Epoxy curing agent and preparation method thereof

Abstract

The invention relates to the field of epoxy hardeners, and particularly discloses an epoxy hardener and a preparation method thereof. The epoxy curing agent is a high-molecular compound obtained by reaction except for a carbon-carbon unsaturated bond, and the reaction process specifically comprises the following steps: performing reaction on isophorone diamine, triglycidyl triisocyanate and dimer acid diglycidyl ester to obtain a product I; performing mixed reaction on phenols, the product I and aldehydes under the protection of inert gas, and performing post-treatment to obtain a product II; mixing the product I and the product II to obtain a mixture; and reacting the mixture with epoxy methoxy silane, adding amino silane, and uniformly mixing. The epoxy resin curing agent provided by the invention can enable an epoxy resin cured product to have good flexibility and relatively high strength and heat resistance, can be widely applied to heat-generating products such as fireproof coatings and electronic and electric appliances, and is particularly suitable for preparation of materials such as intumescent epoxy fireproof coatings and high-temperature-resistant coatings.

Description

Technical Field

[0001] The present invention 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 bonding properties, chemical resistance, electrical insulation properties, and molding and processing properties, among which the bonding properties are the most outstanding. They are widely used in aerospace, automobile, machinery, adhesives, electronic instruments, construction, light industry, paint, electronics and other industries. However, the benzene rings in the structure of epoxy resin itself, while giving it high strength, good adhesion, and strong resistance to chemical media, also make epoxy resin cured products generally have poor flexibility, which greatly limits the application of epoxy resin cured products in many fields.

[0003] Since epoxy resin curing agent is an important component of epoxy resin system, its structure and properties can directly affect the performance of epoxy resin cured product, and compared with modifying epoxy resin, it is simpler to modify epoxy resin curing agent, so many researchers choose to start with epoxy resin curing agent to improve the flexibility of epoxy resin cured product. The existing toughening method is mainly to introduce flexible molecular segments into epoxy resin curing agent, but although this method can improve the toughness of 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 fire retardant coatings, electronic appliances and other heat-generating products. Summary of the invention

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

[0005] In the first aspect, the present application provides an epoxy curing agent, which adopts the following technical solution: An 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 comprises 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.

[0006] By adopting the above technical scheme, the present application first uses isophorone diamine as a basic amine to react with triisocyanate triglycidyl and dimer acid diglycidyl, so that the obtained product I can have good flexibility while also having high strength and heat resistance. Specifically, compared to straight-chain amines, isophorone diamine with a cyclic structure can have better compatibility with epoxy resin, and can provide the rigidity of a network structure for epoxy resin cured product during the curing process, the triazine ring structure contained in triisocyanate triglycidyl gives the material excellent heat resistance, and the addition of dimer acid diglycidyl can make the material have a long fatty chain flexible structure, disperse the stress in the material, thereby ensuring the flexibility of the material. Then the present application reacts product I with phenols and aldehydes to obtain a product II with relatively small mass and high reaction activity, which can further improve the cross-linking density of epoxy resin cured product during the curing process, so that the material has good strength, impact resistance and heat resistance.

[0007] After that, the present application mixes product I and product II and then conducts a subsequent reaction with epoxymethoxysilane, which can make the high molecular weight product and the low molecular weight product better integrated, increase their compatibility and compatibility, balance the various excellent properties of the product, and enable the material to have high strength, high heat resistance and high toughness at the same time. Finally, aminosilane is added, which not only utilizes its two active hydrogens to react with epoxy groups, but also utilizes its three silicon oxygen bonds to hydrolyze to form silanols, which react with hydroxyl groups, thereby increasing the crosslinking density of epoxy resin cured products, further improving the strength and heat resistance of the material, and enabling epoxy resin cured products to be applicable to a wider range of fields.

[0008] Preferably, 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.

[0009] By adopting the above technical scheme, the dimer acid diglycidyl ester prepared by the two-step method of esterification reaction and cyclization reaction in the present application has a high epoxy value, which can greatly improve the impact strength of the material without sacrificing strength, so that the material has excellent flexibility, strength and heat resistance.

[0010] Optionally, the catalyst includes one of anhydrous tin tetrachloride, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide and benzyltriethylammonium chloride.

