Water-based photocureable coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coatings, and particularly relates to a water-based photocureable coating as well as a preparation method and application thereof. The water-based photocureable coating is prepared from the following raw material components in percentage by mass: 20%-40% of water-based UV (ultraviolet) bifunctional polyurethane acrylate resin containing sulfydryl-terminated silane groups, 10%-20% of water-based UV hexa-functional polyurethane acrylate containing sulfydryl-terminated silane groups, 2%-2.5% of a photoinitiator, 2%-3% of a cosolvent, 0.2%-0.6% of a defoaming agent, 0.5%-1% of a wetting dispersant and the balance of water, 1%-1.5% of a thickening agent, 0.2%-0.6% of a pH regulator, 10%-30% of pigment and filler and 10%-20% of deionized water. The resin structure of the water-based photocureable coating contains a sulfydryl-terminated silane group, so that the curing efficiency of the coating is improved, the dosage of the photoinitiator is reduced, toxic or high-VOC substances are avoided, and the water-based photocureable coating is green and environmentally friendly.

Description

Technical Field

[0001] This application belongs to the technical field of coatings, and particularly relates to an aqueous photocurable coating, a preparation method thereof, and an application thereof. Background Art

[0002] The paints long-term used in the industrial wood coatings industry are mainly traditional solvent-based coatings. Solvent-based coatings have a relatively strong odor, exceed the standard of VOC (Volatile Organic Compounds), and have a long drying time. Traditional solvent-based coatings are applied by spraying. The coating film is thin, and the utilization rate of the paint is only 55%. The remaining sprayed coatings cannot cover the surface of the workpiece, and multiple coatings are required to achieve the effect. Therefore, the spraying construction efficiency of traditional solvent-based coatings is low, the cost is high, the environment is polluted, and the health of construction workers is affected. Moreover, traditional solvent-based coatings contain flammable organic volatile solvents such as toluene, acetone, ethyl acetate curing agents and other flammable and explosive dangerous goods. These flammable organic solvents are extremely likely to bring fire hazards to manufacturing enterprises.

[0003] Therefore, there is an urgent need to develop a green, environmentally friendly and highly safe coating. Summary of the Invention

[0004] The purpose of this application is to provide an aqueous photocurable coating, a preparation method thereof, and an application thereof, aiming to solve to a certain extent the problem that traditional solvent-based coatings contain high-VOC substances and cause serious pollution.

[0005] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In the first aspect, this application provides an aqueous photocurable coating. Based on the total raw material mass of the aqueous photocurable coating being 100%, it includes the following raw material components:

[0007] 20% - 40% of an aqueous UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group, 10% - 20% of an aqueous UV hexafunctional polyurethane acrylate containing a mercapto-terminated silyl group, 2% - 2.5% of a photoinitiator, 2% - 3% of a co-solvent, 0.2% - 0.6% of an antifoaming agent, 0.5% - 1% of a wetting and dispersing agent, 1% - 1.5% of a thickening agent, 0.2% - 0.6% of a pH regulator, 10% - 30% of a pigment and filler, and 10% - 20% of deionized water.

[0008] In some possible implementation manners, in the aqueous UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group, the content of the mercapto-terminated silyl group is 6% - 10%.

[0009] In some possible implementations, in the waterborne UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups, the content of mercapto-terminated silane groups is 6% to 10%.

[0010] In some possible implementations, the waterborne difunctional UV polyurethane acrylate containing mercapto-terminated silane groups has a solid content of 40% to 50% and a molecular weight of 5000 to 6000 Daltons.

[0011] In some possible implementations, the water-based UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups has a solid content of 40% to 44% and a molecular weight of 10,000 to 30,000 Daltons.

[0012] In some possible implementations, the pigment filler includes at least one of carbon black, graphene, carbon nanotubes, and hard carbon.

[0013] In some possible implementations, the wetting dispersant includes at least one of Dispers755w dispersant, Dispers740w dispersant, BYK192 dispersant, and DIS-730A.

[0014] In some possible implementations, the defoamer includes at least one of BYK024 defoamer, BYK028 defoamer, TEGOAIREX 902W, and TEGO AIREX 810.

[0015] In some possible implementations, the co-solvent includes at least one of propylene glycol butyl ether acetate, dipropylene glycol dimethyl ether, and dipropylene glycol butyl ether.

[0016] In some possible implementations, the photoinitiator includes at least one of the water-based photoinitiators TPO-L, 819-DW, IGM500, and 1173.

[0017] In some possible implementations, the pH adjuster includes at least one of Deqian AMP-95, triethylamine, dimethylethanolamine, and sodium hydroxide.

[0018] In some possible implementations, the thickener includes at least one of Deqian R299 thickener, Deqian WT-105A, and Dow RM 12W.

[0019] In some possible implementations, the pH value of the water-based photocurable coating is 6.5-8.5.

[0020] In some possible implementations, the fineness of the water-based photocurable coating is no greater than 20 μm.

[0021] In some possible implementation manners, at 25 °C, the viscosity of the aqueous photocurable coating is 600 cps to 700 cps.

[0022] In a second aspect, the present application provides a method for preparing an aqueous photocurable coating, including the following steps:

[0023] Prepare an aqueous UV difunctional polyurethane acrylate resin containing a thiol-terminated silyl group;

[0024] Mix and grind 20 parts to 40 parts of the aqueous UV difunctional polyurethane acrylate resin containing a thiol-terminated silyl group, 10 parts to 20 parts of an aqueous UV hexafunctional polyurethane acrylate containing a thiol-terminated silyl group, 2 parts to 2.5 parts of a photoinitiator, 2 parts to 3 parts of a co-solvent, 0.2 parts to 0.6 parts of an antifoaming agent, 0.5 parts to 1 part of a wetting and dispersing agent, 1 part to 1.5 parts of a thickening agent, 0.2 parts to 0.6 parts of a pH regulator, 10 parts to 30 parts of a pigment and filler, and 10 parts to 20 parts of deionized water to obtain an aqueous photocurable coating.

