Paint for multi-coating chromatography printing scheme of automobile ornament, preparation method and application

Abstract

The invention discloses a coating for an automobile ornament multi-coating chromatography printing scheme, a preparation method and application, and relates to the technical field of industrial coatings, the coating comprises a primer, a chromatography layer and a finishing coat; the primer comprises epoxy modified acrylate resin, talcum powder, mica powder, a coupling agent, a diluent, a defoaming agent and a flatting agent; the color register layer comprises aliphatic polyurethane acrylate, nanoscale color paste, a light stabilizer, a reactive diluent, a dispersing agent, a flatting agent and a polyamide wax anti-settling agent; the finishing paint comprises fluorosilicone modified acrylate, a reactive diluent, a photoinitiator, a hindered amine light stabilizer, an antioxidant and a flatting agent. A multi-coating color register printing system composed of a primer layer, a color register layer and a finish paint layer is constructed, a modified resin system with excellent compatibility is adopted, high-adhesion matching of all coatings is achieved, the interlayer stripping phenomenon is effectively avoided, meanwhile, a high-solid-content and low-VOC coating formula is introduced, and the color register printing effect is good. And the emission of volatile organic compounds in the printing process is obviously reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial coatings, and particularly to a coating, a preparation method and an application of a multi-layer color printing scheme for automotive trim parts. Background Art

[0002] In current multi-layer color printing, good adhesion is required between different coatings to ensure the overall performance of the coatings. However, due to the large differences in chemical properties and surface tensions of different coatings, poor adhesion may occur between coatings. Multi-layer color printing usually requires multiple printing and drying and curing operations, and the process is rather cumbersome. After each printing, it is necessary to wait for the coating to dry and cure before the next printing can be carried out, which results in a long production cycle and low production efficiency. At the same time, in color printing, due to the need to use multiple coatings, the problem of VOC emissions is more prominent. With the increasingly strict environmental protection regulations, how to reduce the VOC content in coatings and reduce VOC emissions is an important challenge faced by coating color printing. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a coating, a preparation method and an application of a multi-layer color printing scheme for automotive trim parts to solve the problems raised in the above background art.

[0004] To achieve the above object, the present invention provides the following technical solutions: The embodiment of the present invention provides a coating for a multi-layer color printing scheme for automotive trim parts, which includes the following specific components: primer, color layer, topcoat; The primer includes epoxy-modified acrylate resin, talcum powder, mica powder, coupling agent, diluent, defoamer, and leveling agent; The color layer includes aliphatic polyurethane acrylate, nano-level color paste, light stabilizer, reactive diluent, dispersant, leveling agent, and polyamide wax anti-settling agent; The topcoat includes fluorosilicon-modified acrylate, reactive diluent, photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent.

[0005] Further optimizing the technical solution, in the primer, by mass, it includes: 50-60 parts of epoxy-modified acrylate resin; 3-6 parts of talcum powder; 3-5 parts of mica powder; 2-3 parts of coupling agent; 20-30 parts of diluent; 1-2 parts of defoamer; 1-2 parts of leveling agent.

[0006] Further optimize this technical solution. In the overprint varnish layer, it includes the following parts by mass: Aliphatic polyurethane acrylate: 50 - 60 parts; Nanoscale color paste: 5 - 10 parts; Light stabilizer: 3 - 5 parts; Reactive diluent: 20 - 30 parts; Dispersant: 1 - 2 parts; Leveling agent: 1 - 2 parts; Polyamide wax anti-settling agent: 0.1 - 0.3 parts.

[0007] Further optimize this technical solution. In the topcoat, it includes the following parts by mass: Fluorosilicon-modified acrylate: 40 - 50 parts; Reactive diluent: 10 - 20 parts; Photoinitiator: 3 - 5 parts; Hindered amine light stabilizer: 2 - 3 parts; Antioxidant: 0.5 - 1 part; Leveling agent: 0.1 - 0.3 parts.

