JP7683264B2 - Composite Propellant - Google Patents

Description

The present invention relates to a composite propellant that has good physical properties and manufacturability.

Composite propellants are mainly composed of an oxidizer and a binder, which acts as both a fuel and a binding agent, and metal powder is usually added as a combustion improver to improve combustion performance. Examples of oxidizers include ammonium perchlorate, nitramine, and ammonium nitrate, while examples of binders include polybutadiene and polyurethane, and examples of combustion improvers include aluminum powder. Due to their excellent combustion and physical properties, composite propellants are widely used as propellants for high-performance rocket motors.

However, although the hydroxyl-terminated polybutadiene (R-45M) used as a binder in conventional composite propellants is highly functional, it is a specialized product that is difficult to obtain and expensive, so various studies have been conducted to improve the physical properties and manufacturability of the material by using general-purpose polybutadiene (R-45HT) and changing the hardener or binder, or adding a chain extender.

For example, Patent Document 1 discloses a composite propellant in which aziridine polyester and amine polyester are used in combination in a binder, and polytetramethylene ether glycol (hereinafter also referred to as "PTG") is used as a chain extender in a composite propellant using the general-purpose R-45HT as a binder. Comparing Example 10 of Patent Document 1 with Comparative Example 4, it is found that the addition of PTG improves the maximum stress strain (maximum load elongation) from 25% to 40%. On the other hand, the maximum stress (maximum tensile strength) decreases from 10.5 kgf/ ^cm2 to 9.3 kgf/ ^cm2 .

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

Japanese Patent Application Publication No. 59-73489 Japanese Unexamined Patent Publication No. 62-202890

In the composite propellants of Patent Documents 1 and 2, which use hydroxyl-terminated polybutadiene such as R-45HT as a binder, the physical properties of the elongation at maximum load are improved, but the maximum tensile strength is not. If the maximum tensile strength is low, excessive deformation occurs under the high pressure, environmental temperature, and acceleration associated with combustion, resulting in a problem of unstable combustion. In addition, if the elongation at maximum load is increased, the occurrence of chipping and cracking is suppressed under the same conditions, so a constant burning rate can be obtained and stable combustion can be achieved. Therefore, in composite propellants using hydroxyl-terminated polybutadiene such as R-45HT, it has been desired to improve both the physical properties of the elongation at maximum load and the maximum tensile strength. In addition, with regard to manufacturability, it is desired to improve the fluidity in order to improve the ease of casting.

The objective of the present invention is to provide a composite propellant that has improved physical properties, such as maximum load elongation and maximum tensile strength, and also has high fluidity.

As a result of intensive research into the above problem, the inventors discovered that in a composite propellant containing a binder mainly composed of hydroxyl-terminated polybutadiene and an oxidizer composed of ammonium perchlorate, the binder contains polytetramethylene ether glycol (PTG) as a chain extender, tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as binding agents, and isophorone diisocyanate (IPDI) as a curing agent, and further, by setting the ratio of polytetramethylene ether glycol in the binder to a specific ratio, a composite propellant having good physical properties in both maximum load elongation and maximum tensile strength and high fluidity can be obtained, and thus completed the present invention. That is, the present invention is the following composite propellant.

[1]
A composite propellant containing a binder mainly composed of hydroxyl-terminated 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 binding agents, and isophorone diisocyanate as a curing agent;
A composite propellant, wherein the proportion of the polytetramethylene ether glycol in the binder is 10 to 20 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 in the binder is 0.1 to 0.5% by mass.
[3]
The composite propellant according to [1] or [2], wherein the polytetramethylene ether glycol has a number average molecular weight of 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 mass%.

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

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 with excellent physical properties and manufacturability can be obtained.

The composite propellant of the present invention is used, for example, as a propellant for high-performance rocket motors, and contains ammonium perchlorate as an oxidizer, a binder having a basic composition of hydroxyl-terminated polybutadiene, a binding agent, a chain extender, and a hardener, aluminum powder as a combustion improver, polytetramethylene ether glycol as a chain extender, and tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as binding agents. Other additives can be added depending on the application.

