A high-adhesion acrylic coating and its preparation method

Abstract

This invention belongs to the field of coating technology, specifically disclosing a high-adhesion acrylic coating and its preparation method. The invention involves microwave irradiation of nano-silica in the presence of dopamine hydrochloride to obtain modified nano-silica, which is then mixed with an acrylic resin emulsion. A continuous flow process is then used to add isocyanate curing agent, titanium dioxide pigment, hydroxyl-terminated hyperbranched polyester, polycarboxylate ammonium salt dispersant, polysiloxane defoamer, and lithium magnesium silicate. After segmental curing, a coating with good adhesion, corrosion resistance, impedance, and low surface roughness is obtained, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically discloses a high-adhesion acrylic coating and its preparation method. Background Technology

[0002] Acrylic coatings are widely used in construction, automotive, and marine engineering due to their excellent weather resistance, chemical resistance, and decorative properties. However, with the diversification of application scenarios and the increasing performance requirements, traditional acrylic coatings have gradually revealed some shortcomings in terms of adhesion and corrosion resistance. Traditional acrylic coatings have limited adhesion to metallic or non-metallic substrates, especially in harsh environments such as high humidity and high salt spray, where they are prone to peeling or detachment, leading to a decrease in coating durability and protective performance. Their corrosion resistance in marine environments is poor, and the coating is easily penetrated by corrosive media, limiting their application in critical components such as marine engineering equipment. Traditional preparation processes struggle to achieve uniform dispersion of nanofillers, resulting in high surface roughness and insufficient density, affecting the coating's mechanical and protective properties. Traditional curing processes are inefficient, energy-intensive, and prone to generating internal stress in the coating, impacting adhesion and durability. Furthermore, the functionality of traditional acrylic coatings is mainly achieved by adding single-functional fillers, making it difficult to meet the needs of multi-scenario applications. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this invention modifies nano-silica by subjecting it to microwave radiation in the presence of dopamine hydrochloride to obtain modified nano-silica. This modified nano-silica is then combined with a continuous flow process and dual-wavelength photocuring technology to produce an acrylic coating by mixing it with acrylic resin emulsion, isocyanate curing agent, titanium dioxide pigment, hydroxyl-terminated hyperbranched polyester, polycarboxylate ammonium salt dispersant, polysiloxane defoamer, and lithium magnesium silicate. This coating exhibits high adhesion, corrosion resistance, low impedance, and low surface roughness.

[0004] To achieve the above objectives, the present invention provides the following technical solution to address the technical problem:

[0005] In a first aspect, the present invention provides a high-adhesion acrylic coating, comprising, by weight, 45-55 parts acrylic resin emulsion, 10-12 parts curing agent, 15-18 parts pigment, 6-8 parts modified nano-silica, 3-5 parts hydroxyl-terminated hyperbranched polyester, 2-3 parts dispersant, 0.8-1.2 parts defoamer, and 1.5-2.5 parts lithium magnesium silicate;

[0006] The modified nano-silica is a polydopamine / nano-silica composite particle.

[0007] This invention utilizes the synergistic effect of polydopamine / nano silica composite particles and hydroxyl-terminated hyperbranched polyester to construct a biomimetic multi-level micro-nano interface structure, which improves coating adhesion by more than 40% (compared to traditional acrylic coatings), while achieving defect-free curing of 150-200μm thick coatings.

[0008] In some of these embodiments, by weight, the composition includes 50 parts acrylic resin emulsion, 11 parts curing agent, 16 parts pigment, 7 parts modified nano silica, 4 parts hydroxyl-terminated hyperbranched polyester, 2.5 parts dispersant, 1 part defoamer, and 2 parts lithium magnesium silicate.

[0009] In some embodiments, the curing agent is an isocyanate curing agent; the pigment is titanium dioxide; the dispersant is a polycarboxylate ammonium salt dispersant; and the defoamer is a polysiloxane defoamer.

[0010] In some embodiments, the preparation of the modified nano-silica includes the following steps:

[0011] S1. Disperse nano-silica in a Tris buffer solution with pH=8-9, and add dopamine hydrochloride to a concentration of 1.5-2.5 mg / mL;

[0012] S2. Apply 80-120W microwave intermittent radiation at 40-50℃ for 6-10 hours;

[0013] S3. After centrifugation and washing with a mixed ethanol / water solvent, composite particles with a polydopamine coating thickness of 5-20 nm are obtained by vacuum freeze-drying.

[0014] By using microwave intermittent radiation technology, the thickness of the polydopamine coating layer can be precisely controlled (5-20nm), which improves the coating uniformity by 65% ​​compared with the traditional water bath method. The dispersion particle size of nanoparticles in the resin is reduced from >1μm to ≤0.5μm.

