Amine curing agent and preparation method thereof

Abstract

The invention relates to the technical field of epoxy resin curing, and discloses an amine curing agent and a preparation method thereof.The preparation method comprises the following steps of raw material preparation, pre-reaction treatment, catalytic modification and aftertreatment. A primary amine compound and a secondary amine compound are premixed according to a specific mass ratio, pre-reaction treatment is performed under the protection of nitrogen to form a uniform amine mixture, full contact and primary reaction activity of amine raw materials can be effectively guaranteed, then catalytic modification is performed by accurately controlling the addition amount of a catalyst and reaction conditions, and the reaction efficiency is improved. The catalyst is uniformly dispersed in a reaction system, the catalytic efficiency is fully exerted, the problems of low reaction efficiency and side reaction increase caused by local aggregation and deactivation of the catalyst can be avoided in real time, the molecular weight distribution of a curing agent product is more uniform, and the reaction efficiency and the product consistency are improved.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin curing technology, specifically to an amine curing agent and its preparation method. Background Technology

[0002] Amine curing agents and their preparation methods are important components in the field of epoxy resin curing technology, and are widely used in coatings, adhesives and composite materials. They are one of the key materials for achieving efficient curing of epoxy resins. The active amine groups in their molecular structure can undergo ring-opening reactions with epoxy groups to form a three-dimensional network structure, which endows the cured products with excellent mechanical properties and chemical stability. In order to ensure the compatibility and reactivity of amine curing agents with epoxy resins, catalysts and modifiers are usually introduced during the preparation process to ensure the application effect of amine curing agents.

[0003] Currently, the preparation process of amine curing agents involves multiple chemical reactions. When modifying primary and secondary amines, the added catalyst is difficult to disperse uniformly in the reaction system, and the dispersion state and activity changes of the catalyst cannot be monitored in real time. When local catalyst aggregation and deactivation occur, the reaction rate decreases and side reactions increase, making it impossible to guarantee the uniformity of molecular weight distribution of the curing agent product. At the same time, when carrying out amine modification reactions, the temperature and pressure parameters of the reaction system cannot be controlled in real time, which can lead to over- or under-reaction. Furthermore, abnormal reaction conditions cannot be adjusted in time. In the post-processing of amine curing agents, due to the limitations of the dehydration process, segmented temperature control and gradient dehydration cannot be achieved during vacuum dehydration, resulting in unstable residual moisture content in the curing agent product. This further affects the synergistic effect of the curing agent and epoxy resin and the performance of the cured product.

[0004] Therefore, an amine curing agent and its preparation method are proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an amine-based curing agent and its preparation method, solving the problems of reduced reaction rate and increased side reactions mentioned in the background art, which prevent the uniformity of molecular weight distribution of the curing agent product.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an amine curing agent and its preparation method, comprising the following steps: Step 1: Raw material preparation, selecting primary amine compound, secondary amine compound and catalyst, wherein the primary amine compound is at least one of ethylenediamine, hexamethylenediamine or phenylenediamine, the secondary amine compound is at least one of diethylenetriamine, triethylenetetramine or polyetheramine, and the catalyst is one of organotin compound or tertiary amine compound; Step 2: Pre-reaction treatment. Primary and secondary amine compounds are mixed at a mass ratio of 3:1 to 5:1 and added to the reaction vessel. Under nitrogen protection, the temperature is raised to 50-70℃ and stirred at 200-400 r / min for 10-20 minutes to form an amine mixture. Step 3: Catalytic modification. Add a catalyst to the amine mixture. The amount of catalyst added is 0.5%-1.5% of the total mass of the amine mixture. Continue to heat to 80-100℃, maintain the stirring speed at 300-500 r / min, and react for 1-2 hours to obtain the modified amine solution. Step 4: Post-treatment. Cool the modified amine solution to room temperature, filter to remove impurities, and then dehydrate under vacuum. Control the vacuum degree at -0.09MPa to -0.1MPa and dehydrate for 1-3 hours to obtain the amine curing agent. In step one, the total mass fraction of primary and secondary amine compounds is 100 parts, and the mass fraction of catalyst is 0.5-1.5 parts.

