An epoxy curing agent, its preparation method and application

Abstract

The present application belongs to the technical field of epoxy curing agent, and particularly relates to an epoxy curing agent, a preparation method and application thereof. The epoxy curing agent is prepared from raw materials including the following components by mass: toughening agent 15-40 parts, aromatic diamine 5-15 parts, alicyclic diamine 5-20 parts, epoxy resin 5-20 parts, hydrogenated alkyl aldehyde-aniline polymer 15-35 parts, epoxy active diluent 1-6 parts, curing accelerator 0.5-4 parts and amino-terminated siloxane coupling agent 0.5-4 parts. The alicyclic diamine, aromatic amine and multi-functional hydrogenated alkyl aldehyde-aniline polymer are modified by addition, and synergistically act with the toughening agent and the curing accelerator, and are combined with the silane coupling agent with a special structure, so that the chemical resistance of the epoxy curing agent, especially the solvent resistance and acid resistance, is greatly improved, and the range of chemical medium resistance of the epoxy curing agent is expanded. The epoxy curing agent provided by the present application has stable performance, low viscosity, good physical properties and good corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of epoxy curing agent technology, specifically relating to an epoxy curing agent, its preparation method, and its application. Background Technology

[0002] Epoxy resins have excellent adhesion, corrosion resistance, water resistance, and good chemical resistance, as well as a relatively low price. Therefore, they are widely used in anti-corrosion coatings for marine corrosion protection, ship and industrial protection, petrochemical pipelines and storage tanks, rail transportation, construction machinery, wind power, and flooring.

[0003] However, some highly corrosive chemicals or strong acidic / alkaline chemical media, such as methyl ethyl ketone (MEK), acetone, crude oil, toluene, benzene, methanol, strong acids, and strong alkalis, present extremely harsh corrosive environments with high requirements for comprehensive protection. Ordinary epoxy coatings are prone to blistering and peeling, which shortens the service life of the substrate or related equipment, limiting the application of epoxy coatings in petrochemical pipelines, chemical tanks, storage tank linings, sewage treatment plants, and industrial floors. The performance of epoxy coatings is influenced not only by the type of epoxy resin, formulation design, and other raw materials, but also primarily by the performance of the epoxy curing agent. In these extremely harsh corrosive environments, solvent-based chemical-resistant and corrosion-resistant coatings are often used. During the drying process, solvent evaporation can easily lead to defects such as micro-pinholes in the coating, resulting in a failure to achieve the expected protective effect. Furthermore, the painting environment in these applications is generally relatively enclosed; excessive solvent not only causes environmental pollution and resource waste and poses safety risks, but also poses significant health hazards to workers.

[0004] Chinese patent CN 113234207B discloses a method for preparing an acid-resistant solvent-free epoxy curing agent and its application. The method uses alicyclic amines 4,4'-diaminodicyclohexylmethane or 3,3'-dimethyl4,4'-diaminodicyclohexylmethane, toughening agents benzyl alcohol, cashew phenol, or nonylphenol, silane coupling agent KH-560, and accelerator DMP-30 to prepare the acid-resistant curing agent. It is directly prepared through physical mixing. Although the viscosity is low and the color is light, the shortcomings of small molecule amines still exist. The cured product obtained with epoxy resin has insufficient physical properties, mediocre anti-corrosion effect, and limited range of chemical resistance. The pure tertiary amine structure accelerator used is prone to react with acids to form tertiary ammonium salts, leading to poor acid resistance.

[0005] Chinese patent CN 102321423B discloses a method for preparing a heavy-duty anti-corrosion phenolic epoxy coating. This method involves using a single type of alicyclic amine, PACM or IPDA, which is added to a modified resin at 80–100°C for 2–3 hours. The resin is then combined with a toughening agent (benzyl alcohol), a silane coupling agent (KH-550), an accelerator (salicylic acid), and a mixed solvent to obtain a modified alicyclic amine. The resulting coating, when combined with the phenolic epoxy coating, exhibits excellent corrosion resistance, heat resistance, and resistance to discoloration. While this method improves the physical properties of the base alicyclic amine, the modified base alicyclic amine alone has limitations in physical and anti-corrosion properties, as well as a certain range of resistance to chemical media. Summary of the Invention

[0006] The purpose of this invention is to provide an epoxy curing agent, its preparation method, and its application. The epoxy curing agent provided by this invention has good physical properties, anti-corrosion properties, and chemical resistance, and has a wide range of chemical media resistance.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides an epoxy curing agent, made from raw materials comprising the following parts by weight:

[0009] Toughening agent 15-40 parts, aromatic diamine 5-15 parts, alicyclic diamine 5-20 parts, epoxy resin 5-20 parts, hydrogenated alkyl aldehyde-aniline polymer 15-35 parts, epoxy reactive diluent 1-6 parts, curing accelerator 0.5-4 parts and amino-terminated siloxane coupling agent 0.5-4 parts;

[0010] The hydrogenated alkyl aldehyde-aniline polymer is a polyfunctional alicyclic amine; the polyfunctional alicyclic amine includes one or more of PACM polymers with polycyclic structures and MACM polymers with polycyclic structures;

[0011] The terminal aminosiloxane coupling agent includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane;

[0012] The epoxy resin is a room-temperature liquid bifunctional epoxy resin with an epoxy equivalent of 165-240 g / eq and a viscosity of 2000-20000 mPa·s.

