Dry powder thin coating type coating compatible with dark pigment, preparation method and preparation equipment

Abstract

The invention provides a dry powder thin coating type coating compatible with a dark pigment as well as a preparation method and preparation equipment of the dry powder thin coating type coating. The coating comprises the following components in parts by mass: 35-45 parts of modified latex powder, 10-20 parts of modified talcum powder, 20-30 parts of modified calcium powder, 5-10 parts of modified wollastonite, 5-15 parts of modified precipitated barium sulfate, 5-15 parts of modified titanium dioxide, 5-10 parts of modified quartz powder, 1-5 parts of nano magnesium oxide, 0.5-2 parts of nano zinc oxide, 0.5-1 part of a flatting agent, 1.5-2.5 parts of sodium dodecyl benzene sulfonate, 0.8-1.2 parts of sodium lignosulfonate, 0.8-1.6 parts of sodium chloride, 1-2 parts of cellulose and 0.3-0.5 part of a defoaming agent. The modified talcum powder, the modified calcium powder, the modified wollastonite, the modified precipitated barium sulfate, the modified titanium dioxide and the modified quartz powder are respectively obtained by modifying with a modifier. The coating can overcome the defects of traces and floating caused by mixing of an inorganic coating and a dark pigment.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more specifically, to a dry powder thin-coat coating compatible with dark pigments, as well as its preparation equipment and method. Background Technology

[0002] The biggest advantage of renovating an old house is that it can be completed and the owner can move in quickly. Therefore, improving the environmental friendliness of the materials used in renovation is crucial for ensuring a healthy living environment. Secondly, to improve the living environment and meet the needs of different interior design styles, interior paints must have good compatibility with pigments to meet the construction requirements of different color schemes on interior walls. At the same time, paints suitable for old wall renovation also need to be easy to apply, allow for thin coats, and be cost-effective. Currently, the renovation materials used on the market are generally latex paints. Although latex paints have good compatibility with colored pigments, they are usually organic chemical products. After renovation, due to odors and formaldehyde issues, ventilation for a period of time is still necessary before moving in.

[0003] To replace latex paint, improve the environmental friendliness of interior wall decoration, and meet the requirements for thin-coat application and short-term occupancy, based on the thick-coat alkali-activated pure inorganic functional interior wall coating disclosed in the invention patent with authorization announcement number CN116272584 B, a basic formula for a dry powder thin-coat coating was developed by changing the proportions of various raw materials. By weight, it includes 35-45 parts of admixture, 10-20 parts of talc powder, 20-30 parts of calcium powder, 5-10 parts of quartz powder, 5-10 parts of wollastonite, 5-15 parts of precipitated barium sulfate, 5-15 parts of titanium dioxide, 1-5 parts of nano-magnesium oxide, 0.5-2 parts of nano-zinc oxide, 1-1.5 parts of sodium hexametaphosphate, 1-2 parts of cellulose, and 0.3-0.5 parts of defoamer. The admixture consists of lime powder, ultrafine mineral powder, and redispersible latex powder. During construction, water is added and stirred at a powder-to-water ratio of 1:1.5 for application. This led to the successful development of a thin-film interior wall coating with a frosted finish, which is highly environmentally friendly. However, when color powder is added to the basic formula of this dry powder thin-film coating for dark-colored interior wall application, uneven coloring and residual application marks appear on the interior wall, making it impossible to achieve a qualified dark-colored interior wall finish.

[0004] In view of this, it is indeed necessary for the present invention to develop a dry powder thin-coat coating compatible with dark pigments, as well as a preparation method and preparation equipment. Summary of the Invention

[0005] Research has found that existing alkali-activated pure inorganic functional dry powder coatings are difficult to apply in thin layers. Even if thin layers can be achieved, a large amount of water needs to be added during the application process, which easily leads to defects such as application marks and uneven coloring. This is especially true when color powder is added during application, as these defects become even more pronounced.

[0006] To address this issue, this invention, based on the principle of geological polymerization, primarily improves the application performance of pure inorganic functional dry powder coatings by adjusting the coating formula, water content, reducing the surface tension of water, decreasing the contact angle between water droplets and particle surfaces, and increasing powder dispersibility. This allows for thin-coat application and more uniform dispersion of the coating powder in water, resulting in smaller aggregate particle sizes. Consequently, the coating improves its application performance, preventing application marks and color variations when adding colorant to interior walls for dark-colored applications. This achieves the goals of environmental protection, reduced production costs, and lower construction costs.

[0007] Therefore, the technical solution adopted in this invention is: a dry powder thin-coat coating compatible with dark pigments, comprising the following raw materials by weight: Modified latex powder 35-45 parts, modified talc powder 10-20 parts, modified calcium powder 20-30 parts, modified wollastonite 5-10 parts, modified precipitated barium sulfate 5-15 parts, modified titanium dioxide 5-15 parts, modified quartz powder 5-10 parts, nano magnesium oxide 1-5 parts, nano zinc oxide 0.5-2 parts, leveling agent 0.5-1 part, sodium dodecylbenzene sulfonate 1.5-2.5 parts, sodium lignosulfonate 0.8-1.2 parts, sodium chloride 0.8-1.6 parts, cellulose 1-2 parts, defoamer 0.3-0.5 parts; The total mass fractions of the modified latex powder, the modified talc powder, the modified calcium powder, the modified wollastonite, the modified precipitated barium sulfate, the modified titanium dioxide, and the modified quartz powder are 100 parts. The modified latex powder is prepared by mixing lime powder, ultrafine mineral powder, and latex powder in a mass ratio of (0.5-1.5):(0.5-1.5):(3-9); the modified talc powder, the modified calcium powder, the modified wollastonite, the modified precipitated barium sulfate, the modified titanium dioxide, and the modified quartz powder are obtained by modifying talc powder, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder respectively with a modifier, wherein the modifier is composed of polycarboxylate superplasticizer and sodium polymetaphosphate in a mass ratio of (0.2-0.6):1.

[0008] Based on the above, when modifying talc powder, the modifier accounts for 5% to 6% of the mass of talc powder; when modifying calcium powder, the modifier accounts for 2.8% to 3.5% of the mass of calcium powder; when modifying wollastonite, the modifier accounts for 2.8% to 3.5% of the mass of wollastonite; when modifying precipitated barium sulfate, the modifier accounts for 1% to 1.5% of the mass of precipitated barium sulfate; when modifying titanium dioxide, the modifier accounts for 3% to 3.8% of the mass of titanium dioxide; and when modifying quartz powder, the modifier accounts for 3% to 3.8% of the mass of quartz powder.

[0009] Based on the above, the mass ratio of sodium dodecylbenzenesulfonate, sodium lignosulfonate, and sodium chloride is (2.0-2.5):(1.0-1.2):(0.8-1.2).

