Liquid purification or separation – Filter – Material
Patent
1985-09-30
1988-05-03
Spear, Frank
Liquid purification or separation
Filter
Material
21050036, 264173, B01D 1300
Patent
active
047418290
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to porous hollow fibers consisting of thermoplastic organic polymers and a method of making the same. More particularly, it relates to novel porous hollow fibers suitable for use in the separation of various substances which fibers are composed of at least two layers consisting of thermoplastic organic polymers of different types or of the same type and having micropores of different sizes and which fibers have a microstructure comprising micropores interconnected within each of the layers and between the layers, as well as a method of making the same.
2. Background Art
It is already known that porous hollow fibers can be produced by using, as base polymers, polypropylene and polyethylene which are typical thermoplastic organic polymers.
U.S. Pat. No. 4,055,696 discloses porous hollow filaments consisting essentially of polypropylene and having fine holes whose radii are distributed over a range of 200 to 1200 .ANG.. It is described therein that these hollow filaments have a wall thickness of 17.5-22.5 .mu.m and a gas permeability of 1.4-6.7.times.10.sup.-6 (cc.multidot.cm/cm.sup.2 .multidot.sec.multidot.cmHg).
U.S. Pat. No. 4,401,567 discloses porous hollow fibers consisting of polyethylene. It is described therein that these hollow fibers have a wall thickness of 50-60 .mu.m, an N.sub.2 gas permeability of 4.9-7.2.times.10.sup.5 (1/m.sup.2 .multidot.hr.multidot.760 mmHg), a water permeability of 1900-3200 (ml/m.sup.2 .multidot.hr.multidot.mmHg) and an albumin permeability of 100%.
Furthermore, it is disclosed in U.S. Pat. No. 3,423,491 that there can be produced polyethylene hollow fibers exhibiting a salt rejection value of not less than 75% and having pores suitable for use in reverse osmosis, and it is disclosed in U.S. Pat. No. 4,020,230 that there can be produced porous polyethylene hollow fibers having a maximum pore radius of up to about 50 .ANG. and capable of rejecting about 95% or more of albumin molecules with a radius of gyration of approximately 30 .ANG..
However, all of these prior patents are concerned with hollow fibers having micropores whose size distribution is uniform. The hollow fibers disclosed in these prior patents have the function of separating substances and, as regards their mechanism, they allow or prevent the passage of certain substances on the basis of the difference between the size of micropores and the geometry of molecules of substances to be separated. From an industrial point of view, it is also important to increase the permeation rates of substances to be permeated in the separation process as much as possible. In the hollow fiber according the aforesaid prior patents, however, the size of micropores must be restricted if it is desired to separate certain substances. Especially where it is desired to separate substances whose molecular sizes are small, the size of micropores must be reduced on the whole. This decreases the effective cross-sectional area of the flow paths through which the substance is transferred, resulting in a reduced permeation rate of the substance to be transferred.
Moreover, in the art of separating substances, the chemical and physical interaction between the material constituting the separating membrane and the substances to be separated is also an important factor. However, the hollow fibers disclosed in the above-described prior patents consist of a single material and it is difficult to meet all the performance and functional requirements for a separating membrane by use of a single material (e.g., a single polymer having a fixed MI value).
Furthermore, in recent years, such porous hollow fibers are being utilized as materials for the manufacture of artificial organs such as artificial kidneys, plasma exchangers and the like, but some materials involve the problem of incompatibility with blood, i.e., the property of causing blood coagulation, hemolysis or the like. Although the mechanisms of blood coagulation, hemolysis and the like have not been adequately elucidated, the interactio
REFERENCES:
patent: 4164437 (1979-08-01), Henne et al.
patent: 4385094 (1983-05-01), Tahaka et al.
patent: 4401567 (1983-08-01), Shindo et al.
patent: 4444710 (1984-04-01), Most, Jr.
Hukunaga Osamu
Takemura Tohru
Yoshida Haruhiko
Mitsubishi Rayon Co. Ltd.
Spear Frank
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