A coating containing a heat-insulating pigment and a preparation method thereof

Abstract

The present invention relates to a coating containing a heat-insulating functional pigment and a preparation method thereof, belonging to the technical field of coatings. The raw materials for preparing the coating include the following raw material components in parts by weight: 40-60 parts of an aqueous resin dispersion, 15-20 parts of a heat-insulating functional pigment, 0.1-0.2 parts of a defoamer, 0.01-0.5 parts of a dispersant, 0.1-0.5 parts of a leveling agent, and 0.5-1 parts of a film-forming aid; the heat-insulating functional pigment is obtained by coating the pigment with a coating treatment and then coating it with a silica sol-gel method and then reacting it with an organic ligand catalysis reaction. The heat-insulating functional pigment proposed by the present invention integrates coloring and heat insulation. Compared with the use of heat-insulating fillers and pigments separately, it avoids affecting the leveling property of the coating and forming a coating film with a uniform texture, while also reducing the covering of the pigment color by the filler. During the treatment process, the pigment particles are all in a protected state, and the color of the pigment particles can be fully retained; the heat-insulating effect is significant compared with the heat-insulating fillers such as SiO2 aerogel, hollow glass microspheres and hollow ceramic microspheres.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a coating containing a heat-insulating functional pigment and a preparation method thereof. Background Art

[0002] Among the coating components, functional pigments are pigments with specific functions such as anti-fouling, temperature indication, luminescence, and rust prevention, which are different from ordinary pigments that are mainly used for coloring. They play an important role in coatings. ‌ Heat-insulating functional pigments‌ are materials that can reflect or absorb solar radiation heat, thereby reducing the surface temperature of objects. Common heat-insulating functional pigments mainly include reflective and barrier types. Reflective pigments mainly include infrared reflective pigments, and barrier pigments mainly include a mixture of heat-insulating fillers such as SiO2 aerogel, hollow glass microspheres, and hollow ceramic microspheres with pigments. For example, CN116851235B discloses a reflective heat-insulating colorful coating.

[0003] In actual use and research, it has been found that while SiO2 aerogel provides excellent thermal insulation for coatings, it also affects the coating's adhesion and hardness, making it prone to cracking and powdering over time and requiring recoating to maintain its insulation. Excessive use of hollow glass microspheres and hollow ceramic microspheres as barrier fillers prevents the coating from fully encapsulating these fillers, weakening film formation, surface gloss, and light reflectivity, ultimately reducing the insulation effect. After high-temperature treatment, the interaction between the molecules of infrared reflective pigments is strong, making them prone to agglomeration and difficult to disperse, and their compatibility with the coating matrix is ​​poor. Currently, a film is generally formed on the surface of the pigment particles to form a core-shell structure to improve the dispersibility of the material. For example, CN103725074B discloses a high-temperature resistant thermal insulation coating. However, the pigment with a core-shell structure will cause damage to the pigment itself during the process of core-shell formation. Other studies have reported that the core-shell structure of the pigment may degrade due to factors such as humidity, temperature, and light. In addition, the thermal insulation performance of the infrared reflective pigment after being added to the coating depends on the cleanliness of the coating surface, which limits the scope of use of the coating. Summary of the Invention

[0004] The purpose of the present invention is to provide a coating containing a heat-insulating functional pigment and a preparation method thereof in order to solve the above problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] The present invention provides a coating containing a heat-insulating pigment. The raw materials for preparing the coating include the following raw material components, calculated by weight: 40-60 parts of an aqueous resin dispersion, 15-20 parts of a heat-insulating pigment, 0.1-0.2 parts of a defoamer, 0.01-0.5 parts of a dispersant, 0.1-0.5 parts of a leveling agent, and 0.5-1 parts of a film-forming aid.

[0007] The heat-insulating functional pigment is obtained by coating the pigment with silica sol-gel method and then reacting with organic ligand for catalysis.

[0008] Furthermore, the solid content of the aqueous resin dispersion is 30-50 wt %; the aqueous resin dispersion is one or a combination of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane, and aqueous acrylic-silicone resin.