[0010] Based on the above, the mass ratio of the ultrafine mineral powder to the latex powder is (0.8-1.2):(0.8-1.3):(6-8).

[0011] Based on the above, the particle size of lime powder is greater than 600 mesh, while talc, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder are all powders with a particle size of 1250 mesh or larger.

[0012] Based on the above, it also includes inorganic color powder added as an admixture during construction, wherein the inorganic color powder includes at least one of iron oxide red, iron oxide green, iron oxide yellow, ultramarine, and iron oxide black.

[0013] The present invention also provides a method for preparing the above-mentioned dry powder thin-coat coating compatible with dark pigments, the steps of which include: The modified powders were prepared by mixing latex powder, lime powder, and ultrafine mineral powder to obtain modified latex powder; polycarboxylate superplasticizer and sodium polymetaphosphate were used as modifiers to modify talc powder, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder separately, respectively, to obtain modified talc powder, modified calcium powder, modified wollastonite, modified precipitated barium sulfate, modified titanium dioxide, and modified quartz powder. Weigh and mix all raw materials and add them to a mixer. Stir for 4 to 6 minutes at a stirring speed of 1100 r / min to 1350 r / min and a stirring temperature of less than 65°C to obtain a dry powder thin-coat coating compatible with dark pigments.

[0014] Specifically, in the preparation step of the modified powder: lime powder, ultrafine mineral powder, and latex powder are added to a high-speed mixer in a mass ratio of (0.5–1.5):(0.5–1.5):(3–9), and stirred for 10–15 minutes at a stirring speed of 1000–1600 r / min and a stirring temperature of less than 65°C. The modified latex powder was prepared by dissolving polycarboxylate superplasticizer and sodium polymetaphosphate in water in appropriate proportions and then atomizing them in a mixer using an atomizer. During the atomization process, talc powder, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide and quartz powder were separately dispersed by airflow and added to the mixer for stirring and mixing. Then, the mixture was conveyed to a drying tank for rotary drying, and finally conveyed to a rotary air-cooled tank for cooling and sieved by a vibrating screen to obtain modified talc powder, modified calcium powder, modified wollastonite, modified precipitated barium sulfate, modified titanium dioxide and modified quartz powder respectively.

[0015] Specifically, by atomizing the liquid raw materials and dispersing the powder raw materials with airflow, the contact area between the liquid and powder raw materials is increased, allowing them to be fully and evenly mixed, thus improving the mixing uniformity of the raw materials from a physical perspective.

[0016] The present invention also provides an apparatus for preparing dry powder thin-coat coatings compatible with the above-mentioned dark pigments, including a mixer, an atomizer, a drying tank, a rotary air-cooled tank, and a vibrating screen.

[0017] The atomizer is connected to the mixer and is used to atomize the liquid raw materials in the dry powder thin-coat paint and add them into the mixer. The mixer is equipped with a first fan, which is used to disperse the powder raw materials in the dry powder thin-coat paint using airflow before adding them into the mixer. The mixer is equipped with first stirring blades, which are used to stir and mix the atomized liquid raw materials with the dispersed powder raw materials. A drying tank is connected to one side of the mixer and is used to dry the material mixed by the mixer through stirring and friction. A rotary air-cooled tank is connected to the drying tank and is used to cool the material dried in the drying tank. A vibrating screen is connected to the rotary air-cooled tank and is used to screen the material cooled by the rotary air-cooled tank.

[0018] Based on the above, the drying tank is connected to the mixer through a premixed material discharge pipe. The drying tank is equipped with a second stirring blade and a guide block. The second stirring blade is used to stir the material after it has been mixed by the mixer, so that friction between the materials and between the materials and the guide block generates heat for drying.

[0019] The rotary air-cooled tank is connected to the drying tank through a dry material discharge pipe. A second fan is installed on the rotary air-cooled tank to introduce cooling air into the rotary air-cooled tank. Lifting plates are installed on the inner wall of the rotary air-cooled tank so that the material is lifted by the lifting plates as the rotary air-cooled tank rotates, and then cooled.

[0020] The mixer is connected to a powder feed pipe at its upper part, the first fan is located directly below the powder feed pipe, and the outlet of the atomizer is located on the opposite side of the powder feed pipe, so that the liquid raw material atomized by the atomizer is sprayed onto the dispersed powder raw material.

[0021] The present invention also provides a method for applying a dry powder thin-coat paint compatible with dark pigments. The steps include first weighing the dry powder thin-coat paint and water according to a powder-to-water ratio of 1:(1.5-2), then adding inorganic pigment to the weighed water and stirring evenly, finally adding the weighed dry powder thin-coat paint and stirring for 3-5 minutes, letting it stand for 4-8 minutes, and then stirring again for 1-3 minutes before application.

[0022] The inorganic pigment includes at least one of iron oxide red, iron oxide green, iron oxide yellow, ultramarine, and iron oxide black, and the mass percentage of the inorganic pigment to water is greater than or equal to 2%.

[0023] This invention has substantial features and advancements compared to existing technologies. Specifically, this invention provides a dry powder thin-coat coating compatible with dark pigments, along with its preparation method and equipment. By analyzing the root cause of the traces and color variations that occur when inorganic coatings are mixed with colored pigments, it is found that this dry powder thin-coat coating compatible with dark pigments is a dry powder type coating. When using it, water needs to be added and stirred at a powder-to-water ratio of 1:(1.5~2). The amount of water added is relatively large, and the surface tension of water is high, making it easy to shrink, which makes it difficult for the color and powder to be evenly dispersed in the water.

[0024] Therefore, this invention addresses the defects of marks and color variation that occur when inorganic coatings used in old house renovations are mixed with dark pigments by reducing the surface tension of water and uniformly modifying talc, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder to improve the wetting of powder particles by water.

[0025] Specifically, this invention utilizes lime powder and ultrafine high-activity mineral powder as improved raw materials for latex powder. The mineral powder and lime powder can undergo a polymerization reaction to produce hydrated calcium aluminate and hydrated aluminum silicate feldspar with gelling properties. This film-forming material is matched with the latex powder, which not only improves the coating strength but also ensures good toughness.

[0026] On the other hand, by using sodium dodecylbenzenesulfonate, sodium lignosulfonate and sodium chloride as surfactants, the surface tension of water is reduced in a synergistic manner, making it easier for water to wet the surface of powder particles and pigments, thereby improving their dispersibility and solving the defects of traces and color mottled appearance when inorganic coatings are mixed with colored pigments.

[0027] Thirdly, by using sodium polymetaphosphate and polycarboxylate superplasticizer as modifiers, talc, calcium carbonate, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder are pre-modified individually. The phosphate ions generated after the hydrolysis of sodium polymetaphosphate readily adsorb onto the positively charged edges of the particle surface, forming negatively charged edges. This results in particles carrying the same charge, creating repulsive forces between particles and preventing agglomeration. Simultaneously, sodium polymetaphosphate reduces the surface tension of water, making it easier for water to wet the powder particles, thus improving the dispersibility of the powder and pigments. Furthermore, during the modification process, high-speed stirring and collision heating of the various modifying materials ensure thorough mixing and modification, guaranteeing complete wetting of the powder particles by water. Ultimately, this results in a dry powder thin-coat coating compatible with dark pigments.

