JPH1176768A - Cleaning method of hollow yarn membrane and cleaning device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a solvent, an additive, a polymer particle and the like remaining in the inside of a hollow yarn membrane by turning the inside of the hollow part of the hollow yarn membrane into a pressure reduced zone before the hollow yarn membrane having a min. pore diameter layer on the outside surface of the membrane is modulated and passing a cleaning liquid from the outside surface side of the membrane to the inside surface side of the membrane. SOLUTION: The removal of the solvent, the additive, the polymer particle and the like remaining in the inside of the hollow yarn membrane is performed by treating so that the cleaning liquid is passed from the outside surface side of the membrane to the inside surface side of the membrane. As the method for passing the cleaning liquid, a method for passing the cleaning liquid by evacuating the inside of the hollow part is preferable and to turn the inside of the hollow part into the pressure reduced zone, such a suction pump, a gear pump is used. The cleaning device for the hollow yarn membrane is constituted so as concretely to provide a vessel 6 for housing the hollow yarn membrane, a means 5 for supplying the cleaning liquid in the vessel 6, a means 7 for discharging the liquid from the vessel 6, a means 2 for connecting the inside of the hollow part to a pressure adjusting device 4 and the pressure adjusting device 4 such as the suction pump, gear pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cleaning a hollow fiber membrane for efficiently removing solvents, additives, polymer particles and the like remaining inside the hollow fiber membrane before modularization.

[0002]

2. Description of the Related Art In recent years, the technology of using a membrane having a selective filtration property in a separation operation has been remarkably developed, and is currently used in fields such as food industry, pharmaceutical industry, electronics industry, medical treatment, drinking water, and nuclear power generation condensate treatment. Has been put to practical use. As the material of the membrane, for example, a resin of cellulose type, polyamide type, polyacrylonitrile type, polycarbonate type, polysulfone type or the like is used.

As the shape of the membrane, a film-like flat membrane, a tubular membrane, and a hollow fiber membrane are known, and various production methods have been proposed. Among them, production of a hollow fiber membrane by a wet or dry-wet spinning method includes, for example, a polymer,
This is performed by simultaneously discharging a film forming stock solution composed of a solvent and an additive and an internal coagulating liquid from a double annular nozzle, passing through an air gap, and then discharging to an external coagulating liquid tank for coagulation.

In this film forming method, a polymer solvent, a non-solvent, an additive, and the like are used for the film forming stock solution and the coagulating solution. Therefore, the hollow fiber membrane formed by coagulation is formed from the film forming stock solution or the coagulating solution. A large amount of the resulting solvent is included. This causes problems such as difficulty in bonding when modularized. Therefore, it is necessary to sufficiently clean the hollow fiber membrane. As a method for cleaning the hollow fiber membrane, warm water cleaning by immersion or ultrasonic cleaning is performed. However, in the cleaning by cleaning the film in a hot water tank, it is necessary to immerse the film in hot water for cleaning for a long period of time in order to remove a solvent or the like, and the productivity is extremely poor. Further, in the case of ultrasonic cleaning, there is a disadvantage that if sufficient cleaning is performed, micropores of the hollow fiber membrane are easily broken. Japanese Patent Application Laid-Open No. 9-57078 discloses a method of washing only a solvent without cutting a membrane. In this method, polymer particles generated inside a hollow fiber membrane and additives remaining therein are removed. Etc. cannot be removed.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method and apparatus for cleaning a hollow fiber membrane for efficiently removing solvents, additives, polymer particles and the like remaining inside the hollow fiber membrane before modularization. Is to provide.

[0006]

The present invention has solved the above-mentioned problems. That is, the present invention provides (1) a method in which a hollow fiber-like membrane having a minimum pore diameter layer at or near the outer surface of the membrane is modularized before the hollow fiber-like membrane is depressurized before the modularization. A method for cleaning a hollow fiber membrane, comprising passing a liquid from the surface side to the inner surface side of the membrane,
(2) The washing method according to the above (1), wherein the hollow fiber membrane is a hollow fiber membrane produced by a wet or dry-wet spinning method, and (3) the hollow fiber membrane is formed from a polysulfone-based polymer. (4) a container for accommodating the hollow fiber membrane, means for supplying a cleaning liquid to the container, pressure in the hollow portion of the hollow fiber membrane, and pressure. The present invention relates to a device for cleaning a hollow fiber membrane, comprising a means for connecting to an adjusting device, and a pressure adjusting device.

