JP2510540B2 - Polyacrylonitrile-based semipermeable membrane and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyacrylonitrile-based semipermeable membrane excellent in stain resistance and selective permeation, and is used for ultrafiltration in the industrial and medical fields. Used as a membrane.

(Prior art) In recent years, application of polymer materials to the industrial and medical fields has advanced,
In particular, regarding the separation of substances, the use of permselective membranes, so-called semipermeable membranes, has been actively performed. For example, in the fields of reverse osmosis, dialysis, ultrafiltration, gas separation, etc., many technical reports have been made on the application of membranes. However,
In these operations, there are problems that the membrane is contaminated with the treatment substance, the treatment capacity is lowered, and the separation performance of the membrane itself is not always sufficient.

As materials for such a semipermeable membrane, regenerated cellulose, various cellulose derivatives, polyacrylonitrile-based polymers, polyvinyl alcohol-based polymers, polymethylmethacrylate-based polymers, polysulfone-based polymers and the like have been hitherto taken up. Furthermore, for the purpose of increasing the stain resistance,
Synthetic polymers containing hydrophilic components such as 2-hydroxyethylmethacrylate, N-vinylpyrrolidone, acrylamide, or (meth) acrylic acid have been investigated.

However, membranes made of these materials have insufficient permeability to substances such as water and solutes, or even introduced a large amount of copolymerization components to achieve their performance, but also reduced mechanical strength. However, the function as a practical film has been impaired. Furthermore, using these membranes, when performing concentration of various protein solutions, sterilization of liquid foods, or ultrafiltration separation in the wastewater treatment process, clogging phenomenon occurs due to adhesion and deposition of solute components on the membrane surface. Operation was hindered. Furthermore, when these membranes are used for medical purposes and come into contact with blood or body fluid, adherence of tangible components such as platelets, leukocytes, erythrocytes and fibroblasts is unavoidable, which causes the formation of thrombus on the membrane surface and It was presumed that activation of the complement system causes a decrease in immune function.

(Problems to be Solved by the Invention) The present inventors have already proposed, as a hydrophilic polymer material, a selectively permeable hollow fiber made of a polymer having a polyethylene oxide unit (JP-A-60-22901). However, the requirements for the membrane performance thereafter have further increased, and it has become difficult to satisfy the filtration performance. In view of such a situation, as a result of further intensive research on the hydrophilic polymer material, a copolymer having polyethylene oxide and a semipermeable membrane containing an ultra-high degree of polymerization polyacrylonitrile polymer have excellent resistance. They have found that they can be used as a practical semipermeable membrane having stain resistance and selective permeability and having sufficient mechanical strength, and thus reached the present invention.

(Means for Solving Problems) The present invention has the following configurations.

(1) A copolymer of acrylonitrile with a monomer having a degree of polymerization of 5 or more and a polymerizable carbon-carbon double bond in the same molecule, and an intrinsic viscosity of 2.0
A polyacrylonitrile-based semipermeable membrane comprising the acrylonitrile-based polymer described above.

(2) The polyacrylonitrile-based semipermeable membrane according to claim 1, which contains 1% by weight or more of the total of polyethylene oxide units having a degree of polymerization of 5 or more.

(3) The polyacrylonitrile-based semipermeable membrane according to claim 1, which contains 10% by weight or more of the acrylonitrile-based polymer having an intrinsic viscosity of 2.0 or more.

(4) A copolymer of acrylonitrile and a monomer having a polyethylene oxide unit having a degree of polymerization of 5 or more and a polymerizable carbon-carbon double bond in the same molecule, and an intrinsic viscosity of 2.0
A method for producing a polyacrylonitrile-based semipermeable membrane, which comprises using a solution prepared by dissolving the above acrylonitrile-based polymer in a solvent as a membrane-forming stock solution.

Examples of the monomer constituting the present invention having a polyethylene oxide unit having a degree of polymerization of 5 or more and a polymerizable carbon-carbon double bond in the same molecule include those represented by the general formula (1). Here, n ≧ 5 R ₁ is H, CH ₃ R ₂ is a hydroxyl group, C _{1 to} C ₄ alkoxy group or acrylic acid or methacrylic acid ester represented by OCHφ ₂ (φ is a phenyl group), or a general formula ( 2) Here, n ≧ 5 R ₁ is a vinyl monomer represented by H or CH ₃ .

