JPH0512969B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a porous hollow fiber membrane, a method for producing the same, and an oxygenator using the hollow fiber membrane. Specifically, the present invention provides a porous hollow fiber membrane having high gas exchange ability and excellent breaking strength;
The present invention relates to a manufacturing method thereof and an artificial lung using the hollow fiber membrane. More specifically, no matter which type of oxygenator is used in which blood flows inside or outside the hollow fiber membrane, there is no damage to blood cell components, no increase in pressure loss, and no damage to the hollow fiber membrane occurs. The present invention relates to a porous hollow fiber membrane that is less likely to cause a decrease in effective membrane area due to oxidation, has no plasma leakage during long-term use, and exhibits high gas exchange capacity, a method for producing the same, and an oxygenator using the hollow fiber membrane. be. (Prior Art) Generally, in cardiac surgery and the like, a hollow fiber membrane oxygenator is used in an extracorporeal circulation circuit to lead a patient's blood outside the body, add oxygen to it, and remove carbon dioxide gas. There are two types of hollow fiber membranes used in such oxygenators: homogeneous membranes and porous membranes.
There are different types. In a homogeneous membrane, the gas molecules that permeate dissolve in the membrane and diffuse, thereby allowing gas to move. A typical example of this is silicone rubber, which has been commercialized as Mela Sirotx (Senko Medical Industry Co., Ltd.), for example. However, from the point of view of gas permeability, only silicone rubber is currently known as a homogeneous membrane that can be used, and the thickness of the silicone rubber membrane cannot be reduced to less than 100 μm due to its strength. For this reason, gas permeation is limited, and carbon dioxide gas permeation is particularly poor. Furthermore, the silicone rubber has the drawbacks of being expensive and having poor processability. On the other hand, in a porous membrane, the fine pores of the membrane are significantly larger than the gas molecules to be passed through, so that the gas passes through the pores as a volumetric flow. For example, various artificial lungs using porous membranes such as microporous polypropylene membranes have been proposed. For example, when polypropylene is spun using a hollow fiber production nozzle, the spinning temperature is
Melt-spun at 210-270℃ and draft ratio 180-600,
Then, after performing the first stage heat treatment at 155℃ or less,
Stretched by 30~200% at less than 110℃, then the first
It has been proposed to produce porous polypropylene hollow fibers by carrying out a second stage heat treatment at a stage heat treatment temperature or higher and 155°C or lower (Japanese Patent Publication No. 56-52123).
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, and The pores are formed by cracking in the axial direction of the hollow fiber depending on the degree of stretching, and therefore have a slit-like cross section. In addition, the pores are continuous and penetrate almost linearly, and the porosity is high.
Therefore, the porous hollow fiber has high water vapor permeability, and when used for long-term blood circulation outside the body,
The drawback was that plasma leaked out. In addition, as a porous membrane that does not cause plasma leakage,
For example, a kneaded product obtained by kneading a polyolefin, an organic filler and a crystal nucleating agent that can be uniformly dispersed in the polyolefin while the polyolefin is melted and is easily soluble in the extract liquid used. is discharged from an annular spinning hole in a molten state, an inert gas is introduced into the center of the interior at the same time, the hollow object is brought into contact with a cooling solidification liquid that does not dissolve the polyolefin, and the hollow object is cooled and solidified. A porous polypropylene hollow fiber membrane has been proposed (Japanese Patent Application No. 59-210466), which is produced by bringing the polyolefin into contact with an extractant that does not dissolve the polyolefin to extract and remove the organic filler. However, the polyolefin hollow fiber membrane, which is one of the hollow fiber membranes and is obtained using a cooling solidification liquid that can dissolve organic fillers and is preferred as a cooling solidification liquid, has small pores and no pore passages. Due to its complexity, plasma leakage does not occur, but since the pore density per unit area is small, there is a risk that the gas exchange ability will be insufficient for use as a membrane for oxygenator lungs. There was a risk that low molecular weight components of polyolefin would be mixed into the cooling solidified liquid and adhere to the inner wall of the cooling bath tube, causing the shape of the hollow fibers to change over time. In order to further improve these points, polypropylene, an organic filler that can be uniformly dispersed in the polypropylene while the polypropylene is melted, and is easily soluble in the extract used, and a crystal nucleating agent are kneaded. The kneaded material thus obtained is discharged in a molten state from an annular spinning hole into a hollow shape, and the hollow material is brought into contact with a liquid consisting of the organic filler or its similar compound to be cooled and solidified, and then cooled and solidified. A porous polypropylene hollow fiber membrane has been proposed (Japanese Patent Application No. 155159/1982), which is produced by bringing the hollow material into contact with an extractant that does not melt the polypropylene to extract and remove the organic filler.
The hollow fiber membrane obtained by this method overcomes the drawbacks mentioned above, but during the cooling process, the organic filler or the cooling solidification liquid is removed from the outermost part of the hollow fiber, which has not yet been completely cooled and solidified. Localized on the surface, the composition fraction of polypropylene on the outermost surface becomes low, resulting in large pores on the outer surface of the hollow fiber.
And polypropylene is connected like a network,
It is formed as a very uneven state. Such hollow fibers are of no use when used in a type of oxygenator in which blood flows inside the hollow fibers and oxygen-containing gas is blown outside the hollow fibers to add oxygen and remove carbon dioxide from the blood. Not a problem, but
On the other hand, when used in a type of oxygenator in which blood flows outside the hollow fibers and oxygen-containing gas is blown inside the hollow fibers, the above-mentioned outer surface properties can cause damage to blood cell components and pressure damage. This brings about disadvantages such as an increase in In addition, regardless of the type of oxygenator, when assembling the oxygenator, such hollow fiber membranes tend to stick to each other, resulting in poor workability and poor potting. There was a drawback. In addition, although the hollow fiber membrane thus obtained has relatively good strength, it cannot be said that its strength is sufficient for practical use, and there remains room for further improvement. Ta. (Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide an improved porous hollow fiber membrane, a method for manufacturing the same, and an oxygenator using the hollow fiber membrane. Another object of the present invention is to provide a porous hollow fiber membrane having high gas exchange ability and excellent breaking strength, a method for producing the same, and an oxygenator using the hollow fiber membrane. Furthermore, when the present invention is used in any type of oxygenator, it does not damage blood cell components or increase pressure loss, there is no plasma leakage during long-term use, and the membrane is effective due to rupture of the porous membrane. The purpose of the present invention is to provide a porous hollow fiber membrane made of polypropylene that has a high gas exchange capacity and is suitable for use in an oxygenator, with little risk of reduction in area, a method for producing the same, and an oxygenator using the hollow fiber membrane. shall be. The present invention further provides a porous hollow fiber membrane having smooth outer surface properties and free from adhesion of hollow fibers during an oxygenator assembly process, a method for producing the same, and an oxygenator using the hollow fiber membrane. With the goal. (Means for solving the problems) These objectives are to create a porous polypropylene hollow fiber membrane, in which the solid phase is formed by densely fused bonding of particulate polypropylene with some parts exposed on its inner surface. The solid phase inside and on the outer surface of the membrane is formed by a large number of polypropylene lumps made of particulate polypropylene connected in the fiber axis direction, and the space between these solid phases is as follows.
