JPS6190704A - Hollow yarn membrane - Google Patents

Abstract

PURPOSE:To obtain a hollow yarn membrane which has high gas exchange ability, obviates plasma outflow even after long-term use and is suitable for the artificial lungs by forming an approximately circular polyolefin hollow yarn membrane the inside surface side of which is a dense layer and the outside surface side of which is an aggregate layer of fine independent particles to form fine through-holes. CONSTITUTION:The blend composed of polyolefin and org. filler such as liquid paraffin is melted and kneaded and thereafter the mixture is discharged from an annular spinning hole of a spinning device into air; at the same time, an inert gas is introduced to the inside center. The formed hollow material is brought into contact with a cooling and solidifying liquid and is then taken up on a bobbin. The org. filler is thereafter extracted away by an extraction liquid. The resulted hollow yarn membrane 1 has approximately the circular shape whose inside diameter D is 150-300mum and the wall thickness T is 10-150mum. The inside surface side of the membrane is the relatively dense layer 2 and the outside surface side is the aggregate layer 4 of the fine indepen dent particles 3 having 0.1-10mum average grain size. The fine through-holes are formed from the inside to the outside surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION (6) Technical Field of the Invention The present invention relates to a hollow fiber membrane. More specifically, the invention relates to hollow fiber membranes used in artificial lungs, plasma separation, and the like. In particular, the present invention relates to a porous hollow fiber membrane that does not cause plasma outflow during long-term use, has a high gas exchange capacity, and is suitable for use in an oxygenator.

Prior Art Generally, in heart surgery, etc., the blood of thoughts is guided outside the body,
A hollow fiber membrane oxygenator is used in the extracorporeal circuit to add oxygen and remove carbon dioxide. Hollow fiber membranes used in such artificial lungs include:
There are two types: homogeneous membrane and porous membrane. A homogeneous membrane has a permeation rate of 1"
Gas movement occurs when gas molecules dissolve in the membrane and diffuse. A typical example of this is silicone gol, which has been commercialized as a colopo membrane type lung.

However, from the point of view of gas permeability, the only homogeneous membrane currently available is silicone rubber, and the silicone rubber membrane has a thickness of 100 μm due to its strength.
It cannot be less than m.

For this reason, gas permeation is limited, and carbon dioxide gas permeation is particularly poor. However, the above-mentioned silicone rubber had the drawbacks of being expensive and having poor processability.

On the other hand, in the case of porous n4), the fine pores on the right side of the membrane are significantly larger than the gas molecules to be passed through, so that the gas molecules flow through the pores in a volumetric manner. For example, a number of artificial lungs using porous membranes such as macroporous polypropylene membranes have been proposed.

For example, polypropylene (hollow fiber membrane) is spun using a blue nostle at a spinning temperature of 210 to 270°C and a draft ratio of 180 to 6.
After melt spinning at 0.00C, then first stage heat treatment at 155°C or lower, stretching by 30 to 200% at lower than 110°C, and then second stage heat treatment at a temperature higher than the second stage heat treatment temperature and 155°C or lower. It has been proposed to produce porous polypropylene hollow fibers (Japanese Patent Publication No. 56-52,
No. 123). However, in the porous hollow fibers obtained in this way, pores are physically formed by stretching the polypropylene hollow fibers, so the pores are linear pores that are approximately horizontal in the film thickness direction. In addition, since the pores are generated by cracking in the axial direction of the hollow fiber depending on the degree of stretching, the cross section is approximately square or rectangular. In addition, the pores are continuous and penetrate almost linearly, and the porosity is high. For this reason, the porous hollow fibers have a high permeability to water vapor, and not only do their performance deteriorate due to condensation water, but they also have the disadvantage that plasma leaks when used while circulating white liquor for a long period of time.

(1) Purpose of the Invention Therefore, the purpose of the present invention is to provide a novel hollow fiber membrane. Another object of the present invention is to provide a porous hollow fiber membrane having high gas exchange capacity. Still another object of the present invention is to provide a porous hollow fiber membrane that does not cause plasma outflow during long-term use, has a high gas exchange capacity, and is suitable for use in an artificial lung.

