JP3199601U - Structure of external pressure hollow fiber membrane - Google Patents

Abstract

[PROBLEMS] To solve problems such as peeling of a round string and a film and to form a non-woven core material having high rigidity continuously at a high speed, so that it is possible to perform core material forming and film application simultaneously. Provides the structure of the empty membrane. As a material to replace a round string, a non-woven fabric 11 is heat-sealed around a core material 13 to form a rigid non-woven fabric 11 around a hollow core material 13, and a film-forming solution is applied to the surface of the non-woven fabric. It was possible to integrate with the hollow fiber membrane by impregnating the inside, and it was possible to adjust physical elongation and elasticity. By adopting a warp filament with an irregular cross section at the center of the core material 13, it is possible to secure a permeate flow path and reduce the cross-sectional area of the core material portion, so the elasticity and elongation of the membrane material 12 applied to the outer periphery of the nonwoven fabric 11. The rate can be adjusted between the core material 13 and the membrane material 12. [Selection] Figure 1

Description

It is an application related to the structure of submerged external pressure hollow fiber membranes used for wastewater treatment, sewage treatment, pretreatment of purified water, etc.

In the sewage treatment and wastewater treatment field, the external pressure-type hollow fiber membrane is immersed in the activated sludge water tank, and suction pressure is applied to the inside of the hollow fiber membrane to control the bacterial concentration in the sludge water tank while suctioning and filtering sludge water. doing.
In the hollow fiber membranes used in this field, it is important to clean the membrane surface, and normally, contamination of the outer surface of the hollow fiber membranes is prevented by using bubbles of aeration air in an activated sludge water tank. At this time, the hollow fiber membrane that moves greatly by the bubbles of aeration air has a problem that it easily breaks due to the addition of tensile force, bending force, and the like.
This problem was solved by applying a film to the outer periphery using a hollow core made of a synthetic fiber round string (hollow woven fabric) devised by Canadian company Zenon (currently part of GE) It is a round string reinforced hollow fiber membrane.
This round string reinforced hollow fiber membrane greatly improved the strength, but the problem is that the string as a hollow core material is too strong, resulting in insufficient elasticity and poor productivity. In other words, the string has a remarkably small elongation compared to the hollow fiber membrane, so that a peeling phenomenon is likely to occur between the membrane material and the string can be produced only at a low speed of 3 m / min or less as a hollow core material. A new issue has arisen.

Japanese Patent Laid-Open No. 50-156030 (Asahi Kasei) is the first device that uses a knitted fiber as a reinforcement for a hollow fiber membrane. USP5472607 discloses a method for producing a hollow core material using a fiber knitted by (ZENON) and forming a film on the outer surface thereof. USP 5914039 and USP 6354444 are similar patents filed by ZENON. Japanese Patent Laid-Open No. 11-319519 (Nitto Denko) is a method of reinforcing a hollow fiber membrane using a single fiber, and Japanese Patent Laid-Open No. 2003-236351 (Mitsubishi Rayon) is a method in which a PVDF membrane is peeled from a string which is a hollow core material. In order to prevent this, a method using an elastic material such as fluororubber as a material for the PVDF membrane has been proposed. JP-A-2008-114180 (Mitsubishi Rayon) says that a maximum production speed of 3 m / min can be achieved by connecting a round string manufacturing machine and a hollow fiber membrane coating equipment. Japanese Unexamined Patent Application Publication Nos. 2009-52190 and 2012-24691 (Mitsubishi Rayon) propose a method of forming in a heating zone in order to improve the rigidity of a round string and obtain a more accurate circular cross section. Japanese Patent Application No. 2012-516455 (USA: VL Technologies) discloses a method of forming a hollow cylinder using warp filaments and a wrap filament wound in the circumferential direction, and forming a film on the outer surface.

1. Introduction of Mitsubishi Rayon hollow fiber membrane Stella Pore ・ Specifications and performance table of PVDF membrane (SADF membrane) http://www.mrc.co.jp/sterapore/haisui_01.html www.mrc.co.jp/press/p10/100629_01.html Use hollow fiber membrane reinforced with woven fabric. Introduction of Water & Process Technologies Division of GE ・ Example of ZeeWeed500D module http://www.gewater.com/products/equipment/mf_uf_mbr/zeeweed_500.jsp Use reinforced hollow fiber membrane

As a result of past prior art investigations, a technique of using a string-like reinforcing material knitted from fibers as a reinforcing material for a hollow fiber membrane is common. As long as the string is used, it has less elasticity and elongation compared to the mechanical properties of general ultrafiltration membranes and microfiltration membranes such as polyvinylidene fluoride (PVDF) and polysulfone (PSF), which are relatively large membrane materials. The peeling problem due to the difference in the elongation rate between the string-like reinforcing materials cannot be avoided. Further, the process of knitting the string is a complicated process, and as disclosed in JP-A-2006-114180, it is difficult to increase the production speed to 3 m / min or more at the maximum. It is also possible to form a tube-like core material by winding a nonwoven fabric tape in a spiral shape and welding with an ultrasonic welding device. It is difficult, and the current minimum diameter is 4 to 5 mm. Also, when this spiral welding is performed, the welded part is formed into a film and welded, so this place cannot be impregnated with the film-forming solution, and is easily peeled off starting from this part. As the area to be converted increases, the effective membrane area decreases. In addition, the small-diameter spiral pipe manufacturing facility also has a production rate of 3 m / min or less, which greatly reduces productivity.

