A weather-resistant water-based LED light-curing topcoat and preparation method thereof

Abstract

The present application relates to the field of coatings, and specifically discloses a weather-resistant water-based LED light-cured topcoat coating and a preparation method thereof. The topcoat coating comprises the following raw materials by weight: 70-90 parts of LED curing resin, 8-20 parts of UV monomer, 0.5-3 parts of hindered amine light stabilizer, 5-10 parts of photoinitiator, 6-12 parts of water-based composite emulsion, 2-6 parts of ceramic microbeads, 2-6 parts of quartz powder, 2-10 parts of auxiliary agent, and 12-25 parts of water-soluble solvent; wherein the water-based composite emulsion is composed of styrene acrylic emulsion and silicone acrylic emulsion. This LED light-cured topcoat coating can be quickly cured under ultraviolet light, and exhibits excellent light stability and weather resistance, and has broad application prospects.

Description

Technical Field

[0001] The present application relates to the field of coatings, and more specifically, to a weather-resistant water-based LED light-curing topcoat coating and a preparation method thereof. Background Art

[0002] Photocurable coatings, also known as photosensitive coatings, use ultraviolet light as the energy source for coating curing, also known as UV-curable coatings. This type of coating does not require heating when used and can quickly cure into a film on flammable substrates such as paper, plastic, leather and wood.

[0003] At present, the photocurable coatings on the market are mainly composed of photosensitive resins, photosensitizers (photoinitiators) and diluents. At the same time, some additives are added, such as heat stabilizers; pigments and fillers are added when preparing color paints. Photosensitive resins are generally low molecular weight resins with unsaturated bonds, such as unsaturated polyesters and acrylic oligomers; photosensitizers are compounds that easily absorb ultraviolet light to produce active free radicals, such as benzophenone and benzoin alkyl ethers. The principle of curing is to use the energy of ultraviolet light to initiate polymerization and cross-linking reactions between low molecular prepolymers or oligomers in the coating and monomer molecules as active diluents to obtain a hardened paint film, which is essentially chemical drying achieved by forming chemical bonds.

[0004] This type of light-curing coating has the advantages of short curing time (a fraction of a second to a few minutes), low curing temperature, and low volatility, and is a new type of coating that saves energy, resources, is pollution-free, and is highly efficient. However, existing light-curing coatings are easily degraded by light oxidation during long-term use, and have poor light stability; they are also easily affected by ambient temperature, air humidity, etc., and have poor weather resistance. Summary of the invention

[0005] In order to improve the stability and weather resistance of existing photocurable coatings, the present application provides a weather-resistant water-based LED photocurable topcoat coating and a preparation method thereof.

[0006] This application adopts the following technical solutions:

[0007] A weather-resistant water-based LED light-curing topcoat coating, the topcoat coating comprising the following raw materials in parts by weight: 70-90 parts of LED curing resin, 8-20 parts of UV monomer, 0.5-3 parts of hindered amine light stabilizer, 5-10 parts of photoinitiator, 6-12 parts of water-based composite emulsion, 2-6 parts of ceramic microbeads, 2-6 parts of quartz powder, 2-10 parts of auxiliary agent, and 12-25 parts of water-soluble solvent; the water-based composite emulsion is composed of styrene-acrylic emulsion and silicone-acrylic emulsion;

[0008] The mass ratio of LED curing resin to UV monomer is 7-9:1.

[0009] The total mass of the LED curing resin and the UV monomer is M, the mass of the hindered amine light stabilizer satisfies: M*(0.01-0.15), and the mass of the photoinitiator satisfies: M*(0.07-0.09).

[0010] Furthermore, the hindered amine light stabilizer is a composite hindered amine light stabilizer, and the composite hindered amine light stabilizer contains benzothiazole or benzoxazole groups.

[0011] Furthermore, the composite hindered amine light stabilizer is a benzoxazole-hindered amine light stabilizer, and its structure is shown in Formula I:

[0012]

[0013] Furthermore, the mass ratio of the above-mentioned styrene acrylic emulsion to the silicone acrylic emulsion is 1:1-2.

[0014] Furthermore, the photoinitiator is a free radical photoinitiator.

