JPH0462767B2 - - Google Patents

Description

[Detailed description of the invention]

<Field of Application> The present invention relates to a permselective hollow fiber made of a specific polymer and having a specific shape, and a fluid separator using the hollow fiber. More specifically, the present invention includes:
The present invention provides a finned permselective cellulosic hollow fiber whose main component is a cellulose polymer having a specific average degree of polymerization, and a fluid separator using the hollow fiber. Specific examples of the fluid separation include liquid separation such as dialysis, ultrafiltration, precision filtration, reverse osmosis, and paper separation, and gas separation such as oxygen enrichment. <Prior Art> Permselective hollow fibers have been practically used in reverse osmosis, hemodialysis, and the like. Hollow fiber hemodialyzers are now often used to purify the blood of patients with renal failure, in particular.
This system houses a large number of dialysis membranes, such as hollow fiber membranes, in a housing, collects the patient's blood in the hollow interior, and flows the dialysate between the hollow fibers to the outside. Through dialysis, waste products in the blood are removed and electrolyte concentration is corrected, and excess water in the blood is removed by ultrafiltration by applying a pressure difference between the inside and outside of the hollow fiber. Furthermore, hollow fibers are used to treat autoimmune diseases and the like by separating only plasma from blood or removing specific components from the plasma. In this way, hollow fibers for blood treatment must selectively allow specific substances to permeate depending on the purpose. Its performance depends on the hollow fiber material, porosity (hole size, number, etc.),
Determined by film thickness, etc. However, it is not just that, for example, how to focus a large number of hollow fibers to make the entire membrane surface function effectively.
This is an important point that determines its performance. For example, during dialysis, when hollow fibers come into close contact with each other along their length, the dialysate flows in the vicinity of that part.
It becomes difficult to flow evenly around each hollow fiber, resulting in the formation of certain flow breaks, and dialysis through the hollow fibers that are not part of this flow is hardly performed, reducing the overall dialysis effect.
In normal dialysis operation, the concentration difference on both sides of the hollow fiber membrane becomes the driving force for mass transfer.
Flow the dialysate as evenly as possible into the outer space of the hollow fiber, reduce as much as possible the area where the outer membrane resistance is greater than the surrounding area, and maintain the concentration between the blood side (inside the hollow fiber) and the dialysate side (outside the hollow fiber). In order to increase the difference, it is necessary to devise the shape of the hollow fiber itself. For example, as previously proposed by some of the present inventors, a method can be used in which the outer surface of the hollow fibers is provided with protrusions to prevent the hollow fibers from coming into close contact (Japanese Patent Application Laid-Open No. 48-1999). No. 75481). However, in the case of cellulose acetate, for example, it is difficult to obtain hollow fibers with high fins. Furthermore, in the case of cellulose acetate, etc., the elongation rate of the hollow fibers when filled with water or an aqueous solution during use after storing the hollow fiber bundle in a substantially dry state and assembling a fluid separator. In other words, because the rewetting elongation rate is large, the entanglement of the hollow fibers in the fluid separator becomes severe, and the local adhesion of the hollow fibers increases.
