CN115746638A

CN115746638A - Low-reflectivity coating and preparation method and application thereof

Info

Publication number: CN115746638A
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: 2023-03-07
Anticipated expiration: 2042-09-28
Also published as: CN115746638B

Abstract

The invention provides a low-reflectivity coating and a preparation method and application thereof, belonging to the technical field of coatings. The composition 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 whitening and graying, 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 and 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.

To be commercially useful, these coatings must have the lowest reflectivity possible and be capable of substantially uniform optical absorption over a wide 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 debris, good thermal shock resistance and moisture resistance. Since coatings are often used locally for highly sensitive electron detectors, such as CCDs (charge coupled devices) or microbolometers, they are a key requirement for industrial and scientific applications. Any contaminants from this coating will inevitably accumulate or condense on the detector causing them to fail or reducing their performance beyond acceptable thresholds.

For glass materials, the strong reflected light causes the transmittance of the materials to be reduced and glare phenomenon to occur, such as glass for laser, automobile glass, spectacle lenses, television screens, instrument display screens, museum show window glass and the like, thereby affecting the use effect, and the development of low reflection technology is promoted. There are many methods for preparing low reflection film on the surface of glass, such as spraying method, vacuum coating process, phase separation leaching method, etc.

The common low-reflectivity coating on the market at present has high reflectivity, and can not meet the ideal reflectivity requirement in a display and an optical lens; in the construction process, the problems of unstable reflectivity and white and grey coating film surface 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 the low-reflectivity coating has the advantages of easiness in spraying and difficulty in whitening and graying in application. The invention has wider application range, has good adhesive force to common plastic base materials such as ABS, PC, ABS + PC and the like, also has good adhesive force to metal base materials such as aluminum, iron and the like, and has wide application prospect.

The technical scheme of the invention is realized as follows:

the invention provides a low-reflectivity coating, which 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.

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 F-180 of Lyar company in Germany.

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

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): dissolving graphene oxide in water, adding samarium nitrate and cerium nitrate, adjusting the pH value of the solution to 9-10, transferring the solution to a hydrothermal reaction kettle, calcining, cooling to room temperature, washing and drying to obtain the Sm-loaded carrier ₂ O ₃ And CeO ₂ The graphene oxide of (3);

s2, preparation of silica sol: mixing 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 loaded Sm prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into the silica sol obtained in the step S2, and uniformly stirring and dispersing 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 an ethanol solution, uniformly dispersing, adding a coupling agent, heating for reaction, filtering, and drying to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

s7, ball milling: performing ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8, preparation of a component A: adding the ground special pigment-loaded carbon black/silicon dioxide composite material obtained in the step S7, polyacrylic resin and acrylic block copolymer 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.B component preparation: 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 between 40 and 60 percent to obtain a component B;

s10, preparing a low-reflectivity coating: mixing the component A, the component B and a diluting solvent according to a mass ratio of 4:1:2-4, spraying with an air spray gun, drying to a dry film thickness of 30-40 μm to obtain a low reflectance coating.

As a further improvement of the present invention, in step S1, the mass ratio of the graphene oxide to the samarium nitrate to the cerium nitrate 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); the reaction temperature is 50-60 ℃ and the reaction time is 3-5h.

As a further improvement of the invention, the carbon black, al powder and supported Sm in the 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;the aluminum powder is floating aluminum powder; in the step S4, the calcining temperature is 400-500 ℃, and the time is 2-3h.

As a further improvement of the invention, the mass ratio of the calcined product, the ammonia water and the hydrazine hydrate in the step S5 is 10-15:3-7:1-3; the concentration of the ammonia water is 25-30wt%; the heating reaction is carried out at the temperature of 75-95 ℃ for 1-3h; in the step S6, the ethanol content in the ethanol solution is 50-70wt%; the mass ratio of the reduction product to the coupling agent is 10; 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 heating reaction temperature is 70-90 deg.C, 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.

The coupling agent A172 is vinyl tri (beta-methoxyethoxy) silane; KH570 is gamma- (methacryloyloxy) propyl trimethoxy silane, both of which have longer alkyl chains, and can be intertwined with polypropylene resin, so that the compatibility of the carbon black/silicon dioxide composite material loaded with special pigments and the resin is enhanced, the mechanical property and the adhesive force of the coating are improved, and the two have synergistic effect.

