Lignin-based super-hydrophobic coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of super-hydrophobic coatings, and particularly relates to a lignin-based super-hydrophobic coating as well as a preparation method and application of the lignin-based super-hydrophobic coating. Comprising the following raw materials in parts by weight: 4 to 20 parts of double-amino-terminated polydimethylsiloxane, 4 to 20 parts of benzenetricarboxaldehyde, 3000 to 4000 parts of an organic solvent, 5 to 20 parts of a lignin nano bottle and 5 to 20 parts of nano silicon dioxide. The thickness of the prepared lignin-based super-hydrophobic coating is smaller than 20 microns, and the lignin-based super-hydrophobic coating has durability, hydrophobicity and photo-thermal performance, can be used in the field of photo-thermal deicing, reduces the possible adverse effect of the icing phenomenon on normal operation of equipment and facilities, and is higher in effectiveness and safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of superhydrophobic coatings, and particularly relates to a lignin-based superhydrophobic coating, a preparation method thereof, and an application thereof. Background Art

[0002] Superhydrophobic coatings (water contact angle > 150°) have shown broad application prospects in the fields of anti-icing, corrosion resistance, biomedical devices, and energy-saving systems due to their self-cleaning properties. Since the 20th century, durable hydrophobic materials have attracted continuous attention from the academic and industrial communities due to their applicability in multiple scenarios. Traditional superhydrophobic materials usually rely on the combination of fluorine-containing compounds (such as perfluoroalkyl substances) and matrices with high mechanical strength to form composite coatings, or achieve hydrophobic properties by constructing complex micro-nano hierarchical structures. However, these strategies face dual challenges in sustainability and practical applications: on the one hand, perfluorinated compounds are difficult to degrade due to their strong chemical stability, and long-term accumulation may pose environmental and health risks; on the other hand, the surface of micro-nano structures is prone to physical damage or chemical degradation under mechanical wear or ultraviolet irradiation, resulting in the failure of hydrophobicity. In addition, the matrix structures of existing composite coatings are generally thick (>200 μm), making it difficult to be compatible with applications such as heat transfer, water collection, and seawater desalination that require a micron-level thickness, and are limited by the type of substrate and large-scale preparation processes.

[0003] Lignin, as the second most abundant polyphenol polymer in plant biomass, has the advantages of wide sources, low cost, and rich natural hydrophobic groups, and is regarded as an ideal candidate to replace fluorine-containing materials. However, existing lignin-based coatings still have significant defects: unmodified lignin molecules have a high polarity, resulting in insufficient hydrophobic angles of the coatings (usually < 140°); the thickening strategies (such as particle packing) introduced to improve hydrophobicity and durability make the coating thickness exceed 200 μm, restricting their application in precision devices. These bottlenecks severely limit the practical promotion of lignin-based coatings. For the above reasons, developing an ultrathin and durable lignin-based superhydrophobic coating has become the key. Summary of the Invention

[0004] The purpose of the present invention is to provide a lignin-based superhydrophobic coating, a preparation method thereof, and an application thereof, which solve the problems of fluorine-containing, high coating thickness, poor durability, and cumbersome process in the existing preparation of lignin-based superhydrophobic coatings.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] In the first aspect, the present invention provides a lignin-based superhydrophobic coating, comprising the following raw materials: 4 - 20 parts of bis(amino)-terminated polydimethylsiloxane, 4 - 20 parts of benzene-1,3,5-tricarbaldehyde, 3000 - 4000 parts of an organic solvent, 5 - 20 parts of lignin nanobottles, and 5 - 20 parts of nano-silica.

[0007] In some other embodiments, by weight parts, it includes the following raw materials: 6-16 parts of diamine-terminated polydimethylsiloxane, 6-16 parts of benzene-1,3,5-tricarbaldehyde, 3500-3800 parts of organic solvent, 5-10 parts of lignin nanobottles, and 5-10 parts of nano-silica.

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

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

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

[0011] In a second aspect, the present invention provides a lignin-based superhydrophobic coating made of the lignin-based superhydrophobic coating material described in the first aspect. The thickness of the lignin-based superhydrophobic coating is <20 μm, the contact angle is >150°, and the sliding angle is <2°.

[0012] In a third aspect, the present invention provides a preparation method of the lignin-based superhydrophobic coating described in the second aspect, including the following steps:

[0013] (1) Add diamine-terminated polydimethylsiloxane and benzene-1,3,5-tricarbaldehyde into an organic solvent and stir and react to obtain a mixed solution;

[0014] (2) Add lignin nanobottles and nano-silica into the mixed solution, stir and react to obtain a superhydrophobic coating material;

[0015] (3) Spray the superhydrophobic coating material on the surface of a substrate, and after drying, a lignin-based superhydrophobic coating is obtained.

