Pyrotechnic particles of large sizes, method of their obtaining, and use

FIELD: weapons and ammunition.

SUBSTANCE: proposed pyrotechnic particles include at least one oxidising component chosen from ammonium, potassium, sodium, barium, strontium nitrates, the main copper nitrate, ammonium, potassium and sodium perchlorates, and their mixtures, at least one reducing component chosen from nitroguanidine, guanidine nitrate and their mixtures and is not included in binding agent; at that, particles essentially have the shape of cylindrical blocks with thickness of more than 5 mm, with equivalent diameter equal to 10 mm or more, and with porosity in the range of 1% to 8%, including boundary values. Particles can be obtained in compliance with the proposed method.

EFFECT: proposed particles have low combustion rate, low working pressure, low dependence of combustion rate on working particle temperature in order to provide good ballistic properties at extreme temperatures; particles are not corrosive in relation to generator and have mechanical characteristics required to maintain the vibration in automobiles or aircrafts.

14 cl, 3 dwg, 3 ex

The technical FIELD

The present invention relates to pyrotechnic particles of large size, method of their production and to their use. In particular, it includes:

- the fireworks particles having the form of blocks (solid blocks) large size;

- by the way they are received; and

- method of generating gas comprising combustion of these particles.

PRIOR art

Gas generation is used in many applications in both civil and military spheres.

In the sector of road safety have been developed generators with short-time work in composition with a high burning rate. These compositions take the form of thin tablets (thickness in the range from 1 mm [mm] up to 3 mm) with a small diameter (3 mm to 7 mm). This provides a large surface combustion, which contributes to a high rate of combustion within a short period of time (which is necessary for use in airbags in the field of road safety, for example - in airbags for drivers). The porosity of such tablets usually less than 4%. The tabletting operation performed with the aim of obtaining these pills, well studied and are similar to the operations used in the processing of medical compositions. In this context, has been used in owani composition based on guanidine nitrate and basic copper nitrate (patent of the United States of America US-A-5608183). Attempts were made to increase the burning rate (US-A-6143102), since the burning rate of such compositions is relatively low compared with other compositions used in the same technical field.

In similar sectors (automotive security for filling gas, the airbag type "curtain"that must remain pressurized for a long time) or in completely different sectors were offered generators, in particular, to:

- inflate or deformation of the structure;

- the movement of liquid or gas;

- the propulsion jacks or other mechanical actuators;

- provide offset.

Generation and gas supply are also used during the operation of fire-fighting means (FR-A-2864905 and FR-A-2870459).

All this relates to the slow generation of gas. For the slow evolution of gas and gas supply under pressure usually use gas stored under pressure. Also described the use of chemical reactions or combustion of pyrotechnic cartridges. During the combustion of pyrotechnic cartridges flow rate of the generated gas is adjusted by selecting the characteristics of explosives, the geometry of the cartridges and/or conditions of the release of generated gas, etc.

The INVENTION

The present invention relates to the field slave is you gas generators, characterized by long duration, low velocity gas flow and low work pressure.

In this context, the present invention provides a pyrotechnic particles having a simple form and meet the following conditions:

a) a long period of combustion (from 50 MS [milliseconds] up 1 min [minutes]) due to the low burning speed (for long period), and/or small ratio of the area of combustion to the thickness of the combustion zone, and/or low operating pressure (for use in gas generators of low pressure and to ensure a low burning speed);

b) a small dependence of the rate of combustion from the operating temperature of the particles to ensure good ballistic properties at extreme temperatures from -60°C to 110°C (hence expanding range of applications (see below), especially in aviation);

C) suitable mechanical properties (without using a binder, the presence of which adversely affect the ballistic properties), is especially conducive to the application of these particles in a hostile environment with vibrations.

Pyrotechnic particles according to the present invention also possess a useful property, namely that they are not aggressive towards the gas generator, in which they are used, and in relation to connected with either the system (i.e. when burned, they do not emit any particles, neither corrosive substances). In addition, eye-catching substances have the advantage of low toxicity.

With regard to paragraph (a) of the above conditions, the specialist in the art will understand that pyrotechnic particle according to the present invention should be thick and have a small area of burning. Therefore, it should be large particle, greater than the tablets described above.