[0009] Furthermore, the preparation method of the heat-insulating functional pigment comprises the following steps:

[0010] (1) The dried pigment is uniformly dispersed in ethanol, polyacrylamide is then added dropwise to the ethanol, stirred and mixed under heating, and the coated pigment is obtained after solid-liquid separation;

[0011] (2) Tetraethoxysilane is mixed with an ethanol solution, the pH is adjusted to a strong acid, and the mixture is reacted under heating. After the reaction is completed, the pH is adjusted to a weak base, the mixture is rapidly stirred and allowed to stand, and the coated pigment is uniformly dispersed in the standing solution. After heating and stirring, the mixture is centrifuged and washed, and vacuum dried to obtain a silica-coated pigment;

[0012] (3) The silica-coated pigment, organic ligand, and polyvinyl alcohol are mixed and dissolved in an organic solvent, a catalyst is added and heated to react, and the reaction product is washed and dried to obtain the heat-insulating functional pigment.

[0013] Furthermore, in step (1):

[0014] The mass concentration of the ethanol is 95wt%;

[0015] The mass ratio of the polyacrylamide to the pigment is 1:10;

[0016] The stirring and mixing under the heating state specifically comprises stirring at a temperature of 60-70° C. for 0.5-1 h.

[0017] Furthermore, in step (2), the mass concentration of the ethanol solution is 75 wt%.

[0018] Furthermore, step (2) specifically includes the following steps:

[0019] Mix tetraethoxysilane and ethanol solution in a mass ratio of 1:(10-12), add concentrated hydrochloric acid dropwise to adjust the pH to 2-3, react at 50-60℃ for 5-6h, and after the reaction, add sodium hydroxide solution dropwise to adjust the pH to 7-8, stir rapidly, and let stand for 30-40min;

[0020] The coated pigment is uniformly dispersed in the static solution at a mass ratio of 1:4, heated to 50-60° C. and stirred for 1-2 hours, then centrifuged and washed, and vacuum dried at 20-25° C. for 24 hours to 48 hours to obtain a silica-coated pigment.

[0021] Furthermore, step (3) specifically includes the following steps:

[0022] The silica-coated pigment, organic ligand, and polyvinyl alcohol are mixed and dissolved in a sufficient amount of organic solvent in a mass ratio of 100:(4-6.4):(0.8-2.4), and acetic acid is added as a catalyst to heat the mixture at 120°C for 12-24 hours. The reaction product is washed three times with tetrahydrofuran, acetone, and ethanol, and then dried in a vacuum drying oven at 60°C for 24 hours to obtain the thermal insulation functional pigment.

[0023] Furthermore, the organic ligand is one of trimesaldehyde, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, and terephthalic acid.

[0024] Furthermore, in step (3), the organic solvent is one of tetrahydrofuran, acetone, and ethanol.

[0025] The present invention also provides a method for preparing the above-mentioned coating containing the heat-insulating functional pigment, comprising: placing the aqueous resin dispersion into a dispersion kettle and dispersing the dispersion at a speed of 1000-1200 rpm for 5-20 minutes; then placing the heat-insulating functional pigment into the dispersion kettle and mixing it evenly with the aqueous resin dispersion to obtain a mixed slurry; then adding a defoamer, a dispersant, and a leveling agent to the mixed slurry; and ball milling the mixed slurry at a speed of 500-1000 rpm for 1-5 hours to obtain the coating.

[0026] The beneficial effects of the present invention are:

[0027] The heat-insulating functional pigment proposed in the present invention integrates coloring and heat insulation. Compared with the use of heat-insulating fillers and pigments separately, it avoids affecting the leveling of the coating and forming a coating film with uniform texture, and at the same time can reduce the covering of the filler on the pigment color.

[0028] During the treatment process, the pigment particles of the present invention are in a protected state, which can fully retain the color of the pigment particles and meet the use of coatings of different systems; the thermal insulation effect is significant compared with thermal insulation fillers such as SiO2 aerogel, hollow glass microspheres and hollow ceramic microspheres, and at the same time has good adhesion and excellent hardness.

