Rare earth antibacterial color-coated sheet and preparation process thereof

Abstract

The rare earth antibacterial color-coated sheet comprises a coating sheet, passivation layers formed through passivation treatment are arranged on the upper surface layer and the lower surface layer of the coating sheet, paint surface layers are arranged outside the passivation layers, each paint surface layer comprises a primer layer and a finish paint layer, each finish paint layer comprises 0.1%-5% of a rare earth antibacterial agent, and the rare earth antibacterial agent is a rare earth antibacterial agent. The rare earth antibacterial agent comprises 20%-40% of a composite rare earth compound, 15%-25% of an auxiliary antibacterial agent, 2%-5% of a surfactant, 3%-8% of a dispersing agent, 30%-50% of silicon dioxide micro powder and 1%-3% of an organic silane coupling agent; the composite rare earth compound is formed by combining cerium oxide, lanthanum oxide and yttrium nitrate according to the weight ratio of 2: 1.5: 1. The process is simple, the antibacterial effect is long-acting and lasting, and the particle size of the rare earth antibacterial agent is accurately controlled, so that the influence on the color of the coating is reduced, and the antibacterial performance and the antibacterial durability are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of color-coated steel sheet technology, specifically to a rare earth antibacterial color-coated steel sheet and its preparation process. Background Technology

[0002] Color-coated steel sheets combine the mechanical strength and easy formability of steel sheets with the excellent decorative properties and corrosion resistance of coating materials. They are also lightweight and easy to install, making them widely used in the construction, decoration, and renovation industries. As people's requirements for building decoration materials continue to increase, some color-coated steel sheets with multiple functions such as antibacterial, sound insulation, and heat insulation have also appeared on the market.

[0003] For antibacterial color-coated steel sheets, current manufacturing processes mostly involve spraying antibacterial coatings onto finished color-coated steel sheets to form the final product. For example, Chinese invention patent application CN119875464A discloses an antibacterial and environmentally friendly color-coated steel sheet and its manufacturing process. This includes a metal substrate with a passivation layer on its surface. The passivation layer is coated with an antibacterial coating, which uses modified epoxy resin as a base material, doped with nano-silver particles and natural antibacterial plant extracts, and combined with specific proportions of colored pigments and additives. The coating is then cured at high temperature to form the color-coated steel sheet. This color-coated steel sheet improves its antibacterial properties by introducing antibacterial materials (nano-silver particles + natural antibacterial plant extracts) and enhances the adhesion and weather resistance of the coating through modified epoxy resin, thus solving the problem of antibacterial durability while also meeting environmental protection requirements.

[0004] However, the aforementioned color-coated steel sheets still have shortcomings. First, when coating the base material with paint to make the color-coated steel sheet, the paint needs to be cured at a high temperature of 300-400℃. At this temperature, the antibacterial activity of natural antibacterial plant extracts cannot be guaranteed, and the nano-silver particles will change color, causing the color-coated steel sheet to yellow and affecting the surface quality. Silver ion antibacterial agents can migrate to the surface of the sheet in normal environments and continuously release to maintain antibacterial activity; however, in high-humidity and high-temperature environments such as hospitals in southern China, coupled with high-frequency wiping, the ion migration rate increases significantly, which may cause silver ion dissolution. This results in excellent initial antibacterial effect of the color-coated steel sheet, but decreased long-term antibacterial durability, making it difficult to meet the needs of medical environments for long-term protection. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the background technology and to provide a rare earth antibacterial color-coated plate and its preparation process that is simple in structure and process, has both aesthetic appeal and antibacterial properties, and has a long-lasting antibacterial effect, specifically for special high humidity and heat environments.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A rare earth antibacterial color-coated steel sheet includes a plated sheet. The upper and lower surfaces of the plated sheet are provided with passivation layers formed through a passivation treatment. A paint layer is provided outside the passivation layers. The paint layer includes a primer layer and a topcoat layer. The topcoat layer contains 0.1%-5% of a rare earth antibacterial agent. The rare earth antibacterial agent includes 20%-40% of a composite rare earth compound, 15%-25% of an auxiliary antibacterial agent, 2%-5% of a surfactant, 3%-8% of a dispersant, 30%-50% of silica micropowder, and 1%-3% of an organosilane coupling agent. The composite rare earth compound is a combination of cerium oxide, lanthanum oxide, and yttrium nitrate in a ratio of 2:1.5:1. The auxiliary antibacterial agent is nano zinc oxide; the particle size of the rare earth antibacterial agent is 5~30μm.