As a further improvement of the invention, the ball milling time in the step S7 is 2-4h; in the step S8, the initiator 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 heating time is 0.5-2h; in the step S10, the diluting solvent 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 The preparation of graphene oxide of (2): dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, and adding 3-5 parts by weight of nitreSamarium acid and 1-2 parts by weight of cerous nitrate are added, the pH value of the solution is adjusted to 9-10, then the solution is transferred to a closed hydrothermal reaction kettle, calcined for 20-30h at 180-200 ℃, cooled to room temperature, washed by deionized water and ethanol in sequence, and dried to obtain the Sm-loaded carrier ₂ O ₃ And CeO ₂ Graphene oxide of (a);

s2, preparation of 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 3-5h to obtain silica sol;

s3, preparing mixed silica sol: 1.5 to 2.5 weight portions of carbon black, 1 to 2 weight portions of floating aluminum powder and 8 to 20 weight portions of Sm-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 20-30 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 30-50min to obtain 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% of ammonia water and 1-3 parts by weight of hydrazine hydrate, heating and reacting at 75-95 ℃ for 1-3h, 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% of ethanol solution, performing ultrasonic dispersion for 20-30min, adding 1-2 parts by weight of coupling agent, heating to 70-90 ℃, reacting for 30-50min, filtering, and drying 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 3-5:2;

s7, ball milling: carrying out ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 for 2-4h to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8, preparation of a component A: adding 9.5-22.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 an ester solvent and 20-30 parts by weight of a benzene solvent, adding 0.6-1.5 parts by weight of an initiator, heating to 50-70 ℃ for reaction for 0.5-2h, then adding 0.1-0.3 part by weight of polyether modified polydimethylsiloxane and 1-2 parts by weight of polyamide wax, and stirring and mixing for 20-40min to obtain a component A;

s9.B component preparation: 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 ambient humidity to be between 40% and 60% to obtain a component B;

s10, preparing a low-reflectivity coating: the component A, the component B and a diluting solvent are mixed according to the mass ratio of 4:1:2-4, spraying with an air spray gun, drying to a dry film thickness of 30-40 μm, and obtaining the low-reflectivity coating.

The invention further protects the application of the low-reflectivity coating in the surface coating of a display and an optical lens.

The invention has the following beneficial effects:

the rare earth oxide has excellent optical, electrical and magnetic properties, wherein Sm is ₂ O ₃ Middle Sm ³⁺ Has strong absorption characteristic to 1.06 mu m special near infrared light, ceO ₂ The oxygen vacancy effect of (2) contributes to the loss of light waves and electromagnetic waves. Sm ₂ O ₃ And CeO ₂ The composite is fixedly carried on the graphene oxide, and the wave-absorbing efficiency, the effective absorption bandwidth and the reflection effect on light waves of the composite are obviously greater than those of single graphene oxide and single Sm ₂ O ₃ And CeO ₂ This is due to Sm ₂ O ₃ And CeO ₂ And the multiple interface polarization effect between the graphene and the graphene is also beneficial to the loss of electromagnetic waves and light waves. The floating aluminum powder has higher conductivity and is cheaper than metals such as Au, ag, cu and the like, so that the floating aluminum powder can be used as a functional pigment of a low infrared emission/reflectivity coating.

Generally, graphene oxide has a low complex dielectric constant, and the most effective method for improving the wave-absorbing capability 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 a graphene sheet layer, so that the complex dielectric constant of the graphene oxide is improved, and the impedance matching capability of the graphene oxide is enhanced. The defects and functional groups on the reduced graphene oxide can also convert energy from a continuous state into a Fermi level, and polarization relaxation and electron dipole relaxation are introduced, so that the attenuation capacity of the material to electromagnetic waves is enhanced, the reflection loss of the reduced graphene oxide is greatly improved, and the reflection capacity, the electromagnetic shielding capacity and the wave absorbing capacity of the material are improved.

Carrying out sol-gel reaction, carrying out hydrolytic polymerization to obtain silica sol, and carrying carbon black, aluminum powder and Sm ₂ O ₃ And CeO ₂ Adding the graphene oxide into silica sol, uniformly dispersing, and calcining to obtain the silicon dioxide loaded carbon black, aluminum powder and Sm loaded silicon dioxide ₂ O ₃ And CeO ₂ The graphene oxide material not only provides a foundation for subsequent modification through a silane coupling agent (the silicon dioxide carrier and the silane coupling agent have better binding capacity), but also the prepared silicon dioxide carrier further improves the mechanical property of the coating, and the silicon oxide structure of the surface of the coating causes more cavities and random surface structures to be generated on the surface of the coating due to the addition of the carbon black/silicon dioxide composite material loaded with the special pigment, and the cavities or the random surface structures can further reduce the reflectivity of the coating.

