U.S. patent application number 16/192977 was filed with the patent office on 2019-07-11 for propellant stabilizer.
The applicant listed for this patent is Thales Australia Limited. Invention is credited to Nicole Barber, Ashley Jones, Garry Warrender.
Application Number | 20190210938 16/192977 |
Document ID | / |
Family ID | 67140473 |
Filed Date | 2019-07-11 |
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United States Patent
Application |
20190210938 |
Kind Code |
A1 |
Warrender; Garry ; et
al. |
July 11, 2019 |
PROPELLANT STABILIZER
Abstract
The invention relates generally to propellant stabilizers. The
invention also relates to methods of producing a propellant
comprising a propellant stabilizer as well as an ammunition
cartridge comprising the stabilized propellant. The propellant
stabilizer comprises a compound of formula 1 ##STR00001## and the
propellant comprises a compound of formula 1 and an energetic
material.
Inventors: |
Warrender; Garry; (Sydney
Olympic Park, AU) ; Barber; Nicole; (Sydney Olympic
Park, AU) ; Jones; Ashley; (Sydney Olympic Park,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Thales Australia Limited |
Sydney Olympic Park |
|
AU |
|
|
Family ID: |
67140473 |
Appl. No.: |
16/192977 |
Filed: |
November 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C06B 23/006 20130101;
F42B 5/16 20130101; C06B 25/20 20130101 |
International
Class: |
C06B 23/00 20060101
C06B023/00; C06B 25/20 20060101 C06B025/20; F42B 5/16 20060101
F42B005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2017 |
AU |
2017904667 |
Claims
1. A propellant comprising: an energetic material; and a compound
of formula 1 ##STR00008## wherein R.sup.1 is selected from the
group consisting of H, --OH, --O(C.sub.1-4alkyl), --C.sub.1-4alkyl,
--NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2, --NO.sub.2,
--NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.2 is
selected from the group consisting of --H, --OH,
--O--(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.3 is selected from the
group consisting of --H and --C.sub.1-4alkyl; and R.sup.4 is
selected from the group consisting of --H, --OH,
--O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; wherein at least one of
R.sup.1, R.sup.2 and R.sup.4 is OH; and wherein the compound of
formula 1 is dispersed evenly throughout the energetic
material.
2. The propellant according to claim 1, wherein the energetic
material is in the form of granules.
3. The propellant according to claim 1, wherein the energetic
material is selected from the group consisting of black powder,
ammonium perchlorate, hexogen, butanetrioltrinitrate,
ethyleneglycol dintrate, diethyleneglycol dinitrate, erithritol
tetranitrate, octogen, hexanitroisowurtzitane, metriol trinitrate,
N-methylnitramine, pentaerythritol tetranitrate,
tetranitrobenzolamine, trinitrotoluene, nitroglycerine,
nitrocellulose, mannitol hexanitrate, triethylene glycol dinitrate,
guanidine, nitroguanidine, 3-nitro-1,2,4-triazol-5-one, ammonium
nitrate, propanediol dinitrate, hexamine, 5-aminotetrazole,
methyltetrazole, phenyltetrazole, polyglycidylnitrate,
polyglycidylazide, poly[3-nitratomethyl-3-methyloxitane],
poly[3-azidomethyl-3-methyloxitane],
poly[3,3-bis(azidomethyl)oxitane], nitrated cyclodextrin polymers,
poly glycidylnitrate, and combinations thereof.
4. The propellant according to claim 1, wherein the energetic
material is nitrocellulose.
5. The propellant according to claim 1, wherein the compound of
formula 1 is 4-(4-hydroxyphenyl)butan-2-one.
6. The propellant according to claim 1, further comprising a
graphite layer.
7. A method of preparing a propellant according to claim 1,
comprising dispersing the compound of formula 1 evenly throughout
an energetic material and granulating the energetic material.
8. The method according to claim 7, wherein the granules of
energetic material are formed by forming a slurry or dough of the
energetic material and the compound of formula 1, extruding the
slurry or dough of the energetic material and the compound of
formula 1 to form an extrudate cord and cutting the extrudate
cord.
9. The method according to claim 7, wherein the compound of formula
1 is 4-(4-hydroxyphenyl)butan-2-one.
10. An ammunition cartridge comprising a propellant according to
claim 1.
11. The ammunition cartridge according to claim 10, further
comprising a casing, a primer and a projectile.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority from Australian
Provisional Patent Application No. 2017904667, which is
incorporated herein by reference in its entirety.
FIELD
[0002] The invention relates generally to propellant stabilizers
and propellants comprising propellant stabilizers. The invention
also relates to methods of producing a propellant comprising a
propellant stabilizer as well as an ammunition cartridge comprising
the stabilized propellant.
BACKGROUND
[0003] Propellants comprising energetic material are used in
ammunition cartridges and in other applications for generating a
propellant gas to propel a projectile. Propellants such as
nitrocellulose and nitrate ester based propellants gradually
decompose with age, producing acidic nitrates and nitrogen oxides.
These compounds of degradation may catalyze further decomposition
of the propellant, which can then lead to autocatalytic
decomposition of the propellant. In the context of ammunition, this
autocatalytic decomposition can in turn lead to combustion,
deflagration or explosion or failure of the ammunition, resulting
in shortening of the service life of the propellant-containing
product.
