CN101649065A - Method for preparing pollution preventing self-cleaning polyvinylidene fluoride (PVDF) film and product thereof - Google Patents

Abstract

The invention relates to a preparation method of an antifouling self-cleaning polyvinylidene fluoride film and a product thereof. The preparation method includes the following processes: (1) preparation of PVDF membrane; (2) alkali solution treatment of PVDF membrane: including two processes of alkali-water solution treatment and alkali-alcohol solution treatment: the alkali-water solution treatment process is: the PVDF membrane is immersed In an alkali-water solution with a mass concentration of 20-40%, treat it at 60-80°C for 2-3 hours, take it out, wash it, and dry it; In a 2-10% alkali-alcohol solution, treat at 25-40°C for 3-5 minutes, take out the membrane, wash it with water, and dry it; then soak the PVDF membrane in an appropriate solution and react at 25-60°C for 3-10 minutes. Then take it out, fully wash it with water, and dry it to get it; (3) modify the PVDF membrane with organic silane to prepare the antifouling self-cleaning polyvinylidene fluoride membrane. The antifouling self-cleaning PVDF membrane product is prepared by the preparation method described in the invention.

Description

A preparation method of antifouling self-cleaning polyvinylidene fluoride film and its products

technical field

The invention relates to a preparation technology of an organic film, in particular to a preparation method of an antifouling self-cleaning polyvinylidene fluoride (PVDF) film and a product thereof.

Background technique

Polyvinylidene fluoride (PVDF) is a high molecular weight semi-crystalline organic fluoropolymer that, under certain circumstances, can form microspheres. The PVDF molecular structure only has C-F bonds and C-H bonds in the opposite direction, so PVDF membranes have high chemical inertness and excellent weather resistance, such as resistance to degradation caused by ultraviolet rays and damage to chemical substances in the atmosphere, as well as resistance to algae Bacterial and fungal attack. Due to the small polarizability of C-F bond and short bond distance of fluorine-containing materials, the cohesion of PVDF molecules is small and the surface free energy is low, so it is difficult for various liquids to adhere to its surface. Because PVDF has such excellent properties, it is often used as the surface layer of substrates such as architectural membrane structural materials, glass and textiles to increase the weather resistance of the substrate.

The lotus leaf has the reputation of leaving the mud without staining. Water on the surface of the lotus leaf will automatically gather into free-rolling water droplets. The rolling of the water droplets can take away the surface dust and keep the surface of the lotus leaf clean. The German scientist Professor Barthlott named this anti-fouling and self-cleaning phenomenon of the lotus leaf as "Lotus Effect". If the lotus leaf effect can be applied to the substrate containing PVDF coating, the substrate can maintain self-cleaning only by rainwater washing during use, which can not only make the substrate beautiful and maintain good light transmission performance, but also greatly It saves people's cleaning and maintenance of the substrate surface, which will bring huge economic and social benefits in terms of environmental protection and energy saving. At present, there are few studies on applying the lotus leaf effect to PVDF membranes at home and abroad, and most of them use the method of adding nanoparticles to prepare antifouling and self-cleaning surfaces. However, this method has problems such as easy agglomeration of nanoparticles and lower light transmission performance of PVDF film.

Contents of the invention

Aiming at the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing an antifouling self-cleaning polyvinylidene fluoride film and its products. The preparation method is simple in process, easy to operate, and convenient for industrial implementation, and the prepared polyvinylidene fluoride film has good self-cleaning function, and does not affect the light transmittance of the PVDF film at the same time.

