Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0033—Shaping the mixture
  • C06B21/0041—Shaping the mixture by compression
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06D—MEANS FOR GENERATING SMOKE OR MIST; GAS-ATTACK COMPOSITIONS; GENERATION OF GAS FOR BLASTING OR PROPULSION (CHEMICAL PART)
  • C06D5/00—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets
  • C06D5/06—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets by reaction of two or more solids

Definitions

• the present invention relates to large pyrotechnic grains based on binder-free formulations, to their production, and to their use. More precisely, it relates to:
• ⁇ pyrotechnic grains which are in the form of blocks (monolithic blocks) with large dimensions;
• Gas generation has a number of applications, both in the civilian and in military fields.
• compositions with a high combustion rate In the automotive safety sector, gas generators have been developed with a short operational duration, which use compositions with a high combustion rate. Those compositions are in the form of thin pellets (1 mm [millimeter] to 3 mm) with a small diameter (3 mm to 7 mm). This provides them with a large combustion surface, encouraging a high rate over a short period (necessary for airbag applications in automotive safety, of the driver's airbag type). The porosity of such pellets is generally less than 4%. Peptization operations carried out to produce said pellets are well known, similar to those used in medicinal formulations. Compositions based on guanidine nitrate and basic copper nitrate have been used in that context (United States patent US-A-5 608 183). An attempt has even been made to improve the combustion rate (US-A-6 143 102) since said combustion rate of such compositions is rather low, compared with that of other compositions used in the same field.
• That relates to the field of slow gas generation.
• a gas stored under pressure is generally used.
• the use of chemical reactions or the combustion of pyrotechnic cartridges has also been mentioned.
• the flow rate of the gas that is generated is controlled by selecting the characteristics of the propellant, the geometry of the cartridges, and/or the conditions for ejecting said generated gas, etc.
• the present invention falls within the context of generators operation providing long duration, low flow rate, and low operating pressure.
• the present invention proposes pyrotechnic grains that are simple in shape and that satisfy the following specifications: a) a long combustion period (50 ms [millisecond] to 1 min [minute]) due to a slow combustion rate (to ensure a long period of operation) and/or to a ratio of combustion area over burning thickness that is low, and/or to a low operating pressure (for use in low pressure generators and to encourage a low combustion rate); b) low dependency of the rate of combustion on the operating temperature of the grain, to ensure good ballistic behavior under extreme temperature conditions from -6O 0 C to 110 0 C (hence an extension of the application range (see below), especially in aeronautics); c) suitable mechanical behavior (without the intervention of a binder, the presence of which would deleteriously affect ballistic performance), especially encouraging the use of said grains in an aggressive vibratory environment.
• the pyrotechnic grains of the invention are also advantageously non-aggressive for the gas generator in which they are used and for the associated system (i.e., on combustion, they generate neither particles nor corrosive species). In the same manner, the generated species are advantageously of low toxicity.
• the pyrotechnic grain of the invention must be thick and have a small combustion area. Thus, it must be a large grain, larger than the pellets mentioned above.
• point b) of the above specifications the skilled person will know that said grain must have low porosity.
• Said pyrotechnic grains of the invention have a composition that comprises at least one (specific) oxidizing charge and at least one (specific) reducing charge, but that includes no binder.
• they are pyrotechnic grains of the pellet type mentioned above.
• the composition of the pyrotechnic grains of the invention generally essentially consists of at least one such (specific) oxidizing charge and at least one such (specific) reducing charge. It generally essentially consists of a (specific) oxidizing charge (an oxidizer) and a (specific) reducing charge (a reducer).