[0004] A propellant stabilizer is typically added to the energetic
material of a propellant in order to prevent or reduce the rate of
decomposition, thereby prolonging the service life of the
propellant. Propellant stabilizers act by scavenging the acidic
nitrates and nitrogen oxides produced to form nitrosated and
nitrated derivatives.
[0005] An example of a commonly used propellant stabilizer is
diphenylamine (DPA). DPA is stable over long periods and is
effective in stabilizing nitrocellulose-based propellants,
nitrocellulose being the major energetic component of most small
arms propellants. However, DPA is toxic, which makes it a chemical
of concern. In particular, DPA is toxic if swallowed, inhaled or in
contact with skin.
[0006] It is an object of the present application to provide a
useful alternative to DPA that is suitable for use as a propellant
stabilizer. In preferred embodiments, it is desired that the
propellant stabilizer has a lower toxicity that DPA, providing a
safer alternative to the use of DPA in propellants.
SUMMARY
[0007] Accordingly, in a first aspect of the present invention,
there is provided a propellant stabilizer comprising a compound of
formula 1
##STR00002##
wherein R.sup.1 is selected from the group consisting of H, --OH,
--O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.2 is selected from the
group consisting of --H, --OH, --O--(C.sub.1-4alkyl),
--C.sub.1-4alkyl, --NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2,
--NO.sub.2, --NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN;
R.sup.3 is selected from the group consisting of --H and
--C.sub.1-4alkyl; and R.sup.4 is selected from the group consisting
of --H, --OH, --O(C.sub.1-4alkyl), --C.sub.1-4alkyl,
--NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2, --NO.sub.2,
--NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN; wherein at
least one of R.sup.1, R.sup.2 and R.sup.4 is OH.
[0008] The present applicant previously identified that
4-(4-hydroxyphenyl)butan-2-one can act as a burn deterrent (i.e. a
burn rate modifier) when applied to granules of propellant as a
coating. The applicant has surprisingly found that
4-(4-hydroxyphenyl)butan-2-one, and derivatives thereof within
formula 1, are capable of acting as propellant stabilizers. This
finding was not expected, as preliminary tests used to indicate
likely efficacy as a stabilizer did not indicate that the compound
had stabilizing properties. However, subsequent work conducted by
the inventors did show that the compound does have stabilizing
properties. In fact, the new propellant stabilizer is capable of
stabilizing energetic materials such as nitrocellulose to a
comparable extent as and to a greater extent than the commonly used
propellant stabilizer DPA, making it suitable for use in
propellants and ammunition cartridges. The new propellant
stabilizer also has a more favourable toxicity profile compared to
DPA, making the workplace environment safer for those involved in
propellant and ammunition manufacture.
[0009] According to a second aspect, there is also provided the use
of the compound of formula 1 as a propellant stabilizer.
[0010] In some embodiments, the compound of formula 1 is
4-(4-hydroxyphenyl)butan-2-one. Although this compound is
preferred, it is appreciated that closely structurally and physical
property-related compounds may also provide further alternative
propellant stabilizers to DPA. In some embodiments, the compound of
formula 1 is 4-(4-hydroxy-3-nitrophenyl)butan-2-one.
[0011] According to a third aspect, there is provided a propellant
comprising an energetic material; and a compound of formula 1
##STR00003##
wherein R.sup.1 is selected from the group consisting of H, --OH,
--O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.2 is selected from the
group consisting of --H, --OH, --O--(C.sub.1-4alkyl),
--C.sub.1-4alkyl, --NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2,
--NO.sub.2, --NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN;
R.sup.3 is selected from the group consisting of --H and
--C.sub.1-4alkyl; and R.sup.4 is selected from the group consisting
of --H, --OH, --O(C.sub.1-4alkyl), --C.sub.1-4alkyl,
--NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2, --NO.sub.2,
--NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN; wherein at
least one of R.sup.1, R.sup.2 and R.sup.4 is OH; and wherein the
compound is dispersed evenly throughout the energetic material.
[0012] In a fourth aspect, there is provided an ammunition
cartridge comprising the propellant described above.
[0013] The ammunition cartridge typically comprises a casing, the
propellant described above, a primer and a projectile. The
ammunition may also contain boosting charges and tracer
compounds.
[0014] According to a fifth aspect, there is provided a method of
preparing a propellant, comprising dispersing a compound of formula
1
##STR00004##
wherein R.sup.1 is selected from the group consisting of H, --OH,
--O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.2 is selected from the
group consisting of --H, --OH, --O--(C.sub.1-4alkyl),
--C.sub.1-4alkyl, --NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2,
--NO.sub.2, --NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN;
R.sup.3 is selected from the group consisting of --H and
--C.sub.1-4alkyl; and R.sup.4 is selected from the group consisting
of --H, --OH, --O(C.sub.1-4alkyl), --C.sub.1-4alkyl,
--NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2, --NO.sub.2,
--NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN; and wherein at
least one of R.sup.1, R.sup.2 and R.sup.4 is OH evenly throughout
an energetic material and granulating the energetic material.
[0015] These aspects are described more fully in the detailed
description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention will be described in further detail, by way of
example only, with reference to the following Figures:
[0017] FIG. 1 is a schematic illustration of a granule of the
propellant composition containing 4-(4-hydroxyphenyl)butan-2-one
according to one embodiment of the invention.