[0007] The antibacterial layer of the antibacterial color-coated steel sheet of this invention contains a rare earth antibacterial agent composed of a combination of various rare earth compounds, cerium oxide, lanthanum oxide, and yttrium nitrate, in a ratio of 2:1.5:1, further compounded with nano-level auxiliary antibacterial agent, nano-zinc oxide, and combined with specific dispersants and anti-agglomeration aids. This mixture is uniformly dispersed within the film-forming epoxy resin system of the antibacterial layer, giving the color-coated steel sheet highly efficient and long-lasting antibacterial capabilities, effectively inhibiting bacterial growth. It is generally believed that the more antibacterial agent added, the better the antibacterial effect of the color-coated steel sheet. However, researchers have discovered that with the addition of antibacterial agents, the antibacterial powder tends to agglomerate. Compared to antibacterial agents with agglomerated particles, the overall specific surface area of ​​the uniformly dispersed antibacterial agent is much larger in the dispersed state, resulting in a significantly better antibacterial effect. Furthermore, agglomerated antibacterial agents cause particle spots to appear on the steel sheet surface, compromising the sheet's surface quality. Meanwhile, if the particle size is too large (e.g., greater than 30μm), the large particles of rare earth antibacterial agent may cause particle defects on the surface of the color-coated steel sheet, ultimately leading to roller jamming or longitudinal stripes during the coating process. If the particle size is too small (e.g., less than 5μm), the rare earth antibacterial powder has a large surface energy and is very prone to agglomeration (especially for nano-level coatings). This invention, by controlling the appropriate addition amount (0.1-5%) and the appropriate particle size (5-30μm) of rare earth antibacterial agent, effectively avoids surface defects and coating problems caused by excessively large or small particle sizes in color-coated steel sheets, improving the quality and appearance smoothness of the sheets. Agglomeration can still lead to surface particle defects, potentially causing roller jamming or longitudinal stripes during the coating process. Compared to silver ions as an antibacterial agent, color-coated steel sheets using rare earth materials as antibacterial agents can also improve the discoloration problem caused by silver ions, enhancing appearance quality and durability.

[0008] This application also found that when rare earth compounds are used as antibacterial agents, the antibacterial durability of color-coated steel sheets is significantly improved. This may be because the suitable particle size of rare earth antibacterial agents is compatible with the slight depressions on the surface of the metal substrate. This gives the rare earth antibacterial agents and the metal substrate a better bonding strength and structural density (possibly due to physical anchoring). For some special working conditions in the high humidity and heat of southern regions, this structure breaks through the durability bottleneck of the silver ion system and significantly reduces the dissolution efficiency of antibacterial agents (antibacterial active ingredients), providing a key guarantee for the long-term antibacterial performance of the material.

[0009] The surfactant is one or more of sodium dodecylbenzenesulfonate, Tween-80, fatty acid polyoxyethylene ester, and hexadecyltrimethylammonium bromide, preferably sodium dodecylbenzenesulfonate.

[0010] By adopting the above technical solution and introducing surfactants, the surface energy of rare earth compound particles is effectively reduced, preventing the agglomeration of these particles. On the one hand, this helps the rare earth antibacterial agent to be uniformly dispersed in coating systems. On the other hand, compared to agglomerated rare earth antibacterial agents, the overall specific surface area of ​​the unagglomerated rare earth antibacterial agent is significantly increased, thus greatly improving the antibacterial effect of the color-coated steel sheet. Furthermore, the uniformly dispersed rare earth antibacterial agent can bind uniformly to the substrate, further reducing the loss rate of the rare earth antibacterial coating and further ensuring the long-lasting antibacterial performance of the color-coated steel sheet.

