Gas-generating composition and its use in pedestrian protection devices

Abstract

Gas generating composition for use in safety devices for vehicles, with a gas yield of at least 85%, the composition consisting of 75 to 98 wt% guanidine nitrate as fuel, 2 to 25 wt.% of a combustion accelerator selected from the group of transition metal compounds, metal nitrates, metal chlorates, metal perchlorates, ammonium perchlorate and mixtures thereof, wherein the transition metal compounds are selected from the compounds of the transition metals Ti, Cr, Mn, Fe, Cu, Zn, Zr and Mo and have an average grain size of at most 5 µm and a specific surface area of ​​at least 1 m 2 / g, 0 to 5 wt.% combustion moderators and / or coolants, and 0 to 3 wt.% processing aids from the group of flow aids, pressing aids and lubricants, each based on the total composition, and wherein the gas generating composition has a burning rate of 3 to 17 mm / s at 20 MPa.

Description

[0001] The invention relates to gas-generating compositions, particularly for use in vehicle safety devices. In particular, the invention relates to such compositions based on guanidine nitrate used in pedestrian protection devices.

[0002] Gas-generating compositions based on guanidine nitrate are known, for example, from EP 1 006 096 A1 and US Pat. No. 6,143,102 A. Almost all manufacturers of vehicle occupant restraint systems use such compositions in the series production of pyrotechnic gas generators for gas bag modules of occupant protection devices, in particular for driver and passenger airbags. The compositions commonly used for these applications, with guanidine nitrate as fuel, exhibit a mass-related gas yield of approximately 65 to 75%, combustion rates of approximately 20 to 30 mm / s, and combustion temperatures of approximately 1700 to 2000 K. The proportion of guanidine nitrate in these compositions is frequently in the range of 40 to 50 wt.%.

[0003] The use of gas bag modules in vehicle interiors places increased demands on the propellant gas produced, as this can, for example, enter the passenger compartment via the gas bag's outlet openings. The limit values ​​for gas components such as CO, NH3, and NO required by the automobile manufacturers' specifications xHowever, these can only be achieved using propellant mixtures with a substantially balanced oxygen balance. Therefore, the proportion of guanidine nitrate in gas-generating compositions for gasbag modules is limited to approximately 65 wt.%, and significant amounts of oxidizers must be used in addition to guanidine nitrate. Since the oxidizers usually do not fully contribute to gas generation, the potential gas yield of such compositions is reduced. Even for compositions with low combustion temperatures, which have a positive effect on the harmful gas composition, a higher proportion of non-gas-forming additives must be accepted, which also has a negative impact on the gas yield. The gas yields achievable with the gas-generating compositions commonly used to date using guanidine nitrate as fuel are therefore a maximum of 75%.

[0004] US Pat. No. 6,893,517 B2 describes gas-generating compositions based on guanidine nitrate with a gas yield of approximately 80%. These compositions contain other organic fuels and are formulated for use in seat belt pretensioners. The compositions therefore exhibit a significantly higher combustion temperature of over 2,000 K and a high combustion rate of over 40 mm / s at 20 MPa.

[0005] Pure guanidine nitrate does not exhibit self-sustaining and complete decomposition after ignition. US Pat. Nos. 2,604,391 A and DE 884 170 B therefore propose improving the ignition behavior and combustion properties of guanidine nitrate through suitable additives. By adding copper and copper compounds to guanidine nitrate, gas-generating compositions with a combustion rate of approximately 1 mm / s at 0.9 MPa are achieved. The addition of vanadium pentoxide is said to increase the combustion rate. However, vanadium pentoxide is toxic and therefore unsuitable for automotive applications.

[0006] DE 697 30 202 T2 discloses a gas-generating composition suitable for inflating a motor vehicle airbag with a passive restraint system. The composition contains a fuel comprising (A) at least one non-azide constituent, for example, guanidine nitrate, and (B) diammonium bitetrazole or 2,4,6-trihydrazino-s-triazine, in a proportion of 5 to 85 weight percent. Furthermore, 10 to 85 weight percent of an oxidizing agent may be included.

[0007] GB 656 315 A discloses gas-generating compositions comprising nitroguanidine and / or guanidine nitrate, as well as at least one non-explosive inorganic component and a heat-resistant filament material with a high specific surface area. The filament material preferably consists of asbestos fibers or wire mesh.

