A high-temperature resistant metallic topcoat and its preparation method

Abstract

This invention belongs to the field of metallic coating technology, specifically relating to a high-temperature resistant metallic coating and its preparation method. The high-temperature resistant metallic coating is prepared from the following raw materials by weight percentage: 50-65% silicone-modified acrylic emulsion, 15-20% epoxy ester emulsion, 3-5% glycidyl methacrylate, 0.3-0.5% zinc acetylacetonate, 10-15% mica powder, 3-5% nano-alumina, 0.1-0.3% defoamer, 0.1-1% dispersant, 0.2-0.5% thickener, 0.3-0.6% pH adjuster, and deionized water to 100%. This invention, through the synergistic effect of the silicone-modified acrylic emulsion, epoxy ester emulsion, and glycidyl methacrylate, enables the prepared metallic coating to possess good high-temperature resistance, damp heat resistance, and salt spray resistance. Furthermore, it has low VOCs, making it environmentally friendly and in line with the zero-VOC development trend. Furthermore, the performance of the metallic topcoat of this invention can be further enhanced by using mica powder and nano-alumina composite filler, making it suitable for comprehensive protection needs in high temperature and high humidity environments.

Description

Technical Field

[0001] This invention belongs to the field of metal topcoat technology, specifically relating to a high-temperature resistant metal topcoat and its preparation method. Background Technology

[0002] Metallic topcoats, as an important component of metal substrate surface protection systems, refer to functional coatings that can be directly applied to metal surfaces to form a continuous solid coating. Their core function lies in mitigating the corrosive effects of environmental media (such as moisture, acids, and alkalis) on the metal substrate through a combination of physical isolation and chemical corrosion prevention. Additionally, they can impart specific decorative effects and functional properties to the metal substrate surface. Depending on the specific application, metallic topcoats typically need to possess key performance indicators such as corrosion resistance, weather resistance, mechanical strength, and temperature resistance.

[0003] Traditional metal topcoat systems primarily utilize organic polymers such as epoxy resins, polyurethanes, and acrylic resins as film-forming substances. These polymers form a dense coating through cross-linking and curing, exhibiting good adhesion and protective performance under normal ambient temperatures. However, with the increasingly stringent environmental requirements of modern industry for metal components, the surface temperature of metal substrates often exceeds 300°C or even higher. At this temperature, the molecular chains of traditional organic resin-based topcoats undergo pyrolysis, leading to powdering, cracking, and even peeling of the coating, completely losing its protective function.

[0004] Existing patent CN115851100A discloses a water-based two-component acrylic topcoat resistant to high temperature and humidity environments and its preparation method. The water-based component, an acrylic polyurethane coating, consists of two components, A and B. Component A includes deionized water, a water-based dispersant, a water-based defoamer, titanium dioxide, a water-based hydroxyl acrylic dispersion resin, triethylamine, a film-forming aid, and a thickener. Component B includes a water-based isocyanate curing agent and propylene glycol ethyl ether acetate. The use of dimethyl methacrylate hydrogen phosphate, with its dipropylene and lignin-acid structure, effectively improves the foaming problem of the paint film under high temperature and humidity conditions.

[0005] While the aforementioned patented topcoat possesses the advantages described, it also has certain drawbacks: Dimethyl methacrylate hydrogen phosphate, as a key monomer, has a high market price, leading to higher production costs. Furthermore, although propylene glycol ethyl ether acetate in component B has relatively low toxicity, it is still a VOC component, contradicting the zero-VOC trend. Secondly, the water-based isocyanate curing agent may contain free isocyanate monomers, posing a certain health risk to construction workers.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a high-temperature resistant metallic topcoat and its preparation method, so as to solve the problems existing in the water-based two-component acrylic topcoat that is resistant to high temperature and high humidity environments in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A high-temperature resistant metallic topcoat is prepared from the following raw materials by weight percentage: 50-65% silicone-modified acrylic emulsion, 15-20% epoxy ester emulsion, 3-5% glycidyl methacrylate, 0.3-0.5% zinc acetylacetone, 10-15% mica powder, 3-5% nano-alumina, 0.1-0.3% defoamer, 0.1-1% dispersant, 0.2-0.5% thickener, 0.3-0.6% pH adjuster, and deionized water to 100%; wherein the silicone-modified acrylic emulsion is obtained by graft copolymerization of methyl methacrylate and vinyl-terminated polydimethylsiloxane.

[0010] Furthermore, by weight percentage, the silicone-modified acrylic emulsion is prepared from the following raw materials: 45-55% methyl methacrylate, 10-14% vinyl-terminated polydimethylsiloxane, 2-4% silane coupling agent KH570, 0.4-0.8% ammonium persulfate, 1.4-1.6% sodium dodecyl sulfate, and deionized water to 100%.

