EP1604963A2 - Pyrotechnic composition with improved mechanical strength - Google Patents

Abstract

The pyrotechnic composition, which includes at least one oxidant and at least one reducing material, incorporates between 1 and 40 per cent, and preferably 1 - 10 per cent of myristic acid, which occurs naturally in animal fats and plant vegetable oils such as copra and palm oil. The reducing material is an organic acid selected from the following group: glutamic acid, acetylsalicylic acid, fumaric acis, stearic acid, ascorbic acid or mixtures of these. The oxidant material is selected from the group comprising potassium perchlorate, ammonium perchlorate, potassium nitrate, ammonium nitrate or mixtures of these, and a typical version of the composition contains 30 - 70 per cent of oxidant material, 20 - 40 per cent of a reducing mixture containing myristic acis and at least one organic acid, 0 - 10 per cent of a bonding agent, and 0 - 10 per cent of a catalyst such as ferric oxide (Fe203).

Description

The technical field of the invention is that of pyrotechnic compositions and in particular that of the pyrotechnic gas generating compositions.

Pyrotechnic compositions are well known the skilled person. They usually associate one or several oxidants with one or more reducing agents. They sometimes incorporate additives such as reaction or binders. Pyrotechnic compositions are compositions whose decomposition or combustion produces one or more specific effects: flame, light, smoke, noise, gas ... Among the compositions known are those used in inflammators pyrotechnics, in smoke generators and in gas generators.

Patent EP 787702 thus describes a composition gas generator which combines a reducing agent (the acid tartaric) with an oxidant (potassium perchlorate). This composition is implemented by mixing in phase aqueous and then drying. Other known compositions are implemented by compression.

One of the problems encountered with the known compositions is the mechanical strength of the blocks or tablets that are made.

Pyrotechnic compositions must be able to be kept for years before being called upon to function. They must retain their characteristics nominal values (flame temperature, volume and gas flow or generated smoke) so that their function is assured.

During these years of storage the compositions are subjected to thermal stress (heating) and mechanical stresses (vibrations).

Fragmentation of the composition leads to a modification of the combustion regime which leads to a modification of the operating characteristics of the composition.

It is known to use a binder to improve the mechanical strength of a pyrotechnic composition. The patent WO9818661 describes for example a composition combining potassium chlorate (KClO ₃ ) and lactose coated with a binder such as an aliphatic polycarbonate. No. 6,117,255 describes a composition combining nitrate or ammonium perchlorate with guanylurea dinitramide, the whole being coated with a rubber, polyurethane or polyethylene binder.

The disadvantage of known binders is that they participate little to the generated reaction. It is the goal of the invention that to propose a pyrotechnic composition not presenting such disadvantages.

Thus, the invention makes it possible to produce tablets with improved mechanical strength while reducing the amount of binder needed.

Thus the invention relates to a composition pyrotechnic material comprising at least one oxidizing material and at less a reducing material, which composition is characterized in that it incorporates myristic acid.

Myristic acid or tetradecanoic acid has the formula CH ₃ - (CH ₂ ) ₁₂ -CO ₂ H. It is an organic compound naturally present in animal and vegetable fats (coconut and palm kernel fats). This compound is mainly used as an additive in the food industry. Its cost is very low and it is not toxic.

When combined with a redox composition in the proportions of 1% to 10% by weight, it presents as an advantage of ensuring an effective coating of the composition for removing dust. By elsewhere he partially plays the role of binder and ensures after compression an increase of the mechanical resistance tablet made.

With constant mechanical characteristics it is then possible to reduce the proportion of another binder possibly necessary to make the tablets.

Another advantage of this component is that it has a acidic radical allowing it to participate in the reaction pyrotechnic as the main reducer used.

We can then use Myristic acid in proportions up to 40% by weight of the composition.