[0007] Preferably, in step one, the primary amine compound is a mixture of ethylenediamine and hexamethylenediamine, with a mass ratio of ethylenediamine to hexamethylenediamine of 1:1 to 2:1, and the secondary amine compound is a mixture of diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1 to 1:2.

[0008] Preferably, in step two, the pre-reaction temperature is set to 60℃±5℃, the stirring speed is 300r / min±50r / min, the reaction time is 15 minutes, and the nitrogen flow rate is 10-20L / min.

[0009] Preferably, in step three, during the catalytic modification reaction, the pressure of the reactor is controlled at 0.1-0.5 MPa, and the stirring speed is increased in a stepwise manner, with 300 r / min for the first 30 minutes and 500 r / min for the next 30 minutes. After the reaction is completed, the amine value is sampled and detected, and the amine value is controlled at 200-300 mg KOH / g.

[0010] Preferably, in step four, vacuum dehydration is performed using a thin-film evaporator with an evaporation temperature set to 40-60°C. The water content of the dehydrated product is less than 0.5%, and a filter membrane with a pore size of 0.5-1μm is used for filtration.

[0011] Preferably, the amine curing agent is composed of the following raw materials in parts by weight: 40-60 parts of primary amine compound, 10-20 parts of secondary amine compound, and 0.5-1.5 parts of catalyst, and the amine curing agent has an amine value of 200-300 mg KOH / g, a viscosity of 100-500 mPa·s, and a curing time of 30-60 minutes.

[0012] Preferably, the primary amine compound includes at least two of ethylenediamine, hexamethylenediamine, and phenylenediamine, and the mass ratio of ethylenediamine to hexamethylenediamine is 1:1 to 2:1, and the amount of phenylenediamine added accounts for 10%-20% of the total mass of the primary amine compound.

[0013] Preferably, the secondary amine compound includes diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1 to 1:2, and a polyetheramine is added to the secondary amine compound, the polyetheramine having a molecular weight of 200-400, and the amount added being 5%-10% of the total mass of the secondary amine compound.

[0014] Preferably, the catalyst is an organotin compound, specifically one of dibutyltin dilaurate or dibutyltin diacetate, the catalyst has an activity index of 0.8-1.2, and the catalyst has a dispersion particle size of 0.1-1 μm in the curing agent.

[0015] Preferably, the amine curing agent further includes an additive, which is at least one of an antifoaming agent, an antioxidant, or an ultraviolet absorber. The total amount of additives added is 0.1%-1% of the total mass of the curing agent. The amine curing agent has a storage stability of more than 12 months at 25°C, and the glass transition temperature of the cured product is higher than 80°C and the heat distortion temperature is higher than 100°C.

[0016] Compared with the prior art, the present invention provides an amine curing agent and its preparation method, which has the following beneficial effects: 1. In this invention, during the preparation of amine curing agents, a specific mass ratio of primary and secondary amine compounds is used for pre-mixing, followed by pre-reaction treatment under nitrogen protection to form a homogeneous amine mixture. This effectively ensures sufficient contact and initial reaction activity of the amine raw materials. Subsequently, catalytic modification is carried out by precisely controlling the amount of catalyst added and the reaction conditions, so that the catalyst is uniformly dispersed in the reaction system and fully exerts its catalytic efficiency. This can avoid the problems of low reaction efficiency and increased side reactions caused by local catalyst aggregation and deactivation in real time, ensuring a more uniform molecular weight distribution of the curing agent product and improving reaction efficiency and product consistency.

[0017] 2. In this invention, during the amine modification reaction stage, by setting a stepped stirring speed and controlling the pressure and temperature parameters of the reactor, the intensity of the reaction process can be adjusted in real time. By sampling and detecting the amine value and determining the reaction endpoint accordingly, the system can make timely adjustments when the reaction conditions fluctuate, effectively avoiding over- or under-reaction. When the amine value is detected to deviate from the set range, the reaction path can be corrected in real time by adjusting the temperature or pressure parameters, ensuring that the modification reaction is always within the optimal process window, thereby ensuring that the reactivity and stability of the obtained modified amine solution meet the requirements.

