A water-based light-heat dual-curing coating and its preparation method and application

Abstract

The present invention discloses a water-based light-heat dual-curing coating and a preparation method and application thereof, including component A, component B and component C; component A includes water-based polyurethane acrylic dispersion resin, water-based hydroxyl-containing acrylic polyurethane dispersion resin, water-based thermosetting acrylic resin, water, solvent, photoinitiator, and auxiliary agent; component B includes isocyanate curing agent and diluent; component C includes water-based crosslinking agent and water. The coating film prepared by the present invention not only has good resistance to extreme chemicals, but also takes into account the wear resistance and flexibility of UV resin and thermosetting acrylic resin, solving the shortcomings of brittle paint film and poor bending resistance when using UV resin alone, and poor chemical resistance and wear resistance when using thermosetting acrylic resin alone.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a water-based light-heat dual-curing coating and a preparation method and application thereof. Background Art

[0002] At present, with the rapid iteration and update of products in the field of electronic consumer products, the functional coating materials on the corresponding products, which were originally dominated by solvent-based coating products, have now been gradually replaced by water-based coatings. Especially for wearable smart devices, the corresponding coating materials have high requirements for toughness, wear resistance and chemical resistance, and special functional coating materials that can meet the corresponding requirements are required. The current market solution is solvent-based functional coatings.

[0003] Currently, there are almost no solutions for water-based functional coating materials for wearable smart devices on the market, mainly due to the high requirements for coating toughness, wear resistance and chemical resistance. While meeting the toughness requirements, the coating needs to have good wear resistance and resistance to extreme chemicals. Although UV coatings have good wear resistance and chemical resistance, due to stress shrinkage of the coating during the photocuring process, the toughness of the paint film is poor, and the stress shrinkage between the coating and the wearable smart device substrate is uneven, which is prone to cracking risks in the environment. Thermosetting resins have good flexibility, can form good adhesion with the substrate and will not crack in the environment, but have low crosslinking density, and poor wear resistance and chemical resistance. In addition, the construction window of multi-component coatings containing curing agents is narrow and the construction time is short. Summary of the invention

[0004] The present invention aims to solve the problems of poor toughness of the paint film when using water-based UV resin alone and poor wear resistance and chemical resistance when using water-based thermosetting resin alone, and provides a water-based light-heat dual-curing coating and a preparation method and application thereof.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A water-based light-heat dual-curing coating, the water-based light-heat dual-curing coating comprising component A, component B and component C;

[0007] Component A includes the following components by weight:

[0008]

[0009] Component B includes the following components by weight:

[0010] Isocyanate curing agent 80-95 parts

[0011] 5-20 parts of diluent

[0012] Component C includes the following components by weight:

[0013] 80-95 parts of water-based crosslinking agent

[0014] 5-20 parts water

[0015] The waterborne polyurethane acrylic dispersion resin is a high-functionality waterborne UV resin with a functionality of 7 to 10;

[0016] The water-based hydroxyl-containing acrylic polyurethane dispersion resin is a hydroxyl-containing low-functionality water-based UV resin with a functionality of 2 to 6;

[0017] The water-based thermosetting acrylic resin is a low-hydroxyl water-based hydroxyl acrylic resin with a Tg of 40 to 60° C. and a hydroxyl value of 25 to 35 mg / KOH.

[0018] Preferably, the component A further comprises the following components in parts by weight:

[0019]

[0020] Preferably, the solvent is at least one of diethylene glycol butyl ether, propylene glycol methyl ether, dipropylene glycol ether or propylene glycol butyl ether.

[0021] Preferably, the isocyanate curing agent is isophorone diisocyanate curing agent.

[0022] Preferably, the diluent is at least one of propylene glycol diacetate, propylene glycol methyl ether acetate or dipropylene glycol dimethyl ether.

[0023] Preferably, the aqueous crosslinking agent is an aqueous carbodiimide polymer or an aqueous aziridine polymer.

[0024] Preferably, the mass proportion of the aqueous polyurethane acrylic dispersion resin is 15 to 20 parts, the mass proportion of the aqueous hydroxyl-containing acrylic polyurethane dispersion resin is 20 to 25 parts, and the mass proportion of the aqueous thermosetting acrylic resin is 25 to 30 parts.

