Triple-base propellant composition

Abstract

To provide a triple-base propellant composition having a reduced content of dibutyl phthalate, an excellent nitroguanidine mixability, a mechanical strength as a triple-base propellant, and no problem in combustibility.SOLUTION: A triple-base propellant composition includes (a) nitrocellulose, (b) nitroglycerin, (c) nitroguanidine, and (d) an adipic acid ester compound or a citric acid ester compound, wherein the content of (d) adipic acid ester compound or citric acid ester compound is 0.5 to 10 pts.mass relative to 100 pts.mass of the total of (a) nitrocellulose, (b) nitroglycerin, and (c) nitroguanidine.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a triple base propellant used in ammunition for use in, for example, large caliber tank guns, field guns, and the like. [Background technology]

[0002] In the field of propellants, triple-base propellants, whose main components are nitrocellulose, nitroglycerin, and nitroguanidine, are widely used as ammunition for large-caliber tank guns and field guns. This triple-base propellant has the characteristics of increasing the explosive power (explosive energy) without increasing the combustion temperature, causing less damage to the gun barrel than double-base propellants, and having more energy than single-base propellants. The nitroguanidine contained in triple-base propellants is a powder with needle-shaped crystals. In the production of triple-base propellants, the powder nitroguanidine is dispersed in a binder consisting of nitrocellulose, nitroglycerin, and a plasticizer, but if the binder composition is poor, the dispersion does not proceed well, resulting in poor manufacturability. In addition, if the binder and nitroguanidine do not bond well, the propellant tends to become brittle after molding. Therefore, triple-base propellants require an appropriate plasticizer. Dibutyl phthalate has been widely used as a plasticizer for triple-base propellants, but its use is restricted by the Consumer Product Safety Improvement Act (CPSIA) in the United States and by Article 18 of the Food Sanitation Act and Ministry of Health and Welfare Notification No. 370 of 1959 in Japan. In addition, dibutyl phthalate was added to the RoHS Directive in the EU on July 22, 2019, limiting the maximum allowable concentration of dibutyl phthalate in electrical and electronic equipment to 0.1 wt% or less. In light of the above, there is a demand for a plasticizer for triple-base propellants that can replace dibutyl phthalate. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "Firearms and Ammunition Technology Handbook," Defense Technology Association, February 2, 2005, p.351-352 Summary of the Invention [Problem to be solved by the invention]

[0004] The triple-base propellant composition described in Non-Patent Document 1, which uses dibutyl phthalate as a plasticizer, has no problems in terms of combustion temperature or manufacturability, but has limitations on the use of dibutyl phthalate. Therefore, there is a demand for a triple-base propellant composition with a reduced content of dibutyl phthalate. However, reducing the dibutyl phthalate content reduces the mixing (manufacturability) of nitroguanidine used in the triple base propellant composition, increases the dispersion time of nitroguanidine, and reduces the mechanical strength, making the triple base propellant brittle. Therefore, the object of the present invention is to provide a triple base propellant composition having a reduced content of dibutyl phthalate, excellent miscibility with nitroguanidine, and further having the mechanical strength of a triple base propellant and no problems with combustion. [Means for solving the problem]

[0005] As a result of intensive research into the above-mentioned problems, the present inventors have discovered that a triple base propellant composition having excellent manufacturability, mechanical properties and combustibility can be provided by adding a specific amount of component (d) an ester compound of adipic acid or an ester compound of citric acid to component (a) nitrocellulose, component (b) nitroglycerin and component (c) nitroguanidine, and have thus completed the present invention. That is, the present invention relates to the following triple base propellant composition.

[0006] The triple base propellant composition of the present invention is a triple base propellant composition containing (a) nitrocellulose, (b) nitroglycerin, (c) nitroguanidine, and (d) an ester compound of adipic acid or an ester compound of citric acid, The composition is characterized in that the content of (d) an ester compound of adipic acid or an ester compound of citric acid is 0.5 to 10 parts by mass per 100 parts by mass of the total mass of (a) nitrocellulose, (b) nitroglycerin, and (c) nitroguanidine.

