JPH02152530A - Production of fungistatic porous hollow fiber - Google Patents

Abstract

PURPOSE:To deposit a small amt. of silver on the whole surface of a hollow fiber and to improve the fungistatic property and water permeability of the fiber by filling an org. solvent compatible with water in the porous layer of the porous hollow fiber wherein the micropore extends from the inner wall to the outer wall and then applying silver mirror reaction treatment. CONSTITUTION:The hollow fiber having a porous layer of the porous layer of the porous hollow fiber wherein the micropore extends from the inner-wall surface to the outer-wall surface is dipped in an org. solvent compatible with water to fill the micropore with the solvent. The solvent deposited on the surface of the hollow fiber is removed as much as possible, and silver mirror reaction treatment is applied. By this treatment a gray porous hollow fiber coated with the absorbed silver is obtained. Polyethylene, polypropylene, polyamide, etc., are used for the hollow fiber. Ethyl alcohol, acetone, methyl ethyl ketone, etc., are exemplified as the org. solvent compatible with water. By this method, a small amt. of silver is deposited almost over the whole surface layer, and an excellent fungistatic property and high water permeability are exhibited. Precision filtration is carried out under sanitary and safe conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing porous hollow fibers with excellent antibacterial properties for use as water filtration membranes.

[Conventional technology]

It has long been known that silver exhibits excellent antibacterial properties and that bacteria do not propagate on the surface of silver. The present inventors took advantage of the properties of silver to form a thin film of silver on the surface layer of porous polyolefin hollow fibers and proposed a microbial-resistant porous polyolefin hollow fiber filtration module (Japanese Patent Application Laid-Open No. 60-
26.5^ Official Gazette). Furthermore, a silver sputtering treatment method has been proposed as a method for forming a thin silver film on the outer surface of a porous hollow fiber (Japanese Patent Laid-Open No. 62-298406).

By the way, when water containing bacteria is filtered using such porous hollow fibers for bacterial separation, the bacteria are usually blocked on the surface of the porous hollow fibers and do not migrate to the inner layer, so the surface layer of the porous hollow fibers is not sufficiently filtered. Any material may be used as long as it has antibacterial properties. or,
The antibacterial effect of metallic silver occurs only on the silver surface, and does not extend to the surrounding area away from the silver surface. Therefore, the antibacterial porous hollow fiber used as a bacterial separation membrane contains silver over the entire surface layer. It is required that it be fixed.

[Problem to be solved by the invention]

However, in the vacuum deposition method described in JP-A-60-261502, it is difficult to adhere silver to the entire surface layer of the porous hollow fibers, and there are portions of the surface layer where silver does not adhere. Furthermore, even with the method described in JP-A-62-298406, it is difficult to fix silver to the entire surface layer of the porous hollow fibers, and the antibacterial properties cannot be said to be sufficient.

Another method is to fill the porous layer of the porous hollow fiber with a silver plating solution and fix silver from the outer layer to the inner layer of the porous layer using an electroless silver plating method. Problems arise when silver is reduced and precipitated inside the layer, clogging the pores and significantly reducing water permeability.

The purpose of the present invention is to solve the problems of the prior art as described above,
Provided is a method for producing a porous hollow fiber, in which silver is fixed to almost the entire surface layer on the outer surface side of the porous hollow fiber, and the pores are less clogged due to silver fixation treatment, and have excellent water permeability and antibacterial properties. Then there is K.

[Means to solve the problem]

The gist of the present invention is to fill the porous layer of a porous hollow fiber in which micropores are connected from the inner wall surface to the outer wall surface with an organic solvent that is compatible with water, and then to perform a silver mirror reaction treatment on the porous hollow fiber. A method for producing a fungal porous hollow fiber.

Porous hollow fibers in which micropores are connected from the inner wall surface to the outer wall surface used in the present invention include polyethylene, celipropylene, folysulfone, polyethersulfone, polycarbonate, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, polyimide, and polychloride. Examples include porous hollow fibers made of vinyl, polymethyl methacrylate, cellulose acetate, and the like.

Examples of organic solvents that are compatible with water include ethyl alcohol, methyl alcohol, acetone, methyl ethyl ketone, dimethyl formamide, dimethyl acetamide, and dimethyl sulfoxide.

As a method for filling the porous layer of the porous hollow fiber with such an organic solvent, a method of immersing the porous hollow fiber in the solvent is preferably used.

