JP2004243263A - Hollow fiber membrane module and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a module incorporated with a hollow fiber which is obtained by using a crimp impartation method excellent in a process stability without causing damage, yarn break and flattening even in the case of the hollow fiber weak in breaking tenacity. <P>SOLUTION: The module is incorporated with the hollow fiber membrane which is ≤25 in the breaking tenacity of single yarn and is fixed with crimps of ≥2.0 mm in amplitude, in which the ratio of the deformed hollow fiber of the hollow fiber membrane is confined to ≤0.05%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a module incorporating a crimped hollow fiber membrane and a method for producing the same. More specifically, the present invention relates to a module using a hollow fiber membrane continuously crimped on-line and a method for producing the same.
[0002]
[Prior art]
In recent years, hollow fibers made of polymers have been developed and used for various purposes and applications. In particular, hollow fiber polymer membranes (hollow fiber membranes) are microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, gas separation membranes, nitrogen-enriched membranes, oxygen-enriched membranes, blood purification membranes, artificial kidneys, artificial lungs, etc. Has been put to practical use in various applications.
[0003]
Hollow fibers are covered or crimped with synthetic fibers. This is to prevent the hollow fiber membranes from closely adhering to each other and forming a concentration boundary film near the membrane, which causes a reduction in the overall mass transfer rate and a decrease in performance. Conventionally, as a method of applying crimp to a yarn, a method called a gear method, in which the yarn is pushed between two continuously rotating gears having meshing teeth and simultaneously or continuously heat treated to fix the crimp (particularly, Japanese Patent Application Laid-Open No. 09-021024) is known, but this method is to impart crimp to the yarn by causing the yarn to crimp. Particularly, in the case of a hollow fiber membrane having a small film thickness and a low yarn strength, the yarn is preferably used. When the strip is bent or pressed, the thread is crushed or flattened, and there is a problem that the function of the object itself is lost. In order to solve such a drawback, a method has been proposed in which a crimped yarn having few flat and irregularly shaped yarns is obtained by giving appropriate stretching at normal temperature (Japanese Patent Application Laid-Open No. 2002-66274). In order to obtain a high strength, it is necessary to perform stronger stretching, so that flattening and irregular shapes are likely to occur, and there is a problem that a sufficient crimp shape cannot be obtained. On the other hand, as a method of imparting crimp by heating, a method of winding the material around a bobbin or the like and then performing a heat treatment at a temperature of 50 ° C. or more to fix the crimp (Japanese Patent Publication No. 4-42222, JP-A-8-010322) However, the crimp cannot be fixed while the hollow fiber is running. A crimping method disclosed in JP-A-6-212520 and JP-B-7-78293 is known as a method in which a continuous yarn is conveyed in a meandering manner between a large number of yarn guides running at regular intervals, and is heat-set by heat treatment. An apparatus and a method for producing a crimped linear body have been proposed.
[0004]
[Patent Document 1]
JP-A-09-021024
[Patent Document 2]
JP-A-2002-66274
[Patent Document 3]
Japanese Patent Publication No. 4-42022 [0007]
[Patent Document 4]
JP-A-8-10322
[Patent Document 5]
JP-A-6-212520
[Patent Document 6]
Japanese Patent Publication No. 7-78293
[Problems to be solved by the invention]
However, in these methods, it is not possible to guarantee that the clearance between the pair of crimp rolls or gears and the timing belt is always kept constant due to backlash between the pair and the driving device or vibration during the timing belt travel. When the size is smaller than the yarn, flattening, crushing or damage, yarn breakage, and the like are likely to occur. Further, in these documents, there is no description about the breaking strength of the hollow fiber and the stretching at the time of applying the crimp, and a method for suppressing flatness and crushing of the hollow fiber having particularly weak breaking strength has not been found so far.
