FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to pyrophoric pellets that can be used as countermeasures
for protecting against incoming missile threats. When exposed to the atmosphere, the
pyrophoric pellets spontaneously break apart into individual particulates or agglomerates
and emit infrared radiation.
BACKGROUND
[0002] Military missiles, such as air-to-air and surface-to-air guided missiles, are designed
to pursue infrared (IR) radiation emitted by a target, for example, an enemy aircraft,
ground vehicles, ships, etc. Flares that emit IR radiation (IR decoys) are therefore
used as countermeasures to protect against incoming missiles. IR decoys can also be
used pre-emptively to prevent the detection of a target. The IR radiation emitted
by the decoy confuses the missile; the missile mistakes the IR radiation emitted by
the decoy as the target and pursues the decoy (or the IR radiation emitted by the
decoy) instead of pursuing the target, thereby sparing the target.
[0003] For example,
US 4,880,483 A describes a fine activated powder, which when discharged into the air forms a warm
cloud that settles very slowly and decoys heat-seeking missiles. IR decoys are designed
to be dispensed from cases that are standardized in size and shape for use in existing
dispensing systems. As such, the design of IR decoys has been restricted to these
predetermined sizes and shapes, which has limited the types of IR radiation profiles
that can ultimately be realized. For example, some techniques utilize stacks of pyrophoric
materials housed in square, rectangular, or circular shaped cartridges that were held
in correspondingly shaped dispensers, for example, dispensers on an aircraft. Advancement
of missile technology, however, has resulted in the development of missiles capable
of identifying a target's unique IR signature and distinguishing it from the IR radiation
emitted from typical decoys. Therefore, the development of IR decoys that are attractive
to advanced missile seekers is needed. It is necessary to design the IR decoy such
that the resulting signature(s) ensure that the approaching missile mistakes the decoy
for the target.
[0004] Designing IR decoys having specialized IR signatures has been challenging. Merely
increasing the amount of an illuminant is not always an option due to the predetermined
sizes and shapes required for existing dispensing systems. Also, the reactive materials
often used in these decoys include thin metal foils coated with self-igniting, pyrophoric
coatings. These pyrophoric foils are often lightweight and have a high surface-to-volume
ratio and therefore experience significant drag, limiting the speed and the distance
of travel.
SUMMARY OF THE DISCLOSURE
[0005] The pyrophoric pellets of the present invention create one or more clouds of IR radiation.
[0006] Upon deployment into the atmosphere, the pellets self-ignite and break apart into
individual particulates or agglomerates (i.e., the pellets disintegrate), and IR radiation
is released during the process. The pellets are designed to be kinematic or pseudo-kinematic,
producing one or more infrared (IR) radiation emitting clouds that give the appearance
of a moving target. Depending on the mechanism of deployments, the clouds produced
by the pellets can be distributed in 3-dimensional space, in both the direction of
deployment and perpendicular to the direction of deployment. The pellets are easily
propelled along their trajectory because they have sufficient mass and a low surface
area-to-volume ratio. Large and intense IR clouds are produced from comparatively
small pyrophoric pellets. The pyrophoric pellets typically include:
- pyrophoric particles;
- thermally expandable particles that are suitable to undergo volume expansion upon
reaching a temperature of at least 50°C, the volume expansion being at least 3 times
the particles' unexpanded volume;
- optionally, one or more additives that modify IR signature; and
- optionally, one or more additives that produce smoke at a temperature of 150°C or
greater.
[0007] The pyrophoric pellets are unique in that they can be formulated to provide an unlimited
number of different IR signatures, cloud shapes, and intensities. By varying the composition
of the pellets, outputs in the various signature regions can be either strengthened
or eliminated. A pyrophoric material can have signatures in the ultraviolet (UV),
visible, near IR (NIR), midwave IR (MWIR) and longwave IR (LWIR). Alternatively, it
is possible to exclude the signature(s) in one or more of these regions by changing
the composition of the pellet. In some cases, it may be desired to provide signatures
only in the MWIR and LWIR. Developments in missile technology have enabled guidance
systems of missiles to discriminate and reject signatures of some conventional flares
utilized in defensive countermeasures. These counter-countermeasure discriminators
may be based on one or multiple properties of the signature, including spectral, temporal,
and kinematic characteristics. Any detected signal that causes the decoy to be ignored
by the missile's guidance system will render the decoy ineffective. The pellets of
the instant case are particularly beneficial because they can be specifically formulated
to provide spectral, temporal, and kinematic signatures that can be designed to defeat
these advanced counter-countermeasures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Implementations of the present technology will now be described, by way of example
only, with reference to the attached figures, wherein:
FIG. 1 shows the speed at which pellets according to the disclosure self-ignited and
emitted IR radiation upon exposure to the atmosphere.
[0009] It should be understood that the various aspects are not limited to the arrangements
and instrumentality shown in the drawings.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0010] The pyrophoric pellets of the present invention include a unique combination of components
that allow the pellets to spontaneously ignite when exposed to the atmosphere, break
apart into individual particulates or agglomerates (i.e., disintegrate), and emit
IR radiation.
[0011] According to a first aspect of the invention, a pyrophoric pellet according to claim
1 is provided, which includes:
- (a) about 35 to about 95 wt.% of pyrophoric particles;
- (b) about 0.05 to about 30 wt.% of thermally expandable particles that are suitable
to undergo volume expansion upon reaching a temperature of at least 50°C, the volume
expansion being at least 3 times the particles' unexpanded volume;
- (c) optionally, about 1 to about 40 wt.% of one or more additives that modify infrared
radiation signature, preferably selected from magnesium, zirconium, zinc, titanium,
aluminium, iron, SnCl2, organic compounds, and a mixture thereof; and
- (d) optionally, one or more additives that produce smoke at a temperature of 150°C
or greater, preferably selected from white phosphorous, red phosphorous, hexachloroethane,
terephthalic acid, an organic compound, an organic dye, and a mixture thereof
preferably wherein the pyrophoric particles have a mean particle size of about 1 nm
to about 250 µm,
preferably wherein the thermally expandable particles are selected from thermally
expandable microspheres, thermally expandable graphite, and a mixture thereof.
[0012] Preferred embodiments are disclosed in the dependent claims.
[0013] According to a second aspect of the invention, a method for making a pyrophoric pellet
according to claim 15 is provided.
[0014] The ingredients of the pellets are typically uniformly combined prior to compression
into a pellet and are therefore substantially uniformly dispersed amongst each other
throughout the body of the pellet. In other words, the pellet typically comprises
a substantially homogenous mixture of components. The powder mixture may be compressed
into a pellet by any one of several consolidation methods, including in a simple die
press. The compression force is chosen such that the resulting pellet is strong, but
is not so compressed that the pyrophoric nature of the particles is destroyed.
[0015] Preferably, the pellets may include compressed metal foam. A metal foam is a cellular
structure of a metal material (frequently aluminium) with gas or air-filled pores
defining a large portion of the volume. A defining characteristic of metal foam is
high porosity. Typically, only about 5% to about 40% (or about 5% to about 25%) of
the volume of the metal foam is a metal material. Metal foams can be open-cell or
closed-cell. Typically, open-cell metal foams are preferable for the instant application
but certainly not required, as closed-cell metal foams are also useful. The metal
foam may be composed of a single metal, multiple metals, metal alloy(s), etc., and
may be a composite metal foam. Non-limiting examples of metal foams include aluminium
metal foams, titanium metal foams, tantalum metal foams, etc.
[0016] It is preferred that one or more ingredient of the pellets described above (e.g.,
components (a), (b), (c), and/or (d)) can be combined with the metal foam or impregnated
into the metal foam, and the combination pressed into a pellet. Metal foams can be
useful for providing mechanical strength to the pellets. The metal material from the
metal foam may form about 5 to about 50 by weight of the compressed pellet. In other
words, in instances where the pellets are made using a metal foam, about 5 to about
50 wt.% of the compressed pellet may be due to the metal material of the foam. Preferably,
the compressed metal foam forms about 5 to about 40 %, about 5 to about 30 %, about
5 to about 25% or about 5 to about 20 %, or about 5 to about 10 % of the weight of
the pellets.
[0017] Upon deployment into the atmosphere, the outside surface of the pellet is first exposed
to oxygen and the pyrophoric particles at the surface of the pellet ignite. The ignition
of the pyrophoric particles at the surface of the pellet causes heat, which results
in the thermally expandable particles at or near the surface of the pellet to activate
(to expand) resulting in the outermost part of the pellet breaking apart. As the outermost
part of the pellet breaks away, the underlying area becomes the outermost part of
the pellet and is exposed to the atmosphere, ignites, and breaks away. The process
continues until the entirety of the pellet disappears. This continuous process has
the advantage of providing a traveling thermal signature as opposed to cloud that
emanates from a single point.
