Phosphoric acid modified cyclic borate bonding agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solid rocket propellants, and particularly discloses a phosphoric acid modified cyclic borate bonding agent and a preparation method and application thereof.The bonding agent does not contain nitrogen atoms, contains a cyclic structure, further introduces high-polarity phosphorus-oxygen (P = O) groups and has multiple hydroxyl groups capable of participating in a curing reaction; the compatibility with nitrate in a high-energy propellant is good, and ammonia release caused by the adoption of a bonding agent containing amido is avoided; the catalyst has good hydrolytic stability, and can generate a bonding effect with a nitramine filler in a coordination bonding manner; by improving the surface and interface performance of the solid filler and increasing the infiltration speed of the adhesive to the solid filler, the pharmaceutical process performance of the propellant can be improved; and the polymer can also be used as a chain extender and a reinforcing agent to optimize and regulate a matrix network structure, so that the purposes of high strength and high elongation are achieved. The bonding agent can meet the development requirements of NEPE high-energy propellants on high mechanical properties and optimized process properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid propellant, in particular to a phosphoric acid modified cyclic borate binder, a preparation method and application thereof. BACKGROUND

[0002] Composite solid propellant is a composite material composed of binder, oxidizer, plasticizer, metal fuel, functional additives, etc. During manufacturing, storage, transportation and use, the propellant is subjected to various loads to produce deformation and damage. Therefore, the propellant must have good mechanical properties to withstand the huge stress generated during launching and transportation and the thermal stress generated during temperature changes during production and long-term storage, so as to ensure the integrity of the grain structure. After A. E. Oberth proposed the role of binder theory, the binder, as an additive to improve the mechanical properties and process performance of composite solid propellant, has attracted widespread attention. A large number of researches on the variety and mechanism of the binder have been carried out at home and abroad, and remarkable results have been achieved.

[0003] According to the different objects, the binder can be divided into two categories: ammonium perchlorate (AP) bonding and nitramine explosive bonding. Alcoholic amine binder such as triethanolamine and boron trifluoride complex (T313) is commonly used in AP-containing composite solid propellant. Its mechanism is as follows: first, the alcoholic amine compound reacts with AP to form an ammonium salt ionic bond and is firmly adsorbed on the surface of AP; then, the hydroxyl group on the alcoholic amine binder reacts with the isocyanate curing agent to form a molecular bridge and enter the binder system, thereby enhancing the interfacial adhesion strength between AP and the binder. However, amine substances have certain alkalinity and poor compatibility with nitrate esters, which restricts their application in nitrate plasticized polyether propellant (NEPE).

[0004] Boric acid ester binder mainly plays a bonding role for nitramine explosive. It forms N→B and O→B coordination bonds with the large number of lone pairs of electrons in N and O atoms in nitramine explosive through boron atoms, and enters the crosslinking network by reacting with the curing agent through the hydroxyl group and other functional groups, thereby playing a good bonding role in the propellant. The B atom in boric acid ester has an empty sp 2 hybrid orbital, which is easily attacked by nucleophilic reagents containing shared electron pairs, enhancing its bonding with the oxidizer in the propellant. On the other hand, water molecules contain unshared electron pairs, which can attack the B atom in boric acid ester, causing hydrolysis, and finally generating the corresponding alcohol and boric acid. Since the traditional boric acid ester binder is easily hydrolyzed, it has poor resistance to humid heat environment and creep resistance in the application process. The design of cyclic molecular structure of boric acid ester and the introduction of intramolecular coordination O→B bond can increase the resistance of boric acid ester to hydrolysis and improve the above problems. SUMMARY In view of the above problems, based on the following aspects, the application designs and synthesizes a phosphoric acid modified cyclic borate ester bonding agent which can be used for NEPE propellant: (1) does not contain amine groups, avoiding compatibility problems; (2) contains a cyclic structure of the borate ester bonding agent, which has good hydrolysis stability, and can produce bonding with nitramine fillers in the form of coordination bonding; (3) contains a strong polar phosphorus oxygen (P=O) group, which can quickly gather to the surface of the solid filler during the propellant manufacturing process, improve the solid filler surface interface performance, speed up the infiltration speed of the adhesive to the solid filler, and improve the process performance of the propellant; (4) contains multiple hydroxyl groups, which are used as chain extenders and reinforcing agents to regulate the matrix network, so as to achieve the purpose of high strength and high elongation.

