Aqueous polyamide epoxy resin curing agent and method for its preparation

Abstract

The application discloses a water-based polyamide epoxy resin curing agent and a preparation method thereof, which is made of 10-80% of polyether amine, 5-40% of alpha, beta-unsaturated acid or ester and 10-60% of polyamine substances. The curing agent prepared by the application has good compatibility with an epoxy emulsion and can be adjusted in construction viscosity by using water. After the paint film is cured, the paint film has high hardness, good flexibility, good adhesion and good corrosion resistance, is suitable for environment-friendly anti-corrosion paint and achieves very good technical effects.

Description

Technical Field

[0001] This invention relates to an epoxy resin curing agent and its preparation method, specifically to a water-based polyamide-type epoxy curing agent suitable for environmentally friendly anti-corrosion coatings, which, when used in conjunction with epoxy emulsion, produces a cured film with high hardness, good flexibility, good adhesion, and excellent corrosion resistance. This invention belongs to the field of polymer materials technology. Background Technology

[0002] Polyamide is an important type of epoxy curing agent. Its cured products with epoxy resin have excellent flexibility, impact resistance, adhesion and corrosion resistance, and outstanding comprehensive performance. Therefore, it occupies an important position in the fields of heavy-duty anti-corrosion coatings and industrial protective coatings.

[0003] Traditional polyamide curing agents have high viscosity; for example, the classic 115 type polyamide has a viscosity exceeding 50,000 mPa·s at 40℃, exhibiting almost no flowability. To meet construction requirements and improve the compatibility of polyamide curing agents with epoxy resins, large amounts of organic solvents (such as xylene and n-butanol) need to be added to the system during use. The use of large amounts of organic solvents not only results in extremely high volatile organic compound (VOC) content in the system, seriously polluting the environment and endangering the health of construction workers, but also poses significant safety hazards due to the low flash point and flammability / explosiveness of solvent-based coatings. With increasingly stringent environmental regulations both domestically and internationally, and the advancement of "dual carbon" goals, the development of low-VOC or even zero-VOC waterborne polyamide curing agents has become an inevitable trend in the industry.

[0004] In recent years, researchers have conducted extensive work on the development of waterborne polyamide curing agents. Key technical routes for endowing curing agents with waterborne capabilities include two main approaches: ionic and nonionic. Ionic approaches introduce hydrophilic groups through neutralization with organic acids to form salts; however, this method carries the risk of flash rust and has limitations in the selection of pigments, fillers, and additives. Nonionic approaches, on the other hand, achieve water dispersibility by introducing polyether hydrophilic segments into the curing agent's molecular structure, avoiding the inherent drawbacks of ionic approaches and thus attracting wider attention.

[0005] Chinese invention patent CN115677981B discloses a polyamide-modified waterborne epoxy curing agent, which is prepared by grafting commercially available polyamide (a product of condensation polymerization of fatty diacid and fatty diamine) with hydrophilic polyether segments. Chinese invention patent CN109608622B proposes a nonionic waterborne polyamide curing agent and its preparation method. The core of this method involves reacting a low molecular weight polyether amine with an unsaturated acid anhydride under reflux at 80-100°C to obtain a polyamic acid intermediate. Then, an alicyclic or aromatic polyamine is added dropwise at 100-120°C to undergo a Michael addition reaction. Finally, the polyamine is amidated and copolymerized at 180-200°C to obtain a brownish-red polyamide curing agent, which is then diluted with water.

[0006] This invention uses hydrophilic polyetheramine as a starting material. First, the polyetheramine undergoes a Michael addition reaction with α,β-unsaturated acids or esters to obtain a key intermediate—a hydrophilic polyacid. Then, it undergoes an amidation reaction with a polyamine to obtain the final product. The resulting waterborne polyamide exhibits good compatibility with epoxy emulsions and its application viscosity can be adjusted with water. After curing, the paint film exhibits high hardness, good flexibility, good adhesion, and excellent corrosion resistance, making it suitable for environmentally friendly anti-corrosion coatings. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a polyamide-type epoxy resin curing agent that is compatible with epoxy emulsions and can be diluted with water, in order to meet the application requirements of environmentally friendly anti-corrosion coatings; another purpose of this invention is to provide a method for preparing the waterborne polyamide epoxy resin curing agent.

[0008] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows: A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in weight percentages: 10-80% polyetheramine, 5-40% α,β-unsaturated acid or ester and 10-60% polyamine substances.

[0009] As a preferred embodiment, the above-mentioned waterborne polyamide epoxy resin curing agent is made from the following raw materials in weight percentages: 10-70% polyetheramine, 10-30% α,β-unsaturated acid or ester and 20-55% polyamine substances.

[0010] As a preferred embodiment, the polyetheramine in the above-mentioned waterborne polyamide epoxy resin curing agent is one or a mixture of several of the following: monofunctional polyetheramines (Hunsmann M-600, M-1000, M-2005, M-2070, M-2095, M-3085), difunctional polyetheramines (Hunsmann D-230, D-400, D-2000, D-4000, ED-600, ED-900, ED-2003), and trifunctional polyetheramines (Hunsmann T-403, T-5000).