[0015] Furthermore, the free radical photoinitiator is a mixture of an α-hydroxyketone derivative and an acylphosphine oxide in a mass ratio of 2-4:1.

[0016] Furthermore, the above-mentioned auxiliary agent includes, by weight:

[0017] PH regulator 0.2-0.5 parts, wetting agent 0.5-2 parts, defoaming agent 0.3-1 parts, leveling agent 0.5-2 parts, bactericide 0.1-1 parts, thickener 0.5-3 parts.

[0018] Furthermore, the thickener is a cross-linked polymer emulsion thickener formed by copolymerization of acrylate and methacrylate.

[0019] In a second aspect, the present application provides a method for preparing the above-mentioned weather-resistant water-based LED light-cured topcoat coating, which comprises:

[0020] Mixing and grinding ceramic microbeads and quartz powder according to weight proportions to obtain a first material, wherein the particle size of the first material is 20-30 μm; dispersing styrene acrylic emulsion and silicone acrylic emulsion in a partially water-soluble solvent to obtain a second material;

[0021] Dispersing LED curing resin, UV monomer and hindered amine light stabilizer in a part of water-soluble solvent to obtain a third material; mixing the first material, the second material, the third material, the auxiliary agent and the remaining water-soluble solvent, and finally adding a photoinitiator and stirring and mixing.

[0022] In summary, this application has the following beneficial effects:

[0023] 1. The weather-resistant water-based LED light-curing topcoat provided in the present application is prepared by mixing LED curing resin, UV monomer and hindered amine light stabilizer. Since the hindered amine light stabilizer can capture free radicals, decompose peroxides and transfer the energy of excited molecules, it can effectively inhibit the photo-oxidative degradation reaction; at the same time, in the process of coordinated use with LED curing resin and UV monomer, it can also synergistically improve the light stabilization effect of the water-based LED light-curing topcoat. When the mass ratio of LED curing resin to UV monomer is 7-9:1 and the mass of hindered amine light stabilizer meets: M*(0.01-0.15), the light stabilization effect is better.

[0024] 2. The weather-resistant water-based LED light-curing topcoat provided in the present application contains a water-based composite emulsion, which is composed of a styrene-acrylic emulsion and a silicone-acrylic emulsion. The glass transition temperature of the styrene-acrylic emulsion is relatively low, while the glass transition temperature of the silicone-acrylic emulsion is relatively high; and both have good adhesion. When used in combination, the weather resistance of the topcoat can be greatly improved.

[0025] 3. The weather-resistant water-based LED light-curing topcoat provided in the present application also contains ceramic microbeads and quartz powder, both of which have high hardness. When added to the topcoat and used in combination with other components, the topcoat can further impart wear resistance after film formation. Moreover, due to the high compactness of the ceramic microbeads, it helps to reduce the permeability of the topcoat after film formation, which helps to further improve the weather resistance of the topcoat. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the synthetic reaction formula of the benzoxazole-hindered amine light stabilizer in the preparation example of the embodiment of the present application. DETAILED DESCRIPTION

[0027] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0028] The technical solution of the present invention is:

[0029] A weather-resistant water-based LED light-curing topcoat coating comprises the following raw materials in parts by weight: 70-90 parts of LED curing resin, 8-20 parts of UV monomer, 0.5-3 parts of hindered amine light stabilizer, 5-10 parts of photoinitiator, 6-12 parts of water-based composite emulsion, 2-6 parts of ceramic microbeads, 2-6 parts of quartz powder, 2-10 parts of additives and 12-25 parts of water-soluble solvent.

[0030] Preferably, the topcoat coating comprises the following raw materials in parts by weight: 75-85 parts of LED curing resin, 10-18 parts of UV monomer, 0.8-2.5 parts of hindered amine light stabilizer, 6-9 parts of photoinitiator, 7-9 parts of aqueous composite emulsion, 3-5 parts of ceramic microbeads, 3-5 parts of quartz powder, 3-8 parts of additives, and 15-23 parts of water-soluble solvent.

[0031] In this application, the LED curing resin is a tetrafunctional water-based acrylic resin purchased from Zhongshan Huamingtai Technology Co., Ltd. The UV monomer is tripropylene glycol diacrylate, which can be used as a reactive diluent. When used in conjunction with the LED curing resin, the flexibility and stability of the light-curing coating after film formation can be improved.

