Fluorine-free super-hydrophobic EVA film and preparation method and application thereof

Abstract

The invention discloses a fluoride-free super-hydrophobic EVA (Ethylene Vinyl Acetate) film as well as a preparation method and application thereof. The preparation method of the fluoride-free super-hydrophobic EVA film disclosed by the invention comprises the following steps: firstly, preparing an ethylene-vinyl acetate copolymer, nano silicon dioxide particles, hexadecyl trimethoxy silane and (3-aminopropyl) triethoxy silane; then mixing the nano silicon dioxide, hexadecyl trimethoxy silane and (3-aminopropyl) triethoxy silane, so as to obtain the modified silicon dioxide. And carrying out hot pressing on the ethylene-vinyl acetate copolymer to obtain the EVA film. And spraying the modified nano silicon dioxide mixed solution on the surface of the EVA film to further obtain the fluoride-free super-hydrophobic EVA film. The prepared EVA film is hot-pressed on PP, PET and the like, has good adhesiveness, hydrophobicity and wear resistance and can be applied to certain food packaging, and the recycling rate of packaging such as fast food boxes in the market is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer packaging materials, and particularly relates to a fluorine-free superhydrophobic EVA film, a preparation method thereof, and an application thereof. Background Art

[0002] Ethylene-vinyl acetate copolymer (EVA) has become an ideal substrate for food packaging due to its excellent flexibility, transparency, and processing performance. However, the strong hydrophilicity of the EVA surface makes it easy to adsorb moisture and pollutants, which limits its application in humid environments. It is necessary to endow it with superhydrophobic properties through surface modification to extend the food shelf life and improve hygienic safety. At the same time, due to the different vinyl acetate contents, the EVA film has certain adhesion properties and tearability, and can be combined with other films to prepare a tearable multi-layer composite film. Therefore, endowing the EVA film with superhydrophobic properties to make it have self-cleaning and anti-pollution capabilities has become the key to improving the performance of food packaging. Although traditional fluorine-containing superhydrophobic coatings have excellent performance, their high cost, bioaccumulation, and environmental risks limit their application in food packaging. At the same time, although fluorine-containing compounds (such as perfluoroalkylsilanes) can effectively reduce the surface energy, their environmental persistence and toxicity issues have caused controversy.

[0003] In recent years, fluorine-free superhydrophobic coatings have attracted much attention due to their environmental friendliness and sustainability. Among them, composite coatings based on silica (SiO2) and silanes have shown great potential. However, existing fluorine-free coatings generally have problems of low mechanical strength and poor abrasion resistance, especially on flexible substrates (such as EVA), the coating is prone to peeling due to deformation. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present invention provides a fluorine-free superhydrophobic EVA film, a preparation method thereof, and an application thereof. SiO2 nanoparticles are selected to construct a micro-nano rough structure, and its high specific surface area and chemical stability provide physical support for the coating. The SiO2 is hydrophobically modified by HDTMS to introduce long-chain alkyl groups (-C 16 H 33 ) to reduce the surface energy; KH550 enhances the interfacial bonding force between SiO2 and the EVA substrate through amino groups (-NH2). Through the synergistic effect of long-chain alkyl silanes (such as HDTMS) and amino silanes (such as KH550), low-surface-energy modification can be achieved while avoiding the environmental risks of fluorocarbon chains.

[0005] The technical solution of the present invention is as follows:

[0006] The first object of the present invention is to provide a preparation method of a fluorine-free superhydrophobic EVA film, comprising the following steps:

[0007] (1) Mix nano-silica, cetyltrimethoxysilane, and (3-aminopropyl)triethoxysilane, add anhydrous ethanol, ammonia water, and water, and stir to react to obtain white emulsion A;

[0008] (2) Centrifuge and dry white emulsion A to obtain white powder B;

[0009] (3) Mix white powder B with anhydrous ethanol and ultrasonicate to obtain white mixture C;

[0010] (4) Spray white mixture C on the surface of a plasma-treated EVA film to obtain a fluorine-free superhydrophobic EVA film.

[0011] In one embodiment of the present invention, in step (1), the particle size of the nano-silica is 30 - 50 nm.

[0012] In one embodiment of the present invention, in step (1), the mass ratio of nano-silica, cetyltrimethoxysilane, and (3-aminopropyl)triethoxysilane is 2 - 8:1 - 2:1 - 2.