[0013] The epoxy reactive diluent is a monofunctional or bifunctional reactive diluent with a viscosity not exceeding 100 mPa·s and an epoxy equivalent of 150–500 g / eq.

[0014] The viscosity of the alicyclic diamine is not higher than 150 mPa·s, and the active hydrogen equivalent is 30-65 g / eq;

[0015] The active hydrogen equivalent of the aromatic diamine is 30–60 g / eq.

[0016] Preferably, the epoxy resin includes one or more of bisphenol A epoxy resin E51, bisphenol A epoxy resin E44, and bisphenol F epoxy resin YDF-170.

[0017] Preferably, the aromatic diamine includes one or more of 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and m-phenylenediamine.

[0018] Preferably, the alicyclic diamine includes one or more of isophorone diamine (IPDA), 1,3-cyclohexanedimethylamine (1,3-BAC), 4,4'-diaminodicyclohexylmethane (PACM), 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (MACM), and methylcyclohexanediamine (HTDA).

[0019] Preferably, the curing accelerator includes one or more of salicylic acid, bisphenol A, N,N-dimethyl-1,3-propanediamine and 3-diethylaminopropylamine.

[0020] Preferably, the epoxy reactive diluent includes one or more of glycidyl tert-carbonate, C12-C14 alkyl glycidyl ether, cashew phenol glycidyl ether, 1,6-hexanediol diglycidyl ether, and cresol monoglycidyl ether.

[0021] Preferably, the toughening agent includes one or more of benzyl alcohol, cashew phenol, and dodecylphenol.

[0022] The present invention also provides a method for preparing the epoxy curing agent described above, comprising the following steps:

[0023] (1) After mixing a portion of the toughening agent, aromatic diamine and alicyclic diamine, the mixture is heated to obtain a first mixture;

[0024] (2) The first mixture and epoxy resin are mixed in batches to carry out the first addition reaction. After each batch is mixed, the second heating and the second cooling are carried out in sequence to obtain the modified amine.

[0025] (3) The modified amine is mixed with hydrogenated alkyl aldehyde-aniline polymer and epoxy reactive diluent in the third step and then heated in the third step to carry out the second addition reaction to obtain the first composite modified amine;

[0026] (4) After the first composite modified amine is cooled down, it is mixed with the curing accelerator and the remaining toughening agent to obtain the second composite modified amine.

[0027] (5) After cooling the second composite modified amine fourth, mix it with the terminal aminosiloxane coupling agent fifth to obtain an epoxy curing agent.

[0028] Preferably, the temperature of the first heating is 60-80°C;

[0029] The second heating temperature is 90–120°C, and the holding time is 0.5–2 hours;

[0030] The second cooling temperature is 60–80°C;

[0031] The third heating temperature is 90–120°C, and the holding time is 0.5–2 hours;

[0032] The third cooling temperature is 60–80°C;

[0033] The temperature of the fourth mixture is 60–80°C, and the holding time is 0.5–1 hour;

[0034] The fourth cooling temperature is 40–60°C.

[0035] The present invention also provides the application of the epoxy curing agent described in the above-described scheme or the epoxy curing agent obtained by the preparation method described in the above-described scheme in epoxy resin coatings.

[0036] This invention provides an epoxy curing agent. Through addition modification of alicyclic diamines, aromatic amines, and multifunctional hydrogenated alkyl aldehyde-aniline polymers, and in synergy with toughening agents and curing accelerators, combined with a specially structured terminal aminosiloxane coupling agent, the chemical resistance, especially solvent and acid resistance, of the epoxy curing agent is significantly improved, expanding its range of chemical resistance. The epoxy curing agent provided by this invention exhibits stable performance, low viscosity, and good physical and anti-corrosion properties, demonstrating excellent overall performance and applicability to high-solids or solvent-free coatings. The terminal aminosiloxane coupling agent used in this invention is dimethoxysiloxane, which exhibits better hydrolysis resistance than conventional silane coupling agents, thus improving the product stability of the epoxy curing agent.

[0037] This invention also provides a method for preparing the epoxy curing agent described in the above-described scheme. The preparation method provided by this invention has simple steps, is easy to operate, and is suitable for industrial production.

