CN1594405A - Method for making PH value-sensitive polyvinylidene fluoride hollow fibre intelligent film and products thereby - Google Patents

Abstract

The invention relates to a preparation method and product of a pH-sensitive PVDF hollow fiber smart membrane, which is obtained by chemical grafting and copolymerization of AAC on the surface of the PVDF membrane, including: (1) pure water moistening membrane: soaking the membrane in pure water (2) Alkali treatment membrane: prepare a 10-20% alkali solution, add 3-4g/L tetrabutylammonium bromide, put the soaked membrane into the alkali solution, and put it in a water bath Heat at 50-80°C for 1-20 minutes, then wash and set aside; alkaline solution refers to one of KOH, NaOH or LiOH; (3) Manufacture of composite membrane: prepare 1-2mol/L AAC solution, and press 40-50ml/ Add dimethylformamide solution to L and mix evenly; put the alkali-treated membrane into _{the mixed} solution and soak at room temperature for _10-20 minutes; ~0.3g solution, put the ready-to-use membrane into the solution, fill it with N ₂ and seal it, heat it in a water bath to 50-80°C for 10-20 minutes and wash it with deionized water; the cross-linked The agent is MBAA or glycol bisacrylate.

Description

Preparation method and product of pH-sensitive polyvinylidene fluoride hollow fiber smart membrane

technical field

The invention relates to a smart membrane and a preparation method thereof, specifically a preparation method of a pH-sensitive polyvinylidene fluoride hollow fiber smart membrane obtained by grafting and copolymerizing acrylic acid monomers and polyvinylidene fluoride (PADF) membranes and The product technology belongs to the field of functional polymer materials, and the international patent classification number is proposed to be Int.C1 ⁷ C08F 20/54.

Background technique

Membrane is the core of membrane technology. The chemical properties of the membrane material and the membrane structure play a decisive role in the membrane separation process. Membrane materials must have the following basic functions: good selective permeability; certain hydrophobicity or hydrophilicity; excellent chemical resistance and biodegradation resistance, which can be used for a long time without deterioration; good heat resistance; Mechanical strength and good processability. Smart film refers to a new type of film that can perceive and accept external environmental information such as sound, light, electricity, magnetism, pH value, temperature, etc., and can automatically change its own state and respond according to changes in environmental information. It is a new type of membrane research, and its characteristic is that it can not only judge the environment, but also adapt to the environment, so as to achieve selective permeability to different substances in different environments. At present, smart membrane has been the focus of research at home and abroad.

Polyvinylidene fluoride (PVDF) hollow fiber membrane has the characteristics of large specific surface area, good tensile strength, impact strength and wear resistance, and also has excellent weather resistance and chemical stability. Corrosion by strong oxidants such as acids and alkalis and halogens, it is also stable to organic solvents such as aliphatic hydrocarbons, aromatic hydrocarbons, alcohols and aldehydes. Polyvinylidene fluoride hollow fiber smart membrane is a type of polyvinylidene fluoride hollow fiber membrane, and it is also a variety of smart membrane. The pH-sensitive polyvinylidene fluoride hollow fiber smart membrane is a kind of polyvinylidene fluoride hollow fiber smart membrane that actively responds to or changes in the pH value of the external environment. It has the characteristics of polyvinylidene fluoride hollow fiber membranes and It also has the characteristics and functions of smart membranes.

Although the polyvinylidene fluoride hollow fiber membrane has many advantages, due to its strong hydrophobicity, when it is used for the separation of aqueous phase systems (such as oil-water separation, protein material separation), adsorption pollution will still occur, resulting in a decrease in membrane flux. , The reduction of membrane separation efficiency is a major weakness of polyvinylidene fluoride hollow fiber membranes, and it cannot meet the requirements of some special membrane processes and special fields. Therefore, many scholars at home and abroad have begun to develop composite membranes with PVDF as the base membrane, that is, composite a layer of PVDF on the porous PVDF base membrane to improve the hydrophilicity of the membrane surface or improve the selective permeation performance of the base membrane. membrane. At present, most of the materials used to improve the ultra-thin surface layer of the hydrophilic composite membrane of PVDF base membrane are compounds with hydrophilic groups, such as: esters, amines, etc. Acrylic falls into this category.

