Preparation method of fluorine-free hydrophobic transparent coating and application thereof on glass, plastic film and metal surface

Abstract

The application discloses a preparation method of fluorine-free hydrophobic transparent paint, which can be uniformly coated on a glass, a plastic film or a smooth surface of metal by using a spraying, brushing or rolling process to make the glass, the plastic film or the smooth surface of metal have aesthetic and functional beneficial effects. The method has the advantages that the hydrophobic coating layer is added to the surface layer while maintaining high transparency, the hydrophobicity of the surface of the sample is improved, and the self-cleaning function is realized, the water contact angle is about 120 DEG, the sample has good scratch resistance and washing resistance durability. The application range includes, but is not limited to, a mobile phone screen, a plastic film, a mobile phone back shell and the like.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and specifically to a method for preparing a fluorine-free hydrophobic transparent coating for use on transparent glass, plastic film, or smooth metal surfaces (e.g., the casing on the back of a mobile phone). Background Technology

[0002] With the rapid development of industries such as information, construction, agriculture, and automobiles, glass, plastic film, and mobile phones are now ubiquitous in our lives. Whether it's windshields in cars, electronic display screens, plastic films for agricultural greenhouses, or the metal back covers of mobile phones, transparent and hydrophobic coating materials are needed. The invention of such materials can greatly facilitate our daily lives, reduce unnecessary waste, and effectively protect the natural environment.

[0003] Hydrophobic coatings currently suffer from various problems, such as low hardness and poor abrasion resistance, making them unsuitable for use in harsh environments. Scratches from hard objects and erosion from mud and sand can damage the coating. Therefore, improving the overall performance of hydrophobic transparent coatings, including scratch resistance, resistance to erosion from mud and sand, extending the service life of the coating, enhancing the self-cleaning function of the hydrophobic coating, and improving the adhesion between the coating and the substrate, are the main problems that urgently need to be solved.

[0004] Currently, hydrophobic coating materials mainly use fluorinated resins, such as polytetrafluoroethylene (PTFE) or Teflon coatings. Their preparation process is complex, with stringent conditions and curing temperatures exceeding 300°C. The main approaches to preparing wear-resistant hydrophobic coatings generally fall into two categories. One involves using perfluorosilane compounds to reduce surface energy and improve the hydrophobicity of the coating. While perfluorosilane compounds have lower surface energy, their long-chain fluorocarbon components result in a soft, non-wear-resistant coating that easily peels off, posing risks of harm and pollution to humans and the environment. Furthermore, fluorinated compounds are expensive, leading to high preparation costs. Patents with application numbers CN106746736A, CN101941000A, CN106928844A, CN105420735A, and CN206725795U all use fluorinated compounds as raw materials. Another type involves adding particles such as silica to the glass surface to increase the microscopic roughness of the glass substrate surface and achieve hydrophobicity. Examples include Chinese patents with application numbers CN105670393A, CN110615619A, CN110616038A, CN101249964, and CN104947169A. This type of patent belongs to the heterogeneous addition method. Because silica and other particles have high surface energy and high brittleness, the mechanical properties of the coating are reduced. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing a fluorine-free hydrophobic transparent coating.

[0006] The technical solution adopted by this invention to solve the technical problem is: to prepare a water-soluble, fluorine-free solution for a hydrophobic, transparent, and wear-resistant coating. The preparation method of the water-soluble, fluorine-free solution includes the following steps: preparation of a polymer, preparation of a binder, preparation of a hydrophobic, transparent coating, and application of the fluorine-free transparent coating to glass, plastic film, and mobile phone metal back cover by spraying, brushing, or rolling. After curing, the comprehensive properties such as transparency, surface contact angle, hardness, and water resistance are tested. The raw materials required for the preparation of the coating include:

[0007] Ethylene glycol butyl ether (EGBE); hydroxyl-terminated polydimethylsiloxane (H-PDMS); glacial acetic acid; deionized water or purified water; isopropyl titanate (TIP), isopropanol, nano silica sol (30% concentration), n-propanol, methyltriethoxysilane (MTES).