[0025] In some possible implementation manners, the preparation steps of the aqueous UV difunctional polyurethane acrylate resin containing a thiol-terminated silyl group and the aqueous UV hexafunctional polyurethane acrylate containing a thiol-terminated silyl group respectively include:

[0026] Perform a thiol-ene click reaction on a silane compound and a thiol compound to prepare thiol-terminated silane nanoparticles;

[0027] Perform a grafting reaction on the thiol-terminated silane nanoparticles and an aqueous UV difunctional polyurethane acrylate resin or an aqueous UV hexafunctional polyurethane acrylate resin to obtain the aqueous UV difunctional polyurethane acrylate resin containing a thiol-terminated silyl group or the aqueous UV hexafunctional polyurethane acrylate containing a thiol-terminated silyl group.

[0028] In some possible implementation manners, the steps of the mixing and grinding treatment include:

[0029] After adding the co-solvent, the photoinitiator, the wetting and dispersing agent, the antifoaming agent, and the pH regulator into a container for a first mixing treatment;

[0030] Then add the aqueous UV difunctional polyurethane acrylate resin containing a thiol-terminated silyl group and the aqueous UV hexafunctional polyurethane acrylate for a second mixing treatment;

[0031] Then sequentially add the deionized water, the thickening agent, and the pigment and filler for a third mixing treatment, and then perform a grinding treatment to obtain the aqueous photocurable coating.

[0032] In some possible implementation manners, the rotation speed of the second mixing process is 1000 r / min to 2000 r / min.

[0033] In some possible implementation manners, the rotation speed of the third mixing process is 1500 r / min to 2500 r / min, and the processing duration is 30 min to 60 min.

[0034] In some possible implementation manners, the grinding process is carried out until the fineness is not higher than 20 μm.

[0035] In a third aspect, the present application provides an application of the waterborne photocurable coating. The above-mentioned waterborne photocurable coating and / or the waterborne photocurable coating prepared by the above method is sprayed onto a workpiece and cured into a film by a light source, so as to form a waterborne photocurable coating on the surface of the workpiece.

[0036] In the waterborne photocurable coating provided by the first aspect of the present application, the molecular structure of the waterborne UV difunctional polyurethane acrylate resin contains a mercapto-terminated silyl group. The mercapto-silyl group can rapidly enhance the curing reaction during the curing of the coating. Even if the waterborne photocurable coating is dark-colored, it can rapidly improve the deep curing efficiency under the condition of deepening the color. Especially under photocuring conditions, the reaction is faster and the yellowing resistance is better. It can effectively reduce the dosage of photoinitiators and avoid using toxic or high-VOC substances such as toluene, acetone, ethyl acetate phosphate, and active amines, which is green and environmentally friendly. In addition, the coating in the present application simultaneously includes a waterborne UV difunctional polyurethane acrylate resin (2-functional PUA) and a waterborne UV hexafunctional polyurethane acrylate (6-functional PUA) containing a mercapto-terminated silyl group. These resins are milky white translucent liquids in appearance, have excellent deep curing ability, especially more thorough curing under lamp curing, and these resins also include characteristics such as wettability to the substrate and low viscosity, and can be mechanically recycled for coating construction. Among them, the 6-functional PUA has a higher functionality, which means that more crosslinking points can be formed during the curing process, thus significantly increasing the crosslinking density of the coating. A higher crosslinking density helps to improve the hardness, abrasion resistance, and chemical resistance of the coating. The curing speed of the 2-functional PUA is relatively slow, while the curing speed of the 6-functional PUA is fast. By adjusting the ratio of the two, precise control of the curing speed can be achieved to meet the requirements of different application scenarios. In addition, the 2-functional PUA has good flexibility, while the 6-functional PUA has high hardness. By combining the two, while ensuring the hardness of the coating, the flexibility can be taken into account, making the coating more tough and durable. The PUA resin itself has excellent weather resistance and chemical resistance. By combining the 2-functional PUA and the 6-functional PUA, these properties can be further enhanced, enabling the coating to maintain its gloss and color stability for a long time while resisting the erosion of various chemical substances. Therefore, the waterborne photocurable coating of the present application has the advantages of higher coating hardness, better scratch resistance, efficient utilization, energy conservation and consumption reduction, and no pollution to the environment through the combined action of each raw material component. Its method process is simple, easy to control, and can be used for mechanical electrostatic coating operations to improve production efficiency.

[0037] The preparation method of the waterborne photocurable coating provided by the second aspect of the present application can obtain the waterborne photocurable coating by mixing and grinding after obtaining the raw material components in the formula amount. The preparation process is simple and suitable for large-scale industrial production and application. In the prepared waterborne photocurable coating, the molecular structure of the waterborne UV difunctional polyurethane acrylate resin contains a thiol-terminated silyl group. The thiol silyl group can rapidly enhance the curing reaction during the curing of the coating. Even if the waterborne photocurable coating is dark, it can rapidly improve the deep curing efficiency under the condition of deepening the color. Especially under the photocuring condition, the reaction is faster and the yellowing resistance is better. It can effectively reduce the dosage of photoinitiator, avoid using toxic or high-VOC substances such as toluene, acetone, ethyl acetate phosphate, and active amine, and is green and environmentally friendly. Through the combined action of each raw material component, the prepared coating has the advantages of higher hardness, better scratch resistance, efficient utilization, energy saving and consumption reduction, and no pollution to the environment. Its method and process are simple, easy to control, and can be mechanically electrostatically coated to improve production efficiency.