[0025] Preferably, the mass ratio of component A, component B and component C is 100:(3-8):(3-8).

[0026] The present invention also provides a method for preparing the water-based light-heat dual-curing coating, comprising the following steps:

[0027] Preparation of component A:

[0028] Mixing water and a solvent to prepare a first mixed liquid;

[0029] Mixing an aqueous polyurethane acrylic dispersion resin, an aqueous hydroxyl-containing acrylic polyurethane dispersion resin and an aqueous thermosetting acrylic resin to prepare a second mixed solution;

[0030] adding the first mixed solution to the second mixed solution, mixing them, and preparing a third mixed solution;

[0031] Adding a photoinitiator, a wetting agent, a leveling agent, a defoaming agent, a matting powder and an aqueous thickener to the third mixed liquid, mixing the mixture, preparing a fourth mixed liquid, and filtering to obtain component A;

[0032] Preparation of component B:

[0033] Mixing the isocyanate curing agent and the diluent, and filtering to obtain component B;

[0034] Preparation of component C:

[0035] The aqueous crosslinking agent and water are mixed and filtered to obtain component C.

[0036] The present invention also provides an application of the water-based light-heat dual-curing coating, which includes: mixing component A, component B and component C, spraying them on a substrate, pre-baking at a temperature of 60 to 80° C. for 10 to 60 minutes, and then UV curing, and the cured product is baked at a temperature of 60 to 80° C. for 1 to 2 hours.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention combines the structural characteristics of UV resin and thermosetting resin, and adopts a unique cross-linking structure model in the product formula design. In the process of drying and curing the coating film, the double bonds, hydroxyl groups and carboxyl groups in the water-based resin system used all participate in the reaction in the system to form a super strong three-dimensional network structure. The advantages of the two types of resins are fully utilized, and the prepared coating film not only has good resistance to extreme chemicals, but also takes into account the wear resistance and flexibility of UV resin and thermosetting acrylic resin, solving the shortcomings of the paint film being brittle and poor in bending resistance when UV resin is used alone, and the poor chemical resistance and wear resistance when thermosetting acrylic resin is used alone.

[0039] At the same time, the present invention uses water-based resins with specific structures when selecting raw materials. During construction, the curing agent and cross-linking agent used have a longer activation period after being mixed with the main agent, ensuring that the coating has a wider construction window.

[0040] The coating of the present invention can be used as a functional coating material for wearable intelligent devices and the like. DETAILED DESCRIPTION

[0041] The water-based light-heat dual-curing coating of some embodiments of the present invention includes three components: component A, component B, and component C:

[0042] Component A includes the following components in parts by weight:

[0043]

[0044] Component B includes the following components in parts by weight:

[0045] Isocyanate curing agent 80-95 parts

[0046] 5-20 parts of diluent

[0047] Component C includes the following components in parts by weight:

[0048] 80-95 parts of water-based crosslinking agent

[0049] 5-20 parts of deionized water

[0050] Component A:

[0051] In some specific embodiments, the waterborne polyurethane acrylic dispersion resin is at least one of high-functionality waterborne UV resins with a functionality of 7 to 10, providing good hardness, wear resistance and chemical resistance. Specifically, one or more of Allnex UCECOAT 7200, Ruishi RS7915, or Changxing Chemical ETERCURE DR-W497S can be selected.

[0052] In some specific embodiments, the water-based hydroxyl-containing acrylic polyurethane dispersion resin is at least one of the hydroxyl-containing low-functionality water-based UV resins with a functionality of 2 to 6, with a hydroxyl value of about 30 mg / KOH (25 to 35 mg / KOH) and a molecular weight of 6000-20000 g / mol. High molecular weight low-functionality UV resins have good flexibility, provide good adhesion to plastic substrates, and participate in the dual cross-linking reaction of UV curing and NCO curing agent. Specifically, one or more of Ruisheng RUW-2040B and Yierfu EV-916 can be selected.

