UV-resistant wave-absorbing coating and preparation method thereof

Abstract

The UV-resistant wave-absorbing coating is characterized by being composed of a component A and a component B. The component A comprises epoxy resin, magnetic wave-absorbing powder, carbon black, a coupling agent, an anti-settling agent and a solvent. The component B comprises a curing agent and a flatting agent. A method for preparing the UV-resistant wave-absorbing coating comprises the following steps: S1, adding the coupling agent into water, uniformly stirring and dispersing to form a coupling agent solution, then respectively adding the carbon black and the magnetic wave-absorbing powder into the coupling agent solution, uniformly stirring at a constant temperature, centrifuging, washing with absolute ethyl alcohol, and drying to obtain the UV-resistant wave-absorbing coating. Heating and drying to obtain coupling agent modified carbon black and magnetic wave-absorbing powder; s2, taking epoxy resin, an anti-settling agent and a solvent, mixing, stirring and dispersing, adding the coupling agent modified carbon black and the magnetic wave-absorbing powder, and uniformly stirring to obtain a component A; s3, mixing and uniformly stirring the curing agent and the flatting agent to obtain a component B; and S4, uniformly mixing the component A and the component B to obtain the UV-resistant wave-absorbing coating.

Description

A UV-resistant absorbing coating and its preparation method Technical Field

[0001] This invention relates to a microwave absorbing coating. Background Technology

[0002] Radar-absorbing coatings are functional coatings that can be applied to the surface of equipment to convert the energy of incident radar waves into other forms of energy and dissipate them, thereby achieving radar stealth effects. Radar-absorbing coatings typically use absorbers as functional fillers and resins as film-forming substances. They are applied to the surface of equipment and cured to form a radar-absorbing coating with durable protective properties.

[0003] In practical applications, microwave absorbing coatings are often exposed to outdoor environments for extended periods. Ultraviolet radiation from sunlight can cause resin degradation, leading to a decline in coating performance or even damage. To reduce the destructive effects of ultraviolet radiation on coating performance and extend the service life of microwave absorbing coatings, there is an urgent need for a UV-resistant microwave absorbing coating. Summary of the Invention

[0004] To overcome the above-mentioned shortcomings of existing microwave absorbing materials, the present invention provides a UV-resistant microwave absorbing coating.

[0005] The technical solution of this invention to solve its technical problem is: a UV-resistant absorbing coating, which is composed of a mixture of component A and component B; wherein component A is composed of the following components: 100 parts by weight of epoxy resin; 400-600 parts by weight of magnetic absorbing powder; 30-50 parts by weight of carbon black; 2-8 parts by weight of coupling agent; 3-10 parts by weight of anti-settling agent; and 200-300 parts by weight of solvent; component B is composed of the following components: 40-50 parts by weight of curing agent; and 0.5-1 parts by weight of leveling agent.

[0006] Preferably, the resin in component A is a composition of hydrogenated bisphenol A epoxy resin, epoxy resin E51, and flexible epoxy resin, wherein the hydrogenated bisphenol A epoxy resin comprises 30-40 parts by weight, epoxy resin E51 comprises 20-30 parts by weight, and flexible epoxy resin comprises 30-50 parts by weight. Hydrogenated bisphenol A epoxy resin does not contain a benzene ring structure and has good UV resistance, but its strength is lower than that of epoxy resin E51, and its curing speed is slower; therefore, it is compounded with E51. When the amount of epoxy resin E51 is less than 20 parts, the coating strength is insufficient; when it is more than 30 parts, the coating becomes brittle, and its UV resistance decreases. The flexible epoxy resin can be one of polyurethane-modified epoxy resin, dimer acid-modified epoxy resin, or polyether-modified epoxy resin, preferably polyether-modified epoxy resin. The addition of flexible resin is to reduce the internal stress generated by shrinkage during coating curing and improve the flexibility of the coating. Compared to other modified epoxy resins, polyether-modified epoxy resins, in addition to their excellent flexibility, do not contain unsaturated double bonds in their flexible segments, thus not affecting the UV resistance of the coating. When the amount of flexible epoxy resin is less than 30 parts, the coating has poor flexibility; when it is more than 40 parts, the coating has lower strength.

