Fog water collecting mulching film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of fog water collecting mulching films, and particularly relates to a fog water collecting mulching film and a preparation method and application thereof.The fog water collecting mulching film is formed by spraying a super-hydrophobic layer on the surface of a flexible substrate, the super-hydrophobic layer is composed of the same solid particles or different solid particles with three different particle sizes, and after modification is conducted through a silane coupling agent, the super-hydrophobic layer is prepared into the fog water collecting mulching film. The surface contact angle of the super-hydrophobic substrate prepared by doping low-surface-energy liquid and curing can reach 165 degrees or above, a conical structure is fixed on the surface of the super-hydrophobic flexible substrate by adopting a mechanical assembly method, and the fog collection efficiency can be regulated and controlled. The conical structure of the bionic cactus is beneficial to capturing fog water and transporting water drops, the super-hydrophobic substrate is beneficial to rapid falling of the water drops, and efficient fog water collection is achieved through cooperation of the bionic cactus and the super-hydrophobic substrate. The mulching film can be recycled for multiple times and can replace a conventional polyethylene mulching film, and environmental pollution is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of fog water collection film preparation, and in particular relates to a fog water collection film and a preparation method and application thereof. Background Art

[0002] Atmospheric water harvesting is a promising technology to alleviate water shortages, among which fog harvesting has attracted much attention due to its low economic cost, long service life, and environmental friendliness. The main principle of fog harvesting is that the kinetic energy of fog droplets is exhausted in the process of colliding with the device and gradually condenses on the surface. When the weight of the fog droplets condensed on the surface is greater than the adhesion force of the device to it, the droplets fall and are collected under the action of gravity.

[0003] After years of research, fog collecting devices have made rapid progress in material selection and preparation technology. However, most substrates are rigid substrates such as copper sheets, aluminum sheets, and zinc sheets with limited usage scenarios. For example, Zhao Jing et al. (Prog. Org. Coat, 2022, 171: 107016-107024) used aluminum alloy substrates as substrates to prepare fog water collectors and fog water collection membranes, and the fog collection efficiency reached 0.3625 g / cm 2 h; Fu Shaohai et al. (Adv. Funct. Mater, 2023, 33(5): 2210730-2210741) prepared the system with copper sheet as the substrate, and the mist collection efficiency reached 7.4 g / cm 2 h. In addition to the choice of substrate, the preparation method is equally important. Most of the existing preparations involve complex preparation processes such as laser etching, template method, and electrochemical oxidation method. For example, Yan Huangping et al. (CN112302100A) used a template method to prepare a tip structure that imitates cactus thorns, and used a laser femtosecond double-pulse method to construct a hydrophilic-hydrophobic synergistic surface preparation; Chen Huawei et al. (ACS.Appl.Mater.Interfaces, 2022, 14, 33993-34001) used 3D printing to prepare the conical thorns of bionic cactus, coupled with a janus film. Due to the shortcomings of limited substrate material selection and complex process preparation, the above-mentioned fog collection devices are difficult to achieve large-scale production and application.

[0004] Fog collectors are mostly used in arid and water-scarce desert areas to provide people with drinking water and irrigation water. However, fog collectors have not been fully used in agriculture. The main component of ordinary agricultural mulch is non-degradable polyethylene, which will pollute the soil. The price of degradable mulch is more than twice that of ordinary mulch. Its main components are starch, cellulose, chitosan and other polysaccharide natural materials. It has weak elasticity and is easy to break. It can only be used once. In addition, the existing degradable mulch cannot collect fog water and cannot be recycled multiple times. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a fog water collection film and a preparation method and application thereof.

[0006] To achieve the above objectives, the specific technical solutions of the present invention are as follows.