Hereinafter, the present invention will be described in detail. The cleaning method of the present invention is very effective for a hollow fiber membrane having a minimum pore size layer on or near the outer surface of the membrane. To remove solvents, additives, polymer particles, etc. remaining inside the hollow fiber membrane having the minimum pore size layer of the membrane at or near the outer membrane surface, pass the cleaning solution from the outer membrane surface to the inner membrane surface. Is preferred. Even if dirt or the like is tentatively mixed into the cleaning liquid, there is an advantage that the possibility of dirt entering the inside of the membrane is reduced by the minimum pore size layer of the membrane near the outer surface of the membrane. Conversely, when the cleaning solution is passed from the inner surface of the membrane to the outer surface of the membrane, polymer particles and the like generated inside the membrane tend to hardly move out of the membrane system due to the smallest pore size layer of the membrane on the outer surface of the membrane. is there. Here, the inside of the film refers to the entire micropores within the film thickness between the outer surface of the film and the inner surface of the film, and the polymer particles are
It refers to particles of about 0.01 μm to 5 μm that are not physically bonded to the film and are generated by particle growth due to phase separation during film formation.

[0008] As a method of passing the cleaning liquid, there are a method of press-fitting from the outer surface of the membrane and a method of passing the cleaning liquid by reducing the pressure in the hollow part. In the present invention, the cleaning liquid is passed by reducing the pressure in the hollow part. The liquid passing method of the present invention is also preferable in that the apparatus can be downsized. The hollow portion refers to a hollow portion penetrating in the length direction of the hollow fiber membrane. For example, a suction pump, a gear pump, or the like is used to reduce the pressure in the hollow portion. To reduce the pressure, the pressure in the hollow portion is reduced by several mmHg from the external pressure to 1 mmHg, preferably 75 mmHg.
0 mmHg to 50 mmHg. If the degree of decompression is small, the solvent removal efficiency becomes poor, so the cleaning time needs to be extended. If it is less than 1 mmHg, it becomes easy to pass the cleaning liquid, but there is a risk of deformation of the hollow fiber membrane and destruction of the membrane structure. Nature occurs.

The washing liquid may be any as long as it can remove solvents, additives, polymer particles and the like and does not damage the hollow fiber membrane. Examples thereof include water, alcohols such as ethanol, and a mixture of water and alcohol. . Further, a surfactant may be added to these as long as the hollow fiber membrane does not swell, damage, etc., but water which does not adversely affect even if it remains is particularly preferably used. When a high molecular weight additive is used in the stock solution for film formation, the additive tends to remain inside the film. In such a case, in order to remove the additive from the inside of the film, the additive is reduced in molecular weight using a decomposing agent such as sodium hypochlorite, and then further washed with another washing liquid such as water. There is a way. The decomposing agent used has a concentration and properties that reduce the molecular weight of the additive but do not adversely affect the polymer forming the film. The cleaning liquid may be heated, and when heated, the temperature is set in consideration of the heat resistance of the polymer forming the film. The use of the heated cleaning liquid can further enhance the diffusion of the solvent and the like contained in the hollow fiber membrane into the cleaning liquid. The washing time may be a concentration at which the amount of the residual solvent in the film, the amount of the additive, etc., do not adversely affect the adhesion. This concentration is changed depending on the type of the solvent to be used, the type of the adhesive, and the use of the module. You.

[0010] The hollow fiber membrane is usually called a module in which a large number of hollow fiber membranes are usually bundled together, inserted into a case and adhered. It is necessary to remove in advance the solvent, additives and the like remaining inside the film in order to carry out the above reliably. Therefore, the present invention is particularly effective for washing a hollow fiber membrane obtained from a stock solution using a solvent such as a wet or dry-wet spinning method. However, the present invention can be suitably applied to washing of a hollow fiber membrane obtained by a melting method in which a solvent is not often used during film formation.

As the hollow fiber membrane to be subjected to the cleaning method of the present invention, for example, a stock solution consisting essentially of a film-forming polymer, a solvent for the polymer, and a specific additive is prepared by converting a stock solution consisting of a good solvent to the polymer. A film produced by discharging from a double annular nozzle together with an internal coagulating liquid composed of an aqueous solution, passing through an air gap, and coagulating with an external coagulating liquid phase (for example, WO 097/22405)
And the like.

The film-forming polymer may be any polymer capable of forming a film by a wet or dry-wet spinning method, such as a polysulfone polymer, a polyvinylidene fluoride polymer, a polyacrylonitrile polymer, a polymethacrylic polymer, Examples include polyimide-based polymers, polyetherimide-based polymers, and cellulose acetate-based polymers. A porous hollow fiber membrane composed of a heat-resistant polymer such as a polysulfone-based polymer is preferable because a heated cleaning solution can be used. In addition, the present invention can be applied to a hollow fiber membrane in an arbitrary step after discharge and coagulation in a wet or dry-wet spinning method, but is preferably applied to a hollow fiber membrane after coagulation and before drying.

