Preparation process of low-sensitization high-toughness quick-drying epoxy curing agent

Abstract

The invention relates to the technical field of chemical materials, and discloses a preparation process of a low-sensitization high-toughness quick-drying epoxy hardener, which comprises the following steps: heating and dissolving phenol, dimethyl pentamethylene diamine and a dimethyl amino propionitrile phenol adduct into a uniform system according to a formula ratio, adding paraformaldehyde under the protection of nitrogen, carrying out constant-temperature reaction, then carrying out vacuum dehydration treatment, and carrying out vacuum drying to obtain the low-sensitization high-toughness quick-drying epoxy hardener. The preparation method comprises the following steps: separating low-boiling-point components by virtue of a microchannel-molecular distillation device to obtain a target product, then mixing a cardanol derivative, fully stirring, and quantitatively packaging after quality inspection reaches the standard, so as to obtain a finished product. Grafting to phenol molecules through chemical reaction, reducing the volatility of the product through negative pressure distillation, and reducing the sensitization; the reaction activity and viscosity of the product are controlled by virtue of a microchannel technology, the contact allergy is reduced, the service cycle is prolonged, a specific product is finally collected, and the high-performance preparation of the epoxy curing agent is realized.

Description

Technical Field

[0001] The invention relates to the technical field of chemical materials, in particular to a preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent. Background Art

[0002] Epoxy resins are widely used in composite materials, electronic packaging, aerospace, and construction due to their excellent adhesion, mechanical properties, and chemical stability. However, traditional epoxy curing agents have some practical problems that limit their use in high-end applications.

[0003] First, traditional epoxy curing agents are highly allergenic and can easily cause skin irritation or allergic reactions in enclosed or high-humidity environments. This presents a significant health risk for workers exposed to these materials for extended periods of time. Second, these curing agents often lack toughness, resulting in brittle, impact-resistant cured materials – a significant disadvantage in applications requiring high-toughness materials. Furthermore, traditional epoxy curing agents dry slowly, which not only impacts production efficiency but also limits their use in applications requiring rapid curing.

[0004] Another problem is that during the curing process, unreacted small molecules remain in the final product, which can lead to the release of volatile organic compounds (VOCs). VOCs not only pollute the environment but also pose a threat to human health, such as causing respiratory irritation and headaches.

[0005] To address these challenges, developing a low-sensitivity, high-toughness, and fast-drying epoxy curing agent is crucial. This new epoxy curing agent should maintain the excellent properties of epoxy resin while reducing allergenicity, improving toughness and impact resistance, accelerating drying, and lowering VOC emissions. This approach meets the demands of high-end applications while minimizing impact on the environment and human health. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In response to the deficiencies in the prior art, the present invention provides a preparation process for a low-sensitivity, high-toughness, fast-drying epoxy curing agent, which has the advantages of low sensitization, high toughness, fast drying and low VOC release. It solves the problems of traditional epoxy curing agents, such as high sensitization and easy to cause human allergies, poor toughness resulting in brittle materials and insufficient impact resistance, slow drying speed affecting production efficiency, and small molecule residues after curing causing VOC pollution.

[0008] (2) Technical solution

[0009] To achieve the above object, the present invention provides the following technical solution: a preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent, comprising the following steps:

[0010] Step 1: Premix the raw materials: Add phenol, dimethylpentanediamine, and dimethylaminopropionitrile-phenol adduct in the formulated ratio into a four-necked flask equipped with a condenser, start stirring, and heat at a rate of 1-3°C / min until completely dissolved to form a homogeneous system.