[0053] In some specific embodiments, the water-based thermosetting acrylic resin is at least one of low-hydroxy water-based hydroxyl acrylic resins with a Tg of 40-60°C, an acid value of 5-30 mg KOH / g, and a hydroxyl value of about 30 mg / KOH (25-35 mg / KOH). It has a higher Tg point and a fast surface drying speed, which is beneficial to improving the yield of spray products and the gloss stability of the coating. Specifically, one or more of KN1522W, KN1533W, and KN3793W can be selected.

[0054] In some specific embodiments, the solvent is at least one of diethylene glycol butyl ether, propylene glycol methyl ether, dipropylene glycol ether or propylene glycol butyl ether.

[0055] In some specific embodiments, the photoinitiator is at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, ethyl 2,4,6-trimethylbenzoylphosphonate and benzophenone.

[0056] In some specific embodiments, the wetting agent is a polyether-modified siloxane, such as BYK 3455, BYK 349, Wet 240, At least one of Wet 270, etc.

[0057] In some specific embodiments, the leveling agent is a polyether-modified siloxane, such as BYK 333, Digo Glide 110, Glide 100, At least one of Rad 2200N, etc.

[0058] In some specific embodiments, the defoaming agent is Digo Airex 902, Foamex830, Foamex 825, At least one of Foamex 822, etc.;

[0059] In some specific embodiments, the matting powder is at least one of Japan Tosoh E-1011, Evonik ACEMATT TS100, ACEMATT OK520, Grace SYLOID 7000, etc.

[0060] In some specific embodiments, the aqueous thickener is Digo ViscoPlus 3030, At least one of ViscoPlus3060, Hemmings RHEOLATE 299, RHEOLATE FX 1010, etc.

[0061] Component B:

[0062] In some specific embodiments, the isocyanate curing agent is isophorone diisocyanate curing agent, for example 401-60, BASF HW 3280MBA, etc. The curing agent used in the present invention reacts with hydroxyl groups, and compared with HDI curing agent, it not only has a longer activation period (up to 8 hours or more), but also has better chemical resistance after cross-linking with the resin.

[0063] In some specific embodiments, the diluent is at least one of propylene glycol diacetate, propylene glycol methyl ether acetate (PMA) or dipropylene glycol dimethyl ether (DMM).

[0064] Component C:

[0065] In some specific embodiments, the water-based crosslinking agent is a water-based carbodiimide polymer or a water-based aziridine polymer. The above crosslinking agent has a long activation period, which can reach more than 24 hours after being mixed with the main agent alone, and has a good construction window. At the same time, it can react with the carboxyl group in the water-based resin to further enhance the chemical resistance of the paint film.

[0066] The present invention uses three different types of water-based resins, which are high-functionality water-based UV resin, hydroxyl-containing water-based UV resin and water-based thermosetting acrylic resin. The paint film after curing with the high-functionality water-based UV resin provides a higher crosslinking density, ensuring that the paint film has good wear resistance and chemical resistance. The hydroxyl-containing water-based UV resin used is a low-hydroxyl light-curing resin, and the UV paint film is cross-linked and combined with the non-photocuring thermosetting resin paint film through the NCO group of the curing agent to form a three-dimensional network crosslinking structure. The water-based thermosetting resin used is a low-hydroxyl quick-drying acrylic dispersion, which participates in the cross-linking and curing of the NCO group of the curing agent and the hydroxyl-containing water-based UV resin, and introduces the water-based thermosetting resin with good flexibility into the paint film, ensuring that the cured paint film has good chemical resistance and good flexibility at the same time, and the quick-drying performance of the corresponding resin gives the coating film a faster surface drying speed, thereby improving the yield of the product after spraying. The water-based resins used above are all dispersion-type. In the step of water-based resin, carboxyl groups are often neutralized with organic amines to ensure that the resin can be stably dispersed in water. The introduction of carboxyl groups reduces the water resistance and environmental resistance test performance of the cured paint film, thereby affecting the overall chemical resistance of the coating film. Therefore, the present invention introduces a carbodiimide or aziridine crosslinking agent that can react with carboxyl groups to ensure that the carboxyl groups in the coating film can also participate in the crosslinking reaction of the coating film, further strengthen the crosslinking density of the coating film, and improve the chemical resistance and wear resistance of the coating film.