In order to increase the strength of the hollow fiber membrane, instead of using a round string knitted from fibers, the use of a polyolefin-based non-woven fabric material, which has been making rapid progress in recent years, has improved the impregnation property with the membrane material. Forming a hollow core material with large elongation close to the physical properties to solve the problem of peeling of the membrane, and at the same time, increase the production speed from 3m / min to 15m to 30m / min. It becomes possible to synchronize with the film forming process, and productivity can be dramatically improved.
Nonwoven fabrics are made by extruding very fine fibers in the order of micron units continuously from a large number of nozzles, and entangle the nonwoven fabric fibers using fluids such as air and water, thereby increasing the strength of the entire nonwoven fabric sheet. It is possible to change the mechanical strength such as rigidity and elongation of the entire nonwoven fabric by compressing or reheating the nonwoven fabric sheet to bring it close to the melting point.
A string or a round string having a structure in which a single fiber or a plurality of fibers are knitted are intertwined firmly like a woven fabric from the beginning, and thus cannot be greatly deformed even if a tensile force is applied.
By utilizing the properties of nonwoven fabrics, we were able to solve the conventional problems by creating a hollow core material and a core tube of nonwoven fabrics that are close to the mechanical properties of membrane materials.
Further, since it is an external pressure type hollow fiber membrane, it is necessary to withstand an external pressure of 1 atm at the maximum from the outside, and to move the permeate that has permeated the outer peripheral membrane in the axial direction (vertical direction) with as little resistance as possible. As a means for this purpose, a warp filament is arranged in the center of the hollow core material, and a structure is provided with a groove that allows permeate to easily move in the longitudinal direction. Various shapes can be proposed as long as the cross-sectional shape of the warp filament is an irregular cross-section in which a permeate passage is secured.
It is easy to simultaneously form a hollow core material and a core tube around the warp filament.

Nonwoven fabrics can greatly expand the range of mechanical properties compared to braided strings. By increasing the packing density of the nonwoven fabric fibers or increasing the melting temperature, the elongation is small and the tensile strength can be increased. On the contrary, the elongation can be increased and the tensile strength can be lowered by reducing the packing density of the nonwoven fabric fibers or lowering the melting temperature. It is also possible to adjust the filling amount, melting temperature, and fiber entanglement in consideration of the affinity with the membrane material and the impregnation property.
Using this function, it is possible to select a nonwoven fabric fiber that matches the mechanical properties of the membrane material. In addition, since the nonwoven fabric has a higher porosity than the string fibers, the nonwoven fabric becomes a membrane material after it is solidified with water or a solvent so that the membrane forming solution (dope) can be easily impregnated between the nonwoven fabric fibers. And the membrane peeling force is greatly improved.
The production speed and manufacturing cost are also big problems, and the conventional reinforcing material knitting fibers can only be 3 m / min at the maximum, but with this method of continuously welding nonwoven fabric, it can be 30 m / min. .
For this reason, it is possible to synchronize with a normal film-forming speed of 20 ～ 30 m / min by solidifying it in a gelled water tank while applying a film-forming solution to the outer layer of the non-woven tube. I can expect.
Moreover, the tensile strength of the whole hollow fiber membrane can be significantly improved by disposing a warp filament having an irregular cross-sectional shape in the center of the hollow core material. Moreover, by adjusting the area of the cross-sectional shape, it became possible to adjust the elongation rate of the hollow core material and the outer peripheral membrane and the elongation rate of the warp filaments, or to prevent peeling.
It is also possible to adjust the flow resistance on the permeate side by devising an irregular cross-sectional shape of the warp filament, and the flow resistance on the permeate side that occurs when the nonwoven fabric fibers fall into the permeate flow path of the warp filament. It became possible to greatly reduce.

