JPH0219205B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to hollow fibers made of acrylonitrile polymers. More specifically, it concerns a new hollow fiber for separation, which is made of a specific block copolymer and an acrylonitrile polymer (hereinafter referred to as AN polymer), and is highly selective in material separation methods using filtration or dialysis. Has separation ability,
The invention also relates to hollow fibers with large water permeability. Conventionally, cellulose-based hollow fibers such as cellulose acetate and cuprohan have been used to separate and purify liquids containing particulate matter such as bacteria, viruses, proteins, and colloidal substances.
Such hollow fibers have low water permeability and are easily clogged, and because of the low water permeability, the contact area with the processing liquid must be increased, which inevitably increases the size of the equipment and reduces operability, making it uneconomical. It had disadvantages such as causing financial disadvantage. On the other hand, hollow fibers made of AN-based polymers have been proposed with the aim of improving water permeability, which is a drawback of these cellulose-based hollow fibers, and have actually been used as ultrafiltration membranes to improve water permeability or reduce clogging. However, when trying to obtain sufficient water permeability in the field of medical applications such as artificial organs, especially artificial kidneys, useful substances other than the substance to be separated will also pass through, making it difficult to attract attention. It is extremely unsatisfactory in terms of the selective separation ability of separating only the substances that are separated, and although various improvements have been investigated, no hollow fiber has yet been obtained that satisfies water permeability and selective separation ability at the same time. The current situation is that there is no such thing. In view of these drawbacks, the present inventors aimed to provide extremely useful hollow fibers that have both excellent water permeability and high selective separation ability in the field of medical applications such as artificial organs, especially artificial kidneys. As a result of intensive research, we have arrived at the present invention. In order to achieve these objectives, the present inventors
Focusing on the excellent water permeability of hollow fibers made of AN-based polymers, we have improved the structure and composition of the polymers that make up the hollow fibers, especially the block copolymer whose main component is AN, to improve the compatibility with the processing liquid. Based on the new technical idea of creating a unique structure that provides selective separation ability, AN-based polymers have been developed with various copolymerization compositions with various vinyl monopolymers, polymerization degrees, and AN-based polymers.
While conducting detailed studies on the block copolymer whose main component is AN and its copolymer composition, we discovered that it consists of a segment whose main component is AN and a segment containing more than a certain percentage of vinyl monomers other than AN. Hollow fibers are made of a polymer composition in which a specific block copolymer is mixed with an AN polymer at a specific mixing ratio.
It was discovered that it has excellent water permeability and extremely high selective separation ability, and as a result of further intensive studies, the present invention was completed. That is, the gist of the present invention is as follows. (A) A hollow fiber having a hollow portion substantially continuous in the fiber axis direction, wherein the hollow fiber has a substantially polymerized amount of acrylonitrile (hereinafter abbreviated as AN) of 40
5 to 50% by weight of acrylonitrile-based polymer (hereinafter referred to as AN-based polymer) that is 80% or more by weight of an acrylonitrile-based polymer (hereinafter referred to as AN-based polymer), and (B) a segment having an AN polymerization amount of 80% or more by weight; AB type block copolymer consisting of a segment (B) containing 20% by weight or more of one or more vinyl monomers having a group, an amide group, an imide group, or an ethyl ester group from 50 to 95% by weight. and the following formulas (1) and (2)
A hollow fiber made of an acrylonitrile-based polymer characterized by simultaneously satisfying the following: It is important that the inulin passage rate and water permeability measured by the method described in detail later satisfy equations (1) and (2) at the same time. For hemodialysis membranes, intermediate molecular weight urinary toxic substances are considered important, and it is necessary to remove these substances from protein metabolites. Therefore, inulin was used in formula (1) as an indicator of the permeability of this medium molecular weight solute. That is, formula (1) shows that the molecular weight of inulin is 5000 to 6300, and that within this molecular weight range,
The so-called inulin passage rate is a measure of fractionation that expresses selective separation ability, and if it is less than 50%, even if it is insufficient, Even if the inulin has good water permeability and satisfies formula (2), the separation of unnecessary and necessary substances from the liquid subjected to separation is not sufficient, and on the other hand, the inulin passage rate is 50%. Even if the water permeation rate is above, if the water permeation rate does not satisfy formula (2), it will take an extremely long time to process the required amount, and in particular, hollow fibers for separation as artificial organs, which is the intended use of the present invention. In this case, the mental and physical fatigue of the patient and the economic disadvantage would be enormous, making it impossible to achieve the purpose of the present invention. In order for the hollow fibers of the present invention to have extremely excellent water permeability and selective separation ability, the key points are that the segment (A) has an extremely high affinity with AN polymers, and is particularly suitable for use as artificial organs. A specific segment (B) that has a high affinity with blood or body fluids to be subjected to separation and purification when
The AB type block copolymer constitutes a hollow fiber together with the AN type polymer, and depending on the specific ratio of the AB type block copolymer and the AN type polymer,
It has a microphase-separated structure that is extremely suitable for purification. Generally, it is already known that molded articles molded from mixtures of different types of polymers or molded articles molded from block copolymers often exhibit a microphase-separated structure. There are no examples of hollow fibers, especially hollow fibers for artificial organs, that have been disclosed to have excellent properties in both water permeability and selective separation ability.
