Hyperbranched neutral polymer bonding agent, preparation method thereof and solid propellant

Abstract

The invention discloses a hyperbranched neutral polymer bonding agent, a preparation method thereof and a solid propellant. The hyperbranched neutral polymer bonding agent provided by the invention is modified hyperbranched polyethyleneimine, and the hyperbranched neutral polymer bonding agent is prepared by carrying out Michael addition reaction on amino on the hyperbranched polyethyleneimine and carbon-carbon double bonds on a nitrogen-containing monomer and a hydroxyl-containing monomer under the action of a catalyst; and introducing a nitrogen-containing group and a hydroxyl group into the hyperbranched polymer to obtain the hyperbranched polymer. The modified hyperbranched polyethyleneimine is used as a hyperbranched neutral polymer bonding agent to be applied to a solid propellant, the dehumidification phenomenon can be inhibited, and the tensile strength and the maximum elongation of the solid propellant are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthesis and solid propellant, and in particular to a hyperbranched neutral polymer bonding agent and a preparation method thereof and a solid propellant. Background Art

[0002] Neutral Polymeric Bonding Agent (NPBA) is a new type of additive for high-energy solid propellants invented by Kim CS of the United States. The polar groups (such as cyano) in NPBA can bond to the surface of solid energetic fillers (such as RDX, Octogen HMX, and hexanitrohexaazaisowurtzitane CL-20); at the same time, the hydroxyl groups in NPBA can react with the NCO groups in the curing agent and effectively connect to the main body of the adhesive. NPBA can prevent the separation between the main body of the adhesive and the solid energetic filler (i.e., the "dehumidification" phenomenon). Adding a small amount of NPBA to the propellant formula can significantly improve the mechanical properties of the propellant.

[0003] Existing NPBA is usually obtained by free radical copolymerization of vinyl monomers, and its chain structure is linear. Its effect of enhancing the mechanical properties of solid propellants is limited, and the mechanical properties of propellants need to be further improved. Summary of the invention

[0004] The purpose of the present invention is to provide a hyperbranched neutral polymer bonding agent and a preparation method thereof and a solid propellant in order to overcome the defects of the above-mentioned prior art.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] The invention provides a hyperbranched neutral polymer bonding agent. The hyperbranched neutral polymer bonding agent is a modified hyperbranched polyethyleneimine, and the side chain of the modified hyperbranched polyethyleneimine contains a hydroxyl group and a nitrogen-containing group.

[0007] The present invention also provides a method for preparing the hyperbranched neutral polymer bonding agent, which comprises: subjecting a hyperbranched polyethyleneimine solution to a Michael addition reaction with a nitrogen-containing monomer and a hydroxyl-containing monomer to obtain the hyperbranched neutral polymer bonding agent.

[0008] The present invention also provides a solid propellant, which comprises the hyperbranched neutral polymer bonding agent or the hyperbranched neutral polymer bonding agent prepared by the above preparation method.

[0009] The present invention has the following beneficial effects:

[0010] The invention provides a hyperbranched neutral polymer bonding agent, a preparation method thereof and a solid propellant. The hyperbranched neutral polymer bonding agent provided by the invention is a modified hyperbranched polyethyleneimine, and the modified hyperbranched polyethyleneimine side chain contains a hydroxyl group and a nitrogen-containing group. The modified hyperbranched polyethyleneimine is used as a hyperbranched neutral polymer bonding agent in a solid propellant, which can inhibit the "dehumidification" phenomenon and greatly improve the tensile strength and maximum elongation of the solid propellant. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0012] Figure 1 Schematic diagram of the synthesis process of hyperbranched neutral polymer bonding agent. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0014] A hyperbranched neutral polymer bonding agent, a preparation method thereof, and a solid propellant provided in an embodiment of the present invention are specifically described below.

[0015] In a first aspect, an embodiment of the present invention provides a hyperbranched neutral polymer bonding agent, wherein the hyperbranched neutral polymer bonding agent is a modified hyperbranched polyethyleneimine, and the modified hyperbranched polyethyleneimine side chain contains a hydroxyl group and a nitrogen-containing group. The modified hyperbranched polyethyleneimine is used as a neutral polymer bonding agent in a solid propellant, which can greatly improve the tensile strength and maximum elongation of the solid propellant.

