Metal medium UV printing method

Abstract

The invention relates to the technical field of UV printing, in particular to a metal medium UV printing method which adopts a vitrification agent, electrostatic powder spraying and acrylate UV printing ink to conduct coating treatment on a metal medium, and the powder raw material of the electrostatic powder spraying is modified thermosetting resin prepared through modification of an amino silane coupling agent. After the modified thermosetting resin is sprayed on the vitrification layer, the amino silane coupling agent and the silane coupling agent in the vitrification layer can generate coupling reaction, the binding force of the vitrification layer and the electrostatic powder spraying layer is improved, the photoinitiator in the acrylate ultraviolet ink can enhance the coupling reaction between the amino silane coupling agent and the acrylate resin, and the ultraviolet curing effect is improved. The binding force of the acrylate ultraviolet ink layer and the classical powder spraying layer is improved, and the adhesive force of the coating on the surface of a metal medium is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of UV printing, and in particular to a metal medium UV printing method. Background Art

[0002] The coating of metal surface is a widely used anti-corrosion method. Usually, the metal surface needs to be treated before coating. The purpose is to establish a protective layer that can accept non-metallic coating on the surface of the protected metal medium, so that the metal medium and the coating film have good adhesion, thereby improving the protective effect of coating on the metal. The traditional pre-treatment process is the phosphating process, but the phosphating process has the problems of poor production continuity, complex process, use of a large amount of strong acid and alkali, and large pollution emissions. Therefore, in order to solve the above problems, those skilled in the art have disclosed phosphating alternative technologies, such as zirconium and silane systems, in which zirconium treatment agents can form ceramic conversion films on the surface of the substrate, and the anti-rust and coating bonding force is much higher than iron phosphating, and can cooperate with processes such as powder spraying, electrophoresis and spray painting, and has the characteristics of environmental protection, energy saving, simple operation and low cost. At present, zirconium treatment agents also have high requirements for workpiece materials and water quality, and there is a problem of rusting for some cold-rolled plates.

[0003] In response to the problems existing in the above-mentioned zirconium-based treatment agent, the prior art CN111040485A discloses an environmentally friendly metal surface treatment agent and a method of use. The treatment agent is phosphorus-free, chromium-free, environmentally friendly, non-toxic and harmless, can form a chemical film on the metal surface, and has excellent anti-rust performance and long-term anti-rust performance. However, when using the above-mentioned metal surface treatment agent, the present applicant found that when the above-mentioned ceramic agent is used in conjunction with electrostatic powder spraying and acrylic ultraviolet ink, there is a problem of poor bonding between the electrostatic powder spraying layer and the acrylic ultraviolet ink layer, and the problem of coating peeling is prone to occur. Summary of the invention

[0004] Aiming at the problem of poor bonding between an electrostatic powder spraying layer and an acrylic ultraviolet ink layer formed by metal coating treatment in the prior art, the present invention provides a metal medium UV printing method, wherein the method adopts a ceramic agent, electrostatic powder spraying and acrylic ultraviolet ink to coat the metal medium, wherein the powder raw material of the electrostatic powder spraying is a modified thermosetting resin modified by an aminosilane coupling agent, after the modified thermosetting resin is sprayed on the ceramic layer, the aminosilane coupling agent and the silane coupling agent in the ceramic layer will produce a coupling reaction, thereby improving the bonding between the ceramic layer and the electrostatic powder spraying layer, and the photoinitiator in the acrylic ultraviolet ink can strengthen the coupling reaction between the aminosilane coupling agent and the acrylic resin, thereby improving the bonding between the acrylic ultraviolet ink layer and the classic powder spraying layer, and significantly improving the adhesion of the coating on the surface of the metal medium.

[0005] The specific technical scheme of the present invention is: A metal medium UV printing method comprises the following steps: pre-treating the surface of a metal medium to obtain a pre-treated metal, cleaning the pre-treated metal with a cleaning agent to obtain a metal medium base, placing the metal medium base in a UV printing device and performing UV printing with acrylic ultraviolet ink, wherein the pre-treatment comprises electrostatic powder spraying, wherein the powder raw material of the electrostatic powder spraying comprises 70 to 80 parts of resin powder, 5 to 10 parts of a curing agent, 3 to 6 parts of a dispersant and 5 to 10 parts of a pigment; the resin powder is a modified thermosetting resin, and the modified thermosetting resin is prepared by modifying a thermosetting epoxy resin with an aminosilane coupling agent.

