An epoxy curing agent and its preparation method

Abstract

This application relates to the field of epoxy curing agents, and specifically discloses an epoxy curing agent and a preparation method thereof. The epoxy curing agent is a high-molecular compound obtained by a reaction other than a carbon-carbon unsaturated bond. The reaction process specifically includes: reacting isophorone diamine, tris(2,3-epoxypropyl) isocyanurate, and diglycidyl dimerate to obtain Product I; mixing and reacting phenols, Product I, and aldehydes under the protection of an inert gas and then performing post-treatment to obtain Product II; mixing Product I and Product II to obtain a mixture; reacting the mixture with epoxy methoxysilane, and then adding aminosilane and mixing evenly. The epoxy resin curing agent of this application can endow the epoxy resin cured product with both good flexibility and high strength and heat resistance, and can be widely used in heat-generating products such as fireproof coatings, electronics, and electrical appliances, and is particularly suitable for the preparation of materials such as intumescent epoxy fireproof coatings and high-temperature resistant coatings.

Description

Technical Field

[0001] This application relates to the field of epoxy curing agents, and more specifically, to an epoxy curing agent and a preparation method thereof. Background Art

[0002] Epoxy resin cured products have excellent comprehensive properties, including excellent adhesion properties, chemical resistance, electrical insulation properties, and molding and processing properties, etc. Among them, the adhesion property is the most prominent, and it is widely used in industries such as aerospace, automotive, machinery, adhesives, electronic instruments, construction, light industry, paints, and electronics. However, the benzene ring existing in the structure of epoxy resin itself, while endowing it with characteristics such as high strength, good adhesion, and strong chemical medium resistance, also makes the epoxy resin cured products generally have the problem of poor flexibility, which greatly limits the application of epoxy resin cured products in many fields.

[0003] Since the epoxy curing agent is an important component of the epoxy resin system, its structure and properties can directly affect the properties of the epoxy resin cured product, and compared with modifying the epoxy resin, modifying the epoxy curing agent is simpler. Therefore, many researchers choose to start from the epoxy curing agent to improve the flexibility of the epoxy resin cured product. The existing toughening methods mainly introduce flexible molecular chain segments into the epoxy curing agent. Although this method can improve the toughness of the epoxy resin cured product, it significantly reduces the strength of the material and greatly sacrifices the heat resistance of the material, making it unable to be widely used in heat-generating products such as fireproof coatings and electronic appliances. Summary of the Invention

[0004] In order to solve the above technical problems, this application provides an epoxy curing agent and a preparation method thereof.

[0005] In the first aspect, an epoxy curing agent provided by this application adopts the following technical solution:

[0006] An epoxy curing agent, which is prepared from isophorone diamine, isocyanuric acid triglycidyl ester, dimer acid diglycidyl ester, phenols, aldehydes, epoxy group methoxysilane, and amino silane through reactions other than carbon-carbon unsaturated bonds; the specific process of this reaction includes the following steps:

[0007] S1. React isophorone diamine, tris(isocyanuric acid triglycidyl ester), and dimer acid diglycidyl ester with a molar ratio of (12 - 14):1:1 at a temperature of 35 - 45 °C for 3 - 4 h, and then remove the unreacted monomer amine by vacuum distillation to obtain Product I;

[0008] S2. At a temperature of 40 - 50 °C, mix phenols, product I, and aldehydes with a molar ratio of 1:(1.4 - 1.6):(1.1 - 1.3), then under the protection of an inert gas, heat up to 100 - 110 °C and keep the temperature for 1.5 - 2.5 h, and then through post-treatment, product II is obtained;

[0009] S3. Mix product I and product II with a weight ratio of (1.8 - 2.2):1 to obtain a mixture;

[0010] S4. At a temperature of 85 - 95 °C, react the mixture with epoxy methoxysilane for 45 - 90 min, then keep the temperature for 30 - 40 min. The molar ratio of epoxy group to amine hydrogen is (0.7 - 1.5):1, and then add aminosilane and mix evenly. The addition amount of aminosilane is 1 - 2% of the total mass of the system to obtain an epoxy curing agent.