[0016] In an optional embodiment, the modified hyperbranched polyethyleneimine is obtained by subjecting a hyperbranched polyethyleneimine solution to a Michael addition reaction with a nitrogen-containing monomer and a hydroxyl-containing monomer.

[0017] Hyperbranched polymers are a type of highly branched three-dimensional macromolecules. Hyperbranched polymers have many branching points, their molecular chains are not easily entangled, their viscosity is low, and they have functions such as reinforcement and toughening. At the same time, they have abundant terminal functional groups, which makes them easy to modify and facilitate the synthesis of a variety of functional materials.

[0018] Based on this, the hyperbranched neutral polymer bonding agent provided in the embodiment of the present invention utilizes the rich terminal functional groups of the hyperbranched polymer to achieve the modification of the hyperbranched polymer, introduces polar groups (such as cyano groups) and hydroxyl groups, and the modified product is used as a neutral polymer bonding agent (NPBA). In addition, according to the characteristics of the hyperbranched polymer, such as the large specific area of ​​the hyperbranched polymer, it is beneficial for NPBA to better cover and bond to the surface of the solid energetic filler; the strengthening and toughening function of the hyperbranched polymer is beneficial to improve the mechanical properties of the propellant; the hyperbranched polymer has a low viscosity, which is also beneficial to the preparation process of the propellant. Therefore, the use effect of the hyperbranched neutral polymer bonding agent provided by the embodiment of the present invention is better than that of the traditional linear neutral polymer bonding agent.

[0019] In an optional embodiment, the relative molecular weight of the hyperbranched polyethyleneimine (HPEI) is 500-100,000.

[0020] In an optional embodiment, the hyperbranched polyethyleneimine solution is obtained by dissolving hyperbranched polyethyleneimine in a solvent, and the solvent is a liquid that can dissolve the hyperbranched polyethyleneimine and the product;

[0021] Preferably, the solvent includes at least one of deionized water, tetrahydrofuran, dichloromethane, chloroform, dimethyl sulfoxide, and N,N-dimethylformamide.

[0022] In an optional embodiment, the nitrogen-containing monomer is a monomer containing a carbon-carbon double bond and a nitrogen element, and the hydroxyl-containing monomer is a monomer containing a carbon-carbon double bond and a hydroxyl group;

[0023] Preferably, the nitrogen-containing monomer includes acrylonitrile and acrylamide monomers, and the acrylamide monomer includes at least one of acrylamide and acryloylmorpholine;

[0024] Preferably, the hydroxyl-containing monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and polyethylene glycol acrylate;

[0025] Preferably, the molar ratio of the nitrogen-containing monomer to the hydroxyl-containing monomer is (10:1) to (2:1), more preferably (6:1) to (4:1), and the total molar number of carbon-carbon double bonds in the two monomers is 50% to 100% of the molar number of hydrogen atoms on the amine group in the hyperbranched polyethyleneimine, more preferably 80% to 100%, and further preferably 80% to 90%.

[0026] The embodiment of the present invention provides a hyperbranched neutral polymer bonding agent, which is obtained by reacting a hyperbranched polyethyleneimine solution with a nitrogen-containing monomer and a hydroxyl-containing monomer. Through the Michael addition reaction between the amine group on the hyperbranched polyethyleneimine and the carbon-carbon double bond on the nitrogen-containing monomer and the hydroxyl-containing monomer, the nitrogen-containing group and the hydroxyl group are introduced into the hyperbranched polyethyleneimine to achieve the modification of the hyperbranched polymer. The modified hyperbranched polymer provided by the embodiment of the present invention can be applied to solid propellants. And the reaction ratio in the process of preparing the hyperbranched polymer can be controlled, and the content of the nitrogen-containing group (such as cyano group) and the hydroxyl group in the hyperbranched polymer can be adjusted. The hyperbranched polymer with a content suitable for the nitrogen-containing group (such as cyano group) and the hydroxyl group can better control the rheological properties of the solid propellant, and has better adaptability and low viscosity. If the modification rate is too high, the polarity of the polymer segment is too large, which is not conducive to spreading and bonding.

