; EP2738150A2; DE102012023549A1

Abstract

The invention relates to the use of a dinitromethane salt as additive to an active pyrotechnic composition for increasing the intensity of radiation produced during the burnup of said composition and for increasing a ratio of the intensity of radiation emitted during burnup of the active composition in the wavelength range from 3.7 to 5.1 pm to the intensity of radiation emitted during burnup of the active composition in the wavelength range from 1.9 to 2.3 pim, a cation of the dinitromethane salt being a base comprising at least the elements nitrogen and hydrogen.

Description

ι 2013257394 11 Nov 2013

USE OF A DINITROMETHANE SALT FIELD OF THE INVENTION

[0001] The invention relates to the use of a dinitromethane salt as additive to an active pyrotechnic composition.

BACKGROUND OF THE INVENTION

[0002] DE 699 10 070 T2 discloses the use of salts of dinitromethane as oxidizers in propellant compositions and pyrotechnic charges.

[0003] Owing to the requirement of a spectral signature, active compositions for spectrally radiating pyrotechnic decoys generally have a relatively low radiation intensity in comparison to an active composition which emits blackbody radiation and comprises magnesium, Teflon and the fluoroelastomer Viton®. In order to be able to use a burning pyrotechnic decoy effectively to mimic an aircraft to a modem two-colour infrared seeker head, an extremely high spectral ratio is required on bumup of the active composition. The spectral ratio here is the ratio of the radiation emitted in the wavelength range from 3.7 to 5.1 pm (MW band) to the radiation emitted in the wavelength range from 1.9 to 2.3 pm (SW band). Conventional active spectral decoy compositions frequently lack a sufficiently high spectral ratio and/or sufficient intensity to achieve this. Such active decoy compositions consist, for example, of ammonium perchlorate as oxidizer and of hydroxyl-terminated polybutadiene (HTPB) as fuel.

[0004] In order to increase the intensity of such active decoy compositions on bumup, an additive is frequently used in order to enlarge the flame produced on burnup. One known such additive is hexamethylenetetramine, which, while it does enlarge the flame and thus increase the intensity, fails to increase, or increases only slightly, the spectral ratio in comparison to a corresponding active composition with the same oxygen balance. A disadvantage here is that the additive often greatly reduces the burnup rate of the active composition. To compensate for this, the active composition is frequently pressed into a shape which has a large surface area. This takes up space, however, meaning 11/11/13,21221 speci,l 2 2013257394 11 Nov 2013 that relatively little active composition can be installed into a decoy with a given volume, meaning that the total energy content of the decoy is relatively small.

[0005] Also known is the use of an active decoy composition comprising nitrocellulose or a double-based propellant charge powder. For an active composition of this kind, relative to an active composition comprising ammonium perchlorate and HTPB, both the spectral ratio and the specific intensity are increased. A disadvantage, however, is that the flame produced as such a composition burns up is quickly blown out by air at a relatively high speed. To eliminate this problem, there are intricately designed decoys in which the active composition is protected from wind as it bums up and is irradiated thermally by means of glow elements which are heated up by the flame. The glow elements must be shielded from the outside so that they cannot give off to the outside any blackbody radiation that reduces the spectral ratio. Devices of this kind are relatively unreliable and expensive. Moreover, they require relatively high volume in the decoy, meaning that the overall intensity of the decoy is not substantially higher than in the case of a decoy comprising ammonium perchlorate and HTPB as active composition.

[0006] It is an object of the present invention to specify the use of an additive which can be added to an active pyrotechnic composition in order to raise the intensity of radiation produced during the burnup of said composition, and to increase the spectral ratio.

[0007] The object is achieved by means of the features of Claim 1. Useful embodiments are apparent from the features of Claims 2 to 6.

