CZ20031998A3 - Propellant for gas producers and use thereof - Google Patents

Abstract

The invention relates to solid gas generator fuel compositions (gas producing mixtures), comprising: (A) nitroguanidine or nitroguanidine stabilised with 0.1 to 0.5% nitroguanidinium hydrogen sulphate and nitroguanidinium nitrate as fuel; (B) an oxidising agent selected from the group comprising alkali and earth alkali nitrates, chlorates and perchlorates, ammonium nitrate and perchlorate, copper compounds with oxidising properties and mixtures thereof; (C) a stabiliser selected from the group comprising hydrophobic SiO2, inorganic and organic acids and mixtures thereof; and optionally (D) a combustion stabiliser or moderator and ash former or trap and mixtures thereof. The above gas generator fuel compositions comprise an improved shelf-life under hot storage conditions at 110° C.

Description

Propellant for gas generators and its use

Technical field

The invention relates to a propellant for gas generators and to its use. The invention therefore relates to solid propellants, i.e. gas generating mixtures, in particular for gas generators for airbags and seat belt tensioners, wherein the propellant for gas generators has a very good long-term thermal stability.

BACKGROUND OF THE INVENTION

The airbag consists essentially of a gas generator housing which is filled with a propellant for generating gas, generally in the form of tablets, a igniter (squib) for igniting the propellant, and a gas bag. Suitable igniters are described, for example, in US 4,931,111. The initially folded gas bag is filled with the gases produced by the combustion of the gas-generating fuel after firing the igniter and reaches its full volume in about 10 to 50 ms. Essentially, sparks, molten substances or solids from the gas generator must not be allowed to escape into the gas bag, as this could damage the gas bag or cause injury to the occupants of the car. This is accomplished by binding and filtering the slag produced by the combustion of the fuel in the gas generator.

The existing fuel charges in gas generators for car airbags are sodium azide-based and have been known for a long time. However, the use of toxic sodium azide requires increased production costs for gas generators. In addition, worldwide a growing number of burnt-out

of gas generators in discarded motor vehicles is becoming a problem in terms of their disposal and safety.

In recent years, therefore, attempts have been made to find suitable propellants for gas generators that contain no sodium azide or other toxic substances.

DE-A-44 35 790 of the same Applicant discloses propellants for gas generators based on guanidine compounds on suitable supports, which have a substantially more favorable burnout and slag formation. DE-A-44 35 790 discloses a propellant for gas generators comprising (A) at least one carbonate, hydrogen carbonate or nitrate of guanidine, aminoguanidine, diaminoguanidine or triaminoguanidine in an amount of about 20 to 55% by weight, based on the total amount of components (A) and (B), (B) at least one alkali metal nitrate or rare earth metal nitrate or ammonium nitrate as oxidizing agent in an amount of about 80 to 45% by weight, based on the total amount of components (A) and (B) and at least one carrier (Cl) in an amount of 5 to 45% by weight, to moderate burn-out and to improve slag formation, based on the total amount of components (A) and (B) selected from the group consisting of Al ₂ O ₃ , alkali metal or rare earth metal aluminosilicates or silicates and / or (C2) at least one oxygen-releasing carrier selected from the group consisting of an oxide ferric, cobalt oxides, manganese dioxide or copper oxide. However, this document does not address the problem of the long-term stability of propellant fuels at elevated temperatures. In relation to stability, this document DE-4435790 refers to the so-called Holland test, in which the propellant for gas generators is heated to 105 ° C for 72 hours. The Holland test is a method developed in 1927 for the determination of the chemical durability of fuels. It shows the loss of weight that occurs after 72 hours of heating of propellants on several bases to 105 ° C or of propellants on one base to 110 ° C. The weight loss occurring, if subtracted during the first eight hours, may not exceed 2% (see J. Kohler and R. Meyer, Explosivstoffe, 9th revised and supplemented 1998, Verlag Wiley-VCH 170).

