CN115746638B

CN115746638B - Low-reflectivity coating and preparation method and application thereof

Info

Publication number: CN115746638B
Application number: CN202211190089.3A
Authority: CN
Inventors: 朱本武
Original assignee: Origin Donbon Paint Dongguan Co ltd
Current assignee: Origin Donbon Paint Dongguan Co ltd
Priority date: 2022-09-28
Filing date: 2022-09-28
Publication date: 2023-08-18
Anticipated expiration: 2042-09-28
Also published as: CN115746638A

Abstract

The invention provides a low-reflectivity coating, a preparation method and application thereof, and belongs to the technical field of coatings. The composite material comprises a component A and a component B, wherein the component A is prepared from the following raw materials in parts by weight: 20-30 parts of polyacrylic resin, 9.5-22.5 parts of carbon black/silicon dioxide composite material loaded with special pigment, 20-30 parts of ester solvent, 20-30 parts of benzene solvent, 2-4 parts of acrylic block copolymer, 0.1-0.3 part of polyether modified polydimethylsiloxane and 1-2 parts of polyamide wax; the component B is prepared from the following raw materials in parts by weight: 15-20 parts of polyisocyanate, 0.3-0.5 part of dehydrating agent, 40-45 parts of benzene solvent and 40-45 parts of ester solvent. The invention has the advantages of low reflectivity, easy spraying in construction, difficult grey hair, and wider application range.

Description

Low-reflectivity coating and preparation method and application thereof

Technical Field

The invention relates to the technical field of coatings, in particular to a low-reflectivity coating, a preparation method and application thereof.

Background

Over a very long period of time, efforts have been made to produce environmentally stable coatings and devices with very low reflectivity for a wide variety of industrial and scientific applications. They are important in imaging systems, calibration targets, instrumentation, light guides, baffles, stray light suppression, and many other applications.

In order to be commercially useful, these coatings must have the lowest possible reflectivity and be capable of optical absorption substantially uniformly over a broad area. It is also important that they should preferably exhibit a flat spectral response, low outgassing when exposed to vacuum, high resistance to mechanical shock and vibration of low particulate scatterers, good thermal shock resistance and moisture resistance. Since coatings are often applied locally to highly sensitive electron detectors, such as CCDs (charge coupled devices) or microbolometers, they are critical requirements for industrial and scientific applications. Any contaminants from this coating will inevitably collect or condense on the detector, causing them to malfunction or degrading their performance beyond acceptable thresholds.

For glass materials, the strong reflected light can reduce the transmittance of the materials and generate glaring phenomena, such as laser glass, automobile glass, spectacle lenses, television screens, instrument display screens, museum showcase glass and the like, thereby influencing the use effect, and promoting the development of low reflection technology. There are many methods for preparing the low reflection film on the glass surface, such as spraying, vacuum coating, phase-separation leaching, etc.

The reflectivity of the low-reflectivity coating commonly used in the market at present is high, and the ideal reflectivity requirement in a display and an optical lens cannot be met; in the construction process, the problems of unstable reflectivity and grey hair on the surface of a coating film are easy to occur, and the construction stability is poor.

Disclosure of Invention

The invention aims to provide a low-reflectivity coating, a preparation method and application thereof, and compared with other low-reflectivity coatings, the low-reflectivity coating has the advantage of lower reflectivity, and has the advantages of easiness in spraying and difficulty in grey hair. The adhesive has wider application range, has good adhesive force to the common plastic substrates such as ABS, PC, ABS +PC and the like, and also has good adhesive force to the metal substrates such as aluminum, iron and the like, thereby having wide application prospect.

The technical scheme of the invention is realized as follows:

the invention provides a low-reflectivity coating which comprises an A component and a B component, wherein the A component is prepared from the following raw materials in parts by weight: 20-30 parts of polyacrylic resin, 9.5-22.5 parts of carbon black/silicon dioxide composite material loaded with special pigment, 20-30 parts of ester solvent, 20-30 parts of benzene solvent, 2-4 parts of acrylic block copolymer, 0.1-0.3 part of polyether modified polydimethylsiloxane and 1-2 parts of polyamide wax; the component B is prepared from the following raw materials in parts by weight: 15-20 parts of polyisocyanate, 0.3-0.5 part of dehydrating agent, 40-45 parts of benzene solvent and 40-45 parts of ester solvent.

Preferably, the benzene solvent is selected from at least one of toluene and xylene; the ester solvent is at least one selected from ethyl acetate, methyl formate and n-propyl acetate. The dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany.

The invention further provides a preparation method of the low-reflectivity coating, which comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving graphene oxide in water, adding samarium nitrate and cerium nitrate, regulating the pH value of the solution to 9-10, transferring into a hydrothermal reaction kettle, calcining, cooling to room temperature, washing, and drying to obtain a load Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing silica sol: mixing the alkyl orthosilicate, water, ethanol and concentrated hydrochloric acid, and reacting to obtain silica sol;

preferably, the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate.

S3, preparing mixed silica sol: carbon black, aluminum powder and the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding the mixture into the silica sol obtained in the step S2, and uniformly stirring and dispersing the mixture to obtain mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 to obtain a calcined product;

S5, reduction: adding the calcined product obtained in the step S4 into water, adding ammonia water and hydrazine hydrate, heating for reaction, filtering and washing to obtain a reduction product;

s6, modification: adding the reduction product obtained in the step S5 into ethanol solution, dispersing uniformly, adding a coupling agent, heating for reaction, filtering, and drying to obtain carbon black/silicon dioxide composite material loaded with special pigment;

s7, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S6 to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s8, preparation of a component A: adding the ground carbon black/silicon dioxide composite material loaded with the special pigment, polyacrylic resin and acrylic block copolymer obtained in the step S7 into a mixed solvent of an ester solvent and a benzene solvent, adding an initiator, heating for reaction, then adding polyether modified polydimethylsiloxane and polyamide wax, and uniformly mixing to obtain a component A;

s9. Preparation of the component B: adding polyisocyanate and a dehydrating agent into a mixed solvent of a benzene solvent and an ester solvent, uniformly stirring, and controlling the environmental humidity to be 40% -60% to obtain a component B;

S10, preparing a low-reflectivity coating: the component A, the component B and the diluting solvent are mixed according to the mass ratio of 4: mixing at a ratio of 1:2-4, spraying with an air spray gun, and drying to obtain a dry film with a thickness of 30-40 μm to obtain the low-reflectivity coating.