[0018] FIGS. 2A through 2E present graphs showing normalised heat
flow for propellant formulations containing DPA, DPA and
4-(4-hydroxyphenyl)butan-2-one, or 4-(4-hydroxyphenyl)butan-2-one
(FIGS. 2A, 2B and 2C); and normalised heat flow for propellant
formulations containing either DPA or
4-(4-hydroxyphenyl)butan-2-one as the stabilizer (FIGS. 2D and
2E).
[0019] FIGS. 3A through 3C present chromatography traces of aged
propellant formulations incorporating
4-(4-hydroxyphenyl)butan-2-one (FIGS. 3A and 3B) compared with a
propellant formulation containing only DPA as the stabilizer (FIG.
3C).
[0020] FIGS. 4A through 4D present chromatography traces of an aged
propellant formulation incorporating 4-(4-hydroxyphenyl)butan-2-one
(FIG. 4A), synthetic 4-(4-hydroxy-3-nitrophenyl)butan-2-one (FIG.
4B), the aged propellant formulation spiked with synthetic
4-(4-hydroxy-3-nitrophenyl)butan-2-one (FIG. 4C), and a mass
spectrum of the 3.6 min peak (FIG. 4D).
[0021] FIGS. 5A and 5B present .sup.1H NMR spectra of an extract
from an aged propellant formulation containing
4-(4-hydroxyphenyl)butan-2-one as the stabilizer (FIG. 5A) compared
with synthetic 4-(4-hydroxy-3-nitrophenyl)butan-2-one (FIG.
5B).
DETAILED DESCRIPTION
[0022] The invention relates generally to propellant stabilizers
and propellants comprising a propellant stabilizer. The invention
also relates to methods of producing a propellant comprising a
propellant stabilizer as well as an ammunition cartridge comprising
the stabilized propellant.
[0023] In the following, we have described features of the method
and the propellant stabilizer and propellant. All features
described below apply independently to the methods and the products
of the invention.
Compounds
[0024] The present invention involves the use of a compound of
formula 1
##STR00005##
wherein R.sup.1 is selected from the group consisting of H, --OH,
--O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; R.sup.2 is selected from the
group consisting of --H, --OH, --O--(C.sub.1-4alkyl),
--C.sub.1-4alkyl, --NHC.sub.1-4alkyl, --N(C.sub.1-4alkyl).sub.2,
--NO.sub.2, --NHNH.sub.2, --N(C.sub.1-4alkyl)NH.sub.2, and --CN;
R.sup.3 is selected from the group consisting of --H and
--C.sub.1-4alkyl; and R.sup.4 is selected from the group consisting
of --H, --OH, --O(C.sub.1-4alkyl), --C.sub.1-4alkyl, --NHC.sub.1-4
alkyl, --N(C.sub.1-4alkyl).sub.2, --NO.sub.2, --NHNH.sub.2,
--N(C.sub.1-4alkyl)NH.sub.2, and --CN; and wherein at least one of
R.sup.1, R.sup.2 and R.sup.4 is OH.
[0025] In some embodiments R.sup.1 is selected from the group
consisting of OH, O--(C.sub.1-4-alkyl) and C.sub.1-4alkyl. In other
embodiments, R.sup.1 is selected from the group consisting of OH
and O--(C.sub.1-4alkyl). In a particularly preferred embodiment,
R.sup.1 is OH.
[0026] R.sup.1 may be in any position around the aromatic ring. For
example, R.sup.1 may be in the ortho, meta or para position. In
some embodiments, R.sup.1 is in the para position.
[0027] In some embodiments, R.sup.2 is selected from the group
consisting of H, OH, O--(C.sub.1-4alkyl) and C.sub.1-4alkyl. In
other embodiments, R.sup.2 is selected from the group consisting of
H, OH and O--(C.sub.1-4alkyl). In a particularly preferred
embodiment, R.sup.2 is H.
[0028] In some preferred embodiments, R.sup.3 is H.
[0029] In some embodiments, R.sup.4 is selected from the group
consisting of H, --NO.sub.2, OH, O--(C.sub.1-4alkyl) and
C.sub.1-4alkyl. In other embodiments, R.sup.4 is selected from the
group consisting of H, --NO.sub.2, OH and O--(C.sub.1-4alkyl). In a
particularly preferred embodiment, R.sup.4 is H. In some
embodiments, R.sup.4 is --NO.sub.2.
[0030] R.sup.4 may be in any position around the aromatic ring. For
example, R.sup.4 may be in the ortho, meta or para position. In
some embodiments, R.sup.4 is in an ortho or meta position.
[0031] In one embodiment, R.sup.1 is OH, R.sup.2 is H, R.sup.3 is H
and R.sup.4 is H.
[0032] In one embodiment, R.sup.1 is OH, R.sup.2 is H, R.sup.3 is H
and R.sup.4 is --NO.sub.2.
[0033] The term C.sub.1-4alkyl refers to a branched or unbranched
alkyl group having from one to four carbon atoms inclusive.
Examples of C.sub.1-4alkyl groups include methyl, ethyl, n-propyl,
isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl. This
definition applies to references to C.sub.1-4alkyl alone or as part
of a substituent such as --O(C.sub.1-4alkyl), --NHC.sub.1-4alkyl,
--N(C.sub.1-4alkyl).sub.2 or --N(C.sub.1-4alkyl)NH.sub.2.