The reflectivity of the whole coating is mainly related to pigment particles, and the resin material in the coating mainly determines the mechanical properties of the coating, such as adhesion, tensile strength and the like. According to the invention, the reduction product is prepared, and is further modified by a silane coupling agent with double bonds, so that the surface of the reduction product is provided with double bond groups, and the reduction product is connected to a polypropylene resin molecular chain after undergoing a copolymerization reaction with a polypropylene resin, so that the carbon black/silicon dioxide composite material loaded with the special pigment can be uniformly distributed in the resin material, and thus, the coagulation of inorganic components is effectively avoided, the coating can be more uniform, the uniform emission effect is achieved, and the phenomenon of over-high or over-low local reflection is effectively avoided.

The polyether modified polydimethylsiloxane has a large number of inorganic silicon-oxygen bonds and active polyether functional groups, the inorganic silicon-oxygen 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 the components from settling and improve the dispersibility of the components. The synergistic addition of the polyether modified polydimethylsiloxane and the polyamide wax improves the hardness of the coating to a certain extent.

Therefore, compared with other low-reflectivity coatings, the coating has the advantage of lower reflectivity, and has the advantages of easy spraying and difficult whitening and graying in application property. The invention has wider application range, has good adhesive force to common plastic base materials such as ABS, PC, ABS + PC and the like, also has good adhesive force to metal base materials such as aluminum, iron and the like, and has wide application prospect.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is an SEM photograph of a special pigment-supporting carbon black/silica composite obtained in step S6 of example 1;

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

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The graphene oxide is prepared by a Hummers method: weighing 10g of graphite powder in a beaker, adding 5g of sodium nitrate and 250mL of concentrated sulfuric acid, stirring for 30min in an ice-water bath, and slowly adding 40g of potassium permanganate into the mixed system. After removing ice, the temperature is raised to 35 ℃ and stirred for 8 hours. After the liquid in the beaker is reduced to room temperature, 30% hydrogen peroxide is added until no bubbles are generated, and the obtained graphene oxide solution is centrifugally washed by using 5wt% dilute hydrochloric acid and deionized water and then is freeze-dried for later use.

The floating aluminum powder with the granularity of 1000 meshes and the floating value of 85 is purchased from Jinan Hua pigment science and technology Limited; carbon black, type F1105, specific surface area 360-380m ² (ii)/g, purchased from Tianjin Huayuan chemical technology, inc.; polyacrylic acid resin, content>99% and viscosity of 40000-60000S, available from Bailijia technologies, inc., guangzhou; acrylic block copolymers available from Jin Tuan chemicals, inc; polyether-modified polydimethylsiloxane in an amount>99% and density of 1.025-1.035kg/m ³ Purchased from Wuhan La Na white pharmaceutical chemical Co., ltd; polyamide wax, content>20% of the total weight of the product, purchased from chemical Co., ltd of Bangdong, bangbangjiaming, gordon, japan; polyisocyanate, type N3390, available from Bayer AG, 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 The preparation of graphene oxide of (2): 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 the solution to a closed hydrothermal reaction kettle, calcining the solution at 180 ℃ for 20 hours, cooling the solution to room temperature, washing the solution with deionized water and ethanol in sequence, and drying the solution at 70 ℃ for 2 hours to obtain the loaded Sm ₂ O ₃ And CeO ₂ Graphene oxide of (a);

s2, preparation of 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 Sm-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 20 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 30min to obtain mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 at 400 ℃ for 2h 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 to react for 1 hour at 75 ℃, filtering, and washing with deionized water to obtain a reduction product;

s6, modification: adding 10 parts by weight of the reduction product prepared in the step S5 into 50wt% ethanol solution, performing ultrasonic dispersion for 20min, adding 1 part by weight of coupling agent, heating to 70 ℃, reacting 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 special pigment-loaded carbon black/silica composite, in which many 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: carrying out ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 for 2 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8, preparation of a component A: adding 9.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 20 parts by weight of polyacrylic resin and 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.B component preparation: 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 to be 40% to obtain a component B; the dehydrating agent is F-180 of Lyar company in Germany;

s10, preparing a low-reflectivity coating: mixing the component A, the component B and ethyl acetate according to a mass ratio of 4: 5363 and mixing at a ratio of 1:2, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm. Fig. 2 is a surface SEM image of the resulting reflectivity coating, which shows that the coating surface has more voids and random surface structures, which can further reduce the reflectivity of the coating.