[0028] Therefore, the present invention ultimately achieves the ability to produce dark colored walls such as deep black, deep blue, and deep red when applying a thin coating, while ensuring that the wall does not exhibit color discoloration or marks. Attached Figure Description

[0029] Figure 1 These are images showing the effects of applying dry powder paint to walls after mixing it with water according to different powder-to-water ratios. Figure 1 Add water according to a powder-to-water ratio of 1:1. Figure 1 b. Add water according to the powder-to-water ratio of 1:1.5. Figure 1 c. Add water and iron oxide blue powder according to the powder-to-water ratio of 1:1.5.

[0030] Figure 2 These are images showing the effects of coating polyester films with aqueous solutions of iron oxide-containing yellow powder containing different amounts of sodium dodecylbenzenesulfonate. Figure 2 a contains 0.2% sodium dodecylbenzenesulfonate, Figure 2 b contains 1% sodium dodecylbenzenesulfonate. Figure 2 c contains 2% sodium dodecylbenzenesulfonate.

[0031] Figure 3 These are images showing the effect of coating polyester films with aqueous solutions of colorant containing different amounts of sodium lignosulfonate. Figure 3 a contains 0.2% sodium lignosulfonate, Figure 3 b contains 0.8% sodium lignosulfonate, Figure 3 c contains 1.5% sodium lignosulfonate.

[0032] Figure 4 This is an image showing the effect of coating a polyester film with an aqueous solution of yellow iron oxide powder containing 1.5% sodium chloride.

[0033] Figure 5 This is an image showing the effect of coating a polyester film with an aqueous solution containing ultramarine pigment containing 1.5% sodium dodecylbenzenesulfonate and 1.5% sodium chloride.

[0034] Figure 6 This image shows the effect of coating a polyester film with an aqueous solution of iron oxide-containing yellow powder containing 2.0% sodium dodecylbenzenesulfonate, 0.8% sodium lignosulfonate, and 0.8% sodium chloride.

[0035] Figure 7 This describes the dispersion of talc powder in water after modification using different methods. Figure 7 a contains only talc, Figure 7 b represents the simultaneous addition of 4.0% sodium polymethphosphate and 1.2% polycarboxylate superplasticizer. Figure 7 c represents the simultaneous addition of 4.5% sodium polymetaphosphate and 1.5% polycarboxylate superplasticizer. Figure 7 d represents the addition of 4.0% sodium polymethphosphate.

[0036] Figure 8 These are images showing the effects of applying different amounts of different colored pigments to walls. Image 8a shows the effect of applying 1% ultramarine pigment, image 8b shows the effect of applying 1% iron oxide yellow pigment, and image 8c shows the effect of applying 2% iron oxide black pigment.

[0037] Figure 9 This is an image showing the effect of applying iron oxide black powder to a wall after adding iron oxide black powder to the dry powder thin-coat type coating that is compatible with dark pigments provided by this invention.

[0038] Figure 10 This describes the dispersion of the dry powder thin-coat coating compatible with dark pigments provided by this invention in water, wherein... Figure 10 No colorant added. Figure 10 bAdd ultramarine powder.

[0039] Figure 11 This is a schematic diagram of the equipment structure for preparing dry powder thin-coat coatings compatible with dark pigments.

[0040] In the diagram: 1. Mixer; 2. First mixing blade; 3. First blower; 4. Powder feed pipe; 5. Atomizer; 6. Liquid feed pipe; 7. Premixed material discharge pipe; 8. Second blower; 9. Rotary air-cooled tank; 10. Cooled material discharge pipe; 11. Vibrating screen; 12. Coarse material pipe; 13. Fine material pipe; 14. Drying tank; 15. Guide block; 16. Collection hopper; 17. Exhaust fan; 18. Dry material discharge pipe; 19. Second mixing blade. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0042] The main objective of this invention is to research an environmentally friendly, low-cost, and easy-to-apply dry powder thin-coat paint. To achieve this objective, based on the principle of geological polymerization reaction, this invention previously developed a basic formula for a dry powder thin-coat inorganic paint that can be mixed with a large amount of water. However, to meet user needs, adding colorant to the previously developed dry powder thin-coat inorganic paint basic formula resulted in defects such as streaks and color variations in the coating during thin-coat application, making it impossible to achieve colored interior wall surfaces.

[0043] Analysis revealed that the main reason for the construction marks and color variations was that the basic formula of the dry powder thin-coat inorganic coating developed in the early stage involved the addition of a large amount of water during construction. Water has a high surface tension. After adding a large amount of water, the coating system was tightly bound and agglomerated by the water. The agglomerates were large in size and unevenly dispersed. Especially when applying a thin coat to dark-colored interior walls after adding a large amount of pigment, the darker wall surface increased the opacity of the coating. The unevenness of the coating surface was magnified and clearly exposed by the difference in light reflection, making the construction marks and color variations more visually apparent.

[0044] To address this problem, this invention first focuses on reducing the surface tension of water. By screening suitable surfactants to reduce the surface tension of water, these surfactants are added to the previously developed dry powder thin-coat inorganic coating base formula to improve the coating's application performance.

[0045] Based on the above concept and specific implementation schemes, the present invention will be further described in detail below.

[0046] I. Basic Formulation of Dry Powder Thin-Coat Coatings By utilizing lime powder and ultrafine highly activated mineral powder as modifying raw materials for latex powder, and taking advantage of the polymerization reaction between mineral powder and lime powder, hydrated calcium aluminate and hydrated aluminum silicate feldspar with gelling properties are produced. This film-forming material, when matched with latex powder, not only improves the coating strength but also ensures good toughness. Based on this, fillers are added to develop a dry powder coating, which specifically includes the following raw materials by weight: 35-45 parts modified latex powder, 10-20 parts talc powder, 20-30 parts calcium powder, 5-10 parts quartz powder, 5-10 parts wollastonite, 5-15 parts precipitated barium sulfate, 5-15 parts titanium dioxide, 1-5 parts nano magnesium oxide, 0.5-2 parts nano zinc oxide, 1-1.5 parts sodium hexametaphosphate, 1-2 parts cellulose, and 0.3-0.5 parts defoamer. The total mass fraction of modified latex powder, talc powder, calcium powder, quartz powder, wollastonite, precipitated barium sulfate, and titanium dioxide is equal to 100 parts.