As a further improvement of the present invention, the mass ratio of graphene oxide, samarium nitrate and cerium nitrate in step S1 is 10:3-5:1-2; the calcination temperature is 180-200 ℃ and the calcination time is 20-30h.

As a further improvement of the invention, the mass ratio of the alkyl orthosilicate, the water, the ethanol and the concentrated hydrochloric acid in the step S2 is 15-20:30-50:1-3:5-7; the reaction temperature is 50-60 ℃ and the reaction time is 3-5h.

As a further improvement of the present invention, the carbon black, al powder, and the load Sm are mentioned in step S3 ₂ O ₃ And CeO ₂ The mass ratio of the graphene oxide to the silica sol is 1.5-2.5:1-2:8-20:20-30; the aluminum powder is floating aluminum powder; the calcining temperature in the step S4 is 400-500 ℃ and the time is 2-3h.

As a further improvement of the invention, the mass ratio of the calcined product, ammonia water and hydrazine hydrate in the step S5 is 10-15:3-7:1-3; the concentration of the ammonia water is 25-30wt%; the temperature of the heating reaction is 75-95 ℃ and the time is 1-3h; the ethanol content of the ethanol solution in the step S6 is 50-70wt%; the mass ratio of the reduction product to the coupling agent is 10:1-2; the coupling agent is a silane coupling agent with double bonds and is selected from at least one of KH570, A172, A151 and A171; the temperature of the heating reaction is 70-90 ℃ and the time is 30-50min.

As a further improvement of the invention, the coupling agent is a compound mixture of A172 and KH570, and the mass ratio is 3-5:2.

Coupling agent A172 is vinyltris (beta-methoxyethoxy) silane; KH570 is gamma- (methacryloyloxy) propyl trimethoxy silane, both of which have longer alkyl chains, and polypropylene resin can be intertwined to enhance the compatibility of the carbon black/silica composite material loaded with special pigment and the resin, so that the mechanical property and adhesive force of the coating are improved, and the two have a synergistic effect.

As a further improvement of the invention, the ball milling time in the step S7 is 2-4h; the initiator in the step S8 is at least one selected from benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate; the addition amount of the initiator is 3-5wt% of the polyacrylic resin, the heating temperature is 50-70 ℃ and the time is 0.5-2h; the diluting solvent in the step S10 is at least one of ethyl acetate, methyl formate and n-propyl acetate.

As a further improvement of the invention, the method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 3-5 parts by weight of samarium nitrate and 1-2 parts by weight of cerium nitrate, regulating the pH value of the solution to 9-10, transferring into a closed hydrothermal reaction kettle, calcining at 180-200 ℃ for 20-30 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying to obtain a load Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing silica sol: mixing 15-20 parts by weight of alkyl orthosilicate, 30-50 parts by weight of water, 1-3 parts by weight of ethanol and 5-7 parts by weight of concentrated hydrochloric acid, and reacting at 50-60 ℃ for 3-5 hours to obtain silica sol;

s3, preparing mixed silica sol: 1.5 to 2.5 parts by weight of carbon black, 1 to 2 parts by weight of floating aluminum powder and 8 to 20 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 20-30 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 30-50min to obtain a mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 at 400-500 ℃ for 2-3h to obtain a calcined product;

s5, reduction: adding 10-15 parts by weight of the calcined product obtained in the step S4 into water, adding 3-7 parts by weight of 25-30wt% ammonia water and 1-3 parts by weight of hydrazine hydrate, heating at 75-95 ℃ for reaction for 1-3 hours, filtering, and washing to obtain a reduction product;

S6, modification: adding 10 parts by weight of the reduction product obtained in the step S5 into 50-70wt% ethanol solution, performing ultrasonic dispersion for 20-30min, adding 1-2 parts by weight of coupling agent, heating to 70-90 ℃ for reaction for 30-50min, filtering, and drying to obtain carbon black/silicon dioxide composite material loaded with special pigment;

the coupling agent is a compound mixture of A172 and KH570, and the mass ratio is 3-5:2;

s7, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S6 for 2-4 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s8, preparation of a component A: adding 9.5-22.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 20-30 parts by weight of polyacrylic resin and 2-4 parts by weight of acrylic block copolymer into a mixed solvent of 20-30 parts by weight of ester solvent and 20-30 parts by weight of benzene solvent, adding 0.6-1.5 parts by weight of initiator, heating to 50-70 ℃ to react for 0.5-2 hours, then adding 0.1-0.3 part by weight of polyether modified polydimethylsiloxane and 1-2 parts by weight of polyamide wax, stirring and mixing for 20-40 minutes to obtain a component A;

s9. Preparation of the component B: adding 15-20 parts by weight of polyisocyanate and 0.3-0.5 part by weight of dehydrating agent into a mixed solvent of 40-45 parts by weight of benzene solvent and 40-45 parts by weight of ester solvent, stirring and mixing for 10-20min, and controlling the environmental humidity to be 40% -60% to obtain a component B;

The invention further provides application of the low-reflectivity coating in surface coatings of displays and optical lenses.

The invention has the following beneficial effects:

the rare earth oxide has excellent optical, electric and magnetic properties, wherein Sm ₂ O ₃ Middle Sm ³⁺ Has strong absorption property to 1.06 mu m special near infrared light, ceO ₂ The oxygen vacancy effects of (2) contribute to the loss of light waves and electromagnetic waves. Sm (Sm) ₂ O ₃ And CeO ₂ Is fixedly supported on graphene oxide, and the wave absorbing efficiency, the effective absorption bandwidth and the reflection effect of the light wave are obviously higher than those of single graphene oxide and Sm ₂ O ₃ And CeO ₂ This is because of Sm ₂ O ₃ And CeO ₂ Multiple interfacial polarizations with graphene are also beneficial to losses to electromagnetic and light waves. Because the floating aluminum powder has higher conductivity and is cheaper than metals such as Au, ag, cu and the like, the floating aluminum powder can be used as a functional pigment of a low-infrared emission/reflectivity coating.