[0011] By adopting the above technical scheme, the present application adopts one of anhydrous tin tetrachloride, tetrabutylammonium bromide, hexadecyltrimethylammonium bromide and benzyltriethylammonium chloride as a catalyst to effectively improve the efficiency and purity of dimer acid diglycidyl ester preparation. Specifically, anhydrous tin tetrachloride, tetrabutylammonium bromide, hexadecyltrimethylammonium 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, easy to operate, and help to reduce production costs and improve the feasibility of the process.

[0012] Preferably, the catalyst comprises tetrabutylammonium bromide.

[0013] By adopting the above technical solution, the present application further selects a quaternary ammonium salt with a tetrabutyl structure as a catalyst, which can make the cyclization reaction more active and the ring closure more complete, so that the glycidyl ester has a better epoxy value, thereby improving its toughening effect on the material.

[0014] Optionally, the phenols include one or more of cardanol, phenol and nonylphenol.

[0015] Through the above technical scheme, the present application adopts one or more of cardanol, phenol and nonylphenol as phenols to react with product I and aldehydes, so that the prepared epoxy resin curing agent has good flexibility, heat resistance, reactivity and strength, thereby improving the various properties of the epoxy resin cured product.

[0016] Preferably, the phenols include cardanol and phenol in a weight ratio of 1:(1.8-2.2).

[0017] By adopting the above technical scheme, the present application further adopts a mixture of cardanol and phenol, so that the prepared curing agent can have excellent impact performance, good heat resistance, high activity, and a more suitable application period, thereby improving the comprehensive performance of epoxy resin cured products.

[0018] Preferably, the phenols are mixed by the following method: 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.

[0019] By adopting the above technical scheme, it is possible to achieve uniform mixing of phenolic substances and effectively promote the subsequent reaction. Specifically, by pre-mixing cardanol and phenol at 40-50 ° C, it is ensured that the two substances are fully dispersed, and then an appropriate amount of p-toluenesulfonic acid is added as a catalyst to further improve the reaction activity. After the p-toluenesulfonic acid is completely dissolved, the temperature is raised to 90-95 ° C and the reaction is kept warm for 1-1.5h, which can effectively improve the reaction efficiency of phenolic substances and the uniformity of the product, thereby providing a more stable performance for the epoxy curing agent finally prepared. Experiments have shown that compared to the method of adding p-toluenesulfonic acid after phenol is completely melted at a temperature of 50-60 ° C, adding p-toluenesulfonic acid, and then adding cardanol after p-toluenesulfonic acid is completely dissolved, and keeping the reaction warm for 3h at a temperature of 125 ° C, the mixed phenol obtained by the method of the present application is better for improving the toughness, strength and heat resistance of the curing agent.

[0020] Preferably, the aldehyde comprises paraformaldehyde.

[0021] By adopting the above technical solution, the present application further adopts polyformaldehyde instead of formaldehyde as the aldehyde, which can achieve a more precise ratio, reduce the side reactions introduced by moisture, and at the same time reduce the energy consumption and wastewater treatment pressure in the industrial process. It is more environmentally friendly, simple in process, and has higher safety.

[0022] In a second aspect, the present application provides a method for preparing an epoxy curing agent, which adopts the following technical solution: A method for preparing an epoxy curing agent comprises 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.

[0023] By adopting the above technical scheme, the epoxy curing agent prepared in the present application can make the epoxy resin cured product not only have good flexibility but also have high strength and heat resistance after being cured with the epoxy resin. It can be widely used in fire retardant coatings, electronic appliances and other heat-generating products, and is particularly suitable for the preparation of materials such as expandable epoxy fire retardant coatings and high-temperature resistant coatings.

[0024] In summary, this application has the following beneficial technical effects: 1. The epoxy resin curing agent of the present application can make the epoxy resin cured product have good flexibility, high strength and heat resistance, and can withstand high temperatures. Under high temperature conditions, it can remain non-powdering and non-cracking for a long time, and can still play a good protective role on the substrate. It can be widely used in fire retardant coatings, electronic appliances and other heat-generating products, especially suitable for the preparation of materials such as intumescent epoxy fire retardant coatings and high temperature resistant coatings; 2. The preparation method of the present application has simple steps, is easy to operate, has high environmental protection and safety, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the raw materials used in this application are all commercially available products, including: Triglycidyl triisocyanate, also known as triglycidyl isocyanurate (TGIC), has a CAS number of 2451-62-9.