As regards paragraph (b) of the above conditions, the expert in the art it will be clear that this particle must have a low porosity.

Specialist in the art will also be well-known difficulties associated with the production of large particles of this type (pyrotechnic particles) with low porosity, with suitable mechanical properties and without the use of binders. He knows that pyrotechnic particles with large sizes and not containing a binder composed typically have porosities that are not acceptable from the point of view of their ballistic properties, in particular from the point of view of speed of combustion. This point is crucial at high operating temperature.

The author of the present invention unexpectedly of specific oxidants and reductants got pyrotechnic particles in a simple form that meets lead is connected to the above conditions. Such pyrotechnic particles represent the first aspect of the present invention.

Pyrotechnic particles according to the present invention have a composition, which includes at least one (specific) oxidizing component and at least one (specific) restorative component, but does not include a binder. Therefore, these pyrotechnic pyrotechnic particles are particles of type tablets described above. The pyrotechnic composition of the particles according to the present invention is generally mainly consists of at least one (specific) oxidizing component and at least one (specific) recovery component. It is usually essentially consists of (specific) oxidizing component (oxidant) and (specific) recovery component (reductant).

At least one specific oxidizing component is selected from the group consisting of nitrates of ammonium, potassium, sodium, barium, strontium, and basic copper nitrate, perchlorates of ammonium, potassium and sodium and mixtures thereof. Preferably it comprises basic copper nitrate and/or potassium perchlorate. Particularly preferably it is a basic copper nitrate.

At least one specific restorative whom onent selected from nitroguanidine, nitrate guanidine and mixtures thereof. Preferably it is a guanidine nitrate.

In the typical case of pyrotechnic particles according to the present invention have the form of essentially cylindrical blocks:

with thickness > 5 mm

- equivalent diameter of 10 mm or more; and

with porosity in the range from 1% to 8%, including the boundary values.

These (monolithic) blocks are blocks of large size, which have a simple form and low porosity.

The units have an almost cylindrical shape. Usually, but not exclusively, they are cylinders of circular cross section or cylinders almost all (QuattroPro) section.

The shape of the particles according to the present invention is the result of the last step of the method of obtaining them: stage compaction during pressing (see below).

The blocks may, in particular, to provide a solid (quasi)cylinders or (quasi)cylindrical tube.

The considered particles are large objects (thickness more than 5 mm, the equivalent diameter (or, in an appropriate case diameter if the particle is a perfect cylinder of circular cross section which is equal to 10 mm or more), and they are relatively dense (porosity in the range from 1% to 8%).

Do not limit the invention, the particle sizes are described in detail below.

Oba is but independently:

- the thickness of the blocks is equal to 75 mm or less; or

- equivalent diameter of blocks equal to 75 mm or less.

Usually the thickness and the equivalent diameter of 75 mm or less.

According to the first preferred form of the invention independently of each:

- the thickness of the blocks is equal to 7.5 mm or more; or

- equivalent diameter of blocks equal to 20 mm or more.

Usually in the context of the first preferred form of implementation of the present invention, the thickness and the equivalent diameter are as defined above.

According to the second preferred form of the invention independently:

- the thickness of the blocks is in the range from 10 mm to 60 mm (including the values of 10 mm and 60 mm); or

- equivalent diameter of the blocks is in the range from 10 mm to 60 mm (including the values of 10 mm and 60 mm).

In General, in the context of this second preferred form of implementation of the present invention, the thickness and the equivalent diameter range from 10 mm to 60 mm (including the values of 10 mm and 60 mm).

In particular, in the context of the present invention obtained pyrotechnic units type solid cylinder with circular cross-sections and dimensions, as specified below:

a diameter equal to 25 mm, and a thickness equal to 10 mm;

- diameter of 50 mm and thickness of 50 mm

It was also fitted is but the porosity of the blocks is in the range from 1% to 8% (it should be noted that this parameter, expressed as a percentage, corresponds to the ratio of the actual density and theoretical density; in fact, it reflects the difference of theoretical density).

The porosity is preferably 5% or less. It should be recalled that the lower the porosity, the less the dependence of the rate of combustion from the operating temperature of the particles.