In general, graphene oxide has a low complex dielectric constant, and the most effective method for improving the absorption capacity of graphene oxide is to reduce a part of oxygen-containing functional groups on graphene oxide and improve the number of free electrons on graphene sheets, so that the complex dielectric constant of graphene oxide is improved and the impedance matching capacity of graphene oxide is improved. Defects and functional groups on the reduced graphene oxide can also enable energy to be converted into fermi energy level from a continuous state, polarization relaxation and electron dipole relaxation are introduced, so that the attenuation capability of the material on electromagnetic waves is enhanced, the reflection loss of the reduced graphene oxide is greatly improved, and the reflection capability, electromagnetic shielding capability and wave absorbing capability of the material are improved.

Through sol-gel reaction, hydrolytic polymerization to obtain silica sol, loading carbon black, aluminium powder and Sm ₂ O ₃ And CeO ₂ Adding graphene oxide into silica sol, dispersing uniformly, and passing throughCalcining to obtain silica-supported carbon black, aluminum powder and Sm ₂ O ₃ And CeO ₂ The graphene oxide material not only provides a foundation for the subsequent modification by a silane coupling agent (the silica carrier and the silane coupling agent have better binding capacity), but also the prepared silica carrier further improves the mechanical property of the coating, and the surface of the coating generates more cavities and random surface structures on the surface of the coating due to the addition of the carbon black/silica composite material loaded with the special pigment due to the silica structure, and the reflectivity of the coating is further reduced due to the cavities or the random surface structures.

The reflectivity of the whole coating is mainly related to pigment particles, wherein the resin material mainly determines the mechanical properties of the coating, such as adhesive force, tensile strength and the like. According to the invention, the reduced product is further modified by the silane coupling agent with double bonds, so that the surface of the reduced product is provided with double bond groups, and the reduced product is connected to a polypropylene resin molecular chain after undergoing a copolymerization reaction with the polypropylene resin, so that the carbon black/silicon dioxide composite material loaded with the special pigment can be uniformly distributed in the resin material, thus effectively avoiding the coagulation of inorganic components, enabling the coating to be more uniform, playing a uniform emission effect, effectively avoiding the phenomenon of overhigh or overlow local reflection, and the reflectivity of the coating is obviously reduced along with the increase of the content of the carbon black/silicon dioxide composite material loaded with the special pigment through experiments.

The polyether modified polydimethylsiloxane has a large number of inorganic silica bonds and active polyether functional groups, the inorganic silica bonds can enable the polyether modified polydimethylsiloxane to have outstanding high temperature resistance, and the active polyether functional groups can enhance the bonding strength between the resin matrix and the filler and between the resin matrix and the substrate, so that the mechanical property of the coating can be enhanced. The addition of the polyamide wax helps to prevent sedimentation of the components and improves the dispersibility of the components. The synergistic addition of polyether modified polydimethylsiloxane and polyamide wax provides a degree of improvement in coating hardness.

Therefore, the invention has the advantage of lower reflectivity compared with other low-reflectivity coatings, and has the advantages of easy spraying and difficult grey hair generation in terms of workability. The adhesive has wider application range, has good adhesive force to the common plastic substrates such as ABS, PC, ABS +PC and the like, and also has good adhesive force to the metal substrates such as aluminum, iron and the like, thereby having wide application prospect.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.

FIG. 1 is an SEM image of a special pigment-loaded carbon black/silica composite prepared in step S6 of example 1;

FIG. 2 is a surface SEM image of a reflectivity coating produced in example 1.

Detailed Description

The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Graphene oxide was prepared using Hummers method: 10g of graphite powder is weighed into a beaker, 5g of sodium nitrate and 250mL of concentrated sulfuric acid are added, stirring is carried out for 30min under an ice water bath, and 40g of potassium permanganate is slowly added into the mixed system. After removal of the ice, the temperature was raised to 35℃and stirred for 8h. After the liquid in the beaker is reduced to room temperature, adding 30% hydrogen peroxide until no bubbles are generated, and performing centrifugal washing on the obtained graphene oxide solution by using 5wt% dilute hydrochloric acid and deionized water, and freeze-drying for later use.

Float type aluminum powder with granularity of 1000 meshes and float value of 85 is purchased from Jinan Hua pigment technology Co., ltd The method comprises the steps of carrying out a first treatment on the surface of the Carbon black, model F1105, specific surface area 360-380m ² And/g, purchased from Tianjin Hua Yuan chemical technology Co., ltd; polyacrylic resin, content>99, viscosity 40000-60000S, available from Bai Li Jia technology Co., guangzhou; acrylic block copolymers were purchased from Jin Tuan chemicals limited; polyether modified polydimethylsiloxane, content>99% and a density of 1.025-1.035kg/m ³ Purchased from wuhan rana white pharmaceutical chemicals limited; polyamide wax, content>20%, purchased from Guangdong Shunshengbangjia chemical industry Co., ltd; polyisocyanate, model N3390, available from bayer, germany.

Example 1

The embodiment provides a preparation method of a low-reflectivity coating, which specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 3 parts by weight of samarium nitrate and 1 part by weight of cerium nitrate, adjusting the pH value of the solution to 9, transferring into a closed hydrothermal reaction kettle, calcining at 180 ℃ for 20 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain a loaded Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing silica sol: mixing 15 parts by weight of ethyl orthosilicate, 30 parts by weight of water, 1 part by weight of ethanol and 5 parts by weight of concentrated hydrochloric acid, and reacting at 50 ℃ for 3 hours to obtain silica sol;

S3, preparing mixed silica sol: 1.5 parts by weight of carbon black, 1 part by weight of floating aluminum powder, and 8 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 20 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 30min to obtain a mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 at 400 ℃ for 2 hours to obtain a calcined product;

s5, reduction: adding 10 parts by weight of the calcined product obtained in the step S4 into 100 parts by weight of water, adding 3 parts by weight of 25wt% ammonia water and 1 part by weight of hydrazine hydrate, heating at 75 ℃ for reaction for 1h, filtering, and washing with deionized water to obtain a reduction product;

s6, modification: adding 10 parts by weight of the reduction product obtained in the step S5 into 50wt% ethanol solution, performing ultrasonic dispersion for 20min, adding 1 part by weight of coupling agent, heating to 70 ℃ for reaction for 30min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment; FIG. 1 is an SEM image of the resulting carbon black/silica composite loaded with a specific pigment, in which a number of fine nanocrystalline structures are formed.