Propellant Stabilizer
[0034] The compound of formula 1 functions as a propellant
stabilizer. The term "stabilizer" refers to any compound which can
be used to stabilize the energetic material.
[0035] The compound of formula 1 is present in the propellant in an
amount which is sufficient to retard the decomposition of the
energetic material compared with the decomposition rate without the
presence of the compound. In some embodiments, the compound of
formula 1 is present in amounts of from about 0.1 to about 10% by
weight of the propellant. For example, the compound of formula 1
may be present in an amount of about 0.2 to about 8%, such as about
0.5 to about 6.5%, or about 0.7 to about 6%. Preferably, the
compound of formula 1 is present in an amount of about 1 to about
5% by weight of the propellant. Most preferably, the compound of
formula 1 is present in an amount of about 1 to about 2% by weight
of the propellant.
[0036] The compound of formula 1 preferably has a melting point of
about 50 to about 90.degree. C. For example, the melting point may
be about 55 to about 85.degree. C., such as about 60 to about
80.degree. C., or about 65 to about 75.degree. C. In some
embodiments, the compound of formula 1 has a melting point of at
least about 50.degree. C. For example, the melting point may be at
least about 60.degree. C., such as at least about 65.degree. C., or
at least about 70.degree. C.
[0037] In some embodiments, the compound of formula 1 is
4-(4-hydroxyphenyl)butan-2-one.
##STR00006##
[0038] Although this compound is preferred, it is appreciated that
closely structurally and physical property-related compounds may
also perform as per 4-(4-hydroxyphenyl)butan-2-one.
[0039] In some embodiments, the compound of formula 1 is
4-(4-hydroxy-3-nitrophenyl)butan-2-one.
##STR00007##
[0040] Tests were conducted by the applicant demonstrating the
efficacy of 4-(4-hydroxyphenyl)butan-2-one as a propellant
stabilizer. The long-term tests showed that
4-(4-hydroxyphenyl)butan-2-one is capable of stabilizing energetic
materials such as nitrocellulose over extended periods of time. In
fact, 4-(4-hydroxyphenyl)butan-2-one is capable of stabilizing
nitrocellulose-based propellants to a comparable extent as or a
greater extent than commonly used propellant stabilizer DPA.
Advantageously, 4-(4-hydroxyphenyl)butan-2-one does not have the
drawbacks of toxicity associated with DPA. The compounds of the
invention provide useful alternatives to DPA and other stabilizers
currently in use to provide new propellant compositions.
[0041] The propellant may also comprise a second stabilizer. The
second stabilizer(s), which is different to the first stabilizer,
may be selected from the group consisting of a second compound of
formula 1, sodium hydrogen carbonate, calcium carbonate, magnesium
oxide, akardites, centralites, 2-nitrosodiphenylamine,
diphenylamine, N-methyl-p-nitroaniline and combinations
thereof.
Energetic Material
[0042] The propellant of the present invention comprises an
energetic material. The term "energetic material" includes any
material which can be burned to generate a propellant gas to propel
a projectile.
[0043] In some embodiments, the energetic material is selected from
the group consisting of black powder, ammonium perchlorate,
hexogen, butanetrioltrinitrate, ethyleneglycol dintrate,
diethyleneglycol dinitrate, erithritol tetranitrate, octogen,
hexanitroisowurtzitane, metriol trinitrate, N-methylnitramine,
pentaerythritol tetranitrate, tetranitrobenzolamine,
trinitrotoluene, nitroglycerine, nitrocellulose, mannitol
hexanitrate, triethylene glycol dinitrate, guanidine,
nitroguanidine, 3-nitro-1,2,4-triazol-5-one, ammonium nitrate,
propanediol dinitrate, hexamine, 5-aminotetrazole, methyltetrazole,
phenyltetrazole, polyglycidylnitrate, polyglycidylazide,
poly[3-nitratomethyl-3-methyloxitane],
poly[3-azidomethyl-3-methyloxitane],
poly[3,3-bis(azidomethyl)oxitane], nitrated cyclodextrin polymers,
poly glycidylnitrate, and combinations thereof.
[0044] In some specific embodiments, the energetic material is
selected from the group consisting of nitroglycerine,
nitrocellulose and combinations thereof.
[0045] In some embodiments, the propellant comprises a single
energetic material. For example, the propellant may only comprise
nitrocellulose. In such circumstances, the energetic material may
be referred to as "single base" and the propellant may be referred
to as "a single base propellant". In other embodiments, the
propellant may comprise two energetic materials. For example, the
propellant may comprise nitrocellulose and nitroglycerin. In such
cases, the energetic material may be referred to as "double base"
and the propellant may be referred to as "a double base
propellant". In still other embodiments, the propellant may
comprise more than two energetic materials. For example, the
propellant may comprise nitrocellulose, nitroguanidine and
nitroglycerin. In such circumstances, the energetic material may be
referred to as "multiple base" and the propellant may be referred
to as "a multiple base propellant".
[0046] In one embodiment, the energetic material is
nitrocellulose.
[0047] The energetic material may be in any form that is suitable
for incorporation into an ammunition cartridge for a firearm.
The Propellant
[0048] The propellant comprises an energetic material and a
compound of formula 1. The energetic material and compound of
formula 1 may be combined in any way, provided that the compound of
formula 1 is dispersed throughout the energetic material.