These are hollow fiber membranes made of polyolefin that are approximately circular in shape and have an inner diameter of 150 to 300 μm and a wall thickness of 10 to 150 μm, and the inner surface of the hollow fiber membrane has a relatively dense layer. This is achieved by a porous hollow fiber membrane characterized in that the outer surface side is in the form of an aggregate of independent fine particles with an average particle diameter of O1. Ru.

Further, the present invention provides a porous hollow fiber membrane having a continuous anisotropic fl membrane structure in which a dense layer is formed between the outer surface and the inner surface of the hollow fiber membrane with smaller gaps between particles toward the inner surface. . Furthermore, the present invention is a porous hollow fiber membrane having a porosity of 5 to 60%.

In the present invention, the 02 gas flux is 1.0X10-5 to 2
．． OXl 03mA/min -c+n2 -atm
, preferably 1.0X10' to 1. OX103ml/
It is a hydrophobic porous hollow fiber membrane that is m1n-01112.atm. Further, the present invention is a porous hollow fiber membrane in which the average particle diameter of independent fine particles on the outer surface side is 1 to 7 μm. Furthermore, the present invention has an inner diameter of 180 to 250 μm and a wall thickness of 20 to 10 μm.
It is a porous hollow fiber membrane with a diameter of 0μ.

The present invention also provides a hydrophobic porous hollow fiber membrane in which the polyolefin is polyethylene or polypropylene, preferably polypropylene.

(1) Specific structure of the invention Next, the present invention will be specifically explained with reference to the drawings. That is, FIG. 1 is a diagram schematically depicting a cross section of the hollow fiber membrane according to the present invention, and it is clear from the diagram that the inner diameter is 150 to 300 μm, preferably 180 to 250 μm.
m, wall thickness T is 10 to 150μ, preferably 20 to 10
This is a hollow fiber membrane 1 made of polyolefin and having a diameter of 0 μm and a substantially perfect circle. A relatively dense layer 2 is formed on the inner surface of the hollow fiber membrane 1, while an average particle diameter d of 10 μm is formed on the outer surface.
Hereinafter, a layer 4 in the form of an aggregate of a large number of fine particles 3 preferably of 1 to 7 μm is formed, and the fine pores 5 in the dense layer 2 communicate with the fine pores 6 in the layer 4 in the form of fine particle aggregates. This is a porous hollow fiber membrane having hydrophobicity and having communicating pores formed from the inner surface to the outer surface.

Such a hydrophobic porous hollow fiber membrane is manufactured, for example, by the following method. That is, as shown in FIG. 2, a blend 11 of polyolefin and an organic filler is supplied from a hopper 12 to a kneader, for example, a twin-screw extruder 13, where the blend is melt-kneaded and extruded. After that, it is sent to the spinning device 1/4 and the spinneret'! The hollow spinning hole 1115 (not shown) is discharged into a gaseous atmosphere, e.g. The material 17 is introduced into a cooling tank 19 containing a cooling solidification liquid 18 and brought into contact with the cooling solidification liquid 18 to be cooled and solidified. In this case, as shown in FIG. 2, the hollow object 17 and the cooling solidification liquid 18 are in contact with each other, for example, through a cooling hole provided downwardly through the bottom of the cooling tank 19. It is desirable to cause the cooled assimilated liquid 18 to flow down into the liquid flow pipe 20 and bring the hollow body 17 into co-current contact with the flow. The cooling solidified liquid 18 that has flowed down is received and stored in a solidification tank 21, into which the hollow object 17 is introduced, and the direction is changed by a deflection rod 22 to bring it into sufficient contact with the cold solidified liquid 18 and solidify it. After being warmed, it is wound up using the winding bobbin 23. Accumulate (
The cooled solidified liquid is discharged through line 24J and pump 2
5 to circulate to the cooling tank 19. In addition, if the cooled and solidified liquid is highly volatile and immiscible with water, such as sea urchin hydrocarbons or halogenated hydrocarbons,
A layer 26 of water or the like may be provided as an upper layer to prevent evaporation.