[0011] By adopting the above technical solutions, in this application, isophorone diamine is first used as the basic amine to react with tris(2,3-epoxypropyl) isocyanurate and diglycidyl dimerate, so that the obtained product I has good flexibility while also having high strength and heat resistance. Specifically, compared with straight-chain amines, isophorone diamine with a cyclic structure has better compatibility with epoxy resins, and can provide the rigidity of a network structure for the epoxy resin cured product during the curing process. The triazine ring structure contained in tris(2,3-epoxypropyl) isocyanurate endows the material with excellent heat resistance, and the addition of diglycidyl dimerate can make the material have a long fatty chain flexible structure, dispersing the stress in the material, thus ensuring the flexibility of the material. Then in this application, product I is reacted with phenols and aldehydes to obtain product II with a relatively small relative mass and high reactivity, which can further increase the crosslinking density of the epoxy resin cured product during the curing process, so that the material has good strength, impact performance, and heat resistance.

[0012] After that, in this application, product I and product II are mixed and then reacted with epoxy methoxysilane in the subsequent reaction, which can make the large molecular weight product and the small molecular weight product better fuse, increase their compatibility and compatibility, balance various excellent properties of the product, and enable the material to simultaneously have high strength, high heat resistance, and high toughness. Finally, aminosilane is added, which not only uses the two active hydrogens it carries to react with epoxy groups, but also uses the three siloxane bonds it carries to hydrolyze to form silanols and react with hydroxyl groups, increasing the crosslinking density of the epoxy resin cured product, further improving the strength and heat resistance of the material, and enabling the epoxy resin cured product to be applicable to a wider range of fields.

[0013] Preferably, the diglycidyl dimerate is prepared by the following method:

[0014] At a temperature of 85 - 95 °C, react dimer acid, epichlorohydrin and a catalyst with a weight ratio of 1:(7 - 10):(0.015 - 0.025) for 1 - 2 h to obtain an intermediate. Then, at a temperature of 50 - 60 °C, react the intermediate with a weight ratio of 1:(3.5 - 4.5) and a sodium hydroxide solution with a concentration of 25 - 35 wt% for 3.5 - 4.5 h to obtain a crude product. After that, perform post-treatment on the crude product to obtain diglycidyl dimerate.

[0015] By adopting the above technical solution, the diglycidyl dimerate prepared by the two-step method of esterification reaction and cyclization reaction in this application has a high epoxy value, and can greatly improve the impact strength of the material with almost no sacrifice of strength, making the material have excellent flexibility, strength and heat resistance.

[0016] Optionally, the catalyst includes one of stannic chloride anhydrous, tetrabutylammonium bromide, cetyltrimethylammonium bromide and benzyltriethylammonium chloride.

[0017] By adopting the above technical solution, using one of stannic chloride anhydrous, tetrabutylammonium bromide, cetyltrimethylammonium bromide and benzyltriethylammonium chloride as the catalyst in this application can effectively improve the efficiency and purity of the preparation of diglycidyl dimerate. Specifically, stannic chloride anhydrous, tetrabutylammonium bromide, cetyltrimethylammonium bromide and benzyltriethylammonium chloride all have good catalytic activity and selectivity, can promote the reaction between dimer acid and epichlorohydrin, reduce the occurrence of side reactions, thereby improving the yield and quality of the product. At the same time, the use conditions of these catalysts are mild and easy to operate, which helps to reduce production costs and enhance the feasibility of the process.

[0018] Preferably, the catalyst includes tetrabutylammonium bromide.

[0019] By adopting the above technical solution, further selecting a quaternary ammonium salt with a tetrabutyl structure as the catalyst in this application can make the cyclization reaction more active and the ring closure more complete, so that the glycidyl ester has a better epoxy value, and further improve its toughening effect on the material.

[0020] Optionally, the phenols include one or more of cardanol, phenol and nonylphenol.

[0021] Through the above technical solution, using one or more of cardanol, phenol and nonylphenol as phenols to react with product I and aldehydes in this application can make the prepared epoxy resin curing agent have good flexibility, heat resistance, reaction activity and strength, thereby improving the various properties of the epoxy resin cured product.

[0022] Preferably, the phenols include cardanol and phenol with a weight ratio of 1:(1.8 - 2.2).

[0023] By adopting the above technical solution, the present application further uses a mixture of cardanol and phenol, which can enable the prepared curing agent to have excellent impact performance while also having good heat resistance, high activity, and a relatively appropriate pot life, improving the comprehensive performance of the epoxy resin cured product.

[0024] Preferably, the phenols are mixed by the following method:

[0025] At a temperature of 40 - 50 °C, cardanol and phenol are mixed evenly, then p-toluenesulfonic acid is added, and the dosage of p-toluenesulfonic acid is 0.8 - 1.2% of the total mass of cardanol and phenol. After the p-toluenesulfonic acid is completely dissolved, the temperature is raised to 90 - 95 °C and the reaction is carried out under insulation for 1 - 1.5 h.

