U.S. patent application number 16/770763 was filed with the patent office on 2021-06-10 for propellant charge.
This patent application is currently assigned to Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO. The applicant listed for this patent is Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO. Invention is credited to Christoffel Adrianus VAN DRIEL.
Application Number | 20210171415 16/770763 |
Document ID | / |
Family ID | 1000005435867 |
Filed Date | 2021-06-10 |
United States Patent
Application |
20210171415 |
Kind Code |
A1 |
VAN DRIEL; Christoffel
Adrianus |
June 10, 2021 |
PROPELLANT CHARGE
Abstract
The invention is directed to a propellant charge for guns, to a
combination of a propellant charge and a primer, to a firearms
cartridge, and to a method for modifying the surface of a
propellant charge. The propellant charge of the invention comprises
multiple propellant grains, wherein an exterior part of part of the
propellant grains has been subjected to a surface modification
treatment comprising the successive steps of suspending propellant
grains in water to prepare a slurry, adding an organic solvent to
the propellant grains before, after and/or during the preparation
of the slurry, mixing the slurry that comprises water and organic
solvent for a period of 120 minutes or less, lowering the
concentration of organic solvent, removing organic solvent, and
drying the propellant grains to remove water; wherein part of the
propellant grains has not been subjected to the surface
modification treatment.
Inventors: |
VAN DRIEL; Christoffel
Adrianus; (Delft, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nederlandse Organisatie voor toegepast-natuurwetenschappelijk
onderzoek TNO |
's-Gravenhage |
|
NL |
|
|
Assignee: |
Nederlandse Organisatie voor
toegepast-natuurwetenschappelijk onderzoek TNO
's-Gravenhage
NL
|
Family ID: |
1000005435867 |
Appl. No.: |
16/770763 |
Filed: |
December 10, 2018 |
PCT Filed: |
December 10, 2018 |
PCT NO: |
PCT/NL2018/050827 |
371 Date: |
June 8, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C06B 45/12 20130101;
C06B 21/0083 20130101 |
International
Class: |
C06B 21/00 20060101
C06B021/00; C06B 45/12 20060101 C06B045/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2017 |
NL |
17206158.2 |
Claims
1. A propellant charge for guns, comprising multiple propellant
grains, wherein an exterior part of part of the propellant grains
has been subjected to a surface modification treatment comprising
the successive steps of suspending propellant grains in water to
prepare a slurry, adding an organic solvent to the propellant
grains before, after and/or during the preparation of the slurry,
mixing the slurry that comprises water and organic solvent for a
period of 120 minutes or less, lowering the concentration of
organic solvent, removing organic solvent, and drying the
propellant grains to remove water; wherein part of the propellant
grains has not been subjected to the surface modification
treatment.
2. The propellant charge for guns of claim 1, wherein the organic
solvent is added to the propellant grains before the preparation of
the slurry.
3. The propellant charge for guns of claim 1, wherein the organic
solvent is added to the propellant grains after the preparation of
the slurry.
4. The propellant charge for guns of claim 1, wherein the organic
solvent is added to the propellant grains during the preparation of
the slurry.
5. The propellant charge for guns of claim 1, wherein the surface
modification treatment further comprises removing water and/or
organic solvent after mixing the slurry that comprises water and
organic solvent for a period of 120 minutes or less and before
lowering the concentration of organic solvent.
6. A propellant charge for guns, comprising multiple propellant
grains, wherein an exterior part of part of the propellant grains
has been subjected to a surface modification treatment comprising
the successive steps of wetting propellant grains with water or
water vapour, adding an organic solvent to the propellant grains
before, after and/or during the wetting of the propellant grains,
allowing the wet propellant grains and the organic solvent to
interact for a period of 120 minutes or less, lowering the
concentration of organic solvent, removing organic solvent, and
drying the propellant grains to remove water; wherein part of the
propellant grains has not been subjected to the surface
modification treatment.
7. The propellant charge for guns of claim 6, wherein the organic
solvent is added to the propellant grains before the wetting of the
propellant grains.
8. The propellant charge for guns of claim 6, wherein the organic
solvent is added to the propellant grains after the wetting of the
propellant grains.
9. The propellant charge for guns of claim 6, wherein the organic
solvent is added to the propellant grains during the wetting of the
propellant grains.
10. The propellant charge for guns of claim 6, wherein the surface
modification treatment further comprises removing water and/or
organic solvent after allowing the wet propellant grains and the
organic solvent to interact for a period of 120 minutes or less,
and before lowering the concentration of organic solvent.
11. The propellant charge for guns of claim 1, wherein the
propellant grains comprise nitrocellulose.
12. The propellant charge for guns of claim 1, wherein the
propellant grains comprise LOVA-propellant.
13. The propellant charge for guns of claim 1, wherein the organic
solvent is more volatile than water.
14. The propellant charge for guns of claim 1, wherein the organic
solvent comprises one or more selected from methyl acetate, ethyl
acetate, isopropyl acetate, isobutyl acetate, t-butyl acetate,
isopropyl ether, t-butyl methyl ether, ethyl ether, acetone, methyl
ethyl ketone, methyl isobutyl ketone, methyl isopropyl ketone,
2-butanone, 3-pentanone, 4-methyl-2-pentanone,
3,3-dimethyl-2-butanone, methyl formate, ethyl formate, propyl
formate, acetol, 1,4-dioxane, 2,2-dimethoxy propane, acetonitrile
and tetrahydrofuran.
