Neutral bonding agent containing enamine structure as well as preparation method and application of neutral bonding agent

Abstract

The invention relates to the technical field of solid rocket propellants, and particularly discloses a neutral bonding agent containing an enamine structure and a preparation method and application of the neutral bonding agent. Glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product, butyl acrylate and hydroxyethyl acrylate are adopted as polymeric monomers, and the neutral bonding agent containing the enamine structure and the preparation method and application of the neutral bonding agent containing the enamine structure are obtained. According to the prepared neutral bonding agent containing the enamine structure, amino in the molecular structure and ammonium perchlorate are easily subjected to acid-base neutralization to form ionic bonding, and a tear-resistant layer is formed; and meanwhile, the molecule also contains cyanoethyl which is far away from the main chain of the neutral bonding agent, so that the bonding effect on a nitramine oxidizing agent is relatively good. According to the invention, the problem that the mechanical property of the NEPE propellant formula is reduced due to introduction of ammonium perchlorate is solved.

Description

Technical Field

[0001] This invention relates to the field of solid propellant technology, specifically to a neutral bonding agent containing an enamine structure, its preparation method, and its application. Background Technology

[0002] Neutral polymeric bonding agents (NPBAs) are high-energy solid propellant bonding agents invented by Chung S. Kim et al. in the United States, and are widely used in nitrate ester-plasticized polyether propellants (NEPEs). NPBAs contain polar groups (such as cyano groups), which adsorb and aggregate on the surface of solid energetic fillers (such as RDX, HMX, and CL-20) bonded to them through phase separation caused by differences in solubility at different temperatures. NPBAs participate in the curing and cross-linking reaction of the binder matrix, forming a high-modulus transition layer. This improves the "dewetting" phenomenon between the binder matrix and the solid energetic filler, thereby enhancing the mechanical properties of the propellant grain. Existing NPBAs are usually obtained by free radical copolymerization of vinyl monomers. Their chain structure is linear, and the cyano groups that have a bonding effect on solid fillers are attached to the main chain, resulting in significant steric hindrance. Their bonding effect on nitramine oxidizers is limited, making it difficult to further improve the mechanical properties of the propellant.

[0003] To reduce burning rate and pressure index, NEPE propellants incorporate increased amounts of ammonium perchlorate in their formulations. The ammonium perchlorate / matrix interface has gradually replaced the nitramine / matrix interface as the primary propellant interface. To enhance adhesion between the ammonium perchlorate / matrix interface and improve mechanical properties, a technique of combining neutral bonding agents with modified alkanolamine bonding agents is often employed. However, because NEPE propellant systems are rich in nitrate plasticizers, modified alkanolamine bonding agents, based on the principle of "like dissolves like," are readily soluble in polar plasticizers and difficult to effectively adsorb onto the surface of ammonium perchlorate particles. Furthermore, because alkanolamine bonding agents contain active groups and have higher reactivity than polyethers, they often preferentially react with isocyanate curing agents, leading to a decrease in the crosslinking density of the cured crosslinked network and severely impacting the performance of this type of material.

[0004] Polyene-polyamines and their derivatives are currently highly efficient bonding agents for ammonium perchlorate. The amine groups in their molecular structure readily form ionic bonds with ammonium perchlorate through acid-base neutralization, creating a tear-resistant layer. By introducing cyanoethyl groups into their molecules for modification, the introduced cyanoethyl groups interact with nitramine explosives through hydrogen bonds, broadening their application to quaternary propellants. Similar to modified alkanolamine bonding agents, cyanoethyl-modified polyene-polyamine bonding agents, due to their polarity and energetic plasticizer nature, are easily soluble in energetic plasticizers, making it difficult for them to accumulate on the surface of solid fillers, resulting in poor performance in NEPE propellants. This invention introduces the results of cyanoethyl-modified polyene-polyamine bonding agents into the structure of neutral bonding agents, simultaneously improving the bonding effect of neutral bonding agents on ammonium perchlorate and nitramine explosives, thus meeting the development needs of NEPE propellants. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a neutral bonding agent containing an enamine structure, its preparation method, and its application. This agent has multiple bonding sites for ammonium perchlorate. By grafting polyene polyamine derivatives onto the NPBA backbone, the mechanical properties of NEPE propellants are reduced due to the large-scale introduction of ammonium perchlorate.

[0006] The technical solution of this invention is a neutral bonding agent containing an enamine structure, the structural formula of which is as follows: ; Where x is the molar amount of monomers in the ring-opening product of glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy, y is the molar amount of monomers in butyl acrylate, z is the molar amount of monomers in hydroxyethyl acrylate, and n is the number of repeating units in the polyene polyamine.