[0067] The present invention combines the curing characteristics of the corresponding reaction functional groups of different types of resins, and uses the coating film formed by light and heat dual curing to form a dense three-dimensional network structure to improve the wear resistance and chemical resistance of the coating film. At the same time, a thermosetting resin with good flexibility is introduced into the coating film to further improve the flexibility of the coating film. The performance characteristics and reaction characteristics of each resin are fully utilized to prepare a coating film with good wear resistance, chemical resistance and bending resistance.

[0068] The preparation method of the water-based light-heat dual-curing coating in some embodiments of the present invention comprises:

[0069] Preparation of component A:

[0070] The above-mentioned deionized water and solvent in parts by weight are mixed to prepare a first mixed solution; preferably, the mixing condition is to disperse at 200 to 500 rpm for 2 to 3 minutes;

[0071] The above parts by weight of the aqueous polyurethane acrylic dispersion resin, the aqueous hydroxyl-containing acrylic polyurethane dispersion resin and the aqueous thermosetting acrylic resin are mixed to prepare a second mixed solution; preferably, the mixing condition is to disperse at 300 to 600 rpm for 3 to 6 minutes;

[0072] Slowly adding the first mixed solution into the second mixed solution, mixing, and preparing a third mixed solution; preferably, the mixing condition is dispersing at 300-600 rpm for 3-6 minutes;

[0073] Add the above-mentioned weight portions of photoinitiator, wetting agent, leveling agent, defoamer, matting powder and aqueous thickener to the third mixed liquid, mix them, prepare the fourth mixed liquid, and filter to obtain component A; preferably, the mixing condition is to disperse at 1000-1500 rpm for 15-30 minutes.

[0074] Preparation of component B:

[0075] The isocyanate curing agent and diluent in the above parts by weight are mixed and filtered to obtain component B; preferably, the mixing condition is to disperse at 300 to 600 r / min for 6 to 15 minutes.

[0076] Preparation of component C:

[0077] The aqueous crosslinking agent and deionized water in the above parts by weight are mixed and filtered to obtain component C; preferably, the mixing condition is to disperse at 200 to 500 r / min for 3 to 6 minutes.

[0078] In some specific embodiments, when used, component A, component B, and component C are mixed in a mass ratio of 100:(3-8):(3-8), and an appropriate amount of deionized water is added and mixed evenly, filtered and then sprayed on the substrate. The mixture is pre-baked at 60-80°C for 10-60 minutes, and then UV-cured. The cured product is baked at 60-80°C for 1-2 hours.

[0079] When the baking time is short for light curing, only the double bonds in the water-based UV resin participate in the cross-linking reaction, while the hydroxyl and carboxyl groups hardly participate in the cross-linking reaction. Post-baking is required to allow the hydroxyl and carboxyl groups to fully participate in the curing reaction of the coating. When the baking time is long before light curing, the hydroxyl and carboxyl groups in the thermal curing group participate in the cross-linking reaction. A certain cross-linking reaction has been formed before light curing. After light curing, only a short post-baking is required to complete the full cross-linking and curing reaction of the coating. In addition, the coating should not be pre-baked for a long time before light curing. When the baking time is too long, the hydroxyl and carboxyl groups have been fully cross-linked and cured, resulting in a smaller "free volume" for the movement of the molecular chain segments. During light curing, the chain movement is restricted, resulting in a decrease in the conversion rate of the double bond part of the light curing. Therefore, the coating should not be pre-baked for a long time.

[0080] The present invention is further described in detail below through specific examples.

[0081] The water-based coatings in Examples 1-4 and Comparative Examples 5-7 all include three components A, B, and C, wherein the components and the amounts (in parts by weight) of the three components A, B, and C are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] The preparation methods of Examples 1-4 and Comparative Examples 5-7 are as follows (Comparative Examples 5-7 do not add corresponding components): Preparation of Component A:

[0086] Disperse the above-mentioned deionized water and solvent in parts by weight at 200-500 rpm for 2-3 minutes to prepare a first mixed solution;

[0087] Dispersing the above-mentioned parts by weight of the aqueous polyurethane acrylic dispersion resin, the aqueous hydroxyl-containing acrylic polyurethane dispersion resin and the aqueous thermosetting acrylic resin at 300-600 rpm for 3-6 minutes to prepare a second mixed solution;

[0088] Slowly add the first mixed solution into the second mixed solution, disperse at 300-600 rpm for 3-6 minutes, and prepare a third mixed solution;

[0089] Add the above-mentioned weight portions of photoinitiator, wetting agent, leveling agent, defoamer, matting powder and aqueous thickener to the third mixed liquid, disperse at 1000-1500 rpm for 15-30 minutes, prepare the fourth mixed liquid, and filter to obtain component A.