[0013] The hollow fiber membrane is washed in the form of a bundle of many bundles (hereinafter simply referred to as a "bundle"). The number of hollow fiber membranes constituting the fiber bundle is determined by the inner diameter and outer diameter of the hollow fiber membrane. The length of the yarn bundle is preferably shorter because the pressure loss between the end and the center of the yarn bundle increases as the pore size of the minimum pore size layer of the membrane increases. There is no particular limitation because it depends on the relationship. Usually, 0.1 m to 5 m, preferably 0.1 m to
3 m, more preferably 0.1 m to 2 m.

Next, an example of the apparatus for cleaning a hollow fiber membrane of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing an example of the cleaning apparatus of the present invention, and FIG. 2 is a front view showing another example. The cleaning apparatus shown in FIG. 1 comprises a container 6 for accommodating a hollow fiber membrane, a means 5 for supplying the cleaning liquid 3 to the container 6, a means 7 for discharging the liquid from the container, and a pressure adjustment in the hollow portion of the hollow fiber membrane. It comprises means 2 for connecting to the device and a pressure regulator 4.

The container 6 for storing the hollow fiber membrane is not particularly limited as long as it can fill the container with the yarn bundle 1 and the washing liquid 3. In order to fix the yarn bundle 1 in a state of being completely immersed in the cleaning liquid, a fixing jig 9 or the like can be used. As the means 2 for connecting the inside of the hollow portion of the hollow fiber membrane and the pressure adjusting device, for example, a conical jig is used, but any device that can fix the end face of the yarn bundle to the pressure adjusting device in an airtight manner is used. Good. For example, it is efficient in terms of workability if a jig that can easily fix the yarn bundle that opens and closes up and down by a power such as a motor or air pressure as shown in FIG. In addition, a portion of the fixing jig in contact with the yarn bundle can be prevented from being damaged by using a soft material such as silicon rubber. Depending on the size of the yarn bundle to be introduced into the container, the shape may be any of a box shape, a cylindrical shape, and a conical shape.

As the cleaning liquid supply means 5 for supplying the cleaning liquid 3 into the container, an ordinary liquid supply pump or the like is used. Further, as the pressure adjusting device 4, a device such as a suction pump or a gear pump that can reduce the pressure inside the hollow portion of the hollow fiber membrane is used. Further, the cleaning apparatus of the present invention may have a means 7 (a waste liquid valve or the like) for discharging the liquid from the container for replacing the cleaning liquid in the cleaning step.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Each measurement method employed in the examples is as follows. The hollow fiber filtration membranes used as measurement samples were all completely impregnated with water. The amount of water permeation of the hollow fiber membrane is determined by permeating ultrafiltration water at 25 ° C. from the inner surface to the outer surface of the hollow fiber membrane having a length of 50 mm from the inner surface to the unit time per unit pressure (unit pressure difference). Calculate the speed,
The amount was expressed in liter / hr · m ² · atm. However, the effective film area was converted to the inner surface. The breaking strength and elongation at break of the film were measured using an Autograph AGS-5D manufactured by Shimadzu Corporation at a sample length of 30 mm and a tensile speed of 50 mm / min.

The elongation at break is determined in kgf / cm ² by dividing the load at break per hollow fiber membrane by the cross-sectional area of the membrane before pulling, and the elongation at break (elongation)
It was expressed as the ratio (%) of the length that elongated before breaking to the original length. The fractionation performance is as follows: a stock solution prepared such that uniform latex particles having a particle size of 0.137 μm are suspended at a concentration of 0.02% by volume in a 0.2 wt% aqueous solution of sodium dodecyl sulfate is mixed with a hollow fiber membrane. 5 shows the rejection after 40 minutes when filtration was performed so that the average pressure difference between the input pressure and the output pressure was 0.5 kgf / cm ² .

The average pore size of the smallest pore size layer is ASTM F3
It measured by the air flow method described in 16-86. Extraction of the residual solvent (NMP) and the residual amount of the additive (PVP) in the membrane was performed by placing 5 g of pure water and 0.5 g of a hollow fiber membrane cut into 5 mm in a sealed 10 ml container, and heating at a constant temperature of 80 ° C. ) × immersion time (6 hours) × shaking speed (120
(Time / min) shaking type thermostat (Yamato Co., Ltd.)
WATER BATH INCUBATOR BT-4
Extracted into pure water in 7). However, a wet hollow fiber membrane was used as the hollow fiber membrane. The amounts of the residual solvent and the additives in the film were represented by the concentration with respect to the dry film. At this time,
Under this extraction condition, it was considered that all the residual solvent in the membrane had moved into the enclosed pure water. On the other hand, the amount of the additive was determined by the sum of the amount extracted by this operation and the amount remaining in the film after the extraction operation. The amount of the additive in the hollow fiber membrane after the extraction operation was determined by analyzing the dried hollow fiber membrane with nitrogen.

