Composite propellant

Abstract

To provide a composite propellant having excellent manufacturability and physical properties.SOLUTION: A composite propellant containing binder having terminal hydroxyl group polybutadiene as a main component and oxidizer including ammonium perchlorate, in which the binder contains polytetramethylene ether glycol as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide and N-methyldiethanolamine as a binding agent, and isophorone diisocyanate as a curing agent, in which the ratio of the polytetramethylene ether glycol in the binder is 10 to 20 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composite propellant having good physical properties and manufacturability.

Background Art

[0002] Composite propellants mainly consist of an oxidizer and a binder that also serves as a fuel binder, and usually, metal powder is added as a combustion improver to improve combustion performance. As the oxidizer, ammonium perchlorate, nitramine, ammonium nitrate, etc. are used. As the binder, polybutadiene, polyurethane, etc. are used. As the combustion improver, aluminum powder, etc. are used. Due to its excellent combustion characteristics and physical properties, this composite propellant is widely used as a propellant for high-performance rocket motors.

[0003] However, although the terminal hydroxyl polybutadiene (R-45M) used in the binder of conventional composite propellants is of high performance, it is a special product with poor availability and high cost. Therefore, various studies have been conducted to improve the physical properties and manufacturability by using general-purpose polybutadiene (R-45HT) and changing the curing agent, binder, and adding a chain extender.

[0004] For example, in Patent Document 1, in a composite propellant using general-purpose R-45HT as a binder in the binder, a composite propellant using aziridine polyester and amine polyester in combination and using polytetramethylene ether glycol (hereinafter also referred to as "PTG") as a chain extender is disclosed. Comparing Example 10 and Comparative Example 4 of Patent Document 1, it is recognized that by adding PTG, the strain at maximum stress (elongation at maximum load) is improved from 25% to 40%. On the other hand, the maximum stress (maximum tensile strength) decreases from 10.5 kg·f / cm 2 to 9.3 kg·f / cm 2 and decreases.

[0005] In addition, Patent Document 2 discloses that in a composite propellant using R-45M as a binder in the binder, when aziridine polyester and amine polyester are used, there is a problem that the elongation becomes small. In response to this problem, as a binder in the binder, tris[1-(2-methyl)-aziridinyl]phosphine oxide (hereinafter also referred to as "MAPO") and N-methyldiethanolamine (hereinafter also referred to as "MDA") are used. A composite propellant is disclosed. When comparing Example 7 and Comparative Example 7 of Patent Document 2, it is recognized that by replacing the mixture of aziridine polyester and amine polyester with a mixture of MAPO and MDA, the strain at maximum stress (elongation at maximum load) is improved from 28% to 40%. On the other hand, the maximum stress (maximum tensile strength) is only slightly improved from 10.5 kg·f / cm 2 to 10.9 kg·f / cm 2 and only a slight improvement is recognized.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the composite propellants of Patent Documents 1 and 2 using terminal hydroxyl polybutadiene such as R-45HT as a binder, although the elongation at maximum load as a physical property was improved, the maximum tensile strength was not improved. When the maximum tensile strength is low, there is a problem that excessive deformation occurs under high pressure, use environmental temperature, and acceleration accompanying combustion, and stable combustion does not occur. Further, when the elongation at maximum load is increased, a certain combustion rate can be obtained and stable combustion can be achieved in order to suppress the occurrence of chipping and cracks under the same conditions. Therefore, in the composite propellant using terminal hydroxyl polybutadiene such as R-45HT, it has been required to improve both physical properties of elongation at maximum load and maximum tensile strength. Further, regarding manufacturability, in order to improve the ease of casting, it is required to improve fluidity.

[0008] Therefore, an object of the present invention is to provide a composite propellant that improves both physical properties of elongation at maximum load and maximum tensile strength and further has high fluidity.

Means for Solving the Problems

[0009] As a result of intensive studies on the above problems, the inventors have found that in a composite propellant containing an oxidizer composed of a binder mainly composed of terminal hydroxyl polybutadiene and ammonium perchlorate, polytetramethylene ether glycol (PTG) as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) as a binder, N-methyldiethanolamine (MDA), and isophorone diisocyanate (IPDI) as a curing agent are contained in the binder. Furthermore, by setting the ratio of polytetramethylene ether glycol in the binder to a specific ratio, a composite propellant having good physical properties of both elongation at maximum load and maximum tensile strength and high fluidity can be obtained, and the present invention has been completed. That is, the present invention is the following composite propellant.