[0038] The application of the waterborne photocurable coating provided by the third aspect of the present application is to spray the above waterborne photocurable coating and / or the waterborne photocurable coating prepared by the above method onto a workpiece and cure it into a film through a light source, so as to form a waterborne photocurable coating on the surface of the workpiece. The application is flexible and convenient, and the coating efficiency is high. Moreover, the waterborne photocurable coating used has the advantages of improving coating environmental protection, enhancing scratch resistance, efficient utilization, energy saving and efficiency increase, being green, low-carbon, pollution-free to the environment, and being mechanically coatable, which further improves the production efficiency. Brief Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0040] Figure 1 It is a schematic flow chart of the preparation method of the waterborne photocurable coating provided by the embodiment of the present application. Detailed Embodiments

[0041] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application more clearly understood, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Here, A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0043] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following items" or its similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0044] It should be understood that in various embodiments of this application, the magnitudes of the sequence numbers of the above processes do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0045] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a" and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0046] The weights of the relevant components mentioned in the embodiments of the specification of this application can not only refer to the specific contents of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the embodiments of the specification of this application are scaled up or down proportionally, they are within the scope disclosed in the embodiments of the specification of this application. Specifically, the mass described in the embodiments of the specification of this application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0047] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of this application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0048] In the first aspect of the embodiment of the present application, a waterborne photocurable coating is provided. Based on the total raw material mass of the waterborne photocurable coating being 100%, it includes the following raw material components:

[0049] 20% - 40% of a waterborne UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group, 10% - 20% of a waterborne UV hexafunctional polyurethane acrylate containing a mercapto-terminated silyl group, 2% - 2.5% of a photoinitiator, 2% - 3% of a co-solvent, 0.2% - 0.6% of an antifoaming agent, 0.5% - 1% of a wetting and dispersing agent, 1% - 1.5% of a thickener, 0.2% - 0.6% of a pH regulator, 10% - 30% of a pigment and filler, and 10% - 20% of deionized water.

[0050] In the waterborne photocurable coating provided by the first aspect of the embodiments of the present application, the molecular structure of the waterborne UV difunctional polyurethane acrylate resin contains a mercapto-terminated silyl group. The mercapto silyl group can rapidly enhance the curing reaction during the curing of the coating. Even if the waterborne photocurable coating is dark in color, it can rapidly improve the deep curing efficiency under the condition of deepening the color. Especially under photocuring conditions, the reaction is faster and the yellowing resistance is better. It can effectively reduce the dosage of photoinitiators and avoid using toxic or high-VOC substances such as toluene, acetone, ethyl acetate phosphate, and active amines, which is green and environmentally friendly. In addition, the coating in the embodiments of the present application simultaneously includes a waterborne UV difunctional polyurethane acrylate resin (2-functional PUA) and a waterborne UV hexafunctional polyurethane acrylate (6-functional PUA) containing a mercapto-terminated silyl group. These resins are milky white translucent liquids in appearance, have excellent deep curing ability, especially more complete curing under lamp curing, and these resins also include characteristics such as wettability to the substrate and low viscosity, and can be mechanically recycled for painting construction. Among them, the 6-functional PUA has a higher functionality, which means that more crosslinking points can be formed during the curing process, thus significantly increasing the crosslinking density of the coating. A higher crosslinking density helps to improve the hardness, wear resistance, and chemical resistance of the coating. The curing speed of the 2-functional PUA is relatively slow, while the curing speed of the 6-functional PUA is faster. By adjusting the ratio of the two, precise control of the curing speed can be achieved to meet the requirements of different application scenarios. In addition, the 2-functional PUA has good flexibility, while the 6-functional PUA has higher hardness. By combining the two, while ensuring the hardness of the coating, the flexibility can be taken into account, making the coating more tough and durable. The PUA resin itself has excellent weather resistance and chemical resistance. By combining the 2-functional PUA and the 6-functional PUA, these properties can be further enhanced, enabling the coating to maintain its gloss and color stability for a long time while resisting the erosion of various chemical substances. Therefore, the waterborne photocurable coating of the embodiments of the present application has the advantages of higher hardness, better scratch resistance, efficient utilization, energy saving and consumption reduction, and no pollution to the environment through the combined action of each raw material component. Its method and process are simple, easy to control, and can be used for mechanical electrostatic painting operations to improve production efficiency.

[0051] The waterborne photocurable coating of the embodiments of the present application is preferably cured using an LED lamp. The energy utilization rate of LED lamp curing is extremely high, which can improve efficiency, quickly complete the curing process of the material, shorten the production cycle, and effectively reduce energy consumption.

[0052] In some possible implementation manners, in the waterborne UV difunctional polyurethane acrylate resin containing mercapto-capped silyl groups, the content of the mercapto-capped silyl groups is 6% to 10%. Exemplarily, the content of the mercapto-capped silyl groups can be any typical but non-limiting point value such as 6%, 7%, 8%, 9%, 10%, etc. or an interval value between any two point values. In some possible implementation manners, in the waterborne UV hexa-functional polyurethane acrylate containing mercapto-capped silyl groups, the content of the mercapto-capped silyl groups is 6% to 10%. Exemplarily, the content of the mercapto-capped silyl groups can be any typical but non-limiting point value such as 6%, 7%, 8%, 9%, 10%, etc. or an interval value between any two point values. In this case, when the waterborne UV difunctional polyurethane acrylate resin and the waterborne UV hexa-functional polyurethane acrylate resin contain mercapto-capped silyl groups, the mercapto-capped silyl groups can react with the functional groups in the resin of the waterborne photocurable coating and the functional groups on the surface of the filler (such as pigments and fillers) respectively, forming a bridging effect between the resin and the filler, thereby enhancing the interaction force between the resin and the filler and improving the dispersibility of the filler and the resin in the coating. In addition, by introducing mercapto-capped silyl groups, the weather resistance and wear resistance of the resin can be improved, thereby improving the overall performance of the resin. And, some mercapto-capped silane coupling agents have a faster hydrolysis rate and curing rate, which helps the resin to form a stable cross-linked structure more quickly during the curing process, thereby improving the curing efficiency of the waterborne photocurable coating and the performance of the cured coating film.