[0008] The combustion speeds required for gas-generating compositions for occupant protection systems (driver, front passenger, and side impact systems) are generally > 20 mm / s. This means that with the commonly used propellant web thicknesses (generally tablets) of 1 to 2 mm, combustion is completed after a maximum of 100 ms. Web thickness here refers to the layer thickness of a propellant that is covered during combustion until the propellant is completely consumed. For example, a cylindrical tablet with a diameter of 6 mm and a height of 3 mm has a web thickness of 1.5 mm, since with uniform combustion from all sides, the entire tablet is consumed after a layer thickness of 1.5 mm has been burned.

[0009] US 2006 / 0 175 115 A1 describes a pedestrian protection device for a vehicle, having a triggering mechanism which is designed to move a hood of the vehicle from a rest position to a raised impact position, and an airbag module assigned to the triggering mechanism which is used to activate the triggering mechanism.

[0010] However, for pedestrian protection applications on the exterior of the vehicle, to protect against pedestrian impact with the hood or windshield, gas delivery times of more than 100 ms are desired. Furthermore, the inflated airbag should have the longest possible service life. To achieve this, it is advantageous if the temperature of the gas generated to inflate the airbag is as low as possible to minimize pressure loss due to gas cooling.

[0011] The object of the invention is to provide gas-generating compositions which can achieve longer gas delivery times and improved service life of the protective devices activated by the release of gas and which are suitable for pedestrian protection applications.

[0012] This object is achieved by a gas-generating composition according to claim 1.

[0013] The invention also relates to a pedestrian protection device in vehicles according to claim 18, in which the gas-generating composition according to the invention is contained, as well as to the use of the gas-generating compositions according to the invention in a gas generator of a safety device according to claim 22 and in pedestrian protection devices of vehicles according to claim 23.

[0014] Advantageous embodiments of the invention are specified in the subclaims, which can optionally be combined with one another.

[0015] The gas-generating composition according to the invention is intended for use in vehicle safety devices and has a gas yield of at least 85%. The composition consists of 75 to 98 wt.% guanidine nitrate as fuel, 2 to 25 wt.% of a combustion accelerator selected from the group of transition metal compounds, metal nitrates, metal chlorates, metal perchlorates, ammonium perchlorate, and mixtures thereof, 0 to 5 wt.% combustion moderators and / or coolants, and 0 to 3 wt.% processing aids from the group of flow aids, pressing aids, and lubricants, each based on the total composition. The combustion rate of the composition is in the range of 3 to 17 mm / s at 20 MPa.

[0016] Transition metal compounds within the meaning of the invention are the compounds, preferably the oxides, hydroxides, carbonates, basic carbonates and basic nitrates, of the metals of the first row of transition metals, namely titanium, chromium, manganese, iron, copper and zinc, as well as of zirconium and molybdenum from the second transition metal row.

[0017] Compounds of the metals vanadium, cobalt, and nickel, as well as cadmium and mercury, are not expressly excluded by the invention, as they are undesirable due to their toxicological properties. Compounds of hexavalent chromium are equally undesirable. The use of these metals or their compounds is explicitly excluded in the vast majority of automobile manufacturers' specifications anyway.

[0018] Metal nitrates, metal chlorates and metal perchlorates are particularly compounds of alkali metals and alkaline earth metals.

[0019] According to a preferred embodiment, the molar gas yield of the gas-generating composition is at least 0.035 mol / g (moles of gas produced / g of fuel), more preferably from 0.039 to 0.043 mol / g, and the volume-related gas yield (moles of gas produced / volume of fuel) is at least 0.059 mol / cm 3 , particularly preferably from 0.059 to 0.062 mol / cm 3 .

[0020] The theoretical molar gas yield for pure guanidine nitrate is 0.042 mol / g, the theoretical volume-related gas yield is 0.061 mol / cm 3 , each calculated for a pressure of 30 MPa. Slightly higher molar or volume-related gas yields can be achieved by using suitable combustion accelerators that lower the molecular weight of the produced gas and / or increase the density of the gas-generating composition.

[0021] The combustion rate of the gas-generating compositions used in airbag modules for pedestrian protection devices outside the passenger compartment is preferably in the range of 7.0 to 16.0 mm / s at 20 MPa. If the gas-generating compositions are used in micro gas generators for activating hood lifters and similar pedestrian protection devices, in which the gas released from the composition actuates a cylinder-piston mechanism, the combustion rate is preferably in the range of 10 to 17 mm / s at 20 MPa. For rapid applications, small tablets with a diameter of 1-4 mm or granules can be used.