[0005] The technical scheme of the application is a phosphoric acid modified cyclic borate ester bonding agent, and the structural formula is as follows: ; In the formula, n is the polymerization degree of polyethylene glycol, and is 4-9.

[0006] The application also relates to a preparation method of the bonding agent, which comprises the following steps: S1, mix phosphoric acid, polyethylene glycol and a water-carrying agent, heat to remove water, then remove the water-carrying agent by vacuum distillation, and obtain viscous solution 1 after cooling, which is ready for use; S2, mix boric acid, 1,2,4-butanetriol and a water-carrying agent, heat to remove water, then remove the water-carrying agent by vacuum distillation, and obtain viscous solution 2 after cooling, which is ready for use; S3, mix the viscous solution 1 and the viscous solution 2, heat until no water is generated, then remove small molecules by vacuum distillation, and obtain the phosphoric acid modified cyclic borate ester bonding agent.

[0007] Further, the molar ratio of phosphoric acid to polyethylene glycol in S1 is 1:1.8-2.2; or 1:2.

[0008] Further, the water-carrying agent is one or more of cyclohexane, toluene, n-hexane and benzene. Further, the mass ratio of the water-carrying agent to phosphoric acid and polyethylene glycol is 1:10-30; or 1:20-25.

[0009] Further, the molar ratio of boric acid to 1,2,4-butanetriol in S2 is 1:0.8-1.2; or 1:1.

[0010] Further, the water-carrying agent in S2 is one or more of cyclohexane, toluene, n-hexane and benzene; or toluene.

[0011] Further, the mass ratio of the water-carrying agent to boric acid and 1,2,4-butanetriol in S2 is 1:15-40; or 1:15-25.

[0012] Further, in S1, the temperature for removing water is 140~165℃. As the rate of water production decreases, the temperature is slowly raised to 180~190℃, then lowered to 100℃ for vacuum distillation. Finally, the temperature is lowered to below 50℃ to obtain viscous solution 1. In S2, the temperature for removing water is 135~145℃. As the rate of water production decreases, the temperature is slowly raised to 160~170℃, then lowered to 100℃ for vacuum distillation. Finally, the temperature is lowered to below 50℃ to obtain viscous solution 2.

[0013] The present invention also relates to the use of the bonding agent in a propellant, wherein the propellant is NEPE propellant and / or GAP propellant.

[0014] The present invention has the following beneficial effects: This invention designs a nitrogen-free borate ester bonding agent, which has good compatibility with nitrate esters in high-energy propellants, avoiding the ammonia release caused by using bonding agents containing amine groups. This bonding agent contains a cyclic structure, exhibiting good hydrolytic stability, and can coordinate with nitramine fillers. The bonding agent introduces highly polar phosphorooxygen (P=O) groups, which can rapidly accumulate on the surface of solid fillers during propellant manufacturing. By improving the interfacial properties of solid fillers and accelerating the wetting speed of the binder on the solid fillers, it can improve the propellant manufacturing process performance. This molecule contains three hydroxyl groups that can participate in the curing reaction, and can act as a chain extender and reinforcing agent to optimize and regulate the matrix network structure, achieving both high strength and high elongation. Attached Figure Description

[0015] Figure 1 The image shows the infrared spectrum of the bonding agent in Example 1.

[0016] Figure 2 The image shows the 1H NMR spectrum of the bonding agent in Example 1.

[0017] Figure 3 The image shows the infrared spectrum of the bonding agent used in Example 2.

[0018] Figure 4 The image shows the 1H NMR spectrum of the bonding agent in Example 2. Detailed Implementation

[0019] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the raw materials or reagents used are commercially available. The embodiments of the present invention will be described in detail below with reference to the examples; however, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention.