• Said at least one specific oxidizing charge is selected from ammonium, potassium, sodium, barium, strontium, and basic copper nitrates, and ammonium, potassium, and sodium perchlorates, and mixtures thereof.
• it comprises basic copper nitrate and/or potassium perchlorate.
• it consists of basic copper nitrate or potassium perchlorate.
• it consists of basic copper nitrate.
• Said at least one specific reducing charge is selected from nitroguanidine, guanidine nitrate, and mixtures thereof.
• it consists of guanidine nitrate.
• said pyrotechnic grains of the invention are in the form of substantially cylindrical blocks:
• Said (monolithic) blocks are large blocks, which are simple in shape and of low porosity.
• Said blocks have a substantially cylindrical shape. Generally, but not exclusively, they are circular cylinders or near (quasi) circular cylinders.
• the shape of the grains of the invention is the signature of the last step of the method by which they are obtained: a compacting step (see below).
• Said blocks may in particular consist of solid (quasi) cylinders or (quasi) cylindrical sleeves.
• the grains in question are large objects (thickness more than 5 mm, equivalent diameter (or, clearly, diameter if it is a perfect circular cylinder) of 10 mm or more), and are relatively dense (porosity in the range 1% to 8%).
• Non-limiting dimensions of said grains are detailed below. Generally and independently : ⁇ the thickness of the blocks is 75 mm or less; or
• the equivalent diameter of said blocks is 75 mm or less.
• said thickness and said equivalent diameter are both 75 mm or less.
• the thickness of the blocks is 7.5 mm or more ; or
• the equivalent diameter of said blocks is 20 mm or more.
• said thickness and said equivalent diameter are both as precised above.
• the thickness of the blocks is in the range 10 mm to 60 mm (values of 10 mm and 60 mm being included); or
• the equivalent diameter of said blocks is in the range 10 mm to 60 mm (values of 10 mm and 60 mm being included).
• said thickness and said equivalent diameter are both in the range 10 mm to 60 mm (values of 10 mm and 60 mm being included).
• the porosity of the blocks is in the range 1% to 8% (it should be noted here that this parameter, expressed as a percentage, corresponds to the ratio between the actual density and the theoretical density; it is in fact the difference from the theoretical density).
• Said porosity is advantageously 5% or less. It should be recalled that the lower said porosity, the lower the dependency of the rate of combustion on the operating temperature of the grain.
• the pyrotechnic grains of the invention which are simple in shape, being substantially cylindrical, may in particular consist of solid cylinders or sleeves.
• the equivalent internal diameter of said sleeves is advantageously more than 10 mm; preferably, it is in the range 12 mm to 35 mm (that implies obviously a greater equivalent diameter of the sleeve).
• the said composition of the pyrotechnic grains of the invention advantageously includes basic copper nitrate as the oxidizing charge and guanidine nitrate as the reducing charge. Highly advantageously, it comprises basic copper nitrate as the only oxidizing charge and guanidine nitrate as the only reducing charge.
• said basic copper nitrate/guanidine nitrate combination is known to have a combustion rate that is rather low relative to that of other compositions used in this field.
• said composition generally comprises: ⁇ 45% to 55% by weight of guanidine nitrate;
• the additives in question are chemical compounds that are known per se as well as for their beneficial involvement in the general production of pyrotechnic grains.
• they may be:
• ⁇ slagging agents supplied with the starting materials oxidizing charge(s) and reducing charge(s) (for example: alumina);
• ⁇ processing aids of the pressing aid or unmolding aid type for example: silica, calcium stearate, mica, etc.
• the present invention provides the production of large pyrotechnic grains, as described above.
• the method in question comprises a series of steps that are known per se. Surprisingly, it has been possible to find operating conditions for this series of steps (which are known per se) that enable, from the selected oxidizing and reducing charges, grains of the invention to be obtained without the involvement of a binder, and having simultaneously large dimensions, low porosity, and also acceptable mechanical properties (which can tolerate the vibrational environment of an automobile or aircraft).
