A single-component water-based paint dedicated to a house building container and a land transportation container and a preparation method thereof

Abstract

This invention provides a single-component waterborne coating specifically for residential and land transport containers and its preparation method. The coating comprises the following components, with the following mass percentages: 35-45 parts modified waterborne self-drying alkyd resin; 5-10 parts titanium dioxide; 0.2-0.5 parts carbon black; 10-20 parts precipitated barium sulfate; 0.4-0.8 parts dispersant; 0.3-0.6 parts wetting agent; 0.1-0.3 parts defoamer, at least part of which is added during the paint mixing stage; 0.5-1.2 parts drier; 0.5-1.0 parts flash rust inhibitor; 0.8-1.5 parts alkali-swellable rheology modifier; 5-8 parts 5% LT water-soluble agent; and 25-35 parts deionized oil. This invention effectively solves the problems of slow drying speed, insufficient initial water resistance and adhesion, and difficulty in achieving both low-temperature film formation and long-term anti-corrosion performance in existing water-based coatings for container applications by using side-chain esterification modification of long-oil water-based alkyd resin with a specific structure, optimizing the additive system and combining it with a refined preparation process.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a single-component waterborne coating specifically for residential and land transport containers and its preparation method. Background Technology

[0002] With increasingly stringent environmental policies and the promotion of green manufacturing concepts, water-based coatings have been widely used in the construction and transportation of shipping containers due to their advantages such as low VOC emissions and environmental friendliness. Traditional solvent-based coatings are gradually being replaced by single-component water-based coatings, especially in applications requiring rapid application and efficient turnover, which places higher demands on the drying speed, application performance, and initial durability of the coatings. Currently, most mainstream water-based coatings on the market are based on acrylic or conventional alkyd systems, which, while possessing certain environmental advantages, still face many challenges in practical applications.

[0003] Existing water-based single-component coatings for containers generally suffer from slow drying rates, leading to coatings being used or stacked before they are fully dry. This can easily cause defects such as blistering and peeling of the paint film, severely affecting initial water resistance and corrosion protection. At the same time, since container bodies use a large amount of silicone sealant to seal joints, ordinary water-based coatings have poor wetting and spreading ability against such materials, making them prone to surface defects such as pinholes and oil pits. This results in decreased adhesion and the risk of localized corrosion, limiting the improvement of overall protective performance.

[0004] Furthermore, to meet the demands of rapid on-site turnover, coatings must possess both fast drying at room temperature and stable film formation at low temperatures. However, existing products are prone to brittleness at low temperatures, leading to film cracking or deterioration of adhesion. Moreover, their long-term salt spray resistance is insufficient, making it difficult to meet the long-term protection requirements of containers in complex transportation and outdoor storage environments. Therefore, there is an urgent need to develop a novel waterborne coating system that combines rapid drying, excellent wetting properties, strong initial resistance, and good adhesion to multiple substrates to overcome current technological bottlenecks.

[0005] The purpose of this invention is to solve the problems of slow drying speed, poor wetting of silicone sealants leading to pinholes, insufficient initial water resistance and adhesion, and difficulty in achieving both low-temperature film formation and long-term anti-corrosion performance in existing water-based coatings used in container applications. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of slow drying speed, poor wetting of silicone sealants leading to pinholes, insufficient initial water resistance and adhesion, and difficulty in simultaneously achieving low-temperature film formation and long-term corrosion protection in existing water-based coatings used in container applications. The invention adopts the following technical solution: A single-component waterborne coating specifically designed for residential and land transport containers, wherein the waterborne coating comprises at least the following components, and the mass percentage ranges of each component are as follows: 35-45 parts of modified waterborne self-drying alkyd resin; 5-10 parts of titanium dioxide; Carbon black 0.2-0.5 parts; Precipitate 10-20 parts of barium sulfate; Dispersant 0.4–0.8 parts; Wetting agent 0.3-0.6 parts; 0.1 to 0.3 parts of defoamer, at least part of which is added during the paint mixing stage; 0.5–1.2 parts of drying agent; Anti-flash rust agent 0.5-1.0 parts; 0.8–1.5 parts of alkali-swellable rheology modifier; 5-8 parts of 5% LT aqueous solution; 25-35 parts deionized water.

