FR2950624A1 - Pyrotechnic compound comprising ammonium perchlorate oxidative charge, nitrogenous organic charge of at least one compound comprising e.g. triazoles and metal oxide charge, useful in gas generator for airbag and inflate cushioning pillows - Google Patents

Abstract

Gas generating pyrotechnic compound (I) comprising: ammonium perchlorate oxidative charge; nitrogenous organic charge of at least one compound comprising triazoles, tetrazole, dinitramide and/or diamides, where the nitrogenous organic charge has an oxygen balance of greater than -120% and a melting temperature of greater then 180[deg] C; and metal oxide charge, where (I) does not contain alkaline nitrate, is claimed.

Description

The present invention relates to pyrotechnic compounds gas generators. Said pyrotechnic compounds have a high swelling capacity (the intrinsic inflation power of a formulation is given by the product of the molar yield of said formulation (in mol / kg) by the temperature T (in K). produces pressure once the volume and thus translates the ability of a formulation to generate a quantity of gas); and a high inflating surface flow rate (the inflation surface flow rate is estimated by the product pxnx T x Vc, where p is the density of the material (in g / cm 3), n the molar gas yield of the combustion (in mol / g), T the combustion temperature (in K) and Vc the combustion rate (in cm / s) Thus, the parameter of the inflating surface flow rate is expressed in mol.K / cm2.

Moreover, the combustion of the pyrotechnic compounds of the invention generates few condensed particles. The present invention is in the technical field of pyrotechnic generation of gas. It is particularly applicable in vehicle occupant protection systems, protection by means of damping cushions (so-called "airbags"), which are inflated by the combustion gases of pyrotechnic compounds. The technical field of airbags inflated by gas generators including pyrotechnic compounds based on pyrotechnic compositions has known for the last twenty years a 'ssor very important. This field is now maturing and the ECT system is being developed and is being used as a basis for formulation.

These are some of the gases that are present in the atmosphere. generally of good quality vis-à-vis the acceptable toxicity standards in force in the field (USCAR). These compositions, on the other hand, have disadvantages which can penalize certain applications, the gas yield is generally low. The necessary mass of product is therefore important; the combustion temperature being relatively low and the gas yield low, the swelling capacity is limited; When combustion emits solid residues, filters are necessary to reduce the emission of particles. These filters further reduce the swelling capacity due to the thermal losses they induce. The filters further induce an increase in the volume and cost of the generator; Due to the high mass associated with the low inflation power, the on-board thermal energy is high and the residual thermal energy in the gas generator is high after combustion. In almost all cases, the cold compositions present low combustion. This cumulative point at low swelling power induces low inflation surface flow rates. These low surface inflation rates are compensated for by the use of thin pellets and small diameters which induce a large initial surface of pyrotechnic product and a low loading density. A strong, strong, initial surface of the product of the past, or, in the future, of the product;

In other words, "U = ndep" (ie, when the bag is heavily exposed to the bag is strongly subject to the positioning constraints in the deployment phase, the strong constraints exerted in the confined environment during the first milliseconds by the set. generator and bag on the support of the module imply a relative oversizing of said support, the combustion of small pellets with decreasing surface evolution induces a sharp decrease in the flow rate as the combustion progresses while the functional need is at contrary to a constant flow rate, or in some cases a progressive flow rate • The high swelling capacity of a composition being associated with the molar yield gaseous temperature pair, the compositions meeting these requirements have a high combustion temperature (greater than 2500 K) and a low rate of particles produced during combustion.The low rate of particles is made necessary to dispense dare the maximum amount of gas emitted and so as to avoid aggression on the bags. Tests in airbag modules have indeed shown that the damage of the bags by the combustion products is exacerbated by the presence of particles when using "hot" compositions and by the internal operating pressure. For all the aforementioned reasons, a composition with high swelling capacity, high inflating surface flow rate and without particles therefore has many advantages vis-à-vis the operation and miniaturization of gas generators for airbag system. This miniaturization has been completed for reasons of weight, with no weight, no emptying, no more than the average value of the product. It should be noted that ammonium hydroxide is used in low to moderate amounts and is used to increase the rate of burning. Patent Application WO 95/25709 describes formulations Based on guanidine nitrate and ammonium or potassium perchlorate, the guanidine nitrate and ammonium perchlorate mixture forms a eutectic around 160 ° C. In the absence of a binder, this mixture causes problems of fusion during Fire resistance tests and frequently induces dangerous behavior Patent application WO 2005/012208 discloses compositions based on guanidine nitrate and basic copper nitrate in which a low level of ammonium perchlorate is added to In order to improve the toxicity of the effluents, in these compositions the chlorine is neutral. The gas yield remains relatively low.