[0090] Preparation of component B:

[0091] The isocyanate curing agent and diluent in the above parts by weight are dispersed at 300-600 r / min for 6-15 minutes, and the component B is obtained by filtering.

[0092] Preparation of component C:

[0093] The aqueous crosslinking agent and deionized water in the above parts by weight are dispersed at 200-500 r / min for 3-6 minutes, and filtered to obtain component C.

[0094] Examples 1 to 4 and comparative examples 5-7 show the effects of different ingredients on the surface properties of the paint film after curing. The specific construction process is as follows: the prepared components are added in the ratio of component A: component B: component C = 100:5:5. After the above components are stirred evenly with a disperser, deionized water in a corresponding appropriate proportion is added to adjust the spraying viscosity to 10 to 12s (viscosity data measured by Cai En 3# cup at 25°C). After mixing evenly, filter with a 200 to 300 mesh filter cloth. The filtered mixture (the activation period of Examples 1 to 4 is up to 8h or more) is sprayed on a PC plastic substrate (a common material for 3C electronic products). The product after spraying the coating is pre-baked at a temperature of 60-80°C for 10-60min, and then placed on a UV curing machine for curing (UV curing energy is UVA 800-1000mJ·cm -2 , UVB 700~900mJ·cm -2 ), the cured product is placed at a temperature of 60-80°C and baked for 1-2h.

[0095] The test results of the coating properties of Examples 1 to 4 and Comparative Examples 5 to 7 are shown in Table 2 (where the bending resistance is tested using GB / T6742-1986):

[0096] Table 2

[0097]

[0098]

[0099] Compared with Examples 1-4 and Comparative Examples 5-7, it can be seen from Example 1 that the paint film has better wear resistance and chemical resistance, but slightly poor bending resistance. It can be seen from Comparative Example 5 and Example 1 that the high-functionality water-based UV resin used has a high crosslinking density, the paint film shrinks greatly when curing, the elongation at break is low, it is easy to crack when bending at a small angle, and the bending resistance of the paint film deteriorates. The higher crosslinking density of the UV resin is beneficial to the wear resistance of the paint film, and it can withstand 300 times of steel wool friction without exposing the substrate.

[0100] It can be seen from Examples 2-4 and Comparative Example 7 that as the content of high-functionality water-based UV decreases and the content of water-based thermosetting acrylic resin increases, the bending resistance of the paint film improves. The corresponding paint films of Examples 2-4 can be bent 180° without cracking, but the wear resistance of the corresponding paint film of Example 4 is slightly worse, resistant to steel wool 300 times, slightly exposed to the substrate, and the resistance to oleic acid chemicals is worse. After 500 hours, the paint film is slightly blistering. Mainly, with the increase of thermosetting resin, the cross-linking density of the paint film after curing is low, and the paint film shows good flexibility of water-based thermosetting resin. Although the paint film has good flexibility, the lower cross-linking density weakens the barrier to the penetration of chemicals into the paint film, and the long-term swelling of the chemicals on the paint film causes the paint film to blister. And the reduction in cross-linking density leads to the poor performance of the paint film in resisting external stress friction, and the wear resistance of the paint film is poor.

[0101] From the performance test results of Examples 1-4 and Comparative Examples 5-7, it can be seen that when a high-functionality water-based UV resin is used alone, although the paint film has a high cross-linking density as a whole, the paint film is brittle and has poor bending resistance, such as Comparative Example 5. When a thermosetting water-based acrylic resin is used alone, compared with a UV resin with a higher cross-linking density, its cross-linking density is lower, and it exhibits better bending resistance. However, if the cross-linking density is too low, the chemical resistance and wear resistance become poor, such as Comparative Examples 6-7.