The coupling agent is a compound mixture of A172 and KH570, and the mass ratio is 3:2;

S7, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S6 for 2 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s8, preparation of a component A: adding 9.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 20 parts by weight of polyacrylic resin, 2 parts by weight of acrylic block copolymer into a mixed solvent of 20 parts by weight of n-propyl acetate and 20 parts by weight of toluene, adding 0.6 part by weight of dicyclohexyl peroxydicarbonate, heating to 50 ℃ for reaction for 0.5h, then adding 0.1 part by weight of polyether modified polydimethylsiloxane and 1 part by weight of polyamide wax, and stirring and mixing for 20min to obtain a component A;

s9. Preparation of the component B: adding 15 parts by weight of polyisocyanate and 0.3 part by weight of dehydrating agent into a mixed solvent of 40 parts by weight of toluene and 40 parts by weight of n-propyl acetate, stirring and mixing for 10min, and controlling the environmental humidity at 40% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

s10, preparing a low-reflectivity coating: the A component, the B component and the ethyl acetate are mixed according to the mass ratio of 4: mixing at a ratio of 1:2, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm. Fig. 2 is a surface SEM image of the resulting reflectivity coating, from which it is evident that the coating surface produces more voids and random surface structures that also cause a further reduction in the reflectivity of the coating.

Example 2

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 5 parts by weight of samarium nitrate and 2 parts by weight of cerium nitrate, adjusting the pH value of the solution to 10, transferring into a closed hydrothermal reaction kettle, calcining at 200 ℃ for 30 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain the loaded Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing silica sol: mixing 20 parts by weight of methyl orthosilicate, 50 parts by weight of water, 3 parts by weight of ethanol and 7 parts by weight of concentrated hydrochloric acid, and reacting at 60 ℃ for 5 hours to obtain silica sol;

s3, preparing mixed silica sol: 2.5 parts by weight of carbon black, 2 parts by weight of floating aluminum powder and 20 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 30 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 50 minutes to obtain a mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 at 500 ℃ for 3 hours to obtain a calcined product;

s5, reduction: adding 15 parts by weight of the calcined product obtained in the step S4 into 100 parts by weight of water, adding 7 parts by weight of 30wt% ammonia water and 3 parts by weight of hydrazine hydrate, heating at 95 ℃ for reaction for 3 hours, filtering, and washing with deionized water to obtain a reduction product;

S6, modification: adding 10 parts by weight of the reduction product obtained in the step S5 into 70wt% ethanol solution, performing ultrasonic dispersion for 30min, adding 2 parts by weight of coupling agent, heating to 90 ℃ for reaction for 50min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

the coupling agent is a compound mixture of A172 and KH570, and the mass ratio is 5:2;

s7, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S6 for 4 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s8, preparation of a component A: adding 22.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 30 parts by weight of polyacrylic resin and 4 parts by weight of acrylic block copolymer into a mixed solvent of 30 parts by weight of methyl formate and 30 parts by weight of dimethylbenzene, adding 1.5 parts by weight of methyl ethyl ketone peroxide, heating to 70 ℃ for reaction for 2 hours, then adding 0.3 part by weight of polyether modified polydimethylsiloxane and 2 parts by weight of polyamide wax, stirring and mixing for 40 minutes to obtain a component A;

s9. Preparation of the component B: adding 20 parts by weight of polyisocyanate and 0.5 part by weight of dehydrating agent into a mixed solvent of 45 parts by weight of dimethylbenzene and 45 parts by weight of methyl formate, stirring and mixing for 20min, and controlling the environmental humidity to be 60% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

S10, preparing a low-reflectivity coating: the component A, the component B and the methyl formate are mixed according to the mass ratio of 4: mixing at a ratio of 1:4, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm.

Example 3

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate, adjusting the pH value of the solution to 9.5, transferring into a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain a load Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing silica sol: 17 parts by weight of tetraethoxysilane, 40 parts by weight of water, 2 parts by weight of ethanol and 6 parts by weight of concentrated hydrochloric acid are mixed and reacted for 4 hours at 55 ℃ to obtain silica sol;

s3, preparing mixed silica sol: 2 parts by weight of carbon black, 1.512 parts by weight of floating aluminum powder and 12 parts by weight of load Sm prepared in step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

S4, calcining: calcining the mixed silica sol obtained in the step S3 at 450 ℃ for 2.5 hours to obtain a calcined product;

s5, reduction: adding 12 parts by weight of the calcined product obtained in the step S4 into 100 parts by weight of water, adding 5 parts by weight of 27wt% ammonia water and 2 parts by weight of hydrazine hydrate, heating at 85 ℃ for reaction for 2 hours, filtering, and washing with deionized water to obtain a reduction product;

s6, modification: adding 10 parts by weight of the reduction product obtained in the step S5 into 60wt% ethanol solution, performing ultrasonic dispersion for 25min, adding 1.5 parts by weight of coupling agent, heating to 80 ℃ for reaction for 40min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

the coupling agent is a compound mixture of A172 and KH570, and the mass ratio is 4:2;

s7, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S6 for 3 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s8, preparation of a component A: adding 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin, 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1h, then adding 0.2 part by weight of polyether modified polydimethylsiloxane and 1.5 parts by weight of polyamide wax, and stirring and mixing for 30min to obtain a component A;

S9. Preparation of the component B: adding 17 parts by weight of polyisocyanate and 0.4 part by weight of dehydrating agent into a mixed solvent of 42 parts by weight of dimethylbenzene and 42 parts by weight of ethyl acetate, stirring and mixing for 15min, and controlling the environmental humidity to be 50% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

s10, preparing a low-reflectivity coating: the component A, the component B and the n-propyl acetate are mixed according to the mass ratio of 4: mixing at a ratio of 1:3, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm.

Example 4

In contrast to example 3, the coupling agent was a single a172, with no other conditions being changed.