[0008] A method for preparing a coating for a multi-layer overprint printing scheme of automotive trim parts, which is prepared based on the coating for the multi-layer overprint printing scheme of automotive trim parts described above, including the preparation of the primer, overprint varnish layer, and topcoat; When preparing the primer: Add epoxy-modified acrylate resin to the diluent and stir; sequentially add talcum powder, mica powder, coupling agent, defoaming agent, and leveling agent, mix, and disperse at high speed until the viscosity ≤ 150 cP to obtain the primer; When preparing the overprint varnish layer: Add nanoscale color paste to the reactive diluent and grind it with a sand mill to control the pigment particle size below 100 nm; add aliphatic polyurethane acrylate and stir; sequentially add light stabilizer, dispersant, leveling agent, and polyamide wax anti-settling agent, and stir evenly to obtain the overprint varnish layer; When preparing the topcoat: Add fluorosilicon-modified acrylate to the reactive diluent and stir; Sequentially add photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent, and continue stirring for 20 - 30 minutes to obtain the topcoat.

[0009] Further optimize this technical solution. When preparing the epoxy-modified acrylate resin, it includes: Select a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet device as the reaction vessel, add epoxy resin to the four-necked flask, stir evenly to completely dissolve the epoxy resin; Turn on the stirrer and stir at a speed of 100 - 200 rpm. Then, add the catalyst and inhibitor in sequence and continue stirring to fully mix all components. Slowly heat the reaction system to 80 - 90 °C. While stirring, slowly add acrylic acid through a constant pressure dropping funnel, and control the dropping time within 1 - 2 hours. After adding acrylic acid, maintain the reaction temperature at 80 - 90 °C and continue the reaction for 3 - 4 hours. The epoxy groups of the epoxy resin and the carboxyl groups of acrylic acid undergo ring-opening esterification reaction to form epoxy-modified acrylate resin.

[0010] To further optimize this technical solution, when preparing the aliphatic polyurethane acrylate, it includes: Select a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet device. Add the weighed polyol into the four-necked flask and dehydrate it under the conditions of 100 - 120 °C and a vacuum degree of -0.09 MPa for 1 - 2 hours. After dehydration is completed, lower the temperature to 50 - 60 °C. Add dibutyltin dilaurate and p-hydroxyanisole to the dehydrated polyol, stir evenly, and then slowly add aliphatic diisocyanate, keeping the reaction temperature not exceeding 80 °C. After the addition is completed, react at 70 - 80 °C for 2 - 3 hours. During this period, monitor the reaction progress by measuring the content of isocyanate group -NCO. Lower the reaction temperature to 60 °C, slowly add hydroxy acrylate, keeping the reaction temperature not exceeding 70 °C. After the addition is completed, continue the reaction at 60 - 70 °C for 2 - 3 hours until the -NCO content drops below the detectable level to obtain aliphatic polyurethane acrylate.

[0011] To further optimize this technical solution, when preparing the fluorosilicon-modified acrylate, it includes: Mix methyl methacrylate, butyl acrylate, hexafluorobutyl acrylate, and silane coupling agent, and add ethyl acetate and ultrasonically disperse for 10 minutes to form a homogeneous solution. Add 1 / 3 of the homogeneous solution to the flask, heat it to 70 °C, add 1 / 2 of the initiator, and react at a constant temperature for 1 hour. The remaining homogeneous solution and the initiator are respectively added dropwise through a constant pressure dropping funnel in an environment of 70 °C within 3 hours at a uniform speed, and then heat it to 80 °C and keep it warm for 2 hours. Lower the temperature to 40 °C, add triethylamine to adjust the pH to 7 - 8, and recover ethyl acetate by vacuum distillation to obtain fluorosilicon-modified acrylate.