[0007] Preferably, the magnetic absorbing powder is one of ferrite, iron carbonyl, nickel carbonyl, Fe-Si, FeSiAl, FeSiCr, FeSiCrMo, and Fe-Ni. Since the magnetic absorbing powder is used for microwave absorption, any combination of the above-mentioned magnetic absorbing powders can also achieve the microwave absorption function. Iron carbonyl powder is preferred because it has advantages such as good absorption performance, a wide adjustable particle size range, and low cost as a low-frequency absorbing material. The particle size of the powder is D10≤10μm, D50≤20μm, and D90≤40μm. When the particle size is too high, both the mechanical properties and microwave absorption performance of the coating decrease.

[0008] Preferably, the carbon black has a particle size of 20-50 nm. When the particle size is less than 20 nm, the carbon black is poorly dispersed and prone to agglomeration; when the particle size is greater than 50 nm, the specific surface area of ​​the carbon black decreases, and its ultraviolet absorption performance declines.

[0009] Preferably, the coupling agent is an epoxy-based silane coupling agent. After the epoxy-based silane coupling agent is grafted onto the surface of the filler, it can improve the compatibility between the filler and the resin, make the filler more uniformly dispersed, and improve the toughness of the coating. The epoxy groups in the coupling agent molecules can also form chemical crosslinks with the base epoxy resin through curing, which is beneficial to improving the strength and UV resistance of the coating.

[0010] Preferably, the anti-settling agent is one or any combination of fumed silica, polyamide wax, modified bentonite, and modified polyurea. The anti-settling agent is added to suppress sedimentation and sagging that occur during coating preparation due to the high density of the magnetic absorber. Modified polyurea is preferred because dispersing fumed silica requires sophisticated dispersion equipment, while polyamide wax and modified bentonite require pre-activation, whereas modified polyurea does not require high-speed dispersion or pre-activation. When the amount of anti-settling agent is less than 3 parts, the anti-settling and anti-sagging effects are not significant; when it is more than 10 parts, the leveling properties of the coating deteriorate.

[0011] Preferably, the solvent is one or any combination of cyclohexanone, xylene, n-butanol, and ethyl acetate. A combination of xylene / n-butanol or ethyl acetate / cyclohexanone is preferred; the solvent used and its ratio are not specifically required.

[0012] Preferably, the curing agent is a composition of polyetheramine curing agent and alicyclic amine curing agent, wherein the polyetheramine curing agent comprises 60-80 parts by weight and the alicyclic amine curing agent comprises 20-40 parts by weight. Neither the polyetheramine nor the alicyclic amine curing agent contains unsaturated bonds, resulting in good UV resistance of the cured product. The combination of these two curing agents balances the flexibility and strength of the cured product. When the polyetheramine content is below 60 parts, the coating toughness deteriorates; when it is above 80 parts, the coating strength decreases.

[0013] Preferably, the leveling agent is an organosilicon leveling agent. When its dosage is less than 1 part, the leveling performance of the coating is poor and there are more surface defects; when it is more than 2 parts, the adhesion of the coating decreases.

[0014] The method for preparing the above-mentioned UV-resistant absorbing coating includes the following steps: S1. Adding a coupling agent to water, stirring and dispersing it evenly to form a coupling agent solution, then adding carbon black and magnetic absorbing powder to the coupling agent solution respectively, stirring evenly at a constant temperature, centrifuging and washing with anhydrous ethanol, heating and drying to obtain coupling agent-modified carbon black and magnetic absorbing powder; S2. Mixing epoxy resin, anti-settling agent, and solvent, stirring and dispersing, adding coupling agent-modified carbon black and magnetic absorbing powder, stirring evenly to obtain component A; S3. Mixing curing agent and leveling agent and stirring evenly to obtain component B; S4. Mixing component A and component B evenly to obtain the UV-resistant absorbing coating.

[0015] The beneficial effects of the present invention are as follows: the microwave absorbing coating formed by the coating of this application has excellent UV resistance and can improve the performance degradation and cracking caused by solar radiation. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments.

[0017] Example 1: The materials used in this example are shown in the table below. For the sake of convenience, the full name of the material will not be written in the following text, but will be replaced by the material model.