[0010] [1] In a composite propellant containing a binder mainly composed of terminal hydroxyl polybutadiene and an oxidizer containing ammonium perchlorate, the binder contains polytetramethylene ether glycol as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide and N-methyldiethanolamine as binders, and isophorone diisocyanate as a curing agent, The composite propellant is characterized in that the proportion of the polytetramethylene ether glycol in the binder is 10 to 20% by mass. [2] The composite propellant according to [1], wherein the proportion of the tris[1-(2-methyl)-aziridinyl]phosphine oxide in the binder is 0.3 to 0.8% by mass, and the proportion of the N-methyldiethanolamine is 0.1 to 0.5% by mass. [3] The composite propellant according to [1] or [2], wherein the number average molecular weight of the polytetramethylene ether glycol is 900 to 2100. [4] The composite propellant according to any one of [1] to [3], wherein the content of the polytetramethylene ether glycol in the total amount of the composite propellant is 1 to 3% by mass. [Advantages of the Invention]

[0011] According to the composite propellant of the present invention, by using polytetramethylene ether glycol as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as binders, and isophorone diisocyanate (IPDI) as a curing agent in the binder, and setting the proportion of the polytetramethylene ether glycol (PTG) in the binder to 10 to 20% by mass, both physical properties of the elongation at maximum load and the maximum tensile strength can be improved, and furthermore, a composite propellant having high fluidity can be provided.

[0012] Furthermore, by using specific amounts of polytetramethylene ether glycol with a specific number average molecular weight, tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO), and N-methyldiethanolamine (MDA), a composite propellant exhibiting excellent physical properties and manufacturability can be obtained.

Mode for Carrying Out the Invention

[0013] The composite propellant of the present invention is used, for example, as a propellant for high-performance rocket motors, etc., and has a basic composition of ammonium perchlorate as an oxidizer, terminal hydroxyl group polybutadiene, a binder, a chain extender, a binder containing a curing agent, and contains aluminum powder as a combustion aid, uses polytetramethylene ether glycol as a chain extender, and uses tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) in combination as a binder. In addition, other additives can be further added according to the application.

[0014] The composite propellant of the present invention uses tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as a binder, and uses polytetramethylene ether glycol as a chain extender, and as a result, with respect to physical properties, an effect is recognized that not only the elongation at maximum load but also the maximum tensile strength is significantly improved. In addition, the composite propellant of the present invention has excellent fluidity with respect to manufacturability. Due to the excellent fluidity, it becomes possible to easily perform casting.

[0015] In addition, for the composite propellant of the present invention, after adding a curing agent to the binder, the time until the viscosity increases (pot life) can be adjusted to a predetermined time. The pot life is not particularly limited, but is preferably 500 minutes or more and less than 700 minutes. By setting the pot life to 500 minutes or more, it is possible to prevent curing during casting and enable stable production. On the other hand, by setting the pot life to less than 700 minutes, it cures promptly after casting, resulting in excellent productivity.

[0016] The maximum tensile strength of the composite propellant of the present invention is not particularly limited, but for example, it is 110 N / cm 2 or more. Preferably it is 120 N / cm 2 or more, and more preferably 130 N / cm 2 or more. The upper limit is, for example, 200 N / cm 2 or less. In addition, the elongation at maximum load of the composite propellant of the present invention is not particularly limited, but for example, it is 30% or more. Preferably it is 35% or more, more preferably 40% or more, and still more preferably 45% or more. The upper limit is, for example, 60% or less. The measurement methods for the maximum tensile strength and the elongation at maximum load are carried out in accordance with the plastic tensile test method "ASTM D638-84" described in the examples.

[0017] Since various rocket motors differ in size and purpose, the required mechanical properties also vary, and it is necessary to manufacture propellants that meet the requirements of each mechanical property. If both the maximum tensile strength and the elongation at maximum load can be greatly improved, the range of selectable compositions will be widened, and it will be possible to respond to high-performance rocket motors. The composite propellant of the present invention can improve both the maximum tensile strength and the elongation at maximum load, so it can be applied to a variety of rocket motors by slightly changing the composition such as the curing agent.

[0018] <Oxidizer> When manufacturing a composite propellant, as the oxidizer, ammonium perchlorate (AP), cyclotetramethylene tetranitramine (HMX), cyclotrimethylene tetranitramine (RDX), ammonium nitrate, etc. are used. Although the oxidizer of the present invention is ammonium perchlorate, it does not necessarily have to be alone and may contain a plurality of the above-mentioned oxidizers. The oxidizer needs to contain at least 50% by weight based on the total amount of the composite propellant, and preferably contains 60% by weight or more. On the other hand, the upper limit value is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less.