It should be stated that, without limiting the scope of the invention, the blocks of type cylinders with circular cross-sections with dimensions specified above, may therefore be obtained with values of porosity, the following:

is the porosity is approximately equal to 5% (diameter = 25 mm, thickness = 10 mm);

is the porosity is approximately equal to 7% (with diameter = thickness = 50 mm).

As stated above, pyrotechnic particles according to the present invention, having a simple shape and, essentially, which is cylindrical, can in particular be a solid cylinder or tube. Equivalent to the internal diameter of the tubes is preferably greater than 10 mm; more preferably it is in the range from 12 mm to 35 mm (which is, of course, assumes a larger equivalent diameter of the tube).

With regard to the composition pyrotechnic particles according to the present invention, it is possible to lead the next, do not limit the invention, for details.

The pyrotechnic composition of the particles according to the present invention preferably contains a basic copper nitrate as the oxidizing component and the guanidine nitrate as a restorative component. In a particularly preferred case it contains basic copper nitrate as the sole oxidizing component and guanidine nitrate as the sole recovery component. From the field of road safety (air bags for drivers) it is known that the combination of the basic copper nitrate/nitrate guanidine has a relatively low burning rate, in comparison with other compositions used in this field. In the context of this particularly preferred form of implementation of the present invention, the composition typically contains:

from 45 to 55 mass % of guanidine nitrate;

from 40 to 50 mass % of basic copper nitrate; and

- from 0 to 5 mass % of additives.

Appropriate additives that may optionally be present, are chemical compounds that are known per se, and also in connection with useful properties when used in the standard production of pyrotechnic particles. In particular, additives can be:

- slag coming together with the original materials oxidizing component (or components) and recovery component (or components) (e.g., aluminum oxide);

tools that facilitate the processing, for example - contribute to pressing, or tools that facilitate the extraction of the form (for example, silicon dioxide, calcium stearate, mica and the like).

In a second aspect the present invention provides a receiving pyrotechnic large particle size described above.

The described method involves a number of stages, which are in themselves known.

Suddenly it was possible to find for this series of steps (which themselves are well known) working conditions, which provide the possibility of obtaining from the selected oxidizing and reducing components without the use of binder particles according to the present invention, simultaneously with the large size, low porosity and acceptable mechanical properties (which can withstand vibration environment in cars or airplanes).

A method of obtaining a pyrotechnic particles according to the present invention includes a sequential execution of the following operations:

- thorough dry or wet mixing of the oxidizing and reducing components used in the form of powders;

dry or wet granulating the resulting mixture of powders;

- sorting the obtained granules in size; and

- giving adareanum sieve pellets of the desired shape by means of pressing;

under conditions to produce the desired result, i.e. receiving a pyrotechnic particles having dimensions and characteristics of porosity, as defined above.

Suitable conditions are, first of all:

- characteristics of the source powders;

features detainees sieve granules; and

- pressing parameters.

The inventor has discovered that it is possible to combine suitable conditions to give the desired result.

Before to describe the conditions (parameters) of the method according to the present invention, is as follows:

what powders are preferably thoroughly mixed by dry mixing;

- pelleting also preferably carried out as a dry granulation (regardless of how thorough mixing);

what pellets are preferably sorted according to size by sieving; and

- that sorted the granules before they are molded by pressing, you can add at least one additive that promotes the formation (a means of facilitating the extrusion, such as calcium stearate or mica).

Usually, to obtain the desired result, in particular for obtaining a low rate of combustion, at least one of the components used in the form of powder has an average particle diameter, significantly bigger the th average diameter of the particles, used on prior art to obtain particles (small size). Therefore, in the context of the implementation of the method according to the present invention, it is recommended to use at least part of the recovery component (or components) in the form of particles with an average diameter exceeding (x4, X6) average particle diameter, usually used to obtain particles in the known prior art. It is recommended to use particles restorative component with an average diameter of 200 microns [μm] or more. In particular, it is recommended to use particles of guanidine nitrate with an average diameter of from 200 μm to 300 μm. Usually, to obtain pyrotechnic particles are particles of guanidine nitrate with an average diameter of 50 microns.

In the typical case, to obtain the desired result, in particular to obtain low porosity, select granules with an average diameter greater than 200 μm, preferably in the range from 500 μm to 1000 μm. Therefore, in the context of the present invention, it is recommended to select granules of the basic copper nitrate/nitrate guanidine with an average diameter in the range from 500 microns to 700 microns or granules of potassium perchlorate/nitrate guanidine with an average diameter in the range from 500 μm to 1000 μm.