This is achieved by a porous hollow fiber membrane that is formed by communicating in a three-dimensional network to form communicating pores and has an axial breaking strength of 80 g/fiber or more. The present invention also provides a porous hollow fiber membrane having a birefringence index of 0.001 to 0.01 in the fiber axis direction. The present invention also has a porosity of 10~
60%, an inner surface porosity of 10 to 30%, and an oxygen gas flux of 100 to 1500/min·m ² ·atm. The present invention further provides a porous hollow fiber membrane having an inner diameter of 150 to 300 μm and a wall thickness of 10 to 150 μm. The present invention also provides
The average particle size of particulate polypropylene is 0.1~2.0μm
This indicates a porous hollow fiber membrane whose inner surface has an average pore diameter of 0.1 to 1.0 μm. The present invention also provides a porous hollow fiber membrane that is substantially free from leakage of plasma and loss of gas exchange capacity within 30 hours when used for an oxygenator. The present invention further provides a porous hollow fiber membrane that causes less damage to blood cell components when used for an oxygenator. The above objects are also achieved by kneading polypropylene, an organic filler which can be homogeneously dispersed in the polypropylene under melting and is easily soluble in the extract liquid used, and a crystal nucleating agent, and in this way. The resulting kneaded material is discharged in a molten state into a hollow shape from an annular spinning hole, and the hollow material is incompatible with the organic filler and has a specific heat capacity of 0.3 to 0.7 cal/g.
The hollow fiber thus obtained is brought into contact with a cooling solidification liquid to be cooled and solidified, and then the cooled and solidified hollow material is brought into contact with an extraction liquid that does not dissolve polypropylene to extract and remove the organic filler. 1 on the membrane
This is achieved by a method for producing a porous hollow fiber membrane, which is characterized by carrying out heat treatment after being stretched by ~30%. The present invention also provides a method for producing a porous hollow fiber membrane using silicone oil or polyethylene glycol as the cooling solidification liquid. The present invention further provides a method for producing a porous hollow fiber membrane in which the polydimethylsiloxane has a viscosity of 2 to 50 cst at 20°C. The present invention further provides a method for producing a porous hollow fiber membrane in which the polyethylene glycol has an average molecular weight of 100 to 400. The present invention also provides 5-30%
This figure shows a method for manufacturing a porous hollow fiber membrane that involves stretching. The present invention further increases 10-25%
This figure shows a method for manufacturing a porous hollow fiber membrane that involves stretching. The present invention further provides a method for producing a porous hollow fiber membrane in which heat treatment is carried out at 70 to 130°C for 5 seconds to 120 minutes. The present invention also provides a method for producing a porous hollow fiber membrane using liquid paraffin as an organic filler. The present invention further provides that the amount of organic filler added to 100 parts by weight of polypropylene is
This shows a method for producing a porous hollow fiber membrane containing 35 to 170 parts by weight. The present invention also provides a method for producing a porous hollow fiber membrane in which the crystal nucleating agent is an organic heat-resistant substance having a melting point of 150° C. or higher and a gelling point higher than the crystallization initiation temperature of the polypropylene used. The present invention further provides a method for producing a porous hollow fiber membrane in which the amount of crystal nucleating agent blended is 0.1 to 5 parts by weight based on 100 parts by weight of polypropylene. The above objects further provide an oxygenator comprising a hollow fiber membrane as a gas exchange membrane, wherein the gas exchange membrane is a porous polypropylene hollow fiber membrane, and on the inner surface, the solid phase is made of particulate polypropylene. It exhibits a continuous phase formed by densely fused bonds with some parts exposed, and the solid phase inside and on the outer surface of the membrane is composed of many polypropylene lumps made up of particulate polypropylene connected in the fiber axis direction. The space between these solid phases communicates in the form of a three-dimensional network to form communication holes, and has an axial breaking strength of 80 g/thread or more. achieved by. The present invention also provides an oxygenator in which the porous hollow fiber membrane has a birefringence index of 0.001 to 0.01 in the fiber axis direction. The present invention also provides that the porosity of the hollow fiber membrane is 10
~60%, an inner surface porosity of 10 to 30%, and an oxygen gas flux of 100 to 1500/min·m ² ·atm. The present invention further provides an oxygenator in which the hollow fiber membrane has an inner diameter of 150 to 300 μm and a wall thickness of 10 to 150 μm. The present invention also provides an artificial lung in which blood is circulated inside the hollow fiber membrane and oxygen-containing gas is blown outside the hollow fiber membrane. The present invention also provides an oxygenator in which blood is circulated outside the hollow fiber membrane and oxygen-containing gas is insufflated inside the hollow fiber membrane. The present invention further provides an artificial lung that exhibits substantially no leakage of plasma and no reduction in gas exchange capacity within 30 hours when blood is circulated extracorporeally. The present invention also provides an artificial lung that causes less damage to blood components when blood is circulated extracorporeally. The present invention further provides that the average particle diameter of the particulate polypropylene of the hollow fiber membrane is 0.1 to
2.0 μm, and the average pore diameter of the inner surface is 0.1 to 1.0 μm. Hereinafter, the present invention will be explained in more detail based on embodiments. The porous hollow fiber membrane according to the present invention has an inner diameter of 150~
300μm, preferably 180~250μm, wall thickness 10~
It is a substantially circular hollow fiber membrane made of polypropylene with a diameter of 150 μm, preferably 20 to 100 μm, and more preferably 40 to 50 μm. The fine structure of this polypropylene hollow fiber membrane varies depending on the manufacturing conditions of the hollow fiber membrane, but as described below, it has been used as a cooling solidified liquid.
Not compatible with organic fillers and has a specific heat capacity of 0.3~
By using a solution with a concentration of 0.7 acl/g, a structure as described below is obtained. That is, on the inner surface side, the solid phase exhibits a dense fusion bond with particulate polypropylene partially exposed, that is, a continuous phase formed by melting, cooling and solidifying. Furthermore, inside the membrane, the solid phase is formed by a large number of particulate polypropylene, which has no directionality in the circumferential direction and is gathered randomly, but is connected in the fiber axis direction. It forms a polypropylene mass,
The polypropylene blocks are interconnected by polypropylene threads. Therefore, inside the membrane, the solid phase is thought to be formed by a large number of polypropylene lumps made up of particulate polypropylene connected in the fiber axis direction. Furthermore, on the outer surface as well as inside the membrane, the solid phase is formed by a large number of polypropylene lumps made up of particulate polypropylene connected in the fiber axis direction. Therefore, the gap between these solid phases is such that in the thick part of the hollow fiber including the inner and outer surfaces, the path to the outer surface is longer than the inner surface, and the pores are not linear but complicated. A three-dimensional network of communicating holes is formed. The complexity of the communication pores is also due to the fact that the birefringence of the porous hollow fiber membrane of the present invention in the fiber axis direction is extremely low at 0.001 to 0.01, and the orientation of the polypropylene crystals is small. It is supported. As described above, in the porous hollow fiber membrane of the present invention, the inner surface is composed of a continuous phase in which particulate polypropylene is partially exposed and is tightly bonded with the other pores, and has a smooth surface texture. Because of this, it is used in artificial lungs, and even if blood is allowed to flow inside the hollow fiber, blood cell components will not be damaged and pressure loss will not increase. On the other hand, its outer surface also has a smooth surface texture, consisting of a solid phase formed by a large number of polypropylene lumps made up of particulate polypropylene arranged in an orderly manner in the direction of the fiber axis, and other pores. Even if blood is allowed to flow outside the hollow fiber used in the lungs, blood cell components will not be damaged and pressure loss will not increase. Furthermore, when used as a hollow fiber membrane for an oxygenator, the pores that serve as gas passages are connected in a complex three-dimensional network, so blood is transferred to the hollow fiber membrane. Even if extracorporeal circulation is carried out either internally or externally, plasma components cannot pass through such a long and complex path; for example, during an extracorporeal circulation time of 30 hours, no plasma leakage occurs, and gas exchange does not occur. Substantially no decrease in performance was observed. In addition, the porous hollow fiber membrane of the present invention has been heat-treated by adding porosity by an extraction method and then stretching at a predetermined ratio as detailed below. Breaking strength is improved without changing membrane structural properties such as axial breaking strength of 80 g/yarn or more, more preferably 85 g/yarn.