[0027] In a second aspect, an embodiment of the present invention provides a method for preparing the above-mentioned neutral polymer bonding agent, which comprises: subjecting a hyperbranched polyethyleneimine solution to a Michael addition reaction with a nitrogen-containing monomer and a hydroxyl-containing monomer to obtain a neutral polymer bonding agent.

[0028] The embodiment of the present invention provides a method for preparing a hyperbranched neutral polymer bonding agent, which uses hyperbranched polyethyleneimine as a raw material, and the hyperbranched polyethyleneimine has abundant primary and secondary amine groups; the primary and secondary amine groups can undergo Michael addition reaction with carbon-carbon double bonds. Through the Michael addition reaction, nitrogen-containing polar groups and hydroxyl groups are introduced into the hyperbranched polyethyleneimine, and the modified hyperbranched polyethyleneimine can be applied to solid propellants, and the tensile strength and maximum elongation of the solid propellant grain are greatly improved.

[0029] In an optional embodiment, the method comprises the following steps: mixing a hyperbranched polyethyleneimine solution with a nitrogen-containing monomer, a hydroxyl-containing monomer and a catalyst, and under the action of the catalyst, utilizing the amine groups on the hyperbranched polyethyleneimine to react with the carbon-carbon double bonds on the nitrogen-containing monomer and the hydroxyl-containing monomer through a Michael addition reaction, thereby introducing nitrogen-containing groups and hydroxyl groups into the hyperbranched polyethyleneimine to obtain a neutral polymer bonding agent.

[0030] In an alternative embodiment, the catalyst is an organic base or an inorganic base;

[0031] Preferably, the organic base includes at least one of triethylamine, piperidine, quaternary ammonium base, and phosphazene base; the inorganic base includes at least one of sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium tertiary butoxide, and sodium amide.

[0032] In an optional embodiment, the reaction temperature is 20-80°C.

[0033] In an optional embodiment, the process further comprises: after the reaction is completed, discharging, precipitating, washing and drying to obtain a neutral polymer bonding agent;

[0034] Preferably, the poor solvent used for precipitation includes at least one of petroleum ether, methanol and ethanol.

[0035] In an alternative embodiment, see Figure 1 Using triethylamine as a catalyst, acrylonitrile as a nitrogen-containing monomer, and hydroxyethyl acrylate as a hydroxyl-containing monomer, a neutral polymer bonding agent is obtained by Michael addition reaction at 60°C. The reaction equation is as follows (all amine groups are converted).

[0036] In a third aspect, an embodiment of the present invention provides a solid propellant, the components of which include the hyperbranched neutral polymer bonding agent described above or the hyperbranched neutral polymer bonding agent prepared by the above preparation method.

[0037] In an optional embodiment, the amount of the hyperbranched neutral polymer bonding agent is 0.1 to 1 wt % of the propellant matrix.

[0038] Exemplarily, the propellant matrix includes the following components by weight percentage: GAP adhesive system: 20% to 30%; CL-20: 30% to 50%; aluminum powder: 10% to 20%; AP: 10% to 20%; curing catalyst di-n-butyltin dilaurate 0.5%, process aid paraffin: 0.1%.

[0039] In actual operation, the solid propellant can be made into a grain form, but is not limited to this.

[0040] The components were mixed in a kneader according to the proportions and then cured at 50±2°C for 7 days.

[0041] As can be seen from the above, the embodiments of the present invention provide a hyperbranched neutral polymer bonding agent and a preparation method thereof, which introduces nitrogen-containing groups (such as cyano groups) and hydroxyl groups with adjustable contents into hyperbranched polyethyleneimine through a Michael addition reaction with simple operation, high selectivity and conversion rate, thereby expanding the application field of hyperbranched polymers. When used as a neutral polymer bonding agent for solid propellants, the hyperbranched polymer bonding agent can suppress the "dehumidification" phenomenon and improve the mechanical properties of the solid propellants.

[0042] The present invention will be further described below in conjunction with the embodiments.