15. The propellant charge for guns of claim 1, wherein the period
of time is from 15-120 minutes, preferably 20-100 minutes, such as
30-90 minutes.
16. The propellant charge for guns of claim 1, wherein said
lowering of the concentration of organic solvent is performed by
adding an additional amount of water.
17. The propellant charge for guns of claim 16, wherein the
additional amount of water is 50-700% by weight of the initial
amount of water.
18. The propellant charge for guns of claim 16, wherein the
additional amount of water is 100-500% by weight of the initial
amount of water.
19. The propellant charge for guns of claim 1, wherein the
additional amount of water is 175-450% by weight of the initial
amount of water.
20. The propellant charge for guns of claim 1, wherein the
propellant charge is in the form of a spherical propellant charge
or a rifle propellant.
21. A propellant charge and a primer, wherein said propellant
charge is the propellant charge of claim 1.
22. The combination of a propellant charge and a primer of claim
21, wherein said primer is present in an amount in the range of
1-10% by total weight of the main propellant charge, preferably
1.5-9%, such as 2-8%.
23. A firearms cartridge comprising the combination of a propellant
charge and a primer of claim 21.
24. A method for modifying the surface of propellant grains,
wherein said method comprises the successive steps of suspending
propellant grains in water to prepare a slurry, adding an organic
solvent to the propellant grains before, after and/or during the
preparation of the slurry, mixing the slurry that comprises water
and organic solvent for a period of 120 minutes or less, lowering
the concentration of organic solvent, removing organic solvent, and
drying the propellant grains to remove water.
25. The method for modifying the surface of propellant grains of
claim 24, wherein the organic solvent is added to the propellant
grains before the preparation of the slurry.
26. The method for modifying the surface of propellant grains of
claim 24, wherein the organic solvent is added to the propellant
grains after the preparation of the slurry.
27. The method for modifying the surface of propellant grains of
claim 24, wherein the organic solvent is added to the propellant
grains during the preparation of the slurry.
28. The method for modifying the surface of propellant grains of
claim 24, wherein the method further comprises removing water
and/or organic solvent after mixing the slurry that comprises water
and organic solvent for a period of 120 minutes or less and before
lowering the concentration of organic solvent.
29. A method for modifying the surface of propellant grains,
wherein said method comprises the successive steps of wetting
propellant grains with water or water vapour, adding an organic
solvent to the propellant grains before, after and/or during the
wetting of the propellant grains, allowing the wet propellant
grains and the organic solvent to interact for a period of 120
minutes or less, lowering the concentration of organic solvent,
removing organic solvent, and drying the propellant grains to
remove water.
30. The method for modifying the surface of propellant grains of
claim 29, wherein the organic solvent is added to the propellant
grains before the wetting of the propellant grains.
31. The method for modifying the surface of propellant grains of
claim 29, wherein the organic solvent is added to the propellant
grains after the wetting of the propellant grains.
32. The method for modifying the surface of propellant grains of
claim 29, wherein the organic solvent is added to the propellant
grains during the wetting of the propellant grains.
33. The method for modifying the surface of propellant grains of
claim 29, wherein the method further comprises removing water
and/or organic solvent after allowing the wet propellant grains and
the organic solvent to interact for a period of 120 minutes or
less, and before lowering the concentration of organic solvent.
Description
[0001] The invention is directed to propellant charges for guns, to
a combination of a propellant charge and a primer, to a firearms
cartridge, and to methods for modifying the surface of propellant
grains.
[0002] Propellant charges for conventional barrel weapon systems
should be configured such that they can function safely and without
problems under different environmental conditions. Temperature
differences during the weapon deployment represent an important
influence, which must be taken into account when developing
propellant charges.
[0003] According to the laws of physics, the combustion rate of a
propellant charge depends on the spontaneous ignition temperature
and the starting temperature of the propellant. This relationship
leads to the typical characteristic of traditional propellant
powders that the linear burn rate more or less depends on the
starting temperature. From this, it necessarily follows that the
maximum gas pressure and the muzzle velocity have a more or less
steep temperature gradient. The temperature dependent performance
of such propellant powders has considerable disadvantages, for
example a considerably lower projectile energy during the
deployment at normal and at low temperatures, and, because the hit
accuracy usually depends on the projectile velocity influencing the
barrel jump, low first hit probability. More specifically, the
projectile velocity will be higher when the ammunition temperature
is higher and lower when the ammunition temperature is lower.
[0004] It is much more favourable to have a propellant charge with
temperature independent behaviour, in that the weapon performance
(and in particular the projectile velocity) is more or less equal
regardless of the ammunition temperature. The main advantage
thereof is the fact that the performance of the weapon over the
entire temperature range can be improved. This is because the
propellant charge is usually dimensioned to the highest possible
weapons performance having the highest gas pressures in the weapon.
Further, the accuracy is improved in comparison to conventional
munition.
[0005] In the art, there have been some attempts in providing a
propellant with temperature independent behaviour when employed in
a weapon.
[0006] U.S. Pat. No. 1,627,861, for instance, reveals the
preparation of a propellant powder having a dense core and a
modified surface.
[0007] GB-A-1 204 659 discloses a process of preparing porous
nitrocellulose powder, comprising the formation of pores by removal
of water-soluble salts from the propellant grains.
