A one-dose two-purpose borate bonding agent, its synthesis method and application

Abstract

The application relates to a one-dose two-purpose borate ester bonding agent, a synthesis method and application thereof. The new borate ester bonding agent is synthesized from boric acid, n-butanol, pinacol and bis(2-hydroxyethyl)amino(trihydroxymethyl) according to a certain proportion through a three-step reaction. The new borate ester bonding agent synthesized by the application can significantly improve the interfacial bonding performance of nitramine explosives (HMX, RDX, CL-20) and a solid propellant binder matrix. Since the structure contains a polyhydroxy structure, the new borate ester bonding agent can also enter a crosslinking network to play a crosslinking agent role, thereby greatly improving the mechanical properties of the solid propellant. The new borate ester bonding agent is suitable for GAP propellant formulations and also suitable for hydroxyl-terminated propellant formulations. The application provides a new borate ester bonding agent design idea. The bonding agent synthesis method is simple and stable, the synthesis raw materials are widely sourced, the quality is easy to enlarge and control, and the mechanical properties of the polyether propellant can be significantly improved.

Description

A dual-purpose borate ester bonding agent, its synthesis method and application Technical Field

[0001] This invention belongs to the field of organic synthesis and composite solid propellant technology, specifically relating to a novel borate ester bonding agent suitable for solid propellants, its synthesis method and application. Background Technology

[0002] Solid propellants are high-solids-content particle-filled polymer composite materials (such as nitramine explosives). Studies have found that under stress, solid propellant failure occurs at the interface between the binder and the filler particles. Commonly used fillers such as HMX, RDX, and ammonium perchlorate (AP) are all non-reinforcing fillers, making solid propellants prone to "dewetting" under certain loads, which is very detrimental to the mechanical properties of the propellant.

[0003] Currently, borate esters are widely used as bonding agents in hydroxyl-butadiene tetrapropellants. The empty orbitals in the molecular structure of borate ester bonding agents can form coordinate bonds with the lone pairs of electrons of other atoms. Through the numerous lone pairs of electrons between boron atoms and the N and O atoms in nitramine explosives, borate ester bonding agents form N→B and O→B coordinate bonds. Furthermore, through functional groups such as hydroxyl groups, they can react with curing agents and enter the cross-linking network, thus playing a good bonding role in the propellant.

[0004] The main problems and shortcomings of existing borate ester bonding agents are as follows:

[0005] (1) Traditional organic borate ester bonding agents use diethanolamine as a raw material. The nitrogen element on the secondary amine group in the bonding agent molecule can undergo N→B internal coordination with the boron element, which will weaken the N→B coordination between the bonding agent and the ammonium nitrate explosive molecule to a certain extent. For example, the borate ester bonding agent synthesized in Chinese patent "Borate Ester Bonding Agents, Their Preparation Methods and Applications in Composite Solid Propellants" (Publication No. CN107628969A, Publication Date: 2024.05.28) has two secondary amine groups in its structure, which makes its effect on improving the mechanical properties of the propellant generally limited.

[0006] (2) Most traditional organoboroester bonding agents have a chain structure, which is sensitive to moisture and has poor hydrolytic stability. For example, the borate bonding agent synthesized in patent CN107628969A has a chain structure, which may lead to unstable decomposition during the synthesis process. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a novel borate ester bonding agent design concept. The bonding agent has a simple and stable synthesis method, and the raw materials are widely available. It is easy to scale up and control the quality, and can significantly improve the mechanical properties of polyether propellants.

[0008] This invention relates to a novel borate ester bonding agent synthesized from boric acid, n-butanol, pinacol, and bis(2-hydroxyethyl)amino(trihydroxymethyl) in a specific ratio through a three-step reaction. The synthesis equation is as follows:

[0009]

[0010] Me is methyl, i.e., -CH3. nBu is n-butyl, which, when combined with an -OH group, forms n-butanol.

