JPH0796152A - Tilted hollow fiber membrane and method for producing the same - Google Patents

Abstract

(57) [Summary] [Structure] By changing the shape of the hollow fiber membrane in an inclined manner, the difference in the amount of permeated water per unit area of the hollow fiber membrane in the length direction is reduced. An inclined hollow fiber membrane. [Effect] The flow pressure loss in the hollow fiber can be made smaller than that of the conventional membrane, and the permeate flow velocity distribution can be made uniform. Therefore, the load and the pollution applied to the local part of the membrane can be dispersed, and further, the bubbling and the backwashing property at the time of performing the membrane cleaning by the dispersion of the contamination can be improved, so that the operation can be prolonged.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hollow fiber membrane. More specifically, when the hollow fiber is formed into a membrane module, the flow resistance in the length direction of the hollow fiber is reduced without lowering the average packing density of the hollow fiber membrane, and the permeation performance is improved. The present invention relates to a hollow fiber having an inclined shape used for a microfiltration membrane or an ultrafiltration membrane and a method for producing the hollow fiber.

[0002]

2. Description of the Related Art Since the hollow fiber membrane separation method has the characteristics of energy saving, space saving, labor saving, etc., it is widely used in the fields of process water treatment, water purification treatment, pure water production, food production, pharmaceuticals, etc. Technology.

The hollow fiber membrane has a dense layer on the inner side, outer side or both sides of the membrane.

In the case of producing a hollow fiber membrane, in a so-called solution method in which a polymer solution is spun, a technique of an asymmetric membrane in which a dense layer is formed on the surface of the hollow fiber membrane and separation is performed by the surface layer is generally used. It is often used for. When an asymmetric membrane microfiltration hollow fiber membrane having such a dense surface layer on the outer surface is used, scrubbing with air, backwashing with permeate,
By back-washing with air and the like, the cake layer such as fine particles adhered and formed on the surface can be easily removed and regenerated.

The hollow fiber membrane module is classified into an internal pressure type and an external pressure type. In the external pressure type module, the outside of the hollow fiber membrane is the stock solution side, and the inside of the hollow fiber membrane is the permeate side. On the contrary, the internal pressure type has a structure in which the stock solution is supplied to the inside of the hollow fiber membrane, and the permeated solution is collected and taken out to the outside of the hollow fiber. It has various advantages such as a large membrane area per unit volume and a simple sealing mechanism for separating the undiluted solution and the permeated solution to be membrane-treated. However, in the case of microfiltration membranes, the solids and particles to be separated are clogged and cleaned.
Since it was not regenerated, a large-sized hollow fiber membrane module that is intended to be regenerated and used for a long time is disadvantageous, and this problem has not been sufficiently solved.

That is, when the stock solution is processed by the external pressure type module, the stock solution is supplied to the outside of the hollow fiber membrane under pressure, and the processing solution from which fine particles and solid substances are removed on the outer surface of the membrane permeates the hollow fiber membrane. Then, it reaches the inside of the hollow portion, flows through the hollow portion as a flow path to the opening portion of the header provided at one end portion or both end portions of the membrane module, and is taken out of the membrane module. In this case, the permeated liquid flowing inside the hollow fiber accumulates as it approaches the open end of the hollow fiber membrane, and the amount of permeated liquid increases. That is, in the case of the conventional ordinary hollow fiber, since the permeate flow passage cross-sectional area in the hollow fiber membrane is constant, the permeate flow velocity increases toward the open end of the hollow fiber, and The flow resistance is maximum at the open end. In other words, the pressure difference across the membrane, that is, the effective pressure difference, decreases as the hollow fiber recedes from the open end, so that the local permeated liquid amount of the hollow fiber membrane decreases. Due to the relationship between the permeability of the hollow fiber and the inner diameter, a sufficient effective differential pressure method cannot be applied to a portion having a certain length or more from the opening, and a portion where liquid does not permeate occurs. If there is such a significant bias in load, local membrane fouling will occur, and even if backwashing with permeate or compressed air is performed, it will be just the opposite of the above phenomenon, and the blocked portion of the membrane will be However, there is a problem that the membrane module cannot be completely regenerated, the filtration differential pressure increases, and the life of the membrane module is shortened.