In this case, in order to sufficiently fill the solvent into the porous layer of the porous hollow fiber, it is effective to use a solvent that has a small difference in surface tension from the porous hollow fiber and is easily wetted. In addition, after filling the porous layer of the porous hollow fiber with the solvent in this way, remove as much of the solvent adhering to the surface of the porous hollow fiber as possible,
Next, silver mirror reaction treatment is performed.

For the silver mirror reaction treatment, conventionally known methods can be used as they are. For example, dissolve 5 tons of silver nitrate in a small amount of water, gradually add aqueous ammonia to it, and when the first silver oxide precipitate is about to dissolve due to excess ammonia, stop adding the ammonia water, and then dissolve the silver oxide through a filter paper. The solution was filtered, and water was added to give a solution of 500%, and this solution was designated as solution A. Separately, dissolve 1 t of silver nitrate in a small amount of water,
Add 500 - of boiling hot water to it, and then add Rochelle salt α839 to make a gray cloudy liquid. This gray hot liquid is directly filtered through a filter paper, and this liquid is designated as liquid B.

Then, the silver mirror reaction treatment solution can be prepared by mixing equal amounts of the liquid silica and the solution B.

Silver mirror reaction treatment can be carried out by immersing a porous hollow fiber filled with a solvent in a silver mirror reaction treatment solution and treating it at, for example, 25°C for about 60 minutes. You can get thread.

After the silver mirror reaction treatment, thoroughly wash with water and dry. The washing process preferably uses an ultrasonic cleaner, and the drying process can use a conventional hot air dryer or vacuum dryer.

When silver mirror reaction treatment is performed with the porous layer of the porous hollow fiber filled with an organic solvent that is compatible with water, the silver mirror reaction treatment solution will diffuse from the outer wall surface of the porous layer to the inner layer. The adsorption of silver by the silver mirror reaction treatment is carried out only on the entire surface layer on the outer surface side of the porous hollow fiber and on the inner layer near the outer surface, making it possible to uniformly and firmly fix a small amount of silver, making it an excellent material. Porous hollow fibers having excellent water permeability and antibacterial properties can be obtained.

Incidentally, when the porous hollow fibers are subjected to the silver mirror reaction treatment by directly immersing them in the silver mirror reaction treatment solution, the following problems occur. In other words, hydrophobic porous hollow fibers, such as porous polyethylene hollow fibers, are highly hydrophobic and have insufficient wettability with the silver mirror reaction treatment solution, so the silver mirror reaction proceeds only on the outer surface of the porous hollow fibers, resulting in a porous polyethylene hollow fiber. It is not possible to improve the adhesion of silver on the surface of the hollow fibers, and even if silver can be retained, it will inevitably fall off easily when washed with water or the like.

On the other hand, when hydrophilized porous polyethylene hollow fibers to which a hydrophilic agent such as a surfactant is fixed are used, the silver mirror reaction treatment solution easily diffuses into the inside of the porous layer and the silver mirror reaction progresses, resulting in the formation of A problem arises in that the silver particles block the micropores of the porous hollow fibers, greatly reducing water permeability.

On the other hand, if the silver mirror reaction treatment is performed by filling the porous layer of the porous hollow fiber with an organic solvent that is incompatible with water, such as a lipophilic liquid such as toluene or benzene, instead of an organic solvent that is compatible with water. Since the surface of the porous hollow fiber is coated with a lipophilic liquid, it is difficult for the silver mirror reaction treatment solution to diffuse onto the surface of the porous hollow fiber, and the silver produced by the silver mirror reaction is hardly adsorbed onto the porous hollow fiber. It is not possible to obtain a porous hollow fiber to which silver is fixed.-0 [Example] The present invention will be explained below with reference to Examples. In the examples, the silver mirror reaction treatment liquids were liquid (2), which was a mixture of the above-mentioned liquids A and B in equal volumes, liquid (2), which was a mixture of liquid (2) and water in equal volumes, and liquid (2), which was a mixture of liquid (2) and water in equal volumes. (2) or liquid (2), which is a mixture of liquid (2) and water in equal volumes, was used. In addition, the amount of silver adhesion, antibacterial properties, and water permeability were measured or evaluated by the following methods.

(1) Measurement of the amount of silver fixed
After being immersed for 20 minutes, the fibers were sufficiently washed with water and dried, and the amount of silver fixed was calculated from the weight change of the porous hollow fibers before and after the nitric acid aqueous solution treatment using the following formula.

