JP2002136847A - Method for cleaning hollow fiber membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a hollow fiber membrane, by which oily materials existing in the hollow fiber membrane can be removed selectively while the structure of the hollow fiber membrane is not changed, a pore size keeping agent such as glycerin is made to remain and an adhesive being a member of a membrane module for removing muddiness can be restrained from eroding a casing. SOLUTION: This method for cleaning the hollow fiber membrane in its manufacturing process comprises selectively removing oily materials existing inside a hollow fiber by making an aliphatic hydrocarbon whose ozone disrupting coefficient is zero and which has 130 deg.C or lower boiling point flow into the inside of the hollow fiber forcibly while the pore size keeping agent is made to remain in the hollow fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for washing a hollow fiber membrane which can be used in various membrane separation processes such as a hollow fiber ultrafiltration membrane and a microfiltration membrane.

[0002]

2. Description of the Related Art Conventionally, cellulose, cellulose acetate,
When extruding a solution or melt of cellulose triacetate, polyacrylonitrile, polymethyl methacrylate, polysulfone, etc. from the orifice, simultaneously eject an oily substance such as liquid paraffin, isopropyl myristylate inside the hollow fiber membrane, A hollow fiber filled with an oily substance is spun. The hollow fiber thus spun is bundled so as to be wound around a core tube arranged near the central axis of the cylindrical container, and both ends of the hollow fiber bundle are fixed with an adhesive such as urethane or epoxy. Then, the adhesive portion is cut, the end of the hollow fiber is opened, and inserted into a cylindrical container to produce a module for opacity removal.

The oily substance filled in the hollow fiber membrane can be efficiently removed by passing Freon through the inside of the hollow fiber membrane. However, CFCs are deteriorating the ozone layer, and production is being halted, especially in developed countries, and it is necessary to immediately switch to alternative cleaning agents. On the other hand, replacement with a fluorinated fluorinated hydrocarbon compound, a fluorinated carbon compound, an organic solvent or the like is being studied.

[0004] However, due to practical limitations, it cannot necessarily be a complete replacement. Fluorinated hydrocarbon compounds such as compounds represented by the structural formula C ₂ H ₃ Cl ₂ F
7-138807) and compounds represented by the structural formula C ₃ HCl ₃ F have erosion to plastics such as acrylic resin and polycarbonate resin (for example, the surface is rough, whitening due to partial dissolution, and cracks), and hollow fibers After assembling the membrane into the case, liquid could not be passed through the inside of the hollow fiber membrane. In addition, in the case of the compound represented by the structural formula C ₃ HCl ₅ F ₅ , there was a disadvantage that glycerin, which is a pore size retaining agent, was partially dissolved, so that membrane performance was lowered.

On the other hand, a fluorocarbon-based compound (Japanese Unexamined Patent Publication No.
285160) basically has no ability to dissolve an oily substance, but because of its low surface tension, it enters between the film material and the oily substance and is removed by peeling off the latter. However, there is a drawback that the efficiency is poor due to physical peeling and a large amount of liquid is required. It is also necessary to consider the impact on global warming.

In a hemodialyzer or the like, the length of the hollow fiber is large.
It is about 0.1 to 0.2 m, and can be washed by immersing the hollow fiber in the washing liquid. However, hollow fibers for ultrafiltration membranes and microfiltration membranes have a length of about 0.6 to 1.2 m longer than that of hemodialyzers, and cannot be washed by immersion alone.

Further, when the hollow fiber bundle is immersed for cleaning, the size of the apparatus becomes large and a large amount of cleaning liquid is required.

[0008]

SUMMARY OF THE INVENTION The present invention uses a detergent having a substantially zero ozone depletion potential and a low global warming potential, does not change the hollow fiber membrane structure, and uses a pore size retention agent such as glycerin. It is a cleaning method that can leave and prevent erosion of the adhesive and casing, which are members of the clarifying membrane module, and can selectively remove oily substances from the hollow fiber membrane. The cleaning of the inside of the hollow fiber is made possible by forcibly flowing the cleaning liquid against the cleaning of the inside of the hollow fiber where is insufficient.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the inner surface of a hollow fiber membrane spun using an oily filler is forcibly applied using an aliphatic hydrocarbon. By rinsing, it is possible to suppress the erosion of the adhesive and casing, which are members of the membrane module for turbidity, while maintaining the pore size retention agent such as glycerin without giving a change in the membrane structure, and selectively removing oily substances. Was successfully removed.