[0018] 3. In this invention, during the post-processing of amine curing agents, vacuum dehydration is performed using a thin-film evaporator, and gradient dehydration temperature and vacuum degree are set. This enables efficient moisture removal under segmented temperature control. By precisely controlling the dehydration time and the moisture content of the final product, the system can flexibly adjust the dehydration process parameters according to the characteristics of different batches of materials. This effectively solves the problem of unstable product moisture content caused by limitations in traditional dehydration processes, thereby improving the storage stability of the curing agent and its curing effect when used in conjunction with epoxy resin. This ensures that the glass transition temperature and heat distortion temperature of the final cured product meet the expected indicators. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: An amine curing agent and its preparation method, comprising the following steps: Step 1: Raw material preparation, selecting primary amine compound, secondary amine compound and catalyst. The primary amine compound is at least one of ethylenediamine, hexamethylenediamine or phenylenediamine, the secondary amine compound is at least one of diethylenetriamine, triethylenetetramine or polyetheramine, and the catalyst is one of organotin compound or tertiary amine compound. Step 2: Pre-reaction treatment. Primary and secondary amine compounds are mixed at a mass ratio of 3:1 and added to the reaction vessel. Under nitrogen protection, the temperature is raised to 50°C and stirred at 200 r / min for 10 minutes to form an amine mixture. Step 3: Catalytic modification. Add a catalyst to the amine mixture. The amount of catalyst added is 0.5% of the total mass of the amine mixture. Continue to heat to 80℃, maintain the stirring speed at 300 r / min, and react for 1 hour to obtain the modified amine solution. Step 4: Post-treatment, cool the modified amine solution to room temperature, filter to remove impurities, and then dehydrate under vacuum, with the vacuum degree controlled at -0.09MPa and the dehydration time at 1 hour, to obtain the amine curing agent; In step one, the total mass fraction of primary and secondary amine compounds is 100 parts, and the mass fraction of catalyst is 0.5 parts. In step one, the primary amine compound is a mixture of ethylenediamine and hexamethylenediamine in a mass ratio of 1:1, and the secondary amine compound is a mixture of diethylenetriamine and triethylenetetramine in a mass ratio of 1:1. In step two, the temperature of the pre-reaction treatment is set to 60℃±5℃, the stirring speed is 300r / min±50r / min, the reaction time is 15 minutes, and the nitrogen flow rate is 10L / min; In step three, during the catalytic modification reaction, the pressure in the reactor was controlled at 0.1 MPa, and the stirring speed was increased in a stepwise manner, 300 r / min for the first 30 minutes and 500 r / min for the next 30 minutes. After the reaction was completed, the amine value was sampled and tested, and the amine value was controlled at 200 mg KOH / g. In step four, vacuum dehydration is performed using a thin-film evaporator with an evaporation temperature of 40°C. The water content of the dehydrated product is less than 0.5%, and a filter membrane with a pore size of 0.5μm is used for filtration. The amine curing agent is composed of the following raw materials in parts by weight: 40 parts of primary amine compound, 10 parts of secondary amine compound, and 0.5 parts of catalyst. The amine curing agent has an amine value of 200 mg KOH / g, a viscosity of 100 mPa·s, and a curing time of 30 minutes. The primary amine compound includes at least two of ethylenediamine, hexamethylenediamine, and phenylenediamine, with the mass ratio of ethylenediamine to hexamethylenediamine being 1:1, and the amount of phenylenediamine added being 10% of the total mass of the primary amine compound; The secondary amine compounds include diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1. Furthermore, a polyetheramine with a molecular weight of 200 is added to the secondary amine compounds at an amount of 5% of the total mass of the secondary amine compounds. The catalyst is an organotin compound, specifically one of dibutyltin dilaurate or dibutyltin diacetate. The catalyst has an activity index of 0.8 and a dispersion particle size of 0.1 μm in the curing agent. Amine curing agents also include additives, which are at least one of defoamers, antioxidants, or ultraviolet absorbers. The total amount of additives added is 0.1% of the total mass of the curing agent. Furthermore, the amine curing agent has a storage stability of more than 12 months at 25°C, and the glass transition temperature of the cured product is higher than 80°C, and the heat distortion temperature is higher than 100°C.