In this case, the inner diameter of the hollow fiber membrane may be increased in order to reduce the flow resistance, but the number of hollow fiber membranes packed in the module is reduced, and the membrane area per volume of the module can be made large. Is lost. Further, if the packing density of the hollow fiber membranes is increased, the hollow fiber membranes in the housing become overly dense, and the flow distribution of the stock solution to be supplied tends to be unevenly distributed, which promotes localization of membrane contamination. Furthermore, the cleaning effects such as scrubbing with air and backwashing are reduced, the regeneration of the membrane module becomes incomplete, and the filtration differential pressure is not recovered.

The deterioration of the module performance due to such a film shape is a factor that hinders the lengthening (upsizing) of the module.

On the other hand, in order to solve the disadvantage of the conventional large-sized hollow fiber membrane module for microfiltration, the both-end collecting type hollow fiber membrane module and the method described in Japanese Patent Laid-Open No. 4-11927. It has been known.

The double-end water collecting type hollow fiber membrane module has a complicated structure as compared with the single-end water collecting type hollow fiber membrane module, and there are problems such as an increase in production cost. In addition, as compared with the single-end water collecting type hollow fiber membrane module, the advantageous length in terms of pressure loss of the hollow fiber membrane is 2
It is only within the range.

On the other hand, in the method disclosed in Japanese Patent Laid-Open No. 4-11927, the permeation coefficient is changed in the length direction of the hollow fiber membrane to reduce the flow resistance of permeated water in the hollow fiber membrane. It is a thing. However, the hollow fiber membrane is a composite membrane prepared by applying a hydrophilic material to a hydrophobic hollow fiber membrane while changing the coating concentration, the crosslinking temperature or the crosslinking time, and has a permeability coefficient in the length direction of the hollow fiber membrane. The technology to change together requires a complicated process and is not economically advantageous.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to, when a hollow fiber membrane is modularized, reduce the flow resistance of the permeate or the stock solution inside the hollow fiber membrane without lowering the average hollow fiber membrane packing density. The permeation performance is improved by lowering the flow resistance in the lengthwise direction of the hollow fiber so that the membrane permeation uniformly occurs in the lengthwise direction of the hollow fiber membrane. Another object of the present invention is to provide a hollow fiber membrane having improved scrubbing cleanability with air and backwashability with permeated liquid, and a method for producing the same.

[0013]

In order to achieve the above object, the present invention has the following constitution. That is, "A tilted hollow fiber membrane characterized by reducing the difference in the amount of permeated water per unit area of the hollow fiber membrane in the length direction by changing the shape of the hollow fiber membrane." Is.

As a method of satisfying the above-mentioned constitution, there is a method of giving a shape in which the cross-sectional area of the hollow portion of the hollow fiber membrane increases as it approaches the opening end.

In particular, the inner pressure type hollow fiber membrane is achieved by changing the shape such as decreasing the thickness of the membrane as it approaches the open end. of course,
Even in the external pressure type, it is effective to change the film thickness.

From the above, a shape in which the cross-sectional area or film thickness of the hollow portion of the hollow fiber membrane increases continuously or stepwise as it approaches the open end of the hollow fiber membrane in the length direction of the hollow fiber membrane. Should be given.

Of these, although not particularly limited, in consideration of the amount of treated water, the packing density, and the cleaning property, in the external pressure type, the film thickness is made constant and the cross-sectional area of the hollow portion is increased. The configuration is particularly preferred.

The features of the present invention will be described below in detail with reference to the drawings. 1 to 6 in FIG. 1 are schematic side sectional views of a hollow fiber membrane of the present invention.

The hollow fiber membrane 1 is obtained by continuously expanding the cross section of the hollow portion in the length direction toward the open end of the hollow fiber while keeping the thickness of the hollow fiber constant.

The hollow fiber membrane 2 is formed by continuously increasing the film thickness in the length direction toward the open end of the hollow fiber while keeping the hollow portion cross-sectional area of the hollow fiber constant.

The hollow fiber 3 is obtained by simultaneously expanding the film thickness and the cross-sectional area of the hollow portion toward the open end in the length direction of the hollow fiber.

The hollow fiber 4 has a constant outer diameter,
The cross-sectional area of the hollow portion is reduced and changed in the direction opposite to the film thickness toward the open end of the hollow fiber.

These hollow fibers are hollow fiber membranes in which the film thickness or the cross-section of the hollow portion is continuously or stepwise changed.

