Reactive microgel water dispersion for two-component waterborne epoxy coating and preparation method of reactive microgel water dispersion

Abstract

The invention discloses a reactive microgel water dispersion for a two-component waterborne epoxy coating and a preparation method of the reactive microgel water dispersion, and belongs to the technical field of waterborne epoxy resin preparation. Comprising the following steps: 1) mixing epoxy resin and flexible diglycidyl ether, adding hydrophobic and hydrophilic long-chain amine chain extenders at 60-120 DEG C, and keeping the temperature for 1-6 hours to obtain an epoxy-terminated prepolymer, and 2) adding flexible steric hindrance amine into the prepolymer, reacting at 50-90 DEG C for 1-6 hours, adding pure water under high-speed stirring, and dispersing to obtain the microgel water dispersion. The prepared microgel water dispersion does not contain an organic solvent, can improve the anti-sagging performance, the anti-settling performance and the sharp edge anti-corrosion performance of a special base material when being used in a two-component waterborne epoxy coating, and can be subjected to a curing reaction with epoxy resin without shortening the working life of the coating.

Description

Technical Field

[0001] This invention relates to the field of waterborne epoxy resin preparation technology, and in particular to a reactive microgel aqueous dispersion for two-component waterborne epoxy coatings and its preparation method. Background Technology

[0002] Microgels are polymer particles that can be stably dispersed in water or solvent media and have an internal cross-linked structure. They exhibit high viscosity after swelling in the medium, but the viscosity decreases significantly after shearing because there are no strong chemical bonds between the particles, thus exhibiting strong thixotropy. Reactive microgels contain functional groups that can react chemically with resins or additives, and can play a variety of functions in coatings.

[0003] Since microgels are defined as crosslinking occurring only within polymer particles, with no chemical bonds connecting the particles, aqueous microgels are mostly prepared using emulsion polymerization, requiring only the introduction of crosslinking monomers into the monomers. For example, patent CN202311542695.1 discloses a microgel acrylate emulsion and its preparation method. This microgel contains a large number of carboxyl groups and exhibits strong thickening and thixotropic properties after alkali neutralization, making it suitable for the directional arrangement of effect pigments such as aluminum powder in water-based metallic paints. Obviously, microgels prepared by emulsion polymerization are more suitable for use in acrylic resin coatings, while epoxy resins and curing agents are mostly produced by solution polymerization, which requires strict control of the degree of crosslinking to achieve the coexistence of low-crosslinked polymers, branched macromolecules, and linear small molecules, and adjustment to a suitable hydrophilic-lipophilic balance value to form a stable microgel dispersion in water.

[0004] Currently, most microgel inventions applicable to waterborne epoxy coating systems are related to cathodic electrophoretic coatings. For example, patent CN112341903A discloses a method for preparing and using a cathodic electrophoretic coating additive with good edge coating effect. This technology obtains a highly branched partially cross-linked structure by reacting a multifunctional epoxy resin with a polyamine. Then, a hydrophobic side chain is introduced by ring-opening the hydroxyl side chain of the epoxy resin with a monoepoxy compound at a high temperature of 130~140℃ to improve wetting and leveling properties. Finally, water is added under acid neutralization conditions to disperse the microgel into a cationic microgel dispersion. When added to the cathodic electrophoretic coating, it can play a good edge coating role by adjusting the fluidity during the drying process of the paint film. This is very important for the corrosion resistance of metal substrates with rough surfaces or sharp edges. Therefore, microgels are very suitable as a functional additive for waterborne epoxy coatings for metal corrosion protection. However, microgels used in cathodic electrophoretic coatings are acid-neutralized cationic hydrophilic systems. In conventional waterborne coatings, the acid cannot be removed from the coating through electrophoresis, resulting in poor compatibility with the coating formulation. Therefore, it is necessary to develop a microgel aqueous dispersion that is simple to process and suitable for conventional amine-cured waterborne epoxy anticorrosive coatings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a two-component reactive microgel aqueous dispersion for waterborne epoxy coatings and its preparation method, mainly solving the following technical difficulties: 1. The chemical structure of the microgel needs to be highly compatible with existing nonionic waterborne epoxy resins and amine curing agents, so as to reduce the impact on the coating film performance while exerting the rheological effect of the microgel and avoid the introduction of acids and ions; 2. During the synthesis of microgels, due to their large average molecular weight, organic solvents are usually added to reduce the viscosity of the material before water dispersion. This will introduce additional VOCs when used in coating formulations. 3. As a reactive microgel for waterborne two-component epoxy coatings, it is more suitable to introduce amine groups rather than epoxy groups as reactive groups from the perspective of hydrophilicity. However, amine-terminated microgels have the characteristics of high molecular weight and high functionality. When reacting with epoxy resin, the cross-linking network develops rapidly, which can easily lead to a shorter pot life of the coating. The objective of this invention is achieved as follows: a two-component reactive microgel aqueous dispersion for waterborne epoxy coatings, prepared from raw materials comprising the following parts by mass: 5-25 parts epoxy resin, 1-10 parts flexible diglycidyl ether, 1-20 parts hydrophobic long-chain amine chain extender, 1-20 parts hydrophilic long-chain amine chain extender, 2-20 parts flexible sterically hindered polyamine, and 40-70 parts water.

