CN117820904A - Simple, environment-friendly and stable starch-enhanced super-hydrophobic coating - Google Patents

Abstract

The present invention discloses a simple, environmentally friendly, stable starch-enhanced super-hydrophobic coating, belonging to the technical field of super-hydrophobic coatings. The present invention hydrophobically modifies silicon dioxide by octadecyl trimethoxysilane, then adds water to cationic starch for gelatinization, further adds tannic acid to the cationic starch solution after gelatinization, and finally adds silicon dioxide with super-hydrophobicity and stirs until uniformly dispersed, to obtain a simple, environmentally friendly, stable starch-based super-hydrophobic coating. The starch-based enhanced super-hydrophobic coating prepared by the present invention has good super-hydrophobicity 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

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

Technical Field

The invention relates to a simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating, belonging to the technical field of super-hydrophobic coatings.

Background technique

Due to the harmful effects of oily wastewater on the environment and human health, green and environmentally friendly oil-water separation materials are constantly attracting attention. Today's oily wastewater treatment materials generally include modified coatings, sponges, textiles and polymer membranes. Among these materials, superhydrophobic coatings with large water contact angles (CA>150°) and small water sliding angles (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/nanostructure (roughness) are two key requirements for achieving superhydrophobic surfaces. Nowadays, with people's increasing attention to pollution problems, the preparation and use of environmentally friendly and biodegradable materials may be an effective way to protect human health and the environment. However, most of the current research on superhydrophobic coatings has a cumbersome preparation process or uses fluorinated reagents to achieve the required low surface energy. Therefore, superhydrophobic coatings with simple preparation processes and environmentally friendly raw materials have good application prospects.

As a non-toxic, widely available, 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 the glucose hydroxyl groups. While retaining the high biocompatibility and hemostatic properties of ordinary starch, cationic starch can maintain a positive charge in 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 of paper and the sewage treatment industry. However, there are few reports on the research and application of cationic starch in super-hydrophobic coatings, and the obtained coatings are not hydrophobic enough due to the hydrophilicity of cationic starch itself.

Silica has the advantages of stable chemical properties, acid resistance, alkali resistance, and high temperature resistance. Since it has a large number of hydroxyl groups on the surface and has high activity, it needs to be hydrophobically modified. At present, the super-hydrophobic modification of silica is often carried out by silanization coupling reaction with different silanes and fluorine-containing reagents to graft hydrophobic groups. Commonly used preparation methods include hydrothermal method, traditional St9ber method, sol-gel method, etc. The preparation process is cumbersome, requires high temperature, time and strong pollution.

Summary of the invention

[technical problem]

The superhydrophobic coating containing starch has poor hydrophobicity;

The existing super-hydrophobic coating preparation process is complicated and cannot be mass-produced.

[Technical solutions]

In order to solve at least one of the above problems, the present invention provides a simple, environmentally friendly, stable starch-enhanced super-hydrophobic coating preparation method. Specifically, the present invention first hydrophobically modifies silicon dioxide with octadecyl trimethoxysilane, then adds water to cationic starch for gelatinization, further adds tannic acid to the cationic starch solution after gelatinization, and finally adds silicon dioxide with super-hydrophobicity to stir until uniformly dispersed, and obtains simple, environmentally friendly, stable starch-enhanced super-hydrophobic coating. The super-hydrophobic coating prepared by the present invention has good super-hydrophobicity and stability. 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.

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

Step 1: Disperse nano-silica in ethanol evenly, add octadecyltrimethoxysilane, adjust the pH of the solution to 2-5, and stir to obtain a super-hydrophobic nano-silica particle solution;

Step 2: Add cationic starch and tannic acid into water, stir, and heat to gelatinize to obtain a mixture;

Step 3: Cool the mixture to room temperature, then add the super-hydrophobic nano-silica particle solution and stir; obtain a super-hydrophobic coating.

In one embodiment, the stirring in step 1 is carried out at 25-45° C. and 200-500 r/min for 1-6 hours.