The hollow object 18 cooled and solidified in this way is attached to the bobbin 23.
A hollow fiber membrane is obtained by winding it up, cutting it into a predetermined size, and then immersing it in an extraction solution to extract and remove the organic filler from the cut hollow material 18, and drying it if necessary. . Further, by heat-treating the hollow fiber membrane thus obtained, a hollow fiber membrane with even better dimensional stability can be obtained.

Polyolefins used as raw materials in the present invention include polypropylene, polyethylene, etc., but those with a melt index (M, J,) of 5 to 70 are preferred, particularly those with M, 1. is preferably 10 to 40. Among the polyolefins, polypropylene is particularly preferred.

The organic filler is required to be one that can be uniformly dispersed in the polyolefin while it is melted and is easily soluble in the extract as described below. As such a filler, flow UJ paraffin (number average molecular ff1100~2,
000), α-first nofin oligomer [e.g., ethylene oligomer (number average molecular ff1100 to 2.000
>, propylene oligomer (number average molecular weight 100-2,
000), ethylene-propylene oligomer (number average molecular weight fi 100 to 2,000), etc.], paraffin wax (number average molecular weight 200 to 2.500>, various hydrocarbons, etc.), and preferably liquid paraffin.

The blending ratio of the polyolefin and the organic filler is 35 to 1 part by weight of the organic filler per 100 parts by weight of the polyolefin.
The amount is 50 parts by weight, preferably 50 to 100 parts by weight. That is, if the organic filler is less than 35 parts by weight, a porous hollow fiber membrane having sufficient gas permeability cannot be obtained;
0! This is because if it exceeds part Ii), the viscosity becomes too low and the moldability into hollow shapes deteriorates. Such raw material formulations are prepared (designed) by a premixing method in which a mixture of a predetermined composition is melt-kneaded using an extruder such as a twin-screw extruder, extruded, and then pelletized. .

The raw material mixture prepared in this way is further heated at 160 to 250°C using an extruder such as a twin-screw extruder.
The material is melted and kneaded preferably at a temperature of 18 to 220°C, and discharged into a gas atmosphere from the annular hole of the spinning device, and at the same time, nitrogen, carbon dioxide, helium, argon, air, etc. are introduced into the center of the spinning device. A hollow object is formed by introducing an inert gas, the hollow object is allowed to fall, and then brought into contact with the cooled solidified liquid in the cooling tank. This falling distance is preferably 5 to 100 mm, particularly preferably 10 to 500 mm. That is, if the falling distance is less than 5 mm, pulsation may occur and the hollow object may be crushed when it enters the cooled and solidified liquid. The hollow object has not yet solidified sufficiently in this cooling tank, and since the center part is filled with inert gas, it is easily deformed by external force.
As shown in the figure, for example, the cooled solidified liquid 18 is made to flow down into a cooled solidified liquid distribution pipe 20 that is provided downwardly through the bottom of the cooling tank 19, and the hollow object is caused to flow along the flow. By contacting the qp flow, the hollow object is forcibly moved downward, and deformation of the hollow object due to external force (fluid pressure, etc.) can be prevented.

The flow rate of this cold D-solidifying liquid is sufficient under gravity flow. Moreover, the cooling temperature at this time is 10 to 60°C, preferably 20 to 50°C. That is, below 10° C., the cooling solidification rate is too fast and most of the thick wall portion becomes a dense layer, resulting in low gas exchange I@ capacity.

On the other hand, if the temperature exceeds 60°C, the crystallization rate of the boria Il nofin becomes slow, and the particle size of the micropores and It particles on the outer surface becomes too large, resulting in the micropores becoming too large. This is because the compact layer becomes extremely thin, or even disappears at high temperatures, which may lead to clogging or plasma outflow when used in an oxygenator, for example. , this J: Una membrane can be used as a hollow fiber membrane in plasma separation by subjecting the inner or outer surface to hydrophilic treatment (for example, alcohol treatment).

As the cooling assimilation liquid, any liquid can be used as long as it does not dissolve the polyolefin, has a relatively high boiling point, and yet dissolves the organic filler.