DE-19812372 A1, which also belongs to the same applicant, discloses propellants for gas generators comprising (A) at least one fuel selected from the group consisting of guanidine nitrate, dicyanodiamide, ammonium dicyanodiamide, sodium dicyanodiamide, copper dicyanodiamide, tin dicyanodiamide, dicyanodiamide calcium, guanidinedicyanodiamide, ammoniumguanidinium bicarbonate, ammoniumguanidinium nitrate, triaminoguanidinium nitrate, nitroguanidine, dicyandiamide, azodicarbonamide, as well as tetrazole, 5-aminotetrazole, 5nitro-1,2,4 triazol-3-one, salts and one of their mixtures, (B) or a noble natural metal nitrate or ammonium nitrate, ammonium chlorate or ammonium perchlorate, (C) at least one high melting, substantially chemically inert slag binder selected from the group consisting of Al ₂ O ₃ , titanium dioxide TiO ₂ , and zirconia ZrO ₂ in highly dispersed form or a mixture thereof i, and optionally (D) at least one slag-forming agent selected from the group consisting of carbonates and oxides of alkali and rare earth metals, silicates, aluminates and aluminum silicates, ferric oxide and silicon nitride which releases 4 nitrogen and 4 nitrogen; silica for further reactions, and optionally (E) at least one water-soluble binder at room temperature.

The high melting, substantially chemically inert slag binding agent in highly dispersed form, i.e. produced by flame hydrolysis, serves as an internal filter, thereby largely preventing the formation and leakage of dust particles from the gas generator. Part of the slag binding agent in highly dispersed form can serve as a support for the catalytic metals. Thus, this document does not address the long-term stability of propellants for hot gas generators.

In view of the ever-increasing number of different airbag systems in motor vehicles, such as head airbags, passenger airbags and side airbags, and taking into account the ever-increasing technical lifetime of motor vehicles, the automotive industry is increasingly demanding the stability of fuels for gas generators. Experiments have shown that satisfactory stability results cannot be achieved with the existing propellant propellants with nitroguanidine as fuel.

Thus, the problem of long-term stability of fuels for hot gas generators during hot storage has not been solved in the prior art.

SUMMARY OF THE INVENTION It is an object of the present invention to provide improved propellants for gas generators which meet the increasing requirements of the automotive industry for stability in the hot storage for at least 400 hours at a temperature of 110 ° C while maintaining their operability.

SUMMARY OF THE INVENTION

This task solves propellant for gas generators, comprising:

(A) nitroguanidine as a fuel stabilized by the addition of 0.1 to 0.5% nitrogaunidinium hydrogen sulfate and nitroguanidinium nitrate, (B) an oxidizing agent selected from the group consisting of alkali and earth alkali nitrates, chlorates and perchlorates, ammonium nitrate and perchlorate, oxidizing copper compounds; mixtures thereof, (C) a stabilizer selected from the group consisting of inorganic and organic acids and mixtures thereof, and optionally (D) a stabilizer or a fire moderator and a means for forming or binding the slag and mixtures thereof.

This propellant for gas generators will stand up to at least 400 hours at 110 ° C for hot storage, meeting the increasing demand of the automotive industry for the stability of propellants for gas generators in air waste.

Further preferred is a propellant for gas generators comprising:

(A) nitroguanidine as a fuel, (B) an oxidizing agent selected from the group consisting of alkali and earth alkali nitrates, chlorates and perchlorates, ammonium nitrate and perchlorate, oxidizing copper compounds and mixtures thereof, (C) boric acid stabilizer, and optionally ( D) a burner stabilizer or moderator and a means for forming or binding the slag and mixtures thereof.

Surprisingly, propellants for nitroguanidine gas generators as fuel and said oxidizing agents, or mixtures thereof, in conjunction with one or more stabilizers of this kind can be surprisingly achieved by storage at 110 ° C for 400 hours, preferably 1000 hours, and in particular 3,000 hours of weight loss of less than 1%, preferably less than 0.5% and in particular less than 0.2%, while maintaining the functionality of the propellant for the gas generators. The stability values achieved apply equally in both open and in practice closed systems.

