Environment-friendly UV curing conformal coating

Abstract

The environment-friendly UV-curable conformal coating comprises the following components in percentage by mass: 25%-50% of environment-friendly resin, 15%-35% of a reactive diluent, 3%-8% of a photoinitiator, 5%-15% of a functional aid, 0.5%-3% of a mildew-proof salt-fog-resistant additive, 1%-5% of a flame retardant, 2%-8% of a flexibilizer and 0.1%-2% of an ultraviolet light absorber, the UV-curable conformal coating has good functional characteristics, and realizes zero emission of volatile organic compounds; and the curing efficiency is extremely high, surface drying can be achieved under specific UV energy only in 5-30 seconds, and the production rhythm is greatly accelerated. The three-proofing performance is excellent, the waterproof, moisture-proof and salt mist-proof effects are outstanding, and a base material can be protected from being eroded in a severe environment for a long time; and the paint also has wide applicability, and can be uniformly coated on various base materials in various modes.

Description

Technical Field

[0001] The invention belongs to the technical field of conformal coatings and relates to an environmentally friendly UV-curable conformal coating. Background Art

[0002] Traditional conformal coatings mostly use solvent-based systems, which contain a large amount of volatile organic compounds (VOCs).

[0003] During the curing process, high temperature or long-term natural drying is required, which has many defects:

[0004] 1. Poor environmental protection: The volatilization of solvents will cause a large amount of VOC emissions, which will pollute the environment and endanger human health.

[0005] 2. Low curing efficiency: High-temperature curing not only consumes a lot of energy, but is also not suitable for heat-sensitive substrates.

[0006] 3. Insufficient three-proof performance: Conventional UV-curing coatings are difficult to meet the requirements of harsh environments in terms of salt spray resistance, adhesion and other properties; in the existing technology, although there have been some attempts at UV-curing three-proof paints, there are still problems such as residual toxicity of photoinitiators, insufficient toughness of coatings, and poor adhesion to the substrate. Summary of the invention

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] An environmentally friendly UV curing conformal coating comprising the following components in percentage by weight:

[0009] It is made of the following materials:

[0010] Environmentally friendly resin 25-50%: at least one of epoxy acrylate, polyurethane acrylate, silicone-modified acrylate or polyester acrylate can be selected; it can provide good film-forming properties and weather resistance, and can be used as a high-performance coating base material.

[0011] Reactive diluent 15-35%: Use low-viscosity monofunctional or multifunctional acrylates with fluorinated acrylates, such as tripropylene glycol diacrylate, perfluorooctyl ethyl acrylate, etc. They can not only reduce the viscosity of the system, but also participate in the curing reaction to ensure zero VOC emissions; at the same time, they can improve the hydrophobicity and stain resistance of the coating; these reactive diluents undergo cross-linking reactions with the resin during the curing process to form a tight network structure, enhance the density of the coating, and thus improve the waterproof and moisture-proof properties.

[0012] Photoinitiator 3-8%: Use low mobility initiators, such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, isopropylthioxanthone (ITX), etc.; these initiators can trigger a rapid curing reaction at a wavelength of 300-420nm. The rapid curing characteristics enable the coating to form a complete protective film in a short time, reduce the erosion of uncured paint by environmental factors, and indirectly improve the three-proof performance.

[0013] Functional additives 5-15%: including:

[0014] Nano-silicon dioxide, used to prevent sedimentation and enhance hardness;

[0015] Organic fluorine-modified leveling agent can improve surface hydrophobicity;

[0016] Phosphate adhesion promoters can enhance the bonding strength with metal / plastic substrates;

[0017] An appropriate amount of antioxidants, such as hindered phenol antioxidant 1010, can effectively inhibit the oxidative aging of the coating during use and extend its service life.

