CN109161012B - Azido terminated ethylene oxide-tetrahydrofuran block copolyether containing carbamate structural unit and synthetic method thereof - Google Patents

Abstract

The invention discloses an azido terminated ethylene oxide-tetrahydrofuran block copolyether adhesive containing a carbamate structural unit, which has a structural formula shown in a figure (I), and a synthetic method comprises the following steps: hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether (HTPE) is used as a matrix, and the hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether (HTPE) and 2-chloroethyl isocyanate undergo nucleophilic addition reaction, and then undergo nucleophilic substitution with sodium azide to finally obtain the terminal azido group adhesive containing a carbamate structural unit, which can be used for Huisgen reaction for curing. The synthesis method is simple, less in side reaction and high in yield, and the synthesized adhesive has wide environmental adaptability in a curing mode. The invention is mainly used for composite solid propellant.

Description

Azido terminated ethylene oxide-tetrahydrofuran block copolyether containing carbamate structural unit and synthetic method thereof

Technical Field

The invention relates to an azido terminated ethylene oxide-tetrahydrofuran block copolyether adhesive containing a carbamate structural unit and a synthesis method thereof, and the compound can be used as an adhesive of a composite solid propellant, belonging to the field of solid propellants.

Background

Hydroxy-terminated ethylene oxide-tetrahydrofuran block copolyether (HTPE) is a multi-block copolyether obtained by polymerizing tetrahydrofuran and ethylene oxide. The HTPE propellant based on the adhesive is a novel insensitive propellant reported abroad, aims to improve the properties of a HTPB composite propellant stunning ammunition based on a hydroxyl-terminated polybutadiene (HTPB) adhesive, and is a insensitive propellant variety which has excellent mechanical properties and can completely meet the technical requirement of MIL-STD-2105C insensitivity at present. HTPE adhesives are typically used in propellants to form polyurethane crosslinked network structures with isocyanate-based curing agents. However, propellants based on conventional polyurethane systems have a number of disadvantages during use and storage: the isocyanate group is an active group and can react with CO in the air in the process of curing with hydroxyl₂The micro water generates side reaction to generate bubbles, thereby influencing the combustion performance, mechanical property, processing cost, safety performance and the like of the propellant; ② the curing system has poor compatibility to energetic oxidizer molecules (such as AND, HNF, etc.), thereby limiting the overall energy level of the propellant.

In order to solve the defects and problems of an isocyanate curing system, researchers at home and abroad develop a curing mode based on click chemistry Huisgen reaction, and the mode utilizes a cross-linked network structure of a polytriazole structure generated by the reaction of terminal alkynyl and azido, and has the advantages of less side reaction, insensitivity to water, good compatibility with energetic oxidant molecules (such as ADN, HNF and the like) and the like. Currently, there are few studies on end-site modification of HTPE, such as: in the patent of terminal alkynyl ethylene oxide-tetrahydrofuran copolyether containing carbamate units and a synthesis method thereof (acceptance number: 201610808357.1), Lihui of the Seisan recent chemical research institute adopts a PDI extended chain to modify HTPE into a block copolyether adhesive PUPE with terminal alkynyl, and the structural formula is shown as (II).

Firstly, in the synthesis process of the method, two separate operations are required: firstly, synthesizing propargyl (3-isocyanate-4-methyl) phenyl carbamate by adopting a TDI (toluene diisocyanate) large excess method (3-5 times), and secondly, reacting with HTPE to generate alkynyl-terminated polybutadiene containing a carbamate unit. The method has complex operation in the synthesis process, strict requirements on environment humidity for the post-treatment of the intermediate, the phenomenon of raw material waste and difficulty in realizing process amplification. Secondly, the PUPE adhesive synthesized by the method has a glass transition temperature of-58.6 ℃, and is greatly increased relative to that of a parent adhesive. Finally, the tensile strength of the elastomer obtained from the PUPE is 1.13MPa, the elongation at break is 320.2%, and the mechanical strength is poor.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the terminal azido-based polyether adhesive containing the carbamate structural unit, which has wide environmental adaptability and higher mechanical property.

