A laser-engravable high-gloss black coating for automotive taillights and its preparation method

Abstract

This invention relates to a laser-engravable high-gloss black coating for automotive taillights and its preparation method, belonging to the field of coating preparation technology. The formulation of the laser-engravable high-gloss black coating is as follows (by weight): 40-60 parts polyurethane acrylate, 3-5 parts modified nano-bismuth oxide, 3-5 parts trimethylolpropane triacrylate, 1-3 parts 4-methylbenzophenone, 1-2 parts carbon black, and 0.5-1.5 parts leveling agent. The modified nano-bismuth oxide is prepared by treatment with ammonium molybdate solution and grafting with a silane coupling agent. Its layered structure synergistically enhances UV absorption efficiency and weather resistance with the molybdate layer. 4-methylbenzophenone and modified nano-bismuth oxide form a light absorption composite system, which, combined with the high cross-linking density network constructed by trimethylolpropane triacrylate, achieves narrow linewidth laser engraving precision. This invention solves the technical problems of low laser engraving precision, poor adhesion, and insufficient solvent resistance in traditional high-gloss black coatings, and is particularly suitable for precision marking applications such as automotive taillights.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, and relates to a laser-engravable high-gloss black coating for use in automobile taillights and its preparation method. Background Technology

[0002] In the automotive taillight manufacturing industry, high-gloss black coatings are widely used due to their unique decorative effect and functional identification purpose. However, traditional high-gloss black coatings exhibit significant technical shortcomings in laser engraving processes. For example, existing high-gloss black coatings mostly use resin systems such as polyester and acrylic, which have low laser absorption rates, requiring a substantial increase in laser power or repeated engraving during the process. Current technologies cannot simultaneously meet the multiple demands of high-precision laser engraving, high weather resistance, and mechanical properties, necessitating the development of a laser-engravable high-gloss black coating for automotive taillights and its preparation method. Summary of the Invention

[0003] The purpose of this invention is to provide a laser-engravable high-gloss black coating for use in automotive taillights and its preparation method, thereby solving the technical problem of poor laser engraving of traditional high-gloss black coatings.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A laser-etchable high-gloss black coating for use in automotive taillights, wherein the formulation of the laser-etchable high-gloss black coating is as follows, by weight: 40-60 parts polyurethane acrylate, 3-5 parts modified nano bismuth oxide, 3-5 parts trimethylolpropane triacrylate, 1-3 parts 4-methylbenzophenone, 1-2 parts carbon black, and 0.5-1.5 parts leveling agent.

[0006] Furthermore, the preparation method of the modified nano-bismuth oxide is as follows:

[0007] S2-1: Add 10-20 parts by weight of nano-bismuth oxide to 100 parts by weight of ammonium molybdate solution, stir at 500-600 r / min at 60 ℃ for 2-3 h, wash with deionized water, and then dry in a vacuum drying oven at 80-100 ℃ for 12-16 h to obtain powder A;

[0008] S2-2: Place powder A in a ball mill and ball mill. Add silane coupling agent KH560 after 30 min of ball milling, and continue ball milling for 1-2 h. Then, place the ball-milled powder at room temperature and dry for 24 h to obtain the modified nano bismuth oxide.

[0009] Furthermore, the leveling agent is one or a combination of BYK-333 and TEGO Glide 450.

[0010] Furthermore, the concentration of the ammonium molybdate solution in S2-1 is 0.3~0.5 mol / L.

[0011] Furthermore, the amount of silane coupling agent KH560 added in S2-2 is 1-3% of the mass of powder A.

[0012] Furthermore, the ball milling speed in S2-2 is 100~120 r / min.

[0013] A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights, the specific steps of which are as follows:

[0014] S7-1: Add polyurethane acrylate, trimethylolpropane triacrylate, and 4-methylbenzophenone in sequence according to the formula ratio, and disperse at 800-1000 r / min for 10-30 min at 25-35 ℃; add modified nano bismuth oxide and carbon black, increase the speed to 1100-1300 r / min, and continue to disperse for 20-40 min; then add leveling agent, adjust the speed to 500-700 r / min, and continue to disperse for 5-10 min to obtain the coating.

[0015] S7-2: The car taillights are wiped with isopropanol and then treated with plasma. The plasma gas is argon, and the treatment time is 20-30 seconds to obtain the pretreated substrate.