The technical solution of the present invention to solve the technical problem of the preparation method is: to design a preparation method of an antifouling self-cleaning polyvinylidene fluoride film, the preparation method comprising the following processes:

1. Preparation of PVDF membrane: Dissolve PVDF powder in acetone, dimethylformamide or dimethylacetamide solvent, prepare a PVDF solution with a mass fraction of 5-10%, and stir at a constant temperature of 50-70°C for 1 -2h, standing for 30min to defoam, coat the film, and dry it at 90-180℃ to get PVDF film;

2. Alkali treatment of PVDF membrane: including alkali-water solution treatment and alkali-alcohol solution treatment two processes:

The alkali-water solution treatment process is as follows: immerse the PVDF membrane in an alkali-water solution with a mass concentration of 20-40%, treat it at 60-80°C for 2-3 hours, take it out, wash it, and dry it; the alkali-water solution Be NaOH-water solution, LiOH-water solution or KOH-water solution;

Alkali-alcohol solution treatment process is as follows: firstly immerse the PVDF membrane in an alkali-alcohol solution with a mass concentration of 2-10%, treat it at 25-40°C for 3-5min, take out the membrane, wash it with water, and dry it; The film is soaked in a suitable solution at 25-60°C for 3-10 minutes, then taken out, fully washed with water, and dried; the alkali-alcohol solution is NaOH-alcohol solution, LiOH-alcohol solution or KOH-alcohol solution; The appropriate solution refers to a mass concentration (4-8%) KMnO ₄ /(20-30%) KOH-water solution, or a mass concentration of 98% H ₂ SO ₄ solution;

3. Surface modification of PVDF membrane: first dissolve organosilane in organic solvent to make organosilane solution with a volume concentration of 1/10-1/3, and put it in a closed container with a relative humidity of 60-80% for use; The organosilane is at least one of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane and fluoroalkylsilane; the organic solvent is benzene, toluene, ether, divinyl ether or Ethylene oxide; then immerse the PVDF membrane treated with lye in the second step in the organosilane solution in the airtight container, and treat the surface for 20-30min; the treated PVDF membrane is first dissolved with the Wash once with an organic solvent of organosilane, then fully wash with ethanol and ethanol-water solution with a volume ratio of 1:1, and then dry at 100-120°C to obtain the antifouling and self-cleaning PVDF film.

The technical solution of the present invention to solve the technical problem of the product is: to design an antifouling self-cleaning PVDF membrane product, which is made by the antifouling self-cleaning PVDF membrane preparation method described in the present invention.

Compared with the prior art, the preparation method of the present invention innovatively uses strong alkali solution to pre-treat the surface of polyvinylidene fluoride (PVDF) membrane, which improves the grafting performance of PVDF membrane, and then uses organosilane solution to treat the PVDF membrane. Surface modification, the process method is simple, easy to operate, and easy to implement in industry. The surface of the prepared PVDF membrane can form a micro-nano double structure similar to the surface of the lotus leaf. The contact area of the dirt on the surface of this PVDF membrane is small, and the adhesion Very low, it is easy to roll off with water droplets under the rain, has good super-hydrophobic and anti-fouling self-cleaning properties, and does not affect the light transmission of PVDF film.

Description of drawings

Fig. 1 (a) is the photogram of the contact angle between the PVDF membrane surface and water without surface modification;

Figure 1(b) is a photo of the antifouling and self-cleaning effect of the PVDF membrane without surface modification (Figure 1(a) membrane);

Fig. 2 (a) is after the PVDF membrane surface of a kind of embodiment (embodiment 1) of the preparation method of the present invention gains is pretreated by NaOH aqueous solution, and after being modified by organosilane, the photogram of the contact angle with water;

Fig. 2 (b) is the antifouling self-cleaning effect photograph figure of the PVDF film (Fig. 2 (a) film) surface of a kind of embodiment of preparation method gained of the present invention;

Fig. 3 (a) is after the PVDF membrane surface of a kind of embodiment (embodiment 2) of the preparation method of the present invention gains is pretreated by KOH-ethanol solution, and after being modified by organosilane, the photogram of the contact angle with water;

Fig. 3 (b) is the antifouling self-cleaning effect photograph figure of the PVDF membrane (Fig. 3 (a) membrane) surface of a kind of embodiment gained of preparation method of the present invention;

Fig. 4 (a) is the PVDF film surface atomic force microscope picture of the PVDF film surface of a kind of embodiment (embodiment 1 step 1) gained of the preparation method of the present invention;

Fig. 4(b) is an atomic force microscope image of a PVDF membrane surface covered with nanostructures after surface chemical modification of the PVDF membrane obtained in an embodiment (Example 1) of the preparation method of the present invention.