[0018] The time from initial exposure to the atmosphere until complete disintegration of
a pellet can vary depending on the desired result (e.g., the desired shape of the
IR cloud, the desired length of burn, etc.) and based on the construction of the pellet
(e.g., the size, shape, compressive force, and content of the pellet). Nonetheless,
the pellets typically break apart relatively quickly, for example, within about 15
seconds from deployment into the atmosphere. Preferably, the pellet disintegrates
within about 12 seconds, about 10 seconds, about 8 seconds, 6 seconds, 5 seconds,
4 seconds, 2 seconds, or 1 second. Particularly preferably, the pellets may break
apart in about 100 milliseconds (ms) to about 15 seconds, about 100 ms to about 12
seconds, about 100 ms, to about 10 seconds, about 100 ms to about 8 seconds, about
100 ms to about 5 seconds, about 100 ms to about 2 seconds, about 500 ms to about
10 seconds, about 500 ms to about 8 seconds, about 500 ms to about 5 seconds, about
500 ms to about 2 seconds, after deployment into the atmosphere. In some cases, however,
the pellet can be purposely designed as "delayed-release" or a "time-release" pellet,
such that the pellet does not immediately ignite upon exposure to the atmosphere,
but ignites at a predetermined time after deployment. This can be accomplished, for
example, by using one or more coatings on the pellet that delay ignition. Furthermore,
the pellet can be designed such that a single pellet releases one IR cloud or multiple
IR clouds. Multiple IR clouds can be achieved by the use of one or more intermediate
layers within the core of the pellet that interrupt the continuous burn of the pellet,
or by forming a single pellet from a plurality of pellets that will break apart and
each individually release independent clouds of IR radiation.
[0019] The size and shape of the pellets can vary. The pellets may be spherical, tablet-shaped
or disk shaped, square, rectangular, conical, pyramidal, cylindrical, etc. In some
instances, it can be useful for the pellets to be a shape and size that is compatible
with existing countermeasure launching equipment. This eliminates the need for reconfiguring
or replacing existing equipment required for deployment. The pellets of the instant
case can be formed in a size and shape according to a desired effect and current needs.
Pellets with higher surface areas will burn faster than pellets with less surface
area. Similarly, a larger pellet will release a greater total amount of IR radiation
than a smaller pellet, but may burn more slowly and for a longer duration. One way
to create additional surface area for a given pellet size is to create additional
access to air to the internal portion of the pellet, such as by drilling holes that
pass through the entirety of the pellet.
[0020] Preferably, a plurality of small pellets may be combined in a unit or package for
deployment together. Advantageously, the surface area of a plurality of small pellets
is large and therefore the simultaneous deployment of a plurality of small pellets
will quickly react with the environment to form an intense single cloud, or multiple
clouds of IR radiation. Multiple pellets (e.g., two or more pellets) may be bound
together for simultaneous launching into the atmosphere. For example, multiple pellets
may be pressed together to form a conglomerate of pellets (a larger pellet that comprises
multiple pellets) or multiple pellets may be bound together using an adhesive material
such as a polymeric binder, etc. A coating may optionally be applied to prevent the
conglomerate of pellets from igniting when initially deployed into the atmosphere.
An explosive charge and/or mechanical device may be incorporated into the conglomerate
of pellets that causes the conglomerate of pellets to break apart at a predetermined
time after launch. The internal charge and/or mechanical device can break apart the
conglomerate of pellets with a force sufficient to cause the individual pellets to
blow apart from each other into multiple directions. Similarly, a mechanical device
may be used as a decoy, wherein the mechanical device houses multiple pellets (e.g.,
two or more pellets). The mechanical device can protect pellets from exposure to the
atmosphere until a predetermined time after launch, and may include one or more mechanisms
to expel the pellets. For example, the mechanical device may include a charge or a
spring mechanism that shoots or forces the pellets from the device into multiple directions.
[0021] The density of the pellets depends on the density of the individual components as
well as the compression force that is used to consolidate the pellet. Typical densities
are in the range of about 0.5 g/cm3 to about 5 g/cm3. Preferably, the density may
be in the range of about 0.5 to about 4 g/cm3, about 0.5 to about 3 g/cm3, about 0.5
to about 2.5 g/cm3, about 1 to about 5 g/cm3, about 1 to about 4 g/cm3, about 1 to
about 3 g/cm3, about 1 to about 2.5 g/cm3, or about 1 to about 2 g/cm3. To increase
the density so as to improve the trajectory and/or distance of travel, high density
powder components can be incorporated into the pellet. Examples of these include tungsten,
molybdenum, hafnium, copper, nickel, and cobalt.
[0022] Regardless of the exact shape of the pellets, the size of the pellets can vary greatly.
For example, in some cases, it may be desirable for the pellet to be relatively large,
having a maximum height of about 2 cm to about 30 cm (about 1 inch to 12 inches),
a maximum width of about 2 cm to about 30 cm (about 1 inch to 12 inches), and a maximum
length of about 2 cm to about 30 cm (about 1 inch to 12 inches). In some cases, it
may be desirable for the pellets to be relatively small, having a maximum height of
about 2 mm to about 25 mm (about 0.1 inch to about 1 inch), a maximum width of about
2 mm to about 25 mm (about 0.1 inch to about 1 inch), and a maximum length of about
2 mm to about 25 mm (about 0.1 inch to about 1 inch). Similarly, in some instances,
the pellets may have a maximum height of about 12 mm to about 100 mm (about 0.5 inches
to about 4 inches), a maximum width of about 12 mm to about 100 mm (about 0.5 inches
to about 4 inches), and a maximum length of about 12 mm to about 100 mm (about 0.5
inches to about 4 inches).
Pyrophoric Particles
[0023] The term "pyrophoric" is used herein to refer to an ability to spontaneously ignite
upon exposure to air of the environment; it reacts spontaneously on contact with atmospheric
oxygen. It does not refer to the spark-generating character of certain alloys when
they are struck or filed. A "pyrophoric material" is a material that ignites spontaneously
in air at or below 55 °C (130 °F). The term "pyrophoric particles" refers to particles
of pyrophoric material, i.e., small fragments or units (less than 1 mm in diameter
of pyrophoric materials).
[0024] The pyrophoric particles can be produced, for example, by the grinding, crushing,
or disintegration of a solid substance. Pyrophoric particles may also be referred
to as "pyrophoric powder." The pyrophoric particles typically have an average particle
size of about 1 nm to about 1 mm. Preferably, the average particle size is about 10
nm to about 500 µm, about 100 nm to about 100 µm, about 500 nm to about 10 µm. The
average particles size may be in the nanometer range or the micrometer range.
[0025] Preferably, the average particle size of the pyrophoric particles is in the nanometer
range, e.g., from about 1 nm to about 1 µm, about 10 nm to about 1 µm , about 50 nm
to about 1 µm, about 100 nm to about 1 µm, about 200 nm to about 1 µm, about 500 nm
to about 1 µm, about 1 nm to about 500 nm, about 1 nm to about 400 nm, about 1 nm
to about 300 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 50
nm to about 500 nm, or about 50 nm to about 250 nm.
[0026] Preferably, the average particle size of the pyrophoric particles is in the micrometer
ranges, e.g., about 1 µm to about 1 mm, about 1 µm to about 500 µm, about 1 µm to
about 250 µm, about 1 µm to about 100 µm, about 1 µm to about 50 µm, about 1 µm to
about 25 µm , about 5 µm to about 1 mm, about 5 µm to about 500 µm, about 5 µm to
about 250 µm, about 5 µm to about 100 µm, about 5 to about 50 µm, about 5 to about
25 µm, about 10 to about 1 mm, about 10 µm to about 500 µm, about 10 to about 250
µm, about 10 to about 100 µm, about 10 to about 50 µm, about 10 to about 25 µm, or
about 10 µm to about 20 µm.
[0027] Non-limiting examples of pyrophoric materials that can be used for the pyrophoric
particles include: organo-metallic reagents (e.g., Grignard reagents), alkali earth
elements (e.g., sodium, potassium, caesium), metals (e.g., Raney nickel, aluminium
powder, zinc powder), metal hydrides (e.g., sodium hydride, germane, lithium aluminium
hydride), alkyl metal hydrides (e.g., butyllithium, trimethylaluminum, triethylboron),
metal carbonyls (e.g., nickel carbonyl, iron pentacarbonyl), and silicone halides
(e.g., dichloromethylsilane).