[0047] The strength and toughness of the coating are important considerations for paints and are significant factors affecting the application effect of dry powder thin-coat paints. The powder-to-water ratio during the application of dry powder paints, i.e., the amount of water added, is crucial in determining whether the dry powder thin-coat paint can be evenly dispersed and applied in a thin layer. Therefore, experiments were conducted to determine the optimal powder-to-water ratio for the aforementioned dry powder paints.

[0048] The specific formula for dry powder coating is as follows: 40 parts modified latex powder, 10 parts talc powder, 20 parts calcium powder, 5 parts quartz powder, 5 parts wollastonite, 15 parts precipitated barium sulfate, 5 parts titanium dioxide, 5 parts nano magnesium oxide, 2 parts nano zinc oxide, 1 part sodium hexametaphosphate, 1 part cellulose, and 0.3 parts defoamer. The total mass of modified latex powder, talc powder, calcium powder, quartz powder, wollastonite, precipitated barium sulfate, and titanium dioxide is equal to 100 parts.

[0049] Powder-to-water ratio test method: Weigh out three groups of equal mass of dry powder paint, then add water to the first three groups at powder-to-water ratios of 1:1, 1:1.5, and 1:3 respectively, and stir. Then, conduct a brushing test on the wall for each group. Specific brushing results are as follows... Figure 1 As shown. Figure 1 Add water according to a powder-to-water ratio of 1:1. Figure 1 b. Add water according to the powder-to-water ratio of 1:1.5.

[0050] from Figure 1 As can be seen from Figure a, when too little water is added, the slurry becomes viscous with high viscosity. When applied to the wall, the slurry exhibits wrinkles, ripples, and other phenomena, resulting in poor construction effects. Figure 1As shown in b, when the powder-to-water ratio is 1:1.5, the slurry can be evenly spread after being applied to the wall, resulting in a matte finish and good coverage. However, when water is added and stirred at a powder-to-water ratio of 1:3, the slurry has lower viscosity and poorer coverage. Therefore, preferably, the optimal powder-to-water ratio for dry powder coatings that can be applied in thin coats is 1:(1.5~2).

[0051] Colored construction effect A paint powder was mixed with water at a powder-to-water ratio of 1:1.5, and ultramarine blue powder was added. A painting test was conducted on the wall, and the results were as follows: Figure 1 As shown in c. From Figure 1 As can be seen from Figure c, directly adding ultramarine pigment to the basic formula of dry powder thin-coat paint will result in a mottled appearance, indicating that the basic formula needs to be improved to meet the purpose of colored painting.

[0052] Analysis suggests that the marks and mottling observed during thin-coat application are primarily due to the need to add a large amount of water to the dry powder coating during application. At temperatures between 20℃ and 25℃, the surface tensions of liquids that can be added to coatings as additives, such as alcohol (22.27 mN / m), styrene-acrylic emulsion (40 mN / m), acrylic emulsion (35 mN / m), benzene (28.88 mN / m), and water (72.75 mN / m), are relatively low.

[0053] Compared to other liquids, water has a higher surface tension, meaning that the inward pulling force between surface molecules is greater. This causes the paint system to be tightly encapsulated by water, resulting in agglomeration. These agglomerates are larger in size and unevenly dispersed. Especially after adding pigments, the agglomeration prevents the liquid-encapsulated powder particles from contacting the pigments, thus preventing them from being fully coated. When using a roller to paint walls, the pressure between the roller and the wall causes liquid to accumulate at both ends of the roller. In this situation, the powder particles that are not effectively coated by pigments will appear slightly lighter in color compared to other areas, making application marks and color variations more visually apparent.

[0054] Therefore, reducing the surface tension of water can be used to solve the problems of uneven application and marks during construction.

[0055] II. Reducing the surface tension of water The following experiment further illustrates the effect of surfactants on the surface tension of pigments and water.

[0056] 2.1 Surfactant Screening To reduce the surface tension of the water, sodium dodecylbenzenesulfonate, sodium lignosulfonate, and sodium chloride were individually mixed with water and inorganic pigments, and then coated onto polyester films using a wire rod coater to observe the dispersion effect of the pigments. Polyester film was chosen as the coating platform for the wire rod coater because its good transparency makes it easier to observe the coating and spreading effects, and more importantly, the water does not wet the polyester film, thus not affecting the experimental results.

[0057] (1) Sodium dodecylbenzenesulfonate In the specific coating process, firstly, a certain mass of water was weighed and added to the polyester film in multiple groups. Then, 1% of the water mass of iron oxide yellow powder was added, and sodium dodecylbenzene sulfonate was added at different concentrations of 0.2%, 1%, 2%, and greater than 2% of the water mass, respectively. After mixing, coating experiments were conducted, and the results are shown in Table 1. Figure 2 As shown. Among them Figure 2 a contains 0.2% sodium dodecylbenzenesulfonate, Figure 2 b contains 1% sodium dodecylbenzenesulfonate. Figure 2 c contains 2% sodium dodecylbenzenesulfonate.

[0058] Table 1. Spreading effect of different amounts of sodium dodecylbenzenesulfonate Serial Number Sodium dodecylbenzenesulfonate (%) Pigment (%) Renderings 1 0.2 1 Figure 2 a 2 1.0 1 Figure 2 b 3 2.0 1 Figure 2 c 4 3.0 1 from Figure 2 As can be seen from Figure a, the yellow liquid presents multiple separate patches with almost no connection between them, indicating that the amount of sodium dodecylbenzenesulfonate added is insufficient. From... Figure 2 As shown in 2b, the yellow liquid appears as multiple interconnected color blocks, but there are discontinuous areas between these blocks, indicating that the amount of sodium dodecylbenzenesulfonate added needs to be further increased. From 2c, it can be seen that the yellow liquid can be evenly coated on the polyester film with a relatively uniform thickness. Furthermore, when the amount of sodium dodecylbenzenesulfonate added reaches 2% of the water mass, further increases in the amount do not show significant visual changes.

[0059] Therefore, when sodium dodecylbenzenesulfonate is used as a surfactant, the optimal addition amount can be determined to be 2% of the water mass.

[0060] (2) Sodium lignosulfonate In the specific coating process, firstly, a certain mass of water was weighed and added to the polyester film in multiple groups. Then, ultramarine pigment powder (1% by mass of water) was added, followed by sodium lignosulfonate (0.2%, 1%, 2%, and greater than 2% by mass of water), and the mixtures were then used for coating experiments. The results are shown in Table 2. Figure 3 As shown. Figure 3 a contains 0.2% sodium lignosulfonate, Figure 3 b contains 0.8% sodium lignosulfonate, Figure 3c contains 1.5% sodium lignosulfonate.