[0015] Secondly, the present invention also provides a method for preparing the above-mentioned high-adhesion acrylic coating, comprising the following steps:

[0016] (1) Acrylic resin emulsion and modified nano-silica were premixed using a microchannel reactor;

[0017] (2) Under nitrogen protection, a continuous flow process is used to add curing agent, pigment and other additives in sequence;

[0018] (3) Segmented curing via dual-wavelength ultraviolet-LED: 365nm irradiation energy 600-1000mJ / cm 2 Followed by 405nm irradiation with an energy of 300-500mJ / cm 2The 365nm and 405nm segmented curing increases the light penetration depth to 0.8mm and improves the cross-linking density of the bottom layer by 22%, solving the adhesion gradient problem caused by uneven curing of thick coatings.

[0019] (4) The medium is dispersed in three stages by a high-pressure homogenizer until the particle size is ≤0.5μm.

[0020] In some embodiments, in step (1), the flow rate ratio of the acrylic resin emulsion to the modified nano silica is (4-6):1.

[0021] In some embodiments, in step (1), the microchannel reactor employs a 3D-printed tree-like fractal structure, achieving a mixing efficiency ≥98% and a single channel length ≤5cm. Using a 3D-printed tree-like fractal reactor increases the mixing efficiency to 98%, and the single channel length ≤5cm avoids localized overheating, reducing energy consumption by 35% compared to traditional T-type mixers and reducing nanoparticle agglomerations by 80%. Preferably, a microchannel reactor employing… Advanced-Flow TM Reactor G4 (Corning AFR G4) microchannel reactor.

[0022] Specifically, the coatings prepared by the above method need to meet the following requirements:

[0023] I. Surface roughness Ra ≤ 10 nm as determined by atomic force microscopy;

[0024] II. Electrochemical impedance spectroscopy (EIS) measurements in 3.5% NaCl solution with a low-frequency impedance modulus ≥ 1 × 10⁸ Ω·cm 2 .

[0025] Ultra-smooth surfaces with Ra≤10nm reduce corrosion sites by 85%, 1×10 8 Ω·cm 2 The impedance modulus is three orders of magnitude higher than that of conventional coatings, meeting the IEC 60529-IP68 protection standard for marine engineering equipment.

[0026] Thirdly, the present invention also provides the application of the above-mentioned coating in marine engineering equipment, specifically for: corrosion-resistant coating of titanium alloy submarine sea valve, with a coating thickness of 150-200μm, and no rust after 3000h salt spray test.

[0027] Fourthly, the present invention also provides the application of the above-mentioned coating in automotive lightweighting, specifically for: a base coating of carbon fiber composite body parts, with adhesion reaching ASTM D3359 standard level 5B.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention involves microwave irradiation of nano-silica in the presence of dopamine hydrochloride to obtain modified nano-silica, which is then mixed with acrylic resin emulsion and followed by the addition of isocyanate curing agent, titanium dioxide pigment, hydroxyl-terminated hyperbranched polyester, polycarboxylate ammonium salt dispersant, polysiloxane defoamer, and lithium magnesium silicate. A coating is then prepared through segmented curing. Compared with traditional acrylic coatings, the prepared coating exhibits excellent adhesion, corrosion resistance, impedance, and low surface roughness, showing broad application prospects. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0032] In this invention, there are no particular limitations on the specific dispersion and stirring methods.

[0033] Unless otherwise specified, the experimental methods used in this invention are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0034] The raw materials used in this invention are shown in Table 1 below.

[0035] Table 1. Raw Material Sources

[0036]

[0037]

[0038] Example 1

[0039] A high-adhesion acrylic coating, the preparation method of which specifically includes:

[0040] 1. Through Advanced-Flow TMThe Reactor G4 microchannel reactor premixes 45g of acrylic resin emulsion with 6g of modified nano-silica at a flow rate ratio of 4:1.

[0041] 2. Under nitrogen protection, a continuous flow process is used to add 10g of isocyanate curing agent, 15g of titanium dioxide pigment, 3g of hydroxyl-terminated hyperbranched polyester, 2g of polycarboxylate ammonium salt dispersant, 0.8g of polysiloxane defoamer, and 1.5g of magnesium lithium silicate in sequence.

[0042] 3. Segmented curing via dual-wavelength ultraviolet-LED: 365nm irradiation, irradiation energy 600mJ / cm² 2 Irradiation time 5 min; followed by irradiation at 405 nm with an irradiation energy of 300 mJ / cm². 2 Irradiation time: 3 minutes.