[0011] A method for preparing a novel borate ester bonding agent with dual-purpose properties includes the following steps:

[0012] Boric acid and n-butanol were added to a container at a molar ratio of 1:0.8–1.2. The mixture was heated to 125–135 °C and reacted for 10–12 h. Tributyl borate was obtained by vacuum distillation, maintaining a vacuum of 0.08–0.1 MPa. Tributyl borate and pinacol were then added to the container at a molar ratio of 1:0.8–1.2. The mixture was heated to 68–72 °C, and vacuum distillation was initiated, maintaining a vacuum of 0.08–0.1 MPa. The temperature was then increased to 77.5–82.5 °C until no more n-butanol was observed in the container. The reaction ends when the butanol evaporates. The colorless liquid in the container is the pinacol-substituted borate intermediate. Di(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO is added to the container, maintaining a molar ratio of 1:0.8–1.2 between bis(2-hydroxyethyl)amino(trihydroxymethyl) and the borate intermediate. The temperature is raised to 110–120°C, and vacuum distillation begins. The vacuum level in the container is maintained at 0.08–0.1 MPa. The reaction ends when no more n-butanol or solvent evaporates from the container, yielding a white, viscous liquid, BAG-PSZ. DMSO is used as the reaction solvent.

[0013] The application of the above-mentioned borate ester bonding agent in GAP propellants and hydroxyl-butyl propellants.

[0014] The application of a borate ester bonding agent in GAP propellant, wherein the binder is poly(glycidyl azide) (GAP), the plasticizers are nitroglycerin (NG) and 1,2,4-butanetriol trinitrate (BTTN), the oxidant is ammonium perchlorate (AP), the explosive is hexanitrohexaazaisowulzane (CL-20), the metallic fuel is aluminum powder (Al), the curing agents are toluene diisocyanate (TDI) and modified hexamethylene polyisocyanate (N-100), and functional components; the functional components include a curing catalyst, a burning rate catalyst, and the bonding agent BAG-PSZ.

[0015] The bonding agent BAG-PSZ has a percentage content of 0.2% to 0.5% based on the total weight of the propellant.

[0016] The application of a borate ester bonding agent in hydroxyl-butadiene propellant, wherein the binder is hydroxyl-terminated polybutadiene (HTPB), the plasticizer is diisooctyl sebacate (KZ), the oxidant is ammonium perchlorate (AP), the explosive is octogen (HMX), the metallic fuel is aluminum powder (Al), the curing agent is isophorone diisocyanate (IPDI), and functional components; the functional components include a curing catalyst, a combustion rate catalyst, and the bonding agent BAG-PSZ.

[0017] The bonding agent BAG-PSZ has a percentage content of 0.2% to 0.5% based on the total weight of the propellant.

[0018] The novel borate ester bonding agent synthesized in this invention can significantly improve the interfacial adhesion between ammonium nitrate explosives and solid propellant binder matrix. Due to the presence of polyhydroxy structures in its structure, it can also enter the crosslinking network and act as a crosslinking agent, thereby greatly improving the mechanical properties of solid propellants. It is suitable for GAP propellant formulations and also for hydroxyl-butyl propellant formulations.

[0019] The novel borate ester bonding agent of the present invention contains multiple active hydroxyl groups in its structure, which can react with the curing agent and enter the adhesive network to act as a crosslinking agent. The N atom can react with AP through chemical reaction to release ammonia gas and form ammonium salt ionic bonds to be firmly adsorbed on the surface of AP. The B atom has empty sp2 hybrid orbitals and can easily form stable complexes with electron donors in ammonium nitrate explosives to form a strong transition interface coating layer.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) In previous organoborolate ester bonding agents, the nitrogen element on the secondary amine group could undergo N→B internal coordination with the boron element, which would weaken the N→B coordination between the bonding agent and the ammonium nitrate explosive molecule to a certain extent, thus weakening the bonding effect. In this invention, the secondary amine group in the molecular structure is converted into a tertiary amine group. Since the steric hindrance of the tertiary amine is greater than that of the secondary amine, the intramolecular coordination bond is more difficult to form, thereby improving the bonding effect.