The concentration of the solvent and the additive in the water can be determined by using a liquid chromatography column (ASAHIPA manufactured by Asahi Kasei Corporation).
KGS-620H) was measured using an ultraviolet spectrometer (UV8010 manufactured by Tosoh Corporation). The operating conditions were as follows: mobile phase: water, column temperature: 38
C., measurement wavelength: 208 nm. The amount of the polymer particles in the hollow fiber membrane was represented by the absorbance when the above extract was measured with an ultraviolet spectrometer at a measurement wavelength of 260 nm.

[0021]

Example 1 Polysulfone (P-35, manufactured by AMOCO)
00) 18% by weight and 20% by weight of polyvinylpyrrolidone having a weight average molecular weight of 45,000 (K30, manufactured by BASF) whose moisture content was reduced to 0.3% by weight or less by drying.
-Methyl-2-pyrrolidone was dissolved in 62% by weight to obtain a uniform solution. The solution was kept at 60 ° C. and N-methyl-2
-Spinner (double annular nozzle 0.5 m) with an internal solution consisting of a mixed solution of 95% by weight of pyrrolidone and 5% by weight of water.
m-0.7mm-1.3mm)
And immersed in a coagulation bath consisting of 70 ° C. water. At this time, the area from the spinneret to the coagulation bath was surrounded by a cylindrical tube, and the humidity of the air gap in the tube was controlled to 100%, and the temperature was controlled to 45 ° C. The spinning speed was fixed at 20 m / min.
The resulting membrane has a minimum pore size layer of the membrane near the outer surface of the membrane,
The membrane had a structure in which the pore diameter increased toward the inner surface of the membrane. Table 1 shows the physical properties of the hollow fiber membrane after the solidification.

Next, the hollow fiber membrane was formed into a bundle of 2,000 bundles, and both ends were cut so that the length of the bundle was 2.7 m. The hollow portion of the hollow fiber membrane at the cut end face did not have any crush at both end faces. 200 thread bundles
It was fixed to a device as shown in FIG. 1 filled with a 0 ppm aqueous solution of hypochlorous acid, and pulled from both ends with a pressure gauge at 360 mmHg by a suction pump 4 to flow into the hollow portion from the outer surface of the membrane.

The aqueous solution of hypochlorous acid in the container was constantly pumped into the container by the pump 5 so that the amount of the solution was constant.
After 1 hour, after extracting the aqueous solution of hypochlorous acid from the container,
Hot water at 80 ° C. was passed under the same conditions. 4 hours after passing
Washing of the membrane was completed. Table 1 shows the physical properties of the film before and after the cleaning, the residual solvent value, and the like. It was clarified that this washing method significantly reduced residual solvents, additives and polymer particles.

[0024]

[Table 1]

[0025]

According to the cleaning method and the cleaning apparatus of the present invention, the solvent, additives, polymer particles and the like remaining inside the hollow fiber membrane can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a cleaning device of the present invention.

FIG. 2 is a front view showing another example of the cleaning device of the present invention.

FIG. 3 is a cross-sectional view showing an example of a jig for connecting a yarn bundle and a pressure adjusting device, viewed from a side direction with respect to a front direction in FIG. 2;

[Description of Signs] 1 Thread bundle made of hollow fiber membrane 2 Means for connecting the inside of hollow part of hollow fiber membrane to pressure regulator 3 Cleaning liquid 4 Pressure regulator 5 Cleaning liquid supply means 6 Container for housing hollow fiber membrane 7 From container Means for discharging liquid 8 Pressure gauge 9 Thread bundle fixing jig 10 Jig for connecting thread bundle and pressure adjusting device

Claims (2)

[Claims] 1. Before the modularization of a hollow fiber membrane having a minimum pore diameter layer of the membrane at or near the outer surface of the membrane, the inside of the hollow part of the hollow fiber membrane is reduced in pressure so that the cleaning liquid is removed from the outer membrane side. A method for cleaning a hollow fiber membrane, comprising passing a liquid through the inner surface of the membrane. 2. A hollow fiber membrane having a container for accommodating a hollow fiber membrane, means for supplying a cleaning liquid to the container, means for connecting the inside of the hollow portion of the hollow fiber membrane to a pressure regulator, and a pressure regulator. Cleaning equipment.