Multifunctional water-borne epoxy resin coating containing modified fly ash and preparation method of multifunctional water-borne epoxy resin coating

Abstract

The invention relates to the technical field of water-borne epoxy resin coating preparation, in particular to a multifunctional water-borne epoxy resin coating containing modified fly ash and a preparation method thereof.The preparation method comprises the steps that 2-5 parts of fly ash is dispersed into 100-500 parts of absolute ethyl alcohol, 10-50 parts of deionized water is added, then 3-10 parts of silane coupling agent is added, the temperature is increased to 50-80 DEG C, a reflux reaction is conducted for 2-8 hours, after the reaction is completed, the temperature is reduced to the room temperature, and the modified fly ash-containing multifunctional water-borne epoxy resin coating is obtained; centrifugally washing with deionized water to obtain functionalized fly ash; 2, dispersing the functionalized fly ash obtained in the step 1 into 2.5-10 parts of deionized water, mixing with 3.75-15 parts of a water-borne epoxy resin curing agent, and stirring to prepare a component B of the water-borne epoxy resin coating; 3-12 parts of bisphenol A type epoxy resin is used as a component A of the water type epoxy resin coating; when in use, the component A and the component B are uniformly stirred and mixed and then are scraped to form a film. The curing effect of a water-borne epoxy resin system is greatly improved, so that the water-borne epoxy resin coating with excellent performance is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of waterborne epoxy resin coating preparation, in particular to a multifunctional waterborne epoxy resin coating containing modified fly ash and a preparation method thereof. Background Art

[0002] Metals are obtained by absorbing energy from metal minerals (oxides, sulfides, etc.) through metal smelting. Therefore, metals are in a thermodynamically unstable state. They tend to transform into metal ions when interacting with the surrounding medium, and metal corrosion occurs. The difference in energy is the driving force for the corrosion reaction. The corrosion process releases energy. Corrosion is a spontaneous process, which will cause irreversible damage to metals. Metal materials are widely used in various fields such as national defense, transportation, and construction. The losses caused by metal corrosion each year are the sum of the losses caused by other natural damage. In addition, metal corrosion will also bring a series of environmental and safety hazards, so the corrosion problem cannot be underestimated.

[0003] In order to protect metals, the protection of metal substrates has been widely studied. Among the many anti-corrosion methods, surface coating technology is widely used because of its effective anti-corrosion and economy. Epoxy resin coating is widely used in surface coating technology because of its excellent adhesion, excellent curing stability, high mechanical strength, excellent electrical insulation, low shrinkage and low water absorption. However, traditional epoxy resins are usually dissolved in organic solvents (aromatic hydrocarbons and ketones), and a large amount of harmful volatile organic compounds (VOCs) will be produced during the actual application process, which will cause certain harm to human health and environmental safety. In recent years, green and environmentally friendly water-based epoxy resin coatings have the advantages of low VOC and excellent metal adhesion, and have gradually replaced traditional solvent-based epoxy coatings. However, there are many hydrophilic groups in water-based epoxy resin coatings, which are easy to form polar channels and reduce the water resistance of the coating. In addition, during the cross-linking and curing process of water-based epoxy resin coatings, due to the continuous evaporation of the solvent, a large number of micropores and defects will be generated. These defects will seriously reduce the corrosion resistance of the coating and accelerate the penetration of corrosive media. Therefore, it is crucial to improve the long-term corrosion resistance of water-based epoxy resin coatings through some scientific methods.

[0004] Fly ash is widely used in polymer coatings due to its microsphere structure and stable physical and chemical properties. Its good barrier properties can significantly improve the corrosion resistance of the coating. However, fly ash has poor dispersibility in polymers, which is not conducive to improving the performance of the coating. Therefore, using silane coupling agent to functionalize the surface of fly ash as a co-curing agent for water-based epoxy resin not only achieves high added value utilization of fly ash, turning solid waste fly ash into treasure, but also can well improve the corrosion resistance and flame retardancy of water-based epoxy resin coatings. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a multifunctional water-based epoxy resin coating containing modified fly ash and a preparation method thereof, so as to solve the problems in the prior art that there are many hydrophilic groups in the water-based epoxy resin, which easily form polar channels, and that in the cross-linking and curing process of the water-based epoxy resin coating, the continuous evaporation of the solvent produces a large number of micropores and defects. The fly ash surface is functionalized with a silane coupling agent as a co-curing agent for the water-based epoxy resin, thereby improving the corrosion resistance of the coating and giving the coating certain flame retardant properties.