[0053] In the waterborne photocurable coating according to the embodiments of the present application, the higher the resin solid content, the more non-volatile substances in the coating, which makes the formation speed of the coating film faster, thereby shortening the drying time, which is of great significance for improving the construction efficiency. The increase in the solid content means the increase in the content of the film-forming substance in the coating, which helps to form a denser coating film structure, thereby improving the hardness of the coating, directly affecting the wear resistance, scratch resistance and weather resistance of the coating film. In addition, for the resin in the waterborne photocurable coating, when the molecular weight increases within a certain range, its mechanical properties such as tensile strength, elongation at break and hardness usually increase. This is because the high molecular weight resin can form longer molecular chains, thereby enhancing the intermolecular interaction force and improving the overall mechanical properties of the coating. The size of the molecular weight also affects the fluidity and workability of the coating. When the molecular weight is moderate, the coating has good fluidity and is easy to construct and coat. When the molecular weight is too large, the fluidity of the coating may become poor, resulting in difficult construction. The size of the molecular weight also affects the curing reaction of the coating. The high molecular weight resin may require a longer time to form a stable cross-linked structure during the curing process. Generally speaking, the high molecular weight resin has better solvent resistance and can resist the erosion and dissolution of solvents.

[0054] In some possible implementation manners, the solid content of the aqueous difunctional UV polyurethane acrylate containing a mercapto-capped silyl group is 40% to 50%, and the molecular weight is 5000 to 6000 Daltons. Exemplarily, the solid content of the aqueous difunctional UV polyurethane acrylate containing a mercapto-capped silyl group can be any typical but non-limiting point value such as 40%, 42%, 44%, 45%, 48%, 50%, etc. or an interval value between any two point values, and the molecular weight can be any typical but non-limiting point value such as 5000 Daltons, 5100 Daltons, 5200 Daltons, 5400 Daltons, 5500 Daltons, 5600 Daltons, 5800 Daltons, 6000 Daltons, etc. or an interval value between any two point values.

[0055] In some possible implementation manners, the solid content of the aqueous UV hexafunctional polyurethane acrylate containing a mercapto-capped silyl group is 40% to 44%, and the molecular weight is 10000 to 30000 Daltons. Exemplarily, the solid content of the aqueous difunctional UV polyurethane acrylate containing a mercapto-capped silyl group can be any typical but non-limiting point value such as 40%, 42%, 44%, etc. or an interval value between any two point values, and the molecular weight can be any typical but non-limiting point value such as 10000 Daltons, 12000 Daltons, 15000 Daltons, 18000 Daltons, 20000 Daltons, 22000 Daltons, 25000 Daltons, 30000 Daltons, etc. or an interval value between any two point values.

[0056] In the case of the above embodiments, the aqueous difunctional UV polyurethane acrylate and the aqueous UV hexafunctional polyurethane acrylate containing a mercapto-capped silyl group can be rapidly cured under UV light irradiation to form a stable crosslinked structure. The relatively fast curing speed helps to improve production efficiency and reduce energy consumption. At the same time, the resin has excellent weather resistance and can resist the erosion of harsh environments such as ultraviolet rays, high temperature, and humidity, maintaining the stability and durability of the coating. The functional groups in the resin can form chemical bonds with the surfaces of various substrates, providing strong adhesion, which helps to ensure a tight fit between the coating and the substrate and prevent the coating from peeling or cracking. The resin has moderate flexibility and hardness, which can meet the requirements of different application scenarios. The better flexibility helps to improve the crack resistance and impact resistance of the coating, while the appropriate hardness can enhance the wear resistance and scratch resistance of the coating. Moreover, the aqueous difunctional UV polyurethane acrylate and the aqueous UV hexafunctional polyurethane acrylate containing a mercapto-capped silyl group use water as a solvent and have a low VOC (volatile organic compound) emission, which helps to reduce environmental pollution. The resin does not produce harmful substances during the curing process, and the cured coating can be recycled, meeting the concept of sustainable development.

[0057] In some possible implementations, the pigments and fillers include at least one of carbon black, graphene, carbon nanotubes, and hard carbon. In this case, the pigments and fillers not only give the paint color and hiding power, but also improve the mechanical properties and durability of the paint coating, and can also give the paint coating special functions such as rust prevention and electrical conductivity. At the same time, the addition of pigments and fillers can also adjust the leveling, suspension, rheological properties and construction performance of the paint, reducing costs.

[0058] In some possible implementations, the wetting and dispersing agent includes at least one of Digo Dispers 755w dispersant, Dispers 740w dispersant, BYK 192 dispersant, and DIS-730A. These wetting and dispersing agents are used in water-based formulations, can strongly disperse pigments and fillers such as carbon black, are very suitable for grinding containing resins, and have excellent tinting power.

[0059] In some possible implementations, the defoamer includes at least one of BYK024 defoamer, BYK028 defoamer, TEGO AIREX902W, and TEGO AIREX 810. These defoamers have excellent defoaming effects in the coating grinding stage.

[0060] In some possible implementations, the cosolvent includes at least one of propylene glycol butyl ether acetate, dipropylene glycol dimethyl ether, and dipropylene glycol butyl ether. These cosolvents have strong solubility for various substrates.

[0061] In some possible implementations, the photoinitiator includes at least one of waterborne photoinitiators TPO-L, 819-DW, IGM 500, and 1173. These photoinitiators can be used as efficient free radical polymerization photoinitiators for different dark color systems, and are particularly suitable for dark color curing of LED waterborne polyurethane dispersion systems.

[0062] In some possible implementations, the pH regulator includes at least one of Deqian AMP-95, triethylamine, dimethylethanolamine, and sodium hydroxide. These pH regulators have the functions of adjusting the pH and stabilizing and promoting the gloss of the paint film.