[0008] DE-A-100 46 146 describes a propellant powder comprising at
least one in situ polymerised surface treatment agent in the
surface layer of the grain surface.
[0009] GB-A-836 546 discloses a method of preparing propellant
powder having a porous interior and a dense outer layer. The grains
are subjected to prolonged impregnation with nitroglycerin and
ethyl acetate.
[0010] U.S. Pat. No. 5,682,009 describes a treatment process to
influence the burn rate of the propellant by using a burn rate
modifier.
[0011] U.S. Pat. No. 4,106,960 discloses a temperature compensating
propellant charge, wherein individual powder particles of
nitrocellulose containing propellant are coated with an acrylic
resin having a molecular weight between 100 000 and 200 000 g/mol,
the coating comprising 10 to 20% by weight of the propellant.
[0012] DE-A-196 35 795 describes a propellant charge for tube
weapons with a main charge and a transmission charge wherein the
transmission charge has burning characteristics which are opposite
to those of the main charge.
[0013] A similar solution is provided by EP-A-0 150 431, which
discloses a propellant charge for tube weapons with a mixture of
homogeneous powder having a burn rate which increases with
increasing temperature, and heterogeneous powder (or HET-powder)
having a burn rate which decreases with increasing temperature.
[0014] US 2002/0 134 269, US 2006/0 266 451 and EP-A-1 241 152
describe a propellant powder wherein plugs are formed inside the
perforations of perforated propellant grains. As a result, the
propellant grains burn practically independent of the propellant
powder temperature. If the propellant powder temperature is high
(resulting in a fast combustion rate), the plugs remain inside the
perforation tunnels and a minimum surface is available for the
burning. With a low temperature (slow combustion rate), the plugs
are all removed by the ignition pressure wave and a maximum surface
area is available for the burning. This solution is somewhat
complex and is not applicable to spherical propellant charges.
[0015] Despite these attempts, there remains a need for alternative
and improved propellant charges that allow temperature independent
performance in a weapon.
[0016] An objective of the present invention is to overcome at
least some of the disadvantages observed in the prior art and to
provide such an improved propellant charge.
[0017] The inventors surprisingly found that this objective can be
met by subjecting at least some propellant grains in a propellant
charge to a surface modification treatment.
[0018] Accordingly, in a first aspect, the invention is directed to
a propellant charge, comprising multiple propellant grains, wherein
an exterior part of part of the propellant grains has been
subjected to a surface modification treatment comprising the
successive steps of
[0019] suspending propellant grains in water to prepare a
slurry,
[0020] adding an organic solvent to the propellant grains before,
after and/or during the preparation of the slurry,
[0021] mixing the slurry that comprises water and organic solvent
for a period of 120 minutes or less,
[0022] optionally removing water and/or organic solvent,
[0023] lowering the concentration of organic solvent,
[0024] removing organic solvent, and
[0025] drying the propellant grains to remove water wherein part of
the propellant grains has not been subjected to the surface
modification treatment.
[0026] The inventors found that the temperature dependence of the
performance of a propellant charge of the invention is surprisingly
reduced.
[0027] As a result, the propellant charge as claimed can be
employed in a weapon at various temperatures while maintaining
sufficient accuracy.
[0028] Alternatively, treatment of the propellant charges can be
performed in vapour phase. In such a treatment, the water and
organic solvent are not mixed in a slurry but mix in vapour or gas
phase.
[0029] Therefore, in a further aspect, the invention is directed to
a propellant charge, comprising multiple propellant grains, wherein
an exterior part of part of the propellant grains has been
subjected to a surface modification treatment comprising the
successive steps of
[0030] wetting propellant grains with water or water vapour,
[0031] adding an organic solvent to the propellant grains before,
after and/or during the wetting of the propellant grains,
[0032] allowing the wet propellant grains and the organic solvent
to interact for a period of 120 minutes or less,
[0033] optionally removing water and/or organic solvent,
[0034] lowering the concentration of organic solvent,
[0035] removing organic solvent, and
[0036] drying the propellant grains to remove water wherein part of
the propellant grains has not been subjected to the surface
modification treatment.
[0037] The term "propellant" as used in this application is meant
to refer to any suitable type of combustible material adapted to
generate gases to propel a projectile from a gun barrel weapons.
The propellant can include a single type of material or multiple
types of materials and, with multiple types of materials, the
materials can be arranged in any suitable type of uniform,
non-uniform, or patterned configurations. The materials can also be
provided as powder, unary, solidified liquid, etc.
[0038] The term "propellant charge" as used in this application is
typically meant to refer to the equally common designations "gun
powder" or "gun propellant", but is also intended to encompass
pyrotechnical charges. A propellant charge typically comprises a
plurality of particulate grains (or propellant grains). When used
in ammunition, the propellant charge is normally contained within a
metal or combustible case (in case of modern modular charges for
artillery systems), or cloth bag. For small arms, the individual
grains of a propellant charge can, for instance, be spherical
(spherical propellants), cylindrical, or cubical. Small arms
propellant charges can have diameters of a few hundred microns. For
larger guns, such as artillery pieces, the individual grains
typically have diameters up to about one and a half centimetres and
lengths of up to about 3 cm.
[0039] The term "propellant grain" as used in this application is
meant to refer to a single mass of propellant. Hence, in a
spherical propellant a grain refers to a single sphere or ball, and
in a perforated propellant a grain refers to a single perforated
mass of propellant.