[0006] In order to achieve the above purpose, the technical solutions provided are as follows:

[0007] A method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash, characterized in that it comprises the following steps:

[0008] Step 1: Disperse 2 to 5 parts of fly ash in 100 to 500 parts of anhydrous ethanol by weight, add 10 to 50 parts of deionized water, and then add 3 to 10 parts of silane coupling agent, heat to 50 to 80° C., reflux for 2 to 8 hours, cool to room temperature after the reaction is completed, and centrifuge and wash with deionized water to obtain functionalized fly ash;

[0009] Step 2: Disperse the functionalized fly ash obtained in step 1 into 2.5 to 10 parts of deionized water, mix with 3.75 to 15 parts of waterborne epoxy resin curing agent, and stir to prepare component B of waterborne epoxy resin coating;

[0010] Step 3: Calculate by mass and use 3 to 12 parts of bisphenol A epoxy resin as component A of the water-based epoxy resin coating. When using, stir and mix component A and component B evenly and then apply them to form a film.

[0011] Preferably, in step 1, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane and vinyltriethoxysilane.

[0012] Preferably, in step 1, the fly ash has a particle size of 100nm to 100000nm.

[0013] Preferably, in step 1, the number of centrifugal washing with deionized water is 2 to 6 times.

[0014] Preferably, in step 2, the functionalized fly ash is dispersed into 2.5 to 10 parts of deionized water by ultrasonic dispersion, and the ultrasonic dispersion time is 0.5 to 1 hour.

[0015] Preferably, in step 2, the water-based epoxy resin curing agent is one or more of Banghe 901, Banghe 916, Shenzhen Yoshida F0705, Suzhou Meiguowang Flooring WG-828 and Huabang Chemical HB-7871.

[0016] Preferably, in step 2, the stirring is performed by a magnetic stirrer, and a Huapuda DJ-2 high-power magnetic stirrer is selected, with a rotation speed of 300 to 1200 rad / min and a stirring time of 12 to 32 hours.

[0017] Preferably, in step 3, the film is scraped using a SZQ four-sided wet film preparation device, and the wet film thickness is 30 to 200 microns. After film formation, the curing time at room temperature is 5 to 10 days, and the thermal curing temperature is 40 to 100° C., and the time is 2 to 10 hours.

[0018] Preferably, in step three, the bisphenol A epoxy resin is one or more of E-51, E-44, BDR6100, BE114, BE186, E-42, E-03 and E-12, and the mass ratio of bisphenol A epoxy resin to water-based epoxy resin curing agent is 1:1.2 to 2.5.

[0019] Preferably, in step three, the amount of the functionalized fly ash added is 0.4% to 2.0% by mass of component A of the waterborne epoxy resin coating.

[0020] A multifunctional water-based epoxy resin coating containing modified fly ash is characterized in that: the coating of the water-based epoxy resin coating is dense and has no needle-shaped holes; the coating adhesion reaches level 0; no corrosion lesions occur after immersion in a 3.5% NaCl solution for 40 days, and the flame retardant ability is also improved to a certain extent.