[0061] Table 2. Spreading effect of different amounts of sodium lignosulfonate Serial Number Sodium lignosulfonate (%) Pigment (%) Renderings 1 0.2 1 Figure 3 a 2 0.8 1 Figure 3 b 3 1.5 1 Figure 3 d 4 2.0 1 from Figure 3 As can be seen from Figure a, the blue solution did not spread on the polyester film after coating, indicating that the surface tension of the water was not significantly reduced, and the amount of sodium lignosulfonate added needs to be further increased. Figure 3 As can be seen from b, compared to Figure 3 Regarding point a, the area covered by the blue patch has increased, but there are still discontinuous areas, indicating that the surface tension of the water needs to be further reduced. From Figure 3 As shown in Figure c, the color blocks can be evenly coated on the polyester film with uniform thickness. Furthermore, when the amount of sodium lignosulfonate added reaches 1.5% of the water mass, virtually no change is observed on the polyester film. Therefore, the optimal addition amount of sodium lignosulfonate as a surfactant can be determined to be 1.5% of the water mass.

[0062] (3) Sodium chloride like Figure 4 As shown, when sodium chloride is added alone to coat a water film on a polyester film, the experimental results show no change with increasing dosage; the water film is not uniformly dispersed on the polyester film but rather clumps together. This indicates that sodium chloride cannot be used alone as a surfactant.

[0063] (4) Combination test of multiple surfactants: Subsequently, following the experimental steps described above, sodium dodecylbenzenesulfonate and sodium chloride were mixed in a 1:1 ratio for testing, and the water dispersion effect was compared with that of sodium dodecylbenzenesulfonate alone (2%). The results are shown in Table 3. Figure 5 As shown.

[0064] Table 3. Spreading effect of different amounts of sodium dodecylbenzenesulfonate and sodium chloride. Serial Number Sodium dodecylbenzenesulfonate (%) Sodium chloride (%) Pigment (%) Renderings 1 1.5 1.5 1 Figure 5 from Figure 5 As can be seen, when sodium dodecylbenzenesulfonate and sodium chloride are used in combination, the effect of coating the polyester film with the aqueous solution is very good when the amount of sodium dodecylbenzenesulfonate added reaches 1.5% of the water mass, which is the same as the effect of adding sodium dodecylbenzenesulfonate alone to 2% of the colorant-containing aqueous solution. This indicates that when the two substances are used simultaneously, sodium chloride can synergistically reduce the surface tension of the water.

[0065] Analysis suggests that the effect is mainly due to the addition of counterions, which reduces the electrostatic repulsion between surface-active ions. The higher the concentration of inorganic salts, the greater the concentration of counterions, resulting in a greater reduction in the electrostatic repulsion between surface-active ions and thus a smaller surface tension.

[0066] (5) Orthogonal experiments with multiple surfactants: Based on the experimental results, the three materials were used in combination, and the ratios and combinations were designed according to the orthogonal experimental table, as shown in Tables 4 and 5.

[0067] Table 4. Dosage of different surfactants Serial Number Sodium dodecylbenzenesulfonate (%) Sodium lignosulfonate (%) Sodium chloride (%) 1 1.0 0.6 0.8 2 1.5 0.8 1.2 3 2.0 1.2 1.6 Table 5: L9 (3) 4 Orthogonal experimental table Test No. 1 2 3 Observation results 1 1.0 0.6 0.8 discontinuous color blocks 2 1.0 0.8 1.2 discontinuous color blocks 3 1.0 1.2 1.6 discontinuous color blocks 4 1.5 0.6 1.2 The color blocks are continuous and evenly applied with uniform thickness. 5 1.5 0.8 1.6 The color blocks are continuous and evenly applied with uniform thickness. 6 1.5 1.2 0.8 The color blocks are continuous and evenly applied with uniform thickness. 7 2.0 0.6 1.6 The color blocks are continuous and evenly applied with uniform thickness. 8 2.0 0.8 0.8 The color blocks are continuous and evenly applied with uniform thickness. 9 2.0 1.2 1.2 The color blocks are continuous and evenly applied with uniform thickness. Based on the orthogonal experimental design, nine groups of experiments with different formulation ratios were conducted following the same experimental procedures to test the coating effect of different formulation ratios on polyester films. The experimental results showed that experiments 1, 2, and 3 in the orthogonal experimental design exhibited insufficient uniformity of color dispersion on the polyester film, which was inferred to be possibly due to insufficient addition of sodium dodecylbenzenesulfonate, resulting in insufficient reduction of the surface tension of water molecules. In contrast, experiments 4, 5, 6, 7, 8, and 9 showed significantly improved color dispersion and better uniformity of the water film. Specifically, as... Figure 6 The image shows the effect of coating a polyester film with an aqueous solution of iron oxide-containing yellow powder containing 2.0% sodium dodecylbenzenesulfonate, 0.8% sodium lignosulfonate, and 0.8% sodium chloride. It can be seen that the yellow liquid can be uniformly coated on the polyester film with a relatively uniform thickness. Experiments 4, 5, 6, 7, and 9 showed the same dispersion effect.

[0068] This demonstrates that sodium dodecylbenzenesulfonate, sodium lignosulfonate, and sodium chloride, as surfactants, exhibit a synergistic effect, working together to reduce the surface tension of water molecules. Furthermore, considering cost, this invention selects 1.5–2.5 parts by weight of sodium dodecylbenzenesulfonate, 0.8–1.2 parts by weight of sodium lignosulfonate, and 0.8–1.6 parts by weight of sodium chloride as surfactants to reduce the surface activity of water.

[0069] 2.2 The basic formula is mixed with surfactants and colorants before interior wall construction. The following method combines the selected surfactants with the basic formulation of the aforementioned dry powder coating, and applies the coating with a total mass of 100 parts of modified latex powder, talc powder, calcium powder, quartz powder, wollastonite, precipitated barium sulfate, and titanium dioxide, along with the addition of colorant, to preliminarily verify the effect of interior wall color application.

[0070] (1) 1% ultramarine blue Specifically, by weight, the raw materials include the following: 30 parts modified latex powder, 8 parts talc powder, 18 parts calcium powder, 4 parts wollastonite, 15 parts precipitated barium sulfate, 18 parts titanium dioxide, 7 parts quartz powder, 5 parts nano magnesium oxide, 2 parts zinc oxide, 1.5 parts sodium dodecylbenzene sulfonate, 0.8 parts sodium lignosulfonate, 0.8 parts sodium chloride, 2 parts cellulose, and 0.5 parts defoamer.

[0071] When constructing the interior wall, first weigh all the above-mentioned raw materials, then weigh 1% of the total mass of the raw materials, and weigh the specific mass of water to be added to the dry powder thin-coat paint according to the powder-to-water ratio of 1:1.5. Then add the ultramarine blue powder to the water and stir evenly. Finally, add the dry powder thin-coat paint to the water containing inorganic pigment and mix evenly before construction.

[0072] The effect after rolling the paint on the wall is as follows Figure 8 As shown in a, from Figure 8 As can be seen from Figure a, compared with the white wall, the wall surface after the roller is a uniform light blue, and the color is relatively uniform, without any white stripes or other color variations.