[0007] The first aspect of the present invention provides a fog water collection ground film, wherein the fog water collection ground film is obtained by uniformly fixing a plurality of conical structures on a flexible substrate coated with a super-hydrophobic layer by mechanical assembly;

[0008] The super hydrophobic layer is prepared by mixing a modified solid particle suspension with a low surface energy liquid, so that the modified solid particles have a rough structure to reduce the surface energy of the super hydrophobic layer;

[0009] The mass volume ratio of the modified solid particle suspension to the low surface energy liquid is 2-20 mL:2 g;

[0010] The modified solid particle suspension is obtained by mixing solid particles of different particle sizes and then modifying them with a silane coupling agent;

[0011] The solid particles are at least one of SiO2, CaCO3, and TiO2;

[0012] The particle sizes of the solid particles with different particle sizes are 25nm-800nm, 1μm-4μm and 1μm-25μm.

[0013] The present invention uses a flexible material as a base material, and coats a layer of hydrophobic material on the flexible base material. By controlling the mass volume ratio of the modified solid particle suspension to the low surface energy liquid to 2-20mL:2g, the hydrophobic effect of the super hydrophobic layer is effectively improved; by controlling the particle size of SiO2, CaCO3 and TiO2, the surface hydrophobic properties of the material can be effectively adjusted. If the particle size is too large or too small, the contact angle is less than 150°, which affects the hydrophobic effect. And by using the principle of cactus thorn water collection, a conical structure is fixed on a flexible substrate coated with a hydrophobic material, so that the obtained fog water collection mulch can be applied to agricultural planting. It can not only collect fog water to provide moisture for crops, but also can be used as a mulch to cover farmland, increase ground temperature, inhibit weed growth and maintain soil humidity; and it is expected to replace ordinary mulch and achieve multiple recycling.

[0014] In another preferred embodiment, solid particles of different particle sizes are dispersed in a mixture of water and ethanol, and after ultrasonic treatment, a suspension is obtained; the suspension is mixed with a silane coupling agent, and stirred at 40° C. to 70° C. for 1 h to 7 h for modification treatment to obtain the modified solid particle suspension;

[0015] The mass ratio of solid particles with particle sizes of 25nm to 800nm, 1μm to 4μm, and 1μm to 25μm is 10 to 50:5 to 1:1;

[0016] The mass volume ratio of the solid particles with a particle size of 25 nm to 800 nm to the silane coupling agent is 200 mg to 265 mg: 0.5 mL.

[0017] In another preferred embodiment, the volume ratio of the water to the ethanol is 2-5:1-3.

[0018] In another preferred embodiment, the silane coupling agent is any one of hexamethyldisilazane, methyltriethoxysilane and methyltrimethoxysilane.

[0019] In another preferred embodiment, the low surface energy liquid is polytetrafluoroethylene emulsion or polydimethylsiloxane.

[0020] In another preferred embodiment, the flexible substrate is any one of polypropylene, polyethylene terephthalate, polyvinyl chloride, and polyethylene. The polypropylene, polyethylene terephthalate, polyvinyl chloride, and polyethylene in the present invention are all UV-resistant, and their UV-resistant properties enable the substrate to resist the aging of the substrate caused by long-term exposure to ultraviolet light in sunlight during use, thereby increasing the service life.

[0021] In another preferred embodiment, the length of each of the conical structures is 0.5 mm to 20 mm, and the spacing is 1 mm to 5 mm.

[0022] The second aspect of the present invention provides a method for preparing a fog water collection mulch for agricultural planting, wherein the fog water collection mulch for agricultural planting is provided by the first aspect of the present invention, and comprises the following steps:

[0023] Mixing a low surface energy liquid with modified solid particles to obtain a superhydrophobic coating;

[0024] The super-hydrophobic coating is sprayed on the flexible substrate, and the super-hydrophobic coating is cured on the flexible substrate under ultraviolet irradiation to obtain a super-hydrophobic flexible substrate with a super-hydrophobic layer fixed on the surface

[0025] A plurality of conical structures are mechanically assembled on the surface of a super-hydrophobic flexible substrate to obtain a fog water collection ground film. The mechanical assembly is to penetrate the conical structure from the back of the super-hydrophobic flexible substrate and fix it with a hot melt gun; or place the conical structure in a hot melt gun and melt it, and then place it on the super-hydrophobic flexible substrate. The conical structure is a hydrophilic thermoplastic plastic with a conical structure, or a conical structure with a layer of polyvinyl alcohol on the surface. The thermoplastic plastic is any one of hydrophilic polypropylene, polyethylene terephthalate, and polyether ester.