[0016] In some other embodiments, in step (1), the mass ratio of the diamine-terminated polydimethylsiloxane to benzene-1,3,5-tricarbaldehyde is (1-3)-(3-1);

[0017] The mixing ratio of benzene-1,3,5-tricarbaldehyde to the organic solvent is (20-100) mg: 20 mL;

[0018] The rotation 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 nanobottles to nano-silica is (5-20):(5-20);

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

[0021] The rotation speed of the stirring reaction is 300 - 800 rpm, and the time is 0.5 - 4 h.

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

[0023] Fourthly, the present invention provides the application of the lignin-based superhydrophobic coating described in the second aspect in hydrophobic de-icing, heat transfer, water collection, seawater desalination, and precision devices.

[0024] In some other embodiments, the application in photothermal superhydrophobic de-icing.

[0025] Advantages of the present invention:

[0026] (1) In the coating preparation process of the present invention, no fluorinating reagent is required, which greatly reduces the impact of the coating on the environment, 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 designable.

[0027] (2) The coating of the present invention uses lignin nanobottles and nano-silica with excellent photothermal properties to construct a nano-rough structure, which has the advantages of simple process and flexible and designable structure; through the nano-rough structure constructed by lignin nanobottles and nano-silica, the surface has superhydrophobic properties, avoiding the complex chemical modification process of lignin nanobottles and low surface energy modification, so the preparation cost of the coating is greatly reduced.

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

[0029] (4) The addition of nano-silica with excellent hardness and wear resistance in the present invention can enhance the mechanical durability of the coating. At the same time, the lignin nanobottles providing a micron-level structure and the nano-silica providing a nano-level structure together construct a biomimetic "lotus leaf" micro-nano rough structure, and this micro-nano rough structure can also provide good wear resistance. This is because when worn, the micron-level lignin nanobottles are first worn, thus effectively protecting the nano-level silica, and thus can effectively protect the hydrophobic structure. Without the rough structure of the micro-nano structure, the hydrophobic structure will be directly damaged when encountering wear, causing the coating to lose its hydrophobicity. Description of the drawings

[0030] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0031] Figure 1 It is the photothermal de-icing process of the sample coating prepared in Example 3 of the present invention;

[0032] Figure 2 Schematic diagram of the contact angle of the sample prepared in Example 3 of the present invention;

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

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

[0035] Figure 5 SEM image of the coating thickness of the sample prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0036] Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions are not indicated in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. Components not indicated by the manufacturer are all conventional products available commercially. Among them, the lignin nanobottles are prepared by the method in Example 1 of Application Publication No. CN118530473 A.

[0037] Currently in the field of hydrophobic de-icing, the thickness, durability, hydrophobicity, and photothermal performance of the coating seriously affect the service life and de-icing effect of hydrophobic de-icing. Since the ultra-thin and durable lignin-based superhydrophobic coating of the present invention is more efficient, effective, and safe in the actual process.

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

[0039] Example 1

[0040] (1) 76.8 mg of diaminopropyl-terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of benzene-1,3,5-tricarbaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 1 h to obtain Solution A;

[0041] (2) 5 mg of lignin nanobottles and 15 mg of nano-silica (particle size 20 nm) were added to 4 mL of Solution A, and after stirring and mixing evenly, a superhydrophobic coating was obtained. The stirring speed was 400 rpm and the stirring time was 1 h..

[0042] (3) 2 mL of the superhydrophobic coating was added to an airbrush and sprayed (the nozzle aperture was 0.45 mm, the spraying temperature was room temperature, and the distance from the spraying surface was 25 cm) on the surface of a 4 cm 2 substrate surface, and then vacuum dried at 80 °C to obtain a superhydrophobic coating.

[0043] Example 2

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

[0045] (2) 5 mg of lignin nanobottles and 15 mg of nano-silica (particle size 20 nm) were added to 4 mL of solution A, and after stirring and mixing evenly, a superhydrophobic coating was obtained. The stirring speed was 400 rpm and the stirring time was 1 h..

[0046] (3) 2 mL of the superhydrophobic coating was added to an airbrush and sprayed (spraying parameters same as in Example 1) on the surface of a 4 cm 2 substrate, and then dried in vacuo at 80 °C to obtain a superhydrophobic coating.

[0047] Example 3

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

[0049] (2) 10 mg of lignin nanobottles and 10 mg of nano-silica (particle size 20 nm) were added to 4 mL of solution A, and after stirring and mixing evenly, a superhydrophobic coating was obtained. The stirring speed was 400 rpm and the stirring time was 1 h..

[0050] (3) 2 mL of the superhydrophobic coating was added to an airbrush and sprayed (spraying parameters same as in Example 1) on the surface of a 4 cm 2 substrate, and then dried in vacuo at 80 °C to obtain a superhydrophobic coating.