[0073] (2) 1% iron oxide yellow With all other conditions remaining unchanged, the effect of replacing ultramarine with iron oxide yellow after roller coating the wall is as follows: Figure 8 As shown in b, from Figure 8 As can be seen in b, compared with the white wall, the wall surface after the roller is a uniform light blue, and the color is relatively uniform, without any white stripes or other color variations.

[0074] (3) 2% iron oxide black Under otherwise unchanged conditions, using iron oxide black instead of ultramarine blue, and limiting the addition of iron oxide black to 2% of the total mass of all raw materials, the effect after roller coating on the wall is as follows: Figure 8 As shown in c, from Figure 8 As shown in Figure c, the wall surface after the roller application reappeared with white streaks and other color variations. Furthermore, the same defect persisted even after changing the amount of surfactant added.

[0075] Therefore, it can be seen that when the amount of pigment added exceeds 2% for dark-colored construction of interior walls, simply using surfactants to reduce the surface tension of water cannot meet the requirements for dark-colored interior wall construction. Additionally, the situation of the powder being wetted by water must be considered.

[0076] Analysis suggests that the dry powder coating, due to the addition of a large amount of water during application, not only suffers from the problem of high surface tension of water, but also from the problem of water failing to wet the color powder and fillers.

[0077] In other words, to ensure that pigments and fillers are completely wetted by water, the contact angle between water and the solid must be reduced. The oil absorption value of the material is a key factor in determining the contact angle, but each material has a different oil absorption value, making simple mixing and modification impossible. Specifically, the oil absorption values ​​of the raw materials are as follows: talc powder 35, heavy calcium carbonate powder 20, titanium dioxide 21, precipitated barium sulfate 8, quartz powder 22, and wollastonite 20. Therefore, each filler needs to be individually and specifically modified to reduce the contact angle between water droplets and the particle surface, ensuring that the powder particles can be completely wetted by water.

[0078] 3. Reduce the contact angle between water droplets and particle surfaces The following experiments further illustrate the effect of the modifier on the contact angle of water droplets and particle surfaces.

[0079] 3.1 Screening of Modifiers To reduce the contact angle between water droplets and particle surfaces, talc powder was first selected as the modification target. Sodium polymetaphosphate and polycarboxylate superplasticizer were mixed and modified separately with talc powder. The modified talc powder to be tested was dropped onto the top of a scraper fineness meter. A steel scraper was pulled down at a 90-degree angle. When a scratch appeared on the scraper, the corresponding scale was considered to be the fineness of the solution, and the dispersibility of the modified talc powder in water was judged.

[0080] (1) Sodium polymethphosphate In the specific modification operation, talc powder and sodium polymethphosphate at mass percentages of 2%, 3%, 4%, 4.5%, and 5.0% of talc powder were mixed using a high-speed mixer. The mixture was stirred for 1 minute at 100℃ to 120℃. The equipment was then stopped, and the modified powder was released to room temperature. The mixture was then added back at a temperature not exceeding 60℃ and stirred again for 1 to 2 minutes. The results were then measured using a scraper fineness meter, and are shown in Table 6. Figure 7 As shown in d.

[0081] Table 6. Dispersion effect of different sodium polyphosphate addition amounts Serial Number Sodium polymethphosphate (%) Effect (mm) Renderings 1 2 0.65 - 2 3.0 0.45 - 3 4.0 0.35 Figure 7 d 4 4.5 0.35 - 5 5.0 0.35 - From Table 6 and Figure 7 As can be seen from d, when the amount of sodium polyphosphate added reached 4.0%, the dispersion performance of talc in water did not continue to increase, the fineness did not continue to decrease, and the expected dispersion effect was not achieved.

[0082] (2) Polycarboxylate superplasticizer Using the same operating steps, talc powder was modified with polycarboxylate superplasticizer, such as... Figure 7As shown in Figure a, it was found that regardless of the amount of polycarboxylate superplasticizer added, the dispersibility of talc remained unchanged compared to unmodified talc. This indicates that polycarboxylate superplasticizer cannot be used alone as a modifier.

[0083] (3) Combined test of sodium polymethphosphate and polycarboxylate superplasticizer: Based on the above experimental results, using the same operating procedures, sodium polyphosphate and polycarboxylate superplasticizer were combined to design a specific ratio and combination. The detailed combination and dispersion results are shown in Table 7. Figure 7 b and Figure 7 As shown in c.

[0084] Table 7. Dispersion effect of different polycarboxylate superplasticizer dosages Serial Number Sodium polymethphosphate (%) Polycarboxylate superplasticizer (%) Effect (mm) Renderings 1 2 0.2 0.60 - 2 2.5 0.5 0.55 - 3 3.0 0.8 0.40 - 4 3.5 1.0 0.25 - 5 4.0 1.2 0.15 Figure 7 b 6 4.5 1.5 0.15 Figure 7 c 7 5.0 2.0 0.15 - From Table 7 and Figure 7 b and Figure 7 As shown in Figure c, the combination of sodium polymetaphosphate and polycarboxylate superplasticizer exhibits a synergistic effect, with experimental group 5 achieving the optimal dispersion effect. Furthermore, considering cost, this invention selects 1.0%–1.2% polycarboxylate superplasticizer (by mass of talc powder) and 3.5%–4.0% sodium polymetaphosphate (by mass of talc powder) as modifiers to modify talc powder.

[0085] When modifying calcium carbonate, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder, the addition amount can be calculated by referring to the addition amount for talc modification. That is, divide the oil absorption value of the material to be modified by the oil absorption value of talc, multiply by the amount of each modifier determined by talc, and use this as the amount of modifier to be added for this raw material.

[0086] Specifically, when modifying calcium powder, the modifier accounts for 2.8% to 3.5% of the mass of calcium powder; when modifying wollastonite, the modifier accounts for 2.8% to 3.5% of the mass of wollastonite; when modifying precipitated barium sulfate, the modifier accounts for 1% to 1.5% of the mass of precipitated barium sulfate; when modifying titanium dioxide, the modifier accounts for 3% to 3.8% of the mass of titanium dioxide; and when modifying quartz powder, the modifier accounts for 3% to 3.8% of the mass of quartz powder.

[0087] 3.2 After modifying the basic formula, mix it with surfactants and colorants before application. The following method combines the selected surfactants with the modified base coating formula, and adds color powder at least 2% of the total mass of each raw material for dark-colored application to verify the application effect.

[0088] (1) 3% iron oxide black powder Specifically, by weight, the raw materials include the following: 45 parts modified latex powder, 10 parts modified talc powder, 20 parts modified calcium powder, 5 parts modified wollastonite, 5 parts modified precipitated barium sulfate, 5 parts modified titanium dioxide, 10 parts modified quartz powder, 1 part nano magnesium oxide, 0.2 parts nano zinc oxide, 1 part leveling agent, 1.5 parts sodium dodecylbenzene sulfonate, 1.2 parts sodium lignosulfonate, 1.6 parts sodium chloride, 2 parts cellulose, and 0.3 parts defoamer.

