U.S. patent application number 15/038116 was filed with the patent office on 2016-10-06 for composite pyrotechnic product with non-crosslinked binder and method for preparing same.
The applicant listed for this patent is EURENCO, HERAKLES. Invention is credited to Caroline CARAYON, Nancy DESGARDIN, Jean-Louis PAULIN, Philippe RAGON, Mathieu W. WERSCHINE.
Application Number | 20160289133 15/038116 |
Document ID | / |
Family ID | 50478442 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160289133 |
Kind Code |
A1 |
DESGARDIN; Nancy ; et
al. |
October 6, 2016 |
COMPOSITE PYROTECHNIC PRODUCT WITH NON-CROSSLINKED BINDER AND
METHOD FOR PREPARING SAME
Abstract
A composite pyrotechnic product, especially a propellant powder
for barrel weapons, has a composition, expressed as weight
percentages, that contains from 78% to 90% of organic energetic
charges, and from 10% to 22% of a polymeric gum, chosen from
polyurethane-polyester gums, polyurethane-polyether gums and
mixtures thereof, the number-average molecular weight of which is
greater than 20 000 g/mol and the Mooney viscosity of which is
between 20 and 70 ML (5+4) at 100.degree. C.
Inventors: |
DESGARDIN; Nancy; (Bouray
Sur Juine, FR) ; RAGON; Philippe; (Bondoufle, FR)
; WERSCHINE; Mathieu W.; (Chatillon, FR) ;
CARAYON; Caroline; (Savigny Sur Orge, FR) ; PAULIN;
Jean-Louis; (Ballancourt, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HERAKLES
EURENCO |
Le Haillan
Massy |
|
FR
FR |
|
|
Family ID: |
50478442 |
Appl. No.: |
15/038116 |
Filed: |
November 21, 2014 |
PCT Filed: |
November 21, 2014 |
PCT NO: |
PCT/FR2014/000250 |
371 Date: |
May 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C06B 45/10 20130101;
C06B 21/0025 20130101 |
International
Class: |
C06B 45/10 20060101
C06B045/10; C06B 21/00 20060101 C06B021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2013 |
FR |
1302707 |
Claims
1. A composite pyrotechnic product whose composition, expressed as
weight percentages, contains: from 78% to 90% of organic energetic
charges, and from 10% to 22% of a polymeric gum, chosen from
polyurethane-polyester gums, polyurethane-polyether gums and
mixtures thereof, a number-average molecular weight of which is
greater than 20 000 g/mol and a Mooney viscosity of which is
between 20 and 70 ML (5+4) at 100.degree. C.
2. The composite pyrotechnic product as claimed in claim 1, wherein
said organic energetic charges consist of hexogen, octogen,
nitroguanidine, ethylene dinitramine, N-guanylurea dinitramide,
1,1-diamino-2,2-dinitroethylene, bis(triaminoguanidinium)
5,5'-azotetrazolate, dihydrazinium 5,5'-azotetrazolate,
5,5'-bis(tetrazolyl)hydrazine, bis(2,2-dinitropropyl)nitramine, a
nitropyrazole, or a mixture of such charges.
3. The composite pyrotechnic product as claimed in claim 1, wherein
said organic energetic charges contain ethylene dinitramine
charges.
4. The composite pyrotechnic product as claimed in claim 1, wherein
said polymeric gum has a number-average molecular weight of greater
than 50 000 g/mol.
5. The composite pyrotechnic product as claimed in claim 1, wherein
said gum is a polyurethane-polyester gum or a
polyurethane-polyether gum.
6. The composite pyrotechnic product as claimed in claim 1, wherein
the composition also contains at least one energetic or
non-energetic plasticizer; said plasticizer representing from 2% to
8% by weight of the composition of said pyrotechnic product.
7. The composite pyrotechnic product as claimed in claim 6, wherein
said at least one plasticizer is an energetic plasticizer of
nitrate and/or nitramine type.
8. The composite pyrotechnic product as claimed in claim 7, wherein
said at least one plasticizer is chosen from diethylene glycol
dinitrate, triethylene glycol dinitrate, butanetriol trinitrate,
trimethylolethane trinitrate, a mixture of
2,4-dinitro-2,4-diazapentane, 2,4-dinitro-2,4-diazahexane and
3,5-dinitro-3,5-diazaheptane, nitratoethylnitramines, and mixtures
thereof.