At present, there are mainly the following methods for preparing PVDF smart composite membranes with PVDF as the base membrane reported in the literature:

1. Plasma grafting modification method of PVDF microporous membrane

This is a technique for modifying microporous membranes by plasma surface grafting. The first step is to use corona discharge or glow discharge to form active center free radicals on the surface of the film, and then the free radicals initiate the polymerization of olefin monomers. Pen Wang et al. used plasma technology to graft polyethylene glycol (PEG) on the surface of PVDF microporous membranes and found that PEG chains can not only be grafted to the surface of PVDF microporous membranes, but also grafted to PVDF microporous membranes. On the inner wall of the membrane micropores, so that the microporous membrane has a stronger hydrophilicity. (see Document 1: Research on grafting polyethylene glycol (PEG) modification on the surface of PVDF microporous membrane with plasma technology, (Peng Wang, Tan K L, Kang E T, et al.Plasma-induced immobilization of poly(ethylene glycol)onto poly(vinylidene flouride)microporous membrane.J Membr Sci, 2002,195:103-114)

2. Irradiation graft modification method of PVDF microporous membrane

This is a technology that utilizes high-energy ray irradiation grafting to modify microporous membranes. Studies have shown that high-energy ray irradiation can replace catalysts to make initiators form free radical active centers on molecular chains on the polymer surface. The active center can initiate the graft polymerization of polymerizable monomers such as olefins on the surface of the polymer. The characteristic of irradiation grafting modification is that the grafting reaction can be carried out at room temperature, the post-treatment is simple, and there is no pollution to the environment. Lu Xiaofeng et al. used Co-60γ-ray pre-irradiation activated PVDF membrane to polymerize styrene monomer in a gas phase medium reactor to obtain a PVDF membrane grafted with a certain length of polystyrene (PS) chains on the surface, and then use the benzene in the PS chain to The reactivity of the ring, using 5g/L silver sulfate as a catalyst, sulfonated the grafted membrane in 9.8mol/L concentrated sulfuric acid to obtain a PVDF microporous membrane modified by hydrophilization of the surface sulfonic acid groups, the contact with water The angle decreased from 68 before modification to 58 after sulfonation modification. Concentration is that 0.5g/L bovine serum albumin interception rate improves from 97.8% to 99.2%, has improved the antipollution ability of PVDF membrane simultaneously, and pollution degree drops nearly 10 percentage points (referring to document 2: Lu Xiaofeng, Wang Yihua, Liang Guoming, Research on irradiation graft modification of polyvinylidene fluoride ultrafiltration membrane, Membrane Science and Technology, 1998, 18(6): 54~57).

3. Photoinitiated grafting modification method of PVDF microporous membrane

This is a technology that utilizes photoinitiated grafting to modify microporous membranes. Photoinitiated grafting, especially the method of ultraviolet photoinitiated grafting, is another kind of grafting modification that can form organic active centers on the surface of polymers besides plasma and high-energy rays, thereby initiating graft polymerization modification on the surface of polymers. technology. It is characterized by easy measurement and control, pure product, and can be carried out at a relatively low temperature. It is a widely used basic method for surface modification. Swanson, Melvin J. Use photochemical methods to improve the surface properties of polymers, increase hydrophilicity, to form permanent wettability or introduce some reactive functional groups, and reduce the hydrophobic membrane surface to protein At the same time of adsorption, the adhesion performance of PVDF film to some materials is improved (see Document 3: A photochemical method to improve the surface properties of polymers, (Swanson MelvinJ, A unique photochemical approach for polymer surface modification[J] Polym .Surface.Interfaces [Porc.Symp.] 1995:19-25).

