A lignin-based super-hydrophobic coating and its preparation method and application

Abstract

The application belongs to the technical field of super-hydrophobic coating, and particularly relates to a lignin-based super-hydrophobic coating, a preparation method and application thereof, and a lignin-based super-hydrophobic coating, which comprises the following raw materials in parts by weight: 4-20 parts of diamino-terminated polydimethylsiloxane, 4-20 parts of trimesaldehyde, 3000-4000 parts of an organic solvent, 5-20 parts of lignin nanobottle, and 5-20 parts of nano-silicon dioxide. The lignin-based super-hydrophobic coating prepared by the application has a thickness of less than 20 microns, and has durability, hydrophobicity, light-heat performance, and can be used in the field of light-heat deicing, so as to reduce the adverse effects of icing phenomena on the normal operation of equipment and facilities, and is more effective and safe.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of super-hydrophobic coating, and particularly relates to a lignin-based super-hydrophobic coating and a preparation method and application thereof. BACKGROUND

[0002] Super-hydrophobic coating (water contact angle > 150°) has broad application prospects in the fields of anti-icing, corrosion resistance, biomedical devices and energy-saving systems due to its self-cleaning characteristics. Since the 20th century, durable hydrophobic materials have attracted continuous attention from the academic and industrial circles due to their multi-scene applicability. Traditional super-hydrophobic materials usually rely on the combination of fluorine-containing compounds (such as perfluoroalkyl substances) and substrates with high mechanical strength to form composite coatings, or achieve hydrophobic performance by constructing complex micro-nano hierarchical structures. However, these strategies face double challenges in sustainability and practical application: on the one hand, perfluoroalkyl substances are difficult to degrade due to their strong chemical stability, and long-term accumulation may cause environmental and health risks; on the other hand, micro-nano structured surfaces are prone to physical damage or chemical degradation under mechanical wear or ultraviolet radiation, resulting in loss of hydrophobicity. In addition, the substrate structure of existing composite coatings is generally thick (> 200 μm), which is difficult to be compatible with applications such as heat transfer, water collection and seawater desalination that require micron-level thickness, and is limited by substrate type and large-scale preparation process.

[0003] Lignin, as the second most abundant polyphenolic polymer in plant biomass, has the advantages of wide source, low cost and rich natural hydrophobic groups, and is considered as an ideal candidate to replace fluorine-containing materials. However, the existing lignin-based coating still has significant defects: the polarity of unmodified lignin molecules is high, resulting in insufficient hydrophobic angle (usually < 140°) of the coating; the thickening strategy (such as particle accumulation) introduced to improve hydrophobicity and durability makes the coating thickness exceed 200 μm, limiting its application in precision devices. These bottlenecks seriously restrict the practical promotion of lignin-based coating. Based on the above reasons, it is crucial to develop an ultra-thin and durable lignin-based super-hydrophobic coating. SUMMARY

[0004] The purpose of the present application is to provide a lignin-based super-hydrophobic coating and a preparation method and application thereof, which solves the problems of fluorine-containing, high coating thickness, poor durability and complicated process in the preparation of existing lignin-based super-hydrophobic coatings.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] In the first aspect, the present application provides a lignin-based super-hydrophobic coating, which comprises the following raw materials: 4-20 parts of diamino-terminated polydimethylsiloxane, 4-20 parts of triformylphloroglucinol, 3000-4000 parts of organic solvent, 5-20 parts of lignin nanobottle and 5-20 parts of nano-silicon dioxide.

[0007] In some other embodiments, the raw materials include, by weight parts, diamino-terminated polydimethylsiloxane 6-16 parts, trimesaldehyde 6-16 parts, organic solvent 3500-3800 parts, lignin nanobottle 5-10 parts, nanosilica 5-10 parts.

[0008] In some other embodiments, the organic solvent is one of tetrahydrofuran and chloroform;

[0009] The particle size of the nanosilica is 7-40 nm;

[0010] The molecular weight of the diamino-terminated polydimethylsiloxane is 2000-3000 Da.

