A water-based leather-like crack-effect UV coating and its preparation method and application

Abstract

The present invention discloses a water-based UV coating with a leather-like crackle effect, as well as a preparation method and application. The raw materials for the coating include the following components by weight: 75-80 parts of a water-based organosilicon-modified UV-curable polyurethane acrylate resin, 2-4 parts of a photoinitiator, 0.2-0.5 parts of a silicate additive, and 10-15 parts of water. The water-based organosilicon-modified UV-curable polyurethane acrylate resin has a functionality of 6 to 8; the silicate additive is a synthetic sheet silicate to which an inorganic polyphosphopeptide is added. The UV coating of the present invention can achieve a crackle effect on the surface while maintaining the performance of the paint film, has a strong smooth feel, and is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a water-based UV coating with imitation leather crack effect, a preparation method and an application thereof. Background Art

[0002] Solvent-based crackle paint typically develops cracks based on three principles: reducing the binder, increasing the amount of pigments and fillers, and increasing the volatility of the solvent. Crackle paint produced using these principles exhibits greater shrinkage and lower flexibility. This results in high tensile strength due to internal stress, leading to uniform cracks. The color of the primer is visible through the cracks. Crackle paint produced using this principle requires no special requirements for the base coat used; it simply adheres to the general principles for solvent-based coatings.

[0003] However, this traditional solvent-based crackle paint has more pigments and fillers and less resin, so its adhesion to the substrate, hardness test, high temperature and high humidity test, cosmetics test and other performance will deteriorate. A layer of varnish must be applied on the surface of the crackle paint to protect the crackle paint from falling off in order to meet the performance test requirements.

[0004] In addition to the above defects, the existing crack paints on the market are usually solvent-based, single-component, self-drying types with high VOC content, generally ≥550g / L, and most of them use more quick-drying solvents, which are highly volatile, toxic to the human body, pollute the environment, are flammable and explosive, and are very dangerous. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a water-based imitation leather crack effect UV coating and its preparation method and application, which can achieve the crack effect on the surface while maintaining the performance of the paint film and is environmentally friendly.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A water-based leather-like crack-effect UV coating, the raw materials for its preparation comprising the following components in parts by weight: 75-80 parts of a water-based organosilicon-modified UV-curable polyurethane acrylic resin, 2-4 parts of a photoinitiator, 0.2-0.5 parts of a silicate additive, and 10-15 parts of water;

[0008] The waterborne organosilicon-modified UV-curable polyurethane acrylic resin has a functionality of 6 to 8;

[0009] The silicate auxiliary agent is a synthetic sheet silicate added with inorganic polyphosphopeptide.

[0010] As a further improvement, the preparation raw materials further include 0.2-0.5 parts of a substrate wetting agent, 0.2-0.5 parts of a pH regulator, 0.2-0.5 parts of a defoaming agent, 2-5 parts of a cosolvent, and 0.2-0.5 parts of a thickener.

[0011] As a further improvement, the water-based organosilicon-modified UV-curable polyurethane acrylic resin is one or any combination of RUW1085A from Ruisheng, UA-2385, UA-2390, and UA-2394 from Zhongshan Jieshida.

[0012] As a further improvement, the silicate additive is LAPONITE RDS and / or LAPONITER D produced by BIC.

[0013] As a further improvement, the silicate additive is added in the form of pre-slurry, which is prepared by dispersing the silicate additive in water to a mass concentration of 8 to 12%.

[0014] As a further improvement, the photoinitiator is a mixture of 184 and BP.

[0015] As a further improvement, the substrate wetting agent is one or any combination of Tego Wet 270 and Twin 4100 from Evonik Chemicals and BYK346 from BIC.

[0016] As a further improvement, the pH regulator is DMEA; and / or

[0017] The cosolvent is PM and / or DPM.

[0018] The present invention also provides a method for preparing the water-based leather-imitation crack-effect UV coating, comprising the following steps:

[0019] Under stirring, a substrate wetting agent, a pH regulator, a defoamer, a pre-dissolved photoinitiator, a pre-dissolved silicate additive and a cosolvent are added to the water-based organosilicon-modified UV-curable polyurethane acrylic resin, and the mixture is evenly dispersed. The remaining water is added, and the viscosity is adjusted with a thickener to obtain the water-based imitation leather crack effect UV coating.