[0027] The epoxymethoxysilane is specifically 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane, with a CAS number of 65799-47-5 and a molecular weight of 220.34.

[0028] The general structural formula of aminosilane is ; When n is 1, the substance is (3-aminopropyl)trimethoxysilane, CAS No. 13822-56-5; when n is 2, the substance is (3-aminopropyl)triethoxysilane, CAS No. 919-30-2; and so on. In the specific implementation of the present application, (3-aminopropyl)triethoxysilane is taken as an example for description.

[0029] Preparation Example 1.1 Dimer acid diglycidyl ester was prepared by the following method: At a temperature of 85°C, 1kg of dimer acid, 7kg of epichlorohydrin and 0.015kg of anhydrous tin tetrachloride were reacted for 1h to obtain an intermediate, and then the intermediate was reacted with a 25wt% sodium hydroxide solution at a temperature of 50°C for 3.5h, and the amount of sodium hydroxide solution used was 3.5 times the weight of the intermediate to obtain a crude product. The crude product was then added to toluene for extraction, allowed to stand, the saline and alkali solution was removed, and the crude product was washed with water to neutralize to a pH of 7. The oil phase was distilled under reduced pressure to remove excess epichlorohydrin and toluene to obtain dimer acid diglycidyl ester, whose epoxy value was 0.1213mol / 100g.

[0030] Preparation Example 1.2 Dimer acid diglycidyl ester was prepared by the following method: At a temperature of 95°C, 1kg of dimer acid, 10kg of epichlorohydrin and 0.025kg of anhydrous tin tetrachloride were reacted for 2h to obtain an intermediate, and then the intermediate was reacted with a 35wt% sodium hydroxide solution at a temperature of 60°C for 4.5h, and the amount of sodium hydroxide solution used was 4.5 times the weight of the intermediate to obtain a crude product. The crude product was then added to toluene for extraction, allowed to stand, the saline and alkali solution was removed, and the crude product was washed with water to neutralize to a pH of 7. The oil phase was distilled under reduced pressure to remove excess epichlorohydrin and toluene to obtain dimer acid diglycidyl ester, whose epoxy value was 0.2275mol / 100g.

[0031] Preparation Example 1.3 The difference from Preparation Example 1.1 is that anhydrous tin tetrachloride is replaced by tetrabutylammonium bromide, and the rest is the same as Preparation Example 1.1. The epoxy value of the obtained dimer acid diglycidyl ester is 0.2076 mol / 100g.

[0032] Preparation Example 1.4 The difference from Preparation Example 1.1 is that anhydrous tin tetrachloride is replaced by hexadecyltrimethylammonium bromide, and the rest is the same as Preparation Example 1.1. The epoxy value of the obtained dimer acid diglycidyl ester is 0.1143 mol / 100g.

[0033] Preparation Example 1.5 The difference from Preparation Example 1.1 is that anhydrous tin tetrachloride is replaced by benzyltriethylammonium chloride, and the rest is the same as Preparation Example 1.1. The epoxy value of the obtained dimer acid diglycidyl ester is 0.1676 mol / 100g.

[0034] Preparation Example 2.1 The phenols were mixed using the following method: At a temperature of 40°C, mix cardanol and phenol in a weight ratio of 1:1.8, and then add p-toluenesulfonic acid. The amount of p-toluenesulfonic acid is 0.8% of the total mass of cardanol and phenol. After the p-toluenesulfonic acid is completely dissolved, raise the temperature to 90°C and keep the reaction for 1.5 hours.

[0035] Preparation Example 2.2 The phenols were mixed using the following method: At a temperature of 50°C, mix cardanol and phenol in a weight ratio of 1:2.2, and then add p-toluenesulfonic acid. The amount of p-toluenesulfonic acid is 1.2% of the total mass of cardanol and phenol. After the p-toluenesulfonic acid is completely dissolved, raise the temperature to 95°C and keep the reaction for 1 hour.