[0011] In a second aspect, the present application provides a lignin-based super-hydrophobic coating layer made of the lignin-based super-hydrophobic coating of the first aspect, wherein the thickness of the lignin-based super-hydrophobic coating layer is <20 μm, the contact angle is all >150°, and the sliding angle is all <2°.

[0012] In a third aspect, the present application provides a preparation method of the lignin-based super-hydrophobic coating layer of the second aspect, comprising the following steps:

[0013] (1) adding diamino-terminated polydimethylsiloxane and trimesaldehyde into an organic solvent to stir and react to obtain a mixed solution;

[0014] (2) adding lignin nanobottle and nanosilica into the mixed solution to stir and react to obtain a super-hydrophobic coating;

[0015] (3) after the super-hydrophobic coating is sprayed on the surface of a substrate, drying to obtain the lignin-based super-hydrophobic coating layer.

[0016] In some other embodiments, in step (1), the mass ratio of the diamino-terminated polydimethylsiloxane and the trimesaldehyde is (1-3)-(3-1);

[0017] The mixing ratio of the trimesaldehyde and the organic solvent is (20-100) mg:20 mL;

[0018] The stirring speed of the stirring reaction is 300-800 rpm, and the time is 0.5-4 h.

[0019] In some other embodiments, in step (2), the mass ratio of the lignin nanobottle and the nanosilica is (5-20):(5-20);

[0020] The mixing ratio of the lignin nanobottle and the mixed solution is (5-20):4 mL;

[0021] The stirring reaction has a rotation speed of 300-800 rpm and a time of 0.5-4 h.

[0022] In some other embodiments, in step (3), the drying is vacuum drying, and the drying temperature of the vacuum drying is 50-100 DEG C.

[0023] In a fourth aspect, the present application provides the application of the lignin-based superhydrophobic coating in the second aspect in hydrophobic deicing, heat transfer, water collection, seawater desalination and precision devices.

[0024] In some other embodiments, the application in photothermal superhydrophobic deicing.

[0025] The present application has the following beneficial effects:

[0026] (1) The coating preparation process of the present application does not require fluorinated reagents, greatly reducing the environmental impact of the coating and making the entire preparation process green and pollution-free. At the same time, the coating preparation process is simple, and the structure is flexible and can be designed.

[0027] (2) The coating of the present application uses lignin nanobottle and nanosilica with excellent photothermal properties to construct a nanometer rough superstructure, which has the advantages of simple process and flexible structure design. The nanometer rough structure constructed by lignin nanobottle and nanosilica makes the surface have superhydrophobic properties, avoiding the complex chemical modification process of lignin nanobottle and low surface energy modification, thereby greatly reducing the preparation cost of the coating.

[0028] (3) The coating of the present application has a thickness of <20 μm, which is beneficial to its application in precision devices.

[0029] (4) The addition of nanosilica with excellent hardness and wear resistance in the present application can enhance the mechanical durability of the coating. At the same time, the lignin nanobottle providing a micrometer-level structure and the nanosilica providing a nanometer-level structure together construct a biomimetic "lotus leaf" micro-nano rough structure. This micro-nano rough structure can also provide good wear resistance. This is because the micrometer-level lignin nanobottle is first worn out during wear, thus effectively protecting the nanometer-level silica, thereby effectively protecting the hydrophobic structure. Rough structures without micro-nano structures will directly damage the hydrophobic structure when encountering wear, causing the coating to lose hydrophobicity. BRIEF DESCRIPTION OF DRAWINGS

[0030] The drawings accompanying the specification of the present application form a part thereof and serve to provide further understanding of the present application, the illustrative embodiments of the present application and its description serve to explain the present application, and do not constitute an improper limitation on the present application.

