JPH0445209B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> The present invention relates to a method for producing irregularly shaped hollow fibers having permselectivity. More specifically, the present invention relates to a method for producing irregularly shaped hollow fibers having fins extending in the longitudinal direction and having permselectivity. <Prior Art> Hemodialyzers are used to purify the blood of patients with renal failure and remove excess water. In this system, a large number of dialysis membranes, such as hollow fiber membranes, are housed in a container, and the patient's blood is poured into the hollow interior of the container, and the dialysate is poured outside, that is, between the hollow fiber membranes, and dialysis is carried out through the hollow fiber membranes. Therefore, waste products in the blood are removed, electrolyte concentration is adjusted, and excess water in the blood is removed by ultrafiltration by applying a pressure difference between the inside and outside of the hollow fiber membrane. In addition, by using only ultrafiltration, large amounts of water and waste products are removed, and excess water is removed along with necessary components such as electrolytes.
Replenishment methods (hemofiltration) are also applied depending on the actual situation. Furthermore, clinical trials have begun to use hollow fiber membranes to separate plasma from blood or remove specific harmful components from the plasma to treat autoimmune diseases. In this way, hollow fiber membranes for blood treatment must selectively permeate substances depending on the purpose. Its performance is determined by the hollow fiber membrane material, porosity (pore size, number, etc.), membrane thickness, and other factors. But that's not all. The key point in determining performance is how to focus a large number of hollow fiber membranes and make them work effectively. For example, when hollow fiber membranes come into contact with each other along their length during dialysis, the dialysate does not flow evenly around the hollow fiber membranes in close proximity, but rather forms a specific flow path. In areas where there is no access, dialysis is hardly performed and the dialysis efficiency decreases. The concentration difference on both sides of the hollow fiber membrane becomes the driving force for dialysis, so
The hollow fiber membranes are housed, and the shape of the hollow fiber membrane itself is designed so that the dialysate flows evenly between the hollow fiber membranes, reducing membrane resistance as much as possible and increasing the concentration difference with the blood side. It is necessary to devise ways to do so. Regarding the former, we first focused the hollow fibers in a crosswise manner and housed them in a container to prevent contact between the hollow fiber membranes, thereby preventing a decrease in the membrane area, and to ensure that the dialysate flowed evenly and that the It was discovered that dialysis efficiency could be improved by reducing membrane resistance (Special Publication 1977-
38837). Regarding the latter, for example,
−75481, JP 1984-148907, JP 58-169510
A method has been proposed in which a similar effect is achieved by providing fins on the outside of a hollow fiber membrane, as shown in . However, these manufacturing methods for hollow fibers with fins often reduce the effective area of the hollow fibers due to the fins, or make stable spinning and forming difficult.
Improvement was desired. <Objective of the Invention> In view of the above, an object of the present invention is to provide a method for stably producing finned irregularly shaped hollow fibers suitable for fluid separation, particularly blood treatment, by melt spinning. Another object of the present invention is to provide a method for stably and easily manufacturing irregularly shaped hollow fibers having fins of various shapes. <Structure of the Invention> In order to achieve the above object, the inventors of the present invention conducted intensive research and found the optimum range for controlling the melt spinning stock solution, thereby achieving the present invention. That is, the present invention provides a method for producing selectively permeable irregularly shaped hollow fibers having a hollow portion penetrating in the longitudinal direction and having at least one fin extending in the longitudinal direction in the outer circumferential portion by melt spinning, in which the spinning stock solution comprises: It contains at least one thermoplastic polymer and, if necessary, at least one additive, and at least one thermoplastic polymer is added to the outside of the double circular slit.
When the melt spinning stock solution is discharged from a spinning nozzle having a discharge port having a shape of notches, the viscosity of the melt spinning stock solution at the nozzle is within the range of 100 to 10,000 poise, and the melt spinning stock solution is discharged from the spinning nozzle. The distance between the solidification point of the irregularly shaped hollow fiber and the end face of the spinning nozzle is 40
cm or less, and the height (H) of the fin is characterized by imparting permselectivity through at least one of the following treatments: further stretching of the spun-solidified hollow fiber, extraction and removal of additives, and chemical reaction treatment. The purpose of the present invention is to provide a method for producing a permselective irregularly shaped hollow fiber having a ratio H/W of width (W) and root width (W) of 0.4 or more. The present invention will be explained in more detail below. That is, the shape of the irregularly shaped hollow fiber with fins obtained by the method of the present invention is, for example, as shown in FIG. Here, it is clear that if the height H of the fins is too low relative to the outer diameter d of the hollow fibers, the effect of the fins will not be sufficiently exhibited. Further, although it depends on the number of fins, it is preferable that the width W of the base of the fin portion be as narrow as possible without bending the fins. If the width W is large, if the number of fins is x, only xW of the outer circumference πd is not effective for material transfer, which is undesirable because the effective area of the hollow fiber decreases. However, the stock solution for hollow fiber spinning is in a liquid state, and after being discharged from the discharge hole, the stock solution in the fin portion tends to concentrate in the root direction due to its surface tension. In order to suppress this tendency, it is necessary to increase the viscosity of the stock solution when yarn is drawn out from the discharge hole and to shorten the time until the hollow fiber shape is formed. As a result of various studies from this point of view, we found that it can be used for blood purification, does not significantly reduce the effective area of the hollow fiber membrane, and when used for hemodialysis, it makes the flow on the dialysate side uniform and sufficiently increases the dialysis effect. It has been found that in order to obtain the shape of the finned irregularly shaped hollow fibers, the melt viscosity of the spinning dope at the nozzle during spinning needs to be 100 to 10,000 poise. Generally, as a base for irregularly shaped hollow fibers with fins, something like the one shown in Figure 2 is used. Gas or liquid for forming the hollow part is discharged from part 1, and hollow fiber membrane material is discharged from part 2 as a undiluted solution. It is discharged in the state of
Thereafter, it is cooled and solidified to fix the shape of the hollow fiber. In order to narrow the base of the fin, shapes such as those shown in Figures 3 and 4 are sometimes implemented, but if the viscosity of the spinning dope is lower than 100 poise, the shape of the fin will not be fixed properly. The purpose is not fully achieved. On the other hand, if the melt viscosity of the spinning stock solution is too high and exceeds 10,000 poise, the pressure loss at the nozzle discharge hole will increase, which not only causes mechanical problems, but also causes smooth draft (drawing) of the yarn discharged from the nozzle.