Specialist in the art will be able to opt myzerowaste this option (granules size), as well as other parameters (average particle diameter of the powder and pressing parameters) depending on the specific nature of the ingredients used.

As for the parameters of the press, in General, to obtain the desired result, in particular to obtain low porosity, provide a pressure in the range from 15×10⁶PA [Pascal] 35×10⁶PA within 0.1 s [seconds] 30 C.

Pressing is carried out in the form, the form of which corresponds to the intended form of manufactured pyrotechnic particles (essentially cylindrical shape).

The method according to the present invention can successfully be used for all preferred forms of the invention described above, namely:

- with an average diameter of at least one restorative component equal to 200 microns or more;

- with an average diameter greater than 200 μm; and

- during the operation of pressing at 15-35×106 PA in a period of from 0.1 to 30 C.

The method according to the present invention, it is preferable to use combinations of the basic copper nitrate or potassium perchlorate/nitrate guanidine; particularly preferable to use it for a combination of basic copper nitrate/ nitrate guanidine. In the context of the present invention, the rate of combustion of compositions on the basis of these two components (foundations of the CSOs of copper nitrate/nitrate guanidine) is reduced. Thus, the idea of the present invention is contrary to the idea disclosed in the patent US-A-6143102.

In a third aspect the present invention provides a method of generating gas; this method includes, in the typical case, the combustion of at least one pyrotechnic particles. In the typical case, the method according to the present invention includes the burning of at least one pyrotechnic particles described above (pyrotechnic particles of large size) and/or obtained using the method described above.

The method of generating gas is carried out in a suitable device, which, in particular, comprises a combustion chamber, adapted to the size of the original pyrotechnic charge based pyrotechnic particles of large size. As presently known devices, the specified device contains:

elements for fixing, positioning and regulation of the pyrotechnic charge based pyrotechnic particles of large sizes (which are the first aspect of the present invention);

elements of ignition;

at least one safety head, providing pressure relief from the gas generator in case of accidental over pressure;

at least one nozzle; and

filter to hold the greater part of the TV is rdih combustion products.

Below is described an interesting application of pyrotechnic particles according to the present invention, that is, areas in which the gas generation must be maintained for a relatively long period.

In particular, assume the following applications:

- gas generation in order to promote fluid, directly or through the separation membrane, for example for extinguishing fires in the engines of civil or military aircraft, for sealing compartments inert gas in a civil or military aircraft for fire fighting in buildings, in all types of civil vehicles (cars etc) or military vehicles (tanks etc), for the injection of grease or active substances, etc.;

- gas generation in a pyrotechnic actuator, intended for the propulsion of, for example, pushers (for example, to open the door in the plane);

- generating gas to inflate or deformation of the inflatable structures, able to be deformed, such as rescue chute in the aircraft, automotive devices, not allowing the passenger to slip out of the belt, or isolators.

In conclusion, next will be described the embodiments of the present invention.

DESCRIPTION of embodiments of the INVENTION

Example 1

Pyrotechnics the e particles according to the present invention were obtained from the following source materials:

- basic copper nitrate (OHM): powder with an average particle diameter equal to 8 microns;

- guanidine nitrate (NG): powder with an average particle diameter equal to 218 microns;

- aluminum oxide (filler): powder with an average particle diameter of 1 μm.

The powders were mixed dry in a mixer for powders type Sofraden® (may also be suitable mixer type Guedu®) in the following proportions (in mass %):

Received thoroughly mixed the mixture of powders was subjected to dry granulation in the granulator type Sahut Conreur® (may also be suitable granulator type Alexanderwerk®). Thoroughly mixed mixture of powders force was passed through a sieve. The particle size distribution of the obtained granules corresponded to the range from 10 μm to 1000 μm.

Then, the resulting granules were sieved and separated granules with an average diameter exceeding 200 μm.

After this selected pellets were pressed using a press single action, developed force equal to 35 (metric) tons. The applied pressure was 230 bar (23×10⁶P is). This pressure was applied for 10 seconds

Were obtained pyrotechnic particles according to the present invention; these particles consisted of a cylindrical monoliths (in accordance with form) with a thickness equal to 10 mm in diameter, equal to 24.6 mm, and a porosity equal to 3%.