- Alcohols such as methanol, ethanol, propatools, butanols, hexanols, octatools, lauryl alcohol, liquid fatty acids such as oleic acid, palmitic acid, myristic acid, stearic acid, and its alkyl esters (for example, esters such as methyl, ethyl, isopropyl, butyl, etc.), liquid hydrocarbons such as octane, nonane, decane, kerosene, light oil, toluene, xylene, methylnaphthalene, etc.;
．． 1. Halogenated hydrocarbons, especially chlorinated hydrocarbons such as 2-trichloro-1,2,2-trifluoroethane, trichlorofluoromethane, dichlorofluoromethane, 1,1,2.2-tetrachloro-1,2-difluoroethane Examples include fluorinated hydrocarbons, and among these, those capable of dissolving the organic filler, such as halogenated hydrocarbons, are particularly preferred as will be described later. In other words, when halogenated hydrocarbons are used, not only is the organic filler extracted to some extent during the solidification of the hollow material in the solidification tank;
This is because if the same extract as that used in the subsequent extraction step is used, there is no need to wash and remove the cooled assimilated liquid, and there is no risk of contaminating the extract. Furthermore, if halogenated hydrocarbons are used, there is no risk of fire. Among these halogenated hydrocarbons, chlorofluorinated hydrocarbons are particularly preferred because they are safe for the human body.

The cooled assimilated liquid flowing through the cooled solidified liquid distribution pipe is received and stored in a solidification tank provided at the bottom, and the hollow object is completely solidified by passing through the cooled assimilated liquid in this solidification tank. . The solidified hollow material is then rolled up.

The wound hollow object has a predetermined size, for example, 20 to 5Q.
After cutting into cm, the extract is heated to a temperature of 0 to 50°C, preferably 20 to 40°C, for 1 to 30 minutes, preferably 30 minutes.
A hollow fiber membrane is obtained by soaking for ~20 minutes. In this case, so-called constant length extraction is most preferable, in which the length is kept constant throughout the extraction process.

Any extract can be used as long as it does not dissolve the polyolefin constituting the hollow fiber membrane and dissolves and extracts the organic filler. - For example, hydrocarbons, 1,1,2-)-lichloro-1,2,2-t
There are halogenated hydrocarbons such as -lifluoroethane, 1-lichlorofluoromethane, dichlorofluoromethane, and 1,1,2.2-chloro-1,2-difluoroethane, among which organic Halogenated hydrocarbons are preferred from the viewpoint of extraction ability for the agent, and 1n fluorocarbons are particularly preferred from the viewpoint of safety to the human body.

The hollow fiber membrane thus obtained (1q) is further subjected to heat treatment if necessary. The heat treatment is carried out in a gaseous atmosphere such as air, nitrogen, carbon dioxide, etc. at a temperature of 50 to 160 DEG C., preferably 70 to 140 DEG C., for 1 to 120 minutes, preferably 2 to 6 degrees Celsius. This heat treatment stabilizes the structure of the hollow fiber membrane and increases its dimensional stability. Further, in this case, stretching may be performed before or during the heat treatment.

The hollow fiber membrane thus obtained has an inner diameter of 150 to 3
00 μm, preferably 180 to 250 μm, wall thickness 10
It has a perfect circular shape of ~150 μm, preferably 20-100 μm. The cross-sectional structure changes depending on the manufacturing conditions of the hollow fiber membrane, but as mentioned above, by using a liquid that can dissolve organic fillers such as alcohols and halogenated hydrocarbons as the cooling assimilation liquid, it is possible to 000x scanning! ! ′! As is clear from Figures 3 to 6, which are electron micrographs, polyolefin fine particles are formed independently from the inner surface to the outer surface, with a dense layer on the inner surface, and a dense layer on the outer surface. A porous layer is obtained near the part A. This cross-sectional structure varies depending on the temperature of the cooled assimilate liquid, and as the temperature increases, the formation of polyolefin fine particles progresses toward the inner surface. However, in either case, the fine particles near the inside are dense, whereas the fine particles near the outer surface are aggregates of independent particles. Therefore, the temperature of the cooled and solidified liquid is 11~o'c in the case of Fig. 3, 8°C in the case of Fig. 4, 17 - 20°C in the case of Fig. 5, and 24°C in the case of Fig. 6. ~27°C. Figures 7 to 10 are scanning electron micrographs of the inner surface at a magnification of 3.000 times.The inner surface has a hexagonal shape in which polyolefin particles are partially fused, and the surface is relatively smooth. It is. In addition, the temperature of the cooled solidified liquid is
In the case of Figure 7, -1 to 0℃, in the case of Figure 8, 8℃, and in the case of Figure 9
In the case of the figure, 17-20℃, in the case of Figure 10, 24-27℃
It is ℃. On the other hand, FIGS. 11 to 14 show the outer surface at a magnification of 3.
This is a scanning electron micrograph taken at a magnification of 1,000 times, and shows that polyolefin fine particles are formed independently on the outer surface, and there are many gaps between the fine particles.