[0007] The above-mentioned single-component waterborne coating specifically for residential and land transport containers comprises 38 parts of modified waterborne self-drying alkyd resin, 15 parts of precipitated barium sulfate, 1 part of alkali-swellable rheology modifier, 0.3 parts of defoamer (added in two parts, with 0.1 parts added during the grinding stage and 0.2 parts added during the paint mixing stage), 0.8 parts of anti-flash rust agent, 6 parts of 5% LT aqueous solution, and 29 parts of deionized water.

[0008] The above-mentioned single-component waterborne coating specifically for residential and land transport containers, wherein the wetting agent is a polyether-modified polysiloxane wetting agent, and the alkali-swellable rheology modifier is a hydrophobic-modified alkali-swellable acrylic emulsion.

[0009] As described above, a single-component waterborne coating specifically for residential and land transport containers, wherein the drier is a zirconium-based or cobalt-based drier, the dispersant is an anionic polymeric dispersant, and the defoamer is a mineral oil-based defoamer and / or a polyether-modified siloxane-based defoamer.

[0010] As described above, a single-component waterborne coating specifically for residential and land transport containers, wherein the modified waterborne self-drying alkyd resin is a long-oil alkyd resin in which some carboxyl groups on the side chain are esterified by C1–C4 lower alkyl groups, with an oil content of 60%–70%, a number-average molecular weight of 8000–12000, an acid value of 30–50 mgKOH / g, and a glass transition temperature Tg of -15℃ to -5℃.

[0011] A method for preparing a single-component waterborne coating specifically for residential and land transport containers, as described above, comprising the following steps: S1. Pulping stage: Add 6 parts deionized water, 6 parts 5% LT aqueous solution, dispersant, 30% to 50% of the total amount of defoamer, titanium dioxide, carbon black and precipitated barium sulfate into a dispersion vessel, disperse at 600 to 800 rpm for 20 to 30 minutes, and grind until the fineness is ≤30μm to obtain a uniform and stable pigment and filler slurry; S2. Paint preparation stage: Add the modified waterborne self-drying alkyd resin to the paint mixing tank, and slowly add the slurry obtained in S1 while stirring at 400-600 rpm. After mixing evenly, add the wetting agent, flash rust inhibitor, drying agent and alkali-swellable rheology modifier in sequence, and continue stirring for 15-25 minutes. S3. Adjustment and filtration: Add the remaining deionized water to a total volume of 25-35 parts, adjust the viscosity of the system to 80-100 KU (25°C, Stormer viscometer), add the remaining defoamer, stir at 200-300 rpm for 10 minutes to eliminate bubbles, and finally filter through a 180-200 mesh filter to obtain the single-component water-based coating.

[0012] As described above, the preparation method of a single-component waterborne coating specifically for residential and land transport containers involves the following steps in the S1 grinding stage: First, 6 parts of deionized water and 6 parts of 5% LT aqueous solution are added to the dispersion vessel for pre-stirring. Then, dispersant, 30%–50% of the total amount of defoamer, titanium dioxide, carbon black, and precipitated barium sulfate are added sequentially. After each solid raw material is added, the stirring speed is maintained at 600 rpm for 3 minutes until the material is initially wetted before adding the next material. After all materials are added, the speed is increased to 800 rpm for high-speed dispersion for 25 minutes, and the fineness of the slurry is tested using a scraper fineness meter. If the fineness does not meet the requirement of not more than 30 μm, the dispersion time is extended until it is qualified.