[0020] The present invention also provides a use of the water-based leather-like crack-effect UV coating in preparing electronic product housings or protective covers.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The water-based imitation leather crack effect UV coating of the present invention breaks through traditional thinking and does not achieve the crack effect by reducing the base material and increasing the color and filler. Instead, the water-based high-hardness UV topcoat shrinks during curing, and the internal stress is balanced by the use of silicate additives, thereby producing uniform cracks and achieving the effect of imitation leather cracks. And because ultraviolet light penetrates from the surface layer to the interior of the paint film, the surface absorption is large, while the internal absorption is small, so when the UV topcoat is cured, the surface layer cures quickly and the internal stress is large. The uniform cracks produced extend from the surface layer to the inside, and even in the innermost layer of the paint film, due to the slow curing, the internal stress is released and no cracks occur. In this case, the crack effect of the surface layer can be obtained while maintaining the performance of the paint film, and there is no need to apply a layer of varnish on the surface of the crack paint to prevent it from falling off.

[0023] 2. The water-based leather-like crack-effect UV coating of the present invention adopts high-functionality UV resin, has high cross-linking density, wear resistance and hardness.

[0024] 3. The water-based imitation leather crack effect UV coating of the present invention adopts a water-based high-functionality silicone-modified polyurethane dispersion as the main resin. In addition to the crack effect and excellent performance, it also has a strong smooth feeling. When used on mobile phone casings, protective cases, or other electronic products, it not only looks high-end and atmospheric, but also has a good tactile experience.

[0025] 4. The organic solvent content in the water-based imitation leather crack effect UV coating of the present invention is ≤5%, and the VOC content during construction is ≤100g / L, which is relatively environmentally friendly; the viscosity of the coating itself is not high, and it can be diluted to a suitable spraying viscosity range by adding less than 5% water without reducing the performance of the coating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a crack effect diagram of the coated leather obtained in Example 1;

[0028] Figure 2 is a microscopic picture of cracks in the coating obtained in Example 1;

[0029] Figure 3 This is a coating effect diagram obtained in Comparative Example 1. DETAILED DESCRIPTION

[0030] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0033] In some specific embodiments, the water-based leather-like crack-effect UV coating of the present invention comprises the following components in parts by weight: 75-80 parts of a water-based silicone-modified UV-curable polyurethane acrylic resin, 0.2-0.5 parts of a substrate wetting agent, 0.2-0.5 parts of a pH regulator, 0.2-0.5 parts of a defoaming agent, 2-5 parts of a cosolvent, 2-4 parts of a photoinitiator, 0.2-0.5 parts of a silicate additive, 0.2-0.5 parts of a thickener, and 10-15 parts of water.

[0034] In some specific embodiments, the waterborne organosilicon-modified UV-curable polyurethane acrylic resin used in the present invention is one or more of Ruisheng's RUW1085A, Zhongshan Jieshida's UA-2385, UA-2390, and UA-2394. These highly functional waterborne organosilicon-modified polyurethane resins have a functionality of 6 to 8, and the cured paint film has high hardness, good chemical resistance, good abrasion resistance, and a good smooth feel. If the functionality is lower and the cross-link density is low, the cracking effect will not be produced.

[0035] In some specific embodiments, the substrate wetting agent used in the present invention is one or more of Evonik Chemical's Tego Wet 270, Twin 4100, and BYK346 from BYK. Its components are polyether-modified polysiloxane surfactants, which function to provide wettability between the substrate and the primer and eliminate problems such as shrinkage holes and oil spots caused by poor wetting.

[0036] In some specific embodiments, the pH adjuster used in the present invention is commonly used DMEA (dimethylethanolamine), which adjusts the pH value of the coating to between 8 and 9 to facilitate construction and maximize the effect of the additive.

[0037] In some specific embodiments, the defoaming agent used in the present invention is Tego825 produced by Digo Company, which is a commonly used defoaming agent. Its main function is to eliminate bubbles in the coating system and facilitate construction.

[0038] In some specific embodiments, the cosolvent used in the present invention is one or two of PM (propylene glycol methyl ether) and DPM (dipropylene glycol methyl ether), which can improve the compatibility of the system, provide a better solvent volatilization gradient during construction, and balance the thixotropy and leveling of the paint film.