[0018]

[0019] A UV-resistant absorbing coating is composed of a mixture of component A and component B. Component A consists of the following components: CYDH300: 60g; E-51: 40g; EP4000: 100g; YW3: 800g; N330: 80g; KH560 as a coupling agent: 10g; BYK410 as an anti-settling agent: 15g; and a mixture of xylene and n-butanol as solvents, wherein xylene: 350g and n-butanol: 150g. Component B consists of the following components: D400 and Ancamine2280 as curing agents, wherein D400: 64g and Ancamine2280: 26g; and BYK378 as a leveling agent: 1g.

[0020] The coating of this embodiment was diluted with solvent and sprayed onto the substrate surface to a thickness of 1 mm. After curing at room temperature for 12 hours, it was then cured at 80°C for four hours to obtain the microwave absorbing coating. The solvent used to disperse the coating can be water, alcohol, etc. In this embodiment, xylene and n-butanol are used, with a volume ratio of xylene to n-butanol of 7:3.

[0021] The coating was subjected to the following tests: Adhesion test: conducted according to GB / T5210-2006 "Paints and Varnishes - Pull-off test"; Flexibility test: conducted according to GB / T 1731–19933 "Determination of Flexibility of Paint Films"; Impact performance test: conducted according to GB / T 1732–1993 "Determination of Impact Resistance of Paint Films"; UV aging test: aged at a constant temperature of 60 ℃ in a UV aging chamber.

[0022] Each UV-aged sample was placed 20 cm away from the lamp source (500W, 340 nm). The lamp source was rotated slowly and uniformly to ensure uniform irradiance of the sample. The aging time was 100 hours. The coating samples after UV aging were subjected to visual inspection and adhesion testing. The test results are shown in the table below.

[0023]

[0024] Example 2: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0025] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 35 parts by mass; epoxy resin E51: 30 parts by mass; flexible epoxy resin: 35 parts by mass, specifically polyether-modified epoxy resin; carbonyl iron powder: 500 parts by mass, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 40 parts by mass, with particle sizes controlled between 20-50nm; γ-glycidyl etheroxypropyltriethoxysilane: 4 parts by mass; hydrophobically modified polyurea: 5 parts by mass; solvent: 250 parts by mass, specifically a solvent with a xylene:n-butanol volume ratio of 1:1. Component B consists of the following components: curing agent: 45 parts by mass, of which 70 parts by mass are polyetheramine curing agent and 30 parts by mass are alicyclic amine curing agent; silicone leveling agent: 0.5 parts by mass.

[0026] Example 3: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0027] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 30 parts by weight; epoxy resin E51: 20 parts by weight; flexible epoxy resin: 50 parts by weight, specifically polyurethane modified epoxy resin; ferrite powder: 450 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 50 parts by weight, with particle sizes controlled between 20-50nm; γ-epoxyethoxypropyltrimethoxysilane: 6.5 parts by weight; polyether modified polyurea: 9 parts by weight; solvent: 230 parts by weight, specifically a solvent with a volume ratio of cyclohexanone to ethyl acetate of 1:1. Component B consists of the following components: curing agent: 40 parts by weight, of which 60 parts by weight are polyetheramine curing agent and 25 parts by weight are alicyclic amine curing agent; silicone leveling agent: 0.1 parts by weight.

[0028] Example 4: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0029] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 40 parts by mass; epoxy resin E51: 25 parts by mass; flexible epoxy resin: 35 parts by mass, specifically dimer acid modified epoxy resin; carbonyl nickel powder: 600 parts by mass, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 30 parts by mass, with particle sizes controlled between 20-50nm; bisphenol A epoxy silane: 2 parts by mass; fumed silica: 8 parts by mass; solvent cyclohexanone: 300 parts by mass. Component B consists of the following components: curing agent: 50 parts by mass, of which 75 parts by mass are polyetheramine curing agent and 20 parts by mass are alicyclic amine curing agent; organosilicon leveling agent: 0.6 parts by mass.

[0030] Example 5: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0031] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 32 parts by weight; epoxy resin E51: 28 parts by weight; flexible epoxy resin: 40 parts by weight, specifically polyether-modified epoxy resin; Fe-Si powder: 400 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 45 parts by weight, with particle sizes controlled between 20-50nm; epoxy-based methylphenyl silane: 7 parts by weight; polyamide wax: 3 parts by weight; and xylene solvent: 200 parts by weight. Component B consists of the following components: curing agent: 43 parts by weight, of which 80 parts by weight are polyether amine curing agent and 40 parts by weight are alicyclic amine curing agent; and silicone leveling agent: 0.7 parts by weight.