9. The composite pyrotechnic product as claimed in claim 1, wherein
the composition also contains from 0.1% to 2% by weight of at least
one additive.
10. The composite pyrotechnic product as claimed in claim 1,
wherein the composite pyrotechnic product consists of a propellant
powder for barrel weapons.
11. A process for preparing at least one composite pyrotechnic
product as claimed in claim 1, the process comprising: a) providing
the ingredients below: organic energetic charges, a polymeric gum,
chosen from polyurethane-polyester gums, polyurethane-polyether
gums and mixtures thereof, a number-average molecular weight of
which is greater than 20 000 g/mol and a Mooney viscosity of which
is between 20 and 70 ML (5+4) at 100.degree. C.; b) mixing the
ingredients in suitable proportions relative to the desired
composition of the final product, to produce a pasty mixture; and
c) producing, from said pasty mixture, said at least one composite
pyrotechnic product in a desired form.
12. The process as claimed in claim 11, further comprising
providing at least one energetic or non-energetic plasticizer
and/or at least one additive, and mixing of said charges and gum
with said at least one plasticizer and/or said at least one
additive to obtain a pasty mixture.
13. The process as claimed in claim 11, wherein said mixture is
prepared with a twin-screw extruder or a two-roll mill.
14. The process as claimed in claim 11, wherein said mixture is
prepared at a temperature of between 60.degree. C. and 120.degree.
C.
15. The process as claimed in claim 11, wherein said at least one
composite pyrotechnic product is obtained by spinning or
calendering.
16. The composite pyrotechnic product as claimed in claim 1,
wherein the composition, expressed as weight percentages, contains
from 80% to 86% of organic energetic charges.
17. The composite pyrotechnic product as claimed in claim 3,
wherein said organic energetic charges contain hexogen charges and
ethylene dinitramine charges.
18. The composite pyrotechnic product as claimed in claim 4,
wherein said polymeric gum has a number-average molecular weight of
greater than 75 000 g/mol.
19. The composite pyrotechnic product as claimed in claim 5,
wherein said gum is a polyurethane-polyester gum.
20. The composite pyrotechnic product as claimed in claim 6,
wherein the composition further contains an energetic plasticizer.
Description
[0001] The present invention relates to composite pyrotechnic
products, which are suitable especially as propellant powders for
barrel weapons (more particularly for tank artillery). It concerns
composite pyrotechnic products, containing a high content of
energetic charges in a binder. Said products are particularly
advantageous, especially in terms of force (of energetic power), of
vulnerability (see below a reminder regarding this notion, which is
familiar to those skilled in the art), and of field of application
as regards the nature of the charges they may contain. They may
conveniently be optimized in terms of erosivity.
[0002] A subject of the present invention is also a process for
preparing said composite pyrotechnic products. Said process is
particularly easy to perform.
[0003] "Homogeneous" propellant powders constituted by one or more
gelatinized energetic bases having a homogeneous appearance (whence
their name) are known. Among the most widely known homogeneous
propellant powders, mention may be made of "smokeless" powders
based on nitrocellulose alone or based on a
nitrocellulose-nitroglycerine mixture. In order to improve the
energy performance of these "homogeneous" powders, it is sought to
incorporate therein organic (pulverulent) energetic charges. These
charged powders no longer have a homogeneous appearance, but a
heterogeneous appearance in which are distinguished, on the one
hand, the energetic binder, and, on the other hand, the charges.
Such charged powders are referred to as "composite" or
"heterogeneous" powders. Such charged powders are described, for
example, in French patent application FR 2 488 246.
[0004] Use of the energetic binder nitrocellulose however has the
drawback of making these powders vulnerable. The term
"vulnerability" refers to the property that the powders have of
being able to ignite and deflagrate under the, effect of an
undesired, random physical phenomenon, for instance the impact of a
projectile. Vulnerability is a major defect for powders intended to
be transported on combat tanks. The development of modern combat
machines thus led those skilled in the art to seek sparingly
vulnerable propellant powders.
