JP2000225326A - Method for cleaning selective permeable membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and effectively reduce the eluation amount of polyvinyl pyrrolidone from a selective permeable membrane containing the polyvinyl pyrrolidone by cleaning the selective permeable membrane containing the polyvinyl pyrrolidone using a solution containing an alcohol. SOLUTION: A selective permeable membrane containing polyvinyl pyrrolidone is cleaned using a solution containing an alcohol. In this case, the selective permeable membrane to be used is such as formed of a polysulfone resin or a polyether sulfone. The solution containing an alcohol to be used is an aqueous solution with the concentration of the alcohol set at 10-100% or an aqueous solution containing 60% or below 1-3C saturated univalent alcohol in terms of carbon atoms constituting one molecule. Further, when the selective permeable membrane is cleaned, the solution is used at a temperature of 20 deg.C or higher and below the boiling point of the alcohol, and further, is filtered before cleaning. The cleaning time is set within the range of 1-60 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for efficiently washing eluting components from a permselective membrane containing polyvinylpyrrolidone.

[0002]

2. Description of the Related Art Polyvinylpyrrolidone is used for modifying a permselective membrane, controlling pore size, and controlling phase separation. Particularly, in a permselective membrane composed of a polymer compatible with polyvinylpyrrolidone, the polymer and polyvinylpyrrolidone are used. Is formed from a solution in which is dissolved in a solvent to impart hydrophilicity and performance. These properties are due to the characteristics that polyvinylpyrrolidone has high hydrophilicity, is easily soluble in a solvent, and is compatible with a synthetic polymer such as a polysulfone resin or a polyamide.

[0003] Polysulfone-based polymers themselves have a strong hydrophobicity, and the permselective membrane consisting of only the polysulfone-based polymer, when brought into contact with blood, adsorbs plasma proteins to the membrane, resulting in reduced performance. Therefore, by mixing the polysulfone-based polymer and polyvinylpyrrolidone, it is possible to impart hydrophilicity to the membrane and suppress adsorption of plasma proteins during blood contact. Also, by mixing polyvinylpyrrolidone with the polysulfone-based selectively permeable membrane,
It is known that dialysis performance is improved, and recently,
Various types of polysulfone-based hemodialysis membranes containing polyvinylpyrrolidone have been marketed and used in large numbers.

[0004] However, in the permselective membrane containing polyvinylpyrrolidone, various inconveniences have been pointed out because polyvinylpyrrolidone in the membrane elutes during use. In particular, in hemodialysis membranes composed of polysulfone and polyvinylpyrrolidone, it is known that severe shock symptoms occur in patients during dialysis treatment, and as one of the causes, eluting polyvinylpyrrolidone is suspected. I have.

[0005] Several attempts have been made to reduce the dissolution of polyvinylpyrrolidone.
For example, Japanese Patent Application Laid-Open No. Hei 10-230148 discloses that a selectively permeable membrane formed is subjected to radiation treatment or heat treatment.
A method is disclosed in which the contained polyvinylpyrrolidone is crosslinked and insolubilized with water. However, polyvinylpyrrolidone cross-linking by radiation requires a large amount of radiation required for complete cross-linking, requires a large radiation source and is difficult to carry out easily. The problem is deterioration of the case itself, the case, and the adhesive, and a decrease in strength. In addition, in crosslinking by heat treatment,
Within the range confirmed by us, it is difficult to obtain a practically usable crosslinking level, and on the contrary, the amount of polyvinylpyrrolidone eluted increases due to decomposition of polyvinylpyrrolidone by heat.