[0011] The dispersant is one or a mixture of sodium polycarboxylate, polyvinylpyrrolidone, sodium polyacrylate, and sodium lignosulfonate.

[0012] The dispersant is a mixture of sodium polycarboxylate, polyvinylpyrrolidone, and sodium lignosulfonate in a mass ratio of 1:1:1. This effectively prevents rare earth particles from agglomerating and improves the dispersion effect.

[0013] The organosilane coupling agent is γ-aminopropyltriethoxysilane. Through modification with the coupling agent, organic functional groups are formed on the silica surface, enhancing compatibility with film-forming substances such as epoxy resins. This prevents rare earth antibacterial agents from agglomerating due to excessively high surface energy. The uniformly dispersed rare earth particles are in a "monodispersed state" in the coating, reducing interference with the consistency of light reflection and ensuring freedom in color design.

[0014] The thickness of the coated plate is 0.3-1.2 mm, and the thickness of the paint layer is 10-50 μm. The structure of each layer of the color-coated plate is further defined.

[0015] This invention also discloses a preparation process for a rare earth antibacterial color-coated steel sheet, comprising: a passivation layer formed by passivation treatment is disposed on the upper and lower surfaces of the coated steel sheet; a paint layer is disposed outside the passivation layer; the paint layer includes a primer layer and a topcoat layer; characterized in that a rare earth antibacterial agent is added during the processing of the topcoat layer, and the rare earth antibacterial agent is prepared by the following steps: (1) Raw material pretreatment: Cerium oxide and lanthanum oxide are ground to a particle size ≤10μm, yttrium nitrate is dried and ground to fine powder, and silica micro powder is calcined at 500-600℃ for 3-4 hours; Coupling agent modification: Calcinated silica micro powder is reacted with γ-aminopropyltriethoxysilane ethanol solution at 50-60℃ for 2-3 hours, and then dried after centrifugation and washing to obtain modified silica. (2) The pretreated rare earth compounds, nano zinc oxide, dispersant, and modified silica are stirred at high speed in deionized water at a speed of 800-1200 r / min for 30-60 minutes to form a uniform slurry; (3) Spray drying and sieving: The slurry is spray dried at an inlet air temperature of 180-200℃ and an outlet air temperature of 80-100℃. The resulting powder is sieved to obtain a rare earth antibacterial agent with a target particle size of 5-30μm.

[0016] The antibacterial color-coated steel sheet preparation process provided by this invention involves adding a rare earth antibacterial agent to the topcoat layer, resulting in superior antibacterial properties on the surface of the color-coated steel sheet. Precise control of the rare earth antibacterial agent particle size reduces its impact on the coating color and ensures optimal antibacterial performance.

[0017] This invention constructs a complete technical solution around antibacterial color-coated steel sheets, and from the aspects of product structure, antibacterial agents, and preparation process, it produces the following beneficial effects: By using rare earth antibacterial agents (cerium oxide: lanthanum oxide: yttrium nitrate = 2:1.5:1) in synergy with nano zinc oxide, and limiting the particle size to 5–30 μm and the addition amount to 0.1–5%, combined with a dispersion / anti-agglomeration system, the antibacterial agent achieves high dispersion and high specific surface area, ensuring long-lasting and efficient antibacterial effect while avoiding surface defects and coating roller jamming and streaks caused by particle agglomeration. Rare earth antibacterial agents with precisely matched particle size to the micro-concave substrate form a physically anchored dense layer, which significantly inhibits the dissolution of active components under high humidity and heat conditions, breaks through the durability bottleneck of silver ion system, and endows color-coated steel sheets with long-lasting antibacterial properties to meet the appropriate requirements of special working conditions. Through physical mixing and coupling agent modification, rare earth antibacterial components are uniformly loaded onto the silica surface, forming a core-shell structure. This structure disperses the concentration of the rare earth white powder, avoiding abrupt color changes caused by local aggregation. At the same time, the high hiding power of silica weakens the color influence of the rare earth itself. Through coupling agent modification, organic functional groups are formed on the silica surface, enhancing compatibility with film-forming materials such as epoxy resin. This prevents the rare earth antibacterial agent from agglomerating due to excessively high surface energy. The uniformly dispersed rare earth particles are in a "monodispersed state" in the coating, reducing interference with the consistency of light reflection and ensuring freedom in color design.

