CN105797591A - Preparation method of super-hydrophobic polyvinylidene fluoride micro-porous film - Google Patents

Abstract

The invention belongs to the technical field of membrane separation, and specifically relates to a method for preparing a superhydrophobic polyvinylidene fluoride microporous membrane, comprising the following steps: firstly, dispersing graphene and nano silicon dioxide in a polar aprotic solvent, Ultrasonic treatment for 3-20 hours to obtain a dispersion; then dissolve polyvinylidene fluoride and polyvinylpyrrolidone in the dispersion at 20-80°C, stir for 3-48 hours, and then ultrasonically for 1-5 hours to obtain a uniform casting solution; casting The film liquid is scraped by a film scraper to generate a primary film, and the primary film is immersed in a gel bath for 0-3h, then transferred to a deionized water bath for 2-8 days to solidify and form a film, and then dried naturally to obtain a superhydrophobic polymer. Vinylidene fluoride microporous membrane; the method of the present invention is environmentally friendly, the reaction conditions are mild, and the preparation method is simple. It is oily and has good application prospects in the petrochemical field.

Description

A kind of preparation method of superhydrophobic polyvinylidene fluoride microporous membrane

[technical field]

The invention belongs to the technical field of membrane separation, in particular to a preparation method of a superhydrophobic polyvinylidene fluoride microporous membrane.

[Background technique]

Due to the advantages of high separation efficiency, no phase change, simple operation, no secondary pollution, easy recovery of separated products, energy saving and environmental protection, membrane separation technology has been used in water desalination and purification, petrochemical, light industry, textile, food, etc. , biotechnology, medicine and other fields have been applied. Membrane material is the core of membrane separation technology, and its properties and structure play a decisive role in the performance of membrane separation.

Polyvinylidene fluoride (PVDF) is a chain crystalline polymer with -CH2-CF2- as the structural unit. In the crystal structure, the carbon chains are arranged in a zigzag shape, and the hydrogen atoms are After the fluorine atom is replaced, it repels each other with the adjacent fluorine atom, so that the fluorine atom is not in the same plane, and is distributed along the carbon chain as a helix, so the carbon chain is surrounded by a series of stable fluorine atoms. The gap-free space barrier makes it impossible for any atom or group to easily enter its structure and destroy the carbon chain. It is precisely because of this structure that PVDF has excellent chemical stability such as excellent resistance to acids, alkalis, and oxidants, thermal stability, and easy film formation. It is widely used in the preparation of membrane materials, especially in the preparation of microporous membranes. .

The term "superhydrophobic" is understood as meaning a surface feature on which a water drop forms a contact angle with the surface morphology of greater than or equal to 150°. PVDF membrane itself has high hydrophobic properties. In recent years, most researchers tend to modify PVDF membranes to be hydrophilic, ignoring the application of its own hydrophobic properties in petrochemical and other fields, and there are few studies on its hydrophobic properties. .

[Content of the invention]

The purpose of the present invention is to solve the above-mentioned deficiencies, utilize the hydrophobic property of polyvinylidene fluoride, provide a kind of preparation method of superhydrophobic polyvinylidene fluoride microporous membrane, in order to improve the compressive capacity of separation membrane, separation efficiency and use life.

In order to achieve the above purpose, a method for preparing a superhydrophobic polyvinylidene fluoride microporous membrane is designed, which includes the following steps: (1) preparation of graphene and nano silicon dioxide dispersion liquid: first weigh a certain amount of graphene and nano Silica is dispersed in a polar aprotic solvent, and ultrasonically treated for 3-20 hours to obtain a dispersion; (2) Preparation of casting solution: first weigh a certain amount of polyvinylidene fluoride and polyvinylpyrrolidone, and then successively mix the polyvinylidene fluoride and polyvinylpyrrolidone Vinylpyrrolidone and polyvinylidene fluoride are added to the dispersion prepared in step (1) and stirred evenly to obtain a casting solution, and the casting solution is ultrasonically degassed for 1-5 hours for later use; (3) film formation by immersion precipitation phase inversion method: The casting solution prepared in step (2) is scraped by a scraper to form a primary film, and the primary film is immersed in a gel bath. After the film is formed, it is taken out and immersed in deionized water for 2-8 days, during which every 5-12h Change the water once, and finally dry it to obtain a superhydrophobic polyvinylidene fluoride microporous membrane.