There is a drawback that bending of the hollow fibers is likely to occur, and improvement of this problem has been strongly desired. <Purpose and Structure of the Invention> From this perspective, the present inventors conducted extensive research with the aim of improving fluid separation efficiency, and as a result, they identified a cellulose-based polymer having a specific degree of polymerization as the main component. It has been found that hollow fibers having the shape of are particularly effective, and the present invention has been achieved. That is, the present invention provides a cellulosic hollow fiber having longitudinally extending fins in the outer circumferential portion and having selective permeability, the main component of which is an average of a cellulose polymer consisting of cellulose or cellulose ester. A cellulose-based hollow fiber for blood treatment, which has a degree of polymerization of 150 or more, a ratio H/W of the height H to width W of the fins of 0.5 or more, and a rewetting elongation rate of 2.5% or less, and selective permeation. In a fluid separator for blood processing that accommodates a permselective hollow fiber as a separation function part, the permselective hollow fiber is provided with fins extending in the longitudinal direction at the outer periphery, and cellulose or cellulose, which is the main component thereof, The average degree of polymerization of the cellulose polymer made of ester is 150 or more, and the ratio H/W of the height H to width W of the fin is 0.5 or more,
A fluid separator characterized in that the fluid separator is made of cellulose-based hollow fibers having a rewetting elongation rate of 2.5% or less. The present invention will be explained in more detail below. First, the permselective cellulose-based hollow fiber of the present invention has a cellulose-based polymer as its main component. Examples of the cellulose-based polymer include cellulose, cellulose acetate such as cellulose diacetate and cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, and cellulose nitrate, and one or two of these may be used. It can be used above. Among these, particularly preferred cellulose polymers include cellulose ester polymers such as cellulose diacetate and cellulose triacetate, and cellulose. The cellulose polymer in the present invention is characterized in that it has an average degree of polymerization of 150 or more.
The average degree of polymerization referred to herein means the value obtained by dividing the weight average molecular weight by the molecular weight of the repeating unit of the polymer. Examples of methods for measuring the weight average molecular weight include gel permeation chromatography, viscosity measurement, sedimentation equilibrium measurement, and light scattering method. When the average degree of polymerization of the cellulose-based polymer is less than 150, it is difficult to obtain selectively permeable cellulose-based hollow fibers with high fins, and the hollow fibers have a low rewetting elongation rate. Hateful. The average degree of polymerization is more preferably 160 or more, particularly 170.
The above is preferable. The upper limit of the average degree of polymerization of the cellulose polymer is not particularly limited,
A value of 230 or less is practically preferred, and a value of 200 or less is more practical. The cellulose hollow fiber of the present invention has such a cellulose polymer as a main component, and its specific content is preferably 50% or more, more preferably 70% or more. The other components included are not particularly limited, and include, for example, organic polymers such as polymethyl methacrylate, polyethylene, polypropylene, polyacrylonitrile, polyvinyl alcohol, and nitrocellulose. Furthermore, the cellulose-based hollow fiber of the present invention has fins extending in the longitudinal direction at the outer periphery, and the ratio H/W of the height H and width W of the fins is
It is characterized by being 0.5 or more. The ratio H/
If W is less than 0.5, it is not preferable because it is difficult to obtain the effect of preventing the hollow fibers from coming into close contact with each other when housed in a fluid separator. A more preferable H/W is 0.8 or more. Note that the width W of the fins means the width at a position of 1/2 of the height H of the fins. Further, the number x of the fins of the hollow fiber in the present invention is at least 1, but when it becomes 11 or more, the effective membrane area due to the fin root portion decreases significantly, and for example, the substance dialysis performance and water permeation performance in a hemodialyzer are deteriorated. It is significantly degraded and is not practical. That is, x is generally from 1 to 10, more preferably from 2 to 8, with a particularly effective range from 3 to 7. Furthermore, the outer diameter d of the hollow fiber of the present invention is 100 to 400μ.
is preferable, and more preferably 200 to 300μ. The film thickness h of the portion without fins is preferably 5 to 50 microns, more preferably 5 to 30 microns, particularly 10 to 25 microns, and the height H of the fins is preferably 5 to 100 microns, more preferably 9 to 60 microns. The ratio H/h between the two is preferably 0.5 to 3, more preferably 1 to 2. Furthermore, the average height H (μ) of the fins and the average outer diameter d of the hollow fibers excluding the fins.
