A simple, environmentally friendly and stable starch-enhanced superhydrophobic coating

Abstract

The present invention discloses a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating, belonging to the technical field of superhydrophobic coatings. In the present invention, octadecyltrimethoxysilane is used to hydrophobically modify silica, then cationic starch is gelatinized by adding water, further tannic acid is added to the gelatinized cationic starch solution, and finally superhydrophobic silica is added and stirred until evenly dispersed to obtain a simple, environmentally friendly and stable starch-based superhydrophobic coating. The starch-based enhanced superhydrophobic coating prepared by the present invention has good superhydrophobicity and stability. In addition, the preparation method of the present invention has a simple process, does not require complex synthesis equipment, and can be mass-produced on a large scale.

Description

Technical Field

[0001] The present invention relates to a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating, belonging to the technical field of superhydrophobic coatings. Background Art

[0002] Due to the harmful effects of oily wastewater on the environment and human health, green and environmentally friendly oil-water separation materials have been continuously attracting people's attention. Nowadays, the materials for treating oily wastewater usually include modified coatings, sponges, textiles, polymer membranes, etc. Among these materials, the materials with superhydrophobic coatings having a large water contact angle (CA>150°) and a small water sliding angle (SA<10°) have broad application prospects in a wide range of fields such as anti-icing, self-cleaning and water / oil separation. Low surface energy and hierarchical micro / nano structures (roughness) are two key requirements for achieving superhydrophobic surfaces. Now, with people's increasing emphasis on pollution problems, preparing and using environmentally friendly and biodegradable materials may be an effective method to protect human health and the environment. However, most of the current research and preparation processes for superhydrophobic coatings are cumbersome, or fluorine-containing reagents are used to achieve the required low surface energy. Therefore, superhydrophobic coatings with a simple preparation process and environmentally friendly raw materials have good application prospects.

[0003] As a non-toxic, widely sourced and biodegradable natural material, starch has been used to manufacture many advanced sustainable materials, such as biological probes, organic electronics and energy wheels. Among them, cationic starch is obtained by modifying ordinary starch by introducing quaternary ammonium groups on glucose hydroxyl groups. Cationic starch retains the characteristics of ordinary starch such as high biocompatibility and hemostasis, and can maintain a positive charge within a large pH range. Therefore, it has certain antibacterial properties in a variety of environments and can adsorb substances with opposite charges. At present, cationic starch has been widely used in the surface sizing and coating fields of paper and the sewage treatment industry. However, there are few reports on the research and application of cationic starch in superhydrophobic coatings, and the coatings obtained have insufficient hydrophobicity due to the hydrophilicity of cationic starch itself.

[0004] Silica has the advantages of stable chemical properties, acid resistance, alkali resistance, high temperature resistance, etc. Due to the large number of hydroxyl groups on its surface, it has high activity, so it needs to be hydrophobically modified. At present, the superhydrophobic modification of silica often uses different silanes and fluorine-containing reagents for silanization coupling reactions to graft hydrophobic groups. Commonly used preparation methods include hydrothermal method, traditional Stöber method, sol-gel method, etc. The preparation process is cumbersome, requiring high temperature, time and strong pollution. Summary of the Invention

[0005] [Technical Problem]

[0006] The superhydrophobic coating containing starch has poor hydrophobicity;

[0007] The existing preparation process of superhydrophobic coatings is complex and cannot be mass-produced.

[0008] [Technical Solution]

[0009] To solve at least one of the above problems, the present invention provides a method for preparing a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating. Specifically, in the present invention, silica is hydrophobically modified with octadecyltrimethoxysilane first, then cationic starch is gelatinized by adding water, further tannic acid is added to the gelatinized cationic starch solution, and finally superhydrophobic silica is added and stirred until evenly dispersed to obtain a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating. The superhydrophobic coating prepared by the present invention has good superhydrophobicity and stable performance. The preparation method of the present invention has a simple process, does not require complex synthesis equipment, and can be mass-produced on a large scale.

[0010] The first object of the present invention is to provide a method for preparing a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating, comprising the following steps:

[0011] Step 1: Take nano-silica and disperse it evenly in ethanol, add octadecyltrimethoxysilane, adjust the pH of the solution to 2-5, and stir to obtain a superhydrophobic nano-silica particle solution;

[0012] Step 2: Add cationic starch and tannic acid to water, stir, and heat up to gelatinize to obtain a mixture;

[0013] Step 3: Cool the mixture to room temperature, then add the superhydrophobic nano-silica particle solution and stir to obtain a superhydrophobic coating.

