JPS5916503A - Porous hollow yarn membrane of polyvinylidene fluoride resin and its production - Google Patents

Abstract

PURPOSE:To obtain a porous hollow yarn membrane having a specific pore structure and having excellent permeation performance and mechanical strength by bringing a vinylidene fluoride resin soln. into contact with liquid exhibiting a specific surface solidifying time. CONSTITUTION:A polyvinylidene fluoride resin is added to dimethyl sulfoxide and is stirred under heating to 60 deg.C so as to be thoroughly dissolved. Such soln. is discharged from an annular spinning hole, and water-DMFA having nine sec surface solidifying time is used as inside solidifying liquid and water-DMFA mixed liquid having seven sec surface solidifying time is used as outside solidifying liquid, whereby a hollow yarn membrane having 420mu outside diameter and 280mu inside diameter is obtd. The hollow yarn membrane consists of roughly uniform and open cells over the entire section of the membrane and since >=20mum microvoids do not exist therein, the membrane has high mechanical strength and since average 0.05-5mum pores exist on both inside and outside surface layers, the membrane has an excellent separating characteristic and permeation performance.

Description

[Detailed description of the invention]

The present invention is a porous hollow fiber membrane made of vinylidene fluoride resin that has uniform micropores with an average pore diameter of 0.05μ to 5μ on both the inner and outer surface layers and has excellent permeability and mechanical strength.
This relates to a manufacturing method. In recent years, porous membranes have been used for the production of ultrapure water such as electronic I collection, industrial wastewater treatment such as two-paper valve drainage, separation and purification in the food industry such as sugar manufacturing, separation of useful components of blood and things, and sterilization. Porous hollow fiber membranes have come to be used in a wide variety of separation and purification technologies, including medical applications such as microfilters. Cellulose acetate-based, polypropylene-based, and other porous hollow fiber membranes have been used for this purpose, but they have drawbacks in permeability, mechanical strength, heat resistance, solvent resistance, etc. It has been pointed out. From this point of view, mechanical strength, heat resistance, solvent resistance, odor °C
Vinylidene fluoride resins have attracted attention due to their excellent properties, and the creation of porous hollow fiber membranes has been studied. for example,
As shown in Japanese Unexamined Patent Publication No. 56-56202, there is a method of coagulating a polymer solution containing a surfactant in a water button, but this method does not require an internal V? Because it has macro voids of 120 μm or more, its strength is low (and it is difficult to use it. Also, because it has to be rapidly coagulated with water, it is necessary to After solidification of the surface, a substantial stretching operation is required, with undesirable deformation of the surface pore shape;
There was a problem. In view of this situation, as a result of intensive research, the present inventors have found that the surface of a vinylidene fluoride resin solution is substantially solidified by contacting it with a liquid whose surface solidification time is 5 to 30 seconds. The layer has pores with an average pore diameter of O, OS ~ 5 μm, has an asymmetric structure in the cross-sectional direction of the porous membrane, does not contain any muck-voids with a pore diameter of 2 () μm or more, and is 25 μm in diameter.
The permeation rate of pure water at ℃ is 0.001~2fAti-
It has been discovered that a porous hollow fiber membrane of a vinylidene fluoride resin having excellent permeability in the range of seC-atm and excellent mechanical strength can be obtained, and the present invention has been achieved. That is, the present invention provides a polyvinylidene fluoride resin porous hollow fiber membrane with an average pore size of 0.0 in both the inner and outer surface layers of the hollow fiber membrane.
The porous membrane has pores of 5 to 5 μm, substantially does not contain voids of 20 μm or more in the cross-sectional direction, and is heated at 25°C.
The permeation rate of pure water at o, o 01~2 f/cr
Membrane production 1 from a polyvinylidene fluoride resin porous hollow fiber membrane whose @ characteristic is in the range of 1-5 ec-atm and a solution containing 8 wt % or more of polyvinylidene fluoride resin
When filtering, the resin solution is brought into contact with a PL body having a surface coagulation time of 5 to jO seconds to substantially coagulate the resin solution. The present invention relates to a manufacturing method. The present invention will be explained in detail below. The polyvinylidene fluoride resin porous hollow fiber membrane manufactured by Mikko Amei has pores with an average pore diameter of 0.05 to 5 μm on both its inner and outer surface layers. The pore size distribution was determined, and the average pore size was determined from this (Kenji Kamide et al. Polymer Proceedings Vol. 1.34 pp.2 '9
9-307). The porous hollow fiber membrane has skin layers on both the inner and outer surfaces, and in the cross-sectional direction following both surface layers having pores with an average pore size of 0.05 to 5 μm, there are vacuoles with an average pore size of 1 to 10 μm. Therefore, the filtration resistance for liquid passing through the surface layer is small and large. Increase the permeation speed. In addition, there are no macrovoids larger than 20 μm in the cross-sectional direction of the porous hollow fiber membrane, and the structure is uniform, so no force is applied locally, creating a porous hollow fiber membrane with excellent mechanical strength. Obtainable. In addition, the porous hollow fiber membrane of the present invention has a specific permeation rate of o, o o 1-2 y/cJ-sec when pure water is permeated at 25°C and under a pressure of 1 atm. -atm
It has excellent properties. Considering other membrane properties such as mechanical strength, separation performance, etc., if the permeation rate is o, no 3 to 0.2? y'c, rd-sec-a
tm, more preferably 0.005 to 0.
Particularly preferred is the range 05f/crl-seC-atm. Next, the method for producing the polyvinylidene fluoride resin porous hollow fiber membrane of the present invention will be described in detail. The polyvinylidene fluoride resin in the present invention refers to vinylidene fluoride homopolymer, copolymer such as EVA, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene heptafluoride/propyl hexafluoride copolymer. polymer, 1
,; and a mixture thereof, but 1. <ha,
Hynylidene fluoride content of 80 molt or more, even better! l:
t-< is preferably vinylidene fluoride homopolymer. The average molecular weight of the vinylidene fluoride polymer is preferably In, 000 or more, preferably 50,000 or more. Yes, the resin concentration of the polyvinyl fluoride resin solution is 15% by weight or more, preferably 15 to 35% by weight.
, Particularly preferred is Ii, 20 to 30 heavy boars. The solvent used for the polyvinylidene fluoride resin solution of the present invention is a) one that dissolves the resin in a temperature range of 100°C or less and dissolves 10% by weight or more, such as N-
Methyl-2-biμlidone, dimethylformamide, dimethyl 7cetamide, diedylacetamide, diethylformamide, tetramethylurea, hexamethylphospol 7mide, dimethyl sulfoxide, and 2 of this et al.
A mixture of more than one species is raised. More preferred 1. < is N-methyl-2-pyrrolidone, :) methylacetamide, dimethylpolamide. Dimethyl sulfoxide is preferably used. In addition to the above solvent, at 100°C or lower, the resin may be
Poor solvents such as propylene carbonate, dimethyl succinate, diethyl succinate, tetraethyl urea, dimethyl phthalate, diethyl adipate, diethyl phthalate, ethylene glycol, etc. that do not have the ability to dissolve 0 weight, t% or more: the resin. By adding to the resin solution a non-solvent that does not have the ability to dissolve but is miscible with the solvent of the resin, such as water, dioxane, methanol, ethanol, cyclohexanol, tetrahydrofuran, glycerin, polyethylene glycol, formamide, etc. By controlling the state of microphase separation during solidification, permeation performance, etc. can be controlled. As the coagulating liquid used in the present invention, the surface coagulating time of a solution containing 8% or more of polyvinylidene fluoride resin is preferably 5 to 30 seconds, preferably 1. < is 6 to 20 seconds for liquid t
, [Rubber] can be used. world

