JPH05228208A - Cellulose acetate base blood purifying hollow thread membrane and its manufacture - Google Patents

Abstract

PURPOSE:To provide a blood purifying hollow thread membrane made of a cellulose acetate base material capable of being sterilized with high-pressure steam by setting the urea permeability coefficient of the hollow thread membrane made of a blended polymer of cellulose triacetate and cellulose diacetate at the specific ratio to a specific value. CONSTITUTION:In a cellulose acetate hollow thread membrane mainly made of cellulose triacetate (CTA) acetylated in a ratio acetylation of 60-62% and cellulose diacetate (CDA) acetylated in a ratio of 52-57%, the weight composition ratio of CTA to CDA is set to 95.0/5.0 to 55.0/45.0, and the permeability coefficient of urea is set to 30X10<-5>cm/sec or above. To manufacture it, the CTA and the CDA are mixed at the mixing ratio of 95.0/5.0 to 55.0/45.0 manufacture a dope, and it is extruded in a coagulation bath directly or indirectly through a double-ring nozzle. The CTA and the CDA are blended, and the objective hollow thread membrane having autoclave resistance and little change of solute permeability when processed with high-pressure steam can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
TECHNICAL FIELD The present invention relates to a hollow fiber membrane for blood purification of a cellulose acetate material that can be sterilized under high pressure by blending cellulose (CTA) and cellulose diacetate (CDA), and a method for producing the same.

[0002]

2. Description of the Related Art Membranes used for artificial kidneys must be used in a sterile condition. Known conventional sterilization methods include formalin water filling sterilization, high-pressure steam sterilization (autoclave sterilization), ethylene oxide gas sterilization, and γ-ray sterilization. It has been pointed out that a membrane that has been sterilized by filling with formalin water and sterilized with ethylene oxide gas has a problem that a small amount of formalin and ethylene oxide remaining in the membrane are accumulated in the body by repeated use. There is no such residue problem with γ-ray sterilization, but problems such as radiation handling, equipment problems, and coloring and deterioration of membrane materials and the like will occur. For these sterilizations, heat sterilization, particularly moist heat sterilization, can be considered. According to the 9th revised Japanese Pharmacy Law, as high pressure steam sterilization method, 115 ℃, 30 minutes, 121 ℃, 20 minutes,
A method for sterilizing microorganisms by heating in a saturated vapor pressure at 126 ° C. for 15 minutes is specified. This heat sterilization method has the advantages that it is easy to install and handle, has no residual toxicity, and can be easily treated before use. However, the membranes currently used as heat sterilization type artificial kidneys are only polysulfone and regenerated cellulose. Cellulose triacetate and cellulose diacetate have low complement activity and excellent solute permeability as membrane materials, but when they are individually treated under high pressure steam, heat treatment causes crystallization and orientation phenomena. It is not possible to obtain sufficient performance.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides excellent solute permeability (autoclave resistance) even by autoclave sterilization by blending cellulose-stearate and cellulose diacetate in an appropriate ratio. The present invention provides a cellulose acetate hollow fiber membrane having a) and a method for producing the same.

[0004]

Means for Solving the Problems The present invention mainly comprises (1) mainly cellulose acetate (CTA) having an acetylation degree of 60 to 62% and cellulose diacetate (CDA) having an acetylation degree of 52 to 57%. A cellulose acetate-based hollow fiber membrane as a component, wherein the weight composition ratio of CTA and CDA is
95.0 / 5.0 to 55.0 / 45.0, and a urea permeability coefficient of 8
Cellulose acetate-based hollow fiber membrane for blood purification with 0 × 10 ^-5 cm / sec or more and cellulose acetate-based with urea permeability coefficient of 55 × 10 ^-5 cm / sec or more after high-pressure steam treatment at 121 ° C. for 20 minutes Hollow fiber membrane for blood purification (2) The mixing ratio of the cellulose triacetate (CTA) and the cellulose diacetate (CDA) is 95.0 / 5.0.
A method for producing a cellulose acetate-based hollow fiber membrane for blood purification, characterized in that a dope of ~ 55.0 / 45.0 is produced and extruded directly or indirectly into a coagulation bath through a double ring nozzle.