[0007] In the present invention, the numerical range "XX to XX" includes the upper limit "XX" and the lower limit (XX) unless otherwise specified. Therefore, more precisely, it means "not less than XX and not more than XX." Effect of the Invention

[0008] According to the triple base propellant composition of the present invention, by controlling the content of component (d) an ester compound of adipic acid or an ester compound of citric acid relative to component (a) nitrocellulose, component (b) nitroglycerin, and component (c) nitroguanidine within a specific range, it is possible to provide a triple base propellant composition having excellent manufacturability, mechanical properties, and combustibility. In the present invention, the manufacturability of a triple base propellant composition means the time required for the triple base propellant composition to become homogeneous after nitroguanidine is added in the step of mixing the composition. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic explanatory diagram of a sealed bomb used in the sealed bomb combustion test of the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present invention will be described in detail. The triple base propellant composition of the present invention is used, for example, in artillery ammunition, and contains component (a) nitrocellulose, component (b) nitroglycerin, component (c) nitroguanidine, and component (d) an ester compound of adipic acid or an ester compound of citric acid in a specific blend ratio. By using the specific blend ratio, a triple base propellant composition excellent in manufacturability, mechanical properties, and combustibility can be obtained.

[0011] <Component (a) Nitrocellulose> Nitrocellulose (NC, soluble nitrocellulose) functions as a fuel and a binder for granulating triple-base propellant compositions. (a) Nitrocellulose is a nitrate ester obtained by treating cellulose with a mixture of nitric and sulfuric acids. The content of nitrocellulose is 20 to 50 parts by mass, preferably 26 to 44 parts by mass, per 100 parts by mass of the total mass of nitrocellulose, nitroglycerin, and nitroguanidine. When the content of nitrocellulose is 50 parts by mass or less, the amount of nitroguanidine, which is an energy base material, can be relatively increased, so that the combustion temperature can be reduced. When the content of nitrocellulose is 20 parts by mass or more, the mechanical properties tend to increase due to the increase in ductility and the decrease in brittleness caused by the sufficient inclusion of the binder component. In addition, the increase in ductility leads to excellent manufacturability.

[0012] <Component (b) Nitroglycerin> Nitroglycerin (NG) is mainly used to improve the explosive power of triple base propellant compositions, and is a material that is easy to manufacture and has excellent low-temperature ignition properties. However, it has the characteristic of being highly sensitive to impacts. The content of nitroglycerin is 15 to 46 parts by mass, preferably 20 to 35 parts by mass, per 100 parts by mass of the total mass of nitrocellulose, nitroglycerin, and nitroguanidine. When the content of nitroglycerin is 46 parts by mass or less, the increase in the combustion temperature of the triple base propellant is suppressed, so that the occurrence of erosion of the gun barrel can be suppressed. On the other hand, when the content of nitroglycerin is 15 parts by mass or more, the manufacturability is improved.

[0013] <Component (c) Nitroguanidine> Nitroguanidine (NQ) is a nitro compound that is an energy base and has the function of lowering the combustion temperature and increasing the explosive power. The content of nitroguanidine is 30 to 55 parts by mass, preferably 35 to 53 parts by mass, per 100 parts by mass of the total mass of nitrocellulose, nitroglycerin and nitroguanidine. When the content of nitroguanidine is 55 parts by mass or less, the blending amount of nitrocellulose and nitroglycerin, which are binder components, increases relatively, so that ductility increases, brittleness decreases, and mechanical properties and manufacturability tend to increase. On the other hand, when the content of nitroguanidine is 30 parts by mass or more, the blending amount of nitrocellulose and nitroglycerin decreases relatively, so that the increase in combustion temperature is suppressed, so that the erosion of the barrel can be suppressed and the barrel life can be improved.