[0018] Among them, nano-silicon dioxide is evenly dispersed in the coating, filling the tiny pores inside the coating, enhancing the barrier effect of the coating, and improving the waterproof and salt spray resistance; the organic fluorine-modified leveling agent makes the coating surface smoother, making it difficult for water and salt spray to adhere to and penetrate; the phosphate adhesion promoter ensures that the coating is tightly bonded to the substrate, preventing the degradation of the three-proof performance due to insufficient adhesion.

[0019] Anti-mildew and anti-salt spray additive 0.5-3%: The compound of benzimidazole compounds containing nano-silver particles and molybdate is used. The synergistic effect of the two can improve the salt spray resistance. At the same time, the antibacterial and anti-mildew properties of nano-silver particles are used to further enhance the coating's ability to resist microbial erosion in a humid environment. Benzimidazole compounds and molybdates form a protective film with salt spray corrosion resistance on the surface of the coating through chemical reactions. Nano-silver particles, with their antibacterial activity, inhibit the growth of microorganisms such as mold on the surface of the coating, maintain the integrity of the coating, and ensure the durability of the three-proof performance.

[0020] Flame retardant 1-5%: Halogen-free phosphate flame retardants such as triphenyl phosphate (TPP) and resorcinol bis(diphenyl phosphate) (RDP) can be selected to meet the UL94V-0 flame retardancy requirements and improve the safety of conformal coatings in electronic equipment applications.

[0021] Toughening agent 2-8%: Using polyurethane elastomer or acrylic elastomer as a toughening agent can effectively improve the flexibility and impact resistance of the coating without affecting the hardness of the coating, so that the coating is not easy to crack or peel off when subjected to external forces; in harsh environments such as humidity and salt spray, external force impact may cause cracks in the coating. The addition of toughening agent can make the coating have better resistance to external damage and maintain the integrity of waterproof, moisture-proof and salt spray-proof.

[0022] 0.1-2% UV absorber: such as benzophenone UV absorber UV-9 or benzotriazole UV absorber UV-326, which can absorb UV energy, reduce UV damage to the coating, enhance the weather resistance of the coating in outdoor environments, and work synergistically with nano zinc oxide to further enhance the UV shielding effect; especially in outdoor environments, long-term exposure to ultraviolet rays may cause the coating to age and crack, affecting the three-proof performance; and under the joint action of UV absorbers and nano zinc oxide, they can effectively block ultraviolet rays, delay coating aging, and ensure the long-term stability of the three-proof performance.

[0023] Beneficial effects of the present invention:

[0024] 1. It is highly environmentally friendly and can achieve the effect of zero volatile organic compounds. No solvent materials are used in the entire preparation process, and no volatiles are generated during the curing process, which meets environmental protection standards.

[0025] 2. It has the characteristics of fast curing, which can achieve the effect of fast curing in 5-30 seconds, at 1000-2000mJ / cm 2 Under the irradiation of UV energy, the surface can be dried quickly, which greatly improves the production efficiency.

[0026] 3. Excellent three-proof performance:

[0027] Waterproof performance: The hydrophobicity of the coating is improved by using fluorinated acrylate in the active diluent, the surface state of the coating is optimized by using organic fluorine-modified leveling agent, and the density of the coating is enhanced by filling the pores with nano-silica. This allows the water contact angle of the coating to reach more than 120°, making it difficult for water droplets to adhere to and penetrate the surface of the coating, effectively blocking moisture intrusion. In a high humidity environment, after more than 1,000 hours of heat and humidity testing, there are no obvious water stains or signs of moisture on the back of the coating.

[0028] Moisture-proof performance: The tight coating structure and good waterproof performance work together to prevent moisture from entering; after being placed in an environment with a relative humidity of more than 95% for 2000 hours, the substrate under the coating has no rust, corrosion or other problems caused by moisture, and maintains good electrical insulation performance.