The patent application EP 372733 describes compositions comprising triazoles and / or tetrazoles, an oxidizing mixture made from ammonium perchlorate and alkaline nitrate, and optionally an additive serving as a combustion rate modifier. Such compositions have a lower gas yield than the compositions of the present invention. In addition, the mixture of ammonium perchlorate with an alkaline nitrate leads to the formation of a eutectic which shows a lowered melting point. Obtaining an eutectic below the auto-ignition temperature leads to the risk of explosion during the test of resistance to fire in a gas generator. In addition, the presence of a nitrate leads to a significant decrease at the end of the day and a daring increase.

drt d "} <,,: WI- (hio`. ~ i off 1fliunium t sinpri, Ition without binder rfi = iu hti) n S ~; j0, _ ') ~? rlle 061dltft 01 nOr ti ci / cirai (~ The latter is, in fact, always in search of gas-generating compounds with a high combustion temperature, even in the latter state of the art. , generating few particles and toxic effluents, these compounds can advantageously be obtained by a dry process, such as in particular described in the application WO 2006/134311. In this context, the inventor wished to propose generating pyrotechnic compounds performance targets, in particular: - to increase the gas yield - to obtain an easily ignitable composition - to remove particles (solid combustion residues) - to have a high speed of combustion to increase the thickness to be burned and therefore the compactness of the generator in order to: - reduce the volume and mass of propellant needed; eliminating the filters that are useful for filtering said particles; and - obtaining said compounds by a dry process (comprising a powder mixing step, a compaction step, followed by a possible granulation step, a possible addition of at least one additive (auxiliary of fabrication,), and a possible final step of pelletizing). The compositions of the pyrotechnic gas-generating compounds according to the invention, which are of particular interest for airbag application, contain: an oxidizing charge of ammonium perchlorate, an organic nitrogen charge (at least one "wide") of at least I ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The compositions of the pyrotechnic compounds of the invention generally contain no binder. and their ingredients, the nature of which is specified above, oxidizing, reducing and at least one metal oxide charges generally represent more than 70% of their mass, advantageously more than 80% of their mass. The invention is also capable of containing: - an additional reducing charge (serving as a cooling agent) consisting of oxalic acid and / or - at least one carboxylic acid (whose function is to facilitate tableting), selected from cyanuric acid, fumaric acid, tartaric acid, malonic acid, succinic acid, glutaric acid, ascorbic acid, adipic acid, transcinnamic acid, 1H-1,2,4-triazole-3-carboxylic acid, sebacic acid and their mixtures; preferentially chosen from 1H-1,2,4-triazole-3-carboxylic acid and sebacic acid; and / or - at least one additive (for example, manufacturing aid), such as calcium stearate. The nitrogenous organic filler has an oxygen balance greater than -120% and preferably greater than -80%, so as to limit the level of ammonium perchlorate and, as a corollary, the level of hydrogen chloride emitted by the compound in question. combustion. Said nitrogenous organic filler has a melting temperature of greater than 180 ° C., so as to ensure good thermal stability and good mechanical strength of the OMOSOSECs, especially in the form of pellets, after aging in said filler. , Ritual of Flo pus trnlor in Jlo ([) (tr-C.TliOrdJ .. This trinuronide Hi ~ 3 this Ce -tiieis dana) vse therrrilci rneianges av PO ni .. 