[0008] Provided in accordance with the invention is the use of a dinitromethane salt as an additive to an active pyrotechnic composition for raising the intensity of radiation produced as said composition bums up and for increasing a ratio of the intensity of radiation emitted during burnup of the active composition in the wavelength range from 3.7 to 5.1 pm to the intensity of radiation emitted during burnup of the active composition in the wavelength range from 1.9 to 2.3 pm. A cation of this dinitromethane salt is a base comprising at least the elements nitrogen and hydrogen. A dinitromethane salt of this kind raises the intensity of the radiation and hence the radiant power by enlarging the flame as a 11/11/13,21221 sped,2 3 2013257394 11 Nov 2013 result of the gaseous products produced during bumup by thermal decomposition of the stated dinitromethane salt. The enlargement of the flame increases the radiating area. The spectral ratio is increased in particular by the raising of the intensity of radiation in the MW band, while the intensity of radiation in the SW band is influenced little, if at all. Through the increase in the spectral ratio, the mimic effect of a pyrotechnic decoy to a two-colour infrared seeker head is enhanced. The likewise-known alkali metal salts of dinitromethane are unsuitable as additives since their bumup produces solid material which acts as a blackbody emitter and so significantly reduces the spectral ratio.

[0009] It has emerged, furthermore, that the stated dinitromethane salt is able to increase the burnup rate. Consequently it is possible, with a tablet of conventional surface form, to achieve the required mass throughput on burnup of the active composition. It is not necessary for the active composition to be pressed into a shape which exhibits a particularly large surface.

[0010] It has been found, furthermore, that by means of the stated dinitromethane salt it is possible to replace nitrocellulose in active decoy compositions of the kind where the decomposition temperature of the nitrocellulose is a factor. The decomposition temperatures of nitrocellulose and of the stated dinitromethane salt lie roughly in the same range of 160 to 200°C. Replacing nitrocellulose by the stated dinitromethane salt increases the shelflife and safety of the active composition, since nitrocellulose, unlike the stated dinitromethane salt, has only limited long-term stability.

[0011] The stated dinitromethane salt also allows a reduction in the sensitivity of the active composition with respect to mechanical loading. Moreover, it is easy to synthesize the stated dinitromethane salt, from readily available and inexpensive starting materials, with a good yield. For the synthesis, the stated salt can be precipitated, for example, from a different dinitromethane salt, such as ammonium dinitromethanate, for example, by means of a corresponding counterion, or can be synthesized directly from dinitrobarbituric acid.

[0012] In one embodiment of the inventive use, the cation further comprises the elements carbon and/or oxygen. If the cation comprises the element carbon, it is useful for 11/11/13,21221 sped,3 4 2013257394 11 Nov 2013 there to be not more than five carbon atoms joined to one another by direct bonding in the cation. At least every sixth atom, therefore, is a heteroatom, such as oxygen or nitrogen, for example. In such a cation there is preferably no aromatic carbon structure present. Through the presence of not more than five carbon atoms joined directly to one another, the production of soot, which is a very efficient blackbody emitter as it glows, is at least largely prevented. As soon as six carbon atoms are joined to one another by direct bonding, pyrolysis may result in ring closure and hence in the formation of an aromatic structure. This then leads to the formation of soot in the form of a polyaromatic material, which shifts the spectrum of the emitted radiation in the direction of the SW band. With not more than five C atoms joined to one another by direct bonding, the formation of aromatic structures is highly unlikely and the formation of soot is greatly suppressed.

[0013] The cation may be a guanidinium ion, an ammonium ion, a hydrazinium ion or a guanylurea ion. Where the guanylurea salt of dinitromethane is used as additive, the radiation intensity of an active pyrotechnic composition in the MW band was increased by up to 60% relative to that of an active composition without this additive. Moreover, the spectral ratio was increased from around 9 up to 10 to 11.

[0014] The active composition may be an active decoy composition which radiates spectrally in the infrared region as it bums up.

[0015] The additive may additionally be used for increasing a bumup rate of the active composition.

[0016] The invention is elucidated in more detail below by means of working examples.

Example 1:

Standard MTV (Magnesium-Teflon-Viton).

[0017] The active composition is a known blackbody emitter, used here as a reference. 11/11/13,21221 sped,4 2013257394 11 Nov 2013 5 Substance Type Wt% Miscellaneous Magnesium powder Ecka LNR 61 60.0 Teflon powder Hoechst TF 9202 25.0 Viton 3M Fluorel FC-2175 10.0 TMD = 1893 Graphite Merck 5.0 lubricant TMD = theoretical maximum density

Substance Type Wt% Miscellaneous Ammonium perchlorate 85.50 HTPB R45HT-M M = 2800 13.47 IPDI 1.01 TMD = 1678 Iron acetonyl acetate 0.02 HTPB = hydroxyl-terminated polybutadiene IPDI = isophorone diisocyanate

Example 2: [0018] Known spectrally adapted active composition based on ammonium perchlorate. This active composition has a relatively high spectral ratio but relatively low energy.

