JPH0523554A - Cellulose hollow fiber - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a cellulosic hollow fiber having increased mechanical strength, which has a reduced film thickness of the hollow fiber and has excellent substance permeability. Is. [Structure] A cellulose-based hollow fiber made of a cellulose-based polymer obtained by substantially saponifying at least a part of acetate groups of cellulose diacetate, wherein the average degree of polymerization of the cellulose-based polymer is in the range of 230 to 400. To use.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a permselective hollow fiber made of a specific polymer. More specifically, the present invention relates to a selectively permeable cellulose-based hollow fiber obtained by saponifying a hollow fiber mainly composed of a cellulose diacetate polymer having a high average degree of polymerization different from the conventional ones. Is provided.

[0002]

2. Description of the Related Art Selectively permeable hollow fibers have been practically used for reverse osmosis and hemodialysis.

In particular, in order to purify the blood of patients with renal failure,
Currently, hollow fiber hemodialyzers are often used. This is a dialysis membrane, for example, a large number of hollow fiber membranes in the housing,
It is stored, the patient's blood is allowed to flow inside the hollow, the dialysate is flowed to the outside, that is, between the hollow fibers, and by dialysis through the hollow fibers, waste products in the blood are removed and the electrolyte concentration is corrected, The excess water in blood is removed by applying a pressure difference between the inside and the outside of the hollow fiber and performing ultrafiltration. Further, hollow fibers are used for separating only plasma from blood or removing specific components from the plasma to treat autoimmune diseases and the like. As described above, the hollow fiber for blood treatment must selectively permeate a specific substance according to the purpose. The performance is determined by the hollow fiber material, porosity (pore size, number, etc.), and film thickness.

In a blood treatment device such as a hemodialyzer, a hollow fiber of cellulose diacetate is first obtained, and then a cellulose hollow having a desired selective permeability is obtained by hydrolyzing the acetate to cellulose by saponification treatment. Thread is used. In addition, according to such a manufacturing method, there is an advantage that desired selective permeability can be easily obtained.

However, in the conventional cellulose diacetate hollow fibers, the degree of polymerization of cellulose itself tends to be lowered at the stage of saponifying cellulose, and only a high degree of polymerization of about 170 to 200 can be obtained.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventors of the present invention have used conventional cellulose diacetates having a degree of polymerization of at most 200, and when the polymer concentration is lowered to increase the substance permeability, the viscosity of the spinning dope is sufficiently increased. In some cases, it may be difficult to reduce the film thickness, and even if it is attempted to form fins extending in the axial direction, it is difficult for the shape to be sharp. In order to improve the difficulty in obtaining a hollow fiber having permeability, an intensive study was conducted.

[0007]

Means for Solving the Problems The present inventor obtains a cellulose hollow fiber by a saponification treatment after forming a hollow fiber using cellulose diacetate having a higher degree of polymerization than that of conventional cellulose diacetate, that is, the degree of polymerization is The inventors have found that the use of a cellulose diacetate having a high denaturation yields a permselective cellulose hollow fiber having more excellent properties, and arrived at the present invention.

That is, the present invention relates to a cellulosic hollow fiber having a permselective wall membrane made of a cellulosic polymer obtained by substantially saponifying at least a part of acetate groups of cellulose diacetate. The present invention provides a cellulosic hollow fiber characterized in that the average degree of polymerization of the polymer is in the range of 230 to 400.

According to the present invention, substantially 50% or more of the acetate groups of cellulose diacetate are saponified, the film thickness in the wet state is 30 μm or less, and the hollow fiber in the wet state is Average cutting strength 0.4g /
Cellulosic hollow fibers having a de or more are included.

Further, according to the present invention, there is provided the above cellulose-based hollow fiber having at least one fin extending along the axial direction on the outer surface side of the wall membrane and having a thickness of 30 μm or less in a portion without the fin. included.

The hollow fiber of the present invention includes a cellulosic hollow fiber whose selective permeability is a selective permeability for body fluid treatment, that is, a cellulosic hollow fiber for body fluid treatment.

The present invention will be described in more detail below.

First, the permselective cellulosic hollow fiber of the present invention is one in which at least a part of the acetate groups of substantially cellulose diacetate polymer is hydrolyzed by saponification treatment and the cellulosic polymer is the main constituent. is there. Such a substantial cellulose diacetate polymer is one that is within the range that is usually handled as cellulose diacetate, and specifically, the average degree of acetylation is 50.
Those in the range of up to 57% can be mentioned.

The cellulose diacetate polymer in the present invention is characterized by having an average degree of polymerization of 230 to 400. The average degree of polymerization as used herein means a value obtained by dividing the weight average molecular weight by the molecular weight of the repeating unit of the polymer. Examples of the method for measuring the polymerization average molecular weight include gel filtration chromatography, viscosity measurement, sedimentation equilibrium measurement, and light scattering method.