[0012] An application of coatings in a multi-layer color printing scheme for automotive trim parts. Based on the coatings of the above-mentioned multi-layer color printing scheme for automotive trim parts, it includes the application of primer, color layer, and topcoat, and at the same time, printing treatment is carried out. When applying the primer: Pretreat the substrate to remove impurities; Apply the primer to the substrate by spraying or brushing; After application, conduct a drying treatment to form a dense protective layer; When applying the color-overlay layer: Select or formulate nanoscale color pastes according to design requirements; Apply the color-overlay layer on the surface of the primer by rubbing or spraying, and conduct a drying treatment after application; Conduct printing treatment on the surface of the color-overlay layer: Clean and pretreat the surface of the color-overlay layer, wipe it with alcohol or acetone; Select a 300 - 400 mesh screen for fine patterns, coat with photosensitive glue, and develop to form a pattern after exposure; Formulate the ink according to the type of printing substrate and conduct the printing operation; Conduct drying and curing after printing; When applying the topcoat: Apply the topcoat evenly by spraying or roller coating; Conduct a drying treatment after application to form a dense protective layer.

[0013] To further optimize this technical solution, the ink used in the printing treatment includes, by mass parts: 40 - 50 parts of polyester resin; 20 - 30 parts of calcium carbonate; 10 - 20 parts of barium sulfate; 5 - 10 parts of pigment; 10 - 15 parts of solvent; 1 - 2 parts of dispersant; 0.5 - 1 part of defoamer.

[0014] Compared with the prior art, the present invention provides a coating, preparation method and application for a multi - layer color - overlay printing scheme of automotive trim parts, having the following beneficial effects: The coating, preparation method and application for the multi - layer color - overlay printing scheme of automotive trim parts, by constructing a multi - layer color - overlay printing system composed of a primer layer, a color - overlay layer and a topcoat layer, and adopting a resin system with excellent compatibility and modification, realizes high - adhesion cooperation between each layer, effectively avoids the occurrence of inter - layer peeling phenomenon. At the same time, by introducing a coating formula with high solid content and low VOC, the emission of volatile organic compounds during the printing process is significantly reduced, and the overall process efficiency and coating quality are improved on the premise of meeting environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0016] Figure 1 Schematic diagram of the composition of the coating for a multi - coating overprinting scheme for automotive trim parts proposed by the present invention; Figure 2 Schematic flow chart of the preparation method of the coating for a multi - coating overprinting scheme for automotive trim parts proposed by the present invention; Figure 3 Schematic flow chart of the application of the coating for a multi - coating overprinting scheme for automotive trim parts proposed by the present invention. Specific Embodiments

[0017] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the following will make a detailed description of the specific embodiments of the present invention with reference to the accompanying drawings of the specification.

[0018] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0019] Secondly, the so - called "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an independent or selectively mutually exclusive embodiment with other embodiments.

[0020] Embodiment 1: Referring to Figure 1 , this is the first embodiment of the present invention. This embodiment provides a coating for a multi - coating overprinting scheme for automotive trim parts, including the following specific components: primer, overprinting layer, topcoat; The primer includes epoxy - modified acrylate resin, talcum powder, mica powder, coupling agent, diluent, defoamer, and leveling agent; The overprinting layer includes aliphatic polyurethane acrylate, nano - grade color paste, light stabilizer, reactive diluent, dispersant, leveling agent, and polyamide wax anti - settling agent; The topcoat includes fluorosilicon - modified acrylate, reactive diluent, photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent.

[0021] In the primer, the components are included in the following parts by mass: Epoxy-modified acrylate resin: 50 parts; Talc powder: 3 parts; Mica powder: 3 parts; Coupling agent: 2 parts; Diluent: 20 parts; Defoaming agent: 1 part; Leveling agent: 1 part.

[0022] This primer has good adhesion and hardness, and has good adaptability to various substrates such as metals and plastics. During the printing process, it can withstand the energy impact of the laser and is not prone to primer peeling or cracking. This primer has excellent flexibility and abrasion resistance, is more suitable for some printed products that need to be bent or are frequently rubbed, and can also provide good chemical resistance and weather resistance.

[0023] In the overprint layer, the components are included in the following parts by mass: Aliphatic polyurethane acrylate: 50 parts; Nanoscale color paste: 5 parts; Light stabilizer: 3 parts; Reactive diluent: 20 parts; Dispersant: 1 part; Leveling agent: 1 part; Polyamide wax anti-settling agent: 0.1 part.