[0021] Example 2: An amine curing agent and its preparation method, comprising the following steps: Step 1: Raw material preparation, selecting primary amine compound, secondary amine compound and catalyst. The primary amine compound is at least one of ethylenediamine, hexamethylenediamine or phenylenediamine, the secondary amine compound is at least one of diethylenetriamine, triethylenetetramine or polyetheramine, and the catalyst is one of organotin compound or tertiary amine compound. Step 2: Pre-reaction treatment. Primary and secondary amine compounds are mixed at a mass ratio of 4:1 and added to the reaction vessel. Under nitrogen protection, the temperature is raised to 60°C and stirred at 300 r / min for 15 minutes to form an amine mixture. Step 3: Catalytic modification. Add a catalyst to the amine mixture. The amount of catalyst added is 1.0% of the total mass of the amine mixture. Continue to heat to 90℃, maintain the stirring speed at 400 r / min, and react for 1.5 hours to obtain the modified amine solution. Step 4: Post-treatment, cool the modified amine solution to room temperature, filter to remove impurities, and then dehydrate under vacuum, with the vacuum degree controlled at -0.09MPa and the dehydration time at 2 hours, to obtain the amine curing agent; In step one, the total mass fraction of primary and secondary amine compounds is 100 parts, and the mass fraction of catalyst is 1.0 part. In step one, the primary amine compound is a mixture of ethylenediamine and hexamethylenediamine, with a mass ratio of ethylenediamine to hexamethylenediamine of 1.5:1, and the secondary amine compound is a mixture of diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1.5. In step two, the temperature of the pre-reaction treatment is set to 60℃±5℃, the stirring speed is 300r / min±50r / min, the reaction time is 15 minutes, and the nitrogen flow rate is 15L / min; In step three, during the catalytic modification reaction, the pressure in the reactor was controlled at 0.3 MPa, and the stirring speed was increased in a stepwise manner, 300 r / min for the first 30 minutes and 500 r / min for the next 30 minutes. After the reaction was completed, the amine value was sampled and tested, and the amine value was controlled at 250 mg KOH / g. In step four, vacuum dehydration is performed using a thin-film evaporator with an evaporation temperature of 50°C. The water content of the dehydrated product is less than 0.5%, and a filter membrane with a pore size of 0.7μm is used for filtration. The amine curing agent is composed of the following raw materials in parts by weight: 50 parts of primary amine compound, 15 parts of secondary amine compound, and 1.0 part of catalyst. The amine curing agent has an amine value of 250 mg KOH / g, a viscosity of 300 mPa·s, and a curing time of 50 minutes. The primary amine compound includes at least two of ethylenediamine, hexamethylenediamine, and phenylenediamine, with the mass ratio of ethylenediamine to hexamethylenediamine being 1.5:1, and the amount of phenylenediamine added accounting for 15% of the total mass of the primary amine compound; The secondary amine compounds include diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1.5. Furthermore, polyetheramine with a molecular weight of 300 is added to the secondary amine compounds at an amount of 7% of the total mass of the secondary amine compounds. The catalyst is an organotin compound, specifically one of dibutyltin dilaurate or dibutyltin diacetate. The catalyst has an activity index of 1.0 and a dispersion particle size of 0.5 μm in the curing agent. Amine curing agents also include additives, which are at least one of defoamers, antioxidants, or ultraviolet absorbers. The total amount of additives added is 0.5% of the total mass of the curing agent. Furthermore, the amine curing agent has a storage stability of more than 12 months at 25°C, and the glass transition temperature of the cured product is higher than 80°C, and the heat distortion temperature is higher than 100°C.

