Sequential Coating and Curing Method for Transparent Protective Layers on Steel Plates Based on Functional Differences

Abstract

This invention relates to the field of steel plate surface protection technology, specifically a method for sequential coating and curing of transparent protective layers on steel plates based on functional differences. The method involves degreasing and dust removal of the color-coated steel plate substrate, followed by plasma bombardment of the surface. The core functional priorities are determined based on the steel plate's service life, with core functions including at least one of weather resistance, scratch resistance, corrosion resistance, and stain resistance. Core functional coatings, auxiliary functional coatings, and interlayer transition coatings are selected. Coating is performed in the order of "core functional coating → interlayer transition coating → auxiliary functional coating." A segmented curing method is used, with different curing parameters set for different functional coatings. The finished product is obtained by cooling to room temperature. By matching functional priorities with the coating sequence and designing differentiated curing parameters, the coating functions are optimized in a targeted manner, improving the bonding strength between the coating and the substrate, as well as between layers, thereby extending the service life of the color-coated steel plate.

Description

Technical Field

[0001] This invention relates to the field of steel plate surface protection technology, and more specifically to a method for sequential coating and curing of transparent protective layers for steel plates based on functional differences. Background Technology

[0002] Color-coated steel sheets are widely used in many industries due to their advantages such as being lightweight, aesthetically pleasing, and corrosion-resistant. However, the complexity of the service environment places diverse functional demands on the transparent protective layer on its surface. For example, steel sheets used for building exterior walls need to prioritize weather resistance, appliance casings need to focus on scratch resistance, and steel sheets used in marine environments need to enhance corrosion resistance.

[0003] In existing technologies, transparent topcoats for steel plates often employ single-coat or fixed-sequence overcoating methods. For example, the conventional three-coat, three-baking process is fixed in the order of primer-topcoat-clear coat, without dynamically adjusting the coating sequence according to functional priorities. Furthermore, the curing parameters use a uniform standard, resulting in the overall coating performance being unable to adapt to the diverse needs of different scenarios. Simultaneously, existing overcoating processes generally suffer from poor interlayer adhesion and insufficient functional synergy, such as easy peeling of local coatings and rapid functional degradation after long-term use. In addition, existing transparent coatings often rely on fluorinated materials to enhance performance, resulting in poor environmental friendliness, and the lack of precise curing parameter design for different functional coatings further limits the maximization of protective effects.

[0004] Therefore, developing a film-forming method that dynamically adjusts the coating sequence based on functional differences and matches personalized curing parameters has become the key to solving the pain points of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a method for sequential coating and curing of transparent protective layers on steel plates based on functional differences. By matching functional priorities and coating order and designing differentiated curing parameters, the method achieves directional optimization of coating functions, improves the bonding strength between the coating and the substrate and between layers, and extends the service life of color-coated steel plates.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: its operation steps are as follows: Step 1, Substrate Pretreatment: The color-coated steel sheet substrate is degreased and dusted, and the surface is bombarded with plasma; Step 2, Functional Requirements Definition: Determine the priority of core functions based on the service scenarios of the steel plate. Core functions include at least one of the following: weather resistance, scratch resistance, corrosion resistance, and stain resistance. Step 3, Coating System Design: Select core functional coatings, auxiliary functional coatings, and interlayer transition coatings; Step 4, Sequential Coating: Coat the coating in the order of "core functional coating → interlayer transition coating → auxiliary functional coating"; Step 5, Differentiated Curing: A segmented curing method is adopted, with different curing parameters set for different functional coatings; Step 6, Post-processing: Cool to room temperature to obtain the finished product.

[0007] Furthermore, in step 1, the plasma bombardment power is 300-500W and the bombardment time is 30-60s.

[0008] Furthermore, in step 3, the auxiliary functional coating is a fluorine-modified acrylic anti-fouling coating or an organosilicon wear-resistant coating; the interlayer transition coating uses a modified isocyanate silane coupling agent with a thickness of 0.5-1 μm.

[0009] Furthermore, in step 4, the coating method is roller coating, the coating speed is 2-5 m / min, the core functional coating thickness is 3-8 μm, and the auxiliary functional coating thickness is 2-5 μm.