Further, like the hollow fibers 5 and 6, "the part which is separated in the lengthwise direction of the hollow fiber toward the open end of the hollow fiber" is the central part of the hollow fiber membrane. When the hollow fibers 5 and 6 are incorporated into the module, the central part of the hollow fiber membrane is the part where the cross-sectional area of the central part of the hollow fiber membrane is minimum.

It should be noted that, due to the processing accuracy of the module and other reasons, it is not always necessary to accurately form the central portion of the hollow fiber membrane module, and 20%, preferably 10%, and more preferably the effective length of the hollow fiber membrane. Is sufficiently deviated within the range of about 5%, the effect of the present invention can be sufficiently exerted. The same applies to the part of the requirement "maximum at the open end" in the claims that the cross-sectional area of the open end and the central part of the hollow fiber membrane is maximum.

FIG. 2 shows a vertically installed single-end water collecting type hollow fiber membrane module in which the hollow fiber membrane 1 is incorporated. One-end water collecting type hollow fiber membrane 1 in which the cross-sectional area of the hollow part continuously changes
Is housed in the housing case 7,
The casting resin fixing ends 8 and 9 are provided at the upper end and the lower end, respectively, and are embedded in the upper casting resin fixing end 9 of the hollow fiber membrane 1. Raw water enters the housing case 7 through the inlet 11, passes from the outer layer of the hollow fiber membrane 1 through the inside of the hollow portion, and reaches the upper end 10.
Leading to. The hollow fiber membrane module having such a method of use is called an external pressure type hollow fiber membrane module, and a mode in which feed water is poured from 10 and taken out from 11 is called an internal pressure type hollow fiber membrane module.

As such a hollow fiber membrane, in addition to a known spinning method from a generally known membrane material, a mechanism for regularly changing the flow passage cross-sectional area inside the hollow fiber membrane in the length direction of the hollow fiber is added,
It can be manufactured.

FIG. 3 shows a horizontally placed both-end water collection type module incorporating a both-ends water collection-type hollow fiber membrane (hollow fiber membrane of reference numeral 5 in FIG. 1) having continuously changing cross-sectional dimensions. The hollow fiber membrane 3 is housed in the housing case 12, and the housing case 7
The casting resin fixing ends 8 are provided at the left end and the right end, respectively, and the left and right ends of the hollow fiber membrane 5 are opened. Raw water flows from the inlet 11 into the housing case 7 from the sparse portion of the hollow fiber membrane bundle in the center, so that the congestion of the yarn in the housing is mitigated, and it has the same advantages as the one-end water collecting type module.

In the case of FIG. 3, since the open ends are at both ends,
The “part farthest from the open end of the hollow fiber in the length direction of the hollow fiber” is the central part of the hollow fiber membrane. In addition, for processing accuracy and other reasons, the portion where the cross-sectional area of the hollow portion of the hollow fiber membrane is the smallest does not necessarily have to be exactly the central portion of the hollow fiber membrane, and the effective length of the hollow fiber membrane is Even if the deviation is in the range of 20%, preferably 10%, more preferably 5%, the effect of the present invention can be sufficiently exhibited. This also applies to the relationship between the open end portion and the portion where the cross-sectional area of the hollow portion of the hollow fiber membrane is maximum, which is the requirement of "maximize at the open end" in the claims.

FIG. 4 is a schematic diagram of a spinning device for inclined hollow fibers according to the present invention, in which a bath roll is provided under the vertical line from the annular spinneret 14 to the coagulation bath. The rolls 19 are paired, the bath rolls under the vertical line are horizontal, and the Nelson rolls facing each other are turned to prevent slip. This can prevent loosening in the bath and improve the followability of the draft. That is, it is preferable to increase the resistance of the hollow fiber membrane in the coagulation process by contacting it with two or more rolls in the bath to the extent that the membrane is not crushed. 0.1 to 20 in the draft ratio (take-off speed / discharge linear velocity coverage) range in which the flow rate cross-sectional area is obtained by simultaneously changing the discharge amount or the take-up speed.
And preferably from 0.3 to 10, more preferably from 0.5 to
It is 3.

As the membrane material, a polymer usually used for an ultrafiltration membrane or a microfiltration membrane can be preferably used.
For example, cellulose acetate type, polyacrylonitrile type,
There are methacrylic acid ester-based, polyamide-based, polyester-based, polyvinyl alcohol-based, polyolefin-based polymers and the like. It can also be applied to a ceramic film of an inorganic hollow fiber thin tube.