Detailed ways

Further describe the present invention below in conjunction with embodiment and accompanying drawing thereof.

Aiming at the unsatisfactory anti-fouling and self-cleaning performance of PVDF membranes at present, the design idea of the present invention is to apply the principle of "lotus leaf effect" to the preparation method of anti-fouling and self-cleaning PVDF membranes, and use alkaline solution to treat the surface of PVDF membranes. In order to introduce hydroxyl groups on the surface of PVDF membranes, overcome the defects that PVDF membranes have high chemical inertness and do not contain reactive groups, and facilitate the generation of silanol groups produced by the hydrolysis of organosilanes in chemical bath deposition reactions with hydroxyl groups on the surface of PVDF membranes. A new type of anti-fouling and self-cleaning PVDF membrane is made by strong chemical bonding.

The antifouling self-cleaning (or superhydrophobic) PVDF film preparation method (abbreviation preparation method) of the present invention comprises following process:

1. Preparation of PVDF film: Dissolve PVDF powder in a solvent, prepare a PVDF solution with a mass fraction of 5-10%, stir at a constant temperature of 50-70°C for 1-2h, let stand for defoaming for 30min, and coat the film at 90 drying at -180°C to obtain a PVDF membrane; the solvent is acetone, dimethylformamide or dimethylacetamide;

2. Alkali treatment of PVDF membrane: Alkaline treatment of PVDF membrane includes two processes: alkali-water solution treatment and alkali-alcohol solution treatment:

The alkali-water solution treatment process is: immerse the PVDF membrane in an alkali-water solution with a mass concentration of 20-40%, treat it at 60-80°C for 2-3 hours, then take it out, wash it, and dry it, that is, directly introduce hydroxyl groups on the surface of the PVDF membrane. ; The alkali-aqueous solution is NaOH-aqueous solution, LiOH-aqueous solution or KOH-aqueous solution;

Alkali-alcohol solution treatment process is as follows: firstly immerse the PVDF membrane in an alkali-alcohol solution with a mass concentration of 2-10%, treat it at 25-40°C for 3-5min, take out the PVDF membrane, wash it with water, dry it, and then Soak the PVDF membrane in an appropriate solution at 25-60°C for 3-10 minutes, then take out the membrane, wash it thoroughly, and dry it; the alkali-alcohol solution is NaOH-alcohol solution, LiOH-alcohol solution or KOH-alcohol solution , the appropriate solution refers to the mass concentration (4-8%) KMnO ₄ /(20-30%) KOH-water solution, or the concentrated H ₂ SO ₄ solution with a mass concentration of 98%. The principle of this process design is that the PVDF membrane first undergoes the elimination reaction of HF in the alkali-alcohol solution to form a C=C double bond, and then uses the KMnO ₄ /KOH solution or concentrated H ₂ SO ₄ to open the C=C double bond. Hydroxyl groups are introduced into the surface of PVDF membrane. The alkali-alcohol solution treatment process seems more complicated than the alkali-water solution process, but it greatly reduces the amount of alkali and reaction time, and has obvious advantages.

3. Surface modification of PVDF membrane: first dissolve organosilane in organic solvent to make organosilane solution with a volume concentration of 1/10-1/3, and put it in a closed container with a relative humidity of 60-80% for use; The organosilane is at least one of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane and fluoroalkylsilane; the organic solvent is benzene, toluene, ether, divinyl ether or cyclic Oxyethane; then immerse the PVDF membrane treated with lye in the second step in the organosilane solution in the airtight container, and treat the surface for 20-30min; Wash once with an organic solvent, then fully wash with ethanol and ethanol-water solution with a volume ratio of 1:1, and then dry at 100-120°C to obtain the antifouling and self-cleaning PVDF membrane.