-B Silver fixation it (qbowf) = Porous hollow fibers of length 11 were lined up on an agar medium seeded with the bacteria, and the bacteria were cultured at 37°C for 24 hours, and the bacteriostatic effect was determined based on the presence or absence of bacterial growth on the surface of the hollow fibers.

(Judgment) ○: No bacterial growth is observed on the sample surface.

×: Growth of bacteria on the sample surface was observed. It will be done.

(3) Measurement of water permeability 400 porous hollow fibers were bundled in a figure 8 shape and the openings of the hollow fibers were solidified with resin to produce a filtration module with a length of the resin-embedded part of 1 and an effective length of the hollow fibers of 16. This module at 25℃
After immersion treatment in ethyl alcohol for 30 minutes, water at a temperature of 20°C was flowed from the outer wall of the porous hollow fiber toward the hollow part for 1 minute at a water pressure of 1 kg 7 cm'' to measure the amount of water permeation.
Water permeation amount per hollow fiber unit surface area (wd/min-
The cm radius was calculated.

Examples 1 to 4 Porous polyethylene hollow fiber (outer diameter 380 μm, inner diameter 27
0 μm) was immersed in ethyl alcohol at 25° C. for 5 minutes and then pulled up to obtain a porous polyethylene hollow fiber in which the porous layer of the hollow fiber was filled with ethyl alcohol.

Subsequently, this porous polyethylene hollow fiber was heated to the following temperature at 25°C.
After performing the silver mirror reaction treatment by immersing it in each of the silver mirror reaction treatment solutions (■, ■, ■, or ■) for 60 minutes, it was washed with water at 25°C for 10 minutes using an ultrasonic cleaner, and then washed with water using a vacuum dryer. By vacuum drying at 40° C. for 24 hours, gray porous polyethylene hollow fibers with silver uniformly adhered to almost the entire outer surface of the porous hollow fibers were obtained.

The amount of silver adhering, water permeability, and antibacterial properties of these porous polyethylene hollow fibers were measured or evaluated, and the results are shown in Table 1.

From Table 1, it can be seen that even in the case of Example 4, in which the amount of fixed silver was extremely small, an excellent antibacterial effect was exhibited. It is also seen that water permeability improves as the amount of silver adhering decreases.

In addition, the hue of the porous hollow fibers, which turned gray due to silver fixation treatment, hardly changes even after long-term water treatment, and the silver is firmly fixed and does not fall off during water treatment.
,-I confirmed that.

Comparative Example 1 A porous polyethylene hollow fiber similar to that used in Example 1 was evaluated for antibacterial properties and water permeability without being subjected to silver mirror reaction treatment, and the results are shown in Table 1.

Example 5 Porous polysulfone hollow fiber (outer diameter 440 μm, inner diameter 33
0 μm) was immersed in 25C ethyl alcohol for 5 minutes and then pulled up to obtain a porous polysulfone hollow fiber in which the porous layer of the hollow fiber was filled with ethyl alcohol.

Subsequently, this porous hollow fiber was treated with silver mirror reaction treatment solution ■ at 25°C.
Medium [After immersing for 60 minutes to perform silver mirror reaction treatment, washing with water for 10 minutes at 25 °C using an ultrasonic cleaner, and drying under vacuum at 40 °C for 24 hours using a vacuum dryer. Thus, gray porous polysulfone hollow fibers were obtained in which silver was uniformly fixed over almost the entire surface layer on the outer surface side of the porous hollow fibers.

This porous polysulfone hollow fiber had excellent bactericidal properties, and no bacterial growth was observed on the surface of the h1 porous hollow fiber. In addition, the water permeability of the porous polysulfone hollow fibers before the silver mirror reaction treatment is 58 dl m1n-1, whereas the water permeability after the silver mirror reaction treatment is 15 td/m1.
It was n-2.

Table 1 [Effects of the Invention] According to the method of the present invention, a small amount of silver can be fixed over almost the entire surface layer on the outer surface side of the 4-cell hollow fiber,
Porous hollow fibers having excellent bacteriostatic properties and high water permeability can be obtained.

Further, by using a filtration module made of such porous hollow fibers, precision filtration that is hygienic and highly safe is possible.

Patent applicant: Mitsubishi Rayon Co., Ltd. Agent: Patent Attorney Toshio Yoshizawa

Claims (1)

[Claims] After filling the porous layer of the porous hollow fiber in which micropores are connected from the inner wall surface to the outer wall surface with an organic solvent that is compatible with water,
A method for producing a bacteriostatic porous hollow fiber, which comprises subjecting the porous hollow fiber to a silver mirror reaction treatment.