The hollow fiber membrane can be advantageously produced by a so-called solution spinning method of spinning from a polymer solution, that is, a wet spinning method or a dry-wet spinning method. In a spinning method such as melt spinning, the spinning speed is remarkably high, and the polymer filaments discharged from the spinneret are remarkably stretched in the spinning technique, so that the hollow fiber has a constant interval of several tens of centimeters to several hundred centimeters. Therefore, it is difficult to change the thickness of the hollow fiber. However, in the solution spinning method, it is possible to form a thread by coagulation at a relatively low speed.
The degree of stretching immediately after being discharged from the die can be made small and it is possible to cope with minute shape changes.

As the solvent that can be used, any conventionally known solvent can be used under known conditions. For example, if the solvent is an acrylonitrile polymer, dimethyl sulfoxide (DMS) is used.
O), dimethylformamide (DMF), dimethylacetamide (DMAC) and the like.

More specifically, a dry and wet process in which a polymer solution is discharged from an outer annular slit through an outer annular slit through a central hole into a gas phase and then spun into a coagulating liquid using an annular die. The polymer solution can be spun or wet spun by spinning the injected fluid directly into the coagulating liquid from the outer annular slit, through the central hole.

Gas or liquid can be used as the injection fluid. Usually, a coagulating solution is used, preferably a coagulating solution containing a solvent common to the spinning solution.

There are two methods for adjusting the coagulation rate for changing the flow path cross section of these hollow fiber membranes in the longitudinal direction. One is a method in which the spinning take-up speed is kept constant by controlling the discharge amount of the spinning solution and the injection fluid, and the other is a method in which the spinning take-up speed is changed while keeping the discharge amounts of the spinning solution and the injection fluid constant. .

The third method is a method in which the above two methods are combined to change the discharge amount and the take-up speed to control the coagulation speed so as to be harmonized.

In these methods, a discharge system pump for discharging the spinning solution and the injection fluid, and a drive system roller for running the hollow fiber after spinning are feedback-controlled by a control system device such as a sequencer, It can be easily manufactured by periodically changing the film thickness and the flow path cross section which is the hollow portion in the length direction of the spun hollow fiber according to the coagulation speed and draft ratio of the spinning solution.

That is, as a method of changing the discharge amount of the stock solution, the discharge performance is determined within the fluid viscosity range which is in the performance curve of the precision gear pump, taking into consideration the viscosity characteristics of the stock solution, the pressure loss due to the piping, the flow resistance, etc. It is possible to issue

As a method of changing the spinning speed, the speed of the drive roll in the yarn making process is adjusted. For speed adjustment, the drive shaft and roll are directly connected to the servomotor by the servo mechanism, and the rotating portion is detected and controlled by a photoelectric detector or the like.
If the feedback circuit is programmed with a sequencer or the like, it is possible to continuously and periodically adjust the speed.

In the former method in which the spinning rate is kept constant and the discharge amount (including the injection fluid) is changed to obtain a tilted hollow fiber membrane, a precision gear pump of the discharge system is directly connected by a servomotor for control. . When the film thickness for forming the film and the cross-sectional area of the flow path of the hollow part are changed to an inclined type, within the proportional region of the solidification rate, the discharge rate (g / min) = (membrane cross-sectional area (square cm)) + Since the flow passage cross-sectional area (square cm) × spinning speed (cm / min) (constant), the discharge rate is numerically controlled as a function of the membrane cross-sectional area and the flow passage cross-sectional area to obtain the target inclined type. It becomes possible to manufacture a hollow fiber membrane having a shape.

In the latter method, in which the discharge amount (including the injection fluid) is kept constant and the spinning speed is changed to obtain an inclined hollow fiber membrane, the draft (drawing) is generally called.
Is.

It is possible to change the yarn diameter by changing the drive system roller with time in order to loosen or tension the solidification process of pulling the hollow fiber membrane or after heat treatment is completed after the solidification is completed. Since it is constant, it is difficult to make the film thickness uniform.

As a third method, in the case of a method of obtaining a tilted hollow fiber membrane by simultaneously changing the discharge amount (including the injecting fluid) and the spinning speed, the change in the discharge amount (including the injecting fluid) over time. The coagulation rate can be averaged by adjusting the above with the take-up rate. Further, there is an advantage that it is possible to cope with a change in which the hollow fiber is relaxed or tensioned while being subjected to heat treatment by controlling the yarn making line. On the other hand, the control mechanism tends to be complicated, but this can be easily done by computerization.