[0016] S7-3: The coating is sprayed onto the pretreated substrate at a spray gun pressure of 0.3~0.5 MPa and a coating thickness of 15~20 μm. It is cured under nitrogen protection using LED-UV with a wavelength of 355 nm, an energy density of 500~700 mJ / cm², and an irradiation time of 5~10 s. Subsequently, laser engraving is performed at a power of 15~20 W, a speed of 1000~1200 mm / s, and a frequency of 60~80kHz to obtain the laser-engravable high-gloss black coating.

[0017] Furthermore, the taillights in S7-2 are made of polycarbonate.

[0018] Furthermore, the plasma processing power in S7-2 is 50~60 W.

[0019] Furthermore, in S7-3, the laser engraving spot size is 0.06~0.08 mm, the mode is dot matrix engraving, and the dot spacing is 0.025 mm.

[0020] Polyurethane acrylate, as the main resin, provides the basic properties of the coating. Containing acrylate double bonds, it forms a cross-linked network through UV curing. Trimethylolpropane triacrylate (TMT), as a cross-linking agent, enhances the cross-linking density and coating performance. Each TMT molecule contains three acrylate double bonds, forming a three-dimensional network structure after curing, significantly improving the coating's hardness and abrasion resistance. Simultaneously, the introduction of TMT further improves the coating's chemical resistance. The high cross-linking density formed by TMT effectively reduces solvent molecule penetration, making the coating resistant to wiping with organic solvents such as ethanol and isopropanol. Furthermore, the short-chain structure of TMT introduces flexible nodes into the cross-linking network, efficiently balancing hardness and adhesion, and preventing brittle cracking of the coating.

[0021] Upon absorbing ultraviolet light energy, 4-methylbenzophenone generates free radicals through intramolecular electron transfer, initiating a rapid polymerization reaction of resins such as polyurethane acrylates, while simultaneously avoiding fluorescence / phosphorescence energy loss. Meanwhile, when the laser energy is absorbed by the coating, the photochemical conversion efficiency of 4-methylbenzophenone directly affects the intensity of the thermal effect. The Gaussian distribution characteristics of the laser beam, in synergy with 4-methylbenzophenone, create a micrometer-scale heat-affected zone in the laser-irradiated area.

[0022] 4-Methylbenzophenone (4-methylbenzophenone) exhibits a synergistic effect with modified nano-bismuth oxide. The modified nano-bismuth oxide generates Mie scattering, increasing the optical path length and significantly enhancing the absorption efficiency of 4-methylbenzophenone. The layered structure of the modified nano-bismuth oxide inhibits oxygen permeation, raising the thermal oxidation temperature of the coating and thus improving its weather resistance. The absorption of 4-methylbenzophenone and the molybdate layer on the surface of the modified nano-bismuth oxide exhibit spectral complementarity, forming a composite absorption system that significantly improves the overall UV absorption rate of the coating. Furthermore, the molybdate layer can capture excess free radicals, reducing the risk of photodegradation of the coating.

[0023] Under stirring conditions at 60°C, ammonium molybdate and nano-bismuth oxide undergo an ion exchange reaction, forming a covalently bonded molybdate layer on the surface of the nano-bismuth oxide, rather than through simple physical adsorption. Simply mixing ammonium molybdate and nano-bismuth oxide relies solely on the inherent absorption of the nano-bismuth oxide; however, in this invention, the absorption band edge of bismuth molybdate exhibits a red shift, significantly broadening the laser absorption bandwidth and greatly improving laser energy utilization. Furthermore, the molybdate layer acts as an ultraviolet shielding layer, absorbing and quenching photogenerated free radicals, thereby enhancing the coating's weather resistance. The molybdate layer composited on the nano-bismuth oxide surface does not decompose at high temperatures, ensuring performance stability during laser engraving. This invention enhances visible light absorption by forming a molybdate layer on the nano-bismuth oxide surface, improving coating blackness. Ball milling to submicron levels effectively reduces light scattering and improves blackness saturation. The molybdate layer can also act as a laser absorber, converting UV laser energy into heat energy during laser engraving, rapidly raising the local temperature to the material's vaporization threshold and creating sharp edges.

[0024] The preparation method includes a substrate pretreatment step. Isopropanol wiping effectively removes oil stains from the surface of the automotive taillight substrate, preventing pinholes in the coating. The plasma treatment power is set to 50-60W for 20-30s, matching the heat distortion temperature of the plastic substrate to avoid substrate burns. Plasma bombardment introduces oxygen-containing polar groups onto the surface, which can form hydrogen bonds with the molybdate layer in the coating, significantly improving coating adhesion.