[0020] Example 1: (1) Accurately measure 98.02g of phosphoric acid and 400.00g of polyethylene glycol 200 and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 19.92g of toluene and slowly heat to 140℃. Water begins to be generated. As the rate of water generation decreases, slowly heat to 185℃ until 36g of water is generated. Cool down to 100℃ and perform vacuum distillation to distill off the water-containing agent. Cool down to 50℃ to obtain viscous solution 1, which is ready for use. (2) Accurately measure 123.66g of boric acid and 212.24g of 1,2,4-butanetriol and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 6.72g of cyclohexane and slowly heat to 140℃. Water begins to form. As the rate of water formation decreases, slowly heat to 165℃ until 72g of water is formed. Cool down to 100℃ and perform vacuum distillation to remove the water-containing agent. Cool down to 50℃ to obtain viscous solution 2, which is ready for use. (3) Add viscous solution 1 and viscous solution 2 to a flask equipped with a dehydration separator and a power stirrer, slowly heat to 165°C, and after no water is generated, perform vacuum distillation to remove small molecules, thereby obtaining a phosphoric acid modified cyclic borate ester bonding agent I for high-energy solid propellants.

[0021] Its infrared spectrum is shown below. Figure 1 The proton NMR spectrum is shown below. Figure 2 .

[0022] Figure 1 Middle, 1660 cm -1 The absorption peak at 3385 cm⁻¹ is the stretching vibration absorption peak of O=P-OH. -1 The absorption peak at 2932 cm⁻¹ is -OH. -1 and 2897 cm -1 The absorption peak at 1465 cm⁻¹ is due to the asymmetric and symmetric stretching vibrations of -CH₂-. -1 and 1406 cm -1 The absorption peak at 1078 cm⁻¹ is the in-plane bending vibration absorption peak of -CH₂-. -1 and 1031 cm -1 The absorption peaks at 979 cm⁻¹ are the stretching vibration absorption peaks of CO. -1 The absorption peak at [location] is the stretching vibration peak of P-OH, and its disappearance indicates that the phosphoric acid reaction is nearing completion. Infrared spectroscopy analysis shows that the phosphoric acid-modified cyclic borate ester bonding agent was successfully synthesized.

[0023] Figure 2In the spectrum, δ (2.50–2.57 ppm) corresponds to the proton peak of the methylene group linked to the hydroxyl group on glycerol, δ (3.00–3.12 ppm) corresponds to the proton peak of the methylene group linked to the BO bond, δ (3.34–3.45 ppm) corresponds to the proton peak of the hydroxyl group, and δ (3.54–3.67 ppm) corresponds to the proton peak of the -CH2O group linked to the BO bond. The chemical shift and integrated area of ​​1H in the analytical spectrum are basically consistent with those of the target compound, and except for a few minor impurity peaks, the rest are consistent with the designed structure. The 1H NMR results further confirm that the phosphoric acid-modified cyclic borate ester bonding agent was successfully synthesized.

[0024] Example 2: (1) Accurately measure 9.80g of phosphoric acid and 60.00g of polyethylene glycol 300 and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 3.49g of cyclohexane and slowly heat to 140℃. Water begins to form. As the rate of water formation decreases, slowly heat to 185℃ until 3.6g of water is formed. Cool down to 100℃ and perform vacuum distillation to remove the water-containing agent. Cool down to 50℃ to obtain viscous solution 1, which is ready for use. (2) Accurately measure 12.37g of boric acid and 21.22g of 1,2,4-butanetriol and add them to a flask equipped with a dehydration separator and a dynamic stirrer. Add 8.40g of n-hexane and slowly heat to 140℃. Water begins to form. As the rate of water formation decreases, slowly heat to 165℃ until 7.2g of water is formed. Cool down to 100℃ and perform vacuum distillation to remove the water-containing agent. Cool down to 50℃ to obtain viscous solution 2, which is ready for use. (3) Add viscous solution 1 and viscous solution 2 to a flask equipped with a dehydration separator and a power stirrer, slowly heat to 165°C, and after no water is generated, perform vacuum distillation to remove small molecules, thereby obtaining a phosphoric acid modified cyclic borate ester bonding agent II for high-energy solid propellants.

[0025] Its infrared spectrum is shown below. Figure 3 The proton NMR spectrum is shown below. Figure 4 .