[0014] <Component (d) Adipic acid ester compound or citric acid ester compound> The ester compound of adipic acid or the ester compound of citric acid exhibits excellent compatibility with the component (c) nitroguanidine, and can improve the miscibility of nitroguanidine. The ester compound of dicarboxylic acid or tricarboxylic acid other than the ester compound of adipic acid or the ester compound of citric acid cannot improve the miscibility of nitroguanidine. Furthermore, by including the ester compound of adipic acid or the ester compound of citric acid in the triple base propellant composition, the composition can function as a plasticizer that provides sufficient mechanical properties, and a flexible triple base propellant composition can be obtained. Therefore, the triple base propellant obtained by molding the triple base propellant composition has mechanical properties and can maintain the shape of the molded product even when a strong impact is applied. In this case, the ester compound of adipic acid or the ester compound of citric acid includes dioctyl adipate obtained by reacting adipic acid with 2-hexanol, and diisononyl adipate obtained by reacting adipic acid with isononanol. The ester compound of citric acid includes triethyl acetyl citrate obtained by acetylating citric acid and then reacting it with ethanol, tributyl acetyl citrate obtained by acetylating citric acid and then reacting it with butanol, and tributyl citrate obtained by reacting citric acid with butanol. These can be used alone or as a mixture of two or more kinds.

[0015] The content of the adipic acid ester compound or the citric acid ester compound is 0.5 to 10 parts by mass, preferably 0.5 to 5.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass, relative to 100 parts by mass of the total mass of nitrocellulose, nitroglycerin, and nitroguanidine. If the content of the adipic acid ester compound or the citric acid ester compound exceeds 10 parts by mass, the combustibility of the triple base propellant tends to decrease. On the other hand, if the content of the adipic acid ester compound or the citric acid ester compound is less than 0.5 parts by mass, the mixing property of nitroguanidine decreases. In addition, the mechanical properties of the triple base propellant also tend to decrease.

[0016] <Other additives> In addition to the above components (a) to (d), the triple base propellant composition of the present invention may contain, as necessary, stabilizers, anti-inflammatory agents, gloss agents, etc. that are generally used in this type of propellant composition. It may also contain dibutyl phthalate, but it is preferable that it is substantially free of dibutyl phthalate.

[0017] Examples of the stabilizer include diphenylurea derivatives such as diphenylurea, methyldiphenylurea, ethyldiphenylurea, diethyldiphenylurea, dimethyldiphenylurea, and methylethyldiphenylurea, diphenylamine derivatives such as diphenylamine and 2-nitrodiphenylamine, phenylurethane derivatives such as ethylphenylurethane and methylphenylurethane, diphenylurethane derivatives such as diphenylurethane, resorcinol, etc. These compounds are used alone or as a mixture of two or more kinds. Among these stabilizers, diphenylurea derivatives, specifically methyldiphenylurea, diphenylurea, or dimethyldiphenylurea, are preferred, since they have a melting point of 120°C or higher and therefore (a) reliably capture nitrogen oxides generated from nitrocellulose even at high temperatures, and (a) are highly effective in suppressing the spontaneous decomposition of nitrocellulose, with methyldiphenylurea or dimethyldiphenylurea being particularly preferred.

[0018] Examples of anti-inflammatory agents include potassium sulfate and potassium nitrate. Examples of the gloss agent include graphite, carbon black, and acetylene black.

[0019] The additives may be added in a proportion within the usual range for this type of triple base propellant composition, specifically, about 1 to 6 parts by mass per 100 parts by mass of the total mass of (a) nitrocellulose, (b) nitroglycerin, and (c) nitroguanidine.

[0020] When producing a triple base propellant consisting of the triple base propellant composition of the present invention, the various raw materials and, if necessary, various additives are placed in a kneader in a predetermined mixing balance together with an organic solvent and kneaded uniformly, and the extruded compound extruded by an extrusion device is cut to a predetermined length to be molded into a predetermined shape and dimensions, and then dried to produce a triple base propellant.

[0021] As the organic solvent used in the extrusion molding, any solvent that dissolves or swells the binder (a) nitrocellulose can be used. Examples of the organic solvent include acetone, methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, butyl acetate, diethyl ether, toluene, methyl ethyl ketone, and the like. Mixtures of these solvents can also be used. In particular, acetone, ethyl alcohol, and diethyl ether are preferred because of their excellent compatibility with (a) nitrocellulose.