[0028] Preferably, activated metals are particularly useful as pyrophoric particles. An
"activated metal" is a metal or metal alloy that has been treated to ensure it is
pyrophoric, for example, treated with an alkaline material that selectively extracts
an alloying component to increase surface area. Activated metals can be prepared from
metal alloys (such as Raney alloy). Common metals include, but are not limited to
nickel, cobalt, copper, iron or mixtures thereof. Aluminium is often used as the alloying
component because it is soluble in alkalis, but other components may also be used,
in particular zinc and silicon or mixtures of these either with or without aluminium.
The metal alloy can be finely milled if it has not already been produced in the desired
particulate form during preparation. The aluminium (or other alloying component) is
then partly or totally removed by extraction with alkalis such as, for example, a
caustic soda solution (other bases such as KOH are also suitable) to activate the
alloy powder. Following extraction of the aluminium, the remaining activated power
has a high specific surface area (BET), for example, between 5 and 150 m
2/g, and is rich in active hydrogen. Accordingly, the pyrophoric pellets of the instant
disclosure preferably include pyrophoric particles (pyrophoric powder) comprising
an activated metal, for example, activated iron, activated nickel, activated copper,
activated cobalt, activated magnesium, activated zirconium, an activated alloy of
iron, an activated alloy of nickel, an activated alloy of copper, an activated alloy
of cobalt, an activated alloy of magnesium, an activated alloy of titanium, an activated
alloy of zirconium, and a mixture thereof.
[0029] One method for manufacturing pyrophoric metal particles such as iron or nickel (or
Raney nickel) involves crushing a nickel/aluminium or iron/aluminium alloy to a fine
powder, which is then treated with a caustic soda (NaOH) solution in order to remove
the aluminium. This leaves a highly porous, un-oxidized iron or nickel powder of large
surface area. The surfaces of these powders are extremely reactive and, when the particles
are washed to remove the caustic soda/by-products and then dried, they will oxidize
very rapidly in air attaining temperatures of around 1000°C.
[0030] The pyrophoric particles can also be recovered from metal-supported pyrophoric coatings.
A pyrophoric coating is formed on the metal substrate, which is subsequently mechanically
removed in the form of a powder. The metal-supported pyrophoric coating can be prepared
by applying to the surface of the metal an aluminium powder or a mixture containing
aluminium powder and one or more additional metal powders, for example, iron, nickel,
cobalt, boron and copper. The aluminium powder or mixture of aluminium powder with
other metal powders (such as iron powder) used to form the aluminide coating on the
surface of the substrate can be applied as a dispersion or slurry of the metal powder(s)
in a liquid. The liquid may include a binder and a solvent, which may be an organic
solvent or water. Examples of preferred binder/solvent systems are nitrocellulose/acetone
systems, acrylate resin/acetone systems and polyvinyl alcohol/water/normal propanol
systems. The dispersion or slurry of the metal powder(s) in a liquid can be applied
to the substrate by dipping, spraying, painting, coating or any other suitable technique
for applying a coating of a dispersion or slurry to a substrate. When additional substances
are added with the aluminium, such as the above-described substances (e.g., at least
one of titanium, zirconium, boron, chromium, tantalum, phosphorous, manganese, iron,
nickel, cobalt and copper), the additional substances are generally added in amounts
of from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, based on the weight
of the aluminium that was applied to the surface of the substrate.
[0031] Powdered lithium is a particularly useful material, inasmuch as powdered lithium
ignites in air at a very low temperature. It also has an extremely low specific gravity
so that pellets containing it are lighter than they would be if they contained other
easily-ignited materials like zirconium. Lithium is also a very soft material so that
when formed into a pellet, it can slightly flow and help anchor in place adjacent
particles of other materials. Powdered sodium, powdered potassium and powdered rubidium
behave very much like powdered lithium and are useful.
[0032] Powdered boron is known to have an extremely large thermal output per unit bulk,
and is accordingly also a very desirable pyrophoric material. To ensure that particles
of boron are pyrophoric, the boron it can be combined with other pyrophoric materials
such as pyrophoric iron powder. When powdered lithium or other alkali metals are mixed
with pyrophoric iron, it reduces the total energy output per unit bulk, and therefore
is best used in pellets that contain powdered boron combined with other pyrophoric
powders.
[0033] Preferably, the pyrophoric particles are pyrophoric iron particles, pyrophoric nickel
particles, or a mixture thereof. The pyrophoric iron particles, the pyrophoric nickel
particles, or the mixture thereof may also be alloyed with boron, for example about
1 to about 10 wt.%, about 1 to about 5 wt.%, or about 1 to about 3 wt.% of boron,
based on the total weight of the pyrophoric particles.
[0034] Preferably, the pyrophoric particles may be derived from the pyrophoric materials
(referred to as "Special Materials") disclosed in
U.S. Patent Nos. 4,435,481,
4,895,609,
4,957,421,
5,182,078,
6,093,498, and
6,193,814, which are incorporated herein by reference.
[0035] The total amount of pyrophoric particles in the pyrophoric pellets can vary depending
on the desired burn rate, IR intensity, cloud volume, etc., but is typically in an
amount of about 35 to about 95 wt.%, based on the total weight of the pyrophoric pellets.
Preferably, the total amount of pyrophoric particles in the pyrophoric pellets is
about 40 to about 90 wt.%, about 45 to about 90 wt.%, about 50 to about 90 wt.%, about
35 to about 85 wt.%, about 40 to about 85 wt.%, about 45 to about 85 wt.%, about 50
to about 85 wt.%, about 35 to about 80 wt.%, about 40 to about 85 wt.%, about 45 to
about 80 wt.%, or about 50 to about 80 wt.%, based on the total weight of the pyrophoric
pellets.
Thermally Expandable Particles
[0036] "Thermally expandable particles" are particles that undergo volume expansion upon
reaching a threshold temperature and are capable of substantially retaining their
expanded structure. The onset temperature required to potentiate volume expansion
is typically at least 50°C, although higher temperatures are common and in some cases
preferable. For example, the onset temperature for expansion may be about 60°C, about
100°C, about 150°C, about 200°C, about 250°C, or higher, but is typically not higher
than about 250°C or 300°C. The degree of expansion is significant. For example, the
particles typically expand from their initial size to have final volume that is multiple
times that of the unexpanded volume, for example, 3, 10, 50, 100, 150, 200, 250, or
300 or more times greater than the unexpanded volume. The particles may expand from
their initial size to have a final volume that is 3 to 400 times, 10 to about 400
times, 50 to 400 times, 100 to 400 times 150 to 400 times, 200 to 400 times, 250 to
400 times, 300 to 400 times, 3 to 350 times, 10 to 350 times, 100 to 350 times, 150
to 350 times, 200 to 350 times, or 250 to 300 times greater than the unexpanded volume.
[0037] Non-limiting examples of thermally expandable particles include thermally expandable
microspheres, thermally expandable graphite, and mixtures thereof.
Thermally Expandable Microspheres
[0038] Preferably, the thermally expandable particles are thermally expandable microspheres.
Non-limiting examples of thermally expandable microspheres include those that enclose
a substance that expands by heating (such as isobutane, propane, and/or pentane) in
an elastic shell. The shell of the thermally expandable microsphere is typically formed
with a thermoplastic substance, a heat-melting substance, a substance that ruptures
by thermal expansion, or the like, and in particular, a polymeric shell. Moreover,
non-limiting examples of substances that form the shell of the thermally expandable
microspheres include vinylidene chloride-acrylonitrile copolymers, polyvinyl alcohols,
polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride,
and polysulfone.
[0039] Commercially available products may be used as the thermally expandable microspheres.
Non-limiting examples include: "Matsumoto Microsphere F-30," "Matsumoto Microsphere
F-50," "Matsumoto Microsphere F-80S," and "Matsumoto Microsphere F-85" (made by Matsumoto
Yushi-Seiyaku Co., Ltd.); and "EXPANCEL" (AkzoNobel), and in particular EXPANCEL DU
series, which relates to dry, unexpanded microspheres. In some instances, the thermally
expandable microspheres include those produced by AkzoNobel NV (see, e.g., https://expancel.akzonobel.com/.
Detailed descriptions of various expandable microspheres and their production can
be found in, for example,
U.S. Pat. Nos. 3,615,972,
3,945,956,
4,287,308,
5,536,756,
6,235,800,
6,235,394 and
6,509,384, in
EP 486080,
EP 1054034,
EP 1288272 and
EP1408097, in
WO 2004/072160, and in
Japanese publication laid open No. 1987-286534, which are all incorporated herein by reference.