It can be seen from the above several existing composite membrane preparation methods that the main purpose of preparing a composite membrane with PVDF as the base membrane is to modify the PVDF membrane, that is, to graft some hydrophilic groups on the surface of the PVDF membrane. group to improve the hydrophilicity of the membrane, but the composite membrane itself is not intelligent. There is no report about the intelligent composite membrane which can not only improve the hydrophilicity of the PVDF hollow fiber membrane, but also make it pH-sensitive.

Contents of the invention

Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a pH-sensitive polyvinylidene fluoride hollow fiber smart membrane and its products. The intelligent film preparation method has the characteristics of good controllability, simple process, low cost, no need for special equipment, easy industrial implementation and the like. This smart membrane product can not only improve the hydrophilicity of PVDF membrane, and the membrane flux does not change much, but also is a new type of PVDF smart membrane that can respond sensitively to changes in environmental pH.

The technical solution of the present invention to solve the technical problem of the product preparation method is: to design a method for preparing a pH-sensitive polyvinylidene fluoride hollow fiber smart membrane, which is carried out by acrylic acid on the surface of the polyvinylidene fluoride hollow fiber membrane. Gained by chemical graft copolymerization, comprising the steps of:

(1) Pure water soaking membrane: Soak the dry polyvinylidene fluoride hollow fiber membrane in pure water for more than 24 hours, so that the surface of the membrane pores is completely infiltrated by water;

(2) Alkali treatment membrane: prepare 10-20% alkali solution, add 3-4g/L tetrabutylammonium bromide into it, put the soaked polyvinylidene fluoride hollow fiber membrane into the prepared In the alkali solution, the reaction is heated in a water bath, the reaction temperature is 60-80°C, and the reaction time is 1-20min; the membrane after the alkali treatment is washed with pure water for use; the alkali solution refers to potassium hydroxide, sodium hydroxide or one of the lithium hydroxide solutions;

(3) Manufacture of composite membrane: prepare 1-2mol/L acrylic acid solution, add dimethylformamide solution at 40-50ml/L and mix evenly; put the alkali-treated polyvinylidene fluoride hollow fiber membrane into the Soak in the mixed solution at room temperature for 10 to 20 minutes; prepare a solution containing 0.01 to 0.09 mol/L of cross-linking agent diene compounds and 0.1 to 0.3 g of initiator potassium persulfate, and make polyvinylidene fluoride treated with acrylic acid solution Put the hollow fiber membrane into the prepared solution, fill it with nitrogen, seal it, heat it in a water bath to 60-80°C, and react for 10-20 minutes; after the composite membrane obtained is repeatedly cleaned with deionized water, the sensitive polyvinylidene fluoride can be obtained Hollow fiber smart membrane; the diene compound is methylene bisacrylamide or ethylene glycol diacrylate.

The technical solution of the present invention to solve the technical problems of the product is to design a pH-sensitive polyvinylidene fluoride hollow fiber smart membrane, which is characterized in that the smart membrane is chemically grafted on the surface of the polyvinylidene fluoride membrane by acrylic acid Copolymerized. The chemical graft copolymerization method is specified by the preparation method described in the present invention.

The preparation method of the pH-sensitive polyvinylidene fluoride hollow fiber smart membrane of the present invention is simple in process and can be carried out under normal pressure. The basic equipment that a chemical plant should have, so it can carry out industrial continuous production without additional equipment, so it has the characteristics of easy industrialization implementation.