[0038] This invention also provides the application of the epoxy curing agent described in the above-described scheme or the epoxy curing agent prepared by the above-described scheme in epoxy resin coatings. The epoxy curing agent of this invention, when used in epoxy coatings, can improve the chemical resistance of the coating, especially its solvent and acid resistance, and enhance its anti-corrosion effect. The epoxy curing agent of this invention is suitable for various epoxy coatings, especially high-solids coatings or solvent-free coatings. Detailed Implementation

[0039] This invention provides an epoxy curing agent, made from raw materials comprising the following parts by weight:

[0040] Toughening agent 15-40 parts, aromatic diamine 5-15 parts, alicyclic diamine 5-20 parts, epoxy resin 5-20 parts, hydrogenated alkyl aldehyde-aniline polymer 15-35 parts, epoxy reactive diluent 1-6 parts, curing accelerator 0.5-4 parts and amino-terminated siloxane coupling agent 0.5-4 parts;

[0041] The hydrogenated alkyl aldehyde-aniline polymer is a polyfunctional alicyclic amine; the polyfunctional alicyclic amine includes one or more of PACM polymers with polycyclic structures and MACM polymers with polycyclic structures;

[0042] The terminal aminosiloxane coupling agent includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane;

[0043] The epoxy resin is a room-temperature liquid bifunctional epoxy resin with an epoxy equivalent of 165-240 g / eq and a viscosity of 2000-2000 mPa·s.

[0044] The epoxy reactive diluent is a monofunctional or bifunctional reactive diluent with a viscosity not exceeding 100 mPa·s and an epoxy equivalent of 150–500 g / eq.

[0045] The viscosity of the alicyclic diamine is not higher than 150 mPa·s, and the active hydrogen equivalent (AHEW) is 30–65 g / eq;

[0046] The active hydrogen equivalent (AHEW) of the aromatic diamine is 30–60 g / eq.

[0047] The epoxy curing agent provided by this invention comprises 15-40 parts by weight of a toughening agent, preferably 25-35 parts, and more preferably 30-35 parts. In this invention, the boiling point of the toughening agent is preferably not lower than 190°C, more preferably not lower than 200°C; the toughening agent preferably includes one or more of benzyl alcohol, cashew phenol, and dodecylphenol, more preferably benzyl alcohol. The toughening agent used in this invention has a high boiling point, is not easily volatile, has low viscosity, and has good compatibility with the resin. It can also promote the reaction between the resin and the amine, thereby effectively promoting the continued full curing of the curing system at room temperature and low temperature. Benzyl alcohol, more preferably, is colorless and has low viscosity, which can effectively reduce the viscosity of the system. Benzyl alcohol does not migrate in the cured product under high temperature conditions, which can significantly improve the gloss of the cured product and effectively reduce the whitening phenomenon.

[0048] The epoxy curing agent provided by the present invention comprises 5 to 15 parts, preferably 7 to 12 parts, of an aromatic diamine, by weight. In the present invention, the active hydrogen equivalent (AHEW) of the aromatic diamine is 30 to 60 g / eq, preferably 35 to 55 g / eq, and more preferably 40 to 50 g / eq; the aromatic diamine preferably comprises one or more of 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and m-phenylenediamine, more preferably m-phenylenediamine.

[0049] The epoxy curing agent provided by the present invention comprises 5 to 20 parts by weight of an alicyclic diamine, preferably 8 to 18 parts, and more preferably 10 to 16 parts. In the present invention, the viscosity of the alicyclic diamine is not higher than 150 mPa·s, preferably not higher than 50 mPa·s, and the active hydrogen equivalent is 30 to 65 g / eq, more preferably 42 to 53 g / eq. The alicyclic diamine preferably includes one or more of isophorone diamine (IPDA), 1,3-cyclohexanedimethylamine (1,3-BAC), 4,4'-diaminodicyclohexylmethane (PACM or HMDA), 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (MACM), and methylcyclohexanediamine (HTDA), more preferably one or two of 4,4'-diaminodicyclohexylmethane and isophorone diamine (IPDA).

[0050] The alicyclic diamine used in this invention has the characteristics of low viscosity, high gloss, moderate curing speed, good physical properties, and good chemical resistance. The aromatic diamine has high reactivity and high curing crosslinking density, which meets the requirements of low-temperature curing and rapid curing. At the same time, it can improve the heat resistance and chemical resistance of the cured product, and has a positive effect on the corrosion resistance and strength of the cured product. After epoxy resin addition modification, the alicyclic diamine and aromatic diamine have improved their compatibility with the resin and reduced their toxicity. At the same time, it combines the advantages of the two polyamines, which improves the physical properties, corrosion resistance and chemical resistance of the cured product to a certain extent.

[0051] The epoxy curing agent provided by this invention comprises 5-20 parts by weight of epoxy resin, preferably 10-20 parts, and more preferably 10-14 parts. In this invention, the epoxy resin is a room-temperature liquid bifunctional epoxy resin with an epoxy equivalent of 165-240 g / eq, preferably 165-185 g / eq, more preferably 175 g / eq, and a viscosity of 2000-20000 mPa·s, preferably 3000-4000 mPa·s, more preferably 3300-3700 mPa·s, and even more preferably 3500 mPa·s. The epoxy resin preferably includes one or more of bisphenol A epoxy resin E51, bisphenol A epoxy resin E44, and bisphenol F epoxy resin YDF-170, more preferably bisphenol F epoxy resin YDF-170. The epoxy resin equivalent used in this invention is relatively low, thus having a smaller impact on the viscosity increase of the epoxy curing agent.