In particular, in an application to a composition pyrotechnic gas generator, we can use from 1% to 40% myristic acid, the latter allowing to increase the mechanical strength of the composition without reducing the volume of generated gases. Myristic acid can be used in substitution for part of the main gear.

According to one embodiment of the invention, it will be realized a pyrotechnic composition generating a gas incorporating a reducing agent comprising at least one organic acid, say an acid including carbon atoms, for example glutamic acid, fumaric acid, ascorbic acid, stearic acid or acetylsalicylic acid or a mixture of these acids.

Moreover, this reducer will be associated with a material oxidant selected from the following materials: potassium, ammonium perchlorate, potassium nitrate, ammonium nitrate and mixtures thereof.

Such a choice of oxidant and reducer makes it possible to reconcile the reduced cost requirements with those of chemical compatibility between components while ensuring a volume and a large gas flow (of the order of 60 liters generated in 80 milliseconds).

It is possible to make tablets of one composition according to the invention associating only oxidant, reducer and myristic acid (without binder).

It will be in some cases advantageous to provide a binder (for example to improve the flow characteristics components or to further increase cohesion). We will preferably choose a binder from the following compounds: polyethylenic wax (micronized or not), acetate of Polyvinyl (PVA), Polyvinyl Chloride (PVC), Nitride vinyl, chlorofluoroethylene copolymer (known as Viton brand).

Finally, it will sometimes be advantageous to incorporate certain additives: for example implementation to facilitate mixing and the coating of the various constituents. We can for example use graphite with a particle size of 20 nanometers and / or nanometric silica (particle size less than 50 nanometers).

In a conventional manner such additives are added to mixture of oxidizing and reducing compounds before coating with wax. The proportions of such additives will be calculated relative to the total mass of the oxidizing mixture and reducer. We can thus provide from 0 to 10% by weight additive.

We can finally incorporate in the composition an additive acting as a catalyst, for example 0 to 10% by weight of ferric oxide (Fe2O3) of particle size 1 to 20 microns.

This additive will be incorporated into the redox mixture before coating with wax.

30 à 70% d'un oxydant (tel le perchlorate de potassium ou d'ammonium),

20 à 40% d'un mélange réducteur associant l'acide myristique avec au moins un acide organique (tel l'acide glutamique, l'acide acétylsalicylique, l'acide ascorbique, l'acide stéarique ou l'acide fumarique),

0 à 10% de liant,

0 à 10% d'un catalyseur (tel l'oxyde ferrique Fe203),

l'acide myristique constituant 10% à 100% du mélange réducteur.

It will thus be possible to produce a gas-generating pyrotechnic composition having the following mass composition:

30 to 70% of an oxidant (such as potassium perchlorate or ammonium),

20 to 40% of a reducing mixture combining myristic acid with at least one organic acid (such as glutamic acid, acetylsalicylic acid, ascorbic acid, stearic acid or fumaric acid),

0 to 10% of binder,

0 to 10% of a catalyst (such as ferric oxide Fe 2 O 3),

the myristic acid constituting 10% to 100% of the reducing mixture.

57% de perchlorate de potassium,

13% à 33% d'acide fumarique,

5% à 20% d'acide myristique,0 à 10% d'un catalyseur (tel l'oxyde ferrique Fe2O3).

In particular, it will be possible to produce a composition associating (proportions in mass):

57% potassium perchlorate,

13% to 33% fumaric acid,

5% to 20% of myristic acid, 0 to 10% of a catalyst (such as ferric oxide Fe 2 O 3).

The following compositions were thus produced:

EXAMPLE 1

A composition combining: 60% by weight of potassium perchlorate (oxidizing), 20% by weight of acid glutamic acid, 10% myristic acid, 5% ferric oxide Fe203, 5% binder (polyethylene wax in the form of granules).

This composition is produced as follows:

First pour into a blender the quantity desired glutamic and myristic acid, one mixes, one add potassium perchlorate, binder (wax), oxide of iron and nanoscale silica (0.2% of the total mass perchlorate + acids + iron oxide). Mix for 10 to 20 minutes.