[0005] With this in mind, composite powders with an inert binder
were proposed (constituted mainly of organic energetic charges in a
synthetic resin). Such powders are markedly less vulnerable than
homogeneous or composite powders with an energetic binder
(nitrocellulose). However, since they contain an inert binder,
these powders must, in order to deliver the necessary energy during
their ignition, contain very high levels of charges, often in the
region of 80% of the total weight of the powder. Composite powders
with an inert binder thus have the characteristic of containing
very little binder relative to their pulverulent charge. The
precursor mixtures of these powders must, however, be able to be
worked (in particular be able to be calendered or drawn through a
die of relatively small diameter, usually comprising pins intended
to create channels present in the final powder strand), and the
powders must conserve their geometrical shape over time. It is
particularly in reference to the production of these composite
propellant powders with an inert binder for barrel weapons that
those skilled in the art came up against and are still coming up
against serious difficulties.
[0006] The inert binders, of synthetic origin, that may be used in
the preparation of composite pyrotechnic products and that are
present in their composition exist to date as thermoplastic binders
and as thermosetting binders (thermosetting binders obtained from
oligomers).
[0007] Those skilled in the art first turned toward the use of
thermoplastic inert binders. Specifically, such thermoplastic
binders allow, in theory, while raising temperature, mechanical
working of the product to give it the desired geometry. Obviously,
however, the working temperature (at which the binder is
deformable) should be compatible with the stability of the charges
present and, in reference to this unavoidable requirement, it is
often necessary to use a solvent. The use of such a solvent
complicates the implementation of the process. Patent application
EP 0 036 481 describes a process for manufacturing composite
explosives with a thermoplastic binder. Patent application IN
498/DEL/2001 describes a process for preparing propergol containing
hexogen charges (RDX) in a thermoplastic binder. Composite products
with a thermoplastic binder are generally not entirely
satisfactory, since their mechanical properties are too sensitive
to thermal variations.
[0008] Those skilled in the art then turned toward the use of
thermosetting inert binders (obtained from oligomers), such as
(crosslinkable) polyurethane binders, making it possible, after
crosslinking, to constitute a three-dimensional network (in which
the charges are found coated), i.e. to definitively set the
geometry of the powder grain (finally obtained). The industrial
scale manufacture of powders (in general composite pyrotechnic
products) with a crosslinked inert binder (thus essentially
constituted of a high content of charges in a minimum amount of
binder) remains very difficult firstly due to the minimum cohesion
and mechanical strength required for the product before
crosslinking (in order to form it) and secondly due to the limited
"pot life" of thermosetting resins (the term "pot life" means the
period of commencement of crosslinking of the resin during which it
may be worked like a plastic). Furthermore, obviously, the
crosslinking temperature must be compatible with the stability of
the charges and the crosslinking agent used must itself also be
compatible with said charges.
[0009] Confronted with these difficulties, in the context of using
thermosetting binders: [0010] those skilled in the art proposed to
work in the presence of solvents. A solvent-based process was
especially described in French patent application FR 2 268 770.
Such processes are, however, difficult and expensive to implement,
and unsatisfactory at the industrial scale; [0011] to work without
solvent, with thermosetting binders, said persons skilled in the
art have widely resorted to the "casting" or "global" technique,
which consists in simultaneously mixing in a blender the liquid
elementary constituents of the resin and the energetic charges and
in casting, before polymerization, the mixture thus obtained in a
mold in order to perform the actual polymerization therein. This
technique, which has been widely described, for example in French
patent applications FR 2 109 102, FR 2 196 998, FR 2 478 623 and FR
2 491 455, may be suitable for manufacturing composite solid
propergols for rocket or missile engines, or alternatively for
manufacturing composite explosives for device heads, which are
usually used in the form of wide-diameter products, but proves to
be entirely unsuitable for the industrial manufacture of large,
medium and small caliber composite powders and more generally for
that of certain composite pyrotechnic products; [0012] for the
solvent-free manufacture of composite pyrotechnic products with a
thermosetting inert binder, especially of small diameters, said
persons skilled in the art have available, at the present time,
only the following two techniques: [0013] a) the first which
consists in mixing in a blender the constituents of the. resin with
the energetic charges, in initiating crosslinking of the resin and,
during crosslinking, in forming the product, within a very short
space of time, as described, for example, in French patent
applications FR 1 409 203 and FR 2 159 826. This technique requires