[0040] The average particle size of the thermally expandable microspheres can vary but is
typically about 1 to about 100 µm. Preferably, the average particle size of the thermally
expandable microspheres is about 1 to about 75 µm, about 1 to about 50 µm, about 2
to about 100 µm, about 2 to about 75 µm, about 2 to about 50 µm, about 5 to about
100 µm, about 5 to about 75 µm , about 5 to about 50 µm, about 5 to about 25 µm, or
about 10 to about 20 µm.
[0041] The onset temperature for expansion is typically about at 50°C but can be much higher,
for example, about 180°C. Typically, the thermally expandable microspheres are expandable
at temperatures from about 80°C to about 235°C (176°F-455°F). When expanded, the microspheres
have a diameter about 3, about 3.5, about 4, or about 5 times their original diameter
resulting in their expanded volume being about 27, about 43, about 64, or about 125
greater than their unexpanded volume. Preferably, the expanded volume is at least
5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 times (up to about 100, 125, or 150
times) greater than the unexpanded volume.
Expandable Graphite
[0042] Preferably, the thermally expandable particles are thermally expandable graphite.
Thermally expandable graphite refers to graphite having a layer lattice structure,
where atoms or molecules (for example, sulfur compounds or nitrogen compounds) may
be incorporated (intercalated) between the layers. Expandable graphite may also be
referred to as expandable flake graphite, intumescent flake graphite, or expandable
flake; and, for the purposes herein, these terms may be used interchangeably. Preferably,
the expandable graphite is intercalated graphite in which an intercallant material
is included between the graphite layers of graphite crystal or particle. Examples
of intercallant materials include halogens, alkali metals, sulfates, nitrates, various
organic acids, aluminium chlorides, ferric chlorides, other metal halides, arsenic
sulfides, and thallium sulfides. It is preferred that the expandable graphite includes
non-halogenated intercallant materials or sulfate intercallants, also referred to
as graphite bisulfate. As is known in the art, bisulfate intercalation is achieved
by treating highly crystalline natural flake graphite with a mixture of sulfuric acid
and other oxidizing agents which act to catalyse the sulfate intercalation. Ideally,
the intercalated compound is located between every monolayer of the graphite but in
reality, however, it is conceivable for certain graphite layers to have no intercalated
compounds.
[0043] On heating, thermally expandable graphite undergoes three-dimensional expansion,
as a result of which the intercalated compound, e.g., nitrogen or sulfur, releases
SO
2 and/or H
2SO
4, and/or derivatives thereof. The onset temperature needed to potentiate volume expansion
is typically at least 50°C, although higher temperatures are common and in some cases
preferable. For example, the onset temperature for expansion may be about 60°C, about
100°C, about 150°C, about 200°C, about 250°C, or higher, but is typically not higher
than about 250°C or 300°C. Preferably, the expandable graphite expands at a temperature
of 130°C or more, 150°C or more, 150°C to 230°C, or 170 to 230°C.
[0044] It is preferred that the expandable graphite may have an onset temperature for expansion
ranging from about 100°C to about 250°C, from about 160°C to about 225°C, or from
about 180°C to about 200°C. Further preferably, the expandable graphite may have an
onset temperature for expansion of at least 100°C, at least 130°C, at least 160°C,
or at least 180°C. Especially preferably, the expandable graphite may have an onset
temperature of at most 250°C, at most 225°C, or at most 200°C. Onset temperature may
also be interchangeably referred to as expansion temperature and also alternatively
referred to as the temperature at which expansion occurs.
[0045] The expandable graphite can have an average pre-expansion particle size of about
0.5 to about 1500 µm, about 10 to about 1500 µm, about 50 to about 1500 µm, about
100 to about 1500 µm, about 150 to about 1500 µm, about 150 to about 1000 µm, or about
150 to about 750 µm. Useful but non-limiting examples of expandable graphite include
Graphite Grade #3772 (Asbury Carbons), having an average pre-expansion particle size
in the range of about 250 µm to about 750 µm, and Graphite Grade #3626 having an average
pre-expansion particle size in the range of about 100 µm to about 300 µm.
[0046] The expandable graphite may have a carbon content in the range of about 80% to about
99%. In some cases, however, the expandable graphite may have a carbon content of
at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least
99% carbon. Similarly, the expandable graphite may have a sulfur content in the range
from about 0% to about 8%, from about 2.6% to about 5.0%, from about 3.0% to about
3.5%. However, the expandable graphite may be characterized as having a sulfur greater
than 0%, at least 2.6%, at least 2.9%, at least 3.2%, or at least 3.5%. Additionally
or alternatively, it is preferred that the expandable graphite may be characterized
as having a sulfur content of at most 8%, at most 5%, or at most 3.5%.
[0047] Advantageously, the expandable graphite has an expansion ratio (cc/g) in the range
from about 10:1 to about 500:1, at least 20:1 to about 450:1, at least 30:1 to about
400:1, or from about 50:1 to about 350:1. The expansion ratio is the quotient of expandable
graphite's post heating expansion volume and original sample mass. The "units" are
reported simply as "expansion ratio", "exfoliation ratio", or "heat expansion". If
one performs a dimensional analysis on the expansion quotient, the units are volume/mass,
which reads like a specific volume. The expandable graphite may have an expansion
ratio (cc/g) of at least 10:1, at least 20:1, at least 30:1, at least 40:1, at least
50:1, at least 60:1, at least 90:1, at least 160:1, at least 210:1, at least 220:1,
at least 230:1, at least 270:1, at least 290:1, or at least 300:1. In some instances,
the expandable graphite may be characterized as having an expansion ratio (cc/g) of
at most 350:1, and in yet other embodiments at most 300:1.
[0048] The total amount of thermally expandable particles in the pyrophoric pellets can
vary but is typically about 0.05 to about 30 wt.%, based on the total weight of the
pyrophoric pellets. Preferably, the total amount of thermally expandable particles
in the pyrophoric pellets is about 0.5 to about 30 wt.%, based on the total weight
of the pyrophoric pellets. The total amount of thermally expandable particles in the
pyrophoric pellets may be about 0.05 to about 25 wt.%, about 0.05 to about 20 wt.%,
about 0.05 to about 15 wt.%, about 0.05 to about 10 wt.%, about 0.5 to about 30 wt.%,
about 0.5 to about 25 wt.%, about 0.5 to about 20 wt.%, about 0.5 to about 20 wt.%,
about 0.5 to about 15 wt.%, about 0.5 to about 10 wt.%, about 1 to about 30 wt.%,
about 1 to about 25 wt.%, about 1 to about 20 wt.%, about 1 to about 15 wt.%, about
1 to about 10 wt.%, about 5 to about 30 wt.%, about 5 to about 25 wt.%, about 5 to
about 20 wt.%, about 5 to about 15 wt.%, or about 5 to about 10 wt.%, based on the
total weight of the pyrophoric pellets.
Additives that Modify IR Signature
[0049] Additives that modify the IR signature are, as the name indicates, for modifying
the IR signature of the pellets. Such additives can be used to enhance the amount
and/or intensity of IR radiation or they may be used to diminish the amount and/or
intensity of IR radiation. Multiple additives may also be used that react with each
other exothermically upon heating, for example, a thermite reaction between aluminium
and iron oxide. Additives that are useful for enhancing the amount and/or intensity
of IR radiation include, for example, materials that undergo an exothermic reaction.
Additives that are useful for diminishing the amount and/or intensity of IR radiation
include, for example, materials that undergo an endothermic reaction or simply act
as a non-reactive heat sink. Additives can also be used to modify aspects of the burn
profile of the pellet such as the rate of heating and the duration of the signature.
[0050] Non-limiting examples of additives that modify IR signature include aluminium, boron,
carbon, lithium, silicon, magnesium, phosphorous, titanium, calcium, zirconium, sulphur,
manganese, cerium, iron, zinc, tungsten, nickel, palladium, platinum, metal sulphide,
a metal hydride, SnCl
2, organic compounds, or a mixture thereof.
[0051] Non-limiting examples of additives that enhance the amount and/or intensity of IR
radiation include aluminium, boron, lithium, magnesium, titanium, zirconium, zinc,
cerium, cobalt, copper, silicon, and vanadium. Non-limiting examples of additives
that diminish the amount and/or intensity of IR radiation include alumina, sodium
bicarbonate, silicon dioxide, silicon carbide, barium sulfate, calcium tungstate,
tantalum, and tungsten. Some additives may act to both enhance and diminish IR radiation
depending on the compound, the other additives in which the compound is combined,
the temperature conditions, etc.