[0022] Joint grinding of the components, for example in a ball mill, vibrating ball mill, or oscillating mill, has proven to be an effective method for increasing the burning rate of a given composition. With the aid of the grinding media, the particle size of the components used is reduced, and high homogeneity is achieved through the intimate mixing and pressing of the individual particles. Both factors promote an increase in the reactivity of the components used and thus also the burning rate. The burning rate of the mixtures can be controlled within a wide range by the duration of the joint grinding and homogenization as well as the grain size of the starting compounds. This allows significantly higher burning rates to be achieved than with the sets described in US Pat. No. 2,604,391, even with the nominally identical composition.

[0023] According to the invention, the transition metal compound is used in a finely divided quality with an average grain size of at most 5 µm and a specific surface area of ​​at least 1 m 2 / g is used.

[0024] Using a mixture of 94.5% guanidine nitrate, 5% copper oxide, and 0.5% calcium stearate, a burning rate of 6.2 mm / s at 20 MPa was achieved. The copper oxide grade used as the starting material had an average grain size of 0.8 µm and a specific surface area of ​​10 m 2 / g. The guanidine nitrate used had an average grain size of 6.5 µm. However, it has been found that the grain size of the guanidine nitrate used as the starting material is of minor importance, since a coarser grain size can be compensated by a longer grinding time.

[0025] The gas-generating composition preferably has an oxygen balance of -10% to -27%, particularly preferably -14% to -24%. The low oxygen balance contributes to a high gas yield and a low combustion temperature. An adverse effect on the carbon monoxide content can be tolerated because the gases released during combustion of the composition do not enter the passenger compartment.

[0026] The oxygen balance is the amount of oxygen released in weight percent upon complete conversion of a compound or mixture to CO2, H2O, N2, Al2O3, B2O3, etc. (oxygen overbalance). If the available oxygen is insufficient for this, the amount required for complete conversion is indicated with a negative sign (oxygen underbalance).

[0027] According to a particularly preferred embodiment, the compositions according to the invention are stable under hot storage conditions at 120°C for over 400 hours. The weight loss in the hot storage test under the stated conditions is preferably less than 2%, particularly preferably less than 1%. Thus, the compositions according to the invention also meet the specifications of automobile manufacturers for applications in the engine compartment.

[0028] The compositions according to the invention preferably have a combustion temperature of at most 1650 K. The combustion temperature is preferably in the range from 1370 to 1650 K, particularly preferably in the range from 1420 to 1630 K. The provision of cool gases is also advantageous for applications in the area outside the passenger compartment and promotes a longer service life of the inflated gas bag or the safety device activated by gas pressure.

[0029] The combustion accelerator is preferably selected from the group consisting of TiO2, Cr2O3, MnO2, Fe2O3, Fe3O4, CuO, Cu2O, ZnO, ZrO2, MoO3, FeOOH, Cu(OH)2, ZnCO3, MnCO3, FeCO3, GuCO3, basic zinc carbonate, basic copper carbonate, basic copper nitrate, basic zinc nitrate, NaNO3, KNO3, Sr(NO3)2, NaClO3, KClO3, NaClO4, KClO4, NH4ClO4 and mixtures thereof.

[0030] According to a particularly preferred embodiment of the composition according to the invention, the combustion accelerator is a mixture of at least one compound from the group of metal nitrates, metal chlorates, metal perchlorates and ammonium perchlorate and additionally at least one transition metal compound of Ti, Cr, Mn, Fe, Cu, Zn, Zr and Mo. With this embodiment, a high gas yield is achieved with a sufficient combustion rate and, at the same time, a low combustion temperature.

[0031] Preferably, the compound is selected from the group of metal nitrates, metal chlorates, and metal perchlorates from the group consisting of NaNO3, KNO3, Sr(NO3)2, NaClO3, KClO3, NaClO4, KClO4, and mixtures thereof. The use of ammonium perchlorate is also contemplated in this embodiment.