0, L Cl eUteChClu 1 These mixtures are preferably composed of one of these compounds, and depending on the desired effects in terms of rate of combustion and compliance with safety constraints, the ammonium perchlorate employed can be used in the preparation of the mixtures. Mufti-modal mixtures can be made to optimize the compromise between safety, ballistics, the production process used and the toxicity of the effluents, The fine granulometries have for rô to increase the speed of combustion. Large granulometries allow to limit the sensitivity to the aggressions and the effects of an intense shock on the product. The charge of at least one metal oxide, employed as a ballistic catalyst, generally consists of an oxide or of transition metal oxides, preferably with a high specific surface area, which makes it possible to increase its effect while limiting the amount introduced. Said at least one metal oxide is advantageously chosen from the family of oxides of iron, copper, manganese and their mixtures. It consists very advantageously of an oxide of iron, copper or manganese. Those skilled in the art are aware that the said iron and copper oxides, which are ballistic catalysts, consist for the most part of ferric oxide and cupric oxide respectively. The additional reducing charge (optional) serving as cooling agent is chosen so that its combustion does not generate particles. Its oxygen level is high. It consists of oxamide and / or oxalic acid. It also has the function of reducing the enslbiiite of the material to mechanical aggression (friction, shock, and! Or e induced ~ risks of transition in the region of France). (Id cadi.) By pelletization 5rht siOn. A _ titi-. The compositions of the compounds of the invention generally comprise, in percentages by mass: 22.9 to 75% of the total weight of the compounds of the invention. said oxidizing charge (of ammonium perchlorate), 10 to 77% of said nitrogenous organic charge, 0.1 to 2% of said charge of at least one metal oxide, 0 to 15%, advantageously 2 to 8, %, of said additional reducing charge, 0 to 10%, advantageously 2 to 8%, of at least one carboxylic acid, 0 to 1% of at least one additive, the compositions of the compounds of the invention being Typically do not include alkaline nitrate (chlorine sensor) In the absence of a chlorine sensor, the hydrogen chloride formed by combustion is predominantly captured by the bag when condensed with water. In any case, its rate is limited by the use of oxygen reducer (s) weakly negative balance, advantageously the most The desired properties described above are attained in the following way: the high gas yield is achieved by the joint use of a nitrogen-containing organic component as a reducing agent and ammonium perchlorate as an oxidizer, without the addition of a sensor chlorine (without the addition of an alkaline nitrate); The presence of ammonium perchlorate and a reducing agent makes the composition easily ignitable; in the absence of a chlorine sensor, the level of particles intrinsically generated by the composition is very low; the use of nitrogen-containing organic reductant (s) of the indicated types results in compounds having a very high rate of combustion; the combination of a high rate of combustion and a high gas yield allows the production of compounds having a high thickness to be burned, which increases the construction index and makes it possible to limit the ignition charge by limiting the surface initiating the possible addition, at a low level, of at least one carboxylic acid, advantageously chosen as a function of its oxygen balance, its melting temperature and its ability to flow under stress, makes it possible to reduce the porosity of the mixture after compression and thus to perfect the control of the ballistics of the compounds of the invention. In addition, unlike guanidine nitrate (guanidine nitrate generally and advantageously absent from the composition of the compounds of the invention) which could provide the same function, these acids do not normally form eutectic with ammonium perchlorate and thus not induce a melting point lowered with ammonium perchlorate. The high rate of combustion allows the production of compounds (pellets (ovoid) or pancakes (planes)) of large dimensions, which have good mechanical properties. The initial gas flow rate can be limited and a flat shape function for the internal pressure curve can be approximated. This type of operation is favorable to reduce the effects of the beginning of deployment of the bag on the module containing the bag and the plastic elements of the dashboard.

For example, a wafer 40 mm in external diameter and 14 mm in internal diameter, 5 mm thick, (large object) has a decreasing surface area burned by a factor of 1.7 while a 6 mm x 2 mm patch (small object) commonly used has a surface degression of a factor of 4.