Example 5

In comparison with example 3, the coupling agent was KH570 alone, and the other conditions were not changed.

Comparative example 1

In contrast to example 3, no samarium nitrate was added in step S1, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, loading CeO ₂ Is prepared from graphene oxide: dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 5.5 parts by weight of cerium nitrate, adjusting the pH value of the solution to 9.5, transferring into a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain the loaded CeO ₂ Is a graphene oxide;

s3, preparing mixed silica sol: 2 parts by weight of carbon black, 1.5 parts by weight of floating aluminum powder and 12 parts by weight of the loaded CeO prepared in the step S1 ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

Comparative example 2

In contrast to example 3, cerium nitrate was not added in step S1, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ Is prepared from graphene oxide: 10 parts by weight of graphene oxide was dissolved in 50 parts by weight of water, and 5.5 parts by weight of nitric acid was addedSamarium, adjusting the pH value of the solution to 9.5, transferring into a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain the loaded Sm ₂ O ₃ Is a graphene oxide;

s3, preparing mixed silica sol: 2 parts by weight of carbon black, 1.5 parts by weight of floating aluminum powder and 12 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

Comparative example 3

In contrast to example 3, graphene oxide was not added in step S1, and the other conditions were not changed.

The method specifically comprises the following steps:

S1.Sm ₂ O ₃ and CeO ₂ Preparation of the mixture: dissolving 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate in 50 parts by weight of water, regulating the pH value of the solution to 9.5, transferring into a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2 hours to obtain Sm ₂ O ₃ And CeO ₂ A mixture;

s3, preparing mixed silica sol: 2 parts by weight of carbon black, 1.5 parts by weight of floating aluminum powder and 12 parts by weight of Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the mixture to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

s5, modification: adding 10 parts by weight of the calcined product obtained in the step S4 into 60wt% ethanol solution, performing ultrasonic dispersion for 25min, adding 1.5 parts by weight of coupling agent, heating to 80 ℃ for reaction for 40min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

s6, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S5 for 3 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s7, preparation of a component A: adding 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S6 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin, 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1h, then adding 0.2 part by weight of polyether modified polydimethylsiloxane and 1.5 parts by weight of polyamide wax, and stirring and mixing for 30min to obtain a component A;

S8, preparation of a component B: adding 17 parts by weight of polyisocyanate and 0.4 part by weight of dehydrating agent into a mixed solvent of 42 parts by weight of dimethylbenzene and 42 parts by weight of ethyl acetate, stirring and mixing for 15min, and controlling the environmental humidity to be 50% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

s9, preparing a low-reflectivity coating: the component A, the component B and the n-propyl acetate are mixed according to the mass ratio of 4: mixing at a ratio of 1:3, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm.

Comparative example 4

In comparison with example 3, no silica sol was prepared and used, and the other conditions were unchanged.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: 10 parts by weight of graphene oxide was dissolved in 50 parts by weight of water, and 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate were added to prepare a mixtureThe pH value of the solution is 9.5, then the solution is transferred into a closed hydrothermal reaction kettle, calcined at 190 ℃ for 25 hours, cooled to room temperature, washed by deionized water and ethanol in sequence, and dried at 70 ℃ for 2 hours, thus obtaining the load Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s2, preparing mixed silica sol: 2 parts by weight of carbon black, 1.5 parts by weight of floating aluminum powder and 12 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture;

s3, reduction: adding 12 parts by weight of the mixture prepared in the step S2 into 100 parts by weight of water, adding 5 parts by weight of 27wt% ammonia water and 2 parts by weight of hydrazine hydrate, heating at 85 ℃ for reaction for 2 hours, filtering, and washing with deionized water to obtain a reduction product;

s4, modification: adding 10 parts by weight of the reduction product obtained in the step S3 into 60wt% ethanol solution, performing ultrasonic dispersion for 25min, adding 1.5 parts by weight of coupling agent, heating to 80 ℃ for reaction for 40min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

s5, ball milling: ball milling the carbon black/silicon dioxide composite material loaded with the special pigment obtained in the step S4 for 3 hours to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s6, preparation of a component A: adding 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S5 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin, 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1h, then adding 0.2 part by weight of polyether modified polydimethylsiloxane and 1.5 parts by weight of polyamide wax, stirring and mixing for 30min to obtain a component A;

S7, preparation of a component B: adding 17 parts by weight of polyisocyanate and 0.4 part by weight of dehydrating agent into a mixed solvent of 42 parts by weight of dimethylbenzene and 42 parts by weight of ethyl acetate, stirring and mixing for 15min, and controlling the environmental humidity to be 50% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

s8, preparing a low-reflectivity coating: the component A, the component B and the n-propyl acetate are mixed according to the mass ratio of 4: mixing at a ratio of 1:3, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm.

Comparative example 5

In contrast to example 3, no carbon black was added in step S3, and the other conditions were not changed.

The method specifically comprises the following steps:

S3, preparing mixed silica sol: 3.5 parts by weight of floating aluminum powder and 12 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

Comparative example 6

In comparison with example 3, no floating-type aluminum powder was added in step S3, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: 10 parts by weight of graphene oxide is dissolved in 50 parts by weight of water, 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate are added, the pH value of the solution is regulated to 9.5, and then the solution is transferred into a closed hydrothermal reaction kettle for calcination at 190 DEG CBurning for 25h, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70deg.C for 2h to obtain Sm-loaded product ₂ O ₃ And CeO ₂ Is a graphene oxide;

s3, preparing mixed silica sol: 3.5 parts by weight of carbon black and 12 parts by weight of the load Sm obtained in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

Comparative example 7

In contrast to example 3, no reduction in step S5 was performed and no other conditions were changed.