Compared with products in the prior art, the pH-sensitive polyvinylidene fluoride hollow fiber intelligent membrane of the present invention has the advantages of large flux, low filtration pressure, easy cleaning and the like. This is because after the polyvinylidene fluoride hollow fiber membrane is treated with strong alkali, the elimination reaction can occur on the surface of the membrane, so that the pores of the membrane can expand to a certain extent, and the flux becomes larger, but as the acrylic acid is grafted on the surface of PVDF, The membrane pores basically returned to the original size, so the flux of the PVDF membrane did not change much after grafting. Since the intelligent composite film sensitive to pH value of the present invention is prepared by combining acrylic acid (AAC) with the base film through chemical bonds, and acrylic acid has hydrophilic groups such as COOH, the product of the present invention not only improves PVDF The hydrophilicity of the membrane makes up for the defects of PVDF itself, and can make the pore size of the PVDF membrane change with the change of the pH value. new smart membrane.

Detailed ways

Further describe the present invention below in conjunction with embodiment:

The invention is a pH-sensitive or responsive PVDF hollow fiber intelligent membrane and a preparation method thereof. The smart membrane uses a polyvinylidene fluoride hollow fiber porous membrane (hereinafter referred to as PVDF membrane) as a base membrane, and adopts acrylic acid and its interface cross-linking polymerization method to prepare a pH-sensitive smart composite membrane. The design principle is that after the PVDF membrane is treated with the above-mentioned strong alkali, C=C double bonds with certain reactivity can be generated on the molecular chain, and grafting or crosslinking reactions can be directly carried out, and the interfacial polymerization is limited to the base membrane The surface of the material is carried out, and the body of the base film does not participate in the reaction, so the excellent performance of the base film body is not affected. The resulting long-chain molecules or gel layer have special properties of pH environmental response. The preparation method of the present invention specifically selects the method of combining the acrylic acid monomer and the PVDF base film through chemical bonds to graft, and then prepares a PVDF intelligent composite film with pH value sensitivity or response. Because acrylic acid has hydrophilic groups such as carbonyl and amine groups, the product of the present invention can not only improve the hydrophilicity of the PVDF membrane, but also the membrane flux of the grafted PVDF membrane does not change greatly, and the PVDF membrane has relatively Good tensile strength, impact strength and wear resistance, also has excellent weather resistance and chemical stability, especially the pore size of PVDF smart membrane can change with the pH value, by adjusting the pH value can be achieved only A membrane that can fractionate mixtures of different molecular weights is a new type of intelligent composite membrane.

In the alkali treatment solution of the present invention, except adding a small amount of tetrabutylammonium bromide, it should not contain oxidants such as K ₂ MnO ₄ to ensure that the C=C double bonds formed on the surface of the PVDF membrane are not oxidized. This is because after PVDF is treated with a strong alkali, an elimination reaction will occur, that is, a carbon-carbon double bond will be formed on the surface of PVDF, so that it is possible to react with a cross-linking agent with a double bond and a grafted monomer. A strong oxidant will oxidize the carbon-carbon double bond formed on the surface of PVDF to form a carbonyl or carboxyl group. In this way, it is impossible to react with the crosslinking agent and the monomer, and it is impossible to make a PVDF smart film.

In the process of manufacturing the composite membrane described in the present invention, the obtained composite membrane should be cleaned repeatedly with deionized water, so as to remove unreacted small molecules.

Although the preparation method described in the present invention preferably uses PVDF hollow fiber membranes as base membranes, it is equally applicable to other types of base membranes, including flat membranes, tubular membranes and other types of PVDF membranes, and to manufacture corresponding PVDF membranes. smart film.

Introduce the specific embodiment of the present invention below:

Example 1:

(1) Pure water soaking membrane: Soak the dry polyvinylidene fluoride hollow fiber membrane in pure water for 24 hours, so that the surface of the membrane pores is completely infiltrated by water;

(2) Alkali-treated membrane: 500 ml of KOH solution with a concentration of 70 g was prepared, and 1.7 g of tetrabutylammonium bromide was added to the solution. Put the PVDF membrane into the prepared alkali solution, heat it in a water bath, the reaction temperature is 50°C, and the reaction time is 20 minutes. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use;

