Reduced-burning composite propellant

Abstract

The invention relates to a composite solid propellant comprising: - a crosslinked polyurethane binder, which is the reaction product of a polyol polymer and a polyisocyanate crosslinking agent, in the presence of a crosslinking catalyst; - ammonium perchlorate; - optionally aluminum; - optionally a ballistic catalyst; - at least one additive comprising a functionalized organic compound comprising 30 to 50 carbon atoms. Figure for the abstract: Fig. 1.

Description

Title of the invention: Composite propellant with reduced combustion rate. Technical field of the invention

[0001] The present invention lies in the technical field of solid propellant propulsion and more specifically relates to composite solid propellants with reduced burn rates. The invention also relates to the use of these propellants. State of the art

[0002] Rocket propulsion is a propulsion method used in space applications (satellite launchers, satellites, orbital stations) and military applications (missiles). In the aerospace field, solid propellant engines are highly valued for their performance and compact size. Indeed, solid propellants are inherently very dense, and therefore generate a greater quantity of propellant gases for the same volume of spacecraft than a liquid propellant, resulting in a reduction in the weight of the structure. Furthermore, these engines are relatively easy to install, giving them a lower structural mass than a cryogenic engine. Finally, their operation requires no moving parts, thus reducing the risk of failure. For these reasons, this type of engine remains a preferred option in the design of missiles for military applications and launchers such as, for example, the Ariane launcher.

[0003] Propellants can be divided into two families according to their composition. The first family, historically the oldest, includes propellants composed of nitrocellulose, a solid cellulose that absorbs liquid nitroglycerin, as well as additives. These homogeneous propellants are known as “dual-base” propellants. Indeed, each of these two energetic materials combines both the oxidizing and reducing agents. Their performance is not very high, but they are generally non-smoke-producing (except in the presence of metallic additives), which has contributed to their use in the design of tactical missiles. The second family of propellants is known as “composite” propellants. They are typically composed of a solid phase held in place by a synthetic gum, the binder (typically polybutadiene), the whole forming a heterogeneous mass.The addition of metallic powder (such as aluminum) increases the propellant's density and performance. Composite propellants offer significantly better performance than dual-base propellants and are widely used in space applications.

[0004] French patent application FR-A-3 139 819 describes a composite solid propellant comprising a crosslinked binder obtained from a polyester polyol and a polyisocyanate-type crosslinking agent, ammonium perchlorate, and optionally aluminum. The tested propellants have a burning rate of approximately 9 to 12 mm / s in a pressure range of 5 MPa to 10 MPa.

[0005] US patent application 2019 / 016645 describes a solid propellant comprising a reaction product between a PBHT (polybutadiene hydroxytelechelic) or PEHT (polyether hydroxytelechelic) type prepolymer, a diol dimer, and a curative isocyanate. The tested propellants have a burning rate of approximately 0.3 inches per second (ips), or about 7.6 mm / s. However, the pressure at which the burning rate was determined is not specified.

[0006] US patent application 2019 / 077725 describes a solid propellant comprising PBHT-type, a diol dimer and an isocyanate.

[0007] The combustion rate of a solid propellant depends on the pressure P prevailing in the combustion chamber and classically follows a law (known as Vieille's law) expressed in the form:

[0008] Vc= aPn.

[0009] Said combustion speed Vc and the pressure exponent n of the propellant are fundamental parameters for the ballistic adjustment of a solid propellant engine (burn time, thrust, combustion stability...). They determine the steady-state operating point of the engine at any instant of firing.

[0010] It is understood that reducing the combustion rate of a solid propellant could be advantageous, for example, in terms of propellant burn time, provided that the fuel's energy and mechanical performance are not affected. Several solutions could contribute to achieving this objective. One solution is to avoid using a ballistic catalyst; a complementary solution would be to identify an advantageous isocyanate as a precursor to the polyurethane matrix. However, this potential solution is not sustainable (in terms of raw material supply).

[0011] It is to the credit of the inventors to propose composite solid propellants having a combustion speed suitable for space and strategic applications, in particular a combustion speed ranging from about 7 to about 9 mm / s in a pressure range from about 5 MPa to about 10 MPa. Summary of the invention

[0012] According to one aspect, the invention relates to a composite solid propellant comprising: - approximately 5.0% to approximately 20.0% by mass of a crosslinked polyurethane-type binder, which is the reaction product of a polyol polymer and a polyisocyanate type crosslinking agent, in the presence of a crosslinking catalyst; - approximately 20.0% to approximately 90.0% by mass of ammonium perchlorate; - 0% to approximately 25.0% by mass of aluminium; - 0% to approximately 5.0% by mass of a ballistic catalyst; - 0.1% to approximately 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 30 to 50 carbon atoms.