[0032] In the described embodiment, the transition metal compound is preferably selected from the group consisting of TiO2, Cr2O3, MnO2, Fe2O3, Fe3O4, CuO, Cu2O, ZnO, ZrO2, MoO3, FeOOH, Cu(OH)2, ZnCO3, MnCO3, FeCO3, CuCO3, basic zinc carbonate, basic copper carbonate, basic copper nitrate, basic zinc nitrate and mixtures thereof.

[0033] The transition metal compounds have an average grain size of at most 5 µm, particularly preferably at most 3 µm, and a specific surface area of ​​at least 1 m 2 / g, particularly preferably at least 3 m 2 / g on.

[0034] In addition to guanidine nitrate as fuel and the aforementioned combustion accelerators, the composition according to the invention may contain up to 5 wt.% of further additives from the group of combustion moderators and / or coolants. These additives stabilize the combustion and keep the combustion temperature low. At the same time, the slagging of the combustion residues is improved, thus preventing the residues from becoming atomized.

[0035] Examples of suitable combustion moderators and / or coolants are B2O3, Al2O3, MgO, SiO2, Mg(OH)2, basic magnesium carbonate, CaCO3 and their mixtures.

[0036] Furthermore, the compositions may contain up to 3% of processing aids such as pressing aids, flow aids and / or lubricants, which, in the stated amount, do not have a significant effect on the burning rate of the composition.

[0037] Examples of suitable processing aids are polyethylene glycol, cellulose, methylcellulose, graphite, wax, calcium stearate, magnesium stearate, zinc stearate, boron nitride, talc, bentonite, silica and molybdenum sulfide and mixtures thereof.

[0038] The invention further relates to a pedestrian protection device for a vehicle, comprising a gas generator and gas-activated means for pedestrian protection, such as an inflatable gas bag or a piston-cylinder system for raising the engine hood, in which the gas generator contains a gas-generating composition according to the invention according to one or more of the embodiments described above.

[0039] Preferably, the gas generator of the pedestrian protection device is arranged outside a passenger compartment of the vehicle, for example, in the engine compartment. In such an embodiment, the improved heat storage stability of the composition according to the invention is particularly advantageous.

[0040] According to a particular embodiment of the pedestrian protection device according to the invention, the gas generator interacts with an inflatable gas bag. In the event of a collision between the vehicle and a pedestrian, the inflated gas bag can significantly reduce the risk of injury to the pedestrian.

[0041] According to another embodiment of the pedestrian protection device, the gas generator drives the piston-cylinder system of a hood lifter. This prevents a pedestrian from striking the vehicle's windshield and reduces the risk of lacerations from broken glass.

[0042] Finally, the invention also relates to the use of the gas-generating compositions according to the invention according to one or more of the embodiments described above in a gas generator of a safety device in a vehicle, wherein the gas generator is arranged outside a passenger compartment of the vehicle.

[0043] The use of the gas-generating compositions in a pedestrian protection device for vehicles is particularly preferred.

[0044] The advantages of the gas-generating compositions according to the invention lie in the fact that high gas yields can be achieved with simultaneously low combustion temperatures and moderate combustion rates, which ensure a long gas delivery time and a longer service life of the gas-activated safety devices. The combustion rates achieved with the compositions according to the invention are lower than those of compositions previously used for gas bag modules in the occupant protection sector, but at the same time are still within a range suitable for use in pedestrian protection devices.

[0045] The high thermal stability of the compositions according to the invention also enables their use in the engine compartment of vehicles, where temperatures of up to 120 °C can easily be reached under operating conditions.

[0046] Finally, the compositions according to the invention rely on proven and non-toxic components that are available on the market at reasonable prices.

[0047] The invention will now be described with reference to preferred embodiments, which, however, should not be understood in a limiting sense. Examples 1 to 18