In the present invention, cellulose acetate (CTA) means acetylation degree of 60-62%, and cellulose diacetate (CDA) means cellulose acetate having acetylation degree of 52-57%. The degree of acetylation is calculated by the following formula. Acetylation degree (%) = (mass in terms of acetyl group acetic acid / cellulosic)
Total mass of suacetate) x 100

The hollow fiber membrane according to the present invention comprises 10 parts of the cellulose acetate and the cellulose diacetate.
Boiling point 15 with non-solvent added to achieve a concentration of over 15% by weight
A dope, which is dissolved in an aprotic polar solvent at 0 ° C. or higher, is passed through a double ring nozzle and extruded into a coagulation bath composed of an aqueous solution of the above solvent and a non-solvent to form a film. The solvent / non-solvent mixing ratio is 50/50 to 90/10. here,
Discharge temperature (T1) and coagulation bath temperature (T2) are 0 <T1-T
It is important to control so that 2 <100 (° C.) in order to obtain high transmission performance.

The extrusion of the polymer dope from the nozzle into the coagulation bath is a direct method of direct extrusion into the coagulation bath, or an indirect method of extruding the polymer dope into the air through the nozzle by providing an air gap between the nozzle and the surface of the coagulation bath. Any method can be applied. Further, when the polymer dope is discharged from the nozzle, it is possible to spin a liquid such as liquid paraffin inside the hollow, but in the present invention, a method of spinning while flowing an inert gas at an appropriate flow rate in the hollow is preferable.

As the aprotic polar solvent, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like are used, and as the nonsolvent,
Polyhydric alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin and polypropylene glycol, and alcohols such as methanol and ethanol can be used. Further, this hollow fiber membrane is hydrophilized in a hydrophilization bath through a coagulation bath and a water washing bath. As the hydrophilizing agent, polyhydric alcohols such as glycerin and polyethylene glycol, and alcohols such as methanol and ethanol can be used. Then, the hollow fiber membrane is wound through a drying process.

When heat treatment is performed on the cellulose triacetate hollow fiber under high pressure steam, crystallization progresses and shrinks in the yarn length direction and in the radial direction, resulting in a marked decrease in performance. Further, in the cellulose diacetate hollow fiber, it is difficult to maintain the shape of the hollow fiber membrane because the cellulose fiber is stretched in the fiber length direction due to orientation. Therefore, by adding cellulose diacetate to the cellulose acetate, it is possible to suppress the crystallization of the cellulose acetate and further suppress the shrinkage, and after the autoclave treatment, the initial performance is improved. It is thought that it can be maintained. Cellulostriate (CT
The mixing ratio of A) and cellulose diacetate (CDA) is
95.0 / 5.0 to 55.0 / 45.0 is suitable, preferably 90/10
It is ~ 70/30.

The solute permeation coefficient P is defined by the following equation. P = Qb / A × ln (C1 / C2) where Qb: blood flow rate (milliliter / min) A: membrane area (cm ² ) C1: inlet solute concentration C2: outlet solute concentration

The water permeability (UFR) of the cellulose acetate hollow fiber membrane of the present invention is 3 to 250 ml / m ² / hr / mmHg. In addition, the permeability of urea here is 121 ° C., 20
Min, the permeation coefficient of urea before high-pressure steam treatment, and its value is
80 × 10 ^-5 cm / sec or more, but if it is less than 95.0 / 5.0, the effect of adding cellulose diacetate cannot be obtained and auto-cure
The initial performance after squeezing is very low, while 55.0 / 4
When it exceeds 5.0, the performance retention is high, but the initial performance itself is low. For the above reasons, the mixing ratio of cellulose triacetate and cellulose diacetate was from 95.0 / 5.0 to 55.0 / 4.
5.0 is suitable.

Further, the dialyzer comprising the hollow fiber membrane for blood purification of the present invention can be sufficiently applied to artificial lung, artificial liver, artificial pancreas and the like. Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

[0013]