[0019] Furthermore, from the viewpoints of adjusting the viscosity of the composite propellant to facilitate the casting process, adjusting the burning rate, and chemically bonding with the binder to improve physical properties, the oxidizer may use a plurality of different particle sizes. As the oxidizer particles, small particles with an average particle size of 1 to 30 μm, medium particles with an average particle size of 150 to 300 μm, and large particles with an average particle size of 350 to 600 μm are preferably mixed in two types of large and medium, large and small, or medium and small, or three types of large, medium, and small. From the viewpoints of adjusting the viscosity of the composite propellant to facilitate the casting process, adjusting the burning rate, and chemically bonding with the binder to improve physical properties, it is particularly preferable to mix 10 to 30% by weight of two types of small and large and 40 to 80% by weight of one type of medium with respect to 100% by weight of the oxidizer. The average particle size is measured using a "Microtrac particle size distribution analyzer" (manufactured by Nikkiso Co., Ltd.).

[0020] <Binder> The composite propellant of the present invention includes a binder having a combustion binder, a binder, a chain extender, and a curing agent as a basic composition. The binder is a component for binding the oxidizer, the combustion aid, and other components. The content of the binder based on the total amount of the composite propellant is usually 7 to 25% by weight. As the lower limit value, it is preferably 10% by weight or more. As the upper limit value, it is preferably 20% by weight or less, more preferably 16% by weight or less. Each component in the binder will be described below.

[0021] (Fuel binder) The composite propellant of the present invention contains hydroxyl-terminated polybutadiene (HTPB) as a fuel binder in the binder. Further, as other fuel binders, it may contain a hydroxyl-terminated polyether having an azidomethyl group, such as glycidyl azide polymer (GAP), 3,3-bis(azidomethyl)methyloxetane / tetrahydrofuran copolymer (BAMO / THF copolymer), and the like.

[0022] Examples of the hydroxyl-terminated polybutadiene, which is a general-purpose product according to the present embodiment, include hydroxyl-terminated polybutadiene having an average of 2 to 2.8 hydroxyl groups at the molecular terminals and a number-average molecular weight of 2,000 to 4,000. The number-average molecular weight (Mn) was measured by the VPO method.

[0023] As the hydroxyl-terminated polybutadiene, those mainly produced by special methods such as anionic polymerization for use as a propellant have been used. However, since it is a special product for propellants, the production volume is small, and it is expected to be difficult to obtain in the future. On the other hand, the widely used hydroxyl-terminated polybutadiene (R-45HT) is produced by radical polymerization for general products such as tires, has no problem in availability, and is inexpensive. However, compared with that for propellants, the physical properties of the propellant are significantly inferior, and the manufacturability is not practical.

[0024] It is preferable to use the hydroxyl-terminated polybutadiene (R-45HT), which is a general-purpose product different from the special product for propellants, as the hydroxyl-terminated polybutadiene of the present invention. Note that R-45HT is a hydroxyl-terminated polybutadiene obtained by radical polymerization. By using R-45HT, not only can the composite propellant be manufactured at low cost, but also there is an effect that the maximum tensile strength is improved compared with R-45M. Further, by using R-45HT, there is an effect that the pot life does not become too long and the productivity is excellent.

[0025] The content of the hydroxyl-terminated polybutadiene with respect to the total amount of the binder is usually 50 to 90% by mass, preferably 60 to 85% by mass. In addition, the content of the terminal hydroxyl group polybutadiene relative to the total amount of the composite propellant is usually 7 to 13% by mass, preferably 8 to 12% by mass.

[0026] (Binder) The binder is blended for the purpose of imparting adhesiveness to the oxidizer particles. The composite propellant of the present invention contains tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as binders in the binder. In addition, as other binders, for example, aziridine-based such as bisisophthaloyl 1-(2-methyl)aziridine (HX-752), N-ethyldiethanolamine (EDA), reaction products of tetraethylenepentamine and acrylonitrile (TEPAN or HX-879), reaction products of tetraethylenepentamine, acrylonitrile and glycidol (TEPANOL or HX-878), etc. amine-based, hydantoin-based such as dihydroxyethyl-5,5-dimethylhydantoin (DHE), and silane coupling agents (A-1100), etc. may also be contained.