[0043] 4. Use a high-pressure homogenizer to disperse the medium in three stages until the particle size is ≤0.5μm.

[0044] In this embodiment, the preparation of the modified nano-silica includes:

[0045] (1) Disperse 8g of nano silica in 1L of Tris buffer solution with pH=8, and add dopamine hydrochloride to a concentration of 1.5mg / mL.

[0046] (2) Apply 80W microwave intermittent radiation at 40℃ for 10h (microwave radiation for 4min, intermittent for 3min).

[0047] (3) Centrifugation parameters: rotation speed 8000 r / min, centrifugation time 15 min, after washing 3 times with ethanol / water mixed solvent (ethanol to water volume ratio of 1:1), vacuum freeze drying to obtain composite particles with a polydopamine coating thickness of 5-10 nm.

[0048] Example 2

[0049] A high-adhesion acrylic coating, the preparation method of which specifically includes:

[0050] 1. Through Advanced-Flow TM The Reactor G4 microchannel reactor premixes 50g of acrylic resin emulsion with 7g of modified nano-silica at a flow rate ratio of 5:1.

[0051] 2. Under nitrogen protection, using a continuous flow process, add 11g of isocyanate curing agent, 16g of titanium dioxide pigment, 4g of hydroxyl-terminated hyperbranched polyester, 2.5g of polycarboxylate ammonium salt dispersant, 1g of polysiloxane defoamer, and 2g of magnesium lithium silicate in sequence.

[0052] 3. Segmented curing via dual-wavelength ultraviolet-LED: 365nm irradiation, irradiation energy 800mJ / cm² 2 Irradiation time 4 min; followed by irradiation at 405 nm with an irradiation energy of 400 mJ / cm². 2 Irradiation time: 2.5 min.

[0053] 4. Use a high-pressure homogenizer to disperse the medium in three stages until the particle size is ≤0.5μm.

[0054] In this embodiment, the preparation of the modified nano-silica includes:

[0055] (1) Disperse 10g of nano silica in 1L of Tris buffer solution with pH=8.5, and add dopamine hydrochloride to a concentration of 2mg / mL.

[0056] (2) Apply 100W microwave intermittent radiation at 45℃ for 8 hours (microwave radiation for 5 minutes, intermittent for 2 minutes).

[0057] (3) Centrifugation parameters: rotation speed 10000r / min, centrifugation time 12min, after washing 3 times with ethanol / water mixed solvent (ethanol to water volume ratio of 1:1), vacuum freeze drying was used to obtain composite particles with a polydopamine coating thickness of 10-15nm.

[0058] Example 3

[0059] A high-adhesion acrylic coating, the preparation method of which specifically includes:

[0060] 1. Through Advanced-Flow TM The Reactor G4 microchannel reactor premixes 55g of acrylic resin emulsion with 8g of modified nano-silica at a flow rate ratio of 6:1.

[0061] 2. Under nitrogen protection, a continuous flow process is used to sequentially add 12g of isocyanate curing agent, 18g of titanium dioxide pigment, 5g of hydroxyl-terminated hyperbranched polyester, 3g of polycarboxylate ammonium salt dispersant, 1.2g of polysiloxane defoamer, and 2.5g of magnesium lithium silicate.

[0062] 3. Segmented curing via dual-wavelength ultraviolet-LED: 365nm irradiation, irradiation energy 1000mJ / cm² 2 Irradiation time 3 min; followed by irradiation at 405 nm with an irradiation energy of 500 mJ / cm². 2 Irradiation time: 2 minutes.

[0063] 4. Use a high-pressure homogenizer to disperse the medium in three stages until the particle size is ≤0.5μm.

[0064] In this embodiment, the preparation of the modified nano-silica includes:

[0065] (1) Disperse 12g of nano silica in 1L of Tris buffer solution with pH=9, and add dopamine hydrochloride to a concentration of 2.5mg / mL.

[0066] (2) Apply 120W microwave intermittent radiation at 50℃ for 6 hours (6 minutes of microwave radiation followed by 1 minute of intermittent radiation).

[0067] (3) Centrifugation parameters: rotation speed 12000 r / min, centrifugation time 10 min, after washing 3 times with ethanol / water mixed solvent (ethanol to water volume ratio of 1:1), vacuum freeze drying was used to obtain composite particles with a polydopamine coating thickness of 15-20 nm.

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 does not add modified nano-silica, and the curing process is different, but everything else is the same.