[0025] The spraying pressure is set to 0.3~0.5MPa to ensure good atomization of the coating and the formation of a uniform wet film. The dry film thickness after curing meets the requirements of laser engraving precision. If the wet film is too thin, the substrate will be translucent and the blackness will be insufficient; if the wet film is too thick, it will increase internal stress and reduce adhesion.

[0026] The beneficial effects of this invention are:

[0027] This invention utilizes the synergistic effect of polyurethane acrylate and trimethylolpropane triacrylate to form a high-crosslink density network in the coating, significantly improving its hardness, abrasion resistance, and chemical resistance. Simultaneously, the composite system of 4-methylbenzophenone and modified nano-bismuth oxide greatly enhances the coating's weather resistance. Furthermore, the modified nano-bismuth oxide improves the absorption efficiency of 4-methylbenzophenone through Mie scattering, and combined with the spectral complementarity effect of the molybdate layer, the coating's ultraviolet absorption rate and laser energy utilization rate are significantly improved, enabling high-precision engraving with narrow linewidths. Detailed Implementation

[0028] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0029] Example 1: A laser-etchable high-gloss black coating for automotive taillights, wherein the laser-etchable high-gloss black coating has the following formula 1, calculated by weight: 50 parts polyurethane acrylate, 4 parts modified nano bismuth oxide, 4 parts trimethylolpropane triacrylate, 2 parts 4-methylbenzophenone, 1.5 parts carbon black, and 1 part BYK-333.

[0030] The preparation method of the modified nano-bismuth oxide is as follows:

[0031] S2-1: 15 parts by weight of nano-bismuth oxide were added to 100 parts by weight of ammonium molybdate solution with a concentration of 0.4 mol / L, and stirred at 550 r / min at 60 ℃ for 2.5 h. The mixture was washed with deionized water and then dried in a vacuum drying oven at 90 ℃ for 14 h to obtain powder A.

[0032] S2-2: Place powder A in a ball mill and ball mill at a speed of 110 r / min. After ball milling for 30 min, add 2% by weight of silane coupling agent KH560 of powder A and continue ball milling for 1.5 h. Then, place the ball-milled powder at room temperature and dry for 24 h to obtain the modified nano bismuth oxide.

[0033] A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights, the specific steps of which are as follows:

[0034] S7-1: Add polyurethane acrylate, trimethylolpropane triacrylate, and 4-methylbenzophenone in sequence according to the proportion of Formula 1, and disperse at 900 r / min for 20 min at 30 ℃; add modified nano bismuth oxide and carbon black, increase the speed to 1200 r / min, and continue to disperse for 30 min; then add BYK-333, adjust the speed to 600 r / min, and continue to disperse for 8 min to obtain the coating.

[0035] S7-2: The polycarbonate car taillight is wiped with isopropanol and then treated with plasma. The plasma gas is argon, the power is 55 W, and the treatment time is 25 s to obtain the pretreated substrate.

[0036] S7-3: The coating is sprayed onto the pretreated substrate at a spray gun pressure of 0.4 MPa and a coating thickness of 18 μm. It is cured under nitrogen protection using LED-UV with a wavelength of 355 nm, an energy density of 600 mJ / cm², and an irradiation time of 8 s. Subsequently, laser engraving is performed at a power of 18 W, a speed of 1100 mm / s, a frequency of 70 kHz, a spot size of 0.07 mm, a dot matrix engraving mode, and a dot pitch of 0.025 mm to obtain the laser-engravable high-gloss black coating.

[0037] Example 2: A laser-etchable high-gloss black coating for automotive taillights. The formula 2 of the laser-etchable high-gloss black coating is as follows, calculated by weight: 40 parts polyurethane acrylate, 3 parts modified nano bismuth oxide, 3 parts trimethylolpropane triacrylate, 1 part 4-methylbenzophenone, 1 part carbon black, and 0.5 parts TEGO Glide 450.

[0038] The preparation method of the modified nano-bismuth oxide is as follows:

[0039] S2-1: 10 parts by weight of nano-bismuth oxide were added to 100 parts by weight of ammonium molybdate solution with a concentration of 0.3 mol / L, and stirred at 500 r / min for 2 h at 60 ℃. After washing with deionized water, the mixture was dried in a vacuum drying oven at 80 ℃ for 12 h to obtain powder A.