The fuel is nitroguanidine (NIGU; NQ). Nitroguanidine is practically non-toxic, non-hygroscopic, poorly water soluble, thermally stable, burns at low temperatures and poorly sensitive to impact and friction. The combustion yield of the gases is high, with the flue gas being largely nitrogen.

Nitroguanidine containing 0.1 to 0.5% nitrogaunidinium hydrogen sulfate and nitroguanidinium nitrate is particularly suitable according to the invention. Such acid stabilized nitroguanidine is hereinafter referred to as stabilized nitroguanidine. The pH of the aqueous extract (5 g of nitroguanidine in 200 ml of water at 20 ° C) of this stabilized nitroguanidine is in the range of 3.5 to 4.4. Such stabilized nitroguanidine is marketed, for example, under the name NIGU LBD SS from NIGU CHEMIE GmbH, Waldkraiburg, Germany.

The present NIGU has a pH in the range of 4.5 to 7.0 (5 g nitroguanidine in 200 ml water at 20 ° C).

The oxidizing agent, i.e. component (B), may be used.

alkali and earth alkali nitrates such as lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate or barium nitrate. Similarly, ammonium nitrate and chlorates and perchlorates of alkali or earth alkali metals such as lithium chlorate, sodium chlorate, potassium chlorate, magnesium chlorate, calcium chlorate, strontium or barium chlorate, and lithium perchlorate, sodium perchlorate, potassium perchlorate, magnesium perchlorate , calcium perchlorate, strontium perchlorate or barium perchlorate and ammonium perchlorate and mixtures thereof. In addition, the used oxidizing copper compounds such as Cu (N0 _{3) 2} í3Cu (OH) ₂ or Cu ₂ (OK) ₃ NO _3, CuCO _3, and CuO, and mixtures thereof. Preferably used potassium nitrate, potassium chlorate, strontium nitrate, arnmoniumnitrát, ammoniumperchlorát and Cu (N0 _{3) 2} and Cu (OH) _2, (trihydroxynitrát divalent copper). Preference is also given to mixtures of alkali and rare earth metal nitrates with ammonium perchlorate, in particular mixtures consisting of potassium nitrate or sodium nitrate with ammonium perchlorate.

Inorganic and organic acids can be used as stabilizers, i.e. component (C). A particularly preferred inorganic acid is boric acid. Suitable organic acids are citric acid, tartaric acid, cyanuric acid, terephthalic acid and fumaric acid.

Another suitable stabilizer is hydrophobic silica SiO ₂ (commercially available as Aerosil R812S from Degussa AG, the hydrophobizing agent is hexamethyldisilazane) when stabilized nitroguanidine is used as the fuel. SiO ₂ is a material that does not wet with water, i.e., floats on the surface of the water (see infra, Schriftenreihe Pigmente, No. 11, p. 55).

and more) . The silica SiO ₂ is preferably present in combination with another stabilizer.

The gaseous products resulting from the combustion of the propellants for the gas generators according to the invention consist essentially of carbon dioxide, nitrogen and water vapor. The concentrations of any toxic gaseous combustion products such as carbon monoxide CO, nitrogen oxides NO _x and ammonia (NH ₃ ) are below the required limit values.

Nitroguanidine, component (A), is present in the propellant for the gas generators of the invention in an amount of about 33 to 60 wt%, preferably about 40 to 60 wt%. The oxidizing agent component (B) is present in an amount of about 35 to 55% by weight, preferably about 38 to 52% by weight. and in particular 40 to 48% by weight, the stabilizer, component (C) is present in an amount of up to about 5% by weight, preferably up to about 3% by weight. and in particular up to about 1.6% by weight, and component (D) is present in an amount of up to about 7% by weight, preferably up to about 5% by weight. % and especially about 0.4 to 5 wt.

It is preferred that as component (C) in addition to hydrophobic silica SiO ₂ is present also inorganic or organic acid as stabilizer.