Preferably, in step (1), the polar aprotic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or triethyl phosphate.

Further, the weight ratio of polyvinylidene fluoride, polyvinylpyrrolidone, and polar aprotic solvent is (10-18):(2-5):(70-84).

Further, the weight ratio of graphene, nano silicon dioxide and polyvinylidene fluoride is (0.01-0.1):(1-4):(10-18).

Further, in step (2), the stirring temperature is 30-90°C, and the stirring time is 6-48h.

Further, in step (3), the gel bath is a 0.1-60wt% ethanol solution.

Further, in step (3), the immersion time of the nascent film formed by the casting solution is 0-30 min in the gel bath, and 3-7 days in deionized water.

Further, in step (3), the temperature of the gel bath is 20-30°C, and the temperature of the deionized water is 20-40°C.

Compared with the prior art, the present invention has the following advantages:

(1) By controlling the specific gravity of graphene, nano-silica, polyvinylpyrrolidone and polar aprotic solvent, a superhydrophobic polyvinylidene fluoride microporous membrane is prepared, and the contact angle between the surface of the microporous membrane and water is 158±1°, it has good compression resistance and good hydrophobicity and lipophilicity;

(2) Utilizing the hydrophobic properties of polyvinylidene fluoride, the preparation method of the provided superhydrophobic polyvinylidene fluoride microporous membrane can improve the pressure resistance, separation efficiency and service life of the separation membrane;

(3) The method of the present invention is environmentally friendly, has mild reaction conditions and simple preparation methods, and has good application prospects in petrochemical and other fields.

[Description of drawings]

Fig. 1 is the scanning electron micrograph of the upper surface structure of superhydrophobic polyvinylidene fluoride microporous membrane prepared in embodiment 1;

Fig. 2 is the scanning electron micrograph of the upper surface structure of superhydrophobic polyvinylidene fluoride microporous membrane prepared in embodiment 2;

3 is a scanning electron microscope image of the upper surface structure of the superhydrophobic polyvinylidene fluoride microporous membrane prepared in Example 3.

[detailed description]

The invention provides a method for preparing a superhydrophobic polyvinylidene fluoride microporous membrane, comprising the following steps:

(1) Preparation of graphene and nano-silica dispersion liquid: first weigh a certain amount of graphene and nano-silica and disperse them in a polar aprotic solvent, and ultrasonically treat them for 3-20 hours to obtain a dispersion liquid. The non-protic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or triethyl phosphate;

(2) Preparation of casting solution: first weigh a certain amount of polyvinylidene fluoride and polyvinylpyrrolidone, then successively add polyvinylidene and polyvinylidene fluoride to the dispersion prepared in step (1) and stir evenly, The temperature is 30-90°C, the stirring time is 6-48h, and the casting solution is obtained, and the casting solution is ultrasonically degassed for 1-5h for later use, wherein the weight ratio of polyvinylidene fluoride, polyvinylpyrrolidone, and polar aprotic solvent (10-18):(2-5):(70-84), the weight ratio of graphene, nano silicon dioxide and polyvinylidene fluoride is (0.01-0.1):(1-4):(10- 18);

(3) Film formation by immersion precipitation phase inversion method: the casting solution prepared in step (2) is scraped by a film scraper to form a primary film, and the primary film is immersed in the gel bath for 0-30min, the temperature of the gel bath 20-30°C, the gel bath is 0.1-60wt% ethanol solution, after the film is formed, take it out and immerse it in deionized water for 2-8 days, preferably 3-7 days, the temperature of deionized water is 20-40°C, During this period, the water is changed every 5-12 hours, and finally dried to obtain a superhydrophobic polyvinylidene fluoride microporous membrane.