When the average degree of polymerization of the cellulose diacetate polymer is less than 230, it is difficult to obtain a cellulose diacetate hollow fiber having a thin fin and a high height and having high selective permeability. Further, it is difficult to obtain a hollow fiber having a low re-wet elongation rate. The average degree of polymerization is 240 to 350.
Is more preferable, and 250 to 300 is particularly preferable.

When the average degree of polymerization of the cellulose diacetate polymer is 400 or more, it is difficult to produce the polymer itself, and when the hollow fiber is melt-spun, the temperature becomes very high and the cellulose diacetate is decomposed. It will be easier.

The hollow fiber of the present invention is obtained by using a cellulose diacetate having such a high degree of polymerization to obtain a hollow fiber, and then hydrolyzing at least a part of the acetate group by saponification treatment to obtain a cellulosic polymer. With respect to the degree of such hydrolysis, in order to impart desired selective permeability, usually 90% or more of the acetate group is preferably hydrolyzed, and particularly 95% or more of the acetate group is hydrolyzed. .

The cellulosic hollow fiber of the present invention contains such a cellulosic polymer as a main component, and its specific content is preferably 50% or more, more preferably 70% or more. In addition, the components contained in other than that are not particularly limited, for example, polymethylmethacrylate,
Examples thereof include organic polymers such as polyethylene, polypropylene, polyacrylonitrile, polyvinyl alcohol, and nitrocellulose.

Further, the outer diameter (d) of the hollow fiber of the present invention is 100 in the case of treating body fluid such as hemodialysis.
˜400 μ is preferable, and 200 to 300 μ is more preferable. The film thickness (h) is 30 μ or less, further 15 to 2
5μ, especially 20-25μ is preferred.

The cellulosic hollow fiber of the present invention preferably has fins extending in the longitudinal direction at the outer peripheral portion, and in that case, the height H and width W of the fins.
It is desirable that the ratio H / W of 0.5 is 0.5 or more. Ratio H /
If W is less than 0.5, it is difficult to obtain the effect of preventing the hollow fibers from adhering to each other when stored in the fluid separator, which is not preferable. A more preferable H / W is 0.8 or more. The width W of the fin is 1 / the height H of the fin.
It means the width at position 2.

Furthermore, the number of fins of the hollow fiber in the present invention x
Is at least 1, but when it is 11 or more, the effective membrane area is significantly reduced by the fin root portion, and, for example, the substance dialysis performance and water permeation performance in a hemodialyzer are significantly reduced, which is not practical. That is, such x is generally from 1 to 10, but more preferably from 2 to 8, and a particularly effective range is 3
~ 7.

In that case, the fin height (H) is 5
-100 μm, and more preferably 9-60 μm. The fin height / film thickness ratio H / h is preferably 0.5 to 3, and more preferably 1 to 2. Further, the ratio H / d of the average height H (μ) of the fins and the average outer diameter d (μ) of the hollow fibers excluding the fins.
Is preferably in the range of 0.01 to 1, more preferably in the range of 0.02 to 0.5, and particularly preferably in the range of 0.03 to 0.2.

Further, it is desirable that the width of the root of the fin is narrower than that of the upper part of the fin, but normally, after the spinning dope is discharged from the spinneret, the surface tension of the dope tends to make the root wide. The width of the root is 15 to 50 μ, preferably 20 to
40μ is suitable.

Hollow fibers in such a range are preferable because they have good circularity and are unlikely to cause blood coagulation and residual blood in the hollow fibers.

Further, among the hollow fibers of the present invention, those having an average breaking strength of 0.4 g / de or more are preferable, and those having an average breaking strength of 0.6 g / de or more are particularly desirable. Strength is 0.4g
If it is less than / de, it is inferior in shape retention and easily breaks during the manufacturing process of the hollow fiber or the manufacturing process of the fluid separator, and especially when the outer diameter d is 100 to 300 µ and the film thickness is in the range of 20 to 25 µ. In the case of hollow fibers, this tendency is large. The upper limit of the strength is not particularly limited, and may be 0.9
It is generally g / de or less.

The hollow fiber of the present invention is characterized in that the rewetting elongation rate is 3% or less. Rewet elongation rate is 3
%, The extension of the hollow fiber is too large when it is stored in a fluid separator in a substantially dry state and then refilled with water or an aqueous solution to re-wet, resulting in local adhesion between the hollow fibers. Is increased, and bending of the hollow fiber is likely to occur, which is not preferable. The re-wet elongation rate is more preferably 2% 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 fiber exhibits an appropriate elongation when rewetting in the fluid separator. The effect of spreading the hollow fiber bundle throughout the fluid separator can also be obtained. The re-wet elongation rate α is about 0.01 when the hollow fiber in a substantially dry state is measured under a load of about 0.1 g / de and the hollow fiber is wetted with water.
Measure the length L ₁ when measured under a load of g / de,
It is obtained by a calculation formula of α = {(L ₁ −L) / L} × 100. Here, the “substantially dry state” means that the hollow fiber is dipped in an aqueous glycerin solution and then dried to obtain a glycerin content of 30 to 60% and a water content of 0.
It means a state of 5 to 9%.