[0026] By adopting the above technical solution, uniform mixing of phenolic substances can be achieved, and the subsequent reaction can be effectively promoted. Specifically, by pre-mixing cardanol and phenol at 40 - 50 °C, ensuring the full dispersion of the two substances, and then adding an appropriate amount of p-toluenesulfonic acid as a catalyst to further improve the reaction activity. After the p-toluenesulfonic acid is completely dissolved, raising the temperature to 90 - 95 °C and carrying out the reaction under insulation for 1 - 1.5 h can effectively improve the reaction efficiency of phenolic substances and the uniformity of the product, thereby providing more stable performance for the finally prepared epoxy curing agent. Experimental results show that compared with the method of adding p-toluenesulfonic acid after phenol is completely melted at a temperature of 50 - 60 °C, adding cardanol after the p-toluenesulfonic acid is completely dissolved, and carrying out the reaction under insulation at 125 °C for 3 h, the mixed phenol obtained by the method of the present application has better effects in improving the toughness, strength, and heat resistance of the curing agent.

[0027] Preferably, the aldehydes include paraformaldehyde.

[0028] By adopting the above technical solution, the present application further uses paraformaldehyde instead of formaldehyde as the aldehyde, which can achieve a more accurate ratio, reduce side reactions introduced by moisture, and at the same time reduce the energy consumption and wastewater treatment pressure in the industrial process, being more environmentally friendly, with a simple process and high safety.

[0029] In the second aspect, a preparation method of an epoxy curing agent provided by the present application adopts the following technical solution:

[0030] A preparation method of an epoxy curing agent includes the following steps:

[0031] S1. React isophorone diamine, tris(isocyanatotrimethyl)glycidyl isocyanurate, and diglycidyl dimerate with a molar ratio of (12 - 14):1:1 at a temperature of 35 - 45 °C for 3 - 4 h, and then remove the unreacted monomer amine by vacuum distillation to obtain product I;

[0032] S2. At a temperature of 40 - 50 °C, mix phenols, product I, and aldehydes with a molar ratio of 1:(1.4 - 1.6):(1.1 - 1.3), then heat up to 100 - 110 °C under the protection of an inert gas and keep the temperature for 1.5 - 2.5 h. After post-treatment, product II is obtained;

[0033] S3. Mix product I and product II with a weight ratio of (1.8 - 2.2):1 to obtain a mixture;

[0034] S4. At a temperature of 85 - 95 °C, react the mixture with epoxy methoxysilane for 45 - 90 min, then keep the temperature for 30 - 40 min. The molar ratio of epoxy group to amine hydrogen is (0.7 - 1.5):1. Then add aminosilane and mix evenly. The addition amount of aminosilane is 1 - 2% of the total mass of the system to obtain an epoxy curing agent.

[0035] By adopting the above technical solution, the epoxy curing agent prepared in this application, after curing with epoxy resin, can make the epoxy resin cured product not only have good flexibility, but also have high strength and heat resistance. It can be widely used in heat-generating products such as fireproof coatings, electronic appliances, etc., and is especially suitable for the preparation of materials such as intumescent epoxy fireproof coatings and high-temperature resistant coatings.

[0036] In summary, this application has the following beneficial technical effects:

[0037] 1. The epoxy resin curing agent of this application can make the epoxy resin cured product have both good flexibility, high strength and heat resistance, and can withstand a relatively high temperature. Under high-temperature conditions, it can remain non-powdering and non-cracking for a long time, and still can play a good protective role for the substrate. It can be widely used in heat-generating products such as fireproof coatings, electronic appliances, etc., and is especially suitable for the preparation of materials such as intumescent epoxy fireproof coatings and high-temperature resistant coatings;

[0038] 2. The preparation method of this application has simple steps, is easy to operate, has high environmental protection and safety, and is suitable for large-scale industrial production. Detailed Embodiments

[0039] The following further elaborates on this application with reference to examples.

[0040] All raw materials used in this application are commercially available products unless otherwise specified, among which:

[0041] Triglycidyl isocyanurate, also known as isocyanuric acid triglycidyl ester (TGIC), with a CAS number of 2451 - 62 - 9.

[0042] The epoxy group methoxysilane is specifically 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, with a CAS number of 65799-47-5 and a molecular weight of 220.34.

