Super-hydrophobic release coating and preparation method thereof
By adding micron-scale wax powder and wax powder wrapped in hydrophilic vapor-phase SiO2 nanoparticles to the polydimethylsiloxane base coating to form core-shell particles, a superhydrophobic release coating was prepared, which solved the problem of insufficient hydrophobic performance of traditional coatings in humid environments and improved the stability and mechanical strength of the coating.
Patent Information
- Application Number
- CN202510496196.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-06-27
AI Technical Summary
Traditional PDMS-based release coatings lack hydrophobic performance in humid environments, and the added silicone oil migration aids will reduce the mechanical strength of the coating and contaminate the protected surfaces during high temperatures or long-term storage.
A superhydrophobic release coating, including polydimethylsiloxane, first wax powder and core-shell particles, is prepared by spraying and heating curing techniques.
It improves the hydrophobicity and release properties of the coating, enhances the stability and mechanical strength of the coating, avoids the use of silicone oil migration additives, and does not contain fluoride, has lower curing temperature and good compatibility.
Smart Images
Figure CN120209699A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a release coating and a preparation method thereof. Background Art
[0002] Polydimethylsiloxane (PDMS) has become the mainstream matrix material for release coatings due to its moderate surface energy (about 21 mN / m) and adjustable crosslinking density. However, traditional PDMS-based release coatings face the following technical limitations under complex working conditions: First, when applied to a humid environment, the insufficient hydrophobic performance of the coating easily leads to the penetration of water molecules to the interface, resulting in an abnormal increase in the release force or adhesion failure. After the coating is cleaned, the residual water droplets affect subsequent production; Second, the silicone oil migration aids added to improve the release stability will accumulate on the surface during high temperature or long-term storage, reducing the mechanical strength of the coating and contaminating the protected surface.
[0003] In order to provide a superhydrophobic surface for the release coating to adapt to a humid environment or for the release of water-based liquid substances, the prior art mainly relies on fluoropolymers (such as PTFE, PVDF) to construct micro-nano rough structures, but there are still two significant problems. One is that perfluorinated compounds may be released during high-temperature processing or long-term use, and the other is that the rough structure will significantly affect the release performance of the coating. Summary of the Invention
[0004] Aiming at the defects of the above-mentioned prior art, the present invention provides a superhydrophobic release coating, aiming to enhance the hydrophobicity of the release coating to improve stability while ensuring the release performance of the coating. The present invention also provides a preparation method of a superhydrophobic release coating.
[0005] The technical solution of the present invention is as follows: A superhydrophobic release coating, comprising polydimethylsiloxane, first wax powder, and core-shell particles, wherein the core-shell particles are micron-sized particles, and the core-shell particles are second wax powder wrapped by hydrophilic fumed SiO₂ nanoparticles.
[0006] Further, the mass ratio of the first wax powder in the superhydrophobic release coating is 0.5% - 10%.
[0007] Further, the mass ratio of the core-shell particles in the superhydrophobic release coating is 0.5% - 10%.
[0008] Further, the mass ratio of the hydrophilic fumed SiO₂ nanoparticles to the second wax powder in the core-shell particles is 1: (1 - 5).
[0009] Further, the first wax powder and the second wax powder are at least one of beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, Chinese insect wax, and spermaceti wax.
[0010] Further, both the first wax powder and the second wax powder are micron-sized particles.
[0011] Another technical solution of the present invention is as follows: A method for preparing a superhydrophobic release coating, comprising:
[0012] Melting the wax raw material and spraying and atomizing it through a nozzle driven by compressed gas, and collecting the atomized particles to obtain the first wax powder and the second wax powder;
[0013] Putting the second wax powder and hydrophilic fumed SiO₂ nanoparticles into absolute ethanol at the same time for sufficient stirring and dispersion, and drying the particulate matter to obtain core-shell particles;
[0014] Adding the first wax powder and the core-shell particles to polydimethylsiloxane together, and stirring evenly to obtain a release coating;
[0015] Spraying the release coating on a substrate, and heating and curing it at a curing temperature within the range of 10 - 25 °C above the melting temperature of the second wax powder to obtain a superhydrophobic release coating.
[0016] Further, the stirring and dispersion time is not less than 2.5 h.