[0007] Optionally, in the structural formula, x:y:z is 0.1:1~3:0.5~1; and the value of n is 0~3.

[0008] Optionally, the ring-opening product of glycidyl acrylate and cyanoethyl-modified polyene polyamine epoxy has the following structure: .

[0009] The present invention also relates to a method for preparing the neutral bonding agent, comprising the following steps: S1. Take glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product and dissolve them in a solvent; then add butyl acrylate monomer and hydroxyethyl acrylate monomer in proportion. S2. Add initiator, chain transfer agent and dispersant to the material obtained in S1, heat and mix, reflux reaction, and then perform post-treatment separation to obtain a neutral bonding agent containing an enamine structure.

[0010] Optionally, the molar ratio of glycidyl acrylate to cyanoethyl modified polyene polyamine epoxy ring-opening product, butyl acrylate monomer, and hydroxyethyl acrylate monomer is 0.1:1-3:0.5-1.

[0011] Optionally, the solvent is acetone, 1,2-dichloroethane, or a mixture of the two; the initiator is azobisisobutyronitrile (AIBN); the chain transfer agent is 2-mercaptoethanol; and the dispersant is polyvinyl alcohol.

[0012] Optionally, the mass ratio of butyl acrylate monomer, solvent, initiator, chain transfer agent and dispersant is 100:300-500:4-8:6-10:2-5.

[0013] Optionally, the reaction temperature in S2 is 60~70℃, and the reaction time is 4~8h.

[0014] Optionally, the post-treatment in S2 involves using ethanol for sedimentation and washing, removing the supernatant after separation, filtering the lower solid layer, and drying it to obtain a neutral bonding agent containing an enamine structure.

[0015] The present invention also relates to the application of the neutral bonding agent containing the enamine structure in propellants, wherein the propellant is NEPE propellant and / or GAP propellant.

[0016] The present invention has the following beneficial effects: This invention develops a neutral bonding agent with multiple bonding sites containing an enamine structure targeting ammonium perchlorate by grafting polyene-polyamine derivatives onto the NPBA backbone. Its side chains contain highly efficient polyene-polyamine structures, hydroxyl groups, and cyano groups. The amine groups readily form ionic bonds with ammonium perchlorate through acid-base neutralization, while the hydroxyl groups can form hydrogen bonds with ammonium perchlorate. Together, these form a tear-resistant layer. Simultaneously, the cyanoethyl groups on the side chains have low steric hindrance, allowing for better van der Waals forces at the interface with nitramine oxidizers, resulting in better bonding. This improves the interfacial adsorption effect of the neutral bonding agent containing the enamine structure and also suppresses the "dewetting" phenomenon. As a bonding agent, it significantly improves the mechanical properties of solid propellant grains, increasing the tensile strength and maximum elongation of the propellant. Attached Figure Description

[0017] Figure 1 The image shows the 1H NMR spectrum of NPBA-P1 in Example 1.

[0018] Figure 2 This is a molecular weight detection graph of NPBA-P1 in Example 1.

[0019] Figure 3 The image shows the 1H NMR spectrum of NPBA-P2 in Example 2.

[0020] Figure 4 This is a molecular weight detection graph of NPBA-P2 in Example 2. Detailed Implementation

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.

[0022] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0023] The structures of the ring-opening products of glycidyl acrylate and cyanoethyl-modified polyene polyamine epoxy in the following examples are as follows: .

[0024] The material is prepared by reacting glycidyl ester with cyanoethyl modified polyene polyamine at room temperature in a molar ratio of 1:1, where n is the number of repeating units of the polyene polyamine, and the value ranges from 0 to 3.

[0025] Example 1: The preparation of a neutral bonding agent containing an enamine structure includes the following steps: S1. Take 0.1 mol of glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product and dissolve it in 645 g of acetone; then add 1 mol of butyl acrylate monomer and 0.5 mol of hydroxyethyl acrylate monomer in proportion. S2. Add 5.16g of initiator azobisisobutyronitrile, 7.74g of chain transfer agent 2-mercaptoethanol and 2.58g of dispersant polyvinyl alcohol to the material obtained in S1. Use a water bath to control the reaction temperature and heat to reflux for 60~70℃ for 8 hours. S3. After the reaction was complete, the mixture was washed with ethanol to allow precipitation. After separation, the supernatant was removed, and the lower solid was filtered and dried to obtain 198.2 g of a neutral bonding agent containing an enamine structure, with a yield of 91.3%; denoted as NPBA-P1.