Below in conjunction with specific embodiment, the present invention is further described as follows:

Example 1

(1) Preparation of graphene and nano-silica dispersion liquid: first weigh 10mg of graphene and 1g of nano-silica and disperse them in 70g of N,N-dimethylformamide solvent, sonicate for 8 hours to obtain the dispersion Liquid standby;

(2) Preparation of the casting solution: Weigh 10 g of polyvinylidene fluoride and 2 g of polyvinylpyrrolidone and dissolve them in the dispersion, stir at 60°C for 12 hours, and ultrasonicate for 1 hour to obtain the casting solution;

(3) Film formation by immersion precipitation phase inversion method: scrape the casting solution onto the glass with a film scraper, stay in the air for 10 seconds, then put it into a 40wt% ethanol gel bath and immerse it for 10 minutes, take it out after film formation and immerse it in deionization In the water for 3 days, the water was changed every 6 hours during the period, and finally dried to obtain a superhydrophobic polyvinylidene fluoride microporous membrane. The surface contact angle was measured by the droplet method to be 148°, and the dry film was taken to scan the surface of the membrane with an electron microscope. , to get Figure 1.

Example 2

(1) Preparation of graphene and nano-silica dispersion liquid: first weigh 55mg of graphene and 2.5g of nano-silica and disperse them in 77g of N,N-dimethylformamide solvent, ultrasonically treat for 3h to obtain the dispersion Liquid standby;

(2) Preparation of casting solution: Weigh 14 g of polyvinylidene fluoride and 3.5 g of polyvinylpyrrolidone and dissolve them in the dispersion, stir at 30° C. for 6 hours, and ultrasonicate for 1 hour to obtain the casting solution;

(3) Film formation by immersion precipitation phase inversion method: scrape the casting solution onto the glass with a film wiper, stay in the air for 5 seconds, then put it into a 60wt% ethanol gel bath and immerse it for 30 minutes, take it out after film formation and immerse it in deionization In the water for 2 days, change the water every 6 hours during this period, and finally dry it to obtain a superhydrophobic polyvinylidene fluoride microporous membrane. The surface contact angle measured by the droplet method is 158°, and the dry film is taken to scan the surface of the film with an electron microscope. , to get Figure 2.

Example 3

(1) Preparation of graphene and nano-silica dispersion: first weigh 100mg graphene and 4g nano-silica and disperse them in 84g of triethyl phosphate solvent, ultrasonically treat for 12h, and obtain the dispersion for subsequent use;

(2) Preparation of casting solution: Weigh 18g of polyvinylidene fluoride powder and 5g of polyvinylpyrrolidone and dissolve them in the dispersion, stir at 60°C for 12 hours, and ultrasonicate for 5 hours to obtain the casting solution;

(3) Film formation by immersion precipitation phase inversion method: scrape the casting solution onto the glass with a film scraper, stay in the air for 10s, then put it into a 40wt% ethanol gel bath and immerse it for 20min, take it out and immerse it in deionization after the film is formed In the water for 7 days, change the water every 6 hours during this period, and finally dry it to obtain a superhydrophobic polyvinylidene fluoride microporous membrane. The surface contact angle measured by the droplet method is 142°, and the dry film is taken to scan the surface of the film with an electron microscope. , to get Figure 3.