Circular cross-sectional view of reinforced hollow fiber membrane Structure of conventional round string type reinforced hollow fiber membrane Example of cross-sectional shape of core material of nonwoven fabric reinforced hollow fiber membrane Cross-sectional photo of the prototype hollow fiber membrane (peripheral membrane solution impregnated)

A sheet-shaped nonwoven fabric in which a low-melting polymer nonwoven fabric and a high-melting polymer nonwoven fabric are mixed is formed using a melt blown nonwoven fabric manufacturing apparatus made of a polyolefin-based material.
The sheet-like nonwoven fabric is wound around a reel with a slitter by a continuous nonwoven fabric tape of about 5 mm to 15 mm. By feeding the tape from this continuous nonwoven fabric reel to the melting head or die and heating inside the melting head to a temperature at which the low melting point polymer melts, the high melting point polymer nonwoven fabric is fixed by the molten low melting point polymer and comes out of the melting head. The non-woven tube has high rigidity.
It is also possible to extrude the non-woven fabric from the nozzle without forming the non-woven fabric in the form of a sheet. At this time, a core material described later is placed in the center of the nozzle and the non-woven fabric is directly molded around the core. It is also possible to go.
The physical properties of this nonwoven fabric tube can be easily adjusted by changing the following parameters.
1) Weight ratio of high-melting polymer and low-melting polymer 2) Melting head temperature 3) Pull-out speed of non-woven tube When a non-woven tube is manufactured, a non-woven fabric having a sheet-like slit around the core using the core It is also possible to form the tape while it is wound around a spiral, or to extrude the nonwoven fabric directly around the core from a nozzle.
By using the core material, the strength in the longitudinal direction of the nonwoven fabric tube can be greatly improved, and by making the raw materials of the core material and the nonwoven fabric tube the same, the fusion performance with the core material can be enhanced.
The purpose of using long fiber yarns is to reduce the resistance of permeate flowing through the inner surface of the hollow fiber membrane.
Even if the long fiber yarns are in close contact with each other, a gap is formed between them, so that the water filtered from the hollow fiber membrane can move inside with little resistance. As a more advantageous shape, a single or a plurality of grooves are provided so that the permeated water that has permeated through the semipermeable membrane and the nonwoven fabric layer can be easily moved in the vertical direction by using a cross-sectional shape of the long fiber as a cross-sectional shape. Is possible.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
The photograph of FIG. 4 is a specific sample photograph of the reinforced hollow fiber membrane of the new model.
Fig. 4 shows a PVDF film formed on the outer surface of a non-woven tube having a core outer diameter of 2.0 mm and an inner diameter of 1.2 mm formed by heat sealing around a core having an outer diameter of 1.2 mm and a rice-shaped cross section. The PVDF film-forming solution that has been applied is colored with a dye, making it easy to understand the impregnation from the outer surface of the nonwoven fabric.
Polyvinylidene fluoride (KF Polymer W # 1100 manufactured by Kureha Chemical Industry Co., Ltd.), dimethylacetamide, and glycerin were heated and dissolved to obtain a uniform film-forming solution, and the film-forming solution was colored with a blue dye. The product was uniformly applied to the outer surface of the nonwoven tube by extruding it from an annular nozzle. Immediately after application, the sample was immersed in water, solidified, extracted with a solvent, and dried to obtain a sample for photography.

By using the nonwoven fabric tube of the present invention as a reinforcing material for a hollow fiber membrane, it is possible to form a reinforcing material at a high speed nearly 10 times by extrusion molding of a reinforcing material that has been knitted into a string with long fibers. It became.
For this reason, it becomes possible to synchronize the manufacturing process of the reinforcing material and the coating process of the film forming liquid, and the two processes were continuously performed by continuously supplying the finished product to the nozzle for coating the film forming liquid while manufacturing the nonwoven fabric tube. Therefore, the manufacturing process can be greatly simplified and rationalized.
Also, unlike the conventional reinforcing material that braids long fibers into a string shape, the reinforcing material of the present invention uses a non-woven fabric, so its physical tensile strength and elongation rate can be flexibly matched to the physical properties of the film-forming solution. Since it becomes possible to adjust, the peeling problem between the reinforcing material and the film-forming layer, which is a problem, can be solved.

Fig. 1: 11: Non-woven tube 12: Hollow fiber membrane 13: Modified cross-section core material Fig. 2: 21: Round string for reinforcement 22: Hollow fiber membrane Fig. 3: Shapes of various irregular cross-section core materials 4: Modified cross-section core material Of a non-woven tube and hollow fiber membrane formed around

Claims (3)

In hollow fiber membranes with ultrafiltration and microfiltration functions, a warp filament made of one or more polymers is placed in the center of the circular cross section, and a nonwoven fabric made of polyolefin polymer is heat-sealed on the outside. A structure of a reinforced external pressure type hollow fiber membrane, wherein the outer layer is formed and a semipermeable membrane is impregnated and applied to the outermost layer portion.
The cross-sectional shape of the warp filament is circular or irregular, and in the warp direction
The reinforced external pressure type according to claim 1, wherein a permeate flow path is secured.
Structure of hollow fiber membrane.
The warp filament is singular and the cross-sectional shape is star-shaped, saddle-shaped, V-shaped, W-shaped
It has a cross section with a different shape, and a permeate flow path is secured in the warp direction.
The structure of the reinforced external pressure type hollow fiber membrane according to claim 1 or 2.

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