[0040] S2-2: Place powder A in a ball mill and ball mill at a speed of 100 r / min. After ball milling for 30 min, add 1% by weight of silane coupling agent KH560 of powder A and continue ball milling for 1 h. Then, place the ball-milled powder at room temperature and dry for 24 h to obtain the modified nano bismuth oxide.

[0041] A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights, the specific steps of which are as follows:

[0042] S7-1: Add polyurethane acrylate, trimethylolpropane triacrylate, and 4-methylbenzophenone in sequence according to the proportion of Formula 2, and disperse at 800 r / min for 10 min at 25 ℃; add modified nano bismuth oxide and carbon black, increase the speed to 1100 r / min, and continue to disperse for 20 min; then add leveling agent, adjust the speed to 500 r / min, and continue to disperse for 5 min to obtain the coating.

[0043] S7-2: The polycarbonate car taillight is wiped with isopropanol and then treated with plasma. The plasma gas is argon, the power is 50 W, and the treatment time is 20 s to obtain the pretreated substrate.

[0044] S7-3: The coating is sprayed onto the pretreated substrate at a spray gun pressure of 0.3 MPa and a coating thickness of 15 μm. It is cured under nitrogen protection using LED-UV with a wavelength of 355 nm, an energy density of 500 mJ / cm², and an irradiation time of 5 s. Subsequently, laser engraving is performed at a power of 15 W, a speed of 1000 mm / s, a frequency of 60 kHz, a spot size of 0.06 mm, a dot matrix engraving mode, and a dot pitch of 0.025 mm to obtain the laser-engravable high-gloss black coating.

[0045] Example 3: A laser-etchable high-gloss black coating for automotive taillights, wherein the laser-etchable high-gloss black coating has the following formula (in parts by weight): 60 parts polyurethane acrylate, 5 parts modified nano bismuth oxide, 5 parts trimethylolpropane triacrylate, 3 parts 4-methylbenzophenone, 2 parts carbon black, 0.5 parts BYK-333, and 0.5 parts TEGO Glide 450.

[0046] The preparation method of the modified nano-bismuth oxide is as follows:

[0047] S2-1: 20 parts by weight of nano-bismuth oxide were added to 100 parts by weight of ammonium molybdate solution with a concentration of 0.5 mol / L, and stirred at 60 ℃ and 600 r / min for 3 h. The mixture was washed with deionized water and then dried in a vacuum drying oven at 100 ℃ for 16 h to obtain powder A.

[0048] S2-2: Place powder A in a ball mill and ball mill at a speed of 120 r / min. After ball milling for 30 min, add 3% by weight of silane coupling agent KH560 of powder A and continue ball milling for 2 h. Then, place the ball-milled powder at room temperature and dry for 24 h to obtain the modified nano bismuth oxide.

[0049] A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights, the specific steps of which are as follows:

[0050] S7-1: Add polyurethane acrylate, trimethylolpropane triacrylate, and 4-methylbenzophenone in sequence according to the proportion of formulation 3, and disperse at 1000 r / min for 30 min at 35 ℃; add modified nano bismuth oxide and carbon black, increase the speed to 1300 r / min, and continue to disperse for 40 min; then add BYK-333 and TEGO Glide 450, adjust the speed to 700 r / min, and continue to disperse for 10 min to obtain the coating.

[0051] S7-2: The polycarbonate car taillights are wiped with isopropanol and then treated with plasma. The plasma gas is argon, the power is 60 W, and the treatment time is 30 s to obtain the pretreated substrate.

[0052] S7-3: The coating is sprayed onto the pretreated substrate at a spray gun pressure of 0.5 MPa and a coating thickness of 20 μm. It is cured under nitrogen protection using LED-UV with a wavelength of 355 nm, an energy density of 700 mJ / cm², and an irradiation time of 10 s. Subsequently, laser engraving is performed at a power of 20 W, a speed of 1200 mm / s, a frequency of 80 kHz, a spot size of 0.08 mm, a dot matrix engraving mode, and a dot pitch of 0.025 mm to obtain the laser-engravable high-gloss black coating.

[0053] Comparative Example 1

[0054] The nano-bismuth oxide was not modified, and the remaining steps were the same as in Example 1.

[0055] Comparative Example 2

[0056] Ammonium molybdate was not added in the preparation of the modified nano-bismuth oxide; the remaining steps were the same as in Example 1.

[0057] Comparative Example 3

[0058] The formulation for the laser-engravable high-gloss black coating does not include 4-methylbenzophenone, and the remaining steps are the same as in Example 1.