The propellant for the gas generators according to the invention optionally also comprises a stabilizer or a burner moderator, i.e. component (D), which can also act as a means for forming or binding the slag. It may be aluminum oxide Al ₂ O ₃ , in particular highly dispersed aluminum oxide Al ₂ O ₃ with a specific surface area according to DIN 66131 in the range of 100 ± 15 m ² / g, which is

- 9 99 9999

999 market, for example, as Aluminum oxide C from the German company Degussa AG. It can also be Fe ₂ O ₃ , SiO ₂ , iron (III) acetylacetonate and mixtures thereof, and mixtures of highly dispersed Al ₂ O ₃ and highly dispersed SiO ₂ , for example a mixture consisting of approximately 16% highly dispersed Al ₂ O ₃ and approximately 84% of highly dispersed silica SiO ₂ , which is marketed, for example, as Aerosil COK 84 from the German company Degussa AG (see Schriftenreihe Pigmente, Grundlagen von Aerosil®, No. 11, 5th edition 1993, p. 38, Degussa AG.

The advantageous effects of using highly dispersed Al ₂ O ₃ alumina in propellants for gas generators are described in DE 19812372 A1, to which reference is expressly made. The highly dispersed alumina Al ₂ O _3, with a primary particle size of approximately 13 nm, acts as a slag trap, i.e., as an internal filter within the propellant propellant that binds the slag. The pyrogenic oxides are prepared by high temperature hydrolysis (flame hydrolysis) of gaseous metal chlorides (A1C1 ₃₎ under the influence of water formed during the reaction of oxyhydrogen gas, and a temperature characteristic of such a reaction (4 A1C1 ₃ + 6H ₂ + 3 0 ₂ 1 ₂ Al ₂ O ₃ + 12 Hel) see Schrif tenreihe Pigmente, Hochdisperse Metalloxide nach dem Aerosil®-Verfahren, No. 56, 4th edition 1989, Degussa AG.

The stabilizers or burner moderators, component (D), induce a linear burnout, i.e., an exponential increase in pressure and temperature during burnout is avoided. For example, iron oxide Fe ₂ O ₃ can also serve as an oxygen source under certain burn-out conditions. In addition, these compounds can be used to form slag to prevent the formation of pulverized combustion products.

- 10 ·· <»· * · ····

Component (D) is present in the propellant for the gas generators in an amount of up to about 7 wt%, preferably up to about 5 wt%. % and in particular in an amount of about 0.4 to 5 wt.

The highly dispersed alumina Al ₂ O ₃ is present in the propellants for the gas generators according to the invention in an amount of up to 5% by weight, preferably in an amount of between 0.5 to 3% by weight. % and in particular in an amount of about 2 - 3 wt. Due to this small proportion of Al ₂ O ₃ , a high gas yield is ensured.

The propellants for the gas generators according to the invention may further comprise at least one binder as component (E). Examples of suitable binders are cellulose compounds, polymerizates of one or more polymerizable olefinic unsaturated monomers, water-insoluble room temperature metal stearic acid salts and graphite. Graphite is particularly preferred.

Examples of cellulose compounds are cellulose ethers such as carboxymethylcellulose, methylcellulose ethers, especially methylhydroxyethylcellulose. A well-used methylhydroxyethylcellulose is CULMINAL® MHEC 30000 from Aqualon. Suitable binder-binding polymers are, for example, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol and polycarbonates.

The binder (E) serves as a means for desensitizing and facilitating the processing of propellant for gas generators in the manufacture of granules or tablets. The binder also serves to reduce the hydrophilicity of propellants for gas generators.

Component (E) is present in an amount of up to about 5% by weight, preferably in an amount of up to about 3% by weight, especially up to about 1% by weight. and especially in an amount of about 0.2 to 0.5 * 44 444 444 4 44

4444 444 44

- 11 4 * 4

4444 wt.