[0021] Mechanism of the invention: The present invention provides a multifunctional waterborne epoxy resin coating containing modified fly ash and a preparation method thereof. Due to its hydrophilic groups and inherent defects, the waterborne epoxy resin coating allows corrosive substances to easily penetrate the coating matrix and reach the coating / steel interface, thereby promoting corrosion reactions on the steel surface. Therefore, a single waterborne epoxy resin coating cannot provide long-term corrosion protection for the steel substrate in a harsh environment. Therefore, the modified fly ash is introduced into the waterborne epoxy resin coating to produce a modified fly ash / waterborne epoxy resin composite coating with excellent corrosion resistance, which can be attributed to the following three key aspects. First, fly ash has a hollow microsphere structure, and when it is distributed in the waterborne epoxy resin coating, it will extend the migration path of the corrosive medium and improve the long-term corrosion resistance of the composite coating. Secondly, after the fly ash is functionalized by the silane coupling agent, the fly ash surface is grafted with active functional groups, and the amino group undergoes a cross-linking reaction with the bisphenol A group in the waterborne epoxy resin, reducing the porosity of the composite coating, improving the compactness of the coating, and thus enhancing the corrosion resistance of the composite coating. Finally, there are a large number of hydrophilic groups on the modified fly ash, which gives the modified fly ash good dispersibility, improves the interfacial compatibility between the modified fly ash and the waterborne epoxy resin, greatly improves the barrier properties of the waterborne epoxy resin matrix, and enables the composite coating to effectively resist the penetration of corrosive media. The flame retardant mechanism of modified fly ash was proposed by analyzing the thermal properties and residual carbon of the waterborne epoxy resin composite coating. At high temperatures, fly ash can promote the dehydration and carbonization of the material surface to form a porous insulating coke layer, which can prevent heat conduction. In addition, fly ash can absorb heat during the combustion process, reduce the temperature of the material surface, and thus slow down the combustion rate. Modified fly ash can make the coke layer of the waterborne epoxy resin continuous and dense, hindering the diffusion of heat and oxygen between the flame area and the matrix. This barrier effect effectively inhibits the combustion and decomposition of the underlying polymer, thereby improving the flame retardant properties of the material. These mechanisms work together to make fly ash an effective flame retardant material that can be used in polymer materials to improve their flame retardant properties.

[0022] The present invention utilizes chemical modification to improve the dispersion stability of fly ash in a waterborne epoxy resin system on the one hand, and on the other hand, based on the active functional groups on the silane coupling agent, promote the curing process of the epoxy resin, greatly improve the curing effect of the waterborne epoxy resin system, thereby obtaining a waterborne epoxy resin coating with excellent performance.

[0023] The functionalized fly ash added in the present invention has two functions; the first is to be used as a curing agent. The modified substance used to modify the fly ash can undergo chemical cross-linking with the epoxy resin matrix. This function solves the problem of easy formation of holes in the water-based epoxy resin coating, improves the film-forming performance, and makes the coating compact, which greatly improves the corrosion resistance of the coating; the fly ash modified in the present invention is used as a curing agent together with the water-based epoxy resin curing agent, because the introduced active functional groups enable the modified fly ash to participate in the curing process of the epoxy resin together with the curing agent, improving the problem of the easy generation of needle-shaped hole structures in the film-forming process of the water-based epoxy resin coating, thereby improving the compactness of the coating. The second is to be used as a physical shielding agent. The modification also solves the problem of poor dispersion of fly ash in the resin matrix, and uses the spherical structure of oxygen fly ash to extend the penetration path of the corrosive medium and improve the corrosion resistance of the coating. Compared with the prior art, the present invention not only simply utilizes the physical shielding effect of fly ash, but also eliminates the needle-shaped holes formed in the preparation process of water-based epoxy resin coating through the chemical action of auxiliary curing, thereby effectively and comprehensively improving the problems of poor film formation and corrosion resistance of water-based epoxy resin.

[0024] The beneficial effects of the present invention are:

[0025] 1. The modified fly ash is used as a curing agent together with water-based epoxy resin curing agent, which provides a new way for the harmless treatment of waste and is environmentally friendly, safe and pollution-free.

[0026] 2. The spherical hollow structure of fly ash microbeads prolongs the path for the corrosive medium to penetrate into the surface of the metal substrate; the functionalized fly ash has greatly enhanced its dispersion ability in the resin and the density of the coating. Modified fly ash can greatly enhance the long-term corrosion resistance of the polymer coating.

[0027] 3. Fly ash has high chemical and thermal stability, can form a porous heat-insulating coke layer, and can absorb the heat during the combustion process, thereby slowing down the combustion rate, giving the coating a certain degree of flame retardancy.

[0028] 4. The polymer coating of the present invention has a dense appearance, low porosity, and is smooth and delicate.

[0029] 5. The solid waste fly ash used in the present invention is widely available and inexpensive.