For example, in dry-wet spinning of a polyacrylonitrile-based stock solution, a precision gear pump and an annular die are used to supply a polyacrylonitrile-based spinning solution from the outer slit of the annular die and dimethylsulfoxide as an injection liquid through a central hole. After injecting an aqueous solution of (DMSO) and discharging a fixed amount in an atmosphere whose temperature and humidity are adjusted, the solution is spun into a coagulating liquid containing dimethylsulfoxide (DMSO). At this time, a change in the take-up speed of the hollow fiber membrane was programmed and incorporated into a sequencer that controls the drive system in advance, the hollow fiber membrane was drawn out from the coagulation bath, and the solvent was repeatedly removed in a washing bath, and then wound up to a module size. Cut and use.

Further, for example, in the case where the film thickness is constant and only the flow path cross-sectional area of the hollow portion is changed to form an inclined type, the spinning solution discharge amount in the low discharge state is P1, the injection liquid discharge amount is S1,
P2 is the spinning solution discharge amount in the high discharge state, and S is the injection liquid discharge amount.
When the value is 2, the following formula is satisfied and the discharge amount is changed between the low discharge state and the high discharge state, whereby a hollow fiber membrane having a substantially desired shape can be obtained. (Fig. 5) 0.7 ≤ (S2 / S1) ^1/2 x P1 / P2 ≤ 1.3 In any case, the method of continuously changing, the predetermined length by changing the speed of the drive system in a pulse shape Any method may be used in which each step is changed step by step. Usually, a method in which the discharge amount of the spinning solution and the injection fluid is changed and the spinning take-up speed is made constant is preferable because the influence of the yarn tension and the like due to the yarn-forming line speed after forming the yarn in the coagulation bath is small.

The ratio of the flow passage cross-sections at both ends of the openings of these hollow fiber membranes is S1 / S2, where S1 is the flow passage cross-section at the maximum open end of the hollow fiber membrane and S2 is the flow passage cross-sectional area at the minimum open end. The ratio is 1.1 to 100, preferably 4 to 64,
The range is more preferably 9 to 36, and the same range can be applied to the membrane cross-sectional area. In this case, the ratio of the cross-sectional area of the membrane and the cross-sectional area of the flow path of the hollow fiber does not need to be uniform.
Regarding the film cross-sectional area, even if the film thickness becomes relatively thin as the film cross-sectional area becomes smaller, there is no significant problem as long as it is designed within the allowable withstand voltage range of the film.

Further, the hollow ratio of the yarn is determined by the thickness t1 of the hollow fiber membrane.
And the value of the ratio t1 / t2 of the t2 forming the hollow portion is 0.1 to 10, preferably 0.25 to 4, and more preferably
It is 0.5 to 2.

Regarding the film thickness, it is preferable that the film thickness is constant, but there is no significant problem even if the film becomes relatively thin as the inner diameter becomes smaller.

Further, when the injection liquid passes through the annular spinneret at a low temperature, the temperature rises in the spinning pack incorporating the annular spinneret, and the dissolved gas of the injection liquid expands from the spinneret under the pressure released after discharge. Air bubbles may be contained in the film, which may cause spinning troubles. Therefore, it is desirable to have a structure of a spinning pack in which there is no temperature difference between the injection liquid and the discharge stock solution line when discharging from the spinneret. The temperature in the vicinity of the base may be fed back to the injection liquid / discharge stock solution line or each tank to control the temperature.

It is preferable that the injectable liquid does not contain a dissolved gas. However, in order to remove the dissolved gas, there is a degassing under reduced pressure, but it is necessary to change the concentration of the injecting liquid and to apply a back pressure to the injecting liquid line. It cannot be used in some cases.

Regarding the viscosity of the discharged stock solution, a capillary viscometer for detecting the differential pressure of the stock solution viscosity is provided in the discharged stock solution line, and the viscosity is corrected by temperature control. Discharged stock solution viscosity is 0.1-100
It is preferably in the range of 0 poise, and in the range of 1 to 500 poise, it is sufficient if there is a proportional relationship between the viscosity of the stock solution and the pressure difference. Next, a hollow fiber membrane module that advantageously realizes the present invention will be described. As the form of the membrane module, there are an external pressure type one-end extraction type and an external pressure type both-end extraction type.