The conception of the invention is as follows: the traditional HTPE adhesive is sensitive to moisture in the curing process so as to influence the mechanical property, the safety performance and the like of a propellant, but the polyurethane elastomer has excellent mechanical property due to the interaction of hydrogen bonds generated by a carbamate unit, while the traditional polytriazole elastomer has wide environmental adaptability such as insensitivity to water in the curing process, but the mechanical property is not ideal due to the lack of interaction among chain segments in the polytriazole elastomer.

In order to solve the technical problems, the invention provides an azido terminated ethylene oxide-tetrahydrofuran block copolyether containing a carbamate structural unit, which has the following structural formula:

wherein X is an integer of 10-60; y is an integer of 10-60; m is a positive integer of 1 or more.

The synthetic route of the terminal azido ethylene oxide-tetrahydrofuran block copolyether containing carbamate structural units is as follows:

wherein X is an integer of 10-60; y is an integer of 10-60; m is a positive integer of 1 or more.

The invention relates to a synthesis method of terminal azido ethylene oxide-tetrahydrofuran block copolyether containing a carbamate structural unit, which comprises the following steps:

the first step is as follows: synthesis of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether

Adding hydroxyl ethylene oxide-tetrahydrofuran block copolyether and dibutyltin dilaurate into a reaction bottle, uniformly stirring, then adding 2-chloroethyl isocyanate, slowly heating to 50-90 ℃ after uniformly stirring, and continuously reacting for 3-24 hours to obtain colorless viscous liquid which is chlorine-terminated ethylene oxide-tetrahydrofuran block copolyether. Wherein the molar ratio of the hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether to the 2-chloroethyl isocyanate is 1: 2-4, and the molar ratio of the hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether to the tetrabutylene dilaurate is 1:1 × 10^-3～4×10^-3；

The second step is that: synthesis of azido terminated ethylene oxide-tetrahydrofuran block copolyether

Adding chloro-ethylene oxide-tetrahydrofuran block copolyether, N-dimethylformamide and sodium azide into a reaction bottle, stirring uniformly, slowly heating to 50-90 ℃, reacting for 12-72 h, cooling a reaction system to room temperature, and removing a solvent by reduced pressure evaporation to obtain an orange viscous liquid, namely the azido-ethylene oxide-tetrahydrofuran block copolyether, wherein the molar ratio of the chloro-ethylene oxide-tetrahydrofuran block copolyether to the sodium azide is 1: 2-6, and the mass-volume ratio of the sodium azide to the N, N-dimethylformamide is 1: 10-100 g/ml.

The invention has the advantages that:

the ATUTPE adhesive related by the invention firstly introduces carbamate groups with stronger hydrogen bond action at two sides of a molecular chain in a molecular structure of azido-terminated ethylene oxide-tetrahydrofuran block copolyether containing a carbamate structural unit, besides two azido-terminated groups, and plays a role of a physical crosslinking point in an elastomer, and when the ATUTPE adhesive is used for synthesizing a polytriazole elastomer, the content of a hard chain segment and the microphase separation degree can be improved, so that the mechanical property is improved, the tensile strength can reach 2.229MPa, the elongation at break is 433.95%, while the tensile strength in the comparison document 1 is 1.13MPa, the elongation at break is 320.2%, and secondly, the adhesive synthesis method adopts a 'one-pot two-step method': the first step, intermediate ClUTPE is almost quantitatively generated, the post-treatment method is easy to operate, and the obtained intermediate can be directly put into the next step; and in the second step, the azide synthesis also belongs to the conventional operation, the post-treatment mode is simple, and the yield is stable. And the glass transition temperature of the obtained AUTPE adhesive is-67.6 ℃, the change of the AUTPE adhesive relative to the matrix adhesive is small, and the low-temperature mechanical property of the elastomer is ensured to a great extent. In addition, the adhesive is a liquid polymer with good fluidity at room temperature, and can realize room-temperature curing in the presence of a proper amount of catalyst.

The specific implementation mode is as follows:

testing an instrument:

the infrared spectrum test adopts a Nexus 870 Fourier transform infrared spectrometer of Nicolet company in the United states;

the nuclear magnetic resonance hydrogen spectrum test adopts an AVANCE AV500 type nuclear magnetic resonance instrument of Bruker company of Germany;

the number average molecular weight was measured by GPC-50 gel permeation chromatography (PL corporation, UK); GPC test conditions: the chromatographic column is series connected by PLGel MIXED-E; the mobile phase is THF; the column temperature was 40 ℃; the detector is a differential refractive detector.