[0011] Furthermore, the preparation method of the organosilicon-modified acrylic emulsion includes the following steps:

[0012] a. Add methyl methacrylate, vinyl-terminated polydimethylsiloxane and silane coupling agent KH570 to a reactor and stir at 300 rpm for 10 min; add 60% of the total amount of deionized water, heat to 50℃, and stir at 5000 rpm for 30 min to obtain a pre-emulsion.

[0013] b. Add the remaining deionized water to the container, heat to 50°C, add 10% of the total amount of pre-emulsion and 1 / 3 of the total amount of ammonium persulfate, and react for 30 min; add the remaining pre-emulsion and ammonium persulfate dropwise at a rate of 2 mL / min, and react at a constant temperature of 80°C for 2 h.

[0014] c. Cool to 40℃ and filter through a 200-mesh filter to obtain a milky white, semi-transparent organosilicon-modified acrylic emulsion.

[0015] Furthermore, the epoxy ester emulsion is a CYD-128 epoxy resin emulsion with an epoxy equivalent of 550; the mica powder has a particle size of 20-60 mesh; the nano-alumina has a particle size of 20-40 nm; the defoamer is BYK-024 defoamer; the dispersant is Tego Dispers 755W dispersant; the thickener is DSX 3290 thickener; and the pH adjuster is AMP-95.

[0016] The present invention also provides a method for preparing the high-temperature resistant metallic topcoat, comprising the following steps:

[0017] S1. Add silicone-modified acrylic emulsion, epoxy ester emulsion and deionized water to a stirred tank at 300 rpm, then add defoamer and dispersant, and stir at 300 rpm for 10 min;

[0018] S2. Add mica powder and nano-alumina, disperse at 1500 rpm for 30 min; grind through a 20 μm sieve using a grinder;

[0019] S3. Add glycidyl methacrylate and zinc acetylacetonate, stir at 600 rpm for 30 min; add pH adjuster, stir at 600 rpm for 20 min;

[0020] S4. Add thickener, seal and mature at 25°C for 24 hours, then filter through a 200-mesh filter to obtain the high-temperature resistant metallic topcoat.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention utilizes the synergistic effect of organosilicon-modified acrylic emulsion, epoxy ester emulsion, and glycidyl methacrylate to produce a metallic topcoat with excellent high-temperature resistance, damp-heat resistance, and salt spray resistance. Furthermore, it exhibits low VOC content, making it environmentally friendly and aligning with the trend towards zero-VOC coatings. The use of mica powder and nano-alumina composite fillers further enhances the performance of this metallic topcoat, making it suitable for comprehensive protection needs in high-temperature and high-humidity environments. Detailed Implementation

[0023] The technical solution of this invention patent will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0024] 1. The Influence of Different Raw Material Formulations on the Performance of Metallic Topcoats

[0025] 1.1 Metallic Topcoat Formulation

[0026] See Table 1.

[0027] Table 1. Metallic Topcoat Formulation (by weight percentage)

[0028]

[0029] 1.2 Organosilicon-modified acrylic emulsion

[0030] By weight percentage, the silicone-modified acrylic emulsions in Table 1 are prepared from the following raw materials: methyl methacrylate 45-55%, vinyl-terminated polydimethylsiloxane 10-14%, silane coupling agent KH570 2-4%, ammonium persulfate 0.4-0.8%, sodium dodecyl sulfate 1.4-1.6%, and deionized water to 100%.

[0031] The preparation method includes the following steps:

[0032] a. Methyl methacrylate (purchased from Shandong Kejian Chemical Co., Ltd.), vinyl-terminated polydimethylsiloxane (purchased from Hubei Maolin New Materials Co., Ltd.) and silane coupling agent KH570 were added to the reactor and stirred at 300 rpm for 10 min; 60% of the total amount of deionized water was added, the temperature was raised to 50℃, and stirred at 5000 rpm for 30 min to obtain a pre-emulsion;

[0033] b. Add the remaining deionized water to the container, heat to 50°C, add 10% of the total amount of pre-emulsion and 1 / 3 of the total amount of ammonium persulfate, and react for 30 min; add the remaining pre-emulsion and ammonium persulfate dropwise at a rate of 2 mL / min, and react at a constant temperature of 80°C for 2 h.

[0034] c. Cool to 40℃ and filter through a 200-mesh filter to obtain a milky white, semi-transparent organosilicon-modified acrylic emulsion.

[0035] 1.3 Preparation method of high temperature resistant metal topcoat

[0036] The preparation method of the high-temperature resistant metallic topcoat in Table 1 includes the following steps:

[0037] S1. Add silicone-modified acrylic emulsion (C2 topcoat is replaced with methyl methacrylate), epoxy ester emulsion and deionized water to a stirred tank at 300 rpm, then add defoamer and dispersant, and stir at 300 rpm for 10 min.