Example 2

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): 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 the solution to a closed hydrothermal reaction kettle, calcining the solution at 200 ℃ for 30 hours, cooling the solution to room temperature, washing the solution with deionized water and ethanol in sequence, and drying the solution at 70 ℃ for 2 hours to obtain the loaded Sm ₂ O ₃ And CeO ₂ Graphene oxide of (a);

s2, preparation of 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 Sm-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 30 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 50min to obtain mixed silica sol;

s4, calcining: calcining the mixed silica sol obtained in the step S3 at 500 ℃ for 3h 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 to react for 3 hours at 95 ℃, filtering, and washing with deionized water to obtain a reduction product;

s6, modification: adding 10 parts by weight of the reduction product prepared in the step S5 into 70wt% ethanol solution, performing ultrasonic dispersion for 30min, adding 2 parts by weight of coupling agent, heating to 90 ℃, reacting 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: carrying out ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 for 4 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8, preparation of a component A: adding 22.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 xylene, 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, and stirring and mixing for 40 minutes to obtain a component A;

s9.B component preparation: 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 ambient humidity to be 60% to obtain a component B; the dehydrating agent is F-180 of Lyar company in Germany;

s10, preparing a low-reflectivity coating: the component A, the component B and methyl formate are mixed according to the mass ratio of 4: 5363 and mixing at a ratio of 1:4, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm.

Example 3

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): 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 the solution to a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25h, cooling to room temperature, washing with deionized water and ethanol in turn, and drying at 70 ℃ for 2h to obtain the loaded Sm ₂ O ₃ And CeO ₂ Graphene oxide of (a);

s2, preparation of silica sol: mixing 17 parts by weight of ethyl orthosilicate, 40 parts by weight of water, 2 parts by weight of ethanol and 6 parts by weight of concentrated hydrochloric acid, and reacting at 55 ℃ for 4 hours to obtain silica sol;

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-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain 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 to react for 2 hours at 85 ℃, filtering, and washing with deionized water to obtain a reduction product;

s6, modification: adding 10 parts by weight of the reduction product prepared 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 ℃, reacting for 40min, filtering, and drying at 70 ℃ for 2h to obtain the special pigment loaded carbon black/silicon dioxide composite material;

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

s7, ball milling: carrying out ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 for 3 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8, preparation of a component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, 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 30 minutes to obtain a component A;

s9.B component preparation: 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 ambient humidity to be 50% to obtain a component B; the dehydrating agent is F-180 of Lyar company in Germany;

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

Example 4

Compared with example 3, the coupling agent is a single A172, and other conditions are not changed.

Example 5

Compared with example 3, the coupling agent is single KH570, and other conditions are not changed.

Comparative example 1

Compared with the example 3, no samarium nitrate is added in the step S1, and other conditions are not changed.

The method specifically comprises the following steps:

s1, loading CeO ₂ The preparation of graphene oxide of (2): 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 the solution to 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 Graphene oxide of (a);

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 CeO-loaded powder prepared in the step S1 ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain mixed silica sol;

s6, modification: adding 10 parts by weight of the reduction product prepared 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 ℃, reacting for 40min, filtering, and drying at 70 ℃ for 2h to obtain the carbon black/silicon dioxide composite material loaded with the special pigment;

s7, ball milling: performing ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S6 for 3 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s10, preparing a low-reflectivity coating: the component A, the component B and n-propyl acetate are mixed according to the mass ratio of 4: 5363 and mixing at a ratio of 1:3, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm.

Comparative example 2

Compared with example 3, cerium nitrate was not added in step S1, and other conditions were not changed.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ The preparation of graphene oxide of (2): dissolving 10 parts by weight of graphene oxide in 50 parts by weight of water, adding 5.5 parts by weight of samarium nitrate, adjusting the pH value of the solution to 9.5, transferring the solution to a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in turn, and drying at 70 ℃ for 2 hours to obtain the loaded Sm ₂ O ₃ Graphene oxide of (a);

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-loaded aluminum powder prepared in step S1 ₂ O ₃ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain mixed silica sol;

s10, preparing a low-reflectivity coating: mixing the component A, the component B and n-propyl acetate according to a mass ratio of 4: 5363 and mixing at a ratio of 1:3, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm.