[0013] As described above, a method for preparing a single-component waterborne coating specifically for residential and land transport containers involves the following steps in the S2 paint mixing stage: After the modified waterborne self-drying alkyd resin is added to the mixing tank, it is first stirred at 400 rpm for 2 minutes to form a stable liquid flow. Then, the pigment and filler slurry obtained in S1 is added in batches at a uniform speed over 15 minutes. During the addition process, the stirring speed is maintained between 400 and 600 rpm to avoid excessively high local concentrations or the formation of eddies that introduce too much air. After all the slurry is added, stirring continues for 10 minutes to fully wet and fuse the resin with the slurry. Then, wetting agent, flash rust inhibitor, drying agent, and alkali-swellable rheology modifier are added sequentially. Each modifier is added slowly along the container wall, and after each addition, stirring is maintained at 500 rpm for 5 minutes to ensure that the components are evenly dispersed and no air bubbles are introduced. After all the modifiers are added, the stirring time is extended to no less than 20 minutes to obtain a uniform coating system with high stability, no particles, and no floating color.

[0014] As described above, the preparation method of a single-component waterborne coating specifically for residential and land transport containers involves the following steps in the S3 adjustment and filtration stage: When adding remaining deionized water, it is added in small, multiple batches, with each addition not exceeding one-third of the total remaining water volume. After each addition, the mixture is stirred at 400 rpm for 3 minutes until the system is homogeneous before the next addition, continuing until the viscosity approaches the target range. Then, the stirring speed is reduced to 200 rpm, and the remaining 30%–40% of the defoamer is added, followed by continuous low-speed stirring for at least 10 minutes. During this time, the vessel wall is gently scraped with a scraper to eliminate any adhering air bubbles. After viscosity adjustment, a Stormer viscometer is used to measure the viscosity three times continuously at a constant temperature of 25°C, and the average value is taken to confirm that the viscosity is stable between 80 and 100 KU. Finally, the coating is discharged through a two-stage filtration system connected in series: the first stage is a 180-mesh stainless steel filter, and the second stage is a 200-mesh nylon filter bag, ensuring that the resulting coating is uniform, stable, and free of mechanical impurities, meeting the construction requirements of automated container spraying systems.

[0015] Implementing the embodiments of the present invention has the following beneficial effects: This invention effectively solves the problems of slow drying speed, insufficient initial water resistance and adhesion, and difficulty in achieving both low-temperature film formation and long-term anti-corrosion performance in existing water-based coatings for container applications by using side-chain esterification modification of long-oil water-based alkyd resin with a specific structure, optimizing the additive system, and combining with a refined preparation process. The prepared coating has fast drying, excellent substrate wetting and leveling ability, dense film and excellent adhesion, and also has good flash rust resistance, freeze-thaw stability and storage stability. Detailed Implementation

[0016] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0017]

[0018] Example 1: Preparation process steps S1. Pulping stage (pre-dispersion of pigments and fillers) Add 6 parts of deionized water and 6 parts of 5% LT aqueous solution to a 50L stainless steel dispersion vessel and stir at low speed of 400 rpm for 1 minute to form a stable liquid surface; Invest in sequence: Dispersant (0.6 parts) 60% (i.e., 0.18 parts) of the defoamer. Titanium dioxide (8 parts) Carbon black (0.3 parts) Precipitated barium sulfate (15 parts) After each solid ingredient is added, stir at 600 rpm for 3 minutes to ensure that the material is fully wetted and to prevent dust from flying or clumping. After all materials have been added, increase the rotation speed to 800 rpm and disperse at high speed for 25 minutes; The fineness of the slurry was measured using a scraper fineness meter, and the result was 28 μm (≤30 μm). Grinding was then stopped, and a uniform and stable pigment and filler slurry was obtained.

[0019] S2. Paint formulation stage (resin mixing and additive addition) 38 portions of modified waterborne self-drying alkyd resin were transferred to a paint mixing tank and stirred at 400 rpm for 2 minutes to form a stable liquid flow. Add the slurry obtained from S1 at a uniform speed and in batches within 15 minutes. During the addition process, maintain the stirring speed between 400 and 600 rpm to prevent local concentration from being too high or to generate eddies that entrain air. After all the slurry is added, continue stirring for 10 minutes to fully integrate the resin with the pigment and filler system; Slowly add the following additives along the wall of the vessel in sequence, stirring at 500 rpm for 5 minutes after each addition: Wetting agent (0.45 parts) Anti-flash rust agent (0.8 parts) Drying agent (0.9 parts) Alkali-swellable rheology modifier (1.0 part) After all the additives have been added, continue stirring for at least 20 minutes and observe the state of the paint film. It should be free of particles and floating color, have good fluidity, and form a uniform and stable paint base.