[0032] Hindered amine light stabilizers, in which the functional structural unit tetramethylpiperidine (TMP) is easily oxidized by photoelectron excitation, can effectively capture free radicals in the polymer degradation chain reaction, and thus help to inhibit the degradation and aging reaction of the polymer. However, the inventors have found that a single hindered amine light stabilizer can only play a limited role in the light stabilization of the topcoat formed by LED-cured resin and UV monomer. In view of this, the inventors further adopted a composite hindered amine light stabilizer, and the composite hindered amine light stabilizer contains benzothiazole or benzoxazole groups. Among them, benzothiazole and benzoxazole groups are ultraviolet absorbing groups, which can capture free radicals through hindered amine groups while absorbing ultraviolet rays, inhibit photooxidative degradation reactions, and greatly improve the light stabilization efficiency.

[0033] Furthermore, the composite hindered amine light stabilizer is a benzoxazole-hindered amine light stabilizer, and its structure is shown in Formula I:

[0034]

[0035] The composite hindered amine light stabilizer contains hindered amine groups and benzoxazole groups, wherein the benzoxazole groups contain both N and O heteroatoms and can form conjugated large π bonds with adjacent 1,3,5-triazine groups, thereby further improving the ultraviolet absorption capacity and light stability.

[0036] The above-mentioned photoinitiator is a free radical photoinitiator. When the mass of the photoinitiator satisfies: M*(0.07-0.09), where M is the total mass of the LED curing resin and the UV monomer, the photocuring effect is better. Furthermore, the above-mentioned free radical photoinitiator is a mixture of an α-hydroxy ketone derivative and an acylphosphine oxide in a mass ratio of 2-4:1; more preferably, the above-mentioned free radical photoinitiator is a mixture of an α-hydroxy ketone derivative and an acylphosphine oxide in a mass ratio of 3:1.

[0037] Furthermore, the above-mentioned auxiliary agent includes, by weight:

[0038] PH regulator 0.2-0.5 parts, wetting agent 0.5-2 parts, defoaming agent 0.3-1 parts, leveling agent 0.5-2 parts, bactericide 0.1-1 parts, thickener 0.5-3 parts.

[0039] Preferably, the above-mentioned auxiliary agent comprises, by weight:

[0040] PH regulator 0.3-0.4 parts, wetting agent 0.9-1.6 parts, defoaming agent 0.5-0.8 parts, leveling agent 0.8-1.5 parts, bactericide 0.3-0.7 parts, thickener 1.2-2.5 parts.

[0041] The thickener is a cross-linked polymer emulsion thickener formed by copolymerization of acrylate and methacrylate.

[0042] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0043] Preparation Example

[0044] Preparation Example provides a method for preparing a benzoxazole-hindered amine light stabilizer, the reaction formula is as follows Figure 1 As shown:

[0045] In a reaction kettle, 1 mol of compound A (2-chloro-4,6-di-[N-n-butyl-N-1,2,2,6,6-pentamethyl-4-piperidinyl]amino]-1,3,5-triazine) and 1.05 mol of compound B (2-amino-6-chloro-benzoxazole) were added, and then 0.5 mol of NaOH was added. Xylene was used as the solvent, and after nitrogen substitution, the reaction was carried out at 150°C for 4 hours. After cooling, the mixture was washed with water, filtered and purified to obtain 106 g of a white solid. After identification by mass spectrometry and nuclear magnetic resonance, the structure was found to be compound (I).

[0046] Example 1

[0047] This embodiment provides a weather-resistant water-based LED light-cured topcoat coating, the components of which are shown in Table 1:

[0048] Table 1. Components and contents of topcoat coatings

[0049]

[0050] Among them, hindered amine light stabilizer HS-944 was purchased from Hubei Hengjing Chemical Co., Ltd.;

[0051] The content of the additives specifically includes:

[0052] PH regulator 0.3kg, wetting agent 1.0kg, defoaming agent 0.5kg, leveling agent 0.7kg, bactericide 1.5kg, thickener 2.0kg.