It is more than a thread. As described above, the porous hollow fiber membrane of the present invention has an extremely excellent breaking strength of 80 g/fiber or more, so there is little risk of the hollow fibers breaking when actually assembled into a module. , it is possible to improve the rate of non-defective modules. Further, in the porous hollow fiber membrane of the present invention, the porosity is 10 to 60%, more preferably 30 to 55%, and the porosity on the inner surface is 10 to 30%, more preferably 12 to 20%. In addition, it is desirable that the oxygen gas flux be 100 to 1500/min·m ² ·atm, more preferably 600 to 1000/min·m ² ·atm for use as a hollow fiber membrane for an oxygenator. In other words, if the porosity is less than 10%, there is a risk that the gas exchange ability will be insufficient;
If the porosity exceeds 10%, there is a risk of plasma leakage, and if the porosity is less than 10%, the formation of communicating pores in the pores of the hollow fiber membrane will be insufficient, resulting in insufficient gas exchange performance. On the other hand, if the porosity exceeds 30%, the communicating pores become simple and there is a risk of plasma leakage.
This is because if it falls outside the range of /min·m ² ·atm, it may not function as a gas exchange membrane. Furthermore, the size and degree of distribution of the particulate polypropylene constituting the porous hollow fiber membrane of the present invention and the communicating pores between these fine particles are preferably determined depending on the manufacturing conditions and raw material composition of the hollow fiber membrane. However, the average particle size of the particulate polypropylene is 0.1 to 2.0 μm, more preferably 0.2 to 1.5 μm, and the average pore size on the inner surface is
The thickness is preferably 0.1 to 1.0 μm, more preferably 0.3 to 0.6 μm. Such a hollow fiber membrane is manufactured, for example, as follows. That is, as shown in FIG. 1, a blend 11 of polypropylene, an organic filler, and a crystal nucleating agent is fed from a hopper 12 to a kneader, for example, a single screw extruder 13, and the blend is melt-kneaded. After being extruded, it was sent to a spinning device 14 and discharged from an annular spinning hole (not shown) of a spinneret device 15 into a gaseous atmosphere, for example, air, and the hollow material 16 that came out contained a cooled and solidified liquid 17. It is introduced into the cooling tank 18 and brought into contact with the cooling solidification liquid 17 to be cooled and solidified. In this case, as shown in FIG. 1, the contact between the hollow object 16 and the cooled solidified liquid 17 is carried out by, for example, a cooled solidified liquid distribution pipe 1 which is provided downwardly by penetrating through the bottom of the cooling tank 18.
It is desirable to cause the cooled solidified liquid 17 to flow down into the hollow body 9 and bring the hollow body 16 into cocurrent contact with the flow. The cooled solidified liquid 17 that has flowed down is received and stored in a solidification tank 20, and the hollow object 16 is placed in the solidification tank 20.
is introduced, the direction is changed by the direction changing rod 21, and the liquid is brought into sufficient contact with the cooling solidification liquid 17 to be solidified. The accumulated cooled solidified liquid 16 is discharged from a circulation line 23 and circulated to the cooling tank 18 by a circulation pump 24. Next, the solidified hollow material 16 is processed by a drive roll 22a into an extracting liquid 25 which dissolves the organic filler but does not dissolve the polypropylene.
It is guided to a shower/conveyor type extractor 27 that drops the liquid in a shower-like manner. In this extractor 27, the hollow material 16 is conveyed on the belt conveyor 26, and the hollow fiber membrane 16' has a porous structure that is sufficiently contacted with the extraction liquid to extract and remove the remaining organic filler. becomes. The hollow membrane 16' led out from the extractor 27 by the drive roll 22b is
After further steps (not shown) such as re-extraction and dry heat treatment as necessary, the drive roll 22c
is guided to the heat treatment apparatus 30 by. Thus, tension is exerted between the drive roll 22c and the first roller 29 of the heat treatment device 30, and the hollow fiber membrane 16' is stretched at a predetermined rate, that is, from 1 to 30%. Inside the heat treatment device 30, a heater 28 is installed.
The hollow fiber membrane 16' is maintained at a predetermined temperature condition by heating means such as the like, and while the hollow fiber membrane 16' is moved between the rollers in the heat treatment device 30, the structure of the heat treated membrane is stabilized. The hollow fiber membrane 16' led out from the heat treatment device 30 is wound onto a bobbin 32 in a winding device 31. The polypropylene used as a raw material in the present invention is not limited to propylene homopolymers, but includes block polymers containing propylene as a main component with other monomers, etc., and those with a melt index (MI) of 5 to 70. is preferable, especially MI
10 to 40 is preferred. Among the polypropylenes, propylene homopolymers are particularly preferred, and among them, those with high crystallinity are most preferred. The organic filler is required to be able to be uniformly dispersed in the polypropylene while it is melted, and to be easily soluble in the extract as described below. Such fillers include:
Liquid paraffin (number average molecular weight 100-2000), α-
Olefin oligomers [e.g. ethylene oligomers (number average molecular weight 100-2000), propylene oligomers (number average molecular weight 100-2000), ethylene-propylene oligomers (number average molecular weight 100-2000)
etc.], paraffin wax (number average molecular weight 200~
2500), various hydrocarbons, etc., and liquid paraffin is preferred. The blending ratio of polypropylene and the organic filler is 35 to 170 parts by weight, preferably 80 to 150 parts by weight, per 100 parts by weight of polypropylene. That is, if the organic filler is less than 35 parts by weight,
A portion of the resulting hollow fiber membrane is composed of a continuous phase of polypropylene, making it unable to exhibit sufficient gas permeability.On the other hand, if it exceeds 170 parts by weight, the viscosity becomes too low, making it difficult to process it into a hollow shape. This is because the quality decreases. Such raw material formulations are prepared (designed) by a pre-kneading 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. . In the present invention, the crystal nucleating agent blended into the raw material has a melting point of 150°C or higher (preferably 200°C or higher).