[0011]
An object of the present invention is to provide a method for manufacturing a hollow fiber membrane built-in module using a crimping method excellent in process stability, which does not cause damage, breakage, or flattening of the hollow fiber membrane in a hollow fiber membrane having low breaking strength. And a hollow fiber membrane built-in module obtained by the method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following configuration. That is,
(1) A module incorporating a hollow fiber membrane having a breaking strength of a single yarn of 25 g or less and having a crimp having an amplitude of 2.0 mm or more immobilized therein, wherein the ratio of the deformed hollow fiber in the hollow fiber membrane is A hollow fiber membrane module having a content of 0.05% or less.
[0013]
(2) The hollow fiber membrane module according to (1), wherein the crimp wavelength is 10 mm or more.
[0014]
(3) The crimp is fixed by intermittently applying a stretch of not more than twice the yield elongation to a part of the circumference of the hollow fiber membrane at a temperature not lower than 60 ° C. and not higher than the glass transition temperature of the hollow fiber membrane material. The hollow fiber membrane module according to (1) or (2).
[0015]
(4) The hollow fiber membrane module according to any one of (1) to (3), wherein the hollow fiber membrane comprises polysulfone and polyvinylpyrrolidone.
[0016]
(5) The hollow fiber membrane module according to any one of (1) to (4), which is used for an artificial kidney.
[0017]
(6) Yield and elongation intermittently on a part of the circumference of the hollow fiber membrane at a temperature of 60 ° C. or higher and the glass transition temperature of the hollow fiber membrane material at a temperature of 60 ° C. or higher and a hollow fiber membrane having a breaking strength of 25 g or less. A method for producing a hollow fiber membrane module, wherein a crimp having an amplitude of 2.0 mm or more and a wavelength of 10 mm or more is imparted by giving a stretching of twice or less the degree and then incorporated in the module.
[0018]
(7) The method for producing a hollow fiber membrane module according to (6), wherein the hollow fiber membrane comprises polysulfone and polyvinylpyrrolidone.
[0019]
(8) The method for producing a hollow fiber membrane module according to (6) or (7), wherein the hollow fiber membrane is for an artificial kidney.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a suitable crimp for a hollow fiber having a low breaking strength of a single yarn of 25 g or less.
[0021]
The crimp in the present invention refers to a waveform shape with respect to a straight line.
[0022]
The hollow fiber membrane of the present invention preferably has an amplitude of 2.0 mm or more from the viewpoint of ensuring a sufficient liquid flow in the module after modularization. On the other hand, it is preferably 5.0 mm or less from the viewpoint of maintaining the membrane performance and ensuring the hollow fiber filling rate.
[0023]
Further, the wavelength is preferably 10 mm or more from the viewpoint of maintaining the membrane performance and securing the hollow fiber filling rate, and more preferably 20 mm or more. On the other hand, it is preferably 50 mm or less from the viewpoint of ensuring a sufficient liquid flow in the module.
[0024]
The amplitude and wavelength are determined as follows. That is, the wavelength of the crimp represents the length from the peak of the peak shown in FIG. 1 to the peak of the next peak, and the amplitude represents the length from the convex side of the peak to the concave side of the bottom of the valley. The method of measuring the amplitude and the wavelength is such that the module case of the module in which the hollow fiber membrane is incorporated is cut with an ultrasonic cutter or the like, and the internal hollow fiber membrane is taken out by applying as little tension as possible. From among them, eight hollow fibers are randomly selected, the amplitude and wavelength of each yarn at an arbitrary position are measured, and the average value of the eight yarns is compared with the amplitude, wavelength and the hollow fiber incorporated in the module. I do.
[0025]
In the present invention, the proportion of the deformed hollow fiber needs to be 0.05% or less. Here, the deformed hollow fiber refers to a combination of a flat yarn, a crushed yarn, and a deformed yarn, and the flat refers to a material having a ratio of the major axis to the minor axis of the hollow fiber cross-sectional diameter of 1/2 or less. Is an extremely flat or substantially crushed one having a ratio of major axis to minor axis of 1/5 or less, and a variant is a non-circular or non-elliptical one whose ratio of major axis to minor axis is unclear. .