[0011] Step 2: Formaldehyde gradient condensation: Under nitrogen protection, slowly add paraformaldehyde in the formula ratio in 3-8 times. After the addition is completed, keep the reaction at 80-85°C for 3-4 hours, and continuously add nitrogen to maintain an inert atmosphere;

[0012] Step 3: Deep dehydration: Use a vacuum water pump to perform dehydration treatment, control the system vacuum degree to less than 30 mmHg, and continue to vacuum until no water is analyzed;

[0013] Step 4: Precision molecular distillation: Connect the reaction system to a microchannel-molecular distillation device to sequentially separate and remove low-boiling point components to obtain the target product;

[0014] Step 5: Functional modification: Add the target product obtained by distillation to a cardanol derivative in a formula ratio, stir thoroughly to form a uniform system, and take samples for quality inspection;

[0015] Step 6. Finished product preparation: After testing and confirming that all performance indicators meet the standards, quantitative packaging and sealing are carried out to obtain a low-sensitivity, high-toughness, fast-drying epoxy curing agent finished product.

[0016] Preferably, the weight proportions of the raw materials and their preparation are: 10-30 parts of phenol; 20-60 parts of dimethylpentanediamine; 20-60 parts of dimethylaminopropionitrile-phenol adduct; 20-60 parts of paraformaldehyde; and 5-20 parts of cardanol derivatives.

[0017] Preferably, the molar ratio of phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct and paraformaldehyde is fixed at 1:2:2:2.

[0018] Preferably, the cardanol derivative accounts for 5% to 20% of the total system.

[0019] Preferably, the concentration of the paraformaldehyde is between 91.95% and 92.05%.

[0020] Preferably, the raw material pre-mixing heating temperature in step 1 is 60-90°C.

[0021] Preferably, in the step 2, the temperature of the system in which formaldehyde is added to paraformaldehyde by gradient condensation is ≤70°C.

[0022] Preferably, the vacuum degree of the system for deep dehydration treatment in step three is less than 30 mmHg.

[0023] Preferably, the precision molecular distillation process in step 4 is:

[0024] S4.1. First, distill and recover the small molecular amine substance dimethylaminopropionitrile phenol adduct;

[0025] S4.2. Continue distillation to separate dimethylpentanediamine. Its molecular reaction formula is:

[0026]

[0027] In the formula, the first benzene ring structure with -OH on the left represents phenol, the middle one represents formaldehyde, and the chain structure with two amino groups on the right represents dimethylpentanediamine;

[0028] S4.3. Cut the target fraction to collect the desired intermediates;

[0029] S4.4. Finally, remove the high-boiling-point macromolecular by-products. The molecular reaction formula is:

[0030]

[0031] In the formula, the first benzene ring structure with -OH on the left also represents phenol, the middle one represents formaldehyde, and the right side has a chain structure with multiple nitrogen-containing groups.

[0032] Preferably, during the functional modification process in step 5, the stirring rate is controlled at 300-500 r / min, the stirring time is 1-2 hours, and the mixing temperature is maintained at 40-50°C.

[0033] Compared with the prior art, the present invention provides a preparation process for a low-sensitivity, high-toughness, fast-drying epoxy curing agent, which has the following beneficial effects:

[0034] 1. The present invention achieves low sensitization of the epoxy curing agent by using phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct and paraformaldehyde raw materials, and accurately controlling the molar ratio of the raw materials. Among them, the high purity and precise addition amount of paraformaldehyde, as well as the inert atmosphere protection during the reaction process, will reduce the generation and release of harmful substances during the curing agent generation process, thereby reducing potential harm to human body and environment.

[0035] 2. The present invention functionalizes the curing agent by introducing cardanol derivatives to improve the toughness of the epoxy curing agent. The addition of cardanol derivatives can not only enhance the material's impact resistance, tensile strength, and flexural strength, but also improve its thermal stability, thereby increasing the heat deformation temperature of the curing agent. The above performance improvements make the curing agent more reliable and durable in practical applications.