[0089] The modified latex powder is prepared by mixing lime powder, ultrafine mineral powder, and latex powder. The mass ratio of the lime powder, ultrafine mineral powder, and latex powder is 1:1:6. The lime powder has a particle size greater than 600 mesh, and the talc, calcium powder, wollastonite, barium sulfate, titanium dioxide, and quartz powder are all powders with a particle size greater than 1250 mesh.

[0090] When constructing the interior wall, first weigh all the above-mentioned raw materials, then weigh 3% of the total mass of the raw materials, and weigh the specific mass of water to be added to the dry powder thin-coat paint according to the powder-to-water ratio of 1:1.5. Then add the iron oxide black powder to the water and stir evenly. Finally, add the dry powder thin-coat paint to the water containing inorganic pigment and mix evenly before construction.

[0091] The effect after rolling the paint on the wall is as follows Figure 9 As shown, from Figure 9 As can be seen, compared to a white wall, the wall surface after roller application exhibits a uniform deep black color with a more even hue, without any white streaks or other color variations. This indicates that the dry powder thin-coat coating provided by this invention has good compatibility with inorganic color powders.

[0092] Meanwhile, to verify the effect of different surfactant ratios on the color of the wall after adding iron oxide black, interior walls were coated by varying the amount of iron oxide black powder, the amount of polycarboxylate superplasticizer and sodium polymetaphosphate added during modification treatment, and the surfactant additives, all while keeping other conditions constant. The results showed that the wall surface after roller coating all exhibited a uniform deep black color with relatively even luster.

[0093] (2) 3% ultramarine blue Specifically, by weight, the raw materials include the following: 35 parts modified latex powder, 15 parts modified talc powder, 20 parts modified calcium powder, 5 parts modified wollastonite, 5 parts modified precipitated barium sulfate, 10 parts modified titanium dioxide, 10 parts modified quartz powder, 3 parts nano magnesium oxide, 2 parts nano zinc oxide, 1 part leveling agent, 2 parts sodium dodecylbenzene sulfonate, 0.9 parts sodium lignosulfonate, 1.5 parts sodium chloride, 2 parts cellulose, and 0.4 parts defoamer.

[0094] When applying the coating to interior walls, first weigh all the raw materials listed above. Then weigh out 3% of the total mass of ultramarine pigment. Weigh out the required amount of water to be added to the dry powder thin-coat paint, according to a powder-to-water ratio of 1:1.5. Add the ultramarine pigment to the water and stir until homogeneous. Finally, add the dry powder thin-coat paint to the water containing the inorganic pigment and mix thoroughly before application. Ultramarine is an inorganic blue pigment with a vibrant blue hue, primarily used in coatings, inks, and plastics.

[0095] After roller coating, compared to a white wall, the wall surface treated with the roller exhibits a uniform deep blue color with a more even hue, without any white streaks or other color variations. This indicates that the dry powder thin-coat coating provided by this invention has good compatibility with inorganic color powders.

[0096] Meanwhile, to verify the effect of different surfactant ratios on the color of the wall after adding ultramarine blue, indoor walls were painted by increasing the amount of ultramarine blue pigment, changing the amount of polycarboxylate superplasticizer and sodium polymetaphosphate added during the modification treatment, and changing the surfactant additives, all while keeping other conditions unchanged. The results showed that the wall surface after roller coating all exhibited a uniform deep blue color with relatively even hue.

[0097] Meanwhile, the present invention also selected inorganic color powders such as iron oxide red, iron oxide green, and iron oxide yellow to add to the dry powder thin-coat coating provided by the present invention for application, and all of them achieved the same uniform coloring effect.

[0098] like Figure 10 As shown, dispersibility tests were conducted on the dry powder thin-coat coating compatible with dark pigments provided by the present invention under conditions of adding ultramarine and not adding ultramarine. The results show that the dry powder thin-coat coating has good dispersibility regardless of whether pigment is added or not.

[0099] This demonstrates that using sodium dodecylbenzenesulfonate, sodium lignosulfonate, and sodium chloride together as surfactants can effectively reduce the surface activity of water. Using polycarboxylate superplasticizer and sodium polymetaphosphate together as modifiers to modify the raw materials can prevent particle agglomeration and improve the wetting of the powder particles by water, ultimately achieving the goal of dark-colored painting of interior walls. This dry powder thin-coat type coating can be applied to create dark-colored interior wall surfaces.

[0100] IV. Modified Equipment This invention, when using polycarboxylate superplasticizer and sodium polymetaphosphate together as modifiers to modify talc, calcium carbonate, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder in the basic formulation individually, also specifically designs a modification device. For example... Figure 11As shown, it includes a mixer 1, an atomizer 5, a drying tank 14, a rotary air-cooled tank 9, and a vibrating screen 11.

[0101] The atomizer 5 is connected to the mixer 1 via a liquid feed pipe 6, and is used to atomize the liquid raw materials in the dry powder thin-coat paint and add them into the mixer 1. The mixer 1 is equipped with a first fan 3, which is used to agitate the powder raw materials in the dry powder thin-coat paint before adding them into the mixer 1. The mixer 1 is internally equipped with a first stirring blade 2, which is used to stir and mix the atomized liquid raw materials with the agitated powder raw materials.

[0102] The drying tank 14 is connected to one side of the mixer 1, and is used to dry the material mixed by the mixer through stirring and friction. The rotary air-cooled tank 9 is connected to the drying tank 14, and is used to cool the material dried by the drying tank 14. The vibrating screen 11 is connected to the rotary air-cooled tank 9, and is used to screen the material cooled by the rotary air-cooled tank.

[0103] Specifically, in this embodiment, the upper part of the mixer 1 is connected to a powder feed pipe 4, the first fan 3 is located directly below the powder feed pipe 4, and the outlet of the atomizer 5 is located on the opposite side of the powder feed pipe, so that the liquid raw material atomized by the atomizer is sprayed onto the dispersed powder raw material. The drying tank 14 is connected to the mixer 1 through a premixed material discharge pipe 7, and the drying tank 14 is provided with a second stirring blade 19 and a guide block 14. The second stirring blade 19 is used to stir the material mixed by the mixer 1, so that friction between the materials and between the materials and the guide block generates heat for drying.

[0104] The rotary air-cooled tank 9 is connected to the drying tank 14 through the dry material discharge pipe 18. The rotary air-cooled tank 9 is equipped with a second fan 8, which is used to introduce cooling air into the rotary air-cooled tank 9. The inner wall of the rotary air-cooled tank 9 is equipped with a lifting plate 20 so that the material is lifted by the lifting plate when the rotary air-cooled tank rotates, and then cooled.