[0040] The term "primer" as used in this application is meant to
refer to any suitable type of initiating charge adapted to initiate
combustion of the main propellant charge.
[0041] Without wishing to be bound by any theory, the inventors
believe that the surface modification treatment results in a
propellant charge, wherein surface modified part of the propellant
grains has different burn properties than the part of the
propellant grains that is not modified (such as propellant grains
that are not surface modified, or the interior part of the
propellant grains). The inventors believe that the temperature
sensitivity of the modified surface is larger than the temperature
sensitivity of non-modified part of the propellant charge. At high
temperatures, the projectile that is to be shot will be accelerated
quickly initially by the fast burning surface modified part of the
propellant charge, thereby increasing the chamber volume and
avoiding extremely high pressures in the chamber when the majority
of the non-modified part of the propellant charge burns. Hence, the
initial increase in chamber volume compensates for the higher burn
rate of the non-modified propellant charge. At low temperatures,
the projectile that is to be shot will be accelerated slowly
thereby maintaining the chamber volume small which allows a quick
pressure build-up to compensate for the lower burn rate. It is not
yet fully understood how the burn characteristics of the propellant
charge are influenced by the surface modification. Possible
features that may play a role are the porosity of the propellant
charge at the surface, the degree of gelation of propellant
constituents like nitrocellulose, and/or another redistribution of
propellant ingredients at a molecular scale.
[0042] The propellant charge of the invention comprises multiple
propellant grains. The type of grains (i.e. spherical propellants
or perforated extruded propellants) in the propellant charge is
usually the same. The propellant charge may, for instance, comprise
one or more selected from black powder, nitroglycerin,
nitroguanidine, bis-nitroxyethylnitramine (DINA), fivonite
(tetramethylolcyclopentanone tetranitrate), diethylene glycol
dinitrate (DGN), acetyl cellulose, LOVA-propellant. As commonly
known in the art, the acronym LOVA stands for LOw Vulnerability
Ammunition and such propellants comprise a solid energetic filler
in a polymeric binder system (see e.g. Agrawal, "High Energy
Materials, Propellants, Explosives and Pyrotechnics", Wiley-VCH,
2010, Weinheim, 228-230). Typically, the propellant charge
comprises nitrocellulose and/or LOVA-propellant. More preferably,
the propellant charge comprises nitrocellulose.
[0043] Propellant charges that comprise nitrocellulose can be
divided into single-base, double-base, triple-base, and
quadruple-base, or multibase compositions. Conventional granular,
nitrocellulose-based propellant compositions typically include
nitrocellulose, selected organic plasticisers for use as ballistic
modifiers, stabilisers, and other additives such as inorganic salts
or carbon black. When energetic plasticisers such as nitroglycerin
(NG) or diethylene glycol dinitrate (DEGDN) are also added, the
propellant is considered a "double base" propellant. Such an
addition of energetic plasticisers within the propellant provides
an effective means to enhance the energy content of the charge as
well as the flame temperature of the combustion gases and thereby
increase performance of the propellant. Thus, a "single-base"
propellant contains nitrocellulose with optional additives. A
"double-base" propellant contains nitrocellulose as well as an
additional energetic plasticiser. A "triple-base" propellant
generally contains nitrocellulose, energetic plasticisers, and
another solid component, such as nitroguanidine (NQ).
[0044] The nitrocellulose content in single-base compositions is
90% or more by total weight of the composition. The nitrocellulose
content in double-base compositions is typically 50-90% by total
weight of the composition. The nitrocellulose content in
triple-base compositions is typically 40-50% by total weight of the
composition. It is also possible that the propellant charge
comprises RDX (cyclotrimethylene trinitramine) and/or HMX
(cyclotetramethylene tetranitramine), and nitrocellulose is used as
a binder. The RDX and/or HMX content is then typically 10-30% by
total weight of the composition, and the nitrocellulose content is
typically 90% or less by total weight of the composition. Such
propellant charges can further comprise other energetic solid
components such as triaminoguanidine nitrate (TAGN),
hexanitrohexa-aza-isowurtzitane (HNIW), n-guanylurea-dinitramide,
1,1-diamino-2,2-dinitro-ethylene (DADNE), and/or non-energetic
plasticisers.
[0045] The production of conventional single-base, double-base, or
triple-base propellant compositions is known in the art. The method
of the invention may also be effective for compositions that are
poor in nitrocellulose, such as composite propellants that contain
70% or more by total weight of the composition of RDX or other
solid energetic materials.
[0046] If necessary, the propellant can contain additives for
thermochemical stabilisation, barrel protection, plasticising, gun
flash damping, improving ignition behaviour and/or, burning
modulation.
[0047] Known additives for increasing stabilisation are, for
example, Acardit II (CAS No. 724-18-5), Centralit I (CAS No.
90-93-7), Centralit II (CAS No. 611-92-7), 2-nitrodiphenylamine,
and diphenylamine.
[0048] Known additives for barrel protection are, for example,
talcum, titanium dioxide, calcium carbonate, and magnesium
silicate.
[0049] Known additives for plasticising, for example, camphor
dibutyl phthalate, dioctyl phthalate, acetyl triethyl citrate,
acetyl tributyl citrate, tributyl citrate, dibutyl adipate, diethyl
adipate, dioctyl adipate, diethyl sebacate, dibutyl sebacate, and
the like.