Comparative example 3

Compared with example 3, no graphene oxide was added in step S1, and 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, adjusting the pH value of the solution to 9.5, transferring the solution to a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25 hours, cooling to room temperature, washing with deionized water and ethanol in turn, and drying at 70 ℃ for 2 hours to obtain Sm ₂ O ₃ And CeO ₂ Mixing;

s2, preparation of silica sol: mixing 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, and reacting at 55 ℃ for 4 hours to obtain silica sol;

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 step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the mixture to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain 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 ℃, reacting 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: carrying out ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S5 for 3 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 micrometers;

s7, preparation of the component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S6, 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 xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, 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 30 minutes to obtain a component A;

s8.B component preparation: 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 ambient humidity to be 50% to obtain a component B; the dehydrating agent is F-180 of Lyar company in Germany;

s9, preparing a low-reflectivity coating: mixing the component A, the component B and n-propyl acetate according to a mass ratio of 4: 5363 and mixing at a ratio of 1:3, spraying with an air spray gun, and naturally drying to obtain a dry film with a 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 not changed.

The method specifically comprises the following steps:

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 Sm-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the 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 to react for 2 hours at 85 ℃, filtering, and washing with deionized water to obtain a reduction product;

s4, modification: adding 10 parts by weight of the reduction product prepared 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 ℃, reacting 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: performing ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S4 for 3 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s6, preparation of the component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S5, 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 xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, 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 30 minutes to obtain a component A;

s7.B component preparation: 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 F-180 of Lyar company in Germany;

s8, preparing a low-reflectivity coating: mixing the component A, the component B and n-propyl acetate according to a mass ratio of 4: 5363 and mixing at a ratio of 1:3, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm.

Comparative example 5

In step S3, no carbon black was added, compared to example 3, 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 Sm-loaded aluminum powder prepared in the step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain mixed silica sol;

Comparative example 6

Compared with example 3, no floating aluminum powder was added in step S3, and other conditions were not changed.

The method specifically comprises the following steps:

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

Comparative example 7

Compared with example 3, the reduction of step S5 was not performed, and other conditions were not changed.

The method specifically comprises the following steps:

s6, ball milling: performing ball milling treatment on the special pigment loaded carbon black/silica composite material obtained in the step S5 for 3 hours to obtain a ground special pigment loaded carbon black/silica composite material with the particle size of less than 5 microns;

s8.B component preparation: 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 F-180 of Lyar company in Germany;

Comparative example 8

The modification of step S6 was not carried out, and the other conditions were not changed as compared with example 3.

The method specifically comprises the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): 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 the solution to a closed hydrothermal reaction kettle, calcining at 190 ℃ for 25h, cooling to room temperature, washing with deionized water and ethanol in turn, and drying at 70 ℃ for 2h to obtain the loaded Sm ₂ O ₃ And CeO ₂ The graphene oxide of (3);

s6, ball milling: performing ball milling treatment on the reduction product obtained in the step S5 for 3 hours to obtain a ground special pigment loaded carbon black/silicon dioxide composite material with the particle size of less than 5 microns;

s9.B component preparation: 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 F-180 of Lyar company in Germany;

s9, preparing a low-reflectivity coating: the component A, the component B and n-propyl acetate are mixed according to the mass ratio of 4: 5363 and mixing at a ratio of 1:3, spraying with an air spray gun, and naturally drying to obtain a dry film with a thickness of 30-40 μm.

Comparative example 9

In step S8, the carbon black/silica composite supporting the special pigment was not added, and the other conditions were not changed, as compared with example 3.

The method specifically comprises the following steps:

s1.A component preparation: 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 xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, heating to 60 ℃ for reaction for 1 hour, 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;

s2.B component preparation: 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 ambient humidity to be 50% to obtain a component B; the dehydrating agent is F-180 of Lyar company in Germany;

s3, preparing the low-reflectivity coating: mixing the component A, the component B and n-propyl acetate according to a mass ratio of 4:1:3, spraying with an air spray gun, and naturally drying to a dry film thickness of 30-40 μm to obtain a low-reflectivity coating.

Comparative example 10

Compared with the example 3, the polyether modified polydimethylsiloxane is not added in the step S8, and other conditions are not changed.