[0018] This invention defines the preparation process of rare earth antibacterial agents. Through steps such as raw material pretreatment, coupling agent modification, mixing and dispersion, spray drying, and sieving, the particle size of the rare earth antibacterial agent is precisely controlled within 5-30 μm. This effectively avoids surface defects and coating problems caused by excessively large or small particle sizes, improving the quality and smoothness of the color-coated steel sheets. Before spray drying, the surface energy of the particles in the slurry is controlled by adjusting the surfactant concentration and stirring speed to prevent agglomeration. After drying, the particle surface is treated by air jet milling to optimize the particle size distribution and improve surface smoothness. Compared to silver ions as antibacterial agents, color-coated steel sheets using rare earth materials as antibacterial agents can also improve the discoloration problem caused by silver ions, enhancing appearance quality and durability. Detailed Implementation

[0019] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments. Any equivalent transformations made based on the technical solutions of the present invention should fall within the scope of protection of the present invention.

[0020] Example 1: Antibacterial Color Coated Steel Sheet Preparation of rare earth antibacterial agents: The formulation consists of 32% composite rare earth compounds, 18% nano zinc oxide, 3% sodium dodecylbenzenesulfonate, 5% polyvinylpyrrolidone, 40% silica micro powder, and 2% γ-aminopropyltriethoxysilane; the composite rare earth compounds are cerium oxide, lanthanum oxide, and yttrium nitrate in a weight ratio of 2:1.5:1.

[0021] Preparation process: (1) Raw material pretreatment: Cerium oxide and lanthanum oxide are ground to a particle size ≤10μm, yttrium nitrate is dried at 80℃ and then ground into fine powder, and silica micro powder is placed in a muffle furnace and calcined at 550℃ for 3.5 hours; Coupling agent modification: Calcined silica micro powder was reacted with γ-aminopropyltriethoxysilane ethanol solution at 55°C for 2.5 hours. After the reaction was completed, the mixture was separated by centrifugation, washed multiple times with ethanol, and then dried at 90°C.

[0022] (2) Mixing and dispersing: Sodium dodecylbenzenesulfonate and polyvinylpyrrolidone were added to deionized water and stirred evenly; then pretreated cerium oxide, lanthanum oxide, yttrium nitrate fine powder, nano zinc oxide and modified silica micro powder were added, and stirred at high speed of 1000 r / min for 45 minutes to form a uniform slurry.

[0023] (3) Spray drying and sieving: The slurry is conveyed to the spray dryer, and the inlet air temperature is set to 190℃ and the outlet air temperature is set to 90℃ for spray drying. The dried powder is sieved to obtain a rare earth antibacterial agent with a particle size of 10~25μm.

[0024] Antibacterial color-coated steel sheet: A rare earth antibacterial color-coated steel sheet is made by selecting a 1.0 mm thick coated steel sheet, cutting it into appropriate specifications, and forming a passivation layer on the upper and lower surfaces of the coated steel sheet through passivation treatment. The passivation layer is covered with a paint layer, which consists of a primer and a topcoat. The primer layer is about 8 μm thick and the topcoat layer is about 35 μm thick. Polyester paint is selected as the topcoat material, and 3.0% rare earth antibacterial agent is added and thoroughly mixed before use.

[0025] Performance testing 1. Antibacterial Performance Testing: The prepared antibacterial color-coated steel sheet was tested for antibacterial performance according to the national standard testing methods. The test results showed that the antibacterial color-coated steel sheet achieved an antibacterial rate of over 99% against common bacteria such as Escherichia coli and Staphylococcus aureus, meeting the usage requirements of hospitals, food processing workshops, and other places with stringent hygiene requirements.