Methods for producing these addition-polymerizable compounds are known, and due to the polymerizable carbon-carbon double bond, ordinary radical initiators such as azobisisobutyronitrile and benzoylperoxide are used without using a special device or method. It can be easily polymerized using oxides, etc., and can be copolymerized with other monomers or polymers, so that a polymer composition having a polyethylene oxide unit can be formed efficiently and reproducibly. . In particular, methoxypolyethylene glycol monomethacrylate is preferably used as the component (1) represented by the formula (1). The content of polyethylene oxide in the copolymer can be confirmed by ordinary methods such as elemental analysis, infrared absorption spectrum and nuclear magnetic resonance spectrum.

It is necessary that the polymer forming the semipermeable membrane of the present invention contains at least 1% by weight or more of polyethylene oxide units of n ≧ 5. The amount of component (1) in the copolymer needed to achieve this depends on the weight fraction of polyethylene oxide, i.e., n, contained in the component. For example, when n = 9, 0.135 mol% or more is required, while n
= 100, 0.012 mol% or more is sufficient. Generally, when the addition amount is the same, the larger n is, the more difficult the polymer is to gel.

When the content of polyethylene oxide units required to achieve the target performance is given to the semipermeable membrane, the obtained semipermeable membrane shows poor spinning stability when the degree of polymerization n <5 of the polyethylene oxide units is poor. It cannot be used because the mechanical strength of the film is insufficient. That is, when the degree of polymerization of polyethylene oxide units is n <5 and the content of polyethylene oxide units is less than 1% by weight, the obtained semipermeable membrane has the desired property of the present invention, that is, stain resistance. Characteristics and excellent selective permeability. The preferred degree of polymerization of polyethylene oxide units is from 9 to 300, particularly preferably 20 to 150, and the preferred content of polyethylene oxide units is from 3 to 50% by weight. Another constituent component, an ultra high degree of polymerization acrylonitrile type The polymer has an intrinsic viscosity of 2.0 or more, preferably 2.5.
It has a degree of polymerization of ~ 3.6. Further, the polymer contains 10 mol% or less, preferably 5 mol% or less of a vinyl compound copolymerizable with acrylonitrile within a range not losing its characteristics.
It is also possible to carry out copolymerization at a mol% or less. The vinyl compound may be any compound having copolymerizability with known acrylonitrile, and preferable copolymerization components include acrylic acid, methyl acrylate, methyl methacrylate, itaconic acid, vinyl acetate, allyl. Sodium sulfonate, sodium methallyl sulfonate, sodium p-styrene sulfonate, 2-acrylamido 2-methylpropane sulfonic acid and the like are used.

In addition to these, it is also possible to mix copolymers with several kinds of vinyl compounds and polymers having different molecular weights.

Next, as a solvent for the film-forming stock solution used in the present invention, any solvent capable of simultaneously dissolving the copolymer and the like can be used, and examples thereof include dimethylformamide, dimethylsulfoxide, dimethylacetamide, and N-methylpyrrolidone. Etc. are preferably used. It is also possible to use a mutual mixture of these.

In dissolving the copolymer and the like in these solvents, it is necessary to consider required performance, mechanical properties, and film-forming properties. That is, the polymer concentration of the membrane-forming stock solution is closely related to the permeability of the membrane, and the mechanical properties.If the concentration is too high, the substance permeability of the membrane is reduced, and conversely, if it is too low, the membrane concentration is low. The mechanical properties of are deteriorated and cannot be put to practical use. Further, the viscosity of the stock solution for film formation is an important factor for the film forming property, and the concentration of the polymer is 5 in order to form a good film.
It should be used in the range of ~ 40% by weight.

Further, for the purpose of controlling the pore diameter of the membrane, adding a water-soluble additive such as salt, water, alcohol (including polyhydric) such as glycerin or polyethylene glycol, or urea is also a commonly practiced means.

Next, the production of the hollow fiber membrane will be described. When the stock solution for film formation obtained as described above is discharged from the spinneret, it is necessary to sufficiently consider the shape retention of the hollow fiber at the same time as forming the smooth yarn. The viscosity of the undiluted solution is an important factor for stable ejection. Therefore, it is possible to control the viscosity of the undiluted solution at the time of ejection by adjusting the die temperature.
It should be noted that the die temperature may affect the performance of the film depending on the conditions. Usually, when drawing is not carried out during the process, the hollow fiber size is almost determined by the coagulation bath. When using a hollow spinneret with a diameter larger than the target size, or when controlling the temperature of the stock solution and the coagulation bath temperature independently, the spinning solution is once discharged into the air and then immersed in the coagulation bath, The so-called dry-wet spinning method of solidifying is an effective means.