[0026]
The method for producing a hollow fiber membrane provided by the present invention is a method in which a hollow fiber-shaped polymer fluid usually spun using a double-ring type die forms a porous material in a falling process, solidifies in a coagulation bath, and a washing bath. This is a method in which the core side fluid is washed, dried, crimped and then wound up.
[0027]
In the present invention, the hollow fiber membrane is crimped by passing the hollow fiber membrane between a pair of crimper rolls.
[0028]
When crimping the hollow fiber membrane, the filament is heated immediately before crimping, then passed through a crimper roll to give a crimp shape, and then cooled to room temperature to fix the crimp.
[0029]
The heating of the yarn is preferably performed immediately before and during passage of the crimper roll for the purpose of easily deforming the hollow fiber membrane by heat. The heating temperature varies depending on the hollow fiber membrane material, but if it is too low, it is not possible to impart a sufficient crimp shape, and if the film is heated above the glass transition point of the membrane, the membrane material itself will deteriorate and the membrane performance will deteriorate. It is not preferable because it lowers. Therefore, it is preferable that the temperature is usually in the range of 60 ° C. or higher and the glass transition point or lower. For example, in the case of a hollow fiber membrane composed of two components of polysulfone and polyvinylpyrrolidone, the temperature is 60 ° C to 120 ° C, more preferably 70 ° C to 110 ° C. Also, since the amplitude of the crimp changes depending on the temperature, it is preferable to control the temperature to a constant value. The heating time must be long enough to raise the temperature of the yarn sufficiently, but if it is too long, thermal decomposition may occur.
[0030]
As shown in FIG. 2, crimper rolls are formed by arranging convex portions or cylindrical bodies on a star-shaped plate of a support in a circular manner at regular intervals. Here, the radius of the convex portion or the cylindrical body of the crimper roll is sufficient to give a deformation exceeding the yield elongation on the side opposite to the side where the hollow fiber membrane is pressed when pressed along the convex portion or the cylinder. It is desirable to have a diameter that gives a deformation of not less than the yield elongation and not more than twice the yield elongation, because flattening, deforming, and crushing are likely to occur in the pressed part if it is smaller than necessary. Is desirable. If this is expressed by the formula, the radius of curvature of the convex portion or the cylindrical body of the crimper roll with which the hollow fiber membrane comes into contact is R1, the length obtained by adding the outer diameter of the hollow fiber to this is R2, and the yield elongation of the hollow fiber is If S (%), the relationship is S ≦ (R2 / R1-1) × 100 ≦ 2S. In the present invention, by heating at the time of crimping, it is possible to impart a sufficient amplitude for securing a flow of a dialysate or the like when modularized without giving a stretching exceeding twice the yield elongation. Here, the yield elongation in the present invention is determined from the relationship between elongation and strength (SS curve) in a yarn tensile test, as shown in JP-A-2002-66274.
[0031]
If the SS curve does not have a maximum point as shown in FIG. 3, an auxiliary line having an extended initial gradient is provided. The point at which the two auxiliary lines intersect is defined as the yield point, the strength at that point is defined as the yield strength, and the elongation is defined as the yield elongation. In addition, as shown in FIG. 4, when there is a local maximum point, a point at which the auxiliary line extending the initial gradient and the auxiliary line with a zero slope at the local maximum point intersect is defined as a yield point, and the strength at that point is defined as the yield strength. The elongation is defined as the yield elongation.
[0032]
In addition, in the present invention, it is preferable to provide intermittent stretching on a part of the circumference of the hollow fiber membrane when the stretching is performed at twice or less the yield elongation. Here, “intermittently” means a state in which a continuous cleaning object flows without interruption.
[0033]
In the crimping method of the present invention, it is preferable that the shortest distance between the pair of crimper rolls at the time of closest approach is constant during roll operation. Thereby, for example, the generation of flat yarns, deformed yarns, and crushed yarns due to backlash between the crimper roll and the driving portion is suppressed. As a means for keeping the shortest distance between the crimper rolls at the time of closest approach, in the axial direction of one crimper roll, the portion where the thread does not pass, that is, the circumference of both ends or one end of the roll, the closest approach between the crimper rolls Wrap the tape with the shortest distance thickness at the time, or set the shortest distance at the time of closest approach to 0 at both ends or only one end of the crimper roll, and make the rolls completely contact each other at the part where the yarn does not pass And the like. When the tape is wound, the material is not particularly limited, but it is preferable that the material is small in deformation due to heat or mechanical pressure. If the deformation is large, the winding thickness changes, so that the rotation of the rolls and the gap between the rollers occur during operation, and the shortest distance between the rolls cannot be stabilized. For this reason, a metal tape such as aluminum is preferably used.