The method specifically comprises the following steps:

s8, preparation of a component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 xylene, 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, and stirring and mixing for 30 minutes to obtain a component A;

Comparative example 11

In step S8, no polyamide wax was added as compared with example 3, and the other conditions were not 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 Sm-loaded aluminum powder prepared in step S1 ₂ O ₃ And CeO ₂ Mixing and grinding the graphene oxide to obtain a mixture, adding the mixture into 25 parts by weight of the silica sol obtained in the step S2, and stirring and dispersing for 40min to obtain mixed silica sol;

s8, preparation of a component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 xylene, 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

Compared with example 3, polyether modified polydimethylsiloxane and polyamide wax were not added in step S8, and other conditions were not changed.

The method specifically comprises the following steps:

s2, preparing silica sol: mixing 17 parts by weight of ethyl orthosilicate, 40 parts by weight of water, 2 parts by weight of ethanol and 6 parts by weight of concentrated hydrochloric acid, and reacting at 55 ℃ for 4 hours to obtain silica sol;

s8, preparation of a component A: adding 15.5 parts by weight of the ground special pigment-loaded carbon black/silica composite material obtained in the step S7, 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 xylene, adding 1.2 parts by weight of di-tert-butyl peroxide, and heating to 60 ℃ for reaction for 1 hour to obtain a component A;

Test example 1 measurement of reflectance

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

And testing the visible light and near infrared light transmittance, visible light and near infrared light reflectance of the coating by using a Meinenda cm-512m3a 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 visible light, ultraviolet light and near infrared light.

Test example 2

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

The hardness of the coating is evaluated according to the method of GB/T6739-2006, pencils with gradually increasing hardness are drawn on the surface of the coating at an angle of 45 degrees, the integrity of the surface of the coating is observed until the surface of the coating is indented, scratched and scratched, the hardness of the last pencil of the corresponding pencil is the hardness of the tested coating, and the hardness of the pencils used in the standard can be divided into the following 20 grades: 9B-1B-HB-F-1H-9H.

The adhesion of the coating is evaluated by adopting a QFZII adhesion circling tester according to the method of GB1720-2020, and the coating adhesion is graded according to the completeness of the coating within the scratch range of a round rolling line, wherein the standard divides the coating adhesion into 1-7 grades, the optimal grade 1 and the worst grade 7.

The impact strength of the coating is evaluated by adopting a GCJ impact strength tester according to the method of GB/T1732-2020, a weight of 1kg is dropped from different heights (the maximum is 50 cm) and is hammered on the coating, the strongest impact strength of the coating is determined by judging whether the coating is intact, and finally, the product of the drop weight height and the weight mass is used for representing the impact strength (kg cm) of the coating.

The results are shown in Table 2.

TABLE 2

As can be seen from the above table, the low-reflectivity coatings prepared in the embodiments 1-3 of the present invention have strong hardness (H), high adhesion level (level 1), high impact strength (56-60 kg. Cm), and good mechanical properties and adhesion.

Test example 3

The low-reflectivity coatings prepared in examples 1-5 and comparative examples 1-12 of the invention were subjected to wave-absorbing property tests.

And measuring the electromagnetic parameters of the composite material by using a vector network analyzer (N5224A), wherein the frequency range is 2-18GHz. According to the transmission line theory, the paint sample-paraffin is pressed into a coaxial ring with the outer diameter of 7mm and the inner diameter of 3mm, the filling ratio of the sample to the paraffin is 1.05, the electromagnetic parameters of the composite material are calculated according to the following formula of Reflection Loss (RL). And (3) researching the wave-absorbing performance of the material through data analysis.

RL＝20log|(Z _in -Z ₀ )/(Z _in +Z ₀ )|

Wherein Z is _in Is the input impedance, Z ₀ Is free space impedance, mu _r = mu '-j mu' is complex permeability, epsilon _r = epsilon' -j epsilon "is the complex dielectric constant, f is the 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, over 90% of incident electromagnetic waves are correspondingly dissipated by the material; when the reflection loss DL is less than-20 dB, more than 99% of the incident electromagnetic wave is correspondingly dissipated by the material. The frequency band range when DL is less than 10dB is called the effective wave-absorbing bandwidth of the material.

The results are shown in Table 3.