The composite propellant of the present invention uses tris[1-(2-methyl)-aziridinyl]phosphine oxide (MAPO) and N-methyldiethanolamine (MDA) as binders and polytetramethylene ether glycol as a chain extender, and as a result, it has been observed that not only the maximum elongation at maximum load but also the maximum tensile strength are remarkably improved with regard to physical properties.
In addition, the composite propellant of the present invention has excellent fluidity in terms of manufacturability. The excellent fluidity allows for easy casting.

In addition, the composite propellant of the present invention can adjust the time (pot life) until the viscosity increases after adding the curing agent to the binder to a predetermined time. There are no particular restrictions on the pot life, but it is preferably 500 minutes or more and less than 700 minutes. By making the pot life 500 minutes or more, hardening during casting can be prevented, enabling stable production. On the other hand, by making the pot life less than 700 minutes, it hardens quickly after casting, which has the effect of improving productivity.

The ultimate tensile strength of the composite propellant of the present invention is not particularly limited, but is, for example, 110 N/cm ² or more. It is preferably 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.
The maximum elongation rate under load of the composite propellant of the present invention is not particularly limited, but is, for example, 30% or more, preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. The upper limit is, for example, 60% or less.
The maximum tensile strength and the elongation at maximum load are measured in accordance with the plastic tensile test method "ASTM D638-84" described in the Examples.

Since various rocket motors differ in size and purpose, the required mechanical properties are also different, and it is necessary to manufacture propellants that meet the requirements of each mechanical property. If it is possible to significantly improve both the maximum tensile strength and the maximum elongation at load, the range of compositions that can be selected will be wider, and it will be possible to accommodate high-performance rocket motors. The composite propellant of the present invention can improve both the maximum tensile strength and the maximum elongation at load, so it can be applied to a wide variety of rocket motors by making slight changes to the composition of the hardener, etc.

<Oxidizing Agent>
When manufacturing a composite propellant, ammonium perchlorate (AP), cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetetranitramine (RDX), ammonium nitrate, etc. are used as the oxidizer. The oxidizer of the present invention is ammonium perchlorate, but it does not necessarily have to be a single oxidizer, and may contain a plurality of the above-mentioned oxidizers. The oxidizer must be contained in an amount of at least 50% by weight, and preferably 60% by weight or more, based on the total amount of the composite propellant. On the other hand, the upper limit is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less.

In addition, the oxidizer may have a plurality of different particle sizes in order to adjust the viscosity of the composite propellant to facilitate the casting process, adjust the burning rate, and chemically bond with the binder to improve physical properties. As the oxidizer particles, it is preferable to use 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, each in two types (large and medium, large and small, or medium and small), or three types (large, medium and small). In order to adjust the viscosity of the composite propellant to facilitate the casting process, adjust the burning rate, and chemically bond with the binder to improve physical properties, it is particularly preferable to mix 10 to 30 mass% each of the small and large types and 40 to 80 mass% of the medium type with respect to 100 mass% of the oxidizer. The average particle size is measured using a "Microtrack particle size distribution meter" (manufactured by Nikkiso).

<Binder>
The composite propellant of the present invention includes a binder having a basic composition including a combustion binder, a binder, a chain extender, and a curing agent. The binder is a component for binding an oxidizer, a combustion improver, and other components. The content of the binder relative to the total amount of the composite propellant is usually 7 to 25% by mass. The lower limit is preferably 10% by mass or more. The upper limit is preferably 20% by mass or less, and more preferably 16% by mass or less. Each component in the binder will be described below.

(Fuel Binder)
The composite propellant of the present invention contains hydroxyl-terminated polybutadiene (HTPB) as a fuel binder in the binder, and may contain other fuel binders such as hydroxyl-terminated polyethers having azidomethyl groups, for example, glycidyl azide polymer (GAP) and 3,3-bisazidomethyl methyloxetane/tetrahydrofuran copolymer (BAMO/THF copolymer).