[0006] The present invention provides a metal medium UV printing method, in which a ceramic agent, electrostatic powder spraying and acrylic ester ultraviolet ink are used to coat the metal medium, and the method can significantly improve the bonding force between the electrostatic powder spraying layer and the ceramic layer and the acrylic ester ultraviolet ink layer, and significantly improve the adhesion of the coating on the surface of the metal medium. In actual operation, the present invention finds that the bonding force between the ceramic layer, the electrostatic powder spraying layer and the acrylic ester ultraviolet ink is poor, and peeling is easy to occur. After analysis, it is found that the ceramic agent of the present invention adopts the environmentally friendly metal surface treatment agent disclosed in the publication number CN111040485A, and the ceramic agent can form a ceramic film layer on the metal surface, so that the metal surface can form a chemical film layer that accepts non-metallic coatings. In addition, the ceramic agent contains a silane coupling agent that can react with the electrostatic powder spraying layer to improve the bonding force between the electrostatic powder spraying layer and the ceramic layer.

[0007] In addition, the present invention finds that the powder raw materials of the current electrostatic spraying powder are mainly thermosetting resin, curing agent, dispersant and pigment. The thermosetting resin usually used is thermosetting epoxy resin. Although epoxy resin has strong adhesion, epoxy resin has poor compatibility with acrylate, which leads to poor bonding between the acrylate UV ink and the electrostatic spraying powder layer. The acrylate UV ink layer is very easy to peel off from the electrostatic spraying powder layer.

[0008] Therefore, in view of the above problems, the present invention proposes to use a silane coupling agent to strengthen the bonding force between the electrostatic spraying powder layer and the acrylic ester ultraviolet ink. In addition, since the electrostatic spraying powder is a solid powder, and the silane coupling agent mainly exists in liquid form, the present invention selects to use a silane coupling agent to modify the epoxy resin to prepare a modified epoxy resin, and then the modified epoxy resin is made into powder for electrostatic powder spraying. The epoxy resin modified by the silane coupling agent can undergo a further coupling reaction with the silane coupling agent in the ceramic layer, which can further improve the bonding force between the ceramic layer and the electrostatic powder layer. At the same time, the silane coupling agent in the electrostatic powder layer can also undergo a coupling reaction with the acrylic ester ultraviolet ink layer, which significantly improves the bonding force between the acrylic ester ultraviolet ink layer and the electrostatic powder spray layer. The present application also selects a silane coupling agent. The present invention finds that when an aminosilane coupling agent is used, the toughness of the electrostatic powder spray layer and the acrylic ester ultraviolet ink layer is significantly improved, and the layer still does not fall off after being impacted, and the impact resistance of the electrostatic powder spray layer and the acrylic ester ultraviolet ink layer is significantly improved.

[0009] Preferably, the conditions for the electrostatic powder spraying are: an electrostatic spray gun pressure of 0.15-0.25 MPa, a voltage of 110-135 kV, a current of 50-70 uA, a curing temperature of 160-200° C., and a curing time of 15-25 min.

[0010] Preferably, the aminosilane coupling agent is one or more of KH-550, H792 and KH602.

[0011] Preferably, the mass ratio of the aminosilane coupling to the thermosetting epoxy resin is 0.5-5:99.5-95.

[0012] Preferably, the pre-treatment also includes rust removal, oil removal and ceramicization.

[0013] Preferably, the ceramic is treated with a ceramic agent, and the ceramic agent is metasilicate pentahydrate, polyvinyl alcohol, zirconium oxide, potassium zirconate, sodium nitrite, nonylphenol polyoxyethylene ether, silane coupling agent, wetting agent, film-forming aid, ethanol and water.

[0014] Preferably, the ceramicizing conditions are: soaking for 1 to 3 minutes and drying at a temperature of 100 to 120°C.

[0015] Preferably, the acrylic ester UV ink comprises acrylic ester, a photoinitiator and a pigment.