The anti-fouling self-cleaning PVDF film product of the present invention is made by the preparation method of the anti-fouling self-cleaning PVDF film of the present invention. The hydrophobic and self-cleaning properties of the PVDF membrane surface are detected by using Young's contact angle and the ash collection experimental test method developed by A.Born of the University of Bonn, Germany. The test results show that the contact angle between the surface of the PVDF membrane prepared by the present invention and water is as high as 155 ° more than (referring to embodiment and accompanying drawing 1-3), have good superhydrophobicity. The droplet is spherical on the surface of the membrane, and the rolling angle is small. When the droplet rolls down, it can easily take away the dirt on the surface of the membrane, showing good antifouling and self-cleaning properties.

Based on the principle of "lotus leaf effect", the present invention adopts PVDF solution coating film to build a micron structure; then treats the PVDF film with appropriate lye to generate hydrophilic groups, and then uses organosilane to undergo hydrolysis polymerization to generate polysiloxane with nanostructure , deposited on the surface of the PVDF membrane, successfully constructing a micro-nano structure double structure similar to the surface of the lotus leaf on the surface of the membrane (see Figure 4), the dirt is not easy to adhere, and the hydrophobicity and self-cleaning function of the PVDF membrane are improved . The preparation method of the invention does not use nanoparticles, and there is no problem that the nanoparticles are easy to agglomerate and reduce the light transmission performance of the PVDF film.

What is not mentioned in the present invention is applicable to the prior art.

Specific examples of the preparation method of the present invention are given below. The specific examples do not limit the invention claims.

Example 1

1. Preparation of PVDF film: Dissolve PVDF powder in dimethylformamide solution, prepare a PVDF solution with a mass fraction of 5%, stir at a constant temperature of 60°C for 2h, let it stand for defoaming for 30min, coat the film, and dry it at 90°C. A PVDF membrane with a micron structure is produced.

2. Alkaline treatment of PVDF membrane: immerse the PVDF membrane in NaOH-water solution with a mass concentration of 35%, treat it at 60°C for 3 hours, then take out the PVDF membrane, wash it with water, and dry it.

3. PVDF membrane surface modification: prepare a toluene solution containing 8% methyltrichlorosilane and 12% dimethyldichlorosilane by volume, put it in an airtight container with a relative humidity of 80% for use, and then put the second Step 2: Immerse the PVDF membrane treated with NaOH solution in the toluene solution in the airtight container, carry out surface treatment for 30min, take out the PVDF membrane after treatment, and use toluene, ethanol and ethanol-water solution with a volume ratio of 1:1 in sequence After fully washing at room temperature and drying at 120°C for 10 minutes, a PVDF membrane with antifouling and self-cleaning functions can be obtained.

In the comparison experiment, the contact angle between the PVDF membrane without surface modification and water is only 88° (see Figure 1(a)), and the dirt on the membrane surface is difficult to roll off with water droplets (see Figure 1(b)). The contact angle of the PVDF film after the surface modification of this embodiment and water is as high as 157 ° (referring to Fig. 2 (a)), the water drop on the surface of the obtained PVDF film is very round, and the contact area with the PVDF film surface is very little; when the PVDF film is inclined ( When the rolling angle) is 1°, the water droplet rolls off the surface rapidly, and the water droplet is still spherical after rolling over a certain distance, and a large amount of dust gathers on the surface of the water droplet, and the surface of the PVDF membrane after the water droplet rolls over is very clean (see Figure 2( b)) shows that the surface of the PVDF membrane of the present invention has a good antifouling and self-cleaning effect.

Example 2

1. Preparation of PVDF membrane: Dissolve PVDF powder in dimethylacetamide solution, prepare a PVDF solution with a mass fraction of 5%, stir at a constant temperature of 70°C for 1.5h, stand for defoaming for 30min, coat the film, and dry at 120°C , to produce a PVDF membrane with a micron structure.