[0020] S3. Adjustment and Filtration Stage (Viscosity Control and Discharge) Add the remaining 17 parts of deionized water (total deionized water 29 parts, 6 parts already used), in three additions of approximately 5.7 parts each time. Stir at 400 rpm for 3 minutes after each addition, and wait until the system is homogeneous before adding the next part. When the viscosity is close to the target range, reduce the stirring speed to 200 rpm, add the remaining 40% of the defoamer (0.12 parts), and continue stirring at low speed for 12 minutes, during which time use a spatula to gently scrape off the tiny air bubbles adhering to the vessel wall. Viscosity was measured using a Stormer viscometer in a constant temperature environment of 25°C, and the reading was 88 KU, which falls within the target range of 80 to 100 KU. The finished coating is discharged through a two-stage filtration system in series: First stage: 180 mesh stainless steel filter screen, to remove coarse particles, scale and fibrous impurities; Second stage: 200 mesh nylon filter bag to intercept fine gel particles and incompletely dispersed additive agglomerates; The filtered coating is milky white, has good fluidity, and is free of visible impurities. It is then stored in a sealed container for later use.

[0021] Example 2:

[0022] Preparation process steps S1. Pulping Stage (Preparation of High-Stability Pigment and Filler Pulp) Add 7 parts of deionized water and 7 parts of 5% LT aqueous solution to the dispersion vessel and pre-stir at 400 rpm for 1 minute; Add them in sequence: Dispersant (0.7 parts) 65% (i.e., 0.1625 parts) of the defoamer. Titanium dioxide (9 parts) Carbon black (0.4 parts) Precipitated barium sulfate (18 parts) After adding each solid ingredient, stir at 600 rpm for 3 minutes to ensure thorough wetting and prevent carbon black from agglomerating or titanium dioxide from floating. After all materials have been added, increase the speed to 800 rpm and disperse for 30 minutes. The fineness of the slurry was tested using a scraper fineness meter, and the result was 25 μm (≤30 μm). Grinding was then stopped, and a stable slurry with high solids content and low flocculation was obtained.

[0023] S2. Coating stage (resin blending and introduction of functional additives) 42 parts of modified waterborne self-drying alkyd resin were added to the paint mixing tank and stirred at 400 rpm for 2 minutes to form a stable liquid flow. Add the slurry obtained from S1 in batches at a uniform speed within 15 minutes, while maintaining the stirring speed between 400 and 600 rpm to prevent the eddy from carrying in air bubbles. After adding the slurry, continue stirring for 10 minutes to ensure that the resin fully coats the pigments and fillers. Slowly add the following additives along the container wall in sequence, stirring at 500 rpm for 5 minutes after each addition: Wetting agent (0.5 parts) Anti-flash rust agent (0.9 parts) Drying agent (0.6 parts zirconium-based + 0.3 parts cobalt-based) Alkali-swellable rheology modifier (1.2 parts) After all the additives were added, the stirring time was extended to 22 minutes. The paint film was observed to have no floating color or particles, the system was uniform, and the fluidity was good.

[0024] S3. Adjustment and filtration stage (precise viscosity control and clean discharge) Add the remaining 23 parts of deionized water (out of a total of 30 parts, 7 parts have already been used), using a three-stage equal-volume addition method (approximately 7.67 parts each time). After each addition, stir at 400 rpm for 3 minutes to ensure a smooth viscosity transition. When the viscosity is close to the target range, reduce the speed to 200 rpm, add the remaining 35% of defoamer (0.0875 parts), and continue stirring at low speed for 12 minutes, during which time use a scraper to gently scrape the vessel wall to release attached air bubbles; Viscosity was measured using a Stormer viscometer in a constant temperature environment of 25℃, and the reading was 92 KU, which meets the 80-100 KU construction window. The finished coating is discharged through a two-stage filtration system in series: First stage: 180-mesh stainless steel filter screen to remove coarse impurities; Second stage: 200-mesh nylon filter bag to intercept fine gel particles; The discharged coating is milky white, free of mechanical impurities, and should be stored in a light-proof, sealed container.