As a result, yarn breakage occurs during spinning and yarn thickness unevenness occurs, making stable yarn spinning difficult. Further, the viscosity of the spinning dope in the spinning nozzle during spinning is more preferably 300 to 2000 poise.
In particular, if it is in the range of 500 to 1500 poise, the shape of the fins will be accurately fixed and stable spinning will be possible. In the present invention, the viscosity of the spinning dope during spinning refers to the viscosity at the spinning nozzle, but strictly speaking, it is the viscosity at the outlet of the spinning nozzle. In addition, even if the viscosity of the stock solution at the time of nozzle discharge is within an appropriate range, if it takes a long time for the spun hollow fibers to solidify, the surface tension of the stock solution will accelerate deformation during that time, resulting in a sharp fin shape. I can't do that. Desirably, the yarn is rapidly cooled and solidified after spinning to fix the yarn shape at the time of spinning. In normal melt spinning, the point at which the fluidity of the yarn is lost and thinning due to winding tension no longer progresses, the so-called solidification point, is approximately 10 cm from the nozzle.
In order to obtain the irregularly shaped hollow fiber with fins for blood purification as related to the present invention, the solidification point must be 40° from the noise tip.
It was found that it is desirable to be within cm. It is more preferable if the distance between the solidification point and the noise tip is in the range of 5 to 40 cm, and especially in the range of 10 to 25 cm, extremely stable spinning is possible. Furthermore, as the spinning conditions in the present invention, the preferable draft range is 20 to 200, particularly 40 to 100.
In this case, it is easy to stably obtain finned hollow fibers having a predetermined shape. The spinning dope in the production method of the present invention mainly consists of a thermoplastic polymer, but may also contain other additives. Preferred examples of the thermoplastic polymer include cellulose ester, polyethylene, polypropylene, polyethylene tetaphthalate, polymethyl methacrylate, and polyether sulfone. Examples of such additives include polyols such as polyalkylene glycol, glycerin, and glycol having an ethylene-propylene chain in the molecule, plasticizers such as sulfolane, caprolactone, dimethyl sulfoxide, and mixtures thereof, and inorganic salts and organic salts. , and the above thermoplastic polymers and other thermoplastic polymers. Their composition is selected depending on the required permselective performance or viscosity control during spinning. In addition, in the production method of the present invention, permselectivity is developed by further subjecting the spun-solidified hollow fiber to a stretching process, extraction and removal of additives, or chemical reaction treatment such as saponification. Such a treatment method is selected depending on the composition of the spinning dope, but it may be any commonly used method and is not particularly limited. Although the shape and size of the finned irregularly shaped hollow fibers according to the present invention are not particularly limited,
The number of fins is 1 to 10, preferably 2 to 7, and the outer diameter (d) is
100 to 500μ, preferably 200 to 300μ, the film thickness (h) of the part without fins is 5 to 50μ, preferably 10 to 40μ, and the height H of the fins is 10 to 65μ, which are generally in the practical range. . The finned hollow fibers obtained by the method of the present invention are used for fluid separation such as ultrafiltration, reverse osmosis, dialysis, and gas separation. It is suitable for blood processing such as, and is particularly effective in hemodialysis. To assemble irregularly shaped hollow fibers with fins into a blood purifier, bundle 5,000 to 10,000 hollow fibers, insert them into a cylindrical container, bond and solidify the hollow fibers at both ends with an adhesive such as urethane, and then Cut the hollow fiber end to open it. Blood distribution ports are attached to the hollow fiber openings at both ends, and after testing the performance as a blood purifier and quality such as leakage, it is sterilized. Generally, a simple circular hollow fiber is used as the hollow fiber, but by using the irregularly shaped hollow fiber with fins according to the present invention, firstly, it is possible to avoid close contact between the single hollow fibers, and it is possible to prevent the dialysis fluid from coming into contact with each other. Unbalanced flow is reduced, dialysis efficiency is greatly improved, and variations in dialysis efficiency between purifiers can be reduced. Secondly, the distribution of the hollow fibers at the end of the blood purifier becomes uniform, the distribution of blood into the hollow fibers becomes uniform, and the blood coagulation properties in the hollow fibers or near the hollow fiber openings are reduced after use. The amount of blood remaining can be reduced. Furthermore, when a large number of hollow fibers are filled into the container, small spaces are created between the closely-adhered fibers, which prevents the adhesive resin from penetrating into these parts, creating unbonded spaces and causing leaks. In the case of irregularly shaped hollow fibers with fins, there is an advantage that the probability of such occurrence is extremely low. By the method of the present invention, it is possible to obtain a modified hollow fiber with fins that fully exhibits the above-mentioned effects when used as a blood purifier. <Effects of the Invention> According to the production method of the present invention, permselective hollow fibers with fins and irregular cross sections can be obtained very stably by melt spinning, which has been difficult to produce stably in many cases. I can do it. Furthermore, the method of the present invention has the excellent advantage that the shape of the fins can be easily selected within a wide range. Furthermore, the hollow fibers obtained by the present invention are particularly useful in blood purifiers and exhibit excellent performance. The present invention will be described below with reference to Examples, but the present invention is not limited to these in any way. Examples 1 to 10, Comparative Examples 4 and 5 Polyethylene glycol (hereinafter abbreviated as PEG) to 100 parts by weight of cellulose diacetate
(molecular weight 300) was added in the weight parts shown in Table 1, and the mixture was melted at 200 to 240°C.
The nozzle shown in (inner diameter of double annular slit)
1.6mm, outer diameter 2mm, notch width 0.15mm, height 0.7
mm) at the outlet temperature shown in Table 1, and then cooled at the room temperature cooling air speed shown in Table 1, and then wound up. The melt viscosity of the polymer melt at each temperature was measured separately using a flow tester. The distance from the tip of the spinneret to the solidification point was measured by taking out a scissors from the yarn being spun, and the point where thinning ended was taken as the fixed point. At a cap temperature of 190℃,
The viscosity of the polymer is too high and thread breakage is likely to occur.
Good winding was not possible. For other types, after saponifying the wound yarn to cellulose with an alkali, the obtained irregularly shaped hollow fiber with fins as shown in Table 1 (the thickness of the film other than the fins is approx.
20~25μ) into the container at almost the same filling rate,
It was assembled as a dialysis machine. Its in vitro dialysis performance was measured and shown in Table 1. The device according to the present invention has a sharp fin shape, a narrow width (W) at the base of the fin, and a sufficient fin height (H), and exhibits high dialysis performance as a dialyzer. There is. On the other hand, in a comparative example that deviates from the present invention, the shape of the rim was rounded and it was not possible to obtain a shape with sufficient height. The urea clearance [ml/min] per 1 m ² of effective area was measured according to the dialyzer performance evaluation standards published by the Japan Society for Artificial Organs in September 1980.

