MXPA01010590A - Family of propellant compositions and method - Google Patents

Abstract

A family of Class 1.3 propellant compositions comprising nitrocellulose, at least one of a selected group of plasticizing nitrate esters, a thermal stabilizer, carbon and an energetic solid, and a method of making the family of propellant compositions is provided.

Description

FAMILY OF PROPELLING COMPOSITIONS AND METHOD FOR THE ELABORATION TECHNICAL FIELD The present invention relates generally to gas generating propellant compositions and specifically to a family of gas, solid and energy generating compositions useful in aerospace applications and with a method for making such compositions.

ANTECEDENTS OF THE TECHNIQUE The development of gas generating compositions capable of optimal operation as propellants in aerospace applications has presented important challenges.

The ideal compositions should be characterized by stability, low sensitivity and an exhaust outlet when burned providing optimal ballistic properties while producing combustion products that are compatible with the components of the system. Such ideal gas generating compositions, moreover, must be formulated optimally so that they are readily available, effective in terms of costs and components. The available propellant composition components have proven to be effective gas generators; however, the cost of component availability and system compatibility have been inconvenient. Additionally, some propellant compositions have a class 1.1 hazard classification, which limits their utility in aerospace and similar applications where highly sensitive compositions are not desirable. Most solid propellants for highly filled rockets also have limited working durations, in part due to processing methods that produce higher end viscosities than desired. The prior art has proposed many of the propellant compositions useful as rocket fuels and the like. The Patent of E.U.A. No. 5,053,086 to Henry et al., For example, discloses a liquid, meltable gas generating composition useful as a solid rocket propellant formed from a solid with high hydrogen content and an energy polymer. The solids with high nitrogen content may be one of several described compounds of tetrazole and bitetrazole, and the energy polymers are liquid curable rubbers, with several copolymers of oxetane being preferred. The composition of Henry et al. it is claimed to produce higher burn rates, on the order of 5.8 to 17 mm (0.23-0.66 inches) / second at 6895 kPa (1000 psia), and flame temperatures of 1037-1254 ° C (1901-2291 ° F).

^^^. J ^ H & ui In the U.S. Patent. No. 3,898,112, Strecker et al. describe a solid propellant gas generator that produces total pressure immediately when the guidance of a missile is independent of the total instantaneous pressurization. This composition incorporates 75 to 87% 5-aminotetrazole nitrate in block copolymer binder, preferably styrene-butadiene-styrene or styrene-isoprene-styrene, with antioxidants and optional plasticizing agents. An exemplary formulation produces a burn rate of 11 mm (0.420 inches) per second at 6895 kPa (1000 psi) and 25 ° C (77 ° F). The propellant composition described in the U.S. Patent. No. 3,354,172 by Takaes is constituted by tria inoguanidinium 5-amino-tetrazolate, an oxidant and a binder. This composition, which is described as being characterized by high stability and having a large capacity for gas formation, includes conventional oxidants and a binder such as nitrocellulose and may include fuels such as aluminum, beryllium and boron. The Patent of E.U.A. No. 3,668,873 to Bauman discloses propellant systems for rockets that provide thrust by utilizing a highly exothermic reaction of inorganic fuels that can be nitridized and a source of oxidizing nitrogen, such as 5-α ??-inotetrazole. ^ ... ^^^^ a ^^ ^ ^ _ ^, "," A. . ". ^, Gawlick et al. in the U.S. Patent. No. 3,707,411, discloses a solid propellant that includes a mixture of nitrocellulose and 5 to 80% by weight of a diazo derivative, triazole or tetrazole sensitive to percussion, such as 5-aminotetrazole. The breaking effect of the mixture can be varied by including explosive nitrated esters. This propellant is described as being useful for ringless propellant cartridges without body, for example, asparagus driving tools in which an explosive action is desired. The gas generating compositions containing -aminotetrazole and an oxidant and a gas-producing, nitrogen-producing energy compound, an oxidizing salt and a cellulose-based binder are described, respectively, in the U.S. Pat. No. 5,661,261 for Ramaswamy et al. and the U.S. Patent. No. 5,125,684 for Cartwright. However, the compositions described in these patents are designed for use in automotive airbags and are formulated to respond to specific functional considerations that are very different from those encountered in aerospace and similar applications. Therefore, the prior art has not disclosed a family of gas generating compositions useful as propellants in aerospace applications having a stable component formulation characterized by low sensitivity, a flame temperature of less than 1675 ° C. ** .- ** * (3050 ° F), the combustion exhaust products with optimum system compatibility, optimal ballistic properties and an increased working life, and that can be formulated effectively in terms of costs from available components. The prior art has also failed to describe a method for making a family of gas generating compositions that produce compositions with improved working life and mechanical properties. There is a need for such a family of compositions and a method for their preparation.