[0024] By adjusting the resin system of this overprint layer, resins with strong adhesion, good flexibility and excellent weather resistance, such as acrylic resins and polyurethane resins, are selected, or resin compounding technology is adopted to improve the comprehensive performance of the overprint layer. Through specific additives or formula adjustments, the phenomenon of color layer sagging during application is prevented, and the coating is ensured to be uniform and flat.

[0025] In the topcoat, the components are included in the following parts by mass: Fluorosilicon-modified acrylate: 40 parts; Reactive diluent: 10 parts; Photoinitiator: 3 parts; Hindered amine light stabilizer: 2 parts; Antioxidant: 0.5 part; Leveling agent: 0.1 part.

[0026] By adding a hindered amine light stabilizer to this topcoat, the molecular structure of the varnish is stabilized and the weather resistance is enhanced. A two-component crosslinking system of 50% hydroxy acrylic emulsion + 30% aqueous polyurethane dispersion is adopted, and the adhesion reaches 5B level (ASTM D3359), and there is no peeling after boiling water for 2 hours.

[0027] Example 2: Reference Figure 2 Figure 2 , which is the second embodiment of the present invention. This embodiment provides a method for preparing a coating for a multi - layer overprinting printing scheme of automotive trim parts. Based on the coating for the multi - layer overprinting printing scheme of automotive trim parts described in Embodiment 1, it includes the preparation of primer, overprinting layer, and topcoat.

[0028] When preparing the primer: Add epoxy - modified acrylate resin to the diluent and stir; sequentially add talcum powder, mica powder, coupling agent, defoaming agent, and leveling agent, mix them, and disperse at high speed until the viscosity ≤ 150 cP to obtain the primer.

[0029] In this embodiment, when preparing the epoxy - modified acrylate resin, it includes: Select a four - necked flask with a stirrer, thermometer, condenser, and nitrogen inlet device as the reaction vessel. Ensure that the device is clean and dry, introduce nitrogen to remove air, create an inert atmosphere, and prevent acrylic acid from being oxidized or self - polymerized at high temperatures. Add epoxy resin to the four - necked flask. If a solvent is used, it can be added simultaneously and stirred evenly to completely dissolve the epoxy resin.

[0030] Turn on the stirrer and stir at a speed of 100 - 200 rpm, then sequentially add the catalyst and inhibitor, and continue to stir to fully mix each component.

[0031] Slowly raise the temperature of the reaction system to 80 - 90 °C. Under stirring, slowly drip acrylic acid through a constant - pressure dropping funnel. Control the dropping speed appropriately to avoid too violent a reaction, and control the dropping time within 1 - 2 hours.

[0032] After dripping acrylic acid, maintain the reaction temperature at 80 - 90 °C and continue to react for 3 - 4 hours. The epoxy groups of the epoxy resin and the carboxyl groups of acrylic acid undergo ring - opening esterification reaction to form epoxy - modified acrylate resin.

[0033] When preparing the overprinting layer: Add nano - level color paste to the reactive diluent and grind it with a sand mill to control the pigment particle size below 100 nm; add aliphatic polyurethane acrylate and stir; sequentially add light stabilizer, dispersant, leveling agent, and polyamide wax anti - settling agent, and stir evenly to obtain the overprinting layer.

[0034] In this embodiment, when preparing the aliphatic polyurethane acrylate, it includes: Select a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen inlet device. Ensure that the device is clean and dry, and introduce nitrogen to remove air to prevent the reaction of isocyanate with moisture in the air. Add the weighed polyol to the four-necked flask and dehydrate it at 100 - 120 °C under a vacuum of -0.09 MPa for 1 - 2 hours to remove the moisture in the polyol and avoid the reaction of moisture with isocyanate to produce carbon dioxide gas, which may affect the product performance. After dehydration, lower the temperature to 50 - 60 °C.

[0035] Add dibutyltin dilaurate and 4-methoxyphenol to the dehydrated polyol, stir well, and then slowly add the aliphatic diisocyanate dropwise, keeping the reaction temperature not exceeding 80 °C.