[0043] The general structural formula of the aminosilane is ;

[0044] When n is 1, this substance is (3-aminopropyl)trimethoxysilane, with a CAS number of 13822-56-5; when n is 2, this substance is (3-aminopropyl)triethoxysilane, with a CAS number of 919-30-2; and so on. In the specific embodiments of the present application, (3-aminopropyl)triethoxysilane is taken as an example for illustration.

[0045] Preparation Example 1.1

[0046] The diglycidyl dimerate is prepared by the following method:

[0047] At a temperature of 85 °C, 1 kg of dimer acid, 7 kg of epichlorohydrin and 0.015 kg of anhydrous stannic chloride are reacted for 1 h to obtain an intermediate. Then, at a temperature of 50 °C, the intermediate is reacted with a sodium hydroxide solution with a concentration of 25 wt% for 3.5 h. The amount of the sodium hydroxide solution used is 3.5 times the weight of the intermediate to obtain a crude product. Then, the crude product is added to toluene for extraction, allowed to stand, the saline-alkali solution is removed, washed and neutralized to a pH value of 7, and the oil phase is subjected to vacuum distillation to remove the excessive epichlorohydrin and toluene to obtain diglycidyl dimerate, and its epoxy value is 0.1213 mol / 100 g.

[0048] Preparation Example 1.2

[0049] The diglycidyl dimerate is prepared by the following method:

[0050] At a temperature of 95 °C, 1 kg of dimer acid, 10 kg of epichlorohydrin and 0.025 kg of anhydrous stannic chloride are reacted for 2 h to obtain an intermediate. Then, at a temperature of 60 °C, the intermediate is reacted with a sodium hydroxide solution with a concentration of 35 wt% for 4.5 h. The amount of the sodium hydroxide solution used is 4.5 times the weight of the intermediate to obtain a crude product. Then, the crude product is added to toluene for extraction, allowed to stand, the saline-alkali solution is removed, washed and neutralized to a pH value of 7, and the oil phase is subjected to vacuum distillation to remove the excessive epichlorohydrin and toluene to obtain diglycidyl dimerate, and its epoxy value is 0.2275 mol / 100 g.

[0051] Preparation Example 1.3

[0052] The difference from Preparation Example 1.1 is that anhydrous stannic chloride is replaced by tetrabutylammonium bromide, and the rest is the same as Preparation Example 1.1. The epoxy value of the diglycidyl dimerate obtained is 0.2076 mol / 100 g.

[0053] Preparation Example 1.4

[0054] The difference from Preparation Example 1.1 is that anhydrous stannic chloride is replaced by cetyltrimethylammonium bromide, and the rest is the same as Preparation Example 1.1. The epoxy value of the diglycidyl dimerate obtained is 0.1143 mol / 100 g.

[0055] Preparation Example 1.5

[0056] The difference from Preparation Example 1.1 is that anhydrous stannic chloride is replaced by benzyltriethylammonium chloride, and the rest is the same as Preparation Example 1.1. The epoxy value of the diglycidyl dimerate obtained is 0.1676 mol / 100 g.

[0057] Preparation Example 2.1

[0058] The phenols are mixed by the following method:

[0059] At a temperature of 40 °C, cardanol and phenol with a weight ratio of 1:1.8 are mixed evenly, and then p-toluenesulfonic acid is added. The dosage of p-toluenesulfonic acid is 0.8% of the total mass of cardanol and phenol. After p-toluenesulfonic acid is completely dissolved, the temperature is raised to 90 °C and the reaction is kept for 1.5 h.

[0060] Preparation Example 2.2

[0061] The phenols are mixed by the following method:

[0062] At a temperature of 50 °C, cardanol and phenol with a weight ratio of 1:2.2 are mixed evenly, and then p-toluenesulfonic acid is added. The dosage of p-toluenesulfonic acid is 1.2% of the total mass of cardanol and phenol. After p-toluenesulfonic acid is completely dissolved, the temperature is raised to 95 °C and the reaction is kept for 1 h.

[0063] Preparation Example 2.3

[0064] The phenols are mixed by the following method:

[0065] Heat phenol to 40°C. After the phenol is completely melted, add p-toluenesulfonic acid. The dosage of p-toluenesulfonic acid is 0.8% of the total mass of cardanol and phenol. After the p-toluenesulfonic acid is completely dissolved, add cardanol. The weight ratio of cardanol to phenol is 1:1.8, and then heat up to 125°C and keep the temperature for reaction for 3 h. After the reaction is completed, while it is still hot, wash away the unreacted phenol with hot water until the washing liquid does not turn the 10% ferric chloride solution purple. Dehydrate under a vacuum condition of -0.097 to -0.098 MPa until no more water is removed (if no water is removed when the dehydration temperature exceeds 90°C, it can be considered that the water has been completely removed, but the dehydration temperature shall not exceed 130°C). After the dehydration is completed, cool to room temperature.