It is not possible to easily obtain a hollow fiber that has both properties by making it a hollow fiber composed of a block copolymer and an AB type block copolymer. The type block copolymer and AN-based polymer form hollow fibers with a unique structure in a specific ratio, which allows for extremely excellent water permeability and a high degree of selective separation. It must be understood that it is a thing. Therefore, in order to obtain a hollow fiber that has excellent water permeability and selective separation ability and satisfies formulas (1) and (2) at the same time, which is the objective of the present invention, the hollow fiber must be made of an AN-based polymer.
It is extremely important that the polymer is composed of both the AB type block copolymer and the AB type block copolymer. Of both polymers constituting the hollow fiber of the present invention,
The AN polymer is considered to be a part that mainly plays a role in exhibiting high water permeability, together with the segment (A) part of the AB type block copolymer, which will be explained in detail later, and is an essential element constituting the hollow fiber. can be,
It is necessary to use an AN-based polymer in which the amount of AN polymerized is 40% by weight or more. When the polymerized amount of AN is less than 40% by weight, it not only causes a decrease in water permeability, but also
Although this is not preferable because sufficient mechanical strength of the hollow fibers cannot be obtained, as long as the amount of AN polymerized is 40% by weight or more, it does not interfere with the present invention in any way. The composition ratio of AN polymer and AB type block copolymer affects not only water permeability and selective separation ability, but also the mechanical strength of hollow fibers, and as the ratio of AN polymer increases, Although water permeability and mechanical strength tend to increase, this is not desirable because it causes a drastic decrease in selective separation ability, making it impossible to achieve the desired selective separation ability.
The proportion of the system polymer must be 5 to 50% by weight. It is important in the hollow fiber of the present invention that segments (A) and (B) of the AB type block copolymer, which is the other polymer substantially constituting the hollow fiber of the present invention, are as shown below. This is the second element. As mentioned above, the segment (A) mainly exhibits high water permeability and mechanical strength characteristics together with the AN polymer, which is the other component constituting the hollow fiber of the present invention. It is thought that this is a part that plays a role in increasing compatibility with
For this purpose, it is necessary to contain 80% by weight or more of AN, and if it is less than 80% by weight, it is difficult to exhibit sufficient water permeability and mechanical strength, which is not preferable. Segment (B) is an essential element for increasing selective separation ability, which is the main objective of the present invention, and the components constituting segment (B) have hydroxyl groups and carboxyl groups in molecules other than AN. It is important to contain at least 20% by weight of vinyl monomers having functional groups other than cyano groups such as , amino groups, amide groups, imide groups, methyl ester groups, and ethyl ester groups. Among these groups, those having a carboxyl group, a hydroxyl group, an amide group, and a methyl ester group are preferred. Specifically preferred vinyl monomers include acrylamide, methacrylamide, allyl alcohol, methallyl alcohol, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, etc., but are not particularly limited to these. do not have. The use of one or more types of vinyl monomers other than acrylonitrile has no problem in achieving the objective of the present invention, but if it is less than 20% by weight, it will be impossible to maintain a high degree of selective separation. Therefore, the object of the present invention cannot be achieved. The degree of polymerization of the AB type block copolymer constituting the hollow fiber of the present invention is segment (A) on the order of oligomers.