[0013] In one embodiment of the present invention, in step (1), the conditions for the stirring reaction are: the stirring speed is 400 - 800 rpm, the reaction temperature is 60 - 70 °C, and the reaction time is 6 - 10 h.

[0014] In one embodiment of the present invention, in step (2), the centrifugation speed is 6000 - 9000 rpm, and it is centrifuged and washed with anhydrous ethanol and centrifuged 3 - 4 times; the drying temperature is 60 - 80 °C, and the time is 10 - 24 h.

[0015] In one embodiment of the present invention, in step (3), the mass concentration of white mixture C is 1 - 3%.

[0016] In one embodiment of the present invention, in step (4), the EVA film is formed by hot pressing; the method of plasma treatment is: treat in an air or oxygen atmosphere for 1 - 5 min.

[0017] In one embodiment of the present invention, in step (4), the spraying conditions are: the gas flow rate is 11 - 13 L / min; the air pressure is 20 - 25 PSI.

[0018] In one embodiment of the present invention, melt ethylene-vinyl acetate copolymer (vinyl acetate content is 28%) at 100 - 200 °C, preheat for 2 - 5 min, exhaust 5 - 10 times, pressurize for 1 - 5 min, the pressure is 5 - 10 MPa, and finally obtain the EVA film.

[0019] In one embodiment of the present invention, in step (4), the thickness of the plasma-treated EVA film is 0.337 mm; the thickness of the fluorine-free superhydrophobic EVA film after spraying is 0.347 - 0.367 mm.

[0020] The second object of the present invention is to provide a fluorine-free superhydrophobic EVA film prepared by the above preparation method.

[0021] The third object of the present invention is to provide an application of the above fluorine-free superhydrophobic EVA film in the field of packaging materials.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] The present invention selects SiO2 nanoparticles to construct a micro-nano rough structure, and its high specific surface area and chemical stability provide physical support for the coating. The hydrophobic modification of SiO2 is carried out by HDTMS, and long-chain alkyl groups (-C 16 H 33 ) are introduced to reduce the surface energy; KH550 enhances the interfacial bonding force between SiO2 and the EVA substrate through amino groups (-NH2). The long-chain alkyl groups of HDTMS endow SiO2 with hydrophobicity, while the amino groups of KH550 bind to the carboxyl groups on the EVA surface through hydrogen bonds to form an "anchoring effect", solving the problem of easy peeling of the coating on the flexible substrate. At the same time, absolute ethanol is used as a green solvent to ensure the environmental protection of the modification process. Description of the Drawings

[0024] Figure 1 It is a contact angle diagram of the comparative example and the example.

[0025] Figure 2 It is a surface morphology diagram of the film coatings prepared in Comparative Example 6 and Example 1 after 30 minutes of water flow impact at 250 g / min.

[0026] Figure 3 It is a process diagram of the tape test of the film coatings prepared in Comparative Example 6 and Example 1.

[0027] Figure 4 It is a diagram of the chemical corrosion resistance of the fluorine-free superhydrophobic EVA film prepared in Example 1 in different acid and alkali solutions, the wear resistance after being rubbed with sandpaper, and the change in water contact angle after soaking in water for three days.

[0028] Figure 5 It is the wetting state of different liquids in the actual application of the fluorine-free superhydrophobic EVA film prepared in Example 1.

[0029] Figure 6 It is a diagram of the change in contact angle and weight during the folding of the fluorine-free superhydrophobic EVA film prepared in Example 1 for 100 times. Detailed Embodiments

[0030] The present invention will be specifically described below in conjunction with the accompanying drawings and embodiments.

[0031] Comparative Example 1

[0032] A method for preparing a hydrophobic EVA film, the steps of which are as follows:

[0033] Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on the iron plate, sandwich the mold flat in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, pressurize for 2 min, and the pressure is 7 Mpa to obtain a hydrophobic EVA film.

[0034] Comparative Example 2

[0035] A method for preparing a hydrophobic EVA film, the steps of which are as follows:

[0036] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on the iron plate, sandwich the mold flat in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, pressurize for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0037] (2) Dissolve 0.3 g of silica in 9.5 g of absolute ethanol to obtain a silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at a distance of 15 cm, spray for 5 s, and then vacuum dry at 70 °C for 12 h to prepare a hydrophobic EVA film.

[0038] Comparative Example 3

[0039] A method for preparing a hydrophobic EVA film, the steps of which are as follows:

[0040] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on the iron plate, sandwich the mold flat in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, pressurize for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0041] (2) Dissolve 0.5 g of silica and 1 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water, stir and react at 60 °C and 600 rpm for 6 h to obtain a milky white modified silica dispersion; centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, namely modified silica particles.