[0034]
The shortest distance between the crimper rolls at the time of the closest approach may be basically equal to or longer than the outer diameter of the hollow fiber membrane.However, when crimping is performed by bundling a plurality of fibers, the shortest distance is set because the yarns overlap each other. It is preferable to appropriately widen it accordingly.
[0035]
The hollow fiber membrane to which the present invention is applied is a hollow fiber-shaped porous membrane, such as a sponge. It is suitably used for liquid permeation, hemodialysis, hemofiltration and the like, and preferably has an inner diameter of 100 to 1000 microns, a film thickness of 10 to 60 microns, and a diameter of 0.1 to 0.5 mm.
[0036]
Examples of the membrane material for the hollow fiber membrane include a membrane material made of a hydrophobic polymer and a blend membrane of a hydrophobic polymer and a hydrophilic polymer. Examples of the hydrophobic polymer include cellulose, cellulose acetate, polyacrylonitrile, polysulfone, and polyethersulfone. Among them, polysulfone is preferably used. Examples of the hydrophilic polymer include polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, dextran or a derivative thereof, polyacrylic acid, and polymethacrylic acid. Among them, polyvinylpyrrolidone is preferably used. These hydrophobic polymers may be used alone or as a blend of a plurality of hydrophobic polymers. Further, a blend of a hydrophobic polymer and a hydrophilic polymer may be used, but a blend film of polysulfone and polyvinylpyrrolidone is suitably used from the viewpoint of film forming properties and membrane performance.
[0037]
The module incorporating the hollow fiber membrane of the present invention is suitably used as an artificial kidney, microfiltration, ultrafiltration, reverse osmosis, gas separation, nitrogen enrichment, oxygen enrichment, blood purification and the like.
[0038]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these ranges.
(Example 1)
16 parts of polysulfone (“Udel” P-3500, manufactured by Teijin Amoko), 4 parts of polyvinylpyrrolidone (K30, manufactured by BASF) and 2 parts of polyvinylpyrrolidone (K90, manufactured by BASF) were added to 77 parts of dimethylacetamide and 1 part of water. The mixture was heated and melted at 14 ° C. for 14 hours. This film forming stock solution was discharged from an orifice-type double cylindrical die having an outer diameter of 0.3 mm and an inner diameter of 0.2 mm, and a solution composed of 64 parts of dimethylacetamide and 36 parts of water was discharged as a core liquid, and passed through a dry length of 350 mm. Thereafter, the mixture was passed through a coagulation bath filled with a solution composed of 20% by weight of dimethylacetamide and 80% by weight of water, a washing bath filled with water, and a drying apparatus. Next, crimp was applied using the crimperol shown in FIG. In FIG. 2, 1 indicates a cylindrical body, and 2 indicates a tape having a thickness of 3 mm. Specifically, a pair of crimper rolls having eight circular cylinders each having a diameter of 8 mm attached to each other, and a crimper applying device set so that the width of the right and left meanders of the yarn is 14.9 mm is used. , And crimped, and wound by a winder to obtain 9,900 hollow fiber membrane yarn bundles. During the operation, no trouble such as thread breakage occurred. After cutting the obtained hollow fiber membrane yarn bundle to a predetermined length, the hollow fiber membrane module is put into a module case, and both ends of the hollow fiber membrane yarn bundle are fixed with a polyurethane resin, and the polyurethane resin ends are cut off to obtain a hollow fiber membrane module. Obtained. The inner diameter of the hollow fiber membrane was 192 microns, and the outer diameter was 275 microns. When the breaking strength of the hollow fiber membrane was measured, the yield was 20 g and the yield elongation was 6.3%. The outermost stretching of the hollow fiber membrane on the side opposite to the side corresponding to the cylinder, calculated from the diameter of the cylinder of crimper roll, was 6.9%. When the crimped shape of the hollow fiber membrane taken out of the hollow fiber membrane module in a tensionless state was measured, the amplitude was 2.3 mm and the wavelength was 32 mm. In order to measure the number of deformed hollow fibers in this module cross section, eight hollow fiber membranes were arbitrarily extracted, and the membrane cross section was observed at a magnification of 200 times with a microscope. .