[0066] Preparation Example 2.4

[0067] The difference from Preparation Example 2.1 is that: the weight ratio of cardanol to phenol is 1:1, and the rest are the same as Preparation Example 2.1.

[0068] Preparation Example 2.5

[0069] The difference from Preparation Example 2.1 is that: the weight ratio of cardanol to phenol is 1:3, and the rest are the same as Preparation Example 2.1.

[0070] Example 1.1

[0071] A preparation method of an epoxy curing agent, comprising the following steps:

[0072] S1. React isophorone diamine, tris(isocyanatotrimethyl)glycidyl ether and the diglycidyl dimer acid ester prepared in Preparation Example 1.1 with a molar ratio of 12:1:1 at a temperature of 35°C for 4 h, and then remove the unreacted monomer amine by vacuum distillation to obtain Product I;

[0073] S2. Cool the phenols prepared in Preparation Example 2.1 to 40°C, then add Product I and paraformaldehyde and mix them evenly, and heat up to 100°C and keep the temperature for reaction for 2.5 h under nitrogen protection. The molar ratio of the phenols prepared in Preparation Example 2.1, Product I and paraformaldehyde is 1:1.4:1.1. After the reaction is completed, cool to 80°C, and dehydrate under a vacuum condition of -0.097 to -0.098 MPa with the dehydration temperature maintained at 80°C until no more water is removed. After the dehydration is completed, obtain Product II;

[0074] S3. Mix Product I and Product II with a weight ratio of 1.8:1 to obtain a mixture;

[0075] S4. At a temperature of 85 °C, react the mixture with 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane for 90 min, then keep warm for 30 min. The molar ratio of epoxy group to amine hydrogen is 0.7:1. Then add (3-aminopropyl)triethoxysilane and mix evenly. The addition amount of (3-aminopropyl)triethoxysilane is 1% of the total mass of the system to obtain an epoxy curing agent.

[0076] Example 1.2

[0077] A preparation method of an epoxy curing agent includes the following steps:

[0078] S1. React isophorone diamine, tris(isocyanatotrimethyl)glycidyl isocyanurate and the dimer acid diglycidyl ester prepared in Preparation Example 1.2 at a molar ratio of 14:1:1 at a temperature of 45 °C for 3 h, then remove the unreacted monomer amine by vacuum distillation to obtain Product I;

[0079] S2. Cool the phenol prepared in Preparation Example 2.2 to 50 °C, then add Product I and paraformaldehyde and mix evenly, and heat up to 110 °C under nitrogen protection and keep warm for 1.5 h. The molar ratio of the phenol prepared in Preparation Example 2.2, Product I and paraformaldehyde is 1:1.6:1.3. After the reaction, cool down to 80 °C, and carry out pressure dehydration under a vacuum condition of -0.097~-0.098 MPa. The dehydration temperature is maintained at 80 °C until no water is removed. After the dehydration is completed, obtain Product II;

[0080] S3. Mix Product I and Product II at a weight ratio of 2.2:1 to obtain a mixture;

[0081] S4. At a temperature of 95 °C, react the mixture with 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane for 45 min, then keep warm for 40 min. The molar ratio of epoxy group to amine hydrogen is 1.5:1. Then add (3-aminopropyl)triethoxysilane and mix evenly. The addition amount of (3-aminopropyl)triethoxysilane is 2% of the total mass of the system to obtain an epoxy curing agent.

[0082] Example 2.1

[0083] A preparation method of an epoxy curing agent, different from Example 1.1 in that: the dimer acid diglycidyl ester prepared in Preparation Example 1.1 is replaced by the dimer acid diglycidyl ester prepared in Preparation Example 1.3, and the rest is the same as Example 1.1.

[0084] Example 2.2

[0085] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the diglycidyl dimerate prepared in Preparation Example 1.1 is replaced with the diglycidyl dimerate prepared in Preparation Example 1.4, and the rest is the same as in Example 1.1.

[0086] Example 2.3

[0087] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the diglycidyl dimerate prepared in Preparation Example 1.1 is replaced with the diglycidyl dimerate prepared in Preparation Example 1.5, and the rest is the same as in Example 1.1.

