An end hexaazide nitrate polyether adhesive and a method of synthesizing the same

Abstract

The application discloses an end hexaazido nitrate polyether adhesive and a synthesis method thereof. The method first takes triazido neopentyl alcohol and glycidyl ether nitrate as raw materials, boron trifluoride-ether complex as a catalyst, and obtains triazido neopentyl polyglycidyl ether nitrate alcohol through cation ring-opening polymerization reaction; then takes triazido neopentyl polyglycidyl ether nitrate alcohol and hexamethylene diisocyanate as raw materials, dibutyl tin dilaurylate as a catalyst, and obtains end hexaazido polyglycidyl ether nitrate through addition reaction, namely the end hexaazido nitrate polyether adhesive. The application is mainly used for solid propellants, is used for synthesizing polytriazole elastomers, improves the content and crosslinking density of hard segments, promotes microphase separation of the elastomers, and thus improves mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of solid propellants and relates to a polyether adhesive for solid propellants, specifically to a terminal hexazonium nitrate polyether adhesive and its synthesis method. Background Technology

[0002] Hydroxyl-terminated ethylene oxide-tetrahydrofuran coether (PET) adhesives possess advantages such as good miscibility with nitrate ester plasticizers, good main chain flexibility, low viscosity, and low glass transition temperature, and have been widely used in nitrate ester plasticized polyether (NEPE) propellants. PET adhesives are generally combined with polyisocyanate curing agents to form an isocyanate curing system. Polyurethane elastomers are prepared through the curing reaction between the terminal hydroxyl groups and isocyanate groups. However, isocyanate curing systems require harsh curing conditions and are sensitive to moisture. Isocyanate groups can react rapidly with water or organic acids to generate CO2, which easily forms pores in the propellant, affecting its mechanical properties, storage performance, and safety performance.

[0003] To address the aforementioned problems with isocyanate curing systems, researchers have developed a novel curing system for preparing polytriazole crosslinked elastomers by curing terminal azido-based adhesives with polyacetylene curing agents. For example, Zhang Hanyu et al. disclosed a terminal hexazo-based nitrate ester polyether adhesive, namely terminal azido-based ethylene oxide-tetrahydrofuran co-ether (N3PET4000), in their paper "Synthesis of Terminal Azido-based Polyethers and Crosslinking Reaction with Polyacetylene Curing Agents" (Journal of Explosives and Pyrotechnics), 2012, 35(5): 45-48. Its structural formula is as follows:

[0004]

[0005] The N3PET4000 was cured with the polyacetylene curing agent triacetylacetonate, and a mixture of plasticizers 2,2-dinitropropanol formaldehyde and 2,2-dinitropropanol acetylacetonate (A3) was added. The effect of different molar ratios (R values) of azide groups to acetylene groups on the mechanical properties of the cured film was investigated at a plasticizer ratio of 0.5. The results showed that when the R value was 1.0, the molecular cross-linking network structure formed after curing was the most complete, and the film exhibited the best mechanical properties, with an elongation at break of 150% and a tensile strength of 0.9 MPa. However, the tensile strength and elongation at break of the film were relatively low. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a terminal hexazonium nitrate polyether adhesive and its synthesis method, so as to overcome the problems of low mechanical properties of the above-mentioned elastomer films.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A terminal hexazonium nitrate ester polyether adhesive, with the following structural formula:

[0009]

[0010] Where n = 8 to 40, and is an integer.

[0011] A method for synthesizing the terminal hexazoyl nitrate polyether adhesive, comprising: firstly, using neopentyl triazide alcohol and glycidyl ether nitrate as raw materials and boron trifluoride-ethyl ether complex as catalyst, obtaining neopentyl triazide polyglycidyl ether nitrate alcohol through cationic ring-opening polymerization; then, using the neopentyl triazide polyglycidyl ether nitrate alcohol and hexamethylene diisocyanate as raw materials and dibutyltin dilaurate as catalyst, obtaining terminal hexazoyl polyglycidyl ether nitrate through addition reaction, which is the terminal hexazoyl nitrate polyether adhesive.

[0012] The present invention also includes the following technical features:

[0013] Specifically, the molar ratio of the triazidopentyl alcohol, glycidyl ether nitrate, and boron trifluoride-ethyl ether complex is 1:8–40:0.3–0.6.

[0014] Specifically, the molar ratio of the triazidoneopentyl polyglycidyl nitrate alcohol and hexamethylene diisocyanate is 2:1, and the mass ratio of the triazidoneopentyl polyglycidyl nitrate alcohol and dibutyltin dilaurate is 1:0.0001 to 0.01.

[0015] Specifically, it includes the following steps:

[0016] Step 1, Synthesis of Triazidoneopentyl polyglycidyl nitrate alcohol: Dichloromethane, triazidoneopentyl alcohol and boron trifluoride-ethyl ether complex were added to a reaction flask. After stirring, the mixture was cooled to 10°C in an ice-water bath. Glycidyl nitrate was then added dropwise. After the addition was complete, the reaction continued. Na2CO3 aqueous solution was added to neutralize and terminate the reaction. The organic phase was washed with water until neutral. After concentration, a pale yellow viscous liquid was obtained.