Japanese Patent Application Laid-Open No. Hei 4-338223 discloses a means for reducing the elution amount by using polyvinylpyrrolidone having a molecular weight of 300,000 or more and adjusting the mixing ratio to the polysulfone resin to 0.5% to 10%. It has been disclosed. At present, there are various grades of commercially available polyvinylpyrrolidone having different average molecular weights. Certainly, the use of polyvinylpyrrolidone having a large molecular weight reduces the amount of elution from the permselective membrane, but commercially available polyvinylpyrrolidone has a relatively wide molecular weight distribution and the highest molecular weight K90 (number average molecular weight 360,000) But
As a result of our examination, it was confirmed that polyvinylpyrrolidone eluted from the permselective membrane was not only of low molecular weight. Further, when the mixing ratio of polyvinylpyrrolidone to the polysulfone resin is 10% or less, when the obtained selectively permeable membrane is applied to a hemodialysis membrane, the solute permeation performance, which is a performance required as a hemodialysis membrane, is reduced. In addition, it is not preferable because the performance is significantly reduced due to the adsorption of the plasma protein at the time of blood contact.

[0007]

Therefore, at present, there is no method for effectively reducing the amount of polyvinylpyrrolidone eluted from the permselective membrane containing polyvinylpyrrolidone. Another object of the present invention is to find a method capable of easily and effectively reducing the amount of polyvinylpyrrolidone eluted from a permselective membrane containing polyvinylpyrrolidone.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found the following method. That is, the present invention provides: (1) a method for cleaning a selectively permeable membrane, comprising washing a selectively permeable membrane containing polyvinylpyrrolidone with a solution containing alcohol. (2) The method for cleaning a selectively permeable membrane according to claim 1, wherein the selectively permeable membrane is made of a polysulfone resin. (3) The method for cleaning a permselective membrane according to the above (1) or (2), wherein the permselective membrane is made of polyethersulfone. (4) The above (1), wherein the solution containing alcohol is an aqueous solution.
The method for cleaning a selectively permeable membrane according to any one of (1) to (3). (5) The method for cleaning a selectively permeable membrane according to any one of the above (1) to (4), wherein the alcohol concentration is 10% or more and 100% or less. (6) The above-mentioned (1) to (5), wherein the alcohol-containing solution is an aqueous solution containing a saturated monohydric alcohol having 1 to 3 carbon atoms constituting one molecule at a content of less than 60%. The method for cleaning a selectively permeable membrane according to any one of the above. (7) The method for cleaning a selectively permeable membrane according to any one of the above (1) to (6), wherein the cleaning is performed at a temperature of 20 ° C. or higher and a boiling point of an alcohol or lower. (8) The method for cleaning a selectively permeable membrane according to any one of the above (1) to (7), wherein the solution containing an alcohol is washed by filtration. (9) The method for cleaning a selectively permeable membrane according to any one of the above (1) to (8), wherein the alcohol-containing solution is washed by partially filtering the solution. (10) The method for cleaning a selectively permeable membrane according to the above (1) to (9), wherein the cleaning time is from 1 minute to 60 minutes.

In the present invention, the shape of the permselective membrane is not particularly limited, and may be any shape such as a hollow fiber shape, a tubular shape, a film shape, and the structure may be uniform or non-uniform. It is also possible to have a sponge structure and a void structure inside. Further, a separation active layer may be provided on one surface or both surfaces of the membrane. The application destination is not particularly limited as long as it is a permselective membrane containing polyvinylpyrrolidone, and includes reverse osmosis, ultrafiltration, microfiltration, hemodialysis, hemofiltration, plasma separation, plasma fractionation, and the like. It is preferably used for applications that may cause inconvenience due to elution of polyvinylpyrrolidone from the membrane, such as purification applications and household water purifiers.

The material of the permselective membrane of the present invention can be applied to any material as long as it contains polyvinylpyrrolidone. However, a solvent capable of dissolving both the polymer as the material and polyvinylpyrrolidone is simple. Among them, for example, aprotic solvents such as N-methyl-2-pyrrolidone, dimethylacetamide, dimethylsulfoxide, and aromatic polysulfone-based polymers and polyamide-based polymers that are compatible with polyvinylpyrrolidone in dimethylformamide are preferable. An aromatic polysulfone polymer having a high affinity for alcohol is more preferable. Examples of the aromatic polysulfone-based polymer include a polymer having a common name of polysulfone and a polymer commercially available as a common name of polyethersulfone.
In the present invention, polyether sulfone has the highest cleaning effect.