[0026] The proton NMR spectrum of the obtained bonding agent is shown in the figure. Figure 1In the figure, δ (0.88–0.95 ppm) corresponds to the methyl proton peak; δ (1.25–1.35 ppm) corresponds to the methylene proton peak linked to the methyl group; δ (1.42–1.50 ppm) corresponds to the methylene proton peak; δ (2.50–2.57 ppm) corresponds to the methylene proton peak; δ (2.62–3.00 ppm) corresponds to the methylene proton peak linked to the nitrogen group; δ (3.60–3.70 ppm) corresponds to the methylene proton peak linked to the hydroxyl group; δ (3.80–3.90 ppm) corresponds to the methylene proton peak linked to the oxygen group; δ (4.00–4.11 ppm) corresponds to the OH proton peak; and δ (7.35–7.38 ppm) corresponds to the OH proton peak linked to the nitrogen group. The number-average molecular weight and distribution range were measured using gel permeation chromatography (GPC), as detailed in [see figure]. Figure 2 Its relative molecular weight is 22532.

[0027] Example 2: The preparation of a neutral bonding agent containing an enamine structure includes the following steps: S1. Take 0.1 mol of glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product and dissolve it in 1960 g of acetone; then add 3 mol of butyl acrylate monomer and 1 mol of hydroxyethyl acrylate monomer in proportion. S2. Add 30.72g of initiator azobisisobutyronitrile, 23.04g of chain transfer agent 2-mercaptoethanol, and 15.36g of dispersant polyvinyl alcohol to the material obtained in S1. Use a water bath to control the reaction temperature and heat to reflux for 60~70℃ for 4 hours. S3. After the reaction is complete, the mixture is washed with ethanol for precipitation. After separation, the supernatant is removed, and the lower solid is filtered and dried to obtain 502.2 g of neutral bonding agent containing an enamine structure, with a yield of 90.3%; denoted as NPBA-P2.

[0028] The proton NMR spectrum of the obtained bonding agent is shown in the figure. Figure 3In the figure, δ (0.88–0.95 ppm) corresponds to the methyl proton peak; δ (1.25–1.35 ppm) corresponds to the methylene proton peak linked to the methyl group; δ (1.42–1.50 ppm) corresponds to the methylene proton peak; δ (2.50–2.57 ppm) corresponds to the methylene proton peak; δ (2.62–3.00 ppm) corresponds to the methylene proton peak linked to the nitrogen group; δ (3.60–3.70 ppm) corresponds to the methylene proton peak linked to the hydroxyl group; δ (3.80–3.90 ppm) corresponds to the methylene proton peak linked to the oxygen group; δ (4.00–4.11 ppm) corresponds to the OH proton peak; and δ (7.35–7.38 ppm) corresponds to the OH proton peak linked to the nitrogen group. The number-average molecular weight and distribution range were measured using gel permeation chromatography (GPC), as detailed in the figure. Figure 4 Its relative molecular weight is 22092.

[0029] Example 3: The preparation of a neutral bonding agent containing an enamine structure includes the following steps: S1. Take 0.1 mol of glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product and dissolve it in 384 g of acetone; then add 1 mol of butyl acrylate monomer and 1 mol of hydroxyethyl acrylate monomer in proportion. S2. Add 5.12g of initiator azobisisobutyronitrile, 12.8g of chain transfer agent 2-mercaptoethanol and 2.56g of dispersant polyvinyl alcohol to the material obtained in S1. Use a water bath to control the reaction temperature and heat to reflux for 60~70℃ for 8 hours. S3. After the reaction was complete, the mixture was washed with ethanol to allow precipitation. After separation, the supernatant was removed, and the lower solid was filtered and dried to obtain 271.2 g of neutral bonding agent containing an enamine structure, with a yield of 90.4%; denoted as NPBA-P3.

[0030] Example 4: The preparation of a neutral bonding agent containing an enamine structure includes the following steps: S1. Take 0.1 mol of glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product and dissolve it in 384 g of acetone; then add 2 mol of butyl acrylate monomer and 0.5 mol of hydroxyethyl acrylate monomer in proportion. S2. Add 10.24 g of initiator azobisisobutyronitrile, 25.6 g of chain transfer agent 2-mercaptoethanol and 5.12 g of dispersant polyvinyl alcohol to the material obtained in S1. Use a water bath to control the reaction temperature and heat to reflux for 60~70℃ for 4 h. S3. After the reaction was complete, the mixture was washed with ethanol to allow precipitation. After separation, the supernatant was removed, and the lower solid was filtered and dried to obtain 333.5 g of a neutral bonding agent containing an enamine structure, with a yield of 90.1%; denoted as NPBA-P4.

[0031] Comparative Example 1 A linear neutral bonding agent prepared using acrylonitrile, methyl acrylate monomer, and hydroxyethyl acrylate monomer in a molar ratio of 8:1:1. Used in NEPE propellant.