TABLE 3

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

In examples 4 and 5, compared with example 3, the coupling agent is A171 or A151 alone, and the impact strength and adhesion of the coating are reduced. Comparative example 8 compared with example 3, without the modification of step S6, the hardness, impact resistance and adhesion of the coating were decreased. The coupling agent A172 is vinyl tri (beta-methoxyethoxy) silane; KH570 is gamma- (methacryloyloxy) propyl trimethoxy silane, both of which have longer alkyl chains, and can be intertwined with polypropylene resin, so that the compatibility of the carbon black/silicon dioxide composite material loaded with special pigments and the resin is enhanced, the mechanical property and the adhesive force of the coating are improved, and the two have synergistic effect. The reflectivity of the whole coating is mainly related to pigment particles, and the resin material in the coating mainly determines the mechanical properties of the coating, such as adhesion, tensile strength and the like. According to the invention, the reduction product is prepared, and is further modified by a silane coupling agent with double bonds, so that the surface of the reduction product is provided with double bond groups, and the reduction product is connected to a polypropylene resin molecular chain after undergoing a copolymerization reaction with polypropylene resin, so that the carbon black/silicon dioxide composite material loaded with the special pigment can be uniformly distributed in the resin material, and thus, the coagulation of inorganic components is effectively avoided, the coating can be more uniform, the effect of uniform emission is achieved, and the phenomenon of over-high or over-low local reflection is effectively avoided.

In comparison with example 3, in comparative examples 1 and 2, no samarium nitrate or cerium nitrate was added in step S1. Comparative example 3 compared to example 3, no graphene oxide was added in step S1. The prepared coating has high reflectivity to ultraviolet light, visible light and near infrared light, and the wave absorbing performance is weakened. The rare earth oxide has excellent optical, electrical and magnetic properties, wherein Sm is ₂ O ₃ Middle Sm ³⁺ Has strong absorption characteristic to 1.06 mu m special near infrared light, ceO ₂ The oxygen vacancy effect of (a) contributes to the loss of light waves and electromagnetic waves. Sm ₂ O ₃ And CeO ₂ To (2)Is prepared and is fixedly carried on the graphene oxide, and the wave-absorbing efficiency, the effective absorption bandwidth and the reflection effect on the optical wave of the composite material are obviously greater than those of the single graphene oxide and Sm ₂ O ₃ And CeO ₂ In general, graphene oxide has a low complex dielectric constant due to Sm ₂ O ₃ And CeO ₂ And the multiple interface polarization effect between the graphene and the graphene is also beneficial to the loss of electromagnetic waves and light waves.

Compared with the example 3, the comparative example 4 has the advantages that the silica sol is not prepared and used, the hardness, the impact resistance and the adhesive force of the coating are obviously reduced, the reflectivity of ultraviolet light, visible light and near infrared light is increased, and the wave absorbing performance is weakened. Carrying out sol-gel reaction, carrying out hydrolytic polymerization to obtain silica sol, and carrying carbon black, aluminum powder and Sm ₂ O ₃ And CeO ₂ Adding the graphene oxide into silica sol, dispersing uniformly, and calcining to obtain the silica-loaded carbon black, aluminum powder and Sm-loaded Sm ₂ O ₃ And CeO ₂ The graphene oxide material not only provides a foundation for subsequent modification through a silane coupling agent (the silicon dioxide carrier and the silane coupling agent have better binding capacity), but also the prepared silicon dioxide carrier further improves the mechanical property of the coating, and the silicon oxide structure of the surface of the coating causes more cavities and random surface structures to be generated on the surface of the coating due to the addition of the carbon black/silicon dioxide composite material loaded with the special pigment, and the cavities or the random surface structures can further reduce the reflectivity of the coating.

Compared with the embodiment 3, the comparative examples 5 and 6 have the advantages that no carbon black or floating aluminum powder is added in the step S3, 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 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. The floating aluminum powder has higher conductivity, is cheaper than metals such as Au, ag, cu and the like, and can be used as a functional pigment of a coating with low infrared emission/reflectivity.

Compared with the embodiment 3, the comparison example 7 has the advantages that the reduction in the step S5 is not carried out, 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 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 a graphene sheet layer, so that the complex dielectric constant of the graphene oxide is improved, and the impedance matching capacity is enhanced. The defects and functional groups on the reduced graphene oxide can also convert energy from a continuous state into a Fermi level, and polarization relaxation and electron dipole relaxation are introduced, so that the attenuation capacity of the material to electromagnetic waves is enhanced, the reflection loss of the reduced graphene oxide is greatly improved, and the reflection capacity, the electromagnetic shielding capacity and the wave absorbing capacity of the material are improved.