A preferred variant of the propellant for gas generators according to the invention comprises as fuel (A) nitroguanidine, in particular nitroguanidine stabilized according to the invention by the addition of 0.1 to 0.5% nitroguanidium hydrogen sulphate and nitroguanidinium nitrate, as oxidant (B) Cu (NO3) 2 <3Cu 12, KN0 ₃ Sr (NO ₃ ) _2; KNO ₃ or a mixture of KNO ₃ and NH ₄ C1O ₄ , at least one stabilizer (C) selected from the group consisting of hydrophobic silica SiO ₂ , boric acid, citric acid, tartaric acid, cyanuric acid, terephthalic acid, fumaric acid, optionally mixed with hydrophobic silica SiO ₂ and as a component (D) highly dispersed alumina Al ₂ O ₃ , optionally mixed with Fe ₂ O ₃ , and graphite as component (E).

In another embodiment, the propellant for the gas generators (A) comprises nitroguanidine stabilized by the addition of 0.1 to 0.5% nitroguanidium hydrogen sulphate and nitroguanidinium nitrate as fuel, (B) Sr (NO ₃ ) ₂ or a mixture of KNO ₃ or and NaNO ₃ and NH ₄ C1O ₄ as oxidizing agent, and optionally (D) at least one stabilizer or moderator burnout and means for generating or binding slag.

Another embodiment is that the propellant for the gas generators comprises a component (D) selected from the group consisting of Al ₂ O ₃ , highly dispersed Al ₂ O ₃ , iron oxide Fe ₂ O ₃ , silica SiO ₂ , iron (III) acetylacetonate and a mixture of highly dispersed Al ₂ O ₃ and highly dispersed SiO ₂ .

In these cases, component (A) is present in the propellant for the gas generators in an amount of approximately 33 to 60% by weight.

%, Preferably about 40 to 60 wt. and in particular about 45 to 55 wt%, component (B) is present in an amount of about 35 to 55 wt%, preferably about 38 to 52 wt%. and in particular 40 to 48 wt%, component (D) is present in an amount of up to about 7 wt%, preferably up to about 5 wt%. % and especially about 0.4 to 5 wt.

It is also preferred that in these cases the propellant for the gas generators further comprises at least one binder as component (E)

In these cases, the binder is selected from the group consisting of cellulose compounds, polymerizates of one or more polymerizable olefinic unsaturated monomers, water-insoluble room temperature metal salt of stearic acid and graphite.

The invention also relates to the use of the described propellant for gas generators as a means for generating gases in air waste and as an extinguishing agent or propellant.

Surprisingly, it has been found that a propellant for gas generators which contains stabilized nitroguanidine nitrate as fuel and Sr (NO ₃ ) ₂ , or a mixture of NaNO ₃ or KNO ₃ with NH ₄ ClO ₄ as an oxidizing agent, even in the presence of stabilizers or burners moderators and the slag forming or binding means has good or excellent long-term storage stability at 110 ° C. A stabilizer additive (component (C)) is not required to stabilize the propellant for the gas generators.

Excellent long-term stability for fuels for

The gas generators of the present invention can be explained by the acidic environment in these propellant propellants.

Examples

Manufacturing code

Generally, the production of propellants and propellants for gas generators was carried out according to the following procedure:

A) Wet process:

The starting components (A), (B), (C) and optionally (D) were mixed and ground and optionally pre-thickened using a ball mill. Granulation of the propellant mixture for the gas generators was performed by mixing in a vertical mixer with an addition of approximately 20 wt. water at a temperature increased to approximately 40 ° C. After briefly venting or pre-drying, the obtained mixed mass was rubbed in a friction machine with a 1 mm sieve. The granulate thus obtained was dried for about 2 hours in a drying oven at about 80 ° C.

The finished propellant granulate for gas generators with a grain size of 0-1 mm was subsequently compressed into tablets by means of a rotary disk press. These gas generator pellets or fuel pellets were dried in a drying oven at 80 ° C.