precise control of the crosslinking kinetics in order to be able to
work the paste and, as a result, it is difficult to manage at the
industrial scale; [0014] b) the second, which is much more
efficient, including at the industrial scale, described in patent
application EP 0 194 180. The composite pyrotechnic products
obtained via this second technique are constituted mainly, on the
one hand, by a polymeric binder (for example polyurethane) obtained
by reaction of a polyhydroxylated prepolymer (polymer) (with a
number-average molecular weight of between 2000 and 5000 and a mean
functionality of hydroxyl groups (OH greater than 2 and less than
3) (PBHT, polyether or polyester, for example) with a crosslinking
agent (diisocyanate), and, on the other hand, by an energetic
charge, preferentially of octogen (HMX) or of hexogen (RDX), in a
content of about 80% by weight. Said second technique consists:
[0015] in a first step, in mixing said polyhydroxylated prepolymer
with said energetic charge and with an amount of diisocyanate of
between 50% and 90% by weight of the stoichiometric amount required
for total polymerization (reaction) of all the hydroxyl groups (OH)
of said prepolymer and in performing the condensation reaction of
the isocyanate groups (NCO) on the hydroxyl groups (OH) so as to
obtain a partially polymerized (crosslinked) paste; [0016] in a
second step, in mixing with said partially polymerized
(crosslinked) paste thus obtained the remainder of the diisocyanate
required to achieve said stoichiometric amount required for total
polymerization (crosslinking) and in extruding the pasty mixture
thus obtained; and then [0017] in a third step, in completing, by
hot curing, the condensation reaction of the isocyanate groups
(NCO) added during the second step to the hydroxyl groups (OH) that
are still free.
[0018] The technique under consideration thus comprises two
polymerization or crosslinking steps, more precisely a first step
of pre-crosslinking (or first crosslinking phase) with an amount of
isocyanate that allows the production of a partially polymerized
(crosslinked) paste, having mechanical strength and cohesion
suitable for the implementation of the rest of the process
(especially extrusion) and a second step of crosslinking leading to
the final product with the desired crosslinked binder. In this,
said technique overcomes the two types of difficulty mentioned
above (difficulty due to the lack of mechanical strength and
cohesion of the product to be extruded and problem of the "pot
life").
[0019] With reference to this second technique, it should, however,
be noted that the operations for metering out the crosslinking
agent (diisocyanate) to perform the pre-crosslinking are difficult.
They require great precision. Moreover, the field of application of
said technique is limited, in view of the nature of the
crosslinking agent involved (of isocyanate type, to react with
hydroxyl functions), as regards the nature of the energetic charges
present, insofar as certain energetic charges (having intrinsic
acidity) are capable of reacting, in a spurious reaction, with said
crosslinking agent (of isocyanate type) present. The presence of
such charges (EDNA, nitropyrazoles, for example) thus poses a
problem for managing the complementary pre-crosslinking and
crosslinking steps. Now, this presence is far from trivial, in the
context of the present invention, that of composite pyrotechnic
products, especially propellant powders for barrel weapons.
Specifically, in this context, the use of high contents of
energetic charges (see above), especially high contents of charges
of RDX type, is targeted. Now, a person skilled in the art knows
the negative impact of a high content of such charges on the
erosivity of the powder containing it. Replacing at least part of
the RDX with other energetic charges (such as EDNA), which are less
erosive, is thus desirable. It would therefore be highly
advantageous to have available a novel type of binder, which
removes the need to use isocyanate crosslinking agents.
[0020] In such a context, the inventors propose composite
pyrotechnic products that are especially suitable as propellant
powders for barrel weapons, of novel type. These (novel) composite
pyrotechnic products contain a high content of charges in a binder
of a novel type (this binder is neither a thermoplastic binder, nor
a thermoset (thermocrosslinked) binder). Said (novel) composite
pyrotechnic products are particularly valuable in terms of force
(they contain a high content of energetic charges), of
vulnerability (they do not contain any nitrocellulose and may
advantageously contain sparingly vulnerable energetic charges) and
of production process (their production process is particularly
easy to perform (in particular, it comprises no crosslinking step
and therefore does not involve the use of crosslinking agent(s))
and they may also be optimized in terms of erosivity (they may
advantageously contain EDNA charges in total or partial replacement
for RDX charges). They are in fact liable to contain any type of
organic energetic charge (see the broad field of application of the
products of the invention as regards the nature of the charges
mentioned above) insofar as, in the absence of crosslinking agent,
no spurious reactions need to be feared (charges/crosslinking
agent(s)).
[0021] According to its first subject, the present invention thus
relates to novel composite pyrotechnic products.