~250℃) and has a gel point higher than the crystallization temperature of the polypropylene used. The reason for blending such a crystal nucleating agent is
The purpose of this method is to reduce the size of polypropylene particles, thereby narrowing the voids between particles, that is, communicating pores, and increasing the pore density. To give an example, for example,
1,3,2,4-dibenzylidene sorbitol,
1,3,2,4-bis(p-methylbenzylidene) sorbitol, 1,3,2,4-bis(p-ethylbenzylidene) sorbitol, bis(4-t
Examples of the crystal nucleating agent include sodium (butylphenyl) phosphate, sodium benzoate, adipic acid, talc, and kaolin. As a crystal nucleating agent, benzylidene sorbitol, especially 1,3,2,4-bis(p-ethylbenzylidene) sorbitol 1,3,2,4-bis(p-methylbenzylidene) sorbitol has a low elution into the blood. preferable. The blending ratio of polypropylene and the crystal nucleating agent is 0.1 to 5 parts by weight, preferably 0.2 to 1.0 parts by weight, per 100 parts by weight of polypropylene. The raw material mixture thus prepared is further processed using an extruder such as a single-screw extruder to
The mixture is melted and kneaded at a temperature of 180 to 220°C, preferably 180 to 220°C, and discharged into a gas atmosphere from an annular hole of a spinning device using a highly quantitative gear pump if necessary to form a hollow object. Note that gases such as nitrogen, carbon dioxide, helium, argon, and air may be self-suctioned into the center of the annular hole, or these gases may be forcibly introduced if necessary. Subsequently, the hollow material discharged from the annular hole is dropped and then brought into contact with the cooled solidified liquid in the cooling tank. The falling distance of the hollow object is preferably 5 to 1000 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 become immersed when it enters the cooling solidification liquid. The hollow object has not yet solidified sufficiently in this cooling tank, and since the central part is gaseous, it is easily deformed by external force. Therefore, as shown in FIG. A cooling solidified liquid distribution pipe 19 that extends downward through the passageway.
The solidified liquid 17 is allowed to flow down into the interior, and the hollow object is brought into co-current contact with the flow, so that the hollow object is forcibly moved, and the deformation of the hollow object due to external force (fluid pressure, etc.) is prevented. It can be prevented. At this time, the flow rate of the cooled and solidified liquid is sufficient under natural flow. Also, the cooling temperature at this time is 10 to 90℃, preferably 20℃.
~75℃. In other words, at temperatures below 10°C, the cooling solidification rate is too fast and most of the thick wall becomes a dense layer, resulting in a low gas exchange ability.
If the temperature exceeds ℃, the hollow objects will not be sufficiently cooled and solidified.
This is because there is a risk that the hollow object may be cut within the cooling solidification layer. Therefore, in the present invention, the cooling solidification liquid is incompatible with the organic filler used and has a specific heat capacity of 0.3 to 0.7 cal/g, more preferably 0.3 to 0.7 cal/g.
Use 0.6 cal/g liquid. Specifically, such cooling solidification liquids include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil having a kinematic viscosity of 2 to 50 cSt, more preferably 8 to 40 cSt at 20°C, and an average molecular weight of Examples include polyethylene glycols having a molecular weight of 100 to 400, more preferably 180 to 330. The reason why a liquid incompatible with the organic filler used and having a specific heat capacity of 0.3 to 0.7 cal/g is used as the cooling solidification liquid is as follows. That is, when a liquid capable of dissolving the organic filler is used as the cooling solidification liquid, for example, liquid paraffin as the organic filler, if halogenated hydrocarbons are used, polypropylene and the organic filler are dissolved in the cooling solidification liquid. While the phase separation is progressing, the organic filler is dissolved and extracted, the organic filler moves from the inside of the hollow object to the outside, and when the hollow object is completely cooled and solidified, The proportion of the organic filler near the inner surface of the hollow object is reduced,
It is presumed that after the organic filler is further completely dissolved and extracted, the porosity on the inner surface becomes low, resulting in a decrease in the gas exchange ability of the membrane. Furthermore, in this example, even the low molecular weight components of the polypropylene in the hollow material are extracted and deposited on the inner wall of the cooling solidified liquid distribution pipe 19 shown in FIG. 20, reducing the inner diameter of the cooling solidified liquid distribution pipe 19. As a result, there is a risk that the shape of the hollow object may change. In addition, when the cooling solidification liquid is the same as the organic filler or a similar compound thereof, for example, when liquid paraffin is used as the organic filler, if liquid paraffin having a number average molecular weight similar to that of the liquid paraffin is used, hollow-shaped The organic filler (liquid paraffin) can provide a predetermined pore density without major migration in the hollow object, and the specific heat is not too large, so an appropriate cooling rate promotes crystallization of polypropylene and maintains a stable shape. However, during the cooling process, the organic filler or cooling solidification liquid is localized on the outermost surface of the hollow fiber, which has not yet been completely cooled and solidified, and the polypropylene composition fraction on the outermost surface becomes low. Therefore, the pores on the outer surface of the hollow fibers are large, and the solid phase has a highly uneven surface in which particulate polypropylene is spread out in the form of a network. Furthermore, as the cooling solidification liquid, even if it is an inert liquid that is incompatible with the organic filler, it has a large specific heat capacity. For example, when liquid paraffin is used as the organic filler, the specific heat capacity is about 1.0 cal. If a large amount of water (/g) is used, the polypropylene will be rapidly cooled due to its high cooling effect, and there is a risk that the outer surface will have a particularly low degree of crystallinity. For this reason, fine particles of polypropylene are not formed, and there is a risk that a hollow fiber membrane with small pores on the outer surface and a low gas exchange ability will be produced. On the other hand, if the specific heat capacity is small, a sufficient cooling effect cannot be obtained, and there is a possibility that a hollow object cannot be obtained as a thread. On the other hand, as a cooled solidified liquid, it is incompatible with the organic filler and has a specific heat capacity of 0.3 to 0.7 cal/
If a solution of g is used, the organic filler will not be localized on the outer surface of the hollow fiber, the cooling rate of the polypropylene will be appropriate, and the polypropylene will be crystallized with an appropriate polypropylene composition fraction on the outer surface. is promoted, the outer surface is formed by a large number of polypropylene lumps made up of fine polypropylene particles connected in the fiber axis direction, similar to the inside of the hollow fiber membrane.
This is because it exhibits a smooth surface texture. The hollow material cooled and solidified in the cooling solidification tank is sent to an extractor or the like via a diversion rod, where the organic filler is dissolved and extracted. Methods for dissolving and extracting the organic filler are not limited to the shower method in which the extract is showered onto a hollow object on a belt conveyor as shown in Figure 1, but also include the extraction tank method, the one-time rolling method, and the method of dissolving and extracting the organic filler. When rolling the hollow ivy object back into another skein, any method may be used as long as the hollow object can come into contact with the extract liquid, such as the unwinding method in which the skein is immersed in the extract solution. It is also possible to combine two or more. As the extraction liquid, any liquid can be used as long as it does not dissolve the polypropylene constituting the hollow fiber membrane and can dissolve and extract the organic filler. Examples include alcohols such as methanol, ethanol, propanols, butanols, pentanols, hexanols, octanols, lauryl alcohol, 1,1,2-trichloro-
1,2,2-trifluoroethane, trichlorofluoromethane, dichlorofluoromethane, 1,
There are halogenated hydrocarbons such as 1,2,2-tetrachloro-1,2-difluoroethane, and among these, halogenated hydrocarbons are preferable from the viewpoint of extraction ability for organic fillers, and are particularly safe for the human body. From this point of view, chlorinated fluorinated hydrocarbons are preferred. The porous hollow fiber membrane obtained in this way has
A stretching treatment of 1-30%, preferably 5-30%, more preferably 10-25% is then applied. That is, if the stretching is less than 1%, the breaking strength of the hollow fiber membrane cannot be substantially improved, while if the stretching is more than 30%, it will affect the microstructure of the hollow fiber membrane. This is because the porosity, gas flux, etc. may change, leading to a decrease in gas exchange ability and plasma leakage. The stretching method is not particularly limited, but it is preferable to apply tension between a drive roll and a roller, or between rollers, as shown in FIG. The hollow fiber membrane thus stretched at a predetermined ratio as described above is further subjected to heat treatment. Heat treatment is performed at 70 to 130℃, preferably 100 to 120℃ in a gaseous atmosphere such as air, nitrogen, carbon dioxide, etc.