In one embodiment, in step 1, the usage ratio of nano-silica, octadecyltrimethoxysilane and ethanol is (1-5) g: (0.5-4) g: (10-60) mL.

In one embodiment, the pH of the solution is adjusted in step 1 by using one of dilute hydrochloric acid solution, hydrochloric acid, glacial acetic acid, sulfuric acid, and acetic acid.

In one embodiment, in step 2, the mass ratio of cationic starch, tannic acid, water, and nano-silicon dioxide is (1-5):(0.1-5):(50-500):(1-5).

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

In one embodiment, the heating gelatinization in step 2 refers to heating to 80-95° C. and performing gelatinization reaction for 2-5 hours.

In one embodiment, the stirring in step 3 is at 25-30° C. and 300-800 r/min for 4-12 hours.

The second object of the present invention is to provide a simple, environmentally friendly, stable starch-enhanced super-hydrophobic coating prepared by the above method.

The third object of the present invention is to provide a super hydrophobic material, the surface of which contains the above-mentioned super hydrophobic coating.

The fourth object of the present invention is to provide a method for preparing a super-hydrophobic material, comprising the following steps: spraying the super-hydrophobic coating uniformly onto the surface of a substrate, and drying to obtain a super-hydrophobic material.

In one embodiment, the drying refers to drying at 70-85° C. for 0.5-3 h.

A fifth object of the present invention is to provide the use of the above-mentioned super-hydrophobic coating or super-hydrophobic material in the fields of oil-water separation, anti-icing, waterproofing, anti-fouling or cleaning.

Beneficial effects of the present invention:

(1) The simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating of the present invention is obtained by uniformly mixing cationic starch and tannic acid solution after modifying nano-silicon dioxide with octadecyltrimethoxysilane to obtain super-hydrophobic nano-silicon dioxide. Tannic acid can react with hydrolyzed silica particles and silane through the condensation cross-linking reaction of polyphenol-silanols, thereby successfully grafting a large amount of hydrophobic long carbon chains to achieve super-hydrophobic modification. This process greatly improves the hydrophilicity of cationic starch coating, and overcomes the defects of unstable and easy-to-fall-off traditional hydrophobic coatings.

(2) The super hydrophobic coating prepared by the present invention through simple hydrogen bonding and Schiff base reaction has a simple process, low cost, high production efficiency, and is suitable for industrial production.

(3) The simple, environmentally friendly and stable starch-enhanced super-hydrophobic 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.

(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

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. 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.

Figure 1 is 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 in 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.

FIG2 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 the filter paper.

FIG3 is a diagram of an oil-water separation test after the simple, environmentally friendly, and stable starch-enhanced super-hydrophobic coating obtained in Example 2 is sprayed on filter paper.

Detailed ways

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.

Test Methods:

1. Contact angle test

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.

2. Stability performance test

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°.

The raw materials used in the embodiment:

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

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

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

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

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

Example 1

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

(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.

(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.

Example 2

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

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.

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

Fig. 1 is sprayed with simple environmental protection, stable starch enhanced super-hydrophobic coating filter paper and unsprayed filter paper physical comparison and SEM picture, wherein, (a) is filter paper base paper physical picture, (b) is the filter paper physical picture of spraying super-hydrophobic coating, (c) is the SEM picture of the filter paper spraying super-hydrophobic coating. Fig. 2 is contact angle test sample. Test its contact angle, rolling angle and stability performance (contact angle ≥ 150 ° of cycles), the contact angle of the super-hydrophobic filter paper obtained is 170.8 °, and the rolling angle is 0.4 °; Stability performance experiment shows that the coating hydrophobic angle sprayed on filter paper after five circulation water flow impact experiments is 152.6 °, still with super-hydrophobicity.

Oil-water separation test:

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.

The test process is shown in FIG3 . After separation, the upper layer of the filter paper is water dyed with methyl blue, and the chloroform dyed with Sudan red completely 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.