[0029] The heat-insulating functional pigment proposed in the present invention has good dispersibility and is not easy to agglomerate in the coating. The interaction force between the heat-insulating functional pigment and the coating matrix is ​​strong. Compared with SiO2 aerogel, it is not easy to powder and crack. Compared with hollow glass microspheres and hollow ceramic microspheres, it has stronger encapsulation with water-based resin dispersion. DETAILED DESCRIPTION

[0030] The present application is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0031] 1. Materials

[0032] Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art, and the reagents and other materials used are commercially available products unless otherwise specified.

[0033] The method for preparing the heat-insulating functional pigment in the raw materials for preparing the coating of the present invention comprises the following steps:

[0034] (1) The dried pigment is evenly dispersed in ethanol with a mass concentration of 95wt%, and then a polyacrylamide solution (v / v with water = 1:1) with a mass of 1 / 10 of the pigment is added dropwise to the ethanol, heated and stirred at 60-70℃ for 0.5-1h, and then solid-liquid separation is performed to obtain a solid coated pigment, which is then dried at 40℃ for later use;

[0035] (2) Tetraethoxysilane and ethanol solution were mixed in a mass ratio of 1: (10-12), concentrated hydrochloric acid was added dropwise to adjust the pH to 2-3, and the mixture was reacted at 50-60°C for 5-6 hours. After the reaction, sodium hydroxide solution was added dropwise to adjust the pH to 7-8, and the mixture was stirred rapidly and allowed to stand for 30-40 minutes. The coated pigment was evenly dispersed in the solution in a mass ratio of 1:4 after standing, heated to 50-60°C, stirred for 1-2 hours, and then centrifuged for washing. The silica-coated pigment was then vacuum-dried at 20-25°C for 24 hours to 48 hours to obtain the silica-coated pigment.

[0036] (3) The silica-coated pigment, organic ligand, and polyvinyl alcohol are mixed and dissolved in a sufficient amount of organic solvent in a mass ratio of 100: (4-6.4): (0.8-2.4), and acetic acid is added as a catalyst to heat the reaction at 120°C for 12-24 hours. The reaction product is washed three times with tetrahydrofuran, acetone, and ethanol, and then placed in a vacuum drying oven at 60°C for 24 hours to obtain a heat-insulating functional pigment.

[0037] 2. Methods

[0038] 2.1 Preparation

[0039] Titanium nickel yellow 1053A was used as the pigment for this study. A commercially available waterborne acrylic resin with a solids content of 30-50 wt% was used as the waterborne resin dispersion. The dispersant was BYK-164, the defoamer was EFKA-2526, the leveling agent was BYK-358N, and the film-forming aid was Texanol.

[0040] 2.1.1 Preparation of coated titanium nickel yellow

[0041] The dried titanium nickel yellow was evenly dispersed in ethanol with a mass concentration of 95wt% to obtain a color slurry. Then, a polyacrylamide solution with a mass ratio of 1 / 10 of the titanium nickel yellow (v / v with water = 1:1) was prepared and added dropwise to the ethanol. The mixture was then heated and stirred at 62°C for 1h, and then the solid-liquid separation was performed by suction filtration to obtain a solid coated titanium nickel yellow, which was then dried at 40°C for later use.

[0042] 2.1.2 Preparation of silica-coated titanium nickel yellow by sol-gel method

[0043] Tetraethoxysilane and 75wt% ethanol were mixed in a mass ratio of 1:10, concentrated hydrochloric acid was added dropwise to adjust the pH to 3, and the mixture was reacted at 50-60°C for 5 hours. After the reaction, sodium hydroxide solution was added dropwise to adjust the pH to 8, and the mixture was rapidly stirred and allowed to stand for 40 minutes. The coated titanium nickel yellow was evenly dispersed in the solution in a mass ratio of 1:4 after standing, heated to 60°C, stirred for 2 hours, and then centrifuged and washed. The silica-coated titanium nickel yellow was obtained after vacuum drying at 25°C for 48 hours.