[0014] In one embodiment, the stirring in Step 1 is carried out at 25-45°C and 200-500 r / min for 1-6 h.

[0015] In one embodiment, in Step 1, the dosage ratio of nano-silica, octadecyltrimethoxysilane and ethanol is (1-5) g:(0.5-4) g:(10-60) mL.

[0016] In one embodiment, the pH of the solution in Step 1 is adjusted by using one of dilute hydrochloric acid solution, hydrochloric acid, glacial acetic acid, sulfuric acid, acetic acid.

[0017] In one embodiment, in Step 2, the mass ratio of cationic starch, tannic acid, water and nano-silica is (1-5):(0.1-5):(50-500):(1-5).

[0018] In one embodiment, the stirring described in step 2 is carried out at 75 - 95 °C and 500 - 800 r / min for 1 - 5 h.

[0019] In one embodiment, the heating and gelatinization described in step 2 means heating to 80 - 95 °C and carrying out the gelatinization reaction for 2 - 5 h.

[0020] In one embodiment, the stirring described in step 3 is carried out at 25 - 30 °C and 300 - 800 r / min for 4 - 12 h.

[0021] The second object of the present invention is to provide a simple, environmentally friendly and stable starch - enhanced superhydrophobic coating prepared by the above - mentioned method.

[0022] The third object of the present invention is to provide a superhydrophobic material, the surface of which contains the above - mentioned superhydrophobic coating.

[0023] The fourth object of the present invention is to provide a preparation method of a superhydrophobic material, which comprises the following steps: uniformly spraying the above - mentioned superhydrophobic coating onto the surface of a substrate and drying to obtain the superhydrophobic material.

[0024] In one embodiment, the drying means drying at 70 - 85 °C for 0.5 - 3 h.

[0025] The fifth object of the present invention is to provide the application of the above - mentioned superhydrophobic coating or superhydrophobic material in the fields of oil - water separation, anti - icing, waterproofing, anti - fouling or cleaning.

[0026] The beneficial effects of the present invention:

[0027] (1) The simple, environmentally friendly and stable starch - enhanced superhydrophobic coating of the present invention is obtained by mixing superhydrophobic nano - silica modified by octadecyltrimethoxysilane with cationic starch and tannic acid solution after mixing them evenly. Due to the large number of phenolic hydroxyl groups in tannic acid, it can carry out a poly - phenol - silanol condensation cross - linking reaction with the hydrolyzed silica particles and silane, thereby successfully grafting a large number of hydrophobic long carbon chains to achieve superhydrophobic modification. This process greatly improves the hydrophilicity of the cationic starch coating and overcomes the defects of traditional hydrophobic coatings, such as instability and easy shedding.

[0028] (2) The superhydrophobic coating prepared by the present invention through simple hydrogen - bond binding and Schiff - base reaction has a simple process, low cost and high production efficiency, and is suitable for industrial production.

[0029] (3) The simple, environmentally friendly and stable starch - enhanced superhydrophobic coating of the present invention has high adhesion, stability and good oil - water separation performance due to the introduction of cationic starch and tannic acid.

[0030] (4) The simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating of the present invention has excellent super-hydrophobicity, stability and oil-water separation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 The present invention provides a physical comparison and SEM image of the filter paper sprayed with a simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating and the unsprayed filter paper of Example 2; wherein (a) is a physical image of the filter paper base, (b) is a physical image of the filter paper sprayed with the super-hydrophobic coating, and (c) is an SEM image of the filter paper sprayed with the super-hydrophobic coating.

[0033] Figure 2 This is a contact angle test sample diagram of the simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating obtained in Example 2 after spraying on filter paper.

[0034] Figure 3 This is an oil-water separation test chart after the simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating obtained in Example 2 was sprayed on filter paper. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Test method:

[0037] 1. Contact angle test

[0038] The contact angle and sliding angle of the sample were measured by using a contact angle meter DSA-25. Distilled water was selected as the test liquid, the droplet volume was set to 10μL, and three different positions were selected for measurement on the same sample surface. The average value of the measurement results was taken as the contact angle value.

[0039] 2. Stability performance test

[0040] Cut out a 5cm*2.5cm coated filter paper / glass slide and fix it at an inclined angle of 45°. Then pour about 100mL of water on the coating at 50cm and continuously impact it for 15s. Finally, after drying in an oven to remove surface moisture, test the changes in the hydrophobic angle at different times to test the stability of the superhydrophobic coating until the water droplet contact angle is less than 150°.