[0022] (2) Previous organic borate ester bonding agents were mostly chain-like molecules with poor hydrolytic stability. In this invention, a five-membered ring structure is formed by the reaction of pinacol with tributyl borate, which greatly improves the hydrolytic stability of borate ester bonding agents.

[0023] (3) This invention provides a novel borate ester bonding agent that can be used as both a bonding agent and a crosslinking agent. The molecule contains nitrogen atoms and borate ester bonds, enabling it to react with oxidants (AP) and nitramine explosives. It also contains a certain number of hydroxyl groups, which can form chemical bonds through reaction with isocyanates, thus entering the crosslinking network of the adhesive. This builds a "molecular bridge" between the nitramine particles and the adhesive, improving the interfacial bonding strength. Furthermore, the molecule contains multiple hydroxyl groups, which act as a crosslinking agent, regulating the matrix network. In summary, this significantly improves the mechanical properties of the propellant. Detailed Implementation

[0024] The present invention will now be described with reference to specific embodiments, but is by no means limited thereto.

[0025] Example 1

[0026] The novel organic borate ester bonding agent is synthesized as follows: Boric acid and n-butanol are added to a three-necked flask in a 1:1 molar ratio, heated to 130℃, and reacted for 10 hours. Tri-n-butyl borate is obtained by vacuum distillation, maintaining a vacuum degree of 0.1 MPa. Tri-n-butyl borate and pinacol are added to the three-necked flask in a 1:1 molar ratio. A vacuum distillation apparatus is set up with a straight condenser, and the oil bath is heated to 70℃. Vacuum distillation begins, maintaining a vacuum degree of 0.1 MPa. The temperature is raised to 80℃, and the reaction ends when no more n-butanol is distilled out of the flask. The colorless liquid in the flask is the pinacol-substituted borate ester intermediate. A certain amount of bis(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO was added to a three-necked flask. The mass ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to DMSO was 1:4. The molar ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to the borate ester intermediate was controlled at 1:1. The temperature was raised to 115°C, and vacuum distillation was started. The vacuum degree in the flask was controlled to reach 0.1 MPa. The reaction was stopped when no more n-butanol and solvent were distilled out of the flask. Finally, a white viscous liquid BAG-PSZ-1 was obtained.

[0027] Example 2

[0028] The novel organoboroester bonding agent is synthesized as follows: Boric acid and n-butanol are added to a three-necked flask at a molar ratio of 1:0.8, the temperature is raised to 130℃, and the reaction is carried out for 10 hours. Tributyl borate is obtained by vacuum distillation, maintaining a vacuum degree of 0.1 MPa. Tributyl borate and pinacol are added to a three-necked flask at a molar ratio of 1:1. A vacuum distillation apparatus is set up with a straight condenser, the oil bath is heated to 70℃, and vacuum distillation begins. The vacuum degree is maintained at 0.1 MPa, and the temperature is raised to 80℃. The reaction is stopped when no more n-butanol is distilled off the flask. The colorless liquid in the flask is the pinacol-substituted borate intermediate. A certain amount of bis(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO was added to a three-necked flask. The mass ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to DMSO was 1:4. The molar ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to the borate ester intermediate was controlled at 1:1. The temperature was raised to 115℃, and vacuum distillation was started. The vacuum degree of the three-necked flask was controlled to reach 0.1 MPa. The reaction was stopped when no more n-butanol and solvent were distilled out of the three-necked flask. Finally, a white viscous liquid BAG-PSZ-2 was obtained.

[0029] Example 3

[0030] The novel organoboroester bonding agent is synthesized as follows: Boric acid and n-butanol are added to a three-necked flask in a molar ratio of 1:1.2, the temperature is raised to 130℃, and the reaction is carried out for 10 hours. Tributyl borate is obtained by vacuum distillation, maintaining a vacuum degree of 0.1 MPa. Tributyl borate and pinacol are added to a three-necked flask in a molar ratio of 1:1. A vacuum distillation apparatus is set up with a straight condenser, the oil bath is heated to 70℃, and vacuum distillation begins. The vacuum degree is maintained at 0.1 MPa, and the temperature is raised to 80℃ until no more n-butanol is distilled off from the three-necked flask. The colorless liquid in the three-necked flask is the pinacol-substituted borate intermediate. A certain amount of bis(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO was added to a three-necked flask. The mass ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to DMSO was 1:3.8. The molar ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to the borate ester intermediate was controlled at 1:0.9. The temperature was raised to 111°C, and vacuum distillation was started. The vacuum degree of the three-necked flask was controlled to reach 0.09 MPa. The reaction was stopped when no more n-butanol and solvent were distilled out of the three-necked flask. Finally, a white viscous liquid BAG-PSZ-3 was obtained.