[0048] Guanidine nitrate with an average particle size of 6.5 to 35 µm, transition metal compounds with an average particle size of between 0.5 and 2 µm and a specific surface area of ​​between 4 and 25 m 2 / g, metal nitrates and perchlorates with an average grain size of around 50 µm as well as pyrogenic aluminum oxide, silicon dioxide and / or calcium stearate were mixed in the parts by weight indicated in Table 1 below, ground together in a vibrating ball mill and pressed into tablets. Table 1 Example No. Components [%] GuN bCN KClO4 KNO3 Sr(NO3)2 CuO Al2O3 SiO2 Fe2O3 Ca stearate 1 87,5 10,0 2,0 0,5 2 92,5 5,0 2,0 0,5 3 92,5 5,0 2,0 0,5 4 89,5 5,0 2,0 3,0 0,5 5 87,5 10,0 2,0 0,5 6 92,5 5,0 2,0 0,5 7 94,5 5,0 0,5 8 89,5 10,0 0,5 9 87,0 7,5 2,0 3,0 0,5 10 87,0 7,5 2,0 3,0 0,5 11 89,5 5,0 2,0 3,0 0,5 12 92,5 5,0 2,0 0,5 13 89,5 5,0 2,0 3,0 0,5 14 87,5 5,0 5,0 2,0 0,5 15 81,0 10,0 5,0 2,5 1,0 0,5 16 76,0 15,0 5,0 2,5 1,0 0,5 17 92,5 5,0 2,0 0,5 18 89,5 5,0 5,0 0,5

[0049] The abbreviations used in Table 1 mean: GuN = guanidine nitrate bCN = basic copper nitrate

[0050] The burning rate (BR) of the compositions according to Examples 1 to 18 was determined by firing 10 grams of propellant each in a closed 100 cm 3 Bomb. The test results and other calculated properties of the compositions are given in Table 2. Table 2 Example No. Characteristics BR[mm / s] T[K] GA[%] O2 balance[%] GA[mol / g] Density [g / cc] GA[mol / ccm] 1 5,3 1427 92,6 -21,3 0,039 23,71 0,060 2 11,4 1500 95,6 -22,9 0,041 23,49 0,061 3 15,9 1447 94,9 -23,2 0,040 23,51 0,060 4 10,8 1432 93,6 -22,4 0,040 23,63 0,059 5 5,7 1427 92,6 -21,3 0,039 23,71 0,060 6 11,9 1500 95,6 -22,9 0,041 23,49 0,061 7 6,2 1379 95,9 -25,1 0,040 23,73 0,060 8 6,2 1384 91,9 -22,8 0,039 23,79 0,060 9 15,3 1559 91,3 -20,3 0,039 23,38 0,059 10 7,2 1498 90,1 -20,9 0,039 23,38 0,059 11 9,7 1426 93,0 -22,4 0,039 23,63 0,059 12 4,3 1370 93,9 -24,6 0,040 23,73 0,060 13 10,1 1483 93,0 -22,1 0,040 23,5 0,060 14 10,5 1499 91,2 -21 0,039 23,53 0,060 15 11,2 1573 88,7 -17,3 0,038 23,53 0,062 16 11,7 1625 85,8 -14,5 0,037 23,2 0,059 17 13,5 1516 96,4 -23,3 0,041 23,7 0,061 18 15,1 1503 93,5 -22,5 0,039 23,71 0,060

[0051] The other abbreviations used in Table 2 mean: T = combustion temperature, calculated in Kelvin GA [%] = mass-related gas yield GA [mol / ccm] = volume-related gas yield GA [mol / g] = molar gas yield

[0052] The compositions according to Examples 1 to 18 were also subjected to an aging test lasting 400 hours at 120 °C. After this test, a weight loss of less than 2% was generally observed. For the composition according to Example 16, a weight loss of only 0.36% was observed. Thus, all compositions meet the increased requirements for aging resistance of gas generator fuels for engine compartment applications.

[0053] The combustion tests described above also demonstrate the suitability of the compositions according to the invention for use in pedestrian protection devices.