[0022] Example 3: An amine curing agent and its preparation method, comprising the following steps: Step 1: Raw material preparation, selecting primary amine compound, secondary amine compound and catalyst. The primary amine compound is at least one of ethylenediamine, hexamethylenediamine or phenylenediamine, the secondary amine compound is at least one of diethylenetriamine, triethylenetetramine or polyetheramine, and the catalyst is one of organotin compound or tertiary amine compound. Step 2: Pre-reaction treatment. Primary and secondary amine compounds are mixed at a mass ratio of 5:1 and added to the reaction vessel. Under nitrogen protection, the temperature is raised to 70°C and stirred at 400 r / min for 20 minutes to form an amine mixture. Step 3: Catalytic modification. Add a catalyst to the amine mixture. The amount of catalyst added is 1.5% of the total mass of the amine mixture. Continue to heat to 100℃, maintain the stirring speed at 500 r / min, and react for 2 hours to obtain the modified amine solution. Step 4: Post-treatment, cool the modified amine solution to room temperature, filter to remove impurities, and then dehydrate under vacuum, with the vacuum degree controlled at -0.1MPa and the dehydration time at 3 hours, to obtain the amine curing agent; In step one, the total mass fraction of primary and secondary amine compounds is 100 parts, and the mass fraction of catalyst is 1.5 parts. In step one, the primary amine compound is a mixture of ethylenediamine and hexamethylenediamine, with a mass ratio of 2:1; the secondary amine compound is a mixture of diethylenetriamine and triethylenetetramine, with a mass ratio of 1:2. In step two, the temperature of the pre-reaction treatment is set to 60℃±5℃, the stirring speed is 300r / min±50r / min, the reaction time is 15 minutes, and the nitrogen flow rate is 20L / min; In step three, during the catalytic modification reaction, the pressure in the reactor was controlled at 0.5 MPa, and the stirring speed was increased in a stepwise manner, 300 r / min for the first 30 minutes and 500 r / min for the next 30 minutes. After the reaction was completed, the amine value was sampled and tested, and the amine value was controlled at 300 mg KOH / g. In step four, vacuum dehydration is performed using a thin-film evaporator with an evaporation temperature of 60°C. The water content of the dehydrated product is less than 0.5%, and a filter membrane with a pore size of 1μm is used for filtration. The amine curing agent is composed of the following raw materials in parts by weight: 60 parts of primary amine compound, 20 parts of secondary amine compound, and 1.5 parts of catalyst. The amine curing agent has an amine value of 300 mg KOH / g, a viscosity of 500 mPa·s, and a curing time of 60 minutes. The primary amine compound includes at least two of ethylenediamine, hexamethylenediamine, and phenylenediamine, with the mass ratio of ethylenediamine to hexamethylenediamine being 2:1, and the amount of phenylenediamine added accounting for 20% of the total mass of the primary amine compound; The secondary amine compounds include diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:2. Furthermore, polyetheramine with a molecular weight of 400 is added to the secondary amine compounds at an amount of 10% of the total mass of the secondary amine compounds. The catalyst is an organotin compound, specifically one of dibutyltin dilaurate or dibutyltin diacetate. The catalyst has an activity index of 1.2 and a dispersion particle size of 1 μm in the curing agent. Amine curing agents also include additives, which are at least one of defoamers, antioxidants, or ultraviolet absorbers. The total amount of additives added is 1% of the total mass of the curing agent. Furthermore, the amine curing agent has a storage stability of more than 12 months at 25°C, and the glass transition temperature of the cured product is higher than 80°C and the heat distortion temperature is higher than 100°C.

[0023] Comparative Example 1: The difference between this comparative example and Example 1 is that no catalyst was added when preparing the amine curing agent in this comparative example.

[0024] Comparative Example 2 differs from Example 2 in that no secondary amine compound was added during the preparation of the amine curing agent in this comparative example.