[0052] The total amount of additives that modify IR radiation signature that may be included
in the pellets may vary. Nonetheless, the total amount of additives that modify IR
radiation signature may be about 1 to about 70 wt.%, based on the total weight of
the pellet. Preferably, the total amount of additives that modify IR radiation signature,
if present, is about 1 to about 60 wt.%, about 1 to about 50 wt.%, about 1 to about
45 wt.%, about 1 to about 40 wt.%, about 1 to about 35 wt.%, about 5 to about 70 wt.%,
about 5 to about 60 wt.%, about 5 to about 50 wt.%, about 5 to about 45 wt.%, about
5 to about 40 wt.%, about 5 to about 35 wt.%, about 10 to about 70 wt.%, about 10
to about 60 wt.%, about 10 to about 50 wt.%, about 10 to about 45 wt.%, about 10 to
about 40 wt.%, or about 10 to about 35 wt.%, based on the total weight of the pellet.
[0053] Two or more additives that react exothermically with one another can also be incorporated
into a given pellet composition. In this case, the heat from the pyrophoric reaction
initiates the reaction between these additives. For example, many metals react exothermically
when they form an intermetallic. Examples include but are not limited to aluminide
reactions such as Fe and Al to form either Fe
3Al or FeAI, Ni and Al to form either Ni
3Al or NiAl, or Zr and Al to form ZrAl
2. Heat, and thus IR signature, can also be produced via a thermite reaction between
a metal and a metal oxide such as the reaction between Al and Fe
3O
4 to yield Al
2O
3 and Fe.
Additives that Produce Smoke
[0054] The pellets described throughout the instant disclosure may optionally include one
or more additives that produce smoke. Additives that produce smoke, as the name indicates,
are additives that cause the pellet to produce smoke (smoke that is visible to the
human eye). Non-limiting examples of additives that produce smoke include white phosphorous,
red phosphorous, hexachloroethane, terephthalic acid, organic compounds including
organic dyes, etc. Red phosphorous is often used to produce a white smoke. White smoke
can also be generated from the combustion of aluminium with hexachloroethane and zinc
oxide. Coloured smokes often derive their colour from organic dyes, such as anthroquinone,
quinoline, substituted anthraquinones, substituted quinolone, and mixtures thereof.
[0055] Non-limiting examples of organic additives that produce smoke include triazines (e.g.,
melamine, acetoguanamine, benzoguanamine or blends thereof), imides (e.g., glutarimide,
succinimide and/or its alkyl and alkenyl substituted derivatives, tetrachlorophthalimide,
tetrabromophthalimide, phthlimide and/or its derivatives, trimellitimide and/or its
esters), amides or salts, alkanolamine borate (e.g., triethanolamine borate (TEAB),
triisopropanolamine borate), cyclic phosphate ester (e.g., pentaerythritol phosphate
alcohol, propylene glycol phosphate, neopentyl glycol phosphate and/or its blends
thereof), cationic amine salt (e.g., tetraalkyl ammonium or mixed tetraalkyl/aryl
ammonium, imidazolium or guanidinium nitrate, acetate, benzoate, carbonate, phosphate,
polyphosphate, borophosphate, oxalate & sulfamate salts), cyclic ester (e.g., lactide,
glycolide, caprolactone, gluconolactone, butyrolactone), organic carbonate (e.g.,
trimethylene carbonate, ethylene carbonate, propylene carbonate, glycerin carbonate
and its ester derivatives, and mixtures thereof.
[0056] The total amount of additives that produce smoke that may optionally be included
in the pellets may vary depending on the amount and type of smoke desired. Nonetheless,
the total amount of additives that produce smoke may be about 0.1 to about 40 wt.%,
based on the total weight of the pellet. Preferably, the total amount of additives
that produce smoke is about 0.1 to about 30 wt.%, about 0.1 to about 20 wt.%, about
0.1 to about 10 wt.%, about 0.1 to about 5 wt.%, about 1 to about 40 wt.%, about 1
to about 30 wt.%, about 1 to about 20 wt.%, about 1 to about 10 wt.%, or about 1 to
about 5 wt.%, based on the total weight of the pellet.
Binding Agents
[0057] A binding agent (also referred to as a "binder") may optionally be used in the pellets.
A binding agent may be added, for example, to prevent particles of the pellets from
being easily degraded, e.g., broken down into potentially dangerous dust during the
manufacturing processes. Binding agents may also increase the mechanical strength
of the pellets, such as by cross-linking, and upon curing or aging react to form a
cross-linked network within the pellet, thereby imparting greater mechanical strength,
and aiding in pressing of the composition into a pellet. The binding agent may be
modified through the use of a plasticizer that further aids in processing.
[0058] Preferably, binding agents are preferably combustible and produce low molecular weight
by-products. Binding agents may include inorganic materials such as silica and/or
organic materials such as organic polymers, including combustible organic polymers.
Unlike inorganic binders such as silica, organic polymers do not increase the quantity
of non-expandable solid combustion products. Non-limiting examples of combustible
organic polymer binders include polyvinylchloride, polyvinylacetate, polyvinylalcohol
and/or copolymers thereof, and epoxy or acrylate resin, epoxidized trimethylolpropane,
trimethylol ethane triglycidyl ether, epoxidized soybean oil and mixtures thereof.
Plasticizers may optionally be included with the binding agents. Non-limiting examples
of plasticizers include dioctyl adipate, dioctyl sebacate, hydrocarbon ester tackifier,
and mixtures thereof.
[0059] The total amount of binding agent that may optionally be included in the pellets
may vary. Nonetheless, the total amount of binding agent may be about 0.1 to about
40 wt.%, based on the total weight of the pellet. Preferably, the total amount of
binding agents is about 0.1 to about 30 wt.%, about 0.1 to about 20 wt.%, about 0.1
to about 10 wt.%, about 0.1 to about 5 wt.%, about 1 to about 40 wt.%, about 1 to
about 30 wt.%, about 1 to about 20 wt.%, about 1 to about 10 wt.%, or about 1 to about
5 wt.%, based on the total weight of the pellet.
Coatings
[0060] The pyrophoric pellets of the instant disclosure may optionally be coated with one
or more coatings. A coating may be used for a variety of different reasons. For example,
one or more coatings may be used to delay ignition of the pellet. In other words,
one or more coatings may be applied to the pellet to protect the pyrophoric particles
of the pellet from immediately igniting upon release into the atmosphere, thereby
resulting in a time-release pellet. The coating can be of a quality and in a quantity
such that after release of the coated pellet into the atmosphere, the coating delays
the combustion of the core of the pellet by restricting the amount of oxygen that
is able to immediately reach the pyrophoric particles of the pellet. As small amounts
of oxygen penetrate the coating after deployment into the atmosphere, the core gradually
heats, until a threshold amount of the coating is melted, dissolved, or burnt away.
At this point, the pyrophoric particles can fully ignite, heat, and break apart to
release the intended cloud of IR radiation. Alternatively, a coating may be used merely
to protect the pellet during storage from minor amounts of oxygen that may inadvertently
or unintentionally come into contact with pellet. Such a coating may be of minimal
thickness so as to not substantially alter the function of the pellet during use.
Non-limiting examples of coatings include wax, a polyethylene, a polypropylene, a
polysaccharide, a cellulose (e.g., hydroxypropyl methylcellulose, ethylcellulose,
etc.), polymeric coatings, talc, calcium stearate, and mixtures thereof.
[0061] The pellets themselves can also be produced to have functionally graded layers. For
example, a small pellet can be compressed using a certain powder mixture. Another
powder mixture can then be compressed around this pellet such that the original pellet
is now the core. Several layers can be produced using this method. Optionally, coatings
can be applied between layers of pyrophoric material, such as polymer coatings and/or
coatings of adhesive/binding materials. The IR radiation signature of these multilayer
pellets can change as the pellet travels through the atmosphere because the pellet
reacts (and therefore degrades) from the outside inward.
