Anti-fouling dynamic ringed PTFE hollow tube membrane and method of making same

Abstract

The application discloses an anti-pollution dynamic ring-pattern PTFE hollow tube type membrane and a preparation method thereof, and belongs to the technical field of filtration. The method provided by the application is that PTFE resin is mixed with 15-28 wt% auxiliary oil, and then is pushed and extruded into a tube blank at a speed of 0.5-2 m / min; after heat treatment at 180-450 DEG C, the tube blank is stretched at a speed of 3-15 m / min and is sintered and shaped at 300-430 DEG C. The obtained tube type membrane has an inner diameter of 0.7-15 mm and an outer diameter of 1-30 mm, and the surface of the tube type membrane has a dynamic ring-pattern structure, that is, the surface is smooth when being flat, and normal annular wrinkles are generated when being curved; the ring-pattern moves along with the change of the liquid flow direction, and through mechanical deformation, it is difficult for pollutants to deposit on the peak of the wrinkles, and space steric hindrance is formed in the valley part; meanwhile, the deposited matters are extruded to promote the falling off of the deposited matters; experiments prove that the deposition amount of the pollutants is reduced by more than 50% when being curved by 30 DEG, the recovery rate of backwashing reaches 96%, and the method is significantly superior to a traditional smooth membrane, and has excellent industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of filtration, and particularly relates to an anti-pollution dynamic ring PTFE hollow tube membrane and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene (PTFE) has strong hydrophobicity, oxidation resistance, acid and alkali resistance and temperature resistance. When prepared into a hollow fiber membrane, it is particularly suitable for processes such as membrane distillation seawater desalination, membrane seawater bromine extraction and membrane gas treatment. After hydrophilic treatment, it can also fully exert its super strong mechanical properties, and is used in membrane bioreactor (MBR) processes and chlor-alkali chemical material treatment processes, thereby prolonging the service life of the membrane. Therefore, in recent years, the research and development of PTFE hollow fiber membranes have attracted much attention. Limited by the characteristics of PTFE resin that it cannot be dissolved or melted, conventional membrane preparation processes such as dry-wet method, thermally induced phase separation method and melt spinning-drawing method cannot be used. At present, the feasible preparation methods mainly include sol-gel-sintering method and push-stretching method. The main disadvantage of the former is that high-temperature sintering is needed to remove the spinning carrier to obtain a microporous structure, which consumes energy and time, and the membrane porosity is low. The latter forms a membrane microporous structure by stretching, and has higher production efficiency, and has become a more recognized PTFE hollow fiber membrane preparation method in the world. SUMMARY

[0003] In view of the above prior art, the application provides an anti-pollution dynamic ring PTFE hollow tube membrane and a preparation method thereof, which solves the problem of poor anti-pollution effect of the existing hollow tube membrane.

[0004] In order to achieve the above purpose, the technical scheme adopted by the application is to provide a preparation method of an anti-pollution dynamic ring PTFE hollow tube membrane, comprising the following steps:

[0005] S1: uniformly mix and stir PTFE resin and an auxiliary oil to obtain a mixture;

[0006] S2: extrude the mixture into a tube blank, and heat treat the tube blank;

[0007] S3: stretch the heat-treated tube blank at a speed of 3-15 m / min to obtain a crude product;

[0008] S4: sinter and shape the crude product at a speed of 1-100 m / min at 300-430 DEG C, and cool to obtain the anti-pollution dynamic ring PTFE hollow tube membrane.

[0009] Further, the auxiliary oil is liquid paraffin or isomeric alkane.

[0010] Further, the proportion of the auxiliary oil in the mixture is 15-28 wt%.

[0011] Further, the heat treatment is to make the pipe blank in 180~450℃ environment for 5~60min.

[0012] Further, the pushing is to push the mixture through the mold with hollow channel at the speed of 0.5~10m / min.

[0013] The anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has the advantages that: the anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has a smooth surface when fully stretched, but the surface can generate normal annular wrinkle ring at the center of the ring membrane after bending with water flow, and the ring can disappear after the membrane is bent and appear on the other side, and the surface can make the adhering objects partially fall off and difficult to be adsorbed and deposited due to the change of the appearance after the tubular membrane is bent to form the ring, the peak part of the wrinkle is difficult to be deposited, and the deposited objects are easy to be taken away by the liquid flow, the valley part is difficult to be deposited, the deposited objects are easy to be squeezed, deformed and relaxed, and the tubular membrane is easy to be washed and deposited in the reverse washing process, and the anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has excellent anti-pollution effect.

[0014] The application further provides a preparation method of the anti-pollution dynamic ring PTFE hollow tubular membrane.