[0036] After the dropwise addition is completed, react at 70 - 80 °C for 2 - 3 hours. During this period, monitor the reaction progress by measuring the content of isocyanate group -NCO. The di-n-butylamine method can be used to measure the -NCO content. When the -NCO content reaches the theoretical value, it indicates that the first-step reaction is completed.

[0037] Lower the reaction temperature to 60 °C, slowly add hydroxyethyl acrylate dropwise, and also control the dropping rate to keep the reaction temperature not exceeding 70 °C. After the dropwise addition is completed, continue to react at 60 - 70 °C for 2 - 3 hours until the -NCO content drops below the detectable level to obtain aliphatic polyurethane acrylate.

[0038] When preparing the topcoat: Add the fluorosilicon-modified acrylate to the reactive diluent and stir. Add photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent in sequence, and continue to stir for 20 - 30 minutes to obtain the topcoat.

[0039] In this example, when preparing the fluorosilicon-modified acrylate, it includes: Mix methyl methacrylate, butyl acrylate, hexafluorobutyl acrylate, and silane coupling agent, add ethyl acetate and ultrasonically disperse for 10 minutes to form a homogeneous solution. Add 1 / 3 of the homogeneous solution to the flask, heat up to 70 °C, add 1 / 2 of the initiator, and react at a constant temperature for 1 hour. The remaining homogeneous solution and the initiator are respectively added dropwise evenly through a constant pressure dropping funnel in an environment of 70 °C within 3 hours, and then heat up to 80 °C and keep warm for 2 hours to ensure that the conversion rate > 95%. Lower the temperature to 40 °C, add triethylamine to adjust the pH to 7 - 8, and recover ethyl acetate by vacuum distillation (60 °C / 10 kPa) to obtain the fluorosilicon-modified acrylate.

[0040] Example 3: Refer to Figure 3, which is the third embodiment of the present invention. This embodiment provides a coating application for a multi - coating color - overprinting scheme of automotive trim parts. Based on the coating for the multi - coating color - overprinting scheme of automotive trim parts described in Embodiment 1, it includes the application of primer, color - overprinting layer, and topcoat, while performing printing treatment.

[0041] When applying the primer: Pretreat the substrate to remove impurities such as dust and grease. Apply the primer to the substrate by spraying or brushing. After application, perform drying treatment to form a dense protective layer.

[0042] When applying the color - overprinting layer: Select or formulate nano - level color paste according to design requirements to ensure color layering and permeability. Apply the color - overprinting layer on the surface of the primer by wiping or spraying. After application, perform drying treatment and wait for the color - overprinting layer to dry completely to ensure it is thoroughly dry.

[0043] Perform printing treatment on the surface of the color - overprinting layer: Substrate preparation: Clean and pretreat the surface of the substrate to remove impurities such as dust and grease. Wipe with alcohol or acetone to ensure the surface tension ≥ 40 mN / m.

[0044] Screen - plate preparation: Select a 300 - 400 - mesh screen - plate for fine patterns, coat a 3 - 5 - μm photosensitive resin, and develop to form a pattern after exposing for 10 - 30 seconds.

[0045] Ink formulation: Formulate the ink according to the type of printing substrate, add an adhesion promoter and additives, and adjust the viscosity to 500 - 1000 mPa・s.

[0046] Printing operation: Set the doctor - blade angle at 45 - 60°, the pressure at 0.1 - 0.3 MPa, and the speed at 10 - 30 cm / s for printing.

[0047] Drying and curing: Solvent - based ink is dried under hot air at 80 - 100 °C for 10 - 15 minutes, and UV ink is cured under a 120 W / cm mercury lamp for 3 - 5 seconds.

[0048] Quality inspection: Comprehensively inspect the printing layer for indicators such as color difference and adhesion.

[0049] In this embodiment, the ink includes, by mass parts: 40 parts of polyester resin; 20 parts of calcium carbonate; 10 parts of barium sulfate; 5 parts of pigment; 10 parts of solvent; 1 part of dispersant; The defoamer is 0.5 part.