[0051] Example 4

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

[0053] (2) 10 mg of lignin nanobottles and 10 mg of nano-silica (particle size 20 nm) were added to 4 mL of solution A, and after stirring and mixing evenly, a superhydrophobic coating was obtained. The stirring speed was 400 rpm and the stirring time was 1 h..

[0054] (3) 4 mL of the superhydrophobic coating was added to an airbrush and sprayed (spraying parameters same as in Example 1) on the surface of a 4 cm 2 substrate, and then dried in vacuo at 80 °C to obtain a superhydrophobic coating.

[0055] Example 5

[0056] (1) 76.8 mg of diamino propyl terminated polydimethylsiloxane (molecular weight 2500 Da) and 33.2 mg of benzene - 1,3,5 - tricarbaldehyde were added to 20 mL of tetrahydrofuran and reacted at 400 rpm for 0.5 h to obtain solution A.

[0057] (2) 10 mg of lignin nanobottles and 10 mg of nano - silica (particle size 20 nm) were added to 4 mL of solution A, and after stirring and mixing evenly, a super - hydrophobic coating was obtained. The stirring speed was 400 rpm and the stirring time was 1 h.

[0058] (3) 2 mL of the super - hydrophobic coating was added to an airbrush and sprayed (spraying parameters are the same as in Example 1) on the surface of a 4 cm 2 substrate, and then dried in vacuo at 100 °C to obtain a super - hydrophobic coating.

[0059] Comparative Example 1

[0060] (1) 2 g of sulfate lignin was weighed using an electronic balance and dispersed in 60 mL of deionized water, and 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 stir. 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 measuring cylinder and poured into a beaker, and 2 mL of FOTS was measured using a measuring cylinder and poured into 36 mL of acetone solution. The beaker was sealed with a sealing film and stirred at 300 r / min for 1 h to obtain solution B. Solution B was added dropwise to solution A using an acid burette, heated to 50 °C and stirred for 24 h, then 300 mL of deionized water was added to precipitate the lignin. After standing for 30 min, solution A was poured into a centrifuge tube, placed in a centrifuge and centrifuged for 10 min to precipitate. The supernatant was poured out, and the precipitate was placed in a vacuum drying oven and dried in vacuo at 85 °C for 12 h to obtain silane - modified lignin.

[0061] (2) 100 mg of silane - modified lignin and 100 mg of nano - silica were weighed respectively 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 pipetted and added to solution C, 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 pipetted and added to solution C, and stirred for 15 min to obtain a super - hydrophobic coating.

[0062] (3) The super - hydrophobic coating was poured into an airbrush at a spraying amount of 0.0016 g / cm 2 , the airbrush nozzle was adjusted to 0.5 mm, the distance between the airbrush and the specimen was 15 cm. After spraying on the specimen surface, it was placed in a vacuum drying oven and cured at 85 °C for 10 h to obtain a super - hydrophobic coating.

[0063] Comparative Example 2

[0064] Different from Example 3, in step (2), nano-silica is not added, and the content of lignin nanobottles is adjusted to 20 mg. Other preparation steps are the same as those in Example 3.

[0065] Comparative Example 3

[0066] Different from Example 3, in step (2), lignin nanobottles are not added, and the content of nano-silica is adjusted to 20 mg. Other preparation steps are the same as those in Example 3.

[0067] Comparative Example 4

[0068] Different from Example 3, lignin nanospheres (LNPs, particle size of 340 nm) are used to replace the lignin nanobottles in step (2). Other preparation steps are the same as those in Example 3.

[0069] Comparative Example 5

[0070] Different from Example 3, dicyclohexylmethane diisocyanate is added on the basis of step (1), and the addition amount of mellitene is adjusted to 15 mg, and the addition amount of dicyclohexylmethane diisocyanate is 18.2 mg. Other preparation steps are the same as those in Example 3.

[0071] Performance Test

[0072] (1) Weather Resistance Test

[0073] Wear Test: The coated surface of the sample prepared in Example 1 with a size of 1 cm × 3 cm was placed face to face on 1000-grit sandpaper with a size of 23 cm × 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. After 10 abrasions, the contact angle and sliding angle of the sample were measured. Table 1 shows the contact angle and sliding angle of Example 3 before and after wear.

[0074] Table 1 Contact Angle and Sliding Angle of Example 1 Before and After Wear

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

[0076] As can be seen from Table 1, the contact angles and sliding angles of the samples in Example 1 changed little before and after wear. Similar situations existed for the changes in contact angles and sliding angles before and after wear corresponding to Examples 2-5. For Comparative Example 1, the contact angle and sliding angle before wear were 158° and 1.3° respectively, and the coating lost its superhydrophobic property after wear with a contact angle > 150°. It can be seen from Table 2 that the coatings in Comparative Examples 2-5 did not have superhydrophobic properties, so it was meaningless to study their wear resistance. This shows that the coatings prepared in the examples of the present invention have wear resistance under mechanical wear, thus maintaining the stability of the coating structure.