[0022] The triple base propellant can be cut to an appropriate size and shape depending on the application. Examples of shapes include a non-perforated tubular shape, a single-perforated tubular shape, a multi-perforated tubular shape, etc. The single-perforated tubular shape refers to a cylindrical or hexagonal prism having one through-hole extending in the axial direction, and the multi-perforated tubular shape refers to a cylindrical or hexagonal prism having multiple (e.g., 7, 19, or 37) through-holes extending in the axial direction. EXAMPLES

[0023] The above embodiment will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the scope of these examples. The abbreviations in Table 1 have the following meanings. NC: Nitrocellulose NG: Nitroglycerin NQ: Nitroguanidine DOA: Dioctyl adipate DINA: Diisononyl adipate ATEC: Acetyl triethyl citrate ATBC: Acetyl tributyl citrate TBC: Tributyl citrate DBP: Dibutyl phthalate DOZ: Dioctyl azelaate DBS: dibutyl sebacate TCP: tricresyl phosphate TOTM: Trioctyl trimellitate

[0024] <Example 1> A triple base propellant molding was produced using the composition shown in Table 1 by the following method. A mixture of 26 parts by mass of nitrocellulose with a nitrogen content of 12.6% by mass, 21.9 parts by mass of nitroglycerin, and 1.6 parts by mass of dioctyl adipate was mixed, to which a mixed solution of 55 parts by mass of acetone and 45 parts by mass of ethyl alcohol was added and mixed uniformly in a so-called Werner mixer. This mixture was used as a binder, and 52.1 parts by mass of nitroguanidine was added and further mixed uniformly to obtain a kneaded triple base propellant composition. The triple base propellant composition mixture was then loaded into an extrusion device. A 12.5 mm die and a 0.5 mm pin were attached to the extrusion device in advance, and the triple base propellant composition mixture was extruded through the die by applying pressure, and was molded into a 19-hole hexagonal prism having 19 through holes. The molded product was cut into a length of 10.0 mm and dried to obtain a granular triple base propellant molded product. The manufacturability was evaluated by the method described below.

[0025] <Examples 2 to 7> In Examples 2 to 7, the propellants were produced in the same manner as described above using the compositions in Table 1. The mechanical properties and combustion properties of the triple base propellants were evaluated using the methods described below. The results are shown in Table 1. The values ​​indicating the compositions in Table 1 are in parts by mass.

[0026] <Comparative Examples 1 to 6> A triple base propellant was manufactured using the composition shown in Table 2 in the same manner as in Example 1, and the properties were evaluated in the same manner as in Example 1. The results are shown in Table 2. The values ​​showing the compositions in Table 2 are in parts by mass.

[0027] Methods for evaluating the properties of the triple base propellant compositions in the examples and comparative examples are shown below. (Method for evaluating the miscibility of nitroguanidine) The method for evaluating the mixability (manufacturability) of nitroguanidine is explained below. In the production of the examples and comparative examples, the time from when nitroguanidine (white) is added to the binder (yellow) until it is confirmed by visual inspection that the whole has become uniformly white is measured. When dibutyl phthalate is used as the plasticizer, the production time is 60 minutes. Therefore, a time of 70 minutes or less is considered to be a pass mark (○), and a time of longer than that is considered to be a fail mark (×).

[0028] (Mechanical property evaluation method) A compression strength test method for evaluating mechanical properties will be described. The compression strength test was performed using a tension and compression tester (AL-50kNB) manufactured by Minebea Co., Ltd. The triple base propellant sample was previously conditioned at -32°C for 24 hours or more, and the triple base propellant molded product was placed at the center of the sample stage and compressed in the length direction at a speed of 30 mm / min to perform a compression test. The elastic modulus was then read from the stress-strain curve to evaluate the mechanical properties. Under these test conditions, an elastic modulus of 70 MPa to 100 MPa was evaluated as a pass mark "○", and any other value was evaluated as a fail mark "×". Furthermore, an elastic modulus of 80 MPa to 100 MPa was evaluated as the best mark "◎".