Example 4

(1) Preparation of graphene and nano-silica dispersion: first weigh 50mg graphene and 2g nano-silica and disperse them in 75g of N,N-dimethylacetamide solvent, ultrasonically treat for 20h to obtain the dispersion spare;

(2) Preparation of casting solution: Weigh 15g of polyvinylidene fluoride and 4g of polyvinylpyrrolidone and dissolve them in the dispersion, stir at 90°C for 12h, and ultrasonicate for 2h to obtain the casting solution;

(3) Film formation by immersion precipitation phase inversion method: scrape the casting solution onto the glass with a film scraper, stay in the air for 10 seconds, then put it into a 40wt% ethanol gel bath and immerse it for 10 minutes, take it out after film formation and immerse it in deionization After 8 days in water, the water was changed every 6 hours during the period, and finally dried to obtain a superhydrophobic polyvinylidene fluoride microporous membrane. The surface contact angle measured by the droplet method was 136°.

Example 5

(1) Preparation of graphene and nano-silica dispersion: first weigh 60 mg of graphene and 2 g of nano-silica and disperse them in 80 g of N-methylpyrrolidone solvent, ultrasonically treat for 18 hours, and obtain the dispersion for subsequent use;

(2) Preparation of casting solution: Weigh 14g of polyvinylidene fluoride and 4g of polyvinylpyrrolidone and dissolve them in the dispersion, stir at 60°C for 48h, and ultrasonically for 1h to obtain the casting solution;

(3) Film formation by immersion precipitation phase inversion method: scrape the casting solution onto the glass with a film scraper, stay in the air for 10 seconds, then put it into a 60wt% ethanol gel bath and immerse it for 10 minutes, take it out after film formation and immerse it in deionization Water for 3 days, during which the water was changed every 6 hours, and finally dried to obtain a superhydrophobic polyvinylidene fluoride microporous membrane. The surface contact angle measured by the droplet method was 138°.

The present invention is not limited by the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the present invention within the scope of protection.

Claims (8)

1. a preparation method of superhydrophobic polyvinylidene fluoride microporous membrane, is characterized in that, comprises the following steps: (1) Preparation of graphene and nano-silicon dioxide dispersion: first weigh a certain amount of graphene and nano-silicon dioxide and disperse them in a polar aprotic solvent, and ultrasonically treat them for 3-20 hours to obtain a dispersion; (2) Preparation of casting solution: first weigh a certain amount of polyvinylidene fluoride and polyvinylpyrrolidone, then successively add polyvinylidene and polyvinylidene fluoride into the dispersion prepared in step (1) and stir evenly to obtain For the casting solution, the casting solution is ultrasonically degassed for 1-5 hours for later use; (3) Film formation by immersion precipitation phase inversion method: the casting solution prepared in step (2) is scraped by a film scraper to form a primary film, and the primary film is immersed in a gel bath. After the film is formed, it is taken out and immersed in deionization Water for 2-8 days, during which the water is changed every 5-12 hours, and finally dried to obtain a super-hydrophobic polyvinylidene fluoride microporous membrane. 2. the preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 1, is characterized in that: in step (1), described polar aprotic solvent is N,N-dimethylformamide , N,N-dimethylacetamide, N-methylpyrrolidone or triethyl phosphate. 3. the preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 1 or 2, is characterized in that: the weight ratio of described polyvinylidene fluoride, polyvinylpyrrolidone, polar aprotic solvent is ( 10-18):(2-5):(70-84). 4. the preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 3 is characterized in that: the weight ratio of described Graphene, nano silicon dioxide, polyvinylidene fluoride is (0.01-0.1) :(1-4):(10-18). 5 . The preparation method of superhydrophobic polyvinylidene fluoride microporous membrane according to claim 4 , characterized in that: in step (2), the stirring temperature is 30-90° C., and the stirring time is 6-48 hours. 6. The preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 5, characterized in that: in step (3), the gel bath is 0.1-60wt% ethanol solution. 7. the preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 6, is characterized in that: in step (3), the nascent membrane that described casting solution forms is 0 in gel bath immersion time -30min, the immersion time in deionized water is 3-7 days. 8. the preparation method of superhydrophobic polyvinylidene fluoride microporous membrane as claimed in claim 7, is characterized in that: in step (3), the temperature of described gel bath is 20-30 ℃, the deionized water The temperature is 20-40°C.