[0070] Acrylic coatings were prepared using traditional methods without the addition of modified nano-silica. A standard T-type mixer was used for mixing the raw materials, and the curing process involved single-stage 365nm ultraviolet irradiation at an energy of 1400 mJ / cm². 2 Irradiation time: 8 minutes.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 uses an equal amount of nano-silica instead of modified nano-silica, and the curing process is different, but everything else is the same.

[0073] Unmodified nano-silica (commercially available nano-silica was used directly) was added, and the raw materials were mixed using a standard T-mixer. The curing process involved single 365nm ultraviolet irradiation at an energy of 1400 mJ / cm². 2 Irradiation time: 8 minutes.

[0074] Comparative Example 3

[0075] The difference between Comparative Example 3 and Example 2 is that Comparative Example 3 uses an equal amount of ordinary aliphatic polyester polyol (molecular weight of 2000) to replace the terminal hydroxyl hyperbranched polyester, while all other aspects are the same.

[0076] Comparative Example 4

[0077] The difference between Comparative Example 4 and Example 2 is that Comparative Example 4 uses an equal amount of sodium dodecylbenzenesulfonate instead of the polycarboxylate ammonium salt dispersant, while everything else is the same.

[0078] Comparative Example 5

[0079] The difference between Comparative Example 5 and Example 2 is that the curing process is different, but everything else is the same.

[0080] Curing was performed using a single 405nm ultraviolet irradiation with an irradiation energy of 1500mJ / cm². 2 Irradiation time: 10 minutes.

[0081] Test Example 1

[0082] The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to tests for adhesion, corrosion resistance, surface roughness, impedance, and antibacterial properties.

[0083] I. Adhesion Test

[0084] Experimental standard: Adhesion test shall be conducted in accordance with ASTM D3359 standard.

[0085] Experimental steps:

[0086] (1) The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were applied to the pretreated titanium alloy substrate to form a coating with a thickness of about 150 μm.

[0087] (2) Curing the coating in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 7 days.

[0088] (3) Use a knife to make 6 parallel cuts on the coating, with a cut spacing of 1 mm and a depth to the substrate.

[0089] (4) Apply pressure-sensitive tape to the cut area and then quickly peel off the tape.

[0090] (5) Observe the extent to which the coating peels off from the substrate and rate it according to ASTM D3359.

[0091] II. Corrosion Resistance Test

[0092] Experimental standard: Salt spray test shall be conducted in accordance with GB / T 1771-2007 standard.

[0093] Experimental steps:

[0094] (1) The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were applied to the pretreated titanium alloy substrate to form a coating with a thickness of about 150 μm.

[0095] (2) Curing the coating in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 7 days.

[0096] (3) Place the coated sample into a salt spray test chamber. The test solution is a 5% sodium chloride solution, the test temperature is 35±2℃, and the salt spray deposition rate is 1-2 mL / (h·80cm). 2 ).

[0097] The test was conducted continuously for 3000 hours, and the coating surface was observed at regular intervals to check for rust.

[0098] III. Surface Roughness Test

[0099] Experimental standard: Surface roughness test shall be conducted in accordance with ISO 25178-2 standard.

[0100] Experimental steps:

[0101] (1) The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were applied to the pretreated titanium alloy substrate to form a coating with a thickness of about 150 μm.

[0102] (2) Curing the coating in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 7 days.

[0103] (3) Use an atomic force microscope to scan the coating surface and measure the surface roughness Ra value.

[0104] IV. Electrochemical Impedance Spectroscopy

[0105] Experimental standard: Electrochemical impedance spectroscopy was performed in accordance with GB / T 30789.3-2014 standard.

[0106] Experimental steps:

[0107] (1) The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were applied to the pretreated titanium alloy substrate to form a coating with a thickness of about 150 μm.

[0108] (2) Curing the coating in a standard environment (temperature 23±2℃, relative humidity 50±5%) for 7 days.

[0109] (3) Using the coated sample as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the auxiliary electrode, electrochemical impedance spectroscopy was performed in a 3.5% NaCl solution. The test frequency range was 10 Hz. 5 -10 -2 Hz.

[0110] The test results are shown in Table 2 below.

[0111] Table 2. Results of Coating Performance Tests

[0112]

[0113]

[0114] As shown in the adhesion test in Table 2, the adhesion of Examples 1-3 is significantly higher than that of Comparative Examples 1-5, indicating that the coating of the present invention has extremely strong bonding force with the substrate. Furthermore, after a 3000-hour salt spray test, the coatings prepared in Examples 1-3 showed no rust, while Comparative Examples 1-5 showed rust after 1500 hours, indicating that the present invention has good corrosion resistance.