[0038] S2. Add mica powder and nano-alumina, disperse at 1500 rpm for 30 min; grind through a 20 μm sieve using a grinder;

[0039] S3. Add glycidyl methacrylate and zinc acetylacetonate, stir at 600 rpm for 30 min; add pH adjuster to adjust pH to 9.0, stir at 600 rpm for 20 min;

[0040] S4. Add thickener, seal and mature at 25°C for 24 hours, then filter through a 200-mesh filter to obtain the high-temperature resistant metallic topcoat.

[0041] 1.4 Determination of the performance of different metallic topcoats

[0042] The test items are shown in Table 2, and the test results are shown in Table 3.

[0043] Table 2 Test Items, Test Methods, Basis and Explanation

[0044]

[0045]

[0046] Table 3. Effects of different raw material formulations on the performance of metallic topcoats

[0047]

[0048] As shown in Table 3, compared to C6, C1 has no filler reinforcement and a higher thermal conductivity, meaning its heat insulation is limited. C2 uses unmodified materials, resulting in poor heat resistance and weak adhesion. The lack of certain components in C3-C5 reduces the performance of metallic topcoats. This also indicates that using silicone-modified acrylic emulsions, epoxy ester emulsions, glycidyl methacrylate, and zinc acetylacetonate can improve the adhesion, abrasion resistance, heat resistance, damp heat resistance, and salt spray corrosion resistance of metallic topcoats. Adding mica powder and nano-alumina can further enhance the performance of metallic topcoats.

[0049] Compared to C6, C7 has the best thermal insulation, but poorer impact resistance and reduced abrasion resistance; C8 has the best abrasion resistance, but weaker thermal conductivity and resistance to damp heat.

[0050] Overall, the C6 metallic paint has the best performance.

[0051] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A high temperature resistant metallic finish, characterized in that, Prepared from the following raw materials in percentage by weight: silicone-modified acrylic emulsion 50-65%, epoxy ester emulsion 15-20%, glycidyl methacrylate 3-5%, zinc acetylacetonate 0.3-0.5%, mica powder 10-15%, nano-alumina 3-5%, defoaming agent 0.1-0.3%, dispersant 0.1-1%, thickening agent 0.2-0.5%, pH regulator 0.3-0.6%, and deionized water to 100%; The silicone-modified acrylic emulsion is prepared by graft copolymerization of methyl methacrylate and vinyl-terminated polydimethylsiloxane; and the epoxy ester emulsion is CYD-128 epoxy resin emulsion.

2. The high temperature resistant metallic finish according to claim 1, characterized in that, The silicone-modified acrylic emulsion is prepared from the following raw materials in percentage by weight: methyl methacrylate 45-55%, vinyl-terminated polydimethylsiloxane 10-14%, silane coupling agent KH570 2-4%, ammonium persulfate 0.4-0.8%, and sodium dodecyl sulfate 1.4-1.6%, and deionized water to 100%.

3. The high temperature resistant metallic finish according to claim 2, characterized in that, The preparation method of the silicone-modified acrylic emulsion comprises the following steps: a. Add methyl methacrylate, vinyl-terminated polydimethylsiloxane, and silane coupling agent KH570 into a reaction kettle, stir and mix at 300 rpm for 10 min; add deionized water in an amount of 60% of the total amount of deionized water, heat to 50°C, and stir at 5000 rpm for 30 min to obtain a pre-emulsion; b. Add the remaining deionized water into a container, heat to 50°C, add the pre-emulsion in an amount of 10% of the total amount of the pre-emulsion, and add ammonium persulfate in an amount of 1 / 3 of the total amount of ammonium persulfate, and react for 30 min; drop the remaining pre-emulsion and ammonium persulfate at a speed of 2 mL / min, and react at 80°C for 2 h; c. Cool to 40°C, filter through a 200-mesh filter screen, and obtain a milky white semi-transparent silicone-modified acrylic emulsion.

4. The high temperature resistant metallic finish of claim 1, wherein, The epoxy ester emulsion is CYD-128 epoxy resin emulsion with an epoxy equivalent weight of 550; the mica powder has a particle size of 20-60 mesh; the nano-alumina has a particle size of 20-40 nm; the defoaming agent is BYK-024 defoaming agent; the dispersant is Tego Dispers 755W dispersant; the thickening agent is DSX 3290 thickening agent; and the pH regulator is AMP-95.

5. A process for the production of the high temperature resistant metallic finish according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1. Add the silicone-modified acrylic emulsion, the epoxy ester emulsion, and deionized water into a 300 rpm stirred kettle, then add the defoaming agent and the dispersant, and stir at 300 rpm for 10 min; S2. Add the mica powder and the nano-alumina, and disperse at 1500 rpm for 30 min; grind through a 20-μm screen; S3. Add the glycidyl methacrylate and the zinc acetylacetonate, and stir at 600 rpm for 30 min; add the pH regulator, and stir at 600 rpm for 20 min; S4. Add the thickening agent, seal, and age at 25°C for 24 h; filter through a 200-mesh filter screen to obtain the high-temperature-resistant metal finish.

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