In the present invention, the alcohol used is not particularly limited, and may be a monohydric, dihydric or trihydric or higher polyhydric alcohol, such as methanol, ethanol, propanol, butanol, ethylene glycol, diethylene glycol, triethylene glycol. Glycol,
Polyethylene glycol, glycerin, etc. are mentioned, but cost, handling, safety, method of recovery from liquid after washing, low viscosity, high solubility with water, low freezing point, methanol, ethanol and propanol Is preferably used.

In the present invention, the effect of the alcohol solution can be obtained by using 100% alcohol or a solution mixed with another solvent. However, from the viewpoint of the danger of handling alcohol, it is possible to mix the alcohol solution with another highly safe solvent. An alcohol aqueous solution in which alcohol is mixed with water is particularly preferable from the viewpoint of cost and ease of obtaining.

The concentration of the alcohol solution is preferably 10% or more. If the concentration is less than 10%, particularly in the case of an aqueous solution, the cleaning effect is almost the same as when water is used as the cleaning solution, and the effect cannot be obtained, which is not preferable. If the alcohol concentration is 10% or more, a higher cleaning effect can be obtained as the alcohol concentration is higher. However, as described above, the handling risk increases.
% To 60%.

The most preferred alcohol solution is an aqueous solution containing less than 60% of a saturated monohydric alcohol having 1 to 3 carbon atoms constituting one molecule. Alcohols are designated as "Class 4 alcohols" by the Fire Services Act,
The place of use is strictly restricted by notification and regulations as a hazardous material handling place, but the above aqueous solution is excluded from dangerous goods, so it can be used relatively easily and the cost is low, and for the purpose of the present invention Most preferred because of its high cleaning effect. Examples of the saturated monohydric alcohol having 1 to 3 carbon atoms constituting one molecule include methanol, ethanol, isopropanol, and normal propanol.

The temperature at the time of cleaning is 20
C. or higher is preferred. If the temperature is lower than 20 ° C., the solubility of the washing solution in polyvinylpyrrolidone becomes low, which is not preferable.
If the temperature is higher than 20 ° C., the higher the temperature, the higher the cleaning effect. However, the risk of handling increases. Therefore, the temperature is preferably lower than the boiling point of the alcohol used, more preferably 25 ° C.
~ (Alcohol boiling point -10 ° C), more preferably 30
° C to (alcohol boiling point-20 ° C), and within this range, a high cleaning effect and safety can be expected.

In the cleaning method of the present invention, it is preferable to filter the membrane with a solution containing alcohol. That is, when the film is simply immersed in an alcohol solution, when the film surface is wiped with an alcohol solution, or when the alcohol solution passes through the film surface, the polyvinylpyrrolidone in the film may not be sufficiently washed. By filtering the alcohol solution through the membrane, the polyvinylpyrrolidone in the membrane comes into contact with the alcohol in the washing solution, and the polyvinylpyrrolidone is easily dissolved in the alcohol solution.

If a separation active layer is provided on one or both sides of the permselective membrane and the molecular weight cut off of the separation active layer is smaller than the used polyvinylpyrrolidone, the polyvinylpyrrolidone on the membrane surface is dissolved in an alcohol solution. However, since the alcohol solution cannot pass through the membrane, if the alcohol solution is partially filtered (cross-flow filtration), it is preferable that the dissolved polyvinylpyrrolidone can be discharged from the membrane surface without being filtered.

In the case of a selective separation membrane having a separation active layer on both sides, the direction of filtration is changed during washing, whereby
It is preferable because polyvinylpyrrolidone can be effectively washed from both separation active layers.

Further, in the present invention, the cleaning time can also be an important factor in determining the cleaning effect. Naturally, by increasing the cleaning time, the cleaning effect can be expected to be improved, but on the contrary, the production / cleaning cost and efficiency are reduced. The washing time largely depends on the properties of the permselective membrane and the properties of the washing solution, but generally the washing time is preferably 1 minute or more and 60 minutes or less. If the time is less than 1 minute, the cleaning efficiency is low, and if it is more than 60 minutes, the amount of the cleaning liquid increases, and the production efficiency decreases, which is not preferable.