[0010] Furthermore, in step 5, the curing parameters for the core functional coating are: temperature 120-160℃, time 15-30min; the curing parameters for the interlayer transition coating are: temperature 80-100℃, time 5-10min; and the curing parameters for the auxiliary functional coating are: temperature 100-140℃, time 10-20min.

[0011] Furthermore, when the core function is weather resistance, an additional UV curing step is added to step 5, with UV irradiation energy of 800-1200 mJ / cm².

[0012] Furthermore, when the core function in step 3 is weather resistance, the core function coating adopts a silane-modified acrylic coating containing nano-titanium dioxide.

[0013] Furthermore, when the core function in step 3 is scratch resistance, the core function coating adopts a high-hardness polyurethane acrylic coating with a pencil hardness ≥4H.

[0014] Furthermore, when the core function in step 3 is corrosion resistance, the core function coating adopts a fluorine-free epoxy-modified silane coating.

[0015] Furthermore, the cooling rate in step 6 is 5-10℃ / min.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a method for sequential coating and curing of transparent protective layers on steel plates based on functional differences. The coating sequence is determined by functional requirements, achieving targeted enhancement of core functions and adapting to the personalized needs of different service scenarios. The introduction of interlayer transition coatings and the use of differentiated curing parameters significantly improve the bonding strength between the coating and the substrate and between layers, avoiding peeling failure. A UV curing step is added for the core function of weather resistance, further enhancing weather resistance. Fluorine-free environmentally friendly coating materials are used, balancing protective performance and environmental requirements. The process is simple and controllable, suitable for industrial mass production. Attached Figure Description

[0017] Figure 1 This is a comparison table of experimental data between the present invention, the embodiments, and the control group. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. The preferred embodiments described are only examples. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: This example is applied to steel plates for building exterior walls, and the specific operation steps are as follows: Step 1, Substrate pretreatment: Select hot-dip galvanized color-coated steel sheet, degrease it with alkaline washing, remove dust by high-pressure water washing, and bombard the surface with 400W plasma for 45 seconds; Step 2, Coating System: The core functional coating is a silane-modified acrylic coating containing 5% nano-titanium dioxide, the interlayer transition coating is a modified 3-isocyanate-based propyltrimethoxysilane, and the auxiliary functional coating is a fluorine-modified acrylic antifouling coating. Step 3, Sequential Coating: Roller coating of core functional coating (thickness 5μm, speed 3m / min) → Roller coating of transition coating (thickness 0.8μm, speed 4m / min) → Roller coating of auxiliary functional coating (thickness 3μm, speed 3m / min). Step 4, Differentiated Curing: Core coating cured at 140℃ for 25 min → Transition coating cured at 90℃ for 8 min → Auxiliary coating cured at 120℃ for 15 min, and finally UV cured at 1000mJ / cm². Step 5, Post-processing: Cool to room temperature at 8℃ / min.

[0020] Example 2: This example is applied to steel plates for appliance casings, and the specific operating steps are as follows: Step 1, Substrate pretreatment: Select cold-rolled color-coated steel sheet, degrease and remove dust, then bombard with 350W plasma for 35s; Step 2, Coating System: The core functional coating is a high-hardness polyurethane acrylic coating (pencil hardness 5H), the interlayer transition coating is a modified 3-isocyanate-based propyltriethoxysilane, and the auxiliary functional coating is an organosilicon wear-resistant coating. Step 3, Sequential Coating: Roller coating of core functional coating (thickness 4μm, speed 4m / min) → Roller coating of transition coating (thickness 0.6μm, speed 5m / min) → Roller coating of auxiliary functional coating (thickness 2μm, speed 4m / min). Step 4, Differentiated Curing: Core coating cured at 150℃ for 20 min → Transition coating cured at 85℃ for 6 min → Auxiliary coating cured at 130℃ for 12 min; Step 5, Post-processing: Cool to room temperature at 10℃ / min.