[0039]
In addition, the cross section of the hollow fiber membrane was observed for all 9,900 pieces after magnifying 200 times, and the number of deformed hollow fibers was 0.
[0040]
(Comparative Example 1)
A hollow fiber membrane yarn bundle was obtained in the same manner as in Example 1 except that the atmospheric temperature of the crimping device was set to room temperature. During the operation, no trouble such as thread breakage occurred. A hollow fiber membrane module was obtained from the obtained hollow fiber membrane yarn bundle in the same manner as in Example 1. The porosity, inner diameter, outer diameter, breaking strength, and yield elongation of the hollow fiber membrane were the same as in Example 1. The crimped shape of the hollow fiber membrane taken out of the wound bundle of hollow fiber membranes in a tensionless state was measured. The amplitude was 1.6 mm and the wavelength was 32 mm. When the number of deformed hollow fibers in this module cross section was measured, it was 0 for 9,900 hollow fibers.
[0041]
【The invention's effect】
When simultaneously crimping a large number of hollow fiber membranes for artificial kidneys supplied continuously, use a crimping method with excellent process stability that does not cause damage, breakage, or deformation of hollow fiber membranes. It is possible to provide a method of manufacturing a hollow fiber membrane module and a hollow fiber membrane module.
[Brief description of the drawings]
FIG. 1 is a diagram showing a wavelength and an amplitude of a crimp provided to a hollow fiber membrane in the present invention.
FIG. 2 is a view showing an embodiment of crimperol of the present invention.
FIG. 3 is a diagram showing a method of determining a yield point when there is no local maximum point in an SS curve showing the relationship between elongation and strength in a yarn pulling test.
FIG. 4 is a diagram showing a method for determining a yield point when the SS curve has a maximum point.

Claims (8)

A module having a built-in hollow fiber membrane in which the breaking strength of a single yarn is 25 g or less and a crimp having an amplitude of 2.0 mm or more is fixed, wherein the ratio of the deformed hollow fiber in the hollow fiber membrane is 0.05%. % Or less. The hollow fiber membrane module according to claim 1, wherein the crimp has a wavelength of 10 mm or more. Claims wherein the crimp is immobilized by intermittently giving a stretch of not more than twice the yield elongation to a part of the circumference of the hollow fiber membrane at a temperature of 60 ° C or higher and a glass transition temperature of the hollow fiber membrane or lower. Item 3. The hollow fiber membrane module according to item 1 or 2. The hollow fiber membrane module according to any one of claims 1 to 3, wherein the hollow fiber membrane comprises polysulfone and polyvinylpyrrolidone. The hollow fiber membrane module according to any one of claims 1 to 4, wherein the hollow fiber membrane module is for an artificial kidney. In a hollow fiber membrane having a breaking strength of a single yarn of 25 g or less, at a temperature of 60 ° C. or more and a glass transition temperature of the hollow fiber membrane, a part of the circumference of the hollow fiber membrane is intermittently twice the yield elongation. A method for producing a hollow fiber membrane module, comprising applying a crimp having an amplitude of 2.0 mm or more and a wavelength of 10 mm or more by applying the following stretching, and then incorporating the crimp into the module. The method for producing a hollow fiber membrane module according to claim 6, wherein the hollow fiber membrane comprises polysulfone and polyvinylpyrrolidone. The method for producing a hollow fiber membrane module according to claim 6, which is for an artificial kidney.

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