[0102] The present invention utilizes double bonds, hydroxyl groups and carboxyl groups in the water-based resin system to participate in the reaction in the system to form a super-strong three-dimensional network structure, fully utilizes the high cross-linking density and high wear and chemical resistance of the water-based UV resin and the high flexibility of the water-based thermosetting resin, utilizes the hydroxyl-containing water-based UV resin to participate in thermal curing and light curing, so that the two types of resins can simultaneously participate in the cross-linking reaction during the curing of the paint film, and at the same time, a cross-linking agent is used to react the residual carboxyl groups in the resin to participate in the cross-linking reaction of the paint film, so as to form a paint film with good bending resistance, wear resistance and chemical resistance.

[0103] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A water-based light-heat dual-curing coating, characterized in that: The water-based light-heat dual-curing coating comprises component A, component B and component C; Component A includes the following components by weight: Component B includes the following components by weight: Component C includes the following components by weight: In the component A: The waterborne polyurethane acrylic dispersion resin is a high-functionality waterborne UV resin with a functionality of 7 to 10; The water-based hydroxyl-containing acrylic polyurethane dispersion resin is a hydroxyl-containing low-functionality water-based UV resin with a functionality of 2 to 6; The water-based thermosetting acrylic resin is a low-hydroxyl water-based hydroxyl acrylic resin with a Tg of 40-60° C. and a hydroxyl value of 25-35 mg / KOH; The mass ratio of component A, component B and component C is 100:(3~8):(3~8).

2. The water-based light-heat dual-curing coating according to claim 1, characterized in that: The component A also includes the following components in parts by weight:

3. The water-based light-heat dual-curing coating according to claim 1 or 2, characterized in that: The solvent is at least one of diethylene glycol butyl ether, propylene glycol methyl ether, dipropylene glycol ether or propylene glycol butyl ether.

4. The water-based light-heat dual-curing coating according to claim 1 or 2, characterized in that: The isocyanate curing agent is isophorone diisocyanate curing agent.

5. The water-based light-heat dual-curing coating according to claim 1 or 2, characterized in that: The diluent is at least one of propylene glycol diacetate, propylene glycol methyl ether acetate or dipropylene glycol dimethyl ether.

6. The water-based light-heat dual-curing coating according to claim 1 or 2, characterized in that: The aqueous crosslinking agent is an aqueous carbodiimide polymer or an aqueous aziridine polymer.

7. The water-based light-heat dual-curing coating according to claim 1 or 2, characterized in that: The mass parts of the waterborne polyurethane acrylic dispersion resin are 15 to 20 parts, the mass parts of the waterborne hydroxyl-containing acrylic polyurethane dispersion resin are 20 to 25 parts, and the mass parts of the waterborne thermosetting acrylic resin are 25 to 30 parts.

8. A method for preparing the water-based light-heat dual-curing coating according to any one of claims 1 to 7, characterized in that: The steps include: Preparation of component A: Mixing water and a solvent to prepare a first mixed liquid; Mixing an aqueous polyurethane acrylic dispersion resin, an aqueous hydroxyl-containing acrylic polyurethane dispersion resin and an aqueous thermosetting acrylic resin to prepare a second mixed solution; adding the first mixed solution to the second mixed solution, mixing them, and preparing a third mixed solution; Adding a photoinitiator, a wetting agent, a leveling agent, a defoaming agent, a matting powder and an aqueous thickener to the third mixed liquid, mixing the mixture, preparing a fourth mixed liquid, and filtering to obtain component A; Preparation of component B: Mixing the isocyanate curing agent and the diluent, and filtering to obtain component B; Preparation of component C: The aqueous crosslinking agent and water are mixed and filtered to obtain component C.

9. An application of the water-based light-heat dual-curing coating according to any one of claims 1 to 7, characterized in that: The application includes: mixing component A, component B and component C, spraying on a substrate, pre-baking at a temperature of 60-80° C. for 10-60 minutes, and then UV curing, and the cured product is baked at a temperature of 60-80° C. for 1-2 hours.

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