[0039] In some specific embodiments, the photoinitiator used in the present invention is a 1:1 mixture of 184 and BP. 184 (1-hydroxycyclohexyl phenyl ketone) has very high photoinitiator activity, excellent thermal stability and does not produce yellowing, with a maximum absorption wavelength of 333nm. It is mainly used to initiate the rapid curing of systems such as acrylates and methacrylates. BP (benzophenone) is a hydrogen-abstracting photoinitiator. In an aqueous system, it has a good initiation efficiency when provided by an amine hydrogen donor, and can better promote the surface curing of the paint film. 184 and BP are mainly selected to provide surface curing. The purpose of selecting this type of photoinitiator is to make the surface cure quickly, obtain a uniform crack effect under the action of a silicate additive, and at the same time, the surface cross-linking density is high, which can provide better coating properties (hardness, wear resistance, chemical resistance, etc.). The two photoinitiators are used in combination and have absorption in different ultraviolet bands, and the effect is better than using 184 or BP alone.

[0040] In some specific embodiments, the silicate additive used in the present invention is LAPONITE RDS or LAPONITE RD from BIC. This additive plays a key role in the present invention. This additive is a synthetic sheet silicate modified with an inorganic polyphosphopeptide. Its hydrate swells in water to form a clear, colorless colloidal dispersion, known as a sol. At a concentration of approximately 10% in water, it remains free-flowing for 24 hours. Upon addition of a small amount of electrolyte, it forms a highly thixotropic gel. Therefore, it is often used as a thixotropic agent to improve application and has a strong anti-settling effect. However, in the present invention, it has an unexpected effect. During the curing of high-functionality water-based UV resins, the surface of the paint film shrinks due to high internal stress, resulting in cracks. However, in the presence of this silicate, the internal stress of the paint film is balanced, making it uniform across the entire film. This results in uniform cracks on the surface of the film, similar to the crack pattern on leather. This silicate must be pre-dispersed in deionized water to form an 8-12% pre-slurry. In the system, as the addition amount increases, the cracks in the paint film formed become denser. The appropriate addition amount can be selected according to the crack size to be obtained.

[0041] In contrast, conventional silicates are powdered and cannot form sols in water. They are usually used as fillers and do not have thixotropic or anti-settling effects, nor do they produce the balancing internal stress and cracking effects of the present invention.

[0042] In some specific embodiments, the thickener used in the present invention is Hemmings 299 or Tego's ViscoPlus 3060 associative thickener, which is used to adjust the viscosity and thixotropy during construction and eliminate edge accumulation and sagging.

[0043] In some specific embodiments, the preparation method of the water-based imitation leather crack effect UV coating of the present invention comprises: adding a wetting agent, a pH adjuster (adjusted to pH 8-9), a defoamer, a pre-dissolved photoinitiator, a pre-dissolved silicate additive (pre-dispersed in water to prepare an 8-12% pre-slurry), and a cosolvent to a water-based organosilicon-modified polyurethane acrylic resin under stirring, dispersing for 20-30 minutes, adding the remaining deionized water, and adjusting the viscosity to 60-70 KU with a thickener.

[0044] The present invention can produce a UV coating with a leather-like crackle effect and a smooth tactile feel, while also maintaining excellent coating properties such as hardness, wear resistance, and chemical resistance. It can be applied to mobile phone or tablet computer casings, or mobile phone cases, offering both aesthetics and a good tactile feel, resembling the appearance and feel of leather. It can also be combined with different colored primers to achieve vibrant colors while maintaining a consistent appearance and feel. This fully water-based UV coating has a VOC content of ≤100g / L, significantly reducing environmental pollution and the physical hazards to workers during application.

[0045] The present invention is a UV type varnish. If color needs to be achieved, there are two ways: one is to directly make the material into the required color, and the other is to make a layer of ordinary primer to adjust the color.

[0046] The present invention is described in detail below through specific examples.

[0047] Example 1

[0048] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this embodiment are shown in Table 1.

[0049] Table 1

[0050]

[0051] Example 2

[0052] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this embodiment are shown in Table 2.

[0053] Table 2

[0054]

[0055] Example 3

[0056] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this embodiment are shown in Table 3.

[0057] Table 3

[0058]

[0059] Example 4

[0060] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this embodiment are shown in Table 4.