[0008] This invention provides a method for preparing a water-soluble, fluorine-free, transparent surface coating, comprising the following steps:

[0009] 1. Polymer preparation:

[0010] Step (1): Weigh out ethylene glycol butyl ether (EGBE) solvent, hydroxyl-terminated polydimethylsiloxane (H-PDMS), glacial acetic acid, and deionized water in a mass ratio of 130:56:1:3.

[0011] Step (2): Add the H-PDMS solution dropwise into the EGBE solvent while magnetically stirring at 400 r / min for 30-60 minutes to ensure thorough mixing and obtain the H-PDMS-EGBE mixture.

[0012] Step (3): Add the weighed glacial acetic acid solution dropwise to deionized water to obtain a hydrolyzed acidic solution.

[0013] Step (4): Add the acidic solution from step (3) dropwise to the H-PDMS-EGBE mixture while magnetically stirring at 400 r / min for 1 hour to ensure thorough mixing, and label the mixture as solution ①.

[0014] Step (5): Weigh out isopropanol and isopropyl titanate in a mass ratio of 2:1. Add isopropyl titanate dropwise to isopropanol. Stir the mixture magnetically for 1 h and label the mixture as solution ②.

[0015] Step (6): Slowly add solution ② to ① while stirring magnetically for 1 h to obtain a mixed solution of ①+②.

[0016] 2. Preparation of adhesive:

[0017] Step (7): Add deionized water to the nano silica sol (30 wt%) solution and stir for 5 min. Then slowly add n-propanol solution to this solution, and finally slowly add triethoxymethylsilane (MTES) solution in a mass ratio of 1:7:7.5:9.55. Stir until a slightly bluish clear solution is obtained. Label this mixture as solution ③ and bottle it for later use.

[0018] 3. Preparation of hydrophobic transparent coatings:

[0019] Step (8): Mix the mixed solution of ①+② prepared in step (6) with solution ③ at a mass ratio of 6:4 and stir to ensure thorough mixing, thereby obtaining a water-soluble fluorine-free coating.

[0020] 4. Coating preparation and curing:

[0021] Step (9): Before coating, clean the glass (or other substrate material) sample thoroughly. Specific steps include: applying 1-2 drops of hand sanitizer to the glass surface, repeatedly rubbing the entire sample surface with gloved fingers, rinsing with tap water, then rinsing 1-2 times with deionized or pure water, finally rinsing the surface once with alcohol in a slightly inclined direction, and gently drying with a nitrogen gun. For plastic film pretreatment, use an atmospheric plasma scanner to scan the XY plane of the sample surface 1-2 times.

[0022] Step (10): Apply the appropriate coating evenly to the glass, plastic film, or smooth metal surface by spraying, brushing, or rolling. Before coating, an appropriate pretreatment process is required to ensure that the surface of the substrate material is clean, free of oil and contaminants. After coating, the coating and the substrate should be kept at a curing temperature of 60°C - 80°C for about 40 minutes. After curing, let it stand at room temperature for 12 hours to obtain a hydrophobic, transparent, and wear-resistant coating.

[0023] The beneficial effects of this invention are as follows: the obtained coating can be evenly coated on glass, plastic film, or smooth metal surfaces to achieve complete transparency, with a water contact angle of about 120°, good scratch resistance, and a certain degree of self-cleaning function. Attached Figure Description

[0024] Figure 1 The results of the light transmittance test of the coating (glass substrate).

[0025] Figure 2 Water contact angle and oil contact angle of the coating on different substrate materials.

[0026] Figure 3 Results of water wash resistance durability tests on coatings on different substrate materials.

[0027] Figure 4Compare the water contact angle and oil contact angle of coatings 1-5 applied to the glass with the original glass substrate (sample 0).

[0028] Figure 5 The water contact angle and oil contact angle of coatings 1-5 on the PET film are compared with those of the original PET film (sample 0).

[0029] Figure 6 Stainless steel surface coating and water droplet shape.

[0030] Figure 7 Cross-cut test to test the adhesion between the coating and the PET substrate (0 is the highest level). Detailed Implementation

[0031] Example 1:

[0032] Step (1): Weigh out 30g of ethylene glycol butyl ether (EGBE) solution, 13g of hydroxyl-terminated polydimethylsiloxane (H-PDMS), 0.23g of glacial acetic acid, and 0.72g of deionized water.

