Organic compounds -- part of the class 532-570 series – Organic compounds – Azides
Reexamination Certificate
2000-09-25
2001-11-27
Geist, Gary (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Azides
C560S155000
Reexamination Certificate
active
06323352
ABSTRACT:
The present invention relates to the field of solid pyrotechnic compositions, in particular that of solid propellants, composite explosives and firearm propellant powders.
A subject-matter of the invention is more specifically novel energetic plasticizers which can be used in the above mentioned solid pyrotechnic compositions.
These pyrotechnic compositions are generally obtained by pouring into a mould and then crosslinking a paste composed essentially of a crosslinkable binder, of a system for crosslinking this binder and of oxidizing and/or reducing charges.
Plasticizers are often incorporated in order to improve the use and the mechanical properties of the finished product, in particular at low temperatures. These plasticizers are preferably energetic compounds which are miscible but unreactive with the other constituents of the paste, in particular with the binder and the crosslinking agent.
The use is known, for this purpose, of alcohol nitrates, such as nitroglycerine and ethylene glycol dinitrate, but these compounds are particularly sensitive, detonatable and dangerous to handle.
Patent FR 2,707,979 furthermore discloses polyglycidyl azides (PGAs) terminated by azide functional groups which can be used as energetic plasticizers in such pyrotechnic compositions but it proves to be the case that these PGAs are also detonatable and that they have to be classified in category 1-1 according to Article 4 of the Interministerial Order of Sept. 26, 1980 relating to the classification of explosive substances (publication in the Official Gazette of the French Republic on Oct. 2, 1980) and the Interministerial Directive for implementation of this Order dated May 8, 1981, that is to say in a category corresponding to particularly sensitive products, such as hexogen, octogen and nitroglycerine, with all the constraints which this results in relating to safety of transportation, of storage and of use and thus with regard to the costs, which are consequently high.
U.S. Pat. No. 4,970,326 discloses PGA diacetates which can be used as plasticizers in solid pyrotechnic compositions but these compounds, which are certainly not detonatable, are markedly less energetic (nitrogen content of the order of 32-33%) than PGAs with azide terminal groups.
A person skilled in the art, who is constantly concerned about improving the safety of the processes and reducing the manufacturing costs, is therefore looking for novel energetic plasticizers entailing fewer pyrotechnic risks than the PGAs with azide terminal groups of the state of the art, in particular plasticizers which would be both energetic and nondetonatable.
A subject-matter of the present invention is such plasticizers, more specifically novel energetic polyglycidyl azides (nitrogen content in the region of 41%), which are liquid under standard temperature and pressure conditions, which can be used as energetic plasticizers in solid pyrotechnic compositions and which are nondetonatable, that is to say that they are classified in particular in category 1-3 according to the above mentioned Interministerial Order, that is to say in a category corresponding to products with reduced risks, such as firearm powders and propellants, and not in category 1-1, such as the detonatable PGAs disclosed in FR 2,707,979.
The novel polyglycidyl azides according to the invention correspond to the general formula (I)
in which:
R
1
represents an alkylene chain comprising 2 to 4 carbon atoms, preferably —(CH
2
)
2
—,
R
2
represents an alkyl chain comprising 1 to 4 carbon atoms, preferably —CH
3
,
x represents an integer such that 4≦x≦10, preferably such that 6≦x≦8.
These novel PGAs of formula (I) according to the invention can be obtained in 3 stages from epichlorohydrin.
In a first stage, a polyepichlorohydrin with a hydroxyl terminal group of general formula (II)
in which x and R
1
have the above mentioned meanings, is synthesized by polymerization, generally in an organic solvent medium, preferably a halogenated organic solvent medium, of epichlorohydrin in the presence of an initiating alcohol of general formula Cl—R
1
—OH (III), in which R
1
has the above mentioned meaning.
Such a reaction is well known to a person skilled in the art and is generally carried out in the presence of a catalyst of Lewis acid type, for example a BF
3
etherate.
In a second stage, a polyepichlorohydrin with an acyloxy terminal group of general formula (IV)
in which R
1
, R
2
and x have the above mentioned meanings, is synthesized by reaction, in the presence of a basic organic catalyst, of the above mentioned polyepichlorohydrin with a hydroxyl terminal group of formula (II) with an acylating agent of general formula
in which R
2
has the above mentioned meaning and Z represents a hydroxyl, halide (preferably Cl or Br) or acyloxy group.
In a particularly preferred way, the acylating agent of formula (V) is an anhydride of formula
The acylating agent is generally used in a very large molar excess with respect to the hydroxyl functional groups. It is possible, for example, to use a molar ratio of between 2 and 8.
The basic organic catalyst is preferably chosen from the group consisting of pyridines and imidazoles. Pyridine and 1-methylimidazole are particularly preferred.
Mention may be made, as examples of other suitable catalysts, of trialkylamines, in particular triethylamine.
The amount of catalyst generally used is between 10 mol % and 50 mol % with respect to the hydroxyl functional groups to be esterified.
According to a preferred alternative form, this second stage is carried out in an organic solvent medium, preferably a halogenated organic solvent medium, more particularly a chlorinated organic solvent medium, such as CHCl
3
, CCl
4
, CH
2
Cl
2
and CH
2
Cl—CH
2
Cl.
The temperature of this acylation reaction is preferably between 40° C. and 100° C. The temperature range 70° C.-90° C. is particularly preferred and the reaction is preferably carried out at reflux of the solvent.
After reacting the polyepichlorohydrin with a hydroxyl terminal group of formula (II) with the acylating agent of formula (V), the polyepichlorohydrin with an acyloxy terminal group of general formula (IV) formed is isolated from the reaction mixture and then identified according to conventional physical, chemical, chromatographic and spectrometric analytical methods.
Infrared spectrometry shows in particular, in comparison with the spectrum of the starting polyepichlorohydrin with a hydroxyl terminal group, the disappearance of the hydroxyl bands and the appearance of a carbonyl band, while the C—Cl band is still present.
In a third stage, an azidation is carried out on the chloride functional groups of the above mentioned polyepichlorohydrin with an acyloxy terminal group of general formula (IV) obtained in the second stage, preferably by means of an alkali metal azide.
It has been found, in a particularly unexpected way, that the acyl functional group carried by the intermediate polyepichlorohydrins of general formula (IV) is inert with regard to the azidation reactants and that it is therefore not, even partially, converted to an azide functional group, whereas the state of the art and in particular the above mentioned U.S. Pat. No. 4,970,329 prompts a person skilled in the art to carry out the azidation reaction before the acylation reaction, with the disadvantages which result therefrom with regard to safety (greater number of pyrotechnic stages) and therefore with regard to costs.
According to the invention, only the third and last stage is a pyrotechnic stage, which significantly limits the pyrotechnic risks and the overall cost.
According to a preferred alternative form, this third azidation stage is carried out by means of an alkali metal azide, for example NaN
3
.
According to another preferred alternative form, this azidation stage is carried out in an organic solvent medium, preferably a polar organic solvent medium, such as dimethyl sulphoxide (DMSO) and dimethylformamide (DMF).
The temperature of the azidation reaction is preferably between 70° C. and 110°
Bouchez Jean-Marc
Graindorge Herve
Soriaux Claude
Bucknam and Archer
Geist Gary
Reyes Hector M
SNPE
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