[0025] Example 3:

[0026] Preparation process steps S1. Pulping Stage (Preparation of Low-Temperature Adaptable Pigment and Filler Pulp) Add 8 parts of deionized water and 6 parts of 5% LT aqueous solution to the dispersion vessel and pre-stir at 400 rpm for 1 minute; Add them in sequence: Dispersant (0.5 parts) 70% (i.e., 0.196 parts) of the defoamer. Titanium dioxide (7 parts) Carbon black (0.3 parts) Precipitated barium sulfate (12 parts) After adding each solid ingredient, maintain stirring at 600 rpm for 3 minutes to ensure thorough wetting; After all materials have been added, increase the speed to 800 rpm and disperse for 28 minutes. The fineness of the slurry was tested using a scraper fineness meter, and the result was 27 μm (≤30 μm), resulting in a uniform and stable low-temperature applicable pigment and filler slurry.

[0027] S2. Paint Mixing Stage Add 40 parts of modified waterborne self-drying alkyd resin to the paint mixing tank and stir at 400 rpm for 2 minutes to form a stable liquid flow; Add the slurry obtained from S1 in batches at a uniform speed within 15 minutes, while maintaining the stirring speed between 400 and 600 rpm to avoid air entrainment. After adding the slurry, continue stirring for 10 minutes to ensure that the resin and pigments / fillers are fully mixed. Slowly add the following additives along the container wall in sequence, stirring at 500 rpm for 5 minutes after each addition: Wetting agent (0.4 parts) Anti-flash rust agent (0.9 parts) Drying agent (0.7 parts zirconium + 0.3 parts zinc) Alkali-swellable rheology modifier (1.1 parts) After all the additives have been added, continue stirring for at least 25 minutes and observe the paint film condition: good fluidity, no floating color, no particles, and the system is uniform and stable.

[0028] S3. Adjustment and Filtering Stage (Adaptability Control for Low-Temperature Construction) Add the remaining 22 parts of deionized water (out of a total of 30 parts, 8 parts have already been used), using a three-stage equal-volume addition method (approximately 7.33 parts each time). After each addition, stir at 400 rpm for 3 minutes to gradually adjust the viscosity. When the viscosity is close to the target range, reduce the speed to 200 rpm, add the remaining 30% of the defoamer (0.084 parts), and continue stirring at low speed for 12 minutes, during which time use a scraper to gently scrape the vessel wall to release any attached air bubbles. Viscosity was measured using a Stormer viscometer in a constant temperature environment of 25°C, and the reading was 86 KU, falling within the 80-100 KU construction window; The finished coating is discharged through a two-stage filtration system in series: First stage: 180 mesh stainless steel filter Second stage: 200-mesh nylon filter bag The discharged coating is milky white, has good fluidity, and is free of impurities. It is then stored in a light-proof, sealed container for later use.

[0029] Comparative Example 1 The differences between this comparative example and Example 1 are as follows: The process of adding water in stages and adding defoamer in multiple stages was not adopted. Specifically, all 35 parts of water (including 29 parts of deionized water and 6 parts of 5% LT aqueous solution) were added at once during the slurry grinding stage, and the total amount of defoamer was also added at once. The order of material addition was not controlled; all pigments, fillers, and additives were added to the dispersion vessel at once and dispersed at high speed for 30 minutes. During the paint preparation stage, the slurry was not added in batches, nor were functional additives added one by one. During the adjustment stage, viscosity was not adjusted step by step, no additional defoamer was added, and only a single-stage 100-mesh filter was used for filtration. The composition and proportions of all other raw materials were the same as in Example 1.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that the long-oil-content modified waterborne alkyd resin (oil content 60%–70%, molecular weight 8000–12000, acid value 30–50 mgKOH / g, Tg -15℃ to -5℃) with C1–C4 alkyl esterification of the side chain carboxyl group was not used. Instead, a conventional unesterified waterborne alkyd resin with an oil content of 50%, a number-average molecular weight of 6000, an acid value of 65 mgKOH / g, and a glass transition temperature (Tg) of 5℃ was used. The remaining raw material composition, proportions, and preparation process are the same as in Example 1.