[0061] Table 4

[0062]

[0063] Example 5

[0064] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this embodiment are shown in Table 5.

[0065] Table 5

[0066]

[0067]

[0068] Comparative Example 1

[0069] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this comparative example are shown in Table 6. Compared with Example 1, the amount of silicate additive used in this comparative example is 0.

[0070] Table 6

[0071]

[0072] Comparative Example 2

[0073] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this comparative example are shown in Table 7. Compared with Example 1, the amount of silicate additive used in this comparative example is 8.

[0074] Table 7

[0075]

[0076] Comparative Example 3

[0077] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this comparative example are shown in Table 8. Compared with Example 1, this comparative example uses ordinary water-based UV-curable polyurethane acrylic resin.

[0078] Table 8

[0079] Preparation of raw materials Manufacturer Number of copies Ordinary water-based UV-curable polyurethane acrylic resin allnex DRW-485S 80.00 Substrate wetting agents BYK346 0.5 Photoinitiator (184:BP=1:1 mixture) 184 / BP 3 pH adjusters DMEA 0.2 defoaming agent Tego 825 0.4 cosolvent PM 3 Silicate (10% pre-pulped) BYK RDS 5 Deionized water 7.6 thickener Tego 3060 0.3 total 100

[0080] Comparative Example 4

[0081] The raw materials and weight parts of the water-based leather-like crack-effect UV coating of this comparative example are shown in Table 9. Compared with Example 1, this comparative example uses a common low-functionality water-based UV-curable polyurethane acrylic resin.

[0082] Table 9

[0083] Preparation of raw materials Manufacturer Number of copies Ordinary low-functionality water-based UV-curable polyurethane acrylic resin Opel Lux260 80.00 Substrate wetting agents BYK346 0.5 Photoinitiator (184:BP=1:1 mixture) 184 / BP 3 pH adjusters DMEA 0.2 defoaming agent Tego 825 0.4 cosolvent PM 3 Silicate (10% pre-pulped) BYK RDS 5 Deionized water 7.6 thickener Tego 3060 0.3 total 100

[0084] Preparation methods of Examples 1 to 5 and Comparative Examples 1 to 4:

[0085] 1. Mix 184 and BP photoinitiator, heat in a 60-80℃ water bath or oven to melt, and dissolve into a clear light yellow transparent liquid. Cool to below 40℃ for later use. Special attention: this photoinitiator mixture will precipitate below 10℃ and needs to be stored at a constant temperature;

[0086] 2. Pre-disperse and dissolve silicate (RDS or RD from BYK) in water to make a 10% pre-slurry for later use;

[0087] 3. Coating preparation: first add water-based organosilicon-modified polyurethane acrylic resin, and at a speed of 600-800r / min, add wetting agent, pH regulator (pH adjusted to 8-9), defoamer, pre-dissolved photoinitiator, pre-dissolved silicate, and cosolvent, disperse for 20-30 minutes, and check the particle size ≤15μm;

[0088] 4. Add the remaining deionized water and adjust the viscosity to 60-70 KU with a thickener to prepare the coating.

[0089] Construction method:

[0090] The water-based UV coatings prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were stirred and mixed in a ratio of coating to deionized water = 100:0-10, and the viscosity was adjusted to 12-18s (Zai En 3# viscosity cup, 25°C) with water. The coatings were then sprayed onto a PC plastic substrate or an ordinary self-drying primer coating. The drying conditions were as follows:

[0091] Spray film thickness: 15-20μm

[0092] Baking: 60±5℃*8-12min

[0093] UV energy: 800~1200mj / cm 2

[0094] UV light intensity: 90-120mw / cm 2

[0095] A water-based UV coating was prepared.

[0096] Performance Testing

[0097] The water-based UV coating prepared above was subjected to the following tests. The test results of the embodiment are shown in Table 10, and the test results of the comparative example are shown in Table 11. The crack effect of the coating leather prepared in Example 1 is shown in Table 10. Figure 1-2 , the coating effect of comparative example 1 is as follows Figure 3 The coatings prepared in Examples 1-5 have an adhesion of ≥4B on commonly used PC, ABS, and PC+ABS substrates.