BRIEF DESCRIPTION OF THE INVENTION A primary objective of the present invention, therefore, is to provide a family of gas generating compositions useful for similar aerospace applications, and a method of producing such compositions that overcomes the disadvantages of the prior art. Another object of the present invention is to provide a family of propellant compositions characterized by low sensitivity, a flame temperature of less than 1675 ° C (3050 ° F) combustion exhaust products with optimum system compatibility and optimum ballistic properties that can be formulate from low-cost, sustainable components.

It is a further object of the present invention to provide a family of class 1.3 gas generating compositions with a maximum flame temperature of 1675 ° C. (3050 ° F) and an acceptable exhaust outlet ratio of CO / C02. Yet another objective of the present invention is to provide a family of propellant compositions that is thermally stable, impervious to moisture, has an optimum working life and has mechanical properties compatible with the final burn of the cartridge charge. A further objective of the present invention is to provide a family of propellant compositions that exhibit stable combustion at relatively low pressures to produce combustion products that are substantially free of particulates, HCl and HF. Another object of the present invention is to provide a method for making a family of propellant compositions using processing viscosities at concentrations resulting in increased working life of propellant. A further objective of the present invention is to provide a method for developing a family of propellant compositions that can be conducted at low temperatures in conventional or standard mixing equipment.

Still another objective of the present invention is to provide a family of propellant compositions that do not rely on crosslinking to obtain physical integrity. Other objects and advantages will be apparent from the following detailed description and claims. In accordance with the foregoing objects, a family of stable, low-sensitivity propellant compositions is provided which generates combustion gas with optimum system compatibility and ballistic properties, suitable for aerospace and similar applications. The family of propellant compositions of the present invention are formulated from an energy solid in a dual base of high energy binder. The preferred energy solids are 5-aminotetrazole and analogues of -aminotetrazole. The double base of high energy binder preferably comprises a combination of nitrocellulose plasticized with at least one of a group selected from nitrate ester plasticizers. Carbon and a thermal stabilizer that removes nitrous acid are additional preferred components of the present family of propellant compositions. The preferred propellant formulation is a class 1.3 composition with a flame temperature of less than 1675 ° C (3050 ° F) a CO / C02 ratio greater than 8 and stable combustion properties. In addition, according to ^^^. a-. < .J¿ ^^. T ... ^. «. ^ ,, ..... -. . . ** ± -. The present invention provides a method for making a family of propellant compositions. This process comprises the steps of adding nitrocellulose to a selected ester nitrate plasticizer with a thermal stabilizer, adding carbon and an energetic solid, combining the mixture at a temperature that is low enough to maintain the homogeneity of the mixture and at the same time Allow the viscosity to reach approximately 1.0 kP, and allow the mixture to cure.

DETAILED DESCRIPTION OF THE INVENTION The family of gas generating propellants of the present invention was developed to replace the highly effective aerospace application propellants currently used, with a formulation that includes components which are more expensive than desired and are not guaranteed to be readily available. In addition, this propellant has a class 1.1 hazard classification and is therefore highly sensitive and must be handled with caution to avoid detonation. The propellant composition of the present invention has been specifically formulated to avoid these disadvantages. The main objective of the inventors of the present invention was to produce a family of 1.3 class propellant formulations based on low cost and affordable or sustainable ingredients. Other major objections to the present family of gas generating compositions include the acceptable processing properties, a maximum flame temperature of 1675 ° C (3050 ° F), combustion product compatible with the system hardware such as valves, and properties. ballistics comparable with the class 1.1 propellants currently used. In addition, the inventors sought to develop a propellant composition with mechanical properties consistent with an end burner design per cartridge that has probably been used, moisture impermeability, optimal thermal stability and aging properties consistent with a shelf life of 40 years.