[0017] Step 2, Synthesis of terminal hexazoyl polyglycidyl ether nitrate: At room temperature, triazidoneopentyl polyglycidyl ether nitrate alcohol, dibutyltin dilaurate and hexamethylene diisocyanate are added to a reaction flask, and the mixture is heated to react and a yellow viscous liquid is obtained, which is the terminal hexazoyl nitrate ether adhesive.

[0018] Specifically, in step 1, the stirring time is 30 minutes to 1 hour.

[0019] Specifically, in step 1, the glycidyl ether nitrate is added dropwise over a period of 6 to 15 hours, and the reaction continues for 12 to 18 hours after the addition is complete.

[0020] Specifically, in step 2, the temperature is raised to 60℃~70℃ and the reaction is carried out for 8h~12h.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] The hexaazide-based nitrate polyether adhesive of the present invention introduces six reactive azide groups at both ends of the molecular chain, resulting in high functionality. On the other hand, it introduces urethane groups with strong inter-group hydrogen bonding in the middle of the main chain. This improves the content of hard segments and crosslinking density in the synthesis of polytriazole elastomers, promotes the separation of elastomer microphases, and thus improves mechanical properties.

[0023] The hexaazido-based nitrate polyether adhesive elastomer film of the present invention has a tensile strength of 1.6 MPa and an elongation at break of 185% at 20°C; while the N3PET4000-based elastomer film in the prior art has a tensile strength of 0.9 MPa and an elongation at break of 150% at 20°C. Detailed Implementation

[0024] The concept of this invention is as follows: The low mechanical properties of N3PET4000-based elastomer films are due to the low average functionality of the N3PET4000 adhesive (around 2) and the low content of polytriazole groups in the hard chain segments, which makes aggregation difficult and promotes microphase separation in the elastomer. To improve the mechanical properties of the elastomer films, this invention proposes using polyglycidyl ether nitrate, a polymer with strong intermolecular forces, as the main chain. On the one hand, multiple reactive azide groups are introduced at both ends of the molecular chain to increase functionality; on the other hand, urethane groups with strong hydrogen bonding between groups are introduced in the middle of the main chain to achieve a physical cross-linking effect, promoting microphase separation in the elastomer and thus improving its mechanical properties.

[0025] The hexaazido-terminated nitrate ester polyether adhesive of the present invention has the following structural formula:

[0026]

[0027] Where n = 8 to 40, and is an integer.

[0028] The synthetic route of the terminal hexazonium nitrate ester polyether adhesive of the present invention is as follows:

[0029]

[0030] Where n = 8 to 40, and is an integer.

[0031] The method for synthesizing the terminal hexaazido nitrate polyether adhesive of the present invention includes the following steps:

[0032] (1) Using neopentyl triazide and glycidyl ether nitrate as raw materials, boron trifluoride · Using an ether complex as a catalyst, a cationic ring-opening polymerization reaction was conducted to obtain triazidoneopentyl polyglycidyl nitrate alcohol.

[0033] (2) Using triazidonepentyl polyglycidyl ether nitrate alcohol and hexamethylene diisocyanate as raw materials and dibutyltin dilaurate as catalyst, terminal hexaazidone polyglycidyl ether nitrate is obtained by addition reaction, which is the terminal hexaazidone nitrate ether adhesive of the present invention.

[0034] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0035] Testing instruments:

[0036] (1) The infrared spectrum was measured using a Nexus 870 Fourier transform infrared spectrometer from Nicolet, USA.

[0037] (2) The hydroxyl value was tested by the phthalic anhydride-pyridine acylation method.

[0038] (3) Number-average molecular weight

[0039] Equipment: GPC-50 gel permeation chromatograph from PL Corporation, UK;

[0040] GPC testing conditions: chromatographic column was PLgel MIXED-E in series; mobile phase was THF; column temperature was 40℃; detector was a differential refractive index detector.

[0041] (4) Mechanical properties

[0042] Equipment: Instron 4505 universal testing machine from Instron Corporation, USA;

[0043] Test method: in accordance with GB / T528-1998.

[0044] Example 1:

[0045] This embodiment provides a terminal hexazoyl nitrate polyether adhesive and its synthesis method, which includes the following steps:

[0046] Step 1, Synthesis of Triazidoneopentyl polyglycidyl ether nitrate alcohol

[0047] 20 mL of dichloromethane, 2.11 g of neopentyl triazide alcohol, and 0.71 g of boron trifluoride-ethyl ether complex were added to a reaction flask. After stirring for 30 min, the mixture was cooled to 10 °C in an ice-water bath. 17.85 g of glycidyl ether nitrate was then added dropwise over 12 h. After the addition was complete, the reaction was continued for 16 h. The reaction was terminated by adding Na2CO3 aqueous solution to neutralize the solution. The organic phase was washed with water until neutral and concentrated to obtain a pale yellow viscous liquid.

[0048] Structural assessment:

[0049] IR(KBr, cm -1 ): 3447(-OH), 2102(-N3), 1630, 1281, 870(-ONO2), 1123(COC).