The method specifically comprises the following steps:

s3, preparing mixed silica sol: 2 parts by weight of carbon black, 1.5 parts by weight of floating aluminum powder and 12 parts by weight of the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding 25 parts by weight of the mixture into the silica sol obtained in the step S2, and stirring and dispersing for 40 minutes to obtain a mixed silica sol;

Comparative example 8

In contrast to example 3, no modification in step S6 was performed, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: 10 parts by weight of graphene oxide is dissolved in 50 parts by weight of water, 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate are added, and dissolution is regulatedThe pH value of the solution is 9.5, and then the solution is transferred into a closed hydrothermal reaction kettle to be calcined at 190 ℃ for 25 hours, cooled to room temperature, washed by deionized water and ethanol in sequence and dried at 70 ℃ for 2 hours, thus obtaining the loaded Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s6, ball milling: ball milling the reduction product obtained in the step S5 for 3 hours to obtain a carbon black/silicon dioxide composite material which is less than 5 mu m and is loaded with special pigment;

Comparative example 9

In contrast to example 3, the carbon black/silica composite carrying the special pigment was not added in step S8, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, preparation of a component A: adding 25 parts by weight of polyacrylic resin and 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1h, then adding 0.2 part by weight of polyether modified polydimethylsiloxane and 1.5 parts by weight of polyamide wax, and stirring and mixing for 30min to obtain a component A;

s2. Preparation of the component B: adding 17 parts by weight of polyisocyanate and 0.4 part by weight of dehydrating agent into a mixed solvent of 42 parts by weight of dimethylbenzene and 42 parts by weight of ethyl acetate, stirring and mixing for 15min, and controlling the environmental humidity to be 50% to obtain a component B; the dehydrating agent is a dehydrating agent F-180 of Lyar company of Germany;

S3, preparing a low-reflectivity coating: the component A, the component B and the n-propyl acetate are mixed according to the mass ratio of 4: mixing at a ratio of 1:3, spraying with an air spray gun, naturally drying, and obtaining the low-reflectivity coating with a dry film thickness of 30-40 μm.

Comparative example 10

In contrast to example 3, the polyether-modified polydimethylsiloxane was not added in step S8, and the other conditions were not changed.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: 10 parts by weight of graphene oxide is dissolved in 50 parts by weight of water, 4 parts by weight of samarium nitrate and 1.5 parts by weight of cerium nitrate are added, the pH value of the solution is regulated to 9.5, and then the solution is transferred to a closed hydrothermal reactionCalcining at 190 ℃ for 25h in a kettle, cooling to room temperature, washing with deionized water and ethanol in sequence, and drying at 70 ℃ for 2h to obtain the loaded Sm ₂ O ₃ And CeO ₂ Is a graphene oxide;

s8, preparation of a component A: adding 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin and 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, then adding 1.7 parts by weight of polyamide wax, stirring and mixing for 30 minutes to obtain a component A;

Comparative example 11

In contrast to example 3, no polyamide wax was added in step S8, and the other conditions were not changed.

The method specifically comprises the following steps:

S8, preparation of a component A: adding 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin and 3 parts by weight of acrylic block copolymer into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, then adding 1.7 parts by weight of polyether modified polydimethylsiloxane, and stirring and mixing for 30 minutes to obtain a component A;

Comparative example 12

In contrast to example 3, the polyether-modified polydimethylsiloxane and the polyamide wax were not added in step S8, and the other conditions were not changed.

The method specifically comprises the following steps:

s8, preparation of a component A: 15.5 parts by weight of the carbon black/silicon dioxide composite material which is obtained in the step S7 and is ground and loaded with special pigment, 25 parts by weight of polyacrylic resin and 3 parts by weight of acrylic block copolymer are added into a mixed solvent of 25 parts by weight of ethyl acetate and 25 parts by weight of dimethylbenzene, 1.2 parts by weight of di-tert-butyl peroxide is added, and the mixture is heated to 60 ℃ for reaction for 1 hour to obtain a component A;

Test example 1 reflectance test

The low-reflectivity coatings prepared in examples 1-5 and comparative examples 1-12 of the present invention were subjected to reflectivity testing.

The coating was tested for visible and near infrared light transmittance, visible and near infrared reflectance using a meridacm-512 m3a spectrocolorimeter.

The results are shown in Table 1.

TABLE 1

As can be seen from the above table, the low reflectivity coatings prepared in examples 1-3 of the present invention have lower reflectivity for all of visible light, ultraviolet light and near infrared light.

Test example 2

The low reflectivity coatings prepared in examples 1-5 and comparative examples 1-12 of the present invention were subjected to basic performance testing.

Evaluating the hardness of the coating according to the GB/T6739-2006 method, drawing a pencil with gradually increasing hardness at an angle of 45 degrees on the surface of the coating, and then observing the integrity of the surface of the coating until the surface of the coating is provided with an indentation, scratch and scratch, wherein the hardness of the last pencil corresponding to the pencil is the hardness of the tested coating, and the hardness of the pencil used by the standard can be classified into the following 20 grades: 9B-1B-HB-F-1H-9H.

The adhesion of the coating is evaluated by a QFZII adhesion circling tester according to the method GB1720-2020, and the coating is rated according to the coating integrity in the circle rolling scratch range, and the coating adhesion is classified into 1-7 grades, the 1 grade is optimal and the 7 grade is worst according to the standard.

The impact strength of the coating is evaluated by adopting a GCJ impact strength tester according to the GB/T1732-2020 method, 1kg of heavy hammer falls from different heights (50 cm at the highest), the heavy hammer is crashed on the coating, the strongest impact resistance height of the coating is determined by judging whether the coating is intact, and finally the impact strength (kg.cm) of the coating is represented by the product of the falling hammer height and the weight of the heavy hammer.

The results are shown in Table 2.

TABLE 2

As shown in the table above, the low-reflectivity coating prepared in the embodiment 1-3 of the invention has the advantages of stronger hardness (H), high adhesion level (level 1), high impact strength (56-60 kg cm), and good mechanical property and adhesion.

Test example 3

The low reflectance coatings prepared in examples 1 to 5 and comparative examples 1 to 12 of the present invention were subjected to a wave-absorbing property test.

Electromagnetic parameters of the composite material are measured by a vector network analyzer (N5224A), and the frequency range is 2-18GHz. According to the transmission line theory, a coating sample-paraffin is pressed into a concentric ring with an outer diameter of 7mm and an inner diameter of 3mm, electromagnetic parameters of the composite material are measured when the filling ratio of the sample to the paraffin is 1:0.05, and the reflection loss of the composite material is calculated according to the following Reflection Loss (RL) calculation formula. The wave-absorbing properties of the materials were studied by data analysis.