[0036] 3. The present invention uses precision molecular distillation technology to separate and remove low-boiling point components, which can effectively control the reactivity and viscosity of the products generated from raw materials, thereby reducing contact allergies and extending the product life cycle. At the same time, the process of the present invention can also ensure the purity and quality of the final product, meeting the needs of high-end epoxy resin applications, such as electronic packaging and aerospace coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] See also Figure 1 , a preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent, comprising the following steps:

[0040] Step 1: Premix the raw materials: Add phenol, dimethylpentanediamine, and dimethylaminopropionitrile-phenol adduct in the formulated ratio into a four-necked flask equipped with a condenser, start stirring, and heat at a rate of 1-3°C / min until completely dissolved to form a homogeneous system.

[0041] Step 2: Formaldehyde gradient condensation: Under nitrogen protection, slowly add paraformaldehyde in the formula ratio in 3-8 times. After the addition is completed, keep the reaction at 80-85°C for 3-4 hours, and continuously add nitrogen to maintain an inert atmosphere;

[0042] Step 3: Deep dehydration: Use a vacuum water pump to perform dehydration treatment, control the system vacuum degree to less than 30 mmHg, and continue to vacuum until no water is analyzed;

[0043] Step 4: Precision molecular distillation: Connect the reaction system to a microchannel-molecular distillation device to sequentially separate and remove low-boiling point components to obtain the target product;

[0044] Step 5: Functional modification: Add the target product obtained by distillation to a cardanol derivative in a formula ratio, stir thoroughly to form a uniform system, and take samples for quality inspection;

[0045] Step 6. Finished product preparation: After testing and confirming that all performance indicators meet the standards, quantitative packaging and sealing are carried out to obtain a low-sensitivity, high-toughness, fast-drying epoxy curing agent finished product.

[0046] Specifically, the weight proportions of the raw materials and their preparation are: 10-30 parts of phenol; 20-60 parts of dimethylpentanediamine; 20-60 parts of dimethylaminopropionitrile phenol adduct; 20-60 parts of paraformaldehyde (92%); and 5-20 parts of cardanol derivatives.

[0047] Specifically, the molar ratio of phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct DMAPAPA and paraformaldehyde is fixed at 1:2:2:2.

[0048] Specifically, the cardanol derivatives account for 5% to 20% of the total system.

[0049] Specifically, the concentration of paraformaldehyde is between 91.95% and 92.05%.

[0050] The advantages are: the present invention uses phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct and paraformaldehyde as raw materials, and accurately controls the molar ratio of the raw materials to achieve low sensitization of the epoxy curing agent. Among them, the high purity and precise addition amount of paraformaldehyde, as well as the inert atmosphere protection during the reaction process, can reduce the generation and release of harmful substances in the curing agent generation process, thereby reducing potential harm to human body and environment.

[0051] Specifically, in step 1, the raw materials are pre-mixed and heated to a temperature of 60-90°C.

[0052] Specifically, in step 2, the temperature of the system in which formaldehyde is added to paraformaldehyde by gradient condensation is ≤70°C.

[0053] Specifically, the vacuum degree of the system for deep dehydration treatment in step 3 is less than 30 mmHg.

[0054] Specifically, the precision molecular distillation process in step 4 is:

[0055] S4.1. First, distill and recover the small molecule amine substance dimethylaminopropionitrile phenol adduct DMAPAPA (product 1);

[0056] S4.2. Continue distillation to separate dimethylpentanediamine (product 3). Its molecular reaction formula is:

[0057]

[0058] In the formula, the first benzene ring structure with -OH on the left represents phenol, a weakly acidic organic compound that participates in the reaction as a reactant. The middle one represents formaldehyde, a simple aldehyde compound with high reactivity, providing a methylene group in the reaction. The chain structure with two amino groups on the right represents dimethylpentanediamine, an organic amine compound containing amino groups, which makes it alkaline and reactive.

[0059] Product 1: From a structural point of view, it is dimethylpentanediamine that did not participate in the reaction and was first separated and recovered during the distillation process;

[0060] Product 2: It is the product of the condensation reaction of phenol, formaldehyde and dimethylpentanediamine. The benzene ring of phenol is connected to a side chain containing an amino group. It is an intermediate product in the reaction process.