The constitution is such that a plurality of elements in which the hollow fiber membranes are bundled and both ends thereof are adhered are housed in an outer cylinder.

For the member of the outer cylinder, general-purpose thermoplastic resins such as vinyl chloride, polycarbonate, polysulfone, polyethylene, polystyrene, polypropylene, polymethylmethacrylate, etc. can be used, but the conditions of use of the membrane module, such as chemical resistance and heat resistance. Select in consideration of.

Reactive resins such as epoxy, polyurethane, polyester, phenol and polyacrylate can be mainly used as the adhesive, but usually epoxy or polyurethane is generally used.

The size of the module is not uniquely determined in consideration of the design of the membrane module, the maintenance of the unit device incorporating the membrane module, and the like, but the hollow fiber membrane having a length of about 5 meters is bundled. It is quite possible to mount the element which consists of.

The filling rate of the hollow fiber depends on the distance between single yarns, the outer diameter of the yarn,
Also, it is necessary to consider the strength of the sealing material (adhesive) to be fixed. In the one-end water collecting type, the filling ratio is 5 to 70%, preferably 20 to 60% in the maximum yarn outer diameter portion, and the range is 1 to 65% in one minimum yarn outer diameter portion. Further, in the double-end water collection type, the filling rate is equal to the maximum outer diameter of the single-end water collection type.

The number of hollow fibers is 2000 to 100,000, and when designing the membrane area, the length of the hollow fiber membrane, the yarn outer diameter,
It is determined by the filling rate and the like, and is not limited to the number described above.

The membrane area can be usually within the range of 5 to 1000 square meters, but it is not limited to this as long as the membrane is designed according to the maximum permeated water amount for the intended use.

From the above, the features of the membrane module of the present invention can be summarized as follows.

Even if the packing density of the adhesive portion is close to the closest packing, the packing density can be reduced to a level that does not cause drift of the supply liquid in the portion that contributes to permeation, and local film contamination can be reduced. Further, the fluctuation of the yarn due to the bubbling can be largely removed, and the peeling filter cake and the like can be easily discharged, and the washing recovery property is improved. Moreover, even if the average packing density is the same as that of the conventional membrane, the flow pressure loss of permeated water in the membrane can be reduced to make the flow velocity distribution uniform.

The features of the tilted hollow fiber membrane of the present invention and the method for producing the same can be summarized as follows.

When the graded hollow fiber membrane is modularized, the average packing density is the same as that of the conventional membrane, but the flow pressure loss of the feed liquid or the permeate liquid in the length direction of the hollow portion is reduced to reduce the flow velocity distribution. Can be made uniform and the permeation performance is stabilized, and the life of the hollow fiber membrane module (use period)
Can be extended. Moreover, the tilted hollow fiber membrane can be easily manufactured by adding a mechanism for regularly changing the cross section of the hollow fiber to the conventional solution spinning technique.

[0064]

【Example】

Example 1 An inclined hollow fiber was dry-wet spun using the spinning device shown in FIG. That is, a polyacrylonitrile-based polymer (molecular weight: about 300,000) was used as a solvent for dimethyl sulfoxide (DM
SO) to a solution concentration of 14.0 weight percent.
The injection fluid was 75 dimethylsulfoxide (DMSO).
A weight percent aqueous solution was used.

A precision gear pump 12 is used for the above spinning solution.
Then, the annular spinneret 14 incorporated in the spinning pack 13 (nozzle diameter 1.2 mm, capillary outer diameter 0.6 mm, inner diameter 0.3)
(mm) outside slit part, and the injection liquid is supplied to the center hole of the annular base 14 by the precision gear pump 15, and the atmospheric humidity is adjusted to 0.0272 kg (water) / kg (dry air). After discharging in the hood 16,
8% by weight of dimethyl sulfoxide (DMSO) was spun into a coagulation bath 17, and the hollow fiber membrane 18 was spun onto the coagulation bath 1.
After removing the solvent from the pair of in-bath rolls 7 of 7 through the take-up roll 20 and interlocking with the water washing machine 21, the solvent was repeatedly cut by the line cutter 22 at intervals of 1.2 meters. At this time, the take-up speed was set to 12 m / min (constant), and the sequencer 23 controlled the spinning gear precision gear pump 12 and the injection liquid precision gear pump 15 in a discharge amount (including the injection liquid) cycle as shown in FIG.