B) Dry process:

The starting components (A), (B), (C) and optionally (D) and (E) were dry blended and then compressed under pressure, for example by means of a gear compactor. The file was then • ·

broken into granules and compressed into tablets using a rotary tablet press.

The fuel tablets used in the gas generators can be prepared by known methods, for example by extrusion, by means of the aforementioned rotary disk press or by tabletting machines. The size of the tablets or pellets depends on the burning time required in the application.

The propellant for the gas generators according to the invention consists of non-toxic, easy-to-manufacture and cost-effective components whose processing is problem-free. Mixtures can be well ignited. The mixtures then burn rapidly and achieve a high gas yield with a low content of carbon monoxide (CO), nitrogen oxides (NO _x ) and ammonia (NH ₃ ) below the permissible maximum values. The compositions of the invention are therefore particularly suitable for use as gas generators in various airbag systems and have very good stability when stored hot at 110 ° C for more than 400 hours. The mixtures are also suitable as extinguishing agents or as propellants.

The invention is further illustrated by the following Examples 1 to 24 (Table II), but are not limited thereto.

In Table I, Examples 1 to 11 are comparative examples.

The data in the tables have the following meanings:

aluminum oxide C, Degussa AG iron oxide 99.9%, ALFA Aesar - Johnson Matthey GmbH

Aerosil COK 84, Degussa AG

- 14 4 Aerosil, R 812 S, Degussa AG

Explanation of fuel structure

T4x2 tablets O diameter 4 mm and height 2 mm T3xl, 5 tablets O diameter 3 mm and height 1.5 mm T3x0,8 tablets O diameter 3 mm and height 0.8 mm T6x2 tablets O diameter 6 mm and height 2 mm

The granulate produced by the wet process described above.

The percentages are in% by weight.

GuNO ₃ stands for guanidium nitrate and serves as an auxiliary fuel with less energy.

In the following examples, the abbreviation NIGU (stabilized) means nitroguanidine which is stabilized with nitroguanidinium hydrosulfate and nitroguanidium nitrate in a total amount of 0.2%.

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Comparative Example 4 shows a significant increase in stability due to the addition of hydrophobic silica SiO ₂ . Compared to the formulation of Comparative Example 5, a tablet with a diameter of 4 mm and a height of 2 mm after storage for 400 hours has a weight loss of only 0.62%, whereas the formulation of Comparative Example 5 is 1.45%. Both formulations according to Comparative Example 4 and Comparative Example 5 contain a sufficient amount of 2.6% by weight. Al ₂ O ₃ . However, this stability improvement is not sufficient to meet the requirements of the automotive industry.

In the case of the formulation according to Comparative Example 6, stabilized nitroguanidine was used for the first time according to the invention. Here, too, it exhibits a marked increase in stability compared to the formulation of Comparative Example 5. However, this stability improvement is not sufficient to achieve satisfactory stability. The formulation of Comparative Example 6 is not a prior art formulation. Based on the results of Comparative Example 6, it has been found by further experiments that an acidic environment is required to stabilize the propellants for nitroguanidine gas generators.

Comparative Example 7 shows the instability of a propellant for gas generators which contains stabilized nitroguanidine in the presence of Cu (NO ₃ ) ₂ * ₃ Cu (OH) ₂ . In Comparative Examples 8 and 9, an oxidation mixture of Sr (NO ₃ ) ₂ and Cu (NO ₃ ) ₂ * ₃ Cu (OH) _{2 was used} . Al ₂ O ₃ additionally present in the formulation according to Comparative Example 9 again reduces stability. In comparative examples 10 and 11, the stability of the stabilized nitroguanidine in the presence of CuCO ₃ and optionally

CuO.

• · · ···············

According to Example 1 of the present invention (Table II), a gas generator propellant containing Al ₂ O ₃ as component (D) achieved very good stabilization by combining stabilized NIGU as fuel and hydrophobic silica SiO ₂ as stabilizer - see Comparison of Example 1 with Comparative Examples 4 and 6.