2. Alkaline treatment of PVDF membrane: immerse the PVDF membrane in KOH-ethanol solution with a mass concentration of 5%, and treat it at 40°C for 3 minutes, then take out the PVDF membrane, wash it with water, and dry it; then immerse the PVDF membrane in a mass concentration of 4% KMnO ₄ /30% KOH-water solution, react at room temperature for 10 minutes, take out, wash with water, and dry.

3. PVDF membrane surface modification: prepare a toluene solution containing 7.4% methyltrichlorosilane and 12.6% dimethyldichlorosilane by volume fraction, put it in an airtight container with a relative humidity of 80% for use, and then put the first Step 2: Immerse the PVDF membrane treated with lye in the toluene solution in the airtight container, carry out surface treatment for 20 minutes, take out the treated PVDF membrane, and use toluene, ethanol and ethanol-water with a volume ratio of 1:1 in sequence. Fully wash at room temperature and dry at 100°C for 12 minutes to obtain a PVDF membrane with antifouling and self-cleaning functions.

After testing, the contact angle between the PVDF membrane obtained in this example and water is 155° (see Figure 3 (a)), and when the PVDF membrane is inclined at 4°, water droplets can easily take away the dirt on the membrane surface (see Figure 3 (a)). b)), showing good hydrophobic self-cleaning properties.

Example 3

1. Preparation of PVDF membrane: same as step 1 of embodiment 1.

2. Alkaline treatment of PVDF membrane: immerse the PVDF membrane in LiOH-water solution with a mass concentration of 25%, treat it at 80°C for 2.5h, then take out the PVDF membrane, wash it with water, and dry it.

3. PVDF membrane surface modification: prepare a benzene solution containing 8% volume fraction of FAS[(CF ₃ (CF ₂ ) ₈ (CH ₂ ) ₂ -Si(OCH ₃ ) ₃ ], and place it at a relative humidity of 60% In the airtight container, stand-by, then immerse the PVDF membrane treated with LiOH-water solution in the second step in the benzene solution in the airtight container, carry out surface treatment for 30min, take out the PVDF membrane after treatment, and successively use benzene , ethanol, and ethanol-water solution with a volume ratio of 1:1 were fully washed at room temperature, and dried at 120°C for 10 minutes to obtain a PVDF membrane with antifouling and self-cleaning functions.

After testing, the contact angle between the PVDF membrane obtained in this example and water is 155°; when the PVDF membrane is inclined at 3°, water droplets can easily take away the dirt on the membrane surface, showing good hydrophobic self-cleaning performance.

Example 4

1. Preparation of PVDF membrane: same as step 1 of embodiment 1.

2. Alkaline treatment of PVDF membrane: immerse the PVDF membrane in KOH-methanol solution with a mass concentration of 2%, and treat it at 25°C for 5 minutes, then take out the PVDF membrane, wash it with water, and dry it; then soak the PVDF membrane in 98% concentrated H ₂ SO ₄ solution, react at 60°C for 3 minutes, take it out, wash it with water, and dry it.

3. Surface modification of PVDF membrane: Prepare an ether solution containing 8% methyltrichlorosilane and 20% trimethylchlorosilane by volume fraction, put it in a closed container with a relative humidity of 70%, and put the second Step 2: Immerse the PVDF membrane treated with KOH solution in the diethyl ether solution in the airtight container, carry out surface treatment for 30 minutes, take out the treated PVDF membrane, and use diethyl ether, ethanol and ethanol-water solution with a volume ratio of 1:1 in sequence. After fully washing at room temperature and drying at 110°C for 10 minutes, a PVDF membrane with antifouling and self-cleaning functions can be obtained.

After testing, the contact angle between the PVDF membrane obtained in this example and water is 155°; when the PVDF membrane is tilted at 4°, water droplets can easily take away the dirt on the surface of the membrane, showing good hydrophobic self-cleaning performance.