EXAMPLE 2

The same process is carried out using a composition comprising: 50% by weight of potassium perchlorate (oxidant), 40% by weight of ascorbic acid, 10% of acid myristic.

In addition, a number of control compositions:

EXAMPLE 3

60% by weight of potassium perchlorate and 40% by weight of glutamic acid.

EXAMPLE 4

70% by weight of potassium perchlorate and 30% by weight of ascorbic acid.

Then we introduce the different compositions and performed in a pelletizing tool of known type.

This tooling makes it possible to compress pellets 8 mm in diameter and having a mass of the order 300 milligrams.

The number of moles of gas has also been calculated generated.

The results are recorded in the following table: No. Example Mechanical strength Number of moles of gas generated per kg Example 1 Pastille Resistance from 3 to 6 daN 35 Example 2 Pastille Resistance from 3 to 6 daN 35 Example 3 Do not skip 31 Example 4 Do not skip 24

We see that myristic acid has allowed to pellet compositions that did not pellet. Moreover, performance from the point of view of gas generation have been increased.

To study more precisely the influence of acid Myristic on the mechanical behavior of a composition pyrotechnic the following compositions were made:

EXAMPLE 5 (composition generating a known gas)

57% by weight of potassium perchlorate, 33% by weight of fumaric acid, 10% by weight of Fe 2 O 3.

EXAMPLE 6

57% by weight of potassium perchlorate, 33% by weight of fumaric acid, 5% by weight of Myristic acid, 5% by weight mass of Fe 2 O 3.

EXAMPLE 7

57% by weight of potassium perchlorate, 33% by weight of fumaric acid, 10% by weight of Myristic acid.

EXAMPLE 8

57% by weight of potassium perchlorate, 28% by weight of fumaric acid, 5% by weight of Myristic acid, 10% mass of Fe 2 O 3.

EXAMPLE 9

57% by weight of potassium perchlorate, 23% by weight of fumaric acid, 10% by weight of Myristic acid, 10% mass of Fe2O3.

EXAMPLE 10

57% by weight of potassium perchlorate, 18% by weight of fumaric acid, 15% by weight of Myristic acid, 10% mass of Fe2O3.

EXAMPLE 11

57% by weight of potassium perchlorate, 13% by weight of fumaric acid, 20% by weight of Myristic acid, 10% by weight mass of Fe 2 O 3.

D'une part deux autres compositions (EXEMPLES 6 et 7) dans les quelles on a substitué à l'oxyde ferrique de l'acide myristique,

D'autre part à quatre autres compositions dans lesquelles on a conservé le taux d'oxyde ferrique mais on a substitué de l'acide Myristique à une partie du réducteur connu (acide fumarique).

We have therefore compared a known composition (EXAMPLE 5) with:

On the one hand two other compositions (EXAMPLES 6 and 7) in which the ferric oxide was substituted for myristic acid,

On the other hand to four other compositions in which the level of ferric oxide has been preserved, but Myristic acid has been substituted for a part of the known reducing agent (fumaric acid).

Tablets of each of these compositions were made using the compression method described above. Then, the compressive strength of the compressed tablets (Rr in Mega Pascals) and the Cohesion Index IC (defined as the ratio of the force required to break the tablet to the compressive strength to to obtain the tablet (× 10 ^5). the higher the index of cohesion, the higher the mechanical strength is important.

The results are recorded in the following table: No. Example IC Rr (MPa) Example 5 499 0.37 Example 6 565 0.41 Example 7 631 0.46 Example 8 530 0.39 Example 9 561 0.40 Example 10 592 0.42 Example 11 623 0.44

It is found that the introduction of Myristic acid in a pyrotechnic composition with varying proportions between 5% in mass and 20% in mass has a very strong influence sensitive on the mechanical strength of the composition.