Thus the gas generator and the associated module can be smaller, conmpacts and less expensive. In addition, lean a strong t (m) i (.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, The loading geometry also allows the design of shapes to deliver a slightly decreasing flow rate, which is not possible with usual pellet feeds.

The advantageous properties mentioned above, achieved, together, in a non-obvious manner, by the compounds of the invention make said compounds particularly interesting. The pyrotechnic compounds of the invention are advantageously obtained by a dry process which comprises a step of compacting a powder mixture containing their constituent powder ingredients, optionally followed by a granulation step, itself followed, if necessary. of a pelletizing step. Said compounds are typically in the form of monoliths, mono- or mufti-perforated. A manufacturing aid intervenes advantageously before the implementation of the shaping step. It is now proposed to illustrate, in a non-limiting manner, the presently claimed invention. Pyrotechnic compound compositions have been evaluated by means of thermodynamic calculations and physical measurements.

Thermodynamic Calculations: Potassium perchlorate / nitrogen organic feed binary mixtures, base blends of the compositions of the compounds of the invention, were compared to deus. compositions A and B, of the prior art, thermodynamic calculation means. 27.45% by mass of sodium nitrate and 0.5% by weight of Fe 2 O 3. It is of the type of the compositions described in the patent application EP 372733.

Table 1 below summarizes the thermodynamic performance of said binary mixtures (nitrogen-containing organic compound + ammonium perchlorate). These blends are designed to achieve an oxygen balance of -2%, which is generally close to the optimum in terms of effluent toxicity, for applications in the field of automotive safety. Table 1 A B Ex. No. 1 Ex. No. 2 Ex. No. 3 Ex. r) 5 Dicyandiamide Di-ammonium-5,5'-5-AmIno-Guenfurea AZODN biterazole Etru zo lu clin iu druide -114 -74 -66 -13 25.8 33.3 36.1 67.8 76 , 1 7U 2669 2932 2947 3053 2844 2884 _ 30.8 36.7 38.3 37.5 37.4 37.8 s 19.4 0 0 0 0 0 1.80 1.78 1.80 1.72 1 , 81 1.77 L 82.2 107.6 112.9 114.5 106.4 109 3 147.9 191.5 203.2 196.9 192.5 193 0 22.9 20.7 19.8 9 The list of nitrogen molecules tested in Table 1 is not exhaustive. In the examples given which scan oxygen balances between -114% and -13%, it is possible to observe a relative constancy of the combustion temperature at 20 MPa, which is around 2950 +/- 100 K, a relative constancy gas yield, which is around 37.5 Al-1 mol / kg. The intrinsic inflation power of these formulations is therefore relatively constant. Depending on the oxygen balance of the nitrogenous organic compound, it is possible to adapt the level of hydrogen chloride emitted by the formulation. The lowest rates are around 7%. Compared to the two reference compositions A and B of the prior art, Examples 1 to 5 of the invention have a reduced residue level, a higher combustion temperature, an increased gas yield, a swelling capacity of 1.3. at 2 times higher, and this, for an equivalent density. On the basis of the aforementioned mixtures or other mixtures based on nitrogenous organic compound (s) and ammonium perchlorate, a ballistic catalyst is added. This catalyst is in the form of a powder of an oxide of a transition metal with a high specific surface area. Ideally, this catalyst is iron, copper or manganese oxide. It is preferably iron oxide and is introduced preferentially to constitute at most 2% (by weight) of the total composition. Ideally, the rate is 1% by mass. The level of particles emitted by the composition is in this case from 0% to approximately 1%.