[0098] Table 10

[0099]

[0100]

[0101] Table 11

[0102]

[0103]

[0104] As can be seen from the above table, Examples 1-5 can all obtain water-based UV coatings with leather-like cracks and a smooth feel. Examples 1-4 have a smaller crack effect, close to leather cracks. Example 5 has a larger crack effect due to a smaller amount of silicate added.

[0105] Comparing Comparative Example 1 with Example 1, Comparative Example 1 lacks silicate (RDS / RD), and a uniform crack effect cannot be obtained. Due to the high functionality of the resin (6 to 8), the paint film is relatively hard, and several large uneven cracks appear.

[0106] Comparing Comparative Example 2 with Example 1, the amount of silicate (RDS / RD) added in Comparative Example 2 was excessive, exceeding the upper limit. The resulting paint film had overly fine cracks, lacking aesthetic appeal. Furthermore, the dense cracks lost their smooth feel. Furthermore, the excessive amount of silicate (RDS / RD) added increased the viscosity of the paint after aging, requiring the addition of significant amounts of water, hindering spray application. Furthermore, the excess water resulted in a low solids content and an abnormal wet film.

[0107] Comparing Comparative Example 3 with Example 1, the ordinary non-silicone modified polyurethane acrylic resin used in Comparative Example 3 has a higher functionality (6). Although it can also obtain a uniform crack effect, it does not have a smooth feel and feels dry.

[0108] Comparing Comparative Example 4 with Example 1, the ordinary non-silicone modified polyurethane acrylic resin used in Comparative Example 4 has a low functionality (3-4 functions) and a low cross-linking density. During UV curing, it will not crack and cannot obtain a leather-like crack effect.

[0109] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A water-based imitation leather crack effect UV coating, characterized in that: The raw materials for its preparation include the following components in parts by weight: 75-80 parts of water-based organosilicon-modified UV-curable polyurethane acrylic resin, 2-4 parts of photoinitiator, 0.2-0.5 parts of silicate additive, and 10-15 parts of water; The waterborne organosilicon-modified UV-curable polyurethane acrylic resin has a functionality of 6 to 8; The silicate auxiliary agent is a synthetic sheet silicate added with inorganic polyphosphopeptide.

2. The water-based imitation leather crack effect UV coating according to claim 1, characterized in that: The preparation raw materials further include 0.2-0.5 parts of a substrate wetting agent, 0.2-0.5 parts of a pH regulator, 0.2-0.5 parts of a defoaming agent, 2-5 parts of a cosolvent, and 0.2-0.5 parts of a thickener.

3. The water-based imitation leather crack effect UV coating according to claim 1 or 2, characterized in that: The water-based organosilicon-modified UV-curable polyurethane acrylic resin is one or any combination of RUW1085A from Ruisheng, UA-2385, UA-2390, and UA-2394 from Zhongshan Jieshida.

4. The water-based imitation leather crack effect UV coating according to claim 1 or 2, characterized in that: The silicate additive is LAPONITE RDS and / or LAPONITE RD from BIC.

5. The water-based leather-like crack effect UV coating according to claim 4, characterized in that: The silicate additive is added in the form of pre-slurry, which is prepared by dispersing the silicate additive in water to a mass concentration of 8 to 12%.

6. The water-based leather-like crack effect UV coating according to claim 1 or 2, characterized in that: The photoinitiator is a mixture of 184 and BP.

7. The water-based leather-like crack effect UV coating according to claim 2, characterized in that: The substrate wetting agent is one or any combination of Tego Wet 270 and Twin 4100 from Evonik Chemicals and BYK346 from BIC.

8. The water-based leather-like crack effect UV coating according to claim 2, characterized in that: The pH regulator is DMEA; and / or The cosolvent is PM and / or DPM.

9. A method for preparing the water-based leather-like crack-effect UV coating according to any one of claims 1 to 8, characterized in that: The following steps are included: Under stirring, a substrate wetting agent, a pH regulator, a defoamer, a pre-dissolved photoinitiator, a pre-dissolved silicate additive and a cosolvent are added to the water-based organosilicon-modified UV-curable polyurethane acrylic resin, and the mixture is evenly dispersed. The remaining water is added, and the viscosity is adjusted with a thickener to obtain the water-based imitation leather crack effect UV coating.

10. Use of the water-based leather-like crack-effect UV coating according to any one of claims 1 to 8 in the preparation of electronic product housings or protective covers.

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