The heating is carried out at a temperature of 5 seconds to 120 minutes, preferably 10 seconds to 60 minutes. This heat treatment stabilizes the structure of the hollow fiber membrane and increases its dimensional stability. The hollow fiber membrane thus obtained is optimal for use in a hollow fiber membrane oxygenator. The gas permeability of hollow fiber membranes obtained by conventional stretching methods was higher than necessary for use as an oxygenator. In other words, when blood is circulated inside the hollow fiber, the oxygenation capacity is affected by the large membrane resistance on the blood side.
The resistance of the hollow fiber membrane is not rate-limiting; on the other hand, the carbon dioxide removal capacity depends on the hollow fiber membrane resistance, but its permeability is excessive, and when blood is circulated outside the hollow fiber, the gas exchange capacity Although it also depends on the resistance of the hollow fiber membrane, its permeability was excessive. However, although the hollow fiber membrane of the present invention has lower gas permeability as a single membrane than that of the conventional stretched method, it has sufficient performance to be used when incorporated into an oxygenator, and moreover, it can be used by extraction method. Therefore, blood leakage due to pinholes does not occur, and therefore, a decrease in gas exchange ability can be prevented. Furthermore, as mentioned above, hollow fiber membranes obtained using liquids made of organic fillers or similar compounds used as cooling solidification liquids have polypropylene networks that form a network, resulting in extremely uneven surfaces. Because of this, when assembling the oxygenator, the threads would stick together and stick together, making the assembly process complicated, and there was a risk that the adhesive would not get around the threads, resulting in poor potting. However, the hollow fiber membrane obtained by the production method of the present invention has an outer surface formed of a large number of polypropylene lumps made of particulate polypropylene connected in the fiber axis direction, similar to the inside of the hollow fiber, and has a smooth surface. Due to its characteristics, such problems do not occur when assembling an oxygenator, and as mentioned above,
Even if blood is allowed to flow on either the outer surface or the inner surface of the hollow fiber membrane, the blood cell components will not be damaged and the pressure loss will be low. Furthermore, the hollow fiber membrane obtained by the production method of the present invention has improved breaking strength because it is stretched at a predetermined rate and heat treated as described above, and has an extremely excellent breaking strength of 80 g/fiber or more in the axial direction. Therefore, there is little risk that the hollow fibers will break when actually assembled into a module, and the rate of non-defective products in the module can be improved. FIG. 2 shows an embodiment of the hollow fiber membrane oxygenator of the present invention, in which blood is circulated inside the hollow fiber membrane and oxygen-containing gas is blown outside the hollow fiber membrane (first embodiment). This shows the assembled state. That is, the hollow fiber membrane oxygenator 51 has a housing 52
The housing 52 has a cylindrical main body 53 with an annular male threaded mounting cover 5 at both ends.
4 and 55 are provided, and within the housing 52 there are a large number of porous hollow fiber membranes 16' having the characteristics described above, for example, 1,000 to 70,000 pieces.
are arranged in parallel and spaced apart from each other along the longitudinal direction of the housing 52. Both ends of this porous hollow fiber membrane 16' are covered with mounting covers 54, 55.
Inside, each opening is fluid-tightly supported by partition walls 57 and 58 in an unobstructed state. In addition, each of the partition walls 57 and 58 is connected to the porous hollow fiber membrane 1.
A gas chamber 59 is formed together with the outer circumferential surface 6' and the inner surface of the housing 52, and is closed, and the gas chamber 59 is connected to a blood circulation space (not shown) formed inside the porous hollow fiber membrane 16'. It is meant to be isolated. Further, one mounting cover 54 is provided with an oxygen-containing gas inlet 60 for supplying oxygen-containing gas, and the other mounting cover 55 is provided with an oxygen-containing gas outlet 61 for discharging oxygen-containing gas. . On the inner surface of the cylindrical main body 53 of the housing 52, a restricting portion 62 may be provided that protrudes from the center in the axial direction. By providing the restricting portion 62 in the center in this way, it is possible to improve the gas exchange efficiency. This restraint part 62 is connected to the cylindrical main body 53.
is formed integrally with the cylindrical body 53 on the inner surface of the cylindrical body 53,
The outer periphery of a hollow fiber bundle 63 consisting of a large number of porous hollow fiber membranes 16' inserted into the cylindrical body 53 is tightened. In this way, the hollow fiber bundle 6
3 is narrowed at the center in the axial direction, and the narrowed part 6
4 is formed. Therefore, the filling factor of the hollow fiber membrane differs in each part along the axial direction, and is highest in the central part. In addition, the desirable filling rate in each part is as follows. First, as shown in FIG. 3, the filling rate A in the central constricted portion 64 is about 60 to 80%, and the filling rate B in the other cylindrical body 53 is about 30 to 60%. The filling rate C at both ends, that is, on the outer surfaces of the partition walls 57 and 58, is approximately
It is 20-40%. Next, the formation of the partition walls 57 and 58 will be described. As mentioned above, the partition walls 57 and 58 perform the important function of isolating the inside and outside of the porous hollow fiber membrane 16'. Usually, this partition wall 5
7,58 is a highly polar polymer potting material,
For example, it is made by pouring polyurethane, silicone, epoxy resin, or the like onto the inner wall surfaces of both ends of the housing 52 using a centrifugal injection method, and then hardening the resin. More specifically, first, the housing 52
A large number of porous hollow fiber membranes 16' having a length longer than 16' are prepared, both open ends of which are sealed with a highly viscous resin, and then placed side by side in the cylindrical body 53 of the housing 52. After this, install the mounting cover 5
Completely cover both ends of the porous hollow fiber membrane 16' with a mold cover having a diameter larger than the diameter of the porous hollow fiber membrane 16'. When the molecular potting material is poured in and the resin is cured, the mold cover is removed and the outer surface of the resin is cut with a sharp knife to expose both open ends of the porous hollow fiber membrane 16' to the surface. . The partition walls 57 and 58 are thus formed. The outer surfaces of the partition walls 57 and 58 are respectively covered with flow path forming members 65 and 66 having annular convex portions. The flow path forming members 65, 66 are composed of liquid distribution members 67, 68 and screw rings 69, 70, respectively, and the end surfaces of protrusions 71, 72 are formed as annular convex portions provided near the peripheral edges of the liquid distribution members 67, 68. are brought into contact with the partition walls 57 and 58, respectively,
Attach screw rings 69 and 70 to covers 54 and 55
Blood inflow chambers 73 and 74 are formed by screwing and fixing, respectively. A blood inlet 75 and a blood outlet 76 are formed in the flow path forming members 65 and 66, respectively. These partition walls 57, 58 and flow path forming members 65, 66
The hollow portions of the peripheral edges of the partition walls 57, 58 formed by the above-mentioned partition walls 57, 58 are in contact with the partition walls 57, 58 through one of at least two holes 77, 78 and 79, 80, respectively, communicating with the hollow portions. It is sealed like this. Alternatively, an O-ring (not shown)
It is also possible to be sealed through. Next, FIG. 4 shows another embodiment of the hollow fiber membrane oxygenator of the present invention, in which blood is circulated outside the hollow fiber membrane and oxygen-containing gas is blown into the inside of the hollow fiber membrane (second embodiment). The assembled state of the embodiment) is shown. That is,
The hollow fiber membrane oxygenator 81 includes a housing 82, which has a cylindrical body 83.