[0031] Figure 1 The photothermal deicing process of the sample coating prepared for Example 3 of the present application;

[0032] Figure 2 Contact angle diagram of the sample prepared for Example 3 of the present application;

[0033] Figure 3 SEM image of the coating thickness of the sample prepared for Example 2 of the present application;

[0034] Figure 4 SEM image of the coating thickness of the sample prepared for Example 3 of the present application;

[0035] Figure 5 SEM image of the coating thickness of the sample prepared for Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0036] A person skilled in the art will understand that the following examples are only for illustration of the present application and should not be considered as limiting the scope of the present application. If no specific conditions are specified in the examples, they are carried out under conventional conditions or under conditions recommended by the manufacturer. If no manufacturer is specified for the components used, they are all conventional products that can be obtained commercially. Among them, the lignin nanobottle is prepared by the method in Example 1 of the application publication No. CN118530473 A.

[0037] At present, in the field of hydrophobic deicing, the thickness, durability, hydrophobicity and photothermal performance of the coating seriously affect the service life and deicing effect of hydrophobic deicing. The ultra-thin and durable lignin-based superhydrophobic coating of the present application has higher efficiency, effectiveness and safety in actual process.

[0038] The technical solutions of the present application will be further described below in conjunction with specific examples.

[0039] Example 1

[0040] (1) 76.8 mg of bis-aminopropyl-terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of trimesaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 1 h to prepare solution A;

[0041] (2) 5 mg of lignin nanobottle and nanosilica (particle size 20 nm) 15 mg were added to 4 mL of solution A, and after stirring and mixing, an ultra-hydrophobic coating was prepared, the stirring speed was 400 rpm, and the stirring time was 1 h.

[0042] (3) 2 mL of the ultra-hydrophobic coating was added to a spray pen, and after spraying (spray nozzle aperture 0.45 mm, spray temperature room temperature, distance from the sprayed surface 25 cm) on the surface of a 4 cm 2 substrate, a vacuum drying at 80°C was carried out to obtain an ultra-hydrophobic coating.

[0043] Example 2

[0044] (1) 33.2 mg of bisaminopropyl terminated polydimethylsiloxane (molecular weight 2500 Da) and 76.8 mg of trimesaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 1 h to prepare solution A;

[0045] (2) 5 mg of lignin nanobottles and nanosilica (particle size 20 nm) 15 mg were added to 4 mL of solution A, and after stirring and mixing, an ultrahydrophobic coating was prepared, the stirring speed was 400 rpm, and the stirring time was 1 h.

[0046] (3) 2 mL of the ultrahydrophobic coating was added to a spray pen, sprayed (spraying parameters same as example 1) on the surface of a 4 cm 2 substrate, and then vacuum dried at 80°C to obtain an ultrahydrophobic coating.

[0047] Example 3

[0048] (1) 76.8 mg of bisaminopropyl terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of trimesaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 0.5 h to prepare solution A;

[0049] (2) 10 mg of lignin nanobottles and nanosilica (particle size 20 nm) 10 mg were added to 4 mL of solution A, and after stirring and mixing, an ultrahydrophobic coating was prepared, the stirring speed was 400 rpm, and the stirring time was 1 h.

[0050] (3) 2 mL of the ultrahydrophobic coating was added to a spray pen, sprayed (spraying parameters same as example 1) on the surface of a 4 cm 2 substrate, and then vacuum dried at 80°C to obtain an ultrahydrophobic coating.

[0051] Example 4

[0052] (1) 76.8 mg of bisaminopropyl terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of trimesaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 0.5 h to prepare solution A;

[0053] (2) 10 mg of lignin nanobottles and nanosilica (particle size 20 nm) 10 mg were added to 4 mL of solution A, and after stirring and mixing, an ultrahydrophobic coating was prepared, the stirring speed was 400 rpm, and the stirring time was 1 h.

[0054] (3) 4 mL of the ultrahydrophobic coating was added to a spray pen, sprayed (spraying parameters same as example 1) on the surface of a 4 cm 2 substrate, and then vacuum dried at 80°C to obtain an ultrahydrophobic coating.