[0063] In some possible implementations, the thickener includes at least one of Deqian R299 thickener, Deqian WT-105A, and Dow RM12W. These thickeners are super strong non-ionic associative thickeners, do not contain organic solvents, and are applied to various resin emulsion systems such as polyurethane.

[0064] In some embodiments, based on the total raw material mass of the waterborne photocurable coating being 100%, in the raw material components, the content of the waterborne UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group can be typical but non-limiting arbitrary point values such as 20%, 25%, 30%, 35%, 40%, etc. or interval values between any two point values; the content of the waterborne UV hexafunctional polyurethane acrylate containing a mercapto-terminated silyl group can be typical but non-limiting arbitrary point values such as 10%, 12%, 15%, 18%, 20%, etc. or interval values between any two point values; the content of the photoinitiator can be typical but non-limiting arbitrary point values such as 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, etc. or interval values between any two point values; the content of the co-solvent can be typical but non-limiting arbitrary point values such as 2%, 2.1%, 2.2%, 2.5%, 2.8%, 3%, etc. or interval values between any two point values; the content of the defoamer can be typical but non-limiting arbitrary point values such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc. or interval values between any two point values; the content of the wetting and dispersing agent can be typical but non-limiting arbitrary point values such as 0.5%, 0.6%, 0.8%, 0.9%, 1%, etc. or interval values between any two point values; the content of the thickener can be typical but non-limiting arbitrary point values such as 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc. or interval values between any two point values; the content of the pH regulator can be typical but non-limiting arbitrary point values such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc. or interval values between any two point values; the content of the pigment and filler can be typical but non-limiting arbitrary point values such as 10%, 15%, 20%, 25%, 30%, etc. or interval values between any two point values, and the balance is deionized water.

[0065] In some possible implementation manners, the pH value of the waterborne photocurable coating is 6.5 - 8.5; by way of example, the pH value of the waterborne photocurable coating can be typical but non-limiting arbitrary point values such as 6.5, 7, 7.5, 8, 8.5, etc. or interval values between any two point values. Within this pH range, the resin has good wrapping property for the filler, good pigment color development property, and fast drying speed.

[0066] In some possible implementation manners, the fineness of the waterborne photocurable coating is not higher than 20 μm, specifically it can be less than 20 μm, further less than 15 μm, and still further less than 10 μm, etc. In this case, the smaller the fineness of the coating, the more uniformly the coating particles are distributed on the surface of the object to be coated, and the smoother and flatter the formed coating film is, thereby improving the appearance quality of the coating film. The coating particles with small fineness can more effectively fill the minute unevenness on the surface of the object to be coated, making the combination between the coating film and the object to be coated closer, which helps to improve the adhesion, abrasion resistance and weather resistance of the coating film. At the same time, the uniform coating film is less likely to have problems such as cracks and peeling, extending the service life of the coating film. It can also reduce the usage amount of the coating, lower the painting cost, and improve the painting efficiency and painting quality.

[0067] In some possible implementation manners, at 25 °C, the viscosity of the waterborne photocurable coating is 600 cps to 700 cps. Exemplarily, the viscosity of the waterborne photocurable coating can be typical but non-limiting arbitrary point values such as 600 cps (25 °C), 620 cps (25 °C), 650 cps (25 °C), 680 cps (25 °C), 700 cps (25 °C), etc. or interval values between any two point values. In this case, the viscosity of the waterborne photocurable coating is conducive to construction and application by spraying and other methods.

[0068] The photocurable coating in the above embodiments of the present application can be prepared by the following example methods.

[0069] In a second aspect, an embodiment of the present application provides a preparation method of a waterborne photocurable coating, as shown in the appendix Figure 1 and includes the following steps:

[0070] S10. Prepare a waterborne UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group;

[0071] S20. Mix and grind 20 parts to 40 parts of the waterborne UV difunctional polyurethane acrylate resin containing a mercapto-terminated silyl group, 10 parts to 20 parts of the waterborne UV hexafunctional polyurethane acrylate containing a mercapto-terminated silyl group, 2 parts to 2.5 parts of a photoinitiator, 2 parts to 3 parts of a cosolvent, 0.2 parts to 0.6 parts of an antifoaming agent, 0.5 parts to 1 part of a wetting and dispersing agent, 1 part to 1.5 parts of a thickening agent, 0.2 parts to 0.6 parts of a pH regulator, 10 parts to 30 parts of a pigment and filler, and 10 parts to 20 parts of deionized water to obtain a waterborne photocurable coating.

[0072] The preparation method of the waterborne photocurable coating in the embodiment of the present application can obtain the waterborne photocurable coating by mixing and grinding after obtaining the raw material components in the formula amount. The preparation process is simple and suitable for large-scale industrial production and application. In the prepared waterborne photocurable coating, the molecular structures of the waterborne UV difunctional polyurethane acrylate resin and the waterborne UV hexafunctional polyurethane acrylate resin contain mercapto-terminated silyl groups. The mercapto-silyl groups can rapidly enhance the curing reaction during the curing of the coating. Even if the waterborne photocurable coating is dark, it can rapidly improve the deep curing efficiency under the condition of deepening the color. Especially under the photocuring condition, the reaction is faster and the yellowing resistance is better. It can effectively reduce the dosage of photoinitiators and avoid using toxic or high-VOC substances such as toluene, acetone, ethyl acetate phosphate, and active amines, which is green and environmentally friendly. Through the combined action of each raw material component, the prepared coating has the advantages of higher hardness, better scratch resistance, high efficiency utilization, energy saving and consumption reduction, and no pollution to the environment. Its method process is simple, the operation is easy to control, and it can be mechanically electrostatically coated to improve production efficiency.

[0073] In the above step S10:

[0074] In some possible implementation manners, the preparation steps of the waterborne UV difunctional polyurethane acrylate resin containing mercapto-terminated silyl groups and the waterborne UV hexafunctional polyurethane acrylate containing mercapto-terminated silyl groups respectively include:

[0075] S11. Carry out a thiol-ene click reaction on a silane compound and a mercapto compound to prepare mercapto-terminated silica nanoparticles.