[0013] According to another aspect, the invention relates to the use of the aforementioned composite solid propellant as fuel for a rocket, satellite or missile engine. Description of the figure

[0014] [Fig-1] represents the comparative combustion rates of binder compositions PBHT. Description of the invention

[0015] According to one aspect, the invention relates to a composite solid propellant comprising:

[0016] - approximately 5.0% to approximately 20.0% by mass of a cross-linked polyurethane-type binder, which is the reaction product of a polyol polymer and a polyisocyanate-type crosslinking agent, in the presence of a crosslinking catalyst;

[0017] - about 20.0% to about 90.0% by mass of ammonium perchlorate;

[0018] - 0% to approximately 25.0% by mass of aluminium;

[0019] - 0% to approximately 5.0% by mass of a ballistic catalyst;

[0020] - 0.1% to approximately 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 30 to 50 carbon atoms.

[0021] Of course, the sum of the quantities of the different constituents of the composite solid propellant is equal to 100%.

[0022] By "functionalized organic compound", for the purposes of the present invention, we mean a compound capable of binding - via the function(s) it carries - to ammonium perchlorate and thus of having an impact on the combustion rate of the propellant.

[0023] In some embodiments, the functionalized organic compound is obtained from a precursor organic compound, comprising 30 to 50 carbon atoms, chosen from a diacid dimer, such as those marketed by Cargill under the name Pripol™, a polyester polyol, such as those marketed by Cargill under the name Priplast™, or a polyamine, preferably a diamine, such as those marketed by Cargill under the name Priamine™.

[0024] The functionalized organic compound comprising 30 to 50 carbon atoms contains at least one aziridine, epoxide, or secondary amine function; advantageously, the functionalized organic compound contains at least one secondary amine function, for example, at least two secondary amine functions. By way of example, the diagram below shows the reaction of a diamine-type precursor organic compound with acrylonitrile to give a functionalized organic compound containing two secondary amine functions: The organic compound of the diamine type is represented by the following structure: being commercially available under the name Priamine™ (Cargill).

[0025] The polyol polymer is typically a hydroxytelechelic polybutadiene (PBHT), for example that marketed under the name R45HT™ by the company Resin Solutions.

[0026] The crosslinked polyurethane binder is obtained by crosslinking the polyol polymer with at least one polyisocyanate crosslinking agent, which is generally used in a controlled quantity, i.e. in a quantity such that the bridging ratio (Rp) NCO / OH is between 0.7 and 1.5, advantageously this ratio is equal to 1. The OH functions are, as will be understood, provided by the polyol polymer.

[0027] The polyisocyanate-type crosslinking agent is suitable for crosslinking such polyol polymers. In some embodiments, the crosslinking agent, known per se, is a polyisocyanate selected from methyl diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), dicyclohexylmethylene diisocyanate (MDCI), hexamethylene diisocyanate (HDI), the trimer of said hexamethylene diisocyanate (in particular marketed by Bayer under the trade name Desmodur® N 3300), biuret trihexane isocyanate (BTHI), 3,5,5-trimethyl-1,6-hexamethylene diisocyanate and mixtures thereof. Such crosslinking agents are conventionally used (i) in the necessary and sufficient quantity to ensure crosslinking of the polyol polymer (not excessive so as not to pollute the crosslinked product obtained) and (ii) in such quantity that the bridging ratio Rp is as defined above.

[0028] The reaction between the polyol polymer and the polyisocyanate-type crosslinking agent is carried out in the presence of a crosslinking catalyst, which is generally used in an amount between approximately 0.1 ppm and approximately 10 ppm, advantageously between about 0.1 ppm and about 1 ppm, this quantity being expressed relative to the mass of the composite solid propellant. In some embodiments, the crosslinking catalyst is selected from triphenylbismuth, tin dibutyl dilaurate (BDTL), a bismuth carboxylate such as bismuth octoate or bismuth neodecanoate (as described in application FR-A-3 102 476), and mixtures thereof.

[0029] The composite solid propellant according to the invention comprises about 20.0% to about 90.0% by mass, such as for example about 60% by mass to about 75% by mass, of ammonium perchlorate (oxidizing charge).

[0030] In certain embodiments, ammonium perchlorate comprises, by mass, the following proportions of different fillers:

[0031] - 40 to 80% by mass of class A charge;

[0032] - 5 to 35% by mass of class B charge;

[0033] - 1 to 35% by mass of class C charge.