[0029] Salt spray resistance performance: Benzimidazole compounds are compounded with molybdates to form an anti-salt spray protective film, and nano silver particles inhibit the erosion of the coating by microorganisms. After the salt spray test according to the ASTM B117 standard, the salt spray resistance time can be ≥ 800 hours, and there are no obvious corrosion, blistering, and peeling phenomena on the coating surface, effectively protecting the substrate from salt spray corrosion. Specific embodiments

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. It should be understood that the present application is not limited by the exemplary embodiments described herein. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0031] Example 1, an environmentally friendly UV-curable three-proof paint in this example, which contains the following components by mass percentage: epoxy acrylate: 35%, tripropylene glycol diacrylate: 25%, perfluorooctyl ethyl acrylate: 10%, 2,4,6-trimethylbenzoyl: 5%, nano-silica: 6%, benzimidazole: 1%, sodium molybdate: 1%, nano silver particles: 0.5%, flame retardant RDP: 4%, polyurethane elastomer (toughening agent): 5%, ultraviolet absorber UV-9: 0.5%, organofluorine-modified leveling agent: 0.5%, hindered phenol antioxidant 1010: 0.5%, phosphate adhesion promoter: 1%;

[0032] This example includes the following steps:

[0033] Raw material mixing: Select a 50L stainless steel reaction kettle with a jacket, equipped with a temperature sensor with an accuracy of ±1°C and a variable-frequency paddle stirrer; weigh 17.5 kg of epoxy acrylate, 12.5 kg of tripropylene glycol diacrylate, 5 kg of perfluorooctyl ethyl acrylate, and 2.5 kg of polyurethane elastomer.

[0034] First, add epoxy acrylate to the reaction kettle, start the stirrer, set the speed to 300 r / min, and pass in 40°C circulating water; after 5 minutes, add tripropylene glycol diacrylate at a speed of 4 L / min, with an addition time of 12 minutes, and the temperature is stable at about 43°C during this period; then add perfluorooctyl ethyl acrylate at a speed of 2 L / min, with an addition time of 5 minutes, and then add polyurethane elastomer, with an addition time of 6 minutes; after the addition is completed, increase the stirring speed to 450 r / min and stir for 35 minutes. Take the mixed liquid under the microscope every 10 minutes to ensure uniformity.

[0035] Additive addition and dispersion: In an environment with a humidity of 25%, premix 2.5 kg of 2,4,6-trimethylbenzoyl, 3 kg of nano-silica, 0.5 kg of benzimidazole, 0.5 kg of sodium molybdate, 0.25 kg of nano-silver particles, 2 kg of flame retardant RDP, 0.25 kg of ultraviolet absorber UV-90, 0.25 kg of organofluorine modified leveling agent, 0.25 kg of hindered phenol antioxidant 1010, and 0.5 kg of phosphate adhesion promoter in a small container; use an ultrasonic disperser with adjustable power, set the frequency to 30 kHz, add the premixed additives to the reaction kettle, and at the same time start ultrasonic dispersion for 25 minutes. During this period, pause the ultrasonic stirring for 1 minute every 5 minutes. The transparency and fluidity of the mixed solution are good.

[0036] Defoaming and filtration: Connect a vacuum pump with an air extraction rate of 100 L / min, and check that the vacuum system has good airtightness; turn on the vacuum pump and raise the vacuum degree in the reaction kettle to -0.08 MPa within 12 minutes, defoam for 15 minutes, and the bubbles significantly decrease after 10 minutes; select a 100-mesh stainless steel filter screen, clean and dry it before filtration, pour the defoamed mixed solution into the filtration device at a flow rate of 4 L / min, and after filtration, it flows into a brown plastic bucket, which is sealed and labeled.

[0037] And the performance test results of an environmentally friendly UV-curable three-proof paint prepared according to this embodiment are as follows:

[0038] Waterproof performance: The water contact angle of the coating is 125°. After being placed in an environment with a relative humidity of 98% for 1200 hours, there are no obvious water stains on the back of the coating.