[0026] The spraying amount of the super hydrophobic coating is 0.1 mL / cm 2 ~5mL / cm 2 .

[0027] In another preferred embodiment, the ultraviolet irradiation time is 5 min to 30 min.

[0028] The third aspect of the present invention provides an application of the mist water collection mulch in agricultural planting, and the mist water collection mulch is used as a mulch in agricultural planting. The mist water collection mulch provided by the first aspect of the present invention is covered on the farmland, and the flexible substrate coated with the super hydrophobic layer can increase the ground temperature, inhibit the growth of weeds and maintain the humidity of the soil. The conical structure can collect the mist water, and the collected mist water forms water droplets and flows along the flexible substrate to the farmland to provide moisture for crops.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention effectively improves the hydrophobic effect of the super-hydrophobic layer by coating a super-hydrophobic layer on a flexible substrate and controlling the mass-to-volume ratio of the modified solid particle suspension to the low surface energy liquid. The present invention can effectively collect fog water through a mechanically fixed conical structure, and the collected fog water flows through the super-hydrophobic layer to the farmland to provide moisture for crops, thereby effectively solving the problem in the prior art that the fog water collector has a rigid substrate and cannot be used in farmland.

[0031] (2) The method for preparing the fog water collection film of the present invention is simple and easy to realize industrial-scale production. The fog collection efficiency of the prepared fog water collection film can reach 7.4 g / cm per hour. 2 .

[0032] (3) The mist water collecting mulch film of the present invention can be used as an agricultural mulch film, which can not only achieve the mulch film effect, increase ground temperature, inhibit weed growth and maintain soil moisture, but also collect mist water to provide moisture for farmland, effectively reducing water waste and improving the soil's utilization of moisture. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic top view of the fog water collection membrane in Example 3 of the present invention.

[0034] Figure 2 This is a front view of the fog water collection film in Example 3 of the present invention.

[0035] Figure 3 This is a three-dimensional diagram of the fog water collection film in Example 3 of the present invention.

[0036] Figure 4This is an optical photograph of mist water collection of the mist water collection film in Example 3 of the present invention.

[0037] Figure 5 This is a diagram of the use of the fog water collection film as a ground film in Example 3 of the present invention.

[0038] Figure 6 Schematic diagram of the super-hydrophobic water contact angle of the fog water collection membrane in Example 3 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0041] Fog water collectors are mostly used in arid and water-scarce desert areas to provide people with drinking water and irrigation water. However, fog water collectors have not been fully utilized in agriculture. This is mainly because the base of existing fog water collectors is usually a rigid base, and during agricultural planting, the surface of the farmland is not flat, and the crop seedlings are relatively fragile. Using rigid materials as the base of the fog water collector is not only inconvenient to install, but also causes damage to the crop seedlings during use. In addition, the process of preparing fog water collectors is complicated and costly, so large-scale production is impossible. At present, the main component of ordinary agricultural mulch is non-degradable polyethylene, which will pollute the soil. The price of degradable mulch is more than twice that of ordinary mulch. Its main components are starch, cellulose, chitosan and other polysaccharide natural materials. They are weak in elasticity and easy to break, and can only be used once.

[0042] A fog water collection mulch provided in an embodiment of the present invention not only uses a flexible substrate so that it can be better applied in farmland, but also will not cause damage to crop seedlings during use. By coating a super hydrophobic layer on a flexible substrate and controlling the mass volume ratio of a modified solid particle suspension to a low surface energy liquid, the hydrophobic effect of the super hydrophobic layer is effectively improved, and the fog water can be effectively collected through a mechanically fixed conical structure. In addition, the fog water collection mulch in an embodiment of the present invention can also be extended to partially replace non-degradable agricultural mulch films. By splicing together multiple fog water collection mulches according to the specific needs of the farmland, a similar effect to that of a mulch film can be achieved, which can not only cover the farmland, increase the ground temperature, inhibit the growth of weeds, and maintain soil moisture, but also collect fog water to provide moisture for crops, thereby achieving multiple cycles of use.