[0050] Molecular weight and distribution: Mn = 1985, Mw = 2958, Mw / Mn = 1.49.

[0051] Hydroxyl value: 27.98 mg KOH / g.

[0052] The above analysis data confirms that the synthesized compound is triazidoneopentyl polyglycidyl nitrate alcohol.

[0053] Step 2, Synthesis of terminal hexazoyl polyglycidyl ether nitrate

[0054] At room temperature, 19.85 g of neopentyl triazide polyglycidyl ether nitrate alcohol, 0.02 g of dibutyltin dilaurate and 0.84 g of hexamethylene diisocyanate were added to a reaction flask, and the mixture was heated to 65 °C and reacted for 8 h to obtain a yellow viscous liquid.

[0055] Structural assessment:

[0056] IR(KBr, cm -1 ): 3309(-NH-), 2102(-N3), 1740(C=O), 1630, 1281, 870

[0057] (-ONO2), 1123(COC).

[0058] Molecular weight and distribution: Mn = 4120, Mw = 6922, Mw / Mn = 1.68.

[0059] The above analysis data confirms that the synthesized compound is terminal hexaazide-based polyglycidyl ether nitrate.

[0060] Application performance of the terminal hexazoyl nitrate polyether adhesive of the present invention:

[0061] (1) Evaluation of miscibility with curing agent

[0062] Triacetylamine was selected as the curing agent, and the miscibility and reactivity of the terminal hexaazido nitrate polyether adhesive and the curing agent were investigated.

[0063] The terminal hexaazidonitrate polyether adhesive of the present invention has good miscibility with the triargylamine curing agent, the mixture is clear and transparent, and the resulting mixture can undergo a stable curing reaction at 50-70°C.

[0064] (2) Mechanical properties of elastomers

[0065] The terminal hexaazidonitrate ester polyether adhesive of the present invention was cured with triargylamine curing agent, and plasticizer A3 was added. When the plasticizing ratio was 0.5, polytriazole elastomer film plasticized by A3 was prepared, and its mechanical properties are shown in Table 1.

[0066] Table 1 Mechanical properties of elastomer films

[0067]

[0068] It is evident that the mechanical properties of the elastomeric film cured with the terminal hexazonium nitrate polyether adhesive of the present invention are significantly better than those of the elastomeric film cured with N3PET4000.

Claims

1. A terminal hexazoyl nitrate polyether adhesive, characterized in that, Its structural formula is as follows: Where n = 8 to 40, and is an integer.

2. A method for synthesizing the terminal hexazoyl nitrate polyether adhesive of claim 1, characterized in that, The method first uses neopentyl triazide alcohol and glycidyl ether nitrate as raw materials, and boron trifluoride-ethyl ether complex as catalyst, to obtain neopentyl triazide polyglycidyl ether nitrate alcohol through cationic ring-opening polymerization; then, using the aforementioned neopentyl triazide polyglycidyl ether nitrate alcohol and hexamethylene diisocyanate as raw materials, and dibutyltin dilaurate as catalyst, an addition reaction is carried out to obtain terminal hexazoyl polyglycidyl ether nitrate, which is the terminal hexazoyl nitrate nitrate polyether adhesive.

3. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 2, characterized in that, The molar ratio of the triazidopentyl alcohol, glycidyl ether nitrate, and boron trifluoride-ethyl ether complex is 1:8-40:0.3-0.

6.

4. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 3, characterized in that, The molar ratio of the triazidoneopentyl polyglycidyl ether nitrate alcohol and hexamethylene diisocyanate is 2:1, and the mass ratio of the triazidoneopentyl polyglycidyl ether nitrate alcohol and dibutyltin dilaurate is 1:0.0001 to 0.

01.

5. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 4, characterized in that, Includes the following steps: Step 1, Synthesis of Triazidoneopentyl polyglycidyl nitrate alcohol: Dichloromethane, triazidoneopentyl alcohol and boron trifluoride-ethyl ether complex were added to a reaction flask. After stirring, the mixture was cooled to 10°C in an ice-water bath. Glycidyl nitrate was then added dropwise. After the addition was complete, the reaction continued. Na2CO3 aqueous solution was added to neutralize and terminate the reaction. The organic phase was washed with water until neutral. After concentration, a pale yellow viscous liquid was obtained. Step 2, Synthesis of terminal hexazoyl polyglycidyl ether nitrate: At room temperature, triazidoneopentyl polyglycidyl ether nitrate alcohol, dibutyltin dilaurate and hexamethylene diisocyanate are added to a reaction flask, and the mixture is heated to react and a yellow viscous liquid is obtained, which is the terminal hexazoyl nitrate ether adhesive.

6. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 5, characterized in that, In step 1, the stirring time is 30 min to 1 h.

7. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 5, characterized in that, In step 1, the glycidyl ether nitrate is added dropwise over a period of 6 to 15 hours, and the reaction continues for 12 to 18 hours after the addition is complete.

8. The method for synthesizing the terminal hexazoyl nitrate polyether adhesive as described in claim 5, characterized in that, In step 2, the temperature is raised to 60℃~70℃ and the reaction is carried out for 8h~12h.

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