Characteristically, their compositions, expressed as weight
percentages, contain: [0022] from 78% to 90%, advantageously from
80% to 86%, of organic energetic charges, and [0023] from 10% to
22% of a polymeric gum, chosen from polyurethane-polyester gums,
polyurethane-polyether gums and mixtures thereof, the
number-average molecular weight of which is greater than 20 000
g/mol and the Mooney viscosity of which is between 20 and 70 ML
(5+4) at 100.degree. C.
[0024] As indicated above, the composite pyrotechnic products of
the invention thus contain a high content of organic energetic
charges in a binder of a novel type: a binder, of non-crosslinked
gum ("raw rubber") type. It is seen later that said binder may
contain a plasticizer.
[0025] The composite pyrotechnic products of the invention thus
contain a high content of organic energetic charges: from 78% to
90% by weight, advantageously from 80% to 86% by weight.
[0026] The charges under consideration (organic charges of any type
(not selected, as in the context of thermocrosslinkable binders,
taking into account the crosslinking reaction to ultimately by
implemented); mineral charges having been set aside insofar as they
generate solid particles) are not per se original. They are organic
energetic charges that are known per se and, for the most part, are
already conditioned according to the prior art in a conventional
organic polymeric binder (such as PBHT), especially crosslinked.
The charges are advantageously hexogen (RDX), octogen (HMX),
nitroguanidine (NGU), ethylene dinitramine (EDNA), N-guanylurea
dinitramide (FOX 12 (GUDN)), 1,1-diamino-2,2-dinitroethylene (FOX 7
(DADE)), bis(triaminoguanidinium) 5,5'-azotetrazolate (TAGZT),
dihydrazinium 5,5'-azotetrazolate (DHDZT),
5,5'-bis(tetrazolyl)hydrazine (HBT),
bis(2,2-dinitropropyl)nitramine (BDNPN), a nitropyrazole, or a
mixture of these energetic charges.
[0027] Within the composite pyrotechnic products of the invention
there is thus a type of energetic charges, advantageously chosen
from the above list, or a mixture of at least two types of
energetic charges, advantageously chosen from the above list. EDNA
organic energetic charges are preferably found therein. A mixture
of EDNA charges and of RDX charges is particularly preferably found
therein. It is in no way excluded to find only RDX charges or only
EDNA charges, but, as indicated above, mixtures of EDNA charges and
of RDX charges make it possible to achieve an optimum with
reference to the force/erosivity compromise. It has been understood
that the more said mixtures contain RDX, the more energetic they
are, but the more erosive they are.
[0028] Energetic charges are in the form of solid grains
homogeneously distributed in the binder. These solid grains
advantageously have, in a manner known per se, several particle
size distributions.
[0029] The organic energetic charges are thus present in a novel
binder. Said novel binder is based on a gum of the type mentioned.
According to one variant, it consists essentially of said gum (at
least one additive being present in small amount), or even it
consists of said gum. According to another variant, it consists
essentially of said gum and at least one plasticizer (at least one
additive being present in small amount), or even it consists of
said gum and at least one plasticizer.
[0030] Said gum: [0031] is chosen from polyurethane-polyester gums
(i.e. of polyurethane nature with flexible segments of polyester
type), polyurethane-polyether gums (i.e. of polyurethane nature
with flexible segments of polyether type) and mixtures thereof,
[0032] it has a number-average molecular weight of greater than 20
000 g/mol (advantageously greater than 50 000 g/mol, very
advantageously greater than 75 000 g/mol (very particularly with
reference to the ageing resistance of the final product), and
[0033] it has a Mooney viscosity of between 20 and 70 ML (5+4) at
100.degree. C. This parameter is widely used in the rubber
industry. "x ML (5+4) at 100.degree. C." is understood as "x M=the
viscosity in Mooney units (or points); L or S (in this instance L)
corresponding to the size of the rotor, 5 indicating the preheating
time of the product and 4 is the time in minutes after starting the
motor at which the reading is taken, 100.degree. C. being the
measuring temperature". The value "x" is generally given as
".+-.y"; it is that value "x" which, according to the invention,
must be within the range 20-70 (limit values included).