[0027] The content of tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) relative to the total amount of the binder is preferably 0.3 to 0.8% by mass, more preferably 0.5 to 0.7% by mass. When the content of tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) relative to the total amount of the binder is 0.3% by mass or more, the tensile strength is improved in the physical properties of the composite propellant, and when it is 0.8% by mass or less, the elongation rate is improved in the physical properties of the composite propellant. The content of N-methyldiethanolamine relative to the total amount of the binder is preferably 0.1 to 0.5% by mass, more preferably 0.2 to 0.4% by mass. When the content of N-methyldiethanolamine relative to the total amount of the binder is 0.1% by mass or more, the elongation rate is improved in the physical properties of the composite propellant, and when it is 0.5% by mass or less, the tensile strength is improved in the physical properties of the composite propellant.

[0028] In addition, the content of tris[1-(2-methyl)aziridinyl]phosphine oxide with respect to the total amount of the composite propellant is 0.04 to 0.12% by mass, preferably 0.07 to 0.10% by mass. The content of N-methyldiethanolamine with respect to the total amount of the composite propellant is 0.01 to 0.07% by mass, preferably 0.02 to 0.06% by mass.

[0029] (Chain extender) The chain extender is compounded for the purpose of increasing the average molecular weight between crosslinking points of the terminal hydroxyl group polybutadiene. The composite propellant of the present invention contains polytetramethylene ether glycol (PTG) as a chain extender in the binder. In addition, as other chain extenders, compounds composed of diols having hydroxyl groups at both ends, such as polyethylene glycol, polypropylene glycol, block copolymers of polyethylene glycol-polypropylene glycol, hydrogenated polybutadiene with hydroxyl groups at both ends, adipic acid-based polyester resins, etc. may be contained.

[0030] The content of polytetramethylene ether glycol (PTG) with respect to the total amount of the binder is preferably 10 to 20% by mass, more preferably 13 to 17% by mass. When the content of polytetramethylene ether glycol (PTG) with respect to the total amount of the binder is less than 10% by mass, the effect as a chain extender is low and it does not contribute to the physical properties and manufacturability of the propellant, so it is not preferable. When it exceeds 20% by mass, the physical properties of the composite propellant, especially the tensile strength, decrease, so it is not preferable.

[0031] In addition, the content of polytetramethylene ether glycol (PTG) with respect to the total amount of the composite propellant is 1 to 3% by mass, preferably 1.8 to 2.4% by mass.

[0032] The number average molecular weight of polytetramethylene ether glycol is preferably from 900 to 2100, and more preferably from 1400 to 1800. If the number average molecular weight of polytetramethylene ether glycol (PTG) is 900 or more, the reaction rate with isocyanate becomes slow, so the productivity is improved, which is preferable. If it is 2100 or less, the reaction rate of isocyanate becomes fast, so the curing is completed within a predetermined curing time, and the occurrence of changes in physical properties due to post-curing is suppressed, which is preferable. The number average molecular weight (Mn) was measured in accordance with JIS K 1557-1.

[0033] (Hardener) The composite propellant of the present invention contains isophorone diisocyanate (IPDI) as a hardener. As other hardeners, for example, diisocyanate compounds such as hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), and dicyclohexylmethane-4,4-diisocyanate (hydrogenated MDI) may be contained.

[0034] When the content of the hardener is expressed by the equivalent ratio of isocyanate group / hydroxyl group as NCO / OH, it is in the range of NCO / OH = 0.7 to 1.1, and preferably in the range of 0.8 to 1.0.

[0035] <Combustion aid> Examples of the combustion aid include metal powders such as aluminum, boron, and magnesium. Among them, in the present invention, it is preferable to use aluminum.

[0036] The content of the combustion aid with respect to the total amount of the composite propellant is, for example, 5 to 40% by mass, and preferably 10 to 30% by mass.

[0037] (Other additives) In addition, additives may be added according to the combustion characteristics, physical properties, and manufacturability required for the composite propellant. As plasticizers, esters such as dioctyl adipate (DOA), dioctyl sebacate (DOS), diisodecyl adipate (DIDA), and isodecyl pelargonate, and nitro plasticizers such as 1,2,4-butanetriol trinitrate (BTTN), trimethylolethane trinitrate (TMETN), and triethylene glycol dinitrate (TEGDN) are used. Among them, in the present invention, it is preferable to use dioctyl adipate (DOA).

[0038] Examples of the curing catalyst include organotin compounds such as dibutyltin dilaurate (DBTDL) and dibutyltin bis(2-ethylhexanoate), organobismuth compounds such as triphenylbismuth, and amines such as triethylenediamine.

