Fluorine-free waxy release coating as well as preparation method and application thereof

Abstract

The invention discloses a fluorine-free waxy release coating which is composed of wax powder and reinforced particles, the reinforced particles are core-shell micron particles formed by wrapping wax particles with hydrophilic vapor phase SiO2 nano particles, and the wax powder and the wax particles are at least one of vegetable wax, animal wax and mineral wax. The invention discloses a preparation method of a fluorine-free waxy release coating. The preparation method comprises the following steps: preparing wax powder and wax particles by melting and spraying, dispersing the wax particles and hydrophilic vapor-phase SiO2 nanoparticles in absolute ethyl alcohol to prepare reinforced particles, and mixing the reinforced particles and the wax powder. According to the application of the fluorine-free wax release coating disclosed by the invention, the fluorine-free wax release coating is obtained through electrostatic spraying and heating curing. The coating does not contain fluoride, solvent and resin, and solves the problems of poor adhesion and low service temperature of a natural release material coating.

Description

Technical Field

[0001] The present invention relates to a release material, a preparation method and an application thereof, and belongs to the technical field of wax compositions. Background Art

[0002] The release coating is a functional surface material. At present, the main material of the release coating is a fluoropolymer (such as PTFE), but the fluorocarbon compounds used in its production process have bioaccumulation and environmental toxicity. Solvent-based coatings will emit volatile organic compounds (VOCs), and the residual solvents may contaminate the end products. In addition, Teflon release coatings have problems such as high curing temperature (usually above 250°C), great impact on the substrate, high energy consumption, difficult construction, and difficult repair after damage.

[0003] Release coatings based on natural wax generally have problems such as poor adhesion, low peel resistance times, and low service temperature. They usually also need to add synthetic resins or solvents to improve the film-forming performance. Summary of the Invention

[0004] In view of the above technical requirements, the present invention provides a fluorine-free wax-based release coating to solve the problems of poor adhesion and low service temperature of release coatings based on natural wax. The present invention also provides a preparation method and an application of a fluorine-free wax-based release coating to solve the problems of difficult construction and high energy consumption of traditional release coatings.

[0005] The technical solution of the present invention is: a fluorine-free wax-based release coating, which is composed of wax powder and reinforcing particles. The reinforcing particles are core-shell micron particles in which hydrophilic fumed SiO2 nanoparticles wrap wax particles. Both the wax powder and the wax particles are at least one of plant wax, animal wax and mineral wax.

[0006] Further, the wax powder and the wax particles are at least one of beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, Chinese insect wax and spermaceti wax.

[0007] Further, the wax powder and the wax particles are the same substance.

[0008] Further, the mass percentage of the reinforcing particles in the fluorine-free wax-based release coating is 0.5% - 15%, preferably 5% - 15%.

[0009] Further, the mass ratio of the hydrophilic fumed SiO2 nanoparticles to the wax particles in the reinforcing particles is 1:(1 - 5).

[0010] Another technical solution of the present invention is: a preparation method of a fluorine-free wax-based release coating, including the steps of:

[0011] Melting the wax raw material and spraying it out through a nozzle driven by compressed gas for atomization, and collecting the atomized particles to obtain the wax powder and the wax particles;

[0012] The wax particles and the hydrophilic gas-phase SiO2 nanoparticles are simultaneously placed in anhydrous ethanol and fully stirred and dispersed, and the particles are dried to obtain reinforced particles;

[0013] The wax powder and the reinforcing particles are uniformly mixed and sieved to obtain the fluorine-free wax release coating.

[0014] Furthermore, the wax particles and the wax powder are prepared simultaneously from the same wax raw material.

[0015] Another technical solution of the present invention is: an application of a fluorine-free wax release coating, comprising applying the fluorine-free wax release coating on a substrate by electrostatic spraying, and then heating the electrostatically sprayed coating at a temperature range from the melting point of the wax powder to 10°C above the melting point to melt the wax powder and then cooling and solidifying it to obtain the fluorine-free wax release coating.

[0016] The advantages of the present invention compared with the prior art are:

[0017] (1) The coating of the present invention has plant wax, animal wax and mineral wax as core components, is easily degraded, does not contain fluoride, does not contain resin, and no organic solvent volatilizes during the curing process. The preparation method of the coating is simple, low in cost, low in difficulty, and easy to mass produce. The coating is made into a coating using an electrostatic spraying process without complex pretreatment, and is compatible with metal, glass, ceramic, polymer and other substrates, has strong compatibility, and a wide range of applications.

[0018] (2) The curing temperature is greatly reduced from 150-250°C of traditional coatings to the wax melting temperature (determined by the type of wax powder), which is suitable for heat-sensitive substrates. Energy consumption is reduced by 40%-60%. The electrostatic spraying process is highly efficient and suitable for continuous production. During the curing process of the coating, the micron wax powder is transformed into a molten state due to the effect of heating, filling the gaps between the powder particles. At the same time, the molten wax wets the substrate, improving its adhesion to the substrate.