[0059] Performance testing:

[0060] The adhesion of the coatings prepared in the examples and comparative examples was tested according to GB / T 9286-2021. The laser engraving linewidth of the coatings prepared in the examples and comparative examples was measured using a laser confocal microscope, and the laser engraving effect of the coatings was observed.

[0061] 100-grid classification Laser engraving line width (μm) Laser engraving effect Example 1 Level 0 50 Very clear Example 2 Level 0 51 Very clear Example 3 Level 0 53 Very clear Comparative Example 1 Level 1 64 Clear Comparative Example 2 Level 1 68 Clear Comparative Example 3 Level 2 76 Generally clear

[0062] As can be seen from the examples and comparative data, the coating obtained by the preparation method of the present invention has good substrate adhesion and laser engraving properties.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. A laser-engravable high-gloss black coating for use in automotive taillights, characterized in that, The formula for the laser-engravable high-gloss black coating is as follows, by weight: 40-60 parts polyurethane acrylate, 3-5 parts modified nano bismuth oxide, 3-5 parts trimethylolpropane triacrylate, 1-3 parts 4-methylbenzophenone, 1-2 parts carbon black, and 0.5-1.5 parts leveling agent. The preparation method of the modified nano-bismuth oxide is as follows: S2-1: Add 10-20 parts by weight of nano-bismuth oxide to 100 parts by weight of ammonium molybdate solution, stir at 500-600 r / min at 60 ℃ for 2-3 h, wash with deionized water, and then dry in a vacuum drying oven at 80-100 ℃ for 12-16 h to obtain powder A; S2-2: Place powder A in a ball mill and ball mill. Add silane coupling agent KH560 after 30 min of ball milling, and continue ball milling for 1-2 h. Then, place the ball-milled powder at room temperature and dry for 24 h to obtain the modified nano bismuth oxide.

2. The laser-engravable high-gloss black coating for automotive taillights according to claim 1, characterized in that, The leveling agent is one or a combination of BYK-333 and TEGO Glide 450.

3. The laser-engravable high-gloss black coating for automotive taillights according to claim 1, characterized in that, The concentration of the ammonium molybdate solution in S2-1 is 0.3~0.5 mol / L.

4. The laser-engravable high-gloss black coating for automotive taillights according to claim 1, characterized in that, The amount of silane coupling agent KH560 added in S2-2 is 1-3% of the mass of powder A.

5. The laser-engravable high-gloss black coating for automotive taillights according to claim 1, characterized in that, The ball milling speed in S2-2 is 100~120 r / min.

6. A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights as described in any one of claims 1 to 5, characterized in that, The specific steps of the preparation method are as follows: S7-1: Add polyurethane acrylate, trimethylolpropane triacrylate, and 4-methylbenzophenone in sequence according to the formula ratio, and disperse at 800-1000 r / min for 10-30 min at 25-35 ℃; add modified nano bismuth oxide and carbon black, increase the speed to 1100-1300 r / min, and continue to disperse for 20-40 min; then add leveling agent, adjust the speed to 500-700 r / min, and continue to disperse for 5-10 min to obtain the coating. S7-2: The car taillights are wiped with isopropanol and then treated with plasma. The plasma gas is argon, and the treatment time is 20-30 seconds to obtain the pretreated substrate. S7-3: The coating is sprayed onto the pretreated substrate at a spray gun pressure of 0.3~0.5 MPa and a coating thickness of 15~20 μm. It is cured under nitrogen protection using LED-UV with a wavelength of 355 nm, an energy density of 500~700 mJ / cm², and an irradiation time of 5~10 s. Subsequently, laser engraving is performed at a power of 15~20 W, a speed of 1000~1200 mm / s, and a frequency of 60~80 kHz to obtain the laser-engravable high-gloss black coating.

7. The method for preparing a laser-engravable high-gloss black coating for use in automotive taillights according to claim 6, characterized in that, The taillights in S7-2 are made of polycarbonate.

8. The method for preparing a laser-engravable high-gloss black coating for automotive taillights according to claim 6, characterized in that, The plasma processing power in S7-2 is 50~60 W.

9. A method for preparing a laser-engravable high-gloss black coating for use in automotive taillights according to claim 6, characterized in that, The laser engraving spot in S7-3 is 0.06~0.08 mm, the mode is dot matrix engraving, and the dot spacing is 0.025 mm.