The hollow fiber membrane cut with a line cutter is
Table 1 shows the results of measuring the diameter of the thread every 30 cm in the length direction of the thread.
Shown in. From this result, it was found that the circularity and the film thickness of the hollow fiber were almost constant, the outer diameter and the inner diameter of the hollow fiber increased proportionally in the inclined portion, and the cross-sectional area of the hollow portion also increased.

[0067]

[Table 1] Example 2 The tilted hollow fiber membrane used is the membrane 1 produced in Example 1, having a thickness of 0.05 mm and a minimum inner diameter φ.
0.25 mm, maximum inner diameter of 0.55 mm, length 1.2 m (module effective length: 1 m) with diameter of cross section of permeated water passage continuously changing from minimum opening end to maximum opening end, diameter 70 It is a UF membrane that eliminates 100% of colloidal silica of -100 nm, and it is built in a case with an inner diameter of 100 mm.
It is a single-end water collection type module. The iron oxide-containing water (concentration: 10 ppmas Fe) was added to each of the module in which the cross section of the permeated water flow passage was continuously changed according to the present invention and the conventional module in which the average inner diameter and the film thickness were matched at an average filtration flow rate of 0.5 m / h. The whole amount was subjected to constant velocity filtration, and the change in the amount of permeated water with respect to the distance from one end of the fixed casting end of the hollow fiber membrane was measured. As shown in the results in Table 2, the permeated water flow rate at the end of the permeated water collection was increased by about 1.7 times compared with the conventional membrane.

[0068]

[Table 2]

[0069]

The tilted hollow fiber membrane and the method for producing the same according to the present invention are configured as described above. The produced tilted hollow fiber membrane can significantly reduce the flow pressure loss as compared with the conventional membrane, and can make the permeated water flow velocity distribution uniform. Therefore, the dispersion of the load and the pollution applied to the local part of the membrane improves the bubbling and backwashing properties when performing the membrane cleaning, and the operation can be prolonged. Further, in this method of manufacturing a tilted hollow fiber membrane, it is only necessary to change the cross-sectional ratio and the flow passage cross-sectional area of the hollow fiber membrane in the length direction of the yarn, and the module configuration is simple.

[Brief description of drawings]

FIG. 1 is a schematic view of a tilted hollow fiber membrane according to the present invention.

FIG. 2 is a schematic view of a tilted hollow fiber membrane according to the present invention incorporated into a single-end water collecting type module.

FIG. 3 is a schematic view of a tilted hollow fiber membrane according to the present invention incorporated in a water collecting module of both ends.

FIG. 4 is a schematic diagram of an inclined hollow fiber spinning apparatus according to the present invention.

FIG. 5 is a chart showing a cycle for controlling a spinning solution of a tilted hollow fiber and an injecting solution discharge amount according to the present invention.

[Explanation of symbols]

1: Gradient hollow fiber membrane in which the cross-sectional area of the hollow portion continuously changes while the cross-sectional area of the membrane remains constant 2: The cross-sectional area of the membrane changes continuously while the cross-sectional area of the hollow portion remains constant Tilted hollow fiber membrane 3: Cross-sectional area of the membrane and hollow part is continuously changing Gradient hollow fiber membrane 4: Cross-sectional area ratio of the membrane and hollow part is reversibly changed Inclined hollow fiber membrane 5: Hollow fiber membrane of both ends collecting type, where the cross-sectional areas of the membrane and hollow part are continuously changing 6: Part with the narrowest cross-sectional area 7: Housing case 8: Top casting Fixed end 9: Lower casting fixed end 10: Upper end of hollow fiber membrane 11: Inlet 12: Precision gear pump for spinning solution 13: Spinning pack 14: Annular spinner 15: Precision gear pump for injection liquid 16: Hood for controlling atmosphere 17 : Coagulating liquid tank 18: Hollow fiber membrane 19: Roll in coagulating bath 20: Collection Roll 21: Water washer 22: Line cutter 23: Sequencer for controlling solution and injection liquid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D01F 6/18 A 7199-3B 6/60 7199-3B

Claims (26)