[0033] Step (2): Add the H-PDMS solution dropwise into the EGBE solvent while stirring magnetically at 400 r / min to ensure thorough mixing and obtain the H-PDMS-EGBE mixed solution.

[0034] Step (3): Add the weighed glacial acetic acid solution dropwise to deionized water and hydrolyze it completely to obtain an acidic aqueous solution.

[0035] Step (4): Add the acidic aqueous solution from step (3) dropwise to the H-PDMS-EGBE mixture while stirring magnetically at 400 r / min for 1 hour to ensure thorough mixing and obtain the mixture, which is labeled as solution ①.

[0036] Step (5): Weigh 5.6 g of isopropanol and 2.8 g of isopropyl titanate. Add 2.8 g of isopropyl titanate dropwise to isopropanol. Stir the mixture magnetically for 1 h and label the mixture as solution ②.

[0037] Step (6): Slowly add solution ② to ① while stirring magnetically for 1 h to obtain a mixed solution of ①+②.

[0038] Step (7): Add 8g of deionized water to 56g of nano silica sol, stir for 5 min, then slowly add 60g of n-propanol solution to this solution, and finally slowly add 76.4g of methyltriethoxysilane (MTES) solution. Stir until a slightly bluish clear solution is obtained. This solution is designated as solution ③ and bottled for later use.

[0039] Step (8): Mix the mixed solution of ①+② with solution ③ in a mass ratio of 6:4 and stir to ensure thorough mixing, thereby obtaining a water-soluble fluorine-free coating.

[0040] Step (9): Clean the glass (or other substrate material) sample thoroughly. Specific steps include: applying 1-2 drops of common hand sanitizer to the glass surface, repeatedly rubbing the entire sample surface with gloved fingers, rinsing thoroughly with tap water, then rinsing 1-2 times with deionized or pure water, finally rinsing the surface once with alcohol in a slightly inclined direction, and gently drying with a nitrogen gun. For plastic film pretreatment, use an atmospheric plasma scanner to scan the XY plane of the sample surface 1-2 times.

[0041] Step (10): Apply the coating to the glass, plastic film, or metal shell on the back of the mobile phone using a medium-pressure, low-flow spraying method. Place it in an oven to cure, set the temperature to 60° - 80°C, and cure for about 40 minutes. After curing, let it stand at room temperature for 12 hours.

[0042] Example 2:

[0043] This embodiment is consistent with the steps (1~7, 9) of embodiment 1. The difference is that in step (8), the ratio of solution ①+② to solution ③ is 5:5 by mass. The other steps are the same as in embodiment 1.

[0044] Example 3:

[0045] This embodiment is consistent with the steps (1~7, 9) of embodiment 1. The difference is that in step (8), the ratio of solution ①+② to solution ③ is 4:6 by mass. The other steps are the same as in embodiment 1.

[0046] Example 4:

[0047] This embodiment is consistent with the steps (1~7, 9) of embodiment 1. The difference is that in step (8), the ratio of solution ①+② to solution ③ is 7:3 by mass. The other steps are the same as in embodiment 1.

[0048] Example 5:

[0049] This embodiment is consistent with the steps (1~7, 9) of embodiment 1. The difference is that in step (8), the ratio of solution ①+② to solution ③ is 3:7 by mass. The other steps are the same as in embodiment 1.

[0050] Test example:

[0051] Water and oil contact angles were measured using a standard contact angle meter with pure water and vegetable oil as the test liquids, respectively. The droplet mass was 0.5 mL, and the contact angle values ​​were automatically generated by the system software. The coating's scratch resistance was assessed using a standard pencil hardness tester. The pencil hardness test kit series of pencils ranged from low to high hardness, from 6B to 9H. The adhesion between the coating and the substrate material was measured using a standard cross-cut test, with levels ranging from 0 to 5, with level 0 being the highest. The wet scrubbing test was performed using an Elastomer 1720 wet abrasion tester, employing a 3M car wash sponge and a 500 g load. The test was repeated up to 10,000 cycles, stopping at various stages to measure the water contact angle before continuing until 10,000 cycles were reached. The contact angle change curve was plotted; a decrease in contact angle within 10% was considered a pass, indicating good durability.