The general-purpose hydroxyl-terminated polybutadiene according to this embodiment is, for example, a hydroxyl-terminated polybutadiene having an average of 2 to 2.8 hydroxyl groups at the ends of the molecule and a number average molecular weight of 2000 to 4000. The number average molecular weight (Mn) was measured by the VPO method.

Hydroxyl-terminated polybutadiene has been used primarily for propellants, manufactured using special methods such as anionic polymerization, but because it is a specialized product for propellants, production volumes are low and it is expected to become difficult to obtain in the future. On the other hand, the commonly used hydroxyl-terminated polybutadiene (R-45HT) is manufactured by radical polymerization for general products such as tires, and is readily available and inexpensive, but compared to propellants, the physical properties of the propellant are significantly inferior, and the manufacturability is such that it is not practical to use.

The hydroxyl-terminated polybutadiene of the present invention is preferably a general-purpose hydroxyl-terminated polybutadiene (R-45HT) that is different from the specialized product for propellants. R-45HT is a hydroxyl-terminated polybutadiene obtained by radical polymerization. The use of R-45HT not only allows the composite propellant to be produced at low cost, but also has the effect of improving the maximum tensile strength compared to R-45M. In addition, the use of R-45HT has the effect of not having an excessively long pot life, resulting in excellent productivity.

The content of the hydroxyl-terminated polybutadiene in the total amount of the binder is usually 50 to 90% by mass, and preferably 60 to 85% by mass.
The content of the hydroxyl-terminated polybutadiene in the total amount of the composite propellant is usually 7 to 13 mass %, and preferably 8 to 12 mass %.

(Binder)
The binder is blended for the purpose of imparting adhesion 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, other binders may be contained, for example, aziridine-based binders such as bisisophthaloyl 1-(2-methyl)aziridine (HX-752), amine-based binders such as N-ethyldiethanolamine (EDA), reaction products of tetraethylenepentamine and acrylonitrile (TEPAN or HX-879), reaction products of tetraethylenepentamine, acrylonitrile, and glycidol (TEPANOL or HX-878), hydantoin-based binders such as dihydroxyethyl-5,5-dimethylhydantoin (DHE), and silane coupling agents (A-1100).

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

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

(Chain extender)
The chain extender is blended for the purpose of increasing the average molecular weight between crosslinking points of the hydroxyl-terminated polybutadiene. The composite propellant of the present invention contains polytetramethylene ether glycol (PTG) as a chain extender in the binder. Other chain extenders may also be included, such as compounds consisting of diols having hydroxyl groups at their ends, such as polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol block copolymers, hydrogenated polybutadiene with hydroxyl groups at both ends, and adipic acid-based polyester resins.

The content of polytetramethylene ether glycol (PTG) relative to the total amount of the binder is preferably 10 to 20% by mass, and more preferably 13 to 17% by mass. If the content of polytetramethylene ether glycol (PTG) relative to the total amount of the binder is less than 10% by mass, it is not preferable because it has a low effect as a chain extender and does not contribute to the physical properties and manufacturability of the propellant, and if it exceeds 20% by mass, it is not preferable because the physical properties of the composite propellant, especially the tensile strength, are reduced.

The content of polytetramethylene ether glycol (PTG) in the total composite propellant is 1 to 3 mass %, and preferably 1.8 to 2.4 mass %.

The number average molecular weight of polytetramethylene ether glycol is preferably 900 to 2100, and more preferably 1400 to 1800. If the number average molecular weight of polytetramethylene ether glycol (PTG) is 900 or more, the reaction rate with isocyanate is slowed down, improving manufacturability, and if it is 2100 or less, the reaction rate with isocyanate is fast, so curing is completed within a specified curing time and changes in physical properties due to post-curing are suppressed, which is preferable. The number average molecular weight (Mn) was measured in accordance with JIS K 1557-1.