The family of propellant compositions of the present invention obtains all of the above objects. These unique formulations are class 1.3 compositions characterized by low sensitivity and a less violent response to the stimulus compared to propellant class 1.1 that was designed to replace. The family of gas generating compositions of the present invention utilizes a double base binder constituted of plasticized nitrocellulose with at least one of a group selected from nitrate ester, preferably a combination of two or more. plus nitrate esters. A combination of high-energy nitrate esters to maintain the flame temperature at approximately 1657 ° C (3000 ° F). The maintenance of the flame temperature at approximately 1647 ° C (3000 ° F), but below 1675 ° C (3050 ° F) is critical for the operation of the gas generating composition. Exemplary nitrate ester plasticizers suitable for this purpose include triethylene glycol dinitrate (TEGDN), butanetriol trinitrate (BTTN), diethylene glycol dinitrate (DEGDN), trimethylol trinitrate (TMETN), nitroglycerin (NG), liquid analogs of nitroglycerin, nitrate of butyl nitrate ester (butyl NENA) and an inert plasticizer, triacetin (TA). Preferred nitrate ester plasticizers are butanetriol trinitrate (BTTN), triethylene glycol dinitrate (TEGDN) as well as an inert plasticizer, triacetin (TA). The propellant formulation of the present invention incorporates an energy solid with a plastisol nitrocellulose (PNC). It has been found that 5-aminotetrazole (5-AT) increases the CO / C02 ratio of the combustion products and improves the ballistic properties and flammability of the propellant. The addition of 5-AT in the nitrocellulose-nitrate ester plasticizer further reinforces the mechanical properties without sensitizing the propellant formulations of the present invention for shock detonation stimuli. Although anhydrous 5-aminotetrazole is preferred for this purpose, it can also be included in the It is present compositions of analogous 5-AT propellants. Exemplary 5-AT analogues that can be used in these compositions are 5-aminotetrazole monohydrate, 5-amino-1H-tetrazole, diammonium salt of 5, 5'-bi-1H-tetrazole (ABT). In addition, oxamides, such as cyanoguanidine or dicyandiamide oxamide, melamine and guanidine nitrate and aminoguanidine nitrate can be used in place of 5-AT as the energy solid in a present propellant. The amount and particle size of 5-AT or the equivalent energy solid is important. The burning speed can be significantly increased by the use of an energy solid with a smaller particle size. Particle sizes of approximately 200-300 microns are preferred. It has been determined that carbon works very effectively to modulate the rate of burning with a double base formulation of the present invention by increasing the surface area. Therefore, a small amount of carbon, preferably in the form of carbon black, is included in this formulation. A thermal stabilizer that removes nitrous acid is also preferably included in the present propellant formulation. A preferred heat stabilizer is para-N-methylnitroaniline (MNA). Other thermal stabilizers that satisfy this purpose include 2-nitro-phenylamine (2-NPA), 4-nitrodiphenylamine (4-NDPA) and diphenylamine (DPA).

The relative amounts of the components of the propellant formulation of the present invention are preferably as follows: nitrocellulose 15 to 40 by weight% 5 nitrate esters 20 to 50 by weight% energetic solid 5 to 35 by weight% carbon 0.1 to 1.5 in weight% thermal stabilizer 0.5 to 2.5 by weight% The relative amounts of these components vary, depending in part, on which nitrate, energetic solid and thermal stabilizer esters are selected for a specific formulation. A wide variety of effective combinations of nitrocellulose, nitrate esters, energy solids, burn rate modulators and thermal scavengers are contemplated to produce the effective propellant compositions, in accordance with the present invention. The processing for the propellant family of the present invention is advantageous and unique. Most of the highly filled solid rocket propellants 20 show mixed end viscosity (EOMV) ranging from 2.0 to 10.0 kilopoises (kP) and having finite effective working lives or shelf lives. The present family of plastisol formulations is not based on classical crosslinking, such as that shown by epoxy or polyurethane binders, to obtain physical integrity. Nitrocellulose -. < aaai > a ^ »a ^? Bai¡iÉaÉÉa¿Éj-jA,. *. a, a¡ ¿*.