[0011] As a preferred embodiment, the α,β-unsaturated acid or ester in the above-mentioned waterborne polyamide epoxy resin curing agent is one or a mixture of several of the following: acrylic acid (ester), methacrylic acid (ester), crotonic acid (ester), cinnamic acid (ester), maleic acid (ester), and itaconic acid (ester).

[0012] As a preferred embodiment, the polyamine in the above-mentioned waterborne polyamide epoxy resin curing agent is one or a mixture of several of the following: ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, pentanediamine, hexanediamine, 2-methylpentanediamine, isofluranediamine, 1,3-cyclohexanedimethylamine, m-phenylenediamine, cyclohexanediamine, cyclopentanediamine, diaminodicyclohexylmethane, and diaminodiphenylmethane.

[0013] The preparation method of the waterborne polyamide epoxy resin curing agent of the present invention is characterized by comprising the following steps: (1) Add polyetheramine, α,β-unsaturated acid or ester into the reactor according to the mass percentage, stir, and mix the materials evenly; (2) Heat the reactants to 50-80℃ and keep them at that temperature for a period of time; (3) Add polyamines, heat to 160-200℃, and keep warm for a period of time; (5) Remove water or small molecule alcohols generated during the reaction and a small amount of unreacted amine raw materials by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0014] As a preferred embodiment, the preparation method of the waterborne polyamide epoxy resin curing agent of the present invention includes the following steps: (1) Add polyetheramine, α,β-unsaturated acid or ester into the reactor according to the mass percentage, stir, and mix the materials evenly; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add polyamines and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove water or small molecule alcohols generated during the reaction and a small amount of unreacted amine raw materials by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages: This invention designs a novel epoxy curing agent. First, a hydrophilic polyether amine undergoes a mild Michael addition reaction to generate a hydrophilic polyacid, which then undergoes condensation polymerization with the polyamine to form a waterborne polyamide. This invention has the following advantages: The reaction process is simple and there are a variety of raw materials to choose from. Therefore, the diversity of product molecular structures can be achieved by selecting raw materials, thereby designing products suitable for different application needs. This product retains the traditional properties of polyamides while exhibiting excellent water solubility, eliminating the need for dilution with organic solvents during use. Chinese invention patent CN109608622B requires high-speed dispersion with water after polyamide production. This process necessitates controlling temperature, water droplet rate, and stirring speed, and the resulting dispersion often suffers from poor storage stability due to this "phase inversion" process. The polyamide obtained by this patent exhibits superior water solubility and can be used with epoxy emulsions with simple manual stirring. Therefore, it eliminates the need for pre-dispersion at high speed, simplifying the production process and enhancing ease of use.

[0016] The reaction intermediate described in Chinese invention patent CN109608622B contains both carboxyl and primary amino groups, and undergoes self-condensation to form polyamide. However, this self-condensation process is prone to cyclization side reactions, resulting in a wide molecular weight distribution of the product, which easily leads to poor storage stability, uneven curing reaction, large fluctuations in paint film properties, and decreased mechanical properties and salt spray resistance. In contrast, this patent uses a different reaction approach, utilizing the condensation reaction of hydrophilic polyacids and polyamines to obtain the finished product. The reaction is controllable, and the properties are stable in all aspects, representing a significant improvement. Attached Figure Description

[0017] Figure 1 This is a reaction flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0018] Example 1

[0019] 1. A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in the following weight percentages: 38% polyetheramine D-230, 28% methacrylic acid, and 34% diethylenetriamine.

[0020] 2. A method for preparing a waterborne polyamide epoxy resin curing agent, comprising the following steps: (1) Add 230g of polyetheramine D-230 and 172g of methacrylic acid into the reactor and stir to make the materials evenly mixed; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add 206g of diethylenetriamine and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove water and a small amount of unreacted raw materials generated during the reaction by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0021] Example 2

[0022] 1. A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in the following weight percentages: 31% polyetheramine D-230, 23% methacrylic acid, and 46% isophorone diamine.

[0023] 2. A method for preparing a waterborne polyamide epoxy resin curing agent, comprising the following steps: (1) Add 230g of polyetheramine D-230 and 172g of methacrylic acid into the reactor and stir to make the materials evenly mixed; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add 340g of isophorone diamine and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove water and a small amount of unreacted raw materials generated during the reaction by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0024] Example 3

[0025] 1. A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in the following weight percentages: 21% polyetheramine D-230, 26% dimethyl maleate, and 53% triethylenetetramine.

[0026] 2. A method for preparing a waterborne polyamide epoxy resin curing agent, comprising the following steps: (1) Add 230g of polyetheramine D-230 and 288g of dimethyl maleate into the reactor and stir to make the materials evenly mixed; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add 584g of triethylenetetramine and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove methanol and a small amount of unreacted raw materials generated during the reaction by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0027] Example 4

[0028] 1. A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in the following weight percentages: 70% polyetheramine M-1000, 10% dimethyl maleate, and 20% triethylenetetramine.