[0019] (3) If the formed coating is damaged, it can be repaired by local heating to a temperature close to the melting temperature of the wax. Local defects in the coating can be repaired by local electrostatic spraying and heating to a temperature close to the melting temperature of the wax.

[0020] (4) The SiO2-coated core-shell structure of the reinforcing particles keeps the silica shell stable during heating. Since the wax particles are wrapped and cannot flow, the overall coating is not prone to flow or deformation. Therefore, the service temperature of the coating is increased by about one time compared to the pure wax coating. The addition of SiO2 forms uniformly dispersed hard points, significantly improving the hardness of the coating. At the same time, this core-shell structure also avoids the agglomeration of SiO2, which may cause cracks or loss of release ability in the coating, improving the quality and yield rate of the coating. The coating has self-similarity and its release performance does not decrease after wear. Description of the Drawings

[0021] Figure 1 It is a photograph of the wax powder obtained in Example 4.

[0022] Figure 2 It is a SEM photograph of the wax powder obtained in Example 4.

[0023] Figure 3 It is a photograph of the reinforcing particles obtained in Example 4.

[0024] Figure 4 It is a SEM photograph of the reinforcing particles obtained in Example 4.

[0025] Figure 5 It is a TEM photograph of the reinforcing particles obtained in Example 4.

[0026] Figure 6 It is a photograph of the self-curling release phenomenon of the flock glue coated on the surface of the coating made of the fluorine-free wax-based release coating obtained in Example 4 on a stainless steel substrate without external force.

[0027] Figure 7 It is a photograph of the local cracking and peeling of the coating made of the fluorine-free wax-based release coating obtained in Comparative Example 3 on a stainless steel substrate. Detailed Description of the Invention

[0028] The following examples are used to further illustrate the present invention, but do not limit the present invention.

[0029] The preparation method of the fluorine-free wax-based release coating in the examples of the present invention is as follows:

[0030] Preparation of wax powder: After melting an appropriate amount of wax raw material, high-pressure gas from an air compressor is ejected through a nozzle for atomization. During the process, the wax raw material is maintained at a heat preservation temperature to keep it in a molten state. After atomization and cooling, the wax powder is collected. Wax particles are prepared in the same way. When the wax particles and the wax powder are made of the same substance, they can be prepared simultaneously. The wax raw material is one or more of plant wax, animal wax, and mineral wax, and specifically, at least one can be selected from beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, insect wax, and spermaceti wax. The average particle size of the obtained wax powder and wax particles is 1 - 10 microns.

[0031] Preparation of reinforcing particles: Hydrophilic fumed SiO₂ nanoparticles (Aladdin Biochemical Technology Co., Ltd.) and the prepared wax particles are simultaneously put into an appropriate amount of absolute ethanol in proportion for dispersion. After stirring evenly and drying the particulate matter, micron-sized core-shell structured reinforcing particles are obtained.

[0032] Preparation of release coating: The wax powder and the reinforcing particles are mixed evenly in proportion and sieved to remove agglomerates to obtain a fluorine-free wax-based release coating.

[0033] When using this fluorine-free wax-based release coating, the fluorine-free wax-based release coating is applied to the substrate by electrostatic spraying, and then the electrostatically sprayed coating is heated by equipment such as a hot air gun or an oven within the temperature range from the melting point of the wax powder and wax particles to 10 °C above the melting point (this temperature is the curing temperature) to make the wax powder in a molten state and then cooled and cured to obtain a fluorine-free wax-based release coating.

[0034] The obtained fluorine-free wax-based release coating is tested as follows:

[0035] Release performance: The cured polyurethane flocking adhesive on the coating surface is peeled off (25 mm wide), and a sensor is used to measure the force required for peeling as the release performance of the coating.

[0036] Service temperature: The substrate with the coating is placed in an oven for heat preservation for 24 hours to obtain the highest temperature at which the coating does not melt and has release performance.

[0037] Adhesion: Measured continuously 5 times by the cross-cut method (ASTM D3359-17 adhesion test standard), and the average value is taken.

[0038] Hardness: Measured continuously 5 times by the pencil hardness method (GB / T 6739-2022 "Paints and varnishes - Determination of film hardness by pencil test"), and the average value is taken.

[0039] Self-healing performance: After the coating is damaged, the damaged part is locally heated to the wax melting temperature and kept warm for 30 minutes. If the coating restores the release performance, it is considered to have self-healing performance.

[0040] The following table shows the differences in raw material composition, preparation parameters, and performance parameters among the examples and comparative examples.