[0017] Compared with the prior art, the advantages of the technical solution provided by the present invention are as follows:
[0018] The surface energy of pure PDMS is relatively low, but due to the smooth surface and lack of rough structure after curing, the contact angle is only 90° - 110°. The addition of the core-shell particles in the present invention introduces a micro-nano composite multi-level rough structure to the coating, increasing the surface roughness of the coating. At the same time, during the heating and curing process of the coating, a small amount of the second wax powder wrapped by silica is released, which can prevent the hydrophilic silica from reducing the hydrophobic performance of the coating (silica does not require hydrophobic modification, such as fluorination and silanization). At the same time, the first wax powder and the second wax powder also have relatively low surface energy and stronger release performance, and cooperate with PDMS to increase the hydrophobic performance and release performance of the coating.
[0019] The nano-silica shell (high modulus, high rigidity) and the PDMS matrix (low modulus, high elasticity) form a "soft-hard" composite interface. When this structure is stressed, the rigid silica layer transfers the interfacial stress, shares the external load, and inhibits the excessive deformation of the matrix. The hydroxyl groups (—OH) on the silica surface form strong interfacial bonding with the siloxane chains in PDMS through hydrogen bonds or covalent coupling, reducing the interfacial slip between the filler and the matrix and enhancing the stress transfer efficiency, thereby improving the overall strength and toughness.
[0020] The coating of the present invention does not contain fluoride and has a lower curing temperature compared to fluoride coatings. At the same time, it has release ability and superhydrophobic properties, does not require the addition of silicone-based migration aids, has strong compatibility with substrates, and a wide range of applications. The coating has self-similarity, and its hydrophobic and release properties do not decrease after abrasion. The coating is flexible and can be bent, and is easy to repair when damaged. Description of the Drawings
[0021] Figure 1 Photograph of the first wax powder obtained in Example 4.
[0022] Figure 2 SEM photograph of the first wax powder obtained in Example 4.
[0023] Figure 3 Photograph of the core-shell particles obtained in Example 4.
[0024] Figure 4 SEM photograph of the core-shell particles obtained in Example 4.
[0025] Figure 5 TEM photograph of the core-shell particles obtained in Example 4.
[0026] Figure 6 Photograph of the process of peeling off the adhesive layer when the superhydrophobic release coating surface obtained in Example 4 is coated with polypropylene flocking adhesive. Detailed Description of the Invention
[0027] The following further illustrates the present invention with reference to embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, various equivalent modifications of this description by those skilled in the art all fall within the scope defined by the appended claims of this application.
[0028] The preparation method of the superhydrophobic release coating in the embodiment of the present invention is as follows:
[0029] Preparation of wax powder: After melting an appropriate amount of wax raw material, high-pressure gas from an air compressor is sprayed through a nozzle for atomization, and the wax raw material is kept in a molten state during the process. After atomization and cooling, micron-sized first wax powder and second wax powder are collected, with an average particle size of 1 to 10 microns. The wax raw material is at least one of plant wax, animal wax, and mineral wax, such as at least one of beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, insect white wax, and spermaceti wax. The first wax powder and the second wax powder can have the same composition or different compositions. It is easy to understand that when the two have the same composition, they can be atomized and prepared at one time, and when they have different compositions, the first wax powder and the second wax powder are prepared separately.
[0030] Preparation of core-shell particles: Hydrophilic gas-phase SiO2 nanoparticles (Aladdin Biochemical Technology Co., Ltd.) and the prepared second wax powder are placed in a proper amount of anhydrous ethanol in proportion and stirred and dispersed fully. The filtered particles are dried to obtain micron-sized core-shell particles.
[0031] Preparation of super-hydrophobic release coating: The prepared first wax powder and core-shell particles were added into polydimethylsiloxane (Dow Corning DC184) at the same time, and the release coating was obtained after planetary stirring for 3 hours.
[0032] Preparation of coating: spray the release coating on a glass substrate, put it into an oven and heat it at a curing temperature for 1 hour to cure it, so as to obtain a super hydrophobic release coating, wherein the curing temperature is a temperature 10 to 25° C. higher than the melting temperature of the second wax powder.
[0033] The obtained super hydrophobic release coating was tested as follows:
[0034] Release performance: Peel off the cured polyurethane flocking glue on the coating surface (25 mm wide), and use a sensor to measure the force required for peeling as the release performance of the coating.
[0035] Adhesion: Measure 5 times in a row using the scribing method (ASTM D3359-17 adhesion test standard) and take the average value.
[0036] Hardness: Use the pencil hardness method (GB / T 6739-2022 "Paints and varnishes pencil method for determination of paint film hardness") to measure 5 times in a row and take the average value.
[0037] Coating quality: Place the coating downward on the surface of No. 1000 sandpaper, apply 500g pressure to the coating and rub it back and forth. The single friction distance is 10cm. Observe the surface quality of the coating with the naked eye after 30 frictions. No cracks indicate that the coating has good toughness.