[0044] 2.1.3 Preparation of thermal insulation pigments

[0045] Silica-coated titanium nickel yellow, trimesaldehyde, and polyvinyl alcohol are put into a reactor in a mass ratio of 100:6.4:2.0 and mixed. A sufficient amount of ethanol is added, and then 5% of the total system mass of catalyst acetic acid is added. The reactor temperature is raised to 120°C and heated to react for 24 hours. The reaction product is washed three times with tetrahydrofuran, acetone, and ethanol, and then placed in a vacuum drying oven at 60°C and dried for 24 hours to obtain a heat-insulating functional pigment.

[0046] 2.1.4 Coating preparation

[0047] By weight, 60 parts of aqueous acrylic resin dispersion were put into a dispersion kettle and dispersed at a speed of 1000 rpm for 10 minutes. Then 20 parts of heat-insulating functional pigment were put into the dispersion kettle and mixed evenly with the aqueous acrylic resin dispersion to obtain a mixed slurry. Then 0.1 parts of defoaming agent, 0.02 parts of dispersant, 0.2 parts of leveling agent and 0.5 parts of film-forming aid were added to the mixed slurry. The mixed slurry was ball-milled at a speed of 500 rpm for 2.5 hours to obtain a coating.

[0048] 2.2 Coating performance test and conclusion

[0049] 2.2.1 Experimental group preparation

[0050] The coating prepared in 2.1.4 was used as Group 1. 80 parts of aqueous acrylic resin dispersion, 0.1 parts of defoamer, 0.02 parts of dispersant, 0.5 parts of leveling agent, and 0.5 parts of film-forming aid were ball-milled at 500 rpm for 2.5 h to obtain a coating as Group 2.

[0051] 10 parts of titanium nickel yellow, 10 parts of SiO2 aerogel and 60 parts of dispersed aqueous acrylic resin dispersion were put into a dispersion kettle and mixed evenly to obtain a mixed slurry. Then 0.1 parts of defoaming agent, 0.02 parts of dispersant, 1 part of leveling agent and 0.8 parts of film-forming aid were added to the mixed slurry. The mixed slurry was ball milled at a speed of 500 rpm for 2.5 hours to obtain a coating, which was referred to as Group 3.

[0052] 10 parts of titanium nickel yellow, 5 parts of hollow glass microspheres, 5 parts of hollow ceramic microspheres and 60 parts of dispersed aqueous acrylic resin dispersion were put into a dispersion kettle and mixed evenly to obtain a mixed slurry. Then, 0.1 parts of defoaming agent, 0.02 parts of dispersant, 2 parts of leveling agent and 1 part of film-forming aid were added to the mixed slurry. The mixed slurry was ball milled at a speed of 500 rpm for 2.5 hours to obtain a coating as Group 4.

[0053] 2.2.2 Testing

[0054] Thermal Conductivity: The four coatings were mixed and sprayed onto a substrate with release paper. After spraying, the substrate was cured until a uniform, stable coating with a thickness of at least 0.8 mm was formed. The release paper was removed to obtain test specimens. Five specimens were obtained from each coating. Thermal conductivity of these specimens was measured using a heat flow meter to determine the thermal conductivity λ1. These specimens were then subjected to 50 cycles of immersion and high-temperature light aging. The thermal conductivity λ2 was then determined by the rate of change (λ2-λ1) / λ1×100%, which served as the basis for the coating's weatherability. (Thermal conductivity is an inherent property of a material, primarily dependent on its composition and structure. Changes in the internal structure of the material will result in changes in thermal conductivity.) Immersion: 1000W ultrasonic treatment for 30 minutes in deionized water at 20±2°C. High-temperature light aging: Immediately after immersion, the specimens were exposed to 3 UV lamps at 240°C for 30 minutes at 0.02kW.

[0055] Thermal insulation temperature difference: carried out in accordance with the standard JC / T1040-2020 "Heat-reflective insulation coatings for building exterior surfaces".

[0056] Adhesion: According to the standard GB / T 9286 "Cross-cut test for paint and varnish films".

[0057] Hardness: According to the standard GB / T 6739 "Paints and varnishes - Determination of film hardness by pencil method".