• the method of producing pyrotechnic grains of the invention comprises carrying out the following steps in succession:
• ⁇ that granulation is also advantageously a dry granulation (independently of the manner of said intimate mixing) ;
• At least one shaping additive (a pressing aid, such as calcium stearate or mica) may advantageously be added to said sized granules before shaping them by compacting.
• At least one of the charges used in the powder state has a median diameter that is substantially larger than that which is used in the prior art to prepare pellets (of small dimensions).
• a median diameter that is substantially higher (x 4, x 6) than that known to be used in the preparation of prior art pellets.
• a reducing charge with a median diameter of 200 ⁇ m [micrometer] or more be used.
• Said guanidine nitrate is conventionally used for the fabrication of pellets, with a median diameter of 50 ⁇ m.
• the granules selected are those that have a median diameter of more than 200 ⁇ m, preferably in the range 500 ⁇ m to 1000 ⁇ m. It is thus recommended, in the context of the present invention, that basic copper nitrate/guanidine nitrate granules with a median diameter in the range 500 ⁇ m to 700 ⁇ m or potassium perchlorate/guanidine nitrate granules with a median diameter in the range 500 ⁇ m to 1000 ⁇ m be selected.
• the method of the invention is advantageously carried out with a combination of basic copper nitrate or potassium perchlorate/guanidine nitrate; highly advantageously, it is carried out with a basic copper nitrate/guanidine nitrate combination.
• the combustion rate of compositions based on these two elements (BCN/NG) is reduced.
• the teaching of the present invention thus goes against that of US-A-6143 102.
• the present invention provides a method of generating gas, the method comprising, in conventional manner, the combustion of at least one pyrotechnic grain.
• said method of the invention comprises the combustion of at least one pyrotechnic grain as described above (large pyrotechnic grain) and/or produced using the method described above.
• Said gas generation method is carried out in a suitable device which, in particular, has a combustion chamber adapted to the dimensions of the original pyrotechnic charge, based on large pyrotechnic grains.
• said device comprises:
• ⁇ at least one safety cap ensuring depressurization of the generator in the event of accidental overpressure
• Pyrotechnic grains of the invention were prepared from the following starting materials:
• BCN basic copper nitrate
• guanidine nitrate (GN) powder with a median diameter of 218 ⁇ m
• alumina (slagging agent) powder with a median diameter of 1 ⁇ m. Said powders were dry mixed in a Sofraden® type powder mixer (a
• the intimate mixture of powders obtained was dry granulated in a
• Sahut Conreur® type granulator (an Alexanderwerk® type granulator would also have been suitable). Said intimate mixture of powders was forced through a screen. The granulometric distribution of the granules obtained was from 10 ⁇ m to 1000 ⁇ m.
• the granules obtained were then sieved, and those with a mean diameter of more than 200 ⁇ m were selected.
• Said selected granules were then compacted on a 35 (metric) tonne single action press.
• the compacting pressure applied was 230 bars (23 x 10 6 Pa). It was applied for 10 s.
• Pyrotechnic grains in accordance with the invention were obtained, which grains were cylindrical monoliths (shape of mold) with a thickness of 10 mm, a diameter of 24.6 mm, and porosity of 3%.
• cylindrical grains were prepared as follows:

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Crystallography & Structural Chemistry (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Cited By (5)

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Citations (11)

Family Cites Families (5)

• 2006
  • 2006-04-04 FR FR0651183A patent/FR2899227B1/fr not_active Expired - Fee Related
• 2007
  • 2007-04-03 RU RU2008142975/05A patent/RU2437867C2/ru active
  • 2007-04-03 EP EP07727712.7A patent/EP2001822B1/en active Active
  • 2007-04-03 US US12/225,812 patent/US20100051149A1/en not_active Abandoned
  • 2007-04-03 CN CNA2007800117600A patent/CN101415659A/zh active Pending
  • 2007-04-03 CA CA2648108A patent/CA2648108C/en not_active Expired - Fee Related
  • 2007-04-03 WO PCT/EP2007/053241 patent/WO2007113299A1/en active Application Filing
• 2008
  • 2008-10-15 NO NO20084308A patent/NO20084308L/no not_active Application Discontinuation

Patent Citations (11)

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