Although combinations of (B) and (B) are also useful, they are usually
It is preferable to have a high molecular weight with an intrinsic viscosity (ηinh) of 0.5 or more as measured in a dimethylformamide solution of 0.2 g/100 ml at 30°C. Such an AB type block copolymer can be produced using a conventional block copolymer synthesis method, such as ionic polymerization technique, and a segment (A) having a functional group having condensation reactivity such as a hydroxyl group or an amino group ( A technique of condensing and bonding B) with a difunctional isocyanate, such as tolylene diisocyanate, 4,4'-diisocyanatodiphenylmethane, etc., or a difunctional reagent such as terephthalic acid chloride, isophthalic acid chloride, etc. Alternatively, it can be synthesized by a radical polymerization technique such as a two-stage polymerization method using a polymerization catalyst having two types of peroxide groups with different activities such as dicyclohexanone peroxide, etc., or a combination of these techniques. Generally, it is difficult to completely convert the entire polymerization system into an AB type block copolymer using such polymerization techniques, and the resulting polymer often contains polymers other than block copolymers. In order to separate only the block copolymer from these mixed polymers, a solvent for the mixed polymer, such as dimethylformamide, N-methyl-2-pyrrolidone, etc., is used.
Fractional precipitation may be performed using a mixed solvent with a non-solvent such as water, acetone, methanol, etc. Furthermore, if the polymer other than the block copolymer in the mixed polymer is an acrylonitrile polymer described later, it is not necessary to separate and take out only the block copolymer.
It is also possible to use the mixed polymer as it is. The AN-based polymer constituting the hollow fiber of the present invention is
Vinyl monomers copolymerizable with AN, specifically acrylamide, methacrylamide, N-methylacrylamide, N-ethylmethacrylamide, maleimide, so that AN is 40% by weight or more,
Allyl alcohol, methallyl alcohol, β-hydroxyethyl methacrylate, methallylamine, β-aminoethyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, methyl acrylate, methyl methacrylate, ethyl methacrylate, α-methylacrylonitrile, α-cyanoacrylonitrile, acetic acid It can be easily obtained by polymerizing one or more of vinyl, vinyl chloride, vinylidene chloride, styrene, etc., by a conventional polymerization method, for example, radical polymerization. In order to make the hollow fiber of the present invention, an AN-based polymer and
A method of manufacturing ordinary hollow fibers by mixing both polymers so that the composition ratio with the AB type block copolymer becomes the composition ratio of the hollow fibers of the present invention, and dissolving them in a common solvent to form a solution, e.g. This solution can be easily produced by introducing a liquid such as water, which is a non-solvent for both polymers, into the coagulation bath from the inside through the outer discharge port of the annular spinneret. A common solvent used for spinning and forming is AN.
There is no particular problem if the solvent can dissolve the block copolymer and the AB block copolymer at the same time, but usually
One or more of organic solvents such as dimethylformamide, dimethylacetamide, N-methyl-2-pyridone, and dimethyl sulfoxide, which are solvents for AN polymers, and inorganic solvents such as nitric acid, rhodan soda aqueous solution, and zinc chloride aqueous solution. A mixed solvent is used. The obtained solution is generally observed as a transparent homogeneous solution in many cases, but when observed using a differential interference microscope or the like, it is an extremely stable solution exhibiting fine phase separation. Adding various additives such as antioxidants, flame retardants, or matting agents to these solutions does not adversely affect the achievement of the objectives of the present invention. The hollow fiber of the present invention obtained in this way has the above-mentioned unique composition and structure, and has the formula (1) and the formula
It has extremely high water permeability and high selective separation ability as shown in (2), and is extremely excellent especially as a hollow fiber used in artificial kidneys. Formula (1) and formula
The water permeability and inulin passage rate shown in (2) are measured by the following method. Water permeability: A certain number of hollow fibers whose inner and outer diameters have been measured in advance are potted at both ends with resin as shown in Figure 1, and a pressure difference of 200 mmHg is created between the injection side and the outflow side, and the physiological flow per unit time is Measure the permeation amount of saline solution, divide the effective area of the inner wall of the hollow fiber by the calculated value, and calculate the value per unit area (ml/
Hr・m ²・mmHg). Inulin passage rate: Inulin passage rate is the reaction product generated from fructose by heating in an acidic solution of hydrochloric acid.