Preferably, the compound of formula 1 is dispersed evenly
throughout the energetic material. In other words, the
concentration of the propellant stabilizer is approximately the
same throughout the energetic material. The compound of formula 1
can be used in conjunction with other established stabilizing
compounds to suit the formulator.
[0049] In some embodiments, the energetic material and the compound
of formula 1 are in the form of granules. The term "granule" may
also be referred to as "kernel" or "pellet". Incorporation of the
compound of formula 1 throughout the energetic material can be
achieved by forming a slurry or dough of the energetic material and
the compound. For example, the energetic material and the compound
of formula 1 can be blended together in a mixer. The resulting
mixture can then be formed into granules.
[0050] The granules of energetic material and the compound of
formula 1 may be prepared by any method known in the art. For
example, a slurry or dough of energetic material and the compound
of formula 1 may be extruded. In another embodiment, the energetic
material and the compound of formula 1 in particulate form may be
compressed into a granule. In another embodiment, particulates of
energetic material and the compound of formula 1 may be coalesced
and shaped into agglomerates by pumping a slurry through shaping
tubes. In some embodiments, the agglomerates may be substantially
spherical in shape. The agglomerates may be referred to as
particles.
[0051] In one embodiment, the granules are prepared by extruding a
slurry or dough of energetic material and the compound of formula 1
to form an extrudate, and granulating the extrudate. The term
"granulating" refers to the process of dividing, or cutting, an
extrudate into granules. In some embodiments, the slurry or dough
of energetic material and the compound of formula 1 is extruded,
for example using an extrusion die, to form an extrudate cord, and
the extrudate cord is cut to the desired length to form granules.
The granules may be of any size suitable for use in ammunition. The
extrudate cord may be cut into the desired granule lengths
immediately upon exit from the extrusion die, or at some time after
the extrudate cord is formed. For example, the extrudate cord may
be cut immediately as the cord extrudes or after the collection of
a suitable length of cord. The cutting may be performed while the
cord is still soft, or when it is dry and hard.
[0052] As a consequence of the processing steps described above,
the granules may also be referred to as agglomerates, grains or
particles.
[0053] The granules can be of any shape. In some embodiments, the
granules have an axial dimension with a consistent cross-section.
For example, the granule may have a substantially circular
cross-section or the cross-section may be elliptical or any other
similar shape. In some embodiments the granules are cylindrical in
shape.
[0054] The granules may be of any size suitable for use in
ammunition. In some embodiments, the granules are about 0.1 to
about 25 mm in length. For example, the granules may be about 0.3
to about 20 mm in length, such as about 0.5 to about 12 mm in
length, or about 0.7 to about 5 mm in length, or about 1 to about 2
mm in length.
[0055] In some embodiments, the granules have a diameter of about
0.1 to about 20 mm. For example, the granules may have a diameter
of about 0.2 to about 15 mm, such as about 0.4 to about 12 mm, or
about 0.5 to about 10 mm, or about 0.6 to about 5 mm, or about 0.7
to about 1 mm.
[0056] The granules may have a greater length than diameter. In
these embodiments, the granules may be referred to as sticks. In
some embodiments, the length of the sticks may be about 6 to about
14 mm, such as about 8 to about 12 mm. In some embodiments, the
diameter of the sticks may be about 0.6 to about 1.2 mm, such as
about 0.7 to about 1 mm.
[0057] After granulation, the granules are dried during which they
may contract slightly. This contraction can be taken into account
when granulating the granules or compressing the particulates of
energetic material and the compound of formula 1. The contracted
granules may be of any size suitable to be used in ammunition. In
some embodiments, the granules are about 0.1 to about 25 mm in
length. For example, the granules may be about 0.3 to about 20 mm
in length, such as about 0.5 to about 12 mm in length, or about 0.7
to about 5 mm in length, or about 1 to about 2 mm in length.
[0058] In some embodiments, the granules have a diameter of about
0.1 to about 20 mm. For example, the granules may have a diameter
of about 0.2 to about 15 mm, such as about 0.4 to about 12 mm, or
about 0.5 to about 10 mm, or about 0.6 to about 5 mm, or about 0.7
to about 1 mm.
[0059] When the contracted granules are sticks, the length of the
sticks may be about 6 to about 14 mm, such as about 8 to about 12
mm. In some embodiments, the diameter of the sticks may be about
0.6 to about 1.2 mm, such as about 0.7 to about 1 mm.
[0060] In some embodiments, the granules comprise a perforation to
enhance burning rates later in the burning cycle and to make the
granules more progressive in burning. Expressed another way, in
some embodiments, the granules comprise one or more perforations.
The term "perforation" refers to an aperture in the granule.
Alternative terms for "perforation" include channel, bore and
cavity.
[0061] The perforation may extend all the way through the granule.
In some embodiments, the perforation extends axially through the
granule.
[0062] The perforation may be of any diameter suitable for the size
of the granule. In some embodiments, the perforation has a diameter
of about 50 to about 1000 .mu.m. For example, the perforation may
have a diameter of about 50 to about 700 .mu.m, such as about 50 to
about 500 .mu.m, or about 100 to about 300 .mu.m.