[0055] Example 5

[0056] (1) 76.8 mg of bisaminopropyl terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of trimesic aldehyde were added to 20 mL of tetrahydrofuran to prepare solution A, which was reacted at 400 rpm for 0.5 h;

[0057] (2) 10 mg of lignin nanobottles and nanosilica (particle size 20 nm) were added to 4 mL of solution A, and after stirring to mix, an ultrahydrophobic coating was prepared, with a stirring speed of 400 rpm and a stirring time of 1 h.

[0058] (3) 2 mL of the ultrahydrophobic coating was added to a spray pen, which was sprayed (spraying parameters were the same as in Example 1) on the surface of a 4 cm 2 substrate, and an ultrahydrophobic coating was obtained after vacuum drying at 100°C.

[0059] Comparative Example 1

[0060] (1) 2 g of sulfated lignin was weighed using an electronic balance and dispersed in 60 mL of deionized water, which was stirred at 300 r / min at room temperature for 5 min to obtain solution A. Solution A was poured into a 250 mL three-necked flask and continued to be stirred, and nitrogen was introduced at a flow rate of 0.5 m3 / h. 3.5 g of imidazole was weighed and added to solution A and stirred for 1 h. Acetone was measured using a graduated cylinder and poured into a beaker, and 2 mL of FOTS was measured using a graduated cylinder and poured into 36 mL of acetone solution. The beaker was sealed with a sealing film, and 300 r / min stirring was performed for 1 h to obtain solution B. Solution B was added to solution A using an acid burette, heated to 50°C and stirred for 24 h, then poured into 300 mL of deionized water to precipitate the lignin, and left to stand for 30 min. Solution A was poured into a centrifuge tube and placed in a centrifuge to precipitate for 10 min. The supernatant was poured out, and the precipitate was placed in a vacuum drying oven and dried at 85°C for 12 h to obtain silane-modified lignin.

[0061] (2) 100 mg of silane-modified lignin and 100 mg of nanosilica were weighed using an electronic balance and blended in 10 mL of acetone to obtain solution C. 0.16 mL of polydimethylsiloxane and 0.05 mL of epoxy resin were discharged into solution C using a pipette, and stirred at 500 r / min at room temperature for 15 min. 0.016 mL of polydimethylsiloxane curing agent and 0.05 mL of diethylenetriamine were discharged into solution C using a pipette, and stirred for 15 min to obtain an ultrahydrophobic coating.

[0062] (3) The ultrahydrophobic coating was poured into a spray pen at a spraying amount of 0.0016 g / cm 2 , the spray pen aperture was adjusted to 0.5 mm, the distance between the spray pen and the sample was 15 cm, and after spraying on the surface of the sample, the sample was placed in a vacuum drying oven and cured at 85°C for 10 h to obtain an ultrahydrophobic coating.

[0063] Comparative Example 2

[0064] Different from Example 3, no nano-silica was added in step (2), the content of lignin nano-bottle was adjusted to 20 mg, and other preparation steps were consistent with Example 3.

[0065] Comparative Example 3

[0066] Different from Example 3, no lignin nano-bottle was added in step (2), the content of nano-silica was adjusted to 20 mg, and other preparation steps were consistent with Example 3.

[0067] Comparative Example 4

[0068] Different from Example 3, lignin nano-microsphere (LNPs, particle size 340 nm) was used to replace lignin nano-bottle in step (2), and other preparation steps were consistent with Example 3.

[0069] Comparative Example 5

[0070] Different from Example 3, dicyclohexyl methane diisocyanate was added on the basis of step (1), and the addition amount of trimesalylformaldehyde was adjusted to 15 mg, and the addition amount of dicyclohexyl methane diisocyanate was 18.2 mg, and other preparation steps were consistent with Example 3.