[0026] Figure 3 Middle, 1660 cm -1 The absorption peak at 3385 cm⁻¹ is the stretching vibration absorption peak of O=P-OH. -1 The absorption peak at 2932 cm⁻¹ is the absorption peak of the -OH stretching vibration. -1 and 2897 cm -1 The absorption peak at 1465 cm⁻¹ is due to the asymmetric and symmetric stretching vibrations of -CH₂-. -1 and 1406 cm -1 The absorption peak at 1078 cm⁻¹ is the in-plane bending vibration absorption peak of -CH₂-.-1 and 1031 cm -1 The absorption peaks at 979 cm⁻¹ are the stretching vibration absorption peaks of CO. -1 The absorption peak at [location] is the stretching vibration peak of P-OH, and its disappearance indicates that the phosphoric acid reaction is nearing completion. Infrared spectroscopy analysis shows that the phosphoric acid-modified cyclic borate ester bonding agent was successfully synthesized.

[0027] Figure 4 In the spectrum, δ (3.17–3.31 ppm) corresponds to the proton peak of the methylene group attached to the hydroxyl group on glycerol, δ (3.74–3.86 ppm) corresponds to the proton peak of the methylene group attached to -OH and the methylene group near the PO bond end, and δ (4.63–4.79 ppm) corresponds to the proton peak of the hydroxyl group. The chemical shift and integrated area of ​​1H in the analytical spectrum are basically consistent with the target compound, and except for a few minor impurity peaks, the rest are consistent with the designed structure. The 1H NMR results further confirm that the phosphoric acid-modified cyclic borate ester bonding agent was successfully synthesized.

[0028] Example 3: (1) Accurately measure 98.02g of phosphoric acid and 800.00g of polyethylene glycol 400 and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 35.92g of n-hexane and slowly heat to 140℃. Water begins to be generated. As the rate of water generation decreases, slowly heat to 185℃ until 36g of water is generated. Cool down to 100℃ and perform vacuum distillation to distill off the water-carrying agent. Cool down to 50℃ to obtain viscous solution 1, which is ready for use. (2) Accurately measure 123.66g of boric acid and 212.24g of 1,2,4-butanetriol and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 8.40g of cyclohexane and slowly heat to 140℃. Water begins to form. As the rate of water formation decreases, slowly heat to 165℃ until 72g of water is formed. Cool down to 100℃ and perform vacuum distillation to remove the water-containing agent. Cool down to 50℃ to obtain viscous solution 2, which is ready for use. (3) Add viscous solution 1 and viscous solution 2 into a flask equipped with a dehydration separator and a power stirrer, slowly heat to 165°C, and after no water is generated, perform vacuum distillation to remove small molecules, thereby obtaining a phosphoric acid modified cyclic borate ester bonding agent III for high-energy solid propellants.

[0029] Example 4: (1) Accurately measure 980.2g of phosphoric acid and 6000.00g of polyethylene glycol 300 and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 279.2g of toluene and slowly heat to 140℃. Water begins to be generated. As the rate of water generation decreases, slowly heat to 185℃ until 360g of water is generated. Cool down to 100℃ and perform vacuum distillation to distill off the water-containing agent. Cool down to 50℃ to obtain viscous solution 1, which is ready for use. (2) Accurately measure 1236.6g of boric acid and 2122.4g of 1,2,4-butanetriol and add them to a flask equipped with a dehydrator and a dynamic stirrer. Add 67.18g of toluene and slowly heat to 140℃. Water begins to form. As the rate of water formation decreases, slowly heat to 165℃ until 720g of water is formed. Cool down to 100℃ and perform vacuum distillation to remove the water-containing agent. Cool down to 50℃ to obtain viscous solution 2, which is ready for use. (3) Add viscous solution 1 and viscous solution 2 to a flask equipped with a dehydration separator and a power stirrer, slowly heat to 165°C, and after no water is generated, perform vacuum distillation to remove small molecules, thereby obtaining a phosphoric acid modified cyclic borate ester bonding agent IV for high-energy solid propellants.

[0030] The physicochemical properties of the phosphoric acid modified cyclic borate ester bonding agents I-IV prepared in the above examples were tested and the propellant formulations were determined. The components of the adjusted NEPE propellant formulation are shown in Table 1, and the physicochemical and mechanical properties are shown in Table 2.