[0062] Preferably, a pyrophoric pellet may comprise:
- (a) about 35 to about 90 wt.%, preferably about 45 to about 80 wt.%, or more preferably
about 50 to about 80 wt.% of pyrophoric particles, the pyrophoric particles having
a mean particle size of about 1 nm to about 1 µm, about 1 µm to about 250 µm, preferably
about 1 µm to about 150 µm, more preferably about 5 µm to about 100 µm, and being
selected from particles of activated iron, activated nickel, activated copper, activated
cobalt, activated magnesium, activated zirconium, an activated alloy of iron, an activated
alloy of nickel, an activated alloy of copper, an activated alloy of cobalt, an activated
alloy of magnesium, an activated alloy of titanium, an activated alloy of zirconium,
or a mixture thereof;
- (b) about 0.05 to about 30 wt.%, preferably about 1 to about 20 wt.%, more preferably
about 5 to about 15 wt.% of thermally expandable particles that undergo volume expansion
upon reaching a temperature of at least 50°C, the volume expansion being at least
3 times the particles' unexpanded volume, wherein the thermally expandable particles
have a mean particles size of about 0.5 to about 1500 µm before expansion and are
selected from thermally expandable microspheres, thermally expandable graphite, and
a mixture thereof;
- (c) optionally, about 1 to about 40 wt.%, preferably about 5 to about 40, more preferably
about 10 to about 35 wt.% of one or more additives that modify infrared radiation
signature, for example, magnesium, zirconium, zinc, titanium, aluminium, iron, SnCl2, organic compounds, and a mixture thereof; and
- (d) optionally, one or more additives that produce smoke at a temperature of 150°C
or greater.
[0063] As already mentioned throughout the disclosure, the pellet may also optionally include
additional components, such as one or more binding agents, one or more coatings, etc.,
and may be formed in the shapes, sizes, and configurations described throughout the
disclosure.
[0064] Further preferably, a pyrophoric pellet may comprise:
- (a) about 35 to about 90 wt.%, preferably about 45 to about 80 wt.%, or more preferably
about 50 to about 80 wt.% of pyrophoric particles, the pyrophoric particles having
a mean particle size of about 1 nm to about 1 µm, about 1 µm to about 250 µm, preferably
about 1 µm to about 150 µm, more preferably about 5 µm to about 100 µm, and being
selected from particles of activated iron, activated nickel, activated copper, activated
cobalt, activated magnesium, activated zirconium, an activated alloy of iron, an activated
alloy of nickel, an activated alloy of copper, an activated alloy of cobalt, an activated
alloy of magnesium, an activated alloy of titanium, an activated alloy of zirconium,
or a mixture thereof;
- (b) about 0.5 to about 30 wt.%, preferably about 1 to about 20 wt.%, more preferably
about 5 to about 15 wt.% of thermally expandable microspheres, wherein the thermally
expandable microspheres undergo volume expansion upon reaching a temperature of at
least 50°C, preferably at least 70°C, more preferably from 80°C to about 235°C, and
have:
- (i) a mean particle size of about 1 to about 100 µm, preferably about 1 to about 50
µm, more preferably about 5 to about 25 µm before expansion;
- (ii) a polymeric shell, for example, a polymeric shell comprising polyvinylidene chloride,
acrylonitrile, polyurethane, or a mixture thereof;
- (iii) a volatile material encapsulated by the polymeric shell, for example, a hydrocarbon
selected from isobutene, isopentane, or a mixture thereof; and wherein the thermally
expandable microspheres, when expanded, have a volume of at least 27 times greater
than their unexpanded volume;
- (c) about 1 to about 40 wt.%, preferably about 5 to about 40, more preferably about
10 to about 35 wt.% of one or more additives that modify infrared radiation signature,
for example, magnesium, zirconium, zinc, titanium, aluminium, iron, SnCl2, organic compounds, and a mixture thereof; and
- (d) optionally, one or more additives that produce smoke at a temperature of 150°C
or greater.
[0065] As already mentioned throughout the disclosure, the pellet may also optionally include
additional components, such as one or more binding agents, one or more coatings, etc.,
and may be formed in the shapes, sizes, and configurations described throughout the
disclosure.
[0066] Even further preferably, a pyrophoric pellet may comprise:
- (a) about 35 to about 90 wt.%, preferably about 45 to about 80 wt.%, or more preferably
about 50 to about 80 wt.% of pyrophoric particles, the pyrophoric particles having
a mean particle size of about 1 nm to about 1 µm, about 1 µm to about 250 µm, preferably
about 1 µm to about 150 µm, more preferably about 5 µm to about 100 µm, and being
selected from particles of activated iron, activated nickel, activated copper, activated
cobalt, activated magnesium, activated zirconium, an activated alloy of iron, an activated
alloy of nickel, an activated alloy of copper, an activated alloy of cobalt, an activated
alloy of magnesium, an activated alloy of titanium, an activated alloy of zirconium,
or a mixture thereof;
- (b) about 0.05 to about 30 wt.%, preferably about 1 to about 20 wt.%, more preferably
about 5 to about 15 wt.% of thermally expandable graphite, wherein the thermally expandable
graphite undergoes volume expansion upon reaching a temperature of at least 130o C
and has:
- (i) a mean particle size of about 1 to about 1500 µm, preferably about 10 to about
1250 µm, more preferably about 100 to about 750 µm;
- (ii) an intercalate material between layers of graphite, the intercalate material
selected from a halogen, an alkali metal, a sulfate, a nitrate, an organic acid, an
aluminium chloride, a ferric chloride, a metal halide, an arsenic sulfide, a thallium
sulfide, and a mixture thereof; and
wherein the thermally expandable graphite, when expanded, have a volume of at least
25 times, preferably, at least 50 times, and more preferably at least 100 times greater
than its unexpanded volume;
- (c) about 1 to about 40 wt.%, preferably about 5 to about 40, more preferably about
10 to about 35 wt.% of one or more additives that modify infrared radiation signature,
for example, magnesium, zirconium, zinc, titanium, aluminium, iron, SnCl2, organic compounds, and a mixture thereof; and
- (d) optionally, one or more additives that produce smoke at a temperature of 150°C
or greater.
[0067] As already mentioned throughout the disclosure, the pellet may also optionally include
additional components, such as one or more binding agents, one or more coatings, etc.,
and may be formed in the shapes, sizes, and configurations described throughout the
disclosure.
[0068] Implementation of the present disclosure is provided by way of the following examples.
The examples serve to illustrate the technology without being limiting in nature.
EXAMPLES
[0069]
Formulation |
1 wt.% |
2 wt.% |
3 wt.% |
4 wt.% |
Pyrophoric Particles |
Activated Iron 1 |
70 |
70 |
60 |
60 |
Thermally Expandable Particles |
Microspheres 2 |
10 |
- |
10 |
- |
Graphite 3 |
|
10 |
|
10 |
Additives for IR Modification |
Mg 4 |
20 |
20 |
10 |
10 |
SnCl2 |
|
|
20 |
20 |
Additives for Smoke |
Optional |
- |
- |
- |
- |
|
|
100% |
100% |
100% |
100% |
1 The activated iron particles had a mean particle size of about 15 µm
2 Expancel (951 DUX 120) (AkzoNobel)
3 Expandable Flake Graphite 3626 (Asbury Carbons)
4 The magnesium had a mean particles size of about 30 µm |
[0070] The components of each formulation were mixed together in a glovebox environment
(a sealed container having an inert environment therein). The mixture was placed into
a ½" diameter metal die and mechanical pressure of 0.5 ton was applied to form a pellet.
The pellets were maintained in an inert environment until use. The pellets were exposed
to air utilizing a specialized test fixture that allows remote operation and the speed
at which the pellets self-ignited and broke apart and emitted IR radiation was analysed.
Also, the IR intensity during the entire reaction was measured. The results are plotted
in the chart of FIG. 1.
[0071] The foregoing description illustrates and describes the invention. The disclosure
shows and describes only the preferred embodiments but it should be understood that
the invention is capable to use in various other combinations, modifications, and
environments and is capable of changes or modifications within the scope of the inventive
concepts as expressed herein, commensurate with the above teachings and/or the skill
or knowledge of the relevant art. The embodiments described herein above are further
intended to explain best modes known by applicant and to enable others skilled in
the art to utilize the disclosure in such, or other, embodiments and with the various
modifications required by the particular applications or uses thereof. Accordingly,
the description is not intended to limit the invention to the form disclosed herein.
[0072] As used herein, the terms "comprising," "having," and "including" (or "comprise,"
"have," and "include") are used in their open, non-limiting sense. The phrase "consisting
essentially of" limits the scope of a claim to the specified materials or steps and
those that do not materially affect the basic and novel characteristics of the claimed
invention.
[0073] The terms "a," "an," and "the" are understood not to exclude the plural form.
[0074] Thus, the term "a mixture thereof" also relates to "mixtures thereof." Throughout
the disclosure, if the term "a mixture thereof' is used, following a list of elements
as shown in the following example where letters A-F represent the elements: "one or
more elements selected from the group consisting of A, B, C, D, E, F, and a mixture
thereof." The term, "a mixture thereof' does not require that the mixture include
all of A, B, C, D, E, and F (although all of A, B, C, D, E, and F may be included).