[0036] Preparation Example 2.3 The phenols were mixed using the following method: Heat phenol to 40°C, add p-toluenesulfonic acid after phenol is completely melted, the amount of p-toluenesulfonic acid is 0.8% of the total mass of cardanol and phenol, and add cardanol after p-toluenesulfonic acid is completely dissolved, the weight ratio of cardanol to phenol is 1:1.8, and heat to 125°C, keep warm for reaction for 3 hours, after the reaction is completed, use hot water to wash away unreacted phenol while hot, until the washing liquid does not make the 10% ferric chloride melt turn purple, and decompress and dehydrate under vacuum conditions of -0.097~-0.098MPa until no water is removed (if the dehydration temperature exceeds 90°C and no water is removed, it can be considered that the water has been completely removed, but the dehydration temperature shall not exceed 130°C), after dehydration, cool to room temperature.

[0037] Preparation Example 2.4 The difference from Preparation Example 2.1 is that the weight ratio of cardanol to phenol is 1:1, and the rest is the same as Preparation Example 2.1.

[0038] Preparation Example 2.5 The difference from Preparation Example 2.1 is that the weight ratio of cardanol to phenol is 1:3, and the rest is the same as Preparation Example 2.1.

[0039] Example 1.1 A method for preparing an epoxy curing agent comprises the following steps: S1, reacting isophorone diamine, triglycidyl triisocyanate and dimer acid diglycidyl ester prepared in Preparation Example 1.1 at a molar ratio of 12:1:1 at 35° C. for 4 h, and then removing unreacted monomer amine by distillation under reduced pressure to obtain product I; S2, the phenols prepared in Preparation Example 2.1 were cooled to 40°C, and then the product I and paraformaldehyde were added and mixed evenly, and the temperature was raised to 100°C under nitrogen protection for 2.5h. The molar ratio of the phenols prepared in Preparation Example 2.1, the product I and the paraformaldehyde was 1:1.4:1.1. After the reaction, the temperature was lowered to 80°C, and pressure dehydration was performed under a vacuum condition of -0.097 to -0.098MPa. The dehydration temperature was maintained at 80°C until no water was removed. After the dehydration, the product II was obtained; S3, mixing product I and product II in a weight ratio of 1.8:1 to obtain a mixture; S4. At a temperature of 85°C, react the mixture with 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane for 90 minutes, and then keep warm for 30 minutes. The molar ratio of epoxy group to amine hydrogen is 0.7:1. Then, (3-aminopropyl)triethoxysilane is added and mixed evenly. The amount of (3-aminopropyl)triethoxysilane added is 1% of the total mass of the system to obtain an epoxy curing agent.

[0040] Example 1.2 A method for preparing an epoxy curing agent comprises the following steps: S1, reacting isophorone diamine, triglycidyl triisocyanate and dimer acid diglycidyl ester prepared in Preparation Example 1.2 at a molar ratio of 14:1:1 at 45° C. for 3 h, and then removing unreacted monomer amine by distillation under reduced pressure to obtain product I; S2, the phenols prepared in Preparation Example 2.2 were cooled to 50°C, and then the product I and paraformaldehyde were added and mixed evenly, and the temperature was raised to 110°C under nitrogen protection for 1.5h. The molar ratio of the phenols prepared in Preparation Example 2.2, the product I and the paraformaldehyde was 1:1.6:1.3. After the reaction, the temperature was lowered to 80°C, and pressure dehydration was performed under a vacuum condition of -0.097 to -0.098MPa. The dehydration temperature was maintained at 80°C until no water was removed. After the dehydration was completed, the product II was obtained; S3, mixing product I and product II in a weight ratio of 2.2:1 to obtain a mixture; S4. At a temperature of 95°C, react the mixture with 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane for 45 minutes, and then keep warm for 40 minutes. The molar ratio of epoxy group to amine hydrogen is 1.5:1. Then, (3-aminopropyl)triethoxysilane is added and mixed evenly. The amount of (3-aminopropyl)triethoxysilane added is 2% of the total mass of the system to obtain an epoxy curing agent.

[0041] Example 2.1 A method for preparing an epoxy curing agent, which is 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.

[0042] Example 2.2 A method for preparing an epoxy curing agent, which is 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 1.4, and the rest is the same as Example 1.1.

[0043] Example 2.3 A method for preparing an epoxy curing agent, which is 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 1.5, and the rest is the same as Example 1.1.