In addition, the temperature of the cooled solidified liquid is 11 to 0 in the case of FIG.
℃, 8℃ for Figure 12, 17-2 for Figure 13
In the case of FIG. 14, it is 24 to 27°C. The average particle size of the polyolefin fine particles thus formed on the outer surface is 0.1 to 10 μm, preferably 1 to 7 μm, and the degree of distribution of these fine particles varies depending on the hollow fiber membrane manufacturing conditions. By this method, a membrane structure having different sizes and ratios of micropores between particles can be obtained. In addition, the draft ratio is 20 to 10001, preferably 50 to 5oo, and the gas flux is 1.0X10-5 to 2, OXl
03mA/min -cm2-atm, preferably 1.0X10-3~1. OX103m! l/min・C
m2・atm.

Next, the present invention will be explained in more detail by giving Examples.

Examples 1-8 M, 1. 40 per 100 parts by weight of polypropylene of 23
A twin-screw extruder (PCM-30- manufactured by Ikegai Iron Works Co., Ltd.) was charged with liquid paraffin (number average molecular weight 324).
25), the mixture was melt-kneaded, extruded, and then pelletized. The pellets were melted at 200 to 210'C using a twin-screw extrusion method (Ikegai Iron Works Co., Ltd. PCM-30-25>13) using the apparatus shown in Figure 2, and the core diameter was 1.0 mm.
Inner diameter 2.9mm, outer diameter 3.7mm, land length 15.0n
On, the annular spinning hole 15 was discharged into the air at a rate of 14,8 mft/min, and nitrogen gas was introduced into the center of the interior at a rate of 8,5 mft/min to form the molten hollow material 17. 1,1,2-trichloro-1,2,2-trifluoroethane (hereinafter referred to as Freon 113) in the cooling tank 19 at a falling distance of 355 mm.

), and then brought into co-current contact with the Fluon 113 flowing down naturally in the cooling solidified liquid flow pipe 20 to cool it. The liquid temperature of Freon 113 at this time was as shown in Table 1. Next, the hollow object 17 is introduced into the Freon 113 in the solidification tank 18, and then the direction is changed by the direction changing frame 22, and the hollow object 17 is run approximately horizontally for about m to completely solidify, and then it is wound up by the bobbin 23. Ta. The winding speed and draft ratio at this time were as shown in Table 1. After cutting the hollow material wound on a bobbin to a length of 3Qcm, it was immersed twice in Freon 113 at a liquid temperature of 23°C for 5 minutes to perform constant length extraction, and then heat treated in air at 140°C for 2 minutes. As a result, a hollow fiber membrane having the properties shown in Table 1 was obtained.

Examples 9 to 14 In the same method as in Example 1, hydrogenated poly-α-olefin type synthetic extraction (number average molecular m
480) and the same method was carried out except that the spinning was carried out with the thread (' shown in Table 1 below), and the results shown in Table 1 were obtained.

Examples 15 to 16 and Comparative Example 1 Hollow fiber membranes were produced in the same manner as in Example 1 by varying the loading depth of liquid paraffin and the spinning conditions as shown in Table 2. Obtained.