Example 3: [0019] Spectrally adapted active composition based on ammonium perchlorate.

This active composition has a relatively high spectral ratio but relatively low energy. This active composition shows the effect of hexamethylenetetramine as further fuel: with the same oxygen balance as the active composition of Example 2, a higher radiant energy is achieved, but the spectral ratio remains unchanged.

Substance Type Wt% Miscellaneous Ammonium perchlorate dso = 25 pm 77.8 HTPB R45HT-M M = 2800 10.32 IPDI 0.78 TMD = 1656 Hexamethylenetetramine crystalline 11.0 Iron acetonyl acetate 0.10 11/11/13,21221 speci,5 6 2013257394 11 Nov 2013

Example 4: [0020] Inventive spectrally radiating active composition with ammonium dinitromethanate as additive, which enlarges the flame and reduces the sensitivity of the active composition.

Substance Type Wt% Miscellaneous Ammonium perchlorate from the drum 69.9 HTPB R45HT-M M = 2800 13.95 IPDI 1.05 TMD = 1586 Ammonium dinitromethanate own synthesis 15.0 Iron acetonylacetate 0.10

Example 5: [0021] Inventive spectrally radiating active composition with guanylurea dinitromethanate as additive, for enlarging the flame and for reducing the sensitivity of the active composition.

Substance Type Wt% Miscellaneous Ammonium perchlorate from the drum 69.9 HTPB R45HT-M M = 2800 13.95 IPDI 1.05 TMD = 1612 Guanylurea dinitromethanate own synthesis 15.0 Iron acetonylacetate 0.10

Table 1: [0022] Results of radiation measurements in the laboratory without wind. All results are average values from five parallel experiments. The pressing pressure for all the charges was 500 bar, 17 mm tool diameter, batch 10.0 g.

Charge Esw fJ/(g sr)] Emw 1 J/(g sr)l (Esw+Emw) fJ/(g sr)] Emw/Esw %MTV (MW channel) Bumup rate fmm/sl Example 1 152 84 236 0.553 100 2.7 Example 2 2.7 19.8 22.5 8.7 24 2.5 Example 3 3.7 31.3 35.0 8.7 37 1.1 Example 4 3.1 31.5 34.6 10.2 38 2.2 Example 5 2.4 28.5 30.9 11.2 34 2.9

Esw = specific intensity in the SW channel (about 1.9 to 2.3 pm) in J/(g sr); Emw = specific intensity in the MW channel (about 3.7 to 5.1 pm) in J/(g sr); 11/11/13,21221 sped,6 7 2013257394 11 Nov 2013 (Esw+Emw) in J/(g sr) = the sum total of SW and MW channels;

Emw/Esw = the ratio of MW to SW channel; %MTV = intensity as a percentage of the intensity of standard MTV; SW = short-wave; MW = medium-wave [0023] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0024] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia. 11/11/13,21221 sped,7

Claims

1. Use of a dinitromethane salt as additive to an active pyrotechnic composition for increasing the intensity of radiation produced during the bumup of said composition and for increasing a ratio of the intensity of radiation emitted during burnup of the active composition in the wavelength range from 3.7 to 5.1 pm to the intensity of radiation emitted during bumup of the active composition in the wavelength range from 1.9 to 2.3 pm, a cation of the dinitromethane salt being a base comprising at least the elements nitrogen and hydrogen.

2. Use according to Claim 1, the cation further comprising the elements carbon and/or oxygen.

3. Use according to Claim 2, the cation comprising the element carbon, there being not more than five carbon atoms joined to one another by direct bonding in the cation.

4. Use according to any of the preceding claims, the cation being a guanidinium ion, an ammonium ion, a hydrazinium ion or a guanylurea ion.

5. Use according to any of the preceding claims, the active composition being an active decoy composition which radiates spectrally in the infrared region during its burnup.

6. Use according to any of the preceding claims, the additive being used additionally for increasing a bumup rate of the active composition.