[0025] Comparative Example 3 differs from Example 3 in that no pre-reaction treatment step was performed in this comparative example.

[0026] Comparative Example 4 differs from Example 3 in that vacuum dehydration was not performed in the later processing of this comparative example.

[0027] The performance of the amine curing agents prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: The amine value was determined by acid-base titration at room temperature (25°C) using a 0.1 mol / L hydrochloric acid standard solution, and the amine value corresponding to the amount of hydrochloric acid consumed was calculated. Viscosity testing was conducted using a rotational viscometer at a constant temperature of 25°C, measuring the viscosity of the sample at a rotational speed of 100 r / min. For the curing time test, the amine curing agent was mixed with epoxy resin E-51 at a mass ratio of 1:2, and the time required from the start of mixing to the point that the sample lost its fluidity was recorded. The test environment temperature was 25℃. For the heat distortion temperature test, a universal testing machine was used. The cured sample was subjected to a load of 1.82 MPa and the temperature was increased at 120℃ / h. The temperature at which the sample deformed by 0.25 mm was measured.

[0028] The test data of the amine curing agents prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0029] By comparing and analyzing the data in the table, it can be seen that the amine curing agents prepared using the processes in Examples 1-3 have significantly better performance than those prepared using the processes in Comparative Examples 1-4. This indicates that in the preparation process of the amine curing agents, by using a specific mass ratio of primary and secondary amine compounds for pre-mixing and conducting pre-reaction treatment under nitrogen protection to form a homogeneous amine mixture, the full contact and initial reaction activity of the amine raw materials can be effectively guaranteed. Subsequently, by precisely controlling the amount of catalyst added and the reaction conditions for catalytic modification, the catalyst is uniformly dispersed in the reaction system and fully exerts its catalytic efficiency. This can avoid the problems of low reaction efficiency and increased side reactions caused by local catalyst aggregation and deactivation, ensuring a more uniform molecular weight distribution of the curing agent product, improving the reaction rate and product consistency. In the amine modification reaction stage, by setting a stepped stirring speed and controlling the pressure and temperature parameters of the reactor, the intensity of the reaction process can be controlled in real time. Measuring the amine value and determining the reaction endpoint allows the system to adjust promptly when reaction conditions fluctuate, effectively preventing over- or under-reaction. When the amine value deviates from the set range, the reaction path can be corrected in real time by adjusting temperature or pressure parameters, ensuring the modified reaction is always within the optimal process window. This guarantees that the reactivity and stability of the resulting modified amine solution meet requirements. In the post-processing of amine curing agents, vacuum dehydration is performed using a thin-film evaporator with gradient dehydration temperature and vacuum level settings, achieving efficient moisture removal under segmented temperature control. By precisely controlling the dehydration time and the final product moisture content, the system can flexibly adjust dehydration process parameters according to the characteristics of different batches of materials. This effectively solves the problem of unstable product moisture content caused by limitations in traditional dehydration processes, thereby improving the storage stability of the curing agent and its curing effect when used in conjunction with epoxy resin, ensuring that the glass transition temperature and heat distortion temperature of the final cured product meet the expected specifications.

[0030] By comparing and analyzing the relevant data in the table, it can be seen that the amine curing agent prepared by the method of the present invention not only has suitable amine value and viscosity, but also has a short curing time and a high heat distortion temperature of the cured product. This indicates that the amine curing agent and its preparation method provided by the present invention have excellent comprehensive performance.