[0050] Known additives for gun flash damping are, for example,
potassium sulphate and potassium cryolite.
[0051] These additives may be added, either alone or in
combination, to the propellant powder dough while preparing the
untreated propellant grain and are thus distributed homogeneously
in the propellant grain matrix. The total amount of additives in
the untreated propellant grain can suitably be between 0-10% by
total weight of the grain, such as 0.1-5%. It is also possible to
introduce one or more additives during the surface modification
treatment, as will be explained.
[0052] According to the invention an exterior part of part of the
propellant grains in the propellant charge has been subjected to a
surface modification treatment. In accordance with the invention,
part of the propellant grains have been subjected to the surface
modification treatment, while another part of the propellant grains
has not been subjected to the surface modification treatment. As a
result, the invention may suitably be applied to spherical
propellant, wherein part of the balls is surface modified, while
another part of the balls is not surface modified. The weight ratio
of surface modified spherical propellant to non-surface modified
spherical propellant can be in the range of 20:80 to 80:20,
preferably 35:65 to 65:35 and more preferably 45:55 to 55:45.
[0053] In an embodiment of the surface modification treatment for
surface modifying at least part of the propellant grains, the
grains are suspended in water to prepare a slurry. Besides water,
it is also possible to use an aqueous solution. The aqueous
solution can comprise components such as emulsion additives, salts,
surface active agents like gelatine, colloid stabilisers, and
combinations thereof. Salts, such as K2504, may for instance be
used to retract water before distilling off organic solvent.
Typically, the amount of water or aqueous solution used is 0.5-20
litre per kilogram of propellant grains, such as 1-10 litre, or 1-5
litre per kilogram of propellant grains.
[0054] The slurry may be agitated to form a homogeneous mixture.
Optionally, the slurry may be heated to a temperature in the range
of 30-80.degree. C., such as in the range of 40-70.degree. C.
[0055] In another embodiment of the surface modification treatment
for surface modifying at least part of the propellant grains, the
grains are wetted with water or water vapour. In this embodiment
the water or water vapour may comprise additional further
components as mentioned above for the aqueous solution.
[0056] In a further step, an organic solvent is added to the
propellant grains. This can be done before, after and/or during
preparation of the slurry, or before, after and/or during wetting
of the propellant grains. Preferably, the organic solvent is added
to the propellant after and/or during preparation of the slurry, or
after and/or during wetting of the propellant grains. It is thus,
for example, possible to add a mixture of organic solvent and water
to the propellant grains so as to prepare a slurry with water, but
also to first prepare the slurry with water and afterwards add
organic solvent. Likewise, it is possible to first wet the
propellant grains with a mixture of organic solvent and water, but
also to first wet the propellant grains with water and afterwards
add organic solvent.
[0057] In the accordance with the first aspect of the invention,
the organic solvent is preferably added in liquid form.
[0058] Preferably, the organic solvent is a solvent that forms a
two phase system with water. The formation of a two phase system
may aid in preventing coagulation of propellant grains. The organic
solvent is preferably more volatile than water. For example, the
vapour pressure of the organic solvent at 25.degree. C. can be 10
kPa or more, such as 10-500 kPa, or 12-400 kPa.
[0059] Suitable examples of possible organic solvents include
methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate,
t-butyl acetate, isopropyl ether, t-butyl methyl ether, ethyl
ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl
isopropyl ketone, 2-butanone, 3-pentanone, 4-methyl-2-pentanone,
3,3-dimethyl-2-butanone, methyl formate, ethyl formate, propyl
formate, acetol, 1,4-dioxane, 2,2-dimethoxy propane, acetonitrile
and tetrahydrofuran. Preferably, the organic solvent comprises one
or more selected from ethyl acetate, methyl ethyl ketone, isopropyl
acetate.
[0060] The amount of organic solvent to be added may be 50-500 ml
per litre of total slurry excluding the organic solvent, such as
80-350 ml per litre of total slurry excluding the organic solvent,
or 100-250 ml per litre of slurry excluding the organic
solvent.
[0061] In accordance with the second aspect of the invention, the
organic solvent can be added in vapour or gas form. The amount of
organic solvent to be added can then be 1-100 ml per kg of wet
propellant grains excluding the organic solvent, such as 2-80 ml
per kg of wet propellant grains excluding the organic solvent, or
5-50 ml per kg of wet propellant grains excluding the organic
solvent.
[0062] Optionally, the organic solvent may comprise further
components, such as one or more deterrents for slowing down the
burn rate, or one or more stabilisers. Suitable deterrents can for
example be selected from the group consisting of centralites
(symmetrical diphenyl urea, primarily diethyl or dimethyl), dibutyl
phthalate, dinitrotoluene, akardite (asymmetrical diphenyl urea),
ortho-tolyl urethane, polyester adipate, and camphor. The total
amount of additional components in the organic solvent can suitably
be in the range of 0.01-5% by total weight of the organic solvent
inclusive additional components, such as 0.2-3%, or 0.3-1%.
[0063] Further optional additives that may be added to the organic
solvent include nitroglycerine (NG), diethylene glycol dinitrate
(DEGDN), n-butyl-2-nitratoethyl-nitramine (butyl-NENA),
ethyl-2-nitratoethyl-nitramine (ethyl-NENA), and other energetic
plasticisers.