[0041] The raw materials used in the embodiment:

[0042] Silicon dioxide: Beijing Inokai Technology Co., Ltd., 20-30nm;

[0043] Octadecyltrimethoxysilane: Nanjing Quanxi Chemical Co., Ltd., 99%;

[0044] Cationic starch: provided by Yueyang Forest and Paper Co., Ltd., degree of substitution: 0.028-0.035;

[0045] Tannic acid: Tannic acid (Shanghai Bailingwei Chemical Technology Co., Ltd., EP);

[0046] Natural corn starch: CAS number: 9005-25-8, content ≥99.5%, moisture: ≤14.0%, acidity: ≤1.8, ash content: ≤0.15%.

[0047] Example 1

[0048] A method for preparing a simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating comprises the following steps:

[0049] (1) 3 g of nano-silica was evenly dispersed in 40 mL of ethanol, and then 1.5 g of octadecyltrimethoxysilane was added. The pH of the solution was adjusted to 5 with a 10% dilute hydrochloric acid solution, and the mixture was stirred at 40° C. and 300 r / min for 2 h to obtain a super-hydrophobic nano-silica particle solution.

[0050] (2) Add 2 g of cationic starch to 50 mL of water, add 0.6 g of tannic acid, stir and gelatinize at 90 ° C and 600 r / min for 3 h, cool to room temperature, add the super-hydrophobic nano-silica particle solution in (1), stir at 30 ° C and 600 r / min for 12 h, and put into a light-proof reagent bottle to obtain a simple, environmentally friendly and stable super-hydrophobic coating.

[0051] Example 2

[0052] A method for preparing a simple, environmentally friendly and stable starch-enhanced super-hydrophobic filter paper comprises the following steps;

[0053] The super-hydrophobic coating in Example 1 was loaded into a spray gun chamber, and then sprayed on filter paper (70 mm) commonly used in the laboratory. The filter paper was dried in an oven at a temperature of 80° C. for 20 minutes to obtain a simple, environmentally friendly and stable super-hydrophobic filter paper.

[0054] The obtained filter paper was subjected to performance test, and the test results are as follows:

[0055] Figure 1The figure shows a physical comparison and SEM image of filter paper sprayed with a simple, environmentally friendly, and stable starch-enhanced superhydrophobic coating and unsprayed filter paper, among which (a) is a physical image of the filter paper base, (b) is a physical image of the filter paper sprayed with the superhydrophobic coating, and (c) is a SEM image of the filter paper sprayed with the superhydrophobic coating. Figure 2 The contact angle test specimen was tested. The contact angle, rolling angle and stability performance (number of cycles with contact angle ≥ 150°) of the obtained super hydrophobic filter paper were 170.8° and 0.4° respectively. The stability performance experiment showed that after five cycles of water flow impact tests, the hydrophobic angle of the coating sprayed on the filter paper was 152.6°, which was still super hydrophobic.

[0056] Oil-water separation test:

[0057] The filter paper prepared in Example 2 was subjected to an oil-water separation test, and the test steps were as follows: the filter paper was placed in a filter, and then a mixed solution containing 50 mL of chloroform (dyed with 0.5 g of Sudan Red III) and water (dyed with 0.5 g of methyl blue) was poured in, and a vacuum pump was used to drive the separation process until the oil and water were completely separated.

[0058] The test process is as follows Figure 3 As shown, after separation, the upper layer of the filter paper is water dyed with methyl blue, and the chloroform dyed with Sudan red all passes through the filter paper and flows into the conical flask. It can be seen that the filter paper prepared in Example 2 has a good oil-water separation effect.

[0059] Example 3

[0060] The addition amounts of tannic acid in Example 1 were adjusted to 1 g and 1.5 g respectively, and other parameters were kept consistent with Example 1 to obtain a simple, environmentally friendly, and stable starch-enhanced super-hydrophobic coating.

[0061] The super hydrophobic filter paper was prepared in the same manner as in Example 2.

[0062] The contact angle, rolling angle and stability performance (number of cycles with contact angle ≥ 150°) of the super hydrophobic filter paper were tested, and the test results are shown in Table 1. As can be seen from Table 1, when the addition amount of tannic acid is 0.6 g (Example 1), the comprehensive performance of the prepared super hydrophobic coating is better from the analysis of contact angle, rolling angle and stability performance.