[0043] The present invention extends the design of the mist collector to partially replace non-degradable agricultural mulch films. This is mainly due to the following current situation: the main component of ordinary agricultural mulch films is non-degradable polyethylene, which will pollute the soil. The price of degradable mulch films is more than twice that of ordinary mulch films. Their main components are starch, cellulose, chitosan and other polysaccharide natural materials. They are weak in elasticity and easy to break, and can only be used once. The present invention achieves the effect of mulch films by splicing multiple mist collection mulch films, which can not only cover farmland, increase ground temperature, inhibit weed growth, and maintain soil moisture, but also collect mist water to provide moisture for crops, thereby achieving multiple recycling uses.

[0044] The following is a detailed description of a fog water collection mulch film for agricultural planting, its preparation method and application.

[0045] The UV-resistant modified polypropylene, polyethylene terephthalate, polyvinyl chloride, polyethylene and the hydrophilic thermoplastic plastic with a cone structure in the following examples were all purchased from Xiangcheng, South China.

[0046] Example 1

[0047] A method for preparing a fog water collection mulch film for agricultural planting comprises the following steps:

[0048] S1. Take 250 mg of SiO2 with a particle size of 25 nm, 60 mg of CaCO3 with a particle size of 4 μm and 15 mg of TiO2 with a particle size of 25 μm, disperse them in a mixture of 20 mL of deionized water and 10 mL of anhydrous ethanol, and ultrasonically disperse them for 2 hours to obtain a suspension.

[0049] S2. Mix the suspension with 0.3 mL of hexamethyldisilazane and stir at 50° C. for 1 h to obtain a modified solid particle suspension.

[0050] S3. Take 2 mL of the modified solid particle suspension and mix it with 2 g of polytetrafluoroethylene emulsion, stir evenly, and obtain a super hydrophobic coating.

[0051] S4, the hydrophobic coating is applied at 0.1mL / cm 2 The super-hydrophobic coating was sprayed on the surface of polypropylene and irradiated with ultraviolet light for 5 minutes to solidify the super-hydrophobic coating on the surface of the flexible substrate, thereby obtaining a super-hydrophobic flexible substrate with a super-hydrophobic layer fixed on the surface.

[0052] S5. After the hydrophilic thermoplastic plastic with a conical structure penetrates the super-hydrophobic flexible substrate, the conical structure is located above the super-hydrophobic layer fixed on the surface of the super-hydrophobic flexible substrate, and the protrusion height is 1 mm, and it is fixed with a hot melt gun, wherein the length of the hydrophilic thermoplastic plastic with a conical structure is 5 mm, and the distance between each hydrophilic thermoplastic plastic with a conical structure is 4 mm, to obtain a fog water collection film, the structure of which is as follows Figure 1 to Figure 3As shown in the figure, the fog collection efficiency of the fog water collection film at a fog volume of 200 mL / h is 1.09 mg / cm per hour. 2 .

[0053] Example 2

[0054] A method for preparing a fog water collection mulch film for agricultural planting comprises the following steps:

[0055] S1. Take 264 mg of SiO2 with a particle size of 50 nm, 25 mg of SiO2 with a particle size of 2 μm and 6 mg of SiO2 with a particle size of 20 μm, disperse them in a mixture of 40 mL of deionized water and 30 mL of anhydrous ethanol, and ultrasonically disperse them for 2 hours to prepare a uniform suspension.

[0056] S2. Add 0.5 mL of methyltriethoxysilane to the suspension and stir at 70° C. for 3 h to obtain a modified solid particle suspension.