[7. The surface coagulation time of the polyvinylidene fluoride resin solution in the present invention is defined as
．． It refers to the time until the solution stops adhering to the surface of another solid or the resin solution even if it comes into contact with 51-. If a liquid with a surface coagulation time of less than 5 seconds is used, a skin layer will be formed on the surface of the porous hollow fiber membrane, resulting in no pores of 0.05 μm or more, or pores with a diameter of 20 μm in the cross-sectional direction of the hollow fiber membrane. This is not preferable because the above macrovoids occur and the strength decreases. Furthermore, if a liquid whose surface coagulation time exceeds 30 seconds is used, the pore diameter of the porous hollow fiber membrane becomes too large and the strength decreases. For example, when water, which is commonly used as a coagulating liquid, is used, the surface coagulation time is 1 second or less, and a skin layer without pores is formed on the surface as shown in Figure 3, and the water permeation rate is In addition, as shown in Figure 4, there are macro voids with a pore diameter of 2゜ttm or more in the cross-sectional direction, so the mechanical strength is as shown in Figures 1 and 2, where such macro voids do not exist. It is smaller than the porous hollow fiber membrane of the present invention. A mixture of it and water is preferably used. Such organic liquids include monohydric alcohols having 1 to 3 carbon atoms and dihydric alcohols having 2 to 4 carbon atoms. Glycerin, ether having 4 to 6 carbon atoms, molecule -6'OO
The following polyethylene glycol and the solvent for the polyvinylidene fluoride resin are used. More preferred as the organic liquid 1. < is methanol, ethanol, iso7'l = panol, ethylene glycol,
Glycerin, dioxane, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone molecule Ji60
0 or less polyethylene glyfur is used. In addition, by changing the mixing ratio of dimethylformamide, dimethylacetamide, methyl sulfoxide, and N-methyl-2-bipropylene, the coagulation rate can be easily and widely varied, so they are preferably used. Such a mixed system of solvent and water is preferably l <
As a solvent, N-methyl 2-pyrrolidone and dimethylacetamide have higher solubility. Use at least one dimethylformamide. When the organic liquid is used in a mixture with water, the concentration of the organic liquid in the aqueous solution is preferably 50% or more.
Yoshiji (70% to 95% by weight, particularly preferred 1.(75% by weight)
A material having a rating of 90 to 90 degrees can be suitably used. The temperature of the coagulation bath is usually about 5 to 60°C,
It is not limited to this. As shown in Figure 1, the polyvinylidene fluoride resin porous hollow fiber membrane obtained by the method of the present invention as described above is made up of nearly uniform, connected vacuoles with an average pore diameter of 1 to 10 μm over the entire cross section of the membrane, IK. Since there are no macrovoids larger than 20 μm, the mechanical strength is strong. Furthermore, as shown in FIG.
Due to the presence of micrometer pores, it has excellent separation properties and the pure water permeation rate at 25°C is 0.001 to 2 f/
A membrane having very excellent permeability of crl, sec, and atm can be easily obtained. (i) The membrane obtained by
19 Membrane filters used for purification etc. 1
．． Alternatively, it can be used in blood processing 11 and 12 that separates specific components from blood, such as plasma separation. The present invention will be explained below using examples, but the present invention is not limited to the examples of Hakore et al. In addition, the following rejection rate (H) is calculated using Example 1 polyvinylidene fluoride resin (Penwalt Co., Ltd. %K).
ynar 3 n ] F ) 660 t was added to dimethyl sulfoxide 23402, heated and stirred at 60°C to completely dissolve, and then vacuum defoamed 1. The stock solution was prepared. This liquid is discharged from one hole of the annular spinning filament, and is mixed with the inner coagulating liquid of the hollow fiber in 1.゛C water 20 chloride methylformamide 8
0 heavy sword: 9! + using a mixed solution (surface solidification time 9 seconds),
evening) Side coagulation liquid and 1. A hollow fiber membrane having an outer diameter of 420 .mu.m and an inner diameter of 280 .mu.m was obtained by using a mixture of 18% by weight of water, 7 ml of dimethylporum, and 82 ml of water (surface coagulation time: 7 seconds). The permeation rate of pure water at 25°C for this product is 2.8
×1o” ?/cJ・sec・atm, the average pore size on the inner surface is 0.8 μm, and the average pore size on the outer surface is 0.7 μm.
It was m. In addition, bovine serum α-globulin 0.1% by weight
The permeation ability at °C was measured using an aqueous suspension solution (average particle size 0.16 μm), and the amount of permeation was 52 oy + e,/n.
? -hr, mn11g, exclusion rate was 22.3%. Examples 2 and 3 Example 1 except that the compositions of the inner coagulating liquid and outer coagulating liquid were changed.
(A hollow fiber membrane was obtained in the same manner. The performance of this membrane is shown in Table 1. Examples 4 to 6 Polyvinylidene fluoride resin 720 , spinning was carried out under the conditions shown in Table 2.The membrane σ) performance is shown in Table 2.Examples 7, 8 Polyvinylidene fluoride resin? Spinning was carried out under the conditions shown below. The performance of the membrane is shown in Table 2. Comparative Example: Same as Example 1 except that water whose surface coagulation time was 1 second or less was used as the inner coagulation liquid of the hollow fiber. A hollow fiber membrane was obtained in the same manner.A skin layer with very small pores was formed on the inner surface of this hollow fiber membrane, and 200 pores were formed in the inner cross-sectional direction.
There were many macrovoids larger than 7+m.