[0105] More specifically, when using this modification equipment for modification, the appropriate proportions of polycarboxylate superplasticizer and sodium polymetaphosphate are dissolved in water and then atomized in a mixer using an atomizer. During the atomization process, talc powder, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder are separately dispersed by airflow and added to the mixer for stirring and mixing. Then, they are conveyed to a drying tank for rotary drying, and finally conveyed to a rotary air-cooled tank for cooling and sieved by a vibrating screen to obtain modified talc powder, modified calcium powder, modified wollastonite, modified precipitated barium sulfate, modified titanium dioxide, and modified quartz powder, respectively.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A dry powder thin-coat coating compatible with dark pigments, characterized in that: By weight, it includes the following raw materials: Modified latex powder 35-45 parts, modified talc powder 10-20 parts, modified calcium powder 20-30 parts, modified wollastonite 5-10 parts, modified precipitated barium sulfate 5-15 parts, modified titanium dioxide 5-15 parts, modified quartz powder 5-10 parts, nano magnesium oxide 1-5 parts, nano zinc oxide 0.5-2 parts, leveling agent 0.5-1 part, sodium dodecylbenzene sulfonate 1.5-2.5 parts, sodium lignosulfonate 0.8-1.2 parts, sodium chloride 0.8-1.6 parts, cellulose 1-2 parts, defoamer 0.3-0.5 parts; The total mass fractions of the modified latex powder, the modified talc powder, the modified calcium powder, the modified wollastonite, the modified precipitated barium sulfate, the modified titanium dioxide, and the modified quartz powder are 100 parts. The modified latex powder is prepared by mixing lime powder, ultrafine mineral powder and latex powder in a mass ratio of (0.5-1.5):(0.5-1.5):(3-9); the modified talc powder, the modified calcium powder, the modified wollastonite, the modified precipitated barium sulfate, the modified titanium dioxide and the modified quartz powder are obtained by modifying talc powder, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide and quartz powder respectively with a modifier, wherein the modifier is composed of polycarboxylate superplasticizer and sodium polymetaphosphate in a mass ratio of 1:(3-4).

2. The dry powder thin-coat coating compatible with dark pigments according to claim 1, characterized in that: When modifying talc powder, the modifier accounts for 5% to 6% of the mass of talc powder; when modifying calcium powder, the modifier accounts for 2.8% to 3.5% of the mass of calcium powder; when modifying wollastonite, the modifier accounts for 2.8% to 3.5% of the mass of wollastonite; when modifying precipitated barium sulfate, the modifier accounts for 1% to 1.5% of the mass of precipitated barium sulfate; when modifying titanium dioxide, the modifier accounts for 3% to 3.8% of the mass of titanium dioxide; and when modifying quartz powder, the modifier accounts for 3% to 3.8% of the mass of quartz powder.

3. A dry powder thin-coat coating compatible with dark pigments according to claim 1 or 2, characterized in that: The mass ratio of sodium dodecylbenzenesulfonate, sodium lignosulfonate, and sodium chloride is (2.0–2.5): (1.0–1.2): (0.8–1.2).

4. A dry powder thin-coat coating compatible with dark pigments according to claim 3, characterized in that: The mass ratio of the ultrafine mineral powder to the latex powder is (0.8-1.2):(0.8-1.3):(6-8).

5. A dry powder thin-coat coating compatible with dark pigments according to claim 1, characterized in that: The particle size of lime powder is greater than 600 mesh, while talc, calcium powder, wollastonite, precipitated barium sulfate, titanium dioxide, and quartz powder are all powders with a particle size of 1250 mesh or larger.

6. A dry powder thin-coat coating compatible with dark pigments according to claim 1, 2, or 5, characterized in that: It also includes inorganic color powders added as admixtures during construction, wherein the inorganic color powders include at least one of iron oxide red, iron oxide green, iron oxide yellow, ultramarine, and iron oxide black.

7. A method for preparing a dry powder thin-coat coating compatible with dark pigments as described in any one of claims 1 to 6, comprising the steps of: The modified powder was prepared by mixing latex powder, lime powder and ultrafine mineral powder. Using polycarboxylate superplasticizer and sodium polymetaphosphate as modifiers, talc, calcium carbonate, wollastonite, precipitated barium sulfate, titanium dioxide and quartz powder were modified separately to obtain modified talc, modified calcium carbonate, modified wollastonite, modified precipitated barium sulfate, modified titanium dioxide and modified quartz powder respectively. Weigh and mix all raw materials and add them to a mixer. Stir for 4 to 6 minutes at a stirring speed of 1100 r / min to 1350 r / min and a stirring temperature of less than 65°C to obtain a dry powder thin-coat coating compatible with dark pigments.

8. An apparatus for preparing a dry powder thin-coat coating compatible with dark pigments as described in any one of claims 1 to 6, characterized in that: Includes mixer, atomizer, drying tank, rotary air-cooled tank and vibrating screen; The atomizer is connected to the mixer and is used to atomize the liquid raw material and add it into the mixer. The mixer is equipped with a first fan, which is used to agitate the unmodified powder raw materials with airflow before adding them into the mixer. The mixer is equipped with a first stirring blade, which is used to stir and mix the atomized liquid raw material with the dispersed powder raw material. The drying tank is connected to one side of the mixer, and the drying tank is used to dry the material after it has been mixed by the mixer through stirring and friction. The rotary air-cooled tank is connected to the drying tank, and the rotary air-cooled tank is used to cool the material after it has been dried in the drying tank; The vibrating screen is connected to the rotary air-cooled tank and is used to screen the material after it has been cooled by the rotary air-cooled tank.

9. The apparatus for preparing dry powder thin-coat coatings compatible with dark pigments according to claim 8, characterized in that: The drying tank is connected to the mixer through a premixed material discharge pipe. The drying tank is equipped with a second stirring blade and a guide block. The second stirring blade is used to stir the material after it has been mixed by the mixer, so that friction between the materials and between the materials and the guide block generates heat for drying. The rotary air-cooled tank is connected to the drying tank through a dry material discharge pipe. A second fan is installed on the rotary air-cooled tank to introduce cooling air into the rotary air-cooled tank. Lifting plates are installed on the inner wall of the rotary air-cooled tank so that the material is lifted by the lifting plates as the rotary air-cooled tank rotates, and then cooled.

10. A method for applying a dry powder thin-coat paint compatible with dark pigments, comprising the following steps: first, weighing the dry powder thin-coat paint and water according to a powder-to-water ratio of 1:(1.5-2); then, adding inorganic pigment to the weighed water and stirring evenly; finally, adding the weighed dry powder thin-coat paint and stirring for 3-5 minutes; letting it stand for 4-8 minutes; and then stirring again for 1-3 minutes before application. The inorganic pigment includes at least one of iron oxide red, iron oxide green, iron oxide yellow, ultramarine, and iron oxide black, and the mass percentage of the inorganic pigment to water is greater than or equal to 2%.

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