[0031] Comparative Example 3 The difference between this comparative example and Example 1 is that: instead of using an alkali-swellable rheology modifier, a conventional polyurethane associative thickener was used; and instead of a polyether-modified polysiloxane wetting agent, a traditional sodium dodecyl sulfate (SDS) anionic surfactant was used. The remaining raw material composition, proportions, and preparation process are the same as in Example 1.

[0032] All samples were sprayed onto sandblasted steel plates (Sa 2.5 grade), with the dry film thickness controlled at 45±5 μm. The test environment was 25℃ and RH 50%, and some low-temperature performance was tested under simulated conditions.

[0033] Performance Comparison Test Results Table

[0034] In summary, this invention solves the problems of slow drying speed, poor wetting of silicone sealants leading to pinholes, insufficient initial water resistance and adhesion, and difficulty in achieving both low-temperature film formation and long-term anti-corrosion performance in existing water-based coatings used in container applications.

[0035] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A single-component water-based coating specifically for residential and land transport containers, characterized in that, The water-based coating comprises at least the following components, with the following mass percentage ranges for each component: 35-45 parts of modified waterborne self-drying alkyd resin; 5-10 parts of titanium dioxide; Carbon black 0.2-0.5 parts; Precipitate 10-20 parts of barium sulfate; Dispersant 0.4–0.8 parts; Wetting agent 0.3-0.6 parts; 0.1 to 0.3 parts of defoamer, at least part of which is added during the paint mixing stage; 0.5–1.2 parts of drying agent; Anti-flash rust agent 0.5-1.0 parts; 0.8–1.5 parts of alkali-swellable rheology modifier; 5-8 parts of 5% LT aqueous solution; 25-35 parts deionized water.

2. The single-component water-based coating for residential and land transport containers according to claim 1, characterized in that, The modified waterborne self-drying alkyd resin consists of 38 parts, precipitated barium sulfate consists of 15 parts, alkali-swellable rheology modifier consists of 1 part, defoamer consists of 0.3 parts in total and is added in two parts, of which 0.1 parts are added during the grinding stage and 0.2 parts are added during the paint preparation stage, flash rust inhibitor consists of 0.8 parts, 5% LT aqueous solution consists of 6 parts, and deionized water consists of 29 parts.

3. A single-component water-based coating specifically for residential and land transport containers according to claim 1, characterized in that, The wetting agent is a polyether-modified polysiloxane wetting agent, and the alkali-swellable rheology modifier is a hydrophobic-modified alkali-swellable acrylic emulsion.

4. A single-component water-based coating specifically for residential and land transport containers according to claim 1, characterized in that, The drying agent is a zirconium-based or cobalt-based drying agent, the dispersant is an anionic polymeric dispersant, and the defoamer is a mineral oil-based defoamer and / or a polyether-modified siloxane-based defoamer.

5. A single-component water-based coating for residential and land transport containers according to claim 1, characterized in that, The modified waterborne self-drying alkyd resin is a long-oil alkyd resin in which some of the carboxyl groups on the side chain are esterified by C1–C4 lower alkyl groups, with an oil content of 60%–70%, a number-average molecular weight of 8000–12000, an acid value of 30–50 mgKOH / g, and a glass transition temperature Tg of -15℃ to -5℃.