[0034] In this disclosure, "Class A load" means a load whose single-mode particle size distribution has a Di0 value between 100 pm and 110 pm, a D50 value between 170 pm and 220 pm and a D90 value between 315 pm and 340 pm.

[0035] In this disclosure, "Class B load" means a load whose single-mode particle size distribution has a Di0 value between 15 pm and 20 pm, a D50 value between 60 pm and 120 pm and a D90 value between 185 pm and 220 pm.

[0036] In this disclosure, "Class C load" means a load whose single-mode particle size distribution has a Di0 value between 1.7 pm and 3.6 pm, a D50 value between 6 pm and 12 pm and a D90 value between 20 pm and 32 pm.

[0037] The values ​​Di0, D50 and D90 represent the diameter for which the cumulative volume percentage is respectively equal to 10%, 50% or 90%. These particle size values ​​are obtained from measurements carried out using a laser particle size analyzer (Mastersizer™ 3000 type or equivalent), according to a procedure defined by standard NF 11-666.

[0038] In certain embodiments, the ammonium perchlorate comprises approximately 40% to approximately 80% by mass of filler "A'", filler whose unimodal particle size distribution has a D50 value between 392 µm and 413 µm. These particle size values ​​are obtained from measurements carried out by sieving, according to a procedure defined by standard NF ISO 2591-1.

[0039] The composite solid propellant according to the invention also comprises 0% to about 25.0% by mass, such as about 15% by mass to about 20% by mass, of aluminium (reducing charge).

[0040] In some embodiments, the aluminum reducing charge has a value of D50 less than or equal to 30 |am.

[0041] The composite solid propellant according to the invention also comprises 0% to about 5.0% by mass of a ballistic catalyst.

[0042] In some embodiments, the ballistic catalyst is chosen from among conventional ballistic catalysts, such as, in particular, metal salts and oxides.

[0043] The composite solid propellant according to the invention also comprises 0.1% to about 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound as defined above.

[0044] In certain embodiments, the composite solid propellant according to the invention comprises, in addition to the functionalized organic compound, at least one additive selected from plasticizers, anti-glare agents, adhesion agents between the binder and the oxidizing charge, antioxidants, and energy charges.

[0045] Examples of plasticizers include dioctyl azelate, diisooctyl sebacate, isodecyl pelargonate, polyisobutylene, dioctyl phthalate, and also energetic plasticizers such as triethylene glycol dinitrate.

[0046] Examples of anti-glare agents include compounds based on alkali metals, sodium (Na2SO4,...) and especially potassium (K2SO4, KNO3, K3AlF6, C4H5KO6, etc.), particularly potassium salts such as potassium cryolite (K3AlF6) or monobasic potassium tartrate (C4H5KO6), said monobasic potassium tartrate being available in L- or D- enantiomer form or in racemic form. These specific potassium salts are commercially available in conventional particle sizes (powders with grains generally having a D50 between 1 and 300 µm).

[0047] Examples of adhesion agents between the binder and the oxidizing charge include bis(2-methylaziridinyl)-methylaminophosphine oxide (methyl BAPO) or triethylene pentamine acrylonitrile (TEPAN).

[0048] Examples of antioxidants include those from the rubber industry, such as ditertiobutylparacresol (DBC) or 2,2'-methylene-bis(4-methyl-6-tertio-butylphenol) (MBP5).

[0049] Examples of energy charges include hexogen (RDX) or octogen (HMX).

[0050] Without limiting the foregoing, the composite solid propellants according to the invention can be prepared by a process comprising the following steps:

[0051] - the formation of a homogeneous paste by:

[0052] a) incorporation, with stirring, at a temperature between approximately 30°C and approximately 70°C, into a liquid polyol polymer, of the other constituent ingredients of the desired composite solid propellant, with the exception of the crosslinking agent and the crosslinking catalyst, and

[0053] b) agitation of the resulting mixture, under partial vacuum, at a temperature between approximately 30°C and approximately 70°C;

[0054] - incorporation into said homogeneous paste formed, under partial vacuum and at a temperature between about 30°C and about 50°C, of ​​said crosslinking agent and about 0.1 ppm to about 10 pm of said crosslinking catalyst, followed by stirring of the mixture formed;

[0055] - the pouring of said mixture constituted in at least one structure; and

[0056] - the heat treatment of said agitated mixture poured into said at least a structure.

[0057] The partial vacuum mentioned is intended for degassing the medium above which it is applied. It is generally around 10 mm Hg. Incidentally, it is not necessarily of constant intensity.

[0058] The heat treatment (for crosslinking the polyol polymer) is generally carried out at a temperature between approximately 30°C and approximately 60°C (30°C < T < 60°C), for several days.