[0015] Further, the surface of the anti-pollution dynamic ring PTFE hollow tubular membrane is a dynamic ring structure.

[0016] Further, the inner diameter of the anti-pollution dynamic ring PTFE hollow tubular membrane is 0.7~15mm, and the outer diameter is 1~30mm.

[0017] The anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has the advantages that: the anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has a smooth surface when fully stretched, but the surface can generate normal annular wrinkle ring at the center of the ring membrane after bending with water flow, and the ring can disappear after the membrane is bent and appear on the other side, and the surface can make the adhering objects partially fall off and difficult to be adsorbed and deposited due to the change of the appearance after the tubular membrane is bent to form the ring, the peak part of the wrinkle is difficult to be deposited, and the deposited objects are easy to be taken away by the liquid flow, the valley part is difficult to be deposited, the deposited objects are easy to be squeezed, deformed and relaxed, and the tubular membrane is easy to be washed and deposited in the reverse washing process, and the anti-pollution dynamic ring PTFE hollow tubular membrane provided by the application has excellent anti-pollution effect. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 It is a real object diagram of the anti-pollution dynamic ring PTFE hollow tubular membrane prepared in Example 1.

[0019] Fig. 2 It is a real object diagram of the anti-pollution dynamic ring PTFE hollow tubular membrane prepared in Example 1 under a microscope. DETAILED DESCRIPTION

[0020] The specific embodiments of the application will be described in detail below with reference to the examples.

[0021] Example 1

[0022] A method for preparing an anti-fouling dynamic ring PTFE hollow tubular membrane, comprising the following steps:

[0023] S1: uniformly mix and stir PTFE resin with liquid paraffin to obtain a mixture, the proportion of liquid paraffin in the mixture being 19.3wt%;

[0024] S2: pass the mixture through a mold with a hollow channel at a speed of 1.5m / min to obtain a pipe blank, and place the pipe blank in an oven for heat treatment at 300℃ for 30min;

[0025] S3: stretch the heat-treated pipe blank to an outer diameter of 5mm and an inner diameter of 3mm at a speed of 12m / min to obtain a crude product;

[0026] S4: sinter and shape the crude product at 380℃ at a speed of 11m / min, and the outer wrinkle appears, and the anti-fouling dynamic ring PTFE hollow tubular membrane is obtained after cooling.

[0027] Example 2

[0028] A method for preparing an anti-fouling dynamic ring PTFE hollow tubular membrane, comprising the following steps:

[0029] S1: uniformly mix and stir PTFE resin with liquid paraffin to obtain a mixture, the proportion of liquid paraffin in the mixture being 15wt%;

[0030] S2: pass the mixture through a mold with a hollow channel at a speed of 10m / min to obtain a pipe blank, and place the pipe blank in an oven for heat treatment at 180℃ for 60min;

[0031] S3: stretch the heat-treated pipe blank to an outer diameter of 30mm and an inner diameter of 15mm at a speed of 3m / min to obtain a crude product;

[0032] S4: sinter and shape the crude product at 300℃ at a speed of 1m / min, and the outer wrinkle appears, and the anti-fouling dynamic ring PTFE hollow tubular membrane is obtained after cooling.

[0033] Example 3

[0034] A method for preparing an anti-fouling dynamic ring PTFE hollow tubular membrane, comprising the following steps:

[0035] S1: uniformly mix and stir PTFE resin with isoparaffin to obtain a mixture, the proportion of isoparaffin in the mixture being 28wt%;

[0036] S2: The mixture was passed through a mold with a hollow channel at a speed of 0.5 m / min to obtain a pipe blank, and the pipe blank was placed in an oven for heat treatment at 450°C for 5 min;

[0037] S3: The pipe blank after heat treatment was stretched at a speed of 15 m / min to a tube outer diameter of 1 mm and an inner diameter of 0.7 mm to obtain a crude product;

[0038] S4: The crude product was sintered and shaped at a speed of 100 m / min at 430°C, and the outer wrinkle appeared, and the anti-pollution dynamic ring PTFE hollow tube membrane was obtained after cooling.

[0039] Comparative Example

[0040] A method for preparing a hollow tube membrane, comprising the following steps:

[0041] S1: PVDF, DMF and polyethylene glycol were mixed in a mass ratio of 2:7:1, and stirred uniformly at 60°C to obtain a mixture;

[0042] S2: The mixture was passed through a mold with a hollow channel at a speed of 1.5 m / min to obtain a pipe blank, and the pipe blank was placed in an oven for heat treatment at 300°C for 30 min;

[0043] S3: The pipe blank after heat treatment was stretched at a speed of 12 m / min to a tube outer diameter of 5 mm and an inner diameter of 3 mm to obtain a crude product;

[0044] S4: The crude product was immersed in a coagulation liquid (30% ethanol solution) for 2 h, then taken out and washed with water for 48 h, then immersed in glycerol for 1 h, and finally air dried at 25°C to obtain a hollow tube membrane.

