Neutral polymer bonding agent, preparation method thereof and application of neutral polymer bonding agent in solid propellant

Abstract

The invention relates to the technical field of solid propellants, and particularly discloses a neutral polymer bonding agent, a preparation method of the neutral polymer bonding agent and application of the neutral polymer bonding agent in the solid propellants. The neutral polymer bonding agent can realize controllable molecular weight and controllable proportion of functional groups in the polymer, and the active group-CN steric hindrance in the neutral polymer bonding agent is small, so that the neutral polymer bonding agent is more easily adsorbed on the surfaces of ammonium nitrate particles, thereby improving the bonding effect.

Description

Technical Field

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

[0002] Since Kim invented neutral polymer bonding agent (NPBA) in 1990, it has been widely used in nitrate plasticized polyether propellants and can effectively improve the mechanical properties of such propellants. The molecular weight, hydroxyl content and cyano content of NPBA determine its application performance. The traditional NPBA synthesis method mainly uses acrylonitrile, hydroxyethyl acrylate, etc. as raw materials, azobisisobutyronitrile as initiator, and thiol compounds as chain transfer agents to achieve the synthesis of target polymer molecules through free radical polymerization. However, due to the different polymerization rates of acrylonitrile and hydroxyethyl acrylate and the different conversion rates of the raw materials in the reaction, it is difficult to achieve simultaneous controllable regulation of NPBA molecular weight and monomer ratio in this method, resulting in difficulty in obtaining NPBA with a specific molecular weight and hydroxyl content, which has an adverse effect on its application performance. The molecular weight distribution of NPBA prepared by this method is wide, which is not conducive to its bonding effect. In addition, the -CN group in the NPBA molecule prepared by this method that reacts with ammonium nitrate is secondary, and the steric hindrance effect is large, which further inhibits its adsorption on the surface of ammonium nitrate. Therefore, the NPBA with controllable molecular weight and functional group ratio developed by the present invention has important application value. Summary of the invention

[0003] The present invention provides a neutral polymer bonding agent and a preparation method thereof and application in solid propellants; the neutral polymer bonding agent has the characteristics of controllable molecular weight and functional group ratio. Meanwhile, the active -CN group has small steric hindrance and is more easily adsorbed on the solid surface of ammonium nitrate, thereby improving the bonding effect.

[0004] The technical solution of the present invention is to provide a neutral polymer bonding agent, the molecular structure of which is as follows: ; The R group is methyl or hydrogen, m and n represent the ratio of the two monomers, m accounts for 70%~95%, and n accounts for 5%~30%.

[0005] Optionally, the polymer molecular weight is 3000-50000.

[0006] The present invention also relates to a method for preparing the neutral polymer bonding agent, comprising the following steps: S1, dissolving polyhydroxyalkyl acrylate in a solvent, adding cyanoacetic acid, a dehydrating agent and a catalyst, and heating to react; The materials obtained from S2 and S1 are washed with water and then with an organic solvent to remove by-products, and the solid phase obtained by drying is a neutral polymer bonding agent.

[0007] Optionally, the polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, and its molecular weight is 2000-40000.

[0008] Optionally, the molar amount of cyanoacetic acid is 0.70 to 0.95 times the mass of the polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate divided by 116 or 130.

[0009] Optionally, the dehydrating agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0010] Optionally, the catalyst is 4-N,N-dimethylpyridine, 4-pyrrolidinopyridine or 1-hydroxybenzotriazole.

[0011] Optionally, the heating temperature in S1 is 40-60° C.; and the reaction time is 4-10 hours.

[0012] Optionally, the organic solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of, including but not limited to, methanol, ethanol, ethyl acetate or diethyl ether.

[0013] The invention also relates to the application of the neutral polymer bonding agent in the preparation of composite solid propellant.

[0014] The present invention has the following beneficial effects: The invention uses polyhydroxyalkyl acrylate and cyanoacetic acid as raw materials to polymerize and prepare a neutral polymer bonding agent, which solves the problem that the molecular weight and the monomer ratio are difficult to be simultaneously regulated due to the different reactivity rates of the two monomers during the conventional copolymerization of acrylonitrile and hydroxyethyl acrylate, and can realize controllable molecular weight and controllable ratio of functional groups in the polymer. In addition, the -CN group in the neutral polymer bonding agent is in the primary position, has small steric hindrance, and is more easily adsorbed on the surface of ammonium nitrate particles, thereby improving the bonding effect.

[0015] The synthesis of the neutral polymer bonding agent of the present invention has the advantages of simple operation, mild reaction conditions, simple post-treatment and the like. DETAILED DESCRIPTION

[0016] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified.

[0017] The present invention provides a neutral polymer bonding agent, the molecular structure of which is as follows: ; The R group is methyl or hydrogen, m and n represent the ratio of the two monomers, m accounts for 70%~95%, n accounts for 5%~30%; the molecular weight is 3000~50000.

[0018] The preparation of the neutral polymer bonding agent comprises the following steps: S1, dissolving polyhydroxyalkyl acrylate in a solvent, adding cyanoacetic acid, a dehydrating agent and a catalyst, and heating to react; The materials obtained from S2 and S1 are washed with water and then with an organic solvent to remove by-products, and the solid phase obtained by drying is a neutral polymer bonding agent.