Annular mounting covers 84 and 85 are provided at both ends of the housing 82, and within the housing 82 there are a large number of porous hollow fiber membranes 16' having the characteristics described above, for example, 1,000 to 70,000 pieces. Housing 8
2 are arranged in parallel and spaced apart from each other along the longitudinal direction. Both ends of the porous hollow fiber membrane 16' are connected to the partition walls 87, 88 with their respective openings not closed within the mounting covers 84, 85.
They are each supported in a liquid-tight manner. The partition walls 87 and 88 together with the outer circumferential surface of the porous hollow fiber membrane 16' and the inner surface of the housing 82 constitute a blood chamber 89, close this, and allow the inside of the porous hollow fiber membrane 16' to be closed. This is to isolate the blood chamber 89 from the oxygen-containing gas circulation space (not shown) that will be formed. A blood inlet 95 for supplying blood is provided on one side of the housing 82, and a blood outlet 96 for discharging blood is provided on the other side of the housing.
is provided. On the inner surface of the cylindrical main body 83 of the housing 82, an aperture restricting portion 92 may be provided that protrudes from the center in the axial direction. That is, the restraint part 92 is formed integrally with the inner surface of the cylindrical body 83, and is inserted into the cylindrical body 83 into a hollow fiber bundle 93 made up of a large number of porous hollow fiber membranes 16'.
It is designed to tighten around the outer circumference of the In this way, the hollow fiber bundle 93 is narrowed at the center in the axial direction, forming a narrowed portion 94. Therefore,
The filling rate of the hollow fiber membrane differs in each part along the axial direction, and is highest in the central part. In addition, the mounting covers 84 and 85 have an oxygen-containing gas inlet 90 and an oxygen-containing gas outlet 91, respectively.
is formed. Other parts, forming methods, etc. are similar to the hollow fiber membrane oxygenator according to the first embodiment described above, and therefore their explanations will be omitted. (Example) Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 4 To 100 parts by weight of a propylene homopolymer having a melt index (MI) of 23, 130 parts by weight of liquid paraffin (number average molecular weight 324) and 0.5 parts by weight of dibenzylidene sorbitol as a crystal nucleating agent were charged. Twin-screw extruder (Ikegai Iron Works Co., Ltd.,
POM-30-25) was melt-kneaded, extruded, and pelletized. These pellets were melted at 180°C using a device as shown in Figure 1, that is, a single-screw extruder (Kasamatsu Seisakusho, WO-30), and the core diameter was 4.
The hollow material 16 was discharged into the air at a rate of 3.6 to 5.0 g/min through an annular spinning hole 15 having an inner diameter of 6 mm, an outer diameter of 7 mm, and a land length of 15 mm. The falling distance was 20 to 30 mm. Next, hollow object 1
6 was brought into contact with polyethylene glycol (Mn=200) as the cooled solidified liquid 17 in the cooling tank 18, and then brought into cocurrent contact with the cooled solidified liquid 17 flowing down naturally in the cooled solidified liquid flow pipe 19 to be cooled. Note that the temperature of the cooled and solidified liquid at this time was 20°C. Next, the hollow object 16 is introduced into the cooled solidified liquid in the solidification tank 20, and then the direction is changed by the direction changing rod 21.
It is guided to a drive roll 22a with a winding speed of 80 m/min, and is continuously passed through a shower conveyor type extractor 2.
In step 7, the liquid paraffin was completely extracted with extractant 25 consisting of Freon 113 (1,1,2-trichloro-1,2,2-trifluoroethane). The hollow fiber membrane 16' imparted with porosity in this way is taken out from the extractor 27 by the drive roll 22b and sent to the heat treatment device 30, while the drive roll 22b and the heat treatment device 3
The film was stretched at the ratio shown in Table 1 between the film and the first roll 29 of No. 0, and was further heat treated at 110° C. for 20 seconds while passing through a heat treatment device 30. The hollow fiber membrane 16' that passed through the heat treatment device 30 was wound up onto a bobbin 34 by a winding machine 33. The shape (inner diameter/thickness), porosity, gas flux, oxygen gas addition capacity, carbon dioxide removal capacity, plasma leakage, and breaking strength of the hollow fiber membrane thus obtained were measured. The results obtained are shown in Table 1. Furthermore, regarding the hollow fiber membrane of Example 1, the birefringence index, which is an index of crystal orientation, was measured. The results are shown in Table 2. Comparative Example 1 For comparison, porous hollow fiber membranes were prepared in the same manner as Examples 1 to 4 except that no stretching treatment was performed, and the shape (inner diameter/thickness),
Porosity, gas flux, oxygen gas addition capacity, carbon dioxide removal capacity, plasma leakage, and breaking strength were measured. The results obtained are shown in Table 1. Also, Example 1
The birefringence index, which is an index of crystal orientation, was measured in the same manner as above. The results are shown in Table 2. Comparative Example 2 For comparison, porous hollow fiber membranes were prepared in the same manner as Examples 1 to 4 except that the stretching ratio was changed as shown in Table 1, and the shape of the obtained porous hollow fiber membrane ( inner diameter/wall thickness), porosity, gas flux,
Oxygen gas addition capacity, carbon dioxide removal capacity, plasma leakage, and breaking strength were measured. The results obtained are shown in Table 1. Comparative Example 3 For comparison, a commercially available polypropylene hollow fiber membrane for oxygenator lungs manufactured by a stretching method was given a shape (inner diameter/
Wall thickness), porosity, gas flux, oxygen gas addition ability, carbon dioxide removal ability, plasma leakage, and breaking strength were measured. The results obtained are shown in Table 1. Further, in the same manner as in Example 1, the birefringence index, which is an index of crystal orientation, was measured. The results are shown in Table 2. The definitions and measurement methods of each term in these Examples and Comparative Examples are as follows. Shape (Inner Diameter/Wall Thickness) Pick out 10 of the obtained hollow fiber membranes and cut them into rounds with a sharp razor to a length of about 0.5 mm.