[0031] Example 4

[0032] The novel organic borate ester bonding agent is synthesized as follows: Boric acid and n-butanol are added to a container in a 1:1 molar ratio, heated to 128℃, and reacted for 10.5 h. Tributyl borate is obtained by vacuum distillation, with the vacuum distillation maintaining a vacuum degree of 0.09 MPa. Tributyl borate and pinacol are added to the container in a 1:1 molar ratio, heated to 71℃ in an oil bath, and vacuum distillation begins. When the vacuum distillation reaches 0.1 MPa, the temperature is raised to 82℃, and the reaction ends when no more n-butanol is distilled off the container. The colorless liquid in the bottle is the pinacol-substituted borate ester intermediate. A certain amount of bis(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO was added to a container. The mass ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to DMSO was 1:4.1. The molar ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to the borate ester intermediate was controlled at 1:1.1. The temperature was raised to 120°C, and vacuum distillation was started. The vacuum degree of the container was controlled to reach 0.08 MPa. The reaction was stopped when no more n-butanol and solvent were distilled out of the container. Finally, a white viscous liquid BAG-PSZ-4 was obtained.

[0033] Example 5

[0034] The novel organic borate ester bonding agent is synthesized as follows: Boric acid and n-butanol are added to a container at a molar ratio of 1:0.9, the temperature is raised to 133℃, and the reaction is carried out for 11 hours. Tributyl borate is obtained by vacuum distillation, with the vacuum distillation maintaining a vacuum degree of 0.1 MPa. Tributyl borate and pinacol are added to the container at a molar ratio of 1:1.1, the oil bath is heated to 69℃, and vacuum distillation is started. When the vacuum distillation reaches a vacuum degree of 0.09 MPa, the temperature is raised to 78℃, and the reaction is stopped when no more n-butanol is distilled out of the container. The colorless liquid in the bottle is the pinacol-substituted borate ester intermediate. A certain amount of bis(2-hydroxyethyl)amino(trihydroxymethyl) dissolved in DMSO was added to a container. The mass ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to DMSO was 1:4. The molar ratio of bis(2-hydroxyethyl)amino(trihydroxymethyl) to the borate ester intermediate was controlled at 1:1.2. The temperature was raised to 115℃, and vacuum distillation was started. The vacuum degree of the container was controlled to reach 0.1MPa. The reaction was stopped when no more n-butanol and solvent were distilled out of the container. Finally, a white viscous liquid BAG-PSZ-5 was obtained.

[0035] The novel bonding agents synthesized above were validated in GAP propellant and hydroxyl-terminated polybutadiene propellant, as shown in Examples 6 and 7.

[0036] Example 6

[0037] The novel borate ester bonding agent BAG-PSZ was applied in GAP (polyazidoglycidyl ether) propellant formulations. The propellant composition is shown in Table 1, and the performance results are shown in Table 2.

[0038] Table 1 GAP Propellant Composition

[0039]

[0040] Table 2 Performance Results

[0041]

[0042]

[0043] The functional components include a curing catalyst, a combustion rate catalyst, and a bonding agent. The novel organoboronic acid ester bonding agent of this invention, BAG-PSZ, has a weight percentage content of 0.2%.

[0044] Based on propellant performance data, the new borate ester bonding agent BAG-PSZ series can significantly improve the normal and high temperature mechanical properties of GAP propellants compared to previous borate ester bonding agents, with BAG-PSZ-3 showing the best effect.