[0032] Example 6: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0033] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 40 parts by weight; epoxy resin E51: 30 parts by weight; flexible epoxy resin: 30 parts by weight, specifically polyurethane modified epoxy resin; FeSiAl powder: 550 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 35 parts by weight, with particle sizes controlled between 20-50nm; γ-glycidyl etheroxypropyltrimethoxysilane: 8 parts by weight; long-chain alkyl quaternary ammonium salt modified bentonite: 10 parts by weight; solvent n-butanol: 280 parts by weight. Component B consists of the following components: curing agent: 48 parts by weight, of which 65 parts by weight are polyetheramine curing agent and 35 parts by weight are alicyclic amine curing agent; organosilicon leveling agent: 0.9 parts by weight.

[0034] Example 7: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0035] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 38 parts by weight; epoxy resin E51: 23 parts by weight; flexible epoxy resin: 39 parts by weight, specifically polyether-modified epoxy resin; FeSiCr powder: 520 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 42 parts by weight, with particle sizes controlled between 20-50nm; γ-glycidyl etheroxypropyltrimethoxysilane: 7.5 parts by weight; aminosilane-modified bentonite: 8.5 parts by weight; solvent ethyl acetate: 260 parts by weight. Component B consists of the following components: curing agent: 45 parts by weight, of which 60 parts by weight are polyetheramine curing agent and 20 parts by weight are alicyclic amine curing agent; organosilicon leveling agent: 0.8 parts by weight.

[0036] Example 8: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0037] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 30 parts by weight; epoxy resin E51: 25 parts by weight; flexible epoxy resin: 45 parts by weight, specifically dimer acid modified epoxy resin; FeSiCrMo powder: 480 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 45 parts by weight, with particle sizes controlled between 20-50nm; epoxy-based methylphenyl silane: 6 parts by weight; fumed silica: 7.5 parts by weight; and xylene solvent: 250 parts by weight. Component B consists of the following components: curing agent: 42 parts by weight, of which 75 parts by weight are polyetheramine curing agent and 35 parts by weight are alicyclic amine curing agent; and silicone leveling agent: 0.5 parts by weight.

[0038] Example 9: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0039] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 30 parts by weight; epoxy resin E51: 20 parts by weight; flexible epoxy resin: 50 parts by weight, specifically polyurethane modified epoxy resin; Fe-Ni powder: 560 parts by weight, with particle sizes conforming to D10≤10μm, D50≤20μm, and D90≤40μm; carbon black: 38 parts by weight, with particle sizes controlled between 20-50nm; γ-epoxyethoxypropyltrimethoxysilane: 7 parts by weight; polyamide wax: 3 parts by weight; solvent n-butanol: 300 parts by weight. Component B consists of the following components: curing agent: 40 parts by weight, of which 70 parts by weight are polyetheramine curing agent and 40 parts by weight are alicyclic amine curing agent; silicone leveling agent: 1 part by weight.

[0040] Example 10: A UV-resistant absorbing coating, which is composed of a mixture of component A and component B.

[0041] Component A consists of the following components: hydrogenated bisphenol A epoxy resin: 35 parts by weight; epoxy resin E51: 25 parts by weight; flexible epoxy resin: 40 parts by weight, specifically polyether-modified epoxy resin; a mixture of ferrite powder, carbonyl iron powder, carbonyl nickel powder, Fe-Si powder, FeSiAl powder, FeSiCr powder, FeSiCrMo powder, and Fe-Ni powder: 520 parts by weight, used as magnetic absorbing powder. The proportions of the powders are not limited, and the particle sizes of the powders meet the following requirements: D10≤10μm, D50≤20μm, D90≤40μm; carbon black: 42 parts by weight, with a particle size controlled between 20-50nm; γ- Glycidyl etheroxypropyltrimethoxysilane: 7.5 parts by mass; Fumed silica: 8.5 parts by mass; Solvent ethyl acetate: 260 parts by mass; Component B consists of the following components: Curing agent: 45 parts by mass, of which 60 parts by mass are polyetheramine curing agent and 20 parts by mass are alicyclic amine curing agent; Organosilicon leveling agent: 0.8 parts by mass.