[0052] The epoxy curing agent provided by the present invention comprises 15-35 parts, preferably 15-30 parts, and more preferably 18-27 parts, of a hydrogenated alkyl aldehyde-aniline polymer by weight. In the present invention, the hydrogenated alkyl aldehyde-aniline polymer is a polyfunctional alicyclic amine; the polyfunctional alicyclic amine includes one or more of PACM polymers and MACM polymers with polycyclic structures, preferably a PACM polymer with a polycyclic structure; the PACM polymer with a polycyclic structure is preferably WANAMINE 2300 from Yantai Wanhua Chemical or H-7013 from Shenzhen Yexu. In a specific embodiment of the present invention, the polyfunctional alicyclic amine is preferably WANAMINE 2300 from Wanhua Chemical.

[0053] The hydrogenated alkyl aldehyde-aniline polymer used in this invention is a special type of multifunctional alicyclic amine. In addition to the characteristics of alicyclic amines, its special multi-ring linked structure and multifunctionality result in a cured product with a superior network structure and crosslinking density compared to conventional difunctional amines (alicyclic diamines). This imparts excellent chemical resistance, water resistance, and mechanical properties to downstream products. Furthermore, this multifunctional alicyclic amine has a significant cost advantage over several basic alicyclic amines, greatly enhancing the market competitiveness of the epoxy curing agent of this invention. During the preparation of the epoxy curing agent, chemical addition modification further improves its compatibility with epoxy resin and the physical properties of the cured film.

[0054] The epoxy curing agent provided by the present invention comprises 1 to 6 parts by weight of epoxy reactive diluent, preferably 2 to 5 parts, and more preferably 3 to 5 parts. In the present invention, the epoxy reactive diluent is preferably a monofunctional or bifunctional reactive diluent with a viscosity not exceeding 100 mPa·s, preferably not exceeding 90 mPa·s, more preferably not exceeding 80 mPa·s, and an epoxy equivalent of 150 to 500 g / eq, preferably 180 to 250 g / eq, and more preferably 200 to 220 g / eq. The epoxy reactive diluent preferably comprises one or more of tert-carbon glycidyl ether, C12-C14 alkyl glycidyl ether, cashew phenol glycidyl ether, 1,6-hexanediol diglycidyl ether, and cresol monoglycidyl ether, more preferably tert-carbon glycidyl ether. The product is selected from one of glycidyl ether and cresol monoglycidyl ether; the glycidyl ether is preferably glycidyl ether E10P from Weisley Chemicals, USA; the cashew phenol glycidyl ether is preferably cashew phenol glycidyl ether WSCM-5110 from Zhejiang Wansheng; the 1,6-hexanediol diglycidyl ether is preferably 1,6-hexanediol diglycidyl ether XY-632 from Anhui Xinyuan; the C12-C14 alkyl glycidyl ether is preferably C12-C14 alkyl glycidyl ether XY-748 from Anhui Xinyuan; and the cresol monoglycidyl ether is preferably cresol monoglycidyl ether DY-K from Huntsman Advanced Materials.

[0055] The epoxy reactive diluent used in this invention is light in color and has low viscosity, which has a relatively small impact on the viscosity of the modified curing agent. At the same time, after addition modification, it effectively improves the physical properties of the base amine, such as flexibility, and reduces toxicity. Among them, the more preferred reactive diluent of this invention is glycidyl tert-carbonate E10P. Due to the steric hindrance of its tert-carbonate groups, during film formation, the hydrophobic tert-carbonate groups act like a small umbrella on the coating surface, forming a "shielding effect". The tert-carbonate groups in the molecular chain support the side segments of the molecular chain like a small umbrella. The polar ester bond groups containing oxygen atoms in the molecular chain are "surrounded" by the tert-carbonate groups and are not "exposed", thus increasing hydrophobicity and increasing the water contact angle of the paint film. Under alkaline conditions, OH- ions have difficulty accessing the ester bonds in the resin molecules. The ester bonds are protected and not easily hydrolyzed, which increases its acid and alkali resistance. It has high reactivity and can fully consume free small molecule amines in the product. It also improves the toughness of the final product to a certain extent. At the same time, the aliphatic properties of the tertiary carbonate group can improve the resin's weather resistance. The suspended tertiary carbonate group can also reduce viscosity and increase the wettability and internal plasticizing effect of pigments.