[0039] Moisture-proof performance: After being placed in an environment with a relative humidity of 95% for 2200 hours, the metal substrate under the coating does not rust, and the electrical insulation performance is good.

[0040] Salt spray resistance performance: Tested according to the ASTM B117 standard, the salt spray resistance time reaches 850 hours, and there is no corrosion or blistering on the surface of the coating.

[0041] Flexibility test: Bend on a 1-mm diameter rod, and there are no cracks in the coating.

[0042] Hardness test: The pencil hardness reaches 3H.

[0043] Example 1. An environment-friendly UV-curable three-proof paint in this example contains the following components by mass percentage: silicone-modified acrylate: 40%, ethoxylated trimethylolpropane triacrylate: 20%, perfluorooctylethyl acrylate: 10%, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO): 6%, nano-silica: 0.4%, nano-silica: 5%, benzimidazole: 1.2%, sodium molybdate: 1.3%, nano-silver particles: 0.6%, flame retardant TPP: 3%, acrylate elastomer (toughening agent): 6%, ultraviolet absorber UV-326: 0.5%, organofluorine-modified leveling agent: 1%, hindered phenol antioxidant 1010: 0.5%, phosphate adhesion promoter: 2%

[0044] This example includes the following steps:

[0045] Raw material mixing: Use a 30L stainless steel reactor with a jacket, the temperature sensor has an accuracy of ±1°C, and the stirrer is a variable-frequency paddle type; weigh 12kg of silicone-modified acrylate, 6kg of ethoxylated trimethylolpropane triacrylate, 3kg of perfluorooctylethyl acrylate, and 1.8kg of acrylate elastomer. First, add the silicone-modified acrylate to the reactor, with a stirring speed of 300r / min, and pass in circulating water at 42°C; after 5 minutes, add ethoxylated trimethylolpropane triacrylate at a speed of 3L / min, with an addition time of 10 minutes, and maintain the temperature at 44°C; then add perfluorooctylethyl acrylate at a speed of 2L / min, with an addition time of 5 minutes, and then add the acrylate elastomer, with an addition time of 7 minutes. After that, adjust the stirring speed to 420r / min and stir for 38 minutes, and sample to observe the uniformity.

[0046] Addition and dispersion of additives: Premix 1.8kg of photoinitiator TPO, 0.12kg of nano-ZnO, 21.5kg of nano-silica, 0.36kg of benzimidazole, 0.39kg of sodium molybdate, 0.18kg of nano-silver particles, 0.9kg of flame retardant TPP, 0.15kg of ultraviolet absorber UV-326, 0.3kg of organofluorine-modified leveling agent, 0.15kg of hindered phenol antioxidant 1010, and 0.6kg of phosphate adhesion promoter in an environment with a humidity of 28%. Use an ultrasonic disperser with a frequency of 25kHz, and ultrasonically disperse for 22 minutes after adding the additives, and pause the stirring operation in the middle to ensure the dispersion effect.

[0047] Defoaming and filtration: Connect a vacuum pump with an air extraction rate of 80L / min to ensure that the vacuum system is well sealed; turn on the vacuum pump and increase the vacuum degree to -0.09MPa within 13 minutes, and defoam for 18 minutes; filter with a 120-mesh stainless steel filter screen, and the filtered product flows into a brown glass bottle, which is sealed and labeled with information.

[0048] The performance test structure of an environmentally friendly UV-curable three-proof paint prepared according to this embodiment is as follows:

[0049] Waterproof performance: The water contact angle of the coating reaches 130°. After 1300 hours of damp heat test in a high humidity environment, there is no sign of moisture on the back of the coating.

[0050] Moisture-proof performance: Placed in an environment with a relative humidity of 97% for 2500 hours, the ceramic substrate under the coating is not damaged by moisture at all, and the electrical performance is stable.

[0051] Salt spray resistance performance: Tested according to the ASTM B117 standard, the salt spray resistance time is 900 hours, and there is no obvious change in the coating.

