JPH03267128A - Porous hollow fiber - Google Patents

Abstract

PURPOSE:To obtain the porous hollow fiber having high water permeability and fractionating property and with its flux not significantly reduced by forming the inner surface of the porous hollow fiber contg. a hydrophobic polymer and a hydrophilic polymer into a porous structure consisting of a dense layer having a minute slit and a reticular structure and providing a pore capable of permeating pure water at a specified rate to the outer surface. CONSTITUTION:The porous hollow fiber contains 0.5-10% hydrophilic polymer (e.g. polyvinyl pyrrolidone) based on the hydrophobic polymer such as polysulfone, and is the porous structure consisting of the dense layer having minute slits at a rate of perforation of 10-50% and having 0-5.5mum thickness on the inner surface and the reticular structure integrated with the dense layer and continuously formed. The outer surface has pores having maximum diameter of 0.5-5mum formed by the partial opening of the reticular structure. The porous hollow fiber useful in separation is obtained by using the hollow fiber capable of permeating pure water at the rate of >=1000l/m<2>.hr.kg.cm<2>.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a porous hollow fiber, which has high water permeability, excellent printability, and excellent hydrophilicity. be.

(Prior Art) In recent years, techniques using hollow fibers having selective permeability in separation operations have made remarkable progress, and have been put into practical use in various fields. As materials for such hollow fibers, resins such as cellulose, polyamide, polyac+1 lnitol, hol+vinyl alcohol, and phorisulfone are used. Among them, polysulfone resin has heat resistance,
Due to its physical and chemical properties such as acid resistance, resistance to unloading +1, and resistance to oxidizing agents, it is used in a variety of applications because it is easy to apply.

However, when the hollow fiber is made of a hydrophobic polymer such as polysulfone resin, the permeation rate decreases significantly when the hollow fiber is dried. As a method to solve all of these drawbacks, for example, Japanese Patent Application Laid-Open No. 58-104940
No. 61-93801 discloses that a polysulfone membrane is rendered hydrophilic by incorporating hydrophilic polyvinylpyrrolidone into the membrane. Also, % Kaisho 6
1-2383 (Publication No. 16 and Jikai 1@61-238
No. 834 discloses polysulfone resin, polyvinylpyrrolidone, and JLL agent.

A hydrophilized polysulfone membrane with high water permeability and having pores with an average pore size of 500 Å or more on both surfaces of the membrane is described using a spinning dope composed of a solvent.0 (Problem to be solved by the invention) However, the former polysulfone membrane has a pore size Q of 001~
Since the membrane has a swine layer with minute pores of 0.05 μm, there is a problem of extremely low water permeability.The latter polysulfone membrane has an average of 50 micropores on the membrane surface.
Since it is 0 Å or more, it has high water permeability.

However, the purpose of the present invention is to provide a hydrophilic material with high water permeability and excellent fractionability, and with a small decrease in FLUX during use. An object of the present invention is to provide a porous hollow fiber having properties.

(Means for Solving &l@) The present invention uses ultra-porous hollow fibers containing 0.5 to 10% of hydrophilic polymers based on #aqueous polymers.

The porous hollow fiber has slit holes on the inner surface with a porosity of 1.
It has a porous structure consisting of a dense layer with a thickness of 0.5 to 5 μm in a proportion of 0 to 50%, and an n-order texture formed integrally and continuously to the dense layer, and the outer surface is It has pores with a maximum pore diameter of 0.5 to 5 μm formed by opening a part of the network, and the pure water permeation rate at 25° C. is 1 OUTljl/n?
- It is a porous hollow fiber characterized in that it is hr·Kg/cm2 or more.

The uninvented hollow fiber has slit-like micropores that are elongated in the length direction of the hollow fiber on the inner surface.

A dense layer with a thickness of 448 m is formed.The average width of such slit-like micropores is usually 500 Å or less, but
In order to have high fractionability, the O average width is particularly preferably 100 to 300. The O average width is the average value of the short diameter of the micropores, and is measured by a scanning electron micrograph. The length of this micropore is usually 3 times or more the slit width, preferably il 0 times or more.