[0058] Color difference and appearance: The above four groups of coatings were applied to the aluminum substrate and baked at about 60-80℃ for about 20-40 minutes to form a film with a thickness of not less than 0.8mm. The sample film was aged in a xenon lamp aging test chamber with the following parameters: xenon lamp aging for 2400h (3168KJ / m 2 ), based on the L*a*b system specified in the JIS Z 8729-2004 color specification, the absolute difference between the color of the sample film after irradiation and the initial color is used as the result of the color difference test, and the appearance of the sample film is observed to see if it is powdering, cracking or peeling.

[0059] The results of the above performance tests are shown in Table 1:

[0060] Table 1 Test results of coating properties of groups 1-4

[0061] The above test results show that the thermal insulation effect of the coatings with added SiO2 aerogel, hollow glass microspheres and hollow ceramic microspheres is better than that of the blank group 2, and the hardness is improved to a certain extent, but the addition of fillers has a slight effect on adhesion. After the coatings of groups 3-4 were subjected to high humidity and high temperature aging treatment, it can be seen that their thermal insulation effect cannot be effectively maintained. In particular, the coatings with added SiO2 aerogel expanded after high humidity and high temperature light aging, resulting in dense pits on the surface of the coating, and its thermal conductivity could not be measured. Although the coatings with added hollow glass microspheres and hollow ceramic microspheres can also maintain good thermal insulation effects, the researchers speculate that this is due to the thermal insulation properties of the fillers themselves. The poor encapsulation with the aqueous acrylic resin dispersion leads to a significant change rate in the thermal insulation effect, and both have defects in adhesion, hardness, color difference and appearance.

[0062] From the results of thermal conductivity and temperature difference, it can be seen that the thermal insulation effect of Group 1 coating is more significant than that of thermal insulation fillers such as SiO2 aerogel, hollow glass microspheres and hollow ceramic microspheres, and Group 1 coating also has good adhesion and excellent hardness.

[0063] The heat-insulating functional pigment of the present invention integrates coloring and heat insulation. Compared with the use of heat-insulating fillers and pigments separately, it avoids affecting the leveling of the coating and forms a coating film with uniform texture, and at the same time can reduce the covering of the pigment color by the filler.

[0064] 2.3 Study the effects of different aqueous dispersions on coating properties

[0065] Based on 2.1, the effects of waterborne epoxy resin, waterborne polyurethane and waterborne acrylic-silicone resin on coating performance were studied.

[0066] The waterborne epoxy resin, waterborne polyurethane and waterborne acrylic-silicone resin in this test are all commercially available, with a solid content of 30-50 wt%.

[0067] According to the preparation process of 2.1.4, replace the aqueous acrylic resin dispersion with 60 parts of aqueous epoxy resin dispersion (Group 5), aqueous polyurethane dispersion (Group 6), and aqueous acrylic-silicone resin dispersion (Group 7), respectively, to obtain coatings.

[0068] The above coatings were tested using method 2.2.2. The results of the performance test are shown in Table 2:

[0069] Table 2 Test results of coating properties of groups 5-7

[0070] It can be seen from the above test results that the thermal conductivity of Group 6 coating is lower and the thermal insulation effect is better. This is because the thermal conductivity of water-based polyurethane itself is lower than that of other dispersions. The thermal insulation functional pigment of the present invention can be applied to water-based resin dispersions of different systems, all of which have good thermal insulation effects, small color difference, good weather resistance, and adhesion and hardness maintained at a certain level.

[0071] 2.4 Study the influence of the preparation method of thermal insulation functional pigments on coatings

[0072] 2.4.1 Impact of the packaging and assembly process

[0073] According to the preparation process in 2.1.4, replace the heat-insulating functional pigments with the following raw materials:

[0074] Titanium nickel yellow was used to replace the heat-insulating pigment to prepare a coating, which is group 8;

[0075] The coated titanium nickel yellow prepared in 2.1.1 was used to replace the heat-insulating pigment to prepare a coating, which is Group 9;

[0076] The thermal insulation pigment was replaced with the silica-coated titanium nickel yellow prepared in 2.1.2 to prepare a coating, which is Group 10;

[0077] In the preparation process of 2.1.2, the uncoated titanium nickel yellow was coated by the sol-gel method, and the obtained coated pigment was used to replace the heat-insulating functional pigment to prepare a coating, which is Group 11;