[0029] 2. A method for preparing a waterborne polyamide epoxy resin curing agent, comprising the following steps: (1) Add 500g of polyetheramine M-1000 and 72g of dimethyl maleate into the reactor and stir to make the materials evenly mixed; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add 146g of triethylenetetramine and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove methanol and a small amount of unreacted raw materials generated during the reaction by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0030] Example 5

[0031] 1. A waterborne polyamide epoxy resin curing agent, which is made from the following raw materials in the following weight percentages: 44% polyetheramine T-403, 26% methyl acrylate, and 30% diethylenetriamine.

[0032] 2. A method for preparing a waterborne polyamide epoxy resin curing agent, comprising the following steps: (1) Add 440g of polyetheramine T-403 and 258g of methyl acrylate into the reactor and stir to make the materials evenly mixed; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 3 hours; (3) Add 309g of diethylenetriamine and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 3 hours; (5) Remove methanol and a small amount of unreacted raw materials generated during the reaction by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

[0033] Example 6 Performance Testing The epoxy emulsion (SMW602 from Jiangsu Sanmu Chemical Co., Ltd., epoxy equivalent 1000 g / eq) was mixed evenly with the waterborne polyamide epoxy resin curing agent prepared in Examples 1-5 (at a 1:1 ratio of epoxy groups to active hydrogens), exhibiting excellent compatibility. The mixture was uniformly coated onto tinplate to form a film with a thickness of 40 μm. The basic properties of the cured finished product are shown in Table 1 below.

[0034] Table 1 .

[0035] The above performance test results demonstrate that the synthesis process described in this patent is reliable, and high-performance waterborne polyamide-type epoxy resin curing agents can be synthesized using various raw materials. The waterborne polyamide curing agents obtained in Examples 1-5 exhibit excellent compatibility with epoxy emulsions, requiring no organic solvent dilution; the viscosity can be adjusted to a suitable level using water. The cured paint film exhibits excellent mechanical properties and salt spray resistance, making it suitable for environmentally friendly anti-corrosion coatings and achieving very good technical results. Based on the proportions, Example 1 shows the best overall performance.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water-based polyamide epoxy resin curing agent, characterized in that, It is made from the following raw materials by weight percentage: 10-80% polyetheramine, 5-40% α,β-unsaturated acid or ester and 10-60% polyamine.

2. The waterborne polyamide epoxy resin curing agent according to claim 1, characterized in that, It is made from the following raw materials by weight percentage: 10-70% polyetheramine, 10-30% α,β-unsaturated acid or ester and 20-55% polyamine substances.

3. The waterborne polyamide epoxy resin curing agent according to claim 1 or 2, characterized in that, The polyetheramine is one or a mixture of several of the following: monofunctional polyetheramine, difunctional polyetheramine, and trifunctional polyetheramine.

4. The waterborne polyamide epoxy resin curing agent according to claim 1 or 2, characterized in that, The α,β-unsaturated acid or ester is one or a mixture of several of the following: acrylic acid (ester), methacrylic acid (ester), crotonic acid (ester), cinnamic acid (ester), maleic acid (ester), and itaconic acid (ester).

5. The waterborne polyamide epoxy resin curing agent according to claim 1 or 2, characterized in that, The polyamines mentioned are one or a mixture of several of the following: ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, pentanediamine, hexanediamine, 2-methylpentanediamine, isoflurone diamine, 1,3-cyclohexanedimethylamine, m-phenylenediamine, cyclohexanediamine, cyclopentanediamine, diaminodicyclohexylmethane, and diaminodiphenylmethane.

6. The method for preparing the waterborne polyamide epoxy resin curing agent according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Add polyetheramine, α,β-unsaturated acid or ester into the reactor according to the mass percentage, stir, and mix the materials evenly; (2) Heat the reactants to 50-80℃ and keep them at that temperature for a period of time; (3) Add polyamines, heat to 160-200℃, and keep warm for a period of time; (5) Remove water or small molecule alcohols generated during the reaction and a small amount of unreacted amine raw materials by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

7. The method for preparing the waterborne polyamide epoxy resin curing agent according to claim 6, characterized in that, Includes the following steps: (1) Add polyetheramine, α,β-unsaturated acid or ester into the reactor according to the mass percentage, stir, and mix the materials evenly; (2) Heat the reactants to 60-70℃ and keep them at 60-70℃ for 1-3 hours; (3) Add polyamines and heat to 180-200℃; (4) Keep the reaction at 180-200℃ for 1-3 hours; (5) Remove water or small molecule alcohols generated during the reaction and a small amount of unreacted amine raw materials by reducing pressure; (6) Cooling, filtering, and packaging to obtain the finished product: water-based polyamide epoxy resin curing agent.

8. The use of the curing agent according to any one of claims 1 to 5 in curing waterborne polyamide epoxy resin.

9. The application according to claim 8, characterized in that, Application of curing agents in improving the corrosion resistance of waterborne polyamide epoxy resins.

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