[0064] The addition of the organic solvent may involve spraying of
the organic solvent so as to homogeneously distribute the organic
solvent over the propellant grains or over the slurry. In case the
organic solvent is added as a vapour or gas, this is not critical.
The solvent may be added to the propellant grains continuously at a
relatively slow rate in order to avoid localised areas which
contain high concentrations of the solvent capable of completely
dissolving the propellant grains. The addition of the organic
solvent may, for instance, be performed at a rate of 5-75 ml per
litre slurry excluding the organic solvent, such as 10-50 ml per
litre slurry excluding the organic solvent, or 12-25 ml per litre
slurry excluding the organic solvent. Typically, the addition of
the organic solvent is completed within a period of 1-30 minutes,
preferably 2-10 minutes. It is preferred that the propellant grains
or the slurry is agitated while adding the organic solvent.
[0065] During the addition of the organic solvent, the temperature
can be maintained in the range of 0-70.degree. C., such as in the
range of 10-40.degree. C.
[0066] After having added the organic solvent, the slurry or the
mixture of wet propellant grains and organic solvent is mixed, or
allowed to interact, for a period of 120 minutes or less. This
period of time typically ranges from 15-120 minutes, preferably
20-100 minutes, such as 30-90 minutes. During mixing, the
temperature of the slurry can be 0-70.degree. C., such as
10-40.degree. C.
[0067] In an optional step, an amount of water and/or organic
solvent is removed. Such removal can, for example, involve
decanting. The optional removal of water and/or organic solvent may
be performed to remove excess water and/or organic solvent.
Accordingly, the removal suitably involves removing part of the
water and/or part of the organic solvent.
[0068] Subsequently, the concentration of organic solvent is
lowered. This may, for instance, be realised by adding an
additional amount of water or water vapour to the mixture. This
additional amount of water is preferably added within 5-120 minutes
from having added the organic solvent, such as within 15-75
minutes.
[0069] The additional amount of water is preferably an amount of
250-1500 ml per litre of total slurry, such as 350-1100 ml per
litre of total slurry, or 500-800 ml per litre of total slurry.
Suitably, the additional amount of water is 50-700% by weight of
the initial amount of water, preferably 100-500% by weight, such as
175-450% by weight.
[0070] If an additional amount of water or water vapour is added to
the mixture of wet propellant grains and organic solvent, the
additional amount of water or water vapour is preferably added
within 5-120 minutes from having added the organic solvent, such as
within 15-75 minutes. In this embodiment, the additional amount of
water is preferably an amount of 5-50 g per kg of wet propellant
grains, preferably 8-40 g per kg of wet propellant grains, or 10-35
g per kg of wet propellant grains. Suitably, the additional amount
of water is 2-20% by weight of the initial amount of water,
preferably 4-12% by weight, such as 5-10% by weight.
[0071] Another way of lowering the concentration of organic solvent
may be by evaporation of organic solvent, such as evaporation part
of the organic solvent. At the same time such evaporation of
organic solvent will result in removal of organic solvent, as
required in the next step of the method of the invention.
Accordingly, these two steps can be combined into a single step of
solvent evaporation.
[0072] Without wishing to be bound by any theory, the inventors
believe that upon addition of the organic solvent, the exterior
surface of the propellant grains is softened because the propellant
slightly dissolves in the organic solvent. The organic solvent is
believed to somewhat penetrate the propellant grain, thereby taking
some water along. The exterior part of the grain then comprises
propellant in a mixture of water and organic solvent. Upon lowering
the concentration of organic solvent, such as by adding an
additional amount of water, organic solvent is believed to be drawn
from the propellant grain, leaving water. Due to low solubility of
propellant in water, this is believed to induce phase separation
between propellant and water or a water phase, causing the
formation of small water droplets in a propellant matrix.
[0073] The slurry or mixture may be agitated for 0-90 minutes, such
as 10-60 minutes, before organic solvent is removed, such as by
evaporation, distillation and/or heating. If the slurry or mixture
is agitated for too long, then the burn rate of the propellant
grains will become undesirably high due to too large a decrease in
density of the propellant.
[0074] It is preferred that substantially all of the organic
solvent is removed. The removal of organic solvent may involve
distillation. The temperature at which distillation is performed
may depend on the type of organic solvent that is used, but can
typically be in the range of 80-105.degree. C., such as
90-99.degree. C. Typically, the distilling temperature is below the
boiling point of water.
[0075] Finally, the propellant grains are dried to remove water.
Drying may involve heating, but removing water by other means, such
as filtration, is also considered a form of drying.
[0076] The surface modification treatment that is required in
accordance with the invention causes a physical-chemical change in
the structure of a part (the surface layer) of the propellant
grains. Accordingly, the treated propellant grains of the invention
may be structurally distinguished from non-treated propellant
grains. This may, for instance, be determined using scanning
electron microscopy.
[0077] For small and medium calibre weapons, the propellant charge
of the invention may either be in the form of a spherical
propellant charge having multiple spherical propellant grains, or
small cylindrical grains. Spherical propellant grains are typically
small spherical balls of propellant material. Cylindrical grains
may be provided with longitudinal perforations.
[0078] For larger calibre weapons, the propellant charge typically
comprises cylindrical grains with an external diameter of, for
example, 1-20 mm, preferably 3-15 mm. The propellant grain geometry
can also be different. For example, it can have a rosette shape or
a hexagonal shape. The propellant grains may be provided with
longitudinal perforations. The number of perforations in the
propellant grain is dependent on the gas evolution rate desired.
