Method for preparing polyvinylidene fluoride porous membrane

A technology of polyvinylidene fluoride and porous membrane, which is applied in the direction of chemical instruments and methods, membranes, membrane technology, etc., can solve the problem of unsatisfactory performance and mechanical strength, which affects the application of polyvinylidene fluoride porous membrane, polyvinylidene fluoride Uneven membrane pore structure and other problems, to ensure water flux and strength, improve extensibility and toughness, and good water permeability

Active Publication Date: 2009-02-11
TSINGHUA UNIV
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Problems solved by technology

[0004] The polyvinylidene fluoride porous membrane is prepared by the TIPS method, and the commonly used solvents include phthalates such as dimethyl phthalate or diethyl phthalate, cyclohexanone, 1,4-butyrolactone, etc. etc., but the use of the above-mentioned solvents has a general disadvantage. The pore structure in the polyvinylidene fluoride membrane is not uniform, showing a loose spherical particle packing structure, and there are many large void defects. The performance and mechanical strength of the membrane are not ideal.
U.S.Pat.No. 5022990 and 6299773, in order to improve the loose spherical structure in the film, 20wt% to 30wt% of inorganic particles (such as hydrophobic silica) are mixed in the system, and the pore formation of inorganic particles inhibits the spherical structure. The formation of inhomogeneous voids improves the permeability of the membrane to a certain extent, but this reduces the strength of the membrane, and the process of removing inorganic particles must be added during the membrane making process, which increases the cost.
Chinese patent publication (CN1792420) discloses a polyvinylidene fluoride porous membrane and a preparation method thereof. The method uses benzophenone as a solvent and obtains an ideal uniform sponge-like cross-sectional structure at a low polymer concentration. Within the concentration range of the polymer solution commonly used in the technology (the polymer mass percentage is 30wt.% to 40wt.%), the cross-section of the porous membrane prepared by this method is a block-like close-packed structure, which affects the polyvinylidene fluoride porous membrane. Application in membrane separation technology

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  • Method for preparing polyvinylidene fluoride porous membrane
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  • Method for preparing polyvinylidene fluoride porous membrane

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[0030] The preparation method of polyvinylidene fluoride porous membrane of the present invention is carried out according to the following steps:

[0031] 1) mixing polyvinylidene fluoride resin with diluent; wherein the mass percentage of polyvinylidene fluoride is 30wt%-60wt%, and the mass percentage of diluent is 70wt%-40wt%;

[0032] 2) Put the mixture in step 1) into a high-temperature stirred tank, heat up to 160°C-220°C to form a polymer homogeneous solution, and let it stand for defoaming;

[0033] 3) The polymer homogeneous solution in step 2) is directly scraped and coated on the support net to form a flat membrane or spun into a hollow fiber membrane through a spinneret, and then the obtained flat membrane or hollow fiber membrane is immersed in a cooling liquid to cool, Make the film-forming solution undergo phase separation, and finally solidify to form a film;

[0034] 4) Extracting the diluent in the membrane obtained in step 3) with an alcohol or ether extrac...

Embodiment 1

[0047] The weight average molecular weight is 370,000 polyvinylidene fluoride resin and diphenyl carbonate, its composition is that the mass percentage of polyvinylidene fluoride resin is 30wt%, and the mass percentage of diphenyl carbonate is 70wt%, put into Heat up to 220°C in a high-temperature stirred tank, stir and mix evenly to form a homogeneous polymer solution, and let stand for 24 hours. Then, the polymer homogeneous solution was directly scraped on the support net to form a flat film with a film thickness of 200 μm, and immersed in a cooling liquid bath at 30 ° C to solidify the solution into a film by phase separation. The cooling liquid bath was a water bath. The cured flat film was extracted with ethanol and dried.

[0048] The cross section of the membrane has a uniform spongy structure with no obvious skin structure on the surface. The membrane pore diameter is about 0.8 μm, the porosity is 76%, the breaking strength is 5.5MPa, the elongation at breaking is 30%...

Embodiment 2

[0050] The weight average molecular weight is 800,000 polyvinylidene fluoride resin and diphenyl carbonate, its composition is that the mass percent composition of polyvinylidene fluoride resin is 40wt%, and the mass percent composition of diphenylcarbonate is 60wt%, put into Heat up to 200°C in a high-temperature stirred tank, stir and mix evenly to form a homogeneous polymer solution, and let stand for 24 hours. Then, the polymer homogeneous solution was directly scraped on the support net to form a flat film with a film thickness of 200 μm, and immersed in a cooling liquid bath at 60 ° C to solidify the solution into a film by phase separation. The cooling liquid bath was a water bath. The cured flat film was extracted with ethanol and dried.

[0051] The cross-section of the membrane is a uniform sponge-like structure, the pore diameter of the membrane is about 0.6μm, the porosity is 70%, the breaking strength is 6.7MPa, the elongation at breaking is 36%, and the pure wate...

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Abstract

The invention discloses a method for preparing a polyvinylidene fluoride porous membrane and relates to a method which makes use of a thermally induced phase separation method to prepare the polyvinylidene fluoride porous membrane. The method comprises the following steps: polyvinylidene fluoride with the weight percentage of 30wt-60wt and diphenyl carbonate with weight percentage of 70wt to 40wt or a composite thinner containing diphenyl carbonate with weight percentage of 70wt to 40wt are added into a high temperature resistant container, heated, rested and defoamed to prepare a polymer homogeneous film-casting solution; the film-casting solution is directly coated on a flat membrane formed by supporting network or spinned into hollow fiber by a spinneret, and then the flat membrane or the hollow fiber is immersed into cooling liquid to be treated with curing and the membrane is formed; the formed membrane is put into an extractant to extract the solvent, therefore, the polyvinylidene fluoride porous membrane is obtained. The method is characterized in that: the method adopts the diphenyl carbonate or the thinner taking the diphenyl carbonate as a main component to prepare the polyvinylidene fluoride porous membrane, the section structure of which is in communicating spongy structure, and the membrane has large water flux, high strength and good toughness.

Description

technical field [0001] The invention relates to a method for preparing a polyvinylidene fluoride porous membrane, in particular to a method for preparing a polyvinylidene fluoride porous membrane by using a thermally induced phase separation method using diphenyl carbonate or a diphenyl carbonate-based diluent , belonging to the field of polymer material science and technology. Background technique [0002] Membrane separation technology has attracted increasing attention due to its energy saving, simple equipment, convenient operation, and no pollution, and has become an effective technology to replace traditional separation methods. Membrane materials in membrane separation technology involve polymer chemistry and polymer physics, and the development of membrane materials is a key aspect of membrane separation technology. [0003] Polyvinylidene fluoride is a thermoplastic semi-crystalline high polymer, which is formed by homopolymerization of vinylidene fluoride or copol...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D71/34B01D69/06B01D69/08
CPCB01D71/34B01D2323/12B01D67/002
Inventor 王晓琳林亚凯唐元晖杨健尚伟娟
Owner TSINGHUA UNIV
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