[0043] Example 1

[0044] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 500), 100 parts of deionized water, 29.5 parts of acrylonitrile, 6 parts of hydroxyethyl acrylate, 0.1 parts of catalyst sodium hydroxide, 1500 parts of methanol. The designed modification rate is 50%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 10:1.

[0045] 50 parts of hyperbranched polyethyleneimine powder were dissolved in deionized water in a reactor, and the reactor was deoxygenated with nitrogen for 30 minutes, and acrylonitrile and hydroxyethyl acrylate were added. The reaction was carried out at room temperature for 12 hours. 500 parts of methanol were used for precipitation three times, and vacuum dried to constant weight to obtain modified hyperbranched polyethyleneimine, which was recorded as hyperbranched neutral polymer bonding agent 1.

[0046] Example 2

[0047] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 500), 100 parts of tetrahydrofuran, 43.4 parts of acrylonitrile, 18 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The designed modification rate is 80%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 5:1.

[0048] Dissolve 50 parts of hyperbranched polyethyleneimine powder in tetrahydrofuran in a reactor, pass nitrogen to deoxygenate the reactor for 30 minutes, add acrylonitrile and hydroxyethyl acrylate, heat to 40°C, and react for 8 hours. Use 500 parts of methanol to precipitate three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 2.

[0049] Example 3

[0050] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 500), 100 parts of tetrahydrofuran, 48.8 parts of acrylonitrile, 20.3 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The designed modification rate is 90%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 5:1.

[0051] Dissolve 50 parts of hyperbranched polyethyleneimine powder in tetrahydrofuran in a reactor, pass nitrogen gas through the reactor for deoxygenation for 30 minutes, add acrylonitrile and hydroxyethyl acrylate, heat to 40°C, and react for 8 hours. Use 500 parts of methanol for precipitation three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 3.

[0052] Example 4

[0053] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 500), 100 parts of N,N-dimethylformamide, 54.3 parts of acrylonitrile, 22.5 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The designed modification rate is 100%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 5:1.

[0054] Dissolve 50 parts of hyperbranched polyethyleneimine powder in N,N-dimethylformamide in a reactor, pass nitrogen to deoxygenate the reactor for 30 minutes, add acrylonitrile and hydroxyethyl acrylate. Heat to 60°C and react for 6 hours. Use 500 parts of methanol to precipitate three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 4.

[0055] Example 5

[0056] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 100000), 100 parts of N,N-dimethylformamide, 43.4 parts of acrylonitrile, 45 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The modification rate is 100%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 2:1.

[0057] Dissolve 50 parts of hyperbranched polyethyleneimine powder in N,N-dimethylformamide in a reactor, pass nitrogen to deoxygenate the reactor for 30 minutes, add acrylonitrile and hydroxyethyl acrylate. Heat to 80°C and react for 6 hours. Use 500 parts of methanol to precipitate three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 5.

[0058] Comparative Example 1

[0059] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 150,000), 100 parts of N,N-dimethylformamide, 43.4 parts of acrylonitrile, 45 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The modification rate is 100%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 2:1.

[0060] Dissolve 50 parts of hyperbranched polyethyleneimine powder in N,N-dimethylformamide in a reactor, pass nitrogen to deoxygenate the reactor for 30 minutes, add acrylonitrile and hydroxyethyl acrylate. Heat to 80°C and react for 6 hours. Use 500 parts of methanol to precipitate three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 6.

[0061] Comparative Example 2

[0062] 50 parts of solid hyperbranched polyethyleneimine powder (relative molecular weight of 300), 100 parts of N,N-dimethylformamide, 43.4 parts of acrylonitrile, 45 parts of hydroxyethyl acrylate, 1 part of catalyst triethylamine, 1500 parts of methanol. The modification rate is 100%, and the molar ratio of acrylonitrile to hydroxyethyl acrylate is 2:1.

[0063] Dissolve 50 parts of hyperbranched polyethyleneimine powder in N,N-dimethylformamide in a reactor, pass nitrogen to deoxygenate the reactor for 30 minutes, add acrylonitrile and hydroxyethyl acrylate. Heat to 80°C and react for 6 hours. Use 500 parts of methanol to precipitate three times, and vacuum dry to constant weight to obtain modified hyperbranched polyethyleneimine, which is recorded as hyperbranched neutral polymer bonding agent 7.