Advantageously, the propellant grains are provided with 7 to 19
holes extending through in axial direction. The ratio of propellant
grain length to propellant grain diameter is normally in the range
of 0.3-5.0, preferably 0.8-2.5. The ratio of the hole diameter to
the grain diameter is normally in the range of 0.01-0.5, for
example, and in particular in the range of 0.03-0.2.
[0079] Untreated extruded propellant grains can be produced in a
manner known in the art by compressing a solvent-containing or
solvent-free propellant powder dough or propellant powder pack with
or without additive in an extruder or by means of extrusion.
Untreated ball propellant grains can be produced in a manner known
in the art in a slurry-in-water process.
[0080] In a further aspect, the invention is directed to a
combination of a propellant charge and a primer, wherein said
propellant charge is a propellant charge according to the
invention. The amount of said primer can be in the range of 1-10%
by total weight of the main propellant charge, preferably 1.5-9%,
such as 2-8%.
[0081] The function of the primer is to generate gaseous products
and/or hot particles. It has been found advantageous in terms of
the invention to use the propellant charge of the invention in
combination with a strong primer charge, which produces a larger
amount of gases than usual. Primer strength may, for instance, be
expressed as the time that is required from the first gas
generation of the primer until 10% of the total pressure has built
up. In accordance with the invention this time may be in the range
of 0.2-10 ms, such as 0.5-20 ms instead of 1-50 ms for usual
systems. This required time from the first gas generation of the
primer until 10% of the total pressure has built up depends on
calibre. For example, for medium calibre munition (such as 35 mm
munition) this time can be in the range of 0.2-5 ms, such as 1.5-3
ms. For large calibre munition (such as 127 mm calibre) this time
can be in the range of 5-50 ms, such as 8-15 ms.
[0082] In yet a further aspect, the invention is directed to a
firearms cartridge comprising a combination of a propellant charge
and a primer as described herein.
[0083] In yet a further aspect, the invention is directed to a
method for modifying the surface of propellant grains, wherein said
method comprises the successive steps of
[0084] suspending propellant grains in water to prepare a
slurry,
[0085] adding an organic solvent to the propellant grains before,
after and/or during the preparation of the slurry,
[0086] mixing the slurry that comprises water and organic solvent
for a period of 120 minutes or less,
[0087] optionally removing water and/or organic solvent,
[0088] lowering the concentration of organic solvent,
[0089] removing organic solvent, and
[0090] drying the propellant grains to remove water.
[0091] In yet a further aspect, the invention is directed to a
method for modifying the surface of propellant grains, wherein said
method comprises the successive steps of
[0092] wetting propellant grains with water or water vapour,
[0093] adding an organic solvent to the propellant grains before,
after and/or during the wetting of the propellant grains,
[0094] allowing the wet propellant grains and the organic solvent
to interact for a period of 120 minutes or less,
[0095] optionally removing water and/or organic solvent,
[0096] lowering the concentration of organic solvent,
[0097] removing organic solvent, and
[0098] drying the propellant grains to remove water.
[0099] Details of these methods are as described above for the
propellant charge of the invention.
[0100] Using this method, it is possible to prepare a propellant
charge according to the invention by subjecting part of the
propellant grains that are used for preparing the propellant charge
to the described method. Hence, in an additional step of the above
two methods for modifying the surface of propellant grains, the
resulting modified propellant grains can be mixed with non-modified
propellant grains to prepare a propellant charge according to the
invention.
[0101] The method is a cheap and easily reproducible method for
surface treatment of propellant charges.
[0102] The invention has been described by reference to various
embodiments, compositions and methods. The skilled person
understands that features of various embodiments, compositions and
methods can be combined with each other. For instance, preferred
coating compositions can be used in the various methods, in the
same way preferred steps of a method can be combined with each
other and with preferred coating compositions.
[0103] All references cited herein are hereby completely
incorporated by reference to the same extent as if each reference
were individually and specifically indicated to be incorporated by
reference and were set forth in its entirety herein.
[0104] 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 claims) are to be construed to cover both the
singular and the plural, unless otherwise indicated herein or
clearly contradicted by context. The terms "comprising", "having",
"including" and "containing" are to be construed as open-ended
terms (i.e., meaning "including, but not limited to") unless
otherwise noted. Recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually
to each separate value falling within the range, unless otherwise
indicated herein, and each separate value is incorporated into the
specification as if it were individually recited herein. The use of
any and all examples, or exemplary language (e.g., "such as")
provided herein, is intended merely to better illuminate the
invention and does not pose a limitation on the scope of the
invention unless otherwise claimed. No language in the
specification should be construed as indicating any non-claimed
element as essential to the practice of the invention. For the
purpose of the description and of the appended claims, except where
otherwise indicated, all numbers expressing amounts, quantities,
percentages, and so forth, are to be understood as being modified
in all instances by the term "about". Also, all ranges include any
combination of the maximum and minimum points disclosed and include
any intermediate ranges therein, which may or may not be
specifically enumerated herein.
[0105] Preferred embodiments of this invention are described
herein. Variation of those preferred embodiments may become
apparent to those of ordinary skill in the art upon reading the
foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject-matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context. The
claims are to be construed to include alternative embodiments to
the extent permitted by the prior art.