[0056] The epoxy curing agent provided by this invention comprises 0.5 to 4 parts by weight, preferably 0.8 to 3 parts, and more preferably 1 to 2 parts by weight. In this invention, the curing accelerator preferably comprises one or more of the following: salicylic acid containing phenolic hydroxyl groups, bisphenol A, N,N-dimethyl-1,3-propanediamine (DMAPA) with reactive groups, and 3-diethylaminopropylamine (DEAPA) with reactive groups; more preferably, a combination of 3-diethylaminopropylamine and salicylic acid with reactive groups. The curing accelerator used in this invention can reduce the activation energy of the system, promote the release of heat from the system, lower the glass transition temperature of the system, and enable the epoxy curing agent and resin to cure more fully at room temperature, thereby improving the crosslinking density and the strength and heat resistance of the curing agent. This invention employs the aforementioned amine curing accelerators (DMAPA and DEAPA) with reactive groups. Compared to commonly used tertiary amine accelerators such as K54, the molecular structures of DMAPA and DEAPA not only contain tertiary amines with curing-promoting effects, but also secondary or primary amines that undergo cross-linking reactions between active hydrogen and epoxy groups. This reduces the impact of reduced acid resistance caused by the free tertiary amine structure easily reacting with acids to form tertiary ammonium salts, while also improving its resistance to other chemicals to a certain extent. Furthermore, the salicylic acid of this invention more preferably contains both conventional phenolic hydroxyl and carboxyl groups, both of which have good promoting effects, giving the curing system good low-temperature curing agent performance. At the same time, salicylic acid does not easily cause the paint film to become brittle and can also improve the surface condition of the cured paint film.

[0057] The epoxy curing agent provided by the present invention comprises 0.5 to 4 parts by weight, preferably 0.8 to 3 parts, and more preferably 1 to 2 parts, of an amino-terminated siloxane coupling agent. In the present invention, the amino-terminated siloxane coupling agent comprises one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, preferably N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; the 3-aminopropylmethyldimethoxysilane is preferably SCA-A10T from Nanjing Nengde or Momentive from Momentive. A-2110; the 3-aminopropylmethyldiethoxysilane is preferably SCA-A10F from Nanjing Nengde or Momentive from the United States. A-2100; the 3-diethylenetriaminepropylmethyldimethoxysilane is preferably SCA-A30T from Nanjing Nengde; the N-2-aminoethyl-3-aminopropylmethyldiethoxysilane is preferably SCA-A20F from Nanjing Nengde; the N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane is preferably Momentive from the United States. A-2120 or Nanjing Nengde's SCA-A20T. This invention uses an amino-terminated siloxane coupling agent. The silane at one end combines with the substrate to produce an alcohol during the curing process, enhancing the adhesion between the cured product and the substrate. At the same time, the amino group at the other end can effectively participate in the ring-opening curing reaction of the epoxy group, which not only avoids precipitation but also effectively reduces the impact on the chemical resistance of the cured product.

[0058] This invention uses methyldimethoxysilane or methyldiethoxysilane, which, compared to trimethoxysilane in conventional siloxane coupling agents, exhibits superior water stability and is less prone to hydrolysis and failure during storage. Simultaneously, the crosslinking density of the cured resin coating is lower, resulting in better coating toughness. More preferably, the N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane of this invention, compared to conventional terminal amino siloxanes, possesses a unique molecular structure with two amino (one primary amino and one secondary amino) functional groups and two hydrolyzable alkoxy-methoxy groups. This dual reactivity allows it to enhance the bonding, adhesion, and compatibility between inorganic materials (glass, metals, and fillers) and organic polymers (thermosetting resins, plastics, and elastomers) through bidirectional chemical reactions, thereby improving the mechanical properties of resin-based composite materials or the adhesive strength and water resistance of resin coatings.

[0059] This invention appropriately increases the amount of coupling agent. In addition to the conventional understanding that alkoxy groups can react with hydroxyl groups or oxides on the surface of materials such as glass, metals and silicates to form covalent chemical bonds, thereby coupling the cured product and the metal substrate together by chemical bonds and forming good adhesion, it can also improve the wetting and adsorption between the resin and the filler, effectively reducing the gap channels in the coating or adhesive during the curing process, and thus providing more effective resistance to highly corrosive chemicals in the end-use environment.

[0060] The present invention also provides a method for preparing the epoxy curing agent described above, comprising the following steps:

[0061] (1) After mixing a portion of the toughening agent, aromatic diamine and alicyclic diamine, the mixture is heated to obtain a first mixture;

[0062] (2) The first mixture and epoxy resin are mixed in batches to carry out the first addition reaction. After each batch is mixed, the second heating and the second cooling are carried out in sequence to obtain the modified amine.

[0063] (3) The modified amine is mixed with hydrogenated alkyl aldehyde-aniline polymer and epoxy reactive diluent in the third step and then heated in the third step to carry out the second addition reaction to obtain the first composite modified amine;

[0064] (4) After the first composite modified amine is cooled down, it is mixed with the curing accelerator and the remaining toughening agent to obtain the second composite modified amine.

[0065] (5) After cooling the second composite modified amine fourth, mix it with the terminal aminosiloxane coupling agent fifth to obtain an epoxy curing agent.

[0066] In this invention, a portion of a toughening agent, an aromatic diamine, and an alicyclic diamine are first mixed and then heated to obtain a first mixture. In this invention, the mass ratio of the portion of the toughening agent to the total mass of the toughening agent is preferably 10–30:15–40, more preferably 15–25:15–40, and even more preferably 16–23:15–40.