Further, in the present invention, the flow rate of the cleaning liquid is an important factor. As described above, the polyvinylpyrrolidone in the membrane cannot be efficiently cleaned only by immersing the selective separation membrane in the alcohol solution or flowing the alcohol solution on the membrane surface. Therefore, it is preferable to filter the solution to be washed through a membrane. According to the present invention, the effect of the shearing force on the membrane of the cleaning liquid by filtration is not so large, but when the filtration flow rate is extremely small, the cleaning liquid is not efficiently replaced inside the membrane, and the cleaning liquid dissolves in polyvinylpyrrolidone. The power is reduced and a high cleaning effect cannot be expected. Although it depends on the properties of the membrane and the alcohol solution, the preferred filtration rate of the alcohol solution is 1
10 ml / min or more per m ² , more preferably 50 m / min
1 / min or more. At less than 10 ml / min, the replacement of the cleaning liquid inside the membrane is not effectively performed as described above, and the dissolving power for polyvinylpyrrolidone decreases,
Washing efficiency decreases. On the other hand, since the effect of the shearing force of the cleaning liquid on cleaning is not so high, even if the filtration flow rate is increased, the cleaning effect does not change at a certain flow rate or more, and conversely, the required amount of cleaning liquid increases and the running cost increases, which is not preferable. Although it depends on the properties of the membrane and the alcohol solution, the preferable filtration rate of the alcohol solution is 10 L / m ² of membrane area.
min or less, more preferably 5 L / min or less.
At a filtration flow rate exceeding 10 L / min, the washing effect is not improved as described above, and only the cost is increased, which is not preferable.

[0021]

The present invention discloses a method for effectively washing away the soluble polyvinylpyrrolidone contained in the selective separation membrane by washing the selective separation membrane with an alcohol solution. It is not clear why polyvinylpyrrolidone can be washed efficiently.

Polyvinylpyrrolidone is a substance having a strong hydrophilicity, and is therefore preferably used for modifying a hydrophobic polysulfone-based selective separation membrane, but its solubility is not so different between water and alcohol. When washed with water, in our investigation, increasing the temperature increases the solubility of polyvinylpyrrolidone, but when the selective separation membrane is washed,
It has been confirmed that the amount of polyvinylpyrrolidone that can be washed off even with washing with hot water at 95 ° C. is 1/10 or less of that of a 20% / 40 ° C. aqueous ethanol solution.

We speculate that the alcohol solution does not act directly on polyvinylpyrrolidone, but rather weakens the entanglement of the polymer forming the selective separation membrane, so that polyvinylpyrrolidone is easily washed out. Hereinafter, the present invention will be described based on examples.

[0024]

EXAMPLE A selective separation membrane used for washing was manufactured in the following manner. 16 parts by weight of polyether sulfone (4800P, manufactured by Sumitomo Chemical) and polyvinylpyrrolidone (Korydone K9
0, BASF) 5 parts by weight, 5 parts by weight of water and 74 parts by weight of dimethylacetamide were mixed, dissolved and defoamed, and used as a stock solution for spinning.
Using a 0% dimethylacetamide aqueous solution, a spinning stock solution and a core liquid were discharged from a tube-in orifice nozzle having a slit outer diameter of 400 μm, a slit inner diameter of 200 μm, and a core liquid discharge hole diameter of 110 μm. After passing through a 50 cm aerial traveling section, the mixture was guided into a coagulation bath made of water at 70 ° C. to form a hollow fiber. The obtained hollow fiber was thoroughly washed with water to completely remove the residual solvent, and then wound at a spinning speed of 30 m. The wound hollow fiber has an inner diameter of 200 μm and a thickness of 40 μm, has a separation active layer on the inner surface, a sponge structure on the membrane wall, and 2 to 5 μm on the outer surface.
Were present at a porosity of 25%. The obtained hollow fiber was dried at 60 ° C. for 20 hours, and then assembled into a module having an effective length of 25 cm, a number of 9600, and an effective membrane area of 1.5 m ² . The performance of this hollow fiber membrane module was determined by an ultrafiltration coefficient of 28 measured according to the artificial kidney performance evaluation standard.
It was 0 ml / m ² · hr · mmHg, and the sieving coefficient of albumin measured using a 0.2% albumin aqueous solution was 0.02. The obtained hollow fiber membrane is subjected to an eluate test (70 ° C., 1 h) according to the approval standard of the hollow fiber type artificial kidney determined by the Ministry of Health and Welfare.
r, extracted with pure water at a bath ratio of 100).
As a result of analysis, most of the components contained in the eluate were polyvinylpyrrolidone.