[0029] (Method of evaluating flammability) Next, a closed bomb combustion test for evaluating flammability will be described. A schematic diagram of the sealed bomb is shown in Figure 1. A cylindrical combustion space 2 with a volume of 160 ml is provided in the bomb body 1, and a triple-base propellant molding 3 is loaded into the combustion space 2. A plug 4 is attached to the base end side (left side of Figure 1) of the bomb body 1 to seal the combustion space 2 after loading the triple-base propellant molding 3 into it, and can be attached and detached with a bolt 5. The volume of the combustion space 2 is calculated by subtracting the volume of a part of the plug 4 from the volume of a cylinder with a diameter of 35 mm and a depth of 165.5 mm. A pair of electrodes 9, 10 are attached to the inner end surface of the plug 4, and an ignition ball (with 0.5 g of black powder) 11 is attached to both electrodes 9, 10 via connection wires. The electrode 9 is connected to one electrode of an externally located ignition device 7 via a connection wire 6, and the electrode 9 is connected to the bomb body 1. The other electrode of the ignition device 7 is connected to the bomb body 1 via a connection wire 8. By operating the ignition device 7, an ignition ball 11 is ignited via the connection wires 6, 8 and the electrodes 9, 10, etc., and the triple base propellant molding 3 in the combustion space 2 is ignited and burned. A gas vent valve 12 is attached to the side of the bomb body 1, and is connected to the combustion space 2 via a sampling tube 13. Gas in the combustion space 2 can be sampled through this gas vent valve 12, and its combustion characteristics can be evaluated. A pressure transducer 14 is attached to the tip of the bomb body 1, and is connected to the combustion space 2 via a connecting tube 15. This pressure transducer 14 makes it possible to determine the combustion pressure. In a closed bomb combustion test using the above apparatus, the triple base propellant molding 3 is loaded into the combustion space 2 with the plug 4 removed. The amount of powder loaded is set so that the loading density is 0.2 g / ml. Then, after closing the plug 4, the triple base propellant molding 3 in the combustion space 2 is ignited by the ignition device 7. The relationship between the combustion time and the combustion pressure during combustion is measured by measuring the pressure history with an oscilloscope (not shown) via the pressure transducer 14, and the combustion completion time is calculated. The combustion completion time is the time from ignition to the time when the maximum pressure is indicated. The triple base propellant molding 3 needs to burn at an appropriate speed, and under the test conditions, completion of combustion within 16 to 25 ms was rated as a pass (O), and anything else was rated as a fail (X).

[0030] [Table 1]

[0031] [Table 2]

[0032] The test results in Table 1 show that the triple base propellants of Examples 1 to 7 all had good manufacturability, mechanical properties and combustion properties. On the other hand, as shown in Table 2, Comparative Example 1, in which the blending amount of DOA was small, had poor mechanical properties, and Comparative Example 2, in which the blending amount of DOA was large, had a problem of prolonged flammability. Comparative Examples 3 and 4, in which DOZ or DBS, an ester compound of the same dicarboxylic acid as the ester compound of adipic acid, were used, had problems with manufacturability and mechanical properties. Comparative Example 5, in which TCP, an ester compound of the same tricarboxylic acid as the ester compound of citric acid, was used, had problems with manufacturability, mechanical properties, and flammability, and Comparative Example 6, in which TOTM was used, had problems with manufacturability and flammability. From the above results, it became clear that in order to obtain a triple base propellant composition that has good manufacturability, mechanical properties, and combustion properties, it is necessary to use 0.5 to 10 parts by mass of (d) an ester compound of adipic acid or an ester compound of citric acid per 100 parts by mass of the total mass of (a) nitrocellulose, (b) nitroglycerin, and (c) nitroguanidine. [Explanation of symbols]

[0033] 1...bomb, 2...combustion space, 3...triple base propellant molding, 4...plug, 5...bolt, 6, 8...connecting wiring, 7...ignition device, 9, 10...electrodes, 11...ignition ball, 12...gas vent valve, 13...sampling tube, 14...pressure transducer, 15...connecting tube

Claims

[Claim 1] A triple base propellant composition comprising: (a) nitrocellulose; (b) nitroglycerin; (c) nitroguanidine; and (d) an ester compound of adipic acid or an ester compound of citric acid, A triple base propellant composition, comprising: (a) nitrocellulose; (b) nitroglycerin; and (c) nitroguanidine; and (d) an adipic acid ester compound or a citric acid ester compound in an amount of 0.5 to 10 parts by mass per 100 parts by mass of the total mass of the (a) nitrocellulose, (b) nitroglycerin, and (c) nitroguanidine.

Images