[0041]

[0042]

[0043] In the above table, the strengthening particle % represents the total mass content of the strengthening particles in the fluorine-free wax-based release coating. The mass ratio of hydrophilic fumed SiO2 particles to wax particles represents the mass ratio of hydrophilic fumed SiO2 particles to wax particles that make up the strengthening particles. The wax particles have the same composition as the wax powder.

[0044] Among them, the photo of the wax powder during the preparation of the fluorine-free release coating in Example 4 is as shown in Figure 1 and its corresponding SEM image is as shown in Figure 2 The photo of the strengthening particles during the preparation of the fluorine-free release coating in Example 4 is as shown in Figure 3 and its corresponding SEM image is as shown in Figure 4 and the transmission electron microscope photo is as shown in Figure 5 shown. Figure 6 This is a photo of the phenomenon that after the fluorine-free release coating is prepared on the stainless steel substrate in Example 4 and the flocking glue is coated on the surface of the coating, the glue layer spontaneously warps and releases without external force, which intuitively reflects the release performance of the coating.

[0045] As can be seen from the above Examples 1 to 8, the fluorine-free wax-based release coating of the present invention achieves the release and non-sticking characteristics without fluorine through the combined action of wax powder and strengthening particles, and the special properties of the wax enable the coating to have self-healing ability.

[0046] From the comparison results of Examples 1 to 5 and Comparative Examples 1 and 2, it can be seen that when the content of the strengthening particles decreases, the release performance of the coating increases, while the hardness and service temperature decrease; when the content of the strengthening particles increases, the release performance of the coating weakens, and the hardness and service temperature increase.

[0047] From the comparison results of Examples 6 to 8 and Comparative Examples 3 and 4, it can be seen that when the mass ratio of hydrophilic fumed SiO2 nanoparticles to wax particles that make up the strengthening particles decreases, the release performance of the coating increases, and the hardness and service temperature decrease; when the mass ratio of hydrophilic fumed SiO2 nanoparticles to wax particles is too high, the release performance of the coating decreases, the hardness and service temperature increase, and SiO2 agglomeration is more likely to occur, resulting in phenomena such as local peeling and cracking of the coating, as shown in Figure 7 shown. When the content of hydrophilic fumed SiO2 nanoparticles that make up the strengthening particles is too high, SiO2 particle agglomeration occurs, resulting in local cracking and peeling.

[0048] The fluorine-free waxy release coating of the present invention can be used in scenarios including but not limited to the following: mold release coatings for service below 200°C, release coatings for PCB lamination, release coatings for OLED screen protectors, temporary fixing coatings for self-adhesive materials, temporary masking coatings during processing, etc.

Claims

1. A fluorine-free wax release coating, characterized in that: The invention is composed of wax powder and strengthening particles. The strengthening particles are core-shell micron particles of wax particles wrapped by hydrophilic gas-phase SiO2 nanoparticles. The wax powder and wax particles are at least one of plant wax, animal wax and mineral wax.

2. The fluorine-free wax release coating according to claim 1, characterized in that: The wax powder and wax particles are at least one of beeswax, candelilla wax, microcrystalline wax, palm wax, soybean wax, insect wax and spermaceti.

3. The fluorine-free wax release coating according to claim 2, characterized in that: The wax powder and wax granules are the same substance.

4. The fluorine-free wax release coating according to claim 1, characterized in that: The mass percentage of the reinforcing particles to the fluorine-free wax release coating is 0.5% to 15%.

5. The fluorine-free wax release coating according to claim 1, characterized in that: The mass percentage of the reinforcing particles to the fluorine-free wax release coating is 5% to 15%.

6. The fluorine-free wax release coating according to claim 1, characterized in that: The mass ratio of the hydrophilic gas-phase SiO2 nanoparticles to the wax particles in the reinforcing particles is 1:(1-5).

7. A method for preparing a fluorine-free wax release coating according to any one of claims 1 to 6, characterized in that: Includes steps: The wax raw material is melted and then driven by compressed gas to be sprayed out through a nozzle for atomization, and the atomized particles are collected to obtain the wax powder and wax particles; The wax particles and the hydrophilic gas-phase SiO2 nanoparticles are simultaneously placed in anhydrous ethanol and fully stirred and dispersed, and the particles are dried to obtain reinforced particles; The wax powder and the reinforcing particles are uniformly mixed and sieved to obtain the fluorine-free wax release coating.

8. The method for preparing the fluorine-free wax release coating according to claim 7, characterized in that: The wax particles and the wax powder are prepared simultaneously from the same wax raw material.

9. An application of a fluorine-free wax release coating, characterized in that: The fluorine-free wax release coating as claimed in any one of claims 1 to 6 is applied to a substrate by electrostatic spraying, and then the electrostatically sprayed coating is heated within a temperature range of the melting point of the wax powder to 10° C. above the melting point to melt the wax powder, and then cooled and solidified to obtain a fluorine-free wax release coating.

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