[0042] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of anhydrous ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at a distance of 15 cm and spray for 5 s. Then, vacuum dry it at 70 °C for 12 h to obtain a hydrophobic EVA film.

[0043] Comparative Example 4

[0044] A method for preparing a hydrophobic EVA film, the steps of which are as follows:

[0045] (1) Put 1 g of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay a Teflon cloth flat on an iron plate, place the mold flat and clamp it in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0046] (2) Dissolve 0.5 g of silica and 1 g of cetyltrimethoxysilane in 15 g of anhydrous ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir and react at 60 °C at 600 rpm for 6 h to obtain a milky white modified silica dispersion; Centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with anhydrous ethanol to finally obtain a white powder, that is, modified silica particles.

[0047] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of anhydrous ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at a distance of 15 cm and spray for 5 s. Then, vacuum dry it at 70 °C for 2 h to obtain a hydrophobic EVA film.

[0048] Comparative Example 5

[0049] A method for preparing a hydrophobic EVA film, the steps of which are as follows:

[0050] (1) Put 1 g of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay a Teflon cloth flat on an iron plate, place the mold flat and clamp it in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0051] (2) Dissolve 0.5 g of silica, 1 g of cetyltrimethoxysilane, and 1 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir and react at 60 °C and 600 rpm for 6 h to obtain a milky white modified silica dispersion. Centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, i.e., modified silica particles.

[0052] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle 15 cm at the EVA film obtained in step (1), spray for 5 s, and then vacuum dry at 70 °C for 2 h to obtain a hydrophobic EVA film.

[0053] Comparative Example 6

[0054] A preparation method of a hydrophobic EVA film, the steps of which are as follows:

[0055] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay a Teflon cloth flat on an iron plate, place the mold flat and clamp it in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, and apply pressure for 2 min with a pressure of 7 Mpa to obtain an EVA film.

[0056] (2) Dissolve 1 g of silica, 0.25 g of cetyltrimethoxysilane, and 0.5 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir and react at 60 °C and 600 rpm for 6 h to obtain a milky white modified silica dispersion. Centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, i.e., modified silica particles.

[0057] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 ml of the dispersion and put it into a spray gun. Point the nozzle 15 cm at the EVA film obtained in step (1), spray for 5 s, and then vacuum dry at 70 °C for 2 h to obtain a hydrophobic EVA film.

[0058] Example 1

[0059] A preparation method of a fluorine-free superhydrophobic EVA film, the steps of which are as follows:

[0060] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on the iron plate, place the mold flat and clamped in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0061] (2) Dissolve 1 g of silica, 0.5 g of cetyltrimethoxysilane, and 0.5 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir and react at 60 °C at 600 rpm for 6 h to obtain a milky white modified silica dispersion; centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, that is, modified silica particles.

[0062] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at 15 cm, spray for 5 s, dry naturally for 5 min, spray again for 5 s, and then dry in vacuum at 70 °C for 12 h to obtain a fluorine-free superhydrophobic EVA film.

[0063] Example 2

[0064] A preparation method of a fluorine-free superhydrophobic EVA film, and its steps are as follows:

[0065] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on the iron plate, place the mold flat and clamped in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0066] (2) Dissolve 1 g of silica, 0.5 g of cetyltrimethoxysilane, and 0.25 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir and react at 60 °C at 600 rpm for 6 h to obtain a milky white modified silica dispersion; centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, that is, modified silica particles.

[0067] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at a distance of 15 cm, spray for 5 s, dry naturally for 5 min, spray again for 5 s, and then vacuum dry at 70 °C for 12 h to obtain a fluorine-free superhydrophobic EVA film.

[0068] Example 3

[0069] A preparation method of a fluorine-free superhydrophobic EVA film, the steps are as follows:

[0070] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on an iron plate, place the mold flat and clamp it in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0071] (2) Dissolve 1 g of silica, 0.25 g of cetyltrimethoxysilane, and 0.25 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water, then add 3 g of ammonia water as a catalyst, and stir and react at 60 °C and 600 rpm for 6 h to obtain a milky white modified silica dispersion; centrifuge the obtained milky white modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, that is, modified silica particles.