[0030] 6. The water-based epoxy resin composite coating of the present invention does not require complicated equipment during preparation, has simple steps, is easy to operate, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is the SEM of the blank waterborne epoxy resin coating and the waterborne epoxy resin composite coating with modified fly ash added in Example 1 of the present invention.

[0032] Figure 2 is the blank waterborne epoxy resin coating and the waterborne epoxy resin composite coating with modified fly ash added in Example 2 of the present invention |Z| 0.01Hz Data chart, used to evaluate the semi-quantitative index of the coating's anti-penetration performance.

[0033] Figure 3 It is a Tafel polarization curve diagram of the blank waterborne epoxy resin coating and the waterborne epoxy resin composite coating with modified fly ash added in Example 3 of the present invention, which is used to evaluate the corrosion resistance of the coating.

[0034] Figure 4 It is a total heat release (HRR) diagram of the blank waterborne epoxy resin coating and the waterborne epoxy resin composite coating with modified fly ash added in Example 4 of the present invention, which is used to evaluate the flame retardant ability of the coating. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] Add 0.3 parts by mass of modified fly ash dispersion to 100 parts by mass of water-based curing agent and 80 parts by mass of water, stir for 12 hours at 500 rad / min to mix evenly. Then add 80 parts by mass of water-based epoxy resin to it and mix evenly to obtain a water-based epoxy resin anti-corrosion coating containing modified fly ash. Apply it on Q235 iron sheet, cure at room temperature for 7 days, and then heat cure for 5 hours. Then, test its performance.

[0038] In the present invention, a scanning electron microscope (SEM, SEM3200) was used to characterize the microscopic condition of the coating in Example 1. The surface morphology of the waterborne epoxy resin coating without fly ash and with modified fly ash was characterized. It can be clearly seen from the test results that Figure 1 a. There are many microscopic shrinkage holes on the surface of the coating without adding co-curing agent, which is caused by the volatilization of water molecules during the film-forming process of water-based epoxy resin. Figure 1 b. After adding the co-curing agent, the shrinkage holes in the film layer disappear, and the obtained water-based epoxy resin coating is dense, which solves the problem of many shrinkage holes in the traditional process, improves the corrosion resistance, and improves the film-forming performance of the coating.

[0039] Example 2

[0040] Add 0.6 parts by mass of modified fly ash dispersion to 100 parts by mass of water-based curing agent and 80 parts by mass of water, stir for 12 hours at 500 rad / min to mix evenly. Then add 80 parts by mass of water-based epoxy resin to it and mix evenly to obtain a water-based epoxy resin anti-corrosion coating containing modified fly ash. Apply it on Q235 iron sheet, cure at room temperature for 7 days, and then heat cure for 5 hours. Then, test its performance.

[0041] In the present invention, for Example 2, the corrosion resistance of the coating is tested by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) test in CHI-760E Shanghai Chenhua electrochemical workstation, and the corrosion results of the water-based epoxy resin coating without fly ash and with functionalized fly ash added after immersion in sodium chloride solution for 40 days are tested. Figure 2 The impedance modulus of the Bode plot test results at 0.01 Hz is statistically analyzed. The larger the impedance value at 0.01 Hz, the better the corrosion resistance. Figure 2 The waterborne epoxy resin coating with modified fly ash is more than 2 orders of magnitude higher than the coating without modified fly ash. The coating has good density and excellent corrosion resistance.

[0042] Example 3

[0043] The waterborne epoxy resin coating obtained in this Example 3 has excellent anti-corrosion performance, high coating adhesion, and good coating density, which makes the coating have excellent long-term corrosion resistance.

[0044] Add 0.9 parts by mass of modified fly ash dispersion to 100 parts by mass of water-based curing agent and 80 parts by mass of water, stir for 12 hours at 500 rad / min to mix evenly. Then add 80 parts by mass of water-based epoxy resin to it and mix evenly to obtain a water-based epoxy resin anticorrosive coating containing modified fly ash. Apply it on Q235 iron sheet, cure at room temperature for 7 days, heat cure for 5 hours, and then test its performance.