[0016] Preferably, the acrylic acid ester is alkyl acrylate and 1,6-hexaglycol diacrylate.

[0017] Preferably, the photoinitiator is 1,6-hexaglycol diacrylate, 2,4,6-trimethylbenzoyl, 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0018] Preferably, the cleaning agent is a solvent, a surfactant, a chelating agent and a pH adjuster.

[0019] Compared with the prior art, this application has the following technical effects: The method adopts ceramic agent, electrostatic powder spraying and acrylic ester ultraviolet ink to coat the metal medium, wherein the powder raw material of the electrostatic powder spraying is a modified thermosetting resin modified by an aminosilane coupling agent. After the modified thermosetting resin is sprayed on the ceramic layer, the aminosilane coupling agent and the silane coupling agent in the ceramic layer will produce a coupling reaction, thereby improving the bonding force between the ceramic layer and the electrostatic powder spraying layer. The photoinitiator in the acrylic ester ultraviolet ink can strengthen the coupling reaction between the aminosilane coupling agent and the acrylic ester resin, thereby improving the bonding force between the acrylic ester ultraviolet ink layer and the classic powder spraying layer, and significantly improving the adhesion of the coating on the surface of the metal medium. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the embodiments.

[0021] Embodiment 1: A metal medium UV printing method, wherein the metal medium is a cast iron plate, comprises the following steps: Step 1: Use a rust remover to remove rust from the surface of the cast iron plate. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the cast iron plate to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the cast iron plate in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cast iron plate with water for 5 minutes. Step 3: Soak the cast iron plate in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH value 7) for 3 minutes, and after the soaking is completed, place it under 110° C. environment for drying to prepare a ceramic layer on the surface of the cast iron plate, the thickness of the ceramic layer is 80 nm, and the cast iron plate is cleaned, blown and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the cast iron plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the cast iron plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder to the spray ring and the electrode needle of the spray gun through the powder pipe. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.2MPa, the voltage is 120kV, and the current is 60uA. Then the sprayed cast iron plate is sent to a curing furnace and cured at 170℃ for 20min. The raw materials for electrostatic powder spraying are 75 parts of resin powder (modified thermosetting resin), 10 parts of curing agent (triglycidyl isocyanurate), 5 parts of dispersant (sodium tripolyphosphate) and 10 parts of pigment; The modified thermosetting powder is made by mixing, curing and crushing aminosilane coupling agent KH-550 and thermosetting epoxy resin in a mass ratio of 2:98; Step 5: Wipe the surface of the cast iron plate with a detergent, place the cast iron plate in a UV printing device after drying, and use acrylic ester UV ink for UV printing to make coated metal. The acrylic ester UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0022] Embodiment 2: A metal medium UV printing method, wherein the metal medium is a cast iron plate, comprises the following steps: Step 1: Use a rust remover to remove rust from the surface of the cast iron plate. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the cast iron plate to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the cast iron plate in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cast iron plate with water for 5 minutes. Step 3: Soak the cast iron plate in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH value 7) for 3 minutes, and place it under 100° C. environment for drying after soaking to prepare a ceramic layer on the surface of the cast iron plate, the thickness of the ceramic layer is 80 nm, and the cast iron plate is cleaned, blown and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the cast iron plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the cast iron plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder to the spray ring and the electrode needle of the spray gun through the powder pipe. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.15MPa, the voltage is 110kV, and the current is 50uA. Then the sprayed cast iron plate is sent to a curing furnace and cured at 160℃ for 25min. The raw materials for electrostatic powder spraying are 75 parts of resin powder (modified thermosetting resin), 10 parts of curing agent (triglycidyl isocyanurate), 5 parts of dispersant (sodium tripolyphosphate) and 10 parts of pigment; The modified thermosetting powder is made by mixing, curing and crushing aminosilane coupling agent KH-550 and thermosetting epoxy resin in a mass ratio of 0.5:99.5; Step 5: Wipe the surface of the cast iron plate with a detergent, place the cast iron plate in a UV printing device after drying, and use acrylic ester UV ink for UV printing to make coated metal. The acrylic ester UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0023] Embodiment 3: A metal medium UV printing method, wherein the metal medium is a cast iron plate, comprises the following steps: Step 1: Use a rust remover to remove rust from the surface of the cast iron plate. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the cast iron plate to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the cast iron plate in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cast iron plate with water for 5 minutes. Step 3: Soak the cast iron plate in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH value 7) for 3 minutes, and place it under 100-120° C. environment for drying after soaking to prepare a ceramic layer on the surface of the cast iron plate, the thickness of the ceramic layer is 80 nm, and the cast iron plate is cleaned, blown and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the cast iron plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the cast iron plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder through the powder pipe to the spray ring and the electrode needle of the spray gun. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.25MPa, the voltage is 135kV, and the current is 70uA. Then, the sprayed cast iron plate is sent to a curing furnace for curing at 200℃ for 15min. The raw materials for electrostatic powder spraying are 80 parts of resin powder (modified thermosetting resin), 5 parts of curing agent (triglycidyl isocyanurate), 5 parts of dispersant (sodium tripolyphosphate) and 10 parts of pigment; The modified thermosetting powder is made by mixing, curing and crushing aminosilane coupling agent KH-550 and thermosetting epoxy resin in a mass ratio of 5:95; Step 5: Wipe the surface of the cast iron plate with a detergent, place the cast iron plate in a UV printing device after drying, and use acrylic ester UV ink for UV printing to make coated metal. The acrylic ester UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0024] Embodiment 4: A metal medium UV printing method, wherein the metal medium is a cast iron plate, comprises the following steps: Step 1: Use a rust remover to remove rust from the surface of the aluminum plate. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the aluminum plate to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the aluminum plate in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cast iron plate with water for 5 minutes. Step 3: Soak the aluminum plate in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH value 7) for 3 minutes, and place it at 100-120° C. for drying after soaking to prepare a ceramic layer on the surface of the aluminum plate. The thickness of the ceramic layer is 80 nm, and the aluminum plate is cleaned, blown and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the aluminum plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the aluminum plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder to the spray ring and the electrode needle of the spray gun through the powder pipe. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.15-0.25MPa, the voltage is 110-135kV, and the current is 50-70uA. Then, the sprayed aluminum plate is sent to a curing furnace for curing at 160-200℃ for 15-25min. The raw materials for electrostatic powder spraying are 70-80 parts of resin powder (modified thermosetting resin), 5-10 parts of curing agent (triglycidyl isocyanurate), 3-6 parts of dispersant (sodium tripolyphosphate) and 5-10 parts of pigment; The modified thermosetting powder is made by mixing, curing and crushing aminosilane coupling agent H792 and thermosetting epoxy resin in a mass ratio of 3:97; Step 5: Wipe the surface of the cast iron plate with a detergent, place the aluminum plate in a UV printing device after drying, and use acrylic ester UV ink for UV printing to make a coated metal. The acrylic ester UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0025] Embodiment 5: A metal medium UV printing method, wherein the metal medium is a cast iron plate, comprises the following steps: Step 1: Use a rust remover to remove rust from the surface of the cold-rolled sheet. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the cold-rolled sheet to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the cold-rolled sheet in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cold-rolled sheet with water for 5 minutes. Step 3: Soak the cold-rolled sheet in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH 7) for 3 minutes, and place it in an environment of 100-120° C. for drying after the soaking. A ceramic layer is prepared on the surface of the cold-rolled sheet, and the thickness of the ceramic layer is 80 nm. The cold-rolled sheet is cleaned, blown dry and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the cold-rolled plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the cold-rolled plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder through the powder pipe to the spray ring and the electrode needle of the spray gun. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.15-0.25MPa, the voltage is 110-135kV, and the current is 50-70uA. Then, the cast iron plate after spraying is sent to a curing furnace for curing at 160-200℃ for 15-25min. The raw materials for electrostatic powder spraying are 70-80 parts of resin powder (modified thermosetting resin), 5-10 parts of curing agent (triglycidyl isocyanurate), 3-6 parts of dispersant (sodium tripolyphosphate) and 5-10 parts of pigment; The modified thermosetting powder is made by mixing, curing and crushing aminosilane coupling agent KH602 and thermosetting epoxy resin in a mass ratio of 2:98; Step 5: Wipe the surface of the cold-rolled plate with a detergent, place the cold-rolled plate in a UV printing device after drying, and use acrylate UV ink for UV printing to make a coated metal. The acrylate UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0026] Comparative Example 1: Compared with Example 1, the powder pressing material for electrostatic powder spraying in Comparative Example 1 uses thermosetting epoxy resin instead of modified thermosetting resin, and includes the following steps: Step 1: Use a rust remover to remove rust from the surface of the cast iron plate. After the rust removal is completed, use 240-grit sandpaper to polish the surface of the cast iron plate to make the metal surface smooth. Then use 0.5mm sand particles for sandblasting for 30s, and then use 1mm sand particles for sandblasting for 10s. The angle of the sandblasting direction is 90°; Step 2: Soak the cast iron plate in a degreasing agent (16 g / L phosphoric acid and 6 g / L emulsifier OP-10) for degreasing. After degreasing, rinse the cast iron plate with water for 5 minutes. Step 3: Soak the cast iron plate in a ceramic agent (components include 6% sodium silicate, 5% chitosan, 0.1% urotropine, 0.08% OP-10 emulsifier, 0.05% catechol, 0.02% PM-WET100 silane coupling agent, 0.02% dodecyl ester, 6% ethanol, water balance, pH value 7) for 3 minutes, and after the soaking is completed, place it under 110° C. environment for drying to prepare a ceramic layer on the surface of the cast iron plate, the thickness of the ceramic layer is 80 nm, and the cast iron plate is cleaned, blown and dried with water; Step 4: Use an electrostatic spray gun to electrostatically spray powder on the cast iron plate to form an electrostatic powder spray layer on the ceramic layer. Connect a high-voltage negative electrode to the metal spray ring and the electrode needle at the head of the electrostatic spray gun, and ground the cast iron plate to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports the powder from the powder supply cylinder to the spray ring and the electrode needle of the spray gun through the powder pipe. The powder carries a negative charge and is sprayed on the surface of the positively charged cast iron plate. The pressure of the electrostatic spray gun is 0.2MPa, the voltage is 120kV, and the current is 60uA. Then the sprayed cast iron plate is sent to a curing furnace and cured at 170℃ for 20min. The raw materials for electrostatic powder spraying are 75 parts of resin powder (thermosetting epoxy resin), 10 parts of curing agent (triglycidyl isocyanurate), 5 parts of dispersant (sodium tripolyphosphate) and 10 parts of pigment; Step 5: Wipe the surface of the cast iron plate with a detergent, place the cast iron plate in a UV printing device after drying, and use acrylic ester UV ink for UV printing to make coated metal. The acrylic ester UV ink includes 40 parts of alkyl acrylate, 40 parts of 1,6-hexaglycol diacrylate, 5 parts of 1,6-hexaglycol diacrylate, 5 parts of 2,4,6-trimethylbenzoyl, 5 parts of 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 5 parts of 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.