Project the cross section with a universal projector (Nikon Profile Projector V-12), and measure its outer diameter with a measuring device (Nikon Digital Counter CM-6S).
d ₁ and the inner diameter d ₂ were measured, and the wall thickness t was calculated by t=d ₁ −d ₂ , and the average value of the 10 pieces was taken as the average value. Porosity (%) Take about 2 g of the obtained hollow fiber membrane and cut it into rounds with a length of 5 mm or less using a sharp razor. The obtained sample was measured using a mercury porosimeter (Carlo Erba 65A).
Apply pressure to 1000 Kg/cm ² using a mold) and obtain the porosity from the total pore volume (pore volume of the hollow fiber membrane per unit weight). Gas flux The obtained hollow fiber membrane has an effective length of 14 cm and a membrane area of
After creating a 0.025 m ² mini module and closing one end, apply a pressure of 1 atm inside the hollow fiber with oxygen, and measure the flow rate of oxygen gas when it reaches a steady state using a flowmeter (manufactured by Kusano Rikagaku Kiki Seisakusho). , float meter). Oxygen gas addition ability, carbon dioxide gas removal ability (first embodiment) The obtained hollow fiber has an effective length of 140 mm and a membrane area of 5.4 m ²
An artificial lung module was created, and a single pass of bovine blood (standard venous blood) was applied inside the hollow fiber.
Path) at a flow rate of 6.0/min., and pure oxygen was flowed outside the hollow fiber at _a flow rate of 6.0/min. Gas partial pressure (P _O2 ) was measured using a blood gas measuring device (Radiometer, BGA type 3).
The partial pressure difference between the oxygenator inlet and outlet was calculated. (Second embodiment) The obtained hollow fiber has an effective length of 90 mm and a membrane area of 2.1 m ²
An artificial lung module was created, and a single pass of bovine blood (standard venous blood) was applied to the outside of the hollow fiber.
Path) at a flow rate of 6.0/min., pure oxygen was flowed inside the hollow fiber at _a flow rate of 6.0/min. Partial pressure (P _O2 ) was measured using a blood gas measuring device (Radiometer, BGA type 3).
The partial pressure difference between the oxygenator inlet and outlet was calculated. In addition,
The hollow fiber membranes of Examples 1 to 4 and Comparative Examples 1 to 2 were
Since the outer surface was smooth, even when blood was circulated outside the hollow fiber membrane in this way, no hemolysis or high pressure loss was observed. Plasma leakage An artificial lung module similar to the one used for oxygen gas addition and carbon dioxide removal was created, and
The artificial lung module (membrane area 1.6 m ² ) was incorporated into a partial V-A bypass circuit using jugular vein and carotid artery cannulation (20 kg),
Extracorporeal circulation was performed for 30 hours, and the amount of plasma leaking from inside the hollow fiber was measured. Furthermore, even if no leakage was confirmed, a trace amount of plasma leakage was also confirmed by examining the protein reaction of droplets with water vapor outside the hollow fiber. Breaking strength (g/thread) Prepare 10 hollow fiber membranes cut into lengths of approximately 10 cm, measure each one using Strograph T manufactured by Toyo Seiki Seisakusho under the following conditions, and calculate the average value of the 10 pieces. was calculated. Chuck used: Wide box chuck Initial length: 25 mm Tensile speed: 50 mm/min Temperature: 23°C Birefringence (Δn) (Retardation method) Take out 10 arbitrarily from the obtained hollow fiber membrane and cut the central part by 3 cm. Cut out. Further, one end of the thus obtained strip is cut diagonally to use as a sample. The hollow fiber membrane sample prepared in this manner is placed on a slide glass, immersed in an immersion liquid (liquid paraffin), and placed on the rotating stage of a polarizing microscope. Substitute this with a monochromatic light source or filter, rotate the sample on the stage under crossed nicols, excluding the compensator, and fix it at the brightest position (rotate it 45 degrees from the darkest position to either direction). Insert the compensator, rotate the analyzer, measure the darkest angle (θ), calculate the retardation (R) from the following formula, and measure the birefringence of the hollow fiber membrane using the following formula. The average value of 10 values was taken as the data value. Retardation R = 180-θ/108λ λ: Used wavelength birefringence Δn = R/d d: Sample thickness (corrected by porosity) Measurement conditions: Polarizing microscope Nikon OPTIPHTO-POL Light source wavelength 546nm compensator
Senarmont type compensator The birefringence Δn of perfectly oriented polypropylene is 0.35 (literature value).

【table】
Occurrence in large quantities
Table 2 Birefringence (Δn) Example 1 0.004 Comparative Example 1 0.003 〃 3 0.014 Fully oriented polypropylene 0.035 (literature value) (Effect of the invention) As described above, the present invention is a porous polypropylene hollow fiber membrane. On the inner surface of the membrane, the solid phase exhibits a continuous phase in which particulate polypropylene is partially exposed and tightly fused together, and on the inside and outer surface of the membrane, the solid phase is composed of particulate polypropylene fibers. It is formed by gathering a large number of polypropylene lumps that are connected in the axial direction, and the spaces between these solid phases communicate in a three-dimensional network to form communicating holes, and there are no axial fractures. strength is
Since it is a porous hollow fiber membrane characterized by having a weight of 80 g/fiber or more, for example, when an oxygenator is created using the porous hollow fiber membrane, the effective membrane area will not decrease due to rupture of the hollow fiber membrane. Although there is little risk of plasma leakage even during long-term use, it has a high gas exchange capacity and is used in a type of oxygenator that circulates blood both inside and outside the hollow fiber membrane. Even when exposed to water, it does not damage blood cell components and does not increase pressure loss. Furthermore, since its outer surface is smooth, it is an extremely excellent porous hollow fiber membrane that does not cause problems when assembling an oxygenator, such as adhesion of the hollow fiber membranes to each other or poor potting due to adhesive. These features include the birefringence of the porous hollow fiber membrane in the fiber axis direction of 0.001 to 0.01;
Also, the porosity is 10 to 60%, and the inner surface porosity is 10 to 30.
%, oxygen gas flux is 100 to 1500/min・
^m2・atm, the inner diameter is 150 to 300 μm, and the wall thickness is 10
~150 μm, and furthermore, the average particle size of the particulate polypropylene is 0.1 ~ 2.0 μm, and the average pore size on the inner surface is
A value of 0.1 to 1.0 μm is better. In addition, the present invention involves kneading polypropylene, an organic filler that can be uniformly dispersed in the polypropylene when the polypropylene is melted, and that is easily soluble in the extract liquid used, and a crystal nucleating agent, and in this way, The resulting kneaded material is discharged in a molten state into a hollow shape from an annular spinning hole, and the hollow material is incompatible with the organic filler and has a specific heat capacity of 0.3 to 0.7 cal/g.
The hollow fiber thus obtained is brought into contact with a cooling solidification liquid to be cooled and solidified, and the hollow fiber thus obtained is brought into contact with an extraction liquid that does not melt polypropylene to extract and remove the organic filler. 1 on the membrane
This is a method for producing a porous hollow fiber membrane, which is characterized by carrying out a heat treatment after being stretched by ~30%.