[0072] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle at the EVA film obtained in step (1) at a distance of 15 cm, spray for 5 s, dry naturally for 5 min, spray again for 5 s, and then vacuum dry at 70 °C for 12 h to obtain a fluorine-free superhydrophobic EVA film.

[0073] Example 4

[0074] A preparation method of a fluorine-free superhydrophobic EVA film, the steps are as follows:

[0075] (1) Put 1 g of ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% into a customized 1-mm mold. Lay the Teflon cloth flat on an iron plate, place the mold flat and clamp it in the Teflon cloth, and put it into a hot press. Set the temperature to 100 °C, preheat for 3 min, exhaust 8 times, apply pressure for 2 min, and the pressure is 7 Mpa to obtain an EVA film.

[0076] (2) Dissolve 1 g of silica, 0.25 g of cetyltrimethoxysilane, and 0.125 g of (3-aminopropyl)triethoxysilane in 15 g of absolute ethanol and 2 g of deionized water. Then add 3 g of ammonia water as a catalyst and stir the reaction at 600 rpm at 60 °C for 6 h to obtain a milky modified silica dispersion. Centrifuge the obtained milky modified silica dispersion at 7000 rpm and wash it 3 times with absolute ethanol to finally obtain a white powder, i.e., modified silica particles.

[0077] (3) Dissolve 0.3 g of the modified silica particles prepared in step (2) in 9.5 g of absolute ethanol to obtain a modified silica dispersion. Take 5 mL of the dispersion and put it into a spray gun. Point the nozzle 15 cm at the EVA film obtained in step (1), spray for 5 s, dry naturally for 5 min, spray again for 5 s, and then vacuum dry at 70 °C for 12 h to obtain a fluorine-free superhydrophobic EVA film.

[0078] Test example:

[0079] Test the hydrophobicity, acid and alkali resistance, abrasion resistance, adhesion between the coating and the substrate, etc. of the EVA films prepared in the test examples and comparative examples. The specific test methods are as follows; the test results are shown in Table 1.

[0080] Use a OCA15EC type video optical contact angle measuring instrument from German DFE Instruments Co., Ltd. to conduct contact angle tests to characterize the wetting performance of the samples. The specific method is: measure at room temperature, and add 4 μL of water each time with the probe. The results are as Figure 1 shown. It can be seen that the hydrophobicity of the EVA film prepared in the example is significantly better than that of the comparative example.

[0081] Place the prepared EVA film 15 cm below the water pipe, and at the same time, rinse the coating with water at a flow rate of 250 g / min for 30 min. Observe the surface of the rinsed coating and characterize the contact angle to characterize the adhesion between the coating and the substrate. The surface morphology diagrams of the coatings of the film prepared in Comparative Example 6 and Example 1 after being impacted by water flow at 250 g / min for 30 min are as Figure 2 shown. It can be seen that there is an obvious peeling phenomenon in the coating of Comparative Example 6.

[0082] Conduct a tape test (cross-cut test) on the coating according to the international standard ASTM D3359-23. The higher the grade, the better the adhesion. Figure 3 The process diagram of the tape test for the coatings of the film prepared in Comparative Example 6 and Example 1 is shown. It can be seen that the coating of Comparative Example 6 has obvious peeling, and the adhesion is significantly worse than that of Example 1.

[0083] Immerse the film coatings in solutions with pH = 3 and pH = 10 respectively, take them out after 3 days, dry them, and measure their surface contact angles to characterize their chemical corrosion resistance.

[0084] Using 600 - mesh sandpaper, place the film prepared with the hydrophobic coating on its surface, then place a 50 - g weight on it to press the film. Apply an external force to make the super - hydrophobic side of the film move horizontally on the sandpaper. After moving 20 cm, rotate the film by 90°, and then move it horizontally by another 20 cm. Take this as one cycle and repeat 10 cycles. After each cycle, characterize the surface contact angle of the film to characterize the wear resistance. Figure 4 For the chemical corrosion resistance of the fluorine - free super - hydrophobic EVA film of Example 1 in different acid - base solutions, the wear resistance under sandpaper friction, and the change of the water contact angle on the film surface after soaking in water for 3 days. As can be seen from Figures a and b, as the film of Example 1 is soaked in different acid - base solutions for 3 days, its water contact angle has no significant change and still reaches the super - hydrophobic state, indicating that the film of Example 1 has good chemical corrosion resistance. As can be seen from Figure c, after the film of Example 1 is soaked in water for 3 days, the water contact angle has no obvious change and still maintains the super - hydrophobic state. As can be seen from Figure d, the film of Example 1 still maintains good stability and hydrophobic state under 50 - cycle friction. Figure 4 It can be further illustrated that the film of Example 1 can better adapt to different environments.