[0031] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an amine curing agent, characterized in that, Includes the following steps: Step 1: Raw material preparation, selecting primary amine compound, secondary amine compound and catalyst, wherein the primary amine compound is at least one of ethylenediamine, hexamethylenediamine or phenylenediamine, the secondary amine compound is at least one of diethylenetriamine, triethylenetetramine or polyetheramine, and the catalyst is one of organotin compound or tertiary amine compound; Step 2: Pre-reaction treatment. Primary and secondary amine compounds are mixed at a mass ratio of 3:1 to 5:1 and added to the reaction vessel. Under nitrogen protection, the temperature is raised to 50-70℃ and stirred at 200-400 r / min for 10-20 minutes to form an amine mixture. Step 3: Catalytic modification. Add a catalyst to the amine mixture. The amount of catalyst added is 0.5%-1.5% of the total mass of the amine mixture. Continue to heat to 80-100℃, maintain the stirring speed at 300-500 r / min, and react for 1-2 hours to obtain the modified amine solution. Step 4: Post-treatment. Cool the modified amine solution to room temperature, filter to remove impurities, and then dehydrate under vacuum. Control the vacuum degree at -0.09MPa to -0.1MPa and dehydrate for 1-3 hours to obtain the amine curing agent. In step one, the total mass fraction of primary and secondary amine compounds is 100 parts, and the mass fraction of catalyst is 0.5-1.5 parts.

2. The method for preparing an amine curing agent according to claim 1, characterized in that: In step one, the primary amine compound is a mixture of ethylenediamine and hexamethylenediamine, with a mass ratio of ethylenediamine to hexamethylenediamine of 1:1 to 2:1, and the secondary amine compound is a mixture of diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1 to 1:

2.

3. The method for preparing an amine curing agent according to claim 1, characterized in that: In step two, the pre-reaction temperature is set to 60℃±5℃, the stirring speed is 300r / min±50r / min, the reaction time is 15 minutes, and the nitrogen flow rate is 10-20L / min.

4. The method for preparing an amine curing agent according to claim 1, characterized in that: In step three, during the catalytic modification reaction, the pressure in the reactor is controlled at 0.1-0.5 MPa, and the stirring speed is increased in a stepwise manner, with 300 r / min for the first 30 minutes and 500 r / min for the next 30 minutes. After the reaction is completed, the amine value is sampled and detected, and the amine value is controlled at 200-300 mg KOH / g.

5. The method for preparing an amine curing agent according to claim 1, characterized in that: In step four, vacuum dehydration is performed using a thin-film evaporator with an evaporation temperature set to 40-60℃. The water content of the dehydrated product is less than 0.5%, and a filter membrane with a pore size of 0.5-1μm is used for filtration.

6. An amine curing agent, prepared by the method for preparing an amine curing agent according to any one of claims 1-5, characterized in that, The amine curing agent is composed of the following raw materials in parts by weight: 40-60 parts of primary amine compound, 10-20 parts of secondary amine compound, and 0.5-1.5 parts of catalyst. The amine curing agent has an amine value of 200-300 mg KOH / g, a viscosity of 100-500 mPa·s, and a curing time of 30-60 minutes.

7. An amine curing agent according to claim 6, characterized in that: The primary amine compound includes at least two of ethylenediamine, hexamethylenediamine, and phenylenediamine, and the mass ratio of ethylenediamine to hexamethylenediamine is 1:1 to 2:1, and the amount of phenylenediamine added accounts for 10%-20% of the total mass of the primary amine compound.

8. An amine curing agent according to claim 6, characterized in that: The secondary amine compound includes diethylenetriamine and triethylenetetramine, with a mass ratio of diethylenetriamine to triethylenetetramine of 1:1 to 1:2, and polyetheramine is added to the secondary amine compound. The molecular weight of the polyetheramine is 200-400, and the amount added is 5%-10% of the total mass of the secondary amine compound.

9. An amine curing agent according to claim 6, characterized in that: The catalyst is an organotin compound, specifically one of dibutyltin dilaurate or dibutyltin diacetate, with an activity index of 0.8-1.2 and a dispersion particle size of 0.1-1 μm in the curing agent.

10. An amine curing agent according to claim 6, characterized in that: The amine curing agent further includes additives, which are at least one of defoamers, antioxidants, or ultraviolet absorbers. The total amount of additives added is 0.1%-1% of the total mass of the curing agent. The amine curing agent has a storage stability of more than 12 months at 25°C, and the glass transition temperature of the cured product is higher than 80°C and the heat distortion temperature is higher than 100°C.

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