(Hardening agent)
The composite propellant of the present invention contains isophorone diisocyanate (IPDI) as a curing agent, and may contain other curing agents such as diisocyanate compounds such as hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), and dicyclohexylmethane-4,4-diisocyanate (hydrogenated MDI).

The content of the curing agent, expressed as the equivalent ratio of isocyanate groups to hydroxyl groups in terms of NCO/OH, is in the range of 0.7 to 1.1, preferably 0.8 to 1.0.

<Combustion improver>
The combustion improver may be a powder of a metal such as aluminum, boron, magnesium, etc. Among these, it is preferable to use aluminum in the present invention.

The content of the combustion improver relative to the total amount of the composite propellant is, for example, 5 to 40 mass%, and preferably 10 to 30 mass%.

<Other additives>
Other additives may be added depending on the combustion characteristics, physical characteristics, and manufacturability required for the composite propellant. As the plasticizer, esters such as dioctyl adipate (DOA), dioctyl sebacate (DOS), diisodecyl adipate (DIDA), and isodecyl pelagonate, as well as nitro plasticizers such as 1,2,4-butanetriol trinitrate (BTTN), trimethylolethane trinitrate (TMETN), and triethylene glycol dinitrate (TEGDN) are used. Among them, it is preferable to use dioctyl adipate (DOA) in the present invention.

Examples of curing catalysts include organotin compounds such as dibutyltin dilaurate (DBTDL) and dibutyltin di(2-ethylhexoate), organobismuth compounds such as triphenylbismuth, and amines such as triethylenediamine.

Examples of antioxidants include 2,2'-methylene-bis(4-methyl-6-t-butylphenol), phenyl-β-naphthylamine, and reaction products of diphenylamine and acetone (Nonflex BA, manufactured by Seiko Chemical Co., Ltd.).

Combustion modifiers include iron oxide, ferrocene derivatives, carborane derivatives, lead salts, carbon, etc.

When manufacturing the composite propellant of the present invention, for example, each raw material and, if necessary, various additives are placed in a mixer in a predetermined mixing balance, uniformly kneaded at a predetermined temperature to form a slurry, and then poured into a predetermined mold and cured at a predetermined temperature for a predetermined time to produce the composite propellant.

The composite propellant of the present invention will be specifically described below 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 have the following meanings.
R-45HT: Polybutadiene with terminal hydroxyl groups 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

<Examples 1 to 7>
The blending compositions of the components of the composite propellants of Examples 1 to 7 are shown in Table 1 below. The manufacturability and physical properties of the composite propellants were measured by the methods described below. The results are also shown in Table 1.

[Manufacturability]
<Liquidity>
A cylindrical core with an outer diameter of 40 mm was attached to the bottom plate of a specified casting mold, and ABS resin with 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. A slurry of the composite propellant of each Example and Comparative Example was poured into the mold, and the ease of pouring into the mold was evaluated according to the following evaluation criteria.
⊚: The propellant slurry had high fluidity and could be poured into a mold very easily.
◯: The propellant slurry had fluidity and could be easily poured into the mold.
Δ: The fluidity of the propellant slurry was poor, and casting took a long time.

<Pot life>
The viscosity was measured at regular intervals using an RE80 viscometer at 60°C and a spindle speed of 5 rpm, and the time from when the hardener was added until the viscosity reached 10 kP at 60°C was determined as the pot life. In order to ensure the castability of rocket motors of any size in the manufacture of various rocket motors with different launch capabilities, the pot life is preferably 500 minutes or more and less than 700 minutes. If the pot life is less than 500 minutes, the pot life is short and casting becomes difficult, while if it is 700 minutes or more, the pot life is long, the curing does not end within the specified curing time, and the physical properties change due to post-curing, which is not preferable.