[0076] In some embodiments, the silane compound includes at least one of KH570, KH-A172, and A-151.

[0077] In some embodiments, the mercapto compound includes at least one of mercaptoethanol, mercaptoacetic acid, and benzenethiol.

[0078] In some specific embodiments, under argon protection, in a 25 mL transparent glass reactor, mercaptoacrylic acid (1.02 g, 10 mmol), KH570 silane coupling agent (2.10 g, 11 mmol), and a photocatalyst (651 (1065) photoinitiator, also known as benzoyl dimethyl ether DMPA) (mass fraction 1%, 0.04 g) are sequentially added. After the reactants are completely dissolved, the reaction is irradiated under ultraviolet light for 20 min while maintaining the stirring state. After the reaction is completed, the reaction product is precipitated three times in n-hexane to remove the unreacted mercapto compounds and catalysts, and then vacuum dried to constant weight to obtain mercapto silane. The product is a colorless transparent liquid with a yield of 97%.

[0079] S12. Perform a grafting reaction on the thiol-terminated silica nanoparticles with the aqueous UV difunctional polyurethane acrylate resin or the aqueous UV hexafunctional polyurethane acrylate resin. Graft the nanoparticles with thiol-terminated groups through the carboxyl groups in the aqueous UV polyurethane acrylate to obtain the aqueous UV difunctional polyurethane acrylate resin containing thiol-terminated silyl groups or the aqueous UV hexafunctional polyurethane acrylate containing thiol-terminated silyl groups.

[0080] In some possible implementation manners, the mass ratio of the aqueous UV difunctional polyurethane acrylate resin or the aqueous UV hexafunctional polyurethane acrylate resin, the silane compound, and the thiol compound is (20 - 45):(3 - 15):(4 - 8). In this case, there is a better reaction efficiency.

[0081] In the above step S20:

[0082] In some possible implementation manners, the steps of the mixing and grinding treatment include:

[0083] S21. Add a cosolvent, a photoinitiator, a wetting and dispersing agent, an antifoaming agent, and a pH regulator into a container, perform a first mixing treatment, and then fully stir and mix all components evenly.

[0084] S22. Then add the aqueous UV difunctional polyurethane acrylate resin containing thiol-terminated silyl groups and the aqueous UV hexafunctional polyurethane acrylate containing thiol-terminated silyl groups for a second mixing treatment; fully stir and mix the added resins evenly.

[0085] In some possible implementation manners, the rotation speed of the second mixing treatment is 1000 r / min to 2000 r / min; specifically, it can be typical but non-limiting arbitrary point values such as 1000 r / min, 1200 r / min, 1500 r / min, 1800 r / min, 2000 r / min, or interval values between any two point values.

[0086] S23. Then sequentially add deionized water, a thickener, and pigments and fillers for a third mixing treatment, and then perform a grinding treatment to obtain an aqueous photocurable coating. Further fully mix all raw material components evenly, grind and refine the particle sizes of all substances, and obtain a uniformly dispersed and stable aqueous photocurable coating.

[0087] In some possible implementation manners, the rotation speed of the third mixing process is 1500 r / min to 2500 r / min, and the processing duration is 30 min to 60 min. Exemplarily, the rotation speed can be typical but non-limiting arbitrary point values such as 1500 r / min, 1800 r / min, 2000 r / min, 2200 r / min, 2400 r / min, 2500 r / min, or interval values between any two point values, and the processing duration can be typical but non-limiting arbitrary point values such as 30 min, 40 min, 50 min, 60 min, or interval values between any two point values.

[0088] In some possible implementation manners, the grinding process is carried out until the fineness is not higher than 20 μm. In this case, the smaller the fineness of the coating, the more uniformly the coating particles are distributed on the surface of the object to be coated, and the smoother and flatter the formed coating film is, thereby improving the appearance quality of the coating film.

[0089] In a third aspect, an embodiment of the present application provides an application of a waterborne photocurable coating. The above-mentioned waterborne photocurable coating and / or the waterborne photocurable coating prepared by the above method are sprayed onto a workpiece and cured into a film by a light source, so as to form a waterborne photocurable coating on the surface of the workpiece.

[0090] In the application of the waterborne photocurable coating in the embodiment of the present application, the above-mentioned waterborne photocurable coating and / or the waterborne photocurable coating prepared by the above method are sprayed onto a workpiece and cured into a film by a light source, so that a waterborne photocurable coating can be formed on the surface of the workpiece. The application is flexible and convenient, and the painting efficiency is high. Moreover, the adopted waterborne photocurable coating has advantages such as improving the environmental protection of the coating, enhancing scratch resistance, efficient utilization, energy saving and efficiency increase, being green and low-carbon without pollution to the environment, and being capable of mechanical painting operation, further improving the production efficiency.

[0091] In some embodiments, the waterborne photocurable coating can use an electrostatic spraying device to adsorb coating particles on the workpiece with high-voltage static electricity, and a relatively thick coating can be obtained in one coating, and the coating utilization rate is high. Then, the coating sprayed by electrostatic spraying is cured by an LED light source, and the coating film can be instantaneously cured into a film, improving the painting efficiency and saving energy.

[0092] To enable those skilled in the art to clearly understand the above implementation details and operations of the present application, and to significantly reflect the progressive performance of the waterborne photocurable coating and its preparation method and application in the embodiments of the present application, the following uses multiple embodiments to illustrate the above technical solutions.

[0093] Example 1

[0094] A water-based LED electrostatic spray black paint comprises raw material components: 400 g of water-based UV polyurethane propylene emulsion containing mercapto-terminated silane groups and 200 g of water-based UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups, 5 g of a wetting dispersant, 3 g of a defoaming agent, 20 g of a cosolvent, 25 g of a photoinitiator, 2 g of a pH regulator, 150 g of deionized water, 15 g of a water-based thickener and 150 g of carbon black powder.