It is carried out by the following procedure using a method of reacting with thiobarbituric acid to develop color and measuring absorbance. Dissolve 1.00 g of inulin in 20 ml of physiological saline, then add 980 ml of serum or bovine blood to make a total volume of 1000 ml to prepare a 100 mg/dl solution of inulin. (This solution is used as the serum stock solution.) This stock solution was poured into the tube with a pressure difference of 200 mmHg between the injection side and the outflow side using a device set up in the same manner as in the water permeability measurement, and after 1 hour, the hollow The serum fluid that comes out through the fiber wall is collected and the amount of inulin is determined. For quantitative determination, add IN-H ₂ SO ₄ to 17.5 g of 3CdSO ₄ 8H ₂ O and 500 ml of purified water to 1 volume of the serum solution that has flowed out through the hollow fiber. 3 volumes, and
This is carried out using the supernatant obtained by adding and mixing 6 volumes of 0.166N-NaOH. Add 1.0 ml of physiological saline and 2N− to 1.0 ml of this supernatant.
Add 0.1 ml of NaOH and heat at 98°C for 15 minutes. After cooling, add 3 ml of a solution of 1.00 g of thiobarbituric acid in 500 ml of 35% concentrated hydrochloric acid, and
C. for 5 minutes, and after cooling to room temperature, spectrophotometric analysis was performed and the inulin passage rate was determined from the value at 435 nm using the following formula. Inulin passage rate (%) = ABS of serum solution/A of serum source solution
BS x 10 ² The present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto, and % in Examples means % by weight unless otherwise specified. (Reference example) Synthesis of AB type block copolymer 12g of dicyclohexanone peroxide represented by the following formula 312 g of acrylonitrile containing 2.5 g of sodium lauryl sulfate was added and suspended in 3000 ml of deionized water containing 2.5 g of sodium lauryl sulfate, 7.2 g of Rongarit was added thereto, and the mixture was heated at 40°C.
The temperature was raised to start the first stage polymerization. Polymerization was carried out for 2 hours while stirring the inside of the reaction system and controlling the temperature so as not to exceed 40°C. When a small amount of acrylonitrile was removed from the system and the remaining amount of acrylonitrile was measured using gas chromatography, it was found that the amount of acrylonitrile remaining in the system was
It was found that 92.6% was polymerized. Next, 200 g of methyl acrylate was added to the polymerization reaction system for second-stage polymerization, and while the temperature inside the system was maintained at 70° C., the mixture was stirred for 3 hours to carry out polymerization. The resulting suspension was filtered, washed with water, and dried to obtain 446 g of a white polymer. In this polymer, polyacrylonitrile produced in the first stage polymerization, polymethyl acrylate produced in the second stage, and the desired acrylonitrile are used as segment (A) components, and methyl acrylate is used as segment (B). Since it contains an AB type block copolymer, about 5000 ml of acetone was added to dissolve only the polymethyl acrylate, and another operation was repeated three times to remove it. This operation resulted in a polymer weight of 310.6 g. A part of this polymer was analyzed by fractional precipitation using a mixed solvent of dimethylformamide and acetone, and it was found that it contained 46.5% polyacrylonitrile and 53.5% AB type block copolymer. The AB type block copolymer obtained by fractionation had an intrinsic viscosity of 1.83. Example 1 An AB type block copolymer having acrylonitrile as the segment (A) and methyl acrylate as the segment (B) polymerized and fractionated by the method of the reference example described above was prepared so as to have the composition shown in Table 1. , an acrylonitrile-based polymer consisting of acrylonitrile/methyl acrylate = 92/8. These polymer compositions were then reduced to a total polymer concentration of 16
Dissolved in 70% nitric acid aqueous solution so that the inner diameter
The outer diameter is 200 microns and the outer diameter is 300 microns.