(3) Manufacture composite membrane: prepare 200ml of acrylic acid solution with a concentration of 1mol/L, add 10ml of dimethylformamide solution and mix evenly; put the PVDF hollow fiber membrane treated with alkali into the mixed solution, soak at room temperature for 15 minutes;

Prepare 100ml of a solution containing 0.1g of crosslinking agent N,N-methylenebisacrylamide (MBAA) and 0.1g of initiator potassium persulfate (K ₂ S ₂ O ₈ ); , filled with N ₂ and then sealed, heated to 50°C in a water bath, and reacted for 10 minutes; after the composite membrane obtained was repeatedly cleaned with deionized water, the PVDF smart membrane sensitive to the pH value of the product of the present invention can be obtained.

Example 2:

(1) with embodiment 1;

(2) Alkali-treated membrane: 500 ml of KOH solution with a concentration of 60 g was prepared, and 2 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 80°C, and the reaction time is 1min. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use.

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 1.5 mol/L, add 10 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 10 minutes. Prepare 100 ml of a solution containing 0.1 g of cross-linking agent N,N-methylenebisacrylamide (MBAA) and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 60°C, and react for 15 minutes. The resulting composite membrane was washed repeatedly with deionized water to remove unreacted small molecules. The pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Example 3:

(1) with embodiment 1;

(2) Alkali-treated membrane: 500 ml of KOH solution with a concentration of 50 g was prepared, and 1.5 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 70°C, and the reaction time is 10 minutes. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use;

(3) Manufacture of composite membrane: Prepare 200 ml of acrylic acid solution with a concentration of 1.5 mol/L, add 8 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 10 minutes.

Prepare 100 ml of a solution containing 0.5 g of cross-linking agent N,N-methylenebisacrylamide (MBAA) and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 60°C, and react for 20 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Example 4:

(1) with embodiment 1;

(2) Alkali-treated membrane: 500 ml of KOH solution with a concentration of 50 g was prepared, and 2 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 60°C, and the reaction time is 20 minutes. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use.

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 2 mol/L, add 9 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak for 17 minutes at room temperature.

Prepare 100 ml of a solution containing 1.0 g of cross-linking agent N,N-methylenebisacrylamide (MBAA) and 0.3 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 80°C, and react for 15 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the present invention can be obtained.

Example 5:

(1) with embodiment 1;

(2) with embodiment 3;

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 1.7 mol/L, add 10 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 20 minutes.

Prepare 100 ml of a solution containing 1.4 g of cross-linking agent N,N-methylenebisacrylamide (MBAA) and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 70°C, and react for 12 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Embodiment 6:

(1) with embodiment 1;

(2) Alkali-treated membrane: 500 ml of NaOH solution with a concentration of 60 g was prepared, and 1.7 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 65°C, and the reaction time is 7 minutes. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use.

(3) with embodiment 4.

Embodiment 7:

(1) with embodiment 1

(2) Alkali-treated membrane: 500 ml of LiOH solution with a concentration of 60 g was prepared, and 1.7 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 60°C, and the reaction time is 8 minutes. After the alkali treatment, the LiOH on the PVDF surface was washed with pure water for use.

(3) with embodiment 4.

Embodiment 8:

(1) with embodiment 1;

(2) with embodiment 3;

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 1.5 mol/L, add 9 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 10 minutes;

Prepare 100 ml of a solution containing 0.15 g of crosslinking agent ethylene glycol diacrylate and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 70°C, and react for 17 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Embodiment 9:

(1) with embodiment 1;

(2) Alkali-treated membrane: 500 ml of KOH solution with a concentration of 60 g was prepared, and 1.7 g of tetrabutylammonium bromide was added to the solution. Put the PVDF hollow fiber membrane into the prepared alkali solution, heat in a water bath, the reaction temperature is 60°C, and the reaction time is 15 minutes. After alkali treatment, wash the KOH on the surface of PVDF with pure water for use.