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

In comparative examples 10 and 11, compared with example 3, the hardness and impact resistance of the coating obtained without adding the polyether-modified dimethylsiloxane or polyamide wax in step S8 were reduced. Comparative example 12 compared to example 3, in step S8, without the polyether modified dimethylsiloxane and the polyamide wax, the hardness, impact resistance and adhesion of the resulting coating were significantly reduced. The polyether modified dimethyl siloxane has a large number of inorganic silicon-oxygen bonds and active polyether functional groups, the inorganic silicon-oxygen bonds can enable the polyether modified dimethyl siloxane 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 the components from settling and improve the dispersibility of the components. The synergistic addition of the polyether modified dimethyl siloxane and the polyamide wax improves the hardness of the coating to a certain extent.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The low-reflectivity coating is characterized by comprising 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.

2. A method of preparing the low reflectance coating of claim 1, comprising the steps of:

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): dissolving graphene oxide in water, adding samarium nitrate and cerium nitrate, adjusting the pH value of the solution to 9-10, transferring the solution to a hydrothermal reaction kettle, calcining, cooling to room temperature, washing and drying to obtain the Sm-loaded carrier ₂ O ₃ And CeO ₂ Graphene oxide of (a);

s7, ball milling: carrying out ball milling treatment on the special pigment loaded carbon black/silicon dioxide composite material obtained in the step S6 to obtain a ground special pigment loaded carbon black/silicon dioxide composite material with the particle size of less than 5 micrometers;

s8, preparation of a component A: adding the carbon black/silicon dioxide composite material loaded with the special pigment, polyacrylic resin and acrylic acid block copolymer which are ground and 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;

3. The preparation method according to claim 2, wherein the mass ratio of the graphene oxide to the samarium nitrate to the cerium nitrate in step S1 is 10:3-5:1-2; the calcination temperature is 180-200 ℃, and the calcination time is 20-30h.

4. The preparation method according to claim 2, wherein the mass ratio of the alkyl orthosilicate, the water, the ethanol and the concentrated hydrochloric acid in the step S2 is 15-20; the reaction temperature is 50-60 ℃ and the reaction time is 3-5h.

5. The method according to claim 2, wherein the carbon black, al powder, sm-supported carbon black, or Sm-supported carbon black is used 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 parts of; the aluminum powder is floating aluminum powder; in the step S4, the calcining temperature is 400-500 ℃ and the time isIs 2-3h.

6. The method according to claim 2, wherein the mass ratio of the calcined product, the ammonia water and the hydrazine hydrate in step S5 is 10 to 15:3-7:1-3; the concentration of the ammonia water is 25-30wt%; the heating reaction is carried out at the temperature of 75-95 ℃ for 1-3h; in the step S6, the ethanol content in the ethanol solution is 50-70wt%; the mass ratio of the reduction product to the coupling agent is 10-2; 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 heating reaction temperature is 70-90 deg.C, and the time is 30-50min.

7. The preparation method according to claim 6, wherein the coupling agent is a compounded mixture of A172 and KH570, and the mass ratio is 3-5:2.

8. The preparation method according to claim 2, wherein the ball milling time in step S7 is 2-4h; in the step S8, the initiator 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 heating time is 0.5-2h; in the step S10, the diluting solvent is at least one of ethyl acetate, methyl formate, and n-propyl acetate.

9. The preparation method according to claim 1, comprising the following steps:

s1, loading Sm ₂ O ₃ And CeO ₂ The preparation of graphene oxide of (2): 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, adjusting the pH value of the solution to 9-10, transferring the solution to a closed hydrothermal reaction kettle, calcining the solution at 180-200 ℃ for 20-30h, cooling the solution to room temperature, and sequentially washing the solution with deionized water and ethanolWashing and drying to obtain the Sm supported material ₂ O ₃ And CeO ₂ Graphene oxide of (a);

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% of ammonia water and 1-3 parts by weight of hydrazine hydrate, heating to react at 75-95 ℃ for 1-3h, filtering, and washing to obtain a reduction product;

s8, preparation of a component A: adding 9.5-22.5 parts by weight of the ground special pigment-loaded carbon black/silicon dioxide composite material obtained in the step S7, 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 an ester solvent and 20-30 parts by weight of a benzene solvent, adding 0.6-1.5 parts by weight of an initiator, heating to 50-70 ℃ for reaction for 0.5-2h, then adding 0.1-0.3 part by weight of polyether modified polydimethylsiloxane and 1-2 parts by weight of polyamide wax, and stirring and mixing for 20-40min to obtain a component A;

s10, preparing a low-reflectivity coating: mixing the component A, the component B and a diluting solvent according to a mass ratio of 4:1:2-4, spraying with an air spray gun, drying to a dry film thickness of 30-40 μm, and obtaining the low-reflectivity coating.

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