[0006] Furthermore, the epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol S type epoxy resin with bifunctionality and epoxy equivalent of 100~400 g / eq. Furthermore, the flexible diglycidyl ether is selected from one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and dimer acid diglycidyl ether. Furthermore, the hydrophobic long-chain amine chain extender is selected from one or more of n-octylamine, isooctylamine, dodecylamine, octadecylamine, and oleylamine; the hydrophilic long-chain amine chain extender is a polyoxyethylene monoamine, including any one or more of polyetheramine M1000, polyetheramine M2000, and polyetheramine M3000; the flexible sterically hindered polyamine is a polyoxypropylene amine containing at least two highly sterically hindered primary amine groups in its structure, including any one or more of polyetheramine D230, polyetheramine D400, and polyetheramine T403. Furthermore, the molar ratio of the total epoxy groups in the epoxy resin and flexible diglycidyl ether to the total amino groups in the hydrophilic / hydrophobic long-chain chain extender is 1.2~1.8:1; the molar ratio of the amino groups in the medium flexible sterically hindered polyamine to the remaining epoxy groups in the prepolymer is 1.5~2:1. A method for preparing a reactive microgel aqueous dispersion for two-component waterborne epoxy coatings includes the following steps: Step 1) Mix epoxy resin and flexible diglycidyl ether to form a bottom liquid, add hydrophobic and hydrophilic long-chain amine chain extender, and keep it at the temperature for a set time to obtain the prepolymer; Step 2) Add flexible sterically hindered polyamine to the prepolymer at a set temperature, keep it at the temperature for a set time, and then add water to disperse it to obtain epoxy resin-based polyol aqueous dispersion.

[0007] Furthermore, the specific process of the reaction in step 1) is as follows: the temperature of the material inside the reactor is maintained at 60~120℃ for 1~6 hours; The specific process of the reaction in step 2) is as follows: the temperature of the material in the reactor is maintained at 50~90℃ for 1~6h, and then the required pure water is added at once. The mixture is dispersed at 50℃ for at least 30min to obtain a two-component waterborne epoxy coating reactive microgel aqueous dispersion.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The introduction of nonionic hydrophilic groups / long carbon chain lipophilic groups ensures that the main structure has good self-emulsification ability, does not contain organic acids and other ionic hydrophilic groups, and has good compatibility with waterborne epoxy resin / waterborne amine curing agent. (2) The prepolymer obtained by chain extension of long-chain monoamine and difunctional epoxy compound has a branched structure. This structure reduces the entanglement between molecular chains. The linear prepolymer with lower molecular weight has a lower viscosity. Combined with low viscosity flexible diglycidyl ether, it can achieve extremely low VOC without the use of cosolvents in the synthesis process. (3) Low-activity sterically hindered polyetheramines are used in the crosslinking stage. The structural feature is that one hydrogen atom in the methylene group connected to the amino group is replaced by a methyl group. Due to the steric hindrance effect, the reaction rate difference between the active hydrogen of the primary amine and the active hydrogen of the secondary amine in this polyetheramine is much greater than that of ordinary aliphatic amines. Therefore, the crosslinking reaction is more controllable. While ensuring a certain degree of crosslinking, the viscosity can be controlled to avoid being too high, and the residue of small molecules such as free amines can be reduced. (4) The final microgel is polyetheramine-terminated. The reactivity of a single active hydrogen is much lower than that of conventional waterborne amine curing agents. Therefore, it has little impact on the pot life of the coating. The high molecular weight and high functionality of the microgel ensure that it is not easy for the microgel to remain in the paint film in a free state and affect the paint film performance. Detailed Implementation