[0088] Example 3.1

[0089] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced with the phenols prepared in Preparation Example 2.3. The phenols prepared in Preparation Example 2.3 are heated to 40 °C, then Product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 100 °C and kept warm for reaction for 2.5 h. The molar ratio of the phenols prepared in Preparation Example 2.3, Product I and paraformaldehyde is 1:1.4:1.1. After the reaction is completed, the temperature is lowered and dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa, and the dehydration temperature is maintained at 80 °C until no water is removed. After the dehydration is completed, Product II is obtained, and the rest is the same as in Example 1.1.

[0090] Example 3.2

[0091] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced with phenol. Phenol is heated to 40 °C, then Product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 85 °C and kept warm for reaction for 2.5 h. The molar ratio of phenol, Product I and paraformaldehyde is 1:1.4:1.1. After the reaction is completed, dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed. After the dehydration is completed, Product II is obtained, and the rest is the same as in Example 1.1.

[0092] Example 3.3

[0093] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced with cardanol. Cardanol is heated to 40 °C, then Product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 75 °C and kept warm for reaction for 4 h. The molar ratio of cardanol, Product I and paraformaldehyde is 1:1.4:1.1. After the reaction is completed, dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed. After the dehydration is completed, Product II is obtained, and the rest is the same as in Example 1.1.

[0094] Example 3.4

[0095] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols obtained in Preparation Example 2.1 are replaced with nonylphenol, the nonylphenol is heated to 40 °C, then Product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 85 °C and kept warm for reaction for 2.5 h. The molar ratio of nonylphenol, Product I and paraformaldehyde is 1:1.4:1.1. After the reaction is completed, dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed. After the dehydration is completed, Product II is obtained, and the rest is the same as Example 1.1.

[0096] Example 3.5

[0097] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols obtained in Preparation Example 2.1 are replaced with the phenols obtained in Preparation Example 2.4, and the rest is the same as Example 1.1.

[0098] Example 3.6

[0099] A preparation method of an epoxy curing agent, which is different from Example 1.1 in that: the phenols obtained in Preparation Example 2.1 are replaced with the phenols obtained in Preparation Example 2.5, and the rest is the same as Example 1.1.

[0100] Comparative Example 1

[0101] It is different from Example 1.1 in that: tris(2,3-epoxypropyl)isocyanurate in step S1 is removed, and the rest is the same as Example 1.1.

[0102] Comparative Example 2

[0103] It is different from Example 1.1 in that: diglycidyl dimerate in step S1 is removed, and the rest is the same as Example 1.1.

[0104] Comparative Example 3

[0105] It is different from Example 1.1 in that: step S3 is removed, and Product II is directly subjected to the subsequent steps, and the rest is the same as Example 1.1.

[0106] Comparative Example 4

[0107] It is different from Example 1.1 in that: (3-aminopropyl)triethoxysilane in step S4 is removed, and the rest is the same as Example 1.1.

[0108] Comparative Example 5

[0109] The difference from Example 1.1 is that isophorone diamine in step S1 is replaced with ethylenediamine, and the rest is the same as in Example 1.1.

[0110] Performance testing

[0111] The epoxy resin curing agents prepared in the above examples and comparative examples were mixed evenly with bisphenol A epoxy resin (model E44) according to a certain ratio, so that the hydrogen atoms on the amino group of the epoxy curing agent and the epoxy groups on the bisphenol A epoxy resin were kept in equimolar amounts. Then, it was poured into a mold and pre-cured at 25 °C for 3 h, and then placed in an oven and cured at 80 °C for 8 h. After taking out and cooling, a test material of epoxy resin cured product was obtained. The tensile properties, impact resistance and heat resistance of the prepared epoxy resin cured products were tested respectively. Among them, the tensile property test was carried out on a universal testing machine with reference to the standard of GB / T 1040.1-2006, the tensile rate was 50 mm / min, the width of the test material was 10 ± 0.5 mm, and the thickness was 4 ± 0.5 mm; the impact resistance was tested with reference to the simple supported beam impact toughness test in the standard of GB / T 1043.1-2008, the pendulum energy was 2.75 J, and the specification of the test material was 80 mm × 10 mm × 4 mm; the heat resistance was tested by using a DIAMOND TG / DTA analyzer of PERKIN ELMER company to test the thermal weight loss of the test material, and the temperature when the test material lost 5% of its weight was recorded. The above results are all recorded in Table 1.