[0042] Example 11: A method for preparing a UV-resistant microwave absorbing coating includes the following steps: S1. Add a coupling agent to water, stir and disperse evenly to form a coupling agent solution, then add carbon black and magnetic microwave absorbing powder to the coupling agent solution, stir evenly at a constant temperature, centrifuge and wash with anhydrous ethanol, heat and dry to obtain coupling agent-modified carbon black and magnetic microwave absorbing powder; S2. Take epoxy resin, anti-settling agent and solvent, mix, stir and disperse, add coupling agent-modified carbon black and magnetic microwave absorbing powder, stir evenly to obtain component A; S3. Mix curing agent and leveling agent and stir evenly to obtain component B; S4. Mix component A and component B evenly to obtain a UV-resistant microwave absorbing coating.

[0043] The preparation method described in Example 11 is capable of preparing the UV-resistant absorbing coatings of Examples 1 to 10.

Claims

1. A UV-resistant absorbing coating, characterized in that... It is composed of a mixture of component A and component B; component A consists of the following components: 100 parts by weight of epoxy resin; 400-600 parts by weight of magnetic microwave absorbing powder; 30-50 parts by weight of carbon black; 2-8 parts by weight of coupling agent; 3-10 parts by weight of anti-settling agent; and 200-300 parts by weight of solvent; component B consists of the following components: 40-50 parts by weight of curing agent; and 0.5-1 parts by weight of leveling agent.

2. The UV-resistant absorbing coating as described in claim 1, characterized in that, The resin in component A is a composition of hydrogenated bisphenol A epoxy resin, epoxy resin E51, and flexible epoxy resin, wherein the hydrogenated bisphenol A epoxy resin comprises 30-40 parts by weight, epoxy resin E51 comprises 20-30 parts by weight, and flexible epoxy resin comprises 30-50 parts by weight.

3. The UV-resistant absorbing coating as described in claim 1, characterized in that, The magnetic absorbing powder is one or any combination of ferrite, carbonyl iron, carbonyl nickel, Fe-Si, FeSiAl, FeSiCr, FeSiCrMo, and Fe-Ni, with a particle size of D10≤10μm, D50≤20μm, and D90≤40μm.

4. The UV-resistant absorbing coating as described in claim 1, characterized in that, The carbon black has a particle size of 20-50 nm.

5. The UV-resistant absorbing coating as described in claim 1, characterized in that, The coupling agent is an epoxy silane coupling agent.

6. The UV-resistant absorbing coating as described in claim 1, characterized in that, The anti-settling agent is one or any combination of fumed silica, polyamide wax, modified bentonite, and modified polyurea.

7. The UV-resistant absorbing coating as described in claim 1, characterized in that, The solvent is one of cyclohexanone, xylene, n-butanol, ethyl acetate, or any combination thereof.

8. The UV-resistant absorbing coating as described in claim 1, characterized in that, The curing agent is a composition of polyetheramine curing agent and alicyclic amine curing agent, wherein the polyetheramine curing agent is 60-80 parts by weight and the alicyclic amine curing agent is 20-40 parts by weight.

9. The UV-resistant absorbing coating as described in claim 1, characterized in that, The leveling agent is an organosilicon leveling agent.

10. A method for preparing the UV-resistant absorbing coating according to claims 1-8, characterized in that... Includes the following steps: S1. Add the coupling agent to water, stir and disperse evenly to form a coupling agent solution. Then, add carbon black and magnetic microwave absorbing powder to the coupling agent solution, stir evenly at a constant temperature, centrifuge, wash with anhydrous ethanol, and heat and dry to obtain coupling agent modified carbon black and magnetic microwave absorbing powder; S2. Take epoxy resin, anti-settling agent, and solvent, mix, stir and disperse, add coupling agent modified carbon black and magnetic microwave absorbing powder, stir evenly to obtain component A; S3. Mix curing agent and leveling agent and stir evenly to obtain component B; S4. Mix component A and component B evenly to obtain UV-resistant microwave absorbing coating.

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