Example 3

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.

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

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), from the analysis of contact angle, rolling angle and stability performance, the comprehensive performance of the prepared super hydrophobic coating is better.

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

Example 4

The dosage ratios of nano-silicon dioxide, octadecyltrimethoxysilane and ethanol in Example 1 were adjusted to 1.5 g: 1 g: 15.8 mL and 2 g: 1 g: 21 mL, respectively, and other parameters were kept consistent with Example 1 to obtain a simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating.

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

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 2. As can be seen from Table 2, when the dosage ratio of nano-silica, octadecyltrimethoxysilane and ethanol is 1 g: 0.5 g: 10.5 mL (Example 1), the simple, environmentally friendly and stable starch-enhanced super hydrophobic coating prepared has good comprehensive performance in terms of contact angle, rolling angle and stability performance.

Table 2 Test results of Example 4

Example 5

The pH in step (1) of Example 1 was adjusted to 2, 3, and 7, respectively, and the other parameters were kept consistent with Example 1 to obtain a simple, environmentally friendly, and stable starch-enhanced super-hydrophobic coating.

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

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

Table 3 Performance test results of simple, environmentally friendly and stable starch-enhanced superhydrophobic coatings obtained at different pH

It can be seen from Table 3 that when the pH is neutral, the prepared starch-enhanced super-hydrophobic coating has poor hydrophobicity and stability.

Comparative Example 1

The octadecyltrimethoxysilane in step (1) of Example 1 was replaced with vinyltrimethoxysilane, and other parameters were kept consistent with Example 1 to obtain a simple, environmentally friendly, and stable starch-enhanced super-hydrophobic coating.

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

Comparative Example 2

The cationic starch in step (2) of Example 1 was replaced with natural corn starch, and other parameters were kept consistent with Example 1 to obtain a simple, environmentally friendly, and stable starch-enhanced super-hydrophobic coating.

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

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 were tested. The test results are shown in Table 4.

Table 4 Performance test results of super hydrophobic coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for preparing a simple, environmentally friendly and stable starch-enhanced super-hydrophobic coating, comprising the following steps: Step 1: Disperse nano-silica in ethanol evenly, add octadecyltrimethoxysilane, adjust the pH of the solution to 2-5, and stir to obtain a super-hydrophobic nano-silica particle solution; Step 2: Add cationic starch and tannic acid into water, stir, and heat to gelatinize to obtain a mixture; Step 3: Cool the mixture to room temperature, then add the super-hydrophobic nano-silica particle solution and stir; obtain a super-hydrophobic coating. 2. The method according to claim 1, characterized in that, in step 1, the amount ratio of nano silicon dioxide, octadecyltrimethoxysilane and ethanol is (1-5) g: (0.5-4) g: (10-60) mL. 3. The method according to claim 1, characterized in that in step 2, the mass ratio of cationic starch, tannic acid, water and nano-silicon dioxide is (1-5):(0.1-5):(50-500):(1-5). 4. The method according to claim 1, characterized in that the stirring in step 1 is carried out at 25-45°C and 200-500 r/min for 1-6 hours. 5. The method according to claim 1, characterized in that the stirring in step 2 is carried out at 75-95°C and 500-800 r/min for 1-5 hours. 6. 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 hours. 7. A simple, environmentally friendly, stable starch-enhanced super-hydrophobic coating prepared by any one of the methods described in claims 1 to 6. 8. A super hydrophobic material, characterized in that its surface contains the super hydrophobic coating according to claim 7. 9. a preparation method of super hydrophobic material, is characterized in that, comprising the following steps: the super hydrophobic coating according to claim 7 is evenly sprayed onto the substrate surface, dried, and obtained the super hydrophobic material. 10. Application of the super-hydrophobic coating according to claim 7 or the super-hydrophobic material according to claim 8 in the fields of oil-water separation, anti-icing, waterproofing, anti-fouling or cleaning.