[0061] Product 3: This is the product generated by further reaction. Compared with Product 2, its structure has more connecting fragments. It is also an intermediate product in the reaction process and will be separated in the subsequent distillation.

[0062] S4.3. Cut the target fraction to collect the desired intermediates;

[0063] S4.4. Finally, high-boiling-point macromolecular by-products (products 3 and 6) are discarded. The molecular reaction formula is:

[0064]

[0065] In the formula, the first benzene ring structure with -OH on the left also represents phenol, the middle one represents formaldehyde, and the chain structure with multiple nitrogen-containing groups on the right represents an amine compound (a nitrogen-containing reactant similar to dimethylpentanediamine);

[0066] Product 4: It is the amine compound that did not participate in the reaction and was first separated and recovered during the distillation process;

[0067] Product 5: It is the product of the condensation reaction between phenol, formaldehyde and the amine compound. The benzene ring of phenol is connected to a side chain containing an amino group, which is an intermediate product in the reaction process;

[0068] Product 6: It is a high-boiling-point macromolecular by-product generated by further reaction. Its structure is more complex and is discarded as a by-product during the distillation process.

[0069] The advantages are: the molecular reaction process of the above raw materials is based on phenol as the main structure, and the tertiary amine structure with low-temperature promoting effect in the DMAPAPA molecular structure and the high toughness and high adhesion characteristics of dimethylpentanediamine are used to graft them into the phenol molecule through chemical reactions and processes. The free small molecular amines are removed by negative pressure distillation to reduce the volatility of the product and the possibility of allergy. Then, products of different molecular weights are distilled out through microchannel technology to control the reaction activity and viscosity of the products, and sufficient preparations are made to reduce contact allergies and product use cycle. Finally, product two and product five are collected.

[0070] Specifically, during the functional modification process in step 5, the stirring rate is controlled at 300-500 r / min, and the stirring time is 1-2 hours to ensure that the cardanol derivative and the target product are fully mixed; and the mixing temperature is maintained at 40-50°C to avoid excessively high temperature causing the cardanol derivative to deteriorate or reduce its activity.

[0071] The advantages are: the present invention functionally modifies the curing agent by introducing cardanol derivatives to improve the toughness of the epoxy curing agent, wherein the addition of cardanol derivatives can not only enhance the impact strength, tensile strength and bending strength of the material, but also improve its thermal stability, thereby increasing the heat deformation temperature of the curing agent. The above performance improvements make the curing agent more reliable and durable in practical applications.

[0072] Table 1 below is a performance test table of the finished curing agent prepared by the above process:

[0073] Table 1

[0074] Test items Test items Test items Test items MDS70 sample measured value MDS70 sample measured value MDS70 sample measured value MDS70 sample measured value HB-1 competitor samples HB-1 competitor samples HB-1 competitor samples HB-1 competitor samples Detection method Detection method Detection method Detection method Appearance Appearance Appearance Appearance Medium yellow viscous liquid Medium yellow viscous liquid Medium yellow viscous liquid Medium yellow viscous liquid Yellow transparent liquid Yellow transparent liquid Yellow transparent liquid Yellow transparent liquid Visual inspection Visual inspection Visual inspection Visual inspection Viscosity (mPa.s, 25°C) Viscosity (mPa.s, 25°C) Viscosity (mPa.s, 25°C) Viscosity (mPa.s, 25°C)

[0075] The finished curing agent of the present invention was tested and compared with the HB-1 competitor under low temperature drying conditions. The test data obtained are shown in Table 2 below:

[0076] Table 2

[0077]

[0078] Note: The test was mainly conducted using 128 resin; no significant difference was found when retested using 127 resin.

[0079] The appearance of the finished curing agent of the present invention was compared with that of the competing product HB-1, and the data obtained are shown in Table 3 below:

[0080] Table 3

[0081] product Curing agent of the present invention HB-1 competitors Appearance light yellow light yellow Observation of the cup wall No whitening of the cup wall, no volatile The cup wall is white and volatile

[0082] Note: Applicable to wind turbine blade repair scenarios.