[0095] Its preparation comprises the steps of:

[0096] 1. Preparation of an aqueous UV polyurethane acrylic emulsion containing mercapto-terminated silane groups: Under argon protection, mercaptoacrylic acid (1.02 g, 10 mmol), KH570 silane coupling agent (2.10 g, 11 mmol), and photocatalyst (651 (1065) photoinitiator, also known as benzyl dimethyl ether DMPA) (mass fraction 1%, 0.04 g) were added in sequence into a 25 mL transparent glass reactor. After the reactants were completely dissolved, the mixture was stirred and irradiated under an ultraviolet lamp for 20 min. After the reaction was completed, the reaction product was precipitated in n-hexane three times to remove unreacted mercapto compounds and catalysts. After vacuum drying to constant weight, mercaptosilane was obtained. The product was a colorless transparent liquid with a yield of 97%. Mercapto-terminated nanoparticles were obtained. Then, the carboxyl groups in waterborne UV polyurethane propylene are grafted with nanoparticles containing mercapto groups to prepare waterborne UV difunctional polyurethane acrylate resin containing mercapto groups-capped silane groups and waterborne UV hexafunctional polyurethane acrylate containing mercapto groups-capped silane groups.

[0097] 2. Weigh the raw material components in the above formula.

[0098] 3. First add 20g of the co-solvent aqueous propylene glycol butyl ether acetate into the container, then slowly add 5g of 819-DW photoinitiator, 20g of TPO-L, 5g of Digo Dispers755w dispersant, 3g of BYK024 defoamer, and 2g of Deqian AMP-95PH regulator. After adding all the above, mix and stir evenly.

[0099] 4. Continue to add 400g of aqueous UV difunctional polyurethane acrylate emulsion containing mercapto-terminated silane groups and 200g of aqueous UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups into the container, stir, and control the speed at about 1000r / min; mix 150g of deionized water and 15g of thickener and stir evenly, then add them into the container; then slowly add 150g of carbon black powder.

[0100] 5. Stir the mixture in a container at a speed of 2000 r / min for 40 minutes, and then grind until the particle size of the paint liquid is ≤20 um, thereby preparing a water-based LED electrostatic spray black paint.

[0101] Example 2

[0102] An aqueous LED electrostatic spraying black paint, which is different from Example 1 in that the raw material components include: 200 g of an aqueous UV polyurethane acrylate emulsion containing a mercapto-terminated silyl group and 100 g of an aqueous UV hexa-functional polyurethane acrylate containing a mercapto-terminated silyl group, 5 g of a wetting and dispersing agent, 1 g of an antifoaming agent, 20 g of a co-solvent, 20 g of a photoinitiator, 2 g of a pH regulator, 100 g of deionized water, 10 g of an aqueous thickener, and 100 g of carbon black powder.

[0103] Example 3

[0104] An aqueous LED electrostatic spraying black paint, which is different from Example 1 in that the raw material components include: 300 g of an aqueous UV polyurethane acrylate emulsion containing a mercapto-terminated silyl group and 150 g of an aqueous UV hexa-functional polyurethane acrylate containing a mercapto-terminated silyl group, 8 g of a wetting and dispersing agent, 4 g of an antifoaming agent, 25 g of a co-solvent, 23 g of a photoinitiator, 4 g of a pH regulator, 200 g of deionized water, 10 g of an aqueous thickener, and 200 g of carbon black powder.

[0105] Example 4

[0106] An aqueous LED electrostatic spraying black paint, which is different from Example 1 in that the raw material components include: 400 g of an aqueous UV polyurethane acrylate emulsion containing a mercapto-terminated silyl group and 200 g of an aqueous UV hexa-functional polyurethane acrylate containing a mercapto-terminated silyl group, 10 g of a wetting and dispersing agent, 3 g of an antifoaming agent, 30 g of a co-solvent, 25 g of a photoinitiator, 6 g of a pH regulator, 300 g of deionized water, 15 g of an aqueous thickener, and 300 g of carbon black powder.

[0107] Comparative Example 1

[0108] Traditional polyurethane solvent-based black paint, specifically including: solvent-based acrylic resin: solvent-based dispersant: propylene glycol methyl ether acetate: S-100 solvent: solvent-based black paste with a mass ratio of 49.1:18.7:12.1:12.1:8.

[0109] Comparative Example 2

[0110] An aqueous LED electrostatic spraying black paint, which is different from Example 1 in that the used aqueous UV difunctional polyurethane acrylate resin does not contain a mercapto-terminated silyl group.

[0111] Comparative Example 3

[0112] An aqueous LED electrostatic spraying black paint, which is different from Example 1 in that the aqueous UV hexa-functional polyurethane acrylate containing a mercapto-terminated silyl group is not added.

[0113] Comparative Example 4

[0114] A water-based LED electrostatic spray black paint, which is different from Example 1 in that: no water-based UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups is added.

[0115] Comparative Example 5

[0116] A water-based LED electrostatic spray black paint, which is different from Example 1 in that the water-based UV hexafunctional polyurethane acrylate resin used does not contain mercapto-terminated silane groups.

[0117] In order to verify the progress of the embodiments of the present application, the water-based LED electrostatic spray black paint prepared by the above-mentioned embodiments and comparative examples was used to adsorb the paint particles on the workpiece using high-voltage static electricity on the electrostatic spray coating equipment, and then applied and cured by LED light. The following performance tests were conducted on the film-forming coated plates of the water-based LED electrostatic spray black paint of each embodiment and comparative example through the electrostatic spray process coating test:

[0118] 1. Pencil hardness tester test: refer to GB / T6739-2006;

[0119] 2. Adhesion test: refer to GB / T9286-1998;

[0120] 3. Paint film water resistance test: observe the changes of the paint film after soaking in water for 24h, 48h and 72h;

[0121] 4. Coating acid resistance test: refer to GB / T9274-1988;

[0122] 5. Weather resistance test: refer to QUV*168H;

[0123] 6. Test on the utilization rate of paint adsorption workpiece:

[0124] The above test results are shown in Table 1 below:

[0125] Table 1

[0126]

[0127]

[0128] From the above test results, it can be seen that the water-based LED electrostatic spray black paint provided in the embodiment of the present application has the advantages of high hardness, full coating, fine surface, good adhesion, excellent durability, high utilization rate, etc. And through LED light curing, it can save energy, reduce energy consumption, and improve production and construction application efficiency.