[0045] Example 7

[0046] The novel borate ester bonding agent BAG-PSZ was applied in the formulation of hydroxyl butyrate propellant. The propellant composition is shown in Table 3, and the performance results are shown in Table 4.

[0047] Table 3 Composition of hydroxyl-butyl propellant

[0048]

[0049] Table 4 Performance Results

[0050]

[0051]

[0052] The functional components include a curing catalyst, a combustion rate catalyst, and a bonding agent. The novel organoboronic acid ester bonding agent of this invention, BAG-PSZ, has a BAG-PSZ content of 0.2%.

[0053] Based on propellant performance data, the new borate ester bonding agent BAG-PSZ series can significantly improve the normal and high temperature mechanical properties of hydroxyl butyrate propellants compared to previous borate ester bonding agents, with BAG-PSZ-3 showing the best performance.

[0054] Examples 6 and 7 lead to the conclusion that the novel borate ester bonding agent BAG-PSZ series can play a dual role in GAP propellants and hydroxyl-butyl propellants, acting as both a bonding agent and a crosslinking agent to improve propellant strength, with BAG-PSZ-3 showing the best performance.

Claims

1. A method for preparing a borate ester bonding agent that serves two purposes, characterized in that, The process includes the following steps: Boric acid and n-butanol are added to a container at a molar ratio of 1:0.8~1.

2. The mixture is heated to 125~135℃ and reacted for 10~12 hours. Tributyl borate is obtained by vacuum distillation, maintaining a vacuum of 0.08~0.1 MPa. Tributyl borate and pinacol are then added to the container at a molar ratio of 1:0.8~1.

2. The mixture is heated to 68-72℃, and vacuum distillation begins, maintaining a vacuum of 0.08~0.1 MPa. The temperature is then raised to 77.5-82.5℃ until no more n-butanol is present in the container. The reaction ends when the butanol is distilled off. The colorless liquid in the container is the pinacol-substituted borate intermediate. Di(2-hydroxyethyl)amino(tris(hydroxymethyl)methane) dissolved in DMSO is added to the container. The molar ratio of bis(2-hydroxyethyl)amino(tris(hydroxymethyl)methane) to the borate intermediate is controlled at 1:0.8~1.

2. The temperature is raised to 110-120℃, and vacuum distillation is started. The vacuum degree of the container is controlled to reach 0.08~0.1MPa. The reaction ends when no more n-butanol and solvent are distilled off in the container. The final white viscous liquid is the bonding agent BAG-PSZ.

2. A borate ester bonding agent prepared by the method of claim 1.

3. The use of the borate ester bonding agent of claim 2 in GAP propellants and hydroxyl-butyl propellants.

4. The application of the borate ester bonding agent according to claim 2 in GAP propellants, characterized in that: The binder is polyazide glycidyl ether, the plasticizer is nitroglycerin and 1,2,4-butanetriol trinitrate, the oxidant is ammonium perchlorate, the explosive is hexanitrohexaazaisowulzane, the metallic fuel is aluminum powder, the curing agent is toluene diisocyanate and modified hexamethylene polyisocyanate, and the functional components include a curing catalyst, a combustion rate catalyst, and a bonding agent BAG-PSZ.

5. The application of the borate ester bonding agent according to claim 4 in GAP propellants, characterized in that: The bonding agent BAG-PSZ has a percentage content of 0.2% to 0.5% based on the total weight of the propellant.

6. The application of the borate ester bonding agent according to claim 2 in hydroxyl-butyl propellant, characterized in that: The binder is hydroxyl-terminated polybutadiene, the plasticizer is diisooctyl sebacate, the oxidant is ammonium perchlorate, the explosive is octogen, the metallic fuel is aluminum powder, the curing agent is isophorone diisocyanate, and the functional components include a curing catalyst, a combustion rate catalyst, and a bonding agent BAG-PSZ.

7. The application of the borate ester bonding agent according to claim 6 in hydroxyl-butyl propellant, characterized in that: The bonding agent BAG-PSZ has a percentage content of 0.2% to 0.5% based on the total weight of the propellant.

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