[0032]

[0033] Comparative Example 2 The linear neutral bonding agent prepared in Comparative Example 1 with a molar ratio of acrylonitrile, methyl acrylate monomer and hydroxyethyl acrylate monomer of 8:1:1 was compounded with triethanolamine and boron trifluoride complex (T313) for use in NEPE propellant. Comparative Example 3 The linear neutral bonding agent prepared in Comparative Example 1 with a molar ratio of acrylonitrile, methyl acrylate monomer and hydroxyethyl acrylate monomer of 8:1:1 was compounded with triethanolamine and boron trifluoride complex (LBA303) for use in NEPE propellant. The bonding agents prepared in the above embodiments and comparative examples were used in the preparation of NEPE propellants. Except for the selection and dosage of the bonding agent, the other raw materials were the same. The usage of the bonding agent is shown in Table 1 below. This application example is for illustrative purposes only, and the specific type of propellant used in this invention is not limited thereto.

[0034] Table 1

[0035] As shown in Table 1, the use of the enamine-containing neutral bonding agent (NPBA-P) in the embodiments of this invention significantly improves the mechanical properties of solid propellant grains compared to traditional linear neutral bonding agents, with both tensile strength σm and maximum elongation εm showing significant increases. While traditional linear and alkanolamine bonding agents (T313 being a triethanolamine-boron trifluoride complex, and LBA303 a triethanolamine-boron trifluoride complex) used in combination (Comparative Examples 2 and 3) also improved the mechanical properties of the propellant to some extent, the effect was not as significant as that achieved using the enamine-containing neutral bonding agent. The neutral bonding agent containing an enamine structure (with a relative molecular weight of around 20,000) has a side chain containing a highly efficient polyene-polyamine structure, hydroxyl groups, and cyano groups targeting ammonium perchlorate. The amine groups in the molecular structure readily form ionic bonds with ammonium perchlorate through acid-base neutralization, while the hydroxyl groups can form hydrogen bonds with ammonium perchlorate. Under the combined action of these two groups, a tear-resistant layer is formed. At the same time, the cyanoethyl groups on the side chain have low steric hindrance, allowing for better van der Waals forces at the interface with the nitramine oxidizer, thus improving the interfacial adsorption effect of the neutral bonding agent containing the enamine structure. This can suppress the "dewetting" phenomenon, and greatly improve the mechanical properties of the solid propellant grain, manifested in a significant increase in tensile strength and maximum elongation.

[0036] 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 neutral linking agent containing an enamine structure, characterized by, The structural formula is as follows: ; In the formula, x is the monomer molar mass of the glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product, y is the monomer molar mass of the butyl acrylate, z is the monomer molar mass of the hydroxyethyl acrylate, and n is the number of polyene polyamine repeating units.

2. The neutral linking agent according to claim 1, characterized in that: In the structural formula, x:y:z is 0.1:1-3:0.5-1; n has a value in the range of 0-3, and the relative molecular mass of the bonding agent is 15000-35000.

3. The neutral linking agent according to claim 1, wherein: The glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product has the following structure: 。 4. The method for preparing the neutral bonding agent according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1. Taking the glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product, dissolving it with a solvent, and then adding butyl acrylate monomers and hydroxyethyl acrylate monomers in proportion; S2. Adding an initiator, a chain transfer agent and a dispersant to the material obtained in S1, heating and mixing, refluxing, post-treatment and separation to obtain a neutral bonding agent containing an enamine structure.

5. The method of claim 4, wherein: In S1, the molar ratio of the glycidyl acrylate and cyanoethyl modified polyene polyamine epoxy ring-opening product, the butyl acrylate monomers and the hydroxyethyl acrylate monomers is 0.1:1-3:0.5-1.

6. The method of claim 4, wherein: The solvent is acetone, 1,2-dichloroethane or a mixture of the two; the initiator is azobisisobutyronitrile AIBN; the chain transfer agent is 2-mercaptoethanol; and the dispersant is polyvinyl alcohol.

7. The method of any one of claims 4 to 6, wherein: The mass ratio of the butyl acrylate monomers, the solvent, the initiator, the chain transfer agent and the dispersant is 100:300-500:4-8:6-10:2-5.

8. The method of claim 7, wherein: The reaction temperature in S2 is 60-70℃, and the reaction time is 4-8h.

9. The method of claim 7, wherein: In S2, the post-treatment is carried out by using ethanol for sedimentation washing, removing the supernatant after layering, and drying the lower layer solid after suction filtration to obtain the neutral bonding agent containing an enamine structure.

10. The neutral bonding agent containing an enamine structure according to any one of claims 1-3 or prepared by the method of any one of claims 4-9, is applied in a propellant, wherein the propellant is an NEPE propellant and / or a GAP propellant.

Images