[0106] For the purpose of clarity and a concise description
features are described herein as part of the same or separate
embodiments, however, it will be appreciated that the scope of the
invention may include embodiments having combinations of all or
some of the features described.
[0107] The invention will now be further illustrated by the
following examples, which are not intended to limit the scope of
protection in any manner.
EXAMPLES
Example 1-Spherical propellant grains (10 wt. % of
nitroglycerine)
[0108] Spherical propellant grains containing 10 wt. % of
nitroglycerine and nitrocellulose and additives were suspended in a
3:1 weight ratio mixture of ethanol and water to prepare a slurry.
The slurry was mixed for 30 minutes. The concentration of organic
solvent was lowered by evaporation of organic solvent. The
spherical propellant grains were then dried in air. The spherical
propellant grains before treatment were compared with the surface
treated spherical propellant grains.
[0109] Scanning electron microscope images of this comparison are
shown in FIG. 1. The picture shown in FIG. 1A shows microscopic
images of the spherical propellant grains before treatment, whereas
the picture shown in FIG. 1B shows microscopic images of the
spherical propellant grains after treatment. Clearly, the treatment
has structurally changed the spherical propellant grains.
Example 2-Extruded double base propellant grains (nitroglycerine
and diethyleneglycol dinitrate)
[0110] Extruded double base propellant grains containing
nitroglycerine and diethylene glycol dinitrate were suspended in a
1:1 weight ratio mixture of acetone and water to prepare a slurry.
The slurry was mixed for 30 minutes. The concentration of organic
solvent was lowered by evaporation of organic solvent. The
spherical propellant grains were then dried in air. The extruded
double base propellant grains before treatment were compared with
the surface treated extruded double base propellant grains.
[0111] Scanning electron microscope images of this comparison are
shown in FIG. 2. The pictures shown in FIGS. 2A and 2B show
microscopic images of the extruded double base propellant grains
before treatment, whereas the pictures shown in FIGS. 2C and 2D
show microscopic images of the extruded double base propellant
grains after treatment. Clearly, the treatment has structurally
changed the extruded double base propellant grains.
Example 3-Film of material of spherical propellant grains (10 wt. %
of nitroglycerine)
[0112] Spherical propellant grains containing 10 wt. % of
nitroglycerine and nitrocellulose and additives as used in example
1 were dissolved in acetone. A film of the propellant material was
prepared by evaporation of the acetone. This film was used for
subsequent treatment.
[0113] Part of the film was submersed in a 1:1 weight ratio mixture
of acetone and water for a period of 30 minutes. Thereafter, the
film was dried in air.
[0114] Scanning electron microscope images were made showing the
boundary line between the untreated part and the treated part of
the film, as shown in FIGS. 3A and 3B. Clearly, the treatment has
structurally changed the material of the spherical propellant
grains. The same structural change is expected to occur on
spherical propellant grains that are subjected to the treatment of
the invention.
Example 4-Film of material of extruded double base propellant
grains (nitroglycerine and diethyleneglycol dinitrate)
[0115] Extruded double base propellant grains containing
nitroglycerine and diethylene glycol dinitrate as used in example 2
were dissolved in acetone. A film of the propellant material was
prepared by evaporation of the acetone. This film was used for
subsequent treatment.
[0116] Part of the film was submersed in a 1:1 weight ratio mixture
of acetone and water for a period of 30 minutes. Thereafter, the
film was dried in air.
[0117] Scanning electron microscope images were made showing the
boundary line between the untreated part and the treated part of
the film, as shown in FIG. 4. Clearly, the treatment has
structurally changed the material of the extruded double base
propellant grains propellant grains. The same structural change is
expected to occur on extruded double base propellant grains that
are subjected to the treatment of the invention.
Example 5-12.7 mm ammunition with spherical double base
[0118] Temperature dependency of untreated and treated propellant
grains was determined by measuring projectile velocity of munition
fired from a conventional 12.7 mm caliber barrel weapon as a
function of temperature. The munition was filled with double base
propellant having a spherical propellant grain geometry. The
treated part of the propellant mixture of untreated and treated
propellant had been treated with an ethyl acetate-water mixture.
The treated part of the propellant mixture of untreated and treated
propellant had been treated by suspending propellant grains in
water, adding ethyl acetate to the obtained slurry, mixing this
slurry for 1 hour, lowering the concentration of ethyl acetate by
adding more water, distilling off the ethyl acetate, and drying the
treated propellant. FIG. 5 shows the resulting graph in which the
projectile velocity in case of the treated propellant grains is
clearly less dependent on temperature than the projectile velocity
in case of the untreated propellant grains.
Example 6-25 mm ammunition with extruded single perforated single
base propellant
[0119] Temperature dependency of untreated and treated propellant
grains was determined by measuring projectile velocity of munition
fired from a conventional 25 mm caliber barrel weapon as a function
of temperature. The munition was filled with extruded single base
propellant with a single perforated propellant grain geometry. The
treated part of the propellant mixture of untreated and treated
propellant had been treated by wetting propellant grains with an
ethanol-water mixture during 30 minutes in a rotating drum after
which the solvent and the water were removed by drying. FIG. 6
shows the resulting graph in which the projectile velocity in case
of the treated propellant grains is clearly less dependent on
temperature than the projectile velocity in case of the untreated
propellant grains.
* * * * *