The ratio H/d of (μ) is preferably in the range of 0.01 to 1, more preferably in the range of 0.02 to 0.5, especially 0.03 to
It is desirable that it be in the range of 0.2. Further, it is desirable that the width of the base of the fin is narrower than the upper part of the fin, but normally, after the spinning stock solution is discharged from the spinneret, the base part tends to become wider due to the surface tension of the stock solution. The appropriate width of the base is 15 to 50μ, preferably 20 to 40μ. Hollow fibers within this range are preferable because they have good roundness and are less likely to cause blood coagulation or residual blood within the hollow fibers. When one hollow fiber has a plurality of fins, the height H and width W of each fin may be the same or different. Further, at least a portion of the fins may be spirally wound around the outer surface of the hollow fiber, or a portion of the fins may be discontinuous. Furthermore, the hollow fiber of the present invention has a rewetting elongation rate of 3%.
It is characterized by the following: If the rewet elongation rate exceeds 3%, the elongation of the hollow fiber is too large when it is stored in a fluid separator in a substantially dry state and then filled with water or an aqueous solution to make it rewet. This is not preferable because local adhesion between the fibers increases and bending of the hollow fibers becomes more likely. The rewetting elongation rate is more preferably 2.5% or less. The lower limit of the rewetting elongation rate is not particularly limited, but if it is 0.5% or more, more preferably 1% or more, the hollow fibers will exhibit appropriate elongation during rewetting in the fluid separator, and the The effect of spreading the hollow fiber bundle throughout the separator can also be obtained. The rewetting elongation rate α is approximately 0.1g/
Measure the length l measured under a load of de and the length l ₁ when the hollow fiber is wetted with water and measured under a load of about 0.01 g/de, α=l ₁ −l/l It is obtained by the calculation formula ×100. Here, the term "substantially dry state" means a state in which the hollow fibers are immersed in an aqueous glycerin solution and then dried to have a glycerin content of 30 to 60% and a water content of 0.5 to 9%. Further, among the hollow fibers of the present invention, those having a wet tensile strength of 0.3 g/de or more are preferable,
In particular, 0.4 g/de or more is desirable. The strength is
If it is less than 0.3 g/de, the formation retention is poor;
It is easy to break during the manufacturing process of hollow fibers and fluid separators, especially when the outer diameter d is 100 to 300μ and the membrane thickness is 5μ.
This tendency is large in the case of hollow fibers in the range of ~25μ. The upper limit of the strength is not particularly limited, and is generally 0.8 g/de or less, for example. Further, among the hollow fibers of the present invention, it is preferable that the bending rigidity in a substantially wet state is in the range of 200 mg/200 fibers or more, and the bursting pressure is 4Kg/
It is preferable that it is at least cm ² . Hollow fibers within this range are easy to handle during the manufacture of fluid separators, the length of each hollow fiber within the fluid separator is likely to be uniform, and it is easy to open the fibers when using the separator. The advantage is that the intermediate yarn is less likely to be damaged due to pressure operation. In addition, the cellulose-based hollow fiber of the present invention has selective permeability for fluids, and more specifically, for example, in the case of a hollow fiber for hemodialysis, the water permeation performance UFR in the part excluding the fins is is 1.0 to 30.0
The range is preferably ml/(m ² ·hr·mmHg), particularly 3.0 to 10.0ml/(m ² ·hr·mmHg). The cellulose-based hollow fiber having permselectivity of the present invention exhibits excellent separation performance in fluid separation. The fluid separation method is not particularly limited, and includes, for example, liquid decomposition such as dialysis, ultrafiltration, and reverse osmosis, and gas separation for artificial lungs. In particular, the hollow fiber of the present invention is useful for separation due to differences in diffusion rates such as dialysis, which requires good fluid flow conditions outside the hollow fiber, and blood processing that requires smooth fluid flow within the hollow fiber. Are suitable. Furthermore, the hollow fibers of the present invention can also be used as a supporting membrane for forming another membrane having a fluid separation function on the inner or outer membrane surface. The method for producing cellulose-based hollow fibers in the present invention uses a liquid mixture containing a cellulose ester polymer with an average degree of polymerization of 150 or more and other additives as a spinning dope, and spins it together with a core