【table】

[Table] Examples 12 to 15 Comparative Examples 3 and 4 In the same manner as in Example 1, the polymers shown in Table 2 were melt-spun and then subjected to microporous treatment by stretching, resulting in the results shown in Table 2. An irregularly shaped hollow fiber having fins having the following shape was obtained.

[Table] Comparative Example 6 50 parts by weight of PEG, nozzle temperature of 235°C, viscosity at nozzle outlet of 85 poise, distance between nozzle discharge surface and solidification point of 35 cm, draft of 60, and cooling air velocity of
A hollow fiber was produced in the same manner as in Example 1 except that the speed was 0.5 m/sec. The fin shape of the obtained hollow fiber was 13μ in H and 39μ in W (H/W 0.33), and the urea clearance of a dialyzer using the hollow fiber was 152.

[Brief explanation of the drawing]

FIG. 1 is an example of an enlarged cross-sectional view of a hollow fiber membrane according to the present invention. 2, 3, and 4 show examples of hollow fiber spinning nozzle shapes according to the present invention.

Claims (1)

[Claims] 1. A method for producing selectively permeable irregularly shaped hollow fibers having a hollow portion passing through the longitudinal direction and having at least one fin extending in the longitudinal direction at the outer peripheral portion by melt spinning, wherein the spinning stock solution contains at least one type of fin. Melt spinning containing a thermoplastic polymer and optionally at least one additive, from a spinning nozzle having a discharge opening shaped like a double annular slit and at least one notch on the outside. The viscosity of the spinning stock solution in the nozzle when discharging the stock solution is within the range of 100 to 10,000 poise,
The distance between the solidification point of the irregularly shaped hollow fiber discharged from the spinning nozzle and the end face of the spinning nozzle is 40 cm or less, and the solidified hollow fiber is subjected to at least one of further stretching, extraction and removal of additives, and chemical reaction treatment. A method for producing a permselective irregularly shaped hollow fiber in which the ratio H/W of the height (H) of the fin to the width (W) of the root is 0.4 or more, characterized in that the permselectivity is imparted by seed treatment.