Method for preparing polyvinylidene fluoride ultra-filtration membranes

A technology of polyvinylidene fluoride membrane and polyvinylidene fluoride, which is applied in the field of preparation of polyvinylidene fluoride ultrafiltration membrane, can solve the problems that the ultrafiltration membrane with separation precision cannot be produced, and achieve easy extraction of diluent, high separation precision, The effect of high porosity

Active Publication Date: 2012-11-07
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The polyvinylidene fluoride membrane with uniform sponge structure can be prepared by

Method used

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  • Method for preparing polyvinylidene fluoride ultra-filtration membranes
  • Method for preparing polyvinylidene fluoride ultra-filtration membranes
  • Method for preparing polyvinylidene fluoride ultra-filtration membranes

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preparation example Construction

[0028] The method for preparing polyvinylidene fluoride ultrafiltration membrane provided by the present invention is carried out according to the following steps:

[0029] 1) mixing polyvinylidene fluoride with a diluent; wherein the mass percentage of polyvinylidene fluoride is 20% to 40%, and the mass percentage of the diluent is 80% to 60%;

[0030] 2) Add the mixture in step 1) into the stirred tank, heat up to 100°C-160°C to form a homogeneous solution, and let it stand for defoaming;

[0031] 3) The homogeneous solution obtained in step 2) is directly scraped and coated on the support net to form a casting solution in the shape of a flat plate or spun into a hollow fiber shape through a spinneret, and then the casting solution is immersed in a cooling liquid to cool, so that The casting solution undergoes phase separation and finally solidifies to form a film;

[0032] 4) Remove the diluent in the membrane obtained in step 3) with an extractant to obtain a polyvinylide...

Embodiment 1

[0040] Put polyvinylidene fluoride (weight average molecular weight 100000), tributyl citrate and diethylene glycol into a high-temperature stirred tank and heat up to 100°C, stir and mix evenly to form a polymer homogeneous solution, and let stand for 2 hours; The mass percentage of polyvinylidene fluoride is 20%, the mass percentage of tributyl citrate is 24%, and the mass percentage of diethylene glycol is 56%. Then the polymer homogeneous solution was directly hang-coated on the support net to form a flat film with a film thickness of 200 μm, and entered into a cooling liquid bath at 30° C. to separate and solidify the solution into a film. The cooling liquid was water. The solidified flat film is dried after being extracted with an extractant, and the extractant is ethanol.

[0041] The cross-section of the membrane is a uniform sponge-like structure, with a porosity of 81%, a breaking strength of 4.51MPa, a bubble point pressure of 0.16MPa, an average surface pore diamet...

Embodiment 2

[0043] Put vinylidene fluoride-hexafluoropropylene copolymer (weight average molecular weight 420000), diethylene glycol ethyl ether and 1-octanol into a high-temperature stirring tank and heat up to 140°C, stir and mix evenly to form a homogeneous polymer solution. Stand still for 2 hours; wherein, the mass percentage of vinylidene fluoride-hexafluoropropylene copolymer is 30%, the mass percentage of diethylene glycol ether is 35%, and the mass percentage of 1-octanol is 35%. Then hang-coat the polymer homogeneous solution directly on the support net to form a flat film with a film thickness of 200 μm, and enter the cooling liquid bath at 30 ° C to solidify the solution into a film by phase separation. The cooling liquid is dibutyl phthalate . The solidified flat film is dried after being extracted with an extractant, and the extractant is benzyl alcohol.

[0044] The cross-section of the membrane is a uniform sponge-like structure, with a porosity of 69%, a breaking strengt...

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Abstract

The invention discloses a method for preparing polyvinylidene fluoride ultra-filtration membranes. The method includes the steps of mixing the polyvinylidene fluoride with diluents, and heating the mixture to form a homogeneous phase solution, wherein the diluents are a mixture of a solvent and a non-solvent of the polyvinylidene fluoride, and at least one of the solvent and the non-solvent of the polyvinylidene fluoride can be dissolved in water; subjecting the homogeneous phase solution to knife coating on a supporting screen to form a plate-shaped membrane casting solution or to be spinned into a membrane casting solution in a hollow fiber shape by a spinneret, submerging the membrane casting solution into a cooling liquid to be cooled, subjecting the membrane casting solution to phase separation and solidifying into membranes; extracting the diluents in the membranes through an extracting agent to obtain the polyvinylidene fluoride membranes. Sections of the polyvinylidene fluoride membranes are in a homogeneous spongeous structure with bore diameters in a range of 0.02 to 4 microns, and the membranes have surface layers with surface bore diameters ranging from 2 nanometers to 100 nanometers. Simultaneously, the polyvinylidene fluoride ultra-filtration membranes have the advantages of high strength, porosity, flux and separation accuracy.

Description

technical field [0001] The invention relates to a method for preparing a polyvinylidene fluoride ultrafiltration membrane. Background technique [0002] Membrane separation technology has obvious advantages such as low energy consumption, simple equipment, less land occupation, and easy automation control. In the context of the current shortage of water resources, as an efficient means of water resource reuse, membrane separation technology is facing great opportunities and challenges. Among them, microfiltration (MF) and ultrafiltration (UF) are currently the most widely used membrane processes in the world. The pore size of the microfiltration membrane ranges from 0.02 to 10 μm. It is generally believed that its main function is to separate particles or substances larger than 0.05 μm. The pore size of the ultrafiltration membrane ranges from 2 to 100nm, which can be used to remove harmful substances such as macromolecular substances, bacteria, and heat sources from water...

Claims

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Application Information

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IPC IPC(8): B01D71/34B01D67/00B01D69/06B01D69/08
Inventor 王晓琳周波林亚凯马文中刘在浩庞博
Owner TSINGHUA UNIV
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