[0053] The preparation method of this water-based LED light-curing topcoat coating comprises the following steps:

[0054] (1) mixing and grinding ceramic micro beads and quartz powder to obtain a first material, wherein the particle size of the first material is 20-30 μm;

[0055] (2) dispersing the styrene acrylic emulsion and the silicone acrylic emulsion in water to obtain a second material;

[0056] (3) dispersing LED curing resin, UV monomer, and hindered amine light stabilizer in part of water to obtain a third material;

[0057] (4) Mix the first material, the second material, the third material, the auxiliary agent and the remaining water-soluble solvent, and finally add the photoinitiator, and stir to mix.

[0058] Performance testing:

[0059] The performance test of the topcoat prepared in Example 1 was carried out

[0060] (1) Adhesion test: The test is carried out in accordance with GB 1720-1979 (1989) "Determination of adhesion of paint films", with a grid spacing of 2 mm. The smaller the adhesion grade value, the better the adhesion;

[0061] (2) The curing speed is measured by the following method: spray the paint evenly onto the PVC board with a coating amount of 50-55g / m 2 , and then perform (365nm) LED curing.

[0062] (3) Weather resistance: measured by artificial weathering test.

[0063] (4) Light stability: The test was conducted using an ultraviolet aging test in accordance with ASTM G154. The light source was UVA-340, with a 12-hour cycle, 8 hours of ultraviolet light and 4 hours of condensation.

[0064] (5) Storage stability: Place the paint at 50°C for 7 days and observe whether there is any abnormal precipitation or discoloration.

[0065] The results are shown in Table 2:

[0066] Table 2. Performance test results of the topcoat coating prepared in Example 1

[0067]

[0068] The first set of embodiments

[0069] Examples 2-4 and Comparative Examples 1-3 are basically the same as Example 1, except that the selection and content of the hindered amine light stabilizer are different, as shown in Table 3:

[0070] Table 3. Effect of hindered amine light stabilizers on the performance of topcoat coatings

[0071]

[0072]

[0073] It can be seen from Table 3 that:

[0074] Comparing Examples 1 to 3 with Comparative Example 1, after adding a light stabilizer to the system, under the same UV irradiation time (3000h), the anti-aging performance of the topcoat coatings of Examples 1-3 is better, specifically manifested as: high gloss retention, low color difference and no powdering.

[0075] When Example 1 is compared with Examples 2-3, when a composite light stabilizer is added to the system, under the same UV irradiation time (3000h), the anti-aging performance of the topcoat coatings of Examples 2 and 3 is better, especially the best performance of Example 3. This shows that when large conjugated groups benzothiazole and benzoxazole are introduced into the light stabilizer, the light stabilization effect can be further effectively improved, thereby improving the anti-aging performance of the topcoat.

[0076] When the light stabilizers are both benzoxazole-hindered amine composite light stabilizers, see Example 3 and Comparative Examples 2-3, when the mass of the light stabilizer satisfies: M*(0.01-0.15) (where M is the total mass of the LED-cured resin and the UV monomer), under the same UV irradiation time (3000h), the performance of Example 3 is the best, while the performance of Comparative Examples 2 and 3 is greatly reduced, which shows that the amount of hindered amine light stabilizer added is crucial to the light stability of the topcoat coating.

[0077] The second set of embodiments:

[0078] Examples 5-6 and Comparative Examples 4-7 are substantially the same as Example 1, except that the selection and content of the aqueous composite emulsion are different, as shown in Table 4:

[0079] Table 4. Investigating the effect of water-based emulsion on the performance of topcoat coatings

[0080]

[0081]

[0082] It can be seen from Table 4 that:

[0083] Compared with Comparative Examples 4 and 5, a single aqueous emulsion is used. Examples 1, 5 and 6 of the present application all use a composite emulsion of styrene-acrylic emulsion and silicone-acrylic emulsion, and the addition amount is 10 kg. However, when the weather resistance performance test was carried out, it was found that when the weather resistance test was carried out for 6000 hours, the topcoat coatings of Comparative Examples 4 and 5 began to show bubbles, peeling, powdering and discoloration. In contrast, the topcoat coating of the present application did not bubble, peel, powder or discolor when the weather resistance test was carried out for 9000 hours, meeting the weather resistance requirements and basically achieving 10-15 years of weather resistance.