It is also preferable that the distribution density of the micropores on the inner surface of the hollow fiber be as uniform as possible and as high as possible. In order to provide excellent subsequent image development and pressure resistance, it is preferable that the width of the micropores be as uniform as possible. The porosity of these slit-like micropores is usually 10 to 50. The porosity referred to in the present invention is
It indicates the ratio of the total pore area of the micropores opened on the inner surface to the outer surface area as a percentage. If the porosity is less than 10%, the water permeability will be low (and if it exceeds 513%, the surface strength will be low, making it difficult to handle the hollow fibers. In particular, if the porosity is 10 to 30%, the hollow fibers will have poor water permeability. It is preferable because it has a good balance between permeation performance and mechanical strength.

By the way, the uninvented hollow fiber is formed on the inner surface, and a porous structure of a network structure is continuously formed in a dense layer, and a part of the network structure is opened on the outer surface, resulting in a maximum Pore diameter 0.1
It has pores of ~5 μm. The network formed inside such hollow fibers has a large number of continuous pores with an average size of 1 to 5 μm, and there are no giant hollow frames of 10 #m or more. Therefore, it has excellent compactability during long-term use and also has excellent strength. The shape and porosity of the pores on the outer surface are not particularly limited, but are usually circular or elliptical, and the pore size is preferably 10 to 50, which is about the same as that of the inner surface.

If the pore diameter on the outer surface is 5 μm or more, not only will it be a problem in terms of pressure resistance, but also residues will easily accumulate inside the membrane when P is passed through the membrane due to external pressure, resulting in a rapid decrease in the permeation rate. There is an undesirable tendency that the membrane is not regenerated sufficiently by chemical washing or backwashing. On the other hand, if the maximum pore diameter is smaller than 0.1 μm, water permeability decreases, which is not preferable.

The hollow fiber of the present invention has a porous structure consisting of a dense layer having microscopic slit holes on the inner surface and a network structure. And because the thickness of the dense layer is as thin as 0.5 to 5 μm, the pure water permeation rate at 25°C is 100 OA/d-hr-K, even though it blocks more than 90% of the particles of 135 people.
Shows high water permeability t of Ii/cIA or higher. If you actually use t-FmL of water, use external pressure filtration.

The outer surface traps particles of submicron order or larger, while the hollow fiber walls and the dense layer on the inner surface trap submicron particles such as dissolved polymers. That is, since the outer surface and the hollow fiber wall play the role of a pre-filter, the permeation rate decreases little and a high permeation rate can be maintained.

On the other hand, internal pressure filtration is effective for one-way filtration using a cloth 70 that has a dense layer on the inner surface, and the material aIP that has passed through the hollow fibers is difficult to retain on the hollow fiber walls, making it difficult to cause contamination.

Also, the hollow fiber of the present invention has a dense layer and a porous structure integrated, and unlike composite hollow fibers obtained by coating methods, there are 11 problems such as pinholes in the dense layer and peeling between the dense layer and the support layer. I don't want to.

Furthermore, the uninvented hollow fiber has 05~
Contains ILN& hydrophilic polymer. To this end, it has excellent hydrophilicity and adsorption of proteins, etc. is small.

P21! The decrease in permeation performance due to In addition, there is no substantial drop in water permeability or dimensional change of the hollow fibers due to drying, making it possible to produce completely dry hollow fibers.
This method is advantageous in many aspects such as handling of hollow fibers, modularization, and transportation of modules, and can improve workability and productivity.

Next, a method for wrapping porous hollow fibers according to the present invention will be explained.

The spinning dope for producing the hollow fibers of the present invention is composed of a hydrophobic polymer, a hydrophilic polymer, a pore-forming agent, and a polar bath IM in which they are mixed.

Examples of hydrophobic polymers include poly/L, phon, polyneedle sulfone, polyvinylidene fluoride, polyethylene, and vinyl chloride. Among these, polysulfone and polyethersulfone are suitable because they have excellent heat resistance, chemical resistance, and oxidizing agent resistance, and they are also easy to spin due to their strong intermolecular cohesive force.

One example of a hydrophilic polymer is folipinylpyrrolidone.