[0052] Flexibility test: Bent on a 2mm diameter rod, the coating remains intact.

[0053] Hardness test: The pencil hardness is 2H.

[0054] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An environmentally friendly UV-curable three-proof paint, characterized in that, Comprising the following components by mass percentage: 25 - 50% of environmentally friendly resin, and the environmentally friendly resin is at least one of epoxy acrylate, polyurethane acrylate, silicone-modified acrylate or polyester acrylate; 15 - 35% of reactive diluent, and the reactive diluent is a low-viscosity monofunctional or polyfunctional acrylate with fluorinated acrylate; 3 - 8% of photoinitiator, and the photoinitiator is a low-migration type initiator, selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, isopropylthioxanthone; 5 - 15% of functional additives, including: nano-silica, organofluorine-modified leveling agent, phosphate adhesion promoter and antioxidant; 0.5 - 3% of mildew and salt spray resistant additive, and the mildew and salt spray resistant additive is a compound of benzimidazole compound with nano silver particles and molybdate; 1 - 5% of flame retardant, and the flame retardant is a halogen-free phosphate flame retardant; 2 - 8% of toughening agent, and the toughening agent is polyurethane elastomer or acrylate elastomer; 0.1 - 2% of ultraviolet absorber, and the ultraviolet absorber is a benzophenone-type ultraviolet absorber or a benzotriazole-type ultraviolet absorber.

2. The environmentally friendly UV-curable three-proof paint according to claim 1, wherein, The environmentally friendly resin is a compound of epoxy acrylate and silicone-modified acrylate, and the mass ratio is 2:

1.

3. The environmentally friendly UV curable three-proof paint according to claim 1, wherein The reactive diluent is made of tripropylene glycol diacrylate and perfluorooctylethyl acrylate, and the mass ratio is 3:

1.

4. The environmentally friendly UV-curable three-proof paint according to claim 1, characterized in that, The ultraviolet absorber is benzotriazole-type ultraviolet absorber UV-326, and is used in combination with nano-zinc oxide, and the addition amount of nano-zinc oxide is 0.3%.

5. The environmentally friendly UV-curable three-proof paint according to claim 1, wherein The toughening agent is polyurethane elastomer, and the addition amount is 5%.

6. A preparation method of the environment-friendly UV-curable three-proof paint according to any one of claims 1-5, characterized in that, Including the following steps: Raw material mixing: Add the environmentally friendly resin into a stainless steel reaction kettle with a jacket, start the stirrer, set the stirring speed to 300 r / min, and pass in circulating water at 40 - 50 °C; after 5 minutes, add the reactive diluent at a speed of 3 - 5 L / min, and control the addition time within 10 - 15 minutes; then add the toughening agent at a speed of 2 - 3 L / min, and control the addition time within 5 - 8 minutes. After all the additions are completed, increase the stirring speed to 400 - 500 r / min and stir for 30 - 40 minutes; Additive addition and dispersion: In an environment with a humidity lower than 30%, premix the photoinitiator, nano-silica, organofluorine-modified leveling agent, phosphate adhesion promoter, mildew and salt spray resistant additive, flame retardant, antioxidant and ultraviolet absorber in a small container; use an ultrasonic disperser with adjustable power, set the ultrasonic frequency at 20 - 40 kHz, add the premixed additives into the reaction kettle, and at the same time start ultrasonic dispersion for 20 - 30 minutes. During this period, pause the ultrasonic every 5 minutes and stir for 1 - 2 minutes; Defoaming and filtration: Connect the vacuum pump, and increase the vacuum degree in the reaction kettle to between -0.08 MPa and -0.09 MPa within 10 - 15 minutes, and defoam for 10 - 20 minutes; Select a stainless steel filter screen with a pore size of 100 - 120 mesh, pour the degassed mixed liquid into the filtering device at a flow rate of 3 - 5 L / min for filtration, and the filtered product flows into a clean, dry and hermetically tested packaging container.