[0034] Such a gum is perfectly suitable for the purposes of the
invention, insofar as, in the proportions indicated (from 10 to 22%
only, remembering that products with a high charge rate are under
consideration), 1) it allows the (charges+gum) mixture to be
mechanically worked at low temperature, i.e. at a temperature below
120.degree. C., or even below 100.degree. C. (which is entirely
compatible with the stability of the charges present), and does so
without the use of solvent; and 2) it gives the final product the
required mechanical hold and cohesion.
[0035] The inventors have, to their credit, identified (selected)
this type of gum, which is perfectly suitable for the purposes of
the invention. Other types of gum were tested and do not give
satisfactory results (as regards the possibility of working the
mixture at low temperature and/or as regards the properties of the
final product).
[0036] A person skilled in the art has already understood that,
with reference to the first of the two stipulations of the
requirement recalled above, the result may be further improved by
incorporating at least one plasticizer.
[0037] Said gum generally consists of a polyurethane-polyester or a
polyurethane-polyether gum, but mixtures of at least two gums (at
least two polyurethane-polyester gums, at least two
polyurethane-polyether gums or at least one polyurethane-polyester
gum and at least one polyurethane-polyether gum; such mixtures of
gums (gums within the meaning of the invention) constituting a gum
within the meaning of the invention) having the required properties
(recalled above) may be used. Said gum advantageously consists of a
polyurethane-polyester gum.
[0038] The composition of the composite pyrotechnic products of the
invention is thus liable to contain at least one plasticizer. Such
an at least one (energetic or non-energetic) plasticizer is
generally present in a proportion of from 2% to 8% by weight (of
the total composition). Such an at least one plasticizer
advantageously consists, with reference to the force of the
product, of at least one energetic plasticizer.
[0039] The composition of the composite pyrotechnic products of the
invention thus advantageously contains at least one energetic
plasticizer (one energetic plasticizer, at least two energetic
plasticizers, or at least one energetic plasticizer and at least
one non-energetic plasticizer), and very advantageously contains
one energetic plasticizer.
[0040] The energetic plasticizer(s) under consideration are
advantageously of nitrate and/or nitramine type.
[0041] The energetic plasticizer(s) under consideration are very
advantageously chosen from diethylene glycol dinitrate (DEGDN),
triethylene glycol dinitrate (TEGDN), butanetriol trinitrate
(1317N), trimethylolethane trinitrate (TMETN), a mixture of
2,4-dinitro-2,4-diazapentane, 2,4-dinitro-2,4-diazahexane and
3,5-dinitro-3,5-diazaheptane (and most particularly DNDA 5,7),
nitratoethylnitramines (especially methyl-2-nitratoethyl nitramine
(methylNENA) and ethyl-2-nitratoethyl nitramine (ethylNENA)), and
mixtures thereof.
[0042] The composition of the composite pyrotechnic products of the
invention is thus constituted essentially, even constituted, of the
energetic charges and of the binder, based on said gum (binder=said
gum or binder=said gum+at least one plasticizer). It may be
constituted to 100% by weight of said energetic charges and of said
binder. It is generally thus constituted to at least 95% by weight,
more generally to at least 98% by weight. In effect, it cannot be
excluded for it to contain in addition at least one additive. Such
an at least one additive, when it is present, is generally present
in a proportion of from 0.1% to 2% by weight. It may especially be
at least one formulation agent (candelilla wax and/or paraffin wax,
for example), and/or at least one stabilizer.
[0043] The composite pyrotechnic products of the invention, as
described above, are entirely suitable as propellant powders for
barrel weapons. Said composite pyrotechnic products of the
invention thus consist advantageously of such powders. The
composite pyrotechnic products of the invention, as described
above, are also suitable, especially, as tactical propergol,
explosive composition and gas generator.
[0044] The major advantage of the products of the invention becomes
apparent from the foregoing text. The products are advantageous per
se (in terms of force, vulnerability and wide field of application
with reference to the nature of the charges) and insofar as they
may be obtained via a process that is simple to perform (much
easier to perform than the processes of the prior art).
[0045] Said process constitutes the second subject of the present
invention. It comprises: [0046] a) the provision of the ingredients
below: organic energetic charges, a polymeric gum, chosen from
polyurethane-polyester gums, polyurethane-polyether gums and
mixtures thereof, the number-average molecular weight of which is
greater than 20 000 g/mol and the Mooney viscosity of which is
between 20 and 70 ML (5+4) at 100.degree. C.; [0047] b) the mixture
of these in suitable proportions relative to the desired
composition of the final product, to produce a pasty mixture;
[0048] c) the production, from said pasty mixture, of the composite
pyrotechnic product(s) in the desired form.