[0112] Table 1 Performance test results

[0113]

[0114] Data analysis:

[0115] As can be seen from Table 1, the epoxy resin curing agents prepared in Examples 1.1 - 1.2 of the present application can make the tensile strength of the epoxy resin cured product reach 81.33 - 82.58 MPa, the impact strength reach 31.22 - 33.56 KJ / m 2 , and the temperature when the mass loss is 5% is 317 - 320 °C, which obviously has relatively high strength, flexibility and heat resistance.

[0116] Examples 2.1 - 2.3 are different from Example 1.1 in that different catalysts are used in the preparation of diglycidyl dimerate. As can be seen from Table 1, the impact strength of the epoxy resin cured product corresponding to Example 2.1 is slightly higher than that of Example 1.1, and the impact strengths corresponding to Examples 2.2 - 2.3 are slightly lower than that of Example 1.1. The experimental data show that the choice of catalyst will affect the epoxy value of diglycidyl dimerate, thereby affecting the flexibility of the epoxy resin cured product. Among them, when anhydrous stannic chloride is selected as the catalyst, the epoxy value of the prepared diglycidyl dimerate is the highest, and the flexibility of the corresponding epoxy resin cured product is the best.

[0117] Examples 3.1 - 3.4 are different from Example 1.1 in that different phenols are used in step S2. As can be seen from Table 1, the properties of the epoxy resin cured product corresponding to Example 3.1 are slightly lower than those of Example 1.1. The experimental results show that compared with the mixing method of Preparation Example 2.3, the mixing method of Preparation Example 2.1 can further improve the properties of the epoxy resin cured product. The impact strength of the epoxy resin cured product corresponding to Example 3.2 is significantly lower than that of Example 1.1. The experimental data show that using only phenol as the phenol will significantly reduce the flexibility of the epoxy resin cured product. The tensile strength and thermal weight loss temperature of the epoxy resin cured product corresponding to Example 3.3 are significantly lower than those of Example 1.1. The experimental data show that using only cardanol as the phenol will significantly reduce the strength and heat resistance of the epoxy resin cured product. The impact strength of the epoxy resin cured product corresponding to Example 3.4 is significantly lower than that of Example 1.1. The experimental data show that using only nonylphenol as the phenol will significantly reduce the flexibility of the epoxy resin cured product.

[0118] Examples 3.5 - 3.6 are different from Example 1.1 in that the ratio of phenol to cardanol in the phenols of step S2 is different. As can be seen from Table 1, the epoxy resin cured products corresponding to Examples 3.5 - 3.6 are either lower than Example 1.1 in terms of tensile strength and thermal weight loss temperature or lower than Example 1.1 in terms of impact strength. The experimental results show that further optimizing the ratio between phenol and cardanol can comprehensively improve the strength, heat resistance and flexibility of the epoxy resin cured product.

[0119] Comparative Example 1 is different from Example 1.1 in that triglycidyl isocyanurate is not added. As can be seen from Table 1, both the tensile strength and thermal weight loss temperature of Comparative Example 1 are significantly lower than those of Example 1.1. The experimental results show that the addition of triglycidyl isocyanurate can improve the strength and heat resistance of the epoxy resin cured product.

[0120] The difference between Comparative Example 2 and Example 1.1 is that diglycidyl dimerate is not added. As can be seen from Table 1, the impact strength of Comparative Example 2 is significantly lower than that of Example 1.1. The experimental results show that the addition of diglycidyl dimerate can improve the flexibility of the epoxy resin cured product.

[0121] The difference between Comparative Example 3 and Example 1.1 is that only small molecule substances are used for the subsequent reaction. As can be seen from Table 1, the tensile strength and thermal weight loss temperature of Comparative Example 3 are both significantly lower than those of Example 1.1. The experimental results show that the combined use of macromolecule substances and small molecule substances can balance the flexibility, strength and heat resistance of the epoxy resin cured product.

[0122] The difference between Comparative Example 4 and Example 1.1 is that (3-aminopropyl)triethoxysilane is not added. As can be seen from Table 1, all the properties of Comparative Example 4 are lower than those of Example 1.1. The experimental results show that the addition of (3-aminopropyl)triethoxysilane can improve the comprehensive properties of the epoxy resin cured product.

[0123] The difference between Comparative Example 5 and Example 1.1 is that aliphatic cyclic amine is replaced by straight-chain amine. As can be seen from Table 1, the tensile strength and thermal weight loss temperature of Comparative Example 5 are both lower than those of Example 1.1. The experimental results show that compared with straight-chain amine, aliphatic cyclic amine can further improve the strength and heat resistance of the epoxy resin cured product.