Using an annular spinneret with a diameter of 0.45 mm and an inner diameter of 0.1 mm, the solution was introduced from the outer annular part, and water was introduced from the inner part, and the solution was encapsulated in the solution and then discharged. The solution discharge linear speed at this time was 16.6 m/min, and this solution was spun into a 30% nitric acid aqueous solution with a space of about 90 mm in between to obtain hollow fibers. The hollow fibers of the present invention are extremely excellent in terms of water permeability and inulin passage rate, and are incomparable with the conventional hollow fibers shown in the comparative examples.

[Table] Examples 2 and 3 Synthesis of an AB type block copolymer containing acrylonitrile as the segment (A) component and acrylic acid as the segment (B) component, and segment (A) component is acrylonitrile segment (B) component is acrylamide
AB type block copolymer was synthesized. After the second stage polymerization is completed, in order to remove the polyacrylic acid and polyacrylamide produced in the second stage polymerization,
Wash each with plenty of warm water, then DMF/
Fractional precipitation was carried out using an aqueous solvent, and only the desired AB type block copolymer was collected. The intrinsic viscosity of these AB type block copolymers and the composition of the segment (B) component in the AB type block copolymers were as follows.

[Table] Polyacrylonitrile (intrinsic viscosity
1.21), and then these polymer compositions of the present invention were dissolved in a 65% nitric acid aqueous solution so that the total polymer concentration was 19.5%. All of the obtained solutions were opaque and homogeneous with microphase separation. This solution was spun using the same apparatus as in Example 1 to obtain hollow fibers shown in Table 3. All exhibited excellent water permeability and selective separation ability.

[Table] Example 4 Synthesis of an AB type block copolymer in which the segment (A) component is acrylonitrile and the segment (B) is a random copolymer with different ratios of acrylonitrile/methyl acrylate using the same method as in the reference example above. did. Dimethylformamide as in the reference example
Only the AB type block copolymer was taken out from the mixed solvent of acetone, and the results of compositional analysis and measurement of intrinsic viscosity were as shown below.

[Table] In addition to these AB type block copolymers, an acrylonitrile copolymer (intrinsic viscosity 1.18) with a composition of acrylonitrile/methyl acrylate/sodium methallylsulfonate = 92.5/7.0/0.5 was added to the total polymer. After mixing to a concentration of 15% by weight, hollow fibers were obtained in the same manner as in Example 1. The performance of the obtained hollow fibers is as shown in Table 5,
All showed high water permeability and inulin passage rate.

【table】 [Brief explanation of drawings]

Figure 1 shows an apparatus for measuring the water permeability and inulin passage rate of hollow fibers obtained from the polymer composition of the present invention, in which 1 indicates the inlet of the treatment liquid, 2 indicates the outlet of the treatment liquid, and 4 is a hollow fiber bundle, and both ends are potted with resin (5 and 6). 3 indicates the outlet of the liquid passed through the hollow fiber wall.

Claims (1)

[Scope of Claims] 1 (A) A hollow fiber having a hollow portion substantially continuous in the fiber axis direction, wherein the hollow fiber has a substantially polymerized amount of acrylonitrile (hereinafter abbreviated as AN) of 40% by weight. % or more of acrylonitrile-based polymer (hereinafter abbreviated as AN-based polymer) is 5 to 50% by weight, and (B) a segment having an AN polymerization amount of 80% or more by weight, and (B) a hydroxyl group, a carboxyl group, or an amino group in the molecule. , amide group, imide group, methyl ester group,
AB type block copolymer consisting of 50 to 95% by weight of a segment containing 20% by weight or more of one or more vinyl monomers having an ethyl ester group, and having the following formula (1) and ( A hollow fiber made of an acrylonitrile polymer, characterized in that it satisfies 2) at the same time. Inulin passage rate ≧50 (1) log (water permeability) ≧110− (inulin passage rate) / 30 (2)