Example 5

1. Preparation of PVDF membrane: same as step 1 of embodiment 1.

2. Alkaline treatment of PVDF membrane: immerse the PVDF membrane in NaOH-methanol solution with a mass concentration of 10%, and treat it at 30°C for 4 minutes, then take out the PVDF membrane, wash it with water, and dry it; then immerse the PVDF membrane in 8% KMnO ₄ /20% KOH-water solution, react at room temperature for 3 minutes, take out, wash with water, and dry.

3. PVDF membrane surface modification: prepare divinyl ether solution containing 5% methyltrichlorosilane and 6% trimethylchlorosilane by volume fraction, put it in a closed container with a relative humidity of 60% for use, and then put The PVDF membrane treated in the second step is immersed in the divinyl ether solution in the airtight container, and the surface is treated for 25 minutes, and the treated PVDF membrane is taken out, and successively soaked with divinyl ether, ethanol and a volume ratio of 1:1. After fully washing with ethanol-water at room temperature and drying at 120°C for 10 minutes, a PVDF membrane with antifouling and self-cleaning functions can be obtained.

After testing, the contact angle between the PVDF membrane obtained in this example and water is 156°; when the PVDF membrane is tilted at 3°, water droplets can easily take away the dirt on the membrane surface, showing good hydrophobic self-cleaning performance.

Claims (2)

1. the preparation method of a pollution preventing self-cleaning polyvinylidene fluoride (PVDF) film, this preparation method comprises following technology:

(1) preparation of .PVDF film: the PVDF powder is dissolved in acetone, dimethyl formamide or the dimethylacetamide solvent, being mixed with massfraction is the PVDF solution of 5-10%, 50-70 ℃ of following constant temperature stirs 1-2h, standing and defoaming 30min, film, under 90-180 ℃ of condition, dry, promptly obtain pvdf membrane;

(2). alkali lye is handled pvdf membrane: comprise that alkali-aqueous solution is handled and alkali-alcoholic solution is handled two kinds of technologies:

Alkali-aqueous solution treatment process is: pvdf membrane is immersed in alkali-aqueous solution of mass concentration 20-40%, 60-80 ℃ down handle 2-3h after, take out washing, after the oven dry promptly; Described alkali-aqueous solution is the NaOH-aqueous solution, the LiOH-aqueous solution or the KOH-aqueous solution;

Alkali-alcoholic solution treatment process is: earlier pvdf membrane is immersed in alkali-alcoholic solution of mass concentration 2-10%, after handling 3-5min under 25-40 ℃, takes out film, washing, oven dry; Again pvdf membrane is immersed in the suitable solution 25-60 ℃ of reaction 3-10min down, takes out then, fully washing, after the oven dry promptly; Described alkali-alcoholic solution is NaOH-alcoholic solution, LiOH-alcoholic solution or KOH-alcoholic solution; Described suitable solution is meant mass concentration (4-8%) KMnO ₄The H of/(20-30%) the KOH-aqueous solution, or mass concentration 98% ₂SO ₄Solution;

(3) .PVDF film finishing: earlier organosilane is dissolved in the organic solvent, making volumetric concentration is the organosilane solution of 1/10-1/3, is placed in the encloses container that relative humidity is 60-80% stand-by; Described organosilane is at least a in METHYL TRICHLORO SILANE, dimethyldichlorosilane(DMCS), trimethylchlorosilane and the fluoroalkyl silanes; Described organic solvent is benzene, toluene, ether, divinyl ether or oxyethane; Again with (2) step in the pvdf membrane that alkali lye was handled is immersed in organosilane solution in the described encloses container, surface treatment 20-30min; The organic solvent washing that pvdf membrane after the processing is used described dissolving organosilane is at normal temperatures earlier once used 1: 1 ethanol-water solution thorough washing of ethanol and volume ratio respectively again, 100-120 ℃ of oven dry down, promptly makes described anti-fouling and self-cleaning pvdf membrane then.

2. pollution preventing self-cleaning polyvinylidene fluoride (PVDF) film goods, these goods adopt the described pollution preventing self-cleaning polyvinylidene fluoride (PVDF) film preparation method of claim 1 to make.

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