Plastisol (PNC) behaves like a thermoplastic; bound hydrogen and intrinsic viscosity provide physical integrity for the final product. The nitrocellulose is added to a selected combination of nitrate esters in a liquid form with a thermal stabilizer such as N-methylnitroaniline (MNA). The carbon, preferably in the form of carbon black, and the necessary complement of 5-aminotetrazole (5-AT) are added to this combination. The mixture is combined at a temperature within the range of 15 to 27 ° C (60-80 ° F) until an optimum viscosity is obtained. Ideally, the viscosity can be about 1.0 kP, preferably 0.4 to 2.0 kP, to maintain the homogeneity of the mixture and to prevent sedimentation of the solid additives. The high viscosity nitrocellulose pastes are not required to obtain the high concentrations of PNC required for the present propellant formulation. The present PNC blends can be processed by standard or conventional vertical mixing equipment. In addition, the flexibility of this processing method allows unplanned process interruptions without losses. These liquid nitrate esters such as nitroglycerin (NG), butanotriol trinitrate (BTTN), tpmethylol trinitrate (TMETN), triethylene glycol trinitrate (TEGDN) and diethylene glycol dinitrate (DEGDN) are preferably mixed with a ., ^^^ ^ ^. ... , .................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... This suspension maintains its flow properties, with the condition that the processing temperatures remain below 38 ° C (100 ° F). Processing temperatures of 15 to 27 ° C (60-80 ° F) are preferred. The viscosity of the suspension will show a small increase unless temperatures above 38 ° C (100 ° F) are reached and maintained. Then the resulting composition is cured. Once the compositions of the present invention cure, the resulting propellants show exceptional mechanical properties. More than 100 propellant mixtures were investigated to determine the formulation parameters such as nitrocellulose concentration, nitrate ester concentrations, nitrate ester combinations and use of inert binder components and solid additives. The results of investigations of four exemplary formulations are set forth in the following. Formulations A, B, C and D are prepared, according to the method of the present invention, wherein nitrocellulose (NC) is added to the selected nitrate ester combination with a thermal stabilizer, in this case MNA. Carbon and 5-AT are added to this combination. Processing is carried out in a vertical mixer at a temperature that is maintained below 38 ° C (100 ° F), at 24 ° C ^ * ^ ^ - Étin-f-- - - - * ms Ék ** mWM * 1 *** m * m (75 ° F). The formulation components are expressed in% by weight.

FORMULATION A NC 22.2% BTTN 21.9% TEGDN 22.2% 10 MNA 0.6% 5-AT 33.0% Coal 0.1% FORMULATION B 15 NC 25.0% BTTN 32.7% TEGDN 13.4% Triacetin 7.8% 20 MNA 1.0% 5-AT 20.0 Coal 0.1% FORMULATION C NC 35.0% BTTN 24.2% TEGDN 13.6% Triacetin 5.1% MNA 2.0% 5-AT 20.0% Coal 0.1% FORMULATION D NC 35.0% BTTN 33.4% Triacetin 9.5% MNA 2.0% 5-AT 20.0% Coal 0.1% Table I establishes the results of the tests carried out regarding the burning speed and mechanical properties of the formulations A, B, C and D. v? ^? áO? W W TABLE I 15 The flame temperature (Tc) for all formulations is less than 1675 ° C (3050 ° F). Relationships CO / C02 vary from 8.9 from formulation D to 13.9 for formulation A. These ratios are sufficient to obtain stable combustion at a pressure less than 6.89 kPa (100 psia). The burning speed data is expressed at 3309 kPa (480 psi), and are within the desired parameters for this type of propellant formulation and indicate stable combustion. The NOL separation card tests indicate that the tested formulations all classify with less than 70 cards and are class 1.3 compositions. The results of the separation card tests clearly indicate that the propellants of the present invention are less sensitive to detonation stimuli compared to the currently available class 1.1 propellants. The mechanical properties, specifically the module, the tension and the traction are exceptional for a non-reticulated propellant system. The working life or shelf life of the propellant compositions of the present invention are still being evaluated. The shelf life data determined so far indicates that the propellants of the present invention will maintain their processing capacity in production. Formulation D, which does not contain TEGDN, demonstrates a significantly improved shelf life compared to the estimated shelf life of the other formulations. The end of life of The shelf is estimated to occur when the viscosity of the propellant mixture exceeds 10 kP after production of the propellant mixture. Table II establishes the results of the tests carried out regarding the burning speed and the mechanical properties of additional formulations E, F, G and H, which are designed to show a flame temperature of approximately 1980 ° C (3600 ° F) and are functional analogues to formulations A, B, C and D.