[0063] There may be more than one perforation in each granule. In
some embodiments, there is a single perforation. In other
embodiments, there are multiple perforations. When the energetic
material is made by extrusion, the extrudate may be extruded with
one or more perforations.
Additional Layers
[0064] The propellant may comprise additional layers. Suitable
layers include a layer of a burn rate modifier, a finishing layer,
an ignition layer and/or a layer of a second energetic
material.
[0065] In embodiments where there is a layer of a burn rate
modifier, the burn rate modifier may be in the form of a coating on
granules of the energetic material. In embodiments where the
granules comprise a perforation, the burn rate modifier layer may
also coat the exposed area of the perforation(s). The coating of
the energetic material may be performed by any method known in the
art. The burn rate modifier coating material may be any burn rate
modifier known in the art. Examples of suitable burn rate modifiers
include, but are not limited to, dinitrotoluene, acetyl triethyl
citrate, triethyl citrate, tri-n-butyl citrate, tributyl acetyl
citrate, acetyl tri-n-butyl citrate, acetyl tri-n-hexyl citrate,
n-butyryl tri-n-hexylcitrate, di-n-butyl adipate, diisopropyl
adipate, diisobutyl adipate, diethylhexyl adipate, nonyl undecyl
adipate, n-decyl-n-octyl adipate, dibutoxy ethoxy ethyl adipate,
dimethyl adipate, hexyl octyl decyl adipate, diisononyl adipate,
dibutyl phthalate, diethyl phthalate, diamyl phthalate,
nonylundecyl phthalate, bis(3,5,5-trimethylhexyl) phthalate,
di-n-propyladipate, di-n-butyl sebacate, dioctyl sebacate, dimethyl
sebacate, diethyl diphenyl urea, dimethyl diphenyl urea, di-n-butyl
phthalate, di-n-hexyl phthalate, dinonyl undecyl phthalate, nonyl
undecyl phthalate, dioctyl terephthalate, dioctyl isophthalate,
1,2-cyclohexane dicarbonic acid diisononylester, dibutyl maleate,
dinonyl maleate, diisooctyl maleate, dibutyl fumarate, dinonyl
fumarate, dimethyl sebacate, dibutyl sebacate, diisooctyl sebacate,
dibutyl azelate, diethylene glycol dibenzoate, trioctyl
trimelliate, trioctyl phosphate, butyl stearate,
methylphenylurethane, N-methyl-N-phenylurethane, ethyl diphenyl
carbamate, camphor, gum Arabic, gelatin, rosin, modified rosin
esters, resins of dibasic acids and alkyl fatty alcohols,
polyesters of molecular weight 1500-30,000 based on dihydric
alcohols and dibasic acids, and combinations thereof.
Alternatively, the burn rate modifier coating material can be a
compound of formula 1. In this embodiment, granules of propellant
would comprise the compound of formula 1 distributed throughout
each granule of energetic material with or without other
co-stabilizing compounds, and a higher concentration of the
compound of formula 1 in an outer region of the granule consistent
with the coating of the granules with additional compound of
formula 1.
[0066] In embodiments where there is a layer of second energetic
material, the energetic material that forms the core of the
propellant will be referred to as a first energetic material. The
layer of second energetic material can be selected from the range
of energetic materials described above. The layer of second
energetic material is suitably different to the first energetic
material.
[0067] In embodiments where the propellant comprises an ignition
layer, the ignition layer comprises an ignition component. The
ignition component may comprise a group I metal salt of
nitrate.
[0068] In embodiments where the propellant comprises a finishing
layer, the finishing layer may be in the form of a graphite layer.
Surface-graphiting is typically the final finishing step, yet
graphiting may be completed prior to or after drying the
propellant. In some embodiments, the graphite finishing layer may
comprise an ignition component. Examples of suitable ignition
components include one or more group I metal salt of nitrate.
[0069] The finishing layer is generally the outermost layer on the
propellant. The additional layers may be complete layers around the
propellant or they may be partial layers.
Additives
[0070] In some embodiments, the propellant further comprises an
additive selected from the group consisting of plasticizers, flash
suppressants, barrel-wear ameliorants and combinations thereof.
[0071] In some embodiments, the additive is incorporated within the
granules of the is energetic material and the compound of formula
1. In other embodiments, the additive is incorporated in the
additional layer(s) of the propellant. Incorporation of the
additive within the granules of energetic material and the compound
of formula 1 can be achieved by adding the additive to the slurry
or dough of energetic material and the compound, which is then
formed into granules.
[0072] The term "plasticizer" refers to any compound which imparts
homogeneity and plasticity to the energetic material. In some
embodiments, the plasticizer may be selected from the group
consisting of diethylphthalate, camphor, dibutylphthalate,
di-n-propyl adipate, methylphenyl urethane, calcium stearate, butyl
stearate, nitroglycerin, glyceroltribenzoate and combinations
thereof.
[0073] The term "flash suppressant", refers to any compound which
can be used to suppress the muzzle flash of a firearm. In some
embodiments, the flash suppressant may be selected from the group
consisting of potassium and ammonium salts of organic and/or
inorganic acids, potassium sulphate, potassium nitrate, potassium
carbonate, potassium bicarbonate, potassium tartrate, potassium
bitartrate, ammonium bicarbonate, ammonium carbonate and
combinations thereof.