[0077] (2) De-icing test

[0078] Photothermal anti-icing test: Under the condition of -20°C, the icing process of water droplets on the coated surface of the sample in Example 3 under 1 sunlight irradiation was recorded, that is, the process of water droplets from transparent to opaque was as Figure 1 shown.

[0079] As Figure 1 can be seen, the coating made from Example 3 showed excellent anti-icing ability. The icing time could be extended from 5 s to 230 s, and the anti-icing effect was significantly improved. The passive extended icing times corresponding to Examples 1, 2, 4, and 5 were 195 s, 189 s, 283 s, and 227 s respectively, while those of Comparative Examples 1-5 were extended to 185 s, 101 s, 34 s, 93 s, and 78 s. Since Comparative Example 1 did not have the nanostructure composed of lignin nanobottles and nanosilica, the lack of the nano effect reduced the light absorption rate, resulting in a decrease in the photothermal conversion ability of the coating. For Comparative Examples 2-5, due to the lack of the air cushion formed by the droplets and the coating surface due to the lack of superhydrophobic structure, the thermal conductivity was high, so the anti-icing ability was poor.

[0080] The hydrophobicity of the sample surface was tested using a contact angle measuring instrument OCA50. 3 μL of water droplets were dropped on the sample surface, and their water contact angles were measured. The cross-section of the coating was intercepted using a scanning electron microscope, and the coating thickness was measured using software Nano Measurer1.2. As shown in Table 2, the contact angles, sliding angles, and coating thicknesses of the coatings prepared in the examples and comparative examples of the present invention are presented.

[0081] Table 2 Contact angles, sliding angles, and coating thicknesses of coatings in examples and comparative examples

[0082]

[0083]

[0084] Note: "-" indicates that this data was not measured. The sliding angle usually describes the wettability of superhydrophobic materials. For non-superhydrophobic materials, the sliding angle is usually too large and thus has no measurement significance.

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

[0086] Figure 2 Schematic diagram of the contact angle of the sample prepared for Example 3. As can be seen from Figure 2 it that 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 enables them to roll easily on its surface.

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

[0088] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lignin-based super-hydrophobic coating, characterized in that, The invention comprises the following raw materials by weight: 4-20 parts of diamino-terminated polydimethylsiloxane, 4-20 parts of trimesaldehyde, 3000-4000 parts of organic solvent, 5-20 parts of lignin nanobottle and 5-20 parts of nano silicon dioxide.

2. The lignin-based super-hydrophobic coating according to claim 1, wherein The raw materials include the following by weight: 6-16 parts of diamino-terminated polydimethylsiloxane, 6-16 parts of trimesaldehyde, 3500-3800 parts of organic solvent, 5-10 parts of lignin nanobottle and 5-10 parts of nano silicon dioxide.

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

4. A lignin-based super-hydrophobic coating made from the lignin-based super-hydrophobic coating according to any one of claims 1 to 3, characterized in that, The thickness of the lignin-based super-hydrophobic coating is less than 20 μm, the contact angle is greater than 150°, and the sliding angle is less than 2°.

5. A method for preparing a lignin-based super-hydrophobic coating according to claim 4, characterized in that: The following steps are involved: (1) adding diamino-terminated polydimethylsiloxane and trimesic acid aldehyde into an organic solvent and stirring to react to prepare a mixed solution; (2) adding lignin nanobottles and nano-silica into the mixed solution, stirring and reacting to obtain a super-hydrophobic coating; (3) After the super-hydrophobic coating is sprayed on the surface of the substrate, the lignin-based super-hydrophobic coating is obtained after drying.

6. The method for preparing a lignin-based super-hydrophobic coating according to claim 5, characterized in that: In step (1), the mass ratio of the bisamino-terminated polydimethylsiloxane to trimesic acid is (1-3)-(3-1); The mixing ratio of the trimesaldehyde and the organic solvent is (20-100) mg: 20 mL; The stirring reaction is carried out at a speed of 300-800 rpm and for a time of 0.5-4 h.

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

8. The method for preparing a lignin-based super-hydrophobic coating according to claim 5, wherein: In step (3), the drying is vacuum drying, and the vacuum drying temperature is 50-100°C.

9. Use of the lignin-based super-hydrophobic coating according to claim 4 in hydrophobic deicing, heat transfer, water collection, seawater desalination and precision devices.

10. The use according to claim 9, characterized in that: Application in photothermal superhydrophobic deicing.

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