Claims

[1] Gas generating composition for use in safety devices for vehicles, with a gas yield of at least 85%, the composition consisting of 75 to 98 wt% guanidine nitrate as fuel, 2 to 25 wt.% of a combustion accelerator selected from the group of transition metal compounds, metal nitrates, metal chlorates, metal perchlorates, ammonium perchlorate and mixtures thereof, wherein the transition metal compounds are selected from the compounds of the transition metals Ti, Cr, Mn, Fe, Cu, Zn, Zr and Mo and have an average grain size of at most 5 µm and a specific surface area of ​​at least 1 m 2 / g, 0 to 5 wt.% combustion moderators and / or coolants, and 0 to 3 wt.% processing aids from the group of flow aids, pressing aids and lubricants, each based on the total composition, and wherein the gas generating composition has a burning rate of 3 to 17 mm / s at 20 MPa. [2] Composition according to claim 1, characterized by that the molar gas yield of the gas-generating composition is at least 0.035 mol / g. [3] Composition according to claim 1, characterized by that the volumetric gas yield of the gas-generating composition is at least 0.059 mol / cm 3 amounts. [4] Composition according to at least one of claims 1 to 3, characterized by that the burning rate is in the range of 7 to 16 mm / s at 20 MPa. [5] Composition according to at least one of claims 1 to 3, characterized by that the burning rate is in the range of 10 to 17 mm / s at 20 MPa. [6] Composition according to at least one of the preceding claims, characterized by that the gas-generating composition has an oxygen balance of -10% to -27%. [7] Composition according to claim 6, characterized by that the oxygen balance is in the range of -14% to -24%. [8] Composition according to at least one of the preceding claims, characterized by that the composition is storage stable at 120 °C for over 400 hours. [9] Composition according to at least one of the preceding claims, characterized by that the gas-generating composition has a combustion temperature of not more than 1650 K. [10] Composition according to claim 9, characterized by that the combustion temperature is in the range of 1420 to 1630 K. [11] Composition according to at least one of the preceding claims, characterized by that the transition metal compound is selected from the group of transition metal oxides, transition metal hydroxides, transition metal carbonates, basic transition metal carbonates and basic transition metal nitrates. [12] Composition according to at least one of the preceding claims, characterized by that the combustion accelerator is selected from the group consisting of TiO2, Cr2O3, MnO2, Fe2O3, Fe3O4, CuO, Cu2O, ZnO, ZrO2, MoO3, FeOOH, Cu(OH)2, ZnCO3, MnCO3, FeCO3, CuCO3, basic zinc carbonate, basic copper carbonate, basic copper nitrate, basic zinc nitrate, NaNO3, KNO3, Sr(NO3)2, NaClO3, KClO3, NaClO4, KClO4, NH4ClO4 and mixtures thereof. [13] Composition according to at least one of the preceding claims, characterized by that the combustion accelerator is a mixture of at least one compound from the group of metal nitrates, metal chlorates, metal perchlorates and ammonium perchlorate and additionally at least one transition metal compound of Ti, Cr, Mn, Fe, Cu, Zn, Zr and Mo. [14] Composition according to claim 13, characterized bythat the compound is selected from the group of metal nitrates, metal chlorates and metal perchlorates from the group consisting of NaNO3, KNO3, Sr(NO3)2, NaClO3, KClO3, NaClO4, KClO4, NH4ClO4 and mixtures thereof. [15] Composition according to claim 13 or 14, characterized by that the transition metal compound is selected from the group consisting of TiO2, Cr2O3, MnO2, Fe2O3, Fe3O4, CuO, Cu2O, ZnO, ZrO2, MoO3, FeOOH, Cu(OH)2, ZnCO3, MnCO3, FeCO3, CuCO3, basic zinc carbonate, basic copper carbonate, basic copper nitrate, basic zinc nitrate and mixtures thereof. [16] Composition according to at least one of the preceding claims, characterized by that the combustion moderators and / or coolants are selected from the group consisting of B2O3, Al2O3, SiO2, MgO, Mg(OH)2, MgCO3, basic magnesium carbonate, CaCO3 and mixtures thereof. [17] Composition according to at least one of the preceding claims characterized bythat the processing aids are selected from the group consisting of polyethylene glycol, cellulose, methylcellulose, graphite, wax, calcium stearate, magnesium stearate, zinc stearate, boron nitride, talc, bentonite, silica and molybdenum sulfide and mixtures thereof. [18] Pedestrian protection device for a vehicle, comprising a gas generator and gas-activated means for pedestrian protection, characterized by that the gas generator contains a gas-generating composition according to one of claims 1 to 17. [19] Pedestrian protection device according to claim 18, characterized by that the gas generator is located outside a passenger compartment of the vehicle. [20] Pedestrian protection device according to claim 18 or 19, characterized by that the gas generator interacts with an inflatable gas bag. [21] Pedestrian protection device according to one of claims 18 or 19, characterized bythat the gas generator drives a hood lifter of the vehicle. [22] Use of a gas-generating composition according to any one of claims 1 to 17 in a gas generator of a safety device in a vehicle, wherein the gas generator is arranged outside a passenger compartment of the vehicle. [23] Use of a gas-generating composition according to any one of claims 1 to 17 in a pedestrian protection device for vehicles.