[0064] Comparative Example 3

[0065] The traditional linear neutral polymer bonding agent is obtained by free radical solution copolymerization. The specific preparation process is as follows: initiator azobisisobutyronitrile (3g), acrylonitrile (53.08g), hydroxyethyl acrylate (23.29g), mercaptoethanol (3.92g) and 125ml acetone are added to a 500ml three-necked flask, nitrogen is passed to deoxygenate for 30min, magnetic stirring is turned on, the reaction is carried out at 60°C for 6 hours, the temperature is lowered, the material is discharged, methanol is added for precipitation three times (1000ml each time), and vacuum drying is performed to constant weight to obtain a random copolymer, which is recorded as a traditional linear neutral polymer bonding agent.

[0066] Performance Testing

[0067] After the preparation of the neutral polymer bonder, a solid propellant grain was prepared and its mechanical properties were measured. The solid propellant includes the following components by mass: GAP adhesive system: 20% to 30%; CL-20: 30% to 50%; aluminum powder: 10% to 20%; AP: 10% to 20%; curing catalyst di-n-butyltin dilaurate 0.5%, process aid paraffin: 0.1%. The slurry was prepared on a 5L vertical kneader, mixed, poured and cured at a curing temperature of (50±2)°C and a curing time of 7d. The amount of neutral polymer bonder was 0.5% of the total mass of the solid propellant (the blank group was a group without the addition of neutral polymer bonder). In the mechanical properties test, the temperature was 20°C and the tensile rate was 100mm / min. The test results of the solid propellant grain are shown in Table 1 below:

[0068] Table 1

[0069]

[0070] As can be seen from Table 1, when the hyperbranched polymer prepared with hyperbranched polyethyleneimine of too large or too small molecular weight as the starting material is used as a neutral polymer bonding agent, the mechanical properties of the solid propellant grain are basically not improved (see Comparative Examples 1, 2 and the blank group), and the tensile strength σ m and the maximum elongation ε m The traditional linear neutral polymer bonding agent can improve the mechanical properties of the propellant, the tensile strength σ m From 0.50MPa to 0.68MPa, the maximum elongation ε mFrom 44.8% to 65.4% (see Comparative Example 3 and the blank group). The hyperbranched polyethyleneimine (relative molecular weight of 500-100000) modified by Michael addition reaction contains a large number of hydroxyl groups and nitrogen-containing groups (such as cyano groups) in the side chain. When the modified hyperbranched polyethyleneimine is used as a neutral polymer bonding agent, the mechanical properties of the solid propellant grain are greatly improved, and the tensile strength and maximum elongation are greatly improved (see Examples 1-5 and the blank group). In addition, the use effect of the hyperbranched neutral polymer bonding agent prepared by the present invention is better than that of the traditional linear neutral polymer bonding agent (see Examples 1-5 and Comparative Example 3), that is, the modified hyperbranched polyethyleneimine can be used as a neutral polymer bonding agent.

[0071] As can be seen from the above, the embodiments of the present invention provide a hyperbranched neutral polymer bonding agent, a preparation method thereof, and a solid propellant. The hyperbranched neutral polymer bonding agent is a modified hyperbranched polyethyleneimine, containing hydroxyl groups and nitrogen-containing groups. The hyperbranched neutral polymer bonding agent is prepared by dissolving the hyperbranched polyethyleneimine and mixing it with a nitrogen-containing monomer, a hydroxyl-containing monomer, and a catalyst, and then subjecting the hyperbranched polyethyleneimine to a Michael addition reaction at a certain temperature, thereby introducing nitrogen-containing groups and hydroxyl groups into the hyperbranched polyethyleneimine, thereby achieving the modification of the hyperbranched polyethyleneimine, and the reaction product can be used as a neutral polymer bonding agent in a solid propellant. The above-mentioned neutral polymer bonding agent provided in the embodiments of the present invention is applied to a solid propellant, which can suppress the "dehumidification" phenomenon and greatly improve the tensile strength and maximum elongation of the solid propellant.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hyperbranched neutral polymer bonding agent, characterized in that: The hyperbranched neutral polymer bonding agent is a modified hyperbranched polyethyleneimine, and the side chain of the modified hyperbranched polyethyleneimine contains a hydroxyl group and a nitrogen-containing group.