[Claims] 1. A gradient type in which the difference in the amount of permeated water per unit area of the hollow fiber membrane in the length direction of the hollow fiber membrane is reduced by changing the shape of the hollow fiber membrane in a tilted manner. Hollow fiber membrane. 2. A difference between the permeated water amount per unit area calculated in a portion of a continuous one-fourth length in the length direction of the hollow fiber membrane and the permeated water amount per unit area calculated over the entire length. Is 4 times or less, The graded hollow fiber membrane of Claim 1 characterized by the above-mentioned. 3. The graded hollow fiber membrane according to claim 2, wherein the difference is 3 times or less. 4. The graded hollow fiber membrane according to claim 2, wherein the difference is 2 times or less. 5. The tilted hollow fiber membrane according to claim 2, wherein the difference is 1.5 times or less. 6. The tilted hollow fiber membrane according to claim 1, which is a single-end water collecting hollow fiber membrane. 7. The tilted hollow fiber membrane according to claim 1, which is a water collecting hollow fiber membrane at both ends. 8. The hollow fiber membrane has a shape in which the cross-sectional area of the hollow part of the hollow fiber membrane increases continuously or stepwise as it approaches the open end of the hollow fiber membrane in the length direction. The tilted hollow fiber membrane according to claim 1, which is characterized in that. 9. The method according to claim 1, wherein the type is an external pressure type.
9. A tilted hollow fiber membrane according to any one of 8 to 8. 10. The tilted hollow fiber membrane according to claim 7, wherein the hollow fiber membrane has a minimum cross-sectional area near the midpoint in the lengthwise direction of the hollow fiber membrane. 11. The hollow fiber membrane is characterized in that the vicinity of the midpoint in the lengthwise direction is within the range of 20% of the total length of the hollow fiber membrane from the midpoint in the lengthwise direction of the hollow fiber membrane. Item 10. A tilted hollow fiber membrane according to item 10. 12. The inclined hollow fiber membrane according to claim 1, which is an internal pressure type. 13. The hollow fiber membrane has a shape in which the film thickness of the hollow fiber membrane increases continuously or stepwise as it approaches the open end of the hollow fiber membrane in the length direction of the hollow fiber membrane. The tilted hollow fiber membrane according to claim 12. 14. The inclination according to claim 1, wherein the following formula is satisfied when the maximum channel cross-sectional area of the hollow part of the hollow fiber membrane is S1 and the minimum channel cross-sectional area is S2. Type hollow fiber membrane. 1.1 ≦ S1 / S2 ≦ 100 15. The tilted hollow fiber membrane according to claim 1, wherein a hollow ratio t1 / t2 satisfies the following equation, where t1 is a membrane thickness of the hollow fiber membrane and t2 is a radius of the hollow portion. 0.1 ≦ t1 / t2 ≦ 10 16. A tilted hollow fiber membrane module using the hollow fiber membrane according to claim 1, wherein the hollow fiber membrane is made of polyacrylonitrile. 17. A tilted hollow fiber membrane module, characterized in that the hollow fiber membrane module uses the hollow fiber membrane according to any one of claims 1 to 16. 18. The method for producing a tilted hollow fiber membrane according to claim 1. 19. The method for producing a tilted hollow fiber membrane according to claim 18, wherein the take-off speed is kept constant and the discharge amount is changed. 20. The spinning solution discharge amount in a low discharge state is P1,
The injection liquid discharge amount is S1, and the spinning solution discharge amount in the high discharge state is P
20. The inclined hollow fiber membrane according to claim 19, wherein when the injection liquid discharge amount is S2, the following formula is satisfied to change the discharge amount between the low discharge state and the high discharge state. Production method. 0.7 ≦ (S2 / S1) ^1/2 × P1 / P2 ≦ 1.3 21. The method for producing a tilted hollow fiber membrane according to claim 19, wherein the change in the discharge amount is linear. 22. The method for producing a tilted hollow fiber membrane according to claim 18, wherein a precision gear is used. 23. The method for producing a tilted hollow fiber membrane according to claim 18, wherein in the coagulation bath, the hollow fiber membrane is wound around a facing roll by being wound and drafted. 24. The method for producing a tilted hollow fiber membrane according to claim 18, wherein the temperature of the spinneret is fed back to adjust the temperature of the coagulating liquid and / or the spinning dope. 25. The method for producing a tilted hollow fiber membrane according to claim 18, wherein the injection liquid and / or the coagulation bath liquid is water or / and a dimethyl sulfoxide solution. 26. A tilted hollow fiber membrane according to any one of claims 1 to 16, a tilted hollow fiber membrane module according to claim 16, or a tilted hollow fiber membrane produced by the method according to any one of claims 18 to 25. A transparent processing method characterized by being used.