material into a spinneret for finned hollow fibers. It is characterized in that the spinning stock solution is discharged with a viscosity in the range of 100 to 10,000 poise. A more preferable range of the viscosity is 200 to 5,000 poise, particularly preferably 500 to 3,000 poise in the case of melt spinning, and 200 to 5,000 poise in the case of semi-dry/semi-wet spinning and wet spinning. Of these viscosities, melt viscosity can be measured using a flow tester, and solution viscosity can be measured using a rotational viscometer. Such a manufacturing method may be any one of melt spinning, wet spinning, semi-dry and semi-wet spinning, etc. That is, in the case of the melt spinning method, the spinning stock solution is a heated melt, and after the melt is discharged from the spinneret and cooled to solidify and form a finned hollow fiber, the cellulose ester polymer is Selective permselectivity is achieved by extracting and removing at least a portion of the additive in the finned hollow fibers using a solvent that can dissolve the additive without dissolving the coalescence, and further performing alkali treatment as necessary. A cellulose-based hollow fiber with fins is obtained. In this method, if the time required for the hollow fibers to substantially solidify by cooling after the heated solution is discharged from the spinneret is 10 seconds or less, more preferably 5 seconds or less, the shape of the fins can be maintained well. can be stably spun. Solidification here means that the spun yarn loses its fluidity and thinning due to the winding tension no longer progresses, and the method for measuring this is to remove the yarn being spun with a scissors and remove the thinning. This is based on the method of finding the ending point. As a specific example of melt spinning, a heated spinning dope (melt or solution) is passed through a hollow hole of a spinneret having a notch on the outer periphery of a double annular ring in accordance with a conventional method. It is extruded into a gas or a spinning bath, and the membrane material is filled with a gas or liquid that does not dissolve or substantially react with the membrane material in the center to maintain the hollow space while spinning. For example, a plasticizer such as polyethylene glycol is added to cellulose diacetate flakes as an additive, melt-spun and extruded into the air through a hollow hole in a spinning nozzle, and the spinning is cooled while blowing nitrogen gas into the center. to make a hollow fiber-like material. The plasticizer is removed from the hollow fibers, and if necessary, saponification is performed with caustic soda to produce finned hollow fibers having selective permselectivity. Examples of the plasticizer include polyalkylene glycols such as polyethylene glycol, glycerin,
Examples include glycols having an ethylene-propylene chain in the molecule, sulfolane, caprolactone, and dimethyl sulfoxide. The amount of the plasticizer added to the spinning stock solution is appropriately selected depending on the use of the hollow fiber, and for example, in the case of hemodialysis, it is preferably 20 to 40 wt%, more preferably 25 to 35 wt%. Furthermore, when the method for producing hollow fibers of the present invention is based on a wet or semi-dry/semi-wet spinning method, the additive contains a solvent for the cellulose ester polymer, and the spinning stock solution is passed through the spinneret. It is manufactured by discharging the liquid from a liquid and then immersing it in a coagulating liquid. Furthermore, it is preferable that the additive contains a poor solvent for the cellulose polymer or a metal salt as a pore-forming agent to facilitate the formation of pores in the hollow fiber membrane. In such a spinning method, the time from discharge from the spinneret to immersion in the coagulation bath is preferably 5 seconds or less, more preferably 1 second or less. The types and amounts of the solvent, poor solvent, and metal salt, and the components and compositions of the coagulating liquid and core agent can be appropriately selected depending on the use of the hollow fiber membrane. The term "solvent" here refers to a liquid that can easily dissolve cellulose-based polymers, and poor solvent refers to liquids that do not easily dissolve cellulose-based polymers by themselves, but can dissolve cellulose-based polymers by coexisting with the above-mentioned solvents. means something to do. In addition, in the hollow fiber manufacturing method of the present invention, it may be preferable to spin at a side winding speed rather than the discharge speed, and the preferable draft range in that case is 30 to 200 for melt spinning, wet or semi-winding. For dry and semi-wet spinning, 5 to 50 can be mentioned. The fluid separator of the present invention houses a bundle of permselective cellulose-based hollow fibers as a fluid separation function part, and the hollow fibers have an average degree of polymerization of 150.