[0009] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0010] Example 1 A method for preparing a reactive microgel aqueous dispersion A for a two-component waterborne epoxy coating includes the following steps: (1) Add 7 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq and 3 parts by weight of 1,6-hexanediol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 3 parts by weight of octadecylamine and 19 parts by weight of polyetheramine M2000, heat to 110℃ and keep warm for 3h to obtain the prepolymer; (2) Cool the prepolymer to 80°C, add 3 parts by weight of polyetheramine D230, maintain the temperature at 80°C for 3 hours, then add 65 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion A for waterborne epoxy coating with a solid content of 35%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion A based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0011] Example 2 A method for preparing a reactive microgel aqueous dispersion B for a two-component waterborne epoxy coating includes the following steps: (1) Add 7 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq and 4 parts by weight of 1,6-hexanediol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 2 parts by weight of dodecylamine and 20 parts by weight of polyetheramine M2000, heat to 110℃ and keep warm for 3h to obtain the prepolymer; (2) Cool the prepolymer to 80°C, add 7 parts by weight of polyetheramine T403, maintain the temperature at 80°C for 3 hours, then add 60 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion B for waterborne epoxy coating with a solid content of 40%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion B based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0012] Example 3 A method for preparing a reactive microgel aqueous dispersion C for a two-component waterborne epoxy coating includes the following steps: (1) Add 10 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq and 4 parts by weight of 1,6-hexanediol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 4 parts by weight of octadecylamine and 13 parts by weight of polyetheramine M1000, heat to 110℃ and keep warm for 3h to obtain the prepolymer; (2) Cool the prepolymer to 80°C, add 5 parts by weight of polyetheramine D230, maintain the temperature at 80°C for 3 hours, then add 65 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion C for waterborne epoxy coating with a solid content of 35%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion C based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0013] Example 4 A method for preparing a reactive microgel aqueous dispersion D for a two-component waterborne epoxy coating includes the following steps: (1) Add 9 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq and 4 parts by weight of 1,6-hexanediol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 2 parts by weight of dodecylamine and 13 parts by weight of polyetheramine M1000, heat to 110℃ and keep warm for 3h to obtain the prepolymer; (2) Cool the prepolymer to 80°C, add 9 parts by weight of polyetheramine D230, maintain the temperature at 80°C for 3 hours, then add 63 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion D for waterborne epoxy coatings with a solid content of 37%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion D based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0014] Example 5 A method for preparing a reactive microgel aqueous dispersion E for a two-component waterborne epoxy coating includes the following steps: (1) Add 7 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq, 4 parts by weight of 1,6-hexanediol diglycidyl ether and 3 parts by weight of polyethylene glycol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 2 parts by weight of dodecylamine and 13 parts by weight of polyetheramine M1000, heat to 110℃ and keep warm for 3h to obtain the prepolymer; (2) Cool the prepolymer to 80°C, add 9 parts by weight of polyetheramine T403, maintain the temperature at 80°C for 3 hours, then add 60 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion E for waterborne epoxy coating with a solid content of 40%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion E based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0015] Example 6 A method for preparing a reactive microgel aqueous dispersion F for a two-component waterborne epoxy coating includes the following steps: (1) Add 10 parts by weight of bisphenol A type epoxy resin with an epoxy equivalent of 190 g / eq and 5 parts by weight of polyethylene glycol diglycidyl ether to the reactor and mix them as the bottom liquid for later use; then add 4 parts by weight of octadecylamine and 15 parts by weight of polyetheramine M1000, heat to 110℃ and keep warm for 3 hours to obtain the prepolymer. (2) Cool the prepolymer to 80°C, add 6 parts by weight of polyetheramine D230, maintain the temperature at 80°C for 3 hours, then add 60 parts by weight of pure water under high speed stirring, and continue stirring at 50°C for 30 minutes to obtain a two-component reactive microgel aqueous dispersion F for waterborne epoxy coating with a solid content of 40%. (3) According to the waterborne two-component epoxy coating formulation shown in Table 1, add reactive microgel dispersion F based on 10% of the total mass of component B to component B. After the two components are mixed evenly, apply the coating to the blade and bake it at 80℃ until dry. Test the salt spray resistance with an intact paint film (refer to national standard GB / T 1771-2007), and focus on observing the corrosion at the blade edge. Place the remaining coating in a 35℃ oven and observe the coating state and film-forming properties every 30 minutes to determine the applicability period.

