Permanent hydrophilic polyvinylidene fluoride membrane and production method thereof

A technology of polyvinylidene fluoride membrane and manufacturing method, which is applied in the field of water treatment, can solve the problems of easy loss, limited selection space, and difficulty in industrialization, and achieve the effect of highly stable hydrophilicity, simple production process, and dense separation layer

Active Publication Date: 2018-06-29
ZHEJIANG CHANGXING CREFLUX MEMBRANE TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The preparation of these hydrophilic polyvinylidene fluoride membranes has its own characteristics, but there are deficiencies, mainly as follows: (1) The membrane surface modification method will change the pore size and pore size distribution on the membrane surface to a certain extent
(2) If the physical adsorption method is used, the hydrophilic substance is only adsorbed by physical adsorption, and it is easy to lose in the actual use process, and the hydrophilic effect is difficult to last
(3) The chemical modification method will destroy the strength of the membrane, and the conditions are harsh, the process is complicated, and it is difficult to industrialize
(4) Using graft polymerization, although the hydrophilic functional groups can be fixed with covalent bonds, the process is complicated, and whether the hydrophilic segment can stay on the membrane surface for a long time is a problem
(5) If the blending modification method is adopted, if water-soluble polymers such as polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol are used, it is difficult to ensure the long-term hydrophilicity of the film; and if water-insoluble hydrophilic polymers are used Since there are few polymers that can be blended with polyvinylidene fluoride, the selection space is also very limited

Method used

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  • Permanent hydrophilic polyvinylidene fluoride membrane and production method thereof
  • Permanent hydrophilic polyvinylidene fluoride membrane and production method thereof
  • Permanent hydrophilic polyvinylidene fluoride membrane and production method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0047] A permanently hydrophilic polyvinylidene fluoride membrane, comprising a microporous support layer 1 and a dense separation layer 2, the dense separation layer 2 is located on the outer surface of the microporous support layer 1, as attached image 3 Shown is the scanning electron microscope (SEM) image of the cross-section of the polyvinylidene fluoride membrane described in this embodiment magnified 1000 times. It can be seen that the microporous support layer 1 is a honeycomb-shaped opening with an average pore size of 1 µm. figure 2 Shown: SEM detection of the outer surface of the dense separation layer 2 under a magnification of 60,000 has no obvious pores.

[0048] A reinforced polyvinylidene fluoride hollow fiber composite membrane is made, with an outer diameter of 2000 μm, a membrane thickness of 200 μm, and a porosity of about 75%. The pure water flux of the membrane is 720 LMH / bar, and the compressive strength is 0.4 MPa. The bubble pressure in Porefil is ab...

Embodiment 2

[0058] Other parts are the same as in Example 1, the difference is:

[0059] Send the homogeneous solution after defoaming at 120°C in Example 1 to the forming scraper mold, and cast it together with the polypropylene non-woven fabric. After staying in the air at room temperature for 1 S, send it to the cooling medium at 60°C Internally solidified into a film, wherein the cooling medium is composed of 20% by weight PEG (200) and 80% by weight of water. After the film is formed, it is naturally dried at room temperature.

[0060] The resulting flat composite membrane has a thickness of 200 μm and a porosity of about 85%. Figure 4 As shown, the separation layer 2 of the membrane is the surface pores of 0.01-0.05 μm detected by SEM on the outer surface at a magnification of 30000, as shown in the attached Figure 5 As shown, the support layer 1 is a sponge-like, open-pore microporous support layer with an average pore diameter of about 2.5 μm. The pure water flux of the membra...

Embodiment 3

[0062] Other parts are the same as in Example 1, the difference is:

[0063] Stir the polymer and solvent together at 90°C to form a homogeneous solution, wherein the hydrophilic resin sulfonated polysulfone (SPSF, sulfonation degree ≈ 30%, [η] ≈ 0.6) weight percent is 2%, glycerin ( The weight percentage of GI) is 6%, the weight percentage of polyvinylidene fluoride PVDF (3F904) is 20%, and the weight percentage of dimethylacetamide DMAc in the solvent system is 72%.

[0064] In the case of maintaining the uniform distribution of the four strands of reinforcing fiber filaments, send the degassed homogeneous solution at 90°C to the forming hollow mold, and introduce internal filler water. After the composite solution stays in the air for 2 seconds, it enters the cooling at 50°C. The medium is solidified to form a film, and finally a reinforced polyvinylidene fluoride film with four strands of fibers evenly distributed in the hollow film is formed, and the cooling medium is com...

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Abstract

The invention relates to the technical field of water treatment and in particular discloses a permanent hydrophilic polyvinylidene fluoride membrane. The permanent hydrophilic polyvinylidene fluoridemembrane comprises a micro-pore supporting layer and a dense separation layer, wherein the micro-pore supporting layer is provided with sponge-shaped pores and the pore diameter is greater than or equal to 0.5mu m; the pore diameter of the dense separation layer is less than or equal to 0.1mu m and the water contact angle of the dense separation layer is less than or equal to 70 degrees; after thepermanent hydrophilic polyvinylidene fluoride membrane is immersed in high-temperature water for a long period, the variation of the water contact angle of the membrane is less than or equal to 10 percent. The invention further discloses a production method of the permanent hydrophilic polyvinylidene fluoride membrane; the production method comprises the following steps: preparing a homogeneous-phase solution; molding through a mold; separating and curing through the cooling medium; removing a dilute phase and drying. According to the permanent hydrophilic polyvinylidene fluoride membrane andthe production method thereof, the sponge-shaped and opened micro-pore supporting layer and the dense separation layer which is denser than the micro-pore supporting layer are arranged, so that the permanent hydrophilic polyvinylidene fluoride membrane has the advantages of low production cost, simple production procedures, dense separation layer, loose supporting layer, high compressive strength, high transmission flow and high stability of hydrophilic performance.

Description

technical field [0001] The invention relates to the technical field of water treatment, in particular to a permanently hydrophilic polyvinylidene fluoride membrane and a manufacturing method thereof. Background technique [0002] Polyvinylidene fluoride (PVDF) is widely used in the preparation of water treatment membrane materials such as microfiltration and ultrafiltration due to its excellent mechanical and chemical properties, and its structure is often asymmetric, such as figure 1 As shown, it is composed of a separation layer (2) and a microporous support layer (1). However, due to the extremely strong hydrophobicity of polyvinylidene fluoride, it often has defects such as low flux and easy pollution in the process of water treatment, which greatly reduces the efficiency of water treatment and the service life of polyvinylidene fluoride membrane. Therefore, its hydrophilic modification has important practical significance. [0003] In general, all techniques of hydrop...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D67/00B01D69/02B01D69/06B01D71/34B01D69/08
CPCB01D67/0013B01D69/02B01D69/06B01D69/08B01D71/34B01D2325/36
Inventor 沈红梅张星星包进锋李芸芳杨永红周凌跃张多鹏
Owner ZHEJIANG CHANGXING CREFLUX MEMBRANE TECH CO LTD
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