Average molecule! Examples include, but are not limited to, polyethylene glycol, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, and modified polymers thereof.

It is desirable that the polymer has good compatibility with the aqueous polymer in the solvent, and in the case of a water-bathable polymer such as polyvinyl pyro 11 tons per liter, one that can be easily made insolubilized by crosslinking or the like is preferable. The higher the molecular weight, the smaller the amount of hydrophilic polymer added. Particularly when using water-soluble polymers, if any residue remains in the hollow fibers, wash them with water.

This is preferable because it reduces elution during hot water treatment or when using hollow fibers. These types of hydrophilic polymers are manufactured by
It can be selected by considering suitability for the intended use.

Micropores are formed in the hollow fibers of the present invention by microphase separation, and a pore-forming agent is added for the purpose of facilitating the occurrence of microphase separation. than before.

As a micropore forming agent, 1 methanol, ethanol, etc., noflucols, ethylene glycol, phlopylene glycol, average molecular weight 400-20. Glycols such as UOU's low molecular weight Bo-11 ethylene glycol.

Many inorganic salts such as Liα and ZnO2, water, etc. are used, and the above-mentioned pore-forming agents can be used even if they are not inventive. The amount of the pore-forming agent added must be kept within a range that allows the spinning dope to remain uniform and transparent, but it is desirable to add as much t as possible since the pore-forming agent is presumed to become the core of the pores. Among them, polyethylene glycol with a low molecular weight of 400 to 20,000 is preferred because it can be added in a large amount to the spinning dope. This low molecular weight Bo-11 ethylene glycol has excellent micropore formation and has the effect of thickening the spinning dope, which has the advantage of improving the stability of spinning. There is no particular restriction as long as it dissolves the polymer and the pore-forming agent, and one example is:
Examples thereof include N,N-dimethylformide, dimenalacetate, N-metal+ruviro 11ton, and dimenethyl sulfoxide.

Can the compositions of these 411 [classes] be selected in arbitrary proportions? In order to produce the hollow fibers of the present invention, phase separation of the spinning dope is carried out below a certain temperature (low-temperature pore separation). It is preferable to prepare the material so that phase separation occurs above a certain temperature (high-temperature phase separation type).

The hollow fiber a of the present invention is produced using the above-mentioned spinning dope by a known dry-wet method. The internal coagulating liquid is discharged from the center of the nozzle along with the spinning dope.

Water, a mixture of water and a polar solvent, alcohols, glycols, etc. alone, or a mixture of two or more of them are used. By changing the composition of this internal coagulation liquid, the structure near the inner surface of the hollow fiber, such as the shape of the micropores on the inner surface, the average pore diameter, the porosity, and the thickness of the dense layer, can be controlled.

To form slit-like micropores on the inner surface, water or a mixture of water and a solvent is usually used as the internal coagulation liquid. The concentration of such internal coagulation liquid (solvent/water) riO/
100 to 85/15 is preferred.

A solvent/water ratio of 41 J/b U to 75/25 is particularly preferable from the viewpoint of balance between spinnability and membrane ME.

The spinning stock solution discharged from the nozzle travels in the air (dry zone) and then is immersed in an external coagulation liquid containing water as a main component. In the present invention, by changing the length of this dry zone, the atmospheric temperature in the dry zone, and the temperature, the trace amount of moisture present in the dry zone can be adjusted.
Controls the pore structure of the outer surface. In terms of the balance between spinning stability and hollow fiber performance, the length of this dry zone is 0.1 to 2.
Normally, 1 to 5 UtM is suitable.The higher the humidity of the dry zone atmosphere, the easier it is to form large pores, and the higher the porosity.