[0027] Comparative Example 2: Compared with Example 1, in Comparative Example 2, trimethoxysilane was used to modify the thermosetting epoxy resin, and other conditions were the same as those in Example 1.

[0028] Test example: The bonding strength and impact resistance of the coated metals prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were tested; the bonding strength test included a primary adhesion test and a secondary adhesion test. The first adhesion test steps are: use a cutting machine to cut the coated metal until the cutting depth reaches the metal material, forming 100 square grids with a side length of 1 mm, and then peel it off with cellophane tape. The bonding strength is evaluated by calculating the number of remaining coatings after peeling; The steps of the secondary adhesion test are as follows: immerse the coated metal in boiling water for two hours, and then conduct another adhesion test after the immersion is completed. The impact resistance is tested in accordance with "GB / T 11548 Test method for impact resistance of hard plastic sheets (drop hammer method)". A drop hammer impact tester is used to drop a 5kg drop hammer freely from a certain height to impact the coated metal, record the energy required to cause 50% damage, and calculate the impact resistance.

[0029] The test results are shown in Table 1; Table 1 Test results One-time adhesion (pieces) Secondary adhesion (pcs) Impact resistance (J / m) Example 1 100 100 15.3 Example 2 100 99 15.1 Example 3 100 99 15.2 Example 4 100 100 16.7 Example 5 100 100 18.3 Comparative Example 1 88 73 10.3 Comparative Example 2 95 88 11.6 As shown in Table 1, the test results of the primary adhesion of Examples 1 to 5 are 100, and the test results of the secondary adhesion are 99 to 100. The above results show that the coating layer on the coated metal surface prepared by the method provided by the present invention has excellent bonding strength.

[0030] In Comparative Example 1, a conventional epoxy resin was used. The primary adhesion test result of Comparative Example 1 was 88, and the secondary adhesion test result of Comparative Example 1 was 73. Compared with Example 1, the bonding force of the coating layer on the coated metal surface in Comparative Example 1 was significantly lower than that in Example 1; in Comparative Example 2, a conventional silane coupling agent was used to modify the thermosetting epoxy resin. The primary adhesion test result of Comparative Example 2 was 95, and the secondary adhesion test result of Comparative Example 2 was 88. Compared with Example 1, the bonding force of the coating layer on the coated metal surface in Comparative Example 2 was lower than that in Example 1. The above results show that after the thermosetting epoxy resin modified by the present invention using the aminosilane coupling agent, the bonding force of the coating layer on the coated metal surface is significantly improved, and the effect of using the aminosilane coupling agent is more significant.

[0031] In addition, from the impact resistance results of Example 1, Comparative Example 1 and Comparative Example 2, it can be found that the use of aminosilane coupling agent can significantly improve the impact resistance of the coating layer on the surface of the coated metal, and can enable the coated metal to still have excellent protection performance during the collision process.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A metal medium UV printing method, characterized in that: The following steps are involved: The surface of a metal medium is pretreated to obtain a pretreated metal, the pretreated metal is cleaned with a cleaning agent to obtain a metal medium base plate, the metal medium base plate is placed in a UV printing device and UV printing is performed using acrylic ultraviolet ink, the pretreatment includes electrostatic powder spraying, the powder raw materials of the electrostatic powder spraying are 70-80 parts of resin powder, 5-10 parts of curing agent, 3-6 parts of dispersant, and 5-10 parts of pigment; the resin powder is a modified thermosetting resin, and the modified thermosetting resin is made of a thermosetting epoxy resin modified by an aminosilane coupling agent.

2. The method according to claim 1, characterized in that: The conditions for the electrostatic powder spraying are as follows: an electrostatic spray gun pressure of 0.15-0.25 MPa, a voltage of 110-135 kV, a current of 50-70 uA, a curing temperature of 160-200° C., and a curing time of 15-25 min.

3. The method according to claim 1, characterized in that: The aminosilane coupling agent is one or more of KH-550, H792 and KH602.

4. The method according to claim 1, characterized in that: The pre-treatment also includes rust removal, oil removal and ceramicization.

5. The method according to claim 4, characterized in that: The ceramic is treated with a ceramic agent, and the ceramic agent is metasilicate pentahydrate, polyvinyl alcohol, zirconium oxide, potassium zirconate, sodium nitrite, nonylphenol polyoxyethylene ether, silane coupling agent, wetting agent, film-forming aid, ethanol and water.

6. The method according to claim 4 or 5, characterized in that: The immersion time of the ceramicization is 1 to 3 minutes.

7. The method according to claim 4 or 5, characterized in that: The drying temperature of the ceramicization is 100-120°C.

8. The method according to claim 1, characterized in that: The acrylic ester ultraviolet ink comprises acrylic ester, a photoinitiator and a pigment.

9. The method according to claim 8, characterized in that: The acrylic acid ester is 10-50 parts of alkyl acrylic acid ester and 5-40 parts of 1,6-hexaglycol diacrylate.

10. The method according to claim 8, characterized in that: The photoinitiator is 1,6-hexaglycol diacrylate, 2,4,6-trimethylbenzoyl, 2-hydroxy-4-hydrooxyethyl-2-methylpropiophenone and 2-methyl-1-(4-methylthiophenyl)-2-pyroline-1-propanone.