[0044] Example 3.1 A method for preparing an epoxy curing agent, which is different from that of Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced by the phenols prepared in Preparation Example 2.3, the phenols prepared in Preparation Example 2.3 are heated to 40°C, and then the product I and polyformaldehyde are added and mixed evenly, and the temperature is raised to 100°C for insulation reaction for 2.5 hours, the molar ratio of the phenols prepared in Preparation Example 2.3, the product I and the polyformaldehyde is 1:1.4:1.1, after the reaction is completed, the temperature is lowered and decompression dehydration is carried out under vacuum conditions of -0.097 to -0.098 MPa, the dehydration temperature is maintained at 80°C until no water is removed, and after the dehydration is completed, the product II is obtained, and the rest is the same as Example 1.1.

[0045] Example 3.2 A method for preparing an epoxy curing agent, which is different from that of Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced by phenol, the phenol is heated to 40°C, and then the product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 85°C for insulation reaction for 2.5 hours, the molar ratio of phenol, product I and paraformaldehyde is 1:1.4:1.1, and after the reaction is completed, decompression dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed, and after the dehydration is completed, product II is obtained, and the rest is the same as Example 1.1.

[0046] Example 3.3 A method for preparing an epoxy curing agent, which is different from that of Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced with cardanol, the cardanol is heated to 40°C, and then the product I and paraformaldehyde are added and mixed evenly, and the temperature is raised to 75°C and kept for reaction for 4 hours, the molar ratio of cardanol, product I and paraformaldehyde is 1:1.4:1.1, and after the reaction is completed, decompression dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed, and after dehydration, product II is obtained, and the rest is the same as Example 1.1.

[0047] Example 3.4 A method for preparing an epoxy curing agent, which differs from that in Example 1.1 in that: the phenols prepared in Preparation Example 2.1 are replaced with nonylphenol, the nonylphenol is heated to 40°C, and then the product I and polyformaldehyde are added and mixed evenly, and the temperature is raised to 85°C and kept for reaction for 2.5 hours, the molar ratio of nonylphenol, product I and polyformaldehyde is 1:1.4:1.1, and after the reaction is completed, decompression dehydration is carried out under a vacuum condition of -0.097 to -0.098 MPa until no water is removed, and after dehydration, product II is obtained, and the rest is the same as in Example 1.1.

[0048] Example 3.5 A method for preparing an epoxy curing agent, which is different from Example 1.1 in that the phenols prepared in Preparation Example 2.1 are replaced by the phenols prepared in Preparation Example 2.4, and the rest are the same as Example 1.1.

[0049] Example 3.6 A method for preparing an epoxy curing agent, which is different from Example 1.1 in that the phenols prepared in Preparation Example 2.1 are replaced by the phenols prepared in Preparation Example 2.5, and the rest are the same as Example 1.1.

[0050] Comparative Example 1 The difference from Example 1.1 is that triglycidyl triisocyanate in step S1 is removed, and the rest is the same as Example 1.1.

[0051] Comparative Example 2 The difference from Example 1.1 is that the dimer acid diglycidyl ester in step S1 is removed, and the rest is the same as Example 1.1.

[0052] Comparative Example 3 The difference from Example 1.1 is that step S3 is removed, and product II is directly subjected to subsequent steps. The rest is the same as Example 1.1.

[0053] Comparative Example 4 The difference from Example 1.1 is that: (3-aminopropyl)triethoxysilane in step S4 is removed, and the rest is the same as Example 1.1.

[0054] Comparative Example 5 The difference from Example 1.1 is that the isophorone diamine in step S1 is replaced by ethylene diamine, and the rest is the same as Example 1.1.