The hollow fibers formed with the coagulating liquid are then washed with water to extract the solvent and pore-forming agent. Next, if necessary, to extract the micropore-forming agent and improve the pressure resistance of the hollow fiber,
The main component is water and is treated with moist heat in a warm bath. If a water-soluble polymer is used as the hydrophilic polymer, the hydrophilic polymer remaining in excess in the hollow fibers can be extracted at the same time by water washing and moist heat treatment. However, since this extraction effect differs depending on the type and molecular weight of the hydrophilic polymer, it is preferable to perform another extraction operation in some cases to adjust the final hydrophilic polymer weight remaining in the hollow fibers. Normally, the hydrophilic polymer remaining in the hollow fiber rarely elutes during use, but for special uses such as medical and medical applications, the hydrophilic polymer is physically or chemically insolubilized. It is preferable to completely prevent elution of the hydrophilic polymer. Quantification of this hydrophilic polymer can be easily carried out by suitable means such as 1-weight method 1,000-element analysis.

The t-9 yarn obtained by the above method contains 0.5 to 1% hydrophilic polymer relative to the R aqueous polymer.

If the content of the hydrophilic polymer exceeds 10%, the hydrophilic polymer may inhibit the properties of the hydrophobic polymer, and if it is less than 0.5%, there is no hydrophilic effect. I can't do anything. What is the content of hydrophilic polymer?

The smallest amount that can impart hydrophilic properties to the hollow fibers is preferred. 1. Although there is no particular restriction on the dispersion state of the hydrophilic polymer in the hollow fibers, it is preferable to disperse them as uniformly as possible in order to impart hydrophilicity to the hollow fibers.

(Example) The present invention will be explained in more detail with reference to Examples below. Please note that the pure water permeation rate and fractionability are measured using the following method.

(1) Pure water permeation rate An external pressure filtration type laboratory module with an effective length of 20 ow was made using 25 hollow fibers, and pure water at 25°C was filtered at a filtration pressure of I kg/
The crA was supplied to the outside of the hollow fiber, and the amount of pure water that had passed through the hollow fiber after a certain period of time was measured.

(11) A 1% dispersion of colloidal silica (catalysts and chemical industry 5I-30) of 1135 people was used as the fractionation measurement liquid.
External pressure filtration was performed at 5 Ky/J, circulation line if, 0.3 m/9 eC, and the weight of the permeated liquid and the evaporated residue of the measured liquid was measured to calculate the removal rate.

Example 1 Polysulfone resin (Amoco gUDEL P-17UI
J) 19 parts by weight, polyvinylpyrrolidone (manufactured by GAF -90, with an average molecular weight of 1.2 million), 1.9 parts by weight, polyethylene glycol (manufactured by Sanyo Chemical Co., Ltd., PE) with an average molecular weight of 600;
G#600) 30.4 parts by weight, dimethylformamide 4
8.7 parts by weight was heated and dissolved at 120°C for 6 hours to form a hole. This spinning dope had a phase fraction of 1111 at temperatures above 75°C and below 29°C. This spinning stock solution was kept at 45° C., and dimethylformamide/water (70/3 (J) 11: 11:1:1:1:1:2) was simultaneously discharged from a double annular nozzle as an internal coagulation liquid, and the length was 10 cM.

After passing through a dry zone with an ambient temperature of 55°C and an atmospheric relative humidity of 85°C, it was immersed in water at 55°C with an outer diameter of 0.6 cm.
, a hollow fiber with an inner diameter of 0.4 mm was carefully designed. This hollow fiber was subjected to a moist heat treatment with warm water at 90° C. for 2 hours.

After washing, dry at 60℃ for 8 hours. The pure water permeation rate of the obtained hollow fiber is 1900j/-・hr-V4
/clA, the removal rate of colloidal silica for 135 people was 95%. As determined from scanning electron micrographs, the average width of the slits provided on the inner surface is 250 mm, the aperture ratio is 15 s, and the thickness of the dense layer is 1.5 mm. The maximum pore diameter on the outer surface is 1.0 μm, and the hollow fiber wall has a network-like porous structure with an average pore size of 1.0 μm. When we measured the amount of polyvinylpyrrolidone in the hollow fiber using single-element analysis, it was found to be 4.2% based on polysulfone. When water was passed through the hollow fibers, the fibers were re-dried after the holes were made, and the water permeability was measured again, no change in water permeability was observed. Photographs of this hollow fiber taken with a scanning electron microscope are shown in FIGS. 1 to 5. Figure 1 shows the outer surface of the hollow fiber, Figure 2 shows the inner surface, Figure 3 shows the cross section of the outer surface, Figure 4 shows the cross section of the approximately central part, and Figure 5 shows the cross section of the inner surface. .