Rather, it indicates that a mixture of any two or more of A, B, C, D, E, and F can
be included. In other words, it is equivalent to the phrase "one or more elements
selected from the group consisting of A, B, C, D, E, F, and a mixture of any two or
more of A, B, C, D, E, and F."
[0075] The expression "one or more" means "at least one" and thus includes individual components
as well as mixtures/combinations.
[0076] Other than in the operating examples, or where otherwise indicated, all numbers expressing
quantities of ingredients and/or reaction conditions can be modified in all instances
by the term "about," meaning within +/- 5% of the indicated number.
[0077] Some of the various categories of components identified for use in the pellets may
overlap.
[0078] In such cases where overlap may exist and the pellet includes two overlapping components
(or more than two overlapping components), an overlapping component does not represent
more than one component. For example, a compound that acts as an additive that modifies
IR signature may also function to generate smoke and therefore also useful as an additive
that produces smoke. Nonetheless, such a compound cannot simultaneously function as
both an additive that modifies IR signature and as the additive that produces smoke
in the claims.
[0079] All percentages, parts and ratios herein are based upon the total weight of the compositions
of the present invention, unless otherwise indicated.
[0080] All ranges and values disclosed herein are inclusive and combinable. For examples,
any value or point described herein that falls within a range described herein can
serve as a minimum or maximum value to derive a sub-range, etc. Furthermore, all ranges
provided are meant to include every specific range within, and combination of sub-ranges
between, the given ranges. Thus, a range from 1-5, includes specifically 1, 2, 3,
4 and 5, as well as sub ranges such as 2-5, 3-5, 2-3, 2-4, 1-4, etc.
1. A pyrophoric pellet comprising:
(a) about 35 to about 95 wt.% of pyrophoric particles;
(b) about 0.05 to about 30 wt.% of one or more thermally expandable particles that
are suitable to undergo volume expansion upon reaching a temperature of at least 50°C,
the volume expansion being at least 3 times the particles' unexpanded volume;
(c) optionally, about 1 to about 40 wt.% of one or more additives that modify infrared
radiation signature, preferably selected from magnesium, zirconium, zinc, titanium,
aluminium, iron, SnCl2, organic compounds, and a mixture thereof; and
(d) optionally, one or more additives that produce smoke at a temperature of 150°C
or greater, preferably selected from white phosphorous, red phosphorous, hexachloroethane,
terephthalic acid, an organic compound, an organic dye, and a mixture thereof
preferably wherein the pyrophoric particles have a mean particle size of about 1 nm
to about 250 µm,
preferably wherein the thermally expandable particles are selected from thermally
expandable microspheres, thermally expandable graphite, and a mixture thereof.
2. The pyrophoric pellet of claim 1, wherein the pyrophoric particles are selected from
an organo-metallic reagent, an alkali earth element, a metal, a metal hydride, an
alkyl metal hydride, a metal carbonyl, a silicone halide, and a mixture thereof, or
wherein the pyrophoric particles are activated metal particles.
3. The pyrophoric pellet of claim 2, wherein the pyrophoric particles are activated metal
particles and wherein the activated metal is selected from activated iron, activated
nickel, activated copper, activated cobalt, activated magnesium, activated zirconium,
an activated alloy of iron, an activated alloy of nickel, an activated alloy of copper,
an activated alloy of cobalt, an activated alloy of magnesium, an activated alloy
of titanium, an activated alloy of zirconium, and a mixture thereof.
4. The pyrophoric pellet of claim 1, wherein the thermally expandable particles comprise
thermally expandable microspheres having an average particles size of about 5 to about
100 µm and optionally comprise a polymeric shell.
5. The pyrophoric pellet of claim 4, wherein the thermally expandable microspheres comprise
a polymeric shell and the polymer shell comprises polyvinylidene chloride, acrylonitrile,
polyurethane, or a mixture thereof.
6. The pyrophoric pellet of claim 4, wherein the thermally expandable microspheres encapsulate
a volatile material chosen from hydrocarbons.
7. The pyrophoric pellet of claim 6, wherein the volatile material volatilizes at a temperature
of 50°C or greater and causes the thermally expandable microspheres to expand, thereby
increasing the volume of the microspheres.
8. The pyrophoric pellet of claim 4, wherein the thermally expandable microspheres, when
expanded, have a volume of at least 27 times greater than their unexpanded volume.
9. The pyrophoric pellet of claim 1, wherein the thermally expandable particles comprise
thermally expandable graphite having an average particle size of about 0.5 to about
1500 µm.
10. The pyrophoric pellet of claim 9, wherein the thermally expandable graphite undergoes
volume expansion upon reaching a temperature of at least 130° C.
11. The pyrophoric pellet of claim 9, wherein the thermally expandable graphite comprises
an intercalate material between layers of graphite selected from a halogen, an alkali
metal, a sulfate, a nitrate, an organic acid, an aluminium chloride, a ferric chloride,
a metal halide, an arsenic sulfide, a thallium sulfide, and a mixture thereof.
12. The pyrophoric pellet of claim 9, wherein the thermally expandable graphite has a
carbon content of about 80 wt.% to about 99% wt.% and a sulfur content of greater
than 0 wt.% to about 8 wt.%, based on the total weight of the thermally expandable
graphite.
13. The pyrophoric pellet of claim 9, wherein the thermally expandable graphite, when
expanded, has a volume of at least 25 times greater than its unexpanded volume.
14. The pyrophoric pellet of claim 1, wherein the pellet separates into its original individual
particulates or agglomerates thereof upon release into the atmosphere in less than
about 30 seconds.
15. A method for making a pyrophoric pellet of claim 1 comprising:
(i) mixing components (a)-(c) and optionally (d) in an environment that is essentially
free of oxygen; and
(ii) compressing the mixture into a pellet.
1. Pyrophores Pellet umfassend:
(a) ungefähr 35 bis ungefähr 95 Gew.-% pyrophore Partikel;
(b) ungefähr 0,05 bis ungefähr 30 Gew.-% eines oder mehrerer thermisch expandierbarer
Partikel, welche geeignet sind, sich bei Erreichen einer Temperatur von mindestens
50 °C einer Volumenexpansion zu unterziehen, wobei die Volumenexpansion mindestens
das Dreifache des unexpandierten Volumens der Partikel ist;
(c) optional ungefähr 1 bis ungefähr 40 Gew.-% eines oder mehrerer Additive, die die
Signatur infraroter Strahlung modifizieren, vorzugsweise ausgewählt aus Magnesium,
Zirkon, Zink, Titan, Aluminium, Eisen, SnCl2, organischen Verbindungen und einer Mischung davon; und
(d) optional ein oder mehrere Additive die Rauch produzieren bei einer Temperatur
von 150 °C oder höher, vorzugsweise ausgewählt aus weißem Phosphor, rotem Phosphor,
Hexachlorethan, Terephthalsäure, einer organischen Verbindung, einem organischen Farbstoff
und eine Mischung davon
vorzugsweise wobei die pyrophoren Partikel eine durchschnittliche Partikelgröße von
ungefähr 1 nm bis ungefähr 250 µm haben,
vorzugsweise wobei die thermisch expandierbaren Partikel ausgewählt sind aus thermisch
expandierbaren Mikrosphären, thermisch expandierbarem Graphit und einer Mischung davon.
2. Pyrophores Pellet gemäß Anspruch 1, wobei die pyrophoren Partikel ausgewählt sind
aus einer organo-metallischen Reagenz, einem Erdalkalimetall, einem Metall, einem
Metallhydrid, einem Alkylmetallhydrid, einem Metallcarbonyl, einem Siliziumhalogenid
und einer Mischung davon, oder wobei die pyrophoren Partikel aktivierte Metallpartikel
sind.
3. Pyrophores Pellet gemäß Anspruch 2, wobei die pyrophoren Partikel aktivierte Metallpartikel
sind und wobei das aktivierte Metall ausgewählt ist aus aktiviertem Eisen, aktiviertem
Nickel, aktiviertem Kupfer, aktiviertem Kobalt, aktiviertem Magnesium, aktiviertem
Zirkon, einer aktivierten Eisenlegierung, einer aktivierten Nickellegierung, einer
aktivierten Kupferlegierung, einer aktivierten Kobaltlegierung, einer aktivierten
Magnesiumlegierung, einer aktivierten Titanlegierung, einer aktivierten Zirkonlegierung
und einer Mischung davon.