[0078] The above coatings were tested using method 2.2.2. The results of the performance test are shown in Table 3:

[0079] Table 3 Test results of coating performance of groups 8-11

[0080] The above test results show that the present invention first uses polyacrylamide to protect the pigment, so that the pigment particles are in a protected state during the treatment process, which can fully preserve the pigment particles' vividness. Then, tetraethoxysilane is selected as the silicon source, and the silica-coated pigment is prepared by a sol-gel method. This can improve the density of the coating or paint film, increase the adhesion and hardness of the coating, and suppress the coating's foaming and permeability. It also enhances the pigment's thermal insulation function. The silica gel coating can also hinder direct contact between the pigment and the surrounding medium and external environment, and can also slow its oxidative degradation by surrounding organic matter. Finally, organic ligands and polyvinyl alcohol are used to form a composite material similar to an organic framework-silica-coated pigment with the silica-coated pigment. On the one hand, it can increase the refractive index and enhance the thermal insulation effect. On the other hand, the organic framework and the silica gel may form chemical bonds or physical crosslinks, which can also support the silica gel, thereby enhancing the mechanical properties of the coating.

[0081] 2.4.2 Effects of inorganic and organic pigments

[0082] In this experiment, titanium chrome brown HM-2401, cobalt blue HM-2801, and cobalt green HM-5002 were selected as inorganic pigments, and benzidine yellow COLORSTEP®O Yellow X1081 and carbazole violet COLORSTEP®O VIOLET B4023 were selected as organic pigments.

[0083] According to the preparation process of 2.1.1-2.1.3, the above-mentioned inorganic pigments and organic pigments are used to replace titanium nickel yellow. The difference is that the organic pigment does not need to be dispersed in 95wt% ethanol. A polyacrylamide solution with a mass ratio of 1 / 10 of the pigment is prepared (v / v with water = 1:1) and added dropwise to the slurry of the organic pigment. After three centrifugal washing processes, the organic pigment particles are obtained and replaced with the coated titanium nickel yellow in the process of 2.1.2.

[0084] According to the above process, six groups of heat-insulating functional pigments were obtained respectively. Then, according to the preparation process of 2.1.4, the heat-insulating functional pigments were replaced to obtain coating group 12 (titanium chrome brown HM-2401), group 13 (cobalt blue HM-2801), group 14 (cobalt green HM-5002), group 15 (benzidine yellow), and group 16 (carbazole violet).

[0085] The above coatings were tested using method 2.2.2. The results of the performance test are shown in Table 4:

[0086] Table 4 Test results of coating properties of groups 12-16

[0087] The above test results indicate that the preparation method of the present invention is highly applicable to inorganic pigments. After treatment, inorganic pigments of different colors exhibit similar performance across the board. However, the color difference of organic pigments decreases significantly. This is presumably because the polyacrylamide and the organic pigments undergo a flocculation process, not an encapsulation process. This subsequently affects the organic pigments through the solvent, resulting in poor color stability and reduced hardness.

[0088] 2.4.3 Effect of organic ligands

[0089] In this experiment, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, and terephthalic acid were selected as organic ligands.

[0090] According to the preparation process of 2.1.3, the above organic ligand is used to replace the trimesaldehyde in 2.1.3 to obtain a heat-insulating functional pigment.

[0091] According to the above process, five groups of heat-insulating functional pigments were obtained respectively. Then, according to the preparation process of 2.1.4, the heat-insulating functional pigments were replaced to obtain coating group 17 (2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde), group 18 (terephthalaldehyde), group 19 (2,5-dihydroxyterephthalic acid), group 20 (2,3,5,6-tetrafluoroterephthalic acid), and group 21 (terephthalic acid).

[0092] The above coatings were tested using method 2.2.2. The results of the performance test are shown in Table 5:

[0093] Table 5 Test results of coating properties of groups 17-21

[0094] From the above test results, it can be seen that the weather resistance of the coatings using 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, terephthalaldehyde and trimesic acid as organic ligands is slightly better than that of 2,5-dihydroxyterephthalic acid, 2,3,5,6-tetrafluoroterephthalic acid and terephthalic acid, and the effect is significant in the change of weather resistance.