[0063] Table 1 Performance test results of super hydrophobic coatings obtained with different tannic acid addition amounts

[0064]

[0065] Example 4

[0066] Adjust the dosage ratios of nano-silica, octadecyltrimethoxysilane and ethanol in Example 1 to 1.5 g: 1 g: 15.8 mL and 2 g: 1 g: 21 mL respectively, and keep other parameters the same as those in Example 1, to obtain a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating.

[0067] Prepare superhydrophobic filter paper according to the same method as in Example 2.

[0068] Test the contact angle, rolling angle and stability performance (number of cycles with contact angle ≥ 150°) of the superhydrophobic filter paper. The test results are shown in Table 2. It can be seen from Table 2 that when the dosage ratios of nano-silica, octadecyltrimethoxysilane and ethanol are 1 g: 0.5 g: 10.5 mL (Example 1), the comprehensive performance of the prepared simple, environmentally friendly and stable starch-enhanced superhydrophobic coating is better in terms of contact angle, rolling angle and stability performance.

[0069] Table 2 Test Results of Example 4

[0070]

[0071] Example 5

[0072] Adjust the pH values in step (1) of Example 1 to 2, 3 and 7 respectively, and keep other parameters the same as those in Example 1, to obtain a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating.

[0073] Prepare superhydrophobic filter paper according to the same method as in Example 2.

[0074] Test the contact angle, rolling angle and stability performance (number of cycles with contact angle ≥ 150°) of the superhydrophobic filter paper. The test results are shown in Table 3.

[0075] Table 3 Performance Test Results of Simple, Environmentally Friendly and Stable Starch-Enhanced Superhydrophobic Coatings Obtained at Different pH Values

[0076]

[0077] It can be seen from Table 3 that when the pH is neutral, the hydrophobicity and stability of the prepared starch-enhanced superhydrophobic coating are poor.

[0078] Comparative Example 1

[0079] Replace octadecyltrimethoxysilane in step (1) of Example 1 with vinyltrimethoxysilane, and keep other parameters the same as those in Example 1, to obtain a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating.

[0080] Prepare superhydrophobic filter paper according to the same method as in Example 2.

[0081] Comparative Example 2

[0082] Change the cationic starch in step (2) of Example 1 to natural corn starch, and keep other parameters the same as those in Example 1 to obtain a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating.

[0083] Prepare a superhydrophobic filter paper according to the same method as in Example 2.

[0084] Test the contact angle, rolling angle and stability performance (number of cycles with contact angle ≥ 150°) of the superhydrophobic filter papers of Comparative Examples 1 and 2. The test results are shown in Table 4.

[0085] Table 4 Performance test results of the superhydrophobic coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2

[0086]

[0087] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a simple, environmentally friendly and stable starch-enhanced superhydrophobic coating, comprising the following steps: Step 1: Take nano-silica and disperse it evenly in ethanol, add octadecyltrimethoxysilane, adjust the pH of the solution to 2-5, and stir to obtain a superhydrophobic nano-silica particle solution; Step 2: Add cationic starch and tannic acid to water, stir, and heat up to gelatinize to obtain a mixture; Step 3: Cool the mixture to room temperature, then add the superhydrophobic nano-silica particle solution and stir to obtain a superhydrophobic coating; In Step 1, the dosage ratio of nano-silica, octadecyltrimethoxysilane and ethanol is 3g: 1.5g: 40mL. In Step 2, the dosage ratio of cationic starch, tannic acid, water and nano-silica is 2g: 0.6g: 50mL: 3g.

2. The method according to claim 1, characterized in that, The stirring described in Step 1 is carried out at 25-45 °C and 200-500 r / min for 1-6 h.

3. The method according to claim 1, wherein The stirring described in Step 2 is carried out at 75-95 °C and 500-800 r / min for 1-5 h.

4. The method according to claim 1, characterized in that, In Step 3, the stirring is carried out at 25-30 °C and 300-800 r / min for 4-12 h.

5. A simple, environmentally friendly and stable starch-enhanced superhydrophobic coating prepared by any of the methods described in Claims 1-4.

6. A superhydrophobic material, characterized in that, Its surface contains the superhydrophobic coating described in Claim 5.

7. A preparation method of a superhydrophobic material, characterized in that, Comprising the following steps: Spray the superhydrophobic coating described in Claim 5 evenly onto the surface of the substrate and dry to obtain a superhydrophobic material.

8. The application of the superhydrophobic coating described in Claim 5 or the superhydrophobic material described in Claim 6 in oil-water separation, anti-icing, waterproofing or anti-fouling.

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