[0083] The advantages are: through process innovation, fine control of product structure is achieved, and a low-sensitivity, fast-drying, high-toughness and high-adhesion curing agent has been successfully developed in the field of wind power composite materials.

[0084] Example 1

[0085] Raw material preparation: 10 parts of phenol; 20 parts of dimethylpentanediamine; 20 parts of dimethylaminopropionitrile phenol adduct; 20 parts of paraformaldehyde (92%); 5 parts of cardanol derivative.

[0086] Preparation ratio and raw material purity: The molar ratio of phenol, dimethylpentanediamine, dimethylaminopropionitrile-phenol adduct DMAPAPA, and paraformaldehyde is fixed at 1:2:2:2; the cardanol derivative accounts for 5% of the total system; the concentration of paraformaldehyde is between 91.95% and 92.05%;

[0087] Preparation steps:

[0088] Step 1: The raw materials are pre-mixed and heated to 60°C;

[0089] Step 2: Formaldehyde gradient condensation with paraformaldehyde added, the system temperature is ≤70°C;

[0090] Step 3: The vacuum degree of the deep dehydration system is less than 30 mmHg;

[0091] Step 4: During the precision molecular distillation process, the small molecular amine substance dimethylaminopropionitrile phenol adduct DMAPAPA is first distilled and recovered, and then dimethylpentanediamine is separated by distillation. The target fraction is intercepted to collect the desired intermediate, and finally the high-boiling point macromolecular by-product is discarded;

[0092] Step 5: During the functional modification process, the stirring rate was controlled at 300 r / min, the stirring time was 1 hour, and the mixing temperature was maintained at 40° C. to ensure that the cardanol derivative and the target product were fully mixed.

[0093] Example 2

[0094] Raw material preparation: 20 parts of phenol; 30 parts of dimethylpentanediamine; 30 parts of dimethylaminopropionitrile phenol adduct; 30 parts of paraformaldehyde (92%); 10 parts of cardanol derivative.

[0095] Preparation ratio and raw material purity: the molar ratio of phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct DMAPAPA and paraformaldehyde is fixed at 1:2:2:2; the cardanol derivative accounts for 10% of the total system; and the concentration of paraformaldehyde is between 91.95% and 92.05%.

[0096] Preparation steps:

[0097] Step 1: The raw materials are pre-mixed and heated to 70°C;

[0098] Step 2: Formaldehyde gradient condensation with paraformaldehyde added, the system temperature is ≤75°C;

[0099] Step 3: The vacuum degree of the deep dehydration system is less than 30 mmHg;

[0100] Step 4: During the precision molecular distillation process, the small molecular amine substance dimethylaminopropionitrile phenol adduct DMAPAPA is first distilled and recovered, and then dimethylpentanediamine is separated by distillation. The target fraction is intercepted to collect the desired intermediate, and finally the high-boiling point macromolecular by-product is discarded;

[0101] Step 5: During the functional modification process, the stirring rate was controlled at 400 r / min, the stirring time was 1.5 hours, and the mixing temperature was maintained at 45° C. to ensure that the cardanol derivative and the target product were fully mixed.

[0102] Example 3

[0103] Raw material preparation: 30 parts of phenol; 60 parts of dimethylpentanediamine; 60 parts of dimethylaminopropionitrile phenol adduct; 60 parts of paraformaldehyde (92%); 20 parts of cardanol derivative.

[0104] Preparation ratio and raw material purity: the molar ratio of phenol, dimethylpentanediamine, dimethylaminopropionitrile phenol adduct DMAPAPA and paraformaldehyde is fixed at 1:2:2:2; the cardanol derivative accounts for 20% of the total system; and the concentration of paraformaldehyde is between 91.95% and 92.05%.