Further, among the Suiice hollow fibers having the film thickness of the present invention,
It is preferable that the bending rigidity is substantially in the range of 200 mg / 200 or more, and the burst pressure is preferably 4 kg / cm ² or more as the pressure resistance when pressurized in the hollow fiber when wet. Those in such a range make it easy to handle the hollow fibers when manufacturing the fluid separator, etc., the length of each hollow fiber in the fluid separator tends to be uniform, and the pressure applied when the separator is used The advantage that the hollow fiber is less likely to be damaged by the operation is obtained.

The thin-film cellulosic hollow fiber of the present invention has selective fluid permeability, and more specifically, for example, in the case of a hemodialysis hollow fiber, the part excluding the fin portion is used. As water permeation performance UFR, 3.0 to 40.0
Those in the range of ml / (m ² · hr · mmHg) are preferable,
Especially, 5.0 to 25.0 ml / (m ² · hr · mmHg) is preferable.

The cellulosic hollow fiber having selective permeability of the present invention exhibits excellent separation performance for fluid separation. The fluid separation is not particularly limited, and examples thereof include liquid separation such as dialysis, ultrafiltration, reverse osmosis, and gas separation for artificial lungs. In particular, the hollow fiber of the present invention requires a good fluid state of the fluid outside the hollow fiber, separation due to a difference in diffusion rate such as dialysis, and blood treatment requiring smooth flow in the hollow fiber. Suitable for body fluid treatment.

As the method for producing the hollow fiber of the present invention, the method for producing the cellulose acetate hollow may be any of melt spinning, wet spinning, semi-dry semi-wet spinning and the like. That is, in the case of the melt spinning method, the spinning solution is a heated melt,
The melt is discharged from the spinneret and solidified by cooling, for example, after molding a hollow fiber with fins, and then added to the hollow fiber with fins by a solvent capable of dissolving the additive without dissolving the cellulose diester polymer. A finned cellulose diacetate hollow fiber is obtained by extracting and removing at least a part of the agent. The thus obtained cellulose diacetate hollow fiber is hydrolyzed to a predetermined degree by a usual method using an aqueous alkaline solution or the like to obtain a thin film cellulosic hollow fiber having a desired selective permeability. To be

The present invention will be described in more detail below with reference to Examples.
The present invention is not limited to these examples.

[0032]

[Examples 1 and 2, Comparative Examples 1 and 2] 80 parts of polyethylene glycol (molecular weight 400) was added to 100 parts of cellulose diacetate having an average degree of polymerization of 260 and 170, and the mixture was melted at 220 ° C. Then, using a die having a double annular slit for hollow fiber with fins, the thickness of the hollow fiber membrane in the part without fins is 18 μm and 20 μm, respectively.
The fiber was spun so as to have μ. The inner diameter of the hollow fiber is 200μ. Then, it was made into cellulose by saponification reaction, and after winding, the hollow fiber bundle was assembled into a hemodialyzer having an effective area of about 1.5 m ² . Air pressure was applied to the blood side of the obtained hemodialyzer, that is, the hollow portion of the hollow fiber to determine the pressure at which the hollow fiber bursts. The results are shown in Table 1.

[0033]

[Table 1]

[0034]

EFFECTS OF THE INVENTION The cellulose hollow fiber of the present invention has a higher degree of polymerization of cellulose diacetate in a reduced amount than that of a usual one, and therefore the obtained cellulose hollow fiber has an increased mechanical strength, especially from the inside of the hollow part of the hollow fiber. Burst pressure increases due to pressure. This means that when hemodialysis is actually carried out, the probability of occurrence of blood leakage is reduced. Further, the increase in the burst pressure of the hollow fiber means that the film thickness of the hollow fiber can be reduced, and it has an advantage that the substance permeability is remarkably improved when assembled as a hemodialyzer.

Claims (4)

[Claims] 1. A cellulosic hollow fiber having a permselective wall membrane composed of a cellulosic polymer obtained by substantially saponifying at least a part of acetate groups of cellulose diacetate, wherein the average of the cellulosic polymer is A cellulosic hollow fiber having a degree of polymerization of 230 to 400. 2. Substantially 50% or more of the acetate groups of the cellulose diacetate are saponified,
The cellulosic hollow fiber according to claim 1, wherein the film thickness in the wet state is 30 μm or less, and the average breaking strength of the hollow fiber in the wet state is 0.4 g / de or more. 3. The cellulosic hollow fiber according to claim 1 or 2, wherein at least one fin extending in the axial direction is provided on the outer surface side of the wall membrane, and the thickness of the non-fin portion is 30 μm or less. . 4. The cellulosic hollow fiber according to claim 1, wherein the selective permeability is a selective permeability for treating a body fluid.