[0026] 2. Appearance Quality Inspection: The appearance of the color-coated steel sheets is inspected using both visual observation and microscopic examination. The surface of the color-coated steel sheets is smooth and flat, free from defects such as particle points, roller jamming, or longitudinal stripes. The color is uniform, meeting the aesthetic requirements of the building decoration industry. Example 2

[0027] A rare earth antibacterial agent was prepared, wherein the dispersant was sodium polycarboxylate, polyvinylpyrrolidone and sodium lignosulfonate mixed in a mass ratio of 1:1:1, and the other components and contents and the preparation method were the same as in Example 1.

[0028] Comparative Example 1: A rare earth antibacterial agent was prepared, wherein the composite rare earth compound was cerium oxide, lanthanum oxide and yttrium nitrate in a ratio of 1:1:1, and the other components and contents and preparation method were the same as in Example 1.

[0029] Comparative Example 2: A rare earth antibacterial agent was prepared, wherein the composite rare earth compound contained only cerium oxide, and the proportion was the same as that of the composite rare earth compound in the example. Other components and contents remained unchanged, and the preparation method was the same as in Example 1.

[0030] Comparative Example 3: A rare earth antibacterial agent was prepared, wherein the composite rare earth compound contained only lanthanum oxide and yttrium nitrate in a ratio of 1:1, and the other components, contents, and preparation methods were the same as in Example 1.

[0031] Experiment: Comparative Test of Antibacterial Properties of Rare Earth Antibacterial Agents 1. Preparation of bacterial suspension: *Escherichia coli* and *Staphylococcus aureus* were inoculated separately into nutrient broth medium and incubated at 37°C for 18-24 hours. After incubation, the bacterial suspension was diluted with sterile physiological saline to adjust the concentration to 1×10⁻⁶. 6 -9×10 6 CFU / mL.

[0032] 2. Antibacterial test: Take the rare earth antibacterial agent samples from Examples 1, 2, and 3, and compress them into circular samples with a diameter of 5 mm and a thickness of 2 mm using a tablet press. Prepare two tablets for each type of sample.

[0033] Place the sample into sterile Petri dishes and add 0.1 mL of bacterial suspension (Escherichia coli or Staphylococcus aureus) to each dish, so that the bacterial suspension evenly covers the sample surface.

[0034] In the control group, ordinary color-coated plate samples without rare earth antibacterial agents were placed in petri dishes, and 0.1 mL of bacterial suspension was added.

[0035] Place all petri dishes in a 37°C incubator and incubate for 24 hours.

[0036] 3. Antibacterial durability test: Samples: Antibacterial color-coated plates of Examples 1, 2 and Comparative Examples 1-3 (circular samples with a diameter of 5 mm, 2 pieces of each). Detergent: METALNOX® M6310, a weakly alkaline water-based metal cleaner (5% dilution, pH=8.5-9.5).

[0037] Each sample was completely immersed in the detergent solution and ultrasonically cleaned (300W) for 5 minutes each time. After cleaning, the sample was rinsed 3 times with deionized water to remove residual detergent and dried at 60℃ for 30 minutes. The above cleaning-rinsing-drying process was repeated 10 times in total. The cleaned samples were subjected to antibacterial testing.

[0038] 4. Colony Counting: After incubation, add 5 mL of sterile physiological saline to each petri dish. Gently wipe the sample surface with a sterile cotton swab to ensure bacteria are fully eluted into the saline. Then, perform 10-fold serial dilutions of the eluent. Inoculate 0.1 mL of the appropriate dilution onto a nutrient agar plate, making three parallel plates for each dilution. Incubate the plates at 37°C for 24-48 hours. After incubation, count the colonies on the plates.

[0039] Table 1: Antibacterial test data

[0040] Formula for calculating antibacterial rate: Antibacterial rate (%) = (Average colony count in control group - Average colony count in experimental group) ÷ Average colony count in control group × 100% The experimental data show that the rare earth antibacterial agents in Examples 1 and 2 have higher antibacterial rates against Escherichia coli and Staphylococcus aureus than the rare earth antibacterial agents in the comparative examples, indicating that the rare earth antibacterial agent with cerium oxide, lanthanum oxide and yttrium nitrate in the examples in a ratio of 2:1.5:1 has better antibacterial performance.