The same observation can be made as well when Myristic acid replaces part of the reducer used only when substituted for some of the additive catalyst.

By way of example, it will also be possible to following composition:

EXAMPLE 12

50% potassium perchlorate,

30% glutamic acid,

10% myristic acid,

10% of a catalyst (such as ferric oxide Fe2O3).

EXAMPLE 13

60% ammonium perchlorate,

20% glutamic acid,

10% myristic acid,

5% binder,

5% of a catalyst (such as ferric oxide Fe2O3).

EXAMPLE 14

50% ammonium perchlorate,

30% glutamic acid,

10% myristic acid,

10% of a catalyst (such as ferric oxide Fe2O3).

EXAMPLE 15

60% potassium perchlorate,

30% acetylsalicylic acid,

5% myristic acid,

5% of a catalyst (such as ferric oxide Fe2O3).

EXAMPLE 16

60% potassium perchlorate,

30% acetylsalicylic acid,

10% myristic acid.

It is of course possible to implement the invention in any other type of composition pyrotechnic. For example an inflammatory composition Aluminum / Copper oxide.

Claims (17)

Pyrotechnic composition comprising at least one oxidizing material and at least one reducing material, characterized in that it incorporates Myristic acid. Pyrotechnic composition according to claim 1, characterized in that it incorporates from 1% to 40% by weight of Myristic acid. Pyrotechnic composition according to claim 2, characterized in that it incorporates from 1% to 10% by weight of Myristic acid. Pyrotechnic composition according to one of Claims 1 to 3, characterized in that the reducing agent comprises at least one organic acid. Pyrotechnic composition according to claim 4, characterized in that the organic acid is selected from the following materials: glutamic acid, acetylsalicylic acid, fumaric acid, stearic acid, ascorbic acid and mixtures thereof. Pyrotechnic composition according to one of claims 1 to 5, characterized in that the oxidizing material is selected from the following materials: potassium perchlorate, ammonium perchlorate, potassium nitrate, ammonium nitrate and mixtures thereof. Pyrotechnic composition according to one of Claims 1 to 6, characterized in that it has the following mass composition: 30 to 70% of oxidant, 20 to 40% of a reducing mixture combining myristic acid and at least one organic acid, 0 to 10% of binder, 0 to 10% of a catalyst (such as ferric oxide Fe 2 O 3), the myristic acid constituting 10% to 100% of the reducing mixture. Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 60% potassium perchlorate, 20% glutamic acid, 10% myristic acid, 5% binder, 5% of a catalyst (such as ferric oxide Fe2O3). Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 50% potassium perchlorate, 30% glutamic acid, 10% myristic acid, 10% of a catalyst (such as ferric oxide Fe 2 O 3). Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 60% ammonium perchlorate, 20% glutamic acid, 10% myristic acid, 5% binder, 5% of a catalyst (such as ferric oxide Fe2O3). Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 50% ammonium perchlorate, 30% glutamic acid, 10% myristic acid, 10% of a catalyst (such as ferric oxide Fe2O3). Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 50% ammonium perchlorate, 40% ascorbic acid, 10% myristic acid. Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 60% potassium perchlorate, 30% acetylsalicylic acid, 5% myristic acid, 5% of a catalyst (such as ferric oxide Fe2O3). Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 60% potassium perchlorate, 30% acetylsalicylic acid, 10% myristic acid. Pyrotechnic composition according to Claim 7, characterized in that it has the following mass composition: 57% potassium perchlorate, 13% to 33% fumaric acid, 5% to 20% of myristic acid, 0 to 10% of a catalyst (such as ferric oxide Fe 2 O 3). Pyrotechnic composition according to claim 15, characterized in that it has the following mass composition: 57% potassium perchlorate, 33% fumaric acid, 10% myristic acid. Pyrotechnic composition according to claim 15, characterized in that it has the following mass composition: 57% potassium perchlorate, 13% fumaric acid, 20% myristic acid. 10% ferric oxide Fe2O3.