(3) Manufacture of composite membrane: Prepare 200 ml of acrylic acid solution with a concentration of 1.7 mol/L, add 8 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 10 minutes.

Prepare 100 ml of a solution containing 1.5 g of crosslinking agent ethylene glycol diacrylate and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, put it in a water bath at 70°C, and react for 15 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Implementation 10:

(1) with embodiment 1;

(2) with embodiment 9;

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 1.2 mol/L, add 10 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak for 17 minutes at room temperature.

Prepare 100 ml of a solution containing 0.6 g of crosslinking agent ethylene glycol diacrylate and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 60°C, and react for 15 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Example 11:

(1) with embodiment 1;

(2) with embodiment 9;

(3) Manufacture of composite membrane: prepare 200 ml of acrylic acid solution with a concentration of 1.5 mol/L, add 9 ml of dimethylformamide solution and mix well. Put the alkali-treated PVDF hollow fiber membrane into the mixed solution and soak at room temperature for 10 minutes.

Prepare 100 ml of a solution containing 1 g of crosslinking agent ethylene glycol diacrylate and 0.2 g of initiator potassium persulfate (K ₂ S ₂ O ₈ ). Put the fiber membrane treated with acrylic acid into the solution, fill it with N ₂ and seal it, heat it in a water bath to 60°C, and react for 16 minutes. After the obtained composite membrane is cleaned with deionized water, the pH-sensitive PVDF smart membrane of the product of the present invention can be obtained.

Claims (3)

1. the preparation method of the responsive polyvinylidene difluoride (PVDF) tubular fibre intelligence film of a pH value, this method is to carry out chemical graft copolymerization gained by vinylformic acid on polyvinylidene difluoride (PVDF) hollow-fibre membrane surface, comprises the steps:

(1) pure water soaks into film: with exsiccant polyvinylidene difluoride (PVDF) hollow-fibre membrane, be immersed in the pure water more than 24 hours, the fenestra surface is soaked into fully by water;

(2) alkaline purification film: the alkaline solution of preparation 10～20%, and add the Tetrabutyl amonium bromide of 3～4g/L therein, the polyvinylidene difluoride (PVDF) hollow-fibre membrane that soaked is put into the alkaline solution that is prepared, heating in water bath for reaction, temperature of reaction is 60～80 ℃, and the reaction times is 1～20min; Film after alkaline purification pure water cleaned standby seam; Described alkaline solution is meant a kind of in potassium hydroxide, sodium hydroxide or the lithium hydroxide solution;

(3) make composite membrane: prepare the acrylic acid solution of 1～2mol/L, and mix by 40～50ml/L adding dimethyl formamide solution; To put into described mixing solutions through the polyvinylidene difluoride (PVDF) hollow-fibre membrane of alkaline purification, soaking at room temperature 10～20 minutes; Preparation contains the solution of linking agent double vinyl compound 0.01～0.09mol/L and initiator potassium persulfate 0.1～0.3g, to put into the solution that is disposed through the polyvinylidene difluoride (PVDF) hollow-fibre membrane that acrylic acid solution is handled, seal behind the inflated with nitrogen, reacted 10～20 minutes heating in water bath to 60～80 ℃; After the gained composite membrane cleans up repeatedly with deionized water, can obtain temperature sensitive polyvinylidene difluoride (PVDF) tubular fibre intelligence film; Described double vinyl compound is methylene-bisacrylamide or two vinylformic acid glycol ester.

2. according to the preparation method of the responsive polyvinylidene difluoride (PVDF) tubular fibre intelligence film of the described pH value of claim 1, it is characterized in that the used alkaline solution of this preparation method is a potassium hydroxide solution: used linking agent is a methylene-bisacrylamide.

3. the polyvinylidene difluoride (PVDF) tubular fibre intelligence film that the pH value is responsive is characterized in that the responsive polyvinylidene difluoride (PVDF) tubular fibre intelligence film of this pH value is made by method according to claim 1 and 2.