[0055] Performance Testing The epoxy resin curing agent prepared in the above embodiments and comparative examples was uniformly mixed with bisphenol A epoxy resin (model E44) in a certain ratio so that the amount of hydrogen atoms on the amine group of the epoxy curing agent and the epoxy group on the bisphenol A epoxy resin was equal, and then poured into a mold, pre-cured at 25°C for 3h, and then placed in an oven at 80°C for curing for 8h, and then taken out and cooled to obtain an epoxy resin cured material test material. The tensile properties, impact resistance and heat resistance of the prepared epoxy resin cured product were tested respectively. The tensile properties test was carried out on a universal testing machine with reference to GB / T 1040.1-2006 standard, the tensile rate was 50mm / min, the test material width was 10±0.5mm, and the thickness was 4±0.5mm; the impact resistance was tested with reference to the simply supported beam impact toughness test in GB / T 1043.1-2008 standard, the pendulum energy was 2.75J, and the test material specification was 80mm×10mm×4mm; the heat resistance was tested by using a DIAMOND TG / DTA analyzer from PERKIN ELMER Company to test the thermal weight loss of the material, and the temperature at which the test material lost 5% of its weight was recorded. The above results are all recorded in Table 1.

[0056] Table 1 Performance test results

[0057] Data Analysis: As can be seen from Table 1, the epoxy resin curing agent 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 and the impact strength reach 31.22-33.56 KJ / m 2The temperature when the mass loss is 5% is 317-320℃, which obviously has higher strength, flexibility and heat resistance.

[0058] The difference between Examples 2.1-2.3 and Example 1.1 is that different catalysts are used in the preparation of dimer acid diglycidyl ester. As can be seen from Table 1, the impact strength of the epoxy resin cured product obtained in Example 2.1 is slightly higher than that in Example 1.1, and the impact strength of Examples 2.2-2.3 is slightly lower than that in Example 1.1. Experimental data show that the choice of catalyst will affect the epoxy value of dimer acid diglycidyl ester, thereby affecting the flexibility of the epoxy resin cured product. When anhydrous tin tetrachloride is selected as the catalyst, the epoxy value of the obtained dimer acid diglycidyl ester is the highest, and the corresponding epoxy resin cured product has the best flexibility.

[0059] The difference between Examples 3.1-3.4 and Example 1.1 is that the phenols used in step S2 are different. It can be seen from Table 1 that the various properties of the epoxy resin cured material obtained in Example 3.1 are slightly lower than those in 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 various properties of the epoxy resin cured material. The impact strength of the epoxy resin cured material obtained in Example 3.2 is significantly lower than that in Example 1.1. The experimental data show that only using phenol as a phenol will significantly reduce the flexibility of the epoxy resin cured material. The tensile strength and thermal weight loss temperature of the epoxy resin cured material obtained in Example 3.3 are significantly lower than those in Example 1.1. The experimental data show that only using cardanol as a phenol will significantly reduce the strength and heat resistance of the epoxy resin cured material. The impact strength of the epoxy resin cured material obtained in Example 3.4 is significantly lower than that in Example 1.1. The experimental data show that only using nonylphenol as a phenol will significantly reduce the flexibility of the epoxy resin cured material.

[0060] The difference between Examples 3.5-3.6 and Example 1.1 is that the ratio of phenol and cardanol in the phenols of step S2 is different. It can be seen from Table 1 that the epoxy resin cured products obtained in Examples 3.5-3.6 are either lower in tensile strength and thermal weight loss temperature than those in Example 1.1, or lower in impact strength than those in Example 1.1. 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.

[0061] The difference between Comparative Example 1 and Example 1.1 is that triglycidyl triisocyanate is not added. As can be seen from Table 1, 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 triisocyanate can improve the strength and heat resistance of epoxy resin cured product.

[0062] The difference between Comparative Example 2 and Example 1.1 is that dimer acid diglycidyl ester 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 dimer acid diglycidyl ester can improve the flexibility of epoxy resin cured product.

[0063] The difference between Comparative Example 3 and Example 1.1 is that only small molecular substances are used for subsequent reactions. It can be seen from Table 1 that the tensile strength and thermal weight loss temperature of Comparative Example 3 are significantly lower than those of Example 1.1. The experimental results show that mixing and using large molecular substances and small molecular substances can balance the flexibility, strength and heat resistance of epoxy resin cured products.

[0064] 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, the various 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 epoxy resin cured product.

[0065] The difference between Comparative Example 5 and Example 1.1 is that a straight-chain amine is used to replace the alicyclic amine. As can be seen from Table 1, the tensile strength and thermal weight loss temperature of Comparative Example 5 are lower than those of Example 1.1. The experimental results show that compared with straight-chain amines, alicyclic amines can further improve the strength and heat resistance of epoxy resin cured products.

[0066] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present 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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