[0039] Examples of the anti-aging agent include 2,2'-methylene-bis(4-methyl-6-t-butylphenol), phenyl-β-naphthylamine, and the reaction product of diphenylamine and acetone (Nonflex BA, manufactured by Seiko Chemical Co., Ltd.).

[0040] Examples of the combustion regulator include iron oxide, ferrocene derivatives, carborane derivatives, lead salts, and carbon.

[0041] When manufacturing the composite propellant of the present invention, for example, each raw material and various additives as required are put into a kneader in a predetermined blending balance, kneaded uniformly at a predetermined temperature to form a slurry state, and then injected into a predetermined mold and cured at a predetermined temperature and time to manufacture the composite propellant.

Examples

[0042] Hereinafter, the composite propellant of the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the scope of these Examples. The abbreviations in Tables 1 and 2 represent the following meanings. R-45HT: Terminal Hydroxyl Group Polybutadiene PTG: Polytetramethylene Ether Glycol MAPO: Tris〔1-(2-Methyl)-aziridinyl〕Phosphine Oxide MDA: N-Methyldiethanolamine N-8: Reaction Product of N-Methyldiethanolamine and Sebacic Acid HX-878: Reaction Product of Tetraethylenepentamine and Acrylonitrile BIDE: 2,2’-(n-Butylimino)diethanol IPDI: Isophorone Diisocyanate DOA: Dioctyl Adipate

[0043] <Examples 1 to 7> The blending compositions of the respective components of the composite propellants of Examples 1 to 7 are shown in Table 1 described below. Also, the manufacturability and physical properties were measured by the method shown below using the composite propellants. The results are also shown in Table 1.

[0044]

Table 1

[0045] [Manufacturability] <Flowability> A cylindrical core having an outer diameter of 40 mm was attached to the bottom plate of a predetermined casting mold, and an ABS resin having an outer diameter of 84 mm, an inner diameter of 80 mm, and a length of 140 mm was applied to the inner surface of the casting mold. The slurry of the composite propellants of each example and comparative example was poured therein, and the ease of pouring when pouring into the mold was evaluated according to the following evaluation criteria. ◎: The flowability of the propellant slurry was high, and it could be poured extremely easily. 〇: The propellant slurry had flowability and could be poured easily. △: The flowability of the propellant slurry was poor, and it took time to pour.

[0046] <Pot Life> Using an RE80 viscometer, the viscosity was measured every specified time under the conditions of 60°C and a spindle rotation speed of 5 rpm. The time from adding the curing agent until the viscosity reached 10 kP at 60°C was determined as the pot life. The pot life is preferably more than 500 minutes and less than 700 minutes so that the casting properties of rocket motors of various sizes with different launching capabilities can be ensured in the production of various rocket motors. If the pot life is less than 500 minutes, the pot life is short and casting becomes difficult. If it is 700 minutes or more, the pot life is long, curing does not finish within the specified curing time, and physical properties change due to post-curing, which is not preferable.

[0047] [Physical properties] From the composite propellant, tensile test specimens were prepared according to the plastic tensile test method "ASTM D638-84", and a tensile test was conducted at a tensile speed of 50 mm / min and a test temperature of 20°C to obtain the maximum tensile strength (N / cm 2 ), and the elongation at maximum load (%). Note that the tensile test specimen is a 10-mm-thick specimen with a total length of 125 mm, both ends having a width of 25 mm, and a central straight part with a length of 50 mm and a width of 10 mm between both ends.

[0048] [Example 1] 9.55 parts by mass of hydroxyl-terminated polybutadiene (HTPB) (number of terminal hydroxyl groups: 2.4 on average, average molecular weight: 2700) (68.2% by mass as the content in the binder. The same applies hereinafter), 1.90 parts by mass (13.6% by mass) of polytetramethylene ether glycol (PTG, number average molecular weight: 1500) as a chain extender, and 1.39 parts by mass (9.9% by mass) of dioctyl adipate (DOA) as a plasticizer were added and mixed. Then, a predetermined amount of aluminum powder as a combustion aid was added and mixed, and further 0.07 parts by mass (0.5% by mass) of tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and 0.03 parts by mass (0.2% by mass) of N-methyldiethanolamine (MDA) as binders were added and mixed.