In order to maintain the hollow fiber form, a liquid is injected into the hollow fiber. The liquid to be injected is, for example, a solvent used in the spinning dope, a coagulant such as water or alcohol (including polyvalent), a water-soluble polymer, a mixture thereof, or a copolymer thereof. Hydrophobic liquids such as non-solvents such as n-octane, aliphatic hydrocarbons such as liquid paraffin, and fatty acid esters such as isopropyl myristate can also be used. However, the composition of these infusates is closely related to the performance of the membrane, so in choosing them,
It is necessary to give due consideration. Further, in the case of an injection liquid having a high solidification property, it is necessary to use a hollow nozzle having a small diameter so that the draft during spinning can be reduced and spinning stability can be maintained.

The discharged yarn may gel due to temperature changes in the air,
In the case of rapidly forming a strong film structure by solidification, an inert gas such as nitrogen gas can be used by self-suction or press-fitting. The gas injection method is an excellent process method because it is not restricted by the size of the die and does not require removal or recovery of the internal injection liquid. However, in the case of an undiluted solution that does not cause gelation in the dry part, it is necessary to adjust the length of the dry part so that local swelling does not occur and sudden draft does not occur. Generally, the preferred dry section length is 2-10 mm.

The coagulation bath is usually composed of a coagulant such as water or alcohol (including polyvalent), or a mixture with a solvent constituting the spinning dope. The composition of the coagulation bath greatly affects the spinning stability and the membrane structure of the hollow fiber due to its coagulability. The temperature of the coagulation bath is also an important factor in the permeability of the membrane. Furthermore, since it depends on the dimensional stability of the film depending on the composition of the bath, it is combined with the composition of the coagulation bath under appropriate conditions for the target film performance.

After coagulation, sufficient washing with water is performed, and then water inside the membrane is replaced with glycerin or ethylene glycol in order to prevent the membrane structure of the hollow fiber from being destroyed by drying. Further, if necessary, heat treatment may be performed with a glycerin aqueous solution or the like to impart dimensional stability.

On the other hand, a known method can be used to obtain a flat film. Under a controlled atmosphere of temperature and humidity, the solution for film formation is dripped onto a glass plate, and after being formed into a film having a required film thickness by a commercially available applicator, etc., it is immersed in a coagulation bath to coagulate and desolvate. To obtain the target membrane. In this case as well, the membrane forming stock solution, the coagulation bath, the post-treatment, etc. have a great influence on the membrane performance, so it is necessary to select appropriate conditions as in the case of the hollow fiber.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

(Example) The degree of polymerization of the polymer and the film performance were measured by the following methods.

-Polymerization degree-The polymer is dissolved in a dimethylformamide solution of 0.1 N sodium thiocyanate at a concentration of 0.3 g / dl as an intrinsic viscosity [η] of the polymer, and η _sp is measured at 20 ° C., It was calculated by the following formula.

(Journal of Polymer Science (A-1) Volume 6, 147
(See page 157 (1968))-Water permeability-Make a small glass module with hollow fiber inserted, and apply water or 5% bovine serum albumin aqueous solution to the inside of the hollow fiber in a constant temperature bath at 37 ° C to apply pressure. The water permeability was calculated from the amount of water permeating through the membrane, the effective membrane area, and the transmembrane pressure difference.

-Protein inhibition rate-The albumin concentration (Ci) of the feed solution and the albumin concentration (Cf) of the filtrate were measured using an ultraviolet spectroscope and calculated from the following formula.

-Protein attachment rate-In a small module similar to that used for water permeability measurement,
Rabbit whole blood or platelet suspension at shear rate of 400 / sec 3
It was circulated for 3 hours while keeping the temperature at 7 ° C. After washing with physiological saline, fix with 3% glutaraldehyde physiological saline,
The amount of protein attached to the surface of the hollow fiber was measured by amino acid analysis.

In addition, the state of platelets and the like adhering to the film surface was observed with a scanning electron microscope.

Example 1 27 parts of methoxypolyethylene glycol monomethacrylate "M100G" and acrylonitrile (hereinafter abbreviated as AN) 143
To 838 parts of dimethylsulfoxide (abbreviated as DMSO), 0.3 parts of 2,2azobis2,4dimethylvaleronitrile was added, polymerized at 40 ° C for 7 hours, reprecipitated with water / methanol and purified to obtain polyethylene. "M100G" copolymerized polyacrylonitrile (hereinafter abbreviated as copolymerized PAN) having an oxide (hereinafter abbreviated as PEO) unit content of 25.5% was obtained.