A fin whose main constituent is the above cellulose polymer, extends in the longitudinal direction at the outer periphery, has a ratio H/W of height H to width W of 0.5 or more, and has a rewetting elongation rate of 2.5% or less. It is characterized by having The filling rate of hollow fibers in the fluid separator of the present invention is
It is preferably 30 to 80%, more preferably 35 to 70%. If the filling rate is less than 30%, even in the hollow fiber of the present invention, which has a good dispersion state, the filling may be non-uniform, which tends to result in non-uniformity such as channeling in the flow of fluid such as dialysate outside the hollow fiber. Undesirable. Further, if the filling rate is 80% or more, it is not preferable because it becomes difficult to fill the hollow fiber bundle. If the filling rate is relatively high within this range, the hollow fiber bundle may be wrapped or covered with other members such as tapes, sheets, threads, nets, etc. It is effective to collect yarn bundles into thin pieces and store them in a container that constitutes a processing device. In particular, the fluid treatment device of the present invention has a rewetting extension rate of 3%.
When the following cellulose ester hollow fibers are housed, when the hollow fibers come into contact with water or an aqueous solution, the elongation is small, and local adhesion between the hollow fibers and bending of the hollow fibers are less likely to occur. There are advantages. Particularly, the advantages are very effectively maintained when the filling rate of the hollow fibers is relatively high, such as 50% or more. If the fluid separator is a hemodialyzer, it generally has a blood distribution member and a blood collection member on the outside of each tube plate, and a dialysate inlet/outlet in the wall of the container. . Specific applications of the fluid separator of the present invention include liquid separation such as dialysis, ultrafiltration, precision filtration, reverse osmosis, etc.
Examples include gas separation such as oxygen enrichment and artificial lungs. Among them, it is suitable for body fluid processing devices such as artificial kidneys, artificial livers, plasma separation processing devices, ascites processing devices, and artificial lungs, and is particularly excellent as a hemodialyzer. EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto. Example 1 Cellulose diacetate (average degree of polymerization 170) 100
per part, polyethylene glycol (molecular weight 200)
The mixture was melted at 230°C and spun at a viscosity of 1500 poise from a spinneret with double annular slits for hollow fibers with fins, together with nitrogen gas in the hollow part. After eluting polyethylene glycol by immersion in hot water, a saponification reaction was performed with a caustic soda aqueous solution, and then immersion in an 80wt% glycerin aqueous solution to determine the relaxation rate of the hollow fiber.
By drying with hot air in a state of 0.985, the inner diameter is approximately 200μ and the film thickness of the part without fins is approximately 18 to 30μ.
A hollow fiber with fins for hemodialysis having six fins having the shapes shown in Table 1 was obtained. The rewet elongation rate, wet tensile strength, bending rigidity, and burst pressure of the hollow fibers were as shown in Table 1. A hemodialyzer was prepared by inserting and filling the hollow fibers obtained in the above manner into a circular tubular container with the effective membrane area and filling rate shown in Table 1. Dialysis performance, residual blood, etc. were measured. The dialysis performance (dialysis) was measured at 37°C with an average blood flow rate of 1.2 cm/sec in the hollow fiber and an average flow rate of 1.8 cm/sec on the dialysate side. The result is the first
It was as shown in the table. Examples 2 to 4 Cellulose diacetate with an average degree of polymerization of 160, 180, and 200 was used, and the spinning viscosity was 1200 and 1200, respectively.
Using 1800 and 2400 poise, spinning was carried out in the same manner as in Example 1, and 6 fins of the shape shown in Table 1 were obtained.