That is, the present invention is as follows. In the production of the hollow fiber membrane, an ozone destruction coefficient is zero and the boiling point is forced to flow aliphatic hydrocarbons having a temperature of 130 ° C. or less into the hollow fiber, and the oily substance present inside the hollow fiber is selectively washed and removed, A method for cleaning a hollow fiber membrane, wherein a pore diameter retaining agent is left in the hollow fiber. The method for cleaning a hollow membrane as described above, wherein the hollow fiber membrane is an ultrafiltration membrane or a microfiltration membrane. The above-mentioned or the above-mentioned method for cleaning a hollow fiber membrane, wherein the hollow fiber membrane comprises a cellulose ester. 4. The method for cleaning a hollow fiber membrane according to any one of the above items, wherein the pore size retaining agent is glycerin. 4. The method for cleaning a hollow fiber membrane according to any one of the above items, wherein the oily substance is liquid paraffin or isopropyl myristylate.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The material of the hollow fiber membrane to be washed by the method of the present invention is not particularly limited as long as it can be spun using an oily filler, and cellulose, cellulose acetate, cellulose triacetate, polyacrylonitrile, and the like can be used. And polymers such as polymethyl methacrylate and polysulfone.

[0012] These polymers are dissolved or melted in a solvent / swelling agent to prepare a spinning dope, which is extruded into a hollow shape from a tube-in orifice. An oily substance such as stylate is simultaneously discharged to spin a hollow fiber filled with the oily substance. Thereafter, for example, in dry-wet spinning, the film is guided through an aerial traveling to a coagulation bath having a reduced concentration with the same solvent and swelling agent composition, and a temperature difference and a concentration difference are driven to cause microphase separation to form a film. Finally, after removing the solvent and the swelling agent in the washing tank, a pore size retaining agent is filled and dried. Glycerin, polyethylene glycol, polypropylene glycol and the like are used as the pore size retaining agent, and glycerin is particularly preferably used.

When the hollow fiber membrane obtained by spinning in this way is used, it is necessary to remove the oily substance filled inside the hollow fiber membrane. In the present invention, an aliphatic hydrocarbon is used to selectively remove the oily substance filling the inside of the hollow fiber membrane. The aliphatic hydrocarbon is not particularly limited as long as it has an ozone destruction coefficient of substantially zero and dissolves an oily substance, and various compounds can be used, for example, pentane / hexane / octane and nonane. When performing the washing, the aliphatic hydrocarbon is forced to flow inside the hollow fiber.

[0014]

The present invention will be specifically described below with reference to examples.

Example 1 When a cellulose acetate solution was extruded from an orifice, an oily substance such as liquid paraffin was simultaneously discharged inside the hollow fiber to spin a hollow fiber filled with the oily substance. The hollow fiber thus spun is bundled so as to be wound around a core tube arranged near the central axis of the cylindrical container, and one side of the hollow fiber bundle is fixed with an adhesive such as urethane or epoxy, and then bonded. The portion is cut to open the end of the hollow fiber, and the other side is left unbonded, leaving the hollow fiber open. 2L of aliphatic hydrocarbon (nonane) is poured from the open surface with a head pressure of 2m,
The inner surface of the hollow fiber was washed. Then, the liquid paraffin present inside the hollow fiber was selectively removed, but the glycerin contained in the hollow city was not dissolved, and most of the glycerin remained. After washing, the inner surface of the hollow fiber is
Air was blown off and dried. The water permeability was equivalent to that obtained by cleaning with CFCs, and was found to be sufficiently effective as a substitute for CFCs.

COMPARATIVE EXAMPLE 1 The same cleaning method as in the above example was carried out using ethyl alcohol for cleaning, but the water permeability of the obtained hollow fiber membrane was significantly reduced.

[Comparative Example 2] The hollow fiber bundle was immersed in a tank (10 L) containing an aliphatic hydrocarbon to wash the internal liquid inside the hollow fiber. More than 5 times more than in the example.

[0018]

According to the present invention, it is possible to prevent a decrease in water permeability due to washing during the manufacturing process of the hollow fiber membrane module for turbidity, to make the washing apparatus compact, and to reduce the required amount of washing liquid.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D06L 1/02 D06L 1/02 (72) Inventor Ichiro Ohama 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo F-term in the Research Institute, Inc. (Reference) 4D006 GA06 GA07 MA01 MC11X MC18X MC37X MC39X MC62X NA05 NA23 NA26 NA61 NA64 4L035 BB66 DD03

Claims (5)

[Claims] 1. In the production of a hollow fiber membrane, an aliphatic hydrocarbon having an ozone depletion potential of zero and a boiling point of 130 ° C. or less is forced to flow inside the hollow fiber to selectively remove oily substances present inside the hollow fiber. A method for cleaning a hollow fiber membrane, comprising washing and removing a pore size retaining agent in a hollow fiber. 2. The method for cleaning a hollow membrane according to claim 1, wherein the hollow fiber membrane is an ultrafiltration membrane or a microfiltration membrane. 3. The method for cleaning a hollow fiber membrane according to claim 1, wherein the hollow fiber membrane is made of cellulose ester. 4. The method according to claim 1, wherein the pore size retaining agent is glycerin.
4. The method for cleaning a hollow fiber membrane according to any one of items 1 to 3. 5. The method for cleaning a hollow fiber membrane according to claim 1, wherein the oily substance is liquid paraffin or isopropyl myristylate.