On the other hand, AN100% was polymerized in DMSO by a known method to obtain a DMSO solution of an ultrahigh molecular weight polymer having [η] = 3.2 and a polymer concentration of 16.5%. Next, the above-mentioned "M100G" copolymer 66
Parts, also 237 parts of ultra high molecular weight polymer DMSO solution and DMSO390
In addition to 10 parts, 0.03 parts of hydroquinone monomethyl ether (hereinafter abbreviated as HQME) is added as a gelation inhibitor at 90 ° C.
Dissolved for 6 hours.

Outer diameter / inner diameter = 1.
It was discharged into the air at a rate of 1.2 g / min from an annular slit type hollow die of 0 / 0.7 mmφ. At the same time, nitrogen gas was injected into the hollow at a pressure of 30 mmAq. The dry portion had a length of 4 mm, and the coagulation bath was 47 ° C. water. After washing with water and pretreatment with 62% glycerin, relaxation heat treatment of 5% was performed with a 75% glycerin aqueous solution at 85 ° C., and sampling was performed at 19 m / min.

The amount of PEO units contained in the polymer of the obtained hollow fiber was 16 wt%. Inner diameter / thickness of the hollow fiber membrane is 244 / 37μ
The water permeability was 84 ml / hr.mmHg.m ² , the water permeability in a 5% albumin aqueous solution was 14 ml / hr.mmHg.m ² , and the blocking rate was 99.8%. The breaking stress of this film is 13 MPa and the breaking elongation is 130
%, And had sufficient mechanical properties. Furthermore, the protein attachment rate by rabbit fresh blood evaluation was as low as 22.6 μg / cm ² ,
No platelet adhesion was observed.

Example 2 PEO unit content obtained in the same manner as in Example 1 28 w
Same as [η] = 3.1 with 43% of tM% "M100G" copolymerized PAN
691 parts of 15.5% DMSO solution of ultra-high molecular weight PAN of was added to 266 parts of DMSO together with 0.02 part of HQME and dissolved at 85 ° C for 8 hours.
A spinning stock solution of poise / 70 ° C. was obtained.

Outer diameter / inner diameter = 0.5 / 0.25mmφ annular slit type hollow mouthpiece is kept at 43 ℃ and discharge rate is 1.6g / min, 1.0cc / min
It was discharged together with the injection liquid (100% of water). The dry portion had a length of 200 mm, and water at 62 ° C. was used as a coagulation bath. After washing with water, 6
It was dried and treated with a 65% aqueous glycerin solution at 0 ° C and wound on a drum.

The water permeability of the hollow fiber membrane containing PEO unit of 8 wt% is 340 ml / hr.m.
mHg.m ² and 85 ml / hr.mmHg.
It showed high filtration performance with m ² and rejection rate of 99.7%. The protein adhesion rate was 6.7 μg / cm ² , and platelet adhesion was slight.

Example 3 44 parts of "M100G" copolymer having a PEO unit content of 28 wt%,
DMSO2 with 204 parts of DMSO solution of ultra high molecular weight PAN with [η] = 3.2
HQME (0.02 parts) was added to 53 parts, and the mixture was dissolved at 90 ° C for 6 hours to obtain a spinning dope at 516 poise / 70 ° C. PE in polymer
The O unit was 16 wt%.

1.2g / min from the base (0.5 / 0.3mmφ) kept warm at 46 ℃
It was discharged at a discharge rate of 1.2 cc / min together with the injection liquid (water 100%). The dry portion was 150 mm, and water at 27 ° C was used as a coagulation bath. After washing with water, relaxation heat treatment and anti-drying treatment were performed with a glycerin aqueous solution at 85 ° C and 72%, and the resultant was wound on a reel.

Permeability of the hollow fiber membrane is at 48ml / hr.mmHg.m ^2, in 5% albumin solution was 30ml / hr.mmHg.m ^2, rejection of 99.5%. In addition, the protein adhesion rate is 0.2 μg / cm ² and the adhesion of platelets
It was a very small amount of 1.3 μg / cm ² .

Comparative Example 1 Acrylonitrile 97 mol%, methyl acrylate 2 mol
%, A copolymer of 1 mol% sodium methallylsulfonate [η] of 1.5 was dissolved in DMSO to give a polymer concentration of 2
A spinning dope of 2.2% was obtained.

Dry-wet spinning was performed in the same manner as in Example 1 while injecting nitrogen gas into the hollow to obtain a hollow fiber having an inner diameter of 231 μm and a film thickness of 33 μm.