[0074] The term "barrel-wear ameliorants" refers to any compound
which can be used to reduce barrel-wear. In some embodiments, the
barrel-wear ameliorant may be selected from the group consisting of
bismuth, bismuth oxide, bismuth citrate, bismuth subcarbonate,
lead, lead carbonate, other salts of lead and bismuth and
combinations thereof.
[0075] FIG. 1 is a schematic illustration of the propellant
according to one embodiment of the invention, in which the
propellant is in the form of a granule of energetic material with
the stabilizer of the invention dispersed throughout (1). The
granule of energetic material and stabilizer is coated with a layer
of a burn rate modifier (2). The propellant further comprises an
ignition layer (3). Such propellant cross-sections may or may not
require perforations, depending on the geometry of the designed
propellant.
[0076] Without limiting the techniques used to form a propellant,
the propellant granule of FIG. 1 may be prepared by forming a dough
or slurry of the energetic material and the stabilizer of the
invention, extruding the dough or slurry to form an extrudate cord,
and then cutting the extrudate cord to the required length. The
extruded cord can have any length at the time of cutting, meaning
the cord can be extruded to metres, centimetres, millimetres or
microns in length prior to cutting. The extruded lengths may be cut
to any useful length known to be suitable for propellant
applications. After further processing to remove unwanted solvents
from the formulation, the granule may then be coated in a layer of
burn rate modifier, and finally coated with the ignition or is
finishing layer.
Ammunition
[0077] In one embodiment, there is provided an ammunition cartridge
comprising the propellant. The ammunition cartridge typically
comprises a casing, the propellant described above, a primer and a
projectile.
[0078] The propellant of the present invention is suitable for use
in a wide range of firearms. It is particularly suitable for use in
.22-.224 calibre firearms, .243 calibre firearms, .27 calibre
firearms, 6 mm calibre firearms, 7 mm calibre firearms .30 calibre
firearms, 8 mm calibre firearms, .338 calibre firearms up to .50
calibre firearms and is even suitable for medium to large calibre
firearms.
[0079] The casing may be made of any material of sufficient
strength and thickness to not rupture during burning of the
propellant. The casing may be of any size and the size will depend
upon the firearm in which the cartridge is to be used. Conventional
casing materials and construction is well known in the art and
applies to the present application.
[0080] The primer, or priming compound, may be comprised of any
substance which is capable of igniting the propellant on
initiation. Examples of priming compounds include but are not
limited to lead azide (dextrinated), lead styphnate, mercury
fulminate and combinations thereof. In some embodiments, the
priming compound is ASA (aluminium, lead styphnate, lead
azide).
[0081] The projectile may be any object which can be projected from
the muzzle of a firearm system (or gun) upon burning of the
propellant. Examples of projectiles include, but are not limited
to, bullets, shot, pellets, slugs, shells, balls, buckshot, bolts,
rockets and cannon balls. In some embodiments, the projectile is
selected from the group consisting of a bullet, pellet, slug and
ball.
Advantages
[0082] The compounds of formula 1 contain only carbon, hydrogen,
oxygen and in some cases nitrogen and do not contain any
potentially toxic or hazardous elements such as halogens. The
compounds are capable of stabilizing energetic materials such as
nitrocellulose over extended periods of time. In fact, the
compounds are capable of stabilizing energetic materials such as
nitrocellulose to a comparable extent as or a greater extent than
commonly used propellant stabilizer DPA, making them suitable for
use in propellants and ammunition cartridges.
EXAMPLES
[0083] The invention will now be described with reference to the
following non-limiting Examples.
Stabilizing effect of 4-(4-hydroxyphenyl)butan-2-one
Preliminary Tests
[0084] Methyl Violet Paper (MVP) and Abel Heat tests were conducted
on samples of small nitrocellulose-based propellants containing
4-(4-hydroxyphenyl)butan-2-one to obtain a preliminary indication
as to the likely efficacy of 4-(4-hydroxyphenyl)butan-2-one as a
stabilizer. The tests did not give a strong indication that that
4-(4-hydroxyphenyl)butan-2-one stabilized the propellant
compositions. Nonetheless, work continued on with further tests
conducted to determine whether 4-(4-hydroxyphenyl)butan-2-one has
stabilizing properties.
Example 1
[0085] STANAG 4582 is a standard NATO stability test procedure for
single base, double base and triple base propellants using heat
flow calorimetry. Propellants that satisfy STANAG 4582 are
considered to remain chemically stable for a minimum of ten years
if stored at temperatures equivalent to an isothermal storage at
25.degree. C.
[0086] Samples of nitrocellulose-based propellants without burn
rate modifier (approximately 1.5 mm long, 0.8 mm outer diameter and
0.2 mm perforation) stabilized with either 1% DPA or 1%
4-(4-hydroxyphenyl)butan-2-one or a combination of the two
stabilizers were compared according to the accepted STANAG 4582
method. The samples were prepared in small quantities of less than
1 kg propellant granules, with the stabilizer materials mixed
evenly throughout the energetic material.
[0087] The results are set out in Table 1. FIG. 2 shows the heat
flow calorimetry traces of the samples stabilized with 1% DPA (FIG.
2A) or 1% 4-(4-hydroxyphenyl)butan-2-one (FIG. 2C), or a
combination (FIG. 2B).