TABLE II ~ * "* -" - '- «-". ...... MUh -. ^. I .j, - »« - «' * - • - ^^? '? Ji'J The compositions propellants of the present invention provide class 1.3 compositions based on inexpensive low cost components that work with the ballistic properties required in systems utilizing propellants or gas generators.In addition, these propellants are moisture stable, thermally stable compositions with lives Desirable working and mechanical properties that are compatible with the physical components of the systems in which they are most likely to be used 10 INDUSTRIAL APPLICABILITY The gas generating propellant compositions of the present invention will find their primary use in aerospace applications. However, other commercial applications for the gas generators in the present invention are contemplated which include, for example, in gas turbine engine starter cartridges. The low sensitivity and the optimal burning speeds of these compositions will also make them suitable for various applications.

Claims (21)

1. A family of propellant compositions class 1.3, characterized in that they comprise an energetic solid in a double-energy high-energy binder, which is composed of nitrocellulose and at least one of a group selected from nitrate ester, carbon and ammonia plasticizers. a thermal stabilizer.

2. The family of propellant compositions, as described in claim 1, wherein the energy solid comprises 5-aminotetrazole, 5-aminotetrazole monohydrate, 5-aminotetrazole analogues, oxamides, melamine and guanidine nitrates.

3. The family of propellant compositions, as described in claim 1, characterized in that the nitrate ester plasticizers comprise trimethylene glycol dinitrate, butanetriol trinitrate, diethylene glycol dinitrate, trimethylol trinitrate, nitroglycerin, liquid analogs of nitroglycerin, ester nitramine. of butyl nitrate and triacetin.

4. The family of propellant compositions, as described in claim 1, characterized in that the thermal stabilizer comprises para-N-methynitroaniline, 2-nitrophenylamine, 4-nitrodiphenylamine and diphenylamide.

5. The family of propellant compositions, as described in claim 1, characterized in that the carbon is in the form of carbon black.

6. The family of propellant compositions, as described in claim 2, characterized in that the energy solid is 5-aminotetrazole.

7. The family of propellant compositions, as described in claim 1, characterized in that the energy solid is 5-aminotetrazole, and is selected from the group of nitrate esters comprising trimethylene glycol dinitrate, butanotriol trinitrate and triacetin, and the thermal stabilizer it is para-N-methylnitroaniline.

8. A propellant composition, as described in claim 7, comprising 5 to 35% by weight of 5-aminotetrazole, 15 to 40% by weight of nitrocellulose, 20 to 50% by weight of at least 1 of the groups selected from nitrate esters, 0.5 to 2.5% by weight of para-N-methylnitroaniline and 0.1 to 1.5% by weight of carbon. | £ ^^^ _, _ iA_uuafci-i M ^ KtSMBttMi mßnj ^^ ****

9. A propellant composition, as described in claim 8, comprising 33.0% of 5-aminotetrazole, 22.2% of nitrocellulose, 21.9% of butanotriol trinitrate, 22.2% of triethylene glycol dinitrate, 0.6% of para-N-5 methylnitroaniline and 0.1% carbon.