6. A method for preparing a single-component waterborne coating specifically for residential and land transport containers according to any one of claims 1 to 5, characterized in that, The preparation method of the coating includes the following steps: S1. Pulping stage: Add 6 parts deionized water, 6 parts 5% LT aqueous solution, dispersant, 30% to 50% of the total amount of defoamer, titanium dioxide, carbon black and precipitated barium sulfate into a dispersion vessel, disperse at 600 to 800 rpm for 20 to 30 minutes, and grind until the fineness is ≤30μm to obtain a uniform and stable pigment and filler slurry; S2. Paint preparation stage: Add the modified waterborne self-drying alkyd resin to the paint mixing tank, and slowly add the slurry obtained in S1 while stirring at 400-600 rpm. After mixing evenly, add the wetting agent, flash rust inhibitor, drying agent and alkali-swellable rheology modifier in sequence, and continue stirring for 15-25 minutes. S3. Adjustment and filtration: Add the remaining deionized water to a total volume of 25-35 parts, adjust the viscosity of the system to 80-100 KU (25°C, Stormer viscometer), add the remaining defoamer, stir at 200-300 rpm for 10 minutes to eliminate bubbles, and finally filter through a 180-200 mesh filter to obtain the single-component water-based coating.

7. A method for preparing a single-component waterborne coating specifically for residential and land transport containers according to claim 6, characterized in that, In the S1 grinding stage, the feeding sequence is as follows: First, add 6 parts of deionized water and 6 parts of 5% LT aqueous solution to the dispersion tank for pre-stirring. Then, add dispersant, 30% to 50% of the total amount of defoamer, titanium dioxide, carbon black, and precipitated barium sulfate in sequence. After each solid raw material is added, maintain a stirring speed of 600 rpm for 3 minutes. After the material is initially wetted, continue to add the next material. After all materials are added, increase the speed to 800 rpm for high-speed dispersion for 25 minutes. Use a scraper fineness meter to check the fineness of the slurry. If it does not meet the requirement of not more than 30 μm, extend the dispersion time until it is qualified.

8. A method for preparing a single-component waterborne coating specifically for residential and land transport containers according to claim 6, characterized in that, In the S2 paint preparation stage, after the modified waterborne self-drying alkyd resin is added to the paint mixing tank, it is first stirred at 400 rpm for 2 minutes to form a stable liquid flow. Then, the pigment and filler slurry obtained in S1 is added in batches at a uniform speed over 15 minutes. During the addition process, the stirring speed is maintained between 400 and 600 rpm to avoid excessive local concentration or the formation of eddies that introduce too much air. After all the slurry is added, stirring is continued for 10 minutes to fully wet and blend the resin with the slurry. Then, wetting agent, flash rust inhibitor, drying agent, and alkali-swellable rheology modifier are added in sequence. Each modifier is added slowly along the container wall, and after each addition, stirring is maintained at 500 rpm for 5 minutes to ensure that the components are evenly dispersed and no air bubbles are introduced. After all the modifiers are added, the stirring time is extended to no less than 20 minutes to obtain a uniform coating system with high stability, no particles, and no floating color.

9. A method for preparing a single-component waterborne coating specifically for residential and land transport containers according to claim 6, characterized in that, During the S3 adjustment and filtration stage, the remaining deionized water is added in small, multiple batches, with each addition not exceeding one-third of the total remaining water volume. After each addition, the mixture is stirred at 400 rpm for 3 minutes until the system is homogeneous before the next addition, continuing until the viscosity approaches the target range. Subsequently, the stirring speed is reduced to 200 rpm, and the remaining 30%–40% of the defoamer is added. The mixture is then stirred at low speed for at least 10 minutes, during which time the vessel wall is gently scraped with a scraper to eliminate any adhering air bubbles. After viscosity adjustment, the viscosity is measured three times consecutively using a Stormer viscometer at a constant temperature of 25°C, and the average value is taken to confirm that the viscosity is stable between 80 and 100 KU. Finally, the coating is discharged through a two-stage filtration system connected in series. The first stage is a 180-mesh stainless steel filter screen, and the second stage is a 200-mesh nylon filter bag, ensuring that the resulting coating is uniform, stable, and free of mechanical impurities, meeting the construction requirements of the container automated spraying system.

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