[0049] It thus comprises the provision of the essential constituent
ingredients of the desired composite pyrotechnic products: the
charges+the gum. In addition to said essential ingredients, it has
been seen that at least one plasticizer and at least one additive
(especially such as a formulation agent and/or stabilizer) may be
used.
[0050] With reference to each of the ingredients used for
performing the process, reference may be made to the first part of
the text relating to the product.
[0051] In a first stage, using the ingredients identified above
(charges+gum+optionally, at least one plasticizer+optionally, at
least one additive), a pasty mixture is thus prepared, which is the
precursor of the targeted final product. Such a pasty mixture is
advantageously prepared with a twin-screw extruder (by extrusion)
or with a two-roll mill, depending on the amounts to be used. It is
generally prepared at a temperature of between 60.degree. C. and
120.degree. C. (inclusive of extreme values). It is often prepared
at a temperature of 80.degree. C. It is understood that this mixing
temperature depends on the type of gum and the presence or absence
of at least one plasticizer.
[0052] Starting with said pasty mixture, in the third step of the
process of the invention, the product in the desired form is
prepared (n products are thus generally prepared). Said third step
is thus analyzed as a step of forming the paste. This forming may
especially comprise spinning or calendering. After such spinning
(performed in a press cylinder, having an outlet orifice of more or
less substantial diameter), the spun product is generally chopped
into strands (of the desired length). Such strands, which are
suitable as propellant powders for barrel weapons, generally have a
length of from 2 to 20 mm, for a diameter of from 1 to 20 mm (more
generally for a diameter of from 2 to 15 mm). On conclusion of such
calendering, the calendered product, in the form of a plate (such a
plate generally has a thickness of from 10 to 20 mm), is generally
chopped into platelets.
[0053] According to implementation variants of the process of the
invention, steps b and c of said process may comprise: [0054]
blending with a twin-screw extruder (or extrusion) and spinning,
[0055] blending with a two-roll mill and spinning, or [0056]
blending (with a twin-screw extruder or a two-roll mill) and
calendering.
[0057] It is now proposed to illustrate the invention, in a manner
that is not in any way limiting, in its product and process
aspects, via the examples below.
1) Starting materials used [0058] a) Commercial products Gums:
Millathane.RTM.76, sold by the company TSE Industries (product of
polyaddition of a urethane and a polyester). It has the
characteristics below: Number-average molecular weight: 40 000
g/mol Mooney viscosity: 35 (.+-.10) ML (1+4) at 100.degree. C.;
[0059] UREPAN.RTM. 641 G: sold by the company RheinChemie (product
of polyaddition of diphenylmethane diisocyanate and of a
polyester). It has the characteristics below: Number-average
molecular weight: 80 000 g/mol Mooney viscosity: 45 (.+-.10) ML
(5+4) at 100.degree. C.; [0060] UREPAN.RTM. 643 G: sold by the
company RheinChemie (product of polyaddition of diphenylmethane
diisocyanate and of a polyester). It has the characteristics below:
Number-average molecular weight: 80 000 g/mol Mooney viscosity: 40
(.+-.10) ML (5+4) at 100.degree. C. [0061] a) Prepared products
Charges: EDNA
[0062] The synthesis of ethylene dinitramine (EDNA) was performed
in two stages via the isolation of an intermediate:
dinitroethyleneurea (DNEU), in wet form, which was then transformed
into EDNA.
[0063] Concentrated nitric acid was introduced into a jacketed 50
cm.sup.3 reactor. The nitrating bath was then cooled to a reaction
temperature at 0.degree. C. Once the bath reached at 0.degree. C.,
the introduction of imidazolidone was commenced. This reagent was
introduced slowly so as not to exceed 20.degree. C. The DNEU
precipitated as soon as its concentration in the medium was greater
than 23% by weight. The introduction of imidazolidone into the
heterogeneous medium (nitrating bath+solid DNEU) was continued.
[0064] After the end of introduction of the imidazolidone, the
medium was left stirring for 30 minutes at room temperature.
[0065] At the end of reaction, the mixture was poured into a bath
of cold water at about 5.degree. C. with stirring. The solid was
then separated from the mother liquors by filtration, and washed
several times with distilled water to neutral pH, then drained by
suction. It was then taken up, in wet form, for the synthesis of
EDNA.