【Example】

(Example 1) Cellulose triacetate having an acetylation degree of 60.8% / cellulose diacetate having an acetylation degree of 55.0% were in a weight ratio of 8/2, a polymer concentration was 20% and N-methylpyrrolidone 64 %, Triethylene glycol 16% were mixed and
I thought This was discharged into a coagulation liquid consisting of an aqueous solution of 24% N-methylpyrrolidone and 6% triethylene glycol using a double ring nozzle, and a hollow fiber membrane was obtained through a washing bath, a glycerin hydrophilization bath and a drying step. .. The discharge temperature and the coagulation bath temperature were 130 ° C. and 50 ° C., respectively. 5 for glycerin bath
It was a 50% aqueous solution at 0 ° C. The obtained hollow fiber membrane was a perfect circle having an outer diameter of about 200 μm and a film thickness of about 15 μm. 800 hollow fibers were bundled in a length of 25 cm (membrane area: 0.0754 m ² ) and bonded to an acrylic pipe with urethane to prepare a mini-module for testing. This mini module
Table 1 shows the change in performance before and after the autoclave treatment at 121 ° C. for 20 minutes. In addition, the permeability of urea was measured by using the above-mentioned mini-module and the amount of urea 5 g / l solution was 17
Milliliter / min (Qb), dialysate (pure water) 4 on the dialysis side
00 ml was run at 2 l / min. The dialysate was constantly stirred to maintain a volume of 400 ml and partially replaced with pure water at 2 l / min. The measurement temperature is 37 ° C. The results are shown in Table 1 (unit: × 10 ^-5 cm / s
ec). According to Table 1, the initial performance of urea permeability and the performance after autoclave are high and can be sufficiently put to practical use.

[0014]

[Table 1]

(Example 2) The same cellulose triacetate / cellulose diacetate as in Example 1 was used in a weight ratio of 9/1.
A hollow fiber membrane was manufactured under the same conditions as in Example 1 and subjected to autoclave treatment. The results are shown in Table 1. as a result,
Similar to Example 1, the initial performance of urea permeability and the performance after autoclave are high and can be sufficiently put to practical use.

(Example 3) The same cellulose triacetate / cellulose diacetate as in Example 1 was used in a weight ratio of 7/3.
A hollow fiber membrane was manufactured under the same conditions as in Example 1 and subjected to autoclave treatment. The results are shown in Table 1. as a result,
Although the urea permeation initial performance is slightly lowered, the performance retention after autoclave is high and it can be sufficiently put to practical use.

(Comparative Example 1) The same cellulose striatate / cellulose diacetate as in Example 1 was used in a weight ratio of 4 /.
6, a hollow fiber membrane was produced under the same conditions as in Example 1, and
A toclave treatment was performed. The results are shown in Table 1. As a result, the urea permeation initial performance itself is low, which is not practical.

(Comparative Example 2) The same cellulosic triacetate as in Example 1 was used alone, and the polymer concentration was 20%.
A hollow fiber membrane was produced under the same conditions as above and subjected to autoclave treatment. The results are shown in Table 1. As a result, the initial urea permeation performance is high, but the performance retention rate after autoclave is low, which is not practical.

[0019]

Industrial Applicability According to the present invention, a hollow having autoclave resistance with little change in solute permeability even when subjected to high pressure steam treatment by blending cellulose striatate and cellulose diacetate. A thread film can be provided.

Claims (3)

[Claims] 1. A cellulose acetate-based hollow containing, as main components, cellulose triacetate having an acetylation degree of 60 to 62% (hereinafter referred to as CTA) and cellulose diacetate (hereinafter referred to as CDA) having an acetylation degree of 52 to 57%. It is a thread film and is C
A cellulose acetate-based hollow fiber membrane for blood purification, in which the weight composition ratio of TA and CDA is 95.0 / 5.0 to 55.0 / 45.0, and the permeability coefficient of urea is 80 × 10 ⁻⁵ cm / sec or more. 2. The cellulose acetate-based hollow fiber membrane containing CTA and CDA as main components according to claim 1, wherein the weight composition ratio of CTA and CDA is 95.0 / 5.0 to 55.0 / 45.0, and 121 ° C. A cellulose acetate-based blood purification hollow fiber membrane having a urea permeability coefficient of 55 × 10 ⁻⁵ cm / sec or more after high-pressure steam treatment for 20 minutes. 3. A mixing ratio of cellulose acetate (CTA) having an acetylation degree of 60 to 62% and cellulose diacetate (CDA) having an acetylation degree of 52 to 57% is 95.0 / 5.0 to 55.0 / 45.
A method for producing a cellulose acetate-based hollow fiber membrane for blood purification, which comprises producing a dope of 0 and extruding it directly or indirectly into a coagulation bath through a double ring nozzle.