(Example 1) 40
C., a 40% aqueous ethanol solution is flowed at 150 ml / min, the inner half 75 ml / min is filtered from the inside of the hollow fiber to the outside, and the remainder is flown inside the hollow fiber membrane without filtering.
The cross-flow filtration was performed for 1 hour in a single pass (the filtrate and the effluent were not restored) (the amount of the ethanol aqueous solution passed through the hollow fiber was 9 L). After completely replacing the aqueous alcohol solution in the module subjected to cross-flow filtration with pure water,
The moisture in the module was completely dried. When an eluate test was performed on the hollow fiber membrane subjected to such treatment, the ultraviolet absorbance was 0.007, and no polyvinylpyrrolidone was detected in the eluate.

Comparative Example 1 70 ° C.
Of hot water at 150 ml / min and the inner half 75 ml
/ Min is filtered from the inside of the hollow fiber to the outside, and the remainder is passed through the inside of the hollow fiber membrane without being filtered. Cross-flow filtration is performed for 1 hr in a single pass (the filtrate and effluent are not returned).
(The amount of the aqueous ethanol solution passed through the hollow fiber was 9 L).
The moisture in the module subjected to the cross-flow filtration was completely dried. When an eluate test was performed on the hollow fiber membrane subjected to such treatment, the ultraviolet absorbance was 0.11, and as a result of the analysis, most of the components contained in the eluate were polyvinylpyrrolidone.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C11D 7/26 C11D 7/26 F term (Reference) 4C077 AA05 AA12 BB01 BB02 KK01 LL01 LL02 LL05 NN03 PP15 PP18 PP27 4D006 GA03 GA06 GA07 GA13 HA01 MA01 MA02 MA03 MA06 MB02 MB06 MC40X MC54 MC62 MC63X MC83 NA04 NA64 PA01 PB06 PB09 PC41 PC47 PC52 4H003 BA12 DA12 DA20 DB03 ED02 ED28 FA01

Claims (10)

[Claims] 1. A method for cleaning a selectively permeable membrane, comprising washing a selectively permeable membrane containing polyvinylpyrrolidone with a solution containing alcohol. 2. The method for cleaning a selectively permeable membrane according to claim 1, wherein the selectively permeable membrane is made of a polysulfone resin. 3. The method for cleaning a permselective membrane according to claim 1, wherein the permselective membrane is made of polyether sulfone. 4. The method for cleaning a selectively permeable membrane according to claim 1, wherein the solution containing an alcohol is an aqueous solution. 5. An alcohol having a concentration of 10% or more and 100% or more.
The method for cleaning a selectively permeable membrane according to any one of claims 1 to 4, which is as follows. 6. The solution according to claim 1, wherein the alcohol-containing solution is an aqueous solution containing a saturated monohydric alcohol having 1 to 3 carbon atoms constituting one molecule at a content of less than 60%. The method for washing a selectively permeable membrane according to any one of the above. 7. The method for cleaning a selectively permeable membrane according to claim 1, wherein the cleaning is performed at a temperature of 20 ° C. or higher and a boiling point of an alcohol or lower. 8. The method for cleaning a selectively permeable membrane according to claim 1, wherein the cleaning is performed by filtering a solution containing an alcohol. 9. The method for cleaning a selectively permeable membrane according to claim 1, wherein the solution containing an alcohol is washed by partially filtering the solution. 10. The method for cleaning a selectively permeable membrane according to claim 1, wherein the cleaning time is 1 minute or more and 60 minutes or less.