[0021] Example 3: This example applies to steel plates used in marine environments, and the specific operating steps are as follows: Step 1, Substrate pretreatment: Select weather-resistant color-coated steel plate, degrease and remove dust, then bombard with 450W plasma for 50s; Step 2, Coating System: The core functional coating is a fluorine-free epoxy modified silane coating, the interlayer transition coating is a modified 3-isocyanate-based propylmethyl dimethoxysilane, and the auxiliary functional coating is a fluorine-containing modified acrylic antifouling coating. Step 3, Sequential Coating: Roller coating of core functional coating (7μm thickness, 2m / min speed) → Roller coating of transition coating (0.9μm thickness, 3m / min speed) → Roller coating of auxiliary functional coating (4μm thickness, 2m / min speed). Step 4, Differentiated Curing: Core coating cured at 160℃ for 30 min → Transition coating cured at 95℃ for 10 min → Auxiliary coating cured at 140℃ for 20 min; Step 5, Post-processing: Cool to room temperature at 6℃ / min.

[0022] Comparative experiment: The conventional three-coat, three-bake process in the prior art (fixed sequence: primer-topcoat-clear coat, uniform curing temperature 180℃, time 30min) was selected as the control group, and Examples 1 to 3 of this invention were selected as the experimental group. Performance tests were conducted according to relevant standards, and the results are as follows: Figure 1 As shown in the figure. Experimental data shows that the coating prepared by the method of this invention is significantly superior to the prior art in terms of core functional indicators, and the interlayer adhesion is greatly improved, achieving precise protection in differentiated scenarios.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. By defining the functional requirements, the coating sequence can be determined to achieve targeted enhancement of core functions and adapt to the personalized needs of different service scenarios; 2. By introducing an interlayer transition coating and using differentiated curing parameters, the bonding strength between the coating and the substrate, as well as between layers, is significantly improved, thus preventing peeling failure. 3. A UV curing step has been added to enhance the core function of weather resistance, further improving weather resistance; 4. Uses fluorine-free environmentally friendly coating materials, balancing protective performance and environmental protection requirements; 5. The process is simple and controllable, making it suitable for industrial mass production.

[0024] For those skilled in the art, modifications can be made to the technical solutions described in the foregoing embodiments, and equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for sequentially coating and curing a transparent protective layer onto a steel plate based on functional differences, characterized in that: Its operation steps are as follows: Step (1) Substrate pretreatment: Degrease and remove dust from the color-coated steel plate substrate, and bombard the surface with plasma; Step (2) Functional requirements positioning: Determine the priority of core functions based on the service scenarios of the steel plate. The core functions include at least one of weather resistance, scratch resistance, corrosion resistance, and stain resistance. Step (3), Coating system design: Select core functional coatings, auxiliary functional coatings, and interlayer transition coatings; Step (4), sequential coating: Coating is performed in the order of "core functional coating → interlayer transition coating → auxiliary functional coating"; Step (5), Differentiated curing: A segmented curing method is adopted, and different curing parameters are set for different functional coatings; Step (6), Post-processing: Cool to room temperature to obtain the finished product.

2. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: In step (1), the plasma bombardment power is 300-500W and the bombardment time is 30-60s.

3. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: In step (3), the auxiliary functional coating is a fluorine-modified acrylic anti-fouling coating or an organosilicon wear-resistant coating; the interlayer transition coating uses a modified isocyanate silane coupling agent with a thickness of 0.5-1 μm.

4. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: In step (4), the coating method is roller coating, the coating speed is 2-5m / min, the core functional coating thickness is 3-8μm, and the auxiliary functional coating thickness is 2-5μm.

5. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: In step (5), the curing parameters for the core functional coating are: temperature 120-160℃ and time 15-30min; the curing parameters for the interlayer transition coating are: temperature 80-100℃ and time 5-10min; and the curing parameters for the auxiliary functional coating are: temperature 100-140℃ and time 10-20min.

6. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: When the core function is weather resistance, an additional UV curing step is added in step (5), with UV irradiation energy of 800-1200mJ / cm².

7. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: When the core function in step (3) is weather resistance, the core function coating is a silane-modified acrylic coating containing nano-titanium dioxide.

8. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: When the core function in step (3) is scratch resistance, the core function coating adopts a high-hardness polyurethane acrylic coating with a pencil hardness ≥4H.

9. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: When the core function in step (3) is corrosion resistance, the core function coating adopts a fluorine-free epoxy modified silane coating.

10. The method for sequential coating and curing of a transparent protective layer for steel plates based on functional differences according to claim 1, characterized in that: The cooling rate in step (6) is 5-10℃ / min.

Images