[0045] In the present invention, the corrosion resistance of the coating is tested by using a CHI-760E Shanghai Chenhua electrochemical workstation to measure the potential polarization curve of Example 3. The corrosion results of the waterborne epoxy resin coating without fly ash and with functionalized fly ash after immersion in sodium chloride solution for 40 days are tested. Figure 3 It can be seen that the coating after introduction simultaneously inhibits the anodic and cathodic reactions on the surface of the substrate, reducing the rate of the entire electrochemical reaction; in addition, the polarization curve of the water-based epoxy coating with modified fly ash moves toward the positive potential direction and the corrosion current becomes smaller, indicating that the addition of modified fly ash enhances the barrier ability of the coating, making the corrosion resistance of the coating more excellent.

[0046] Example 4

[0047] Add 1.2 parts by mass of modified fly ash dispersion to 100 parts by mass of water-based curing agent and 80 parts by mass of water, stir for 12 hours at 500 rad / min to mix evenly. Then add 80 parts by mass of water-based epoxy resin to it and mix evenly to obtain a water-based epoxy resin anticorrosive coating containing modified fly ash. Apply it on Q235 iron sheet, cure at room temperature for 7 days, heat cure for 5 hours, and then test its performance.

[0048] In the present invention, a cone calorimeter was used to test Example 4 to test the flame retardancy of the waterborne epoxy resin coating without modified fly ash and with modified fly ash. Figure 4 The total heat release diagram shows that the total heat release of the waterborne epoxy resin coating with modified fly ash is 35% less than that of the coating without modified fly ash. It can be seen that the obtained coating has good flame retardant ability.

[0049] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash, characterized in that: The steps include: Step 1: Disperse 2 to 5 parts of fly ash in 100 to 500 parts of anhydrous ethanol by weight, add 10 to 50 parts of deionized water, and then add 3 to 10 parts of silane coupling agent, heat to 50 to 80° C., reflux for 2 to 8 hours, cool to room temperature after the reaction is completed, and centrifuge and wash with deionized water to obtain functionalized fly ash; Step 2: Disperse the functionalized fly ash obtained in step 1 into 2.5 to 10 parts of deionized water, mix with 3.75 to 15 parts of waterborne epoxy resin curing agent, and stir to prepare component B of waterborne epoxy resin coating; Step 3: Calculate by mass and use 3 to 12 parts of bisphenol A epoxy resin as component A of the water-based epoxy resin coating. When using, stir and mix component A and component B evenly and then apply them to form a film.

2. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 1, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane and vinyltriethoxysilane.

3. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 1, the fly ash has a particle size of 100nm to 100000nm; the number of centrifugal washing with deionized water is 2 to 6 times.

4. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 2, the functionalized fly ash is dispersed into 2.5 to 10 parts of deionized water by ultrasonic dispersion, and the ultrasonic dispersion time is 0.5 to 1 hour.

5. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 2, the water-based epoxy resin curing agent is one or more of Banghe 901, Banghe 916, Shenzhen Yoshida F0705, Suzhou Meiguowang Flooring WG-828 and Huabang Chemical HB-7871.

6. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 2, the stirring is performed by a magnetic stirrer, the stirring speed is 300 to 1200 rad / min, and the stirring time is 12 to 32 hours.

7. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step 3, the film is scraped using the SZQ four-sided wet film preparation device, and the wet film thickness is 30 to 200 microns. After film formation, the curing time at room temperature is 5 to 10 days, and the thermal curing temperature is 40 to 100°C, and the time is 2 to 10 hours.

8. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step three, the bisphenol A epoxy resin is one or more of E-51, E-44, BDR6100, BE114, BE186, E-42, E-03 and E-12.

9. The method for preparing a multifunctional waterborne epoxy resin coating containing modified fly ash according to claim 1, characterized in that: In step three, the mass ratio of bisphenol A epoxy resin to waterborne epoxy resin curing agent is 1:1.2-2.5; the added amount of the functionalized fly ash is 0.4%-2.0% of the mass of component A of the waterborne epoxy resin coating.

10. A multifunctional waterborne epoxy resin coating containing modified fly ash prepared according to the preparation method of claim 1, characterized in that: The coating of the waterborne epoxy resin coating is dense, and has no pinholes; the coating adhesion reaches level 0; no corrosion lesions occur after immersion in a 3.5% NaCl solution for 40 days, and the flame retardant ability is also improved to a certain extent.

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