Example 2

In the same way were obtained cylindrical particles with the following characteristics:

- thickness of 50 mm;

- diameter of 50 mm;

- porosity equal to 7%.

Example 3 (prior art)

In the same way particles were obtained, corresponding to the prior art, which consisted of a cylindrical particle with the following characteristics:

the thickness of 1.8 mm;

the diameter of 6.3 mm;

- porosity equal to 2%.

The particles obtained in accordance with Examples 1-3 were tested in the generators of the same design. In the attached Figures 1-3 shows the graphs of operating pressures generators as functions of time.

As expected, in the case of particles, the relevant prior art was obtained peak operating pressure (Figure 3). In the case of blocks according to the present invention was observed desired pressure distribution over time (Figures 1 and 2).

In addition, it was tested the change in the mechanical properties of the particles according to the present is obreteniyu under the influence of aircraft vibrations with satisfactory results (standard RTCA DO-160D: "Environmental Conditions and Test Procedures for Airborne Equipment").

1. Pyrotechnic particle, which includes at least one oxidizing component selected from the nitrates of ammonium, potassium, sodium, barium, strontium, basic copper nitrate, perchlorates of ammonium, potassium and sodium, and mixtures thereof, at least one recovery component selected from nitroguanidine, guanidine nitrate and mixtures thereof, and does not include a binder, characterized in that it has the shape of an essentially cylindrical block:
- of a thickness exceeding 5 mm;
- equivalent diameter of 10 mm or more; and
with porosity in the range from 1% to 8%, including the boundary values.

2. Pyrotechnic particle according to claim 1, characterized in that the thickness of the block is equal to 7.5 mm or more, and/or equivalent diameter of the block is equal to 20 mm or more.

3. Pyrotechnic particle according to claim 1, characterized in that the thickness and/or the equivalent diameter of the block are in the range from 10 mm to 60 mm, including the boundary values.

4. Pyrotechnic particle according to any one of claims 1 to 3, characterized in that the porosity of the block is equal to or less than 5%.

5. Pyrotechnic particle according to any one of claims 1 to 3, characterized in that it has the shape of a tube with internal equivalent diameter, preferably greater than 10 mm

6. Pyrotechnic particle according to any one of claims 1 to 3, characterized in that at least one oxidizing whom onent is a basic copper nitrate.

7. Pyrotechnic particle according to any one of claims 1 to 3, characterized in that at least one recovery component is a guanidine nitrate.

8. Pyrotechnic particle according to any one of claims 1 to 3, characterized in that it includes:
- 45-55 wt.% nitrate guanidine;
- 40-50 wt.% basic copper nitrate; and
- 0-5 wt.% additives.

9. A method of obtaining a pyrotechnic particles according to any one of claims 1 to 8, characterized in that it includes:
- thorough dry or wet mixing of the oxidizing and reducing components used in the form of powders;
dry or wet granulating the resulting mixture of powders;
- sorting the obtained granules in size; and
- giving detainees sieve pellets of the desired shape by extrusion;
the characteristics of the original powders detained sieve granules and settings pressing selected such that they ensured pyrotechnic particles with the specified dimensions and characteristics of porosity.

10. The method according to claim 9, characterized in that the mixing and/or granulating is carried out using a dry method.

11. The method according to claim 9, characterized in that the granules are sorted by size by sieving.

12. The method according to claim 9, characterized in that it includes:
- use at least one in stanowiacego component with an average particle diameter, equal to 200 μm or more; and/or, preferably, and
- screening the granules to separate the granules with an average diameter greater than 200 μm; and/or, preferably, and
- giving the appropriate form of granules by extrusion using a pressure in the range from 15·10⁶PA to 35·10⁶PA for 0.1-30 s

13. The method according to claim 9, characterized in that it is carried out by using guanidine nitrate as a regenerative component and a basic copper nitrate or potassium perchlorate as the oxidizing component.

14. The method of generating gas including combustion, at least one pyrotechnic particles, characterized in that at least one pyrotechnic particle is a particle according to any one of claims 1 to 8 and/or a particle obtained according to any of PP-13.