[0085] Figure 5 For the wetting states of different liquids of the fluorine - free super - hydrophobic EVA film of Example 1 in practical applications, it can be seen that in practical applications, the film of Example 1 can maintain the super - hydrophobic state for different liquids such as water, milk, coffee, juice, and dipping sauces, better expanding its practical application range.

[0086] Take the fluorine - free super - hydrophobic EVA film of Example 1 and fold it horizontally, vertically, and at an oblique angle 10 times as one cycle, repeat 10 cycles. After each cycle, characterize the surface contact angle of the film and weigh it at the same time. The results are as Figure 6 shown. As can be seen from the figure, after the film of Example 1 undergoes multiple folds, the water contact angle has no obvious change and still maintains the super - hydrophobic state. The weight of the film of Example 1 has no obvious change during folding and maintains good stability, further indicating that the film of Example 1 can better adapt to different environments.

[0087] Table 1

[0088] Sample Contact Angle (°) Acid Resistance Alkali Resistance Wear Resistance Adhesion Example 1 157 155 154 151 4B Example 2 151 150 150 151 4B Example 3 151 150 150 151 4B Example 4 153 152 151 150 4B Comparative Example 1 56 - - - - Comparative Example 2 51 - - - - Comparative Example 3 91 - - - - Comparative Example 4 97 - - - - Comparative Example 5 94 - - - - Comparative Example 6 135 130 130 127 0B

[0089] As can be seen from Table 1, the hydrophobicity of the EVA film prepared in the embodiment of the present invention is higher than that of the comparative example, and the comprehensive performance of the embodiment is better than that of the comparative example. It shows that modifying silica and spraying it on the surface of the EVA film can improve the hydrophobicity of the EVA film to reach a super - hydrophobic surface. At the same time, the addition of the silane coupling agent can effectively combine the surface of the EVA film with the modified silica, enhance the interfacial bonding force with the EVA substrate, form an "anchoring effect", and solve the problem of easy shedding of the flexible substrate coating.

[0090] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit the order of their execution. Obvious improvements made by those skilled in the art to the present invention in combination with the existing well-known general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A preparation method of a fluorine-free superhydrophobic EVA film, characterized in that, It includes the following steps: (1) Mix nano-silica, cetyltrimethoxysilane, and (3-aminopropyl)triethoxysilane, add absolute ethanol, ammonia water, and water, and stir and react to obtain white emulsion A; (2) Centrifuge and dry white emulsion A to obtain white powder B; (3) Mix white powder B with absolute ethanol and ultrasonic to obtain white mixed solution C; (4) Spray white mixed solution C on the surface of the plasma-treated EVA film to obtain a fluorine-free superhydrophobic EVA film.

2. The preparation method according to claim 1, wherein In step (1), the mass ratio of nano-silica, cetyltrimethoxysilane, and (3-aminopropyl)triethoxysilane is 2-8:1-2:1-2.

3. The preparation method according to claim 1, characterized in that, In step (1), the conditions for stirring and reacting are: the stirring speed is 400-800 rpm, the reaction temperature is 60-70 °C, and the reaction time is 6-10 h.

4. The preparation method according to claim 1, wherein In step (2), the centrifugation speed is 6000-9000 rpm, and it is centrifuged and washed with absolute ethanol for 3-4 cycles; the drying temperature is 60-80 °C, and the time is 10-24 h.

5. The preparation method according to claim 1, characterized in that, In step (3), the mass concentration of white mixed solution C is 1-3%.

6. The preparation method according to claim 1, characterized in that, In step (4), the EVA film is formed by hot pressing; the method of plasma treatment is: treat in an air or oxygen atmosphere for 1-5 min.

7. The preparation method according to claim 1, wherein In step (4), the spraying conditions are: the air flow rate is 11-13 L / min; the air pressure is 20-25 PSI.

8. The preparation method according to claim 1, characterized in that, In step (4), the thickness of the plasma-treated EVA film is 0.337 mm; the thickness of the fluorine-free superhydrophobic EVA film after spraying is 0.347-0.367 mm.

9. A fluorine-free superhydrophobic EVA film prepared by the preparation method according to any one of claims 1-8.

10. An application of the fluorine-free superhydrophobic EVA film according to claim 9 in the field of packaging materials.

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