[0059] The composite solid propellants according to the invention advantageously have a burning rate of less than approximately 10 mm / s, for example, in the range of approximately 5 mm / s to approximately 9 mm / s, for example, from approximately 6 mm / s to approximately 9 mm / s, or from approximately 7 mm / s to approximately 9 mm / s, over an operating pressure range of approximately 5 MPa to approximately 10 MPa. They are particularly suitable as propellant for rocket, satellite, or missile engines. Their use for this purpose is especially recommended. This is an integral part of the present invention and constitutes another aspect thereof.

[0060] According to another aspect, the invention relates to a propellant charge containing at least one composite solid propellant as defined above. Such a charge is suitable not only for satellite or missile engines, but also for engines for space launch vehicles such as, for example, those of the Ariane rocket. The propellant charges contained in these engines have a mass ranging from a few hundred kilograms to several hundred tons.

[0061] According to another aspect, the invention relates to a rocket, satellite or missile engine comprising a propellant charge as defined above.

[0062] The invention will be better understood with the aid of the examples below, given by way of illustration. Example 1

[0063] A propellant was prepared from a "conventional" binder containing a polyisocyanate and a PBHT-type polyol polymer (R45HT™, marketed by Resin Solutions), and optionally a plasticizer (such as dioctyl azelate), according to the following protocol:

[0064] - incorporation into the binder, with stirring, at a temperature of 70°C, of ​​a functionalized diamine organic compound (obtained by reaction of Priamine™, marketed by the Cargill company, with an acrylonitrile), and constituent ingredients of the composite solid propellant (mainly 68% ammonium perchlorate and 20% aluminium) with the exception of the crosslinking agent and the crosslinking catalyst;

[0065] - agitation of the resulting mixture, under partial vacuum, at a temperature of 70°C for 60 minutes;

[0066] - incorporation into said homogeneous paste formed, under partial vacuum and at a temperature of 50°C, MDCI crosslinking agents and 0.3 ppm of DBTL, followed by stirring of the resulting mixture;

[0067] - the pouring of said mixture constituted in a mold;

[0068] - the heat treatment of 2 weeks at 50°C. Comparative example

[0069] The protocol of Example 1 was repeated, but omitting the functionalized acrylonitrile diamine organic compound. The comparative example was repeated, under the same operating conditions, a few months later.

[0070] The combustion rate (Vc) of the propellants thus prepared was measured. The results are shown in [Fig. 1]. The upper curves represent the Vc of the propellant in the comparative example, and the lower curve represents the Vc of the propellant in Example 1.

[0071] Over the operating pressure range of 5 MPa to 10 MPa, a significant decrease in the combustion rate (of at least -1.5 mm / s) of the propellant containing the functionalized organic compound is observed compared to the propellant not containing it.

Claims

Demands

1. Solid composite propellant comprising: - 5.0% to 20.0% by mass of a crosslinked polyurethane binder, which is the reaction product of a polyol polymer and a polyisocyanate crosslinking agent, in the presence of a crosslinking catalyst; - 20.0% to 90.0% by mass of ammonium perchlorate; - 0% to 25.0% by mass of aluminum; - 0% to 5.0% by mass of a ballistic catalyst; - 0.1% to 20.0% by mass of at least one additive, said at least one additive comprising a functionalized organic compound comprising 30 to 50 carbon atoms.

2. Solid composite propergol according to claim 1, wherein the organic compound comprising 30 to 50 carbon atoms contains at least one secondary aziridine, epoxide or amine function.

3. Solid composite propergol according to claim 1 or claim 2, wherein said organic compound contains at least one secondary amine function.

4. Solid composite propergol according to claim 3, wherein the functionalized organic compound comprising 30 to 50 carbon atoms is obtained from a diamine of formula: w

5. Solid composite propergol according to any one of the preceding claims, wherein the crosslinking agent is selected from methyl diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate trimer, biuret trihexane isocyanate, 3,5,5-trimethyl-1,6-hexamethylene diisocyanate and mixtures thereof.

6. Solid composite propergol according to any one of the preceding claims, wherein the crosslinking catalyst is selected from triphenylbismuth, tin dibutyl dilaurate, a bismuth carboxylate, and mixtures thereof.

7. Solid composite propellant according to any one of the preceding claims, wherein the ballistic catalyst, when present, is selected from metal salts and oxides.

8. Use of a composite solid propellant as defined in any of the preceding claims as rocket, satellite or missile engine fuel.

9. Propellant loading comprising at least one composite solid propellant as defined in any one of claims 1 to 7

10. Rocket, satellite or missile engine comprising a propellant charge according to claim 9.

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