The elastic mechanical property test adopts a Japanese SHAMADZU AG-X Plus type electronic universal material tester.

Example 1

The first step is as follows: synthesis of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether (ClTUTPE)

A250 mL three-necked round-bottomed flask equipped with a mechanical stirrer, reflux condenser and thermometer was charged with hydroxy ethylene oxide-tetrahydrofuran block copolyether (22.200g, 7.818mmol) and dibutyltin dilaurate (0.0138g, 0.022mmol) in this order and stirred well. Then 2-chloroethyl isocyanate (1.741g, 16.5mmol) is added, after stirring uniformly, the temperature is slowly raised to 80 ℃, and the reaction is continued for 19 h. After the reaction is finished, the unreacted 2-chloroethyl isocyanate is removed, and 23.8189g of the chloro-terminated ethylene oxide-tetrahydrofuran block copolyether as colorless viscous liquid is obtained, and the yield is 99.87%.

And (3) structural identification:

IR，ν_max(cm^-1)：3510、3330(-NH-)，2940、2860(-CH₂-)，1724(C＝O)，1114(-C-O-C-)，778(C-Cl)。

¹H NMR(CDCl₃，500MHz)：5.47，4.23，3.63，3.58，3.47，3.41，2.46，1.62。

¹³C NMR(CDCl₃，500MHz)：156.26，70.56，69.44，68.85，64.11，43.76，42.76，25.35。

the second step is that: synthesis of azido-terminated ethylene oxide-tetrahydrofuran block copolyether (ATUTPE)

A250 mL three-neck round-bottom flask equipped with a mechanical stirring, reflux condenser and thermometer was charged with chloro-ethylene oxide-tetrahydrofuran block copolyether (15.892g, 5.537mmol), 30mL N, N-dimethylformamide and sodium azide (1.443g, 22.200mmol) in this order, stirred well and slowly warmed to 70 ℃ for 72 h. After the reaction is finished, the solvent is evaporated under reduced pressure to obtain orange viscous liquid which is 15.986g of azido terminated ethylene oxide-tetrahydrofuran block copolyether, and the yield is as follows: 94.23 percent.

And (3) structural identification:

IR，ν_max(cm^-1)：3505、3330(-NH-)，2940、2860(-CH₂-)，2100(-N₃)，1724(C＝O)，1114(-C-O-C-)。

¹H NMR(CDCl₃，500MHz)：5.29，4.23，3.64，3.58，3.47，3.41，2.93，2.25，1.62。

¹³C NMR(CDCl₃，500MHz)：156.34，70.57，69.49，68.89，64.15，51.05，40.36，25.35。

physical and chemical properties: the appearance is orange yellow viscous liquid, the number average molecular weight is 5199, and the glass transition temperature is-67.6 ℃.

Example 2

The first step is as follows: synthesis of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether (ClTUTPE)

A250 mL three-necked round bottom flask equipped with a mechanical stirring, reflux condenser and thermometer was charged with hydroxy ethylene oxide-tetrahydrofuran block copolyether (22.200g, 7.818mmol) and dibutyltin dilaurate (0.0095g, 0.015mmol) in this order and stirred well. Then 2-chloroethyl isocyanate (2.146g, 20.338mmol) is added, after stirring uniformly, the temperature is slowly raised to 70 ℃, and the reaction is continued for 22 h. After the reaction is finished, the unreacted 2-chloroethyl isocyanate is removed by reduced pressure distillation, and 23.843g of the chloro-terminated ethylene oxide-tetrahydrofuran block copolyether as colorless viscous liquid is obtained, with the yield of 99.97%.

The second step is that: synthesis of azido-terminated ethylene oxide-tetrahydrofuran block copolyether (ATUTPE) in a 250mL three-neck round-bottom flask equipped with a mechanical stirring, reflux condenser and thermometer, chloroethylene oxide-tetrahydrofuran block copolyether (15.892g, 5.537mmol), 100mL N, N-dimethylformamide and sodium azide (1.080g, 16.611mmol) are added in sequence, stirred uniformly and slowly heated to 80 ℃ for reaction for 36 h. After the reaction is finished, the solvent is evaporated under reduced pressure to obtain orange viscous liquid which is 15.508g of azido terminated ethylene oxide-tetrahydrofuran block copolyether, and the yield is as follows: 97.16 percent.