[0084] At the same time, by comparing Example 1, Example 5 and Example 6, as well as Comparative Example 6 and Comparative Example 7, it can be found that when the mass ratio between the styrene acrylic emulsion / the silicone acrylic emulsion is 1:1-2, the weather resistance of the topcoat coating is good; and when the addition ratio of the silicone acrylic emulsion is small (1:0.5) or large (1:2.5), the weather resistance exhibited by the topcoat coating decreases to a certain extent.

[0085] The third group of embodiments:

[0086] Comparative Examples 8-10 are basically the same as Example 1, except that the ceramic microbeads and quartz powder are different, as shown in Table 5:

[0087] Table 5. Investigating the effects of ceramic microspheres and quartz powder on the performance of topcoat coatings

[0088]

[0089]

[0090] As can be seen from Table 5, when ceramic microbeads and quartz powder are added to the raw material system of the topcoat (Example 1), the weather resistance of the prepared topcoat coating is significantly improved compared to when no or only one is added. This shows that the addition of ceramic microbeads and quartz powder helps to reduce the permeability of the topcoat after film formation, and helps to further improve the weather resistance of the topcoat coating.

[0091] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A weather-resistant water-based LED light-curing topcoat coating, characterized in that: The topcoat coating comprises the following raw materials in parts by weight: 70-90 parts of LED curing resin, 8-20 parts of UV monomer, 0.5-3 parts of hindered amine light stabilizer, 5-10 parts of photoinitiator, 6-12 parts of water-based composite emulsion, 2-6 parts of ceramic microbeads, 2-6 parts of quartz powder, 2-10 parts of additives, and 12-25 parts of water-soluble solvent; The aqueous composite emulsion is composed of styrene-acrylic emulsion and silicone-acrylic emulsion; The mass ratio of the LED curing resin to the UV monomer is 7-9:1, The total mass of the LED curing resin and the UV monomer is M, the mass of the hindered amine light stabilizer satisfies: M*(0.01-0.15), and the mass of the photoinitiator satisfies: M*(0.07-0.09).

2. The weather-resistant water-based LED light-curing topcoat coating according to claim 1, characterized in that: The hindered amine light stabilizer is a composite hindered amine light stabilizer, and the composite hindered amine light stabilizer contains benzothiazole or benzoxazole groups.

3. The weather-resistant water-based LED light-curing topcoat coating according to claim 2, characterized in that: The composite hindered amine light stabilizer is a benzoxazole-hindered amine light stabilizer, and its structure is shown in Formula I:

4. The weather-resistant water-based LED light-curing topcoat coating according to claim 1, characterized in that: The mass ratio of the styrene acrylic emulsion to the silicone acrylic emulsion is 1:1-2.

5. The weather-resistant water-based LED light-curing topcoat coating according to claim 1, characterized in that: The photoinitiator is a free radical photoinitiator.

6. The weather-resistant water-based LED light-curing topcoat coating according to claim 5, characterized in that: The free radical photoinitiator is a mixture of an α-hydroxy ketone derivative and an acylphosphine oxide in a mass ratio of 2-4:

1.

7. The weather-resistant water-based LED light-curing topcoat according to any one of claims 1 to 6, characterized in that: The auxiliary agent includes, by weight: PH regulator 0.2-0.5 parts, wetting agent 0.5-2 parts, defoaming agent 0.3-1 parts, leveling agent 0.5-2 parts, bactericide 0.1-1 parts, thickener 0.5-3 parts.

8. The weather-resistant water-based LED light-curing topcoat coating according to claim 7, characterized in that: The thickener is a cross-linked polymer emulsion thickener formed by copolymerization of acrylate and methacrylate.

9. A method for preparing a weather-resistant water-based LED light-curing topcoat according to any one of claims 1 to 8, characterized in that: It includes: The ceramic microbeads and quartz powder are mixed and ground according to weight to obtain a first material, wherein the particle size of the first material is 20-30 μm; Dispersing the styrene acrylic emulsion and the silicone acrylic emulsion in part of the water-soluble solvent to obtain a second material; Dispersing the LED curable resin, UV monomer, and hindered amine light stabilizer in part of the water-soluble solvent to obtain a third material; The first material, the second material, the third material, the auxiliary agent and the remaining water-soluble solvent are mixed, and finally a photoinitiator is added and stirred to mix.

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