[0031] Table 1

[0032] Table 2

[0033] As shown in Table 2, compared to the T313 bonding agent, the bonding agent of this invention does not contain amine groups, exhibits better compatibility with nitrate esters in high-energy propellants, reduces ammonia release, and has no adverse effect on the structural integrity of the propellant. The cyclic borate ester in the bonding agent of this invention has better hydrolysis resistance, while the boron atoms in the T313 bonding agent exist in the form of boron trifluoride, which is easily hydrolyzed. Trace amounts of moisture can lead to a decrease in interfacial bonding, manifesting as propellant "dehydration." The coordination bond between the B atom in the bonding agent of this invention and the nitramine oxidant is stronger than the weak hydrogen bond between the cyano group or hydroxyl group and the nitramine in neutral bonding agents, making it a more ideal interfacial reinforcing group. Furthermore, this molecule contains three hydroxyl groups that can participate in the curing reaction, serving as a chain extender and reinforcing agent to optimize and regulate the matrix network structure, significantly improving the mechanical properties of the propellant and achieving both high strength and high elongation. Phosphoric acid modified cyclic borate ester bonding agent contains highly polar phosphorus oxygen (P=O) groups, which can rapidly aggregate onto the surface of solid fillers during propellant manufacturing. At the same time, its molecular structure contains polyethylene glycol, which has the same molecular structure as NEPE propellant binder. The solubility parameters of the two are similar. By improving the interfacial properties of solid fillers, the wetting speed of the binder on solid fillers is accelerated, thereby improving the propellant process performance.

[0034] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A phosphate-modified cyclic borate ester bonding agent, characterized in that, Its structural formula is as follows: ; Where n is the degree of polymerization of polyethylene glycol, ranging from 4 to 9.

2. The method for preparing the bonding agent according to claim 1, characterized in that, Includes the following steps: S1. Take phosphoric acid, polyethylene glycol and dehydrating agent, mix and heat to remove moisture, then remove dehydrating agent by vacuum distillation, and after cooling, obtain viscous solution 1 for later use; S2. Mix boric acid, 1,2,4-butanetriol and dehydrating agent and heat to remove water, then remove the dehydrating agent by vacuum distillation, and after cooling, obtain viscous solution 2 for later use; S3. Mix viscous solution 1 and viscous solution 2 and heat until no water is generated. Then, remove small molecules by vacuum distillation to obtain the phosphoric acid modified cyclic borate ester bonding agent.

3. The preparation method according to claim 2, characterized in that: The molar ratio of phosphoric acid to polyethylene glycol in S1 is 1:1.8~2.2; or 1:

2.

4. The preparation method according to claim 2, characterized in that: The water-removing agent is one or more of cyclohexane, toluene, n-hexane, and benzene.

5. The preparation method according to claim 4, characterized in that: The ratio of the amount of water-removing agent to the mass of phosphoric acid and polyethylene glycol is 1:10~30; or 1:20~25.

6. The preparation method according to claim 2, characterized in that: In S2, the molar ratio of boric acid to 1,2,4-butanetriol is 1:0.8~1.2; or 1:

1.

7. The preparation method according to claim 2, characterized in that: The water-carrying agent in S2 is one or more of cyclohexane, toluene, n-hexane, and benzene; or it may be toluene.

8. The preparation method according to claim 7, characterized in that: The ratio of the amount of water-removing agent in S2 to the mass of boric acid and 1,2,4-butanetriol is 1:15-40 or 1:15-25.

9. The preparation method according to any one of claims 2 to 8, characterized in that: In S1, the temperature for removing water is 140~165℃. As the rate of water production decreases, the temperature is slowly raised to 180~190℃, then lowered to 100℃ for vacuum distillation. Finally, the temperature is lowered to below 50℃ to obtain viscous solution 1. In S2, the temperature for removing water is 135~145℃. As the rate of water production decreases, the temperature is slowly raised to 160~170℃, then lowered to 100℃ for vacuum distillation. Finally, the temperature is lowered to below 50℃ to obtain viscous solution 2.

10. The application of the bonding agent according to claim 1 or the bonding agent obtained by the preparation method according to any one of claims 2 to 9 in a propellant, wherein the propellant is NEPE propellant and / or GAP propellant.

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