[0016] Comparative Example 1 According to the water-based two-component epoxy anti-corrosion coating formulation shown in Table 1, without adding the reactive microgel water from the examples, the two components were mixed evenly and then coated on the blade. After baking at 80°C until dry, the salt spray resistance was tested with an intact paint film (refer to national standard GB / T 1771-2007), with particular attention to the corrosion at the blade edge. The remaining coating was placed in a 35°C oven, and the coating state and film-forming properties were observed every 30 minutes to determine the usable period.

[0017] 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.

[0018] Table 1: Formulation of Waterborne Two-Component Epoxy Anticorrosion Coatings The performance test results of the above embodiments and comparative examples are shown in Table 2: Table 2: Performance of epoxy resin-based polyol aqueous dispersions and hydroxypropyl dispersions when combined As shown in Table 2, the two-component waterborne epoxy coating with added microgels exhibited excellent anti-corrosion performance at sharp edges. This indicates that the microgels inhibited the flow of the coating at the edges due to uneven surface tension during the film drying process, realizing the unique rheological properties of the microgels. Furthermore, the microgels can participate in the resin curing reaction without affecting the pot life of the coating. As a novel rheology modifier that can replace traditional non-reactive thickeners, it has high application value.

[0019] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A reactive microgel aqueous dispersion for two-component waterborne epoxy coatings, characterized in that, It is prepared from raw materials comprising the following parts by weight: 5-25 parts epoxy resin, 1-10 parts flexible diglycidyl ether, 1-20 parts hydrophobic long-chain amine chain extender, 1-20 parts hydrophilic long-chain amine chain extender, 2-20 parts flexible sterically hindered polyamine, and 40-70 parts water.

2. The reactive microgel aqueous dispersion for two-component waterborne epoxy coatings according to claim 1, characterized in that, The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol S type epoxy resin with bifunctionality and epoxy equivalent of 100~400 g / eq.

3. The reactive microgel aqueous dispersion for a two-component waterborne epoxy coating according to claim 2, characterized in that, The flexible diglycidyl ether is selected from one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and dimer acid diglycidyl ether.

4. A reactive microgel aqueous dispersion for a two-component waterborne epoxy coating according to any one of claims 1-3, characterized in that, The hydrophobic long-chain amine chain extender is selected from one or more of n-octylamine, isooctylamine, dodecylamine, octadecylamine, and oleylamine; the hydrophilic long-chain amine chain extender is a polyoxyethylene monoamine, including any one or more of polyetheramine M1000, polyetheramine M2000, and polyetheramine M3000; the flexible sterically hindered polyamine is a polyoxypropylene amine containing at least two highly sterically hindered primary amine groups in its structure, including any one or more of polyetheramine D230, polyetheramine D400, and polyetheramine T403.

5. A reactive microgel aqueous dispersion for a two-component waterborne epoxy coating according to any one of claims 1-4, characterized in that, The molar ratio of the total epoxy groups in the epoxy resin and flexible diglycidyl ether to the total amino groups in the hydrophilic / hydrophobic long-chain chain extender is 1.2~1.8:1; the molar ratio of the amino groups in the medium-flexible sterically hindered polyamine to the remaining epoxy groups in the prepolymer is 1.5~2:

1.

6. A method for preparing a reactive microgel aqueous dispersion for two-component waterborne epoxy coatings as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1) Mix epoxy resin and flexible diglycidyl ether to form a bottom liquid, add hydrophobic and hydrophilic long-chain amine chain extender, and keep it at the temperature for a set time to obtain the prepolymer; Step 2) Add flexible sterically hindered polyamine to the prepolymer at a set temperature, keep it at the temperature for a set time, and then add water to disperse it to obtain epoxy resin-based polyol aqueous dispersion.

7. The method for preparing the reactive microgel aqueous dispersion for two-component waterborne epoxy coatings according to claim 6, characterized in that, The specific process of the reaction in step 1) is as follows: the temperature of the material in the reactor is maintained at 60~120℃ for 1~6 hours; The specific process of the reaction in step 2) is as follows: the temperature of the material in the reactor is maintained at 50~90℃ for 1~6h, and then the required pure water is added at once. The mixture is dispersed at 50℃ for at least 30min to obtain a two-component waterborne epoxy coating reactive microgel aqueous dispersion.

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