[0019] In some embodiments, the polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, and has a molecular weight of 2,000-40,000.

[0020] In some embodiments, the molar amount of cyanoacetic acid is 0.70 to 0.95 times the mass of the raw polymer divided by 116 or 130.

[0021] In some embodiments, the dehydrating agent is one of dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and the molar amount thereof is 1.0 to 2.0 times that of the raw material cyanoacetic acid.

[0022] In some embodiments, the catalyst is one of 4-N,N-dimethylpyridine (DMAP), 4-pyrrolidinylpyridine (4-PPY), and 1-hydroxybenzotriazole (HOBt), and its molar amount is 0.02 to 0.15 times that of the raw material cyanoacetic acid.

[0023] In some embodiments, the organic solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of methanol, ethanol, ethyl acetate or diethyl ether.

[0024] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0025] Example 1 (1) Weigh 11.60 g of poly(hydroxyethyl acrylate) with a molecular weight of 2000, add it into a three-necked reaction flask equipped with a stirrer, a reflux condenser and a thermometer, add 300 mL of dichloromethane, and start stirring until the polymer is completely dissolved; (2) Add 7.65 g of cyanoacetic acid, 20.39 g of DCC and 1.10 g of DMAP to the system in step 1, and heat the reaction system to 50°C and reflux for 7 h until the cyanoacetic acid reacts completely.

[0026] (3) Add water to the system in step 2 and wash three times with ethanol, to obtain wet product micelles. Dry the wet product in an oven at 90°C to obtain the product.

[0027] The obtained product was tested by GPC, and the molecular weight was 3000, with m accounting for 90% and n accounting for 10%.

[0028] Example 2 (1) Weigh 13.00 g of poly(hydroxyethyl methacrylate) with a molecular weight of 10,000 and add it to a three-necked reaction flask equipped with a stirrer, a reflux condenser and a thermometer. Add 400 mL of dichloromethane and stir until the polymer is completely dissolved. (2) Add 6.88 g of cyanoacetic acid, 15.12 g of DIC, and 1.20 g of 4-PPY to the system in step 1, and heat the reaction system to 40°C and reflux for 9 hours until the cyanoacetic acid reacts completely.

[0029] (3) Add water to the system in step 2 and wash three times, then add methanol to wash three times to obtain a wet product floc. Dry the wet product in an oven at 90°C to obtain the product.

[0030] The molecular weight of the obtained product is 14000, with m accounting for 80% and n accounting for 20%.

[0031] Example 3 (1) Weigh 13.00 g of poly(hydroxyethyl methacrylate) with a molecular weight of 30,000 and add it to a three-necked reaction flask equipped with a stirrer, a reflux condenser and a thermometer. Add 400 mL of dichloromethane and stir until the polymer is completely dissolved. (2) Add 5.95 g of cyanoacetic acid, 24.10 g of EDCI and 1.13 g of HOBt to the system in step 1, and heat the reaction system to 60°C and reflux for 8 h until the cyanoacetic acid reacts completely.

[0032] (3) Add water to the system in step 2 and wash three times with ethyl acetate, to obtain a wet product floc. Dry the wet product in an oven at 90°C to obtain the product.

[0033] The molecular weight of the obtained product is 41000, with m accounting for 70% and n accounting for 30%.

[0034] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A neutral polymer bonding agent, characterized in that The molecular structure of the neutral polymer bonding agent is as follows: ； The R group is methyl or hydrogen, m and n represent the ratio of the two monomers, m accounts for 70%~95%, and n accounts for 5%~30%.

2. The neutral polymer bonding agent according to claim 1, characterized in that: The molecular weight of the polymer is 3000~50000.

3. The method for preparing the neutral polymer bonding agent according to claim 1 or 2, characterized in that: The following steps are involved: S1, dissolving polyhydroxyalkyl acrylate in a solvent, adding cyanoacetic acid, a dehydrating agent and a catalyst, and heating to react; The materials obtained from S2 and S1 are washed with water and then with an organic solvent to remove by-products, and the solid phase obtained by drying is a neutral polymer bonding agent.

4. The preparation method according to claim 3, characterized in that: The polyhydroxyalkyl acrylate is polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate, and has a molecular weight of 2000-40000.

5. The preparation method according to claim 4, characterized in that: The molar dosage of cyanoacetic acid is 0.70 to 0.95 times the mass of the polyhydroxyethyl methacrylate or polyhydroxyethyl acrylate divided by 116 or 130.

6. The preparation method according to claim 3, characterized in that: The dehydrating agent is dicyclohexylcarbodiimide, diisopropylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

7. The preparation method according to claim 3, characterized in that: The catalyst is 4-N,N-dimethylpyridine, 4-pyrrolidinopyridine or 1-hydroxybenzotriazole.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The heating temperature in S1 is 40-60°C; the reaction time is 4-10 hours.

9. The preparation method according to any one of claims 3 to 7, characterized in that: The organic solvent in S1 is dichloromethane; the organic solvent in S2 is one or more of methanol, ethanol, ethyl acetate or ether.

10. Use of the neutral polymer bonding agent according to claim 1 or 2 in the preparation of composite solid propellants.

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