[0067] In this invention, the first mixing is preferably stirred; the first mixing is preferably: premixing a portion of the toughening agent and the aromatic diamine, and then mixing the resulting premix (transparent liquid) with the alicyclic diamine (transparent liquid).

[0068] In this invention, the temperature of the first heating is preferably 60-80°C, more preferably 65-75°C, and even more preferably 70°C; the first heating is preferably carried out under stirring conditions; the stirring is preferably consistent with the first mixing.

[0069] After obtaining the first mixture, the present invention performs a first addition reaction by mixing the first mixture and epoxy resin in batches, and after each batch is mixed, a second heating and a second cooling are performed sequentially to obtain the modified amine. In the present invention, the batch mixing is preferably performed by dividing the epoxy resin into even batches and then mixing it with the first mixture sequentially; the number of even batches is preferably 2 to 3 batches, more preferably 3 batches.

[0070] In this invention, the second heating temperature is preferably 90-120°C, more preferably 95-115°C, and even more preferably 100-110°C; the holding time is preferably 0.5-2h, more preferably 1-1.5h; the second heating is preferably carried out under stirring conditions; the stirring is preferably consistent with the batch mixing.

[0071] In this invention, the temperature of the second cooling is preferably 60-80°C, more preferably 65-75°C, and even more preferably 70°C.

[0072] After obtaining the modified amine, the present invention further involves a third addition reaction, in which the modified amine is mixed with a hydrogenated alkyl aldehyde-aniline polymer and an epoxy reactive diluent, followed by a third heating, to obtain a first composite modified amine. In the present invention, the third mixing is preferably performed by premixing the modified amine with the hydrogenated alkyl aldehyde-aniline polymer, and then mixing the resulting premix with the epoxy reactive diluent.

[0073] In this invention, the third mixing is preferably a stirring mixture.

[0074] In this invention, the temperature of the third heating is preferably 90-120°C, more preferably 95-115°C, and even more preferably 100-110°C; the holding time is preferably 0.5-2 hours, more preferably 1-1.5 hours; the third heating is preferably carried out under stirring conditions; the stirring is preferably consistent with the third mixing.

[0075] After obtaining the first composite modified amine, the present invention further cools the first composite modified amine a third time and mixes it with a curing accelerator and the remaining toughening agent a fourth time to obtain a second composite modified amine. In the present invention, the temperature of the third cooling is preferably 60-80°C, more preferably 70-80°C, and even more preferably 75°C.

[0076] In this invention, the fourth mixing is preferably stirred and mixed, and the temperature of the fourth mixing is preferably 60-80°C, more preferably 70-80°C, and even more preferably 75°C.

[0077] In this invention, the ratio of the mass of the remaining toughening agent to the total mass of the toughening agent is preferably 5-10:15-40, more preferably 6-9:15-40, and even more preferably 6-7:15-40.

[0078] After obtaining the second composite modified amine, the present invention further cools the second composite modified amine and mixes it with a fifth amino-terminated siloxane coupling agent to obtain an epoxy curing agent (transparent liquid). In the present invention, the fourth cooling temperature is preferably 40-60°C, more preferably 45-55°C, and even more preferably 50°C.

[0079] In this invention, the fifth mixing is preferably a stirring mixture.

[0080] The present invention also provides the application of the epoxy curing agent described in the above-described scheme or the epoxy curing agent obtained by the preparation method described in the above-described scheme in epoxy resin coatings.

[0081] The epoxy curing agent provided by this invention is suitable for epoxy resin coatings, especially for epoxy coatings in the field of chemical resistance.

[0082] In this invention, the application of the epoxy curing agent in epoxy resin coating preferably includes the following steps: mixing the epoxy curing agent and epoxy resin coating, applying the mixture, and then drying it.

[0083] In this invention, the mass ratio of the epoxy resin coating to the epoxy curing agent is preferably 100:50-65, more preferably 100:55-60, and even more preferably 100:57; the epoxy resin in the epoxy resin coating is preferably one or both of epoxy resin E51 and bisphenol F type epoxy resin YDF-170; the epoxy resin coating is preferably epoxy resin paint; the epoxy resin paint is preferably solvent-free epoxy resin paint; the mass ratio of the epoxy resin coating to the epoxy curing agent is preferably 100:18-28, more preferably 100:21-25, and even more preferably 100:22.

[0084] To further illustrate the present invention, the following detailed description of the embodiments is provided in conjunction with the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0085] Example 1

[0086] Add 30 parts benzyl alcohol and 7 parts m-phenylenediamine to a four-necked flask, and while stirring, add 10 parts alicyclic diamine PACM. Heat to 80°C, add 6 parts epoxy resin YDF-170, heat to 100°C and hold for 1 hour. Then add a second batch of 6 parts epoxy resin YDF-170, hold at 100°C for 1 hour, and then add 27 parts hydrogenated alkyl aldehyde-aniline polymer Wanamine2300, and add 3 parts epoxy diluent. E10P was heated to 100℃ for 0.5 hours, then heated to 120℃ for 2 hours, and then cooled to 80℃. Two parts of curing accelerator salicylic acid, one part of DEAPA and six parts of toughening agent benzyl alcohol were added. The mixture was stirred for 30 minutes until the salicylic acid was completely dissolved. After cooling to 60℃, two parts of siloxane coupling agent N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane A-2120 were added. The mixture was stirred evenly and then filtered to obtain the epoxy curing agent.