Examples 2 to 4 Using the same polysulfone resin, polyvinylpyrrolidone, and polyethylene glycol as in Example 1, hollow fibers were produced by changing the composition of the spinning stock solution and spinning conditions, and the pure water permeation rate and The complete table of removal rates of colloidal force for 135 people is shown in the table below.

The following procedure was carried out fl15: 18 parts by weight of the same polysulfone as in Example 1, 2 parts by weight of polyvinylpyrrolidone, 1 nits of anhydrous 11thium chloride,
79 parts by weight of dimethylformamide was heated and dissolved at 60° C. for 8 hours to obtain a spinning stock solution. This stock solution is a high temperature separation type stock solution that undergoes phase separation at 45℃. Hollow fibers were prepared under the same spinning conditions as in Example 1, and the pure water permeation rate and removal rate of 135 human nocoloidal fibers of the obtained hollow fibers were measured.

1 h U (+ l/rn”-hr- to 4/
crA, 97% complete. The average width of the slits on the surface was determined from scanning electron micrographs.
The porosity of S11t is 131, and the thickness of the dense layer is 2.5 μm.
, the maximum pore diameter of the numerous pores provided on the outer surface is 1.5 μm.
The hollow fiber wall had a network porous structure with an average pore diameter of 1 μm. Well done.

The amount of polyvinylpyrrolidone in the hollow fibers was measured by elemental analysis and was found to be 4.6% based on polysulfone.

Comparison fill Example 1 except for dry zone i0 (wet spinning) and
The hollow fibers were manufactured under the same conditions as above. The pure water permeation rate of this hollow fiber was 250J/Zhr-positive/-c, and the results were obtained by observing scanning electron micrographs.

There were no pores larger than 1.1 μm on the outer surface of the hollow fiber, and a dense layer was observed on both the inner and outer surfaces of the hollow fiber.

Example 6 Using the hollow fibers obtained in Example 1 and Comparative Example 1,
An external pressure filtration module with an effective membrane area l- was fabricated and ftQ
Using these two types of modules, tap water t-filtration pressure 0
．． The amount of filtration was measured when the permeation rate was halved by performing full filtration under an external pressure of 5 Kg/-.However, in the module containing the hollow fibers obtained in Comparative Example 1, the amount of filtration was 30 pi. On the other hand, the module containing ft7 hollow fibers obtained in Example 1 was 65-.

(Effect of the invention) The porous hollow fiber of the present invention has a specific structure and has excellent water permeability, fractionation property, and stain resistance, and is hydrophilic, so it can be used for a long period of time. Therefore, it is suitable and economical for industrial and blood applications.

Can be applied to a wide range of fields such as ascites PA and other medical applications.

[Brief explanation of drawings]

1 to 3 are scanning electron micrographs of the polysulfone hollow fibers obtained in Example 1. Figure 1 shows the structure of the outer surface of the hollow fiber (magnification: 5,000). Figure 2 shows the structure of the inner surface of the hollow fiber (magnification s, ooo). Figure 3 shows the cross-sectional structure of the outer surface of the hollow fiber (magnification: 5,000
). Figure 4 shows the inside of the hollow fiber (center of the fiber).
, 0oo) and FIG. 5 show the cross-sectional structure (magnification s, ooo) between the inner surfaces of the hollow fibers.

Claims (1)

[Claims] A porous hollow fiber containing 0.5 to 10% of a hydrophilic polymer to a hydrophobic polymer, the porous hollow fiber having a slit-like micropore opening rate of 10 to 50% on the inner surface. It has a porous structure consisting of a dense layer with a thickness of 0.5 to 5 μm and a network structure integrally and continuously formed in the dense layer, and the outer surface has a part of the network structure. It has pores with a maximum pore diameter of 0.5 to 5 μm, and the pure water permeation rate at 25°C is 1000 l/m^2・hr・Kg/cm^
A porous hollow fiber characterized by having a porous hollow fiber of 2 or more.