An even greater improvement in stability is achieved by the presence of another stabilizer selected from the group consisting of inorganic and organic acids - see comparison with Examples 2-4.

Very good stability is also achieved with propellants for gas generators containing existing NIGU as fuel and Al ₂ O ₃ alumina as component (D) and using stabilizers selected from the group consisting of inorganic and organic acids - see comparison with examples 5 to 10.

In Examples 1 to 10, KNO ₃ in combination with alumina was used as the oxidizing agent, i.e. component (hlin). Al ₂ O ₃ in highly dispersed form and iron (III) acetylacetonate as component (D).

According to Example 11, very good stability was also achieved in combination with Aerosil COK 84 and iron (III) acetylacetonate as component (D).

The formulation of Example 12 contains KClO ₄ as an oxidizing agent, i.e. component (Β), and Aerosil COK 84 as component (D). Here too, very good stability has been achieved with the granulate.

Finally, Examples 13 to 15 show that stable propellants for gas generators can be achieved even in the presence of oxide. · · ············ Aluminum Al ₂ O ₃ (cf. example 14) without stabilizer when a KNO ₃ mixture is used as the oxidizing agent · Aluminum Al ₂ O ₃ (cf. Example 14) and NH ₄ C1O ₄ in combination with stabilized NIGU fuel. Comparison with Comparative Example 5 shows that such good stability cannot be achieved with existing nitroguanidine as fuel and KNO ₃ as oxidizing agent in the presence of Al ₂ O ₃ .

Finally, Example 15 shows good fuel stability for gas generators which, in addition to nitroguanidine as fuel, also contain guanidinium nitrate as an energy-poor auxiliary fuel.

According to Examples 16 and 17, very good stability even in the presence of Al ₂ O _{3 is} achieved using Cu (NO ₃ ) ₂ * ₃ Cu (OH) ₂ as the oxidizing agent and boric acid as the stabilizer.

In Examples 18 to 20, Sr (NO ₃ ) ₂ was used as the oxidizing agent. The stability of stabilized nitroguanidine in the presence of Sr (NO ₃ ) ₂ and alumina Al ₂ O ₃ has been demonstrated. By adding boric acid as a stabilizer, this stability is further improved.

Examples 21 and 22 show the stabilizing effect of boric acid in mixtures containing Sr (NO ₃ ) ₂ and Cu (NO ₃ ) ₂ * ₃ Cu (OH) ₂ as oxidizing agent - see Comparative Examples 8 and 9.

Finally, Examples 23 and 24 show the stabilizing effect of boric acid in mixtures containing it as an oxidizing agent

CuCO ₃ and CuO respectively - see Comparative Examples 10 and 11.

Claims (17)