[0071] Performance test

[0072] (1) Weather resistance test

[0073] Abrasion test: the sample coating surface of Example 1 with a size of 1 cm x 3 cm was placed face to face on a 1000 grit sandpaper with a size of 23 cm x 28 cm. A 200 g weight was attached to the back of the sample using double-sided tape, thereby applying a pressure of 3.1 kPa to the coating. The sample was manually ground at a speed of 0.08 m / s -1 for different times over a distance of more than 20 cm. The contact angle and sliding angle of the sample were measured after 10 scratches. Table 1 is the contact angle and sliding angle of Example 3 before and after abrasion.

[0074] Table 1 Contact angle and sliding angle of Example 1 before and after abrasion

[0075] Contact angle (°) Slip angle (°) Before wear 154 1.7 After wear 151 2.3

[0076] As can be seen from Table 1, the contact angle and sliding angle of the sample of Example 1 before and after abrasion change little. The contact angle and sliding angle of Examples 2-5 before and after abrasion change similarly, while the contact angle and sliding angle of Comparative Example 1 before abrasion are 158° and 1.3°, and the coating after abrasion loses the super-hydrophobic property with a contact angle > 150°. As can be seen from Table 2, the coatings of Comparative Examples 2-5 do not have the super-hydrophobic property, and thus it is meaningless to study the abrasion resistance thereof. Thus, it is shown that the coating prepared in the examples of the present application has the abrasion resistance under mechanical abrasion, thereby maintaining the stability of the coating structure.

[0077] (2) De-icing test

[0078] Photo-thermal anti-icing test: under the condition of -20℃, the ice formation process of water droplets on the coating surface of the sample of Example 3 under 1 sun irradiation was recorded, i.e. the process from transparent to opaque as shown in Figure 1

[0079] As can be seen from Figure 1 , the coating prepared in Example 3 exhibits excellent anti-icing ability. The ice formation time can be passively extended from 5s to 230s, and the anti-icing effect is significantly improved. The passively extended ice formation time of Examples 1, 2, 4 and 5 is 195s, 189s, 283s and 227s respectively, while the passively extended ice formation time of Comparative Examples 1-5 is 185s, 101s, 34s, 93s and 78s respectively. Since Comparative Example 1 does not have the nanostructure composed of lignin nanobottle and nanosilica, the nano effect is lacking, which reduces the light absorption rate and leads to the reduction of the photo-thermal conversion ability of the coating. Since Comparative Examples 2-5 lack the air cushion formed by the liquid droplets on the super-hydrophobic structure, the thermal conductivity is high, and thus the anti-icing ability is poor.

[0080] The hydrophobicity of the sample surface was tested by using a contact angle measuring instrument OCA50, 3μL of water droplets was dropped on the sample surface, and the water contact angle was measured. The cross section of the coating was intercepted by using a scanning electron microscope, and the coating thickness was measured by using software Nano Measurer 1.2. As shown in Table 2, the contact angle, sliding angle and coating thickness of the coating prepared in the examples and comparative examples of the present application are shown.

[0081] Table 2 Contact angle, sliding angle and coating thickness of the coating of the examples and comparative examples

[0082]

[0083]

[0084] Note: "-" means that the data is not measured. The sliding angle usually describes the wettability of super-hydrophobic materials, and the sliding angle of non-super-hydrophobic materials is usually too large to have no measurement significance. ​

[0085] As shown in Table 2, the contact angles of Examples 1-5 and Comparative Example 1 are all >150°, meeting the requirements for contact angle (water contact angle >150°) of superhydrophobic coatings; the sliding angles are all <2°, meeting the requirements for sliding angle (sliding angle <10°) of superhydrophobic coatings; the coating thicknesses of Examples 1-5 are all <20μm, which is beneficial for their application in precision devices. However, the coating thickness of Comparative Example 1 is all >200μm, making it difficult to be compatible with applications requiring micron-level thicknesses, such as heat transfer, water collection, and seawater desalination. In addition, the coatings prepared in Comparative Examples 2-5 do not possess superhydrophobic properties (water contact angle >150°).