In the process of cooling and solidifying the spinning stock solution that has been uniformly dispersed under molten conditions, the polypropylene and organic filler in the stock solution are phase-separated at an appropriate cooling rate without localizing the organic filler on the outer surface and are appropriately crystallized. Many micropores can be formed between the generated particulate polypropylene, and the outer surface has a solid phase with particulate polypropylene aligned in the fiber axis direction, similar to the thick part of the hollow fiber, and has a smooth surface. In the step of further stretching 1 to 30% and heat treatment, the porous hollow fiber membrane thus formed has excellent pore structure, surface properties, and gas exchange efficiency. The breaking strength of porous hollow fiber membranes can be improved without any loss in properties, etc., and hollow fiber membranes having the above-mentioned excellent performance can be manufactured. Further, in the manufacturing method of the present invention, the stretching ratio is 5 to 30%, more preferably 10 to 25%, and the heat treatment is 70 to 30%.
When carried out at 130°C for 5 seconds to 120 minutes, a stable porous membrane with an extremely excellent structure in terms of breaking strength and other properties can be obtained. is a silicone oil with a viscosity of 2 to 50 cSt or an average molecular weight
100 to 400 polyethylene glycol is used, liquid paraffin is used as an organic filler, the blending amount is 35 to 170 parts by weight per 100 parts by weight of polypropylene, and the melting point is 150°C as a crystal nucleating agent.
If an organic heat-resistant substance with a gelation point higher than the crystallization start temperature of polypropylene is used and the amount is 0.1 to 5 parts by weight based on 100 parts by weight of polypropylene, porous pores with better performance can be used. A quality hollow fiber membrane can be obtained. Furthermore, the present invention provides an oxygenator comprising a hollow fiber membrane as a gas exchange membrane, wherein the gas exchange membrane is a porous polypropylene hollow fiber membrane, and on its inner surface, the solid phase is made of particulate polypropylene. It exhibits a continuous phase formed by densely fused bonds with some parts exposed, and the solid phase inside and on the outer surface of the membrane is composed of many polypropylene lumps made up of particulate polypropylene connected in the fiber axis direction. The space between these solid phases communicates in the form of a three-dimensional network to form communication holes, and has an axial breaking strength of 80 g/thread or more. Therefore, there is no risk of a decrease in the effective membrane area due to rupture of the hollow fiber membrane, and there is no risk of a decrease in the effective membrane area due to rupture of the hollow fiber membrane. In any type of oxygenator that circulates blood to the outside and blows oxygen-containing gas into the inside of a hollow fiber membrane, the oxygenation ability and carbon dioxide removal ability remain unchanged even during long-term extracorporeal circulation, and blood or plasma remains intact. It can be said that it is an extremely excellent artificial lung, as it does not cause any leakage, nor does it damage blood cell components or exhibit high pressure loss. The oxygenator of the present invention typically does not experience plasma leakage or decrease in gas exchange capacity during extracorporeal circulation for 30 hours. In addition, the birefringence in the axial direction of the hollow fiber membrane used is 0.001~
0.01, the porosity of the hollow fiber membrane is 10 to 60%, the porosity of the inner surface is 10 to 30%, and the oxygen gas flux is 10
~1500/min・^m2・atm, and the inner diameter is 150~
300 μm, the wall thickness is 10 to 150 μm, and the average particle size of the particulate polypropylene is 0.1 to 2.0 μm,
Furthermore, when the average pore diameter of the inner surface is 0.1 to 1.0 μm, the performance of the obtained oxygenator is further improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an apparatus used in the method for producing a porous hollow fiber membrane according to the present invention, FIG. 2 is a half-sectional view showing an embodiment of a hollow fiber membrane oxygenator according to the present invention, and FIG. The figure is a sectional view showing various parts related to the hollow fiber membrane filling rate in the same embodiment, and FIG. 4 is a half sectional view showing another embodiment of the hollow fiber membrane oxygenator according to the present invention. 11... Raw material blend, 12... Hopper, 13... Single screw extruder, 14... Spinning device, 15... Spinneret device, 1
6... Hollow object, 16'... Hollow fiber membrane, 17... Cooled solidified liquid, 18... Cooling tank, 19... Cooled solidified liquid distribution pipe,
20...Solidification tank, 21...Direction changing rod, 22a, 22b,
22c... Drive roll, 23... Circulation line, 2
4...Circulation pump, 25...Extract liquid, 26...Belt conveyor, 27...Shower conveyor type extractor, 2
8... Heater, 29... Heat treatment device first roll, 3
0... Heat treatment device, 31... Winding machine, 32... Bobbin,
51, 81... Hollow fiber membrane oxygenator, 52, 82... Housing, 53, 83... Cylindrical main body, 57, 58,
87, 88... partition wall, 59, 89... gas chamber, 60,
90...Oxygen-containing gas inlet, 61,91...Oxygen-containing gas outlet, 63,93...Hollow fiber bundle, 75,9
5...Blood inlet, 76, 96...Blood outlet, 89
...blood chamber.

Claims (1)

[Scope of Claims] 1 A porous polypropylene hollow fiber membrane, on the inner surface of which the solid phase exhibits a continuous phase formed by densely fused bonding of particulate polypropylene with some exposed parts; On the inner and outer surfaces, the solid phase is formed by a large number of polypropylene lumps made of particulate polypropylene connected in the fiber axis direction, and the spaces between these solid phases communicate in the form of a three-dimensional network. A porous hollow fiber membrane having continuous pores formed therein and having an axial breaking strength of 80 g/fiber or more. 2. The porous hollow fiber membrane according to claim 1, wherein the porous hollow fiber membrane has a birefringence index of 0.001 to 0.01 in the fiber axis direction. 3 The average particle size of particulate polypropylene is 0.1~
The porous hollow fiber membrane according to claim 1 or 2, wherein the average pore diameter on the inner surface is 2.0 μm and 0.1 to 1.0 μm. 4. Knead polypropylene, an organic filler that can be uniformly dispersed in the polypropylene when the polypropylene is melted, and that is easily soluble in the extract liquid used, and a crystal nucleating agent, and then knead the kneaded product thus obtained. The molten material is discharged from an annular spinning hole into a hollow shape, and the hollow material is cooled and solidified by contacting with a cooling solidification liquid that is incompatible with the organic filler and has a specific heat capacity of 0.3 to 0.7 cal/g. Then, the cooled and solidified hollow material is brought into contact with an extractant that does not dissolve polypropylene to extract and remove the organic filler, and the thus obtained hollow fiber membrane is stretched by 1 to 30%. A method for producing a porous hollow fiber membrane, which comprises performing heat treatment. 5. The method for producing a porous hollow fiber membrane according to claim 4, wherein silicone oil or polyethylene glycol is used as the cooling solidification liquid. 6. The method for producing a porous hollow fiber membrane according to claim 4 or 5, wherein the heat treatment is performed at 70 to 130°C for 5 seconds to 120 minutes. 7. Production of a porous hollow fiber membrane according to any one of claims 4 to 6, wherein the crystal nucleating agent is an organic heat-resistant substance having a melting point of 150°C or higher and a gelation point higher than the crystallization initiation temperature of the polypropylene used. Method. 8. An artificial lung comprising a hollow fiber membrane as a gas exchange membrane, wherein the gas exchange membrane is the porous polypropylene hollow fiber membrane according to any one of claims 1 to 3.