[0066] The decarboxylation step was performed by addition of DNEU
to a hot aqueous solution buffered with sodium acetate. Evolution
of gas (of CO.sub.2) was observed, which necessitates portionwise
introduction of the powder.
[0067] Once the introduction of the DNEU was complete, the mixture
was maintained at a stage of 95.degree. C. to complete the
formation of EDNA.
[0068] The reaction medium was then cooled to make the EDNA
precipitate. The suspension was then filtered and then dried. A
yield of 85% was obtained.
[0069] The production of EDNA was confirmed by infrared.
[0070] IR: 2936 cm.sup.-1 aliphatic CH, 1593 cm.sup.-1 NO.sub.2,
1448 cm.sup.-1 N=N, 1360 cm.sup.-1 C-H. The EDNA crystals obtained
are coarse crystals (they have a D.sub.50 of greater than or equal
to 100 .mu.m (D.sub.50=diameter for which the cumulative volume
percentage is 50%)). To use them, they are ground in a SWECO.RTM.
mill. On conclusion of said grinding, they have a D.sub.50 of 30
.mu.m.
[0071] Plasticizer: TEGDN
[0072] Trioxyethylene glycol dinitrate (TEGDN) was obtained by
nitration in sulfonitric medium of trioxyethylene glycol.
2) Process for preparing composite pyrotechnic products of the
invention
[0073] Composite pyrotechnic products of the invention of three
types (Examples 1, 2 and 3) were prepared and tested. Their weight
composition and their force (measured or calculated) are given,
respectively, in Tables 1, 2 and 3 below. Below each of said Tables
1, 2 and 3, other characteristics of said products are
indicated.
[0074] These composite pyrotechnic products of the invention were
obtained from the starting materials identified above.
[0075] Step b of the process of the invention: the pasty mixtures
were obtained in a two-roll mill, in a manner known per se. The gum
was first introduced between the rollers of the two-roll mill
(rolling mill), brought to a temperature of 65.degree. C. It was
thus softened. Next, a charges+plasticizer mixture (prepared
beforehand in a container) was added. Candelilla wax was then
subsequently added to the resulting mixture.
[0076] Step c of the process of the invention: the pasty mixtures
obtained were introduced into a press cylinder heated to 80.degree.
C. to perform spinning at a pressure of between 280 and 320 bar.
After chopping, powder strands were obtained (diameter: 10 mm,
length: 11 mm).
Example 1
TABLE-US-00001 [0077] TABLE 1 weight % Binder Millathane .RTM. 76
14.6 20 TRENO 4.9 Candelilla wax 0.5 Charge EDNA 80.0 80 100 F
0.985 measured (MJ/kg)
[0078] Characteristics of the product obtained (after mixing with
the two-roll mill and spinning) are indicated below.
Mechanical properties at 20.degree. C. in compression (10 mm/min):
[0079] Sm=0.9 MPa (maximum stress at break) [0080] E=10.2 MPa
(elastic modulus) [0081] Em=14.2% (maximum crush before break).
Example 2
TABLE-US-00002 [0082] TABLE 2 weight % Binder UREPAN .RTM. 641 G
14.6 20 TRENO 4.9 Candelilla wax 0.5 Charge EDNA 80.0 80 100 F
calculated (MJ/kg) 1.003
[0083] Characteristics of the product obtained (after mixing with
the two-roll mill and spinning) are indicated below.
Mechanical properties at 20.degree. C. in compression (10 mm/min):
[0084] Sm=13.7 MPa (maximum stress at break) [0085] E=14.6 MPa
(elastic modulus) [0086] Em=1.4% (maximum crush before break)
Example 3
TABLE-US-00003 [0087] TABLE 3 weight % Binder UREPAN .RTM. 643 G
15.1 18 TRENO 2.6 Candelilla wax 0.3 Charge EDNA 82.0 82 100 F
calculated (MJ/kg) 1.008
[0088] Characteristics of the product obtained (after mixing with
the two-roll mill and spinning) are indicated below.
Mechanical properties at 20.degree. C. in compression (10 mm/min):
[0089] Sm=7.9 MPa (maximum stress at break) [0090] E=40.6 MPa
(elastic modulus) [0091] Em=29.7% (maximum crush before break).
* * * * *