[0049] Next, 1.06 parts by mass (7.6% by mass) of isophorone diisocyanate (IPDI), which is a curing agent, was added and vacuum mixing was performed. After that, a predetermined amount of ammonium perchlorate, which is an oxidizing agent, was charged and heated to 60°C, and vacuum mixing was performed to obtain a slurry-like mixture. Then, this mixture was cast into a predetermined container under reduced pressure, and after degassing, it was cured at 60°C for 7 days to obtain a composite propellant.

[0050] 〔Examples 2 to 3〕 In Example 1, when the number average molecular weight of polytetramethylene ether glycol (PTG), which is a chain extender, was set to 1000 (Example 2) and 2000 (Example 3), a composite propellant was produced in the same manner as in Example 1.

[0051] 〔Examples 4 to 7〕 The binder composition was changed in the same manner as in Example 1, and the weight ratios of polytetramethylene ether glycol (PTG), which is a chain extender, and tris〔1-(2-methyl)-aziridinyl〕phosphine oxide (MAPO) and N-methyldiethanolamine (MDA), which are binders, were changed to produce a composite propellant, and the physical properties and manufacturability were measured in the same manner as in Example 1.

[0052] <Comparative Examples 1 to 5> In the same manner as in Examples 1 to 7, a composite propellant was produced with the propellant formulation composition shown in Table 2. Also, the manufacturability and physical properties were measured using the composite propellant, and the results are shown in Table 2.

[0053]

Table 2

[0054] From the test results in Table 1, the following was found. The composite propellants of Examples 1 to 7 had high values for both physical properties, namely the maximum tensile strength and the elongation at maximum load, and were found to be excellent in physical properties. Furthermore, in terms of manufacturability, while maintaining high fluidity, all satisfied the range of more than 500 minutes and less than 700 minutes, and it was confirmed that there were no problems in manufacturability.

[0055] Next, comparing Example 1 with Comparative Example 2 shown in Table 2, in the composite propellant containing R-45HT, MAPO, and MDA, when PTG was added, not only the elongation at maximum load but also the maximum tensile strength increased. In the invention described in Patent Document 1, since it was a composite propellant not containing MAPO and MDA, the maximum tensile strength did not increase even when PTG was added. However, in the present invention, by adding PTG in addition to MAPO and MDA, both the elongation at maximum load and the maximum tensile strength could be increased. Also, comparing Example 2 with Comparative Examples 2, 6, and 7, in the composite propellant containing MAPO and MDA, when the content of PTG was 10 to 20% by mass, extremely high results were obtained for the maximum tensile strength and the elongation at maximum load. On the other hand, when the content of PTG exceeded 20% by mass (Comparative Example 7), a tendency for the maximum tensile strength and the elongation at maximum load to decrease was observed. That is, in the composite propellant containing MAPO and MDA, a critical significance was recognized in that the content of PTG was 10 to 20% by mass.

[0056] From the above results, in order to obtain a composite propellant having good physical properties and manufacturability, it is essential to use polytetramethylene ether glycol (PTG) as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) as a binder, and N-methyldiethanolamine (MDA) in combination in the binder. Also, it became clear that the proportion in the binder should be 10 to 20% by mass for polytetramethylene ether glycol as the chain extender. Further, it was found that the content of tris[1-(2-methyl)-aziridinyl]phosphine oxide with respect to the binder is preferably 0.3 to 0.8% by mass, the content of N-methyldiethanolamine is preferably 0.1 to 0.5% by mass, and the number average molecular weight of polytetramethylene ether glycol (PTG) is preferably 900 to 2100.

Claims

1. In a composite propellant containing a binder mainly composed of terminal hydroxyl polybutadiene having an average of 2 to 2.8 hydroxyl groups at the molecular ends and a number average molecular weight of 2,000 to 4,000, and an oxidizing agent containing ammonium perchlorate, the binder contains polytetramethylene ether glycol as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide and N-methyldiethanolamine as binders, and isophorone diisocyanate as a curing agent, The composite propellant is characterized in that the proportion of the polytetramethylene ether glycol in the binder is 10 to 20% by mass.

2. The composite propellant according to claim 1, wherein the proportion of the tris[1-(2-methyl)-aziridinyl]phosphine oxide in the binder is 0.3 to 0.8% by mass, and the proportion of the N-methyldiethanolamine is 0.1 to 0.5% by mass.

3. The composite propellant according to claim 1 or 2, wherein the number average molecular weight of the polytetramethylene ether glycol is 900 to 2,100.

4. The composite propellant according to any one of claims 1 to 3, wherein the content of the polytetramethylene ether glycol in the total amount of the composite propellant is 1 to 3% by mass.

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