[0087] Example 2

[0088] 16 parts benzyl alcohol and 12 parts m-phenylenediamine were added to a four-necked flask. While stirring, 18 parts alicyclic diamine PACM were added. The temperature was raised to 80°C, and 10 parts epoxy resin YDF-170 were added. The temperature was raised to 90°C and held for 1 hour. Then, a second batch of 10 parts epoxy resin YDF-170 was added and held at 90°C for 1 hour. Then, 18 parts of hydrogenated alkyl aldehyde-aniline polymer Wanamine2300 and 5 parts epoxy diluent E10P were added. The temperature was held at 90°C for 0.5 hours, then raised to 120°C and held for 2 hours. The temperature was then lowered to 80°C, and 2 parts of curing accelerator DEAPA and 6 parts of toughening agent benzyl alcohol were added. The mixture was stirred for 30 minutes and then cooled to 60°C. Then, 3 parts of siloxane coupling agent N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane were added. The mixture was stirred evenly and then filtered to obtain the epoxy curing agent.

[0089] Example 3

[0090] 28 parts benzyl alcohol and 14 parts m-phenylenediamine were added to a four-necked flask. While stirring, 15 parts alicyclic diamine PACM were added. The temperature was raised to 60°C, and 6 parts epoxy resin YDF-170 were added. The temperature was raised to 95°C and held for 1 hour. Then, a second batch of 6 parts epoxy resin YDF-170 was added and held at 95°C for 1 hour. Then, 15 parts of hydrogenated alkyl aldehyde-aniline polymer Wanamine2300 and 5 parts epoxy reactive diluent cresol monoglycidyl ether were added. The temperature was held at 95°C for 0.5 hours, then raised to 120°C and held for 2 hours. The temperature was then lowered to 80°C, and 2 parts of curing accelerator DEAPA and 7 parts of toughening agent benzyl alcohol were added. The mixture was stirred for 30 minutes and then cooled to 60°C. Finally, 2 parts of siloxane coupling agent N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane were added. The mixture was stirred evenly and then filtered to obtain the epoxy curing agent.

[0091] Example 4

[0092] Add 23 parts cashew nut shell powder and 5 parts m-phenylenediamine to a four-necked flask, and while stirring, add 8 parts isophorone diamine (IPDA) and 8 parts PACM. Raise the temperature to 80°C, add 5 parts epoxy resin YDF-170, raise the temperature to 100°C and hold for 1 hour, then add a second batch of 5 parts epoxy resin YDF-170. After holding at 100°C for 1 hour, add 33 parts hydrogenated alkyl aldehyde-aniline polymer Wanamine2300. Add 5 parts of epoxy diluent E10P, keep at 100℃ for 0.5h, raise the temperature to 120℃ and keep at 120℃ for 2h, then cool down to 80℃, add 2 parts of curing accelerator DEAPA, 1 part of salicylic acid and 6 parts of toughening agent benzyl alcohol, stir for 30min, cool down to 60℃ and add 1 part of siloxane coupling agent N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, stir evenly and filter to obtain epoxy curing agent.

[0093] The application performance of the epoxy curing agents prepared in Examples 1-4 of this invention was tested. The test method was as follows: the epoxy curing agents prepared in Examples 1-4 of this invention were mixed with epoxy resin E51 (EEW=190) at a mass ratio of 100:57, and the coating films were prepared in a suitable manner according to the relevant national standards. The basic physical properties and corrosion resistance of the cured coating films were tested, and the results are shown in Table 1.

[0094] Table 1. Properties of the coatings obtained from epoxy curing agents and epoxy resins in Examples 1-4

[0095]

[0096] The epoxy curing agent prepared in Examples 1-4 of this invention was used as component B, and component A was a solvent-free epoxy coating (epoxy resin paint). The composition is shown in Table 2. The two components were mixed to prepare a paint film. The paint film was prepared in accordance with the relevant national standards and the chemical resistance of the cured paint film was tested. The results are shown in Table 3.

[0097] Table 2. Composition of Component A (solvent-free epoxy coating)

[0098]

[0099]

[0100] Table 3 Chemical resistance properties of the coating films obtained from epoxy curing agents and component A in Examples 1-4 of this invention.

[0101]

[0102]

[0103] As shown in Tables 1 and 3, the epoxy curing agents prepared in Examples 1-4 of this invention not only have excellent adhesion and flexibility, as well as good impact resistance and corrosion resistance, but also meet the long-term anti-corrosion requirements of various chemical-resistant fields. When applied to chemical-resistant epoxy coatings, they exhibit good resistance to salt spray, salt water immersion, and damp heat under room temperature curing conditions, as well as excellent resistance to acids, alkalis, solvents, and oils. In particular, they have excellent resistance to methanol, acids, cyclohexanone, concentrated sulfuric acid, and high-temperature acid solutions, which is difficult for general chemical-resistant coatings to achieve.