The water permeability of the hollow fiber was 94 ml / hr.mmHg.m ² , 5% albumin was 8 ml / hr.mmHg.m ² , and the inhibition rate was 99.8%. A large amount of protein was attached at 116 μg / cm ² .

Comparative Example 2 As in Example 1, 100% of AN was polymerized in DMSO, and the polymer concentration of ultrahigh molecular weight PAN with [η] = 3.2 was 15.5.
%, And the viscosity of the stock solution was 1600 poise / 70 ° C. to obtain a spinning stock solution.

In the same manner as in Example 2, while pouring water into the inside, spinning was performed from a spinneret at 60 ° C through a coagulating bath at 30 ° C in water. The resulting hollow fiber has a water permeability of 364 ml / hr.mmHg.m ² and a protein attachment rate.
Although it was low at 9.3 μg / cm ² , a large amount of platelets adhered to the inner surface of the hollow fiber.

Comparative Example 3 18 parts of methoxypolyethylene glycol monomethacrylate "M100G" and 145 parts of AN were added to 836 parts of DMSO, 0.3 part of 2,2azobis2,4 dimethylvaleronitrile was added, and the mixture was mixed at 40 ° C. for 7 days.
After polymerization for a period of time, reprecipitate with water / methanol, purify and purify
A copolymerized PAN having a content of 16% was obtained. 152 parts of this copolymerized PAN
In addition to 848 parts of MSO, 0.03 part of HQME was added and dissolved at 90 ° C. for 6 hours. The obtained spinning solution was kept at 63 ° C and the outside diameter / inner diameter = 1.0 / 0.7mmφ annular slit type hollow fiber spinneret
It was discharged into the air at a rate of g / min. At the same time, nitrogen gas was injected into the hollow fiber at a pressure of 30 mmAq. The length of the dry part was 4 mm, and 48 ° C. water was used for the coagulation bath. After washing with water and pretreatment with 62% glycerin, relaxation heat treatment of 5% was performed with a 75% glycerin aqueous solution at 85 ° C., and sampling was performed at a spinning speed of 19 m / min.

The amount of PEO unit contained in the polymer in the obtained hollow fiber was 16 wt%. Inner diameter / membrane thickness of the hollow fiber membrane is 242 / 38μ
In m, water permeability water permeability at 83ml / hr.mmHg.m ^2, 5% aqueous albumin solution is 13ml / hr.mmHg.m ^2, rejection was 99.8%. As a result of the rabbit fresh blood evaluation, there was little protein adhesion and no platelet adhesion was observed. However, the breaking stress of this film was 7 MPa and the breaking elongation was 60%, which was significantly lower than the mechanical properties of Example 1.

(Effects of the Invention) The polyacrylonitrile-based semipermeable membrane of the present invention has excellent mechanical strength, and has high filtration performance and selective permeability in addition to the anti-staining effect of the treated membrane surface. Therefore, it can be widely used for industrial or medical use by converting it into a target module by a known method. In particular, its high resistance to contamination is preferably used as a blood filtration membrane, as a non-heparin continuous slow water removing device, or as a portable artificial kidney.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location D01F 6/18 D01F 6/18 A 6/54 6/54 D (56) References JP-A-56 -9424 (JP, A) JP-A-55-90616 (JP, A) JP-A-60-22901 (JP, A) JP-A-61-176359 (JP, A)

Claims (4)

(57) [Claims] 1. A copolymer of acrylonitrile and a monomer having a polyethylene oxide unit having a degree of polymerization of 5 or more and a polymerizable carbon-carbon double bond in the same molecule, and an acrylonitrile polymer having an intrinsic viscosity of 2.0 or more. A polyacrylonitrile-based semipermeable membrane composed of and. 2. A polyacrylonitrile-based semipermeable membrane according to claim 1, which contains 1% by weight or more of polyethylene oxide units having a degree of polymerization of 5 or more. 3. The polyacrylonitrile-based semipermeable membrane according to claim 1, wherein the acrylonitrile-based polymer having an intrinsic viscosity of 2.0 or more is contained in an amount of 10% by weight or more of the whole. 4. A copolymer of acrylonitrile and a monomer having a polyethylene oxide unit having a degree of polymerization of 5 or more and a polymerizable carbon-carbon double bond in the same molecule, and an acrylonitrile polymer having an intrinsic viscosity of 2.0 or more. A method for producing a polyacrylonitrile-based semipermeable membrane, which comprises using a solution dissolved in a solvent as a membrane-forming stock solution.