[0124] The examples of this specific implementation mode are all preferred examples of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of this application should be covered within the protection scope of this application.

Claims

1. An epoxy curing agent, characterized in that The epoxy curing agent is prepared by using isophorone diamine, triglycidyl isocyanate, diglycidyl dimer acid, phenols, aldehydes, epoxymethoxysilane and aminosilane as raw materials through a reaction other than carbon-carbon unsaturated bonds; the reaction process specifically includes the following steps: S1, reacting isophorone diamine, triglycidyl triisocyanate and dimer acid diglycidyl ester in a molar ratio of (12-14):1:1 at a temperature of 35-45°C for 3-4h, and then removing unreacted monomer amine by distillation under reduced pressure to obtain product I; S2. At a temperature of 40-50°C, phenols, product I and aldehydes in a molar ratio of 1:(1.4-1.6):(1.1-1.3) are mixed, and then the temperature is raised to 100-110°C under the protection of inert gas for 1.5-2.5 hours, and then post-treated to obtain product II; S3, mixing product I and product II in a weight ratio of (1.8-2.2):1 to obtain a mixture; S4. At a temperature of 85-95°C, react the mixture with epoxymethoxysilane for 45-90 minutes, and then keep warm for 30-40 minutes. The molar ratio of epoxy group to amine hydrogen is (0.7-1.5):

1. Aminosilane is then added and mixed evenly. The amount of aminosilane added is 1-2% of the total mass of the system to obtain an epoxy curing agent.

2. An epoxy curing agent according to claim 1, characterized in that: The dimer acid diglycidyl ester is prepared by the following method: At a temperature of 85-95°C, dimer acid, epichlorohydrin and a catalyst in a weight ratio of 1: (7-10): (0.015-0.025) are reacted for 1-2 hours to obtain an intermediate, and then at a temperature of 50-60°C, the intermediate in a weight ratio of 1: (3.5-4.5) is reacted with a sodium hydroxide solution with a concentration of 25-35wt% for 3.5-4.5 hours to obtain a crude product, and then the crude product is post-treated to obtain dimer acid diglycidyl ester.

3. An epoxy curing agent according to claim 2, characterized in that: The catalyst includes one of anhydrous tin tetrachloride, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide and benzyltriethylammonium chloride.

4. An epoxy curing agent according to claim 3, characterized in that: The catalyst includes tetrabutylammonium bromide.

5. An epoxy curing agent according to claim 1, characterized in that: The phenols include one or more of cardanol, phenol and nonylphenol.

6. An epoxy curing agent according to claim 5, characterized in that: The phenols include cardanol and phenol in a weight ratio of 1:(1.8-2.2).

7. An epoxy curing agent according to claim 6, characterized in that: The phenols are mixed in the following manner: At a temperature of 40-50°C, mix cardanol and phenol evenly, then add p-toluenesulfonic acid, the amount of p-toluenesulfonic acid is 0.8-1.2% of the total mass of cardanol and phenol. After the p-toluenesulfonic acid is completely dissolved, heat to 90-95°C and keep the reaction for 1-1.5 hours.

8. An epoxy curing agent according to claim 1, characterized in that: The aldehydes include paraformaldehyde.

9. A method for preparing an epoxy curing agent, characterized in that: The following steps are involved: S1, reacting isophorone diamine, triglycidyl triisocyanate and dimer acid diglycidyl ester in a molar ratio of (12-14):1:1 at a temperature of 35-45°C for 3-4h, and then removing unreacted monomer amine by distillation under reduced pressure to obtain product I; S2. At a temperature of 40-50°C, phenols, product I and aldehydes in a molar ratio of 1:(1.4-1.6):(1.1-1.3) are mixed, and then the temperature is raised to 100-110°C under the protection of inert gas for 1.5-2.5 hours, and then post-treated to obtain product II; S3, mixing product I and product II in a weight ratio of (1.8-2.2):1 to obtain a mixture; S4. At a temperature of 85-95°C, react the mixture with epoxymethoxysilane for 45-90 minutes, and then keep warm for 30-40 minutes. The molar ratio of epoxy group to amine hydrogen is (0.7-1.5):

1. Aminosilane is then added and mixed evenly. The amount of aminosilane added is 1-2% of the total mass of the system to obtain an epoxy curing agent.

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