[0050] Different mesh count stencils and inks with different viscosities are adopted to adapt to different types of printing patterns, ensuring excellent printing effects. Combined with equipment upgrades such as laser positioning and numerical control rotary tables, high-precision stencil tension, squeegee pressure, and printing speed are matched to meet high-difficulty requirements such as curved surface printing and multi-station linkage.

[0051] When applying the topcoat: The topcoat is evenly applied by spraying or rolling; After application, drying treatment is carried out to form a dense protective layer.

[0052] Meanwhile, the coatings used are subjected to performance tests using the test items shown in Table 1.

[0053] Example 4: To adapt to different application environments and requirements, the following several changeable design schemes are proposed in this example: Regarding the primer: For metal substrates such as steel and aluminum alloy, the content of anti-rust pigments (such as zinc phosphate and aluminum tripolyphosphate) should be increased in the primer to improve the anti-rust performance of the primer.

[0054] For low surface energy plastic substrates such as polypropylene (PP) and polyethylene (PE), special adhesion promoters such as chlorinated polypropylene resin need to be added to the primer to improve the adhesion between the primer and the plastic surface.

[0055] By adjusting the molecular structure of the epoxy-modified acrylate resin, the flexibility and ultraviolet resistance of its molecular chain are increased. Introducing fluorine-containing or silicon-containing monomers for copolymerization modification can improve the weather resistance and water resistance of the primer.

[0056] Adding hindered amine light stabilizers and ultraviolet absorbers to the primer can effectively absorb and scatter ultraviolet rays, reduce the damage of ultraviolet rays to the primer, and improve the weather resistance of the primer.

[0057] Regarding the overprint layer: Optimize the pigment selection: Select pigments with high purity, uniform particle size, and good dispersibility. For example, using organic pigments to replace part of the inorganic pigments to improve the color brightness and saturation.

[0058] Graphene nanosheets (0.5%) replace part of the SiO2, while maintaining the hardness, the tensile strength is increased by 30% and the cost is reduced by 15%.

[0059] Regarding the printing process: For fine patterns, a high-mesh screen (300 - 400 meshes) is used in combination with a low-viscosity ink (500 - 1000 mPa・s).

[0060] For thick-film printing, a low-mesh screen (80 - 120 meshes) is used in combination with a high-thixotropic ink, adding 2% - 5% bentonite (sodium-based montmorillonite) to form a three-dimensional network structure through hydrogen bonds.

[0061] In plastic printing, the number of screen plates is 250 - 300, the hardness of the squeegee is 75 - 85A, drying is carried out at 80°C for 15 min, and the film thickness is 8 - 12 μm.

[0062] In metal printing, the number of screen plates is 150 - 200, the hardness of the squeegee is 80 - 90A, drying is carried out at 180°C for 30 min, and the film thickness is 12 - 18 μm.

[0063] Regarding the topcoat: In the interior topcoat, by introducing nanocellulose and quaternary ammonium salt-modified graphene, scratch resistance and long-term antibacterial properties are achieved while maintaining flexibility.

[0064] In the exterior topcoat, core-shell TiO2-SiO2 particles are used to achieve low surface energy self-cleaning and excellent weather resistance, and in combination with a dual-curing system, the salt spray resistance is improved.

[0065] Adding special functional additives such as light stabilizers and antioxidants can improve the aging resistance of the varnish and prevent problems such as yellowing and powdering after long-term use.

[0066] At the same time, in this embodiment, the following design method changes can also be made: Optimization of the primer material: Use an epoxy-modified acrylate resin primer, which has good adhesion and hardness and has good adaptability to various substrates such as metals and plastics. During the printing process, it can withstand screen scraping and is not prone to primer peeling.

[0067] Personalization of the overprint layer: Adjust the resin system, select resins with strong adhesion, good flexibility and excellent weather resistance, such as acrylic resins and polyurethane resins, or use resin compounding technology to improve the comprehensive performance of the overprint layer.

[0068] Adjustment of the printing process: For fine printing, use a high-tension screen (tension 25 - 30 N / cm) with 250 - 400 meshes, in combination with a hard squeegee (hardness 85 - 90A) and an angle of 60 - 75°; for thick-film printing, use a low-tension screen (tension 18 - 22 N / cm) with 80 - 150 meshes, in combination with a soft squeegee (hardness 60 - 70A) and an angle of 45 - 60° to ensure uniform ink transfer.