[0086] Figure 2 This is a schematic diagram of the contact angle of the sample prepared in Example 3. Figure 2 As can be seen, the contact angle of the coating is 158.1°. This special surface property makes it almost impossible for water droplets to adhere when in contact, and they can easily roll on its surface.

[0087] Figure 3 SEM images of the coating thickness of the sample prepared in Example 2, from... Figure 3 It can be seen that the coating thickness on the substrate surface is 15.1 μm. Figure 4 SEM images of the coating thickness of the sample prepared in Example 3, from... Figure 4 It can be seen that the coating thickness on the substrate surface is 17.7 μm. Figure 5 The coating thickness of the sample prepared in Comparative Example 1 was 206.7 μm, which is difficult to be compatible with application scenarios that require micron-level thickness, such as heat transfer, water collection and seawater desalination.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lignin-based superhydrophobic coating, characterized in that, The raw materials, by weight, are as follows: 4-20 parts of diamino-terminated polydimethylsiloxane, 4-20 parts of pyromellitic trimethylaldehyde, 3000-4000 parts of organic solvent, 5-20 parts of lignin nanobottle, and 5-20 parts of nano silica. The coating thickness obtained by the lignin-based superhydrophobic coating is <20μm.

2. The lignin-based superhydrophobic coating according to claim 1, characterized in that, By weight, it includes the following raw materials: 6-16 parts of diamino-terminated polydimethylsiloxane, 6-16 parts of pyromellitic trimethylaldehyde, 3500-3800 parts of organic solvent, 5-10 parts of lignin nanobottle, and 5-10 parts of nano silica.

3. The lignin-based superhydrophobic coating according to claim 1, characterized in that, The organic solvent is one of tetrahydrofuran and chloroform; The particle size of the nano-silica is 7-40 nm; The molecular weight of the diamino-terminated polydimethylsiloxane is 2000-3000 Da.

4. A lignin-based superhydrophobic coating made from the lignin-based superhydrophobic coating according to any one of claims 1-3, characterized in that, The contact angle of the lignin-based superhydrophobic coating is greater than 150° and the sliding angle is less than 2°.

5. A method for preparing the lignin-based superhydrophobic coating according to claim 4, characterized in that, Includes the following steps: (1) A mixed solution was prepared by adding diamino-terminated polydimethylsiloxane and pyromellitic aldehyde to an organic solvent and stirring the mixture. (2) Add lignin nanobottle and nano silica to a mixed solution and stir to react to obtain a superhydrophobic coating; (3) After the superhydrophobic coating is sprayed onto the surface of the substrate, the lignin-based superhydrophobic coating is obtained after drying.

6. The method for preparing the lignin-based superhydrophobic coating according to claim 5, characterized in that, In step (1), the mass ratio of the diamino-terminated polydimethylsiloxane to pyromellitic aldehyde is 1:3-3:

1. The mixing ratio of the pyromellitic aldehyde to the organic solvent is (20-100) mg: 20 mL; The stirring reaction is carried out at a speed of 300-800 rpm for a duration of 0.5-4 hours.

7. The method for preparing the lignin-based superhydrophobic coating according to claim 5, characterized in that, In step (2), the mass ratio of the lignin nanobottle to the nano silica is (5-20):(5-20). The mixing ratio of the lignin nanobottle to the mixed solution is (5-20) mg: 4 mL; The stirring reaction is carried out at a speed of 300-800 rpm for a duration of 0.5-4 hours.

8. The method for preparing the lignin-based superhydrophobic coating according to claim 5, characterized in that, In step (3), the drying is vacuum drying, and the temperature of the vacuum drying is 50-100 ℃.

9. The application of the lignin-based superhydrophobic coating of claim 4 in hydrophobic de-icing, heat transfer, water collection, seawater desalination and precision devices.

10. The application according to claim 9, characterized in that, Application in photothermal superhydrophobic de-icing.

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