A hollow fiber with striations was obtained. A hemodialyzer was produced in the same manner as in Example 1 using the hollow fiber. The results of measuring various characteristics of these hollow fibers and hemodialyzer are shown in Table 1. Comparative Examples 1 and 2 Using cellulose diacetate with an average degree of polymerization of 120 and 140, respectively, the spinning viscosity was 70 and 140, respectively.
90 poise, a hollow fiber and a hemodialyzer using the same were obtained in the same manner as in Example 2. The various characteristics obtained for these hollow fibers and hemodialyzers are also
Shown in the table. Examples 5, 6 and Comparative Example 3 Cellulose diacetate (average degree of polymerization 180 in Examples 5 and 6, average degree of polymerization 140 in Comparative Example 3) 100
135 parts of polyethylene glycol and diethylene glycol were added to each part, and the mixture was melted at 200°C to give a viscosity of 300, 300, and 80 poise, respectively.
After spinning from a spinneret with double annular slits for hollow fibers with fins, the plasticizer is eluted with hot water to create a fabric with 6 fins with an inner diameter of 205μ and a film thickness of 12 to 15μ in the part without fins. A hollow fiber and a hemodialyzer using the hollow fiber were obtained. Its various properties are shown in Table 1. Example 7 Hollow fibers were manufactured in the same manner as in Example 2, except that the relaxation rate of the hollow fibers during hot air drying was set to 0.990, and a hemodialyzer was created using the hollow fibers. The rewetting elongation rate of the obtained hollow fiber was 1.5%, and as a result of the evaluation of the dialyzer, the residual blood volume was less than 0.1ml.
No occurrence of blood clots was observed. Comparative Example 4 Hollow fibers were manufactured in the same manner as in Example 2, except that the relaxation rate of the hollow fibers during hot air drying was set to 0.965, and a hemodialyzer was created using the hollow fibers. The rewetting elongation rate of the obtained hollow fiber was 3.2, and as a result of the evaluation of the dialyzer, the residual blood volume was 0.3 ml, and a small amount of blood clot occurred. It was thus found that even when cellulose diacetate having an average degree of polymerization of 160 was used, blood coagulation was likely to occur if the rewet elongation rate was as high as 3.2.

[Table] <Effects of the invention> The present invention has achieved heights that were previously thought to be difficult to obtain.
The present invention provides cellulose ester hollow fibers having a specific shape with a width of 0.5 or more. In particular, since the rewet elongation rate of the hollow fibers is as small as 3% or less, it is an excellent product that prevents local adhesion between hollow fibers, bending, and damage of the hollow fibers in a fluid separator that houses them. Has characteristics. Furthermore, the hollow fibers of the present invention have excellent shape retention. In particular, in the hemodialyzer using the hollow fibers of the present invention, the hollow fibers are unlikely to adhere or break even in a highly filled state, and the special effects of excellent dialysis performance and less residual blood and blood clots can be obtained.

Claims (1)

[Scope of Claims] 1. A cellulose-based hollow fiber having longitudinally extending fins in its outer circumference and having selective permeability, the main component of which is a cellulose-based polymer consisting of cellulose or cellulose ester. A cellulose-based hollow fiber for blood treatment, which has an average degree of polymerization of 150 or more, a ratio H/W of height H to width W of the fins of 0.5 or more, and a rewetting elongation rate of 2.5% or less. 2. In a fluid separator for blood processing that accommodates a permselective hollow fiber as a separation function section, the permselective hollow fiber is provided with fins extending in the longitudinal direction at the outer periphery, and is a main component thereof. The average degree of polymerization of the cellulose-based polymer made of cellulose or cellulose ester is 150 or more, the ratio H/W of the height H to width W of the fin is 0.5 or more, and the rewetting elongation rate is 2.5% or less. A fluid separator characterized by being made of cellulose-based hollow fibers.