TABLE-US-00001 TABLE 1 Normalised Heat Flow Sample Stabilizer
Output (.mu.W/g) Propellant I 1% DPA 8 Propellant II 0.5% DPA +
0.5% 4-(4- 18 hydroxyphenyl)butan-2-one Propellant III 1%
4-(4-hydroxyphenyl)butan-2-one 33
[0088] The results show that all three propellants fulfilled the
requirements of STANAG 4582, with the 4-(4-hydroxyphenyl)
butan-2-one-stabilized sample having a normalised heat flow output
of 33 .mu.W/g, compared with a normalized heat flow output of 8
.mu.W/g for the DPA-stabilized sample. This data demonstrates that
4-(4-hydroxyphenyl)butan-2-one is capable of long term
stabilization of nitrocellulose-based propellants.
Example 2
[0089] Samples of nitrocellulose-based propellants without burn
rate modifier (approximately 1.5 mm long, 0.8 mm outer diameter and
0.2 mm perforation) stabilized with either 1% DPA or 1%
4-(4-hydroxyphenyl) butan-2-one were compared according to the
accepted STANAG 4582 method. The samples were prepared in larger
quantities of up to 5 kg propellant granules, with the stabilizer
mixed evenly throughout the energetic material.
[0090] The results are set out in Table 2. FIG. 2 shows the heat
flow calorimetry is traces of the samples stabilized with 1% DPA
(FIG. 2D) or 1% 4-(4-hydroxyphenyl) butan-2-one (FIG. 2E).
TABLE-US-00002 TABLE 2 Normalised Heat Flow Sample Stabilizer
Output (.mu.W/g) Propellant A ~1% DPA 44 Propellant B ~1%
4-(4-hydroxyphenyl) butan-2-one 120
[0091] The results show that both propellants fulfilled the
requirements of STANAG 4582, with the 4-(4-hydroxyphenyl)
butan-2-one-stabilized sample having a normalised heat flow output
of 44 .mu.W/g, compared with a normalized heat flow output of 120
.mu.W/g for the DPA-stabilized sample. This data demonstrates that
4-(4-hydroxyphenyl)butan-2-one is capable of long term
stabilization of nitrocellulose-based propellants.
Mechanism of Stabilizing Effect of
4-(4-hydroxyphenyl)butan-2-one
[0092] FIG. 3 shows chromatography traces of nitrocellulose-based
propellants (approximately 1.8 mm long, 0.8 mm diameter, 0.18
micron perforation) including 1% DPA and 6% DNT (FIG. 3A), 1% DPA
and 2% 4-(4-hydroxyphenyl)butan-2-one (FIG. 3B), or 1% DPA and 6%
4-(4-hydroxyphenyl)butan-2-one (FIG. 3C), which had been aged for
40 days at 65.5.degree. C. The traces of samples containing
4-(4-hydroxyphenyl)butan-2-one show new peaks not present in the
sample containing DPA and DNT. Without wishing to be bound by
theory, the inventors hypothesise that
4-(4-hydroxyphenyl)butan-2-one acts as a propellant stabilizer by
scavenging acidic nitrates and nitric oxides, and that these new
peaks correspond to daughter compounds derived from
4-(4-hydroxyphenyl)butan-2-one. Daughter compounds may include
4-(4-hydroxy-3-nitrophenyl)butan-2-one and
4-(4-hydroxy-3,5-dinitrophenyl)butan-2-one.
[0093] FIG. 4A shows a chromatography trace of a sample of a
nitrocellulose-based propellant (1.39 mm long, 0.7 mm diameter, 50
micron perforation) including 1% 4-(4-hydroxyphenyl)butan-2-one,
aged for 40 days at 65.5.degree. C. Without wishing to be bound by
theory, the inventors hypothesis that the peak at approximately 3.6
minutes corresponds to 4-(4-hydroxy-3-nitrophenyl)butan-2-one.
Subsequent investigations supported this hypothesis. FIG. 4B shows
a chromatography trace of a sample of synthetic
4-(4-hydroxy-3-nitrophenyl)butan-2-one under the same conditions,
the synthetic sample eluting at approximately 3.6 minutes. FIG. 4C
shows a chromatography trace of a sample of the aged propellant
formulation spiked with synthetic
4-(4-hydroxy-3-nitrophenyl)butan-2-one, in which the peak at
approximately 3.6 minutes was shown to have grown. FIG. 4D shows
the mass spectrum of the 3.6 minute peak compound, which
corresponds to the mass of 4-(4-hydroxy-3-nitrophenyl)butan-2-one.
FIG. 5A shows the .sup.1H NMR spectrum of the 3.6 minute peak
compound, which corresponds to the .sup.1H NMR spectrum of
synthetic 4-(4-hydroxy-3-nitrophenyl)butan-2-one shown in FIG. 5B.
These data indicate that 4-(4-hydroxyphenyl)butan-2-one acts as a
propellant stabilizer by scavenging acidic nitrates and nitric
oxides to generate daughter compound
4-(4-hydroxy-3-nitrophenyl)butan-2-one.
[0094] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
[0095] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context.
[0096] In the claims which follow and in the preceding description
of the invention, except where the context requires otherwise due
to express language or necessary implication, the word "comprise"
or variations such as "comprises" or "comprising" is used in an
inclusive sense, i.e. to specify the presence of the stated
features but not to preclude the presence or addition of further
features in various embodiments of the invention.
* * * * *