[0069] Optimization of topcoat materials: To improve the hardness and wear resistance of the varnish, fillers such as nano-scale silica and alumina are added to enhance the scratch resistance of the varnish.

[0070] In summary, the coating system provided by the present invention not only solves the problem of interlayer adhesion in traditional multi-layer spot color printing, but also significantly improves the performance and aesthetics of the coating, extends the service life, and has broad application prospects and market value.

[0071] 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 the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A coating for a multi - coating color - over - color printing solution of automotive trim parts, characterized in that, It includes the following specific components: primer, overprint varnish layer, topcoat; The primer includes epoxy-modified acrylate resin, talcum powder, mica powder, coupling agent, diluent, defoamer, and leveling agent; The overprint varnish layer includes aliphatic polyurethane acrylate, nano-level color paste, light stabilizer, reactive diluent, dispersant, leveling agent, and polyamide wax anti-settling agent; The topcoat includes fluorosilicon-modified acrylate, reactive diluent, photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent.

2. The coating for a multi - coating overprinting scheme of automotive trim parts according to claim 1, characterized in that, In the primer, it includes the following parts by mass: Epoxy-modified acrylate resin is 50 - 60 parts; Talcum powder is 3 - 6 parts; Mica powder is 3 - 5 parts; Coupling agent is 2 - 3 parts; Diluent is 20 - 30 parts; Defoamer is 1 - 2 parts; Leveling agent is 1 - 2 parts.

3. The coating for a multi - layer overprinting scheme of automotive trim parts according to claim 1, characterized in that, In the overprint varnish layer, it includes the following parts by mass: Aliphatic polyurethane acrylate is 50 - 60 parts; Nano-level color paste is 5 - 10 parts; Light stabilizer is 3 - 5 parts; Reactive diluent is 20 - 30 parts; Dispersant is 1 - 2 parts; Leveling agent is 1 - 2 parts; Polyamide wax anti-settling agent is 0.1 - 0.3 parts.

4. The coating for a multi - coating color - over - color printing solution of automotive trim parts according to claim 1, characterized in that, In the topcoat, it includes the following parts by mass: Fluorosilicon-modified acrylate is 40 - 50 parts; Reactive diluent is 10 - 20 parts; Photoinitiator is 3 - 5 parts; Hindered amine light stabilizer is 2 - 3 parts; Antioxidant is 0.5 - 1 part; Leveling agent is 0.1 - 0.3 part.

5. A method for preparing a coating for a multi-layer overprinting printing solution of automotive trim parts, which is prepared based on the coating for the multi-layer overprinting printing solution of automotive trim parts according to any one of claims 1-4, characterized in that, It includes the preparation of the primer, overprint varnish layer, and topcoat; When preparing the primer: Add epoxy-modified acrylate resin into the diluent and stir; sequentially add talcum powder, mica powder, coupling agent, defoamer, and leveling agent, and mix them. Disperse at high speed until the viscosity ≤ 150 cP to obtain the primer; When preparing the overprint varnish layer: Add nano-level color paste into the reactive diluent and grind it with a sand mill to control the pigment particle size below 100 nm; add aliphatic polyurethane acrylate and stir; sequentially add light stabilizer, dispersant, leveling agent, and polyamide wax anti-settling agent, and stir evenly to obtain the overprint varnish layer; When preparing the topcoat: Add fluorosilicon-modified acrylate into the reactive diluent and stir; Sequentially add photoinitiator, hindered amine light stabilizer, antioxidant, and leveling agent, and continue to stir for 20 - 30 minutes to obtain the topcoat.