10. A propellant composition, as described in claim 8, comprising 20.0% 5-aminotetrazole, 25.0% nitrocellulose, 32.2% butanotriol trinitrate, 10 13.4% triethylene glycol dinitrate, 7.8% triacetin, 1.0% para-N-methynitroaniline and 0.1% carbon.

11. A propellant composition, as described in claim 8, comprising 20.0% 5-aminotetrazole, 15 35.0% nitrocellulose, 24.2% butanotriol trinitrate, 13.6% triethylene glycol dinitrate, 5.1% triacetin, 2.0% para-N-methynitroaniline and 0.1% carbon.

12. A propellant composition, as described in claim 8, comprising 20.0% 5-aminotetrazole, 35. 0% nitrocellulose, 33.4% butanotriol trinitrate, 9.5% triacetin, 2.0% para-N-methynitroaniline and 0.1% carbon. Mm tíe et tíy? J? K *. * .. *, ". ,. *. " - »^. . . ,. ,,. ~ ^. ± m »*», - o. .. > "To ~ - .- .. ^ .... ^^ 4

13. A method for making a family of propellant compositions class 1.3, defined by thermal stability, exceptional mechanical properties and an improved working life, characterized in that it includes the steps of: (a) adding nitrocellulose to a combination of at least one of a group that is selected from nitrate esters and a thermal stabilizer to produce a suspension without solvent; (b) add to the suspension without solvent, carbon and an energetic solid; (c) combining the mixture that is formed in step (b) at a temperature sufficiently low to maintain a homogeneous mixture until the viscosity of the mixture is greater than about 1.0 kP; and (d) curing the resulting product to produce a solid propellant composition.

14. The method according to claim 13, characterized in that the group of nitrate esters comprises butanotriol trinitrate, triethylene glycol dinitrate and triacetipa, the thermal stabilizer comprises para-N-methynitroaniline and the energy solid comprises 5-aminotetrazole. t *.

15. The method according to claim 13, characterized in that the temperature does not exceed 38 ° C (100 ° F).

16. The method in accordance with the claim 13, characterized in that the group of nitrate esters comprises trimethylene glycol dinitrate, butanetriol trinitrate, diethylene glycol dinitrate, trimethylol trinitrate, nitroglycerin, liquid nitroglycerin analogs, butyl nitrate ester nitrate and triacetin.

17. The method according to claim 13, characterized in that the thermal stabilizer comprises para-N-methylnitroaniline, 2-nitrophenylamine, 4-nitrodiphenylamine and diphenylamine.

18. The method according to claim 13, characterized in that the energy solid comprises 5-aminotetrazole, 5-aminotetrazole monohydrate, 5-aminotetrazole analogues, oxamides, melamine and guanidine nitrate.

19. A family of class 1.3 of propellant compositions, characterized by a flame temperature lower than 1675 ° C (3050 ° F), a burn-rate behavior adaptable to 3447 kPa (500 psi) from 2.3 to 5 mm (0.09 a 0.20 -. * AA ................ . . ^ .. ^ -. and ... ~. ^.?. M ~ ** M ** .. -.... .. > ^ ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡/ Sec, a behavior of exponent of speed of burning of n = 0.50 to 0.80, and a shelf life greater than 10 hours.

20. A propellant composition according to claim 19, comprising nitrocellulose, a combination of plasticizing nitrate esters, a thermal stabilizer, carbon and an energy solid.

21. The family of propellant compositions, according to claim 1, characterized in that the energy solid comprises 5-aminotetrazole, 5-aminotetrazole monoohydrate, 5-aminotetrazole analogues, oxamides, melamine and guanidine nitrate; Nitrate ester plasticizers include trimethylene glycol dinitrate, butanetriol trinitrate, diethylene glycol dinitrate, trimethylol trinitrate, nitroglycerin, liquid analogs of nitroglycerin, nitrate of butyl nitrate ester and triacetin, and the thermal stabilizer comprises para-N-methylnitroaniline. , 2-nitrophenylamine, 4-nitrodiphenylamine and diphenylamine, and the carbon is in the form of carbon black. ftut m ^ ii a m