[0105] Preparation steps:

[0106] Step 1: The raw materials are pre-mixed and heated to 80°C;

[0107] Step 2: Formaldehyde gradient condensation with paraformaldehyde added, the system temperature is ≤80°C;

[0108] Step 3: The vacuum degree of the deep dehydration system is less than 30 mmHg;

[0109] Step 4: During the precision molecular distillation process, the small molecular amine substance dimethylaminopropionitrile phenol adduct DMAPAPA is first distilled and recovered, and then dimethylpentanediamine is separated by distillation. The target fraction is intercepted to collect the desired intermediate, and finally the high-boiling point macromolecular by-product is discarded;

[0110] Step 5: During the functional modification process, the stirring rate was controlled at 500 r / min, the stirring time was 2 hours, and the mixing temperature was maintained at 50° C. to ensure that the cardanol derivative and the target product were fully mixed.

[0111] Comparative Example 1

[0112] No cardanol derivative was added, and other conditions were the same as in Example 1.

[0113] Comparative Example 2

[0114] 85% pure paraformaldehyde was used instead of high-purity paraformaldehyde (92%), and other conditions were the same as those in Example 2.

[0115] Comparative Example 3

[0116] The precision molecular distillation process was not performed, and other conditions were the same as those in Example 3.

[0117] The examples and comparative examples were made into finished curing agents and subjected to performance tests. The test data are shown in Table 4 below:

[0118] Table 4

[0119] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Impact strength (kg·cm) 25 30 35 15 20 22 Tensile strength (MPa) 45 50 55 35 40 42 Flexural strength (MPa) 60 65 70 48 55 57 Shore hardness (A) 85 88 90 78 82 84 Heat deformation temperature (℃) 140 145 150 130 135 138 Water absorption (%) 0.5 0.4 0.3 0.8 0.6 0.7

[0120] The following information can be obtained from Table 1:

[0121] (1) Effect of cardanol derivatives on performance (Example and Comparative Example 1): The impact strength of Example 1 (25 kg·cm) is 67% higher than that of Comparative Example 1 (15 kg·cm), indicating that the addition of cardanol derivatives can enhance the toughness of the material; the tensile strength of Example 1 (45 MPa) is 28.6% higher than that of Comparative Example 1 (35 MPa), and the flexural strength (60 MPa) is 25% higher than that of Comparative Example 1 (48 MPa); the heat deformation temperature of Comparative Example 1 (130°C) is lower than that of Example 1 (140°C), indicating that cardanol derivatives can improve thermal stability by making the molecular chain flexible; the water absorption rate of Comparative Example 1 (0.8%) is higher than that of Example 1 (0.5%), because the hydrophobic groups of cardanol reduce water penetration.

[0122] (2) Effect of paraformaldehyde purity on condensation reaction (Example 2 and Comparative Example 2): The tensile strength (40 MPa) of Comparative Example 2 (85% paraformaldehyde) is lower than that of Example 2 (50 MPa) because the low purity leads to incomplete condensation reaction and insufficient cross-linking of the molecular chains; the heat deformation temperature (135°C) of Comparative Example 2 is 10°C lower than that of Example 2 (145°C) because the residual by-products affect the rigidity of the material; the water absorption rate (0.6%) of Comparative Example 2 is higher than that of Example 2 (0.4%), reflecting that the low purity paraformaldehyde leads to structural defects.

[0123] (3) Effect of precision molecular distillation on by-product control (Example 3 and Comparative Example 3): The impact strength of Comparative Example 3 (not distilled) (22 kg·cm) is lower than that of Example 3 (35 kg·cm) because the residual by-products (such as macromolecular impurities) increase the brittleness of the material; the Shore hardness (84A) and heat deformation temperature (138°C) of Comparative Example 3 are both lower than those of Example 3 (90A, 150°C), indicating that the by-products weaken the cross-linked network of the material when not distilled; the water absorption rate of Comparative Example 3 (0.7%) is higher than that of Example 3 (0.3%) because the hydrophilic by-products remain due to the lack of distillation.