Example 3

The first step is as follows: synthesis of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether (ClTUTPE)

A250 mL three-necked round-bottomed flask equipped with a mechanical stirrer, reflux condenser and thermometer was charged with hydroxy ethylene oxide-tetrahydrofuran block copolyether (22.200g, 7.818mmol) and dibutyltin dilaurate (0.016g, 0.025mmol) in this order and stirred well. Then 2-chloroethyl isocyanate (3.282g, 31.099mmol) is added, after stirring evenly, the temperature is slowly raised to 90 ℃, and the reaction is continued for 7 h. After the reaction is finished, the unreacted 2-chloroethyl isocyanate is removed by reduced pressure distillation, and 23.810g of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether as colorless viscous liquid is obtained, with the yield of 99.83%.

The second step is that: synthesis of azido-terminated ethylene oxide-tetrahydrofuran block copolyether (ATUTPE)

A250 mL three-neck round-bottom flask with a mechanical stirring, reflux condenser and thermometer was charged with chloro-ethylene oxide-tetrahydrofuran block copolyether (15.892g, 5.537mmol), 80mL N, N-dimethylformamide and sodium azide (2.024g, 31.134mmol) in that order, stirred well and then slowly warmed to 90 ℃ for 24 h. After the reaction is finished, the solvent is evaporated under reduced pressure to obtain orange viscous liquid, namely 15.000g of azido terminated ethylene oxide-tetrahydrofuran block copolyether with the yield of 93.98%.

The application performance of the terminal azido block copolyether adhesive

(1) Evaluation of miscibility with curing agent

Tripropargylamine is selected as a curing agent, and the miscibility and reactivity of the terminal azido-based block copolyether adhesive AUTPE and the curing agent are examined. The AUTPE adhesive and the tripropargylamine curing agent have good miscibility, the mixture is clear and transparent, and the formed mixed solution can be stably subjected to curing reaction at room temperature to 80 ℃.

(2) Mechanical properties of elastomers

The azido-terminated block copolyether adhesive AUTPE and the tripropargylamine curing agent are cured without adding a plasticizer, and the mechanical property results are shown in a table 1:

TABLE 1 mechanical Properties of elastomer films

Therefore, the mechanical property of the elastomer film of the ATUTPE is obviously superior to that of the polytriazole elastomers reported in the literature.

Claims (2)

1. An azido-terminated ethylene oxide-tetrahydrofuran block copolyether adhesive containing urethane structural units has a structural formula shown as (I):

wherein x is an integer of 10-60; y is an integer of 10-60; m is a positive integer of 1 or more.

2. A method for synthesizing the azido-terminated ethylene oxide-tetrahydrofuran block copolyether adhesive containing urethane structural units according to claim 1, comprising the steps of:

the first step is as follows: synthesis of chloro-terminated ethylene oxide-tetrahydrofuran block copolyether

Adding hydroxyl ethylene oxide-tetrahydrofuran block copolyether and dibutyltin dilaurate into a reaction bottle, uniformly stirring, then adding 2-chloroethyl isocyanate, slowly heating to 50-90 ℃ after uniformly stirring, and continuously reacting for 3-24 hours to obtain colorless viscous liquid which is chloro ethylene oxide-tetrahydrofuran block copolyether; wherein the molar ratio of the hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether to the 2-chloroethyl isocyanate is 1: 2-4, and the molar ratio of the hydroxyl-terminated ethylene oxide-tetrahydrofuran block copolyether to the tetrabutylene dilaurate is 1:1 × 10^-3～4×10^-3；

The second step is that: synthesis of azido terminated ethylene oxide-tetrahydrofuran block copolyether

Adding chloro-ethylene oxide-tetrahydrofuran block copolyether, N-dimethylformamide and sodium azide into a reaction bottle, stirring uniformly, slowly heating to 50-90 ℃, reacting for 12-72 h, cooling a reaction system to room temperature, and removing a solvent by reduced pressure evaporation to obtain an orange viscous liquid, namely the azido-ethylene oxide-tetrahydrofuran block copolyether, wherein the molar ratio of the chloro-ethylene oxide-tetrahydrofuran block copolyether to the sodium azide is 1: 2-6, and the mass-volume ratio of the sodium azide to the N, N-dimethylformamide is 1: 10-100 g/ml.