[0104] As can be seen from the above embodiments, the epoxy curing agent provided by the present invention has good physical properties, anti-corrosion properties and chemical resistance, a wide range of chemical media resistance, and excellent comprehensive performance.

[0105] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An epoxy curing agent, made from the following raw materials in parts by weight: Toughening agent 15-40 parts, aromatic diamine 5-15 parts, alicyclic diamine 5-20 parts, epoxy resin 5-20 parts, hydrogenated alkyl aldehyde-aniline polymer 15-35 parts, epoxy reactive diluent 1-6 parts, curing accelerator 0.5-4 parts and amino-terminated siloxane coupling agent 0.5-4 parts; The hydrogenated alkyl aldehyde-aniline polymer is a multifunctional alicyclic amine; the multifunctional alicyclic amine is Wanhua Chemical's WANAMINE 2300; The terminal aminosiloxane coupling agent includes one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; The epoxy resin is a room-temperature liquid bifunctional epoxy resin with an epoxy equivalent of 165~240 g / eq and a viscosity of 2000~20000 mPa.s. The epoxy reactive diluent is a monofunctional or bifunctional reactive diluent with a viscosity not exceeding 100 mPa·s and an epoxy equivalent of 150~500 g / eq. The viscosity of the alicyclic diamine is not higher than 150 mPa·s, and the active hydrogen equivalent is 30~65 g / eq; The active hydrogen equivalent of the aromatic diamine is 30~60 g / eq; The curing accelerator includes one or more of salicylic acid, bisphenol A, N,N-dimethyl-1,3-propanediamine and 3-diethylaminopropylamine; The toughening agent includes one or more of benzyl alcohol, cashew nut phenol and dodecylphenol; The preparation method of the epoxy curing agent includes the following steps: (1) After mixing a portion of the toughening agent, aromatic diamine and alicyclic diamine, the mixture is heated to obtain a first mixture; (2) The first mixture and epoxy resin are mixed in batches to carry out the first addition reaction, and the reaction is carried out sequentially after each batch is mixed. A second heating and a second cooling process yields the modified amine; (3) The modified amine is mixed with hydrogenated alkyl aldehyde-aniline polymer and epoxy reactive diluent in the third step and then heated in the third step to carry out the second addition reaction to obtain the first composite modified amine; (4) After the first composite modified amine is cooled down, it is mixed with the curing accelerator and the remaining toughening agent to obtain the second composite modified amine. (5) After cooling the second composite modified amine fourth, mix it with the terminal aminosiloxane coupling agent fifth to obtain an epoxy curing agent.

2. The epoxy curing agent according to claim 1, characterized in that, The epoxy resin includes one or more of bisphenol A epoxy resin E51, bisphenol A epoxy resin E44, and bisphenol F epoxy resin YDF-170.

3. The epoxy curing agent according to claim 1, characterized in that, The aromatic diamine includes one or more of 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and m-phenylenediamine.

4. The epoxy curing agent according to claim 1, characterized in that, The alicyclic diamine includes one or more of isoflavone diamine, 1,3-cyclohexanedimethylamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and methylcyclohexanediamine.

5. The epoxy curing agent according to claim 1, characterized in that, The epoxy reactive diluent includes one or more of glycidyl tert-carbonate, C12-C14 alkyl glycidyl ether, cashew phenol glycidyl ether, 1,6-hexanediol diglycidyl ether, and cresol monoglycidyl ether.

6. A method for preparing the epoxy curing agent according to any one of claims 1 to 5, comprising the following steps: (1) After mixing a portion of the toughening agent, aromatic diamine and alicyclic diamine, the mixture is heated to obtain a first mixture; (2) The first mixture and epoxy resin are mixed in batches to carry out the first addition reaction, and the reaction is carried out sequentially after each batch is mixed. A second heating and a second cooling process yields the modified amine; (3) The modified amine is mixed with hydrogenated alkyl aldehyde-aniline polymer and epoxy reactive diluent in the third step and then heated in the third step to carry out the second addition reaction to obtain the first composite modified amine; (4) After the first composite modified amine is cooled down, it is mixed with the curing accelerator and the remaining toughening agent to obtain the second composite modified amine. (5) After cooling the second composite modified amine fourth, mix it with the terminal aminosiloxane coupling agent fifth to obtain an epoxy curing agent.

7. The preparation method according to claim 6, characterized in that, The first heating temperature is 60~80℃; The second heating temperature is 90~120℃, and the holding time is 0.5~2h; The second cooling temperature is 60~80℃; The third heating temperature is 90~120℃, and the holding time is 0.5~2h; The third cooling temperature is 60~80℃; The fourth mixing temperature is 60~80℃, and the holding time is 0.5~1h; The fourth cooling temperature is 40~60℃.

8. The application of the epoxy curing agent according to any one of claims 1 to 5 or the epoxy curing agent obtained by the preparation method according to any one of claims 6 to 7 in epoxy resin coatings.

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