2. The hyperbranched neutral polymer bonding agent according to claim 1, characterized in that The hyperbranched neutral polymer bonding agent is obtained by subjecting a hyperbranched polyethyleneimine solution to a Michael addition reaction with a nitrogen-containing monomer and a hydroxyl-containing monomer.

3. The hyperbranched neutral polymer bonding agent according to claim 1, characterized in that The relative molecular weight of the hyperbranched polyethyleneimine (HPEI) is 500 to 100000; Preferably, the hyperbranched polyethyleneimine solution is obtained by dissolving hyperbranched polyethyleneimine in a solvent, and the solvent is a liquid that can dissolve the hyperbranched polyethyleneimine and the product; Preferably, the solvent includes at least one of deionized water, tetrahydrofuran, dichloromethane, chloroform, dimethyl sulfoxide, and N,N-dimethylformamide.

4. The hyperbranched neutral polymer bonding agent according to claim 2, characterized in that The nitrogen-containing monomer is a monomer containing a carbon-carbon double bond and a nitrogen element in its molecular formula, and the hydroxyl-containing monomer is a monomer containing a carbon-carbon double bond and a hydroxyl group in its molecular formula; Preferably, the nitrogen-containing monomer includes acrylonitrile and acrylamide monomers, and the acrylamide monomer includes at least one of acrylamide and acryloylmorpholine; Preferably, the hydroxyl-containing monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and polyethylene glycol acrylate; Preferably, the molar ratio of the nitrogen-containing monomer to the hydroxyl-containing monomer is (10:1) to (2:1), more preferably (6:1) to (4:1), and the total molar number of carbon-carbon double bonds in the two monomers is 50% to 100% of the molar number of hydrogen atoms on the amine group in the hyperbranched polyethyleneimine, more preferably 80% to 100%, and further preferably 80% to 90%.

5. A method for preparing a hyperbranched neutral polymer bonding agent according to any one of claims 1 to 4, characterized in that: It includes: The hyperbranched polyethyleneimine solution is mixed with nitrogen-containing monomers and hydroxyl-containing monomers, and then subjected to Michael addition reaction to obtain a hyperbranched neutral polymer bonding agent.

6. The preparation method according to claim 5, characterized in that: The following steps are involved: A hyperbranched polyethyleneimine solution is mixed with a nitrogen-containing monomer, a hydroxyl-containing monomer and a catalyst. Under the action of the catalyst, the amine groups on the hyperbranched polyethyleneimine react with the carbon-carbon double bonds on the nitrogen-containing monomer and the hydroxyl-containing monomer to undergo Michael addition reaction, so that the nitrogen-containing groups and hydroxyl groups are introduced into the hyperbranched polyethyleneimine to obtain a hyperbranched neutral polymer bonding agent.

7. The preparation method according to claim 6, characterized in that: The catalyst is an organic base or an inorganic base; Preferably, the organic base includes at least one of triethylamine, piperidine, quaternary ammonium base, and phosphazene base; the inorganic base includes at least one of sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium tertiary butoxide, and sodium amide.

8. The preparation method according to claim 6, characterized in that: The reaction temperature is 20-80°C; Preferably, the method further comprises: after the reaction is completed, discharging, precipitating, washing and drying to obtain a hyperbranched neutral polymer bonding agent; Preferably, the poor solvent used for precipitation includes at least one of petroleum ether, methanol and ethanol.

9. A solid propellant, characterized in that: The invention comprises the hyperbranched neutral polymer bonding agent described in any one of claims 1 to 4 or the hyperbranched neutral polymer bonding agent prepared by the preparation method described in any one of claims 5 to 8.

10. The solid propellant according to claim 9, characterized in that The hyperbranched neutral polymer bonding agent is used in an amount of 0.1 to 1 wt % of the propellant matrix.

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