[0115] Lower surface roughness helps improve the appearance quality and gloss of the coating, while reducing the adhesion of dirt and corrosive media. As can be seen from the surface roughness test in Table 2, the surface roughness Ra values ​​of Examples 1-3 are 8nm, 9nm and 7nm respectively, which are all at a low level, indicating that the coating surface is relatively smooth. In contrast, the surface roughness Ra values ​​of Comparative Examples 1-5 are basically higher than 12nm, which is significantly higher than that of Examples 1-3. This shows that the coating of the present invention reduces the surface roughness of the coating, which is beneficial to increasing the service life of the coating.

[0116] The higher the low-frequency impedance modulus, the better the protective performance of the coating. As can be seen from the electrochemical impedance spectroscopy test results in Table 2, the low-frequency impedance modulus of Examples 1-3 are all within 1×10⁸ Ω·cm. 2 The above demonstrates that the coating exhibits extremely high impedance performance, effectively preventing the passage of corrosion current, while the low-frequency impedance modulus of the coating in Comparative Example 1 is only 8 × 10⁵ Ω·cm. 2 Comparative Example 2 has a strength of 6 × 10⁶ Ω·cm. 2 Comparative Example 3 has a strength of 7 × 10⁶ Ω·cm. 2 Comparative Example 4 is 5 × 10⁵ Ω·cm 2 Comparative Example 5 has a strength of 9 × 10⁶ Ω·cm. 2 This demonstrates that the coating of the present invention can form a denser protective layer and improve the impedance performance of the coating.

[0117] In summary, this invention constructs a multi-level rough interface by modifying nano-silica with polydopamine, and combines it with continuous flow processing and dual-wavelength photocuring technology to produce a coating with high adhesion, corrosion resistance, low surface roughness, and good impedance properties. The coating has a surface roughness Ra ≤ 10 nm and an impedance modulus ≥ 1 × 10⁻⁶ in 3.5% NaCl solution. 8 Ω·cm 2 It can be used as a corrosion-resistant coating for the sea valve of alloy submarines, with a coating thickness of 150-200μm, and no rust after 3000h salt spray test; it can also be used as a base coating for carbon fiber composite body parts, with adhesion reaching ASTM D3359 standard 5B level.

[0118] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-adhesion acrylic coating, characterized in that, By weight, it includes 50 parts acrylic resin emulsion, 11 parts curing agent, 16 parts pigment, 7 parts modified nano silica, 4 parts hydroxyl-terminated hyperbranched polyester, 2.5 parts dispersant, 1 part defoamer, and 2 parts lithium magnesium silicate. The modified nano-silica is a polydopamine / nano-silica composite particle. The preparation of the modified nano-silica includes the following steps: S1. Disperse nano-silica in a buffer solution with pH=8-9, and add dopamine hydrochloride to a concentration of 1.5-2.5 mg / mL; S2. Apply 80-120W microwave intermittent radiation at 40-50℃ for 6-10 hours; S3. After centrifugation and cleaning with organic solvent, composite particles with a polydopamine coating thickness of 5-20 nm are obtained by vacuum freeze drying.

2. The high-adhesion acrylic coating according to claim 1, characterized in that, The curing agent is an isocyanate curing agent; the pigment is titanium dioxide; the dispersant is a polycarboxylic acid ammonium salt dispersant; and the defoamer is a polysiloxane defoamer.

3. A method for preparing a high-adhesion acrylic coating as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Acrylic resin emulsion and modified nano-silica were premixed using a microchannel reactor; (2) Under nitrogen protection, a continuous flow process is used to add curing agent, pigment and other additives in sequence; (3) Three-stage dispersion using a high-pressure homogenizer until the medium particle size is ≤0.5μm; (4) Segmented curing by dual-wavelength ultraviolet-LED: 365nm irradiation energy of 600-1000mJ / cm² followed by 405nm irradiation energy of 300-500mJ / cm².

4. The preparation method according to claim 3, characterized in that, In step (1), the flow rate ratio of the acrylic resin emulsion to the modified nano silica is (4-6):

1.

5. The preparation method according to claim 3, characterized in that, In step (1), the microchannel reactor adopts a 3D printed tree-like fractal structure with a mixing efficiency of ≥98% and a single channel length of ≤5cm.

6. The application of the coating as described in claim 1 in marine engineering equipment, characterized in that, Specifically used for: corrosion-resistant coatings on titanium alloy submarine sea valves, with a coating thickness of 150-200μm, showing no rust after 3000h salt spray testing.

7. The application of the coating as described in claim 1 in automotive lightweighting, characterized in that, Specifically used for: base coating of carbon fiber composite body parts, with adhesion reaching ASTM D3359 standard 5B level.

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