[0038] The following table shows the differences in raw material composition, preparation parameters and performance parameters between the embodiments and comparative examples.
[0039]
[0040]
[0041]
[0042] In the examples and comparative examples involved in the above table, the first wax powder and the second wax powder have the same composition, so they are collectively referred to as wax powder. Wax powder % represents the mass content of the first wax powder in the superhydrophobic release coating (excluding the second wax powder in the core-shell particles), core-shell particle % represents the mass content of the core-shell particles in the superhydrophobic release coating, and the mass ratio of hydrophilic fumed SiO2 particles to wax powder represents the mass ratio of hydrophilic fumed SiO2 particles and the second wax powder that make up the core-shell particles.
[0043] Among them, the photo of the first wax powder obtained during the preparation of the superhydrophobic release coating in Example 4 is as Figure 1 shown, and its corresponding SEM image is as Figure 2 shown. The photo of the core-shell particles obtained during the preparation of the superhydrophobic release coating in Example 4 is as Figure 3 shown, and its corresponding SEM image is as Figure 4 shown, and the transmission electron microscope photo is as Figure 5 shown. Figure 6 is a photo of the process of coating polypropylene flocking glue on the surface of the superhydrophobic release coating obtained in Example 4 and the release and peeling of the glue layer. It can be seen that the glue layer can be easily peeled off, proving good release performance.
[0044] From the comparison results of Examples 1-5 and Comparative Examples 1 and 2, it can be seen that when the content of the first wax powder decreases, the hydrophobic performance of the coating decreases; when the content of the first wax powder increases, the release performance of the coating slightly increases, the adhesion slightly decreases, and the toughness decreases.
[0045] From the comparison results of Examples 6-10 and Comparative Examples 3 and 4, it can be seen that when the content of the core-shell particles decreases, the hardness, wear resistance and toughness of the coating decrease; when the content of the core-shell particles increases, the release performance of the coating weakens, the contact angle decreases, and the hardness and toughness increase.
[0046] From the comparison results of Examples 11-13 and Comparative Examples 5 and 6, it can be seen that when the mass ratio of hydrophilic fumed SiO2 nanoparticles to wax powder (the second wax powder) that make up the core-shell particles decreases, the release performance increases, and the hardness and toughness decrease; when the mass ratio of hydrophilic fumed SiO2 nanoparticles to wax powder (the second wax powder) increases, the release performance of the coating slightly decreases, and the hardness and toughness increase.
Claims
1. A super hydrophobic release coating, characterized in that: The invention comprises polydimethylsiloxane, a first wax powder and core-shell particles, wherein the core-shell particles are micron-sized particles and the core-shell particles are second wax powders wrapped by hydrophilic gas-phase SiO2 nanoparticles.
2. The super hydrophobic release coating according to claim 1, characterized in that: The mass proportion of the first wax powder in the super-hydrophobic release coating is 0.5% to 10%.
3. The super hydrophobic release coating according to claim 1, characterized in that: The mass proportion of the core-shell particles in the super-hydrophobic release coating is 0.5% to 10%.
4. The super hydrophobic release coating according to claim 1, characterized in that: The mass ratio of the hydrophilic gas-phase SiO2 nanoparticles to the second wax powder in the core-shell particles is 1:(1-5).
5. The super hydrophobic release coating according to claim 1, characterized in that: The first wax powder and the second wax powder are at least one of beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, insect wax, and spermaceti.
6. The super hydrophobic release coating according to claim 1, characterized in that: The first wax powder and the second wax powder are both micron-sized particles.
7. A method for preparing a super hydrophobic release coating according to any one of claims 1 to 6, characterized in that: include: The wax raw material is melted and then driven by compressed gas to be sprayed through a nozzle for atomization, and the atomized particles are collected to obtain the first wax powder and the second wax powder; The second wax powder and the hydrophilic gas-phase SiO2 nanoparticles are simultaneously placed in anhydrous ethanol for full stirring and dispersion, and the particles are dried to obtain core-shell particles; Adding the first wax powder and the core-shell particles into polydimethylsiloxane, and stirring evenly to obtain a release coating; The release coating is sprayed on a substrate, and heated and cured at a temperature within a range of 10 to 25° C. above the melting temperature of the second wax powder to obtain a super-hydrophobic release coating.
8. The method for preparing a super-hydrophobic release coating according to claim 7, characterized in that: The stirring and dispersing time is not less than 2.5 hours.