4. Pyrophores Pellet gemäß Anspruch 1, wobei die thermisch expandierbaren Partikel thermisch
expandierbare Mikrosphären umfassen, welche eine durchschnittliche Partikelgröße von
ungefähr 5 bis ungefähr 100 µm haben und optional eine Polymerhülle umfassen.
5. Pyrophores Pellet gemäß Anspruch 4, wobei die thermisch expandierbaren Mikrosphären
eine Polymerhülle umfassen und die Polymerhülle Polyvinylidenchlorid, Acrylnitril,
Polyurethan oder eine Mischung davon umfasst.
6. Pyrophores Pellet gemäß Anspruch 4, wobei die thermisch expandierbaren Mikrosphären
ein volatiles Material ausgewählt aus Kohlenwasserstoffen einkapseln.
7. Pyrophores Pellet gemäß Anspruch 6, wobei sich das volatile Material bei einer Temperatur
von 50 °C oder höher verflüchtigt und die thermisch expandierbaren Mikrosphären zur
Expansion veranlasst und dadurch das Volumen der Mikrosphären vergrößert.
8. Pyrophores Pellet gemäß Anspruch 4, wobei die thermisch expandierbaren Mikrosphäen,
wenn expandiert, ein mindestens 27 Mal größeres Volumen als ihr unexpandiertes Volumen
aufweist.
9. Pyrophores Pellet gemäß Anspruch 1, wobei die thermisch expandierbaren Partikel thermisch
expandierbares Graphit umfassen, welches eine durchschnittliche Partikelgröße von
ungefähr 0.5 bis ungefähr 1500 µm aufweist.
10. Pyrophores Pellet gemäß Anspruch 9, wobei sich das thermisch expandierbare Graphit
bei Erreichen einer Temperatur von mindestens 130 °C einer Volumenexpansion unterzieht.
11. Pyrophores Pellet gemäß Anspruch 9, wobei das thermisch expandierbare Graphit ein
interkalierendes Material zwischen Graphitschichten umfasst ausgewählt aus Halogen,
einem Alkalimetall, einem Sulfat, einem Nitrat, einer organischen Säure, einem Aluminiumchlorid,
einem Eisenchlorid, einem Metallhalogenid, einem Arsensulfid, einem Thalliumsulfid
und einer Mischung davon.
12. Pyrophores Pellet gemäß Anspruch 9, wobei das thermisch expandierbare Graphit einen
Kohlenstoffgehalt von ungefähr 80 Gew.-% bis ungefähr 99 Gew.-% und einen Schwefelgehalt
von größer als 0 Gewichts-% bis ungefähr 8 Gew.-% aufweist, basierend auf dem Gesamtgewicht
des thermisch expandierbaren Graphits.
13. Pyrophores Pellet gemäß Anspruch 9, wobei das thermisch expandierbare Graphit, wenn
expandiert, ein mindestens 25 Mal größeres Volumen als sein unexpandiertes Volumen
aufweist.
14. Pyrophores Pellet gemäß Anspruch 1, wobei sich das Pellet bei Freisetzung in die Atmosphäre
in weniger als ungefähr 30 Sekunden in seine ursprünglichen einzelnen Partikel oder
Agglomerate davon auftrennt.
15. Verfahren zur Herstellung eines pyrophoren Pellets gemäß Anspruch 1 umfassend:
(i) Mischen der Komponenten (a) - (c) und optional (d) in einer im Wesentlichen sauerstofffreien
Umgebung; und
(ii) Komprimieren der Mischung zu einem Pellet.
1. Pellet pyrophorique comprenant:
(a) environ 35 à environ 95 % en poids de particules pyrophoriques;
(b) environ 0,05 à environ 30 % en poids d'une ou de plusieurs particules thermiquement
expansibles qui conviennent pour subir une expansion volumique lorsqu'elles atteignent
une température d'au moins 50 °C, l'expansion volumique étant au moins 3 fois le volume
non expansé des particules;
(c) en option, environ 1 à environ 40 % en poids d'un ou de plusieurs additifs qui
modifient la signature de rayonnement infrarouge, de préférence choisis parmi le magnésium,
le zirconium, le zinc, le titane, l'aluminium, le fer, le SnCl2, les composés organiques et un mélange de ceux-ci; et
(d) en option, un ou plusieurs additifs qui produisent de la fumée à une température
de 150 °C ou plus, de préférence choisis parmi le phosphore blanc, le phosphore rouge,
l'hexachloroéthane, l'acide téréphtalique, un composé organique, un colorant organique
et un mélange de ceux-ci,
de préférence dans lequel les particules pyrophoriques présentent une taille moyenne
de particule d'environ 1 nm à environ 250 µm,
de préférence dans lequel les particules thermiquement expansibles sont choisies parmi
les microsphères thermiquement expansibles, le graphite thermiquement expansible et
un mélange de ceux-ci.
2. Pellet pyrophorique selon la revendication 1, dans lequel les particules pyrophoriques
sont choisies parmi un réactif organo-métallique, un élément alcalino-terreux, un
métal, un hydrure métallique, un hydrure alkyle métallique, un carbonyle de métal,
un halogénure de silicium, et un mélange de ceux-ci,
ou dans lequel les particules pyrophoriques sont des particules métalliques activées.
3. Pellet pyrophorique selon la revendication 2, dans lequel les particules pyrophoriques
sont des particules métalliques activées et dans lequel le métal activé est choisi
parmi le fer activé, le nickel activé, le cuivre activé, le cobalt activé, le magnésium
activé, le zirconium activé, un alliage activé de fer, un alliage activé de nickel,
un alliage activé de cuivre, un alliage activé de cobalt, un alliage activé de magnésium,
un alliage activé de titane, un alliage activé de zirconium, et un mélange de ceux-ci.
4. Pellet pyrophorique selon la revendication 1, dans lequel les particules thermiquement
expansibles comprennent des microsphères thermiquement expansibles ayant une taille
moyenne de particule d'environ 5 à environ 100 µm et comprennent en option une enveloppe
polymère.
5. Pellet pyrophorique selon la revendication 4, dans lequel les microsphères thermiquement
expansibles comprennent une enveloppe polymère et ladite enveloppe polymère comprend
du chlorure de polyvinylidène, de l'acrylonitrile, du polyuréthane ou un mélange de
ceux-ci.
6. Pellet pyrophorique selon la revendication 4, dans lequel les microsphères thermiquement
expansibles encapsulent un matériau volatil choisi parmi les hydrocarbures.
7. Pellet pyrophorique selon la revendication 6, dans lequel le matériau volatil se volatilise
à une température de 50 °C ou plus et provoque l'expansion des microsphères thermiquement
expansibles, augmentant ainsi le volume des microsphères.
8. Pellet pyrophorique selon la revendication 4, dans lequel les microsphères thermiquement
expansibles, lorsqu'elles sont expansées, présentent un volume au moins 27 fois supérieur
à leur volume non expansé.
9. Pellet pyrophorique selon la revendication 1, dans lequel les particules thermiquement
expansibles comprennent du graphite thermiquement expansible ayant une taille moyenne
de particule d'environ 0,5 à environ 1500 µm.
10. Pellet pyrophorique selon la revendication 9, dans lequel le graphite thermiquement
expansible subit une expansion volumique lorsqu'il atteint une température d'au moins
130 °C.
11. Pellet pyrophorique selon la revendication 9, dans lequel le graphite thermiquement
expansible comprend un matériau intercalant entre des couches de graphite qui est
choisi parmi un halogène, un métal alcalin, un sulfate, un nitrate, un acide organique,
un chlorure d'aluminium, un chlorure ferrique, un halogénure métallique, un sulfure
d'arsenic, un sulfure de thallium et un mélange de ceux-ci.
12. Pellet pyrophorique selon la revendication 9, dans lequel le graphite thermiquement
expansible présente une teneur en carbone d'environ 80 % en poids à environ 99 % en
poids et une teneur en soufre supérieure à 0 % en poids à environ 8 % en poids, sur
la base du poids total du graphite thermiquement expansible.
13. Pellet pyrophorique selon la revendication 9, dans lequel le graphite thermiquement
expansible, lorsqu'il est expansé, présente un volume au moins 25 fois supérieur à
son volume non expansé.
14. Pellet pyrophorique selon la revendication 1, dans lequel le pellet se sépare en ses
particules individuelles d'origine ou en agglomérats de celles-ci lors de la libération
dans l'atmosphère en moins de 30 secondes à peu près.
15. Procédé de fabrication d'un pellet pyrophorique selon la revendication 1, comprenant:
(i) mélanger les composants (a) à (c) et en option (d) dans un environnement qui est
pour l'essentiel exempt d'oxygène; et
(ii) comprimer le mélange en un pellet.