[0057] S3, take 10mL of modified solid particle suspension, add 2g of polydimethylsiloxane, stir evenly to obtain a super hydrophobic coating;

[0058] S4, the hydrophobic coating was heated to 3mL / cm 2 The super-hydrophobic coating was sprayed on the surface of polyethylene terephthalate with a spray amount of , and irradiated with ultraviolet light for 15 minutes to cure the super-hydrophobic coating on the surface of the flexible substrate, thereby obtaining a super-hydrophobic flexible substrate with a super-hydrophobic layer fixed on the surface.

[0059] S5. After the hydrophilic thermoplastic plastic with a conical structure penetrates the super-hydrophobic flexible substrate, the conical structure is located above the super-hydrophobic layer fixed on the surface of the super-hydrophobic flexible substrate, and the protrusion height is 10 mm. It is fixed with a hot melt gun, wherein the length of the hydrophilic thermoplastic plastic with a conical structure is 10 mm, and the spacing between the hydrophilic thermoplastic plastics of each conical structure is 2 mm, to obtain a fog water collection film.

[0060] The fog collection efficiency of the fog water collection film at a fog volume of 200 mL / h is 4.67 g / cm per hour. 2 .

[0061] Example 3

[0062] A method for preparing a fog water collection mulch film for agricultural planting comprises the following steps:

[0063] S1. Take 204 mg of SiO2 with a particle size of 500 nm, 60 mg of CaCO3 with a particle size of 1 μm and 16 mg of CaCO3 with a particle size of 10 μm, disperse them in a mixture of 50 mL of deionized water and 20 mL of anhydrous ethanol, and ultrasonically disperse them for 2 hours to obtain a suspension.

[0064] S2. Mix the suspension with 0.5 mL of methyltrimethoxysilane and stir at 40° C. for 7 h to obtain a modified solid particle suspension.

[0065] S3. Take 20 mL of the modified solid particle suspension and mix it with 2 g of polytetrafluoroethylene emulsion, stir evenly, and obtain a super hydrophobic coating.

[0066] S4, the hydrophobic coating was heated to 5 mL / cm 2 The coating amount was sprayed on the polyethylene terephthalate surface and irradiated with ultraviolet light for 30 minutes to cure the super-hydrophobic coating on the surface of the flexible substrate to obtain a super-hydrophobic flexible substrate with a super-hydrophobic layer fixed on the surface.

[0067] S5. After the hydrophilic thermoplastic plastic with a conical structure penetrates the super-hydrophobic flexible substrate, the conical structure is located above the super-hydrophobic layer fixed on the surface of the super-hydrophobic flexible substrate, and the protrusion height is 5 mm, wherein the length of the hydrophilic thermoplastic plastic with the conical structure is 15 mm, and the distance between the hydrophilic thermoplastic plastics of each conical structure is 1.3 mm, so as to obtain a fog water collection film.

[0068] The fog collection efficiency of the fog water collection film at a fog volume of 200 mL / h is 7.48 g / cm per hour. 2 .

[0069] Embodiments 1 to 3 all obtained a kind of fog water collecting ground film. Taking the fog water collecting ground film in Embodiment 3 as an example, the following experiment was carried out.

[0070] The fog water collection mulch prepared in Example 3 was placed in the field, and the water mist collection conditions at different times were recorded. The results are as follows: Figure 4 As shown, from Figure 4 It can be seen that as time goes by, the water droplets collected on the conical plastic gradually increase, indicating that the fog water collection film in the present invention has a good effect of collecting fog water.

[0071] The fog water collecting mulch film in Example 3 is laid as a mulch film in a farmland. Figure 5 As shown, the experiment was conducted on soil with a moisture content of 15%. When conventional polyethylene mulch was used, the average soil moisture content within 24 hours was 19%; when the mist water collection mulch in the present invention was used, the average soil moisture content within 24 hours was 25%. It can be seen that the mist water collection mulch in the present invention can effectively increase the moisture content of the soil.