6. The method for preparing a coating for a multi-coat color printing solution of automotive trim parts according to claim 5, wherein, When preparing the epoxy-modified acrylate resin, it includes: Select a four-necked flask with a stirrer, thermometer, condenser, and nitrogen inlet device as the reaction vessel. Add epoxy resin into the four-necked flask and stir evenly to completely dissolve the epoxy resin; Turn on the stirrer and stir at a speed of 100 - 200 rpm. Then sequentially add the catalyst and inhibitor, and continue to stir to fully mix each component; Slowly raise the reaction system temperature to 80 - 90 °C. Under stirring, slowly drip acrylic acid through a constant pressure dropping funnel, and control the dropping time within 1 - 2 hours; After dripping acrylic acid, maintain the reaction temperature at 80 - 90 °C and continue the reaction for 3 - 4 hours. The epoxy group of the epoxy resin and the carboxyl group of acrylic acid undergo ring-opening esterification reaction to generate epoxy-modified acrylate resin.

7. A method for preparing a coating for a multi-layer color printing solution of automotive trim parts according to claim 5, characterized in that, The aliphatic polyurethane acrylate, when prepared, comprises: Select a four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen inlet device, add the weighed polyol into the four-necked flask, dehydrate for 1-2 hours at 100-120°C and a vacuum degree of -0.09MPa, and after the dehydration is completed, reduce the temperature to 50-60°C; Add dibutyltin dilaurate and p-hydroxyanisole to the dehydrated polyol, stir evenly, and then slowly drop aliphatic diisocyanate so that the reaction temperature does not exceed 80°C; After the addition is completed, the reaction is carried out at 70-80°C for 2-3 hours, during which the progress of the reaction is monitored by measuring the content of isocyanate group -NCO; The reaction temperature was lowered to 60°C, and hydroxy acrylate was slowly added dropwise so that the reaction temperature did not exceed 70°C. After the addition was completed, the reaction was continued at 60-70°C for 2-3 hours until the -NCO content was reduced to an undetectable level, thereby obtaining aliphatic polyurethane acrylate.

8. A method for preparing a coating for a multi - coating color - printing solution of automotive trim parts according to claim 5, characterized in that, The fluorosilicone modified acrylate comprises: Methyl methacrylate, butyl acrylate, hexafluorobutyl acrylate and silane coupling agent were mixed, and ethyl acetate was added for ultrasonic dispersion for 10 minutes to form a homogeneous solution; Add 1 / 3 of the homogeneous solution into the flask, raise the temperature to 70°C, add 1 / 2 of the initiator, and react at constant temperature for 1 hour; The remaining homogeneous solution and the initiator were added dropwise at a constant speed within 3 hours at 70°C through a constant pressure dropping funnel, and the temperature was raised to 80°C and kept for 2 hours; The temperature was lowered to 40°C, triethylamine was added to adjust the pH to 7-8, and ethyl acetate was recovered by reduced pressure distillation to obtain fluorosilicone modified acrylate.

9. Application of coating for a multi-coat overprinting scheme of automotive trim parts. The coating is applied based on the coating for the multi-coat overprinting scheme of automotive trim parts according to any one of claims 1-4, characterized in that, Includes the application of primer, color layer, topcoat, and printing process at the same time; When applying the primer: Pre-treat the substrate to remove impurities; Apply the primer by spraying or brushing on the substrate; After application, it is dried to form a dense protective layer; When applying to a color layer: Select or mix nano-scale color paste according to design requirements; The color layer is applied on the surface of the primer by rubbing or spraying, and then dried; Printing treatment is performed on the surface of the color layer: Clean and pre-treat the surface of the color layer, wipe it with alcohol or acetone; Choose 300-400 mesh screen for fine patterns, apply photosensitive glue, and develop to form patterns after exposure; Prepare ink according to the type of substrate and perform printing operations; After printing is completed, it is dried and cured; When applying topcoat: Apply the topcoat evenly by spraying or rolling; After application, it is dried to form a dense protective layer.

10. The coating application of a multi - coating color - overprinting printing solution for automotive trim parts according to claim 9, wherein, The ink used in the printing process includes, by weight: Polyester resin is 40-50 parts; Calcium carbonate is 20-30 parts; Barium sulfate is 10-20 parts; Pigment is 5-10 parts; The solvent is 10-15 parts; Dispersant is 1-2 parts; The defoaming agent is 0.5-1 part.

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