[0045] The anti-pollution dynamic ring PTFE hollow tube membranes prepared in Examples 1-3 have similar properties, and the anti-pollution dynamic ring PTFE hollow tube membrane prepared in Example 1 has a physical map as shown in Figs. 1-2 , and the internal ring structure can be seen in the bent state.

[0046] Experimental Example

[0047] The tubular membranes of Example 1 and the comparative example were used in a simulated application of sewage, and the specific steps were as follows: simulated sewage containing humic acid + sodium alginate + diatomite was prepared, the membrane tube was fixed by a bendable clamp, the membrane tube was bent at 0° (straight), 30° and 60°, the simulated sewage passed through the membrane tube at a cross-flow speed (2 m / s and 0.5 m / s), the water flow direction was switched every 2 h, and the process lasted for 12 h, the deposition amount of pollutants was calculated for 12 h, then fluorescent microspheres were injected into the simulated sewage, the microspheres passed through the membrane tube at a flow rate of 0.1 m / s, and the deposition (pollution degree) of the microspheres was observed; finally, the tubular membranes of Example 1 and the comparative example were backwashed (high-speed cross-flow flushing), and the recovery rate of the membrane tube was calculated by passing through clean water; the experimental results are shown in Table 1.

[0048] Table 1: Results of simulation experiment

[0049]

[0050] The tubular membrane prepared in Example 1 has similar anti-pollution performance to the tubular membrane of the comparative example when it is not bent, because the dynamic ring structure on the surface of the membrane is not activated, but when it is bent at 30° or 60°, the pollution adhesion is partially detached and difficult to be adsorbed and deposited due to the change in the morphology of the membrane surface, the peak part of the fold is difficult to deposit, and the deposited material is easily carried away by the liquid flow and detached, the valley part is difficult to enter the deposition, so the deposition amount of pollutants decreases by more than 50%, and the recovery rate of the tubular membrane prepared in Example 1 is higher than that of the comparative example after backwashing under the bent state, which shows that the dynamic ring structure is more easily washed off the pollution deposition; at the same time, it is observed in the pollution experiment of fluorescent microspheres that the microspheres are carried away by the vortex at the ring peak and are difficult to enter the valley part, while the microspheres are uniformly deposited in the comparative example; the experiment shows that the anti-pollution dynamic ring PTFE hollow tubular membrane prepared in the application has very excellent anti-pollution performance and has the value of industrial application.

[0051] Although the specific embodiments of the present application are described in detail in combination with the examples, it should not be understood as limiting the protection scope of the patent. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the protection scope of the patent.

Claims

1. A method for producing a pollution resistant dynamic annular PTFE hollow tube type membrane, characterized by, The method comprises the following steps: S1: mixing and stirring PTFE resin and auxiliary oil to obtain a mixture, wherein the proportion of the auxiliary oil in the mixture is 15-28wt%; S2: passing the mixture through a mold with a hollow channel at a speed of 0.5-10m / min to obtain a pipe blank, and performing heat treatment on the pipe blank; S3: stretching the heat-treated pipe blank at a speed of 3-15m / min to obtain a rough product; S4: sintering and shaping the rough product at a speed of 1-100m / min at 300-430℃, and cooling to obtain the anti-pollution dynamic ring PTFE hollow tube membrane; The auxiliary oil is liquid paraffin or isomeric alkane; The heat treatment is to make the pipe blank in an environment of 180-450℃ for 5-60min; The PTFE hollow tube membrane prepared by the method has a dynamic ring structure on the surface, and the surface is smooth when fully stretched, and the surface produces a normal annular wrinkle ring at the center of the ring after bending with water flow, and the ring disappears after the membrane is bent in the other direction and appears on the other side.

2. The anti-fouling dynamic ring-ribbed PTFE hollow tube membrane prepared by the method of claim 1, characterized in that: The anti-pollution dynamic ring PTFE hollow tube membrane has a dynamic ring structure on the surface.

3. The anti-fouling dynamic ring-ze nked PTFE hollow tube membrane according to claim 2, characterized in that: The anti-pollution dynamic ring PTFE hollow tube membrane has an inner diameter of 0.7-15mm and an outer diameter of 1-30mm.

Images