[0095] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A coating containing a heat-insulating pigment, characterized in that: The raw materials for preparing the coating include the following raw material components, calculated by weight: 40-60 parts of aqueous resin dispersion, 15-20 parts of heat-insulating functional pigment, 0.1-0.2 parts of defoaming agent, 0.01-0.5 parts of dispersant, 0.1-0.5 parts of leveling agent, and 0.5-1 parts of film-forming aid; The heat-insulating functional pigment is obtained by coating the pigment with silica sol-gel method and then reacting with organic ligand for catalysis. The preparation method of the heat-insulating functional pigment comprises the following steps: (1) The dried pigment is evenly dispersed in ethanol, and polyacrylamide is then added dropwise to the ethanol. The mixture is stirred at 60-70°C, and the coated pigment is obtained after solid-liquid separation. The mass ratio of polyacrylamide to pigment is 1:

10. (2) Tetraethoxysilane and ethanol solution are mixed in a mass ratio of 1: (10-12), concentrated hydrochloric acid is added dropwise to adjust the pH to 2-3, and the mixture is reacted under heating. After the reaction is completed, the pH is adjusted to 7-8, and the mixture is rapidly stirred and allowed to stand. The coated pigment is uniformly dispersed in the solution in a mass ratio of 1:4 after standing, and the mixture is heated and stirred, then centrifuged and washed, and vacuum dried to obtain a silica-coated pigment; (3) The silica-coated pigment, organic ligand, and polyvinyl alcohol are mixed and dissolved in a sufficient amount of organic solvent in a mass ratio of 100: (4-6.4): (0.8-2.4), and acetic acid is added as a catalyst to heat the mixture at 120°C for 12-24 hours. The reaction product is washed and dried to obtain the heat-insulating functional pigment; the organic ligand is one of trimesic, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, and terephthalic acid.

2. The coating containing heat-insulating pigment according to claim 1, characterized in that: The solid content of the aqueous resin dispersion is 30-50 wt %; the aqueous resin dispersion is one or a combination of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane, and aqueous acrylic-silicone resin.

3. The coating containing heat-insulating pigment according to claim 1, characterized in that: In step (1): The mass concentration of the ethanol is 95wt%; and the stirring mixing time is 0.5-1h.

4. The coating containing heat-insulating pigment according to claim 1, characterized in that: In step (2), the mass concentration of the ethanol solution is 75wt%.

5. The coating containing heat-insulating pigment according to claim 1, characterized in that: In step (2), After adding concentrated hydrochloric acid to the tetraethoxysilane and ethanol solution to adjust the pH to 2-3, react at 50-60°C for 5-6 hours. After the reaction, add sodium hydroxide solution to adjust the pH to 7-8, stir rapidly and let it stand for 30-40 minutes. The coated pigment is evenly dispersed in the solution after standing, heated to 50-60° C. and stirred for 1-2 hours, then centrifuged and washed, and vacuum dried at 20-25° C. for 24 hours to 48 hours to obtain the silica-coated pigment.

6. The coating containing heat-insulating pigment according to claim 1, characterized in that: In step (3), the reaction product is washed three times with tetrahydrofuran, acetone, and ethanol, and then placed in a vacuum drying oven at 60° C. for 24 hours to obtain the heat-insulating functional pigment.

7. The coating containing heat-insulating pigment according to claim 1, characterized in that: In step (3), the organic solvent is one of tetrahydrofuran, acetone, and ethanol.

8. A method for preparing a coating containing a heat-insulating pigment according to any one of claims 1 to 7, characterized in that: The aqueous resin dispersion is added into a dispersion kettle and dispersed at a speed of 1000-1200 rpm for 5-20 minutes. The heat-insulating functional pigment is then added into the dispersion kettle and mixed evenly with the aqueous resin dispersion to obtain a mixed slurry. A defoamer, a dispersant, and a leveling agent are then added to the mixed slurry. The mixed slurry is ball-milled at a speed of 500-1000 rpm for 1-5 hours to obtain a coating.