[0129] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the protection scope of the present application.

Claims

1. A water-based photocurable coating, characterized in that: Taking the total raw material mass of the water-based light-curing coating as 100%, the water-based light-curing coating includes the following raw material components: The invention relates to a water-based UV difunctional polyurethane acrylate resin containing a mercapto-terminated silane group 20% to 40%, a water-based UV hexafunctional polyurethane acrylate containing a mercapto-terminated silane group 10% to 20%, a photoinitiator 2% to 2.5%, a cosolvent 2% to 3%, a defoamer 0.2% to 0.6%, a wetting and dispersing agent 0.5% to 1%, a thickener 1% to 1.5%, a pH regulator 0.2% to 0.6%, a pigment and filler 10% to 30% and a deionized water 10% to 23%.

2. The water-based light-curing coating according to claim 1, characterized in that: The content of the mercapto-terminated silane group in the waterborne UV bifunctional polyurethane acrylate resin is 6% to 10%; And / or, in the waterborne UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups, the content of mercapto-terminated silane groups is 6% to 10%.

3. The water-based photocurable coating according to claim 1 or 2, characterized in that: The water-based difunctional UV polyurethane acrylate containing mercapto-terminated silane groups has a solid content of 40% to 50% and a molecular weight of 5000 to 6000 Daltons; And / or, the water-based UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups has a solid content of 40% to 44% and a molecular weight of 10,000 to 30,000 Daltons.

4. The water-based photocurable coating according to claim 3, characterized in that: The pigment filler includes at least one of carbon black, graphene, carbon nanotubes, and hard carbon; And / or, the wetting dispersant includes at least one of Dispers755w dispersant, Dispers740w dispersant, BYK192 dispersant, and DIS-730A; and / or, the defoamer comprises at least one of BYK024 defoamer, BYK028 defoamer, TEGO AIREX 902W, and TEGO AIREX810; And / or, the cosolvent includes at least one of propylene glycol butyl ether acetate, dipropylene glycol dimethyl ether, and dipropylene glycol butyl ether; And / or, the photoinitiator comprises at least one of water-based photoinitiators TPO-L, 819-DW, IGM 500, and 1173; And / or, the pH regulator includes at least one of Deqian AMP-95, triethylamine, dimethylethanolamine, and sodium hydroxide; And / or, the thickener includes at least one of Deqian R299 thickener, Deqian WT-105A, and Dow RM 12W.

5. The water-based light-curing coating according to any one of claims 1, 2 or 4, characterized in that: The pH value of the water-based light-curing coating is 6.5 to 8.5; and / or, the fineness of the water-based light-curing coating is not higher than 20 μm; And / or, at 25° C., the viscosity of the water-based photocurable coating is 600 cps to 700 cps.

6. A method for preparing a water-based photocurable coating, characterized in that: The following steps are involved: Preparation of waterborne UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups; 20 to 40 parts of the aqueous UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups, 10 to 20 parts of the aqueous UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups, 2 to 2.5 parts of a photoinitiator, 2 to 3 parts of a cosolvent, 0.2 to 0.6 parts of a defoamer, 0.5 to 1 parts of a wetting and dispersing agent, 1 to 1.5 parts of a thickener, 0.2 to 0.6 parts of a pH adjuster, 10 to 30 parts of a pigment and filler, and 10 to 20 parts of deionized water are mixed and ground to obtain an aqueous light-curing coating.

7. The method for preparing a water-based photocurable coating according to claim 6, characterized in that: The preparation steps of the waterborne UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups and the waterborne UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups respectively include: The silane compound is combined with a thiol compound to carry out a thiol-ene click reaction to prepare thiol-terminated silane nanoparticles; The mercapto-terminated silane nanoparticles are grafted with a waterborne UV difunctional polyurethane acrylate resin or a waterborne UV hexafunctional polyurethane acrylate resin to obtain the waterborne UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups or the waterborne UV hexafunctional polyurethane acrylate containing mercapto-terminated silane groups.

8. The method for preparing a water-based photocurable coating according to claim 6 or 7, characterized in that: The steps of the mixing and grinding process include: After adding the cosolvent, the photoinitiator, the wetting and dispersing agent, the defoaming agent and the pH adjuster into a container for a first mixing treatment; Then, the water-based UV difunctional polyurethane acrylate resin containing mercapto-terminated silane groups and the water-based UV hexafunctional polyurethane acrylate are added to perform a second mixing process; Then, the deionized water, the thickener and the pigment are added in sequence for a third mixing process, followed by a grinding process to obtain the water-based light-curing coating.

9. The method for preparing a water-based photocurable coating according to claim 8, characterized in that: The rotation speed of the second mixing process is 1000r / min to 2000r / min; And / or, the rotation speed of the third mixing treatment is 1500r / min to 2500r / min, and the treatment time is 30min to 60min; And / or, the grinding process is performed to a fineness not higher than 20 μm.

10. An application of a water-based photocurable coating, characterized in that: The water-based photocurable coating according to any one of claims 1 to 5 and / or the water-based photocurable coating prepared by the method according to any one of claims 6 to 9 is sprayed onto a workpiece, cured into a film by a light source, and a water-based photocurable coating is formed on the surface of the workpiece.

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