RL＝20log|(Z _in -Z ₀ )/(Z _in +Z ₀ )|

Wherein Z is _in Z is the input impedance ₀ Is the free space impedance, mu _r =μ' -jμ″ is complex permeability, ε _r =ε' -j ε "is complex permittivity, f is frequency, d is the thickness of the composite, and c is the speed of light. When the reflection loss DL is less than-10 dB, the corresponding incident electromagnetic wave is more than 90% dissipated by the material; when the reflection loss DL is less than-20 dB, a corresponding incident electromagnetic wave of more than 99% is dissipated by the material. The frequency band range where DL is less than 10dB is referred to as the effective absorption bandwidth of the material.

The results are shown in Table 3.

TABLE 3 Table 3

As can be seen from the above table, the low-reflectivity coatings prepared in examples 1-3 of the present invention have good wave-absorbing properties, and most of the incident electromagnetic waves are dissipated by the material at frequencies of 12GHz and 18 GHz.

Examples 4 and 5 were inferior to example 3 in impact strength and adhesion of the coating layer, because the coupling agent was a single a171 or a 151. Comparative example 8 was compared with example 3, the hardness, impact resistance and adhesion of the coating were reduced without the modification of step S6. Coupling agent A172 is vinyltris (beta-methoxyethoxy) silane; KH570 is gamma- (methacryloyloxy) propyl trimethoxy silane, both of which have longer alkyl chains, and polypropylene resin can be intertwined to enhance the compatibility of the carbon black/silica composite material loaded with special pigment and the resin, so that the mechanical property and adhesive force of the coating are improved, and the two have a synergistic effect. The reflectivity of the whole coating is mainly related to pigment particles, wherein the resin material mainly determines the mechanical properties of the coating, such as adhesive force, tensile strength and the like. According to the invention, the reduced product is further modified by the silane coupling agent with double bonds, so that the surface of the reduced product is provided with double bond groups, and the reduced product is connected to a polypropylene resin molecular chain after undergoing a copolymerization reaction with the polypropylene resin, so that the carbon black/silicon dioxide composite material loaded with special pigment can be uniformly distributed in the resin material, thus effectively avoiding the coagulation of inorganic components, enabling the coating to be more uniform, achieving the effect of uniform emission, and effectively avoiding the phenomenon of overhigh or overlow local reflection.

In comparative examples 1 and 2, samarium nitrate or cerium nitrate was not added in step S1, as compared with example 3. Comparative example 3 in contrast to example 3, no graphene oxide was added in step S1. The reflectivity of the prepared coating to ultraviolet light, visible light and near infrared light is increased, and the wave absorbing performance is weakened. The rare earth oxide has excellent optical, electric and magnetic properties, wherein Sm ₂ O ₃ Middle Sm ³⁺ Has strong absorption property to 1.06 mu m special near infrared light, ceO ₂ The oxygen vacancy effects of (2) contribute to the loss of light waves and electromagnetic waves. Sm (Sm) ₂ O ₃ And CeO ₂ Is fixedly supported on graphene oxide, and the wave absorbing efficiency, the effective absorption bandwidth and the reflection effect of the light wave are obviously higher than those of single graphene oxide and Sm ₂ O ₃ And CeO ₂ Graphene oxide generally has a low complex dielectric constant because of Sm ₂ O ₃ And CeO ₂ Multiple interfacial polarizations with graphene are also beneficial to losses to electromagnetic and light waves.

Comparative example 4 compared with example 3, the hardness, impact resistance and adhesion of the coating were remarkably reduced, the reflectivity to ultraviolet light, visible light and near infrared light was increased, and the wave absorbing performance was reduced without preparing and using the silica sol. Hydrolytic polymerization by sol-gel reaction Obtaining silica sol, loading Sm with carbon black, aluminum powder ₂ O ₃ And CeO ₂ Adding graphene oxide into silica sol, dispersing uniformly, calcining to obtain silica-loaded carbon black, aluminum powder and Sm-loaded carbon black ₂ O ₃ And CeO ₂ The graphene oxide material not only provides a foundation for the subsequent modification by a silane coupling agent (the silica carrier and the silane coupling agent have better binding capacity), but also the prepared silica carrier further improves the mechanical property of the coating, and the surface of the coating generates more cavities and random surface structures on the surface of the coating due to the addition of the carbon black/silica composite material loaded with the special pigment due to the silica structure, and the reflectivity of the coating is further reduced due to the cavities or the random surface structures.

In comparative examples 5 and 6, compared with example 3, the reflectivity of the obtained coating layer to ultraviolet light, visible light and near infrared light is increased and the wave absorbing performance is reduced without adding carbon black or floating aluminum powder in step S3. The synergistic addition of the carbon black and the floating aluminum powder improves the wave absorption of the coating and reduces the reflectivity to a certain extent. Because the floating aluminum powder has higher conductivity and is cheaper than metals such as Au, ag, cu and the like, the floating aluminum powder can be used as a functional pigment with low infrared emission/reflectivity coating.

Comparative example 7 compared with example 3, the reflectivity of the obtained coating layer to ultraviolet light, visible light and near infrared light is increased and the wave absorbing performance is reduced without performing the reduction of step S5. The graphene oxide has a low complex dielectric constant, and the most effective method for improving the wave absorbing capacity of the graphene oxide is to reduce a part of oxygen-containing functional groups on the graphene oxide and improve the number of free electrons on graphene sheets, so that the complex dielectric constant of the graphene oxide is improved, and the impedance matching capacity is enhanced. Defects and functional groups on the reduced graphene oxide can also enable energy to be converted into fermi energy level from a continuous state, polarization relaxation and electron dipole relaxation are introduced, so that the attenuation capability of the material on electromagnetic waves is enhanced, the reflection loss of the reduced graphene oxide is greatly improved, and the reflection capability, electromagnetic shielding capability and wave absorbing capability of the material are improved.

Comparative example 9 in comparison with example 3, no special pigment-supporting carbon black/silica composite was added in step S8. The hardness and the wave absorbing performance of the paint are greatly reduced, the reflectivity of ultraviolet light, visible light and near infrared light is increased, and the wave absorbing performance is weakened.