[0052] The glass coating samples of Examples 1-5 were subjected to various performance tests, and the specific results are shown in Table 1 and Appendix 2 below. Figure 1-6 :

[0053] Table 1: Performance test results of samples from Examples 1-5

[0054] Experimental Project Water contact angle (°) Oil contact angle (°) Pencil hardness Adhesion (1mm grid test) Appearance Example 1 100 47.6 5H 0 The coating is uniform and transparent. Example 2 105 48.5 5H 0 The coating is uniform and transparent. Example 3 106 56.7 5H 0 The coating is uniform and transparent. Example 4 117 71.4 5H 0 The coating is uniform and transparent. Example 5 105 60.2 5H 0 The coating is uniform and transparent. Original glass 48 16 6H - -

[0055] The above embodiments are merely a description of the fluorine-free hydrophobic transparent coating, but do not limit the scope of the present invention in any way.

Claims

1. A method for preparing a water-soluble, fluorine-free coating that can be applied to the surface of glass, plastic film, and metal as a hydrophobic, transparent, and wear-resistant coating, the method comprising the following steps: Step (1): Weigh out ethylene glycol butyl ether (EGBE) solvent, hydroxyl-terminated polydimethylsiloxane (H-PDMS), glacial acetic acid, and deionized water respectively, with a mass ratio of 130:56:1:

3. Step (2): Add the H-PDMS solution dropwise into the EGBE solvent while stirring magnetically at 400 r / min for 30-60 minutes to ensure thorough mixing and obtain the H-PDMS-EGBE mixture. Step (3): Add the weighed glacial acetic acid solution dropwise to deionized water to obtain a hydrolyzed acidic aqueous solution; Step (4): Add the acidic aqueous solution from step (3) dropwise to the H-PDMS-EGBE mixture while stirring magnetically at 400 r / min for 1 hour to ensure thorough mixing and obtain the mixture, which is labeled as solution ①. Step (5): Weigh out isopropanol and isopropyl titanate in a mass ratio of 2:

1. Add isopropyl titanate dropwise to isopropanol. Stir the mixture magnetically for 1 hour and label the mixture as solution ②. Step (6): Slowly add solution ② to ① while stirring magnetically for 1 hour to obtain a mixed solution of ① + ②; Step (7): Add deionized water to a 30wt% solution of nano-silica sol, stir for 5 minutes, then slowly add n-propanol solution to this solution, and finally slowly add triethoxymethylsilane MTES solution in a mass ratio of 1:7:7.5:9.

55. Stir until a slightly bluish clear solution is obtained. Label this mixture as solution ③ and bottle it for later use. Step (8): Mix the mixed solution of ①+② prepared in step (6) with solution ③ in different mass ratios and stir to make them fully mixed to obtain a water-soluble fluorine-free coating. The mass ratio range includes: 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:

8.

2. The method for preparing the water-soluble fluorine-free coating according to claim 1, wherein the coating preparation method is as follows: Before coating, the substrate sample must be thoroughly cleaned. Specific steps include: Apply 1 to 2 drops of common hand sanitizer to the surface of the substrate material, repeatedly rub the entire sample surface with gloved fingers, rinse with tap water, then rinse 1-2 times with deionized water or pure water, and finally rinse the surface once with alcohol in a certain inclined direction, and gently blow dry with a nitrogen gun; the pretreatment method for plastic film is to use an atmospheric plasma machine to scan the XY plane of the sample surface 1-2 times. Apply the appropriate coating evenly to the glass, plastic film, or smooth metal surface using spraying, brushing, or roller coating methods. Before coating, a proper pretreatment process is required to ensure that the substrate surface is clean, free of oil and contaminants. After coating, the coating and substrate should be kept at a curing temperature of 60℃-80℃ for about 40 minutes. After curing, let it stand at room temperature for 12 hours to obtain a hydrophobic, transparent, and wear-resistant coating.

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