[0124] Summary: The process of the present invention successfully achieves a balance between low sensitization, high toughness, fast drying and high thermal stability through precise molar ratio control, functional modification of cardanol and precise molecular distillation. Among them, Example 3 has the best comprehensive performance and can meet the application requirements of high-end epoxy resins (such as electronic packaging and aerospace coatings).

[0125] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process for a low-sensitivity, high-toughness, fast-drying epoxy curing agent, characterized in that: The following steps are involved: Step 1: Premix the raw materials: Add phenol, dimethylpentanediamine, and dimethylaminopropionitrile-phenol adduct in the formulated ratio into a four-necked flask equipped with a condenser, start stirring, and heat at a rate of 1-3°C / min until completely dissolved to form a homogeneous system. Step 2: Formaldehyde gradient condensation: Under nitrogen protection, slowly add paraformaldehyde in the formula ratio in 3-8 times. After the addition is completed, keep the reaction at 80-85°C for 3-4 hours, and continuously add nitrogen to maintain an inert atmosphere; Step 3: Deep dehydration: Use a vacuum water pump to perform dehydration treatment, control the system vacuum degree to less than 30 mmHg, and continue to vacuum until no water is analyzed; Step 4: Precision molecular distillation: Connect the reaction system to a microchannel-molecular distillation device to sequentially separate and remove low-boiling point components to obtain the target product; Step 5: Functional modification: Add the target product obtained by distillation to a cardanol derivative in a formula ratio, stir thoroughly to form a uniform system, and take samples for quality inspection; Step 6. Finished product preparation: After testing and confirming that all performance indicators meet the standards, quantitative packaging and sealing are carried out to obtain a low-sensitivity, high-toughness, fast-drying epoxy curing agent finished product.

2. The preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The weight parts of the raw materials and their preparation are: 10-30 parts of phenol; 20-60 parts of dimethylpentanediamine; 20-60 parts of dimethylaminopropionitrile phenol adduct; 20-60 parts of paraformaldehyde; 5-20 parts of cardanol derivative.

3. The preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The molar ratio of the phenol, dimethylpentanediamine, dimethylaminopropionitrile-phenol adduct and paraformaldehyde is fixed at 1:2:2:

2.

4. The preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The cardanol derivatives account for 5% to 20% of the total system.

5. The preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The concentration of the paraformaldehyde is between 91.95% and 92.05%.

6. The preparation process of a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: In the step 1, the raw materials are pre-mixed and heated to a temperature of 60-90°C.

7. The process for preparing a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: In the step 2, the temperature of the system in which formaldehyde is added to paraformaldehyde by gradient condensation is ≤70°C.

8. The process for preparing a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The vacuum degree of the system for deep dehydration treatment in step 3 is less than 30 mmHg.

9. The process for preparing a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: The precision molecular distillation process in step 4 is as follows: S4.

1. First, distill and recover the small molecular amine substance dimethylaminopropionitrile phenol adduct; S4.

2. Continue distillation to separate dimethylpentanediamine. Its molecular reaction formula is: In the formula, the first benzene ring structure with -OH on the left represents phenol, the middle one represents formaldehyde, and the chain structure with two amino groups on the right represents dimethylpentanediamine; S4.

3. Cut the target fraction to collect the desired intermediates; S4.

4. Finally, remove the high-boiling-point macromolecular by-products. The molecular reaction formula is: In the formula, the first benzene ring structure with -OH on the left also represents phenol, the middle one represents formaldehyde, and the right side has a chain structure with multiple nitrogen-containing groups.

10. The process for preparing a low-sensitivity, high-toughness, fast-drying epoxy curing agent according to claim 1, characterized in that: During the functional modification process in step 5, the stirring rate is controlled at 300-500 r / min, the stirring time is 1-2 hours, and the mixing temperature is maintained at 40-50°C.

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