[0072] Figure 6 : This is the contact angle between the fog water collection film and the water droplets in Example 3, where the contact angle is not less than 165°, while the contact angle of most hydrophobic materials currently is around 150°. It can be seen that the fog water collection film in the present invention can have a larger contact angle, indicating that it has better hydrophobicity.

[0073] The fog water collection mulch film in the present invention has a simple preparation method, low economic cost and strong scalability. The fog collecting devices can be spliced ​​around seeds or seedlings to replace the function of the mulch film. It can not only cover the farmland, increase the ground temperature, inhibit the growth of weeds and maintain soil moisture, but also collect fog water to provide moisture for crops, realize multiple recycling and avoid soil pollution. It is expected to partially replace agricultural mulch films and avoid the harm to the environment caused by the disposable mulch films currently used on a large scale.

[0074] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fog water collection film, characterized in that: The fog water collection ground film is obtained by uniformly fixing a plurality of cone structures on a flexible substrate coated with a super-hydrophobic layer through mechanical assembly; The super hydrophobic layer is prepared by mixing a modified solid particle suspension with a low surface energy liquid, so that the modified solid particles have a rough structure to reduce the surface energy of the super hydrophobic layer; The mass volume ratio of the modified solid particle suspension to the low surface energy liquid is 2-20 mL:2 g; The modified solid particle suspension is obtained by mixing solid particles of different particle sizes and then modifying them with a silane coupling agent; The solid particles are at least one of SiO2, CaCO3, and TiO2; The particle sizes of the solid particles with different particle sizes are 25nm-800nm, 1μm-4μm and 1μm-25μm.

2. The fog water collection film according to claim 1, characterized in that: The specific preparation process of the modified solid particle suspension is as follows: Dispersing solid particles of different particle sizes in a mixture of water and ethanol, and obtaining a suspension after ultrasonic treatment; mixing the suspension with a silane coupling agent, and stirring at 40° C. to 70° C. for 1 h to 7 h for modification treatment to obtain the modified solid particle suspension; The mass ratio of solid particles with particle sizes of 25nm to 800nm, 1μm to 4μm, and 1μm to 25μm is 10 to 50:5 to 1:1; The mass volume ratio of the solid particles with a particle size of 25 nm to 800 nm to the silane coupling agent is 200 mg to 265 mg: 0.5 mL.

3. The fog water collection film according to claim 2, characterized in that: The volume ratio of the water to the ethanol is 2-5:1-3.

4. The fog water collection film according to claim 2, characterized in that: The silane coupling agent is any one of hexamethyldisilazane, methyltriethoxysilane and methyltrimethoxysilane.

5. The fog water collection film according to claim 1, characterized in that: The low surface energy liquid is polytetrafluoroethylene emulsion or polydimethylsiloxane.

6. The fog water collection film according to claim 1, characterized in that: The flexible substrate is any one of polypropylene, polyethylene terephthalate, polyvinyl chloride and polyethylene.

7. The fog water collection ground film according to claim 1, characterized in that: The length of each of the conical structures is 0.5 mm to 20 mm.

8. A method for preparing a fog water collection film according to any one of claims 1 to 7, characterized in that: The following steps are involved: Mixing the low surface energy liquid with the modified solid particle suspension to obtain a super hydrophobic coating; The super-hydrophobic coating is sprayed on the flexible substrate, and the super-hydrophobic coating is cured on the surface of the flexible substrate under ultraviolet irradiation to obtain a super-hydrophobic flexible substrate with a super-hydrophobic layer fixed on the surface; Mechanically assembling a plurality of cone structures on the surface of a super-hydrophobic flexible substrate, wherein the spacing between each cone structure is 1 mm to 5 mm, to obtain a fog water collection film; The spraying amount of the super hydrophobic coating is 0.1 mL / cm 2 ~5mL / cm 2 .

9. The preparation method according to claim 8, characterized in that: The ultraviolet irradiation time is 5 minutes to 30 minutes.

10. Use of the fog water collection mulch film according to any one of claims 1 to 7 in agricultural planting, characterized in that: The mist water collecting mulch film is used as a mulch film in agricultural planting.

Images