Comparative Example 2 The same tests as in Examples 15 to 17 were conducted on commercially available polypropylene hollow fiber membranes for artificial lungs, and the results shown in Table 2 were obtained.

(The following is a blank space) ■0 Specific effects of the invention As stated above, the present invention has an inner diameter of 150 to 300 μm.
A hollow fiber membrane made of polyolefin having a substantially circular shape with a wall thickness of 10 to 150 μm, the inner surface of the hollow fiber membrane exhibits a relatively dense layer, and the outer surface has an average particle size of 0.1 to 10 μm.
Since this is a hydrophobic porous hollow fiber membrane characterized by exhibiting an aggregate-like layer of independent microparticles of μm in size and having fine communicating pores formed from the inner surface to the outer surface, the fine communicating pores are formed in the direction of the membrane thickness. The uniformity is very high because the particles are not made of pores that penetrate linearly through the particles, but are made of a large number of interconnected micropores that are formed between the particles from the outer surface to the inside. Therefore, when the hollow fiber membrane is used, for example, in an oxygenator, there is no plasma outflow even after long-term use, and it has a high gas exchange capacity.

Further, when the porosity is 15 to 60%, the plasma outflow prevention ability and gas exchange ability are high. Therefore, the hollow fiber membrane is extremely useful as a membrane for artificial lungs.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a hydrophobic porous hollow fiber membrane according to the present invention, and FIG. 2 is a schematic cross-sectional view of an apparatus used for manufacturing the hollow fiber membrane according to the present invention. Figures 3 to 14 are electron micrographs showing the structure of the hollow fiber membrane according to the present invention. DESCRIPTION OF SYMBOLS 1... Hollow fiber membrane, 2... Dense layer, 3... Fine particles, 4... Fine particle aggregate layer, 5.6... Fine pores,
11... Raw 11 pellets, 12... Hopper,
13...Extraction machine, 14...Spinning device, 15...
Base device, 16... Inert gas supply line, 17...
・Hollow object, 18... Cooled solidified liquid, 19... Cooling tank, 20... Cooled solidified liquid distribution pipe, 21... Solidified 1
fq, 22... direction change frame, 23... bobbin, 24.
...Cooled solidified liquid circulation line, 25...Circulation pump, 26...Evaporation spinning water tank.

Claims (9)

[Claims] (1) Inner diameter is 150-300μm, wall thickness is 10-150μm
A hollow fiber membrane made of polyolefin having an approximately perfect circular shape of μm, the inner surface of the hollow fiber membrane exhibits a relatively dense layer, and the outer surface is an aggregate of independent fine particles with an average particle size of 0.1 to 10 μm. 1. A porous hollow fiber membrane characterized in that it exhibits a layered structure and has fine communicating pores formed from the inner surface to the outer surface. (2) The inner surface and the outer surface of the hollow fiber membrane have a continuous anisotropic membrane structure exhibiting a dense layer with smaller gaps between particles as it progresses toward the inner surface. The porous hollow fiber membrane described. (3) The porous fiber membrane according to claim 1 or 2, having a porosity of 5 to 60%. (4) O_2 gas flux is 1.0×10^-^5 ~
The porous hollow fiber membrane according to any one of claims 1 to 3, which has a flow rate of 2.0×10^3 ml/min·cm^2·atm. (5) O_2 gas flux is 1.0×10^-^3 ~
The porous hollow fiber membrane according to any one of claims 1 to 3, which has a flow rate of 1.0×10^3 ml/min·cm^2·atm. (6) The porous hollow fiber membrane according to any one of claims 1 to 5, wherein the independent fine particles on the outer surface side have an average particle diameter of 1 to 7 μm. (7) Inner diameter is 180-250μm, wall thickness is 20-100μm
The porous hollow fiber membrane according to any one of claims 1 to 6, wherein the porous hollow fiber membrane has a diameter of .mu.m. (8) The porous hollow fiber membrane according to any one of claims 1 to 6, wherein the polyolefin is polyethylene. (9) The porous hollow fiber membrane according to any one of claims 1 to 6, wherein the polyolefin is polypropylene.