[Brief explanation of drawings]

Fig. 1 shows a cross-sectional scanning electron micrograph (1000x magnification) of the polyfluorinated vinyl IJ tensile resin porous hollow fiber membrane of the present invention, and Fig. 2 shows a surface scanning electron micrograph of the porous hollow fiber membrane. Figure 3 shows the cross-sectional movement of a hollow fiber membrane using water with a surface coagulation time of 1 second or less as the inner coagulation liquid. It is a mirror photograph (magnification 10 il 0x), and it is an electron micrograph K (magnification 1000x) of the inner surface of Figure 4 ii Figure 3.

Claims (3)

[Claims] (1) In a polyvinylidene fluoride resin porous hollow fiber membrane, the inner and outer surfaces of the hollow fiber membrane have an average pore diameter of 0.05 to
The hollow fiber membrane has pores of 5 μm, substantially contains no macrovoids with a pore diameter of 20 μm or more in the cross-sectional direction, and is heated at 25°C.
The permeation rate of pure water is o, o o 1~2 f/c
A polyvinylidene fluoride resin porous hollow fiber membrane characterized in that the porous hollow fiber membrane is in the range of nf/sec-atm. (2) The polyvinylidene fluoride resin porous hollow fiber membrane according to claim 1, wherein the cross section of the hollow fiber membrane is substantially formed from a linear structure consisting of continuous vacuoles of 1 to 10 μm. (3) When forming a membrane from a solution containing 8% by weight or more of polyvinylidene fluoride resin, a method for producing a porous hollow fiber membrane of polyvinylidene fluoride resin