[0041] The antibacterial effect of Example 2 is slightly better than that of Example 1. This is probably because the dispersant used is a mixture of sodium polycarboxylate, polyvinylpyrrolidone and sodium lignosulfonate in a mass ratio of 1:1:1, which results in better dispersion of the antibacterial agent. Antimicrobial durability data

[0042]

[0043] After 10 cleanings, the antibacterial rates of Examples 1 and 2 remained at 99.25%-99.30% and 99.43%-99.48%, respectively, both higher than the 98.5% qualification standard. Furthermore, Example 2 (composite dispersant) showed slightly better antibacterial durability than Example 1 because the antibacterial agent was more evenly dispersed and more tightly bonded to the coating.

[0044] The antibacterial rates of all comparative samples after cleaning were less than 98.5%, indicating that the composite rare earth combination and dispersion system of the present invention can significantly improve the durability of antibacterial color-coated steel sheets.

Claims

1. A rare earth antibacterial color-coated steel sheet, comprising a coated sheet, wherein the upper and lower surfaces of the coated sheet are provided with passivation layers formed by passivation treatment, and a paint layer is provided outside the passivation layers, the paint layer comprising a primer layer and a topcoat layer, the topcoat layer containing 0.1%-5% of a rare earth antibacterial agent, wherein the rare earth antibacterial agent comprises 20%-40% of a composite rare earth compound, 15%-25% of an auxiliary antibacterial agent, 2%-5% of a surfactant, 3%-8% of a dispersant, 30%-50% of silica micro powder and 1%-3% of an organosilane coupling agent; wherein the composite rare earth compound is a combination of cerium oxide, lanthanum oxide and yttrium nitrate in a weight ratio of 2:1.5:

1.

2. The rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that, The auxiliary antibacterial agent is nano zinc oxide; the particle size of the rare earth antibacterial agent is 5~30μm.

3. The rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that, The surfactant is one or a mixture of sodium dodecylbenzenesulfonate, Tween-80, fatty acid polyoxyethylene ester, and hexadecyltrimethylammonium bromide.

4. The rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that... The dispersant is one or a mixture of sodium polycarboxylate, polyvinylpyrrolidone, sodium polyacrylate, and sodium lignosulfonate.

5. A rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that... The dispersant is a mixture of sodium polycarboxylate, polyvinylpyrrolidone, and sodium lignosulfonate in a mass ratio of 1:1:

1.

6. A rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that... The organosilane coupling agent is γ-aminopropyltriethoxysilane.

7. A rare earth antibacterial color-coated steel sheet according to claim 1, characterized in that... The thickness of the coating plate is 0.3-1.2mm, and the thickness of the paint layer is 10-50μm.

8. The preparation process of rare earth antibacterial color-coated steel sheet according to any one of claims 1 to 7, comprising: providing a passivation layer formed by passivation treatment on the upper and lower surfaces of the coated steel sheet; and providing a paint layer outside the passivation layer, wherein the paint layer comprises a primer layer and a topcoat layer, characterized in that... A rare earth antibacterial agent is added during the topcoat layer processing. The rare earth antibacterial agent is prepared by the following steps: (1) Raw material pretreatment: Cerium oxide and lanthanum oxide are ground to a particle size ≤10μm, yttrium nitrate is dried and ground to fine powder, and silica micro powder is calcined at 500-600℃ for 3-4 hours; Coupling agent modification: Calcinated silica micro powder is reacted with γ-aminopropyltriethoxysilane ethanol solution at 50-60℃ for 2-3 hours, and then dried after centrifugation and washing to obtain modified silica. (2) The pretreated rare earth compounds, nano zinc oxide, dispersant, and modified silica are stirred at high speed in deionized water at a speed of 800-1200 r / min for 30-60 minutes to form a uniform slurry; (3) Spray drying and sieving: The slurry is spray dried at an inlet air temperature of 180-200℃ and an outlet air temperature of 80-100℃. The resulting powder is sieved to obtain a rare earth antibacterial agent with a target particle size of 5-30μm.

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