The compounds of the invention have the disadvantage of emitting hydrogen chloride at the end of combustion, said hilfi hydrogen chloride. ## EQU1 ## where ## EQU1 ##, ## EQU1 ## This mother has to be muted in the United States of America, under the same conditions. ba Combustion and Ballistic Tests: Compositions based on the binary mixtures according to Examples 1 and 2 were subjected to combustion tests, so as to confirm the advantages in terms of burning speed and therefore compactness of loading. . The composition according to Example 1 supplemented with a part by weight of iron oxide with a high specific surface area (as a ballistic catalyst) has the following characteristics: - pressure exponent: 0.7 between 15 and 45 MPa and combustion rate at 20 MPa of 70 mm / s - pressure exponent above 30 MPa: 0.6 and 5OMPa combustion rate of 140 mm / s. The composition according to Example 2 supplemented with one part by weight of high surface area iron oxide (as a ballistic catalyst) has the following characteristics: pressure exponent: 0.5 between 15 and 45 MPa and combustion rate at 20 MPa of 115 mm / s exposing pressure above 30 MPa: 0.4 and burn rate 20 to 50 MPa of 185 mm / s. For comparison, the composition according to Comparative Example A is frequently employed with a pressure peak of 30 MPa and a pellet size of 2 mm. Taking into account the rate of combustion as a function of pressure, this type of loading and thickness leads to operating times of the order of 10 to 50 ms with a high flow rate at the beginning of operation and

t_c ~ cern esjtinn `; ~ r ~ en ~ r ~, ~, dditio n a rti _n i ~ nids u o / d: [scinting a. : test of o mPi, sn) n dE '; 50 to 1 m 30> p 1P ~? . Load the front and front air bag for the driver. Under the same conditions, a compound according to the composition of Example 2 (supplemented with one part by weight of iron oxide) can perform the same type of function with about 20 g of product in the form of a monolithic block 40 mm in diameter and 10 mm thick with a central housing (for igniter) of 14 mm.

Claims (6)

REVENDICATIONS1. A pyrotechnic gas generating compound whose composition contains an oxidizing charge of ammonium perchlorate; a nitrogenous organic filler of at least one compound chosen from triazoles, tetrazoles, dinitramides, diamides and their mixtures; said nitrogenous organic filler having an oxygen balance greater than -120% and a melting temperature above 180 ° C; a charge of at least one metal oxide does not contain alkaline nitrate. 2. Compound according to claim 1, characterized in that said nitrogenous organic filler has an oxygen balance greater than -80%. 3. Compound according to claim 1 or 2, characterized in that said nitrogenous organic filler and ammonium perchlorate do not form eutectic below 180 ° C. 4. Compound according to any one of claims 1 to 3, characterized in that said nitrogenous organic filler is selected from dicyandiamide, di-ammonium-5,5'-biterazole, 5-aminotetrazole, ganyl urea dinitramide, azodiformamidine dinitrate and mixtures thereof. 5. Compound according to any one of claims 1 to 4, characterized in that said charge of at least one metal oxide comprises at least one oxide selected from oxides of iron, copper, manganér; their mixtures. 6. (.) `LGro elon one. Any of these claims adds to the idea that the con ~ lu ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Ut 'su ce Il gos n ren5e 1 n t1 + l_1 P ~ ..J'i 0, ._ 1 dCIC J.Ie Dniqu ~.: Empty sr the acidi ~, .i <~ rique rh,. Jipiqui Vacuum r ~. ~ 1H oxy 'aci, -er t selected l, the ~ ~ ~ ~ ~ ~ ~ e8 ee. Compound according to any one of claims 1 to 7, characterized in that its composition comprises, expressed in percentages by weight 22.9% of the oxidizing charge of ammonium perchlorate, 10 to 77% of said organic charge nitrogen, 0.1 to 2% of said metal oxide charge, 0 to 15%, advantageously 2 to 8%, of said additional reducing charge, 0 to 10%, advantageously 2 to 8%, minus one carboxylic acid, and - 0 to 1% of at least one additive. 9. Compound according to any one of claims 1 to 8, characterized in that it is obtained by a dry process which comprises a step of compacting a powder mixture containing the constituent ingredients of said powdered compound, optionally followed a granulation step, itself followed, if necessary, a pelletizing step. 10. Pyrotechnic compound according to any one of claims 1 to 9, monolithic type, mono- or mufti-perforated.