[Physical properties]
Tensile test pieces were prepared from the composite propellant in accordance with the plastic tensile testing method "ASTM D638-84", and tensile tests were carried out at a tensile speed of 50 mm/min and a test temperature of 20° C. to determine the maximum tensile strength (N/cm ² ) and elongation at maximum load (%).
The tensile test piece was a 10 mm thick test piece with a total length of 125 mm, both ends 25 mm wide, and a central straight section 50 mm long and 10 mm wide between the ends.

Example 1
9.55 parts by mass of hydroxyl-terminated polybutadiene (HTPB) (number of terminal hydroxyl groups: average 2.4, average molecular weight: 2700) (content in binder: 68.2% by mass; same below), 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. A predetermined amount of aluminum powder as a combustion improver 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.

Next, 1.06 parts by mass (7.6% by mass) of isophorone diisocyanate (IPDI) was added as a curing agent and mixed in a vacuum. After that, a specified amount of ammonium perchlorate as an oxidizing agent was added and heated to 60°C, and mixed in a vacuum to obtain a slurry-like mixture. This mixture was then poured into a specified container under reduced pressure, degassed, and cured at 60°C for 7 days to obtain a composite propellant.

[Examples 2 to 3]
In Example 1, composite propellants were produced in the same manner as in Example 1, except that the number average molecular weight of the chain extender, polytetramethylene ether glycol (PTG), was changed to 1,000 (Example 2) and 2,000 (Example 3).

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

<Comparative Examples 1 to 5>
In the same manner as in Examples 1 to 7, a composite propellant was produced with the propellant blend composition shown in Table 2. The manufacturability and physical properties of the composite propellant were measured, and the results are shown in Table 2.

The test results in Table 1 reveal the following: The composite propellants of Examples 1 to 7 had high values for both maximum tensile strength and elongation at maximum load, demonstrating excellent physical properties. Furthermore, in terms of manufacturability, all of them maintained high fluidity while satisfying the requirement of 500 minutes or more and less than 700 minutes, confirming that there are no problems with manufacturability.

Next, comparing Example 1 with Comparative Example 2 shown in Table 2, in a composite propellant containing R-45HT, MAPO, and MDA, the addition of PTG increased not only the maximum elongation at maximum load but also the maximum tensile strength. In the invention described in Patent Document 1, the composite propellant did not contain MAPO or MDA, so the addition of PTG did not increase the maximum tensile strength, but in the present invention, by adding PTG in addition to MAPO and MDA, it was possible to increase both the maximum elongation at maximum load and the maximum tensile strength.
Furthermore, comparing Example 2 with Comparative Examples 2, 6, and 7, in the composite propellant containing MAPO and MDA, when the PTG content was 10 to 20 mass%, the maximum tensile strength and elongation at maximum load were extremely high. On the other hand, when the PTG content exceeded 20 mass% (Comparative Example 7), the maximum tensile strength and elongation at maximum load tended to decrease. In other words, in the composite propellant containing MAPO and MDA, it was recognized that the PTG content of 10 to 20 mass% is critical.

From the above results, it was revealed that 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) and N-methyldiethanolamine (MDA) as binding agents in the binder, and that the proportion of polytetramethylene ether glycol as a chain extender in the binder must be 10 to 20 mass %. It was also revealed that the content of tris[1-(2-methyl)-aziridinyl]phosphine oxide in the binder is preferably 0.3 to 0.8 mass %, the content of N-methyldiethanolamine is preferably 0.1 to 0.5 mass %, and the number average molecular weight of polytetramethylene ether glycol (PTG) is preferably 900 to 2100.

Claims (4)

A composite propellant containing a binder mainly composed of 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, 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 binding agents, and isophorone diisocyanate as a curing agent;
A composite propellant, wherein the proportion of the polytetramethylene ether glycol in the binder is 10 to 20 mass %. 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 mass %, and the proportion of the N-methyldiethanolamine is 0.1 to 0.5 mass %. The composite propellant according to claim 1 or 2, wherein the number average molecular weight of the polytetramethylene ether glycol is 900 to 2100. 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 mass%.