PATENT CLAIMS 1. Propellant for gas generators, comprising: (A) nitroguanidine as a fuel stabilized by the addition of 0.1 to 0.5% nitrogaunidinium hydrogen sulfate and nitroguanidinium nitrate, (B) an oxidizing agent selected from the group consisting of alkali and earth alkali nitrates, chlorates and perchlorates, ammonium nitrate and perchlorate, oxidizing copper compounds; mixtures thereof, (C) a stabilizer selected from the group consisting of inorganic and organic acids and mixtures thereof, and optionally (D) a stabilizer or a fire moderator and a means for forming or binding the slag and mixtures thereof. 2. Propellant for gas generators, containing: (A) nitroguanidine as a fuel, (B) an oxidizing agent selected from the group consisting of alkali and earth alkali nitrates, chlorates and perchlorates, ammonium nitrate and perchlorate, oxidizing copper compounds and mixtures thereof, (C) boric acid stabilizer, and optionally ( D) a burner stabilizer or moderator and a means for forming or binding the slag and mixtures thereof. Propellant for gas generators according to claim 1 or 2, characterized in that component (A) is present in an amount of approximately 33 to 60% by weight, preferably approximately 40 to 60% by weight. and in particular about 45 to 55% • 4 ··· ·· «• · · · · · · · · ♦ ·« _«φ" wt. component (B) is present in an amount of about 35 to 55 wt.%, with preferably about 38 to 52 wt. and in particular 40 to 48 wt%, component (C) is present in an amount of up to about 5 wt%, preferably up to about 3 wt%. and in particular up to about 1.6% by weight, and component (D) is present in an amount of up to about 7% by weight, preferably up to about 5% by weight. % and especially about 0.4 to 5 wt. Propellant for gas generators according to one of Claims 1 to 3, characterized in that component (C) additionally contains hydrophobic silica SiO ₂ as a stabilizer. A propellant for gas generators according to any one of the claims 1-4, characterized in that component (B) is selected from the group consisting of sodium nitrate, potassium nitrate, strontium nitrate, ammonium perchlorate, potassium perchlorate, trivalent copper trihydroxynitrate and mixtures thereof. 6. The propellant for gas generators according to claim 1, wherein component (B) is a mixture of potassium nitrate and ammonium perchlorate. Propellant for gas generators according to one of Claims 1 to 3, characterized in that component (C) is selected from the group consisting of boric acid, citric acid, tartaric acid, cyanoic acid, - terephthalic acid and fumaric acid. Propellant for gas generators according to one of Claims 1 to 7, characterized in that in addition to the hydrophobic silica SiO ₂ , inorganic or organic acid as a stabilizer is also present as component (C). Propellant for gas generators according to any one of claims 1 to 8, characterized in that component (D) is selected from the group consisting of alumina Al ₂ O ₃ , ferrous oxide Fe ₂ O ₃ , silica SiO ₂ , acetylacetonate oxide and a mixture of highly dispersed Al ₂ O ₃ and highly dispersed SiO ₂ . 10th Propellant for gas generators according to claim 9, characterized in that aluminum oxide Al ₂ O ₃ is present in highly dispersed form. The propellant for gas generators according to claim 9, wherein component (D) is a mixture consisting of about 16% highly dispersed Al ₂ O ₃ alumina and about 84% highly dispersed silica SiO ₂ . Propellant for gas generators according to one of Claims 1 to 11, characterized in that it further comprises at least one binder as component (E). 13. The propellant for gas generators according to claim 12, wherein component (E) is selected from the group consisting of cellulose compounds, polymerizates of one or more polymerizable olefinic unsaturated monomers, water-insoluble, at room temperature, metal stearic acid salt and graphite. . Propellant for gas generators according to claim 12 or 13, characterized in that component (E) is 1 * 99 · 99,999 9 9 9 99 9 9,999 i 9% is present in an amount of about 5% by weight, preferably in an amount of about 3% by weight, especially up to about 1% by weight. and especially in an amount of about 0.2 to 0.5 wt. A propellant for gas generators according to any one of claims 1 to 14, characterized in that it comprises (A) nitroguanidine stabilized by the addition of 0.1 to 0.5% nitroguanidium hydrogen sulphate and nitroguanidinium nitrate as fuel, (B) KNO ₃ or a mixture of KNO ₃ and NH ₄ ClO ₄ as oxidizing agent, (C) a stabilizer selected from the group consisting of hydrophobic silica SiO ₂ , boric acid, citric acid, tartaric acid, cyanoic acid, terephthalic acid, fumaric acid and mixtures thereof, (D) highly dispersed oxide aluminum Al ₂ O ₃ , optionally mixed with iron oxide by Fe ₂ O ₃ , and (E) graphite. 16. A propellant for gas generators comprising (A) nitroguanidine stabilized by the addition of 0,1 to 0,5% nitroguanidium hydrogen sulphate and nitroguanidinium nitrate as fuel, (B) Sr (NO ₃ ) 2 or a mixture of KN0 ₃ thereof and NaNO ₃ and NH ₄ C _{10 4} as an oxidizing agent, and optionally (D) at least one stabilizer or fire moderator and a means for forming or binding the slag. 17. The propellant for gas generators according to claim 16, wherein component (D) is selected from the group consisting of alumina, Al ₂ O ₃ ,