In comparative examples 10 and 11, the hardness and impact resistance of the coating obtained in step S8 were reduced as compared with example 3, without adding polyether-modified dimethylsiloxane or polyamide wax. Comparative example 12 the hardness, impact resistance and adhesion of the coating obtained were significantly reduced compared to example 3 without the addition of polyether modified dimethylsiloxane and polyamide wax in step S8. The polyether modified dimethyl siloxane has a large number of inorganic siloxane bonds and active polyether functional groups, the existence of the inorganic siloxane bonds can enable the polyether modified dimethyl siloxane to have outstanding high temperature resistance, and the existence of the active polyether functional groups can enhance the bonding strength between a resin matrix and a filler and between the resin matrix and a substrate, so that the mechanical property of the coating can be enhanced. The addition of the polyamide wax helps to prevent sedimentation of the components and improves the dispersibility of the components. The synergistic addition of polyether modified dimethylsiloxane and polyamide wax provides a degree of improvement in coating hardness.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims

1. The low-reflectivity coating is characterized by comprising an A component and a B component, wherein the A component is prepared from the following raw materials in parts by weight: 20-30 parts of polyacrylic resin, 9.5-22.5 parts of carbon black/silicon dioxide composite material loaded with special pigment, 20-30 parts of ester solvent, 20-30 parts of benzene solvent, 2-4 parts of acrylic block copolymer, 0.1-0.3 part of polyether modified polydimethylsiloxane and 1-2 parts of polyamide wax; the component B is prepared from the following raw materials in parts by weight: 15-20 parts of polyisocyanate, 0.3-0.5 part of dehydrating agent, 40-45 parts of benzene solvent and 40-45 parts of ester solvent;

the preparation method of the carbon black/silicon dioxide composite material loaded with the special pigment comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ Is prepared from graphene oxide: dissolving graphene oxide in water, adding samarium nitrate and cerium nitrate, regulating the pH value of the solution to 9-10, transferring into a hydrothermal reaction kettle, calcining, cooling to room temperature, washing, and drying to obtain a load Sm ₂ O ₃ And CeO ₂ Is a graphene oxide; the mass ratio of the graphene oxide to the samarium nitrate to the cerium nitrate is 10:3-5:1-2;

s2, preparing silica sol: mixing the alkyl orthosilicate, water, ethanol and concentrated hydrochloric acid, and reacting to obtain silica sol; the mass ratio of the alkyl orthosilicate to the water to the ethanol to the concentrated hydrochloric acid is 15-20:30-50:1-3:5-7;

s3, preparing mixed silica sol: carbon black, aluminum powder and the load Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding graphene oxide to obtain a mixture, adding the mixture into the silica sol obtained in the step S2, and uniformly stirring and dispersing the mixture to obtain mixed silica sol; the carbon black, al powder and load Sm ₂ O ₃ And CeO ₂ The mass ratio of the graphene oxide to the silica sol is 1.5-2.5:1-2:8-20:20-30;

s5, reduction: adding the calcined product obtained in the step S4 into water, adding ammonia water and hydrazine hydrate, heating for reaction, filtering and washing to obtain a reduction product; the mass ratio of the calcined product to the ammonia water to the hydrazine hydrate is 10-15:3-7:1-3;

s6, modification: adding the reduction product obtained in the step S5 into ethanol solution, dispersing uniformly, adding a coupling agent, heating for reaction, filtering, and drying to obtain carbon black/silicon dioxide composite material loaded with special pigment; the mass ratio of the reduction product to the coupling agent is 10:1-2.

2. The low reflectivity coating of claim 1, wherein the calcination temperature in step S1 is 180-200 ℃ for 20-30 hours.

3. The low reflectivity coating of claim 1, wherein the reaction temperature in step S2 is 50-60 ℃ for 3-5 hours.

4. The low-reflectivity coating of claim 1, wherein the aluminum powder in step S3 is a floating aluminum powder; the calcining temperature in the step S4 is 400-500 ℃ and the time is 2-3h.

5. The low reflectivity coating of claim 1, wherein the ammonia concentration in step S5 is 25-30wt%; the temperature of the heating reaction is 75-95 ℃ and the time is 1-3h; the ethanol content of the ethanol solution in the step S6 is 50-70wt%; the coupling agent is a silane coupling agent with double bonds and is selected from at least one of KH570, A172, A151 and A171; the temperature of the heating reaction is 70-90 ℃ and the time is 30-50min.

6. The low reflectivity coating of claim 5, wherein the coupling agent is a compounded mixture of a172 and KH570 in a mass ratio of 3-5:2.

7. A method of preparing a low reflectivity coating according to any one of claims 1 to 6, comprising the steps of:

S1, ball milling: ball milling is carried out on the carbon black/silicon dioxide composite material loaded with the special pigment to obtain a ground carbon black/silicon dioxide composite material loaded with the special pigment, wherein the size of the ground carbon black/silicon dioxide composite material is less than 5 mu m;

s2. Preparation of the component A: adding the ground carbon black/silicon dioxide composite material loaded with the special pigment, polyacrylic resin and acrylic block copolymer obtained in the step S1 into a mixed solvent of an ester solvent and a benzene solvent, adding an initiator, heating for reaction, then adding polyether modified polydimethylsiloxane and polyamide wax, and uniformly mixing to obtain a component A;

s3. Preparation of the component B: adding polyisocyanate and a dehydrating agent into a mixed solvent of a benzene solvent and an ester solvent, uniformly stirring, and controlling the environmental humidity to be 40% -60% to obtain a component B;

s4, preparing a low-reflectivity coating: the component A, the component B and the diluting solvent are mixed according to the mass ratio of 4: mixing at a ratio of 1:2-4, spraying with an air spray gun, and drying to obtain a dry film with a thickness of 30-40 μm to obtain the low-reflectivity coating.

8. The method according to claim 7, wherein the ball milling time in step S1 is 2 to 4 hours; the initiator in the step S2 is at least one selected from benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate; the addition amount of the initiator is 3-5wt% of the polyacrylic resin, the heating temperature is 50-70 ℃ and the time is 0.5-2h; the diluting solvent in the step S4 is at least one of ethyl acetate, methyl formate and n-propyl acetate.

9. Use of the low reflectivity coating of claim 1 in display and optical lens surface coatings.